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Note: This page contains sample records for the topic "front 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.


1

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.

2

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.

3

Hybrid: Braking  

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

button highlighted Stopped Button subbanner graphic: gray bar BRAKING: PART 1 Regenerative braking converts otherwise wasted energy from braking into electricity and stores it in...

4

Multidisciplinary design optimization of an automotive magnetorheological brake design  

Science Conference Proceedings (OSTI)

This paper presents the development of a new electromechanical brake system using magnetorheological (MR) fluid. The proposed brake system consists of rotating disks immersed in a MR fluid and enclosed in an electromagnet, where the yield stress of the ... Keywords: Automotive brake, Computational fluid dynamics, Electric brake actuator, Finite element analysis, Magnetorheological fluid, Multidisciplinary design optimization

Edward J. Park; Luis Falco da Luz; Afzal Suleman

2008-02-01T23:59:59.000Z

5

Gravity brake  

DOE Patents (OSTI)

A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

Lujan, Richard E. (Santa Fe, NM)

2001-01-01T23:59:59.000Z

6

Braking system  

DOE Patents (OSTI)

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

Norgren, D.U.

1982-09-23T23:59:59.000Z

7

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.

8

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.

9

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.

10

Vehicle brake testing system  

SciTech Connect

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

Stevens, Samuel S [Harriman, TN; Hodgson, Jeffrey W [Lenoir City, TN

2002-11-19T23:59:59.000Z

11

Svendborg Brakes | Open Energy Information  

Open Energy Info (EERE)

energy Product Denmark-based manufacturer of braking systems for the wind industry, as well as for the oil sector. References Svendborg Brakes1 LinkedIn Connections CrunchBase...

12

Combined hydraulic and regenerative braking system  

DOE Patents (OSTI)

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

Venkataperumal, R.R.; Mericle, G.E.

1979-08-09T23:59:59.000Z

13

Combined hydraulic and regenerative braking system  

DOE Patents (OSTI)

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

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

1981-06-02T23:59:59.000Z

14

Oxygen-Diffused Titanium as a Candidate Brake Rotor Material  

SciTech Connect

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

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

2009-01-01T23:59:59.000Z

15

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

Science Conference Proceedings (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

16

Regenerative braking device  

DOE Patents (OSTI)

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

Hoppie, Lyle O. (Birmingham, MI)

1982-01-12T23:59:59.000Z

17

Variable ratio regenerative braking device  

DOE Patents (OSTI)

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

Hoppie, Lyle O. (Birmingham, MI)

1981-12-15T23:59:59.000Z

18

Commercial Motor Vehicle Brake Assessment Tools  

E-Print Network (OSTI)

Commercial Motor Vehicle Brake Assessment Tools Commercial Motor Vehicle Roadside Technology Corridor Safety Technology Showcase October 14, 2010 Commercial Motor Vehicle Roadside Technology Corridor #12;Overview · Commercial Motor Vehicle (CMV) Air Brake System · North American Standard Level-1

19

Brake blending strategy for a hybrid vehicle  

DOE Patents (OSTI)

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

Boberg, Evan S. (Hazel Park, MI)

2000-12-05T23:59:59.000Z

20

CMV Brake Wear and Performance Test Little is known about the brake  

E-Print Network (OSTI)

inspections were due to brake defects. Additionally, brake maintenance and repair present a significant cost Center for Transportation Analysis (CTA) Research Areas Aviation Safety Air Traffic Management Analysis Environmental Policy Analysis Highway Safety Intelligent Transportation Systems Logistics Management Supply

Note: This page contains sample records for the topic "front 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

Improved braking torque generation capacity of an eddy current brake with time varying magnetic fields: A numerical study  

Science Conference Proceedings (OSTI)

Eddy current brakes (ECB) are electrically controlled and non-contact actuators used as assistive brakes in vehicles. ECBs exhibit insufficient generated braking torque at low speeds. In order to overcome this, the use of AC magnetic fields with fixed ... Keywords: Automotive applications, Brake-by-wire, Eddy current brakes, Finite element analysis, Time-varying magnetic field

Kerem Karakoc; Edward J. Park; Afzal Suleman

2012-10-01T23:59:59.000Z

22

Commercial Motor Vehicle Brake-Related Research  

E-Print Network (OSTI)

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

23

The Application of Fuzzy Logic in Regenerative Braking of EV  

Science Conference Proceedings (OSTI)

Regenerative braking can improve energy usage efficiency and prolong the driving distance of electric vehicle per charge, effectively. In the paper, we design a sugenos fuzzy logic controller which has four inputs including drivers braking ... Keywords: regenerative braking, fuzzy logic control, braking force distribution, ADVISOR

Zijian Zhang; Guoqing Xu; Weimin Li; Liang Zheng

2010-08-01T23:59:59.000Z

24

Method and apparatus for wind turbine braking  

DOE Patents (OSTI)

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

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

2009-02-10T23:59:59.000Z

25

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

26

Adaptive controller for regenerative and friction braking system  

DOE Patents (OSTI)

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

Davis, R.I.

1990-10-16T23:59:59.000Z

27

Model and Simulation of a Super-capacitor Braking Energy Recovery System for Urban Railway Vehicles  

Science Conference Proceedings (OSTI)

In this paper, a braking energy recovery system based on super-capacitor was presented. The method use super-capacitor and the conventional braking resistance constitute a new braking unit to realize the regenerative energy recovery, when braking, braking ... Keywords: Urban railway transportation, regeneration braking, super-capacitor, energy recovery, electric traction

Chen Xiao-li; Yang Jian; Fang Yu

2010-08-01T23:59:59.000Z

28

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

29

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 hydraulic braking control, or requiring traction control are required. The processor then employs a control strategy based on the determined vehicle state and provides command signals to a motor controller to control the operation of the electric traction motor and to a brake controller to control fluid pressure applied at each vehicle wheel to provide the appropriate regenerative antiskid braking control, hydraulic braking control, and traction control. 10 figs.

Cikanek, S.R.

1995-09-12T23:59:59.000Z

30

The Research of Traction Motor Energy-Saving Regenerative Braking Control Technology  

Science Conference Proceedings (OSTI)

In all the motor braking control systems, regenerative braking is the only way of energy-saving braking control mode. It can convert dynamic energy which generate during braking period into electric energy, then return to the grid. In this paper, through ... Keywords: regenerative braking, traction motor, direct torque, stator flux, slip frequency

Yuhua Wang; Jianlin Miao; Yuanfang Wei

2010-05-01T23:59:59.000Z

31

Niobium Alloying in Grey Cast Iron for Vehicle Brake Discs  

Science Conference Proceedings (OSTI)

Presentation Title, Niobium Alloying in Grey Cast Iron for Vehicle Brake Discs. Author(s) ... Microtexture Analysis of a Hot Rolled Silicon Electric Steel Niobium

32

Braking system for use with an arbor of a microscope  

DOE Patents (OSTI)

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

Norgren, Duane U. (Orinda, CA)

1984-01-01T23:59:59.000Z

33

VIN# JHMFA36216S019329 Vehicle Specifications  

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

16S019329 Vehicle Specifications Engine: 1.3 L 4-cylinder Electric Motor: 15 kW Battery: NiMH Seatbelt Positions: Five Payload: 968 lbs Features: Front disk brakes wEBD brake...

34

VIN# JHMFA36246S018725 Vehicle Specifications  

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

46S018725 Vehicle Specifications Engine: 1.3 L 4-cylinder Electric Motor: 15 kW Battery: NiMH Seatbelt Positions: Five Payload: 968 lbs Features: Front disk brakes wEBD brake...

35

The expandable network disk  

E-Print Network (OSTI)

This thesis presents a virtual disk cluster called END, the Expandable Network Disk. END aggregates storage on a cluster of servers into a single virtual disk. END's main goals are to offer good performance during normal ...

Muthitacharoen, Athicha, 1976-

2008-01-01T23:59:59.000Z

36

Study on Regenerative Brake Method of Hybrid Electric Drive System of Armored Vehicle  

Science Conference Proceedings (OSTI)

Aiming at characteristics of regenerative brake of hybrid electric drive system of tracked armored vehicle, mechanism of regenerative brake by pulse width modulation is in-depth analyzed, motor speed, brake current, feedback current, feedback energy ... Keywords: hybrid electric drive, motor, regenerative brake

Li Hua; Zhong Meng-chun; Zhang Jian; Xu Da; Lin Hai

2011-10-01T23:59:59.000Z

37

Regenerative braking on bicycles to power LED safety flashers  

E-Print Network (OSTI)

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

Collier, Ian M

2005-01-01T23:59:59.000Z

38

Computational model design and performance estimation in registration brake control  

Science Conference Proceedings (OSTI)

Electric motorcycles are applicable to both toys and real motorcycles, and also is a reference for constructing larger electrical vehicles. A design computational model of regenerative braking control of electric motorcycles and an experimental identification ...

P. S. Pa; S. C. Chang

2009-06-01T23:59:59.000Z

39

Investigation of aerodynamic braking devices for wind turbine applications  

DOE Green Energy (OSTI)

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

40

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. 123 figs.

Cikanek, S.R.

1994-10-25T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

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

42

Regenerative braking device with rotationally mounted energy storage means  

DOE Patents (OSTI)

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

Hoppie, Lyle O. (Birmingham, MI)

1982-03-16T23:59:59.000Z

43

Intensification of Ocean Fronts by Down-Front Winds  

Science Conference Proceedings (OSTI)

Many ocean fronts experience strong local atmospheric forcing by down-front winds, that is, winds blowing in the direction of the frontal jet. An analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by ...

Leif N. Thomas; Craig M. Lee

2005-06-01T23:59:59.000Z

44

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

45

The German Front Experiment 1987  

Science Conference Proceedings (OSTI)

The German Front Experiment, 1987 (GFE87) is a field experiment using aircraft, radar, surface, and upper-air observations to determine the influence of the European Alps on cold fronts. Measurements are concentrated in the Rhine Valley and in ...

Klaus P. Hoinka; Hans Volkert

1987-11-01T23:59:59.000Z

46

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

47

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

Science Conference Proceedings (OSTI)

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

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

2013-10-01T23:59:59.000Z

48

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

DOE Green Energy (OSTI)

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

Peter J. Blau

2000-04-26T23:59:59.000Z

49

Dust in Protoplanetary Disks  

E-Print Network (OSTI)

We critically examine the best lines of evidence for grain growth in protoplanetary disks, based on modelling of observed spectral energy distributions and images of T Tauri and Herbig Ae stars. The data are consistent with millimeter-sized grains near disk midplanes, and micron-sized grains near disk surfaces. We review three channels by which grains can grow, including direct condensation from the vapor phase, grain-grain collisional sticking, and gravitational instability. The utility of dust in identifying as yet unseen extrasolar planets is highlighted.

Chiang, E I

2003-01-01T23:59:59.000Z

50

Dust in Protoplanetary Disks  

E-Print Network (OSTI)

We critically examine the best lines of evidence for grain growth in protoplanetary disks, based on modelling of observed spectral energy distributions and images of T Tauri and Herbig Ae stars. The data are consistent with millimeter-sized grains near disk midplanes, and micron-sized grains near disk surfaces. We review three channels by which grains can grow, including direct condensation from the vapor phase, grain-grain collisional sticking, and gravitational instability. The utility of dust in identifying as yet unseen extrasolar planets is highlighted.

E. I. Chiang

2003-09-08T23:59:59.000Z

51

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

E-Print Network (OSTI)

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

Alexander Bolonkin

2008-02-13T23:59:59.000Z

52

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

E-Print Network (OSTI)

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

Bolonkin, Alexander

2008-01-01T23:59:59.000Z

53

Brake rotor design and comparison using finite element analysis : an investigation in topology optimization.  

E-Print Network (OSTI)

??Disc brake technology used for mountain bikes, and mountain bike technology in general, has improved significantly as the sport of mountain biking has evolved. Disc (more)

Domond, Kenneth

2010-01-01T23:59:59.000Z

54

Numerical Simulation of Brake Discs of CRH3 High-Speed Trains ...  

Science Conference Proceedings (OSTI)

... the research object?the course of emergency brake was simulated by ANSYS. .... Energy X-Ray Diffraction Microscopy Studies of Bulk Polycrystal Responses.

55

Tachyon cosmology, supernovae data, and the big brake singularity  

SciTech Connect

We compare the existing observational data on type Ia supernovae with the evolutions of the Universe predicted by a one-parameter family of tachyon models which we have introduced recently [Phys. Rev. D 69, 123512 (2004)]. Among the set of the trajectories of the model which are compatible with the data there is a consistent subset for which the Universe ends up in a new type of soft cosmological singularity dubbed big brake. This opens up yet another scenario for the future history of the Universe besides the one predicted by the standard {lambda}CDM model.

Keresztes, Z.; Gergely, L. A.; Gorini, V.; Moschella, U.; Kamenshchik, A. Yu. [Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Department of Experimental Physics, University of Szeged, Dom Ter 9, Szeged 6720 (Hungary); Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Department of Experimental Physics, University of Szeged, Dom Ter 9, Szeged 6720 (Hungary); Department of Applied Science, London South Bank University, 103 Borough Road, London SE1 OAA (United Kingdom); Dipartimento di Scienze Fisiche e Mathematiche, Universita dell'Insubria, Via Valleggio 11, 22100 Como (Italy); INFN, sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Dipartimento di Fisica and INFN, via Irnerio 46, 40126 Bologna (Italy); L. D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, Kosygin street 2, 119334 Moscow (Russian Federation)

2009-04-15T23:59:59.000Z

56

Observations of Circumstellar Disks  

E-Print Network (OSTI)

The imaging of disks around young stars presents extreme challenges in high dynamic range, angular resolution, and sensitivity. Recent instrumental advances have met these challenges admirably, leading to a marked increase in imaging discoveries. These have opened up a new era in studies of the origin of planetary systems. Questions about our own solar system's formation, and of the prevalence of extra-solar planets, are now addressed with complementary techniques at different wavelengths. Optical and near-infrared images detail scattered light from disks at the highest possible resolution. Mid-infrared, sub-millimeter, and millimeter-wave techniques probe thermal dust continuum radiation. Millimeter-wave interferometry details the small-scale structure of the molecular gas. Kinematic imaging studies affirm the disk interpretation of mm-wave continuum surveys, and the high incidence rate for solar nebula analogs. Inner holes, azimuthal asymmetries, and gaps suggest the presence of underlying planetary bodies. The combined techniques provide a multi-dimensional picture of disks in time and have strengthened our understanding of the connection between disks and planets. Future progress is assured by the presence of much-improved imaging capability looming on the horizon.

David W. Koerner

2001-03-28T23:59:59.000Z

57

Dual-channel Haptic Synthesis of Viscoelastic Tissue Properties using Programmable Eddy Current Brakes  

Science Conference Proceedings (OSTI)

We describe a novel method for haptic synthesis of viscoelastic responses which employs a dual-channel haptic interface. It has motors that generate torque independently of velocity and brakes that generate viscous torque independently of position. ... Keywords: eddy current brakes, haptic simulation, viscoelastic simulation

Andrew H. C. Gosline; Vincent Hayward

2009-10-01T23:59:59.000Z

58

Simulation of PSO Fuzzy Control Stratety for Regenerative Braking of HEV  

Science Conference Proceedings (OSTI)

Based on particle swarm optimization algorithm, a new fuzzy controller was constructed and a fuzzy control strategy of regenerative braking for HEV was proposed. A model of a parallel hybrid electric vehicle was built. The performance of the default ... Keywords: hybrid electric vehicle, fuzzy control, regenerative braking, particle swarm optimization

Wang Chun; Tang Lan

2012-04-01T23:59:59.000Z

59

Operation Pattern Recognition and Control for Super Capacitor Braking Energy Regeneration System of Micro EV  

Science Conference Proceedings (OSTI)

Super capacitor has some advantages of high charge-discharge rate, long life, simple structure and reliable performance, and it is especially suitable as braking energy renewable energy storage device for electric vehicle and hybrid electric vehicle. ... Keywords: Super capacitor, braking energy regeneration, micro EV, pattern recognition and control

Jinyu Qu; Liyan Liang; Zhongyu Yang

2009-12-01T23:59:59.000Z

60

Cold Fronts in CDM clusters  

E-Print Network (OSTI)

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

Daisuke Nagai; Andrey V. Kravtsov

2002-06-26T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

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 -

62

Wind turbine trailing-edge aerodynamic brake design  

DOE Green Energy (OSTI)

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

63

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

64

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

65

The Sea-Breeze Front Analytical Model  

Science Conference Proceedings (OSTI)

Analytical solutions to the nonlinear equations of motion are used to describe the sea breeze front.

Yizhak Feliks

1988-03-01T23:59:59.000Z

66

Collisional Particle Disks  

E-Print Network (OSTI)

We present a new, simple, fast algorithm to numerically evolve disks of inelastically colliding particles surrounding a central star. Our algorithm adds negligible computational cost to the fastest existing collisionless N-body codes, and can be used to simulate, for the first time, the interaction of planets with disks over many viscous times. Though the algorithm is implemented in two dimensions-i.e., the motions of bodies need only be tracked in a plane-it captures the behavior of fully three-dimensional disks in which collisions maintain inclinations that are comparable to random eccentricities. We subject the algorithm to a battery of tests for the case of an isolated, narrow, circular ring. Numerical simulations agree with analytic theory with regards to how particles' random velocities equilibrate; how the ring viscously spreads; and how energy dissipation, angular momentum transport, and material transport are connected. We derive and measure the critical value of the coefficient of restitution above which viscous stirring dominates inelastic damping and the particles' velocity dispersion runs away.

Yoram Lithwick; Eugene Chiang

2006-07-11T23:59:59.000Z

67

Nonlinear Control Synthesis for a Self-energizing Electro-Hydraulic Brake  

E-Print Network (OSTI)

Nonlinear control algorithm for a self-energizing electro-hydraulic brake is analytically designed. The desired closed-loop system behavior is reached via a synthesized nonlinear controller.

Starykh, Alexey

2010-01-01T23:59:59.000Z

68

Observations of the Tasman Front  

Science Conference Proceedings (OSTI)

Ship and air surveys were conducted in 197879 to examine the thermal structure in and near the Tasman Front between Australia and New Zealand at latitudes between Brisbane and Bass Strait. After separation from the continental slope, the East ...

John C. Andrews; Martin W. Lawrence; Carl S. Nilsson

1980-11-01T23:59:59.000Z

69

The Dispersal of Protoplanetary Disks  

E-Print Network (OSTI)

Protoplanetary disks are the sites of planet formation, and the evolution and eventual dispersal of these disks strongly influences the formation of planetary systems. Disk evolution during the planet-forming epoch is driven by accretion and mass-loss due to winds, and in typical environments photoevaporation by high-energy radiation from the central star is likely to dominate final gas disk dispersal. We present a critical review of current theoretical models, and discuss the observations that are used to test these models and inform our understanding of the underlying physics. We also discuss the role disk dispersal plays in shaping planetary systems, considering its influence on both the process(es) of planet formation and the architectures of planetary systems. We conclude by presenting a schematic picture of protoplanetary disk evolution and dispersal, and discussing prospects for future work.

Alexander, Richard; Andrews, Sean; Armitage, Philip; Cieza, Lucas

2013-01-01T23:59:59.000Z

70

Light-Front Quantization and QCD Phenomena  

E-Print Network (OSTI)

The light-front quantization of QCD provides an alternative to lattice gauge theory for computing the mass spectrum, scattering amplitudes, and other physical properties of hadrons directly in Minkowski space. Nonperturbative light-front methods for solving gauge theory and obtaining light-front wavefunctions, such as discretized light-front quantization, the transverse lattice, and light-front resolvents are reviewed. The resulting light-front wavefunctions give a frame-independent interpolation between hadrons and their quark and gluon degrees of freedom, including an exact representation of spacelike form factors, transition form factors such as $B \\to \\ell \\bar \

S. J. Brodsky

2003-11-05T23:59:59.000Z

71

front  

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

Carbon Carbon Carbon Sequestration Sequestration State of the Science roadmapping future carbon sequestration R&D February 1999 A working paper for U.S. Department of Energy Office of Science Office of Fossil Energy i Carbon Sequestration DRAFT (February 1999) Dave Reichle, ORNL John Houghton, DOE Sally Benson, LBNL John Clarke, PNNL Roger Dahlman, DOE George Hendrey, BNL Howard Herzog, MIT Jennie Hunter-Cevera, LBNL Gary Jacobs, ORNL Rod Judkins, ORNL WORKING PAPER ON CARBON SEQUESTRATION SCIENCE AND TECHNOLOGY Office of Science Office of Fossil Energy U.S. Department of Energy Bob Kane, DOE Jim Ekmann, FETC Joan Ogden, Princeton Anna Palmisano, DOE Robert Socolow, Princeton John Stringer, EPRI Terry Surles, LLNL Alan Wolsky, ANL Nicholas Woodward, DOE Michael York, DOE ii DRAFT (February 1999) Carbon Sequestration

72

Kelvin Fronts on the Equatorial Thermocline  

Science Conference Proceedings (OSTI)

Properties of internal wave fronts or Kelvin fronts travelling eastward in the equatorial waveguide are studied, motivated by recent studies on coastal Kelvin waves and jumps and new data on equatorial Kelvin waves. It has been recognized for ...

Alexey V. Fedorov; W. Kendall Melville

2000-07-01T23:59:59.000Z

73

PV Frontogenesis and Upper-Tropospheric Fronts  

Science Conference Proceedings (OSTI)

Upper-tropospheric fronts and frontogenesis are viewed from a potental vorticity (PV) perspective. The rudiments of this approach are to regard such a front as a zone of strong PV gradient on isentropic surfaces, and to treat the accompanying ...

H. C. Davies; A. M. Rossa

1998-06-01T23:59:59.000Z

74

Turbulent Mixing at the Pacific Subtropical Front  

Science Conference Proceedings (OSTI)

Some advection of water across the North Pacific subtropical front occurs by the subduction of surface mixed layers from the north side of the front underneath surface waters on the south side. Cross-frontal advection in the thermocline is ...

Rolf G. Lueck

1988-12-01T23:59:59.000Z

75

BLM Sierra Front Field Office | Open Energy Information  

Open Energy Info (EERE)

Sierra Front Field Office Jump to: navigation, search Name BLM Sierra Front Field Office Short Name Sierra Front Parent Organization BLM Carson City District Office Address 5665...

76

Modelling Accretion in Transitional Disks  

E-Print Network (OSTI)

Transitional disks are protoplanetary disk around young stars that display inner holes in the dust distribution within a few AU, which is accompanied nevertheless by some gas accretion onto the central star. These cavities could possibly be created by the presence of one or more massive planets. If the gap is created by planets and gas is still present in it, then there should be a flow of gas past the planet into the inner region. It is our goal to study the mass accretion rate into the gap and in particular the dependency on the planet's mass and the thermodynamic properties of the disk. We performed 2D hydro simulations for disks with embedded planets. We added radiative cooling from the disk surfaces, radiative diffusion in the disk midplane, and stellar irradiation to the energy equation to have more realistic models. The mass flow rate into the gap region depends, for given disk thermodynamics, non-monotonically on the mass of the planet. Generally, more massive planets open wider and deeper gaps which ...

Mller, Tobias W A

2013-01-01T23:59:59.000Z

77

Control of a dynamic brake to reduce turbine-generator shaft transient torques  

SciTech Connect

A resistive, thyristor-controlled brake is used to damp transient torques in large thermo-electric generators supplying series-compensated transmission lines. Emphasis is placed on developing a suitable control algorithm and testing the algorithm through a wide variety of different operating configurations. Discrete-level Generalized Predictive Control is examined as one possible approach to optimal control of the brake. Some problems with implementation of GPC on the system are discussed. Prony analysis is used to identify system transfer functions which are then related to control design considerations and robustness properties.

Donnelly, M.K.; Smith, J.R.; Johnson, R.M. (Montana State Univ., Bozeman, MT (United States)); Hauer, J.F. (Bonneville Power Administration, Kalispell, MT (United States)); Brush, R.W. (Montana Power Co., Butte, MT (United States)); Adapa, R. (Electric Power Research Inst., Palo Alto, CA (United States))

1993-02-01T23:59:59.000Z

78

Trends for Outer Disk Profiles  

E-Print Network (OSTI)

The surface-brightness profiles of galaxy disks fall into three main classes, based on whether they are simple exponentials (Type I), bend down at large radii (Type II, "truncations") or bend up at large radii (Type III, "antitruncations"). Here, we discuss how the frequency of these different profiles depends on Hubble type, environment, and the presence or absence of bars; these trends may herald important new tests for disk formation models.

Peter Erwin; Michael Pohlen; Leonel Gutierrez; John E. Beckman

2007-12-10T23:59:59.000Z

79

Light-Front Holographic QCD  

SciTech Connect

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

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

2012-02-16T23:59:59.000Z

80

Front Vehicle Setup Information Downloadable Dynamometer Database...  

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

Chevrolet Volt- 20F Test cell location Front Vehicle Setup Information Downloadable Dynamometer Database (D 3 )- Test Summary Sheet Vehicle architecture EREV Vehicle dynamometer...

Note: This page contains sample records for the topic "front 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

Intrusion Characteristics in the Antarctic Polar Front  

Science Conference Proceedings (OSTI)

Data obtained on two cruises to the Antarctic Polar Front are used to investigate the nature of thermohaline intrusions in the front. These data, obtained in the Drake Passage and south of New Zealand, include CTD time series made relative to ...

John M. Toole

1981-06-01T23:59:59.000Z

82

Cold Front Acceleration over Lake Michigan  

Science Conference Proceedings (OSTI)

High-resolution Eta Model simulations of a strong but relatively dry late winter surface cold front that occurred during the STORM-FEST project depicted a pronounced acceleration of the front during the afternoon hours over the southern end of ...

William A. Gallus Jr.; Moti Segal

1999-10-01T23:59:59.000Z

83

The light-front vacuum and dynamics  

E-Print Network (OSTI)

I give a quantum theoretical description of kinematically invariant vacuua on the algebra of free fields restricted to a light front and discuss the relation between the light-front Hamiltonian, P-, the vacuum, and Poincare invariance. This provides a quantum theoretical description of zero modes.

W. N. Polyzou

2004-09-22T23:59:59.000Z

84

Using Solid State Disk Array as a Cache for LHC ATLAS Data Analysis  

E-Print Network (OSTI)

User data analysis in high energy physics presents a challenge to spinning-disk based storage systems. The analysis is data intense, yet reads are small, sparse and cover a large volume of data files. It is also unpredictable due to users' response to storage performance. We describe here a system with an array of Solid State Disk as a non-conventional, standalone file level cache in front of the spinning disk storage to help improve the performance of LHC ATLAS user analysis at SLAC. The system uses a long period of data access records to make caching decisions. It can also use information from other sources such as a work-flow management system. We evaluate the performance of the system both in terms of caching and its impact on user analysis jobs. The system currently uses Xrootd technology, but the technique can be applied to any storage system.

Yang, W; The ATLAS collaboration; Mount, R

2013-01-01T23:59:59.000Z

85

Beta Pictoris Debris Disk is a Proto-planetary Disk  

E-Print Network (OSTI)

Abstract: The debris disk around the star Beta Pictoris is a proto-planetary disk which was caused by a collision of two or more aging stars. Beta Pictoris is shown to possess a large debris disk which glows in the infared. [1] It has been hypothesized that this debris disk is not evidence for the formation of new stars/exoplanets [2] but of the destruction of older stars colliding with each other, thus taking up new orbits around the proto-star Beta Pictoris, which is a very young planet, and leaving a very large debris field similar to our own asteroid belt. [3] The larger stars that collided will stabilize after losing incredible amounts of material and forming rings (like Saturn, Jupiter, Uranus, Neptune). The smaller much more traveled stars will stabilize and take up orbit around the younger stars and form round, undifferentiated objects similar to the moon Callisto [4] , or the many other arrangements of moons around Saturn or Jupiter and smaller objects such as Ceres. This could also explain why they do not possess iron cores but are mostly volatiles such as water, ammonia, methane and sulfur dioxide which have a relatively low equilibrium condensation as opposed to refractory elements and molecules which have a much higher boiling point, and play a large part

Jeffrey J Wolynski

2012-01-01T23:59:59.000Z

86

Pressure transient method for front tracking  

DOE Green Energy (OSTI)

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

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

1983-08-01T23:59:59.000Z

87

A cool disk in the Galactic Center?  

E-Print Network (OSTI)

We study the possibility of a cool disk existing in the Galactic Center in the framework of the disk-corona evaporation/condensation model. Assuming an inactive disk, a hot corona should form above the disk since there is a continuous supply of hot gas from stellar winds of the close-by massive stars. Whether the cool disk can survive depends on the mass exchange between the disk and corona. If the disk-corona interaction is dominated by evaporation and the rate is larger than the Bondi accretion rate in the Galactic Center, the disk will be depleted within a certain time period and no persistent disk will exist. On the other hand, if the interaction results in hot gas steadily condensing into the disk, an inactive cool disk might survive. For this case we further investigate the Bremsstrahlung radiation from the hot corona and compare it with the observed X-ray luminosity. Our model shows that, for standard viscosity in the corona (alpha=0.3), the mass evaporation rate is much higher than the Bondi accretion rate and the coronal density is much larger than that inferred from Chandra observations. An inactive disk can not survive such strong evaporation. For small viscosity (alphanature.

B. F. Liu; F. Meyer; E. Meyer-Hofmeister

2004-03-18T23:59:59.000Z

88

Rapid low fidelity turbomachinery disk optimization  

Science Conference Proceedings (OSTI)

Turbomachinery disks are heavy, highly stressed components used in gas turbines. Improved design of turbomachinery disks could yield a significant reduction in engine weight. This paper focuses on rapid low fidelity design and optimization of isotropic ... Keywords: Flywheel, Optimization, Plane stress, Turbomachinery disk

David P. Gutzwiller; Mark G. Turner

2010-05-01T23:59:59.000Z

89

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

E-Print Network (OSTI)

This simulator experiment is a preliminary study examining the effects of different auditory signals on braking force and reaction time in a rear-end collision warning system. A driving simulator was built in which subjects operated a computer 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 driving situation by applying his/her brakes. Closing velocities of 10 miles per hour and 30 miles per hour were used. Braking times and forces were measured for four different warning sounds: 1) no warning; 2) a pulsed warning sound that increased in repetition rate; 3) a sound that increased in frequency; and, 4) a sound that increased in intensity. Results suggested that an auditory warning signal would decrease reaction time and increase maximum braking force applied. The sound that increased in frequency and the sound that increased in intensity provided the greatest savings in reaction time, approximately one quarter second, when compared to the no warning condition. The pulsed warning sound provided the greatest increase in braking force. Participants preferred the pulsed sound over the other warning sounds. Further research must be done to determine if the warning sounds decrease the reaction time enough to cause a significant reduction in accidents.

Hopkins, Jennifer Susan

1995-01-01T23:59:59.000Z

90

Collapse and Fragmentation of Molecular Cloud Cores. X. Magnetic Braking of Prolate and Oblate Cores  

E-Print Network (OSTI)

The collapse and fragmentation of initially prolate and oblate, magnetic molecular clouds is calculated in three dimensions with a gravitational, radiative hydrodynamics code. The code includes magnetic field effects in an approximate manner: magnetic pressure, tension, braking, and ambipolar diffusion are all modelled. The parameters varied for both the initially prolate and oblate clouds are the initial degree of central concentration of the radial density profile, the initial angular velocity, and the efficiency of magnetic braking (represented by a factor $f_{mb} = 10^{-4}$ or $10^{-3}$). The oblate cores all collapse to form rings that might be susceptible to fragmentation into multiple systems. The outcome of the collapse of the prolate cores depends strongly on the initial density profile. Prolate cores with central densities 20 times higher than their boundary densities collapse and fragment into binary or quadruple systems, whereas cores with central densities 100 times higher collapse to form single...

Boss, Alan P

2009-01-01T23:59:59.000Z

91

Bay Front Biomass Facility | Open Energy Information  

Open Energy Info (EERE)

Front Biomass Facility Front Biomass Facility Jump to: navigation, search Name Bay Front Biomass Facility Facility Bay Front Sector Biomass Location Ashland County, Wisconsin Coordinates 46.9794969°, -90.4824892° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":46.9794969,"lon":-90.4824892,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

92

On the stability of subsonic thermal fronts  

Science Conference Proceedings (OSTI)

The stability of subsonic thermal fronts against corrugation is analyzed and an exact dispersion relation is obtained taking into account the compressibility of the gas. For heat fronts, this dispersion equation has an unstable root ({omega}{sub ex}) corresponding to the Landau-Darrieus unstable mode ({omega}{sub 0}) modified by the compressional effects. In particular, the exact solution shows a conspicuous maximum very close to the value of the intake Mach number M{sub 1} at which a Chapman-Jouguet deflagration wave behind the heat front is formed. Cooling fronts are stable for corrugation-like disturbances. A maximum damping as well as a maximum in the frequency occur at a value of M{sub 1} depending on the value of the normalized cooling q.

Ibanez S, Miguel H.; Shchekinov, Yuri; Bessega L, Maria C. [Centro de Fisica Fundamental, Facultad de Ciencias, Universidad de los Andes, Apartado 26, Ipostel, La Hechicera, Merida (Venezuela); Department of Physics, University of Rostov, Rostov on Don, 34409 (Russian Federation); Centro de Fisica Teorica y Computacional, Escuela de Fisica, Facultad de Ciencias, Universidad Central de Venezuela, Caracas (Venezuela)

2005-08-15T23:59:59.000Z

93

On the Minimum Scale of Surface Fronts  

Science Conference Proceedings (OSTI)

A series of numerical experiments of a surface front forced by stretching deformation using Clark's nonhydrostatic model at very high resolution is presented. These simulations are compared to those reported by Williams who used hydrostatic ...

R. L. Gall; R. T. Williams; T. L. Clark

1987-09-01T23:59:59.000Z

94

Climatology of Strong Intermountain Cold Fronts  

Science Conference Proceedings (OSTI)

Motivated by the intensity and severity of winds and temperature falls that frequently accompany rapidly developing cold fronts in northern Utah, this paper presents a 25-yr climatology of strong cold frontal passages over the Intermountain West ...

Jason C. Shafer; W. James Steenburgh

2008-03-01T23:59:59.000Z

95

Moist Convection at a Surface Cold Front  

Science Conference Proceedings (OSTI)

The motion of a surface cold front in an environment that is unstable to moist convection is studied with the aid ofboth hydrostatic and nonhydrostatic two-dimensional models. Simulations with the hydrostatic model essentially extend the work ...

N. Andrew Crook

1987-12-01T23:59:59.000Z

96

The Formation of New England Coastal Fronts  

Science Conference Proceedings (OSTI)

Coastal fronts are a frequent late fall and early winter feature of eastern New England weather. Data from a mesoscale observing network is used to describe the process of coastal frontogenesis and to determine the causes of formation. Three ...

John W. Nielsen

1989-07-01T23:59:59.000Z

97

Stationary Shock Fronts in a Continuously Stratified Thermocline Model  

Science Conference Proceedings (OSTI)

Fronts are ubiquitous in the ocean. Recent work by Dewar has considered the formation of oceanic fronts in a simple layered model.

A. J. George Nurser

1995-12-01T23:59:59.000Z

98

How Many CVs are Crossing the Period Gap? A Test for the Disruption of Magnetic Braking  

E-Print Network (OSTI)

We apply population synthesis techniques to calculate the present day number of two types of white dwarf-main sequence star (WDMS) binaries within the cataclysmic variable period gap. The first are post-common envelope binaries with secondary stars that have masses between 0.17 and 0.36 Msun (gPCEBs), such that they will commence mass transfer within the period gap. The second type are systems that were CVs at some point in their past, but detached once they evolved down in orbital period to ~3 h as a consequence of disrupted magnetic braking, and are crossing the period gap via gravitational radiation (dCVs). Full population synthesis calculations are performed where we assume either constant, global values of the common envelope ejection efficiency, or consider the ejection efficiency as a function of secondary mass. Several forms of magnetic braking are also considered. We predict an excess of dCVs over gPCEBs within the period gap of ~4 to ~13 assuming an ejection efficiency between 0.1 and 0.6, and a flat initial mass ratio distribution. This excess is revealed as a prominent peak at the location of the period gap in the orbital period distribution of the combined gPCEB and dCV population. We suggest that if such a feature is observed in the orbital period distribution of an observed sample of short orbital period WDMS binaries, this would strongly corroborate the disruption of magnetic braking.

P. J. Davis; U. Kolb; B. Willems; B. T. Gnsicke

2008-05-30T23:59:59.000Z

99

Variations in gear fatigue life for different wind turbine braking strategies  

SciTech Connect

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

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

1991-06-01T23:59:59.000Z

100

Variations in gear fatigue life for different wind turbine braking strategies  

DOE Green Energy (OSTI)

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

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

1991-06-01T23:59:59.000Z

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101

QCD and Light-Front Dynamics  

SciTech Connect

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

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

2011-01-10T23:59:59.000Z

102

Light-Front Holography and the Light-Front Schrodinger Equation  

SciTech Connect

One of the most important nonperturbative methods for solving QCD is quantization at fixed light-front time {tau} = t+z=c - Dirac's 'Front Form'. The eigenvalues of the light-front QCD Hamiltonian predict the hadron spectrum and the eigensolutions provide the light-front wavefunctions which describe hadron structure. More generally, we show that the valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. We outline a method for computing the required potential from first principles in QCD. The holographic mapping of gravity in AdS space to QCD, quantized at fixed light-front time, yields the same light front Schrodinger equation; in fact, the soft-wall AdS/QCD approach provides a model for the light-front potential which is color-confining and reproduces well the light-hadron spectrum. One also derives via light-front holography a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The light-front AdS/QCD holographic approach thus gives a frame-independent first approximation of the color-confining dynamics, spectroscopy, and excitation spectra of relativistic light-quark bound states in QCD.

Brodsky, Stanley J.; de Teramond, Guy

2012-08-15T23:59:59.000Z

103

DSD front models : nonideal explosive detonation  

SciTech Connect

The Detonation Shock Dynamics (DSD) method for propagating detonation in numerical simulation of detonation in high explosive (HE) is based on three elements: (1) a subscale theory of multi-dimensional detonation that treats the evolving detonation as a front with dynamics that depends only on metrics of the front (such as curvature, etc.), (2) high-resolution direct numerical sirnuliltion of detonation serving both to test existing subscale theories and suggest modifications, and (3) physical experiments to characterize multi-dimensional detonation propagation on real explosives and to calibrate the front models for use in engineering simulations. In this paper we describe our work on all three of these elements of the DSD method as it applies to detonation in nonideal explosives.

Bdzil, J. B. (John Bohdan); Short, M. (Mark Short); Aslam, T. D. (Tariq D.); Catanach, R. A. (Richard A.); Hill, L. G. (Larry G.)

2001-01-01T23:59:59.000Z

104

Energy Proportionality for Disk Storage Using Replication  

E-Print Network (OSTI)

one tenth of the power in standby mode as compared withlower energy mode (sleep/standby mode) after they experiencetransitioning the disk to standby mode. Expected length of

Kim, Jinoh

2010-01-01T23:59:59.000Z

105

PATENT: Nickel Base Superalloy Turbine Disk - TMS  

Science Conference Proceedings (OSTI)

Feb 10, 2007 ... A low solvus, high refractory alloy having unusually versatile processing mechanical property capabilities for advanced disks and rotors in gas...

106

ON THE TRANSITIONAL DISK CLASS: LINKING OBSERVATIONS OF T TAURI STARS AND PHYSICAL DISK MODELS  

Science Conference Proceedings (OSTI)

Two decades ago 'transitional disks' (TDs) described spectral energy distributions (SEDs) of T Tauri stars with small near-IR excesses, but significant mid- and far-IR excesses. Many inferred this indicated dust-free holes in disks possibly cleared by planets. Recently, this term has been applied disparately to objects whose Spitzer SEDs diverge from the expectations for a typical full disk (FD). Here, we use irradiated accretion disk models to fit the SEDs of 15 such disks in NGC 2068 and IC 348. One group has a 'dip' in infrared emission while the others' continuum emission decreases steadily at all wavelengths. We find that the former have an inner disk hole or gap at intermediate radii in the disk and we call these objects 'transitional disks' and 'pre-transitional disks' (PTDs), respectively. For the latter group, we can fit these SEDs with FD models and find that millimeter data are necessary to break the degeneracy between dust settling and disk mass. We suggest that the term 'transitional' only be applied to objects that display evidence for a radical change in the disk's radial structure. Using this definition, we find that TDs and PTDs tend to have lower mass accretion rates than FDs and that TDs have lower accretion rates than PTDs. These reduced accretion rates onto the star could be linked to forming planets. Future observations of TDs and PTDs will allow us to better quantify the signatures of planet formation in young disks.

Espaillat, C.; Andrews, S.; Qi, C.; Wilner, D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Ingleby, L.; Calvet, N. [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Hernandez, J. [Centro de Investigaciones de Astronomia (CIDA), Merida 5101-A (Venezuela, Bolivarian Republic of); Furlan, E. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States); D'Alessio, P. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, 58089 Morelia, Michoacan (Mexico); Muzerolle, J., E-mail: cespaillat@cfa.harvard.edu, E-mail: sandrews@cfa.harvard.edu, E-mail: cqi@cfa.harvard.edu, E-mail: dwilner@cfa.harvard.edu, E-mail: lingleby@umich.edu, E-mail: ncalvet@umich.edu, E-mail: jesush@cida.ve, E-mail: Elise.Furlan@jpl.nasa.gov, E-mail: p.dalessio@crya.unam.mx, E-mail: muzerol@stsci.edu [Space Telescope Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-03-10T23:59:59.000Z

107

An Objective Climatology of Carolina Coastal Fronts  

E-Print Network (OSTI)

This study describes a simple objective method to identify cases of coastal frontogenesis offshore of the Carolinas and to characterize the sensible weather associated with frontal passage at measurement sites near the coast. The identification method, based on surface hourly data from offshore and adjacent land stations, was applied to an 11-yr dataset (198494). A total of 379 coastal fronts was found, 70 of which eventually made landfall along the North Carolina coast; 112 that remained offshore, and 197 were termed diurnal since they remained offshore but disappeared during daylight hours. Results show that most coastal and offshore sites experience a wind shift of about 4070 and a warming of about 23C during the hour of frontal passage. Exceptions include sites near colder waters where the rates are markedly reduced and frontal passage is often less discernible. Excluding diurnal fronts, just over half the cases were associated with cold-air damming (CAD) during the cold season of 16 October15 April. Most of these winter cases linked with CAD were onshore fronts. During the warm season, most fronts were diurnal, but the association with CAD was still significant. To explore the synoptic-scale environment, composite maps for the cold season were generated for all three frontal subtypes from NCEPNCAR reanalysis data. Results show a strong surface anticyclone

K. Wyat Appel; Allen J. Riordan; Timothy A. Holley

2004-01-01T23:59:59.000Z

108

An Instability of Mature Cold Fronts  

Science Conference Proceedings (OSTI)

An instability of a cold front possessing a low-level warm-band precursor is examined within an f-plane, quasi- and semigeostrophic framework. The basic frontal state is taken to be two-dimensional and of uniform potential vorticity. Theoretical ...

Christoph Schr; Huw C. Davies

1990-04-01T23:59:59.000Z

109

Stability and Evolution of Supernova Fallback Disks  

E-Print Network (OSTI)

We show that thin accretion disks made of Carbon or Oxygen are subject to the same thermal ionization instability as Hydrogen and Helium disks. We argue that the instability applies to disks of any metal content. The relevance of the instability to supernova fallback disks probably means that their power-law evolution breaks down when they first become neutral. We construct simple analytical models for the viscous evolution of fallback disks to show that it is possible for these disks to become neutral when they are still young (ages of a few 10^3 to 10^4 years), compact in size (a few 10^9 cm to 10^11 cm) and generally accreting at sub-Eddington rates (Mdot ~ a few 10^14 - 10^18 g/s). Based on recent results on the nature of viscosity in the disks of close binaries, we argue that this time may also correspond to the end of the disk activity period. Indeed, in the absence of a significant source of viscosity in the neutral phase, the entire disk will likely turn to dust and become passive. We discuss various applications of the evolutionary model, including anomalous X-ray pulsars and young radio pulsars. Our analysis indicates that metal-rich fallback disks around newly-born neutron stars and black holes become neutral generally inside the tidal truncation radius (Roche limit) for planets, at \\~10^11 cm. Consequently, the efficiency of the planetary formation process in this context will mostly depend on the ability of the resulting disk of rocks to spread via collisions beyond the Roche limit. It appears easier for the merger product of a doubly degenerate binary, whether it is a massive white dwarf or a neutron star, to harbor planets because it can spread beyond the Roche limit before becoming neutral.[Abridged

Kristen Menou; Rosalba Perna; Lars Hernquist

2001-02-27T23:59:59.000Z

110

Microsoft Word - ffort-07.html  

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

8SK100655 Seating Capacity: 2 Adults Features: AMFM Stereo, Battery Thermal Management, Power Steering, Power Brakes, Front Disc Brakes & Anti-Lock Brakes DIMENSIONS Wheelbase:...

111

On reducing energy management delays in disks  

Science Conference Proceedings (OSTI)

Enterprise computing systems consume a large amount of energy, the cost of which contributes significantly to the operating budget. Consequently, dynamic energy management techniques are prevalent. Unfortunately, dynamic energy management for disks impose ... Keywords: Disk energy management, Peer memory sharing, Spin-up delay reduction

Krish K.R., Guanying Wang, Puranjoy Bhattacharjee, Ali R. Butt, Chris Gniady

2013-06-01T23:59:59.000Z

112

The Structure of Brown Dwarf Circumstellar Disks  

E-Print Network (OSTI)

We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. Under the assumption of vertical hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in excess of three times those derived for classical T Tauri (CTTS) disks. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find could have a significant impact on the optical and near-IR detectability of such systems. Our radiation transfer calculations show that such highly flared disks around brown dwarfs will result in a large fraction of obscured sources due to extinction of direct starlight by the disk over a wide range of sightlines. The obscured fraction for a 'typical' CTTS is less than 20%. We show that the obscured fraction for brown dwarfs may be double that for CTTS, but this depends on stellar and disk mass. We also comment on possible confusion in identifying brown dwarfs via color-magnitude diagrams: edge-on CTTS display similar colors and magnitudes as a face-on brown dwarf plus disk systems.

Christina Walker; Kenneth Wood; C. J. Lada; Thomas Robitaille; J. E. Bjorkman; Barbara Whitney

2004-03-11T23:59:59.000Z

113

Efficient maximal poisson-disk sampling  

Science Conference Proceedings (OSTI)

We solve the problem of generating a uniform Poisson-disk sampling that is both maximal and unbiased over bounded non-convex domains. To our knowledge this is the first provably correct algorithm with time and space dependent only on the ... Keywords: Poisson disk, blue noise, linear complexity, maximal, provable convergence, sampling

Mohamed S. Ebeida; Andrew A. Davidson; Anjul Patney; Patrick M. Knupp; Scott A. Mitchell; John D. Owens

2011-08-01T23:59:59.000Z

114

BACKPRESSURE TESTING OF ROTARY MICROFILTER DISKS  

Science Conference Proceedings (OSTI)

The Savannah River National Laboratory (SRNL), under the Department of Energy (DOE) Office of Environmental Management (EM), is modifying and testing the SpinTek{trademark} rotary microfilter (RMF) for radioactive filtration service in the Department of Energy (DOE) complex. The RMF has been shown to improve filtration throughput when compared to other conventional methods such as cross-flow filtration. A concern with the RMF was that backpressure, or reverse flow through the disk, would damage the filter membranes. Reverse flow might happen as a result of an inadvertent valve alignment during flushing. Testing was completed in the Engineering Development Laboratory (EDL) located in SRNL to study the physical effects of backpressure as well as to determine the maximum allowable back-pressure for RMF disks. The RMF disks tested at the EDL were manufactured by SpinTek{trademark} Filtration and used a Pall Corporation PMM050 filter membrane (0.5 micron nominal pore size) made from 316L stainless steel. Early versions of the RMF disks were made from synthetic materials that were incompatible with caustic solutions and radioactive service as well as being susceptible to delaminating when subjected to backpressure. Figure 1-1 shows the essential components of the RMF; 3 rotating disks and 3 stationary turbulence promoters (or shear elements) are shown. Figure 1-2 show the assembly view of a 25 disk RMF proposed for use at the Savannah River Site (SRS) and at the Hanford Facility. The purpose of the testing discussed in this report was to determine the allowable backpressure for RMF disks as well as study the physical effects of backpressure on RMF disks made with the Pall PMM050 membrane. This was accomplished by pressurizing the disks in the reverse flow direction (backpressure) until the test limit was reached or until membrane failure occurred. Backpressure was applied to the disks with air while submerged in deionized (DI) water. This method provided a visual representation of membrane integrity via bubble flow patterns. Membrane failure was defined as the inability to filter effectively at the nominal filter pore size. Effective filtration was determined by turbidity measurements of filtrate that was produced by applying forward-pressure to the disks while submerged in a representative simulant. The representative simulant was Tank 8F simulated sludge produced for SRNL by Optima Chemical. Two disks were tested. Disk 1 was tested primarily to determine approximate levels of backpressure where membrane failure occurred. These levels were then used to define the strategy for testing the Disk 2; a strategy that would better define and quantify the mode of failure.

Fowley, M.; Herman, D.

2011-04-14T23:59:59.000Z

115

Turbine inter-disk cavity cooling air compressor  

DOE Patents (OSTI)

The inter-disk cavity between turbine rotor disks is used to pressurize cooling air. A plurality of ridges extend radially outwardly over the face of the rotor disks. When the rotor disks are rotated, the ridges cause the inter-disk cavity to compress air coolant flowing through the inter-disk cavity en route to the rotor blades. The ridges eliminate the need for an external compressor to pressurize the air coolant.

Chupp, Raymond E. (Oviedo, FL); Little, David A. (Oviedo, FL)

1998-01-01T23:59:59.000Z

116

Turbine inter-disk cavity cooling air compressor  

DOE Patents (OSTI)

The inter-disk cavity between turbine rotor disks is used to pressurize cooling air. A plurality of ridges extend radially outwardly over the face of the rotor disks. When the rotor disks are rotated, the ridges cause the inter-disk cavity to compress air coolant flowing through the inter-disk cavity en route to the rotor blades. The ridges eliminate the need for an external compressor to pressurize the air coolant. 5 figs.

Chupp, R.E.; Little, D.A.

1998-01-06T23:59:59.000Z

117

Coordinated Garbage Collection for RAID Array of Solid State Disks  

... or it can query the disks to determine the best time to start a global collection . Advantages Solid state disks have no mechanical moving ...

118

Front Range Energy LLC | Open Energy Information  

Open Energy Info (EERE)

Energy LLC Energy LLC Jump to: navigation, search Logo: Front Range Energy LLC Name Front Range Energy LLC Address 31375 Great Western Dr Place Windsor, Colorado Zip 80550 Sector Biofuels Product Ethanol producer Website http://www.frontrangeenergy.co Coordinates 40.4605154°, -104.8565272° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":40.4605154,"lon":-104.8565272,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

119

Front contact solar cell with formed emitter  

SciTech Connect

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

Cousins, Peter John (Menlo Park, CA)

2012-07-17T23:59:59.000Z

120

Pentan isomers compound flame front structure  

DOE Green Energy (OSTI)

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

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

1995-08-13T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

A Conservative Front Tracking Method in N-Dimensions  

Science Conference Proceedings (OSTI)

We propose a fully conservative Front Tracking algorithm for systems of nonlinear conservation laws. The algorithm can be applied uniformly in one, two, three and N dimensions. Implementation details for this algorithm ... Keywords: Front tracking, conservation, discontinuity

Jinjie Liu; Hyun-Kyung Lim; James Glimm; Xiaolin Li

2007-05-01T23:59:59.000Z

122

The Vertical Structure of New England Coastal Fronts  

Science Conference Proceedings (OSTI)

Aircraft data from the New England Winter Storms Experiment (NEWSEX) are used to examine the vertical structure of four New England coastal fronts. The aircraft made multiple passes at varying elevations through the coastal fronts. The ...

John W. Nielsen; Peter P. Neilley

1990-09-01T23:59:59.000Z

123

Gust Front Characteristics as Detected by Doppler Radar  

Science Conference Proceedings (OSTI)

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use ...

Diana L. Klingle; David R. Smith; Marilyn M. Wolfson

1987-05-01T23:59:59.000Z

124

Progress with the SNS front-end systems  

E-Print Network (OSTI)

47317 PROGRESS WITH THE SNS FRONT-END SYSTEMS* R. Keller,**the FES Team, Status of the SNS Front-End Sys- tems, Paperof the LEBT Layout for SNS, Paper MOD19, Linac 2000,

2001-01-01T23:59:59.000Z

125

Mutual Intrusion of a Gravity Current and Density Front Formation  

Science Conference Proceedings (OSTI)

A two-dimensional prognostic model was employed to examine the mutual intrusion of a gravity current and the formation of a density front. The results indicated strong vertical motion near the front and, with Earth rotation included, a baroclinic ...

Dono-Ping Wang

1984-07-01T23:59:59.000Z

126

Thermally induced wave-front distortions in laser windows  

SciTech Connect

A simple analytical expression is given for wave-front distortions and birefringence due to heating in laser windows. (AIP)

Greninger, C.E.

1986-08-01T23:59:59.000Z

127

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

E-Print Network (OSTI)

based on eddy current brakes because they are inexpensive, friction- e-mail: andrewg@cim.mcgill.ca e-mail: champ@cim.mcgill.ca e-mail: hayward@cim.mcgill.ca free, capable of fast turn-on time, and linear

Hayward, Vincent

128

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

129

An improved front tracking method for the Euler equations  

Science Conference Proceedings (OSTI)

An improved front tracking method for hyperbolic conservation laws is presented. The improved method accurately resolves discontinuities as well as continuous phenomena. The method is based on an improved front interaction model for a physically more ... Keywords: 35L65, 35L67, 65M12, 76L05, 76N15, Euler equations, Front tracking, Gas dynamics, Hyperbolic conservation laws

J. A. S. Witteveen; B. Koren; P. G. Bakker

2007-06-01T23:59:59.000Z

130

The Resonant Interaction of a Tropical Cyclone and a Tropopause Front in a Barotropic Model. Part I: Zonally Oriented Front  

Science Conference Proceedings (OSTI)

The interaction of a tropical cyclone and a zonally aligned tropopause front is investigated in an idealized framework. A nondivergent barotropic model is used in which the front is represented by a vorticity step, giving a jetlike velocity ...

Leonhard Scheck; Sarah C. Jones; Martin Juckes

2011-03-01T23:59:59.000Z

131

THERMAL RADIATION FROM AN ACCRETION DISK  

E-Print Network (OSTI)

An effect of stimulated radiation processes on thermal radiation from an accretion disk is considered. The radial density waves triggering flare emission and producing quasiperiodic oscillations in radiation from an accretion disk are discussed. It is argued that the observational data suggest the existence of the weak laser sources in a twotemperature plasma of an accretion disk. It was shown earlier that thermal radio emission has a stimulated character and that this statement is probably valid for thermal blackbody radiation in others spectral ranges (Prigara 2003). According to this conception thermal radiation from non-uniform gas is produced by an ensemble of individual emitters.

unknown authors

2004-01-01T23:59:59.000Z

132

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

133

Injection Timing Effects on Brake Fuel Conversion Efficiency and Engine System's Respones  

E-Print Network (OSTI)

Societal concerns on combustion-based fuel consumption are ever-increasing. With respect to internal combustion engines, this translates to a need to increase brake fuel conversion efficiency (BFCE). Diesel engines are a relatively efficient internal combustion engine to consider for numerous applications, but associated actions to mitigate certain exhaust emissions have generally deteriorated engine efficiency. Conventionally, diesel engine emission control has centered on in-cylinder techniques. Although these continue to hold promise, the industry trend is presently favoring the use of after-treatment devices which create new opportunities to improve the diesel engine's brake fuel conversion efficiency. This study focuses on injection timing effects on the combustion processes, engine efficiency, and the engine system's responses. The engine in the study is a medium duty diesel engine (capable of meeting US EPA Tier III off road emission standards) equipped with common rail direct fuel injection, variable geometry turbo charging, and interfaced with a custom built engine controller. The study found that injection timing greatly affected BFCE by changing the combustion phasing. BFCE would increase up to a maximum then begin to decrease as phasing became less favorable. Combustion phasing would change from being mostly mixing controlled combustion to premixed combustion as injection timing would advance allowing more time for fuel to mix during the ignition delay. Combustion phasing, in turn, would influence many other engine parameters. As injection timing is advanced, in-cylinder temperatures and pressures amplify, and intake and exhaust manifold pressures deteriorate. Rate of heat release and rate of heat transfer increase when injection timing is advanced. Turbocharger speed falls with the advancing injection timing. Torque, however, rose to a maximum then fell off again even though engine speed and fueling rate were held constant between different injection timings. Interestingly, the coefficient of heat transfer changes from a two peak curve to a smooth one peak curve as the injection timing is advanced further. The major conclusion of the study is that injection advance both positively and negatively influences the diesel engine's response which contributes to the brake fuel conversion efficiency.

McLean, James Elliott

2011-08-01T23:59:59.000Z

134

Stochastic oscillations of general relativistic disks  

E-Print Network (OSTI)

We analyze the general relativistic oscillations of thin accretion disks around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modeled via a friction force, and a random force, respectively. The general equations describing the stochastically perturbed disks are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force we show that the dynamics of the stochastically perturbed disks can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the disks in the Schwarzschild and Kerr geometries are considered in detail, and they are analyzed by numerically integrating the corresponding Langevin equations. The vertical displacement...

Harko, Tiberiu

2012-01-01T23:59:59.000Z

135

Gas Phase diagnostics of Protoplanetary disk extension  

E-Print Network (OSTI)

We investigate the potential of using ratios of fine structure and near-infrared forbidden line transitions of atomic carbon to diagnose protoplanetary disk extension. Using results from 2D photoionisation and radiative transfer modeling of a realistic protoplanetary disk structure irradiated by X-rays from a T Tauri star, we obtain theoretical emission maps from which we construct radial distributions of the strongest emission lines produced in the disk. We show that ratios of fine structure to near-infrared forbidden line emission of atomic carbon are especially promising to constrain the minimum size of gaseous protoplanetary disks. While theoretically viable, the method presents a number of observational difficulties that are also discussed here.

B. Ercolano; J. J. Drake; C. J. Clarke

2008-11-21T23:59:59.000Z

136

Hydraulic/Shock-Jumps in Protoplanetary Disks  

E-Print Network (OSTI)

In this paper, we describe the nonlinear outcome of spiral shocks in protoplanetary disks. Spiral shocks, for most protoplanetary disk conditions, create a loss of vertical force balance in the post-shock region and result in rapid expansion of the gas perpendicular to the disk midplane. This expansion has characteristics similar to hydraulic jumps, which occur in incompressible fluids. We present a theory to describe the behavior of these hybrids between shocks and hydraulic jumps (shock bores) and then compare the theory to three-dimensional hydrodynamics simulations. We discuss the fully three-dimensional shock structures that shock bores produce and discuss possible consequences for disk mixing, turbulence, and evolution of solids.

A. C. Boley; R. H. Durisen

2005-10-11T23:59:59.000Z

137

The Kuiper Belt and Other Debris Disks  

E-Print Network (OSTI)

We discuss the current knowledge of the Solar system, focusing on bodies in the outer regions, on the information they provide concerning Solar system formation, and on the possible relationships that may exist between our system and the debris disks of other stars. Beyond the domains of the Terrestrial and giant planets, the comets in the Kuiper belt and the Oort cloud preserve some of our most pristine materials. The Kuiper belt, in particular, is a collisional dust source and a scientific bridge to the dusty "debris disks" observed around many nearby main-sequence stars. Study of the Solar system provides a level of detail that we cannot discern in the distant disks while observations of the disks may help to set the Solar system in proper context.

Jewitt, David; Lacerda, Pedro

2008-01-01T23:59:59.000Z

138

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.

Woods, Paul M

2008-01-01T23:59:59.000Z

139

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

140

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

E-Print Network (OSTI)

7.2 Heat conduction between a slider and a disk . . . . . .compared to heat conduction . . . . . 7.4.1 Importance ofof the currently used heat conduction model . . . . . . . .

Liu, Nan

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

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

E-Print Network (OSTI)

The nature of foot movement time (MT) in an actual braking maneuver and in a stationary vehicle was investigated regarding the effects of age and gender of the driver and nature of the stimulus to which the driver was responding. ANOVAs showed that the nature of the stimulus was not a significant factor in length of MT, but distance between pedals and age-gender levels were found to have significant effects. For the actual braking maneuver, gender and the gender-by-age interaction were significant; in the stationary vehicle portion of the study, they were not. Mean foot MT for both genders over all conditions were 0.28 seconds for women and 0.22 seconds for men. For older drivers, over all conditions, the mean foot MT was 0.25 seconds, and, for the younger drivers, 0.24 seconds. Linear regressions revealed high intra-subject variation in MT, which was corroborated by comparing with data from other parts of the study. Poor r2 values for fitting the data to Fitts' Law and to a modification of Fitts' Law were attributed to this high intra-subject variation and to obtaining data from only two different movement amplitudes. It was found that drivers' foot MTs tended to converge to a common value when controlling the vehicle at 88 km/hr (55 mph) as opposed to sitting in the driver's seat while the vehicle was stationary; mean foot MT for each subject group decreased, and differences between genders and age groups significantly diminished while the car was in motion.

Berman, Andrea Helene

1994-01-01T23:59:59.000Z

142

Disk evaporation in a planetary nebula  

E-Print Network (OSTI)

We study the Galactic bulge planetary nebula M 2-29 (for which a 3-year eclipse event of the central star has been attributed to a dust disk) using HST imaging and VLT spectroscopy, both long-slit and integral field. The central cavity of M 2-29 is filled with a decreasing, slow wind. An inner high density core is detected, with radius less than 250 AU, interpreted as a rotating gas/dust disk with a bipolar disk wind. The evaporating disk is argued to be the source of the slow wind. The central star is a source of a very fast wind (1000 km/s). An outer, partial ring is seen in the equatorial plane, expanding at 12 km/s. The azimuthal asymmetry is attributed to mass-loss modulation by an eccentric binary. M 2-29 presents a crucial point in disk evolution, where ionization causes the gas to be lost, leaving a low-mass dust disk behind.

Gesicki, K; Szyszka, C; Hajduk, M; Lagadec, E; Ramirez, L Guzman

2010-01-01T23:59:59.000Z

143

Spatially hybrid computations for streamer discharges with generic features of pulled fronts: I. Planar fronts  

Science Conference Proceedings (OSTI)

Streamers are the first stage of sparks and lightning; they grow due to a strongly enhanced electric field at their tips; this field is created by a thin curved space charge layer. These multiple scales are already challenging when the electrons are ... Keywords: 52.65.Kj, 52.80.Pi, Hybrid model, Large deviations, Pulled fronts, Streamer discharge

Chao Li; Ute Ebert; Willem Hundsdorfer

2010-01-01T23:59:59.000Z

144

EVOLVING GRAVITATIONALLY UNSTABLE DISKS OVER COSMIC TIME: IMPLICATIONS FOR THICK DISK FORMATION  

Science Conference Proceedings (OSTI)

Observations of disk galaxies at z {approx} 2 have demonstrated that turbulence driven by gravitational instability can dominate the energetics of the disk. We present a one-dimensional simulation code, which we have made publicly available, that economically evolves these galaxies from z {approx} 2 to z {approx} 0 on a single CPU in a matter of minutes, tracking column density, metallicity, and velocity dispersions of gaseous and multiple stellar components. We include an H{sub 2}-regulated star formation law and the effects of stellar heating by transient spiral structure. We use this code to demonstrate a possible explanation for the existence of a thin and thick disk stellar population and the age-velocity-dispersion correlation of stars in the solar neighborhood: the high velocity dispersion of gas in disks at z {approx} 2 decreases along with the cosmological accretion rate, while at lower redshift the dynamically colder gas forms the low velocity dispersion stars of the thin disk.

Forbes, John; Krumholz, Mark [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Burkert, Andreas, E-mail: jforbes@ucolick.org, E-mail: krumholz@ucolick.org, E-mail: burkert@usm.uni-muenchen.de [University Observatory Munich (USM), Scheinerstrasse 1, 81679 Munich (Germany)

2012-07-20T23:59:59.000Z

145

Rayleigh-Taylor Instability of Ionization Front around Black Holes  

E-Print Network (OSTI)

We examine the role of ionizing radiation emitted from black holes (BHs) in suppressing the growth of the Rayleigh-Taylor instability (RTI) across the ionization front (I-front) that forms when the gas fueling the BH is neutral. We use radiation-hydrodynamic simulations to show that the RTI is suppressed for non-accelerating fronts on all scales resolved in our simulations. A necessary condition for the stability of the I-front is that the radius of the Str\\"omgren sphere is larger than the Bondi radius. When this condition is violated the I-front collapses producing an accretion luminosity burst. Transient growth of the RTI occurs only during the accretion burst when the effective acceleration in the frame of reference of the I-front increases significantly due to the rapid expansion of the Str\\"omgren sphere.

Park, KwangHo; Di Matteo, Tiziana; Reynolds, Christopher S

2013-01-01T23:59:59.000Z

146

Stochastic oscillations of general relativistic disks  

E-Print Network (OSTI)

We analyze the general relativistic oscillations of thin accretion disks around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modeled via a friction force, and a random force, respectively. The general equations describing the stochastically perturbed disks are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force we show that the dynamics of the stochastically perturbed disks can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the disks in the Schwarzschild and Kerr geometries are considered in detail, and they are analyzed by numerically integrating the corresponding Langevin equations. The vertical displacements, velocities and luminosities of the stochastically perturbed disks are explicitly obtained for both the Schwarzschild and the Kerr cases.

Tiberiu Harko; Gabriela Mocanu

2012-01-11T23:59:59.000Z

147

Front Tracking Model of Simultaneous Melting and Solidification ...  

Science Conference Proceedings (OSTI)

This results in dynamic melting and solidification throughout the weld pool, which can be modelled using the authors' Front Tracking algorithm. Melting is...

148

Antitruncated Stellar Disks via Minor Mergers  

E-Print Network (OSTI)

We use hydrodynamic simulations of minor mergers of galaxies to investigate the nature of surface brightness excesses at large radii observed in some spiral galaxies: antitruncated stellar disks. We find that this process can produce the antitruncation via two competing effects: (1) merger-driven gas inflows that concentrate mass in the center of the primary galaxy and contract its inner density profile; and (2) angular momentum transferred outwards by the interaction, causing the outer disk to expand. In our experiments, this requires both a significant supply of gas in the primary disk, and that the encounter be prograde with moderate orbital angular momentum. The stellar surface mass density profiles of our remnants both qualitatively and quantitatively resemble the broken exponentials observed in local face--on spirals that display antitruncations. Moreover, the observed trend towards more frequent antitruncation relative to classical truncation in earlier Hubble types is consistent with a merger-driven scenario.

Joshua D. Younger; T. J. Cox; Anil C. Seth; Lars Hernquist

2007-07-30T23:59:59.000Z

149

Grain Retention and Formation of Planetesimals near the Snow Line in MRI-driven Turbulent Protoplanetary Disks  

E-Print Network (OSTI)

The first challenge in the formation of both terrestrial planets and the cores of gas giants is the retention of grains in protoplanetary disks. In most regions of these disks, gas attains sub-Keplerian speeds as a consequence of a negative pressure gradient. Hydrodynamic drag leads to orbital decay and depletion of the solid material in the disk, with characteristic timescales as short as only a few hundred years for meter-sized objects at 1 AU. In this paper, we suggest a particle retention mechanism which promotes the accumulation of grains and the formation of planetesimals near the water sublimation front or ``snow line.'' This model is based on the assumption that, in the regions most interesting for planet formation, the viscous evolution of the disk is due to turbulence driven by the magneto-rotational instability (MRI) in the surface layers of the disk. The depth to which MRI effectively generates turbulence is a strong function of the grain size and abundance. A sharp increase in the grain-to-gas density ratio across the snow line reduces the column depth of the active layer. As the disk evolves towards a quasi-steady-state, this change in the active layer creates a local maximum in radial distribution of the gas surface density and pressure, causing the gas to rotate at super-Keplerian speed and halting the inward migration of grains. This senario presents a robust process for grain retention which may aid in the formation of proto-gas-giant cores preferentially near the snow line.

Katherine A. Kretke; D. N. C. Lin

2007-06-08T23:59:59.000Z

150

Dynamics of Line-Driven Disk Winds in Active Galactic Nuclei II: Effects of Disk Radiation  

E-Print Network (OSTI)

We explore consequences of a radiation driven disk wind model for mass outflows from active galactic nuclei (AGN). We performed axisymmetric time-dependent hydrodynamic calculations using the same computational technique as Proga, Stone and Kallman (2000). We test the robustness of radiation launching and acceleration of the wind for relatively unfavorable conditions. In particular, we take into account the central engine radiation as a source of ionizing photons but neglect its contribution to the radiation force. Additionally, we account for the attenuation of the X-ray radiation by computing the X-ray optical depth in the radial direction assuming that only electron scattering contributes to the opacity. Our new simulations confirm the main result from our previous work: the disk atmosphere can 'shield' itself from external X-rays so that the local disk radiation can launch gas off the disk photosphere. We also find that the local disk force suffices to accelerate the disk wind to high velocities in the radial direction. This is true provided the wind does not change significantly the geometry of the disk radiation by continuum scattering and absorption processes; we discuss plausibility of this requirement. Synthetic profiles of a typical resonance ultraviolet line predicted by our models are consistent with observations of broad absorption line (BAL) QSOs.

D. Proga; T. R. Kallman

2004-08-16T23:59:59.000Z

151

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

SciTech Connect

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

Cousins, Peter John

2012-06-26T23:59:59.000Z

152

Gravitational influences on magnetic field structure in accretion disks  

E-Print Network (OSTI)

Black holes and compact objects are often surrounded by structures known as accretion disks which consist of ionized plasma. Due to the immense forces present in the disk, interesting and complex magnetic field structures ...

Schneck, Kristiana E. (Kristiana Elizabeth)

2010-01-01T23:59:59.000Z

153

Trading capacity for performance in a disk array  

Science Conference Proceedings (OSTI)

A variety of performance-enhancing techniques, such as striping, mirroring, and rotational data replication, exist in the disk array literature. Given a fixed budget of disks, one must intelligently choose what combination of these techniques to employ. ...

Xiang Yu; Benjamin Gum; Yuqun Chen; Randolph Y. Wang; Kai Li; Arvind Krishnamurthy; Thomas E. Anderson

2000-10-01T23:59:59.000Z

154

On the existence of high Lewis number combustion fronts  

Science Conference Proceedings (OSTI)

We study a mathematical model for high Lewis number combustion processes with the reaction rate of the form of an Arrhenius law with or without an ignition cut-off. An efficient method for the proof of the existence and uniqueness of combustion fronts ... Keywords: Combustion fronts, Geometric singular perturbation theory, Ignition cut-off

Anna Ghazaryan; Christopher Jones

2012-02-01T23:59:59.000Z

155

FLUCTUATIONS OF THE FRONT IN A STOCHASTIC COMBUSTION MODEL  

E-Print Network (OSTI)

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

Quastel, Jeremy

156

Combustion fronts in porous media with two layers Steve Schecter  

E-Print Network (OSTI)

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

Schecter, Stephen

157

Wind-Driven Motion near a Shelf-Slope Front  

Science Conference Proceedings (OSTI)

A two-dimensional, two-layered frontal system is used to examine the wind-driven motion near a shelf-slope front. In the linear regime, the along-frontal current is characterized by barotropic perturbations. The front is dynamically passive and ...

Hsien Wang Ou

1984-06-01T23:59:59.000Z

158

Investigation of the Brazil Current front variability from altimeter data  

E-Print Network (OSTI)

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

159

Topographic Effects on a Wintertime Cold Front in Taiwan  

Science Conference Proceedings (OSTI)

This paper describes an observational and numerical study of an intense wintertime cold front that occurred in Taiwan on 8 January 1996. The front was associated with rope clouds at the leading edge, and a broad area of stratiform clouds behind. ...

Fang-Ching Chien; Ying-Hwa Kuo

2006-11-01T23:59:59.000Z

160

Plant Guide to Turbine Disk Rim Inspection  

Science Conference Proceedings (OSTI)

Steam turbine disk rims are one of the most highly stressed areas of the rotor. Periodic inspection of the rims provides information on the operability of the rotor, including the identification of conditions that could result in catastrophic failure of the rotor.

2006-12-18T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

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

162

An hydrodynamic shear instability in stratified disks  

E-Print Network (OSTI)

We discuss the possibility that astrophysical accretion disks are dynamically unstable to non-axisymmetric disturbances with characteristic scales much smaller than the vertical scale height. The instability is studied using three methods: one based on the energy integral, which allows the determination of a sufficient condition of stability, one using a WKB approach, which allows the determination of the necessary and sufficient condition for instability and a last one by numerical solution. This linear instability occurs in any inviscid stably stratified differential rotating fluid for rigid, stress-free or periodic boundary conditions, provided the angular velocity $\\Omega$ decreases outwards with radius $r$. At not too small stratification, its growth rate is a fraction of $\\Omega$. The influence of viscous dissipation and thermal diffusivity on the instability is studied numerically, with emphasis on the case when $d \\ln \\Omega / d \\ln r =-3/2$ (Keplerian case). Strong stratification and large diffusivity are found to have a stabilizing effect. The corresponding critical stratification and Reynolds number for the onset of the instability in a typical disk are derived. We propose that the spontaneous generation of these linear modes is the source of turbulence in disks, especially in weakly ionized disks.

B. Dubrulle; L. Mari; Ch. Normand; D. Richard; F. Hersant; J. -P. Zahn

2004-10-08T23:59:59.000Z

163

Protoplanetary Migration and Creation of Scattered Planetismal Disks  

E-Print Network (OSTI)

The relationship between protoplanet migration and the formation of the Kuiper Belt (planetesimal disk scattering) is examined.

Bruce D. Lindsay; Truell W. Hyde

2004-01-28T23:59:59.000Z

164

Model Spectral Energy Distributions of Circumstellar Debris Disks I. Analytic Disk Density Distributions  

E-Print Network (OSTI)

We present results of a study aimed at deriving fundamental properties of circumstellar debris disks from observed infrared to submillimeter spectral energy distributions. This investigation is motivated by increasing telescope/detector sensitivity, in particular the expected availability of the Space Infrared Telescope Facility (SIRTF) followed by the Stratospheric Observatory for Infrared Astronomy (SOFIA), which will enable detailed studies with large source samples of late stage circumstellar disk and planetary system evolution. We base our study on an analytic model of the disk density distribution and geometry, taking into account existing constraints from observations and results of theoretical investigations of debris disks. We also outline the effects of the most profound characteristics of circumstellar dust including the grain size distribution and dust chemical composition. In particular we find that an increasing iron content in silicates mainly causes an increase of the dust absorption effiency and thus increases the dust reemission continuum. Furthermore, the influence of the sp 2 /sp 3 hybridization

Sebastian Wolf; Lynne A. Hillenbr

2003-01-01T23:59:59.000Z

165

Spectral Energy Distributions of Circumstellar Debris Disks I. Analytic Disk Density Distributions  

E-Print Network (OSTI)

We present results of a study aimed at deriving fundamental properties of circumstellar debris disks from observed infrared to submillimeter spectral energy distributions. This investigation is motivated by increasing telescope/detector sensitivity, in particular the expected availability of the Space Infrared Telescope Facility (SIRTF) followed by the Stratospheric Observatory for Infrared Astronomy (SOFIA), which will enable detailed studies with large source samples of late stage circumstellar disk and planetary system evolution. We base our study on an analytic model of the disk density distribution and geometry, taking into account existing constraints from observations and results of theoretical investigations of debris disks. We also outline the effects of the most profound characteristics of circumstellar dust including the grain size distribution and dust chemical composition.

Sebastian Wolf; Lynne Hillenbrand

2003-06-23T23:59:59.000Z

166

Front lighted optical tooling method and apparatus  

DOE Patents (OSTI)

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

Stone, William J. (Kansas City, MO)

1985-06-18T23:59:59.000Z

167

Using Hard Disks For Digital Preservation David S. H. Rosenthal  

E-Print Network (OSTI)

Using Hard Disks For Digital Preservation David S. H. Rosenthal Stanford University Libraries the hard disk holding the copy used for access as a preser- vation medium; the cooperative damage detection system as an example of the techniques needed to use hard disks as a medium for long- term preservation

Baker, Mary G.

168

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

169

Microsoft Word - chvs10.html  

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

7 Chevrolet S-10 Electric 7 Chevrolet S-10 Electric VEHICLE SPECIFICATIONS PURPOSE-BUILT VEHICLE Base Vehicle: 1997 Chevrolet S-10 VIN: 1GCDE14H4V80003EX Seatbelt Positions: Three Standard Features: Heat Pump Climate Control System Auxillary Diesel Fuel Fired Heater (Only operates Below 40 F) Cruise Control Tilt Steering Wheel Front Wheel Drive Power Steering Power Brakes Anti-Lock Brakes Front Disk Brakes Regenerative Braking Drivers Side Air Bags AM/FM Stereo Radio Half-Bed Tonneau Cover BATTERY Manufacturer: Delphi Energy Type: Valve Regulated Lead Acid Number of Modules: 26 Weight of Module: 19 kg Weight of Pack(s): 575 kg Pack Locations: Underbody Nominal Module Voltage: 12 V Nominal System Voltage: 312 V Nominal Capacity (C/2): 48 Ah WEIGHTS Design Curb Weight: 4300 lbs

170

Light-Front Holographic QCD and the Confinement Potential  

E-Print Network (OSTI)

Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time \\tau = t+z/c, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian predict the hadronic mass spectrum, and the eigensolutions provide the light-front wavefunctions describing hadron structure. The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. The potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. The holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrodinger equation. It also gives a precise relation between the bound-state amplitudes in the fifth dimension z of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The predictions include a zero-mass pion in the chiral limit, and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. The light-front AdS/QCD holographic approach thus gives a frame-independent representation of color-confining dynamics and the excitation spectra of light-quark hadrons in terms of a single mass parameter. We also discuss the implications of the underlying conformal template of QCD for renormalization scale-setting and the implications of light-front quantization for the value of the cosmological constant.

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

2013-08-23T23:59:59.000Z

171

Helicase activity on DNA as a propagating front  

E-Print Network (OSTI)

We develop a propagating front analysis, in terms of a local probability of zipping, for the helicase activity of opening up a double stranded DNA (dsDNA). In a fixed-distance ensemble (conjugate to the fixed-force ensemble) the front separates the zipped and unzipped phases of a dsDNA and a drive acts locally around the front. Bounds from variational analysis and numerical estimates for the speed of a helicase are obtained. Different types of helicase behaviours can be distinguished by the nature of the drive.

Somendra M. Bhattacharjee

2003-07-16T23:59:59.000Z

172

Light front approach to correlations in hot quark matter  

E-Print Network (OSTI)

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

S. Strauss; M. Beyer; S. Mattiello

2005-11-01T23:59:59.000Z

173

METALLICITY GRADIENTS OF THICK DISK DWARF STARS  

Science Conference Proceedings (OSTI)

We examine the metallicity distribution of the Galactic thick disk using F, G, and K dwarf stars selected from the Sloan Digital Sky Survey, Data Release 8. Using the large sample of dwarf stars with proper motions and spectroscopically determined stellar parameters, metallicity gradients in the radial direction for various heights above the Galactic plane and in the vertical direction for various radial distances from the Galaxy center have been found. In particular, we find a vertical metallicity gradient of -0.113 {+-} 0.010 (-0.125 {+-} 0.008) dex kpc{sup -1} using an isochrone (photometric) distance determination in the range 1 kpc solar neighborhood. Metallicity gradients in the thin and thick disks are important probes into possible formation scenarios for our Galaxy and a consistent picture is beginning to emerge from results using large spectroscopic surveys, such as the ones presented here.

Carrell, Kenneth; Chen Yuqin; Zhao Gang, E-mail: carrell@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2012-12-01T23:59:59.000Z

174

Terabyte IDE RAID-5 Disk Arrays  

Science Conference Proceedings (OSTI)

High energy physics experiments are currently recording large amounts of data and in a few years will be recording prodigious quantities of data. New methods must be developed to handle this data and make analysis at universities possible. We examine some techniques that exploit recent developments in commodity hardware. We report on tests of redundant arrays of integrated drive electronics (IDE) disk drives for use in offline high energy physics data analysis. IDE redundant array of inexpensive disks (RAID) prices now are less than the cost per terabyte of million-dollar tape robots! The arrays can be scaled to sizes affordable to institutions without robots and used when fast random access at low cost is important.

David A. Sanders et al.

2003-09-30T23:59:59.000Z

175

A preliminary assessment of asbestos awareness and control measures in brake and clutch repair services in Knoxville and Knox County, Tennessee  

SciTech Connect

The pending OSHA standard revision proposed in 1990 to lower the asbestos Permissible Exposure Limit (PEL) and to mandate effective asbestos control measures (ACM) in brake and clutch assembly work may have a profound effect on industries involved in such operations. Health protection of workers will be improved and costs of improved control methods and training will increase. Considering these facts, this preliminary study was designed to assess the level of worker and management awareness of asbestos hazards associated with brake and clutch repair and to determine what ACM had been implemented by businesses in Knoxville and Knox County, Tennessee. The study, in a metropolitan area of approximately 336,000 people, revealed eight different categories of businesses conducting brake and clutch repair work with an estimated 363 potentially exposed employees. Results of the study suggest that managers and employees of the 80 businesses studied were in need of asbestos hazard awareness training and more adequate asbestos control measures.

Phillips, C.C. (Oak Ridge National Lab., TN (United States)); Hamilton, C.B.

1994-04-01T23:59:59.000Z

176

The chemistry of multiply deuterated molecules in protoplanetary disks. I. The outer disk  

E-Print Network (OSTI)

We present new models of the deuterium chemistry in protoplanetary disks, including, for the first time, multiply deuterated species. We use these models to explore whether observations in combination with models can give us clues as to which desorption processes occur in disks. We find, in common with other authors, that photodesorption can allow strongly bound molecules such as HDO to exist in the gas phase in a layer above the midplane. Models including this process give the best agreement with the observations. In the midplane, cosmic ray heating can desorb weakly bound molecules such as CO and N$_2$. We find the observations suggest that N$_2$ is gaseous in this region, but that CO must be retained on the grains to account for the observed DCO$^+$/HCO$^+$. This could be achieved by CO having a higher binding energy than N$_2$ (as may be the case when these molecules are accreted onto water ice) or by a smaller cosmic ray desorption rate for CO than assumed here, as suggested by recent theoretical work. For gaseous molecules the calculated deuteration can be greatly changed by chemical processing in the disk from the input molecular cloud values. On the grains singly deuterated species tend to retain the D/H ratio set in the molecular cloud, whereas multiply deuterated species are more affected by the disk chemistry. Consequently the D/H ratios observed in comets may be partly set in the parent cloud and partly in the disk, depending on the molecule.

K. Willacy

2007-01-16T23:59:59.000Z

177

Cold Fronts Research Programme: Progress, Future Plans, and Research Directions  

Science Conference Proceedings (OSTI)

Following the analysis of data collected during Phases land II of the Cold Fronts Research Programme (CFRP) a conceptual model for the Australian summertime cool change has been proposed. The model provides a focus and a framework for the ...

B. F. Ryan; J. R. Garratt; K. J. Wilson; R. K. Smith

1985-09-01T23:59:59.000Z

178

Diabatically Driven Discrete Propagation of Surface Fronts: A Numerical Analysis  

Science Conference Proceedings (OSTI)

Discrete frontal propagation has been identified as a process whereby a surface front discontinuously moves forward, without evidence of frontal passage across a mesoscale region. Numerical simulations are employed to examine the upper-level ...

George H. Bryan; J. Michael Fritsch

2000-07-01T23:59:59.000Z

179

A Marker Chain Front Tracking Method for Modelling Meniscus ...  

Science Conference Proceedings (OSTI)

Feb 1, 2002 ... A Marker Chain Front Tracking Method for Modelling Meniscus Dynamics in the Al Ingot Casting Process by F. Iversen, J.A. Bakken and S.T....

180

Misocyclone Characteristics along Florida Gust Fronts during CaPE  

Science Conference Proceedings (OSTI)

Multiple-Doppler radar and rawinsonde data are used to examine misocyclone characteristics along gust fronts observed during the Convection and Precipitation/Electrification (CaPE) project in Florida. The objective of this study is to investigate ...

Katja Friedrich; David E. Kingsmill; Carl R. Young

2005-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility...  

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

DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in Idaho Uranium Enrichment Project to Create Over 1,000 Jobs in Idaho Washington, DC As part of a broad...

182

Observations of Seven Atmospheric Density Current Fronts in Dixon, California  

Science Conference Proceedings (OSTI)

Seven atmospheric density current fronts are identified in sequences of ground-based, scanning aerosol backscatter lidar images and in situ micrometeorological time series data that were collected simultaneously and nearly continuously between 15 ...

Shane D. Mayor

2011-05-01T23:59:59.000Z

183

Cold Fronts Research: The Australian Summertime Cool Change  

Science Conference Proceedings (OSTI)

Much of the significant weather of southeastern Australia is associated with the passage of cold fronts. In summer, such passages are often accompanied by rapid and extreme temperature fails, as hot continental northerly winds are replaced with ...

R. K. Smith; B. F. Ryan; A. J. Troup; K. J. Wilson

1982-09-01T23:59:59.000Z

184

Meteorological Tower Measurements of a Surface Cold Front  

Science Conference Proceedings (OSTI)

measurements from the Boulder Atmospheric Observatory meteorological research tower are used to describe the structure and physical processes of a strong surface cold front. Analysis reveals that the horizontal gradients in temperature and wind ...

M. A. Shapiro

1984-08-01T23:59:59.000Z

185

Tracking Gravity Waves in Baroclinic Jet-Front Systems  

Science Conference Proceedings (OSTI)

Using a two-dimensional Fourier decomposition and a four-dimensional ray-tracing technique, the propagating characteristics and source mechanisms of mesoscale gravity waves simulated in idealized baroclinic jet-front systems are investigated. The ...

Yonghui Lin; Fuqing Zhang

2008-07-01T23:59:59.000Z

186

Internal-Inertial Waves in a Surgasso Sea Front  

Science Conference Proceedings (OSTI)

This work examines the presence of internal-inertial waves in a front in the North Atlantic subtropical convergence zone. Results of Doppler shear profiler and towed thermistor chain surveys are displayed to document the position and magnitude of ...

Richard P. Mied; Colin Y. Shen; Clifford L. Trump; Gloria J. Lindemann

1986-11-01T23:59:59.000Z

187

Observations of Near-Inertial Waves in a Front  

Science Conference Proceedings (OSTI)

Near-inertial with horizontal scales O(10 km) dominate profiles of velocity finestructure collected in the North Pacific Subtropical Front during January 1980. Considerable spatial variability is observed. Two features in particular contain most ...

Eric Kunze; Thomas B. Sanford

1984-03-01T23:59:59.000Z

188

Advanced integrated safeguards using front-end-triggering devices  

SciTech Connect

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

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

1995-12-01T23:59:59.000Z

189

The Circulation Dynamics and Thermodynamics of Upper Ocean Density Fronts  

Science Conference Proceedings (OSTI)

This paper extends a previous hydrodynamic circulation model of established, persistent upper ocean density fronts by including a thermodynamic or buoyancy equation in the integral treatment. An analysis is also conducted of the variables related ...

Richard W. Garvine

1980-12-01T23:59:59.000Z

190

Generation and Separation of Mesoscale Eddies from Surface Ocean Fronts  

Science Conference Proceedings (OSTI)

This study is motivated by Arctic Ocean observations of sub-mixed layer eddies found at large distances from their assumed formation region of a surface ocean front. We explore eddy formation through high resolution numerical simulations of ...

Georgy E. Manucharyan; Mary-Louise Timmermans

191

Vertical Velocities in a Thunderstorm Gust Front and Outflow  

Science Conference Proceedings (OSTI)

Continuous vertically pointing measurements of a thunderstorm outflow, including its gust front, were obtained with a Doppler radar near New Salem, North Dakota. The measurements provide a high-resolution depiction of the vertical structure of ...

Brooks E. Martner

1997-05-01T23:59:59.000Z

192

Results of the SNS front end commissioning at Berkeley Lab  

E-Print Network (OSTI)

RESULTS OF THE SNS FRONT END COMMISSIONING AT BERKELEY LAB *USA A. Aleksandrov for the SNS Accelerator Physics Group andT. Shea for the SNS Beam Diagnostics Collaboration Oak Ridge

2002-01-01T23:59:59.000Z

193

The Behavior of Dry Cold Fronts Traveling Along a Coastline  

Science Conference Proceedings (OSTI)

Observations of intense, dry summertime cold fronts in southeast Australia provide evidence for frontal deformation (cold air surges) in the coastal region well to the west of the main mountain range. This compares with the severe deformation ...

J. R. Garratt; P. A. C. Howells; E. Kowalczyk

1989-06-01T23:59:59.000Z

194

A Geostrophic Adjustment Model of a Tidal Mixing Front  

Science Conference Proceedings (OSTI)

This paper presents a model of a tidal mixing front as occurring between well mixed and (seasonally) stratified water in tidally energetic areas in continental shelf seas. The model examines the geostrophic adjustment of a stratified two-layer ...

G. J. F. van Heijst

1985-09-01T23:59:59.000Z

195

Town of Front Royal, Virginia (Utility Company) | Open Energy Information  

Open Energy Info (EERE)

Town of Front Royal, Virginia (Utility Company) Town of Front Royal, Virginia (Utility Company) Jump to: navigation, search Name Town of Front Royal Place Virginia Utility Id 6803 Utility Location Yes Ownership M NERC Location SERC Activity Distribution Yes References EIA Form EIA-861 Final Data File for 2010 - File1_a[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Utility Rate Schedules Grid-background.png Commercial Commercial Dusk to Dawn Light poles Commercial Residential Residential Average Rates Residential: $0.0928/kWh Commercial: $0.0796/kWh References ↑ "EIA Form EIA-861 Final Data File for 2010 - File1_a" Retrieved from "http://en.openei.org/w/index.php?title=Town_of_Front_Royal,_Virginia_(Utility_Company)&oldid=411737"

196

Formation and Maintenance of Shelfbreak Fronts in an Unstratified Flow  

Science Conference Proceedings (OSTI)

A depth-averaged model with no density variations was used by Chapman to describe the formation of a passive tracer front at a shelfbreak. The relevance of this frontogenesis mechanism to cases that allow vertical variations is examined by ...

Glen Gawarkiewicz; David C. Chapman

1991-08-01T23:59:59.000Z

197

Influence of Mesoscale Orography on Idealized Cold Fronts  

Science Conference Proceedings (OSTI)

A three-dimensional numerical model based on the inviscid and adiabatic primitive equations in the Boussinesq approximation is used to investigate the retardation of cold fronts by high two and three-dimensional mountains, approximately the same ...

U. Schumann

1987-12-01T23:59:59.000Z

198

Parametric Study of Front-End Nuclear Fuel Cycle Costs  

Science Conference Proceedings (OSTI)

This study provides an overview of front-end fuel cost components for nuclear plants, specifically uranium concentrates, uranium conversion services, uranium enrichment services, and nuclear fuel fabrication services. A parametric analysis of light-water reactor (LWR) fuel cycle costs is also included in order to quantify the impacts that result from changes in the cost of one or more front-end components on overall fuel cycle costs.

2009-02-20T23:59:59.000Z

199

Front Range Forest Health Partnership Phase 1 feasibility study  

DOE Green Energy (OSTI)

The Front Range Forest Health Partnership is an alliance of individuals, citizen groups, federal, state, private, and nonprofit organizations that formed to promote forest health restoration and reduce fire risks on Colorado's Front Range. The partnership promotes selective thinning to restore forest health and supports economically feasible end uses for wood waste materials. The Phase I study was initiated to determine the environmental and economic feasibility of using wood wastes from forested and urban areas for the production of fuel-grade ethanol.

Volkin, P

1998-09-01T23:59:59.000Z

200

Nucleosynthesis in the accretion disks of Type II collapsars  

E-Print Network (OSTI)

We investigate nucleosynthesis inside the gamma-ray burst (GRB) accretion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star and a mild supernova explosion is driven. However, this supernova ejecta lack momentum and falls back onto the neutron star which gets transformed to a stellar mass black hole. In order to study the hydrodynamics and nucleosynthesis of such an accretion disk formed from the fallback material of the supernova ejecta, we use the well established hydrodynamic models. In such a disk neutrino cooling becomes important in the inner disk where the temperature and density are higher. Higher the accretion rate (dot{M}), higher is the density and temperature in the disks. In this work we deal with accretion disks with relatively low accretion rates: 0.001 M_sun s^{-1} \\lesssim dot{M} \\lesssim 0.01 M_sun s^{-1} and hence these disks are predominantly advection dominated. We use He-rich and Si-rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like {31}P, {39}K, {43}Sc, {35}Cl, and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthesized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.

Indrani Banerjee; Banibrata Mukhopadhyay

2013-05-08T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

STAR FORMATION IN THE OUTER DISK OF SPIRAL GALAXIES  

SciTech Connect

We combine new deep and wide field of view H{alpha} imaging of a sample of eight nearby (d Almost-Equal-To 17 Mpc) spiral galaxies with new and archival H I and CO imaging to study the star formation and the star formation regulation in the outer disk. We find that, in agreement with previous studies, star formation in the outer disk has low covering fractions, and star formation is typically organized into spiral arms. The star formation in the outer disk is at extremely low levels, with typical star formation rate surface densities of {approx}10{sup -5} to 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}. We find that the ratio of the radial extent of detected H II regions to the radius of the H I disk is typically {approx}>85%. This implies that in order to further our understanding of the implications of extended star formation, we must further our understanding of the formation of extended H I disks. We measure the gravitational stability of the gas disk, and find that the outer gaseous disk is typically a factor of {approx}2 times more stable than the inner star-forming disk. We measure the surface density of outer disk H I arms, and find that the disk is closer to gravitational instability along these arms. Therefore, it seems that spiral arms are a necessary, but not sufficient, requirement for star formation in the outer disk. We use an estimation of the flaring of the outer gas disk to illustrate the effect of flaring on the Schmidt power-law index; we find that including flaring increases the agreement between the power-law indices of the inner and outer disks.

Barnes, Kate L.; Van Zee, Liese [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Cote, Stephanie [Canadian Gemini Office, Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada); Schade, David, E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: Stephanie.Cote@nrc-cnrc.gc.ca, E-mail: David.Schade@nrc-cnrc.gc.ca [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada)

2012-09-20T23:59:59.000Z

202

THE DISPERSAL OF PROTOPLANETARY DISKS AROUND BINARY STARS  

SciTech Connect

I present models of disk evolution around young binary stars. I show that the primary factor in determining circumbinary disk lifetimes is the rate of disk photoevaporation. I also find that photoevaporative clearing leaves a signature on the distribution of circumbinary disk lifetimes, with a sharp increase in disk lifetimes for binary separations a {approx}< 0.3-1 AU. Observations of young binary stars can therefore be used to test models of disk evolution, and I show that current data set a strong upper limit to the rate of on-going photoevaporation (<10{sup -9} M{sub Sun} yr{sup -1}). Finally I discuss the implications of these results for planet formation and suggest that circumbinary planets around close (a {approx}< 1 AU) binaries should be relatively common.

Alexander, Richard, E-mail: richard.alexander@leicester.ac.uk [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)

2012-10-01T23:59:59.000Z

203

Nucleosynthesis in the Outflow from Gamma Ray Burst Accretion Disks  

E-Print Network (OSTI)

We examine the nucleosynthesis products that are produced in the outflow from rapidly accreting disks. We find that the type of element synthesis varies dramatically with the degree of neutrino trapping in the disk and therefore the accretion rate of the disk. Disks with relatively high accretion rates such as ? M = 10 M?/s can produce very neutron rich nuclei that are found in the r process. Disks with more moderate accretion rates can produce copious amounts of Nickel as well as the light elements such as Lithium and Boron. Disks with lower accretion rates such as ? M = 1 M?/s produce large amounts of Nickel as well as some unusual nuclei such as 49 Ti,

R. Surman; G. C. Mclaughlin; W. R. Hix; Zn

2005-01-01T23:59:59.000Z

204

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

205

DISK WINDS AND THE ACCRETIONOUTFLOW CONNECTION  

E-Print Network (OSTI)

We review recent observational and theoretical results on the relationship between circumstellar accretion disks and jets in young stellar objects. We then present a theoretical framework that interprets jets as accretion-powered, centrifugally driven winds from magnetized accretion disks. Recent progress in the numerical simulation of such outflows is described. We also discuss the structure of the underlying magnetized protostellar disks, emphasizing the role that large-scale, open magnetic fields can play in angular momentum transport. I.

Arieh K nigl; Ralph E. Pudritz

1999-01-01T23:59:59.000Z

206

Normal Modes of Black Hole Accretion Disks  

SciTech Connect

This paper studies the hydrodynamical problem of normal modes of small adiabatic oscillations of relativistic barotropic thin accretion disks around black holes (and compact weakly magnetic neutron stars). Employing WKB techniques, we obtain the eigen frequencies and eigenfunctions of the modes for different values of the mass and angular momentum of the central black hole. We discuss the properties of the various types of modes and examine the role of viscosity, as it appears to render some of the modes unstable to rapid growth.

Ortega-Rodriguez, Manuel; /Stanford U., Appl. Phys. Dept. /Costa Rica U.; Silbergleit, Alexander S.; /Stanford U., HEPL; Wagoner, Robert V.; /Stanford U., Phys. Dept.

2006-11-07T23:59:59.000Z

207

DISK CHOPPER TIME-OF-FLIGHT SPECTROMETER (DCS)  

Science Conference Proceedings (OSTI)

... almost all of the high energy neutrons and gamma-rays in the initial ... disk choppers that collectively produce clean monochromatic bursts of neutrons ...

208

Development of Gatorized MERL 76 for Gas Turbine Disk Applications  

Science Conference Proceedings (OSTI)

FOR GAS TURBINE DISK APPLICATIONS. R. H. Caless and D. F. Paulonis. Materials. Engineering. Pratt & Whitney. 400 Main Street. East Hartford,. CT 06108.

209

Abundance trends in the thin and thick disks  

E-Print Network (OSTI)

The Milky Way harbours two disks that appear distinct concerning scale-heights, kinematics, and elemental abundance patterns. Recent years have seen a surge of studies of the elemental abundance trends in the disks using high resolution spectroscopy. Here I will review and discuss the currently available data. Special focus will also be put on how we define stars to be members of either disk, and how current models of galaxy formation favour that thick disks are formed from several accreted bodies. The ability for the stellar abundance trends to test such predictions are discussed.

Sofia Feltzing

2004-11-07T23:59:59.000Z

210

PROBABILISTIC LIFE OF DA718 FOR AIRCRAFT ENGINE DISKS  

Science Conference Proceedings (OSTI)

PROBABILISTIC LIFE OF DA718 FOR AIRCRAFT ENGINE DISKS. S.DEYBER. 1. , F.ALEXANDRE. 2. , J.VAISSAUD. 2. , A.PINEAU. 2. 1. Snecma Materials...

211

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...

212

P/M AF115 Dual Property Disk Process Development  

Science Conference Proceedings (OSTI)

logs. The logs were sliced to produce disks of thickness ranging from 1 inch .... properties. The data also showed a trend of higher strength and ductility with.

213

Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim  

E-Print Network (OSTI)

This paper introduces a new disk code, called ProDiMo, to calculate the thermo-chemical structure of protoplanetary disks and to interpret gas emission lines from UV to sub-mm. We combine frequency-dependent 2D dust continuum radiative transfer, kinetic gas-phase and UV photo-chemistry, ice formation, and detailed non-LTE heating & cooling balance with the consistent calculation of the hydrostatic disk structure. We include FeII and CO ro-vibrational line heating/cooling relevant for the high-density gas close to the star, and apply a modified escape probability treatment. The models are characterized by a high degree of consistency between the various physical, chemical and radiative processes, where the mutual feedbacks are solved iteratively. In application to a T Tauri disk extending from 0.5AU to 500AU, the models are featured by a puffed-up inner rim and show that the dense, shielded and cold midplane (z/r<0.1, Tg~Td) is surrounded by a layer of hot (5000K) and thin (10^7 to 10^8 cm^-3) atomic ga...

Woitke, Peter; Thi, Wing-Fai

2009-01-01T23:59:59.000Z

214

PLANETESIMAL AND PROTOPLANET DYNAMICS IN A TURBULENT PROTOPLANETARY DISK: IDEAL STRATIFIED DISKS  

SciTech Connect

Due to the gravitational influence of density fluctuations driven by magneto-rotational instability in the gas disk, planetesimals and protoplanets undergo diffusive radial migration as well as changes in other orbital properties. The magnitude of the effect on particle orbits can have important consequences for planet formation scenarios. We use the local-shearing-box approximation to simulate an ideal, isothermal, magnetized gas disk with vertical density stratification and simultaneously evolve numerous massless particles moving under the gravitational field of the gas and the host star. We measure the evolution of the particle orbital properties, including mean radius, eccentricity, inclination, and velocity dispersion, and its dependence on the disk properties and the particle initial conditions. Although the results converge with resolution for fixed box dimensions, we find the response of the particles to the gravity of the turbulent gas correlates with the horizontal box size, up to 16 disk scale heights. This correlation indicates that caution should be exercised when interpreting local-shearing-box models involving gravitational physics of magneto-rotational turbulence. Based on heuristic arguments, nevertheless, the criterion L{sub h} /R {approx} O(1), where L{sub h} is the horizontal box size and R is the distance to the host star, is proposed to possibly circumvent this conundrum. If this criterion holds, we can still conclude that magneto-rotational turbulence seems likely to be ineffective at driving either diffusive migration or collisional erosion under most circumstances.

Yang, Chao-Chin [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Mac Low, Mordecai-Mark [Department of Astrophysics, American Museum of Natural History, New York, NY 10024 (United States); Menou, Kristen, E-mail: ccyang@ucolick.org, E-mail: mordecai@amnh.org, E-mail: kristen@astro.columbia.edu [Department of Astronomy, Columbia University, New York, NY 10027 (United States)

2012-04-01T23:59:59.000Z

215

Beta Pictoris Debris Disk is Not a Proto-planetary Disk  

E-Print Network (OSTI)

Abstract: The debris disk around the star Beta Pictoris is not a proto-planetary disk but of the result of a collision of two or more aging stars as a result of the formation of the Proto-star Beta Pictoris. Beta Pictoris is shown to possess a large debris disk which glows in the infared. [1] It has been hypothesized that this debris disk is not evidence for the formation of new stars/exoplanets [2] but of the formation of smaller moons caused by the collision of older stars taking up new orbits around the proto-star Beta Pictoris, which is a very young star. [3] These will stabilize and become round and undifferentiated similar to the moon Callisto [4] , or the many other arrangements of moons around Saturn or Jupiter and smaller objects such as Ceres. This would also explain why they do not possess iron cores but are mostly volatiles such as water, ammonia, methane and sulfur dioxide which have a relatively low equilibrium condensation as opposed to refractory elements and molecules which have a much higher boiling point, and play a large part in the differentiation process. [5] References

Jeffrey J Wolynski

2012-01-01T23:59:59.000Z

216

Cross-Front Mixing and Frontal Upwelling in a Controlled Quasi-Permanent Density Front in the Gulf of St. Lawrence  

Science Conference Proceedings (OSTI)

CTD data obtained from three transects across a controlled quasi-permanent density front in the Gulf of St. Lawrence were analyzed for the purpose of investigating cross-front mixing, mechanisms for frontal convergence, secondary circulation ...

C. L. Tang

1983-08-01T23:59:59.000Z

217

ICE LINES IN CIRCUMBINARY PROTOPLANETARY DISKS  

Science Conference Proceedings (OSTI)

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}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

218

Photon Bubbles and the Vertical Structure of Accretion Disks  

E-Print Network (OSTI)

We consider the effects of "photon bubble" shock trains on the vertical structure of radiation pressure-dominated accretion disks. These density inhomogeneities are expected to develop spontaneously in radiation-dominated accretion disks where magnetic pressure exceeds gas pressure, even in the presence of magnetorotational instability. They increase the rate at which radiation escapes from the disk, and may allow disks to exceed the Eddington limit by a substantial factor. We first generalize the theory of photon bubbles to include the effects of finite optical depths and radiation damping. Modifications to the diffusion law at low optical depth tend to fill in the low-density regions of photon bubbles, while radiation damping inhibits the formation of photon bubbles at large radii, small accretion rates, and small heights above the equatorial plane. Accretion disks dominated by photon bubble transport may reach luminosities of 10 to >100 times the Eddington limit (L_E), depending on the mass of the central object, while remaining geometrically thin. However, photon bubble-dominated disks with alpha-viscosity are subject to the same thermal and viscous instabilities that plague standard radiation pressure-dominated disks, suggesting that they may be intrinsically unsteady. Photon bubbles can lead to a "core-halo" vertical disk structure. In super-Eddington disks the halo forms the base of a wind, which carries away substantial energy and mass, but not enough to prevent the luminosity from exceeding L_E. Photon bubble-dominated disks may have smaller color corrections than standard accretion disks of the same luminosity. They remain viable contenders for some ultraluminous X-ray sources and may play a role in the rapid growth of supermassive black holes at high redshift.

Mitchell C. Begelman

2006-02-01T23:59:59.000Z

219

Obscuring Active Galactic Nuclei with Nuclear Starburst Disks  

E-Print Network (OSTI)

We assess the potential of nuclear starburst disks to obscure the Seyfert-like AGN that dominate the hard X-ray background at z~1. Over 1200 starburst disk models, based on the theory developed by Thompson et al., are calculated for five input parameters: the black hole mass, the radial size of the starburst disk, the dust-to-gas ratio, the efficiency of angular momentum transport in the disk, and the gas fraction at the outer disk radius. We find that a large dust-to-gas ratio, a relatively small starburst disk, a significant gas mass fraction, and efficient angular momentum transport are all important to produce a starburst disk that can potentially obscure an AGN. The typical maximum star-formation rate in the disks is ~10 solar masses per year. Assuming no mass-loss due to outflows, the starburst disks feed gas onto the black hole at rates sufficient to produce hard X-ray luminosities of 10^{43}-10^{44} erg s^{-1}. The starburst disks themselves should be detectable at mid-infrared and radio wavelengths; at z=0.8, the predicted fluxes are ~1 mJy at 24microns and ~10-30 microJy at 1.4GHz. Thus, we predict a large fraction of radio/X-ray matches in future deep radio surveys. The starburst disks should be easily distinguished from AGN in future 100microns surveys by Herschel with expected fluxes of ~5 mJy. Any AGN-obscuring starbursts will be associated with hot dust, independent of AGN heating, resulting in observable signatures for separating galactic and nuclear star-formation. Finally, because of the competition between gas and star-formation, nuclear starbursts will be associated with lower-luminosity AGN. Thus, this phenomenon is a natural explanation for the observed decrease in the fraction of obscured AGN with luminosity.

D. R. Ballantyne

2008-06-17T23:59:59.000Z

220

NETL's Supercomputer Addresses Energy Issues on Two Fronts | Department of  

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

NETL's Supercomputer Addresses Energy Issues on Two Fronts NETL's Supercomputer Addresses Energy Issues on Two Fronts NETL's Supercomputer Addresses Energy Issues on Two Fronts September 26, 2013 - 10:42am Addthis The visualization center for the SBEUC (Simulation Based Engineering User Center). Located at the Department’s National Energy Technology Laboratory in Morgantown, W. Va., the SBEUC will be powered by a high performance computer that will allow researchers to simulate phenomena that are difficult or impossible to probe experimentally. The results from simulations will become accessible through user centers that provide advanced visualization capabilities and foster collaboration among researchers. The SBEUC will be used for developing and deploying simulation tools required for overcoming energy technology barriers quickly and reliably.

Note: This page contains sample records for the topic "front 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
to obtain the most current and comprehensive results.


221

Rayleigh-Taylor Instability at Ionization Fronts: Perturbation Analysis  

E-Print Network (OSTI)

The linear growth rate of the Rayleigh-Taylor instability (RTI) at ionization fronts is investigated via perturbation analysis in the limit of incompressible fluids. In agreement with previous numerical studies is found that absorption of ionizing radiation inside the HII region due to hydrogen recombinations suppresses the growth of instabilities. In the limit of a large density contrast at the ionization front the RTI growth rate has the simple analytical solution n=-nur+(nur^2+gk)^(1/2), where nur is the hydrogen recombination rate inside the HII region, k is the perturbation's wavenumber and g is the effective acceleration in the frame of reference of the front. Therefore, the growth of surface perturbations with wavelengths lambda >> lambda_{cr} = 2\\pi g/nur^2 is suppressed by a factor (lambda_{cr}/4lambda)^(1/2) with respect to the non-radiative incompressible RTI. Implications on stellar and black hole feedback are briefly discussed.

Ricotti, Massimo

2013-01-01T23:59:59.000Z

222

Methods for enhancing mapping of thermal fronts in oil recovery  

DOE Patents (OSTI)

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

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

1987-01-01T23:59:59.000Z

223

Methods for enhancing mapping of thermal fronts in oil recovery  

DOE Patents (OSTI)

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

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

1984-03-30T23:59:59.000Z

224

HINS Linac front end focusing system R&D  

SciTech Connect

This report summarizes current status of an R&D program to develop a focusing system for the front end of a superconducting RF linac. Superconducting solenoids will be used as focusing lenses in the low energy accelerating sections of the front end. The development of focusing lenses for the first accelerating section is in the production stage, and lens certification activities are in preparation at FNAL. The report contains information about the focusing lens design and performance, including solenoid, dipole corrector, and power leads, and about cryogenic system design and performance. It also describes the lens magnetic axis position measurement technique and discusses scope of an acceptance/certification process.

Apollinari, G.; Carcagno, R.H.; Dimarco, J.; Huang, Y.; Kashikhin, V.V.; Orris, D.F.; Page, T.M.; Rabehl, R.; Sylvester, C.; Tartaglia, M.A.; Terechkine, I.; /Fermilab /Argonne

2008-08-01T23:59:59.000Z

225

THE THERMAL STRUCTURE OF GRAVITATIONALLY DARKENED CLASSICAL Be STAR DISKS  

Science Conference Proceedings (OSTI)

The effect of gravitational darkening on models of the thermal structure of Be star disks is systematically studied for a wide range of Be star spectral types and rotation rates. Gravitational darkening causes a reduction of the stellar effective temperature toward the equator and a redirection of energy toward the poles. It is an important physical effect in these star-disk systems because the photoionizing radiation from the central B star is the main energy source for the disk. We have added gravitational darkening to the BEDISK code to produce circumstellar disk models that include both the variation in the effective temperature with latitude and the non-spherical shape of the star in the calculation of the stellar photoionizing radiation field. The effect of gravitational darkening on global measures of disk temperature is generally significant for rotation rates above 80% of critical rotation. For example, a B0V model rotating at 95% of critical has a density-averaged disk temperature Almost-Equal-To 2500 K cooler than its non-rotating counterpart. However, detailed differences in the temperature structure of disks surrounding rotating and non-rotating stars reveal a complex pattern of heating and cooling. Spherical gravitational darkening, an approximation that ignores the changing shape of the star, gives good results for disk temperatures for rotation rates less than Almost-Equal-To 80% of critical. However for the highest rotation rates, the distortion of the stellar surface caused by rotation becomes important.

McGill, M. A.; Sigut, T. A. A.; Jones, C. E. [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)

2011-12-20T23:59:59.000Z

226

Neutrinos and Nucleosynthesis in Gamma-Ray Burst Accretion Disks  

E-Print Network (OSTI)

We calculate the nuclear composition of matter in accretion disks surrounding stellar mass black holes as are thought to accompany gamma-ray bursts (GRBs). We follow a mass element in the accretion disk starting at the point of nuclear dissociation and calculate the evolution of the electron fraction due to electron, positron, electron neutrino and electron antineutrino captures. We find that the neutronization of the disk material by electron capture can be reversed by neutrino interactions in the inner regions of disks with accretion rates of 1 M_solar/s and higher. For these cases the inner disk regions are optically thick to neutrinos, and so to estimate the emitted neutrino fluxes we find the surface of last scattering for the neutrinos (the equivalent of the proto-neutron star neutrinosphere) for each optically thick disk model. We also estimate the influence of neutrino interactions on the neutron-to-proton ratio in outflows from GRB accretion disks, and find it can be significant even when the disk is optically thin to neutrinos.

R. Surman; G. C. McLaughlin

2003-07-31T23:59:59.000Z

227

Dynamic data reorganization for energy savings in disk storage systems  

Science Conference Proceedings (OSTI)

High performance computing (HPC) systems utilize parallel file systems that are striped over large number of disks to address the I/O performance requirement of data intensive applications. These large number of disks are typically configured into RAID ... Keywords: RAID system configuration, energy saving, energy-aware storage

Ekow Otoo; Doron Rotem; Shih-Chiang Tsao

2010-06-01T23:59:59.000Z

228

Performance directed energy management for main memory and disks  

Science Conference Proceedings (OSTI)

Much research has been conducted on energy management for memory and disks. Most studies use control algorithms that dynamically transition devices to low power modes after they are idle for a certain threshold period of time. The control algorithms ... Keywords: Disk energy management, adaptation algorithms, control algorithms, low-power design, memory energy management, multiple-power mode device, performance guarantee

Xiaodong Li; Zhenmin Li; Yuanyuan Zhou; Sarita Adve

2005-08-01T23:59:59.000Z

229

Dual Structure Turbine Disks Via Partial Immersion Heat Treatment  

Science Conference Proceedings (OSTI)

turbine disk forging. The method is termed partial immersion treatment. It includes ... to improve gas turbine operating efficiencies generally results in increased turbine inlet .... to aid in this manual advance. (Figure lb). ... A second Astroloy disk was ..... engineer. (prime contractor) was Mr. R. M. Gasior, of Cytemp Specialty.

230

B-tries for disk-based string management  

Science Conference Proceedings (OSTI)

A wide range of applications require that large quantities of data be maintained in sort order on disk. The B-tree, and its variants, are an efficient general-purpose disk-based data structure that is almost universally used for this task. The B-trie ... Keywords: B-tree, Burst trie, Data structures, Secondary storage, Vocabulary accumulation, Word-level indexing

Nikolas Askitis; Justin Zobel

2009-01-01T23:59:59.000Z

231

RESOLVING THE CIRCUMSTELLAR DISK OF HL TAURI AT MILLIMETER WAVELENGTHS  

SciTech Connect

We present results of high-resolution imaging toward HL Tau by the Combined Array for Research in Millimeter-wave Astronomy. We have obtained {lambda} = 1.3 mm and 2.7 mm dust continua with an angular resolution down to 0.''13. Through simultaneous model fitting to the two wavelength data sets in Bayesian inference using a flared viscous accretion disk model, we estimate the physical properties of HL Tau, such as density distribution, dust opacity spectral index, disk mass, disk size, inclination angle, position angle, and disk thickness. HL Tau has a circumstellar disk mass of 0.13 M{sub sun}, a characteristic radius of 79 AU, an inclination of 40{sup 0}, and a position angle of 136{sup 0}. Although a thin disk model is preferred by our two wavelength data sets, a thick disk model is needed to explain the high mid- and far-infrared emission of the HL Tau spectral energy distribution. This could imply large dust grains settled down on the midplane with fine dust grains mixed with gas. The HL Tau disk is likely gravitationally unstable and can be fragmented between 50 and 100 AU of radius. However, we did not detect dust thermal continuum supporting the protoplanet candidate claimed by a previous study using observations of the Very Large Array at {lambda} = 1.3 cm.

Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Mundy, Lee G., E-mail: wkwon@illinois.edu [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2011-11-01T23:59:59.000Z

232

Workload-Adaptive Management of Energy-Smart Disk Storage Systems  

E-Print Network (OSTI)

the disks are kept in standby mode until some data residingis requested. Powering up a standby disk to serve a requestto spin up a powered-off (standby) disk as compared with the

Otoo, Ekow

2010-01-01T23:59:59.000Z

233

Molecular and Stellar Disks Galaxies Lisa Young (New Mexico Tech) and Martin Bureau (Oxford)  

E-Print Network (OSTI)

Molecular and Stellar Disks Galaxies Lisa Young (New Mexico Tech) and Martin Bureau (Oxford galaxies contain molecular disks. These internal structures evolution galaxies. to place observational constraints on the formation in early galaxies studying the relationships between embedded disks, molecular

Bureau, Martin

234

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

235

FORMING AN O STAR VIA DISK ACCRETION?  

Science Conference Proceedings (OSTI)

We present a study of outflow, infall, and rotation in a {approx}10{sup 5} L{sub Sun} star-forming region, IRAS 18360-0537, with Submillimeter Array and IRAM 30 m observations. The 1.3 mm continuum map shows a 0.5 pc dust ridge, of which the central compact part has a mass of {approx}80 M{sub Sun} and harbors two condensations, MM1 and MM2. The CO (2-1) and SiO (5-4) maps reveal a biconical outflow centered at MM1, which is a hot molecular core (HMC) with a gas temperature of 320 {+-} 50 K and a mass of {approx}13 M{sub Sun }. The outflow has a gas mass of 54 M{sub Sun} and a dynamical timescale of 8 Multiplication-Sign 10{sup 3} yr. The kinematics of the HMC are probed by high-excitation CH{sub 3}OH and CH{sub 3}CN lines, which are detected at subarcsecond resolution and unveil a velocity gradient perpendicular to the outflow axis, suggesting a disk-like rotation of the HMC. An infalling envelope around the HMC is evidenced by CN lines exhibiting a profound inverse P Cygni profile, and the estimated mass infall rate, 1.5 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}, is well comparable to that inferred from the mass outflow rate. A more detailed investigation of the kinematics of the dense gas around the HMC is obtained from the {sup 13}CO and C{sup 18}O (2-1) lines; the position-velocity diagrams of the two lines are consistent with the model of a free-falling and Keplerian-like rotating envelope. The observations suggest that the protostar of a current mass {approx}10 M{sub Sun} embedded within MM1 will develop into an O star via disk accretion and envelope infall.

Qiu Keping [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Zhang Qizhou [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Beuther, Henrik; Fallscheer, Cassandra, E-mail: kqiu@mpifr-bonn.mpg.de [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

2012-09-10T23:59:59.000Z

236

Mean Flow Evolution of a Baroclinically Unstable Potential Vorticity Front  

Science Conference Proceedings (OSTI)

Quasi-linear theory and numerical models are used to study the mean flow modification of a two-layer shallow water baroclinically unstable flow as a function of Rossby number. This flow has an upper-layer potential vorticity front overlying a ...

Emmanuel Boss; Lu Anne Thompson

1999-02-01T23:59:59.000Z

237

Dynamics of Potential Vorticity Fronts and Eddy Detachment  

Science Conference Proceedings (OSTI)

The formation and detachment of quasi-geostrophic eddies in a 1 layer jet is studied using a piecewise uniform potential vorticity model. A vorticity front separates the two pieces, and thus the jet has cusplike character. The evolution of large ...

L. J. Pratt; Melvin E. Stern

1986-06-01T23:59:59.000Z

238

(front end fuel cycle) 2.1 (CANDU  

E-Print Network (OSTI)

2 (front end fuel cycle) 2.1 (CANDU: CANada Deuterium Uranium; . ( 2.2) . 70-80% , (uranium concentrate) . () 2.1 . 2.2 2.3 #12; 2; . Mine Car Load Skip Geiger Counter 8"~3/2"" . (2

Hong, Deog Ki

239

Observation of Atmospheric Fronts Using Raman Lidar Moisture Measurements  

Science Conference Proceedings (OSTI)

This paper presents the results of a field program using a ground-based Raman lidar system to observe changes in moisture profiles as a cold and a warm front passed over the NASA/Goddard Space Flight Center in Greenbelt, Maryland. The lidar ...

S. H. Melfi; D. Whiteman; R. Ferrare

1989-09-01T23:59:59.000Z

240

the Front Line of Medicine to Prevent Needless Work Disability  

E-Print Network (OSTI)

Preparing the Front Line of Medicine to Prevent Needless Work Disability: Private 4. Free on-line CME; "Medical Rounds" in a talk show format 3. Free live;6 Approaches 1. Sessions at exis9ng medical educa9on events 2. Offer of on-line CME training

Note: This page contains sample records for the topic "front 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

Front and backside processed thin film electronic devices  

DOE Patents (OSTI)

This invention provides methods for fabricating thin film electronic devices with both front- and backside processing capabilities. Using these methods, high temperature processing steps may be carried out during both frontside and backside processing. The methods are well-suited for fabricating back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

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

2010-10-12T23:59:59.000Z

242

On the propagation of a coupled saturation and pressure front  

SciTech Connect

Using an asymptotic technique, valid for a medium with smoothly varying heterogeneity, I derive an expression for the velocity of a propagating, coupled saturation and pressure front. Due to the nonlinearity of the governing equations, the velocity of the propagating front depends upon the magnitude of the saturation and pressure changes across the front in addition to the properties of the medium. Thus, the expression must be evaluated in conjunction with numerical reservoir simulation. The propagation of the two-phase front is governed by the background saturation distribution, the saturation-dependent component of the fluid mobility, the porosity, the permeability, the capillary pressure function, the medium compressibility, and the ratio of the slopes of the relative permeability curves. Numerical simulation of water injection into a porous layer saturated with a nonaqueous phase liquid indicates that two modes of propagation are important. The fastest mode of propagation is a pressure-dominated disturbance that travels through the saturated layer. This is followed, much later, by a coupled mode with a large saturation change. These two modes are also observed in a simulation using a heterogeneous porous layer. A comparison between the propagation times estimated from the results of the numerical simulation and predictions from the asymptotic expression indicates overall agreement.

Vasco, D. W.

2010-12-01T23:59:59.000Z

243

Benthic Observations on the Madeira Abyssal Plain: Fronts  

Science Conference Proceedings (OSTI)

Analysis of data from a mooring with five vector-averaging current meters between 10 and 70 m above the bed of the Madeira Abyssal Plain reveals the existence of narrow regions with relatively large gradients of potential temperature, or fronts....

S. A. Thorpe

1983-08-01T23:59:59.000Z

244

A FRONT END DESIGN FOR THE ADVANCED PHOTON SOURCE  

E-Print Network (OSTI)

X-ray sources on next generation low emittance/high brilliance synchrotrons such as the 7-GeV Advanced Photon Source (APS) (1) have unique properties which directly affect the design of the front end of the beam line. The most striking of these are the large peak photon power densities

P. J. Viccaro

1988-01-01T23:59:59.000Z

245

Move-to-Front, Distance Coding, and Inversion Frequencies revisited  

Science Conference Proceedings (OSTI)

Move-to-Front, Distance Coding and Inversion Frequencies are three simple and effective techniques used to process the output of the Burrows-Wheeler Transform. In this paper we provide the first complete comparative analyses of these techniques, establishing ... Keywords: Burrows-Wheeler Transform, Data Compression, Empirical entropy

Travis Gagie; Giovanni Manzini

2010-06-01T23:59:59.000Z

246

Front and backside processed thin film electronic devices  

Science Conference Proceedings (OSTI)

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

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

2012-01-03T23:59:59.000Z

247

DiscPOP: Power-aware buffer management for disk accesses  

Science Conference Proceedings (OSTI)

Much research has been conducted on energy efficient cache buffer management for disk based storage systems. Some of them use greedy prefetching technique to artificially increase disk idle intervals if there are a large number of known future requests. ... Keywords: greedy partition, DiscPOP, power-aware buffer management, disk accesses, disk based storage systems, greedy prefetching, I/O access pattern, application pattern, CPU-bound application, energy conservation, efficient prefetching scheme, disk power consumption, performance guarantee, disk reliability, disk characteristic based power-optimal prefetching, energy-efficient cache buffer management, disk I/O system, optimization problem, integer linear programming, divide-and-conquer based offline algorithm

Xiongzi Ge; Dan Feng; David H. C. Du

2011-07-01T23:59:59.000Z

248

STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES  

SciTech Connect

We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ({sup U}-shapes{sup )} in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third ({<=}36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks ({approx}11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail ({>=}50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely focused on field galaxies, fail to reproduce these results, thus calling for adequate hydrodynamical simulations of dense galaxy environments if we are to understand cluster disks. The current paper highlights numerous constraints for such simulations. In the Appendix, we confirm the claim by Erwin et al. that Type II breaks are absent in Virgo cluster S0s and discuss the detection of Type III breaks in such galaxies.

Roediger, Joel C.; Courteau, Stephane [Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, Ontario (Canada); Sanchez-Blazquez, Patricia [Deptartamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); McDonald, Michael, E-mail: jroediger@astro.queensu.ca, E-mail: courteau@astro.queensu.ca, E-mail: p.sanchezblazquez@uam.es, E-mail: mcdonald@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology Cambridge, MA (United States)

2012-10-10T23:59:59.000Z

249

Kinematic and Moisture Characteristics of a Nonprecipitating Cold Front Observed during IHOP. Part I: Across-Front Structures  

Science Conference Proceedings (OSTI)

A wide array of ground-based and airborne instrumentation is used to examine the kinematic and moisture characteristics of a nonprecipitating cold front observed in west-central Kansas on 10 June 2002 during the International H2O Project (IHOP). ...

Katja Friedrich; David E. Kingsmill; Cyrille Flamant; Hanne V. Murphey; Roger M. Wakimoto

2008-01-01T23:59:59.000Z

250

Theory of self-assembled smectic-A "crenellated disks"  

E-Print Network (OSTI)

Smectic-A monolayers self-assembled in aqueous solutions of chiral fd viruses and a polymer depletant have been shown to exhibit a variety of structures including large, flat disks and twisted ribbons. The virus particles twist near the edge of the structure in a direction determined by the chirality of the viruses. When fd viruses and their mutants of opposite chirality are mixed together in nearly equal amounts unusual structures referred to as "crenellated disks" can appear. These disks are achiral overall but the twist at the edge alternates between left- and right-handedness. To minimize the mismatch where the two regions of opposing twist meet, the "crenellated" structure exhibits cusps rising out of the plane of the monolayer. We use a phenomenological elastic theory previously applied to flat disks and twisted ribbons to analyze an analytic model proposed to describe the "crenellated" structure . When compared with flat, circular disks, we find that the model "crenellated disks" are stable or at least metastable in a wide region of the phase diagram spanned by the Gaussian curvature modulus and the edge energy modulus, with a large energy barrier separating the two structures. The director pattern and geometric parameters of the "crenellated disks" are found to be in qualitative agreement with experimental observations.

Hao Tu; Robert A. Pelcovits

2013-01-09T23:59:59.000Z

251

Spectral Energy Distributions of Passive T Tauri Disks Inclination  

E-Print Network (OSTI)

We compute spectral energy distributions (SEDs) for passive T Tauri disks viewed at arbitrary inclinations. Semi-analytic models of disks in radiative and hydrostatic equilibrium are employed. Over viewing angles for which the flared disk does not occult the central star, the SED varies negligibly with inclination. For such aspects, the SED shortward of ~80 microns is particularly insensitive to orientation, since short wavelength disk emission is dominated by superheated surface layers which are optically thin. The SED of a nearly edge-on disk is that of a class I source. The outer disk occults inner disk regions, and emission shortward of ~30 microns is dramatically extinguished. Spectral features from dust grains may appear in absorption. However, millimeter wavelength fluxes decrease by at most a factor of 2 from face-on to edge-on orientations. We present illustrative applications of our SED models. The class I source 04108+2803B is considered a T Tauri star hidden from view by an inclined circumstellar ...

Chiang, E I

1999-01-01T23:59:59.000Z

252

Nucleosynthesis in the Outflow from Gamma Ray Burst Accretion Disks  

E-Print Network (OSTI)

We examine the nucleosynthesis products that are produced in the outflow from rapidly accreting disks. We find that the type of element synthesis varies dramatically with the degree of neutrino trapping in the disk and therefore the accretion rate of the disk. Disks with relatively high accretion rates such as 10 M_solar/s can produce very neutron rich nuclei that are found in the r process. Disks with more moderate accretion rates can produce copious amounts of Nickel as well as the light elements such as Lithium and Boron. Disks with lower accretion rates such as 0.1 M_solar/s produce large amounts of Nickel as well as some unusual nuclei such as Ti-49, Sc-45, Zn-64, and Mo-92. This wide array of potential nucleosynthesis products is due to the varying influence of electron neutrinos and antineutrinos emitted from the disk on the neutron-to-proton ratio in the outflow. We use a parameterization for the outflow and discuss our results in terms of entropy and outflow acceleration.

R. Surman; G. C. McLaughlin; W. R. Hix

2005-09-13T23:59:59.000Z

253

Radio frequency circuits for wireless receiver front-ends  

E-Print Network (OSTI)

The beginning of the 21st century sees great development and demands on wireless communication technologies. Wireless technologies, either based on a cable replacement or on a networked environment, penetrate our daily life more rapidly than ever. Low operational power, low cost, small form factor, and function diversity are the crucial requirements for a successful wireless product. The receiver??s front-end circuits play an important role in faithfully recovering the information transmitted through the wireless channel. Bluetooth is a short-range cable replacement wireless technology. A Bluetooth receiver architecture was proposed and designed using a pure CMOS process. The front-end of the receiver consists of a low noise ampli?er (LNA) and mixer. The intermediate frequency was chosen to be 2MHz to save battery power and alleviate the low frequency noise problem. A conventional LNA architecture was used for reliability. The mixer is a modi?ed Gilbert-cell using the current bleeding technique to further reduce the low frequency noise. The front-end draws 10 mA current from a 3 V power supply, has a 8.5 dB noise ?gure, and a voltage gain of 25 dB and -9 dBm IIP3. A front-end for dual-mode receiver is also designed to explore the capability of a multi-standard application. The two standards are IEEE 802.11b and Bluetooth. They work together making the wireless experience more exciting. The front-end is designed using BiCMOS technology and incorporating a direct conversion receiver architecture. A number of circuit techniques are used in the front-end design to achieve optimal results. It consumes 13.6 mA from a 2.5 V power supply with a 5.5 dB noise ?gure, 33 dB voltage gain and -13 dBm IIP3. Besides the system level contributions, intensive studies were carried out on the development of quality LNA circuits. Based on the multi-gated LNA structure, a CMOS LNA structure using bipolar transistors to provide linearization is proposed. This LNA con?guration can achieve comparable linearity to its CMOS multi-gated counterpart and work at a higher frequency with less power consumption. A LNA using an on-chip transformer source degeneration is proposed to realize input impedance matching. The possibility of a dual-band cellular application is studied. Finally, a study on ultra-wide band (UWB) LNA implementation is performed to explore the possibility and capability of CMOS technology on the latest UWB standard for multimedia applications.

Xin, Chunyu

2004-08-01T23:59:59.000Z

254

Front-end utility rate updates | OpenEI Community  

Open Energy Info (EERE)

Front-end utility rate updates Front-end utility rate updates Home > Groups > Utility Rate Rmckeel's picture Submitted by Rmckeel(297) Contributor 13 February, 2013 - 14:28 Utility Rates A few utility rate updates worth noting. We used to have a limit of 100 for results returned on the utility gateway. That has been increased, along with a few UI updates. There is now a 15em height window (sorry if that's too technical) to browse results, so all the hundreds of results don't extend the page. For the naming page however, perhaps the long list is preferred? I'm willing to tweak these heights, as well as have separate heights if it is requested for the public view and the editor view. Improvement to have results show within the block instead of outside of. Minor increase in results width on editor page.

255

Tracking thermal fronts with temperature-sensitive, chemically reactive tracers  

DOE Green Energy (OSTI)

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

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

1987-01-01T23:59:59.000Z

256

Laser supported solid state absorption fronts in silica  

SciTech Connect

We develop a model based on simulation and experiment that explains the behavior of solid-state laser-supported absorption fronts generated in fused silica during high intensity (up to 5GW/cm{sup 2}) laser exposure. We find that the absorption front velocity is constant in time and is nearly linear in laser intensity. Further, this model can explain the dependence of laser damage site size on these parameters. This behavior is driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. The regime of parameter space critical to this problem spans and extends that measured by other means. It serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

Carr, C W; Bude, J D

2010-02-09T23:59:59.000Z

257

Episodic Dust Events of Utahs Wasatch Front and Adjoining Region  

Science Conference Proceedings (OSTI)

Episodic dust events cause hazardous air quality along Utahs Wasatch Front and dust loading of the snowpack in the adjacent Wasatch Mountains. This paper presents a climatology of episodic dust events of the Wasatch Front and adjoining region ...

W. James Steenburgh; Jeffrey D. Massey; Thomas H. Painter

2012-09-01T23:59:59.000Z

258

An Investigation of an Arctic Front with a Vertically Nested Mesoscale Model  

Science Conference Proceedings (OSTI)

A vertically mesoscale regional numerical weather prediction model is used to simulate an arctic front. The front was observed during the Arctic Cyclone Expedition of 1984. The regional model employs a unique vertical nesting scheme in which the ...

William T. Thompson; Stephen D. Burk

1991-02-01T23:59:59.000Z

259

Cold Fronts with and without Prefrontal Wind Shifts in the Central United States  

Science Conference Proceedings (OSTI)

Time series of cold fronts from stations in the central United States possess incredible variety. For example, time series of some cold fronts exhibit a sharp temperature decrease coincident with a pressure trough and a distinct wind shift. Other ...

David M. Schultz

2004-08-01T23:59:59.000Z

260

The Development of the Piedmont Front and Associated Outbreak of Severe Weather on 13 March 1986  

Science Conference Proceedings (OSTI)

An investigation was conducted of the mesoscale evolution of a quasi-stationary front, termed the Piedmont front owing to its location through the central Carolinas, and an associated outbreak of severe weather on 13 March 1986. Space-time ...

Steven Businger; William H. Bauman III; Gerald F. Watson

1991-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

Low-Frequency Variability in the Midlatitude Baroclinic Atmosphere Induced by an Oceanic Thermal Front  

Science Conference Proceedings (OSTI)

This study examines the flow induced by an eastwest-oriented oceanic thermal front in a highly idealized baroclinic model. Previous work showed that thermal fronts could produce energetic midlatitude jets in an equivalent-barotropic atmosphere ...

Yizhak Feliks; Michael Ghil; Eric Simonnet

2007-01-01T23:59:59.000Z

262

Two Types of Surface Wind Response to the East China Sea Kuroshio Front  

Science Conference Proceedings (OSTI)

Effects of the sea surface temperature (SST) front along the East China Sea Kuroshio on sea surface winds at different time scales are investigated. In winter and spring, the climatological vector wind is strongest on the SST front while the ...

Jing-Wu Liu; Su-Ping Zhang; Shang-Ping Xie

2013-11-01T23:59:59.000Z

263

Mesoscale Subduction at the Antarctic Polar Front Driven by Baroclinic Instability  

Science Conference Proceedings (OSTI)

A study of mesoscale subduction at the Antarctic Polar Front (PF) is conducted by use of hydrographic data from a high-resolution, quasi-synoptic survey of the front. The geostrophic velocity and isopycnal potential vorticity (PV) fields are ...

Alberto C. Naveira Garabato; Harry Leach; John T. Allen; Raymond T. Pollard; Volker H. Strass

2001-08-01T23:59:59.000Z

264

Radiation-Dominated Disks Are Thermally Stable  

E-Print Network (OSTI)

When the accretion rate is more than a small fraction of Eddington, the inner regions of accretion disks around black holes are expected to be radiation-dominated. However, in the alpha-model, these regions are also expected to be thermally unstable. In this paper, we report two 3-d radiation MHD simulations of a vertically-stratified shearing box in which the ratio of radiation to gas pressure is ~ 10, and yet no thermal runaway occurs over a timespan ~ 40 cooling times. Where the time-averaged dissipation rate is greater than the critical dissipation rate that creates hydrostatic equilibrium by diffusive radiation flux, the time-averaged radiation flux is held to the critical value, with the excess dissipated energy transported by radiative advection. Although the stress and total pressure are well-correlated as predicted by the alpha-model, we show that stress fluctuations precede pressure fluctuations, contrary to the usual supposition that the pressure controls the saturation level of the magnetic energy. This fact explains the thermal stability. Using a simple toy-model, we show that independently-generated magnetic fluctuations can drive radiation pressure fluctuations, creating a correlation between the two while maintaining thermal stability.

Shigenobu Hirose; Julian H. Krolik; Omer Blaes

2008-09-10T23:59:59.000Z

265

Energy Proportionality for Disk Storage Using Replication  

Science Conference Proceedings (OSTI)

Energy saving has become a crucial concern in datacenters as several reports predict that the anticipated energy costs over a three year period will exceed hardware acquisition. In particular, saving energy for storage is of major importance as storage devices (and cooling them off) may contribute over 25 percent of the total energy consumed in a datacenter. Recent work introduced the concept of energy proportionality and argued that it is a more relevant metric than just energy saving as it takes into account the tradeoff between energy consumption and performance. In this paper, we present a novel approach, called FREP (Fractional Replication for Energy Proportionality), for energy management in large datacenters. FREP includes areplication strategy and basic functions to enable flexible energy management. Specifically, our method provides performance guarantees by adaptively controlling the power states of a group of disks based on observed and predicted workloads. Our experiments, using a set of real and synthetic traces, show that FREP dramatically reduces energy requirements with a minimal response time penalty.

Kim, Jinoh; Rotem, Doron

2010-09-09T23:59:59.000Z

266

PLANET-PLANET SCATTERING IN PLANETESIMAL DISKS  

Science Conference Proceedings (OSTI)

We study the final architecture of planetary systems that evolve under the combined effects of planet-planet and planetesimal scattering. Using N-body simulations we investigate the dynamics of marginally unstable systems of gas and ice giants both in isolation and when the planets form interior to a planetesimal belt. The unstable isolated systems evolve under planet-planet scattering to yield an eccentricity distribution that matches that observed for extrasolar planets. When planetesimals are included the outcome depends upon the total mass of the planets. For M {sub tot} {approx}> 1 M{sub J} the final eccentricity distribution remains broad, whereas for M {sub tot} {approx}< 1 M{sub J} a combination of divergent orbital evolution and recircularization of scattered planets results in a preponderance of nearly circular final orbits. We also study the fate of marginally stable multiple planet systems in the presence of planetesimal disks, and find that for high planet masses the majority of such systems evolve into resonance. A significant fraction leads to resonant chains that are planetary analogs of Jupiter's Galilean satellites. We predict that a transition from eccentric to near-circular orbits will be observed once extrasolar planet surveys detect sub-Jovian mass planets at orbital radii of a {approx_equal} 5-10 AU.

Raymond, Sean N. [Center for Astrophysics and Space Astronomy, 389 UCB, University of Colorado, Boulder, CO 80309 (United States); Armitage, Philip J. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Gorelick, Noel [Google, Inc., 1600 Amphitheatre Parkway, Mountain View, CA 94043 (United States)], E-mail: sean.raymond@colorado.edu

2009-07-10T23:59:59.000Z

267

Current Production Status of Alloy 718 Turbine Disks in China  

Science Conference Proceedings (OSTI)

For the past few years the production of high quality alloy 7 18 turbine disks has made great strides ... The main technology studies which led to the production of.

268

The Microstructure Prediction of Alloy 720LI for Turbine Disk ...  

Science Conference Proceedings (OSTI)

Applications, Supemhoys 1996, (1996), 697-703. 3. H.Hattori et al., Evaluation of PA4 U720 for Gas Turbine. Engine Disk Application, 2hpxalloys 1996, (1996) ...

269

Multiwavelength studies of accretion disks around compact objects  

E-Print Network (OSTI)

(cont.) to the XPS in SNR RCW 103. The multiple IR band measurements of 1E 1048.1-5937 provide marginal evidence for spectral flattening, and cannot rule out an accretion disk scenario for AXPs.

Wang, Zhongxiang, 1968-

2004-01-01T23:59:59.000Z

270

Controlling the collimation and rotation of hydromagnetic disk winds  

E-Print Network (OSTI)

(Abriged) We present a comprehensive set of axisymmetric, time-dependent simulations of jets from Keplerian disks whose mass loading as a function of disk radius is systematically changed. For a reasonable model for the density structure and injection speed of the underlying accretion disk, mass loading is determined by the radial structure of the disk's magnetic field structure. We vary this structure by using four different magnetic field configurations, ranging from the "potential" configuration (Ouyed&Pudritz 1997), to the increasingly more steeply falling Blandford&Payne (1982) and Pelletier&Pudritz (1992) models, and ending with a quite steeply raked configuration that bears similarities to the Shu X-wind model. We find that the radial distribution of the mass load has a profound effect on both the rotational profile of the underlying jet as well as the degree of collimation of its outflow velocity and magnetic field lines. We show analytically, and confirm by our simulations, that the colli...

Pudritz, R E; Ouyed, R; Pudritz, Ralph E.; Rogers, Conrad; Ouyed, Rachid

2006-01-01T23:59:59.000Z

271

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

272

A turnstile mechanism for fronts propagating in fluid flows  

E-Print Network (OSTI)

We consider the propagation of fronts in a periodically driven flowing medium. It is shown that the progress of fronts in these systems may be mediated by a turnstile mechanism akin to that found in chaotic advection. We first define the modified ("active") turnstile lobes according to the evolution of point sources across a transport boundary. We then show that the lobe boundaries may be constructed from stable and unstable \\emph{burning invariant manifolds}---one-way barriers to front propagation analogous to traditional invariant manifolds for passive advection. Because the burning invariant manifolds (BIMs) are one-dimensional curves in a three-dimensional ($xy\\theta$) phase space, their projection into $xy$-space exhibits several key differences from their advective counterparts: (lobe) areas are not preserved, BIMs may self-intersect, and an intersection between stable and unstable BIMs does not map to another such intersection. These differences must be accommodated in the correct construction of the new turnstile. As an application, we consider a lobe-based treatment protocol for protecting an ocean bay from an invading algae bloom.

John R. Mahoney; Kevin A. Mitchell

2013-05-22T23:59:59.000Z

273

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

E-Print Network (OSTI)

and the functional layers ­ a magnetic coating, anti-corrosion coating, protective coating and a lubricate layer: alterable magnetic disk packages; alterable information modules "Winchester"; magnetic disk packages magnetic disk packages represent in their essence one or more single magnetic disks with a hard substrate

Borissova, Daniela

274

Occluded Fronts and the Occlusion Process: A Fresh Look at Conventional Wisdom  

Science Conference Proceedings (OSTI)

Traditionally, the formation of an occluded front during the occlusion process in extratropical cyclones has been viewed as the catch-up of a faster-moving cold front to a slower-moving warm front separating the warm-sector air from the low center, as ...

David M. Schultz; Geraint Vaughan

2011-04-01T23:59:59.000Z

275

GASLESS COMBUSTION FRONTS WITH HEAT LOSS ANNA GHAZARYAN, STEPHEN SCHECTER, AND PETER L. SIMON  

E-Print Network (OSTI)

GASLESS COMBUSTION FRONTS WITH HEAT LOSS ANNA GHAZARYAN, STEPHEN SCHECTER, AND PETER L. SIMON Abstract. For a model of gasless combustion with heat loss, we use geometric singular perturbation theory to show existence of traveling combustion fronts. We show that the fronts are nonlinearly stable

Schecter, Stephen

276

Towards front-tracking based on conservation in two space dimensions III, tracking interfaces  

Science Conference Proceedings (OSTI)

This is the third paper in the series of our conservative front-tracking method. In this paper, we describe how our method tracks fluid interfaces in multi-fluid flows. Two important ingredients in our conservative front-tracking method in tracking fluid ... Keywords: Conservative front-tracking, Fluid interface, Numerical surface dissipation, Velocity and pressure equilibrium

Mohammed Aman Ullah, Wenbin Gao, De-Kang Mao

2013-06-01T23:59:59.000Z

277

Analysis of a Surface Front during the Early Summer Rainy Season over Taiwan  

Science Conference Proceedings (OSTI)

A case study of a relatively dry front during TAMEX IOP-4 is presented. At 0000 UTC 27 May, the broad cloud band extended from the China plain and southern Japan to east of 150E, along and north of the surface front. This front possessed ...

Yi-Leng Chen; Yu-Xia Zhang; Norman B-F. Hui

1989-05-01T23:59:59.000Z

278

THE GRAVO-MAGNETO LIMIT CYCLE IN ACCRETION DISKS  

Science Conference Proceedings (OSTI)

Previous theoretical studies have found that repeating outbursts can occur in certain regions of an accretion disk due to sudden transitions in time from gravitationally produced turbulence to magnetically produced turbulence. We analyze the disk evolution in a state diagram that plots the mass accretion rate versus disk surface density. We determine steady state accretion branches that involve gravitational and magnetic sources of turbulence. Using time-dependent numerical disk simulations, we show that cases having outbursts track along a nonsteady 'dead zone' branch and some steady state accretion branches. The outburst is the result of a rapid inter-branch transition. The gravo-magneto outbursts are then explained on this diagram as a limit cycle that is analogous to the well-known S-curve that has been applied to dwarf nova outbursts. The diagram and limit cycle provide a conceptual framework for understanding the nature of the outbursts that may occur in accretion disks of all scales, from circumplanetary to protoplanetary to active galactic nucleus accretion disks.

Martin, R. G.; Lubow, S. H. [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

2011-10-10T23:59:59.000Z

279

FORMATION OF ORGANIC MOLECULES AND WATER IN WARM DISK ATMOSPHERES  

Science Conference Proceedings (OSTI)

Observations from Spitzer and ground-based infrared spectroscopy reveal significant diversity in the molecular emission from the inner few AU of T Tauri disks. We explore theoretically the possible origin of this diversity by expanding on our earlier thermal-chemical model of disk atmospheres. We consider how variations in grain settling, X-ray irradiation, accretion-related mechanical heating, and the oxygen-to-carbon ratio can affect the thermal and chemical properties of the atmosphere at 0.25-40 AU. We find that these model parameters can account for many properties of the detected molecular emission. The column density of the warm (200-2000 K) molecular atmosphere is sensitive to grain settling and the efficiency of accretion-related heating, which may account, at least in part, for the large range in molecular emission fluxes that have been observed. The dependence of the atmospheric properties on the model parameters may also help to explain trends that have been reported in the literature between molecular emission strength and mid-infrared color, stellar accretion rate, and disk mass. We discuss whether some of the differences between our model results and the observations (e.g., for water) indicate a role for vertical transport and freezeout in the disk midplane. We also discuss how planetesimal formation in the outer disk (beyond the snowline) may imprint a chemical signature on the inner few AU of the disk and speculate on possible observational tracers of this process.

Najita, Joan R. [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Adamkovics, Mate; Glassgold, Alfred E. [Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2011-12-20T23:59:59.000Z

280

VERTICAL STRUCTURE OF NEUTRINO-DOMINATED ACCRETION DISKS AND NEUTRINO TRANSPORT IN THE DISKS  

SciTech Connect

We investigate the vertical structure of neutrino-dominated accretion disks by self-consistently considering the detailed microphysics, such as the neutrino transport, the vertical hydrostatic equilibrium, the conservation of lepton number, as well as the balance between neutrino cooling, advection cooling, and viscosity heating. After obtaining the emitting spectra of neutrinos and antineutrinos by solving the one-dimensional Boltzmann equation of neutrino and antineutrino transport in the disk, we calculate the neutrino/antineutrino luminosity and their annihilation luminosity. We find that the total neutrino and antineutrino luminosity is about 10{sup 54} erg s{sup -1} and their annihilation luminosity is about 5 Multiplication-Sign 10{sup 51} erg s{sup -1} with an extreme accretion rate 10 M{sub Sun} s{sup -1} and an alpha viscosity {alpha} = 0.1. In addition, we find that the annihilation luminosity is sensitive to the accretion rate and will not exceed 10{sup 50} erg s{sup -1}, which is not sufficient to power the fireball of most energetic gamma-ray bursts (GRBs) if the accretion rate is lower than 1 M{sub Sun} s{sup -1}. Therefore, the effects of the spin of the black hole or/and the magnetic field in the accretion flow might play a role in powering the central engine of GRBs.

Pan Zhen; Yuan Yefei, E-mail: yfyuan@ustc.edu.cn [Key Laboratory for Research in Galaxies and Cosmology CAS, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2012-11-10T23:59:59.000Z

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281

Effects of curvature and compressibility on the stability of thermal fronts  

Science Conference Proceedings (OSTI)

The stability of subsonic thermal fronts against corrugation is analyzed and an exact dispersion relation is obtained taking into account the effects of the curvature of the distorted front as well as the compressibility of the gas. At a certain value of the Mach number ahead of the thermal front, unstable rates show a maximum; these rates drop to zero when a Chapman-Jouguet regime is established behind heat fronts. It is shown that curvature effects tend to stabilize conductive heat fronts propagating in a compressible gas.

Ibanez S, Miguel H.; Bessega L, Maria C.; Shchekinov, Yuri [Centro de Fisica Fundamental, Facultad de Ciencias, Universidad de los Andes, Apartado 26, Ipostel, La Hechicera, Merida (Venezuela); Centro de Fisica Teorica y Computacional, Escuela de Fisica, Facultad de Ciencias, Universidad Central de Venezuela, Caracas (Venezuela); Department of Physics, University of Rostov, Rostov on Don, 34409 (Russian Federation)

2006-06-15T23:59:59.000Z

282

Activation, Heating and Exposure Rates for Mo?99 Experiments with 25?Disk Targets  

Science Conference Proceedings (OSTI)

An MCNPX model of the 25-disk target assembly inside the vacuum cube inside the shielded box was prepared. This was used to calculate heating and photon and neutron fluxes throughout the model. Production rates for photonuclear reaction products were calculated using the photon fluxes and ENDF/B-VII cross sections. Measured isomer to ground state yield ratios were used where available. Where not available the new correlation between spin deficit and isomer to ground state yield ratios presented at AccApp'11 was used. The photonuclear production rates and neutron fluxes were input to CINDER2008 for transmutation calculations. A cross section update file was used to supply (n,n') reactions missing from CINDER2008 libraries. Decay photon spectra produced by CINDER2008 were then used to calculate exposure rates using the MCNPX model. Two electron beam irradiations were evaluated. The first was for a thermal test at 15 MeV with 1300 {micro}A incident on one target end and the second was for a production test at 35 MeV with 350 {micro}A incident on both target ends (700 {micro}A total current on target). For the thermal test 1, 2, 3, 4, 5 and 6 h irradiation times were simulated, each followed by decay time steps out to 42 days. For the production test 6, 12, 18, 24, 30 and 36 h irradiation times were simulated followed by the same decay periods. For all simulations beam FWHMs in x and y were both assumed to be 6 mm. Simulations were run for Mo-100 enriched and natural Mo targets for both tests. It is planned that thermal test will be run for 4 h with natural target disks and production test will be run for 24 h with enriched target disks. Results for these two simulations only are presented in this report. Other results can be made available upon request. Post irradiation exposure rates were calculated at 30 cm distances from left, right, front and back of the following configurations: (1) Shielded box with everything in it (beam pipes, cooling pipes, vacuum cube, target housing weldment and target assembly), (2) Shielded box with everything in it except the target assembly, (3) Shielded box with nothing in it, (4) Target assembly taken outside of shielded box, (5) Target disks in cradle (target assembly with thermocouple weldment and flange removed), (6) Empty cradle, and (7) Target disks alone. Decay photon spectra from the CINDER2008 calculations were used as sources for the exposure rate calculations in the same model used for the flux calculations with beam on. As components were removed to simulate the seven cases considered the material compositions were changed to air and their respective sources were turned off. The MCNPX model geometry is plotted in Figure 1. The left and right detector locations for cases 1, 2 and 3 were 30 cm from the shielded box walls and 30 cm from the beam pipe openings in the left and right sides of the model (they are not in the beam line). A zoomed in plot of the target assembly alone is in Figure 2. Exposure rates for the seven cases are plotted as a function of time after irradiation in Figures 3, 4 and 5. To aid in comparison between the cases, all of these figures have been plotted using the same scale. Figures 3 and 4 are respectively the thermal and production test results for cases 1 through 6. Figure 5 includes case 7 results for both. Differences between cases 1 and 2 for both tests are not statistically significant showing that activation of components other than the target assembly, many of which are also shielding the target assembly, dominates exposure rates outside the shielded box. Case 3 shows the contribution from activation of the shield box itself. In front where shielded box wall is thickest box activation accounts for essentially all of the exposure rate outside. Differences between cases 4 and 5 are also minimal, showing that the contribution to target assembly exposure rates from the thermocouple flange and weldment are small compared to the target disks and cradle. From the numerical results the contribution is about 1%. Results for case 6, the cradle itself, are ini

Kelsey, Charles T. IV [Los Alamos National Laboratory

2012-05-09T23:59:59.000Z

283

Instrument Front-Ends at Fermilab During Run II  

SciTech Connect

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

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

2011-07-13T23:59:59.000Z

284

Protective coatings for front surface reflectors. Phase I, final report  

DOE Green Energy (OSTI)

Silicone resins were evaluated as protective coatings for front surface aluminum and silver reflectors. The solar weighted hemispherical reflectances and specular reflectances of float glass squares metallized with silver and aluminum and protected with silicone coatings were measured. The float glass squares metallized with silver and aluminum were highly reflective. The total reflectances of the silver samples were 5 to 7% higher than the aluminized samples. The resin coated aluminum samples were much more specular than the silver samples. Coupling agents used to improve the adhesion of the protective silicone resin coating to the silver surface adversely affected the specularities.

Dennis, W.E.

1979-09-01T23:59:59.000Z

285

Multilayer coatings for the EUVL front-end test bed  

SciTech Connect

Good illumination uniformity at the mask and wafer planes, and high wafer thoroughput in the EUVL front-end test bed facility at LLNL require graded period multilayer (ML) coatings on several of the optics. The ML deposition was accomplished using a newly developed deposition technique which avoids the use of {open_quotes}uniformity masks{close_quotes} to define the spatial dependence of the ML period variation. The capabilities of the process in providing the specified ML coatings are discussed for both EUVL condenser and imaging systems.

Vernon, S.P.; Carey, M.J.; Gaines, D.P.; Weber, F.J.

1995-01-19T23:59:59.000Z

286

Energy Loss at Propagating Jamming Fronts in Granular Gas Clusters  

E-Print Network (OSTI)

We explore the initial moments of impact between two dense granular clusters in a two-dimensional geometry. The particles are composed of solid CO$_{2}$ and are levitated on a hot surface. Upon collision, the propagation of a dynamic "jamming front" produces a distinct regime for energy dissipation in a granular gas in which the translational kinetic energy decreases by over 90%. Experiments and associated simulations show that the initial loss of kinetic energy obeys a power law in time, $\\Delta E=-Kt^{3/2}$, a form that can be predicted from kinetic arguments.

Justin C. Burton; Peter Y. Lu; Sidney R. Nagel

2013-06-12T23:59:59.000Z

287

MAGNETOROTATIONAL-INSTABILITY-DRIVEN ACCRETION IN PROTOPLANETARY DISKS  

Science Conference Proceedings (OSTI)

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

288

Disk magnetohydrodynamic power conversion system for NERVA reactor  

Science Conference Proceedings (OSTI)

The combination of a magnetohydrodynamic (MHD) generator of the disk type with a NERVA reactor yields an advanced power system particularly suited to space applications with the capability of producing up to gigawatt pulses and multi-megawatt continuous operation. Several unique features result from the combination of this type of reactor and a disk MHD generator in which hydrogen serves as the plasma working fluid. Cesium seedings is utilized under conditions which enable the generator to operate stably in the non-equilibrium electrical conduction mode. In common with all practical MHD generators, the disk output is DC and voltages in the range 20--100 kV are attainable. This leads to a simplification of the power conditioning system and a major reduction in specific mass. Taken together with the high performance capabilities of the NERVA reactor, the result is an attractively low overall system specific mass. Further, the use of non-equilibrium ionization enables system specific enthalpy extractions in excess of 40% to be attained. This paper reports the results of a study to establish the basis for the design of a cesium seeded hydrogen MHD disk generator. Generator performance results are presented in terms of a stability factor which is related to cesium seeded hydrogen plasma behavior. It is shown that application of the results already obtained with cesium seeded noble gases (argon and helium) to the case of hydrogen as the working fluid in a disk MHD generator enables a high performance power system to be defined.

Jackson, W.D. (HMJ Corporation. 10400 Connecticut Ave., Kensington, Maryland 20895 (United States)); Bernard, F.E. (Westinghouse Corp., P.O. Box 355, Pittsburgh, Pennsylvania 15230 (United States)); Holman, R.R. (HMJ Corporation, 10400 Connecticut Ave., Kensington, Maryland 20895 (United States)); Maxwell, C.D. (STD Research Corp., P.O. Box C, Arcadia, California 91006 (United States)); Seikel, G.R. (SeiTec, Inc., P.O. Box 81264, Cleveland, Ohio 44181 (United States))

1993-01-15T23:59:59.000Z

289

Gas phase water in the surface layer of protoplanetary disks  

E-Print Network (OSTI)

Recent observations of the ground state transition of HDO at 464 GHz towards the protoplanetary disk of DM Tau have detected the presence of water vapor in the regions just above the outer disk midplane (Ceccarelli et al 2005). In the absence of non-thermal desorption processes, water should be almost entirely frozen onto the grain mantles and HDO undetectable. In this Letter we present a chemical model that explores the possibility that the icy mantles are photo-desorbed by FUV (6eV water vapor above the disk midplane over the entire disk. Assuming a photo-desorption yield of 10^{-3}, the water abundance in this layer is predicted to be ~ 3 x 10^{-7} and the average H2O column density is ~ 1.6x 10^{15} cm^{-2}. The predictions are very weakly dependent on the details of the model, like the incident FUV radiation field, and the gas density in the disk. Based on this model, we predict a gaseous HDO/H2O ratio in DM Tau of ~1%. In addition, we predict the ground state transition of water at 557 GHz to be undetectable with ODIN and/or HSO-HIFI.

C. Dominik; C. Ceccarelli; D. Hollenbach; M. Kaufman

2005-10-21T23:59:59.000Z

290

The Relative Age of the Thin and Thick Galactic Disks  

E-Print Network (OSTI)

We determine the relative ages of the open cluster NGC 188 and selected Hipparcos field stars by isochrone fitting, and compare them to the age of the thick disk globular cluster 47 Tuc. The best fit age for NGC 188 was determined to be $6.5 \\pm 1.0$ Gyr. The solar metallicity Hipparcos field stars yielded a slightly older thin disk age, $7.5 \\pm 0.7$ Gyr. Two slightly metal-poor ($\\feh = -0.22$) field stars whose kinematic and orbital parameters indicate that they are members of the thin disk were found to have an age of $9.7\\pm 0.6$ Gyr. The age for 47 Tuc was determined to be $12.5 \\pm 1.5$ Gyr. All errors are internal errors due to the uncertainty in the values of metallicity and reddening. Thus, the oldest stars dated in the thin disk are found to be $2.8\\pm 1.6$ Gyr younger than 47 Tuc. Furthermore, as discussed by \\citet{Chb99} 47 Tuc has a similar age to three globular clusters located in the inner part of the Galactic halo, implying that star formation in the thin disk started within $2.8\\pm 1.6$ Gyr of star formation in the halo.

Wilson M. Liu; Brian Chaboyer

2000-07-13T23:59:59.000Z

291

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

292

FITDisk: A Cataclysmic Variable Accretion Disk Demonstration Tool  

E-Print Network (OSTI)

We present the software tool FITDisk, a precompiled-binary Windows GUI version of our smoothed particle hydrodynamics cataclysmic variable accretion disk research code. Cataclysmic variables are binary star systems in which a compact stellar remnant, typically a white dwarf star, is stripping mass from a lower-main-sequence companion star by way of an accretion disk. Typically the disk is the brightest component of the system, because the plasma is heated dramatically as it spirals down in the gravitational well of the primary white dwarf star. The shortest-period systems can display disk "superhump" oscillations driven by the rotating tidal field of the secondary star. FITDisk models these accretion disk phenomena using a fully three-dimensional hydrodynamics calculation, and data can be visualized as they are computed or stored to hard drive for later playback at a fast frame rate. Simulations are visualized using OpenGL graphics and the viewing angle can be changed interactively. Pseudo light curves of sim...

Wood, M A; Simpson, J C; Wood, Matt A.; Dolence, Josh; Simpson, James C.

2005-01-01T23:59:59.000Z

293

FITDisk: A Cataclysmic Variable Accretion Disk Demonstration Tool  

E-Print Network (OSTI)

We present the software tool FITDisk, a precompiled-binary Windows GUI version of our smoothed particle hydrodynamics cataclysmic variable accretion disk research code. Cataclysmic variables are binary star systems in which a compact stellar remnant, typically a white dwarf star, is stripping mass from a lower-main-sequence companion star by way of an accretion disk. Typically the disk is the brightest component of the system, because the plasma is heated dramatically as it spirals down in the gravitational well of the primary white dwarf star. The shortest-period systems can display disk "superhump" oscillations driven by the rotating tidal field of the secondary star. FITDisk models these accretion disk phenomena using a fully three-dimensional hydrodynamics calculation, and data can be visualized as they are computed or stored to hard drive for later playback at a fast frame rate. Simulations are visualized using OpenGL graphics and the viewing angle can be changed interactively. Pseudo light curves of simulated systems can be plotted along with the associated Fourier amplitude spectrum. FITDisk is available for free download at www.astro.fit.edu/cv/fitdisk.html.

Matt A. Wood; Josh Dolence; James C. Simpson

2005-11-11T23:59:59.000Z

294

SPH Simulations of Accretion Disks and Narrow Rings  

E-Print Network (OSTI)

We model a massless viscous disk using Smoothed Particle Hydrodynamics (SPH) and note that it evolves according to the Lynden-Bell \\& Pringle theory (1974) until a non-axisymmetric instability develops at the inner edge of the disk. This instability may have the same origin as the instability of initially axisymmetric viscous disks discussed by Lyubarskij et al. (1994). To clarify the evolution we evolved single and double rings of particles. It is actually inconsistent with the SPH scheme to set up a single ring as an initial condition because SPH assumes a smoothed initial state. As would be expected from an SPH simulation, the ring rapidly breaks up into a band. We analyse the stability of the ring and show that the predictions are confirmed by the simulation.

Sarah T. Maddison; James R. Murray; Joe J. Monaghan

1995-07-12T23:59:59.000Z

295

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

296

Disk Planet Interactions and Early Evolution in Young Planetary Systems  

E-Print Network (OSTI)

We study and review disk protoplanet interactions using local shearing box simulations. These suffer the disadvantage of having potential artefacts arising from periodic boundary conditions but the advantage, when compared to global simulations, of being able to capture much of the dynamics close to the protoplanet at high resolution for low computational cost. Cases with and without self sustained MHD turbulence are considered. The conditions for gap formation and the transition from type I migration are investigated and found to depend on whether the single parameter M_p R^3/(M_* H^3), with M_p, M_*, R and H being the protoplanet mass, the central mass, the orbital radius and the disk semi-thickness respectively exceeds a number of order unity. We also investigate the coorbital torques experienced by a moving protoplanet in an inviscid disk. This is done by demonstrating the equivalence of the problem for a moving protoplanet to one where the protoplanet is in a fixed orbit which the disk material flows through radially as a result of the action of an appropriate external torque. For sustainable coorbital torques to be realized a quasi steady state must be realized in which the planet migrates through the disk without accreting significant mass. In that case although there is sensitivity to computational parameters, in agreement with earlier work by Masset & Papaloizou (2003) based on global simulations, the coorbital torques are proportional to the migration speed and result in a positive feedback on the migration, enhancing it and potentially leading to a runaway. This could lead to a fast migration for protoplanets in the Saturn mass range in massive disks and may be relevant to the mass period correlation for extrasolar planets which gives a preponderance of sub Jovian masses at short orbital period.

J. C. B. Papaloizou

2004-12-30T23:59:59.000Z

297

THE STRUCTURE OF GRAVITATIONALLY UNSTABLE GAS-RICH DISK GALAXIES  

Science Conference Proceedings (OSTI)

We use a series of idealized, numerical smoothed particle hydrodynamics simulations to study the formation and evolution of galactic, gas-rich disks forming from gas infall within dark matter halos. The temperature and density structure of the gas is varied in order to differentiate between (1) simultaneous gas infall at a large range of radii and (2) the inside-out buildup of a disk. In all cases, the disks go through phases of ring formation, gravitational instability and break-up into massive clumps. Ring formation can be enhanced by a focal point effect. The position of the ring is determined by the angular momentum distribution of the material it forms from. We study the ring and clump morphologies, the characteristic properties of the resulting velocity dispersion field and the effect of star formation. In the early phases, gas accretion leads to a high vertical velocity dispersion. We find that the disk fragmentation by gravitational instability and the subsequent clump-clump interactions drive high velocity dispersions mainly in the plane of the disk while at the same time the vertical velocity dispersion dissipates. The result is a strong variation of the line-of-sight velocity dispersion with inclination angle. For a face-on view, clumps appear as minima in the (vertical) dispersion, whereas for a more edge-on view, they tend to correspond to maxima. There exists observational evidence of a systematic variation of the velocity dispersion with inclination angle in high-redshift disks, which could be partly explained by our simulation results. Additional energetic sources to drive velocity dispersion that are not included in our models are also expected to contribute to the observational results.

Aumer, Michael; Burkert, Andreas; Johansson, Peter H. [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, D-81679 Muenchen (Germany); Genzel, Reinhard, E-mail: aumer@usm.lmu.d, E-mail: burkert@usm.lmu.d, E-mail: pjohan@usm.lmu.d, E-mail: genzel@mpe.mpg.d [UC Berkeley Department of Physics, Berkeley, CA 94720 (United States)

2010-08-20T23:59:59.000Z

298

MIGRATION OF GAS GIANT PLANETS IN GRAVITATIONALLY UNSTABLE DISKS  

Science Conference Proceedings (OSTI)

Characterization of migration in gravitationally unstable disks is necessary to understand the fate of protoplanets formed by disk instability. As part of a larger study, we are using a three-dimensional radiative hydrodynamics code to investigate how an embedded gas giant planet interacts with a gas disk that undergoes gravitational instabilities (GIs). This Letter presents results from simulations with a Jupiter-mass planet placed in orbit at 25 AU within a 0.14 M{sub sun} disk. The disk spans 5-40 AU around a 1 M{sub sun} star and is initially marginally unstable. In one simulation, the planet is inserted prior to the eruption of GIs; in another, it is inserted only after the disk has settled into a quasi-steady GI-active state, where heating by GIs roughly balances radiative cooling. When the planet is present from the beginning, its own wake stimulates growth of a particular global mode with which it strongly interacts, and the planet plunges inward 6 AU in about 10{sup 3} years. In both cases with embedded planets, there are times when the planet's radial motion is slow and varies in direction. At other times, when the planet appears to be interacting with strong spiral modes, migration both inward and outward can be relatively rapid, covering several AUs over hundreds of years. Migration in both cases appears to stall near the inner Lindblad resonance of a dominant low-order mode. Planet orbit eccentricities fluctuate rapidly between about 0.02 and 0.1 throughout the GI-active phases of the simulations.

Michael, Scott; Durisen, Richard H. [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Boley, Aaron C., E-mail: scamicha@indiana.edu, E-mail: durisen@astro.indiana.edu, E-mail: aaron.boley@gmail.com [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)

2011-08-20T23:59:59.000Z

299

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

300

On Why Disks Generate Magnetic Towers and Collimate Jets  

E-Print Network (OSTI)

We show that accretion disks with magnetic fields in them ought to make jets provided that their electrical conductivity prevents slippage and there is an ambient pressure in their surroundings. We study equilibria of highly wound magnetic structures. General Energy theorems demonstrate that they form tall magnetic towers whose height grows with every turn at a velocity related to the circular velocity in the accretion disk. The pinch effect amplifies the magnetic pressures toward the axis of the towers whose stability is briefly considered.

D Lynden-Bell

2002-08-21T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

On Why Disks Generate Magnetic Towers and Collimate Jets  

E-Print Network (OSTI)

We show that accretion disks with magnetic fields in them ought to make jets provided that their electrical conductivity prevents slippage and there is an ambient pressure in their surroundings. We study equilibria of highly wound magnetic structures. General Energy theorems demonstrate that they form tall magnetic towers whose height grows with every turn at a velocity related to the circular velocity in the accretion disk. The pinch effect amplifies the magnetic pressures toward the axis of the towers whose stability is briefly considered.

Lynden-Bell, Donald

2002-01-01T23:59:59.000Z

302

Light-Front Holography and QCD Hadronization at the Amplitude Level  

E-Print Network (OSTI)

Light-front holography allows hadronic amplitudes in the AdS/QCD fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The AdS coordinate z is identified with an invariant light-front coordinate zeta which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schrodinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. A new method for computing the hadronization of quark and gluon jets at the amplitude level using AdS/QCD light-front wavefunctions is outlined.

Stanley J. Brodsky; Guy de Teramond

2009-01-07T23:59:59.000Z

303

Evolutionary algorithm for the neutrino factory front end design  

Science Conference Proceedings (OSTI)

The Neutrino Factory is an important tool in the long-term neutrino physics program. Substantial effort is put internationally into designing this facility in order to achieve desired performance within the allotted budget. This accelerator is a secondary beam machine: neutrinos are produced by means of the decay of muons. Muons, in turn, are produced by the decay of pions, produced by hitting the target by a beam of accelerated protons suitable for acceleration. Due to the physics of this process, extra conditioning of the pion beam coming from the target is needed in order to effectively perform subsequent acceleration. The subsystem of the Neutrino Factory that performs this conditioning is called Front End, its main performance characteristic is the number of the produced muons.

Poklonskiy, Alexey A.; /Michigan State U.; Neuffer, David; /Fermilab

2009-01-01T23:59:59.000Z

304

The Diskionary: A Glossary of Terms Commonly Used for Disks and Related Objects, First Edition  

E-Print Network (OSTI)

Based on a panel discussion at the meeting "New Light on Young Stars: Spitzer's View of Circumstellar Disks", we provide some definitions of common usage of terms describing disks and related objects.

Evans, Neal; Cieza, Lucas; Forbrich, Jan; Hillenbrand, Lynne; Lada, Charlie; Mern, Bruno; Strom, Steve; Watson, Dan

2009-01-01T23:59:59.000Z

305

Flow and heat transfer in gas turbine disk cavities subject to nonuniform external pressure field  

SciTech Connect

Ingestion of hot gas from the main-stream gas path into turbine disk cavities, particularly the first-stage disk cavity, has become a serious concern for the next-generation industrial gas turbines features high rotor inlet temperature. Fluid temperature in the cavities increases further due to windage generated by fluid drag at the rotating and stationary surfaces. The resulting problem of rotor disk heat-up is exacerbated by the high disk rim temperature due to adverse (relatively flat) temperature profile of the mainstream gas in the annular flow passage of the turbine. This describes an investigation into local convective heat transfer coefficient and cooling effectiveness of the rotor disk, flow field in the disk cavity, computation of the flow field and heat transfer in the disk cavity, and mainstream gas injection and rotor disk cooling effectiveness by mass transfer analogy.

Roy, R.P.; Kim, Y.W.; Tong, T.W. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering

1995-12-31T23:59:59.000Z

306

Commissioning of the SNS front-end systems at Berkeley Lab  

E-Print Network (OSTI)

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

2002-01-01T23:59:59.000Z

307

Front Row (left to right): Bryan Reed, Wayne King, Nigel Browning ...  

DTEM Team Members: Front Row (left to right): Bryan Reed, Wayne King, Nigel Browning, Judy Kim, Michael Armstrong Back Row (left to right): Thomas LaGrange ...

308

Recursion relations and scattering amplitudes in the light-front formalism  

E-Print Network (OSTI)

The fragmentation functions and scattering amplitudes are investigated in the framework of light-front perturbation theory. It is demonstrated that, the factorization property of the fragmentation functions implies the recursion relations for the off-shell scattering amplitudes which are light-front analogs of the Berends-Giele relations. These recursion relations on the light-front can be solved exactly by induction and it is shown that the expressions for the off-shell light-front amplitudes are represented as a linear combinations of the on-shell amplitudes. By putting external particles on-shell we recover the scattering amplitudes previously derived in the literature.

Christian A. Cruz-Santiago; Anna M. Stasto

2013-08-05T23:59:59.000Z

309

Factors controlling streambed coverage of Didymosphenia geminata in two regulated streams in the Colorado Front Range  

E-Print Network (OSTI)

of dissolved substances from a Colorado mountain watershed.11: CDOT, 2009. Colorado Department of Transportation.two regulated streams in the Colorado Front Range Matthew P.

Miller, Matthew P.; McKnight, Diane M.; Cullis, James D.; Greene, Alicia; Vietti, Kristin; Liptzin, Daniel

2009-01-01T23:59:59.000Z

310

Nonlinear fibre-optic devices pumped by semiconductor disk lasers  

Science Conference Proceedings (OSTI)

Semiconductor disk lasers offer a unique combination of characteristics that are particularly attractive for pumping Raman lasers and amplifiers. The advantages of disk lasers include a low relative noise intensity (-150 dB Hz{sup -1}), scalable (on the order of several watts) output power, and nearly diffraction-limited beam quality resulting in a high ({approx}70 % - 90 %) coupling efficiency into a single-mode fibre. Using this technology, low-noise fibre Raman amplifiers operating at 1.3 {mu}m in co-propagation configuration are developed. A hybrid Raman-bismuth doped fibre amplifier is proposed to further increase the pump conversion efficiency. The possibility of fabricating mode-locked picosecond fibre lasers operating under both normal and anomalous dispersion is shown experimentally. We demonstrate the operation of 1.38-{mu}m and 1.6-{mu}m passively mode-locked Raman fibre lasers pumped by 1.29-{mu}m and 1.48-{mu}m semiconductor disk lasers and producing 1.97- and 2.7-ps pulses, respectively. Using a picosecond semiconductor disk laser amplified with an ytterbium-erbium fibre amplifier, the supercontinuum generation spanning from 1.35 {mu}m to 2 {mu}m is achieved with an average power of 3.5 W. (invited paper)

Chamorovskiy, A Yu; Okhotnikov, Oleg G [Optoelectronics Research Center, Tampere University of Technology, Tampere (Finland)

2012-11-30T23:59:59.000Z

311

ACCRETION DISKS IN TWO-DIMENSIONAL HOYLE-LYTTLETON FLOW  

SciTech Connect

We investigate the flip-flop instability observed in two-dimensional planar hydrodynamic simulations of Hoyle-Lyttleton accretion in the case of an accreting object with a radius much smaller than the nominal accretion radius, as one would expect in astrophysically relevant situations. Contrary to previous results with larger accretors, accretion from a homogenous medium onto a small accretor is characterized by a robust, quasi-Keplerian accretion disk. For gas with a ratio of specific heats of 5/3, such a disk remains locked in one direction for a uniform ambient medium. The accretion flow is more variable for gas with a ratio of specific heats of 4/3, with more dynamical interaction of the disk flow with the bow shock leading to occasional flips in the direction of rotation of the accretion disk. In both cases the accretion of angular momentum is determined by the flow pattern behind the accretion shock rather than by the parameters of the upstream flow.

Blondin, John M., E-mail: John_Blondin@ncsu.edu [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)

2013-04-20T23:59:59.000Z

312

Optimizing disk storage to support statistical analysis operations  

Science Conference Proceedings (OSTI)

Data stored in spreadsheets and relational database tables can be viewed as "worksheets" consisting of rows and columns, with rows corresponding to records. Correspondingly, the typical practice is to store the data on disk in row major order. While ... Keywords: business intelligence tools, data mining, data warehouses, database systems, statistical tools

Allen Parrish; Susan Vrbsky; Brandon Dixon; Weigang Ni

2005-01-01T23:59:59.000Z

313

VARIABILITY OF THE INFRARED EXCESS OF EXTREME DEBRIS DISKS  

SciTech Connect

Debris disks with extremely large infrared excesses (fractional luminosities >10{sup -2}) are rare. Those with ages between 30 and 130 Myr are of interest because their evolution has progressed well beyond that of protoplanetary disks (which dissipate with a timescale of order 3 Myr), yet they represent a period when dynamical models suggest that terrestrial planet building may still be progressing through large, violent collisions that could yield large amounts of debris and large infrared excesses. For example, our Moon was formed through a violent collision of two large protoplanets during this age range. We report two disks around the solar-like stars ID8 and HD 23514 in this age range where the 24 {mu}m infrared excesses vary on timescales of a few years, even though the stars are not variable in the optical. Variations this rapid are difficult to understand if the debris is produced by collisional cascades, as it is for most debris disks. It is possible that the debris in these two systems arises in part from condensates from silicate-rich vapor produced in a series of violent collisions among relatively large bodies. If their evolution is rapid, the rate of detection of extreme excesses would indicate that major collisions may be relatively common in this age range.

Meng, Huan Y. A.; Rieke, George H. [Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Su, Kate Y. L.; Rujopakarn, Wiphu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Ivanov, Valentin D. [European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, Santiago, 19001 (Chile); Vanzi, Leonardo [Department of Electrical Engineering and Center of Astro Engineering, Pontificia Universidad Catolica de Chile, Ave. Vicuna Mackenna 4860, Santiago (Chile)

2012-05-20T23:59:59.000Z

314

A Simple Family of Models for Eccentric Keplerian Fluid Disks  

E-Print Network (OSTI)

In order to be in a long-lived configuration, the density in a fluid disk should be constant along streamlines to prevent compressional (PdV) work from being done cyclically around every orbit. In a pure Kepler potential, flow along aligned, elliptical streamlines of constant eccentricity will satisfy this condition. For most density profiles, differential precession driven by the pressure gradient will destroy the alignment; however, in the razor-thin approximation there is a family of simple equilibria in which the precession frequency is the same at all radii. These disks may therefore be long-lived at significant eccentricities. The density can be made axisymmetric as r goes to 0, while maintaining the precession rate, by relaxing the requirement of constancy along streamlines in an arbitrarily small transition region near the center. In the limit of small eccentricity, the models can be seen as acoustically perturbed axisymmetric disks, and the precession rate is shown to agree with linear theory. The perturbation is a traveling wave similar to an ocean wave, with the fluid rising and falling epicyclically in the gravitational field of the central mass. The expected emission line profiles from the eccentric disks are shown to be strongly asymmetric in general, and, in extreme cases, prone to misinterpretation as single narrow lines with significant velocity offsets.

T. S. Statler

2001-08-06T23:59:59.000Z

315

MHV Fleet Testing - Maintenance Sheet for 2010 Smart Fortwo  

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

472012 47,544 Changed oil and filter 64.33 4112012 47,840 Replaced left front tire (labor) 45.00 4122012 47,847 Replaced front brake pads, adjusted rear brake shoes...

316

A UNIVERSAL NEUTRAL GAS PROFILE FOR NEARBY DISK GALAXIES  

SciTech Connect

Based on sensitive CO measurements from HERACLES and H I data from THINGS, we show that the azimuthally averaged radial distribution of the neutral gas surface density ({Sigma}{sub HI}+ {Sigma}{sub H2}) in 33 nearby spiral galaxies exhibits a well-constrained universal exponential distribution beyond 0.2 Multiplication-Sign r{sub 25} (inside of which the scatter is large) with less than a factor of two scatter out to two optical radii r{sub 25}. Scaling the radius to r{sub 25} and the total gas surface density to the surface density at the transition radius, i.e., where {Sigma}{sub HI} and {Sigma}{sub H2} are equal, as well as removing galaxies that are interacting with their environment, yields a tightly constrained exponential fit with average scale length 0.61 {+-} 0.06 r{sub 25}. In this case, the scatter reduces to less than 40% across the optical disks (and remains below a factor of two at larger radii). We show that the tight exponential distribution of neutral gas implies that the total neutral gas mass of nearby disk galaxies depends primarily on the size of the stellar disk (influenced to some degree by the great variability of {Sigma}{sub H2} inside 0.2 Multiplication-Sign r{sub 25}). The derived prescription predicts the total gas mass in our sub-sample of 17 non-interacting disk galaxies to within a factor of two. Given the short timescale over which star formation depletes the H{sub 2} content of these galaxies and the large range of r{sub 25} in our sample, there appears to be some mechanism leading to these largely self-similar radial gas distributions in nearby disk galaxies.

Bigiel, F. [Institut fuer theoretische Astrophysik, Zentrum fuer Astronomie der Universitaet Heidelberg, Albert-Ueberle Str. 2, D-69120 Heidelberg (Germany); Blitz, L., E-mail: bigiel@uni-heidelberg.de [Department of Astronomy, Radio Astronomy Laboratory, University of California at Berkeley, CA 94720 (United States)

2012-09-10T23:59:59.000Z

317

GALACTIC ULTRACOMPACT X-RAY BINARIES: DISK STABILITY AND EVOLUTION  

SciTech Connect

We study the mass-transfer rates and disk stability conditions of ultracompact X-ray binaries (UCXBs) using empirical time-averaged X-ray luminosities from Paper I and compiled information from the literature. The majority of UCXBs are consistent with evolutionary tracks for white dwarf donors. Three UCXBs with orbital periods longer than 40 minutes have mass-transfer rates above 10{sup -10} M{sub Sun} yr{sup -1}, inconsistent with white dwarf donor tracks. We show that if helium star donors can retain their initial high entropy, they can explain the observed mass-transfer rates of these UCXBs. Several UCXBs show persistent luminosities apparently below the disk instability limit for irradiated He accretion disks. We point out that a predominantly C and/or O disk (as observed in the optical spectra of several) lowers the disk instability limit, explaining this disagreement. The orbital period and low time-averaged mass-transfer rate of 2S 0918-549 provide evidence that the donor star is a low-entropy C/O white dwarf, consistent with optical spectra. We combine existing information to constrain the masses of the donors in 4U 1916-053 (0.064 {+-} 0.010 M{sub Sun }) and 4U 1626-67 (<0.036 M{sub Sun} for a 1.4 M{sub Sun} neutron star). We show that 4U 1626-67 is indeed persistent, and not undergoing a transient outburst, leaving He star models as the best explanation for the donor.

Heinke, C. O.; Ivanova, N.; Engel, M. C.; Pavlovskii, K.; Sivakoff, G. R.; Gladstone, J. C. [Physics Department, University of Alberta, 4-183 CCIS, Edmonton, AB T6G 2E1 (Canada); Cartwright, T. F., E-mail: heinke@ualberta.ca [International Space University, 1 rue Jean-Dominique Cassini, 67400 Illkirch-Graffenstaden (France)

2013-05-10T23:59:59.000Z

318

Forced oscillations in a hydrodynamical accretion disk and QPOs  

E-Print Network (OSTI)

This is the second of a series of papers aimed to look for an explanation on the generation of high frequency quasi-periodic oscillations (QPOs) in accretion disks around neutron star, black hole, and white dwarf binaries. The model is inspired by the general idea of a resonance mechanism in the accretion disk oscillations as was already pointed out by Abramowicz & Klu{\\'z}niak (\\cite{Abramowicz2001}). In a first paper (P\\'etri \\cite{Petri2005a}, paper I), we showed that a rotating misaligned magnetic field of a neutron star gives rise to some resonances close to the inner edge of the accretion disk. In this second paper, we suggest that this process does also exist for an asymmetry in the gravitational potential of the compact object. We prove that the same physics applies, at least in the linear stage of the response to the disturbance in the system. This kind of asymmetry is well suited for neutron stars or white dwarfs possessing an inhomogeneous interior allowing for a deviation from a perfectly spherically symmetric gravitational field. We show by a linear analysis that the disk initially in a cylindrically symmetric stationary state is subject to three kinds of resonances: a corotation resonance, a Lindblad resonance due to a driven force and a parametric sonance. The highest kHz QPOs are then interpreted as the orbital frequency of the disk at locations where the response to the resonances are maximal. It is also found that strong gravity is not required to excite the resonances.

J. Petri

2005-09-22T23:59:59.000Z

319

Active learning based intervertebral disk classification combining shape and texture similarities  

Science Conference Proceedings (OSTI)

We consider the problem of the computer aided diagnosis on intervertebral disk degeneration in this paper, where a framework of classifying the disks into healthy and degenerated groups is proposed. First, we propose to separately model the shape and ... Keywords: Active learning, Computer aided diagnosis, Intervertebral disk degeneration, Shape, Texture

Shijie Hao; Jianguo Jiang; Yanrong Guo; Hong Li

2013-02-01T23:59:59.000Z

320

Thin superconducting disk with field-dependent critical current: Magnetization and ac susceptibilities  

E-Print Network (OSTI)

Thin superconducting disk with field-dependent critical current: Magnetization and ac of a superconducting thin disk are calculated in the critical-state model assuming a field-dependent critical current for the flux and current distributions Phys. Rev. B 60, 13 112 1999 for a disk placed in a perpendicular

Johansen, Tom Henning

Note: This page contains sample records for the topic "front 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

Dust distribution in disks supplied by small bodies: Is the Beta Pictoris disk a gigantic multi-cometary tail?  

E-Print Network (OSTI)

We have evaluated the spatial distribution of dust in disks supplied by colliding or evaporating bodies spread in a small belt. The gradient of the distribution of dust expelled by radiation pressure is generally steeper than the one observed around \\bp. It follows that, to generate the \\bp\\ disk distribution in such a way, one should extract relatively more small particles in the production process: thanks to radiation forces, these smaller particles have large eccentricities and thus could be seen at very large distances from their injection place. The evaporation process of comet-like bodies moving slowly inwards may yield the necessary particle size distribution. It is interesting to note that this dynamical description is able to account for the main observational properties of the \\bp\\ disk, such as the power law distribution with possibly a change in slope, the asymmetry at large distances, and the total mass, all of which have remained unexplained up to now. If confirmed, this scenario may indicate that the \\bp\\ disk could be looked on as a gigantic multi-cometary tail with its natural constituents: gas and dust.

A. Lecavelier des Etangs; A. Vidal-Madjar; R. Ferlet

1995-08-08T23:59:59.000Z

322

The Interruption of Alpine Foehn by a Cold Front. Part I: Observations  

E-Print Network (OSTI)

in Inn and Wipp Valley Temperature slope profile Doppler wind lidar in Wipp Valley #12;6 of 13 Case study study Wipp Valley: AWS network Pot. Temp. and Wind ­ Hovmoeller diagram Strong and warm foehn in the lower Wipp Valley Western Inn-Valley gust front enters Wipp Valley Cold front propagates southward

Gohm, Alexander

323

Higher-order differencing for phase-front propagation in geothermal systems  

DOE Green Energy (OSTI)

We are testing higher-order differencing total variation diminishing schemes implemented in the reservoir simulator TOUGH2 to reduce numerical dispersion of phase fronts in geothermal flow problems. The schemes are called total variation diminishing because they employ flux limiters to prevent spurious oscillations that sometimes occur with other higher-order differencing schemes near sharp fronts. Thus it appears that total variation diminishing schemes rely on an implicit assumption that the overall variability of advected quantities stays constant or diminishes with time. We use the Leonard total variation diminishing scheme in two special problems designed to test the applicability of the scheme for cases where this implicit assumption is violated. In the first problem, we investigate the isothermal propagation of a phase front in a composite porous medium where phase saturation increases as the front enters the second medium. In the second problem, we investigate the propagation of a phase front where boiling increases the saturation difference across the front as it propagates. In the composite porous medium problem, we find that spurious phase saturations can arise if the weighting scheme is based on relative permeability; for weighting based on phase saturation, no such oscillation arises. In the boiling front propagation problem, the front position is highly sensitive to weighting scheme, and the Leonard total variation diminishing scheme is more accurate than upstream weighting because it decreases numerical dispersion in the thermal energy equation.

Oldenburg, Curtis; Pruess, Karsten

1998-01-09T23:59:59.000Z

324

Fronts Formed by Obliquely Reflecting Internal Waves at a Sloping Boundary  

Science Conference Proceedings (OSTI)

A characteristic of internal waves reflecting from sloping boundaries is that they form fronts that travel with the component of the phase speed of the waves up the boundary. The strength of the fronts is assessed by estimating the magnitude of ...

S. A. Thorpe

1999-09-01T23:59:59.000Z

325

Large-Scale Response of the Pacific Ocean Subarctic Front to Momentum Transfer: A Numerical Study  

Science Conference Proceedings (OSTI)

A numerical four-layer hydrodynamical model is implemented to investigate the role the atmosphere exerts on the dynamics of the subarctic front. While the effect of the westerly winds causes a southward shift of the front, the effect of a ...

Alejandro Camerlengo

1982-10-01T23:59:59.000Z

326

PHYSICS RESULTS OF THE NSLS-II LINAC FRONT END TEST STAND  

Science Conference Proceedings (OSTI)

The Linac Front End Test Stand (LFETS) was installed at the Source Development Laboratory (SDL) in the fall of 2011 in order to test the Linac Front End. The goal of these tests was to test the electron source against the specifications of the linac. In this report, we discuss the results of these measurements and the effect on linac performance.

Fliller R. P.; Gao, F.; Yang, X.; Rose, J.; Shaftan, T.; Piel, C

2012-05-20T23:59:59.000Z

327

A front-tracking method for computation of interfacial flows with soluble surfactants  

Science Conference Proceedings (OSTI)

A finite-difference/front-tracking method is developed for computations of interfacial flows with soluble surfactants. The method is designed to solve the evolution equations of the interfacial and bulk surfactant concentrations together with the incompressible ... Keywords: Buoyancy-driven flow, Drop cleavage, Front-tracking method, Soluble surfactant

Metin Muradoglu; Gretar Tryggvason

2008-02-01T23:59:59.000Z

328

Discrete Event Front-tracking Simulation of a Physical Fire-spread Model  

Science Conference Proceedings (OSTI)

Simulation of moving interfaces such as a fire front usually requires resolution of a large-scale and detailed domain. Such computing involves the use of supercomputers to process the large amount of data and calculations. This limitation is mainly due ... Keywords: DEVS, asynchronous, discrete events, envelope, fire spread, flame, forest, front tracking, interface, simulation

Jean-Baptiste Filippi; Frdric Morandini; Jacques Henri Balbi; David Rc Hill

2010-10-01T23:59:59.000Z

329

Two Types of Surface Wind Response to the East China Sea Kuroshio Front  

Science Conference Proceedings (OSTI)

Effects of the sea surface temperature (SST) front along the East China Sea Kuroshio on sea surface winds at different time scales are investigated. In winter and spring, the climatological vector wind is strongest right on the SST front while the ...

Jing-Wu Liu; Su-Ping Zhang; Shang-Ping Xie

330

Electrical double layers at shock fronts in glow discharges and afterglows  

Science Conference Proceedings (OSTI)

This paper examines the propagation of spark-generated shockwaves (1.0front in these weakly-ionized, nonmagnetized, collisional plasmas. We used a microwave hairpin resonator to measure the electron number density, and, for all cases, we measured an increase in the electron number density at the shock front. By comparing the increase in electron number density at the shock front in the active discharge and in the afterglow, we conclude that electrons with a temperature much greater than room temperature can be compressed at the shock front. The ratio of electron number density before and after the shock front can be approximately predicted using the Rankine-Hugoniot relationship. The large gradient in electron density, and hence a large gradient in the flux of charged species, created a region of space-charge separation, i.e., a double layer, at the shock front. The double layer balances the flux of charged particles on both sides of the shock front. The double layer voltage drop was measured in the current-carrying discharge using floating probes and compared with previous models. As well, we measured argon 1s{sup 5} metastable-state density and demonstrate that metastable-state neutral species can be compressed across a shock front and approximately predicted using the Rankine-Hugoniot relationship.

Siefert, Nicholas S. [Air Force Research Laboratory, Wright Patterson, Ohio 45433 (United States)

2010-12-15T23:59:59.000Z

331

Finescale Vertical Structure of a Cold Front as Revealed by an Airborne Doppler Radar  

Science Conference Proceedings (OSTI)

In the afternoon of 24 May 2002, a well-defined and frontogenetic cold front moved through the Texas panhandle. Detailed observations from a series of platforms were collected near the triple point between this cold front and a dryline boundary.

Bart Geerts; Rick Damiani; Samuel Haimov

2006-01-01T23:59:59.000Z

332

Mineral paragenesis and textures associated with sandstone-hosted roll-front uranium deposits, NW China  

E-Print Network (OSTI)

Mineral paragenesis and textures associated with sandstone-hosted roll-front uranium deposits, NW, People's Republic of China c Northwest Institute of Uranium Geology, China National Nuclear Corporation, Wuyiyi and Shihongtan sandstone-hosted roll-front uranium deposits, northwest China. The mineralization

Fayek, Mostafa

333

Evidence of uranium biomineralization in sandstone-hosted roll-front uranium deposits, northwestern China  

E-Print Network (OSTI)

Evidence of uranium biomineralization in sandstone-hosted roll-front uranium deposits, northwestern Available online 25 January 2005 Abstract We show evidence that the primary uranium minerals, uraninite-front uranium deposits, Xinjiang, northwestern China were biogenically precipitated and psuedomorphically

Fayek, Mostafa

334

Real-Time Detection of Split Fronts Using Mesoscale Models and WSR-88D Radar Products  

Science Conference Proceedings (OSTI)

A structured methodology for detecting the presence of split cold fronts in an operational forecast environment is developed and applied to a case in which a split front passed over a region of cold air damming in the southeastern United States. ...

Steven E. Koch

2001-02-01T23:59:59.000Z

335

Upper-Level Frontogenesis: Two Case Studies from the FRONTS 87 Experiment  

Science Conference Proceedings (OSTI)

This study describes the structure of two cold fronts observed during the European experiment FRONTS 87. The selection of these two particular cases is based on the existence of well-marked upper-level features, such as strong jet streams, upper-...

Konstantinos Lagouvardos; Vassiliki Kotroni

1995-04-01T23:59:59.000Z

336

Silicon Solar Cells with Front Hetero-contact and Aluminum Alloy Back Junction (Poster)  

DOE Green Energy (OSTI)

The objectives of this report are: (1) to apply industrial back Al process in efficient n-wafer cells with a-Si:H front surface passivation; and (2) to evaluate the surface recombination velocity (SRV) of the a-Si:H passivated front surface with different surface preparation procedures.

Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q.; Branz, H. M.; Meier, D. L.

2008-05-01T23:59:59.000Z

337

Trapping of a Coastal Density Front by the Bottom Boundary Layer  

Science Conference Proceedings (OSTI)

The dynamics of a surface-to-bottom density front on a uniformly sloping continental shelf and the role of density advection in the bottom boundary layer are examined using a three-dimensional, primitive equation numerical model. The front is ...

David C. Chapman; Steven J. Lentz

1994-07-01T23:59:59.000Z

338

Merger Histories of Galaxy Halos and Implications for Disk Survival  

Science Conference Proceedings (OSTI)

The authors study the merger histories of galaxy dark matter halos using a high resolution {Lambda}CDM N-body simulation. The merger trees follow {approx} 17,000 halos with masses M{sub 0} = (10{sup 11} - 10{sup 13})h{sup -1}M{sub {circle_dot}} at z = 0 and track accretion events involving objects as small as m {approx_equal} 10{sup 10} h{sup -1}M{sub {circle_dot}}. They find that mass assembly is remarkably self-similar in m/M{sub 0}, and dominated by mergers that are {approx}10% of the final halo mass. While very large mergers, m {approx}> 0.4 M{sub 0}, are quite rare, sizeable accretion events, m {approx} 0.1 M{sub 0}, are common. Over the last {approx} 10 Gyr, an overwhelming majority ({approx} 95%) of Milky Way-sized halos with M{sub 0} = 10{sup 12} h{sup -1}M{sub {circle_dot}} have accreted at least one object with greater total mass than the Milky Way disk (m > 5 x 10{sup 10} h{sup -1}M{sub {circle_dot}}), and approximately 70% have accreted an object with more than twice that mass (m > 10{sup 11} h{sup -1}M{sub {circle_dot}}). The results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a {Lambda}CDM universe. in order to achieve a {approx} 70% disk-dominated fraction in Milky Way-sized {Lambda}CDM halos, mergers involving m {approx_equal} 2 x 10{sup 11} h{sup -1}M{sub {circle_dot}} 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.

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

2008-05-16T23:59:59.000Z

339

Spectral Energy Distributions of T Tauri Stars With Passive Circumstellar Disks  

E-Print Network (OSTI)

We derive hydrostatic, radiative equilibrium models for passive disks surrounding T Tauri stars. Each disk is encased by an optically thin layer of superheated dust grains. This layer re-emits directly to space about half the stellar energy it absorbs. The other half is emitted inward and regulates the interior temperature of the disk. The heated disk flares. As a consequence, it absorbs more stellar radiation, especially at large radii, than a flat disk would. The portion of the spectral energy distribution contributed by the disk is fairly flat throughout the thermal infrared. At fixed frequency, the contribution from the surface layer exceeds that from the interior by about a factor 3 and is emitted at more than an order of magnitude greater radius. Spectral features from dust grains in the superheated layer appear in emission if the disk is viewed nearly face-on.

Chiang, E I

1997-01-01T23:59:59.000Z

340

Neutrino Interactions in the Outflow from Gamma-Ray Burst Accretion Disks  

E-Print Network (OSTI)

We examine the composition of matter as it flows away from gamma ray burst accretion disks, in order to determine what sort of nucleosynthesis may occur. Since there is a large flux of neutrinos leaving the surface of the disk, the electron fraction of the outflowing material will change due to charged current neutrino interactions. We calculate the electron fraction in the wind using detailed neutrino fluxes from every point on the disk and study a range of trajectories and outflow conditions for several different accretion disk models. We find that low electron fractions, conducive to making r-process elements, only appear in outflows from disks with high accretion rates that have a significant region both of trapped neutrinos and antineutrinos. Disks with lower accretion rates that have only a significant region of trapped neutrinos can have outflows with very high electron fractions, whereas the lowest accretion rate disks with little trapping have outflow electrons fractions of closer to one half.

R. Surman; G. C. McLaughlin

2004-07-09T23:59:59.000Z

Note: This page contains sample records for the topic "front 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
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341

3-D Simulations of Ergospheric Disk Driven Poynting Jets  

E-Print Network (OSTI)

This Letter reports on 3-dimensional simulations of Kerr black hole magnetospheres that obey the general relativistic equations of perfect magnetohydrodynamics (MHD). In particular, we study powerful Poynting flux dominated jets that are driven from dense gas in the equatorial plane in the ergosphere. The physics of which has been previously studied in the simplified limit of an ergopsheric disk. For high spin black holes, $a/M > 0.95$, the ergospheric disk is prominent in the 3-D simulations and is responsible for greatly enhanced Poynting flux emission. Any large scale poloidal magnetic flux that is trapped in the equatorial region leads to an enormous release of electromagnetic energy that dwarfs the jet energy produced by magnetic flux threading the event horizon. The implication is that magnetic flux threading the equatorial plane of the ergosphere is a likely prerequisite for the central engine of powerful FRII quasars.

Brian Punsly

2007-04-05T23:59:59.000Z

342

Harrison transformation of hyperelliptic solutions and charged dust disks  

E-Print Network (OSTI)

We use a Harrison transformation on solutions to the stationary axisymmetric Einstein equations to generate solutions of the Einstein-Maxwell equations. The case of hyperelliptic solutions to the Ernst equation is studied in detail. Analytic expressions for the metric and the multipole moments are obtained. As an example we consider the transformation of a family of counter-rotating dust disks. The resulting solutions can be interpreted as disks with currents and matter with a purely azimuthal pressure or as two streams of freely moving charged particles. We discuss interesting limiting cases as the extreme limit where the charge becomes identical to the mass, and the ultrarelativistic limit where the central redshift diverges.

C. Klein

2005-12-22T23:59:59.000Z

343

The Disk and Extraplanar Regions of NGC 2403  

E-Print Network (OSTI)

Wide field images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope are used to probe the spatial distribution of young stars in the Sc galaxy NGC 2403. Bright main sequence stars and blue supergiants are detected out to projected galactocentric distances of ~14 kpc (~7 disk scale lengths) along the major axis. The star formation rate (SFR) in the disk of NGC 2403 during the past 10 Myr has been 1 solar masses per year based on the number of bright main sequence stars. The radially-averaged number density of red supergiants (RSGs) per unit r-band surface brightness is constant throughout the disk, indicating that (1) RSGs follow the integrated r-band light, and (2) the SFR per unit mass has been constant with radius when averaged over time scales of a few tens of millions of years. The mean color of RSGs varies with galactocentric distance, suggesting that there is a metallicity gradient among recently formed stars. A comparison of the radially-averaged number density of bright main sequence stars also indicates that the SFR per unit stellar mass in NGC 2403 has been ~3 times higher than in NGC 247 during recent epochs, and this is in rough agreement with what would be predicted from the far infrared fluxes of these galaxies. Finally, the data are used to investigate the extraplanar regions of NGC 2403. A population of M giants with peak brightness M_K = -8 is detected at projected distances between 12 and 14 kpc above the disk plane, and six new globular cluster candidates are identified.

T. J. Davidge

2007-06-25T23:59:59.000Z

344

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

345

Controlling the collimation and rotation of hydromagnetic disk winds  

E-Print Network (OSTI)

(Abriged) We present a comprehensive set of axisymmetric, time-dependent simulations of jets from Keplerian disks whose mass loading as a function of disk radius is systematically changed. For a reasonable model for the density structure and injection speed of the underlying accretion disk, mass loading is determined by the radial structure of the disk's magnetic field structure. We vary this structure by using four different magnetic field configurations, ranging from the "potential" configuration (Ouyed&Pudritz 1997), to the increasingly more steeply falling Blandford&Payne (1982) and Pelletier&Pudritz (1992) models, and ending with a quite steeply raked configuration that bears similarities to the Shu X-wind model. We find that the radial distribution of the mass load has a profound effect on both the rotational profile of the underlying jet as well as the degree of collimation of its outflow velocity and magnetic field lines. We show analytically, and confirm by our simulations, that the collimation of a jet depends on its radial current distribution, which in turn is prescribed by the mass load. Models with steeply descending mass loads have strong toroidal fields, and these collimate to cylinders (this includes the Ouyed-Pudritz and Blandford-Payne outflows). On the other hand, the more gradually descending mass load profiles (the PP92 and monopolar distributions) have weaker toroidal fields, and these result in wide-angle outflows with parabolic collimation. We also present detailed structural information about jets such as their radial profiles of jet density, toroidal magnetic field, and poloidal jet speed, as well as an analysis of the bulk energetics of our different simulations.

Ralph E. Pudritz; Conrad Rogers; Rachid Ouyed

2005-08-12T23:59:59.000Z

346

Elliptic and magneto-elliptic instabilities of disk vortices  

E-Print Network (OSTI)

Vortices are the fundamental units of turbulent flow. Understanding their stability properties therefore provides fundamental insights on the nature of turbulence itself. In this contribution I briefly review the phenomenological aspects of the instability of elliptic streamlines, in the hydro (elliptic instability) and hydromagnetic (magneto-elliptic instability) regimes. Vortex survival in disks is a balance between vortex destruction by these mechanisms, and vortex production by others, namely, the Rossby wave instability and the baroclinic instability.

Lyra, Wlad

2013-01-01T23:59:59.000Z

347

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

348

GALACTOSEISMOLOGY: DISCOVERY OF VERTICAL WAVES IN THE GALACTIC DISK  

Science Conference Proceedings (OSTI)

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

349

Request Bridging and Interleaving: Improving the Performance of Small Synchronous Updates under Seek-Optimizing Disk Subsystems  

Science Conference Proceedings (OSTI)

Write-through caching in modern disk drives enables the protection of data in the event of power failures as well as from certain disk errors when the write-back cache does not. Host system can achieve these benefits at the price of significant performance ... Keywords: Request merging, cross-layer optimizations, disk drive, disk scheduling algorithm, trace-driven analysis

Dong In Shin; Young Jin Yu; Hyeong S. Kim; Hyeonsang Eom; Heon Young Yeom

2011-07-01T23:59:59.000Z

350

Microsoft Word - ffort-09.html  

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

VIN: 2CIMR5299567000106 Seating Capacity: 4 Adults Features: AMFM Radio, Heater, Battery Thermal Management, Power Steering, Power Brakes, Front Wheel Drive, Front Disc...

351

Microscopic Examination of a Corrosion Front in Spent Nuclear Fuel  

Science Conference Proceedings (OSTI)

Spent uranium oxide nuclear fuel hosts a variety of trace chemical constituents, many of which must be sequestered from the biosphere during fuel storage and disposal. In this paper we present synchrotron x-ray absorption spectroscopy and microscopy findings that illuminate the resultant local chemistry of neptunium and plutonium within spent uranium oxide nuclear fuel before and after corrosive alteration in an air-saturated aqueous environment. We find the plutonium and neptunium in unaltered spent fuel to have a +4 oxidation state and an environment consistent with solid-solution in the UO{sub 2} matrix. During corrosion in an air-saturated aqueous environment, the uranium matrix is converted to uranyl U(VI)O{sub 2}{sup 2+} mineral assemblage that is depleted in plutonium and neptunium relative to the parent fuel. At the corrosion front interface between intact fuel and the uranyl-mineral corrosion layer, we find evidence of a thin ({approx}20 micrometer) layer that is enriched in plutonium and neptunium within a predominantly U{sup 4+} environment. Available data for the standard reduction potentials for NpO{sup 2+}/Np{sup 4+} and UO{sub 2}{sup 2+}/U{sup 4+} couples indicate that Np(IV) may not be effectively oxidized to Np(V) at the corrosion potentials of uranium dioxide spent nuclear fuel in air-saturated aqueous solutions. Neptunium is an important radionuclide in dose contribution according to performance assessment models of the proposed U. S. repository at Yucca Mountain, Nevada. A scientific understanding of how the UO{sub 2} matrix of spent nuclear fuel impacts the oxidative dissolution and reductive precipitation of neptunium is needed to predict its behavior at the fuel surface during aqueous corrosion. Neptunium would most likely be transported as aqueous Np(V) species, but for this to occur it must first be oxidized from the Np(IV) state found within the parent spent nuclear fuel [1]. In the immediate vicinity of the spent fuel's surface the redox and nucleation behavior is likely to promote/enhance nucleation of NpO{sub 2} and Np{sub 2}O{sub 5}. Alternatively, Np may be incorporated into uranyl (UO{sub 2}{sup 2+}) alteration phases [2]. In some cases, less-soluble elements such as plutonium will be enriched near the surface of the corroding fuel [3]. We have used focused synchrotron x-rays from the MRCAT beam line at the Advanced Photon Source (APS) at Argonne National Lab to examine a specimen of spent nuclear fuel that had been subject to 10 years of corrosion testing in an environment of humid air and dripping groundwater at 90 C [4]. We find evidence of a region, approximately 20 microns in thickness, enriched in plutonium and neptunium at the corrosion front that exists between the uranyl silicate alteration mineral rind and the unaltered uranium oxide fuel (Figures 1 and 2). The uranyl silicate is itself found to be depleted in these transuranic elements relative to their abundance relative to uranium in the parent fuel. This suggests a low mobility of these components owing to a resistance to oxidize further in the presence of a UO{sub 2}{sup 2+}/U{sup 4+} couple [5].

J.A> Fortner; A.J. Kropf; R.J. Finch; J.C. Cunnane

2006-06-20T23:59:59.000Z

352

Observations of the Sea-Breeze Front during CaPE. Part II: Dual-Doppler and Aircraft Analysis  

Science Conference Proceedings (OSTI)

The three-dimensional kinematic structures of offshore and onshore flow sea-breeze fronts observed during the CaPE experiment are shown using high resolution dual-Doppler and aircraft data. The fronts interact with horizontal convective rolls (...

Nolan T. Atkins; Roger M. Wakimoto; Tammy M. Weckwerth

1995-04-01T23:59:59.000Z

353

SiGe receiver front ends and flip-chip integrated wideband antennas for millimeter-wave passive imaging  

E-Print Network (OSTI)

SiGe wideband 77-GHz and 94-GHz front end receivers with integrated antennas for passive imaging have been designed and characterized. These front end systems exhibit wideband performance with the highest gain and lowest ...

Powell, Johnna, 1980-

2009-01-01T23:59:59.000Z

354

A Simple Model of the Formation and Maintenance of the Shelf/Slope Front in the Middle Atlantic Bight  

Science Conference Proceedings (OSTI)

The strong salinity and temperature gradients across the shelf/slope front in the Middle Atlantic Bight often compensate such that the cross-front density gradient is nearly eliminated. The suggests that the density field may not be as ...

David C. Chapman

1986-07-01T23:59:59.000Z

355

Magnetohydrodynamic Simulations of the Formation of Cold Fronts in Clusters of Galaxies including Heat Conduction  

E-Print Network (OSTI)

Recent Chandra observations of clusters of galaxies revealed the existence of a sharp ridge in the X-ray surface brightness where the temperature drops across the front. This front is called the cold front. We present the results of two-dimensional magnetohydrodynamic simulations of the time evolution of a dense subcluster plasma moving in a cluster of galaxies. Anisotropic heat conduction along the magnetic field lines is included. In the models without magnetic fields, the numerical results indicate that the heat conduction from the hot ambient plasma heats the cold dense plasma of the subcluster and diffuses out the cold front. When magnetic fields exist in a cluster of galaxies, however, cold fronts can be maintained because the heat conduction across the magnetic field lines is suppressed. We found that, even when the magnetic fields in a cluster of galaxies are disordered, heat conduction across the front is restricted because the magnetic field lines are stretched along the front. Numerical results reproduced the X-ray intensity distribution observed in the A3667 cluster of galaxies.

Naoki Asai; Naoya Fukuda; Ryoji Matsumoto

2004-04-07T23:59:59.000Z

356

Light-Front Holography, AdS/QCD, and Hadronic Phenomena  

E-Print Network (OSTI)

AdS/QCD, the correspondence between theories in a modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate $z$ with an invariant light-front coordinate $\\zeta$ which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schr\\"odinger equation with a confining potential which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The mapping of electromagnetic and gravitational form factors in AdS space to their corresponding expressions in light-front theory confirms this correspondence. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. The distinction between static structure functions, such as the probability distributions computed from the square of the light-front wavefunctions, versus dynamical structure functions which include the effects of rescattering, is emphasized. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

Stanley J. Brodsky; Guy F. de Teramond

2009-09-22T23:59:59.000Z

357

THE MISSING CAVITIES IN THE SEEDS POLARIZED SCATTERED LIGHT IMAGES OF TRANSITIONAL PROTOPLANETARY DISKS: A GENERIC DISK MODEL  

Science Conference Proceedings (OSTI)

Transitional circumstellar disks around young stellar objects have a distinctive infrared deficit around 10 {mu}m in their spectral energy distributions, 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 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 {mu}m-sized grains, with little discontinuity in the surface density of the {mu}m-sized grains at the cavity edge. Here we present a generic disk model that can simultaneously account for the general features in IRS, SMA, and Subaru observations. Particularly, the scattered light images for this model are computed, which agree with the general trend seen in Subaru data. Decoupling between the spatial distributions of the {mu}m-sized dust and mm-sized dust inside the cavity is suggested by the model, which, if confirmed, necessitates a mechanism, such as dust filtration, for differentiating the small and big dust in the cavity clearing process. Our model also suggests an inwardly increasing gas-to-dust ratio in the inner disk, and different spatial distributions for the small dust inside and outside the cavity, echoing the predictions in grain coagulation and growth models.

Dong, R.; Rafikov, R.; Zhu, Z.; Brandt, T.; Janson, M. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Hartmann, L. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105 (United States); Whitney, B. [Astronomy Department, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Muto, T. [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan); Hashimoto, J.; Kuzuhara, M. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Grady, C. [ExoPlanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Follette, K. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Tanii, R.; Itoh, Y. [Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501 (Japan); Thalmann, C. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Wisniewski, J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Mayama, S. [Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Abe, L. [Laboratoire Lagrange, UMR7293, Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, 06300 Nice (France); Brandner, W. [Max Planck Institute for Astronomy, Heidelberg (Germany); Carson, J., E-mail: rdong@astro.princeton.edu [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); and others

2012-05-10T23:59:59.000Z

358

Front Vehicle Setup Information Downloadable Dynamometer Database (D  

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

Chevrolet Volt- 20F Chevrolet Volt- 20F Test cell location Front Vehicle Setup Information Downloadable Dynamometer Database (D 3 )- Test Summary Sheet Vehicle architecture EREV Vehicle dynamometer Input Document date 8/7/2013 Advanced Powertrain Research Facility Test weight [lb] Target A [lb] 4000 28.66 Target B [lb/mph] Target C [lb/mph^2] -0.0132 0.0202 Revision Number 3 Notes: Test Fuel Information Fuel type EPA Tier II EEE Fuel density [g/ml] Fuel Net HV [BTU/lbm] 0.743 18490 T e s t I D [ # ] C y c l e C o l d s t a r t ( C S t ) H o t s t a r t [ H S t ] D a t e T e s t C e l l T e m p [ C ] T e s t C e l l R H [ % ] T e s t C e l l B a r o [ i n / H g ] V e h i c l e c o o l i n g f a n s p e e d : S p e e d M a t c h [ S M ] o r c o n s t a n t s p e e d [ C S ] S o l a r L a m p s [ W / m 2 ] V e i c l e C l i m a t e C o n t r o l s e t t i n g s H o o d P o s i t i o n [ U p ] o r [ C l o s e d ] W i n d o w P o s i t i o n [ C l o s e d ] o r [ D o w n ] C y c l e D i s t a n c e [ m i ] C y c l e F u

359

On the Diversity of the Taurus Transitional Disks: UX Tau A & Lk Ca 15  

E-Print Network (OSTI)

The recently recognized class of "transitional disk" systems consists of young starswith optically-thick outer disks but inner disks which are mostly devoid of small dust. Here we introduce a further class of "pre-transitional disks" with significant near-infrared excesses which indicate the presence of an optically thick inner disk separated from an optically thick outer disk; thus, the spectral energy distributions of pre-transitional disks suggest the incipient development of disk gaps rather than inner holes. In UX Tau A, our analysis of the Spitzer IRS spectrum finds that the near-infrared excess is produced by an inner optically thick disk and a gap of ~56 AU is present. The Spitzer IRS spectrum of LkCa 15 is suggestive of a gap of ~46 AU, confirming previous millimeter imaging. In addition, UX Tau A contains crystalline silicates in its disk at radii >~ 56 AU which poses a challenge to our understanding of the production of this crystalline material. In contrast, LkCa 15's silicates are amorphous and pristine. UX Tau A and LkCa 15 increase our knowledge of the diversity of dust clearing in low-mass star formation.

C. Espaillat; N. Calvet; P. D'Alessio; J. Hernandez; C. Qi; L. Hartmann; E. Furlan; D. M. Watson

2007-10-15T23:59:59.000Z

360

Propagation of Front Waves in Myelinated Nerve Fibres: New Electrical Transmission Lines Constituted of Linear and Nonlinear Portions  

Science Conference Proceedings (OSTI)

In this paper, the authors examine the propagation of wave fronts in myelinated nerve fibres and applications as electrical transmission lines constituted of linear and nonlinear portions. Numerical simulations show that the front introduced in the nonlinear ... Keywords: Demyelination, Electrical Line, Front Wave, Myelinated Fibre, Regenerative, Remyelination

Assatou Mboussi Nkomidio; Paul Woafo

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

The Opacity of Spiral Galaxy Disks: dust opacity from calibrated counts of distant galaxies  

E-Print Network (OSTI)

The opacity of foreground spiral disks can be probed from the number of distant galaxies seen through them. To calibrate this number for effects other than the dust extinction, Gonzalez et al (1998) developed the "Synthetic Field Method". A synthetic field is an extincted Hubble Deep Field added to the science field. The relation between the dimming and the number of retrieved synthetic galaxies calibrates the number found in the science field. Here I present results from counts in 32 HST/WFPC2 fields. The relation between opacity and radius, arm and disk, surface brightness and HI are presented. The opacity is found to be caused by a clumpy distribution of clouds in the disk. The brighter parts of the disk -the center and arms- are also the more opaque ones. The dust distribution in spiral disks is found to be more extended than the stellar disk. A comparison between HI column densities and opacity shows little relation between the two.

B. W. Holwerda; R. A. Gonzalez; Ronald J. Allen; P. C. van der Kruit

2005-08-11T23:59:59.000Z

362

On rapid migration and accretion within disks around supermassive black holes  

E-Print Network (OSTI)

Galactic nuclei should contain a cluster of stars and compact objects in the vicinity of the central supermassive black hole due to stellar evolution, minor mergers and gravitational dynamical friction. By analogy with protoplanetary migration, nuclear cluster objects (NCOs) can migrate in the accretion disks that power active galactic nuclei by exchanging angular momentum with disk gas. Here we show that an individual NCO undergoing runaway outward migration comparable to Type III protoplanetary migration can generate an accretion rate corresponding to Seyfert AGN or quasar luminosities. Multiple migrating NCOs in an AGN disk can dominate traditional viscous disk accretion and at large disk radii, ensemble NCO migration and accretion could provide sufficient heating to prevent the gravitational instability from consuming disk gas in star formation. The magnitude and energy of the X-ray soft excess observed at ~0.1-1keV in Seyfert AGN could be explained by a small population of ~10^{2}-10^{3} accreting stella...

McKernan, B; Lyra, W; Perets, H B; Winter, L M; Yaqoob, T

2011-01-01T23:59:59.000Z

363

DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in  

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

DOE Offers Conditional Loan Guarantee for Front End Nuclear DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in Idaho DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in Idaho May 20, 2010 - 12:00am Addthis Washington, DC - As part of a broad effort to expand the use of nuclear power in the United States and reduce carbon pollution, U.S. Secretary of Energy Steven Chu announced today the Department's first conditional commitment for a front-end nuclear facility. The $2 billion loan guarantee will support AREVA's Eagle Rock Enrichment Facility near Idaho Falls, Idaho, which will supply uranium enrichment services for the U.S. nuclear power industry. "Increasing uranium enrichment in the United States is critical to the nation's energy and national security," said Secretary Chu. "Existing

364

Midtropospheric Anticyclonic Vortex Street Associated with a Cloud Band near a Cold Front  

Science Conference Proceedings (OSTI)

The characteristics and formation mechanism of an anticyclonic vortex street of meso-? scale, which appeared near a cold front around the Ryukyu Islands, Japan, on 11 April 1995, were examined by an analysis of observational data, a numerical ...

Eizi Toyoda; Hiroshi Niino; Kazuhisa Tsuboki; Ryuji Kimura; Masanori Yoshizaki

1999-08-01T23:59:59.000Z

365

Major Cloud Plumes in the Arctic and Their Relation to Fronts and Ice Movement  

Science Conference Proceedings (OSTI)

A study of the movement of orographic cloud plumes from one island to another in the Svalbard-Novaya Zemlya region of the Barents Sea revealed a close association with similar movements of arctic fronts. Strong northerly winds behind arctic ...

Robert W. Fett

1992-06-01T23:59:59.000Z

366

Influences of the Sierra Nevada on Intermountain Cold-Front Evolution  

Science Conference Proceedings (OSTI)

Recent studies indicate that strong cold fronts develop frequently downstream of the Sierra Nevada over the Intermountain West. To help ascertain why, this paper examines the influence of the Sierra Nevada on the rapidly developing Intermountain ...

Gregory L. West; W. James Steenburgh

2011-10-01T23:59:59.000Z

367

Kinematic and Moisture Characteristics of a Nonprecipitating Cold Front Observed during IHOP. Part II: Alongfront Structures  

Science Conference Proceedings (OSTI)

Kinematic and thermodynamic structures of a nonprecipitating cold front observed in west-central Kansas on 10 June 2002 during the International H2O Project (IHOP) are examined with dropsondes and airborne instrumentation that includes Doppler ...

Katja Friedrich; David E. Kingsmill; Cyrille Flamant; Hanne V. Murphey; Roger M. Wakimoto

2008-10-01T23:59:59.000Z

368

Numerical Study of Precipitation Core-Gap Structure along Cold Fronts  

Science Conference Proceedings (OSTI)

The mechanism responsible for the core-gap structure of precipitation along narrow cold-frontal rainbands (NCFRs) is investigated through analyses of idealized cloud-resolving simulations of cold fronts. The control simulation, in which the ...

Masayuki Kawashima

2007-07-01T23:59:59.000Z

369

Influence of the Subtropical Andes on Baroclinic Disturbances: A Cold Front Case Study  

Science Conference Proceedings (OSTI)

The Andes Cordillera produces a significant disruption to the structure and evolution of the weather systems that cross South America. In particular, cold fronts tend to be channeled to the north immediately to the east of the Andes, fostering ...

Marcelo E. Seluchi; RenD. Garreaud; Federico A. Norte; A. Celeste Saulo

2006-11-01T23:59:59.000Z

370

The Orographic Modulation of Pre-Warm-Front Precipitation in Southern New England  

Science Conference Proceedings (OSTI)

Topographic forcing over the hills and small mountains of southern New England plays an important role in determining the distribution of pre-warm-front precipitation from winter cyclones. Upslope regions receive 2060% more precipitation than do ...

Richard E. Passarelli Jr.; Hannah Boehme

1983-05-01T23:59:59.000Z

371

Forecasting the Impacts of Strong Wintertime Post-Cold Front Winds in the Northern Plains  

Science Conference Proceedings (OSTI)

Strong post-cold front wind events in the northern plains of the United States are a difficult problem for operational forecasters. The various atmospheric ingredients that lead to these events are examined from an operational point of view. ...

Anton F. Kapela; Preston W. Leftwich; Richard Van Ess

1995-06-01T23:59:59.000Z

372

Sensitivity of Mesoscale Gravity Waves to the Baroclinicity of Jet-Front Systems  

Science Conference Proceedings (OSTI)

This study investigates the sensitivity of mesoscale gravity waves to the baroclinicity of the background jet-front systems by simulating different life cycles of baroclinic waves with a high-resolution mesoscale model. Four simulations are made ...

Shuguang Wang; Fuqing Zhang

2007-02-01T23:59:59.000Z

373

Ocean Fronts off California: A New Product from GOES Satellite Data  

E-Print Network (OSTI)

COASTAL OCEAN RESEARCH R/CZ-181: 3.1.20022.28.2005 Ocean Fronts off California: A Newsurfers who complain that the ocean is coldest in spring are

Breaker, Laurence

2004-01-01T23:59:59.000Z

374

Applications of AdS/QCD and Light-Front Holography to Baryon Physics  

SciTech Connect

The correspondence between theories in anti-de Sitter space and field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. These equations, for both mesons and baryons, give a very good representation of the observed hadronic spectrum, including a zero mass pion. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The meson and baryon wavefunctions derived from light-front holography and AdS/QCD also have remarkable phenomenological features, including predictions for the electromagnetic form factors and decay constants. The approach can be systematically improved using light-front Hamiltonian methods. Some novel features of QCD for baryon physics are also discussed.

Brodsky, Stanley J.; /SLAC; de Teramond, Guy F.; /Costa Rica U.

2011-08-22T23:59:59.000Z

375

Simulation of chemical reaction fronts in anaerobic digestion of solid waste  

Science Conference Proceedings (OSTI)

A case study for parallelisation of a code for a nonlinear system of evolution equations is presented. It describes the propagation of reaction fronts in anaerobic waste digestion. These occur as a consequence of heterogeneous initial distributions of ...

Hermann J. Eberl

2003-05-01T23:59:59.000Z

376

Mesoscale Modeling of a Cold Front and Its Interaction with a Diurnally Heated Land Mass  

Science Conference Proceedings (OSTI)

A mesoscale numerical model incorporating a detailed planetary boundary-layer scheme, including momentum, heat and moisture exchange with the lower boundary, is used to study the change in structure of a dry summertime front as it moves towards a ...

William L. Physick

1988-11-01T23:59:59.000Z

377

VHF Radar Observations of Gravity-Wave Production by Cold Fronts over Southern Australia  

Science Conference Proceedings (OSTI)

Four extended observational campaigns were conducted during August and November 1988 with an ST (stratospheretroposphere) radar in southern Australia during the passage of cold fronts over the system, giving around 30 days of three-dimensional ...

Stephen D. Eckermann; Robert A. Vincent

1993-03-01T23:59:59.000Z

378

The Southerly Burster of South Eastern Australia: An Orographically Forced Cold Front  

Science Conference Proceedings (OSTI)

This paper presents an observational study of the southerly burster, or southerly buster, a particularly intense type of orographically and thermally influenced cold front which occurs in spring and summer along the southern coast of New ...

J. R. Colquhoun; D. J. Shepherd; C. E. Coulman; R. K. Smith; K. McInnes

1985-12-01T23:59:59.000Z

379

On the Movement and Low-Level Structure of Cold Fronts  

Science Conference Proceedings (OSTI)

This paper presents a review of theoretical and observational studies relating to the low-level structure of cold fronts and explores the factors that are pertinent to frontal motion.

Roger K. Smith; Michael J. Reeder

1988-10-01T23:59:59.000Z

380

Downwelling-Front Instability and Eddy Formation in the Eastern Mediterranean  

Science Conference Proceedings (OSTI)

The instability of the downwelling front along the southern coast of Asia Minor is studied with a multimode quasigeostrophic model. Linear analysis shows that the most unstable wave has a length of about 100 km, The wavelength depends only very ...

Yizhak Feliks; Michael Ghil

1993-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

What Maintains the SST Front North of the Eastern Pacific Equatorial Cold Tongue?  

Science Conference Proceedings (OSTI)

A coupled oceanatmosphere regional model suggests a mechanism for formation of a sharp sea surface temperature (SST) front north of the equator in the eastern Pacific Ocean in boreal summer and fall. Meridional convergence of Ekman transport at ...

Simon P. de Szoeke; Shang-Ping Xie; Toru Miyama; Kelvin J. Richards; R. Justin O. Small

2007-06-01T23:59:59.000Z

382

Diapycnal Diffusivity Inferred from Scalar Microstructure Measurements near the New England Shelf/Slope Front  

Science Conference Proceedings (OSTI)

Conductivity microstructure was used to estimate the diapycnal thermal eddy diffusivity KT near the New England shelf/slope front in early August 1997. Two datasets were collected with a towed vehicle. One involved several horizontal tows in and ...

Chris R. Rehmann; Timothy F. Duda

2000-06-01T23:59:59.000Z

383

The Cold Front of 15 April 1994 over the Central United States. Part I: Observations  

Science Conference Proceedings (OSTI)

Detailed observations of the interactions of a cold front and a dryline over the central United States that led to dramatic undulations in the boundary layer, including an undular bore, are investigated using high-resolution water vapor mixing ...

B. B. Demoz; D. OC. Starr; K. D. Evans; A. R. Lare; D. N. Whiteman; G. Schwemmer; R. A. Ferrare; J. E. M. Goldsmith; S. E. Bisson

2005-06-01T23:59:59.000Z

384

A Laboratory Model of Thermocline Depth and Exchange Fluxes across Circumpolar Fronts  

Science Conference Proceedings (OSTI)

A laboratory experiment has been constructed to investigate the possibility that the equilibrium depth of a circumpolar front is set by a balance between the rate at which potential energy is created by mechanical and buoyancy forcing and the ...

Claudia Cenedese; John Marshall; J. A. Whitehead

2004-03-01T23:59:59.000Z

385

Topographic Distortion of a Cold Front over the Snake River Plain and Central Idaho Mountains  

Science Conference Proceedings (OSTI)

The topographic distortion of a cold front over the Snake River Plain (SRP) and central Idaho Mountains on 3 December 1998 is described using high-density surface observations from MesoWest, a collection of meteorological networks over the ...

W. James Steenburgh; Thomas R. Blazek

2001-06-01T23:59:59.000Z

386

Location of the Antarctic Polar Front from AMSR-E Satellite Sea Surface Temperature Measurements  

Science Conference Proceedings (OSTI)

The location of the Southern Ocean polar front (PF) is mapped from the first 3 yr of remotely sensed Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) sea surface temperature (SST) measurements. In agreement with ...

Shenfu Dong; Janet Sprintall; Sarah T. Gille

2006-11-01T23:59:59.000Z

387

Use of Synthetic Aperture Radar in Finescale Surface Analysis of Synoptic-Scale Fronts at Sea  

Science Conference Proceedings (OSTI)

The viability of synthetic aperture radar (SAR) as a tool for finescale marine meteorological surface analyses of synoptic-scale fronts is demonstrated. In particular, it is shown that SAR can reveal the presence of, and the mesoscale and ...

G. S. Young; T. N. Sikora; N. S. Winstead

2005-06-01T23:59:59.000Z

388

The Life Cycle of an Undular Bore and Its Interaction with a Shallow, Intense Cold Front  

Science Conference Proceedings (OSTI)

The evolution of an undular bore and its associated wind shift, spawned by the passage of a shallow surface cold front over the Southern Great Plains of the United States, is examined using surface and remote sensing observations along with ...

Daniel C. Hartung; Jason A. Otkin; Jonathan E. Martin; David D. Turner

2010-03-01T23:59:59.000Z

389

The Life Cycle of Thunderstorm Gust Fronts as Viewed with Doppler Radar and Rawinsonde Data  

Science Conference Proceedings (OSTI)

This paper presents the time-dependent analysis of the thunderstorm gust front with the use of Project NIMROD data. RHI cross sections of reflectivity and Doppler velocity are constructed to determine the entire vertical structure. The life cycle ...

Roger M. Wakimoto

1982-08-01T23:59:59.000Z

390

Observations of a Subtropical Cold Front in a Region of Complex Terrain  

Science Conference Proceedings (OSTI)

The passage of shallow cold fronts during the late spring and early summer months over the island of Taiwan is often accompanied by heavy rainfall and occasional flash flood episodes. Previous studies have emphasized the weak baroclinicity of ...

Stanley B. Trier; David B. Parsons; Thomas J. Matejka

1990-12-01T23:59:59.000Z

391

Identification of Atmospheric Fronts over the Ocean with Microwave Measurements of Water Vapor and Rain  

Science Conference Proceedings (OSTI)

This Paper describes some basic research techniques and algorithms developed to diagnose fronts in cyclonic storms over the ocean with data from satellite-borne microwave radiometers. The need for this research stems from the limited availability ...

Kristina B. Kanaros; Iffekhar Bhatti; Llynn A. Mcmurdie; Grant W. Petty

1989-12-01T23:59:59.000Z

392

The Norwegian IPYTHORPEX: Polar Lows and Arctic Fronts during the 2008 Andya Campaign  

Science Conference Proceedings (OSTI)

From a weather forecasting perspective, the Arctic poses particular challenges for mainly two reasons: 1) The observational data are sparse and 2) the weather phenomena responsible for severe weather, such as polar lows, Arctic fronts, and orographic ...

J. E. Kristjnsson; I. Barstad; T. Aspelien; I. Fre; . Gody; . Hov; E. Irvine; T. Iversen; E. Kolstad; T. E. Nordeng; H. McInnes; R. Randriamampianina; J. Reuder; . Saetra; M. Shapiro; T. Spengler; H. lafsson

2011-11-01T23:59:59.000Z

393

Light-Front Quantization of the Polyakov D1 Brane Action With a Scalar Dilaton Field  

E-Print Network (OSTI)

Light-front quantization of the conformally gauge-fixed Polyakov D1 brane action with a scalar dilaton field is studied using the equal light-cone world-sheet time framework.

D. S. Kulshreshtha

2007-11-08T23:59:59.000Z

394

Cold Fronts Aloft and the Forecasting of Precipitation and Severe Weather East of the Rocky Mountains  

Science Conference Proceedings (OSTI)

Brief descriptions are given of four cases that illustrate the important role that cold fronts aloft (CFA) can play in producing significant weather cast of the Rocky Mountains. In all four cases, the CFA, and its associated short wave, were ...

Peter V. Hobbs; John D. Locatelli; Jonathan E. Martin

1990-12-01T23:59:59.000Z

395

Comparative Analysis of Low-Level Cold Fronts: Wavelet, Fourier, and Empirical Orthogonal Function Decompositions  

Science Conference Proceedings (OSTI)

Atmospheric cold fronts observed in the boundary layer represent relatively sharp transition zones between air masses of disparate physical characteristics. Further, wavelike features and/or eddy structures are often observed in conjunction with ...

Nimal Gamage; William Blumen

1993-10-01T23:59:59.000Z

396

Coevolution of inverse cascade and nonlinear heat front in shear flows of strongly coupled Yukawa liquids  

Science Conference Proceedings (OSTI)

Using classical molecular dynamics (MD) simulations, we report on the development and propagation of a nonlinear heat front in parallel shear flows of a strongly coupled Yukawa liquid. At a given coupling strength, a subsonic shear profile is superposed on an equilibrated Yukawa liquid and Kelvin Helmholtz (KH) instability is observed. Coherent vortices are seen to emerge towards the nonlinear regime of the instability. It is seen that while inverse cascade leads to a continuous transfer of flow energy towards the largest scales, there is also a simultaneous transfer of flow energy into the thermal velocities of grains at the smallest scale. The latter is an effect of velocity shear and thus leads to the generation of a nonlinear heat front. In the linear regime, the heat front is seen to propagate at speed much lesser than the adiabatic sound speed of the liquid. Spatio-temporal growth of this heat front occurs concurrently with the inverse cascade of KH modes.

Ashwin, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382428, Gujarat (India)

2011-08-15T23:59:59.000Z

397

Commissioning of the SNS front-end systems at Berkeley Lab  

E-Print Network (OSTI)

Results Obtained with the SNS H - Ion Source and LEBT atVarious contributions by SNS authors to these conferenceCOMMISSIONING OF THE SNS FRONT-END SYSTEMS AT BERKELEY LAB*

2002-01-01T23:59:59.000Z

398

The SNS front-end, an injector for a high-power hydrogen-ion accelerator  

E-Print Network (OSTI)

Stockli, R. Welton, and M. White (SNS-ORNL); J. Power and M.VI. REFERENCES N. Holtkamp, The SNS Linac and Storage Ring:the FES Team, Status of the SNS Front-End Sys- tems, Paper

Keller, R.

2002-01-01T23:59:59.000Z

399

The Marine Boundary Layer in the Vicinity of an Ocean Front  

Science Conference Proceedings (OSTI)

Aircraft observations obtained during the Frontal AirSea Interaction Experiment (FASINEX) are used to investigate the structure of the marine atmospheric boundary layer in the vicinity of an ocean front. A quasi-stationary sea surface ...

David P. Rogers

1989-07-01T23:59:59.000Z

400

Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front  

Science Conference Proceedings (OSTI)

By mapping the three-dimensional density field while simultaneously tracking a subsurface, isopycnal float, direct observations of upwelling along a shelfbreak front were made on the southern flank of Georges Bank. The thermohaline and bio-...

John A. Barth; Dave Hebert; Andrew C. Dale; David S. Ullman

2004-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

A Mean Synoptic View of the Subantarctic Front South of Australia  

Science Conference Proceedings (OSTI)

A mean synoptic view of the subantarctic front (SAF) is obtained from current meter and hydrographic data by averaging absolute and baroclinic velocity measurements in bins defined by a cross-stream coordinate that moves with the current. The ...

Helen E. Phillips; Stephen R. Rintoul

2002-05-01T23:59:59.000Z

402

A New Statistical Modeling Approach to Ocean Front Detection from SST Satellite Images  

Science Conference Proceedings (OSTI)

Ocean fronts are narrow zones of intense dynamic activity that play an important role in global oceanatmosphere interactions. Owing to their highly variable nature, both in space and time, they are notoriously difficult features to adequately ...

Jo Hopkins; Peter Challenor; Andrew G. P. Shaw

2010-01-01T23:59:59.000Z

403

Relationship between a Weakening Cold Front, Misocyclones, and Cloud Development on 10 June 2002 during IHOP  

Science Conference Proceedings (OSTI)

The finescale structure and evolution of a cold front in the presence of small-scale circulations are examined using overdetermined dual-Doppler syntheses of mobile radar data along with thermodynamic data and cloud imagery collected on 10 June ...

Nettie R. Arnott; Yvette P. Richardson; Joshua M. Wurman; Erik M. Rasmussen

2006-01-01T23:59:59.000Z

404

Experimental evaluation of the in-plane seismic behavior of store-front window systems  

E-Print Network (OSTI)

J. , (1960). Behavior of window panels under in-planeC. , (1997). Behavior of window glass panels duringBehavior of Store-front Window Systems A thesis submitted in

Eva, Charles Almond

2009-01-01T23:59:59.000Z

405

The Stability of Steady Fronts and the Adjoint Method: Nonmodal Frontal Waves  

Science Conference Proceedings (OSTI)

The adjoint method for finding optimal or singular modes is employed for studying the finite time stability of steady, tw0-dimensional atmospheric fronts as represented by the uniform potential vorticity semigeostrophic model.

Alain Joly

1995-09-01T23:59:59.000Z

406

Unstable Waves on Oceanic Fronts: Large Amplitude Behavior and Mean Flow Generation  

Science Conference Proceedings (OSTI)

A primitive equation numerical model is used to study the large amplitude behavior of unstable waves on an oceanic density front, concentrating on a single wave mode corresponding to the fastest growing linear solution. At Small amplitude the ...

Richard A. Wood

1988-05-01T23:59:59.000Z

407

Mesoscale Energy Spectra of Mei-Yu Front System. Part I: Kinetic Energy Spectra  

Science Conference Proceedings (OSTI)

The mesoscale kinetic energy (KE) spectra of Mei-Yu front system are investigated through idealized numerical simulations. In the mature stage, the upper tropospheric KE spectrum resembles a -3 power law for wavelengths between 1000 and 400 km and ...

Jun Peng; Lifeng Zhang; Yu Luo; Yun Zhang

408

The Evolution of an Observed Cold Front. Part II: Mesoscale Dynamics  

Science Conference Proceedings (OSTI)

A detailed analysis is made of a three-dimensional numerical simulation of the evolution of an observed moist frontal system over a 48 h period. The simulated front undergoes an initial period of frontogenetic growth, characterized by an ...

Isidoro Orlanski; Bruce B. Ross

1984-05-01T23:59:59.000Z

409

The Evolution of an Observed Cold Front. Part I. Numerical Simulation  

Science Conference Proceedings (OSTI)

The 48 h evolution of an observed cold front is simulated by a three-dimensional mesoscale-numerical model for a typical springtime synoptic situation over the southeastern United States. The model used in this study employs anelastic equations ...

Bruce B. Ross; Isidoro Orlanski

1982-02-01T23:59:59.000Z

410

A survey of front end modularity as an automotive architecture and its ability to deliver value  

E-Print Network (OSTI)

The partitioning of a system can and will dictate the creative space for a designer or engineer. This thesis will analyze how using a new automotive architecture known as a Front End Module (FEM) can affect a limited ...

Mah, Vincent R. (Vincent Robert)

2008-01-01T23:59:59.000Z

411

Absolute Transports of Mass and Temperature for the North Atlantic Current Subpolar Front System  

Science Conference Proceedings (OSTI)

The flow of subtropical waters carried into the northern North Atlantic Ocean by the North Atlantic Current subpolar front system (NACSPF) is an important component of the meridional overturning circulation. These waters become colder and ...

Paula Prez-Brunius; Tom Rossby; D. Randolph Watts

2004-08-01T23:59:59.000Z

412

A 6-yr Climatology of Fronts Affecting Helsinki, Finland, and Their Boundary Layer Structure  

Science Conference Proceedings (OSTI)

A 6-yr climatology of the frequency, characteristics, and boundary layer structure of synoptic-scale fronts in Helsinki, Finland, was created using significant weather charts and observations from a 327-m-tall mast and from the Station for ...

Victoria A. Sinclair

2013-09-01T23:59:59.000Z

413

Boundary layer convergence induced by strong winds across a midlatitude SST front  

Science Conference Proceedings (OSTI)

Recent studies indicate that midlatitude SST fronts influence extends through the marine atmospheric boundary layer (MABL) into the free atmosphere, with implications for climate variability. To better understand the mechanisms of this ocean-to-...

Thomas Kilpatrick; Niklas Schneider; Bo Qiu

414

Variability of the Intertropical Front (ITF) and Rainfall over the West African SudanSahel Zone  

Science Conference Proceedings (OSTI)

The Intertropical Front (ITF) is a fundamental feature of the atmospheric circulation over West Africa. It separates the wedge of warm moist southwesterly monsoon flow off the tropical Atlantic from much hotter and very dry northeasterly wind ...

M. Issa Ll; Peter J. Lamb

2010-07-01T23:59:59.000Z

415

Low-Frequency Variability in the Midlatitude Atmosphere Induced by an Oceanic Thermal Front  

Science Conference Proceedings (OSTI)

This study examines the flow induced in a highly idealized atmospheric model by an eastwest-oriented oceanic thermal front. The model has a linear marine boundary layer coupled to a quasigeostrophic, equivalent- barotropic free atmosphere. The ...

Yizhak Feliks; Michael Ghil; Eric Simonnet

2004-05-01T23:59:59.000Z

416

DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in  

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

DOE Offers Conditional Loan Guarantee for Front End Nuclear DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in Idaho DOE Offers Conditional Loan Guarantee for Front End Nuclear Facility in Idaho May 20, 2010 - 12:00am Addthis Washington, DC - As part of a broad effort to expand the use of nuclear power in the United States and reduce carbon pollution, U.S. Secretary of Energy Steven Chu announced today the Department's first conditional commitment for a front-end nuclear facility. The $2 billion loan guarantee will support AREVA's Eagle Rock Enrichment Facility near Idaho Falls, Idaho, which will supply uranium enrichment services for the U.S. nuclear power industry. "Increasing uranium enrichment in the United States is critical to the nation's energy and national security," said Secretary Chu. "Existing

417

The Role of Stratification in the Formation and Maintenance of Shelf-Break Fronts  

Science Conference Proceedings (OSTI)

A mechanism is described for the formation or a front at the edge of a continental shelf in an initially linearly stratified fluid lacking horizontal density gradients. A primitive equation numerical model is used with a specified vertically ...

Glen Gawarkiewicz; David C. Chapman

1992-07-01T23:59:59.000Z

418

Occurrence and Structure of Mesoscale Fronts and Cyclones near Icy Bay, Alaska  

Science Conference Proceedings (OSTI)

When synoptic-scale cyclones stagnate against the mountains of southeast Alaska, a trough extends to the northwest, along the southern Alaskan coast. A front between maritime and continental air masses develops along the coast. During early ...

Michael Reynolds

1983-10-01T23:59:59.000Z

419

Boundary Layer Control of Buoyant Coastal Currents and the Establishment of a Shelfbreak Front  

Science Conference Proceedings (OSTI)

The bottom boundary layer exerts a powerful control over buoyant coastal currents that contact the bottom, providing a mechanism for trapping density fronts along isobaths. Recent observations suggest that this mechanism may play a role in ...

David C. Chapman

2000-11-01T23:59:59.000Z

420

Examination of the Mesoscale Features of the GALE Coastal Front of 24-25 January 1986  

Science Conference Proceedings (OSTI)

The early evolution of a coastal front that formed off the southeast coast of the United States on 24 January 1986 is examined. Satellite and radar imagery together with the intensive surface, upper0air, and aircraft observations available during ...

Allen J. Riordan

1990-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

Analysis and Diagnosis of the Composition of Ageostrophic Circulations in Jet-Front Systems  

Science Conference Proceedings (OSTI)

Diagnostic case studies of ageostrophic circulations in upper-tropospheric jet-front systems are presented, using the numerical analyses of the ECMWF model as data sources. The impact of the ECMWF analysis procedure on the retrieved ageostrophic ...

Jean-Pierre Cammas; Daniel Ramond

1989-11-01T23:59:59.000Z

422

On the Front Lines 162 Los Alamos Science Number 23 1995  

E-Print Network (OSTI)

On the Front Lines 162 Los Alamos Science Number 23 1995 I n 1943, the Manhattan Project. Baumbach, S. Fried, P. L. Kirk and, R. S. Rosenfels (Manhattan Project Report CK-1143, December 1943

Massey, Thomas N.

423

Potential Vorticity and Vertical Velocity at the Iceland-Frs Front  

Science Conference Proceedings (OSTI)

Using data from high-resolution surveys of the Iceland- Frs Front, the authors have calculated synoptic maps of the geostrophic velocity, vorticity, and potential vorticity on isopycnal surfaces. The data have also been used to diagnose the ...

J. T. Allen; D. A. Smeed

1996-12-01T23:59:59.000Z

424

Proceedings: Workshop on Corrosion of Steam Turbine Blading and Disks in the Phase Transition Zone  

Science Conference Proceedings (OSTI)

Most outage hours for steam turbines are due to corrosion of low pressure (LP) blades and disks in the phase transition zone (PTZ). EPRI's Workshop on Corrosion of Steam Turbine Blading and Disks in the PTZ critically reviewed the state of knowledge of corrosion fatigue and stress corrosion cracking of LP blade and disk materials, with particular emphasis on the influence of the local environment.

1998-12-17T23:59:59.000Z

425

HUBBLE SPACE TELESCOPE OBSERVATIONS OF THE HD 202628 DEBRIS DISK  

SciTech Connect

A ring-shaped debris disk around the G2V star HD 202628 (d = 24.4 pc) was imaged in scattered light at visible wavelengths using the coronagraphic mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The ring is inclined by {approx}64 Degree-Sign from face-on, based on the apparent major/minor axis ratio, with the major axis aligned along P.A. = 130 Degree-Sign . It has inner and outer radii (>50% maximum surface brightness) of 139 AU and 193 AU in the northwest ansae and 161 AU and 223 AU in the southeast ({Delta}r/r Almost-Equal-To 0.4). The maximum visible radial extent is {approx}254 AU. With mean surface brightness of V Almost-Equal-To 24 mag arcsec{sup -2}, this is the faintest debris disk observed to date in reflected light. The center of the ring appears offset from the star by {approx}28 AU (deprojected). An ellipse fit to the inner edge has an eccentricity of 0.18 and a = 158 AU. This offset, along with the relatively sharp inner edge of the ring, suggests the influence of a planetary-mass companion. There is a strong similarity with the debris ring around Fomalhaut, though HD 202628 is a more mature star with an estimated age of about 2 Gyr. We also provide surface brightness limits for nine other stars in our study with strong Spitzer excesses around which no debris disks were detected in scattered light (HD 377, HD 7590, HD 38858, HD 45184, HD 73350, HD 135599, HD 145229, HD 187897, and HD 201219).

Krist, John E.; Bryden, Geoffrey [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Stapelfeldt, Karl R. [Laboratory for Exoplanets and Stellar Astrophysics, Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Plavchan, Peter [NASA Exoplanet Science Institute, California Institute of Technology, 770 S Wilson Ave., Pasadena, CA 91125 (United States)

2012-08-15T23:59:59.000Z

426

Non-Adiabatic Effects on Combustion Front Propagation in Porous Media: Multiplicity of Steady States  

Science Conference Proceedings (OSTI)

The sustained propagation of combustion fronts in porous media is a necessary condition for the success of an in situ combustion project for oil recovery. Compared to other recovery methods, in situ combustion involves the added complexity of exothermic reactions and temperature-dependent chemical kinetics. In the presence of heat losses, the possibility of ignition and extinction (quenching) exists. In this report, we address the properties of combustion fronts propagating at a constant velocity in the presence of heat losses.

Akkutlu, I. Yucel; Yortsos, Yanis C.

2002-03-11T23:59:59.000Z

427

Influence of p-method finite element parameters on predictions of crack front geometry  

Science Conference Proceedings (OSTI)

The effect of various p-method finite element model parameters on the prediction of planar crack front geometry in three dimensional structures is evaluated. An automatic crack growth method was developed using the commercial software StressCheck coupled ... Keywords: ?, Corner crack, Crack front, Finite element, Mesh, Stress intensity factor, a, b, b/a, c, ctrat, ipr, m, mrat, p-method, trans

Diane Wowk, Kyle Gamble, Ross Underhill

2013-10-01T23:59:59.000Z

428

Wave front fragmentation due to ventricular geometry in a model of the rabbit heart  

Science Conference Proceedings (OSTI)

The role of the hearts complex shape in causing the fragmentation of activation wave fronts characteristic of ventricular fibrillation (VF) has not been well studied. We used a finite element model of cardiac propagation capable of simulating functional reentry on curved two-dimensional surfaces to test the hypothesis that uneven surface curvature can cause local propagation block leading to proliferation of reentrant wave fronts. We found that when reentry was induced on a flat sheet

Jack M. Rogers

2002-01-01T23:59:59.000Z

429

Coordinate-free description of corrugated flames with realistic density drop at the front  

E-Print Network (OSTI)

The complete set of hydrodynamic equations for a corrugated flame front is reduced to a system of coordinate-free equations at the front using the fact that vorticity effects remain relatively weak even for corrugated flames. It is demonstrated how small but finite flame thickness may be taken into account in the equations. Similar equations are obtained for turbulent burning in the flamelet regime. The equations for a turbulent corrugated flame are consistent with the Taylor hypothesis of stationary external turbulence.

Vitaly Bychkov; Maxim Zaytsev; V'yacheslav Akkerman

2012-10-30T23:59:59.000Z

430

CHEMICAL EVOLUTION OF TURBULENT PROTOPLANETARY DISKS AND THE SOLAR NEBULA  

SciTech Connect

We study the influence of transport processes on the chemical evolution of DM Tau-like protoplanetary disks. Turbulent transport of gases and ices is implicitly modeled in full two dimensions (2D), using the mixing-length approximation, along with the time-dependent chemistry. We find that turbulent transport enhances abundances and column densities of many gas-phase species and ices, particularly, complex ones. The influence of turbulent mixing on disk chemistry is more pronounced in the inner, planet-forming disk region where gradients of temperature and high-energy radiation intensities are steeper than in the outer region. The molecules that are unresponsive to transport include, e.g., C{sub 2}H, C{sup +}, CH{sub 4}, CN, CO, HCN, HNC, H{sub 2}CO, OH, as well as water and ammonia ice. Their column densities computed with the laminar and 2D mixing model differ by a factor of {approx}< 2-5. Molecules whose vertical column densities in the laminar and dynamical models differ by up to two orders of magnitude include, e.g., C{sub 2}H{sub 2}, some carbon chains, CS, H{sub 2}CS, H{sub 2}O, HCO{sup +}, HCOOH, HNCO, N{sub 2}H{sup +}, NH{sub 3}, CO ice, H{sub 2}CO ice, CH{sub 3}OH ice, and electrons. Molecules whose column densities are altered by diffusion by more than two orders of magnitude include, e.g., C{sub 2}S, C{sub 3}S, C{sub 6}H{sub 6}, CO{sub 2}, O{sub 2}, SiO, SO, SO{sub 2}, long carbon chain ices, CH{sub 3}CHO ice, HCOOH ice, O{sub 2} ice, and OCN ice. We indicate several observable or potentially detectable tracers of transport processes in protoplanetary disks and the solar nebula, such as heavy hydrocarbon ices, complex organics, CO{sub 2}, O{sub 2}, SO, SO{sub 2}, C{sub 2}S, C{sub 3}S compared to CO and water ice.

Semenov, D. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Wiebe, D., E-mail: semenov@mpia.de, E-mail: dwiebe@inasan.ru [Institute of Astronomy of the RAS, Pyatnitskaya St. 48, 119017 Moscow (Russian Federation)

2011-10-01T23:59:59.000Z

431

AdS/QCD, Light-Front Holography, and Color Confinement  

E-Print Network (OSTI)

A remarkable holographic feature of dynamics in AdS space in five dimensions is that it is dual to Hamiltonian theory in physical space-time, quantized at fixed light-front time {\\tau} = t+z/c. This light-front holographic principle provides a precise relation between the bound-state amplitudes in AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The fifth dimension coordinate z is dual to the light front variable {\\zeta} describing the invariant separation of the quark constituents. The resulting valence Fock-state wavefunction eigensolutions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schr\\"odinger equation. The soft-wall dilaton profile exp ({\\kappa}^2 {\\zeta}^2) provides a model for the light-front potential which is color-confining and reproduces well the linear Regge behavior of the light-quark hadron spectrum in both L, the orbital angu...

Brodsky, Stanley J

2013-01-01T23:59:59.000Z

432

Radiation-induced solitary waves in hot plasmas of accretion disks  

E-Print Network (OSTI)

It is shown that the existence of radiation-induced solitary waves in hot plasmas of accretion disks depends on the radial temperature profile.

Fedor V. Prigara

2005-07-08T23:59:59.000Z

433

Depletion and harvesting thermal energy from actuator arm electronics in hard disk drives.  

E-Print Network (OSTI)

??In recent years, thermally assistive magnetic recording (TAMR) has been applied on actuator arm electronics (AE) in hard disk drive (HDD). When HDD operates, temperature (more)

Wu, Di

2011-01-01T23:59:59.000Z

434

The Development of Direct Age 718 for Gas Turbine Engine Disk ...  

Science Conference Proceedings (OSTI)

as a commercial gas turbine aircraft engine disk material are described. Initial ... Engines (GEAE) in the production of gas turbine engine components (1).

435

NEUTRINO SPECTRA FROM ACCRETION DISKS: NEUTRINO GENERAL RELATIVISTIC EFFECTS AND THE CONSEQUENCES FOR NUCLEOSYNTHESIS  

Science Conference Proceedings (OSTI)

Black hole (BH) accretion disks have been proposed as good candidates for a range of interesting nucleosynthesis, including the r-process. The presence of the BH influences the neutrino fluxes and affects the nucleosynthesis resulting from the interaction of the emitted neutrinos and hot outflowing material ejected from the disk. We study the impact of general relativistic effects on the neutrinos emitted from BH accretion disks. We present abundances obtained by considering null geodesics and energy shifts for two different disk models. We find that both the bending of the neutrino trajectories and the energy shifts have important consequences for the nucleosynthetic outcome.

Caballero, O. L.; McLaughlin, G. C. [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Surman, R., E-mail: lcaballe@uw.edu, E-mail: olcaball@ncsu.edu, E-mail: gail_mclaughlin@ncsu.edu, E-mail: surmanr@union.edu [Department of Physics and Astronomy, Union College, Schenectady, NY 12308 (United States)

2012-02-01T23:59:59.000Z

436

Neutrino Spectra from Accretion Disks: Neutrino General Relativistic Effects and the Consequences for Nucleosynthesis  

E-Print Network (OSTI)

Black hole accretion disks have been proposed as good candidates for a range of interesting nucleosynthesis, including the r-process. The presence of the black hole influences the neutrino fluxes and affects the nucleosynthesis resulting from the interaction of the emitted neutrinos and hot outflowing material ejected from the disk. We study the impact of general relativistic effects on the neutrinos emitted from black hole accretion disks. We present abundances obtained by considering null geodesics and energy shifts for two different disk models. We find that both the bending of the neutrino trajectories and the energy shifts have important consequences for the nucleosynthetic outcome

O. L Caballero; G. C. McLaughlin; R. Surman

2011-05-31T23:59:59.000Z

437

GLOBAL MODELING OF RADIATIVELY DRIVEN ACCRETION OF METALS FROM COMPACT DEBRIS DISKS ONTO WHITE DWARFS  

Science Conference Proceedings (OSTI)

Recent infrared observations have revealed the presence of compact (radii {approx}rate M-dot{sub PR}{approx}10{sup 8} g s{sup -1}. Here we extend this local analysis by exploring the global evolution of the debris disk under the action of the PR drag for a variety of assumptions about the disk properties. We find that massive disks (mass {approx}> 10{sup 20} g), which are optically thick to incident stellar radiation, inevitably give rise to metal accretion at rates M-dot {approx}>0.2 M-dot{sub PR}. The magnitude of M-dot and its time evolution are determined predominantly by the initial pattern of the radial distribution of the debris (i.e., ring-like versus disk-like) but not by the total mass of the disk. The latter determines only the disk lifetime, which can be several Myr or longer. The evolution of an optically thick disk generically results in the development of a sharp outer edge of the disk. We also find that the low-mass ({approx}< 10{sup 20} g), optically thin disks exhibit M-dot << M-dot{sub PR} and evolve on a characteristic timescale {approx}10{sup 5}-10{sup 6} yr, independent of their total mass.

Bochkarev, Konstantin V. [Department of General and Applied Physics, Moscow Institute of Physics and Technology, Dolgoprudny, 141700 (Russian Federation); Rafikov, Roman R., E-mail: bochkarevkv@gmail.com, E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540 (United States)

2011-11-01T23:59:59.000Z

438

WWW Database of Models of Accretion Disks Irradiated by The Central Star  

E-Print Network (OSTI)

We announce the release of a catalog of physical models of irradiated accretion disks around young stars based on the modelling techniques by D'Alessio et al. The WWW catalog includes ~ 3000 disk models for different central stars, disk sizes, inclinations, dust contents and mass accretion rates. For any of them, radial profiles of disk physical parameters and synthetic spectral energy distributions can be browsed and downloaded to compare with observations. It can be accessed at http://www-cfa.harvard.edu/youngstars/dalessio/ (US), http://www.astrosmo.unam.mx/~dalessio/ (Mexico), and at http://www.laeff.esa.es/models/dalessio/ (Spain).

Paola D'Alessio; Bruno Merin; Nuria Calvet; Lee Hartmann; Benjamin Montesinos

2004-12-14T23:59:59.000Z

439

Microsoft Word - solcar95.html  

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

FORCE FORCE VEHICLE SPECIFICATIONS CONVERTED VEHICLE Base Vehicle: 1995 Geo Metro VIN:2C1MR529XS6783464 Seatbelt Positions: Three Standard Features: Power Brakes Front Disk Brakes Front Wheel Drive Dual Air Bags AM/FM Stereo Radio w/Cassette Electric Heater Options as Tested: None BATTERY Manufacturer: GM Ovonic Type: 13.2EV85 Nickel Metal Hydride Number of Modules: 14 Weight of Module: 18 kg Weight of Pack(s): 254 kg Pack Locations: Undertrunk/Underhood Nominal Module Voltage: 13.2 V Nominal System Voltage: 185 V Nominal Capacity (1C): 85 Ah WEIGHTS Design Curb Weight: 2246 lbs Delivered Curb Weight: 2304 lbs Distribution F/R: 50/50 % GVWR: 2755 lbs GAWR F/R: 1432/1366 lbs Payload: 451 lbs Performance Goal: 664 lbs DIMENSIONS Wheelbase: 93.5 inches

440

Is There a Fundamental Line for Disk Galaxies?  

E-Print Network (OSTI)

We show that there are strong local correlations between metallicity, surface brightness, and dynamical mass-to-light ratio within M33, analogous to the fundamental line of dwarf galaxies identified by Prada & Burkert (2002). Using near-infrared imaging from 2MASS, the published rotation curve of M33, and literature measurements of the metallicities of HII regions and supergiant stars, we demonstrate that these correlations hold for points at radial distances between 140 pc and 6.2 kpc from the center of the galaxy. At a given metallicity or surface brightness, M33 has a mass-to-light ratio approximately four times as large as the Local Group dwarf galaxies; other than this constant offset, we see broad agreement between the M33 and dwarf galaxy data. We use analytical arguments to show that at least two of the three fundamental line correlations are basic properties of disk galaxies that can be derived from very general assumptions. We investigate the effect of supernova feedback on the fundamental line with numerical models and conclude that while feedback clearly controls the scatter in the fundamental line, it is not needed to create the fundamental line itself, in agreement with our analytical calculations. We also compare the M33 data with measurements of a simulated disk galaxy, finding that the simulation reproduces the trends in the data correctly and matches the fundamental line, although the metallicity of the simulated galaxy is too high, and the surface brightness is lower than that of M33.

Joshua D. Simon; Francisco Prada; Jose M. Vilchez; Leo Blitz; Brant Robertson

2006-06-22T23:59:59.000Z

Note: This page contains sample records for the topic "front 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

Water in Protoplanetary Disks: Deuteration and Turbulent Mixing  

E-Print Network (OSTI)

We investigate water and deuterated water chemistry in turbulent protoplanetary disks. Chemical rate equations are solved with the diffusion term, mimicking turbulent mixing in vertical direction. Water near the midplane is transported to the disk atmosphere by turbulence and destroyed by photoreactions to produce atomic oxygen, while the atomic oxygen is transported to the midplane and reforms water and/or other molecules. We find that this cycle significantly decreases column densities of water ice at r water ice effectively. The radial extent of such region depends on the desorption energy of atomic hydrogen. Our model indicates that water ice could be deficient even outside the sublimation radius. Outside this radius, the cycle decreases the D/H ratio of water ice from 2x10^-2, which is set by the collapsing core model, to 10^-4-10^-2 in 10^6 yr, without significantly decreasing the water ice column density. The resultant D/H ratios depend on the ...

Furuya, Kenji; Nomura, Hideko; Hersant, Franck; Wakelam, Valentine

2013-01-01T23:59:59.000Z

442

GLOBAL DRAG-INDUCED INSTABILITIES IN PROTOPLANETARY DISKS  

SciTech Connect

We use the Fokker-Planck equation and model the dispersive dynamics of solid particles in annular protoplanetary disks whose gas component is more massive than the particle phase. We model particle-gas interactions as hard sphere collisions, determine the functional form of diffusion coefficients, and show the existence of two global unstable modes in the particle phase. These modes have spiral patterns with the azimuthal wavenumber m = 1 and rotate slowly. We show that in ring-shaped disks, the phase-space density of solid particles increases linearly in time toward an accumulation point near the location of pressure maximum, while instabilities grow exponentially. Therefore, planetesimals and planetary cores can be efficiently produced near the peaks of unstable density waves. In this mechanism, particles migrating toward the accumulation point will not participate in the formation of planets, and should eventually form a debris ring like the main asteroid belt or classical Kuiper Belt objects. We present the implications of global instabilities to the formation of ice giants and terrestrial planets in the solar system.

Jalali, Mir Abbas, E-mail: mjalali@sharif.edu [Computational Mechanics Laboratory, Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11155-9567, Tehran (Iran, Islamic Republic of)

2013-07-20T23:59:59.000Z

443

Why Buckling Stellar Bars Weaken in Disk Galaxies  

E-Print Network (OSTI)

Young stellar bars in disk galaxies experience a vertical buckling instability which terminates their growth and thickens them, resulting in a characteristic peanut/boxy shape when viewed edge on. Using N-body simulations of galactic disks embedded in live halos, we have analyzed the bar structure throughout this instability and found that the outer third of the bar dissolves completely while the inner part (within the vertical inner Lindblad resonance) becomes less oval. The bar acquires the frequently observed peanut/boxy-shaped isophotes. We also find that the bar buckling is responsible for a mass injection above the plane, which is subsequently trapped by specific 3-D families of periodic orbits of particular shapes explaining the observed isophotes, in line with previous work. Using a 3-D orbit analysis and surfaces of sections, we infer that the outer part of the bar is dissolved by a rapidly widening stochastic region around its corotation radius -- a process related to the bar growth. This leads to a...

Martinez-Valpuesta, I

2004-01-01T23:59:59.000Z

444

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

445

Accretion disks around black holes in modified strong gravity  

E-Print Network (OSTI)

Stellar-mass black holes offer what is perhaps the best scenario to test theories of gravity in the strong-field regime. In particular, f(R) theories, which have been widely discuss in a cosmological context, can be constrained through realistic astrophysical models of phenomena around black holes. We aim at building radiative models of thin accretion disks for both Schwarzschild and Kerr black holes in f(R) gravity. We study particle motion in f(R)-Schwarzschild and Kerr space-times. We present the spectral energy distribution of the accretion disk around constant Ricci scalar f(R) black holes, and constrain specific f(R) prescriptions using features of these systems. A precise determination of both the spin and accretion rate onto black holes along with X-ray observations of their thermal spectrum might allow to identify deviations of gravity from General Relativity. We use recent data on the high-mass X-ray binary Cygnus X-1 to restrict the values of the parameters of a class of f(R) models.

Daniela Prez; Gustavo E. Romero; Santiago E. Perez Bergliaffa

2012-12-11T23:59:59.000Z

446

EVIDENCE FOR A SNOW LINE BEYOND THE TRANSITIONAL RADIUS IN THE TW Hya PROTOPLANETARY DISK  

SciTech Connect

We present an observational reconstruction of the radial water vapor content near the surface of the TW Hya transitional protoplanetary disk, and report the first localization of the snow line during this phase of disk evolution. The observations are comprised of Spitzer-IRS, Herschel-PACS, and Herschel-HIFI archival spectra. The abundance structure is retrieved by fitting a two-dimensional disk model to the available star+disk photometry and all observed H{sub 2}O lines, using a simple step-function parameterization of the water vapor content near the disk surface. We find that water vapor is abundant ({approx}10{sup -4} per H{sub 2}) in a narrow ring, located at the disk transition radius some 4 AU from the central star, but drops rapidly by several orders of magnitude beyond 4.2 AU over a scale length of no more than 0.5 AU. The inner disk (0.5-4 AU) is also dry, with an upper limit on the vertically averaged water abundance of 10{sup -6} per H{sub 2}. The water vapor peak occurs at a radius significantly more distant than that expected for a passive continuous disk around a 0.6 M{sub Sun} star, representing a volatile distribution in the TW Hya disk that bears strong similarities to that of the solar system. This is observational evidence for a snow line that moves outward with time in passive disks, with a dry inner disk that results either from gas giant formation or gas dissipation and a significant ice reservoir at large radii. The amount of water present near the snow line is sufficient to potentially catalyze the (further) formation of planetesimals and planets at distances beyond a few AU.

Zhang, K. [Division of Physics, Mathematics and Astronomy, MC 150-21, California Institute of Technology, Pasadena, CA 91125 (United States)] [Division of Physics, Mathematics and Astronomy, MC 150-21, California Institute of Technology, Pasadena, CA 91125 (United States); Pontoppidan, K. M. [Space Telescope Science Institute, Baltimore, MD 21218 (United States)] [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Salyk, C. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States)] [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States); Blake, G. A., E-mail: kzhang@caltech.edu [Division of Geological and Planetary Sciences, MC 150-21, California Institute of Technology, Pasadena, CA 91125 (United States)

2013-04-01T23:59:59.000Z

447

AdS/QCD and Applications of Light-Front Holography  

SciTech Connect

Light-Front Holography leads to a rigorous connection between hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space and frame-independent light-front wavefunctions of hadrons in 3 + 1 physical space-time, thus providing a compelling physical interpretation of the AdS/CFT correspondence principle and AdS/QCD, a useful framework which describes the correspondence between theories in a modified AdS5 background and confining field theories in physical space-time. To a first semiclassical approximation, where quantum loops and quark masses are not included, this approach leads to a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role. We give an overview of the light-front holographic approach to strongly coupled QCD. In particular, we study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The results for the TFFs for the {eta} and {eta}' mesons are also presented. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

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

2012-02-16T23:59:59.000Z

448

A Resolved Molecular Gas Disk around the Nearby A Star 49 Ceti  

E-Print Network (OSTI)

The A star 49 Ceti, at a distance of 61 pc, is unusual in retaining a substantial quantity of molecular gas while exhibiting dust properties similar to those of a debris disk. We present resolved observations of the disk around 49 Ceti from the Submillimeter Array in the J=2-1 rotational transition of CO with a resolution of 1.0x1.2 arcsec. The observed emission reveals an extended rotating structure viewed approximately edge-on and clear of detectable CO emission out to a distance of ~90 AU from the star. No 1.3 millimeter continuum emission is detected at a 3-sigma sensitivity of 2.1 mJy/beam. Models of disk structure and chemistry indicate that the inner disk is devoid of molecular gas, while the outer gas disk between 40 and 200 AU from the star is dominated by photochemistry from stellar and interstellar radiation. We determine parameters for a model that reproduces the basic features of the spatially resolved CO J=2-1 emission, the spectral energy distribution, and the unresolved CO J=3-2 spectrum. We investigate variations in disk chemistry and observable properties for a range of structural parameters. 49 Ceti appears to be a rare example of a system in a late stage of transition between a gas-rich protoplanetary disk and a tenuous, virtually gas-free debris disk.

A. M. Hughes; D. J. Wilner; I. Kamp; M. R. Hogerheijde

2008-03-24T23:59:59.000Z

449

The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk  

E-Print Network (OSTI)

The edge-on disk surrounding the nearby young star Beta Pictoris is the archetype of the "debris disks", which are composed of dust and gas produced by collisions and evaporation of planetesimals, analogues of Solar System comets and asteroids. These disks provide a window on the formation and early evolution of terrestrial planets. Previous observations of Beta Pic concluded that the disk gas has roughly solar abundances of elements [1], but this poses a problem because such gas should be rapidly blown away from the star, contrary to observations of a stable gas disk in Keplerian rotation [1, 2]. Here we report the detection of singly and doubly ionized carbon (CII, CIII) and neutral atomic oxygen (OI) gas in the Beta Pic disk; measurement of these abundant volatile species permits a much more complete gas inventory. Carbon is extremely overabundant relative to every other measured element. This appears to solve the problem of the stable gas disk, since the carbon overabundance should keep the gas disk in Keplerian rotation [3]. New questions arise, however, since the overabundance may indicate the gas is produced from material more carbon-rich than the expected Solar System analogues.

Aki Roberge; Paul D. Feldman; Alycia J. Weinberger; Magali Deleuil; Jean-Claude Bouret

2006-04-19T23:59:59.000Z

450

THE STRUCTURE OF A SELF-GRAVITATING PROTOPLANETARY DISK AND ITS IMPLICATIONS FOR DIRECT IMAGING OBSERVATIONS  

SciTech Connect

We consider the effects of self-gravity on the hydrostatic balance in the vertical direction of a gaseous disk and discuss the possible signature of the self-gravity that may be captured by direct imaging observations of protoplanetary disks in the future. In this paper, we consider a vertically isothermal disk in order to isolate the effects of self-gravity. The specific disk model we consider in this paper is the one with a radial surface density gap, at which the Toomre's Q-parameter of the disk varies rapidly in the radial direction. We calculate the vertical structure of the disk including the effects of self-gravity. We then calculate the scattered light and the dust thermal emission. We find that if the disk is massive enough and the effects of self-gravity come into play, a weak bump-like structure at the gap edge appears in the near-infrared (NIR) scattered light, while no such bump-like structure is seen in the submillimeter (sub-mm) dust continuum image. The appearance of the bump is caused by the variation of the height of the surface in the NIR wavelength. If such a bump-like feature is detected in future direct imaging observations, combined with sub-mm observations, it will give us useful information about the physical states of the disk.

Muto, Takayuki, E-mail: muto@geo.titech.ac.jp [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan)

2011-09-20T23:59:59.000Z

451

Stress and Fracture Analysis of Shrunk-On Steam Turbine Disks  

Science Conference Proceedings (OSTI)

Utilities spend millions of dollars each year to repair or replace cracked shrunk-on disks in low-pressure steam turbines. One reason for cracking, this project concludes, is that stress approaches the yield strength of disks in many current turbine designs.

1984-01-01T23:59:59.000Z

452

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

453

PLANET-DISK INTERACTION IN THREE DIMENSIONS: THE IMPORTANCE OF BUOYANCY WAVES  

SciTech Connect

We carry out local three-dimensional (3D) hydrodynamic simulations of planet-disk interaction in stratified disks with varied thermodynamic properties. We find that whenever the Brunt-Vaeisaelae frequency (N) in the disk is non-zero, the planet exerts a strong torque on the disk in the vicinity of the planet, with a reduction in the traditional 'torque cutoff'. In particular, this is true for adiabatic perturbations in disks with isothermal density structure, as should be typical for centrally irradiated protoplanetary disks. We identify this torque with buoyancy waves, which are excited (when N is non-zero) close to the planet, within one disk scale height from its orbit. These waves give rise to density perturbations with a characteristic 3D spatial pattern which is in close agreement with the linear dispersion relation. The torque due to these waves can amount to as much as several tens of percent of the total planetary torque, which is not expected based on analytical calculations limited to axisymmetric or low-m modes. Buoyancy waves should be ubiquitous around planets in the inner, dense regions of protoplanetary disks, where they might possibly affect planet migration.

Zhu Zhaohuan; Stone, James M.; Rafikov, Roman R., E-mail: zhzhu@astro.princeton.edu, E-mail: jstone@astro.princeton.edu, E-mail: rrr@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2012-10-20T23:59:59.000Z

454

Brief paper: Multi-frequency disturbance rejection via blending control technique for hard disk drives  

Science Conference Proceedings (OSTI)

This paper is concerned with the rejection of multiple narrowband disturbances in hard disk drives (HDDs). Inspired by a control blending idea, the multi-frequency disturbance rejection is formulated as a blending control problem. Each disturbance rejection ... Keywords: Blending control, H2 control, Hard disk drives, Servo control, Vibration rejection

Chunling Du; Lihua Xie; F. L. Lewis; Youyi Wang

2009-10-01T23:59:59.000Z

455

A Wind Tunnel Investigation on the Riming of Snowflakes. Part I: Porous Disks and Large Stellars  

Science Conference Proceedings (OSTI)

The effects of porosity on the accretional growth characteristics of ice crystal aggregates (snowflakes) are investigated by riming circular disks of ice in a cloud tunnel. Twelve disk models were used, sized 5 to 6 mm and 10 to 11 mm in diameter,...

Jeffrey K. Lew; Derek C. Montague; Hans R. Pruppacher; Roy M. Rasmussen

1986-11-01T23:59:59.000Z

456

RAID0.5: design and implementation of a low cost disk array data protection method  

Science Conference Proceedings (OSTI)

RAID has long been established as an effective way to provide highly reliable as well as high-performance disk subsystems. However, reliability in RAID systems comes at the cost of extra disks. In this paper, we describe a mechanism that we have termed ... Keywords: Availability, RAID, Reliability, Storage

John A. Chandy

2008-11-01T23:59:59.000Z

457

INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS  

SciTech Connect

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range {approx}0.03-30 cm.

Rafikov, Roman R.; Garmilla, Jose A., E-mail: rrr@astro.princeton.edu, E-mail: garmilla@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)

2012-12-01T23:59:59.000Z

458

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

Science Conference Proceedings (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 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

459

Design of the NSLS-II Linac Front End Test Stand  

SciTech Connect

The NSLS-II operational parameters place very stringent requirements on the injection system. Among these are the charge per bunch train at low emittance that is required from the linac along with the uniformity of the charge per bunch along the train. The NSLS-II linac is a 200 MeV linac produced by Research Instruments Gmbh. Part of the strategy for understanding to operation of the injectors is to test the front end of the linac prior to its installation in the facility. The linac front end consists of a 100 kV electron gun, 500 MHz subharmonic prebuncher, focusing solenoids and a suite of diagnostics. The diagnostics in the front end need to be supplemented with an additional suite of diagnostics to fully characterize the beam. In this paper we discuss the design of a test stand to measure the various properties of the beam generated from this section. In particular, the test stand will measure the charge, transverse emittance, energy, energy spread, and bunching performance of the linac front end under all operating conditions of the front end.

Fliller III, R.; Johanson, M.; Lucas, M.; Rose, J.; Shaftan, T.

2011-03-28T23:59:59.000Z

460

Apparatus for characterizing the temporo-spatial properties of a dynamic fluid front and method thereof  

SciTech Connect

Methods and apparatus are described for characterizing the temporal-spatial properties of a dynamic fluid front within a mold space while the mold space is being filled with fluid. A method includes providing a mold defining a mold space and having one or more openings into the mold space; heating a plurality of temperature sensors that extend into the mold space; injecting a fluid into th emold space through the openings, the fluid experiencing a dynamic fluid front while filling the mold space with a fluid; and characterizing temporal-spatial properties of the dynamic fluid front by monitoring a termperature of each of the plurality of heated temperature sensors while the mold space is being filled with the fluid. An apparatus includes a mold defining a mold space; one or more openings for introducing a fluid into th emold space and filling the mold space with the fluid, the fluid experiencing a dynamic fluid front while filling the mold space; a plurality of heated temperature sensors extending into the mold space; and a computer coupled to the plurality of heated temperature sensors for characterizing the temporal-spatial properties of the dynamic fluid front.

Battiste, Richard L

2013-12-31T23:59:59.000Z

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461

3D Radiative Hydrodynamics for Disk Stability Simulations: A Proposed Testing Standard and New Results  

E-Print Network (OSTI)

Recent three-dimensional radiative hydrodynamics simulations of protoplanetary disks report disparate disk behaviors, and these differences involve the importance of convection to disk cooling, the dependence of disk cooling on metallicity, and the stability of disks against fragmentation and clump formation. To guarantee trustworthy results, a radiative physics algorithm must demonstrate the capability to handle both the high and low optical depth regimes. We develop a test suite that can be used to demonstrate an algorithm's ability to relax to known analytic flux and temperature distributions, to follow a contracting slab, and to inhibit or permit convection appropriately. We then show that the radiative algorithm employed by Meji\\'a (2004) and Boley et al. (2006) and the algorithm employed by Cai et al. (2006) and Cai et al. (2007, in prep.) pass these tests with reasonable accuracy. In addition, we discuss a new algorithm that couples flux-limited diffusion with vertical rays, we apply the test suite, an...

Boley, Aaron C; Nordlund, Aake; Lord, Jesse

2007-01-01T23:59:59.000Z

462

Accretion Disks Around Binary Black Holes: A Simple GR-Hybrid Evolution Model  

E-Print Network (OSTI)

We consider a geometrically thin, Keplerian disk in the orbital plane of a binary black hole (BHBH) consisting of a spinning primary and low-mass secondary (mass ratio q important prior to binary-disk decoupling, when the orbital separation is large and resides in the weak-field regime. The tidal torque on the disk diminishes during late merger and vanishes altogether following merger. By contrast, the viscous torque drives the flow into the strong-field region and onto the primary during all epochs. Following binary coalescence, the viscous torque alone governs the time-dependent accretion onto the remnant, as well as the temporal behavior, strength and spectrum of the aftermath electromagnetic radiation from the disk. We solve our GR-hybrid equation for a representative BHBH-disk system, identify several observable EM signatures of the merger, and compare results obtained for the gas and EM radiation with those found with the Newtonian prescription.

Stuart L. Shapiro

2013-04-22T23:59:59.000Z

463

Transport coefficients for dense hard-disk systems  

E-Print Network (OSTI)

A study of the transport coefficients of a system of elastic hard disks, based on the use of Helfand-Einstein expressions is reported. The self-diffusion, the viscosity, and the heat conductivity are examined with averaging techniques especially appropriate for the use in event-driven molecular dynamics algorithms with periodic boundary conditions. The density and size dependence of the results is analyzed, and comparison with the predictions from Enskog's theory is carried out. In particular, the behavior of the transport coefficients in the vicinity of the fluid-solid transition is investigated and a striking power law divergence of the viscosity in this region is obtained, while all other examined transport coefficients show a drop in that density range.

Ramn Garca-Rojo; Stefan Luding; J. Javier Brey

2005-11-28T23:59:59.000Z

464

Why Buckling Stellar Bars Weaken in Disk Galaxies  

E-Print Network (OSTI)

Young stellar bars in disk galaxies experience a vertical buckling instability which terminates their growth and thickens them, resulting in a characteristic peanut/boxy shape when viewed edge on. Using N-body simulations of galactic disks embedded in live halos, we have analyzed the bar structure throughout this instability and found that the outer third of the bar dissolves completely while the inner part (within the vertical inner Lindblad resonance) becomes less oval. The bar acquires the frequently observed peanut/boxy-shaped isophotes. We also find that the bar buckling is responsible for a mass injection above the plane, which is subsequently trapped by specific 3-D families of periodic orbits of particular shapes explaining the observed isophotes, in line with previous work. Using a 3-D orbit analysis and surfaces of sections, we infer that the outer part of the bar is dissolved by a rapidly widening stochastic region around its corotation radius -- a process related to the bar growth. This leads to a dramatic decrease in the bar size, decrease in the overall bar strength and a mild increase in its pattern speed, but is not expected to lead to a complete bar dissolution. The buckling instability appears primarily responsible for shortening the secular diffusion timescale to a dynamical one when building the boxy isophotes. The sufficiently long timescale of described evolution, ~1 Gyr, can affect the observed bar fraction in local universe and at higher redshifts, both through reduced bar strength and the absence of dust offset lanes in the bar.

Inma Martinez-Valpuesta; Isaac Shlosman

2004-08-13T23:59:59.000Z

465

A Model for Tracking Fronts of Stress-Induced Permeability Enhancement  

E-Print Network (OSTI)

Using an analogy to the classical Stefan problem, we construct evolution equations for the fluid pore pressure on both sides of a propagating stress-induced damage front. Closed form expressions are derived for the position of the damage front as a function of time for the cases of thermally-induced damage as well as damage induced by over-pressure. We derive expressions for the flow rate during constant pressure fluid injection from the surface corresponding to a spherically shaped subsurface damage front. Finally, our model results suggest an interpretation of field data obtained during constant pressure fluid injection over the course of 16 days at an injection site near Desert Peak, NV.

K. C. Lewis; Satish Karra; Sharad Kelkar

2013-05-15T23:59:59.000Z

466

A Model for Tracking Fronts of Stress-Induced Permeability Enhancement  

E-Print Network (OSTI)

Using an analogy to the classical Stefan problem, we construct evolution equations for the fluid pore pressure on both sides of a propagating stress-induced damage front. Closed form expressions are derived for the position of the damage front as a function of time for the cases of thermally-induced damage as well as damage induced by over-pressure. We derive expressions for the flow rate during constant pressure fluid injection from the surface corresponding to a spherically shaped subsurface damage front. Finally, our model results suggest an interpretation of field data obtained during constant pressure fluid injection over the course of 16 days at an injection site near Desert Peak, NV.

Lewis, K C; Kelkar, Sharad

2013-01-01T23:59:59.000Z

467

Report on the value engineering workshop on APS beamline front ends  

SciTech Connect

A formal value engineering evaluation process was developed to address the front end components of the beamlines for the Advanced Photon Source (APS). This process (described in Section 2) involved an information phase, a creative phase, a judgment phase, a development phase, and a recommendation phase. Technical experts from other national laboratories and industry were invited to a two-day Value Engineering Workshop on November 5-6, 1992. The results of this Workshop are described in Section 4. Following the Workshop, various actions by the APS staff led to the redesign of the front end components, which are presented in Sections 5 and 6. The cost benefit analysis is presented in Section 7. It is important of realize that an added benefit of the Workshop was to obtain numerous design evaluations and enhancements of the front end components by experts in the field. As the design work proceeds to Title II completion, the APS staff is including many of these suggestions.

Kuzay, T.

1993-01-01T23:59:59.000Z

468

Measures of the Environmental Footprint of the Front End of the Nuclear Fuel Cycle  

Science Conference Proceedings (OSTI)

Previous estimates of environmental impacts associated with the front end of the nuclear fuel cycle have focused primarily on energy consumption and CO2 emissions. Results have varied widely. Section 2 of this report provides a summary of historical estimates. This study revises existing empirical correlations and their underlying assumptions to fit to a more complete set of existing data. This study also addresses land transformation, water withdrawals, and occupational and public health impacts associated with the processes of the front end of the once-through nuclear fuel cycle. These processes include uranium mining, milling, refining, conversion, enrichment, and fuel fabrication. Metrics are developed to allow environmental impacts to be summed across the full set of front end processes, including transportation and disposition of the resulting depleted uranium.

Brett Carlsen; Emily Tavrides; Erich Schneider

2010-08-01T23:59:59.000Z

469

Characteristics of Medical Research News Reported on Front Pages of Newspapers  

E-Print Network (OSTI)

Background: The placement of medical research news on a newspapers front page is intended to gain the publics attention, so it is important to understand the source of the news in terms of research maturity and evidence level. Methodology/Principal Findings: We searched LexisNexis to identify medical research reported on front pages of major newspapers published from January 1, 2000 to December 31, 2002. We used MEDLINE and Google Scholar to find journal articles corresponding to the research, and determined their evidence level. Of 734 front-page medical research stories identified, 417 (57%) referred to mature research published in peer-reviewed journals. The remaining 317 stories referred to preliminary findings presented at scientific or press meetings; 144 (45%) of those stories mentioned studies that later matured (i.e. were published in journals within 3 years after news coverage). The evidence-level distribution of the 515

William Yuk; Yeu Lai; Trevor Lane

2008-01-01T23:59:59.000Z

470

G-SCAN: a novel real-time disk scheduling using grouping and branch-and-bound strategy  

Science Conference Proceedings (OSTI)

For mixed-media workload, disk scheduling strategies have to guarantee the QoS (Quality of Service) of requests with timing constraints while optimizing the disk utilization. In this paper, we present a novel real-time disk scheduling algorithm which ...

Taeseok Kim; Eungkyu Song; Yunji Koh; Youjip Won; Kern Koh

2006-05-01T23:59:59.000Z

471

Alternative Muon Front-end for the International Design Study (IDS)  

E-Print Network (OSTI)

We discuss alternative designs of the muon capture front end of the Neutrino Factory International Design Study (IDS). In the front end, a proton bunch on a target creates secondary pions that drift into a capture channel, decaying into muons. A sequence of RF cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. This design is affected by limitations on accelerating gradients within magnetic fields. The effects of gradient limitations are explored, and mitigation strategies are presented

Alekou, A; Martini, M; Prior, G; Rogers, C; Stratakis, D; Yoshikawa, C; Zisman, M

2010-01-01T23:59:59.000Z

472

Spiral Disk Opacity from Occulting Galaxy Pairs in the Sloan Digital Sky Survey  

E-Print Network (OSTI)

A spiral galaxy partially ovelapping a more distant elliptical offers an unique opportunity to measure the dust extinction in the foreground spiral. From the Sloan Digital Sky Survey DR4 spectroscopic sample, we selected 83 occulting galaxy pairs and measured disk opacity over the redshift range z = 0.0-0.2 with the goal to determine the recent evolution of disk dust opacity. The enrichment of the ISM changes over the lifetime of a disk and it is reasonable to expect the dust extinction properties of spiral disks as a whole to change over their lifetime. When they do, the change will affect our measurements of galaxies over the observable universe. From the SDSS pairs we conclude that spiral disks show evidence of extinction to ~2 effective radii. However, no evidence for recent evolution of disk opacity is evident, due to the limited redshift range and our inability to distinguish other factors on disk opacity such as the presence of spiral arms and Hubble type. Such effects also mask any relation between su...

Holwerda, B W; Bolton, A

2007-01-01T23:59:59.000Z

473

Spiral Disk Opacity from Occulting Galaxy Pairs in the Sloan Digital Sky Survey  

E-Print Network (OSTI)

A spiral galaxy partially ovelapping a more distant elliptical offers an unique opportunity to measure the dust extinction in the foreground spiral. From the Sloan Digital Sky Survey DR4 spectroscopic sample, we selected 83 occulting galaxy pairs and measured disk opacity over the redshift range z = 0.0-0.2 with the goal to determine the recent evolution of disk dust opacity. The enrichment of the ISM changes over the lifetime of a disk and it is reasonable to expect the dust extinction properties of spiral disks as a whole to change over their lifetime. When they do, the change will affect our measurements of galaxies over the observable universe. From the SDSS pairs we conclude that spiral disks show evidence of extinction to ~2 effective radii. However, no evidence for recent evolution of disk opacity is evident, due to the limited redshift range and our inability to distinguish other factors on disk opacity such as the presence of spiral arms and Hubble type. Such effects also mask any relation between surface brightness and optical depth that has been found in nearby galaxies. Hence, we conclude that the SDSS spectral catalog is an excellent way to find occulting pairs and construct a uniform local sample. However, higher resolution than the SDSS images is needed to disentangle the effects of spiral arms and Hubble type from evolution since z = 0.2.

B. W. Holwerda; W. C. Keel; A. Bolton

2007-08-08T23:59:59.000Z

474

Analysis of Trade-Off Between Power Saving and Response Time in Disk Storage Systems  

Science Conference Proceedings (OSTI)

It is anticipated that in the near future disk storage systems will surpass application servers and will become the primary consumer of power in the data centers. Shutting down of inactive disks is one of the more widespread solutions to save power consumption of disk systems. This solution involves spinning down or completely shutting off disks that exhibit long periods of inactivity and placing them in standby mode. A file request from a disk in standby mode will incur an I/O cost penalty as it takes time to spin up the disk before it can serve the file. In this paper, we address the problem of designing and implementing file allocation strategies on disk storage that save energy while meeting performance requirements of file retrievals. We present an algorithm for solving this problem with guaranteed bounds from the optimal solution. Our algorithm runs in O(nlogn) time where n is the number of files allocated. Detailed simulation results and experiments with real life workloads are also presented.

Otoo, Ekow J; Rotem, Doron; Tsao, Shih-Chiang

2009-02-03T23:59:59.000Z

475

Nucleosynthesis in the outflows associated with accretion disks of Type II collapsars  

E-Print Network (OSTI)

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 explosion is driven. The supernova 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 has 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. 56Ni 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 supernova explosion. It is mainly present when outflow is considered from the He-rich, 56Ni/54Fe rich zones of the disks. However, outflow from the Si-ric