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Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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1

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

E-Print Network (OSTI)

front steering and rear braking in a driver- assist system for vehicle yaw control. The proposed control system aims at stabilizing the vehicle while achieving a desired yaw rate. During normal driving braking could be used for yaw rate control. An active suspension system, by controlling the wheel load

Paris-Sud XI, Université de

2

DOES MAGNETIC-FIELD-ROTATION MISALIGNMENT SOLVE THE MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION?  

SciTech Connect

Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. In the simplest case of a laminar (non-turbulent) core with the magnetic field aligned with the rotation axis, both analytic considerations and numerical simulations have shown that the formation of a large, 10{sup 2} AU scale, rotationally supported protostellar disk is suppressed by magnetic braking in the ideal MHD limit for a realistic level of core magnetization. This theoretical difficulty in forming protostellar disks is termed the ''magnetic braking catastrophe''. A possible resolution to this problem, proposed by Hennebelle and Ciardi and Joos et al., is that misalignment between the magnetic field and rotation axis may weaken the magnetic braking enough to enable disk formation. We evaluate this possibility quantitatively through numerical simulations. We confirm the basic result of Joos et al. that the misalignment is indeed conducive to disk formation. In relatively weakly magnetized cores with dimensionless mass-to-flux ratio {approx}> 4, it enabled the formation of rotationally supported disks that would otherwise be suppressed if the magnetic field and rotation axis are aligned. For more strongly magnetized cores, disk formation remains suppressed, however, even for the maximum tilt angle of 90 Degree-Sign . If dense cores are as strongly magnetized as indicated by OH Zeeman observations (with a mean dimensionless mass-to-flux ratio {approx}2), it would be difficult for the misalignment alone to enable disk formation in the majority of them. We conclude that, while beneficial to disk formation, especially for the relatively weak field case, misalignment does not completely solve the problem of catastrophic magnetic braking in general.

Li Zhiyun [Astronomy Department, University of Virginia, Charlottesville, VA (United States); Krasnopolsky, Ruben; Shang, Hsien [Academia Sinica, Theoretical Institute for Advanced Research in Astrophysics, Taipei, Taiwan (China)

2013-09-01T23:59:59.000Z

3

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

E-Print Network (OSTI)

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...

Hopkins, Jennifer Susan

1995-01-01T23:59:59.000Z

4

Why Brake-By-Wire (BBW) ? Advantages of BBW  

E-Print Network (OSTI)

Conventional Brake System http://www.conti-online.com #12;BBW Survey [ SKF (Motor + PGT +Ball Screw)] [ DELPHI (Motor + PGT +Ball Screw)] [Continental Teves (Motor + PGT + Roller Screw)] [Continental Teves installed at wheel] #12;Sectional Drawing of the Electromechanically Actuated Disk Brake From ITT Brake Pads Caliper

Yao, Bin

5

Hybrid: Braking  

Alternative Fuels and Advanced Vehicles Data Center (EERE)

1 1 Regenerative braking converts otherwise wasted energy from braking into electricity and stores it in the battery. In regenerative braking, the electric motor is reversed so that, instead of using electricity to turn the wheels, the rotating wheels turn the motor and create electricity. Using energy from the wheels to turn the motor slows the vehicle down. Go to next… stage graphic: vertical blue rule Main stage: See through car with battery, engine, and electric motor visible. The car is decelerating. There are arrows flowing from the front wheels to the electric motor to the battery. Main stage: See through car with battery, engine, and electric motor visible. The car is decelerating. There are arrows flowing from the front wheels to the electric motor to the battery.

6

Hybrid: Braking  

Alternative Fuels and Advanced Vehicles Data Center (EERE)

2 2 If additional stopping power is needed, conventional friction brakes (e.g., disc brakes) are also applied automatically. Go back… stage graphic: vertical blue rule Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Battery: The battery stores energy generated from the gasoline engine or, during regenerative braking, from the electric motor. Since the battery helps power the vehicle, it is larger and holds much more energy than batteries used to start conventional vehicles. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection.

7

Hybrid: Braking  

NLE Websites -- All DOE Office Websites (Extended Search)

Button Stopped button highlighted subbanner graphic: gray bar Button Stopped button highlighted subbanner graphic: gray bar STOPPED When the vehicle is stopped, such as at a red light, the gasoline engine and electric motor shut off automatically so that energy is not wasted in idling. The battery continues to power auxillary systems, such as the air conditioning and dashboard displays. stage graphic: vertical blue rule Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Battery: The battery stores energy generated from the gasoline engine or, during regenerative braking, from the electric motor. Since the battery helps power the vehicle, it is larger and holds much more energy than batteries used to start conventional vehicles. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection.

8

Hybrid: Braking  

Alternative Fuels and Advanced Vehicles Data Center (EERE)

Button Stopped button highlighted subbanner graphic: gray bar Button Stopped button highlighted subbanner graphic: gray bar STOPPED When the vehicle is stopped, such as at a red light, the gasoline engine and electric motor shut off automatically so that energy is not wasted in idling. The battery continues to power auxillary systems, such as the air conditioning and dashboard displays. stage graphic: vertical blue rule Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection. Battery: The battery stores energy generated from the gasoline engine or, during regenerative braking, from the electric motor. Since the battery helps power the vehicle, it is larger and holds much more energy than batteries used to start conventional vehicles. Main stage: See through car with battery, engine, and electric motor visible. The car is stopped at an intersection.

9

Full Hybrid: Braking  

Alternative Fuels and Advanced Vehicles Data Center (EERE)

Braking button highlighted Stopped button Braking button highlighted Stopped button BRAKING PART 1 Regenerative braking converts otherwise wasted energy from braking into electricity and stores it in the battery. In regenerative braking, the electric motor is reversed so that, instead of using electricity to turn the wheels, the rotating wheels turn the motor and create electricity. Using energy from the wheels to turn the motor slows the vehicle down. Go to next… stage graphic: vertical blue rule Main stage: See through car with battery, engine, generator, power split device, and electric motor visible. The car is decelerating. There are arrows flowing from the front wheels to the power split device to the electric motor to the battery. Main stage: See through car with battery, engine, generator, power split device, and electric motor visible. The car is decelerating. There are arrows flowing from the front wheels to the power split device to the electric motor to the battery.

10

Svendborg Brakes | Open Energy Information  

Open Energy Info (EERE)

Name: Svendborg Brakes Place: Denmark Sector: Wind energy Product: Denmark-based manufacturer of braking systems for the wind industry, as well as for the oil sector....

11

WIND BRAKING OF MAGNETARS  

SciTech Connect

We explore the wind braking of magnetars considering recent observations challenging the traditional magnetar model. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin-down measurements may be strongly biased by particle wind. Recent observations challenging the traditional model of magnetars may be explained naturally by the wind braking scenario: (1) the supernova energies of magnetars are of normal value; (2) the non-detection in Fermi observations of magnetars; (3) the problem posed by low magnetic field soft gamma-ray repeaters; (4) the relation between magnetars and high magnetic field pulsars; and (5) a decreasing period derivative during magnetar outbursts. Transient magnetars with L{sub x}<- E-dot{sub rot} may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. A strong reduction of the dipole magnetic field is possible only when the particle wind is very collimated at the star surface. A small reduction of the dipole magnetic field may result from detailed considerations of magnetar wind luminosity. In the wind braking scenario, magnetars are neutron stars with a strong multipole field. For some sources, a strong dipole field may no longer be needed. A magnetism-powered pulsar wind nebula will be one of the consequences of wind braking. For a magnetism-powered pulsar wind nebula, we should see a correlation between the nebula luminosity and the magnetar luminosity. Under the wind braking scenario, a braking index smaller than three is expected. Future braking index measurement of a magnetar may tell us whether magnetars are wind braking or magnetic dipole braking.

Tong, H. [Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, Xinjiang 830011 (China); Xu, R. X.; Qiao, G. J. [KIAA and School of Physics, Peking University, Beijing 100871 (China); Song, L. M., E-mail: tonghao@xao.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

2013-05-10T23:59:59.000Z

12

Chapter 9 - Brake Testing  

Science Journals Connector (OSTI)

Abstract This chapter describes and explains the role and methods of experimental testing in the design and verification of brakes and their components. It starts by discussing the increasing capability of computer-based predictive techniques, which can simulate many aspects of brake operation and save time and cost compared with previous methods of experimental evaluation. Preparation, procedures, instrumentation, data acquisition and results analysis, interpretation and reporting for experimental testing ranging from whole vehicle braking performance on a test track to component performance and material thermophysical properties in the laboratory, are explained and discussed. By the end of the chapter the design and operation of test rigs including inertia dynamometers for full-size brakes, scale rigs for small-sample friction and wear measurement, machines for cyclic loading and material property measurement, etc. are described. The importance of careful preparation of the friction pair (bedding-in and burnishing) for brake performance testing and the evaluation of variability by repeat testing is emphasised.

Andrew Day

2014-01-01T23:59:59.000Z

13

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

DOE Patents (OSTI)

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.

Rau, Scott James

2013-01-29T23:59:59.000Z

14

Vehicle rear suspension mechanism  

SciTech Connect

A vehicle rear suspension mechanism is described which consists of: a suspension member connected with a vehicle body; wheel hub means supporting a rear wheel having a wheel center plane for rotation about a rotating axis; and connecting means for connecting the wheel hub means with the suspension member. The connecting means include ball joint means having a pivot center located forwardly of and below the rotating axis of the rear wheel and connecting the wheel hub means to the suspension member pivotably about the pivot center, first resilient means located between the wheel hub means and the suspension member rearwardly of and above the rotating axis of the rear wheel, and second resilient means located between the wheel hub means and the suspension member forwardly of and above the rotating axis of the rear wheel.

Kijima, T.; Maebayashi, J.

1986-08-05T23:59:59.000Z

15

Modeling of air brakes for onboard diagnostics of heavy trucks  

E-Print Network (OSTI)

declared out of service. Worn brake pads and tires, air leaks at hoses, connections, valves and brake chambers of the airbrake system along with the significant time delay in the actuation of tractor and trailer brakes degrade the vehicle braking...

Kankanala, Penchala N

2012-06-07T23:59:59.000Z

16

Innovative vibration measurement technology for brake development  

Science Journals Connector (OSTI)

Apart from working reliably and providing safety, the comfort features of brakes in vehicles these days have become very significant. The requirement of a noiseless brake system always poses an important chall...

Dipl.-Ing. Holger Marschner; Dr. rer. nat. Dirk Reckwerth

2008-02-01T23:59:59.000Z

17

Heavy Overweight Vehicle Brake Testing (HOVBT)  

E-Print Network (OSTI)

Heavy Overweight Vehicle Brake Testing (HOVBT) Oak Ridge National Laboratory managed by UT for a real-time on-board brake assessment tool. Test Overview A combination tractor-trailer will be given a complete brake rebuild prior to several tests performed at fully -laden and several overweight loading

18

6 - Engine brake performance in diesel engine system design  

Science Journals Connector (OSTI)

Abstract: This chapter provides a comprehensive theory on engine brake performance. It first discusses vehicle braking requirement and the impact on enginevehicle matching in engine brake operation, followed by a comparison between engine brakes and drivetrain retarders. It then introduces drivetrain retarders in detail including their torque and cooling characteristics. The performance characteristics of exhaust brakes and compression brakes are elaborated including their mechanisms and the interactions with valvetrain, variable valve actuation (VVA) and turbocharger. The principles of engine brake design are introduced through comprehensive simulation analysis on engine thermodynamic cycles in braking operation. A braking gas recirculation (BGR) theory is developed.

Qianfan Xin

2013-01-01T23:59:59.000Z

19

Disturbance Control of the Hydraulic Brake in a Wind Turbine  

E-Print Network (OSTI)

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

Yang, Zhenyu

20

Wide speed range for traction motor in braking force of electric braking control system  

Science Journals Connector (OSTI)

A vehicle stopping method using an electric brake until a traction motor is stopped is studied. At the moment of vehicle stop, electric brake is changed to control mode where ... is controlled by estimating the l...

Young-Choon Kim; Moon-Taek Cho

2014-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Electric Braking Control System to Secure Braking Force in the Wide Speed Range of Traction Motor  

Science Journals Connector (OSTI)

In this paper, a vehicle stopping method using an electric brake until a traction motor is stopped is studied. At the moment of vehicle stop, electric brake is changed to control mode wherein ... is controlled by...

Young-Choon Kim; Moon-Taek Cho; Ok-Hwan Kim

2014-01-01T23:59:59.000Z

22

PREDICTING RANGES FOR PULSARS' BRAKING INDICES  

SciTech Connect

The theoretical determination of braking indices of pulsars is still an open problem. In this paper we report results of a study concerning such determination based on a modification of the canonical model, which admits that pulsars are rotating magnetic dipoles, and on data from the seven pulsars with known braking indices. In order to test the modified model, we predict ranges for the braking indices of other pulsars.

Magalhaes, Nadja S.; Miranda, Thaysa A. [Federal University of Sao Paulo, DCET, Rua Sao Nicolau 210, Diadema, SP 09913-030 (Brazil); Frajuca, Carlos, E-mail: nadjasm@gmail.com [Federal Institute of Education, Science and Technology of Sao Paulo, R. Pedro Vicente 625, Sao Paulo, SP 01109-010 (Brazil)

2012-08-10T23:59:59.000Z

23

Hybrid Braking System for Non-Drive Axles  

Energy.gov (U.S. Department of Energy (DOE))

A hybrid braking system is designed to conserve diesel fuel (or alternative fuels) by using regenerative braking, which extends hybrid technology to non-drive axles.

24

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

25

Chapter 6 - Brake System Layout Design  

Science Journals Connector (OSTI)

Abstract This chapter brings together high-level braking system design (Chapters 3 and 4Chapter 3Chapter 4) and the design of friction brakes (Chapter 5) to complete the layout design of road vehicle braking systems. Two actuation systems are studied: hydraulic (used on passenger cars and light commercial vehicles) and pneumatic (used on heavy commercial vehicles). Other braking technologies (e.g. regenerative) and actuation systems (e.g. power hydraulic and electromechanical) are also mentioned. A four-step design procedure is presented, which includes designing the basic braking system parameters based on the vehicle configuration, specifying the brakes (size and torque capacity), designing the actuation system, and verification (legislative requirements). Examples are presented for a hydraulic system with a vacuum booster (passenger car) and a pneumatic system (articulated commercial vehicle), which illustrate the important features of achieving a good basic system configuration. In passenger cars, the importance of driver interface parameters such as pedal feel is explained, and for commercial vehicles, compatibility, load sensing, and predominance between the trailer and towing vehicle brake systems is discussed.

Andrew Day

2014-01-01T23:59:59.000Z

26

Contactless magnetic brake for automotive applications  

E-Print Network (OSTI)

CONTACTLESS MAGNETIC BRAKE FOR AUTOMOTIVE APPLICATIONS A Dissertation by SEBASTIEN EMMANUEL GAY Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR... OF PHILOSOPHY May 2005 Major Subject: Electrical Engineering CONTACTLESS MAGNETIC BRAKE FOR AUTOMOTIVE APPLICATIONS A Dissertation by SEBASTIEN EMMANUEL GAY Submitted to Texas A&M University in partial fulfillment of the requirements...

Gay, Sebastien Emmanuel

2009-05-15T23:59:59.000Z

27

Adaptive controller for regenerative and friction braking system  

DOE Patents (OSTI)

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.

Davis, Roy I. (Ypsilanti, MI)

1990-01-01T23:59:59.000Z

28

The braking performance of tractor-trailer combinations  

Science Journals Connector (OSTI)

Equations are derived for the maximum decelerations which can be obtained with balanced and unbalanced trailers with and without trailer brakes. The equations are used to produce graphs showing the maximum decelerations of trailers having typical dimensions, of different weights relative to the towing tractor on surfaces of different adhesion coefficients and with different types and degrees of braking on the trailers. Results measured during braking tests on tractors and trailers are given. Unbalanced trailers are shown to have a better braking performance than balanced trailers and it is therefore, recommended that trailers should be designed to carry the maximum permissible proportion of their weight on the tractor. Both over-run and power brakes on trailers are shown to provide very useful improvements in braking performance. Power brakes are preferred because of the difficulty of fitting over-run brakes on unbalanced trailers. The tractor's external hydraulics are considered to be the most convenient source of power. On-off brakes providing a fixed braking force equal to approximately 510% of the trailer maximum gross laden weight are considered to be a useful and simple means of improving existing trailers, but the development of trailer braking systems providing a braking force proportional to the tractor brake pedal force up to a maximum of approximately 2030% of the trailer maximum gross laden weight is considered to be very desirable.

M.J. Dwyer

1970-01-01T23:59:59.000Z

29

Thermal cracking in disc brakes Thomas J. Mackin *,1  

E-Print Network (OSTI)

Thermal cracking in disc brakes Thomas J. Mackin *,1 , Steven C. Noe, K.J. Ball, B.C. Bedell, D, or hub, which is connected to the wheel and axle, and an inboard and outboard braking surface

Salvaggio, Carl

30

Electric vehicle regenerative antiskid braking and traction control system  

DOE Patents (OSTI)

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.

Cikanek, Susan R. (Wixom, MI)

1995-01-01T23:59:59.000Z

31

A diagnostic system for air brakes in commercial vehicles  

E-Print Network (OSTI)

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 systems is sensitive...

Coimbatore Subramanian, Shankar Ram

2007-09-17T23:59:59.000Z

32

Airborne wear particles railway research group FEM Simulation of train disc brake behavior  

E-Print Network (OSTI)

1 Airborne wear particles railway research group FEM Simulation of train disc brake behavior a modern train disc brake with brake caliper and high speed pads. During braking, a considerable amount. A model of train brake caliper Aim The overall aim of the MSc degree project is to develop a thermoelastic

Haviland, David

33

Development of Diagnostic Algorithms for Air Brakes in Trucks  

E-Print Network (OSTI)

for di erent clearances and supply pressures : : : 6 4 Modes of operation of the air brake system [19] : : : : : : : : : : : : 11 5 A simpli ed layout of air brake system for a tractor : : : : : : : : : : 15 6 S-cam foundation brake..., causing it to rotate the slack adjuster. The slack adjuster, in turn, rotates 15 Fig. 5. A simpli ed layout of air brake system for a tractor the S-cam as it is connected to the S-cam through a splined shaft. The rotational mo- tion of the S-cam pushes...

Dhar, Sandeep

2011-10-21T23:59:59.000Z

34

Cooperative fish rearing projects at Hanford  

SciTech Connect

This presentation details the success of the cooperative efforts to develop fish rearing projects at the Hanford Site, Richland,WA.

Betsch, M.D., Westinghouse Hanford

1996-06-25T23:59:59.000Z

35

Measurement and control of brake pedal feel quality in automobile manufacturing  

E-Print Network (OSTI)

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 ...

Cerilles, Jeffrey T. (Jeffrey Thomas)

2005-01-01T23:59:59.000Z

36

E-Print Network 3.0 - air brakes Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

brakes to predominantly air disc brakes. Compare and contrast the impact of such conversions in Europe... Energy Efficiency in Heavy Vehicle Tires, Drivetrains, and ......

37

E-Print Network 3.0 - antilock brake systems Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

such as trucks, tractor... -trailers and buses. In these brake systems, compressed air is used as the energy transmitting medium to actuate... the foundation brakes mounted...

38

E-Print Network 3.0 - anti-lock braking system Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

such as trucks, tractor... -trailers and buses. In these brake systems, compressed air is used as the energy transmitting medium to actuate... the foundation brakes mounted...

39

A pressure control scheme for air brakes in commercial vehicles  

E-Print Network (OSTI)

This research is focused on developing a control scheme for regulating the pressure in the brake chamber of an air brake system found in most commercial vehicles like trucks, tractor-trailers and buses. Such a control scheme can be used...

Bowlin, Christopher Leland

2007-04-25T23:59:59.000Z

40

Many applications require brakes, for instance to decelerate or to  

E-Print Network (OSTI)

surfaces in order to generate the braking torque. Typically, actuators Statically balancing A team of TU 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

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Investigation of aerodynamic braking devices for wind turbine applications  

SciTech Connect

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.

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

1997-04-01T23:59:59.000Z

42

Disk filter  

DOE Patents (OSTI)

An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

Bergman, W.

1985-01-09T23:59:59.000Z

43

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

E-Print Network (OSTI)

Statistics indicate that defects in brake system contribute significantly to fatal crashes involving commercial vehicles. Hence there is a need for developing preventive and active safety measures for assessing the performance of an air brake system...

Vilayannur Natarajan, Shankar

2005-08-29T23:59:59.000Z

44

Fuzzy logic electric vehicle regenerative antiskid braking and traction control system  

DOE Patents (OSTI)

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.

Cikanek, Susan R. (Wixom, MI)

1994-01-01T23:59:59.000Z

45

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

E-Print Network (OSTI)

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...

Picha, Dale Louis

2012-06-07T23:59:59.000Z

46

E-Print Network 3.0 - air brake association Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

... Source: Southwest Region University Transportation Center Collection: Engineering ; Energy Storage, Conversion and Utilization 2 Commercial Motor Vehicle Brake Assessment...

47

Switched reluctance motor based electromechanical brake-by-wire system  

Science Journals Connector (OSTI)

This article presents an overview of electronic braking systems using SR (Switched Reluctance) machines. The advantages presented by this structure when compared to the conventional hydraulic systems are discussed. A justification for the choice of the SRM as a valid candidate is provided, with a detailed analysis of its control structure and performance. Experimental results obtained using a digital signal processor are also presented.

S. Underwood; A. Khalil; I. Husain; H. Klode; B. Lequesne; S. Gopalakrishnan; A. Omekanda

2004-01-01T23:59:59.000Z

48

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

E-Print Network (OSTI)

model for an air brake system in the presence of leaks. Brake systems in trucks are crucial for ensuring the safety of vehicles and passengers on the roadways. Most trucks in the US are equipped with S-cam drum brake systems and they are sensitive.... Overview Air brake systems are used in heavy commercial vehicles like buses, straight trucks and combination vehicles such as tractor-trailers[1]. More than 85% of the commer- cial vehicles in the US are equipped with S-cam drum brakes[2]. Proper...

Ramaratham, Srivatsan

2008-10-10T23:59:59.000Z

49

Design and test of a wet type helium turbo-expander with an alternator as a brake  

SciTech Connect

A wet type helium turbo-expander with expected adiabatic efficiency of 70% at inlet pressure, temperature, and outlet pressure of 1.3 MPa, 6.0 K, and 0.2 MPa, respectively, has been developed. An alternator is adopted as a brake where a permanent magnet is held in the turbine shaft. And a self-acting gas bearing is used at thrust and journal bearings. An electromagnet supports thrust bearing to lift up the thrust disk when initiating operation. Design mass flow rate of the turbine is determined to be 60 g/s, corresponding to the JT mass flow rate in the existing helium liquefier/refrigerator. In the cryogenic performance test, the turbine had increased helium liquefaction rate by four times larger than the liquefaction rate without turbine operation.

Kato, T.; Miyake, A.; Kawano, K.; Hamada, K.; Hiyama, T.; Iwamoto, S.; Ebisu, H.; Tsuji, H. [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan); Saji, N.; Kaneko, Y. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)] [and others

1994-12-31T23:59:59.000Z

50

Catalog of Waters Important for the Spawning, Rearing or Migration...  

Open Energy Info (EERE)

Spawning, Rearing or Migration of Anadromous Fishes Organization Alaska Department of Fish and Game Published Divisions of Sport Fish and Habitat, 2012 Report Number 12-05 DOI...

51

E-Print Network 3.0 - automatic braking Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

for an Urban Electric Vehicle Summary: , Automatic Braking, Electric Vehicles, Personal Rapid Transit, Public Transit, Advanced Vehicle Control... the design modification,...

52

E-Print Network 3.0 - automotive brake materials Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

such as trucks, tractor... -trailers and buses. In these brake systems, compressed air is used as the energy transmitting medium to ... Source: Southwest Region University...

53

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

E-Print Network (OSTI)

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...

Coimbatore Subramanian, Shankar

2004-09-30T23:59:59.000Z

54

Vehicle yaw control via coordinated use of steering/braking systems  

E-Print Network (OSTI)

Vehicle yaw control via coordinated use of steering/braking systems M. Doumiati, O. Sename, J. Martinez, L. Dugard P. Gaspar, Z. Szabo, J. Bokor Gipsa-Lab UMR CNRS 5216, Control Systems Department with steer- ing/braking coordination task for vehicle yaw control. For steerability enhancement, only active

Paris-Sud XI, Université de

55

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

E-Print Network (OSTI)

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...

Hsien, Li-Wei

2012-06-07T23:59:59.000Z

56

Plant and Environment Interactions Arsenic Accumulation in the Hyperaccumulator Chinese Brake and Its Utilization  

E-Print Network (OSTI)

in a greenhouse. At recently, however, has Chinese brake (Pteris vittata L.)harvest, the Chinese brake produced soils (0.47­7.56 mg As kg 1 ),concentration to water-soluble arsenic in soil) of 1450 and a transloca to remediate arsenic contaminated soils. schullat, 2000), soil arsenic concentration (Jiang and Singh, 1994

Ma, Lena

57

Microsoft PowerPoint - Real-Time Dynamic Brake Assessment poster.ppt [Compatibility Mode]  

NLE Websites -- All DOE Office Websites (Extended Search)

Dynamic Brake Assessment Dynamic Brake Assessment Purpose Conduct a proof-of-concept test to examine the feasibility of developing an on-board system to assess a vehicle's ability to stop based on typical low-pressure in-service braking events. Partnerships H.T. Hackney Company MGM Brakes Overview Funded through the Federal Motor Carrier Safety Administration's Vehicle and Roadside Operations Division Concept stemming from on the Department of Energy's Medium Truck Duty Cycle research as well as previous research conducted for the National Highway Transportation Safety Administration. Signals to be collected Real-time brake application pressure Vehicle speed and acceleration GPS location and grade information Vehicle weight (current load) Engine parameters such as RPM and torque To be conducted October 2010 -

58

Disk Quota Increase Request  

NLE Websites -- All DOE Office Websites (Extended Search)

Disk Disk Quota Increase Disk Quota Increase Request NERSC will consider reasonable requests for changes in disk space and inode limits. Please submit a request through the "Request Forms" section at the NERSC help portal. If you select "Hopper scratch directory" from the "File System" menu below, the quota value requested applies to the combined contents of $SCRATCH and $SCRATCH2. Please ask for the least amount of resources you need, since the sum of disk space and inodes allocated to users already exceeds system capacity. In other words, system resources would be exhausted before all users could use their existing quotas. You can find out the current quotas and usage of disk space and inodes for your home and scratch file systems with the myquota command. You can find

59

Wind turbine trailing-edge aerodynamic brake design  

SciTech Connect

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.

Quandt, G.

1996-01-01T23:59:59.000Z

60

Glass rupture disk  

DOE Patents (OSTI)

A frangible rupture disk and mounting apparatus for use in blocking fluid flow, generally in a fluid conducting conduit such as a well casing, a well tubing string or other conduits within subterranean boreholes. The disk can also be utilized in above-surface pipes or tanks where temporary and controllable fluid blockage is required. The frangible rupture disk is made from a pre-stressed glass with controllable rupture properties wherein the strength distribution has a standard deviation less than approximately 5% from the mean strength. The frangible rupture disk has controllable operating pressures and rupture pressures.

Glass, S. Jill (Albuquerque, NM); Nicolaysen, Scott D. (Albuquerque, NM); Beauchamp, Edwin K. (Albuquerque, NM)

2002-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Environmental Assessment K Pool 'Fish Rearing, Hanford Site, Richland, Washington  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

DOERA-1 11 1 DOERA-1 11 1 Environmental Assessment K Pool 'Fish Rearing, Hanford Site, Richland, Washington U.S. Department of Emrgy Richland, Washington December 1996 DOEEA-1111 ENVIRONMJ3'NTAL ASSESSMENT K POOL 'F'ISH REARING HANFORD SITE, RICHLAND, WASHINGTON U.S. DEPARTMENT OF ENERGY RICHLAND, WASHINGTON December 1996 This page intentionally left blank. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. 1 ' U.S. Department of Energy summary The U.S. Department of Energy (DOE) has a need to respond to a request to lease facilities at the Hanford Site 100-KE and 100-KW filter plant pools (K Pools) for fish rearing activities. These fish rearing activities would be: (1) business ventures with public h

62

EA-1111: K Pool Fish Rearing, Hanford Site, Richland, Washington  

Energy.gov (U.S. Department of Energy (DOE))

This EA evaluates the environmental impacts of the proposal to enter into a use permit or lease agreement with the Yakama Indian Nation or other parties who would rear fish in the 100-K Area Pools.

63

Environmental assessment, K Pool fish rearing, Hanford Site, Richland, Washington  

SciTech Connect

The US Department of Energy (DOE) has a need to respond to a request to lease facilities at the Hanford Site 100-KE and 100-KW filter plant pools (K Pools) for fish rearing activities. These fish rearing activities would be: (1) business ventures with public and private funds and (2) long-term enhancement and supplementation programs for game fish populations in the Columbia River Basin. The proposed action is to enter into a use permit or lease agreement with the YIN or other parties who would rear fish in the 100-K Area Pools. The proposed action would include necessary piping, pump, and electrical upgrades of the facility; cleaning and preparation of the pools; water withdrawal from the Columbia River, and any necessary water or wastewater treatment; and introduction, rearing and release of fish. Future commercial operations may be included.

NONE

1996-12-01T23:59:59.000Z

64

The Magnetic Field in the Class 0 Protostellar Disk of L1527  

E-Print Network (OSTI)

We present subarcsecond (~0.35") resolved observations of the 1.3 mm dust polarization from the edge-on circumstellar disk around the Class 0 protostar L1527. The inferred magnetic field is consistent with a dominantly toroidal morphology; there is no significantly detected vertical poloidal component to which observations of an edge-on disk are most sensitive. This suggests that angular momentum transport in Class 0 protostars (when large amounts of material are fed down to the disk from the envelope and accreted onto the protostar) is driven mainly by magnetorotational instability rather than magnetocentrifugal winds at 50 AU scales. In addition, with the data to date there is an early, tentative trend that R>30 AU disks have so far been found in Class 0 systems with average magnetic fields on the 1000 AU scale strongly misaligned with the rotation axis. The absence of such a disk in the aligned case could be due to efficient magnetic braking that disrupts disk formation. If this is the case, this implies t...

Segura-Cox, Dominique M; Stephens, Ian W; Fernandez-Lopez, Manuel; Kwon, Woojin; Tobin, John J; Li, Zhi-Yun; Crutcher, Richard

2014-01-01T23:59:59.000Z

65

Effect of Nanoclay Reinforcement on the Friction Braking Performance of Hybrid Phenolic Friction Composites  

Science Journals Connector (OSTI)

Friction composite formulation consisting of decreasing nanoclay/lapinus fibres content, increasing graphite/aramid fibres ... is adopted for evaluating braking performance. The nanoclay content (?2.25wt.%) enha...

Tej Singh; Amar Patnaik

2013-03-01T23:59:59.000Z

66

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

E-Print Network (OSTI)

, the characteristics of combustion for swept injection timings along the maximum brake torque plateau are determined. The research is conducted by varying injection timing at constant engine speed and load while measuring engine emissions and in-cylinder pressure...

Kroeger, Timothy H

2013-09-19T23:59:59.000Z

67

INTRODUCTION In birds, the quality of rearing conditions is a  

E-Print Network (OSTI)

major, nest- ling condition affected recruitment probability but not reproductive success (Verboven- ling condition and survival better than with repro- ductive success and adult survival. These lifeINTRODUCTION In birds, the quality of rearing conditions is a major determinant of nestling body

Alvarez, Nadir

68

Urat Rear Banner Jihe Orient Wind Energy Co Ltd | Open Energy Information  

Open Energy Info (EERE)

Urat Rear Banner Jihe Orient Wind Energy Co Ltd Urat Rear Banner Jihe Orient Wind Energy Co Ltd Jump to: navigation, search Name Urat Rear Banner Jihe Orient Wind Energy Co Ltd Place Inner Mongolia Autonomous Region, China Sector Wind energy Product Urat Rear Banner Jihe Orient Wind Energy was established by Beijing Keval-East Technology Development in 2006 to develop wind power projects. References Urat Rear Banner Jihe Orient Wind Energy Co Ltd[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Urat Rear Banner Jihe Orient Wind Energy Co Ltd is a company located in Inner Mongolia Autonomous Region, China . References ↑ "Urat Rear Banner Jihe Orient Wind Energy Co Ltd" Retrieved from "http://en.openei.org/w/index.php?title=Urat_Rear_Banner_Jihe_Orient_Wind_Energy_Co_Ltd&oldid=352581

69

RO-VIBRATIONAL CO DETECTED IN THE {beta} PICTORIS CIRCUMSTELLAR DISK  

SciTech Connect

We present high-resolution near-infrared spectra of {beta} Pictoris-a nearby young star with a debris disk. Fundamental low-J CO absorption lines are detected and strict upper limits are placed on the flux of v = 2-1 low-J CO emission lines. The limit on the UV fluorescent emission flux in the v = 2-1 lines is used to place a tight constraint on the inner extent of the CO gas. Assuming H I is the primary collision partner, the sub-thermal population of the low-J v = 0 rotational levels constrains the density of the gas in the disk to n{sub H} = (2.5{sup +7.1}{sub -1.2}) x 10{sup 5} cm{sup -3}. If the distribution of hydrogen follows that of the other metals in the disk, we find that the mass of the gas in the disk is 0.17{sup +0.47}{sub -0.08} M{sub +}. We compare this mass to the gas mass necessary to brake the metals in the disk through ion-neutral reactions.

Troutman, Matthew R. [Department of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121 (United States); Hinkle, Kenneth H.; Najita, Joan R. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Rettig, Terrence W. [Center for Astrophysics, University of Notre Dame, Notre Dame, IN 46556 (United States); Brittain, Sean D., E-mail: mtroutm@clemson.edu, E-mail: khinkle@noao.edu, E-mail: najita@noao.edu, E-mail: trettig@nd.edu, E-mail: sbritt@clemson.edu [Department of Physics and Astronomy, 118 Kinard Laboratory, Clemson University, Clemson, SC 29634 (United States)

2011-09-01T23:59:59.000Z

70

Premixed direct injection disk  

DOE Patents (OSTI)

A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin; Zuo, Baifang; Uhm, Jong Ho

2013-04-23T23:59:59.000Z

71

Fuel for Galaxy Disks  

E-Print Network (OSTI)

Halo clouds have been found about the three largest galaxies of the Local Group and in the halos of nearby spirals. This suggests they are a relatively generic feature of the galaxy evolution process and a source of fuel for galaxy disks. In this review, two main sources of disk star formation fuel, satellite material and clouds condensing from the hot halo medium, are discussed and their contribution to fueling the Galaxy quantified. The origin of the halo gas of M31 and M33 is also discussed.

M. E. Putman; J. Grcevich; J. E. G. Peek

2008-03-20T23:59:59.000Z

72

Low frequency vibrations in disc brakes at high car speed. Part II: mathematical model and simulation  

Science Journals Connector (OSTI)

In the present paper, a mathematical model is constructed for judder in disc brakes at high speed. Vehicle suspension is modelled by means of finite elements. Vibration modes and frequencies are derived that can be used in the classification of modes in main and secondary based in the relative disc-calliper displacement; the finite element model is also used as well as in forced-response analysis. Brake pads are defined through the friction coefficient as a function of speed, pressure, and temperature, in light of which one may consider the various braking conditions and types of pad. Since the line of reasoning introduces equivalent-damping terms into the equations of dynamics, these equations cannot be uncoupled by means of modal transformation. Two techniques are proposed for the solution of the problem. One of these consists in an examination of the 'main-modes', while the other is based on direct integration of the quasi-uncoupled equations. A computer program has been implemented which allows the simulation of this kind of judder with different pads, brake systems and braking conditions.

R. Aviles; G. Hennequet; E. Amezua; J. Vallejo

1995-01-01T23:59:59.000Z

73

Disk Roughness and Defect Monitoring  

Science Journals Connector (OSTI)

Disk surface monitoring and certification refer to the testing and certification of a disk surface in terms of roughness and defect ... as well as the capability to accommodate a flying slider. It includes glide ...

Gang Sheng; Jizhong He; Shuanlin Duan

2013-01-01T23:59:59.000Z

74

Erasable digital audio disk system  

Science Journals Connector (OSTI)

Following the popularization of the compact disc, much attention has been paid to development of an erasable optical disk. A magnetooptical disk has proved the most useful in our...

Torazawa, Kenji; Sumi, Satoshi; Murata, Seiji; Minechika, Shigekazu; Ishii, Yasuhiro

1986-01-01T23:59:59.000Z

75

Flight characteristics of pen-reared and wild prairie-chickens and an evaluation of a greenhouse to rear prairie-chickens  

E-Print Network (OSTI)

FLIGHT CHARACTERISTICS OF PEN-REARED AND WILD PRAIRIE- CHICKENS AND AN EVALUATION OF A GREENHOUSE TO REAR PRAIRIE-CHICKENS A Thesis by MARC FREDERICK HESS Submitted to the Office of Graduate Studies of Texas A... AND AN EVALUATION OF A GREENHOUSE TO REAR PRAIRIE-CHICKENS A Thesis by MARC FREDERICK HESS Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved as to style and content by...

Hess, Marc Frederick

2004-09-30T23:59:59.000Z

76

Extremal black disks in QCD  

E-Print Network (OSTI)

We argue that in the high energy QCD a true black disk wave function necessarily contains many quarks. This corresponds to necessity of non-vacuum reggeon loops in formation of a black disk. The result comes from decomposition of the black disk S-matrix in characters on group manifold.

Alexey V. Popov

2008-05-12T23:59:59.000Z

77

Compliant mechanism road bicycle brake: a rigid-body replacement case study  

SciTech Connect

The design of high-performance bicycle brakes is complicated by the competing design objectives of increased performance and low weight. But this challenge also provides a good case study to demonstrate the design of compliant mechanisms to replace current rigid-link mechanisms. This paper briefly reviews current road brake designs, demonstrates the use of rigid-body replacement synthesis to design a compliant mechanism, and illustrates the combination of compliant mechanism design tools. The resulting concept was generated from the modified dual-pivot brake design and is a partially compliant mechanism where one pin has the dual role of a joint and a mounting pin. The pseudo-rigid-body model, finite element analysis, and optimization algorithms are used to generate design dimensions, and designs are considered for both titanium and E-glass flexures. The resulting design has the potential of reducing the part count and overall weight while maintaining a performance similar to the benchmark.

Olsen, Brian M [Los Alamos National Laboratory; Howell, Larry L [NON LANL; Magleby, Spencer P [NON LANL

2011-01-19T23:59:59.000Z

78

Genetic programming approach to predict torque and brake specific fuel consumption of a gasoline engine  

Science Journals Connector (OSTI)

This study presents genetic programming (GP) based model to predict the torque and brake specific fuel consumption a gasoline engine in terms of spark advance, throttle position and engine speed. The objective of this study is to develop an alternative robust formulations based on experimental data and to verify the use of GP for generating the formulations for gasoline engine torque and brake specific fuel consumption. Experimental studies were completed to obtain training and testing data. Of all 81 data sets, the training and testing sets consisted of randomly selected 63 and 18 sets, respectively. Considerable good performance was achieved in predicting gasoline engine torque and brake specific fuel consumption by using GP. The performance of accuracies of proposed GP models are quite satisfactory (R2=0.9878 for gasoline engine torque and R2=0.9744 for gasoline engine brake specific fuel consumption). The prediction of proposed GP models were compared to those of the neural network modeling, and strictly good agreement was observed between the two predictions. The proposed GP formulation is quite accurate, fast and practical.

Necla Togun; Sedat Baysec

2010-01-01T23:59:59.000Z

79

Real-Time Dynamic Brake Assessment Conduct a proof-of-concept  

E-Print Network (OSTI)

Real-Time Dynamic Brake Assessment Purpose Conduct a proof-of-concept test to examine the Federal Motor Carrier Safety Administration's Vehicle and Roadside Operations Division Concept stemming conducted for the National Highway Transportation Safety Administration. Signals to be collected Real

80

Dynamical Evolution of Protoplanetary Disks  

E-Print Network (OSTI)

This paper reviews the theory of protostellar debris disks. After a brief introduction to accretion disk physics, I describe coagulation models of planet formation in the outer regions of planetesimal disks. Coagulation models for the Kuiper Belt produce Pluto-sized objects on timescales of 10-40 Myr. These models yield size distributions which agree with observations of Kuiper Belt objects with red magnitudes, R = 20-27. Velocity stirring models for other debris disk systems demonstrate that 500 km or larger objects can stir the velocities of small objects up to the shattering limit needed to begin a collisional cascade.

Scott J. Kenyon

2000-10-02T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Reared microgastrine wasps (Hymenoptera: Braconidae) from Yanayacu Biological Station and environs (Napo Province,  

E-Print Network (OSTI)

(Napo Province, Ecuador): Diversity and host specialization James B. Whitfield, Josephine J. Rodriguez: Whitfield JB, Rodriguez JJ, Masonick PK. 2009. Reared microgastrine wasps (Hymenoptera: Braconidae) from

Whitfield, James B.

82

Mechanically versus electro-magnetically braked cycle ergometer: performance and energy cost of the Wingate Anaerobic Test  

Science Journals Connector (OSTI)

Performance and metabolic profiles of the Wingate Anaerobic Test (WAnT) were compared between a mechanically resisted (ME) and an electro-magnetically braked (EE) cycle ergometer. Fifteen healthy subjects (24....

D. Micklewright; A. Alkhatib; R. Beneke

2006-04-01T23:59:59.000Z

83

The effectiveness of using the calculated braking current for longitudinal differential protection of 110 - 750 kV shunt reactors  

SciTech Connect

The use of the function of effective current braking of the longitudinal differential protection of shunt reactors to offset current surges, which enables the sensitivity of differential protection to be increased when there are short circuits with low damage currents, is considered. It is shown that the use of the calculated braking characteristic enables the reliability of offset protection from transients to be increased when the reactor is connected, which is accompanied by the flow of asymmetric currents containing an aperiodic component.

Vdovin, S. A. [JSC 'E and E' (Russian Federation); Shalimov, A. S. [LLC Selekt Co. (Russian Federation)

2013-05-15T23:59:59.000Z

84

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

E-Print Network (OSTI)

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.

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

2014-10-23T23:59:59.000Z

85

Resonant relaxation in protoplanetary disks  

E-Print Network (OSTI)

Resonant relaxation is a novel form of two-body relaxation that arises in nearly Keplerian disks such as protoplanetary disks. Resonant relaxation does not affect the semimajor axes of the particles, but enhances relaxation of particle eccentricities and inclinations. The equilibrium state after resonant relaxation is a Rayleigh distribution, with the mean-square eccentricity and inclination inversely proportional to mass. The rate of resonant relaxation depends strongly on the precession rate of the disk. If the precession due to the disk's self-gravity is small compared to the total precession, then the relaxation is concentrated near the secular resonance between each pair of interacting bodies; on the other hand if the precession rate is dominated by the disk's self-gravity then relaxation occurs through coupling to the large-scale low-frequency m=1 normal modes of the disk. Depending on the disk properties, resonant relaxation may be either stronger or weaker than the usual non-resonant relaxation.

Scott Tremaine

1998-05-27T23:59:59.000Z

86

REAR-SIDE POINT-CONTACTS BY INLINE THERMAL EVAPORATION OF ALUMINUM Christoph Mader  

E-Print Network (OSTI)

REAR-SIDE POINT-CONTACTS BY INLINE THERMAL EVAPORATION OF ALUMINUM Christoph Mader 1 , Jens Müller of point-contacted aluminum rear-sides for silicon solar cells that are metalized by inline thermal evaporation. We deposit aluminum layers of 2 µm thickness at dynamic deposition rates of 1.0, 2.9 and 5.0 µm

87

Research Report Ganglion cell densities in normal and dark-reared turtle retinas  

E-Print Network (OSTI)

Research Report Ganglion cell densities in normal and dark-reared turtle retinas Eun-Jin Lee, David 2005 Abstract In dark-reared, neonatal turtle retinas, ganglion cell receptive fields and dendritic on densities and soma sizes of turtle retinal ganglion cells. For this purpose, we marked these cells using

Grzywacz, Norberto

88

THE BRAKING INDEX OF PSR J1734-3333 AND THE MAGNETAR POPULATION  

SciTech Connect

PSR J1734-3333 is a radio pulsar rotating with a period P = 1.17 s and slowing down with a period derivative P-dot =2.28x10{sup -12}, the third largest among rotation-powered pulsars. These properties are midway between those of normal rotation-powered pulsars and magnetars, two populations of neutron stars that are notably different in their emission properties. Here we report on the measurement of the second period derivative of the rotation of PSR J1734-3333 and calculate a braking index n = 0.9 {+-} 0.2. This value is well below 3, the value expected for an electromagnetic braking due to a constant magnetic dipole, and indicates that this pulsar may soon have the rotational properties of a magnetar. While there are several mechanisms that could lead to such a low braking index, we discuss this observation, together with the properties exhibited by some other high- P-dot rotation-powered pulsars, and interpret it as evidence of a possible evolutionary route for magnetars through a radio-pulsar phase, supporting a unified description of the two classes of the object.

Espinoza, C. M.; Lyne, A. G. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Kramer, M. [MPI fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Manchester, R. N. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Kaspi, V. M., E-mail: cme@jb.man.ac.uk [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada)

2011-11-01T23:59:59.000Z

89

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)

momentum in the industry [4]. These vehicles (BEVs and HEVS) use electric motor/generator pairs to propel themselves and to recapture braking energy (electric RBS) and the power source is the battery. The regenerative braking system uses a generator..., aerodynamic and road losses. 4. Improvised Transmission design to reduce losses. 5. Hybrid and Alternative Energy Propulsion systems e.g. the Hybrid Electric Vehicle (HEV), the Fuel Cell Vehicle (FCV). 6. Recycling Braking energy Storage and reuse...

Pochiraju, Anirudh

2012-08-31T23:59:59.000Z

90

Spinning disk for compressive imaging  

Science Journals Connector (OSTI)

We report the first, to the best of our knowledge, experimental implementation of a spinning-disk configuration for high-speed compressive image acquisition. A single rotating mask...

Shen, H; Gan, L; Newman, N; Dong, Y; Li, C; Huang, Y; Shen, Y C

2012-01-01T23:59:59.000Z

91

Application of Rarefied Gas Dynamics to the Head-Disk Interface in Hard Disk Drives  

E-Print Network (OSTI)

of a magnetic disk and a thermal flying height control (TFC)gration on the flying head slider at the head-disk interfaceThermal flying-height control sliders in hard disk drives

Liu, Nan

2010-01-01T23:59:59.000Z

92

Slow modes in Keplerian disks  

E-Print Network (OSTI)

Low-mass disks orbiting a massive body can support "slow" normal modes, in which the eigenfrequency is much less than the orbital frequency. Slow modes are lopsided, i.e., the azimuthal wavenumber m=1. We investigate the properties of slow modes, using softened self-gravity as a simple model for collective effects in the disk. We employ both the WKB approximation and numerical solutions of the linear eigenvalue equation. We find that all slow modes are stable. Discrete slow modes can be divided into two types, which we label g-modes and p-modes. The g-modes involve long leading and long trailing waves, have properties determined by the self-gravity of the disk, and are only present in narrow rings or in disks where the precession rate is dominated by an external potential. In contrast, the properties of p-modes are determined by the interplay of self-gravity and other collective effects. P-modes involve both long and short waves, and in the WKB approximation appear in degenerate leading/trailing pairs. Disks support a finite number---sometimes zero---of discrete slow modes, and a continuum of singular modes.

Scott Tremaine

2000-11-30T23:59:59.000Z

93

Dynamical Constraints on Disk Masses  

E-Print Network (OSTI)

While the total interior mass of a galaxy is reasonably well determined by a good rotation curve, the relative contributions from disk, bulge and halo are only weakly constrained by one-dimensional data. Barred galaxies are intrinsically more complicated, but provide much tighter constraints on the disk masses and support the idea that most of the mass in the inner parts of bright galaxies is in their stars. There appears to be no systematic difference in dark matter content between barred and unbarred galaxies, consistent with the theoretical result that the global stability of galaxies with dense centers does not depend on their halo fraction. The rotation curve shapes of lower luminosity and low-surface-brightness galaxies, on the other hand, indicate significant mass in the DM halo even near their centers. We find that most DM halos appear to have large cores, inconsistent with the predictions from cosmological simulations. We also show that such large-core halos can result from compression by disk infall of physically reasonable initial halos. Maximum disks, while apparently required by the data, do seem to present some puzzles; most notably they re-open the old disk-halo ``conspiracy'' issue and incorrectly predict that surface brightness should be a second parameter in the Tully-Fisher relation.

J. A. Sellwood

1999-03-11T23:59:59.000Z

94

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

SciTech Connect

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.

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

95

Head/disk interface tribology in the nanometer regime  

E-Print Network (OSTI)

contact between flying slider and disk becomes increasinglythe highest amplitude was observed when flying on disk 3 andthe lowest when flying on disk 1. The amplitudes for the

Xu, Jianfeng

2008-01-01T23:59:59.000Z

96

Thermo-mechanical characterization of nano filled and fiber reinforced brake friction materials  

Science Journals Connector (OSTI)

Brake friction materials filled with multiwalled carbon nanotubes (MWCNT) and nanoclay have been fabricated and characterize for thermo-mechanical properties. Thermo gravimetric analysis (TGA) show that the stability of the friction composites increased with increase in MWCNT and nanoclay contents. Dynamic mechanical analysis (DMA) of the composite have been carried out to characterize the storage modulus (E?) loss modulus (E?) and damping factor (Tan ?) as a function of temperature. The storage and loss modulus show a maxima at lower content of MWCNT and nanoclay.

2013-01-01T23:59:59.000Z

97

Design and manufacture of a rear driveline package including limited slip differential for Formula SAE applications  

E-Print Network (OSTI)

This document describes the design and manufacture of a lightweight rear driveline package for a Formula SAE race car. The design focuses on all components needed to transfer power from the chain driven Honda CBR600 F4i ...

Yazicioglu, Tolga T

2008-01-01T23:59:59.000Z

98

E-Print Network 3.0 - asian child-rearing attitudes Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Princeton University Collection: Biology and Medicine 13 The New Dad: I th ll b d fIs there really a new breed of Summary: Many Men Want an Equal Share of the Child-rearing...

99

A Review of Downdrafts at the Rear of Tropical Squall Lines  

Science Journals Connector (OSTI)

The observational evidence for the formation of downdrafts at the rear of tropical squall lines is reviewed. Some mechanisms, which have been proposed for the formation of such downdrafts, also are reviewed. Although the mechanisms are different, ...

Walter Fernandez

1982-11-01T23:59:59.000Z

100

E-Print Network 3.0 - adult rearing diet Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

55:153168 (2004) 2004 Wiley-Liss, Inc. Summary: . The one study employing natural diets (Smith, 1960) used plants reared from seed on media vary- ing... controlled conditions,...

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Highly Efficient Multi-crystalline Solar Cells Using Rear Surface Passivation Technology  

Science Journals Connector (OSTI)

Abstract In this work, we have successfully demonstrated the rear side passivation technology applied to multi-crystalline p-type wafers. The AlOx/SiNx stack was selected as rear side passivation layer combined with suitable laser opening source and metallization materials. The performance of multi-crystalline cell reached an efficiency level of 18%-19% applying this technology and the light induced degradation and module power output performance are attractive compared with current cell type.

Yan-Kai Chiou; Hung-Ming Lin; Kuang-Hui Hung; Cheng-Yu Ko; Chia-Hung Wu; Hsieng-Chen Yen; Shyuan-Fang Chen; Nai-Tien Ou; Walt K.W. Huang

2014-01-01T23:59:59.000Z

102

Fault detection and diagnosis within a wind turbine mechanical braking system using condition monitoring  

Science Journals Connector (OSTI)

Renewable energy sources have a key role to play in the global energy mix as a means of reducing the impact of energy production on climate change. Wind energy is the most developed of all renewable energy technologies with more than 200GW of globally installed capacity as of 2011. Analyses of wind farm maintenance costs show that up to 40% of the outlay is related to unexpected component failures that lead to costly unscheduled amendments. Wind farm operators are constantly looking for new technological developments in condition monitoring that can contribute to the minimisation of wind turbine maintenance expenditure. Early fault detection through condition monitoring can help prevent major breakdowns as well as significantly decrease associated costs. Moreover it enables the optimisation of maintenance schedules, reduces downtime, increases asset availability and enhances safety and operational reliability. Faults in the braking system are of particularly concern since they can result in catastrophic failure of the wind turbine. The present study investigates online condition monitoring based on voltages and currents for mechanical wind turbine brake system fault diagnosis.

M. Entezami; S. Hillmansen; P. Weston; M.Ph. Papaelias

2012-01-01T23:59:59.000Z

103

Rotational evolution of the Crab pulsar in the wind braking model  

E-Print Network (OSTI)

The pulsar wind model is updated by considering the effect of particle density and pulsar death. It can describe both the short term and long term rotational evolution of pulsars consistently. It is applied to model the rotational evolution of the Crab pulsar. The pulsar is spun down by a combination of magnetic dipole radiation and particle wind. The parameters of the Crab pulsar, including magnetic field, inclination angle, and particle density are calculated. The particle density in acceleration region is about 10^3 times the Goldreich-Julian charge density. The lower braking index between glitches is due to a larger particle density. This may be glitch induced magnetospheric activities in normal pulsars. Evolution of braking index and the Crab pulsar in P-Pdot diagram are calculated. The Crab pulsar will evolve from magnetic dipole radiation dominated case towards particle wind dominated case. Considering the effect of pulsar "death", the Crab pulsar (and other normal pulsars) will not evolve to the clust...

Kou, F F

2015-01-01T23:59:59.000Z

104

2. Disks and the Buffer Cache 2-1 Part 2: Disks and Caching  

E-Print Network (OSTI)

2. Disks and the Buffer Cache 2-1 Part 2: Disks and Caching References: · Elmasri Implementierung. · Mark Gurry, Peter Corrigan: Oracle Performance Tuning, 2nd Edition (with disk). · Oracle 8i.com/] · Wikipedia (RAID systems): [http://en.wikipedia.org/wiki/Redundant Array of Independent Disks] · The PC Guide

Brass, Stefan

105

Effect of thermal pole tip protrusion and disk roughness on slider disk contacts  

Science Journals Connector (OSTI)

Ultra-high areal density for hard disk drives requires a stable head disk interface at a flying height lower than 8nm. At such a low flying height, small flying height variations may cause slider/disk contacts. Slider/disk contacts can also occur ...

Jianfeng Xu; James D. Kiely; Yiao-Tee Hsia; Frank E. Talke

2009-03-01T23:59:59.000Z

106

Detecting Accretion Disks in Active Galactic Nuclei  

Science Journals Connector (OSTI)

......black hole with an accretion disk was produced by Luminet (1979...how the BH and the accretion disk are seen by an observer who is flying near the hole. Images of the...temperature of the gas in the disk. We have extended the above......

Claudio Fanton; Massimo Calvani; Fernando de Felice; Andrej Cadez

1997-04-01T23:59:59.000Z

107

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

E-Print Network (OSTI)

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 ...

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

2010-01-01T23:59:59.000Z

108

Enhanced quantum efficiency of amorphous silicon thin film solar cells with the inclusion of a rear-reflector thin film  

SciTech Connect

We investigated the growth mechanism of amorphous silicon thin films by implementing hot-wire chemical vapor deposition and fabricated thin film solar cell devices. The fabricated cells showed efficiencies of 7.5 and 8.6% for the samples without and with the rear-reflector decomposed by sputtering, respectively. The rear-reflector enhances the quantum efficiency in the infrared spectral region from 550 to 750?nm. The more stable quantum efficiency of the sample with the inclusion of a rear-reflector than the sample without the rear-reflector due to the bias effect is related to the enhancement of the short circuit current.

Park, Seungil [Department of Mechanical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Energy Conversions Technology Center, Korea Institute of Industrial Technology, Cheonan 331-825 (Korea, Republic of); Yong Ji, Hyung; Jun Kim, Myeong; Hyeon Peck, Jong [Energy Conversions Technology Center, Korea Institute of Industrial Technology, Cheonan 331-825 (Korea, Republic of); Kim, Keunjoo, E-mail: kimk@chonbuk.ac.kr [Department of Mechanical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

2014-02-17T23:59:59.000Z

109

Accretion Disks and Eruptive Phenomena  

E-Print Network (OSTI)

This paper describes eruptive phenomena in pre-main sequence stars. The eruptions of FU Orionis stars have much in common with outbursts in other accreting systems, such as dwarf novae and some symbiotic stars. These common features are best understood as increases in the rate material flows through an accretion disk. The spectroscopic properties, decay of the light curves, and outflow phenomena suggest that these outbursts arise from thermal instabilities in the disk. Available data and estimates for recurrence times indicate that young stars can accrete much, perhaps all, of their mass in FU Ori accretion events. Future observations can test this notion and place better constraints on the importance of eruptive events in the early life of a low mass star.

Scott J. Kenyon

1999-04-05T23:59:59.000Z

110

Axisymmetric bending oscillations of stellar disks  

E-Print Network (OSTI)

Self-gravitating stellar disks with random motion support both exponentially growing and, in some cases, purely oscillatory axisymmetric bending modes, unlike their cold disk counterparts. A razor-thin disk with even a very small degree of random motion in the plane is both unstable and possesses a discrete spectrum of neutral modes, irrespective of the sharpness of the edge. Random motion normal to the disk plane has a stabilizing effect but at the same time allows bending waves to couple to the internal vibrations of the particles, which causes the formerly neutral modes to decay through Landau damping. Focusing first on instabilities, I here determine the degree of random motion normal to the plane needed to suppress global, axisymmetric, bending instabilities in a family of self-gravitating disks. As found previously, bending instabilities are suppressed only when the thickness exceeds that expected from a na\\"\\i ve local criterion when the degree of pressure support within the disk plane is comparable to, or exceeds, the support from rotation. A modest disk thickness is adequate for the bending stability of most disk galaxies, except perhaps near their centers. The discretization of the neutral spectrum in a zero-thickness disk is due to the existence of a turning point for bending waves in a warm disk, which is absent when the disk is cold. When the disk is given a finite thickness, the discrete neutral modes generally become strongly damped through wave-particle interactions. It is surprising therefore that I find some simulations of warm, stable disks can support (quasi-)neutral, large-scale, bending modes that decay very slowly, if at all.

J A Sellwood

1996-04-21T23:59:59.000Z

111

Industrial high performance crystalline silicon solar cells and modules based on rear surface passivation technology  

Science Journals Connector (OSTI)

Abstract Stimulated by the extreme market conditions, the increase in performance and the reduction of manufacturing costs of standard crystalline silicon solar cells and modules have been quite significant in the last years. This progress was achieved mainly by process and material improvements avoiding additional process complexity. As todays cells are predominantly limited by optical and recombination losses at the rear surface, dielectric rear surface passivation represents an obvious approach to overcome the limitations. In recent years several concepts have been developed to implement dielectric rear side passivation into industrial-scale mass production. In this paper a short review is given about the evolution of dielectric rear side passivation technologies as well as on state-of-the-art cell and module results. Simple and cost effective cell and module designs utilizing standard as well as innovative manufacturing technologies are presented. Furthermore, it is shown that for all major steps multiple process options are available to further reduce the manufacturing costs. Using an optimized emitter and screen-printed metallization on commercially available 156mm156mm p-type Czochralski-grown crystalline silicon wafers best cell efficiencies of 19.9% without dielectric rear surface passivation and 21.0% with dielectric rear surface passivation are demonstrated. Replacing the screen-printed front contacts by electroplated nickelcopper contacts record efficiencies of up to 21.3% are reached. By optimizing the module design and materials to reduce the resistive and optical losses, a peak module power of up to 306W and 19.5% aperture area efficiency are achieved.

Axel Metz; Dennis Adler; Stefan Bagus; Henry Blanke; Michael Bothar; Eva Brouwer; Stefan Dauwe; Katharina Dressler; Raimund Droessler; Tobias Droste; Markus Fiedler; Yvonne Gassenbauer; Thorsten Grahl; Norman Hermert; Wojtek Kuzminski; Agata Lachowicz; Thomas Lauinger; Norbert Lenck; Mihail Manole; Marcel Martini; Rudi Messmer; Christine Meyer; Jens Moschner; Klaus Ramspeck; Peter Roth; Ruben Schnfelder; Berthold Schum; Jrg Sticksel; Knut Vaas; Michael Volk; Klaus Wangemann

2014-01-01T23:59:59.000Z

112

E-Print Network 3.0 - accretion disk contamination Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

+ accretion disk. Left panel: Disks of various accretion, inner... disk hole, and inclination properties. ... Source: Hillenbrand, Lynne - Astronomy Department, California...

113

E-Print Network 3.0 - accretion disk size Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

+ accretion disk. Left panel: Disks of various accretion, inner... disk hole, and inclination properties. ... Source: Hillenbrand, Lynne - Astronomy Department, California...

114

Sterrewacht Gas evolution in protoplanetary disks  

E-Print Network (OSTI)

Sterrewacht Leiden Gas evolution in protoplanetary disks W.F. Thi , E.F. van Dishoeck , G are surrounded by 10 ­10 M of gas+dust in disks with sizes of 100­400 AU. This material may form extrasolar planets. 3 Disks have also been imaged around Vega-like stars, but are thought to be gas­poor with "!#$ M

Zadelhoff, Gerd-Jan van

115

To brake or to accelerate? Safety effects of combined speed and red light cameras  

Science Journals Connector (OSTI)

AbstractIntroduction The present study evaluates the traffic safety effect of combined speed and red light cameras at 253 signalized intersections in Flanders, Belgium that were installed between 2002 and 2007. Method The adopted approach is a before-and-after study with control for the trend. Results The analyses showed a non-significant increase of 5% in the number of injury crashes. An almost significant decrease of 14% was found for the more severe crashes. The number of rear-end crashes turned out to have increased significantly (+44%), whereas a non-significant decrease (?6%) was found in the number of side crashes. The decrease for the severe crashes was mainly attributable to the effect on side crashes, for which a significant decrease of 24% was found. Practical Applications It is concluded that combined speed and red light cameras have a favorable effect on traffic safety, in particular on severe crashes. However, future research should examine the circumstances of rear-end crashes and how this increase can be managed.

Ellen De Pauw; Stijn Daniels; Tom Brijs; Elke Hermans; Geert Wets

2014-01-01T23:59:59.000Z

116

HEATING AND COOLING PROTOSTELLAR DISKS  

SciTech Connect

We examine heating and cooling in protostellar disks using three-dimensional radiation-MHD calculations of a patch of the Solar nebula at 1 AU, employing the shearing-box and flux-limited radiation diffusion approximations. The disk atmosphere is ionized by stellar X-rays, well coupled to magnetic fields, and sustains a turbulent accretion flow driven by magnetorotational instability, while the interior is resistive and magnetically dead. The turbulent layers are heated by absorbing the light from the central star and by dissipating the magnetic fields. They are optically thin to their own radiation and cool inefficiently. The optically thick interior in contrast is heated only weakly, by re-emission from the atmosphere. The interior is colder than a classical viscous model and isothermal. The magnetic fields support an extended atmosphere that absorbs the starlight 1.5 times higher than the hydrostatic viscous model. The disk thickness thus measures not the internal temperature, but the magnetic field strength. Fluctuations in the fields move the starlight-absorbing surface up and down. The height ranges between 13% and 24% of the radius over timescales of several orbits, with implications for infrared variability. The fields are buoyant, so the accretion heating occurs higher in the atmosphere than the stresses. The heating is localized around current sheets, caused by magnetorotational instability at lower elevations and by Parker instability at higher elevations. Gas in the sheets is heated above the stellar irradiation temperature, even though accretion is much less than irradiation power when volume averaged. The hot optically thin current sheets might be detectable through their line emission.

Hirose, S. [Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showamachi, Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan); Turner, N. J., E-mail: shirose@jamstec.go.jp, E-mail: neal.turner@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2011-05-10T23:59:59.000Z

117

Dynamical Evolution of Disk Galaxies  

E-Print Network (OSTI)

Spiral patterns are important agents of galaxy evolution. In this review, I describe how the redistribution of angular momentum by recurrent transient spiral patterns causes the random speeds of stars to rise over time, metallicity gradients to be reduced, and drives large-scale turbulence in the disk, which could be important for galactic dynamos. I also outline a possible mechanism for the recurrence of spiral instabilities and supporting evidence from solar neighborhood kinematics. Finally, I confirm that cloud scattering alone would predict the local velocity ellipsoid to be flattened, contrary to long-held expectations.

J. A. Sellwood

2008-03-11T23:59:59.000Z

118

Author's personal copy What can the braking indices tell us about the nature of pulsars?  

E-Print Network (OSTI)

additional torques by particle outflow or accretion disk, changes in inclination angle or magnetic field's personal copy pole radiation and relativistic particle flow/wind (Dar, 1999; Allen and Horvath, 2000; Xu and Qiao, 2001; Wu et al., 2003; Contopoulos et al., 2006), the models with changing inclination angles (e

Xu, Ren-Xin

119

Research Report Long lasting effects of rearing by an ethanol-consuming dam  

E-Print Network (OSTI)

Research Report Long lasting effects of rearing by an ethanol-consuming dam on voluntary ethanol rats as subjects, we examined effects of exposure during weaning to a dam consuming ethanol on adolescents' later affinity for ethanol. In a preliminary experiment, we offered rat pups a choice between 8

Galef Jr., Bennett G.

120

Toto the Robot Figure 1. Toto, front view. Figure 2. Toto, rear view.  

E-Print Network (OSTI)

Toto the Robot Figure 1. Toto, front view. Figure 2. Toto, rear view. Toto the Robot was created so in the back to allow the tape- recorder to be held inside, and the figure was spray-painted. With his metallic a robot, helps account for his lack of verbal charm. Second, some younger children may recognize in Toto

Indiana University

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

The effects of early rearing environment on the hormonal induction of maternal behavior in virgin rats  

E-Print Network (OSTI)

rats Marko Novakov, Alison S. Fleming* Psychology Department, University of Toronto at Mississauaga rearing paradigm (AR), on the hormonal induction of maternal behavior (MB) in female Sprague�Dawley rats. Between postnatal days (PND) 4 and 18, rat pups were raised either with their mothers (MR) or artificially

Sokolowski, Marla

122

COBE's Galactic Bar and Disk  

E-Print Network (OSTI)

A model of the bar and old stellar disk of the Galaxy has been derived from the survey of the Diffuse Infrared Background Experiment (DIRBE) of the Cosmic Background Explorer at wavelengths of 1.25, 2.2, 3.5, and 4.9 microns. It agrees very well with the data, except in directions in which the near- infrared optical depth is high. Among the conclusions drawn from the model: The Sun is located approximately 16.5 pc above the midpoint of the Galactic plane. The disk has an outer edge four kpc from the Sun, and is warped like the HI layer. It has a central hole roughly the diameter of the inner edge of the "three-kiloparsec" molecular cloud ring, and within that hole lies a bright, strong, "early-type" bar, tilted approximately 14 degrees from the Sun-Galactic center line. The model has 47 free parameters. The model is discussed in detail and contour plots and images of the residuals presented.

H. T. Freudenreich

1997-08-04T23:59:59.000Z

123

Numerical and experimental investigations of the head/disk interface  

E-Print Network (OSTI)

The E?ects of Disk Morphology on Flying-Height Modulation:5 NM Flying Height Air Bearing Sliders in Hard Disk Drives.5 NM Flying Height Air Bearing Sliders in Hard Disk Drives.

Duwensee, Maik

2007-01-01T23:59:59.000Z

124

ROM Type Holographic Disk Using Computer Generated Hologram  

Science Journals Connector (OSTI)

Holographic ROM disk that can be made by the optical disk cutting method was studied. CGH was recorded on the master disk. The simulation showed that multiplex recoding became...

Yoshida, Shuhei; Sano, Takumi; Yamamoto, Manabu; Nakajima, Masahiro; Kobayashi, Toshihiro

125

VISCOSITY IN ACCRETION DISKS PAUL J. WIITA  

E-Print Network (OSTI)

VISCOSITY IN ACCRETION DISKS PAUL J. WIITA Department of Physics & Astronomy, Georgia State University Atlanta, Georgia, USA Abstract. Various proposals and prescriptions for the viscosity in accretion a solution to this difficult problem. 1. Introduction The nature of the viscosity within accretion disks

Wiita, Paul J.

126

A MODEL OF MAGNETIC BRAKING OF SOLAR ROTATION THAT SATISFIES OBSERVATIONAL CONSTRAINTS  

SciTech Connect

The model of magnetic braking of solar rotation considered by Charbonneau and MacGregor has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic with the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method.

Denissenkov, Pavel A., E-mail: pavel.denisenkov@gmail.co [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, B.C., V8W 3P6 (Canada)

2010-08-10T23:59:59.000Z

127

Double-Disk Dark Matter  

Science Journals Connector (OSTI)

Abstract Based on observational tests of large scale structure and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant components interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy (depending on precise alignment) can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.

JiJi Fan; Andrey Katz; Lisa Randall; Matthew Reece

2013-01-01T23:59:59.000Z

128

Molecular Hydrogen Emission from Protoplanetary Disks  

E-Print Network (OSTI)

We have modeled self-consistently the density and temperature profiles of gas and dust in protoplanetary disks, taking into account irradiation from a central star. Making use of this physical structure, we have calculated the level populations of molecular hydrogen and the line emission from the disks. As a result, we can reproduce the observed strong line spectra of molecular hydrogen from protoplanetary disks, both in the ultraviolet (UV) and the near-infrared, but only if the central star has a strong UV excess radiation.

H. Nomura; T. J. Millar

2005-05-06T23:59:59.000Z

129

Effect of rearing and laying house environments on performance of incross egg production type pullets  

E-Print Network (OSTI)

'ts ~ ~ ~ ~ ~ ~ ~ ~ e e ~ e ~ ~ ~ ~ ~ ~ ~ ~ F 10 Experimental design of rearing treatments of incross pullets ~ o ~ ~ a ~ ~ a ~ ~ e ~ ~ e ~ ~ ~ ~ ~ ~ F 11 Experimental design of the laying phase of incross pullets. . . e e . . . . . . . . . . . . . . . . . , . 12 IV...' colony cage. . . 34 Egg production of birds from the different laying managements ~ ~ ~ ~ ~ ~ ~ o o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 36 Statistical analysi. s of egg product1on of birds from the d1ffsrsnt lay1ng managements . ~ . . ~ . ~ ~ ~ ~ F 37 Average...

Shupe, William Dale

2012-06-07T23:59:59.000Z

130

Resolving Molecular Line Emission from Protoplanetary Disks: Observational Prospects for Disks Irradiated by Infalling Envelopes  

E-Print Network (OSTI)

Molecular line observations that could resolve protoplanetary disks of ~100 AU both spatially and kinematically would be a useful tool to unambiguously identify these disks and to determine their kinematical and physical characteristics. In this work we model the expected line emission from a protoplanetary disk irradiated by an infalling envelope, addressing the question of its detectability with subarcsecond resolution. We adopt a previously determined disk model structure that gives a continuum spectral energy distribution and a mm intensity spatial distribution that are consistent with observational constraints of HL Tau. An analysis of the capability of presently working and projected interferometers at mm and submm wavelengths shows that molecular transitions of moderate opacity at these wavelengths (e.g., C17O lines) are good candidates for detecting disk lines at subarcsecond resolution in the near future. We suggest that, in general, disks of typical Class I sources will be detectable.

Jose F. Gomez; Paola D'Alessio

1999-12-02T23:59:59.000Z

131

Resolving Molecular Line Emission from Protoplanetary Disks Observational Prospects for Disks Irradiated by Infalling Envelopes  

E-Print Network (OSTI)

Molecular line observations that could resolve protoplanetary disks of ~100 AU both spatially and kinematically would be a useful tool to unambiguously identify these disks and to determine their kinematical and physical characteristics. In this work we model the expected line emission from a protoplanetary disk irradiated by an infalling envelope, addressing the question of its detectability with subarcsecond resolution. We adopt a previously determined disk model structure that gives a continuum spectral energy distribution and a mm intensity spatial distribution that are consistent with observational constraints of HL Tau. An analysis of the capability of presently working and projected interferometers at mm and submm wavelengths shows that molecular transitions of moderate opacity at these wavelengths (e.g., C17O lines) are good candidates for detecting disk lines at subarcsecond resolution in the near future. We suggest that, in general, disks of typical Class I sources will be detectable.

Gomes, J F; Gomez, Jose F.; Alessio, Paola D'

1999-01-01T23:59:59.000Z

132

Carbon isotope fractionation in protoplanetary disks  

E-Print Network (OSTI)

We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of protoplanetary disks. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12C/13C, of the system varies with radius and height in the disk. Different behaviour is seen in the fractionation of different species. We compare our results with 12C/13C ratios in the Solar System comets, and find a stark contrast, indicative of reprocessing.

Paul M. Woods; Karen Willacy

2008-12-01T23:59:59.000Z

133

Heat Transfer from a Rotating Disk  

Science Journals Connector (OSTI)

...August 1956 research-article Heat Transfer from a Rotating Disk E. C. Cobb...little has been published on the heat transfer. For laminar conditions theoretical...experimental investigation of the heat transfer for a range of conditions from...

1956-01-01T23:59:59.000Z

134

Final Environmental Assessment - Idaho Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Idaho Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon Final Environmental Assessment DOE/EA-1301 October 2000 Idaho Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon Final Environmental Assessment - Need and Purpose for Action Bonneville Power Administration i Contents 1. NEED AND PURPOSE FOR ACTION ..................................................................................1 1.1. Introduction ........................................................................................................................1 1.2. Need for Action ...................................................................................................................1 1.3. Purposes (Decision Factors)...............................................................................................2

135

The Debris Disk Explorer: a balloon-borne coronagraph for observing debris disks  

E-Print Network (OSTI)

The Debris Disk Explorer (DDX) is a proposed balloon-borne investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. DDX will measure the size, shape, brightness, and color of tens of disks. These measurements will enable us to place the Solar System in context. By imaging debris disks around nearby stars, DDX will reveal the presence of perturbing planets via their influence on disk structure, and explore the physics and history of debris disks by characterizing the size and composition of disk dust. The DDX instrument is a 0.75-m diameter off-axis telescope and a coronagraph carried by a stratospheric balloon. DDX will take high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Two flights are planned; an overnight test flight within the United States followed by a month-long science flight launched from New Zealand. The long flight will fully explore the set of known de...

Roberts, Lewis C; Traub, Wesley; Unwin, Stephen; Trauger, John; Krist, John; Aldrich, Jack; Brugarolas, Paul; Stapelfeldt, Karl; Wyatt, Mark; Stuchlik, David; Lanzi, James

2013-01-01T23:59:59.000Z

136

Hadron collisions at ultrahigh energies: black disk or resonant disk modes?  

E-Print Network (OSTI)

The analysis of current ultrahigh energy data for hadronic total cross sections and diffractive scattering cross sections points to a steady growth of the optical density with energy for elastic scattering amplitudes in the impact parameter space, $b$. At LHC energy the profile function of the $pp$-scattering amplitude, $T(b)$, reaches the black disk limit at small $b$. Two scenarios are possible at larger energies, $\\sqrt{s}\\ga 100$ TeV. First, the profile function gets frozen in the black disk limit, $T(b)\\simeq 1$ while the radius of the black disk $R_{black\\;disk}$ is increasing with $\\sqrt s$, providing $\\sigma_{tot}\\sim \\ln^2s$, $\\sigma_{el}\\sim \\ln^2s$, $\\sigma_{inel}\\sim \\ln^2s$. In another scenario the profile function continues to grow at $\\sqrt{s}\\ga 100$ TeV approaching the maximal value, $T(b)\\simeq 2$, that means the resonant disk mode. We discuss features of the resonant disk mode when the disk radius, $R_{resonant\\;disk}\\,$, increases providing the growth of the total and elastic cross sections $\\sigma_{tot}\\sim \\ln^2s$, $\\sigma_{el}\\sim \\ln^2s$, but a more slow increase of inelastic cross section, $\\sigma_{inel}\\sim \\ln s$.

V. V. Anisovich; V. A. Nikonov; J. Nyiri

2014-08-11T23:59:59.000Z

137

The Galactic thick and thin disks: differences in evolution  

E-Print Network (OSTI)

Recent observations demonstrate that the thin and thick disks of the Galaxy have different chemical abundance trends and evolution timescales. The relative abundances of $\\alpha$-elements in the thick Galactic disk are increased relative to the thin disk. Our goal is to investigate the cause of such differences in thick and thin disk abundances. We investigate the chemical evolution of the Galactic disk in the framework of the open two-zone model with gas inflow. The Galactic abundance trends for $\\alpha$-elements (Mg, Si, O) and Fe are predicted for the thin and thick Galactic disks. The star formation histories of the thin and thick disks must have been different and the gas infall must have been more intense during the thick disk evolution that the thin disk evolution.

T. V. Nykytyuk; T. V. Mishenina

2006-05-26T23:59:59.000Z

138

E-Print Network 3.0 - accretion disk rim Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

Summary: that the matter accreting through the disk is deflected along the magnetic field lines (of stellar andor disk... ): (A) the dust thermal emission from the disk inner...

139

E-Print Network 3.0 - accretion disk signatures Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

wind to disk accretion rates, the viscosity in the disk... Accretion Disk Evolution with Wind Infall II. Results of 3D Hydrodynamical Simulations... how the evolution and...

140

Flying height calibration with bump disk  

Science Journals Connector (OSTI)

It is a big challenge to determine ultralow slider Flying Height (FH) accurately. The standard bump disk method is probably a reliable and acceptable method. The accuracy of the bump disk method on FH calibration depends on two key factors. One is the detection of the occurrence of slider??bump contact. The other is the understanding of the complicated slider??bump interaction process and the possible disturbance of the bumps on the slider flying performance. In this paper, the research work aiming to resolve these two key issues is reviewed. Key parameters that limit the accuracy of the bump disk method are discussed. Possible strategies to further improve the accuracy of the method are proposed.

Yansheng Ma; Bo Liu

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Vehicle System Dynamics, Vol. 26, No.4, October 1996, pp.301-320. Traction/Braking Force Distribution for Optimal Longitudinal  

E-Print Network (OSTI)

as the desired level of vehicle yaw motion, and the control system was designed to follow the yaw motion commandVehicle System Dynamics, Vol. 26, No.4, October 1996, pp.301-320. Traction/Braking Force in the past twenty years through the use of electronic devices. Four-wheel-steering (4WS) systems have been

Peng, Huei

142

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)

. The main components of the model include an electric motor, hydraulic pump, hydraulic motor and two 1 flow during regenerative braking Electric Motor: Provides rotational energy to the hydraulic drivetrain (% kinetic energy recovered) 24.73% Drivetrain Efficiency 67.02% Overall Efficiency 53.47% Current Electric

Carpick, Robert W.

143

Nanosecond cryogenic Yb:YAG disk laser  

Science Journals Connector (OSTI)

A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ~108.

E A Perevezentsev; I B Mukhin; I I Kuznetsov; O L Vadimova; O V Palashov

2014-01-01T23:59:59.000Z

144

Disk Mass from Large-scale Dynamics  

E-Print Network (OSTI)

The radial distribution of mass in a disk galaxy is strongly constrained by its rotation curve. The separate contributions from the individual stellar populations and dark matter (DM) are not easily disentangled, however, especially since there is generally no feature to indicate where the component dominating the central attraction switches from luminous to dark matter. Here I summarize three recent thesis projects at Rutgers University which all suggest that DM has a low density in the inner parts of bright galaxies, and that most of the mass therefore resides in the disk. In addition, I present some preliminary work on the Milky Way.

J A Sellwood

1997-11-27T23:59:59.000Z

145

Heat Transfer from an Air-Cooled Rotating Disk  

Science Journals Connector (OSTI)

19 February 1974 research-article Heat Transfer from an Air-Cooled Rotating Disk J. M. Owen C...theoretical and experimental investigation into the heat transfer from a disk rotating close to a stator with a radial...

1974-01-01T23:59:59.000Z

146

Observation of Slider Landing Process in Hard Disk Drive  

Science Journals Connector (OSTI)

With the decrease in slider flying height, slider flying instability caused by sliderdisk interactions is becoming a big concern. Novel ... employed to further improve our understandings about sliderdisk intera...

Y. S. Ma; B. Liu

2005-10-01T23:59:59.000Z

147

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

SciTech Connect

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.

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

1995-11-01T23:59:59.000Z

148

Final Environmental Assessment - Idaho Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Department of Fish and Game Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon Finding of No Significant Impact October 2000 DEPARTMENT OF ENERGY Bonneville Power Administration Idaho Department of Fish and Game Captive Rearing Initiative for Salmon River Chinook Salmon Finding of No Significant Impact Summary: Bonneville Power Administration (BPA), Department of Energy (DOE), is proposing to fund the Idaho Department of Fish and Game (IDFG) Captive Rearing Initiative for Salmon River Chinook Salmon Program (IDFG Program). The IDFG Program is a small-scale research and production initiative designed to increase numbers of three weak but recoverable populations of spring/summer chinook salmon in the Salmon River drainage. This would increase numbers of spring/summer chinook salmon within the Snake River

149

UNVEILING THE STRUCTURE OF PRE-TRANSITIONAL DISKS  

SciTech Connect

In the past few years, several disks with inner holes that are relatively empty of small dust grains have been detected and are known as transitional disks. Recently, Spitzer has identified a new class of 'pre-transitional disks' with gaps based on near-infrared photometry and mid-infrared spectra; these objects have an optically thick inner disk separated from an optically thick outer disk by an optically thin disk gap. A near-infrared spectrum provided the first confirmation of a gap in the pre-transitional disk of LkCa 15 by verifying that the near-infrared excess emission in this object was due to an optically thick inner disk. Here, we investigate the difference between the nature of the inner regions of transitional and pre-transitional disks using the same veiling-based technique to extract the near-infrared excess emission above the stellar photosphere. However, in this work we use detailed disk models to fit the excess continua as opposed to the simple blackbody fits previously used. We show that the near-infrared excess emission of the previously identified pre-transitional disks of LkCa 15 and UX Tau A in the Taurus cloud as well as the newly identified pre-transitional disk of ROX 44 in Ophiuchus can be fit with an inner disk wall located at the dust destruction radius. We also present detailed modeling of the broadband spectral energy distributions of these objects, taking into account the effect of shadowing by the inner disk on the outer disk, but considering the finite size of the star, unlike other recent treatments. The near-infrared excess continua of these three pre-transitional disks, which can be explained by optically thick inner disks, are significantly different from that of the transitional disks of GM Aur, whose near-infrared excess continuum can be reproduced by emission from sub-micron-sized optically thin dust, and DM Tau, whose near-infrared spectrum is consistent with a disk hole that is relatively free of small dust. The structure of pre-transitional disks may be a sign of young planets forming in these disks and future studies of pre-transitional disks will provide constraints to aid in theoretical modeling of planet formation.

Espaillat, C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); D'Alessio, P. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Morelia, Michoacan, Mexico 58089 (Mexico); Hernandez, J. [Centro de Investigaciones de Astronomia (CIDA), Merida, 5101-A (Venezuela, Bolivarian Republic of); Nagel, E. [Departamento de Astronomia, Universidad de Guanajuato, Guanajuato, Gto, Mexico 36240 (Mexico); Luhman, K. L. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Watson, D. M. [Department of Physics and Astronomy, University of Rochester, NY 14627-0171 (United States); Calvet, N.; McClure, M. [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Muzerolle, J., E-mail: cespaillat@cfa.harvard.ed, E-mail: p.dalessio@crya.unam.m, E-mail: jesush@cida.v, E-mail: erick@astro.ugto.m, E-mail: kluhman@astro.psu.ed, E-mail: dmw@pas.rochester.ed, E-mail: ncalvet@umich.ed, E-mail: melisma@umich.ed, E-mail: muzerol@stsci.ed [Space Telescope Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-07-01T23:59:59.000Z

150

Thickness Change in Molecularly Thin Lubricant Under Flying Head in Hard Disk Drives  

Science Journals Connector (OSTI)

In hard disk drives (HDDs), lubricants on disks are very important material to reduce head and disk wear. Thus, it is necessary to ... thickness to keep lubricant thickness constant on rotating disks. For this pu...

K. Yanagisawa; T. Watanabe; Y. Kawakubo; M. Yoshino

2010-10-01T23:59:59.000Z

151

Colour and lipid oxidation changes in dry-cured loins from free-range reared and intensively reared pigs as affected by ionizing radiation dose level  

Science Journals Connector (OSTI)

The effect of irradiation (0, 5 and 10 kGy) of vacuum-packaged Iberian dry-cured loin slices from pigs fed on concentrate (CON) or free-range reared (FRG) was studied in relation to colour changes, TBA-RS and hexanal content. Both, ionizing radiation and type of loin had a significant effect on the instrumental colour parameters of the samples. Irradiation resulted in significantly higher a*-values in both sets of loins, indicating a redder colour. Numerically calculated total colour difference (?E) changes were significantly less intense in CON vacuum-packaged dry-cured loin slices than in FRG samples and changed significantly at 10 kGy dose levels in both types of samples. TBA-RS numbers were significantly affected by irradiation dose and type of loin and increased linearly with dose in both types of slices. Increments in TBA-RS numbers in FRG loin slices was dose-dependent and was closely related to the type of dry-cured loin. Irradiation of dry-cured loin slices significantly increased hexanal contents in both groups of loins and the increases were dose-dependent and greater in FRG samples than in CON samples. Differences in the characteristics of the raw material and initial lipid oxidation level could play an important role in the irradiation-induced changes in vacuum-packaged dry-cured loin slices.

A. Carrasco; R. Trrega; M.R. Ramrez; F.J. Mingoarranz; R. Cava

2005-01-01T23:59:59.000Z

152

MPEG-aware disk storage system  

E-Print Network (OSTI)

In the past decades the demand for systems that can process and deliver massive amount of storage has increased. Multimedia applications such as streaming audio and video require large amounts of data to be read from disk and processed for timely...

Ren, Qian

2000-01-01T23:59:59.000Z

153

DUST-DRIVEN WIND FROM DISK GALAXIES  

SciTech Connect

We study gaseous outflows from disk galaxies driven by radiation pressure on dust grains. We include the effect of bulge and dark matter halo and show that the existence of such an outflow implies a maximum value of disk mass-to-light ratio. We show that the terminal wind speed is proportional to the disk rotation speed in the limit of a cold gaseous outflow, and that in general there is a contribution from the gas sound speed. Using the mean opacity of dust grains and the evolution of the luminosity of a simple stellar population, we then show that the ratio of the wind terminal speed (v{sub {infinity}}) to the galaxy rotation speed (v{sub c}) ranges between 2 and 3 for a period of {approx}10 Myr after a burst of star formation, after which it rapidly decays. This result is independent of any free parameter and depends only on the luminosity of the stellar population and the relation between disk and dark matter halo parameters. We briefly discuss the possible implications of our results.

Sharma, Mahavir; Nath, Biman B. [Raman Research Institute, Sadashiva Nagar, Bangalore 560080 (India); Shchekinov, Yuri, E-mail: mahavir@rri.res.in, E-mail: biman@rri.res.in, E-mail: yus@sfedu.ru [Department of Physics, Southern Federal University, Rostov on Don 344090 (Russian Federation)

2011-08-01T23:59:59.000Z

154

Geodesic Disks and Clustering in a Simple Magdalene G. Borgelt  

E-Print Network (OSTI)

Geodesic Disks and Clustering in a Simple Polygon Magdalene G. Borgelt Marc van Kreveld Jun Luo.cs.uu.nl ISSN: 0924-3275 #12;Geodesic Disks and Clustering in a Simple Polygon Magdalene G. Borgelt European points lying in the interior of P. A geodesic disk GD(p, r) with center p and radius r is the set

Utrecht, Universiteit

155

Automated Design, Analysis, and Optimization of Turbomachinery Disks  

E-Print Network (OSTI)

Automated Design, Analysis, and Optimization of Turbomachinery Disks A thesis submitted of Cincinnati June 2008 Committee Chair: Dr. Mark G. Turner #12;#12;ABSTRACT Turbomachinery disks are used weight. Proper design and optimization of turbomachinery disks is an important topic that could yield

Cincinnati, University of

156

Computer Architecture Disk-based storage in computers  

E-Print Network (OSTI)

over any track! The read/write head! is attached to the end! of the arm and flies over! the disk198:211 Computer Architecture Topics: System I/O Buses #12;Disk-based storage in computers Memory Hierarchy registers! on-chip L1! cache (SRAM)! main memory! (DRAM)! local secondary storage! (local disks

Badrinath, B. R.

157

Dynamics simulation of MEMS device embedded hard disk drive systems  

Science Journals Connector (OSTI)

Currently, hard disk drives (HDD) use rotating disks to store digital data and magnetic recording heads are flying on the disk to read/write data. The recording heads are mounted on a slidersuspension assembly, which makes heads move from one ...

J. P. Yang; J. Chai; Y. Lu

2004-01-01T23:59:59.000Z

158

On the Solar System-Debris Disk Connecction  

E-Print Network (OSTI)

This paper emphasizes the connection between solar and extra-solar debris disks: how models and observations of the Solar System are helping us understand the debris disk phenomenon, and vice versa, how debris disks are helping us place our Solar System into context.

Amaya Moro-Martin

2007-12-14T23:59:59.000Z

159

Data Reconstruction from a Hard Disk Drive using Magnetic Force Microscopy  

E-Print Network (OSTI)

flying over the magnetization pattern written on the disk,disks be free of even microscopic particles, since the flying

Kanekal, Vasu

160

Photoevaporation of protostellar disks III. The appearance of photoevaporating disks around young intermediate mass stars  

E-Print Network (OSTI)

We present theoretical continuum emission spectra (SED's), isophotal maps and line profiles for several models of photoevaporating disks at different orientations with respect to the observer. The hydrodynamic evolution of these models has been the topic of the two previous papers of this series. We discuss in detail the numerical scheme used for these diagnostic radiation transfer calculations. Our results are qualitatively compared to observed ultracompact Hii-regions (UCHii's). Our conclusion is that the high fraction of ``unresolved'' UCHii's from the catalogues of Wood & Churchwell (1989) and Kurtz et al. (1994) cannot be explained by disks around massive stars. In particular, the observed infrared spectra of these objects indicate dust temperatures which are about one order of magnitude lower than expected. We suggest that disks around close companions to OB stars may be necessary to resolve this inconsistency. Alternatively, strong stellar winds and radiative acceleration could remove disk material from the immediate vicinity of luminous O stars, whereas for the lower luminosity sources considered here this will not occur. We also find that line profiles tracing the evaporated material originating from the disk are not influenced significantly by the existence of stellar winds over a wide range of wind velocities (400 - 1000 km/s). We compare our results to the bright IRAS source MWC349A. Many of its properties, especially its spatial appearance in high-resolution radio maps, can be well explained by a disk surrounding a UV luminous star with a high velocity stellar wind.

Olaf Kessel; Harold W. Yorke; Sabine Richling

1998-06-16T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Why Disks Shine: the Transport of Angular Momentum in Hot, Thin Disks  

E-Print Network (OSTI)

I review recent work on the radial transport of angular momentum in ionized, Keplerian accretion disks. Proposed mechanisms include hydrodynamic and MHD local instabilities and long range effects mediated by wave transport. The most promising models incorporate the Velikhov-Chandrasekhar instability, caused by an instability of the magnetic field embedded in a differentially rotating disk. This has the important feature that the induced turbulent motions necessarily transport angular momentum outward. By contrast, convective modes may transport angular momentum in either direction. Combining the magnetic field instability with an $\\alpha-\\Omega$ dynamo driven by internal waves leads to a model in which the dimensionless viscosity scales as $(H/r)^{4/3}$. However, this model has a phenomenology which is quite different from the $\\alpha$ disk model. For example, an active disk implies some source of excitation for the internal waves. In binary systems with a mass ratio of order unity the most likely exciting mechanism is a parametric instability due to tidal forces. This implies that in systems where the accretion stream is intermittent, like MV Lyrae or TT Ari, epochs when the mass flow is absent or very small will be epochs in which the disk shrinks and becomes relatively inactive and dark. This model also implies that forced vertical mixing is important, even in convectively stable disks. I discuss various observational tests of this model and the focus of current theoretical work.

E. T. Vishniac

1993-09-28T23:59:59.000Z

162

Head wear reduction in future hard-disk drives  

Science Journals Connector (OSTI)

Head wear and head vibration due to head-disk contact are two main issues that must be resolved for the future high-density Hard Disk Drives (HDDs). To reduce head wear, disk lubricant, carbon overcoat films on head and disk surfaces, head flying characteristics and so on have been studied. In this paper, we first show the effects of several parameters on head wear, including lubricant types, their MW, and disk burnishing. Our recent results on the effects of humidity and temperature on head wear are also explained. We then explain our extended wear equation and estimate the head wear life with present technologies.

Youichi Kawakubo; Shinnichi Nakazawa; Shinnichi Kobatake

2008-01-01T23:59:59.000Z

163

The First Detailed Look at a Brown Dwarf Disk  

E-Print Network (OSTI)

The combination of mid-infrared and recent submm/mm measurements allows us to set up the first comprehensive spectral energy distribution (SED) of the circumstellar material around a young Brown Dwarf. Simple arguments suggest that the dust is distributed in the form of a disk. We compare basic models to explore the disk parameters. The modeling shows that a flat disk geometry fits well the observations. A flared disk explains the SED only if it has a puffed-up inner rim and an inner gap much larger than the dust sublimation radius. Similarities and differences with disks around T Tauri stars are discussed.

I. Pascucci; D. Apai; Th. Henning; C. P. Dullemond

2003-05-12T23:59:59.000Z

164

Response to IRSP. Project ID 35027: Evaluation of Two Captive Rearing Methods for Assisting with Recovery of Naturally Spawning  

E-Print Network (OSTI)

general procedures cited by Paul Moran and Robin Waples (P.I's.) under Project No. 198909600. The USFWSResponse to IRSP. Project ID 35027: Evaluation of Two Captive Rearing Methods for Assisting. We will store the fin clips at room temperature prior to DNA extraction. Procedures for DNA

165

Safety First Safety Last Safety Always Accessible areas within the swing radius of the rear of the  

E-Print Network (OSTI)

Safety First Safety Last Safety Always Accessible areas within the swing radius of the rear is permissible to meet the OSHA barricade requirement. Crane Swing Radius Safety Tip #12 Better to be dead sure on the reverse side of this safety tip sheet. Please refrain from reading the information verbatim

Minnesota, University of

166

EXPONENTIAL GALAXY DISKS FROM STELLAR SCATTERING  

SciTech Connect

Stellar scattering off of orbiting or transient clumps is shown to lead to the formation of exponential profiles in both surface density and velocity dispersion in a two-dimensional non-self gravitating stellar disk with a fixed halo potential. The exponential forms for both nearly flat rotation curves and near-solid-body rotation curves. The exponential does not depend on initial conditions, spiral arms, bars, viscosity, star formation, or strong shear. After a rapid initial development, the exponential saturates to an approximately fixed scale length. The inner exponential in a two-component profile has a break radius comparable to the initial disk radius; the outer exponential is primarily scattered stars.

Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)] [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Struck, Curtis, E-mail: bge@watson.ibm.com, E-mail: curt@iastate.edu [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)] [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

2013-10-01T23:59:59.000Z

167

Alfvenic Heating of Protostellar Accretion Disks  

E-Print Network (OSTI)

We investigate the effects of heating generated by damping of Alfven waves on protostellar accretion disks. Two mechanisms of damping are investigated, nonlinear and turbulent, which were previously studied in stellar winds (Jatenco-Pereira & Opher 1989a, b). For the nominal values studied, f=delta v/v_{A}=0.002 and F=varpi/Omega_{i}=0.1, where delta v, v_{A} and varpi are the amplitude, velocity and average frequency of the Alfven wave, respectively, and Omega_{i} is the ion cyclotron frequency, we find that viscous heating is more important than Alfven heating for small radii. When the radius is greater than 0.5 AU, Alfvenic heating is more important than viscous heating. Thus, even for the relatively small value of f=0.002, Alfvenic heating can be an important source of energy for ionizing protostellar disks, enabling angular momentum transport to occur by the Balbus-Hawley instability.

M. J. Vasconcelos; V. Jatenco-Pereira; R. Opher

1999-12-22T23:59:59.000Z

168

Gray disks in perturbative Reggeon calculus  

Science Journals Connector (OSTI)

We discuss the connection between the opacity of a gray disk and its diffraction-dissociation cross section in the multichannel eikonal model which is formulated in such a way as to take account of continuum intermediate states of the projectile. The model is equivalent to Reggeon calculated to a finite order in the triple-Pomeron coupling and where the bare-Pomeron intercept exceeds unity.

G. A. Winbow

1977-07-15T23:59:59.000Z

169

CO gas inside the protoplanetary disk cavity in HD 142527: disk structure from ALMA  

E-Print Network (OSTI)

Inner cavities and annular gaps in circumstellar disks are possible signposts of giant planet formation. The young star HD 142527 hosts a massive protoplanetary disk with a large cavity that extends up to 140 au from the central star, as seen in continuum images at infrared and millimeter wavelengths. Estimates of the survival of gas inside disk cavities are needed to discriminate between clearing scenarios. We present a spatially and spectrally resolved carbon monoxide isotopologue observations of the gas-rich disk HD 142527, in the J=2-1 line of 12CO, 13CO and C18O, obtained with the Atacama Large Millimeter Array (ALMA). We detect emission coming from inside the dust-depleted cavity in all three isotopologues. Based on our analysis of the gas in the dust cavity, the 12CO emission is optically thick, while 13CO and C18O emission are both optically thin. The total mass of residual gas inside the cavity is about 1.5-2 Jupiter masses. We model the gas with an axisymmetric disk model. Our best fit model shows t...

Perez, Sebastian; Mnard, F; Roman, P; van der Plas, G; Cieza, L; Pinte, C; Christiaens, V; Hales, A S

2014-01-01T23:59:59.000Z

170

Composite polymer: Glass edge cladding for laser disks  

DOE Patents (OSTI)

Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation. 18 figs.

Powell, H.T.; Wolfe, C.A.; Campbell, J.H.; Murray, J.E.; Riley, M.O.; Lyon, R.E.; Jessop, E.S.

1987-11-02T23:59:59.000Z

171

Composite polymer-glass edge cladding for laser disks  

DOE Patents (OSTI)

Large neodymium glass laser disks for disk amplifiers such as those used in the Nova laser require an edge cladding which absorbs at 1 micrometer. This cladding prevents edge reflections from causing parasitic oscillations which would otherwise deplete the gain. Nova now utilizes volume-absorbing monolithic-glass claddings which are fused at high temperature to the disks. These perform quite well but are expensive to produce. Absorbing glass strips are adhesively bonded to the edges of polygonal disks using a bonding agent whose index of refraction matches that of both the laser and absorbing glass. Optical finishing occurs after the strips are attached. Laser disks constructed with such claddings have shown identical gain performance to the previous Nova disks and have been tested for hundreds of shots without significant degradation.

Powell, Howard T. (Livermore, CA); Riley, Michael O. (San Ramon, CA); Wolfe, Charles R. (Palo Alto, CA); Lyon, Richard E. (Livermore, CA); Campbell, John H. (Livermore, CA); Jessop, Edward S. (Tracy, CA); Murray, James E. (Livermore, CA)

1989-01-01T23:59:59.000Z

172

MOLECULAR DISK PROPERTIES IN EARLY-TYPE GALAXIES  

SciTech Connect

We study the simulated CO emission from elliptical galaxies formed in the mergers of gas-rich disk galaxies. The cold gas not consumed in the merger-driven starburst quickly resettles into a disk-like configuration. By analyzing a variety of arbitrary merger orbits that produce a range of fast- to slow-rotating remnants, we find that molecular disk formation is a fairly common consequence of gas-rich galaxy mergers. Hence, if a molecular disk is observed in an early-type merger remnant, it is likely the result of a 'wet merger' rather than a 'dry merger'. We compare the physical properties from our simulated disks (e.g., size and mass) and find reasonably good agreement with recent observations. Finally, we discuss the detectability of these disks as an aid to future observations.

Xu, X.; Walker, C. [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Narayanan, D., E-mail: xxu@as.arizona.ed [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS 51, Cambridge, MA 02138 (United States)

2010-10-01T23:59:59.000Z

173

Study of ring and ring-disk electrodes  

SciTech Connect

Rotating ring and ring-disk electrodes were modeled. The primary, secondary, and below-the-limiting current distributions for ring electrodes were computed. The ring-disk system was modeled for secondary and below-the-limiting current distributions. Mass transfer measurements in laminar, transition, and turbulent flows were made for thin rotating rings. The effect of cell walls on the potential distribution of disk electrodes was computed.

Pierini, P.E.

1981-05-01T23:59:59.000Z

174

High average power scaleable thin-disk laser  

DOE Patents (OSTI)

Using a thin disk laser gain element with an undoped cap layer enables the scaling of lasers to extremely high average output power values. Ordinarily, the power scaling of such thin disk lasers is limited by the deleterious effects of amplified spontaneous emission. By using an undoped cap layer diffusion bonded to the thin disk, the onset of amplified spontaneous emission does not occur as readily as if no cap layer is used, and much larger transverse thin disks can be effectively used as laser gain elements. This invention can be used as a high average power laser for material processing applications as well as for weapon and air defense applications.

Beach, Raymond J. (Livermore, CA); Honea, Eric C. (Sunol, CA); Bibeau, Camille (Dublin, CA); Payne, Stephen A. (Castro Valley, CA); Powell, Howard (Livermore, CA); Krupke, William F. (Pleasanton, CA); Sutton, Steven B. (Manteca, CA)

2002-01-01T23:59:59.000Z

175

Computer disk with personal information of Department of Energy...  

NLE Websites -- All DOE Office Websites (Extended Search)

Computer disk with personal information of Department of Energy's Idaho site employees lost in transit The Department of Energy's Office of Health, Safety and Security has been...

176

TIDAL DISRUPTION FLARES: THE ACCRETION DISK PHASE  

SciTech Connect

The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically hydrodynamic equations. The present investigation aims to study the dependence of resulting light curves on dynamical and physical properties of such a transient disk during its existence. One of the main results derived from our simulations is that blackbody fits of X-ray data tend to overestimate the true mean disk temperature. In fact, the temperature derived from blackbody fits should be identified with the color X-ray temperature rather than the average value derived from the true temperature distribution along the disk. The time interval between the beginning of the circularization of the bound debris and the beginning of the accretion process by the black hole is determined by the viscous (or accretion) timescale, which also fixes the rising part of the resulting light curve. The luminosity peak coincides with the beginning of matter accretion by the black hole and the late evolution of the light curve depends on the evolution of the debris fallback rate. Peak bolometric luminosities are in the range 10{sup 45}-10{sup 46} erg s{sup -1}, whereas peak luminosities in soft X-rays (0.2-2.0 keV) are typically one order of magnitude lower. The typical timescale derived from our preferred models for the flare luminosity to decay by two orders of magnitude is about 3-4 yr. Predicted soft X-ray light curves reproduce quite well data on galaxies in which a variable X-ray emission possibly related to a tidal event was detected. In the cases of NGC 3599 and IC 3599, data are reproduced well by models defined by a black hole with mass {approx}10{sup 7} M{sub sun} and a disrupted star of about 1 solar mass. The X-ray variation observed in XMMSL1 is consistent with a model defined by a black hole with mass {approx}3 x 10{sup 6} M{sub sun} and a disrupted star of 1 solar mass, while that observed in the galaxy situated in the cluster A1689 is consistent with a model including a black hole of {approx}10{sup 7} M{sub sun} and a disrupted star of {approx}0.5 M{sub sun}.

Montesinos Armijo, Matias; De Freitas Pacheco, Jose A. [Observatoire de la Cote d'Azur, Laboratoire Cassiopee, Universite de Nice Sophia-Antipolis Bd de l'Observatoire, BP 4229, 06304 Nice Cedex 4 (France)

2011-08-01T23:59:59.000Z

177

Investigations of the cause of fishkills in fish-rearing facilities in Raven Fork watershed  

SciTech Connect

An investigation was undertaken to determine the cause of fishkills in trout-rearing facilities located adjacent to Raven Fork Creek within the Cherokee Indian Reservation in North Carolina. Approximately 50,000 rainbow trout were lost at the Blankenship trout farm-a commercial facility-following eight storm events between March 31 and December 2, 1981. In addition, 524 trophy-size trout died in three ponds operated by the Cherokee tribe for stocking reservation streams. It was found fishkills in the trout farm could be prevented by adding lime to water from the creek as it was pumped into the facility; this strengthened the assumption acidity (H/sup +/) was responsible for the fishkills. Mortality of trophy trout was stopped by routing water from nearby springs to the ponds during and following rain events. Because of concern that these fishkills might be caused by acid rain, TVA was requested by the Cherokee tribe to assist in determining the cause. Limited studies were conducted during March through August 1982 to test two hypotheses: (1) concentrations of H/sup +/ and soluble aluminum in Raven Fork following storm events were high enough to kill rainbow trout and (2) atmospheric deposition was a greater source of stream H/sup +/ than acid-producing geologic formations or the forest soils.

Jones, H.C.; Noggle, J.C.; Young, R.C.; Kelly, J.M.; Olem, H.; Ruane, R.J.; Pasch, R.W.; Hyfantis, G.J.; Parkhurst, W.J.

1983-04-01T23:59:59.000Z

178

Feasibility study 100 K East Area water purification pools fish-rearing program  

SciTech Connect

As part of the feasibility study, a design analysis was conducted to determine the usefulness of the existing sand filters and associated media for reuse. The sand filters which were studied for potential reuse are located on the northern end of the 100-K East Area water filtration plant on the Hanford Site. This plant is located about one- half mile from the Columbia River. The sand filters were originally part of a system which was used to provide cooling water to the nearby plutonium production K Reactors. This Cold War operation took place until 1971, at which time the K Reactors were closed for eventual decontamination and decommissioning. Recently, it was decided to study the concept of putting the sand filter structures back into use for fish-rearing purposes. Because the water that circulated through the water purification pools (K Pools) and associated sand filters was clean river water, there is little chance of the structures being radioactively contaminated. To date, separate K Pools have been used for raising a variety of cold water fish species, including white sturgeon and fall chinook salmon, as well as for providing potable water to the 100 K Area of the Hanford Site for fire and service water purposes.

Betsch, M.D., Westinghouse Hanford

1996-07-03T23:59:59.000Z

179

ICE LINES IN CIRCUMBINARY PROTOPLANETARY DISKS  

SciTech Connect

I examine the position of the ice line in circumbinary disks heated by steady mass accretion and stellar irradiation and compare with the critical semimajor axis, interior to which planetary orbits are unstable. There is a critical binary separation, dependent on the binary parameters and disk properties, for which binaries with separations larger than this critical value have ice lines that lie interior to the boundary of stability. For an equal-mass binary comprised of 1 M{sub Sun} components, this critical separation is Almost-Equal-To 1.04 AU, and scales weakly with mass accretion rate and Rosseland mean opacity ({proportional_to}[ M-dot {kappa}{sub R}]{sup 2/9}). Assuming a steady mass accretion rate of M-dot {approx}10{sup -8} M{sub Sun} yr{sup -1} and a Rosseland mean opacity of {kappa}{sub R} {approx} 1 cm{sup 2} g{sup -1}, I show that {approx}> 80% of all binary systems with component masses M{sub *} {approx}< 2.0 M{sub Sun} have ice lines that lie interior to the critical semimajor axis. This suggests that rocky planets should not form in these systems, a prediction which can be tested by looking for planets around binaries with separations larger than the critical separation with Kepler (difficult) and with microlensing.

Clanton, Christian, E-mail: clanton@astronomy.ohio-state.edu [Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States)

2013-05-01T23:59:59.000Z

180

Nano-scale positioning, control and motion planning in hard disk drives  

E-Print Network (OSTI)

Dynamic flying height adjustment in hard disk drives throughprocessing for flying height control in hard disk drives . .for sub-3- nm flying height head-disk systems. Journal of

Boettcher, Uwe

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Dynamics and Stability of Thermal Flying-height Control Sliders in Hard Disk Drives  

E-Print Network (OSTI)

in ultra-low flying head-disk interfaces," Tribologyinto the gap between the flying head and disk, and they candifferent ways when flying over disks of different roughness

Zheng, Jinglin

2012-01-01T23:59:59.000Z

182

Properties of carbon overcoats and perfluoro-polyether lubricants in hard disk drives  

E-Print Network (OSTI)

stable head-disk interface at ultralow flying height," IEEElow flying sliders during contact with a lubricated disk,"for stable flying of the slider over the disk [16], [17].

Brunner, Ralf

2009-01-01T23:59:59.000Z

183

Numerical Investigation of Operational Shocks and Vibrations in Mobile Hard Disk Drives  

E-Print Network (OSTI)

Suspension Load Disk RPM Nominal Flying Height Pitch Rollwrite head and the disk is known as flying height of thefor a slider flying on top of the disk will be a negative

Rai, Rahul

2011-01-01T23:59:59.000Z

184

Effects of diffusion on lubricant distribution under flying headon thin-film disks  

Science Journals Connector (OSTI)

Lubricants on thin-film disks have large effects on headdisk interface characteristics. They reduce head and disk wear while thick lubricant film increases friction ... in many cases. Lubricant depletion due to

K. Yanagisawa; Y. Kawakubo; M. Yoshino

2005-01-01T23:59:59.000Z

185

E-Print Network 3.0 - accretion disk properties Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

23 CONSTRAINTS ON ACCRETION DISK LIFETIMES Summary: accretion, inner disk hole, and inclination properties. Compared to the non-accreting no-hole pole-on disk... of various...

186

E-Print Network 3.0 - astrophysical disk models Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

accretion disk models. The Astrophysical... disk material to the outer disk is the X-wind model (Shu et al. 1996). The notion that young stars... of material transported to...

187

CAPTURE OF PLANETESIMALS BY GAS DRAG FROM CIRCUMPLANETARY DISKS  

SciTech Connect

Growing giant planets have circumplanetary disks around them in the late stage of their formation if their mass is sufficiently large. We examine capture of relatively large planetesimals that are decoupled from the gas inflow, due to gas drag from a circumplanetary disk of a growing giant planet. Assuming that the structure of the circumplanetary disk is axisymmetric, and solving the three-body problem including gas drag, we perform analytic and numerical calculations for capture of planetesimals. When planetesimal random velocity is small, planetesimals approaching in the retrograde direction are more easily captured, owing to their larger velocity relative to the gas. Planetesimals with large orbital inclinations interact with the disk for a short period of time and show lower capture rates. The effect of ablation on capture rates seems insignificant, although mass loss due to ablation would be significant in the case of high random velocity. We also examine the effect of non-uniform radial distribution of planetesimals in the protoplanetary disk due to gap opening by the planet. When the random velocity of planetesimals is small, the planetesimal capture rate decreases rapidly as the half width of the gap in the planetesimal disk increases from two planetary Hill radii to three planetary Hill radii; planetesimals with low random velocities cannot approach the planet in the case of a sufficiently wide gap. Our results show that the radial distribution and random velocity of planetesimals in the protoplanetary disk are essentially important for the understanding of capture of planetesimals by circumplanetary disks.

Fujita, Tetsuya; Ohtsuki, Keiji; Suetsugu, Ryo [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Tanigawa, Takayuki [Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 (Japan)

2013-12-01T23:59:59.000Z

188

A Normal Stellar Disk in the Galaxy Malin 1  

E-Print Network (OSTI)

Since its discovery, Malin 1 has been considered the prototype and most extreme example of the class of giant low surface brightness disk galaxies. Examination of an archival Hubble Space Telescope I-band image reveals that Malin 1 contains a normal stellar disk that was not previously recognized, having a central I-band surface brightness of mu_0 = 20.1 mag arcsec^-2 and a scale length of 4.8 kpc. Out to a radius of ~10 kpc, the structure of Malin 1 is that of a typical SB0/a galaxy. The remarkably extended, faint outer structure detected out to r~100 kpc appears to be a photometrically distinct component and not a simple extension of the inner disk. In terms of its disk scale length and central surface brightness, Malin 1 was originally found to be a very remote outlier relative to all other known disk galaxies. The presence of a disk of normal size and surface brightness in Malin 1 suggests that such extreme outliers in disk properties probably do not exist, but underscores the importance of the extended outer disk regions for a full understanding of the structure and formation of spiral galaxies.

A. J. Barth

2006-12-31T23:59:59.000Z

189

Managing hard-disk PCs in the introductory laboratory  

Science Journals Connector (OSTI)

A method is described for managing stand-alone hard-disk PCs, in an environment in which students are allowed to explore the hard disk. The system, application, and student-created files are safeguarded by management software which helps eliminate "accidental" ...

David K. Walker; David S. Tucker

1991-11-01T23:59:59.000Z

190

The gas temperature in circumstellar disks: effects of dust settling  

E-Print Network (OSTI)

The gas temperature in circumstellar disks: effects of dust settling F. Faas, G.J. van Zadelhoff, E distributions. The disk gas-temperature (T ¢¡¢£ ) is in general assumed to be equal to the dust-temperature (T¤¦¥ £ § ), due to collisions. Dust settling depends on both the gas and dust temperature. T

Zadelhoff, Gerd-Jan van

191

An Eccentric Disk Model for the Nucleus of M31  

E-Print Network (OSTI)

The nucleus of M31 may be a thick eccentric disk, composed of stars traveling on nearly Keplerian orbits around a black hole or other dark compact object. This hypothesis reproduces most of the features seen in HST photometry of the center of M31; in particular the bright off-center source P1 is the apoapsis of the disk. An eccentric disk can also explain the rotation curve and asymmetric dispersion profile revealed by ground-based observations. The central object must be smaller than 1 pc so that the potential felt by the disk is nearly Keplerian. The disk eccentricity may be excited by a secular instability driven by dynamical friction from the bulge.

Scott Tremaine

1995-02-13T23:59:59.000Z

192

PROTOPLANETARY DISK STRUCTURE WITH GRAIN EVOLUTION: THE ANDES MODEL  

SciTech Connect

We present a self-consistent model of a protoplanetary disk: 'ANDES' ('AccretioN disk with Dust Evolution and Sedimentation'). ANDES is based on a flexible and extendable modular structure that includes (1) a 1+1D frequency-dependent continuum radiative transfer module, (2) a module to calculate the chemical evolution using an extended gas-grain network with UV/X-ray-driven processes and surface reactions, (3) a module to calculate the gas thermal energy balance, and (4) a 1+1D module that simulates dust grain evolution. For the first time, grain evolution and time-dependent molecular chemistry are included in a protoplanetary disk model. We find that grain growth and sedimentation of large grains onto the disk midplane lead to a dust-depleted atmosphere. Consequently, dust and gas temperatures become higher in the inner disk (R {approx}< 50 AU) and lower in the outer disk (R {approx}> 50 AU), in comparison with the disk model with pristine dust. The response of disk chemical structure to the dust growth and sedimentation is twofold. First, due to higher transparency a partly UV-shielded molecular layer is shifted closer to the dense midplane. Second, the presence of big grains in the disk midplane delays the freeze-out of volatile gas-phase species such as CO there, while in adjacent upper layers the depletion is still effective. Molecular concentrations and thus column densities of many species are enhanced in the disk model with dust evolution, e.g., CO{sub 2}, NH{sub 2}CN, HNO, H{sub 2}O, HCOOH, HCN, and CO. We also show that time-dependent chemistry is important for a proper description of gas thermal balance.

Akimkin, V.; Wiebe, D.; Pavlyuchenkov, Ya. [Institute of Astronomy of the RAS, Pyatnitskaya str. 48, Moscow (Russian Federation)] [Institute of Astronomy of the RAS, Pyatnitskaya str. 48, Moscow (Russian Federation); Zhukovska, S.; Semenov, D.; Henning, Th. [Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)] [Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Vasyunin, A. [Department of Chemistry, The University of Virginia, VA (United States)] [Department of Chemistry, The University of Virginia, VA (United States); Birnstiel, T., E-mail: akimkin@inasan.ru, E-mail: dwiebe@inasan.ru, E-mail: pavyar@inasan.ru, E-mail: zhukovska@mpia.de, E-mail: semenov@mpia.de, E-mail: henning@mpia.de, E-mail: anton.vasyunin@gmail.com, E-mail: tbirnstiel@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-03-20T23:59:59.000Z

193

PAH chemistry and IR emission from circumstellar disks  

E-Print Network (OSTI)

Aims. The chemistry of, and infrared (IR) emission from, polycyclic aromatic hydrocarbons (PAHs) in disks around Herbig Ae/Be and T Tauri stars are investigated. The equilibrium distribution of the PAHs over all accessible charge/hydrogenation states depends on the size and shape of the PAHs and on the physical properties of the star and surrounding disk. Methods. A chemistry model is created to calculate this equilibrium distribution. Destruction of PAHs by ultraviolet (UV) photons, possibly in multi-photon absorption events, is taken into account. The chemistry model is coupled to a radiative transfer code to provide the physical parameters and to combine the PAH emission with the spectral energy distribution (SED) from the star+disk system. Results. Normally hydrogenated PAHs in Herbig Ae/Be disks account for most of the observed PAH emission, with neutral and positively ionized species contributing in roughly equal amounts. Close to the midplane, the PAHs are more strongly hydrogenated and negatively ionized, but these species do not contribute to the overall emission because of the low UV/optical flux deep inside the disk. PAHs of 50 carbon atoms are destroyed out to 100 AU in the disk's surface layer, and the resulting spatial extent of the emission does not agree well with observations. Rather, PAHs of about 100 carbon atoms or more are predicted to cause most of the observed emission. The emission is extended on a scale similar to that of the size of the disk. Furthermore, the emission from T Tauri disks is much weaker and concentrated more towards the central star than that from Herbig Ae/Be disks. Positively ionized PAHs are predicted to be largely absent in T Tauri disks because of the weaker radiation field.

R. Visser; V. C. Geers; C. P. Dullemond; J. -C. Augereau; K. M. Pontoppidan; E. F. van Dishoeck

2007-01-22T23:59:59.000Z

194

MHD Stellar and Disk Winds: Application to Planetary Nebulae  

E-Print Network (OSTI)

MHD winds can emanate from both stars and surrounding accretion disks. It is of interest to know how much wind power is available and which (if either) of the two rotators dominates that power. We investigate this in the context of multi-polar planetary nebulae (PNe) and proto-planetary nebulae (PPNe), for which recent observations have revealed the need for a wind power source in excess of that available from radiation driving, and a possible need for magnetic shaping. We calculate the MHD wind power from a coupled disk and star, where the former results from binary disruption. The resulting wind powers depend only on the accretion rate and stellar properties. We find that if the stellar envelope were initially slowly rotating, the disk wind would dominate throughout the evolution. If the envelope of the star were rapidly rotating, the stellar wind could initially be of comparable power to the disk wind until the stellar wind carries away the star's angular momentum. Since an initially rapidly rotating star can have its spin and magnetic axes misaligned to the disk, multi-polar outflows can result from this disk wind system. For times greater than a spin-down time, the post-AGB stellar wind is slaved to the disk for both slow and rapid initial spin cases and the disk wind luminosity dominates. We find a reasonably large parameter space where a hybrid star+disk MHD driven wind is plausible and where both or either can account for PPNe and PNe powers. We also speculate on the morphologies which may emerge from the coupled system. The coupled winds might help explain the shapes of a number of remarkable multi-shell or multi-polar nebulae. Magnetic activity such as X-ray flares may be associated with the both central star and the disk and would be a valuable diagnostic for the dynamical role of MHD processes in PNe.

Eric G. Blackman; Adam Frank; Carl Welch

2000-05-12T23:59:59.000Z

195

E-Print Network 3.0 - accretion disk flows Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

39 Manuel Gdel Switzerland Summary: II Diagnoses Different Regions Rkm.com.au disk wind, photoevap. flow jet accretion columns 12;END 12;... - stellar? (Taurus) Disk...

196

E-Print Network 3.0 - accretion disks crystalline Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

(MIT) Collection: Physics 87 SPECTRAL ENERGY DISTRIBUTIONS OF PASSIVE T TAURI DISKS: INCLINATION Summary: --- stars: pre- main sequence --- accretion, accretion disks ---...

197

DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI  

SciTech Connect

The truncation of an optically thick, geometrically thin accretion disk is investigated in the context of low-luminosity AGNs (LLAGNs). We generalize the disk evaporation model used in the interpretative framework of black hole X-ray binaries by including the effect of a magnetic field in accretion disks surrounding supermassive black holes. The critical transition mass accretion rate for which the disk is truncated is found to be insensitive to magnetic effects, but its inclusion leads to a smaller truncation radius in comparison to a model without its consideration. That is, a thin viscous disk is truncated for LLAGNs at an Eddington ratio less than 0.03 for a standard viscosity parameter ({alpha} = 0.3). An increase of the viscosity parameter results in a higher critical transition mass accretion rate and a correspondingly smaller truncation distance, the latter accentuated by greater magnetic energy densities in the disk. Based on these results, the truncation radii inferred from spectral fits of LLAGNs published in the literature are consistent with the disk evaporation model. The infrared emission arising from the truncated geometrically thin accretion disks may be responsible for the red bump seen in such LLAGNs.

Taam, Ronald E. [Academia Sinica Institute of Astronomy and Astrophysics-TIARA, P.O. Box 23-141, Taipei 10617, Taiwan (China); Liu, B. F.; Yuan, W.; Qiao, E., E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China)

2012-11-01T23:59:59.000Z

198

Planetesimal Capture in the Disk Instability Model  

E-Print Network (OSTI)

We follow the contraction and evolution of a typical Jupiter-mass clump created by the disk instability mechanism, and compute the rate of planetesimal capture during this evolution. We show that such a clump has a slow contraction phase lasting ~3x10^5 years. By following the trajectories of planetesimals as they pass through the envelope of the protoplanet, we compute the cross-section for planetesimal capture at all stages of the protoplanet's evolution. We show that the protoplanet can capture a large fraction of the solid material in its feeding zone, which will lead to an enrichment of the protoplanet in heavy elements. The exact amount of this enrichment depends upon, but is not very sensitive to the size and random speed of the planetesimals.

Ravit Helled; Morris Podolak; Attay Kovetz

2006-06-29T23:59:59.000Z

199

The Cosmic Battery in Astrophysical Accretion Disks  

E-Print Network (OSTI)

The aberrated radiation pressure at the inner edge of the accretion disk around an astrophysical black hole imparts a relative azimuthal velocity on the electrons with respect to the ions which gives rise to a ring electric current that generates large scale poloidal magnetic field loops. This is the Cosmic Battery established by Contopoulos and Kazanas in 1998. In the present work we perform realistic numerical simulations of this important astrophysical mechanism in advection-dominated accretion flows-ADAF. We confirm the original prediction that the inner parts of the loops are continuously advected toward the central black hole and contribute to the growth of the large scale magnetic field, whereas the outer parts of the loops are continuously diffusing outward through the turbulent accretion flow. This process of inward advection of the axial field and outward diffusion of the return field proceeds all the way to equipartition, thus generating astrophysically significant magnetic fields on astrophysicall...

Contopoulos, Ioannis; Katsanikas, Matthaios

2015-01-01T23:59:59.000Z

200

TESTING CONVERGENCE FOR GLOBAL ACCRETION DISKS  

SciTech Connect

Global disk simulations provide a powerful tool for investigating accretion and the underlying magnetohydrodynamic turbulence driven by magneto-rotational instability (MRI). Using them to accurately predict quantities such as stress, accretion rate, and surface brightness profile requires that purely numerical effects, arising from both resolution and algorithm, be understood and controlled. We use the flux-conservative Athena code to conduct a series of experiments on disks having a variety of magnetic topologies to determine what constitutes adequate resolution. We develop and apply several resolution metrics: (Q{sub z} ) and (Q{sub {phi}}), the ratio of the grid zone size to the characteristic MRI wavelength, {alpha}{sub mag}, the ratio of the Maxwell stress to the magnetic pressure, and /, the ratio of radial to toroidal magnetic field energy. For the initial conditions considered here, adequate resolution is characterized by (Q{sub z} ) {>=} 15, (Q{sub {phi}}) {>=} 20, {alpha}{sub mag} Almost-Equal-To 0.45, and /{approx}0.2. These values are associated with {>=}35 zones per scaleheight H, a result consistent with shearing box simulations. Numerical algorithm is also important. Use of the Harten-Lax-van Leer-Einfeldt flux solver or second-order interpolation can significantly degrade the effective resolution compared to the Harten-Lax-van Leer discontinuities flux solver and third-order interpolation. Resolution at this standard can be achieved only with large numbers of grid zones, arranged in a fashion that matches the symmetries of the problem and the scientific goals of the simulation. Without it, however, quantitative measures important to predictions of observables are subject to large systematic errors.

Hawley, John F.; Richers, Sherwood A.; Guan Xiaoyue [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Krolik, Julian H., E-mail: jh8h@virginia.edu, E-mail: xg3z@virginia.edu, E-mail: jhk@pha.jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

2013-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

DEBRIS DISKS IN KEPLER EXOPLANET SYSTEMS  

SciTech Connect

The Kepler mission recently identified 997 systems hosting candidate extrasolar planets, many of which are super-Earths. Realizing these planetary systems are candidates to host extrasolar asteroid belts, we use mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) to search for emission from dust in these systems. We find excesses around eight stars, indicating the presence of warm to hot dust ({approx}100-500 K), corresponding to orbital distances of 0.1-10 AU for these solar-type stars. The strongest detection, KOI 1099, demands {approx}500 K dust interior to the orbit of its exoplanet candidate. One star, KOI 904, may host very hot dust ({approx}1200 K, corresponding to 0.02 AU). Although the fraction of these exoplanet-bearing stars with detectable warm excesses ({approx}3%) is similar to that found by Spitzer surveys of solar-type field stars, the excesses detectable in the WISE data have much higher fractional luminosities (L{sub dust}/L{sub *}) than most known debris disks, implying that the fraction with debris disks of comparable luminosity may actually be significantly higher. It is difficult to explain the presence of dust so close to the host stars, generally corresponding to dust rings at radii <0.3 AU; both the collisional and Poynting-Robertson drag timescales to remove dust from the system are hundreds of years or less at these distances. Assuming a steady state for these systems implies large mass consumption rates with these short removal timescales, meaning that the dust production mechanism in these systems must almost certainly be episodic in nature.

Lawler, S. M.; Gladman, B. [Department of Physics and Astronomy, University of British Columbia, 6244 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada)

2012-06-10T23:59:59.000Z

202

Barium even-to-odd isotope abundance ratios in thick disk and thin disk stars  

E-Print Network (OSTI)

We present the Ba even-to-odd isotope abundance ratios in 25 cool dwarf stars with the metallicity [Fe/H] ranged between 0.25 and --1.35. Our method takes advantage of the hyperfine structure (HFS) affecting the \\ion{Ba}{ii} resonance line of the odd isotopes. The fractional abundance of the odd isotopes of Ba is derived from a requirement that Ba abundances from the resonance line $\\lambda 4554$ and subordinate lines $\\lambda 5853$ and $\\lambda 6496$ must be equal. The results are based on NLTE line formation and analysis of high resolution (R $\\sim60000$) high signal-to-noise (S/N $\\ge 200$) observed spectra. We find that the fraction of the odd isotopes of Ba grows toward the lower Ba abundance (or metallicity) and the mean value in the thick disk stars equals 33 $\\pm$ 4%. This indicates the higher contribution of the $r-$process to barium in the thick disk stars compared to the solar system matter. The obtained fraction increases with the [Eu/Ba] abundance ratio growth in agreement with expectations. A significant fraction of the \\emph{even} isotopes of Ba found in old Galactic stars (the thick disk stars), $\\sim67$%, is in contrast to the prediction of the "classical" model of the $s-$process and favors the value predicted by the "stellar" models of Arlandini et al. (1999) and Travaglio et al. (1999).

L. Mashonkina; G. Zhao

2006-04-10T23:59:59.000Z

203

DYNAMICAL EVOLUTION OF VISCOUS DISKS AROUND Be STARS. I. PHOTOMETRY  

SciTech Connect

Be stars possess gaseous circumstellar disks that modify in many ways the spectrum of the central B star. Furthermore, they exhibit variability at several timescales and for a large number of observables. Putting the pieces together of this dynamical behavior is not an easy task and requires a detailed understanding of the physical processes that control the temporal evolution of the observables. There is an increasing body of evidence that suggests that Be disks are well described by standard {alpha}-disk theory. This paper is the first of a series that aims at studying the possibility of inferring several disk and stellar parameters through the follow-up of various observables. Here we study the temporal evolution of the disk density for different dynamical scenarios, including the disk build-up as a result of a long and steady mass injection from the star, the disk dissipation that occurs after mass injection is turned off, as well as scenarios in which active periods are followed by periods of quiescence. For those scenarios, we investigate the temporal evolution of continuum photometric observables using a three-dimensional non-LTE radiative transfer code. We show that light curves for different wavelengths are specific of a mass loss history, inclination angle, and {alpha} viscosity parameter. The diagnostic potential of those light curves is also discussed.

Haubois, X.; Carciofi, A. C. [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, Sao Paulo, SP 05508-900 (Brazil); Rivinius, Th. [European Organisation for Astronomical Research in the Southern Hemisphere, Casilla 19001, Santiago 19 (Chile); Okazaki, A. T. [Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo 062-8605 (Japan); Bjorkman, J. E., E-mail: xhaubois@astro.iag.usp.br [Ritter Observatory, Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States)

2012-09-10T23:59:59.000Z

204

WATER VAPOR IN THE PROTOPLANETARY DISK OF DG Tau  

SciTech Connect

Water is key in the evolution of protoplanetary disks and the formation of comets and icy/water planets. While high-excitation water lines originating in the hot inner disk have been detected in several T Tauri stars (TTSs), water vapor from the outer disk, where most water ice reservoirs are stored, was only reported in the nearby TTS TW Hya. We present spectrally resolved Herschel/HIFI observations of the young TTS DG Tau in the ortho- and para-water ground-state transitions at 557 and 1113 GHz. The lines show a narrow double-peaked profile, consistent with an origin in the outer disk, and are {approx}19-26 times brighter than in TW Hya. In contrast, CO and [C II] lines are dominated by emission from the envelope/outflow, which makes H{sub 2}O lines a unique tracer of the disk of DG Tau. Disk modeling with the thermo-chemical code ProDiMo indicates that the strong UV field, due to the young age and strong accretion of DG Tau, irradiates a disk upper layer at 10-90 AU from the star, heating it up to temperatures of 600 K and producing the observed bright water lines. The models suggest a disk mass of 0.015-0.1 M{sub Sun }, consistent with the estimated minimum mass of the solar nebula before planet formation, and a water reservoir of {approx}10{sup 2}-10{sup 3} Earth oceans in vapor and {approx}100 times larger in the form of ice. Hence, this detection supports the scenario of ocean delivery on terrestrial planets by the impact of icy bodies forming in the outer disk.

Podio, L.; Dougados, C.; Thi, W.-F.; Menard, F.; Pinte, C. [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d'Astrophysique de Grenoble (IPAG) UMR 5274, F-38041 Grenoble (France); Kamp, I.; Meijerink, R.; Spaans, M.; Aresu, G. [Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen (Netherlands); Codella, C. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Florence (Italy); Cabrit, S. [LERMA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure, Universite Pierre et Marie Curie, Universite de Cergy-Pontoise, 61 Av. de l'Observatoire, F-75014 Paris (France); Nisini, B. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone (Italy); Sandell, G. [SOFIA-USRA, NASA Ames Research Center, MS 232-12, Building N232, Rm. 146, P.O. Box 1, Moffett Field, CA 94035-0001 (United States); Williams, J. P. [Institute for Astronomy (IfA), University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States); Testi, L. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Woitke, P. [SUPA, School of Physics and Astronomy, University of St. Andrews, KY16 9SS (United Kingdom)

2013-03-20T23:59:59.000Z

205

Corrections to kinetic measurements taken on a disk electrode  

SciTech Connect

Below the limiting current, the rotating disk electrode has a nonuniform current distribution. When the nonuniformities are not explicitly accounted for, errors in values of kinetic parameters determined through measurements on a disk can result. In this analysis, valid for Tafel kinetics, correction factors are obtained as a function of the dimensionless average current density.It is assumed that ohmic corrections are made by the interruption of current. The results indicate that, under certain conditions, the errors are negligible and that the disk geometry, despite its nonuniformities, is adequate for the investigation of systems characterized by Tafel kinetics.

West, A.C.; Newman, J.

1989-01-01T23:59:59.000Z

206

Characteristics of a multiple disk pump with turbulent rotor flow  

E-Print Network (OSTI)

DIRHETER IINIt tl, DISCHARGE OIANETER IINlt 3. CLEARANCE OETHEEN DISKS 0. 13636 IN. TYPE SEALJ PRCKING DISKFLO PUHP; NODEL K03 TOTRL HERO HORSEPOHER X EFFICIENCY + NPSH AVAIL V Figure 12. Performance of the 11 Disk Pump at 890 rpm (Test 2) C& C...: D. 13636 IN 111'E 5EAI. PACK(NO OISKFLD PL'. "P: HDD L 40 TOTAL HERO HDRSEPOHER X EFFICIENCY + NPSH AVAIL Y Figure 14 . Performance of the 1 1 Disk Pump at 1 790 rpm ( Tes t 1 ) CV o O C) CI O C) O \\ C CC C O I-!-W I o O O O 6 )3...

Roddy, Patrick James

1985-01-01T23:59:59.000Z

207

Heterogeneous Integration of InGaAs Nanowires on the Rear Surface of Si Solar Cells for Efficiency Enhancement  

Science Journals Connector (OSTI)

We demonstrate energy-conversion-efficiency (?) enhancement of silicon (Si) solar cells by the heterogeneous integration of an InxGa1xAs nanowire (NW) array on the rear surface. ... (10, 11) We note that the catalyst-free self-assembled NW array formation process is simple and economical, with a total growth time of around 1 h from wafer loading to unloading, and the total consumption of the metalorganic sources and hydride gas for the growth of around 0.01 and 1 g, respectively. ...

Jae Cheol Shin; Parsian K. Mohseni; Ki Jun Yu; Stephanie Tomasulo; Kyle H. Montgomery; Minjoo L. Lee; John A. Rogers; Xiuling Li

2012-11-05T23:59:59.000Z

208

Identification of the Spawning, Rearing and Migratory Requirements of Fall Chinook Salmon in the Columbia River Basin, Annual Report 1992.  

SciTech Connect

This document is the 1992 annual progress report for selected studies of fall chinook Salmon Oncorhynchus tshawytscha conducted by the National Biological Survey (NBS) and the US Fish and Wildlife Service. The decline in abundance of fall chinook salmon in the Snake River basin has become a growing concern. Effective recovery efforts for fall chinook salmon cannot be developed until we increase our knowledge of the factors that are limiting the various life history stages. This study attempts to identify those physical and biological factors which influence spawning of fall chinook salmon in the free-flowing Snake River and their rearing and seaward migration through Columbia River basin reservoirs.

Rondorf, Dennis W.; Miller, William H.

1994-03-01T23:59:59.000Z

209

SmartSaver: Turning Flash Drive into a Disk Energy Saver for Mobile , Song Jiang2  

E-Print Network (OSTI)

- cies usually take conservative approaches to save disk energy, and disk energy consumption remains drive -- saving disk energy. This is achieved by using the flash drive as a standby buffer for caching to 41% of disk energy can be saved with a relatively small amount of data written to the flash drive

210

HyLog: A High Performance Approach to Managing Disk Layout  

Science Journals Connector (OSTI)

Our objective is to improve disk I/O performance in multi-disk systems supporting multiple concurrent users, such as file servers, database servers, and email servers. In such systems, many disk reads are absorbed by large in-memory buffers, and so disk ...

Wenguang Wang; Yanping Zhao; Rick Bunt

2004-03-01T23:59:59.000Z

211

HyLog: a high performance approach to managing disk layout  

Science Journals Connector (OSTI)

Our objective is to improve disk I/O performance in multi-disk systems supporting multiple concurrent users, such as file servers, database servers, and email servers. In such systems, many disk reads are absorbed by large in-memory buffers, and so disk ...

Wenguang Wang; Yanping Zhao; Rick Bunt

2004-03-01T23:59:59.000Z

212

Breaking the Disk/Halo Degeneracy with Gravitational Lensing  

E-Print Network (OSTI)

The degeneracy between the disk and the dark matter contribution to galaxy rotation curves remains an important uncertainty in our understanding of disk galaxies. Here we discuss a new method for breaking this degeneracy using gravitational lensing by spiral galaxies, and apply this method to the spiral lens B1600+434 as an example. The combined image and lens photometry constraints allow models for B1600+434 with either a nearly singular dark matter halo, or a halo with a sizable core. A maximum disk model is ruled out with high confidence. Further information, such as the circular velocity of this galaxy, will help break the degeneracies. Future studies of spiral galaxy lenses will be able to determine the relative contribution of disk, bulge, and halo to the mass in the inner parts of galaxies.

Ariyeh H. Maller; Luc Simard; Puragra Guhathakurta; Jens Hjorth; Andreas O. Jaunsen; Ricardo A. Flores; Joel R. Primack

1999-10-12T23:59:59.000Z

213

Backscattering cross section of a tilted, roughened disk  

Science Journals Connector (OSTI)

An expression is derived for the cross correlation of the electric field scattered from a roughened metallic disk to two points in the far zone. Both exponential and Gaussian surface...

Schertler, Donald J; George, Nicholas

1992-01-01T23:59:59.000Z

214

Zooming in on quasar accretion disks using chromatic microlensing  

E-Print Network (OSTI)

Observing the temperature profiles of accretion disks around black holes is a fundamental test of an important astrophysical process. However, angular resolution limitations have prevented such a measurement for distant ...

Blackburne, Jeffrey A

2009-01-01T23:59:59.000Z

215

Data partitioning and load balancing in parallel disk systems  

Science Journals Connector (OSTI)

...Parallel disk systems provide opportunities for exploiting I/O parallelism in two possible ways, namely via inter-request and intra-request parallelism. In this paper, we discuss the main issues in performance...

Peter Scheuermann; Gerhard Weikum; Peter Zabback

1998-02-01T23:59:59.000Z

216

Modeling Disk Arrays Using Genetic Programming Evan Kirshenbaum  

E-Print Network (OSTI)

Page Mill Road Palo Alto, CA 94304 kirshenbaum@hpl.hp.com Abstract This paper describes the results to population size but not run length. 1 BACKGROUND In the past decade, enterprises have turned to disk arrays

Fernandez, Thomas

217

Modeling Adhesive Forces for Ultra Low Flying Head Disk Interfaces  

Science Journals Connector (OSTI)

This paper addresses a major issue in microtribology related to the head/disk interface (HDI) in magnetic storage. This is the issue of strong intermolecular (adhesive) forces that may be present at the interf...

Andreas A. Polycarpou

2003-01-01T23:59:59.000Z

218

Innovation incentives and competition in the hard disk drive industry  

E-Print Network (OSTI)

Firms in the hard disk drive industry are continually engaging in R & D and improving the quality of their products. We explore various determinants of the product innovation incentives for firms concerned with both their ...

Wu, Xiaohua Sherry

2011-01-01T23:59:59.000Z

219

Nanolithographically defined magnetic structures and quantum magnetic disk (invited)  

E-Print Network (OSTI)

is demonstrated along with a low-cost method for mass producing such disks. Other impacts that nanofabrication can- veloped in a cellosolve and methanol solution to form a re- sist template on the substrate. Ferromagnetic

220

Detecting planets in protoplanetary disks: A prospective study  

E-Print Network (OSTI)

We investigate the possibility to find evidence for planets in circumstellar disks by infrared and submillimeter interferometry. We present simulations of a circumstellar disk around a solar-type star with an embedded planet of 1 Jupiter mass. The three-dimensional (3D) density structure of the disk results from hydrodynamical simulations. On the basis of 3D radiative transfer simulations, images of this system were calculated. The intensity maps provide the basis for the simulation of the interferometers VLTI (equipped with the mid-infrared instrument MIDI) and ALMA. While MIDI/VLTI will not provide the possibility to distinguish between disks with or without a gap on the basis of visibility measurements, ALMA will provide the necessary basis for a direct gap detection.

S. Wolf; F. Gueth; Th. Henning; W. Kley

2002-01-12T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Photophoresis in protoplanetary disks: a numerical approach  

E-Print Network (OSTI)

It is widely accepted that rocky planets form in the inner regions of protoplanetary disks (PPD) about 1 - 10 AU from the star. However, theoretical calculations show that when particles reach the size for which the radial migration is the fastest they tend to be accreted very efficiently by the star. This is known as the radial-drift barrier. We explore the photophoresis in the inner regions of PPD as a possible mechanism for preventing the accretion of solid bodies onto the star. Photophoresis is the thermal creep induced by the momentum exchange of an illuminated solid particle with the surrounding gas. Recent laboratory experiments predict that photophoresis would be able to stop the inward drift of macroscopic bodies (from 1 mm to 1 m in size). This extra force has been included in our two-fluid (gas+dust) SPH code in order to study its efficiency. We show that the conditions of pressure and temperature encountered in the inner regions of PPD result in strong dynamical effects on the dust particles due t...

Cuello, Nicolas; Gonzalez, Jean-Franois

2014-01-01T23:59:59.000Z

222

Large grains in the disk of CQ Tau  

E-Print Network (OSTI)

We present 7mm observations of the dusty disk surrounding the 10 Myr old 1.5 Msun pre-main-sequence star CQ Tauri obtained at the Very Large Array with 0.8 arcsecond resolution and 0.1 mJy rms sensitivity. These observations resolve the 7mm emission in approximately the north-south direction, confirming previous results obtained with lower resolution. We use a two-layer flared disk model to interpret the observed fluxes from 7mm to 1.3mm together with the resolved 7mm structure. We find that the disk radius is constrained to the range 100 to 300 AU, depending on the steepness of the disk surface density distribution. The power law index of the dust opacity coefficient, beta, is constrained to be 0.5 to 0.7. Since the models indicate that the disk is optically thin at millimeter wavelengths for radii greater than 8 AU, the contribution of an optically thick region to the emission is less than 10%. This implies that high optical depth or complex disk geometry cannot be the cause of the observed shallow millimeter spectral index. Instead, the new analysis supports the earlier suggestion that dust particles in the disk have grown to sizes as large as a few centimeters. The dust in the CQ Tauri system appears to be evolved much like that in the TW Hydra system, a well-studied pre-main-sequence star of similar age and lower mass. The survival of gas-rich disks with incomplete grain evolution at such old ages deserves further investigations.

L. Testi; A. Natta; D. S. Shepherd; D. J. Wilner

2003-03-18T23:59:59.000Z

223

STAR CLUSTER POPULATIONS IN THE OUTER DISKS OF NEARBY GALAXIES  

SciTech Connect

We present a Large Binocular Telescope imaging study that characterizes the star cluster component of nearby galaxy outer disks (beyond the optical radius R{sub 25}). Expanding on the pilot project of Herbert-Fort et al., we present deep ({approx}27.5 mag V-band point-source limiting magnitude) U- and V-band imaging of six galaxies: IC 4182, NGC 3351, NGC 4736, NGC 4826, NGC 5474, and NGC 6503. We find that the outer disk of each galaxy is populated with marginally resolved star clusters with masses {approx}10{sup 3} M{sub Sun} and ages up to {approx}1 Gyr (masses and ages are limited by the depth of our imaging and uncertainties are large given how photometry can be strongly affected by the presence or absence of a few stars in such low-mass systems), and that they are typically found out to at least 2 R{sub 25} but sometimes as far as 3-4 R{sub 25}-even beyond the apparent H I disk. The mean rate of cluster formation for 1 R{sub 25} {<=} R {<=} 1.5 R{sub 25} is at least one every {approx}2.5 Myr and the clusters are spatially correlated with the H I, most strongly with higher density gas near the periphery of the optical disk and with lower density neutral gas at the H I disk periphery. We hypothesize that the clusters near the edge of the optical disk are formed in the extension of spiral structure from the inner disk and are a fairly consistent phenomenon and that the clusters formed at the periphery of the H I disk are the result of accretion episodes.

Herbert-Fort, Stephane; Zaritsky, Dennis [Department of Astronomy/Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Moustakas, John [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States); Di Paola, Andrea [INAF, Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio (Italy); Pogge, Richard W. [Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210-1173 (United States); Ragazzoni, Roberto, E-mail: s.herbertfort@gmail.com, E-mail: dennis.zaritsky@gmail.com [INAF, Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, I-35122 Padova (Italy)

2012-08-01T23:59:59.000Z

224

Apparatus and method for pressure testing closure disks  

DOE Patents (OSTI)

A method and device are described for testing the burst pressure of closure disks which provides high pressure to both sides of a disk and rapidly releases pressure from one side thereof causing a high rate of change of pressure. A hollow notched plug allows the rapid release of pressure upon rupturing. A tensile load is transmitted by a piston in combination with fluid pressure to the hollow notched plug. 5 figs.

Merten, C.W. Jr.

1992-01-21T23:59:59.000Z

225

Identification of new transitional disk candidates in Lupus with Herschel  

E-Print Network (OSTI)

New data from the Herschel Space Observatory are broadening our understanding of the physics and evolution of the outer regions of protoplanetary disks in star forming regions. In particular they prove to be useful to identify transitional disk candidates. The goals of this work are to complement the detections of disks and the identification of transitional disk candidates in the Lupus clouds with data from the Herschel Gould Belt Survey. We extracted photometry at 70, 100, 160, 250, 350 and 500 $\\mu$m of all spectroscopically confirmed Class II members previously identified in the Lupus regions and analyzed their updated spectral energy distributions. We have detected 34 young disks in Lupus in at least one Herschel band, from an initial sample of 123 known members in the observed fields. Using the criteria defined in Ribas et al. (2013) we have identified five transitional disk candidates in the region. Three of them are new to the literature. Their PACS-70 $\\mu$m fluxes are systematically higher than thos...

Bustamante, I; Ribas, ; Bouy, H; Prusti, T; Pilbratt, G L; Andr, Ph

2015-01-01T23:59:59.000Z

226

Merger Histories of Galaxy Halos and Implications for Disk Survival  

E-Print Network (OSTI)

We study the merger histories of galaxy dark matter halos using a high resolution LCDM N-body simulation. Our merger trees follow ~17,000 halos with masses M_0 = (10^11--10^13) Msun at z=0 and track accretion events involving objects as small as m = 10^10 Msun. We find that mass assembly is remarkably self-similar in m/M_0, and dominated by mergers that are ~10% of the final halo mass. While very large mergers, m > 0.4 M_0, are quite rare, sizeable accretion events, m ~ 0.1 M_0, are common. Over the last 10 Gyr, an overwhelming majority (~95%) of Milky Way-sized halos with M_0 = 10^12 Msun have accreted at least one object with greater total mass than the Milky Way disk (m > 5x10^10 Msun), and approximately 70% have accreted an object with more than twice that mass (m > 10^11 Msun). Our results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a CDM universe. In order to achieve a ~70% disk-dominated fraction in Milky Way-sized CDM halos, mergers involving m ~ 2x10^11 Msun objects must not destroy disks. Considering that most thick disks and bulges contain old stellar populations, the situation is even more restrictive: these mergers must not heat disks or drive gas into their centers to create young bulges.

Kyle R. Stewart; James S. Bullock; Risa H. Wechsler; Ariyeh H. Maller; Andrew R. Zentner

2007-11-30T23:59:59.000Z

227

Spin-Induced Disk Precession in Sagittarius A*  

E-Print Network (OSTI)

In Sgr A* at the Galactic center, by far the closest and easiest supermassive black hole we can study, the observational evidence is increasingly pointing to the presence of a compact, hot, magnetized disk feeding the accretor. In such low-Mach-number plasmas, forces arising, e.g., from pressure gradients in the plasma, can altogether negate the warping of disks around Kerr black holes caused by the Bardeen-Petterson effect and can lead to coherent precession of the entire disk. In this Letter, we present for the first time highly detailed 3D SPH simulations of the accretion disk evolution in Sgr A*, guided by observational constraints on its physical characteristics, and conclude that indeed the Bardeen-Petterson effect is probably absent in this source. Given what we now understand regarding the emission geometry in this object, we suggest that a ~ 50-500-day modulation in Sgr A*'s spectrum, arising from the disk precession, could be an important observational signature; perhaps the ~ 106-day period seen earlier in its radio flux, if confirmed, could be due to this process. On the other hand, if future observations do not confirm this long modulation in Sgr A*'s spectrum, this would be an indication that either the disk size or orientation is very different from current estimates, or that the black hole is not spinning at all (unlikely), or that our current understanding of how it produces its radiative output is incorrect.

Gabriel Rockefeller; Christopher L. Fryer; Fulvio Melia

2005-08-03T23:59:59.000Z

228

Disks, young stars, and radio waves: the quest for forming planetary systems  

E-Print Network (OSTI)

Kant and Laplace suggested the Solar System formed from a rotating gaseous disk in the 18th century, but convincing evidence that young stars are indeed surrounded by such disks was not presented for another 200 years. As we move into the 21st century the emphasis is now on disk formation, the role of disks in star formation, and on how planets form in those disks. Radio wavelengths play a key role in these studies, currently providing some of the highest spatial resolution images of disks, along with evidence of the growth of dust grains into planetesimals. The future capabilities of EVLA and ALMA provide extremely exciting prospects for resolving disk structure and kinematics, studying disk chemistry, directly detecting proto-planets, and imaging disks in formation.

Claire J. Chandler; Debra S. Shepherd

2008-01-24T23:59:59.000Z

229

A SEMI-ANALYTICAL DESCRIPTION FOR THE FORMATION AND GRAVITATIONAL EVOLUTION OF PROTOPLANETARY DISKS  

SciTech Connect

We investigate the formation process of self-gravitating protoplanetary disks in unmagnetized molecular clouds. The angular momentum is redistributed by the action of gravitational torques in the massive disk during its early formation. We develop a simplified one-dimensional accretion disk model that takes into account the infall of gas from the envelope onto the disk and the transfer of angular momentum in the disk with an effective viscosity. First we evaluate the gas accretion rate from the cloud core onto the disk by approximately estimating the effects of gas pressure and gravity acting on the cloud core. We formulate the effective viscosity as a function of the Toomre Q parameter that measures the local gravitational stability of the rotating thin disk. We use a function for viscosity that changes sensitively with Q when the disk is gravitationally unstable. We find a strong self-regulation mechanism in the disk evolution. During the formation stage of protoplanetary disks, the evolution of the surface density does not depend on the other details of the modeling of effective viscosity, such as the prefactor of the viscosity coefficient. Next, to verify our model, we compare the time evolution of the disk calculated with our formulation with that of three-dimensional hydrodynamical simulations. The structures of the resultant disks from the one-dimensional accretion disk model agree well with those of the three-dimensional simulations. Our model is a useful tool for the further modeling of chemistry, radiative transfer, and planet formation in protoplanetary disks.

Takahashi, Sanemichi Z.; Inutsuka, Shu-ichiro [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602 (Japan); Machida, Masahiro N., E-mail: takahashi.sanemichi@a.mbox.nagoya-u.ac.jp, E-mail: inutsuka@nagoya-u.jp, E-mail: sanemichi@tap.scphys.kyoto-u.ac.jp, E-mail: machida.masahiro.018@m.kyushu-u.ac.jp [Department of Earth and Planetary Science, Kyushu University, Higashi-ku, Fukuoka 812-8581 (Japan)

2013-06-10T23:59:59.000Z

230

MAGNETOROTATIONAL-INSTABILITY-DRIVEN ACCRETION IN PROTOPLANETARY DISKS  

SciTech Connect

Non-ideal MHD effects play an important role in the gas dynamics in protoplanetary disks (PPDs). This paper addresses the influence of non-ideal MHD effects on the magnetorotational instability (MRI) and angular momentum transport in PPDs using the most up-to-date results from numerical simulations. We perform chemistry calculations using a complex reaction network with standard prescriptions for X-ray and cosmic-ray ionizations. We first show that whether or not grains are included, the recombination time is at least one order of magnitude less than the orbital time within five disk scale heights, justifying the validity of local ionization equilibrium and strong coupling limit in PPDs. The full conductivity tensor at different disk radii and heights is evaluated, with the MRI active region determined by requiring that (1) the Ohmic Elsasser number {Lambda} be greater than 1 and (2) the ratio of gas to magnetic pressure {beta} be greater than {beta}{sub min}(Am) as identified in the recent study by Bai and Stone, where Am is the Elsasser number for ambipolar diffusion. With full flexibility as to the magnetic field strength, we provide a general framework for estimating the MRI-driven accretion rate M-dot and the magnetic field strength in the MRI active layer. We find that the MRI active layer always exists at any disk radius as long as the magnetic field in PPDs is sufficiently weak. However, the optimistically predicted M-dot in the inner disk (r = 1-10 AU) appears insufficient to account for the observed range of accretion rates in PPDs (around 10{sup -8} M{sub sun} yr{sup -1}) even in the grain-free calculation, and the presence of solar abundance sub-micron grains further reduces M-dot by one to two orders of magnitude. Moreover, we find that the predicted M-dot increases with radius in the inner disk where accretion is layered, which would lead to runaway mass accumulation if disk accretion is solely driven by the MRI. Our results suggest that stronger sources of ionization and/or additional mechanisms such as magnetized wind are needed to explain the observed accretion rates in PPDs. In contrast, our predicted M-dot is on the order of 10{sup -9} M{sub sun} yr{sup -1} in the outer disk, consistent with the observed accretion rates in transitional disks.

Bai Xuening, E-mail: xbai@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2011-09-20T23:59:59.000Z

231

Giant disk galaxies : Where environment trumps mass in galaxy evolution  

E-Print Network (OSTI)

We identify some of the most HI massive and fastest rotating disk galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disk galaxies. By combining data from the Cosmic Flows project, which has consistently reanalyzed archival galaxy HI profiles, and 3.6$\\mu$m photometry obtained with the Spitzer Space Telescope, with which we can measure stellar mass, we use the baryonic Tully-Fisher (BTF) relationship to explore whether these massive galaxies are distinct. We discuss several results, but the most striking is the systematic offset of the HI-massive sample above the BTF. These galaxies have both more gas and more stars in their disks than the typical disk galaxy of similar rotational velocity. The "condensed" baryon fraction, $f_C$, the fraction of the baryons in a dark matter halo that settle either as cold gas or stars into the disk, is twice as high in the HI-massive sample than typical, and almost reaches the universal baryon fraction in some cases,...

Courtois, H M; Sorce, J G; Pomarede, D

2015-01-01T23:59:59.000Z

232

Non-LTE modeling of supernova-fallback disks  

E-Print Network (OSTI)

We present a first detailed spectrum synthesis calculation of a supernova-fallback disk composed of iron. We assume a geometrically thin disk with a radial structure described by the classical alpha-disk model. The disk is represented by concentric rings radiating as plane-parallel slabs. The vertical structure and emission spectrum of each ring is computed in a fully self-consistent manner by solving the structure equations simultaneously with the radiation transfer equations under non-LTE conditions. We describe the properties of a specific disk model and discuss various effects on the emergent UV/optical spectrum. We find that strong iron-line blanketing causes broad absorption features over the whole spectral range. Limb darkening changes the spectral distribution up to a factor of four depending on the inclination angle. Consequently, such differences also occur between a blackbody spectrum and our model. The overall spectral shape is independent of the exact chemical composition as long as iron is the dominant species. A pure iron composition cannot be distinguished from silicon-burning ash. Non-LTE effects are small and restricted to few spectral features.

K. Werner; T. Nagel; T. Rauch

2006-08-24T23:59:59.000Z

233

Chemistry and line emission from evolving Herbig Ae disks  

E-Print Network (OSTI)

Aims: To calculate chemistry and gas temperature of evolving protoplanetary disks with decreasing mass or dust settling, and to explore the sensitivity of gas-phase tracers. Methods: The density and dust temperature profiles for a range of models of flaring and self-shadowed disks around a typical Herbig Ae star are used together with 2-dimensional ultraviolet (UV) radiative transfer to calculate the chemistry and gas temperature. In each model the line profiles and intensities for the fine structure lines of [O I], [C II] and [C I] and the pure rotational lines of CO, CN, HCN and HCO+ are determined. Results: The chemistry shows a strong correlation with disk mass. Molecules that are easily dissociated, like HCN, require high densities and large extinctions before they can become abundant. The products of photodissociation, like CN and C2H, become abundant in models with lower masses. Dust settling mainly affects the gas temperature, and thus high temperature tracers like the O and C+ fine structure lines. The carbon chemistry is found to be very sensitive to the adopted PAH abundance. The line ratios CO/13CO, CO/HCO+ and [O I] 63 um/146 um can be used to distinguish between disks where dust growth and settling takes place, and disks that undergo overall mass loss.

B. Jonkheid; C. P. Dullemond; M. R. Hogerheijde; E. F. van Dishoeck

2006-11-07T23:59:59.000Z

234

RELAXATION OF WARPED DISKS: THE CASE OF PURE HYDRODYNAMICS  

SciTech Connect

Orbiting disks may exhibit bends due to a misalignment between the angular momentum of the inner and outer regions of the disk. We begin a systematic simulational inquiry into the physics of warped disks with the simplest case: the relaxation of an unforced warp under pure fluid dynamics, i.e., with no internal stresses other than Reynolds stress. We focus on the nonlinear regime in which the bend rate is large compared to the disk aspect ratio. When warps are nonlinear, strong radial pressure gradients drive transonic radial motions along the disk's top and bottom surfaces that efficiently mix angular momentum. The resulting nonlinear decay rate of the warp increases with the warp rate and the warp width, but, at least in the parameter regime studied here, is independent of the sound speed. The characteristic magnitude of the associated angular momentum fluxes likewise increases with both the local warp rate and the radial range over which the warp extends; it also increases with increasing sound speed, but more slowly than linearly. The angular momentum fluxes respond to the warp rate after a delay that scales with the square root of the time for sound waves to cross the radial extent of the warp. These behaviors are at variance with a number of the assumptions commonly used in analytic models to describe linear warp dynamics.

Sorathia, Kareem A.; Krolik, Julian H. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Hawley, John F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States)

2013-05-10T23:59:59.000Z

235

Identification of the Spawning, Rearing, and Migratory Requirements of Fall Chinook Salmon in the Columbia River Basin, Annual Report 1993.  

SciTech Connect

Recovery efforts for the endangered fall chinook salmon necessitates knowledge of the factors limiting the various life history stages. This study attempts to identify those physical and biological factors which affect spawning of the fish in the free-flowing Snake River and their rearing seward migration through Columbia River basin reservoirs. The spawning was generally a November event in 1993, with some activity in late Oct. and early Dec. Spawning habitat availability was assessed by applying hydraulic and habitat models to known fall chinook salmon spawning sites. Juveniles were seined and PIT tagged in the free-flowing Snake River, and in the Columbia River in he Hanford Reach and in McNary Reservoir. Subyearling fish were marked at McNary Dam to relate river flow and migration patterns of juveniles to adult returns. Hydroacoustic surveys were conducted on McNary and John Day reservoirs and in net pens.

Rondorf, Dennis W.; Tiffan, Kenneth F.

1994-12-01T23:59:59.000Z

236

PROTOSTELLAR DISK FORMATION ENABLED BY WEAK, MISALIGNED MAGNETIC FIELDS  

SciTech Connect

The gas from which stars form is magnetized, and strong magnetic fields can efficiently transport angular momentum. Most theoretical models of this phenomenon find that it should prevent formation of large (>100 AU), rotationally supported disks around most protostars, even when non-ideal magnetohydrodynamic (MHD) effects that allow the field and gas to decouple are taken into account. Using recent observations of magnetic field strengths and orientations in protostellar cores, we show that this conclusion is incorrect. The distribution of magnetic field strengths is very broad, and alignments between fields and angular momentum vectors within protostellar cores are essentially random. By combining the field strength and misalignment data with MHD simulations showing that disk formation is expected for both weak and misaligned fields, we show that these observations imply that we should expect disk fractions of {approx}10%-50% even when protostars are still deeply embedded in their parent cores, and even if the gas is governed by ideal MHD.

Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Crutcher, Richard M. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801 (United States); Hull, Charles L. H., E-mail: mkrumhol@ucsc.edu [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States)

2013-04-10T23:59:59.000Z

237

A gaseous metal disk around a white dwarf  

E-Print Network (OSTI)

The destiny of planetary systems through the late evolution of their host stars is very uncertain. We report a metal-rich gas disk around a moderately hot and young white dwarf. A dynamical model of the double-peaked emission lines constrains the outer disk radius to just 1.2 solar radii. The likely origin of the disk is a tidally disrupted asteroid, which has been destabilised from its initial orbit at a distance of more than 1000 solar radii by the interaction with a relatively massive planetesimal object or a planet. The white dwarf mass of 0.77 solar masses implies that planetary systems may form around high-mass stars.

B. T. Gaensicke; T. R. Marsh; J. Southworth; A. Rebassa-Mansergas

2006-12-22T23:59:59.000Z

238

Debris Disks Around White Dwarfs: The DAZ Connection  

E-Print Network (OSTI)

We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these white dwarfs (G29-38 and GD362) are known to display significant K-band excesses due to circumstellar debris disks. Here we report the discovery of excess K-band radiation from another DAZ white dwarf, WD0408-041 (GD56). Using spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a warm debris disk. Our observations strengthen the connection between the debris disk phenomena and the observed metal abundances in cool DAZ white dwarfs. However, we do not find any excess infrared emission from the most metal rich DAZs with $T_{\\rm eff}=$ 16000 -- 20000 K. This suggests that the metal abundances in warmer DAZ white dwarfs may require another explanation.

Mukremin Kilic; Ted von Hippel; S. K. Leggett; D. E. Winget

2006-03-28T23:59:59.000Z

239

Low-mass planets in nearly inviscid disks: Numerical treatment  

E-Print Network (OSTI)

Embedded planets disturb the density structure of the ambient disk and gravitational back-reaction will induce possibly a change in the planet's orbital elements. The accurate determination of the forces acting on the planet requires careful numerical analysis. Recently, the validity of the often used fast orbital advection algorithm (FARGO) has been put into question, and special numerical resolution and stability requirements have been suggested. In this paper we study the process of planet-disk interaction for small mass planets of a few Earth masses, and reanalyze the numerical requirements to obtain converged and stable results. One focus lies on the applicability of the FARGO-algorithm. Additionally, we study the difference of two and three-dimensional simulations, compare global with local setups, as well as isothermal and adiabatic conditions. We study the influence of the planet on the disk through two- and three-dimensional hydrodynamical simulations. To strengthen our conclusions we perform a detai...

Kley, Wilhelm; Kolb, Stefan M; Benitez-Llambay, Pablo; Masset, Frederic

2012-01-01T23:59:59.000Z

240

Interferometric Detection of Planets/Gaps in Protoplanetary Disks  

E-Print Network (OSTI)

We investigate the possibility to find evidence for planets in circumstellar disks by infrared and submillimeter interferometry. Hydrodynamical simulations of a circumstellar disk around a solar-type star with an embedded planet of 1 Jupiter mass are presented. On the basis of 3D radiative transfer simulations, images of this system are calculated. These intensity maps provide the basis for the simulation of the interferometers VLTI (equipped with the mid-infrared instrument MIDI) and ALMA. While ALMA will provide the necessary basis for a direct gap and therefore indirect planet detection, MIDI/VLTI will provide the possibility to distinguish between disks with or without accretion on the central star on the basis of visibility measurements.

S. Wolf; F. Gueth; Th. Henning; W. Kley

2002-08-26T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Does Dissipation in AGN Disks Couple to the Total Pressure?  

E-Print Network (OSTI)

Recent work on the transport of angular momentum in accretion disks suggests that the Velikhov-Chandrasekhar instability, in which a large scale magnetic field generates small scale eddys in a shearing environment, may be ultimately responsible for this process. Although there is considerable controversy about the origin and maintenance of this field in accretion disks, it turns out that it is possible to argue, quite generally, using scaling arguments, that this process is sensitive to the total pressure in an AGN disk, rather than the pressure contributed by gas alone. We conclude that the resolution of the conceptual difficulties implied by the presence of strong thermal and viscous instabilities in radiation pressure and electron scattering dominated does not lie in models that couple the total dissipation rate to the gas pressure alone, or to some weighted mean of the gas and radiation pressures.

E. T. Vishniac

1993-08-12T23:59:59.000Z

242

Spectral modeling of gaseous metal disks around DAZ white dwarfs  

E-Print Network (OSTI)

We report on our attempt for the first non-LTE modeling of gaseous metal disks around single DAZ white dwarfs recently discovered by Gaensicke et al. and thought to originate from a disrupted asteroid. We assume a Keplerian rotating viscous disk ring composed of calcium and hydrogen and compute the detailed vertical structure and emergent spectrum. We find that the observed infrared CaII emission triplet can be modeled with a hydrogen-deficient gas ring located at R=1.2 R_sun, inside of the tidal disruption radius, with Teff about 6000 K and a low surface mass density of about 0.3 g/cm**2. A disk having this density and reaching from the central white dwarf out to R=1.2 R_sun would have a total mass of 7 10**21 g, corresponding to an asteroid with about 160 km diameter.

K. Werner; T. Nagel; T. Rauch

2008-09-30T23:59:59.000Z

243

Testing protostellar disk formation models with ALMA observations  

E-Print Network (OSTI)

Abridged: Recent simulations have explored different ways to form accretion disks around low-mass stars. We aim to present observables to differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects and infer their masses and sizes. Two 3D magnetohydrodynamics (MHD) formation simulations and 2D semi-analytical model are studied. The dust temperature structure is determined through continuum radiative transfer RADMC3D modelling. A simple temperature dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to $J_{\\rm u} = 10$ are simulated. All models predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1$"$ (70-140 AU) typical of the observations to date. A spatial resolution of $\\sim$14 AU and high dynamic range ($> 1000$) are required to differentiate between RSD and pseudo-disk in the continuum. The peak-position velocity diagrams indicate that the...

Harsono, Daniel; Bruderer, Simon; Li, Zhi-Yun; Jorgensen, Jes

2015-01-01T23:59:59.000Z

244

Disk Space Quota Management | Argonne Leadership Computing Facility  

NLE Websites -- All DOE Office Websites (Extended Search)

Account Information Accounts and Access FAQ Connect & Log In Using CRYPTOCards SSH Keys on Surveyor Disk Space Quota Management Allocations Decommissioning of BG/P Systems and Resources Blue Gene/Q Versus Blue Gene/P Mira/Cetus/Vesta Intrepid/Challenger/Surveyor Tukey Eureka / Gadzooks Policies Documentation Feedback Please provide feedback to help guide us as we continue to build documentation for our new computing resource. [Feedback Form] Disk Space Quota Management As you manage your project's disk space quota, it's important to remember that users you approve as to be added as project members are also added to the project's Unix Group. Unix Group members have the ability to write to the project directory and to access project data. You can manually add or remove Unix

245

Hall-effect Controlled Gas Dynamics in Protoplanetary Disks: II. Full 3D Simulations toward the Outer Disk  

E-Print Network (OSTI)

We perform 3D stratified shearing-box MHD simulations on the gas dynamics of protoplanetary disks threaded by net vertical magnetic field Bz. All three non-ideal MHD effects, Ohmic resistivity, the Hall effect and ambipolar diffusion are included in a self-consistent manner based on equilibrium chemistry. We focus on regions toward outer disk radii, from 5-60AU, where Ohmic resistivity tends to become negligible, ambipolar diffusion dominates over an extended region across disk height, and the Hall effect largely controls the dynamics near the disk midplane. We find that around R=5AU, the system launches a laminar/weakly turbulent magnetocentrifugal wind when the net vertical field Bz is not too weak, as expected. Moreover, the wind is able to achieve and maintain a configuration with reflection symmetry at disk midplane. The case with anti-aligned field polarity (Omega. Bz<0) is more susceptible to the MRI when Bz drops, leading to an outflow oscillating in radial directions and very inefficient angular m...

Bai, Xue-Ning

2014-01-01T23:59:59.000Z

246

EFFECTS OF LOCAL DISSIPATION PROFILES ON MAGNETIZED ACCRETION DISK SPECTRA  

SciTech Connect

We present spectral calculations of non-LTE accretion disk models appropriate for high-luminosity stellar mass black hole X-ray binary systems. We first use a dissipation profile based on scaling the results of shearing box simulations of Hirose et al. to a range of annuli parameters. We simultaneously scale the effective temperature, orbital frequency, and surface density with luminosity and radius according to the standard {alpha}-model. This naturally brings increased dissipation to the disk surface layers (around the photospheres) at small radii and high luminosities. We find that the local spectrum transitions directly from a modified blackbody to a saturated Compton scattering spectrum as we increase the effective temperature and orbital frequency while decreasing midplane surface density. Next, we construct annuli models based on the parameters of a L/L{sub Edd} = 0.8 disk orbiting a 6.62 solar mass black hole using two modified dissipation profiles that explicitly put more dissipation per unit mass near the disk surface. The new dissipation profiles are qualitatively similar to the one found by Hirose et al., but produce strong near power-law spectral tails. Our models also include physically motivated magnetic acceleration support based once again on scaling the Hirose et al. results. We present three full-disk spectra, each based on one of the dissipation prescriptions. Our most aggressive dissipation profile results in a disk spectrum that is in approximate quantitative agreement with certain observations of the steep power-law spectral states from some black hole X-ray binaries.

Tao, Ted [Department of Physics, St. Mary's College of Maryland, St. Mary's City, MD 20686 (United States); Blaes, Omer [Department of Physics, University of California, Santa Barbara, CA 93106 (United States)

2013-06-10T23:59:59.000Z

247

Ejection of Supernova-Enriched Gas From Dwarf Disk Galaxies  

E-Print Network (OSTI)

We examine the efficiency with which supernova-enriched gas may be ejected from dwarf disk galaxies, using a methodology previously employed to study the self-enrichment efficiency of dwarf spheroidal systems. Unlike previous studies that focused on highly concentrated starbursts, in the current work we consider discrete supernova events spread throughout various fractions of the disk. We model disk systems having gas masses of 10^8 and 10^9 solar masses with supernova rates of 30, 300, and 3000 per Myr. The supernova events are confined to the midplane of the disk, but distributed over radii of 0, 30, and 80% of the disk radius, consistent with expectations for Type II supernovae. In agreement with earlier studies, we find that the enriched material from supernovae is largely lost when the supernovae are concentrated near the nucleus, as expected for a starburst event. In contrast, however, we find the loss of enriched material to be much less efficient when the supernovae occur over even a relatively small fraction of the disk. The difference is due to the ability of the system to relax following supernova events that occur over more extended regions. Larger physical separations also reduce the likelihood of supernovae going off within low-density "chimneys" swept out by previous supernovae. We also find that, for the most distributed systems, significant metal loss is more likely to be accompanied by significant mass loss. A comparison with theoretical predications indicates that, when undergoing self-regulated star formation, galaxies in the mass range considered shall efficiently retain the products of Type II supernovae.

P. Chris Fragile; Stephen D. Murray; Douglas N. C. Lin

2004-08-24T23:59:59.000Z

248

Modelling the formation and evolution of disk galaxies  

E-Print Network (OSTI)

Inspired by recent work on feedback in disk galaxies (Efstathiou 2000, Silk 2003) and on the angular momentum distribution in simulated gas halos (Sharma and Steinmetz 2005), a fully dynamic model of disk galaxy formation and evolution has been developed. This is used to demonstrate how observed galactic systems could have formed from halos similar to those found in simulations and applies physically motivated models of star formation and feedback to explore whether the true nature of these processes would be manifest from local and cosmological observables. This is made possible by computational integration with the galaxy formation model developed originally by the group at Durham University (Cole et al. 2000).

M. J. Stringer; A. J. Benson

2007-12-05T23:59:59.000Z

249

The Evolution of Dusty Debris Disks around Solar Type Stars  

Science Journals Connector (OSTI)

We used chromospheric activity to determine the ages of 2820 field stars. We searched these stars for excess emission at 22 ?m with the Wide-Field Infrared Survey Explorer. Such excess emission is indicative of a dusty debris disk around a star. We investigated how disk incidence trends with various stellar parameters, and how these parameters evolve with time. We found 22 ?m excesses around 98 stars (a detection rate of 3.5%). Of these 98 excess sources, 74 are presented here for the first time. We also measured the abundance of lithium in eight dusty stars in order to test our stellar age estimates.

Laura Vican; Adam Schneider

2014-01-01T23:59:59.000Z

250

Chemistry and line emission of outer protoplanetary disks  

E-Print Network (OSTI)

The structure and chemistry of protoplanetary disks depends strongly on the nature of the central star around which it has formed. The dust temperature is mainly set by the stellar luminosity, while the chemistry of the upper disk layers depends on the amount of intercepted UV and X-ray flux. We will study the differences in chemistry, thermal sturcture and line emission around Herbig Ae/Be, T Tauri stars and low mass M dwarfs. Predictions will be made for future observations with SOFIA and Herschel.

Inga Kamp; Cornelis P. Dullemond; Michiel Hogerheijde; Jesus Emilio Enriquez

2005-09-21T23:59:59.000Z

251

INJECTION OF SUPERNOVA DUST IN NEARBY PROTOPLANETARY DISKS  

SciTech Connect

The early solar system contained a number of short-lived radionuclides (SLRs) such as {sup 26}Al with half-lives <15 Myr. The one-time presence of {sup 60}Fe strongly suggests that the source of these radionuclides was a nearby supernova. In this paper, we investigate the 'aerogel' model, which hypothesizes that the solar system's SLRs were injected directly into the solar system's protoplanetary disk from a supernova within the same star-forming region. Previous work has shown that disks generally survive the impact of supernova ejecta, but also that little gaseous ejecta can be injected into the disk. The aerogel model hypothesizes that radionuclides in the ejecta condensed into micron-sized dust grains that were injected directly into the solar nebula disk. Here, we discuss the density structure of supernova ejecta and the observational support for dust condensation in the ejecta. We argue that supernova ejecta are clumpy and describe a model to quantify this clumpiness. We also argue that infrared observations may be underestimating the fraction of material that condenses into dust. Building on calculations of how supernova ejecta interact with protoplanetary disks, we calculate the efficiency with which dust grains in the ejecta are injected into a disk. We find that about 70% of material in grains roughly 0.4 {mu}m in diameter can be injected into disks. If ejecta are clumpy, the solar nebula was struck by a clump with higher-than-average {sup 26}Al and {sup 60}Fe, and these elements condensed efficiently into large grains, then the abundances of SLRs in the early solar system can be explained, even if the disk lies 2 pc from the supernova explosion. The probability that all these factors are met is low, perhaps {approx}10{sup -3}-10{sup -2}, and receiving as much {sup 26}Al and {sup 60}Fe as the solar system did may be a rare event. Still, the aerogel model remains a viable explanation for the origins of the radionuclides in the early solar system, and may be the most plausible one.

Ouellette, N. [Department of Physics, Arizona State University, P.O. Box 871504, Tempe, AZ 85287-1504 (United States); Desch, S. J.; Hester, J. J. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States)

2010-03-10T23:59:59.000Z

252

Investigation of bit patterned media, thermal flying height control sliders and heat assisted magnetic recording in hard disk drives  

E-Print Network (OSTI)

experienced by sliders flying over disk coated with Z-the concept of one flying head per disk surface [22]. Theseslider when flying over textured magnetic disk media, in

Zheng, Hao

2011-01-01T23:59:59.000Z

253

Investigation of the effect of shock, vibration, surface texture and surface pattern on the dynamics of the head disk interface  

E-Print Network (OSTI)

Figure 7.8: Flying height as a function of disk speed forFigure 7.9: Flying height as a function of disk radius fortextured Flying Head Slider Bearings in Magnetic Hard Disk

Murthy, Aravind N.

2007-01-01T23:59:59.000Z

254

The missing cavities in the SEEDS polarized scattered light images of transitional protoplanetary disks: a generic disk model  

E-Print Network (OSTI)

Transitional circumstellar disks around young stellar objects have a distinctive infrared deficit around 10 microns in their Spectral Energy Distributions (SED), recently measured by the Spitzer Infrared Spectrograph (IRS), suggesting dust depletion in the inner regions. These disks have been confirmed to have giant central cavities by imaging of the submillimeter (sub-mm) continuum emission using the Submillimeter Array (SMA). However, the polarized near-infrared scattered light images for most objects in a systematic IRS/SMA cross sample, obtained by HiCIAO on the Subaru telescope, show no evidence for the cavity, in clear contrast with SMA and Spitzer observations. Radiative transfer modeling indicates that many of these scattered light images are consistent with a smooth spatial distribution for micron-sized grains, with little discontinuity in the surface density of the micron-sized grains at the cavity edge. Here we present a generic disk model that can simultaneously account for the general features in...

Dong, R; Zhu, Z; Hartmann, L; Whitney, B; Brandt, T; Muto, T; Hashimoto, J; Grady, C; Follette, K; Kuzuhara, M; Tanii, R; Itoh, Y; Thalmann, C; Wisniewski, J; Mayama, S; Janson, M; Abe, L; Brandner, W; Carson, J; Egner, S; Feldt, M; Goto, M; Guyon, O; Hayano, Y; Hayashi, M; Hayashi, S; Henning, T; Hodapp, K W; Honda, M; Inutsuka, S; Ishii, M; Iye, M; Kandori, R; Knapp, G R; Kudo, T; Kusakabe, N; Matsuo, T; McElwain, M W; Miyama, S; Morino, J -I; Moro-Martin, A; Nishimura, T; Pyo, T -S; Suto, H; Suzuki, R; Takami, M; Takato, N; Terada, H; Tomono, D; Turner, E L; Watanabe, M; Yamada, T; Takami, H; Usuda, T; Tamura, M

2012-01-01T23:59:59.000Z

255

A Novel Approximation Algorithm for Minimum Geometric Disk Cover Problem with Hexagon Tessellation  

Science Journals Connector (OSTI)

Given a set P ofn...points in the Euclidean plane, the minimum geometric disk cover (MGDC) problem is to identify a minimally sized set of congruent disks with prescribed radiusr that cover all the points in P. I...

Chi-Yu Chang; Chi-Chang Chen; Cheng-Chun Liu

2013-01-01T23:59:59.000Z

256

Room temperature and cryogenic Yb:YAG thin disk laser : single crystal and ceramic.  

E-Print Network (OSTI)

??The focus of this dissertation is to design, optimize and build an efficient high power multi kilowatt thin-disk laser system. We improve the thin-disk beam (more)

Vretenar, Natasa

2012-01-01T23:59:59.000Z

257

The flying height analysis of patterned sliders in magnetic hard disk drives  

Science Journals Connector (OSTI)

The ultra-low spacing of patterned sliders flying above a rotating disk with smooth surface in a hard disk drive is analyzed for high areal density ... slider are solved numerically to obtain the steady flying at...

W.-L. Li; S.-C. Lee; C.-W. Chen; F.-R. Tsai; M.-D. Chen

2005-01-01T23:59:59.000Z

258

Contact and temperature rise of thermal flying height control sliders in hard disk drives  

Science Journals Connector (OSTI)

Contact and interfacial temperature rise upon slider-disk contact in hard disk drives is investigated using thermal flying height control (TFC) sliders. To achieve ... increasing bias. The temperature rise during...

Liane Matthes; Uwe Boettcher; Bernhard Knigge

2012-09-01T23:59:59.000Z

259

Experimental study of sliderdisk interaction process with thermal-flying-height controlled slider  

Science Journals Connector (OSTI)

Thermal flying height (TFC) controlled slider has been introduced in hard disk drive recently. Flying height at the read/write elements of ... protrusion. Interactions between the TFC slider and disk can be very ...

Yansheng Ma; Bo Liu

2011-06-01T23:59:59.000Z

260

Dynamics of air bearing sliders flying on partially planarized bit patterned media in hard disk drives  

Science Journals Connector (OSTI)

Bit patterned media (BPM) recording is one of the promising techniques for future disk drives in order to increase the areal...2.... However, the BPM can change the topography of the disk surface and thus have an...

Liping Li; David B. Bogy

2011-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

E-Print Network 3.0 - accretion disk candidates Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

beamed bright spot on the accretion disk around the compact star. The long... the orbital inclination because the contribution of theM . accretion disk to the observed ux is...

262

E-Print Network 3.0 - accretion disk revealed Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

beamed bright spot on the accretion disk around the compact star. The long... the orbital inclination because the contribution of theM . accretion disk to the observed ux is...

263

Thermoplastic strengthening of a gas-turbine engine disk lock joint. Determination of the residual stresses  

Science Journals Connector (OSTI)

1. A unit has been created for investigating thermoplastic strengthening of turbine disk lock grooves on special...

B. A. Kravchenko; G. N. Gutman; L. E. Batrin; V. G. Fokin

1980-09-01T23:59:59.000Z

264

Modeling Hard-Disk Power Consumption John Zedlewski  

E-Print Network (OSTI)

, exhibit an almost insatiable demand for storage capacity. These devices have traditionally relied-limited. Recent advances in magnetic disk technology have made possible the development of high capacity, small of a note- book computer with a powerful lithium-ion battery, these levels of energy consumption are quite

Krishnamurthy, Arvind

265

General Relativistic Flux Modulations from Disk Instabilities in Sagittarius A*  

E-Print Network (OSTI)

Near-IR and X-ray flares have been detected from the supermassive black hole Sgr A* at the center of our Galaxy with a (quasi)-period of ~17-20 minutes, suggesting an emission region only a few Schwarzschild radii above the event horizon. The latest X-ray flare, detected with XMM-Newton, is notable for its detailed lightcurve, yielding not only the highest quality period thus far, but also important structure reflecting the geometry of the emitting region. Recent MHD simulations of Sgr A*'s disk have demonstrated the growth of a Rossby wave instability, that enhances the accretion rate for several hours, possibly accounting for the observed flares. In this Letter, we carry out ray-tracing calculations in a Schwarzschild metric to determine as accurately as possible the lightcurve produced by general relativistic effects during such a disruption. We find that the Rossby wave induced spiral pattern in the disk is an excellent fit to the data, implying a disk inclination angle of ~77 deg. Note, however, that if this association is correct, the observed period is not due to the underlying Keplerian motion but, rather, to the pattern speed. The favorable comparison between the observed and simulated lightcurves provides important additional evidence that the flares are produced in Sgr A*'s inner disk.

Maurizio Falanga; Fulvio Melia; Michel Tagger; Andrea Goldwurm; Guillaume Belanger

2007-05-02T23:59:59.000Z

266

A probable giant planet imaged in the Beta Pictoris disk  

E-Print Network (OSTI)

Since the discovery of its dusty disk in 1984, Beta Pictoris has become the prototype of young early-type planetary systems, and there are now various indications that a massive Jovian planet is orbiting the star at ~ 10 AU. However, no planets have been detected around this star so far. Our goal was to investigate the close environment of Beta Pic, searching for planetary companion(s). Deep adaptive-optics L'-band images of Beta Pic were recorded using the NaCo instrument at the Very Large Telescope. A faint point-like signal is detected at a projected distance of ~ 8 AU from the star, within the North-East side of the dust disk. Various tests were made to rule out with a good confidence level possible instrumental or atmospheric artifacts. The probability of a foreground or background contaminant is extremely low, based in addition on the analysis of previous deep Hubble Space Telescope images. The object L'=11.2 apparent magnitude would indicate a typical temperature of ~1500 K and a mass of ~ 8 Jovian masses. If confirmed, it could explain the main morphological and dynamical peculiarities of the Beta Pic system. The present detection is unique among A-stars by the proximity of the resolved planet to its parent star. Its closeness and location inside the Beta Pic disk suggest a formation process by core accretion or disk instabilities rather than a binary-like formation process.

A. -M. Lagrange; D. Gratadour; G. Chauvin; T. Fusco; D. Ehrenreich; D. Mouillet; G. Rousset; D. Rouan; F. Allard; E. Gendron; J. Charton; L. Mugnier; P. Rabou; J. Montri; F. Lacombe

2008-11-21T23:59:59.000Z

267

Characterization of Thermal Response Induced by Head/Disk Interaction in Current TGMR Head  

E-Print Network (OSTI)

, resulting in variations in head flying characteristics. Therefore, head- disk interaction in real disk driveCharacterization of Thermal Response Induced by Head/Disk Interaction in Current TGMR Head Suwatana with a lower areal resistance (RA) value. However, as the areal density increases, the actual flying clearance

Kovintavewat, Piya

268

STRAIN SENSING WITH PIEZOELECTRIC ZINC OXIDE THIN FILMS FOR VIBRATION SUPPRESSION IN HARD DISK DRIVES  

E-Print Network (OSTI)

was successfully obtained while the suspension was flying on a disk as in normal drive operation. PreliminarySTRAIN SENSING WITH PIEZOELECTRIC ZINC OXIDE THIN FILMS FOR VIBRATION SUPPRESSION IN HARD DISK This paper describes the integration of thin film ZnO strain sensors onto hard disk drive suspensions

Horowitz, Roberto

269

Formation of Sets and Subsets of Informative Features of Information Carriers with Magnetic Hard Disks*  

E-Print Network (OSTI)

to the substrate. The Protective Layer (PL) improves the flying of the magnetic heads above the magnetic disks Hard Disks* Ognjan Tzarnoretchki, Daniela Borissova Institute of Information Technologies, 1113 Sofia magnetic disk, new informative features are presented, which form a substantial subset of the informative

Borissova, Daniela

270

Limits on iron-dominated fallback disk in SN 1987A  

E-Print Network (OSTI)

The non-detection of a point source in SN1987A imposes an upper limit for the optical luminosity of L=2L_sun. This limits the size of a possible fallback disk around the stellar remnant. Assuming a steady-state thin disk with blackbody emission requires a disk smaller than 100,000 km if the accretion rate is at 30% of the Eddington rate (Graves et al. 2005). We have performed detailed non-LTE radiation transfer calculations to model the disk spectrum more realistically. It turns out that the observational limit on the disk extension becomes even tighter, namely 70,000 km.

K. Werner; T. Nagel; T. Rauch

2007-03-20T23:59:59.000Z

271

THE 0.5-2.22 {mu}m SCATTERED LIGHT SPECTRUM OF THE DISK AROUND TW Hya: DETECTION OF A PARTIALLY FILLED DISK GAP AT 80 AU  

SciTech Connect

We present a 0.5-2.2 {mu}m scattered light spectrum of the circumstellar disk around TW Hya from a combination of spatially resolved Hubble Space Telescope STIS spectroscopy and NICMOS coronagraphic images of the disk. We investigate the morphology of the disk at distances >40 AU over this wide range of wavelengths, and identify the presence of a depression in surface brightness at {approx}80 AU that could be caused by a gap in the disk. Additionally, we quantify the surface brightness, azimuthal symmetry, and spectral character of the disk as a function of radius. Our analysis shows that the scattering efficiency of the dust is largely neutral to blue over the observed wavelengths. We model the disk as a steady {alpha}-disk with an ad hoc gap structure. The thermal properties of the disk are self-consistently calculated using a three-dimensional radiative transfer code that uses ray tracing to model the heating of the disk interior and scattered light images. We find a good fit to the data over a wide range of distances from the star if we use a model disk with a partially filled gap of 30% depth at 80 AU and with a self-similar truncation knee at 100 AU. The origin of the gap is unclear, but it could arise from a transition in the nature of the disk's dust composition or the presence of a planetary companion. Based on scalings to previous hydrodynamic simulations of gap-opening criteria for embedded proto-planets, we estimate that a planetary companion forming the gap could have a mass between 6 and 28 M{sub Circled-Plus }.

Debes, John H. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Jang-Condell, Hannah [University of Wyoming, Laramie, WY 82071 (United States); Weinberger, Alycia J. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Roberge, Aki [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Schneider, Glenn [Steward Observatory, University of Arizona, Tuscon, AZ 85721 (United States)

2013-07-01T23:59:59.000Z

272

Galaxies that Shine: radiation-hydrodynamical simulations of disk galaxies  

E-Print Network (OSTI)

Radiation feedback is typically implemented using subgrid recipes in hydrodynamical simulations of galaxies. Very little work has so far been performed using radiation-hydrodynamics (RHD), and there is no consensus on the importance of radiation feedback in galaxy evolution. We present RHD simulations of isolated galaxy disks of different masses with a resolution of 18 pc. Besides accounting for supernova feedback, our simulations are the first galaxy-scale simulations to include RHD treatments of photo-ionisation heating and radiation pressure, from both direct optical/UV radiation and multi-scattered, re-processed infrared (IR) radiation. Photo-heating smooths and thickens the disks and suppresses star formation about as much as the inclusion of ("thermal dump") supernova feedback does. These effects decrease with galaxy mass and are mainly due to the prevention of the formation of dense clouds, as opposed to their destruction. Radiation pressure, whether from direct or IR radiation, has little effect, but ...

Rosdahl, Joakim; Teyssier, Romain; Agertz, Oscar

2015-01-01T23:59:59.000Z

273

Tribo-chemistry at the head/disk interface  

SciTech Connect

Tribo-chemical studies at the head/disk interface (HDI) were conducted on hydrogenated (CH{sub x}), nitrogenated (CN{sub x}), and cathodic-arc amorphous hard carbon disk samples coated with perfluoropolyether ZDOL and X1P/ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated Al{sub 2}O{sub 3}-TiC sliders and thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber followed with a surface chemistry analysis by X-ray Photo Emission Electron Microscopy (X-PEEM) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The friction and catalytic decomposition mechanisms of ZDOL are described, as well as the tribo-chemical performance of cathodic-arc carbon overcoats coated with ZDOL, and data demonstrating the chemical alteration of the lubricant and carbon overcoat are also presented.

Bhatia, C.S. [SSD/IBM, San Jose, CA (United States)] [SSD/IBM, San Jose, CA (United States); Fong, W.; Chen, C.Y.; Wei, J.; Bogy, D.B. [Univ. of California, Berkeley, CA (United States). Computer Mechanics Lab.] [Univ. of California, Berkeley, CA (United States). Computer Mechanics Lab.; Anders, S.; Stammler, T. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States); Stoehr, J. [IBM Research Div., San Jose, CA (United States)] [IBM Research Div., San Jose, CA (United States)

1999-03-01T23:59:59.000Z

274

THE MASS DEPENDENCE BETWEEN PROTOPLANETARY DISKS AND THEIR STELLAR HOSTS  

SciTech Connect

We present a substantial extension of the millimeter (mm) wave continuum photometry catalog for circumstellar dust disks in the Taurus star-forming region, based on a new ''snapshot'' {lambda} = 1.3 mm survey with the Submillimeter Array. Combining these new data with measurements in the literature, we construct a mm-wave luminosity distribution, f(L{sub mm}), for Class II disks that is statistically complete for stellar hosts with spectral types earlier than M8.5 and has a 3{sigma} depth of roughly 3 mJy. The resulting census eliminates a longstanding selection bias against disks with late-type hosts, and thereby demonstrates that there is a strong correlation between L{sub mm} and the host spectral type. By translating the locations of individual stars in the Hertzsprung-Russell diagram into masses and ages, and adopting a simple conversion between L{sub mm} and the disk mass, M{sub d} , we confirm that this correlation corresponds to a statistically robust relationship between the masses of dust disks and the stars that host them. A Bayesian regression technique is used to characterize these relationships in the presence of measurement errors, data censoring, and significant intrinsic scatter: the best-fit results indicate a typical 1.3 mm flux density of {approx}25 mJy for 1 M{sub Sun} hosts and a power-law scaling L{sub mm}{proportional_to}M{sub *}{sup 1.5-2.0}. We suggest that a reasonable treatment of dust temperature in the conversion from L{sub mm} to M{sub d} favors an inherently linear M{sub d} {proportional_to}M{sub *} scaling, with a typical disk-to-star mass ratio of {approx}0.2%-0.6%. The measured rms dispersion around this regression curve is {+-}0.7 dex, suggesting that the combined effects of diverse evolutionary states, dust opacities, and temperatures in these disks imprint a full width at half-maximum range of a factor of {approx}40 on the inferred M{sub d} (or L{sub mm}) at any given host mass. We argue that this relationship between M{sub d} and M{sub *} likely represents the origin of the inferred correlation between giant planet frequency and host star mass in the exoplanet population, and provides some basic support for the core accretion model for planet formation. Moreover, we caution that the effects of incompleteness and selection bias must be considered in comparative studies of disk evolution, and illustrate that fact with statistical comparisons of f(L{sub mm}) between the Taurus catalog presented here and incomplete subsamples in the Ophiuchus, IC 348, and Upper Sco young clusters.

Andrews, Sean M.; Rosenfeld, Katherine A.; Kraus, Adam L.; Wilner, David J., E-mail: sandrews@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-07-10T23:59:59.000Z

275

Adaptor assembly for coupling turbine blades to rotor disks  

DOE Patents (OSTI)

An adaptor assembly for coupling a blade root of a turbine blade to a root slot of a rotor disk is described. The adaptor assembly includes a turbine blade having a blade root and an adaptor body having an adaptor root. The adaptor body defines a slot having an open end configured to receive the blade root of the turbine blade such that the adaptor root of the adaptor body and the blade root of the turbine blade are adjacent to one another when the blade root of the turbine blade is positioned within the slot. Both the adaptor root of the adaptor body and the blade root of the turbine blade are configured to be received within the root slot of the rotor disk.

Garcia-Crespo, Andres Jose; Delvaux, John McConnell

2014-09-23T23:59:59.000Z

276

Fracture toughness measurements with subsize disk compact specimens  

SciTech Connect

Special fixtures and test methods have been developed for testing small disk compact specimens (1.25 mm diam by 4.6 mm thick). Specimens of European type 316L austenitic stainless steel were irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 or 250 C and tested over a temperature range from 20 to 250 C. Results show that irradiation to this dose level at these temperatures reduces the fracture toughness but the toughness remains quite high. The toughness decreases as the test temperature increases. Irradiation at 250 C is more damaging than at 90 C, causing larger decreases in the fracture toughness. The testing shows that it is possible to generate useful fracture toughness data with a small disk compact specimens.

Alexander, D.J.

1994-12-31T23:59:59.000Z

277

Kinematics of classical Cepheids in the Nuclear Stellar Disk  

E-Print Network (OSTI)

Classical Cepheids are useful tracers of the Galactic young stellar population because their distances and ages can be determined from their period-luminosity and period-age relations. In addition, the radial velocities and chemical abundance of the Cepheids can be derived from spectroscopic observations, providing further insights into the structure and evolution of the Galaxy. Here, we report the radial velocities of classical Cepheids near the Galactic Center, three of which were reported in 2011, the other reported for the first time. The velocities of these Cepheids suggest that the stars orbit within the Nuclear Stellar Disk, a group of stars and interstellar matter occupying a region of 200 pc around the Center, although the three-dimensional velocities cannot be determined until the proper motions are known. According to our simulation, these four Cepheids formed within the Nuclear Stellar Disk like younger stars and stellar clusters therein.

Matsunaga, N; Yamamoto, R; Kobayashi, N; Inno, L; Genovali, K; Bono, G; Baba, J; Fujii, M S; Kondo, S; Ikeda, Y; Hamano, S; Nishiyama, S; Nagata, T; Aoki, W; Tsujimoto, T

2014-01-01T23:59:59.000Z

278

Wet-steam erosion of steam turbine disks and shafts  

SciTech Connect

A study of wet-steam erosion of the disks and the rotor bosses or housings of turbines in thermal and nuclear power plants shows that the rate of wear does not depend on the diagrammed degree of moisture, but is determined by moisture condensing on the surfaces of the diaphragms and steam inlet components. Renovating the diaphragm seals as an assembly with condensate removal provides a manifold reduction in the erosion.

Averkina, N. V. [JSC 'NPO TsKTI' (Russian Federation); Zheleznyak, I. V. [Leningradskaya AES branch of JSC 'Kontsern Rosenergoatom' (Russian Federation); Kachuriner, Yu. Ya.; Nosovitskii, I. A.; Orlik, V. G., E-mail: orlikvg@mail.ru [JSC 'NPO TsKTI' (Russian Federation); Shishkin, V. I. [Leningradskaya AES branch of JSC 'Kontsern Rosenergoatom' (Russian Federation)

2011-01-15T23:59:59.000Z

279

Massive Pellet and Rupture Disk Testing for Disruption Mitigation Applications  

SciTech Connect

Injection of massive quantities of noble gases or D2 has proven to be effective at mitigating some of the deleterious effects of disruptions in tokamaks. Two alternative methods that might offer some advantages over the present technique for massive gas injection are shattering massive pellets and employing close-coupled rupture disks. Laboratory testing has been carried out to evaluate their feasibility. For the study of massive pellets, a pipe gun pellet injector cooled with a cryogenic refrigerator was fitted with a relatively large barrel (16.5 mm bore), and D2 and Ne pellets were made and were accelerated to speeds of ~600 and 300 m/s, respectively. Based on the successful proof-of-principle testing with the injector and a special double-impact target to shatter pellets, a similar system has been prepared and installed on DIII-D and should be ready for experiments later this year. To study the applicability of rupture disks for disruption mitigation, a simple test apparatus was assembled in the lab. Commercially available rupture disks of 1 in. nominal diameter were tested at conditions relevant for the application on tokamaks, including tests with Ar and He gases and rupture pressures of ~54 bar. Some technical and practical issues of implementing this technique on a tokamak are discussed.

Combs, Stephen Kirk [ORNL] [ORNL; Meitner, Steven J [ORNL] [ORNL; Baylor, Larry R [ORNL] [ORNL; Caughman, John B [ORNL] [ORNL; Commaux, Nicolas JC [ORNL] [ORNL; Fehling, Dan T [ORNL] [ORNL; Foust, Charles R [ORNL] [ORNL; Jernigan, Thomas C [ORNL] [ORNL; McGill, James M [ORNL] [ORNL; Parks, P. B. [General Atomics] [General Atomics; Rasmussen, David A [ORNL] [ORNL

2009-01-01T23:59:59.000Z

280

GALACTOSEISMOLOGY: DISCOVERY OF VERTICAL WAVES IN THE GALACTIC DISK  

SciTech Connect

We present evidence for a Galactic North-South asymmetry in the number density and bulk velocity of solar neighborhood stars. The number density profile, which is derived from main-sequence stars in the Sloan Digital Sky Survey, shows a (North-South)/(North+South) deficit at |z| {approx_equal} 400 pc and an excess at |z| {approx} 800 pc. The bulk velocity profile, which is derived from the Sloan Extension for Galactic Understanding and Exploration, shows a gradual trend across the Galactic midplane as well as smaller-scale features. We speculate that the North-South asymmetry, which has the appearance of a wavelike perturbation, is intrinsic to the disk. We explore the physics of this phenomenon through an analysis of the linearized Boltzmann and Poisson equations and through one-dimensional simulations. The perturbation may be excited by the passage of a satellite galaxy or dark matter subhalo through the Galactic disk, in which case we are witnessing a recent disk-heating event.

Widrow, Lawrence M. [Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, ON K7L 3N6 (Canada); Gardner, Susan [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States); Yanny, Brian; Dodelson, Scott [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Chen, Hsin-Yu [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

2012-05-10T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

The dynamical structure of HR 8799's inner debris disk  

E-Print Network (OSTI)

The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 million years. These simulations have enabled the characterisation of the extent and st...

Contro, Bruna; Horner, Jonti; Marshall, Jonathan P

2015-01-01T23:59:59.000Z

282

Stationary Nonaxisymmetric Configurations of Magnetized Singular Isothermal Disks  

E-Print Network (OSTI)

Accepted.... Received...; in original form... We construct both aligned and unaligned (logarithmic spiral) stationary configurations of nonaxisymmetric magnetohydrodynamic (MHD) disks from either a full or a partial razor-thin power-law axisymmetric magnetized singular isothermal disk (MSID) that is embedded with a coplanar azimuthal magnetic field B? of a non-force-free radial scaling r?1/2 and that rotates differentially with a flat rotation curve of speed aD, where a is the isothermal sound speed and D is the dimensionless rotation parameter. Analytical solutions and stability criteria for determining D2 are derived. For aligned nonaxisymmetric MSIDs, eccentric m = 1 displacements may occur at arbitrary D2 in a full MSID but are allowed only with a2D2 = C2 A /2 in a partial MSID (CA is the Alfvn speed), while each case of |m | ? 1 gives two possible values of D2 for purely azimuthal propagations of fast and slow MHD density waves (FMDWs and SMDWs) that appear stationary in an inertial frame of reference. For disk galaxies modeled by a partial MSID resulting from a massive dark-matter halo with a flat rotation curve and a2D2 ? C2 A, stationary aligned perturbations of m = 1 are not allowed. For

Yu-qing Lou

2003-01-01T23:59:59.000Z

283

Laser illuminator and optical system for disk patterning  

SciTech Connect

Magnetic recording media are textured over areas designated for contact in order to minimize friction with data transducing heads. In fabricating a hard disk, an aluminum nickel-phosphorous substrate is polished to a specular finish. A mechanical means is then used to roughen an annular area intended to be the head contact band. An optical and mechanical system allows thousands of spots to be generated with each laser pulse, allowing the textured pattern to be rapidly generated with a low repetition rate laser and an uncomplicated mechanical system. The system uses a low power laser, a beam expander, a specially designed phase plate, a prism to deflect the beam, a lens to transmit the diffraction pattern to the far field, a mechanical means to rotate the pattern and a trigger system to fire the laser when sections of the pattern are precisely aligned. The system generates an annular segment of the desired pattern with which the total pattern is generated by rotating the optical system about its optic axis, sensing the rotational position and firing the laser as the annular segment rotates into the next appropriate position. This marking system can be integrated into a disk sputtering system for manufacturing magnetic disks, allowing for a very streamlined manufacturing process.

Hackel, L.A.; Dane, C.B.; Dixit, S.N.; Everett, M.; Honig, J.

2000-03-14T23:59:59.000Z

284

Disk-averaged Spectra & light-curves of Earth  

E-Print Network (OSTI)

We are using computer models to explore the observational sensitivity to changes in atmospheric and surface properties, and the detectability of biosignatures, in the globally averaged spectra and light-curves of the Earth. Using AIRS (Atmospheric Infrared Sounder) data, as input for atmospheric and surface properties, we have generated spatially resolved high-resolution synthetic spectra using the SMART radiative transfer model, for a variety of conditions, from the UV to the far-IR (beyond the range of current Earth-based satellite data). We have then averaged over the visible disk for a number of different viewing geometries to quantify the sensitivity to surface types and atmospheric features as a function of viewing geometry, and spatial and spectral resolution. These results have been processed with an instrument simulator to improve our understanding of the detectable characteristics of Earth-like planets as viewed by the first generation extrasolar terrestrial planet detection and characterization missions (Terrestrial Planet Finder/Darwin and Life finder). The wavelength range of our results are modelled over are applicable to both the proposed visible coronograph and mid-infrared interferometer TPF architectures. We have validated this model against disk-averaged observations by the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES). This model was also used to analyze Earth-shine data for detectability of planetary characteristics and biosignatures in disk-averaged spectra.

G. Tinetti; V. S. Meadows; D. Crisp; W. Fong; N. Kiang; E. Fishbein; T. Velusamy; E. Bosc; M. Turnbull

2005-02-11T23:59:59.000Z

285

Star Cluster Populations in the Outer Disks of Nearby Galaxies  

E-Print Network (OSTI)

We present a Large Binocular Telescope (LBT) imaging study that characterizes the star cluster component of nearby galaxy outer disks (beyond the optical radius R_25). Expanding on the pilot project of Herbert-Fort et al. (2009), we present deep (~ 27.5 mag V-band point-source limiting magnitude) U- and V-band imaging of six galaxies: IC 4182, NGC 3351, NGC 4736, NGC 4826, NGC 5474, and NGC 6503. We find that the outer disk of each galaxy is populated with marginally-resolved star clusters with masses ~10^3 M_sun and ages up to ~ 1 Gyr (masses and ages are limited by the depth of our imaging and uncertainties are large given how photometry can be strongly affected by the presence or absence of a few stars in such low mass systems), and that they are typically found out to at least 2 R_25 but sometimes as far as 3 to 4 R_25- even beyond the apparent HI disk. The mean rate of cluster formation for 1 R_25<= R <= 1.5R_25 is at least one every ~2.5 Myr and the clusters are spatially correlated with the HI, m...

Herbert-Fort, Stphane; Moustakas, John; Di Paola, Andrea; Pogge, Richard W; Ragazzoni, Roberto

2012-01-01T23:59:59.000Z

286

Laser illuminator and optical system for disk patterning  

DOE Patents (OSTI)

Magnetic recording media are textured over areas designated for contact in order to minimize friction with data transducing heads. In fabricating a hard disk, an aluminum nickel-phosphorous substrate is polished to a specular finish. A mechanical means is then used to roughen an annular area intended to be the head contact band. An optical and mechanical system allows thousands of spots to be generated with each laser pulse, allowing the textured pattern to be rapidly generated with a low repetition rate laser and an uncomplicated mechanical system. The system uses a low power laser, a beam expander, a specially designed phase plate, a prism to deflect the beam, a lens to transmit the diffraction pattern to the far field, a mechanical means to rotate the pattern and a trigger system to fire the laser when sections of the pattern are precisely aligned. The system generates an annular segment of the desired pattern with which the total pattern is generated by rotating the optical system about its optic axis, sensing the rotational position and firing the laser as the annular segment rotates into the next appropriate position. This marking system can be integrated into a disk sputtering system for manufacturing magnetic disks, allowing for a very streamlined manufacturing process.

Hackel, Lloyd A. (Livermore, CA); Dane, C. Brent (Livermore, CA); Dixit, Shamasundar N. (Livermore, CA); Everett, Mathew (Pleasanton, CA); Honig, John (Livermore, CA)

2000-01-01T23:59:59.000Z

287

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)

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.

Giovanni Santostasi

2008-07-16T23:59:59.000Z

288

DISK EVOLUTION IN THE THREE NEARBY STAR-FORMING REGIONS OF TAURUS, CHAMAELEON, AND OPHIUCHUS  

SciTech Connect

We analyze samples of Spitzer Infrared Spectrograph spectra of T Tauri stars in the Ophiuchus, Taurus, and Chamaeleon I star-forming regions, whose median ages lie in the <1-2 Myr range. The median mid-infrared spectra of objects in these three regions are similar in shape, suggesting, on average, similar disk structures. When normalized to the same stellar luminosity, the medians follow each other closely, implying comparable mid-infrared excess emission from the circumstellar disks. We use the spectral index between 13 and 31 {mu}m and the equivalent width of the 10 {mu}m silicate emission feature to identify objects whose disk configuration departs from that of a continuous, optically thick accretion disk. Transitional disks, whose steep 13-31 {mu}m spectral slope and near-IR flux deficit reveal inner disk clearing, occur with about the same frequency of a few percent in all three regions. Objects with unusually large 10 {mu}m equivalent widths are more common (20%-30%); they could reveal the presence of disk gaps filled with optically thin dust. Based on their medians and fraction of evolved disks, T Tauri stars in Taurus and Chamaeleon I are very alike. Disk evolution sets in early, since already the youngest region, the Ophiuchus core (L1688), has more settled disks with larger grains. Our results indicate that protoplanetary disks show clear signs of dust evolution at an age of a few Myr, even as early as approx1 Myr, but age is not the only factor determining the degree of evolution during the first few million years of a disk's lifetime.

Furlan, E. [NASA Astrobiology Institute, and Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Watson, Dan M.; McClure, M. K., E-mail: Elise.Furlan@jpl.nasa.go, E-mail: dmw@pas.rochester.ed, E-mail: manoj@pas.rochester.ed [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

2009-10-01T23:59:59.000Z

289

NEAR-INFRARED DETECTION OF A SUPER-THIN DISK IN NGC 891  

SciTech Connect

We probe the disk structure of the nearby, massive, edge-on spiral galaxy NGC 891 with subarcsecond resolution JHK{sub s}-band images covering {approx} {+-}10 kpc in radius and {+-}5 kpc in height. We measure intrinsic surface brightness (SB) profiles using realistic attenuation corrections constrained from near- and mid-infrared (Spitzer) color maps and three-dimensional Monte Carlo radiative-transfer models. In addition to the well-known thin and thick disks, a super-thin disk with 60-80 pc scale-height-comparable to the star-forming disk of the Milky Way-is visibly evident and required to fit the attenuation-corrected light distribution. Asymmetries in the super-thin disk light profile are indicative of young, hot stars producing regions of excess luminosity and bluer (attenuation-corrected) near-infrared color. To fit the inner regions of NGC 891, these disks must be truncated within {approx}3 kpc, with almost all their luminosity redistributed in a bar-like structure 50% thicker than the thin disk. There appears to be no classical bulge but rather a nuclear continuation of the super-thin disk. The super-thin, thin, thick, and bar components contribute roughly 30%, 42%, 13%, and 15% (respectively) to the total K{sub s}-band luminosity. Disk axial ratios (length/height) decrease from 30 to 3 from super-thin to thick components. Both exponential and sech{sup 2} vertical SB profiles fit the data equally well. We find that the super-thin disk is significantly brighter in the K{sub s}-band than typically assumed in integrated spectral energy distribution models of NGC 891: it appears that in these models the excess flux, likely produced by young stars in the super-thin disk, has been mistakenly attributed to the thin disk.

Schechtman-Rook, Andrew; Bershady, Matthew A., E-mail: andrew@astro.wisc.edu [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States)

2013-08-10T23:59:59.000Z

290

Compact ultrafast semiconductor disk laser: targeting GFP based nonlinear applications in living organisms  

Science Journals Connector (OSTI)

We present a portable ultrafast Semiconductor Disk Laser (SDL) (or vertical extended cavity surface emitting laserVECSELs), to be used for nonlinear microscopy. The SDL is...

Aviles-Espinosa, Rodrigo; Filippidis, George; Hamilton, Craig; Malcolm, Graeme; Weingarten, Kurt J; Sdmeyer, Thomas; Barbarin, Yohan; Keller, Ursula; Santos, Susana I C O; Artigas, David; Loza-Alvarez, Pablo

2011-01-01T23:59:59.000Z

291

Application of the Cubed-Sphere Grid to Tilted Black-Hole Accretion Disks  

SciTech Connect

In recent work we presented the first results of global general relativistic magnetohydrodynamic (GRMHD) simulations of tilted (or misaligned) accretion disks around rotating black holes. The simulated tilted disks showed dramatic differences from comparable untilted disks, such as asymmetrical accretion onto the hole through opposing 'plunging streams' and global precession of the disk powered by a torque provided by the black hole. However, those simulations used a traditional spherical-polar grid that was purposefully underresolved along the pole, which prevented us from assessing the behavior of any jets that may have been associated with the tilted disks. To address this shortcoming we have added a block-structured 'cubed-sphere' grid option to the Cosmos++ GRMHD code, which will allow us to simultaneously resolve the disk and polar regions. Here we present our implementation of this grid and the results of a small suite of validation tests intended to demonstrate that the new grid performs as expected. The most important test in this work is a comparison of identical tilted disks, one evolved using our spherical-polar grid and the other with the cubed-sphere grid. We also demonstrate an interesting dependence of the early-time evolution of our disks on their orientation with respect to the grid alignment. This dependence arises from the differing treatment of current sheets within the disks, especially whether they are aligned with symmetry planes of the grid or not.

Fragile, P C; Lindner, C C; Anninos, P; Salmonson, J D

2008-09-24T23:59:59.000Z

292

A rotating disk around the very young massive star AFGL 490  

E-Print Network (OSTI)

We observed the embedded, young 8--10 Msun star AFGL 490 at subarcsecond resolution with the Plateau de Bure Interferometer in the C17O (2--1) transition and found convincing evidence that AFGL 490 is surrounded by a rotating disk. Using two-dimensional modeling of the physical and chemical disk structure coupled to line radiative transfer, we constrain its basic parameters. We obtain a relatively high disk mass of 1 Msun and a radius of ~ 1500 AU. A plausible explanation for the apparent asymmetry of the disk morphology is given.

K. Schreyer; D. Semenov; Th. Henning; J. Forbrich

2006-01-12T23:59:59.000Z

293

E-Print Network 3.0 - accretion disk emission Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

the accretion disk and the white dwarf) is irradiated and is a source of emission lines (Dhillon... lines originate primarily in an extended bright spot, with weaker emission...

294

E-Print Network 3.0 - accretion disk instability Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Queen Mary, University of London Collection: Physics 29 Accretion Disk Evolution with Wind Infall II. Results of 3D Hydrodynamical Simulations with an Illustrative Application...

295

E-Print Network 3.0 - agn accretion-disk outflows Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Jet NLR clouds BLR clouds 1 pc Accretion disk 12... .g., Reyolds & Nowak 2003) 2) The inclination ... Source: Evans, Daniel A. - Kavli Institute for Astrophysics and Space...

296

E-Print Network 3.0 - advection-dominated accretion disks Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

Universit Paris 7 Denis Diderot Collection: Physics 5 Accretion Disk Evolution with Wind Infall II. Results of 3D Hydrodynamical Simulations with an Illustrative Application...

297

E-Print Network 3.0 - accretion disks formed Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

California Institute of Technology Collection: Physics 36 Accretion Disk Evolution With Wind Infall I. General Solution and Application to Sgr A* Summary: , slowly accreting,...

298

E-Print Network 3.0 - accretion disk structure Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Physics Laboratory Collection: Plasma Physics and Fusion 27 Accretion Disk Evolution With Wind Infall I. General Solution and Application to Sgr A* Summary: and thus change the...

299

E-Print Network 3.0 - accretion disk spectra Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

along the magnetic field lines (of stellar andor disk... an outflow (stellardisk wind) andor from the accreting columns. However, because of insufficient spectral......

300

E-Print Network 3.0 - agn accretion disks Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

Accretion disk? (pc Rs) 12; Accretion flow surrounded by dusty torus BB... ) The inclination of the accretion ... Source: Evans, Daniel A. - Kavli Institute for...

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Nanoscale Graphene Disk: A Natural Functionally Graded Material --The Thermal Conductivity of Nanoscale Graphene Disk by Molecular Dynamics Simulation  

E-Print Network (OSTI)

In this letter, we investigate numerically (by non-equilibrium molecular dynamics) and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize FGM with only one material, NGDs. We found that the NGD has a graded thermal conductivity and can be used as FGM in a large temperature range. Moreover, we show the dependent of NGDs' thermal conductivity on radius and temperature. Our study may inspire experimentalists to develop NGD based FGMs and help heat removal of hot spots on chips by graphene.

Yang, Nuo; Ma, Dengke; Lu, Tingyu; Li, Baowen

2014-01-01T23:59:59.000Z

302

REEXAMINATION OF INDUCTION HEATING OF PRIMITIVE BODIES IN PROTOPLANETARY DISKS  

SciTech Connect

We reexamine the unipolar induction mechanism for heating asteroids originally proposed in a classic series of papers by Sonett and collaborators. As originally conceived, induction heating is caused by the 'motional electric field' that appears in the frame of an asteroid immersed in a fully ionized, magnetized solar wind and drives currents through its interior. However, we point out that classical induction heating contains a subtle conceptual error, in consequence of which the electric field inside the asteroid was calculated incorrectly. The problem is that the motional electric field used by Sonett et al. is the electric field in the freely streaming plasma far from the asteroid; in fact, the motional field vanishes at the asteroid surface for realistic assumptions about the plasma density. In this paper we revisit and improve the induction heating scenario by (1) correcting the conceptual error by self-consistently calculating the electric field in and around the boundary layer at the asteroid-plasma interface; (2) considering weakly ionized plasmas consistent with current ideas about protoplanetary disks; and (3) considering more realistic scenarios that do not require a fully ionized, powerful T Tauri wind in the disk midplane. We present exemplary solutions for two highly idealized flows that show that the interior electric field can either vanish or be comparable to the fields predicted by classical induction depending on the flow geometry. We term the heating driven by these flows 'electrodynamic heating', calculate its upper limits, and compare them to heating produced by short-lived radionuclides.

Menzel, Raymond L.; Roberge, Wayne G., E-mail: menzer@rpi.edu, E-mail: roberw@rpi.edu [New York Center for Astrobiology and Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States)

2013-10-20T23:59:59.000Z

303

THE FREQUENCY OF DEBRIS DISKS AT WHITE DWARFS  

SciTech Connect

We present near- and mid-infrared photometry and spectroscopy from PAIRITEL, IRTF, and Spitzer of a metallicity-unbiased sample of 117 cool, hydrogen-atmosphere white dwarfs (WDs) from the Palomar-Green survey and find five with excess radiation in the infrared, translating to a 4.3{sup +2.7} {sub -1.2}% frequency of debris disks. This is slightly higher than, but consistent with the results of previous surveys. Using an initial-final mass relation, we apply this result to the progenitor stars of our sample and conclude that 1-7 M {sub Sun} stars have at least a 4.3% chance of hosting planets; an indirect probe of the intermediate-mass regime eluding conventional exoplanetary detection methods. Alternatively, we interpret this result as a limit on accretion timescales as a fraction of WD cooling ages; WDs accrete debris from several generations of disks for {approx}10 Myr. The average total mass accreted by these stars ranges from that of 200 km asteroids to Ceres-sized objects, indicating that WDs accrete moons and dwarf planets as well as solar system asteroid analogs.

Barber, Sara D.; Patterson, Adam J.; Kilic, Mukremin [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Leggett, S. K. [Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720 (United States); Dufour, P. [Departement de Physique, Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec H3C 3J7 (Canada); Bloom, J. S.; Starr, D. L., E-mail: barber@nhn.ou.edu [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

2012-11-20T23:59:59.000Z

304

DRPM: Dynamic Speed Control for Power Management in Server Class Disks Sudhanva Gurumurthi  

E-Print Network (OSTI)

[5] that power densities of data centers could grow to over 100 Watts per square foot and that the caDRPM: Dynamic Speed Control for Power Management in Server Class Disks Sudhanva Gurumurthi portion of the power budget in server environ- ments goes into the I/O subsystem - the disk array in par

Sivasubramaniam, Anand

305

Dynamic Speed Control for Server Class Disks Sudhanva Gurumurthi Anand Sivasubramaniam Mahmut Kandemir  

E-Print Network (OSTI)

been observed [5] that power densities of data centers could grow to over 100 Watts per square foot Abstract A large portion of the power budget in server environments goes into the I/O subsystem - the disk array in particular. Traditional approaches to disk power management involve completely stopping

Gurumurthi, Sudhanva

306

ApJ, accepted 16 March 1999 A 1000 AU Rotating Disk around the  

E-Print Network (OSTI)

a luminosity #24; 3 #2; 10 3 L#12; which implies the presence of a mid to early B star (Shepherd & Churchwell.16 3.82 D.S. Shepherd 1 & S. E. Kurtz 2 ABSTRACT We present evidence for a circumstellar disk around exists around the central B2 star. The disk major axis is roughly perpendicular to the out ow

Shepherd, Debra

307

The Conquest File System: Better Performance Through a Disk/Persistent-RAM Hybrid Design  

E-Print Network (OSTI)

memory, except providing large storage capacity. Unlike caching, Conquest uses memory with battery backup storage capacity is advancing at a rapid rate, the mechanical latency of disk has improved only at 15% per as persistent storage, and provides specialized and separate data paths to memory and disk. Therefore

Wang, Andy

308

Distributed Mobile Disk Cover A Building Block for Mobile Backbone Networks  

E-Print Network (OSTI)

1 Distributed Mobile Disk Cover ­ A Building Block for Mobile Backbone Networks Anand Srinivas, Gil of Mobile Backbone Networks has been recently studied by a few different approaches. An important subproblem a Geometric Disk Cover (GDC) under mobility. While from the context of static nodes and centralized solutions

Zussman, Gil

309

GRAVITATIONAL DRAG ON A POINT MASS IN HYPERSONIC MOTION WITHIN A GAUSSIAN DISK  

SciTech Connect

We develop an analytical model for the accretion and gravitational drag on a point mass that moves hypersonically in the midplane of a gaseous disk with a Gaussian vertical density stratification. Such a model is of interest for studying the interaction between a planet and a protoplanetary disk, as well as the dynamical decay of massive black holes in galactic nuclei. The model assumes that the flow is ballistic, and gives fully analytical expressions for both the accretion rate onto the point mass and the gravitational drag it suffers. The expressions are further simplified by taking the limits of a thick and of a thin disk. The results for the thick disk reduce correctly to those for a uniform density environment. We find that for a thin disk (small vertical scaleheight compared to the gravitational radius), the accretion rate is proportional to the mass of the moving object and to the surface density of the disk, while the drag force is independent of the velocity of the object. The gravitational deceleration of the hypersonic perturber in a thin disk was found to be independent of its parameters (i.e., mass or velocity) and depends only on the surface mass density of the disk. The predictions of the model are compared to the results of three-dimensional hydrodynamical simulations, with reasonable agreement.

Canto, J.; Sanchez-Salcedo, F. J. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-468, 04510 D.F. (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-468, 04510 D.F. (Mexico); Esquivel, A.; Raga, A. C., E-mail: jsanchez@astro.unam.mx, E-mail: esquivel@nucleares.una.mx, E-mail: raga@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico D.F. (Mexico)

2013-01-01T23:59:59.000Z

310

Accretion Disk Evolution With Wind Infall I. General Solution and Application to Sgr A*  

E-Print Network (OSTI)

The evolution of an accretion disk can be influenced significantly by the deposition of mass and angular momentum by an infalling Bondi-Hoyle wind. Such a mass influx impacts the long-term behavior of the disk by providing additional sources of viscosity and heating. In this paper, we derive and solve the disk equations when these effects are taken into account. We present a survey of models with various wind configurations and demonstrate that the disk spectrum may then differ substantially from that of a standard alpha-disk. In particular, it is likely that a wind-fed disk has a significant infrared bump due to the deposition of energy in its outer region. We apply some of the results of our calculations to the Galactic Center black hole candidate Sgr A* and show that if a fossil disk is present in this source, it must have a very low viscosity parameter (alpha<10^-4) and the Bondi-Hoyle wind must be accreting with a very high specific angular momentum to prevent it from circularizing in the inner disk region where its impact would be most noticeable.

Heino Falcke; Fulvio Melia

1996-11-12T23:59:59.000Z

311

arXiv:astro-ph/0508261v111Aug2005 THE OPACITY OF SPIRAL GALAXY DISKS  

E-Print Network (OSTI)

Figure 2 shows the stacked radial opacity profile of our entire sample of 32 HST/WFPC2 fields. FromarXiv:astro-ph/0508261v111Aug2005 THE OPACITY OF SPIRAL GALAXY DISKS Dust opacity from calibrated Abstract The opacity of foreground spiral disks can be probed from the number of distant galaxies seen

Kruit, Piet van der

312

Deep Spitzer spectroscopy of the `Flying Saucer' edge-on disk: Large grains beyond 50 AU  

E-Print Network (OSTI)

We present deep Spitzer-IRS low-resolution (lambda/Delta lambda ~ 100) 5-35 micron spectroscopy of the edge-on disk ``the Flying Saucer'' (2MASS J16281370-2431391) in the Ophiuchus molecular cloud. The spectral energy distribution exhibits the characteristic two-peak shape predicted for a circumstellar disk viewed very close to edge-on. The short-wavelength peak is entirely due to photons scattered off the surface of the disk, while the long-wavelength peak is due to thermal emission from the disk itself. The Spitzer spectrum represents the first spectroscopic detection of scattered light out to 15 micron from a bona-fide, isolated edge-on disk around a T Tauri star. The depth and the wavelength of the mid-infrared "valley" of the SED give direct constraints on the size distribution of large grains in the disk. Using a 2D continuum radiative transfer model, we find that a significant amount of 5-10 micron-sized grains is required in the surface layers of the disk at radii of 50-300 AU. The detection of relatively large grains in the upper layers implies that vertical mixing is effective, since grain growth models predict the grains would otherwise settle deep in the disk on short time scales. Additionally, we tentatively detect the 9.66 micron S(3) line of H2 and the 11.2 micron emission feature due to PAHs.

Klaus M. Pontoppidan; Karl R. Stapelfeldt; Geoffrey A. Blake; Ewine F. van Dishoeck; Cornelis P. Dullemond

2007-02-14T23:59:59.000Z

313

ZnO Nanostructures Single-Crystal Hexagonal Disks and Rings of  

E-Print Network (OSTI)

ZnO Nanostructures Single-Crystal Hexagonal Disks and Rings of ZnO: Low-Temperature, Large of Chemistry University of New Orleans New Orleans, LA 70148 (USA) Fax: (+1)504-280-6860 E-mail: fli@uno.edu Dr to ellipsoids to disks, and even much more complex shapes, by adjusting experimental parameters,[33] we can

Wang, Zhong L.

314

Dynamics of air bearing sliders flying on partially planarized bit patterned media in hard disk drives  

Science Journals Connector (OSTI)

Bit patterned media (BPM) recording is one of the promising techniques for future disk drives in order to increase the areal density above 1Tbit/in2. However, the BPM can change the topography of the disk surface and thus have an effect ...

Liping Li; David B. Bogy

2011-06-01T23:59:59.000Z

315

Structural modal interaction of a four degree of freedom bladed disk and casing model  

E-Print Network (OSTI)

Structural modal interaction of a four degree of freedom bladed disk and casing model Mathias specific interaction phenomenon that may occur in turbo- machines due to radial rub between a bladed disk requirements leading to reduced clearance between blade-tips and casing together with the rotation of the blade

Boyer, Edmond

316

Model reduction applied to multi-stage assemblies of bladed disks  

E-Print Network (OSTI)

consisted in modelling separately each stage of the assembly of bladed disks that compose the rotor of a jetModel reduction applied to multi-stage assemblies of bladed disks A. Sternch¨uss, E. Balm, France e-mail: arnaud.sternchuss@ecp.fr P. Jean, J.-P. Lombard Snecma (Safran Group) Rond-point Ren

Boyer, Edmond

317

Energy-Aware Prefetching for Parallel Disk Systems Algorithms, Models, and Evaluation  

E-Print Network (OSTI)

system grows, the energy consumed by the I/O system often becomes a large part of the total cost significantly reduce energy consumption in parallel disk systems by up to 50 percent. In addition, we of ownership [16]. Reducing the energy costs of operating these large-scale disk I/O systems often becomes one

Qin, Xiao

318

Probing the electronic structure and optical response of a graphene quantum disk supported on monolayer graphene  

E-Print Network (OSTI)

Probing the electronic structure and optical response of a graphene quantum disk supported on monolayer graphene This article has been downloaded from IOPscience. Please scroll down to see the full text.1088/0953-8984/24/31/314213 Probing the electronic structure and optical response of a graphene quantum disk supported on monolayer

Pennycook, Steve

319

HIGH-CONTRAST NEAR-INFRARED IMAGING POLARIMETRY OF THE PROTOPLANETARY DISK AROUND RY TAU  

SciTech Connect

We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution ({approx}0.''05) for the first time, using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.

Takami, Michihiro; Karr, Jennifer L.; Kim, Hyosun; Chou, Mei-Yin [Institute of Astronomy and Astrophysics, Academia Sinica. P.O. Box 23-141, Taipei 10617, Taiwan (China); Hashimoto, Jun; Kandori, Ryo; Kusakabe, Nobuhiko; Kwon, Jungmi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Wisniewski, John [H. L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Henning, Thomas; Brandner, Wolfgang [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 North A'ohoku Place, Hilo, HI 96720 (United States); Kudo, Tomoyuki [Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Itoh, Yoichi [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo, Hyogo 679-5313 (Japan); Momose, Munetake [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan); Mayama, Satoshi [The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON (Canada); Follette, Katherine B. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ 85721 (United States); Abe, Lyu, E-mail: hiro@asiaa.sinica.edu.tw [Laboratoire Lagrange (UMR 7293), Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, 28 Avenue Valrose, F-06108 Nice Cedex 2 (France); and others

2013-08-01T23:59:59.000Z

320

An evaluation of the storage systems based on network-attached disks  

E-Print Network (OSTI)

show that (a) The advantages of distributing the server's network processing workload to disks may be offset by the decreased cache hit ratios in a file system based on network-attached disks. (b) Performance can be significantly improved in a Web...

Ma, Gang

1998-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Nano-compact disks with 400 Gbit/in2 storage density fabricated  

E-Print Network (OSTI)

Nano-compact disks with 400 Gbit/in2 storage density fabricated using nanoimprint lithography and read with proximal probe Peter R. Kraussa) and Stephen Y. Choub) NanoStructure Laboratory, Department for publication 30 September 1997 Nano-compact disks Nano-CDs with 400 Gbit/in2 topographical bit density nearly

322

The influence of convective heat transfer on flow stability in rotating disk chemical vapor deposition reactors  

SciTech Connect

Flow and heat transfer of NH{sub 3} and He were studied in a rotating disk system with applications to chemical vapor deposition reactors. Flow field and disk heat flux were obtained over a range of operating conditions. Comparisons of disk convective heat transfer were made to infinite rotating disk results to appraise uniformity of transport to the disk. Important operating variables include disk spin rate, disk and enclosure temperatures, flow rate, composition, pressure, and gas mixture temperature at the reactor inlet. These variables were studied over ranges of the spin Reynolds number, Re{omega}; disk mixed convection parameter, MCP{sub w}; and wall mixed convection parameter, MCP{sub w}. Results obtained for NH{sub 3} show that increasing Re{omega} from 314.5 to 3145 increases the uniformity of rotating disk heat flux and results in thinner thermal boundary layers at the disk surface. At Re{omega}=314.5, increasing MCP{sub d} to 15 leads to significant departure from the infinite disk result with nonuniform disk heat fluxes and recirculating flow patterns; flow becomes increasingly complex at larger values of MCP{sub d}. At Re{omega} of 3145, results are closer to the infinite disk for MCP{sub d} up to 15. For large negative (hot walls) and positive (cold walls) values of MCP{sub w}, flow recirculates and there is significant deviation from the infinite disk result; nonuniformities occur at both values of Re{omega}. The influence of MCP{sub w} on flow stability is increased at larger MCP{sub d} and lower Re{omega}. To determine the influence of viscosity and thermal conductivity variation with temperature, calculations were made with He and NH{sub 3}; He transport property variation is low relative to NH{sub 3}. Results show that the flow of NH{sub 3} is less stable than that of He as MCP{sub d} is increased for MCP{sub w}=0 and Re{omega}=314.5. 16 refs., 15 figs., 1 tab.

Winters, W.S.; Evans, G.H. [Sandia National Labs., Livermore, CA (United States); Grief, R. [Univ. of California, Berkeley, CA (United States). Mechanical Engineering Dept.

1997-06-01T23:59:59.000Z

323

Precession of neutrino-cooled accretion disks in gamma-ray burst engines  

E-Print Network (OSTI)

We study the precession of accretion disks in the context of gamma-ray burst inner engines. With an accretion disk model that allows for neutrino cooling, we evaluate the possible periods of disk precession and nutation due to the Lense-Thirring effect. Assuming jet ejection perpendicular to the disk midplane and a typical intrinsic time dependence for the burst, we find possible gamma-ray light curves with temporal microstructure similar to what is observed in some subsamples. We conclude that the precession and nutation of a neutrino-cooled accretion disk in the burst engine might be responsible for some events, especially those with a slow rise and a fast decay.

Matias M. Reynoso; Gustavo E. Romero; Oscar A. Sampayo

2006-07-14T23:59:59.000Z

324

Residual stress profiles for mitigating fretting fatigue in gas turbine engine disks  

Science Journals Connector (OSTI)

The driving force for fretting fatigue in engine disks is the contact stresses generated by fretting of the blade and the disk surfaces in the attachment region. This paper examines the use of different residual compressive stress profiles to counteract the undesirable effects of contact stresses and to mitigate fretting fatigue. A global finite-element analysis of the disk blade assembly is first performed. The contact pressure and shear traction at the attachment region are extracted from the FEM results and used to compute the contact stress distribution. The contact stresses are then combined with the residual stresses and the bulk stresses. The overall stress distribution is then utilized in a probabilistic crack growth model to predict the risk of disk failure for a military engine under simulated loading conditions. The results are used to identify the minimum residual stress profile for mitigating fretting fatigue in engine disks.

Kwai S. Chan; Michael P. Enright; Jonathan P. Moody; Patrick J. Golden; Ramesh Chandra; Alan C. Pentz

2010-01-01T23:59:59.000Z

325

A gap capacitance method for slider flying height measurement in near-field optical disk drives  

Science Journals Connector (OSTI)

In order to overcome the diffraction limit of conventional optical disk drives, and substantially increase data storage capacity and density, near-field optical disk drives remain to be realized. The slider of a flying pickup head in a near-field optical disk drive has to fly at a stable spacing above the disk surface. To sense the slider flying height, a gap capacitance method is developed in this study to measure capacitance variation between the pickup head and disk surface. The capacitance varying with the flying height is modulated by a Colpitts oscillator. Subsequent demodulation accounts for height variation of the flying pickup head. Measurement results of this method are verified by using a laser Doppler interferometer.

J.W. Chen; T.S. Liu

2004-01-01T23:59:59.000Z

326

Cooling a Hot Disk Around a Supermassive Black Hole by a Star  

E-Print Network (OSTI)

If a supermassive black hole resides in the centers of galaxies, there are several effects expected to be observed. It is likely that accretion disks are around the supermassive black hole. Stellar interactions with the accretion flows around the supermassive black hole play a role in that an flying-by star may cool a hot accretion disk as a result of Comptonization. It is shown that the Comptonization of the stellar emission will take place in a hot accretion disk such as the ADAFs around the supermassive black hole and become a relatively important source of the accretion disk cooling when the mass accretion rate is low, and stars are passing outer parts of the hot accretion disk. We suggest that such a stellar cooling can be observed in the radio frequency regime since synchrotron luminosity of the ADAFs depends strongly on the electron temperature and occurs much more frequently than a tidal disruption event.

Chang, H Y

2000-01-01T23:59:59.000Z

327

Cooling a Hot Disk Around a Supermassive Black Hole by a Star  

E-Print Network (OSTI)

If a supermassive black hole resides in the centers of galaxies, there are several effects expected to be observed. It is likely that accretion disks are around the supermassive black hole. Stellar interactions with the accretion flows around the supermassive black hole play a role in that an flying-by star may cool a hot accretion disk as a result of Comptonization. It is shown that the Comptonization of the stellar emission will take place in a hot accretion disk such as the ADAFs around the supermassive black hole and become a relatively important source of the accretion disk cooling when the mass accretion rate is low, and stars are passing outer parts of the hot accretion disk. We suggest that such a stellar cooling can be observed in the radio frequency regime since synchrotron luminosity of the ADAFs depends strongly on the electron temperature and occurs much more frequently than a tidal disruption event.

Heon-Young Chang

2000-12-18T23:59:59.000Z

328

Lenticular galaxy IC 719: current building of the counterrotating large-scale stellar disk  

E-Print Network (OSTI)

We have obtained and analyzed long-slit spectral data for the lenticular galaxy IC 719. In this gas-rich S0 galaxy, its large-scale gaseous disk counterrotates the global stellar disk. Moreover in the IC 719 disk we have detected a secondary stellar component corotating the ionized gas. By using emission-line intensity ratios, we have proved the gas excitation by young stars and so are claiming current star formation, most intense in a ring-like zone at the radius of 10" (1.4 kpc). The oxygen abundance of the gas in the starforming ring is about half of the solar abundance. Since the stellar disk remains dynamically cool, we conclude that smooth prolonged accretion of the external gas from a neighboring galaxy provides urrent building of the thin large-scale stellar disk.

Katkov, Ivan Yu; Afanasiev, Victor L

2013-01-01T23:59:59.000Z

329

Gas-phase CO in protoplanetary disks: a challenge for turbulent mixing  

E-Print Network (OSTI)

This is the first paper in a series where we study the influence of turbulent diffusion and advective transport on the chemical evolution of protoplanetary disks, using a 2D flared disk model and a 2D mixing gas-grain chemical code with surface reactions. A first interesting result concerns the abundance of gas-phase CO in the outer regions of protoplanetary disks. In this Letter we argue that the gas-phase CO concentration in the disk regions, where the temperature is lower than $\\sim25$ K, can be significantly enhanced due to the combined effect of vertical and radial mixing. This finding has a potential implication for the current observational data on the DM~Tau disk chemistry.

D. Semenov; D. Wiebe; Th. Henning

2006-07-02T23:59:59.000Z

330

Air Entrapment in Nanometer-Thick Lubricant Films and its Effect on Slider Flying Height in a Hard Disk Drive  

Science Journals Connector (OSTI)

Experimental data are presented, showing that the flying height of a slider in a hard disk drive can be altered by the chemical ... of the molecularly-thin lubricant film on the disk surface. It is suggested that...

B. Marchon; X. C. Guo; S. Canchi; R. H. Wang; N. Supper; J. Burns

2012-09-01T23:59:59.000Z

331

Investigation of wear resistance and lifetime of diamond-like carbon (DLC) coated glass disk in flying height measurement process  

Science Journals Connector (OSTI)

Flying height has been greatly reduced to less ... -density magnetic storage. This leads to significant disk wear especially, glass disks used in flying height measurement process. This paper reports the ... the ...

Korakoch Phetdee; Alongkorn Pimpin; Werayut Srituravanich

2011-08-01T23:59:59.000Z

332

Thin film gas lubrication characteristics of flying head slider bearings over patterned media in hard disk drives  

Science Journals Connector (OSTI)

...? This paper describes the effects of moving patterned disk surfaces on thin film gas lubrication characteristics for flying head slider bearings in magnetic hard disk drives. In order to perform the most real...

N. Tagawa; A. Mori

2003-05-01T23:59:59.000Z

333

Real-Time Parallel Disk Scheduling for VBR Video Servers Ozgur Ertu g Mahesh Kallahalla Peter J. Varman  

E-Print Network (OSTI)

the potential to alleviate this problem by providing a higher disk bandwidth. However harnessing the raw disk J. Varman Department of Electrical and Computer Engineering Rice University Houston TX 77251

Mellor-Crummey, John

334

VERTICAL STRUCTURE OF STATIONARY ACCRETION DISKS WITH A LARGE-SCALE MAGNETIC FIELD  

SciTech Connect

In earlier works we pointed out that the disk's surface layers are non-turbulent and thus highly conducting (or non-diffusive) because the hydrodynamic and/or magnetorotational instabilities are suppressed high in the disk where the magnetic and radiation pressures are larger than the plasma thermal pressure. Here, we calculate the vertical profiles of the stationary accretion flows (with radial and azimuthal components), and the profiles of the large-scale, magnetic field taking into account the turbulent viscosity and diffusivity and the fact that the turbulence vanishes at the surface of the disk. Also, here we require that the radial accretion speed be zero at the disk's surface and we assume that the ratio of the turbulent viscosity to the turbulent magnetic diffusivity is of order unity. Thus, at the disk's surface there are three boundary conditions. As a result, for a fixed dimensionless viscosity {alpha}-value, we find that there is a definite relation between the ratio R of the accretion power going into magnetic disk winds to the viscous power dissipation and the midplane plasma-{beta}, which is the ratio of the plasma to magnetic pressure in the disk. For a specific disk model with R of order unity we find that the critical value required for a stationary solution is {beta}{sub c} Almost-Equal-To 2.4r/({alpha}h), where h is the disk's half thickness. For weaker magnetic fields, {beta} > {beta}{sub c}, we argue that the poloidal field will advect outward while for {beta} < {beta}{sub c} it will advect inward. Alternatively, if the disk wind is negligible (R<<1), there are stationary solutions with {beta} >> {beta}{sub c}.

Bisnovatyi-Kogan, G. S. [Space Research Institute, Russian Academy of Sciences, Moscow (Russian Federation); Lovelace, R. V. E., E-mail: gkogan@mx.iki.rssi.ru, E-mail: RVL1@cornell.edu [Department of Astronomy, Cornell University, Ithaca, NY 14853-6801 (United States)

2012-05-10T23:59:59.000Z

335

On the aerodynamic redistribution of chondrite components in protoplanetary disks  

E-Print Network (OSTI)

Despite being all roughly of solar composition, primitive meteorites (chondrites) present a diversity in their chemical, isotopic and petrographic properties, and in particular a first-order dichotomy between carbonaceous and non-carbonaceous chondrites. We investigate here analytically the dynamics of their components (chondrules, refractory inclusions, metal/sulfide and matrix grains) in protoplanetary disks prior to their incorporation in chondrite parent bodies. We find the dynamics of the solids, subject to gas drag, to be essentially controlled by the "gas-solid decoupling parameter" $S\\equiv \\textrm{St}/\\alpha$, the ratio of the dimensionless stopping time to the turbulence parameter. The decoupling of the solid particles relative to the gas is significant when $S$ exceeds unity. $S$ is expected to increase with time and heliocentric distance. On the basis of (i) abundance of refractory inclusions (ii) proportion of matrix (iii) lithophile element abundances and (iv) oxygen isotopic composition of chon...

Jacquet, Emmanuel; Fromang, Sbastien

2012-01-01T23:59:59.000Z

336

Vibrated polar disks: spontaneous motion, binary collisions, and collective dynamics  

E-Print Network (OSTI)

We study the spontaneous motion, binary collisions, and collective dynamics of "polar disks", i.e. purpose-built particles which, when vibrated between two horizontal plates, move coherently along a direction strongly correlated to their intrinsic polarity. The motion of our particles, although nominally three-dimensional and complicated, is well accounted for by a two-dimensional persistent random walk. Their binary collisions are spatiotemporally extended events during which multiple actual collisions happen, yielding a weak average effective alignment. We show that this well-controlled, "dry active matter" system can display collective motion with orientationally-ordered regions of the order of the system size. We provide evidence of strong number density in the most ordered regimes observed. These results are discussed in the light of the limitations of our system, notably those due to the inevitable presence of walls.

Julien Deseigne; Sbastien Lonard; Olivier Dauchot; Hugues Chat

2012-01-29T23:59:59.000Z

337

Radial disk heating by more than one spiral density wave  

E-Print Network (OSTI)

We consider a differentially rotating, 2D stellar disk perturbed by two steady state spiral density waves moving at different patterns speeds. Our investigation is based on direct numerical integration of initially circular test-particle orbits. We examine a range of spiral strengths and spiral speeds and show that stars in this time dependent gravitational field can be heated (their random motions increased). This is particularly noticeable in the simultaneous propagation of a 2-armed spiral density wave near the corotation resonance (CR), and a weak 4-armed one near the inner and outer 4:1 Lindblad resonances. In simulations with 2 spiral waves moving at different pattern speeds we find: (1) the variance of the radial velocity, sigma_R^2, exceeds the sum of the variances measured from simulations with each individual pattern; (2) sigma_R^2 can grow with time throughout the entire simulation; (3) sigma_R^2 is increased over a wider range of radii compared to that seen with one spiral pattern; (4) particles diffuse radially in real space whereas they don't when only one spiral density wave is present. Near the CR with the stronger, 2-armed pattern, test particles are observed to migrate radially. These effects take place at or near resonances of both spirals so we interpret them as the result of stochastic motions. This provides a possible new mechanism for increasing the stellar velocity dispersion in galactic disks. If multiple spiral patterns are present in the Galaxy we predict that there should be large variations in the stellar velocity dispersion as a function of radius.

I. Minchev; A. C. Quillen

2005-10-28T23:59:59.000Z

338

Efficient Failure Recovery in Multi-Disk Multimedia Servers Harrick M. Vin, Prashant J. Shenoy and Sriram Rao  

E-Print Network (OSTI)

-invoked on-the-fly failure recovery process does not impose any additional load on the disk array. We also that each surviving disk would see an on-the-fly reconstruction load increase of G,1=D,1 instead of D,1=D,1Efficient Failure Recovery in Multi-Disk Multimedia Servers Harrick M. Vin, Prashant J. Shenoy

Vin, Harrick M.

339

ACCRETION OF GAS ONTO GAP-OPENING PLANETS AND CIRCUMPLANETARY FLOW STRUCTURE IN MAGNETIZED TURBULENT DISKS  

SciTech Connect

We have performed three-dimensional magnetohydrodynamical simulations of stellar accretion disks, using the PLUTO code, and studied the accretion of gas onto a Jupiter-mass planet and the structure of the circumplanetary gas flow after opening a gap in the disk. We compare our results with simulations of laminar, yet viscous disks with different levels of an {alpha}-type viscosity. In all cases, we find that the accretion flow across the surface of the Hill sphere of the planet is not spherically or azimuthally symmetric, and is predominantly restricted to the mid-plane region of the disk. Even in the turbulent case, we find no significant vertical flow of mass into the Hill sphere. The outer parts of the circumplanetary disk are shown to rotate significantly below Keplerian speed, independent of viscosity, while the circumplanetary disk density (therefore the angular momentum) increases with viscosity. For a simulation of a magnetized turbulent disk, where the global averaged alpha stress is {alpha}{sub MHD} = 10{sup -3}, we find the accretion rate onto the planet to be M-dot {approx}2 Multiplication-Sign 10{sup -6}M{sub J} yr{sup -1} for a gap surface density of 12 g cm{sup -2}. This is about a third of the accretion rate obtained in a laminar viscous simulation with equivalent {alpha} parameter.

Uribe, A. L. [University of Chicago, Chicago, IL 60637 (United States); Klahr, H.; Henning, Th., E-mail: uribe@oddjob.uchicago.edu [Max-Planck-Institut fuer Astronomie, Heidelberg (Germany)

2013-06-01T23:59:59.000Z

340

A SPITZER IRS SURVEY OF NGC 1333: INSIGHTS INTO DISK EVOLUTION FROM A VERY YOUNG CLUSTER  

SciTech Connect

We report on the {lambda} = 5-36 {mu}m Spitzer Infrared Spectrograph (IRS) spectra of 79 young stellar objects in the very young nearby cluster NGC 1333. NGC 1333's youth enables the study of early protoplanetary disk properties, such as the degree of settling and the formation of gaps and clearings. We construct spectral energy distributions (SEDs) using our IRS data as well as published photometry and classify our sample into SED classes. Using 'extinction-free' spectral indices, we determine whether the disk, envelope, or photosphere dominates the spectrum. We analyze the dereddened spectra of objects that show disk-dominated emission using spectral indices and properties of silicate features in order to study the vertical and radial structure of protoplanetary disks in NGC 1333. At least nine objects in our sample of NGC 1333 show signs of large (several AU) radial gaps or clearings in their inner disk. Disks with radial gaps in NGC 1333 show more nearly pristine silicate dust than their radially continuous counterparts. We compare properties of disks in NGC 1333 to those in three other well-studied regions, Taurus-Auriga, Ophiuchus, and Chamaeleon I, and find no difference in their degree of sedimentation and dust processing.

Arnold, L. A.; Watson, Dan M.; Kim, K. H.; Manoj, P.; Remming, I.; Sheehan, P.; Forrest, W. J.; Mamajek, E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Adame, L.; McClure, M. [Department of Astronomy, University of Michigan, 500 Church Street, Dennison Building, Ann Arbor, MI 48109 (United States); Furlan, E. [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 264-723, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Espaillat, C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Ausfeld, K.; Rapson, V. A., E-mail: laa@pas.rochester.edu, E-mail: dmw@pas.rochester.edu [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2012-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
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341

Gross crack initiation and propagation in brittle thin solid and annular disks subjected to impact loading  

SciTech Connect

This paper derives from a study of grinding wheel break-up behavior due to impact. The impact fracture characteristics of circular disks of plaster of Paris with a concentric central hole were studied experimentally for three types of loading: (a) when the disks were suspended freely and loaded intensely at one point on their circumference by an explosive detonator; (b) when the disks were allowed to fall under gravity from a certain height on to a rigid base; and (c) when a disk, resting on a rigid base, was struck by a flat ended rigid body which was dropped on to it from a certain height. Quasi-static flattening tests on the disks were also carried out. The paper describes a theoretical investigation into the stress analysis of disks under impact, classifies the relevant damage sustained by them and attempts to unify the ''gross'' impact fracture patterns which arise in different modes of dynamic loading. The extent of local flattening of the quasi-statically loaded disks before fracture, is also reported. Good correlation between the theory and experimental results is obtained, especially for rings of diameter ratio (D /SUB i/ /D/sub 0/) of around 0.5.

Johnson, W.; Bai, Y.L.; Ghosh, S.K.

1984-04-01T23:59:59.000Z

342

Deep Spitzer spectroscopy of the `Flying Saucer' edge-on disk: Large grains beyond 50 AU  

E-Print Network (OSTI)

We present deep Spitzer-IRS low-resolution (lambda/Delta lambda ~ 100) 5-35 micron spectroscopy of the edge-on disk ``the Flying Saucer'' (2MASS J16281370-2431391) in the Ophiuchus molecular cloud. The spectral energy distribution exhibits the characteristic two-peak shape predicted for a circumstellar disk viewed very close to edge-on. The short-wavelength peak is entirely due to photons scattered off the surface of the disk, while the long-wavelength peak is due to thermal emission from the disk itself. The Spitzer spectrum represents the first spectroscopic detection of scattered light out to 15 micron from a bona-fide, isolated edge-on disk around a T Tauri star. The depth and the wavelength of the mid-infrared "valley" of the SED give direct constraints on the size distribution of large grains in the disk. Using a 2D continuum radiative transfer model, we find that a significant amount of 5-10 micron-sized grains is required in the surface layers of the disk at radii of 50-300 AU. The detection of relati...

Pontoppidan, K M; Blake, G A; Van Dishoeck, E F; Dullemond, C P; Pontoppidan, Klaus M.; Stapelfeldt, Karl R.; Blake, Geoffrey A.; Dishoeck, Ewine F. van; Dullemond, Cornelis P.

2007-01-01T23:59:59.000Z

343

ON THE SIZE EVOLUTION OF A GALACTIC DISK IN HIERARCHICAL MERGING OF COLD DARK MATTER HALOS  

SciTech Connect

We investigate the dynamical effects of dark matter subhalos on the structure and evolution of a galactic disk, using the semi-analytic method that includes approximated and empirical relations as achieved in detailed numerical simulations of the cold dark matter model. We calculate the upper limit for the size of a galactic disk at a specific redshift z, based on the orbital properties of subhalos characterized by their pericentric distances from the center of a host halo. We find that this possibly largest size of a disk as determined by the smallest pericentric distances of subhalos shows the characteristic properties, which are basically in agreement with an observed galactic disk at low and high z. Namely, it is found that a massive disk can have a larger size than a less massive one, because of its stability against the destruction effect of subhalos. Also, with fixed mass, the size of a galactic disk at low z can be larger than that at high z, reflecting the orbital evolution of subhalos with respect to a host halo. These results suggest that the presence and structure of a galactic disk may be dynamically limited by the interaction with dark matter substructures, especially at high z.

Hayashi, Hirohito; Chiba, Masashi [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)

2009-09-10T23:59:59.000Z

344

VISCOUS ACCRETION OF A POLYTROPIC SELF-GRAVITATING DISK IN THE PRESENCE OF WIND  

SciTech Connect

Self-similar and semi-analytical solutions are found for the height-averaged equations governing the dynamical behavior of a polytropic, self-gravitating disk under the effects of winds around the nascent object. In order to describe the time evolution of the system, we adopt a radius-dependent mass loss rate, then highlight its importance on both the traditional {alpha} and innovative {beta} models of viscosity prescription. In agreement with some other studies, our solutions represent that the Toomre parameter is less than one in most regions on the {beta}-disk, which indicates that in such disks gravitational instabilities can occur at various distances from the central accretor. So, the {beta}-disk model might provide a good explanation of how the planetary systems form. The purpose of the present work is twofold: examining the structure of a disk with wind in comparison to a no-wind solution and seeing whether the adopted viscosity prescription significantly affects the dynamical behavior of the disk-wind system. We also considered the temperature distribution in our disk by a polytropic condition. The solutions imply that, under our boundary conditions, the radial velocity is larger for {alpha}-disks and increases as wind becomes stronger in both viscosity models. Also, we noticed that the disk thickness increases by amplifying the wind or adopting larger values for the polytropic exponent {gamma}. It also may globally decrease if one prescribes a {beta}-model for the viscosity. Moreover, in both viscosity models, the surface density and mass accretion rate diminish as the wind gets stronger or {gamma} increases.

Abbassi, Shahram; Nourbakhsh, Erfan [School of Physics, Damghan University, P.O. Box 36715-364, Damghan (Iran, Islamic Republic of); Shadmehri, Mohsen, E-mail: abbassi@ipm.ir, E-mail: e.nourbakhsh@mail.sbu.ac.ir, E-mail: m.shadmehri@gu.ac.ir [Department of Physics, Golestan University, Basij Square, Gorgan (Iran, Islamic Republic of)

2013-03-10T23:59:59.000Z

345

Modeling the Resolved Disk around the Class0 Protostar L1527  

Science Journals Connector (OSTI)

We present high-resolution sub/millimeter interferometric imaging of the Class0 protostar L1527 IRS (IRAS04368+2557) at ? = 870 ?m and 3.4mm from the Submillimeter Array and Combined Array for Research in Millimeter Astronomy. We detect the signature of an edge-on disk surrounding the protostar with an observed diameter of 180AU in the sub/millimeter images. The mass of the disk is estimated to be 0.007 M ?, assuming optically thin, isothermal dust emission. The millimeter spectral index is observed to be quite shallow at all the spatial scales probed: ? ~ 2, implying a dust opacity spectral index ? ~ 0. We model the emission from the disk and surrounding envelope using Monte Carlo radiative transfer codes, simultaneously fitting the sub/millimeter visibility amplitudes, sub/millimeter images, resolved L' image, spectral energy distribution, and mid-infrared spectrum. The best-fitting model has a disk radius of R = 125AU, is highly flared (H?R 1.3), has a radial density profile ??R 2.5, and has a mass of 0.0075 M ?. The scale height at 100AU is 48AU, about a factor of two greater than vertical hydrostatic equilibrium. The resolved millimeter observations indicate that disks may grow rapidly throughout the Class0 phase. The mass and radius of the young disk around L1527 are comparable to disks around pre-main-sequence stars; however, the disk is considerably more vertically extended, possibly due to a combination of lower protostellar mass, infall onto the disk upper layers, and little settling of ~1 ?m-sized dust grains.

John J. Tobin; Lee Hartmann; Hsin-Fang Chiang; David J. Wilner; Leslie W. Looney; Laurent Loinard; Nuria Calvet; Paola D'Alessio

2013-01-01T23:59:59.000Z

346

MODELING THE RESOLVED DISK AROUND THE CLASS 0 PROTOSTAR L1527  

SciTech Connect

We present high-resolution sub/millimeter interferometric imaging of the Class 0 protostar L1527 IRS (IRAS 04368+2557) at {lambda} = 870 {mu}m and 3.4 mm from the Submillimeter Array and Combined Array for Research in Millimeter Astronomy. We detect the signature of an edge-on disk surrounding the protostar with an observed diameter of 180 AU in the sub/millimeter images. The mass of the disk is estimated to be 0.007 M{sub Sun }, assuming optically thin, isothermal dust emission. The millimeter spectral index is observed to be quite shallow at all the spatial scales probed: {alpha} {approx} 2, implying a dust opacity spectral index {beta} {approx} 0. We model the emission from the disk and surrounding envelope using Monte Carlo radiative transfer codes, simultaneously fitting the sub/millimeter visibility amplitudes, sub/millimeter images, resolved L' image, spectral energy distribution, and mid-infrared spectrum. The best-fitting model has a disk radius of R = 125 AU, is highly flared (H{proportional_to}R {sup 1.3}), has a radial density profile {rho}{proportional_to}R {sup -2.5}, and has a mass of 0.0075 M{sub Sun }. The scale height at 100 AU is 48 AU, about a factor of two greater than vertical hydrostatic equilibrium. The resolved millimeter observations indicate that disks may grow rapidly throughout the Class 0 phase. The mass and radius of the young disk around L1527 are comparable to disks around pre-main-sequence stars; however, the disk is considerably more vertically extended, possibly due to a combination of lower protostellar mass, infall onto the disk upper layers, and little settling of {approx}1 {mu}m-sized dust grains.

Tobin, John J. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Hartmann, Lee; Calvet, Nuria [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Chiang, Hsin-Fang; Looney, Leslie W. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Loinard, Laurent; D'Alessio, Paola, E-mail: jtobin@nrao.edu [Centro de Radioastronomia y Astrofisica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacan (Mexico)

2013-07-01T23:59:59.000Z

347

NUCLEOSYNTHESIS IN THE OUTFLOWS ASSOCIATED WITH ACCRETION DISKS OF TYPE II COLLAPSARS  

SciTech Connect

We investigate nucleosynthesis inside the outflows from gamma-ray burst (GRB) accretion disks formed by the Type II collapsars. In these collapsars, massive stars undergo core collapse to form a proto-neutron star initially, and a mild supernova (SN) explosion is driven. The SN ejecta lack momentum, and subsequently this newly formed neutron star gets transformed to a stellar mass black hole via massive fallback. The hydrodynamics and the nucleosynthesis in these accretion disks have been studied extensively in the past. Several heavy elements are synthesized in the disk, and much of these heavy elements are ejected from the disk via winds and outflows. We study nucleosynthesis in the outflows launched from these disks by using an adiabatic, spherically expanding outflow model, to understand which of these elements thus synthesized in the disk survive in the outflow. While studying this, we find that many new elements like isotopes of titanium, copper, zinc, etc., are present in the outflows. {sup 56}Ni is abundantly synthesized in most of the cases in the outflow, which implies that the outflows from these disks in a majority of cases will lead to an observable SN explosion. It is mainly present when outflow is considered from the He-rich, {sup 56}Ni/{sup 54}Fe-rich zones of the disks. However, outflow from the Si-rich zone of the disk remains rich in silicon. Although emission lines of many of these heavy elements have been observed in the X-ray afterglows of several GRBs by Chandra, BeppoSAX, XMM-Newton, etc., Swift seems to have not yet detected these lines.

Banerjee, Indrani; Mukhopadhyay, Banibrata, E-mail: indrani@physics.iisc.ernet.in, E-mail: bm@physics.iisc.ernet.in [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India)

2013-11-20T23:59:59.000Z

348

The Spitzer Infrared Spectrograph Debris Disk Catalog. I. Continuum Analysis of Unresolved Targets  

Science Journals Connector (OSTI)

During the Spitzer Space Telescope cryogenic mission, Guaranteed Time Observers, Legacy Teams, and General Observers obtained Infrared Spectrograph (IRS) observations of hundreds of debris disk candidates. We calibrated the spectra of 571 candidates, including 64 new IRAS and Multiband Imaging Photometer for Spitzer (MIPS) debris disks candidates, modeled their stellar photospheres, and produced a catalog of excess spectra for unresolved debris disks. For 499 targets with IRS excess but without strong spectral features (and a subset of 420 targets with additional MIPS 70?m observations), we modeled the IRS (and MIPS data) assuming that the dust thermal emission was well-described using either a one- or two-temperature blackbody model. We calculated the probability for each model and computed the average probability to select among models. We found that the spectral energy distributions for the majority of objects (~66%) were better described using a two-temperature model with warm (T gr ~100-500K) and cold (T gr ~50-150K) dust populations analogous to zodiacal and Kuiper Belt dust, suggesting that planetary systems are common in debris disks and zodiacal dust is common around host stars with ages up to ~1Gyr. We found that younger stars generally have disks with larger fractional infrared luminosities and higher grain temperatures and that higher-mass stars have disks with higher grain temperatures. We show that the increasing distance of dust around debris disks is inconsistent with self-stirred disk models, expected if these systems possess planets at 30-150AU. Finally, we illustrate how observations of debris disks may be used to constrain the radial dependence of material in the minimum mass solar nebula.

Christine H. Chen; Tushar Mittal; Marc Kuchner; William J. Forrest; Carey M. Lisse; P. Manoj; Benjamin A. Sargent; Dan M. Watson

2014-01-01T23:59:59.000Z

349

Effects of a Supermassive Black Hole Binary on a Nuclear Gas Disk  

E-Print Network (OSTI)

We study influence of a galactic central supermassive black hole (SMBH) binary on gas dynamics and star formation activity in a nuclear gas disk by making three-dimensional Tree+SPH simulations. Due to orbital motions of SMBHs, there are various resonances between gas motion and the SMBH binary motion. We have shown that these resonances create some characteristic structures of gas in the nuclear gas disk, for examples, gas elongated or filament structures, formation of gaseous spiral arms, and small gas disks around SMBHs. In these gaseous dense regions, active star formations are induced. As the result, many star burst regions are formed in the nuclear region.

Hidenori Matsui; Asao Habe; Takayuki R. Saitoh

2006-06-07T23:59:59.000Z

350

Star Formation in Isolated Disk Galaxies. II. Schmidt Laws and Efficiency of Gravitational Collapse  

E-Print Network (OSTI)

(Abridged). We model gravitational instability in a wide range of isolated disk galaxies, using GADGET, a three-dimensional, smoothed particle hydrodynamics code. The model galaxies include a dark matter halo and a disk of stars and isothermal gas. The global Schmidt law observed in disk galaxies is quantitatively reproduced by our models. We find that the surface density of star formation rate directly correlates with the strength of local gravitational instability. The local Schmidt laws of individual galaxies in our models show clear evidence of star formation thresholds. Our results suggest that the non-linear development of gravitational instability determines the local and global Schmidt laws, and the star formation thresholds.

Yuexing Li; Mordecai-Mark Mac Low; Ralf S. Klessen

2006-02-21T23:59:59.000Z

351

Sub-mm disk waviness characteristics and slider flying dynamics under thermal FH control  

Science Journals Connector (OSTI)

The flying dynamics and flying stability of a slider are the key issues at sub-5nm flying height (FH) under thermal FH control. The resonant frequencies of current sliders are at 100kHz level. At present linear disk velocities, the disk waviness at sub-mm level and 10 micron level can excite the resonant modes of the slider and induce FH modulation. This work uses the triple-harmonic method to monitor the dynamic FH signal during the process of thermal FH control. As the FH reduces, the same disk waviness characteristics excite larger dynamic FH modulation.

Zhi-Min Yuan; Siang Huei Leong; Sumitro Joyo Taslim; Ka Wei Ng; Bo Liu

2008-01-01T23:59:59.000Z

352

Identification of the Spawning, Rearing, and Migratory Requirements of Fall Chinook Salmon in the Columbia River Basin, 1991 Annual Progress Report.  

SciTech Connect

This document is the 1991 annual progress report for selected studies of fall chinook salmon Oncorhynchus tshawytscha conducted by the US Fish and Wildlife Service. The decline in abundance of fall chinook salmon in the Snake River basin has become a growing concern. In April 1992, Snake River fall chinook salmon were listed as ``threatened`` under the Endangered Species Act. Effective recovery efforts for fall chinook salmon can not be developed until we increase our knowledge of the factors that are limiting the various life history stages. This study attempts to identify those physical and biological factors which influence spawning of fall chinook salmon in the free-flowing Snake River and their rearing and seaward migration through Columbia River basin reservoirs.

Rondorf, Dennis W.; Miller, William H.

1993-07-01T23:59:59.000Z

353

THE SPITZER c2d SURVEY OF WEAK-LINE T TAURI STARS. III. THE TRANSITION FROM PRIMORDIAL DISKS TO DEBRIS DISKS  

SciTech Connect

We present 3.6 to 70 {mu}m Spitzer photometry of 154 weak-line T Tauri stars (WTTSs) in the Chamaeleon, Lupus, Ophiuchus, and Taurus star formation regions, all of which are within 200 pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars which are located in the same star-forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8 {mu}m) and the 24 {mu}m MIPS band. In the 70 {mu}m MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTSs survey in the mid- to far-infrared to date and reveal the frequency of outer disks (r = 3-50 AU) around WTTSs. The 70 {mu}m photometry for half the c2d WTTSs sample (the on-cloud objects), which were not included in the earlier papers in this series, those of Padgett et al. and Cieza et al., are presented here for the first time. We find a disk frequency of 19% for on-cloud WTTSs, but just 5% for off-cloud WTTSs, similar to the value reported in the earlier works. WTTSs exhibit spectral energy distributions that are quite diverse, spanning the range from optically thick to optically thin disks. Most disks become more tenuous than L{sub disk}/L{sub *} = 2 x 10{sup -3} in 2 Myr and more tenuous than L{sub disk}/L{sub *} = 5 x 10{sup -4} in 4 Myr.

Wahhaj, Zahed; Cieza, Lucas [Institute for Astronomy, University of Hawaii, Honolulu, HI 96814 (United States); Koerner, David W.; Case, April [Northern Arizona University, Building 19, Rm. 209, Flagstaff, AZ 86011-6010 (United States); Stapelfeldt, Karl R.; Chapman, Nicholas [Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Padgett, Deborah L.; Brooke, Tim [Spitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States); Keller, James R. [Department of Physics, 301 Weniger Hall, Oregon State University, Corvallis, OR 97331-6507 (United States); MerIn, Bruno [Herschel Science Centre, European Space Astronomy Centre (ESA), P.O. Box 78, 28691 Villanueva de la Canada (Madrid) (Spain); Evans, Neal J.; Harvey, Paul [Astronomy Department, University of Texas, 1 University Station C1400, Austin, TX 78712 (United States); Sargent, Anneila [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States); Van Dishoeck, Ewine F. [Leiden Observatory, Postbus 9513, 2300 R.A. Leiden (Netherlands); Allen, Lori [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Blake, Geoff [Division of Geological and Planetary Sciences, California Institute of Technology, MS 150-21, Pasadena, CA 91125 (United States); Mundy, Lee [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); Myers, Philip C. [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge, MA 02138 (United States)

2010-12-01T23:59:59.000Z

354

E-Print Network 3.0 - accreting protostellar disks Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

<< < 1 2 3 4 5 > >> 1 The University of Western Ontario DEPARTMENT OF PHYSICS AND ASTRONOMY Summary: from the protostellar disk as the jet mass outflow is comparable to the...

355

E-Print Network 3.0 - accretion disk gamma-ray Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

gamma-ray Search Powered by Explorit Topic List Advanced Search Sample search results for: accretion disk gamma-ray Page: << < 1 2 3 4 5 > >> 1 Lecture 4Lecture 4 Galactic...

356

Augmentation of Power Output of Axisymmetric Ducted Wind Turbines by Porous Trailing Edge Disks  

E-Print Network (OSTI)

This paper presents analytical and experimental results that demonstrated that the power output from a ducted wind turbine can be dramatically increased by the addition of a trailing edge device such as a porous disk. In ...

widnall, sheila

2014-06-30T23:59:59.000Z

357

The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk  

Science Journals Connector (OSTI)

...terrestrial Pb contamination (21). Fig. 2 Pb-Pb isochron diagrams for Efremovka CAI 22E (A), Allende...39 Zanni C. Ferrari A. Rosner R. Bodo G. Massaglia S. , MHD simulations of jet acceleration from Keplerian accretion disks...

James N. Connelly; Martin Bizzarro; Alexander N. Krot; ke Nordlund; Daniel Wielandt; Marina A. Ivanova

2012-11-02T23:59:59.000Z

358

HEATING IN AN EXTENDED ACCRETION DISK CORONA ALONG THE Z-PATTERN IN CYG X-2  

E-Print Network (OSTI)

We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting ...

Schulz, Norbert S.

359

Rotating disk sorptive extraction of triclosan and methyl-triclosan from water samples  

Science Journals Connector (OSTI)

A method of sample preparation based on use of rotating disk sorptive extraction (RDSE) has been developed for determination of triclosan (TCS) and methyl-triclosan (MTCS) in water samples. The sorptive...w/v), d...

Lourdes Jachero; Betsabet Seplveda; Ins Ahumada

2013-09-01T23:59:59.000Z

360

Air Bearing Slider Simulation and Modeling for Hard Disk Drives with Ultra-Low Flying Heights  

Science Journals Connector (OSTI)

As non-traditional application of hard disk drives (HDDs) emerges, their mechanical robustness...13...]. Normal drives can not malfunction during the operating state, damage during initial assembly, testing, ins...

B. J. Shi; D. W. Shu; B. Gu; M. R. Parlapalli; C. N. Delia

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Drive level measurement of flying height modulation and control of slider disk contact  

Science Journals Connector (OSTI)

A drive level measurement of flying height modulation and a demonstration of slider-disk contact control was conducted. The results of the flying height modulation strongly agree with those obtained ... modulatio...

J. Xu; Y. Shimizu; L. Su

2006-11-01T23:59:59.000Z

362

Contact between a thermal flying height control slider and a disk asperity  

Science Journals Connector (OSTI)

Contact between a thermal flying height control slider and an asperity on a disk is investigated using finite element analysis. The ... write element are determined as a function of flying height of the slider, l...

Wenping Song; Andrey Ovcharenko; Min Yang; Hao Zheng

2012-09-01T23:59:59.000Z

363

Characterization of light contact in head disk interface with dynamic flying height control  

Science Journals Connector (OSTI)

This paper presents an investigation of the light contact in a head disk interface with dynamic flying height control. The touchdown test is conducted for a dynamic flying height control slider and the response i...

Jianfeng Xu; Gang Sheng

2011-06-01T23:59:59.000Z

364

Dynamics of ultra low flying sliders during contact with a lubricated disk  

Science Journals Connector (OSTI)

Magnetic recording sliders are expected to fly at a spacing of 3 to 5nm above the disk in the near future. At such a small spacing, flying height modulations are becoming an increasingly more ... the past concer...

Jianfeng Xu; James D. Kiely; Yiao-Tee Hsia; Frank E. Talke

2007-05-01T23:59:59.000Z

365

Servo signal processing for flying height control in hard disk drives  

Science Journals Connector (OSTI)

In recent years, thermal actuated flying height control has been implemented in hard disk drives (HDD) to reduce the effect of flying height variations due to manufacturing tolerances or...2005). A stable low flying

Uwe Boettcher; Christopher A. Lacey; Hui Li; Kensuke Amemiya

2011-06-01T23:59:59.000Z

366

MASS AND TEMPERATURE OF THE TWA 7 DEBRIS DISK Brenda C. Matthews  

E-Print Network (OSTI)

lithium abundance, X-ray activity, and evidence of strong chromospheric activity. Disk systems were inferred around four of the 18 association members (Zuckerman & Song 2004) from measurements of IR excess) excess emission several times. The presence of a

Kalas, Paul G.

367

E-Print Network 3.0 - atomic circumnuclear disk Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

1 2 3 4 5 > >> 1 The Role of Neutral Hydrogen in the Evolution of Nearby Summary: disk of atomic hydrogen in Centaurus A 101 4.1 Introduction... nuclear H I absorption . . . . . ....

368

Slit disk for modified faraday cup diagnostic for determining power density of electron and ion beams  

DOE Patents (OSTI)

A diagnostic system for characterization of an electron beam or an ion beam includes an electrical conducting disk of refractory material having a circumference, a center, and a Faraday cup assembly positioned to receive the electron beam or ion beam. At least one slit in the disk provides diagnostic characterization of the electron beam or ion beam. The at least one slit is located between the circumference and the center of the disk and includes a radial portion that is in radial alignment with the center and a portion that deviates from radial alignment with the center. The electron beam or ion beam is directed onto the disk and translated to the at least one slit wherein the electron beam or ion beam enters the at least one slit for providing diagnostic characterization of the electron beam or ion beam.

Teruya, Alan T. (Livermore, CA); Elmer; John W. (Danville, CA); Palmer, Todd A. (State College, PA)

2011-03-08T23:59:59.000Z

369

Design and Analysis on Face-Cooled Disk Faraday Rotator under High Average Power Lasers  

Science Journals Connector (OSTI)

A novel, scalable Faraday rotator has been designed for high-average-power lasers in a gas-cooled multi-disk scheme. The concept with a negligible thermal distortion and birefringence...

Yasuhara, Ryo; Yamanaka, Masanobu; Norimatsu, Takayoshi; Izawa, Yasukazu; Kawashima, Toshiyuki; Ikegawa, Tadashi; Matsumoto, Osamu; Sekine, Takashi; Kurita, Takashi; Kan, Hirofumi; Furukawa, Hiroyuki

370

Design and Analysis on Face-Cooled Disk Faraday Rotator for High Average Power Lasers  

Science Journals Connector (OSTI)

A novel, scalable Faraday rotator has been designed for high-average-power lasers in a gas-cooled multi-disk scheme. The concept with a negligible thermal distortion and birefringence...

Yasuhara, R; Yamanaka, M; Norimatsu, T; Izawa, Y; Kawashima, T; Ikegawa, T; Matsumoto, O; Sekine, T; Kurita, T; Kan, H; Furukawa, H

371

E-Print Network 3.0 - accretion disk annulus Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

I. General Solution and Application to Sgr A* Summary: Accretion Disk Evolution With Wind Infall I. General Solution and Application to Sgr A* Heino... (melia@as.arizona.edu)...

372

E-Print Network 3.0 - accretion disk systems Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

accretion disk in SW Sex, assuming a distance to the binary system of 450 pc... the high-inclination systems, suggesting that their origin is not in a at, Keplarian accretion...

373

Planck's confirmation of the M31 disk and halo rotation  

E-Print Network (OSTI)

Planck's data acquired during the first 15.4 months of observations towards both the disk and halo of the M31 galaxy are analyzed. We confirm the existence of a temperature asymmetry, previously detected by using the 7-year WMAP data, along the direction of the M31 rotation, therefore indicative of a Doppler-induced effect. The asymmetry extends up to about 10 degrees (about 130 kpc) from the M31 center. We also investigate the recent issue raised in Rubin and Loeb (2014) about the kinetic Sunyaev-Zeldovich effect from the diffuse hot gas in the Local Group, predicted to generate a hot spot of a few degrees size in the CMB maps in the direction of M31, where the free electron optical depth gets the maximum value. We also consider the issue whether in the opposite direction with respect to the M31 galaxy the same effect induces a minimum in temperature in the Planck's maps of the sky. We find that the Planck's data at 100 GHz show an effect even larger than that expected.

De Paolis, F; Nucita, A A; Ingrosso, G; Kashin, A L; Khachatryan, H G; Mirzoyan, S; Poghosian, E; Jetzer, Ph; Qadir, A; Vetrugno, D

2014-01-01T23:59:59.000Z

374

Environmental Effects on Gaseous Disks of the Virgo Spiral Galaxies  

E-Print Network (OSTI)

We found high molecular fractions ($f_{\\rm mol}$; ratio of the molecular to total gas surface densities) in three of five Virgo spiral galaxies in spite of their low total gas column density, based on $^{12}$CO$(J=1-0)$ observations with the Nobeyama 45 m telescope equipped with a multi-beam receiver, BEARS. We interpret this as a result of environmental effects. Combining the CO data with HI data, the relationship between the surface density of the total gas (HI plus H$_2$) and $f_{\\rm mol}$ indicates that the three galaxies near the cluster center have larger $f_{\\rm mol}$ values than expected for field galaxies, while the others show normal $f_{\\rm mol}$. The large $f_{\\rm mol}$ is interpreted as being due either to effective HI gas stripping, even in the inner disks, or to large ISM pressure induced by the high ICM pressure and/or ram pressure, although the possibility of an unusually high metallicity cannot be ruled out.

Hiroyuki Nakanishi; Nario Kuno; Yoshiaki Sofue; Naoko Sato; Naomasa Nakai; Yasuhiro Shioya; Tomoka Tosaki; Sachiko Onodera; Kazuo Sorai; Fumi Egusa; Akihiko Hirota

2006-10-27T23:59:59.000Z

375

Shadowing of the Nascent Jet in NGC 4261 by a Line-Emitting Supersonic Accretion Disk  

E-Print Network (OSTI)

NGC 4261 (3C 270) is a low-luminosity radio galaxy with two symmetric kiloparsec-scale jets. Earlier Hubble Space Telescope observations indicated the presence of a hundred-parsec scale disk of cool dust and gas surrounding a central, supermassive ($\\sim 4.9\\times 10^8\\msun$) black hole. The recent detection of free-free radio absorption by a small, geometrically-thin disk, combined with earlier studies of the disk's large scale properties, provide the strictest constraints to date on the nature of the accretion process in this system. We show here that a supersonic disk, illuminated by the active galactic nucleus (AGN), can not only account for the observed radio shadowing, but can also produce the optical broad lines emitted from this region. Beyond a critical radius $r_c$, line cooling dominates over gravitational dissipation and the gas is effectively cooled down to temperatures below $10^4$ K. Within $r_c$, however, heating due to the release of gravitational energy overwhelms line cooling and the plasma is heated very quickly to a temperature close to its virial value as it falls toward the central engine. The disk is optically-thin to UV and X-ray radiation within $r_c$, so the ionizing radiation from the AGN is preferentially absorbed near $r_c$, affecting the disk structure significantly. To include the ensuing photoionization effect, we have used the algorithm Cloudy with additional heating introduced by gravitational dissipation to calculate the temperature profile and line emission from the disk in a self-consistent manner. The results of our model calculation are consistent with current multiwavelength observations of the disk in this source.

Siming Liu; Michael J. Fromerth; Fulvio Melia

2003-06-27T23:59:59.000Z

376

Disk clamping distortion and slider crown sensitivity induced flying height variation  

Science Journals Connector (OSTI)

The disk clamping distortion and slider crown sensitivity induced flying height (FH) variation is investigated. The experimental results which were measured with in situ method were compared with simulated numerical results. Both results indicate that the disk clamping distortion has significant influence on the FH variation. Crown sensitivity of the sliders is one of the factors that determine the amplitude of the FH variation. Higher crown sensitivity sliders exhibit greater FH variation.

Ng Ka Wei; Yuan Zhimin; Liu Bo

2006-01-01T23:59:59.000Z

377

Diffusive Particle Acceleration in Shocked, Viscous Accretion Disks: Green's Function Energy Distribution  

Science Journals Connector (OSTI)

The acceleration of relativistic particles in a viscous accretion disk containing a standing shock is investigated as a possible explanation for the energetic outflows observed around radio-loud black holes. The energy/space distribution of the accelerated particles is computed by solving a transport equation that includes the effects of first-order Fermi acceleration, bulk advection, spatial diffusion, and particle escape. The velocity profile of the accreting gas is described using a model for shocked viscous disks recently developed by the authors, and the corresponding Green's function distribution for the accelerated particles in the disk and the outflow is obtained using a classical method based on eigenfunction analysis. The accretion-driven, diffusive shock acceleration scenario explored here is conceptually similar to the standard model for the acceleration of cosmic rays at supernova-driven shocks. However, in the disk application, the distribution of the accelerated particles is much harder than would be expected for a plane-parallel shock with the same compression ratio. Hence the disk environment plays a key role in enhancing the efficiency of the shock acceleration process. The presence of the shock helps to stabilize the disk by reducing the Bernoulli parameter, while channeling the excess binding energy into the escaping relativistic particles. In applications to M87 and SgrA*, we find that the kinetic power in the jet is , and the outflowing relativistic particles have a mean energy ~300 times larger than that of the thermal gas in the disk at the shock radius. Our results suggest that a standing shock may be an essential ingredient in accretion onto underfed black holes, helping to resolve the long-standing problem of the stability of advection-dominated accretion disks.

Peter A. Becker; Santabrata Das; Truong Le

2011-01-01T23:59:59.000Z

378

DISCOVERY OF AN H{alpha} EMITTING DISK AROUND THE SUPERMASSIVE BLACK HOLE OF M31  

SciTech Connect

Due to its proximity, the mass of the supermassive black hole in the nucleus of the Andromeda galaxy (M31), the most massive black hole in the Local Group of galaxies, has been measured by several methods involving the kinematics of a stellar disk which surrounds it. We report here the discovery of an eccentric H{alpha} emitting disk around the black hole at the center of M31 and show how modeling this disk can provide an independent determination of the mass of the black hole. Our model implies a mass of 5.0{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 7} M{sub Sun} for the central black hole, consistent with the average of determinations by methods involving stellar dynamics, and compatible (at 1{sigma} level) with measurements obtained from the most detailed models of the stellar disk around the central black hole. This value is also consistent with the M-{sigma} relation. In order to make a comparison, we applied our simulation on the stellar kinematics in the nucleus of M31 and concluded that the parameters obtained for the stellar disk are not formally compatible with the parameters obtained for the H{alpha} emitting disk. This result suggests that the stellar and the H{alpha} emitting disks are intrinsically different from each other. A plausible explanation is that the H{alpha} emission is associated with a gaseous disk. This hypothesis is supported by the detection of traces of weaker nebular lines in the nuclear region of M31. However, we cannot exclude the possibility that the H{alpha} emission is, at least partially, generated by stars.

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br [Instituto de Astronomia Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, Sao Paulo, SP CEP 05508-090 (Brazil)

2013-01-10T23:59:59.000Z

379

Raman Spectroscopy Characterization of amorphous carbon coatings for computer hard disks  

SciTech Connect

Amorphous carbon films are used as protective coatings on magnetic media to protect the magnetic layer from wear and abrasion caused by the read/write head during hard disk drive start-up and operation. A key requirement in increasing the storage capacity and reliability of hard-disk drives is improving the performance of these coatings. This cooperative agreement used optical characterization techniques developed at LBNL to study thin-film hard disk media produced by Seagate Technology, major US hard drive manufacturer. The chief scientific goal was relating quantitatively the results of the optical characterization to the underlying chemical structure of the overcoat. In a collaboration with Seagate, LBNL, and Cambridge University, optical and electron-based characterization were used to evaluate the chemical structure of overcoats. The sp3 fraction of the sputtered amorphous carbon films was measured quantitatively for the first time and related to the optical spectroscopy results. This work and other selected aspects of the research performed under the agreement were presented at technical meetings and published in the open literature. The chief technical goal was designing manufacturing processes for the protective carbon overcoat for use in new generations of Seagate disk drives. To this end, joint research carried out under this agreement enabled Seagate to speed development of new coatings which are currently being used in the production of disk media in Seagate's disk-media manufacturing plants in Fremont, CA.

Ager III, Joel W.

1998-05-07T23:59:59.000Z

380

Gravitational drag on a point mass in hypersonic motion within a Gaussian disk  

E-Print Network (OSTI)

We develop an analytical model for the accretion and gravitational drag on a point mass that moves hypersonically in the midplane of a gaseous disk with a Gaussian vertical density stratification. Such a model is of interest for studying the interaction between a planet and a protoplanetary disk, as well as the dynamical decay of massive black holes in galactic nuclei. The model considers that the flow is ballistic, and gives fully analytical expressions for both the accretion rate onto the point mass, and the gravitational drag it suffers. The expressions are further simplified by taking the limits of a thick, and of a thin disk. The results for the thick disk reduce correctly to those for a uniform density environment (Cant\\'o et al. 2011). We find that for a thin disk (small vertical scaleheight compared to the gravitational radius) the accretion rate is proportional to the mass of the moving object and to the surface density of the disk, while the drag force is independent of the velocity of the object. T...

Cant, J; Raga, A C

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Time-Dependent Disk Models for the Microquasar GRS1915+105  

E-Print Network (OSTI)

We investigate different accretion disk models and viscosity prescriptions in order to provide a basic explanation for the exotic temporal behavior in GRS 1915+105. Based on the fact that the overall cycle times are very much longer than the rise/fall time scales in GRS 1915, we rule out the geometry of ADAF or a hot quasi-spherical region plus a cold outer disk for this source. We thus concentrate on geometrically thin Shakura-Sunyaev type disks (Shakura & Sunyaev 1973; hereafter SS73). We have devised a modified viscosity law that has a quasi-stable upper branch. Via numerical simulations, we show that the model does account for several gross observational features of GRS 1915+105. On the other hand, the rise/fall time scales are not short enough, and no rapid oscillations on time scales $\\simlt$ 10 s emerge naturally from the model. We then consider and numerically test a more elaborate model that includes the cold disk, a corona, and plasma ejections from the inner disk region and show that this model allows us to reproduce several additional observed features of GRS 1915+105. We conclude that the most likely structure of the accretion flow in this source is that of a cold disk with a modified viscosity prescription, plus a corona that accounts for much of the X-ray emission, and unsteady plasma ejections that occur when the luminosity of the source is high.

Sergei Nayakshin; Saul Rappaport; Fulvio Melia

1999-05-27T23:59:59.000Z

382

Water vapour and hydrogen in the terrestrial-planet-forming region of a protoplanetary disk  

E-Print Network (OSTI)

Planetary systems, ours included, are formed in disks of dust and gas around young stars. Disks are an integral part of the star and planet formation process, and knowledge of the distribution and temperature of inner disk material is crucial for understanding terrestrial planet formation, giant planet migration, and accretion onto the central star. While the inner regions of protoplanetary disks in nearby star forming regions subtend only a few nano-radians, near-IR interferometry has recently enabled the spatial resolution of these terrestrial zones. Most observations have probed only dust, which typically dominates the near-IR emission. Here I report spectrally dispersed near-IR interferometric observations that probe gas (which dominates the mass and dynamics of the inner disk), in addition to dust, within one astronomical unit of the young star MWC 480. I resolve gas, including water vapor and atomic hydrogen, interior to the edge of the dust disk; this contrasts with results of previous spectrally dispersed interferometry observations. Interactions of this accreting gas with migrating planets may lead to short-period exoplanets like those detected around main-sequence stars. The observed water vapor is likely produced by the sublimation of migrating icy bodies, and provides a potential reservoir of water for terrestrial planets.

J. A. Eisner

2007-06-08T23:59:59.000Z

383

TESTING ACCRETION DISK STRUCTURE WITH SUZAKU DATA OF LMC X-3  

SciTech Connect

The Suzaku observation of LMC X-3 gives the best data to date on the shape of the accretion disk spectrum. This is due to the combination of very low absorbing column density along this line of sight, which allows the shape of the disk emission to be constrained at low energies by the CCDs while the tail can be simultaneously determined up to 30 keV by the high-energy detectors. These data clearly demonstrate that the observed disk spectrum is broader than a simple 'sum of blackbodies', and relativistic smearing of the emission is strongly required. However, the intrinsic emission should be more complex than a (color-corrected) sum of blackbodies as it should also contain photoelectric absorption edges from the partially ionized disk photosphere. These are broadened by the relativistic smearing, but the models predict {approx}3%-5% deviations for 1/3-1 solar abundance around the edge energies, significantly stronger than observed. This indicates that the models need to include more physical processes such as self-irradiation, bound-bound (line) absorption, and/or emission from recombination continua and/or lines. Alternatively, if none of these match the data, it may instead require that the accretion disk density and/or emissivity profile with height is different to that assumed. Thus, these data demonstrate the feasibility of observational tests of our fundamental understanding of the vertical structure of accretion disks.

Kubota, Aya [Department of Electronic Information Systems, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama 337-8570 (Japan); Done, Chris [Department of Physics, University of Durham, South Road, Durham, DH1 3LE (United Kingdom); Davis, Shane W. [School of Natural Sciences, Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Dotani, Tadayasu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan); Mizuno, Tsunefumi [Department of Physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ueda, Yoshihiro, E-mail: aya@shibaura-it.ac.j [Department of Astronomy, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)

2010-05-01T23:59:59.000Z

384

Warm Gas in the Inner Disks around Young Intermediate Mass Stars  

E-Print Network (OSTI)

The characterization of gas in the inner disks around young stars is of particular interest because of its connection to planet formation. In order to study the gas in inner disks, we have obtained high-resolution K-band and M-band spectroscopy of 14 intermediate mass young stars. In sources that have optically thick inner disks, i.e. E(K-L)>1, our detection rate of the ro-vibrational CO transitions is 100% and the gas is thermally excited. Of the five sources that do not have optically thick inner disks, we only detect the ro-vibrational CO transitions from HD 141569. In this case, we show that the gas is excited by UV fluorescence and that the inner disk is devoid of gas and dust. We discuss the plausibility of the various scenarios for forming this inner hole. Our modeling of the UV fluoresced gas suggests an additional method by which to search for and/or place stringent limits on gas in dust depleted regions in disks around Herbig Ae/Be stars.

Sean Brittain; Theodore Simon; Joan Najita; Terrence Rettig

2006-12-08T23:59:59.000Z

385

KECK ADAPTIVE OPTICS OBSERVATIONS OF THE PROTOSTELLAR DISK AROUND RADIO SOURCE I IN THE ORION KLEINMANN-LOW NEBULA  

SciTech Connect

We have made the first detection of a near-infrared counterpart associated with the disk around Radio Source ''I'', a massive protostar in the Kleinmann-Low nebula in Orion, using imaging with laser guide star adaptive optics on the Keck II telescope. The infrared emission is evident in images acquired using L' (3.8 {mu}m) and Ms (4.7 {mu}m) filters and is not detectable at K' (2.1 {mu}m). The observed morphology strongly suggests that we are seeing some combination of scattered and thermal light emanating from the disk. The disk is also manifest in the L'/Ms flux ratio image. We interpret the near-infrared emission as the illuminated surface of a nearly edge-on disk, oriented so that only the northern face is visible; the opposite surface remains hidden by the disk. We do not see infrared radiation associated directly with the star proposed to be associated with Source ''I''. The data also suggest that there is a cavity above and below the disk that is oriented perpendicular to the disk and is sculpted by the known, strong outflow from the inner disk of Source I. We compare our data to models of a protostar with a surrounding disk, envelope, and wind-blown cavity in order to elucidate the nature of the disk around Radio Source I.

Sitarski, Breann N.; Morris, Mark R.; Becklin, E. E.; Ghez, Andrea M. [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095-1547 (United States); Lu, Jessica R. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Duchene, Gaspard [Department of Astronomy, University of California, Berkeley, C-203 Hearst Field Annex, Berkeley, CA 94720-3411 (United States); Stolte, Andrea [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Zinnecker, Hans, E-mail: bsitarski@astro.ucla.edu [NASA-Ames Research Center, MS 232-12, Moffett Field, CA 94035 (United States)

2013-06-20T23:59:59.000Z

386

MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES  

SciTech Connect

We compare molecular gas traced by {sup 12}CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between {Sigma}{sub mol} and {Sigma}{sub SFR} but also find important second-order systematic variations in the apparent molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}. At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed {alpha}{sub CO} equivalent to the Milky Way value, our data yield a molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}{approx}2.2 Gyr with 0.3 dex 1{sigma} scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, {Sigma}{sub SFR}{proportional_to}{Sigma}{sub mol}{sup N}. We find N = 1 {+-} 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between {tau}{sub dep}{sup mol} and other local and global quantities. The strongest of these are a decreased {tau}{sub dep}{sup mol} in low-mass, low-metallicity galaxies and a correlation of the kpc-scale {tau}{sub dep}{sup mol} with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H{sub 2} conversion factor ({alpha}{sub CO}) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed {tau}{sub dep}{sup mol} trends. After applying a D/G-dependent {alpha}{sub CO}, some weak correlations between {tau}{sub dep}{sup mol} and local conditions persist. In particular, we observe lower {tau}{sub dep}{sup mol} and enhanced CO excitation associated with nuclear gas concentrations in a subset of our targets. These appear to reflect real enhancements in the rate of star formation per unit gas, and although the distribution of {tau}{sub dep} does not appear bimodal in galaxy centers, {tau}{sub dep} does appear multivalued at fixed {Sigma}{sub H2}, supporting the idea of ''disk'' and ''starburst'' modes driven by other environmental parameters.

Leroy, Adam K.; Munoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva [Max Planck Institute fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Schruba, Andreas [California Institute for Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Bigiel, Frank [Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Bolatto, Alberto [Department of Astronomy, University of Maryland, College Park, MD (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); De Blok, W. J. G. [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Rosolowsky, Erik [University of British Columbia, Okanagan Campus, Kelowna, BC (Canada); Schuster, Karl-Friedrich [IRAM, 300 rue de la Piscine, F-38406 St. Martin d'Heres (France); Usero, Antonio [Observatorio Astronomico Nacional, C/ Alfonso XII, 3, E-28014 Madrid (Spain)

2013-08-01T23:59:59.000Z

387

A compact dusty disk around the Herbig Ae star HR 5999 resolved with VLTI / MIDI  

E-Print Network (OSTI)

We have used mid-infrared long-baseline interferometry with MIDI at the VLTI to resolve the circumstellar material around the Herbig Ae star HR 5999, providing the first direct measurement of its angular size, and to derive constraints on the spatial distribution of the dust. A set of ten spectrally dispersed (8-13 micron) interferometric measurements of HR 5999 was obtained. The characteristic size of the emission region depends on the projected baseline length and position angle, and it ranges between ~ 5-15 milliarcseconds (Gauss FWHM), corresponding to remarkably small physical sizes of ~ 1-3 AU. To derive constraints on the geometrical distribution of the dust, we compared our interferometric measurements to 2D, frequency-dependent radiation transfer simulations of circumstellar disks and envelopes. For disk models with radial power-law density distributions, the relatively weak but very extended emission from outer disk regions (>~ 3 AU) leads to model visibilities that are significantly lower than the observed visibilities, making these models inconsistent with the MIDI data. Disk models in which the density is truncated at outer radii of ~ 2-3 AU, on the other hand, provide good agreement with the data. A satisfactory fit to the observed MIDI visibilities of HR 5999 is found with a model of a geometrically thin disk that is truncated at 2.6 AU and seen under an inclination angle of 58 degr. Neither models of a geometrically thin disk seen nearly edge-on, nor models of spherical dust shells can achieve agreement between the observed and predicted visibilities. The reason why the disk is so compact remains unclear; we speculate that it has been truncated by a close binary companion.

Thomas Preibisch; Stefan Kraus; Thomas Driebe; Roy van Boekel; Gerd Weigelt

2006-07-21T23:59:59.000Z

388

Tomographic Simulations of Accretion Disks in Cataclysmic Variables - Flickering and Wind  

E-Print Network (OSTI)

Both continuum and emission line flickering are phenomena directly associated with the mass accretion process. In this work we simulate accretion disk Doppler maps including the effects of winds and flickering flares. Synthetic flickering Doppler maps are calculated and the effect of the flickering parameters on the maps is explored. Jets and winds occur in many astrophysical objects where accretion disks are present. Jets are generally absent among the cataclysmic variables (CVs), but there is evidence of mass loss by wind in many objects. CVs are ideal objects to study accretion disks and consequently to study the wind associated with these disks. We also present simulations of accretion disks including the presence of a wind with orbital phase resolution. Synthetic H-alpha line profiles in the optical region are obtained and their corresponding Doppler maps are calculated. The effect of the wind simulation parameters on the wind line profiles is also explored. From this study we verified that optically thick lines and/or emission by diffuse material into the primary Roche lobe are necessary to generate single peaked line profiles, often seen in CVs. The future accounting of these effects is suggested for interpreting Doppler tomography reconstructions.

Fabiola M. A. Ribeiro; Marcos P. Diaz

2007-11-22T23:59:59.000Z

389

A SPITZER SPACE TELESCOPE STUDY OF THE DEBRIS DISKS AROUND FOUR SDSS WHITE DWARFS  

SciTech Connect

We present Spitzer Space Telescope data of four isolated white dwarfs that were previously known to harbor circumstellar gaseous disks. Infrared Array Camera photometry shows a significant infrared excess in all of the systems, SDSS0738+1835, SDSS0845+2257, SDSS1043+0855, and SDSS1617+1620, indicative of a dusty extension to those disks. The 4.5 {mu}m excesses seen in SDSS0738, SDSS0845, and SDSS1617 are 7.5, 5.7, and 4.5 times the white dwarf contribution, respectively. In contrast, in SDSS1043, the measured flux density at 4.5 {mu}m is only 1.7 times the white dwarf contribution. We compare the measured IR excesses in the systems to models of geometrically thin, optically thick disks, and find that we are able to match the measured spectral energy distributions to within 3{sigma} of the uncertainties, although disks with unfeasibly hot inner dust temperatures generally provide a better fit than those below the dust sublimation temperature. Possible explanations for the dearth of dust around SDSS1043+0855 are briefly discussed. Including our previous study of SDSS1228+1040, all five white dwarfs with gaseous debris disks have significant amounts of dust around them. It is evident that gas and dust can coexist around these relatively warm, relatively young white dwarfs.

Brinkworth, C. S.; Girven, J. M.; Hoard, D. W. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Gaensicke, B. T.; Marsh, T. R.; Parsons, S. G. [Department of Physics and Astronomy, University of Warwick, Warwick CV4 7AL (United Kingdom); Koester, D. [Institut fuer Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel (Germany)

2012-05-01T23:59:59.000Z

390

Characterization of irradiated AISI 316L stainless steel disks removed from the Spallation Neutron Source  

SciTech Connect

Irradiated AISI 316L stainless steel disks were removed from the Spallation Neutron Source (SNS) for post-irradiation examination (PIE) to assess mechanical property changes due to radiation damage and erosion of the target vessel. Topics reviewed include high-resolution photography of the disk specimens, cleaning to remove mercury (Hg) residue and surface oxides, profile mapping of cavitation pits using high frequency ultrasonic testing (UT), high-resolution surface replication, and machining of test specimens using wire electrical discharge machining (EDM), tensile testing, Rockwell Superficial hardness testing, Vickers microhardness testing, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effectiveness of the cleaning procedure was evident in the pre- and post-cleaning photography and permitted accurate placement of the test specimens on the disks. Due to the limited amount of material available and the unique geometry of the disks, machine fixturing and test specimen design were critical aspects of this work. Multiple designs were considered and refined during mock-up test runs on unirradiated disks. The techniques used to successfully machine and test the various specimens will be presented along with a summary of important findings from the laboratory examinations.

Vevera, Bradley J [ORNL] [ORNL; Hyres, James W [ORNL] [ORNL; McClintock, David A [ORNL] [ORNL; Riemer, Bernie [ORNL] [ORNL

2014-01-01T23:59:59.000Z

391

Filling the disk hollow following binary black hole merger: The transient accretion afterglow  

SciTech Connect

Tidal torques from a binary black hole empty out the central regions in any circumbinary gaseous accretion disk. The balance between tidal torques and viscosity maintain the inner edge of the disk at a radius r{approx}1.5a-2a, where a is the binary semimajor axis. Eventually, the inspiraling binary decouples from the disk and merges, leaving behind a central hollow (''donut hole'') in the disk orbiting the remnant black hole. We present a simple, time-dependent, Newtonian calculation that follows the secular (viscous) evolution of the disk as it fills up the hollow down to the black hole innermost stable circular orbit and then relaxes to stationary equilibrium. We use our model to calculate the electromagnetic radiation (''afterglow'') spectrum emitted during this transient accretion epoch. Observing the temporal increase in the total electromagnetic flux and the hardening of the spectrum as the donut hole fills may help confirm a binary black hole merger detected by a gravitational wave interferometer. We show how the very existence of the initial hollow can lead to super-Eddington accretion during this secular phase if the rate is not very far below Eddington prior to decoupling. Our model, though highly idealized, may be useful in establishing some of the key parameters, thermal emission features and scalings that characterize this transient. It can serve as a guide in the design and calibration of future radiation-magnetohydrodynamic simulations in general relativity.

Shapiro, Stuart L. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2010-01-15T23:59:59.000Z

392

THE CASE OF AB AURIGAE'S DISK IN POLARIZED LIGHT: IS THERE TRULY A GAP?  

SciTech Connect

Using the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) coronagraph, we have obtained high-contrast 2.0 mum imaging polarimetry and 1.1 mum imaging of the circumstellar disk around AB Aurigae on angular scales of 0.''3-3'' (40-550 AU). Unlike previous observations, these data resolve the disk in both total and polarized intensity, allowing accurate measurement of the spatial variation of polarization fraction across the disk. Using these observations, we investigate the apparent 'gap' in the disk reported by Oppenheimer et al.. In polarized intensity, the NICMOS data closely reproduce the morphology seen by Oppenheimer et al., yet in total intensity we find no evidence for a gap in either our 1.1 or 2.0 mum images. We find instead that region has lower polarization fraction, without a significant decrease in total scattered light, consistent with expectations for backscattered light on the far side of an inclined disk. Radiative transfer models demonstrate this explanation fits the observations. Geometrical scattering effects are entirely sufficient to explain the observed morphology without any need to invoke a gap or a protoplanet at that location.

Perrin, Marshall D. [Division of Astronomy, University of California, Los Angeles, CA 90095 (United States); Schneider, Glenn [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Duchene, Gaspard [University of California, Berkeley, Berkeley, CA 94720 (United States); Pinte, Christophe [Universite Joseph Fourier-Grenoble 1/CNRS, Laboratoire d'Astrophysique de Grenoble (LAOG) UMR 5571, BP 53, 38041 Grenoble, Cedex 09 (France); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Wisniewski, John P. [Department of Astronomy, University of Washington Seattle, WA 98195-1580 (United States); Hines, Dean C., E-mail: mperrin@ucla.ed [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States)

2009-12-20T23:59:59.000Z

393

THE LIFETIME OF PROTOPLANETARY DISKS IN A LOW-METALLICITY ENVIRONMENT  

SciTech Connect

The extreme outer Galaxy (EOG), the region with a Galactic radius of more than 18 kpc, is known to have a very low metallicity, about one-tenth that of the solar neighborhood. We obtained the deep near-infrared (NIR) images of two very young (approx0.5 Myr) star-forming clusters that are two of the most distant embedded clusters in the EOG. We find that in both clusters the fraction of stars with NIR excess, which originates from the circumstellar dust disk at radii of <=0.1 AU, is significantly lower than those in the solar neighborhood. Our results suggest that most of the stars forming in the low-metallicity environment experience disk dispersal at an earlier stage (<1 Myr) than those forming in the solar metallicity environment (as much as approx5-6 Myr). Such a rapid disk dispersal may make the formation of planets difficult, and the shorter disk lifetime with a lower metallicity, could contribute to the strong metallicity dependence of the well-known 'planet-metallicity correlation', which states that the probability of a star hosting a planet increases steeply with stellar metallicity. The reason for the rapid disk dispersal could be the increase of the mass accretion rate and/or the effective far-ultraviolet photoevaporation due to the low extinction; however, another unknown mechanism for the EOG environment could be contributing significantly.

Yasui, Chikako; Kobayashi, Naoto [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Tokunaga, Alan T. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Saito, Masao [ALMA Project, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Tokoku, Chihiro, E-mail: ck_yasui@ioa.s.u-tokyo.ac.j [Astronomical Institute, Tohoku University, Aramaki, Aoba, Sendai 980-8578 (Japan)

2009-11-01T23:59:59.000Z

394

Accretion disks around binary black holes of unequal mass: GRMHD simulations near decoupling  

E-Print Network (OSTI)

We report on simulations in general relativity of magnetized disks onto black hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the systems when they orbit near the binary-disk decoupling radius. We compare (surface) density profiles, accretion rates (relative to a single, non-spinning black hole), variability, effective $\\alpha$-stress levels and luminosities as functions of the mass ratio. We treat the disks in two limiting regimes: rapid radiative cooling and no radiative cooling. The magnetic field lines clearly reveal jets emerging from both black hole horizons and merging into one common jet at large distances. The magnetic fields give rise to much stronger shock heating than the pure hydrodynamic flows, completely alter the disk structure, and boost accretion rates and luminosities. Accretion streams near the horizons are among the densest structures; in fact, the 1:10 no-cooling evolution results in a refilling of the cavity. The typical effective temperature in the bulk of the disk is $\\sim 10^5 (M/10^8 M_\\odot)^{-1/4} (L/L_{\\rm edd})^{1/4} {\\rm K}$ yielding characteristic thermal frequencies $\\sim 10^{15} (M/10^8 M_\\odot)^{-1/4} (L/L_{\\rm edd})^{1/4}(1+z)^{-1}{\\rm Hz} $. These systems are thus promising targets for many extragalactic optical surveys, such as LSST, WFIRST, and PanSTARRS.

Roman Gold; Vasileios Paschalidis; Zachariah B. Etienne; Stuart L. Shapiro; Harald P. Pfeiffer

2013-12-02T23:59:59.000Z

395

3-D GRMHD Simulations of Disk-Jet Coupling and Emission  

E-Print Network (OSTI)

We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity nearly 0.3c) is created as shown by previous two-dimensional axisymmetric simulations with mirror symmetry at the equator. The 3-D simulation ran over one hundred light-crossing time units which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted due in part to magnetic pressure from the twisting the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3r_S. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outwards with a wider angle than the initial jet. The widening of the jet is consistent with the outward moving torsional Alfven waves (TAWs). This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk due to the lack of streaming material from an accompanying star.

K. -I. Nishikawa; Y. Mizuno; S. Fuerst; K. Wu; P. Hardee; G. Richardson; S. Koide; K. Shibata; T. Kudoh; G. J. Fishman

2005-09-20T23:59:59.000Z

396

3?D GRMHD Simulations of Disk?Jet Coupling and Emission  

Science Journals Connector (OSTI)

We have performed a fully three?dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free?falling corona. The initial simulation results show that a bipolar jet (velocity ? 0.3c) is created as shown by previous two?dimensional axisymmetric simulations with mirror symmetry at the equator. The 3?D simulation ran over one hundred light?crossing time units (?S = r S/c where r S ? 2GM/c 2) which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted due in part to magnetic pressure from the twisting the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3r S. At later times the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus?like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outwards with a wider angle than the initial jet. The widening of the jet is consistent with the outward moving torsional Alfvn waves (TAWs). This evolution of disk?jet coupling suggests that the jet fades with a thickened accretion disk due to the lack of streaming material from an accompanying star.

K.?I. Nishikawa; Y. Mizuno; S. Fuerst; K. Wu; P. Hardee; G. Richardson; S. Koide; K. Shibata; T. Kudoh; G. J. Fishman

2005-01-01T23:59:59.000Z

397

Dynamics of Sheared Ellipses and Circular Disks: Effects of Particle Shape  

E-Print Network (OSTI)

Much recent effort has focused on glassy and jamming properties of spherical particles. Very little is known about such phenomena for non-spherical particles, and we take a first step by studying ellipses. We find important differences between the dynamical and structural properties of disks and two-dimensional ellipses subject to continuous Couette shear. In particular, ellipses show slow dynamical evolution, without a counterpart in disks, in the mean velocity, local density, orientational order, and local stress. starting from an unjammed state, ellipses can first jam under shear, and then slowly unjam. The slow unjamming process is understood as a result of gradual changes in their orientations, leading to a denser packing. For disks, the rotation of particles only contributes to relaxation of frictional forces, and hence, does not significantly cause structural changes. For the shear-jammed states, the global building up and relaxation of stress, which occurs in the form of stress avalanches, is qualitatively different for disks and ellipses, and is manifested by different forms of rate-dependence for ellipses vs. disks. Unlike the weak rate dependence typical for many granular systems, ellipses show power-law dependence on the shearing rate, {\\Omega}.

Somayeh Farhadi; Robert P. Behringer

2014-02-18T23:59:59.000Z

398

The gas-rich disk of HR 4049: A study of the infrared spectrum  

SciTech Connect

Here, we present a summary of our analyses of the mid-and near-infrared spectrum of the unusual evolved binary HR 4049. We f nd that the disk is massive (M > 8 10{sup ?3} M{sub ?}), warm and radially extended. We also report some enrichment in {sup 17}O and {sup 18}O and a comparison of observations from Spitzer-IRS to those obtained by ISO-SWS 10 years earlier reveals that the CO{sub 2} f ux has more than doubled in this time, indicating active and ongoing chemical evolution in the circumbinary disk. Given the high column densities of the gas in the disk, we expect that the molecular gas plays a crucial role in the thermal properties of the circumbinary disk by allowing visible light to heat the dust and then trapping the IR photons emitted by the dust. This will result in higher temperatures and a more homogeneous temperature structure in the disk. Finally, we estimate a mass for the primary in HR 4049 which is too low for the star to have experienced a typical evolutionary path.

Malek, Sarah E. [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Cami, Jan [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 Canada and SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94034 (United States)

2014-05-02T23:59:59.000Z

399

THE GAS/DUST RATIO OF CIRCUMSTELLAR DISKS: TESTING MODELS OF PLANETESIMAL FORMATION  

SciTech Connect

We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. {sup 12}CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig et al.

Horne, David [New York Center for Astrobiology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180-3590 (United States); Gibb, Erika [Department of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121 (United States); Rettig, Terrence W.; Tilley, David; Balsara, Dinshaw [Center for Astrophysics, University of Notre Dame, Notre Dame, IN 46556 (United States); Brittain, Sean [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)

2012-07-20T23:59:59.000Z

400

SMACK: A NEW ALGORITHM FOR MODELING COLLISIONS AND DYNAMICS OF PLANETESIMALS IN DEBRIS DISKS  

SciTech Connect

We present the Superparticle-Method/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in three dimensions, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10{sup 7} yr and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.

Nesvold, Erika R. [Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Kuchner, Marc J.; Pan, Margaret [NASA Goddard Space Flight Center Exoplanets and Stellar Astrophysics Laboratory, Code 667, Greenbelt, MD 21230 (United States); Rein, Hanno, E-mail: Erika.Nesvold@umbc.edu, E-mail: Marc.Kuchner@nasa.gov, E-mail: Margaret.Pan@nasa.gov, E-mail: rein@ias.edu [Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540 (United States)

2013-11-10T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Review of fluid flow and convective heat transfer within rotating disk cavities with impinging jet  

E-Print Network (OSTI)

Fluid flow and convective heat transfer in rotor-stator configurations, which are of great importance in different engineering applications, are treated in details in this review. The review focuses on convective heat transfer in predominantly outward air flow in the rotor-stator geometries with and without impinging jets and incorporates two main parts, namely, experimental/theoretical methodologies and geometries/results. Experimental methodologies include naphthalene sublimation techniques, steady state (thin layer) and transient (thermochromic liquid crystals) thermal measurements, thermocouples and infra-red cameras, hot-wire anemometry, laser Doppler and particle image velocimetry, laser plane and smoke generator. Theoretical approaches incorporate modern CFD computational tools (DNS, LES, RANS etc). Geometries and results part being mentioned starting from simple to complex elucidates cases of a free rotating disk, a single disk in the crossflow, single jets impinging onto stationary and rotating disk,...

Harmand, Souad; Poncet, Sbastien; Shevchuk, Igor V; 10.1016/j.ijthermalsci.2012.11.009

2013-01-01T23:59:59.000Z

402

Ferromagnetic cluster spin waves in molecular disks studied by inelastic neutron scattering  

Science Journals Connector (OSTI)

Structurally, the two mixed-valence manganese disks Mn7-11 and Mn7-16 differ only in the peripheral ligand but, as a result of a subtle interplay of intramolecular exchange interactions, differ strongly in their magnetic properties, e.g., Mn7-11 possesses a ground-state spin of S=11 and Mn7-16 of S=16. The exchange interactions in the disks were studied by inelastic neutron scattering. The analysis of the Q dependence of the observed magnetic transition intensities reveals that ferromagnetic cluster spin-wave excitations were observed. In this framework, it was possible to successfully model the experimental data and provide a physical understanding of the magnetism in the two disks.

J. Nehrkorn; S. Mukherjee; S. Stuiber; H. Mutka; Th. Strssle; G. Christou; O. Waldmann

2012-10-19T23:59:59.000Z

403

Maximal spin and energy conversion efficiency in a symbiotic system of black hole, disk and jet  

E-Print Network (OSTI)

We study a combined model of black hole - accretion disk - magnetosphere - jet symbiosis, applicable for supermassive black holes. We quantify the mass and spin evolution and we analyze how the limiting value of the spin parameter and the conversion efficiency of accreted mass into radiation depend on the interplay of electromagnetic radiation reaction, magnetosphere characteristics and truncation radius of radiation. The dominant effect comes from the closed magnetic field line region, which reduces the spin limit to values ~0.89 (instead ~0.99 in its absence). Therefore observations on black hole spins could favour or disfavour the existence of the closed magnetic field line region (or its coupling to the disk). We also find that the suppression of radiation from the innermost part of the accretion disk, inferred from observations, and a collimated jet both increase the spin limit and the energy conversion efficiency.

Zoltn Kovcs; Lszl . Gergely; Peter L. Biermann

2010-07-24T23:59:59.000Z

404

Constraints on properties of the protoplanetary disks around UX Ori and CQ Tau  

E-Print Network (OSTI)

We present Very Large Array observations of the intermediate mass pre-main-sequence stars UX Ori and CQ Tau at 7mm, 3.6cm, and 6cm. These stars are members of the UX Ori variability class, where the origin of optical variability is thought to derive from inhomogeneities in circumstellar disks. Both stars are detected at 7mm but not at longer wavelengths, which confirms that the millimeter emission is dominated by dust. The UX Ori system exhibits a remarkably flat spectral index in the millimeter range, with alpha_mm 2 (F_nu nu^alpha_mm). Two different disk models can reproduce this property: i) a physically small disk with optically thick emission, truncated at a radius about 30 AU, or ii) a massive (~0.3-1 Msun) disk mainly composed of dust particles grown to radii of 10cm (``pebbles''). The observations do not spatially resolve the 7mm emission. We discuss implications of these two models and suggest observational tests that will discriminate between them. The CQ Tau system exhibits a spectral index in the millimeter range of alpha_mm 2.6, consistent with values commonly found for disks around pre-main-sequence stars. The observations marginally resolve the 7mm emission as an elongated structure with full width at half maximum of 2.4"x1.1" (240x110 AU at 100pc distance). The size and inclination of ~63 degrees (implied by circular symmetry) are consistent with flared disk models previously suggested to explain the optical colors and polarization properties.

L. Testi; A. Natta; D. S. Shepherd; D. J. Wilner

2001-02-27T23:59:59.000Z

405

Semi-Analytical Computation of Acoustic Scattering by Spheroids and Disks  

E-Print Network (OSTI)

Analytical solutions to acoustic scattering problems involving nonspherical shapes, such as spheroids and disks, have long been known and have many applications. However, these solutions require special functions that are not easily computable. For this reason, their asymptotic forms are typically used since they are more readily available. We explore these solutions and provide computational software for calculating their nonasymptotic forms, which are accurate over a wide range of frequencies and distances. This software, which runs in MATLAB, computes the solutions to acoustic scattering problems involving spheroids and disks by semi-analytical means, and is freely available from our webpage.

Adelman, Ross; Duraiswami, Ramani

2014-01-01T23:59:59.000Z

406

Device for testing closure disks at high rates of change of pressure  

DOE Patents (OSTI)

A device is described for testing the burst pressure of closure disks which provides high pressure to both sides of a disk and rapidly releases pressure from one side thereof causing a high rate of change of pressure. A hollow notched plug allows the rapid release of pressure upon rupturing. A means is also disclosed for transmitting a tensile load from a piston to a hollow notched plug and for sealing the means for transmitting load within a hole in a piston. 5 figures.

Merten, C.W. Jr.

1993-11-09T23:59:59.000Z

407

November 18, 2009 22:50 Vehicle System Dynamics VSD09 Vehicle System Dynamics  

E-Print Network (OSTI)

November 18, 2009 22:50 Vehicle System Dynamics VSD09 Vehicle System Dynamics Vol. 00, No. 00), involving the steering and braking actuators. This VDSC aims at improving automotive vehicle yaw stability the rear wheels) and use the steering actuator only if it is necessary (e.g. if the braking system

Boyer, Edmond

408

Noncontact Free-Rotating Disk Triboelectric Nanogenerator as a Sustainable Energy Harvester and Self-Powered Mechanical Sensor  

E-Print Network (OSTI)

Noncontact Free-Rotating Disk Triboelectric Nanogenerator as a Sustainable Energy Harvester and sustainable development.1,2 Harvesting energy from the ambient environ- ment is a good choice to solve an innovative noncontact, free-rotating disk triboelectric nanogenerator (FRD-TENG) for sustainably scavenging

Wang, Zhong L.

409

Effect of contact conditions during thermo-mechanical contact between a thermal flying height control slider and a disk asperity  

E-Print Network (OSTI)

is developed for the transient contact between a thermal flying height control (TFC) slider and a disk asperityEffect of contact conditions during thermo-mechanical contact between a thermal flying height control slider and a disk asperity Wenping Song a,c,n , Andrey Ovcharenko b , Bernhard Knigge b , Min Yang

Wang, Deli

410

Ecient failure recovery in multi-disk multimedia servers Harrick M. Vin, Prashant J. Shenoy, and Sriram S. Rao  

E-Print Network (OSTI)

E?cient failure recovery in multi-disk multimedia servers Harrick M. Vin, Prashant J. Shenoy-8885 ABSTRACT In this paper, we present two disk failure recovery methods that utilize the inherent characteristics of video streams to ensure that the user­invoked on­the­fly failure recovery process does

Massachusetts at Amherst, University of

411

Analytical protostellar disk models 1: the effect of internal dissipation and surface irradiation on the structure of disks and the location of the snow line around Sun-like stars  

E-Print Network (OSTI)

We construct a new set of self-consistent analytical disk models by taking into account both viscous and radiative sources of thermal energy. We analyze the non-isothermal structure of the disk across the mid-plane for optically thick disks, and use the standard two-temperature model in the case of optically thin disks. We deduce a set of general formula for the relationship between the mass accretion rate and the surface density profile. Our results recover those of Chiang & Goldreich in the optically thin regions, but extend their work for the opaque regions of the disk. For the purpose of illustration, we apply our theory in this paper to determine the structure of protostellar disks around T Tauri stars under a state of steady accretion and derive the corresponding radial distribution function of various disk properties such as surface density and temperature near the mid-plane. We calculate the position of the snow line around a sun-like T Tauri star, and deduce that it can evolve from well outside 10 AU during FU Orionis outbursts, to about 4 AU during passive accretion phase, to the present-day orbital radius of Venus and finally re-expand to over 2.2 AU during the protostellar- to-debris disk transition. This non-monotonous evolution of the snow line may provide some novel and deterministic explanation for the total water content and its isotopic composition of both Venus and the Earth. In the optically thin, outermost regions of the disk we find that the surface density profile of the dust varies roughly as 1/r, which is consistent with mm observations of spatially resolved disk of Mundy et al. (2000).

Pascale Garaud; Douglas N. C. Lin

2006-05-03T23:59:59.000Z

412

A DUSTY COMPONENT TO THE GASEOUS DEBRIS DISK AROUND THE WHITE DWARF SDSS J1228+1040  

SciTech Connect

We present Infrared Spectrometer And Array Camera (ISAAC) spectroscopy and ISAAC, UKIDSS, and Spitzer Space Telescope broadband photometry of SDSS J1228+1040-a white dwarf for which evidence of a gaseous metal-rich circumstellar disk has previously been found from optical emission lines. The data show a clear excess in the near- and mid-infrared (IR), providing compelling evidence for the presence of dust in addition to the previously identified gaseous debris disk around the star. The IR excess can be modeled in terms of an optically thick but geometrically thin disk. We find that the inner disk temperatures must be relatively high ({approx}1700 K) in order to fit the spectral energy distribution in the near-IR. These data provide the first evidence for the coexistence of both gas and dust in a disk around a white dwarf, and show that their presence is possible even around moderately hot ({approx}22,000 K) stars.

Brinkworth, C. S.; Hoard, D. W. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Gaensicke, B. T.; Marsh, T. R. [Department of Physics and Astronomy, University of Warwick, Warwick CV4 7AL (United Kingdom); Tappert, C. [Dpto de AstronomIa y AstrofIsica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)

2009-05-10T23:59:59.000Z

413

INFLUENCE OF CORIOLIS FORCE ON DNA MOLECULE MIGRATION AND HYBRIDIZATION IN COMPACT DISK (CD)  

E-Print Network (OSTI)

) MICROFLUIDICS PLATFORMS _______________ A Thesis Presented to the Faculty of San Diego State University in Compact Disk (CD) Microfluidics Platforms by Nithesh Paramesh Master of Science in Mechanical Engineering and hybridization of DNA molecules in CD microfluidics platform where centrifugal force is used as the driving force

Kassegne, Samuel Kinde

414

EVOLUTION OF COATED GRAINS IN SPIRAL SHOCKS OF SELF-GRAVITATING PROTOPLANETARY DISKS  

SciTech Connect

We investigate the evolution of grains composed of an ice shell surrounding an olivine core as they pass through a spiral shock in a protoplanetary disk. We use published three-dimensional radiation-hydrodynamics simulations of massive self-gravitating protoplanetary disks to extract the thermodynamics of spiral shocks in the region between 10 and 20 AU from the central star. As the density wave passes, it heats the grains, causing them to lose their ice shell and resulting in a lowering of the grain opacity. In addition, since grains of different sizes will have slightly different temperatures, there will be a migration of ice from hotter grains to cooler ones. The rate of migration depends on the temperature of the background gas, so a grain distribution that is effectively stable for low temperatures can undergo an irreversible change in opacity if the gas is temporarily heated to above {approx}150 K. We find that the opacity can drop more and at a significantly faster rate throughout the spiral shocks relative to the prediction of the standard dust grain model adopted in hydrodynamical calculations of protoplanetary disks. This would lead to faster gas cooling within spiral arms. We discuss the implications of our results on the susceptibility of disks to fragment into sub-stellar objects at distances of a few tens of astronomical units.

Podolak, M. [Department of Geophysics and Planetary Science, Tel Aviv University, Tel Aviv 69978 (Israel); Mayer, L. [Institute for Theoretical Physics, University of Zurich, 8057 Zurich (Switzerland); Quinn, T. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States)

2011-06-10T23:59:59.000Z

415

THE SPINDLE: AN IRRADIATED DISK AND BENT PROTOSTELLAR JET IN ORION  

SciTech Connect

We present Hubble Space Telescope observations of a bent, pulsed Herbig-Haro jet, HH 1064, emerging from the young star Parenago 2042 embedded in the H II region NGC 1977 located about 30' north of the Orion Nebula. This outflow contains eight bow shocks in the redshifted western lobe and five bow shocks in the blueshifted eastern lobe. Shocks within a few thousand AU of the source star exhibit proper motions of {approx}160 km s{sup -1} but motions decrease with increasing distance. Parenago 2042 is embedded in a proplyd-a photoevaporating protoplanetary disk. A remarkable set of H{alpha} arcs resembling a spindle surround the redshifted (western) jet. The largest arc with a radius of 500 AU may trace the ionized edge of a circumstellar disk inclined by {approx}30 Degree-Sign . The spindle may be the photoionized edge of either a {approx}3 km s{sup -1} FUV-driven wind from the outer disk or a faster MHD-powered flow from an inner disk. The HH 1064 jet appears to be deflected north by photoablation of the south-facing side of a mostly neutral jet beam. V2412 Ori, located 1' west of Parenago 2042 drives a second bent flow, HH 1065. Both HH 1064 and 1065 are surrounded by LL Ori-type bows marking the boundary between the outflow cavity and the surrounding nebula.

Bally, John; Youngblood, Allison; Ginsburg, Adam, E-mail: John.Bally@colorado.edu, E-mail: Allison.Youngblood@colorado.edu, E-mail: Adam.Ginsburg@colorado.edu [Department of Astrophysical and Planetary Sciences, University of Colorado, UCB 389, Boulder, CO 80309 (United States)

2012-09-10T23:59:59.000Z

416

Can We Improve Energy Efficiency of Secure Disk Systems without Modifying Security Mechanisms?  

E-Print Network (OSTI)

Can We Improve Energy Efficiency of Secure Disk Systems without Modifying Security Mechanisms--Improving energy efficiency of security-aware storage systems is challenging, because security and energy security and energy efficiency is to profile encryption algorithms to decide if storage systems would

Qin, Xiao

417

Integrable boundary value problems for elliptic type Toda lattice in a disk  

SciTech Connect

The concept of integrable boundary value problems for soliton equations on R and R{sub +} is extended to regions enclosed by smooth curves. Classes of integrable boundary conditions in a disk for the Toda lattice and its reductions are found.

Guerses, Metin; Habibullin, Ismagil; Zheltukhin, Kostyantyn [Department of Mathematics, Faculty of Sciences, Bilkent University, 06800 Ankara (Turkey); Department of Mathematics, Faculty of Sciences, Middle East Technical University, 06531 Ankara (Turkey)

2007-10-15T23:59:59.000Z

418

Review of fluid flow and convective heat transfer within rotating disk cavities  

E-Print Network (OSTI)

Review of fluid flow and convective heat transfer within rotating disk cavities with impinging jet * Corresponding author : souad.harmand@univ-valenciennes.fr Abstract Fluid flow and convective heat transfer, are treated in details in this review. The review focuses on convective heat transfer in predominantly outward

Boyer, Edmond

419

Review of fluid flow and convective heat transfer within rotating disk cavities  

E-Print Network (OSTI)

1 Review of fluid flow and convective heat transfer within rotating disk cavities with impinging axial direction #12;5 Introduction Fluid flow and convective heat transfer in rotor-stator configuration heat transfer in rotor-stator configurations, which are of great importance in different engineering

Paris-Sud XI, Université de

420

From Spider Robots to Half Disk Robots J-D. Boissonnat O. Devillers S. Lazard  

E-Print Network (OSTI)

From Spider Robots to Half Disk Robots J-D. Boissonnat O. Devillers S. Lazard INRIA, BP 93 06902 robot. The body of this robot is a single point and the legs are line segments attached to the body. The robot can only put its feet on some regions, called the foothold regions. Moreover, the robot is subject

Paris-Sud XI, Université de

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

SURVIVAL OF INTERSTELLAR MOLECULES TO PRESTELLAR DENSE CORE COLLAPSE AND EARLY PHASES OF DISK FORMATION  

SciTech Connect

An outstanding question of astrobiology is the link between the chemical composition of planets, comets, and other solar system bodies and the molecules formed in the interstellar medium. Understanding the chemical and physical evolution of the matter leading to the formation of protoplanetary disks is an important step for this. We provide some new clues to this long-standing problem using three-dimensional chemical simulations of the early phases of disk formation: we interfaced the full gas-grain chemical model Nautilus with the radiation-magnetohydrodynamic model RAMSES, for different configurations and intensities of the magnetic field. Our results show that the chemical content (gas and ices) is globally conserved during the collapsing process, from the parent molecular cloud to the young disk surrounding the first Larson core. A qualitative comparison with cometary composition suggests that comets are constituted of different phases, some molecules being direct tracers of interstellar chemistry, while others, including complex molecules, seem to have been formed in disks, where higher densities and temperatures allow for an active grain surface chemistry. The latter phase, and its connection with the formation of the first Larson core, remains to be modeled.

Hincelin, U. [Department of Chemistry, University of Virginia, Charlottesville, VA 22904 (United States); Wakelam, V.; Hersant, F.; Guilloteau, S. [University of Bordeaux, LAB, UMR 5804, F-33270 Floirac (France); Commeron, B., E-mail: ugo.hincelin@virginia.edu [Laboratoire de radioastronomie, LERMA, Observatoire de Paris, Ecole Normale Suprieure (UMR 8112 CNRS), 24 rue Lhomond, F-75231 Paris Cedex 05 (France)

2013-09-20T23:59:59.000Z

422

Long-Term Radio Modulation in Sagittarius A* from Spin-Induced Disk Precession  

E-Print Network (OSTI)

There is some evidence, though yet unconfirmed, that Sagittarius A*--the supermassive black hole at the Galactic center--emits its radio waves modulated with a ~100-day period. What is intriguing about this apparent quasi-periodicity is that, though the amplitude of the modulation increases with decreasing wavelength (from 3.6 to 1.3 cm), the quasi-period itself does not seem to depend on the frequency of the radiation. It is difficult to imagine how a binary companion, were that the cause of this modulation, could have escaped detection until now. Instead, it has been suggested that the spin-induced precession of a disk surrounding a slowly rotating black hole could have the right period to account for this behavior. In this paper, we examine how Sagittarius A*'s light curve could be modulated by this mechanism. We demonstrate that the partial occultation of a nonthermal halo by a compact, radio-opaque disk does indeed produce the observed frequency-dependent amplitude. This appears to be in line with other observational arguments suggesting that Sagittarius A*'s mm/sub-mm spectrum is produced by a ~10 Schwarzschild-radius disk, whereas its cm-waves originate from a nonthermal particle distribution in a halo extending out to over 20 Schwarzschild radii. Interestingly, this model suggests that the observed period corresponds to half the precession period and that a non-axisymmetric disk could produce a second period roughly twice as long as the first.

Martin Prescher; Fulvio Melia

2005-06-25T23:59:59.000Z

423

Application of cathodic arc deposited amorphous hard carbon films to the head/disk tribology  

SciTech Connect

Amorphous hard carbon films deposited by filtered cathodic arc deposition exhibit very high hardness and elastic modulus, high mass density, low coefficient of friction, and the films are very smooth. All these properties are beneficial to applications of these films for the head/disk interface tribology. The properties of cathodic arc deposited amorphous carbon films are summarized, and they are compared to sputter deposited, hydrogenated (CH{sub x}), and nitrogenated (CN{sub x}) carbon films which are the present choice for hard disk and slider coatings. New developments in cathodic arc coaters are discussed which are of interest to the disk drive industry. Experiments on the nanotribology, mass density and hardness, corrosion behavior, and tribochemical behavior of cathodic arc films are reported. A number of applications of cathodic arc deposited films to hard disk and slider coatings are described. It is shown that their tribological performance is considerably better compared to CH{sub x} and CN{sub x} films.

Anders, S. [Lawrence Berkeley National Lab., CA (United States). Advanced Light Source Div.; Bhatia, C.S. [SSD/IBM, San Jose, CA (United States); Fong, W.; Lo, R.Y.; Bogy, D.B. [Univ. of California, Berkeley, CA (United States). Computer Mechanics Lab.

1998-04-01T23:59:59.000Z

424

Reduction of multi-stage disk models: Application to an industrial rotor  

E-Print Network (OSTI)

of the rotor into sectors. The bladed disks are coupled by intermediate rings which remove the problem that of a small portion, typically a bladed sector. This configuration no longer holds in real rotors due with multi-stage rotors. However, as underlined by Bladh et al.6 , the critical point is the choice

Boyer, Edmond

425

Present performance & future directions in two-photon addressed volumetric optical disk storage systems  

E-Print Network (OSTI)

Present performance & future directions in two-photon addressed volumetric optical disk storage data storage is presented and future directions discussed. Influence of numerical aperture in a 3-D multi-layer optical data storage system is analyzed. Keywords: volumetric data storage, multi-layer data

Esener, Sadik C.

426

Optical disk resonators with micro-wave free spectral range for optoelectronic oscillator  

E-Print Network (OSTI)

Optical disk resonators with micro-wave free spectral range for optoelectronic oscillator Herv to the resonator relaxation time = Q/ [2]. The optoelectronic delayed feed- back loop can thus oscillate at all. frequency selective resonator (e.g with a high Q factor). The detailed architecture is an optoelectronic

Paris-Sud XI, Université de

427

Generation of Magnetic Field on the Accretion Disk around a Proto-First-Star  

E-Print Network (OSTI)

The generation process of magnetic field around a proto-first-star is studied. Utilizing the recent numerical result of proto-first-star formation based upon the radiation hydrodynamics simulations, we assess the magnetic field strength generated by the radiative force and the Biermann battery effect. We find that magnetic field of \\sim 10^{-9} G is generated on the surface of the accretion disk around the proto-first-star. The field strength on the accretion disk is smaller by two orders of magnitude than the critical value, above which the gravitational fragmentation of the disk is suppressed. Thus, the generated seed magnetic field hardly affect the dynamics of on-site first star formation directly, unless efficient amplification process is taken into consideration. We also find that the generated magnetic field is continuously blown out from the disk on the outflows to the poles, that are driven by the thermal pressure of photoheated gas. The strength of the diffused magnetic field in low density regions ...

Shiromoto, Yuki; Hosokawa, Takashi

2014-01-01T23:59:59.000Z

428

A Quantitative Analysis of Disk Drive Power Management in Portable Computers  

E-Print Network (OSTI)

the question of power management begins with an analysis of where the energy is being consumed. Table 1 gives) Percent of Total Display Compaq monochrome lite25c 3.5 68% Disk Drive (105 Mbytes) Maxtor MXL­105 III 1 of inactivity. In this paper, we perform a quantitative analysis of the potential costs and benefits of spinning

Anderson, Tom

429

PRE-BUD: Prefetching for Energy-Efficient Parallel I/O Systems with Buffer Disks  

E-Print Network (OSTI)

of the total cost of ownership [Pinheiro and Bianchini 2004; Wang et al. 2008; Xie 2008]. Reducing the energy configuration is more cost-effective and energy-efficient than the first one. Finally, we quantitatively compare that PRE-BUD is able to reduce energy dissipation in parallel disk systems by up to 50 percent when

Qin, Xiao

430

Approximation by complex Bernstein-Schurer and Kantorovich-Schurer polynomials in compact disks  

Science Journals Connector (OSTI)

In this paper, the order of simultaneous approximation and Voronovskaja-type results with quantitative estimate for complex Bernstein-Schurer and Kantorovich-Schurer polynomials attached to analytic functions on compact disks are obtained. In this way, ... Keywords: Complex Bernstein-Schurer and Kantorovich-Schurer polynomials, Simultaneous approximation, Voronovskaja-type result

George A. Anastassiou; Sorin G. Gal

2009-08-01T23:59:59.000Z

431

Hibernator: Helping Disk Arrays Sleep through the Winter Qingbo Zhu, Zhifeng Chen, Lin Tan, Yuanyuan Zhou  

E-Print Network (OSTI)

{kkeeton, wilkes}hpl.hp.com Abstract Energy consumption has become an important issue in high-end data are getting larger, and their energy consumption is increasing, too, as power densities increase. Typical centers, and disk arrays are one of the largest energy con- sumers within them. Although several attempts

Zhou, Yuanyuan

432

Hibernator: Helping Disk Arrays Sleep through the Winter Qingbo Zhu, Zhifeng Chen, Lin Tan, Yuanyuan Zhou  

E-Print Network (OSTI)

{kkeeton, wilkes}hpl.hp.com Abstract Energy consumption has become an important issue in high­end data are getting larger, and their energy consumption is increasing, too, as power densities increase. Typical centers, and disk arrays are one of the largest energy con­ sumers within them. Although several attempts

Zhou, Yuanyuan

433

Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks  

E-Print Network (OSTI)

The growth of solid particles towards meter sizes in protoplanetary disks has to circumvent at least two hurdles, namely the rapid loss of material due to radial drift and particle fragmentation due to destructive collisions. In this paper, we present the results of numerical simulations with more and more realistic physics involved. Step by step, we include various effects, such as particle growth, radial/vertical particle motion and dust particle fragmentation in our simulations. We demonstrate that the initial dust-to-gas ratio is essential for the particles to overcome the radial drift barrier. If this value is increased by a factor of 2 compared with the canonical value for the interstellar medium, km-sized bodies can form in the inner disk 30 m/s), particles are able to grow to larger sizes in low turbulent disks. We also find that less than 5% of the small dust grains remain in the disk after 1 Myrs due to radial drift, no matter whether fragmentation is included in the simulations or not. In this paper, we also present considerable improvements to existing algorithms for dust-particle coagulation, which speed up the coagulation scheme by a factor of 10 thousand.

F. Brauer; C. P. Dullemond; Th. Henning

2007-11-14T23:59:59.000Z

434

Outflows from accretion disks formed in neutron star mergers: effect of black hole spin  

E-Print Network (OSTI)

The accretion disk that forms after a neutron star merger is a source of neutron-rich ejecta. The ejected material contributes to a radioactively-powered electromagnetic transient, with properties that depend sensitively on the composition of the outflow. Here we investigate how the spin of the black hole remnant influences mass ejection on the thermal and viscous timescales. To this end, we carry out two-dimensional, time-dependent hydrodynamic simulations of merger remnant accretion disks including viscous angular momentum transport and approximate neutrino self-irradiation. The gravity of the spinning black hole is included via a pseudo-Newtonian potential. We find that a disk around a spinning black hole ejects more mass, up to a factor of several, relative to the non-spinning case. The enhanced mass loss is due to energy release by accretion occurring deeper in the gravitational potential, raising the disk temperature and hence the rate of viscous heating in regions where neutrino cooling is ineffective....

Fernndez, Rodrigo; Metzger, Brian D; Quataert, Eliot

2014-01-01T23:59:59.000Z

435

Outflows from accretion disks formed in neutron star mergers: effect of black hole spin  

E-Print Network (OSTI)

The accretion disk that forms after a neutron star merger is a source of neutron-rich ejecta. The ejected material contributes to a radioactively-powered electromagnetic transient, with properties that depend sensitively on the composition of the outflow. Here we investigate how the spin of the black hole remnant influences mass ejection on the thermal and viscous timescales. We carry out two-dimensional, time-dependent hydrodynamic simulations of merger remnant accretion disks including viscous angular momentum transport and approximate neutrino self-irradiation. The gravity of the spinning black hole is included via a pseudo-Newtonian potential. We find that a disk around a spinning black hole ejects more mass, up to a factor of several, relative to the non-spinning case. The enhanced mass loss is due to energy release by accretion occurring deeper in the gravitational potential, raising the disk temperature and hence the rate of viscous heating in regions where neutrino cooling is ineffective. The mean electron fraction of the outflow increases moderately with BH spin due to a highly-irradiated (though not neutrino-driven) wind component. While the bulk of the ejecta is still very neutron-rich, thus generating heavy r-process elements, the leading edge of the wind contains a small amount of Lanthanide-free material. This component can give rise to a ~1 day blue optical `bump' in a kilonova light curve, even in the case of prompt BH formation, which may facilitate its detection.

Rodrigo Fernndez; Daniel Kasen; Brian D. Metzger; Eliot Quataert

2014-09-15T23:59:59.000Z

436

The Escape of Ionizing Photons from OB Associations in Disk Galaxies Radiation Transfer Through Superbubbles  

E-Print Network (OSTI)

By solving the time-dependent radiation transfer problem of stellar radiation through evolving superbubbles within a smoothly varying H I distribution, we have estimated the fraction of ionizing photons emitted by OB associations that escapes the H I disk of our Galaxy. We considered a coeval star-formation history and a Gaussian star-formation history with a time spread sigma_t = 2 Myr. We find that the shells of the expanding superbubbles quickly trap or attenuate the ionizing flux, such that most of the escaping radiation escapes shortly after the formation of the superbubble. Superbubbles of large associations can blowout of the H I disk and form dynamic chimneys, which allow the ionizing radiation directly to escape the H I disk. However, blowout occurs when the ionizing photon luminosity has dropped well below the association's maximum luminosity. For the coeval star-formation history, the fraction of photons that escape each side of the disk in the solar vicinity is f_esc approx 6% (the total fraction ...

Dove, J B; Ferrara, A; Dove, James B.; Ferrara, Andrea

1999-01-01T23:59:59.000Z

437

The Interaction of the Disk with the Halo MordecaiMark Mac Low 1  

E-Print Network (OSTI)

in the halo or even ejection of mass along open field lines in a galactic wind. In these models, the energy and energy to the halo, as well as opening up lines of sight for ionizing radiation to escape from the disk external sources could contribute). The most likely energy source for these processes are massive OB stars

Low, Mordecai-Mark Mac

438

Fabrication and Optimal Strain Sensor Placement in an Instrumented Disk Drive Suspension for Vibration Suppression  

E-Print Network (OSTI)

for Vibration Suppression Kenn Oldham, Stanley Kon Computer Mechanics Laboratory (CML) University of California drive suspension with vibra- tion sensing strain gages can enhance vibration suppression in hard disk bits. As the industry targets bit densities of 1 terabit per square inch, airflow induced vibration

Horowitz, Roberto

439

A Kinematic Measurement of Ram Pressure in the Outer Disk of Regular Galaxies  

E-Print Network (OSTI)

While most ram pressure studies have focused on ram pressure stripping in galaxy clusters, we devise a novel approach based on a kinematic measurement of ram pressure perturbations in HI velocity fields for intergalactic material (IGM) densities and relative velocities that are one to two orders of magnitude lower than in galaxies showing ram pressure stripping. Our model evaluates ram pressure induced kinematic terms in gas disks with constant inclination as well as those with a warped geometry. Ram pressure perturbations are characterized by kinematic modes of even order, m=0 and m=2, corresponding to a ram wind perpendicular and parallel to the gas disk, respectively. Long-term consequences of ram pressure, such as warped disks as well as uncertainties in the disk geometry typically generate uneven modes (m=1 and m=3), that are clearly distinguishable from the kinematic ram pressure terms. We have applied our models to three nearby isolated galaxies, utilizing Markov Chain Monte Carlo fitting routines to d...

Haan, Sebastian

2014-01-01T23:59:59.000Z

440

How Reliable are Parallel Disk Systems When Energy-Saving Schemes are Involved? Shu Yin, Xiaojun Ruan, Adam Manzanares, and Xiao Qin  

E-Print Network (OSTI)

How Reliable are Parallel Disk Systems When Energy-Saving Schemes are Involved? Shu Yin, Xiaojun, growing evidence shows that energy-saving schemes in disk drives usually have negative impacts on storage - called MINT - to evaluate the reliability of a parallel disk system where energy-saving mechanisms

Qin, Xiao

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

CURVED WALLS: GRAIN GROWTH, SETTLING, AND COMPOSITION PATTERNS IN T TAURI DISK DUST SUBLIMATION FRONTS  

SciTech Connect

The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best fits to the near- and mid-IR excesses are found for curved, two-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe) = 0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10{sup 8} to 10{sup 10} M{sub ?} yr{sup 1}, the maximum grain size in the lower layer decreases from ?3 to 0.5 ?m. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1 10{sup 4} of the interstellar medium (ISM) value, while the midplane is enhanced to eight times the ISM value. For all accretion rates, the wall contributes at least half of the flux in the optically thin 10 ?m silicate feature. Finally, we find evidence for an iron gradient in the disk, suggestive of that found in our solar system.

McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L. [Department of Astronomy, The University of Michigan, 500 Church Street, 830 Dennison Building., Ann Arbor, MI 48109 (United States); D'Alessio, P. [Centro de Radioastronoma y Astrofsica, Universidad Nacional Autnoma de Mxico, 58089 Morelia, Michoacn (Mexico); Espaillat, C. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sargent, B. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Watson, D. M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Hernndez, J., E-mail: melisma@umich.edu, E-mail: ncalvet@umich.edu, E-mail: lhartm@umich.edu, E-mail: lingleby@umich.edu, E-mail: p.dalessio@astrosmo.unam.mx, E-mail: cespaillat@cfa.harvard.edu, E-mail: baspci@rit.edu, E-mail: dmw@pas.rochester.edu, E-mail: hernandj@cida.ve [Centro de Investigaciones de Astronoma (CIDA), Mrida 5101-A (Venezuela, Bolivarian Republic of)

2013-10-01T23:59:59.000Z

442

The jet-disk symbiosis. I. Radio to X-ray emission models for quasars  

E-Print Network (OSTI)

Starting from the assumption that radio jets and accretion disks are symbiotic features present in radio loud and radio quiet quasars we scale the bulk power of radio jets with the accretion power by adding mass- and energy conservation of the whole jet-disk system to the standard Blandford \\& K\\"onigl theory for compact radio cores. The model depends on only few parameters and can be constrained by observations. Thus we are able to show that radio and X-ray fluxes (SSC emission) of cores and lobes and typical dimensions of radio loud quasars are consistent with a jet being produced in the central engine. We present a synthetic broadband spectrum from radio to X-ray for a jet-disk system. The only way to explain the high efficiency of radio loud objects is to postulate that these objects consist of `maximal jets' with `total equipartition' where the magnetic energy flow of the jet is comparable to the kinetic jet power and the total jet power is a large fraction of the disk power. As the number of electrons is limited by the accretion flow, this is only possible when the minimum Lorentz factor of the electron distribution is $\\gamma_{\\rm e,min}\\ga100$ ($E\\ga 50 {\\rm MeV}$) or/and a large number of pairs are present. Such an electron/positron population would be a necessary consequence of hadronic interactions and may lead to some interesting effects in the low frequency self-absorbed spectrum. Emission from radio weak quasars can be explained with an initially identical jet. The difference between radio loud and radio weak could be due to a different efficiency in accelerating relativistic electrons on the sub-parsec scale. Finally we demonstrate that in order to appease the ravenous hunger of radio loud jets its production must be somehow linked to the dissipation process in the inner part of the disk.

Heino Falcke; Peter L. Biermann

1994-11-23T23:59:59.000Z

443

THE IMPACT OF BARS ON DISK BREAKS AS PROBED BY S{sup 4}G IMAGING  

SciTech Connect

We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6 {mu}m images from the Spitzer Survey of Stellar Structure in Galaxies. In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single-exponential profile have a scale length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the particular case of barred galaxies, the ratio between the break and the bar radii (R{sub br}/R{sub bar}) depends strongly on the total stellar mass of the galaxy. For galaxies more massive than 10{sup 10} M{sub Sun }, the distribution is bimodal, peaking at R{sub br}/R{sub bar} {approx} 2 and {approx}3.5. The first peak, which is the most populated one, is linked to the outer Lindblad resonance of the bar, whereas the second one is consistent with a dynamical coupling between the bar and the spiral pattern. For galaxies below 10{sup 10} M{sub Sun }, breaks are found up to {approx}10 R{sub bar}, but we show that they could still be caused by resonances given the rising nature of rotation curves in these low-mass disks. While not ruling out star formation thresholds, our results imply that radial stellar migration induced by non-axisymmetric features can be responsible not only for those breaks at {approx}2 R{sub bar}, but also for many of those found at larger radii.

Munoz-Mateos, Juan Carlos; Sheth, Kartik; Kim, Taehyun [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Gil de Paz, Armando [Departamento de Astrofisica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Meidt, Sharon [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Athanassoula, E.; Bosma, Albert [Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Comeron, Sebastien; Laine, Jarkko; Laurikainen, Eija [Department of Physical Sciences/Astronomy Division, University of Oulu, FIN-90014 (Finland); Elmegreen, Debra M. [Department of Physics and Astronomy, Vassar College, Poughkeepsie, NY 12604 (United States); Elmegreen, Bruce G. [IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY 10598 (United States); Erroz-Ferrer, Santiago; Knapen, Johan H. [Instituto de Astrofisica de Canarias, E-38205 La Laguna (Spain); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Hinz, Joannah L. [University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States); Ho, Luis C.; Madore, Barry F. [The Observatories, Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Holwerda, Benne [European Space Agency, ESTEC, Keplerlaan 1, 2200-AG, Noordwijk (Netherlands); Jarrett, Thomas H., E-mail: jmunoz@nrao.edu [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); and others

2013-07-01T23:59:59.000Z

444

ON THE UNUSUAL GAS COMPOSITION IN THE {beta} PICTORIS DEBRIS DISK  

SciTech Connect

The metallic gas associated with the {beta} Pic debris disk is not believed to be primordial, but arises from the destruction of dust grains. Recent observations have shown that carbon and oxygen in this gas are exceptionally overabundant compared to other elements, by some 400 times. We study the origin of this enrichment under two opposing hypotheses: preferential production, where the gas is produced with the observed unusual abundance (as may happen if gas is produced by photodesorption from C/O-rich icy grains), and preferential depletion, where the gas evolves to the observed state from an original solar abundance (if outgassing occurs under high-speed collisions) under a number of dynamical processes. We include in our study the following processes: radiative blowout of metallic elements, dynamical coupling between different species, and viscous accretion onto the star. We find that, if gas viscosity is sufficiently low (the conventional {alpha} parameter {approx}< 10{sup -3}), differential blowout dominates. While gas accumulates gradually in the disks, metallic elements subject to strong radiation forces, such as Na and Fe, deplete more quickly than C and O, naturally leading to the observed overabundance of C and O. On the other hand, if gas viscosity is high ({alpha} {approx}> 10{sup -1}, as expected for this largely ionized disk), gas is continuously produced and viscously accreted toward the star. This removal process does not discriminate between elements so the observed overabundance of C and O has to be explained by a preferential production that strongly favors C and O to other metallic elements. One such candidate is photodesorption off the grains. We compare our calculation against all observed elements ({approx}10) in the gas disk and find a mild preference for the second scenario, based on the abundance of Si alone. If true, {beta} Pic should still be accreting at an observable rate, well after its primordial disk has disappeared.

Xie, Ji-Wei; Wu, Yanqin [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)] [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Brandeker, Alexis, E-mail: jwxie@astro.utoronto.ca, E-mail: wu@astro.utoronto.ca, E-mail: alexis@astro.su.se [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden)] [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden)

2013-01-10T23:59:59.000Z

445

MAGNETOHYDRODYNAMIC SIMULATION OF A DISK SUBJECTED TO LENSE-THIRRING PRECESSION  

SciTech Connect

When matter orbits around a central mass obliquely with respect to the mass's spin axis, the Lense-Thirring effect causes it to precess at a rate declining sharply with radius. Ever since the work of Bardeen and Petterson, it has been expected that when a fluid fills an orbiting disk, the orbital angular momentum at small radii should then align with the mass's spin. Nearly all previous work has studied this alignment under the assumption that a phenomenological 'viscosity' isotropically degrades fluid shears in accretion disks, even though it is now understood that internal stress in flat disks is due to anisotropic MHD turbulence. In this paper we report a pair of matched simulations, one in MHD and one in pure (non-viscous) HD in order to clarify the specific mechanisms of alignment. As in the previous work, we find that disk warps induce radial flows that mix angular momentum of different orientation; however, we also show that the speeds of these flows are generically transonic and are only very weakly influenced by internal stresses other than pressure. In particular, MHD turbulence does not act in a manner consistent with an isotropic viscosity. When MHD effects are present, the disk aligns, first at small radii and then at large; alignment is only partial in the HD case. We identify the specific angular momentum transport mechanisms causing alignment and show how MHD effects permit them to operate more efficiently. Last, we relate the speed at which an alignment front propagates outward (in the MHD case) to the rate at which Lense-Thirring torques deliver angular momentum at smaller radii.

Sorathia, Kareem A.; Krolik, Julian H. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Hawley, John F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States)

2013-11-01T23:59:59.000Z

446

On the temperature profile of radiatively efficient geometrically thin disks in black hole binaries with the ASCA GIS  

E-Print Network (OSTI)

X-ray spectra of black hole binaries(BHBs) in the high/soft state were studied comprehensively by using ASCA GIS data, and partially RXTE PCA data. A mathematical disk model was applied to several BHBs to see if the observed accretion disk temperature profile was consistent with that expected from the standard accretion disk model. This model is called p-free disk, and assumes that the spectrum is composed of multi-temperature blackbody emission of which the local temperature T(r) at radius r is given by T(r) ~ r^-p with p being a positive free parameter. The standard disk roughly requires p~3/4, while a small deviation is expected depending on the inner boundary conditions, general relativistic effects and disk vertical structures.Our sample objects included LMC X-1, LMC X-3, XTE J2012+381, and GRO J1655-40. During the ASCA observations, these BHBs showed characteristics of the standard high/soft state. Under the standard modeling of high-state black hole binaries, the sources show Tin=0.76-1.17keV, the disk...

Kubota, A; Makishima, K; Nakazawa, K; Kubota, Aya; Ebisawa, Ken; Makishima, Kazuo; Nakazawa, Kazuhiro

2005-01-01T23:59:59.000Z

447

THE WIRED SURVEY. IV. NEW DUST DISKS FROM THE McCOOK and SION WHITE DWARF CATALOG  

SciTech Connect

We have compiled photometric data from the Wide-field Infrared Survey Explorer All Sky Survey and other archival sources for the more than 2200 objects in the original McCook and Sion Catalog of Spectroscopically Identified White Dwarfs. We applied color-selection criteria to identify 28 targets whose infrared spectral energy distributions depart from the expectation for the white dwarf (WD) photosphere alone. Seven of these are previously known WDs with circumstellar dust disks, five are known central stars of planetary nebulae, and six were excluded for being known binaries or having possible contamination of their infrared photometry. We fit WD models to the spectral energy distributions of the remaining ten targets, and find seven new candidates with infrared excess suggesting the presence of a circumstellar dust disk. We compare the model dust disk properties for these new candidates with a comprehensive compilation of previously published parameters for known WDs with dust disks. It is possible that the current census of WDs with dust disks that produce an excess detectable at K-band and shorter wavelengths is close to complete for the entire sample of known WDs to the detection limits of existing near-IR all-sky surveys. The WD dust disk candidates now being found using longer wavelength infrared data are drawn from a previously underrepresented region of parameter space, in which the dust disks are overall cooler, narrower in radial extent, and/or contain fewer emitting grains.

Hoard, D. W.; Wachter, Stefanie [Max Planck Institut fuer Astronomie, D-69117 Heidelberg (Germany); Debes, John H. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Leisawitz, David T. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cohen, Martin, E-mail: hoard@mpia.de [Monterey Institute for Research in Astronomy, Marina, CA 93933 (United States)

2013-06-10T23:59:59.000Z

448

On the temperature profile of radiatively efficient geometrically thin disks in black hole binaries with the ASCA GIS  

E-Print Network (OSTI)

X-ray spectra of black hole binaries(BHBs) in the high/soft state were studied comprehensively by using ASCA GIS data, and partially RXTE PCA data. A mathematical disk model was applied to several BHBs to see if the observed accretion disk temperature profile was consistent with that expected from the standard accretion disk model. This model is called p-free disk, and assumes that the spectrum is composed of multi-temperature blackbody emission of which the local temperature T(r) at radius r is given by T(r) ~ r^-p with p being a positive free parameter. The standard disk roughly requires p~3/4, while a small deviation is expected depending on the inner boundary conditions, general relativistic effects and disk vertical structures.Our sample objects included LMC X-1, LMC X-3, XTE J2012+381, and GRO J1655-40. During the ASCA observations, these BHBs showed characteristics of the standard high/soft state. Under the standard modeling of high-state black hole binaries, the sources show Tin=0.76-1.17keV, the disk fraction to the total 0.7-10keV flux of 54-98%, and Nh=(0.7--12)E21/cm^2. The best-fit p-values were found in 0.6-0.8, and the standard value of p=3/4 was accepted for all the sources.The obtained p-values are also compared with those expected for the standard accretion disk in the Schwarzschild metric, and they were consistent with those expected from the standard accretion disk.

Aya Kubota; Ken Ebisawa; Kazuo Makishima; Kazuhiro Nakazawa

2005-05-17T23:59:59.000Z

449

Femtosecond laser fabrication of micro and nano-disks in single layer graphene using vortex Bessel beams  

SciTech Connect

We report the fabrication of micro and nano-disks in single layer chemical vapor deposition graphene on glass substrate using femtosecond laser ablation with vortex Bessel beams. The fabricated graphene disks with diameters ranging from 650?nm to 4??m were characterized by spatially resolved micro-Raman spectroscopy. The variation of ablation threshold was investigated as a function of the number of pulses showing an incubation effect. A very high degree of size control of the fabricated graphene disks is enabled using a sequence of femtosecond pulses with different vortex orders.

Wetzel, Benjamin, E-mail: benjamin.wetzel@femto-st.fr; Xie, Chen; Lacourt, Pierre-Ambroise; Dudley, John M.; Courvoisier, Francois [Dpartement d'Optique P.M. Duffieux, Institut FEMTO-ST, UMR6174 CNRS, Universit de Franche-Comt, 25030 Besanon (France)] [Dpartement d'Optique P.M. Duffieux, Institut FEMTO-ST, UMR6174 CNRS, Universit de Franche-Comt, 25030 Besanon (France)

2013-12-09T23:59:59.000Z

450

Traditional and Microwave-Assisted Solvothermal Synthesis and Surface Modification of Co7 Brucite Disk Clusters and Their Magnetic Properties  

Science Journals Connector (OSTI)

Traditional and Microwave-Assisted Solvothermal Synthesis and Surface Modification of Co7 Brucite Disk Clusters and Their Magnetic Properties ... Three CoII7 compounds with similar brucite disk core structures show markedly different solution stability and magnetic behaviors as a result of small changes in the inner bridges modifying the symmetry of the core and the magnitude of exchange constants. ... The structures contain Co7 brucite disk [Co7(?3-X)6(?2-O)6]2+, where the ligands are arranged in two open hemispheres and the flat inner surface is functionalized when X is OH?, CH3O?, and N3?. ...

Yan-Ling Zhou; Ming-Hua Zeng; Lian-Qiang Wei; Bin-Wen Li; Mohamedally Kurmoo

2010-06-24T23:59:59.000Z

451

Effect of contact conditions during thermo-mechanical contact between a thermal flying height control slider and a disk asperity  

Science Journals Connector (OSTI)

A three-dimensional thermo-mechanical model is developed for the transient contact between a thermal flying height control (TFC) slider and a disk asperity. The effect of contact conditions is investigated, including the friction coefficient and the circumferential disk velocity. The damage of the readwrite shields due to contacts with disk asperities is studied along with the maximum temperature at the location of the read element. The effect of diameter and material properties of the asperity is also investigated. Strong dependence of deformation and maximum temperature is observed as a function of the diameter and material properties of the asperity.

Wenping Song; Andrey Ovcharenko; Bernhard Knigge; Min Yang; Frank E. Talke

2012-01-01T23:59:59.000Z

452

Application of off-specular polarized neutron reflectometry to measurements on an array of mesoscopic ferromagnetic disks  

SciTech Connect

Using off-specular polarized neutron reflectometry with neutron spin analysis, we determined the magnetic properties of a large array of in-plane magnetized ferromagnetic Co disks. Resonant peaks are clearly observed in the off-specular reflectivity, due to the lateral periodicity of the disk array. Using polarized neutrons, the intensity of the resonant peak in the off-specular reflectivity is studied as a function of the magnetic field applied in the sample plane. Spin analysis of the reflected neutrons reveals the magnetization reversal and saturation within the disks. {copyright} 2001 American Institute of Physics.

Temst, K.; Van Bael, M. J.; Fritzsche, H.

2001-08-13T23:59:59.000Z

453

Excess Infrared Radiation from a Massive DAZ White Dwarf: GD362 - a Debris Disk?  

E-Print Network (OSTI)

We report the discovery of excess K-band radiation from a massive DAZ white dwarf star, GD362. Combining infrared photometric and spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a debris disk. This would be only the second such system known, discovered 18 years after G29-38, the only single white dwarf currently known to be orbited by circumstellar dust. Both of these systems favor a model with accretion from a surrounding debris disk to explain the metal abundances observed in DAZ white dwarfs. Nevertheless, observations of more DAZs in the mid-infrared are required to test if this model can explain all DAZs.

Mukremin Kilic; Ted von Hippel; S. K. Leggett; D. E. Winget

2005-09-07T23:59:59.000Z

454

Molecular Gas Clumps from the Destruction of Icy Bodies in the $\\beta$ Pictoris Debris Disk  

E-Print Network (OSTI)

Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at submm wavelengths of the archetypal debris disk around $\\beta$ Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85AU from the star, in a plane closely aligned with the orbit of the inner planet, $\\beta$ Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

Dent, W R F; Roberge, A; Augereau, J -C; Casassus, S; Corder, S; Greaves, J S; de Gregorio-Monsalvo, I; Hales, A; Jackson, A P; Hughes, A Meredith; Lagrange, A -M; Matthews, B; Wilner, D

2014-01-01T23:59:59.000Z

455

The Ising Model on a Dynamically Triangulated Disk with a Boundary Magnetic Field  

E-Print Network (OSTI)

We use Monte Carlo simulations to study a dynamically triangulated disk with Ising spins on the vertices and a boundary magnetic field. For the case of zero magnetic field we show that the model possesses three phases. For one of these the boundary length grows linearly with disk area, while the other two phases are characterized by a boundary whose size is on the order of the cut-off. A line of continuous magnetic transitions separates the two small boundary phases. We determine the critical exponents of the continuous magnetic phase transition and relate them to predictions from continuum 2-d quantum gravity. This line of continuous transitions appears to terminate on a line of discontinuous phase transitions dividing the small boundary phases from the large boundary phase. We examine the scaling of bulk magnetization and boundary magnetization as a function of boundary magnetic field in the vicinity of this tricritical point.

Scott McGuire; Simon Catterall; Mark Bowick; Simeon Warner

2001-05-02T23:59:59.000Z

456

Experimental Study on Finishing Forces in Double Disk Magnetic Abrasive Finishing Process While Finishing Paramagnetic Workpiece  

Science Journals Connector (OSTI)

Abstract Knowledge of finishing forces is important in any manufacturing process as the surface integrity of the finished surface is being affected. In the present work finishing force and torque were measured for a recently developed double disk magnetic abrasive finishing process. Investigations have been made to understand the effect of process factors namely upper and lower working gap rotational speed, abrasive weight percentage on the normal finishing force and finishing torque. Experiments were planned and performed based on Taguchi L9 orthogonal array. Analysis of variance has been used to analyze the experimental data. The analysis of the experimental data showed that normal finishing forces is affected most significantly by lower and upper working gap and finishing torque is effected mostly by the lower working gap and rotational speed of the magnetic disk. The surfaces finished by DDMAF process are characterized by SEM and the surface morphology has been correlated to finishing force and torque values.

Prateek Kala; Pulak M. Pandey

2014-01-01T23:59:59.000Z

457

Identifying Nearby, Young, Late-type Stars by Means of Their Circumstellar Disks  

E-Print Network (OSTI)

It has recently been shown that a significant fraction of late-type members of nearby, very young associations (age excess emission at mid-IR wavelengths indicative of dusty circumstellar disks. We demonstrate that the detection of mid-IR excess emission can be utilized to identify new nearby, young, late-type stars including two definite new members ("TWA 33" and "TWA 34") of the TW Hydrae Association. Both new TWA members display mid-IR excess emission in the Wide-field Infrared Survey Explorer (WISE) catalog and they show proper motion and youthful spectroscopic characteristics -- namely H\\alpha emission, strong lithium absorption, and low surface gravity features consistent with known TWA members. We also detect mid-IR excess -- the first unambiguous evidence of a dusty circumstellar disk -- around a previously identified UV-bright, young, accreting star (2M1337) that is a likely member of the Lower-Centaurus Crux region of the Scorpius Centaurus Complex.

Schneider, Adam; Melis, Carl; Zuckerman, Ben; Bessell, Mike

2012-01-01T23:59:59.000Z

458

Virial tests for post-Newtonian stationary black-hole-disk systems  

E-Print Network (OSTI)

We investigated hydrodynamical post-Newtonian models of selfgravitating stationary black-hole-disk systems. The post-Newtonian scheme presented here and also in our recent paper is a continuation of previous, purely Newtonian studies of selfgravitating hydrodynamical disks rotating according to the Keplerian rotation law. The post-Newtonian relativistic corrections are significant even at the 1PN level. The 1PN correction to the angular velocity can be of the order of 10% of its Newtonian value. It can be expressed as a combination of geometric and hydrodynamical terms. Moreover, in contrast to the Newtonian Poincare-Wavre theorem, it depends both on the distance from the rotation axis and the distance from the equatorial plane.

Jaranowski, Piotr; Malec, Edward; Pirog, Michal

2015-01-01T23:59:59.000Z

459

Heat transfer and fluid flow over a single disk in a fluid rotating as a rigid body  

Science Journals Connector (OSTI)

Laminar heat transfer problem is analyzed for a disk rotating ... the angular speed ? in a co-rotating fluid (with the angular speed ?). The fluid is swirled in accordance with a forced- ... self-similar profiles...

Igor V. Shevchuk Ph.D.; Matthias H. Buschmann

2004-08-01T23:59:59.000Z

460

Adhesion and Friction Evaluation of Textured Slider Surfaces in Ultra-Low Flying Head-Disk Interfaces  

Science Journals Connector (OSTI)

To achieve extremely high-density magnetic recording of 1?Tbit per square inch using conventional technologies, the distance between the recording slider and the rotating disk needs to be less than 5?nm. For succ...

A.Y. Suh; S.-C. Lee; A.A. Polycarpou

2004-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "rear disk brakes" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Melt-Mixing by Novel Pitched-Tip Kneading Disks in a co-rotating Twin-Screw Extruder  

E-Print Network (OSTI)

Melt-mixing in twin-screw extruders is a key process for development of polymer composites, and quantification of mixing performance of kneading elements based on the physical process in them is a challenging problem. We discuss melt-mixing by novel kneading elements, called "pitched-tip kneading disk (ptKD)". Disk-stagger angle and tip angle are the main geometrical parameters of the ptKDs. We investigated four typical arrangements of the ptKDs, which are forwarding and backwarding disk-staggers combined with forwarding and backwarding tips, respectively. Numerical simulations under a certain feed rate and screw revolution speed were performed and mixing process was investigated by using Lagrangian statistics. It is found that the four types had different mixing characteristics, and their mixing processes were explained by a coupling effect of drag flow by disk staggering and pitched-tip and pressure flow, which is controlled by operational conditions.

Nakayama, Yasuya; Shigeishi, Takashi; Tomiyama, Hideki; Kajiwara, Toshihisa

2010-01-01T23:59:59.000Z

462

Nd:GdVO4 in Face-Cooled Geometries: Thin-Disk and High-Power Microchip Lasers  

Science Journals Connector (OSTI)

The potential of Nd:GdVO4 for face-cooled geometries is discussed. Particular emphasis is given to experimental and finite element studies of thin-disk and high-power, monolithic,...

Kemp, Alan J; Valentine, Gareth J; Burns, David

463

Nd:GdVO4 in face-cooled geometries: thin-disk and high-power microchip lasers  

Science Journals Connector (OSTI)

The potential of Nd:GdVO4 for face-cooled geometries is discussed. Particular emphasis is given to experimental and finite element studies of thin-disk and...

Kemp, Alan J; Valentine, Gareth J; Burns, David

464

SATURATION OF THE MAGNETO-ROTATIONAL INSTABILITY IN STRONGLY RADIATION-DOMINATED ACCRETION DISKS  

SciTech Connect

The saturation level of the magneto-rotational instability (MRI) in a strongly radiation-dominated accretion disk is studied using a new Godunov radiation MHD code in the unstratified shearing box approximation. Since vertical gravity is neglected in this work, our focus is on how the MRI saturates in the optically thick mid-plane of the disk. We confirm that turbulence generated by the MRI is very compressible in the radiation-dominated regime, as found by previous calculations using the flux-limited diffusion approximation. We also find little difference in the saturation properties in calculations that use a larger horizontal domain (up to four times the vertical scale height in the radial direction). However, in strongly radiation pressure dominated disks (one in which the radiation energy density reaches {approx}1% of the rest mass energy density of the gas), we find that Maxwell stress from the MRI turbulence is larger than the value produced when radiation pressure is replaced with the same amount of gas pressure. At the same time, the ratio between Maxwell stress and Reynolds stress is increased by almost a factor of eight compared with the gas pressure dominated case. We suggest that this effect is caused by radiation drag, which acts like bulk viscosity and changes the effective magnetic Prandtl number of the fluid. Radiation viscosity significantly exceeds both the microscopic plasma viscosity and resistivity, ensuring that radiation-dominated systems occupy the high magnetic Prandtl number regime. Nevertheless, we find that radiative shear viscosity is negligible compared to the Maxwell stress and Reynolds stress in the flow. This may have important implications for the structure of radiation-dominated accretion disks.

Jiang Yanfei; Stone, James M. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Davis, Shane W. [Canadian Institute for Theoretical Astrophysics, Toronto, ON M5S3H4 (Canada)

2013-04-20T23:59:59.000Z

465

Hot Organic Molecules Toward a Young Low-Mass Star: A Look at Inner Disk Chemistry  

E-Print Network (OSTI)

Spitzer Space Telescope spectra of the low mass young stellar object (YSO) IRS 46 (L_bol ~ 0.6 L_sun) in Ophiuchus reveal strong vibration-rotation absorption bands of gaseous C2H2, HCN, and CO2. This is the only source out of a sample of ~100 YSO's that shows these features and the first time they are seen in the spectrum of a solar-mass YSO. Analysis of the Spitzer data combined with Keck L- and M-band spectra gives excitation temperatures of > 350 K and abundances of 10(-6)-10(-5) with respect to H2, orders of magnitude higher than those found in cold clouds. In spite of this high abundance, the HCN J=4-3 line is barely detected with the James Clerk Maxwell Telescope, indicating a source diameter less than 13 AU. The (sub)millimeter continuum emission and the absence of scattered light in near-infrared images limits the mass and temperature of any remnant collapse envelope to less than 0.01 M_sun and 100 K, respectively. This excludes a hot-core type region as found in high-mass YSO's. The most plausible origin of this hot gas rich in organic molecules is in the inner (<6 AU radius) region of the disk around IRS 46, either the disk itself or a disk wind. A nearly edge-on 2-D disk model fits the spectral energy distribution (SED) and gives a column of dense warm gas along the line of sight that is consistent with the absorption data. These data illustrate the unique potential of high-resolution infrared spectroscopy to probe organic chemistry, gas temperatures and kinematics in the planet-forming zones close to a young star.

F. Lahuis; E. F. van Dishoeck; A. C. A. Boogert; K. M. Pontoppidan; G. A. Blake; C. P. Dullemond; N. J. Evans II; M. R. Hogerheijde; J. K. Joergensen; J. E. Kessler-Silacci; C. Knez

2005-11-29T23:59:59.000Z

466

The inner edge of the accretion disk around a supermassive black hole  

Science Journals Connector (OSTI)

... material giving rise to the line is within 2.6 0.3 times the Schwarzschild radiusthe event horizon of a non-rotating black holeat the 95% confidence ... of the disk is within a few Rs (where Rs ? 2GM/c2 is the Schwarzschild radius) of an object of mass M. Unfortunately, the inner radius inferred from ...

B. C. Bromley; W. A. Miller; V. I. Pariev

1998-01-01T23:59:59.000Z

467

A determination of the power absorbed by flat disks rotating in a liquid  

E-Print Network (OSTI)

A DETERMINATION OF THE POWER ABSORBED BY FLAT DISKS ROTATING IN A LIQUID A Thesis JOHN ROBERT NASSEY Approved as to style and content by Chairman of Committee ~c, Pr. ~ ~a ~- Head of De@'artment of Mechanical Engineering A DETERMINATION... August l952 Ma)or Sub]ectt Mechanical Engineering AC KIOWLEDOWEKT The writer wishes to express appreciation for advice and enoouragement reoeived during the preparation of this thesis from Professors E, S. Holdredge and R. M. Wlngren, TABLF. OF CO...

Massey, John Robert

1952-01-01T23:59:59.000Z

468

Persistence-Length Renormalization of Polymers in a Crowded Environment of Hard Disks  

E-Print Network (OSTI)

The most conspicuous property of a semiflexible polymer is its persistence length, defined as the decay length of tangent correlations along its contour. Using an efficient stochastic growth algorithm to sample polymers embedded in a quenched two-dimensional hard-disk fluid, we find apparent wormlike chain statistics with a renormalized persistence length. We identify a universal form of the disorder renormalization that suggests itself as a quantitative measure of molecular crowding.

Sebastian Schbl; Sebastian Sturm; Wolfhard Janke; Klaus Kroy

2014-10-22T23:59:59.000Z

469

X-ray flares, neutrino cooled disks, and the dynamics of late accretion in GRB engines  

E-Print Network (OSTI)

We compute the average luminosity of X-ray flares as a function of time, for a sample of 10 long-duration gamma-ray burst afterglows. The mean luminosity, averaged over a timescale longer than the duration of the individual flares, declines as a power-law in time with index ~-1.5. We elaborate on the properties of the central engine that can produce such a decline. Assuming that the engine is an accreting compact object, and for a standard conversion factor between accretion rate and jet luminosity, the switch between a neutrino-cooled thin disk and a non-cooled thick disk takes place at the transition from the prompt to the flaring phase. We discuss the implications of this coincidence under different scenarios for the powering of the GRB outflow. We also show that the interaction of the outflow with the envelope of the progenitor star cannot produce flares out of a continuous relativistic flow, and conclude that it is the dynamics of the disk or the jet-launching mechanism that generates an intrinsically unsteady outflow on timescales much longer than the dynamical timescale of the system. This is consistent with the fact that X-ray flares are observed in short-duration GRBs as well as in long-duration ones.

Davide Lazzati; Rosalba Perna; Mitchell C. Begelman

2008-05-01T23:59:59.000Z

470

New insight into the Solar System's transition disk phase provided by the unusual meteorite Isheyevo  

E-Print Network (OSTI)

Many aspects of planet formation are controlled by the amount of gas remaining in the natal protoplanetary disk (PPDs). Infrared observations show that PPDs undergo a transition stage at several Myr, during which gas densities are reduced. Our Solar System would have experienced such a stage. However, there is currently no data that provides insight into this crucial time in our PPD's evolution. We show that the Isheyevo meteorite contains the first definitive evidence for a transition disk stage in our Solar System. Isheyevo belongs to a class of metal-rich meteorites whose components have been dated at almost 5 Myr after the first solids in the Solar System, and exhibits unique sedimentary layers that imply formation through gentle sedimentation. We show that such layering can occur via gentle sweep-up of material found in the impact plume resulting from the collision of two planetesimals. Such sweep-up requires gas densities consistent with observed transition disks. As such, Isheyevo presents the first ev...

Morris, Melissa A; Knauth, L Paul

2014-01-01T23:59:59.000Z

471

REVISITING PUTATIVE COOL ACCRETION DISKS IN ULTRALUMINOUS X-RAY SOURCES  

SciTech Connect

Soft, potentially thermal spectral components observed in some ultra-luminous X-ray sources (ULXs) can be fit with models for emission from cool, optically thick accretion disks. If that description is correct, the low temperatures that are observed imply accretion onto 'intermediate-mass' black holes. Subsequent work has found that these components may follow an inverse relationship between luminosity and temperature, implying a non-blackbody origin for this emission. We have re-analyzed numerous XMM-Newton spectra of extreme ULXs. Crucially, observations wherein the source fell on a chip gap were excluded owing to their uncertain flux calibration, and the neutral column density along the line of sight to a given source was jointly determined by multiple spectra. The luminosity of the soft component is found to be positively correlated with temperature, and to be broadly consistent with L?T {sup 4} in the measured band pass, as per blackbody emission from a standard thin disk. These results are nominally consistent with accretion onto black holes with masses above the range currently known in Galactic X-ray binaries, though there are important caveats. Emission from inhomogeneous or super-Eddington disks may also be consistent with the data.

Miller, J. M.; King, A. L.; Reynolds, M. T.; Reis, R. C. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States)] [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Walton, D. J. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)] [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Fabian, A. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom)] [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Miller, M. C., E-mail: jonmm@umich.edu [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2013-10-20T23:59:59.000Z

472

Hybrid viscosity and the magnetoviscous instability in hot, collisionless accretion disks  

E-Print Network (OSTI)

We aim to illustrate the role of hot protons in enhancing the magnetorotational instability (MRI) via the ``hybrid'' viscosity, which is due to the redirection of protons interacting with static magnetic field perturbations, and to establish that it is the only relevant mechanism in this situation. It has recently been shown by Balbus \\cite{PBM1} and Islam & Balbus \\cite{PBM11} using a fluid approach that viscous momentum transport is key to the development of the MRI in accretion disks for a wide range of parameters. However, their results do not apply in hot, advection-dominated disks, which are collisionless. We develop a fluid picture using the hybrid viscosity mechanism, that applies in the collisionless limit. We demonstrate that viscous effects arising from this mechanism can significantly enhance the growth of the MRI as long as the plasma $\\beta \\gapprox 80$. Our results facilitate for the first time a direct comparison between the MHD and quasi-kinetic treatments of the magnetoviscous instability in hot, collisionless