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1

Head-on parallel blade-vortex interaction  

NASA Technical Reports Server (NTRS)

An experimental and computational study was carried out to investigate the parallel head-on blade-vortex interaction (BVI) and its noise generation mechanism. A shock tube, with an enlarged test section, was used to generate a compressible starting vortex which interacted with a target airfoil. The dual-pulsed holographic interferometry (DPHI) technique and airfoil surface pressure measurements were employed to obtain quantitative flow data during the BVI. A thin-layer Navier-Stokes code (BV12D), with a high-order upwind-biased scheme and a multizonal grid, was also used to simulate numerically the phenomena occurring in the head-on BVI. The detailed structure of a convecting vortex was studied through independent measurements of density and pressure distributions across the vortex center. Results indicate that, in a strong head-on BVI, the opposite pressure peaks are generated on both sides of the leading edge as the vortex approaches. Then, as soon as the vortex passes by the leading edge, the high-pressure peak suddenly moves toward the low-peak-reducing in magnitude as it moves--simultaneously giving rise to the initial sound wave. In both experiment and computation, it is shown that the viscous effect plays a significant role in head-on BVIs.

Lee, Soogab; Bershader, Daniel

1994-01-01

2

Measurement of parallel blade–vortex interaction at low Reynolds numbers  

Microsoft Academic Search

In this study parallel blade–vortex interaction for a Schmidt-propeller configuration has been examined using particle image\\u000a velocimetry (PIV). This tandem configuration consists of a leading airfoil (forefoil), used to generate a vortical wake of\\u000a leading-edge vortices (LEVs) and trailing-edge vortices (TEVs) through a pitching or plunging motion, and a trailing airfoil\\u000a (hindfoil), held fixed with a specified angle of attack

David Rival; Roland Manejev; Cam Tropea

2010-01-01

3

High-Resolution Simulations of Parallel BladeVortex Interactions  

E-print Network

contribution coming from the trailing edge. The simulations are then extended to three-dimensional moving by the interaction is seen to primarily radiate from the leading-edge section of the airfoil with a weaker­vortex interaction computations Introduction A MAJOR source of rotorcraft noise is generated by the rotor blades

Alonso, Juan J.

4

Rotor blade vortex interaction noise  

NASA Astrophysics Data System (ADS)

Blade-vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade control techniques. The important parameters to control rotor blade-vortex interaction noise and vibration have been identified: blade tip vortex structures and its trajectory, blade aeroelastic deformation, and airloads. Several blade tip design concepts have been investigated for diffusing tip vortices and also for reducing noise. However, these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance. Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. The HHC technique has proved the substantial blade-vortex interaction noise reduction, up to 6 dB, while vibration and low-frequency noise have been increased. Tests with IBC techniques have shown the simultaneous reduction of rotor noise and vibratory loads with 2/rev pitch control inputs. Recently, active blade control concepts with smart structures have been investigated with the emphasis on active blade twist and trailing edge flap. Smart structures technologies are very promising, but further advancements are needed to meet all the requirements of rotorcraft applications in frequency, force, and displacement.

Yu, Yung H.

2000-02-01

5

Rotor blade–vortex interaction noise  

Microsoft Academic Search

Blade–vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade

Young H. Yu

2000-01-01

6

A reduced Blade-Vortex Interaction rotor  

E-print Network

. CONCLUSION 55 APPENDIX . 57 VITA 58 LIST OF FIGURES Page Figure 1. 1 Blade / Vortex Interactions of a Helicopter Rotor in Forward Flight. . . 2 Figure 2. 1 Special - Purpose BVI Experimental Test Configuration, showing 7 Wing Tip Vortex Generator... Vortex Attenuation Device . . 10 Figure 3. 1 Figure 4. 1 Schematic of the Helicopter Rotor in the Tunnel Test Section . . A Samlple Time History of BVI Events . . . 12 17 Figure 4. 2 Retreating Side BVI Events . . . 18 Figure 4. 3 Advancing Side...

Mani, Somnath

1996-01-01

7

Rotor blade-vortex interaction  

NASA Technical Reports Server (NTRS)

The vortex lattice method has been extended to a single bladed rotor operating at high advance ratios and encountering a free vortex from a fixed wing upstream of the rotor. The predicted unsteady load distributions on the model rotor blade are generally in agreement with the experimental results. This method has also been extended to full scale rotor flight cases in which vortex induced loads near the tip of a rotor blade were indicated. Using conformal transformation methods an exact analysis of the effects of thickness on the lift due to a two dimensional wing vortex interaction is presented.

Mccormick, B. W.

1973-01-01

8

An adaptive mesh method for the simulation of Blade Vortex Interaction  

E-print Network

An adaptive mesh method for the simulation of parallel ics. Blade Vortex Interaction (BV1) with an active Trailing Edge Flap (TEF) is presented. The two-dimensional 1111-steady problem is solved by a higher order upwind Euler method...

Kim, Kyu-Sup

2012-06-07

9

An analysis of blade vortex interaction aerodynamics and acoustics  

NASA Technical Reports Server (NTRS)

The impulsive noise associated with helicopter flight due to Blade-Vortex Interaction, sometimes called blade slap is analyzed especially for the case of a close encounter of the blade-tip vortex with a following blade. Three parts of the phenomena are considered: the tip-vortex structure generated by the rotating blade, the unsteady pressure produced on the following blade during the interaction, and the acoustic radiation due to the unsteady pressure field. To simplify the problem, the analysis was confined to the situation where the vortex is aligned parallel to the blade span in which case the maximum acoustic pressure results. Acoustic radiation due to the interaction is analyzed in space-fixed coordinates and in the time domain with the unsteady pressure on the blade surface as the source of chordwise compact, but spanwise non-compact radiation. Maximum acoustic pressure is related to the vortex core size and Reynolds number which are in turn functions of the blade-tip aerodynamic parameters. Finally noise reduction and performance are considered.

Lee, D. J.

1985-01-01

10

Blade vortex interaction noise reduction techniques for a rotorcraft  

NASA Technical Reports Server (NTRS)

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Charles, Bruce D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); JanakiRam, Ram D. (Inventor); Sankar, Lakshmi N. (Inventor)

1996-01-01

11

Blade vortex interaction noise reduction techniques for a rotorcraft  

NASA Technical Reports Server (NTRS)

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

Charles, Bruce D. (Inventor); Hassan, Ahmed A. (Inventor); Tadghighi, Hormoz (Inventor); JanakiRam, Ram D. (Inventor); Sankar, Lakshmi N. (Inventor)

1998-01-01

12

Rotating hot-wire investigation of the vortex responsible for blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

This distribution of the circumferential velocity of the vortex responsible for blade-vortex interaction noise was measured using a rotating hot-wire rake synchronously meshed with a model helicopter rotor at the blade passage frequency. Simultaneous far-field acoustic data and blade differential pressure measurements were obtained. Results show that the shape of the measured far-field acoustic blade-vortex interaction signature depends on the blade-vortex interaction geometry. The experimental results are compared with the Widnall-Wolf model for blade-vortex interaction noise.

Fontana, Richard Remo

1988-01-01

13

Rotor blade system with reduced blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

A rotor blade system with reduced blade-vortex interaction noise includes a plurality of tube members embedded in proximity to a tip of each rotor blade. The inlets of the tube members are arrayed at the leading edge of the blade slightly above the chord plane, while the outlets are arrayed at the blade tip face. Such a design rapidly diffuses the vorticity contained within the concentrated tip vortex because of enhanced flow mixing in the inner core, which prevents the development of a laminar core region.

Leishman, John G. (Inventor); Han, Yong Oun (Inventor)

2005-01-01

14

Two- and three-dimensional blade vortex interactions  

NASA Technical Reports Server (NTRS)

A three-dimensional time dependent Navier-Stokes analysis was applied to the rotor blade vortex interaction (BVI) problem. The numerical procedure is an iterative implicit procedure using three point central differences to represent spatial derivatives. A series of calculations were made to determine the time steps, pseudo-time steps, iterations, artificial dissipation level, etc. required to maintain a nondissipative vortex. Results show the chosen method to have excellent non-dissipative properties provided the correct parameters are chosen. This study was used to set parameters for both two- and three-dimensional blade vortex interaction studies. The two-dimensional study considered the interaction between a vortex and a NACA0012 airfoil. The results showed the detailed physics during the interaction including the pressure pulse propagating from the blade. The simulated flow physics was qualitatively similar to that experimentally observed. The 2-D BVI phenomena is the result of the buildup and violent collapse of the shock waves and local supersonic pockets on the blade surfaces. The resulting pressure pulse build-up appears to be centered at the blade leading edge. The three-dimensional interaction study considered the case of a vortex at 20 deg incidence to the blade leading edge. Although the qualitative results were similar to that of the two-dimensional interaction, details clearly showed the three-dimensional nature of the interaction process.

Davoudzadeh, F.; Liu, N.-S; Briley, W. R.; Buggeln, R. C.; Shamroth, S. J.

1990-01-01

15

Flow visualizations of perpendicular blade vortex interactions  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

16

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

17

A Novel Method for Reducing Rotor Blade-Vortex Interaction  

NASA Technical Reports Server (NTRS)

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-vortex interactions, the flip-tip rotor blade concept was devised. The flip-tip rotor increases the miss distance between the shed vortices and the rotor blades, reducing BVI noise. The distance is increased by rotating an outboard portion of the rotor tip either up or down depending on the flight condition. The proposed plan for the grant consisted of a computational simulation of the rotor aerodynamics and its wake geometry to determine the effectiveness of the concept, coupled with a series of wind tunnel experiments exploring the value of the device and validating the computer model. The computational model did in fact show that the miss distance could be increased, giving a measure of the effectiveness of the flip-tip rotor. However, the wind experiments were not able to be conducted. Increased outside demand for the 7'x lO' wind tunnel at NASA Ames and low priority at Ames for this project forced numerous postponements of the tests, eventually pushing the tests beyond the life of the grant. A design for the rotor blades to be tested in the wind tunnel was completed and an analysis of the strength of the model blades based on predicted loads, including dynamic forces, was done.

Glinka, A. T.

2000-01-01

18

A parametric study of transonic blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

Several parameters of transonic blade-vortex interactions (BVI) are being studied and some ideas for noise reduction are introduced and tested using numerical simulation. The model used is the two-dimensional high frequency transonic small disturbance equation with regions of distributed vorticity (VTRAN2 code). The far-field noise signals are obtained by using the Kirchhoff method with extends the numerical 2-D near-field aerodynamic results to the linear acoustic 3-D far-field. The BVI noise mechanisms are explained and the effects of vortex type and strength, and angle of attack are studied. Particularly, airfoil shape modifications which lead to noise reduction are investigated. The results presented are expected to be helpful for better understanding of the nature of the BVI noise and better blade design.

Lyrintzis, A. S.

1991-01-01

19

Full-scale measurements of blade-vortex interaction noise  

NASA Astrophysics Data System (ADS)

Full-scale far-field acoustic data on four different two-bladed rotors encountering blade-vortex interaction are compared. The UH-1H helicopter was tested with its standard NACA 0012 airfol rotor. Data are also presented for the AH-1S helicopter configured with its standard 540 rotor, the Kaman K747 rotor, and the OGEE tip rotor. The data were reduced using 'time-windowing' of the impulsive noise event, thus enhancing the signal-to-noise ratio of the in-flight data. Strong pressure gradients, isolated in the UH-1H and AH-1S 540 rotor signatures, strongly influenced the subjective annoyance of the rotor. The peak amplitudes and power spectrum of the K747 and OGEE rotors were about equal and generated less annoyance than the standard AH-1S or UH-1H rotors.

Boxwell, D. A.; Schmitz, F. H.

1982-10-01

20

An experimental and computational study of 2-D blade-vortex interaction  

NASA Technical Reports Server (NTRS)

An experimental and computational study is carried out to investigate the dominant physical factors of 2D parallel blade-vortex interaction (BVI) and its noise generation. A shock tube was used to generate a starting vortex which interacted with a target airfoil. Double-exposed holographic interferometry and airfoil surface pressure measurements were employed to obtain quantitative data during the BVI. As a numerical approach, thin-layer Navier-Stokes code, with a multizonal grid, was also used to resolve the phenomena occuring in the BVI, especially in the head-on collision case.

Lee, Soogab; Bershader, Daniel; Rai, Man M.

1991-01-01

21

Effects of trailing edge flap dynamic deployment on blade-vortex interactions  

E-print Network

A theoretical and experimental investigation is undertaken to determine the effects of an actively deployable trailing edge flap on the disturbances created during blade-vortex interactions (BVI). The theoretical model consists of an unsteady panel...

Nelson, Carter T.

2012-06-07

22

Transonic blade-vortex interactions noise: A parametric study  

NASA Technical Reports Server (NTRS)

Transonic Blade-Vortex Interactions (BVI) are simulated numerically and the noise mechanisms are investigated. The 2-D high frequency transonic small disturbance equation is solved numerically (VTRAN2 code). An Alternating Direction Implicit (ADI) scheme with monotone switches is used; viscous effects are included on the boundary and the vortex is simulated by the cloud-in-cell method. The Kirchoff method is used for the extension of the numerical 2-D near field aerodynamic results to the linear acoustic 3-D far field. The viscous effect (shock/boundary layer interaction) on BVI is investigated. The different types of shock motion are identified and compared. Two important disturbances with different directivity exist in the pressure signal and are believed to be related to the fluctuating lift and drag forces. Noise directivity for different cases is shown. The maximum radiation occurs at an angle between 60 and 90 deg below the horizontal for an airfoil fixed coordinate system and depends on the details of the airfoil shape. Different airfoil shapes are studied and classified according to the BVI noise produced.

Lyrintzis, A. S.; Xue, Y.

1990-01-01

23

HART-II: Prediction of Blade-Vortex Interaction Loading  

NASA Technical Reports Server (NTRS)

During the HART-I data analysis, the need for comprehensive wake data was found including vortex creation and aging, and its re-development after blade-vortex interaction. In October 2001, US Army AFDD, NASA Langley, German DLR, French ONERA and Dutch DNW performed the HART-II test as an international joint effort. The main objective was to focus on rotor wake measurement using a PIV technique along with the comprehensive data of blade deflections, airloads, and acoustics. Three prediction teams made preliminary correlation efforts with HART-II data: a joint US team of US Army AFDD and NASA Langley, German DLR, and French ONERA. The predicted results showed significant improvements over the HART-I predicted results, computed about several years ago, which indicated that there has been better understanding of complicated wake modeling in the comprehensive rotorcraft analysis. All three teams demonstrated satisfactory prediction capabilities, in general, though there were slight deviations of prediction accuracies for various disciplines.

Lim, Joon W.; Tung, Chee; Yu, Yung H.; Burley, Casey L.; Brooks, Thomas; Boyd, Doug; vanderWall, Berend; Schneider, Oliver; Richard, Hugues; Raffel, Markus

2003-01-01

24

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

25

The effect of tip vortex structure on helicopter noise due to blade/vortex interaction  

NASA Technical Reports Server (NTRS)

A potential cause of helicopter impulsive noise, commonly called blade slap, is the unsteady lift fluctuation on a rotor blade due to interaction with the vortex trailed from another blade. The relationship between vortex structure and the intensity of the acoustic signal is investigated. The analysis is based on a theoretical model for blade/vortex interaction. Unsteady lift on the blades due to blade/vortex interaction is calculated using linear unsteady aerodynamic theory, and expressions are derived for the directivity, frequency spectrum, and transient signal of the radiated noise. An inviscid rollup model is used to calculate the velocity profile in the trailing vortex from the spanwise distribution of blade tip loading. A few cases of tip loading are investigated, and numerical results are presented for the unsteady lift and acoustic signal due to blade/vortex interaction. The intensity of the acoustic signal is shown to be quite sensitive to changes in tip vortex structure.

Wolf, T. L.; Widnall, S. E.

1978-01-01

26

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

NASA Astrophysics Data System (ADS)

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 available for rotor blade-vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

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

27

Reduction of Helicopter Blade-Vortex Interaction Noise by Active Rotor Control Technology  

NASA Technical Reports Server (NTRS)

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 available for rotor blade vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

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

1997-01-01

28

Helicopter Blade-Vortex Interaction Noise with Comparisons to CFD Calculations  

NASA Technical Reports Server (NTRS)

A comparison of experimental acoustics data and computational predictions was performed for a helicopter rotor blade interacting with a parallel vortex. The experiment was designed to examine the aerodynamics and acoustics of parallel Blade-Vortex Interaction (BVI) and was performed in the Ames Research Center (ARC) 80- by 120-Foot Subsonic Wind Tunnel. An independently generated vortex interacted with a small-scale, nonlifting helicopter rotor at the 180 deg azimuth angle to create the interaction in a controlled environment. Computational Fluid Dynamics (CFD) was used to calculate near-field pressure time histories. The CFD code, called Transonic Unsteady Rotor Navier-Stokes (TURNS), was used to make comparisons with the acoustic pressure measurement at two microphone locations and several test conditions. The test conditions examined included hover tip Mach numbers of 0.6 and 0.7, advance ratio of 0.2, positive and negative vortex rotation, and the vortex passing above and below the rotor blade by 0.25 rotor chords. The results show that the CFD qualitatively predicts the acoustic characteristics very well, but quantitatively overpredicts the peak-to-peak sound pressure level by 15 percent in most cases. There also exists a discrepancy in the phasing (about 4 deg) of the BVI event in some cases. Additional calculations were performed to examine the effects of vortex strength, thickness, time accuracy, and directionality. This study validates the TURNS code for prediction of near-field acoustic pressures of controlled parallel BVI.

McCluer, Megan S.

1996-01-01

29

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

NASA Astrophysics Data System (ADS)

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 the composite blade in this study is shown to have a significant influence upon the noise caused by blade-vortex interactions; the predicted sound pressures are shown to be especially sensitive to torsional stiffness. The effect of frequency placement and control system stiffness on sound levels is also discussed.

Derham, Robert C.; Oh, Byung K.

1991-05-01

30

Flow structure generated by perpendicular blade vortex interaction and implications for helicopter noise predictions  

NASA Technical Reports Server (NTRS)

This report summarizes accomplishments and progress for the period ending April 1995. Much of the work during this period has concentrated on preparation for an analysis of data produced by an extensive wind tunnel test. Time has also been spent further developing an empirical theory to account for the effects of blade-vortex interaction upon the circulation distribution of the vortex and on preliminary measurements aimed at controlling the vortex core size.

Devenport, William J.; Glegg, Stewart A. L.

1995-01-01

31

Full-Potential Modeling of Blade-Vortex Interactions. Degree awarded by George Washington Univ., Feb. 1987  

NASA Technical Reports Server (NTRS)

A study of the full-potential modeling of a blade-vortex interaction was made. A primary goal of this study was to investigate the effectiveness of the various methods of modeling the vortex. The model problem restricts the interaction to that of an infinite wing with an infinite line vortex moving parallel to its leading edge. This problem provides a convenient testing ground for the various methods of modeling the vortex while retaining the essential physics of the full three-dimensional interaction. A full-potential algorithm specifically tailored to solve the blade-vortex interaction (BVI) was developed to solve this problem. The basic algorithm was modified to include the effect of a vortex passing near the airfoil. Four different methods of modeling the vortex were used: (1) the angle-of-attack method, (2) the lifting-surface method, (3) the branch-cut method, and (4) the split-potential method. A side-by-side comparison of the four models was conducted. These comparisons included comparing generated velocity fields, a subcritical interaction, and a critical interaction. The subcritical and critical interactions are compared with experimentally generated results. The split-potential model was used to make a survey of some of the more critical parameters which affect the BVI.

Jones, Henry E.

1997-01-01

32

Flow structure generated by perpendicular blade vortex interaction and implications for helicopter noise predictions  

NASA Technical Reports Server (NTRS)

Activities carried out in support of research on flow structure generated by perpendicular blade vortex interaction and implications for helicopter noise prediction are summarized. Progress in the following areas is described: (1) construction of 8 inch-chord NACA 0012 full-span blade; (2) Acquisition of two full-span blades; (3) preparation for hot wire measurements; (4) related work on a modified Betz's theory; and (5) work related to helicopter noise prediction. In addition, a list of publications based on the results of prior experimentation is presented.

Devenport, William J.; Glegg, Stewart A. L.

1994-01-01

33

Experimental blade vortex interaction noise characteristics of a utility helicopter at 1/4 scale  

NASA Technical Reports Server (NTRS)

Models of both the advanced main rotor system and the standard or "baseline" UH-1 main rotor system were tested at one-quarter scale in the Langley 4- by 7-Meter (V/STOL) Tunnel using the general rotor model system. Tests were conducted over a range of descent angles which bracketed the blade-vortex interaction phenomenon for a range of simulated forward speeds. The tunnel was operated in the open-throat configuration with acoustic treatment to improve the semi-anechoic characteristics of the test chamber. Acoustical data obtained for these two rotor systems operating at similar flight conditions are presented without analysis or discussion.

Conner, D. A.; Hoad, D. R.

1984-01-01

34

An Euler code calculation of blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

An Euler code has been developed for calculation of noise radiation due to the interaction of a distributed vortex with a Joukowski airfoil. THe time-dependent incompressible flow field is first determined and then integrated to yield the resulting sound production through use of the elegant low-frequency Green's function approach. This code has several interesting numerical features involved in the vortex motion and in continuous satisfaction of the Kutta condition. In addition, it removes the limitations on Reynolds number and is much more efficient than an earlier Navier-Stokes code. Results indicate that the noise production is due to the deceleration and subsequent acceleration of the vortex as it approaches and passes the airfoil. Predicted acoustic levels and frequencies agree with measured data although a precise comparison would require the strength, size, and position of the incoming vortex to be known.

Hardin, J. C.; Lamkin, S. L.

1987-01-01

35

Effect of leading-edge porosity on blade-vortex interaction noise  

NASA Technical Reports Server (NTRS)

The effect of the porous leading-edge of an airfoil on the blade-vortex interaction noise, which dominates far-field acoustic spectrum of the helicopter, is investigated. The thin-layer Navier-Stokes equations are solved with a high-order upwind-biased scheme and a multizonal grid system. The Baldwin-Lomax turbulence model is modified for considering transpiration on the surface. The amplitudes of the propagating acoustic wave in the near-field are calculated directly from the computation. The porosity effect on the surface is modeled. Results show leading-edge transpiration can suppress pressure fluctuations at the leading-edge during BVI, and consequently reduce the amplitude of propagating noise by 30 percent at maximum in the near-field. The effect of porosity factor on the noise level is also investigated.

Lee, Soogab

1993-01-01

36

Helicopter Model Rotor-Blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations  

NASA Technical Reports Server (NTRS)

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, in-flight acoustic data under similar non-dimensional test conditions using an improved data analysis technique. At low advance ratios (mu = 0.164 - 0.194), the BVI impulsive noise data scale remarkably well in level, waveform, and directivity patterns. At moderate advance ratios (mu = 0.224 - 0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise. Presently, no proved explanation of this discrepancy exists. Measured BVI noise radiation is highly sensitive to all of the four governing nondimensional parameters--hover tip Mach number, advance ratio, local inflow ratio, and thrust coefficient.

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

1987-01-01

37

Mach number scaling of helicopter rotor blade/vortex interaction noise  

NASA Technical Reports Server (NTRS)

A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.

Leighton, Kenneth P.; Harris, Wesley L.

1985-01-01

38

Reduction of Blade-Vortex Interaction (BVI) noise through X-force control  

NASA Technical Reports Server (NTRS)

Momentum theory and the longitudinal force balance equations of a single rotor helicopter are used to develop simple expressions to describe tip-path-plane tilt and uniform inflow to the rotor. The uniform inflow is adjusted to represent the inflow at certain azimuthal locations where strong Blade-Vortex Interaction (BVI) is likely to occur. This theoretical model is then used to describe the flight conditions where BVI is likely to occur and to explore those flight variables that can be used to minimize BVI noise radiation. A new X-force control is introduced to help minimize BVI noise. Several methods of generating the X-force are presented that can be used to alter the inflow to the rotor and thus increasing the likelihood of avoiding BVI during approaches to a landing.

Schmitz, Fredric H.

1995-01-01

39

Effect of wake structure on blade-vortex interaction phenomena: Acoustic prediction and validation  

NASA Technical Reports Server (NTRS)

During the Higher Harmonic Control Aeroacoustic Rotor Test, extensive measurements of the rotor aerodynamics, the far-field acoustics, the wake geometry, and the blade motion for powered, descent, flight conditions were made. These measurements have been used to validate and improve the prediction of blade-vortex interaction (BVI) noise. The improvements made to the BVI modeling after the evaluation of the test data are discussed. The effects of these improvements on the acoustic-pressure predictions are shown. These improvements include restructuring the wake, modifying the core size, incorporating the measured blade motion into the calculations, and attempting to improve the dynamic blade response. A comparison of four different implementations of the Ffowcs Williams and Hawkings equation is presented. A common set of aerodynamic input has been used for this comparison.

Gallman, Judith M.; Tung, Chee; Schultz, Klaus J.; Splettstoesser, Wolf; Buchholz, Heino

1995-01-01

40

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

41

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

NASA Technical Reports Server (NTRS)

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.

1988-01-01

42

A study of the noise mechanisms of transonic blade-vortex interactions  

NASA Technical Reports Server (NTRS)

Transonic blade-vortex interactions (BVI) are simulated numerically and the noise mechanisms are investigated. The two-dimensional high frequency transonic small disturbance equation is solved numerically (VTRAN2 code). An ADI scheme with monotone switches is used; viscous effects are included on the boundary, and the vortex is simulated by the cloud in cell method. The Kirchhoff method is used for the extension of the numerical two-dimensional near-field aerodynamic results to the linear acoustic three dimensional far field. The viscous effects (shock/boundary layer interactions) on BVI is investigated. The different types of shock motion are identified and compared. Two important disturbances with different directivity exist in the pressure signal and are believed to be related to the fluctuating lift and drag forces. Noise directivity for different cases is shown. The maximum radiation occurs at an angle between 60 and 90 degrees below the horizontal for an airfoil-fixed coordinate system and depends on the details of the airfoil shape. Different airfoil shapes are studied and classified according to the BVI noise produced.

Lyrintzis, Anastasios S.; Xue, Y.

1990-01-01

43

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

NASA Technical Reports Server (NTRS)

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 scaling 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.

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

1984-01-01

44

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

NASA Technical Reports Server (NTRS)

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.

1989-01-01

45

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

NASA Technical Reports Server (NTRS)

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.

1988-01-01

46

Signal Analysis of Helicopter Blade-Vortex-Interaction Acoustic Noise Data  

NASA Technical Reports Server (NTRS)

Blade-Vortex-Interaction (BVI) produces annoying high-intensity impulsive noise. NASA Ames collected several sets of BVI noise data during in-flight and wind tunnel tests. The goal of this work is to extract the essential features of the BVI signals from the in-flight data and examine the feasibility of extracting those features from BVI noise recorded inside a large wind tunnel. BVI noise generating mechanisms and BVI radiation patterns an are considered and a simple mathematical-physical model is presented. It allows the construction of simple synthetic BVI events that are comparable to free flight data. The boundary effects of the wind tunnel floor and ceiling are identified and more complex synthetic BVI events are constructed to account for features observed in the wind tunnel data. It is demonstrated that improved recording of BVI events can be attained by changing the geometry of the rotor hub, floor, ceiling and microphone. The Euclidean distance measure is used to align BVI events from each blade and improved BVI signals are obtained by time-domain averaging the aligned data. The differences between BVI events for individual blades are then apparent. Removal of wind tunnel background noise by optimal Wiener-filtering is shown to be effective provided representative noise-only data have been recorded. Elimination of wind tunnel reflections by cepstral and optimal filtering deconvolution is examined. It is seen that the cepstral method is not applicable but that a pragmatic optimal filtering approach gives encouraging results. Recommendations for further work include: altering measurement geometry, real-time data observation and evaluation, examining reflection signals (particularly those from the ceiling) and performing further analysis of expected BVI signals for flight conditions of interest so that microphone placement can be optimized for each condition.

Rogers, James C.; Dai, Renshou

1998-01-01

47

Flow structure generated by perpendicular blade-vortex interaction and implications for helicopter noise prediction. Volume 1: Measurements  

NASA Technical Reports Server (NTRS)

The perpendicular interaction of a streamwise vortex with an infinite span helicopter blade was modeled experimentally in incompressible flow. Three-component velocity and turbulence measurements were made using a sub-miniature four sensor hot-wire probe. Vortex core parameters (radius, peak tangential velocity, circulation, and centerline axial velocity deficit) were determined as functions of blade-vortex separation, streamwise position, blade angle of attack, vortex strength, and vortex size. The downstream development of the flow shows that the interaction of the vortex with the blade wake is the primary cause of the changes in the core parameters. The blade sheds negative vorticity into its wake as a result of the induced angle of attack generated by the passing vortex. Instability in the vortex core due to its interaction with this negative vorticity region appears to be the catalyst for the magnification of the size and intensity of the turbulent flowfield downstream of the interaction. In general, the core radius increases while peak tangential velocity decreases with the effect being greater for smaller separations. These effects are largely independent of blade angle of attack; and if these parameters are normalized on their undisturbed values, then the effects of the vortex strength appear much weaker. Two theoretical models were developed to aid in extending the results to other flow conditions. An empirical model was developed for core parameter prediction which has some rudimentary physical basis, implying usefulness beyond a simple curve fit. An inviscid flow model was also created to estimate the vorticity shed by the interaction blade, and to predict the early stages of its incorporation into the interacting vortex.

Wittmer, Kenneth S.; Devenport, William J.

1996-01-01

48

Prediction of blade-vortex interaction noise from measured blade pressure  

NASA Technical Reports Server (NTRS)

The impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied. The time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement. Particularly, the physical understanding of the characteristic features of a waveform is extensively studied in order to understand the generating mechanism and to identify the important parameters. The interaction trajectory of a tip vortex on an acoustic planform is shown to be a very important parameter for the impulsive shape of the noise. The unsteady nature of the pressure distribution at the very leading edge is also important to the pulse shape. The theoretical model using noncompact liner acoustics predicts the general shape of interaction impulse pretty well except for peak amplitude which requires more continuous information along the span at the leading edge.

Nakamura, Y.

1981-01-01

49

Non-harmonic root-pitch individual-blade control for the reduction of blade-vortex interaction noise in rotorcraft  

NASA Astrophysics Data System (ADS)

One of the greatest obstacles to public acceptance of rotorcraft is the high levels of noise they produce, particularly in low-speed descent. In this flight condition, the trailing edge vortex of one blade often passes in close proximity to other blades resulting in impulsive changes in lift. This Blade-Vortex Interaction (BVI) creates high levels of both noise and vibration. The objective of this dissertation is to evaluate the effectiveness of using physically motivated pulse-type Individual Blade Control for reducing the noise associated with the BVI. First, the major parameters that affect the severity of the interaction, such as vortex strength and blade-vortex miss-distance, are analyzed. Second, inputs designed specifically to alter the parameters previously identified as key are explored, resulting in elimination of advancing side noise and overall peak BVI Sound Pressure Level (BVISPL) reductions of up to 4.6 dB. Lastly, different feedback mechanisms for closed-loop control of IBC are examined to allow implementation of the developed inputs.

Malovrh, Brendon D.

50

Perpendicular blade vortex interaction and its implications for helicopter noise prediction: Wave-number frequency spectra in a trailing vortex for BWI noise prediction  

NASA Technical Reports Server (NTRS)

Perpendicular blade vortex interactions are a common occurrence in helicopter rotor flows. Under certain conditions they produce a substantial proportion of the acoustic noise. However, the mechanism of noise generation is not well understood. Specifically, turbulence associated with the trailing vortices shed from the blade tips appears insufficient to account for the noise generated. The hypothesis that the first perpendicular interaction experienced by a trailing vortex alters its turbulence structure in such a way as to increase the acoustic noise generated by subsequent interactions is examined. To investigate this hypothesis a two-part investigation was carried out. In the first part, experiments were performed to examine the behavior of a streamwise vortex as it passed over and downstream of a spanwise blade in incompressible flow. Blade vortex separations between +/- one eighth chord were studied for at a chord Reynolds number of 200,000. Three-component velocity and turbulence measurements were made in the flow from 4 chord lengths upstream to 15 chordlengths downstream of the blade using miniature 4-sensor hot wire probes. These measurements show that the interaction of the vortex with the blade and its wake causes the vortex core to loose circulation and diffuse much more rapidly than it otherwise would. Core radius increases and peak tangential velocity decreases with distance downstream of the blade. True turbulence levels within the core are much larger downstream than upstream of the blade. The net result is a much larger and more intense region of turbulent flow than that presented by the original vortex and thus, by implication, a greater potential for generating acoustic noise. In the second part, the turbulence measurements described above were used to derive the necessary inputs to a Blade Wake Interaction (BWI) noise prediction scheme. This resulted in significantly improved agreement between measurements and calculations of the BWI noise spectrum especially for the spectral peak at low frequencies, which previously was poorly predicted.

Devenport, William J.; Glegg, Stewart A. L.

1993-01-01

51

A parametric study of blade vortex interaction noise for two, three, and four-bladed model rotors at moderate tip speeds Theory and experiment  

NASA Technical Reports Server (NTRS)

An investigation of blade slap due to blade vortex interaction (BVI) has been conducted. This investigation consisted of an examination of BVI blade slap for two, three, and four-bladed model rotors at tip Mach numbers ranging from 0.20 to 0.50. Blade slap contours have been obtained for each configuration tested. Differences in blade slap contours, peak sound pressure level, and directivity for each configuration tested are noted. Additional fundamental differences, such as multiple interaction BVI, are observed and occur for only specific rotor blade configurations. The effect of increasing the Mach number on the BVI blade slap for various rotor blade combinations has been quantified. A peak blade slap Mach number scaling law is proposed. Comparison of measured BVI blade slap with theory is made.

Leighton, K. P.; Harris, W. L.

1984-01-01

52

Effect of higher harmonic control on helicopter rotor blade-vortex interaction noise: Prediction and initial validation  

NASA Technical Reports Server (NTRS)

The paper presents a status of theoretical tools of AFDD, DLR, NASA and ONERA for prediction of the effect of HHC on helicopter main rotor BVI noise. Aeroacoustic predictions from the four research centers, concerning a wind tunnel simulation of a typical descent flight case without and with HHC are presented and compared. The results include blade deformation, geometry of interacting vortices, sectional loads and noise. Acoustic predictions are compared to experimental data. An analysis of the results provides a first insight of the mechanisms by which HHC may affect BVI noise.

Beaumier, P.; Prieur, J.; Rahier, G.; Spiegel, P.; Demargne, A.; Tung, C.; Gallman, J. M.; Yu, Y. H.; Kube, R.; Vanderwall, B. G.

1995-01-01

53

Full-potential modeling of blade-vortex interactions  

NASA Technical Reports Server (NTRS)

A comparison is made of four different models for predicting the unsteady loading induced by a vortex passing close to an airfoil. (1) The first model approximates the vortex effect as a change in the airfoil angle of attack. (2) The second model is related to the first but, instead of imposing only a constant velocity on the airfoil, the distributed effect of the vortex is computed and used. This is analogous to a lifting surface method. (3) The third model is to specify a branch cut discontinuity in the potential field. The vortex is modeled as a jump in potential across the branch cut, the edge of which represents the center of the vortex. (4) The fourth method models the vortex expressing the potential as the sum of a known potential due to the vortex and an unknown perturbation due to the airfoil. The purpose of the current study is to investigate the four vortex models described above and to determine their relative merits and suitability for use in large three-dimensional codes.

Jones, H. E.; Caradonna, F. X.

1986-01-01

54

Numerical investigation of parallel airfoil-vortex interaction using large eddy simulation  

NASA Astrophysics Data System (ADS)

Helicopter Blade-Vortex Interaction (BVI) occurs under certain conditions of powered descent or during extreme maneuvering. The vibration and acoustic problems associated with the interaction of rotor tip vortices and the following blades are major aerodynamic concerns for the helicopter community. Researchers have performed numerous experimental and computational studies over the last two decades in order to gain a better understanding of the physical mechanisms involved in BVI. The most severe interaction, in terms of generated noise, happens when the vortex filament is parallel to the blade, thus affecting a great portion of it. The majority of the previous numerical studies of parallel BVI fall within a potential flow framework, therefore excluding all viscous phenomena. Some Navier-Stokes approaches using dissipative numerical methods in conjunction with RANS-type turbulence models have also been attempted, but with limited success. In this work, the situation is improved by increasing the fidelity of both the numerical method and the turbulence model. A kinetic-energy conserving finite-volume scheme using a collocated-mesh arrangement, specially designed for simulation of turbulence in complex geometries, was implemented. For the turbulence model, a cost-effective zonal hybrid RANS/LES technique is used. A BANS zone covers the boundary layers on the airfoil and the wake region behind, while the remainder of the flow field, including the region occupied by the vortex makes up the dynamic LES zone. The concentrated tip vortex is not attenuated as it is convected downstream and over a NACA 0012 airfoil. The lift, drag, moment and friction coefficients induced by the passage of the vortex are monitored in time and compared with experimental data.

Felten, Frederic N.

55

Rotor system having alternating length rotor blades for reducing blade-vortex interaction (BVI) noise  

NASA Technical Reports Server (NTRS)

A rotor system (4) having odd and even blade assemblies (O.sub.b, E.sub.b) mounting to and rotating with a rotor hub assembly (6) wherein the odd blade assemblies (O.sub.b) define a radial length R.sub.O, and the even blade assemblies (E.sub.b) define a radial length R.sub.E and wherein the radial length R.sub.E is between about 70% to about 95% of the radial length R.sub.O. Other embodiments of the invention are directed to a Variable Diameter Rotor system (4) which may be configured for operating in various operating modes for optimizing aerodynamic and acoustic performance. The Variable Diameter Rotor system (4) includes odd and even blade assemblies (O.sub.b, E.sub.b) having inboard and outboard blade sections (10, 12) wherein the outboard blade sections (12) telescopically mount to the inboard blade sections (10). The outboard blade sections (12) are positioned with respect to the inboard blade sections (10 such that the radial length R.sub.E of the even blade assemblies (E.sub.b) is equal to the radial length R.sub.O of the odd blade assemblies (O.sub.b) in a first operating mode, and such that the radial length R.sub.E is between about 70% to about 95% of the length R.sub.O in a second operating mode.

Moffitt, Robert C. (Inventor); Visintainer, Joseph A. (Inventor)

1997-01-01

56

Interactions between flames on parallel solid surfaces  

NASA Technical Reports Server (NTRS)

The interactions between flames spreading over parallel solid sheets of paper are being studied in normal gravity and in microgravity. This geometry is of practical importance since in most heterogeneous combustion systems, the condensed phase is non-continuous and spatially distributed. This spatial distribution can strongly affect burning and/or spread rate. This is due to radiant and diffusive interactions between the surface and the flames above the surfaces. Tests were conducted over a variety of pressures and separation distances to expose the influence of the parallel sheets on oxidizer transport and on radiative feedback.

Urban, David L.

1995-01-01

57

The parallel implementation of a full configuration interaction program  

NASA Astrophysics Data System (ADS)

Both the replicated and distributed data parallel full configuration interaction (FCI) implementations are described. The implementation of the FCI algorithm is organized in a hybrid strings-integral driven approach. Redundant communication is avoided, and the network performance is further optimized by an improved distributed data interface library. Examples show linear scalability of the distributed data code on both PC and workstation clusters. The new parallel implementation greatly extends the hardware on which parallel FCI calculations can be performed. The timing data on the workstation cluster show great potential for using the new parallel FCI algorithm in expanding applications of complete active space self-consistent field applications.

Gan, Zhengting; Alexeev, Yuri; Gordon, Mark S.; Kendall, Ricky A.

2003-07-01

58

Investigation of helicopter rotor blade/wake interactive impulsive noise  

NASA Technical Reports Server (NTRS)

An analysis of the Tip Aerodynamic/Aeroacoustic Test (TAAT) data was performed to identify possible aerodynamic sources of blade/vortex interaction (BVI) impulsive noise. The identification is based on correlation of measured blade pressure time histories with predicted blade/vortex intersections for the flight condition(s) where impulsive noise was detected. Due to the location of the recording microphones, only noise signatures associated with the advancing blade were available, and the analysis was accordingly restricted to the first and second azimuthal quadrants. The results show that the blade tip region is operating transonically in the azimuthal range where previous BVI experiments indicated the impulsive noise to be. No individual blade/vortex encounter is identifiable in the pressure data; however, there is indication of multiple intersections in the roll-up region which could be the origin of the noise. Discrete blade/vortex encounters are indicated in the second quadrant; however, if impulsive noise were produced here, the directivity pattern would be such that it was not recorded by the microphones. It is demonstrated that the TAAT data base is a valuable resource in the investigation of rotor aerodynamic/aeroacoustic behavior.

Miley, S. J.; Hall, G. F.; Vonlavante, E.

1987-01-01

59

VIPP: Visual Interactive Parallel Performance Tool Edmund M. Johnson  

E-print Network

VIPP: Visual Interactive Parallel Performance Tool Edmund M. Johnson International Business 92093­0114 USA Email address: baden@cs.ucsd.edu Phone: (619) 534­8861 Abstract VIPP is an instructional on distributed memory MIMD computers. VIPP enables its user to interactively visualize factors affecting

Baden, Scott B.

60

Parallelism in interactive operations in finite-element simulation  

Microsoft Academic Search

The parallelizing of interactive operations that are part of the finite-element simulation of electromagnetic fields is examined. The total solution time in finite-element analysis is the time assigned to (1) preprocessing, (2) assembling and solving the matrix equation, and (3) postprocessing the solution. In the analysis the tasks of pre- and postprocessing are interactive, with the user sitting at a

S. R. H. Hoole; G. Mahinthakumar

1990-01-01

61

Nature of the water/aromatic parallel alignment interactions.  

PubMed

The water/aromatic parallel alignment interactions are interactions where the water molecule or one of its O?H bonds is parallel to the aromatic ring plane. The calculated energies of the interactions are significant, up to ?ECCSD(T)(limit) = -2.45 kcal mol(-1) at large horizontal displacement, out of benzene ring and CH bond region. These interactions are stronger than CH···O water/benzene interactions, but weaker than OH···? interactions. To investigate the nature of water/aromatic parallel alignment interactions, energy decomposition methods, symmetry-adapted perturbation theory, and extended transition state-natural orbitals for chemical valence (NOCV), were used. The calculations have shown that, for the complexes at large horizontal displacements, major contribution to interaction energy comes from electrostatic interactions between monomers, and for the complexes at small horizontal displacements, dispersion interactions are dominant binding force. The NOCV-based analysis has shown that in structures with strong interaction energies charge transfer of the type ? ? ?*(O?H) between the monomers also exists. © 2014 Wiley Periodicals, Inc. PMID:25393085

Mitoraj, Mariusz P; Janji?, Goran V; Medakovi?, Vesna B; Veljkovi?, Dušan Ž; Michalak, Artur; Zari?, Snežana D; Mil?i?, Miloš K

2015-01-30

62

An interactive parallel programming environment applied in atmospheric science  

NASA Technical Reports Server (NTRS)

This article introduces an interactive parallel programming environment (IPPE) that simplifies the generation and execution of parallel programs. One of the tasks of the environment is to generate message-passing parallel programs for homogeneous and heterogeneous computing platforms. The parallel programs are represented by using visual objects. This is accomplished with the help of a graphical programming editor that is implemented in Java and enables portability to a wide variety of computer platforms. In contrast to other graphical programming systems, reusable parts of the programs can be stored in a program library to support rapid prototyping. In addition, runtime performance data on different computing platforms is collected in a database. A selection process determines dynamically the software and the hardware platform to be used to solve the problem in minimal wall-clock time. The environment is currently being tested on a Grand Challenge problem, the NASA four-dimensional data assimilation system.

vonLaszewski, G.

1996-01-01

63

Interaction of a turbulent vortex with a lifting surface  

NASA Technical Reports Server (NTRS)

The impulsive noise due to blade-vortex-interaction is analyzing in the time domain for the extreme case when the blade cuts through the center of the vortex core with the assumptions of no distortion of the vortex path or of the vortex core. An analytical turbulent vortex core model, described in terms of the tip aerodynamic parameters, is used and its effects on the unsteady loading and maximum acoustic pressure during the interaction are determined.

Lee, D. J.; Roberts, L.

1985-01-01

64

Introduction Parallel SAMR Fluid-structure interaction Conclusions Massively parallel fluid-structure interaction simulation of  

E-print Network

-structure interaction simulation of blast and explosions impacting on realistic building structures with a block Verification and validation configurations Blast-driven deformation Detonation-driven deformations Conclusions, blast, detonations) http://www.cacr.caltech.edu/asc Papers: [Deiterding, 2011, Deiterding et al., 2009

Deiterding, Ralf

65

Long-range interactions & parallel scalability in molecular simulations  

E-print Network

Typical biomolecular systems such as cellular membranes, DNA, and protein complexes are highly charged. Thus, efficient and accurate treatment of electrostatic interactions is of great importance in computational modelling of such systems. We have employed the GROMACS simulation package to perform extensive benchmarking of different commonly used electrostatic schemes on a range of computer architectures (Pentium-4, IBM Power 4, and Apple/IBM G5) for single processor and parallel performance up to 8 nodes - we have also tested the scalability on four different networks, namely Infiniband, GigaBit Ethernet, Fast Ethernet, and nearly uniform memory architecture, i.e., communication between CPUs is possible by directly reading from or writing to other CPUs' local memory. It turns out that the particle-mesh Ewald method (PME) performs surprisingly well and offers competitive performance unless parallel runs on PC hardware with older network infrastructure are needed. Lipid bilayers of sizes 128, 512 and 2048 lipid molecules were used as the test systems representing typical cases encountered in biomolecular simulations. Our results enable an accurate prediction of computational speed on most current computing systems, both for serial and parallel runs. These results should be helpful in, for example, choosing the most suitable configuration for a small departmental computer cluster.

Michael Patra; Marja T. Hyvonen; Emma Falck; Mohsen Sabouri-Ghomi; Ilpo Vattulainen; Mikko Karttunen

2004-10-08

66

Parallel Force Assay for Protein-Protein Interactions  

PubMed Central

Quantitative proteome research is greatly promoted by high-resolution parallel format assays. A characterization of protein complexes based on binding forces offers an unparalleled dynamic range and allows for the effective discrimination of non-specific interactions. Here we present a DNA-based Molecular Force Assay to quantify protein-protein interactions, namely the bond between different variants of GFP and GFP-binding nanobodies. We present different strategies to adjust the maximum sensitivity window of the assay by influencing the binding strength of the DNA reference duplexes. The binding of the nanobody Enhancer to the different GFP constructs is compared at high sensitivity of the assay. Whereas the binding strength to wild type and enhanced GFP are equal within experimental error, stronger binding to superfolder GFP is observed. This difference in binding strength is attributed to alterations in the amino acids that form contacts according to the crystal structure of the initial wild type GFP-Enhancer complex. Moreover, we outline the potential for large-scale parallelization of the assay. PMID:25546146

Aschenbrenner, Daniela; Pippig, Diana A.; Klamecka, Kamila; Limmer, Katja; Leonhardt, Heinrich; Gaub, Hermann E.

2014-01-01

67

Simulation of Parallel Interacting Faults and Earthquake Predictability  

NASA Astrophysics Data System (ADS)

Numerical shear experiments of a granular region using the lattice solid model often exhibit accelerating energy release in the lead-up to large events (Mora et al, 2000) and a growth in correlation lengths in the stress field (Mora and Place, 2002). While these results provide evidence for a Critical Point-like mechanism in elasto-dynamic systems and the possibility of earthquake forecasting but they do not prove such a mechanism occurs in the crust. Cellular automaton models simulations exhibit accelerating energy release prior to large events or unpredictable behaviour in which large events may occur at any time depending on tuning parameters such as dissipation ratio and stress transfer ratio (Weatherley and Mora, 2003). The mean stress plots from the particle simulations are most similar to the CA mean stress plots near the boundary of the predictable and unpredictable regimes suggesting that elasto-dynamic systems may be close to the borderline of predictable and unpredictable. To progress in resolving the question of whether more realistic fault system models exhibit predictable behaviour and to determine whether they also have an unpredictable and predictable regime depending on tuning parameters like that seen in CA simulations, we developed a 2D elasto-dynamic model of parallel interacting faults. The friction is slip weakening until a critical slip distance. Henceforth, the friction is at the dynamic value until the slip rate drops below the value it attained when the critical slip distance was exceeded. As the slip rate continues to drop, the friction increases back to the static value as a function of slip rate. Numerical shear experiments are conducted in a model with 41 parallel interacting faults. Calculations of the inverse metric defined in Klein et al (2000) indicate that the system is non-ergodic. Furthermore, by calculating the correllation between the stress fields at different times we determine that the system exhibits so called ``glassy'' behaviour. This implies that mean field theoretical analysis such as Klein et al, 2000 requires introduction of a memory kernel in order to properly account for the glassy behaviour of interacting fault system models. The elasto-dynamic parallel interacting fault model helps to provide a crucial link between CA maps of phase space and the behaviour of more realistic elasto-dynamic interacting fault system models, and thus, a means to improve understanding of the dynamics and predictability of real fault systems. REFERENCES W. Klein and M. Anghel and C.D. Ferguson and J.B. Rundle and J.S. Sá Martins (2000) Statistical Analysis of a Model for Earthquake Faults with Long-Range Stress Transfer, in: Geocomplexity and the Physics of Earthquakes (Geophysical Monograph series; no. 120), eds. J.B. Rundle and D. L. Turcotte and W. Klein, pp 43-71 (American Geophysical Union, Washington, DC). Mora, P., Place, D., Abe, S. and Jaumé, S. (2000) Lattice solid simulation of the physics of earthquakes: the model, results and directions, in: GeoComplexity and the Physics of Earthquakes (Geophysical Monograph series; no. 120), eds. Rundle, J.B., Turcotte, D.L. &Klein, W., pp 105-125 (American Geophys. Union, Washington, DC). Mora, P., and Place, D. (2002) Stress correlation function evolution in lattice solid elasto-dynamic models of shear and fracture zones and earthquake prediction, Pure Appl. Geophys, 159, 2413-2427. Weatherley, D. and Mora, P. (2003) Accelerating Precursory Activity within a Class of Earthquake Analog Automata, Pure Appl. Geophysics, submitted.

Mora, P.; Weatherley, D.; Klein, B.

2003-04-01

68

VisIt: Interactive Parallel Visualization and Graphical Analysis Tool  

NASA Astrophysics Data System (ADS)

VisIt is a free interactive parallel visualization and graphical analysis tool for viewing scientific data on Unix and PC platforms. Users can quickly generate visualizations from their data, animate them through time, manipulate them, and save the resulting images for presentations. VisIt contains a rich set of visualization features so that you can view your data in a variety of ways. It can be used to visualize scalar and vector fields defined on two- and three-dimensional (2D and 3D) structured and unstructured meshes. VisIt was designed to handle very large data set sizes in the terascale range and yet can also handle small data sets in the kilobyte range. See the table below for more details about the tool’s features. VisIt was developed by the Department of Energy (DOE) Advanced Simulation and Computing Initiative (ASCI) to visualize and analyze the results of terascale simulations. It was developed as a framework for adding custom capabilities and rapidly deploying new visualization technologies. Although the primary driving force behind the development of VisIt was for visualizing terascale data, it is also well suited for visualizing data from typical simulations on desktop systems.

Department Of Energy (DOE) Advanced Simulation; Computing Initiative (ASCI)

2011-03-01

69

ParaLearn: a massively parallel, scalable system for learning interaction networks on FPGAs  

Microsoft Academic Search

ParaLearn is a scalable, parallel FPGA-based system for learning interaction networks using Bayesian statistics. ParaLearn includes problem specific parallel\\/scalable algorithms, system software and hardware architecture to address this complex problem. Learning interaction networks from data uncovers causal relationships and allows scientists to predict and explain a system's behavior. Interaction networks have applications in many fields, though we will discuss them

Narges Bani Asadi; Christopher W. Fletcher; Greg Gibeling; John Wawrzynek; Wing H. Wong; Garry P. Nolan; Zoey Zhou

2010-01-01

70

Combined Series and Parallel Circuits: Interactive Lecture Demonstrations  

NSDL National Science Digital Library

Three in-class lecture demonstration questions to test and build understanding of DC circuits are presented. These questions cover simple series and parallel circuits, and a more complicated circuit that is fundamental for understanding this topic.

Bruce Mason

71

Parallel multireference configuration interaction calculations on mini-beta-carotenes and beta-carotene  

Microsoft Academic Search

We present a parallelized version of a direct selecting multireference configuration interaction (MRCI) code [S. Grimme and M. Waletzke, J. Chem. Phys. 111, 5645 (1999)]. The program can be run either in ab initio mode or as semiempirical procedure combined with density functional theory (DFT\\/MRCI). We have investigated the efficiency of the parallelization in case studies on carotenoids and porphyrins.

Martin Kleinschmidt; Christel M. Marian; Mirko Waletzke; Stefan Grimme

2009-01-01

72

The displacement field characterization of two interacting parallel edge cracks in a finite body  

E-print Network

The goals of this research were to: (1) develop a model to represent the displacement field surrounding two interacting, parallel edge cracks; and (2) use this model to investigate the influence of crack separation and relative crack length...

Keener, Todd Whitney

1996-01-01

73

Interactive Parallel Programming Using the ParaScope Editor  

E-print Network

between regions that are executed in parallel may correspond to a data race, indicating the existence the existence of dependences. If it cannot be proven that a dependence does not exist, automatic tools must alike. Programmers, eager to use new machines to speed up existing sequential scienti c codes, want

McKinley, Kathryn S.

74

Interactive animation of fault-tolerant parallel algorithms  

SciTech Connect

Animation of algorithms makes understanding them intuitively easier. This paper describes the software tool Raft (Robust Animator of Fault Tolerant Algorithms). The Raft system allows the user to animate a number of parallel algorithms which achieve fault tolerant execution. In particular, we use it to illustrate the key Write-All problem. It has an extensive user-interface which allows a choice of the number of processors, the number of elements in the Write-All array, and the adversary to control the processor failures. The novelty of the system is that the interface allows the user to create new on-line adversaries as the algorithm executes.

Apgar, S.W.

1992-02-01

75

Long-range interactions & parallel scalability in molecular simulations  

Microsoft Academic Search

Typical biomolecular systems such as cellular membranes, DNA, and protein complexes are highly charged. Thus, efficient and accurate treatment of electrostatic interactions is of great importance in computational modelling of such systems. We have employed the GROMACS simulation package to perform extensive benchmarking of different commonly used electrostatic schemes on a range of computer architectures (Pentium-4, IBM Power 4, and

Michael Patra; Marja T. Hyvonen; Emma Falck; Mohsen Sabouri-Ghomi; Ilpo Vattulainen; Mikko Karttunen

2004-01-01

76

Plasma acceleration by the interaction of parallel propagating Alfvén waves  

NASA Astrophysics Data System (ADS)

abstract-type="normal"> It is shown that two circularly polarized Alfvén waves that propagate along the ambient magnetic field in an uniform plasma trigger non oscillating electromagnetic field components when they cross each other. The non-oscilliating field components can accelerate ions and electrons with great efficiency. This work is based on particle-in-cell (PIC) numerical simulations and on analytical non-linear computations. The analytical computations are done for two counter-propagating monochromatic waves. The simulations are done with monochromatic waves and with wave packets. The simulations show parallel electromagnetic fields consistent with the theory, and they show that the particle acceleration results in plasma cavities and, if the waves amplitudes are high enough, in ion beams. These acceleration processes could be relevant in space plasmas. For instance, they could be at work in the auroral zone and in the radiation belts of the Earth magnetosphere. In particular, they may explain the origin of the deep plasma cavities observed in the Earth auroral zone.

Mottez, F.

2015-01-01

77

Propeller tip vortex interactions  

NASA Technical Reports Server (NTRS)

Propeller wakes interacting with aircraft aerodynamic surfaces are a source of noise and vibration. For this reason, flow visualization work on the motion of the helical tip vortex over a wing and through the second stage of a counterrotation propeller (CRP) has been pursued. Initially, work was done on the motion of a propeller helix as it passes over the center of a 9.0 aspect ratio wing. The propeller tip vortex experiences significant spanwise displacements when passing across a lifting wing. A stationary propeller blade or stator was installed behind the rotating propeller to model the blade vortex interaction in a CRP. The resulting vortex interaction was found to depend on the relative vortex strengths and vortex sign.

Johnston, Robert T.; Sullivan, John P.

1990-01-01

78

Bayesian seismic tomography by parallel interacting Markov chains  

NASA Astrophysics Data System (ADS)

The velocity field estimated by first arrival traveltime tomography is commonly used as a starting point for further seismological, mineralogical, tectonic or similar analysis. In order to interpret quantitatively the results, the tomography uncertainty values as well as their spatial distribution are required. The estimated velocity model is obtained through inverse modeling by minimizing an objective function that compares observed and computed traveltimes. This step is often performed by gradient-based optimization algorithms. The major drawback of such local optimization schemes, beyond the possibility of being trapped in a local minimum, is that they do not account for the multiple possible solutions of the inverse problem. They are therefore unable to assess the uncertainties linked to the solution. Within a Bayesian (probabilistic) framework, solving the tomography inverse problem aims at estimating the posterior probability density function of velocity model using a global sampling algorithm. Markov chains Monte-Carlo (MCMC) methods are known to produce samples of virtually any distribution. In such a Bayesian inversion, the total number of simulations we can afford is highly related to the computational cost of the forward model. Although fast algorithms have been recently developed for computing first arrival traveltimes of seismic waves, the complete browsing of the posterior distribution of velocity model is hardly performed, especially when it is high dimensional and/or multimodal. In the latter case, the chain may even stay stuck in one of the modes. In order to improve the mixing properties of classical single MCMC, we propose to make interact several Markov chains at different temperatures. This method can make efficient use of large CPU clusters, without increasing the global computational cost with respect to classical MCMC and is therefore particularly suited for Bayesian inversion. The exchanges between the chains allow a precise sampling of the high probability zones of the model space while avoiding the chains to end stuck in a probability maximum. This approach supplies thus a robust way to analyze the tomography imaging uncertainties. The interacting MCMC approach is illustrated on two synthetic examples of tomography of calibration shots such as encountered in induced microseismic studies. On the second application, a wavelet based model parameterization is presented that allows to significantly reduce the dimension of the problem, making thus the algorithm efficient even for a complex velocity model.

Gesret, Alexandrine; Bottero, Alexis; Romary, Thomas; Noble, Mark; Desassis, Nicolas

2014-05-01

79

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

80

Amplification of Three-Dimensional Perturbations during Nominally Parallel Vortex-Cylinder Interaction  

NASA Astrophysics Data System (ADS)

A computational study is reported which examines the amplification of three-dimensional flow features for nominally parallel vortex-cylinder interaction problems. We consider a helical vortex with small-amplitude perturbations that is advected onto a circular cylinder whose axis is parallel to the nominal vortex axis. The study assesses the applicability of the two-dimensional flow assumption for parallel vortex-body interaction problems in which the body impinges on the vortex core. The computations are performed using an unstructured finite-volume method for an incompressible flow, with periodic boundary conditions along the cylinder axis. Growth of three-dimensional flow features is quantified by use of a proper-orthogonal decomposition of the Fourier-transformed velocity and vorticity fields in the cylinder azimuthal and axial directions. The interaction is examined for different axial wavelengths and amplitudes of the initial helical waves on the vortex core, and the results for cylinder force are compared to the two-dimensional results.

Liu, Xiongbin

2005-11-01

81

Parallel implementation of three-dimensional molecular dynamic simulation for laser-cluster interaction  

SciTech Connect

The objective of this article is to report the parallel implementation of the 3D molecular dynamic simulation code for laser-cluster interactions. The benchmarking of the code has been done by comparing the simulation results with some of the experiments reported in the literature. Scaling laws for the computational time is established by varying the number of processor cores and number of macroparticles used. The capabilities of the code are highlighted by implementing various diagnostic tools. To study the dynamics of the laser-cluster interactions, the executable version of the code is available from the author.

Holkundkar, Amol R. [Department of Physics, Birla Institute of Technology and Science, Pilani-333 031 (India)] [Department of Physics, Birla Institute of Technology and Science, Pilani-333 031 (India)

2013-11-15

82

Validity of the Consensus Building System using a Parallel Distributed Interactive Genetic Algorithm  

NASA Astrophysics Data System (ADS)

We propose a parallel distributed interactive genetic algorithm(PDIGA) as a new design collaboration method. PDIGA uses an IGA and a parallel distributed genetic algorithm, which combines several IGA systems, and it has a scheme that best ones among the design solutions based on the subjective evaluation of each user are shared among users for every generation. A collaboration system using PDIGA is developed to make good design solutions among several people at difference locations. To verify a validity of the PDIGA system, we conducted experiments for comparing IGA and PDIGA. In particular, we examined each user's evaluation to the final design, compared the averages of the individual evaluation value, and examined the similarity of the design solution. These showed that the collaboration system using PDIGA become a consensus building system, and users' design solutions are unified in a group.

Miki, Mitsunori; Hiroyasu, Tomoyuki; Tomioka, Hiroshi

83

Formation of electron kappa distributions due to interactions with parallel propagating whistler waves  

SciTech Connect

In space plasmas, charged particles are frequently observed to possess a high-energy tail, which is often modeled by a kappa-type distribution function. In this work, the formation of the electron kappa distribution in generation of parallel propagating whistler waves is investigated using fully nonlinear particle-in-cell (PIC) simulations. A previous research concluded that the bi-Maxwellian character of electron distributions is preserved in PIC simulations. We now demonstrate that for interactions between electrons and parallel propagating whistler waves, a non-Maxwellian high-energy tail can be formed, and a kappa distribution can be used to fit the electron distribution in time-asymptotic limit. The ?-parameter is found to decrease with increasing initial temperature anisotropy or decreasing ratio of electron plasma frequency to cyclotron frequency. The results might be helpful to understanding the origin of electron kappa distributions observed in space plasmas.

Tao, X., E-mail: xtao@ustc.edu.cn; Lu, Q. [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China) [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Mengcheng National Geophysical Observatory, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2014-02-15

84

Structure and effective interactions in parallel monolayers of charged spherical colloids  

NASA Astrophysics Data System (ADS)

We study the microstructure and the effective interactions of model suspensions consisting of Yukawa-like colloidal particles homogeneously distributed in equally spaced parallel planar monolayers. All the particles interact with each other, but particle transfer between monolayers is not allowed. The spacing between the layers defines the effective system dimensionality. When the layer spacing is comparable to the particle size, the system shows quasi-three-dimensional behavior, whereas for large distances the layers behave as effective two-dimensional systems. We find that effective attractions between like-charged particles can be triggered by adjusting the interlayer spacing, showing that the distance between adjacent layers is an excellent control parameter for the effective interparticle interactions. Our study is based on Brownian dynamics simulations and the integral equations theory of liquids. The effective potentials are accounted for by exploiting the invariance of the Ornstein-Zernike matrix equation under contractions of the description, and on assuming that the difference between bare and effective bridge functions can be neglected. We find that the hypernetted chain approximation does not account properly for the effective interactions in layered systems.

Contreras-Aburto, C.; Méndez-Alcaraz, J. M.; Castañeda-Priego, R.

2010-05-01

85

Discovery of protein interactions using parallel analysis of translated ORFs (PLATO).  

PubMed

Parallel analysis of translated open reading frames (ORFs) (PLATO) can be used for the unbiased discovery of interactions between full-length proteins encoded by a library of 'prey' ORFs and surface-immobilized 'bait' antibodies, polypeptides or small-molecular-weight compounds. PLATO uses ribosome display (RD) to link ORF-derived mRNA molecules to the proteins they encode, and recovered mRNA from affinity enrichment is subjected to analysis using massively parallel DNA sequencing. Compared with alternative in vitro methods, PLATO provides several advantages including library size and cost. A unique advantage of PLATO is that an alternative reverse transcription-quantitative PCR (RT-qPCR) protocol can be used to test binding of specific, individual proteins. To illustrate a typical experimental workflow, we demonstrate PLATO for the identification of the immune target of serum antibodies from patients with inclusion body myositis (IBM). Beginning with an ORFeome library in an RD vector, the protocol can produce samples for deep sequencing or RT-qPCR within 4 d. PMID:24336473

Larman, H Benjamin; Liang, Anthony C; Elledge, Stephen J; Zhu, Jian

2014-01-01

86

Parallel 3D computation of unsteady wake flows with complex geometries and fluid-structure interactions  

NASA Astrophysics Data System (ADS)

New powerful parallel computational tools are developed for 3D simulation of unsteady wake flows with complex geometries and fluid-structure interactions. The base method for flow simulation is a finite element formulation for the Navier-Stokes equations. The finite element formulation is based on the streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) techniques. These stabilization techniques facilitate simulation of flows with high Reynolds numbers, and allow us to use equal-order interpolation functions for velocity and pressure without generating numerical oscillations. A multi-domain computational method is developed to simulate wake flow both in the near and far downstream. The formulations lead to coupled nonlinear equation systems which are solved, at every time step, with the Newton-Raphson method. The overall formulation and solution techniques are implemented on parallel platforms such as the CRAY T3E and SGI PowerChallenge. Two phases of vortex shedding for flow past a cylinder is simulated to verify the accuracy of this method. The Enhanced-Discretization Interface Capturing Technique (EDICT) is utilized to simulate wake flow accurately. Fluid-structure coupling solution method based on the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation is applied to simulate a parachute behavior in the unsteady wake.

Osawa, Yasuo

87

Numerical investigation of two interacting parallel thruster-plumes and comparison to experiment  

NASA Astrophysics Data System (ADS)

Clusters of orbital thrusters are an attractive option to achieve graduated thrust levels and increased redundancy with available hardware, but the heavily under-expanded plumes of chemical attitude control thrusters placed in close proximity will interact, leading to a local amplification of downstream fluxes and of back-flow onto the spacecraft. The interaction of two similar, parallel, axi-symmetric cold-gas model thrusters has recently been studied in the DLR High-Vacuum Plume Test Facility STG under space-like vacuum conditions, employing a Patterson-type impact pressure probe with slot orifice. We reproduce a selection of these experiments numerically, and emphasise that a comparison of numerical results to the measured data is not straight-forward. The signal of the probe used in the experiments must be interpreted according to the degree of rarefaction and local flow Mach number, and both vary dramatically thoughout the flow-field. We present a procedure to reconstruct the probe signal by post-processing the numerically obtained flow-field data and show that agreement to the experimental results is then improved. Features of the investigated cold-gas thruster plume interaction are discussed on the basis of the numerical results.

Grabe, Martin; Holz, André; Ziegenhagen, Stefan; Hannemann, Klaus

2014-12-01

88

Parallel kinetic Monte Carlo simulation framework incorporating accurate models of adsorbate lateral interactions  

SciTech Connect

Ab initio kinetic Monte Carlo (KMC) simulations have been successfully applied for over two decades to elucidate the underlying physico-chemical phenomena on the surfaces of heterogeneous catalysts. These simulations necessitate detailed knowledge of the kinetics of elementary reactions constituting the reaction mechanism, and the energetics of the species participating in the chemistry. The information about the energetics is encoded in the formation energies of gas and surface-bound species, and the lateral interactions between adsorbates on the catalytic surface, which can be modeled at different levels of detail. The majority of previous works accounted for only pairwise-additive first nearest-neighbor interactions. More recently, cluster-expansion Hamiltonians incorporating long-range interactions and many-body terms have been used for detailed estimations of catalytic rate [C. Wu, D. J. Schmidt, C. Wolverton, and W. F. Schneider, J. Catal. 286, 88 (2012)]. In view of the increasing interest in accurate predictions of catalytic performance, there is a need for general-purpose KMC approaches incorporating detailed cluster expansion models for the adlayer energetics. We have addressed this need by building on the previously introduced graph-theoretical KMC framework, and we have developed Zacros, a FORTRAN2003 KMC package for simulating catalytic chemistries. To tackle the high computational cost in the presence of long-range interactions we introduce parallelization with OpenMP. We further benchmark our framework by simulating a KMC analogue of the NO oxidation system established by Schneider and co-workers [J. Catal. 286, 88 (2012)]. We show that taking into account only first nearest-neighbor interactions may lead to large errors in the prediction of the catalytic rate, whereas for accurate estimates thereof, one needs to include long-range terms in the cluster expansion.

Nielsen, Jens; D’Avezac, Mayeul; Hetherington, James [Research Software Development Team, Research IT Services, University College London, Torrington Place, London WC1E 6BT (United Kingdom)] [Research Software Development Team, Research IT Services, University College London, Torrington Place, London WC1E 6BT (United Kingdom); Stamatakis, Michail, E-mail: m.stamatakis@ucl.ac.uk [Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)] [Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

2013-12-14

89

Structure and drug interactions of parallel-stranded DNA studied by infrared spectroscopy and fluorescence.  

PubMed Central

The infrared spectra of three different 25-mer parallel-stranded DNAs (ps-DNA) have been studied. We have used ps-DNAs containing either exclusively dA x dT base pairs or substitution with four dG x dC base pairs and have them compared with their antiparallel-stranded (aps) reference duplexes in a conventional B-DNA conformation. Significant differences have been found in the region of the thymine C = O stretching vibrations. The parallel-stranded duplexes showed characteristic marker bands for the C2 = O2 and C4 = O4 carbonyl stretching vibrations of thymine at 1685 cm-1 and 1668 cm-1, respectively, as compared to values of 1696 cm-1 and 1663 cm-1 for the antiparallel-stranded reference duplexes. The results confirm previous studies indicating that the secondary structure in parallel-stranded DNA is established by reversed Watson--Crick base pairing of dA x dT with hydrogen bonds between N6H...O2 and N1...HN3. The duplex structure of the ps-DNA is much more sensitive to dehydration than that of the aps-DNA. Interaction with three drugs known to bind in the minor groove of aps-DNA--netropsin, distamycin A and Hoechst 33258--induces shifts of the C = O stretching vibrations of ps-DNA even at low ratio of drug per DNA base pair. These results suggest a conformational change of the ps-DNA to optimize the DNA-drug interaction. As demonstrated by excimer fluorescence of strands labeled with pyrene at the 5'-end, the drugs induce dissociation of the ps-DNA duplex with subsequent formation of imperfectly matched aps-DNA to allow the more favorable drug binding to aps-DNA. Similarly, attempts to form a triple helix of the type d(T)n.d(A)n.d(T)n with ps-DNA failed and resulted in the dissociation of the ps-DNA duplex and reformation of a triple helix based upon an aps-DNA duplex core d(T)10.d(A)10. PMID:7504812

Fritzsche, H; Akhebat, A; Taillandier, E; Rippe, K; Jovin, T M

1993-01-01

90

Design and modular parallel synthesis of a MCR derived ?-helix mimetic protein–protein interaction inhibitor scaffold  

Microsoft Academic Search

A terphenyl ?-helix mimetic scaffold recognized to be capable of disrupting protein–protein interactions was structurally morphed into an easily amenable and versatile multicomponent reaction (MCR) backbone. The design, modular in-parallel library synthesis, initial cell based biological data, and preliminary in vitro screening for the disruption of the Bcl-w\\/Bak protein–protein interaction by representatives of the MCR derived scaffold are presented.

Walfrido Antuch; Sanjay Menon; Quin-Zene Chen; Yingchun Lu; Sukumar Sakamuri; Barbara Beck; Vesna Schauer-Vukašinovi?; Seema Agarwal; Sibylle Hess; Alexander Dömling

2006-01-01

91

Beowulf Analysis Symbolic INterface BASIN: Interactive Parallel Data Analysis for Everyone  

E-print Network

The advent of affordable parallel computers such as Beowulf PC clusters and, more recently, of multi-core PCs has been highly beneficial for a large number of scientists and smaller institutions that might not otherwise have access to substantial computing facilities. However, there has not been an analogous progress in the development and dissemination of parallel software: scientists need the expertise to develop parallel codes and have to invest a significant amount of time in the development of tools even for the most common data analysis tasks. We describe the Beowulf Analysis Symbolic INterface (BASIN) a multi-user parallel data analysis and visualization framework. BASIN is aimed at providing scientists with a suite of parallel libraries for astrophysical data analysis along with general tools for data distribution and parallel operations on distributed data to allow them to easily develop new parallel libraries for their specific tasks.

Enrico Vesperini; David M. Goldberg; Stephen L. W. McMillan; James Dura; Douglas Jones

2008-04-29

92

Highly scalable parallel implementation of turbulent collision of aerodynamically interacting cloud droplets  

NASA Astrophysics Data System (ADS)

Hybrid direct numerical simulation (HDNS) has advanced our understanding of turbulent collision-coalescence of cloud droplets. In this approach, the background fluid turbulence is simulated by a pseudospectral method and disturbance flows of droplets are treated analytically. To better realize its potential on PetaScale computers with ˜100,000 processors, here we implement and test a parallel implementation using two-dimensional domain decomposition. The purpose is to increase both the range of flow scales and the number of droplets realizable in the simulations, so the dependence of collision statistics on flow Reynolds number and droplet size can be explored. We expect that the 2D domain-decomposition HDNS code can be used to produce statistics of aerodynamically-interacting droplets with Taylor microscale flow Reynolds number R? up to ˜1000 and a system of O(10^7) polydisperse droplets. We will present the implementation details as well as results of turbulent collision statistics (e.g., collision kernel, radial distribution function, relative velocity statistics) of sedimenting cloud droplets from our latest high-resolution HDNS.

Parishani, Hossein; Ayala, Orlando; Wang, Lian-Ping; Rosa, Bogdan; Grabowski, Wojciech

2011-11-01

93

A three-phase line-interactive UPS system implementation with series-parallel active power-line conditioning capabilities  

Microsoft Academic Search

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using a synchronous reference frame (SRF) based controller, which allows an effective power factor correction, load harmonic current suppression and output voltage regulation. The three-phase UPS system is composed of two active power filter topologies. The first one is a series active power

S. A. Oliveira da Silva; P. Donoso-Garcia; P. C. Cortizo; P. F. Seixas

2001-01-01

94

A three-phase line-interactive UPS system implementation with series-parallel active power-line conditioning capabilities  

Microsoft Academic Search

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using a synchronous-reference-frame (SRF)-based controller, which allows an effective power-factor correction, load harmonic current suppression, and output voltage regulation. The three-phase UPS system is composed of two active power filter topologies. The first one is a series active power filter, which works as

Sérgio Augusto Oliveira da Silva; P. F. Donoso-Garcia; P. C. Cortizo; P. F. Seixas

2002-01-01

95

A combined finite element based soil–structure interaction model for large-scale systems and applications on parallel platforms  

Microsoft Academic Search

A finite element (FE) based soil–structure interaction (SSI) model is presented and parallelized for applications on distributed systems. The SSI model is established by combining two methods: the Consistent Infinitesimal FE Cell Method (also referred to as ‘the scaled boundary-finite element method’) proposed by Wolf and Song (Finite-element modelling of unbounded media, Wiley, England, 1996) for modelling the soil region

M. C. Genes; S. Kocak

2002-01-01

96

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

NASA Astrophysics Data System (ADS)

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 version of the code is based on PVM. It splits the grid into several spatial domains each belonging to one processor. Since particles can cross boundaries of cells as well as domains, the processor loads will generally change in time. This is counteracted by adjusting the domain sizes dynamically, for which the use of chained lists has proven to be very convenient. Moreover, an option for restarting the simulation from intermediate stages of the time evolution has been implemented even in the parallel version. The code will be published and distributed freely.

Pfund, R. E. W.; Lichters, R.; Meyer-ter-Vehn, J.

1998-02-01

97

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

E-print Network

memory architecture. Using these resources effi- ciently in a seamless way is a challenging issue parallelization approaches have been proposed but usually focused on one aspect of the physics pipe objects, deformable solids, fluids). The physics pipe-line is classically split in two main steps

Boyer, Edmond

98

Parallel computation of three-dimensional aeroelastic fluid-structure interaction  

NASA Astrophysics Data System (ADS)

This dissertation presents a numerical method for the parallel computation of aeroelasticity (ParCAE). A flow solver is coupled to a structural solver by use of a fluid-structure interface method. The integration of the three-dimensional unsteady Navier-Stokes equations is performed in the time domain, simultaneously to the integration of a modal three-dimensional structural model. The flow solution is accelerated by using a multigrid method and a parallel multiblock approach. Fluid-structure coupling is achieved by subiteration. A grid-deformation algorithm is developed to interpolate the deformation of the structural boundaries onto the flow grid. The code is formulated to allow application to general, three-dimensional, complex configurations with multiple independent structures. Computational results are presented for various configurations, such as turbomachinery blade rows and aircraft wings. Investigations are performed on vortex-induced vibrations, effects of cascade mistuning on flutter, and cases of nonlinear cascade and wing flutter.

Sadeghi, Mani

99

Parallel approximation of non-interactive zero-sum quantum games  

E-print Network

This paper studies a simple class of zero-sum games played by two competing quantum players: each player sends a mixed quantum state to a referee, who performs a joint measurement on the two states to determine the players' payoffs. We prove that an equilibrium point of any such game can be approximated by means of an efficient parallel algorithm, which implies that one-turn quantum refereed games, wherein the referee is specified by a quantum circuit, can be simulated in polynomial space.

Rahul Jain; John Watrous

2008-08-20

100

DC Circuits: Parallel Resistances  

NSDL National Science Digital Library

In this interactive learning activity, students will learn about parallel circuits. They will measure and calculate the resistance of parallel circuits and answer several questions about the example circuit shown.

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

Simulation of the Quasi-Monoenergetic Protons Generation by Parallel Laser Pulses Interaction with Foils  

NASA Astrophysics Data System (ADS)

A new scheme of radiation pressure acceleration for generating high-quality protons by using two overlapping-parallel laser pulses is proposed. Particle-in-cell simulation shows that the overlapping of two pulses with identical Gaussian profiles in space and trapezoidal profiles in the time domain can result in a composite light pulse with a spatial profile suitable for stable acceleration of protons to high energies. At ~2.46 × 1021 W/cm2 intensity of the combination light pulse, a quasi-monoenergetic proton beam with peak energy ~200 MeV/nucleon, energy spread <15%, and divergency angle <4° is obtained, which is appropriate for tumor therapy. The proton beam quality can be controlled by adjusting the incidence points of two laser pulses.

Wang, Wei-Quan; Yin, Yan; Zou, De-Bin; Yu, Tong-Pu; Yang, Xiao-Hu; Xu, Han; Yu, Ming-Yang; Ma, Yan-Yun; Zhuo, Hong-Bin; Shao, Fu-Qiu

2014-11-01

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

The Spatial Consequences of Autarky in Land-Use Regulation: Strategic Interaction or Parallelism?  

Microsoft Academic Search

In most of the United States, land-use regulations are determined independently by the cities and towns within a metropolitan housing market. Despite theoretical analysis of the interaction among regulatory decisions across jurisdictions, empirical evidence is limited. In this paper, we explore the spatial distribution of specific categories of land-use regulations based upon original data collected for the San Francisco Bay

Paavo Monkkonen; John M. Quigley

2008-01-01

105

Guided Analysis of Hurricane Trends Using Statistical Processes Integrated with Interactive Parallel Coordinates  

E-print Network

Guided Analysis of Hurricane Trends Using Statistical Processes Integrated with Interactive. The system's utility is demonstrated with an extensive hurricane climate study that was conducted by a hurricane expert. In the study, the expert used a new data set of environmental weather data, composed of 28

Swan II, J. Edward

106

Interaction between a laminar starting immersed micro-jet and a parallel wall  

NASA Astrophysics Data System (ADS)

In the present work, we study the starting transient of an immersed micro-jet in close vicinity to a solid wall parallel to its axis. The experiments concern laminar jets (Re < 200) issuing from a 100 ?m internal tip diameter glass micro-pipette. The effect of the confinement was studied placing the micro-pipette at different distances from the wall. The characterization of the jet was carried out by visualizations on which the morphology of the vortex head and trajectories was analyzed. Numerical simulations were used as a complementary tool for the analysis. The jet remains stable for very long distances away from the tip allowing for a similarity analysis. The self-similar behavior of the starting jet has been studied in terms of the frontline position with time. A symmetric and a wall dominated regime could be identified. The starting jet in the wall type regime, and in the symmetric regime as well, develops a self-similar behavior that has a relative rapid loss of memory of the preceding condition of the flow. Scaling for both regimes are those that correspond to viscous dominated flows.

Cabaleiro, Juan Martin; Laborde, Cecilia; Artana, Guillermo

2015-01-01

107

Why Structured Parallel Programming Matters Murray Cole  

E-print Network

Many (most?) parallel applications don't actually involve arbitrary, dynamic interaction patterns Computing Many (most?) parallel applications don't actually involve arbitrary, dynamic interaction patterns1 Why Structured Parallel Programming Matters Murray Cole Institute for Computing Systems

Cole, Murray

108

A fluid-structure interaction model to characterize bone cell stimulation in parallel-plate flow chamber systems.  

PubMed

Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment and strain-induced flow of interstitial fluid is believed to be the primary mediator of mechanical stimuli to bone cells in vivo. In vitro investigations have shown that bone cells produce important biochemical signals in response to fluid flow applied using parallel-plate flow chamber (PPFC) systems. However, the exact mechanical stimulus experienced by the cells within these systems remains unclear. To fully understand this behaviour represents a most challenging multi-physics problem involving the interaction between deformable cellular structures and adjacent fluid flows. In this study, we use a fluid-structure interaction computational approach to investigate the nature of the mechanical stimulus being applied to a single osteoblast cell under fluid flow within a PPFC system. The analysis decouples the contribution of pressure and shear stress on cellular deformation and for the first time highlights that cell strain under flow is dominated by the pressure in the PPFC system rather than the applied shear stress. Furthermore, it was found that strains imparted on the cell membrane were relatively low whereas significant strain amplification occurred at the cell-substrate interface. These results suggest that strain transfer through focal attachments at the base of the cell are the primary mediators of mechanical signals to the cell under flow in a PPFC system. Such information is vital in order to correctly interpret biological responses of bone cells under in vitro stimulation and elucidate the mechanisms associated with mechanotransduction in vivo. PMID:23365189

Vaughan, T J; Haugh, M G; McNamara, L M

2013-04-01

109

A fluid–structure interaction model to characterize bone cell stimulation in parallel-plate flow chamber systems  

PubMed Central

Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment and strain-induced flow of interstitial fluid is believed to be the primary mediator of mechanical stimuli to bone cells in vivo. In vitro investigations have shown that bone cells produce important biochemical signals in response to fluid flow applied using parallel-plate flow chamber (PPFC) systems. However, the exact mechanical stimulus experienced by the cells within these systems remains unclear. To fully understand this behaviour represents a most challenging multi-physics problem involving the interaction between deformable cellular structures and adjacent fluid flows. In this study, we use a fluid–structure interaction computational approach to investigate the nature of the mechanical stimulus being applied to a single osteoblast cell under fluid flow within a PPFC system. The analysis decouples the contribution of pressure and shear stress on cellular deformation and for the first time highlights that cell strain under flow is dominated by the pressure in the PPFC system rather than the applied shear stress. Furthermore, it was found that strains imparted on the cell membrane were relatively low whereas significant strain amplification occurred at the cell–substrate interface. These results suggest that strain transfer through focal attachments at the base of the cell are the primary mediators of mechanical signals to the cell under flow in a PPFC system. Such information is vital in order to correctly interpret biological responses of bone cells under in vitro stimulation and elucidate the mechanisms associated with mechanotransduction in vivo. PMID:23365189

Vaughan, T. J.; Haugh, M. G.; McNamara, L. M.

2013-01-01

110

An experimental investigation of the chopping of helicopter main rotor tip vortices by the tail rotor  

NASA Technical Reports Server (NTRS)

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 model rotor and an isolated vortex and was designed to isolate BVI noise from other types of rotor noise. Tip Mach number, radical BVI station, and free stream velocity were varied. Fluctuating blade pressures, farfield sound pressure level and directivity, velocity field of the incident vortex, and blade vortex interaction angles were measured. Blade vortex interaction was found to produce impulsive noise which radiates primarily ahead of the blade. For interaction away from the blade tip, the results demonstrate the dipole character of BVI radiation. For BVI close to the tip, three dimensional relief effect reduces the intensity of the interaction, despite larger BVI angle and higher local Mach number. Furthermore, in this case, the radiation patern is more complex due to diffraction at and pressure communication around the tip.

Ahmadi, A. R.

1984-01-01

111

A line-interactive UPS system implementation with series-parallel active power-line conditioning for three-phase, four-wire systems  

Microsoft Academic Search

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with active series-parallel power-line conditioning capabilities. Synchronous reference frame (SRF)-based controller is used to harmonic and reactive power compensation generated from any configuration of non-linear load. Under normal line conditions the UPS system works with universal filtering capabilities, such as compensating the input currents and output voltages. Two three-phase

S. A. Oliveira da Silva; P. Donoso-Garcia; P. C. Cortizo; P. F. Seixas

2004-01-01

112

A comparative analysis of control algorithms for three-phase line-interactive UPS systems with series-parallel active power-line conditioning using SRF method  

Microsoft Academic Search

This paper presents alternative control algorithms using synchronous reference frame (SRF) based controllers, which allow an effective power factor correction, load harmonic current suppression and output voltage regulation for three-phase line-interactive UPS systems with active series-parallel power-line conditioning capability. The proposed UPS systems are composed of two active power filter topologies. The first one works as a series active power

S. A. O. da Silva; P. F. Donoso-Garcia; P. C. Cortizo; P. F. Seixas

2000-01-01

113

A three-phase series-parallel compensated line-interactive UPS system with sinusoidal input current and sinusoidal output voltage  

Microsoft Academic Search

This paper deals with a three-phase line-interactive uninterruptible power supply system with active series-parallel power-line conditioning capability, which has sinusoidal output voltage regulation capability and unity power factor. In this system, two active power filter topologies are applied. The first one is a series active power filter which can compensate supply voltage harmonics and voltage unbalances as well. The other

S. A. O. Da Silva; Pedro F. Donoso-Garcia; Porfirio C. Cortizo

1999-01-01

114

Interaction of an oblique shock wave with a pair of parallel vortices: Shock dynamics and mechanism of sound generation  

E-print Network

and the mechanism of sound generation in the interaction between an oblique shock wave and a pair of vortices. We is related to the interaction of the reflected shock waves and sound waves. The first mechanism is dominating affected by the interaction of the reflected shock waves and sound waves. © 2006 American Institute

Zhang, Yong-Tao

115

MEGADOCK 3.0: a high-performance protein-protein interaction prediction software using hybrid parallel computing for petascale supercomputing environments  

PubMed Central

Background Protein-protein interaction (PPI) plays a core role in cellular functions. Massively parallel supercomputing systems have been actively developed over the past few years, which enable large-scale biological problems to be solved, such as PPI network prediction based on tertiary structures. Results We have developed a high throughput and ultra-fast PPI prediction system based on rigid docking, “MEGADOCK”, by employing a hybrid parallelization (MPI/OpenMP) technique assuming usages on massively parallel supercomputing systems. MEGADOCK displays significantly faster processing speed in the rigid-body docking process that leads to full utilization of protein tertiary structural data for large-scale and network-level problems in systems biology. Moreover, the system was scalable as shown by measurements carried out on two supercomputing environments. We then conducted prediction of biological PPI networks using the post-docking analysis. Conclusions We present a new protein-protein docking engine aimed at exhaustive docking of mega-order numbers of protein pairs. The system was shown to be scalable by running on thousands of nodes. The software package is available at: http://www.bi.cs.titech.ac.jp/megadock/k/. PMID:24004986

2013-01-01

116

Aeroacoustic theory for noncompact wing-gust interaction  

NASA Technical Reports Server (NTRS)

Three aeroacoustic models for noncompact wing-gust interaction were developed for subsonic flow. The first is that for a two dimensional (infinite span) wing passing through an oblique gust. The unsteady pressure field was obtained by the Wiener-Hopf technique; the airfoil loading and the associated acoustic field were calculated, respectively, by allowing the field point down on the airfoil surface, or by letting it go to infinity. The second model is a simple spanwise superposition of two dimensional solutions to account for three dimensional acoustic effects of wing rotation (for a helicopter blade, or some other rotating planform) and of finiteness of wing span. A three dimensional theory for a single gust was applied to calculate the acoustic signature in closed form due to blade vortex interaction in helicopters. The third model is that of a quarter infinite plate with side edge through a gust at high subsonic speed. An approximate solution for the three dimensional loading and the associated three dimensional acoustic field in closed form was obtained. The results reflected the acoustic effect of satisfying the correct loading condition at the side edge.

Martinez, R.; Widnall, S. E.

1981-01-01

117

A Parallel Code for Lifetime Simulations in Hadron Storage Rings in the Presence of Parasitic Beam-Beam Interactions  

SciTech Connect

The usual approach to predict particle loss in storage rings in the presence of nonlinearities consists in the determination of the dynamic aperture of the machine. This method, however, will not directly predict the lifetimes of beams. We have developed a code which can, by parallelization and careful speed optimization, predict lifetimes in the presence of 100 parasitic beam-beam crossings by tracking > 10{sup 10} particles-turns. An application of this code to the anti-proton lifetime in the Tevatron at injection is discussed.

Kabel, A.C.; Cai, Y.; Erdelyi, B.; Sen, T.; Xiao, M.; /SLAC /Fermilab

2008-03-17

118

Parallel rendering  

NASA Technical Reports Server (NTRS)

This article provides a broad introduction to the subject of parallel rendering, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel rendering algorithms and systems. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition, task granularity, scalability, and load balancing, are considered in relation to the rendering problem. We also explore concepts from computer graphics, such as coherence and projection, which have a significant impact on the structure of parallel rendering algorithms. Our survey covers a number of practical considerations as well, including the choice of architectural platform, communication and memory requirements, and the problem of image assembly and display. We illustrate the discussion with numerous examples from the parallel rendering literature, representing most of the principal rendering methods currently used in computer graphics.

Crockett, Thomas W.

1995-01-01

119

Parallel sorting algorithms for optimizing particle simulations  

Microsoft Academic Search

Real world particle simulation codes have to handle a huge number of particles and their interactions. Thus, parallel implementations are required to get suitable production codes. Parallel sorting is often used to organize the set of particles or to redistribute data for locality and load balancing concerns. In this article, the use and design of parallel sorting algorithms for parallel

Michael Hofmann; G. Runger; P. Gibbon; R. Speck

2010-01-01

120

A parallel multistate framework for atomistic non-equilibrium reaction dynamics of solutes in strongly interacting organic solvents  

E-print Network

We describe a parallel linear-scaling computational framework developed to implement arbitrarily large multi-state empirical valence bond (MS-EVB) calculations within CHARMM. Forces are obtained using the Hellman-Feynmann relationship, giving continuous gradients, and excellent energy conservation. Utilizing multi-dimensional Gaussian coupling elements fit to CCSD(T)-F12 electronic structure theory, we built a 64-state MS-EVB model designed to study the F + CD3CN -> DF + CD2CN reaction in CD3CN solvent. This approach allows us to build a reactive potential energy surface (PES) whose balanced accuracy and efficiency considerably surpass what we could achieve otherwise. We use our PES to run MD simulations, and examine a range of transient observables which follow in the wake of reaction, including transient spectra of the DF vibrational band, time dependent profiles of vibrationally excited DF in CD3CN solvent, and relaxation rates for energy flow from DF into the solvent, all of which agree well with experime...

Glowacki, David R; Harvey, Jeremy N

2014-01-01

121

Suppression of electron magnetotunneling between parallel two-dimensional GaAs/InAs electron systems by the correlation interaction  

SciTech Connect

Magnetotunneling between two-dimensional GaAs/InAs electron systems in vertical resonant tunneling GaAs/InAs/AlAs heterostructures is studied. A new-type of singularity in the tunneling density of states, specifically a dip at the Fermi level, is found; this feature is drastically different from that observed previously for the case of tunneling between two-dimensional GaAs tunnel systems in terms of both the kind of functional dependence and the energy and temperature parameters. As before, this effect manifests itself in the suppression of resonant tunneling in a narrow range near zero bias voltage in a high magnetic field parallel to the current direction. Magnetic-field and temperature dependences of the effect's parameters are obtained; these dependences are compared with available theoretical and experimental data. The observed effect can be caused by a high degree of disorder in two-dimensional correlated electron systems as a result of the introduction of structurally imperfect strained InAs layers.

Khanin, Yu. N.; Vdovin, E. E., E-mail: vdov62@yandex.ru [Russian Academy of Sciences, Institute of Microelectronics Technology and High Purity Materials (Russian Federation); Makarovsky, O. [University of Nottingham, School of Physics and Astronomy (United Kingdom)] [University of Nottingham, School of Physics and Astronomy (United Kingdom); Henini, M. [University of Nottingham, School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Center (United Kingdom)] [University of Nottingham, School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Center (United Kingdom)

2013-09-15

122

Research investigation of helicopter main rotor/tail rotor interaction noise  

NASA Technical Reports Server (NTRS)

Acoustic measurements were obtained in a Langley 14 x 22 foot Subsonic Wind Tunnel to study the aeroacoustic interaction of 1/5th scale main rotor, tail rotor, and fuselage models. An extensive aeroacoustic data base was acquired for main rotor, tail rotor, fuselage aerodynamic interaction for moderate forward speed flight conditions. The details of the rotor models, experimental design and procedure, aerodynamic and acoustic data acquisition and reduction are presented. The model was initially operated in trim for selected fuselage angle of attack, main rotor tip-path-plane angle, and main rotor thrust combinations. The effects of repositioning the tail rotor in the main rotor wake and the corresponding tail rotor countertorque requirements were determined. Each rotor was subsequently tested in isolation at the thrust and angle of attack combinations for trim. The acoustic data indicated that the noise was primarily dominated by the main rotor, especially for moderate speed main rotor blade-vortex interaction conditions. The tail rotor noise increased when the main rotor was removed indicating that tail rotor inflow was improved with the main rotor present.

Fitzgerald, J.; Kohlhepp, F.

1988-01-01

123

Parallel Optimisation  

NSDL National Science Digital Library

An introduction to optimisation techniques that may improve parallel performance and scaling on HECToR. It assumes that the reader has some experience of parallel programming including basic MPI and OpenMP. Scaling is a measurement of the ability for a parallel code to use increasing numbers of cores efficiently. A scalable application is one that, when the number of processors is increased, performs better by a factor which justifies the additional resource employed. Making a parallel application scale to many thousands of processes requires not only careful attention to the communication, data and work distribution but also to the choice of the algorithms to use. Since the choice of algorithm is too broad a subject and very particular to application domain to include in this brief guide we concentrate on general good practices towards parallel optimisation on HECToR.

124

Interactive Visualization of Large-Scale Hydrological Data using Emerging Technologies in Web Systems and Parallel Programming  

NASA Astrophysics Data System (ADS)

As geoscientists are confronted with increasingly massive datasets from environmental observations to simulations, one of the biggest challenges is having the right tools to gain scientific insight from the data and communicate the understanding to stakeholders. Recent developments in web technologies make it easy to manage, visualize and share large data sets with general public. Novel visualization techniques and dynamic user interfaces allow users to interact with data, and modify the parameters to create custom views of the data to gain insight from simulations and environmental observations. This requires developing new data models and intelligent knowledge discovery techniques to explore and extract information from complex computational simulations or large data repositories. Scientific visualization will be an increasingly important component to build comprehensive environmental information platforms. This presentation provides an overview of the trends and challenges in the field of scientific visualization, and demonstrates information visualization and communication tools developed within the light of these challenges.

Demir, I.; Krajewski, W. F.

2013-12-01

125

DC Circuits: Series-Parallel Resistances  

NSDL National Science Digital Library

In this interactive learning activity, students will learn more about series-parallel circuits. They will measure and calculate the resistance of series-parallel circuits and answer several questions about the example circuit shown.

126

IU parallel processing benchmark  

Microsoft Academic Search

A benchmark is presented that was designed to evaluate the merits of various parallel architectures as applied to image understanding (IU). This benchmark exercise addresses the issue of system performance on an integrated set of tasks, where the task interactions that are typical of complex vision application are present. The goal of this exercise is to gain a better understanding

Charles Weems; Edward Riseman; Allen Hanson; Azriel Rosenfeld

1988-01-01

127

Multithreading and Parallel Microprocessors  

E-print Network

Multithreading and Parallel Microprocessors Stephen Jenks Electrical Engineering and Computer Scalable Parallel and Distributed Systems Lab 4 Outline Parallelism in Microprocessors Multicore Processor Parallelism Parallel Programming for Shared Memory OpenMP POSIX Threads Java Threads Parallel Microprocessor

Shinozuka, Masanobu

128

Determining kinetics and affinities of protein interactions using a parallel real-time label-free biosensor, the Octet.  

PubMed

ForteBio's Octet optical biosensor harnesses biolayer interferometry to detect and quantify molecular interactions using disposable fiber-optic biosensors that address samples from an open shaking microplate without any microfluidics. We recruited a monoclonal antibody against a panel of peptides to compare the Octet directly with Biacore's well-established 3000 platform and Bio-Rad's recently launched ProteOn XPR36 array system, which use surface plasmon resonance (SPR) to detect the binding of one analyte over four surfaces and six analytes over six surfaces, respectively. A sink method was used to prevent analyte from rebinding the ligand-coated Octet tips and enabled us to extract accurate kinetic rate constants, as judged by their close agreement with those determined by SPR. Although the Octet is not sensitive enough to detect the binding of small molecules directly, it can access their affinities indirectly via solution competition experiments. We conducted similar experiments on the SPR instruments to validate these measurements. The Octet is emerging as a versatile complement to other more sophisticated biosensors, and the ProteOn provides high-quality data near the sensitivity of Biacore but in a more multiplexed format. Our results provide a benchmark for assessing the performance of the above-mentioned sensors. PMID:18405656

Abdiche, Yasmina; Malashock, Dan; Pinkerton, Alanna; Pons, Jaume

2008-06-15

129

Parallel Processing in Amplitude Analysis  

E-print Network

electromagnetic interactions weak interactions strong interactions Quantum Chromodynamics (QCD) Quantum tube" model Energy density from "Lattice QCD" #12;M. R. Shepherd Parallel Processing Lecture 2 March 31 March 31, 2011 Hybrid Mesons · Conventional mesons: flux tube is in ground state · Hybrid mesons: flux

Evans, Hal

130

The Vortex Lattice Method for the Rotor-Vortex Interaction Problem  

NASA Technical Reports Server (NTRS)

The rotor blade-vortex interaction problem and the resulting impulsive airloads which generate undesirable noise levels are discussed. A numerical lifting surface method to predict unsteady aerodynamic forces induced on a finite aspect ratio rectangular wing by a straight, free vortex placed at an arbitrary angle in a subsonic incompressible free stream is developed first. Using a rigid wake assumption, the wake vortices are assumed to move downsteam with the free steam velocity. Unsteady load distributions are obtained which compare favorably with the results of planar lifting surface theory. The vortex lattice method has been extended to a single bladed rotor operating at high advance ratios and encountering a free vortex from a fixed wing upstream of the rotor. The predicted unsteady load distributions on the model rotor blade are generally in agreement with the experimental results. This method has also been extended to full scale rotor flight cases in which vortex induced loads near the tip of a rotor blade were indicated. In both the model and the full scale rotor blade airload calculations a flat planar wake was assumed which is a good approximation at large advance ratios because the downwash is small in comparison to the free stream at large advance ratios. The large fluctuations in the measured airloads near the tip of the rotor blade on the advance side is predicted closely by the vortex lattice method.

Padakannaya, R.

1974-01-01

131

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

Michael Horton

2009-05-30

132

The Effects of Wind Tunnel Walls on the Near-field Behavior of a Wingtip Vortex  

E-print Network

vortex structures on dynamics of towed vehicles, tail buffeting, and icing arrays. Blade/vortex interaction on helicopter blades can impact performance and cause undesirable noise and vibration. Vortex

Hu, Hui

133

Development of a prototype PET scanner with depth-of-interaction measurement using solid-state photomultiplier arrays and parallel readout electronics.  

PubMed

In this study, we developed a prototype animal PET by applying several novel technologies to use solid-state photomultiplier (SSPM) arrays to measure the depth of interaction (DOI) and improve imaging performance. Each PET detector has an 8 × 8 array of about 1.9 × 1.9 × 30.0 mm(3) lutetium-yttrium-oxyorthosilicate scintillators, with each end optically connected to an SSPM array (16 channels in a 4 × 4 matrix) through a light guide to enable continuous DOI measurement. Each SSPM has an active area of about 3 × 3 mm(2), and its output is read by a custom-developed application-specific integrated circuit to directly convert analogue signals to digital timing pulses that encode the interaction information. These pulses are transferred to and are decoded by a field-programmable gate array-based time-to-digital convertor for coincident event selection and data acquisition. The independent readout of each SSPM and the parallel signal process can significantly improve the signal-to-noise ratio and enable the use of flexible algorithms for different data processes. The prototype PET consists of two rotating detector panels on a portable gantry with four detectors in each panel to provide 16 mm axial and variable transaxial field-of-view (FOV) sizes. List-mode ordered subset expectation maximization image reconstruction was implemented. The measured mean energy, coincidence timing and DOI resolution for a crystal were about 17.6%, 2.8 ns and 5.6 mm, respectively. The measured transaxial resolutions at the center of the FOV were 2.0 mm and 2.3 mm for images reconstructed with and without DOI, respectively. In addition, the resolutions across the FOV with DOI were substantially better than those without DOI. The quality of PET images of both a hot-rod phantom and mouse acquired with DOI was much higher than that of images obtained without DOI. This study demonstrates that SSPM arrays and advanced readout/processing electronics can be used to develop a practical DOI-measureable PET scanner. PMID:24556629

Shao, Yiping; Sun, Xishan; Lan, Kejian A; Bircher, Chad; Lou, Kai; Deng, Zhi

2014-03-01

134

Weka-Parallel: Machine Learning in Parallel  

Microsoft Academic Search

We present Weka-Parallel, which is a modification to Weka, a popularmachine learning software package. Weka-Parallel expands uponthe original program by allowing one to perform n-fold cross-validationsin parallel. This added parallelism causes Weka-Parallel to demonstratea significant speed increase over Weka by lowering the amountof time necessary to evaluate a dataset using any given classifier. WekaParallelis designed for the researcher who needs

Sebastian Celis; David R. Musicant

135

A portable parallel particle program  

Microsoft Academic Search

We describe our implementation of the parallel hashed oct-tree (HOT) code, and in particular its application to neighbor finding in a smoothed particle hydrodynamics (SPH) code. We also review the error bounds on the multipole approximations involved in treecodes, and extend them to include general cell-cell interactions. Performance of the program on a variety of problems (including gravity, SPH, vortex

Michael S. Warren; John K. Salmon

1995-01-01

136

Parallel Discrete Event Simulation to Network Emulation  

E-print Network

Applying Parallel Discrete Event Simulation to Network Emulation Rob Simmonds, Russell Bradford y of a system that uses a parallel discrete event simulator to act as a high speed network emulator. With this can interact with modelled traffic in the emulator, thus providing a controlled test envi­ ronment

Bradford, Russell

137

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

138

To appear in the IEEE 2001 Symposium on Parallel and Large Data Visualization and Graphics proceedings Jupiter: A Toolkit for Interactive Large Model Visualization  

E-print Network

proceedings Jupiter: A Toolkit for Interactive Large Model Visualization Dirk Bartz, Dirk Staneker, Wolfgang Jupiter, a toolkit for the interactive visualization of large models which exploits the above mentioned techniques. Jupiter was originally developed by Hewlett-Packard and EAI, and it was recently equipped

Bartz, Dirk

139

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

140

A parallel processing tutorial  

Microsoft Academic Search

An overview of parallel computing is provided, with reference to numerical analysis and, in particular, to computational electromagnetics. The history of parallelism is reviewed, and the general principles are provided. The two main types of parallelism encountered, pipelining and replication are discussed, and an example of each is described. A parallel algorithm for forming a matrix-vector product is presented and

David B. Davidson

1990-01-01

141

Parallel Mandelbrot Set Model  

NSDL National Science Digital Library

The Parallel Mandelbrot Set Model is a parallelization of the sequential MandelbrotSet model, which does all the computations on a single processor core. This parallelization is able to use a computer with more than one cores (or processors) to carry out the same computation, thus speeding up the process. The parallelization is done using the model elements in the Parallel Java group. These model elements allow easy use of the Parallel Java library created by Alan Kaminsky. In particular, the parallelization used for this model is based on code in Chapters 11 and 12 of Kaminsky's book Building Parallel Java. The Parallel Mandelbrot Set Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double click the ejs_chaos_ParallelMandelbrotSet.jar file to run the program if Java is installed.

Franciscouembre

2011-11-24

142

Parallel rendering techniques for massively parallel visualization  

SciTech Connect

As the resolution of simulation models increases, scientific visualization algorithms which take advantage of the large memory. and parallelism of Massively Parallel Processors (MPPs) are becoming increasingly important. For large applications rendering on the MPP tends to be preferable to rendering on a graphics workstation due to the MPP`s abundant resources: memory, disk, and numerous processors. The challenge becomes developing algorithms that can exploit these resources while minimizing overhead, typically communication costs. This paper will describe recent efforts in parallel rendering for polygonal primitives as well as parallel volumetric techniques. This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume render use a MIMD approach. Implementations for these algorithms are presented for the Thinking Ma.chines Corporation CM-5 MPP.

Hansen, C.; Krogh, M.; Painter, J.

1995-07-01

143

Massively Parallel QCD  

SciTech Connect

The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.

Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G

2007-04-11

144

Parallelization of a treecode  

E-print Network

I describe here the performance of a parallel treecode with individual particle timesteps. The code is based on the Barnes-Hut algorithm and runs cosmological N-body simulations on parallel machines with a distributed memory architecture using the MPI message-passing library. For a configuration with a constant number of particles per processor the scalability of the code was tested up to P=128 processors on an IBM SP4 machine. In the large $P$ limit the average CPU time per processor necessary for solving the gravitational interactions is $\\sim 10 %$ higher than that expected from the ideal scaling relation. The processor domains are determined every large timestep according to a recursive orthogonal bisection, using a weighting scheme which takes into account the total particle computational load within the timestep. The results of the numerical tests show that the load balancing efficiency $L$ of the code is high ($>=90%$) up to P=32, and decreases to $L\\sim 80%$ when P=128. In the latter case it is found that some aspects of the code performance are affected by machine hardware, while the proposed weighting scheme can achieve a load balance as high as $L\\sim 90%$ even in the large $P$ limit.

R. Valdarnini

2003-03-18

145

Applied Parallel Metadata Indexing  

SciTech Connect

The GPFS Archive is parallel archive is a parallel archive used by hundreds of users in the Turquoise collaboration network. It houses 4+ petabytes of data in more than 170 million files. Currently, users must navigate the file system to retrieve their data, requiring them to remember file paths and names. A better solution might allow users to tag data with meaningful labels and searach the archive using standard and user-defined metadata, while maintaining security. last summer, I developed the backend to a tool that adheres to these design goals. The backend works by importing GPFS metadata into a MongoDB cluster, which is then indexed on each attribute. This summer, the author implemented security and developed the user interfae for the search tool. To meet security requirements, each database table is associated with a single user, which only stores records that the user may read, and requires a set of credentials to access. The interface to the search tool is implemented using FUSE (Filesystem in USErspace). FUSE is an intermediate layer that intercepts file system calls and allows the developer to redefine how those calls behave. In the case of this tool, FUSE interfaces with MongoDB to issue queries and populate output. A FUSE implementation is desirable because it allows users to interact with the search tool using commands they are already familiar with. These security and interface additions are essential for a usable product.

Jacobi, Michael R [Los Alamos National Laboratory

2012-08-01

146

Task parallel implementation of NAS parallel benchmarks.  

E-print Network

??The multi-core era brings new challenges to the programming community. Parallelization requirements of applications in mainstream computing and applications in emergent fields of high performance… (more)

Nanjaiah, Shashi Kumar

2010-01-01

147

The ParaScope parallel programming environment  

NASA Technical Reports Server (NTRS)

The ParaScope parallel programming environment, developed to support scientific programming of shared-memory multiprocessors, includes a collection of tools that use global program analysis to help users develop and debug parallel programs. This paper focuses on ParaScope's compilation system, its parallel program editor, and its parallel debugging system. The compilation system extends the traditional single-procedure compiler by providing a mechanism for managing the compilation of complete programs. Thus, ParaScope can support both traditional single-procedure optimization and optimization across procedure boundaries. The ParaScope editor brings both compiler analysis and user expertise to bear on program parallelization. It assists the knowledgeable user by displaying and managing analysis and by providing a variety of interactive program transformations that are effective in exposing parallelism. The debugging system detects and reports timing-dependent errors, called data races, in execution of parallel programs. The system combines static analysis, program instrumentation, and run-time reporting to provide a mechanical system for isolating errors in parallel program executions. Finally, we describe a new project to extend ParaScope to support programming in FORTRAN D, a machine-independent parallel programming language intended for use with both distributed-memory and shared-memory parallel computers.

Cooper, Keith D.; Hall, Mary W.; Hood, Robert T.; Kennedy, Ken; Mckinley, Kathryn S.; Mellor-Crummey, John M.; Torczon, Linda; Warren, Scott K.

1993-01-01

148

Speculative parallelization of partially parallel loops  

E-print Network

, and applied a fully parallel data dependence test to determine if it had any cross–processor depen- dences. If the test failed, then the loop was re–executed serially. While this method exploits doall parallelism well, it can cause slowdowns for loops...

Dang, Francis Hoai Dinh

2009-05-15

149

A Fast Parallel Simulation Code for Interaction between Proto-Planetary Disk and Embedded Proto-Planets: Implementation for 3D Code  

Microsoft Academic Search

We develop a 3D simulation code for interaction between the proto-planetary disk and embedded proto-planets. The protoplanetary disk is treated as a three-dimensional (3D), self-gravitating gas whose motion is described by the locally isothermal Navier-Stokes equations in a spherical coordinate centered on the star. The differential equations for the disk are similar to those given in Kley et al. (2009)

Shengtai Li; Hui Li

2012-01-01

150

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

151

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

Amy Apon

152

Special issue on parallelism  

Microsoft Academic Search

The articles presented in our Special Issue on parallel processing on the supercomputing scale reflect, to some extent, splits in the community developing these machines. There are several schools of thought on how best to implement parallel processing at both the hard- and software levels. Controversy exists over the wisdom of aiming for general- or special-purpose parallel machines, and what

Karen A. Frenkel

1986-01-01

153

CFD on parallel computers  

NASA Astrophysics Data System (ADS)

CFD or Computational Fluid Dynamics is one of the scientific disciplines that has always posed new challenges to the capabilities of the modern, ultra-fast supercomputers, and now to the even faster parallel computers. For applications where number crunching is of primary importance, there is perhaps no escaping parallel computers since sequential computers can only be (as projected) as fast as a few gigaflops and no more, unless, of course, some altogether new technology appears in future. For parallel computers, on the other hand, there is no such limit since any number of processors can be made to work in parallel. Computationally demanding CFD codes and parallel computers are therefore soul-mates, and will remain so for all foreseeable future. So much so that there is a separate and fast-emerging discipline that tackles problems specific to CFD as applied to parallel computers. For some years now, there is an international conference on parallel CFD. So, one can indeed say that parallel CFD has arrived. To understand how CFD codes are parallelized, one must understand a little about how parallel computers function. Therefore, in what follows we will first deal with parallel computers, how a typical CFD code (if there is one such) looks like, and then the strategies of parallelization.

Basu, A. J.

1994-10-01

154

Coordinating heterogeneous parallelism  

Microsoft Academic Search

Our goal is to produce a client-server based programming environment to enable massively parallel symbolic computing on heterogeneous ensembles of parallel hardware. Multiple users should be able to log on as clients and use any combination of the resources available, via a single simple language. We want our users to have control over the Kind of parallelism employed by their

Duncan J. Batey; Julian A. Padget

1995-01-01

155

Parallel simulation today  

NASA Technical Reports Server (NTRS)

This paper surveys topics that presently define the state of the art in parallel simulation. Included in the tutorial are discussions on new protocols, mathematical performance analysis, time parallelism, hardware support for parallel simulation, load balancing algorithms, and dynamic memory management for optimistic synchronization.

Nicol, David; Fujimoto, Richard

1992-01-01

156

Research in parallel computing  

NASA Technical Reports Server (NTRS)

This report summarizes work on parallel computations for NASA Grant NAG-1-1529 for the period 1 Jan. - 30 June 1994. Short summaries on highly parallel preconditioners, target-specific parallel reductions, and simulation of delta-cache protocols are provided.

Ortega, James M.; Henderson, Charles

1994-01-01

157

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

158

Parallel distributed computing using Python  

NASA Astrophysics Data System (ADS)

This work presents two software components aimed to relieve the costs of accessing high-performance parallel computing resources within a Python programming environment: MPI for Python and PETSc for Python. MPI for Python is a general-purpose Python package that provides bindings for the Message Passing Interface (MPI) standard using any back-end MPI implementation. Its facilities allow parallel Python programs to easily exploit multiple processors using the message passing paradigm. PETSc for Python provides access to the Portable, Extensible Toolkit for Scientific Computation (PETSc) libraries. Its facilities allow sequential and parallel Python applications to exploit state of the art algorithms and data structures readily available in PETSc for the solution of large-scale problems in science and engineering. MPI for Python and PETSc for Python are fully integrated to PETSc-FEM, an MPI and PETSc based parallel, multiphysics, finite elements code developed at CIMEC laboratory. This software infrastructure supports research activities related to simulation of fluid flows with applications ranging from the design of microfluidic devices for biochemical analysis to modeling of large-scale stream/aquifer interactions.

Dalcin, Lisandro D.; Paz, Rodrigo R.; Kler, Pablo A.; Cosimo, Alejandro

2011-09-01

159

Optimistic Parallelization of Communicating Sequential Processes  

Microsoft Academic Search

We present a transparent program transformation whichconverts a sequential execution of S1 ; S2 by a process in amultiprocess environment into an optimistic parallel executionof S1 and S2 .Such a transformation is valuable in the case where S1 andS2 cannot be parallelized by static analysis either because S2reads a value from S1 or because S1 and S2 each interact withan

David F. Bacon; Robert E. Strom

1991-01-01

160

Genome-Wide Fitness and Genetic Interactions Determined by Tn-seq, a High-Throughput Massively Parallel Sequencing Method for Microorganisms.  

PubMed

The lagging annotation of bacterial genomes and the inherent genetic complexity of many phenotypes is hindering the discovery of new drug targets and the development of new antimicrobial agents and vaccines. This unit presents Tn-seq, a method that has made it possible to quantitatively determine fitness for most genes in a microorganism and to screen for quantitative genetic interactions on a genome-wide scale and in a high-throughput fashion. Tn-seq can thus direct studies on the annotation of genes and untangle complex phenotypes. The method is based on the construction of a saturated transposon insertion library. After library selection, changes in the frequency of each insertion mutant are determined by sequencing flanking regions en masse. These changes are used to calculate each mutant's fitness. The method was originally developed for the Gram-positive bacterium Streptococcus pneumoniae, a causative agent of pneumonia and meningitis, but has now been applied to several different microbial species. © 2015 by John Wiley & Sons, Inc. PMID:25641100

van Opijnen, Tim; Lazinski, David W; Camilli, Andrew

2015-01-01

161

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

162

Fast Parallel Particle Methods: Angstroms to Gigaparsecs  

Microsoft Academic Search

Fast multipole methods have become an ubiquitous tool for the simulation of physical systems with long-range interactions. Since their introduction they have been applied to a vast range of problems. Our own parallel hashed oct-tree code (HOT) has been applied to a number of physical systems with long-range interactions, including gravitational and smoothed particle hydrodynamic interactions in astrophysical systems, fluid

Michael Warren

2006-01-01

163

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

164

Mirror versus parallel bimanual reaching  

PubMed Central

Background In spite of their importance to everyday function, tasks that require both hands to work together such as lifting and carrying large objects have not been well studied and the full potential of how new technology might facilitate recovery remains unknown. Methods To help identify the best modes for self-teleoperated bimanual training, we used an advanced haptic/graphic environment to compare several modes of practice. In a 2-by-2 study, we compared mirror vs. parallel reaching movements, and also compared veridical display to one that transforms the right hand’s cursor to the opposite side, reducing the area that the visual system has to monitor. Twenty healthy, right-handed subjects (5 in each group) practiced 200 movements. We hypothesized that parallel reaching movements would be the best performing, and attending to one visual area would reduce the task difficulty. Results The two-way comparison revealed that mirror movement times took an average 1.24 s longer to complete than parallel. Surprisingly, subjects’ movement times moving to one target (attending to one visual area) also took an average of 1.66 s longer than subjects moving to two targets. For both hands, there was also a significant interaction effect, revealing the lowest errors for parallel movements moving to two targets (p?parallel movements with a veridical display (moving to two separate targets). These results point to the expected levels of challenge for these bimanual training modes, which could be used to advise therapy choices in self-neurorehabilitation. PMID:23837908

2013-01-01

165

PCLIPS: Parallel CLIPS  

NASA Technical Reports Server (NTRS)

A parallel version of CLIPS 5.1 has been developed to run on Intel Hypercubes. The user interface is the same as that for CLIPS with some added commands to allow for parallel calls. A complete version of CLIPS runs on each node of the hypercube. The system has been instrumented to display the time spent in the match, recognize, and act cycles on each node. Only rule-level parallelism is supported. Parallel commands enable the assertion and retraction of facts to/from remote nodes working memory. Parallel CLIPS was used to implement a knowledge-based command, control, communications, and intelligence (C(sup 3)I) system to demonstrate the fusion of high-level, disparate sources. We discuss the nature of the information fusion problem, our approach, and implementation. Parallel CLIPS has also be used to run several benchmark parallel knowledge bases such as one to set up a cafeteria. Results show from running Parallel CLIPS with parallel knowledge base partitions indicate that significant speed increases, including superlinear in some cases, are possible.

Hall, Lawrence O.; Bennett, Bonnie H.; Tello, Ivan

1994-01-01

166

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. PMID:23275573

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

2013-01-01

167

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

168

NAS Parallel Benchmark Results  

Microsoft Academic Search

The NAS Parallel Benchmarks have been developed at NASA Ames Research Center to studythe performance of parallel supercomputers. The eight benchmark problems are specified in a"pencil and paper" fashion. In other words, the complete details of the problem to be solved aregiven in a technical document, and except for a few restrictions, benchmarkers are free to selectthe language constructs and

Subhash Saini; David H. Bailey

1995-01-01

169

Parallelizing quantum circuits  

Microsoft Academic Search

We present a novel automated technique for parallelizing quantum circuits via forward and backward translation to measurement-based quantum computing patterns and analyze the trade off in terms of depth and space complexity. As a result we distinguish a class of polynomial depth circuits that can be parallelized to logarithmic depth while adding only polynomial many auxiliary qubits. In particular, we

Anne Broadbent; Elham Kashefi

2009-01-01

170

Applied Parallel Metadata Indexing  

Microsoft Academic Search

The GPFS Archive is parallel archive is a parallel archive used by hundreds of users in the Turquoise collaboration network. It houses 4+ petabytes of data in more than 170 million files. Currently, users must navigate the file system to retrieve their data, requiring them to remember file paths and names. A better solution might allow users to tag data

Jacobi; Michael R

2012-01-01

171

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

172

Characterization of parallel subtraction  

PubMed Central

Parallel subtraction is an operation defined on pairs of positive operators. In terms of electrical networks, one may pose the following problem: Given an electrical network, represented by a specified positive operator, determine the set of positive operators which when connected in parallel with the specified operator yield another prescribed operator. The set of solutions of this electrical network problem is shown to have a minimum. The minimum is termed “the parallel difference of the fixed operators,” and the operation is termed “parallel subtraction.” The parallel difference is used to obtain explicit error estimates for an iteration procedure which approximates the geometric mean of positive operators. This concept of the geometric mean reduces to the square root of the product of the operators if the operators commute. Finally, by using the geometric mean, an operator version of the Gaussian mean is presented. PMID:16592689

Anderson, W. N.; Morley, T. D.; Trapp, G. E.

1979-01-01

173

Code Parallelization with CAPO: A User Manual  

NASA Technical Reports Server (NTRS)

A software tool has been developed to assist the parallelization of scientific codes. This tool, CAPO, extends an existing parallelization toolkit, CAPTools developed at the University of Greenwich, to generate OpenMP parallel codes for shared memory architectures. This is an interactive toolkit to transform a serial Fortran application code to an equivalent parallel version of the software - in a small fraction of the time normally required for a manual parallelization. We first discuss the way in which loop types are categorized and how efficient OpenMP directives can be defined and inserted into the existing code using the in-depth interprocedural analysis. The use of the toolkit on a number of application codes ranging from benchmark to real-world application codes is presented. This will demonstrate the great potential of using the toolkit to quickly parallelize serial programs as well as the good performance achievable on a large number of toolkit to quickly parallelize serial programs as well as the good performance achievable on a large number of processors. The second part of the document gives references to the parameters and the graphic user interface implemented in the toolkit. Finally a set of tutorials is included for hands-on experiences with this toolkit.

Jin, Hao-Qiang; Frumkin, Michael; Yan, Jerry; Biegel, Bryan (Technical Monitor)

2001-01-01

174

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

175

The NAS parallel benchmarks  

NASA Technical Reports Server (NTRS)

A new set of benchmarks has been developed for the performance evaluation of highly parallel supercomputers in the framework of the NASA Ames Numerical Aerodynamic Simulation (NAS) Program. These consist of five 'parallel kernel' benchmarks and three 'simulated application' benchmarks. Together they mimic the computation and data movement characteristics of large-scale computational fluid dynamics applications. The principal distinguishing feature of these benchmarks is their 'pencil and paper' specification-all details of these benchmarks are specified only algorithmically. In this way many of the difficulties associated with conventional benchmarking approaches on highly parallel systems are avoided.

Bailey, D. H.; Barszcz, E.; Barton, J. T.; Carter, R. L.; Lasinski, T. A.; Browning, D. S.; Dagum, L.; Fatoohi, R. A.; Frederickson, P. O.; Schreiber, R. S.

1991-01-01

176

The NAS parallel benchmarks  

NASA Technical Reports Server (NTRS)

A new set of benchmarks was developed for the performance evaluation of highly parallel supercomputers. These benchmarks consist of a set of kernels, the 'Parallel Kernels,' and a simulated application benchmark. Together they mimic the computation and data movement characteristics of large scale computational fluid dynamics (CFD) applications. The principal distinguishing feature of these benchmarks is their 'pencil and paper' specification - all details of these benchmarks are specified only algorithmically. In this way many of the difficulties associated with conventional benchmarking approaches on highly parallel systems are avoided.

Bailey, David (editor); Barton, John (editor); Lasinski, Thomas (editor); Simon, Horst (editor)

1993-01-01

177

NAS parallel benchmark results  

NASA Technical Reports Server (NTRS)

The NAS (Numerical Aerodynamic Simulation) parallel benchmarks have been developed at NASA Ames Research Center to study the performance of parallel supercomputers. The eight benchmark problems are specified in a 'pencil and paper' fashion. The performance results of various systems using the NAS parallel benchmarks are presented. These results represent the best results that have been reported to the authors for the specific systems listed. They represent implementation efforts performed by personnel in both the NAS Applied Research Branch of NASA Ames Research Center and in other organizations.

Bailey, D. H.; Barszcz, E.; Dagum, L.; Simon, H. D.

1992-01-01

178

Parallelization of thermochemical nanolithography  

NASA Astrophysics Data System (ADS)

One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons.One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons. Electronic supplementary information (ESI) available: Details on the cantilevers array, on the sample preparation, and on the GO AFM experiments. See DOI: 10.1039/c3nr05696a

Carroll, Keith M.; Lu, Xi; Kim, Suenne; Gao, Yang; Kim, Hoe-Joon; Somnath, Suhas; Polloni, Laura; Sordan, Roman; King, William P.; Curtis, Jennifer E.; Riedo, Elisa

2014-01-01

179

The Parallel Axiom  

ERIC Educational Resources Information Center

Criteria for a reasonable axiomatic system are discussed. A discussion of the historical attempts to prove the independence of Euclids parallel postulate introduces non-Euclidean geometries. Poincare's model for a non-Euclidean geometry is defined and analyzed. (LS)

Rogers, Pat

1972-01-01

180

Series and Parallel Circuits  

NSDL National Science Digital Library

In this activity, learners demonstrate and discuss simple circuits as well as the differences between parallel and serial circuit design and functions. Learners test two different circuit designs through the use of low voltage light bulbs.

IEEE

2013-08-30

181

Parallels with nature  

NASA Astrophysics Data System (ADS)

Adam Nelson and Stuart Warriner, from the University of Leeds, talk with Nature Chemistry about their work to develop viable synthetic strategies for preparing new chemical structures in parallel with the identification of desirable biological activity.

2014-10-01

182

Parallelization of CFD codes  

NASA Astrophysics Data System (ADS)

The use of parallelization is examined for conducting CFD representations such as 3D Navier-Stokes simulations of flows about aircraft for engineering purposes. References are made to fine-, medium-, and coarse-grain levels of parallelism, the use of artificial viscosity, and the use of explicit Runge-Kutta time integration. The inherent parallelism in CFD is examined with attention given to the use of patched multiblocks on shared-memory and local-memory MIMD machines. Medium-grain parallelism is effective for the shared-memory MIMDs when using a compiler directive that advances the equations in time after copying them onto several independent processors. Local-memory computers can be used to avoid the performance restrictions of memory access by using processors with built-in memories. The microblock concept is described, and some examples are given of decomposed domains including a computational result for a simulated Euler equations.

Bergman, C. M.; Vos, J. B.

1991-08-01

183

Series/Parallel Batteries  

NSDL National Science Digital Library

It is important for students to understand how resistors, capacitors, and batteries combine in series and parallel. The combination of batteries has a lot of practical applications in science competitions. This lab also reinforces how to use a voltmeter t

Michael Horton

2009-05-30

184

Parallel programming with PCN  

SciTech Connect

PCN is a system for developing and executing parallel programs. It comprises a high-level programming language, a set of tools for developing and debugging programs in this language, and interfaces to Fortran and C that allow the reuse of existing code in multilingual parallel programs. Programs developed using PCN are portable across many different workstations, networks, and parallel computers. This document provides all the information required to develop parallel programs with the PCN programming system. It includes both tutorial and reference material. It also presents the basic concepts that underlie PCN, particularly where these are likely to be unfamiliar to the reader, and provides pointers to other documentation on the PCN language, programming techniques, and tools. PCN is in the public domain. The latest version of both the software and this manual can be obtained by anonymous FTP from Argonne National Laboratory at info.mcs.anl.gov.

Foster, I.; Tuecke, S.

1991-09-01

185

Parallel programming with PCN  

SciTech Connect

PCN is a system for developing and executing parallel programs. It comprises a high-level programming language, tools for developing and debugging programs in this language, and interfaces to Fortran and C that allow the reuse of existing code in multilingual parallel programs. Programs developed using PCN are portable across many different workstations, networks, and parallel computers. This document provides all the information required to develop parallel programs with the PCN programming system. In includes both tutorial and reference material. It also presents the basic concepts that underly PCN, particularly where these are likely to be unfamiliar to the reader, and provides pointers to other documentation on the PCN language, programming techniques, and tools. PCN is in the public domain. The latest version of both the software and this manual can be obtained by anonymous FTP from Argonne National Laboratory in the directory pub/pcn at info.mcs.anl.gov (c.f. Appendix A).

Foster, I.; Tuecke, S.

1991-12-01

186

Scalable parallel communications  

NASA Technical Reports Server (NTRS)

Coarse-grain parallelism in networking (that is, the use of multiple protocol processors running replicated software sending over several physical channels) can be used to provide gigabit communications for a single application. Since parallel network performance is highly dependent on real issues such as hardware properties (e.g., memory speeds and cache hit rates), operating system overhead (e.g., interrupt handling), and protocol performance (e.g., effect of timeouts), we have performed detailed simulations studies of both a bus-based multiprocessor workstation node (based on the Sun Galaxy MP multiprocessor) and a distributed-memory parallel computer node (based on the Touchstone DELTA) to evaluate the behavior of coarse-grain parallelism. Our results indicate: (1) coarse-grain parallelism can deliver multiple 100 Mbps with currently available hardware platforms and existing networking protocols (such as Transmission Control Protocol/Internet Protocol (TCP/IP) and parallel Fiber Distributed Data Interface (FDDI) rings); (2) scale-up is near linear in n, the number of protocol processors, and channels (for small n and up to a few hundred Mbps); and (3) since these results are based on existing hardware without specialized devices (except perhaps for some simple modifications of the FDDI boards), this is a low cost solution to providing multiple 100 Mbps on current machines. In addition, from both the performance analysis and the properties of these architectures, we conclude: (1) multiple processors providing identical services and the use of space division multiplexing for the physical channels can provide better reliability than monolithic approaches (it also provides graceful degradation and low-cost load balancing); (2) coarse-grain parallelism supports running several transport protocols in parallel to provide different types of service (for example, one TCP handles small messages for many users, other TCP's running in parallel provide high bandwidth service to a single application); and (3) coarse grain parallelism will be able to incorporate many future improvements from related work (e.g., reduced data movement, fast TCP, fine-grain parallelism) also with near linear speed-ups.

Maly, K.; Khanna, S.; Overstreet, C. M.; Mukkamala, R.; Zubair, M.; Sekhar, Y. S.; Foudriat, E. C.

1992-01-01

187

Parallelization: Binary Tree Traversal  

NSDL National Science Digital Library

This module teaches the use of binary trees to sort through large data sets, different traversal methods for binary trees, including parallel methods, and how to scale a binary tree traversal on multiple compute cores. Upon completion of this module, students should be able to recognize the structure of a binary tree, employ different methods for traversing a binary tree, understand how to parallelize a binary tree traversal, and how to scale a binary tree traversal over multiple compute cores.

Aaron Weeden

188

Parallel Composition Communication and Allow Hiding Parallel Processes  

E-print Network

Communication and Allow Hiding The Saga of Axiomatizing Parallel Composition Challenge (Dish1+Dish2) || Coke ? = (Dish1 || Coke)+(Dish2 || Coke) Mousavi: Parallel Processes #12;Parallel Composition Communication and Allow Hiding The Saga of Axiomatizing Parallel Composition Challenge (Dish1+Dish2) || Coke ? = (Dish1

Groote, Jan Friso

189

Parallel Composition Communication and Allow Hiding Parallel Processes  

E-print Network

Parallel Composition Challenge (Dish1+Dish2) || Coke ? = (Dish1 || Coke)+(Dish2 || Coke) Mousavi: Parallel Composition Challenge (Dish1+Dish2) || Coke ? = (Dish1 || Coke)+(Dish2 || Coke) Faron Moller's Result Parallel Parallel Composition and |: Raisons d'^etre (Dish1 + Dish2) Coke (Dish1 Coke) + (Dish2 Coke) (Dish1 + Dish

Mousavi, Mohammad

190

Sublattice parallel replica dynamics  

NASA Astrophysics Data System (ADS)

Exascale computing presents a challenge for the scientific community as new algorithms must be developed to take full advantage of the new computing paradigm. Atomistic simulation methods that offer full fidelity to the underlying potential, i.e., molecular dynamics (MD) and parallel replica dynamics, fail to use the whole machine speedup, leaving a region in time and sample size space that is unattainable with current algorithms. In this paper, we present an extension of the parallel replica dynamics algorithm [A. F. Voter, Phys. Rev. B 57, R13985 (1998), 10.1103/PhysRevB.57.R13985] by combining it with the synchronous sublattice approach of Shim and Amar [Y. Shim and J. G. Amar, Phys. Rev. B 71, 125432 (2005), 10.1103/PhysRevB.71.125432], thereby exploiting event locality to improve the algorithm scalability. This algorithm is based on a domain decomposition in which events happen independently in different regions in the sample. We develop an analytical expression for the speedup given by this sublattice parallel replica dynamics algorithm and compare it with parallel MD and traditional parallel replica dynamics. We demonstrate how this algorithm, which introduces a slight additional approximation of event locality, enables the study of physical systems unreachable with traditional methodologies and promises to better utilize the resources of current high performance and future exascale computers.

Martínez, Enrique; Uberuaga, Blas P.; Voter, Arthur F.

2014-06-01

191

Is quantum parallelism real?  

NASA Astrophysics Data System (ADS)

In this paper we raise questions about the reality of computational quantum parallelism. Such questions are important because while quantum theory is rigorously established, the hypothesis that it supports a more powerful model of computation remains speculative. More specifically, we suggest the possibility that the seeming computational parallelism offered by quantum superpositions is actually effected by gate-level parallelism in the reversible implementation of the quantum operator. In other words, when the total number of logic operations is analyzed, quantum computing may not be more powerful than classical. This fact has significant public policy implications with regard to the relative levels of effort that are appropriate for the development of quantumparallel algorithms and associated hardware (i.e., qubit-based) versus quantum-scale classical hardware.

Lanzagorta, Marco; Uhlmann, Jeffrey

2008-04-01

192

Parallel optical sampler  

DOEpatents

An optical sampler includes a first and second 1.times.n optical beam splitters splitting an input optical sampling signal and an optical analog input signal into n parallel channels, respectively, a plurality of optical delay elements providing n parallel delayed input optical sampling signals, n photodiodes converting the n parallel optical analog input signals into n respective electrical output signals, and n optical modulators modulating the input optical sampling signal or the optical analog input signal by the respective electrical output signals, and providing n successive optical samples of the optical analog input signal. A plurality of output photodiodes and eADCs convert the n successive optical samples to n successive digital samples. The optical modulator may be a photodiode interconnected Mach-Zehnder Modulator. A method of sampling the optical analog input signal is disclosed.

Tauke-Pedretti, Anna; Skogen, Erik J; Vawter, Gregory A

2014-05-20

193

Parallelizing Quantum Circuits  

E-print Network

We present a novel automated technique for parallelizing quantum circuits via forward and backward translation to measurement-based quantum computing patterns and analyze the trade off in terms of depth and space complexity. As a result we distinguish a class of polynomial depth circuits that can be parallelized to logarithmic depth while adding only polynomial many auxiliary qubits. In particular, we provide for the first time a full characterization of patterns with flow of arbitrary depth, based on the notion of influencing paths and a simple rewriting system on the angles of the measurement. Our method leads to insightful knowledge for constructing parallel circuits and as applications, we demonstrate several constant and logarithmic depth circuits. Furthermore, we prove a logarithmic separation in terms of quantum depth between the quantum circuit model and the measurement-based model.

Anne Broadbent; Elham Kashefi

2007-04-13

194

SPINning parallel systems software.  

SciTech Connect

We describe our experiences in using Spin to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and terminates. This dynamic nature is easily expressible in the Spin/Promela framework but poses performance and scalability challenges. We present here the results of expressing some of the parallel algorithms of MPD and executing both simulation and verification runs with Spin.

Matlin, O.S.; Lusk, E.; McCune, W.

2002-03-15

195

Parallel signal processing  

NASA Astrophysics Data System (ADS)

The potential application of parallel computing techniques to digital signal processing for radar is discussed and two types of regular array processor are discussed. The first type of processor is the systolic or wavefront processor. The application of this type of processor to adaptive beamforming is discussed and the joint STL-RSRE adaptive antenna processor test-bed is reviewed. The second type of regular array processor is the SIMD parallel computer. One such processor, the Mil-DAP, is described, and its application to a varied range of radar signal processing tasks is discussed.

McWhirter, John G.

1989-12-01

196

Adaptive parallel logic networks  

NASA Technical Reports Server (NTRS)

Adaptive, self-organizing concurrent systems (ASOCS) that combine self-organization with massive parallelism for such applications as adaptive logic devices, robotics, process control, and system malfunction management, are presently discussed. In ASOCS, an adaptive network composed of many simple computing elements operating in combinational and asynchronous fashion is used and problems are specified by presenting if-then rules to the system in the form of Boolean conjunctions. During data processing, which is a different operational phase from adaptation, the network acts as a parallel hardware circuit.

Martinez, Tony R.; Vidal, Jacques J.

1988-01-01

197

Parallel programming with PCN  

SciTech Connect

PCN is a system for developing and executing parallel programs. It comprises a high-level programming language, tools for developing and debugging programs in this language, and interfaces to Fortran and Cthat allow the reuse of existing code in multilingual parallel programs. Programs developed using PCN are portable across many different workstations, networks, and parallel computers. This document provides all the information required to develop parallel programs with the PCN programming system. It includes both tutorial and reference material. It also presents the basic concepts that underlie PCN, particularly where these are likely to be unfamiliar to the reader, and provides pointers to other documentation on the PCN language, programming techniques, and tools. PCN is in the public domain. The latest version of both the software and this manual can be obtained by anonymous ftp from Argonne National Laboratory in the directory pub/pcn at info.mcs. ani.gov (cf. Appendix A). This version of this document describes PCN version 2.0, a major revision of the PCN programming system. It supersedes earlier versions of this report.

Foster, I.; Tuecke, S.

1993-01-01

198

Parallelism and evolutionary algorithms  

Microsoft Academic Search

This paper contains a modern vision of the paral- lelization techniques used for evolutionary algorithms (EAs). The work is motivated by two fundamental facts: first, the different families of EAs have naturally converged in the last decade while parallel EAs (PEAs) seem still to lack unified studies, and second, there is a large number of improvements in these algorithms and

Enrique Alba; Marco Tomassini

2002-01-01

199

Parallelization for reaction  

E-print Network

Parallelization for reaction waves with complex chemistry Context Application Background Numerical with complex chemistry S. Descombes 2 M. Duarte 3 T. Dumont 1 V. Louvet 1 M. Massot 3 1Camille Jordan Institute - France 3EM2C Laboratory - Ecole Centrale Paris - France Workshop on Computational and Applied Mathematics

Louvet, Violaine

200

High performance parallel architectures  

SciTech Connect

In this paper the author describes current high performance parallel computer architectures. A taxonomy is presented to show computer architecture from the user programmer's point-of-view. The effects of the taxonomy upon the programming model are described. Some current architectures are described with respect to the taxonomy. Finally, some predictions about future systems are presented. 5 refs., 1 fig.

Anderson, R.E. (Lawrence Livermore National Lab., CA (USA))

1989-09-01

201

NAS Parallel Benchmarks Results  

NASA Technical Reports Server (NTRS)

The NAS Parallel Benchmarks (NPB) were developed in 1991 at NASA Ames Research Center to study the performance of parallel supercomputers. The eight benchmark problems are specified in a pencil and paper fashion i.e. the complete details of the problem to be solved are given in a technical document, and except for a few restrictions, benchmarkers are free to select the language constructs and implementation techniques best suited for a particular system. In this paper, we present new NPB performance results for the following systems: (a) Parallel-Vector Processors: Cray C90, Cray T'90 and Fujitsu VPP500; (b) Highly Parallel Processors: Cray T3D, IBM SP2 and IBM SP-TN2 (Thin Nodes 2); (c) Symmetric Multiprocessing Processors: Convex Exemplar SPP1000, Cray J90, DEC Alpha Server 8400 5/300, and SGI Power Challenge XL. We also present sustained performance per dollar for Class B LU, SP and BT benchmarks. We also mention NAS future plans of NPB.

Subhash, Saini; Bailey, David H.; Lasinski, T. A. (Technical Monitor)

1995-01-01

202

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.

Gong Chen

203

Parallel hierarchical global illumination  

SciTech Connect

Solving the global illumination problem is equivalent to determining the intensity of every wavelength of light in all directions at every point in a given scene. The complexity of the problem has led researchers to use approximation methods for solving the problem on serial computers. Rather than using an approximation method, such as backward ray tracing or radiosity, the authors have chosen to solve the Rendering Equation by direct simulation of light transport from the light sources. This paper presents an algorithm that solves the Rendering Equation to any desired accuracy, and can be run in parallel on distributed memory or shared memory computer systems with excellent scaling properties. It appears superior in both speed and physical correctness to recent published methods involving bidirectional ray tracing or hybrid treatments of diffuse and specular surfaces. Like progressive radiosity methods, it dynamically refines the geometry decomposition where required, but does so without the excessive storage requirements for ray histories. The algorithm, called Photon, produces a scene which converges to the global illumination solution. This amounts to a huge task for a 1997-vintage serial computer, but using the power of a parallel supercomputer significantly reduces the time required to generate a solution. Currently, Photon can be run on most parallel environments from a shared memory multiprocessor to a parallel supercomputer, as well as on clusters of heterogeneous workstations.

Snell, Q.O.

1997-10-08

204

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

205

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

206

Equalizer: a scalable parallel rendering framework.  

PubMed

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 often only application specific implementations have been proposed. The task of developing a scalable parallel rendering framework is even more difficult if it should be generic to support various types of data and visualization applications, and at the same time work efficiently on a cluster with distributed graphics cards. In this paper we introduce a novel system called Equalizer, a toolkit for scalable parallel rendering based on OpenGL which provides an application programming interface (API) to develop scalable graphics applications for a wide range of systems ranging from large distributed visualization clusters and multi-processor multipipe graphics systems to single-processor single-pipe desktop machines. We describe the system architecture, the basic API, discuss its advantages over previous approaches, present example configurations and usage scenarios as well as scalability results. PMID:19282550

Eilemann, Stefan; Makhinya, Maxim; Pajarola, Renato

2009-01-01

207

A parallel world in the dark  

SciTech Connect

The baryon-dark matter coincidence is a long-standing issue. Interestingly, the recent observations suggest the presence of dark radiation, which, if confirmed, would pose another coincidence problem of why the density of dark radiation is comparable to that of photons. These striking coincidences may be traced back to the dark sector with particle contents and interactions that are quite similar, if not identical, to the standard model: a dark parallel world. It naturally solves the coincidence problems of dark matter and dark radiation, and predicts a sterile neutrino(s) with mass of O(0.1?1) eV, as well as self-interacting dark matter made of the counterpart of ordinary baryons. We find a robust prediction for the relation between the abundance of dark radiation and the sterile neutrino, which can serve as the smoking-gun evidence of the dark parallel world.

Higaki, Tetsutaro [Mathematical Physics Lab., RIKEN Nishina Center, Saitama 351-0198 (Japan); Jeong, Kwang Sik; Takahashi, Fuminobu, E-mail: tetsutaro.higaki@riken.jp, E-mail: ksjeong@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)

2013-08-01

208

ZAMBEZI: a parallel pattern parallel fault sequential circuit fault simulator  

Microsoft Academic Search

Sequential circuit fault simulators use the multiple bits in a computer data word to accelerate simulation. We introduce, and implement, a new sequential circuit fault simulator, a parallel pattern parallel fault simulator, ZAMBEZI, which simultaneously simulates multiple faults with multiple vectors in one data word. ZAMBEZI is developed by enhancing the control flow, of existing parallel pattern algorithms. For a

Minesh B. Amin; Bapiraju Vinnakota

1996-01-01

209

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

210

Parallel Consensual Neural Networks  

NASA Technical Reports Server (NTRS)

A new neural network architecture is proposed and applied in classification of remote sensing/geographic data from multiple sources. The new architecture is called the parallel consensual neural network and its relation to hierarchical and ensemble neural networks is discussed. The parallel consensual neural network architecture is based on statistical consensus theory. The input data are transformed several times and the different transformed data are applied as if they were independent inputs and are classified using stage neural networks. Finally, the outputs from the stage networks are then weighted and combined to make a decision. Experimental results based on remote sensing data and geographic data are given. The performance of the consensual neural network architecture is compared to that of a two-layer (one hidden layer) conjugate-gradient backpropagation neural network. The results with the proposed neural network architecture compare favorably in terms of classification accuracy to the backpropagation method.

Benediktsson, J. A.; Sveinsson, J. R.; Ersoy, O. K.; Swain, P. H.

1993-01-01

211

Parallelization: Sieve of Eratosthenes  

NSDL National Science Digital Library

This module presents the Sieve of Eratosthenes, a method for finding the prime numbers below a certain integer. One can model the sieve for small integers by hand. For bigger integers, it becomes necessary to use a coded implementation. This code can be either serial (sequential) or parallel. Students will explore the various forms of parallelism (shared memory, distributed memory, and hybrid) as well as the scaling of the algorithm on multiple cores in its various forms, observing the relationship between run time of the program and number of cores devoted to the program. An assessment rubric, two exercises, and two student project ideas allow the student to consolidate her/his understanding of the material presented in the module.

Weeden, Aaron

212

Parallel Anisotropic Tetrahedral Adaptation  

NASA Technical Reports Server (NTRS)

An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.

Park, Michael A.; Darmofal, David L.

2008-01-01

213

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

214

Parallel Subconvolution Filtering Architectures  

NASA Technical Reports Server (NTRS)

These architectures are based on methods of vector processing and the discrete-Fourier-transform/inverse-discrete- Fourier-transform (DFT-IDFT) overlap-and-save method, combined with time-block separation of digital filters into frequency-domain subfilters implemented by use of sub-convolutions. The parallel-processing method implemented in these architectures enables the use of relatively small DFT-IDFT pairs, while filter tap lengths are theoretically unlimited. The size of a DFT-IDFT pair is determined by the desired reduction in processing rate, rather than on the order of the filter that one seeks to implement. The emphasis in this report is on those aspects of the underlying theory and design rules that promote computational efficiency, parallel processing at reduced data rates, and simplification of the designs of very-large-scale integrated (VLSI) circuits needed to implement high-order filters and correlators.

Gray, Andrew A.

2003-01-01

215

Collisionless parallel shocks  

NASA Technical Reports Server (NTRS)

Consideration is given to a collisionless parallel shock based on solitary-type solutions of the modified derivative nonlinear Schroedinger equation (MDNLS) for parallel Alfven waves. The standard derivative nonlinear Schroedinger equation is generalized in order to include the possible anisotropy of the plasma distribution and higher-order Korteweg-de Vies-type dispersion. Stationary solutions of MDNLS are discussed. The anisotropic nature of 'adiabatic' reflections leads to the asymmetric particle distribution in the upstream as well as in the downstream regions of the shock. As a result, nonzero heat flux appears near the front of the shock. It is shown that this causes the stochastic behavior of the nonlinear waves, which can significantly contribute to the shock thermalization.

Khabibrakhmanov, I. KH.; Galeev, A. A.; Galinskii, V. L.

1993-01-01

216

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

217

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

218

Standard Templates Adaptive Parallel Library  

E-print Network

STAPL (Standard Templates Adaptive Parallel Library) is a parallel C++ library designed as a superset of the C++ Standard Template Library (STL), sequentially consistent for functions with the same name, and executed on uni- or multi- processor...

Arzu, Francisco Jose

2012-06-07

219

A Parallel Repetition Theorem  

Microsoft Academic Search

We show that a parallel repetition of any two-prover one-round proof system (MIP(2,1)) decreases the probability of error at an exponential rate. No constructive bound was previously known. The constant in the exponent (in our analysis) depends only on the original probability of error and on the total number of possible answers of the two provers. The dependency on the

Ran Raz

1998-01-01

220

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.

Aaron Weeden

221

Massively parallel neural computation  

E-print Network

and communication resources is developed and then used to implement a neural computation system on the multi- FPGA platform. Finding suitable benchmark neural networks for a massively parallel neural com- putation system proves to be a challenge. A synthetic... .2.4 Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 7.2.5 Memory spike source . . . . . . . . . . . . . . . . . . . . . . . 116 7.2.6 Spike injector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.2.7 Spike auditor...

Fox, Paul James

2013-03-12

222

Parallel sphere rendering  

SciTech Connect

Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the M.

Krogh, M.; Painter, J.; Hansen, C.

1996-10-01

223

Parallel Pascal - An extended Pascal for parallel computers  

NASA Technical Reports Server (NTRS)

Parallel Pascal is an extended version of the conventional serial Pascal programming language which includes a convenient syntax for specifying array operations. It is upward compatible with standard Pascal and involves only a small number of carefully chosen new features. Parallel Pascal was developed to reduce the semantic gap between standard Pascal and a large range of highly parallel computers. Two important design goals of Parallel Pascal were efficiency and portability. Portability is particularly difficult to achieve since different parallel computers frequently have very different capabilities.

Reeves, A. P.

1984-01-01

224

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

225

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

226

Falcon: On-line Monitoring and Steering of Parallel Programs  

Microsoft Academic Search

Advances in high performance computing, communications, and user interfaces are enabling developers to construct increasingly interactive high performance applications. The Falcon system presented in this paper supports such interactivity by providing runtime libraries, tools, and user interfaces that jointly permit the on-line monitoring and steering of large-scale parallel codes. The principal aspects of Falcon described in this paper are its

Weiming Gu; Greg Eisenhauer; Karsten Schwan; Jeffrey Vetter

1995-01-01

227

Parallelized direct execution simulation of message-passing parallel programs  

NASA Technical Reports Server (NTRS)

As massively parallel computers proliferate, there is growing interest in findings ways by which performance of massively parallel codes can be efficiently predicted. This problem arises in diverse contexts such as parallelizing computers, parallel performance monitoring, and parallel algorithm development. In this paper we describe one solution where one directly executes the application code, but uses a discrete-event simulator to model details of the presumed parallel machine such as operating system and communication network behavior. Because this approach is computationally expensive, we are interested in its own parallelization specifically the parallelization of the discrete-event simulator. We describe methods suitable for parallelized direct execution simulation of message-passing parallel programs, and report on the performance of such a system, Large Application Parallel Simulation Environment (LAPSE), we have built on the Intel Paragon. On all codes measured to date, LAPSE predicts performance well typically within 10 percent relative error. Depending on the nature of the application code, we have observed low slowdowns (relative to natively executing code) and high relative speedups using up to 64 processors.

Dickens, Phillip M.; Heidelberger, Philip; Nicol, David M.

1994-01-01

228

Hybrid particle-field molecular dynamics simulations: parallelization and benchmarks.  

PubMed

The parallel implementation of a recently developed hybrid scheme for molecular dynamics (MD) simulations (Milano and Kawakatsu, J Chem Phys 2009, 130, 214106) where self-consistent field theory (SCF) and particle models are combined is described. Because of the peculiar formulation of the hybrid method, considering single particles interacting with density fields, the most computationally expensive part of the hybrid particle-field MD simulation can be efficiently parallelized using a straightforward particle decomposition algorithm. Benchmarks of simulations, including comparisons of serial MD and MD-SCF program profiles, serial MD-SCF and parallel MD-SCF program profiles, and parallel benchmarks compared with efficient MD program GROMACS 4.5.4 are tested and reported. The results of benchmarks indicate that the proposed parallelization scheme is very efficient and opens the way to molecular simulations of large scale systems with reasonable computational costs. PMID:22278759

Zhao, Ying; De Nicola, Antonio; Kawakatsu, Toshihiro; Milano, Giuseppe

2012-03-30

229

Parallelized nested sampling  

NASA Astrophysics Data System (ADS)

One of the important advantages of nested sampling as an MCMC technique is its ability to draw representative samples from multimodal distributions and distributions with other degeneracies. This coverage is accomplished by maintaining a number of so-called live samples within a likelihood constraint. In usual practice, at each step, only the sample with the least likelihood is discarded from this set of live samples and replaced. In [1], Skilling shows that for a given number of live samples, discarding only one sample yields the highest precision in estimation of the log-evidence. However, if we increase the number of live samples, more samples can be discarded at once while still maintaining the same precision. For computer code running only serially, this modification would considerably increase the wall clock time necessary to reach convergence. However, if we use a computer with parallel processing capabilities, and we write our code to take advantage of this parallelism to replace multiple samples concurrently, the performance penalty can be eliminated entirely and possibly reversed. In this case, we must use the more general equation in [1] for computing the expectation of the shrinkage distribution: E [- log t]= (N r-r+1)-1+(Nr-r+2)-1+⋯+Nr-1, for shrinkage t with Nr live samples and r samples discarded at each iteration. The equation for the variance Var (- log t)= (N r-r+1)-2+(Nr-r+2)-2+⋯+Nr-2 is used to find the appropriate number of live samples Nr to use with r > 1 to match the variance achieved with N1 live samples and r = 1. In this paper, we show that by replacing multiple discarded samples in parallel, we are able to achieve a more thorough sampling of the constrained prior distribution, reduce runtime, and increase precision.

Henderson, R. Wesley; Goggans, Paul M.

2014-12-01

230

Highly parallel computation  

NASA Technical Reports Server (NTRS)

Highly parallel computing architectures are the only means to achieve the computation rates demanded by advanced scientific problems. A decade of research has demonstrated the feasibility of such machines and current research focuses on which architectures designated as multiple instruction multiple datastream (MIMD) and single instruction multiple datastream (SIMD) have produced the best results to date; neither shows a decisive advantage for most near-homogeneous scientific problems. For scientific problems with many dissimilar parts, more speculative architectures such as neural networks or data flow may be needed.

Denning, Peter J.; Tichy, Walter F.

1990-01-01

231

Parallel sphere rendering  

SciTech Connect

Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel divide-and-conquer algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the T3D.

Krogh, M.; Hansen, C.; Painter, J. [Los Alamos National Lab., NM (United States); de Verdiere, G.C. [CEA Centre d`Etudes de Limeil, 94 - Villeneuve-Saint-Georges (France)

1995-05-01

232

Parallel Eclipse Project Checkout  

NASA Technical Reports Server (NTRS)

Parallel Eclipse Project Checkout (PEPC) is a program written to leverage parallelism and to automate the checkout process of plug-ins created in Eclipse RCP (Rich Client Platform). Eclipse plug-ins can be aggregated in a feature project. This innovation digests a feature description (xml file) and automatically checks out all of the plug-ins listed in the feature. This resolves the issue of manually checking out each plug-in required to work on the project. To minimize the amount of time necessary to checkout the plug-ins, this program makes the plug-in checkouts parallel. After parsing the feature, a request to checkout for each plug-in in the feature has been inserted. These requests are handled by a thread pool with a configurable number of threads. By checking out the plug-ins in parallel, the checkout process is streamlined before getting started on the project. For instance, projects that took 30 minutes to checkout now take less than 5 minutes. The effect is especially clear on a Mac, which has a network monitor displaying the bandwidth use. When running the client from a developer s home, the checkout process now saturates the bandwidth in order to get all the plug-ins checked out as fast as possible. For comparison, a checkout process that ranged from 8-200 Kbps from a developer s home is now able to saturate a pipe of 1.3 Mbps, resulting in significantly faster checkouts. Eclipse IDE (integrated development environment) tries to build a project as soon as it is downloaded. As part of another optimization, this innovation programmatically tells Eclipse to stop building while checkouts are happening, which dramatically reduces lock contention and enables plug-ins to continue downloading until all of them finish. Furthermore, the software re-enables automatic building, and forces Eclipse to do a clean build once it finishes checking out all of the plug-ins. This software is fully generic and does not contain any NASA-specific code. It can be applied to any Eclipse-based repository with a similar structure. It also can apply build parameters and preferences automatically at the end of the checkout.

Crockett, Thomas M.; Joswig, Joseph C.; Shams, Khawaja S.; Powell, Mark W.; Bachmann, Andrew G.

2011-01-01

233

A stereoscopic PIV study on the behavior of near-field wingtip vortex structures  

Microsoft Academic Search

Wingtip vortex flow is of great importance because of its effect on practical problems such as landing separation distances for aircraft, blade\\/vortex interactions on helicopter blades, and propeller cavitations on ships. Extensive investigations have been conducted to improve the understanding of the tip vortex structure and its dissipation or persistence analytically, numerically, and experimentally. The universal feature of the water\\/wind

Hirofumi Igarashi

2011-01-01

234

LES for wing tip vortex around an airfoil  

Microsoft Academic Search

The wing tip vortex is very important because of its effects on the noise generation, blade\\/vortex interactions on helicopter blades, propeller cavitations on ships, and other fields. The objective of this work is to use the numerical simulation with high order accuracy and high resolution to investigate the formation and the near field evolution of a wing tip vortex at

Jiangang Cai

2006-01-01

235

Rotary wing aerodynamically generated noise  

NASA Technical Reports Server (NTRS)

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.

Schmitz, F. J.; Morse, H. A.

1982-01-01

236

Active control system for a rotor blade trailing-edge flap  

Microsoft Academic Search

Reducing the external noise is becoming a major issue for helicopter manufacturers. The idea beyond this goal is to reduce or even avoid the blade vortex interaction (BVI), especially during descent and flights over inhabited areas. This can be achieved by changing locally the lift of the blade. Several strategies to reach this goal are under investigation at EUROCOPTER such

Marc Duvernier; Livier Reithler; Jean Y. Guerrero; Rinaldo A. Rossi

2000-01-01

237

AIAA 2001-0821 Towards Adjoint-Based Methods for  

E-print Network

leading edge (Ref. 1), passive blade design (Ref. 2), and actively controlled trail- ing edge flaps (Ref of aeroacoustic noise generated by blade-vortex interaction. We discuss some problem formulation issues- coustic noise where the acoustic source is predicted by the unsteady, compressible, Navier

Heinkenschloss, Matthias

238

596 IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL. 7, NO. 5, SEPTEMBER 1999 Feedback Attenuation and Adaptive Cancellation of  

E-print Network

. The aim of control is to achieve attenuation of vortex noise by control of trailing edge flaps of a trailing edge flap. Lift fluctuations caused by vortices are taken as output disturbance. The contribution. Ariyur and Miroslav Krsti´c Abstract--Blade vortex interaction (BVI) noise has been rec- ognized

Krstic, Miroslav

239

GTC++: An Object-Oriented, Parallel, Gyrokinetic PIC Simulation  

Microsoft Academic Search

We describe GTC++, a global-cross-section, gyrokinetic, PIC code for simulating tokamak microinstabilities. In GTC++, we use objects to represent physical and numerical abstractions such as the magnetic geometry and the gyrokinetic particle-mesh interactions. The basic software infrastructure is the POOMA Framework (Parallel Object-Oriented Methods and Applications). This C++ class library provides high-level data-parallel programming interfaces for particles and for fields

Timothy J. Williams; James A. Crotinger; Julian C. Cummings; Zhihong Lin

1998-01-01

240

Programming parallel architectures: The BLAZE family of languages  

NASA Technical Reports Server (NTRS)

Programming multiprocessor architectures is a critical research issue. An overview is given of the various approaches to programming these architectures that are currently being explored. It is argued that two of these approaches, interactive programming environments and functional parallel languages, are particularly attractive since they remove much of the burden of exploiting parallel architectures from the user. Also described is recent work by the author in the design of parallel languages. Research on languages for both shared and nonshared memory multiprocessors is described, as well as the relations of this work to other current language research projects.

Mehrotra, Piyush

1988-01-01

241

Performance characteristics of a parallel treecode  

E-print Network

I describe here the performances of a parallel treecode with individual particle timesteps. The code is based on the Barnes-Hut algorithm and runs cosmological N-body simulations on parallel machines with a distributed memory architecture using the MPI message passing library. For a configuration with a constant number of particles per processor the scalability of the code has been tested up to P=32 processors. The average CPU time per processor necessary for solving the gravitational interactions is within $\\sim 10 %$ of that expected from the ideal scaling relation. The load balancing efficiency is high ($\\simgt90%$) if the processor domains are determined every large timestep according to a weighting scheme which takes into account the total particle computational load within the timestep.

R. Valdarnini

2002-12-11

242

Parallel Computing in SCALE  

SciTech Connect

The SCALE computational architecture has remained basically the same since its inception 30 years ago, although constituent modules and capabilities have changed significantly. This SCALE concept was intended to provide a framework whereby independent codes can be linked to provide a more comprehensive capability than possible with the individual programs - allowing flexibility to address a wide variety of applications. However, the current system was designed originally for mainframe computers with a single CPU and with significantly less memory than today's personal computers. It has been recognized that the present SCALE computation system could be restructured to take advantage of modern hardware and software capabilities, while retaining many of the modular features of the present system. Preliminary work is being done to define specifications and capabilities for a more advanced computational architecture. This paper describes the state of current SCALE development activities and plans for future development. With the release of SCALE 6.1 in 2010, a new phase of evolutionary development will be available to SCALE users within the TRITON and NEWT modules. The SCALE (Standardized Computer Analyses for Licensing Evaluation) code system developed by Oak Ridge National Laboratory (ORNL) provides a comprehensive and integrated package of codes and nuclear data for a wide range of applications in criticality safety, reactor physics, shielding, isotopic depletion and decay, and sensitivity/uncertainty (S/U) analysis. Over the last three years, since the release of version 5.1 in 2006, several important new codes have been introduced within SCALE, and significant advances applied to existing codes. Many of these new features became available with the release of SCALE 6.0 in early 2009. However, beginning with SCALE 6.1, a first generation of parallel computing is being introduced. In addition to near-term improvements, a plan for longer term SCALE enhancement activities has been developed to provide an integrated framework for future methods development. Some of the major components of the SCALE parallel computing development plan are parallelization and multithreading of computationally intensive modules and redesign of the fundamental SCALE computational architecture.

DeHart, Mark D [ORNL] [ORNL; Williams, Mark L [ORNL] [ORNL; Bowman, Stephen M [ORNL] [ORNL

2010-01-01

243

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

244

The STAPL Parallel Container Framework  

E-print Network

programming. stapl is a parallel C++ library with functionality similar to stl, the ISO adopted C++ Standard Template Library [49]. stl is a collection of basic algorithms, containers and iterators that can be used as high-level building blocks... for sequential applications. Similar to stl, stapl provides a collection of parallel algorithms (pAlgorithms), parallel and distributed containers (pContainers) [63, 65, 64, 15, 66], and pViews to abstract the data access in pContainers. stapl provides...

Tanase, Ilie Gabriel

2012-02-14

245

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. PMID:21704835

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

2011-01-01

246

Parallel Grid Manipulations in Earth Science Calculations  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration (NASA) Data Assimilation Office (DAO) at the Goddard Space Flight Center is moving its data assimilation system to massively parallel computing platforms. This parallel implementation of GEOS DAS will be used in the DAO's normal activities, which include reanalysis of data, and operational support for flight missions. Key components of GEOS DAS, including the gridpoint-based general circulation model and a data analysis system, are currently being parallelized. The parallelization of GEOS DAS is also one of the HPCC Grand Challenge Projects. The GEOS-DAS software employs several distinct grids. Some examples are: an observation grid- an unstructured grid of points at which observed or measured physical quantities from instruments or satellites are associated- a highly-structured latitude-longitude grid of points spanning the earth at given latitude-longitude coordinates at which prognostic quantities are determined, and a computational lat-lon grid in which the pole has been moved to a different location to avoid computational instabilities. Each of these grids has a different structure and number of constituent points. In spite of that, there are numerous interactions between the grids, e.g., values on one grid must be interpolated to another, or, in other cases, grids need to be redistributed on the underlying parallel platform. The DAO has designed a parallel integrated library for grid manipulations (PILGRIM) to support the needed grid interactions with maximum efficiency. It offers a flexible interface to generate new grids, define transformations between grids and apply them. Basic communication is currently MPI, however the interfaces defined here could conceivably be implemented with other message-passing libraries, e.g., Cray SHMEM, or with shared-memory constructs. The library is written in Fortran 90. First performance results indicate that even difficult problems, such as above-mentioned pole rotation- a sparse interpolation with little data locality between the physical lat-lon grid and a pole rotated computational grid- can be solved efficiently and at the GFlop/s rates needed to solve tomorrow's high resolution earth science models. In the subsequent presentation we will discuss the design and implementation of PILGRIM as well as a number of the problems it is required to solve. Some conclusions will be drawn about the potential performance of the overall earth science models on the supercomputer platforms foreseen for these problems.

Sawyer, W.; Lucchesi, R.; daSilva, A.; Takacs, L. L.

1999-01-01

247

Parallel Programming in the Age of Ubiquitous Parallelism  

NASA Astrophysics Data System (ADS)

Multicore and manycore processors are now ubiquitous, but parallel programming remains as difficult as it was 30-40 years ago. During this time, our community has explored many promising approaches including functional and dataflow languages, logic programming, and automatic parallelization using program analysis and restructuring, but none of these approaches has succeeded except in a few niche application areas. In this talk, I will argue that these problems arise largely from the computation-centric foundations and abstractions that we currently use to think about parallelism. In their place, I will propose a novel data-centric foundation for parallel programming called the operator formulation in which algorithms are described in terms of actions on data. The operator formulation shows that a generalized form of data-parallelism called amorphous data-parallelism is ubiquitous even in complex, irregular graph applications such as mesh generation/refinement/partitioning and SAT solvers. Regular algorithms emerge as a special case of irregular ones, and many application-specific optimization techniques can be generalized to a broader context. The operator formulation also leads to a structural analysis of algorithms called TAO-analysis that provides implementation guidelines for exploiting parallelism efficiently. Finally, I will describe a system called Galois based on these ideas for exploiting amorphous data-parallelism on multicores and GPUs

Pingali, Keshav

2014-04-01

248

Parallel Smoothed Aggregation Multigrid: Aggregation Strategies on Massively Parallel Machines  

SciTech Connect

Algebraic multigrid methods offer the hope that multigrid convergence can be achieved (for at least some important applications) without a great deal of effort from engineers and scientists wishing to solve linear systems. In this paper the authors consider parallelization of the smoothed aggregation multi-grid method. Smoothed aggregation is one of the most promising algebraic multigrid methods. Therefore, developing parallel variants with both good convergence and efficiency properties is of great importance. However, parallelization is nontrivial due to the somewhat sequential aggregation (or grid coarsening) phase. In this paper, they discuss three different parallel aggregation algorithms and illustrate the advantages and disadvantages of each variant in terms of parallelism and convergence. Numerical results will be shown on the Intel Teraflop computer for some large problems coming from nontrivial codes: quasi-static electric potential simulation and a fluid flow calculation.

Ray S. Tuminaro

2000-11-09

249

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

250

The parallel composition of processes  

E-print Network

We suggest that the canonical parallel operation of processes is composition in a well-supported compact closed category of spans of reflexive graphs. We present the parallel operations of classical process algebras as derived operations arising from monoid objects in such a category, representing the fact that they are protocols based on an underlying broadcast communication.

Albasini, L de Francesco; Walters, R F C

2009-01-01

251

Parallel Matlab MIT Lincoln Laboratory  

E-print Network

­ Sensor analysis systems are implemented in other languages ­ Transformation involves years of software ­ Most users will not touch any solution that requires other languages (even cmex) · Portability ­ Most_Recv(source,comm,tag); #12;MIT Lincoln LaboratorySlide-7 Parallel Matlab MatlabMPI fuctionality · "Core Lite" Parallel

Kepner, Jeremy

252

Limited width parallel prefix circuits  

Microsoft Academic Search

In this paper, we present lower and upper bounds on the size of limited width, bounded and unbounded fan-out parallel prefix circuits. The lower bounds on the sizes of such circuits are a function of the depth, width, and number of inputs. The size requirement of an N input bounded fan-out parallel prefix circuit having limited width W and extra

David A. Carlson; Binay Sugla

1990-01-01

253

Parallel processing in the mammalian retina.  

PubMed

Our eyes send different 'images' of the outside world to the brain - an image of contours (line drawing), a colour image (watercolour painting) or an image of moving objects (movie). This is commonly referred to as parallel processing, and starts as early as the first synapse of the retina, the cone pedicle. Here, the molecular composition of the transmitter receptors of the postsynaptic neurons defines which images are transferred to the inner retina. Within the second synaptic layer - the inner plexiform layer - circuits that involve complex inhibitory and excitatory interactions represent filters that select 'what the eye tells the brain'. PMID:15378035

Wässle, Heinz

2004-10-01

254

Interference effects on scattering by parallel fibers  

NASA Technical Reports Server (NTRS)

The present examination of radiative heat transfer through fibrous materials gives attention to the interactions between radiation scattered from individual parallel fibers for the case of a normally-incident plane EM wave and different representative geometries. Experimental results are obtained for the specific case corresponding to fibers in one plane. Analytical models are developed for the radiative scattering behavior of fibrous media when the interference mechanism is accounted for; the results obtained indicate that interference decreases the scattering efficiency of fibrous media containing a large number of randomly positioned fibers.

White, Susan M.; Kumar, Sunil

1989-01-01

255

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux  

SciTech Connect

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Guo Zehua; Tang Xianzhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-06-15

256

High Performance Parallel Architectures  

NASA Technical Reports Server (NTRS)

Traditional remote sensing instruments are multispectral, where observations are collected at a few different spectral bands. Recently, many hyperspectral instruments, that can collect observations at hundreds of bands, have been operational. Furthermore, there have been ongoing research efforts on ultraspectral instruments that can produce observations at thousands of spectral bands. While these remote sensing technology developments hold great promise for new findings in the area of Earth and space science, they present many challenges. These include the need for faster processing of such increased data volumes, and methods for data reduction. Dimension Reduction is a spectral transformation, aimed at concentrating the vital information and discarding redundant data. One such transformation, which is widely used in remote sensing, is the Principal Components Analysis (PCA). This report summarizes our progress on the development of a parallel PCA and its implementation on two Beowulf cluster configuration; one with fast Ethernet switch and the other with a Myrinet interconnection. Details of the implementation and performance results, for typical sets of multispectral and hyperspectral NASA remote sensing data, are presented and analyzed based on the algorithm requirements and the underlying machine configuration. It will be shown that the PCA application is quite challenging and hard to scale on Ethernet-based clusters. However, the measurements also show that a high- performance interconnection network, such as Myrinet, better matches the high communication demand of PCA and can lead to a more efficient PCA execution.

El-Ghazawi, Tarek; Kaewpijit, Sinthop

1998-01-01

257

Parallel consensual neural networks.  

PubMed

A new type of a neural-network architecture, the parallel consensual neural network (PCNN), is introduced and applied in classification/data fusion of multisource remote sensing and geographic data. The PCNN architecture is based on statistical consensus theory and involves using stage neural networks with transformed input data. The input data are transformed several times and the different transformed data are used as if they were independent inputs. The independent inputs are first classified using the stage neural networks. The output responses from the stage networks are then weighted and combined to make a consensual decision. In this paper, optimization methods are used in order to weight the outputs from the stage networks. Two approaches are proposed to compute the data transforms for the PCNN, one for binary data and another for analog data. The analog approach uses wavelet packets. The experimental results obtained with the proposed approach show that the PCNN outperforms both a conjugate-gradient backpropagation neural network and conventional statistical methods in terms of overall classification accuracy of test data. PMID:18255610

Benediktsson, J A; Sveinsson, J R; Ersoy, O K; Swain, P H

1997-01-01

258

Distributing a GIS using a parallel data approach  

NASA Astrophysics Data System (ADS)

The limitations of serial processors for managing large computationally intensive dataset problems in fields such as visualization and Geographical Information Systems (GIS) are well known. Parallel processing techniques, where one or many computational tasks are distributed across a number of processing elements, have been proposed as a solution to the problem. We describe a model for visualizing oceanographic data that extends an earlier technique of using data parallel algorithms on a dedicated parallel computer to an object- oriented distributed visualization system that forms a virtual parallel machine on a network computers. This paper presents a visualization model being developed by the University of Southern Mississippi demonstrating interactive visualization of oceanographic data. The test case involves visualization of two and three-dimensional oceanographic data (salinity, sound speed profile, currents, temperature, and depth) with Windows NT Pentium class computers serving as both severs and client workstations.

Monde, John R.; Wild, Michael

1998-05-01

259

Parallel node placement method by bubble simulation  

NASA Astrophysics Data System (ADS)

An efficient Parallel Node Placement method by Bubble Simulation (PNPBS), employing METIS-based domain decomposition (DD) for an arbitrary number of processors is introduced. In accordance with the desired nodal density and Newton’s Second Law of Motion, automatic generation of node sets by bubble simulation has been demonstrated in previous work. Since the interaction force between nodes is short-range, for two distant nodes, their positions and velocities can be updated simultaneously and independently during dynamic simulation, which indicates the inherent property of parallelism, it is quite suitable for parallel computing. In this PNPBS method, the METIS-based DD scheme has been investigated for uniform and non-uniform node sets, and dynamic load balancing is obtained by evenly distributing work among the processors. For the nodes near the common interface of two neighboring subdomains, there is no need for special treatment after dynamic simulation. These nodes have good geometrical properties and a smooth density distribution which is desirable in the numerical solution of partial differential equations (PDEs). The results of numerical examples show that quasi linear speedup in the number of processors and high efficiency are achieved.

Nie, Yufeng; Zhang, Weiwei; Qi, Nan; Li, Yiqiang

2014-03-01

260

Appendix E: Parallel Pascal development system  

NASA Technical Reports Server (NTRS)

The Parallel Pascal Development System enables Parallel Pascal programs to be developed and tested on a conventional computer. It consists of several system programs, including a Parallel Pascal to standard Pascal translator, and a library of Parallel Pascal subprograms. The library includes subprograms for using Parallel Pascal on a parallel system with a fixed degree of parallelism, such as the Massively Parallel Processor, to conveniently manipulate arrays which have dimensions than the hardware. Programs can be conveninetly tested with small sized arrays on the conventional computer before attempting to run on a parallel system.

1985-01-01

261

A Comparison of Automatic Parallelization Tools/Compilers on the SGI Origin 2000 Using the NAS Benchmarks  

NASA Technical Reports Server (NTRS)

Porting applications to new high performance parallel and distributed computing platforms is a challenging task. Since writing parallel code by hand is extremely time consuming and costly, porting codes would ideally be automated by using some parallelization tools and compilers. In this paper, we compare the performance of the hand written NAB Parallel Benchmarks against three parallel versions generated with the help of tools and compilers: 1) CAPTools: an interactive computer aided parallelization too] that generates message passing code, 2) the Portland Group's HPF compiler and 3) using compiler directives with the native FORTAN77 compiler on the SGI Origin2000.

Saini, Subhash; Frumkin, Michael; Hribar, Michelle; Jin, Hao-Qiang; Waheed, Abdul; Yan, Jerry

1998-01-01

262

DPF: A Data Parallel Fortran Benchmark Suite  

E-print Network

DPF: A Data Parallel Fortran Benchmark Suite Yu Charlie Hu S. Lennart Johnsson Dimitris Kehagias Parallel Processing Symposium, Geneva, Switzerland, April 1997. #12; DPF: A Data Parallel Fortran Benchmark@deas.harvard.edu Abstract We present the Data Parallel Fortran (DPF) benchmark suite, a set of data parallel Fortran codes

Johnsson, S. Lennart

263

Parallel processing and expert systems  

NASA Technical Reports Server (NTRS)

Whether it be monitoring the thermal subsystem of Space Station Freedom, or controlling the navigation of the autonomous rover on Mars, NASA missions in the 1990s cannot enjoy an increased level of autonomy without the efficient implementation of expert systems. Merely increasing the computational speed of uniprocessors may not be able to guarantee that real-time demands are met for larger systems. Speedup via parallel processing must be pursued alongside the optimization of sequential implementations. Prototypes of parallel expert systems have been built at universities and industrial laboratories in the U.S. and Japan. The state-of-the-art research in progress related to parallel execution of expert systems is surveyed. The survey discusses multiprocessors for expert systems, parallel languages for symbolic computations, and mapping expert systems to multiprocessors. Results to date indicate that the parallelism achieved for these systems is small. The main reasons are (1) the body of knowledge applicable in any given situation and the amount of computation executed by each rule firing are small, (2) dividing the problem solving process into relatively independent partitions is difficult, and (3) implementation decisions that enable expert systems to be incrementally refined hamper compile-time optimization. In order to obtain greater speedups, data parallelism and application parallelism must be exploited.

Lau, Sonie; Yan, Jerry C.

1991-01-01

264

Is Monte Carlo embarrassingly parallel?  

SciTech Connect

Monte Carlo is often stated as being embarrassingly parallel. However, running a Monte Carlo calculation, especially a reactor criticality calculation, in parallel using tens of processors shows a serious limitation in speedup and the execution time may even increase beyond a certain number of processors. In this paper the main causes of the loss of efficiency when using many processors are analyzed using a simple Monte Carlo program for criticality. The basic mechanism for parallel execution is MPI. One of the bottlenecks turn out to be the rendez-vous points in the parallel calculation used for synchronization and exchange of data between processors. This happens at least at the end of each cycle for fission source generation in order to collect the full fission source distribution for the next cycle and to estimate the effective multiplication factor, which is not only part of the requested results, but also input to the next cycle for population control. Basic improvements to overcome this limitation are suggested and tested. Also other time losses in the parallel calculation are identified. Moreover, the threading mechanism, which allows the parallel execution of tasks based on shared memory using OpenMP, is analyzed in detail. Recommendations are given to get the maximum efficiency out of a parallel Monte Carlo calculation. (authors)

Hoogenboom, J. E. [Delft Univ. of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Delft Nuclear Consultancy, IJsselzoom 2, 2902 LB Capelle aan den IJssel (Netherlands)

2012-07-01

265

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

266

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

267

Parallel discrete event simulation of Lyme disease.  

PubMed

Our research concerns the dynamic processes underlying the rapid increase in the geographic distribution of Lyme disease, currently the most frequently reported vector-borne disease of humans in the United States [10, 1]. More specifically, we ask how spatially localized ecological interactions drive the Lyme disease epidemic at extended spatial and temporal scales. We have developed a parallel discrete event simulation system in C++ for the IBM SP2. The simulation model discussed here models the mouse-tick interaction, an essential element of the epidemic's ecology. The main entities of the simulation are ticks in various stages of development (larval, nymphal, and adult) and mice. We track the behavior of mice and the spread of disease over the course of 180 days (late spring, summer, and early fall). Our goal is to understand patterns in the Lyme disease epidemic at the regional scale through studying the spread of the pathogen across a single white-footed mouse deme. PMID:9390232

Deelman, E; Caraco, T; Szymanski, B K

1996-01-01

268

Massively Parallel Finite Element Programming  

Microsoft Academic Search

\\u000a Today’s large finite element simulations require parallel algorithms to scale on clusters with thousands or tens of thousands\\u000a of processor cores. We present data structures and algorithms to take advantage of the power of high performance computers\\u000a in generic finite element codes.\\u000a \\u000a \\u000a Existing generic finite element libraries often restrict the parallelization to parallel linear algebra routines. This is\\u000a a limiting

Timo Heister; Martin Kronbichler; Wolfgang Bangerth

2010-01-01

269

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

270

Parallel stochastic systems biology in the cloud.  

PubMed

The stochastic modelling of biological systems, coupled with Monte Carlo simulation of models, is an increasingly popular technique in bioinformatics. The simulation-analysis workflow may result computationally expensive reducing the interactivity required in the model tuning. In this work, we advocate the high-level software design as a vehicle for building efficient and portable parallel simulators for the cloud. In particular, the Calculus of Wrapped Components (CWC) simulator for systems biology, which is designed according to the FastFlow pattern-based approach, is presented and discussed. Thanks to the FastFlow framework, the CWC simulator is designed as a high-level workflow that can simulate CWC models, merge simulation results and statistically analyse them in a single parallel workflow in the cloud. To improve interactivity, successive phases are pipelined in such a way that the workflow begins to output a stream of analysis results immediately after simulation is started. Performance and effectiveness of the CWC simulator are validated on the Amazon Elastic Compute Cloud. PMID:23780997

Aldinucci, Marco; Torquati, Massimo; Spampinato, Concetto; Drocco, Maurizio; Misale, Claudia; Calcagno, Cristina; Coppo, Mario

2014-09-01

271

Benchmarking Parallel Java Master's Project Report  

E-print Network

Benchmarking Parallel Java Master's Project Report Asma'u Sani Mohammed Java API by implementing the OpenMP version of the NAS Parallel Benchmark (NPB in comparison with FORTRAN OpenMP. Benchmarking Parallel Java allows us to understand

Kaminsky, Alan

272

Parallel Marker Based Image Segmentation with Watershed  

E-print Network

Parallel Marker Based Image Segmentation with Watershed Transformation Alina N. Moga Albert; Parallel Marker Based Watershed Transformation Abstract. The parallel watershed transformation used homogeneity with the watershed transformation. Boundary­based region merging is then effected to condense non

273

Uhlmann's parallelism Nagaoka's quantum information geometry  

E-print Network

Uhlmann's parallelism and Nagaoka's quantum information geometry Keiji Matsumoto METR 97-09 October 1997 #12;Uhmann's parallelism and Nagaoka's quantum information geometry Keiji Matsumoto 1 Abstract: Uhlmann's parallelism and Nagaoka's quantum information geometry. In this paper, intrinsic relation

Yamamoto, Hirosuke

274

Automatic Generation of Parallel CRC Circuits  

Microsoft Academic Search

A parallel CRC circuit simultaneously processes multiple data bits. A generic VHDL description of parallel CRC circuits lets designers synthesize CRC circuits for any generator polynomial or required amount of parallelism

Michael Sprachmann

2001-01-01

275

"Feeling" Series and Parallel Resistances.  

ERIC Educational Resources Information Center

Equipped with drinking straws and stirring straws, a teacher can help students understand how resistances in electric circuits combine in series and in parallel. Follow-up suggestions are provided. (ZWH)

Morse, Robert A.

1993-01-01

276

Parallel Inversion of Sparse Matrices  

Microsoft Academic Search

This paper presents a parallel algorithm for obtaining the inverse of a large, nonsingular symmetric matrix A of dimension nxn. The inversion method proposed is based on the triangular factors of A. The task of obtaining the \\

Ramon Betancourt; Fernando L. Alvarado

1986-01-01

277

PARALLEL GREEDY RANDOMIZED ADAPTIVE SEARCH ...  

E-print Network

Dec 6, 2004 ... up of those elements that can be added to the current solution under construction without ...... The execution times of the independent parallel program executing ... processing a finite set of jobs on a finite set of machines.

2004-12-06

278

Turbomachinery CFD on parallel computers  

NASA Technical Reports Server (NTRS)

The role of multistage turbomachinery simulation in the development of propulsion system models is discussed. Particularly, the need for simulations with higher fidelity and faster turnaround time is highlighted. It is shown how such fast simulations can be used in engineering-oriented environments. The use of parallel processing to achieve the required turnaround times is discussed. Current work by several researchers in this area is summarized. Parallel turbomachinery CFD research at the NASA Lewis Research Center is then highlighted. These efforts are focused on implementing the average-passage turbomachinery model on MIMD, distributed memory parallel computers. Performance results are given for inviscid, single blade row and viscous, multistage applications on several parallel computers, including networked workstations.

Blech, Richard A.; Milner, Edward J.; Quealy, Angela; Townsend, Scott E.

1992-01-01

279

Parallel architecture for OPS5  

Microsoft Academic Search

An architecture that captures some of the inherent parallelism of the OPS5 expert system language has been designed and implemented at Oak Ridge National Laboratory. A central feature of this architecture is a network bus over which a single host processor broadcasts messages to a set of parallel rule processors. This transmit-only bus is implemented by a memory-mapped scheme which

Philip L. Butler; J. D. Allen Jr.; Donald W. Bouldin

1988-01-01

280

Parallel Algorithms for Term Matching  

Microsoft Academic Search

We present a new randomized parallel algorithm for term matching. Let n be the number of nodes of the directed acyclic graphs (dags) representing the terms to be matched, then our algorithm uses O(log2n) parallel time and M(n) processors, where M(n) is the complexity of n by n matrix multiplication. The number of processors is a significant improvement over previously

Cynthia Dwork; Paris C. Kanellakis; Larry J. Stockmeyer

1986-01-01

281

Architectures for reasoning in parallel  

NASA Technical Reports Server (NTRS)

The research conducted has dealt with rule-based expert systems. The algorithms that may lead to effective parallelization of them were investigated. Both the forward and backward chained control paradigms were investigated in the course of this work. The best computer architecture for the developed and investigated algorithms has been researched. Two experimental vehicles were developed to facilitate this research. They are Backpac, a parallel backward chained rule-based reasoning system and Datapac, a parallel forward chained rule-based reasoning system. Both systems have been written in Multilisp, a version of Lisp which contains the parallel construct, future. Applying the future function to a function causes the function to become a task parallel to the spawning task. Additionally, Backpac and Datapac have been run on several disparate parallel processors. The machines are an Encore Multimax with 10 processors, the Concert Multiprocessor with 64 processors, and a 32 processor BBN GP1000. Both the Concert and the GP1000 are switch-based machines. The Multimax has all its processors hung off a common bus. All are shared memory machines, but have different schemes for sharing the memory and different locales for the shared memory. The main results of the investigations come from experiments on the 10 processor Encore and the Concert with partitions of 32 or less processors. Additionally, experiments have been run with a stripped down version of EMYCIN.

Hall, Lawrence O.

1989-01-01

282

Efficiency of parallel direct optimization  

NASA Technical Reports Server (NTRS)

Tremendous progress has been made at the level of sequential computation in phylogenetics. However, little attention has been paid to parallel computation. Parallel computing is particularly suited to phylogenetics because of the many ways large computational problems can be broken into parts that can be analyzed concurrently. In this paper, we investigate the scaling factors and efficiency of random addition and tree refinement strategies using the direct optimization software, POY, on a small (10 slave processors) and a large (256 slave processors) cluster of networked PCs running LINUX. These algorithms were tested on several data sets composed of DNA and morphology ranging from 40 to 500 taxa. Various algorithms in POY show fundamentally different properties within and between clusters. All algorithms are efficient on the small cluster for the 40-taxon data set. On the large cluster, multibuilding exhibits excellent parallel efficiency, whereas parallel building is inefficient. These results are independent of data set size. Branch swapping in parallel shows excellent speed-up for 16 slave processors on the large cluster. However, there is no appreciable speed-up for branch swapping with the further addition of slave processors (>16). This result is independent of data set size. Ratcheting in parallel is efficient with the addition of up to 32 processors in the large cluster. This result is independent of data set size. c2001 The Willi Hennig Society.

Janies, D. A.; Wheeler, W. C.

2001-01-01

283

The parallelization of SPIDER on distributed-memory computers using MPI  

Microsoft Academic Search

We describe the strategies and implementation details we employed to parallelize the SPIDER software package on distributed-memory parallel computers using the message passing interface (MPI). The MPI-enabled SPIDER preserves the interactive command line and batch interface used in the sequential version of SPIDER, thus does not require users to modify their existing batch programs. We show the excellent performance of

Chao Yang; Pawel A. Penczek; ArDean Leith; Francisco J. Asturias; Esmond G. Ng; Robert M. Glaeser; Joachim Frank

2007-01-01

284

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

285

Exploiting Parallelism to Accelerate Keyword Search On Deep-web Sources  

E-print Network

Exploiting Parallelism to Accelerate Keyword Search On Deep-web Sources Tantan Liu Fan Wang Gagan,wangfa,agrawal}@cse.ohio-state.edu Abstract. Increasingly, biological data is being shared over the deep web. Many biological queries can only that exploits parallelization for accelerating search over multiple deep web data sources. An interactive, two

Agrawal, Gagan

286

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

287

Endpoint-based parallel data processing in a parallel active messaging interface of a parallel computer  

DOEpatents

Endpoint-based parallel data processing in a parallel active messaging interface ('PAMI') of a parallel computer, the PAMI composed of data communications endpoints, each endpoint including a specification of data communications parameters for a thread of execution on a compute node, including specifications of a client, a context, and a task, the compute nodes coupled for data communications through the PAMI, including establishing a data communications geometry, the geometry specifying, for tasks representing processes of execution of the parallel application, a set of endpoints that are used in collective operations of the PAMI including a plurality of endpoints for one of the tasks; receiving in endpoints of the geometry an instruction for a collective operation; and executing the instruction for a collective opeartion through the endpoints in dependence upon the geometry, including dividing data communications operations among the plurality of endpoints for one of the tasks.

Archer, Charles J; Blocksome, Michael E; Ratterman, Joseph D; Smith, Brian E

2014-02-11

288

Endpoint-based parallel data processing in a parallel active messaging interface of a parallel computer  

DOEpatents

Endpoint-based parallel data processing in a parallel active messaging interface (`PAMI`) of a parallel computer, the PAMI composed of data communications endpoints, each endpoint including a specification of data communications parameters for a thread of execution on a compute node, including specifications of a client, a context, and a task, the compute nodes coupled for data communications through the PAMI, including establishing a data communications geometry, the geometry specifying, for tasks representing processes of execution of the parallel application, a set of endpoints that are used in collective operations of the PAMI including a plurality of endpoints for one of the tasks; receiving in endpoints of the geometry an instruction for a collective operation; and executing the instruction for a collective operation through the endpoints in dependence upon the geometry, including dividing data communications operations among the plurality of endpoints for one of the tasks.

Archer, Charles J.; Blocksome, Michael A.; Ratterman, Joseph D.; Smith, Brian E.

2014-08-12

289

Parallel Object Oriented Implementation of a 2D Bounded Electrostatic Plasma PIC Simulation \\Lambda  

E-print Network

Parallel Object Oriented Implementation of a 2D Bounded Electrostatic Plasma PIC Simulation \\Lambda of Technology, Pasadena CA 91109, USA. 1 #12; 2 Norton et al. heat, pressure or electric discharges. Fusion the electrostatic (coloumb) interactions are inc

Bystroff, Chris

290

Development of Apple Workgroup Cluster and Parallel Computing for Phase Field Model of Magnetic Materials  

E-print Network

ferromagnets, there exist two main challenges: the complicated microelasticity due to the magnetostrictive strain, and very expensive computation mainly caused by the calculation of long-range magnetostatic and elastic interactions. A parallel computing...

Huang, Yongxin

2010-01-16

291

Simultaneous Glycan-Peptide Characterization Using Hydrophilic Interaction Chromatography and Parallel Fragmentation by CID, Higher Energy Collisional Dissociation, and Electron Transfer Dissociation MS Applied to the N-Linked Glycoproteome of Campylobacter jejuni*  

PubMed Central

Campylobacter jejuni is a gastrointestinal pathogen that is able to modify membrane and periplasmic proteins by the N-linked addition of a 7-residue glycan at the strict attachment motif (D/E)XNX(S/T). Strategies for a comprehensive analysis of the targets of glycosylation, however, are hampered by the resistance of the glycan-peptide bond to enzymatic digestion or ?-elimination and have previously concentrated on soluble glycoproteins compatible with lectin affinity and gel-based approaches. We developed strategies for enriching C. jejuni HB93-13 glycopeptides using zwitterionic hydrophilic interaction chromatography and examined novel fragmentation, including collision-induced dissociation (CID) and higher energy collisional (C-trap) dissociation (HCD) as well as CID/electron transfer dissociation (ETD) mass spectrometry. CID/HCD enabled the identification of glycan structure and peptide backbone, allowing glycopeptide identification, whereas CID/ETD enabled the elucidation of glycosylation sites by maintaining the glycan-peptide linkage. A total of 130 glycopeptides, representing 75 glycosylation sites, were identified from LC-MS/MS using zwitterionic hydrophilic interaction chromatography coupled to CID/HCD and CID/ETD. CID/HCD provided the majority of the identifications (73 sites) compared with ETD (26 sites). We also examined soluble glycoproteins by soybean agglutinin affinity and two-dimensional electrophoresis and identified a further six glycosylation sites. This study more than doubles the number of confirmed N-linked glycosylation sites in C. jejuni and is the first to utilize HCD fragmentation for glycopeptide identification with intact glycan. We also show that hydrophobic integral membrane proteins are significant targets of glycosylation in this organism. Our data demonstrate that peptide-centric approaches coupled to novel mass spectrometric fragmentation techniques may be suitable for application to eukaryotic glycoproteins for simultaneous elucidation of glycan structures and peptide sequence. PMID:20360033

Scott, Nichollas E.; Parker, Benjamin L.; Connolly, Angela M.; Paulech, Jana; Edwards, Alistair V. G.; Crossett, Ben; Falconer, Linda; Kolarich, Daniel; Djordjevic, Steven P.; Højrup, Peter; Packer, Nicolle H.; Larsen, Martin R.; Cordwell, Stuart J.

2011-01-01

292

Parallel aeroelastic computations for wing and wing-body configurations  

NASA Technical Reports Server (NTRS)

The objective of this research is to develop computationally efficient methods for solving fluid-structural interaction problems by directly coupling finite difference Euler/Navier-Stokes equations for fluids and finite element dynamics equations for structures on parallel computers. This capability will significantly impact many aerospace projects of national importance such as Advanced Subsonic Civil Transport (ASCT), where the structural stability margin becomes very critical at the transonic region. This research effort will have direct impact on the High Performance Computing and Communication (HPCC) Program of NASA in the area of parallel computing.

Byun, Chansup

1994-01-01

293

Application of the hypercube parallel processor to a large-scale moment method code  

NASA Technical Reports Server (NTRS)

The applicability of a parallel computing architecture to the solution of a large-scale moment-method code is investigated. Specifically, the NEC (Numerical Electromagnetics Code) method-of-moments scattering program is implemented on a hypercube parallel processor. The accuracy and the increase in the speed of execution on this parallel architecture are demonstrated. The results show a very large reduction in execution time for large problems. The great potential of this parallel processor is shown for interactive solution of large NEC problems as well as other moment-method techniques such as the finite-element method.

Manshadi, Farzin; Liewer, Paulet C.; Patterson, Jean E.

1988-01-01

294

Computing contingency statistics in parallel.  

SciTech Connect

Statistical analysis is typically used to reduce the dimensionality of and infer meaning from data. A key challenge of any statistical analysis package aimed at large-scale, distributed data is to address the orthogonal issues of parallel scalability and numerical stability. Many statistical techniques, e.g., descriptive statistics or principal component analysis, are based on moments and co-moments and, using robust online update formulas, can be computed in an embarrassingly parallel manner, amenable to a map-reduce style implementation. In this paper we focus on contingency tables, through which numerous derived statistics such as joint and marginal probability, point-wise mutual information, information entropy, and {chi}{sup 2} independence statistics can be directly obtained. However, contingency tables can become large as data size increases, requiring a correspondingly large amount of communication between processors. This potential increase in communication prevents optimal parallel speedup and is the main difference with moment-based statistics where the amount of inter-processor communication is independent of data size. Here we present the design trade-offs which we made to implement the computation of contingency tables in parallel.We also study the parallel speedup and scalability properties of our open source implementation. In particular, we observe optimal speed-up and scalability when the contingency statistics are used in their appropriate context, namely, when the data input is not quasi-diffuse.

Bennett, Janine Camille; Thompson, David; Pebay, Philippe Pierre

2010-09-01

295

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

296

Method for resource control in parallel environments using program organization and run-time support  

NASA Technical Reports Server (NTRS)

A system and method for dynamic scheduling and allocation of resources to parallel applications during the course of their execution. By establishing well-defined interactions between an executing job and the parallel system, the system and method support dynamic reconfiguration of processor partitions, dynamic distribution and redistribution of data, communication among cooperating applications, and various other monitoring actions. The interactions occur only at specific points in the execution of the program where the aforementioned operations can be performed efficiently.

Ekanadham, Kattamuri (Inventor); Moreira, Jose Eduardo (Inventor); Naik, Vijay Krishnarao (Inventor)

1999-01-01

297

Experiments with OR-parallel logic programs  

SciTech Connect

We present here the results of several experiments involving OR-parallelism, based on the implementation of a parallel Warren Abstract Machine at Argonne National Laboratory. The experiments illustrate a variety of effects resulting from various types of programs, and raise issues that must be dealt with in any parallel implementation. We also demonstrate a tool for obtaining a visual representation of the parallelism.

Disz, T.; Lusk, E.; Overbeek, R.

1987-02-01

298

Parallel computational complexity in statistical physics  

Microsoft Academic Search

We examine several models in statistical physics from the perspective of parallel computational complexity theory. In each case, we describe a parallel method of simulation that is faster than current sequential methods. We find that parallel complexity results are in accord with intuitive notions of physical complexity for the models studied. First, we investigate the parallel complexity of sampling Lorentz

Kenneth J. Moriarty

1998-01-01

299

DPF: A Data Parallel Fortran Benchmark Suite  

Microsoft Academic Search

We present the Data Parallel Fortran (DPF) benchmark suite, a set of data parallel Fortran codes for evaluating data parallel compilers appropriate for any target parallel archi- tecture, with shared or distributed memory. The codes are provided in basic, optimized and several library versions. The functionality of the benchmarks cover collective commu- nication functions, scientific software library functions, and application

Y. Charlie Hu; S. Lennart Johnsson; Dimitris Kehagias; Nadia Shalaby

1997-01-01

300

Language Extensions in Support of Compiler Parallelization  

E-print Network

to compare the performance of four versions of each benchmark: 1) sequential Java, 2) sequential X10, 3) hand-parallelized X10, 4) parallel Java. Averaged over ten JGF Section 2 and 3 benchmarks, the parallel X10 version also speed up code due to elimination of runtime checks. For the eight benchmarks for which parallel

Kasahara, Hironori

301

Open architecture for multilingual parallel texts  

E-print Network

Multilingual parallel texts (abbreviated to parallel texts) are linguistic versions of the same content ("translations"); e.g., the Maastricht Treaty in English and Spanish are parallel texts. This document is about creating an open architecture for the whole Authoring, Translation and Publishing Chain (ATP-chain) for the processing of parallel texts.

Benitez, M T Carrasco

2008-01-01

302

Refinement Transformation Using Abstract Parallel Machines  

E-print Network

for circuit specification--- `concrete parallel machines'. #12; The ability to define Abstract ParallelRefinement Transformation Using Abstract Parallel Machines Joy Goodman 1 , John O'Donnell 1 and Gudula R¨unger 2 1 University of Glasgow 2 Universit¨at Leipzig Abstract. Abstract Parallel Machines

Goodman, Joy

303

Dynamic parallel complexity of computational circuits  

Microsoft Academic Search

The dynamic parallel complexity of general computational circuits (defined in introduction) is discussed. We exhibit some relationships between parallel circuit evaluation and some uniform closure properties of a certain class of unary functions and present a systematic method for the design of processor efficient parallel algorithms for circuit evaluation. Using this method: (1) we improve the algorithm for parallel Boolean

Gary L. Miller; Shang-Hua Teng

1987-01-01

304

Visualizing Parallel Computer System Performance  

NASA Technical Reports Server (NTRS)

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 system pose equally vexing performance interpretation problems. Data from hardware and software performance monitors must be presented in ways that emphasize important events while eluding irrelevant details. Design approaches and tools for performance visualization are the subject of this paper.

Malony, Allen D.; Reed, Daniel A.

1988-01-01

305

Massively Parallel MRI Detector Arrays  

PubMed Central

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, 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

2013-01-01

306

Parallel Adaptive Mesh Refinement Library  

NASA Technical Reports Server (NTRS)

Parallel Adaptive Mesh Refinement Library (PARAMESH) is a package of Fortran 90 subroutines designed to provide a computer programmer with an easy route to extension of (1) a previously written serial code that uses a logically Cartesian structured mesh into (2) a parallel code with adaptive mesh refinement (AMR). Alternatively, in its simplest use, and with minimal effort, PARAMESH can operate as a domain-decomposition tool for users who want to parallelize their serial codes but who do not wish to utilize adaptivity. The package builds a hierarchy of sub-grids to cover the computational domain of a given application program, with spatial resolution varying to satisfy the demands of the application. The sub-grid blocks form the nodes of a tree data structure (a quad-tree in two or an oct-tree in three dimensions). Each grid block has a logically Cartesian mesh. The package supports one-, two- and three-dimensional models.

Mac-Neice, Peter; Olson, Kevin

2005-01-01

307

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

308

Parallel integrated frame synchronizer chip  

NASA Technical Reports Server (NTRS)

A parallel integrated frame synchronizer which implements a sequential pipeline process wherein serial data in the form of telemetry data or weather satellite data enters the synchronizer by means of a front-end subsystem and passes to a parallel correlator subsystem or a weather satellite data processing subsystem. When in a CCSDS mode, data from the parallel correlator subsystem passes through a window subsystem, then to a data alignment subsystem and then to a bit transition density (BTD)/cyclical redundancy check (CRC) decoding subsystem. Data from the BTD/CRC decoding subsystem or data from the weather satellite data processing subsystem is then fed to an output subsystem where it is output from a data output port.

Ghuman, Parminder Singh (Inventor); Solomon, Jeffrey Michael (Inventor); Bennett, Toby Dennis (Inventor)

2000-01-01

309

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

310

Parallel algorithms for mapping pipelined and parallel computations  

NASA Technical Reports Server (NTRS)

Many computational problems in image processing, signal processing, and scientific computing are naturally structured for either pipelined or parallel computation. When mapping such problems onto a parallel architecture it is often necessary to aggregate an obvious problem decomposition. Even in this context the general mapping problem is known to be computationally intractable, but recent advances have been made in identifying classes of problems and architectures for which optimal solutions can be found in polynomial time. Among these, the mapping of pipelined or parallel computations onto linear array, shared memory, and host-satellite systems figures prominently. This paper extends that work first by showing how to improve existing serial mapping algorithms. These improvements have significantly lower time and space complexities: in one case a published O(nm sup 3) time algorithm for mapping m modules onto n processors is reduced to an O(nm log m) time complexity, and its space requirements reduced from O(nm sup 2) to O(m). Run time complexity is further reduced with parallel mapping algorithms based on these improvements, which run on the architecture for which they create the mappings.

Nicol, David M.

1988-01-01

311

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

312

Parallel computation of seismic analysis of high arch dam  

NASA Astrophysics Data System (ADS)

Parallel computation programs are developed for three-dimensional meso-mechanics analysis of fully-graded dam concrete and seismic response analysis of high arch dams (ADs), based on the Parallel Finite Element Program Generator (PFEPG). The computational algorithms of the numerical simulation of the meso-structure of concrete specimens were studied. Taking into account damage evolution, static preload, strain rate effect, and the heterogeneity of the meso-structure of dam concrete, the fracture processes of damage evolution and configuration of the cracks can be directly simulated. In the seismic response analysis of ADs, all the following factors are involved, such as the nonlinear contact due to the opening and slipping of the contraction joints, energy dispersion of the far-field foundation, dynamic interactions of the dam-foundation-reservoir system, and the combining effects of seismic action with all static loads. The correctness, reliability and efficiency of the two parallel computational programs are verified with practical illustrations.

Chen, Houqun; Ma, Huaifa; Tu, Jin; Cheng, Guangqing; Tang, Juzhen

2008-03-01

313

A vestibular prosthesis with highly-isolated parallel multichannel stimulation.  

PubMed

This paper presents an implantable vestibular stimulation system capable of providing high flexibility independent parallel stimulation to the semicircular canals in the inner ear for restoring three-dimensional sensation of head movements. To minimize channel interaction during parallel stimulation, the system is implemented with a power isolation method for crosstalk reduction. Experimental results demonstrate that, with this method, electrodes for different stimulation channels located in close proximity ( mm) can deliver current pulses simultaneously with minimum inter-channel crosstalk. The design features a memory-based scheme that manages stimulation to the three canals in parallel. A vestibular evoked potential (VEP) recording unit is included for closed-loop adaptive stimulation control. The main components of the prototype vestibular prosthesis are three ASICs, all implemented in a 0.6- ?m high-voltage CMOS technology. The measured performance was verified using vestibular electrodes in vitro. PMID:25073175

Jiang, Dai; Cirmirakis, Dominik; Demosthenous, Andreas

2015-02-01

314

Parallel 3-D Electromagnetic Particle code using High Performance Fortran: Parallel TRISTAN  

E-print Network

Parallel 3-D Electromagnetic Particle code using High Performance Fortran: Parallel TRISTAN using High Performance Fortran (HPF) as a RPM (Real Parallel Machine). In the parallelized HPF code and Hitachi SR-8000 etc. using High Performance Fortran (HPF). In our parallel program, the simulation domain

Nishikawa, Ken-Ichi

315

A polymorphic reconfigurable emulator for parallel simulation  

NASA Technical Reports Server (NTRS)

Microprocessor and arithmetic support chip technology was applied to the design of a reconfigurable emulator for real time flight simulation. The system developed consists of master control system to perform all man machine interactions and to configure the hardware to emulate a given aircraft, and numerous slave compute modules (SCM) which comprise the parallel computational units. It is shown that all parts of the state equations can be worked on simultaneously but that the algebraic equations cannot (unless they are slowly varying). Attempts to obtain algorithms that will allow parellel updates are reported. The word length and step size to be used in the SCM's is determined and the architecture of the hardware and software is described.

Parrish, E. A., Jr.; Mcvey, E. S.; Cook, G.

1980-01-01

316

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

317

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.

318

Parallel Supercomputing with Commodity Components  

Microsoft Academic Search

We have implemented a parallel computer architec- ture based entirely upon commodity personal computer components. Using 16 Intel Pentium Pro microproces- sors and switched fast ethernet as a communication fab- ric, we have obtained sustained performance on sci- entific applications in excess of one Gigaflop. Dur- ing one production astrophysics treecode simulation, we performed floating point operations (1.2 Petaflops) over

Michael S. Warren; Donald J. Becker; M. Patrick Goda; John K. Salmon; Thomas L. Sterling

1997-01-01

319

Parallel circuit simulation on supercomputers  

Microsoft Academic Search

Circuit simulation is a very time-consuming and numerically intensive application, especially when the problem size is large as in the case of VLSI circuits. To improve the performance of circuit simulators without sacrificing accuracy, a variety of parallel processing algorithms have been investigated due to the recent availability of a number of commercial multiprocessor machines. In this paper, research in

R. A. Saleh; K. A. Gallivan; M.-C. Chang; I. N. Hajj; T. N. Trick; D. Smart

1989-01-01

320

Tutorial: Parallel Simulation on Supercomputers  

SciTech Connect

This tutorial introduces typical hardware and software characteristics of extant and emerging supercomputing platforms, and presents issues and solutions in executing large-scale parallel discrete event simulation scenarios on such high performance computing systems. Covered topics include synchronization, model organization, example applications, and observed performance from illustrative large-scale runs.

Perumalla, Kalyan S [ORNL

2012-01-01

321

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

322

The Everett axiom of parallelism  

E-print Network

In this work we consider the meaningfulness of the concept parallel worlds. To that extent we propose the model of the infinite-dimensionaly multievent space, generating everettics altervers in each point of Minkowski space time. Our research reveals fractal character of such alterverse.

Lebedev, Yury A; Dulphan, Anna Ya

2013-01-01

323

Real-time\\/parallel computing  

Microsoft Academic Search

This book discusses the real-time, parallel computing of digitized images including both the symbolic and semantic data derived from such images. The processing, storing, and transmitting of images and image data are examined. Techniques and algorithms for the analysis and manipulation of images are explored both theoretically and in terms of implementation in hardware and software. The main subject areas

M. Onoe; K. Preston; A. Rosenfield

1983-01-01

324

Optimal Circuits for Parallel Multipliers  

Microsoft Academic Search

Abstract—We present new design and analysis techniques for the synthesis of parallel multiplier circuits that have smaller predicted delay than the best current multipliers. In [4], Oklobdzija et al. suggested a new approach, the Three-Dimensional Method (TDM), for Partial Product Reduction Tree (PPRT) design that produces multipliers that outperform the current best designs. The goal of TDM is to produce

Paul F. Stelling; Charles U. Martel; Vojin G. Oklobdzija; R. Ravi

1998-01-01

325

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

326

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

327

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

328

Extensive parallel processing on scale-free networks.  

PubMed

We adapt belief-propagation techniques to study the equilibrium behavior of a bipartite spin glass, with interactions between two sets of N and P=?N spins each having an arbitrary degree, i.e., number of interaction partners in the opposite set. An equivalent view is then of a system of N neurons storing P diluted patterns via Hebbian learning, in the high storage regime. Our method allows analysis of parallel pattern processing on a broad class of graphs, including those with pattern asymmetry and heterogeneous dilution; previous replica approaches assumed homogeneity. We show that in a large part of the parameter space of noise, dilution, and storage load, delimited by a critical surface, the network behaves as an extensive parallel processor, retrieving all P patterns in parallel without falling into spurious states due to pattern cross talk, as would be typical of the structural glassiness built into the network. Parallel extensive retrieval is more robust for homogeneous degree distributions, and is not disrupted by asymmetric pattern distributions. For scale-free pattern degree distributions, Hebbian learning induces modularity in the neural network; thus, our Letter gives the first theoretical description for extensive information processing on modular and scale-free networks. PMID:25526165

Sollich, Peter; Tantari, Daniele; Annibale, Alessia; Barra, Adriano

2014-12-01

329

Extensive Parallel Processing on Scale-Free Networks  

NASA Astrophysics Data System (ADS)

We adapt belief-propagation techniques to study the equilibrium behavior of a bipartite spin glass, with interactions between two sets of N and P =? N spins each having an arbitrary degree, i.e., number of interaction partners in the opposite set. An equivalent view is then of a system of N neurons storing P diluted patterns via Hebbian learning, in the high storage regime. Our method allows analysis of parallel pattern processing on a broad class of graphs, including those with pattern asymmetry and heterogeneous dilution; previous replica approaches assumed homogeneity. We show that in a large part of the parameter space of noise, dilution, and storage load, delimited by a critical surface, the network behaves as an extensive parallel processor, retrieving all P patterns in parallel without falling into spurious states due to pattern cross talk, as would be typical of the structural glassiness built into the network. Parallel extensive retrieval is more robust for homogeneous degree distributions, and is not disrupted by asymmetric pattern distributions. For scale-free pattern degree distributions, Hebbian learning induces modularity in the neural network; thus, our Letter gives the first theoretical description for extensive information processing on modular and scale-free networks.

Sollich, Peter; Tantari, Daniele; Annibale, Alessia; Barra, Adriano

2014-12-01

330

Blade-mounted trailing edge flap control for BVI noise reduction  

NASA Technical Reports Server (NTRS)

Numerical procedures based on the 2-D and 3-D full potential equations and the 2-D Navier-Stokes equations were developed to study the effects of leading and trailing edge flap motions on the aerodynamics of parallel airfoil-vortex interactions and on the aerodynamics and acoustics of the more general self-generated rotor blade vortex interactions (BVI). For subcritical interactions, the 2-D results indicate that the trailing edge flap can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, the results show the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented. For the OLS model rotor, contours of a BVI noise metric were used to quantify the effects of the trailing edge flap on the size and directivity of the high/low intensity noise region(s). Average reductions in the BVI noise levels on the order of 5 dB with moderate power penalties on the order of 18 pct. for a four bladed rotor and 58 pct. for a two bladed rotor were obtained.

Hassan, A. A.; Charles, B. D.; Tadghighi, H.; Sankar, L. N.

1992-01-01

331

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

332

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

333

Parallel processing spacecraft communication system  

NASA Technical Reports Server (NTRS)

An uplink controlling assembly speeds data processing using a special parallel codeblock technique. A correct start sequence initiates processing of a frame. Two possible start sequences can be used; and the one which is used determines whether data polarity is inverted or non-inverted. Processing continues until uncorrectable errors are found. The frame ends by intentionally sending a block with an uncorrectable error. Each of the codeblocks in the frame has a channel ID. Each channel ID can be separately processed in parallel. This obviates the problem of waiting for error correction processing. If that channel number is zero, however, it indicates that the frame of data represents a critical command only. That data is handled in a special way, independent of the software. Otherwise, the processed data further handled using special double buffering techniques to avoid problems from overrun. When overrun does occur, the system takes action to lose only the oldest data.

Bolotin, Gary S. (Inventor); Donaldson, James A. (Inventor); Luong, Huy H. (Inventor); Wood, Steven H. (Inventor)

1998-01-01

334

Parallel and distributed information systems  

SciTech Connect

As you know, this conference focuses specifically on the management of information in parallel or distributed systems. Due to the emergence of new applications, we are seeing many new advances in the field. These application areas include multimedia data on demand, the information superhighway, data mining in large commercial and scientific databases, and mobile computing. Concurrent with these new applications, we are witnessing changes in the both research and commercial computing environments - high-end computing, once the domain of traditional mainframes, is being replaced by parallel processors based on off-the-shelf components. At the low end, personal digital assistants and personal communication services point to the emergence of a large consumer-oriented distributed information environment. In between, the client/server model long familiar to research environments has become commonplace in business computing.

Not Available

1994-01-01

335

Parallel supercomputing with commodity components  

NASA Technical Reports Server (NTRS)

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.; Becker, D. J.

1997-01-01

336

Parallel multiplex laser feedback interferometry  

SciTech Connect

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian, E-mail: zsl-dpi@mail.tsinghua.edu.cn [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)

2013-12-15

337

Parallel multiplex laser feedback interferometry  

NASA Astrophysics Data System (ADS)

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian

2013-12-01

338

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

339

Adaptively Parallel Processor Allocation for Cilk Jobs  

E-print Network

The problem of allocating processor resources fairly and efficiently to parallel jobs has been studied extensively in the past. Most of this work, however, assumes that the instantaneous parallelism of the jobs is known ...

Sen, Siddhartha

340

On-the-fly pipeline parallelism  

E-print Network

Pipeline parallelism organizes a parallel program as a linear sequence of s stages. Each stage processes elements of a data stream, passing each processed data element to the next stage, and then taking on a new element ...

Lee, I-Ting Angelina

341

Parallel Coupled Micro-Macro Actuators  

E-print Network

This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. ...

Morrell, John Bryant

1996-01-01

342

Implementing clips on a parallel computer  

NASA Technical Reports Server (NTRS)

The C language integrated production system (CLIPS) is a forward chaining rule based language to provide training and delivery for expert systems. Conceptually, rule based languages have great potential for benefiting from the inherent parallelism of the algorithms that they employ. During each cycle of execution, a knowledge base of information is compared against a set of rules to determine if any rules are applicable. Parallelism also can be employed for use with multiple cooperating expert systems. To investigate the potential benefits of using a parallel computer to speed up the comparison of facts to rules in expert systems, a parallel version of CLIPS was developed for the FLEX/32, a large grain parallel computer. The FLEX implementation takes a macroscopic approach in achieving parallelism by splitting whole sets of rules among several processors rather than by splitting the components of an individual rule among processors. The parallel CLIPS prototype demonstrates the potential advantages of integrating expert system tools with parallel computers.

Riley, Gary

1987-01-01

343

The Parallel Grammar Project Miriam Butt  

E-print Network

The Parallel Grammar Project Miriam Butt Cent. for Computational Linguistics UMIST Manchester M60 1 range of purposes. In this paper, we report on the Parallel Grammar (ParGram) project (Butt et al., 1999

344

Automated Instrumentation and Monitoring of Data Movement for Parallel Programs  

NASA Technical Reports Server (NTRS)

Writing efficient parallel programs is complicated by the need to select the right data structure alignments and distributions, which determine the nature and volume of inter-processor communications. A large number of performance tools for parallel programs have been developed recently to expose these inter-processor communications. However, none of them support performance views or provide statistics in terms of inter-processor data structure interactions. A performance tool that tracks the interaction between individual data structures and the context of these interactions is essential for understanding the performance of both explicit message passing programs and data-parallel languages such as HPF. In this paper we discuss the use of compiler front end tools for automatically tracking data structure movements in message passing programs, and low-overhead monitoring and postprocessing of such codes. We demonstrate that robust instrumentation and low overhead monitoring of inter-processor data structure movements is possible, with the use of a number of NAS benchmark codes, run on the i860 hypercube. We also show that the data so collected can be used effectively by post processing tools that expose performance bottlenecks using graphical displays and performance statistics.

Sarukkai, Sekhar; Yan, Jerry C.; Schmidt, Melisa; Tucker, Deanne (Technical Monitor)

1994-01-01

345

Highly parallel sparse Cholesky factorization  

NASA Technical Reports Server (NTRS)

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 conceptually supplies one processor per data element. In contrast to special purpose algorithms in which the matrix structure conforms to the connection structure of the machine, the focus is on matrices with arbitrary sparsity structure. The most promising algorithm is one whose inner loop performs several dense factorizations simultaneously on a 2-D grid of processors. Virtually any massively parallel dense factorization algorithm can be used as the key subroutine. The sparse code attains execution rates comparable to those of the dense subroutine. Although at present architectural limitations prevent the dense factorization from realizing its potential efficiency, it is concluded that a regular data parallel architecture can be used efficiently to solve arbitrarily structured sparse problems. A performance model is also presented and it is used to analyze the algorithms.

Gilbert, John R.; Schreiber, Robert

1990-01-01

346

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.

347

Automatic Multilevel Parallelization Using OpenMP  

NASA Technical Reports Server (NTRS)

In this paper we describe the extension of the CAPO (CAPtools (Computer Aided Parallelization Toolkit) OpenMP) parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report some results for several benchmark codes and one full application that have been parallelized using our system.

Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

2002-01-01

348

Parallel machine architecture and compiler design facilities  

NASA Technical Reports Server (NTRS)

The objective is to provide an integrated simulation environment for studying and evaluating various issues in designing parallel systems, including machine architectures, parallelizing compiler techniques, and parallel algorithms. The status of Delta project (which objective is to provide a facility to allow rapid prototyping of parallelized compilers that can target toward different machine architectures) is summarized. Included are the surveys of the program manipulation tools developed, the environmental software supporting Delta, and the compiler research projects in which Delta has played a role.

Kuck, David J.; Yew, Pen-Chung; Padua, David; Sameh, Ahmed; Veidenbaum, Alex

1990-01-01

349

Understanding Language Support for Irregular Parallelism  

Microsoft Academic Search

. While software support for array-based, data-parallel algorithmshas been studied extensively, less attention has been devoted toirregular parallel applications. The majority of these applications areunstructured, that is, they possess asynchronous components that donot fit the data-parallel model. Examples of unstructured applicationsinclude sparse matrix and n-body problems. Previous research, such asParti[11] and CHAOS[13], has concentrated on extending the array-baseddata-parallel...

Mukund Raghavachari; Anne Rogers

1995-01-01

350

Parallel MRI Reconstruction Using Variance Partitioning Regularization  

E-print Network

Parallel MRI Reconstruction Using Variance Partitioning Regularization Fa-Hsuan Lin,1,2* Fu be utilized to enhance the spatiotempo- ral resolution of MRI by employing the parallel imaging tech- nique set in parallel MRI data. The proposed Variance Partition- ing Regularization (VPR) method can improve

351

Functional MRI Using Regularized Parallel Imaging Acquisition  

E-print Network

Functional MRI Using Regularized Parallel Imaging Acquisition Fa-Hsuan Lin,1* Teng-Yi Huang,1,2 Nan. Kwong1 Parallel MRI techniques reconstruct full-FOV images from un- dersampled k-space data by using the uncorrelated information from RF array coil elements. One disadvantage of parallel MRI is that the image signal

352

Measuring CS1 perceptions of parallelism  

Microsoft Academic Search

Educators in Computer Science (CS) generally agree that teaching concurrency can be difficult. CS programs typically offer parallel and distributed computing topics as advanced courses. A potential alternative approach is to provide instruction on parallelism early in the undergraduate curriculum, emphasizing conceptual design rather than implementation issues. This introduction of “parallel-thinking” to beginning CS undergraduates represents an innovation and significant

Brian Rague

2011-01-01

353

Space-efficient scheduling of nested parallelism  

Microsoft Academic Search

Many of today's high-level parallel languages support dynamic, fine-grained parallelism. These languages allow the user to expose all the parallelism in the program, which is typically of a much higher degree than the number of processors. Hence an efficient scheduling algorithm is required to assign computations to processors at runtime. Besides having low overheads and good load balancing, it is

Girija J. Narlikar; Guy E. Blelloch

1999-01-01

354

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

355

Developing Parallel Finite Element Software Using MPI  

Microsoft Academic Search

: This paper presents an introduction to writing parallel finite elementprograms using the Message Passing Interface (MPI) library. It is assumed thatthe reader has a working knowledge of the finite element method but has littleor no prior experience with parallel computing. Hence the paper begins witha short review of some of the key concepts in parallel programming under adistributed memory

P. k. Jimack; N. Touheed

2000-01-01

356

Exploiting Parallelism Between Control and Data Computation  

Microsoft Academic Search

In order to obtain continued performance improvements from microprocessors, ways must be found to increase the degree of parallel execution. However, the parallelism of single-threaded programs is limited by the control flow within the code. This paper proposes a technique to reduce the control flow bottleneck by observing that much of the control flow computation can be performed in parallel

Aqeel Mahesri; Sanjay Patel

357

Pthreads for Dynamic Parallelism Girija J. Narlikar  

E-print Network

POSIX threads (Pthreads) library on a shared memory machine using a set of parallel benchmarks improved space and time performance. With the modified Pthreads library, each of the parallel benchmarksPthreads for Dynamic Parallelism Girija J. Narlikar narlikar@cs.cmu.edu Guy E. Blelloch blelloch

358

THE KREMLIN ORACLE FOR SEQUENTIAL CODE PARALLELIZATION  

E-print Network

compiler, and manual parallelization efforts on the Rodinia benchmark suite.4 The icc compiler could. Similarly lackluster results have been shown with the NAS Parallel Benchmarks (NPB) benchmark suite.5 of benchmarks. Moreover, it is effec- tive at identifying the regions that should be parallelized, even when

Fainman, Yeshaiahu

359

Automatic Parallelization of the AVL FIRE Benchmark  

E-print Network

Automatic Parallelization of the AVL FIRE Benchmark for a Distributed­Memory System ? Peter Brezany a , Viera Sipkova a , Barbara Chapman b , Robert Greimel c a Institute for Software Technology and Parallel Systems b European Centre for Parallel Computing at Vienna University of Vienna, Liechtensteinstrasse 22

Brezany, Peter

360

Kismet: parallel speedup estimates for serial programs  

Microsoft Academic Search

Software engineers now face the difficult task of refactoring serial programs for parallel execution on multicore processors. Currently, they are offered little guidance as to how much benefit may come from this task, or how close they are to the best possible parallelization. This paper presents Kismet, a tool that creates parallel speedup estimates for unparallelized serial programs. Kismet differs

Donghwan Jeon; Saturnino Garcia; Chris Louie; Michael Bedford Taylor

2011-01-01

361

Earthquake ground motion modeling on parallel computers  

Microsoft Academic Search

We describe the design and discuss the performance of a parallel elastic wave propagation simulator that is being used to model and study earthquake-induced ground motion in large sedimentary basins. The components of the system include mesh generators, a mesh partitioner, a parceler, and a parallel code generator, as well as parallel numerical methods for applying seismic forces, incorporating absorbing

Hesheng Bao; Jacobo Bielak; Omar Ghattas; Loukas F. Kallivokas; David R. O'Hallaron; Jonathan R. Shewchuk; Jifeng Xu

1996-01-01

362

Perfect Pipelining: A New Loop Parallelization Technique  

Microsoft Academic Search

Parallelizing compilers do not handle loops in a satisfactory manner. Fine-grain transformationscapture irregular parallelism inside a loop body not amenable to coarser approaches but have limitedability to exploit parallelism across iterations. Coarse methods sacrifice irregular forms of parallelismin favor of pipelining (overlapping) iterations. In this paper we present a new transformation, PerfectPipelining, that bridges the gap between these fine- and

Alexander Aiken; Alexandru Nicolau

1988-01-01

363

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

364

MAPS: multi-algorithm parallel circuit simulation  

Microsoft Academic Search

The emergence of multi-core and many-core processors has introduced new opportunities and challenges to EDA research and development. While the availability of increasing parallel computing power holds new promise to address many computing challenges in CAD, the leverage of hardware parallelism can only be possible with a new generation of parallel CAD applications. In this paper, we propose a novel

Xiaoji Ye; Wei Dong; Peng Li; Sani R. Nassif

2008-01-01

365

Parallel browsing behavior on the web  

Microsoft Academic Search

Parallel browsing describes a behavior where users visit Web pages in multiple concurrent threads. Web browsers explicitly support this by providing tabs. Although parallel browsing is more prevalent than linear browsing online, little is known about how users perform this activity. We study the use of parallel browsing through a log-based study of millions of Web users and present findings

Jeff Huang; Ryen W. White

2010-01-01

366

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

367

Support for Debugging Automatically Parallelized Programs  

Microsoft Academic Search

We describe a system that simplifies the process of debugging programs produced by computer-aided parallel- ization tools. The system uses relative debugging tech- niques to compare serial and parallel executions in order to show where the computations begin to differ. If the origi- nal serial code is correct, errors due to parallelization will be isolated by the comparison. One of

Robert Hood; Gabriele Jost

2000-01-01

368

A parallel thinning algorithm for grayscale images  

E-print Network

A parallel thinning algorithm for grayscale images Michel Couprie1 , Nivando Bezerra2 , and Gilles no general and well defined framework has been proposed until now for parallel grayscale thinning. We introduce in this paper a parallel thinning algorithm for grayscale images, and prove its topological

Boyer, Edmond

369

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

370

MASSIVELY PARALLEL MICROFLUIDIC CELL-PAIRING PLATFORM FOR THE STATISTICAL STUDY OF IMMUNOLOGICAL CELL-CELL  

E-print Network

MASSIVELY PARALLEL MICROFLUIDIC CELL-PAIRING PLATFORM FOR THE STATISTICAL STUDY OF IMMUNOLOGICAL in presumably homogeneous populations has been neglected in immunology due to the limitations of conventional to study immune cell-cell interactions A) Current methods to image cell-cell interactions in immunology

Voldman, Joel

371

Collective Interaction of a Compressible Periodic Parallel Jet Flow  

NASA Technical Reports Server (NTRS)

A linear instability model for multiple spatially periodic supersonic rectangular jets is solved using Floquet-Bloch theory. The disturbance environment is investigated using a two dimensional perturbation of a mean flow. For all cases large temporal growth rates are found. This work is motivated by an increase in mixing found in experimental measurements of spatially periodic supersonic rectangular jets with phase-locked screech. The results obtained in this paper suggests that phase-locked screech or edge tones may produce correlated spatially periodic jet flow downstream of the nozzles which creates a large span wise multi-nozzle region where a disturbance can propagate. The large temporal growth rates for eddies obtained by model calculation herein are related to the increased mixing since eddies are the primary mechanism that transfer energy from the mean flow to the large turbulent structures. Calculations of growth rates are presented for a range of Mach numbers and nozzle spacings corresponding to experimental test conditions where screech synchronized phase locking was observed. The model may be of significant scientific and engineering value in the quest to understand and construct supersonic mixer-ejector nozzles which provide increased mixing and reduced noise.

Miles, Jeffrey Hilton

1997-01-01

372

Interacting Parallel Constructions of Knowledge in a CAS Context  

ERIC Educational Resources Information Center

We consider the influence of a CAS context on a learner's process of constructing a justification for the bifurcations in a logistic dynamical process. We describe how instrumentation led to cognitive constructions and how the roles of the learner and the CAS intertwine, especially close to the branching and combining of constructing actions. The…

Kidron, Ivy; Dreyfus, Tommy

2010-01-01

373

Interactive Parallel Programming Using the ParaScope Editor  

E-print Network

to a data race, indicating the existence of potential nondeterminism in the program. In general that a dependence does not exist, automa, eager to use new machines to speed up existing sequential scientific codes, want maximal performance

Tseng, Chau-Wen

374

Parallel multiscale simulations of a brain aneurysm  

PubMed Central

Cardiovascular pathologies, such as a brain aneurysm, are affected by the global blood circulation as well as by the local microrheology. Hence, developing computational models for such cases requires the coupling of disparate spatial and temporal scales often governed by diverse mathematical descriptions, e.g., by partial differential equations (continuum) and ordinary differential equations for discrete particles (atomistic). However, interfacing atomistic-based with continuum-based domain discretizations is a challenging problem that requires both mathematical and computational advances. We present here a hybrid methodology that enabled us to perform the first multi-scale simulations of platelet depositions on the wall of a brain aneurysm. The large scale flow features in the intracranial network are accurately resolved by using the high-order spectral element Navier-Stokes solver ?? ?r. The blood rheology inside the aneurysm is modeled using a coarse-grained stochastic molecular dynamics approach (the dissipative particle dynamics method) implemented in the parallel code LAMMPS. The continuum and atomistic domains overlap with interface conditions provided by effective forces computed adaptively to ensure continuity of states across the interface boundary. A two-way interaction is allowed with the time-evolving boundary of the (deposited) platelet clusters tracked by an immersed boundary method. The corresponding heterogeneous solvers ( ?? ?r and LAMMPS) are linked together by a computational multilevel message passing interface that facilitates modularity and high parallel efficiency. Results of multiscale simulations of clot formation inside the aneurysm in a patient-specific arterial tree are presented. We also discuss the computational challenges involved and present scalability results of our coupled solver on up to 300K computer processors. Validation of such coupled atomistic-continuum models is a main open issue that has to be addressed in future work. PMID:23734066

Grinberg, Leopold; Fedosov, Dmitry A.; Karniadakis, George Em

2012-01-01

375

Parallel multiscale simulations of a brain aneurysm  

NASA Astrophysics Data System (ADS)

Cardiovascular pathologies, such as a brain aneurysm, are affected by the global blood circulation as well as by the local microrheology. Hence, developing computational models for such cases requires the coupling of disparate spatial and temporal scales often governed by diverse mathematical descriptions, e.g., by partial differential equations (continuum) and ordinary differential equations for discrete particles (atomistic). However, interfacing atomistic-based with continuum-based domain discretizations is a challenging problem that requires both mathematical and computational advances. We present here a hybrid methodology that enabled us to perform the first multiscale simulations of platelet depositions on the wall of a brain aneurysm. The large scale flow features in the intracranial network are accurately resolved by using the high-order spectral element Navier-Stokes solver N??T?r. The blood rheology inside the aneurysm is modeled using a coarse-grained stochastic molecular dynamics approach (the dissipative particle dynamics method) implemented in the parallel code LAMMPS. The continuum and atomistic domains overlap with interface conditions provided by effective forces computed adaptively to ensure continuity of states across the interface boundary. A two-way interaction is allowed with the time-evolving boundary of the (deposited) platelet clusters tracked by an immersed boundary method. The corresponding heterogeneous solvers (N??T?r and LAMMPS) are linked together by a computational multilevel message passing interface that facilitates modularity and high parallel efficiency. Results of multiscale simulations of clot formation inside the aneurysm in a patient-specific arterial tree are presented. We also discuss the computational challenges involved and present scalability results of our coupled solver on up to 300 K computer processors. Validation of such coupled atomistic-continuum models is a main open issue that has to be addressed in future work.

Grinberg, Leopold; Fedosov, Dmitry A.; Karniadakis, George Em

2013-07-01

376

Large-Scale Parallel Programming: Experience with the BBN Butterfly Parallel Processor  

E-print Network

Large-Scale Parallel Programming: Experience with the BBN Butterfly Parallel Processor Thomas J. Le of Rochester have used a collection of BBN Butterfly TM Parallel Processors to conduct research in parallel with the Butterfly we have ported three compilers, developed five major and several minor library packages, built two

Scott, Michael L.

377

A New Approach to Parallel Program Development and Scheduling of Parallel Jobs on Distributed Systems  

E-print Network

A New Approach to Parallel Program Development and Scheduling of Parallel Jobs on Distributed of Technology Abstract A typical way to increase the performance of a parallel program on a given parallel an initial and time- consuming development phase. We propose an alter- native approach to program development

378

Parallel Lines Cut By A Transversal  

NSDL National Science Digital Library

This project will help you to understand the different angles created by a transversal cutting across two parallel lines. Please watch for alternate exterior, alternate interior, consecutive, and corresponding angles. Here is an overview of the concepts that will be discussed in this lesson. Take notes.... Parallel Lines and the Angles they Create See if you understand these concepts by completing the following online practice page: Practice with Parallel Lines and Angles This activity from Class Zone will help you to further understand parallel line and perpendicular line theorems. Parallel and Perpendicular Lines Explore this website: Please notice that when you ...

Neubert, Mrs.

2010-09-28

379

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. PMID:18328753

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

2008-01-01

380

Heart Fibrillation and Parallel Supercomputers  

NASA Technical Reports Server (NTRS)

The Luo and Rudy 3 cardiac cell mathematical model is implemented on the parallel supercomputer CRAY - T3D. The splitting algorithm combined with variable time step and an explicit method of integration provide reasonable solution times and almost perfect scaling for rectilinear wave propagation. The computer simulation makes it possible to observe new phenomena: the break-up of spiral waves caused by intracellular calcium and dynamics and the non-uniformity of the calcium distribution in space during the onset of the spiral wave.

Kogan, B. Y.; Karplus, W. J.; Chudin, E. E.

1997-01-01

381

True Shear Parallel Plate Viscometer  

NASA Technical Reports Server (NTRS)

This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.

Ethridge, Edwin; Kaukler, William

2010-01-01

382

The PARTY parallel runtime system  

NASA Technical Reports Server (NTRS)

In the present automated system for the organization of the data and computational operations entailed by parallel problems, in ways that optimize multiprocessor performance, general heuristics for partitioning program data and control are implemented by capturing and manipulating representations of a computation at run time. These heuristics are directed toward the dynamic identification and allocation of concurrent work in computations with irregular computational patterns. An optimized static-workload partitioning is computed for such repetitive-computation pattern problems as the iterative ones employed in scientific computation.

Saltz, J. H.; Mirchandaney, Ravi; Smith, R. M.; Crowley, Kay; Nicol, D. M.

1989-01-01

383

Parallel Assembly of LIGA Components  

SciTech Connect

In this paper, a prototype robotic workcell for the parallel assembly of LIGA components is described. A Cartesian robot is used to press 386 and 485 micron diameter pins into a LIGA substrate and then place a 3-inch diameter wafer with LIGA gears onto the pins. Upward and downward looking microscopes are used to locate holes in the LIGA substrate, pins to be pressed in the holes, and gears to be placed on the pins. This vision system can locate parts within 3 microns, while the Cartesian manipulator can place the parts within 0.4 microns.

Christenson, T.R.; Feddema, J.T.

1999-03-04

384

Instant well-log inversion with a parallel computer  

SciTech Connect

Well-log analysis requires several vectors of input data to be inverted with a physical model that produces more vectors of output data. The problem is inherently suited to either vectorization or parallelization. PLATO (parallel log analysis, timely output) is a research prototype system that uses a parallel architecture computer with memory-mapped graphics to invert vector data and display the result rapidly. By combining this high-performance computing and display system with a graphical user interface, the analyst can interact with the system in real time'' and can visualize the result of changing parameters on up to 1,000 levels of computed volumes and reconstructed logs. It is expected that such instant'' inversion will remove the main disadvantages frequently cited for simultaneous analysis methods, namely difficulty in assessing sensitivity to different parameters and slow output response. Although the prototype system uses highly specific features of a parallel processor, a subsequent version has been implemented on a conventional (Serial) workstation with less performance but adequate functionality to preserve the apparently instant response. PLATO demonstrates the feasibility of petroleum computing applications combining an intuitive graphical interface, high-performance computing of physical models, and real-time output graphics.

Kimminau, S.J.; Trivedi, H.

1993-08-01

385

Digital Control of Three-Phase Series-Parallel Uninterruptible Power Supply Systems  

Microsoft Academic Search

In this paper, a new digital deadbeat controller is designed, implemented, and applied to a three-phase series-parallel line-interactive uninterruptible power supply (UPS). This kind of UPS system provides input power factor correction, output voltage conditioning, and high efficiency. The objective of the controller is to achieve deadbeat dynamic response for the parallel and series converters. The proposed controller adjusts the

Adel Nasiri

2007-01-01

386

Novel Kinetic 3D MHD Algorithm for High Performance Parallel Computing Systems  

E-print Network

The impressive progress of the kinetic schemes in the solution of gas dynamics problems and the development of effective parallel algorithms for modern high performance parallel computing systems led to the development of advanced methods for the solution of the magnetohydrodynamics problem in the important area of plasma physics. The novel feature of the method is the formulation of the complex Boltzmann-like distribution function of kinetic method with the implementation of electromagnetic interaction terms. The numerical method is based on the explicit schemes. Due to logical simplicity and its efficiency, the algorithm is easily adapted to modern high performance parallel computer systems including hybrid computing systems with graphic processors.

Chetverushkin, B; Saveliev, V

2013-01-01

387

A Semi-Empirical Noise Modeling Method for Helicopter Maneuvering Flight Operations  

NASA Technical Reports Server (NTRS)

A new model for Blade-Vortex Interaction noise generation during maneuvering flight is developed in this paper. Acoustic and performance data from both flight and wind tunnels are used to derive a non-dimensional and analytical performance/acoustic model that describes BVI noise in steady flight. The model is extended to transient maneuvering flight (pure pitch and roll transients) by using quasisteady assumptions throughout the prescribed maneuvers. Ground noise measurements, taken during maneuvering flight of a Bell 206B helicopter, show that many of the noise radiation details are captured. The result is a computationally efficient Blade-Vortex Interaction noise model with sufficient accuracy to account for transient maneuvering flight. The code can be run in real time to predict transient maneuver noise and is suitable for use in an acoustic mission-planning tool.

Greenwood, Eric; Schmitz, Fredric; Sickenberger, Richard D.

2012-01-01

388

The Economist Interactive: Equivalent Country Comparisons  

NSDL National Science Digital Library

This interactive tools allows the user to learn which countries parallel the states, provinces or territories of the United States, China, India and Brazil and  presents country equivalent data for both GDP and population.

389

Characterizations of parallel complexity classes  

SciTech Connect

A new two-person pebble game that abstracts the control structure of many parallel algorithms is defined and studied. This game extends the two-person pebble game defined by Dymond and Tompa (JCSS, Vol. 30, no.2, 1985, pp. 149-161) in two ways: (a) the game is played on a Boolean circuit rather than on an unlabeled graph, and takes into consideration the types of the gates in the circuit, and (b) the two players' roles are completely symmetric. The new game is used to study the relationship between two natural parallel complexity classes, namely LOGCFL and AC/sup 1/. LOGCFL is the class of languages log space reducible to context-free languages. AC/sup 1/ is the class of languages accepted by an alternating Turning machine in space O(log n) and alternation depth O(log n). LOGCFL is a subclass of AC/sup 1/, but it is not known whether the inclusion is proper. For many problems in LOGCFL the algorithms that show their membership in that class also show their membership in AC/sup 1/. However, these algorithms do not use the full power of AC/sup 1/ computations. The two-person game defined here provides a model of computation in which this perceived difference can be quantified. This is done by characterizing the two classes using the same measures of resources in the game model.

Venkateswaran, H.

1986-01-01

390

Parallel computation of electromagnetic fields  

SciTech Connect

The DSI3D code is designed to numerically solve electromagnetics problems involving complex objects by solving Maxwell`s curl equations in the time-domain and in three space dimensions. The code has been designed to run on the new parallel processing computers as well as on conventional serial computers. The DSI3D code is unique for the following reasons: It runs efficiently on a variety of parallel computers, Allows the use of unstructured non-orthogonal grids, Allows a variety of cell or element types, Reduces to be the Finite Difference Time Domain (FDID) method when orthogonal grids are used, Preserves charge or divergence locally (and globally), Is non- dissipative, and Is accurate for non-orthogonal grids. This method is derived using a Discrete Surface Integration (DSI) technique. As formulated, the DSI technique can be used with essentially arbitrary unstructured grids composed of convex polyhedral cells. This implementation of the DSI algorithm allows the use of unstructured grids that are composed of combinations of non-orthogonal hexahedrons, tetrahedrons, triangular prisms and pyramids. This algorithm reduces to the conventional FDTD method when applied on a structured orthogonal hexahedral grid.

Madsen, N.K.

1997-05-21

391

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

392

Integrated Task and Data Parallel Programming  

NASA Technical Reports Server (NTRS)

This research investigates the combination of task and data parallel language constructs within a single programming language. There are an number of applications that exhibit properties which would be well served by such an integrated language. Examples include global climate models, aircraft design problems, and multidisciplinary design optimization problems. Our approach incorporates data parallel language constructs into an existing, object oriented, task parallel language. The language will support creation and manipulation of parallel classes and objects of both types (task parallel and data parallel). Ultimately, the language will allow data parallel and task parallel classes to be used either as building blocks or managers of parallel objects of either type, thus allowing the development of single and multi-paradigm parallel applications. 1995 Research Accomplishments In February I presented a paper at Frontiers 1995 describing the design of the data parallel language subset. During the spring I wrote and defended my dissertation proposal. Since that time I have developed a runtime model for the language subset. I have begun implementing the model and hand-coding simple examples which demonstrate the language subset. I have identified an astrophysical fluid flow application which will validate the data parallel language subset. 1996 Research Agenda Milestones for the coming year include implementing a significant portion of the data parallel language subset over the Legion system. Using simple hand-coded methods, I plan to demonstrate (1) concurrent task and data parallel objects and (2) task parallel objects managing both task and data parallel objects. My next steps will focus on constructing a compiler and implementing the fluid flow application with the language. Concurrently, I will conduct a search for a real-world application exhibiting both task and data parallelism within the same program. Additional 1995 Activities During the fall I collaborated with Andrew Grimshaw and Adam Ferrari to write a book chapter which will be included in Parallel Processing in C++ edited by Gregory Wilson. I also finished two courses, Compilers and Advanced Compilers, in 1995. These courses complete my class requirements at the University of Virginia. I have only my dissertation research and defense to complete.

Grimshaw, A. S.

1998-01-01

393

Fully Parallel MHD Stability Analysis Tool  

NASA Astrophysics Data System (ADS)

Feasibility study of fully parallelizing plasma stability code MARS is made. MARS calculates eigenmodes in 2D axisymmetric toroidal equilibria in MHD-kinetic plasma models. It is a powerful tool for studying MHD and MHD-kinetic instabilities and it is widely used by fusion community. Parallel version of MARS is intended for simulations on local parallel clusters. It will be an efficient tool for simulation of MHD instabilities with low, intermediate and high toroidal mode numbers within both fluid and kinetic plasma models, already implemented in MARS. Parallelization of the code includes parallelization of the construction of the matrix for the eigenvalue problem and parallelization of the inverse iterations algorithm, implemented in MARS for the solution of the formulated eigenvalue problem. Construction of the matrix is parallelized by distributing the load among processors assigned to different magnetic surfaces. Two approaches of parallelization of the solution of the eigenvalue problem are evaluated: 1) repeat steps of the present MARS algorithm using parallel libraries and procedures; 2) solve linear block-diagonal sets of equations, formulated in the inverse iteration algorithm in MARS, by parallel libraries and procedures. The results of these studies will be reported.

Svidzinski, Vladimir; Galkin, Sergei; Kim, Jin-Soo; Liu, Yueqiang

2012-10-01

394

Parallel Many--Body Simulations Without All--to--All Communication  

Microsoft Academic Search

Simulations of interacting particles are common in science and engineering, appearing insuch diverse disciplines as astrophysics, fluid dynamics, molecular physics, and materials science.These simulations are often computationally intensive and so natural candidates for massivelyparallel computing. Many--body simulations that directly compute interactions between pairsof particles, be they short--range or long--range interactions, have been parallelized in severalstandard ways. The...

Bruce Hendrickson; Steve Plimpton Sandia

1993-01-01

395

Reducing neural network training time with parallel processing  

NASA Technical Reports Server (NTRS)

Obtaining optimal solutions for engineering design problems is often expensive because the process typically requires numerous iterations involving analysis and optimization programs. Previous research has shown that a near optimum solution can be obtained in less time by simulating a slow, expensive analysis with a fast, inexpensive neural network. A new approach has been developed to further reduce this time. This approach decomposes a large neural network into many smaller neural networks that can be trained in parallel. Guidelines are developed to avoid some of the pitfalls when training smaller neural networks in parallel. These guidelines allow the engineer: to determine the number of nodes on the hidden layer of the smaller neural networks; to choose the initial training weights; and to select a network configuration that will capture the interactions among the smaller neural networks. This paper presents results describing how these guidelines are developed.

Rogers, James L., Jr.; Lamarsh, William J., II

1995-01-01

396

Parallelization of MRCI based on hole-particle symmetry.  

PubMed

The parallel implementation of multireference configuration interaction program based on the hole-particle symmetry is described. The platform to implement the parallelization is an Intel-Architectural cluster consisting of 12 nodes, each of which is equipped with two 2.4-G XEON processors, 3-GB memory, and 36-GB disk, and are connected by a Gigabit Ethernet Switch. The dependence of speedup on molecular symmetries and task granularities is discussed. Test calculations show that the scaling with the number of nodes is about 1.9 (for C1 and Cs), 1.65 (for C2v), and 1.55 (for D2h) when the number of nodes is doubled. The largest calculation performed on this cluster involves 5.6 x 10(8) CSFs. PMID:15538769

Suo, Bing; Zhai, Gaohong; Wang, Yubin; Wen, Zhenyi; Hu, Xiangqian; Li, Lemin

2005-01-15

397

Single-cell mechanics: The parallel plates technique.  

PubMed

We describe here the parallel plates technique which enables quantifying single-cell mechanics, either passive (cell deformability) or active (whole-cell traction forces). Based on the bending of glass microplates of calibrated stiffness, it is easy to implement on any microscope, and benefits from protocols and equipment already used in biology labs (coating of glass slides, pipette pullers, micromanipulators, etc.). We first present the principle of the technique, the design and calibration of the microplates, and various surface coatings corresponding to different cell-substrate interactions. Then we detail the specific cell preparation for the assays, and the different mechanical assays that can be carried out. Finally, we discuss the possible technical simplifications and the specificities of each mechanical protocol, as well as the possibility of extending the use of the parallel plates to investigate the mechanics of cell aggregates or tissues. PMID:25640430

Bufi, Nathalie; Durand-Smet, Pauline; Asnacios, Atef

2015-01-01

398

Parallel discrete event simulation: A shared memory approach  

NASA Technical Reports Server (NTRS)

With traditional event list techniques, evaluating a detailed discrete event simulation model can often require hours or even days of computation time. Parallel simulation mimics the interacting servers and queues of a real system by assigning each simulated entity to a processor. By eliminating the event list and maintaining only sufficient synchronization to insure causality, parallel simulation can potentially provide speedups that are linear in the number of processors. A set of shared memory experiments is presented using the Chandy-Misra distributed simulation algorithm to simulate networks of queues. Parameters include queueing network topology and routing probabilities, number of processors, and assignment of network nodes to processors. These experiments show that Chandy-Misra distributed simulation is a questionable alternative to sequential simulation of most queueing network models.

Reed, Daniel A.; Malony, Allen D.; Mccredie, Bradley D.

1987-01-01

399

A fast ultrasonic simulation tool based on massively parallel implementations  

NASA Astrophysics Data System (ADS)

This paper presents a CIVA optimized ultrasonic inspection simulation tool, which takes benefit of the power of massively parallel architectures: graphical processing units (GPU) and multi-core general purpose processors (GPP). This tool is based on the classical approach used in CIVA: the interaction model is based on Kirchoff, and the ultrasonic field around the defect is computed by the pencil method. The model has been adapted and parallelized for both architectures. At this stage, the configurations addressed by the tool are : multi and mono-element probes, planar specimens made of simple isotropic materials, planar rectangular defects or side drilled holes of small diameter. Validations on the model accuracy and performances measurements are presented.

Lambert, Jason; Rougeron, Gilles; Lacassagne, Lionel; Chatillon, Sylvain

2014-02-01

400

UH60A airloads data acquisition and processing system  

Microsoft Academic Search

National Aeronautics and Space Administration, Ames Research Center, recently completed the joint NASA\\/Army UH-60A Airloads Program. The objective of this program was to make in-flight the measurements of rotor blade airloads, blade vortex interaction, and blade acoustics. An advanced digital instrumentation system, capable of synchronous acquisition of several hundred high frequency pressure channels was designed and developed to gather the

Joseph G. M. Leung; Mei Yueh Wei; M. Aoyagi

1994-01-01

401

Performance Metrics for Monitoring Parallel Program Executions  

NASA Technical Reports Server (NTRS)

Existing tools for debugging performance of parallel programs either provide graphical representations of program execution or profiles of program executions. However, for performance debugging tools to be useful, such information has to be augmented with information that highlights the cause of poor program performance. Identifying the cause of poor performance necessitates the need for not only determining the significance of various performance problems on the execution time of the program, but also needs to consider the effect of interprocessor communications of individual source level data structures. In this paper, we present a suite of normalized indices which provide a convenient mechanism for focusing on a region of code with poor performance and highlights the cause of the problem in terms of processors, procedures and data structure interactions. All the indices are generated from trace files augmented with data structure information.. Further, we show with the help of examples from the NAS benchmark suite that the indices help in detecting potential cause of poor performance, based on augmented execution traces obtained by monitoring the program.

Sarukkai, Sekkar R.; Gotwais, Jacob K.; Yan, Jerry; Lum, Henry, Jr. (Technical Monitor)

1994-01-01

402

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

403

A generic fine-grained parallel C  

NASA Technical Reports Server (NTRS)

With the present availability of parallel processors of vastly different architectures, there is a need for a common language interface to multiple types of machines. The parallel C compiler, currently under development, is intended to be such a language. This language is based on the belief that an algorithm designed around fine-grained parallelism can be mapped relatively easily to different parallel architectures, since a large percentage of the parallelism has been identified. The compiler generates a FORTH-like machine-independent intermediate code. A machine-dependent translator will reside on each machine to generate the appropriate executable code, taking advantage of the particular architectures. The goal of this project is to allow a user to run the same program on such machines as the Massively Parallel Processor, the CRAY, the Connection Machine, and the CYBER 205 as well as serial machines such as VAXes, Macintoshes and Sun workstations.

Hamet, L.; Dorband, John E.

1988-01-01

404

Design considerations for parallel graphics libraries  

NASA Technical Reports Server (NTRS)

Applications which run on parallel supercomputers are often characterized by massive datasets. Converting these vast collections of numbers to visual form has proven to be a powerful aid to comprehension. For a variety of reasons, it may be desirable to provide this visual feedback at runtime. One way to accomplish this is to exploit the available parallelism to perform graphics operations in place. In order to do this, we need appropriate parallel rendering algorithms and library interfaces. This paper provides a tutorial introduction to some of the issues which arise in designing parallel graphics libraries and their underlying rendering algorithms. The focus is on polygon rendering for distributed memory message-passing systems. We illustrate our discussion with examples from PGL, a parallel graphics library which has been developed on the Intel family of parallel systems.

Crockett, Thomas W.

1994-01-01

405

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

406

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

407

Parallel processing for scientific computations  

NASA Technical Reports Server (NTRS)

The main contribution of the effort in the last two years is the introduction of the MOPPS system. After doing extensive literature search, we introduced the system which is described next. MOPPS employs a new solution to the problem of managing programs which solve scientific and engineering applications on a distributed processing environment. Autonomous computers cooperate efficiently in solving large scientific problems with this solution. MOPPS has the advantage of not assuming the presence of any particular network topology or configuration, computer architecture, or operating system. It imposes little overhead on network and processor resources while efficiently managing programs concurrently. The core of MOPPS is an intelligent program manager that builds a knowledge base of the execution performance of the parallel programs it is managing under various conditions. The manager applies this knowledge to improve the performance of future runs. The program manager learns from experience.

Alkhatib, Hasan S.

1991-01-01

408

Parallel discovery of Alzheimer's therapeutics.  

PubMed

As the prevalence of Alzheimer's disease (AD) grows, so do the costs it imposes on society. Scientific, clinical, and financial interests have focused current drug discovery efforts largely on the single biological pathway that leads to amyloid deposition. This effort has resulted in slow progress and disappointing outcomes. Here, we describe a "portfolio approach" in which multiple distinct drug development projects are undertaken simultaneously. Although a greater upfront investment is required, the probability of at least one success should be higher with "multiple shots on goal," increasing the efficiency of this undertaking. However, our portfolio simulations show that the risk-adjusted return on investment of parallel discovery is insufficient to attract private-sector funding. Nevertheless, the future cost savings of an effective AD therapy to Medicare and Medicaid far exceed this investment, suggesting that government funding is both essential and financially beneficial. PMID:24944190

Lo, Andrew W; Ho, Carole; Cummings, Jayna; Kosik, Kenneth S

2014-06-18

409

Automatic Multilevel Parallelization Using OpenMP  

NASA Technical Reports Server (NTRS)

In this paper we describe the extension of the CAPO parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report first results for several benchmark codes and one full application that have been parallelized using our system.

Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

2002-01-01

410

The NAS Parallel Benchmarks in Titanium  

Microsoft Academic Search

Titanium is an explicitly parallel dialect of JavaTM designed for high-performance scientific programming. It offers object-orientation, strong typing, and safe memory management in the context of a language that supports high performance and scal- able parallelism. We present an overview of the language features and demonstrate their use in the context of the NAS Parallel Benchmarks, a benchmark suite of

Kaushik Datta

2006-01-01

411

Parallelization Strategies for Network Interface Firmware  

Microsoft Academic Search

Typical data-intensive embedded applications have large amounts of instruction-level parallelism that is often ex- ploited with wide-issue VLIW processors. In contrast, event-driven embedded applications are believed to have very little instruction-level parallelism, so these appli ca- tions often utilize much simpler processor cores. Pro- grammable network interface cards, for example, utilize thread-level parallelism across multiple processor cores to handle multiple

Michael Brogioli; Paul Willmann; Scott Rixner

412

Conservation of writhe helicity under anti-parallel reconnection  

E-print Network

Reconnection is a fundamental event in many areas of science, from the interaction of vortices in classical and quantum fluids, and magnetic flux tubes in magnetohydrodynamics and plasma physics, to the recombination in polymer physics and DNA biology. By using fundamental results in topological fluid mechanics, the helicity of a flux tube can be calculated in terms of writhe and twist contributions. Here we show that the writhe is conserved under anti-parallel reconnection. Hence, for a pair of interacting flux tubes of equal flux, if the twist of the reconnected tube is the sum of the original twists of the interacting tubes, then helicity is conserved during reconnection. Thus, any deviation from helicity conservation is entirely due to the intrinsic twist inserted or deleted locally at the reconnection site. This result has important implications for helicity and energy considerations in various physical contexts.

Christian E. Laing; Renzo L. Ricca; De Witt L. Sumners

2014-10-14

413

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

414

Conformal pure radiation with parallel rays  

NASA Astrophysics Data System (ADS)

We define pure radiation metrics with parallel rays to be n-dimensional pseudo-Riemannian metrics that admit a parallel null line bundle K and whose Ricci tensor vanishes on vectors that are orthogonal to K. We give necessary conditions in terms of the Weyl, Cotton and Bach tensors for a pseudo-Riemannian metric to be conformal to a pure radiation metric with parallel rays. Then, we derive conditions in terms of the tractor calculus that are equivalent to the existence of a pure radiation metric with parallel rays in a conformal class. We also give analogous results for n-dimensional pseudo-Riemannian pp-waves.

Leistner, Thomas; Nurowski, Pawe?

2012-03-01

415

Parallel auto-correlative statistics with VTK.  

SciTech Connect

This report summarizes existing statistical engines in VTK and presents both the serial and parallel auto-correlative statistics engines. It is a sequel to [PT08, BPRT09b, PT09, BPT09, PT10] which studied the parallel descriptive, correlative, multi-correlative, principal component analysis, contingency, k-means, and order statistics engines. The ease of use of the new parallel auto-correlative statistics engine is illustrated by the means of C++ code snippets and algorithm verification is provided. This report justifies the design of the statistics engines with parallel scalability in mind, and provides scalability and speed-up analysis results for the autocorrelative statistics engine.

Pebay, Philippe Pierre [Kitware, France; Bennett, Janine Camille

2013-08-01

416

A parallel algorithm for global routing  

NASA Technical Reports Server (NTRS)

A Parallel Hierarchical algorithm for Global Routing (PHIGURE) is presented. The router is based on the work of Burstein and Pelavin, but has many extensions for general global routing and parallel execution. Main features of the algorithm include structured hierarchical decomposition into separate independent tasks which are suitable for parallel execution and adaptive simplex solution for adding feedthroughs and adjusting channel heights for row-based layout. Alternative decomposition methods and the various levels of parallelism available in the algorithm are examined closely. The algorithm is described and results are presented for a shared-memory multiprocessor implementation.

Brouwer, Randall J.; Banerjee, Prithviraj

1990-01-01

417

Parallel algorithms for electromagnetic moment method formulations.  

E-print Network

??ENGLISH ABSTRACT: This dissertation investigates the moment method solution of electromagnetic radiation and scattering problems using parallel computers. In particular, electromagnetically large problems with arbitrary… (more)

Davidson, David Bruce

1991-01-01

418

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

419

Interactive epistemology I: Knowledge  

Microsoft Academic Search

.   Formal Interactive Epistemology deals with the logic of knowledge and belief when there is more than one agent or “player.”\\u000a One is interested not only in each person's knowledge about substantive matters, but also in his knowledge about the others'\\u000a knowledge. This paper examines two parallel approaches to the subject. The first is the semantic approach, in which knowledge

Robert J. Aumann

1999-01-01

420

Interactive epistemology II: Probability  

Microsoft Academic Search

.   Formal Interactive Epistemology deals with the logic of knowledge and belief when there is more than one agent or “player.”\\u000a One is interested not only in each person's knowledge and beliefs about substantive matters, but also in his knowledge and\\u000a beliefs about the others' knowledge and beliefs. This paper examines two parallel approaches to the subject. The first is

Robert J. Aumann

1999-01-01

421

The language parallel Pascal and other aspects of the massively parallel processor  

NASA Technical Reports Server (NTRS)

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

422

Parallel contributions of distinct human memory systems during probabilistic learning  

PubMed Central

Regions within the medial temporal lobe and basal ganglia are thought to subserve distinct memory systems underlying declarative and nondeclarative processes, respectively. One question of interest is how these multiple memory systems interact during learning to contribute to goal directed behavior. While some hypotheses suggest that regions such as the striatum and the hippocampus interact in a competitive manner, alternative views posit that these structures may operate in a parallel manner to facilitate learning. In the current experiment, we probed the functional connectivity between regions in the striatum and hippocampus in the human brain during an event related probabilistic learning task that varied with respect to type of difficulty (easy or hard cues) and type of learning (via feedback or observation). We hypothesized that the hippocampus and striatum would interact in a parallel manner during learning. We identified regions of interest (ROI) in the striatum and hippocampus that showed an effect of cue difficulty during learning and found that such ROIs displayed a similar pattern of blood oxygen level dependent (BOLD) responses, irrespective of learning type, and were functionally correlated as assessed by a Granger causality analysis. Given the connectivity of both structures with dopaminergic midbrain centers, we further applied a reinforcement learning algorithm often used to highlight the role of dopamine in human reward related learning paradigms. Activity in both the striatum and hippocampus positively correlated with a prediction error signal during feedback learning. These results suggest that distinct human memory systems operate in parallel during probabilistic learning, and may act synergistically particularly when a violation of expectation occurs, to jointly contribute to learning and decision making. PMID:21056678

Dickerson, Kathryn C.; Li, Jian; Delgado, Mauricio R.

2010-01-01

423

Computing Degree of Parallelism for BPMN Processes Computing Degree of Parallelism  

E-print Network

Document Archive (1 Day) (1 Day) (1 Day) (1 Day) (3 Days) (1 Day) #12;Dec 2011 Computing DegreeComputing Degree of Parallelism for BPMN Processes Dec 6 2011 Computing Degree of Parallelism 2011 Computing Degree of Parallelism for BPMN Processes 2 Find Peak Workload Demands · Apartment

California at Santa Barbara, University of

424

Parallelization of VQ codebook generation by two algorithms: parallel LBG and aggressive PNN [image compression applications  

Microsoft Academic Search

Summary form only given. We evaluate two parallel algorithms for the codebook generation of the VQ compression: parallel LBG and aggressive PNN. Parallel LBG is based on the LBG algorithm with the K-mean method. The cost of both latter algorithms mainly consists of: a) the computation part; b) the communication part; and c) the update part. Aggressive PNN is a

A. Wakatani

2005-01-01

425

3: Parallelism in Microprocessors Course on "Scalable Computing". Vittorio Scarano 3: Parallelism in Microprocessors  

E-print Network

3: Parallelism in Microprocessors Course on "Scalable Computing". Vittorio Scarano 3: Parallelism in Microprocessors Seminars in Scalable Computing Vittorio Scarano Universit`a di Salerno Dottorato di Ricerca in Informatica 1/65 3: Parallelism in Microprocessors Course on "Scalable Computing". Vittorio Scarano Plan 1

Scarano, Vittorio

426

J. Parallel Distrib. Comput. 63 (2003) 674682 Parallel Genehunter: implementation of a linkage analysis package  

E-print Network

J. Parallel Distrib. Comput. 63 (2003) 674­682 Parallel Genehunter: implementation of a linkage Received 4 December 2002; revised 15 April 2003; accepted 16 May 2003 Abstract We present a parallel to run on distributed-memory platforms for the first time. Our preliminary benchmarks indicate reasonable

Wagner, Andreas

427

Parallel Spectral Transform Shallow Water Model: a runtime-tunable parallel benchmark code  

Microsoft Academic Search

Fairness is an important issue when benchmarking parallel computers using application codes. The best parallel algorithm on one platform may not be the best on another. While it is not feasible to re-evaluate parallel algorithms and reimplement large codes whenever new machines become available, it is possible to embed algorithmic options into codes that allow them to be “tuned” for

P. H. Worley; I. T. Foster

1994-01-01

428

A new index for the performance evaluation of parallel manipulators: A study on planar parallel manipulators  

Microsoft Academic Search

This paper addresses the issue of performance evaluation of parallel manipulators. In the analysis and design process of parallel manipulators, the performance evaluation is the most important problem. The developed index will be fundamentally involved in the process, especially in that of optimum design. Although parallel manipulators have been extensively studied for more than twenty years, unfortunately, the concepts of

Xin-Jun Liu; Chao Wu; Jinsong Wang

2008-01-01

429

Parallel computation of invariant measures  

SciTech Connect

A parallel numerical algorithm for computing invariant measures is presented. Let I{sup N} {triple_bond} [0,1]{sup N} be the unit N-cube in R N and let S : I{sup N}{r_arrow} I{sup N} be a nonsingular transformation, that is, S is Borel-measurable and m(A) = 0 implies m(S{sup -1}(A)) = 0, where m is the Lebesgue measure. The motivation of this study is the parallel computation of an absolutely continuous invariant measure {mu} under S, that is, {mu} {much_lt} m and {mu}(A) = {mu}(S{sup -1}(A)) for all Borel sets A {contained_in} I{sup N}. It is well-known that an absolutely continuous finite invariant measure {mu} can be obtained by computing a fixed density of the Frobenius-Perron operator Ps: L{sup 1} (I{sup N}) {r_arrow} L{sup 1}(I{sup N}) associated with S which is defined by (1) {integral}{sub A} P{sub S}fdm = {integral}{sub s-1(A)} fdm, {forall}f {element_of} L{sup 1} (I{sup N}). Using any suitable discretization scheme, the infinite dimensional eigenvector problem P{sub S}f = f in L{sup 1}(I{sup N}) can be approximated by an algebraic eigenvector problem P{sub l}f{sub l} = f{sub l} in {gradient}{sub l}, where P{sub l} is a finite approximation of P{sub s} associated with a finite element subspace {gradient}{sub l} of L{sup l} (I{sup N}) {intersection} L{sup {infinity}} (I{sup N}). It has been shown that for P{sub l} arising from Galerkin`s projection principle or the Markov finite approximation principle, there always exists a eigenvector f{sub l} to P{sub l}, and that a sequence of normalized eigenvectors (f{sub l}) converges to the density of an absolutely continuous probability invariant measure {mu} for a class of piecewise C{sup 2} expanding maps of I{sup N} under which the existence of {mu} is guaranteed by Gora-Boyarsky`s theorem which is reduced to Lasota-Yorke`s thoerem when N = 1.

Ding, J.; Liu, Y. [Univ. of Southern Mississippi, Hattiesburg, MS (United States)

1995-12-01

430

Large Parallel UPS Systems Utilizing PWM Technology  

Microsoft Academic Search

In the past large Uninterruptible Power Supply (UPS) applications requiring parallel operation of Pulse Width Modulated (PWM) inverters was not practical. New developments in PWM logic design have made load sharing of PWM inverters very precise. This paper addresses the critical factors of the inverter and system design which permit parallel operation and enhancement of system reliability. Taking full advantage

John Reed; Naresh Sharma

1984-01-01

431

Parallel operation of digital controlled UPS system  

Microsoft Academic Search

A digital control algorithm for parallel connected three-phase inverters used in a UPS (uninterruptible power supply) is proposed. Each inverter module has an LC filter. The digital voltage controller, which has high-speed current control as a minor loop, provides low voltage distortion even for nonlinear loads. A parallel operation controller supplements the voltage controller in each inverter module. Voltage reference

S. Tamai; M. Kinoshita

1991-01-01

432

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

433

Ohio Supercomputer Center Parallel Programming with MPI  

E-print Network

Ohio Supercomputer Center Parallel Programming with MPI Science & Technology Support High Performance Computing Ohio Supercomputer Center 1224 Kinnear Road Columbus, OH 43212-1163 #12;Parallel Programming with MPI 2Ohio Supercomputer Center Table of Contents · Setting the Stage · Brief History of MPI

Adler, Joan

434

Parallel processing in power systems computation  

Microsoft Academic Search

The availability of parallel processing hardware and software presents an opportunity and a challenge to apply this new computation technology to solve power system problems. The allure of parallel processing is that this technology has the potential to be cost effectively used on computationally intense problems. The objective of this paper is to define the state of the art and

D. J. Tylavsky; A. Bose; F. Alvarado; R. Betancourt; K. Clements; G. T. Heydt; G. Huang; M. Ilic; M. La Scala; M. A. Pai

1992-01-01

435

Parallel boxing in B-spline intersection  

Microsoft Academic Search

A modified formulation of oriented boxing called oriented slab boxing is presented. It almost doubles the speed of the oriented boxing component in B-spline intersection. The method used to accelerate B-spline intersection includes algorithmic improvements and parallelization of the algorithm at different levels of granularity to find an optimum solution on a network of parallel processors. The software testbed is

J. Yen; S. Spach; M. T. Smith; R. W. Pulleyblank

1991-01-01

436

Balancing Domain Decomposition with Nonlinear Relocalization: Parallel  

E-print Network

finite element code. And the technique utilized to parallelized the problem. Finally, the forth sectionBalancing Domain Decomposition with Nonlinear Relocalization: Parallel Implementation for Laminates is to develop a program capable of simulating structures on an industrial level using the latest models

Paris-Sud XI, Université de

437

Parallel programming with message passing and directives  

Microsoft Academic Search

The authors discuss methods for expressing and tuning the performance of parallel programs, using two programming models in the same program: distributed and shared memory. Such methods are important for anyone who uses these large machines for parallel programs as well as for those who study combinations of the two programming models. The article outlines applications in hydrology, computational chemistry,

S. W. Bova; C. P. Breshears; HENRY GABB; BOB KUHN; BILL MAGRO; RUDOLF EIGENMANN; GREG GAERTNER; STEFANO SALVINI; HOWARD SCOTT

2001-01-01

438

Parallelism and Compilers Christoph W. Keler  

E-print Network

dis- cussed in this thesis. In particular, it gives a comprehensive survey of my scientific work and compiling for parallel architectures, Chapters 2, 3, and 4 are self-contained and may be read independently. Chapter 5 discusses compilation aspects of the parallel programming languages introduced in Chapter 4

Kessler, Christoph

439

Parallelism and Compilers Christoph W. Keler  

E-print Network

dis­ cussed in this thesis. In particular, it gives a comprehensive survey of my scientific work and compiling for parallel architectures, Chapters 2, 3, and 4 are self­contained and may be read independently. Chapter 5 discusses compilation aspects of the parallel programming languages introduced in Chapter 4

Kessler, Christoph

440

AIAA 20031347 Parallel Computation of Wing Flutter  

E-print Network

AIAA 2003­1347 Parallel Computation of Wing Flutter with a Coupled Navier-Stokes/CSD Method M Alexander Bell Drive, Suite 500, Reston, VA 20191­4344 #12;Parallel Computation of Wing Flutter of three-dimensional aeroelastic problems such as wing flutter. The unsteady Navier-Stokes flow solver

Liu, Feng

441

January 1990 Parallel Distributed Approaches to Combinatorial  

E-print Network

January 1990 LU TP 90­2 Parallel Distributed Approaches to Combinatorial Optimization ­ Benchmark and summarize the results from 50­, 100­ and 200­city TSP benchmarks presented at the 1989 NIPS post this elastic net algorithm and the Potts approach [9][10][11]. Parallel to these developments genetic

Lunds Universitet,

442

Parallel benchmarks on the Transtech Paramid  

Microsoft Academic Search

This paper presents the results of running the some benchmarks from the Genesis suite on the Transtech Paramid. The benchmarks use the PARMACS parallel processing standard, and are based on applications in the fields of general relativity, molecular dynamics and QCD. The Paramid is a distributed memory parallel computer, using up to 64 Intel i860-XP processors. The results demonstrate good

R. S. Stephens

1994-01-01

443

Parallel algorithms for finding trigonometric sums  

SciTech Connect

Parallel versions of Goertzel and Reinsch algorithms for finding trigonometric sums are introduced as a special case of effcient parallel algorithms for solving linear recurrence systems. The results of the experiments performed on a 20-processors Sequent Symmetry are presented and discussed.

Stpiczynski, P. [Marie Curie-Sklodowska Univ., Lublin (Poland); Paprzycki, M. [Univ. of Texas of the Permian Basin, Odessa, TX (United States)

1995-12-01

444

Implementation of an efficient parallel BDD package  

Microsoft Academic Search

Large BDD applications push computing resources to their limits. One solution to overcoming resource limitations is to dis- tribute the BDD data structure across multiple networked worksta- tions. This paper presents an efficient parallel BDD package for a distributed environment such as a network of workstations (NOW) or a distributed memory parallel computer. The implementation exploits a number of different

Tony Stornetta; Forrest Brewer

1996-01-01

445

Implementation of an efficient parallel BDD package  

Microsoft Academic Search

Large BDD applications push completing resources to their limits. One solution to overcoming resource limitations is to distribute the BDD data structure across multiple networked workstations. This paper presents an efficient parallel BDD package for a distributed environment such as a network of workstations (NOW) or a distributed memory parallel computer. The implementation exploits a number of different forms of

Tony Stornetta; Forrest Brewer

1996-01-01

446

Adaptive parallel algorithms for integral knapsack problems  

NASA Astrophysics Data System (ADS)

In this paper, the design of a time-efficient and processor-efficient parallel algorithm for the integral knapsack problem is considered. A parallel integral knapsack algorithm is presented, which is adaptive to all parameters, especially to the maximum size of items. The parallel complexity of another important packing problem, the integral exactly-packing problem, is also considered. An optimal O(log n log m) time, parallel integral exactly-packing algorithm is given. Since the partition problem has a constant time, constant processor reduction to the exactly-packing problem, our parallel integral exactly-packing algorithm can be used for job scheduling, task partition, and many other important practical problems. Moreover, the methods and techniques used in this paper can be used for developing processor-efficient and time-efficient parallel algorithms for many other problems. Using the new parallel integral knapsack algorithm, the previously known parallel approximation schemes for the 0-1 knapsack problem and the binpacking problem, by E. W. Mayr and P. S. Gopalkrishnan, are improved upon significantly. Supported in part by the National Science Foundation through Grant DCR-8514961. Present address: School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213.

Teng, Shang-Hua

1990-04-01

447

Calypso NT: Reliable, Efficient Parallel Processing  

E-print Network

Calypso NT: Reliable, Efficient Parallel Processing on Windows NT Networks 1 Donald Mclaughlin processing system that runs on Windows NT workstations. The system allows a parallel program written in C to run on the Windows NT platform and made significant changes to the programming interface

Dasgupta, Partha

448

Lineal Feature Extraction by Parallel Stick Growing  

Microsoft Academic Search

Finding lineal features in an image is an important step in many object recognition and scene analysis procedures. Previous featu re extraction algorithms exhibit poor parallel performance because features often e xtend across large areas of the data set. This paper describes a parallel method for ex tracting lineal features based on an earlier sequential algorithm, stick growing. Th e

Galen C. Hunt; Randal C. Nelson

1996-01-01

449

A fast tunable parallel optical delay line  

Microsoft Academic Search

We demonstrate a new rapidly tunable parallel optical delay line (PODL) capable of accessing multiple high speed OTDM channels with very low latency using only one modulator operating below baseband. The PODL uses a new parallel compression scheme to rapidly tune pulses into different time slots within an OTDM frame. Since the modulator bandwidth is actually lower than the baseband

B. C. Wang; I. Glesk; R. J. Runser; P. R. Prucnal

2000-01-01

450

Efficient parallel algorithms for some graph problems  

Microsoft Academic Search

We study parallel algorithms for a number of graph problems, using the Single Instruction Stream-Multiple Data Stream model. We assume that the processors have access to a common memory and that no memory or data alignment time penalties are incurred. We derive a general time bound for a parallel algorithm that uses K processors for finding the connected components of

Francis Y. L. Chin; John Lam; I-Ngo Chen

1982-01-01

451

Non-Cartesian parallel imaging reconstruction.  

PubMed

Non-Cartesian parallel imaging has played an important role in reducing data acquisition time in MRI. The use of non-Cartesian trajectories can enable more efficient coverage of k-space, which can be leveraged to reduce scan times. These trajectories can be undersampled to achieve even faster scan times, but the resulting images may contain aliasing artifacts. Just as Cartesian parallel imaging can be used to reconstruct images from undersampled Cartesian data, non-Cartesian parallel imaging methods can mitigate aliasing artifacts by using additional spatial encoding information in the form of the nonhomogeneous sensitivities of multi-coil phased arrays. This review will begin with an overview of non-Cartesian k-space trajectories and their sampling properties, followed by an in-depth discussion of several selected non-Cartesian parallel imaging algorithms. Three representative non-Cartesian parallel imaging methods will be described, including Conjugate Gradient SENSE (CG SENSE), non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA), and Iterative Self-Consistent Parallel Imaging Reconstruction (SPIRiT). After a discussion of these three techniques, several potential promising clinical applications of non-Cartesian parallel imaging will be covered. PMID:24408499

Wright, Katherine L; Hamilton, Jesse I; Griswold, Mark A; Gulani, Vikas; Seiberlich, Nicole

2014-11-01

452

Parallel Activation in Bilingual Phonological Processing  

ERIC Educational Resources Information Center

In bilingual language processing, the parallel activation hypothesis suggests that bilinguals activate their two languages simultaneously during language processing. Support for the parallel activation mainly comes from studies of lexical (word-form) processing, with relatively less attention to phonological (sound) processing. According to…

Lee, Su-Yeon

2011-01-01

453

Improved parallel interference cancellation for CDMA  

Microsoft Academic Search

This paper introduces an improved nonlinear parallel interference cancellation scheme for code-division multiple access (CDMA) that significantly reduces the degrading effect on the desired user of interference from the other users that share the channel. The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each

Dariush Divsalar; Marvin K. Simon; Dan Raphaeli

1998-01-01

454

Logic verification algorithms and their parallel implementation  

Microsoft Academic Search

LOVER incorporates a novel approach to combinational logic verification and obtains good results when compared to existing techniques. In this paper we describe a new verification algorithm, LOVER-PODEM, whose enumeration phase is based on PODEM. A variant of LOVER-PODEM, called PLOVER, is presented. We have developed, for the first time, parallel logic verification schemes. Issues in efficiently parallelizing both general

Hi-Keung Tony Ma; Srinivas Devadas; Alberto L. Sangiovanni-Vincentelli; R. Wei

1987-01-01

455

Large parallel processing revisited: a second tutorial  

Microsoft Academic Search

An efficient parallel LU algorithm that is suitable for a local-memory MIMD (multiple input multiple data) computer, such as an array of transputers, is described. A graphical approach is used to elucidate the algorithm. The results of a theoretical timing analysis are given. Some methods for reducing the communication load, by intelligent exploitation of the capabilities of certain parallel hardware,

David B. Davidson

1992-01-01

456

New bounds for parallel prefix circuits  

Microsoft Academic Search

In this paper, new upper and lower bounds are obtained for the number of gates in parallel prefix circuits with minimum depth when the number of inputs is a power of two. In addition, structural information concerning these circuits is described. Parallel prefix circuits with bounds imposed on the fan-out of the gates are also considered. In both cases, the

Faith E. Fich

1983-01-01

457

Data parallel sequential circuit fault simulation  

Microsoft Academic Search

Sequential circuit fault simulation is a compute-intensive problem. Parallel simulation is one method to reduce fault simulation time. In this paper, we discuss a novel technique to partition the fault set for the fault parallel simulation of sequential circuits on multiple processors. When applied statically, the technique can scale well for up to thirty two processors on an ethernet. The

Minesh B. Amin; Bapiraju Vinnakota

1996-01-01

458

Massively parallel computing: A Sandia perspective  

Microsoft Academic Search

The computing power available to scientists and engineers has increased dramatically in the past decade, due in part to progress in making massively parallel computing practical and available. The expectation for these machines has been great. The reality is that progress has been slower than expected. Nevertheless, massively parallel computing is beginning to realize its potential for enabling significant break-throughs

David E. Womble; Sudip S. Dosanjh; Bruce Hendrickson; Michael A. Heroux; Steve J. Plimpton; James L. Tomkins; David S. Greenberg

1999-01-01

459

Parallel computation with the spectral element method  

SciTech Connect

Spectral element models for the shallow water equations and the Navier-Stokes equations have been successfully implemented on a data parallel supercomputer, the Connection Machine model CM-5. The nonstaggered grid formulations for both models are described, which are shown to be especially efficient in data parallel computing environment.

Ma, Hong

1995-12-01

460

Exploring Parallelization Strategies for NUFFT Data Translation  

E-print Network

Exploring Parallelization Strategies for NUFFT Data Translation Yuanrui Zhang Mahmut Kandemir parallelization strategies for the Non-Uniform FFT (NUFFT) data translation on multicore architectures. The NUFFT and image processing as well as in scientific computing. The critical extension lies at the translation

Pitsianis, Nikos P.

461

Dynamic analysis of Clavel's delta parallel robot  

Microsoft Academic Search

Some iterative matrix relations for the geometric, kinematic and dynamic analysis of a Delta parallel robot are established in this paper. The prototype of this manipulator is a three degree of freedom spatial mechanism, which consists of a system of parallel chains. Supposing that the position and the translation motion of the platform are known, an inverse dynamic problem is

Stefan Staicu; D. C. Carp-ciocardia

2003-01-01

462

Dynamics analysis of the Star parallel manipulator  

Microsoft Academic Search

Matrix relations in kinematics and dynamics of the Star parallel manipulator are established in this paper. The prototype of the manipulator is a three-degree-of-freedom mechanism, which consists of a system of parallel kinematical chains connecting to a moving platform. Knowing the translation motion of the platform, we develop first the inverse kinematics problem and determine the position, velocity and acceleration

Stefan Staicu

2009-01-01

463

The NAS Parallel Benchmarks in Titanium  

E-print Network

Titanium is an explicitly parallel dialect of Java TM designed for high-performance scientific programming. It offers object-orientation, strong typing, and safe memory management in the context of a language that supports high performance and scalable parallelism. We present an overview of the language features and demonstrate their use in the context of the NAS Parallel Benchmarks, a benchmark suite of common scientific kernels. We argue that parallel languages like Titanium provide greater expressive power than conventional approaches, thereby enabling more concise and expressive code and minimizing time to solution. Moreover, the Titanium implementations of three of the NAS Parallel Benchmarks can match or even exceed the performance of the standard Fortran/MPI implementations at realistic problem sizes and processor scales, while still using far cleaner, shorter and more maintainable code.

Kaushik Datta; Kaushik Datta

464

National Combustion Code: Parallel Implementation and Performance  

NASA Technical Reports Server (NTRS)

The National Combustion Code (NCC) is being developed by an industry-government team for the design and analysis of combustion systems. CORSAIR-CCD is the current baseline reacting flow solver for NCC. This is a parallel, unstructured grid code which uses a distributed memory, message passing model for its parallel implementation. The focus of the present effort has been to improve the performance of the NCC flow solver to meet combustor designer requirements for model accuracy and analysis turnaround time. Improving the performance of this code contributes significantly to the overall reduction in time and cost of the combustor design cycle. This paper describes the parallel implementation of the NCC flow solver and summarizes its current parallel performance on an SGI Origin 2000. Earlier parallel performance results on an IBM SP-2 are also included. The performance improvements which have enabled a turnaround of less than 15 hours for a 1.3 million element fully reacting combustion simulation are described.

Quealy, A.; Ryder, R.; Norris, A.; Liu, N.-S.

2000-01-01

465

A parallel variable metric optimization algorithm  

NASA Technical Reports Server (NTRS)

An algorithm, designed to exploit the parallel computing or vector streaming (pipeline) capabilities of computers is presented. When p is the degree of parallelism, then one cycle of the parallel variable metric algorithm is defined as follows: first, the function and its gradient are computed in parallel at p different values of the independent variable; then the metric is modified by p rank-one corrections; and finally, a single univariant minimization is carried out in the Newton-like direction. Several properties of this algorithm are established. The convergence of the iterates to the solution is proved for a quadratic functional on a real separable Hilbert space. For a finite-dimensional space the convergence is in one cycle when p equals the dimension of the space. Results of numerical experiments indicate that the new algorithm will exploit parallel or pipeline computing capabilities to effect faster convergence than serial techniques.

Straeter, T. A.

1973-01-01

466

Differences Between Distributed and Parallel Systems  

SciTech Connect

Distributed systems have been studied for twenty years and are now coming into wider use as fast networks and powerful workstations become more readily available. In many respects a massively parallel computer resembles a network of workstations and it is tempting to port a distributed operating system to such a machine. However, there are significant differences between these two environments and a parallel operating system is needed to get the best performance out of a massively parallel system. This report characterizes the differences between distributed systems, networks of workstations, and massively parallel systems and analyzes the impact of these differences on operating system design. In the second part of the report, we introduce Puma, an operating system specifically developed for massively parallel systems. We describe Puma portals, the basic building blocks for message passing paradigms implemented on top of Puma, and show how the differences observed in the first part of the report have influenced the design and implementation of Puma.

Brightwell, R.; Maccabe, A.B.; Rissen, R.

1998-10-01

467

Components and interfaces of a process management system for parallel programs.  

SciTech Connect

Parallel jobs are different from sequential jobs and require a different type of process management. We present here a process management 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 thousands of processes is quick, that signals can be quickly delivered to processes, and that stdin, stdout, and stderr are managed intuitively. Our primary target is parallel machines made up of clusters of SMPs, but the system is also useful in more tightly integrated environments. We describe how MPD enables much faster startup and better runtime management of parallel jobs. We show how close control of stdio can support the easy implementation of a number of convenient system utilities, even a parallel debugger. We describe a simple but general interface that can be used to separate any process manager from a parallel library, which we use to keep MPD separate from MPICH.

Butler, R.; Gropp, W.; Lusk, E.

2001-02-23

468

Seismic response of adjacent filled parallel rock fractures with dissimilar properties  

NASA Astrophysics Data System (ADS)

The purpose of this study is to analytically predict and to experimentally investigate the seismic response of adjacent filled parallel rock fractures with dissimilar properties (e.g., fracture thickness and stiffness). The time-domain recursive method is extended to predict that a P-wave propagates normally across the filled parallel fractures using the specific stiffness of each filled fracture and considering multiple wave reflections between the parallel fractures. The split Hopkinson rock bar technique is modified to simulate P-wave propagation normally across the sand-filled parallel fractures and to characterize the stress-closure relation of each sand-filled fracture. The P-wave transmission and the seismic response of the filled parallel fractures are an interactive process. The experimental results show the decreases of loading rate and dominant frequency when the P-wave propagates across each sand-filled fracture. The P-wave transmitted from the first sand-filled fracture strongly affects the seismic response of the second one. The P-wave attenuation in the filled parallel fractures is mainly due to the dynamic compaction of the filling sands. By comparison, the analytical method provides a satisfactory prediction to the experimental result. This study suggests considering the specific stiffness of each filled fracture to precisely predict the seismic response of filled parallel rock fractures.

Wu, W.; Li, J. C.; Zhao, J.

2013-09-01

469

The Design and Evaluation of "CAPTools"--A Computer Aided Parallelization Toolkit  

NASA Technical Reports Server (NTRS)

Writing applications for high performance computers is a challenging task. Although writing code by hand still offers the best performance, it is extremely costly and often not very portable. The Computer Aided Parallelization Tools (CAPTools) are a toolkit designed to help automate the mapping of sequential FORTRAN scientific applications onto multiprocessors. CAPTools consists of the following major components: an inter-procedural dependence analysis module that incorporates user knowledge; a 'self-propagating' data partitioning module driven via user guidance; an execution control mask generation and optimization module for the user to fine tune parallel processing of individual partitions; a program transformation/restructuring facility for source code clean up and optimization; a set of browsers through which the user interacts with CAPTools at each stage of the parallelization process; and a code generator supporting multiple programming paradigms on various multiprocessors. Besides describing the rationale behind the architecture of CAPTools, the parallelization process is illustrated via case studies involving structured and unstructured meshes. The programming process and the performance of the generated parallel programs are compared against other programming alternatives based on the NAS Parallel Benchmarks, ARC3D and other scientific applications. Based on these results, a discussion on the feasibility of constructing architectural independent parallel applications is presented.

Yan, Jerry; Frumkin, Michael; Hribar, Michelle; Jin, Haoqiang; Waheed, Abdul; Johnson, Steve; Cross, Jark; Evans, Emyr; Ierotheou, Constantinos; Leggett, Pete; Saini, Subhash (Technical Monitor)

1998-01-01

470

Parallel processing for scientific computations  

NASA Technical Reports Server (NTRS)

The scope of this project dealt with the investigation of the requirements to support distributed computing of scientific computations over a cluster of cooperative workstations. Various experiments on computations for the solution of simultaneous linear equations were performed in the early phase of the project to gain experience in the general nature and requirements of scientific applications. A specification of a distributed integrated computing environment, DICE, based on a distributed shared memory communication paradigm has been developed and evaluated. The distributed shared memory model facilitates porting existing parallel algorithms that have been designed for shared memory multiprocessor systems to the new environment. The potential of this new environment is to provide supercomputing capability through the utilization of the aggregate power of workstations cooperating in a cluster interconnected via a local area network. Workstations, generally, do not have the computing power to tackle complex scientific applications, making them primarily useful for visualization, data reduction, and filtering as far as complex scientific applications are concerned. There is a tremendous amount of computing power that is left unused in a network of workstations. Very often a workstation is simply sitting idle on a desk. A set of tools can be developed to take advantage of this potential computing power to create a platform suitable for large scientific computations. The integration of several workstations into a logical cluster of distributed, cooperative, computing stations presents an alternative to shared memory multiprocessor systems. In this project we designed and evaluated such a system.

Alkhatib, Hasan S.

1995-01-01

471

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

472

Resolutions of the Coulomb operator: VIII. Parallel implementation using the modern programming language X10.  

PubMed

Use of the modern parallel programming language X10 for computing long-range Coulomb and exchange interactions is presented. By using X10, a partitioned global address space language with support for task parallelism and the explicit representation of data locality, the resolution of the Ewald operator can be parallelized in a straightforward manner including use of both intranode and internode parallelism. We evaluate four different schemes for dynamic load balancing of integral calculation using X10's work stealing runtime, and report performance results for long-range HF energy calculation of large molecule/high quality basis running on up to 1024 cores of a high performance cluster machine. PMID:25209872

Limpanuparb, Taweetham; Milthorpe, Josh; Rendell, Alistair P

2014-10-30

473

Fast electrostatic force calculation on parallel computer clusters  

NASA Astrophysics Data System (ADS)

The fast multipole method (FMM) and smooth particle mesh Ewald (SPME) are well known fast algorithms to evaluate long range electrostatic interactions in molecular dynamics and other fields. FMM is a multi-scale method which reduces the computation cost by approximating the potential due to a group of particles at a large distance using few multipole functions. This algorithm scales like O(N) for N particles. SPME algorithm is an O(NlnN) method which is based on an interpolation of the Fourier space part of the Ewald sum and evaluating the resulting convolutions using fast Fourier transform (FFT). Those algorithms suffer from relatively poor efficiency on large parallel machines especially for mid-size problems around hundreds of thousands of atoms. A variation of the FMM, called PWA, based on plane wave expansions is presented in this paper. A new parallelization strategy for PWA, which takes advantage of the specific form of this expansion, is described. Its parallel efficiency is compared with SPME through detail time measurements on two different computer clusters.

Kia, Amirali; Kim, Daejoong; Darve, Eric

2008-10-01

474

Automatic Generation of Directive-Based Parallel Programs for Shared Memory Parallel Systems  

NASA Technical Reports Server (NTRS)

The shared-memory programming model is a very effective way to achieve parallelism on shared memory parallel computers. As great progress was made in hardware and software technologies, performance of parallel programs with compiler directives has demonstrated large improvement. The introduction of OpenMP directives, the industrial standard for shared-memory programming, has minimized the issue of portability. Due to its ease of programming and its good performance, the technique has become very popular. In this study, we have extended CAPTools, a computer-aided parallelization toolkit, to automatically generate directive-based, OpenMP, parallel programs. We outline techniques used in the implementation of the tool and present test results on the NAS parallel benchmarks and ARC3D, a CFD application. This work demonstrates the great potential of using computer-aided tools to quickly port parallel programs and also achieve good performance.

Jin, Hao-Qiang; Yan, Jerry; Frumkin, Michael

2000-01-01

475

XcalableMP implementation and performance of NAS Parallel Benchmarks  

Microsoft Academic Search

XcalableMP is a parallel extension of existing languages, such as C and Fortran, that was proposed as a new programming model to facilitate program parallel applications for distributed memory systems. In order to investigate the performance of parallel programs written in XcalableMP, we have implemented NAS Parallel Benchmarks, specifically, the Embarrassingly Parallel (EP) benchmark, the Integer Sort (IS) benchmark, and

Masahiro Nakao; Jinpil Lee; Taisuke Boku; Mitsuhisa Sato

2010-01-01

476

Data Parallel SwitchLevel Simulation \\Lambda Randal E. Bryant  

E-print Network

Mellon University Abstract Data parallel simulation involves simulating the be­ havior of a circuit over runs on a a massively­ parallel SIMD machine, with each processor simulat­ ing the circuit behavior parallelism in simulation utilize circuit parallelism. In this mode, the simulator extracts parallelism from

Bryant, Randal E.

477

Parallel systems in the control of speech.  

PubMed

Modern neuroimaging techniques have advanced our understanding of the distributed anatomy of speech production, beyond that inferred from clinico-pathological correlations. However, much remains unknown about functional interactions between anatomically distinct components of this speech production network. One reason for this is the need to separate spatially overlapping neural signals supporting diverse cortical functions. We took three separate human functional magnetic resonance imaging (fMRI) datasets (two speech production, one "rest"). In each we decomposed the neural activity within the left posterior perisylvian speech region into discrete components. This decomposition robustly identified two overlapping spatio-temporal components, one centered on the left posterior superior temporal gyrus (pSTG), the other on the adjacent ventral anterior parietal lobe (vAPL). The pSTG was functionally connected with bilateral superior temporal and inferior frontal regions, whereas the vAPL was connected with other parietal regions, lateral and medial. Surprisingly, the components displayed spatial anti-correlation, in which the negative functional connectivity of each component overlapped with the other component's positive functional connectivity, suggesting that these two systems operate separately and possibly in competition. The speech tasks reliably modulated activity in both pSTG and vAPL suggesting they are involved in speech production, but their activity patterns dissociate in response to different speech demands. These components were also identified in subjects at "rest" and not engaged in overt speech production. These findings indicate that the neural architecture underlying speech production involves parallel distinct components that converge within posterior peri-sylvian cortex, explaining, in part, why this region is so important for speech production. PMID:23723184

Simmonds, Anna J; Wise, Richard J S; Collins, Catherine; Redjep, Ozlem; Sharp, David J; Iverson, Paul; Leech, Robert

2014-05-01

478

Parallel preoptic pathways for thermoregulation  

PubMed Central

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.

2009-01-01

479

Solar Wind Turbulence: Perpendicular and Parallel Spectral Transfer  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) turbulence provides a useful framework for understanding the nature and behavior of solar wind fluctuations1. We present a review of MHD turbulence in the solar wind context, where typically ? B / B0 ˜ 1, rather than ? 1. Here B0 denotes the mean or large-scale magnetic field and ? B the rms fluctuation amplitude. We will discuss various consequences of the the well-known anisotropy induced by B0 . For example, the energy transfer is no longer isotropic, with transfer in directions approximately perpendicular to B0 remaining strong whereas parallel transfer is suppressed. Thus, differences in the slope of the energy spectrum in the perpendicular and parallel directions are to be expected. This in turn has implications for scattering of energetic particles. Another consequence of the suppression of parallel transfer is that it restricts the energy available to any kinetic processes which act at large parallel wavenumbers, e.g., ion-cyclotron damping. Since such kinetic processes are likely to be involved in the heating of solar wind fluctuations, the anisotropy of spectral transfer influences heating processes. On the modeling front, anisotropy of spectral transfer helps motivate treating the fluctuations as belonging to two distinct groups, conveniently referred to as the quasi-two-dimensional and the wave-like components. The partitioning is based on the ratio of the nonlinear timescale ? NL(k) to the Alfvén timescale ? A( k) at each wavevector k (see figure). The self interaction of the quasi-2D component is predominantly nonlinear with wave effects being relatively weak. For the wave-like component, the situation is, roughly speaking, reversed. Our presentation will review these concepts and the associated physics. The relevance of the equations of Reduced MHD---originally developed for ? B / B0 ? 1---to solar wind plasma is also discussed. 1 Bruno, R. and Carbone, V., The Solar Wind as a Turbulence Laboratory, Liv. Rev. Sol. Phys., 2 (2005)

Oughton, S.

2011-12-01

480

Parallel Evolutionary Dynamics of Adaptive Diversification in Escherichia coli  

PubMed Central

The causes and mechanisms of evolutionary diversification are central issues in biology. Geographic isolation is the traditional explanation for diversification, but recent theoretical and empirical studies have shown that frequency-dependent selection can drive diversification without isolation and that adaptive diversification occurring in sympatry may be an important source of biological diversity. However, there are no empirical examples in which sympatric lineage splits have been understood at the genetic level, and it is unknown how predictable this process is—that is, whether similar ecological settings lead to parallel evolutionary dynamics of diversification. We documented the genetic basis and the evolutionary dynamics of adaptive diversification in three replicate evolution experiments, in which competition for two carbon sources caused initially isogenic populations of the bacterium Escherichia coli to diversify into two coexisting ecotypes representing different physiological adaptations in the central carbohydrate metabolism. Whole-genome sequencing of clones of each ecotype from different populations revealed many parallel and some unique genetic changes underlying the derived phenotypes, including changes to the same genes and sometimes to the same nucleotide. Timelines of allele frequencies extracted from the frozen “fossil” record of the three evolving populations suggest parallel evolutionary dynamics driven at least in part by a co-evolutionary process in which mutations causing one type of physiology changed the ecological environment, allowing the invasion of mutations causing an alternate physiology. This process closely corresponds to the evolutionary dynamics seen in mathematical models of adaptive diversification due to frequency-dependent ecological interactions. The parallel genetic changes underlying similar phenotypes in independently evolved lineages provide empirical evidence of adaptive diversification as a predictable evolutionary process. PMID:23431270

Herron, Matthew D.; Doebeli, Michael

2013-01-01