Sample records for front disc brakes

  1. How to play a disc brake

    E-Print Network [OSTI]

    Oleg N. Kirillov

    2007-08-22T23:59:59.000Z

    We consider a gyroscopic system under the action of small dissipative and non-conservative positional forces, which has its origin in the models of rotating bodies of revolution being in frictional contact. The spectrum of the unperturbed gyroscopic system forms a "spectral mesh" in the plane "frequency -gyroscopic parameter" with double semi-simple purely imaginary eigenvalues at zero value of the gyroscopic parameter. It is shown that dissipative forces lead to the splitting of the semi-simple eigenvalue with the creation of the so-called "bubble of instability" - a ring in the three-dimensional space of the gyroscopic parameter and real and imaginary parts of eigenvalues, which corresponds to complex eigenvalues. In case of full dissipation with a positive-definite damping matrix the eigenvalues of the ring have negative real parts making the bubble a latent source of instability because it can "emerge" to the region of eigenvalues with positive real parts due to action of both indefinite damping and non-conservative positional forces. In the paper, the instability mechanism is analytically described with the use of the perturbation theory of multiple eigenvalues. As an example stability of a rotating circular string constrained by a stationary load system is studied in detail. The theory developed seems to give a first clear explanation of the mechanism of self-excited vibrations in the rotating structures in frictional contact, that is responsible for such well-known phenomena of acoustics of friction as the squealing disc brake and the singing wine glass.

  2. Neutron scattering residual stress measurements on gray cast iron brake discs

    SciTech Connect (OSTI)

    Spooner, S.; Payzant, E.A.; Hubbard, C.R. [and others

    1996-11-01T23:59:59.000Z

    Neutron diffraction was used to investigate the effects of a heat treatment designed to remove internal residual stresses in brake discs. It is believed that residual stresses may change the rate of deformation of the discs during severe braking conditions when the disc temperature is increased significantly. Neutron diffraction was used to map out residual strain distributions in a production disc before and after a stress-relieving heat treatment. Results from these neutron diffraction experiments show that some residual strains were reduced by as much as 400 microstrain by stress relieving. 5 refs., 5 figs., 1 tab.

  3. Integrated vehicle dynamics control via coordination of active front steering and rear braking

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Integrated vehicle dynamics control via coordination of active front steering and rear brakingComputer and Automation Research Institue, Hungarian Academy of Sciences, Kende u. 13-17, H-1111, Budapest, Hungary, Email front steering and rear braking in a driver- assist system for vehicle yaw control. The proposed control

  4. Storm fronts over galaxy discs: Models of how waves generate extraplanar gas and its anomalous kinematics

    E-Print Network [OSTI]

    Curtis Struck; Daniel C. Smith

    2009-05-15T23:59:59.000Z

    The existence of partially ionized, diffuse gas and dust clouds at kiloparsec scale distances above the central planes of edge-on, galaxy discs was an unexpected discovery about 20 yrs ago. Subsequent observations showed that this EDIG (extended or extraplanar diffuse interstellar gas) has rotation velocities approximately 10-20% lower than those in the central plane, and have been hard to account for. Here we present results of hydrodynamic models, with radiative cooling and heating from star formation. We find that in models with star formation generated stochastically across the disc an extraplanar gas layer is generated as long as the star formation is sufficiently strong. However, this gas rotates at nearly the same speed as the mid-plane gas. We then studied a range of models with imposed spiral or bar waves in the disc. EDIG layers were also generated in these models, but primarily over the wave regions, not over the entire disc. Because of this partial coverage, the EDIG clouds move radially, as well as vertically, with the result that observed kinematic anomalies are reproduced. The implication is that the kinematic anomalies are the result of three-dimensional motions when the cylindrical symmetry of the disc is broken. Thus, the kinematic anomalies are the result of bars or strong waves, and more face-on galaxies with such waves should have an asymmetric EDIG component. The models also indicate that the EDIG can contain a significant fraction of cool gas, and that some star formation can be triggered at considerable heights above the disc midplane. We expect all of these effects to be more prominent in young, forming discs, to play a role in rapidly smoothing disc asymmetries, and in working to self-regulate disc structure.

  5. Braking system

    DOE Patents [OSTI]

    Norgren, D.U.

    1982-09-23T23:59:59.000Z

    A balanced braking system comprising a plurality of braking assemblies located about a member to be braked. Each of the braking assemblies consists of a spring biased piston of a first material fitted into a body of a different material which has a greater contraction upon cooling than the piston material. The piston is provided with a recessed head portion over which is positioned a diaphragm and forming a space therebetween to which is connected a pressurized fluid supply. The diaphragm is controlled by the fluid in the space to contact or withdraw from the member to be braked. A cooling means causes the body within which the piston is fitted to contract more than the piston, producing a tight shrink fit therebetween. The braking system is particularly applicable for selectively braking an arbor of an electron microscope which immobilizes, for example, a vertically adjustable low temperature specimen holder during observation. The system provides balanced braking forces which can be easily removed and re-established with minimal disturbance to arbor location.

  6. automotive drum brakes: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    well-known phenomena of acoustics of friction as the squealing disc brake and the singing wine glass. Oleg N. Kirillov 2007-08-07 130 The Ultra-High Energy Cosmic Ray Spectrum...

  7. Magnetic braking of T Tauri stars

    E-Print Network [OSTI]

    P. J. Armitage; C. J. Clarke

    1995-12-05T23:59:59.000Z

    We construct models for the rotation rates of T Tauri stars whose spin is regulated by magnetic linkage between the star and a surrounding accretion disc. Our models utilise a time-dependent disc code to follow the accretion process and include the effects of pre-main-sequence stellar evolution. We find that the initial disc mass controls the evolution of the star-disc system. For sufficiently massive discs, a stellar field of $\\sim$ 1 kG is able to regulate the spin rate to the observed values during the classical T Tauri phase. The field then acts to expel the disc and the star spins up at constant angular momentum as a weak-line system. Lower mass discs are ejected at an early epoch and fail to brake the star significantly. We extend the model to close binary systems, and find that the removal of angular momentum from the disc by the secondary significantly prolongs the inner disc lifetime. Such systems should therefore be relatively slow rotators. We also discuss the implications of our model for the spectral energy distributions and variability of T Tauri stars.

  8. Vehicle brake testing system

    DOE Patents [OSTI]

    Stevens, Samuel S. (Harriman, TN); Hodgson, Jeffrey W. (Lenoir City, TN)

    2002-11-19T23:59:59.000Z

    This invention relates to a force measuring system capable of measuring forces associated with vehicle braking and of evaluating braking performance. The disclosure concerns an invention which comprises a first row of linearly aligned plates, a force bearing surface extending beneath and beside the plates, vertically oriented links and horizontally oriented links connecting each plate to a force bearing surface, a force measuring device in each link, a transducer coupled to each force measuring device, and a computing device coupled to receive an output signal from the transducer indicative of measured force in each force measuring device. The present invention may be used for testing vehicle brake systems.

  9. Combined hydraulic and regenerative braking system

    DOE Patents [OSTI]

    Venkataperumal, Rama R. (Troy, MI); Mericle, Gerald E. (Mount Clemens, MI)

    1981-06-02T23:59:59.000Z

    A combined hydraulic and regenerative braking system and method for an electric vehicle, with the braking system being responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

  10. Speciation of Sb in airborne particulate matter, vehicle brake linings, and brake pad wear residues

    E-Print Network [OSTI]

    Short, Daniel

    Speciation of Sb in airborne particulate matter, vehicle brake linings, and brake pad wear residues: XAS XANES EXAFS Antimony Particulate matter Brake linings a b s t r a c t Insights into the speciation of Sb in samples of brake linings, brake pad wear residues, road dust, and atmospheric particulate

  11. Regenerative braking device

    DOE Patents [OSTI]

    Hoppie, Lyle O. (Birmingham, MI)

    1982-01-12T23:59:59.000Z

    Disclosed are several embodiments of a regenerative braking device for an automotive vehicle. The device includes a plurality of rubber rollers (24, 26) mounted for rotation between an input shaft (14) connectable to the vehicle drivetrain and an output shaft (16) which is drivingly connected to the input shaft by a variable ratio transmission (20). When the transmission ratio is such that the input shaft rotates faster than the output shaft, the rubber rollers are torsionally stressed to accumulate energy, thereby slowing the vehicle. When the transmission ratio is such that the output shaft rotates faster than the input shaft, the rubber rollers are torsionally relaxed to deliver accumulated energy, thereby accelerating or driving the vehicle.

  12. Variable ratio regenerative braking device

    DOE Patents [OSTI]

    Hoppie, Lyle O. (Birmingham, MI)

    1981-12-15T23:59:59.000Z

    Disclosed is a regenerative braking device (10) for an automotive vehicle. The device includes an energy storage assembly (12) having a plurality of rubber rollers (26, 28) mounted for rotation between an input shaft (36) and an output shaft (42), clutches (38, 46) and brakes (40, 48) associated with each shaft, and a continuously variable transmission (22) connectable to a vehicle drivetrain and to the input and output shafts by the respective clutches. The rubber rollers are torsionally stressed to accumulate energy from the vehicle when the input shaft is clutched to the transmission while the brake on the output shaft is applied, and are torsionally relaxed to deliver energy to the vehicle when the output shaft is clutched to the transmission while the brake on the input shaft is applied. The transmission ratio is varied to control the rate of energy accumulation and delivery for a given rotational speed of the vehicle drivetrain.

  13. Turbulent drag reduction through oscillating discs

    E-Print Network [OSTI]

    Wise, Daniel J

    2014-01-01T23:59:59.000Z

    The changes of a turbulent channel flow subjected to oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations. The Reynolds number is $R_\\tau$=$180$, based on the friction velocity of the stationary-wall case and the half channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20%. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim to identify the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6%. The Rosenblat viscous pump flow is used to predict the power spent for disc motion in the turbulent channel flow and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The...

  14. Commercial Motor Vehicle Brake Assessment Tools

    E-Print Network [OSTI]

    Commercial Motor Vehicle Brake Assessment Tools Commercial Motor Vehicle Roadside Technology to deceleration in g's ­ Passing score: BE43.5 · Enforcement tool for only 3 years. · Based solely on brake Brake Research · CMVRTC research built on these enforcement tools ­ Correlation Study ­ Level-1 / PBBT

  15. Brake blending strategy for a hybrid vehicle

    DOE Patents [OSTI]

    Boberg, Evan S. (Hazel Park, MI)

    2000-12-05T23:59:59.000Z

    A hybrid electric powertrain system is provided including a transmission for driving a pair of wheels of a vehicle and a heat engine and an electric motor/generator coupled to the transmission. A friction brake system is provided for applying a braking torque to said vehicle. A controller unit generates control signals to the electric motor/generator and the friction brake system for controllably braking the vehicle in response to a drivers brake command. The controller unit determines and amount of regenerative torque available and compares this value to a determined amount of brake torque requested for determining the control signals to the electric motor/generator and the friction brake system.

  16. Disturbance Control of the Hydraulic Brake in a Wind Turbine

    E-Print Network [OSTI]

    Yang, Zhenyu

    Disturbance Control of the Hydraulic Brake in a Wind Turbine Frank Jepsen, Anders Søborg brake in a wind turbine. Brake torque is determined by friction coefficient and clamp force; the latter brake is one1 of the two independent brake systems in a wind turbine. As a consequence of the gearing

  17. Commercial Motor Vehicle Brake-Related Research

    E-Print Network [OSTI]

    Commercial Motor Vehicle Brake-Related Research Commercial Motor Vehicle Roadside Technology Corridor Safety Technology Showcase October 14, 2010 Commercial Motor Vehicle Roadside Technology Corridor

  18. Throttle And Brake Control Systems For Automatic Vehicle Following

    E-Print Network [OSTI]

    Ioannou, P.; Xu, Z.

    1994-01-01T23:59:59.000Z

    and Brake Control Systems for Automatic Vehicle Following P.and Brake Control Systems for Automatic Vehicle Following *Transit Systems, Proceedings of 1977 Joint Automatic Control

  19. Brake Defect Causation and Abatement Study (BDCAS)

    E-Print Network [OSTI]

    on various lining materials for comparison study #12;Center for Transportation Analysis 2360 CherahalaBrake Defect Causation and Abatement Study (BDCAS) Oak Ridge National Laboratory managed by UT Based Brake Testers (PBBTs) part of the out-of- service criterion for commercial motor vehicles in 2007

  20. TMV Technology Capabilities Brake Stroke Monitor

    E-Print Network [OSTI]

    TMV Technology Capabilities Brake Stroke Monitor Brake monitoring systems are proactive maintenance This technology allows for CMV operators to have knowledge of their steer, drive, and tandem axle group weights setup is required. Current Safety/Enforcement Technologies EOBR (electronic on-board recorder) On

  1. Thin discs, thick discs and transition zones

    E-Print Network [OSTI]

    Guillaume Dubus

    2002-06-13T23:59:59.000Z

    Accretion onto a compact object must occur through a disc when the material has some initial angular momentum. Thin discs and the thicker low radiative efficiency accretion flows are solutions to this problem that have been widely studied and applied. This is an introduction to these accretion flows within the context of X-ray binaries and cataclysmic variables.

  2. Turbulent protostellar discs

    E-Print Network [OSTI]

    Axel Brandenburg

    2008-08-07T23:59:59.000Z

    Aspects of turbulence in protostellar accretion discs are being reviewed. The emergence of dead zones due to poor ionization and alternatives to the magneto-rotational instability are discussed. The coupling between dust and gas in protostellar accretion discs is explained and turbulent drag is compared with laminar drag in the Stokes and Epstein regimes. Finally, the significance of magnetic field generation in turbulent discs is emphasized in connection with driving outflows and with star-disc coupling.

  3. Turbine disc sealing assembly

    DOE Patents [OSTI]

    Diakunchak, Ihor S.

    2013-03-05T23:59:59.000Z

    A disc seal assembly for use in a turbine engine. The disc seal assembly includes a plurality of outwardly extending sealing flange members that define a plurality of fluid pockets. The sealing flange members define a labyrinth flow path therebetween to limit leakage between a hot gas path and a disc cavity in the turbine engine.

  4. Contactless magnetic brake for automotive applications

    E-Print Network [OSTI]

    Gay, Sebastien Emmanuel

    2009-05-15T23:59:59.000Z

    consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent...

  5. An engine air-brake integration study

    E-Print Network [OSTI]

    Mulchandani, Hiten

    2011-01-01T23:59:59.000Z

    The feasibility of operating an engine air-brake (EAB) integrated with a pylon duct bifurcation in a realistic aircraft engine environment has been analyzed. The EAB uses variable exit guide vanes downstream of a high ...

  6. Method and apparatus for wind turbine braking

    DOE Patents [OSTI]

    Barbu, Corneliu (Laguna Hills, CA); Teichmann, Ralph (Nishkayuna, NY); Avagliano, Aaron (Houston, TX); Kammer, Leonardo Cesar (Niskayuna, NY); Pierce, Kirk Gee (Simpsonville, SC); Pesetsky, David Samuel (Greenville, SC); Gauchel, Peter (Muenster, DE)

    2009-02-10T23:59:59.000Z

    A method for braking a wind turbine including at least one rotor blade coupled to a rotor. The method includes selectively controlling an angle of pitch of the at least one rotor blade with respect to a wind direction based on a design parameter of a component of the wind turbine to facilitate reducing a force induced into the wind turbine component as a result of braking.

  7. Constraining the Braking Indices of Magnetars

    E-Print Network [OSTI]

    Gao, Z F; Wang, N; Yuan, J P; Peng, Q H; Du, Y J

    2015-01-01T23:59:59.000Z

    Due to the lack of long term pulsed emission in quiescence and the strong timing noise, it is impossible to directly measure the braking index $n$ of a magnetar. Based on the estimated ages of their potentially associated supernova remnants (SNRs), we estimate the values of $n$ of nine magnetars with SNRs, and find that they cluster in a range of $1\\sim$41. Six magnetars have smaller braking indices of $13$ for other three magnetars are attributed to the decay of external braking torque, which might be caused by magnetic field decay. We estimate the possible wind luminosities for the magnetars with $13$ within the updated magneto-thermal evolution models. We point out that there could be some connections between the magnetar's anti-glitch event and its braking index, and the magnitude of $n$ should be taken into account when explaining the event. Although the constrained range of the magnetars' braking indices is tentative, our method provides an effective way to constrain the magnetars' braking indices if th...

  8. Black hole accretion discs

    E-Print Network [OSTI]

    Lasota, Jean-Pierre

    2015-01-01T23:59:59.000Z

    This is an introduction to models of accretion discs around black holes. After a presentation of the non-relativistic equations describing the structure and evolution of geometrically thin accretion discs we discuss their steady-state solutions and compare them to observation. Next we describe in detail the thermal-viscous disc instability model and its application to dwarf novae for which it was designed and its X-ray irradiated-disc version which explains the soft X--ray transients, i.e. outbursting black-hole low-mass X-ray binaries. We then turn to the role of advection in accretion flow onto black holes illustrating its action and importance with a toy model describing both ADAFs and slim discs. We conclude with a presentation of the general-relativistic formalism describing accretion discs in the Kerr space-time.

  9. Adaptive controller for regenerative and friction braking system

    DOE Patents [OSTI]

    Davis, Roy I. (Ypsilanti, MI)

    1990-01-01T23:59:59.000Z

    A regenerative and friction braking system for a vehicle having one or more roadwheels driven by an electric traction motor includes a driver responsive device for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver and friction and regenerative brakes operatively connected with the roadwheels of the vehicle. A system according to this invention further includes control means for operating the friction and regenerative braking subsystems so that maximum brake torques sustainable by the roadwheels of the vehicle without skidding or slipping will not be exceeded.

  10. Adaptive controller for regenerative and friction braking system

    DOE Patents [OSTI]

    Davis, R.I.

    1990-10-16T23:59:59.000Z

    A regenerative and friction braking system for a vehicle having one or more road wheels driven by an electric traction motor includes a driver responsive device for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver and friction and regenerative brakes operatively connected with the road wheels of the vehicle. A system according to this invention further includes control means for operating the friction and regenerative braking subsystems so that maximum brake torques sustainable by the road wheels of the vehicle without skidding or slipping will not be exceeded. 8 figs.

  11. A diagnostic system for air brakes in commercial vehicles

    E-Print Network [OSTI]

    Coimbatore Subramanian, Shankar Ram

    2007-09-17T23:59:59.000Z

    This dissertation deals with the development of a model-based diagnostic system for air brake systems that are widely used in commercial vehicles, such as trucks, tractor-trailers, buses, etc. The performance of these brake ...

  12. Electric vehicle regenerative antiskid braking and traction control system

    DOE Patents [OSTI]

    Cikanek, S.R.

    1995-09-12T23:59:59.000Z

    An antiskid braking and traction control system for an electric or hybrid vehicle having a regenerative braking system operatively connected to an electric traction motor, and a separate hydraulic braking system includes one or more sensors for monitoring present vehicle parameters and a processor, responsive to the sensors, for calculating vehicle parameters defining the vehicle behavior not directly measurable by the sensors and determining if regenerative antiskid braking control, requiring hydraulic braking control, or requiring traction control are required. The processor then employs a control strategy based on the determined vehicle state and provides command signals to a motor controller to control the operation of the electric traction motor and to a brake controller to control fluid pressure applied at each vehicle wheel to provide the appropriate regenerative antiskid braking control, hydraulic braking control, and traction control. 10 figs.

  13. Electric vehicle regenerative antiskid braking and traction control system

    DOE Patents [OSTI]

    Cikanek, Susan R. (Wixom, MI)

    1995-01-01T23:59:59.000Z

    An antiskid braking and traction control system for an electric or hybrid vehicle having a regenerative braking system operatively connected to an electric traction motor, and a separate hydraulic braking system includes one or more sensors for monitoring present vehicle parameters and a processor, responsive to the sensors, for calculating vehicle parameters defining the vehicle behavior not directly measurable by the sensors and determining if regenerative antiskid braking control, requiring hydrualic braking control, or requiring traction control are required. The processor then employs a control strategy based on the determined vehicle state and provides command signals to a motor controller to control the operation of the electric traction motor and to a brake controller to control fluid pressure applied at each vehicle wheel to provide the appropriate regenerative antiskid braking control, hydraulic braking control, and traction control.

  14. Disc-Disc Encounters between Low-Mass Protoplanetary Accretion Discs

    E-Print Network [OSTI]

    S. Pfalzner; S. Umbreit; Th. Henning

    2005-04-27T23:59:59.000Z

    Simulations of the collapse and fragmentation of turbulent molecular clouds and dense young clusters show that encounters between disc-surrounded stars are relatively common events which should significantly influence the resulting disc structure. In turn this should alter the accretion rate of disc matter onto the star and the conditions under which planet formation occurs. Although the effects of star-disc encounters have been previously investigated, very little is known about encounters where both stars are surrounded by discs. In this paper encounters of such disc-disc systems are studied quantitatively. It is found that for low-mass discs ($M_D$= 0.01 $M_\\sun$) the results from star-disc encounters can be straightforwardly generalized to disc-disc encounters as long as there is no mass transport between the discs. Differences to star-disc encounters occur naturally where significant amounts of matter are transported between the discs. In this case it is found that although the mass distribution does not change significantly, matter caught onto highly eccentric orbits is transported surprisingly far inside the disc. The captured mass partly replenishes the disc, but has a much lower angular momentum. This can lead to a reduction of the angular momentum in the entire disc and thus considerably increased accretion shortly after the encounter as well as in the long term.

  15. The effect of friction on drum brakes

    SciTech Connect (OSTI)

    Huang, Y.M.; Shyr, J.S. [National Taiwan Univ. (China)

    1995-12-31T23:59:59.000Z

    The boundary element method (BEM) has been developed for a long period of time. Cruse and Wilson developed an isoparametric quadratic element. Rizzo, Cruse, Rizzo and Shippy, and Swedlow and cruse applied the method to various problems. It shows that the BEM can provide a very good analytical result in the linear problem and it can reduce time in preparation of numerical data. Watson and Newcomb pointed out that the pressure distribution on the contact surface of the brake drum and the lining plate do not vary significantly along the axis. The deflection can be reduced by an appropriate design of the web; therefore, two dimensional analysis with the BEM is used in this analysis. Based on the authors` knowledge, this is the first paper to analyze the drum brake by using the BEM. The assumptions are the brake drum to be a rigid body, perfect interface contact between the drum and the shoe, the constant friction coefficient of the friction material and the thermal effect to be neglected. The two dimensional equations are derived based on the Somigliana`s identity. Since there is no shape function and no need of the Jacobin for the coordinate transform, to integrate numerically is easier and to write a computer code is simpler for the constant value element than the second order element. The linear element is inappropriate to treat the comer problem. Using the linear elements or second order elements creates discontinuous phenomena along the irregular boundary. The common nodal point has different normal vector and boundary conditions. It is necessary to have an extra equation to provide a unique solution for the final linear equation. Using the constant value element can get rid of this problem. The effect of the friction on the pressure distribution at the friction interface is studied. The calculated results of the pressure distribution are compared with the available data. The mathematical model can be used as a design tool to predict the performance of drum brakes.

  16. A diagnostic system for air brakes in commercial vehicles

    E-Print Network [OSTI]

    Coimbatore Subramanian, Shankar Ram

    2007-09-17T23:59:59.000Z

    ]. It is appropriate to point out that, in an appraisal of the future needs of the trucking industry [16], the authors, who represent a broad spectrum of the trucking industry, call for the development of improved methods of brake inspections. 6 B. Objectives... States railway industry, air brake systems were initially introduced during the nineteenth century. Before the introduction of the air brake system, railway cars were retarded mainly by mechanical means (for example, by levers, chains and other linkages...

  17. Design, Modeling And Control Of Steering And Braking For An Urban Electric Vehicle

    E-Print Network [OSTI]

    Maciua, Dragos

    1996-01-01T23:59:59.000Z

    Design, Modeling and Control of Steering and Braking for anDesign, Modeling and Control of Steering and Braking for anDesign, Modeling and Control of Steering and Braking for an

  18. Measurement and control of brake pedal feel quality in automobile manufacturing

    E-Print Network [OSTI]

    Cerilles, Jeffrey T. (Jeffrey Thomas)

    2005-01-01T23:59:59.000Z

    Customer perception of brake pedal feel quality, as related to the perception of the brake pedal feeling soft or mushy, depends on both the customer's subjective judgment of quality and the actual build quality of the brake ...

  19. Radiation from Dwarf Nova Discs

    E-Print Network [OSTI]

    Irit Idan; Jean-Pierre Lasota; Jean-Marie Hameury; Giora Shaviv

    1998-06-04T23:59:59.000Z

    We use the Shaviv and Wehrse (1991) code to model the vertical structure and the emission properties of quiescent dwarf nova discs. We find that in the case of HT Cas the quiescent disc must be optically thin, in contradiction with the requirements of the standard disc instability model. We find a viscosity parameter alpha > 1. Although this is much less than values (~ 100) obtained in isothermal slab models it is not consistent with the accretion disc model assumptions.

  20. Pneumatic brake control for precision stopping of heavy-duty vehicles

    E-Print Network [OSTI]

    Bu, Fanping; Tan, Han-Shue

    2007-01-01T23:59:59.000Z

    desirable that the automatic brake control system uses thesystems, IEEE Transactions on Automatic Control, vol. 41,enables automatic control of the pneumatic brake system and

  1. Self-gravitating accretion discs

    E-Print Network [OSTI]

    G. Lodato

    2008-01-25T23:59:59.000Z

    I review recent progresses in the dynamics and the evolution of self-gravitating accretion discs. Accretion discs are a fundamental component of several astrophysical systems on very diverse scales, and can be found around supermassive black holes in Active Galactic Nuclei (AGN), and also in our Galaxy around stellar mass compact objects and around young stars. Notwithstanding the specific differences arising from such diversity in physical extent, all these systems share a common feature where a central object is fed from the accretion disc, due to the effect of turbulence and disc instabilities, which are able to remove the angular momentum from the gas and allow its accretion. In recent years, it has become increasingly apparent that the gravitational field produced by the disc itself (the disc's self-gravity) is an important ingredient in the models, especially in the context of protostellar discs and of AGN discs. Indeed, it appears that in many cases (and especially in the colder outer parts of the disc) the development of gravitational instabilities can be one of the main agents in the redistribution of angular momentum. In some cases, the instability can be strong enough to lead to the formation of gravitationally bound clumps within the disc, and thus to determine the disc fragmentation. As a result, progress in our understanding of the dynamics of self-gravitating discs is essential to understand the processes that lead to the feeding of both young stars and of supermassive black holes in AGN. At the same time, understanding the fragmentation conditions is important to determine under which conditions AGN discs would fragment and form stars and whether protostellar discs might form giant gaseous planets through disc fragmentation.

  2. Warp propagation in astrophysical discs

    E-Print Network [OSTI]

    Nixon, Chris

    2015-01-01T23:59:59.000Z

    Astrophysical discs are often warped, that is, their orbital planes change with radius. This occurs whenever there is a non-axisymmetric force acting on the disc, for example the Lense-Thirring precession induced by a misaligned spinning black hole, or the gravitational pull of a misaligned companion. Such misalignments appear to be generic in astrophysics. The wide range of systems that can harbour warped discs - protostars, X-ray binaries, tidal disruption events, quasars and others - allows for a rich variety in the disc's response. Here we review the basic physics of warped discs and its implications.

  3. Pulsar Braking Index and Mass Accretion

    E-Print Network [OSTI]

    P. D. Morley

    1993-11-15T23:59:59.000Z

    I show that the braking index, $N$, a fundamental pulsar experimental quantity, naturally differs from the canonical value of 3 by terms which involve mass accretion. Using the measured values of $N$ for PSR1509-58 and PSR0531+21, I determine that for constant density neutron stars their present mass accretion rates are $(3.10\\pm.51)\\times10^{-5}$ M year$^{-1}$ and $(9.946\\pm.089)\\times10^{-5}$ M year$^{-1}$ respectively, where M is the mass of each pulsar. Finally, I demonstrate that mass accretion removes the outstanding problem of the origin of the big glitches of the Vela Pulsar.

  4. Do Si stars undergo any magnetic braking?

    E-Print Network [OSTI]

    P. North

    1998-02-23T23:59:59.000Z

    The old question of rotational braking of Ap Si stars is revisited on the empirical side, taking advantage of the recent Hipparcos results. Field stars with various evolutionary states are considered, and it is shown that the loose correlation between their rotational period and their surface gravity is entirely compatible with conservation of angular momentum. No evidence is found for any loss of angular momentum on the Main Sequence, which confirms earlier results based on less reliable estimates of surface gravity. The importance of reliable, fundamental Teff determinations of Bp and Ap stars is emphasized.

  5. Development of Diagnostic Algorithms for Air Brakes in Trucks

    E-Print Network [OSTI]

    Dhar, Sandeep

    2011-10-21T23:59:59.000Z

    causes a reduction in the steady-state pressure in the brake chamber and an increase in the lag of the braking pressure response thereby increasing the stopping distance of the vehicle. Currently a presence of leak in the system is detected...

  6. Braking system for use with an arbor of a microscope

    DOE Patents [OSTI]

    Norgren, Duane U. (Orinda, CA)

    1984-01-01T23:59:59.000Z

    A balanced braking system comprising a plurality of braking assemblies located about a member to be braked. Each of the braking assemblies consists of a spring biased piston of a first material fitted into a body of a different material which has a greater contraction upon cooling than the piston material. The piston is provided with a recessed head portion over which is positioned a diaphragm and forming a space therebetween to which is connected a pressurized fluid supply. The diaphragm is controlled by the fluid in the space to contact or withdraw from the member to be braked. A cooling device causes the body within which the piston is fitted to contract more than the piston, producing a tight shrink fit therebetween. The braking system is particularly applicable for selectively braking an arbor of an electron microscope which immobilizes, for example, a vertically adjustable low temperature specimen holder during observation. The system provides balanced braking forces which can be easily removed and re-established with minimal disturbance to arbor location.

  7. Front Burner- Issue 14

    Broader source: Energy.gov [DOE]

    The Cybersecurity Front Burner Issue No. 14 addresses the 2013 National Cybersecurity Awareness Month (NCSAM) Campaign and Phishing Scams.

  8. Front Burner- Issue 15

    Broader source: Energy.gov [DOE]

    The Cybersecurity Front Burner Issue No. 15 addresses the DOE eSCRM Program and Secure Online Shopping.

  9. Enclosed rotary disc air pulser

    DOE Patents [OSTI]

    Olson, A. L. (Idaho Falls, ID); Batcheller, Tom A. (Idaho Falls, ID); Rindfleisch, J. A. (Arco, ID); Morgan, John M. (Arco, ID)

    1989-01-01T23:59:59.000Z

    An enclosed rotary disc air pulser for use with a solvent extraction pulse olumn includes a housing having inlet, exhaust and pulse leg ports, a shaft mounted in the housing and adapted for axial rotation therein, first and second disc members secured to the shaft within the housing in spaced relation to each other to define a chamber therebetween, the chamber being in communication with the pulse leg port, the first disc member located adjacent the inlet port, the second disc member being located adjacent the exhaust port, each disc member having a milled out portion, the disc members positioned on the shaft so that as the shaft rotates, the milled out portions permit alternative cyclical communication between the inlet port and the chamber and the exhaust port and the chamber.

  10. New Phase-coherent Measurements of Pulsar Braking Indices

    E-Print Network [OSTI]

    Margaret A. Livingstone; Victoria M. Kaspi; Fotis P. Gavriil; Richard N. Manchester; E. V. Gotthelf; Lucien Kuiper

    2007-02-07T23:59:59.000Z

    Pulsar braking indices offer insight into the physics that underlies pulsar spin-down. Only five braking indices have been measured via phase-coherent timing; all measured values are less than 3, the value expected from magnetic dipole radiation. Here we present new measurements for three of the five pulsar braking indices, obtained with phase-coherent timing for PSRs J1846-0258 (n=2.65+/-0.01), B1509-58 (n=2.839+/-0.001) and B0540-69 (n=2.140+/-0.009). We discuss the implications of these results and possible physical explanations for them.

  11. Volume One Disc Two

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What'sis Taking Over OurThe Iron SpinPrincetonUsing Maps1 -Visualizing Brain Metals inVolume-One-Disc-Two

  12. Regenerative braking on bicycles to power LED safety flashers

    E-Print Network [OSTI]

    Collier, Ian M

    2005-01-01T23:59:59.000Z

    This work develops a method for capturing some of the kinetic energy ordinarily lost during braking on bicycles to power LED safety flashers. The system is designed to eliminate: (a) battery changing in popular LED flashers, ...

  13. Adaptive Rollover Prevention for Automotive Vehicles with Differential Braking

    E-Print Network [OSTI]

    Duffy, Ken

    Adaptive Rollover Prevention for Automotive Vehicles with Differential Braking Selim Solmaz, switching, and tuning (MMST) paradigm [13, 14, 15] for preventing untripped rollover in automotive vehicles performance than its fixed robust counterpart. Keywords: Automotive control; Multiple models; Parameter

  14. Gravitating discs around black holes

    E-Print Network [OSTI]

    V. Karas; J. -M. Hure; O. Semerak

    2004-01-16T23:59:59.000Z

    Fluid discs and tori around black holes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a black hole--disc system by analytical solutions of stationary, axially symmetric Einstein's equations. Then, more detailed considerations are focused to middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring, however, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging and completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the environment around. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star--disc interactions, which can be recognised in observational properties, such as the relation between the central mass and stellar velocity dispersion.

  15. Investigation of aerodynamic braking devices for wind turbine applications

    SciTech Connect (OSTI)

    Griffin, D.A. [R. Lynette & Associates, Seattle, WA (United States)

    1997-04-01T23:59:59.000Z

    This report documents the selection and preliminary design of a new aerodynamic braking system for use on the stall-regulated AWT-26/27 wind turbines. The goal was to identify and design a configuration that offered improvements over the existing tip brake used by Advanced Wind Turbines, Inc. (AWT). Although the design objectives and approach of this report are specific to aerodynamic braking of AWT-26/27 turbines, many of the issues addressed in this work are applicable to a wider class of turbines. The performance trends and design choices presented in this report should be of general use to wind turbine designers who are considering alternative aerodynamic braking methods. A literature search was combined with preliminary work on device sizing, loads and mechanical design. Candidate configurations were assessed on their potential for benefits in the areas of cost, weight, aerodynamic noise, reliability and performance under icing conditions. As a result, two configurations were identified for further study: the {open_quotes}spoiler-flap{close_quotes} and the {open_quotes}flip-tip.{close_quotes} Wind tunnel experiments were conducted at Wichita State University to evaluate the performance of the candidate aerodynamic brakes on an airfoil section representative of the AWT-26/27 blades. The wind tunnel data were used to predict the braking effectiveness and deployment characteristics of the candidate devices for a wide range of design parameters. The evaluation was iterative, with mechanical design and structural analysis being conducted in parallel with the braking performance studies. The preliminary estimate of the spoiler-flap system cost was $150 less than the production AWT-26/27 tip vanes. This represents a reduction of approximately 5 % in the cost of the aerodynamic braking system. In view of the preliminary nature of the design, it would be prudent to plan for contingencies in both cost and weight.

  16. Asbestos-free brake-lining materials for hydrogenerators

    SciTech Connect (OSTI)

    Lalonde, S.; Lanteigne, J. [Hydro-Quebec, Varennes, Quebec (Canada)

    1995-11-01T23:59:59.000Z

    Three different asbestos-free materials currently considered as new lining materials for hydrogenerator brakes were tested and compared to the original asbestos lining. Results show that these substitutes not only vary greatly from the original material in terms of mechanical properties and physical characteristics but also exhibit significantly different performances in braking tests. Consequently, these new materials are not entirely suitable for the intended application.

  17. Tidally-induced warps in protostellar discs

    E-Print Network [OSTI]

    C. Terquem; J. Papaloizou; R. Nelson

    1998-10-01T23:59:59.000Z

    We review results on the dynamics of warped gaseous discs. We consider tidal perturbation of a Keplerian disc by a companion star orbiting in a plane inclined to the disc. The perturbation induces the precession of the disc, and thus of any jet it could drive. In some conditions the precession rate is uniform, and as a result the disc settles into a warp mode. The tidal torque also leads to the truncation of the disc, to the evolution of the inclination angle (not necessarily towards alignment of the disc and orbital planes) and to a transport of angular momentum in the disc. We note that the spectral energy distribution of such a warped disc is different from that of a flat disc. We conclude by listing observational effects of warps in protostellar discs.

  18. Front Burner- Issue 13

    Broader source: Energy.gov [DOE]

    The Cybersecurity Front Burner Issue No. 13 contained a message from the Associate Chief Information Officer (ACIO) for Cybersecurity as well as a listing of recommended cybersecurity practices.

  19. Front Burner- Issue 18

    Broader source: Energy.gov [DOE]

    The Cybersecurity Front Burner Issue No. 18 addresses keeping kids safe on the Internet, cyber crime, and DOE Cyber awareness and training initiatives.

  20. Front Burner- Issue 16

    Broader source: Energy.gov [DOE]

    The Cybersecurity Front Burner Issue No. 16 addresses Malware, the Worst Passwords of 2013, and the Flat Stanley and Stop.Think.Connect. Campaign.

  1. Influence of physical parameters and operating conditions for structural integrity of mechanical system subjected to squeal noise

    E-Print Network [OSTI]

    Paris-Sud XI, Universit de

    for the static load and circular wave front lines for the ramp loading. Introduction Disc brake systems-linear vibrations, acoustic radiation, brake squeal, friction Abstract. This work proposes to study the effects of physical parameters and loading conditions on both dynamic and acoustic responses of a brake system

  2. Fuzzy logic electric vehicle regenerative antiskid braking and traction control system

    DOE Patents [OSTI]

    Cikanek, S.R.

    1994-10-25T23:59:59.000Z

    An regenerative antiskid braking and traction control system using fuzzy logic for an electric or hybrid vehicle having a regenerative braking system operatively connected to an electric traction motor, and a separate hydraulic braking system includes sensors for monitoring present vehicle parameters and a processor, responsive to the sensors, for calculating vehicle parameters defining the vehicle behavior not directly measurable by the sensor and determining if regenerative antiskid braking control, requiring hydraulic braking control, and requiring traction control are required. The processor then employs fuzzy logic based on the determined vehicle state and provides command signals to a motor controller to control operation of the electric traction motor and to the brake controller to control fluid pressure applied at each vehicle wheel to provide the appropriate regenerative braking control, hydraulic braking control, and traction control. 123 figs.

  3. Control Engineering Practice 11 (2003) 163170 A mechatronic conception of a new intelligent braking system

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    , residual friction, noise, vibrations, a new brake has been designed according to a modular principle which describes a new intelligent braking system for motor vehicles. A mechatronic approach helped to avoid some

  4. Evaluation of driver braking performance to an unexpected object in the roadway

    E-Print Network [OSTI]

    Picha, Dale Louis

    1994-01-01T23:59:59.000Z

    components, specifically whether the equation accurately reflects driver and vehicle behaviors during a braking maneuver. This research evaluated the two components of the SSD equation. Four field studies were conducted that evaluated driver braking...

  5. Fuzzy logic electric vehicle regenerative antiskid braking and traction control system

    DOE Patents [OSTI]

    Cikanek, Susan R. (Wixom, MI)

    1994-01-01T23:59:59.000Z

    An regenerative antiskid braking and traction control system using fuzzy logic for an electric or hybrid vehicle having a regenerative braking system operatively connected to an electric traction motor, and a separate hydraulic braking system includes sensors for monitoring present vehicle parameters and a processor, responsive to the sensors, for calculating vehicle parameters defining the vehicle behavior not directly measurable by the sensor and determining if regenerative antiskid braking control, requiring hydraulic braking control, and requiring traction control are required. The processor then employs fuzzy logic based on the determined vehicle state and provides command signals to a motor controller to control operation of the electric traction motor and to the brake controller to control fluid pressure applied at each vehicle wheel to provide the appropriate regenerative braking control, hydraulic braking control, and traction control.

  6. Evaluation of driver braking performance to an unexpected object in the roadway

    E-Print Network [OSTI]

    Picha, Dale Louis

    1994-01-01T23:59:59.000Z

    components, specifically whether the equation accurately reflects driver and vehicle behaviors during a braking maneuver. This research evaluated the two components of the SSD equation. Four field studies were conducted that evaluated driver braking...

  7. Regenerative braking device with rotationally mounted energy storage means

    DOE Patents [OSTI]

    Hoppie, Lyle O. (Birmingham, MI)

    1982-03-16T23:59:59.000Z

    A regenerative braking device for an automotive vehicle includes an energy storage assembly (12) having a plurality of rubber rollers (26, 28) mounted for rotation between an input shaft (30) and an output shaft (32), clutches (50, 56) and brakes (52, 58) associated with each shaft, and a continuously variable transmission (22) connectable to a vehicle drivetrain and to the input and output shafts by the respective clutches. In a second embodiment the clutches and brakes are dispensed with and the variable ratio transmission is connected directly across the input and output shafts. In both embodiments the rubber rollers are torsionally stressed to accumulate energy from the vehicle when the input shaft rotates faster or relative to the output shaft and are torsionally relaxed to deliver energy to the vehicle when the output shaft rotates faster or relative to the input shaft.

  8. Evaluation of Corrosion Failure in Tractor-Trailer Brake System

    SciTech Connect (OSTI)

    Wilson, DF

    2002-10-22T23:59:59.000Z

    As reported to ORNL, concomitant with the introduction of different deicing and anti-icing compounds, there was an increase in the brake failure rate of tractor-trailer trucks. A forensic evaluation of a failed brake system was performed. Optical and scanning electron microscopic evaluation showed corrosion to be mostly confined to the brake table/lining interface. The corrosion is non-uniform as is to be expected for plain carbon steel in chloride environments. This initial analysis found no evidence for the chlorides of calcium and magnesium, which are the newly introduced deicing and antiicing compounds and are less soluble in water than the identified chlorides of sodium and potassium, in the scale. The result could be as a result of non-exposure of the examined brake table to calcium and magnesium chloride. The mechanisms for the increased failure rate are postulated as being an increased rate of corrosion due to positive shifts in the corrosion potential, and an increased amount of corrosion due to an increased ''time of wetness'' that results from the presence of hygroscopic salts. Laboratory scale evaluation of the corrosion of plain carbon steel in simulated deicing and anti-icing solutions need to be performed to determine corrosion rates and morphological development of corrosion product, to compare laboratory data to in-service data, and to rank economically feasible replacement materials for low carbon steel. In addition, the mechanical behavior of the lining attached to the brake shoe table needs to be assessed. It is opined that an appropriate adjustment of materials could easily allow for a doubling of a brake table/lining lifetime. Suggestions for additional work, to clarify the mechanisms of rust jacking and to develop possible solutions, are described.

  9. Calibration, Information, and Control Strategies for Braking to Avoid a Collision

    E-Print Network [OSTI]

    effect. A new model is introduced according to which braking is controlled by keeping the perceived idealCalibration, Information, and Control Strategies for Braking to Avoid a Collision Brett R. Fajen Rensselaer Polytechnic Institute This study explored visual control strategies for braking to avoid collision

  10. Airbus A320 Braking as Predicate-Action Peter B. Ladkin

    E-Print Network [OSTI]

    Ladkin, Peter B.

    Airbus A320 Braking as Predicate-Action Diagrams Peter B. Ladkin Universitat Bielefeld, Technische of the Airbus A320 braking systems contained in the Flight Crew Operating Manual. This helps identify to interest us and others in the design of the A320 braking system [FI.93a, FI.93b, FI.93c]. This paper

  11. Kinematic Detection of the Galactic Nuclear Disc

    E-Print Network [OSTI]

    Schnrich, Ralph; Sale, Stuart E

    2015-01-01T23:59:59.000Z

    We report the detection of the Galactic nuclear disc in line-of-sight kinematics of stars, measured with infrared spectroscopy from APOGEE. The nuclear disc is found to have a rotation velocity V ~ 120km/s comparable to the gas disc. The current data suggest that this disc is kinematically quite cold and has a small vertical extent of order 50pc. The stellar kinematics suggest a truncation radius of the stellar disc at a galactocentric radius R ~ 150pc, and provide tentative evidence for an overdensity at the position of the ring found in the molecular gas disc.

  12. Oxygen-Diffused Titanium as a Candidate Brake Rotor Material

    SciTech Connect (OSTI)

    Qu, Jun [ORNL; Blau, Peter Julian [ORNL; Jolly, Brian C [ORNL

    2009-01-01T23:59:59.000Z

    Titanium alloys are one of several candidate materials for the next generation of truck disk brake rotors. Despite their advantages of lightweight relative to cast iron and good strength and corrosion resistance, titanium alloys are unlikely to be satisfactory brake rotor materials unless their friction and wear behavior can be significantly improved. In this study, a surface engineering process oxygen diffusion was applied to titanium rotors and has shown very encouraging results. The oxygen diffused Ti-6Al-4V (OD-Ti) was tested on a sub-scale brake tester against a flat block of commercial brake lining material and benchmarked against several other Ti-based materials, including untreated Ti-6Al-4V, ceramic particle-reinforced Ti composites (MMCs), and a thermal-spray-coated Ti alloy. With respect to friction, the OD-Ti outperformed all other candidate materials under the imposed test conditions with the friction coefficient remaining within a desirable range of 0.35-0.50, even under the harshest conditions when the disk surface temperature reached nearly 600 ?C. In addition, the OD-Ti showed significantly improved wear-resistance over the non-treated one and was even better than the Ti-based composite materials.

  13. automotive brake materials: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    brake materials First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Multidisciplinary design optimization...

  14. aircraft brake materials: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    brake materials First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 26 REDUCTION OF CADMTUM PLATING ON...

  15. Brake Wear and Performance Test Final December 2009

    E-Print Network [OSTI]

    Brake Wear and Performance Test Final Report December 2009 #12;FOREWORD This study focuses on using with assisting the State of Tennessee in identifying suitable PBBT machines, procuring a PBBT machine, installing the PBBT machine to be used in this research, and training Tennessee Department of Safety (TDOS) Staff

  16. Many applications require brakes, for instance to decelerate or to

    E-Print Network [OSTI]

    an error occurs in the process of a robotic arm. The energy consumption and actuation force of these brakes is very high. A team of TU Delft scientists developed a method to reduce the energy consumption. The energy consumption is high because an actuator has to generate a normal force between two friction

  17. Braking index of isolated pulsars: open questions and ways forward

    E-Print Network [OSTI]

    Hamil, Oliver

    2015-01-01T23:59:59.000Z

    Isolated pulsars are rotating neutron stars with accurately measured angular velocities $\\Omega$, and their time derivatives which show unambiguously that the pulsars are slowing down. Although the exact mechanism of the spin-down is a question of debate, the commonly accepted view is that it arises either through emission of magnetic dipole radiation (MDR) from a rotating magnetized body, through emission of a relativistic particle wind, or via higher order magnetic multipole or gravitational quadrupole radiation. The calculated energy loss by a rotating pulsar is model dependent and leads to the power law $\\dot{\\Omega}$ = -K $\\Omega^{\\rm n}$ where $n$ is called the braking index. The theoretical value for braking index is $n = 1, 3, 5$ for wind, MDR, quadrupole radiation respectively. The accepted view is that pulsar braking is strongly dominated by MDR. Highly precise observations of isolated pulsars yield braking index values in the range $1 < n < 2.8$ which are consistently less than the value pred...

  18. TOWARDS GLOBAL CHASSIS CONTROL BY INTEGRATING THE BRAKE AND

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    . Szab´o*, J. Bokor*, C. Poussot-Vassal**, O. Sename**, L. Dugard** *Computer and Automation Research active suspensions and an active brake is proposed to improve the safety of vehicles. The design is based of the method is demonstrated through a complex simulation example containing vehicle maneuvers. Keywords: LPV

  19. DISC-UK DataShare

    E-Print Network [OSTI]

    Rice, Robin

    DISC-UK DataShare (http://www.disc-uk.org/datashare.html) is a JISC-funded collaborative project led by EDINA and Edinburgh University Data Library, with the Universities of Oxford and Southampton as partners, and the ...

  20. Computer animation via optical video disc

    E-Print Network [OSTI]

    Bender, Walter

    1981-01-01T23:59:59.000Z

    This paper explores the notion of marrying two technologies: raster-scan computer animation and optical video discs. Animated sequences, generated at non real-time rates, then transfered to video disc, can be recalled under ...

  1. Physics and chemistry of gas in discs

    E-Print Network [OSTI]

    Tilling, Ian

    2013-11-28T23:59:59.000Z

    Protoplanetary discs set the initial conditions for planet formation. By combining observations with detailed modelling, it is possible to constrain the physics and chemistry in such discs. I have used the detailed ...

  2. Thin, thick and dark discs in LCDM

    E-Print Network [OSTI]

    J. I. Read; G. Lake; O. Agertz; Victor P. Debattista

    2008-06-26T23:59:59.000Z

    In a LCDM cosmology, the Milky Way accretes satellites into the stellar disc. We use cosmological simulations to assess the frequency of near disc plane and higher inclination accretion events, and collisionless simulations of satellite mergers to quantify the final state of the accreted material and the effect on the thin disc. On average, a Milky Way-sized galaxy has 3 subhalos with vmax>80km/s; 7 with vmax>60km/s; and 15 with vmax>40km/s merge at redshift z>1. Assuming isotropic accretion, a third of these merge at an impact angle disc plane by dynamical friction. Their accreted stars and dark matter settle into a thick disc. The stellar thick disc qualitatively reproduces the observed thick disc at the solar neighbourhood, but is less massive by a factor ~2-10. The dark matter disc contributes 0.25-1 times the halo density at the solar position. Although not likely to be dynamically interesting, the dark disc has important implications for the direct detection of dark matter because of its low velocity with respect to the Earth. Higher inclination encounters (>20 degrees) are twice as likely as low inclination ones. These lead to structures that closely resemble the recently discovered inner/outer stellar halos. They also do more damage to the Milky Way stellar disc creating a more pronounced flare, and warp; both long-lived and consistent with current observations. The most massive mergers (vmax>80km/s) heat the thin disc enough to produce a thick disc. These heated thin disc stars are essential for obtaining a thick disc as massive as that seen in the Milky Way; they likely comprise some ~50-90% of the thick disc stars. The Milky Way thin disc must reform from fresh gas after z=1 [abridged].

  3. The Warped Disc of NGC 4258

    E-Print Network [OSTI]

    Rebecca G. Martin

    2008-04-07T23:59:59.000Z

    We consider the properties of the warped accretion disc in NGC 4258 which is delineated by maser emission. We use our analytical models to consider whether the disc could be warped by Lense-Thirring precession. We show that such models fit the shape of the disc well and we determine the goodness of fit for various combinations of the warp radius and the disc and black hole configurations. Though the fits are compelling evidence, we note that such a model has implications for the formation and longevity of the disc which might be problematic for the current understanding of Seyfert Galaxies.

  4. Heavy and Overweight Vehicle Brake Testing: Five-Axle Combination Tractor-Flatbed Final Report

    SciTech Connect (OSTI)

    Lascurain, Mary Beth [ORNL; Capps, Gary J [ORNL; Franzese, Oscar [ORNL

    2013-10-01T23:59:59.000Z

    The Federal Motor Carrier Safety Administration, in coordination with the Federal Highway Administration, sponsored the Heavy and Overweight Vehicle Brake Testing (HOVBT) program in order to provide information about the effect of gross vehicle weight (GVW) on braking performance. Because the Federal Motor Carrier Safety Regulations limit the number of braking system defects that may exist for a vehicle to be allowed to operate on the roadways, the examination of the effect of brake defects on brake performance for increased loads is also relevant. The HOVBT program seeks to provide relevant information to policy makers responsible for establishing load limits, beginning with providing test data for a combination tractor/trailer. This testing was conducted on a five-axle combination vehicle with tractor brakes meeting the Reduced Stopping Distance requirement rulemaking. This report provides a summary of the testing activities, the results of various analyses of the data, and recommendations for future research. Following a complete brake rebuild, instrumentation, and brake burnish, stopping tests were performed from 20 and 40 mph with various brake application pressures (15 psi, 25 psi, 35 psi, 45 psi, 55 psi, and full system pressure). These tests were conducted for various brake conditions at the following GVWs: 60,000, 80,000, 91,000, 97,000, 106,000, and 116,000 lb. The 80,000-lb GVWs included both balanced and unbalanced loads. The condition of the braking system was also varied. To introduce these defects, brakes (none, forward drive axle, or rear trailer axle) were made inoperative. In addition to the stopping tests, performance-based brake tests were conducted for the various loading and brake conditions. Analysis of the stopping test data showed the stopping distance to increase with load (as expected) and also showed that more braking force was generated by the drive axle brakes than the trailer axle brakes. The constant-pressure stopping test data revealed a linear relationship between brake application pressure and was used to develop an algorithm to normalize stopping data for weight and initial speed.

  5. Development of Diagnostic Algorithms for Air Brakes in Trucks

    E-Print Network [OSTI]

    Dhar, Sandeep

    2011-10-21T23:59:59.000Z

    and the rear brake chamber using the predicted primary circuit pressure : : : : : : : : : : : : : : : : : : : : 54 33 Simulated response of the hybrid system : : : : : : : : : : : : : : : : 64 34 Steady-state estimate of z1 of the pneumatic hybrid system... with massless piston : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 67 xii FIGURE Page 35 Steady-state estimates of z1 and z2 of the pneumatic hybrid system : 70 36 (a) Mechanical hybrid system, (b) non-hybrid counterpart : : : : : : 70 37...

  6. Energy Efficiency in Heavy Vehicle Tires, Drivetrains, and Braking Systems

    SciTech Connect (OSTI)

    Peter J. Blau

    2000-04-26T23:59:59.000Z

    This document was prepared to support the primary goals of the Department of Energy, Office of Heavy Vehicle Technologies. These were recently stated as follows: ''Develop by 2004 the enabling technologies for a class 7-8 truck with a fuel efficiency of 10 mpg (at 65 mph) which will meet prevailing emission standards. For Class 3-6 trucks operating on an urban driving cycle, develop by 2004 commercially viable vehicles that achieve at least double the fuel economy of comparable current vehicles (1999), and as a research goal, reduce criteria pollutants to 30% below EPA standards. Develop by 2004 the diesel engine enabling technologies to support large-scale industry dieselization of Class 1 and 2 trucks, achieving a 35 % fuel efficiency improvement over comparable gasoline-fueled trucks, while meeting applicable emissions standards.'' The enabling technologies for improving the fuel efficiency of trucks, include not only engine technologies but also technologies involved with lowering the rolling resistance of tires, reducing vehicle aerodynamic drag, improving thermal management, and reducing parasitic frictional losses in drive train components. Opportunities also exist for making better use of the energy that might ordinarily be dissipated during vehicle braking. Braking systems must be included in this evaluation since safety in truck operations is vital, and braking requirements are greater for vehicles having lowered resistance to rolling. The Office of Heavy Vehicle Technologies has initiated a program to improve the aerodynamics of heavy vehicles through wind tunnel testing, computational modeling, and on-road evaluations. That activity is described in a separate multi-year plan; therefore, emphasis in this document will be on tires, drive trains, and braking systems. Recent, dramatic fluctuations in diesel fuel prices have emphasized the importance of effecting savings in truck fuel economy by implementing new component designs and materials.

  7. On the Eddington limit in accretion discs

    E-Print Network [OSTI]

    D. Heinzeller; W. J. Duschl

    2006-10-25T23:59:59.000Z

    Although the Eddington limit has originally been derived for stars, recently its relevance for the evolution of accretion discs has been realized. We discuss the question whether the classical Eddington limit - which has been applied globally for almost all calculations on accretion discs - is a good approximation if applied locally in the disc. For this purpose, a critical accretion rate corresponding to this type of modified classical Eddington limit is calculated from thin alpha-disc models and slim disc models. We account for the non-spherical symmetry of the disc models by computing the local upper limits on the accretion rate from vertical and radial force equilibria separately. It is shown that the results can differ considerably from the classical (global) value: The vertical radiation force limits the maximum accretion rate in the inner disc region to much less than the classical Eddington value in thin alpha-discs, while it allows for significantly higher accretion rates in slim discs. We discuss the implications of these results for the evolution of accretion discs and their central objects.

  8. Accretion Discs with Strong Toroidal Magnetic Fields

    E-Print Network [OSTI]

    M. C. Begelman; J. E. Pringle

    2006-12-12T23:59:59.000Z

    Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure exceeds the combined gas + radiation pressure in the disc. Arguing from the recent analysis by Pessah and Psaltis, and other MRI results in the literature, we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We examine the properties of such magnetically-dominated discs, and show that they resolve a number of outstanding problems in accretion disc theory. The discs would be thicker than standard (Shakura-Sunyaev) discs at the same radius and accretion rate, and would tend to have higher colour temperatures. If they transport angular momentum according to an alpha-prescription, they would be stable against the thermal and viscous instabilities that are found in standard disc models. In discs fuelling active galactic nuclei, magnetic pressure support could also alleviate the restriction on accretion rate imposed by disc self-gravity.

  9. A mathematical model for air brake systems in the presence of leaks

    E-Print Network [OSTI]

    Ramaratham, Srivatsan

    2008-10-10T23:59:59.000Z

    of the pneumatic subsystem. . . . . . . . . . . . . . . . . . 20 16 Pressure transients at 722 kPa (90 psi) supply pressure with no leak. 22 17 Schematic of the setup for leak corroboration tests. . . . . . . . . . . 27 18 Comparison of measured and predicted mass... of detecting and locating leaks[6]. Most of the performance tests and visual based inspection tests of the air brake system indirectly correlate pressure in the brake chamber with the torque output, brake pad temperature, push rod strokes etc[7], [8]. More...

  10. Real-Time Dynamic Brake Assessment Proof of Concept Final Report

    SciTech Connect (OSTI)

    Lascurain, Mary Beth [ORNL; Franzese, Oscar [ORNL; Capps, Gary J [ORNL

    2011-11-01T23:59:59.000Z

    This proof-of-concept research was performed to explore the feasibility of using real-world braking data from commercial motor vehicles to make a diagnosis of brake condition similar to that of the performance-based brake tester (PBBT). This was done by determining the relationship between pressure and brake force (P-BF), compensating for the gross vehicle weight (GVW). The nature of this P-BF relationship (e.g., low braking force for a given brake application pressure) may indicate brake system problems. In order to determine the relationship between brake force and brake application pressure, a few key parameters of duty cycle information were collected. Because braking events are often brief, spanning only a few seconds, a sample rate of 10 Hz was needed. The algorithm under development required brake application pressure and speed (from which deceleration was calculated). Accurate weight estimation was also needed to properly derive the braking force from the deceleration. In order to ensure that braking force was the predominant factor in deceleration for the segments of data used in analysis, the data was screened for grade as well. Also, the analysis needed to be based on pressures above the crack pressure. The crack pressure is the pressure below which the individual brakes are not applied due the nature of the mechanical system. This value, which may vary somewhat from one wheel end to another, is approximately 10 psi. Therefore, only pressures 15 psi and above were used in the analysis. The Department of Energy s Medium Truck Duty Cycle research has indicated that under the real-world circumstances of the test vehicle brake pressures of up to approximately 30 psi can be expected. Several different types of data were collected during the testing task of this project. Constant-pressure stopping tests were conducted at several combinations of brake application pressure (15, 20, 25, and 30 psi), load conditions (moderately and fully laden), and speeds (20 and 30 mph). Data was collected at 10 Hz. Standard and stepped-pressure performance-based brake tests with brake pressure transducers were performed for each loading condition. The stepped-pressure test included the constant-pressure intervals of brake application at 15, 20, 25, and 30 psi. The PBBT data files included 10 Hz streaming data collected during the testing of each axle. Two weeks of real-world duty cycle (driving and braking) data was also collected at 10 Hz. Initial analysis of the data revealed that the data collected in the field (i.e., day-to-day operations) provided the same information as that obtained from the controlled tests. Analysis of the data collected revealed a strong linear relationship between brake application pressure and deceleration for given GVWs. As anticipated, initial speed was not found to be a significant factor in the deceleration-pressure relationship, unlike GVW. The positive results obtained from this proof of concept test point to the need for further research to expand this concept. A second phase should include testing over a wider range of speeds and include medium brake application pressures in addition to the low pressures tested in this research. Testing on multiple vehicles would also be of value. This future phase should involve testing to determine how degradation of braking performance affects the pressure-deceleration relationship.

  11. Accretion and plasma outflow from dissipationless discs

    E-Print Network [OSTI]

    Sergei Bogovalov; Stanislav Kelner

    2008-09-02T23:59:59.000Z

    We consider an extreme case of disc accretion onto a gravitating centre when the viscosity in the disc is negligible. The angular momentum and the rotational energy of the accreted matter is carried out by a magnetized wind outflowing from the disc. The outflow of matter from the disc occurs due to the Blandford & Payne(1982) centrifugal mechanism. The disc is assumed to be cold. Accretion and outflow are connected by the conservation of the energy, mass and the angular momentum. The basic properties of the outflow, angular momentum flux and energy flux per particle in the wind, do not depend on the details of the structure of the accretion disc. In the case of selfsimilar accretion/outflow, the dependence of the rate of accretion $\\dot M$ in the disc depends on the disc radius $r$ on the law $\\dot M \\sim r^{{1\\over2(\\alpha^2-1)}}$, where $\\alpha$ is a dimensionless Alfvenic radius. In the case of $\\alpha \\gg 1$, the accretion in the disc is provided by very weak matter outflow from the disc and the outflow predominantly occurs from the very central part of the disc. The solution obtained in the work provides mechanism which transforms the gravitational energy of the accreted matter into the energy of the outflowing wind with efficiency close to 100%. The final velocity can essentially exceed Kepler velocity at the site of the wind launch. This mechanism allows us to understand the nature of the astrophysical objects with low luminosity discs and energetic jet-like outflows.

  12. The Roles of Discs for Planetary Systems

    E-Print Network [OSTI]

    Li-Chin Yeh; Ing-Guey Jiang

    2007-01-29T23:59:59.000Z

    It is known that the discs are detected for some of the extra-solar planetary systems. It is also likely that there was a disc mixing with planets and small bodies while our Solar System was forming. From our recent results, we conclude that the discs play two roles: the gravity makes planetary systems more chaotic and the drag makes planetary systems more resonant.

  13. AB-Net Method of Protection from Projectiles (city, military base, battle-front, etc.)

    E-Print Network [OSTI]

    Alexander Bolonkin

    2008-02-13T23:59:59.000Z

    The author suggests a low cost special AB-Net from artificial fiber, which may protect cities and important objects from rockets, artillery and mortar shells, projectiles, bullets, and strategic weapons. The idea is as follows: The offered AB-Net joins an incoming projectile to a small braking parachute and this incoming projectile loses speed by air braking after a drag distance of 50 - 150 meters. A following interception net after the first may serve to collect the slowed projectiles and their fragments or bomblets so that they do not reach the aimpoint. The author offers the design of AB-Net, a developed theory of snagging with a small braking parachute by AB-Net; and sample computations. These nets may be used for defense of a town, city, military base, battle-front line, road (from terrorists), or any important objects or installations (for example nuclear electric station, government buildings, etc.). Computed projects are: Net to counter small rockets (for example, from Qassam), net to counter artillery projectile (caliber 76 mm), net to counter bullets (caliber 7.6 mm). The offered method is cheaper by thousands of times than protection of a city by current anti-rocket systems. Discussion and results are at the end of the article. Key words: Protection from missile and projectile weapons, mortar, rocket, AB-Net, Qassam defense, incoming defense, armor.

  14. HD 98800: A most unusual debris disc

    E-Print Network [OSTI]

    P. E. Verrier; N. W. Evans

    2008-07-31T23:59:59.000Z

    The dynamics of planetesimals in the circumbinary debris disc of the quadruple star system HD 98800 are investigated. Evolving a spherical shell of test particles from a million years ago to the present day indicates that both coplanar and retrograde warped discs could exist, as well as a high inclination halo of material. Significant gaps are seen in the discs, as well as unexpected regions of stability due to the retrograde nature of the stellar orbits. Despite a viewing angle almost perpendicular to the direction of the warp of the planetesimal disc it is still intersected by the line of sight for eccentricities of the outer orbit of 0.5 or less.

  15. ARM - Front Page

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006Datastreamstwrcam40m DocumentationJanuary 9, 2009 [Events, Feature StoriesgovCampaignsSurfacegovFront Page

  16. accretion disc 2d: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  17. accretion discs ii: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  18. accretion disc origin: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  19. accretion disc viewed: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  20. accretion disc structure: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  1. Accelerated planetesimal growth in self-gravitating protoplanetary discs

    E-Print Network [OSTI]

    Rice, William K; Lodato, G; Pringle, J E; Armitage, P J; Bonnell, I A

    2004-01-01T23:59:59.000Z

    self-gravitating protoplanetary discs W. K. M. Rice, 1 G.in marginally stable, self-gravitating protoplanetary discs.The drag force between the disc gas and the em- bedded

  2. From the front

    SciTech Connect (OSTI)

    Price, Stephen [Los Alamos National Laboratory

    2009-01-01T23:59:59.000Z

    The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground. For the last decade, many outlet glaciers in Greenland that terminate in the ocean have accelerated, thinned, and retreated. To explain these dynamic changes, two hypotheses have been discussed. Atmospheric warming has increased surface melting and may also have increased the amount of meltwater reaching the glacier bed, increasing lubrication at the base and hence the rate of glacier sliding. Alternatively, a change in the delicate balance of forces where the glacier fronts meet the ocean could trigger the changes. Faezeh Nick and colleagues5 present ice-sheet modeling experiments that mimic the observations on Helheim glacier, East Greenland, and suggest that the dynamic behaviour of outlet glaciers follows from perturbations at their marine fronts. Greenland's ice sheet loses mass partly through surface melting and partly through fast flowing outlet glaciers that connect the vast plateau of inland ice with the ocean. Earlier ice sheet models have failed to reproduce the dynamic variability exhibited by ice sheets over time. It has therefore not been possible to distinguish with confidence between basal lubrication from surface meltwater and changes at the glaciers' marine fronts as causes for the observed changes on Greenland's outlet glaciers. But this distinction bears directly on future sea-level rise, the raison d'etre of much of modern-day glaciology: If the recent dynamic mass loss Greenland's outlet glaciers is linked to changing atmospheric temperatures, it may continue for as long as temperatures continue to increase. On the other hand, if the source of the dynamic mass loss is a perturbation at the ice-ocean boundary, these glaciers will lose contact with that perturbation after a finite amount of thinning and retreat. Therefore, the first hypothesis implies continued retreat of outlet glaciers into the foreseeable future, while the second does not -- provided the bedrock topography prohibits a connection between the retreating glacier and the ocean. Nick and coauthors test the physical mechanisms implied in each hypotbesis in an innovative ice-flow model, and use that model to try to match a time series of observations from Helheim glacier, one of Greenland's three largest outlet glaciers. Along with many observations, the simulations strongly support the contention that the recent retreat of Greenland's outlet glaciers is the result of changes at their marine fronts.Further, the simulations confirm the earlier hypotheses that bedrock topography largely controlled Helheim glacier's rapid acceleration and retreat in 2004 and 2005, and its deceleration and stabilization in 2006. Finally, the current work implies that if requirements of observational data (high-resolution bed topography) and computational resources (fine computational grid resolution) can be met, improved predictive capability for ice-sheet models is attainable. With respect to the concerns raised by the IPCC, this study signals progress.

  3. Vehicle yaw control via coordinated use of steering/braking systems

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Vehicle yaw control via coordinated use of steering/braking systems M. Doumiati, O. Sename, J.sename@gipsa-lab.grenoble-inp.fr) Computer and Automation Research Institute, Hungarian Academy of Sciences, Kende u. 13-17, H-1111, Budapest with steer- ing/braking coordination task for vehicle yaw control. For steerability enhancement, only active

  4. Modeling the pneumatic subsystem of a S-cam air brake system

    E-Print Network [OSTI]

    Coimbatore Subramanian, Shankar

    2004-09-30T23:59:59.000Z

    The air brake system is one of the critical components in ensuring the safe operation of any commercial vehicle. This work is directed towards the development of a fault-free model of the pneumatic subsystem of the air brake system. This model can...

  5. Modeling the pneumatic relay valve of an s-cam air brake

    E-Print Network [OSTI]

    Vilayannur Natarajan, Shankar

    2005-08-29T23:59:59.000Z

    by the driver, when there are no faults or defects in the brake system. This thesis is aimed at modeling and experimentally corroborating a subsystem of an air brake system, namely the pneumatic relay valve. The pneumatic relay valve takes a input signal from...

  6. Fault tolerant control of automatically controlled vehicles in response to brake system failures

    E-Print Network [OSTI]

    Hsien, Li-Wei

    1998-01-01T23:59:59.000Z

    in the brake system is vital. In this thesis, nonlinear failure detection filters are used for fault detection of sensors and actuators in a class of nonlinear systems. In this thesis, the effects of brake system failures in an AHS where the vehicle steering...

  7. Fault tolerant control of automatically controlled vehicles in response to brake system failures

    E-Print Network [OSTI]

    Hsien, Li-Wei

    1998-01-01T23:59:59.000Z

    in the brake system is vital. In this thesis, nonlinear failure detection filters are used for fault detection of sensors and actuators in a class of nonlinear systems. In this thesis, the effects of brake system failures in an AHS where the vehicle steering...

  8. Emission Factor for Antimony in Brake Abrasion Dusts as One of the

    E-Print Network [OSTI]

    Short, Daniel

    originating from automobiles. Abrasion dusts from commercially available brake pads (nonasbestos organic type factors originating from automobiles were approximately 32 µg Sb/braking/car for PM10 and 22 µg Sb of automobiles to the atmospheric Sb concen- tration. The emission factors of pollutants from automobiles have

  9. Spectral energy distributions of selfgravitating QSO discs

    E-Print Network [OSTI]

    Edwin Sirko; Jeremy Goodman

    2002-09-23T23:59:59.000Z

    We calculate spectral energy distributions (SEDs) of steady accretion discs at high accretion rates, as appropriate for bright QSOs, under the assumption that the outer parts are heated sufficiently to maintain marginal gravitational stability, presumably by massive stars formed within the disc. The SED is independent of the nature of these auxiliary sources if their inputs are completely thermalized. Standard assumptions are made for angular momentum transport, with an alpha parameter less than unity. With these prescriptions, the luminosity of the disc is sensitive to its opacity, in contrast to standard discs powered by release of orbital energy alone. Compared to the latter, our discs have a broader SED, with a second peak in the near-infrared that is energetically comparable to the blue bump. The energy in the second peak increases with the outer radius of the disc, provided that the accretion rate is constant with radius. By comparing our computed SEDs with observed ones, we limit the outer radius of the disc to be less than 10^5 Schwarzschild radii, or about one parsec, in a typical QSO. We also discuss some properties of our minimum-Q discs in the regions where auxiliary heating is dominant (10^3-10^5 Schwarzschild radii).

  10. The tidal disruption of protoplanetary accretion discs

    E-Print Network [OSTI]

    John D. Larwood

    1997-05-30T23:59:59.000Z

    In this paper we revisit the problem of the tidal interaction occuring between a protostellar accretion disc and a secondary point mass following a parabolic trajectory. We model the disc response analytically and we compare our results with three-dimensional SPH simulations. Inviscid as well as viscous hydrodynamics is considered. We show that in a viscous system the response derived from inviscid considerations is predominant even for the highest estimates of an anomalous disc shear viscosity. The angular momentum lost from the disc during the encounter is derived from linear theory, for distant fly-bys, as well as the changes to the disc orientation expected in non-coplanar encounters. It is shown that the target discs can become warped and precess by a small amount during non-coplanar encounters. This small precession is shown to give rise to a relative tilt of the disc which is always more important for determining its final orientation than is the change to the orbital inclination. We discuss the implications of our results for protostellar accretion discs and planetary systems.

  11. From discs to planetesimals I: evolution of gas and dust discs

    E-Print Network [OSTI]

    Richard Alexander

    2007-12-03T23:59:59.000Z

    I review the processes that shape the evolution of protoplanetary discs around young, solar-mass stars. I first discuss observations of protoplanetary discs, and note in particular the constraints these observations place on models of disc evolution. The processes that affect the evolution of gas discs are then discussed, with the focus in particular on viscous accretion and photoevaporation, and recent models which combine the two. I then discuss the dynamics and growth of dust grains in discs, considering models of grain growth, the gas-grain interaction and planetesimal formation, and review recent research in this area. Lastly, I consider the so-called "transitional" discs, which are thought to be observed during disc dispersal. Recent observations and models of these systems are reviewed, and prospects for using statistical surveys to distinguish between the various proposed models are discussed.

  12. artificial disc replacement: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    in three-dimensional discs CERN Preprints Summary: Vortex formation through the Rossby wave instability (RWI) in protoplanetary discs has been invoked to play a role in planet...

  13. artificial cervical disc: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    in three-dimensional discs CERN Preprints Summary: Vortex formation through the Rossby wave instability (RWI) in protoplanetary discs has been invoked to play a role in planet...

  14. artificial disc arthroplasty: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    in three-dimensional discs CERN Preprints Summary: Vortex formation through the Rossby wave instability (RWI) in protoplanetary discs has been invoked to play a role in planet...

  15. Wind turbine trailing-edge aerodynamic brake design

    SciTech Connect (OSTI)

    Quandt, G.

    1996-01-01T23:59:59.000Z

    This report describes the design of a centrifugally actuated aerodynamic-overspeed device for a horizontal-axis wind turbine. The device will meet the following criteria; (1) It will be effective for airfoil angles of attack 0{degrees} to 45{degrees}. (2) It will be stowed inside the blade profile prior to deployment. (3) It will be capable of offsetting the positive torque produced by the overall blade. (4) Hinge moments will be minimized to lower actuator loads and cost. (5) It will be evaluated as a potential power modulating active rotor-control system. A literature review of aerodynamic braking devices was conducted. Information from the literature review was used to conceptualize the most effective devices for subsequent testing and design. Wind-tunnel test data for several braking devices are presented in this report. Using the data for the most promising configuration, a preliminary design was developed for a MICON 65/13 wind turbine with Phoenix 7.9-m rotor blades.

  16. Structure and kinematics of edge-on galaxy discs -- V. The dynamics of the stellar discs

    E-Print Network [OSTI]

    M. Kregel; P. C. van der Kruit; K. C. Freeman

    2005-01-24T23:59:59.000Z

    In earlier papers in this series we determined the intrinsic stellar disc kinematics of fifteen intermediate to late type edge-on spiral galaxies using a dynamical modeling technique. From the photometry we find that intrinsically more flattened discs tend to have a lower face-on central surface brightness and a larger dynamica mass-to-light ratio. This observation suggests that at a constant maximum rotational velocity lower surface brightness discs have smaller vertical stellar velocity dispersions.Although the individual uncertainties are large, we find from the dynamical modeling that at least twelve discs are submaximal. The average disc contributes 53$\\pm$4 percent to the observed rotation at 2.2 disc scalelengths, with a 1$\\sigma$ scatter of 15 percent. This percentage becomes somewhat lower when effects of finite disc flattening and gravity by the dark halo and the gas are taken into account. Since boxy and peanut-shaped bulges are probably associated with bars, the result suggests that at 2.2$h_{\\rm R}$ the submaximal nature of discs is independent of barredness. The possibility remains that very high surface brightness discs are maximal.We confirm that the radial stellar disc velocity dispersion is related to the galaxy maximum rotational velocity. The scatter in this $\\sigma-v_{\\rm max}$ relation appears to correlate with the disc flattening, face-on central surface brightness and dynamical mass-to-light ratio. Low surface brightness discs tend to be more flattened and have smaller stellar velocity dispersions. The findings are consistent with the observed correlation between disc flattening and dynamical mass-to-light ratio.

  17. Gravitationally coupled scale-free discs

    E-Print Network [OSTI]

    Yue Shen; Yu-Qing Lou

    2004-06-16T23:59:59.000Z

    In a composite fluid system of two gravitationally coupled barotropic scale-free discs bearing a rotation curve $v\\propto r^{-\\beta}$ and a power-law surface mass density $\\Sigma_0\\propto r^{-\\alpha}$ with $\\alpha=1+2\\beta$, we construct coplanar stationary aligned and spiral perturbation configurations in the two discs. Due to the mutual gravitational interaction, there are two independent classes of perturbation modes with surface mass density disturbances in the two coupled discs being either in-phase or out-of-phase. We derive analytical criteria for such perturbation modes to exist and show numerical examples. We compute the aligned and spiral perturbation modes systematically to explore the entire parameter regime. For the axisymmetric $m=0$ case with radial oscillations, there are two unstable regimes of ring-fragmentation and collapse corresponding to short and long radial wavelengths, respectively. Only within a certain range of the rotation parameter $D_s^2$ (square of the effective Mach number for the stellar disc), can a composite disc system be stable against all axisymmetric perturbations. Compared with a single-disc system, the coupled two-disc system becomes less stable against such axisymmetric instabilities.

  18. Preliminary survey report: control technology for brake lining at Northwest Local School District, Cincinnati, Ohio

    SciTech Connect (OSTI)

    Cooper, T.C.; McGlothlin, J.D.; Godbey, F.W.; Sheehy, J.W.; O'Brien, D.M.

    1986-05-01T23:59:59.000Z

    A walk-through survey of control technology for reducing asbestos exposure during maintenance and repair of vehicular brakes was conducted at Northwest Local School District, Cincinnati, Ohio in January, 1986. The primary method for controlling and collecting dust during brake servicing was a wet-washing technique and good work practices, ensuring that exposure to hazardous physical or chemical agents was reduced or eliminated. Also available was an enclosed-type brake assembly cleaner designed to be connected to the shop air and a vacuum system. The brake assembly cleaner did not have a viewing port to examine the area being cleaned. The operator had to remove the unit to inspect the cleaned area potentially exposing himself to any dust remaining on the brake shoes or hub. The unit itself was a potential dust source as it was designed to fit 16-inch wheels and did not form a tight seal on the smaller 15-inch wheels of the newer buses. The authors conclude that the wet wash technique is an excellent method for controlling asbestos emissions during brake maintenance. The vacuum brake-assembly cleaner is inadequate and potentially hazardous. An in-depth survey of the wet technique is recommended.

  19. Three-dimensional SPH simulations of accretion discs

    E-Print Network [OSTI]

    Henri M. J. Boffin; Kei Haraguchi; Takuya Matsuda

    1998-12-01T23:59:59.000Z

    We discuss some 3D numerical simulations of accretion discs using the SPH method and a polytropic equation of state. We show that discs exist even for as large value of the polytropic index as 1.2, and that these discs are always in hydrostatic balance. We also show that even without any inflow, spiral shocks appear in the discs.

  20. Cold Fronts in CDM clusters

    E-Print Network [OSTI]

    Daisuke Nagai; Andrey V. Kravtsov

    2003-01-08T23:59:59.000Z

    Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters (Vikhlinin et. al., 2001). These features, called ``cold fronts'', are characterized by an increase in surface brightness by a factor >2 over 10-50 kpc, accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM), if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter (CDM) models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging sub-cluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the amplitude of gas density and temperature gradients across the front. Our results indicate that cold fronts are non-equilibrium transient phenomena and can be observed for a period of less than a billion years. We show that the velocity and density fields of gas surrounding the cold front can be very irregular which would complicate analyses aiming to put constraints on the physical conditions of the intracluster medium in the vicinity of the front.

  1. Variability of black hole accretion discs: The cool, thermal disc component

    E-Print Network [OSTI]

    M. Mayer; J. E. Pringle

    2006-01-29T23:59:59.000Z

    We extend the model of King et al. (2004) for variability in black hole accretion discs, by taking proper account of the thermal properties of the disc. Because the degree of variability in the King et al. (2004) model depends sensitively on the ratio of disc thickness to radius, H/R, it is important to follow the time-dependence of the local disc structure as the variability proceeds. In common with previous authors, we develop a one-zone model for the local disc structure. We agree that radial heat advection plays an important role in determining the inner disc structure, and also find limit-cycle behaviour. When the stochastic magnetic dynamo model of King et al. (2004) is added to these models, we find similar variability behaviour to before. We are now better placed to put physical constraints on model parameters. In particular, we find that in order to be consistent with the low degree of variability seen in the thermal disc component of black hole binaries, we need to limit the energy density of the poloidal field that can be produced by local dynamo cells in the disc to less than a few percent of the energy density of the dynamo field within the disc itself.

  2. Planet formation in self-gravitating discs

    E-Print Network [OSTI]

    Gibbons, Peter George

    2013-11-28T23:59:59.000Z

    The work performed here studies particle dynamics in local two-dimensional simulations of self-gravitating accretion discs with a simple cooling law. It is well known that the structure which arises in the gaseous component ...

  3. Particle Acceleration in (by) Accretion Discs

    E-Print Network [OSTI]

    J. I. Katz

    1992-05-04T23:59:59.000Z

    I present a model for acceleration of protons by the second-order Fermi process acting on randomly scrambled magnetic flux arches above an accretion disc. The accelerated protons collide with thermal protons in the disc, producing degraded energetic protons, charged and neutral pions, and neutrons. The pions produce gamma-rays by spontaneous decay of $\\pi^0$ and by bremsstrahlung and Compton processes following the decay of $\\pi^\\pm$ to $e^\\pm$.

  4. Photoevaporation of protoplanetary discs I: hydrodynamic models

    E-Print Network [OSTI]

    R. D. Alexander; C. J. Clarke; J. E. Pringle

    2006-03-09T23:59:59.000Z

    In this paper we consider the effect of the direct ionizing stellar radiation field on the evolution of protoplanetary discs subject to photoevaporative winds. We suggest that models which combine viscous evolution with photoevaporation of the disc (e.g. Clarke, Gendrin & Sotomayor 2001) incorrectly neglect the direct field after the inner disc has drained, at late times in the evolution. We construct models of the photoevaporative wind produced by the direct field, first using simple analytic arguments and later using detailed numerical hydrodynamics. We find that the wind produced by the direct field at late times is much larger than has previously been assumed, and we show that the mass-loss rate scales as $R_{in}^{1/2}$ (where $R_{in}$ is the radius of the instantaneous inner disc edge). We suggest that this result has important consequences for theories of disc evolution, and go on to consider the effects of this result on disc evolution in detail in a companion paper (Alexander, Clarke & Pringle 2006b).

  5. The Disc-Jet Connection

    E-Print Network [OSTI]

    Ralph E. Pudritz; Robi Banerjee

    2005-07-11T23:59:59.000Z

    A large body of theoretical and computational work shows that jets - modelled as magnetized disk winds - exert an external torque on their underlying disks that can efficiently remove angular momentum and act as major drivers of disk accretion. These predictions have recently been confirmed in direct HST measurements of the jet rotation and angular momentum transport in low mass protostellar systems. We review the theory of disc winds and show that their physics is universal and scales to jets from both low and high mass star forming regions. This explains the observed properties of outflows in massive star forming regions, before the central massive star generates an ultracompact HII region. We also discuss the recent numerical studies on the formation of massive accretion disks and outflows through gravitational collapse, including our own work on 3D Adaptive Mesh simulations (using the FLASH code) of the hydromagnetic collapse of an initial rotating, and cooling Bonner-Ebert sphere. Magnetized collapse gives rise to outflows. Our own simulations show that both a jet-like disk wind on sub AU scales, and a larger scale molecular outflow occur (Banerjee and Pudritz 2005).

  6. Slug pellet spreading: the double-disc performances available with a single disc spreader

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Slug pellet spreading: the double-disc performances available with a single disc spreader D for slug pellets application. The principal aim of this paper is to show the chosen way to reach spreading pellets 1 Introduction In France, slugs are considered as a harmful destroyer for crops. Their activities

  7. The Evolution of Stellar Exponential Discs

    E-Print Network [OSTI]

    Annette Ferguson; Cathie Clarke

    2001-03-14T23:59:59.000Z

    Models of disc galaxies which invoke viscosity-driven radial flows have long been known to provide a natural explanation for the origin of stellar exponential discs, under the assumption that the star formation and viscous timescales are comparable. We present models which invoke simultaneous star formation, viscous redistribution of gas and cosmologically-motivated gaseous infall and explore the predictions such models make for the scale length evolution and radial star formation history of galactic stellar discs. While the inclusion of viscous flows is essential for ensuring that the stellar disc is always exponential over a significant range in radius, we find that such flows play essentially no role in determining the evolution of the disc scale length. In models in which the main infall phase precedes the onset of star formation and viscous evolution, we find the exponential scale length to be rather invariant with time. On the other hand, models in which star formation/viscous evolution and infall occur concurrently result in a smoothly increasing scale length with time, reflecting the mean angular momentum of material which has fallen in at any given epoch. The disc stellar populations in these models are predominantly young (ie. ages < 5 Gyr) beyond a few scale lengths. In both cases, viscous flows are entirely responsible for transporting material to very large radii. We discuss existing observational constraints on these models from studies of both local and moderate redshift disc galaxies. In particular, a good agreement is found between the solar neighbourhood star formation history predicted by our infall model and the recent observational determination of this quantity by Rocha-Pinto et al (2000).

  8. Shocks and cold fronts in galaxy clusters

    E-Print Network [OSTI]

    Maxim Markevitch; Alexey Vikhlinin

    2007-04-24T23:59:59.000Z

    Table of contents (abridged): COLD FRONTS Origin and evolution of merger cold fronts Cold fronts in cluster cool cores . . . Simulations of gas sloshing. Origin of density discontinuity. . . . Effect of sloshing on cluster mass estimates and cooling flows. Zoology of cold fronts COLD FRONTS AS EXPERIMENTAL TOOL Velocities of gas flows Thermal conduction and diffusion across cold fronts Stability of cold fronts . . . Rayleigh-Taylor instability. Kelvin-Helmholtz instability. Possible future measurements using cold fronts . . . Plasma depletion layer and magnetic field. Effective viscosity of ICM. SHOCK FRONTS AS EXPERIMENTAL TOOL Cluster merger shocks Mach number determination Front width Mach cone and reverse shock? Test of electron-ion equilibrium . . . Comparison with other astrophysical plasmas Shocks and cluster cosmic ray population . . . Shock acceleration. Compression of fossil electrons. . . . Yet another method to measure intracluster magnetic field.

  9. Exact General Relativistic Discs and the Advance of Perihelion

    E-Print Network [OSTI]

    D. Vogt; P. S. Letelier

    2008-05-20T23:59:59.000Z

    The advance of perihelion for geodesic motion on the galactic plane of some exact general relativistic disc solutions is calculated. Approximate analytical and numerical results are presented for the static Chazy-Curzon and the Schwarzschild discs in Weyl coordinates, the Schwarzschid disc in isotropic coordinantes and the stationary Kerr disc in the Weyl-Lewis-Papapetrou metrics. It is found that for these disc models the advance of perihelion may be an increasing or decreasing function of the orbital excentricity. The precession due to Newtonian gravity for these disc models is also calculated.

  10. Satellites in Discs: Regulating the Accretion Luminosity

    E-Print Network [OSTI]

    Dave Syer; Cathie Clarke

    1995-05-04T23:59:59.000Z

    We demonstrate, using a simple analytic model, that the presence of a massive satellite can globally modify the structure and emission properties of an accretion disc to which it is tidally coupled. We show, using two levels of numerical approximation, that the analytic model gives reasonable results. The results are applicable to two astrophysical situations. In the case of an active galactic nucleus, we consider the case of a $\\sim 10^3\\Msun$ compact companion to the central black-hole and show that it could modulate the emitted spectrum on a timescale of $\\sim10^5$ years. In the case of a T Tauri accretion disc, a satellite such as a sub-dwarf or giant planet could modify the disc spectral energy distribution over a substantial fraction of the T Tauri star lifetime.

  11. Braking index of isolated uniformly rotating magnetized pulsars

    E-Print Network [OSTI]

    Hamil, Oliver; Urbanec, Martin; Urbancova, Gabriela

    2015-01-01T23:59:59.000Z

    Isolated pulsars are rotating neutron stars with accurately measured angular velocities $\\Omega$, and their time derivatives which show unambiguously that the pulsars are slowing down. Although the exact mechanism of the spin-down is a question of debate in detail, the commonly accepted view is that it arises through emission of magnetic dipole radiation (MDR) from a rotating magnetized body. Other processes, including the emission of gravitational radiation, and of relativistic particles (pulsar wind), are also being considered. The calculated energy loss by a rotating pulsar with a constant moment of inertia is assumed proportional to a model dependent power of $\\Omega$. This relation leads to the power law $\\dot{\\Omega}$ = -K $\\Omega^{\\rm n}$ where $n$ is called the braking index. The MDR model predicts $n$ exactly equal to 3. Selected observations of isolated pulsars provide rather precise values of $n$, individually accurate to a few percent or better, in the range 1$ <$ n $ < $ 2.8, which is consi...

  12. Appearance of Keplerian discs orbiting Kerr superspinars

    E-Print Network [OSTI]

    Zdenek Stuchlik; Jan Schee

    2011-01-19T23:59:59.000Z

    We study optical phenomena related to appearance of Keplerian accretion discs orbiting Kerr superspinars predicted by the string theory. The superspinar exterior is described by the standard Kerr naked singularity geometry breaking the black hole limit on the internal angular momentum (spin). We construct local photon escape cones for a variety of orbiting sources that enable to determine the superspinars silhouette in the case of distant observers. We show that the superspinar silhouette depends strongly on the assumed edge where the external Kerr spacetime is joined to the internal spacetime governed by the string theory and significantly differs from the black hole silhouette. The appearance of the accretion disc is strongly dependent on the value of the superspinar spin in both their shape and frequency shift profile. Apparent extension of the disc grows significantly with growing spin, while the frequency shift grows with descending spin. This behavior differs substantially from appearance of discs orbiting black holes enabling thus, at least in principle, to distinguish clearly the Kerr superspinars and black holes. In vicinity of a Kerr superspinar the non-escaped photons have to be separated to those captured by the superspinar and those being trapped in its strong gravitational field leading to self-illumination of the disc that could even influence its structure and causes self-reflection effect of radiation of the disc. The amount of trapped photons grows with descending of the superspinar spin. We thus can expect significant self-illumination effects in the field of Kerr superspinars with near-extreme spin $a \\sim 1$.

  13. The runaway instability of thick discs around black holes. II. Non constant angular momentum discs

    E-Print Network [OSTI]

    Frederic Daigne; Jose A. Font

    2003-11-28T23:59:59.000Z

    We present results from a comprehensive number of relativistic, time-dependent, axisymmetric simulations of the runaway instability of non-constant angular momentum thick discs around black holes. This second paper extends earlier results where only constant angular momentum discs were considered. All relevant aspects of the theory of stationary thick discs around rotating black holes, necessary to build the initial state in our simulations, are presented in great detail. The angular momentum of the discs is assumed to increase outwards with the radial distance according to a power law. The main simplifying assumptions of our approach are not to include magnetic fields and self-gravity in the discs. Furthermore, the dynamics of the spacetime is accounted for by computing the transfer of mass and angular momentum from the disc to the black hole through the event horizon : the evolution of the central black hole is assumed to follow a sequence of Kerr black holes of increasing mass and spin. In agreement with previous results based on stationary models we find that by allowing the mass and the spin of the black hole to grow, constant angular momentum discs rapidly become unstable on a dynamical timescale. The comparison with the results of paper I shows that the effect of the angular momentum transfer from the torus to the black hole is to make constant angular momentum discs less unstable, increasing the timescale of the instability. However, we find that non-constant angular momentum discs are dramatically stabilized for very small values of the angular momentum slope. Our time-dependent simulations confirm, thus, the predictions of stationary studies concerning the stabilizing effect of non-constant angular momentum distributions.

  14. Disc valve for sampling erosive process streams

    DOE Patents [OSTI]

    Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

    1986-01-07T23:59:59.000Z

    A four-port disc valve is described for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of [alpha] silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions. 1 fig.

  15. Hard Discs on the Hyperbolic Plane

    E-Print Network [OSTI]

    Carl D. Modes; Randall D. Kamien

    2007-11-30T23:59:59.000Z

    We examine a simple hard disc fluid with no long range interactions on the two dimensional space of constant negative Gaussian curvature, the hyperbolic plane. This geometry provides a natural mechanism by which global crystalline order is frustrated, allowing us to construct a tractable model of disordered monodisperse hard discs. We extend free area theory and the virial expansion to this regime, deriving the equation of state for the system, and compare its predictions with simulation near an isostatic packing in the curved space.

  16. accretion disc radii: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  17. accretion discs due: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  18. accretion discs formed: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  19. accretion discs induced: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    and the rotational energy of the accreted matter is carried out by a magnetized wind outflowing from the disc. The outflow of matter from the disc occurs due to the...

  20. accretion disc particle: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  1. accretion disc dynamo: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  2. accretion disc boundary: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the...

  3. Demographics of Transition Discs in Ophiuchus and Taurus

    E-Print Network [OSTI]

    Najita, Joan R; Muzerolle, James

    2015-01-01T23:59:59.000Z

    Transition disc systems are young stars that appear to be on the verge of dispersing their protoplanetary discs. We explore the nature of these systems by comparing the stellar accretion rates and disc masses of transition discs and normal T Tauri stars in Taurus and Ophiuchus. After controlling for the known dependencies of stellar accretion rate and disc mass and on age, stellar accretion rate on stellar mass, and disc mass on the presence of stellar or sub-stellar companions, we find that the normal T Tauri stars show a trend of stellar accretion rate increasing with disc mass. The transition discs tend to have higher average disc masses than normal T Tauri stars as well as lower accretion rates than normal T Tauri stars of the same disc mass. These results are most consistent with the interpretation that the transition discs have formed objects massive enough to alter the accretion flow, i.e., single or multiple giant planets. Several Ophiuchus T Tauri stars that are not known transition disc systems also...

  4. DISC1ATF4 transcriptional repression complex: dual regulation of the cAMP-PDE4 cascade by DISC1

    E-Print Network [OSTI]

    Ishizuka, K

    Disrupted-In-Schizophrenia 1 (DISC1), a risk factor for major mental illnesses, has been studied extensively in the context of neurodevelopment. However, the role of DISC1 in neuronal signaling, particularly in conjunction ...

  5. Disc valve for sampling erosive process streams

    DOE Patents [OSTI]

    Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

    1984-08-16T23:59:59.000Z

    This is a patent for a disc-type, four-port sampling valve for service with erosive high temperature process streams. Inserts and liners of ..cap alpha..-silicon carbide respectively, in the faceplates and in the sampling cavities, limit erosion while providing lubricity for a smooth and precise operation. 1 fig.

  6. Preliminary survey report: evaluation of brake-drum service controls at Pennsylvania Bureau of Vehicle Management, Vehicle Maintenance Division, Harrisburg, Pennsylvania

    SciTech Connect (OSTI)

    Van Wagenen, H.D.

    1987-03-01T23:59:59.000Z

    Exposure to asbestos during the servicing of brakes on state-owned vehicles at the Bureau of Vehicle Management Maintenance Division, Harrisburg, Pennsylvania, was investigated as part of a study of control technologies. Brakes had been serviced at this garage facility for the previous year using a BCE-1000 Clayton brake-cleaning unit, sized for cars, vans, and pickups. The brake-cleaning unit consisted of a transparent enclosure hood and a HEPA vacuum filter dust collector, designed to contain and collect all brake-lining dust during vehicular brake maintenance and replacement. The authors conclude that the Clayton BCE-1000 dust-control unit appeared to be effective in containing and collecting brake dust during all vehicular brake maintenance and replacement jobs in this situation.

  7. Design of an Anti-Lock Regenerative Braking System for a ...14 International Journal of Automotive Engineering Vol. 1, Number 2, June 2011

    E-Print Network [OSTI]

    Vaziri, Ashkan

    energy storage system and subsequently used for the propulsion, significantly reducing the vehicle the brake of a vehicle [1]. The total energy dissipated through braking during a typical urban area drive

  8. Magnesium Front End Design and Development

    Broader source: Energy.gov (indexed) [DOE]

    by: Alan A. Luo and R. C. McCune Presented by: James Quinn, General Motors Unibody Architecture 3-piece Mg front end (bodyframe) USAMP AMD 603 - Magnesium Front End Design and...

  9. Ocean fronts trigger high latitude phytoplankton blooms

    E-Print Network [OSTI]

    Taylor, John R.

    Density fronts are ubiquitous features of the upper ocean. Here, numerical simulations show that restratification at fronts inhibits vertical mixing, triggering phytoplankton blooms in low-light conditions. The stability ...

  10. Operations & Maintenance Best Practices Guide: Front Matter

    Broader source: Energy.gov [DOE]

    Guide describes the front matter of the Operations and Maintenance Best Practices: a Guide to Achieving Operational Efficiency.

  11. Counterrotating perfect fluid discs as sources of electrovacuum static spacetimes

    E-Print Network [OSTI]

    Gonzalo Garca-Reyes; Guillermo A. Gonzlez

    2008-10-14T23:59:59.000Z

    The interpretation of some electrovacuum spacetimes in terms of counterrotating perfect fluid discs is presented. The interpretation is mades by means of an "inverse problem" approach used to obtain disc sources of known static solutions of the Einstein-Maxwell equations. In order to do such interpretation, a detailed study is presented of the counterrotating model (CRM) for generic electrovacuum static axially symmetric relativistic thin discs with nonzero radial pressure. Four simple families of models of counterrotating charged discs based on Chazy-Curzon-type, Zipoy-Voorhees-type, Bonnor-Sackfield-type, and charged and magnetized Darmois electrovacuum metrics are considered where we obtain some discs with a CRM well behaved.

  12. Tilted accretion discs in cataclysmic variables: tidal instabilities and superhumps

    E-Print Network [OSTI]

    J. R. Murray; P. J. Armitage

    1998-09-10T23:59:59.000Z

    We investigate the growth of tidal instabilities in accretion discs in a binary star potential, using three dimensional numerical simulations. As expected from analytic work, the disc is prone to an eccentric instability provided that it is large enough to extend to the 3:1 resonance. The eccentric disc leads to positive superhumps in the light curve. It has been proposed that negative superhumps might arise from a tilted disc, but we find no evidence that the companion gravitational tilt instability can grow fast enough in a fluid disc to create a measurable inclination. The origin of negative superhumps in the light curves of cataclysmic variables remains a puzzle.

  13. On The Use of Eddy Current Brakes as Tunable, Fast Turn-On Viscous Dampers For Haptic Rendering

    E-Print Network [OSTI]

    Hayward, Vincent

    On The Use of Eddy Current Brakes as Tunable, Fast Turn-On Viscous Dampers For Haptic Rendering, linear dampers for haptic rendering using a prototype haptic device outfitted with eddy current brakes discuss the results from haptic experiments for rendering viscosity, virtual walls and virtual friction

  14. Initial results using Eddy Current Brakes as Fast Turn-on, Programmable Physical Dampers for Haptic Rendering

    E-Print Network [OSTI]

    Hayward, Vincent

    Initial results using Eddy Current Brakes as Fast Turn-on, Programmable Physical Dampers for Haptic Machines McGill University, Montreal, Quebec, Canada ABSTRACT We demonstrate the use of eddy current propose an alternate method to create damping in a haptic interface that uses eddy current brakes. 2 EDDY

  15. Broad reprocessed Balmer emission from warped accretion discs

    E-Print Network [OSTI]

    Sheng-Miao Wu; Ting-Gui Wang; Xiao-Bo Dong

    2008-07-11T23:59:59.000Z

    Double peaked broad emission lines in active galactic nuclei are generally considered to be formed in an accretion disc. In this paper, we compute the profiles of reprocessing emission lines from a relativistic, warped accretion disc around a black hole in order to explore the possibility that certain asymmetries in the double-peaked emission line profile which can not be explained by a circular Keplerian disc may be induced by disc warping. The disc warping also provides a solution for the energy budget in the emission line region because it increases the solid angle of the outer disc portion subtended to the inner portion of the disc. We adopted a parametrized disc geometry and a central point-like source of ionizing radiation to capture the main characteristics of the emission line profile from such discs. We find that the ratio between the blue and red peaks of the line profiles becoming less than unity can be naturally predicted by a twisted warped disc, and a third peak can be produced in some cases. We show that disc warping can reproduce the main features of multi-peaked line profiles of four active galactic nuclei from the Sloan Digital Sky Survey.

  16. Accretion Disc Evolution in Single and Binary T Tauri Stars

    E-Print Network [OSTI]

    Philip J. Armitage; C. J. Clarke; C. A. Tout

    1998-10-30T23:59:59.000Z

    We present theoretical models for the evolution of T Tauri stars surrounded by circumstellar discs. The models include the effects of pre-main-sequence stellar and time dependent disc evolution, and incorporate the effects of stellar magnetic fields acting on the inner disc. For single stars, consistency with observations in Taurus-Auriga demands that disc dispersal occurs rapidly, on much less than the viscous timescale of the disc, at roughly the epoch when heating by stellar radiation first dominates over internal viscous dissipation. Applying the models to close binaries, we find that because the initial conditions for discs in binaries are uncertain, studies of extreme mass ratio systems are required to provide a stringent test of theoretical disc evolution models. We also note that no correlation of the infra-red colours of T Tauri stars with their rotation rate is observed, in apparent contradiction to the predictions of simple magnetospheric accretion models.

  17. Recycled brake linings as partial aggregate substitute in asphalt paving. Construction and final report. Report for July 1992-August 1996

    SciTech Connect (OSTI)

    Miller, P.A.; Sukley, R.

    1996-09-01T23:59:59.000Z

    The purpose of this project was to evaluate the performance of asphalt containing various percentages of brake lining as an aggregate, and compare its performance to that of normal asphalt containing natural aggregate. This project is an effort to explore alternate ways to use waste product. Four test section of FB-2 Modified mix containing brake lining materials were placed in July 1992 along with one control section on SR 3022 in Mercer county. To date all sections are performing satisfactory, and Brake linings should be recommended as a viable partial replacement of aggregate in bituminous materials. This study only considered the performance of only off-spec brake linings, therefore, any performance data or enviromental effects of placement of used brake material should be addressed.

  18. REPORT on the TRUCK BRAKE LINING WORKSHOP and FLEET OPERATORS' SURVEY

    SciTech Connect (OSTI)

    Blau, P.J.

    2003-02-03T23:59:59.000Z

    The report summarizes what transpired during brake linings-related workshop held at the Fall 2003 meeting of the Technology and Maintenance Council (TMC) in Charlotte, NC. The title of the workshop was ''Developing a Useful Friction Material Rating System''. It was organized by a team consisting of Peter Blau (Oak Ridge National Laboratory), Jim Britell (National Highway Traffic Safety Administration), and Jim Lawrence (Motor and Equipment Manufacturers Association). The workshop was held under the auspices of TMC Task Force S6 (Chassis), chaired by Joseph Stianche (Sanderson Farms, Inc.). Six invited speakers during the morning session provided varied perspectives on testing and rating aftermarket automotive and truck brake linings. They were: James R. Clark, Chief Engineer, Foundation Brakes and Wheel Equipment, Dana Corporation, Spicer Heavy Axle and Brake Division; Charles W. Greening, Jr, President, Greening Test Labs; Tim Duncan, General Manager, Link Testing Services;Dennis J. McNichol, President, Dennis NationaLease; Jim Fajerski, Business Manager, OE Sales and Applications Engineering, Federal Mogul Corporation; and Peter J. Blau, Senior Materials Development Engineer, Oak Ridge National Laboratory. The afternoon break-out sessions addressed nine questions concerning such issues as: ''Should the federal government regulate aftermarket lining quality?''; ''How many operators use RP 628, and if so, what's good or bad about it?''; and ''Would there be any value to you of a vocation-specific rating system?'' The opinions of each discussion group, consisting of 7-9 participants, were reported and consolidated in summary findings on each question. Some questions produced a greater degree of agreement than others. In general, the industry seems eager for more information that would allow those who are responsible for maintaining truck brakes to make better, more informed choices on aftermarket linings. A written fleet operator survey was also conducted during the TMC meeting. Twenty-one responses were received, spanning fleet sizes between 12 and 170,000 vehicles. Responses are summarized in a series of tables separated into responses from small (100 or fewer powered vehicles), medium (101-1000 vehicles), and large fleets (>1000 vehicles). The vast majority of fleets do their own brake maintenance, relying primarily on experience and lining manufactures to select aftermarket linings. At least half of the responders are familiar to some extent with TMC Recommended Practice 628 on brake linings, but most do not use this source of test data as the sole criterion to select linings. Significant shortfalls in the applicability of TMC RP 628 to certain types of brake systems were noted.

  19. Classical and quantum Big Brake cosmology for scalar field and tachyonic models

    SciTech Connect (OSTI)

    Kamenshchik, A. Yu. [Dipartimento di Fisica e Astronomia and INFN, Via Irnerio 46, 40126 Bologna (Italy) and L.D. Landau Institute for Theoretical Physics of the Russian Academy of Sciences, Kosygin str. 2, 119334 Moscow (Russian Federation); Manti, S. [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy)

    2013-02-21T23:59:59.000Z

    We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity - the model based on a scalar field and two models based on a tachyon-pseudo-tachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical - quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable.

  20. Virial theorem for radiating accretion discs

    E-Print Network [OSTI]

    Patryk Mach

    2012-04-18T23:59:59.000Z

    A continuum version of the virial theorem is derived for a radiating self-gravitating accretion disc around a compact object. The central object is point-like, but we can avoid the regularization of its gravitational potential. This is achieved by applying a modified Pohozaev-Rellich identity to the gravitational potential of the disk only. The theorem holds for general stationary configurations, including discontinuous flows (shock waves, contact discontinuities). It is used to test numerical solutions of a model of self-gravitating radiative accretion discs. The presented virial theorem should be useful in the analysis of those (possibly radiating) hydrodynamical systems in astrophysics where the central mass and the mass of the fluid are comparable and none of them can be neglected.

  1. The Photoevaporation of Discs Around Young Stars in Massive Clusters

    E-Print Network [OSTI]

    C. J. Clarke

    2007-02-05T23:59:59.000Z

    We present models in which the photoevaporation of discs around young stars by an external ultraviolet source (as computed by Adams et al 2004) is coupled with the internal viscous evolution of the discs. These models are applied to the case of the Orion Nebula Cluster, where the presence of a strong ultraviolet field from the central OB stars, together with a detailed census of circumstellar discs and photoevaporative flows, is well established. In particular we investigate the constraints that are placed on the initial disc properties in the ONC by the twin requirement that most stars possess a disc on a scale of a few A.U., but that only a minority ($ 0.1 M_\\odot$). The ubiquity of discs on a small scale, on the other hand, mainly constrains the timespan over which the discs have been exposed to the ultraviolet field ($< 2 $Myr). We argue that the discs that are resolved by HST represent a population of discs in which self-gravity was important at the time that the dominant central OB star switched on, but that, according to our models, self-gravity is unlikely to be important in these discs at the present time. We discuss the implications of our results for the so-called proplyd lifetime problem.

  2. Astrometric signatures of self-gravitating protoplanetary discs

    E-Print Network [OSTI]

    W. K. M. Rice; P. J. Armitage; M. R. Bate; I. A. Bonnell

    2002-09-09T23:59:59.000Z

    We use high resolution numerical simulations to study whether gravitational instabilities within circumstellar discs can produce astrometrically detectable motion of the central star. For discs with masses of M_disc = 0.1 M_star, which are permanantly stable against fragmentation, we find that the magnitude of the astrometric signal depends upon the efficiency of disc cooling. Short cooling times produce prominent filamentary spiral structures in the disc, and lead to stellar motions that are potentially observable with future high precision astrometric experiments. For a disc that is marginally unstable within radii of \\~10 au, we estimate astrometric displacements of 10-100 microarcsec on decade timescales for a star at a distance of 100 pc. The predicted displacement is suppressed by a factor of several in more stable discs in which the cooling time exceeds the local dynamical time by an order of magnitude. We find that the largest contribution comes from material in the outer regions of the disc and hence, in the most pessimistic scenario, the stellar motions caused by the disc could confuse astrometric searches for low mass planets orbiting at large radii. They are, however, unlikely to present any complications in searches for embedded planets orbiting at small radii, relative to the disc size, or Jupiter mass planets or greater orbiting at large radii.

  3. Dispersal of Gaseous Circumstellar Discs around High-Mass Stars

    E-Print Network [OSTI]

    Yue Shen; Yu-Qing Lou

    2006-05-19T23:59:59.000Z

    We study the dispersal of a gaseous disc surrounding a central high-mass stellar core once this circumstellar disc becomes fully ionized. If the stellar and surrounding EUV and X-ray radiations are so strong as to rapidly heat up and ionize the entire circumstellar disc as further facilitated by disc magnetohydrodynamic (MHD) turbulence, a shock can be driven to travel outward in the fully ionized disc, behind which the disc expands and thins. For an extremely massive and powerful stellar core, the ionized gas pressure overwhelms the centrifugal and gravitational forces in the disc. In this limit, we construct self-similar shock solutions for such an expansion and depletion phase. As a significant amount of circumstellar gas being removed, the relic disc becomes vulnerable to strong stellar winds and fragments into clumps. We speculate that disc disappearance happens rapidly, perhaps on a timescale of $\\sim 10^3-10^4\\hbox{yr}$ once the disc becomes entirely ionized sometime after the onset of thermal nuclear burning in a high-mass stellar core.

  4. Mass Flow and Accretion through gaps in Accretion Discs

    E-Print Network [OSTI]

    Willy Kley

    1998-09-21T23:59:59.000Z

    We study the structure and dynamics of the gap created by a protoplanet in an accretion disc. The hydrodynamic equations for a flat, two-dimensional, non-selfgravitating protostellar accretion disc with an embedded, Jupiter sized protoplanet on a circular orbit are solved. To simulate possible accretion of mass onto the protoplanet we continually remove mass from the interior of the planet's Roche lobe which is monitored. Firstly, it is shown that consistent results independent on numerical issues (such as boundary or initial conditions, artificial viscosity or resolution) can be obtained. Then, a detailed parameter study delineates the influence of the disc viscosity and pressure on the magnitude of the accretion rate. We find that, even after the formation of a gap in the disc, the planet is still able to accrete more mass from the disc. This accretion occurs from regions of the disc which are radially exterior and interior to the planet's orbital radius. The rate depends on the magnitude of the viscosity and vertical thickness of the disc. For a disc viscosity alpha=10^{-3} and vertical thickness H/r=0.05 we estimate the time scale for the accumulation of one Jupiter mass to be of order hundred thousand years. For a larger(smaller) viscosity and disc thickness this accretion rate is increasing(decreasing). For a very small viscosity (alpha disc.

  5. Achieving Consistent Maximum Brake Torque with Varied Injection Timing in a DI Diesel Engine

    E-Print Network [OSTI]

    Kroeger, Timothy H

    2013-09-19T23:59:59.000Z

    The brake torque of a direct-injection diesel engine is known to plateau over a range of injection timings. Injection timing affects the engines ignition delay and the fractions of fuel which burn in premixed and diffusion modes. Therefore...

  6. Regenerative Braking for an Electric Vehicle Using Ultracapacitors and a Buck-Boost Converter

    E-Print Network [OSTI]

    Catholic University of Chile (Universidad Catlica de Chile)

    Regenerative Braking for an Electric Vehicle Using Ultracapacitors and a Buck-Boost Converter Juan for an Electric Vehicle has been simulated. The purpose of this device is to allow higher accelerations, similar in shape and size to a Chevrolet S-10. This vehicle was already converted to an electric car

  7. A study of factors affecting foot movement time in a braking maneuver

    E-Print Network [OSTI]

    Berman, Andrea Helene

    1994-01-01T23:59:59.000Z

    The nature of foot movement time (MT) in an actual braking maneuver and in a stationary vehicle was investigated regarding the effects of age and gender of the driver and nature of the stimulus to which the driver was responding. ANOVAs showed...

  8. Accretion disc viscosity: a limit on the anisotropy

    E-Print Network [OSTI]

    Nixon, Chris

    2015-01-01T23:59:59.000Z

    Observations of warped discs can give insight into the nature of angular momentum transport in accretion discs. Only a few objects are known to show strong periodicity on long timescales, but when such periodicity is present it is often attributed to precession of the accretion disc. The X-ray binary Hercules X-1/HZ Herculis (Her X-1) is one of the best examples of such periodicity and has been linked to disc precession since it was first observed. By using the current best-fitting models to Her X-1, which invoke precession driven by radiation warping, I place a constraint on the effective viscosities that act in a warped disc. These effective viscosities almost certainly arise due to turbulence induced by the magneto-rotational instability. The constraints derived here are in agreement with analytical and numerical investigations into the nature of magneto-hydrodynamic disc turbulence, but at odds with some recent global simulations.

  9. [NeII] emission line profiles from photoevaporative disc winds

    E-Print Network [OSTI]

    R. D. Alexander

    2008-09-01T23:59:59.000Z

    I model profiles of the [NeII] forbidden emission line at 12.81um, emitted by photoevaporative winds from discs around young, solar-mass stars. The predicted line luminosities (~ 1E-6 Lsun) are consistent with recent data, and the line profiles vary significantly with disc inclination. Edge-on discs show broad (30-40km/s) double-peaked profiles, due to the rotation of the disc, while in face-on discs the structure of the wind results in a narrower line (~10km/s) and a significant blue-shift (5-10km/s). These results suggest that observations of [NeII] line profiles can provide a direct test of models of protoplanetary disc photoevaporation.

  10. On the observability of spiral structures in CV accretion discs

    E-Print Network [OSTI]

    Danny Steeghs; Rudolf Stehle

    1999-02-25T23:59:59.000Z

    We use the grid of hydrodynamic accretion disc calculations of Stehle (1999) to construct orbital phase dependent emission line profiles of thin discs carrying spiral density waves. The observational signatures of spiral waves are explored to establish the feasibility of detecting spiral waves in cataclysmic variable discs using prominent emission lines in the visible range of the spectrum. For high Mach number accretion discs (M = 15-30), we find that the spiral shock arms are so tightly wound that they leave few obvious fingerprints in the emission lines. Only a minor variation of the double peak separation in the line profile at a level of 8% is produced. For accretion discs in outburst (M = 5-20) however, the lines are dominated by the emission from an m=2 spiral pattern in the disc. We show that reliable Doppler tomograms of spiral shock patterns can be reconstructed provided that a signal to noise of at least 15, a wavelength resolution of 80 km/s and a time resolution of 50 spectra per binary orbit is achieved. We confirm that the observed spiral pattern in the disc of IP Pegasi can be reproduced by tidal density waves in the accretion disc and demands the presence of a large, hot disc, at least in the early outburst stages.

  11. Three-integral models for axisymmetric galactic discs

    E-Print Network [OSTI]

    B. Famaey; K. Van Caelenberg; H. Dejonghe

    2002-05-21T23:59:59.000Z

    We present new equilibrium component distribution functions that depend on three analytic integrals in a Stackel potential, and that can be used to model stellar discs of galaxies. These components are generalizations of two-integral ones and can thus provide thin discs in the two-integral approximation. Their most important properties are the partly analytical expression for their moments, the disc-like features of their configuration space densities (exponential decline in the galactic plane and finite extent in the vertical direction) and the anisotropy of their velocity dispersions. We further show that a linear combination of such components can fit a van der Kruit disc.

  12. Analysis of rabbit intervertebral disc physiology based on water metabolism. II. Changes in normal intervertebral discs under axial vibratory load

    SciTech Connect (OSTI)

    Hirano, N.; Tsuji, H.; Ohshima, H.; Kitano, S.; Itoh, T.; Sano, A.

    1988-11-01T23:59:59.000Z

    Metabolic changes induced by axial vibratory load to the spine were investigated based on water metabolism in normal intervertebral discs of rabbits with or without pentobarbital anesthesia. Tritiated water concentration in the intervertebral discs of unanesthetized rabbits was reduced remarkably by axial vibration for 30 minutes using the vibration machine developed for this study. Repeated vibratory load for 18 and 42 hours duration showed the recovery of /sup 3/H/sub 2/O concentration of the intervertebral disc without anesthesia. Computer simulation suggested a reduction of blood flow surrounding the intervertebral disc following the vibration stress. However, no reduction of the /sup 3/H/sub 2/O concentration in the intervertebral disc was noted under anesthesia. Emotional stress cannot be excluded as a factor in water metabolism in the intervertebral disc.

  13. Light-Front Holographic QCD

    SciTech Connect (OSTI)

    Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16T23:59:59.000Z

    The relation between the hadronic short-distance constituent quark and gluon particle limit and the long-range confining domain is yet one of the most challenging aspects of particle physics due to the strong coupling nature of Quantum Chromodynamics, the fundamental theory of the strong interactions. The central question is how one can compute hadronic properties from first principles; i.e., directly from the QCD Lagrangian. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time. Lattice numerical results follow from computation of frame-dependent moments of distributions in Euclidean space and dynamical observables in Minkowski spacetime, such as the time-like hadronic form factors, are not amenable to Euclidean lattice computations. The Dyson-Schwinger methods have led to many important insights, such as the infrared fixed point behavior of the strong coupling constant, but in practice, the analyses are limited to ladder approximation in Landau gauge. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. New theoretical tools are thus of primary interest for the interpretation of the results expected at the new mass scale and kinematic regions accessible to the JLab 12 GeV Upgrade Project. The AdS/CFT correspondence between gravity or string theory on a higher-dimensional anti-de Sitter (AdS) space and conformal field theories in physical space-time has led to a semiclassical approximation for strongly-coupled QCD, which provides physical insights into its nonperturbative dynamics. The correspondence is holographic in the sense that it determines a duality between theories in different number of space-time dimensions. This geometric approach leads in fact to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian 'Light-Front Holography'. Light-Front Holography is in fact one of the most remarkable features of the AdS/CFT correspondence. The Hamiltonian equation of motion in the light-front (LF) is frame independent and has a structure similar to eigenmode equations in AdS space. This makes a direct connection of QCD with AdS/CFT methods possible. Remarkably, the AdS equations correspond to the kinetic energy terms of the partons inside a hadron, whereas the interaction terms build confinement and correspond to the truncation of AdS space in an effective dual gravity approximation. One can also study the gauge/gravity duality starting from the bound-state structure of hadrons in QCD quantized in the light-front. The LF Lorentz-invariant Hamiltonian equation for the relativistic bound-state system is P{sub {mu}}P{sup {mu}}|{psi}(P)> = (P{sup +}P{sup -} - P{sub {perpendicular}}{sup 2})|{psi}(P)> = M{sup 2}|{psi}(P)>, P{sup {+-}} = P{sup 0} {+-} P{sup 3}, where the LF time evolution operator P{sup -} is determined canonically from the QCD Lagrangian. To a first semiclassical approximation, where quantum loops and quark masses are not included, this leads to a LF Hamiltonian equation which describes the bound-state dynamics of light hadrons in terms of an invariant impact variable {zeta} which measures the separation of the partons within the hadron at equal light-front time {tau} = x{sup 0} + x{sup 3}. This allows us to identify the holographic variable z in AdS space with an impact variable {zeta}. The resulting Lorentz-invariant Schroedinger equation for general spin incorporates color confinement and is systematically improvable. Light-front holographic methods were originally introduced by matching the electromagnetic current matrix elements in AdS space with the corresponding expression using LF theory in physical space time. It was also shown that one obtains identical holographic mapping using the matrix elements of the energy-momentum tensor by perturbing the AdS metric around its static solution. A gravity dual to QCD is not known, but th

  14. 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved.

    E-Print Network [OSTI]

    Zhang, Meirong

    © 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved

  15. 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved.

    E-Print Network [OSTI]

    Qian, Weihong

    1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12; 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12; 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12; 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved

  16. 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved.

    E-Print Network [OSTI]

    Zhang, Ke-Min

    © 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. #12;© 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved

  17. Far-infrared and sub-millimetre surveys of circumstellar discs.

    E-Print Network [OSTI]

    Phillips, Neil Matthew

    2011-06-27T23:59:59.000Z

    . This thesis focuses on observational studies at far-infrared and sub-millimetre wavelengths of debris discs and the late stages of protoplanetary disc evolution. An overview of surveys for debris discs performed to date is presented, highlighting...

  18. accretion discs non-barotropic: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of a dwarf novae disc through its outburst cycle, from isolating the spectrum of a disc wind to revealing the geometry of disc spiral shocks. I end with an outline of the future...

  19. DISC1 & GSK3? modulate PDE4 activity: functional integration of psychiatric associated signalling pathways

    E-Print Network [OSTI]

    Carlyle, Becky Catherine

    2010-01-01T23:59:59.000Z

    Following the discovery of the DISC1 gene in 2000, subsequent research has led to DISC1 becoming one of the most promising candidate genes for psychiatric disorders. Acting as a scaffold protein, DISC1 has a large number ...

  20. Discs Large Homolog 1: Identifying Molecular Mechanisms that Guide Functional Specificity in Lymphocytes

    E-Print Network [OSTI]

    Crocetti, Jillian Ann

    2014-01-01T23:59:59.000Z

    homolog of the Drosophila discs-large tumor suppressor. EMBOHumphries, L.A. & Miceli, M.C. Discs Large Homolog 1 (Dlg1)C. Shaw, W. Swat, B. Seed, Discs large (Dlg1) complexes in

  1. Self-regulated gravitational accretion in protostellar discs

    E-Print Network [OSTI]

    E. I. Vorobyov; S. Basu

    2007-09-13T23:59:59.000Z

    We present a numerical model for the evolution of a protostellar disc that has formed self-consistently from the collapse of a molecular cloud core. The global evolution of the disc is followed for several million years after its formation. The capture of a wide range of spatial and temporal scales is made possible by use of the thin-disc approximation. We focus on the role of gravitational torques in transporting mass inward and angular momentum outward during different evolutionary phases of a protostellar disc with disc-to-star mass ratio of order 0.1. In the early phase, when the infall of matter from the surrounding envelope is substantial, mass is transported inward by the gravitational torques from spiral arms that are a manifestation of the envelope-induced gravitational instability in the disc. In the late phase, when the gas reservoir of the envelope is depleted, the distinct spiral structure is replaced by ongoing irregular nonaxisymmetric density perturbations. The amplitude of these density perturbations decreases with time, though this process is moderated by swing amplification aided by the existence of the disc's sharp outer edge. Our global modelling of the protostellar disc reveals that there is typically a residual nonzero gravitational torque from these density perturbations, i.e. their effects do not exactly cancel out in each region. In particular, the net gravitational torque in the inner disc tends to be negative during first several million years of the evolution, while the outer disc has a net positive gravitational torque. Our global model of a self-consistently formed disc shows that it is also self-regulated in the late phase, so that it is near the Toomre stability limit, with a near-uniform Toomre parameter Q\\approx 1.5-2.0. (Abstract abridged).

  2. Secular evolution of viscous and self-gravitating circumstellar discs

    E-Print Network [OSTI]

    E. I. Vorobyov; Shantanu Basu

    2008-12-06T23:59:59.000Z

    We add the effect of turbulent viscosity via the \\alpha-prescription to models of the self-consistent formation and evolution of protostellar discs. Our models are non-axisymmetric and carried out using the thin-disc approximation. Self-gravity plays an important role in the early evolution of a disc, and the later evolution is determined by the relative importance of gravitational and viscous torques. In the absence of viscous torques, a protostellar disc evolves into a self-regulated state with disk-averaged Toomre parameter Q \\sim 1.5-2.0, non-axisymmetric structure diminishing with time, and maximum disc-to-star mass ratio \\xi = 0.14. We estimate an effective viscosity parameter \\alpha_eff associated with gravitational torques at the inner boundary of our simulation to be in the range 10^{-4}-10^{-3} during the late evolution. Addition of viscous torques with a low value \\alpha = 10^{-4} has little effect on the evolution, structure, and accretion properties of the disc, and the self-regulated state is largely preserved. A sequence of increasing values of \\alpha results in the discs becoming more axisymmetric in structure, being more gravitationally stable, having greater accretion rates, larger sizes, shorter lifetimes, and lower disc-to-star mass ratios. For \\alpha=10^{-2}, the model is viscous-dominated and the self-regulated state largely disappears by late times. (Abridged)

  3. Nonlinear analysis of time series of vibration data from a friction brake: SSA, PCA, and MFDFA

    E-Print Network [OSTI]

    Nikolay K. Vitanov; Norbert P. Hoffmann; Boris Wernitz

    2014-10-23T23:59:59.000Z

    We use the methodology of singular spectrum analysis (SSA), principal component analysis (PCA), and multi-fractal detrended fluctuation analysis (MFDFA), for investigating characteristics of vibration time series data from a friction brake. SSA and PCA are used to study the long time-scale characteristics of the time series. MFDFA is applied for investigating all time scales up to the smallest recorded one. It turns out that the majority of the long time-scale dynamics, that is presumably dominated by the structural dynamics of the brake system, is dominated by very few active dimensions only and can well be understood in terms of low dimensional chaotic attractors. The multi-fractal analysis shows that the fast dynamical processes originating in the friction interface are in turn truly multi-scale in nature.

  4. Giant Planet Migration in Viscous Power-Law Discs

    E-Print Network [OSTI]

    R. G. Edgar

    2007-04-03T23:59:59.000Z

    Many extra-solar planets discovered over the past decade are gas giants in tight orbits around their host stars. Due to the difficulties of forming these `hot Jupiters' in situ, they are generally assumed to have migrated to their present orbits through interactions with their nascent discs. In this paper, we present a systematic study of giant planet migration in power law discs. We find that the planetary migration rate is proportional to the disc surface density. This is inconsistent with the assumption that the migration rate is simply the viscous drift speed of the disc. However, this result can be obtained by balancing the angular momentum of the planet with the viscous torque in the disc. We have verified that this result is not affected by adjusting the resolution of the grid, the smoothing length used, or the time at which the planet is released to migrate.

  5. Modeling the pneumatic relay valve of an s-cam air brake

    E-Print Network [OSTI]

    Vilayannur Natarajan, Shankar

    2005-08-29T23:59:59.000Z

    inspections. For example, defects like chafed hoses do not show pronounced effect in performance based tests. In the past only a few cases of air leak violations have been detected by the conventional performance based testers namely roller dynamometer... detected by the performance based system since they had a pronounced effect on the brake force. Reference [6] emphasizes on the need for a standardized, hand held diagnostic tool for improving the existing inspections. A model based, performance based diag...

  6. Variations in gear fatigue life for different wind turbine braking strategies

    SciTech Connect (OSTI)

    McNiff, B.P. (Second Wind, Inc., Somerville, MA (USA)); Musial, W.D. (Solar Energy Research Inst., Golden, CO (USA)); Errichello, R. (GEARTECH, Albany, CA (USA))

    1991-06-01T23:59:59.000Z

    A large number of gearbox failures have occurred in the wind industry in a relatively short period, many because service loads were underestimated. High-torque transients that occur during starting and stopping are difficult to predict and may be overlooked in specifying gearbox design. Although these events comprise a small portion of total load cycles, they can be the most damaging. The severity of these loads varies dramatically with the specific configuration of the wind turbine. The large number of failures in Danish-designed Micon 65 wind turbines prompted this investigation. The high-speed and low-speed shaft torques were measured on a two-stage helical gearbox of a single Micon 65 turbine. Transient events and normal running loads were combined statistically to obtain a typical annual load spectrum. The pitting and bending fatigue lives of the gear teeth were calculated by using Miner's rule for four different high-speed shaft brake configurations. Each breaking scenario was run for both a high- and a low-turbulence normal operating load spectrum. The analysis showed increases in gear life by up to a factor of 25 when the standard high-speed shaft brake is replaced with a dynamic brake or modified with a damper. 9 refs., 9 figs., 3 tabs.

  7. Pressure transient method for front tracking

    SciTech Connect (OSTI)

    Benson, S.M.; Bodvarsson, G.S.

    1983-08-01T23:59:59.000Z

    A pressure transient technique for tracking the advance of cold water fronts during water flooding and goethermal injection operations has been developed. The technique is based on the concept that the steady state pressure buildup in the reservoir region inside the front can be calculated by a fluid skin factor. By analyzing successive pressure falloff tests, the advance of the front in the reservoir can be monitored. The validity of the methods is demonstrated by application to three numerically simulated data sets, a nonisothermal step-rate injection test, a series of pressure falloffs in a multilayered reservoir, and a series of pressure falloff tests in a water flooded oil reservoir.

  8. Photoevaporation of protoplanetary discs II: evolutionary models and observable properties

    E-Print Network [OSTI]

    R. D. Alexander; C. J. Clarke; J. E. Pringle

    2006-03-09T23:59:59.000Z

    We present a new model for protoplanetary disc evolution. This model combines viscous evolution with photoevaporation of the disc, in a manner similar to Clarke, Gendrin & Sotomayor (2001). However in a companion paper (Alexander, Clarke & Pringle 2006a) we have shown that at late times such models must consider the effect of stellar radiation directly incident on the inner disc edge, and here we model the observational implications of this process. We find that the entire disc is dispersed on a time-scale of order $10^5$yr after a disc lifetime of a few Myr, consistent with observations of T Tauri (TT) stars. We use a simple prescription to model the spectral energy distribution of the evolving disc, and demonstrate that the model is consistent with observational data across a wide range of wavelengths. We note also that the model predicts a short ``inner hole'' phase in the evolution of all TT discs, and make predictions for future observations at mid-infrared and millimetre wavelengths.

  9. Does the stellar disc flattening depend on the galaxy type?

    E-Print Network [OSTI]

    Mosenkov, A V; Reshetnikov, V P; Bizyaev, D V; Kautsch, S J

    2015-01-01T23:59:59.000Z

    We analyze the dependence of the stellar disc flatness on the galaxy morphological type using 2D decomposition of galaxies from the reliable subsample of the Edge-on Galaxies in SDSS (EGIS) catalogue. Combining these data with the retrieved models of the edge-on galaxies from the Two Micron All Sky Survey (2MASS) and the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G) catalogue, we make the following conclusions: (1) The disc relative thickness $z_0/h$ in the near- and mid-infrared passbands correlates weakly with morphological type and does not correlate with the bulge-to-total luminosity ratio $B/T$ in all studied bands. (2) Applying an 1D photometric profile analysis overestimates the disc thickness in galaxies with large bulges making an illusion of the relationship between the disc flattening and the ratio $B/T$. (3) In our sample the early-type disc galaxies (S0/a) have both flat and "puffed" discs. The early spirals and intermediate-type galaxies have a large scatter of the disc flatness, whic...

  10. Lindblad resonance torques in relativistic discs: I. Basic equations

    E-Print Network [OSTI]

    Christopher M. Hirata

    2011-03-01T23:59:59.000Z

    Lindblad resonances have been suggested as an important mechanism for angular momentum transport and heating in discs in binary black hole systems. We present the basic equations for the torque and heating rate for relativistic thin discs subjected to a perturbation. The Lindblad resonance torque is written explicitly in terms of metric perturbations for an equatorial disc in a general axisymmetric, time-stationary spacetime with a plane of symmetry. We show that the resulting torque formula is gauge-invariant. Computations for the Schwarzschild and Kerr spacetimes are presented in the companion paper.

  11. Back Cover Front Cover Office of Continuing

    E-Print Network [OSTI]

    Goodman, Robert M.

    Back Cover Front Cover Office of Continuing Professional Education 20122013 Professional Landscape of Golf Course Irrigation Systems (p. 13) Basics of Turf Management (p. 21) Turfgrass Establishment (p

  12. COLORADO FRONT RANGE SEISMICITY AND SEISMIC HAZARD

    E-Print Network [OSTI]

    Sheehan, Anne F.

    COLORADO FRONT RANGE SEISMICITY AND SEISMIC HAZARD Anne F. Sheehan University of Colorado, seismic, seismicity, crust, fault, hazard ABSTRACT Construction of seismic hazard and risk maps depends upon carefully constrained input parameters including background seismicity, seismic attenuation

  13. Light front Casimir effect at finite temperature

    E-Print Network [OSTI]

    P. L. M. Rodrigues; Silvana Perez; Danilo T. Alves; Van Srgio Alves; Charles R. Silva

    2015-01-06T23:59:59.000Z

    The correct description of the standard Casimir effect for periodic boundary conditions via light front formalism implies in these conditions imposed at fixed Minkowski times [Almeida {\\it et al.} Phys. Rev. {\\bf D 87}, 065028 (2013); Chabysheva and Hiller, Phys. Rev. {\\bf D 88}, 085006 (2013)] instead of fixed light front times. The unphysical nature of this latter condition is manifested in the vacuum part by no regularization yielding a finite Casimir energy density [Lenz and Steinbacher, Phys. Rev. {\\bf D 67}, 045010 (2003)]. In the present paper, we extend this discussion and analyze the problem of the light front quantization with simultaneous presence of a thermal bath and boundary conditions. Considering both the oblique light front as well as Dirac light front coordinates, we show that the imposition of periodic boundary conditions at fixed Minkowski times recovers the expected behaviors for the energy density and Casimir entropy. We also investigate how the unphysical nature of the periodic boundary conditions imposed at fixed light front times manifests in the thermal part of the energy and entropy, showing that in the classical limit the Casimir entropy decreases linearly with the temperature (not becoming independent of the temperature as expected), and also that the Kirchhoff theorem is not respected.

  14. Dynamic Bayesian networks for the classification of spinning discs

    E-Print Network [OSTI]

    Schmidt, Aurora Clare, 1981-

    2004-01-01T23:59:59.000Z

    This thesis considers issues for the application of particle filters to a class of nonlinear filtering and classification problems. Specifically, we study a prototype system of spinning discs. The system combines linear ...

  15. The structure of protoplanetary discs around evolving young stars

    E-Print Network [OSTI]

    Bitsch, Bertram; Lambrechts, Michiel; Morbidelli, Alessandro

    2014-01-01T23:59:59.000Z

    The formation of planets with gaseous envelopes takes place in protoplanetary accretion discs on time-scales of several millions of years. Small dust particles stick to each other to form pebbles, pebbles concentrate in the turbulent flow to form planetesimals and planetary embryos and grow to planets, which undergo substantial radial migration. All these processes are influenced by the underlying structure of the protoplanetary disc, specifically the profiles of temperature, gas scale height and density. The commonly used disc structure of the Minimum Mass Solar Nebular (MMSN) is a simple power law in all these quantities. However, protoplanetary disc models with both viscous and stellar heating show several bumps and dips in temperature, scale height and density caused by transitions in opacity, which are missing in the MMSN model. These play an important role in the formation of planets, as they can act as sweet spots for the formation of planetesimals via the streaming instability and affect the direction...

  16. Spiral density waves in the outer galactic gaseous discs

    E-Print Network [OSTI]

    Khoperskov, S A

    2015-01-01T23:59:59.000Z

    Deep HI observations of the outer parts of disc galaxies demonstrate the frequent presence of extended, well-developed spiral arms far beyond the optical radius. To understand the nature and the origin of such outer spiral structure, we investigate the propagation in the outer gaseous disc of large-scale spiral waves excited in the bright optical disc. Using hydrodynamical simulations, we show that non-axisymmetric density waves, penetrating in the gas through the outer Lindblad resonance, can exhibit relatively regular spiral structures outside the bright optical stellar disc. For low-amplitude structures, the results of numerical simulations match the predictions of a simple WKB linear theory. The amplitude of spiral structure increases rapidly with radius. Beyond $\\approx 2$ optical radii, spirals become nonlinear (the linear theory becomes quantitatively and qualitatively inadequate) and unstable to Kelvin-Helmholtz instability. In numerical simulations, in models for which gas is available very far out, ...

  17. accretion disc plasmas: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    should give insight into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a...

  18. accretion disc theory: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We...

  19. accretion disc models: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We...

  20. accretion disc model: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We...

  1. attenuating disc wind: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    point located at (x,z)(0,-d) and (ii) streamlines that emerge at a constant inclination angle from the disc midplane (the x-axis, as we consider geometrically thin...

  2. Noncommutative Field Theory: Numerical Analysis with the Fuzzy Disc

    E-Print Network [OSTI]

    Fedele Lizzi; Bernardino Spisso

    2012-07-28T23:59:59.000Z

    The fuzzy disc is a discretization of the algebra of functions on the two dimensional disc using finite matrices which preserves the action of the rotation group. We define a $\\varphi^4$ scalar field theory on it and analyze numerically for three different limits for the rank of the matrix going to infinity. The numerical simulations reveal three different phases: uniform and disordered phases already the present in the commutative scalar field theory and a nonuniform ordered phase as a noncommutative effects. We have computed the transition curves between phases and their scaling. This is in agreement with studies on the fuzzy sphere, although the speed of convergence for the disc seems to be better. We have performed also three the limits for the theory in the cases of the theory going to the commutative plane or commutative disc. In this case the theory behaves differently, showing the intimate relationship between the nonuniform phase and noncommutative geometry.

  3. The precession of eccentric discs in close binaries

    E-Print Network [OSTI]

    James R. Murray

    1999-11-25T23:59:59.000Z

    We consider the precession rates of eccentric discs in close binaries, and compare theoretical predictions with the results of numerical disc simulations and with observed superhump periods. A simple dynamical model for precession is found to be inadequate. For mass ratios less than approximately 1/4 a linear dynamical model does provide an upper limit for disc precession rates. Theory suggests that pressure forces have a significant retrograde impact upon the precession rate (Lubow 1992). We find that the disc precession rates for three systems with accurately known mass ratios are significantly slower than predicted by the dynamical theory, and we attribute the difference to pressure forces. By assuming that pressure forces of similar magnitude occur in all superhumping systems, we obtain an improved fit to superhump observations.

  4. The instantaneous radial growth rate of stellar discs

    E-Print Network [OSTI]

    Pezzulli, Gabriele; Boissier, Samuel; Muoz-Mateos, Juan Carlos

    2015-01-01T23:59:59.000Z

    We present a new and simple method to measure the instantaneous mass and radial growth rates of the stellar discs of spiral galaxies, based on their star formation rate surface density (SFRD) profiles. Under the hypothesis that discs are exponential with time-varying scalelengths, we derive a universal theoretical profile for the SFRD, with a linear dependence on two parameters: the specific mass growth rate $\

  5. Developments on the CENS Structural Health Monitoring Front

    E-Print Network [OSTI]

    2009-01-01T23:59:59.000Z

    on the CENS Structural Health Monitoring Front D. Skolnik,Introduction: Structural Health Monitoring (SHM) Systems

  6. Developments on the CENS Structural Health Monitoring Front

    E-Print Network [OSTI]

    2007-01-01T23:59:59.000Z

    on the CENS Structural Health Monitoring Front D. Skolnik,Introduction: Structural Health Monitoring (SHM) Systems

  7. Electromagnetic counterparts from counter-rotating relativistic kicked discs

    E-Print Network [OSTI]

    Olindo Zanotti

    2011-08-23T23:59:59.000Z

    We show the results of two dimensional general relativistic inviscid and isothermal hydrodynamical simulations comparing the behavior of co-rotating (with respect to the black hole rotation) and counter-rotating circumbinary quasi-Keplerian discs in the post merger phase of a supermassive binary black hole system. While confirming the spiral shock generation within the disc due to the combined effects of mass loss and recoil velocity of the black hole, we find that the maximum luminosity of counter-rotating discs is a factor ~(2-12) higher than in the co-rotating case, depending on the spin of the black hole. On the other hand, the luminosity peak happens ~10 days later with respect to the co-rotating case, for a binary with a total mass M~10^6 M_\\odot. Although the global dynamics of counter-rotating discs in the post merger phase of a merging event is very similar to that for co-rotating discs, an important difference has been found. In fact, increasing the spin of the central black hole produces more luminous co-rotating discs while less luminous counter-rotating ones.

  8. Collapse of Magnetized Singular Isothermal Toroids: II. Rotation and Magnetic Braking

    E-Print Network [OSTI]

    A. Allen; Z. Y. Li; F. H. Shu

    2003-11-17T23:59:59.000Z

    We study numerically the collapse of rotating, magnetized molecular cloud cores, focusing on rotation and magnetic braking during the main accretion phase of isolated star formation. Motivated by previous numerical work and analytic considerations, we idealize the pre-collapse core as a magnetized singular isothermal toroid, with a constant rotational speed everywhere. The collapse starts from the center, and propagates outwards in an inside-out fashion, satisfying exact self-similarity in space and time. For rotation rates and field strengths typical of dense low-mass cores, the main feature remains the flattening of the mass distribution along field lines -- the formation of a pseudodisk, as in the nonrotating cases. The density distribution of the pseudodisk is little affected by rotation. On the other hand, the rotation rate is strongly modified by pseudodisk formation. Most of the centrally accreted material reaches the vicinity of the protostar through the pseudodisk. The specific angular momentum can be greatly reduced on the way, by an order of magnitude or more, even when the pre-collapse field strength is substantially below the critical value for dominant cloud support. The efficient magnetic braking is due to the pinched geometry of the magnetic field in the pseudodisk, which strengthens the magnetic field and lengthens the level arm for braking. Both effects enhance the magnetic transport of angular momentum from inside to outside. The excess angular momentum is carried away in a low-speed outflow that has, despite claims made by other workers, little in common with observed bipolar molecular outflows. We discuss the implications of our calculations for the formation of true disks that are supported against gravity by rotation.

  9. Probability of failure of the waste hoist brake system at the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect (OSTI)

    Greenfield, M.A. [Univ. of California, Los Angeles, CA (United States); Sargent, T.J. [Univ. of Chicago, IL (United States)]|[Stanford Univ., CA (United States). Hoover Institution

    1998-01-01T23:59:59.000Z

    In its most recent report on the annual probability of failure of the waste hoist brake system at the Waste Isolation Pilot Plant (WIPP), the annual failure rate is calculated to be 1.3E({minus}7)(1/yr), rounded off from 1.32E({minus}7). A calculation by the Environmental Evaluation Group (EEG) produces a result that is about 4% higher, namely 1.37E({minus}7)(1/yr). The difference is due to a minor error in the US Department of Energy (DOE) calculations in the Westinghouse 1996 report. WIPP`s hoist safety relies on a braking system consisting of a number of components including two crucial valves. The failure rate of the system needs to be recalculated periodically to accommodate new information on component failure, changes in maintenance and inspection schedules, occasional incidents such as a hoist traveling out-of-control, either up or down, and changes in the design of the brake system. This report examines DOE`s last two reports on the redesigned waste hoist system. In its calculations, the DOE has accepted one EEG recommendation and is using more current information about the component failures rates, the Nonelectronic Parts Reliability Data (NPRD). However, the DOE calculations fail to include the data uncertainties which are described in detail in the NPRD reports. The US Nuclear Regulatory Commission recommended that a system evaluation include mean estimates of component failure rates and take into account the potential uncertainties that exist so that an estimate can be made on the confidence level to be ascribed to the quantitative results. EEG has made this suggestion previously and the DOE has indicated why it does not accept the NRC recommendation. Hence, this EEG report illustrates the importance of including data uncertainty using a simple statistical example.

  10. Wakes of ram pressure stripped disc galaxies

    E-Print Network [OSTI]

    Roediger, E; Hoeft, M

    2006-01-01T23:59:59.000Z

    Spiral galaxies that move through the intracluster medium lose a substantial amount of their gas discs due to ram pressure stripping. The recent observations of NGC 4388 by Oosterloo & van Gorkom 2005 reveal a tail of stripped gas of ~ 100 kpc behind the source galaxy. We present first 3D hydrodynamical simulations of the evolution of such ram pressure stripped tails. We find that if the ICM wind does not vary significantly over a period of a few 100 Myr, subsonic galaxies produce a tail with regular features similar to a von-Karman vortex street. In this case, the tail widens systematically by about 45 kpc per 100 kpc distance behind the source galaxy. The widening rate is independent of the galaxy's inclination for a large range of inclinations. For supersonic galaxies, the tail is more irregular than for subsonic ones. The tail observed for NGC 4388 is narrower than the tails in our simulations. Reasons for this difference may be additional physical processes such as heat conduction or viscosity. In ad...

  11. Wakes of ram pressure stripped disc galaxies

    E-Print Network [OSTI]

    E. Roediger; M. Brueggen; M. Hoeft

    2006-03-21T23:59:59.000Z

    Spiral galaxies that move through the intracluster medium lose a substantial amount of their gas discs due to ram pressure stripping. The recent observations of NGC 4388 by Oosterloo & van Gorkom 2005 reveal a tail of stripped gas of ~ 100 kpc behind the source galaxy. We present first 3D hydrodynamical simulations of the evolution of such ram pressure stripped tails. We find that if the ICM wind does not vary significantly over a period of a few 100 Myr, subsonic galaxies produce a tail with regular features similar to a von-Karman vortex street. In this case, the tail widens systematically by about 45 kpc per 100 kpc distance behind the source galaxy. The widening rate is independent of the galaxy's inclination for a large range of inclinations. For supersonic galaxies, the tail is more irregular than for subsonic ones. The tail observed for NGC 4388 is narrower than the tails in our simulations. Reasons for this difference may be additional physical processes such as heat conduction or viscosity. In addition, we conclude that the observed S-shape of this tail is not due to von Karman oscillations, because this galaxy is likely to move supersonically. A reason for the observed shape may be motions in the ambient ICM. Finally, we discuss implications for the distribution of metals in the ICM due to ram pressure stipping.

  12. Hybrid Braking System for Non-Drive Axles | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't YourTransport(Fact Sheet), GeothermalGridHYDROGEND D e e pShade YourHybirdBraking System for

  13. Solar tracker motor having a fixed caliper and a translating caliper each with an electromagnetic brake system

    DOE Patents [OSTI]

    Rau, Scott James

    2013-01-29T23:59:59.000Z

    Concepts and technologies described herein provide for an accurate and cost-effective method for rotating a solar array disk for tracking the movement of the sun. According to various aspects, a motor includes a fixed caliper and a translating caliper positioned adjacent to one another. Electromagnetically controlled brakes on the translating caliper grip the solar array disk while adjacent, but spaced apart, electromagnets on the fixed caliper and the translating caliper are energized to create an attractive force that pulls the translating caliper with the solar array disk toward the fixed caliper. After reaching the fixed caliper, brakes on the fixed caliper are engaged with the disk, brakes on the translating caliper are released from the disk, and the translating caliper is pushed back to the starting location where the process repeats until the desired rotation is completed.

  14. Restoration of disc height through non-invasive spinal decompression is associated with decreased discogenic low back pain: a retrospective cohort study

    E-Print Network [OSTI]

    2010-01-01T23:59:59.000Z

    in reduction of lumbar disc prolapse by traction. Arch Physeffect of traction on lumbar disc herniations. Spine 1989,Innervation of "painful" lumbar discs. Spine 1997, 22:2342-

  15. Verification tests of the U. S. Electricar Corporation Lectric Leopard. Technical report 3 Aug-25 Sep 81

    SciTech Connect (OSTI)

    Dowgiallo, E.J. Jr; Snellings, I.R.; Chapman, R.D.

    1982-04-01T23:59:59.000Z

    The Lectric Leopard manufactured by U.S. Electricar Corporation was tested at MERADCOM as part of the Department of Energy project to verify conformity to performance standards of electric vehicles. The Leopard is a standard Fiat Strada sedan which has been converted to an electric vehicle. It is powered by 16 6-V batteries through a silicon-controlled rectifier (SCR) Controller to a 23-hp series-wound d.c. motor. It is equipped with a five-speed manual transmission, power-assisted disc brakes in the front and drum brakes in the rear. It is not equipped with regenerative braking.

  16. Nuclear stellar discs in early-type galaxies --- II. Photometric properties

    E-Print Network [OSTI]

    Cecilia Scorza; Frank C. van den Bosch

    1998-06-04T23:59:59.000Z

    Hubble Space Telescope images of two early-type galaxies harboring both nuclear and outer stellar discs are studied in detail. By means of a photometric decomposition, the images of NGC 4342 and NGC 4570 are analyzed and the photometric properties of the nuclear discs investigated. We find a continuity of properties in the parameter space defined by the central surface brightness and the scalelength of discs in spirals, S0s and embedded discs in ellipticals, in the sense that the nuclear discs extend the observed disc properties even further towards smaller scalelengths and brighter central surface brightnesses. When including the nuclear discs, disc properties span more than four orders of magnitude in both scalelength and central surface brightness. The nuclear discs studied here are the smallest and brightest stellar discs known, and as such, they are as extreme in their photometric properties as Malin I, when compared to typical galactic discs that obey Freeman's law. We discuss a possible formation scenario in which the double-disc structure observed in these galaxies has been shaped by now dissolved bars. Based on the fact that the black holes known to exist in some of these galaxies have masses comparable to those of the nuclear discs, we explore a possible link between the black holes and the nuclear discs.

  17. Friction forces on phase transition fronts

    E-Print Network [OSTI]

    Ariel Megevand

    2013-03-31T23:59:59.000Z

    In cosmological first-order phase transitions, the microscopic interaction of the phase transition fronts with non-equilibrium plasma particles manifests itself macroscopically as friction forces. In general, it is a nontrivial problem to compute these forces, and only two limits have been studied, namely, that of very slow walls and, more recently, ultra-relativistic walls which run away. In this paper we consider ultra-relativistic velocities and show that stationary solutions still exist when the parameters allow the existence of runaway walls. Hence, we discuss the necessary and sufficient conditions for the fronts to actually run away. We also propose a phenomenological model for the friction, which interpolates between the non-relativistic and ultra-relativistic values. Thus, the friction depends on two friction coefficients which can be calculated for specific models. We then study the velocity of phase transition fronts as a function of the friction parameters, the thermodynamic parameters, and the amount of supercooling.

  18. Propagating and stationary superfluid turbulent fronts

    SciTech Connect (OSTI)

    Castiglione, J.; Murphy, P.J.; Tough, J.T.; Hayot, F. [Ohio State Univ., Columbus, OH (United States)] [and others

    1995-09-01T23:59:59.000Z

    The authors have observed that the critical heat current for the transition to superfluid turbulence in weakly nonuniform circular channels depends strongly on the flow direction. This observation is particularly surprising since no other property of the turbulence appears to have such a dependence. In a nonuniform channel the critical heat current is associated with a stationary front between the laminar and turbulent flow. The authors propose a new model for super-fluid turbulent fronts which explains the asymmetry of the critical heat currents in a simple way. The model is based on the subcritical nature of the transition, and the generic description of such a bifurcation by the Ginzburg-Landau equation. As a bonus, the model also explains a long-standing problem in superfluid physics-the nature of propagating fronts in uniform channels. The results of this analysis of both the uniform and nonuniform channel data also provide new information about the vortex line drift velocity.

  19. Light-front nuclear shell-model

    SciTech Connect (OSTI)

    Johnson, M.B.

    1990-01-01T23:59:59.000Z

    I examine the effects of nuclear structure on high-energy, high-momentum transfer processes, specifically the EMC effect. For pedagogical reasons, a fictitious but simple two-body system consisting of two equal-mass particles interacting in a harmonic oscillator potential has been chosen. For this toy nucleus, I utilize a widely-used link between instant-form and light-front dynamics, formulating nuclear structure and deep-inelastic scattering consistently in the laboratory system. Binding effects are compared within conventional instant-form and light-front dynamical frameworks, with appreciable differences being found in the two cases. 20 refs.

  20. Oscillations of Thick Accretion Discs Around Black Holes - II

    E-Print Network [OSTI]

    Eduardo Rubio-Herrera; William H. Lee

    2005-05-21T23:59:59.000Z

    We present a numerical study of the global modes of oscillation of thick accretion discs around black holes. We have previously studied the case of constant distributions of specific angular momentum. In this second paper, we investigate (i) how the size of the disc affects the oscillation eigenfrequencies, and (ii) the effect of power-law distributions of angular momentum on the oscillations. In particular, we compare the oscillations of the disc with the epicyclic eigenfrequencies of a test particle with different angular momentum distributions orbiting around the central object. We find that there is a frequency shift away from the epicyclic eigenfrequency of the test particle to lower values as the size of the tori is increased. We have also studied the response of a thick accretion disc to a localized external perturbation using non constant specific angular momentum distributions within the disc. We find that in this case it is also possible (as reported previously for constant angular momentum distributions) to efficiently excite internal modes of oscillation. In fact we show here that the local perturbations excite global oscillations (acoustic p modes) closely related to the epicyclic oscillations of test particles. Our results are particularly relevant in the context of low mass X-ray binaries and microquasars, and the high frequency Quasi-Periodic Oscillations (QPOs) observed in them. Our computations make use of a Smooth Particle Hydrodynamics (SPH) code in azimuthal symmetry, and use a gravitational potential that mimics the effects of strong gravity.

  1. Silicate features in Galactic and extragalactic post-AGB discs

    E-Print Network [OSTI]

    Gielen, C; Van Winckel, H; Evans, T Lloyd; Woods, P M; Kemper, F; Marengo, M; Meixner, M; Sloan, G C; Tielens, A G G M

    2011-01-01T23:59:59.000Z

    Aims. In this paper we study the Spitzer and TIMMI2 infrared spectra of post-AGB disc sources, both in the Galaxy and the LMC. Using the observed infrared spectra we determine the mineralogy and dust parameters of the discs, and look for possible differences between the Galactic and extragalactic sources. Methods. Modelling the full spectral range observed allows us to determine the dust species present in the disc and different physical parameters such as grain sizes, dust abundance ratios, and the dust and continuum temperatures. Results. We find that all the discs are dominated by emission features of crystalline and amorphous silicate dust. Only a few sample sources show features due to CO2 gas or carbonaceous molecules such as PAHs and C60 fullerenes. Our analysis shows that dust grain processing in these discs is strong, resulting in large average grain sizes and a very high crystallinity fraction. However, we do not find any correlations between the derived dust parameters and properties of the central...

  2. Black hole mergers: do gas discs lead to spin alignment?

    E-Print Network [OSTI]

    Giuseppe Lodato; Davide Gerosa

    2012-11-01T23:59:59.000Z

    In this Letter we revisit arguments suggesting that the Bardeen-Petterson effect can coalign the spins of a central supermassive black hole binary accreting from a circumbinary (or circumnuclear) gas disc. We improve on previous estimates by adding the dependence on system parameters, and noting that the nonlinear nature of warp propagation in a thin viscous disc affects alignment. This reduces the disc's ability to communicate the warp, and can severely reduce the effectiveness of disc-assisted spin alignment. We test our predictions with a Monte Carlo realization of random misalignments and accretion rates and we find that the outcome depends strongly on the spin magnitude. We estimate a generous upper limit to the probability of alignment by making assumptions which favour it throughout. Even with these assumptions, about 40% of black holes with $a \\gtrsim 0.5$ do not have time to align with the disc. If the residual misalignment is not small and it is maintained down to the final coalescence phase this can give a powerful recoil velocity to the merged hole. Highly spinning black holes are thus more likely of being subject to strong recoils, the occurrence of which is currently debated.

  3. CityCarControl : an electric vehicle drive-by-wire solution for distributed steering, braking and throttle control

    E-Print Network [OSTI]

    Brown, Thomas B., M. Eng. Massachusetts Institute of Technology

    2010-01-01T23:59:59.000Z

    In this paper, we propose CityCarControl, a system to manage the steering, braking, and throttle of a new class of intra-city electric vehicles. These vehicles have a focus on extreme light-weight and a small parking ...

  4. Use of an auditory signal in a rear-end collision warning system: effects on braking force and reaction time

    E-Print Network [OSTI]

    Hopkins, Jennifer Susan

    1995-01-01T23:59:59.000Z

    driving game. Superimposed on the game screen was the image of a car which appeared to the driver to be ahead of him/her. The image enlarged in size, appearing to be a car applying its brakes. The participant was instructed to react as he would in a real...

  5. Uncertainty-Enabled Design of a Rocket Sled Track Switch Drs. Jordan E. Massad and Matthew R. Brake

    E-Print Network [OSTI]

    Uncertainty-Enabled Design of a Rocket Sled Track Switch Drs. Jordan E. Massad and Matthew R. Brake Sandia National Laboratories, New Mexico Rocket sled tracks provide a dynamically rich environment acceleration profile, the switch closes to complete a circuit for instrument activation. Preliminary tests

  6. Hybrid: Braking

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuels Data Center Home PageStationGreenhouse GasCalifornia State0

  7. Hybrid: Braking

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuels Data Center Home PageStationGreenhouse GasCalifornia State0Button Stopped button

  8. Hybrid: Braking

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuels Data Center HomeIdle Reduction WeightRebate -

  9. Dispersion in the lifetime and accretion rate of T Tauri discs

    E-Print Network [OSTI]

    Philip J. Armitage; Cathie J. Clarke; Francesco Palla

    2003-03-14T23:59:59.000Z

    We compare evolutionary models for protoplanetary discs that include disc winds with observational determinations of the disc lifetime and accretion rate in Taurus. Using updated estimates for stellar ages in Taurus, together with published classifications, we show that the evolution of the disc fraction with stellar age is similar to that derived for ensembles of stars within young clusters. Around 30 percent of stars lose their discs within 1 Myr, while the remainder have disc lifetimes that are typically in the 1-10 Myr range. We show that the latter range of ages is consistent with theoretical models for disc evolution, provided that there is a dispersion of around 0.5 in the log of the initial disc mass. The same range of initial conditions brackets the observed variation in the accretion rate of Classical T Tauri stars at a given age. We discuss the expected lifetime of discs in close binary systems, and show that our models predict that the disc lifetime is almost constant for separations exceeding 10 au. This implies a low predicted fraction of binaries that pair a Classical T Tauri star with a Weak-lined T Tauri star, and is in better agreement with observations of the disc lifetime in binaries than disc models that do not include disc mass loss in a wind.

  10. Accretion Discs Around Black Holes: Developement of Theory

    E-Print Network [OSTI]

    G. S. Bisnovatyi-Kogan

    1999-11-11T23:59:59.000Z

    Standard accretion disk theory is formulated which is based on the local heat balance. The energy produced by a turbulent viscous heating is supposed to be emitted to the sides of the disc. Sources of turbulence in the accretion disc are connected with nonlinear hydrodynamic instability, convection, and magnetic field. In standard theory there are two branches of solution, optically thick, and optically thin. Advection in accretion disks is described by the differential equations what makes the theory nonlocal. Low-luminous optically thin accretion disc model with advection at some suggestions may become advectively dominated, carrying almost all the energy inside the black hole. The proper account of magnetic filed in the process of accretion limits the energy advected into a black hole, efficiency of accretion should exceed $\\sim 1/4$ of the standard accretion disk model efficiency.

  11. Constraints on AGN accretion disc viscosity derived from continuum variability

    E-Print Network [OSTI]

    Rhaana L. C. Starling; Aneta Siemiginowska; Phil Uttley; Roberto Soria

    2003-09-10T23:59:59.000Z

    We estimate a value of the viscosity parameter in AGN accretion discs for the PG quasar sample. We assume that optical variability on time-scales of months to years is caused by local instabilities in the inner accretion disc. Comparing the observed variability time-scales to the thermal time-scales of alpha-disc models we obtain constraints on the viscosity parameter for the sample. We find that, at a given L/L_Edd, the entire sample is consistent with a single value of the viscosity parameter, alpha. We obtain constraints of 0.01 < alpha < 0.03 for 0.01 < L/L_Edd < 1.0. This narrow range suggests that these AGN are all seen in a single state, with a correspondingly narrow spread of black hole masses or accretion rates. The value of alpha we derive is consistent with predictions by current simulation s in which MHD turbulence is the primary viscosity mechanism.

  12. Some challenges and directions for next generation accretion disc theory

    E-Print Network [OSTI]

    Blackman, Eric G

    2015-01-01T23:59:59.000Z

    Accretion disc theory is far less developed than that of stellar evolution, although a similarly mature phenomenological picture is ultimately desired. While conceptual progress from the interplay of theory and numerical simulations has amplified awareness of the role of magnetic fields in angular momentum transport, there remains a significant gap between the output of magneto-rotational instability (MRI) simulations and the synthesis of lessons learned into improved practical models. If discs are turbulent, then axisymmetric models must be recognized to be sensible only as mean field theories. Such is the case for the wonderfully practical and widely used framework of Shakura-Sunyaev (SS73). This model is most justifiable when the radial angular momentum transport dominates in discs and the transport is assumed to take the form of a local viscosity. However, the importance of large scale fields in coronae and jets and numerical evidence from MRI simulations points to a significant fraction of transport bein...

  13. Density waves in the shearing sheet III. Disc heating

    E-Print Network [OSTI]

    B. Fuchs

    2001-04-25T23:59:59.000Z

    The problem of dynamical heating of galactic discs by spiral density waves is discussed using the shearing sheet model. The secular evolution of the disc is described quantitatively by a diffusion equation for the distribution function of stars in the space spanned by integrals of motion of the stars, in particular the radial action integral and an integral related to the angular momentum. Specifically, disc heating by a succession of transient, `swing amplified' density waves is studied. It is shown that such density waves lead predominantly to diffusion of stars in radial action space. The stochastical changes of angular momenta of the stars and the corresponding stochastic changes of the guiding centre radii of the stellar orbits induced by this process are much smaller.

  14. Solution of the H3+ model on a disc

    E-Print Network [OSTI]

    Kazuo Hosomichi; Sylvain Ribault

    2007-01-17T23:59:59.000Z

    We determine all the correlators of the H3+ model on a disc with AdS2-brane boundary conditions in terms of correlators of Liouville theory on a disc with FZZT-brane boundary conditions. We argue that the Cardy-Lewellen constraints are weaker in the H3+ model than in rational conformal field theories due to extra singularities of the correlators, but strong enough to uniquely determine the bulk two-point function on a disc. We confirm our results by detailed analyses of the bulk-boundary two-point function and of the boundary two-point function. In particular we find that, although the target space symmetry preserved by AdS2-branes is the group SL(2,R), the open string states between two distinct parallel AdS2-branes belong to representations of the universal covering group.

  15. Dust trapping by spiral arms in gravitationally unstable protostellar discs

    E-Print Network [OSTI]

    Dipierro, Giovanni; Lodato, Giuseppe; Testi, Leonardo

    2015-01-01T23:59:59.000Z

    In this paper we discuss the influence of gravitational instabilities in massive protostellar discs on the dynamics of dust grains. Starting from a Smoothed Particle Hydrodynamics (SPH) simulation, we have computed the evolution of the dust in a quasi-static gas density structure typical of self-gravitating disc. For different grain size distributions we have investigated the capability of spiral arms to trap particles. We have run 3D radiative transfer simulations in order to construct maps of the expected emission at (sub-)millimetre and near-infrared wavelengths. Finally, we have simulated realistic observations of our disc models at (sub-)millimetre and near-infrared wavelengths as they may appear with the Atacama Large Millimetre/sub-millimetre Array (ALMA) and the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) in order to investigate whether there are observational signatures of the spiral structure. We find that the pressure inhomogeites induced by gravitational instabilities produce a...

  16. Abundances of metal-weak thick-disc candidates

    E-Print Network [OSTI]

    P. Bonifacio; M. Centurion; P. Molaro

    1999-06-03T23:59:59.000Z

    High resolution spectra of 5 candidate metal-weak thick-disc stars suggested by Beers & Sommer-Larsen (1995) are analyzed to determine their chemical abundances. The low abundance of all the objects has been confirmed with metallicity reaching [Fe/H]=-2.9. However, for three objects, the astrometric data from the Hipparcos catalogue suggests they are true halo members. The remaining two, for which proper-motion data are not available, may have disc-like kinematics. It is therefore clear that it is useful to address properties of putative metal-weak thick-disc stars only if they possess full kinematic data. For CS 22894-19 the abundance pattern similar to those of typical halo stars is found, suggesting that chemical composition is not a useful discriminant between thick-disc and halo stars. CS 29529-12 is found to be C enhanced with [C/Fe]=+1.0; other chemical peculiarities involve the s process elements: [Sr/Fe]=-0.65 and [Ba/Fe]=+0.62, leading to a high [Ba/Sr] considerably larger than what is found in more metal-rich carbon-rich stars, but similar to LP 706-7 and LP 625-44 discussed by Norris et al (1997a). Hipparcos data have been used to calculate the space velocities of 25 candidate metal-weak thick-disc stars, thus allowing us to identify 3 bona fide members, which support the existence of a metal-poor tail of the thick-disc, at variance with a claim to the contrary by Ryan & Lambert (1995).

  17. Is the Dark Disc contribution to Dark Matter Signals important ?

    E-Print Network [OSTI]

    Fu-Sin Ling

    2010-07-11T23:59:59.000Z

    Recent N-body simulations indicate that a thick disc of dark matter, co-rotating with the stellar disc, forms in a galactic halo after a merger at a redshift $zdisc component in the Milky Way could affect dramatically dark matter signals in direct and indirect detection. In this letter, we discuss the possible signal enhancement in connection with the characteristics of the local velocity distributions. We argue that the enhancement is rather mild, but some subtle effects may arise. In particular, the annual modulation observed by DAMA becomes less constrained by other direct detection experiments.

  18. Probing self-gravitating protostellar discs using smoothed particle hydrodynamics and radiative transfer

    E-Print Network [OSTI]

    Forgan, Duncan Hugh

    2011-01-01T23:59:59.000Z

    Stars are likely to form with non-zero initial angular momentum, and will consequently possess a substantial gaseous protostellar disc in the early phases of their evolution. At this early stage, the disc mass is expected ...

  19. The effect of cooling on the global stability of self-gravitating protoplanetary discs

    E-Print Network [OSTI]

    W. K. M. Rice; P. J. Armitage; M. R. Bate; I. A. Bonnell

    2002-11-05T23:59:59.000Z

    Using a local model Gammie (2001) has shown that accretion discs with cooling times t_cool 3/Omega evolve into a quasi-steady state. We use three-dimensional smoothed particle hydrodynamic simulations of protoplanetary accretion discs to test if the local results hold globally. We find that for disc masses appropriate for T Tauri discs, the fragmentation boundary still occurs at a cooling time close to t_cool = 3/Omega. For more massive discs, which are likely to be present at an earlier stage of the star formation process, fragmentation occurs for longer cooling times, but still within a factor of two of that predicted using a local model. These results have implications not only for planet formation in protoplanetary discs and star formation in AGN discs, but also for the redistribution of angular momentum which could be driven by the presence of relatively massive objects within the accretion disc.

  20. Front-end electronics and trigger systems - status and challenges

    E-Print Network [OSTI]

    Spieler, Helmuth G

    2008-01-01T23:59:59.000Z

    of the 12th Workshop on Electronics For LHC and Future19-24, 2007 Front-end electronics and trigger systems about a revolution in front-end electronics for large- scale

  1. A correspondence between H3+ WZW and Liouville theories on discs

    E-Print Network [OSTI]

    Kazuo Hosomichi

    2007-01-29T23:59:59.000Z

    We discuss how the disc correlators of H3+ WZW model are determined in terms of those of Liouville theory.

  2. The Formation and Survival of Discs in a Lambda-CDM Universe

    E-Print Network [OSTI]

    Cecilia Scannapieco; Simon D. M. White; Volker Springel; Patricia B. Tissera

    2009-04-03T23:59:59.000Z

    We study the formation of galaxies in a Lambda-CDM Universe using high resolution hydrodynamical simulations with a multiphase treatment of gas, cooling and feedback, focusing on the formation of discs. Our simulations follow eight haloes similar in mass to the Milky Way and extracted from a large cosmological simulation without restriction on spin parameter or merger history. This allows us to investigate how the final properties of the simulated galaxies correlate with the formation histories of their haloes. We find that, at z = 0, none of our galaxies contain a disc with more than 20 per cent of its total stellar mass. Four of the eight galaxies nevertheless have well-formed disc components, three have dominant spheroids and very small discs, and one is a spheroidal galaxy with no disc at all. The z = 0 spheroids are made of old stars, while discs are younger and formed from the inside-out. Neither the existence of a disc at z = 0 nor the final disc-to-total mass ratio seems to depend on the spin parameter of the halo. Discs are formed in haloes with spin parameters as low as 0.01 and as high as 0.05; galaxies with little or no disc component span the same range in spin parameter. Except for one of the simulated galaxies, all have significant discs at z > ~2, regardless of their z = 0 morphologies. Major mergers and instabilities which arise when accreting cold gas is misaligned with the stellar disc trigger a transfer of mass from the discs to the spheroids. In some cases, discs are destroyed, while in others, they survive or reform. This suggests that the survival probability of discs depends on the particular formation history of each galaxy. A realistic Lambda-CDM model will clearly require weaker star formation at high redshift and later disc assembly than occurs in our models.

  3. Collapse of Magnetized Singular Isothermal Toroids: II. Rotation and Magnetic Braking

    E-Print Network [OSTI]

    Allen, A; Shu, F H

    2003-01-01T23:59:59.000Z

    We study numerically the collapse of rotating, magnetized molecular cloud cores, focusing on rotation and magnetic braking during the main accretion phase of isolated star formation. Motivated by previous numerical work and analytic considerations, we idealize the pre-collapse core as a magnetized singular isothermal toroid, with a constant rotational speed everywhere. The collapse starts from the center, and propagates outwards in an inside-out fashion, satisfying exact self-similarity in space and time. For rotation rates and field strengths typical of dense low-mass cores, the main feature remains the flattening of the mass distribution along field lines -- the formation of a pseudodisk, as in the nonrotating cases. The density distribution of the pseudodisk is little affected by rotation. On the other hand, the rotation rate is strongly modified by pseudodisk formation. Most of the centrally accreted material reaches the vicinity of the protostar through the pseudodisk. The specific angular momentum can b...

  4. Developments on the CENS Structural Health Monitoring Front (SEI 2)

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    on the CENS Structural Health Monitoring Front M. Kohler, J.framework for structural health monitoring (SHM). hea lth

  5. Mechanical front wheel drive tractors: a field performance study

    E-Print Network [OSTI]

    Babacz, William Adam

    1986-01-01T23:59:59.000Z

    . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of 2WD and NFWD Tractors . . . . . . . . . . . . . . . . . . Comparison of NFWD Tractors Operating in FWA and 2WO Modes III TRACTOR PERFORNANCE NONITORING SYSTEM Instrumentation System Rear Axle Torque . Front Axle Driveline Torque Front...-sized tractors and may be operated with the mechanical front wheel drive engaged in a front wheel assist (FWA) mode or disengaged in a two-wheel drive (2WD) mode. The advertised benefits of NFWD are increased traction and reduced fuel consumption. Agricultural...

  6. Comparison of alternative methods for deriving hydraulic properties and scaling factors from single-disc tension

    E-Print Network [OSTI]

    Mohanty, Binayak P.

    Comparison of alternative methods for deriving hydraulic properties and scaling factors from single-disc] Analysis of single-disc tension infiltrometer data is commonly based on the interpretation of the steady and the time needed to wet the contact sand under the disc was successfully filtered from the raw data using

  7. A laboratory plasma experiment for studying magnetic dynamics of accretion discs and jets

    E-Print Network [OSTI]

    Hsu, Scott

    A laboratory plasma experiment for studying magnetic dynamics of accretion discs and jets S. C. Hsu into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a collimated plasma, similar to MHD models of disc jets, and also

  8. Feedback in simulations of disc-galaxy major mergers

    E-Print Network [OSTI]

    T. J. Cox; Patrik Jonsson; Joel R. Primack; Rachel S. Somerville

    2007-09-25T23:59:59.000Z

    Using hydrodynamic simulations of disc-galaxy major mergers, we investigate the star formation history and remnant properties when various parametrizations of a simple stellar feedback model are implemented. The simulations include radiative cooling, a density-dependent star formation recipe and a model for feedback from massive stars. The feedback model stores supernova feedback energy within individual gas particles and dissipates this energy on a time-scale specified by two free parameters; tau_fb, which sets the dissipative time-scale, and n, which sets the effective equation of state in star-forming regions. Using a self-consistent disc galaxy, modelled after a local Sbc spiral, in both isolated and major-merger simulations, we investigate parametrizations of the feedback model that are selected with respect to the quiescent disc stability. These models produce a range of star formation histories that are consistent with the star formation relation found by Kennicutt. All major mergers produce a population of new stars that is highly centrally concentrated, demonstrating a distinct break in the r1/4 surface density profile, consistent with previous findings. The half-mass radius and one-dimensional velocity dispersion are affected by the feedback model used. Finally, we compare our results to those of previous simulations of star formation in disc-galaxy major mergers, addressing the effects of star formation normalization, the version of smoothed particle hydrodynamics (SPH) employed and assumptions about the interstellar medium.

  9. NIHAO III: The constant disc gas mass conspiracy

    E-Print Network [OSTI]

    Stinson, G S; Wang, L; Macci, A V; Herpich, J; Bradford, J D; Quinn, T R; Wadsley, J; Keller, B

    2015-01-01T23:59:59.000Z

    We show that the cool gas masses of galactic discs reach a steady state that lasts many Gyr after their last major merger in cosmological hydrodynamic simulations. The mass of disc gas, M$_{\\rm gas}$, depends upon a galaxy halo's spin and virial mass, but not upon stellar feedback. Halos with low spin have high star formation efficiency and lower disc gas mass. Similarly, lower stellar feedback leads to more star formation so the gas mass ends up nearly the same irregardless of stellar feedback strength. Even considering spin, the M$_{\\rm gas}$ relation with halo mass, M$_{200}$ only shows a factor of 3 scatter. The M$_{\\rm gas}$--M$_{200}$ relation show a break at M$_{200}$=$2\\times10^{11}$ M$_\\odot$ that corresponds to an observed break in the M$_{\\rm gas}$--M$_\\star$ relation. The constant disc mass stems from a shared halo gas density profile in all the simulated galaxies. In their outer regions, the profiles are isothermal. Where the profile rises above $n=10^{-3}$ cm$^{-3}$, the gas readily cools and th...

  10. A fast algorithm for random sequential adsorption of discs

    E-Print Network [OSTI]

    Jian-Sheng WANG

    1994-02-17T23:59:59.000Z

    An efficient algorithm for random sequential adsorption of hard discs in two dimensions is implemented. A precise value for the coverage is obtained: theta(infty) = 0.547069. The asymptotic law theta(t) = theta(infty) - ct^{-1/2} is verified to a high accuracy. Pair correlation function is analyzed.

  11. Solution of the Percus-Yevick equation for hard discs

    E-Print Network [OSTI]

    M. Adda-Bedia; E. Katzav; D. Vella

    2008-01-31T23:59:59.000Z

    We solve the Percus-Yevick equation in two dimensions by reducing it to a set of simple integral equations. We numerically obtain both the pair correlation function and the equation of state for a hard disc fluid and find good agreement with available Monte-Carlo calculations. The present method of resolution may be generalized to any even dimension.

  12. Pentan isomers compound flame front structure

    SciTech Connect (OSTI)

    Mansurov, Z.A.; Mironenko, A.W.; Bodikov, D.U.; Rachmetkaliev, K.N. [Kazakh Al-Farabi State National Univ., Almaty (Kazakhstan)

    1995-08-13T23:59:59.000Z

    The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to the side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.

  13. Interaction Dynamics of Singular Wave Fronts

    E-Print Network [OSTI]

    Holm, Darryl D

    2013-01-01T23:59:59.000Z

    Some of the most impressive singular wave fronts seen in Nature are the transbasin oceanic internal waves, which may be observed from the Space Shuttle as they propagate and interact with each other, for example, in the South China Sea. The characteristic feature of these strongly nonlinear wavefronts is that they reconnect when two of them collide transversely. We derive the EPDiff equation, and use it to model this phenomenon as elastic collisions between singular wave fronts (solitons) whose momentum is distributed along curves moving in the plane. Numerical methods for EPDiff based on compatible differencing algorithms (CDAs) are used for simulating these collisions among curves. The numerical results show the same nonlinear behavior of wavefront reconnections as that observed for internal waves in the South China Sea. We generalize the singular solutions of EPDiff for other applications, in computational anatomy and in imaging science, where the singular wavefronts are evolving image outlines, whose mome...

  14. Front contact solar cell with formed emitter

    DOE Patents [OSTI]

    Cousins, Peter John

    2014-11-04T23:59:59.000Z

    A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

  15. Front contact solar cell with formed emitter

    DOE Patents [OSTI]

    Cousins, Peter John (Menlo Park, CA)

    2012-07-17T23:59:59.000Z

    A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

  16. Light-front chiral effective field theory

    SciTech Connect (OSTI)

    Mathiot, J.-F. [Laboratoire de Physique Corpusculaire (France)] [Laboratoire de Physique Corpusculaire (France); Tsirova, N. A., E-mail: ntsirova@ssu.samara.ru [Samara State University (Russian Federation)

    2013-11-15T23:59:59.000Z

    We propose a general framework to calculate the nonperturbative structure of relativistic bound state systems. The state vector of the bound state is calculated in the covariant formulation of light-front dynamics. In this scheme, the state vector is defined on the light front of general position {omega} {center_dot} x = 0, where {omega} is an arbitrary light-like four-vector. This enables a strict control of any violation of rotational invariance. The state vector is then decomposed in Fock components. Our formalism is applied to the description of the nucleon properties at low energy, in chiral perturbation theory. We also show that the use of a recently proposed regularization scheme, the so-called Taylor-Lagrange regularization scheme, is very adequate in order to treat divergences in this nonperturbative framework.

  17. Colloid Formation at Waste Plume Fronts

    SciTech Connect (OSTI)

    Wan, Jiamin; Tokunaga, Tetsu K.; Saiz, Eduardo; Larsen, Joern T.; Zheng, Zuoping; Couture, Rex A.

    2004-05-22T23:59:59.000Z

    Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U. S. Department of Energy (DOE) facilities such as the Hanford Site (Washington State). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass%, and their particle-sizes ranged from tens of nm to a few {micro}m. Colloid chemical composition and mineralogy depended on temperature. During infiltration of the leaked high Na{sup +} waste solution, rapid and completed Na{sup +} replacement of exchangeable Ca{sup 2+} and Mg{sup 2+} from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca{sup 2+}/Mg{sup 2+}-bearing minerals caused dramatic pH reduction at the plume front. In turn, the reduced pH caused precipitation of other minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions, and could not have been obtained through conventional batch studies.

  18. Design Principles of a flywheel Regenerative Braking System (f-RBS) for Formula SAE type racecar and system testing on a Virtual Test Rig modeled on MSC ADAMS

    E-Print Network [OSTI]

    Pochiraju, Anirudh

    2012-08-31T23:59:59.000Z

    This thesis presents a flywheel based mechanical regenerative braking system (RBS) concept for a Formula SAE type race car application, to improve the performance and/or efficiency of the racecar. A mechanical system is chosen to eliminate losses...

  19. Jupiter and Super-Earth embedded in a gaseous disc

    E-Print Network [OSTI]

    E. Podlewska; E. Szuszkiewicz

    2007-12-19T23:59:59.000Z

    In this paper we investigate the evolution of a pair of interacting planets - a Jupiter mass planet and a Super-Earth with the 5.5 Earth masses - orbiting a Solar type star and embedded in a gaseous protoplanetary disc. We focus on the effects of type I and II orbital migrations, caused by the planet-disc interaction, leading to the Super-Earth capture in first order mean motion resonances by the Jupiter. The stability of the resulting resonant system in which the Super-Earth is on the internal orbit relatively to the Jupiter has been studied numerically by means of full 2D hydrodynamical simulations. Our main motivation is to determine the Super-Earth behaviour in the presence of the gas giant in the system. It has been found that the Jupiter captures the Super-Earth into the interior 3:2 or 4:3 mean motion resonances and the stability of such configurations depends on the initial planet positions and eccentricity evolution. If the initial separation of planet orbits is larger or close to that required for the exact resonance than the final outcome is the migration of the pair of planets with the rate similar to that of the gas giant at least for time of our simulations. Otherwise we observe a scattering of the Super-Earth from the disc. The evolution of planets immersed in the gaseous disc has been compared with their behaviour in the case of the classical three-body problem when the disc is absent.

  20. Surface density profiles of collisionless disc merger remnants

    E-Print Network [OSTI]

    Thorsten Naab; Ignacio Trujillo

    2006-03-01T23:59:59.000Z

    We present a detailed surface density analysis of a large sample of simulated collisionless mergers of disc galaxies with bulges (mass ratios 1:1, 2:1, 3:1, 4:1, and 6:1) and without bulges (mass ratios 1:1 and 3:1). They were classified, according to their bulge--to--total ($B/T$) ratio, either as a one-component system or as a two-component systems. In general projection effects change the classification of a remnant. Only merger remnants of discs with bulges show properties similar to observed early--type galaxies. Their B/T ratios are in the range $0.2discs for 6:1 remnants. We found distinct correlations between the fitting parameters which are very similar to observed relations (e.g. larger bulges have lower effective surface densities). No indications for a correlation between the surface density profiles and other global parameters are found. The remnants have properties similar to giant elliptical galaxies in the intermediate mass regime. A binary disc merger origin for all early-type galaxies, especially the most massive ones, is unlikely. Observed nearby merger remnants have properties similar to the simulated remnants. They can have formed from binary disc mergers and might evolve into early--type galaxies within a few Gyrs (abbreviated).

  1. Migration of massive black hole binaries in self--gravitating accretion discs: Retrograde versus prograde

    E-Print Network [OSTI]

    Constanze Roedig; Alberto Sesana

    2013-07-24T23:59:59.000Z

    We study the interplay between mass transfer, accretion and gravitational torques onto a black hole binary migrating in a self-gravitating, retrograde circumbinary disc. A direct comparison with an identical prograde disc shows that: (i) because of the absence of resonances, the cavity size is a factor a(1+e) smaller for retrograde discs; (ii) nonetheless the shrinkage of a circular binary semi--major axis, a, is identical in both cases; (iii) a circular binary in a retrograde disc remains circular while eccentric binaries grow more eccentric. For non-circular binaries, we measure the orbital decay rates and the eccentricity growth rates to be exponential as long as the binary orbits in the plane of its disc. Additionally, for these co-planar systems, we find that interaction (~ non--zero torque) stems only from the cavity edge plus a(1+e) in the disc, i.e. for dynamical purposes, the disc can be treated as a annulus of small radial extent. We find that simple 'dust' models in which the binary- disc interaction is purely gravitational can account for all main numerical results, both for prograde and retrograde discs. Furthermore, we discuss the possibility of an instability occurring for highly eccentric binaries causing it to leave the disc plane, secularly tilt and converge to a prograde system. Our results suggest that there are two stable configurations for binaries in self-gravitating discs: the special circular retrograde case and an eccentric (e~ 0.6) prograde configuration as a stable attractor.

  2. Time-dependent models of two-phase accretion discs around black holes

    E-Print Network [OSTI]

    M. Mayer; J. E. Pringle

    2006-12-28T23:59:59.000Z

    We present time-dependent simulations of a two-phase accretion flow around a black hole. The accretion flow initially is composed of an optically thick and cool disc close to the midplane, while on top and below the disc there is a hot and optically thin corona. We consider several interaction mechanisms as heating of the disc by the corona and Compton cooling of the corona by the soft photons of the disc. Mass and energy can be exchanged between the disc and the corona due to thermal conduction. For the course of this more exploratory work, we limit ourselves to one particular model for a stellar mass black hole accreting at a low accretion rate. We confirm earlier both theoretical and observational results which show that at low accretion rates the disc close to the black hole cannot survive and is evaporated. Given the framework of this model, we now can follow through this phase of disc evaporation time dependently.

  3. Chemo-spectrophotometric evolution of spiral galaxies: III. Abundance and colour gradients in discs

    E-Print Network [OSTI]

    N. Prantzos; S. Boissier

    1999-11-07T23:59:59.000Z

    We study the relations between luminosity and chemical abundance profiles of spiral galaxies, using detailed models for the chemical and spectro-photometric evolution of galactic discs. The models are ``calibrated'' on the Milky Way disc and are successfully extended to other discs with the help of simple ``scaling'' relations, obtained in the framework of semi-analytic models of galaxy formation. We find that our models exhibit oxygen abundance gradients that increase in absolute value with decreasing disc luminosity (when expressed in dex/kpc) and are independent of disc luminosity (when expressed in dex/scalelength), both in agreement with observations. We notice an important strong correlation between abundance gradient and disc scalelength. These results support the idea of ``homologuous evolution'' of galactic discs.

  4. A Braking Index for the Young, High-Magnetic-Field, Rotation-Powered Pulsar in Kes 75

    E-Print Network [OSTI]

    Margaret A. Livingstone; Victoria M. Kaspi; E. V. Gotthelf; Lucien Kuiper

    2006-04-21T23:59:59.000Z

    We present the first phase-coherent measurement of a braking index for the young, energetic rotation-powered pulsar PSR J1846-0258. This 324 ms pulsar is located at the center of the supernova remnant Kes 75 and has a characteristic age of tau_c = 723 years, a spin-down energy of 8.3x10^{36}erg/s, and inferred magnetic field of 4.9x10^{13} G. Two independent phase-coherent timing solutions are derived which together span 5.5 yr of data obtained with the Rossi X-ray Timing Explorer. In addition, a partially phase-coherent timing analysis confirms the fully phase-coherent result. The measured value of the braking index, n=2.65+/-0.01, is significantly less than 3, the value expected from magnetic dipole radiation, implying another physical process must contribute to the pulsar's rotational evolution. Assuming the braking index has been constant since birth, we place an upper limit on the spin-down age of J1846-0258 of 884 yr, the smallest age estimate of any rotation-powered pulsar.

  5. Nonperturbative calculations in light-front QED

    SciTech Connect (OSTI)

    Chabysheva, Sophia S. [Department of Physics, University of Minnesota-Duluth, Duluth, Minnesota 55812 (United States)

    2010-12-22T23:59:59.000Z

    The methods of light-front quantization and Pauli-Villars regularization are applied to a nonperturbative calculation of the dressed-electron state in quantum electrodynamics. This is intended as a test of the methods in a gauge theory, as a precursor to possible methods for the nonperturbative solution of quantum chromodynamics. The electron state is truncated to include at most two photons and no positrons in the Fock basis, and the wave functions of the dressed state are used to compute the electrons's anomalous magnetic moment. A choice of regularization that preserves the chiral symmetry of the massless limit is critical for the success of the calculation.

  6. Front Range Energy LLC | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnual SiteofEvaluating A PotentialJumpGermanFife EnergyFreight Best PracticeFrey| Open EnergyFront

  7. On the black hole limit of rotating discs and rings

    E-Print Network [OSTI]

    Andreas Kleinwchter; Hendrick Labranche; Reinhard Meinel

    2010-07-20T23:59:59.000Z

    Solutions to Einstein's field equations describing rotating fluid bodies in equilibrium permit parametric (i.e. quasi-stationary) transitions to the extreme Kerr solution (outside the horizon). This has been shown analytically for discs of dust and numerically for ring solutions with various equations of state. From the exterior point of view, this transition can be interpreted as a (quasi) black hole limit. All gravitational multipole moments assume precisely the values of an extremal Kerr black hole in the limit. In the present paper, the way in which the black hole limit is approached is investigated in more detail by means of a parametric Taylor series expansion of the exact solution describing a rigidly rotating disc of dust. Combined with numerical calculations for ring solutions our results indicate an interesting universal behaviour of the multipole moments near the black hole limit.

  8. Disc amplitudes, picture changing and space-time actions

    E-Print Network [OSTI]

    Katrin Becker; Guangyu Guo; Daniel Robbins

    2011-06-16T23:59:59.000Z

    We study in detail the procedure for obtaining couplings of D-branes to closed string fields by evaluating string theory disc amplitudes. We perform a careful construction of the relevant vertex operators and discuss the effects of inserting the boundary state which encodes the presence of the D-brane. We confront the issue of non-decoupling of BRST-exact states and prove that the problem is evaded for the computations we need, thus demonstrating that our amplitudes are automatically gauge-invariant and independent of the distribution of picture charge. Finally, we compute explicitly the two-point amplitudes of two NS-NS fields or one NS-NS and one R-R field on the disc, and we carefully compare all the lowest order terms with predictions from supergravity.

  9. Characterising the Gravitational Instability in Cooling Accretion Discs

    E-Print Network [OSTI]

    Peter Cossins; Giuseppe Lodato; Cathie Clarke

    2008-11-21T23:59:59.000Z

    We perform numerical analyses of the structure induced by gravitational instabilities in cooling gaseous accretion discs. For low enough cooling rates a quasi-steady configuration is reached, with the instability saturating at a finite amplitude in a marginally stable disc. We find that the saturation amplitude scales with the inverse square root of the cooling parameter beta = t_cool / t_dyn, which indicates that the heating rate induced by the instability is proportional to the energy density of the induced density waves. We find that at saturation the energy dissipated per dynamical time by weak shocks due is of the order of 20 per cent of the wave energy. From Fourier analysis of the disc structure we find that while the azimuthal wavenumber is roughly constant with radius, the mean radial wavenumber increases with radius, with the dominant mode corresponding to the locally most unstable wavelength. We demonstrate that the density waves excited in relatively low mass discs are always close to co-rotation, deviating from it by approximately 10 per cent. This can be understood in terms of the flow Doppler-shifted phase Mach number -- the pattern speed self-adjusts so that the flow into spiral arms is always sonic. This has profound effects on the degree to which transport through self-gravity can be modelled as a viscous process. Our results thus provide (a) a detailed description of how the self-regulation mechanism is established for low cooling rates, (b) a clarification of the conditions required for describing the transport induced by self-gravity through an effective viscosity, (c) an estimate of the maximum amplitude of the density perturbation before fragmentation occurs, and (d) a simple recipe to estimate the density perturbation in different thermal regimes.

  10. Mirror Symmetry, D-Branes and Counting Holomorphic Discs

    E-Print Network [OSTI]

    Mina Aganagic; Cumrun Vafa

    2000-12-05T23:59:59.000Z

    We consider a class of special Lagrangian subspaces of Calabi-Yau manifolds and identify their mirrors, using the recent derivation of mirror symmetry, as certain holomorphic varieties of the mirror geometry. This transforms the counting of holomorphic disc instantons ending on the Lagrangian submanifold to the classical Abel-Jacobi map on the mirror. We recover some results already anticipated as well as obtain some highly non-trivial new predictions.

  11. Radial mixing and the transition between the thick and thin Galactic discs

    E-Print Network [OSTI]

    Misha Haywood

    2008-05-13T23:59:59.000Z

    The analysis of the kinematics of solar neighbourhood stars shows that the low and high metallicity tails of the thin disc are populated by objects which orbital properties suggest an origin in the outer and inner galactic disc, respectively. Signatures of radial migration are identified in various recent samples, and are shown to be responsible for the high metallicity dispersion in the age-metallicity distribution. Most importantly, it is shown that the population of low metallicity wanderers of the thin disc (-0.7disc (which terminal metallicity is about -0.2 dex). It implies that the thin disc at the solar circle has started to form stars at about this same metallicity. This is also consistent with the fact that 'transition' objects, which have alpha-element abundance intermediate between that of the thick and thin discs, are found in the range [-0.4,-0.2] dex. Once the metal-poor thin disc stars are recognised for what they are - wanderers from the outer thin disc - the parenthood between the two discs can be identified on stars genuinely formed at the solar circle through an evolutionary sequence in [alpha/Fe] and [Fe/H] . Another consequence is that stars that can be considered as truly resulting of the chemical evolution at the solar circle have a metallicity restricted to about [-0.2,+0.2] dex, confirming an old idea that most chemical evolution in the Milky Way have preceded the thin disc formation.

  12. Warped discs and the directional stability of jets in Active Galactic Nuclei

    E-Print Network [OSTI]

    Priyamvada Natarajan; Philip J. Armitage

    1999-06-27T23:59:59.000Z

    Warped accretion discs in Active Galactic Nuclei (AGN) exert a torque on the black hole that tends to align the rotation axis with the angular momentum of the outer disc. We compute the magnitude of this torque by solving numerically for the steady state shape of the warped disc, and verify that the analytic solution of Scheuer and Feiler (1996) provides an excellent approximation. We generalise these results for discs with strong warps and arbitrary surface density profiles, and calculate the timescale on which the black hole becomes aligned with the angular momentum in the outer disc. For massive holes and accretion rates of the order of the Eddington limit the alignment timescale is always short (less than a Myr), so that jets accelerated from the inner disc region provide a prompt tracer of the angular momentum of gas at large radii in the disc. Longer timescales are predicted for low luminosity systems, depending on the degree of anisotropy in the disc's hydrodynamic response to shear and warp, and for the final decay of modest warps at large radii in the disc that are potentially observable via VLBI. We discuss the implications of this for the inferred accretion history of those Active Galactic Nuclei whose jet directions appear to be stable over long timescales. The large energy deposition rate at modest disc radii during rapid realignment episodes should make such objects transiently bright at optical and infrared wavelengths.

  13. Three dimensional SPH simulations of radiation-driven warped accretion discs

    E-Print Network [OSTI]

    Stephen B. Foulkes; Carole A. Haswell; James R. Murray

    2006-01-06T23:59:59.000Z

    We present three dimensional smoothed particle hydrodynamics (SPH) calculations of warped accretion discs in X-ray binary systems. Geometrically thin, optically thick accretion discs are illuminated by a central radiation source. This illumination exerts a non-axisymmetric radiation pressure on the surface of the disc resulting in a torque that acts on the disc to induce a twist or warp. Initially planar discs are unstable to warping driven by the radiation torque and in general the warps also precess in a retrograde direction relative to the orbital flow. We simulate a number of X-ray binary systems which have different mass ratios using a number of different luminosities for each. Radiation-driven warping occurs for all systems simulated. For mass ratios q ~ 0.1 a moderate warp occurs in the inner disc while the outer disc remains in the orbital plane (c.f. X 1916-053). For less extreme mass ratios the entire disc tilts out of the orbital plane (c.f. Her X-1). For discs that are tilted out of the orbital plane in which the outer edge material of the disc is precessing in a prograde direction we obtain both positive and negative superhumps simultaneously in the dissipation light curve (c.f. V603 Aql).

  14. Methanol Along the Path from Envelope to Protoplanetary Disc

    E-Print Network [OSTI]

    Drozdovskaya, Maria N; Visser, Ruud; Harsono, Daniel; van Dishoeck, Ewine F

    2014-01-01T23:59:59.000Z

    Interstellar methanol is considered to be a parent species of larger, more complex organic molecules. A physicochemical simulation of infalling parcels of matter is performed for a low-mass star-forming system to trace the chemical evolution from cloud to disc. An axisymmetric 2D semi-analytic model generates the time-dependent density and velocity distributions, and full continuum radiative transfer is performed to calculate the dust temperature and the UV radiation field at each position as a function of time. A comprehensive gas-grain chemical network is employed to compute the chemical abundances along infall trajectories. Two physical scenarios are studied, one in which the dominant disc growth mechanism is viscous spreading, and another in which continuous infall of matter prevails. The results show that the infall path influences the abundance of methanol entering each type of disc, ranging from complete loss of methanol to an enhancement by a factor of > 1 relative to the prestellar phase. Critical ch...

  15. Global m=1 modes and migration of protoplanetary cores in eccentric protoplanetary discs

    E-Print Network [OSTI]

    J. C. B. Papaloizou

    2002-04-11T23:59:59.000Z

    We calculate global $m=1$ modes with low pattern speed corresponding to introducing a finite eccentricity into a protoplanetary disc. We consider disc models which are either isolated or contain one or two protoplanets orbiting in an inner cavity. Global modes that are strongly coupled to inner protoplanets are found to have disc orbits which tend to have apsidal lines antialigned with respect to those of the inner protoplanets. Other modes corresponding to free disc modes may be global over a large range of length scales and accordingly be long lived. We consider the motion of a protoplanet in the earth mass range embedded in an eccentric disc and determine the equilibrium orbits which maintain fixed apsidal alignment with respect to the disc gas orbits. Equilibrium eccentricities are found to be comparable or possibly exceed the disc eccentricity. We then approximately calculate the tidal interaction with the disc in order to estimate the orbital migration rate. Results are found to deviate from the case of axisymmetric disc with near circular protoplanet orbit once eccentricities of protoplanet and disc orbits become comparable to the disc aspect ratio in magnitude. Aligned protoplanet orbits with very similar eccentricity to that of the gas disc are found to undergo litle eccentricity change while undergoing inward migration in general. However, for significantly larger orbital eccentricities, migration may be significantly reduced or even reverse from inwards to outwards. Thus the existence of global non circular motions in discs with radial excursions comparable to the semi-thickness may have important consequences for the migration and survival of protoplanetary cores in the earth mass range.

  16. "By the hundred's of thousand's, these unlikely transportation revolutionaries are forgoing the safety of a steel cage with airbags and anti-lock brakes for a wispy two-wheeled exoskeleton as they make their way to work,

    E-Print Network [OSTI]

    Duchowski, Andrew T.

    the safety of a steel cage with airbags and anti-lock brakes for a wispy two-wheeled exoskeleton as they make

  17. Identifying Lagrangian fronts with favourable fishery conditions

    E-Print Network [OSTI]

    S. V. Prants; M. V. Budyansky; M. Yu. Uleysky

    2013-06-20T23:59:59.000Z

    Lagrangian fronts (LF) in the ocean delineate boundaries between surface waters with different Lagrangian properties. They can be accurately detected in a given velocity field by computing synoptic maps of the drift of synthetic tracers and other Lagrangian indicators. Using Russian ship's catch and location data for a number of commercial fishery seasons in the region of the northwest Pacific with one of the richest fishery in the world, it is shown statistically that the saury fishing grounds with maximal catches are not randomly distributed over the region but located mainly along those LFs where productive cold waters of the Oyashio Current, warmer waters of the southern branch of the Soya Current, and waters of warm-core Kuroshio rings converge. Computation of those fronts with the altimetric geostrophic velocity fields both in the years with the First and Second Oyashio Intrusions shows that in spite of different oceanographic conditions the LF locations may serve good indicators of potential fishing grounds. Possible reasons for saury aggregation near LFs are discussed. We propose a mechanism of effective export of nutrient rich waters based on stretching of material lines in the vicinity of hyperbolic objects in the ocean. The developed method, based on identifying LFs in any velocity fields, is quite general and may be applied to forecast potential fishing grounds for the other pelagic fishes in different seas and the oceans.

  18. apennine front kreep: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Department of Chemical Engineering References and links 1. J. Warnatz, U. Maas, and R.W. Dibble, Combustion - physical and chemical fundamentals, "Characterization of flame front...

  19. One-way, real time wave front converters

    SciTech Connect (OSTI)

    Kwong, S.; Yariv, A.

    1986-03-03T23:59:59.000Z

    Optical one-way, real time wave front cleanup by means of photorefractively pumped oscillators is reported. A factor of 4000 increase in beam brightness has been achieved.

  20. Front instabilities in evaporatively dewetting nanofluids and U. Thiele

    E-Print Network [OSTI]

    Front instabilities in evaporatively dewetting nanofluids I. Vancea and U. Thiele Department of nanoparticles often called nanofluids have recently been used to produce structured nanoparticle layers

  1. Global MHD simulations of stratified and turbulent protoplanetary discs. I. Model properties

    E-Print Network [OSTI]

    Sebastien Fromang; Richard P. Nelson

    2006-06-29T23:59:59.000Z

    We present the results of global 3-D MHD simulations of stratified and turbulent protoplanetary disc models. The aim of this work is to develop thin disc models capable of sustaining turbulence for long run times, which can be used for on-going studies of planet formation in turbulent discs. The results are obtained using two codes written in spherical coordinates: GLOBAL and NIRVANA. Both are time--explicit and use finite differences along with the Constrained Transport algorithm to evolve the equations of MHD. In the presence of a weak toroidal magnetic field, a thin protoplanetary disc in hydrostatic equilibrium is destabilised by the magnetorotational instability (MRI). When the resolution is large enough (25 vertical grid cells per scale height), the entire disc settles into a turbulent quasi steady-state after about 300 orbits. Angular momentum is transported outward such that the standard alpha parameter is roughly 4-6*10^{-3}. We find that the initial toroidal flux is expelled from the disc midplane and that the disc behaves essentially as a quasi-zero net flux disc for the remainder of the simulation. As in previous studies, the disc develops a dual structure composed of an MRI--driven turbulent core around its midplane, and a magnetised corona stable to the MRI near its surface. By varying disc parameters and boundary conditions, we show that these basic properties of the models are robust. The high resolution disc models we present in this paper achieve a quasi--steady state and sustain turbulence for hundreds of orbits. As such, they are ideally suited to the study of outstanding problems in planet formation such as disc--planet interactions and dust dynamics.

  2. Front lighted optical tooling method and apparatus

    DOE Patents [OSTI]

    Stone, W.J.

    1983-06-30T23:59:59.000Z

    An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument.

  3. Flame front configuration of turbulent premixed flames

    SciTech Connect (OSTI)

    Furukawa, Junichi [Tokyo Metropolitan Technical Coll. (Japan). Dept. of Mechanical Engineering] [Tokyo Metropolitan Technical Coll. (Japan). Dept. of Mechanical Engineering; Maruta, Kaoru [Tohoku Univ., Sendai (Japan). Inst. of Fluid Science] [Tohoku Univ., Sendai (Japan). Inst. of Fluid Science; Hirano, Toshisuke [Univ. of Tokyo (Japan). Dept. of Chemical System Engineering] [Univ. of Tokyo (Japan). Dept. of Chemical System Engineering

    1998-02-01T23:59:59.000Z

    The present study is performed to explore dependence of the wrinkle scale of propane-air turbulent premixed flames on the characteristics of turbulence in the nonreacting flow, burner size, and mixture ratio. The wrinkle scales are examined and expressed in the frequency distribution of the radii of flame front curvatures. The average wrinkle scale depends not only on the characteristics of turbulence in the nonreacting flow but also on burner diameter and mixture ratio. The average wrinkle scale of a lean propane-air flame is larger than those of the near stoichiometric and rich flames. The smallest wrinkle scale of turbulent premixed flame is in the range of 0.75--1.0 mm, which is much larger than the Kolmogorov scale of turbulence in the nonreacting flow.

  4. Front instabilities in evaporatively dewetting nanofluids

    E-Print Network [OSTI]

    Vancea, I; Pauliac-Vaujour, E; Stannard, A; Martn, C P; Blunt, M O; Moriarty, P J

    2008-01-01T23:59:59.000Z

    Various experimental settings that involve drying solutions or suspensions of nanoparticles -- often called nanofluids -- have recently been used to produce structured nanoparticle layers. In addition to the formation of polygonal networks and spinodal-like patterns, the occurrence of branched structures has been reported. After reviewing the experimental results we use a modified version of the Monte Carlo model first introduced by Rabani et al. [Nature 426, 271 (2003)] to study structure formation in evaporating films of nanoparticle solutions for the case that all structuring is driven by the interplay of evaporating solvent and diffusing nanoparticles. After introducing the model and its general behavior we focus on receding dewetting fronts which are initially straight but develop a transverse fingering instability. We analyze the dependence of the characteristics of the resulting branching patterns on the driving chemical potential, the mobility and concentration of the nanoparticles, and the interactio...

  5. Front instabilities in evaporatively dewetting nanofluids

    E-Print Network [OSTI]

    I. Vancea; U. Thiele; E. Pauliac-Vaujour; A. Stannard; C. P. Martin; M. O. Blunt; P. J. Moriarty

    2008-06-25T23:59:59.000Z

    Various experimental settings that involve drying solutions or suspensions of nanoparticles -- often called nanofluids -- have recently been used to produce structured nanoparticle layers. In addition to the formation of polygonal networks and spinodal-like patterns, the occurrence of branched structures has been reported. After reviewing the experimental results we use a modified version of the Monte Carlo model first introduced by Rabani et al. [Nature 426, 271 (2003)] to study structure formation in evaporating films of nanoparticle solutions for the case that all structuring is driven by the interplay of evaporating solvent and diffusing nanoparticles. After introducing the model and its general behavior we focus on receding dewetting fronts which are initially straight but develop a transverse fingering instability. We analyze the dependence of the characteristics of the resulting branching patterns on the driving chemical potential, the mobility and concentration of the nanoparticles, and the interaction strength between liquid and nanoparticles. This allows us to understand the underlying instability mechanism.

  6. Webinar: Testing Oxygen Reduction Reaction Activity with the Rotating Disc Electrode Technique

    Broader source: Energy.gov [DOE]

    Video recording of the Fuel Cell Technologies Office webinar, Testing Oxygen Reduction Reaction Activity with the Rotating Disc Electrode Technique, originally presented on March 12, 2013.

  7. Dust filtration at gap edges: Implications for the spectral energy distributions of discs with embedded planets

    E-Print Network [OSTI]

    W. K. M. Rice; Philip J. Armitage; Kenneth Wood; Giuseppe Lodato

    2006-09-29T23:59:59.000Z

    The spectral energy distributions (SEDs) of some T Tauri stars display a deficit of near-IR flux that could be a consequence of an embedded Jupiter-mass planet partially clearing an inner hole in the circumstellar disc. Here, we use two-dimensional numerical simulations of the planet-disc interaction, in concert with simple models for the dust dynamics, to quantify how a planet influences the dust at different radii within the disc. We show that pressure gradients at the outer edge of the gap cleared by the planet act as a filter - letting particles smaller than a critical size through to the inner disc while holding back larger particles in the outer disc. The critical particle size depends upon the disc properties, but is typically of the order of 10 microns. This filtration process will lead to discontinuous grain populations across the planet's orbital radius, with small grains in the inner disc and an outer population of larger grains. We show that this type of dust population is qualitatively consistent with SED modelling of systems that have optically thin inner holes in their circumstellar discs. This process can also produce a very large gas-to-dust ratio in the inner disc, potentially explaining those systems with optically thin inner cavities that still have relatively high accretion rates.

  8. The spectra of accretion discs in low-mass X-ray binaries

    E-Print Network [OSTI]

    R. R. Ross; A. C. Fabian

    1995-11-14T23:59:59.000Z

    We present self-consistent models for the radiative transfer in Shakura-Sunyaev accretion discs in bright low-mass X-ray binaries (LMXB). Our calculations include the full effects of incoherent Compton scattering and the vertical temperature structure within the disc, as well as the effects of Doppler blurring and gravitational redshift. We find that the observed X-ray spectra are well fit by exponentially cutoff power-law models. The difference between the observed total spectrum and our calculated disc spectrum should reveal the spectrum of the disc/neutron star boundary layer and other emitting regions considered to be present in LMXB.

  9. Properties of vertically self-gravitating accretion discs with a dissipative corona

    E-Print Network [OSTI]

    Fazeleh Khajenabi; Peter Duffy

    2008-05-30T23:59:59.000Z

    The steady-state structure of a disc with a corona is analyzed when the vertical component of the gravitational force due to the self-gravity of the disc is considered. For the energy exchange between the disc and the corona, we assume a fraction f of the dissipated energy inside the accretion disc is transported to the corona via the magnetic tubes. Analytical solutions corresponding to a prescription for f (in which this parameter directly depends on the ratio of the gas pressure to the total pressure) or free f are presented and their physical properties are studied in detail. We show that the existence of the corona not only decreases the temperature of the disc, but also increases the surface density.The vertical component of the gravitational force due to the self-gravity of the disc decreases the self-gravitating radius and the mass of the fragments at this radius. However, as more energy is transported from the disc to the corona, the effect of the vertical component of the gravitational force due to the self-gravity of the disc on the self-gravitating radius becomes weaker, though the mass of the fragments is reduced irrespective of the amount of the energy exchange from the disc to the corona.

  10. Hydrodynamic Simulations of Propagating Warps and Bending Waves In Accretion Discs

    E-Print Network [OSTI]

    Richard P. Nelson; John C. B. Papaloizou

    1999-07-06T23:59:59.000Z

    We present the results of a study of propagating warp or bending waves in accretion discs. Three dimensional hydrodynamic simulations were performed using SPH, and the results of these are compared with calculations based on the linear theory of warped discs. We consider primarily the physical regime in which the dimensionless viscosity parameter `alpha' disc aspect ratio, so that bending waves are expected to propagate. We also present calculations in which `alpha' > H/r, where the warps are expected to behave diffusively. Small amplitude perturbations are studied in both Keplerian and slightly non Keplerian discs, and we find that the SPH results can be reasonably well fitted by those of the linear theory. The main results of these calculations are: (1) the warp in Keplerian discs when `alpha' H/r, (3) the non Keplerian discs exhibit a substantially more dispersive behaviour of the warps. Initially imposed higher amplitude nonlinear warping disturbances were studied in Keplerian discs. The results indicate that nonlinear warps can lead to the formation of shocks, and that the evolution of the warp becomes less wave-like and more diffusive in character. This work is relevant to the study of the warped accretion discs that may occur around Kerr black holes or in misaligned binary systems. The results indicate that SPH can accurately model the hydrodynamics of warped discs, even when using rather modest numbers of particles.

  11. Dependence of fragmentation in self-gravitating accretion discs on small scale structure

    E-Print Network [OSTI]

    Young, Matthew D

    2015-01-01T23:59:59.000Z

    We propose a framework for understanding the fragmentation criterion for self-gravitating discs which, in contrast to studies that emphasise the `gravoturbulent' nature of such discs, instead focuses on the properties of their quasi-regular spiral structures. Within this framework there are two evolutionary paths to fragmentation: i) collapse on the free-fall time, which requires that the ratio of cooling time to dynamical time ($\\beta$) $disc. We perform 2D grid simulations which demonstrate numerically converged fragmentation at $\\beta disc. Such simulations thus only allow fragmentation via route i) above...

  12. Eccentric discs in binaries with intermediate mass ratios: Superhumps in the VY Sculptoris stars

    E-Print Network [OSTI]

    J. R. Murray; B. Warner; D. T. Wickramasinghe

    2000-02-23T23:59:59.000Z

    We investigate the role of the eccentric disc resonance in systems with mass ratios q greater than 1/4, and demonstrate the effects that changes in the mass flux from the secondary star have upon the disc radius and structure. The addition of material with low specific angular momentum to its outer edge restricts a disc radially. Should the mass flux from the secondary be reduced, it is possible for the disc in a system with mass ratio as large as 1/3 to expand to the 3:1 eccentric inner Lindblad resonance and for superhumps to be excited.

  13. Strong effect of the cluster environment on the size of protoplanetary discs?

    E-Print Network [OSTI]

    Vincke, Kirsten; Pfalzer, Susanne

    2015-01-01T23:59:59.000Z

    Context. Most stars are born in clusters, thus the protoplanetary discs surrounding the newly formed stars might be influenced by this environment. Isolated star-disc encounters have previously been studied, and it was shown that very close encounters are necessary to completely destroy discs. However, relatively distant encounters are still able to change the disc size considerably. Aims. We quantify the importance of disc-size reduction that is due to stellar encounters in an entire stellar population. Methods. We modelled young, massive clusters of different densities using the code Nbody6 to determine the statistics of stellar encounter parameters. In a second step, we used these parameters to investigate the effect of the environments on the disc size. For this purpose, we performed a numerical experiment with an artificial initial disc size of 105 AU. Results. We quantify to which degree the disc size is more sensitive to the cluster environment than to the disc mass or frequency. We show that in all in...

  14. Front contact solar cell with formed electrically conducting layers on the front side and backside

    DOE Patents [OSTI]

    Cousins, Peter John

    2012-06-26T23:59:59.000Z

    A bipolar solar cell includes a backside junction formed by a silicon substrate and a first doped layer of a first dopant type on the backside of the solar cell. A second doped layer of a second dopant type makes an electrical connection to the substrate from the front side of the solar cell. A first metal contact of a first electrical polarity electrically connects to the first doped layer on the backside of the solar cell, and a second metal contact of a second electrical polarity electrically connects to the second doped layer on the front side of the solar cell. An external electrical circuit may be electrically connected to the first and second metal contacts to be powered by the solar cell.

  15. FLUCTUATIONS OF THE FRONT IN A STOCHASTIC COMBUSTION MODEL

    E-Print Network [OSTI]

    Quastel, Jeremy

    FLUCTUATIONS OF THE FRONT IN A STOCHASTIC COMBUSTION MODEL #1; (FLUCTUATIONS DU FRONT DANS UN MODLE DE COMBUSTION) FRANCIS COMETS 1 , JEREMY QUASTEL 2 AND ALEJANDRO F. RAMREZ 3 Abstract. We consider an interacting particle system on the one dimensional lattice Z modeling combustion. The process

  16. Combustion fronts in porous media with two layers Steve Schecter

    E-Print Network [OSTI]

    Schecter, Stephen

    Combustion fronts in porous media with two layers layer 1 layer 2 Steve Schecter North Carolina Subject: Propagation of a combustion front through a porous medium with two parallel layers having different properties. Each layer admits a traveling combustion wave. The layers are coupled by heat

  17. Investigation of the Brazil Current front variability from altimeter data

    E-Print Network [OSTI]

    Investigation of the Brazil Current front variability from altimeter data Gustavo J. Goni Atlantic, Brazil Abstract. The southwestern Atlantic Ocean is characterized by the confluence of the Brazil in conjunction with a two-layer dynamical ocean scheme to monitor the Brazil Current front and to investigate its

  18. Light-Front Holography: A First Approximation to QCD

    SciTech Connect (OSTI)

    de Teramond, Guy F.; Brodsky, Stanley J.

    2008-10-03T23:59:59.000Z

    Starting from the Hamiltonian equation of motion in QCD, we identify an invariant light-front coordinate {zeta} which allows the separation of the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space. This allows us to establish formally a gauge/gravity correspondence between an effective gravity theory defined on AdS5 and light front QCD.

  19. Criticality and Big Brake singularities in the tachyonic evolutions of closed Friedmann universes with cold dark matter

    E-Print Network [OSTI]

    Horvth, Zsolt; Kamenshchik, Alexander Yu; Gergely, Lszl

    2015-01-01T23:59:59.000Z

    The evolution of a closed Friedmann universe filled by a tachyon scalar field with a trigonometric potential and cold dark matter (CDM) is investigated. A subset of the evolutions consistent to 1$\\sigma $ confidence level with the Union 2.1 supernova data set is identified. The evolutions of the tachyon field are classified. Some of them evolve into a de Sitter attractor, while others proceed through a pseudo-tachyonic regime into a sudden future singularity. Critical evolutions leading to Big Brake singularities in the presence of CDM are found and a new type of cosmological evolution characterized by singularity avoidance in the pseudo-tachyon regime is presented.

  20. A closed-loop quasi-optimal dynamic braking resistor and shunt reactor control strategy for transient stability

    SciTech Connect (OSTI)

    Rahim, A.H.M.A.; Alamgir, D.A.H.

    1988-08-01T23:59:59.000Z

    A control strategy for dynamic braking resistor and shunt reactor is proposed for stabilization of power systems when subject to large disturbances. The time optimal control is derived as a function of synchronous machine power, its rotor angular position and speed deviation. The response for a single machine system with the proposed control has been compared with that from the time optimal solution obtained through the steepest descent method. The strategy has also been tested on two multimachine systems. Results indicate that the proposed strategy provides a simple and effective method of stabilization under transient emergency conditions.

  1. Dark Matter Disc Enhanced Neutrino Fluxes from the Sun and Earth

    E-Print Network [OSTI]

    Tobias Bruch; Annika H. G. Peter; Justin Read; Laura Baudis; George Lake

    2009-04-21T23:59:59.000Z

    As disc galaxies form in a hierarchical cosmology, massive merging satellites are preferentially dragged towards the disc plane. The material accreted from these satellites forms a dark matter disc that contributes 0.25 - 1.5 times the non-rotating halo density at the solar position. Here, we show the importance of the dark disc for indirect dark matter detection in neutrino telescopes. Previous predictions of the neutrino flux from WIMP annihilation in the Earth and the Sun have assumed that Galactic dark matter is spherically distributed with a Gaussian velocity distribution, the standard halo model. Although the dark disc has a local density comparable to the dark halo, its higher phase space density at low velocities greatly enhances capture rates in the Sun and Earth. For typical dark disc properties, the resulting muon flux from the Earth is increased by three orders of magnitude over the SHM, while for the Sun the increase is an order of magnitude. This significantly increases the sensitivity of neutrino telescopes to fix or constrain parameters in WIMP models. The flux from the Earth is extremely sensitive to the detailed properties of the dark disc, while the flux from the Sun is more robust. The enhancement of the muon flux from the dark disc puts the search for WIMP annihilation in the Earth on the same level as the Sun for WIMP masses < 100 GeV.

  2. Magnetized accretion-ejection structures IV. Magnetically-driven jets from resistive, viscous, Keplerian discs

    E-Print Network [OSTI]

    Fabien Casse; Jonathan Ferreira

    1999-11-25T23:59:59.000Z

    We present steady-state calculations of self-similar magnetized accretion discs driving cold, adiabatic, non-relativistic jets. For the first time, both the magnetic torque due to the jets and a turbulent "viscous" torque are taken into account. This latter torque allows a dissipation of the accretion power as radiation at the disc surfaces, while the former predominantly provides jets with power. The parameter space of these structures has been explored. It is characterized by four free parameters, namely the disc aspect ratio and three MHD turbulence parameters, related to the anomalous magnetic diffusivities and viscosity. It turns out that launching cold jets from thin, dissipative discs implies anisotropic turbulent dissipation. Jets that asymptotically reach a high Alfvenic Mach number are only produced by weakly dissipative discs. We obtained general analytical relations between disc and jet quantities that must be fulfilled by any steady-state model of cold jets, launched from a large radial extension of thin discs. We also show that such discs cannot have a dominant viscous torque. This is because of the chosen geometry, imposing the locus of the Alfven surface. Some observational consequences of these cold magnetized accretion-ejection structures are also briefly discussed.

  3. A SCUBA-2 850 micron Survey of Protoplanetary Discs in the IC 348 Cluster

    E-Print Network [OSTI]

    Cieza, L; Kourkchi, E; Andrews, S; Casassus, S; Graves, S; Schreiber, M

    2015-01-01T23:59:59.000Z

    We present 850 micron observations of the 2-3 Myr cluster IC 348 in the Perseus molecular cloud using the SCUBA-2 camera on the James Clerk Maxwell Telescope. Our SCUBA-2 map has a diameter of 30 arcmin and contains ~370 cluster members, including ~200 objects with IR excesses. We detect a total of 13 discs. Assuming standard dust properties and a gas to dust mass ratio of 100, we derive disc masses ranging from 1.5 to 16 M_JUP . We also detect 8 Class 0/I protostars. We find that the most massive discs (M_Disc > 3 MJUP ; 850 micron fux > 10 mJy) in IC 348 tend to be transition objects according to the characteristic "dip" in their infrared Spectral Energy Distributions (SEDs). This trend is also seen in other regions. We speculate that this could be an initial conditions effect (e.g., more massive discs tend to form giant planets that result in transition disc SEDs) and/or a disc evolution effect (the formation of one or more massive planets results in both a transition disc SED and a reduction of the accret...

  4. Quantum McKay correspondence for disc invariants of orbifold vertex

    E-Print Network [OSTI]

    Hua-Zhong Ke; Jian Zhou

    2014-10-16T23:59:59.000Z

    In this note, we describe a a systematic procedure to find toric crepant resolutions of orbifold vertex, and show that the generating series of certain disc invariants of the orbifold vertex can be suitably identified with the generating series of certain disc invariants of its toric crepant resolutions.

  5. Front lighted optical tooling method and apparatus

    DOE Patents [OSTI]

    Stone, William J. (Kansas City, MO)

    1985-06-18T23:59:59.000Z

    An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument. A method of measuring a radius of curvature of an unknown surface includes positioning the spherometer on a surface between the surface and a depth measuring optical instrument. As the spherometer is frontally illuminated, the distance from the depth measuring instrument to the fiducial mark and the underlying surface are alternately measured and the difference in these measurements is used as the sagittal height to calculate a radius of curvature.

  6. High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo

    E-Print Network [OSTI]

    Johansen, Anders

    2008-01-01T23:59:59.000Z

    Hydromagnetic stresses in accretion discs have been the subject of intense theoretical research over the past one and a half decades. Most of the disc simulations have assumed a small initial magnetic field and studied the turbulence that arises from the magnetorotational instability. However, gaseous discs in galactic nuclei and in some binary systems are likely to have significant initial magnetisation. Motivated by this, we performed ideal magnetohydrodynamic simulations of strongly magnetised, vertically stratified discs in a Keplerian potential. Our initial equilibrium configuration, which has an azimuthal magnetic field in equipartion with thermal pressure, is unstable to the Parker instability. This leads to the expelling of magnetic field arcs, anchored in the midplane of the disc, to around five scale heights from the midplane. Transition to turbulence happens primarily through magnetorotational instability in the resulting vertical fields, although magnetorotational shear instability in the unpertur...

  7. Spin-1 Particles with Light-Front Approach

    E-Print Network [OSTI]

    J. P. B. C. de Melo; Anac N. da Silva; Clayton S. Mello; T. Frederico

    2015-04-27T23:59:59.000Z

    For the vector sector, i.e, mesons with spin-1, the electromagnetic form factors and anothers observables are calculated with the light-front approach. However, the light-front quantum field theory have some problems, for example, the rotational symmetry breaking. We solve that problem added the zero modes contribuition to the matrix elements of the electromagnetic current, besides the valence contribuition. We found that among the four independent matrix elements of the plus component in the light-front helicity basis only the $0\\to 0$ one carries zero mode contributions.

  8. Electron g-2 in Light-front Quantization

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhao, Xingbo; Honkanen, Heli; Maris, Pieter; Vary, James P.; Brodsky, Stanley J.

    2014-10-01T23:59:59.000Z

    Basis Light-front Quantization has been proposed as a nonperturbative framework for solving quantum field theory. We apply this approach to Quantum Electrodynamics and explicitly solve for the light-front wave function of a physical electron. Based on the resulting light-front wave function, we evaluate the electron anomalous magnetic moment. Nonperturbative mass renormalization is performed. Upon extrapolation to the infinite basis limit our numerical results agree with the Schwinger result obtained in perturbation theory to an accuracy of 0.06%.

  9. Electron g-2 in Light-Front Quantization

    E-Print Network [OSTI]

    Xingbo Zhao; Heli Honkanen; Pieter Maris; James P. Vary; Stanley J. Brodsky

    2014-08-24T23:59:59.000Z

    Basis Light-front Quantization has been proposed as a nonperturbative framework for solving quantum field theory. We apply this approach to Quantum Electrodynamics and explicitly solve for the light-front wave function of a physical electron. Based on the resulting light-front wave function, we evaluate the electron anomalous magnetic moment. Nonperturbative mass renormalization is performed. Upon extrapolation to the infinite basis limit our numerical results agree with the Schwinger result obtained in perturbation theory to an accuracy of 0.06%.

  10. Light front approach to correlations in hot quark matter

    E-Print Network [OSTI]

    S. Strauss; M. Beyer; S. Mattiello

    2006-01-30T23:59:59.000Z

    We investigate two-quark correlations in hot and dense quark matter. To this end we use the light front field theory extended to finite temperature $T$ and chemical potential $\\mu$. Therefore it is necessary to develop quantum statistics formulated on the light front plane. As a test case for light front quantization at finite $T$ and $\\mu$ we consider the NJL model. The solution of the in-medium gap equation leads to a constituent quark mass which depends on $T$ and $\\mu$. Two-quark systems are considered in the pionic and diquark channel. We compute the masses of the two-body system using a $T$-matrix approach.

  11. Muon capture for the front end of a muon collider

    SciTech Connect (OSTI)

    Neuffer, D.; /Fermilab; Yoshikawa, C.; /MUONS Inc., Batavia

    2011-03-01T23:59:59.000Z

    We discuss the design of the muon capture front end for a {mu}{sup +}-{mu}{sup -} Collider. In the front end, a proton bunch on a target creates secondary pions that drift into a capture transport channel, decaying into muons. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. The muons are then cooled and accelerated to high energy into a storage ring for high-energy high luminosity collisions. Our initial design is based on the somewhat similar front end of the International Design Study (IDS) neutrino factory.

  12. On the fragility of nuclear stellar discs against galaxy mergers: surviving photometric and kinematic signatures of nuclear discs

    E-Print Network [OSTI]

    Sarzi, M; Dotti, M

    2015-01-01T23:59:59.000Z

    Nuclear stellar discs (NSDs) can help to constrain the assembly history of their host galaxies, as long as we can assume them to be fragile structures that are disrupted during merger events. In this work we investigate the fragility of NSDs by means of N-body simulations reproducing the last phases of a galaxy encounter, when the nuclear regions of the two galaxies merge. For this, we exposed a NSD set in the gravitational potential of the bulge and supermassive black hole of a primary galaxy to the impact of the supermassive black hole from a secondary galaxy. We explored merger events of different mass ratios, from major mergers with a 1:1 mass ratio to intermediate and minor interactions with 1:5 and 1:10 ratios, while considering various impact geometries. We analyse the end results of such mergers from different viewing angles and looked for possible photometric and kinematic signatures of the presence of a disc in the remnant surface density and velocity maps, while adopting detection limits from real ...

  13. Iron line profiles and self-shadowing from relativistic thick accretion discs

    E-Print Network [OSTI]

    Sheng-Miao Wu; Ting-Gui Wang

    2008-07-11T23:59:59.000Z

    We present Fe Kalpha line profiles from and images of relativistic discs with finite thickness around a rotating black hole using a novel code. The line is thought to be produced by iron fluorescence of a relatively cold X-ray illuminated material in the innermost parts of the accretion disc and provides an excellent diagnostic of accretion flows in the vicinity of black holes. Previous studies have concentrated on the case of a thin, Keplerian accretion disc. This disc must become thicker and sub-Keplerian with increasing accretion rates. These can affect the line profiles and in turn can influence the estimation of the accretion disc and black hole parameters from the observed line profiles. We here embark on, for the first time, a fully relativistic computation which offers key insights into the effects of geometrical thickness and the sub-Keplerian orbital velocity on the line profiles. We include all relativistic effects such as frame-dragging, Doppler boost, time dilation, gravitational redshift and light bending. We find that the separation and the relative height between the blue and red peaks of the line profile diminish as the thickness of the disc increases. This code is also well-suited to produce accretion disc images. We calculate the redshift and flux images of the accretion disc and find that the observed image of the disc strongly depends on the inclination angle. The self-shadowing effect appears remarkable for a high inclination angle, and leads to the black hole shadow being completely hidden by the disc itself.

  14. Advanced integrated safeguards using front-end-triggering devices

    SciTech Connect (OSTI)

    Howell, J.A.; Whitty, W.J.

    1995-12-01T23:59:59.000Z

    This report addresses potential uses of front-end-triggering devices for enhanced safeguards. Such systems incorporate video surveillance as well as radiation and other sensors. Also covered in the report are integration issues and analysis techniques.

  15. Speed-up of combustion fronts in shear flows

    E-Print Network [OSTI]

    Hamel, Francois

    2011-01-01T23:59:59.000Z

    This paper is concerned with the analysis of speed-up of reaction-diffusion-advection traveling fronts in infinite cylinders with periodic boundary conditions. The advection is a shear flow with a large amplitude and the reaction is nonnegative, with either positive or zero ignition temperature. The unique or minimal speeds of the traveling fronts are proved to be asymptotically linear in the flow amplitude as the latter goes to infinity, solving an open problem from \\cite{b}. The asymptotic growth rate is characterized explicitly as the unique or minimal speed of traveling fronts for a limiting degenerate problem, and the convergence of the regular traveling fronts to the degenerate ones is proved for positive ignition temperatures under an additional H{\\"{o}}rmander-type condition on the flow.

  16. Helpful Numbers Cougar Place Front Desk (713) 743-

    E-Print Network [OSTI]

    Azevedo, Ricardo

    Helpful Numbers Cougar Place Front Desk (713) 743- 6994 Housing Office (713) 743-6000 RLC Office) 743-7529 Facebook.com/UHCougarPlace Twitter & IG : UHCougarPlace #12;What's Going On? Parents

  17. Home Front as Warfront: African American World War I Drama

    E-Print Network [OSTI]

    Egging, Anna Katherine

    2010-08-31T23:59:59.000Z

    This dissertation recovers little-known African American World War I plays that blur the boundary between the home front and warfront. I argue that with this focus, the plays wage their own war for African American citizenship ...

  18. RF CMOS UWB transmitter and receiver front-end design

    E-Print Network [OSTI]

    Miao, Meng

    2009-05-15T23:59:59.000Z

    The low-cost low-power complementary metal-oxide semiconductor (CMOS) ultra wideband (UWB) transmitter and receiver front-ends based on impulse technology were developed. The CMOS UWB pulse generator with frequency-band tuning capability...

  19. Stability of Propagating Fronts in Damped Hyperbolic Equations

    E-Print Network [OSTI]

    Stability of Propagating Fronts in Damped Hyperbolic Equations Th. Gallay, G. Raugel Analyse Num'erique et EDP CNRS et Universit'e de Paris­Sud F­91405 Orsay Cedex, France Thierry.Gallay

  20. Carbon Emissions from Smouldering Peat in Shallow and Strong Fronts

    E-Print Network [OSTI]

    Rein, Guillermo; Cohen, Simon; Simeoni, Albert

    2009-01-01T23:59:59.000Z

    A series of experiments of shallow and strong smouldering fronts in boreal peat have been conducted under laboratory conditions to study the CO and CO2 emissions. Peat samples of 100 mm by 100 mm in cross section and 50 ...

  1. Front End Loading (FEL) and Process Engineering Workflow

    E-Print Network [OSTI]

    Spangler, Ryan

    2005-05-20T23:59:59.000Z

    Project development for the oil refining industry is typically performed through a process called Front End Loading (FEL). In recent years, the Process and Industrial Division of Burns and McDonnell has performed several ...

  2. Global optimization of silicon photovoltaic cell front coatings

    E-Print Network [OSTI]

    Ghebrebrhan, Michael

    The front-coating (FC) of a solar cell controls its efficiency, determining admission of light into the absorbing material and potentially trapping light to enhance thin absorbers. Single-layer FC designs are well known, ...

  3. Colorado Front Range Fuel Photo Series Michael A. Battaglia

    E-Print Network [OSTI]

    Fried, Jeremy S.

    Colorado Front Range Fuel Photo Series Michael A. Battaglia Jonathan M. Dodson Wayne D. Shepperd of Agriculture Forest Service Rocky Mountain Research Station June 2005 #12;Battaglia, Michael A.; Dodson

  4. Renormalized Light Front Hamiltonian in the Pauli-Villars Regularization

    E-Print Network [OSTI]

    M. Yu. Malyshev; S. A. Paston; E. V. Prokhvatilov; R. A. Zubov

    2014-09-03T23:59:59.000Z

    We address the problem of nonperturbative calculations on the light front in quantum field theory regularized by Pauli-Villars method. As a preliminary step we construct light front Hamiltonians in (2+1)-dimensional $\\lambda\\phi^4$ model, for the cases without and with spontaneous symmetry breaking. The renormalization of these Hamiltonians in Pauli-Villars regularization is carried out via comparison of all-order perturbation theory, generated by these Hamiltonians, and the corresponding covariant perturbation theory in Lorentz coordinates.

  5. Radio frequency circuits for wireless receiver front-ends

    E-Print Network [OSTI]

    Xin, Chunyu

    2005-11-01T23:59:59.000Z

    . . . . . . . . 69 2. Implementation of the Down-Conversion Mixer . . . . 69 3. Layout Considerations and Simulation Results . . . . 74 4. Experimental Results of the Mixer Within the Receiver 77 IV BLUETOOTH/WI-FI DUAL-STANDARD RECEIVER RF FRONT...-END : : : : : : : : : : : : : : : : : : : : : : : : : : : : 80 A. Direct Conversion Bluetooth/Wi-Fi Dual-Standard Receiver 81 B. RF Front-End Design Considerations . . . . . . . . . . . . 83 C. Circuits Implementations . . . . . . . . . . . . . . . . . . . 86 1. LNA Implementation...

  6. Hydraulic Drivetrain and Regenerative Braking Team 13: Andrew Brown, Karan Desai, Andrew McGrath, Hurst Nuckols, Grant Wilson Adviser: Dr. Andrew Jackson

    E-Print Network [OSTI]

    Carpick, Robert W.

    Hydraulic Drivetrain and Regenerative Braking Team 13: Andrew Brown, Karan Desai, Andrew Mc Pressure Reservior Filter Variable Vane Pump Motor/Pump Hydraulic Accumulators Solenoid Valve Relief Valve Suction Line Since their development in 2006, hydraulic drivetrain systems have gained considerable

  7. Finite element analysis of the effect of up-armouring on the off-road braking and sharp-turn performance

    E-Print Network [OSTI]

    Grujicic, Mica

    Finite element analysis of the effect of up-armouring on the off-road braking and sharp-mobility multi-purpose wheeled vehicle, off-road vehicle performance, finite element modelling and simulations revision for publication on 15 June 2009. DOI: 10.1243/09544070JAUTO1187 Abstract: A comprehensive finite

  8. Jamming Transition and Inherent Structures of Hard Spheres and Discs

    E-Print Network [OSTI]

    Misaki Ozawa; Takeshi Kuroiwa; Atsushi Ikeda; Kunimasa Miyazaki

    2012-11-17T23:59:59.000Z

    Recent studies show that volume fractions $\\phiJ$ at the jamming transition of frictionless hard spheres and discs are not uniquely determined but exist over a continuous range. Motivated by this observation, we numerically investigate dependence of $\\phiJ$ on the initial configurations of the parent fluids equilibrated at a fraction $\\phiini$, before compressing to generate a jammed packing. We find that $\\phiJ$ remains constant when $\\phiini$ is small but sharply increases when $\\phiini$ exceeds the dynamic transition point which the mode-coupling theory predicts. We carefully analyze configurational properties of both jammed packings and parent fluids and find that, while all jammed packings remain isostatic, the increase of $\\phiJ$ is accompanied with subtle but distinct changes of (i) local orders, (ii) a static length scale, and (iii) an exponent of the finite size scaling. These results quantitatively support the scenario of the random first order transition theoryof the glass transition.

  9. The Complete Jamming Landscape of Confined Hard Discs

    E-Print Network [OSTI]

    S. S. Ashwin; Richard k. Bowles

    2009-03-25T23:59:59.000Z

    An exact description of the complete jamming landscape is developed for a system of hard discs of diameter $\\sigma$, confined between two lines separated by a distance $1+\\sqrt{3/4} < H/\\sigma < 2$. By considering all possible local packing arrangements, the generalized ensemble partition function of jammed states is obtained using the transfer matrix method, which allows us to calculate the configurational entropy and the equation of state for the packings. Exploring the relationship between structural order and packing density, we find that the geometric frustration between local packing environments plays an important role in determining the density distribution of jammed states and that structural "randomness" is a non-monotonic function of packing density. Molecular dynamics simulations show that the properties of the equilibrium liquid are closely related to those of the landscape.

  10. Normal modes analysis of the microscopic dynamics in hard discs

    E-Print Network [OSTI]

    Carolina Brito; Matthieu Wyart

    2008-05-09T23:59:59.000Z

    We estimate numerically the normal modes of the free energy in a glass of hard discs. We observe that, near the glass transition or after a rapid quench deep in the glass phase, the density of states (i) is characteristic of a marginally stable structure, in particular it di splays a frequency scale $\\omega^*\\sim p^{1/2}$, where $p$ is the pressure and (ii) gives a faithful representation of the short-time dyn amics. This brings further evidences that the boson peak near the glass transition corresponds to the relaxation of marginal modes of a we akly-coordinated structure, and implies that the mean square displacement in the glass phase is anomalously large and goes as $ \\sim p^{-3/2}$, a prediction that we check numerically.

  11. Massive planets in FU Orionis discs: implications for thermal instability models

    E-Print Network [OSTI]

    G. Lodato; C. J. Clarke

    2004-06-10T23:59:59.000Z

    FU Orionis are young stellar objects undergoing episodes of enhanced luminosity, which are generally ascribed to a sudden increase of mass accretion rate in the surrounding protostellar disc. Models invoking a thermal instability in the disc are able to reproduce many features of the outburst, but cannot explain the rapid rise time-scale observed in many cases. Here we explore the possibility (originally suggested by Clarke & Syer 1996) that the thermal instability is triggered away from the disc inner edge (at a distance of $\\approx 10R_{\\odot}$ from the central protostar) due to the presence of a massive planet embedded in the disc. We have constructed simple, one-dimensional, time-dependent models of the disc evolution, taking into account both the interaction between the disc and the planet, and the thermal evolution of the disc. We are indeed able to reproduce rapid rise outbursts (with rise time-scale $\\approx 1$ yr), with a planet mass $M_{\\mathrm{s}}=10-15M_{\\mathrm{Jupiter}}$. We show that the luminosity and the duration of the outbursts are increasing functions of planet mass. We also show that the inward migration of the planet is significantly slowed once it reaches the radius where it is able to trigger FU Orionis outbursts, thus suggesting that a single planet may be involved in triggering several outbursts.

  12. On fan-shaped cold MHD winds from Keplerian accretion discs

    E-Print Network [OSTI]

    Ferreira, Jonathan

    2012-01-01T23:59:59.000Z

    We investigate under which conditions cold, fan-shaped winds can be steadily launched from thin (Keplerian) accretion discs. Such winds are magneto-centrifugal winds launched from a thin annulus in the disc, along open magnetic field lines that fan out above the disc. In principle, such winds could be found in two situations: (1) at the interface between an inner Jet Emitting Disc, which is itself powering magneto-centrifugally driven winds, and an outer standard accretion disc; (2) at the interface between an inner closed stellar magnetosphere and the outer standard accretion disc. We refer to Terminal or T-winds to the former kind and to Magnetospheric or M-winds to the latter. The full set of resistive and viscous steady state MHD equations are analyzed for the disc (the annulus), which allow us to derive general expressions valid for both configurations. We find that, under the framework of our analysis, the only source of energy able to power any kind of fan-shaped winds is the viscous transport of rotat...

  13. High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo

    E-Print Network [OSTI]

    Anders Johansen; Yuri Levin

    2008-08-26T23:59:59.000Z

    Hydromagnetic stresses in accretion discs have been the subject of intense theoretical research over the past one and a half decades. Most of the disc simulations have assumed a small initial magnetic field and studied the turbulence that arises from the magnetorotational instability. However, gaseous discs in galactic nuclei and in some binary systems are likely to have significant initial magnetisation. Motivated by this, we performed ideal magnetohydrodynamic simulations of strongly magnetised, vertically stratified discs in a Keplerian potential. Our initial equilibrium configuration, which has an azimuthal magnetic field in equipartion with thermal pressure, is unstable to the Parker instability. This leads to the expelling of magnetic field arcs, anchored in the midplane of the disc, to around five scale heights from the midplane. Transition to turbulence happens primarily through magnetorotational instability in the resulting vertical fields, although magnetorotational shear instability in the unperturbed azimuthal field plays a significant role as well, especially in the midplane where buoyancy is weak. High magnetic and hydrodynamical stresses arise, yielding an effective $\\alpha$-value of around 0.1 in our highest resolution run. Azimuthal magnetic field expelled by magnetic buoyancy from the disc is continuously replenished by the stretching of a radial field created as gas parcels slide in the linear gravity field along inclined magnetic field lines. This dynamo process, where the bending of field lines by the Parker instability leads to re-creation of the azimuthal field, implies that highly magnetised discs are astrophysically viable and that they have high accretion rates.

  14. Eccentricity growth of planetesimals in a self-gravitating protoplanetary disc

    E-Print Network [OSTI]

    M. Britsch; C. J. Clarke; G. Lodato

    2008-01-14T23:59:59.000Z

    We investigate the orbital evolution of planetesimals in a self-gravitating circumstellar disc in the size regime ($\\sim 1-5000$ km) where the planetesimals behave approximately as test particles in the disc's non-axisymmetric potential. We find that the particles respond to the stochastic, regenerative spiral features in the disc by executing large random excursions (up to a factor of two in radius in $\\sim 1000$ years), although typical random orbital velocities are of order one tenth of the Keplerian speed. The limited time frame and small number of planetesimals modeled does not permit us to discern any {\\it net} direction of planetesimal migration. Our chief conclusion is that the high eccentricities ($\\sim 0.1$) induced by interaction with spiral features in the disc is likely to be highly unfavourable to the collisional growth of planetesimals in this size range while the disc is in the self-gravitating regi me. Thus {\\it if}, as recently argued by Rice et al 2004, 2006, the production of planetesimals gets under way when the disc is in the self-gravitating regime (either at smaller planetesimal size scales, where gas drag is important, or via gravitational fragmentation of the solid component), then the planetesimals thus produced would not be able to grow collisionally until the disc ceased to be self-gravitating. It is unclear, however,given the large amplitude excursions undergone by planetesimals in the self-gravitating disc, whether they would be retained in the disc throughout this period, or whether they would instead be lost to the central star.

  15. Maximally Random Jamming of Two-Dimensional One-Component and Binary Hard Disc Fluids

    E-Print Network [OSTI]

    Xinliang Xu; Stuart A. Rice

    2010-10-05T23:59:59.000Z

    We report calculations of the density of maximally random jamming (aka random close packing) of one-component and binary hard disc fluids. The theoretical structure used provides a common framework for description of the hard disc liquid to hexatic, the liquid to hexagonal crystal and the liquid-to-maximally random jammed state transitions. Our analysis is based on locating a particular bifurcation of the solutions of the integral equation for the inhomogeneous single particle density at the transition between different spatial structures. The bifurcation of solutions we study is initiated from the dense metastable fluid, and we associate it with the limit of stability of the fluid, which we identify with the transition from the metastable fluid to a maximally random jammed state. For the one-component hard disc fluid the predicted packing fraction at which the metastable fluid to maximally random jammed state transition occurs is 0.84, in excellent agreement with the experimental value 0.84 \\pm 0.02. The corresponding analysis of the limit of stability of a binary hard disc fluid with specified disc diameter ratio and disc composition requires extra approximations in the representations of the direct correlation function, the equation of state, and the number of order parameters accounted for. Keeping only the order parameter identified with the largest peak in the structure factor of the highest density regular lattice with the same disc diameter ratio and disc composition as the binary fluid, the predicted density of maximally random jamming is found to be 0.84 to 0.87, depending on the equation of state used, and very weakly dependent on the ratio of disc diameters and the fluid composition, in agreement with both experimental data and computer simulation data.

  16. An analysis of the annual probability of failure of the waste hoist brake system at the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect (OSTI)

    Greenfield, M.A. [Univ. of California, Los Angeles, CA (United States); Sargent, T.J.

    1995-11-01T23:59:59.000Z

    The Environmental Evaluation Group (EEG) previously analyzed the probability of a catastrophic accident in the waste hoist of the Waste Isolation Pilot Plant (WIPP) and published the results in Greenfield (1990; EEG-44) and Greenfield and Sargent (1993; EEG-53). The most significant safety element in the waste hoist is the hydraulic brake system, whose possible failure was identified in these studies as the most important contributor in accident scenarios. Westinghouse Electric Corporation, Waste Isolation Division has calculated the probability of an accident involving the brake system based on studies utilizing extensive fault tree analyses. This analysis conducted for the U.S. Department of Energy (DOE) used point estimates to describe the probability of failure and includes failure rates for the various components comprising the brake system. An additional controlling factor in the DOE calculations is the mode of operation of the brake system. This factor enters for the following reason. The basic failure rate per annum of any individual element is called the Event Probability (EP), and is expressed as the probability of failure per annum. The EP in turn is the product of two factors. One is the {open_quotes}reported{close_quotes} failure rate, usually expressed as the probability of failure per hour and the other is the expected number of hours that the element is in use, called the {open_quotes}mission time{close_quotes}. In many instances the {open_quotes}mission time{close_quotes} will be the number of operating hours of the brake system per annum. However since the operation of the waste hoist system includes regular {open_quotes}reoperational check{close_quotes} tests, the {open_quotes}mission time{close_quotes} for standby components is reduced in accordance with the specifics of the operational time table.

  17. On the accumulation of solid bodies in global turbulent protoplanetary disc models

    E-Print Network [OSTI]

    Sebastien Fromang; Richard P. Nelson

    2005-09-23T23:59:59.000Z

    We study the migration of solid bodies in turbulent protoplanetary accretion discs by means of global MHD simulations. The bodies range in size from 5 centimetres up to 1 metre, and so include objects whose migration is expected to be the most rapid due to gas drag interaction with the disc. As they drift inward through the disc, some of them are trapped in regions where gas pressure maxima are created by long lived anticyclonic vortices. This accumulation is very efficient, locally increasing the dust--to--gas ratio by a factor > 100 in some cases. We discuss the possible implications of this result for theories of planet formation.

  18. A viscous-convective instability in laminar Keplerian thin discs. II. Anelastic approximation

    E-Print Network [OSTI]

    Shakura, N

    2015-01-01T23:59:59.000Z

    Using the anelastic approximation of linearised hydrodynamic equations, we investigate the development of axially symmetric small perturbations in thin Keplerian discs. The sixth-order dispersion equation is derived and numerically solved for different values of relevant physical parameters (viscosity, heat conductivity, disc semi-thickness and vertical structure). The analysis reveals the appearance of two overstable modes which split out from the classical Rayleigh inertial modes in a wide range of the parameters in both ionized and neutral gases. These modes have a viscous-convective nature and can serve as a seed for turbulence in astrophysical discs even in the absence of magnetic fields.

  19. A collagen-GAG matrix for the growth of intervertebral disc tissue

    E-Print Network [OSTI]

    Hastreiter, Dawn (Dawn Marie), 1973-

    2002-01-01T23:59:59.000Z

    Intervertebral disc (IVD) degeneration and herniation is a significant problem, more so in the aviation field. The IVD also changes during spaceflight. Current treatments for IVD problems can have unfavorable long-term ...

  20. Retinal imaging tool for assessment of the parapapillary atrophy and the optic disc

    E-Print Network [OSTI]

    Lu, Cheng-Kai

    2012-11-29T23:59:59.000Z

    Ophthalmic diseases such as glaucoma are associated with progressive changes in the structure of the optic disc (OD) and parapapillary atrophy (PPA). These structural changes may therefore have relevance to other systemic ...

  1. E-Print Network 3.0 - accretion disc variability Sample Search...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    370, L61L65 (2006) doi:10.1111j.1745-3933.2006.00189.x The late time evolution of gamma-ray bursts: ending hyperaccretion Summary: of GRBs. Key words: accretion, accretion discs -...

  2. Spectra of disc operator for twisted acceleration-enlarged Newton-Hooke space-times

    E-Print Network [OSTI]

    Marcin Daszkiewicz

    2011-01-10T23:59:59.000Z

    The time-dependent spectra of disc area operator for twisted acceleration-enlarged Newton-Hooke space-times are derived. It is demonstrated that the corresponding area quanta are expanding or oscillating in time.

  3. NDE1 in the DISC1 pathway: interactions of schizophrenia-related proteins

    E-Print Network [OSTI]

    Bradshaw, Nicholas James

    2009-01-01T23:59:59.000Z

    The Disrupted-In-Schizophrenia 1 (DISC1) gene is one of the most established risk genes for psychiatric illness currently being studied, having originally been identified as being directly disrupted by a balanced chromosomal ...

  4. Dynamics of perturbation modes in protoplanetary discs : new effects of self-gravity and velocity shear

    E-Print Network [OSTI]

    Mamatsashvili, George

    2011-06-27T23:59:59.000Z

    Protoplanetary discs, composed of gas and dust, usually surround young stellar objects and serve two main purposes: they determine the accretion of matter onto the central object and also represent sites of planet ...

  5. Quantum McKay correspondence for disc invariants of toric Calabi-Yau 3-orbifolds

    E-Print Network [OSTI]

    Hua-Zhong Ke; Jian Zhou

    2014-10-16T23:59:59.000Z

    We announce a result on quantum McKay correspondence for disc invariants of outer legs in toric Calabi-Yau 3-orbifolds, and illustrate our method in a special example $[\\mathbb C^3 /\\mathbb Z_5 (1, 1, 3)]$.

  6. Spectral Evolution of the Continuum and Disc Line in Dipping in GRO J1655-40

    E-Print Network [OSTI]

    M. Balucinska-Church

    2001-01-22T23:59:59.000Z

    The discovery is reported of emission features in the X-ray spectrum of GRO J1655-40 obtained using Rossi-XTE on 1997, Feb 26. The features have been fitted firstly by two Gaussian lines, which in four spectra have average energies of 5.85+/-0.08 keV and 7.32+/-0.13 keV, strongly suggestive that these are the red- and blueshifted wings of an iron disc line from material with velocity ~0.33 c. The blue wing is apparently less bright than expected for a disc line subject to Doppler boosting, however, known absorption in the spectrum of GRO J1655-40 at energies between ~7 and 8 keV can reduce the apparent brightness of the blue wing. The spectra have also been fitted well using the full relativistic disc line model of Laor, plus an absorption line. This gives a restframe energy between 6.4 and 6.8 keV indicating that the line is from highly ionized iron K_alpha. The Laor model also shows that the line originates at radii extending from ~10 Schwarzschild radii (r_S) outwards. The line is direct evidence for the black hole nature of the compact object. The continuum is well described by dominant disc blackbody emission plus Comptonized emission. During dipping, spectral evolution is well modelled by allowing progressive covering of the disc blackbody and simple absorption of the Comptonized emission showing that the thermal emission is more extended. Acceptable fits are only obtained by including the disc line in the covering term, indicating that it originates in the same inner disc region as the thermal continuum. Dip ingress times and durations are used to provide the radius of the disc blackbody emitter as 170-370 r_S, and the radius of the absorber.

  7. Hard discs under steady shear: comparison of Brownian dynamics simulations and mode coupling theory

    E-Print Network [OSTI]

    O. Henrich; F. Weysser; M. E. Cates; M. Fuchs

    2010-01-19T23:59:59.000Z

    Brownian dynamics simulations of bidisperse hard discs moving in two dimensions in a given steady and homogeneous shear flow are presented close to and above the glasstransition density. The stationary structure functions and stresses of shear-melted glass are compared quantitatively to parameter-free numerical calculations of monodisperse hard discs using mode coupling theory within the integration through transients framework. Theory qualitatively explains the properties of the yielding glass but quantitatively overestimatesthe shear-driven stresses and structural anisotropies.

  8. Secular resonant dressed orbital diffusion II : application to an isolated self similar tepid galactic disc

    E-Print Network [OSTI]

    Fouvry, Jean-Baptiste

    2015-01-01T23:59:59.000Z

    The main orbital signatures of the secular evolution of an isolated self-gravitating stellar Mestel disc are recovered using a dressed Fokker-Planck formalism in angle-action variables. The shot-noise-driven formation of narrow ridges of resonant orbits is recovered in the WKB limit of tightly wound transient spirals, for a tepid Toomre-stable tapered disc. The relative effect of the bulge, the halo, the disc temperature and the spectral properties of the shot noise are investigated in turn. For such galactic discs all elements seem to impact the locus and direction of the ridge. For instance, when the halo mass is decreased, we observe a transition between a regime of heating in the inner regions of the disc through the inner Lindblad resonance to a regime of radial migration of quasi-circular orbits via the corotation resonance in the outer part of the disc. The dressed secular formalism captures both the nature of collisionless systems (via their natural frequencies and susceptibility), and their nurture v...

  9. Searching for the metal-weak thick disc in the solar neighbourhood

    E-Print Network [OSTI]

    Bacham E. Reddy; David L. Lambert

    2008-09-05T23:59:59.000Z

    An abundance analysis is presented of 60 metal-poor stars drawn from catalogues of nearby stars provided by Ariyanto et al. (2005) and Schuster et al. (2006). In an attempt to isolate a sample of metal-weak thick disc stars, we applied the kinematic criteria $V_{\\rm rot} \\geq 100$ km s$^{-1}$, $|U_{LSR}| \\leq 140$ km s$^{-1}$, and $|W_{LSR}| \\leq 100$ km s$^{-1}$. Fourteen stars satisfying these criteria and having [Fe/H] $\\leq -1.0$ are included in the sample of 60 stars. Eight of the 14 have [Fe/H] $\\geq -1.3$ and may be simply thick disc stars of slightly lower than average [Fe/H]. The other six have [Fe/H] from -1.3 to -2.3 and are either metal-weak thick disc stars or halo stars with kinematics mimicking those of the thick disc. The sample of 60 stars is completed by eight thick disc stars, 20 stars of a hybrid nature (halo or thick disc stars), and 18 stars with kinematics distinctive of the halo.

  10. One-armed spirals in locally isothermal, radially structured self-gravitating discs

    E-Print Network [OSTI]

    Lin, Min-Kai

    2015-01-01T23:59:59.000Z

    We describe a new mechanism that leads to the destabilisation of non-axisymmetric waves in astrophysical discs with an imposed radial temperature gradient. This might apply, for example, to the outer parts of protoplanetary discs. We use linear density wave theory to show that non-axisymmetric perturbations generally do not conserve their angular momentum in the presence of a forced temperature gradient. This implies an exchange of angular momentum between linear perturbations and the background disc. In particular, when the disturbance is a low-frequency trailing wave and the disc temperature decreases outwards, this interaction is unstable and leads to the growth of the wave. We demonstrate this phenomenon through numerical hydrodynamic simulations of locally isothermal discs in 2D using the FARGO code and in 3D with the ZEUS-MP and PLUTO codes. We consider radially structured discs with a self-gravitating region which remains stable in the absence of a temperature gradient. However, when a temperature grad...

  11. The Gaia-ESO Survey: Insights on the inner-disc evolution from open clusters

    E-Print Network [OSTI]

    Magrini, L; Donati, P; Bragaglia, A; Adibekyan, V; Romano, D; Smiljanic, R; Blanco-Cuaresma, S; Tautvaisiene, G; Friel, E; Overbeek, J; Jacobson, H; Cantat-Gaudin, T; Vallenari, A; Sordo, R; Pancino, E; Geisler, D; Roman, I San; Villanova, S; Casey, A; Hourihane, A; Worley, C C; Francois, P; Gilmore, G; Bensby, T; Flaccomio, E; Korn, A J; Recio-Blanco, A; Carraro, G; Costado, M T; Franciosini, E; Heiter, U; Jofree, P; Lardo, C; de Laverny, P; Monaco, L; Morbidelli, L; Sacco, G; Sousa, S G; Zaggia, S

    2015-01-01T23:59:59.000Z

    Context. The inner disc, linking the thin disc with the bulge, has been somehow neglected in the past because of intrinsic difficulties in its study, due, e.g., to crowding and high extinction. Open clusters located in the inner disc are among the best tracers of its chemistry at different ages and distances. Aims. We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic Centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods. We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of 5.4 kpc. We construct the chemical patterns of clusters and we compare them with those of field stars in the Solar neighbourhood and in the inner-disc samples. Results. Comparing the three populations we observe that inner-disc clusters and field stars are both, on average, enhanced in [O/Fe], [Mg/Fe] and [Si/Fe]. Using the idr2/3 results of M67, we estimate...

  12. Liberation of specific angular momentum through radiation and scattering in relativistic black hole accretion discs

    E-Print Network [OSTI]

    Adam R. H. Stevens

    2015-02-26T23:59:59.000Z

    A key component of explaining the array of galaxies observed in the Universe is the feedback of active galactic nuclei, each powered by a massive black hole's accretion disc. For accretion to occur, angular momentum must be lost by that which is accreted. Electromagnetic radiation must offer some respite in this regard, the contribution for which is quantified in this paper using solely general relativity under the thin-disc regime. Herein, I calculate extremised situations where photons are entirely responsible for energy removal in the disc and then extend and relate this to the standard relativistic accretion disc outlined by Novikov & Thorne that includes the effect of viscosity. While there is potential for the contribution of angular-momentum removal from photons to be >~1% out to ~10^4 Schwarzschild radii, especially if the disc is irradiated and is liberated of angular momentum through scattering, it is more likely of order 10^2 Schwarzschild radii if thermal emission from the disc itself is stronger. Near the horizons of fast-spinning black holes, these modes of angular-momentum liberation become dominant.

  13. Methods for enhancing mapping of thermal fronts in oil recovery

    DOE Patents [OSTI]

    Lee, David O. (Albuquerque, NM); Montoya, Paul C. (Albuquerque, NM); Wayland, Jr., James R. (Albuquerque, NM)

    1987-01-01T23:59:59.000Z

    A method for enhancing the resistivity contrasts of a thermal front in an oil recovery production field as measured by the CSAMT technique is disclosed. This method includes the steps of: (a) preparing a CSAMT-determined topological resistivity map of the production field; (b) introducing a solution of a dopant material into the production field at a concentration effective to alter the resistivity associated with the thermal front; said dopant material having a high cation exchange capacity which might be selected from the group consisting of montmorillonite, illite, and chlorite clays; said material being soluble in the connate water of the production field; (c) preparing a CSAMT-determined topological resistivity map of the production field while said dopant material is moving therethrough; and (d) mathematically comparing the maps from step (a) and step (c) to determine the location of the thermal front. This method is effective with the steam flood, fire flood and water flood techniques.

  14. Acoustic wave front reversal in a three-phase media

    E-Print Network [OSTI]

    N. I. Pushkina

    2015-03-05T23:59:59.000Z

    Acoustic wave front conjugation is studied in a sandy marine sediment that contains air bubbles in its fluid fraction. The considered phase conjugation is a four-wave nonlinear parametric sound interaction process caused by nonlinear bubble oscillations which are known to be dominant in acoustic nonlinear interactions in three-phase marine sediments. Two various mechanisms of phase conjugation are studied. One of them is based on the stimulated Raman-type sound scattering on resonance bubble oscillations. The second one is associated with sound interactions with bubble oscillations which frequencies are far from resonance bubble frequencies. Nonlinear equations to solve the wave-front conjugation problem are derived, expressions for acoustic wave amplitudes with a reversed wave front are obtained and compared for various frequencies of the excited bubble oscillations.

  15. Acoustic wave front conjugation in a three-phase media

    E-Print Network [OSTI]

    Pushkina, N I

    2015-01-01T23:59:59.000Z

    Acoustic wave front reversal is studied in a sandy marine sediment that contains air bubbles in its fluid fraction. The considered phase conjugation is a four-wave nonlinear parametric sound interaction process caused by nonlinear bubble oscillations which are known to be dominant in acoustic nonlinear interactions in three-phase marine sediments. Two various mechanisms of phase conjugation are studied. One of them is based on the stimulated Raman-type sound scattering on resonance bubble oscillations. The second one is associated with sound interactions with bubble oscillations which frequencies are far from resonance bubble frequencies. Nonlinear equations to solve the wave-front conjugation problem are derived, expressions for acoustic wave amplitudes with a reversed wave front are obtained and compared for various frequencies of the excited bubble oscillations.

  16. Methods for enhancing mapping of thermal fronts in oil recovery

    DOE Patents [OSTI]

    Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

    1984-03-30T23:59:59.000Z

    A method for enhancing the resistivity contrasts of a thermal front in an oil recovery production field as measured by the controlled source audio frequency magnetotelluric (CSAMT) technique is disclosed. This method includes the steps of: (1) preparing a CSAMT-determined topological resistivity map of the production field; (2) introducing a solution of a dopant material into the production field at a concentration effective to alter the resistivity associated with the thermal front; said dopant material having a high cation exchange capacity which might be selected from the group consisting of montmorillonite, illite, and chlorite clays; said material being soluble in the conate water of the production field; (3) preparing a CSAMT-determined topological resistivity map of the production field while said dopant material is moving therethrough; and (4) mathematically comparing the maps from step (1) and step (3) to determine the location of the thermal front. This method is effective with the steam flood, fire flood and water flood techniques.

  17. Light-front holographic QCD and emerging confinement

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Brodsky, Stanley J.; de Tramond, Guy F.; Dosch, Hans Gnter; Erlich, Joshua

    2015-07-01T23:59:59.000Z

    In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. Themorelight-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.less

  18. Light-Front Holographic QCD and Emerging Confinement

    E-Print Network [OSTI]

    Stanley J. Brodsky; Guy F. de Teramond; Hans Gunter Dosch; Joshua Erlich

    2015-02-13T23:59:59.000Z

    In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here gives a precise interpretation of holographic variables and quantities in AdS in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound states in physical space-time. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large $q^2$ the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low $q^2$ the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

  19. Light-front holographic QCD and emerging confinement

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Brodsky, Stanley J. [SLAC National Accelerator Laboratory, Stanford, CA (United States); de Tramond, Guy F. [Universidad de Costa Rica, San Jos, (Costa Rica); Dosch, Hans Gnter [Institut fr Theoretische Physik, Heidelberg (Germany); Erlich, Joshua [College of William and Mary, Williamsburg, VA (United States)

    2015-07-01T23:59:59.000Z

    In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

  20. Emergent Mesoscale Phenomena in Magnetized Accretion Disc Turbulence

    E-Print Network [OSTI]

    Simon, Jacob B; Armitage, Philip J

    2012-01-01T23:59:59.000Z

    We study how the structure and variability of magnetohydrodynamic (MHD) turbulence in accretion discs converge with domain size. Our results are based on a series of vertically stratified local simulations, computed using the Athena code, that have fixed spatial resolution, but varying radial and azimuthal extent (from \\Delta R = 0.5H to 16H, where H is the vertical scale height). We show that elementary local diagnostics of the turbulence, including the Shakura-Sunyaev {\\alpha} parameter, the ratio of Maxwell stress to magnetic energy, and the ratio of magnetic to fluid stresses, converge to within the precision of our measurements for spatial domains of radial size Lx \\geq 2H. We obtain {\\alpha} = 0.02-0.03, consistent with recent results. Very small domains (Lx = 0.5H) return anomalous results, independent of spatial resolution. The convergence with domain size is only valid for a limited set of diagnostics: larger spatial domains admit the emergence of dynamically important mesoscale structures. In our la...

  1. Measuring the configurational temperature of a binary disc packing

    E-Print Network [OSTI]

    Song-Chuan Zhao; Matthias Schrter

    2014-06-20T23:59:59.000Z

    Jammed packings of granular materials differ from systems normally described by statistical mechanics in that they are athermal. In recent years a statistical mechanics of static granular media has emerged where the thermodynamic temperature is replaced by a configurational temperature X which describes how the number of mechanically stable configurations depends on the volume. Four different methods have been suggested to measure X. Three of them are computed from properties of the Voronoi volume distribution, the fourth takes into account the contact number and the global volume fraction. This paper answers two questions using experimental binary disc packings: First we test if the four methods to measure compactivity provide identical results when applied to the same dataset. We find that only two of the methods agree quantitatively. Secondly, we test if X is indeed an intensive variable; this becomes true only for samples larger than roughly 200 particles. This result is shown to be due to recently found correlations between the particle volumes [Zhao et al., Europhys. Lett., 2012, 97, 34004].

  2. Survival and Structure of Dusty Vortices in Protoplanetary Discs

    E-Print Network [OSTI]

    Crnkovic-Rubsamen, Ivo; Stone, James M

    2015-01-01T23:59:59.000Z

    We have studied the impact of dust feedback on the survival and structure of vortices in protoplanetary discs using 2-D shearing box simulations with Lagrangian dust particles. We consider dust with a variety of sizes (stopping time $t_s = 10^{-2}\\Omega^{-1} - 10^{2}\\Omega^{-1}$, from fully coupled with the gas to the decoupling limit. We find that a vortex is destroyed by dust feedback when the total dust-to-gas mass ratio within the vortex is larger than 30-50%, independent of the dust size. The dust distribution can still be asymmetric in some cases after the vortex has been destroyed. With smaller amounts of dust, a vortex can survive for at least 100 orbits, and the maximum dust surface density within the vortex can be more than 100 times larger than the gas surface density, potentially facilitating planetesimal formation. On the other hand, in these stable vortices, small ($t_s \\Omega^{-1}$) dust grains concentrate differently and affect the gas dynamics in different ways. The distribution of large dus...

  3. Jammed frictionless discs: connecting local and global response

    E-Print Network [OSTI]

    Wouter G. Ellenbroek; Martin van Hecke; Wim van Saarloos

    2009-11-04T23:59:59.000Z

    By calculating the linear response of packings of soft frictionless discs to quasistatic external perturbations, we investigate the critical scaling behavior of their elastic properties and non-affine deformations as a function of the distance to jamming. Averaged over an ensemble of similar packings, these systems are well described by elasticity, while in single packings we determine a diverging length scale $\\ell^*$ up to which the response of the system is dominated by the local packing disorder. This length scale, which we observe directly, diverges as $1/\\Delta z$, where $\\Delta z$ is the difference between contact number and its isostatic value, and appears to scale identically to the length scale which had been introduced earlier in the interpretation of the spectrum of vibrational modes. It governs the crossover from isostatic behavior at the small scale to continuum behavior at the large scale; indeed we identify this length scale with the coarse graining length needed to obtain a smooth stress field. We characterize the non-affine displacements of the particles using the \\emph{displacement angle distribution}, a local measure for the amount of relative sliding, and analyze the connection between local relative displacements and the elastic moduli.

  4. On the speed of fast and slow rupture fronts along frictional interfaces

    E-Print Network [OSTI]

    Trmborg, Jrgen Kjoshagen; Thgersen, Kjetil; Scheibert, Julien; Malthe-Srenssen, Anders

    2015-01-01T23:59:59.000Z

    The transition from stick to slip at a dry frictional interface occurs through the breaking of the junctions between the two contacting surfaces. Typically, interactions between the junctions through the bulk lead to rupture fronts propagating from weak and/or highly stressed regions, whose junctions break first. Experiments find rupture fronts ranging from quasi-static fronts with speeds proportional to external loading rates, via fronts much slower than the Rayleigh wave speed, and fronts that propagate near the Rayleigh wave speed, to fronts that travel faster than the shear wave speed. The mechanisms behind and selection between these fronts are still imperfectly understood. Here we perform simulations in an elastic 2D spring--block model where the frictional interaction between each interfacial block and the substrate arises from a set of junctions modeled explicitly. We find that a proportionality between material slip speed and rupture front speed, previously reported for slow fronts, actually holds ac...

  5. Travel Reimbursement Request Form Submit to: Front Desk

    E-Print Network [OSTI]

    Rose, Michael R.

    Travel Reimbursement Request Form Submit to: Front Desk Department of Pharmaceutial Sciences 147 expenses) If travel time does not include overnight stay (between 7AM - 8PM), the traveler should not claim before 11 AM and arrival after 2 PM; dinner - departure before 5 PM. PM and arrival after 7 PM NOTE

  6. Travel Reimbursement Request Form Submit to: Front Desk

    E-Print Network [OSTI]

    Loudon, Catherine

    Travel Reimbursement Request Form Submit to: Front Desk Department of Pharmaceutical Sciences 147 : Maximum: $71.00 (Itemize meal expenses) If travel time does not include overnight stay (between 7AM - 8PM; lunch - departure before 11 AM and arrival after 2 PM; dinner - departure before 5 PM. PM and arrival

  7. IDENTIFICATION OF MOBILITIES FOR THE BUCKLEYLEVERETT EQUATION BY FRONT TRACKING

    E-Print Network [OSTI]

    IDENTIFICATION OF MOBILITIES FOR THE BUCKLEYLEVERETT EQUATION BY FRONT TRACKING VIDAR HAUGSE Multi--phase flow in porous media is modelled by Darcy's law. This empirical relation relates is also used to solve the saturation equation in a commercial reservoir simulator [1]. 2. Equations

  8. An Adaptive Front-end Readout System for Radiation Detection

    E-Print Network [OSTI]

    Stanacevic, Milutin

    An Adaptive Front-end Readout System for Radiation Detection Xiao Yun and Milutin Stana to compensate for the variations of the detector and readout circuitry. II. READOUT SYSTEM FOR RADIATION DETECTION Readout circuitry is directly interfaced to the photodiode and produces a voltage signal

  9. Flame front tracking by laser induced fluorescence spectroscopy and advanced

    E-Print Network [OSTI]

    Hamarneh, Ghassan

    surface characteristics in turbulent premixed propane/air combustion," Combustion and Flame 120(4), 407 References and links 1. J. Warnatz, U. Maas, and R.W. Dibble, Combustion - physical and chemical fundamentals, "Characterization of flame front surfaces in turbulent premixed methane/air combustion," Combustion and Flame 101

  10. Front Vehicle Blind Spot Translucentization Based on Augmented Reality

    E-Print Network [OSTI]

    Wang, Yuan-Fang

    Front Vehicle Blind Spot Translucentization Based on Augmented Reality Che-Tsung Lin, Yu-Chen Lin--Recently, WAVE/DSRC has become an attrac- tive technology for vehicular safety applications. Vehicles with WAVE/DSRC devices can communicate with their neighboring vehicles to exchange information to achieve collaborative

  11. Front and backside processed thin film electronic devices

    DOE Patents [OSTI]

    Evans, Paul G. (Madison, WI); Lagally, Max G. (Madison, WI); Ma, Zhenqiang (Middleton, WI); Yuan, Hao-Chih (Lakewood, CO); Wang, Guogong (Madison, WI); Eriksson, Mark A. (Madison, WI)

    2012-01-03T23:59:59.000Z

    This invention provides thin film devices that have been processed on their front- and backside. The devices include an active layer that is sufficiently thin to be mechanically flexible. Examples of the devices include back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

  12. The effects of X-ray photoionization and heating on the structure of circumstellar discs

    E-Print Network [OSTI]

    R. D. Alexander; C. J. Clarke; J. E. Pringle

    2004-06-29T23:59:59.000Z

    We present the results of a theoretical study investigating the effects of photoionization and heating by X-rays on discs around low-mass stars. In particular we address the question of whether or not X-rays can drive a disc wind. First, we construct a 1-dimensional ``quasi-hydrostatic'' model, which solves for the vertical structure introduced by X-ray heating. We consider uniform X-ray illumination of the disc, but the X-ray fluxes required to heat the disc significantly are much greater than those seen by recent observations. When the model is extended to consider heating from a central X-ray source we find that the 1-dimensional model is only valid very close to the star. We extend our analysis to consider a simple 2-dimensional model, treating the disc as a two-layered structure and solving for its density profile self-consistently. For T Tauri stars we are able to set a crude upper limit on the mass-loss rate that can be driven by X-ray photoevaporation, with a value of ~10^-13 g/cm^2/s. Our model is designed to maximise this value, and most likely over-estimates it significantly. However we still find a mass-loss rate which is less than that found in studies of ultraviolet photoevaporation. We conclude that in the presence of a significant UV field, X-ray driven disc winds are unlikely to play a significant role in the evolution of discs around low-mass stars.

  13. Evolution of binary black holes in self gravitating discs: dissecting the torques

    E-Print Network [OSTI]

    Constanze Roedig; Alberto Sesana; Massimo Dotti; Jorge Cuadra; Pau Amaro-Seoane; Francesco Haardt

    2012-08-14T23:59:59.000Z

    We study the interplay between gas accretion and gravity torques in changing a binary elements and its total angular momentum (L) budget. Especially, we analyse the physical origin of the gravity torques (T_g) and their location within the disc. We analyse 3D SPH simulations of the evolution of initially quasi-circular massive black hole binaries (BHBs) residing in the central hollow of massive self-gravitating circumbinary discs. We use different thermodynamics within the cavity and for the numerical size of the black holes to show that (i) the BHB eccentricity growth found previously is a general result, independent of the accretion and the adopted thermodynamics; (ii) the semi-major axis decay depends both on the T_g and on the interplay with the disc-binary L-transfer due to accretion; (iii) the spectral structure of the T_g is predominately caused by disc edge overdensities and spiral arms developing in the body of the disc and, in general, does not reflect directly the period of the binary; (iv) the net T_g changes sign across the BHB corotation radius. We quantify the relative importance of the two, which appear to depend on the thermodynamical properties of the instreaming gas, and which is crucial in assessing the disc-binary L-transfer; (v) the net torque manifests as a purely kinematic (non-resonant) effect as it stems from the cavity, where the material flows in and out in highly eccentric orbits. Both accretion onto the black holes and the interaction with gas streams inside the cavity must be taken into account to assess the fate of the BHB. Moreover, the total torque exerted by the disc affects L(BHB) by changing all the elements (mass, mass ratio, eccentricity, semimajor axis) of the BHB. Common prescriptions equating tidal torque to semi-major axis shrinking might therefore be poor approximations for real astrophysical systems.

  14. Accretion Disc Turbulence and the X-Ray Power Spectra of Black Hole High States

    E-Print Network [OSTI]

    Michael A. Nowak; Robert V. Wagoner

    1994-10-06T23:59:59.000Z

    The high state of black hole candidates is characterized by a quasi- thermal emission component at $kT \\sim 1$ keV. In addition, this state tends to have very low variability which indicates that it is relatively stable, at least on {\\it short} time scales. Most models of the high state imply that the bulk of the emission comes from an optically thick accretion disc; therefore, this state may be an excellent laboratory for testing our ideas about the physics of accretion discs. In this work we consider the implications of assuming that accretion disc viscosity arises from some form of turbulence. Specifically, we consider the simple case of three dimensional hydrodynamic turbulence. It is found that the coupling of such turbulence to acoustic modes in the disc can alter the disc emission. We calculate the amplitude and frequencies of this modulation, and we express our results in terms of the X-ray power spectral density. We compare our calculations with observations of the black hole candidate GS 1124-683, and show that for certain parameters we can reproduce some of the high frequency power. We then briefly explore mechanisms for producing the low frequency power, and note the difficulty that a single variability mechanism has in reproducing the full range of observed variability. In addition, we outline ways in which future spacecraft missions -- such as USA and XTE -- can further constrain our model, especially at frequencies above $\\sim 10^2$ Hz.

  15. On the migration of two planets in a disc and the formation of mean motion resonances

    E-Print Network [OSTI]

    Migaszewski, Cezary

    2015-01-01T23:59:59.000Z

    We study the dynamics of a system of two super-Earths embedded in a protoplanetary disc. Depending on the disc parameters, planets' masses and positions in the disc, the migration of a planet can be inward or outward and the migration of a two-planet system can be convergent or divergent. The convergent migration means that the period ratio P2/P1 decreases in time. In such a case mean motion resonance (MMR) can be formed when the period ratio reaches a resonant value of a first order MMR (p+1)/p, where p is a small integer. When the divergent migration occurs, P2/P1 increases in time and a system initially close to MMR moves away from the resonance. We build a simple model of an irradiated viscous disc and use analytical prescriptions for the planet-disc interactions. We performed 3500 simulations of the migration of two-planet systems with various masses and initial orbits. We found that approximately half of the systems end up as configurations involved in one of the first order MMRs such as 2:1, 3:2, 4:3 a...

  16. The evolution of disc galaxies with and without classical bulges since z~1

    E-Print Network [OSTI]

    Sachdeva, Sonali; Saha, Kanak; Singh, Harinder P

    2015-01-01T23:59:59.000Z

    Establishing the relative role of internally and externally driven mechanisms responsible for disc and bulge growth is essential to understand the evolution of disc galaxies. In this context, we have studied the physical properties of disc galaxies without classical bulges in comparison to those with classical bulges since z~0.9. Using images from the Hubble Space Telescope and Sloan Digital Sky Survey, we have computed both parametric and non-parametric measures, and examined the evolution in size, concentration, stellar mass, effective stellar mass density and asymmetry. We find that both disc galaxies with and without classical bulges have gained more than 50% of their present stellar mass over the last ~8 Gyrs. Also, the increase in disc size is found to be peripheral. While the average total (Petrosian) radius almost doubles from z~0.9 to z~0, the average effective radius undergoes a marginal increase in comparison. Additionally, increase in the density of the inner region is evident through the evolutio...

  17. Massively Parallel Computation of Sti Propagating Combustion frontsMarc Garbey and Damien Tromeur-Dervout

    E-Print Network [OSTI]

    Garbey, Marc

    In this paper we study the computation of combustion fronts using MIMD archi- tecture. Our applications in gas models of combustion fronts: rst, a classical thermo-di usive model describing the combustion of a gasMassively Parallel Computation of Sti Propagating Combustion frontsMarc Garbey and Damien Tromeur

  18. Magnetic Turbulence and Thermodynamics in the Inner Region of Protoplanetary Discs

    E-Print Network [OSTI]

    Hirose, Shigenobu

    2015-01-01T23:59:59.000Z

    Using radiation magnetohydrodynamics simulations with realistic opacities and equation of state, and zero net magnetic flux, we have explored thermodynamics in the inner part of protoplanetary discs where magnetic turbulence is expected. The thermal equilibrium curve consists of the upper, lower, and middle branches. The upper (lower) branch corresponds to hot (cool) and optically very (moderately) thick discs, respectively, while the middle branch is characterized by convective energy transport near the midplane. Convection is also the major energy transport process near the low surface density end of the upper branch. There, convective motion is fast with Mach numbers reaching $\\gtrsim 0.01$, and enhances both magnetic turbulence and cooling, raising the ratio of vertically-integrated shear stress to vertically-integrated pressure by a factor of several. This convectively enhanced ratio seems a robust feature in accretion discs having an ionization transition. We have also examined causes of the S-shaped th...

  19. On the black hole limit of rotating discs of charged dust

    E-Print Network [OSTI]

    Martin Breithaupt; Yu-Chun Liu; Reinhard Meinel; Stefan Palenta

    2015-05-04T23:59:59.000Z

    Investigating the rigidly rotating disc of dust with constant specific charge, we find that it leads to an extreme Kerr-Newman black hole in the ultra-relativistic limit. A necessary and sufficient condition for a black hole limit is, that the electric potential in the co-rotating frame is constant on the disc. In that case certain other relations follow. These relations are reviewed with a highly accurate post-Newtonian expansion. Remarkably it is possible to survey the leading order behaviour close to the black hole limit with the post-Newtonian expansion. We find that the disc solution close to that limit can be approximated very well by a "hyper\\-extreme" Kerr-Newman solution with the same gravitational mass, angular momentum and charge.

  20. The structure and radiation spectra of illuminated accretion discs in AGN. I. Moderate illumination

    E-Print Network [OSTI]

    A. R?a?ska; A. -M. Dumont; B. Czerny; S. Collin

    2002-02-12T23:59:59.000Z

    We present detailed computations of the vertical structure of an accretion disc illuminated by hard X-ray radiation with the code {\\sc titan-noar} suitable for Compton thick media. The energy generated via accretion is dissipated partially in the cold disc as well as in the X-ray source. We study the differences between the case where the X-ray source is in the form of a lamp post above the accretion disc and the case of a heavy corona. We consider radiative heating via Comptonization together with heating via photo-absorption on numerous heavy elements as carbon, oxygen, silicon, iron. The transfer in lines is precisely calculated. A better description of the heating/cooling through the inclusion of line transfer, a correct description of the temperature in the deeper layers, a correct description of the entire disc vertical structure, as well as the study of the possible coronal pressure effect, constitute an improvement in comparison to previous works. We show that exact calculations of hydrostatic equilibrium and determination of the disc thickness has a crucial impact on the optical depth of the hot illuminated zone. We assume a moderate illumination where the viscous flux equals the X-ray radiation flux. A highly ionized skin is created in the lamp post model, with the outgoing spectrum containing many emission lines and ionization edges in emission or absorption in the soft X-ray domain, as well as an iron line at $\\sim 7 $ keV consisting of a blend of low ionization line from the deepest layers and hydrogen and helium like resonance line from the upper layers, and almost no absorption edge, contrary to the case of a slab of constant density.A full heavy corona completely suppresses the highly ionized zone on the top of the accretion disc and in such case the spectrum is featureless.

  1. Physics design of front ends for superconducting ion linacs

    SciTech Connect (OSTI)

    Ostroumov, P.N.; /Argonne; Carneiro, J.P.; /Fermilab

    2009-01-01T23:59:59.000Z

    Superconducting (SC) technology is the only option for CW linacs and is also an attractive option for pulsed linacs. SC cavities are routinely used for proton and H{sup -} beam acceleration above 185 MeV. Successful development of SC cavities covering the lower velocity range (down to 0.03c) is a very strong basis for the application of SC structures in the front ends of high energy linacs. Lattice design and related high-intensity beam physics issues in a {approx}400 MeV linac that uses SC cavities will be presented in this talk. In particular, axially-symmetric focusing by SC solenoids provides strong control of beam space-charge and a compact focusing lattice. As an example, we discuss the SC front-end of the H{sup -} linac for the FNAL Proton Driver.

  2. Physics design of front ends for superconducting ion linacs

    SciTech Connect (OSTI)

    Ostroumov, P.N.; /Argonne; Carneiro, J.-P.; /Fermilab

    2008-09-01T23:59:59.000Z

    Superconducting (SC) technology is the only option for CW linacs and is also an attractive option for pulsed linacs. SC cavities are routinely used for proton and H{sup -} beam acceleration above 185 MeV. Successful development of SC cavities covering the lower velocity range (down to 0.03c) is a very strong basis for the application of SC structures in the front ends of high energy linacs. Lattice design and related high-intensity beam physics issues in a {approx}400 MeV linac that uses SC cavities will be presented in this talk. In particular, axially-symmetric focusing by SC solenoids provides strong control of beam space charge and a compact focusing lattice. As an example, we discuss the SC front end of the H{sup -} linac for the FNAL Proton Driver.

  3. Towards the Light Front Variables for High Energy Production Processes

    E-Print Network [OSTI]

    N. S. Amaglobeli; S. M. Esakia; V. R. Garsevanishvili; G. O. Kuratashvili; N. K. Kutsidi; R. A. Kvatadze; Yu V. Tevzadze; T. P. Topuria

    1997-03-21T23:59:59.000Z

    Scale invariant presentation of inclusive spectra in terms of light front variables is proposed. The variables introduced go over to the well-known scaling variables x_F = 2p_z/sqrt(s) and x_T=2p_T/sqrt{s} in the high p_z and high p_T limits respectively. So Some surface is found in the phase space of produced pi-mesons in the inclusive reaction anti p p -> pi+- X at 22.4 GeV/c, which separates two groups of particles with significantly different characteristics. In one of these regions a naive statistical model seems to be in a good agreement with data, whereas it fails in the second region. Key words: Light front, inclusive, hadron-hadron, electron-positron, relativistic heavy ions, deep inelastic.

  4. Tracking thermal fronts with temperature-sensitive, chemically reactive tracers

    SciTech Connect (OSTI)

    Robinson, B.A.; Birdsell, S.A.

    1987-01-01T23:59:59.000Z

    Los Alamos is developing tracer techniques using reactive chemicals to track thermal fronts in fractured geothermal reservoirs. If a nonadsorbing tracer flowing from the injection to production well chemically reacts, its reaction rate will be a strong function of temperature. Thus the extent of chemical reaction will be greatest early in the lifetime of the system, and less as the thermal front progresses from the injection to production well. Early laboratory experiments identified tracers with chemical kinetics suitable for reservoirs in the temperature range of 75 to 100/sup 0/C. Recent kinetics studies have focused on the kinetics of hydrolysis of derivatives of bromobenzene. This class of reactions can be used in reservoirs ranging in temperature from 150 to 275/sup 0/C, which is of greater interest to the geothermal industry. Future studies will include laboratory adsorption experiments to identify possibly unwanted adsorption on granite, development of sensitive analytical techniques, and a field demonstration of the reactive tracer concept.

  5. Ionization front-driven turbulence in the clumpy interstellar medium

    E-Print Network [OSTI]

    Thomas Peters; Robi Banerjee; Ralf S. Klessen

    2008-08-20T23:59:59.000Z

    We present 3D radiation-gasdynamical simulations of an ionization front running into a dense clump. In our setup, a B0 star irradiates an overdensity which is at a distance of 10 pc and modelled as a supercritical 100 M_sol Bonnor-Ebert sphere. The radiation from the star heats up the gas and creates a shock front that expands into the interstellar medium. The shock compresses the clump material while the ionizing radiation heats it up. The outcome of this "cloud-crushing" process is a fully turbulent gas in the wake of the clump. In the end, the clump entirely dissolves. We propose that this mechanism is very efficient in creating short-living supersonic turbulence in the vicinity of massive stars.

  6. W.C. Heraeus GmbH and its activities regarding large grain Niobium Discs

    SciTech Connect (OSTI)

    Spaniol, Bernd [W.C.Heraeus GmbH, Engineered Material Division, Heraeusstrasse 12-14, 63450 Hanau (Germany)

    2007-08-09T23:59:59.000Z

    W.C. Heraeus is one of the leading companies in the field of precious and refractory metals. The refractory metals activities have been started in 1940. W.C. Heraeus is one of the qualified suppliers for high pure Niobium for the use in high-frequency-super-conducting cavities. The latest activities in that field are the development of a stable Electron-Beam-Melting and reliable cutting processes to produce large grain Niobium discs directly cut from the Ingot in an industrial scale. The first cavities out of these discs have been tested and are showing excellent magnetic properties.

  7. Adaptive two-regime method: Application to front propagation

    SciTech Connect (OSTI)

    Robinson, Martin, E-mail: martin.robinson@maths.ox.ac.uk; Erban, Radek, E-mail: erban@maths.ox.ac.uk [Mathematical Institute, University of Oxford, Andrew Wiles Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG (United Kingdom)] [Mathematical Institute, University of Oxford, Andrew Wiles Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG (United Kingdom); Flegg, Mark, E-mail: mark.flegg@monash.edu [School of Mathematical Sciences, Faculty of Science, Monash University Wellington Road, Clayton, Victoria 3800 (Australia)] [School of Mathematical Sciences, Faculty of Science, Monash University Wellington Road, Clayton, Victoria 3800 (Australia)

    2014-03-28T23:59:59.000Z

    The Adaptive Two-Regime Method (ATRM) is developed for hybrid (multiscale) stochastic simulation of reaction-diffusion problems. It efficiently couples detailed Brownian dynamics simulations with coarser lattice-based models. The ATRM is a generalization of the previously developed Two-Regime Method [Flegg et al., J. R. Soc., Interface 9, 859 (2012)] to multiscale problems which require a dynamic selection of regions where detailed Brownian dynamics simulation is used. Typical applications include a front propagation or spatio-temporal oscillations. In this paper, the ATRM is used for an in-depth study of front propagation in a stochastic reaction-diffusion system which has its mean-field model given in terms of the Fisher equation [R. Fisher, Ann. Eugen. 7, 355 (1937)]. It exhibits a travelling reaction front which is sensitive to stochastic fluctuations at the leading edge of the wavefront. Previous studies into stochastic effects on the Fisher wave propagation speed have focused on lattice-based models, but there has been limited progress using off-lattice (Brownian dynamics) models, which suffer due to their high computational cost, particularly at the high molecular numbers that are necessary to approach the Fisher mean-field model. By modelling only the wavefront itself with the off-lattice model, it is shown that the ATRM leads to the same Fisher wave results as purely off-lattice models, but at a fraction of the computational cost. The error analysis of the ATRM is also presented for a morphogen gradient model.

  8. A Life Cycle Assessment of a Magnesium Automotive Front End

    SciTech Connect (OSTI)

    Das, Sujit [ORNL; Dubreuil, Alain [Natural Resources Canada; Bushi, Lindita [GreenhouseGasMeasurement.com; Tharumarajah, Ambalavanar [CSIRO/CAST-CRC

    2009-01-01T23:59:59.000Z

    The Magnesium Front End Research and Development (MFERD) project under the sponsorship of Canada, China and USA aims to develop key technologies and a knowledge base for increased use of magnesium in automobile. The goal of this life cycle assessment (LCA) study is to compare the energy and potential environmental impacts of advanced magnesium based front end parts of a North America built 2007 GM-Cadillac CTS with the standard carbon steel based design. This LCA uses the 'cradle-to-grave' approach by including primary material production, semi-fabrication production, autoparts manufacturing and assembly, transportation, use phase and end-of-life processing of autoparts. This LCA study was done in compliance with international standards ISO 14040:2006 and ISO 14044:2006. Furthermore, the LCA results for aluminum based front end autopart are presented. While weight savings result in reductions in energy use and carbon dioxide emissions during the use of the car, the impacts of fabrication and recycling of lightweight materials are substantial in regard to steel. Pathways for improving sustainability of magnesium use in automobiles through material management and technology improvements including recycling are also discussed.

  9. The Gaia-ESO Survey: a quiescent Milky Way with no significant dark/stellar accreted disc

    E-Print Network [OSTI]

    Ruchti, G R; Feltzing, S; Serenelli, A M; McMillan, P; Lind, K; Bensby, T; Bergemann, M; Asplund, M; Vallenari, A; Flaccomio, E; Pancino, E; Korn, A J; Recio-Blanco, A; Bayo, A; Carraro, G; Costado, M T; Damiani, F; Heiter, U; Hourihane, A; Jofre, P; Kordopatis, G; Lardo, C; de Laverny, P; Monaco, L; Morbidelli, L; Sbordone, L; Worley, C C; Zaggia, S

    2015-01-01T23:59:59.000Z

    According to our current cosmological model, galaxies like the Milky Way are expected to experience many mergers over their lifetimes. The most massive of the merging galaxies will be dragged towards the disc-plane, depositing stars and dark matter into an accreted disc structure. In this work, we utilize the chemo-dynamical template developed in Ruchti et al. to hunt for accreted stars. We apply the template to a sample of 4,675 stars in the third internal data release from the Gaia-ESO Spectroscopic Survey. We find a significant component of accreted halo stars, but find no evidence of an accreted disc component. This suggests that the Milky Way has had a rather quiescent merger history since its disc formed some 8-10 billion years ago and therefore possesses no significant dark matter disc.

  10. Energetics of star-disc encounters in the non-linear regime

    E-Print Network [OSTI]

    S. M. Hall; C. J. Clarke; J. E. Pringle

    1995-10-31T23:59:59.000Z

    We investigate the response of a circumstellar accretion disc to the fly-by of a perturbing mass on a parabolic orbit. The energy and angular momentum transferred during the encounter are calculated using a reduced three-body method. In almost all close encounters the energy and angular momentum transfer is dominated by disc material becoming unbound from the system, with the contributions from close disc particle -- star encounters being significant. For more distant encounters with some prograde element to the motion the disc material loses energy and angular momentum to the perturber's orbit through a resonance feature. The magnitude of the energy transfer calculated in our simulations is greater than that of the binding energy of material exterior to periastron by a factor of two in the prograde case, and up to a factor of five in the case of the retrograde encounter. The destructive nature of the encounters indicates that a non-linear treatment is essential in all but the most distant encounters.

  11. Anisotropic radiation from accretion disc-coronae in active galactic nuclei

    E-Print Network [OSTI]

    Xu, Ya-Di

    2015-01-01T23:59:59.000Z

    In the unification scheme of active galactic nuclei (AGN), Seyfert 1s and Seyfert 2s are intrinsically same, but they are viewed at different angles. However, the Fe K\\alpha emission line luminosity of Seyfert 1s was found in average to be about twice of that of Seyfert 2s at given X-ray continuum luminosity in the previous work (Ricci et al. 2014). We construct an accretion disc-corona model, in which a fraction of energy dissipated in the disc is extracted to heat the corona above the disc. The radiation transfer equation containing Compton scattering processes is an integro-differential equation, which is solved numerically for the corona with a parallel plane geometry. We find that the specific intensity of X-ray radiation from the corona changes little with the viewing angle \\theta when \\theta is small (nearly face-on), and it is sensitive to \\theta if the viewing angle is large (\\theta> 40 degrees). The radiation from the cold disc, mostly in infrared/optical/UV bands, is almost proportional to cos\\thet...

  12. Internal Alignments of Red Versus Blue Discs in Dark Matter Halos

    E-Print Network [OSTI]

    Debattista, Victor P; Roskar, Rok; Quinn, Thomas; Moore, Ben; Cole, David R

    2015-01-01T23:59:59.000Z

    Large surveys have shown that red galaxies are preferentially aligned with their halos while blue galaxies have a more isotropic distribution. Since halos generally align with their filaments this introduces a bias in the measurement of the cosmic shear from weak lensing. It is therefore vitally important to understand why this difference arises. We explore the stability of different disc orientations within triaxial halos. We show that, in the absence of gas, the disc orientation is most stable when its spin is along the minor axis of the halo. Instead when gas cools onto a disc it is able to form in almost arbitrary orientation, including off the main planes of the halo (but avoiding an orientation perpendicular to the halo's intermediate axis). Substructure helps gasless galaxies reach alignment with the halo faster, but have less effect on galaxies when gas is cooling onto the disc. Our results provide a novel and natural interpretation for why red, gas poor galaxies are preferentially aligned with their ...

  13. The local star formation history of the thin disc derived from kinematic data

    E-Print Network [OSTI]

    A. Just; H. Jahreiss

    2010-12-27T23:59:59.000Z

    We present an evolutionary disc model for the thin disc in the solar cylinder based on a continuous star formation history and a continuous dynamical heating of the stellar subpopulations. The vertical distribution of the stellar subpopulations are calculated self-consistently in dynamical equilibrium. The SFR and AVR of the stellar subpopulations are determined by fitting the velocity distribution functions of main sequence stars. The SFR shows a maximum 10 Gyr ago declining by a factor of 10 until present time. A constant SFR can be ruled out. The velocity dispersion of the stellar subpopulations increase with age according to a power law with index 0.375. The new scale heights lead to a best fit IMF with power-law indices of 1.5 below and 4.0 above 1.6 Msun, which has no kink around 1 Msun. Including a thick disc component results in slight variations of the thin disc properties, but has a negligible influence on the SFR. A variety of predictions are made concerning the number density, age and metallicity distributions of stellar subpopulations as a function of z above the galactic plane.

  14. Searching for signatures of planet formation in stars with circumstellar debris discs

    E-Print Network [OSTI]

    Maldonado, J; Villaver, E; Montesinos, B; Mora, A

    2015-01-01T23:59:59.000Z

    (Abridged) Tentative correlations between the presence of dusty debris discs and low-mass planets have been presented. In parallel, detailed chemical abundance studies have reported different trends between samples of planet and non-planet hosts. We determine in a homogeneous way the metallicity, and abundances of a sample of 251 stars including stars with known debris discs, with debris discs and planets, and only with planets. Stars with debris discs and planets have the same [Fe/H] behaviour as stars hosting planets, and they also show a similar -Tc trend. Different behaviour in the -Tc trend is found between the samples of stars without planets and the samples of planet hosts. In particular, when considering only refractory elements, negative slopes are shown in cool giant planet hosts, whilst positive ones are shown in stars hosting low-mass planets. Stars hosting exclusively close-in giant planets show higher metallicities and positive -Tc slope. A search for correlations between the -Tc slopes and the ...

  15. The structure and radiation spectra of illuminated accretion discs in AGN. I. Moderate illumination

    E-Print Network [OSTI]

    Rzanska, A R; Czerny, B; Collin, S

    2002-01-01T23:59:59.000Z

    We present detailed computations of the vertical structure of an accretion disc illuminated by hard X-ray radiation with the code {\\sc titan-noar} suitable for Compton thick media. The energy generated via accretion is dissipated partially in the cold disc as well as in the X-ray source. We study the differences between the case where the X-ray source is in the form of a lamp post above the accretion disc and the case of a heavy corona. We consider radiative heating via Comptonization together with heating via photo-absorption on numerous heavy elements as carbon, oxygen, silicon, iron. The transfer in lines is precisely calculated. A better description of the heating/cooling through the inclusion of line transfer, a correct description of the temperature in the deeper layers, a correct description of the entire disc vertical structure, as well as the study of the possible coronal pressure effect, constitute an improvement in comparison to previous works. We show that exact calculations of hydrostatic equilib...

  16. Gathering data on allegations of sexual abuse made against former disc jockey, Jimmy Savile

    E-Print Network [OSTI]

    Smith, Mark; Kirkwood, Steve; Llewellyn, Clare

    2014-08-26T23:59:59.000Z

    This paper will report on a collaboration between Social Work and Informatics academics and Library staff at the University. The focus of the work is to secure a data set on allegations of sexual abuse made against the former disc jockey, Jimmy...

  17. DiSC: Benchmarking Secure Chip DBMS Nicolas Anciaux, Luc Bouganim, Philippe Pucheral, and Patrick Valduriez

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    DiSC: Benchmarking Secure Chip DBMS Nicolas Anciaux, Luc Bouganim, Philippe Pucheral, and Patrick irrelevant. The main problem faced by secure chip DBMS designers is to be able to assess various design choices and trade-offs for different applications. Our solution is to use a benchmark for secure chip DBMS

  18. 2D-Zernike polynomials and coherent state quantization of the unit disc

    E-Print Network [OSTI]

    K. Thirulogasanthar; Nasser Saad; G. Honnouvo

    2015-01-07T23:59:59.000Z

    Using the orthonormality of the 2D-Zernike polynomials, reproducing kernels, reproducing kernel Hilbert spaces, and ensuring coherent states attained. With the aid of the so-obtained coherent states, the complex unit disc is quantized. Associated upper symbols, lower symbols and related generalized Berezin transforms also obtained. A number of necessary summation formulas for the 2D-Zernike polynomials proved.

  19. Resonant Trapping in the Galactic Disc and Halo and its Relation with Moving Groups

    E-Print Network [OSTI]

    Moreno, Edmundo; Schuster, William

    2015-01-01T23:59:59.000Z

    With the use of a detailed Milky Way nonaxisymmetric potential, observationally and dynamically constrained, the e?ects of the bar and the spiral arms in the Galaxy are studied in the disc and in the stellar halo. Especially the trapping of stars in the disc and Galactic halo by resonances on the Galactic plane, induced by the Galactic bar, has been analysed in detail. To this purpose, a new method is presented to delineate the trapping regions using empirical diagrams of some orbital properties obtained in the Galactic potential. In these diagrams we plot in the inertial Galactic frame a characteristic orbital energy versus a characteristic orbital angular momentum, or versus the orbital Jacobi constant in the reference frame of the bar, when this is the only nonaxisymmetric component in the Galactic potential. With these diagrams some trapping regions are obtained in the disc and halo using a sample of disc stars and halo stars in the solar neighbourhood. We compute several families of periodic orbits on th...

  20. Tidal disruptions in circumbinary discs (I): Star formation, dynamics, and binary evolution

    E-Print Network [OSTI]

    Pau Amaro-Seoane; Patrick Brem; Jorge Cuadra

    2012-12-11T23:59:59.000Z

    In our current interpretation of the hierarchical structure of the universe it is well established that galaxies collide and merge with each other during their lifetime. If massive black holes (MBHs) reside in galactic centres, we expect them to form binaries in galactic nuclei surrounded by a circumbinary disc. If cooling is efficient enough, the gas in the disc will clump and trigger stellar formation in situ. In this first paper we address the evolution of the binary under the influence of the newly formed stars, which form individually and also clustered. We use SPH techniques to evolve the gas in the circumbinary disc and to study the phase of star formation. When the amount of gas in the disc is negligible, we further evolve the system with a high-accurate direct-summation $N-$body code to follow the evolution of the stars, the innermost binary and tidal disruption events (TDEs). For this, we modify the direct N-body code to (i) include treatment of TDEs and to (ii) include "gas cloud particles" that mimic the gas, so that the stellar clusters do not disolve when we follow their infall on to the MBHs. We find that the amount of stars disrupted by either infalling stellar clusters or individual stars is as large as 10^{-4}/yr per binary, higher than expected for typical galaxies.

  1. Sedimenting discs in a two-dimensional foam I. T. Davies, S. J. Cox

    E-Print Network [OSTI]

    Cox, Simon

    -dimensional foams can be thought of as a monolayer of bubbles squeezed between two glass plates. We choose to probeSedimenting discs in a two-dimensional foam I. T. Davies, S. J. Cox Institute of Mathematics in a dry two-dimensional, monodisperse foam is studied. This, a variation of the classical Stokes

  2. Environmentally benign manufacturing of compact disc stampers [Final Phase II report

    SciTech Connect (OSTI)

    None

    1999-07-08T23:59:59.000Z

    Optical data storage is currently a $10B/yr. business. With the introduction of the high capacity Digital Versatile Disc (D/D) as well as the continued growth of CD-Audio and CD-ROM worldwide sales of optical data products as a whole are growing at rate of more than 10% per year. In North America, more than 2.5 billion optical discs will be sold in 1998. By 1999, the numbers of optical discs produced for the North American market will grow to almost three billion. The optical disc manufacturing industry is dominated by Asian and European companies (e.g. Sony of Japan and Philips of Netherlands). Prism Corporation has created a process that could significantly improve US competitiveness in the business of optical disc production. The objectives of the Phase II STTR project were to build and test an ion machining system (IMS) for stamper fabrication, prove overall manufacturing system feasibility by fabrication stampers and replicas, and evaluate alternative materials and alternative process parameters to optimize the process. During tie period of the Phase II project Prism Corporation was able to meet these objectives. In the course of doing so, adjustments had been made to better the project and in turn the final product. An ion machining system was designed and built that produced stampers ready for the molding process. Also, many control steps in the manufacturing process were studied to improve the current process and make it even more compatible with the industry standards, fitting seamlessly into current manufacturing lines.

  3. Automatic signal processing of front monitor radar for tunneling machines

    SciTech Connect (OSTI)

    Sato, Toru [Kyoto Univ. (Japan). Dept. of Electronics and Communication] [Kyoto Univ. (Japan). Dept. of Electronics and Communication; Takeda, Kenya [NTT Co. Ltd., Chiba (Japan)] [NTT Co. Ltd., Chiba (Japan); Nagamatsu, Takashi [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)] [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan); Wakayama, Toshio [Mitsubishi Electric Corp., Kamakura, Kanagawa (Japan)] [Mitsubishi Electric Corp., Kamakura, Kanagawa (Japan); Kimura, Iwane [Osaka Inst. of Tech., Hirakata, Osaka (Japan)] [Osaka Inst. of Tech., Hirakata, Osaka (Japan); Shinbo, Tetsuya [Komatsu Co. Ltd., Kanagawa (Japan)] [Komatsu Co. Ltd., Kanagawa (Japan)

    1997-03-01T23:59:59.000Z

    It is planned to install a front monitoring impulse radar on the surface of the rotating drill of tunneling machines in order to detect obstacles such as casing pipes of vertical borings. The conventional aperture synthesis technique can no more be applied to such cases because the radar image of a pipe dies not constituent a hyperbola as is the case for linear scanning radars. The authors have developed a special purpose signal processing algorithm with the aid of the discrete model fitting method, which can be used for any pattern of scanning. The details of the algorithm are presented together with the results of numerical simulations and test site experiments.

  4. Consistent perturbative light front formulation of Yang-Mills theories

    SciTech Connect (OSTI)

    Morara, M.; Soldati, R. [Dipartimento di Fisica 'A. Righi', Universita di Bologna (Italy); McCartor, G. [Department of Physics, SMU, Dallas, Texas (United States)

    1999-11-22T23:59:59.000Z

    It is shown how to obtain the consistent light front form quantization of a non-Abelian pure Yang-Mills theory (gluondynamics) in the framework of the standard perturbative approach. After a short review of the previous attempts in the light cone gauge A{sub -}=0, it is explained how the difficulties can be overcome after turning to the anti light cone gauge A{sub +}=0. In particular, the generating functional of the renormalized Green's functions turns out to be the same as in the conventional instant form approach, leading to the Mandelstam-Leibbrandt prescription for the free gluon propagator.

  5. Instrument Front-Ends at Fermilab During Run II

    SciTech Connect (OSTI)

    Meyer, Thomas; Slimmer, David; Voy, Duane; /Fermilab

    2011-07-13T23:59:59.000Z

    The optimization of an accelerator relies on the ability to monitor the behavior of the beam in an intelligent and timely fashion. The use of processor-driven front-ends allowed for the deployment of smart systems in the field for improved data collection and analysis during Run II. This paper describes the implementation of the two main systems used: National Instruments LabVIEW running on PCs, and WindRiver's VxWorks real-time operating system running in a VME crate processor.

  6. Front surface thermal property measurements of air plasma spray coatings

    SciTech Connect (OSTI)

    Bennett, Ted; Kakuda, Tyler [University of California, Santa Barbara, California 93106-5070 (United States); Kulkarni, Anand [Siemens Energy, Orlando, Florida 32826-2399 (United States)

    2009-04-15T23:59:59.000Z

    A front-surface measurement for determining the thermal properties of thermal barrier coatings has been applied to air plasma spray coatings. The measurement is used to determine all independent thermal properties of the coating simultaneously. Furthermore, with minimal requirements placed on the sample and zero sample preparation, measurements can be made under previously impossible conditions, such as on serviceable engine parts. Previous application of this technique was limited to relatively thin coatings, where a one-dimensional heat transfer model is applied. In this paper, the influence of heat spreading on the measurement of thicker coatings is investigated with the development of a two-dimensional heat transfer model.

  7. BLM Sierra Front Field Office | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directedAnnualProperty EditCalifornia: EnergyAvignon, France: Energy ResourcesBurleyBLM Sierra Front Field

  8. The response of self-graviting protostellar discs to slow reduction in cooling timescale: the fragmentation boundary revisited

    E-Print Network [OSTI]

    C. Clarke; E. Harper-Clark; G. Lodato

    2007-08-06T23:59:59.000Z

    A number of previous studies of the fragmentation of self-gravitating protostellar discs have modeled radiative cooling with a cooling timescale (t_{cool}) parameterised as a simple multiple (beta_{cool}) of the local dynamical timescale. Such studies have delineated the `fragmentation boundary' in terms of a critical value of beta_{cool} (beta_{crit}), where the disc fragments if beta_{cool} < beta_{crit}. Such an approach however begs the question of how in reality a disc could ever be assembled with beta_{cool} < beta_{crit}. Here we adopt the more realistic approach of gradually reducing beta_{cool}, as might correspond to changes in thermal regime due to secular changes in the disc density profile. We find that when beta_{cool} is gradually reduced (on a timescale longer than t_{cool}), the disc is stabilised against fragmentation, compared with models in which beta_{cool} is reduced rapidly. We therefore conclude that a disc's ability to remain in a self-regulated, self-gravitating state (without fragmentation) is partly dependent on its thermal history, as well as its current cooling rate. Nevertheless, a slow reduction in t_{cool} appears only to lower the fragmentation boundary by about a factor two in t_{cool} and thus only permits maximum alpha values (parameterising the efficiency of angular momentum transfer in the disc) that are about a factor two higher than determined hitherto. Our results therefore do not undermine the notion of a fundamental upper limit to the heating rate that can be delivered by gravitational instabilities before the disc is subject to fragmentation. An important implication of this work, therefore, is that self-gravitating discs can enter into the regime of fragmentation via secular evolution and it is not necessary to invoke rapid (impulsive) events to trigger fragmentation.

  9. Commissioning of the SNS front-end systems at Berkeley Lab

    E-Print Network [OSTI]

    2002-01-01T23:59:59.000Z

    COMMISSIONING OF THE SNS FRONT-END SYSTEMS AT BERKELEY LAB*Details of other MEBT commissioning efforts, especiallywere provided by LANL. Commissioning topics included beam

  10. Pion light-front wave function, parton distribution and the electromagnetic form factor

    E-Print Network [OSTI]

    Thomas Gutsche; Valery E. Lyubovitskij; Ivan Schmidt; Alfredo Vega

    2014-10-23T23:59:59.000Z

    We derive a light-front wave function of the pion, which reproduces its valence parton distribution and a electromagnetic form factor consistent with data.

  11. Formation of planetary debris discs around white dwarfs II: Shrinking extremely eccentric collisionless rings

    E-Print Network [OSTI]

    Veras, Dimitri; Eggl, Siegfried; Gaensicke, Boris T

    2015-01-01T23:59:59.000Z

    The formation channel of the tens of compact debris discs which orbit white dwarfs (WDs) at a distance of one Solar radius remains unknown. Asteroids that survive the giant branch stellar phases beyond a few au are assumed to be dynamically thrust towards the WD and tidally disrupted within its Roche radius, generating extremely eccentric (e>0.98) rings. Here, we establish that WD radiation compresses and circularizes the orbits of super-micron to cm-sized ring constituents to entirely within the WD's Roche radius. We derive a closed algebraic formula which well-approximates the shrinking time as a function of WD cooling age, the physical properties of the star and the physical and orbital properties of the ring particles. The shrinking timescale increases with both particle size and cooling age, yielding age-dependent WD debris disc size distributions.

  12. AN EMPIRICAL FORMULA FOR THE DISTRIBUTION FUNCTION OF A THIN EXPONENTIAL DISC

    SciTech Connect (OSTI)

    Sharma, Sanjib; Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

    2013-08-20T23:59:59.000Z

    An empirical formula for a Shu distribution function that reproduces a thin disc with exponential surface density to good accuracy is presented. The formula has two free parameters that specify the functional form of the velocity dispersion. Conventionally, this requires the use of an iterative algorithm to produce the correct solution, which is computationally taxing for applications like Markov Chain Monte Carlo model fitting. The formula has been shown to work for flat, rising, and falling rotation curves. Application of this methodology to one of the Dehnen distribution functions is also shown. Finally, an extension of this formula to reproduce velocity dispersion profiles that are an exponential function of radius is also presented. Our empirical formula should greatly aid the efficient comparison of disc models with large stellar surveys or N-body simulations.

  13. Method and system for assigning a confidence metric for automated determination of optic disc location

    DOE Patents [OSTI]

    Karnowski, Thomas P. (Knoxville, TN); Tobin, Jr., Kenneth W. (Harriman, TN); Muthusamy Govindasamy, Vijaya Priya (Knoxville, TN); Chaum, Edward (Memphis, TN)

    2012-07-10T23:59:59.000Z

    A method for assigning a confidence metric for automated determination of optic disc location that includes analyzing a retinal image and determining at least two sets of coordinates locating an optic disc in the retinal image. The sets of coordinates can be determined using first and second image analysis techniques that are different from one another. An accuracy parameter can be calculated and compared to a primary risk cut-off value. A high confidence level can be assigned to the retinal image if the accuracy parameter is less than the primary risk cut-off value and a low confidence level can be assigned to the retinal image if the accuracy parameter is greater than the primary risk cut-off value. The primary risk cut-off value being selected to represent an acceptable risk of misdiagnosis of a disease having retinal manifestations by the automated technique.

  14. Applying Schwarzschild's orbit superposition method to barred or non-barred disc galaxies

    E-Print Network [OSTI]

    Vasiliev, Eugene

    2015-01-01T23:59:59.000Z

    We present an implementation of the Schwarzschild orbit superposition method which can be used for constructing self-consistent equilibrium models of barred or non-barred disc galaxies, or of elliptical galaxies with figure rotation. This is a further development of the publicly available code SMILE; its main improvements include a new efficient representation of an arbitrary gravitational potential using two-dimensional spline interpolation of Fourier coefficients in the meridional plane, as well as the ability to deal with rotation of the density profile and with multicomponent mass models. We compare several published methods for constructing composite axisymmetric disc--bulge--halo models and demonstrate that our code produces the models that are closest to equilibrium. We also apply it to create models of triaxial elliptical galaxies with cuspy density profiles and figure rotation, and find that such models can be found and are stable over many dynamical times in a wide range of pattern speeds and angula...

  15. Free motion around black holes with discs or rings: between integrability and chaos - I

    E-Print Network [OSTI]

    O. Semerk; P. Sukov

    2012-11-17T23:59:59.000Z

    Geodesic dynamics is regular in the fields of isolated stationary black holes. However, due to the presence of unstable periodic orbits, it easily becomes chaotic under various perturbations. Here we examine what amount of chaoticity is induced in Schwarzschild space-time by a presence of an additional source. Following astrophysical motivation, we specifically consider thin rings or discs lying symmetrically around the hole, and describe the total field in terms of exact static and axially symmetric solutions of Einstein's equations. The growth of chaos in time-like geodesic motion is illustrated on Poincar\\'e sections, on time series of position or velocity and their Fourier spectra, and on time evolution of the orbital `latitudinal action'. The results are discussed in dependence on the mass and position of the ring/disc and on geodesic parameters (energy and angular momentum). In the Introduction, we also add an overview of the literature.

  16. A Fragile-Strong Fluid Crossover and Universal Relaxation Times in a Confined Hard Disc Fluid

    E-Print Network [OSTI]

    Mahdi Zaeifi Yamchi; S. S. Ashwin; Richard K. Bowles

    2012-10-22T23:59:59.000Z

    We show that a system of hard discs confined to a narrow channel exhibits a fragile-strong fluid crossover located at the maximum of the isobaric heat capacity and that the relaxation times for different channel widths fall onto a single master curve when rescaled by the relaxation times and temperatures of the crossover. Calculations of the configurational entropy and the inherent structure equation of state find that the crossover is related to properties of the jamming landscape for the model but that the Adams-Gibbs relation does not predict the relaxation behavior. We also show that a facilitated dynamics description of the system, where kinetically excited regions are identified with local packing arrangements of the discs, successfully describes the fragile-strong crossover.

  17. Snow-lines as probes of turbulent diffusion in protoplanetary discs

    E-Print Network [OSTI]

    Owen, James E

    2014-01-01T23:59:59.000Z

    Sharp chemical discontinuities can occur in protoplanetary discs, particularly at `snow-lines' where a gas-phase species freezes out to form ice grains. Such sharp discontinuities will diffuse out due to the turbulence suspected to drive angular momentum transport in accretion discs. We demonstrate that the concentration gradient - in the vicinity of the snow-line - of a species present outside a snow-line but destroyed inside is strongly sensitive to the level of turbulent diffusion (provided the chemical and transport time-scales are decoupled) and provides a direct measurement of the radial `Schmidt number' (the ratio of the angular momentum transport to radial turbulent diffusion). Taking as an example the tracer species N$_2$H$^+$, which is expected to be destroyed inside the CO snow-line (as recently observed in TW Hya) we show that ALMA observations possess significant angular resolution to constrain the Schmidt number. Since different turbulent driving mechanisms predict different Schmidt numbers, a d...

  18. Flame front disturbance induced by a weak pressure wave

    SciTech Connect (OSTI)

    Dobashi, Ritsu; Hirano, Toshisuke; Tsuruda, Takashi [Univ. of Tokyo (Japan)

    1994-12-31T23:59:59.000Z

    An experimental study has been conducted on the effect of unburned mixture properties on flame front disturbance induced by acceleration. Experiments were performed using a rectangular combustion chamber of 80 x 80 x 440 mm. The flame front disturbance was observed in two different directions by high-speed schlieren photography. Mixtures used are of three different concentrations (C = 0.8, 1.0, and 1.25) of methane/air and two different concentrations (C = 1.0 and 1.5) of propane/air. For the methane/air mixture of C = 1.0, experiments were performed at three different initial pressures (P{sub i} = 50, 70, and 101 kPa). The observed disturbance was of a very fine structure of circular spikes, which penetrated into the burned gas. The scales of disturbance were measured and indicated to be in the range of 1.7--4.0 mm. The circular spike shape is a typical structure induced by accelerating the flame front where the density changes steeply. However, the shape of the disturbance observed for a rich propane/air mixture was not of circular spikes but of a net of ridges. For the rich propane/air mixture, the effect by preferential diffusion was remarkable and the disturbance of a different structure was generated. For the methane/air mixtures, the scale was the smallest at C = 1.0 and larger at C = 0.8 and 1.25. The scale for the propane/air mixture of C = 1.0 was slightly larger than that in the methane/air mixture of C = 1.0. The scale became larger with the decrease of the initial pressure. The measure scales were compared with the preheat zone thicknesses of corresponding flames. It was shown that the scale is closely related with the flame thickness. The scale of disturbance is found to be about 15 times as large as the preheat zone thickness.

  19. Gas cooling performance in disc winding of large-capacity gas-insulated transformer

    SciTech Connect (OSTI)

    Nakadate, M.; Toda, K.; Sato, K.; Biswas, D.; Nakagawa, C.; Yanari, T. [Toshiba Corp., Kawasaki (Japan)] [Toshiba Corp., Kawasaki (Japan)

    1996-04-01T23:59:59.000Z

    The authors have developed the gas-cooling system of a 275 kV, 300 MVA class gas-insulated transformer. In this study model experiments in which gas flow was substituted by water flow equivalently and 2-dimensional numerical flow analyses and network analyses were conducted. In this paper the outline of the development and optimization condition to get high cooling performance in SF{sub 6} gas-disc winding system of the transformer are presented.

  20. Free motion around black holes with discs or rings: between integrability and chaos - III

    E-Print Network [OSTI]

    P. Sukov; O. Semerk

    2013-08-20T23:59:59.000Z

    We continue the study of time-like geodesic dynamics in exact static, axially and reflection symmetric space-times describing the fields of a Schwarzschild black hole surrounded by thin discs or rings. In the first paper of this series, the rise (and decline) of geodesic chaos with ring/disc mass and position and with test particle energy was revealed on Poincar\\'e sections and on time series of position or velocity and their power spectra. In the second paper we compared these results with those obtained by two recurrence methods, focusing on "sticky" orbits whose different parts show different degrees of chaoticity. Here we complement the analysis by using several Lyapunov-type coefficients which quantify the rate of orbital divergence. After comparing the results with those obtained by the previous methods, we specifically consider a system involving a black hole surrounded by a small thin disc or a large ring, having in mind the configuration which probably occurs in galactic nuclei. Within the range of parameters which roughly corresponds to our Galactic center, we found that the black-hole accretion disc does not have a significant gravitational effect on the dynamics of free motion at larger radii, while the inner circumnuclear molecular ring (concentrated above 1 parsec radius) can only induce some irregularity in motion of stars ("particles") on smaller radii if its mass reaches 10 to 30% of the central black hole (which is the upper estimate given in the literature), if it is sufficiently compact (which does not hold but maybe for its inner rim) and if the stars can get to its close vicinity. The outer dust ring between 60 and 100 parsecs appears to be less important for the geodesic dynamics in its interior.

  1. Computer simulation of Poisson's ratio of soft polydisperse discs at zero temperature

    E-Print Network [OSTI]

    Jakub Narojczyk; Krzysztof W. Wojciechowski

    2015-04-09T23:59:59.000Z

    A simple algorithm is proposed for studies of structural and elastic properties in the presence of structural disorder at zero temperature. The algorithm is used to determine the properties of the polydisperse soft disc system. It is shown that the Poisson's ratio of the system essentially depends on the size polydispersity parameter - larger polydispersity implies larger Poisson's ratio. In the presence of any size polidispersity the Poisson's ratio increases also when the interactions between the particles tend to the hard potential.

  2. Full Hybrid: Braking

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuels Data Center HomeIdle Reduction WeightRebate - LADWPPublicE85 RetailNREL

  3. The ejection of T Tauri stars from molecular clouds and the fate of circumstellar discs

    E-Print Network [OSTI]

    P. J. Armitage; C. J. Clarke

    1996-10-21T23:59:59.000Z

    We investigate the evolution of circumstellar discs around T Tauri stars that are ejected from small stellar clusters within molecular clouds. In particular, we study how the interaction that leads to ejection may hasten the transition between Classical and Weak-lined T Tauri status. In our models, ejections of T Tauri stars at velocities of 3-10 km/s truncate the accretion disc at radii between 1 and 10 a.u., reducing the viscous evolution time of the disc so that accretion rapidly ceases. The observational appearance of the resulting systems is then dependent on the presence or absence of a stellar magnetic field. For non-magnetic stars we find that a near-infra red excess should persist due to reprocessing of stellar radiation, but that this is greatly diminished for magnetic T Tauri stars by the presence of a magnetosphere extending to corotation. In either case, there is a period when ejected stars should appear as non-accreting systems with detectable circumstellar material at wavelengths of 5 microns and beyond. We discuss the implications of these results for models in which ejected stars contribute to the halo of pre-main-sequence objects discovered from ROSAT observations of star forming regions and the All-Sky Survey.

  4. The Gemini NICI Planet-Finding Campaign: Asymmetries in the HD 141569 disc

    E-Print Network [OSTI]

    Biller, Beth A; Rice, W Ken; Wahhaj, Zahed; Nielsen, Eric; Hayward, Thomas; Kuchner, Marc; Close, Laird M; Chun, Mark; Ftaclas, Christ; Toomey, Douglas W

    2015-01-01T23:59:59.000Z

    We report here the highest resolution near-IR imaging to date of the HD 141569A disc taken as part of the NICI Science Campaign. We recover 4 main features in the NICI images of the HD 141569 disc discovered in previous HST imaging: 1) an inner ring / spiral feature. Once deprojected, this feature does not appear circular. 2) an outer ring which is considerably brighter on the western side compared to the eastern side, but looks fairly circular in the deprojected image. 3) an additional arc-like feature between the inner and outer ring only evident on the east side. In the deprojected image, this feature appears to complete the circle of the west side inner ring and 4) an evacuated cavity from 175 AU inwards. Compared to the previous HST imaging with relatively large coronagraphic inner working angles (IWA), the NICI coronagraph allows imaging down to an IWA of 0.3". Thus, the inner edge of the inner ring/spiral feature is well resolved and we do not find any additional disc structures within 175 AU. We note ...

  5. HERO: A 3D General Relativistic Radiative Postprocessor for Accretion Discs around Black Holes

    E-Print Network [OSTI]

    Zhu, Yucong; Sadowski, Aleksander; Psaltis, Dimitrios

    2015-01-01T23:59:59.000Z

    HERO (Hybrid Evaluator for Radiative Objects) is a 3D general relativistic radiative transfer code which has been tailored to the problem of analyzing radiation from simulations of relativistic accretion discs around black holes. HERO is designed to be used as a postprocessor. Given some fixed fluid structure for the disc (i.e. density and velocity as a function of position from a hydrodynamics or magnetohydrodynamics simulation), the code obtains a self-consistent solution for the radiation field and for the gas temperatures using the condition of radiative equilibrium. The novel aspect of HERO is that it combines two techniques: 1) a short characteristics (SC) solver that quickly converges to a self consistent disc temperature and radiation field, with 2) a long characteristics (LC) solver that provides a more accurate solution for the radiation near the photosphere and in the optically thin regions. By combining these two techniques, we gain both the computational speed of SC and the high accuracy of LC. W...

  6. EM counterparts of recoiling black holes: general relativistic simulations of non-Keplerian discs

    E-Print Network [OSTI]

    Olindo Zanotti; Luciano Rezzolla; Luca Del Zanna; Carlos Palenzuela

    2010-09-12T23:59:59.000Z

    We investigate the dynamics of a circumbinary disc that responds to the loss of mass and to the recoil velocity of the black hole produced by the merger of a binary system of supermassive black holes. We perform the first two-dimensional general relativistic hydrodynamics simulations of \\textit{extended} non-Keplerian discs and employ a new technique to construct a "shock detector", thus determining the precise location of the shocks produced in the accreting disc by the recoiling black hole. In this way we can study how the properties of the system, such as the spin, mass and recoil velocity of the black hole, affect the mass accretion rate and are imprinted on the electromagnetic emission from these sources. We argue that the estimates of the bremsstrahlung luminosity computed without properly taking into account the radiation transfer yield cooling times that are unrealistically short. At the same time we show, through an approximation based on the relativistic isothermal evolution, that the luminosity produced can reach a peak value above $L \\simeq 10^{43} \\ {\\rm erg/s} $ at about $\\sim 30\\,{\\rm d}$ after the merger of a binary with total mass $M\\simeq 10^6 M_\\odot$ and persist for several days at values which are a factor of a few smaller. If confirmed by more sophisticated calculations such a signal could indeed lead to an electromagnetic counterpart of the merger of binary black-hole system.

  7. Evidence for temporal evolution in the M33 disc as traced by its star clusters

    E-Print Network [OSTI]

    Beasley, Michael A; Gallart, Carme; Sarajedini, Ata; Aparicio, Antonio

    2015-01-01T23:59:59.000Z

    We present precision radial velocities and stellar population parameters for 77 star clusters in the Local Group galaxy M33. Our GTC and WHT observations sample both young, massive clusters and known/candidate globular clusters, spanning ages ~ 10^6 - 10^10 yr, and metallicities, [M/H] ~-1.7 to solar. The cluster system exhibits an age-metallicity relation; the youngest clusters are the most metal-rich. When compared to HI data, clusters with [M/H] ~ -1.0 and younger than ~ 4 Gyr are clearly identified as a disc population. The clusters show evidence for strong time evolution in the disc radial metallicity gradient (d[M/H]dt / dR = 0.03 dex/kpc/Gyr). The oldest clusters have stronger, more negative gradients than the youngest clusters in M33. The clusters also show a clear age-velocity dispersion relation. The line of sight velocity dispersions of the clusters increases with age similar to Milky Way open clusters and stars. The general shape of the relation is reproduced by disc heating simulations, and the s...

  8. Photometric scaling relations of antitruncated stellar discs in S0-Scd galaxies

    E-Print Network [OSTI]

    Eliche-Moral, M Carmen; Beckman, John E; Gutierrez, Leonel

    2015-01-01T23:59:59.000Z

    It has been recently found that the characteristic photometric parameters of antitruncated discs in S0 galaxies follow tight scaling relations. We investigate if similar scaling relations are satisfied by galaxies of other morphological types. We have analysed the trends in several photometric planes relating the characteristic surface brightness and scalelengths of the breaks and the inner and outer discs of local antitruncated S0-Scd galaxies, using published data and fits performed to the surface brightness profiles of two samples of Type-III galaxies in the R and Spitzer 3.6 microns bands. We have performed linear fits to the correlations followed by different galaxy types in each plane, as well as several statistical tests to determine their significance. We have found that: 1) the antitruncated discs of all galaxy types from Sa to Scd obey tight scaling relations both in R and 3.6 microns, as observed in S0s; 2) the majority of these correlations are significant accounting for the numbers of the availab...

  9. IRAS 19135+3937: An SRd variable as interacting binary surrounded by a circumbinary disc

    E-Print Network [OSTI]

    Gorlova, N; Ikonnikova, N P; Burlak, M A; Komissarova, G V; Jorissen, A; Gielen, C; Debosscher, J; Degroote, P

    2015-01-01T23:59:59.000Z

    Semi-regular (SR) variables are not a homogeneous class and their variability is often explained due to pulsations and/or binarity. This study focuses on IRAS 19135+3937, an SRd variable with an infra-red excess indicative of a dusty disc. A time-series of high-resolution spectra, UBV photometry as well as a very accurate light curve obtained by the Kepler satellite, allowed us to study the object in unprecedented detail. We discovered it to be a binary with a period of 127 days. The primary has a low surface gravity and an atmosphere depleted in refractory elements. This combination of properties unambiguously places IRAS 19135+3937 in the subclass of post-Asymptotic Giant Branch stars with dusty discs. We show that the light variations in this object can not be due to pulsations, but are likely caused by the obscuration of the primary by the circumbinary disc during orbital motion. Furthermore, we argue that the double-peaked Fe emission lines provide evidence for the existence of a gaseous circumbinary Kep...

  10. Status of the warm front end of PXIE

    E-Print Network [OSTI]

    Shemyakin, A; Andrews, R; Baffes, C; Chen, A; Hanna, B; Prost, L; Saewert, G; Scarpine, V; Steimel, J; Sun, D; Li, D; D'Arcy, R

    2015-01-01T23:59:59.000Z

    A CW-compatible, pulsed H- superconducting linac is envisaged as a possible path for upgrading Fermilab's injection complex. To validate the concept of the front- end of such a machine, a test accelerator (a.k.a. PXIE) is under construction. The warm part of this accelerator comprises a 10 mA DC, 30 keV H- ion source, a 2m-long LEBT, a 2.1 MeV CW RFQ, and a 10-m long MEBT that is capable of creating a large variety of bunch structures. The paper will report commissioning results of a partially assembled LEBT, status of RFQ manufacturing, and describe development of the MEBT, in particular, of elements of its chopping system.

  11. Lattice Boltzmann BGK simulation of non-linear sound waves: The development of a shock front

    E-Print Network [OSTI]

    Boyer, Edmond

    Lattice Boltzmann BGK simulation of non-linear sound waves: The development of a shock front J. M Boltzmannsimulationsofthe development of a shock front are performed when a sound wave is emitted from a high amplitude.1088/0305-4470/33/21/305 #12;Lattice Boltzmann BGK simulation of non-linear sound waves 2 1. Introduction The lattice

  12. Fast 3D Brain Segmentation Using Dual-Front Active Contours with Optional User-Interaction

    E-Print Network [OSTI]

    Cohen, Laurent

    Fast 3D Brain Segmentation Using Dual-Front Active Contours with Optional User-Interaction Hua Li1 attributes of 3D brain segmentation algorithms in- clude robustness, accuracy, computational efficiency result. We propose a novel 3D brain cortex segmentation procedure utilizing dual- front active contours

  13. Mineral paragenesis and textures associated with sandstone-hosted roll-front uranium deposits, NW China

    E-Print Network [OSTI]

    Fayek, Mostafa

    Mineral paragenesis and textures associated with sandstone-hosted roll-front uranium deposits, NW Sciences, State Key Laboratory of Mineral Deposit Research, Nanjing University, Nanjing 210093, People, Wuyiyi and Shihongtan sandstone-hosted roll-front uranium deposits, northwest China. The mineralization

  14. The Interruption of Alpine Foehn by a Cold Front. Part I: Observations

    E-Print Network [OSTI]

    Gohm, Alexander

    propagation speed wf 1 m/s Inclination of the frontal surface is wf /uf 1/7.5 8 Freitag (1990 in valleys Interaction with local winds (e.g., foehn) foehn cold front Cold front in complex terrain ? ? #12 in Inn and Wipp Valley Temperature slope profile Doppler wind lidar in Wipp Valley #12;6 of 13 Case study

  15. Wave Front Interaction Model of Stabilized Propagating Wave Segments Vladimir S. Zykov1

    E-Print Network [OSTI]

    Showalter, Kenneth

    Wave Front Interaction Model of Stabilized Propagating Wave Segments Vladimir S. Zykov1 and Kenneth; published 14 February 2005) A wave front interaction model is developed to describe the relationship between excitability and the size and shape of stabilized wave segments in a broad class of weakly excitable media

  16. High-Level Information An Approach for Integrating Front-End and Back-End Compilers

    E-Print Network [OSTI]

    Li, Zhiyuan

    High-Level Information ­ An Approach for Integrating Front-End and Back-End Compilers Sangyeun Cho-end and back-end compilers by passing front-end information to the back-end compiler. Importing this information into an existing back- end leverages the state-of-the-art analysis and transforma- tion

  17. Hierarchical Modelling of Automotive Sensor Front-Ends For Structural Diagnosis of Aging Faults

    E-Print Network [OSTI]

    Wieringa, Roel

    h.g.kerkhoff@utwente.nl Abstract: The semiconductor industry for automotive applications is growingHierarchical Modelling of Automotive Sensor Front-Ends For Structural Diagnosis of Aging Faults, dependability, reliability, aging models, hierarchical interfacing, analogue automotive front-ends. I

  18. Observed low frequency variability of the Brazil Current front Gustavo Jorge Goni,1

    E-Print Network [OSTI]

    of the Brazil Current front. Trends of eddy kinetic energy, sea height anomaly, sea surface temperature and windObserved low frequency variability of the Brazil Current front Gustavo Jorge Goni,1 Francis Bringas; published 29 October 2011. [1] The Brazil Current is a weak western boundary current, the southwest

  19. MESOSCALE ANALYSIS OF A CAROLINA COASTAL FRONT SETHU RAMAN, NEERAJA C. REDDY and DEVDUTTA S. NIYOGI

    E-Print Network [OSTI]

    Niyogi, Dev

    MESOSCALE ANALYSIS OF A CAROLINA COASTAL FRONT SETHU RAMAN, NEERAJA C. REDDY and DEVDUTTA S. NIYOGI the shore. Key words: GALE, Coastal front, Atmospheric boundary layer, Gulf Stream, Mesoscale analysis turbulent heat fluxes. These strong gradients in heat fluxes enhance mesoscale circulation

  20. REQUIRED FOR ALL FRONT/BACK UNIVERSITY PUBLICATIONS o University of NebraskaLincoln logo (wordmark)

    E-Print Network [OSTI]

    Farritor, Shane

    REQUIRED FOR ALL FRONT/BACK UNIVERSITY PUBLICATIONS o University of NebraskaLincoln logo (wordmark 1 color front cover UNIVERSITY SEAL o Replace with Academic N (icon) SECONDARY LOGO o Not approved (see Toolbox p. 16 for review process) UNIVERSITY OF NEBRASKALINCOLN LOGO o "Lincoln" not included

  1. A generalization of Thue's theorem to packings of non-equal discs, and an application to a discrete approximation of entropy

    E-Print Network [OSTI]

    Rom Pinchasi; Gershon Wolansky

    2014-10-13T23:59:59.000Z

    In this paper we generalize the classical theorem of Thue about the optimal circular disc packing in the plane. We are given a family of circular discs, not necessarily of equal radii, with the property that the inflation of every disc by a factor of $2$ around its center does not contain any center of another disc in the family (notice that this implies that the family of discs is a packing). We show that in this case the density of the given packing is at most $\\frac{\\pi}{2\\sqrt{3}}$, which is the density of the optimal unit disc packing. This result is used to obtain a discrete approximation to the Entropy functional in two dimensional domain.

  2. SiGe receiver front ends and flip-chip integrated wideband antennas for millimeter-wave passive imaging

    E-Print Network [OSTI]

    Powell, Johnna, 1980-

    2009-01-01T23:59:59.000Z

    SiGe wideband 77-GHz and 94-GHz front end receivers with integrated antennas for passive imaging have been designed and characterized. These front end systems exhibit wideband performance with the highest gain and lowest ...

  3. Light-Front Quantization Approach to the Gauge-Gravity Correspondence and Hadron Spectroscopy

    SciTech Connect (OSTI)

    Teramond, Guy F. de [Universidad de Costa Rica, San Jose (Costa Rica); Brodsky, Stanley J. [SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309 (United States)

    2010-08-05T23:59:59.000Z

    We find a correspondence between semiclassical QCD quantized on the light-front and a dual gravity model in anti--de Sitter (AdS) space, thus providing an initial approximation to QCD in its strongly coupled regime. This correspondence--light-front holography--leads to a light-front Hamiltonian and relativistic bound-state wave equations that are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within hadrons at equal light-front time. The eigenvalues of the resulting light-front Schroedinger and Dirac equations are consistent with the observed light meson and baryon spectrum, and the eigenmodes provide the light-front wavefunctions, the probability amplitudes describing the dynamics of the hadronic constituents. The light-front equations of motion, which are dual to an effective classical gravity theory, possess remarkable algebraic and integrability properties which are dictated by the underlying conformal properties of the theory. We extend the algebraic construction to include a confining potential while preserving the integrability of the mesonic and baryonic bound-state equations.

  4. HIGH-EFFICIENCY BACK-JUNCTION SILICON SOLAR CELL WITH AN IN-LINE EVAPORATED ALUMINUM FRONT GRID

    E-Print Network [OSTI]

    HIGH-EFFICIENCY BACK-JUNCTION SILICON SOLAR CELL WITH AN IN-LINE EVAPORATED ALUMINUM FRONT GRID M-diffused back-junction emitter. The aluminum front side grid is evaporated in an industrial-type in-thick silicon shadow masks for the in-line evaporation of the aluminum front grid. The masks are fabricated

  5. Disc evolution and the relationship between $L_{\\rm acc}$ and $L_\\ast$ in T Tauri stars

    E-Print Network [OSTI]

    I. Tilling; C. J. Clarke; J. E. Pringle; C. A. Tout

    2008-01-14T23:59:59.000Z

    We investigate the evolution of accretion luminosity $L_{\\rm acc}$ and stellar luminosity ${L_\\ast}$ in pre-mainsequence stars. We make the assumption that when the star appears as a Class II object, the major phase of accretion is long past, and the accretion disc has entered its asymptotic phase. We use an approximate stellar evolution scheme for accreting pre-mainsequence stars based on Hartmann, Cassen & Kenyon, 1997. We show that the observed range of values $k = L_{\\rm acc}/L_\\ast$ between 0.01 and 1 can be reproduced if the values of the disc mass fraction $M_{\\rm disc}/M_*$ at the start of the T Tauri phase lie in the range 0.01 -- 0.2, independent of stellar mass. We also show that the observed upper bound of $L_{\\rm acc} \\sim L_\\ast$ is a generic feature of such disc accretion. We conclude that as long as the data uniformly fills the region between this upper bound and observational detection thresholds, then the degeneracies between age, mass and accretion history severely limit the use of this data for constraining possible scalings between disc properties and stellar mass.

  6. Equatorial scattering and the structure of the broad-line region in Seyfert nuclei: evidence for a rotating disc

    E-Print Network [OSTI]

    J. E. Smith; A. Robinson; S. Young; D. J. Axon; Elizabeth A. Corbett

    2005-01-28T23:59:59.000Z

    We present detailed scattering models confirming that distinctive variations in polarization across the broad Halpha line, which are observed in a significant fraction of Seyfert 1 galaxies, can be understood in terms of a rotating line-emitting disc surrounded by a co-planar scattering region (the equatorial scattering region). The predicted polarization properties are: averaged over wavelength, the position angle of polarization is aligned with the projected disc rotation axis and hence also with the radio source axis; (ii) the polarization PA rotates across the line profile, reaching equal but opposite (relative to the continuum PA) rotations in the blue and red wings; (iii) the degree of polarization peaks in the line wings and passes through a minimum in the line core. We identify 11 objects which exhibit these features to different degrees. In order to reproduce the large amplitude PA rotations observed in some cases, the scattering region must closely surround the emission disc and the latter must itself be a relatively narrow annulus -- presumably the Halpha-emitting zone of a larger accretion disc. Asymmetries in the polarization spectra may be attributable to several possible causes, including bulk radial infall in the equatorial scattering region, or contamination by polar scattered light. The broad Halpha lines do not, in general, exhibit double-peaked profiles, suggesting that a second Halpha-emitting component of the broad-line region is present, in addition to the disc.

  7. Eclipse maps of spiral shocks in the accretion disc of IP Pegasi in outburst

    E-Print Network [OSTI]

    Raymundo Baptista; E. Harlaftis; D. Steeghs

    2000-02-08T23:59:59.000Z

    Eclipse lightcurves of the dwarf nova IP Peg during the November 1996 outburst are analysed with eclipse mapping techniques to constrain the location and investigate the spatial structure of the spiral shocks observed in the Doppler tomograms (Harlaftis et al. 1999). Eclipse maps in the blue continuum and in the CIII+NIII 4650 emission line show two asymmetric arcs of \\sim 90 degrees in azimuth and extending from intermediate to the outer disc regions (R \\simeq 0.2 - 0.6 R_{L1}, where R_{L1} is the distance from disc centre to the inner Lagrangian point) which are interpreted as being the spiral shocks seen in the Doppler tomograms. The HeII 4686 eclipse map also shows two asymmetric arcs diluted by a central brightness source. The central source probably corresponds to the low-velocity component seen in the Doppler tomogram and is understood in terms of gas outflow in a wind emanating from the inner parts of the disc. We estimate that the spirals contribute about 16 and 30 per cent of the total line flux, respectively, for the HeII and CIII+NIII lines. Comparison between the Doppler and eclipse maps reveal that the Keplerian velocities derived from the radial position of the shocks are systematically larger than those inferred from the Doppler tomography indicating that the gas in the spiral shocks has sub-Keplerian velocities. We undertake simulations with the aim to investigate the effect of artifacts on the image reconstruction of the spiral structures.

  8. Uranium roll front study in the upper Jackson group, Atascosa County, Texas

    E-Print Network [OSTI]

    Miller, Michael Eugene

    1979-01-01T23:59:59.000Z

    ) that the ore zone is continually enriched by the constant migra- tion of uranium-bearing groundwater. Although roll-type deposits have sim1lar morphologies, they may form under different conditions. Iron disulfide minerals, producing the reducing... front. The ore body being examined in this study was chosen because 1t is a particularly good exposure of a roll front deposit. A roll front 1s the boundary produced when alkaline, uranium-bear1ng groundwaters encountered reducing condit1ons...

  9. Travelling fronts of the CO oxidation on Pd(111) with coverage-dependent diffusion

    SciTech Connect (OSTI)

    Cisternas, Jaime, E-mail: jecisternas@miuandes.cl [Facultad de Ingeniera y Ciencias Aplicadas, Universidad de los Andes, Monseor Alvaro del Portillo 12455, Las Condes, Santiago (Chile); Karpitschka, Stefan [Physics of Fluids, University of Twente, Drienerlolaan 5, 7522 NB Enschede (Netherlands); Wehner, Stefan [Institut fr Integrierte Naturwissenschaften - Physik, Universitt Koblenz-Landau, 56070 Koblenz (Germany)

    2014-10-28T23:59:59.000Z

    In this work, we study a surface reaction on Pd(111) crystals under ultra-high-vacuum conditions that can be modeled by two coupled reaction-diffusion equations. In the bistable regime, the reaction exhibits travelling fronts that can be observed experimentally using photo electron emission microscopy. The spatial profile of the fronts reveals a coverage-dependent diffusivity for one of the species. We propose a method to solve the nonlinear eigenvalue problem and compute the direction and the speed of the fronts based on a geometrical construction in phase-space. This method successfully captures the dependence of the speed on control parameters and diffusivities.

  10. applied modal analysis: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    instability. Introduction Disc brake noise continues to be object of investigation for automotive-mail: francesco.massi@uniroma1.it Abstract In this paper, an experimental...

  11. Improved Reliability of PV Modules with Lexan PC Sheet-Front...

    Broader source: Energy.gov (indexed) [DOE]

    sheet application LEXAN(tm) sheet for front sheet application HYDROTHERMAL RESISTANCE OF PET AND NORYL(tm) FILM AS CORE LAYER OF BACKSHEET PET Fluoropolymer (F) PET(P) PE layer (E)...

  12. Soil water content dependent wetting front characteristics in sands T.W.J. Bautersa

    E-Print Network [OSTI]

    Walter, M.Todd

    affects wetting front instability. A series of experiments were conducted where water was infiltrated in a 0.94 cm thick, 30 cm wide, and 55 cm long polycarbonate chamber filled with clean, 2030 (US sieve

  13. Autonomous detection and anticipation of jam fronts from messages propagated by inter-vehicle communication

    E-Print Network [OSTI]

    Sch"onhof, M; Kesting, A; Helbing, D; Sch\\"onhof, Martin; Treiber, Martin; Kesting, Arne; Helbing, Dirk

    2006-01-01T23:59:59.000Z

    In this paper, a minimalist, completely distributed freeway traffic information system is introduced. It involves an autonomous, vehicle-based jam front detection, the information transmission via inter-vehicle communication, and the forecast of the spatial position of jam fronts by reconstructing the spatiotemporal traffic situation based on the transmitted information. The whole system is simulated with an integrated traffic simulator, that is based on a realistic microscopic traffic model for longitudinal movements and lane changes. The function of its communication module has been explicitly validated by comparing the simulation results with analytical calculations. By means of simulations, we show that the algorithms for a congestion-front recognition, message transmission, and processing predict reliably the existence and position of jam fronts for vehicle equipment rates as low as 3%. A reliable mode of operation already for small market penetrations is crucial for the successful introduction of inter-...

  14. ANL/APS/TB-44, Guidelines for Beamline and Front-End Radiation...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    section 4. All designs of beamline and front-end components that fall within the defined envelope will not require specific additional safety review. The designs that fall outside...

  15. Experimental evaluation of the in-plane seismic behavior of store-front window systems

    E-Print Network [OSTI]

    Eva, Charles Almond

    2009-01-01T23:59:59.000Z

    of architectural glass curtain walls under in-plane loadsracking tests of curtain wall glass elements with in-planethat causes glass fallout from curtain wall and store-front

  16. This page does not print. Please use front-and-back

    E-Print Network [OSTI]

    Duchowski, Andrew T.

    This page does not print. Please use front-and-back cover layout at end of file. #12;Craig Mahaffey's astonishing to realize that the same basic knowledge used to conserve a historic submarine can be applied

  17. Detection technique and front-end RF tunable filter for cognitive radio systems

    E-Print Network [OSTI]

    Park, Sanghoon

    2010-01-01T23:59:59.000Z

    dual-mode WiMAX/WLAN direct- conversion receiver, in Proc.Hamilton, Aspects of direct conversion receiver design, inand M. Ismail, A direct conversion WiMAX RF receiver front-

  18. A survey of front end modularity as an automotive architecture and its ability to deliver value

    E-Print Network [OSTI]

    Mah, Vincent R. (Vincent Robert)

    2008-01-01T23:59:59.000Z

    The partitioning of a system can and will dictate the creative space for a designer or engineer. This thesis will analyze how using a new automotive architecture known as a Front End Module (FEM) can affect a limited ...

  19. Vehicle Technologies Office Merit Review 2015: Magnesium-Intensive Front End Sub-Structure Development

    Broader source: Energy.gov [DOE]

    Presentation given by USAMP at 2015 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about magnesium-intensive front end sub...

  20. Migration of Earth-size planets in 3D radiative discs

    E-Print Network [OSTI]

    Lega, E; Bitsch, B; Morbidelli, A

    2014-01-01T23:59:59.000Z

    In this paper, we address the migration of small mass planets in 3D radiative disks. Indeed, migration of small planets is known to be too fast inwards in locally isothermal conditions. However, thermal effects could reverse its direction, potentially saving planets in the inner, optically thick parts of the protoplanetary disc. This effect has been seen for masses larger than 5 Earth masses, but the minimum mass for this to happen has never been probed numerically, although it is of crucial importance for planet formation scenarios. We have extended the hydro-dynamical code FARGO to 3D, with thermal diffusion. With this code, we perform simulations of embedded planets down to 2 Earth masses. For a set of discs parameters for which outward migration has been shown in the range of $[5, 35]$ Earth masses, we find that the transition to inward migration occurs for masses in the range $[3, 5]$ Earth masses. The transition appears to be due to an unexpected phenomenon: the formation of an asymmetric cold and dense...

  1. Kinetics of rapid oxidant consumption: measurements with a rotating ring disc electrode

    SciTech Connect (OSTI)

    Jaworske, D.A.

    1983-01-01T23:59:59.000Z

    Coastal and marine waters receive strong oxidants, such as ozone and chlorine, from several natural and anthropogenic sources. These oxidants react rapidly with Br/sup -/ and I/sup -/ in seawater to produce Br/sub 2/, I/sub 2/ and various hydrolysis products. The fate of these halogen products is of geochemical and biological interest. The rotating ring disc electrode (RRDE) was used to study the rapid decay of these oxidants in natural waters. Copper-plated disc experiments address the hypothesis that Cu catalyzes the decomposition of oxidant. Pseudo first-order and second-order reaction kinetics of model compounds and field samples were also studied, via in situ generation of Br/sub 3/. Pseudo first-order behavior is observed for ammonia and glycine, and the rate constants obtained from the RRDE method compare favorably with the literature (8.1 x 10/sup 7/ and 8.5 x 10/sup 7/ L/mol-sec, respectively). Second-order behavior is observed in natural water samples collected from the Patuxent River. Calculations suggest that the observed fast demand has a rate constant in excess of 10/sup 7/ L/mol-sec, and that the substrate responsible for the demand approaches concentrations of 1 x 10/sup -5/ M. The ubiquitous distribution of rapid demand, as measured in the Patuxent estuary, suggests that proteinaceous organosulfur may contribute to the observed rapid demand.

  2. Collisionless kinetic regimes for quasi-stationary axisymmetric accretion disc plasmas

    SciTech Connect (OSTI)

    Cremaschini, C. [International School for Advanced Studies (SISSA) and INFN, Trieste (Italy); Tessarotto, M. [Department of Mathematics and Geosciences, University of Trieste, Trieste (Italy)

    2012-08-15T23:59:59.000Z

    This paper is concerned with the kinetic treatment of quasi-stationary axisymmetric collisionless accretion disc plasmas. The conditions of validity of the kinetic description for non-relativistic magnetized and gravitationally bound plasmas of this type are discussed. A classification of the possible collisionless plasma regimes which can arise in these systems is proposed, which can apply to accretion discs around both stellar-mass compact objects and galactic-center black holes. Two different classifications are determined, which are referred to, respectively, as energy-based and magnetic field-based classifications. Different regimes are pointed out for each plasma species, depending both on the relative magnitudes of kinetic and potential energies and the magnitude of the magnetic field. It is shown that in all cases, there can be quasi-stationary Maxwellian-like solutions of the Vlasov equation. The perturbative approach outlined here permits unique analytical determination of the functional form for the distribution function consistent, in each kinetic regime, with the explicit inclusion of finite Larmor radius-diamagnetic and/or energy-correction effects.

  3. Free motion around black holes with discs or rings: between integrability and chaos - II

    E-Print Network [OSTI]

    O. Semerk; P. Sukov

    2012-11-17T23:59:59.000Z

    We continue the study of time-like geodesic dynamics in exact static, axially and reflection symmetric space-times describing the fields of a Schwarzschild black hole surrounded by thin discs or rings. In the previous paper, the rise (and decline) of geodesic chaos with ring/disc mass and position and with test particle energy was revealed on Poincar\\'e sections, on time series of position or velocity and their power spectra, and on time evolution of the orbital `latitudinal action'. In agreement with the KAM theory of nearly integrable dynamical systems and with the results observed in similar gravitational systems in the literature, we found orbits of very different degrees of chaoticity in the phase space of perturbed fields. Here we compare selected orbits in more detail and try to classify them according to the characteristics of the corresponding phase-variable time series, mainly according to the shape of the time-series power spectra, and also applying two recurrence methods: the method of `average directional vectors', which traces the directions in which the trajectory (recurrently) passes through a chosen phase-space cell, and the `recurrence-matrix' method, which consists of statistics over the recurrences themselves. All the methods proved simple and powerful, while it is interesting to observe how they differ in sensitivity to certain types of behaviour.

  4. Lindblad resonance torques in relativistic discs: II. Computation of resonance strengths

    E-Print Network [OSTI]

    Christopher M. Hirata

    2011-03-01T23:59:59.000Z

    We present a fully relativistic computation of the torques due to Lindblad resonances from perturbers on circular, equatorial orbits on discs around Schwarzschild and Kerr black holes. The computation proceeds by establishing a relation between the Lindblad torques and the gravitational waveforms emitted by the perturber and a test particle in a slightly eccentric orbit at the radius of the Lindblad resonance. We show that our result reduces to the usual formula when taking the nonrelativistic limit. Discs around a black hole possess an m=1 inner Lindblad resonance with no Newtonian Keplerian analogue; however its strength is very weak even in the moderately relativistic regime (r/M ~ few tens), which is in part due to the partial cancellation of the two leading contributions to the resonant amplitude (the gravitoelectric octupole and gravitomagnetic quadrupole). For equatorial orbits around Kerr black holes, we find that the m=1 ILR strength is enhanced for retrograde spins and suppressed for prograde spins. We also find that the torque associated with the m>=2 inner Lindblad resonances is enhanced relative to the nonrelativistic case; the enhancement is a factor of 2 for the Schwarzschild hole even when the perturber is at a radius of 25M.

  5. Non-Adiabatic Effects on Combustion Front Propagation in Porous Media: Multiplicity of Steady States

    SciTech Connect (OSTI)

    Akkutlu, I. Yucel; Yortsos, Yanis C.

    2002-03-11T23:59:59.000Z

    The sustained propagation of combustion fronts in porous media is a necessary condition for the success of an in situ combustion project for oil recovery. Compared to other recovery methods, in situ combustion involves the added complexity of exothermic reactions and temperature-dependent chemical kinetics. In the presence of heat losses, the possibility of ignition and extinction (quenching) exists. In this report, we address the properties of combustion fronts propagating at a constant velocity in the presence of heat losses.

  6. The Communist revolution in Republican China: the conceptual development of the second united front.

    E-Print Network [OSTI]

    Hope, Brian Lannes

    1974-01-01T23:59:59.000Z

    THE COMMUNIS( RE'JOLUT ION IN REPUBL ICAN CHINA: THE CONCEPTUAL DEVELOPMENT OF THE SECOND UNITED FRONT A Thesis by BRIAN LANNES HOPE Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement... for the degree oi MASTER OF ARTS December, 1974 Major Subject: Political Science THE COMMUNIST REVOLUTION IN REPUBLICAN CHINA: THE CONCEPTUAL DEVELOPMENT OF THE SECOND UNITED FRONT A Thesis by BRIAN LANNES HOPE Approved as to style and content by: +~9...

  7. Light-Front Quantization Approach to the Gauge Gravity Correspondence and Hadron Spectroscopy

    SciTech Connect (OSTI)

    de Teramond, Guy F.; /Costa Rica U.; Brodsky, Stanley J.; /SLAC

    2010-05-26T23:59:59.000Z

    We find a correspondence between semiclassical QCD quantized on the light-front and a dual gravity model in anti-de Sitter (AdS) space, thus providing an initial approximation to QCD in its strongly coupled regime. This correspondence - light-front holography - leads to a light-front Hamiltonian and relativistic bound-state wave equations that are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within hadrons at equal lightfront time. The eigenvalues of the resulting light-front Schrodinger and Dirac equations are consistent with the observed light meson and baryon spectrum, and the eigenmodes provide the light-front wavefunctions, the probability amplitudes describing the dynamics of the hadronic constituents. The light-front equations of motion, which are dual to an effective classical gravity theory, possess remarkable algebraic and integrability properties which are dictated by the underlying conformal properties of the theory. We extend the algebraic construction to include a confining potential while preserving the integrability of the mesonic and baryonic bound-state equations.

  8. Semi-flexible gas-insulated transmission line using sandwiched discs for intermittent flexing joints

    DOE Patents [OSTI]

    Kommineni, P.R.

    1983-02-15T23:59:59.000Z

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by the use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements are formed by sandwiching together, by fusing, a pair of thin hollow discs which are fixedly secured to both the main conductor sections and the conductor hub section. 4 figs.

  9. Towards a fully consistent Milky Way disc model - III. Constraining the initial mass function

    E-Print Network [OSTI]

    Rybizki, Jan

    2015-01-01T23:59:59.000Z

    We use our vertical Milky Way disc model together with Galaxia to create mock observations of stellar samples in the solar neighbourhood. We compare these to the corresponding volume complete observational samples of dereddened and binary accounted data from Hipparcos and the Catalogue of Nearby Stars. Sampling the likelihood in the parameter space we determine a new fiducial IMF considering constraints from dwarf and giant stars. The resulting IMF observationally backed in the range from 0.5 to 10 Msun is a two slope broken power law with -1.49 +- 0.08 for the low mass slope, a break at 1.39 +- 0.05 Msun and a high mass slope of -3.02 +- 0.06. The Besancon group also converging to a similar IMF even though their observational sample being quite different to ours shows that the forward modelling technique is a powerful diagnostic to test theoretical concepts like the local field star IMF.

  10. Large-eddy simulations of isolated disc galaxies with thermal and turbulent feedback

    E-Print Network [OSTI]

    Braun, Harald; Niemeyer, Jens C; Almgren, Ann S

    2014-01-01T23:59:59.000Z

    We present a subgrid-scale model for the Multi-phase Interstellar medium, Star formation, and Turbulence (MIST) and explore its behaviour in high-resolution large-eddy simulations of isolated disc galaxies. MIST follows the evolution of a clumpy cold and a diffuse warm component of the gas within a volume element which exchange mass and energy via various cooling, heating and mixing processes. The star formation rate is dynamically computed from the state of the gas in the cold phase. An important feature of MIST is the treatment of unresolved turbulence in the two phases and its interaction with star formation and feedback by supernovae. This makes MIST a particularly suitable model for the interstellar medium in galaxy simulations. We carried out a suite of simulations varying fundamental parameters of our feedback implementation. Several observational properties of galactic star formation are reproduced in our simulations, such as an average star formation efficiency ~1%, a typical velocity dispersion arou...

  11. Biaxial nematic phase in the Maier-Saupe model for a mixture of discs and cylinders

    E-Print Network [OSTI]

    E. F. Henriques; S. R. Salinas

    2011-10-25T23:59:59.000Z

    We analyze the global phase diagram of a Maier-Saupe lattice model with the inclusion of disorder degrees of freedom to mimic a mixture of oblate and prolate molecules (discs and cylinders). In the neighborhood of a Landau multicritical point, solutions of the statistical problem can be written as a Landau-de Gennes expansion for the free energy. If the disorder degrees of freedom are quenched, we confirm the existence of a biaxial nematic strucure. If orientational and disorder degrees of freedom are allowed to thermalize, this biaxial solution becomes thermodynamically unstable. Also, we use a two-temperature formalism to mimic the presence of two distinct relaxation times, and show that a slight departure from complete thermalization is enough to stabilize a biaxial nematic phase.

  12. Lindblad Zones: resonant eccentric orbits to aid bar and spiral formation in galaxy discs

    E-Print Network [OSTI]

    Struck, Curtis

    2015-01-01T23:59:59.000Z

    The apsidal precession frequency in a fixed gravitational potential increases with the radial range of the orbit (eccentricity). Although the frequency increase is modest it can have important implications for wave dynamics in galaxy discs, which have not been previously explored in detail. One of the most interesting consequences is that for a given pattern frequency, each Lindblad resonance does not exist in isolation, but rather is the parent of a continuous sequence of resonant radii, a Lindblad Zone, with each radius in this zone characterized by a specific eccentricity. In the epicyclic approximation the precession or epicyclic frequency does not depend on epicycle size, and this phenomenon is not captured. A better approximation for eccentric orbits is provided by p-ellipse curves (Struck 2006), which do exhibit this effect. Here the p-ellipse approximation and precession-eccentricity relation are used as tools for finding the resonant radii generated from various Lindblad parent resonances. Simple, id...

  13. The effect of boundary adaptivity on hexagonal ordering and bistability in circularly confined quasi hard discs

    E-Print Network [OSTI]

    Ian Williams; Erdal C. O?uz; Robert L. Jack; Paul Bartlett; Hartmut Lwen; C. Patrick Royall

    2013-11-19T23:59:59.000Z

    The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the `strictness' of that wall.

  14. Cooperativity and Spatial Correlations near the Glass Transition: Computer Simulation Results for Hard Spheres and Discs

    E-Print Network [OSTI]

    Burkhard Doliwa; Andreas Heuer

    1999-12-23T23:59:59.000Z

    We examine the dynamics of hard spheres and discs at high packing fractions in two and three dimensions, modeling the simplest systems exhibiting a glass transition. As it is well known, cooperativity and dynamic heterogeneity arise as central features when approaching the glass transition from the liquid phase, so an understanding of their underlying physics is of great interest. Cooperativity implies a reduction of the effective degrees of freedom, and we demonstrate a simple way of quantification in terms of the strength and the length scale of dynamic correlations among different particles. These correlations are obtained for different dynamical quantities $X_i(t)$ that are constructed from single-particle displacements during some observation time $t$. Of particular interest is the dependence on $t$. Interestingly, for appropriately chosen $X_i(t)$ we obtain finite cooperativity in the limit $t \\to \\infty$.

  15. Semi-flexible gas-insulated transmission line using sandwiched discs for intermittent flexing joints

    DOE Patents [OSTI]

    Kommineni, Prasad R. (Westboro, MA)

    1983-02-15T23:59:59.000Z

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by the use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements are formed by sandwiching together, by fusing, a pair of thin hollow discs which are fixedly secured to both the main conductor sections and the conductor hub section.

  16. Self-similar Evolution of Self-Gravitating Viscous Accretion Discs

    E-Print Network [OSTI]

    Illenseer, Tobias F

    2015-01-01T23:59:59.000Z

    A new one-dimensional, dynamical model is proposed for geometrically thin, self-gravitating viscous accretion discs. The vertically integrated equations are simplified using the slow accretion limit and the monopole approximation with a time-dependent central point mass to account for self-gravity and accretion. It is shown that the system of partial differential equations can be reduced to a single non-linear advection diffusion equation which describes the time evolution of angular velocity. In order to solve the equation three different turbulent viscosity prescriptions are considered. It is shown that for these parametrizations the differential equation allows for similarity transformations depending only on a single non-dimensional parameter. A detailed analysis of the similarity solutions reveals that this parameter is the initial power law exponent of the angular velocity distribution at large radii. The radial dependence of the self-similar solutions is in most cases given by broken power laws. At sma...

  17. Free motion around black holes with discs or rings: between integrability and chaos -- IV

    E-Print Network [OSTI]

    V. Witzany; O. Semerak; P. Sukova

    2015-03-31T23:59:59.000Z

    The dynamical system studied in previous papers of this series, namely a bound time-like geodesic motion in the exact static and axially symmetric space-time of an (originally) Schwarzschild black hole surrounded by a thin disc or ring, is considered to test whether the often employed "pseudo-Newtonian" approach (resorting to Newtonian dynamics in gravitational potentials modified to mimic the black-hole field) can reproduce phase-space properties observed in the relativistic treatment. By plotting Poincar\\'e surfaces of section and using two recurrence methods for similar situations as in the relativistic case, we find similar tendencies in the evolution of the phase portrait with parameters (mainly with mass of the disc/ring and with energy of the orbiters), namely those characteristic to weakly non-integrable systems. More specifically, this is true for the Paczy\\'nski--Wiita and a newly suggested logarithmic potential, whereas the Nowak--Wagoner potential leads to a different picture. The potentials and the exact relativistic system clearly differ in delimitation of the phase-space domain accessible to a given set of particles, though this mainly affects the chaotic sea whereas not so much the occurrence and succession of discrete dynamical features (resonances). In the pseudo-Newtonian systems, the particular dynamical features generally occur for slightly smaller values of the perturbation parameters than in the relativistic system, so one may say that the pseudo-Newtonian systems are slightly more prone to instability. We also add remarks on numerics (a different code is used than in previous papers), on the resemblance of dependence of the dynamics on perturbing mass and on orbital energy, on the difference between the Newtonian and relativistic Bach--Weyl rings, and on the relation between Poincar\\'e sections and orbital shapes within the meridional plane.

  18. Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

    DOE Patents [OSTI]

    Battiste, Richard L

    2013-12-31T23:59:59.000Z

    Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into th emold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with a fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a termperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into th emold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

  19. Localized structures and front propagation in the Lengyel-Epstein model

    SciTech Connect (OSTI)

    Jensen, O.; Pannbacker, V.O.; Mosekilde, E.; Dewel, G.; Borckmans, P. (Physics Department, Technical University of Denmark, 2800 Lyngby (Denmark) Service de Chimie-Physique, Code Postal 231 Universite Libre de Bruxelles, 1050 Brussels (Belgium))

    1994-08-01T23:59:59.000Z

    Pattern selection, localized structure formation, and front propagation are analyzed within the framework of a model for the chlorine dioxide--iodine--malonic acid reaction that represents a key to understanding recently obtained Turing structures. This model is distinguished from previously studied, simple reaction-diffusion models by producing a strongly subcritical transition to stripes. The wave number for the modes of maximum linear gain is calculated and compared with the dominant wave number for the finally selected, stationary structures grown from the homogeneous steady state or developed behind a traveling front. The speed of propagation for a front between the homogeneous steady state and a one-dimensional (1D) Turing structure is obtained. This velocity shows a characteristic change in behavior at the crossover between the subcritical and supercritical regimes for the Turing bifurcation. In the subcritical regime there is an interval where the front velocity vanishes as a result of a pinning of the front to the underlying structure. In 2D, two different nucleation mechanisms for hexagonal structures are illustrated on the Lengyel-Epstein and the Brusselator model. Finally, the observation of 1D and 2D spirals with Turing-induced cores is reported.

  20. Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof

    DOE Patents [OSTI]

    Battiste, Richard L. (Oak Ridge, TN)

    2007-12-25T23:59:59.000Z

    Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into the mold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with the fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a temperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into the mold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

  1. Gauge/Gravity Duality and Strongly Coupled Light-Front Dynamics

    SciTech Connect (OSTI)

    de Teramond, Guy F.; /Costa Rica U.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

    2011-08-12T23:59:59.000Z

    We find a correspondence between semiclassical gauge theories quantized on the light-front and a dual gravity model in anti-de Sitter (AdS) space, thus providing an initial approximation to QCD in its strongly coupled regime. This correspondence - light-front holography - leads to a light-front Hamiltonian and relativistic bound-state wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. Light-front holography also allows a precise mapping of transition amplitudes from AdS to physical space-time. In contrast with the usual AdS/QCD framework, the internal structure of hadrons is explicitly introduced in the gauge/gravity correspondence and the angular momentum of the constituents plays a key role. We also discuss how to introduce higher Fock-states in the correspondence as well as their relevance for describing the detailed structure of space and time-like form factors.

  2. Deep Chandra observation and numerical studies of the nearest cluster cold front in the sky

    E-Print Network [OSTI]

    Werner, N; Zhuravleva, I; Ichinohe, Y; Simionescu, A; Allen, S W; Markevitch, M; Fabian, A C; Keshet, U; Roediger, E; Ruszkowski, M; Sanders, J S

    2015-01-01T23:59:59.000Z

    We present the results of a very deep (500 ks) Chandra observation, along with tailored numerical simulations, of the nearest, best resolved cluster cold front in the sky, which lies 90 kpc (19 arcmin) to the northwest of M 87. The northern part of the front appears the sharpest, with a width smaller than 2.5 kpc (1.5 Coulomb mean free paths; at 99 per cent confidence). Everywhere along the front, the temperature discontinuity is narrower than 4-8 kpc and the metallicity gradient is narrower than 6 kpc, indicating that diffusion, conduction and mixing are suppressed across the interface. Such transport processes can be naturally suppressed by magnetic fields aligned with the cold front. However, the northwestern part of the cold front is observed to have a nonzero width. The broadening is consistent with the presence of Kelvin-Helmholtz instabilities (KHI) on length scales of a few kpc. Based on comparison with simulations, the presence of KHI would imply that the effective viscosity of the intra-cluster medi...

  3. Front-flash thermal imaging characterization of continuous fiber ceramic composites.

    SciTech Connect (OSTI)

    Deemer, C.

    1999-04-23T23:59:59.000Z

    Infrared thermal imaging has become increasingly popular as a nondestructive evaluation method for characterizing materials and detecting defects. One technique, which was utilized in this study, is front-flash thermal imaging. We have developed a thermal imaging system that uses this technique to characterize advanced material systems, including continuous fiber ceramic composite (CFCC) components. In a front-flash test, pulsed heat energy is applied to the surface of a sample, and decay of the surface temperature is then measured by the thermal imaging system. CFCC samples with drilled flat-bottom holes at the back surface (to serve as ''flaws'') were examined. The surface-temperature/time relationship was analyzed to determine the depths of the flaws from the front surface of the CFCC material. Experimental results on carbon/carbon and CFCC samples are presented and discussed.

  4. Front-end Electronics Test for the LHCb Muon Wire Chambers

    E-Print Network [OSTI]

    Nobrega, R; Carboni, G; Massafferri, A; Santovetti, E

    2007-01-01T23:59:59.000Z

    This document describes the apparatus and procedures implemented to test Multi Wire Proportional Chambers (MWPC) after front-end assembly for the LHCb Muon Detector. Results of measurements of key noise parameters are also described. Given a fully equipped chamber, this system is able to diagnose every channel performing an analysis of front-end output drivers response and noise rate versus threshold. Besides, it allows to assess if the noise rate at the experiment threshold region is within appropriate limits. Aiming at an automatic, fast and user-friendly system for mass production tests of MWPC, the project has foreseen as well electronic identification of every chamber and front-end board, and data archiving in such a way to make it available to the Experiment Control System (ECS) while in operation.

  5. Report on the value engineering workshop on APS beamline front ends

    SciTech Connect (OSTI)

    Kuzay, T.

    1993-01-01T23:59:59.000Z

    A formal value engineering evaluation process was developed to address the front end components of the beamlines for the Advanced Photon Source (APS). This process (described in Section 2) involved an information phase, a creative phase, a judgment phase, a development phase, and a recommendation phase. Technical experts from other national laboratories and industry were invited to a two-day Value Engineering Workshop on November 5-6, 1992. The results of this Workshop are described in Section 4. Following the Workshop, various actions by the APS staff led to the redesign of the front end components, which are presented in Sections 5 and 6. The cost benefit analysis is presented in Section 7. It is important of realize that an added benefit of the Workshop was to obtain numerous design evaluations and enhancements of the front end components by experts in the field. As the design work proceeds to Title II completion, the APS staff is including many of these suggestions.

  6. The Wave-Front Correction System for the Sunrise Balloon-Borne Solar Observatory

    E-Print Network [OSTI]

    Berkefeld, T; Soltau, D; Bell, A; Doerr, H P; Feger, B; Friedlein, R; Gerber, K; Heidecke, F; Kentischer, T; Lhe, O v d; Sigwarth, M; Wlde, E; Barthol, P; Deutsch, W; Gandorfer, A; Germerott, D; Grauf, B; Meller, R; Alvarez-Herrero, A; Knlker, M; Pillet, V Martinez; Solanki, S K; Title, A M

    2010-01-01T23:59:59.000Z

    This paper describes the wave-front correction system developed for the Sunrise balloon telescope, and provides information about its in-flight performance. For the correction of low-order aberrations, a Correlating Wave-Front Sensor (CWS) was used. It consisted of a six-element Shack-Hartmann wave-front sensor (WFS), a fast tip-tilt mirror for the compensation of image motion, and an active telescope secondary mirror for focus correction. The CWS delivered a stabilized image with a precision of 0.04 arcsec (rms), whenever the coarse pointing was better than 90 arcsec peak-to-peak. The automatic focus adjustment maintained a focus stability of 0.01 waves in the focal plane of the CWS. During the 5.5 day flight, good image quality and stability was achieved during 33 hours, containing 45 sequences that lasted between 10 and 45 minutes.

  7. Apparatus and method for phase fronts based on superluminal polarization current

    DOE Patents [OSTI]

    Singleton, John (Los Alamos, NM); Ardavan, Houshang (Cambridge, GB); Ardavan, Arzhang (Cambridge, GB)

    2012-02-28T23:59:59.000Z

    An apparatus and method for a radiation source involving phase fronts emanating from an accelerated, oscillating polarization current whose distribution pattern moves superluminally (that is, faster than light in vacuo). Theoretical predictions and experimental measurements using an existing prototype superluminal source show that the phase fronts from such a source can be made to be very complex. Consequently, it will be very difficult for an aircraft imaged by such a radiation to detect where this radiation has come from. Moreover, the complexity of the phase fronts makes it almost impossible for electronics on an aircraft to synthesize a rogue reflection. A simple directional antenna and timing system should, on the other hand, be sufficient for the radar operators to locate the aircraft, given knowledge of their own source's speed and modulation pattern.

  8. Light-front representation of chiral dynamics in peripheral transverse densities

    E-Print Network [OSTI]

    Granados, C

    2015-01-01T23:59:59.000Z

    The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances $b = O(M_\\pi^{-1})$ the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independent and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantiz...

  9. Dynamical model for longitudinal wave functions in light-front holographic QCD

    SciTech Connect (OSTI)

    Chabysheva, Sophia S.; Hiller, John R., E-mail: jhiller@d.umn.edu

    2013-10-15T23:59:59.000Z

    We construct a Schrdinger-like equation for the longitudinal wave function of a meson in the valence qq{sup -bar} sector, based on the t Hooft model for large-N two-dimensional QCD, and combine this with the usual transverse equation from light-front holographic QCD, to obtain a model for mesons with massive quarks. The computed wave functions are compared with the wave function ansatz of Brodsky and de Tramond and used to compute decay constants and parton distribution functions. The basis functions used to solve the longitudinal equation may be useful for more general calculations of meson states in QCD. -- Highlights: Provide relativistic quark model based on light-front holographic QCD. Incorporate dependence on quark mass. Consistent with the Brodskyde Tramond quark-wave-function ansatz. Compute meson decay constants and parton distribution functions. Illustrate use of basis functions that could be convenient for more general numerical calculations in light-front QCD.

  10. Light-Front Dynamic Analysis of Bound States in Scalar Field Model

    E-Print Network [OSTI]

    Chueng-Ryong Ji; Yukihisa Tokunaga

    2012-05-16T23:59:59.000Z

    The light-front dynamics (LFD) of the scalar field model theory is analyzed to solve the two-body bound-state problem. The light-front two-body bound-state equation is extended to the full LFD kernel including the ladder, cross-ladder, stretched-box, and particle-antiparticle creation/annihilation effects to study the contributions of higher Fock-states. The light-front two-body equation is also modified by the term corresponding to the self-energy corrections and counter-terms. Using the variational principle, we obtain the numerical result of the binding energy B versus the coupling constant \\alpha\\ for various mass ratios of the constituent particles including the cases of non-zero exchange particle mass. We also discuss the correlation between the mass spectrum and the corresponding bound-state wavefunction.

  11. Measures of the Environmental Footprint of the Front End of the Nuclear Fuel Cycle

    SciTech Connect (OSTI)

    Brett Carlsen; Emily Tavrides; Erich Schneider

    2010-08-01T23:59:59.000Z

    Previous estimates of environmental impacts associated with the front end of the nuclear fuel cycle have focused primarily on energy consumption and CO2 emissions. Results have varied widely. Section 2 of this report provides a summary of historical estimates. This study revises existing empirical correlations and their underlying assumptions to fit to a more complete set of existing data. This study also addresses land transformation, water withdrawals, and occupational and public health impacts associated with the processes of the front end of the once-through nuclear fuel cycle. These processes include uranium mining, milling, refining, conversion, enrichment, and fuel fabrication. Metrics are developed to allow environmental impacts to be summed across the full set of front end processes, including transportation and disposition of the resulting depleted uranium.

  12. CW Room Temperature Re-Buncher for the Project X Front End

    SciTech Connect (OSTI)

    Romanov, Gennady; Awida, Mohamed H.; Chen, Meiyu; Gonin, Ivan V.; Kazakov, Sergey; Kostin, Roman; Lebedev, Valeri; Solyak, Nikolay; Yakovlev, Vyacheslav P.; /Fermilab

    2012-05-09T23:59:59.000Z

    At Fermilab there is a plan to construct the Project X Injector Experiment (PXIE) facility - a prototype of the front end of the Project X, a multi-MW proton source based on superconducting linac. The construction and successful operations of this facility will validate the concept for the Project X front end, thereby minimizing the primary technical risk element within the Project. The room temperature front end of the linac contains an ion source, an RFQ accelerator and a Medium Energy Beam Transport (MEBT) section comprising a high bandwidth bunch selective chopper. The MEBT length is about 10 m, so three re-bunching CW cavities are used to support the beam longitudinal dynamics. The paper reports a RF design of the re-bunchers along with preliminary beam dynamic and thermal analysis of the cavities.

  13. Comparison of quantum field perturbation theory for the light front with the theory in lorentz coordinates

    E-Print Network [OSTI]

    S. A. Paston; V. A. Franke

    1999-01-22T23:59:59.000Z

    The relationship between the perturbation theory in light-front coordinates and Lorentz-covariant perturbation theory is investigated. A method for finding the difference between separate terms of the corresponding series without their explicit evaluation is proposed. A procedure of constructing additional counter-terms to the canonical Hamiltonian that compensate this difference at any finite order is proposed. For the Yukawa model, the light-front Hamiltonian with all of these counter-terms is obtained in a closed form. Possible application of this approach to gauge theories is discussed.

  14. Eddy conductivity in and near dry cold fronts in the layer, 70 to 1270 feet

    E-Print Network [OSTI]

    Conlan, Edward Francis

    1965-01-01T23:59:59.000Z

    EDDY CONDUCTIVITY IN AND NEAR DRY COLD FRONTS IN THE LAYER, 70 TO 1270 FEET A Thesis By EDWARD FRANCIS CONLAN Captain, USAF Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE January 1965 Major Subject: METEOROLOGY EDDY CONDUCTIVITY IN AND NEAR DRY COLD FRONTS IN THE LAYER) 70 TO 1270 FEET A Thesis By EDWARD FRANCIS CONLAN Captain, USAF Approved as to style and content by: i J 8~. . c6~h arrmanf o...

  15. Upper and lower limits on the Crab pulsar's astrophysical parameters set from gravitational wave observations by LIGO: braking index and energy considerations

    E-Print Network [OSTI]

    Giovanni Santostasi

    2008-07-16T23:59:59.000Z

    The Laser Interferometer Gravitational Observatory (LIGO) has recently reached the end of its fifth science run (S5), having collected more than a year worth of data. Analysis of the data is still ongoing but a positive detection of gravitational waves, while possible, is not realistically expected for most likely sources. This is particularly true for what concerns gravitational waves from known pulsars. In fact, even under the most optimistic (and not very realistic) assumption that all the pulsar's observed spin-down is due to gravitational waves, the gravitational wave strain at earth from all the known isolated pulsars (with the only notable exception of the Crab pulsar) would not be strong enough to be detectable by existing detectors. By August 2006, LIGO had produced enough data for a coherent integration capable to extract signal from noise that was weaker than the one expected from the Crab pulsar's spin-down limit. No signal was detected, but beating the spin-down limit is a considerable achievement for the LIGO Scientific Collaboration (LSC). It is customary to translate the upper limit on strain from a pulsar into a more astrophysically significant upper limit on ellipticity. Once the spin-down limit has been beaten, it is possible to release the constraint that all the spin-down is due to gravitational wave emission. A more complete model with diverse braking mechanisms can be used to set limits on several astrophysical parameters of the pulsar. This paper shows possible values of such parameters for the Crab pulsar given the current limit on gravitational waves from this neutron star.

  16. Effect of autologous platelet-rich plasma-releasate on intervertebral disc degeneration in the rabbit anular puncture model: a preclinical study

    E-Print Network [OSTI]

    2012-01-01T23:59:59.000Z

    discs. Autologous PRP and PPP (platelet-poor plasma) werethe initial puncture, releasate isolated from clotted PPP orPRP (PPP- or PRP-releasate), or phosphate-buffered saline (

  17. Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

    SciTech Connect (OSTI)

    Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au [School of Physics, University of Western Australia, Crawley, WA (Australia); Stamps, R. L. [School of Physics, University of Western Australia, Crawley, WA (Australia); SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2014-09-21T23:59:59.000Z

    Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.

  18. Dust Settling in Magnetorotationally-Driven Turbulent Discs I: Numerical Methods and Evidence for a Vigorous Streaming Instability

    E-Print Network [OSTI]

    Dinshaw S. Balsara; David A. Tilley; Terrence Rettig; Sean A. Brittain

    2008-10-01T23:59:59.000Z

    (Abridged) In this paper we have used the RIEMANN code for computational astrophysics to study the interaction of a realistic distribution of dust grains with gas in a vertically stratified protostellar accretion disc. The disc was modeled to have the density and temperature of a minimum mass solar nebula, and was driven to a fully-developed turbulence via the magnetorotational instability (MRI). We find that the inclusion of standard dust to gas ratios does not have any significant effect on the MRI even when the dust sediments to the midplane of the accretion disc. The density distribution of the dust reaches a Gaussian profile, and the scale heights for the dust that we derive are shown to be proportional to the reciprocal of the square root of the dust radius. The largest dust shows a strong tendency to settle to the midplane of the accretion disc, and tends to organize itself into elongated clumps of high density. The dynamics of these clumps is shown to be consistent with a streaming instability. The streaming instability is seen to be very vigorous and persistent once it forms. Each stream of high density dust displays a reduced RMS velocity dispersion, and the densest clumpings of large dust are shown to form where the streams intersect. We have also shown that the mean free path and collision time for the dust that participates in the streaming instability is reduced by almost two orders of magnitude relative to the average mean free paths and collision times. We show that some of the large dust in our 10 au simulations should have a propensity for grain coalescence.

  19. A 65nm CMOS Ultra Low Power and Low Noise 131M Front-End Transimpedance Amplifier

    E-Print Network [OSTI]

    Ayers, Joseph

    A 65nm CMOS Ultra Low Power and Low Noise 131M Front-End Transimpedance Amplifier Jiaping Hu and simulation of a high-transimpedance gain, ultra low-power dissipation and low-noise CMOS front- end control [3]. However, it introduces design challenges in the form of trade-offs between noise, power

  20. Design of a Very Low-power, Low-cost 60 GHz Receiver Front-End Implemented

    E-Print Network [OSTI]

    Boyer, Edmond

    Design of a Very Low-power, Low-cost 60 GHz Receiver Front-End Implemented in 65 nm CMOS Technology- noise amplifier (LNA), mixer, a voltage controlled oscillator (VCO), a local oscillator (LO) buffer, France The research on the design of receiver front-ends for very high data-rate communication in the 60