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1

Measurement of parallel blade-vortex interaction at low Reynolds numbers  

NASA Astrophysics Data System (ADS)

In this study parallel blade-vortex interaction for a Schmidt-propeller configuration has been examined using particle image velocimetry (PIV). This tandem configuration consists of a leading airfoil (forefoil), used to generate a vortical wake of leading-edge vortices (LEVs) and trailing-edge vortices (TEVs) through a pitching or plunging motion, and a trailing airfoil (hindfoil), held fixed with a specified angle of attack and vertical spacing in its wake. The hindfoil incidence (loading) and not the vertical spacing to the incoming vortical wake has been found to dictate the nature of the interaction (inviscid vs. viscous). For cases where the vortex-blade offset is small and the hindfoil is loaded, vortex distortion and vortex-induced separations are observed. By tracking the circulation of the LEV and TEV, it has been found that the vortices are strengthened for the tandem arrangement and in certain cases dissipate quicker in the wake when interacting with the hindfoil. Time-averaged forces obtained using a standard control-volume analysis are then obtained and used to evaluate these vortex-interaction cases. A subsequent analysis of the varying pressure distribution over the suction side of the hindfoil is performed by integrating the Navier-Stokes equations through the velocity field. This allows for a direct comparison of the vortex-induced loading for the various configurations.

Rival, David; Manejev, Roland; Tropea, Cam

2010-07-01

2

Novel Method for Reducing Rotor Blade-Vortex Interaction.  

National Technical Information Service (NTIS)

One of the major hindrances to expansion of the rotorcraft market is the high-amplitude noise they produce, especially during low-speed descent, where blade-vortex interactions frequently occur. In an attempt to reduce the noise levels caused by blade-vor...

A. T. Glinka

2000-01-01

3

A mechanism for mitigation of blade–vortex interaction using leading edge blowing flow control  

Microsoft Academic Search

The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure\\u000a interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic\\u000a side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI,\\u000a the parallel blade–vortex interaction (BVI) is the

Chris Weiland; Pavlos P. Vlachos

2009-01-01

4

Flow visualizations of perpendicular blade vortex interactions  

NASA Astrophysics Data System (ADS)

Helium bubble flow visualizations have been performed to study perpendicular interaction of a turbulent trailing vortex and a rectangular wing in the Virginia Tech Stability Tunnel. Many combinations of vortex strength, vortex-blade separation (Z(sub s)) and blade angle of attack were studied. Photographs of representative cases are presented. A range of phenomena were observed. For Z(sub s) greater than a few percent chord the vortex is deflected as it passes the blade under the influence of the local streamline curvature and its image in the blade. Initially the interaction appears to have no influence on the core. Downstream, however, the vortex core begins to diffuse and grow, presumably as a consequence of its interaction with the blade wake. The magnitude of these effects increases with reduction in Z(sub s). For Z(sub s) near zero the form of the interaction changes and becomes dependent on the vortex strength. For lower strengths the vortex appears to split into two filaments on the leading edge of the blade, one passing on the pressure and one passing on the suction side. At higher strengths the vortex bursts in the vicinity of the leading edge. In either case the core of its remnants then rapidly diffuse with distance downstream. Increase in Reynolds number did not qualitatively affect the flow apart from decreasing the amplitude of the small low-frequency wandering motions of the vortex. Changes in wing tip geometry and boundary layer trip had very little effect.

Rife, Michael C.; Davenport, William J.

1992-10-01

5

Reduction of helicopter blade-vortex interaction noise by active rotor control technology  

Microsoft Academic Search

Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently

Yung H. Yu; Bernd Gmelin; Wolf Splettstoesser; Jean J. Philippe; Jean Prieur; Thomas F. Brooks

1997-01-01

6

Reduction of Blade-Vortex Interaction Noise Using Higher Harmonic Pitch Control.  

National Technical Information Service (NTIS)

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rot...

T. F. Brooks E. R. Booth J. R. Jolly W. T. Yeager M. L. Wilbur

1989-01-01

7

Neural control of helicopter blade-vortex interaction noise  

NASA Astrophysics Data System (ADS)

Significant reduction of helicopter blade-vortex interaction (BVI) noise is currently one of the most advanced research topics in the helicopter industry. This is due to the complex flow, the close aerodynamic and structural coupling, and the interaction of the blades with the trailing edge vortices. Analytical and numerical modeling techniques are therefore currently still far from a sufficient degree of accuracy to obtain satisfactory results using classical model based control concepts. Neural networks with a proven potential to learn nonlinear relationships implicitly encoded in a training data set are therefore an appropriate and complementary technique for the alternative design of a nonlinear controller for BVI noise reduction. For nonlinear and adaptive control different neural control strategies have been proposed. Two possible approaches, a direct and an indirect neural controller are described. In indirect neural control, the plant has to be identified first by training a network with measured data. The plant network is then used to train the controller network. On the other hand the direct control approach does not rely on an explicit plant model, instead a specific training algorithm (like reinforcement learning) uses the information gathered from interactions with the environment. In the investigation of the BVI noise phenomena, helicopter developers have undertaken substantial efforts in full scale flight tests and wind tunnel experiments. Data obtained in these experiments have been adequately preprocessed using wavelet analysis and filtering techniques and are then used in the design of a neural controller. Neural open-loop control and neural closed-loop control concepts for the BVI noise reduction problem are conceived, simulated and compared against each other in this work in the above mentioned framework.

Glaessel, Holger; Kloeppel, Valentin; Rudolph, Stephan

2001-06-01

8

The role of blade elasticity in the prediction of blade-vortex interaction noise  

Microsoft Academic Search

An analytical study of the role of a main rotor blade's flap, chord and torsional stiffnesses on vibratory airloads and sound pressures has been carried out. A rotor analysis code typically applied to blade dynamics and performance was modified to capture the airload due to blade-vortex and blade-wake interaction by using a finer azimuthal computation grid. The blade elasticity of

Robert C. Derham; Byung K. Oh

1991-01-01

9

Blade-vortex interaction noise reduction with active twist smart rotor technology  

Microsoft Academic Search

The results of this analytical feasibility study suggest that active blade twist technology is a viable means to reduce blade-vortex interaction (BVI) noise in rotorcraft systems. A linearized unsteady aerodynamics analysis was formulated and successfully validated with computation fluid dynamics (CFD) analysis. A simple control scheme with three control points was found to be effective for active BVI noise reduction.

Peter C. Chen; James D. Baeder; Robert A. D. Evans; John Niemczuk

2001-01-01

10

Rotor blade-vortex interaction noise reduction and vibration using higher harmonic control  

Microsoft Academic Search

The use of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) noise is examined by means of a rotor acoustic test. A dynamically scaled, four-bladed, articulated rotor model was tested in a heavy gas (Freon-12) medium. Acoustic and vibration measurements were made for a large range of matched flight conditions where prescribed (open loop) HHC pitch

Thomas F. Brooks; Earl R. Booth Jr.

1990-01-01

11

Reduction of blade-vortex interaction noise using higher harmonic pitch control  

Microsoft Academic Search

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of

Thomas F. Brooks; Earl R. Booth Jr.; J. Ralph Jolly Jr.; William T. Yeager Jr.; Matthew L. Wilbur

1989-01-01

12

Reduction of blade-vortex interaction noise through higher harmonic pitch control  

Microsoft Academic Search

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of

Thomas F. Brooks; Earl R. Booth Jr.; J. Ralph Jolly Jr.; William T. Yeager Jr.; Matthew L. Wilbur

1990-01-01

13

Active twist smart rotor technology for blade-vortex interaction noise reduction  

NASA Astrophysics Data System (ADS)

The results of this feasibility study suggest that active blade twist technology is a viable means to reduce blade- vortex interaction (BVI) noise in rotorcraft systems. A linearized unsteady aerodynamics analysis was formulated and successfully validated with computation fluid dynamics analysis. A simple control scheme with three control points was found to be effective for active BVI noise reduction. Based on current-day actuation technology where 1 to 2 degrees of twist per blade activation span is expected, measurable noise reductions of 2 to 4 dB were predicted for the relatively strong, close vortex interactions. For weaker vortex interactions, reductions of 7 to 10 dB were predicted. The required twist actuation per blade span for complete unsteady loading cancellation, however, may be infeasible because of the large stroke and high frequency activation requirements.

Chen, Peter C.; Baeder, James D.; Evans, Robert A.; Niemczuk, Jack; Ross, Paul A.

1999-06-01

14

Blade-vortex interaction noise reduction with active twist smart rotor technology  

NASA Astrophysics Data System (ADS)

The results of this analytical feasibility study suggest that active blade twist technology is a viable means to reduce blade-vortex interaction (BVI) noise in rotorcraft systems. A linearized unsteady aerodynamics analysis was formulated and successfully validated with computation fluid dynamics (CFD) analysis. A simple control scheme with three control points was found to be effective for active BVI noise reduction. Based on current-day actuation technology where one to two degrees of twist per blade activation span is expected, measurable noise reductions of 2-4 dB were predicted for the relatively strong, close vortex interactions. For weaker vortex interactions, reductions of 7-10 dB were predicted. The required twist actuation per blade span for complete unsteady loading cancellation, however, may be infeasible because of the large stroke and high-frequency activation requirements.

Chen, Peter C.; Baeder, James D.; Evans, Robert A. D.; Niemczuk, John

2001-02-01

15

Acoustic Measurements from a Rotor Blade-Vortex Interaction Noise Experiment in the German-Dutch Wind Tunnel (DNW).  

National Technical Information Service (NTIS)

Acoustic data are presented from a 40 percent scale model of the 4-bladed BO-105 helicopter main rotor, measured in the large European aeroacoustic wind tunnel, the DNW. Rotor blade-vortex interaction (BVI) noise data in the low speed flight range were ac...

R. M. Martin W. R. Splettstoesser J. W. Elliott K. Schultz

1988-01-01

16

Blade-vortex interaction data obtained from a pressure-instrumented model rotor at the DNW  

NASA Astrophysics Data System (ADS)

Blade surface pressure data obtained during a model helicopter rotor test are examined to determine the locations and strengths of impulsive loading events caused by blade vortex interactions (BVI). Data from 43 descent conditions are used to identify, locate, and characterize the BVI events. The combination of azimuthal, radial, and chordwise resolution has generated a detailed picture of the aerodynamic response of a rotor blade to BVI. The paper examines both global and local features of the interaction. Global features include the dependence of the impulsive airload strength and position on three independent parameters: rotor tip path plane angle, rotor thrust, and advance ratio. Local features are examined by using the unsteady pressure distributions to determine the strength and the chordwise dependence of the amplitude and phase of a representative BVI event.

Lorber, Peter F.

17

Prediction of blade-vortex interaction noise using measured blade pressures  

NASA Astrophysics Data System (ADS)

In the study reported here, blade-vortex interaction noise was predicted using a simplified model of blade pressures measured on a one-seventh scale model AH-1/OLS main rotor. The methods used for the acoustic prediction are based on the acoustic analogy and have been developed by Nakamura (1981) and by Brentner, Nystrom, and Farassat (referred to as the WOPWOP method). The waveforms predicted by the two methods are in good agreement with each other and with the measurements in terms of the number of pulses, the pulse widths, and the separation times between the pulses. The peak amplitude of the dominant pulse may, however, be underpredicted by up to 40 percent, depending on flight conditions. Ways of improving the accuracy of the prediction methods are suggested.

Joshi, Mahendra C.; Liu, Sandy R.; Boxwell, Donald A.

1987-10-01

18

Technique for providing a signal for controlling blade vortex interaction noise of a rotorcraft  

US Patent & Trademark Office Database

A technique for providing a signal representative of blade vortex interaction (BVI) noise for a multi-blade rotorcraft. The fluid (air) pressure at one, two, or more predetermined locations on a rotor blade is measured during at least one predetermined azimuthal segment of blade rotation during operation to provide respective pressure measurements. The pressure measurements are processed to provide a signal for use as a control variable in a control system for the active control of BVI noise. The pressure measurements are made within 10% blade chord length of the blade leading edge and preferably two or more are made between 65% and 95% of blade radial-length. The pressure measurements are filtered and the band of retained frequencies is between 20 and 48 times the rotor rotation frequency. An algorithm operative over a determined blade frequency range optimizes the signal for control use.

Lorber; Peter F. (Coventry, CT)

2001-01-09

19

Acoustic measurements from a rotor blade-vortex interaction noise experiment in the German-Dutch Wind Tunnel (DNW)  

NASA Astrophysics Data System (ADS)

Acoustic data are presented from a 40 percent scale model of the 4-bladed BO-105 helicopter main rotor, measured in the large European aeroacoustic wind tunnel, the DNW. Rotor blade-vortex interaction (BVI) noise data in the low speed flight range were acquired using a traversing in-flow microphone array. The experimental apparatus, testing procedures, calibration results, and experimental objectives are fully described. A large representative set of averaged acoustic signals is presented.

Martin, Ruth M.; Splettstoesser, W. R.; Elliott, J. W.; Schultz, K.-J.

1988-03-01

20

Acoustic measurements from a rotor blade-vortex interaction noise experiment in the German-Dutch Wind Tunnel (DNW)  

Microsoft Academic Search

Acoustic data are presented from a 40 percent scale model of the 4-bladed BO-105 helicopter main rotor, measured in the large European aeroacoustic wind tunnel, the DNW. Rotor blade-vortex interaction (BVI) noise data in the low speed flight range were acquired using a traversing in-flow microphone array. The experimental apparatus, testing procedures, calibration results, and experimental objectives are fully described.

Ruth M. Martin; W. R. Splettstoesser; J. W. Elliott; K.-J. Schultz

1988-01-01

21

Acoustic results of the blade-vortex interaction acoustic test of a 40 percent model rotor in the DNW  

Microsoft Academic Search

Acoustic data of a 40 percent scale model of the 4-bladed B0-105 main rotor, measured in a large test section aeroacoustic wind tunnel, are presented. Rotor blade-vortex interaction (BVI) noise data were acquired using a traversing in-flow microphone array in the low to moderate speed flight range. Results are presented which document the flight conditions for maximum BVI impulsive noise;

Ruth M. Martin; Wolf R. Splettstoesser

1987-01-01

22

Analysis of helicopter blade-vortex interaction noise with application to adaptive-passive and active alleviation methods  

Microsoft Academic Search

This study focuses on detection and analysis methods of helicopter blade-vortex interactions (BVI) and applies these methods to two different BVI noise alleviation schemes---an adaptive-passive and an active scheme. A standard free-wake analysis based on relaxation methods is extended in this study to compute high-resolution blade loading, to account for blade-to-blade dissimilarities, and dual vortices when there is negative loading

Lionel Christian Tauszig

2002-01-01

23

Analysis of helicopter blade-vortex interaction noise with application to adaptive-passive and active alleviation methods  

NASA Astrophysics Data System (ADS)

This study focuses on detection and analysis methods of helicopter blade-vortex interactions (BVI) and applies these methods to two different BVI noise alleviation schemes---an adaptive-passive and an active scheme. A standard free-wake analysis based on relaxation methods is extended in this study to compute high-resolution blade loading, to account for blade-to-blade dissimilarities, and dual vortices when there is negative loading at the blade tips. The free-wake geometry is still calculated on a coarse azimuthal grid and then interpolated to a high-resolution grid to calculate the BVI induced impulsive loading. Blade-to-blade dissimilarities are accounted by allowing the different blades to release their own vortices. A number of BVI detection criteria, including the spherical method (a geometric criterion developed in this thesis) are critically examined. It was determined that high-resolution azimuthal discretization is required in virtually all detection methods except the spherical method which detected the occurrence of parallel BVI even while using a low-resolution azimuthal mesh. Detection methods based on inflow and blade loads were, in addition, found to be sensitive to vortex core size. While most BVI studies use the high-resolution airloads to compute BVI noise, the total noise can often be due to multiple dominant interactions on the advancing and retreating sides. A methodology is developed to evaluate the contribution of an individual interaction to the total BVI noise, based on using the loading due to an individual vortex as an input to the acoustic code WOPWOP. The adaptive-passive BVI alleviation method considered in this study comprises of reducing the length of one set of opposite blades (of a 4-bladed rotor) in low-speed descent. Results showed that differential coning resulting from the blade dissimilarity increases the blade-vortex miss-distances and reduces the BVI noise by 4 dB. The Higher Harmonic Control Aeroacoustic Rotor Test (HART) has been studied as an active method for BVI noise alleviation. Good validation of a baseline case without Higher Harmonic Control (HHC) is obtained. However the present analysis is unable to capture all the features of two specific HHC pitch input schedules examined. Some partial insight on the mechanisms at work is provided.

Tauszig, Lionel Christian

24

Helicopter model rotor-blade vortex interaction impulsive noise - Scalability and parametric variations  

NASA Astrophysics Data System (ADS)

Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scalig deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.

Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.

25

Laser velocimetry and blade pressure measurements of a blade-vortex interaction  

NASA Astrophysics Data System (ADS)

An investigation of the flowfield chracteristics around a rotor blade during a blade-vortex interaction (BVI) was conducted at the NASA Langley Research Center by the Army's Aeroperformance Division and the Boeing Defense and Space Group, Helicopter Division, during a wind-tunnel test in the 14 by 22-foot Subsonic Tunnel. A two-component laser velocimeter was used to measure the blade pressure during a BVI. This paper presents velocity measurements that indicate the presence of a vortex in the streamlines and vectors of the induced velocity, when studied in conjunction with the blade surface pressures, indicate how the flowfield is behaving during a BVI. The following conclusions can be made from this investigation: (1) The streamlines and vectors of the induced velocity, when studied in conjunction with the blade surface pressures, indiacte how the flowfield is behaving during a BVI. The blade approaches and intersects a vortex, and the vortex slides beneath the blade. (2) The data provide detailed flowfield information for validating computational predictions of BVI and also for evaluating and improving current wake models. Among the options investigated, only the free-wake calculation by TECH-01 indicated any BVI activity in the first quadrant.

Gorton, Susan Althoff; Poling, David R.; Dadone, Leo

1995-04-01

26

Reduction of blade-vortex interaction noise through higher harmonic pitch control  

NASA Astrophysics Data System (ADS)

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.; Booth, Earl R., Jr.; Jolly, J. Ralph, Jr.; Yeager, William T., Jr.; Wilbur, Matthew L.

1990-01-01

27

Rotor blade-vortex interaction noise reduction and vibration using higher harmonic control  

NASA Astrophysics Data System (ADS)

The use of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) noise is examined by means of a rotor acoustic test. A dynamically scaled, four-bladed, articulated rotor model was tested in a heavy gas (Freon-12) medium. Acoustic and vibration measurements were made for a large range of matched flight conditions where prescribed (open loop) HHC pitch schedules were superimposed on the normal (baseline) collective and cyclic trim pitch. A novel sound power measurement technique was developed to take advantage of the reverberance in the hard walled tunnel. Quantitative sound power results are presented for a 4/rev (4P) collective pitch HHC. By comparing the results using 4P HHC to corresponding baseline (no HHC) conditions, significant midfrequency noise reductions of 5-6 dB are found for low-speed descent conditions where BVI is most intense. For other flight conditions, noise is found to increase with the use of HHC. LF loading noise, as well as fixed and rotating frame vibration levels, show increased levels.

Brooks, Thomas F.; Booth, Earl R., Jr.

1990-09-01

28

Reduction of blade-vortex interaction noise using higher harmonic pitch control  

NASA Astrophysics Data System (ADS)

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.; Booth, Earl R., Jr.; Jolly, J. Ralph, Jr.; Yeager, William T., Jr.; Wilbur, Matthew L.

1989-07-01

29

Advancing-side directivity and retreating-side interactions of model rotor blade-vortex interaction noise  

NASA Astrophysics Data System (ADS)

Acoustic data are presented from a 40 percent scale model of the four-bladed BO-105 helicopter main rotor, tested in a large aerodynamic wind tunnel. Rotor blade-vortex interaction (BVI) noise data in the low-speed flight range were acquired using a traversing in-flow microphone array. Acoustic results presented are used to assess the acoustic far field of BVI noise, to map the directivity and temporal characteristics of BVI impulsive noise, and to show the existence of retreating-side BVI signals. The characterics of the acoustic radiation patterns, which can often be strongly focused, are found to be very dependent on rotor operating condition. The acoustic signals exhibit multiple blade-vortex interactions per blade with broad impulsive content at lower speeds, while at higher speeds, they exhibit fewer interactions per blade, with much sharper, higher amplitude acoustic signals. Moderate-amplitude BVI acoustic signals measured under the aft retreating quadrant of the rotor are shown to originate from the retreating side of the rotor.

Martin, R. M.; Splettstoesser, W. R.; Elliott, J. W.; Schultz, K.-J.

1988-05-01

30

Rotorcraft acoustic radiation prediction based on a refined blade-vortex interaction model  

NASA Astrophysics Data System (ADS)

The analysis of rotorcraft aerodynamics and acoustics is a challenging problem, primarily due to the fact that a rotorcraft continually flies through its own wake. The generation mechanism for a rotorcraft wake, which is dominated by strong, concentrated blade-tip trailing vortices, is similar to that in fixed wing aerodynamics. However, following blades encounter shed vortices from previous blades before they are swept downstream, resulting in sharp, impulsive loading on the blades. The blade/wake encounter, known as Blade-Vortex Interaction, or BVI, is responsible for a significant amount of vibratory loading and the characteristic rotorcraft acoustic signature in certain flight regimes. The present work addressed three different aspects of this interaction at a fundamental level. First, an analytical model for the prediction of trailing vortex structure is discussed. The model as presented is the culmination of a lengthy research effort to isolate the key physical mechanisms which govern vortex sheet rollup. Based on the Betz model, properties of the flow such as mass flux, axial momentum flux, and axial flux of angular momentum are conserved on either a differential or integral basis during the rollup process. The formation of a viscous central core was facilitated by the assumption of a turbulent mixing process with final vortex velocity profiles chosen to be consistent with a rotational flow mixing model and experimental observation. A general derivation of the method is outlined, followed by a comparison of model predictions with experimental vortex measurements, and finally a viscous blade drag model to account for additional effects of aerodynamic drag on vortex structure. The second phase of this program involved the development of a new formulation of lifting surface theory with the ultimate goal of an accurate, reduced order hybrid analytical/numerical model for fast rotorcraft load calculations. Currently, accurate rotorcraft airload analyses are limited by the massive computational power required to capture the small time scale events associated with BVI. This problem has two primary facets: accurate knowledge of the wake geometry, and accurate resolution of the impulsive loading imposed by a tip vortex on a blade. The present work addressed the second facet, providing a mathematical framework for solving the impulsive loading problem analytically, then asymptotically matching this solution to a low-resolution numerical calculation. A method was developed which uses continuous sheets of integrated boundary elements to model the lifting surface and wake. Special elements were developed to capture local behavior in high-gradient regions of the flow, thereby reducing the burden placed on the surrounding numerical method. Unsteady calculations for several classical cases were made in both frequency and time domain to demonstrate the performance of the method. Finally, a new unsteady, compressible boundary element method was applied to the problem of BVI acoustic radiation prediction. This numerical method, combined with the viscous core trailing vortex model, was used to duplicate the geometry and flight configuration of a detailed experimental BVI study carried out at NASA Ames Research Center. Blade surface pressure and near- and far-field acoustic radiation calculations were made. All calculations were shown to compare favorably with experimentally measured values. The linear boundary element method with non-linear corrections proved sufficient over most of the rotor azimuth, and particular in the region of the blade vortex interaction, suggesting that full non-linear CFD schemes are not necessary for rotorcraft noise prediction.

Rule, John Allen

1997-08-01

31

Acoustic results of the blade-vortex interaction acoustic test of a 40 percent model rotor in the DNW  

NASA Astrophysics Data System (ADS)

Acoustic data of a 40 percent scale model of the 4-bladed B0-105 main rotor, measured in a large test section aeroacoustic wind tunnel, are presented. Rotor blade-vortex interaction (BVI) noise data were acquired using a traversing in-flow microphone array in the low to moderate speed flight range. Results are presented which document the flight conditions for maximum BVI impulsive noise; assess the acoustic farfield by BVI noise; map the directivity of BVI impulsive noise in a large plane below and upstream of the rotor; illustrate the temporal characteristics of the BVI signals as a function of tip-speed-ratio; and show the existence of retreating side BVI signals. The occurrence of a strongly focused radiation pattern, as opposed to a more omnidirectional pattern, was found to be very dependent on the rotor operating condition. Multiple interactions per blade were observed at the lowest speed cases, with broader impulsive content, while the higher speed cases exhibited fewer interactions per blade, with much sharper, higher amplitude acoustic signals. BVI acoustic signals were measured under the aft retreating quadrant of the rotor and found to originate from the retreating side of the rotor.

Martin, Ruth M.; Splettstoesser, Wolf R.

1987-02-01

32

Study of the blade/vortex interaction: Acoustics, aerodynamics and models  

NASA Astrophysics Data System (ADS)

A program for calculating the load noise of a helicopter rotor was developed. The method, which requires the knowledge of the local blade load values, was extended to calculate the two dimensional flow around a foil in a field of vortices. A three dimensional method based on the lifting surface theory was developed to simulate the turbulent field developed by a pitch oscillating foil and interacting with another foil placed downstream. The calculated and the measured lift evolution values were compared. The flow velocity was measured by laser velocimetry and the configuration of the rotational flow field was obtained.

Gnemmi, P.; Haertig, J.; Johe, C.; Schaffar, M.

1992-04-01

33

Blade-vortex interaction noise - Prediction and comparison with flight and wind tunnel tests  

NASA Astrophysics Data System (ADS)

The BVI noise prediction method developed at ONERA is a combination of three computer programs. The first program (MESIR) calculates the geometry and the intensity of the main rotor wake using a free wake analysis. The second program (ARHIS) provides the blade pressure fluctuations induced by the rotor wake even for close interactions. The third code (PARIS), based on the Ffowcs Williams and Hawkings equation, computes the resulting radiated noise. The last two programs have been specially developed to save computing time. The main lines of the computer programs are presented. Emphasis is laid on aerodynamic and acoustic predictions using these three codes. Comparisons are made with two tests: a wind tunnel test of the US Army AH1G-OLS rotor model, and an Aerospatiale Gazelle flight test. Lift coefficients, blade pressures coefficients and radiated noise are compared.

Spiegel, P.; Rahier, G.; Michea, B.

34

Analysis of helicopter blade vortex structure by laser velocimetry  

Microsoft Academic Search

In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the

A. Boutier; J. Lefèvre; F. Micheli

1996-01-01

35

Analysis of helicopter blade vortex structure by laser velocimetry  

NASA Astrophysics Data System (ADS)

In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the HART program (Higher Harmonic Control Aeroacoustic Rotor Test, jointly conducted by US Army, NASA, DLR, DNW and ONERA), a series of tests have been made in the German Dutch Wind Tunnel (DNW) on a helicopter rotor with 2 m long blades, rotating at 1040 rpm; several flight configurations, with an advance ratio of 0.15 and a shaft angle of 5.3°, have been studied with different higher harmonic blade pitch angles superposed on the conventional one (corresponding to the baseline case). The flow on the retreating side has been analyzed with an especially designed 3D laser velocimeter, and, simultaneously, the blade tip attitude has been determined in order to get the blade-vortex miss distance, which is a crucial parameter in the noise reduction. A 3D laser velocimeter, in backscatter mode with a working distance of 5 m, was installed on a platform 9 m high, and flow seeding with submicron incense smoke was achieved in the settling chamber using a remotely controlled displacement device. Acquisition of instantaneous velocity vectors by an IFA 750 yielded mean velocity and turbulence maps across the vortex as well as the vortex position, intensity and viscous radius. The blade tip attitude (altitude, jitter, angle of incidence) was recorded by the TART method (Target Attitude in Real Time) which makes use of a CCD camera on which is formed the image of two retroreflecting targets attached to the blade tip and lighted by a flash lamp. In addition to the mean values of the aforementioned quantities, spectra of their fluctuations have been established up to 8 Hz.

Boutier, A.; Lefèvre, J.; Micheli, F.

1996-05-01

36

Parallel Programming with Interacting Processes  

Microsoft Academic Search

Abstract In this paper, we argue that interacting processes (IP) with multiparty interactions are an ideal model for parallel programming. The IP model with multiparty interactions was originally proposed by N. Francez and I. R. Forman [1] for distributed programming,of reactive applications. We analyze the IP model and provide the new insights into it from the parallel programming perspective. We

Peiyi Tang; Yoichi Muraoka

1999-01-01

37

Rotorcraft acoustic radiation prediction based on a refined blade-vortex interaction model  

Microsoft Academic Search

The analysis of rotorcraft aerodynamics and acoustics is a challenging problem, primarily due to the fact that a rotorcraft continually flies through its own wake. The generation mechanism for a rotorcraft wake, which is dominated by strong, concentrated blade-tip trailing vortices, is similar to that in fixed wing aerodynamics. However, following blades encounter shed vortices from previous blades before they

John Allen Rule

1997-01-01

38

SUIF Explorer: An Interactive and Interprocedural Parallelizer  

Microsoft Academic Search

The SUIF Explorer is an interactive parallelization tool that is more effective than previous systems in minimizing the number of lines of code that require programmer assistance. First, the interprocedural analyses in the SUIF system is successful in parallelizing many coarse-grain loops, thus minimizing the number of spurious dependences requiring attention. Second, the system uses dynamic execution analyzers to identify

Shih-Wei Liao; Amer Diwan; Robert P. Bosch Jr.; Anwar M. Ghuloum; Monica S. Lam

1999-01-01

39

SUIF Explorer: an interactive and interprocedural parallelizer  

Microsoft Academic Search

The SUIF Explorer is an interactive parallelization tool that is more effective than previous systems in minimizing the number of lines of code that require programmer assistance. First, the interprocedural analyses in the SUIF system is successful in parallelizing many coarse-grain loops, thus minimizing the number of spurious dependences requiring attention. Second, the system uses dynamic execution analyzers to identify

Shih-Wei Liao; Amer Diwan; Robert P. Bosch Jr.; Anwar Ghuloum; Monica S. Lam

1999-01-01

40

Parallel Methods for Fluid-Structure Interaction  

Microsoft Academic Search

A parallel CFD code capable of simulating flow within moving boundaries has been coupled to a beam element structural dynamics\\u000a code. The coupled codes are used to simulate fluid- structure interaction for a class of applications involving long and slender\\u000a structures, e.g. suspension bridges and offshore risers. Due to the difference in size and dimensionality of the 3D CFD problem

Carl B. Jenssen; Trond Kvamsdal; Knut M. Okstad; Jørn Amundsen

1998-01-01

41

Comparison of Full-Scale XV-15 Blade-Vortex Interaction Noise Calculations with Wind Tunnel Data.  

National Technical Information Service (NTIS)

Results from the TRAC acoustic prediction system were correlated with data from a test of an isolated full-scale XV-15 rotor in the NASA Ames 80- by 120-Foot Wind Tunnel. The airloads calculation provided by the original CAMRAD.Mod1 code in the standard T...

C. Kitaplioglu W. Johnson

2002-01-01

42

COMPARISON OF FULL-SCALE XV-15 BLADE-VORTEX INTERACTION NOISE CALCULATIONS WITH WIND TUNNEL DATA  

Microsoft Academic Search

Results from the TRAC acoustic prediction system were correlated with data from a test of an isolated full-scale XV-15 rotor in the NASA Ames 80- by 120-Foot Wind Tunnel. The airloads calculation provided by the original CAMRAD.Mod1 code in the standard TRAC system was exercised with several high resolution options, including the FPXBVI CFD code. In addition, the more recent

Cahit Kitaplioglu; Wayne Johnson

2002-01-01

43

Interactions of evaportranspiration between two parallel columns  

NASA Astrophysics Data System (ADS)

Moisture flux across the land-atmosphere boundary (through soil evaporation and plant transpiration) is an important component of many large-scale hydrological processes, which were often quantified through simulation of multiple realizations (stream tubes) of independent one-dimensional local scale flow. A major problem of this approach is that it ignores the interactions among different stream tubes. Lateral flows might be prominent for long and narrow tubes and heterogeneous hydraulic properties and plant covers. This study is to investigate whether using this stream tube modeling will produce unacceptable errors for large scale evapotranspiration simulations. Instead of using convenient parallel column models of independent hydrologic processes, this study simulates two-dimensional transpiration and evaporation in two parallel columns which allow lateral interactions. The impact of both plant characteristics and soil hydraulic properties on evapotranspitration is addressed and discussed in comparison to those of independent stream tube models. The results provide applicable guidance for applications of stream tube models to simulate large scale evapotranspiration in a heterogeneous landscape.

Sun, D.; Zhu, J.

2010-12-01

44

A Parallel Engine for Graphical Interactive Molecular Dynamics Simulations  

Microsoft Academic Search

The current work proposes a parallel implementation for interactive molecular dynamics simulations (MD). The interactive capability is modeled by finite automata that are executed in the processing nodes. Any interaction implies in a communication between the user interface and the finite automata. The ADKS, an interactive sequential MD code that provides graphical output was chosen as a case study. A

Eduardo Rocha Rodrigues; Airam Jonatas Preto; Stephan Stephany

2004-01-01

45

Interactive scientific visualization and parallel display techniques  

Microsoft Academic Search

In this paper, we describe a new graphics environment for essentially real-time interactive visualization of computational fluid mechanics. Within this environment, the researcher may interactively examine fluid data on a framebuffer with animated flow visualization diagnostics which mimic those in the experimental laboratory. This provides an effective and interactive way to analyze the underlying physical mechanisms, and to compare results

James A. Sethian; J. B. Salem; A. F. Ghoniem

1988-01-01

46

Interaction of Parallel Turbulent Jets (Parhuzamos Turbulens Sugarak Kolcsonhatasa).  

National Technical Information Service (NTIS)

The authors use the Reichardt inductive theory to describe the interaction of two turbulent, parallel jets. This theory was resorted to because there is as yet no better theory available. Reichardt maintains, that with the determination of the experimenta...

E. Szucs J. Toth

1967-01-01

47

Prediction of BVI noise patterns and correlation with wake interaction locations  

Microsoft Academic Search

High resolution fluctuating airloads data were acquired during a test of a contemporary design United Technologies model rotor in the Duits-Nederlandse Windtunnel (DNW). The airloads are used as input to the noise prediction program WOPWOP, in order to predict the blade-vortex interaction (BVI) noise field on a large plane below the rotor. Trends of predicted advancing and retreating side BVI

Michael A. Marcolini; Ruth M. Martin; Peter F. Lorber; T. A. Egolf

1992-01-01

48

Etude de l'Interaction Pale/Tourbillon: Acoustique, Aerodynamique, Modelisations (Study of the Blade/Vortex Interaction: Acoustics, Aerodynamics and Models).  

National Technical Information Service (NTIS)

A program for calculating the load noise of a helicopter rotor was developed. The method, which requires the knowledge of the local blade load values, was extended to calculate the two dimensional flow around a foil in a field of vortices. A three dimensi...

P. Gnemmi J. Haertig C. Johe M. Schaffar

1992-01-01

49

Interaction corrections at intermediate temperatures: Magnetoresistance in a parallel field  

Microsoft Academic Search

We consider the correction to conductivity of a 2D electron gas due to\\u000aelectron-electron interaction in the parallel magnetic field at arbitrary\\u000arelation between temperature and the elastic mean free time. The correction\\u000aexhibits non-trivial dependence on both temperature and the field. This\\u000adependence is determined by the Fermi liquid constant, which accounts for the\\u000aspin-exchange interaction. In particular, the

Gábor Zala; B. N. Narozhny; I. L. Aleiner

2001-01-01

50

A massively parallel multireference configuration interaction program : the parallel COLUMBUS program.  

SciTech Connect

A massively parallel version of the configuration interaction (CI) section of the COLUMBUS multireference singles and doubles CI (MRCISD) program system is described. In an extension of our previous parallelization work, which was based on message passing, the global array (GA) toolkit has now been used. For each process, these tools permit asynchronous and efficient access to logical blocks of 1- and 2-dimensional (2-D) arrays physically distributed over the memory of all processors. The GAs are available on most of the major parallel computer systems enabling very convenient portability of our parallel program code. To demonstrate the features of the parallel COLUMBUS CI code, benchmark calculations on selected MRCI and SRCI test cases are reported for the CRAY T3D, Intel Paragon, and IBM SP2. Excellent scaling with the number of processors up to 256 processors (CRAY T3D) was observed. The CI section of a 19 million configuration MRCISD calculation was carried out within 20 min wall clock time on 256 processors of a CRAY T3D. Computations with 38 million configurations were performed recently; calculations up to about 100 million configurations seem possible within the near future.

Dachsel, H.; Lischka, H.; Shepard, R.; Nieplocha, J.; Harrison, R. J.; Chemistry; Univ. of Wien; PNNL

1997-01-01

51

Modular Coupling for Parallel Fluid-Structure Interaction Computations  

Microsoft Academic Search

A parallel CFD code capable of simulating flow within moving boundaries is coupled to a beam el- ement structural dynamics code. The coupled codes are used to simulate fluid-structure interaction for a class of applications involving long and slender structures, e.g., suspension bridges and offshore risers. Due to the differ- ence in size and dimensionality of the 3D CFD problem

Trond Kvamsdal; Knut Morten Okstad; Carl Birger Jenssen; Jørn Amundsen

52

Framework for Interactive Parallel Dataset Analysis on the Grid  

SciTech Connect

We present a framework for use at a typical Grid site to facilitate custom interactive parallel dataset analysis targeting terabyte-scale datasets of the type typically produced by large multi-institutional science experiments. We summarize the needs for interactive analysis and show a prototype solution that satisfies those needs. The solution consists of desktop client tool and a set of Web Services that allow scientists to sign onto a Grid site, compose analysis script code to carry out physics analysis on datasets, distribute the code and datasets to worker nodes, collect the results back to the client, and to construct professional-quality visualizations of the results.

Alexander, David A.; Ananthan, Balamurali; /Tech-X Corp.; Johnson, Tony; Serbo, Victor; /SLAC

2007-01-10

53

Parallel interaction-free measurement using spatial adiabatic passage  

NASA Astrophysics Data System (ADS)

Interaction-free measurement (IFM) is a surprising consequence of quantum interference, where the presence of objects can be sensed without any disturbance of the object being measured. Here, we show an extension of IFM using techniques from spatial adiabatic passage, specifically multiple recipient adiabatic passage. Due to subtle properties of the adiabatic passage, it is possible to image an object without interaction between the imaging photons and the sample. The technique can be used on multiple objects in parallel and is entirely deterministic in the adiabatic limit. Unlike more conventional IFM schemes, this adiabatic process is driven by the symmetry of the system, and not by more usual interference effects. As such it provides an interesting alternative quantum protocol that may be applicable to photonic implementations of spatial adiabatic passage. We also show that this scheme can be used to implement a collision-free quantum routing protocol.

Hill, Charles D.; Greentree, Andrew D.; Hollenberg, Lloyd C. L.

2011-12-01

54

Dynamic interaction of parallel moving ships in close proximity  

NASA Astrophysics Data System (ADS)

Nowadays, there are many studies conducted in the field of marine hydrodynamics which focus on two vessels traveling and floating in sufficiently close proximity to experience significant interactions. The hydrodynamic behavior of parallel moving ships in waves is an interesting and important topic of late. A numerical investigation has been carried out for the prediction of wave exciting forces and motion responses of parallel moving ships in regular waves. The numerical solution was based on 3D distribution technique and using the linear wave theory to determine the exciting forces and ship's motion. The speed effects have been considered in the Green function for more realistic results. The numerical computations of wave exciting forces and motion responses were carried out for a Mariner and Series 60 for the purpose of discovering different Froude numbers and different separation distances in head sea conditions. Based on the numerical computations, it was revealed that the sway, roll and yaw have a significant effect due to hydrodynamic interaction.

Islam, M. Rafiqul; Murai, Motohiko

2013-09-01

55

Some Measurements of Interaction between Ship Models Passing on Parallel Courses.  

National Technical Information Service (NTIS)

Hydrodynamic interaction between model ships moving on parallel courses was studied for three types of passing encounter: (i) where ships passed on parallel courses - the overtaking encounter; (ii) where ships encountered head-on, and (iii) where a statio...

I. W. Dand

1981-01-01

56

A new parallel environment for interactive simulations implementing safe multithreading with MPI  

Microsoft Academic Search

This work presents a new parallel environment for interactive simulations. This environment integrates a MPI-based parallel simulation engine, a visualization module, and a user interface that supports modification of simulation parameters and visualization at runtime. This requires multiple threads, one to execute the simulation or the visualization, and other to receive user input. Since many MPI implementations are not thread-safe,

Eduardo Rocha Rodrigues; Airam Jonatas Preto; Stephan Stephany

2005-01-01

57

Space-Time Memory: A Parallel Programming Abstraction for Interactive Multimedia Applications  

Microsoft Academic Search

Realistic interactive multimedia involving vision, animation, and multimedia collaboration is likely to become an important aspect of future computer applications. The scalable parallelism inherent in such applications coupled with their computational demands make them ideal candidates for SMPs and clusters of SMPs. These applications have novel requirements that offer new kinds of challenges for parallel system design.We have designed a

Umakishore Ramachandran; Rishiyur S. Nikhil; Nissim Harel; James M. Rehg; Kathleen Knobe

1999-01-01

58

Architecture for Visualization and User Interaction in Parallel Environments.  

National Technical Information Service (NTIS)

An application-independent visualization interaction system is proposed with potential for application-binding at any stage of the modeling process. Advantages of this approach include ease of use, flexibility, code reuse, and modularity. Our design ideas...

E. Mascarenhas V. Rego

1996-01-01

59

An Architecture for Web-Based Interaction and Steering of Adaptive Parallel\\/Distributed Applications  

Microsoft Academic Search

This paper presents an environment for Web-based interaction and steering of adaptive parallel\\/distributed scientific applications. The architecture is composed of detachable thin-clients at the front-end, a network of Java interaction servers i n the middle, and a control network of sensors, actuators, interaction agents, and an application interaction proxy, superimposed on the application data-network, at the back-end. There are three

Rajeev Muralidhar; Samian Kaur; Manish Parashar

2000-01-01

60

Experiences Using the ParaScope Editor: an Interactive Parallel Programming Tool  

Microsoft Academic Search

The ParaScope Editor is an interactive parallel pro- gramming tool that assists knowledgeable users in de- veloping scientific Fortran programs. It displays the re- sults of sophisticated program analyses, provides a set of powerful interactive transformations, and supports program editing. This paper summarizes experiences of scientific programmers and tool designers using the ParaScope Editor. We evaluate existing features and describe

Mary W. Hall; Timothy J. Harvey; Ken Kennedy; Nathaniel McIntosh; Kathryn S. McKinley; Jeffrey D. Oldham; Michael H. Paleczny; Gerald Roth

1993-01-01

61

Experiences using the ParaScope Editor: an interactive parallel programming tool  

Microsoft Academic Search

The ParaScope Editor is an interactive parallel programming tool that assists knowledgeable users in developing scientific Fortran programs. It displays the results of sophisticated program analyses, provides a set of powerful interactive transformations, and supports program editing. This paper summarizes experiences of scientific programmers and tool designers using the ParaScope Editor. We evaluate existing features and describe enhancements in three

Mary W. Hallt; Timothy J. Harvey; Ken Kennedy; Nathaniel McIntosh; Kathryn S. McKinley; Jeffrey D. Oldham; Michael H. Paleczny; Gerald Roth

1993-01-01

62

Polarity of dynein-microtubule interactions in vitro: cross-bridging between parallel and antiparallel microtubules  

PubMed Central

Ciliary doublet microtubules produced by sliding disintegration in 20 muM MgATP2-reassociate in the presence of exogenous 30S dynein and 6 mM MgSO4. The doublets form overlapping arrays, held together by dynein cross-bridges. Dynein arms on both A and B subfibers serve as unambiguous markers of microtubule polarity within the arrays. Doublets reassociate via dynein cross-bridges in both parallel and antiparallel modes, although parallel interactions are favored 2:1. When 20 muM ATP is added to the arrays, the doublets undergo both vanadate-sensitive and insensitive forms of secondary disintegration to reproduce the original population of doublets. The results demonstrate that both parallel and antiparallel doublet cross-bridging is sensitive to dissociation by ATP even though normal ciliary motion depends strictly on dynein interactions between parallel microtubules.

1981-01-01

63

Parallel simulation of beam-beam interaction in high energy accelerators  

SciTech Connect

In this paper, we present a self-consistent simulation model of beam-beam interaction in high energy accelerators. Using a parallel particle-in-cell approach, we have calculated the electromagnetic fields between two colliding beams. Dynamic load balance is implemented to improve the parallel efficiency. A preliminary performance test on IBM SP Power3, Cray T3E and PC cluster is presented. As an application, we studied the coherent beam-beam oscillation in the proposed Large Hadron Collider.

Qiang, Ji; Furman, Miguel A.; Ryne, Robert D.

2002-02-02

64

Parallel Retrieval of Nanometer-Scale Light-Matter Interactions for Nanophotonic Systems  

Microsoft Academic Search

\\u000a Exploiting the unique attributes of nanometer-scale optical near-field interactions in a completely parallel manner is important\\u000a for innovative nanometric optical processing systems. In this paper, we propose the basic concepts necessary for parallel\\u000a retrieval of light–matter interactions on the nanometer-scale instead of the conventional one-dimensional scanning method.\\u000a One is the macro-scale observation of optical near-fields, and the other is the

Naoya Tate; Wataru Nomura; Takashi Yatsui; Tadashi Kawazoe; Makoto Naruse; Motoichi Ohtsu

2010-01-01

65

Specific absorption rate benefits of including measured electric field interactions in parallel excitation pulse design.  

PubMed

Specific absorption rate management and excitation fidelity are key aspects of radiofrequency pulse design for parallel transmission at ultra-high magnetic field strength. The design of radiofrequency pulses for multiple channels is often based on the solution of regularized least-squares optimization problems for which a regularization term is typically selected to control the integrated or peak pulse waveform amplitude. Unlike single-channel transmission, the specific absorption rate of parallel transmission is significantly influenced by interferences between the electric fields associated with the individual transmission elements, which a conventional regularization term does not take into account. This work explores the effects upon specific absorption rate of incorporating experimentally measurable electric field interactions into parallel transmission pulse design. Results of numerical simulations and phantom experiments show that the global specific absorption rate during parallel transmission decreases when electric field interactions are incorporated into pulse design optimization. The results also show that knowledge of electric field interactions enables robust prediction of the net power delivered to the sample or subject by parallel radiofrequency pulses before they are played out on a scanner. PMID:22135040

Deniz, Cem Murat; Alon, Leeor; Brown, Ryan; Sodickson, Daniel K; Zhu, Yudong

2011-08-29

66

Design and fabrication of arrays of nanoelectromechanical resonators for parallel detection of biomolecular interactions  

Microsoft Academic Search

The recent achievements of surface and bulk micro and nanomachining techniques combined with the fabrication techniques of integrated circuits have led to the development of miniaturized sensors and actuators exhibiting unprecedented sensitivity. This work is dedicated to the design and fabrication of nanoelectromechanical resonators for parallel detection of biomolecular interactions. The aim is to obtain piezoresistive nanoresonators with a high

C. Bergaud; E. Cocheteau; M. Guirardel; L. Nicu; B. Belier

2001-01-01

67

A Theory of Interactive Parallel Processing: New Capacity Measures and Predictions for a Response Time Inequality Series  

ERIC Educational Resources Information Center

|The authors present a theory of stochastic interactive parallel processing with special emphasis on channel interactions and their relation to system capacity. The approach is based both on linear systems theory augmented with stochastic elements and decisional operators and on a metatheory of parallel channels' dependencies that incorporates…

Townsend, James T.; Wenger, Michael J.

2004-01-01

68

A parallel 3D computational method for fluid–structure interactions in parachute systems  

Microsoft Academic Search

We present a parallel finite element computational method for 3D simulation of fluid–structure interactions (FSI) in parachute systems. The flow solver is based on a stabilized finite element formulation applicable to problems involving moving boundaries and governed by the Navier–Stokes equations of incompressible flows. The structural dynamics (SD) solver is based on the total Lagrangian description of motion, with cable

Vinay Kalro; Tayfun E. Tezduyar

2000-01-01

69

Control Strategy for Flexible Microgrid Based on Parallel Line-Interactive UPS Systems  

Microsoft Academic Search

In this paper, the control strategy for a flexible microgrid is presented. The microgrid presented here consists of several line-interactive uninterruptible power supply (UPS) systems connected in parallel. The control technique is based on the droop method to avoid critical communications among UPS units. Thus, a flexible microgrid is obtained to operate in either grid-connected or islanded mode. A small-signal

Josep M. Guerrero; Juan C. Vasquez; JosÉ Matas; Miguel Castilla; Luis Garcia de Vicuna

2009-01-01

70

Interactions between glide dislocations and parallel interfacial dislocations in nanoscale strained layers  

SciTech Connect

Plastic deformation in nanoscale multilayered structures is thought to proceed by the successive propagation of single dislocation loops at the interfaces. Based on this view, we simulate the effect of predeposited interfacial dislocation on the stress (channeling stress) needed to propagate a new loop parallel to existing loops. Single interfacial dislocations as well as finite parallel arrays are considered in the computation. When the gliding dislocation and the predeposited interfacial array have collinear Burgers vectors, the channeling stress increases monotonically as the density of dislocations in the array increases. In the case when their Burgers vectors are inclined at 60 deg. , a regime of perfect plasticity is observed which can be traced back to an instability in the flow stress arising from the interaction between the glide dislocation and a single interfacial dislocation dipole. This interaction leads to a tendency for dislocations of alternating Burgers vectors to propagate during deformation leading to nonuniform arrays. Inclusion of these parallel interactions in the analysis improves the strength predictions as compared with the measured strength of a Cu-Ni multilayered system in the regime where isolated glide dislocation motion controls flow, but does not help to explain the observed strength saturation when the individual layer thickness is in the few nanometer range.

Akasheh, F.; Zbib, H. M.; Hirth, J. P.; Hoagland, R. G.; Misra, A. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 (United States); MST Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-08-01

71

String interactions in a plane-fronted parallel-wave spacetime.  

PubMed

We argue that string interactions in a plane-fronted parallel-wave spacetime are governed by an effective coupling g(eff)=g(s)(micro p(+)alpha('))f(micro p(+)alpha(')) where f(microp(+)alpha(')) is proportional to the light-cone energy of the string states involved in the interaction. This simply follows from generalities of a matrix string description of this background. g(eff) nicely interpolates between the expected result (g(s)) for flat space (small micro p(+)alpha(')) and a recently conjectured expression from the perturbative gauge theory side (large micro p(+)alpha(')). PMID:12398656

Gopakumar, Rajesh

2002-10-03

72

Nice Guys Finish Fast and Bad Guys Finish Last: Facilitatory vs. Inhibitory Interaction in Parallel Systems  

PubMed Central

Systems Factorial Technology is a powerful framework for investigating the fundamental properties of human information processing such as architecture (i.e., serial or parallel processing) and capacity (how processing efficiency is affected by increased workload). The Survivor Interaction Contrast (SIC) and the Capacity Coefficient are effective measures in determining these underlying properties, based on response-time data. Each of the different architectures, under the assumption of independent processing, predicts a specific form of the SIC along with some range of capacity. In this study, we explored SIC predictions of discrete-state (Markov process) and continuous-state (Linear Dynamic) models that allow for certain types of cross-channel interaction. The interaction can be facilitatory or inhibitory: one channel can either facilitate, or slow down processing in its counterpart. Despite the relative generality of these models, the combination of the architecture-oriented plus the capacity oriented analyses provide for precise identification of the underlying system.

Eidels, Ami; Houpt, Joseph W.; Altieri, Nicholas; Pei, Lei; Townsend, James T.

2011-01-01

73

Orbital-based insights into parallel-displaced and twisted conformations in ?-? interactions.  

PubMed

Dispersion and electrostatics are known to stabilize ?-? interactions, but the preference for parallel-displaced (PD) and/or twisted (TW) over sandwiched (S) conformations is not well understood. Orbital interactions are generally believed to play little to no role in ?-stacking. However, orbital analysis of the dimers of benzene, pyridine, cytosine and several polyaromatic hydrocarbons demonstrates that PD and/or TW structures convert one or more ?-type dimer MOs with out-of-phase or antibonding inter-ring character at the S stack to in-phase or bonding in the PD/TW stack. This change in dimer MO character can be described in terms of a qualitative stack bond order (SBO) defined as the difference between the number of occupied in-phase/bonding and out-of-phase/antibonding inter-ring ?-type MOs. The concept of an SBO is introduced here in analogy to the bond order in molecular orbital theory. Thus, whereas the SBO of the S structure is zero, parallel displacement or twisting the stack results in a non-zero SBO and overall bonding character. The shift in bonding/antibonding character found at optimal PD/TW structures maximizes the inter-ring density, as measured by intermolecular Wiberg bond indices (WBIs). Values of WBIs calculated as a function of the parallel-displacement are found to correlate with the dispersion and other contributions to the ?-? interaction energy determined by the highly accurate density-fitting DFT symmetry adapted perturbation theory (DF-DFT-SAPT) method. These DF-DFT-SAPT calculations also suggest that the dispersion and other contributions are maximized at the PD conformation rather than the S when conducted on a potential energy curve where the inter-ring distance is optimized at fixed slip distances. From these results of this study, we conclude that descriptions of the qualitative manner in which orbitals interact within ?-stacking interactions can supplement high-level calculations of the interaction energy and provide an intuitive tool for applications to crystal design, molecular recognition and other fields where non-covalent interactions are important. PMID:23665910

Lutz, Patricia B; Bayse, Craig A

2013-05-10

74

Precision control of charge coherence in parallel double dot systems through spin-orbit interaction.  

PubMed

In terms of the exact quantum master equation solution for open electronic systems, the coherent dynamics of two charge states described by two parallel quantum dots with one fully polarized electron on either dot is investigated in the presence of spin-orbit interaction. We demonstrate that the double dot system can stay in a dynamically decoherence free space. The coherence between two double dot charge states can be precisely manipulated through a spin-orbit coupling. The effects of the temperature, the finite bandwidth of lead, and the energy deviations during the coherence manipulation are also explored. PMID:23947879

Jin, Jinshuang; Tu, Matisse Wei-Yuan; Wang, Nien-En; Zhang, Wei-Min

2013-08-14

75

Precision control of charge coherence in parallel double dot systems through spin-orbit interaction  

NASA Astrophysics Data System (ADS)

In terms of the exact quantum master equation solution for open electronic systems, the coherent dynamics of two charge states described by two parallel quantum dots with one fully polarized electron on either dot is investigated in the presence of spin-orbit interaction. We demonstrate that the double dot system can stay in a dynamically decoherence free space. The coherence between two double dot charge states can be precisely manipulated through a spin-orbit coupling. The effects of the temperature, the finite bandwidth of lead, and the energy deviations during the coherence manipulation are also explored.

Jin, Jinshuang; Tu, Matisse Wei-Yuan; Wang, Nien-En; Zhang, Wei-Min

2013-08-01

76

Efficient Parallel Analysis of Shell-fluid Interaction Problem by Using Monolithic Method Based on Consistent Pressure Poisson Equation  

NASA Astrophysics Data System (ADS)

In this paper, a parallel monolithic method for shell-fluid interaction based on the consistent Pressure Poisson Equation (PPE) is developed and its parallel computational efficiency is demonstrated. The Conjugate Gradient (CG) method without any preconditioner works well to solve the consistent PPE, even though the coefficient matrix of the original coupled equation system becomes ill-conditioned due to (a) the inhomogeneity of submatrix elements between the fluid and the structure and (b) the ill-conditioned submatrix of shell structure. Thus our parallel monolithic method using the consistent PPE and the CG method without any preconditioner is efficient for parallel analyses of shell-fluid interaction problems. The present parallel solution procedure is based on the mesh decomposition. To demonstrate the performances of the developed method, it is applied to simulate the vibration of an elastic plate situated in the wake of a rectangular prism and a flapping elastic wing in quiescent fluid.

Ishihara, Daisuke; Kanei, Shigeo; Yoshimura, Shinobu; Horie, Tomoyoshi

77

Parallel strong-strong/strong-weak simulations of beam-beam interaction in hadron accelerators  

SciTech Connect

In this paper, we present a parallel computational tool, BeamBeam3D, developed at Lawrence Berkeley National Laboratory, for strong-strong/strong-weak beam-beam modeling. This tool calculates self-consistently the electromagnetic beam-beam forces for arbitrary distributions during each collision when a strong-strong beam-beam interaction model is used. When a strong-weak model is used, the code has the option of using a Gaussian approximation for the strong beam. BeamBeam3D uses a multiple-slice model, so finite bunch length effects can be studied. The code also includes a Lorentz boost and rotation to treat collisions with finite collision crossing angle. It handles arbitrary closed-orbit separation (static or time dependent) and models long-range beam-beam interactions using a newly developed shifted Green function approach. It can also handle multiple interaction points using externally supplied linear maps between interaction points in the strong-weak model. The code has been used to study beam-beam effects in the RHIC, Tevatron, and LHC. In this paper we will describe the BeamBeam3D code, present example simulations, and describe the code performance.

Qiang, Ji; Furman, Miguel; Ryne, Robert D.; Fischer, Wolfram; Sen, Tanaji; Xiao, Meiqin

2003-09-18

78

Experimental Investigation of the Chopping of Helicopter Main Rotor Tip Vortices by the Tail Rotor.  

National Technical Information Service (NTIS)

The chopping of helicopter main rotor tip vortices by the tail rotor was experimentally investigated. This is a problem of blade vortex interaction (BVI) at normal incidence where the vortex is generally parallel to the rotor axis. The experiment used a m...

A. R. Ahmadi

1984-01-01

79

A new 3D parallel multi-species hybrid model for Solar Wind - Mars interaction  

NASA Astrophysics Data System (ADS)

Due to the absence of strong intrinsic magnetic field, the Martian atmosphere/exosphere is directly in contact with the Solar Wind, exchanging part of its momentum and energy. This coupling occurs via ionization processes and contributes to the erosion of the neutral environment of the planet. Several space missions (past, active and future), such as Phobos-2, MGS, Mars-Express and soon MAVEN, are dedicated to reveal the Martian neutral and ionized environment properties. Many in situ observations are available and characterize the plasma (and neutral) environment in the near vicinity of the spacecraft but these observations are highly localized in space and time. With a single spacecraft it is difficult to separate spatial from temporal structures and we often resort to global simulation to set back the observation in a global context. In the frame of the HELIOSARES project (granted by the French National Agency), we have parallelized our previous hybrid model. This study presents the first simulation results with an improved 75 km spatial resolution from a 3-dimensional parallel multi-species hybrid model of the Martian interaction with the Solar Wind.

Hess, S.; Modolo, R.; Mancini, M.; Allioux, R.; Richer, E.; Leblanc, F.; Chaufray, J.; Yagi, M.; Chanteur, G. M.

2011-12-01

80

Massively parallel measurements of molecular interaction kinetics on a microfluidic platform  

PubMed Central

Quantitative biology requires quantitative data. No high-throughput technologies exist capable of obtaining several hundred independent kinetic binding measurements in a single experiment. We present an integrated microfluidic device (k-MITOMI) for the simultaneous kinetic characterization of 768 biomolecular interactions. We applied k-MITOMI to the kinetic analysis of transcription factor (TF)—DNA interactions, measuring the detailed kinetic landscapes of the mouse TF Zif268, and the yeast TFs Tye7p, Yox1p, and Tbf1p. We demonstrated the integrated nature of k-MITOMI by expressing, purifying, and characterizing 27 additional yeast transcription factors in parallel on a single device. Overall, we obtained 2,388 association and dissociation curves of 223 unique molecular interactions with equilibrium dissociation constants ranging from 2 × 10-6 M to 2 × 10-9 M, and dissociation rate constants of approximately 6 s-1 to 8.5 × 10-3 s-1. Association rate constants were uniform across 3 TF families, ranging from 3.7 × 106 M-1 s-1 to 9.6 × 107 M-1 s-1, and are well below the diffusion limit. We expect that k-MITOMI will contribute to our quantitative understanding of biological systems and accelerate the development and characterization of engineered systems.

Geertz, Marcel; Shore, David; Maerkl, Sebastian J.

2012-01-01

81

Extensions of parallel coordinates for interactive exploration of large multi-timepoint data sets.  

PubMed

Parallel coordinate plots (PCPs) are commonly used in information visualization to provide insight into multi-variate data. These plots help to spot correlations between variables. PCPs have been successfully applied to unstructured datasets up to a few millions of points. In this paper, we present techniques to enhance the usability of PCPs for the exploration of large, multi-timepoint volumetric data sets, containing tens of millions of points per timestep. The main difficulties that arise when applying PCPs to large numbers of data points are visual clutter and slow performance, making interactive exploration infeasible. Moreover, the spatial context of the volumetric data is usually lost. We describe techniques for preprocessing using data quantization and compression, and for fast GPU-based rendering of PCPs using joint density distributions for each pair of consecutive variables, resulting in a smooth, continuous visualization. Also, fast brushing techniques are proposed for interactive data selection in multiple linked views, including a 3D spatial volume view. These techniques have been successfully applied to three large data sets: Hurricane Isabel (Vis'04 contest), the ionization front instability data set (Vis'08 design contest), and data from a large-eddy simulation of cumulus clouds. With these data, we show how PCPs can be extended to successfully visualize and interactively explore multi-timepoint volumetric datasets with an order of magnitude more data points. PMID:18988994

Blaas, Jorik; Botha, Charl P; Post, Frits H

82

Parallel computation of fluid-structural interactions using high resolution upwind schemes  

NASA Astrophysics Data System (ADS)

An efficient and accurate solver is developed to simulate the non-linear fluid-structural interactions in turbomachinery flutter flows. A new low diffusion E-CUSP scheme, Zha CUSP scheme, is developed to improve the efficiency and accuracy of the inviscid flux computation. The 3D unsteady Navier-Stokes equations with the Baldwin-Lomax turbulence model are solved using the finite volume method with the dual-time stepping scheme. The linearized equations are solved with Gauss-Seidel line iterations. The parallel computation is implemented using MPI protocol. The solver is validated with 2D cases for its turbulence modeling, parallel computation and unsteady calculation. The Zha CUSP scheme is validated with 2D cases, including a supersonic flat plate boundary layer, a transonic converging-diverging nozzle and a transonic inlet diffuser. The Zha CUSP2 scheme is tested with 3D cases, including a circular-to-rectangular nozzle, a subsonic compressor cascade and a transonic channel. The Zha CUSP schemes are proved to be accurate, robust and efficient in these tests. The steady and unsteady separation flows in a 3D stationary cascade under high incidence and three inlet Mach numbers are calculated to study the steady state separation flow patterns and their unsteady oscillation characteristics. The leading edge vortex shedding is the mechanism behind the unsteady characteristics of the high incidence separated flows. The separation flow characteristics is affected by the inlet Mach number. The blade aeroelasticity of a linear cascade with forced oscillating blades is studied using parallel computation. A simplified two-passage cascade with periodic boundary condition is first calculated under a medium frequency and a low incidence. The full scale cascade with 9 blades and two end walls is then studied more extensively under three oscillation frequencies and two incidence angles. The end wall influence and the blade stability are studied and compared under different frequencies and incidence angles. The Zha CUSP schemes are the first time to be applied in moving grid systems and 2D and 3D calculations. The implicit Gauss-Seidel iteration with dual time stepping is the first time to be used for moving grid systems. The NASA flutter cascade is the first time to be calculated in full scale.

Hu, Zongjun

83

Parallel Finite Element Particle-In-Cell Code for Simulations of Space-Charge Dominated Beam-Cavity Interactions.  

National Technical Information Service (NTIS)

Over the past years, SLACs Advanced Computations Department (ACD) has developed the parallel finite element (FE) particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by spacecharge effects. As opposed to standard space...

A. C. Kabel A. E. Candel L. Lee R. Uplenchwar Y. K. Ko

2007-01-01

84

A Tool for On-line Visualization and Interactive Steering of Parallel HPC Applications  

Microsoft Academic Search

Tools for parallel systems today range from specification over debugging to performance analysis and more. Typ- ically, they help the programmers of parallel algorithms from the early development stages to a certain level of pro- gram optimization. However, in HPC ( High Performance Computing) today the end-user of massively parallel CFD (ComputationalFluid Dynamics)-programs has little or no support in his

Sabine Rathmayer; Michael Lenke

1997-01-01

85

Software tools for developing parallel applications. Part 2: Interactive control and performance tuning  

SciTech Connect

This paper continues the discussion of parallel tool support with an overview of the current state of tools for runtime control and performance tuning. Each is discussed in terms of the programmer needs addressed, the extent to which representative current tools meet those needs, and what new levels of tool support are important if parallel computing is to become more widespread.

Brown, J. [Los Alamos National Lab., NM (United States); Geist, A. [Oak Ridge National Lab., TN (United States). Computer Science and Mathematics Div.; Pancake, C. [Oregon State Univ., Corvallis, OR (United States). Dept. of Computer Science; Rover, D. [Michigan State Univ., East Lansing, MI (United States). Dept. of Electrical Engineering

1997-04-01

86

Implementation of Parallel Algorithms.  

National Technical Information Service (NTIS)

Contents: Intermediate Representation for Parallel Implementation; Data Movement on Processor Arrays; Data-Parallel Implementations of Fast Multipole Algorithms for N-Body Interaction; Rate Control in Parallel Algorithms; Implementing Asynchronous Paralle...

J. H. Reif R. Wagner

1993-01-01

87

LPIC++ a parallel one-dimensional relativistic electromagnetic Particle-In-Cell code for simulating laser-plasma-interaction  

Microsoft Academic Search

We report on a recently developed electromagnetic relativistic 1D3V (one spatial, three velocity dimensions) Particle-In-Cell code for simulating laser-plasma interaction at normal and oblique incidence. The code is written in C++ and easy to extend. The data structure is characterized by the use of chained lists for the grid cells as well as particles belonging to one cell. The parallel

R. E. W. Pfund; R. Lichters; J. Meyer-Ter-Vehn

1998-01-01

88

Studies on the Interaction of Dna-Ligands with Modified Parallel-Stranded Duplex-Dna Oligomers  

Microsoft Academic Search

We have investigated the minor groove binders netropsin (Nt) and related lexitropsins for possible interactions with parallel-stranded DNA (ps-DNA). The fluorescence emission spectra and their temperature dependence between 4°C and 30°C led to two conclusions: (i) The specific ligand Nt induces a conversion of the ps-DNA to an antiparallel-stranded DNA (aps-DNA) with mismatched base pairs, a reaction which is much

I. Förtsch; E. Birch-Hirschfeld; T. M. Jovin; A. Stelzner; C. Zimmer

1998-01-01

89

Parallelizing assistant for parallel architectures  

SciTech Connect

This research presents the design and implementation of a prototype programming tool for vectorization and parallelization assistance, called the Workstation Vectorization and Parallelization Assistance Environment (WVPAE). The proposed working environment for WVPAE is the workstation. The WVPAE is designed to function as an experimentation facility for interactive vectorization and parallelization assistance during the implementation or maintenance of parallel-computing applications. The target high-level language for implementing parallel-computing applications is chosen to be a Fortran-like language, and the target parallel machine has to be specified by the user. The target parallel-machine architecture can be either a vector or a multiprocessor machine. The assistance provided by the WVPAE is based on analyzing user programs to discover all barriers that may cause either vectorization blocking or parallelization blocking. Vectorization and parallelization barriers are categorized in this research into barriers due to sequential language constructs and those due to dependence relationships. The WVPAE tool provides diagnostic messages and advice for most of the barriers defined in this research.

Arafeh, B.R.

1986-01-01

90

Self-assembled monolayers of aromatic thiols stabilized by parallel-displaced pi-pi stacking interactions.  

PubMed

Parallel-displaced pi-pi stacking interactions have been known to be the dominant force in stabilizing the double helical structure of DNA and the tertiary structure of proteins. However, little is known about their roles in self-assembled monolayers of other large pi molecules such as aromatic thiols. Here we report on a systematic study of the self-assembled monolayers of four kinds of anthracene-based thiols, 9-mercaptoanthracene (MA), (4-mercaptophenyl) (9-anthryl) acetylene (MPAA), (4-mercaptophenyl) (10-nitro-9-anthryl) acetylene (MPNAA), and (4-mercaptophenyl) (10-carboxyl-9-anthryl) acetylene (MPCAA) on Au(111), in which a spacer and different functional groups (NO2 and COOH) are intentionally designed to introduce and thus allow the investigation of various intermolecular interactions, in addition to pi-pi interactions in the base molecules. We find that all molecules form long-range-ordered monolayers and, more interestingly, that these assembled monolayers exhibit essentially the same fundamental packing structure. On the basis of high-resolution scanning tunneling microscopy observations, we propose the space-filling models for the observed superstructures and demonstrate that all superstructures can be understood in terms of the parallel-displaced pi-pi stacking interactions, despite the presence of competing dipole-dipole and H-bonding interactions associated with these specially designed functional groups. PMID:16548556

Dou, Rui-Fen; Ma, Xu-Cun; Xi, Luan; Yip, Hin Lap; Wong, King Young; Lau, Woon Ming; Jia, Jin-Feng; Xue, Qi-Kun; Yang, Wei-Sheng; Ma, Hong; Jen, Alex K-Y

2006-03-28

91

Flecs, a flexible coupling shell - Parallel application to fluid-structure interaction  

NASA Astrophysics Data System (ADS)

In this paper we discuss the second version of Flecs, a generic, open-source coupling shell that can be used to join two or more arbitrary solvers. In general multidisciplinary computations are very computing-intensive. A remedy against long computing times is large-scale parallelism. The challenge of the present parallelization work is to obtain acceptable computing times and to get rid of severe memory requirements that exist on sequential machines, for the generic flow problems at hand. The aim is to provide a flexible platform for developing new data transfer algorithms and coupling schemes.

Nool, Margreet; Lingen, Erik Jan; van Zuijlen, Sander; Stroeven, Martijn; Bijl, Hester

2012-12-01

92

An Interactive 3D Integration of Parallel Coordinates and Star Glyphs  

Microsoft Academic Search

Parallel Coordinates are a powerful method for visualizing multi- dimensional data, however, with large data sets they can become cluttered and difficult to read. On the other hand, a Star Glyph can be used to display either the attributes of a data item or the values across all items for a single attribute. Star Glyphs may readily pro- vide a

Elena Fanea; M. Sheelagh T. Carpendale; Tobias Isenberg

2005-01-01

93

Parallel Simulation Algorithms for the Three Dimensional Strong-Strong Beam-Beam Interaction  

SciTech Connect

The strong-strong beam-beam effect is one of the most important effects limiting the luminosity of ring colliders. Little is known about it analytically, so most studies utilize numeric simulations. The two-dimensional realm is readily accessible to workstation-class computers (cf.,e.g.,[1, 2]), while three dimensions, which add effects such as phase averaging and the hourglass effect, require vastly higher amounts of CPU time. Thus, parallelization of three-dimensional simulation techniques is imperative; in the following we discuss parallelization strategies and describe the algorithms used in our simulation code, which will reach almost linear scaling of performance vs. number of CPUs for typical setups.

Kabel, A.C.; /SLAC

2008-03-17

94

Multi-GPU and Multi-CPU Parallelization for Interactive Physics Simulations  

Microsoft Academic Search

\\u000a Today, it is possible to associate multiple CPUs and multiple GPUs in a single shared memory architecture. Using these resources\\u000a efficiently in a seamless way is a challenging issue. In this paper, we propose a parallelization scheme for dynamically balancing\\u000a work load between multiple CPUs and GPUs. Most tasks have a CPU and GPU implementation, so they can be executed

Everton Hermann; Bruno Raffin; François Faure; Thierry Gautier; Jérémie Allard

2010-01-01

95

Highly Parallel Fast KD-tree Construction for Interactive Ray Tracing of Dynamic Scenes  

Microsoft Academic Search

We present a highly parallel, linearly scalable technique of kd-tree construction for ray tracing of dynamic ge- ometry. We use conventional kd-tree compatible with the high performing algorithms such as MLRTA or frustum tracing. Proposed technique offers exceptional construction speed maintaining reasonable kd-tree quality for ren- dering stage. The algorithm builds a kd-tree from scratch each frame, thus prior knowledge

Maxim Shevtsov; Alexei Soupikov; Alexander Kapustin

2007-01-01

96

Wave-particle interaction in parallel transport of long mean-free-path plasmas along open field magnetic field lines  

NASA Astrophysics Data System (ADS)

A tokamak fusion reactor dumps a large amount of heat and particle flux to the divertor through the scrape-off plasma (SOL). Situation exists either by necessity or through deliberate design that the SOL plasma attains long mean-free-path along large segments of the open field lines. The rapid parallel streaming of electrons requires a large parallel electric field to maintain ambipolarity. The confining effect of the parallel electric field on electrons leads to a trap/passing boundary in the velocity space for electrons. In the normal situation where the upstream electron source populates both the trapped and passing region, a mechanism must exist to produce a flux across the electron trap/passing boundary. In a short mean-free-path plasma, this is provided by collisions. For long mean-free-path plasmas, wave-particle interaction is the primary candidate for detrapping the electrons. Here we present simulation results and a theoretical analysis using a model distribution function of trapped electrons. The dominating electromagnetic plasma instability and the associated collisionless scattering, that produces both particle and energy fluxes across the electron trap/passing boundary in velocity space, are discussed.

Guo, Zehua; Tang, Xianzhu

2012-03-01

97

Identifying interacting SNPs with parallel fish-agent based logic regression  

Microsoft Academic Search

Understanding the genotype-phenotype associa- tion is a fundamental problem in genetics. A major open prob- lem in mapping complex traits is identifying a set of interacting genetic variants (such as single nucleotide polymorphisms or SNPs) that influence disease susceptibility. Logic regression (LR) is a statistical approach that has been proposed to model interactions of SNPs. Several LR-based association detection approaches

Jiayin Wang; Jin Zhang; Yufeng Wu

2011-01-01

98

Simulations of hydrodynamic interactions among immersed particles in stokes flow using a massively parallel computer  

SciTech Connect

In this paper, a massively parallel implementation of the boundary element method to study particle transport in Stokes flow is discussed. The numerical algorithm couples the quasistatic Stokes equations for the fluid with kinematic and equilibrium equations for the particles. The formation and assembly of the discretized boundary element equations is based on the torus-wrap mapping as opposed to the more traditional row- or column-wrap mappings. The equation set is solved using a block Jacobi iteration method. Results are shown for an example application problem, which requires solving a dense system of 6240 equations more than 1200 times.

Ingber, M.S. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Mechanical Engineering; Womble, D.E.; Mondy, L.A. [Sandia National Labs., Albuquerque, NM (United States)

1995-05-01

99

Model calculations of the interaction of two parallel antiaromatic 4n ?-electron systems  

PubMed Central

The nature of the interaction between decks of a pentalene dimer and an s-indacene dimer has been studied by semi-empirical MNDO/1 and MINDO/3 calculations for distances between decks of from 5 Å to 2 Å. In contradiction to qualitative predictions from a frontier orbital analysis, it is found that the 4n-4n ?-electron interaction between decks for such dimers is destabilizing for distances exceeding about 2.5 Å.

Bohm, Michael C.; Bickert, Peter; Hafner, Klaus; Boekelheide, V.

1984-01-01

100

Study of the parallel-plate EMP simulator and the simulator-obstacle interaction. Final technical report  

SciTech Connect

The Parallel-Plate Bounded-Wave EMP Simulator is typically used to test the vulnerability of electronic systems to the electromagnetic pulse (EMP) produced by a high altitude nuclear burst by subjecting the systems to a simulated EMP environment. However, when large test objects are placed within the simulator for investigation, the desired EMP environment may be affected by the interaction between the simulator and the test object. This simulator/obstacle interaction can be attributed to the following phenomena: (1) mutual coupling between the test object and the simulator, (2) fringing effects due to the finite width of the conducting plates of the simulator, and (3) multiple reflections between the object and the simulator's tapered end-sections. When the interaction is significant, the measurement of currents coupled into the system may not accurately represent those induced by an actual EMP. To better understand the problem of simulator/obstacle interaction, a dynamic analysis of the fields within the parallel-plate simulator is presented. The fields are computed using a moment method solution based on a wire mesh approximation of the conducting surfaces of the simulator. The fields within an empty simulator are found to be predominately transversse electromagnetic (TEM) for frequencies within the simulator's bandwidth, properly simulating the properties of the EMP propagating in free space. However, when a large test object is placed within the simulator, it is found that the currents induced on the object can be quite different from those on an object situated in free space. A comprehensive study of the mechanisms contributing to this deviation is presented.

Gedney, S.D.

1990-12-01

101

Parallel adaptive fluid-structure interaction simulation of explosions impacting on building structures  

SciTech Connect

We pursue a level set approach to couple an Eulerian shock-capturing fluid solver with space-time refinement to an explicit solid dynamics solver for large deformations and fracture. The coupling algorithms considering recursively finer fluid time steps as well as overlapping solver updates are discussed in detail. Our ideas are implemented in the AMROC adaptive fluid solver framework and are used for effective fluid-structure coupling to the general purpose solid dynamics code DYNA3D. Beside simulations verifying the coupled fluid-structure solver and assessing its parallel scalability, the detailed structural analysis of a reinforced concrete column under blast loading and the simulation of a prototypical blast explosion in a realistic multistory building are presented.

Deiterding, Ralf [ORNL; Wood, Stephen L [University of Tennessee, Knoxville (UTK)

2013-01-01

102

RKKY Interaction and the Nature of the Ground State of Double Dots in Parallel  

SciTech Connect

We argue through a combination of slave-boson mean-field theory and the Bethe ansatz that the ground state of closely spaced double quantum dots in parallel coupled to a single effective channel are Fermi liquids. We do so by studying the dots conductance, impurity entropy, and spin correlation. In particular, we find that the zero-temperature conductance is characterized by the Friedel sum rule, a hallmark of Fermi-liquid physics, and that the impurity entropy vanishes in the limit of zero temperature, indicating that the ground state is a singlet. This conclusion is in opposition to a number of numerical renormalization-group studies. We suggest a possible reason for the discrepancy.

Kulkarni, M.; Konik, R.

2011-06-23

103

Gamma ray bursts from comet neutron star magnetosphere interaction, field twisting and E sub parallel formation  

SciTech Connect

Consider the problem of a comet in a collision trajectory with a magnetized neutron star. The question addressed in this paper is whether the comet interacts strongly enough with a magnetic field such as to capture at a large radius or whether in general the comet will escape a magnetized neutron star. 6 refs., 4 figs.

Colgate, S.A.

1990-01-01

104

A parallel edge-betweenness clustering tool for Protein-Protein Interaction networks  

Microsoft Academic Search

The increasing availability of protein-protein interaction graphs (PPI) requires new efficient tools capable of extracting valuable biological knowledge from these networks. Among the wide range of clustering algorithms, Girvan and Newman's edge betweenness algorithm showed remarkable performances in discovering clustering structures in several real-world networks. Unfortunately, their algorithm suffers from high computational cost and it is impractical for inputs of

Qiaofeng Yang; Stefano Lonardi

2007-01-01

105

Prediction of BVI noise patterns and correlation with wake interaction locations  

NASA Astrophysics Data System (ADS)

High resolution fluctuating airloads data were acquired during a test of a contemporary design United Technologies model rotor in the Duits-Nederlandse Windtunnel (DNW). The airloads are used as input to the noise prediction program WOPWOP, in order to predict the blade-vortex interaction (BVI) noise field on a large plane below the rotor. Trends of predicted advancing and retreating side BVI noise levels and directionality as functions of flight condition are presented. The measured airloads have been analyzed to determine the BVI locations on the blade surface, and are used to interpret the predicted BVI noise radiation patterns. Predicted BVI locations are obtained using the free wake model in CAMRAD/JA, the UTRC Generalized Forward Flight Distorted Wake Model, and the UTRC FREEWAKE analysis. These predicted BVI locations are compared with those obtained from the measured pressure data.

Marcolini, Michael A.; Martin, Ruth M.; Lorber, Peter F.; Egolf, T. A.

106

OSIRIS - an object-oriented parallel 3D PIC code for modeling laser and particle beam-plasma interaction  

NASA Astrophysics Data System (ADS)

The advances in computational speed make it now possible to do full 3D PIC simulations of laser plasma and beam plasma interactions, but at the same time the increased complexity of these problems makes it necessary to apply modern approaches like object oriented programming to the development of simulation codes. We report here on our progress in developing an object oriented parallel 3D PIC code using Fortran 90. In its current state the code contains algorithms for 1D, 2D, and 3D simulations in cartesian coordinates and for 2D cylindrically-symmetric geometry. For all of these algorithms the code allows for a moving simulation window and arbitrary domain decomposition for any number of dimensions. Recent 3D simulation results on the propagation of intense laser and electron beams through plasmas will be presented.

Hemker, Roy

1999-11-01

107

PARALLEL STRINGS - PARALLEL UNIVERSES  

Microsoft Academic Search

Sometimes different parts of the battery community just don't seem to operate on the same level, and attitudes towards parallel battery strings are a prime example of this. Engineers at telephone company central offices are quite happy operating 20 or more parallel strings on the same dc bus, while many manufacturers warn against connecting more than four or five strings

Jim McDowall; Saft America

108

Massively parallel full configuration interaction. Benchmark electronic structure calculations on the Intel Touchstone Delta  

SciTech Connect

We describe an implementation of the benchmark ab initio electronic structure full configuration interaction model on the Intel Touchstone Delta. Its performance is demonstrated with several calculations, the largest of which (95 million configurations, 418 million determinants) is the largest full-CI calculation yet completed. The feasibility of calculations with over one billion configurations is discussed. A sustained computation rate in excess of 4 GFLOP/s on 512 processors is achieved, with an average aggregate communication rate of 155 Mbytes/s. Data-compression techniques and a modified diagonalization method were required to minimize I/O. The object-oriented design has increased portability and provides the distinction between local and non-local data essential for use of a distributed-data model.

Harrison, R.J. [Argonne National Lab., IL (United States); Stahlberg, E.A. [Pacific Northwest Lab., Richland, WA (United States)

1994-10-01

109

Tensor contraction engine: Abstraction and automated parallel implementation of configuration-interaction, coupled-cluster, and many-body perturbation theories  

SciTech Connect

We develop a symbolic manipulation program and program generator (Tensor Contraction Engine or TCE) that automatically derives the working equations of a well-defined model of second-quantized many-electron theories and synthesizes efficient parallel computer programs on the basis of these equations. Provided an ansatz of a many-electron theory model, TCE performs valid contractions of creation and annihilation operators according to Wick's theorem, consolidates identical terms, and reduces the expressions into the form of multiple tensor contractions acted by permutation operators. Subsequently, it determines the binary contraction order for each multiple tensor contraction with the minimal operation and memory cost, factorizes common binary contractions (defines intermediate tensors), and identifies reusable intermediates. The resulting ordered list of binary tensor contractions, additions, and index permutations is translated into an optimized program that is combined with the NWChem and UTChem computational chemistry software packages. The programs synthesized by TCE take advantage of spin symmetry, Abelian point-group symmetry, and index permutation symmetry at every stage of calculations to minimize the number of arithmetic operations and storage requirement, adjust the peak local memory usage by index range tiling, and support parallel I/O interfaces and dynamic load balancing for parallel executions. We demonstrate the utility of TCE through automatic derivation and implementation of parallel programs for various models of configuration-interaction theory (CISD, CISDT, CISDTQ), many-body perturbation theory [MBPT(2), MBPT(3), MBPT(4)], and coupled-cluster theory (LCCD, CCD, LCCSD, CCSD, QCISD, CCSDT, and CCSDTQ).

Hirata, So

2003-11-20

110

Large-scale parallel configuration interaction. II. Two- and four-component double-group general active space implementation with application to BiH  

NASA Astrophysics Data System (ADS)

We present a parallel implementation of a large-scale relativistic double-group configuration interaction (CI) program. It is applicable with a large variety of two- and four-component Hamiltonians. The parallel algorithm is based on a distributed data model in combination with a static load balancing scheme. The excellent scalability of our parallelization scheme is demonstrated in large-scale four-component multireference CI (MRCI) benchmark tests on two of the most common computer architectures, and we also discuss hardware-dependent aspects with respect to possible speedup limitations. With the new code we have been able to calculate accurate spectroscopic properties for the ground state and the first excited state of the BiH molecule using extensive basis sets. We focused, in particular, on an accurate description of the splitting of these two states which is caused by spin-orbit coupling. Our largest parallel MRCI calculation thereby comprised an expansion length of 2.7×109 Slater determinants.

Knecht, Stefan; Jensen, Hans Jørgen Aa.; Fleig, Timo

2010-01-01

111

Large-scale parallel configuration interaction. II. Two- and four-component double-group general active space implementation with application to BiH.  

PubMed

We present a parallel implementation of a large-scale relativistic double-group configuration interaction (CI) program. It is applicable with a large variety of two- and four-component Hamiltonians. The parallel algorithm is based on a distributed data model in combination with a static load balancing scheme. The excellent scalability of our parallelization scheme is demonstrated in large-scale four-component multireference CI (MRCI) benchmark tests on two of the most common computer architectures, and we also discuss hardware-dependent aspects with respect to possible speedup limitations. With the new code we have been able to calculate accurate spectroscopic properties for the ground state and the first excited state of the BiH molecule using extensive basis sets. We focused, in particular, on an accurate description of the splitting of these two states which is caused by spin-orbit coupling. Our largest parallel MRCI calculation thereby comprised an expansion length of 2.7x10(9) Slater determinants. PMID:20078150

Knecht, Stefan; Jensen, Hans Jørgen Aa; Fleig, Timo

2010-01-01

112

Parallel processing  

SciTech Connect

This report examines the current techniques of parallel processing, transputers, vector and vector supercomputers and covers such areas as transputer applications, programming models and language design for parallel processing.

Jesshop, C.

1987-01-01

113

Parallel Algorithms  

NSDL National Science Digital Library

Content prepared for the Supercomputing 2002 session on "Using Clustering Technologies in the Classroom". Contains a series of exercises for teaching parallel computing concepts through kinesthetic activities.

Gray, Paul

114

Interaction of Pyrrolobenzodiazepine (PBD) Ligands with Parallel Intermolecular G-Quadruplex Complex Using Spectroscopy and ESI-MS  

Microsoft Academic Search

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine

Gajjela Raju; Ragampeta Srinivas; Vangala Santhosh Reddy; Mohammed M. Idris; Ahmed Kamal; Narayana Nagesh

2012-01-01

115

Scalable parallel methods for monolithic coupling in fluid-structure interaction with application to blood flow modeling  

SciTech Connect

We introduce and study numerically a scalable parallel finite element solver for the simulation of blood flow in compliant arteries. The incompressible Navier-Stokes equations are used to model the fluid and coupled to an incompressible linear elastic model for the blood vessel walls. Our method features an unstructured dynamic mesh capable of modeling complicated geometries, an arbitrary Lagrangian-Eulerian framework that allows for large displacements of the moving fluid domain, monolithic coupling between the fluid and structure equations, and fully implicit time discretization. Simulations based on blood vessel geometries derived from patient-specific clinical data are performed on large supercomputers using scalable Newton-Krylov algorithms preconditioned with an overlapping restricted additive Schwarz method that preconditions the entire fluid-structure system together. The algorithm is shown to be robust and scalable for a variety of physical parameters, scaling to hundreds of processors and millions of unknowns.

Barker, Andrew T. [Department of Applied Mathematics, University of Colorado, 526 UCB, Boulder, CO 80309-0526 (United States)], E-mail: andrew.barker@colorado.edu; Cai Xiaochuan [Department of Computer Science, University of Colorado, 430 UCB, Boulder, CO 80309-0430 (United States)], E-mail: cai@cs.colorado.edu

2010-02-01

116

Interaction of pyrrolobenzodiazepine (PBD) ligands with parallel intermolecular G-quadruplex complex using spectroscopy and ESI-MS.  

PubMed

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mixed imine-amide pyrrolobenzodiazepine dimer (PBD2) and 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) were studied. G-rich single-stranded oligonucleotide d(5'GGGGTTGGGG3') designated as d(T(2)G(8)), from the telomeric region of Tetrahymena Glaucoma, was considered for the interaction with ligands. ESI-MS and spectroscopic methods viz., circular dichroism (CD), UV-Visible, and fluorescence were employed to investigate the G-quadruplex structures formed by d(T(2)G(8)) sequence and its interaction with PBD and TMPyP4 ligands. From ESI-MS spectra, it is evident that the majority of quadruplexes exist as d(T(2)G(8))(2) and d(T(2)G(8))(4) forms possessing two to ten cations in the centre, thereby stabilizing the complex. CD band of PBD1 and PBD2 showed hypo and hyperchromicity, on interaction with quadruplex DNA, indicating unfolding and stabilization of quadruplex DNA complex, respectively. UV-Visible and fluorescence experiments suggest that PBD1 bind externally where as PBD2 intercalate moderately and bind externally to G-quadruplex DNA. Further, melting experiments using SYBR Green indicate that PBD1 unfolds and PBD2 stabilizes the G-quadruplex complex. ITC experiments using d(T(2)G(8)) quadruplex with PBD ligands reveal that PBD1 and PBD2 prefer external/loop binding and external/intercalative binding to quadruplex DNA, respectively. From experimental results it is clear that the interaction of PBD2 and TMPyP4 impart higher stability to the quadruplex complex. PMID:22558271

Raju, Gajjela; Srinivas, Ragampeta; Reddy, Vangala Santhosh; Idris, Mohammed M; Kamal, Ahmed; Nagesh, Narayana

2012-04-27

117

Interaction of Pyrrolobenzodiazepine (PBD) Ligands with Parallel Intermolecular G-Quadruplex Complex Using Spectroscopy and ESI-MS  

PubMed Central

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mixed imine-amide pyrrolobenzodiazepine dimer (PBD2) and 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) were studied. G-rich single-stranded oligonucleotide d(5?GGGGTTGGGG3?) designated as d(T2G8), from the telomeric region of Tetrahymena Glaucoma, was considered for the interaction with ligands. ESI-MS and spectroscopic methods viz., circular dichroism (CD), UV-Visible, and fluorescence were employed to investigate the G-quadruplex structures formed by d(T2G8) sequence and its interaction with PBD and TMPyP4 ligands. From ESI-MS spectra, it is evident that the majority of quadruplexes exist as d(T2G8)2 and d(T2G8)4 forms possessing two to ten cations in the centre, thereby stabilizing the complex. CD band of PBD1 and PBD2 showed hypo and hyperchromicity, on interaction with quadruplex DNA, indicating unfolding and stabilization of quadruplex DNA complex, respectively. UV-Visible and fluorescence experiments suggest that PBD1 bind externally where as PBD2 intercalate moderately and bind externally to G-quadruplex DNA. Further, melting experiments using SYBR Green indicate that PBD1 unfolds and PBD2 stabilizes the G-quadruplex complex. ITC experiments using d(T2G8) quadruplex with PBD ligands reveal that PBD1 and PBD2 prefer external/loop binding and external/intercalative binding to quadruplex DNA, respectively. From experimental results it is clear that the interaction of PBD2 and TMPyP4 impart higher stability to the quadruplex complex.

Raju, Gajjela; Srinivas, Ragampeta; Santhosh Reddy, Vangala; Idris, Mohammed M.; Kamal, Ahmed; Nagesh, Narayana

2012-01-01

118

Parallel quicksort  

SciTech Connect

This paper reports on the development of a parallel version of quicksort on a CRCW PRAM. The algorithm uses n processors and a linear space to sort n keys in the expected time O(log n) with large probability.

Vrto, I. (Inst. of Technical Cybernetics, Slovac Academy of Sciences, Dubravska Cesta 9, 842-37 Bratislava (CS)); Chelbus, B.S. (Dept. of Computer Science, Univ. of California, Riverside, CA (US))

1991-04-01

119

Modeling Interactions of Surface-Subsurface Flow Using a Free-Surface Overland Flow Boundary Condition in a Parallel Flow Simulator  

SciTech Connect

Models incorporating interactions between surface and subsurface flow are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. In these models the subsurface and surface domains are linked via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in the field, a more general coupled modeling approach would be preferable. We present a more general approach that incorporates a two-dimensional overland flow simulator into the parallel three-dimensional variably saturated subsurface flow code ParFlow developed at LLNL. This overland flow simulator takes the form of an upper, free-surface boundary condition and is, thus, fully integrated without relying on the conductance concept. Another advantage of this approach is the efficient parallelism of ParFlow, which is exploited by the overland flow simulator. Several verification and simulation examples are presented that focus on the two main processes of runoff production: excess infiltration and saturation. The usefulness of our approach is demonstrated in an application of the model to an urban watershed. The influence of heterogeneity of the shallow subsurface on overland flow and transport is also examined. The results show the uncertainty in flow and transport predictions due to heterogeneity. This is important in determining, for example, total maximum daily loads of surface water systems.

Kollet, S J; Maxwell, R M

2005-10-25

120

Parallel computing and multitasking  

NASA Astrophysics Data System (ADS)

Over the past decade we have witnessed an evolution of scientific computers in which more and more concurrent or parallel arithmetic operations are allowed. The segmented pipeline arithmetic functional units, direct vectorization, indirect vectorization, multiprocessing and finally multitasking represent stages of development of parallel computation. Algorithms for the solution of physics problems must be tailored, if possible, to the forms required for these various kinds of parallelism. We report on some experiences we have had building and running various parallelized physics codes with particular emphasis on the Cray-2. We show that the implementation of multitasking and the subsequent debugging effort are straightforward. These techniques are applicable to more methods, including implicit ones, than was originally predicted. We present arguments that favor the use of interactive timesharing operating systems, particularly for the multitasking situation.

Anderson, David V.; Horowitz, Eric J.; Koniges, Alice E.; McCoy, Michael G.

1986-12-01

121

SHAKE parallelization  

PubMed Central

SHAKE is a widely used algorithm to impose general holonomic constraints during molecular simulations. By imposing constraints on stiff degrees of freedom that require integration with small time steps (without the constraints) we are able to calculate trajectories with time steps larger by approximately a factor of two. The larger time step makes it possible to run longer simulations. Another approach to extend the scope of Molecular Dynamics is parallelization. Parallelization speeds up the calculation of the forces between the atoms and makes it possible to compute longer trajectories with better statistics for thermodynamic and kinetic averages. A combination of SHAKE and parallelism is therefore highly desired. Unfortunately, the most widely used SHAKE algorithm (of bond relaxation) is inappropriate for parallelization and alternatives are needed. The alternatives must minimize communication, lead to good load balancing, and offer significantly better performance than the bond relaxation approach. The algorithm should also scale with the number of processors. We describe the theory behind different implementations of constrained dynamics on parallel systems, and their implementation on common architectures.

Elber, Ron; Ruymgaart, A. Peter; Hess, Berk

2011-01-01

122

Parallel Monte Carlo reactor neutronics  

SciTech Connect

The issues affecting implementation of parallel algorithms for large-scale engineering Monte Carlo neutron transport simulations are discussed. For nuclear reactor calculations, these include load balancing, recoding effort, reproducibility, domain decomposition techniques, I/O minimization, and strategies for different parallel architectures. Two codes were parallelized and tested for performance. The architectures employed include SIMD, MIMD-distributed memory, and workstation network with uneven interactive load. Speedups linear with the number of nodes were achieved.

Blomquist, R.N.; Brown, F.B.

1994-03-01

123

Parallel Resistors  

NSDL National Science Digital Library

Students will measure the resistance of resistors that they have drawn on paper with a graphite pencil. They will then connect two resistors in parallel and measure the resistance of the combination. In this activity, it is important that students color v

Horton, Michael

2009-05-30

124

Flowfield-Dependent Variation (FDV) method for compressible, incompressible, viscous, and inviscid flow interactions with FDV adaptive mesh refinements and parallel processing  

NASA Astrophysics Data System (ADS)

A new approach to solution-adaptive grid refinement using the finite element method and Flowfield-Dependent Variation (FDV) theory applied to the Navier-Stokes system of equations is discussed. Flowfield-Dependent Variation (FDV) parameters are introduced into a modified Taylor series expansion of the conservation variables, with the Navier-Stokes system of equations substituted into the Taylor series. The FDV parameters are calculated from the current Fowfield conditions, and automatically adjust the resulting equations from elliptic to parabolic to hyperbolic in type to assure solution accuracy in evolving fluid flowfields that may consist of interactions between regions of compressible and incompressible flow, viscous and inviscid flow, and turbulent and laminar flow. The system of equations is solved using an element-by-element iterative GMRES solver with the elements grouped together to allow the element operations to be performed in parallel. The FDV parameters play many roles in the numerical scheme. One of these roles is to control formations of shock wave discontinuities in high speeds and pressure oscillations in low speeds. To demonstrate these abilities, various example problems are shown, including supersonic flows over a flat plate and a compression corner, and flows involving triple shock waves generated on fin geometries for high speed compressible flows. Furthermore, analysis of low speed incompressible flows is presented in the form of flow in a lid-driven cavity at various Reynolds numbers. Another role of the FDV parameters is their use as error indicators for a solution-adaptive mesh. The finite element grid is refined as dictated by the magnitude of the FDV parameters. Examples of adaptive grids generated using the FDV parameters as error indicators are presented for supersonic flow over flat plate/compression ramp combinations in both two and three dimensions. Grids refined using the FDV parameters as error indicators are comparable to ones refined using primitive variable error indicators, and require less computational time to generate the grids. The use of parallel processing in performing some element operations is shown to reduce the wall clock time approximately forty-five percent in going from one to eight processors. Finally, the algorithm's ability to solve a flowfield containing interactions and transitions between regions of incompressible and compressible, viscous and inviscid, and laminar and turbulent flow is demonstrated by modeling the flowfield generated by supersonic flow over a compression ramp located between two fins. The structure of the resulting systems of shock waves are analyzed and compared with planar laser scattering images obtained experimentally for similar flow structures.

Heard, Gary Wayne

125

Identification of the tri-Al tricitrate complex in Plantago almogravensis by hydrophilic interaction LC with parallel ICP-MS and electrospray Orbitrap MS/MS detection.  

PubMed

The identification of the ligands binding Al is essential to understand the mechanisms by which plants detoxify Al internally. However, studies concerning the speciation of Al have been frustrated by its complex chemistry. This work describes the identification of the tri-Al tricitrate (Al3cit3) complex in Plantago almogravensis, encompassing an integrated mass spectrometry approach based on hydrophilic interaction liquid chromatography (HILIC) and parallel detection by ICP-MS and ESI-MS/MS. This work also reports that both Al and Fe are bound by tricitrate, sometimes simultaneously, and the consequences of this finding are discussed. Of the complexes separated by size exclusion chromatography, Al3cit3 is the most stable occurring in P. almogravensis as it was the only one recovered after HILIC. This approach provided new information on the mechanism of Al detoxification in P. almogravensis, namely that Al is bound by the organic acid citrate and that the relative concentration of the detected complexes is affected by the organ type and internal Al concentration, and has potential for studying the speciation of Al in less tolerant plants. PMID:23877102

Grevenstuk, Tomás; Flis, Paulina; Ouerdane, Laurent; Lobinski, Ryszard; Romano, Anabela

2013-09-01

126

Parallel biocomputing  

Microsoft Academic Search

Background  With the advent of high throughput genomics and high-resolution imaging techniques, there is a growing necessity in biology\\u000a and medicine for parallel computing, and with the low cost of computing, it is now cost-effective for even small labs or individuals\\u000a to build their own personal computation cluster.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Here we briefly describe how to use commodity hardware to build a low-cost,

Kenneth S Kompass; Thomas J Hoffmann; John S Witte

2011-01-01

127

Prevision du Bruit Externe des Helicopteres: Les Methodes Numeriques Vues Par UN Industriel (Predicting Helicopter External Noise: Numerical Methods as Conceived by an Industrialist).  

National Technical Information Service (NTIS)

This paper investigates the methods used for rotor rotational noise, impulsive noise from blade/vortex interaction, high speed noise, rotor broadband noise, the various types of fenestron noise, and noise from the turboshaft engines. From the helicopter m...

F. Toulmay D. Falchero G. Arnaud

1995-01-01

128

Parallel Information Processing.  

ERIC Educational Resources Information Center

|Examines parallel computer architecture and the use of parallel processors for text. Topics discussed include parallel algorithms; performance evaluation; parallel information processing; parallel access methods for text; parallel and distributed information retrieval systems; parallel hardware for text; and network models for information…

Rasmussen, Edie M.

1992-01-01

129

Amyloid-like Fibrils from a Domain-swapping Protein Feature a Parallel, in-Register Conformation without Native-like Interactions*  

PubMed Central

The formation of amyloid-like fibrils is characteristic of various diseases, but the underlying mechanism and the factors that determine whether, when, and how proteins form amyloid, remain uncertain. Certain mechanisms have been proposed based on the three-dimensional or runaway domain swapping, inspired by the fact that some proteins show an apparent correlation between the ability to form domain-swapped dimers and a tendency to form fibrillar aggregates. Intramolecular ?-sheet contacts present in the monomeric state could constitute intermolecular ?-sheets in the dimeric and fibrillar states. One example is an amyloid-forming mutant of the immunoglobulin binding domain B1 of streptococcal protein G, which in its native conformation consists of a four-stranded ?-sheet and one ?-helix. Under native conditions this mutant adopts a domain-swapped dimer, and it also forms amyloid-like fibrils, seemingly in correlation to its domain-swapping ability. We employ magic angle spinning solid-state NMR and other methods to examine key structural features of these fibrils. Our results reveal a highly rigid fibril structure that lacks mobile domains and indicate a parallel in-register ?-sheet structure and a general loss of native conformation within the mature fibrils. This observation contrasts with predictions that native structure, and in particular intermolecular ?-strand interactions seen in the dimeric state, may be preserved in “domain-swapping” fibrils. We discuss these observations in light of recent work on related amyloid-forming proteins that have been argued to follow similar mechanisms and how this may have implications for the role of domain-swapping propensities for amyloid formation.

Li, Jun; Hoop, Cody L.; Kodali, Ravindra; Sivanandam, V. N.; van der Wel, Patrick C. A.

2011-01-01

130

Scattering points in parallel coordinates.  

PubMed

In this paper, we present a novel parallel coordinates design integrated with points (Scattering Points in Parallel Coordinates, SPPC), by taking advantage of both parallel coordinates and scatterplots. Different from most multiple views visualization frameworks involving parallel coordinates where each visualization type occupies an individual window, we convert two selected neighboring coordinate axes into a scatterplot directly. Multidimensional scaling is adopted to allow converting multiple axes into a single subplot. The transition between two visual types is designed in a seamless way. In our work, a series of interaction tools has been developed. Uniform brushing functionality is implemented to allow the user to perform data selection on both points and parallel coordinate polylines without explicitly switching tools. A GPU accelerated Dimensional Incremental Multidimensional Scaling (DIMDS) has been developed to significantly improve the system performance. Our case study shows that our scheme is more efficient than traditional multi-view methods in performing visual analysis tasks. PMID:19834165

Yuan, Xiaoru; Guo, Peihong; Xiao, He; Zhou, Hong; Qu, Huamin

131

Detached-eddy simulation of flow non-linearity of fluid-structural interactions using high order schemes and parallel computation  

NASA Astrophysics Data System (ADS)

The objective of this research is to develop an efficient and accurate methodology to resolve flow non-linearity of fluid-structural interaction. To achieve this purpose, a numerical strategy to apply the detached-eddy simulation (DES) with a fully coupled fluid-structural interaction model is established for the first time. The following novel numerical algorithms are also created: a general sub-domain boundary mapping procedure for parallel computation to reduce wall clock simulation time, an efficient and low diffusion E-CUSP (LDE) scheme used as a Riemann solver to resolve discontinuities with minimal numerical dissipation, and an implicit high order accuracy weighted essentially non-oscillatory (WENO) scheme to capture shock waves. The Detached-Eddy Simulation is based on the model proposed by Spalart in 1997. Near solid walls within wall boundary layers, the Reynolds averaged Navier-Stokes (RANS) equations are solved. Outside of the wall boundary layers, the 3D filtered compressible Navier-Stokes equations are solved based on large eddy simulation(LES). The Spalart-Allmaras one equation turbulence model is solved to provide the Reynolds stresses in the RANS region and the subgrid scale stresses in the LES region. An improved 5th order finite differencing weighted essentially non-oscillatory (WENO) scheme with an optimized epsilon value is employed for the inviscid fluxes. The new LDE scheme used with the WENO scheme is able to capture crisp shock profiles and exact contact surfaces. A set of fully conservative 4th order finite central differencing schemes are used for the viscous terms. The 3D Navier-Stokes equations are discretized based on a conservative finite differencing scheme. The unfactored line Gauss-Seidel relaxation iteration is employed for time marching. A general sub-domain boundary mapping procedure is developed for arbitrary topology multi-block structured grids with grid points matched on sub-domain boundaries. Extensive numerical experiments are conducted to test the performance of the numerical algorithms. The RANS simulation with the Spalart-Allmaras one equation turbulence model is the foundation for DES and is hence validated with other transonic flows. The predicted results agree very well with the experiments. The RANS code is then further used to study the slot size effect of a co-flow jet (CFJ) airfoil. The DES solver with fully coupled fluid-structural interaction methodology is validated with vortex induced vibration of a cylinder and a transonic forced pitching airfoil. For the cylinder, the laminar Navier-Stokes equations are solved due to the low Reynolds number. The 3D effects are observed in both stationary and oscillating cylinder simulation because of the flow separations behind the cylinder. For the transonic forced pitching airfoil DES computation, there is no flow separation in the flow field. The DES results agree well with the RANS results. These two cases indicate that the DES is more effective on predicting flow separation. The DES code is used to simulate the limited cycle oscillation of NLR7301 airfoil. For the cases computed in this research, the predicted LCO frequency, amplitudes, averaged lift and moment, all agree excellently with the experiment. The solutions appear to have bifurcation and are dependent on the initial perturbation. The developed methodology is able to capture the LCO with very small amplitudes measured in the experiment. This is attributed to the high order low diffusion schemes, fully coupled FSI model, and the turbulence model used. This research appears to be the first time that a numerical simulation of LCO matches the experiment. The DES code is also used to simulate the CFJ airfoil jet mixing at high angle of attack. In conclusion, the numerical strategy of the high order DES with fully coupled FSI model and parallel computing developed in this research is demonstrated to have high accuracy, robustness, and efficiency. Future work to further maturate the methodology is suggested. (Abstract shortened by UMI.)

Wang, Baoyuan

132

Parallel incremental compilation. Doctoral thesis  

SciTech Connect

The time it takes to compile a large program has been a bottleneck in the software development process. When an interactive programming environment with an incremental compiler is used, compilation speed becomes even more important, but existing incremental compilers are very slow for some types of program changes. We describe a set of techniques that enable incremental compilation to exploit fine-grained concurrency in a shared-memory multi-processor and achieve asymptotic improvement over sequential algorithms. Because parallel non-incremental compilation is a special case of parallel incremental compilation, the design of a parallel compiler is a corollary of our result. Instead of running the individual phases concurrently, our design specifies compiler phases that are mutually sequential. However, each phase is designed to exploit fine-grained parallelism. By allowing each phase to present its output as a complete structure rather than as a stream of data, we can apply techniques such as parallel prefix and parallel divide-and-conquer, and we can construct applicative data structures to achieve sublinear execution time. Parallel algorithms for each phase of a compiler are presented to demonstrate that a complete incremental compiler can achieve execution time that is asymptotically less than sequential algorithms.

Gafter, N.M.

1990-06-01

133

Totally Parallel Multilevel Algorithms.  

National Technical Information Service (NTIS)

Four totally parallel algorithms for the solution of a sparse linear system have common characteristics which become quite apparent when they are implemented on a highly parallel hypercube such as the CM2. These four algorithms are Parallel Superconvergen...

P. O. Frederickson

1988-01-01

134

Special parallel processing workshop  

SciTech Connect

This report contains viewgraphs from the Special Parallel Processing Workshop. These viewgraphs deal with topics such as parallel processing performance, message passing, queue structure, and other basic concept detailing with parallel processing.

NONE

1994-12-01

135

An Automatic and Symbolic Parallelization System for Distributed Memory Parallel Computers  

Microsoft Academic Search

This paper describes ASPAR (Automalx and Symbolic PARallelization) which consisv: of a source-to-source parallelizer and a set of interactive graphic tools. While the issues of data 3ependency have already been explored and used in many parallel computer systems such as vex or and shared memory machines, distributed memory parallel computers require, in addition, explic*it data decomposition. New symbolic analysis and

K. Iitudome; G. C. Fox; A. Kolawa; J. W. Flower

1990-01-01

136

Why Structured Parallel Programming Matters  

Microsoft Academic Search

Abstract. Simple parallel programming frameworks such as Pthreads, or the six function core of MPI, are universal in the sense that they support the expression of arbitrarily complex patterns of computation and interaction between concurrent activities. Pragmatically, their de-scriptive power is constrained only by the programmer's creativity and capacity for attention to detail. Meanwhile, as our understanding of the structure

Murray Cole

2004-01-01

137

Equalizer: a scalable parallel rendering framework  

Microsoft Academic Search

Continuing improvements in CPU and GPU performances as well as increasing multi-core processor and cluster-based parallelism demand for flexible and scalable parallel rendering solutions that can exploit multipipe hardware accelerated graphics. In fact, to achieve interactive visualization, scalable rendering systems are essential to cope with the rapid growth of data sets. However, parallel rendering systems are non-trivial to develop and

Stefan Eilemann; Maxim Makhinya; Renato Pajarola

2008-01-01

138

Equalizer: A Scalable Parallel Rendering Framework  

Microsoft Academic Search

Continuing improvements in CPU and GPU performances as well as increasing multi-core processor and cluster-based parallelism demand for flexible and scalable parallel rendering solutions that can exploit multipipe hardware accelerated graphics. In fact, to achieve interactive visualization, scalable rendering systems are essential to cope with the rapid growth of data sets. However, parallel rendering systems are non-trivial to develop and

Stefan Eilemann; Maxim Makhinya; Renato Pajarola

2009-01-01

139

Teaching parallel programming early  

Microsoft Academic Search

In this position paper, we point out the importance of teaching a basic understanding of parallel computations and parallel programming early in computer science education, in order to give students the necessary expertise to cope with future computer architectures that will exhibit an explicitly parallel programming model. We elaborate on a programming model, namely shared- memory bulk-synchronous parallel programming with

Christoph W. Kessler

2006-01-01

140

Virtual Reality and Parallel Systems Performance Analysis  

Microsoft Academic Search

Recording and analyzing the dynamics of application program, system software, and hardware interactions are the keys to understanding and tuning the performance of massively parallel systems. Because massively parallel systems contain hundreds or thousands of processors, each potentially with many dynamic performance metrics, the performance data occupy a sparsely populated, high-dimensional space. These dynamic performance metrics for each processor define

Daniel A. Reed; Keith A. Shields; Will H. Scullin; Luis F. Tawera; Christopher L. Elford

1995-01-01

141

Parallel Computing in Optimization.  

National Technical Information Service (NTIS)

One of the major developments in computing in recent years has been the introduction of a variety of parallel computers, and the development of algorithms that effectively utilize their capabilities. Very little of this parallel algorithm development, how...

R. B. Schnabel

1984-01-01

142

Parallel Particle Swarm Optimizer.  

National Technical Information Service (NTIS)

Time requirements for the solving of complex large-scale engineering problems can be substantially reduced by using parallel computation. Motivated by a computationally demanding biomechanical system identification problem, we introduce a parallel impleme...

J. F. Schutte B. Fregly R. T. Haftka A. D. George

2003-01-01

143

Parallel flow diffusion battery  

DOEpatents

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, Hsu-Chi (Albuquerque, NM); Cheng, Yung-Sung (Albuquerque, NM)

1984-08-07

144

Parallel flow diffusion battery  

DOEpatents

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, H.C.; Cheng, Y.S.

1984-01-01

145

Model of Parallel Performance.  

National Technical Information Service (NTIS)

This report introduces a general model of parallel performance. With the goal of developing conceptual and empirical methods for characterizing and understanding parallel algorithms, new definitions of speedup and efficiency have been formulated. These de...

E. A. Carmona M. D. Rice

1989-01-01

146

Pthreads for Dynamic Parallelism  

Microsoft Academic Search

Expressing a large number of lightweight, parallel threads in a shared address space significantly eases the task of writing a parallel program. Threads can be dynamically created to execute individual parallel tasks; the implementation schedules these threads onto the processors and effectively balances the load. However, unless the threads scheduler is designed carefully, such a p arallel program may suffer

Girija J. Narlikar; Guy E. Blelloch

1998-01-01

147

Decomposing the Potentially Parallel  

NSDL National Science Digital Library

This course provides an introduction to the issues involved in decomposing problems onto parallel machines, and to the types of architectures and programming styles commonly found in parallel computers. The list of topics discussed includes types of decomposition, task farming, regular domain decomposition, unbalanced grids, and parallel molecular dynamics.

Elspeth Minty, Robert Davey, Alan Simpson, David Henty

148

Verbal and Visual Parallelism  

ERIC Educational Resources Information Center

This study investigates the practice of presenting multiple supporting examples in parallel form. The elements of parallelism and its use in argument were first illustrated by Aristotle. Although real texts may depart from the ideal form for presenting multiple examples, rhetorical theory offers a rationale for minimal, parallel presentation. The…

Fahnestock, Jeanne

2003-01-01

149

Parallel I/O Systems  

NSDL National Science Digital Library

* Redundant disk array architectures,* Fault tolerance issues in parallel I/O systems,* Caching and prefetching,* Parallel file systems,* Parallel I/O systems, * Parallel I/O programming paradigms, * Parallel I/O applications and environments, * Parallel programming with parallel I/O

Apon, Amy

150

Introduction to parallel computing  

SciTech Connect

Today's supercomputers and parallel computers provide an unprecedented amount of computational power in one machine. A basic understanding of the parallel computing techniques that assist in the capture and utilization of that computational power is essential to appreciate the capabilities and the limitations of parallel supercomputers. In addition, an understanding of technical vocabulary is critical in order to converse about parallel computers. The relevant techniques, vocabulary, currently available hardware architectures, and programming languages which provide the basic concepts of parallel computing are introduced in this document. This document updates the document entitled Introduction to Parallel Supercomputing, M88-42, October 1988. It includes a new section on languages for parallel computers, updates the hardware related sections, and includes current references.

Lafferty, E.L.; Michaud, M.C.; Prelle, M.J.; Goethert, J.B.

1992-05-01

151

Prediction of in vivo drug-drug interactions from in vitro data: impact of incorporating parallel pathways of drug elimination and inhibitor absorption rate constant  

PubMed Central

Aims Success of the quantitative prediction of drug–drug interactions via inhibition of CYP-mediated metabolism from the inhibitor concentration at the enzyme active site ([I]) and the in vitro inhibition constant (Ki) is variable. The aim of this study was to examine the impact of the fraction of victim drug metabolized by a particular CYP (fmCYP) and the inhibitor absorption rate constant (ka) on prediction accuracy. Methods Drug–drug interaction studies involving inhibition of CYP2C9, CYP2D6 and CYP3A4 (n = 115) were investigated. Data on fmCYP for the probe substrates of each enzyme and ka values for the inhibitors were incorporated into in vivo predictions, alone or in combination, using either the maximum hepatic input or the average systemic plasma concentration as a surrogate for [I]. The success of prediction (AUC ratio predicted within twofold of in vivo value) was compared using nominal values of fmCYP = 1 and ka = 0.1 min?1. Results The incorporation of fmCYP values into in vivo predictions using the hepatic input plasma concentration resulted in 84% of studies within twofold of in vivo value. The effect of ka values alone significantly reduced the number of over-predictions for CYP2D6 and CYP3A4; however, less precision was observed compared with the fmCYP. The incorporation of both fmCYP and ka values resulted in 81% of studies within twofold of in vivo value. Conclusions The incorporation of substrate and inhibitor-related information, namely fmCYP and ka, markedly improved prediction of 115 interaction studies with CYP2C9, CYP2D6 and CYP3A4 in comparison with [I]/Ki ratio alone.

Brown, Hayley S; Ito, Kiyomi; Galetin, Aleksandra; Houston, J Brian

2005-01-01

152

Parallel execution and scriptability in micromagnetic simulations  

NASA Astrophysics Data System (ADS)

We demonstrate the feasibility of an ``encapsulated parallelism'' approach toward micromagnetic simulations that combines offering a high degree of flexibility to the user with the efficient utilization of parallel computing resources. While parallelization is obviously desirable to address the high numerical effort required for realistic micromagnetic simulations through utilizing now widely available multiprocessor systems (including desktop multicore CPUs and computing clusters), conventional approaches toward parallelization impose strong restrictions on the structure of programs: numerical operations have to be executed across all processors in a synchronized fashion. This means that from the user's perspective, either the structure of the entire simulation is rigidly defined from the beginning and cannot be adjusted easily, or making modifications to the computation sequence requires advanced knowledge in parallel programming. We explain how this dilemma is resolved in the NMAG simulation package in such a way that the user can utilize without any additional effort on his side both the computational power of multiple CPUs and the flexibility to tailor execution sequences for specific problems: simulation scripts written for single-processor machines can just as well be executed on parallel machines and behave in precisely the same way, up to increased speed. We provide a simple instructive magnetic resonance simulation example that demonstrates utilizing both custom execution sequences and parallelism at the same time. Furthermore, we show that this strategy of encapsulating parallelism even allows to benefit from speed gains through parallel execution in simulations controlled by interactive commands given at a command line interface.

Fischbacher, Thomas; Franchin, Matteo; Bordignon, Giuliano; Knittel, Andreas; Fangohr, Hans

2009-04-01

153

Parallel digital forensics infrastructure.  

SciTech Connect

This report documents the architecture and implementation of a Parallel Digital Forensics infrastructure. This infrastructure is necessary for supporting the design, implementation, and testing of new classes of parallel digital forensics tools. Digital Forensics has become extremely difficult with data sets of one terabyte and larger. The only way to overcome the processing time of these large sets is to identify and develop new parallel algorithms for performing the analysis. To support algorithm research, a flexible base infrastructure is required. A candidate architecture for this base infrastructure was designed, instantiated, and tested by this project, in collaboration with New Mexico Tech. Previous infrastructures were not designed and built specifically for the development and testing of parallel algorithms. With the size of forensics data sets only expected to increase significantly, this type of infrastructure support is necessary for continued research in parallel digital forensics. This report documents the implementation of the parallel digital forensics (PDF) infrastructure architecture and implementation.

Liebrock, Lorie M. (New Mexico Tech, Socorro, NM); Duggan, David Patrick

2009-10-01

154

Interaction  

NSDL National Science Digital Library

Set values for the initial position, velocity, and mass of the two particles, and click on the button "Initialize Animation" to play the animation using your specified values. Note, if m or v are too large, the particles may actually pass through one another which will seem a little strange. Note: the interaction between the particles is a "non-contact" interaction, much like the electrostatic force on two charges. Mathematically, it is actually a Hooke's law interaction.

Christian, Wolfgang; Belloni, Mario

2008-02-19

155

Advanced parallel processing with supercomputer architectures  

SciTech Connect

This paper investigates advanced parallel processing techniques and innovative hardware/software architectures that can be applied to boost the performance of supercomputers. Critical issues on architectural choices, parallel languages, compiling techniques, resource management, concurrency control, programming environment, parallel algorithms, and performance enhancement methods are examined and the best answers are presented. The authors cover advanced processing techniques suitable for supercomputers, high-end mainframes, minisupers, and array processors. The coverage emphasizes vectorization, multitasking, multiprocessing, and distributed computing. In order to achieve these operation modes, parallel languages, smart compilers, synchronization mechanisms, load balancing methods, mapping parallel algorithms, operating system functions, application library, and multidiscipline interactions are investigated to ensure high performance. At the end, they assess the potentials of optical and neural technologies for developing future supercomputers.

Hwang, K.

1987-10-01

156

Parallelizing Conditional Recurrences  

Microsoft Academic Search

Recursive functions which use conditional constructs are common in functional (and imperative) programs. We present a collection of techniques for handling such functions for a parallel synthesis method. These techniques can help us enlarge the class of sequential functions which could be systematically transformed to parallel equivalent.

Wei-ngan Chin; John Darlington; Yike Guo

1996-01-01

157

The Nas Parallel Benchmarks  

Microsoft Academic Search

A new set of benchmarks has been developed for the performance evaluation of highly parallel supercomputers. These benchmarks consist of five parallel kernels and three simulated application benchmarks. Together theymimic the computation and data movement characteristics of large scale computational fluid dynamics (CFD) applications.The principal distinguishing feature of these benchmarks is their penciland paper specification---all details of these benchmarks are

D. Bailey; E. Barszcz; J. Barton; D. Browning; R. Carter; L. Dagum

1994-01-01

158

Parallel discrete event simulation  

Microsoft Academic Search

Parallel discrete event simulation (PDES), sometimes called distributed simulation, refers to the execution of a single discrete event simulation program on a parallel computer. PDES has attracted a considerable amount of interest in recent years. From a pragmatic standpoint, this interest arises from the fact that large simulations in engineering, computer science, economics, and military applications, to mention a few,

Richard M. Fujimoto

1990-01-01

159

Performance of Parallel Algorithms.  

National Technical Information Service (NTIS)

A notation to express the performance of a parallel computation is developed. A formalization of the performance measures for a parallel algorithm in which Amdahl's law is a special case is given. The general formulation of Amdahl's law is summarized. The...

J. J. Lukkien

1989-01-01

160

Massively parallel mathematical sieves  

SciTech Connect

The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.

Montry, G.R.

1989-01-01

161

Parallel computing works  

SciTech Connect

An account of the Caltech Concurrent Computation Program (C{sup 3}P), a five year project that focused on answering the question: Can parallel computers be used to do large-scale scientific computations '' As the title indicates, the question is answered in the affirmative, by implementing numerous scientific applications on real parallel computers and doing computations that produced new scientific results. In the process of doing so, C{sup 3}P helped design and build several new computers, designed and implemented basic system software, developed algorithms for frequently used mathematical computations on massively parallel machines, devised performance models and measured the performance of many computers, and created a high performance computing facility based exclusively on parallel computers. While the initial focus of C{sup 3}P was the hypercube architecture developed by C. Seitz, many of the methods developed and lessons learned have been applied successfully on other massively parallel architectures.

Not Available

1991-10-23

162

Parallel Adaptive Mesh Refinement  

SciTech Connect

As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution is smooth. Examples include chemically-reacting flows with radiative heat transfer, high Reynolds number flows interacting with solid objects, and combustion problems where the flame front is essentially a two-dimensional sheet occupying a small part of a three-dimensional domain. Modeling such problems numerically requires approximating the governing partial differential equations on a discrete domain, or grid. Grid spacing is an important factor in determining the accuracy and cost of a computation. A fine grid may be needed to resolve key local features while a much coarser grid may suffice elsewhere. Employing a fine grid everywhere may be inefficient at best and, at worst, may make an adequately resolved simulation impractical. Moreover, the location and resolution of fine grid required for an accurate solution is a dynamic property of a problem's transient features and may not be known a priori. Adaptive mesh refinement (AMR) is a technique that can be used with both structured and unstructured meshes to adjust local grid spacing dynamically to capture solution features with an appropriate degree of resolution. Thus, computational resources can be focused where and when they are needed most to efficiently achieve an accurate solution without incurring the cost of a globally-fine grid. Figure 1.1 shows two example computations using AMR; on the left is a structured mesh calculation of a impulsively-sheared contact surface and on the right is the fuselage and volume discretization of an RAH-66 Comanche helicopter [35]. Note the ability of both meshing methods to resolve simulation details by varying the local grid spacing.

Diachin, L; Hornung, R; Plassmann, P; WIssink, A

2005-03-04

163

Compositional C++: Compositional Parallel Programming  

Microsoft Academic Search

A compositional parallel program is a program constructed by composing component programs in parallel, where the composed program inherits properties of its components. In this paper, we describe a small extension of C++ called Compositional C++ or CC++ which is an object-oriented notation that supports compositional parallel programming. CC++ integrates different paradigms of parallel programming: data-parallel, task-parallel and object-parallel paradigms;

K. Mani Chandy; Carl Kesselman

1992-01-01

164

Aerodynamic, aeroacoustic, and aeroelastic investigations of airfoil-vortex interaction using large-eddy simulation  

NASA Astrophysics Data System (ADS)

In helicopters, vortices (generated at the tip of the rotor blades) interact with the next advancing blades during certain flight and manoeuvring conditions, generating undesirable levels of acoustic noise and vibration. These Blade-Vortex Interactions (BVIs), which may cause the most disturbing acoustic noise, normally occur in descent or high-speed forward flight. Acoustic noise characterization (and potential reduction) is one the areas generating intensive research interest to the rotorcraft industry. Since experimental investigations of BVI are extremely costly, some insights into the BVI or AVI (2-D Airfoil-Vortex Interaction) can be gained using Computational Fluid Dynamics (CFD) numerical simulations. Numerical simulation of BVI or AVI has been of interest to CFD for many years. There are still difficulties concerning an accurate numerical prediction of BVI. One of the main issues is the inherent dissipation of CFD turbulence models, which severely affects the preservation of the vortex characteristics. Moreover this is not an issue only for aerodynamic and aeroacoustic analysis but also for aeroelastic investigations as well, especially when the strong (two-way) aeroelastic coupling is of interest. The present investigation concentrates mainly on AVI simulations. The simulations are performed for Mach number, Ma = 0.3, resulting in a Reynolds number, Re = 1.3 x 106, which is based on the chord, c, of the airfoil (NACA0012). Extensive literature search has indicated that the present work represents the first comprehensive investigation of AVI using the LES numerical approach, in the rotorcraft research community. The major factor affecting the aerodynamic coefficients and aeroacoustic field as a result of airfoil-vortex interaction is observed to be the unsteady pressure generated at the location of the interaction. The present numerical results show that the aerodynamic coefficients (lift, moment, and drag) and aeroacoustic field are strongly dependent on the airfoil-vortex vertical miss-distance, airfoil angle of attack, vortex characteristics, and aeroelastic response of airfoil to airfoil-vortex interaction. A decay of airfoil-vortex interactions with the increase of vertical miss-distance and angle of attack was observed. Also, a decay of airfoil-vortex interactions is observed for the case of a flexible structure when compared with the case of a rigid structure. The decay of vortex core size produces a decrease in the aerodynamic coefficients.

Ilie, Marcel

165

Parallel visual computation  

NASA Astrophysics Data System (ADS)

The functional abilities and parallel architecture of the human visual system are a rich source of ideas about visual processing. Any visual task that we can perform quickly and effortlessly is likely to have a computational solution using a parallel algorithm. Recently, several such parallel algorithms have been found that exploit information implicit in an image to compute intrinsic properties of surfaces, such as surface orientation, reflectance and depth. These algorithms require a computational architecture that has similarities to that of visual cortex in primates.

Ballard, Dana H.; Hinton, Geoffrey E.; Sejnowski, Terrence J.

1983-11-01

166

Parallel processing in Ada  

SciTech Connect

Ada was designed from the beginning with parallel processing applications in mind. Its tasking mechanism is a coherent response to the language issues involved in parallel processing, and carefully balances the often conflicting goals of high-level language features on the one hand and efficient implementation on the other. The purpose of this discussion is to place the design of Ada's parallel processing in its proper historical and technical context. In the process we will show how Ada itself has clarified some issues and thus established trends in language design.

Mundie, D.A.; Fisher, D.A.

1986-08-01

167

Radiative Heat Transfer in Combustion Applications: Parallel Efficiencies of Two Gas Models, Turbulent Radiation Interactions in Particulate Laden Flows, and Coarse Mesh Finite Difference Acceleration for Improved Temporal Accuracy  

NASA Astrophysics Data System (ADS)

We investigate several aspects of the numerical solution of the radiative transfer equation in the context of coal combustion: the parallel efficiency of two commonly-used opacity models, the sensitivity of turbulent radiation interaction (TRI) effects to the presence of coal particulate, and an improvement of the order of temporal convergence using the coarse mesh finite difference (CMFD) method. There are four opacity models commonly employed to evaluate the radiative transfer equation in combustion applications; line-by-line (LBL), multigroup, band, and global. Most of these models have been rigorously evaluated for serial computations of a spectrum of problem types [1]. Studies of these models for parallel computations [2] are limited. We assessed the performance of the Spectral-Line-Based weighted sum of gray gasses (SLW) model, a global method related to K-distribution methods [1], and the LBL model. The LBL model directly interpolates opacity information from large data tables. The LBL model outperforms the SLW model in almost all cases, as suggested by Wang et al. [3]. The SLW model, however, shows superior parallel scaling performance and a decreased sensitivity to load imbalancing, suggesting that for some problems, global methods such as the SLW model, could outperform the LBL model. Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modified the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [4] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect are amplified by increased particulate loading. Monte Carlo radiative heat transfer simulations of time-dependent combustion processes generally involve an explicit evaluation of emission source because of the expense of the transport solver. Recently, Park et al. [5] have applied quasi-diffusion with Monte Carlo in high energy density radiative transfer applications. We employ a Crank-Nicholson temporal integration scheme in conjunction with the coarse mesh finite difference (CMFD) method, in an effort to improve the temporal accuracy of the Monte Carlo solver. Our results show that this CMFD-CN method is an improvement over Monte Carlo with CMFD time-differenced via Backward Euler, and Implicit Monte Carlo [6] (IMC). The increase in accuracy involves very little increase in computational cost, and the figure of merit for the CMFD-CN scheme is greater than IMC.

Cleveland, Mathew A.

168

A dual-site simultaneous binding mode in the interaction between parallel-stranded G-quadruplex [d(TGGGGT)]4 and cyanine dye 2,2?-diethyl-9-methyl-selenacarbocyanine bromide  

PubMed Central

G-quadruplexes have attracted growing attention as a potential cancer-associated target for both treatment and detection in recent years. For detection purpose, high specificity is one of the most important factors to be considered in G-quadruplex probe design. It is well known that end stacking and groove binding are two dominated quadruplex-ligand binding modes, and currently most reported G-quadruplex probes are designed based on the former, which has been proven to show good selectivity between quadruplexes and non-quadruplexes. Because groove of G-quadruplex also has some unique chemical properties, it could be inferred that probes that can interact with both the groove and G-tetrad site of certain G-quadruplexes simultaneously might possess higher specificity in aspects of discriminating different quadruplexes. In this article, we report a cyanine dye as a potential novel probe scaffold that could occupy both the 5?-end external G-tetrad and the corresponding groove of the G-quadruplex simultaneously. By using various spectrum and nuclear magnetic resonance techniques, we give a detailed binding characterization for this dual-site simultaneous binding mode. A preliminary result suggests that this mode might provide highly specific recognition to a parallel-stranded G-quadruplex. These findings and the structural elucidation might give some clues in aspects of developing highly specific G-quadruplex probes.

Gai, Wei; Yang, Qianfan; Xiang, Junfeng; Jiang, Wei; Li, Qian; Sun, Hongxia; Guan, Aijiao; Shang, Qian; Zhang, Hong; Tang, Yalin

2013-01-01

169

Parallel Program Archetypes.  

National Technical Information Service (NTIS)

The research supported by this grant falls into three categories: distributed systems, parallel programming, and theory of concurrent compositions. We developed a distributed systems framework, called Infospheres, that allows any Java programmer to create...

M. Chandy

1997-01-01

170

High Performance Parallel Computing.  

National Technical Information Service (NTIS)

The accomplishments of the research project 'High Performance Parallel Computing' for the year 1983 span algorithm formulation, paralle programming languages, basic software for the Texas Reconfigurable Array Computer and validation of design concpets for...

J. C. Browne G. J. Lipovski M. Malek

1985-01-01

171

Simplified Parallel Domain Traversal  

SciTech Connect

Many data-intensive scientific analysis techniques require global domain traversal, which over the years has been a bottleneck for efficient parallelization across distributed-memory architectures. Inspired by MapReduce and other simplified parallel programming approaches, we have designed DStep, a flexible system that greatly simplifies efficient parallelization of domain traversal techniques at scale. In order to deliver both simplicity to users as well as scalability on HPC platforms, we introduce a novel two-tiered communication architecture for managing and exploiting asynchronous communication loads. We also integrate our design with advanced parallel I/O techniques that operate directly on native simulation output. We demonstrate DStep by performing teleconnection analysis across ensemble runs of terascale atmospheric CO{sub 2} and climate data, and we show scalability results on up to 65,536 IBM BlueGene/P cores.

Erickson III, David J [ORNL

2011-01-01

172

Parallel Lisp Simulator,  

National Technical Information Service (NTIS)

CSIM is a simulator for parallel Lisp, based on a continuation passing interpreter. It models a shared-memory multiprocessor executing programs written in Common Lisp, extended with several primitives for creating and controlling processes. This paper des...

J. S. Weening

1988-01-01

173

Partitioning and parallel radiosity  

NASA Astrophysics Data System (ADS)

This paper proposes a theoretical framework, based on domain subdivision for parallel radiosity. Moreover, three various implementation approaches, taking advantage of partitioning algorithms and global shared memory architecture, are presented.

Merzouk, S.; Winkler, C.; Paul, J. C.

1996-03-01

174

Parallel lumigraph reconstruction  

Microsoft Academic Search

This paper presents three techniques for reconstructing Lumigraphs\\/Lightfields on commercial ccNUMA parallel distributed shared memory computers. The first method is a parallel extension of the software-based method proposed in the Lightfield paper. This expands the ray\\/two-plane intersection test along the film plane, which effectively becomes scan conversion. The second method extends this idea by using a shear\\/warp factorization that accelerates

Peter-Pike Sloan; Charles Hansen

1999-01-01

175

UCLA Parallel PIC Framework  

Microsoft Academic Search

The UCLA Parallel PIC Framework (UPIC) has been developed to provide trusted components for the rapid construction of new, parallel Particle-in-Cell (PIC) codes. The Framework uses object-based ideas in Fortran95, and is designed to provide support for various kinds of PIC codes on various kinds of hardware. The focus is on student programmers. The Framework supports multiple numerical methods, different

Viktor K. Decyk; Charles D. Norton

2004-01-01

176

Parallel DC notch filter  

NASA Astrophysics Data System (ADS)

In the process of image acquisition, the object of interest may not be evenly illuminated. So an image with shading irregularities would be produced. This type of image is very difficult to analyze. Consequently, a lot of research work concentrates on this problem. In order to remove the light illumination problem, one of the methods is to filter the image. The dc notch filter is one of the spatial domain filters used for reducing the effect of uneven light illumination on the image. Although the dc notch filter is a spatial domain filter, it is still rather time consuming to apply, especially when it is implemented on a microcomputer. To overcome the speed problem, a parallel dc notch filter is proposed. Based on the separability of the algorithm dc of notch filter, image parallelism (parallel image processing model) is used. To improve the performance of the microcomputer, an INMOS IMS B008 Module Mother Board with four IMS T800-17 is installed in the microcomputer. In fact, the dc notch filter is implemented on the transputer network. This parallel dc notch filter creates a great improvement in the computation time of the filter in comparison with the sequential one. Furthermore, the speed-up is used to analyze the performance of the parallel algorithm. As a result, parallel implementation of the dc notch filter on a transputer network gives a real-time performance of this filter.

Kwok, Kam-Cheung; Chan, Ming-Kam

1991-12-01

177

Component specification for parallel coupling infrastructure.  

SciTech Connect

Coupled systems comprise multiple mutually interacting subsystems, and are an increasingly common computational science application, most notably as multiscale and multiphysics models. Parallel computing, and in particular message-passing programming have spurred the development of these models, but also present a parallel coupling problem (PCP) in the form of intermodel data dependencies. The PCP complicates model coupling through requirements for the description, transfer, and transformation of the distributed data that models in a parallel coupled system exchange. Component-based software engineering has been proposed as one means of conquering software complexity in scientific applications, and given the compound nature of coupled models, it is a natural approach to addressing the parallel coupling problem. We define a software component specification for solving the parallel coupling problem. This design draws from the already successful Common Component Architecture (CCA). We abstract the parallel coupling problem's elements and map them onto a set of CCA components, defining a parallel coupling infrastructure toolkit. We discuss a reference implementation based on the Model Coupling Toolkit. We demonstrate how these components might be deployed to solve a relevant coupling problems in climate modeling.

Larson, J. W.; Norris, B.; Mathematics and Computer Science; Australian National Univ.

2007-01-01

178

Performance Bounds for Parallel Processors.  

National Technical Information Service (NTIS)

A general model of computation on a p-parallel processor is proposed, distinguishing clearly between the logical parallelism (p* processes) inherent in a computation, and the physical parallelism (p processor) available in the computer organization. This ...

R. B. L. Lee

1976-01-01

179

Parallel Molecular Dynamics Simulations of Biomolecular Systems  

Microsoft Academic Search

. We describe a general purpose parallel molecular dynamicscode, for simulations of arbitrary mixtures of flexible molecules in solution.The program allows us to simulate molecular systems describedby standard force fields like AMBER, GROMOS or CHARMM, containingterms for short-range interactions of the Lennard-Jones type,electrostatic interactions, covalent bonds, covalent angles and torsionalangles and a few other optional terms. The state-of-the-art molecular dynamicstechniques

Alexander Lyubartsev; Aatto Laaksonen

1998-01-01

180

Parallel processing architecture  

DOEpatents

The parallel processing architecture provides a processor array which accepts input data at a faster rate that its processing elements are able to execute. The main features of this architecture are its programmability, scalability, high bandwidth communication and low cost. It provides high connectivity while maintaining minimum distance between processor elements. This architecture enables construction of a parallel processing with high bandwidth communication in six directions among the neighboring processors. It provides for future growth into more complex and optimized algorithms, and facilitiates incorporation of hardware advances with little effect on currently installed systems. Parallel processing architecture is useful for data sharing in an array, pattern recognition within a data array and sustaining a data input rate which is higher than the pattern recognition algorithm execution time (particle identification in high energy physics).

Crosetto, D.B.

1992-01-01

181

Languages for Parallel Processors  

NASA Astrophysics Data System (ADS)

The effective programming of parallel computers is much more complex then the programming of conventional serial computers. There are two fundamental models of highly parallel computer architectures: single instruction stream-multiple data stream in which a single program control unit is used to control a set of slave processing elements and multiple instruction stream-multiple data stream in which a set of interconnected independent processors cooperate on a single task. The high level programming language constructs appropriate for each model are discussed.

Reeves, A. P.

182

Scalable Parallel Crash Simulations  

SciTech Connect

We are pleased to submit our efforts in parallelizing the PRONTO application suite for con- sideration in the SuParCup 99 competition. PRONTO is a finite element transient dynamics simulator which includes a smoothed particle hydrodynamics (SPH) capability; it is similar in scope to the well-known DYNA, PamCrash, and ABAQUS codes. Our efforts over the last few years have produced a fully parallel version of the entire PRONTO code which (1) runs fast and scalably on thousands of processors, (2) has performed the largest finite-element transient dynamics simulations we are aware of, and (3) includes several new parallel algorithmic ideas that have solved some difficult problems associated with contact detection and SPH scalability. We motivate this work, describe the novel algorithmic advances, give performance numbers for PRONTO running on Sandia's Intel Teraflop machine, and highlight two prototypical large-scale computations we have performed with the parallel code. We have successfully parallelized a large-scale production transient dynamics code with a novel algorithmic approach that utilizes multiple decompositions for different key segments of the computations. To be able to simulate a more than ten million element model in a few tenths of second per timestep is unprecedented for solid dynamics simulations, especially when full global contact searches are required. The key reason is our new algorithmic ideas for efficiently parallelizing the contact detection stage. To our knowledge scalability of this computation had never before been demonstrated on more than 64 processors. This has enabled parallel PRONTO to become the only solid dynamics code we are aware of that can run effectively on 1000s of processors. More importantly, our parallel performance compares very favorably to the original serial PRONTO code which is optimized for vector supercomputers. On the container crush problem, a Teraflop node is as fast as a single processor of the Cray Jedi. This means that on the Teraflop machine we can now run simulations with tens of millions of elements thousands of times faster than we could on the Jedi! This is enabling transient dynamics simulations of unprecedented scale and fidelity. Not only can previous applications be run with vastly improved resolution and speed, but qualitatively new and different analyses have been made possible.

Attaway, Stephen; Barragy, Ted; Brown, Kevin; Gardner, David; Gruda, Jeff; Heinstein, Martin; Hendrickson, Bruce; Metzinger, Kurt; Neilsen, Mike; Plimpton, Steve; Pott, John; Swegle, Jeff; Vaughan, Courtenay

1999-06-01

183

Massively parallel computing system  

DOEpatents

A parallel computing system and method having improved performance where a program is concurrently run on a plurality of nodes for reducing total processing time, each node having a processor, a memory, and a predetermined number of communication channels connected to the node and independently connected directly to other nodes. The present invention improves performance of the parallel computing system by providing a system which can provide efficient communication between the processors and between the system and input and output devices. A method is also disclosed which can locate defective nodes with the computing system.

Benner, R.E.; Gustafson, J.L.; Montry, G.R.

1989-03-01

184

Pillar: A Parallel Implementation Language  

Microsoft Academic Search

As parallelism in microprocessors becomes mainstream, new program- ming languages and environments are emerging to meet the challenges of parallel programming. To support research on these languages, we are developing a low- level language infrastructure called Pillar (derived from Parallel Implementation Language). Although Pillar programs are intended to be automatically generated from source programs in each parallel language, Pillar programs

Todd Anderson; Neal Glew; Peng Guo; Brian T. Lewis; Wei Liu; Zhanglin Liu; Leaf Petersen; Mohan Rajagopalan; James M. Stichnoth; Gansha Wu; Dan Zhang

2007-01-01

185

Initial results of a model rotor higher harmonic control (HHC) wind tunnel experiment on BVI impulsive noise reduction  

NASA Astrophysics Data System (ADS)

Initial acoustic results are presented from a higher harmonic control (HHC) wind tunnel pilot experiment on helicopter rotor blade-vortex interaction (BVI) impulsive noise reduction, making use of the DFVLR 40-percent-scaled BO-105 research rotor in the DNW 6m by 8m closed test section. Considerable noise reduction (of several decibels) has been measured for particular HHC control settings, however, at the cost of increased vibration levels and vice versa. The apparently adverse results for noise and vibration reduction by HHC are explained. At optimum pitch control settings for BVI noise reduction, rotor simulation results demonstrate that blade loading at the outer tip region is decreased, vortex strength and blade vortex miss-distance are increased, resulting altogether in reduced BVI noise generation. At optimum pitch control settings for vibration reduction adverse effects on blade loading, vortex strength and blade vortex miss-distance are found.

Splettstoesser, W. R.; Lehmann, G.; van der Wall, B.

1989-09-01

186

Parallel Computational Geometry  

Microsoft Academic Search

We present efficient parallel algorithms for several basic problems in computational geometry: convex hulls, Voronoi diagrams,\\u000a detecting line segment intersections, triangulating simple polygons, minimizing a circumscribing triangle, and recursive data-structures\\u000a for three-dimensional queries.

Alok Aggarwal; Bernard Chazelle; Leonidas J. Guibas; Colm Ó'dúnlaing; Chee-keng Yap

1988-01-01

187

Parallel Spectral Numerical Methods  

NSDL National Science Digital Library

This module teaches the principals of Fourier spectral methods, their utility in solving partial differential equation and how to implement them in code. Performance considerations for several Fourier spectral implementations are discussed and methods for effective scaling on parallel computers are explained.

Chen, Gong; Cloutier, Brandon; Li, Ning; Muite, Benson; Rigge, Paul

188

Parallel fast gauss transform  

SciTech Connect

We present fast adaptive parallel algorithms to compute the sum of N Gaussians at N points. Direct sequential computation of this sum would take O(N{sup 2}) time. The parallel time complexity estimates for our algorithms are O(N/n{sub p}) for uniform point distributions and O( (N/n{sub p}) log (N/n{sub p}) + n{sub p}log n{sub p}) for non-uniform distributions using n{sub p} CPUs. We incorporate a plane-wave representation of the Gaussian kernel which permits 'diagonal translation'. We use parallel octrees and a new scheme for translating the plane-waves to efficiently handle non-uniform distributions. Computing the transform to six-digit accuracy at 120 billion points took approximately 140 seconds using 4096 cores on the Jaguar supercomputer. Our implementation is 'kernel-independent' and can handle other 'Gaussian-type' kernels even when explicit analytic expression for the kernel is not known. These algorithms form a new class of core computational machinery for solving parabolic PDEs on massively parallel architectures.

Sampath, Rahul S [ORNL; Sundar, Hari [Siemens Corporate Research; Veerapaneni, Shravan [New York University

2010-01-01

189

Pringle Parallel Computer.  

National Technical Information Service (NTIS)

The Pringle is a 64 processor MIMD computer with a 64 M (8 bit) instructions per second execution rate. The Pringle runs programs written for the Configurable, Highly Parallel (CHiP) Computer. That is, the Pringle executes the 64 separate instruction stre...

A. A. Kapauau J. T. Field D. B. Gannon L. Snyder

1984-01-01

190

Parallel Adaptive Mesh Refinement  

Microsoft Academic Search

As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution

L Diachin; R Hornung; P Plassmann; A WIssink

2005-01-01

191

Simple Fast Parallel Hashing  

Microsoft Academic Search

A hash table is a representation of a set in a linear size data structure that supports constant-time membership queries. We show how to construct a hash table for any given set of n keys in O(lg lg n) parallel time with high probability, using n processors on a weak version of a

Joseph Gil; Yossi Matias

1994-01-01

192

Parallelism and Functionalism  

Microsoft Academic Search

It has recently been argued by Paul Thagard (1986) that parallel computational models of cognition demonstrate the falsity of the popular theory of mind known as funct\\/onal\\/sm. It is my contention that his argument is seriously mistaken and rests on a misunderstanding of the functionalist position. While my primary aim is to defend functionalism from Thagard's attack, in the process

William M. Ramsey

1989-01-01

193

Optimizing parallel reduction operations  

SciTech Connect

A parallel program consists of sets of concurrent and sequential tasks. Often, a reduction (such as array sum) sequentially combines values produced by a parallel computation. Because reductions occur so frequently in otherwise parallel programs, they are good candidates for optimization. Since reductions may introduce dependencies, most languages separate computation and reduction. The Sisal functional language is unique in that reduction is a natural consequence of loop expressions; the parallelism is implicit in the language. Unfortunately, the original language supports only seven reduction operations. To generalize these expressions, the Sisal 90 definition adds user-defined reductions at the language level. Applicable optimizations depend upon the mathematical properties of the reduction. Compilation and execution speed, synchronization overhead, memory use and maximum size influence the final implementation. This paper (1) Defines reduction syntax and compares with traditional concurrent methods; (2) Defines classes of reduction operations; (3) Develops analysis of classes for optimized concurrency; (4) Incorporates reductions into Sisal 1.2 and Sisal 90; (5) Evaluates performance and size of the implementations.

Denton, S.M.

1995-06-01

194

PARALLEL TRIANGULAR MESH REDUCTION  

Microsoft Academic Search

The visualization of large and complex models is required frequently. This is followed by number of operations which must be done before visualization itself, whether it is an analysis of input data or a model simplification. One of the techniques that enhance the computational power is parallel computation. It can be seen that multiprocessor computers are more often available even

MARTIN FRANC; VÁCLAV SKALA

2000-01-01

195

Interprocedural Analysis for Parallelization  

Microsoft Academic Search

This paper presents an extensive empirical evaluation of an interprocedural parallelizing compiler, developed as part of the Stanford SUIF compiler system. The system incorporates a comprehensive and integrated collection of analyses, including privatization and reduction recognition for both array and scalar variables, and symbolic analysis of array subscripts. The interprocedural analysis framework is designed to provide analysis results nearly as

Mary W. Hallt; Brian R. Murphy; Saman P. Amarasinghe; Shih-wei Liao; Monica S. Lam

1995-01-01

196

Parallel Traveling Salesman Problem  

NSDL National Science Digital Library

The traveling salesman problem is a classic optimization problem in which one seeks to minimize the path taken by a salesman in traveling between N cities, where the salesman stops at each city one and only one time, never retracing his/her route. This implementation is designed to run on UNIX systems with X-Windows, and includes parallelization using MPI.

Joiner, David; Hassinger, Jonathan

197

Parallel hierarchical radiosity rendering.  

National Technical Information Service (NTIS)

In this dissertation, the step-by-step development of a scalable parallel hierarchical radiosity renderer is documented. First, a new look is taken at the traditional radiosity equation, and a new form is presented in which the matrix of linear system coe...

M. Carter

1993-01-01

198

Parallel hierarchical radiosity rendering  

SciTech Connect

In this dissertation, the step-by-step development of a scalable parallel hierarchical radiosity renderer is documented. First, a new look is taken at the traditional radiosity equation, and a new form is presented in which the matrix of linear system coefficients is transformed into a symmetric matrix, thereby simplifying the problem and enabling a new solution technique to be applied. Next, the state-of-the-art hierarchical radiosity methods are examined for their suitability to parallel implementation, and scalability. Significant enhancements are also discovered which both improve their theoretical foundations and improve the images they generate. The resultant hierarchical radiosity algorithm is then examined for sources of parallelism, and for an architectural mapping. Several architectural mappings are discussed. A few key algorithmic changes are suggested during the process of making the algorithm parallel. Next, the performance, efficiency, and scalability of the algorithm are analyzed. The dissertation closes with a discussion of several ideas which have the potential to further enhance the hierarchical radiosity method, or provide an entirely new forum for the application of hierarchical methods.

Carter, M.

1993-07-01

199

Parallel molecular genetic analysis  

Microsoft Academic Search

We describe recent progress in parallel molecular genetic analyses using DNA microarrays, gel-based systems, and capillary electrophoresis and utilization of these approaches in a variety of molecular biology assays. These applications include use of polymorphic markers for mapping of genes and disease-associated loci and carrier detection for genetic diseases. Application of these technologies in molecular diagnostics as well as fluorescent

Steven E McKenzie; Elaine Mansfield; Eric Rappaport; Saul Surrey; Paolo Fortina

1998-01-01

200

Volcano - An Extensible and Parallel Query Evaluation System  

Microsoft Academic Search

To investigate the interactions of extensibility and parallelism in database query processing, we have developed a new dataflow query execution system called Volcano. The Vol- cano effort provides a rich environment for research and edu- cation in database systems design, heuristics for query opti- mization, parallel query execution, and resource allocation. Volcano uses a standard interface between algebra opera- tors,

Goetz Graefe

1994-01-01

201

A Diblock-Diblock Copolymer Mixture under Parallel Wall Confinement  

NASA Astrophysics Data System (ADS)

A cell dynamics simulation is performed for a diblock-diblock copolymers mixture confined between parallel walls. Much richer morphologies are observed in the mixture than in pure diblock copolymers. Multiple novel morphological transitions occur by changing the wall-block interaction and the distance between walls (confinement degree), and both perpendicular and parallel multilayered sandwich structures are obtained in the mixture.

Pan, Jun-Xing; Zhang, Jin-Jun; Wang, Bao-Feng; Wu, Hai-Shun; Sun, Min-Na

2013-04-01

202

Parallel computing: at the interface of high school and industry  

Microsoft Academic Search

This paper is an experience report describing the interaction between parallel programmers from industry and a select group of 16 high school students and six faculty from a Technical High School during a three-day \\

Robert A. Chesebrough; Ivan Turner

2010-01-01

203

Ultrascalable petaflop parallel supercomputer  

DOEpatents

A massively parallel supercomputer of petaOPS-scale includes node architectures based upon System-On-a-Chip technology, where each processing node comprises a single Application Specific Integrated Circuit (ASIC) having up to four processing elements. The ASIC nodes are interconnected by multiple independent networks that optimally maximize the throughput of packet communications between nodes with minimal latency. The multiple networks may include three high-speed networks for parallel algorithm message passing including a Torus, collective network, and a Global Asynchronous network that provides global barrier and notification functions. These multiple independent networks may be collaboratively or independently utilized according to the needs or phases of an algorithm for optimizing algorithm processing performance. The use of a DMA engine is provided to facilitate message passing among the nodes without the expenditure of processing resources at the node.

Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton On Hudson, NY); Chiu, George (Cross River, NY); Cipolla, Thomas M. (Katonah, NY); Coteus, Paul W. (Yorktown Heights, NY); Gara, Alan G. (Mount Kisco, NY); Giampapa, Mark E. (Irvington, NY); Hall, Shawn (Pleasantville, NY); Haring, Rudolf A. (Cortlandt Manor, NY); Heidelberger, Philip (Cortlandt Manor, NY); Kopcsay, Gerard V. (Yorktown Heights, NY); Ohmacht, Martin (Yorktown Heights, NY); Salapura, Valentina (Chappaqua, NY); Sugavanam, Krishnan (Mahopac, NY); Takken, Todd (Brewster, NY)

2010-07-20

204

Parallel multilevel preconditioners  

SciTech Connect

In this paper, we shall report on some techniques for the development of preconditioners for the discrete systems which arise in the approximation of solutions to elliptic boundary value problems. Here we shall only state the resulting theorems. It has been demonstrated that preconditioned iteration techniques often lead to the most computationally effective algorithms for the solution of the large algebraic systems corresponding to boundary value problems in two and three dimensional Euclidean space. The use of preconditioned iteration will become even more important on computers with parallel architecture. This paper discusses an approach for developing completely parallel multilevel preconditioners. In order to illustrate the resulting algorithms, we shall describe the simplest application of the technique to a model elliptic problem.

Bramble, J.H.; Pasciak, J.E.; Xu, Jinchao.

1989-01-01

205

Parallelization: Infectious Disease  

NSDL National Science Digital Library

Epidemiology is the study of infectious disease. Infectious diseases are said to be "contagious" among people if they are transmittable from one person to another. Epidemiologists can use models to assist them in predicting the behavior of infectious diseases. This module will develop a simple agent-based infectious disease model, develop a parallel algorithm based on the model, provide a coded implementation for the algorithm, and explore the scaling of the coded implementation on high performance cluster resources.

Weeden, Aaron

206

Scalable Parallel Crash Simulations  

Microsoft Academic Search

We are pleased to submit our efforts in parallelizing the PRONTO application suite for con- sideration in the SuParCup 99 competition. PRONTO is a finite element transient dynamics simulator which includes a smoothed particle hydrodynamics (SPH) capability; it is similar in scope to the well-known DYNA, PamCrash, and ABAQUS codes. Our efforts over the last few years have produced a

Stephen Attaway; Ted Barragy; Kevin Brown; David Gardner; Jeff Gruda; Martin Heinstein; Bruce Hendrickson; Kurt Metzinger; Mike Neilsen; Steve Plimpton; John Pott; Jeff Swegle; Courtenay Vaughan

1999-01-01

207

Xyce parallel electronic simulator.  

SciTech Connect

This document is a reference guide to the Xyce Parallel Electronic Simulator, and is a companion document to the Xyce Users' Guide. The focus of this document is (to the extent possible) exhaustively list device parameters, solver options, parser options, and other usage details of Xyce. This document is not intended to be a tutorial. Users who are new to circuit simulation are better served by the Xyce Users' Guide.

Keiter, Eric Richard; Mei, Ting; Russo, Thomas V.; Rankin, Eric Lamont; Schiek, Richard Louis; Thornquist, Heidi K.; Fixel, Deborah A.; Coffey, Todd Stirling; Pawlowski, Roger Patrick; Santarelli, Keith R.

2010-05-01

208

Parallel reduced area multipliers  

Microsoft Academic Search

As developed by Wallace and Dadda, a method for high-speed, parallel multiplication is to generate a matrix of partial products\\u000a and then reduce the partial products to two numbers whose sum is equal to the final product. The resulting two numbers are\\u000a then summed using a fast carry-propagate adder. This paper presents Reduced Area multipliers, which employ a modified reduction

K'andrea C. Bickerstaff; Michael J. Schulte; Earl E. Swartzlander Jr.

1995-01-01

209

Globality and speed of optical parallel processors.  

PubMed

The chances of optical computing are probably best if a large number of processing elements act in parallel. The efficiency of parallel processors depends, among other things, on the time it takes to communicate signals from one processor to any other processor. In an optical parallel processor one hopes to be able to transmit a signal from one processor to any other processor within only one cycle period, no matter how far apart the processors are. Such a global communications network is desirable especially for algorithms with global interactions. The fast Fourier algorithm is an example. We define a degree of globality and we show how speed and globality are related. Our result applies to a specific architecture based on spatial filtering. PMID:20555787

Lohmann, A W; Marathay, A S

1989-09-15

210

Supporting dynamic parallel object arrays  

Microsoft Academic Search

ABSTRACT We present efficient support for generalized arrays of parallel data driven objects. Array elements are regular C++ objects, and are scattered across the parallel machine. An individual element is addressed by its \\

Orion Sky Lawlor; Laxmikant V. Kalé

2003-01-01

211

Resistor Combinations for Parallel Circuits.  

ERIC Educational Resources Information Center

To help simplify both teaching and learning of parallel circuits, a high school electricity/electronics teacher presents and illustrates the use of tables of values for parallel resistive circuits in which total resistances are whole numbers. (MF)

McTernan, James P.

1978-01-01

212

Design of a Parallel Language.  

National Technical Information Service (NTIS)

Concurr is a new language for parallel systems. The language is designed as an easy-to-use parallel programming facility. The language also attempts to overcome some 'unnatural' restrictions of previous sequential languages. Clearly, new languages are nee...

J. R. Weisbecker

1988-01-01

213

The eect of blade aerodynamic modelling on the prediction of high-frequency rotor airloads  

Microsoft Academic Search

Interactions between the blades and vortical structures within the wake of a helicopter rotor are a significant source of impulsive loading and noise, particularly in descending flight. Brown's Vorticity Transport Model has been used to investigate the influence of the fidelity of the local blade aerodynamic model on the accuracy with which the high-frequency airloads associated with blade-vortex interactions can

Mary E. Kelly; Richard E. Brown

2009-01-01

214

Parallel Metaheuristics for Workforce Planning  

Microsoft Academic Search

Workforce planning is an important activity that enables organizations to determine the workforce needed for continued success.\\u000a A workforce planning problem is a very complex task requiring modern techniques to be solved adequately. In this work, we\\u000a describe the development of three parallel metaheuristic methods, a parallel genetic algorithm, a parallel scatter search,\\u000a and a parallel hybrid genetic algorithm, which

Enrique Alba; Gabriel Luque; Francisco Luna

2007-01-01

215

Synchronous Parallel Kinetic Monte Carlo  

SciTech Connect

A novel parallel kinetic Monte Carlo (kMC) algorithm formulated on the basis of perfect time synchronicity is presented. The algorithm provides an exact generalization of any standard serial kMC model and is trivially implemented in parallel architectures. We demonstrate the mathematical validity and parallel performance of the method by solving several well-understood problems in diffusion.

Mart?nez, E; Marian, J; Kalos, M H

2006-12-14

216

Workforce planning with parallel algorithms  

Microsoft Academic Search

Workforce planning is an important activity that en- ables organizations to determine the workforce needed for continued success. A workforce planning problem is a very complex task that requires modern techniques to be solved adequately. In this work, we describe the development of two parallel metaheuristic methods, a parallel genetic algorithm and a parallel scatter search, which can find high-quality

Enrique Alba; Gabriel Luque; Francisco Luna

2006-01-01

217

Roo: A parallel theorem prover  

SciTech Connect

We describe a parallel theorem prover based on the Argonne theorem-proving system OTTER. The parallel system, called Roo, runs on shared-memory multiprocessors such as the Sequent Symmetry. We explain the parallel algorithm used and give performance results that demonstrate near-linear speedups on large problems.

Lusk, E.L.; McCune, W.W.; Slaney, J.K.

1991-11-01

218

Interprocedural parallelization analysis in SUIF  

Microsoft Academic Search

As shared-memory multiprocessor systems become widely available, there is an increasing need for tools to simplify the task of developing parallel programs. This paper describes one such tool, the automatic parallelization system in the Stanford SUIF compiler. This article represents a culmination of a several-year research effort aimed at making parallelizing compilers significantly more effective. We have developed a system

Mary W. Hall; Saman P. Amarasinghe; Brian R. Murphy; Shih-Wei Liao; Monica S. Lam

2005-01-01

219

Dependency-driven Parallel Programming  

Microsoft Academic Search

The appearance of low-cost highly parallel hardware architectures has raised the alarm that a radically new way of thinking is required in programming to face the continually increasing parallelism of hard- ware. In our data dependency based framework, we treat data dependencies as first class entities in pro- grams. Programming a highly parallel machine or chip is formulated as finding

Eva Burrows; Magne Haveraaen

220

Time sharing massively parallel machines. Draft  

SciTech Connect

As part of the Massively Parallel Computing Initiative (MPCI) at the Lawrence Livermore National Laboratory, the authors have developed a simple, effective and portable time sharing mechanism by scheduling gangs of processes on tightly coupled parallel machines. By time-sharing the resources, the system interleaves production and interactive jobs. Immediate priority is given to interactive use, maintaining good response time. Production jobs are scheduled during idle periods, making use of the otherwise unused resources. In this paper the authors discuss their experience with gang scheduling over the 3 year life-time of the project. In section 2, they motivate the project and discuss some of its details. Section 3.0 describes the general scheduling problem and how gang scheduling addresses it. In section 4.0, they describe the implementation. Section 8.0 presents results culled over the lifetime of the project. They conclude this paper with some observations and possible future directions.

Gorda, B.; Wolski, R.

1995-03-01

221

A parallel, portable and versatile treecode  

SciTech Connect

Portability and versatility are important characteristics of a computer program which is meant to be generally useful. We describe how we have developed a parallel N-body treecode to meet these goals. A variety of applications to which the code can be applied are mentioned. Performance of the program is also measured on several machines. A 512 processor Intel Paragon can solve for the forces on 10 million gravitationally interacting particles to 0.5% rms accuracy in 28.6 seconds.

Warren, M.S. [Los Alamos National Lab., NM (United States); Salmon, J.K. [Australian National Univ., Canberra, ACT (Australia)]|[California Inst. of Technology, Pasadena, CA (United States)

1994-10-01

222

Optical absorption for parallel cylinder arrays  

Microsoft Academic Search

We study the long-wavelength electromagnetic resonances of interacting cylinder arrays. By using a normal-modes expansion where the effects of geometry and material are separated, it is shown that two parallel cylinders with different radii have electromagnetic modes distributed symmetrically about depolarization factor 1\\/2. Both sets couple to longitudinal and transverse components of the external field, but amplitudes of symmetric depolarization

P. Robles; R. Rojas; F. Claro

2002-01-01

223

Benchmarking massively parallel architectures  

SciTech Connect

The purpose of this paper is to summarize some initial experiences related to measuring the performance of massively parallel processors (MPPs) at Los Alamos National Laboratory (LANL). Actually, the range of MPP architectures the authors have used is rather limited, being confined mostly to the Thinking Machines Corporation (TMC) Connection Machine CM-2 and CM-5. Some very preliminary work has been carried out on the Kendall Square KSR-1, and efforts related to other machines, such as the Intel Paragon and the soon-to-be-released CRAY T3D are planned. This paper will concentrate more on methodology rather than discuss specific architectural strengths and weaknesses; the latter is expected to be the subject of future reports. MPP benchmarking is a field in critical need of structure and definition. As the authors have stated previously, such machines have enormous potential, and there is certainly a dire need for orders of magnitude computational power over current supercomputers. However, performance reports for MPPs must emphasize actual sustainable performance from real applications in a careful, responsible manner. Such has not always been the case. A recent paper has described in some detail, the problem of potentially misleading performance reporting in the parallel scientific computing field. Thus, in this paper, the authors briefly offer a few general ideas on MPP performance analysis.

Lubeck, O.; Moore, J.; Simmons, M.; Wasserman, H.

1993-07-01

224

Benchmarking massively parallel architectures  

SciTech Connect

The purpose of this paper is to summarize some initial experiences related to measuring the performance of massively parallel processors (MPPs) at Los Alamos National Laboratory (LANL). Actually, the range of MPP architectures the authors have used is rather limited, being confined mostly to the Thinking Machines Corporation (TMC) Connection Machine CM-2 and CM-5. Some very preliminary work has been carried out on the Kendall Square KSR-1, and efforts related to other machines, such as the Intel Paragon and the soon-to-be-released CRAY T3D are planned. This paper will concentrate more on methodology rather than discuss specific architectural strengths and weaknesses; the latter is expected to be the subject of future reports. MPP benchmarking is a field in critical need of structure and definition. As the authors have stated previously, such machines have enormous potential, and there is certainly a dire need for orders of magnitude computational power over current supercomputers. However, performance reports for MPPs must emphasize actual sustainable performance from real applications in a careful, responsible manner. Such has not always been the case. A recent paper has described in some detail, the problem of potentially misleading performance reporting in the parallel scientific computing field. Thus, in this paper, the authors briefly offer a few general ideas on MPP performance analysis.

Lubeck, O.; Moore, J.; Simmons, M.; Wasserman, H.

1993-01-01

225

Parallel superconvergent multigrid  

SciTech Connect

We describe a class of multiscale algorithms for the solution of large sparse linear systems that are particularly well adapted to massively parallel supercomputers. While standard multigrid algorithms are unable to effectively use all processors when computing on coarse grids, the new algorithms utilize the same number of processors at all times. The basic idea is to solve many coarse scale problems simultaneously, combining the results in an optimal way to provide an improved fine scale solution. As a result, convergence rates are much faster than for standard multigrid methods - we have obtained V-cycle convergence rates as good as .0046 with one smoothing application per cycle, and .0013 with two smoothings. On massively parallel machines the improved convergence rate is attained at no extra computational cost since processors that would otherwise be sitting idle are utilized to provide the better convergence. On serial machines the algorithm is slower because of the extra time spent on multiple coarse scales, though in certain cases the improved convergence rate may justify this - particularly in cases where other methods do not converge. In constant coefficient situations the algorithm is easily analyzed theoretically using Fourier methods on a single grid. The fact that only one grid is involved substantially simplifies convergence proofs. A feature of the algorithms is the use of a matched pair of operators: an approximate inverse for smoothing and a superinterpolation operator to move the correction from coarse to fine scales, chosen to optimize the rate of convergence.

Frederickson, P.O.; McBryan, O.A.

1987-01-01

226

A systolic array parallelizing compiler  

SciTech Connect

This book presents a completely new approach to the problem of systolic array parallelizing compiler. It describes the AL parallelizing compiler for the Warp systolic array, the first working systolic array parallelizing compiler which can generate efficient parallel code for complete LINPACK routines. This book begins by analyzing the architectural strength of the Warp systolic array. It proposes a model for mapping programs onto the machine and introduces the notion of data relations for optimizing the program mapping. Also presented are successful applications of the AL compiler in matrix computation and image processing. A complete listing of the source program and compiler-generated parallel code are given to clarify the overall picture of the compiler. The book concludes that systolic array parallelizing compiler can produce efficient parallel code, almost identical to what the user would have written by hand.

Tseng, P.S. (Bell Communications Research, Inc. (US))

1990-01-01

227

Toward Parallel Document Clustering  

SciTech Connect

A key challenge to automated clustering of documents in large text corpora is the high cost of comparing documents in a multimillion dimensional document space. The Anchors Hierarchy is a fast data structure and algorithm for localizing data based on a triangle inequality obeying distance metric, the algorithm strives to minimize the number of distance calculations needed to cluster the documents into “anchors” around reference documents called “pivots”. We extend the original algorithm to increase the amount of available parallelism and consider two implementations: a complex data structure which affords efficient searching, and a simple data structure which requires repeated sorting. The sorting implementation is integrated with a text corpora “Bag of Words” program and initial performance results of end-to-end a document processing workflow are reported.

Mogill, Jace A.; Haglin, David J.

2011-09-01

228

Series and Parallel Circuits  

NSDL National Science Digital Library

Tony R. Kuphaldt is the creator of All About Circuits, a collection of online textbooks about circuits and electricity. The site is split into volumes, chapters, and topics to make finding and learning about these subjects convenient. Volume 1, Chapter 5: Series and Parallel Circuits begins by explaining the basic differences between the two types of circuits. The topics then progress to more difficult subject matter such as conductance, and OhmâÂÂs law, with a section on building circuits for a more hands-on component. This website would be a great jumping off point for educators who want to teach circuits or a fantastic supplemental resource for students who want or need to learn more.

Kuphaldt, Tony R.

2008-07-01

229

Parallel Imaging Microfluidic Cytometer  

PubMed Central

By adding an additional degree of freedom from multichannel flow, the parallel microfluidic cytometer (PMC) combines some of the best features of flow cytometry (FACS) and microscope-based high-content screening (HCS). The PMC (i) lends itself to fast processing of large numbers of samples, (ii) adds a 1-D imaging capability for intracellular localization assays (HCS), (iii) has a high rare-cell sensitivity and, (iv) has an unusual capability for time-synchronized sampling. An inability to practically handle large sample numbers has restricted applications of conventional flow cytometers and microscopes in combinatorial cell assays, network biology, and drug discovery. The PMC promises to relieve a bottleneck in these previously constrained applications. The PMC may also be a powerful tool for finding rare primary cells in the clinic. The multichannel architecture of current PMC prototypes allows 384 unique samples for a cell-based screen to be read out in approximately 6–10 minutes, about 30-times the speed of most current FACS systems. In 1-D intracellular imaging, the PMC can obtain protein localization using HCS marker strategies at many times the sample throughput of CCD-based microscopes or CCD-based single-channel flow cytometers. The PMC also permits the signal integration time to be varied over a larger range than is practical in conventional flow cytometers. The signal-to-noise advantages are useful, for example, in counting rare positive cells in the most difficult early stages of genome-wide screening. We review the status of parallel microfluidic cytometry and discuss some of the directions the new technology may take.

Ehrlich, Daniel J.; McKenna, Brian K.; Evans, James G.; Belkina, Anna C.; Denis, Gerald V.; Sherr, David; Cheung, Man Ching

2011-01-01

230

Parallel Detection of Cathodoluminescence.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. A GEC P8600 Charge-coupled device has been used in the design and fabrication of a parallel detection system or optical multichannel analyser for the analysis of Cathodoluminescence Spectra. The P8600, whilst designed for video applications, is used as a linear array by merging entire rows of pixels together on the on-board output amplifier. A dual slope integration method of correlated double sampling has been used for noise reduction. An analysis of the performance of this system is given and the achieved noise level of 22 electrons is found to be in good agreement with that theoretically possible. A complete description of the circuits is given together with details of its use with a "Link 860" computer/analyser and a "Philips 400" electron microscope. To demonstrate the system, a study of the cathodoluminescent properties of Cadmium Telluride grown by molecular beam epitaxy has been made. In particular the effect of dislocations, stacking faults and twins on luminescence has been studied. Dislocations are seen to cause a quenching of excitonic emission with no corresponding increase in any other emission. The effect of stacking faults was seen to vary between different samples with an enhancement of long wavelength emission seen in poor quality samples. This supports the premise that the faults are nucleated by surface impurities which are also responsible for the enhanced emission. Some twin defects have been found to cause enhanced excitonic emission. This is compatible with the existence of natural quantum wells at twin faults proposed by other workers. The speed with which the parallel detection system can acquire spectra makes it a valuable tool in the study of beam sensitive materials. To demonstrate this, measurements were made of the decay rates of the weak cathodoluminescence from the organic crystal Coronene. These rates were seen to have time constants less than two minutes and such measurements would not have been amenable by conventional methods.

Day, John C. C.

231

Kinematics analysis, workspace, design and control of 3RPS and TRIGLIDE medical parallel robots  

Microsoft Academic Search

Parallel robots find many applications in human-systems interaction, medical robots, rehabilitation, exoskeletons, to name a few. These applications are characterized by many imperatives, with robust precision and dynamic workspace computation as the two ultimate ones. This paper presents kinematic analysis, workspace, design and control to 3 degrees of freedom (DOF) parallel robots. Parallel robots have received considerable attention from both

Dan Verde?; Sergiu-Dan Stan; Milos Manic; R. Balan; V. Maties

2009-01-01

232

Components and Interfaces of a Process Management System for Parallel Programs  

Microsoft Academic Search

Parallel jobs are different from sequential jobs and require a different type of process management. We present here a process man- agement system for parallel programs such as those written using MPI. A primary goal of the system, which we call MPD (for multipurpose daemon), is to be scalable. By this we mean that startup of interactive parallel jobs comprising

Ralph Butler; William Gropp; Ewing L. Lusk

2001-01-01

233

Concatenation Algorithms for Parallel Numerical Simulation of Radiation Hydrodynamics coupled with Neutron Transport  

Microsoft Academic Search

Complex physical phenomena can be usually split into several interacting physical computational models and can be numerically simulated by coupling parallel codes individually designed for these models. Besides rational splitting and efficient numerical methods for different models, we must design scalable parallel algorithms to concatenate these parallel codes. Meanwhile, three objectives should be well balanced. The first is how to

Mo Zeyao

2005-01-01

234

Using Motivational Interviewing Techniques to Address Parallel Process in Supervision  

ERIC Educational Resources Information Center

|Supervision offers a distinct opportunity to experience the interconnection of counselor-client and counselor-supervisor interactions. One product of this network of interactions is parallel process, a phenomenon by which counselors unconsciously identify with their clients and subsequently present to their supervisors in a similar fashion…

Giordano, Amanda; Clarke, Philip; Borders, L. DiAnne

2013-01-01

235

BVI Noise for the AH-1/OLS Model Rotor in Forward Flight, Taking into Account the Rotor Stand in the DNW Wind Tunnel.  

National Technical Information Service (NTIS)

This paper examines whether the rotor stand has to be taken into account in the Blade-vortex interaction (BVI) noise calculation for the AH-1/OLS model rotor tested in the DNW wind tunnel. The tests show that the presence of the stand changes the heights ...

M. Schaffar J. Haertig P. Gnemmi

1994-01-01

236

Rotary wing aerodynamically generated noise  

Microsoft Academic Search

The history and methodology of aerodynamic noise reduction in rotary wing aircraft are presented. Thickness noise during hover tests and blade vortex interaction noise are determined and predicted through the use of a variety of computer codes. The use of test facilities and scale models for data acquisition are discussed.

F. J. Schmitz; H. A. Morse

1982-01-01

237

BVI induced vibration and noise alleviation by active and passive approaches  

Microsoft Academic Search

This dissertation describes the development of a comprehensive aeroelastic\\/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and

Li Liu

2005-01-01

238

ACTIVE TWIST CONTROL OF SMART HELICOPTER ROTOR - A SURVEY  

Microsoft Academic Search

Helicopter vibration and blade-vortex interaction (BVI) noise are major problems restricting the wider use of helicopters in civil and military applications. Traditional methods based on vibration isolators and absorbers and passive designs of the rotor blade to reduce BVI noise have reached the point of diminishing returns and are increasingly unable to meet the stringent requirements of next generation helicopters.

Dipali Thakkar; Ranjan Ganguli

2005-01-01

239

A near wake model for trailing vorticity compared with the blade element momentum theory  

Microsoft Academic Search

A near wake model for trailing vorticity originally proposed by Beddoes for high-resolution helicopter blade vortex interaction computations has been implemented and compared with the usual blade element momentum models used for wind turbine calculations. The model is in principle a lifting line model for the rotating blade, where only a quarter revolution of the wake system behind the blade

Helge Aagaard Madsen; Flemming Rasmussen

2004-01-01

240

Application of high resolution airload calculations to helicopter noise prediction  

Microsoft Academic Search

Recent studies of blade\\/vortex interactions have resulted in the development of aerodynamic models with which the very detailed loading data necessary for noise predictions can be calculated. The methods employed not only obviate the need for some of the simplifying assumptions that have previously reduced the precision and sensitivity of acoustic calculations but also achieve this improvement at little cost

A. C. Pike

1987-01-01

241

Parametric studies of model helicopter blade slap and rotational noise  

Microsoft Academic Search

A parametric study of model helicopter rotor blade slap due to blade\\/vortex interaction was studied in an anechoic wind tunnel. The parameters studied were blade number, advance ratio, pitch, and shaft angle. The separate effect of each parameter was studied with other parameters held fixed. The intensity of blade slap was found to decrease with an increase in the number

J. E. Hubbard Jr.; N. G. Humbad; P. Bauer; W. L. Harris

1979-01-01

242

Aeroacoustic research programs at the Army Aviation Research and Technology Activity  

Microsoft Academic Search

The Army rotorcraft aeroacoustic programs are reviewed, highlighting the theoretical and experimental progress made by Army researchers in the physical understanding of helicopter impulsive noise. The two impulsive noise sources addressed over this past decade are high-speed impulsive noise and blade-vortex interaction noise, both of which have had and will continue to have an increasing influence on Army rotorcraft design

Yung H. Yu; Fredric H. Schmitz; H. Andrew Morse

1988-01-01

243

Parallel RF transmission in MRI.  

PubMed

Following the development of parallel imaging, parallel transmission describes the use of multiple RF transmit coils. Parallel transmission can be applied to improve RF excitation, in particular, multidimensional, spatially selective RF excitation. For instance, parallel transmission is able to shorten spatially selective RF pulses in two or three dimensions, or to minimize the occurring SAR. One potential major application might be the compensation of patient-induced B(1) inhomogeneities, particularly at high main fields. This paper provides an overview of selected aspects of this new transmission approach. The basic principles of parallel transmission are discussed, initial experimental proofs are described, and the impact of error propagation on coil design for parallel transmission is outlined. PMID:16705630

Katscher, Ulrich; Börnert, Peter

2006-05-01

244

A Survey of Parallel Sorting Algorithms.  

National Technical Information Service (NTIS)

A rather comprehensive survey of parallel sorting algorithms is included herein. Parallel sorting algorithms are considered in two major categories - the internal parallel sorting algorithms and the external parallel sorting algorithms. Because external s...

D. J. DeWitt D. Friedland D. K. Hsiao M. J. Menon

1981-01-01

245

Parallel Search On Video Cards  

Microsoft Academic Search

Recent approaches exploiting the massively parallel ar- chitecture of graphics processors (GPUs) to acceler- ate database operations have achieved intriguing results. While parallel sorting received significant attention, par- allel search has not been explored. With p-ary search we present a novel parallel search algorithm for large-scale database index operations that scales with the number of processors and outperforms traditional thread-level

Tim Kaldewey; Jeff Hagen; Eric Sedlar

246

Cost-Effective Parallel Computing  

Microsoft Academic Search

Many academic papers imply that parallel computing is only worthwhile when applications achieve nearly linear speedup (i.e., execute nearly p times faster on p processors). This note shows that parallel computing is cost-effective whenever speedup exceeds costup---the parallel system cost divided by uniprocessor cost. Furthermore, when applications have large memory requirements (e.g., 512 megabytes), the costup---and hence speedup necessary to

David A. Wood; Mark D. Hill

1995-01-01

247

Exploiting Parallelism to Accelerate Keyword Search on Deep-Web Sources  

Microsoft Academic Search

Increasingly, biological data is being shared over the deep web. Many biological queries can only be answered by successively search- ing a number of distinct web-sites. This paper introduces a system that exploits parallelization for accelerating search over multiple deep web data sources. An interactive, two-stage multi-threading system is devel- oped to achieve task parallelization, thread parallelization, and pipelined parallelization.

Tantan Liu; Fan Wang; Gagan Agrawal

2009-01-01

248

Revisiting parallel catadioptric goniophotometers  

NASA Astrophysics Data System (ADS)

A thorough knowledge of the angular distribution of light scattered by an illuminated surface under different angles is essential in numerous industrial and research applications. Traditionally, the angular distribution of a reflected or transmitted light flux as function of the illumination angle, described by the Bidirectional Scattering Distribution Function (BSDF), is measured with a point-by-point scanning goniophotometer yielding impractically long acquisition times. Significantly faster measurements can be achieved by a device capable of simultaneously imaging the far-field distribution of light scattered by a sample onto a two-dimensional sensor array. Such an angular-to-spatial mapping function can be realized with a parallel catadioptric mapping goniophotometer (CMG). In this contribution, we formally establish the design requirement for a reliable CMG. Based on heuristic considerations we show that, to avoid degrading the angular-to-spatial function, the acceptance angle of the lens system inherent to a CMG must be smaller than 60°. By means of a parametric study, we investigate the practical design limitations of a CMG caused by the constraints imposed by the properties of a real lens system. Our study reveals that the values of the key design parameters of a CMG fall within a relatively small range. This imposes the shape of the ellipsoidal reflector and drastically restricts the room for a design trade-off between the sample size and the angular resolution. We provide a quantitative analysis for the key parameters of a CMG for two relevant cases.

Karamata, Boris; Andersen, Marilyne

2013-04-01

249

Parallel data processor  

US Patent & Trademark Office Database

A parallel processor has a controller for generating control signals, and a plurality of identical processing cells, each of which is connected to at least one neighboring cell and responsive to the controller for processing data in accordance with the control signals. Each processing cell includes a memory, a first register, a second register, and an arithmetic logic unit (ALU). An input of the first register is coupled to a memory output. The output of the first register is coupled to a second register located in a neighboring cell. An input of the second register is coupled to receive an output from a first register located in a neighboring cell. The output of the second register is coupled to an input of the ALU. In another feature, mask logic is interposed between A and B operand sources, and two inputs of the ALU. The mask logic also inputs a mask source, and in response to control signals, can output the A operand logically OR'ed with the mask, and can output the B operand logically AND'ed with the mask. In another feature, each cell includes a multiplexor coupled to a neighboring cell for selectively transmitting cell data to the neighbor, or for effectively bypassing the cell during data shift operations by transmitting data that is received from a neighboring cell to a neighboring cell. Other enhancements to a cell architecture are also disclosed.

2000-06-06

250

Parallel bargrams for consumer-based information exploration and choice  

Microsoft Academic Search

In this paper we introduce multidimensional visualization and interaction techniques that are an extension to related work in parallel histograms and dynamic querying. Bargrams are, in effect, histograms whose bars have been tipped over and lined up end-to-end. We discuss affordances of parallel bargrams in the context of systems that support consumer-based information exploration and choice based on the attributes

Kent Wittenburg; Tom Lanning; Michael Heinrichs; Michael Stanton

2001-01-01

251

High Dimensional Clustering Using Parallel Coordinates and the Grand Tour  

Microsoft Academic Search

In this paper, we present some graphical techniquesfor cluster analysis of high-dimensional data. Parallel coordinateplots and parallel coordinate density plots aregraphical techniques which map multivariate data into atwo-dimensional display. The method has some elegantduality properties with ordinary Cartesian plots so thathigher-dimensional mathematical structures can be analyzed.Our high interaction software allows for rapidediting of data to remove outliers and isolate clusters

Edward J. Wegman; Qiang Luo

1996-01-01

252

Tile-based Level of Detail for the Parallel Age  

SciTech Connect

Today's PCs incorporate multiple CPUs and GPUs and are easily arranged in clusters for high-performance, interactive graphics. We present an approach based on hierarchical, screen-space tiles to parallelizing rendering with level of detail. Adapt tiles, render tiles, and machine tiles are associated with CPUs, GPUs, and PCs, respectively, to efficiently parallelize the workload with good resource utilization. Adaptive tile sizes provide load balancing while our level of detail system allows total and independent management of the load on CPUs and GPUs. We demonstrate our approach on parallel configurations consisting of both single PCs and a cluster of PCs.

Niski, K; Cohen, J D

2007-08-15

253

Distributed computing with parallel networking  

Microsoft Academic Search

For many large scientific applications, computing on a cluster is a viable, economical alternative to a dedicated parallel machine. Application performance on a cluster is largely determined by the speed of the underlying communication network. The authors use a parallel network approach to improve the communication network performance. More specifically, they use multiple networks based on Ethernet to improve the

K. Maly; M. Zubair; S. Kelbar

1993-01-01

254

PARALLEL METAHEURISTICS FOR COMBINATORIAL OPTIMIZATION  

Microsoft Academic Search

In this paper, we review parallel metaheuristics for approximating the global optimal solution of combinatorial optimization problems. Recent developments on parallel implementation of genetic algorithms, simulated an- nealing, tabu search, variable neighborhood search, and greedy randomized adaptive search procedures (GRASP) are discussed.

MAURICIO G. C. RESENDE; PANOS M. PARDALOS; SANDRA DUNI

1999-01-01

255

Analytical Modeling of Pipeline Parallelism  

Microsoft Academic Search

Parallel programming is a requirement in the multi-core era. One of the most promising techniques to make paral- lel programming available for the general users is the use of parallel programming patterns. Functional pipeline par- allelism is a pattern that is well suited for many emerging applications, such as streaming and \\

Angeles G. Navarro; Rafael Asenjo; Siham Tabik; Calin Cascaval

2009-01-01

256

Supporting dynamic parallel object arrays  

Microsoft Academic Search

We present efficient support for generalized arrays of parallel data driven objects. The “array elements” are scattered across a parallel machine. Each array element is an object that can be thought of as a virtual processor. The individual elements are addressed by their “index”, which can be an arbitrary object rather than a simple integer. For example, it can be

Orion Sky Lawlor; Laxmikant V. Kalé

2001-01-01

257

Parallel Programming for Computer Vision  

Microsoft Academic Search

Two Unix environments developed for programming parallel computers to handle image-processing and vision applications are described. Visx is a portable environment for the development of vision applications that has been used for many years on serial computers in research. Visx was adapted to run on a multiprocessor with modest parallelism by using functional decomposition and standard operating-system capabilities to exploit

Anthony P. Reeves

1991-01-01

258

Parallel Programming Using Skeleton Functions  

Microsoft Academic Search

Prograxnming parallel machines is notoriously difficult. Factors contribut- ing to this difficulty include the complexity of concurrency, the effect of resource allocation on performance and the current diversity of parallel machine models. The net result is that effective portability, which de- pends crucially on the predictability of performance, has been lost. Functional programming languages have been put forward as solutions

John Darlington; A. J. Field; Peter G. Harrison; Paul H. J. Kelly; David W. N. Sharp; Qian Wu; R. While

1993-01-01

259

Another view on parallel speedup  

Microsoft Academic Search

In this paper three models of parallel speedup are studied. They are The simplified memory-bounded speedup contains both Amdahl's law and Gustafson's scaled speedup as its special cases. This study proposes a new metric for performance evaluation and leads to a better understanding of parallel processing.

Xian-He Sun; Lionel M. Ni

1990-01-01

260

Parallel contingency statistics with Titan.  

SciTech Connect

This report summarizes existing statistical engines in VTK/Titan and presents the recently parallelized contingency statistics engine. It is a sequel to [PT08] and [BPRT09] which studied the parallel descriptive, correlative, multi-correlative, and principal component analysis engines. The ease of use of this new parallel engines is illustrated by the means of C++ code snippets. Furthermore, this report justifies the design of these engines with parallel scalability in mind; however, the very nature of contingency tables prevent this new engine from exhibiting optimal parallel speed-up as the aforementioned engines do. This report therefore discusses the design trade-offs we made and study performance with up to 200 processors.

Thompson, David C.; Pebay, Philippe Pierre

2009-09-01

261

Agents' Strategies for the Dual Parallel Search in Partnership Formation Applications  

Microsoft Academic Search

In many two-sided search applications, autonomous agents can enjoy the advantage of parallel search, powered by their ability to handle an enormous amount of information, in a short time, and the capability to maintain interaction with several other agents in parallel. The adoption of the new technique by an agent suggests a reduction in the average cost per interaction with

David Sarne; Sarit Kraus

2004-01-01

262

Surface Aggregation of Candida albicanson Glass in the Absence and Presence of Adhering Streptococcus gordoniiin a Parallel-Plate Flow Chamber: A Surface Thermodynamical Analysis Based on Acid–Base Interactions  

Microsoft Academic Search

Adhesive interactions between yeasts and bacteria are important in the maintenance of infectious mixed biofilms on natural and biomaterial surfaces in the human body. In this study, the extended DLVO (Derjaguin–Landau–Verwey–Overbeek) approach has been applied to explain adhesive interactions betweenC. albicansATCC 10261 andS. gordoniiNCTC 7869 adhering on glass. Contact angles with different liquids and the ? potentials of both the

Kevin W Millsap; Rolf Bos; Henk J Busscher; Henny C van der Mei

1999-01-01

263

Adaptive, multiresolution visualization of large data sets using parallel octrees.  

SciTech Connect

The interactive visualization and exploration of large scientific data sets is a challenging and difficult task; their size often far exceeds the performance and memory capacity of even the most powerful graphics work-stations. To address this problem, we have created a technique that combines hierarchical data reduction methods with parallel computing to allow interactive exploration of large data sets while retaining full-resolution capability. The hierarchical representation is built in parallel by strategically inserting field data into an octree data structure. We provide functionality that allows the user to interactively adapt the resolution of the reduced data sets so that resolution is increased in regions of interest without sacrificing local graphics performance. We describe the creation of the reduced data sets using a parallel octree, the software architecture of the system, and the performance of this system on the data from a Rayleigh-Taylor instability simulation.

Freitag, L. A.; Loy, R. M.

1999-06-10

264

Parallel processing for control applications  

SciTech Connect

Parallel processing has been a topic of discussion in computer science circles for decades. Using more than one single computer to control a process has many advantages that compensate for the additional cost. Initially multiple computers were used to attain higher speeds. A single cpu could not perform all of the operations necessary for real time operation. As technology progressed and cpu's became faster, the speed issue became less significant. The additional processing capabilities however continue to make high speeds an attractive element of parallel processing. Another reason for multiple processors is reliability. For the purpose of this discussion, reliability and robustness will be the focal paint. Most contemporary conceptions of parallel processing include visions of hundreds of single computers networked to provide 'computing power'. Indeed our own teraflop machines are built from large numbers of computers configured in a network (and thus limited by the network). There are many approaches to parallel configfirations and this presentation offers something slightly different from the contemporary networked model. In the world of embedded computers, which is a pervasive force in contemporary computer controls, there are many single chip computers available. If one backs away from the PC based parallel computing model and considers the possibilities of a parallel control device based on multiple single chip computers, a new area of possibilities becomes apparent. This study will look at the use of multiple single chip computers in a parallel configuration with emphasis placed on maximum reliability.

Telford, J. W. (John W.)

2001-01-01

265

Implementing a parallel C++ runtime system for scalable parallel systems  

Microsoft Academic Search

pC++ is a language extension to C++ designed toallow programmers to compose "concurrent aggregate"collection classes which can be aligned and distributedover the memory hierarchy of a parallel machine ina manner modeled on the High Performance FortranForum (HPFF) directives for Fortran 90. pC++ allowsthe user to write portable and efficient code whichwill run on a wide range of scalable parallel computersystems.

A. Malony; B. Mohr; P. Beckman; D. Gannon; S. Yang; F. Bodin; S. Kesavan

1993-01-01

266

Software for parallel processing applications  

SciTech Connect

Parallel computing has been used to solve large computing problems in high-energy physics. Typical problems include offline event reconstruction, monte carlo event-generation and reconstruction, and lattice QCD calculations. Fermilab has extensive experience in parallel computing using CPS (cooperative processes software) and networked UNIX workstations for the loosely-coupled problems of event reconstruction and monte carlo generation and CANOPY and ACPMAPS for Lattice QCD. Both systems will be discussed. Parallel software has been developed by many other groups, both commercial and research-oriented. Examples include PVM, Express and network-Linda for workstation clusters and PCN and STRAND88 for more tightly-coupled machines.

Wolbers, S.

1992-10-01

267

Parallel Strategies for Crash and Impact Simulations  

SciTech Connect

We describe a general strategy we have found effective for parallelizing solid mechanics simula- tions. Such simulations often have several computationally intensive parts, including finite element integration, detection of material contacts, and particle interaction if smoothed particle hydrody- namics is used to model highly deforming materials. The need to balance all of these computations simultaneously is a difficult challenge that has kept many commercial and government codes from being used effectively on parallel supercomputers with hundreds or thousands of processors. Our strategy is to load-balance each of the significant computations independently with whatever bal- ancing technique is most appropriate. The chief benefit is that each computation can be scalably paraIlelized. The drawback is the data exchange between processors and extra coding that must be written to maintain multiple decompositions in a single code. We discuss these trade-offs and give performance results showing this strategy has led to a parallel implementation of a widely-used solid mechanics code that can now be run efficiently on thousands of processors of the Pentium-based Sandia/Intel TFLOPS machine. We illustrate with several examples the kinds of high-resolution, million-element models that can now be simulated routinely. We also look to the future and dis- cuss what possibilities this new capabUity promises, as well as the new set of challenges it poses in material models, computational techniques, and computing infrastructure.

Attaway, S.; Brown, K.; Hendrickson, B.; Plimpton, S.

1998-12-07

268

Parallel computing in conceptual sewer simulations.  

PubMed

Integrated urban drainage modelling is used to analyze how existing urban drainage systems respond to particular conditions. Based on these integrated models, researchers and engineers are able to e.g. estimate long-term pollution effects, optimize the behaviour of a system by comparing impacts of different measures on the desired target value or get new insights on systems interactions. Although the use of simplified conceptual models reduces the computational time significantly, searching the enormous vector space that is given by comparing different measures or that the input parameters span, leads to the fact, that computational time is still a limiting factor. Owing to the stagnation of single thread performance in computers and the rising number of cores one needs to adapt algorithms to the parallel nature of the new CPUs to fully utilize the available computing power. In this work a new developed software tool named CD3 for parallel computing in integrated urban drainage systems is introduced. From three investigated parallel strategies two showed promising results and one results in a speedup of up to 4.2 on an eight-way hyperthreaded quad core CPU and shows even for all investigated sewer systems significant run-time reductions. PMID:20107253

Burger, G; Fach, S; Kinzel, H; Rauch, W

2010-01-01

269

Parallel Shear Flows Over Cavities.  

National Technical Information Service (NTIS)

Incompressible separated flows have long presented problems to the theoretician. Parallel shear flow over a cavity is an ideal flow configuration to evaluate numerically to shed light on fundamental relationships. It also provides a basis to predict flow ...

V. O'Brien

1970-01-01

270

Highly Parallel Sparse Cholesky Factorization.  

National Technical Information Service (NTIS)

Several fine grained parallel algorithms were developed and compared to compute the Cholesky factorization of a sparse matrix. The experimental implementations are on the Connection Machine, a distributed memory SIMD machine whose programming model concep...

J. R. Gilbert R. Schreiber

1990-01-01

271

Highly Parallel Sparse Cholesky Factorization.  

National Technical Information Service (NTIS)

The paper develops and compares several fine-grained parallel algorithms to compute the Cholesky factorization of a sparse matrix. The experimental implementations are on the Connection Machine, a distributed-memory SIMD machine whose programming model co...

J. R. Gilbert R. Schreiber

1990-01-01

272

Parallel computing and domain decomposition  

SciTech Connect

Domain decomposition techniques appear a natural way to make good use of parallel computers. In particular, these techniques divide a computation into a local part, which may be done without any interprocessor communication, and a part that involves communication between neighboring and distant processors. This paper discusses some of the issues in designing and implementing a parallel domain decomposition algorithm. A framework for evaluating the cost of parallelism is introduced and applied to answering questions such as which and how many processors should solve global problems and what impact load balancing has on the choice of domain decomposition algorithm. The sources of performance bottlenecks are discussed. This analysis suggests that domain decomposition techniques will be effective on high-performance parallel processors and on networks of workstations. 17 refs., 8 figs.

Gropp, W.

1991-01-01

273

Interpreting Quantum Parallelism by Sequents  

NASA Astrophysics Data System (ADS)

We introduce an interpretation of quantum superposition in predicative sequent calculus, in the framework of basic logic. Then we introduce a new predicative connective for the entanglement. Our aim is to represent quantum parallelism in terms of logical proofs.

Battilotti, Giulia

2010-12-01

274

Parallel computing and domain decomposition.  

National Technical Information Service (NTIS)

Domain decomposition techniques appear a natural way to make good use of parallel computers. In particular, these techniques divide a computation into a local part, which may be done without any interprocessor communication, and a part that involves commu...

W. Gropp

1991-01-01

275

Challenge of Massively Parallel Computing.  

National Technical Information Service (NTIS)

Since the mid-1980's, there have been a number of commercially available parallel computers with hundreds or thousands of processors. These machines have provided a new capability to the scientific community, and they been used successfully by scientists ...

D. E. Womble

1999-01-01

276

Performance Model for Massive Parallelism.  

National Technical Information Service (NTIS)

A popular argument is that vector and parallel architectures should not be carried to extremes because the scalar or serial portion of the code will eventually dominate. Since pipeline stages and extra processors obviously add hardware cost, a corollary t...

J. L. Gustafson

1988-01-01

277

Parallel Implicit Algorithms for CFD.  

National Technical Information Service (NTIS)

The main goal of this project was efficient distributed parallel and workstation cluster implementations of Newton-Krylov-Schwarz (NKS) solvers for implicit Computational Fluid Dynamics (CFD.) 'Newton' refers to a quadratically convergent nonlinear iterat...

D. E. Keyes

1998-01-01

278

Demonstrating Forces between Parallel Wires.  

ERIC Educational Resources Information Center

|Describes a physics demonstration that dramatically illustrates the mutual repulsion (attraction) between parallel conductors using insulated copper wire, wooden dowels, a high direct current power supply, electrical tape, and an overhead projector. (WRM)|

Baker, Blane

2000-01-01

279

New Methodologies for Parallel Architecture  

Microsoft Academic Search

Moore's law continues to grant computer architects ever more transistors in the foreseeable future, and parallelism is the\\u000a key to continued performance scaling in modern microprocessors. In this paper, the achievements in our research project, which\\u000a is supported by the National Basic Research 973 Program of China, on parallel architecture, are systematically presented.\\u000a The innovative approaches and techniques to solve

Dong-Rui Fan; Xiao-Wei Li; Guo-Jie Li

2011-01-01

280

Debugging in a parallel environment  

SciTech Connect

This paper describes the preliminary results of a project investigating approaches to dynamic debugging in parallel processing systems. Debugging programs in a multiprocessing environment is particularly difficult because of potential errors in synchronization of tasks, data dependencies, sharing of data among tasks, and irreproducibility of specific machine instruction sequences from one job to the next. The basic methodology involved in predicate-based debuggers is given as well as other desirable features of dynamic parallel debugging. 13 refs.

Wasserman, H.J.; Griffin, J.H.

1985-01-01

281

Sumatra and Cascadia: Parallels Explored  

Microsoft Academic Search

The 2004 Sumatra-Andaman Mw9.2 earthquake has spawned superficial parallels between the Sumatra and Cascadia convergent margins in terms of rupture length and tsunami generation, however the parallels go deeper than these simple parameters. The accretionary wedges of both systems are fed by large accreting submarine fans at their northern ends, sourcing sediments from remote continental interiors. The Astoria and Nitinat

C. Goldfinger; L. C. McNeill

2006-01-01

282

Parallelization of the SIP algorithm  

NASA Astrophysics Data System (ADS)

This work is devoted to the development of an algorithm for the parallelization of the SIP-solver for pentadiagonal matrices. It bases on the so-called block Jacobi algorithm. The parallelization of the matrix solver is done using the OpenMP standard. The performance of the new algorithm is illustrated with the numerical solution of a 2D Laplace's equation problem and a 2D Navier-Stokes equation problem (lid driven cavity).

Dierich, F.; Nikrityuk, P. A.

2012-09-01

283

Parallelization of FM-Index  

Microsoft Academic Search

A parallel design and implementation of FM-index is presented in this paper. In applications, the performance of the FM-index is crucial, which is a self-contained, highly compressed indexing algorithm. With the popularity of multi-core processors, parallel computing allows the FM-index to run faster by performing multiple computations simultaneously when possible. Our approach works by splitting input data into overlapping blocks

Di Zhang; Yunquan Zhang; Shengfei Liu; Xiaodi Huang

2008-01-01

284

Prioritization in Parallel Symbolic Computing  

Microsoft Academic Search

It is argued that scheduling is an important determinant of performance for many parallel symbolic computations, in addition\\u000a to the issues of dynamic load balancing and grain size control. We propose associating unbounded levels of priorities with\\u000a tasks and messages as the mechanism of choice for specifying scheduling strategies. We demonstrate how priorities can be used\\u000a in parallelizing computations in

Laxmikant V. Kalé; Balkrishna Ramkumar; Vikram A. Saletore; Amitabh Sinha

1992-01-01

285

Another view on parallel speedup  

Microsoft Academic Search

In this paper three models of parallel speedup are studied. They are fixed-size speedup, fixed-time speedup and memory-bounded speedup. Two sets of speedup formulations are derived for these three models. One set requires more information and gives more accurate estimation. Another set considers a simplified case and provides a clear picture of possible performance gain of parallel processing. The simplified

Xian-He Sun; Lionel M. Ni

1990-01-01

286

A parallel string search algorithm  

Microsoft Academic Search

A new parallel processing algorithm for solving string search problems is presented. The proposed algorithm uses O(m×n) processors where n is the length of a text and m is the length of a pattern. It requires two and only two iteration steps to find the pattern in the text, while the best existing parallel algorithm needs the computation time O(loglog

Yoshiyasu Takefuji; Toshimitsu Tanaka; Kuo Chun Lee

1992-01-01

287

Adaptive Explicitly Parallel Instruction Computing  

Microsoft Academic Search

Poor scalability of Superscalar architectures with increasinginstruction-level parallelism (ILP) has resulted in a trend towards staticallyscheduled horizontal architectures such as Very Large Instruction Word(VLIW) processors and their more sophisticated successors called ExplicitlyParallel Instruction Computing (EPIC) architectures. We extend the EPiCmodel with additional capabilities to reconfigure the datapath at runtimein terms of the number and types of functional units...

Krishna V. Palem; Surendranath Talla; Patrick W. Devaney

1999-01-01

288

Parallel asynchronous particle swarm optimization  

PubMed Central

SUMMARY The high computational cost of complex engineering optimization problems has motivated the development of parallel optimization algorithms. A recent example is the parallel particle swarm optimization (PSO) algorithm, which is valuable due to its global search capabilities. Unfortunately, because existing parallel implementations are synchronous (PSPSO), they do not make efficient use of computational resources when a load imbalance exists. In this study, we introduce a parallel asynchronous PSO (PAPSO) algorithm to enhance computational efficiency. The performance of the PAPSO algorithm was compared to that of a PSPSO algorithm in homogeneous and heterogeneous computing environments for small- to medium-scale analytical test problems and a medium-scale biomechanical test problem. For all problems, the robustness and convergence rate of PAPSO were comparable to those of PSPSO. However, the parallel performance of PAPSO was significantly better than that of PSPSO for heterogeneous computing environments or heterogeneous computational tasks. For example, PAPSO was 3.5 times faster than was PSPSO for the biomechanical test problem executed on a heterogeneous cluster with 20 processors. Overall, PAPSO exhibits excellent parallel performance when a large number of processors (more than about 15) is utilized and either (1) heterogeneity exists in the computational task or environment, or (2) the computation-to-communication time ratio is relatively small.

Koh, Byung-Il; George, Alan D.; Haftka, Raphael T.; Fregly, Benjamin J.

2006-01-01

289

Parallel Algorithms For Globally Adaptive Quadrature  

Microsoft Academic Search

12Declaration 13Copyright 14The Author 15Acknowledgements 161 Introduction 172 Parallel Computing 232.1 Why use parallel computers? . . . . . . . . . . . . . . . . . . . . . 232.2 Architecture of parallel computers . . . . . . . . . . . . . . . . . . 242.2.1

Jonathan Mark Bull

1997-01-01

290

Parallel plasma fluid turbulence calculations  

SciTech Connect

The study of plasma turbulence and transport is a complex problem of critical importance for fusion-relevant plasmas. To this day, the fluid treatment of plasma dynamics is the best approach to realistic physics at the high resolution required for certain experimentally relevant calculations. Core and edge turbulence in a magnetic fusion device have been modeled using state-of-the-art, nonlinear, three-dimensional, initial-value fluid and gyrofluid codes. Parallel implementation of these models on diverse platforms--vector parallel (National Energy Research Supercomputer Center`s CRAY Y-MP C90), massively parallel (Intel Paragon XP/S 35), and serial parallel (clusters of high-performance workstations using the Parallel Virtual Machine protocol)--offers a variety of paths to high resolution and significant improvements in real-time efficiency, each with its own advantages. The largest and most efficient calculations have been performed at the 200 Mword memory limit on the C90 in dedicated mode, where an overlap of 12 to 13 out of a maximum of 16 processors has been achieved with a gyrofluid model of core fluctuations. The richness of the physics captured by these calculations is commensurate with the increased resolution and efficiency and is limited only by the ingenuity brought to the analysis of the massive amounts of data generated.

Leboeuf, J.N.; Carreras, B.A.; Charlton, L.A.; Drake, J.B.; Lynch, V.E.; Newman, D.E.; Sidikman, K.L.; Spong, D.A.

1994-12-31

291

Parallel Filter: A Visual Classifier Based on Parallel Coordinates and Multivariate Data Analysis  

NASA Astrophysics Data System (ADS)

Multivariate visualization techniques are often used as assistant tools for classification tasks up to now. However, few classification systems fully utilize the capability of multivariate visualization and integrate them with multivariate analysis algorithms into a compact system. We propose an interactive visual classification model based on some multivariate graphical presentation in this paper. As an example of it, a visual classifier based on parallel coordinates plot is developed. The multivariate data is first mapped to the parallel coordinates plot, and then an optimizer based on linear discriminant analysis optimizes it into the visualization more fit for classification tasks. This optimized visualization then can be processed by decision tree algorithm and attain classification rules. It has the merit of making the invisible visible and users can steer the classification process, consequently favor the understanding and knowledge discovery of original data.

Xu, Yonghong; Hong, Wenxue; Chen, Na; Li, Xin; Liu, Wenyuan; Zhang, Tao

292

Session-Based Programming for Parallel Algorithms: Expressiveness and Performance  

Microsoft Academic Search

This paper investigates session programming and typing of benchmark examples to compare pro- ductivity, safety and performance with other communications programming languages. Parallel al- gorithms are used to examine the above aspects due to their extensive use of message passing for interaction, and their increasing prominence in algorithmic research with the rising availability of hardware resources such as multicore machines

Andi Bejleri; Raymond Hu; Nobuko Yoshida

2010-01-01

293

Designing Interface Alternatives with Parallel Exploration and Runtime Tuning  

Microsoft Academic Search

Simultaneous externalization of design alternatives through multiple prototypes enables designers to see choices in context and facilitates comparative reasoning and discus- sion. This paper introduces two techniques for interactively manipulating multiple software alternatives. First, this work demonstrates a novel environment for constructing multiple design alternatives through (selectively) parallel editing and execution. Second, this environment's architecture intro- duces a mechanism for

Björn Hartmann; Loren Yu; Scott R. Klemmer

294

A neural network parallel algorithm for meeting schedule problems  

Microsoft Academic Search

A parallel algorithm for solving meeting schedule problems is presented in this paper, where the problem is NP-complete. The proposed system is composed of two maximum neural networks which interact with each other. One is an M X S neural network to assign meetings to available time slots on a timetable where M and S are the number of meetings

Kazuhiro Tsuchiya; Yoshiyasu Takefuji; Ken-ichi Kurotani; Kunio Wakahara

1996-01-01

295

Parallelization Issues and Particle-In Codes.  

NASA Astrophysics Data System (ADS)

"Everything should be made as simple as possible, but not simpler." Albert Einstein. The field of parallel scientific computing has concentrated on parallelization of individual modules such as matrix solvers and factorizers. However, many applications involve several interacting modules. Our analyses of a particle-in-cell code modeling charged particles in an electric field, show that these accompanying dependencies affect data partitioning and lead to new parallelization strategies concerning processor, memory and cache utilization. Our test-bed, a KSR1, is a distributed memory machine with a globally shared addressing space. However, most of the new methods presented hold generally for hierarchical and/or distributed memory systems. We introduce a novel approach that uses dual pointers on the local particle arrays to keep the particle locations automatically partially sorted. Complexity and performance analyses with accompanying KSR benchmarks, have been included for both this scheme and for the traditional replicated grids approach. The latter approach maintains load-balance with respect to particles. However, our results demonstrate it fails to scale properly for problems with large grids (say, greater than 128-by-128) running on as few as 15 KSR nodes, since the extra storage and computation time associated with adding the grid copies, becomes significant. Our grid partitioning scheme, although harder to implement, does not need to replicate the whole grid. Consequently, it scales well for large problems on highly parallel systems. It may, however, require load balancing schemes for non-uniform particle distributions. Our dual pointer approach may facilitate this through dynamically partitioned grids. We also introduce hierarchical data structures that store neighboring grid-points within the same cache -line by reordering the grid indexing. This alignment produces a 25% savings in cache-hits for a 4-by-4 cache. A consideration of the input data's effect on the simulation may lead to further improvements. For example, in the case of mean particle drift, it is often advantageous to partition the grid primarily along the direction of the drift. The particle-in-cell codes for this study were tested using physical parameters, which lead to predictable phenomena including plasma oscillations and two-stream instabilities. An overview of the most central references related to parallel particle codes is also given.

Elster, Anne Cathrine

1994-01-01

296

Massively parallel MRI detector arrays.  

PubMed

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas via reception, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called "ultimate" SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

Keil, Boris; Wald, Lawrence L

2013-02-07

297

Visualizing parallel computer system performance  

SciTech Connect

Parallel computer systems are among the most complex of man's creations, making satisfactory performance characterization difficult. Despite this complexity, there are strong, indeed, almost irresistible, incentives to quantify parallel system performance using a single metric. The fallacy lies in succumbing to such temptations. A complete performance characterization requires not only an analysis of the system's constituent levels, it also requires both static and dynamic characterizations. Static or average behavior analysis may mask transients that dramatically alter system performance. Although the human visual system is remarkedly adept at interpreting and identifying anomalies in false color data, the importance of dynamic, visual scientific data presentation has only recently been recognized. Large, complex parallel systems pose equally vexing performance interpretation problems. Data from hardware and software performance monitors must be presented in ways that emphasize important events while eliding irrelevant details. Design approaches and tools for performance visualization are the subject of this paper.

Malony, A.D.; Reed, D.A. (Illinois Univ., Urbana, IL (USA). Dept. of Computer Science)

1988-01-01

298

Fast data parallel polygon rendering  

SciTech Connect

This paper describes a parallel method for polygonal rendering on a massively parallel SIMD machine. This method, based on a simple shading model, is targeted for applications which require very fast polygon rendering for extremely large sets of polygons such as is found in many scientific visualization applications. The algorithms described in this paper are incorporated into a library of 3D graphics routines written for the Connection Machine. The routines are implemented on both the CM-200 and the CM-5. This library enables a scientists to display 3D shaded polygons directly from a parallel machine without the need to transmit huge amounts of data to a post-processing rendering system.

Ortega, F.A.; Hansen, C.D.

1993-09-01

299

Massively parallel MRI detector arrays  

NASA Astrophysics Data System (ADS)

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas via reception, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called "ultimate" SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays.

Keil, Boris; Wald, Lawrence L.

2013-04-01

300

Two portable parallel tridiagonal solvers  

SciTech Connect

Many scientific computer codes involve linear systems of equations which are coupled only between nearest neighbors in a single dimension. The most common situation can be formulated as a tridiagonal matrix relating source terms and unknowns. This system of equations is commonly solved using simple forward and back substitution. The usual algorithm is spectacularly ill suited for parallel processing with distributed data, since information must be sequentially communicated across all domains. Two new tridiagonal algorithms have been implemented in FORTRAN 77. The two algorithms differ only in the form of the unknown which is to be found. The first and simplest algorithm solves for a scalar quantity evaluated at each point along the single dimension being considered. The second algorithm solves for a vector quantity evaluated at each point. The solution method is related to other recently published approaches, such as that of Bondeli. An alternative parallel tridiagonal solver, used as part of an Alternating Direction Implicit (ADI) scheme, has recently been developed at LLNL by Lambert. For a discussion of useful parallel tridiagonal solvers, see the work of Mattor, et al. Previous work appears to be concerned only with scalar unknowns. This paper presents a new technique which treats both scalar and vector unknowns. There is no restriction upon the sizes of the subdomains. Even though the usual tridiagonal formulation may not be theoretically optimal when used iteratively, it is used in so many computer codes that it appears reasonable to write a direct substitute for it. The new tridiagonal code can be used on parallel machines with a minimum of disruption to pre-existing programming. As tested on various parallel computers, the parallel code shows efficiency greater than 50% (that is, more than half of the available computer operations are used to advance the calculation) when each processor is given at least 100 unknowns for which to solve.

Eltgroth, P.G.

1994-07-15

301

Hybrid parallel programming with MPI and Unified Parallel C.  

SciTech Connect

The Message Passing Interface (MPI) is one of the most widely used programming models for parallel computing. However, the amount of memory available to an MPI process is limited by the amount of local memory within a compute node. Partitioned Global Address Space (PGAS) models such as Unified Parallel C (UPC) are growing in popularity because of their ability to provide a shared global address space that spans the memories of multiple compute nodes. However, taking advantage of UPC can require a large recoding effort for existing parallel applications. In this paper, we explore a new hybrid parallel programming model that combines MPI and UPC. This model allows MPI programmers incremental access to a greater amount of memory, enabling memory-constrained MPI codes to process larger data sets. In addition, the hybrid model offers UPC programmers an opportunity to create static UPC groups that are connected over MPI. As we demonstrate, the use of such groups can significantly improve the scalability of locality-constrained UPC codes. This paper presents a detailed description of the hybrid model and demonstrates its effectiveness in two applications: a random access benchmark and the Barnes-Hut cosmological simulation. Experimental results indicate that the hybrid model can greatly enhance performance; using hybrid UPC groups that span two cluster nodes, RA performance increases by a factor of 1.33 and using groups that span four cluster nodes, Barnes-Hut experiences a twofold speedup at the expense of a 2% increase in code size.

Dinan, J.; Balaji, P.; Lusk, E.; Sadayappan, P.; Thakur, R.; Mathematics and Computer Science; The Ohio State Univ.

2010-01-01

302

Detecting coarse-grain parallelism using an interprocedural parallelizing compiler  

Microsoft Academic Search

This paper presents an extensive empirical evaluation of an interprocedural parallelizing compiler, developed as part of the Stanford SUIF compiler system. The system incorporates a comprehensive and integrated collection of analyses, including privatization and reduction recognition for both array and scalar variables, and symbolic analysis of array subscripts. The interprocedural analysis framework is designed to provide analysis results nearly as

Mary H. Hall; Saman P. Amarasinghe; Brian R. Murphy; Shih-Wei Liao; Monica S. Lam

1995-01-01

303

Constructions: Parallel Through A Point  

NSDL National Science Digital Library

After review of Construction Basics, the technique of constructing a parallel line through a point not on the line will be learned. Let's review the basics of Constructions in Geometry first: Constructions - General Rules Review of how to copy an angle is helpful; please review that here: Constructions: Copy a Line Segment and an Angle Now, using a paper, pencil, straight edge, and compass, you will learn how to construct a parallel through a point. A video demonstration is available to help you. (Windows Media ...

Neubert, Mrs.

2010-12-31

304

Gang scheduling a parallel machine  

SciTech Connect

Program development on parallel machines can be a nightmare of scheduling headaches. We have developed a portable time sharing mechanism to handle the problem of scheduling gangs of processes. User programs and their gangs of processes are put to sleep and awakened by the gang scheduler to provide a time sharing environment. Time quantum are adjusted according to priority queues and a system of fair share accounting. The initial platform for this software is the 128 processor BBN TC2000 in use in the Massively Parallel Computing Initiative at the Lawrence Livermore National Laboratory.

Gorda, B.C.; Brooks, E.D. III.

1991-12-01

305

Gang scheduling a parallel machine  

SciTech Connect

Program development on parallel machines can be a nightmare of scheduling headaches. We have developed a portable time sharing mechanism to handle the problem of scheduling gangs of processors. User program and their gangs of processors are put to sleep and awakened by the gang scheduler to provide a time sharing environment. Time quantums are adjusted according to priority queues and a system of fair share accounting. The initial platform for this software is the 128 processor BBN TC2000 in use in the Massively Parallel Computing Initiative at the Lawrence Livermore National Laboratory. 2 refs., 1 fig.

Gorda, B.C.; Brooks, E.D. III.

1991-03-01

306

Vectorized and Parallelized Algorithms for Multi-Million Particle Md-Simulation  

NASA Astrophysics Data System (ADS)

We present fully vectorized and parallelized algorithms for the molecular dynamics simulation of particle systems with short-range interaction. Speed of million particle updates per second are achieved with modern vector and parallel computers, thus making the simulation of million particle systems possible. We present results for the Cray YMP, JAERI/NEC MONTE-4 vector computers and the Intel Paragon XP/S and Thinking Machine CM-5 parallel computers.

Form, Wolfgang; Ito, Nobuyasu; Kohring, Gregory A.

307

Approximate Time-Parallel Cache Simulation  

Microsoft Academic Search

In time-parallel simulation, the simulation time axis is de- composed into a number of slices which are assigned to parallel processes for concurrent simulation. Although a promising parallelization technique, it is difficult to be ap- plied. Recently, using approximation with time-parallel simulation has been proposed to extend the class of suit- able models and to improve the performance of existing

Tobias Kiesling

2004-01-01

308

A Parallel Communication Infrastructure for STAPL  

Microsoft Academic Search

Communicationis an important but difficult as- pect of parallel programming. This paper describes a parallel communication infrastructure, based on remote method invo- cation, to simplify parallel programming by abstracting low- level shared-memory or message passing details while main- taining high performance and portability. STAPL, the Stan- dard Template Adaptive Parallel Library, builds upon this in- frastructure to make communication transparent

Steven Saunders; Lawrence Rauchwerger

309

Residual Splash for Optimally Parallelizing Belief Propagation  

Microsoft Academic Search

As computer architectures move towards multi- core we must build a theoretical understanding of parallelism in machine learning. In this paper we focus on parallel inference in graphical mod- els. We demonstrate that the natural, fully syn- chronous parallelization of belief propagation is highly inefficient. By bounding the achievable parallel performance in chain graphical models we develop a theoretical understanding

Joseph E. Gonzalez; Yucheng Low; Carlos Guestrin

2009-01-01

310

Performance considerations for parallel FFT algorithms  

Microsoft Academic Search

The authors describe parallel algorithm performance evaluation in a programming and instrumentation environment (PIE), an environment geared toward efficient parallel programming and the prediction, implementation, measurement, and evaluation of parallel fast Fourier transform (FFT) algorithms. An example of a mature technology for evaluating parallel applications is provided, emphasizing the need for integration between modeling and measurements. Performance tradeoffs for a

Masakatsu Kosaka; Zary Segall

1990-01-01

311

Parallel p-code for parallel Pascal and other high level languages  

SciTech Connect

Parallel p-code is an intermediate compiler language for parallel processors. It was originally designed as part of a parallel Pascal compiler for NASA's massively parallel processor (MPP). However, it should also be suitable for a wide variety of high level languages and parallel architectures. Parallel p-code is based on a p-code language for serial processors. The authors describe the extensions which were necessary for the parallel environment. 6 references.

Bruner, J.D.; Reeves, A.P.

1983-01-01

312

Parallel P-code for Parallel Pascal and other high level languages  

SciTech Connect

Parallel P-code is an intermediate compiler language for parallel processors. It was originally designed as part of a Parallel Pascal compiler for NASA's Massively Parallel Processor (MPP). However, it should also be suitable for a wide variety of high level languages and parallel architectures. Parallel P-code is based on a P-code language for serial processors; this paper describes the extensions which were necessary for the parallel environment.

Bruner, J.D.; Reeves, A.P.

1983-07-21

313

Experimental Assessment of Parallel Systems  

Microsoft Academic Search

In the research reported in this paper, transient faults were injected in the nodes and in the communication subsystem (by using software fault injection) of a commercial parallel machine running several real applications. The results showed that a significant percentage of faults caused the system to produce wrong results while the application seemed to terminate normally, thus demonstrating that fault

João Gabriel Silva; Joao Carreira; Henrique Madeira; Francisco Moreira; P. Moreira

1996-01-01

314

Parallel performance characteristics of ICEPIC  

Microsoft Academic Search

Fast, efficient results from the ICEPIC (improved concurrent electromagnetic particle in cell) code are key to the Air Force Research Laboratory's efforts to design high power microwave sources for electronic warfare and nonlethal weaponry. Parallelization of ICEPIC allows the use of DoD supercomputer assets to perform device simulations which would previously have been impossible, and also to obtain these results

P. Mardahl; A. Greenwood; T. Murphy; K. Cartwright

2003-01-01

315

Ejs Parallel Plate Capacitor Model  

NSDL National Science Digital Library

The Ejs Parallel Plate Capacitor model displays a parallel-plate capacitor which consists of two identical metal plates, placed parallel to one another. The capacitor can be charged by connecting one plate to the positive terminal of a battery and the other plate to the negative terminal. The dielectric constant and the separation of the plates can be changed via sliders. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. Ejs Parallel Plate Capacitor model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_capacitor.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Duffy, Andrew

2008-07-14

316

Parallel, Distributed Scripting with Python  

SciTech Connect

Parallel computers used to be, for the most part, one-of-a-kind systems which were extremely difficult to program portably. With SMP architectures, the advent of the POSIX thread API and OpenMP gave developers ways to portably exploit on-the-box shared memory parallelism. Since these architectures didn't scale cost-effectively, distributed memory clusters were developed. The associated MPI message passing libraries gave these systems a portable paradigm too. Having programmers effectively use this paradigm is a somewhat different question. Distributed data has to be explicitly transported via the messaging system in order for it to be useful. In high level languages, the MPI library gives access to data distribution routines in C, C++, and FORTRAN. But we need more than that. Many reasonable and common tasks are best done in (or as extensions to) scripting languages. Consider sysadm tools such as password crackers, file purgers, etc ... These are simple to write in a scripting language such as Python (an open source, portable, and freely available interpreter). But these tasks beg to be done in parallel. Consider the a password checker that checks an encrypted password against a 25,000 word dictionary. This can take around 10 seconds in Python (6 seconds in C). It is trivial to parallelize if you can distribute the information and co-ordinate the work.

Miller, P J

2002-05-24

317

Coupled parallel waveguide semiconductor laser  

SciTech Connect

The operation of a new type of tunable laser, where the two separately controlled individual lasers are placed vertically in parallel, has been demonstrated. One of the cavities (''control'' cavity) is operated below threshold and assists the longitudinal mode selection and tuning of the other laser. With a minor modification, the same device can operate as an independent two-wavelength laser source.

Mukai, S.; Kapon, E.; Katz, J.; Lindsey, C.; Rav-Noy, Z.; Margalit, S.; Yariv, A.

1984-03-01

318

Cathodic protection with parallel cylinders  

Microsoft Academic Search

This paper reports that anodes should be placed so as to supply a uniform current density to the surface of the protected cathode to maintain it within a specified potential range relative to the adjacent electrolytic medium. Analysis of two or more parallel circular cylinders is carried out by solving Laplace's equation with the uniform current density on the cathode.

John Newman

1991-01-01

319

Bloom and Hypertext: Parallel Taxonomies?  

ERIC Educational Resources Information Center

Discusses parallels between Bloom's taxonomy for cognitive learning outcomes and hypertext design, and argues that hypertext designs should be consistent with desired learning outcomes. Bloom's taxonomy is explained; hypertext designs are described and diagrammed; and the need for more research connecting hypertext design and effective learning is…

Ross, Tweed W.

1993-01-01

320

Coarray Fortran for parallel programming  

Microsoft Academic Search

Co-Array Fortran, formerly known as F--, is a small extension of Fortran 95 for parallel processing. A Co-Array Fortran program is interpreted as if it were replicated a number of times and all copies were executed asynchronously. Each copy has its own set of data objects and is termed an image. The array syntax of Fortran 95 is extended with

Robert W. Numrich; John Reid

1998-01-01

321

Making Massively Parallel Systems Work  

Microsoft Academic Search

Massively parallel systems are based on distributed memory concepts and consistof several hundreds to thousands of nodes interconnected by a very highbandwidth network. Making these systems work requires a very careful operatingsystem design. A distributed operating system is required that takesthe form of a functionally dedicated server system. This approach reduces systemoverhead on the nodes and enables a problem-oriented mapping

R. Berg; J. Cordsen; J. Heuer; J. Nolte; B. Oestmann; M. Sander; H. Schmidt; F. Schön; W. Schröder-preikschat

1990-01-01

322

Microeconomic Scheduler for Parallel Computers.  

National Technical Information Service (NTIS)

We describe a scheduler based on the microeconomic paradigm for scheduling on-line a set of parallel jobs in a multiprocessor system. In addition to increasing the system throughput and reducing the response time, we consider fairness in allocating system...

I. Stoica H. Abdel-Wahab

1995-01-01

323

Aligning Sentences in Parallel Corpora  

Microsoft Academic Search

In this paper we describe a statistical technique for aligning sentences with their translations in two parallel corpora. In addition to certain anchor points that are available in our data, the only information about the sentences that we use for calculating alignments is the number of tokens that they contain. Because we make no use of the lexical details of

Peter F. Brown; Jennifer C. Lai; Robert L. Mercer

1991-01-01

324

Microeconomic Scheduler for Parallel Computers.  

National Technical Information Service (NTIS)

We describe a scheduler based on the microeconomic paradigm for scheduling on-line a set of parallel jobs in a multiprocessor system. In addition to the classical objectives of increasing the system throughput and reducing the response time, we consider f...

I. Stoica H. Abdel-wahab A. Pothen

1995-01-01

325

Parallel Programming Examples using MPI  

NSDL National Science Digital Library

Despite the rate at which computers have advanced in recent history, human imagination has advanced faster. Often greater computing power can be achieved by having multiple computers work together on a single problem. This tutorial discusses how Message Passing Interface (MPI) can be used to implement parallel programming solutions in a variety of cases.

Joiner, David; The Shodor Education Foundation, Inc.

326

Scalable parallel suffix array construction  

Microsoft Academic Search

Abstract. Suffix arrays are a simple and powerful data structure for text processing that can be used for full text indexes, data compression, and many,other applications in particular in bioinformatics. We describe the first implementation and experimental evaluation of a scalable parallel algorithm for suffix array construction. The implementation works on distributed memory computers using MPI, Experiments with up to

Fabian Kulla; Peter Sanders

2007-01-01

327

The plane with parallel coordinates  

Microsoft Academic Search

By means ofParallel Coordinates planar “graphs” of multivariate relations are obtained. Certain properties of the relationship correspond tothe geometrical properties of its graph. On the plane a point ?? line duality with several interesting properties is induced. A new duality betweenbounded and unbounded convex sets and hstars (a generalization of hyperbolas) and between Convex Unions and Intersections is found. This

Alfred Inselberg

1985-01-01

328

Resequencing Considerations in Parallel Downloads  

Microsoft Academic Search

Several recent studies have proposed methods to ac- celerate the receipt of a file by downloading its parts from differ- ent servers in parallel. This paper formulates models for an ap- proach based on receiving only one copy of each of the data pack- ets in a file, while different packets may be obtained from different sources. This approach guarantees

Yoav Nebat; Moshe Sidi

2002-01-01

329

Portable Parallel Programming in HPC  

Microsoft Academic Search

HPC++ is a C++ library and language extension framework that is being developed by the HPC++ consortium as a standard model for portable parallel C++ programming. This paper provides a brief introduction to HPC++ style programming and outlines some of the unresolved issues

Peter H. Beckman; Dennis Gannon; Elizabeth Johnson

1996-01-01

330

Cluster-based parallel image processing toolkit  

NASA Astrophysics Data System (ADS)

Many image processing tasks exhibit a high degree of data locality and parallelism and map quite readily to specialized massively parallel computing hardware. However, as network technologies continue to mature, workstation clusters are becoming a viable and economical parallel computing resource, so it is important to understand how to use these environments for parallel image processing as well. In this paper we discuss our implementation of parallel image processing software library (the Parallel Image Processing Toolkit). The Toolkit uses a message- passing model of parallelism designed around the Message Passing Interface (MPI) standard. Experimental results are presented to demonstrate the parallel speedup obtained with the Parallel Image Processing Toolkit in a typical workstation cluster over a wide variety of image processing tasks. We also discuss load balancing and the potential for parallelizing portions of image processing tasks that seem to be inherently sequential, such as visualization and data I/O.

Squyres, J. M.; Lumsdaine, A.; Stevenson, Robert L.

1995-03-01

331

Softspec: Software-based Speculative Parallelism  

Microsoft Academic Search

We present Softspec, a technique for parallelizing sequential applications using a hybrid compile-time and run-time technique. Softspec parallelizes loops whose memory references are stride-predictable. By detecting and speculatively executing potential parallelism at runtime Softspec eliminates the need for complex program analysis required by parallelizing compilers. By using runtime information Softspec succeeds in parallelizing loops whose memory access patterns are statically...

Derek Bruening; Srikrishna Devabhaktuni; Saman Amarasinghe

2000-01-01

332

Reservoir Thermal Recover Simulation on Parallel Computers  

Microsoft Academic Search

The rapid development of parallel computers has provided a hardware background for massive refine reservoir simulation. However,\\u000a the lack of parallel reservoir simulation software has blocked the application of parallel computers on reservoir simulation.\\u000a Although a variety of parallel methods have been studied and applied to black oil, compositional, and chemical model numerical\\u000a simulations, there has been limited parallel software

Baoyan Li; Yuanle Ma

2000-01-01

333

Identification of mercury and other metals complexes with metallothioneins in dolphin liver by hydrophilic interaction liquid chromatography with the parallel detection by ICP MS and electrospray hybrid linear/orbital trap MS/MS.  

PubMed

A novel analytical procedure for the identification of metal (Hg, Cd, Cu, Zn) complexes with individual metallothionein (MT) isoforms in biological tissues by electrospray MS/MS was developed. The sample preparation was reduced to three rapid steps: the two-fold dilution of the sample cytosol with acetonitrile, the recovery of the supernatant containing MT-complexes by centrifugation and its concentration under nitrogen flow. The replacement of reversed phase HPLC by hydrophilic interaction LC (HILIC) allowed the preservation of the unstable and low abundant metallothionein zinc-mercury mixed complexes (MT-Zn(6)Hg). The MT complexes eluted were detected by ICP MS and identified in terms of molecular mass by electrospray high resolution (100,000) MS. The identification was completed by on line demetallation and the determination of the molecular mass of the apoform, followed by amino acid sequencing in the top-down mode using high energy collision fragmentation (HCD). The method was applied to the identification of MT complexes in a white-sided dolphin (Lagenorhynchus acutus) liver homogenate. The Zn complex of the N-acetylated MT2 isoform was found to be predominant, the presence of mixed complexes with Cd, Cu and, for the first time ever, Hg, was demonstrated. The latter finding has the potential to shed new light on the mercury detoxification mechanism in marine organisms. PMID:22456936

Pedrero, Z; Ouerdane, L; Mounicou, S; Lobinski, R; Monperrus, M; Amouroux, D

2012-03-29

334

A mechanism for efficient debugging of parallel programs  

SciTech Connect

This paper addresses the design and implementation of an integrated debugging system for parallel programs running on shared memory multi-processors (SMMP). The authors describe the use of flowback analysis to provide information on causal relationships between events in a program's execution without re-executing the program for debugging. The authors introduce a mechanism called incremental tracing that, by using semantic analyses of the debugged program, makes the flowback analysis practical with only a small amount of trace generated during execution. The extend flowback analysis to apply to parallel programs and describe a method to detect race conditions in the interactions of the co-operating processes.

Miller, B.P.; Choi, J.D.

1988-01-01

335

Evolutionary approach to optimal design of 3 DOF translation exoskeleton and medical parallel robots  

Microsoft Academic Search

Parallel robots find many applications in human-systems interaction, medical robots, rehabilitation, exoskeletons, to name a few. These applications are characterized by many imperatives, with robust precision and dynamic workspace computation as the two ultimate ones. This paper presents a multi-objective optimum design procedure to 3 degrees of freedom (DOF) parallel robots with regards to four optimality criteria: workspace boundary, transmission

Sergiu-Dan Stan; Milos Manic; V. Maties; R. Balan

2008-01-01

336

Web based parallel/distributed medical data mining using software agents  

SciTech Connect

This paper describes an experimental parallel/distributed data mining system PADMA (PArallel Data Mining Agents) that uses software agents for local data accessing and analysis and a web based interface for interactive data visualization. It also presents the results of applying PADMA for detecting patterns in unstructured texts of postmortem reports and laboratory test data for Hepatitis C patients.

Kargupta, H.; Stafford, B.; Hamzaoglu, I.

1997-12-31

337

Parallel algorithms and architectures for CPUs and dedicated processors: development and trends  

Microsoft Academic Search

Parallel algorithms are usually intended as those related to problems to be run on supercomputers characterized by a large number of processors interacting via a communication network. Parallel algorithms and architectures are relevant also at a lower levels. Of particular interest is the CPU level where elementary arithmetic (and higher order) operations are executed. It might be surprising to notice

Luigi Dadda

1995-01-01

338

Cellular automata with object-oriented features for parallel molecular network modeling  

Microsoft Academic Search

Cellular automata are an important modeling paradigm for studying the dynamics of large, parallel systems composed of multiple, interacting components. However, to model biological systems, cellular automata need to be extended beyond the large-scale parallelism and intensive communication in order to capture two fundamental properties characteristic of complex biological systems: hierarchy and heterogeneity. This paper proposes extensions to a cellular

Hao Zhu; Yinghui Wu; Sui Huang; Yan Sun; Pawan Dhar

2005-01-01

339

Non-Uniform Flow Behavior in a Parallel Plate Flow Chamber Alters Endothelial Cell Responses  

Microsoft Academic Search

Arterial flow characteristics determine vessel health by modulating vascular endothelial cells. One system used to study these interactions is the parallel plate flow chamber. The present in vitro study quantified the uniformity of fluid flow across a parallel plate flow chamber and characterized plate-location dependent endothelial cell gene expression. More specifically, shear stress varied by as much as 11% across

Jennifer A. McCann; Sean D. Peterson; Michael W. Plesniak; Thomas J. Webster; Karen M. Haberstroh

2005-01-01

340

Parallel test description and analysis of parallel test system speedup through Amdahl's law  

Microsoft Academic Search

This paper will outline various types of parallel test, discuss an adaptation of Amdahl's law to parallel test, and discuss possible extensions to ATML for parallel test. Amdahl's law is an equation in computer science that is used to derive the speedup gained through parallelizing the software; it expresses the speedup as a function of number of processors. Parallel test

Nathan Waivio; Rolling Meadows

2007-01-01

341

Numerical analysis and parallel processing  

SciTech Connect

Each week of this three week meeting was a self-contained event, although each had the same underlying theme-the effect of parallel processing on numerical analysis. Each week provided the opportunity for intensive study to broaden participants' research interests or deepen their understanding of topics of which they already had some knowledge. There was also the opportunity for continuing individual research in the stimulating environment created by the presence of several experts of international stature. This book contains lecture notes for most of the major courses of lectures presented at the meeting; they cover topics in parallel algorithms for large sparse linear systems and optimization, an introductory survey of level-index arithmetic and superconvergence in the finite element method.

Turner, P.R. (U.S. Naval Academy, Annapolis, MD (US))

1989-01-01

342

Parallel supercomputing with commodity components  

SciTech Connect

We have implemented a parallel computer architecture based entirely upon commodity personal computer components. Using 16 Intel Pentium Pro microprocessors and switched fast ethernet as a communication fabric, we have obtained sustained performance on scientific applications in excess of one Gigaflop. During one production astrophysics treecode simulation, we performed 1.2 x 10{sup 15} floating point operations (1.2 Petaflops) over a three week period, with one phase of that simulation running continuously for two weeks without interruption. We report on a variety of disk, memory and network benchmarks. We also present results from the NAS parallel benchmark suite, which indicate that this architecture is competitive with current commercial architectures. In addition, we describe some software written to support efficient message passing, as well as a Linux device driver interface to the Pentium hardware performance monitoring registers.

Warren, M.S.; Goda, M.P. [Los Alamos National Lab., NM (United States); Becker, D.J. [Goddard Space Flight Center, Greenbelt, MD (United States)] [and others

1997-09-01

343

Parallel Materialization of Large ABoxes  

PubMed Central

This paper is concerned with the efficient computation of materialization in a knowledge base with a large ABox. We present a framework for performing this task on a shared-nothing parallel machine. The framework partitions TBox and ABox axioms using a min-min strategy. It utilizes an existing system, like SwiftOWLIM, to perform local inference computations and coordinates exchange of relevant information between processors. Our approach is able to exploit parallelism in the axioms of the TBox to achieve speedup in a cluster. However, this approach is limited by the complexity of the TBox. We present an experimental evaluation of the framework using datasets from the Lehigh University Benchmark (LUBM).

Narayanan, Sivaramakrishnan; Catalyurek, Umit; Kurc, Tahsin; Saltz, Joel

2011-01-01

344

Algorithms for parallel polygon rendering  

SciTech Connect

This book is the result of research in the implementation of polygon-based graphics operations on certain general purpose parallel processors; the aim is to provide a speed-up over sequential implementations of the graphics operations concerned, and the resulting software can be viewed as a subset of the application suites of the relevant parallel machines. A literature review and a brief description of the architectures considered give an introduction into the field. Most algorithms are consistently presented in an extension of the Occam language which includes single instruction multiple data stream (SIMD) data types and operations on them. Methods for polygon rendering - including the operations of filling, hidden surface elimination and smooth shading - are presented for SIMD architectures like the DAP and for a dual-paradigm (SIMD-MIMD) machine constructed out of a DAP-like processor array and a transputer network. Polygon clipping algorithms for both transputer and the DAP are described and contrasted.

Theoharis, T. (St. Catherine's College, Cambridge (GB))

1989-01-01

345

An efficient SAR parallel processor  

Microsoft Academic Search

A parallel architecture especially designed for a synthetic-aperture-radar (SAR) processing algorithm based on an appropriate two-dimensional fast Fourier transform (FFT) code is presented. The algorithm is briefly summarized, and the FFT code is given for the one-dimensional case, although all results can be immediately generalized to the double FFT. The computer architecture, which consists of a toroidal net with transputers

Giorgio Franceschetti; ANTONINO MAZZEO; NICOLA MAZZOCCA; V. Pascazio; GILDA SCHIRINZI

1991-01-01

346

The Jitney Parallel Optical Interconnect  

Microsoft Academic Search

The Jitney Parallel Optical Interconnect consists of a transmitter module, a receiver module, and a cable capable of sending 1 GigaByte\\/sec over 1-100 meter spans. This technology has been developed to be cost competitive with copper bus technology, while still offering all the features of optical interconnects. Jitney has a two Byte wide interface with extra lines for clocking and

J. D. Crow; Joong-Ho Choi; M. S. Cohen; G. Johnson; D. Kuchta; D. Lacey; S. Ponnapalli; P. Pepeljugoski; K. Stawiasz; J. Trewhella; P. Xiao; S. Tremblay; S. Ouimet; A. Lacerte; M. Gauvin; D. Booth; W. Nation; T. L. Smith; B. A. DeBaun; G. D. Henson; S. A. Igl; N. A. Lee; A. J. Piekarczyk; A. S. Kuczma; S. L. Spanoudis

1996-01-01

347

Parallel Structured Adaptive Mesh Refinement  

Microsoft Academic Search

Parallel structured adaptive mesh refinement is a technique for efficient utilization of computational resources. It reduces\\u000a the computational effort and memory requirements needed for numerical simulation of complex phenomena, described by partial\\u000a differential equations. Structured adaptive mesh refinement (SAMR) is applied in simulations where the domain is divided into\\u000a logically rectangular patches, where each patch is discretized with a structured

Jarmo Rantakokko; Michael Thuné

348

Load balancing for parallel forwarding  

Microsoft Academic Search

Workload distribution is critical to the performance of network processor based parallel forwarding systems. Scheduling schemes that operate at the packet level, e.g., round-robin, cannot preserve packet-ordering within individual TCP connections. Moreover, these schemes create duplicate information in processor caches and therefore are inefficient in resource utilization. Hashing operates at the flow level and is naturally able to maintain per-connection

Weiguang Shi; M. H. MacGregor; Pawel Gburzynski

2005-01-01

349

Parallel strategies for SAR processing  

NASA Astrophysics Data System (ADS)

This article proposes a series of strategies for improving the computer process of the Synthetic Aperture Radar (SAR) signal treatment, following the three usual lines of action to speed up the execution of any computer program. On the one hand, it is studied the optimization of both, the data structures and the application architecture used on it. On the other hand it is considered a hardware improvement. For the former, they are studied both, the usually employed SAR process data structures, proposing the use of parallel ones and the way the parallelization of the algorithms employed on the process is implemented. Besides, the parallel application architecture classifies processes between fine/coarse grain. These are assigned to individual processors or separated in a division among processors, all of them in their corresponding architectures. For the latter, it is studied the hardware employed on the computer parallel process used in the SAR handling. The improvement here refers to several kinds of platforms in which the SAR process is implemented, shared memory multicomputers, and distributed memory multiprocessors. A comparison between them gives us some guidelines to follow in order to get a maximum throughput with a minimum latency and a maximum effectiveness with a minimum cost, all together with a limited complexness. It is concluded and described, that the approach consisting of the processing of the algorithms in a GNU/Linux environment, together with a Beowulf cluster platform offers, under certain conditions, the best compromise between performance and cost, and promises the major development in the future for the Synthetic Aperture Radar computer power thirsty applications in the next years.

Segoviano, Jesus A.

2004-12-01

350

Parallel multi-delay simulation  

Microsoft Academic Search

ABSTRACT The Multi-DelayPara llel (MDP) algorithm is an unconventional multi-delay algorithm in that it uses no timing wheel, or any event-sorting mechanism of any kind. Instead, wide bit-fields containing net values for several different times are used to resolve out-of-order events, and bit-parallel operations are performed to simulate the required gates. The MDP algorithm was designed to be implemented in

Yun Sik Lee; Peter M. Maurer

1993-01-01

351

Enabling parallel computing in CRASH  

NASA Astrophysics Data System (ADS)

We present the new parallel version (PCRASH2) of the cosmological radiative transfer code CRASH2 for distributed memory supercomputing facilities. The code is based on a static domain decomposition strategy inspired by geometric dilution of photons in the optical thin case that ensures a favourable performance speed-up with an increasing number of computational cores. Linear speed-up is ensured as long as the number of radiation sources is equal to the number of computational cores or larger. The propagation of rays is segmented and rays are only propagated through one sub-domain per time-step to guarantee an optimal balance between communication and computation. We have extensively checked PCRASH2 with a standardized set of test cases to validate the parallelization scheme. The parallel version of CRASH2 can easily handle the propagation of radiation from a large number of sources and is ready for the extension of the ionization network to species other than hydrogen and helium.

Partl, A. M.; Maselli, A.; Ciardi, B.; Ferrara, A.; Müller, V.

2011-06-01

352

UW Madison Libraries: Parallel Press  

NSDL National Science Digital Library

UW-Madison Libraries' Parallel Press combines book publishing traditions with new technology to provide print-on-demand books and a series of chapbooks (small, inexpensive books featuring the works of authors and poets with a Wisconsin connection). Print-on-demand books parallel the online editions created by the Libraries' digitizing initiatives. Currently, four titles, including David Hayman's A First-Draft Version of Finnegan's Wake (originally published in 1963) and The Book of Beasts (1954), by T.H. White, are available via Parallel Press print-on-demand service. The poetry chapbook series began in 1999 with the publication of four Wisconsin poets (Elizabeth Oness, Max Garland, Katharine Whitcomb, and Andrea Potos) and has continued with six chapbooks per year. A prose chapbook series began in 2002 with American Trilogy. This chapbook consists of historical reproductions of the American Declaration of Independence, Constitution, and Bill of Rights, with introductory material by UW Professor Stephen E. Lucas, and an afterword by John P. Kaminski, Director of the Center for the Study of the American Constitution -- published as part of a one year later, university-wide reflection, on the impact of the Sept. 11, 2001, terrorist attacks.

353

Parallel Environment for Quantum Computing  

NASA Astrophysics Data System (ADS)

To facilitate numerical study of noise and decoherence in QC algorithms,and of the efficacy of error correction schemes, we have developed a Fortran 90 quantum computer simulator with parallel processing capabilities. It permits rapid evaluation of quantum algorithms for a large number of qubits and for various ``noise'' scenarios. State vectors are distributed over many processors, to employ a large number of qubits. Parallel processing is implemented by the Message-Passing Interface protocol. A description of how to spread the wave function components over many processors, along with how to efficiently describe the action of general one- and two-qubit operators on these state vectors will be delineated.Grover's search and Shor's factoring algorithms with noise will be discussed as examples. A major feature of this work is that concurrent versions of the algorithms can be evaluated with each version subject to diverse noise effects, corresponding to solving a stochastic Schrodinger equation. The density matrix for the ensemble of such noise cases is constructed using parallel distribution methods to evaluate its associated entropy. Applications of this powerful tool is made to delineate the stability and correction of QC processes using Hamiltonian based dynamics.

Tabakin, Frank; Diaz, Bruno Julia

2009-03-01

354

NWChem: scalable parallel computational chemistry  

SciTech Connect

NWChem is a general purpose computational chemistry code specifically designed to run on distributed memory parallel computers. The core functionality of the code focuses on molecular dynamics, Hartree-Fock and density functional theory methods for both plane-wave basis sets as well as Gaussian basis sets, tensor contraction engine based coupled cluster capabilities and combined quantum mechanics/molecular mechanics descriptions. It was realized from the beginning that scalable implementations of these methods required a programming paradigm inherently different from what message passing approaches could offer. In response a global address space library, the Global Array Toolkit, was developed. The programming model it offers is based on using predominantly one-sided communication. This model underpins most of the functionality in NWChem and the power of it is exemplified by the fact that the code scales to tens of thousands of processors. In this paper the core capabilities of NWChem are described as well as their implementation to achieve an efficient computational chemistry code with high parallel scalability. NWChem is a modern, open source, computational chemistry code1 specifically designed for large scale parallel applications2. To meet the challenges of developing efficient, scalable and portable programs of this nature a particular code design was adopted. This code design involved two main features. First of all, the code is build up in a modular fashion so that a large variety of functionality can be integrated easily. Secondly, to facilitate writing complex parallel algorithms the Global Array toolkit was developed. This toolkit allows one to write parallel applications in a shared memory like approach, but offers additional mechanisms to exploit data locality to lower communication overheads. This framework has proven to be very successful in computational chemistry but is applicable to any engineering domain. Within the context created by the features above NWChem has grown into a general purpose computational chemistry code that supports a wide variety of energy expressions and capabilities to calculate properties based there upon. The main energy expressions are classical mechanics force fields, Hartree-Fock and DFT both for finite systems and condensed phase systems, coupled cluster, as well as QM/MM. For most energy expressions single point calculations, geometry optimizations, excited states, and other properties are available. Below we briefly discuss each of the main energy expressions and the critical points involved in scalable implementations thereof.

van Dam, Hubertus JJ; De Jong, Wibe A.; Bylaska, Eric J.; Govind, Niranjan; Kowalski, Karol; Straatsma, TP; Valiev, Marat

2011-11-01

355

Parallel processing of atmospheric chemistry calculations: Preliminary considerations  

SciTech Connect

Global climate calculations are already saturating the class modern vector supercomputers with only a few central processing units. Increased resolution and inclusion of routines to deal with biogeochemical portions of the terrestrial climate system will soon demand massively parallel approaches. The atmospheric photochemistry ensemble is intimately linked to climate through the trace greenhouse gases ozone and methane and modules for representing it are being attached to global three dimensional transport and GCM frameworks. Atmospheric kinetics involve dozens of highly interactive tracers and so will accentuate the need for parallel processing of earth system simulations. In the present text we lay some of the groundwork for addition of atmospheric kinetics packages to GCM and global scale atmospheric models on multiply parallel computers. The discussion is tailored for consumption by the photochemical modelling community. After a review of numerical atmospheric chemistry methods, we examine how kinetics can be implemented on a parallel computer. We concentrate especially on data layout and flexibility and how these can be implemented in various programming models. We conclude that chemistry can be implemented rather easily within existing frameworks of several parallel atmospheric models. However, memory limitations may preclude high resolution studies of global chemistry.

Elliott, S.; Jones, P.

1995-01-01

356

Multifrontal Parallel Distributed Symmetric and Unsymmetric Solvers.  

National Technical Information Service (NTIS)

The authors consider the solution of both symmetric of sparse linear equations. A new parallel distributed memory multifrontal approach is described. To handle numerical pivoting efficiently, a parallel asynchronous algorithm with dynamic scheduling of th...

P. R. Amestoy I. S. Duff J. Y. L'Excellent

1998-01-01

357

Multilist Scheduling. A New Parallel Programming Model.  

National Technical Information Service (NTIS)

Parallel programming requires task scheduling to optimize performance; this primarily involves balancing the load over the processors. In many cases, it is critical to perform task scheduling at runtime. For example, (1) in many parallel applications the ...

I. C. Wu H. T. Kung P. Steenkiste D. O'Hallaron G. Thompson

1993-01-01

358

Delft Parallel Processor 84/16.  

National Technical Information Service (NTIS)

The development of the Delft Parallel Processor started in 1976. Since then the machine has grown to a processor with 16 independently operating, but tightly connected processing elements. The parallel processor is supervised by a host processor. In the f...

J. H. M. Andriessen

1986-01-01

359

Massive Parallelism in the Future of Science.  

National Technical Information Service (NTIS)

Massive parallelism appears in three domains of action of concern to scientists, where it produces collective action that is not possible from any individual agent's behavior. In the domain of data parallelism, computers comprising very large numbers of p...

P. J. Denning

1988-01-01

360

Parallel computational fluid dynamics - Implementations and results  

SciTech Connect

The present volume on parallel CFD discusses implementations on parallel machines, numerical algorithms for parallel CFD, and performance evaluation and computer science issues. Attention is given to a parallel algorithm for compressible flows through rotor-stator combinations, a massively parallel Euler solver for unstructured grids, a fast scheme to analyze 3D disk airflow on a parallel computer, and a block implicit multigrid solution of the Euler equations. Topics addressed include a 3D ADI algorithm on distributed memory multiprocessors, clustered element-by-element computations for fluid flow, hypercube FFT and the Fourier pseudospectral method, and an investigation of parallel iterative algorithms for CFD. Also discussed are fluid dynamics using interface methods on parallel processors, sorting for particle flow simulation on the connection machine, a large grain mapping method, and efforts toward a Teraflops capability for CFD.

Simon, H.D.

1992-01-01

361

Parallel computational fluid dynamics - Implementations and results  

NASA Astrophysics Data System (ADS)

The present volume on parallel CFD discusses implementations on parallel machines, numerical algorithms for parallel CFD, and performance evaluation and computer science issues. Attention is given to a parallel algorithm for compressible flows through rotor-stator combinations, a massively parallel Euler solver for unstructured grids, a fast scheme to analyze 3D disk airflow on a parallel computer, and a block implicit multigrid solution of the Euler equations. Topics addressed include a 3D ADI algorithm on distributed memory multiprocessors, clustered element-by-element computations for fluid flow, hypercube FFT and the Fourier pseudospectral method, and an investigation of parallel iterative algorithms for CFD. Also discussed are fluid dynamics using interface methods on parallel processors, sorting for particle flow simulation on the connection machine, a large grain mapping method, and efforts toward a Teraflops capability for CFD.

Simon, Horst D.

362

Parallels between wind and crowd loading of bridges.  

PubMed

Parallels between the dynamic response of flexible bridges under the action of wind and under the forces induced by crowds allow each field to inform the other. Wind-induced behaviour has been traditionally classified into categories such as flutter, galloping, vortex-induced vibration and buffeting. However, computational advances such as the vortex particle method have led to a more general picture where effects may occur simultaneously and interact, such that the simple semantic demarcations break down. Similarly, the modelling of individual pedestrians has progressed the understanding of human-structure interaction, particularly for large-amplitude lateral oscillations under crowd loading. In this paper, guided by the interaction of flutter and vortex-induced vibration in wind engineering, a framework is presented, which allows various human-structure interaction effects to coexist and interact, thereby providing a possible synthesis of previously disparate experimental and theoretical results. PMID:23690640

McRobie, Allan; Morgenthal, Guido; Abrams, Danny; Prendergast, John

2013-05-20

363

Interactional analysis of suicidal behavior  

Microsoft Academic Search

Analyzes the limitations inherent in 5 empirical research models (pure environmental, pure individual differences, discrete parallel, nonparallel typological, and parallel typological models) that have been used to study suicidal behavior. These extant models are shown to have specific limitations in terms of their ability to reflect an interactional perspective on suicidal behavior. A more adequate research model was then developed

G. Nicholas Braucht

1979-01-01

364

ENABLING PRIMITIVES FOR COMPILING PARALLEL LANGUAGES  

Microsoft Academic Search

This paper presents three novel languageimplementation primitives---lazy threads,stacklets, andsynchronizers---andshows how they combine to provide a parallel call at nearly the efficiency ofa sequential call. The central idea is to transform parallel calls into parallel-ready sequential calls.Excess parallelism degrades into sequential calls with the attendant efficient stack managementand direct transfer of control and data, unless a call truly needs to execute

1995-01-01

365

Parallelizing Algorithms for Symbolic Computation using ||MAPLE||  

Microsoft Academic Search

kMAPLEk (speak: parallel Maple) is a portable system forparallel symbolic computation. The system is built as aninterface between the parallel declarative programming languageStrand and the sequential computer algebra systemMaple, thus providing the elegance of Strand and the powerof the existing sequential algorithms in Maple.The implementation of different parallel programmingparadigms shows that it is fairly easy to parallelize evencomplex algebraic algorithms

Kurt Siegl

1993-01-01

366

Hybrid Parallel Programming on HPC Platforms  

Microsoft Academic Search

Summary Most HPC systems are clusters of shared memory nodes. Parallel programming must combine the distributed mem- ory parallelization on the node inter-connect with the shared memory parallelization inside of each node. Various hybrid MPI+OpenMP programming models are compared with pure MPI. Benchmark results of several platforms are presented. This paper analyzes the strength and weakness of several parallel programming

Rolf Rabenseifner

2003-01-01

367

Debugging and analysis of large-scale parallel programs. Doctoral thesis  

SciTech Connect

One of the most serious problems in the development cycle of large-scale parallel programs is the lack of tools for debugging and performance analysis. Parallel programs are more difficult to analyze than their sequential counterparts for several reasons. First, race conditions in parallel programs can cause non-deterministic behavior, which reduces the effectiveness of traditional cyclic debugging techniques. Second, invasive, interactive analysis can distort a parallel program's execution beyond recognition. Finally, comprehensive analysis of a parallel program's execution requires collection, management, and presentation of an enormous amount of information. This dissertation addresses the problem of debugging and analysis of large-scale parallel programs executing on shared-memory multiprocessors. It proposes a methodology for top-down analysis of parallel program executions that replaces previous ad-hoc approaches. To support this methodology, a formal model for shared-memory communication among processes in a parallel program is developed. It is shown how synchronization traces based on this abstract model can be used to create indistinguishable executions that form the basis for debugging. This result is used to develop a practical technique for tracing parallel program executions on shared-memory parallel processors so that their executions can be repeated deterministically on demand.

Mellor-Crummey, J.M.

1989-09-01

368

Parallel MRI at microtesla fields  

PubMed Central

Parallel imaging techniques have been widely used in high-field magnetic resonance imaging (MRI). Multiple receiver coils have been shown to improve image quality and allow accelerated image acquisition. Magnetic resonance imaging at ultra-low fields (ULF MRI) is a new imaging approach that uses SQUID (superconducting quantum interference device) sensors to measure the spatially encoded precession of pre-polarized nuclear spin populations at microtesla-range measurement fields. In this work, parallel imaging at microtesla fields is systematically studied for the first time. A seven-channel SQUID system, designed for both ULF MRI and magnetoencephalography (MEG), is used to acquire 3D images of a human hand, as well as 2D images of a large water phantom. The imaging is performed at 46 microtesla measurement field with pre-polarization at 40 mT. It is shown how the use of seven channels increases imaging field of view and improves signal-to-noise ratio for the hand images. A simple procedure for approximate correction of concomitant gradient artifacts is described. Noise propagation is analyzed experimentally, and the main source of correlated noise is identified. Accelerated imaging based on one-dimensional undersampling and 1D SENSE (sensitivity encoding) image reconstruction is studied in the case of the 2D phantom. Actual 3-fold imaging acceleration in comparison to single-average fully encoded Fourier imaging is demonstrated. These results show that parallel imaging methods are efficient in ULF MRI, and that imaging performance of SQUID-based instruments improves substantially as the number of channels is increased.

Zotev, Vadim S.; Volegov, Petr L.; Matlashov, Andrei N.; Espy, Michelle A.; Mosher, John C.; Kraus, Robert H.

2008-01-01

369

A parallel radiosity algorithm for virtual reality  

Microsoft Academic Search

This paper presents a parallel algorithm for radiosity computation in virtual reality environment by computing the parallel eigenvalues and eigenvectors of form factor matrix. This leads to a novel approach to radiosity computation for virtual reality which called parallel eigenvector radiosity. Through the performance evaluation, this method significantly decreases the execution time for complex environments on cluster of PCs.

Qiong Zhang; Zhichao Li; Riwei Wang

2010-01-01

370

Parallel Processing at the High School Level.  

ERIC Educational Resources Information Center

This study investigated the ability of high school students to cognitively understand and implement parallel processing. Data indicates that most parallel processing is being taught at the university level. Instructional modules on C, Linux, and the parallel processing language, P4, were designed to show that high school students are highly…

Sheary, Kathryn Anne

371

Building Bilingual Dictionaries from Parallel Web Documents  

Microsoft Academic Search

In this paper we describe a system for automatically constructing a bilingual dictionary for cross-language information retrieval applications. We describe how we automatically target candidate parallel documents, filter the candidate documents and process them to create parallel sentences. The parallel sentences are then automatically translated using an adaptation of the EMIM technique and a dictionary of translation terms is created.

Craig J. A. Mcewan; Iadh Ounis; Ian Ruthven

2002-01-01

372

Inductive Information Retrieval Using Parallel Distributed Computation.  

ERIC Educational Resources Information Center

|This paper reports on an application of parallel models to the area of information retrieval and argues that massively parallel, distributed models of computation, called connectionist, or parallel distributed processing (PDP) models, offer a new approach to the representation and manipulation of knowledge. Although this document focuses on…

Mozer, Michael C.

373

Deterministic asynchronous interpretation of parallel microprograms  

SciTech Connect

This paper is a continuation of the study of the deterministic properties of asynchronous interpretation of parallel microprograms. The author describes classes of parallel microprograms that generate deterministic asynchronous computations, presents the Petri nets modeling these computation, considers their special features for certain classes of microprograms, and states a necessary and sufficient condition for deterministic asynchronous interpretations of parallel microprograms.

Achasova, S.M.

1986-07-01

374

A Container-Iterator Parallel Programming Model  

Microsoft Academic Search

There are several parallel programming models available for numerical computations at different levels of expressibility and ease of use. For the development of new domain specific programming models, a splitting into a distributed data container and parallel data iterators is proposed. Data distribution is implemented in application specific li- braries. Data iterators are directly analysed and compiled automatically into parallel

Gerhard W. Zumbusch

2007-01-01

375

Parallel Computing Using Web Servers and "Servlets".  

ERIC Educational Resources Information Center

|Describes parallel computing and presents inexpensive ways to implement a virtual parallel computer with multiple Web servers. Highlights include performance measurement of parallel systems; models for using Java and intranet technology including single server, multiple clients and multiple servers, single client; and a comparison of CGI (common…

Lo, Alfred; Bloor, Chris; Choi, Y. K.

2000-01-01

376

Happe Honeywell Associative Parallel Processing Ensemble  

Microsoft Academic Search

Many problems, inherent in air traffic control, weather analysis and prediction, nuclear reaction, missile tracking, and hydrodynamics have common processing characteristics that can most efficiently be solved using parallel “non-conventional” techniques. Because of high sensor data rates, these parallel problem solving techniques cannot be economically applied using the standard sequential computer. The application of special processing techniques such as parallel\\/associative

Orin E. Marvel

1973-01-01

377

A new type of parallel finger mechanism  

Microsoft Academic Search

Based on the principle of parallel robot mechanism and bionics, a new type of three degree-of-freedom parallel finger mechanism is proposed. The basic unit of mechanism is parallelogram linkage. In the paper, the emphasis is laid on the study of the finger mechanism; the forward solution and inverse solution of the finger mechanism are obtained, an idea of parallel finger

Dejun Mu; Zhen Huang

2007-01-01

378

Identifying, Quantifying, Extracting and Enhancing Implicit Parallelism  

ERIC Educational Resources Information Center

The shift of the microprocessor industry towards multicore architectures has placed a huge burden on the programmers by requiring explicit parallelization for performance. Implicit Parallelization is an alternative that could ease the burden on programmers by parallelizing applications "under the covers" while maintaining sequential semantics…

Agarwal, Mayank

2009-01-01

379

Hyperdimensional Data Analysis Using Parallel Coordinates  

Microsoft Academic Search

This article presents the basic results of using the parallel coordinate representation as a high-dimensional data analysis tool. Several alternatives are reviewed. The basic algorithm for parallel coordinates is laid out and a discussion of its properties as a projective transformation is given. Several duality results are discussed along with their interpretations as data analysis tools. Permutations of the parallel

Edward J. Wegman

1990-01-01

380

Global approach to detection of parallelism  

Microsoft Academic Search

Modern computers will increasingly rely on parallelism to achieve high computation rates. Techniques to automatically detect and exploit parallelism have shown effective for computers with vector capabilities. To employ similar techniques for asynchronous multiprocessor machines, the analysis and transformations used for vectorization must be extended to apply to entire programs rather than single loops. Three subproblems are addressed. A sequential-to-parallel

David Callahan; C. D. II

1987-01-01

381

OPALS - Optical parallel array logic system  

Microsoft Academic Search

A new optical-digital computing system called OPALS (optical parallel array logic system) is presented. OPALS can execute various parallel neighborhood operations such as cellular logic as well as parallel logical operations for two-dimensional sampled objects. The system has the ability to perform iterative operations. OPALS is systemized, centering on the optical logic method using image coding and optical correlation techniques.

Jun Tanida; Yoshiki Ichioka

1986-01-01

382

VCSEL-based parallel optical transmission module  

Microsoft Academic Search

This paper describes the design process and performance of the optimized parallel optical transmission module. Based on 1×12 VCSEL (Vertical Cavity Surface Emitting Laser) array, we designed and fabricated the high speed parallel optical modules. Our parallel optical module contains a 1×12 VCSEL array, a 12 channel CMOS laser driver circuit, a high speed PCB (Printed Circuit Board), a MT

Rongxuan Shen; Hongda Chen; Chao Zuo; Weihua Pei; Yi Zhou; Jun Tang

2005-01-01

383

Inductive Information Retrieval Using Parallel Distributed Computation.  

ERIC Educational Resources Information Center

This paper reports on an application of parallel models to the area of information retrieval and argues that massively parallel, distributed models of computation, called connectionist, or parallel distributed processing (PDP) models, offer a new approach to the representation and manipulation of knowledge. Although this document focuses on…

Mozer, Michael C.

384

Series-Parallel Combination Circuits  

NSDL National Science Digital Library

Tony R. Kuphaldt is the creator of All About Circuits, a collection of online textbooks about circuits and electricity. The site is split into volumes, chapters, and topics to make finding and learning about these subjects convenient. Volume 1, Chapter 7: Series-Parallel Combination Circuits digs deeper into these circuits than Chapter 5. This chapter offers a step-by-step analysis technique in order to identify all changes in voltage and current. It also offers a set of detailed instructions for component failure analysis. All in all, this is a great resource for educators or students.

Kuphaldt, Tony R.

2008-07-01

385

On Parallelism in Turing Machines  

Microsoft Academic Search

A model of parallel computation based on a generalization of nondeterminism in Turing machines is introduced. Complexity classes \\/\\/T(n)-TIME, \\/\\/L(n)-SPACE, \\/\\/LOGSPACE, \\/\\/PTIME, etc. are defined for these machines in a way analogous to T(n)-TIME, L(n)-SPACE, LOGSPACE, PTIME, etc. for deterministic machines. It is shown that, given appropriate honesty conditions, L(n)-SPACE ? \\/\\/L(n)2-TIME T(n)-TIME ? \\/\\/log T(n)-SPACE \\/\\/L(n)-SPACE ? exp L(n)-TIME

Dexter Kozen

1976-01-01

386

Parallel Mapping Approaches for GNUMAP  

PubMed Central

Mapping short next-generation reads to reference genomes is an important element in SNP calling and expression studies. A major limitation to large-scale whole-genome mapping is the large memory requirements for the algorithm and the long run-time necessary for accurate studies. Several parallel implementations have been performed to distribute memory on different processors and to equally share the processing requirements. These approaches are compared with respect to their memory footprint, load balancing, and accuracy. When using MPI with multi-threading, linear speedup can be achieved for up to 256 processors.

Clement, Nathan L.; Clement, Mark J.; Snell, Quinn; Johnson, W. Evan

2013-01-01

387

A CS1 pedagogical approach to parallel thinking  

NASA Astrophysics Data System (ADS)

Almost all collegiate programs in Computer Science offer an introductory course in programming primarily devoted to communicating the foundational principles of software design and development. The ACM designates this introduction to computer programming course for first-year students as CS1, during which methodologies for solving problems within a discrete computational context are presented. Logical thinking is highlighted, guided primarily by a sequential approach to algorithm development and made manifest by typically using the latest, commercially successful programming language. In response to the most recent developments in accessible multicore computers, instructors of these introductory classes may wish to include training on how to design workable parallel code. Novel issues arise when programming concurrent applications which can make teaching these concepts to beginning programmers a seemingly formidable task. Student comprehension of design strategies related to parallel systems should be monitored to ensure an effective classroom experience. This research investigated the feasibility of integrating parallel computing concepts into the first-year CS classroom. To quantitatively assess student comprehension of parallel computing, an experimental educational study using a two-factor mixed group design was conducted to evaluate two instructional interventions in addition to a control group: (1) topic lecture only, and (2) topic lecture with laboratory work using a software visualization Parallel Analysis Tool (PAT) specifically designed for this project. A new evaluation instrument developed for this study, the Perceptions of Parallelism Survey (PoPS), was used to measure student learning regarding parallel systems. The results from this educational study show a statistically significant main effect among the repeated measures, implying that student comprehension levels of parallel concepts as measured by the PoPS improve immediately after the delivery of any initial three-week CS1 level module when compared with student comprehension levels just prior to starting the course. Survey results measured during the ninth week of the course reveal that performance levels remained high compared to pre-course performance scores. A second result produced by this study reveals no statistically significant interaction effect between the intervention method and student performance as measured by the evaluation instrument over three separate testing periods. However, visual inspection of survey score trends and the low p-value generated by the interaction analysis (0.062) indicate that further studies may verify improved concept retention levels for the lecture w/PAT group.

Rague, Brian William

388

Parallel play in medical anthropology and medical sociology  

Microsoft Academic Search

In recent years, the disciplinary emphasis in the social sciences has been challenged, but barriers remain to multidisciplinary\\u000a discourse. Scholars may examine similar problems or even use the same concepts, and neglect or overlook the work in sister\\u000a disciplines. Developmental psychologists have identified a stage in child development called parallel play, characterized\\u000a by children playing side-by-side but not interacting with

Peter Conrad

1997-01-01

389

Segmented ray casting for data parallel volume rendering  

Microsoft Academic Search

Interactive volume rendering is important for the timely analysis of three-dimensional data, but workstations take seconds to minutes to render data sets of a few megabytes. We have developed a parallel ray-casting technique. called Sepnenred Ray Cnsting, which can render a 128x128~128 data set at 2-3 frames per second on a 4K processor DECmpp 12OOO\\/Sx Model 100. Pixel values in

William M. Hsu

1993-01-01

390

Fully Parallelized Multi-Prover Protocols for NEXP-Time  

Microsoft Academic Search

A major open problem in the theory of multi-prover interactive proofs is to characterize the languages which can be accepted by fully parallelized multi-prover protocols with an exponentially low probability of cheating. In this paper we solve this problem by proving that any language which can be accepted by a sequential multi-prover protocol can also be accepted by a single-round

Dror Lapidot; Adi Shamir

1997-01-01

391

Efficient and correct execution of parallel programs that share memory  

Microsoft Academic Search

In this paper we consider an optimization problem that arises in the execution of parallel programs on shared-memory multiple-instruction-stream, multiple-data-stream (MIMD) computers. A program on such machines consists of many sequential program segments, each executed by a single processor. These segments interact as they access shared variables. Access to memory is asynchronous, and memory accesses are not necessarily executed in

Dennis Shasha; Marc Snir

1988-01-01

392

Parallel expression profiling of barley-stem rust interactions.  

PubMed

The dominant barley stem rust resistance gene Rpg1 confers resistance to many but not all pathotypes of the stem rust fungus Puccinia graminis f. sp. tritici (Pgt). Transformation of Rpg1 into susceptible cultivar Golden Promise rendered the transgenic plants resistant to Pgt pathotype MCC but not to Pgt pathotype QCC. Our objective was to identify genes that are induced/repressed during the early stages of pathogen infection to elucidate the molecular mechanisms and role of Rpg1 in defense. A messenger ribonucleic acid expression analysis using the 22K Barley1 GeneChip was conducted in all pair-wise combinations of two isolines (cv. Golden Promise and Rpg1 transgenic line G02-448F-3R) and two Pgt pathotypes (MCC and QCC) across six time points. Analysis showed that a total of 34 probe sets exhibited expression pattern differences between Golden Promise (susceptible) and G02-448F-3R (resistant) infected with Pgt-MCC. A total of 14 probe sets exhibited expression pattern differences between Pgt-MCC (avirulent) and Pgt-QCC (virulent) inoculated onto G02-448F-3R. These differentially expressed genes were activated during the early infection process, before the hypersensitive response or fungal growth inhibition occurred. Our analysis provides a list of candidate signaling components, which can be analyzed for function in Rpg1-mediated disease resistance. PMID:18196301

Zhang, Ling; Castell-Miller, Claudia; Dahl, Stephanie; Steffenson, Brian; Kleinhofs, Andris

2008-01-15

393

Xyce parallel electronic simulator design.  

SciTech Connect

This document is the Xyce Circuit Simulator developer guide. Xyce has been designed from the 'ground up' to be a SPICE-compatible, distributed memory parallel circuit simulator. While it is in many respects a research code, Xyce is intended to be a production simulator. As such, having software quality engineering (SQE) procedures in place to insure a high level of code quality and robustness are essential. Version control, issue tracking customer support, C++ style guildlines and the Xyce release process are all described. The Xyce Parallel Electronic Simulator has been under development at Sandia since 1999. Historically, Xyce has mostly been funded by ASC, the original focus of Xyce development has primarily been related to circuits for nuclear weapons. However, this has not been the only focus and it is expected that the project will diversify. Like many ASC projects, Xyce is a group development effort, which involves a number of researchers, engineers, scientists, mathmaticians and computer scientists. In addition to diversity of background, it is to be expected on long term projects for there to be a certain amount of staff turnover, as people move on to different projects. As a result, it is very important that the project maintain high software quality standards. The point of this document is to formally document a number of the software quality practices followed by the Xyce team in one place. Also, it is hoped that this document will be a good source of information for new developers.

Thornquist, Heidi K.; Rankin, Eric Lamont; Mei, Ting; Schiek, Richard Louis; Keiter, Eric Richard; Russo, Thomas V.

2010-09-01

394

Overview of IBM system\\/390 parallel sysplex-a commercial parallel processing system  

Microsoft Academic Search

Scalability has never been more a part of System\\/390 than with Parallel Sysplex. The Parallel Sysplex environment permits a mainframe or Parallel Enterprise Server to grow from a single system to a configuration of 32 systems (initially), and appear as a single image to the end user and applications. The IBM S\\/390 Parallel Sysplex provides capacity for today's largest commercial

Jeffrey M. Nick; Jen-Yao Chung; Nicholas S. Bowen

1996-01-01

395

STALK : an interactive virtual molecular docking system.  

SciTech Connect

Several recent technologies-genetic algorithms, parallel and distributed computing, virtual reality, and high-speed networking-underlie a new approach to the computational study of how biomolecules interact or 'dock' together. With the Stalk system, a user in a virtual reality environment can interact with a genetic algorithm running on a parallel computer to help in the search for likely geometric configurations.

Levine, D.; Facello, M.; Hallstrom, P.; Reeder, G.; Walenz, B.; Stevens, F.; Univ. of Illinois

1997-04-01

396

Exploiting fine grain parallelism in Prolog  

SciTech Connect

The goals of this paper is to design a Prolog system that automatically exploits parallelism in Prolog with low overhead memory management and task management schemes, and to demonstrate by means of detailed simulations that such a Prolog system can indeed achieve a significant speedup over the fastest sequential Prolog systems. The authors achieve these goals by first identifying the large sources of overhead in parallel Prolog execution: side-effects caused by parallel tasks, choicepoints created by parallel tasks, tasks creation, task scheduling, task suspension and context switching. The authors then identify a form of parallelism, called flow parallelism, that can be exploited with low overhead because parallel execution is restricted to goals that do not cause side-effects and do not create choicepoints. The authors develop a master-slave model of parallel execution that eliminates task suspension and context switching. The model uses program partitioning and task scheduling techniques that do not require task suspension and context switching to prevent deadlock. The authors identify architectural techniques to support the parallel execution model and develop the Flow Parallel Prolog Machines (FPPM) architecture and implementation. Finally, the authors evaluate the performance of FPPM and investigate the design tradeoffs using measurements on a detailed, register- transfer level simulator. FPPM achieves an average speedup of about a factor of 2 (as much as a factor of 5 for some programs) over the current highest performance sequential Prolog implementation, the VLSI-BAM. The speedups over other parallel Prolog systems are much larger.

Singhal, A.

1990-01-01

397

Performance prediction for complex parallel applications  

SciTech Connect

Today`s massively parallel machines are typically message-passing systems consisting of hundreds or thousands of processors. Implementing parallel applications efficiently in this environment is a challenging task, and poor parallel design decisions can be expensive to correct. Tools and techniques that allow the fast and accurate evaluation of different parallelization strategies would significantly improve the productivity of application developers and increase throughput on parallel architectures. This paper investigates one of the major issues in building tools to compare parallelization strategies: determining what type of performance models of the application code and of the computer system are sufficient for a fast and accurate comparison of different strategies. The paper is built around a case study employing the Performance Prediction Tool (PerPreT) to predict performance of the Parallel Spectral Transform Shallow Water Model code (PSTSWM) on the Intel Paragon. 13 refs., 6 tabs.

Brehm, J. [Hannover Univ. (Germany). Inst. fuer Rechnerstrukturen und Betriebssysteme; Worley, P.H. [Oak Ridge National Lab., TN (United States)

1997-04-01

398

Semantics for Compiling Data Parallelism.  

National Technical Information Service (NTIS)

Research in semantics and in compiler construction is often separated. The first has a theoretical character, in general, whereas the second has a more applied character. However, both fields are of fundamental importance in the interaction between a prog...

P. F. G. Dechering

1998-01-01

399

Device for balancing parallel strings  

DOEpatents

A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

Mashikian, Matthew S. (Storrs, CT)

1985-01-01

400

Parallel Network Simulations with NEURON  

PubMed Central

The NEURON simulation environment has been extended to support parallel network simulations. Each processor integrates the equations for its subnet over an interval equal to the minimum (interprocessor) presynaptic spike generation to postsynaptic spike delivery connection delay. The performance of three published network models with very different spike patterns exhibits superlinear speedup on Beowulf clusters and demonstrates that spike communication overhead is often less than the benefit of an increased fraction of the entire problem fitting into high speed cache. On the EPFL IBM Blue Gene, almost linear speedup was obtained up to 100 processors. Increasing one model from 500 to 40,000 realistic cells exhibited almost linear speedup on 2000 processors, with an integration time of 9.8 seconds and communication time of 1.3 seconds. The potential for speed-ups of several orders of magnitude makes practical the running of large network simulations that could otherwise not be explored.

Migliore, M.; Cannia, C.; Lytton, W.W; Markram, Henry; Hines, M. L.

2009-01-01

401

Parallel network simulations with NEURON.  

PubMed

The NEURON simulation environment has been extended to support parallel network simulations. Each processor integrates the equations for its subnet over an interval equal to the minimum (interprocessor) presynaptic spike generation to postsynaptic spike delivery connection delay. The performance of three published network models with very different spike patterns exhibits superlinear speedup on Beowulf clusters and demonstrates that spike communication overhead is often less than the benefit of an increased fraction of the entire problem fitting into high speed cache. On the EPFL IBM Blue Gene, almost linear speedup was obtained up to 100 processors. Increasing one model from 500 to 40,000 realistic cells exhibited almost linear speedup on 2,000 processors, with an integration time of 9.8 seconds and communication time of 1.3 seconds. The potential for speed-ups of several orders of magnitude makes practical the running of large network simulations that could otherwise not be explored. PMID:16732488

Migliore, M; Cannia, C; Lytton, W W; Markram, Henry; Hines, M L

2006-05-26

402

Information hiding in parallel programs  

SciTech Connect

A fundamental principle in program design is to isolate difficult or changeable design decisions. Application of this principle to parallel programs requires identification of decisions that are difficult or subject to change, and the development of techniques for hiding these decisions. We experiment with three complex applications, and identify mapping, communication, and scheduling as areas in which decisions are particularly problematic. We develop computational abstractions that hide such decisions, and show that these abstractions can be used to develop elegant solutions to programming problems. In particular, they allow us to encode common structures, such as transforms, reductions, and meshes, as software cells and templates that can reused in different applications. An important characteristic of these structures is that they do not incorporate mapping, communication, or scheduling decisions: these aspects of the design are specified separately, when composing existing structures to form applications. This separation of concerns allows the same cells and templates to be reused in different contexts.

Foster, I.

1992-01-30

403

An MIMD parallel computer system  

NASA Astrophysics Data System (ADS)

The need to run large, compute-bound programs encountered in research, coupled with the high availability of mini- and microcomputers in the laboratory environment, has prompted the linking of independent processors to form multicomputer systems. Important characteristics of the system presented here are the lack of shared memory between processors and the use of purely standard hardware to effect the linking. The resulting MIMD machine is suitable for executing asynchronous and weakly synchronous parallel programs. This is facilatated by assembly language software support to handle communication and to organise the independent sections of executable code for the individual processors. The design principles involved in this hardware configuration and the attendant software are introduced. A brief description of program execution behaviour is given. Applications and examples of programming problems which have been implemented on the system are discussed. An empirical method for assessing the timewise gain which ensues from use of the system is presented and experimental results obtained are outlined.

Joubert, G. R.; Maeder, A. J.

1982-06-01

404

Parallel computing in enterprise modeling.  

SciTech Connect

This report presents the results of our efforts to apply high-performance computing to entity-based simulations with a multi-use plugin for parallel computing. We use the term 'Entity-based simulation' to describe a class of simulation which includes both discrete event simulation and agent based simulation. What simulations of this class share, and what differs from more traditional models, is that the result sought is emergent from a large number of contributing entities. Logistic, economic and social simulations are members of this class where things or people are organized or self-organize to produce a solution. Entity-based problems never have an a priori ergodic principle that will greatly simplify calculations. Because the results of entity-based simulations can only be realized at scale, scalable computing is de rigueur for large problems. Having said that, the absence of a spatial organizing principal makes the decomposition of the problem onto processors problematic. In addition, practitioners in this domain commonly use the Java programming language which presents its own problems in a high-performance setting. The plugin we have developed, called the Parallel Particle Data Model, overcomes both of these obstacles and is now being used by two Sandia frameworks: the Decision Analysis Center, and the Seldon social simulation facility. While the ability to engage U.S.-sized problems is now available to the Decision Analysis Center, this plugin is central to the success of Seldon. Because Seldon relies on computationally intensive cognitive sub-models, this work is necessary to achieve the scale necessary for realistic results. With the recent upheavals in the financial markets, and the inscrutability of terrorist activity, this simulation domain will likely need a capability with ever greater fidelity. High-performance computing will play an important part in enabling that greater fidelity.

Goldsby, Michael E.; Armstrong, Robert C.; Shneider, Max S.; Vanderveen, Keith; Ray, Jaideep; Heath, Zach; Allan, Benjamin A.

2008-08-01

405

New multilevel parallelism management for multimedia processors  

NASA Astrophysics Data System (ADS)

This paper presents a new parallelism manager for multimedia multiprocessors. An analysis of recent multimedia applications shows that the available parallelism moves from the data-level to the control-level. New architectures are required to be able to extract this kind of dynamic parallelism. Our proposed parallelism management describes the parallelism with a topological description of the task dependence graph. It allows to represent various and complex parallelism patterns. This parallelism description is separated from the program code to allow the task manager to decode it in parallel with the task execution. The task manager is based on a queue bank that stores the task graph. Control commands are inserted in the task dependence graph to allow a dynamic modification of this graph, depending on the processed data. Simulations on classical multiprocessing benchmarks show that in case of simple parallelism, we have similar performances than classical systems. However, the performances on complex applications are improved up to 12%. Multimedia applications have also bee simulated. The results show that our task manager can efficiently handle complex dynamic parallelism structures.

Verians, Xavier; Legat, Jean-Didier; Macq, Benoit M.; Quisquater, Jean-Jacques

1998-12-01

406

Parallel processing considerations for image recognition tasks  

NASA Astrophysics Data System (ADS)

Many image recognition tasks are well-suited to parallel processing. The most obvious example is that many imaging tasks require the analysis of multiple images. From this standpoint, then, parallel processing need be no more complicated than assigning individual images to individual processors. However, there are three less trivial categories of parallel processing that will be considered in this paper: parallel processing (1) by task; (2) by image region; and (3) by meta-algorithm. Parallel processing by task allows the assignment of multiple workflows-as diverse as optical character recognition [OCR], document classification and barcode reading-to parallel pipelines. This can substantially decrease time to completion for the document tasks. For this approach, each parallel pipeline is generally performing a different task. Parallel processing by image region allows a larger imaging task to be sub-divided into a set of parallel pipelines, each performing the same task but on a different data set. This type of image analysis is readily addressed by a map-reduce approach. Examples include document skew detection and multiple face detection and tracking. Finally, parallel processing by meta-algorithm allows different algorithms to be deployed on the same image simultaneously. This approach may result in improved accuracy.

Simske, Steven J.

2011-01-01

407

Toward an automated parallel computing environment for geosciences  

NASA Astrophysics Data System (ADS)

Software for geodynamic modeling has not kept up with the fast growing computing hardware and network resources. In the past decade supercomputing power has become available to most researchers in the form of affordable Beowulf clusters and other parallel computer platforms. However, to take full advantage of such computing power requires developing parallel algorithms and associated software, a task that is often too daunting for geoscience modelers whose main expertise is in geosciences. We introduce here an automated parallel computing environment built on open-source algorithms and libraries. Users interact with this computing environment by specifying the partial differential equations, solvers, and model-specific properties using an English-like modeling language in the input files. The system then automatically generates the finite element codes that can be run on distributed or shared memory parallel machines. This system is dynamic and flexible, allowing users to address different problems in geosciences. It is capable of providing web-based services, enabling users to generate source codes online. This unique feature will facilitate high-performance computing to be integrated with distributed data grids in the emerging cyber-infrastructures for geosciences. In this paper we discuss the principles of this automated modeling environment and provide examples to demonstrate its versatility.

Zhang, Huai; Liu, Mian; Shi, Yaolin; Yuen, David A.; Yan, Zhenzhen; Liang, Guoping

2007-08-01

408

Acoustic predictions using measured pressures from a model rotor in the DNW  

NASA Astrophysics Data System (ADS)

A contemporary design, 4-bladed United Technologies model rotor with pressure-instrumented blades was tested in the Duits-Nederslandse Windtunnel. Simultaneous acoustic and pressure measurements were made for a wide range of operating conditions. Microphones were optimally positioned at a number of locations in the flow forward of the rotor to measure rotor thickness noise, high-speed impulsive noise (both in the rotor plane), and blade-vortex interaction noise (forward and 25 deg below the rotor plane). The blade surface pressure data are used as aerodynamic input to WOPWOP, which is a state-of-the-art rotor noise prediction program that predicts rotor thickness and loading noise. The predicted results using WOPWOP are compared to the measured noise levels for cases where either thickness noise, blade-vortex interaction noise, or high-speed impulsive noise is the dominant noise mechanism. The comparisons show regions of good agreement, as well as areas where further improvement is necessary.

Visintainer, Joseph A.; Burley, Casey L.; Marcolini, Michael A.; Liu, Sandy R.

409

The acoustic results of a United Techologies scale model helicopter rotor tested at DNW  

NASA Astrophysics Data System (ADS)

An initial summary is presented of the acoustic measurements acquired for some of the different configurations of a 1/6 geometrically and aeroelastically scaled UTC model helicopter rotor which was tested in the open-jet anechoic test section of the Duits-Nederlandse Windtunnel in the Netherlands. Of particular interest are high-speed impulsive noise and blade-vortex interaction. An analysis is provided of baseline swept tip rotor acoustic characteristics in the regimes of high-speed forward flight, where high-speed impulsive noise dominates, and low-speed descent, where severe blade vortex interaction noise occurs. Also discussed are more recent studies of data which involve the animation of the acoustic field upstream of the rotor to evaluate the detailed radiation patters caused by BVI and HSI noise sources. The trends of these primary noise sources are examined as the first step in validating the data for release and application.

Liu, Sandy R.; Marcolini, Michael A.

1990-10-01

410

Aeroacoustic flowfield and acoustics of a model helicopter tail rotor at high advance ratio  

NASA Astrophysics Data System (ADS)

Some results, relevant to rotorcraft noise generation process at high advance ratio, are presented in this paper from schlieren flow visualization and acoustic tests of a model tail rotor. The measured in-plane noise trends are consistent with the growth of the tip supersonic region seen in the schlieren visuals. Schlieren flow visuals reveal a propagating pressure wave in the second quadrant. Simultaneously measured acoustic data and the results of two-dimensional transonic Blade-Vortex Interaction analysis code ATRAN-2 indicate that this pressure wave is attributable to BVI activity in the first quadrant. This paper establishes that the transonic Blade-Vortex Interactions contribute to noise at high advance ratio level flight conditions.

Shenoy, Rajarama K.

411

Parallel Computing for Terrestrial Ecosystem Carbon Modeling  

SciTech Connect

Terrestrial ecosystems are a primary component of research on global environmental change. Observational and modeling research on terrestrial ecosystems at the global scale, however, has lagged behind their counterparts for oceanic and atmospheric systems, largely because the unique challenges associated with the tremendous diversity and complexity of terrestrial ecosystems. There are 8 major types of terrestrial ecosystem: tropical rain forest, savannas, deserts, temperate grassland, deciduous forest, coniferous forest, tundra, and chaparral. The carbon cycle is an important mechanism in the coupling of terrestrial ecosystems with climate through biological fluxes of CO{sub 2}. The influence of terrestrial ecosystems on atmospheric CO{sub 2} can be modeled via several means at different timescales. Important processes include plant dynamics, change in land use, as well as ecosystem biogeography. Over the past several decades, many terrestrial ecosystem models (see the 'Model developments' section) have been developed to understand the interactions between terrestrial carbon storage and CO{sub 2} concentration in the atmosphere, as well as the consequences of these interactions. Early TECMs generally adapted simple box-flow exchange models, in which photosynthetic CO{sub 2} uptake and respiratory CO{sub 2} release are simulated in an empirical manner with a small number of vegetation and soil carbon pools. Demands on kinds and amount of information required from global TECMs have grown. Recently, along with the rapid development of parallel computing, spatially explicit TECMs with detailed process based representations of carbon dynamics become attractive, because those models can readily incorporate a variety of additional ecosystem processes (such as dispersal, establishment, growth, mortality etc.) and environmental factors (such as landscape position, pest populations, disturbances, resource manipulations, etc.), and provide information to frame policy options for climate change impact analysis.

Wang, Dali [ORNL; Post, Wilfred M [ORNL; Ricciuto, Daniel M [ORNL; Berry, Michael [University of Tennessee, Knoxville (UTK)

2011-01-01

412

Towards Distributed Memory Parallel Program Analysis  

SciTech Connect

This paper presents a parallel attribute evaluation for distributed memory parallel computer architectures where previously only shared memory parallel support for this technique has been developed. Attribute evaluation is a part of how attribute grammars are used for program analysis within modern compilers. Within this work, we have extended ROSE, a open compiler infrastructure, with a distributed memory parallel attribute evaluation mechanism to support user defined global program analysis required for some forms of security analysis which can not be addressed by a file by file view of large scale applications. As a result, user defined security analyses may now run in parallel without the user having to specify the way data is communicated between processors. The automation of communication enables an extensible open-source parallel program analysis infrastructure.

Quinlan, D; Barany, G; Panas, T

2008-06-17

413

Response matrix transport calculations on parallel computers  

SciTech Connect

The response matrix method offers an excellent vehicle for adapting three-dimensional neutron transport methods to parallel computers. Our current thrust is in utilizing the three-dimensional Variational nodal code VARIANT as a point of departure for performing three- dimensional parallel computations on the IBM SPx at Argonne National Laboratory. The code employs a planar red-black iteration with a secondary red-black or four-color iteration within each plane. Speed- up and efficiency results have been obtained with a two-stage parallel implementation. First, the response matrix coefficients are calculated in parallel for each unique node type. Second, parallel iterations are performed with one red-black pair of planes assigned to each processor. A hierarchical structure may be employed to obtain finer parallel granularity by assigning multiple processors to the planer red-black or four-color iterations.

Hanebutte, U.R.; Palmiotti, G.; Khalil, H.S. [Argonne National Lab., IL (United States). Reactor Analysis Div.; Tatsumi, M. [Nuclear Fuel Industries, Ltd., Osaka (Japan). Nuclear Engineering Div.; Lewis, E.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

1996-12-31

414

Heavy ion acceleration at parallel shocks  

NASA Astrophysics Data System (ADS)

A study of alpha particle acceleration at parallel shock due to an interaction with Alfvén waves self-consistently excited in both upstream and downstream regions was conducted using a scale-separation model (Galinsky and Shevchenko, 2000, 2007). The model uses conservation laws and resonance conditions to find where waves will be generated or damped and hence where particles will be pitch-angle scattered. It considers the total distribution function (for the bulk plasma and high energy tail), so no standard assumptions (e.g. seed populations, or some ad-hoc escape rate of accelerated particles) are required. The heavy ion scattering on hydromagnetic turbulence generated by both protons and ions themselves is considered. The contribution of alpha particles to turbulence generation is important because of their relatively large mass-loading parameter P?=n?m?/npmp (mp, np and m?, n? are proton and alpha particle mass and density) that defines efficiency of wave excitation. The energy spectra of alpha particles are found and compared with those obtained in test particle approximation.

Galinsky, V. L.; Shevchenko, V. I.

2010-11-01

415

Multipactor saturation in parallel-plate waveguides  

SciTech Connect

The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.

Sorolla, E.; Mattes, M. [Ecole Polytechnique Federale de Lausanne, Laboratoire d'Electromagnetisme et d'Acoustique (LEMA), Station 11, CH-1015 Lausanne (Switzerland)

2012-07-15

416

Dynamic force spectroscopy of parallel individual mucin1-antibody bonds  

SciTech Connect

We used atomic force microscopy (AFM) to measure the binding forces between Mucin1 (MUC1) peptide and a single chain antibody fragment (scFv) selected from a scFv library screened against MUC1. This binding interaction is central to the design of the molecules for targeted delivery of radioimmunotherapeutic agents for prostate and breast cancer treatment. Our experiments separated the specific binding interaction from non-specific interactions by tethering the antibody and MUC1 molecules to the AFM tip and sample surface with flexible polymer spacers. Rupture force magnitude and elastic characteristics of the spacers allowed identification of the bond rupture events corresponding to different number of interacting proteins. We used dynamic force spectroscopy to estimate the intermolecular potential widths and equivalent thermodynamic off rates for mono-, bi-, and tri-valent interactions. Measured interaction potential parameters agree with the results of molecular docking simulation. Our results demonstrate that an increase of the interaction valency leads to a precipitous decline in the dissociation rate. Binding forces measured for mono and multivalent interactions match the predictions of a Markovian model for the strength of multiple uncorrelated bonds in parallel configuration. Our approach is promising for comparison of the specific effects of molecular modifications as well as for determination of the best configuration of antibody-based multivalent targeting agents.

Sulchek, T A; Friddle, R W; Langry, K; Lau, E; Albrecht, H; Ratto, T; DeNardo, S; Colvin, M E; Noy, A

2005-05-02

417

Synchronized update over distributed and parallel database  

Microsoft Academic Search

To achieve synchronized update, two-phase commit protocol (2PC) has been broadly used for distributed databases. However, this is not enough for distributed and parallel database system (DPDBS), which has a distributed and parallel I\\/O interface and absolute peer to peer management among server nodes. Therefore, a distributed and parallel commit protocol (DP2PC) is proposed to improve the 2PC effectiveness. Transactions

Jianying Chen; Xinsong Liu; Tao Li; Jianhua Zhang; Yan Wang

2009-01-01

418

Prototyping parallel and distributed programs in Proteus  

Microsoft Academic Search

This paper presents Proteus, an architecture-independent language suitable for prototyping parallel and distributed programs. Proteus is a high-level imperative notation based on sets and sequences with a single construct for the parallel composition of processes. Although a shared-memory model is the basis for communication between processes, this memory can be partitioned into shared and private variables. Parallel processes operate on

Peter H. Millst; Lars S. Nyland; Jan F. Prim; John H. Reift; Robert A. Wagnert

1991-01-01

419

Hardware-modulated parallelism in chip multiprocessors  

Microsoft Academic Search

Chip multi-processors (CMPs) already have widespread com- mercial availability, and technology roadmaps project enough on-chip transistors to replicate tens or hundreds of current pro- cessor cores. How will we express parallelism, partition appli- cations, and schedule\\/place\\/migrate threads on these highly- parallel CMPs? This paper presents and evaluates a new approach to highly- parallel CMPs, advocating a new hardware-software contract. The

Julia Chen; Philo Juang; Kevin Ko; Gilberto Contreras; David Penry; Ram Rangan; Adam Stoler; Li-shiuan Peh; Margaret Martonosi

2005-01-01

420

Application of Parallel Programming in Collaborative Design  

Microsoft Academic Search

Aiming at improving the design and assembly efficiency of complex products in collaborative design, this paper proposes a\\u000a parallel assembly model which is based on parallel computing. It divides assembly task into subtasks according to main branch\\u000a in the virtual-link structure, and finally the subtasks run in parallel. This model supports large scale design, improves\\u000a the speed and at the

Tieming Su; Xiaoliang Tai; Zhixiang Xu

2008-01-01

421

Motion planning of a climbing parallel robot  

Microsoft Academic Search

Abstract—This paper,proposes,a,novel application of,the Stewart?Gough parallel platform as a climbing robot and its kine- matics control to climb through long structures describing unknown spatial trajectories, such as palm trunks, tubes, etc. First, the description and design of the climbing parallel robot is presented. Second, the inverse and forward kinematics analysis of a mobile six-degrees-of-freedom parallel robot is described, based on

Miguel Almonacid; Roque J. Saltarén; Rafael Aracil; Óscar Reinoso

2003-01-01

422

Analysis of Parallel Decodable Turbo Codes  

NASA Astrophysics Data System (ADS)

Turbo codes suffer from high decoding latency which hinders their utilization in many communication systems. Parallel decodable turbo codes (PDTCs) are suitable for parallel decoding and hence have low latency. In this article, we analyze the worst case minimum distance of parallel decodable turbo codes with both S-random interleaver and memory collision free Row-Column S-random interleaver. The effect of minimum distance on code performance is determined through computer simulations.

Gazi, Orhan

423

The NAS Parallel Benchmarks 2.0  

Microsoft Academic Search

We describe a set of implementations of the NAS Parallel Benchmarks based on Fortran 77 and the MPI message passing standard. These implementations,which are intended to be run with little or no tuning, approximate the performance a typical user can expect for a portable parallel program on a distributed memory computer. They complement rather than replace the originalNAS Parallel Benchmarks.We

David Bailey; Tim Harris; William Saphir; Rob Van Der Wijngaart; Alex Woo; Maurice Yarrow

1995-01-01

424

New Challenges of Parallel Job Scheduling  

Microsoft Academic Search

The workshop on job scheduling strategies for parallel processing (JSSPP) studies the myriad aspects of managing resources\\u000a on parallel and distributed computers. These studies typically focus on large-scale computing environments, where allocation\\u000a and management of computing resources present numerous challenges. Traditionally, such systems consisted of massively parallel\\u000a supercomputers, or more recently, large clusters of commodity processor nodes. These systems are

Eitan Frachtenberg; Uwe Schwiegelshohn

2007-01-01

425

Portable QCD codes for massively parallel processors  

NASA Astrophysics Data System (ADS)

We present a new set of QCD codes in both message passing and data parallel versions. The message passing package used is PARMACS, although other packages may be used. Data parallel software is written in High Performance Fortran, an emerging standard based on Fortran 90. Software engineering methods have been applied to a physics application to create thoroughly tested and documented codes for the next generation of massively parallel supercomputers. Department of Physics, University of Edinburgh, Edinburgh EH9 3JZ, Scotland, UK

1994-04-01

426

Desktop 3-axis parallel kinematic milling machine  

Microsoft Academic Search

Parallel kinematic machines (PKM) are still a research-and-development topic in many laboratories although many of them, unfortunately,\\u000a have no PKM at all. Therefore, the use of a desktop educational 3-axis parallel kinematic milling machine is suggested as\\u000a a help in the process of acquiring basic experiences in the field of PKM. The developed desktop educational 3-axis parallel\\u000a kinematic milling machine

Milos Glavonjic; Dragan Milutinovic; Sasa Zivanovic; Zoran Dimic; Vladimir Kvrgic

2010-01-01

427

Design and Evaluation of a Novel Real-Shared Cache Module for High Performance Parallel Processor Chip  

Microsoft Academic Search

\\u000a Nowadays, it is very important that integrating parallel processors on a chip offers high performance and low interactive\\u000a response time on applications with fine-grained parallelism and high degree of data sharing. We propose a novel real-shared\\u000a cache module with new multiport ring-bus architecture to overcome the bus bottleneck problem of the existing parallel processors\\u000a chip on shared cache level. A

Zhe Liu; Jeoungchill Shim; Hiroyuki Kurino; Mitsumasa Koyanagi

2004-01-01

428

Analysis of the numerical effects of parallelism on a parallel genetic algorithm  

SciTech Connect

This paper examines the effects of relaxed synchronization on both the numerical and parallel efficiency of parallel genetic algorithms (GAs). We describe a coarse-grain geographically structured parallel genetic algorithm. Our experiments show that asynchronous versions of these algorithms have a lower run time than-synchronous GAs. Furthermore, we demonstrate that this improvement in performance is partly due to the fact that the numerical efficiency of the asynchronous genetic algorithm is better than the synchronous genetic algorithm. Our analysis includes a critique of the utility of traditional parallel performance measures for parallel GAs, and we evaluate the claims made by several researchers that parallel GAs can have superlinear speedup.

Hart, W.E.; Belew, R.K.; Kohn, S. [Sandia National Labs., Albuquerque, NM (United States); Baden, S. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Computer Science and Engineering

1995-09-18

429

Computational physics and the need for parallelism  

NASA Astrophysics Data System (ADS)

This paper will give an introduction to parallelism in computer systems and discuss the technological limitations which have motivated this departure. In order to make efficient use of this new generation of parallel architectures many new techniques have been developed. These include new languages which contain explicit parallelism and new parallel algorithms. These developments will be discussed with reference to both arrat architecture, multiprocessors and vector pipelined architectures. Finally, this paper will discuss the implication of a rapidly changing technological base on computer architecture and the effect that this is likely to have on software engineering.

Jesshope, C. R.

1986-08-01

430

Multimodule parallel series-loaded resonant converters  

NASA Astrophysics Data System (ADS)

The design and implementation of a multimodule parallel series-loaded resonant (SLR) converter system is presented. The SLR converter to be paralleled is operated in the n = 2 discontinuous mode (DCM). Its dc analysis and dynamic modeling are made. In parallel operation, an average control technique is proposed to compensate the mismatch in current control characteristics of each parallel converter. Good dynamic and static current sharing characteristics are obtained. In addition, to obtain good output voltage regulating control performance, a design procedure is presented to find the parameters of feedback voltage controller according to the prescribed specifications.

Chiang, S. J.; Liaw, C. M.; Ouyang, J. H.; Chiang, C. C.

1995-01-01

431

A Parallel Multigrid Method for Neutronics Applications  

SciTech Connect

The multigrid method has been shown to be the most effective general method for solving the multi-dimensional diffusion equation encountered in neutronics. This being the method of choice, we develop a strategy for implementing the multigrid method on computers of massively parallel architecture. This leads us to strategies for parallelizing the relaxation, contraction (interpolation), and prolongation operators involved in the method. We then compare the efficiency of our parallel multigrid with other parallel methods for solving the diffusion equation on selected problems encountered in reactor physics.

Alcouffe, Raymond E.

2001-01-01

432

Parallel Genetic Algorithm for Alpha Spectra Fitting  

NASA Astrophysics Data System (ADS)

We present a performance study of alpha-particle spectra fitting using parallel Genetic Algorithm (GA). The method uses a two-step approach. In the first step we run parallel GA to find an initial solution for the second step, in which we use Levenberg-Marquardt (LM) method for a precise final fit. GA is a high resources-demanding method, so we use a Beowulf cluster for parallel simulation. The relationship between simulation time (and parallel efficiency) and processors number is studied using several alpha spectra, with the aim of obtaining a method to estimate the optimal processors number that must be used in a simulation.

García-Orellana, Carlos J.; Rubio-Montero, Pilar; González-Velasco, Horacio

2005-01-01

433

FFT for the APE Parallel Computer  

NASA Astrophysics Data System (ADS)

We present a parallel FFT algorithm for SIMD systems following the "Transpose Algorithm" approach. The method is based on the assignment of the data field onto a one-dimensional ring of systolic cells. The systolic array can be universally mapped onto any parallel system. In particular for systems with next-neighbor connectivity our method has the potential to improve the efficiency of matrix transposition by use of hyper-systolic communication. We have realized a scalable parallel FFT on the APE100/Quadrics massively parallel computer, where our implementation is part of a two-dimensional hydrodynamics code for turbulence studies.

Lippert, Thomas; Schilling, Klaus; Trentmann, Sven; Toschi, Federico; Tripiccione, Raffaele

434

A parallel processing system of images  

NASA Astrophysics Data System (ADS)

In order to speedup image processing in embedded environment, we construct a parallel processing system of images. The parallel processing system includes a parallel hardware, a new defined language for parallel image processing and a set of software tools. From the view of high performance, low power dissipation and the characteristics of image processing, we construct a SIMD coprocessor as an image processing accelerator. Using a RISC host processor manages the whole system. The SIMD processor is scalable. We also define a new language which is extended from standard C. A new data type "stream" and a new keyword "kernel" are added to the language to explicitly describe parallelism. For the new hardware and language of parallel image processing, we also research software tools for this parallel system. The software tools maps programs to code that runs on the new hardware. For example develop a scheduler to transfer stream data between memories and register files. From the analysis we found that the parallel image processing system can not only match image applications' characteristics but also easy to implement by using VLSI technology. With new language and software tools supporting, an embedded real-time parallel image processing system becomes available for programmers.

Duan, ZongTao; Zhou, XingShe

2005-11-01

435

Nerve-pulse interactions  

SciTech Connect

Some recent experimental and theoretical results on mechanisms through which individual nerve pulses can interact are reviewed. Three modes of interactions are considered: (1) interaction of pulses as they travel along a single fiber which leads to velocity dispersion; (2) propagation of pairs of pulses through a branching region leading to quantum pulse code transformations; and (3) interaction of pulses on parallel fibers through which they may form a pulse assembly. This notion is analogous to Hebb's concept of a cell assembly, but on a lower level of the neural hierarchy.

Scott, A.C.

1982-01-01

436

Parallel processing in immune networks  

NASA Astrophysics Data System (ADS)

In this work, we adopt a statistical-mechanics approach to investigate basic, systemic features exhibited by adaptive immune systems. The lymphocyte network made by B cells and T cells is modeled by a bipartite spin glass, where, following biological prescriptions, links connecting B cells and T cells are sparse. Interestingly, the dilution performed on links is shown to make the system able to orchestrate parallel strategies to fight several pathogens at the same time; this multitasking capability constitutes a remarkable, key property of immune systems as multiple antigens are always present within the host. We also define the stochastic process ruling the temporal evolution of lymphocyte activity and show its relaxation toward an equilibrium measure allowing statistical-mechanics investigations. Analytical results are compared with Monte Carlo simulations and signal-to-noise outcomes showing overall excellent agreement. Finally, within our model, a rationale for the experimentally well-evidenced correlation between lymphocytosis and autoimmunity is achieved; this sheds further light on the systemic features exhibited by immune networks.

Agliari, Elena; Barra, Adriano; Bartolucci, Silvia; Galluzzi, Andrea; Guerra, Francesco; Moauro, Francesco

2013-04-01

437

Parallel cascade of Alfvén waves  

NASA Astrophysics Data System (ADS)

A heuristic semi-classical kinetic theory of turbulence in magnetized plasmas was formulated in the 1960s, but the statistical mechanical formulation of the same problem, which is necessary for a quantitative analysis, has not been accomplished. Recently, the present authors formulated the statistical mechanical kinetic turbulence theory in a formal manner (P H Yoon 2007 Phys. Plasmas 14 10230, P H Yoon and T-M Fang 2007 Phys. Plasmas 14 102303). In this paper, the parallel cascade of Alfvén waves via the three-wave decay process is numerically investigated on the basis of the results outlined in the above references. It is shown that the cascade of low-frequency Alfvén waves to high-frequency ion-cyclotron and magnetosonic waves takes place mediated by ion-sound turbulence. The Alfvén wave cascade is important, for instance, in the solar wind acceleration and coronal heating problem, since the low-frequency, long-wavelength Alfvén waves must first undergo cascade to high-frequency, short-wavelength modes in order for cyclotron resonant absorption to take place. The cyclotron resonance is believed to be important for charged-particle acceleration in the aforementioned applications. The present analysis may be important in such a context.

Yoon, Peter H.; Fang, Ta-Ming

2008-08-01

438

Correlation study of a rotor in descending flight using DYMORE with a freewake model  

Microsoft Academic Search

In this work, the Blade Vortex Interaction (BVI) airloads characteristic for a rotor in descending flight condition is investigated\\u000a using a nonlinear flexible multibody dynamics analysis code DYMORE. A free vortex wake model is incorporated into the comprehensive\\u000a analysis system and improvement of airloads prediction as well as collective and cyclic pitch control settings is obtained\\u000a over the finite-state dynamic

Jae-Sang Park; Sung Nam Jung; Soo Hyung Park; Yung Hoon Yu

2010-01-01

439

HHC study in the DNW to reduce BVI noise - An analysis  

Microsoft Academic Search

The noise of an aeroelastically scaled helicopter rotor has been studied in the German-Dutch wind tunnel in order to assess the utility of higher-harmonic control (HHC) in reducing blade-vortex interaction (BVI) noise. Acoustic data are presented for 3\\/rev, 4\\/rev, and 5\\/rev HHC, as applied to a typical landing approach rotor operating condition; noise reduction of up to 6 dB were

Thomas F. Brooks; Earl R. Booth Jr.; D. D. Boyd Jr.; Wolf R. Splettstoesser; Klaus-J. Schultz; Roland Kube; Georg H. Niesl; Olivier Streby

1991-01-01

440

The German-Dutch wind tunnel - An aeroacoustics experimentator's dream  

Microsoft Academic Search

The German-Dutch Wind Tunnel\\/DNW, when used in the acoustic mode, provides a realistic environment for aeroacoustic testing and high-quality data. Two research projects are discussed: (1) helicopter noise research, which concerns itself with high speed impulsive noise and blade\\/vortex interaction impulsive noise; and (2) propeller noise research. The data obtained proved to be excellent, and in the case of propeller

H. Heller; W. Dobrzynski; W. Splettstoesser; K. Schultz

1985-01-01

441

Initial results of a model rotor higher harmonic control (HHC) wind tunnel experiment on BVI impulsive noise reduction  

Microsoft Academic Search

Initial acoustic results are presented from a higher harmonic control (HHC) wind tunnel pilot experiment on helicopter rotor blade-vortex interaction (BVI) impulsive noise reduction, making use of the DFVLR 40-percent-scaled BO-105 research rotor in the DNW 6m by 8m closed test section. Considerable noise reduction (of several decibels) has been measured for particular HHC control settings, however, at the cost

W. R. Splettstoesser; G. Lehmann; B. van der Wall

1989-01-01

442

The German-Dutch wind tunnel - An aeroacoustics experimentator's dream  

NASA Astrophysics Data System (ADS)

The German-Dutch Wind Tunnel/DNW, when used in the acoustic mode, provides a realistic environment for aeroacoustic testing and high-quality data. Two research projects are discussed: (1) helicopter noise research, which concerns itself with high speed impulsive noise and blade/vortex interaction impulsive noise; and (2) propeller noise research. The data obtained proved to be excellent, and in the case of propeller noise research, such data could not have been obtained through flight tests.

Heller, H.; Dobrzynski, W.; Splettstoesser, W.; Schultz, K.

443

Results of the 1986 NASA\\/FAA\\/DFVLR main rotor test entry in the German-Dutch wind tunnel (DNW)  

Microsoft Academic Search

An acoustics test of a 40%-scale MBB BO-105 helicopter main rotor was conducted in the Deutsch-Niederlandischer Windkanal (DNW). The research, directed by NASA Langley Research Center, concentrated on the generation and radiation of broadband noise and impulsive blade-vortex interaction (BVI) noise over ranges of pertinent rotor operational envelopes. Both the broadband and BVI experimental phases are reviewed, along with highlights

Thomas F. Brooks; Ruth M. Martin

1987-01-01

444

BVI impulsive noise reduction by higher harmonic pitch control - Results of a scaled model rotor experiment in the DNW  

Microsoft Academic Search

Results are presented of a model rotor acoustics test performed to examine the benefit of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) impulsive noise. A dynamically scaled, four-bladed, rigid rotor model, a 40-percent replica of the B0-105 main rotor, was tested in the German Dutch Wind Tunnel. Noise characteristics and noise directivity patterns as well

Wolf R. Splettstoesser; Klaus-J. Schultz; Roland Kube; Thomas F. Brooks; Earl R. Booth Jr.; Georg Niesl; Olivier Streby

1991-01-01

445

Longitudinal-Plane Simultaneous Non-Interfering Approach Trajectory Design for Noise Minimization  

Microsoft Academic Search

Runway-independent aircraft (RIA) operating under simultaneous non-interfering (SNI) traffic procedures have been proposed to alleviate airspace congestion at crowded urban airports. This paper introduces a methodology for designing minimum-noise longitudinal SNI approach trajectories for rotorcraft. An analytical model for ground noise annoyance associated with out of plane Blade-Vortex Interaction (BVI) noise is introduced and its application as the cost function

Gaurav Gopalan; Min Xue; Ella M. Atkins; Fredric H. Schmitz

446

Application of stereoscopic PIV to helicopter rotor blade tip vortices  

Microsoft Academic Search

Stereoscopic PIV technique was applied to the blade tip vortices of helicopter model in order to acquire the information that is needed by the understanding of the tip vortex structure during the blade-vortex interaction (BVI). The measurements have been performed in the NAL 6.5 m×5.5 m low-speed wind tunnel. The test blades have a rectangular tip and twisted NACA 0012

Hiroyuki Kato; S. Watanabe; N. Kondo; Shigetu Saito

2003-01-01

447

The acoustic results of a United Techologies scale model helicopter rotor tested at DNW  

Microsoft Academic Search

An initial summary is presented of the acoustic measurements acquired for some of the different configurations of a 1\\/6 geometrically and aeroelastically scaled UTC model helicopter rotor which was tested in the open-jet anechoic test section of the Duits-Nederlandse Windtunnel in the Netherlands. Of particular interest are high-speed impulsive noise and blade-vortex interaction. An analysis is provided of baseline swept

Sandy R. Liu; Michael A. Marcolini

1990-01-01

448

Aeroacoustics - Historical perspective and important issues  

Microsoft Academic Search

Theoretical and experimental studies of helicopter rotor noise are reviewed, covering the period 1962-1987. Topics examined include the increased importance of rotor-induced noise with the advent of gas-turbine-powered helicopters in the early 1960s, the impact of improved acoustic instruments, harmonic analyses of rotor noise, aeroacoustic theory, rotational noise, fluctuating forces, broadband noise, blade slap, blade-vortex interaction, thickness noise, tail-rotor noise,

John W. Leverton

1987-01-01

449

The parallel Fortran family and a new perspective  

Microsoft Academic Search

Various parallel Fortran languages have been developed over the years. The research work in creating this Parallel Fortran Family has made significant contributions to parallel programming language design and implementation. In this paper, various parallel Fortran languages are studied based on a uniform co-ordination approach towards parallel programming. That is, new language constructs in parallel Fortran systems are regarded as

John Darlington; Yi-ke Guo; Jin Yang

1995-01-01

450

a Parallel Raycast Algorithm of Csg Models on CM2  

NASA Astrophysics Data System (ADS)

One of the main problems for CSG models manipulators is the fast visualization of the results. The high computational cost on single-processor architectures makes the CSG scheme useless for the interactive creation of the model. This article deals with a parallel algorithm based on general purpose SIMD architecture, such as the Connection Machine 2, for the visualization of high quality shaded images of CSG models in nearly real time. The technique is based on a pixels parallelization of the Ray Casting algorithm. The Frame Buffer is divided into severals regions and for each of them we determine the CSG reduced model projected on it. Then a processor is assigned to each pixel in the sub-area; it determines the equation of the ray crossing the pixel and, using the Ray Casting technique, the nearest intersection point to the pixel on which it calculates the illumination model.

Pili, Piero

451

[Parallel virtual reality visualization of extreme large medical datasets].  

PubMed

On the basis of a brief description of grid computing, the essence and critical techniques of parallel visualization of extreme large medical datasets are discussed in connection with Intranet and common-configuration computers of hospitals. In this paper are introduced several kernel techniques, including the hardware structure, software framework, load balance and virtual reality visualization. The Maximum Intensity Projection algorithm is realized in parallel using common PC cluster. In virtual reality world, three-dimensional models can be rotated, zoomed, translated and cut interactively and conveniently through the control panel built on virtual reality modeling language (VRML). Experimental results demonstrate that this method provides promising and real-time results for playing the role in of a good assistant in making clinical diagnosis. PMID:20481303

Tang, Min

2010-04-01

452

3D Visualization of Molecular Simulations in High-performance Parallel Computing Environments  

Microsoft Academic Search

This paper presents a novel tool for interactive 3D visualization and computational steering of molecular simulations and other computer simulation techniques such as computational fluid dynamics in parallel computing environments. The visualization system consists of three major components—data source, streaming server and viewer—which are distributed in intra\\/internet networks. A parallelized data extraction and visualization library, which generates 3D scenes, is

Karsten Meier; Christopher Holzknecht; Stephan Kabelac; Stephan Olbrich; Karsten Chmielewski

2004-01-01

453

The parallelism phenomenon in psychoanalysis and supervision: its reconsideration as a triadic system.  

PubMed

In psychoanalytic superivision, supervisees manifest toward their supervisors many psychic patterns which parallel processes that are prominent in their interactions with their patients. The reverse influence is also observed: analyst and patient re-enact events of the supervisory situation. An expanded explanation for parallelism is offered which indicates how the structural and dynamic similarities of analysis and supervision link patient, analyst, and supervisor in a complex, multidirectional network that guarantees the emergence of this phenomenon. PMID:7375592

Gediman, H K; Wolkenfeld, F

1980-04-01

454

The Model Coupling Toolkit: A New Fortran90 Toolkit for Building Multiphysics Parallel Coupled Models  

Microsoft Academic Search

ABSTRACT Many problems,in science and engineering,are best simulated,as a set of mu- tually interacting models, resulting in a coupled or multiphysics model. These models,present challenges stemming,from their interdisciplinary nature and from their computational,and algorithmic,complexities. The computational,complex- ity of individual models, combined with the popularity of the distributed-memory parallel programming model used on commodity microprocessor-based clusters, results in a parallel coupling

Jay Walter Larson; Robert L. Jacob; Everest T. Ong

2005-01-01

455

Multilevel Parallelization of AutoDock 4.2  

PubMed Central

Background Virtual (computational) screening is an increasingly important tool for drug discovery. AutoDock is a popular open-source application for performing molecular docking, the prediction of ligand-receptor interactions. AutoDock is a serial application, though several previous efforts have parallelized various aspects of the program. In this paper, we report on a multi-level parallelization of AutoDock 4.2 (mpAD4). Results Using MPI and OpenMP, AutoDock 4.2 was parallelized for use on MPI-enabled systems and to multithread the execution of individual docking jobs. In addition, code was implemented to reduce input/output (I/O) traffic by reusing grid maps at each node from docking to docking. Performance of mpAD4 was examined on two multiprocessor computers. Conclusions Using MPI with OpenMP multithreading, mpAD4 scales with near linearity on the multiprocessor systems tested. In situations where I/O is limiting, reuse of grid maps reduces both system I/O and overall screening time. Multithreading of AutoDock's Lamarkian Genetic Algorithm with OpenMP increases the speed of execution of individual docking jobs, and when combined with MPI parallelization can significantly reduce the execution time of virtual screens. This work is significant in that mpAD4 speeds the execution of certain molecular docking workloads and allows the user to optimize the degree of system-level (MPI) and node-level (OpenMP) parallelization to best fit both workloads and computational resources.

2011-01-01

456

GOTPM: a parallel hybrid particle-mesh treecode  

NASA Astrophysics Data System (ADS)

We describe a parallel, cosmological N-body code based on a hybrid scheme using the particle-mesh (PM) and Barnes-Hut (BH) oct-tree algorithm. We call the algorithm GOTPM for Grid-of-Oct-Trees-Particle-Mesh. The code is parallelized using the Message Passing Interface (MPI) library and is optimized to run on Beowulf clusters as well as symmetric multi-processors. The gravitational potential is determined on a mesh using a standard PM method with particle forces determined through interpolation. The softened PM force is corrected for short range interactions using a grid of localized BH trees throughout the entire simulation volume in a completely analogous way to P3M methods. This method makes no assumptions about the local density for short range force corrections and so is consistent with the results of the P3M method in the limit that the treecode opening angle parameter, ?-->0. The PM method is parallelized using one-dimensional slice domain decomposition. Particles are distributed in slices of equal width to allow mass assignment onto mesh points. The Fourier transforms in the PM method are done in parallel using the MPI implementation of the FFTW package. Parallelization for the tree force corrections is achieved again using one-dimensional slices but the width of each slice is allowed to vary according to the amount of computational work required by the particles within each slice to achieve load balance. The tree force corrections dominate the computational load and so imbalances in the PM density assignment step do not impact the overall load balance and performance significantly. The code performance scales well to 128 processors and is significantly better than competing methods. We present preliminary results from simulations run on different platforms containing up to N=1G particles to verify the code.

Dubinski, John; Kim, Juhan; Park, Changbom; Humble, Robin

2004-02-01

457

A new parallel P 3 M code for very large-scale cosmological simulations  

Microsoft Academic Search

We have developed a parallel Particle–Particle, Particle–Mesh (P3M) simulation code for the Cray T3E parallel supercomputer that is well suited to studying the time evolution of systems of particles interacting via gravity and gas forces in cosmological contexts. The parallel code is based upon the public-domain serial Adaptive P3M-SPH (http:\\/\\/coho.astro.uwo.ca\\/pub\\/hydra\\/hydra.html) code of Couchman et al. (1995)[ApJ, 452, 797]. The algorithm

Tom MacFarland; H. M. P. Couchman; Frazer Pearce; Jakob Pichlmeier

1998-01-01

458

Pringle: A Parallel Processor to Emulate CHiP (Configurable Highly Parallel) Computers.  

National Technical Information Service (NTIS)

The Pringle is a 64 processor parallel computer designed to serve as a laboratory instrument for studying Configurable, Highly Parallel (CHiP) Computers. The Pringle's design objectives, architecture and physical characteristics are presented. A key compo...

A. A. Kapauan J. T. Field L. Snyder

1983-01-01

459

Language Parallel Pascal and other aspects of the massively parallel processor  

SciTech Connect

A high level language for the Massively Parallel Processor (MPP) was designed. This language, called Parallel Pascal, is described in detail. A description of the language design, a description of the intermediate language, Parallel P-Code, and details for the MPP implementation are included. Formal descriptions of Parallel Pascal and Parallel P-Code are given. A compiler was developed which converts programs in Parallel Pascal into the intermediate Parallel P-Code language. The code generator to complete the compiler for the MPP is being developed independently. A Parallel Pascal to Pascal translator was also developed. The architecture design for a VLSI version of the MPP was completed with a description of fault tolerant interconnection networks. The memory arrangement aspects of the MPP are discussed and a survey of other high level languages is given.

Reeves, A.P.; Bruner, J.D.

1982-01-01

460

Virtual reality visualization of parallel molecular dynamics simulation  

SciTech Connect

When performing communications mapping experiments for massively parallel processors, it is important to be able to visualize the mappings and resulting communications. In a molecular dynamics model, visualization of the atom to atom interaction and the processor mappings provides insight into the effectiveness of the communications algorithms. The basic quantities available for visualization in a model of this type are the number of molecules per unit volume, the mass, and velocity of each molecule. The computational information available for visualization is the atom to atom interaction within each time step, the atom to processor mapping, and the energy resealing events. We use the CAVE (CAVE Automatic Virtual Environment) to provide interactive, immersive visualization experiences.

Disz, T.; Papka, M.; Stevens, R.; Pellegrino, M. [Argonne National Lab., IL (United States); Taylor, V. [Northwestern Univ., Evanston, IL (United States). Electrical Engineering and Computer Science

1995-12-31

461

Parallel preoptic pathways for thermoregulation.  

PubMed

Sympathetic premotor neurons in the rostral medullary raphe (RMR) regulate heat conservation by tail artery vasoconstriction and brown adipose tissue thermogenesis. These neurons are a critical relay in the pathway that increases body temperature. However, the origins of the inputs that activate the RMR during cold exposure have not been definitively identified. We investigated the afferents to the RMR that were activated during cold by examining Fos expression in retrogradely labeled neurons after injection of cholera toxin B subunit (CTb) in the RMR. These experiments identified a cluster of Fos-positive neurons in the dorsomedial hypothalamic nucleus and dorsal hypothalamic area (DMH/DHA) with projections to the RMR that may mediate cold-induced elevation of body temperature. Also, neurons in the median preoptic nucleus (MnPO) and dorsolateral preoptic area (DLPO) and in the A7 noradrenergic cell group were retrogradely labeled but lacked Fos expression, suggesting that they may inhibit the RMR. To investigate whether individual or common preoptic neurons project to the RMR and DMH/DHA, we injected CTb into the RMR and Fluorogold into the DMH/DHA. We found that projections from the DLPO and MnPO to the RMR and DMH/DHA emerge from largely separate neuronal populations, indicating they may be differentially regulated. Combined cell-specific lesions of MnPO and DLPO, but not lesions of either one alone, caused baseline hyperthermia. Our data suggest that the MnPO and DLPO provide parallel inhibitory pathways that tonically inhibit the DMH/DHA and the RMR at baseline, and that hyperthermia requires the release of this inhibition from both nuclei. PMID:19776281

Yoshida, Kyoko; Li, Xiaodong; Cano, Georgina; Lazarus, Michael; Saper, Clifford B

2009-09-23

462

Bayer image parallel decoding based on GPU  

NASA Astrophysics Data System (ADS)

In the photoelectrical tracking system, Bayer image is decompressed in traditional method, which is CPU-based. However, it is too slow when the images become large, for example, 2K×2K×16bit. In order to accelerate the Bayer image decoding, this paper introduces a parallel speedup method for NVIDA's Graphics Processor Unit (GPU) which supports CUDA architecture. The decoding procedure can be divided into three parts: the first is serial part, the second is task-parallelism part, and the last is data-parallelism part including inverse quantization, inverse discrete wavelet transform (IDWT) as well as image post-processing part. For reducing the execution time, the task-parallelism part is optimized by OpenMP techniques. The data-parallelism part could advance its efficiency through executing on the GPU as CUDA parallel program. The optimization techniques include instruction optimization, shared memory access optimization, the access memory coalesced optimization and texture memory optimization. In particular, it can significantly speed up the IDWT by rewriting the 2D (Tow-dimensional) serial IDWT into 1D parallel IDWT. Through experimenting with 1K×1K×16bit Bayer image, data-parallelism part is 10 more times faster than CPU-based implementation. Finally, a CPU+GPU heterogeneous decompression system was designed. The experimental result shows that it could achieve 3 to 5 times speed increase compared to the CPU serial method.

Hu, Rihui; Xu, Zhiyong; Wei, Yuxing; Sun, Shaohua

2012-11-01

463

Acoustic simulation in architecture with parallel algorithm  

Microsoft Academic Search

In allusion to complexity of architecture environment and Real-time simulation of architecture acoustics, a parallel radiosity algorithm was developed. The distribution of sound energy in scene is solved with this method. And then the impulse response between sources and receivers at frequency segment, which are calculated with multi-process, are combined into whole frequency response. The numerical experiment shows that parallel

Xiaohong Li; Xinrong Zhang; Dan Li

2004-01-01

464

Singularity analysis of planar parallel manipulators  

Microsoft Academic Search

With regard to planar parallel-manipulators, a general classification of singularities into three groups is introduced. The classification scheme relies on the properties of the Jacobian matrices of the manipulator at hand. The Jacobian matrices of two classes of planar parallel manipulators are derived and the three types of singularities are identified for them. The first class contains 20 manipulators constructed

H. R. Mohammadi Daniali; P. J. Zsombor-Murray; J. Angeles

1995-01-01

465

Unrelated parallel machine scheduling with job splitting  

Microsoft Academic Search

Scheduling jobs on unrelated parallel machines is an activity that is very much a part of industrial scheduling. We report a methodology for minimizing the total weighted tardiness of all jobs intended to be processed on unrelated parallel machines in the presence of dynamic job releases and dynamic machine availability. More importantly, the mixed (binary) integer linear programming model formulated

RASARATNAM LOGENDRAN; FENNY SUBUR

2004-01-01

466

Parallel Search Algorithms for Robot Motion Planning  

Microsoft Academic Search

In this paper we show that parallel search techniques derived from their sequential counterparts can enable the solution of instances of the robot motion planning problem that are computationally infeasible on sequential machines. We present a simple parallel version of a robot motion planning algorithm based on \\

Daniel J. Challou; Maria L. Gini; Vipin Kumar

1993-01-01

467

Multifrontal parallel distributed symmetric and unsymmetric solvers  

Microsoft Academic Search

We consider the solution of both symmetric and unsymmetric systems of sparse linear equations. A new parallel distributed memory multifrontal approach is described. To handle numerical pivoting efficiently, a parallel asynchronous algorithm with dynamic scheduling of the computing tasks has been developed. We discuss some of the main algorithmic choices and compare both implementation issues and the performance of the

P. R. Amestoy; I. S. Duff; J.-Y. L'Excellent

2000-01-01

468

Multifrontal parallel distributed symmetric and unsymmetric solvers  

Microsoft Academic Search

We consider the solution of both symmetric and unsymmetric systems of sparselinear equations. A new parallel distributed memory multifrontal approach isdescribed. To handle numerical pivoting efficiently, a parallel asynchronousalgorithm with dynamic scheduling of the computing tasks has been developed. Wediscuss some of the main algorithmic choices and compare both implementationissues and the performance of the LDLTand LU factorizations. Performanceanalysis on

P. R. Amestoy; I. S. Duff; J Y L'Excellent

1998-01-01

469

Parallel multi-computers and artificial intelligence  

Microsoft Academic Search

This book examines the present state and future direction of multicomputer parallel architectures for artificial intelligence research and development of artificial intelligence applications. The book provides a survey of the large variety of parallel architectures, describing the current state of the art and suggesting promising architectures to produce artificial intelligence systems such as intelligence systems such as intelligent robots. This

Uhr

1986-01-01

470

Parallel Organization: A Structural Change Theory.  

ERIC Educational Resources Information Center

|Discussion of organizational development and change focuses on parallel organization, a theory that combines changes in organizational theory with Quality of Work Life (QWL) theory. Criteria for effective employee participation groups are described, design and implementation of the parallel organization are explained, applications to libraries…

Fisher, William; Brin, Beth L.

1991-01-01

471

Parallel PSO using MapReduce  

Microsoft Academic Search

In optimization problems involving large amounts of data, such as web content, commercial transaction information, or bioinformatics data, individual function evaluations may take minutes or even hours. particle swarm optimization (PSO) must be parallelized for such functions. However, large-scale parallel programs must communicate efficiently, balance work across all processors, and address problems such as failed nodes. We present mapreduce particle

Andrew W. Mcnabb; Christopher K. Monson; Kevin D. Seppi

2007-01-01

472

Latin Squares for Parallel Array Access  

Microsoft Academic Search

A parallel memory system for efficient parallel array access using perfect latin squares asskewing functions is discussed. Simple construction methods for building perfect latinsquares are presented. The resulting skewing scheme provides conflict free access toseveral important subsets of an array. The address generation can be performed inconstant time with simple circuitry. The skewing scheme can provide constant timeaccess to rows,

Kichul Kim; Viktor K. Prasanna

1993-01-01

473

Perfect Latin squares and parallel array access  

Microsoft Academic Search

A new nonlinear skewing scheme is proposed for parallel array access. We introduce a new Latin square(perfect Latin square) which has several properties useful for parallel array access. A sufficient condition for the existence of perfect Latin squares and a simple construction method for perfect Latin squares are presented. The resulting skewing scheme provides conflict free access to various subsets

Kichul Kim; V. K. Prasanna-Kumar

1989-01-01

474

Performance analysis of parallel processing systems  

Microsoft Academic Search

A centralized parallel processing system with job splitting is considered. In such a system, jobs wait in a central queue, which is accessible by all the processors, and are split into independent tasks that can be executed on separate processors. This parallel processing system is modeled as a bulk arrival MX\\/M\\/c queueing system where customers and bulks correspond to tasks

R. Nelson; D. Towsley; A. N. Tantawi

1987-01-01

475

Parallel simulation of the Sharks World problem  

Microsoft Academic Search

The Sharks World problem has been suggested as a suitable application to evaluate the effectiveness of parallel simulation algorithms. This paper develops a simulation model in Maisie, a C-based simulation language. With minor modifications, a Maisie progrmm may be executed using either sequential or parallel simulation algorithms. The paper presents the results of executing the Maisie model on a multicomputer

Rajive L. Bagrodia; Wen-Toh Liao

1990-01-01

476

Pthreads for dynamic and irregular parallelism  

Microsoft Academic Search

High performance applications on shared memory machines have typically been written in a coarse grained style, with one heavyweight thread per processor. In comparison, programming with a large number of lightweight, parallel threads has several advantages, including simpler coding for programs with irregular and dynamic parallelism, and better adaptability to a changing number of processors. The programmer can express a

Girija J. Narlikar; Guy E. Blelloch

1998-01-01

477

Parallel Tiled QR Factorization for Multicore Architectures  

Microsoft Academic Search

As multicore systems continue to gain ground in the High Performance Computing world, linear algebra algorithms have to be reformulated or new algorithms have to be developed in order to take advantage of the architectural features on these new processors. Fine grain parallelism becomes a major requirement and introduces the necessity of loose syn- chronization in the parallel execution of

Alfredo Buttari; Julien Langou; Jakub Kurzak; Jack Dongarra

2007-01-01

478

Object-based modeling of parallel programs  

Microsoft Academic Search

The Parse Project has been investigating software development issues covering a range of parallel applications. Parse itself is an object-based design methodology that incorporates design management strategies based on data and function encapsulation, hierarchical decomposition, and staged refinement. Parse represents parallel software designs with a graphical notation called process graphs. After capturing a design's important structural features, this notation systematically

Ian Gorton; Jonathan P. Gray; I. Jelly

1995-01-01

479

Enhancing Parallel Robots Accuracy with Redundant Sensors  

Microsoft Academic Search

This paper introduces a control strategy based on redundant sensors that leads to parallel robots accuracy enhancement. The method is presented in general, then applied to a 4-dof parallel robot. Practical implementation issues, simulation results and experimental validation are addressed.

Frédéric Marquet; Sébastien Krut; François Pierrot

2002-01-01

480

Parallel Algorithms on the ASTRA SIMD Machine  

Microsoft Academic Search

In view of the tremendous computing power jump of modern RISC processors the interest in parallel computing seems to be thinning out. Why use a complicated system of parallel processors, if the problem can be solved by a single powerful micro-chip? It is a general law, however, that exponential growth will always end by some kind of a saturation, and

G. Odor; F. Rohrbach; G. Vesztergombi; G. Varga; F. Tatrai

1995-01-01

481

An exercise in proving parallel programs correct  

Microsoft Academic Search

A parallel program, Dijkstra's on-the-fly garbage collector, is proved correct using a proof method developed by Owicki. The fine degree of interleaving in this program makes it especially difficult to understand, and complicates the proof greatly. Difficulties with proving such parallel programs correct are discussed.

David Gries

1975-01-01

482

Parallel algorithms for adaptive mesh refinement  

Microsoft Academic Search

Computational methods based on the use of adaptively constructed nonuniform meshes reduce the amount of computation and storage necessary to perform many scientific calculations. The adaptive construction of such nonuniform meshes is an important part of these methods. In this paper, the authors present a parallel algorithm for adaptive mesh refinement that is suitable for implementation on distributed-memory parallel computers.

Mark T. Jones; Paul E. Plassmann

1997-01-01

483

Parallel Adaptive Mesh Coarsening for Seismic Tomography  

Microsoft Academic Search

Seismic tomography enables to model the internal struc- ture of the Earth. In order to improve the precision of exist- ing models, a huge amount of acquired seismic data must be analyzed. The analysis of such massive data require a con- siderable computing power which can only be delivered by parallel computational equipments. Yet, parallel computa- tion is not sufficient

Marc Grunberg; Stéphane Genaud; Catherine Mongenet

2004-01-01

484

Parallel adaptive mesh generation and decomposition  

Microsoft Academic Search

An important class of methodologies for the parallel processing of computational models defined on some discrete geometric data structures (i.e. meshes, grids) is the so calledgeometry decomposition or splitting approach. Compared to the sequential processing of such models, the geometry splitting parallel methodology requires an additional computational phase. It consists of the decomposition of the associated geometric data structure into

Poting Wu; Elias N. Houstis

1996-01-01

485

PARALLEL WALLS AS AN ABUTMENT SCOUR COUNTERMEASURE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Scour at bridge abutments can cause damage or failure of bridges and result in excessive repairs, loss of accessibility, or even death. To mitigate abutment scour, clear-water and live-bed laboratory experiments in a compound channel were performed using parallel walls. Two types of parallel walls ...

486

Parallel supercomputing today and the cedar approach  

Microsoft Academic Search

More and more scientists and engineers are becoming interested in using supercomputers. Earlier barriers to using these machines are disappearing as software for their use improves. Meanwhile, new parallel supercomputer architectures are emerging that may provide rapid growth in performance. These systems may use a large number of processors with an intricate memory system that is both parallel and hierarchical;

D. J. Kuck; E. S. Davidson; D. H. Lawrie; A. H. Sameh

1986-01-01

487

Parallel Computer Modeling of Complex Electromagnetic Systems  

Microsoft Academic Search

The HFSS frequency domain computer code, installed on an AIX-3 computer, was used to model a geometrically complex electromagnetic system operating over many decades of frequencies in nonhomogeneous media. First, we used a single processor unit, and then 16 processors operating in parallel. Since the Maxwell equations used in the HFSS code show no time dependence, parallel processing can be

A. S. Podgorski; Marek B. Zaremba; M. Vogel

2000-01-01

488

Role for optics in future parallel processing  

Microsoft Academic Search

There is real opportunity for optical computing, especially free-space optical communication, to improve the performance of supercomputers that exploit parallel processing techniques. In order to seize this opportunity, this paper reviews some of the needs of parallel architectures that appear hard to satisfy with standard electronic techniques and that may be more amenable to optics. The ability to vary the

Larry Rudolph