Sample records for parallel blade-vortex interaction

  1. Head-on parallel blade-vortex interaction

    NASA Technical Reports Server (NTRS)

    Lee, Soogab; Bershader, Daniel

    1994-01-01

    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.

  2. Measurement of parallel blade-vortex interaction at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Rival, David; Manejev, Roland; Tropea, Cam

    2010-07-01

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

  3. Rotorcraft Blade-Vortex Interaction Controller

    NASA Technical Reports Server (NTRS)

    Schmitz, Fredric H. (Inventor)

    1995-01-01

    Blade-vortex interaction noises, sometimes referred to as 'blade slap', are avoided by increasing the absolute value of inflow to the rotor system of a rotorcraft. This is accomplished by creating a drag force which causes the angle of the tip-path plane of the rotor system to become more negative or more positive.

  4. An adaptive mesh method for the simulation of Blade Vortex Interaction

    E-print Network

    Kim, Kyu-Sup

    1998-01-01

    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...

  5. Experimental observations of two dimensional blade-vortex interaction

    NASA Technical Reports Server (NTRS)

    Booth, E. R., Jr.

    1987-01-01

    Blade-vortex interaction (BVI) is the source mechanism for a prominent impulsive noise created by rotorcraft. An experimental study of two dimensional BVI, a simplified case representing the most intense and impulsive noise generation condition, was performed to explore the fundamental physics associated with the blade-vortex interaction process. The purpose of this paper is to report cumulative results from this experimental study. The interaction process is shown to involve a combination of effects on the vortex including changes in trajectory and distortion of the vortex core shape. The blade involved undergoes significant transient loading. The effects of the interaction process on the blade and the vortex are shown to be increased by both reduction of blade-to-vortex spacing and increase in blade loading. Calculations of the acoustic field produced by the interaction using measured unsteady blade surface pressure data are presented and show acoustic waveforms similar to those obtained from model helicopter acoustic tests.

  6. Blade vortex interaction noise reduction techniques for a rotorcraft

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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).

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

    NASA Technical Reports Server (NTRS)

    Fontana, Richard Remo

    1988-01-01

    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.

  8. Rotor blade system with reduced blade-vortex interaction noise

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  9. Two- and three-dimensional blade vortex interactions

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  10. A Novel Method for Reducing Rotor Blade-Vortex Interaction

    NASA Technical Reports Server (NTRS)

    Glinka, A. T.

    2000-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  12. Transonic blade-vortex interactions noise: A parametric study

    NASA Technical Reports Server (NTRS)

    Lyrintzis, A. S.; Xue, Y.

    1990-01-01

    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.

  13. HART-II: Prediction of Blade-Vortex Interaction Loading

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  15. A comparison of model helicopter rotor Primary and Secondary blade/vortex interaction blade slap

    NASA Technical Reports Server (NTRS)

    Hubbard, J. E., Jr.; Leighton, K. P.

    1983-01-01

    A study of the relative importance of blade/vortex interactions which occur on the retreating side of a model helicopter rotor disk is described. Some of the salient characteristics of this phenomenon are presented and discussed. It is shown that the resulting Secondary blade slap may be of equal or greater intensity than the advancing side (Primary) blade slap. Instrumented model helicopter rotor data is presented which reveals the nature of the retreating blade/vortex interaction. The importance of Secondary blade slap as it applies to predictive techniques or approaches is discussed. When Secondary blade slap occurs it acts to enlarge the window of operating conditions for which blade slap exists.

  16. Helicopter Blade-Vortex Interaction Noise with Comparisons to CFD Calculations

    NASA Technical Reports Server (NTRS)

    McCluer, Megan S.

    1996-01-01

    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.

  17. On the Use of Vortex-Fitting in the Numerical Simulation of Blade-Vortex Interaction

    NASA Technical Reports Server (NTRS)

    Srinivasan, G. R.; VanDalsem, William (Technical Monitor)

    1997-01-01

    The usefulness of vortex-fitting in the computational fluid dynamics (CFD) methods to preserve the vortex strength and structure while convecting in a uniform free stream is demonstrated through the numerical simulations of two- and three-dimensional blade-vortex interactions. The fundamental premise of the formulation is the velocity and pressure field of the interacting vortex are unaltered either in the presence of an airfoil or a rotor blade or by the resulting nonlinear interactional flowfield. Although, the governing Euler and Navier-Stokes equations are nonlinear and independent solutions cannot be superposed, the interactional flowfield can be accurately captured by adding and subtracting the flowfield of the convecting vortex at each instant. The aerodynamics and aeroacoustics of two- and three-dimensional blade-vortex interactions have been calculated in Refs. 1-6 using this concept. Some of the results from these publications and similar other published material will be summarized in this paper.

  18. A new experimental approach to study helicopter blade-vortex interaction noise

    NASA Astrophysics Data System (ADS)

    Koushik, Sudarshan N.

    A unique and novel experimental approach has been developed to study the aerodynamics and acoustics of the helicopter Blade-Vortex Interaction in a controlled hover environment. This is achieved by having a non-lifting single-bladed rotor with a rigid hub interact with a carefully controlled gust disturbance that replicates the essential characteristics of the vortex velocity. This experimental approach termed the Blade-Controlled Disturbance-Interaction or the BCDI, decouples the rotor parameters from the charactersitics of the incident disturbance velocity, thus providing an ideal setup for studying the blade's aerodynamics and acoustic response in detail. Moreover, the angle of interaction between the disturbance field and the rotor blade can be controlled by orienting the gust, providing the ability to study both parallel and oblique interactions. The noise data was recorded at thirty different microphone locations. A series of experiments at various rotor tip Mach numbers and interaction angles, replicating many of the conditions of helicopter BVI, were performed. The results show that the the directionality of the BVI noise is strongly determined by the interaction angle. A small change in interaction angle results in the radiation of noise over a larger azimuthal area compared to the parallel interaction. Moreover, as the interaction becomes more oblique, the peak noise elevation angle approaches closer to the rotor plane. A linear unsteady lifting-line aerodynamic theory (corrected for chord-wise non-compactness) was used to estimate the blade aerodynamics during the interaction and hence the radiated noise. Although the theory under-predicted the noise levels for most of the cases, and did not replicate exactly the general pulse shape, the general directionality trends were predicted reasonably well. The theory was used to separate the contribution to the acoustics, from different spanwise blade sections, providing significant insights into the phasing mechanism of BVI noise.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Jones, Henry E.

    1997-01-01

    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.

  1. A mechanism for mitigation of blade-vortex interaction using leading edge blowing flow control

    NASA Astrophysics Data System (ADS)

    Weiland, Chris; Vlachos, Pavlos P.

    2009-09-01

    The interaction of a vortical unsteady flow with structures is often encountered in engineering applications. Such flow structure interactions (FSI) can be responsible for generating significant loads and can have many detrimental structural and acoustic side effects, such as structural fatigue, radiated noise and even catastrophic results. Amongst the different types of FSI, the parallel blade-vortex interaction (BVI) is the most common, often encountered in helicopters and propulsors. In this work, we report on the implementation of leading edge blowing (LEB) active flow control for successfully minimizing the parallel BVI. Our results show reduction of the airfoil vibrations up to 38% based on the root-mean-square of the vibration velocity amplitude. This technique is based on displacing an incident vortex using a jet issued from the leading edge of a sharp airfoil effectively increasing the stand-off distance of the vortex from the body. The effectiveness of the method was experimentally analyzed using time-resolved digital particle image velocimetry (TRDPIV) recorded at an 800 Hz rate, which is sufficient to resolve the spatio-temporal dynamics of the flow field and it was combined with simultaneous accelerometer measurements of the airfoil, which was free to oscillate in a direction perpendicular to the freestream. Analysis of the flow field spectra and a Proper Orthogonal Decomposition (POD) of the TRDPIV data of the temporally resolved planar flow fields indicate that the LEB effectively modified the flow field surrounding the airfoil and increased the convecting vortices stand-off distance for over half of the airfoil chord length. It is shown that LEB also causes a redistribution of the flow field spectral energy over a larger range of frequencies.

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

    NASA Astrophysics Data System (ADS)

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

    1984-01-01

    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.

  3. A descriptive model of the flows underlying the impulsive loading produced by blade-vortex interaction

    SciTech Connect

    Horner, M.B. [Univ. of Colorado, Boulder, CO (United States). Dept. of Aerospace Engineering; Galbraith, R.A.M.; Coton, F.N. [Univ. of Glasgow (United Kingdom). Dept. of Aerospace Engineering; Grant, I. [Heriot-Watt Univ., Edinburgh (United Kingdom). Dept. of Civil and Offshore Engineering; Stewart, J.N. [Imperial College, London (United Kingdom). Dept. of Aeronautics; Iglesia Moreno, F. de la [Univ. of Madrid (Spain). Dept. of Aerospace Engineering

    1995-09-01

    The results of two experimental studies and one numerical simulation of the flows generated about the rotor blade during Blade-Vortex Interaction (BVI) are summarized, and the salient findings of these studies are encapsulated i a descriptive model of the BVI flow field. In this model the flow field is reduced to a collection of discrete vortical components. These vortical structures are characterized as acting independently, with the net effect upon blade performance resulting from a superposition of the effects of each structure.

  4. An Euler code calculation of blade-vortex interaction noise

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  5. A new look at sound generation by blade/vortex interaction

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.; Mason, J. P.

    1985-01-01

    As a preliminary attempt to understand the dynamics of blade/vortex interaction, the two-dimensional problem of a rectilinear vortex filament interacting with a Joukowski airfoil is analyzed in both the lifting and nonlifting cases. The vortex velocity components could be obtained analytically and integrated to determine the vortex trajectory. With this information, the aeroacoustic low-frequency Green's function approach could then be employed to calculate the sound produced during the encounter. The results indicate that the vortex path deviates considerably from simple convection due to the presence of the airfoil and that a reasonably sharp sound pulse is radiated during the interaction whose fundamental frequency is critically dependent upon whether the vortex passes above or below the airfoil. Determination of this gross parameter of the interaction is shown to be highly nonlinearly dependent upon airfoil circulation, vortex circulation, and initial position.

  6. Numerical simulations of three-dimensional rotor blade-vortex interactions

    NASA Technical Reports Server (NTRS)

    Hassan, A. A.; Charles, B. D.

    1990-01-01

    A numerical procedure which has been developed (Hassan and Charles, 1989) for the prediction of helicopter blade loads during self-generated blade-vortex interactions (BVI) is described. These BVIs result in significant and frequent impulsive changes in the rotor blade aerodynamic loads and moments that are known to lead to vibrations and severe noise problems. Potential BVIs are identified and tracked in time at even increments of rotor azimuth employing the lifting line helicopter/rotor trim code CAMRAD. The accuracy of the predicted leading edge pressures for self-generated interactions is shown to rely heavily on the user-specified vortex core radius, and more significantly on the CAMRAD-predicted geometry of the interaction vortex elements and their relative orientation with respect to the blade. Thus, the robustness of the surface transpiration approach for modeling subcritical-type BVIs is proven.

  7. A study of blade-vortex interaction sound generation and directionality

    NASA Astrophysics Data System (ADS)

    Ringler, Todd D.; George, Albert R.; Steele, James B.

    1991-05-01

    The directionality and strength of blade-vortex interactions (BVI) is explained through the radiation cone concept. BVI acoustic radiation is primarily the result of two sound mechanisms: the tip effect, and the radiation cone effect. The radiation cone effect is a highly directional mechanism which results when a lift distribution moves supersonically with respect to the fluid. After a physical explanation of the BVI mechanisms, sample cases using translating and rotating blades interacting with a straight line vortex are shown. The radiation cone concept is then applied to specific rotorcraft cases where it helps to explain zones of intense sound pressure level found in experimental results for the XV-15 tiltrotor and for a BO-105 helicopter scale model.

  8. Lift distribution and velocity field measurements for a three-dimensional, steady blade/vortex interaction

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.; Norman, Thomas R.

    1987-01-01

    A wind tunnel experiment simulating a steady three-dimensional helicopter rotor blade/vortex interaction is reported. The experimental configuration consisted of a vertical semispan vortex-generating wing, mounted upstream of a horizontal semispan rotor blade airfoil. A three-dimensional laser velocimeter was used to measure the velocity field in the region of the blade. Sectional lift coefficients were calculated by integrating the velocity field to obtain the bound vorticity. Total lift values, obtained by using an internal strain-gauge balance, verified the laser velocimeter data. Parametric variations of vortex strength, rotor blade angle of attack, and vortex position relative to the rotor blade were explored. These data are reported (with attention to experimental limitations) to provide a dataset for the validation of analytical work.

  9. Mach number scaling of helicopter rotor blade/vortex interaction noise

    NASA Technical Reports Server (NTRS)

    Leighton, Kenneth P.; Harris, Wesley L.

    1985-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Schmitz, Fredric H.

    1995-01-01

    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.

  11. Correlation of helicopter impulsive noise from blade-vortex interaction with rotor mean inflow

    NASA Technical Reports Server (NTRS)

    Connor, Andrew B.; Martin, R. M.

    1987-01-01

    Data from a test made in the Langley 4 x 7 Meter Tunnel were parametrically studied with respect to the occurrence of blade-vortex interaction (BVI) as a function of tunnel speed and rotor angle of attack. Three microphones on the tunnel centerline forward of the model and one microphone forward and 45 degrees to the right provided the data. The rotor model was tested with a set of high-twist blades (-10 degrees) and a set of low-twist blades (-5 degrees) over the midspeed range (50 to 80 knots) at angles of attack ranging from -6 degrees (shallow climb) to 10 degrees (steep descent). The data from all four microphones indicated that the most probable time of occurrence of BVI is when the rotor descent is approximately equal to the rotor mean inflow velocity. However, some of the data showed no conclusive relationship to the mean inflow velocity.

  12. Blade-Vortex Interaction (BVI) Noise and Airload Prediction Using Loose Aerodynamic/Structural Coupling

    NASA Technical Reports Server (NTRS)

    Sim, B. W.; Lim, J. W.

    2007-01-01

    Predictions of blade-vortex interaction (BVI) noise, using blade airloads obtained from a coupled aerodynamic and structural methodology, are presented. This methodology uses an iterative, loosely-coupled trim strategy to cycle information between the OVERFLOW-2 (CFD) and CAMRAD-II (CSD) codes. Results are compared to the HART-II baseline, minimum noise and minimum vibration conditions. It is shown that this CFD/CSD state-of-the-art approach is able to capture blade airload and noise radiation characteristics associated with BVI. With the exception of the HART-II minimum noise condition, predicted advancing and retreating side BVI for the baseline and minimum vibration conditions agrees favorably with measured data. Although the BVI airloads and noise amplitudes are generally under-predicted, this CFD/CSD methodology provides an overall noteworthy improvement over the lifting line aerodynamics and free-wake models typically used in CSD comprehensive analysis codes.

  13. Wake Geometry Effects on Rotor Blade-Vortex Interaction Noise Directivity

    NASA Technical Reports Server (NTRS)

    Martin, R. M.; Marcolini, Michael A.; Splettstoesser, W. R.; Schultz, K.-J.

    1990-01-01

    Acoustic measurements from a model rotor wind tunnel test are presented which show that the directionality of rotor blade vortex interaction (BVI) noise is strongly dependent on the rotor advance ratio and disk attitude. A rotor free wake analysis is used to show that the general locus of interactions on the rotor disk is also strongly dependent on advance ratio and disk attitude. A comparison of the changing directionality of the BVI noise with changes in the interaction locations shows that the strongest noise radiation occurs in the direction of motion normal to the blade span at the time of interaction, for both advancing and retreating side BVI. For advancing side interactions, the BVI radiation angle down from the tip-path plane appears relatively insensitive to rotor operating condition and is typically between 40 and 55 deg below the disk. However, the azimuthal radiation direction shows a clear trend with descent speed, moving towards the right of the flight path with increasing descent speed. The movement of the strongest radiation direction is attributed to the movement of the interaction locations on the rotor disk with increasing descent speed.

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

    NASA Astrophysics Data System (ADS)

    Tauszig, Lionel Christian

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Lyrintzis, Anastasios S.; Xue, Y.

    1990-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Rogers, James C.; Dai, Renshou

    1998-01-01

    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.

  20. Effects of a trailing edge flap on the aerodynamics and acoustics of rotor blade-vortex interactions

    NASA Technical Reports Server (NTRS)

    Charles, B. D.; Tadghighi, H.; Hassan, A. A.

    1992-01-01

    The use of a trailing edge flap on a helicopter rotor has been numerically simulated to determine if such a device can mitigate the acoustics of blade vortex interactions (BVI). The numerical procedure employs CAMRAD/JA, a lifting-line helicopter rotor trim code, in conjunction with RFS2, an unsteady transonic full-potential flow solver, and WOPWOP, an acoustic model based on Farassat's formulation 1A. The codes were modified to simulate trailing edge flap effects. The CAMRAD/JA code was used to compute the far wake inflow effects and the vortex wake trajectories and strengths which are utilized by RFS2 to predict the blade surface pressure variations. These pressures were then analyzed using WOPWOP to determine the high frequency acoustic response at several fixed observer locations below the rotor disk. Comparisons were made with different flap deflection amplitudes and rates to assess flap effects on BVI. Numerical experiments were carried out using a one-seventh scale AH-1G rotor system for flight conditions simulating BVI encountered during low speed descending flight with and without flaps. Predicted blade surface pressures and acoustic sound pressure levels obtained have shown good agreement with the baseline no-flap test data obtained in the DNW wind tunnel. Numerical results indicate that the use of flaps is beneficial in reducing BVI noise.

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

    NASA Technical Reports Server (NTRS)

    Wittmer, Kenneth S.; Devenport, William J.

    1996-01-01

    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.

  2. Prediction of blade-vortex interaction noise from measured blade pressure

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.

    1981-01-01

    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.

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

    E-print Network

    Nelson, Carter T.

    1997-01-01

    noise occur are shown in Figure 2 for a particular helicopter (adapted from Smith and Sigl2). It can be seen that the high speed impulsive noise is basically a locus of points formed by the proper combination of forward speed and rate of climb...- vortex interaction, a second issue must also be addressed: How will the flap be deployed? Due to the extremely confining space inside a typical helicopter rotor blade as well as the high g- loadings, most conventional means of actuation...

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

    NASA Astrophysics Data System (ADS)

    Malovrh, Brendon D.

    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.

  5. 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)

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

    1984-01-01

    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.

  6. Numerical simulation and validation of helicopter blade-vortex interaction using coupled CFD/CSD and three levels of aerodynamic modeling

    NASA Astrophysics Data System (ADS)

    Amiraux, Mathieu

    Rotorcraft Blade-Vortex Interaction (BVI) remains one of the most challenging flow phenomenon to simulate numerically. Over the past decade, the HART-II rotor test and its extensive experimental dataset has been a major database for validation of CFD codes. Its strong BVI signature, with high levels of intrusive noise and vibrations, makes it a difficult test for computational methods. The main challenge is to accurately capture and preserve the vortices which interact with the rotor, while predicting correct blade deformations and loading. This doctoral dissertation presents the application of a coupled CFD/CSD methodology to the problem of helicopter BVI and compares three levels of fidelity for aerodynamic modeling: a hybrid lifting-line/free-wake (wake coupling) method, with modified compressible unsteady model; a hybrid URANS/free-wake method; and a URANS-based wake capturing method, using multiple overset meshes to capture the entire flow field. To further increase numerical correlation, three helicopter fuselage models are implemented in the framework. The first is a high resolution 3D GPU panel code; the second is an immersed boundary based method, with 3D elliptic grid adaption; the last one uses a body-fitted, curvilinear fuselage mesh. The main contribution of this work is the implementation and systematic comparison of multiple numerical methods to perform BVI modeling. The trade-offs between solution accuracy and computational cost are highlighted for the different approaches. Various improvements have been made to each code to enhance physical fidelity, while advanced technologies, such as GPU computing, have been employed to increase efficiency. The resulting numerical setup covers all aspects of the simulation creating a truly multi-fidelity and multi-physics framework. Overall, the wake capturing approach showed the best BVI phasing correlation and good blade deflection predictions, with slightly under-predicted aerodynamic loading magnitudes. However, it proved to be much more expensive than the other two methods. Wake coupling with RANS solver had very good loading magnitude predictions, and therefore good acoustic intensities, with acceptable computational cost. The lifting-line based technique often had over-predicted aerodynamic levels, due to the degree of empiricism of the model, but its very short run-times, thanks to GPU technology, makes it a very attractive approach.

  7. A reduced Blade-Vortex Interaction rotor

    E-print Network

    Mani, Somnath

    1996-01-01

    180 210 330 0 0 240 300 270 150 120 0 0 901 8. 8 0. 6 0. 4 30 180 210 330 240 270 300 150 120 0 0 901 60 0. 6 0. 4 30 180 210 330 240 270 300 150 120 0 901 60 0. 8 o 0. 6 0. 4 30 180 210 330 0 240 270 300... 330 240 270 300 150 120 0 901 0. 6 0. 4 60 30 180 210 330 240 270 300 'I 50 120 0 901 60 0. 8 0. 6 0. 4 30 180 210 330 0 240 270 300 35 3. 00 2. 00 @=at a=1 CO 0 1. 00 CV X 4) fo il K 0. 00 -1. 00 0. 00 4000...

  8. Aerodynamic loads and blade vortex interaction noise prediction

    Microsoft Academic Search

    M. Schaffar; J. Haertig; P. Gnemmi

    1990-01-01

    The vortex lattice method is described and applied in order to predict the aerodynamic loads on a thin two-bladed rotor. A local conformal mapping for each position in span is used to transform the thin rotor into a thick one. The pressure coefficients obtained for the thick rotor are fed into an acoustic code which is based on the Ffowcs-Williams-Hawkings

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  10. Parallel processing interactively simulates complex VLSI logic

    SciTech Connect

    Howard, J.K.; Malm, R.L.; Warren, L.M.

    1983-12-15

    To break the simulation bottleneck that has slowed designers of very large-scale integrated circuits, engineers at IBM developed the logic simulation machine, a hardware logic simulator. This dedicated, highly parallel computer simulates logic at a functional or gate level at speeds up to 100000 times faster than software simulators. In fact, it is so fast that designers can perform logic simulations interactively, experimenting with several designs and choosing the best one.

  11. Parallel Vegetation Stripe Formation Through Hydrologic Interactions

    NASA Astrophysics Data System (ADS)

    Cheng, Yiwei; Stieglitz, Marc; Turk, Greg; Engel, Victor

    2010-05-01

    It has long been a challenge to theoretical ecologists to describe vegetation pattern formations such as the "tiger bush" stripes and "leopard bush" spots in Niger, and the regular maze patterns often observed in bogs in North America and Eurasia. To date, most of simulation models focus on reproducing the spot and labyrinthine patterns, and on the vegetation bands which form perpendicular to surface and groundwater flow directions. Various hypotheses have been invoked to explain the formation of vegetation patterns: selective grazing by herbivores, fire, and anisotropic environmental conditions such as slope. Recently, short distance facilitation and long distance competition between vegetation (a.k.a scale dependent feedback) has been proposed as a generic mechanism for vegetation pattern formation. In this paper, we test the generality of this mechanism by employing an existing, spatially explicit, advection-reaction-diffusion type model to describe the formation of regularly spaced vegetation bands, including those that are parallel to flow direction. Such vegetation patterns are, for example, characteristic of the ridge and slough habitat in the Florida Everglades and which are thought to have formed parallel to the prevailing surface water flow direction. To our knowledge, this is the first time that a simple model encompassing a nutrient accumulation mechanism along with biomass development and flow is used to demonstrate the formation of parallel stripes. We also explore the interactive effects of plant transpiration, slope and anisotropic hydraulic conductivity on the resulting vegetation pattern. Our results highlight the ability of the short distance facilitation and long distance competition mechanism to explain the formation of the different vegetation patterns beyond semi-arid regions. Therefore, we propose that the parallel stripes, like the other periodic patterns observed in both isotropic and anisotropic environments, are self-organized and form as a result of scale dependent feedback. Results from this study improve upon the current understanding on the formation of parallel stripes and provide a more general theoretical framework for future empirical and modeling efforts.

  12. Parallel Mean Shift for Interactive Volume Segmentation

    NASA Astrophysics Data System (ADS)

    Zhou, Fangfang; Zhao, Ying; Ma, Kwan-Liu

    In this paper we present a parallel dynamic mean shift algorithm based on path transmission for medical volume data segmentation. The algorithm first translates the volume data into a joint position-color feature space subdivided uniformly by bandwidths, and then clusters points in feature space in parallel by iteratively finding its peak point. Over iterations it improves the convergent rate by dynamically updating data points via path transmission and reduces the amount of data points by collapsing overlapping points into one point. The GPU implementation of the algorithm can segment 256x256x256 volume in 6 seconds using an NVIDIA GeForce 8800 GTX card for interactive processing, which is hundreds times faster than its CPU implementation. We also introduce an interactive interface to segment volume data based on this GPU implementation. This interface not only provides the user with the capability to specify segmentation resolution, but also allows the user to operate on the segmented tissues and create desired visualization results.

  13. Fracture closure in extension and mechanical interaction of parallel joints

    Microsoft Academic Search

    Leonid N. Germanovich; Dmitriy K. Astakhov

    2004-01-01

    It is well known that in many cases rock permeability depends upon in situ stress conditions and on the pressure of the flowing fluid. Parallel and quasi-parallel joints represent one of the most often observed permeability structures. Frequently, joint sets are closely spaced and although joint mechanical interaction could significantly affect their aperture, the interaction is usually ignored in the

  14. Interaction between overlapping parallel cracks; a photoelastic study

    Microsoft Academic Search

    F. F. Lange

    1968-01-01

    The interaction between two parallel cracks with a variable overlap distance in a tensile stress field was investigated. The principal stress trajectory patterns and the curves of constant shear stress for the interacting crack tips are presented. It was found that a) the stresses at the interacting crack tips are smaller than the noninteracting or outer crack tips and b)

  15. Investigation of helicopter rotor blade/wake interactive impulsive noise

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  16. Verifiable Computation with Massively Parallel Interactive Proofs

    E-print Network

    Thaler, Justin; Mitzenmacher, Michael; Pfister, Hanspeter

    2012-01-01

    As the cloud computing paradigm has gained prominence, the need for verifiable computation has grown increasingly urgent. The concept of verifiable computation enables a weak client to outsource difficult computations to a powerful, but untrusted, server. Protocols for verifiable computation aim to provide the client with a guarantee that the server performed the requested computations correctly, without requiring the client to perform the computations herself. By design, these protocols impose a minimal computational burden on the client. However, existing protocols require the server to perform a large amount of extra bookkeeping in order to enable a client to easily verify the results. Verifiable computation has thus remained a theoretical curiosity, and protocols for it have not been implemented in real cloud computing systems. Our goal is to leverage GPUs to reduce the server-side slowdown for verifiable computation. To this end, we identify abundant data parallelism in a state-of-the-art general-purpose...

  17. An interactive parallel programming environment applied in atmospheric science

    SciTech Connect

    Laszewski, G. von

    1996-12-31

    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.

  18. An interactive parallel programming environment applied in atmospheric science

    NASA Technical Reports Server (NTRS)

    vonLaszewski, G.

    1996-01-01

    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.

  19. Interaction of a turbulent vortex with a lifting surface

    NASA Technical Reports Server (NTRS)

    Lee, D. J.; Roberts, L.

    1985-01-01

    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.

  20. Framework for Interactive Parallel Dataset Analysis on the Grid

    SciTech Connect

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

    2007-01-10

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

  1. Long-Range Hydrodynamic Interactions Implemented into LAMMPS (Parallel MD)

    NASA Astrophysics Data System (ADS)

    Mackay, Frances; Denniston, Colin

    2009-03-01

    We use an explicit solvent method to study the interaction between particles and a fluid. Similar to the Particle-Mesh-Ewald schemes for electrodynamics, the long range hydrodynamic interactions are treated by interpolating the particle density onto a mesh. This is then coupled to the fluid, which we model using a thermal lattice Boltzmann scheme. Mass and momentum conserving noise in the lattice Boltzmann fluid scheme provides a thermostat for both the fluid and the particles. This work has been fully parallelized and implemented into LAMMPS, an open-source molecular dynamics code. We demonstrate the scheme with some examples from colloidal physics and flow over rough surfaces.

  2. Time-to-Coalescence for Interacting Particle Systems: Parallel versus Sequential Updating

    E-print Network

    Potsdam, Universität

    Time-to-Coalescence for Interacting Particle Systems: Parallel versus Sequential Updating Pierre Wahrscheinlichkeitstheorie Time-to-Coalescence for Interacting Particle Systems: Parallel versus Sequential Updating Pierre@math.uni-potsdam.de ISSN 1613-3307 #12;Time-to-Coalescence for Interacting Particle Systems: Parallel versus Sequential

  3. Parallel algorithms for interactive manipulation of digital terrain models

    NASA Technical Reports Server (NTRS)

    Davis, E. W.; Mcallister, D. F.; Nagaraj, V.

    1988-01-01

    Interactive three-dimensional graphics applications, such as terrain data representation and manipulation, require extensive arithmetic processing. Massively parallel machines are attractive for this application since they offer high computational rates, and grid connected architectures provide a natural mapping for grid based terrain models. Presented here are algorithms for data movement on the massive parallel processor (MPP) in support of pan and zoom functions over large data grids. It is an extension of earlier work that demonstrated real-time performance of graphics functions on grids that were equal in size to the physical dimensions of the MPP. When the dimensions of a data grid exceed the processing array size, data is packed in the array memory. Windows of the total data grid are interactively selected for processing. Movement of packed data is needed to distribute items across the array for efficient parallel processing. Execution time for data movement was found to exceed that for arithmetic aspects of graphics functions. Performance figures are given for routines written in MPP Pascal.

  4. Long-range interactions and parallel scalability in molecular simulations

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

    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 modeling 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.

  5. Parallel Force Assay for Protein-Protein Interactions

    PubMed Central

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

    2014-01-01

    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

  6. Mutual interaction between parallel Gaussian electromagnetic beams in plasmas

    SciTech Connect

    Sodha, Mahendra Singh; Agarwal, Sujeet Kumar; Sharma, Ashutosh [Disha Academy of Research and Education, Disha Crown, Katchna Road, Shankar Nagar, Raipur-492007 (India); DST Project, Department of Education Building, Lucknow University, Lucknow-226007 (India)

    2006-10-15

    In this paper, the interaction between two Gaussian electromagnetic beams in a plasma has been investigated, when the axes of the two beams are initially (z=0) parallel along the z axis in the x-z plane; the beams are initially propagating in the z direction. For the three types of nonlinearities (viz., collisional, ponderomotive, and relativistic) the dielectric function has been expressed as a function of the irradiances of the two beams; this expression for the dielectric function has been substituted in the wave equation and a solution of the resulting nonlinear equation obtained in the paraxial approximation. The paraxial approximation is justified since the phenomena of interest occur when the beams are initially close ({radical}(2)x{sub 0}{<=}r{sub 0}). Further, the absorption of the beam in the plasma has been neglected, which is justified when the electron collision frequency is much less than the frequencies of the beams. Second-order coupled ordinary differential equations have been obtained for the distance between the centers of the beams and the beam widths in the x and y directions as a function of the distance of propagation along the z axis. The equations have been solved numerically for a range of parameters and a discussion of the results is presented.

  7. VisIt: Interactive Parallel Visualization and Graphical Analysis Tool

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

  8. Interaction of a pair of parallel scroll waves.

    PubMed

    Kupitz, Dennis; Hauser, Marcus J B

    2013-12-01

    Interactions of pairs of scroll waves in three-dimensional excitable media were studied experimentally in the Belousov-Zhabotinsky reaction by optical tomography. The behavior of two scroll waves depended on the distance d between their filaments. When the interfilament distance was shorter than the wavelength ? of the scroll waves (but larger than the diameter of the spiral core), the filaments repelled each other. Once d ? ?, the two scroll waves synchronized, rotating around their filaments with both a common rotation frequency and a common pitch. The interfilament distance of synchronized scroll waves did not change. When fluctuations broke the symmetry of the rotation periods, the scroll with higher rotation frequency displaced the slower rotating one, until the latter was ousted or even annihilated. These behaviors were independent of the sense of rotation (co- or counter-rotating), the filament dynamics (rigidly rotating or meandering tip motion in two-dimensional media), and the presence or absence of a gradient of excitability parallel to the filaments. PMID:24199616

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

    Microsoft Academic Search

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

    2010-01-01

    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

  10. Combined Series and Parallel Circuits: Interactive Lecture Demonstrations

    NSDL National Science Digital Library

    Bruce Mason

    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.

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

    E-print Network

    Keener, Todd Whitney

    1996-01-01

    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...

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

    Microsoft Academic Search

    Rajeev Muralidhar; Samian Kaur; Manish Parashar

    2000-01-01

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

  13. Interactive animation of fault-tolerant parallel algorithms

    SciTech Connect

    Apgar, S.W.

    1992-02-01

    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.

  14. Simulations of Ion Thruster Plume–Spacecraft Interactions on Parallel Supercomputer

    Microsoft Academic Search

    Joseph Wang; Yong Cao; Raed Kafafy; Julien Pierru; Viktor K. Decyk

    2006-01-01

    A parallel three-dimensional electrostatic Particle-In-Cell (PIC) code is developed for large-scale simulations of ion thruster plume-spacecraft interactions on parallel supercomputers. This code is based on a newly developed immersed finite-element (IFE) PIC. The IFE-PIC is designed to handle complex boundary conditions accurately while maintaining the computational speed of the standard PIC code. Domain decomposition is used in both field solve

  15. Plasma acceleration by the interaction of parallel propagating Alfvén waves

    NASA Astrophysics Data System (ADS)

    Mottez, F.; Mottez

    2015-01-01

    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.

  16. Propeller tip vortex interactions

    NASA Technical Reports Server (NTRS)

    Johnston, Robert T.; Sullivan, John P.

    1990-01-01

    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.

  17. The prediction of blade wake interaction noise based on a turbulent vortex model

    NASA Technical Reports Server (NTRS)

    Glegg, Stewart A. L.

    1989-01-01

    Blade wake interaction is defined as the broadband noise generated by the interaction of helicopter rotor blades with their own wake. Experimental observations have shown that this is a strong function of advance ratio and tip path plane angle. This paper describes how this noise source can be associated with the blade vortex interactions in the forward sector of the rotor. Measured levels of turbulence in the vortex core are used to predict the broadband noise levels with some success. However, more detailed information on the turbulence spectrum and the trajectory of the shed vortices is required before more accurate noise predictions can be made.

  18. Bayesian seismic tomography by parallel interacting Markov chains

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  19. Parallel finite element simulation of 3D incompressible flows: Fluid-structure interactions

    Microsoft Academic Search

    S. Mittal; T. E. Tezduyar

    1995-01-01

    SUMMARY Massively parallel finite element computations of 3D, unsteady incompressible flows, including those involving fluid-structure interactions, are presented. The computations with time-varying spatial domains are based on the deforming spatial domain\\/stabilized space-time (DSD\\/SST) finite element formulation. The capability to solve 3D problems involving fluid-structure interactions is demonstrated by investigating the dynamics of a fle~ible cantilevered pipe conveying fluid. Computations of

  20. Theory and modelling of the interaction of two parallel supersonic plasma jets

    Microsoft Academic Search

    E. Gidalevich; R. L. Boxman; S. Goldsmith

    1998-01-01

    The objective of the present work is to predict the profile of the shock front formed by the interaction of two parallel diverging supersonic plasma jets. The form of the front is determined by the divergence of the plasma jets and by the distance between their sources, but the maximum angle of the front inclination at the head point of

  1. A parallel iterative partitioned coupling analysis system for large-scale acoustic fluid-structure interactions

    NASA Astrophysics Data System (ADS)

    Kataoka, Shunji; Minami, Satsuki; Kawai, Hiroshi; Yamada, Tomonori; Yoshimura, Shinobu

    2014-06-01

    In many engineering fields, dynamic response in fluid-structure interaction (FSI) is important, and some of the FSI phenomena are treated as acoustic FSI (AFSI) problems. Dynamic interactions between fluids and structures may change dynamic characteristics of the structure and its response to external excitation parameters such as seismic loading. This paper describes a parallel coupling analysis system for large-scale AFSI problems using iterative partitioned coupling techniques. We employ an open source parallel finite element analysis system called ADVENTURE, which adopts an efficient preconditioned iterative linear algebraic solver. In addition, we have recently developed a parallel coupling tool called ADVENTURE_Coupler to efficiently handle interface variables in various parallel computing environments. We also employ the Broyden method for updating interface variables to attain robust and fast convergence of fixed-point iterations. This paper describes key features of the coupling analysis system developed, and we perform tests to validate its performance for several AFSI problems. The system runs efficiently in a parallel environment, and it is capable of analyzing three-dimensional-complex-shaped structures with more than 20 million degrees-of-freedom (DOFs). Its numerical results also show good agreement with experimental results.

  2. Cell interaction with graphene microsheets: near-orthogonal cutting versus parallel attachment

    NASA Astrophysics Data System (ADS)

    Yi, Xin; Gao, Huajian

    2015-03-01

    Recent experiments indicate that graphene microsheets can either undergo a near-orthogonal cutting or a parallel attachment mode of interaction with cell membranes. Here we perform a theoretical analysis to characterize the deformed membrane microstructure and investigate how these two interaction modes are influenced by the splay, tilt, compression, tension, bending and adhesion energies of the membrane. Our analysis indicates that, driven by the membrane splay and tension energies, a two-dimensional microsheet such as graphene would adopt a near-perpendicular configuration with respect to the membrane in the transmembrane penetration mode, whereas the membrane bending and tension energies would lead to parallel attachment in the absence of cross membrane penetration. These interaction modes may have broad implications in applications involving drug delivery, cell encapsulation and protection, and the measurement of the dynamic cell response.

  3. Interactive Parallel Data Analysis within Data-Centric Cluster Facilities using the IPython Notebook

    NASA Astrophysics Data System (ADS)

    Pascoe, S.; Lansdowne, J.; Iwi, A.; Stephens, A.; Kershaw, P.

    2012-12-01

    The data deluge is making traditional analysis workflows for many researchers obsolete. Support for parallelism within popular tools such as matlab, IDL and NCO is not well developed and rarely used. However parallelism is necessary for processing modern data volumes on a timescale conducive to curiosity-driven analysis. Furthermore, for peta-scale datasets such as the CMIP5 archive, it is no longer practical to bring an entire dataset to a researcher's workstation for analysis, or even to their institutional cluster. Therefore, there is an increasing need to develop new analysis platforms which both enable processing at the point of data storage and which provides parallelism. Such an environment should, where possible, maintain the convenience and familiarity of our current analysis environments to encourage curiosity-driven research. We describe how we are combining the interactive python shell (IPython) with our JASMIN data-cluster infrastructure. IPython has been specifically designed to bridge the gap between the HPC-style parallel workflows and the opportunistic curiosity-driven analysis usually carried out using domain specific languages and scriptable tools. IPython offers a web-based interactive environment, the IPython notebook, and a cluster engine for parallelism all underpinned by the well-respected Python/Scipy scientific programming stack. JASMIN is designed to support the data analysis requirements of the UK and European climate and earth system modeling community. JASMIN, with its sister facility CEMS focusing the earth observation community, has 4.5 PB of fast parallel disk storage alongside over 370 computing cores provide local computation. Through the IPython interface to JASMIN, users can make efficient use of JASMIN's multi-core virtual machines to perform interactive analysis on all cores simultaneously or can configure IPython clusters across multiple VMs. Larger-scale clusters can be provisioned through JASMIN's batch scheduling system. Outputs can be summarised and visualised using the full power of Python's many scientific tools, including Scipy, Matplotlib, Pandas and CDAT. This rich user experience is delivered through the user's web browser; maintaining the interactive feel of a workstation-based environment with the parallel power of a remote data-centric processing facility.

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

    Microsoft Academic Search

    Yasuo Osawa

    1999-01-01

    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,

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

    SciTech Connect

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

    2007-08-01

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

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

    SciTech Connect

    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

    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.

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

    PubMed

    Gopakumar, Rajesh

    2002-10-21

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

  8. Rotor-vortex interaction noise

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1983-01-01

    A theoretical and experimental study was conducted to develop a validated first principles analysis for predicting noise generated by helicopter main-rotor shed vortices interacting with the tail rotor. The generalized prediction procedure requires a knowledge of the incident vortex velocity field, rotor geometry, and rotor operating conditions. The analysis includes compressibility effects, chordwise and spanwise noncompactness, and treats oblique intersections with the blade planform. Assessment of the theory involved conducting a model rotor experiment which isolated the blade-vortex interaction noise from other rotor noise mechanisms. An isolated tip vortex, generated by an upstream semispan airfoil, was convected into the model tail rotor. Acoustic spectra, pressure signatures, and directivity were measured. Since assessment of the acoustic prediction required a knowledge of the vortex properties, blade-vortes intersection angle, intersection station, vortex stength, and vortex core radius were documented. Ingestion of the vortex by the rotor was experimentally observed to generate harmonic noise and impulsive waveforms.

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

    SciTech Connect

    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

    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.

  10. Van Der Waals Interaction between Two Parallel Radially Deformed Single Wall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Popescu, Adrian; Woods, Lilia; Bondarev, Igor

    2008-03-01

    The van der Waals potential energy is calculated between two parallel infinitely long radially deformed single walled carbon nanotubes within the pairwise Lennard-Jones approximation for extended systems. The nanotubes will undergo different geometrical radial shape transitions if an external hydrostatic pressure with an increasing strength is applied. We describe these shapes with analytically in order to facilitate the calculations. The most preferred mutual orientations are determined in all considered cases in terms of their potential well depths, equilibrium distances, and geometrical parameters. We find that the interaction evolves in such a way as to keep the distance between the interacting surfaces comparable to the graphene-graphene distance in graphite. In addition, the universal graphitic potential concept is extended to radially deformed carbon nanotubes. These results can be used as a guide for future experiments to investigate interactions between deformed carbon nanotubes.

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

    PubMed Central

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

    2011-01-01

    Systems Factorial Technology is a powerful framework for investigating the fundamental properties of human information processing such as architecture (i.e., serial or parallel processing) and capacity (how processing efficiency is affected by increased workload). The Survivor Interaction Contrast (SIC) and the Capacity Coefficient are effective measures in determining these underlying properties, based on response-time data. Each of the different architectures, under the assumption of independent processing, predicts a specific form of the SIC along with some range of capacity. In this study, we explored SIC predictions of discrete-state (Markov process) and continuous-state (Linear Dynamic) models that allow for certain types of cross-channel interaction. The interaction can be facilitatory or inhibitory: one channel can either facilitate, or slow down processing in its counterpart. Despite the relative generality of these models, the combination of the architecture-oriented plus the capacity oriented analyses provide for precise identification of the underlying system. PMID:21516183

  12. Dynamical interaction effects on an electric dipole moving parallel to a flat solid surface

    NASA Astrophysics Data System (ADS)

    Villó-Pérez, Isidro; Abril, Isabel; Garcia-Molina, Rafael; Arista, Néstor R.

    2005-05-01

    The interaction experienced by a fast electric dipole moving parallel and close to a flat solid surface is studied using the dielectric formalism. Analytical expressions for the force acting on the dipole, for random and for particular orientations, are obtained. Several features related to the dynamical effects on the induced forces are discussed, and numerical values are obtained for the different cases. The calculated energy loss of the electric dipole provides useful estimations which could be of interest for small-angle scattering experiments using polar molecules.

  13. Far-field approximation for hydrodynamic interactions in parallel-wall geometry

    E-print Network

    S. Bhattacharya; J. Blawzdziewicz; E. Wajnryb

    2005-04-27

    A complete analysis is presented for the far-field creeping flow produced by a multipolar force distribution in a fluid confined between two parallel planar walls. We show that at distances larger than several wall separations the flow field assumes the Hele-Shaw form, i.e., it is parallel to the walls and varies quadratically in the transverse direction. The associated pressure field is a two-dimensional harmonic function that is characterized by the same multipolar number m as the original force multipole. Using these results we derive asymptotic expressions for the Green's matrix that represents Stokes flow in the wall-bounded fluid in terms of a multipolar spherical basis. This Green's matrix plays a central role in our recently proposed algorithm [Physica A xx, {\\bf xxx} (2005)] for evaluating many-body hydrodynamic interactions in a suspension of spherical particles in the parallel-wall geometry. Implementation of our asymptotic expressions in this algorithm increases its efficiency substantially because the numerically expensive evaluation of the exact matrix elements is needed only for the neighboring particles. Our asymptotic analysis will also be useful in developing hydrodynamic algorithms for wall-bounded periodic systems and implementing acceleration methods by using corresponding results for the two-dimensional scalar potential.

  14. Three-wave interactions of dispersive plasma waves propagating parallel to the magnetic field

    E-print Network

    F. Spanier; R. Vainio

    2008-10-31

    Three-wave interactions of plasma waves propagating parallel to the mean magnetic field at frequencies below the electron cyclotron frequency are considered. We consider Alfv\\'en--ion-cyclotron waves, fast-magnetosonic--whistler waves, and ion-sound waves. Especially the weakly turbulent low-beta plasmas like the solar corona are studied, using the cold-plasma dispersion relation for the transverse waves and the fluid-description of the warm plasma for the longitudinal waves. We analyse the resonance conditions for the wave frequencies $\\omega$ and wavenumbers $k$, and the interaction rates of the waves for all possible combinations of the three wave modes, and list those reactions that are not forbidden.

  15. Fluid/Structure Interaction Studies of Aircraft Using High Fidelity Equations on Parallel Computers

    NASA Technical Reports Server (NTRS)

    Guruswamy, Guru; VanDalsem, William (Technical Monitor)

    1994-01-01

    Abstract Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional super computers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

  16. Parallel changes of taxonomic interaction networks in lacustrine bacterial communities induced by a polymetallic perturbation

    PubMed Central

    Laplante, Karine; Sébastien, Boutin; Derome, Nicolas

    2013-01-01

    Heavy metals released by anthropogenic activities such as mining trigger profound changes to bacterial communities. In this study we used 16S SSU rRNA gene high-throughput sequencing to characterize the impact of a polymetallic perturbation and other environmental parameters on taxonomic networks within five lacustrine bacterial communities from sites located near Rouyn-Noranda, Quebec, Canada. The results showed that community equilibrium was disturbed in terms of both diversity and structure. Moreover, heavy metals, especially cadmium combined with water acidity, induced parallel changes among sites via the selection of resistant OTUs (Operational Taxonomic Unit) and taxonomic dominance perturbations favoring the Alphaproteobacteria. Furthermore, under a similar selective pressure, covariation trends between phyla revealed conservation and parallelism within interphylum interactions. Our study sheds light on the importance of analyzing communities not only from a phylogenetic perspective but also including a quantitative approach to provide significant insights into the evolutionary forces that shape the dynamic of the taxonomic interaction networks in bacterial communities. PMID:23789031

  17. A Force-Based, Parallel Assay for the Quantification of Protein-DNA Interactions

    PubMed Central

    Limmer, Katja; Pippig, Diana A.; Aschenbrenner, Daniela; Gaub, Hermann E.

    2014-01-01

    Analysis of transcription factor binding to DNA sequences is of utmost importance to understand the intricate regulatory mechanisms that underlie gene expression. Several techniques exist that quantify DNA-protein affinity, but they are either very time-consuming or suffer from possible misinterpretation due to complicated algorithms or approximations like many high-throughput techniques. We present a more direct method to quantify DNA-protein interaction in a force-based assay. In contrast to single-molecule force spectroscopy, our technique, the Molecular Force Assay (MFA), parallelizes force measurements so that it can test one or multiple proteins against several DNA sequences in a single experiment. The interaction strength is quantified by comparison to the well-defined rupture stability of different DNA duplexes. As a proof-of-principle, we measured the interaction of the zinc finger construct Zif268/NRE against six different DNA constructs. We could show the specificity of our approach and quantify the strength of the protein-DNA interaction. PMID:24586920

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

    NASA Astrophysics Data System (ADS)

    Osawa, Yasuo

    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.

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

    PubMed

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

    2014-01-01

    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

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

    SciTech Connect

    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

    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.

  1. ``Thermal layer'' effect in MHD: Interaction of a parallel shock with a layer of decreased density

    NASA Astrophysics Data System (ADS)

    Aleksandrov, P. E.

    1993-09-01

    Interaction of a parallel fast MHD shock with a layer of decreased density is discussed using ideal MHD approach. This is an extrapolation of gas dynamic “thermal layer” effect on ideal MHD. Computer simulations show that a magnetic field of a moderate intensity ( ? ˜ 1) may change the character of the flow for intermediate Mach numbers ( M ? 5) and a new “raking” regime may occur which is not observed in the absence of a magnetic field. Self similar precursor analogous to that in gas dynamics may develop in the case of high M and low density in the layer but magnetic forces essentially decrease its growth rate. This problem appears in connection with cosmical shock propagation where planetary magnetic tails play the role of the “thermal layer”, and it may also be observed in the laboratory when the shock is strong enough to heat the walls ahead of it.

  2. Many-particle hydrodynamic interactions in parallel-wall geometry: Cartesian-representation method

    E-print Network

    S. Bhattacharya; J. Blawzdziewicz; E. Wajnryb

    2005-04-27

    This paper describes the results of our theoretical and numerical studies of hydrodynamic interactions in a suspension of spherical particles confined between two parallel planar walls, under creeping-flow conditions. We propose a novel algorithm for accurate evaluation of the many-particle friction matrix in this system--no such algorithm has been available so far. Our approach involves expanding the fluid velocity field into spherical and Cartesian fundamental sets of Stokes flows. The interaction of the fluid with the particles is described using the spherical basis fields; the flow scattered with the walls is expressed in terms of the Cartesian fundamental solutions. At the core of our method are transformation relations between the spherical and Cartesian basis sets. These transformations allow us to describe the flow field in a system that involves both the walls and particles. We used our accurate numerical results to test the single-wall superposition approximation for the hydrodynamic friction matrix. The approximation yields fair results for quantities dominated by single particle contributions, but it fails to describe collective phenomena, such as a large transverse resistance coefficient for linear arrays of spheres.

  3. Parallel multireference configuration interaction calculations on mini-?-carotenes and ?-carotene

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    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. The performance is found to depend heavily on the cluster architecture. While the speed-up on the older Intel Netburst technology is close to linear for up to 12-16 processes, our results indicate that it is not favorable to use all cores of modern Intel Dual Core or Quad Core processors simultaneously for memory intensive tasks. Due to saturation of the memory bandwidth, we recommend to run less demanding tasks on the latter architectures in parallel to two (Dual Core) or four (Quad Core) MRCI processes per node. The DFT/MRCI branch has been employed to study the low-lying singlet and triplet states of mini-n-?-carotenes (n =3, 5, 7, 9) and ?-carotene (n =11) at the geometries of the ground state, the first excited triplet state, and the optically bright singlet state. The order of states depends heavily on the conjugation length and the nuclear geometry. The B1u+ state constitutes the S1 state in the vertical absorption spectrum of mini-3-?-carotene but switches order with the 2 A1g- state upon excited state relaxation. In the longer carotenes, near degeneracy or even root flipping between the B1u+ and B1u- states is observed whereas the 3 A1g- state is found to remain energetically above the optically bright B1u+ state at all nuclear geometries investigated here. The DFT/MRCI method is seen to underestimate the absolute excitation energies of the longer mini-?-carotenes but the energy gaps between the excited states are reproduced well. In addition to singlet data, triplet-triplet absorption energies are presented. For ?-carotene, where these transition energies are known from experiment, excellent agreement with our calculations is observed.

  4. Distinct cerebellar lobules process arousal, valence and their interaction in parallel following a temporal hierarchy.

    PubMed

    Styliadis, Charis; Ioannides, Andreas A; Bamidis, Panagiotis D; Papadelis, Christos

    2015-04-15

    The cerebellum participates in emotion-related neural circuits formed by different cortical and subcortical areas, which sub-serve arousal and valence. Recent neuroimaging studies have shown a functional specificity of cerebellar lobules in the processing of emotional stimuli. However, little is known about the temporal component of this process. The goal of the current study is to assess the spatiotemporal profile of neural responses within the cerebellum during the processing of arousal and valence. We hypothesized that the excitation and timing of distinct cerebellar lobules is influenced by the emotional content of the stimuli. By using magnetoencephalography, we recorded magnetic fields from twelve healthy human individuals while passively viewing affective pictures rated along arousal and valence. By using a beamformer, we localized gamma-band activity in the cerebellum across time and we related the foci of activity to the anatomical organization of the cerebellum. Successive cerebellar activations were observed within distinct lobules starting ~160ms after the stimuli onset. Arousal was processed within both vermal (VI and VIIIa) and hemispheric (left Crus II) lobules. Valence (left VI) and its interaction (left V and left Crus I) with arousal were processed only within hemispheric lobules. Arousal processing was identified first at early latencies (160ms) and was long-lived (until 980ms). In contrast, the processing of valence and its interaction to arousal was short lived at later stages (420-530ms and 570-640ms respectively). Our findings provide for the first time evidence that distinct cerebellar lobules process arousal, valence, and their interaction in a parallel yet temporally hierarchical manner determined by the emotional content of the stimuli. PMID:25665964

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

    E-print Network

    Vesperini, Enrico; McMillan, Stephen L W; Dura, James; Jones, Douglas

    2008-01-01

    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.

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

    E-print Network

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

    2008-04-29

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    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.

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

    SciTech Connect

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

    1997-04-01

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

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

    Microsoft Academic Search

    F. Akasheh; H. M. Zbib; J. P. Hirth; R. G. Hoagland; A. Misra

    Plastic deformation in nanoscale multilayered structures is thought to proceed by the successive propagation of single dislocation loops at the interfaces. Based on this view, we simulate the effect of predeposited interfacial dislocation on the stress channeling stress needed to propagate a new loop parallel to existing loops. Single interfacial dislocations as well as finite parallel arrays are considered in

  10. A Graph-Theoretic Analysis of the Human Protein-Interaction Network Using Multicore Parallel Algorithms

    Microsoft Academic Search

    David A. Bader; Kamesh Madduri

    2007-01-01

    Protein-interaction network (PIN) analysis provides valuable insight into an organism's functional organization and evolutionary behavior. In this paper, we study a PIN formed by high-confidence human protein interactions ob- tained from various public interaction databases. This is the largest human PIN studied to date, comprising nearly 18,000 proteins and 44,000 interactions. A novel contribu- tion of this paper is the

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

    SciTech Connect

    Kabel, A.C.; /SLAC

    2008-03-17

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

  12. Parallel approximation of non-interactive zero-sum quantum games

    E-print Network

    Rahul Jain; John Watrous

    2008-08-20

    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.

  13. 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.

  14. Computation of interactional aerodynamics for noise prediction of heavy lift rotorcraft

    NASA Astrophysics Data System (ADS)

    Hennes, Christopher C.

    Many computational tools are used when developing a modern helicopter. As the design space is narrowed, more accurate and time-intensive tools are brought to bear. These tools are used to determine the effect of a design decision on the performance, handling, stability and efficiency of the aircraft. One notable parameter left out of this process is acoustics. This is due in part to the difficulty in making useful acoustics calculations that reveal the differences between various design configurations. This thesis presents a new approach designed to bridge the gap in prediction capability between fast but low-fidelity Lagrangian particle methods, and slow but high-fidelity Eulerian computational fluid dynamics simulations. A multi-pronged approach is presented. First, a simple flow solver using well-understood and tested flow solution methodologies is developed specifically to handle bodies in arbitrary motion. To this basic flow solver two new technologies are added. The first is an Immersed Boundary technique designed to be tolerant of geometric degeneracies and low-resolution grids. This new technique allows easy inclusion of complex fuselage geometries at minimal computational cost, improving the ability of a solver to capture the complex interactional aerodynamic effects expected in modern rotorcraft design. The second new technique is an extension of a concept from flow visualization where the motion of tip vortices are tracked through the solution using massless particles convecting with the local flow. In this extension of that concept, the particles maintain knowledge of the expected and actual vortex strength. As a post-processing step, when the acoustic calculations are made, these particles are used to augment the loading noise calculation and reproduce the highly-impulsive character of blade-vortex interaction noise. In combination these new techniques yield a significant improvement to the state of the art in rotorcraft blade-vortex interaction noise prediction.

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

    SciTech Connect

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

    2013-01-01

    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.

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

    E-print Network

    Swan II, J. Edward

    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

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

    SciTech Connect

    Colgate, S.A.

    1990-01-01

    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.

  18. Nonlinear fluid-structure interaction problem. Part II: space discretization, implementation aspects, nested parallelization and application examples

    NASA Astrophysics Data System (ADS)

    Kassiotis, Christophe; Ibrahimbegovic, Adnan; Niekamp, Rainer; Matthies, Hermann G.

    2011-03-01

    The main focus of the present article is the development of a general solution framework for coupled and/or interaction multi-physics problems based upon re-using existing codes into software products. In particular, we discuss how to build this software tool for the case of fluid-structure interaction problem, from finite element code FEAP for structural and finite volume code OpenFOAM for fluid mechanics. This is achieved by using the Component Template Library (CTL) to provide the coupling between the existing codes into a single software product. The present CTL code-coupling procedure accepts not only different discretization schemes, but different languages, with the solid component written in Fortran and fluid component written in C++ . Moreover, the resulting CTL-based code also accepts the nested parallelization. The proposed coupling strategy is detailed for explicit and implicit fixed-point iteration solver presented in the Part I of this paper, referred to Direct Force-Motion Transfer/Block- Gauss-Seidel. However, the proposed code-coupling framework can easily accommodate other solution schemes. The selected application examples are chosen to confirm the capability of the code-coupling strategy to provide a quick development of advanced computational tools for demanding practical problems, such as 3D fluid models with free-surface flows interacting with structures.

  19. Parallel Three-Dimensional Computation of Fluid Dynamics and Fluid-Structure Interactions of Ram-Air Parachutes

    NASA Technical Reports Server (NTRS)

    Tezduyar, Tayfun E.

    1998-01-01

    This is a final report as far as our work at University of Minnesota is concerned. The report describes our research progress and accomplishments in development of high performance computing methods and tools for 3D finite element computation of aerodynamic characteristics and fluid-structure interactions (FSI) arising in airdrop systems, namely ram-air parachutes and round parachutes. This class of simulations involves complex geometries, flexible structural components, deforming fluid domains, and unsteady flow patterns. The key components of our simulation toolkit are a stabilized finite element flow solver, a nonlinear structural dynamics solver, an automatic mesh moving scheme, and an interface between the fluid and structural solvers; all of these have been developed within a parallel message-passing paradigm.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  1. DNS of hydrodynamically interacting droplets in turbulent clouds: Parallel implementation and scalability analysis using 2D domain decomposition

    NASA Astrophysics Data System (ADS)

    Ayala, Orlando; Parishani, Hossein; Chen, Liu; Rosa, Bogdan; Wang, Lian-Ping

    2014-12-01

    The study of turbulent collision of cloud droplets requires simultaneous considerations of the transport by background air turbulence (i.e., geometric collision rate) and influence of droplet disturbance flows (i.e., collision efficiency). In recent years, this multiscale problem has been addressed through a hybrid direct numerical simulation (HDNS) approach (Ayala et al., 2007). This approach, while currently is the only viable tool to quantify the effects of air turbulence on collision statistics, is computationally expensive. In order to extend the HDNS approach to higher flow Reynolds numbers, here we developed a highly scalable implementation of the approach using 2D domain decomposition. The scalability of the parallel implementation was studied using several parallel computers, at 5123 and 10243 grid resolutions with O(106)-O(107) droplets. It was found that the execution time scaled with number of processors almost linearly until it saturates and deteriorates due to communication latency issues. To better understand the scalability, we developed a complexity analysis by partitioning the execution tasks into computation, communication, and data copy. Using this complexity analysis, we were able to predict the scalability performance of our parallel code. Furthermore, the theory was used to estimate the maximum number of processors below which the approximately linear scalability is sustained. We theoretically showed that we could efficiently solved problems of up to 81923 with O(100,000) processors. The complexity analysis revealed that the pseudo-spectral simulation of background turbulent flow for a dilute droplet suspension typical of cloud conditions typically takes about 80% of the total execution time, except when the droplets are small (less than 5 ?m in a flow with energy dissipation rate of 400 cm2/s3 and liquid water content of 1 g/m3), for which case the particle-particle hydrodynamic interactions become the bottleneck. The complexity analysis was also used to explore some alternative methods to handle FFT calculations within the flow simulation and to advance droplets less than 5 ?m in radius, for better computational efficiency. Finally, preliminary results are reported to shed light on the Reynolds number-dependence of collision kernel of non-interacting droplets.

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

    SciTech Connect

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

    1994-10-01

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

  3. A Quantum Statistical Theory of Ferromagnetic Resonance with Parallel Pumping. II Correlation Function Treatment of Parametric Spin Wave Excitation and Nonlinear Interactions

    Microsoft Academic Search

    Th. Klupsch

    1969-01-01

    Based on equations, symmetry and boundary conditions of quantum statistical correlation functions of renormalized spin wave excitations in a HEISENBERG ferromagnet including dipolar coupling, the parallel pumping effect under special considering the nonlinear three magnon interaction is discussed. An asymptotic approximation procedure enables us to interpret the fundamental equations in terms of the LANGEVIN theory of BROWNian motion and to

  4. Quantitative analysis of RNA-protein interactions on a massively parallel array reveals biophysical and evolutionary landscapes.

    PubMed

    Buenrostro, Jason D; Araya, Carlos L; Chircus, Lauren M; Layton, Curtis J; Chang, Howard Y; Snyder, Michael P; Greenleaf, William J

    2014-06-01

    RNA-protein interactions drive fundamental biological processes and are targets for molecular engineering, yet quantitative and comprehensive understanding of the sequence determinants of affinity remains limited. Here we repurpose a high-throughput sequencing instrument to quantitatively measure binding and dissociation of a fluorescently labeled protein to >10(7) RNA targets generated on a flow cell surface by in situ transcription and intermolecular tethering of RNA to DNA. Studying the MS2 coat protein, we decompose the binding energy contributions from primary and secondary RNA structure, and observe that differences in affinity are often driven by sequence-specific changes in both association and dissociation rates. By analyzing the biophysical constraints and modeling mutational paths describing the molecular evolution of MS2 from low- to high-affinity hairpins, we quantify widespread molecular epistasis and a long-hypothesized, structure-dependent preference for G:U base pairs over C:A intermediates in evolutionary trajectories. Our results suggest that quantitative analysis of RNA on a massively parallel array (RNA-MaP) provides generalizable insight into the biophysical basis and evolutionary consequences of sequence-function relationships. PMID:24727714

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

    NASA Astrophysics Data System (ADS)

    Ahmadi, A. R.

    1984-09-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Ahmadi, A. R.

    1984-01-01

    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.

  7. Parallel unstructured multigrid simulation of 3D unsteady flows and fluid–structure interaction in mechanical heart valve using immersed membrane method

    Microsoft Academic Search

    G. H. Xia; Yong Zhao; J. H. Yeo

    2009-01-01

    In this work, a second-order accurate immersed membrane method (IMM) is adopted to simulate the fluid–structure interaction phenomena in the mechanical heart valves (MHVs). The leaflets of the MHV are immersed in the fluid flows and move on top of the fixed fluid mesh. The blood flow is computed by a 3D parallel unstructured multigrid implicit finite-volume Navier–Stokes solver for

  8. Parallel Atomistic Simulations

    SciTech Connect

    HEFFELFINGER,GRANT S.

    2000-01-18

    Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

  9. Nucleic Acids Research, 1993, Vol. 21, No. 22 5085-5091 Structure and drug interactions of parallel-stranded DNA

    E-print Network

    Rippe, Karsten

    structure in parallel-stranded DNA is established by reversed Watson - Crick base pairing of dA d-6). It was suggested that ps-DNA is formed by reverse Watson-Crick base pairing (7). The consequence ofthis base-DNA and aps-DNA are significantly different, and the reverse Watson-Crick base pairing was confirmed (9

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

    PubMed Central

    2013-01-01

    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

  11. Aeroacoustic theory for noncompact wing-gust interaction

    NASA Technical Reports Server (NTRS)

    Martinez, R.; Widnall, S. E.

    1981-01-01

    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.

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

    SciTech Connect

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

    2008-03-17

    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.

  13. Nonlinear fluid–structure interaction problem. Part II: space discretization, implementation aspects, nested parallelization and application examples

    Microsoft Academic Search

    Christophe Kassiotis; Adnan Ibrahimbegovic; Rainer Niekamp; Hermann G. Matthies

    2011-01-01

    The main focus of the present article is the development of a general solution framework for coupled and\\/or interaction multi-physics\\u000a problems based upon re-using existing codes into software products. In particular, we discuss how to build this software tool\\u000a for the case of fluid–structure interaction problem, from finite element code FEAP for structural and finite volume code OpenFOAM for fluid

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

    Microsoft Academic Search

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

    2012-01-01

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

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

    SciTech Connect

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

    2010-02-01

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

  16. Parallel rendering

    NASA Technical Reports Server (NTRS)

    Crockett, Thomas W.

    1995-01-01

    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.

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

    SciTech Connect

    Kollet, S J; Maxwell, R M

    2005-10-25

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

  18. Investigation of the interaction between As and Sb species and dissolved organic matter in the Yangtze Estuary, China, using excitation-emission matrices with parallel factor analysis.

    PubMed

    Wang, Ying; Zhang, Di; Shen, Zhen-Yao; Feng, Cheng-Hong; Zhang, Xiao

    2015-02-01

    The interactions between trivalent or pentavalent As/Sb and dissolved organic matter (DOM) in four regions (the river channel, the adjacent coastal area, and the northern and southern nearshore areas) of the Yangtze Estuary, China, were studied using fluorescence quenching titration combined with excitation-emission matrix spectroscopy and parallel factor analysis (PARAFAC). The As/Sb-DOM complexation characteristics were investigated using FTIR and UV absorbance spectroscopy and zeta potential analysis. Four protein-like components and one humic-like component were identified in the DOM from the Yangtze Estuary, China, by PARAFAC analysis. The tryptophan-like substance represented by component 2 was the dominant component and played an important role in the complexation between DOM and As/Sb. The results of complexation modeling demonstrated that the binding capacity of trivalent As/Sb with DOM was higher than that of pentavalent As/Sb with DOM. The DOM from the north nearshore area with the most acidic functional groups and greatest aromaticity possessed the highest binding capacity for trivalent and pentavalent As/Sb. The increase in the UV absorbance and the charge neutralization further indicated the interaction between As/Sb and DOM. The higher binding capacity of Sb(III) with DOM was mainly due to the hydroxyl and carboxyl groups. Our study demonstrates that the use of the advanced EEM-PARAFAC method in fluorescence quenching studies is very useful for evaluating the properties of DOM-pollutant interactions. PMID:25172458

  19. Parallel Algorithms

    NSDL National Science Digital Library

    Paul Gray

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

  20. Research investigation of helicopter main rotor/tail rotor interaction noise

    NASA Technical Reports Server (NTRS)

    Fitzgerald, J.; Kohlhepp, F.

    1988-01-01

    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.

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Demir, I.; Krajewski, W. F.

    2013-12-01

    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.

  4. Multithreading and Parallel Microprocessors

    E-print Network

    Shinozuka, Masanobu

    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

  5. Substituent-modulated affinities of halobenzene derivatives to the HIV-1 integrase recognition site. Analyses of the interaction energies by parallel quantum chemical and polarizable molecular mechanics.

    PubMed

    El Hage, Krystel; Piquemal, Jean-Philip; Hobaika, Zeina; Maroun, Richard G; Gresh, Nohad

    2014-10-16

    The C-X bond of halobenzenes (X = Cl, Br) has a dual character, its electron density being depleted in its prolongation and built-up on its sides. We have recently considered three protein or nucleic acid recognition sites of halobenzenes and quantified the energy gains that either electron-attracting substituents or electron-donating ones contribute due to such a character (El Hage et al., paper in revision). Nonadditivity was found to impact the total interaction energies. We focus here on one recognition site, that of the HIV-1 integrase, in which the halobenzene ring of the drug elvitegravir is sandwiched between a guanine and a cytosine base. We perform energy-decomposition analyses of the ab initio quantum-chemistry (QC) binding energies of the parent halobenzene ring and its derivatives with this G-C base pair. In these complexes, the nonadditivity of ?E could be traced back mostly to the polarization contribution Epol. In view of large-scale applications to the entirety of the complex formed between the integrase, the viral DNA, and the whole drug, the analyses were performed in parallel with a polarizable molecular mechanics method, SIBFA. This method could faithfully reproduce most features of the QC energies. This is due to its use of QC-derived distributed multipoles and polarizabilities, which enable us to account for both nonisotropy and nonadditivity. PMID:25230384

  6. Parallel LOCFES

    E-print Network

    Shah, Ronak C.

    1991-01-01

    I'sge III. A Review III. B MasPar System Architecture 18 III. C MasPar FORTRAN 21 III. D MasPar Programming Environment IV MLOCFES: PARALLEL VERSION IV. A Potential Regions of Parallelism in LOCFES IV. B FORTRAN gg Adaptations IV. C Program.... 2 MasPar MP-1 System Diagram (Adapted from MasPar System Overview). . . 19 3 The flow of control. 31 LIST OF TABLES TABLE Page Analytical vs computational (MLOCFES) solution for I = 1, K = 1, and L=1 Analytical vs computational (MLOCFES...

  7. The Vortex Lattice Method for the Rotor-Vortex Interaction Problem

    NASA Technical Reports Server (NTRS)

    Padakannaya, R.

    1974-01-01

    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.

  8. Parallel Universes

    Microsoft Academic Search

    Max Tegmark

    2003-01-01

    I survey physics theories involving parallel universes, which form a natural four-level hierarchy of multiverses allowing progressively greater diversity. Level I: A generic prediction of inflation is an infinite ergodic universe, which contains Hubble volumes realizing all initial conditions - including an identical copy of you about 10^{10^29} meters away. Level II: In chaotic inflation, other thermalized regions may have

  9. Brian Munsky Center for Nonlinear Studies, Mail-stop B258

    E-print Network

    Gandhi Thesis topic: Fluid/Structural/Acoustic Analyses of Helicopter Blade-Vortex Interactions. The Pennsylvania State University (PSU) B.S. in Aerospace Engineering (2000), Advisors: Farhan S. Gandhi and Edward

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

    PubMed Central

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

    2014-01-01

    In this study, we developed a prototype animal PET by applying several novel technologies to use the solid-state photomultiplier (SSPM) arrays for measuring the depth-of-interaction (DOI) and improving imaging performance. Each PET detector has an 8×8 array of about 1.9×1.9×30.0 mm3 lutetium-yttrium-oxyorthosilicate (LYSO) scintillators, with each end optically connected to a SSPM array (16-channel in a 4×4 matrix) through a light guide to enable continuous DOI measurement. Each SSPM has an active area of about 3×3 mm2, and its output is read by a custom-developed application-specific-integrated-circuit (ASIC) to directly convert analog signals to digital timing pulses that encode the interaction information. These pulses are transferred to and be decoded by a field-programmable-gate-array (FPGA) 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 using 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 mm3 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 mm2, 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.

  12. Anomalous values of interaction constants in the two-dimensional electron gas of a silicon metal-oxide-semiconductor field-effect transistor measured by parallel- and perpendicular-field magnetoconductivity

    Microsoft Academic Search

    M. S. Burdis; C. C. Dean

    1988-01-01

    Comprehensive measurements of magnetic-field and temperature dependence of electrical conductivity in the two-dimensional electron gas of a silicon metal-oxide-semiconductor field-effect transistor reveal unexpected values of interaction constants. Parallel-magnetic-field measurements show previously unseen dependencies on both temperature and carrier concentration, and these observations are corroborated by analysis of the temperature dependence of conductivity in both zero and small perpendicular magnetic fields.

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

    SciTech Connect

    Li, Shengtai [Los Alamos National Laboratory; Li, Hui [Los Alamos National Laboratory

    2012-06-14

    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) with a different gravitational potential that is defined in Nelson et al. (2000). The equations are solved by directional split Godunov method for the inviscid Euler equations plus operator-split method for the viscous source terms. We use a sub-cycling technique for the azimuthal sweep to alleviate the time step restriction. We also extend the FARGO scheme of Masset (2000) and modified in Li et al. (2001) to our 3D code to accelerate the transport in the azimuthal direction. Furthermore, we have implemented a reduced 2D (r, {theta}) and a fully 3D self-gravity solver on our uniform disk grid, which extends our 2D method (Li, Buoni, & Li 2008) to 3D. This solver uses a mode cut-off strategy and combines FFT in the azimuthal direction and direct summation in the radial and meridional direction. An initial axis-symmetric equilibrium disk is generated via iteration between the disk density profile and the 2D disk-self-gravity. We do not need any softening in the disk self-gravity calculation as we have used a shifted grid method (Li et al. 2008) to calculate the potential. The motion of the planet is limited on the mid-plane and the equations are the same as given in D'Angelo et al. (2005), which we adapted to the polar coordinates with a fourth-order Runge-Kutta solver. The disk gravitational force on the planet is assumed to evolve linearly with time between two hydrodynamics time steps. The Planetary potential acting on the disk is calculated accurately with a small softening given by a cubic-spline form (Kley et al. 2009). Since the torque is extremely sensitive to the position of the planet, we adopt the corotating frame that allows the planet moving only in radial direction if only one planet is present. This code has been extensively tested on a number of problems. For the earthmass planet with constant aspect ratio h = 0.05, the torque calculated using our code matches quite well with the the 3D linear theory results by Tanaka et al. (2002). The code is fully parallelized via message-passing interface (MPI) and has very high parallel efficiency. Several numerical examples for both fixed planet and moving planet are provided to demonstrate the efficacy of the numerical method and code.

  14. Parallel Computing Explained

    NSDL National Science Digital Library

    NCSA

    Several tutorials on parallel computing. Overview of parallel computing. Porting and code parallelization. Scalar, cache, and parallel code tuning. Timing, profiling and performance analysis. Overview of IBM Regatta P690.

  15. An Automatic and Symbolic Parallelization System for Distributed Memory Parallel Computers

    Microsoft Academic Search

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

    1990-01-01

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

  16. A Quantum Statistical Theory of Ferromagnetic Resonance with Parallel Pumping. I GREEN'S Function and Non-Equilibrium Correlation Function Treatment of a Heisenberg Ferromagnet Including Dipolar Interactions

    Microsoft Academic Search

    Th. Klupsch

    1969-01-01

    The method of causal GREEN'S functions is used to derive equations and boundary conditions of non-equilibrium correlation functions which describe spin wave like elementary excitations in a HEISENBERG ferromagnet with dipolar coupling influenced by a r. f. magnetic field parallel to the d.c. field. Starting with a matrix of four GREEN'S functions each containing two PAULI operators, by means of

  17. Parallel pivoting combined with parallel reduction

    NASA Technical Reports Server (NTRS)

    Alaghband, Gita

    1987-01-01

    Parallel algorithms for triangularization of large, sparse, and unsymmetric matrices are presented. The method combines the parallel reduction with a new parallel pivoting technique, control over generations of fill-ins and a check for numerical stability, all done in parallel with the work being distributed over the active processes. The parallel technique uses the compatibility relation between pivots to identify parallel pivot candidates and uses the Markowitz number of pivots to minimize fill-in. This technique is not a preordering of the sparse matrix and is applied dynamically as the decomposition proceeds.

  18. One hundred spots parallel monitoring of DNA interactions by SPR imaging of polymer-functionalized surfaces applied to the detection of cystic fibrosis mutations

    Microsoft Academic Search

    Nathalie Bassil; Emmanuel Maillart; Michael Canva; Yves Lévy; Marie-Claude Millot; Serge Pissard; Rémy Narwa; Michel Goossens

    2003-01-01

    In the present paper, we report the detection of mutations implicated in human cystic fibrosis (CF). Nine different oligonucleotides are studied, including three possible mutations related to this specific genetic disease: a deletion of three bases, ?F508, and two single-nucleotide polymorphisms 1540A\\/G and 1716G\\/A. We monitor, in real time and in parallel, hybridizations of a solution of unlabeled oligonucleotide targets

  19. Modeling the Backscatter and Transmitted Light of High Power Smoothed Beams with pF3D, a Massively Parallel Laser Plasma Interaction Code

    Microsoft Academic Search

    R. L. Berger; L. Divol; S. Glenzer; D. E. Hinkel; R. K. Kirkwood; A. B. Langdon; J. D. Moody; C. H. Still; L. Suter; E. A. Williams; P. E. Young

    2000-01-01

    Using the three-dimensional wave propagation code, F3D[Berger et al., Phys. Fluids B 5,2243 (1993), Berger et al., Phys. Plasmas 5,4337(1998)], and the massively parallel version pF3D, [Still et al. Phys. Plasmas 7 (2000)], we have computed the transmitted and reflected light for laser and plasma conditions in experiments that simulated ignition hohlraum conditions. The frequency spectrum and the wavenumber spectrum

  20. Modeling with backscatter and transmitted light of high-power smoothed beams with pF3D: a massively parallel laser plasma interaction code

    Microsoft Academic Search

    R. L. Berger; L. M. Divol; S. H. Glenzer; D. E. Hinkel; R. K. Kirkwood; A. B. Langdon; James D. Moody; C. H. Still; Larry J. Suter; E. A. Williams; Peter E. Young

    2001-01-01

    Using the 3D wave propagation code, F3D, Berger et al., Phys. Plasmas 5,4337, and the massively parallel version pF3D, we have computed the transmitted and reflected light for laser and plasma conditions in experiments that simulated ignition hohlraum conditions. The frequency spectrum and the wavenumber spectrum of the transmitted light are calculated and used to identify the relative contributions of

  1. Modeling the Backscatter and Transmitted Light of High Power Smoothed Beam with pF3D, a Massively parallel Laser Plasma Interaction Code

    Microsoft Academic Search

    R. L. Berger; S. H. Glenzer; D. E. Hinkel; R. K. Kirkwood; A. B. Langdon

    2000-01-01

    Using the three-dimensional wave propagation code, F3D, and the massively parallel version pF3D, we have computed the transmitted and reflected light for laser and plasma conditions in experiments that simulated ignition hohlraum conditions. The frequency spectrum and the wavenumber spectrum of the transmitted light are calculated and used to identify the relative contributions of stimulated forward Brillouin and self-focusing in

  2. Special parallel processing workshop

    SciTech Connect

    NONE

    1994-12-01

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

  3. Computer-Aided Parallelizer and Optimizer

    NASA Technical Reports Server (NTRS)

    Jin, Haoqiang

    2011-01-01

    The Computer-Aided Parallelizer and Optimizer (CAPO) automates the insertion of compiler directives (see figure) to facilitate parallel processing on Shared Memory Parallel (SMP) machines. While CAPO currently is integrated seamlessly into CAPTools (developed at the University of Greenwich, now marketed as ParaWise), CAPO was independently developed at Ames Research Center as one of the components for the Legacy Code Modernization (LCM) project. The current version takes serial FORTRAN programs, performs interprocedural data dependence analysis, and generates OpenMP directives. Due to the widely supported OpenMP standard, the generated OpenMP codes have the potential to run on a wide range of SMP machines. CAPO relies on accurate interprocedural data dependence information currently provided by CAPTools. Compiler directives are generated through identification of parallel loops in the outermost level, construction of parallel regions around parallel loops and optimization of parallel regions, and insertion of directives with automatic identification of private, reduction, induction, and shared variables. Attempts also have been made to identify potential pipeline parallelism (implemented with point-to-point synchronization). Although directives are generated automatically, user interaction with the tool is still important for producing good parallel codes. A comprehensive graphical user interface is included for users to interact with the parallelization process.

  4. Parallel local search

    Microsoft Academic Search

    M. G. A. Verhoeven; E. H. L. Aarts

    1995-01-01

    We present a survey of parallel local search algorithms in which we review the concepts that can be used to incorporate parallelism\\u000a into local search. For this purpose we distinguish between single-walk and multiple-walk parallel local search and between\\u000a asynchronous and synchronous parallelism. Within the class of single-walk algorithms we differentiate between multiple-step\\u000a and single-step parallelism. To describe parallel local

  5. Two Fundamental Concepts in Skeletal Parallel Programming

    E-print Network

    Cole, Murray

    to be fundamental to the definition of any skeletal parallel programming system, but which have been addressed onlyTwo Fundamental Concepts in Skeletal Parallel Programming Anne Benoit and Murray Cole School define the concepts of nesting mode and interaction mode as they arise in the description of skeletal

  6. 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

    Bartz, Dirk

    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

  7. Interaction

    NSDL National Science Digital Library

    Wolfgang Christian

    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.

  8. Parallel computations and control of adaptive structures

    NASA Technical Reports Server (NTRS)

    Park, K. C.; Alvin, Kenneth F.; Belvin, W. Keith; Chong, K. P. (editor); Liu, S. C. (editor); Li, J. C. (editor)

    1991-01-01

    The equations of motion for structures with adaptive elements for vibration control are presented for parallel computations to be used as a software package for real-time control of flexible space structures. A brief introduction of the state-of-the-art parallel computational capability is also presented. Time marching strategies are developed for an effective use of massive parallel mapping, partitioning, and the necessary arithmetic operations. An example is offered for the simulation of control-structure interaction on a parallel computer and the impact of the approach presented for applications in other disciplines than aerospace industry is assessed.

  9. Data parallel algorithms

    Microsoft Academic Search

    W. Daniel Hillis; Guy L. Steele Jr.

    1986-01-01

    Parallel computers with tens of thousands of processors are typically programmed in a data parallel style, as opposed to the control parallel style used in multiprocessing. The success of data parallel algorithms—even on problems that at first glance seem inherently serial—suggests that this style of programming has much wider applicability than was previously thought.

  10. Parallelization of a treecode

    E-print Network

    R. Valdarnini

    2003-03-18

    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.

  11. Making parallel lines meet

    PubMed Central

    Baskin, Tobias I.; Gu, Ying

    2012-01-01

    The extracellular matrix is constructed beyond the plasma membrane, challenging mechanisms for its control by the cell. In plants, the cell wall is highly ordered, with cellulose microfibrils aligned coherently over a scale spanning hundreds of cells. To a considerable extent, deploying aligned microfibrils determines mechanical properties of the cell wall, including strength and compliance. Cellulose microfibrils have long been seen to be aligned in parallel with an array of microtubules in the cell cortex. How do these cortical microtubules affect the cellulose synthase complex? This question has stood for as many years as the parallelism between the elements has been observed, but now an answer is emerging. Here, we review recent work establishing that the link between microtubules and microfibrils is mediated by a protein named cellulose synthase-interacting protein 1 (CSI1). The protein binds both microtubules and components of the cellulose synthase complex. In the absence of CSI1, microfibrils are synthesized but their alignment becomes uncoupled from the microtubules, an effect that is phenocopied in the wild type by depolymerizing the microtubules. The characterization of CSI1 significantly enhances knowledge of how cellulose is aligned, a process that serves as a paradigmatic example of how cells dictate the construction of their extracellular environment. PMID:22902763

  12. Massively Parallel QCD

    SciTech Connect

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

    2007-04-11

    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.

  13. Applied Parallel Metadata Indexing

    SciTech Connect

    Jacobi, Michael R [Los Alamos National Laboratory

    2012-08-01

    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.

  14. The ParaScope parallel programming environment

    NASA Technical Reports Server (NTRS)

    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

    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.

  15. Fluid-Structure Interaction Simulation of Detonation-Driven Rupture Events of Thin-Walled Tubes with a Parallel Adaptive Level Set Method

    E-print Network

    Deiterding, Ralf

    of Engineering, Cambridge, CB2 1PZ, UK Technically relevant fluid-structure interaction simulation of detonation application, we consider the induction of large plastic deformations and the fracture of thin aluminum tubes conditions on the CFD solver and the hydrodynamic pressure is used as force boundary condition acting

  16. Parallel flow diffusion battery

    DOEpatents

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

    1984-01-01

    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.

  17. Parallel flow diffusion battery

    DOEpatents

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

    1984-08-07

    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.

  18. Parallel I/O Systems

    NSDL National Science Digital Library

    Amy Apon

    * 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

  19. Parallel processing ITS

    SciTech Connect

    Fan, W.C.; Halbleib, J.A. Sr.

    1996-09-01

    This report provides a users` guide for parallel processing ITS on a UNIX workstation network, a shared-memory multiprocessor or a massively-parallel processor. The parallelized version of ITS is based on a master/slave model with message passing. Parallel issues such as random number generation, load balancing, and communication software are briefly discussed. Timing results for example problems are presented for demonstration purposes.

  20. Coordinating Parallel Processes on Networks of Workstations

    Microsoft Academic Search

    Xing Du; Xiaodong Zhang

    1997-01-01

    The network of workstations (NOW) we consider for schedul- ing is heterogeneous and nondedicated, where computing power varies among the workstations and local and parallel jobs may interact with each other in execution. An effective NOW schedul- ing scheme needs sufficient information about system heterogene- ity and job interactions. We use the measured power weight of each workstation to quantify

  1. CFD on parallel computers

    NASA Astrophysics Data System (ADS)

    Basu, A. J.

    1994-10-01

    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.

  2. Adaptive Parallelism and Piranha

    Microsoft Academic Search

    Nicholas Carriero; Eric Freeman; David Gelernter; David Kaminsky

    1995-01-01

    . Under "adaptive parallelism," the set of processors executing a parallel programmay grow or shrink as the program runs. Potential gains include the capacity to runa parallel program on the idle workstations in a conventional LAN---processors join thecomputation when they become idle, and withdraw when their owners need them---and tomanage the nodes of a dedicated multiprocessor efficiency. Experience to date

  3. Parallel simulation today

    NASA Technical Reports Server (NTRS)

    Nicol, David; Fujimoto, Richard

    1992-01-01

    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.

  4. Decomposing the Potentially Parallel

    NSDL National Science Digital Library

    Elspeth Minty, Robert Davey, Alan Simpson, David Henty

    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.

  5. Parallel Faster-X Evolution of Gene Expression and Protein Sequences in Drosophila: Beyond Differences in Expression Properties and Protein Interactions

    PubMed Central

    Llopart, Ana

    2015-01-01

    Population genetics models predict that the X (or Z) chromosome will evolve at faster rates than the autosomes in XY (or ZW) systems. Studies of molecular evolution using large datasets in multiple species have provided evidence supporting this faster-X effect in protein-coding sequences and, more recently, in transcriptomes. However, X-linked and autosomal genes differ significantly in important properties besides hemizygosity in males, including gene expression levels, tissue specificity in gene expression, and the number of interactions in which they are involved (i.e., protein-protein or DNA-protein interactions). Most important, these properties are known to correlate with rates of evolution, which raises the question of whether differences between the X chromosome and autosomes in gene properties, rather than hemizygosity, are sufficient to explain faster-X evolution. Here I investigate this possibility using whole genome sequences and transcriptomes of Drosophila yakuba and D. santomea and show that this is not the case. Additional factors are needed to account for faster-X evolution of both gene expression and protein-coding sequences beyond differences in gene properties, likely a higher incidence of positive selection in combination with the accumulation of weakly deleterious mutations. PMID:25789611

  6. Homooligomeric dA·dU and dA·dT Sequences in Parallel and Antiparallel Strand Orientation: Consequence of the 5-methyl Groups on Stability, Structure and Interaction with the Minor Groove Binding Drug HOECHST 33258

    Microsoft Academic Search

    Markus W. Germann; Bernd W. Kalisch; Johan H. van de Sande

    1996-01-01

    Oligodeoxyribonucleotides containing dA·dU base combinations were shown to form parallel stranded DNA. CD spectra and hyperchromicity profiles provide evidence that the structure is very similar to that of a related parallel stranded dA·oligomer. Thermal denaturation studies show that these parallel dAdU sequences are significantly less stable than their dA·analogues in either antiparallel or parallel stranded orientations. The stabilizing effect of

  7. Parallel algorithm development

    SciTech Connect

    Adams, T.F.

    1996-06-01

    Rapid changes in parallel computing technology are causing significant changes in the strategies being used for parallel algorithm development. One approach is simply to write computer code in a standard language like FORTRAN 77 or with the expectation that the compiler will produce executable code that will run in parallel. The alternatives are: (1) to build explicit message passing directly into the source code; or (2) to write source code without explicit reference to message passing or parallelism, but use a general communications library to provide efficient parallel execution. Application of these strategies is illustrated with examples of codes currently under development.

  8. Synchronization Of Parallel Discrete Event Simulations

    NASA Technical Reports Server (NTRS)

    Steinman, Jeffrey S.

    1992-01-01

    Adaptive, parallel, discrete-event-simulation-synchronization algorithm, Breathing Time Buckets, developed in Synchronous Parallel Environment for Emulation and Discrete Event Simulation (SPEEDES) operating system. Algorithm allows parallel simulations to process events optimistically in fluctuating time cycles that naturally adapt while simulation in progress. Combines best of optimistic and conservative synchronization strategies while avoiding major disadvantages. Algorithm processes events optimistically in time cycles adapting while simulation in progress. Well suited for modeling communication networks, for large-scale war games, for simulated flights of aircraft, for simulations of computer equipment, for mathematical modeling, for interactive engineering simulations, and for depictions of flows of information.

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

    PubMed

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

    2015-01-01

    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

  10. New Computational Methods for the Prediction and Analysis of Helicopter Noise

    NASA Technical Reports Server (NTRS)

    Strawn, Roger C.; Oliker, Leonid; Biswas, Rupak

    1996-01-01

    This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise.

  11. Parallel digital forensics infrastructure.

    SciTech Connect

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

    2009-10-01

    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.

  12. Adaptive Parallelism with Piranha

    Microsoft Academic Search

    Nicholas Carriero; David Gelernter; David Kaminsky; Jeffery Westbrook

    "Adaptive parallelism" refers to parallel computations on a dynamically changingset of processors: processors may join or withdraw from the computation as it proceeds.Networks of fast workstations are the most important setting for adaptive parallelism atpresent. Workstations at most sites are typically idle for significant fractions of the day,and those idle cycles may constitute in the aggregate a powerful computing resource.For

  13. PCLIPS: Parallel CLIPS

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  14. Unique features of the anti-parallel, heterodimeric coiled-coil interaction between methyl-cytosine binding domain 2 (MBD2) homologues and GATA zinc finger domain containing 2A (GATAD2A/p66?).

    PubMed

    Walavalkar, Ninad M; Gordon, Nathaniel; Williams, David C

    2013-02-01

    The methyl-cytosine binding domain 2 (MBD2)-nucleosome remodeling and deacetylase (NuRD) complex recognizes methylated DNA and silences expression of associated genes through histone deacetylase and nucleosome remodeling functions. Our previous structural work demonstrated that a coiled-coil interaction between MBD2 and GATA zinc finger domain containing 2A (GATAD2A/p66?) proteins recruits the chromodomain helicase DNA-binding protein (CHD4/Mi2?) to the NuRD complex and is necessary for MBD2-mediated DNA methylation-dependent gene silencing in vivo (Gnanapragasam, M. N., Scarsdale, J. N., Amaya, M. L., Webb, H. D., Desai, M. A., Walavalkar, N. M., Wang, S. Z., Zu Zhu, S., Ginder, G. D., and Williams, D. C., Jr. (2011) p66?-MBD2 coiled-coil interaction and recruitment of Mi-2 are critical for globin gene silencing by the MBD2-NuRD complex. Proc. Natl. Acad. Sci. U.S.A. 108, 7487-7492). The p66?-MBD2 interaction differs from most coiled-coils studied to date by forming an anti-parallel heterodimeric complex between two peptides that are largely monomeric in isolation. To further characterize unique features of this complex that drive heterodimeric specificity and high affinity binding, we carried out biophysical analyses of MBD2 and the related homologues MBD3, MBD3-like protein 1 (MBD3L1), and MBD3-like protein 2 (MBD3L2) as well as specific mutations that modify charge-charge interactions and helical propensity of the coiled-coil domains. Analytical ultracentrifugation analyses show that the individual peptides remain monomeric in isolation even at 300 ?M in concentration for MBD2. Circular dichroism analyses demonstrate a direct correlation between helical content of the coiled-coil domains in isolation and binding affinity for p66?. Furthermore, complementary electrostatic surface potentials and inherent helical content of each peptide are necessary to maintain high-affinity association. These factors lead to a binding affinity hierarchy of p66? for the different MBD2 homologues (MBD2 ? MBD3 > MBD3L1 ? MBD3L2) and suggest a hierarchical regulatory model in tissue and life cycle stage-specific silencing by NuRD complexes. PMID:23239876

  15. 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

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

    2013-01-01

    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

  16. Compositional C++: Compositional Parallel Programming

    Microsoft Academic Search

    K. Mani Chandy; Carl Kesselman

    1992-01-01

    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;

  17. Extracting task-level parallelism

    Microsoft Academic Search

    Milind Girkar; Constantine D. Polychronopoulos

    1995-01-01

    Automatic detection of task-level parallelism (also referred to as functional, DAG, unstructured, or thread parallelism) at various levels of program granularity is becoming increasingly important for parallelizing and back-end compilers. Parallelizing compilers detect iteration-level or coarser granularity parallelism which is suitable for parallel computers; detection of parallelism at the statement-or operation-level is essential for most modern microprocessors, including superscalar and

  18. Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel

    E-print Network

    Verschelde, Jan

    Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel the Fastest Fourier Transform February 2014 Introduction to Supercomputing (MCS 572) Parallel FFT & Isoefficiency L-14 14 February 2014 1 / 25 #12;Parallel FFT & Isoefficiency 1 The Fast Fourier Transform in Parallel the Fastest Fourier

  19. Parallel Lisp simulator

    SciTech Connect

    Weening, J.S.

    1988-05-01

    CSIM is a simulator for parallel Lisp, based on a continuation passing interpreter. It models a shared-memory multiprocessor executing programs written in Common Lisp, extended with several primitives for creating and controlling processes. This paper describes the structure of the simulator, measures its performance, and gives an example of its use with a parallel Lisp program.

  20. Parallel Programming Workshop

    NSDL National Science Digital Library

    This is an online course for parallel programming. Topics include MPI basics, point-to-point communication, derived datatypes, virtual topologies, collective communication, parallel I/O, and performance analysis and profiling. Other languages will be discussed such as OpenMP and High Performance Fortran (HPF). A Computational Fluid Dynamics section includes flux functions, Riemann solver, Euler equations, and Navier-Stokes equations.

  1. Grid Aware Parallelizing Algorithms

    Microsoft Academic Search

    Thomas Dramlitsch; Gabrielle Allen; Ed Seidel

    Running tightly coupled parallel MPI applications in a real grid environment using distributed MPI implementations (1, 2) can, in principle, make better and more fle xible use of computational resources, but for most parallel applications it has a major downside: The performance of such codes tends to be very poor. Most often the natural characteristics of realworld grids are responsible

  2. Parallelizing quantum circuits

    Microsoft Academic Search

    Anne Broadbent; Elham Kashefi

    2009-01-01

    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

  3. Code Parallelization with CAPO: A User Manual

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  4. Parallel computing works

    SciTech Connect

    Not Available

    1991-10-23

    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.

  5. Totally parallel multilevel algorithms

    NASA Technical Reports Server (NTRS)

    Frederickson, Paul O.

    1988-01-01

    Four totally parallel algorithms for the solution of a sparse linear system have common characteristics which become quite apparent when they are implemented on a highly parallel hypercube such as the CM2. These four algorithms are Parallel Superconvergent Multigrid (PSMG) of Frederickson and McBryan, Robust Multigrid (RMG) of Hackbusch, the FFT based Spectral Algorithm, and Parallel Cyclic Reduction. In fact, all four can be formulated as particular cases of the same totally parallel multilevel algorithm, which are referred to as TPMA. In certain cases the spectral radius of TPMA is zero, and it is recognized to be a direct algorithm. In many other cases the spectral radius, although not zero, is small enough that a single iteration per timestep keeps the local error within the required tolerance.

  6. Comprehensive Study on Tip Vortex with Lateral Jet Flow

    NASA Astrophysics Data System (ADS)

    Yang, Choongmo; Baek, Jehyun; Saito, Shigeru; Aoyama, Takashi

    Comprehensive numerical and experimental investigations of tip vortical characteristics were conducted for lateral tip jet flow over a fixed wing as a step to reduce blade vortex interaction noise. The tip vortex of a NACA0012 blade was measured and visualized for the fundamental study of tip vortical flow, and the results were compared with numerical data as a validation of numerical solvers. Three-dimensional compressible Euler/Navier-Stokes codes were used to calculate the effect of jet flow from the tip of an OLS (modified BHT 540) fixed blade at various freestream velocities and jet conditions. The results show that the jet flowing from the wing tip can diffuse the tip vortex enlarging the core size of tip vortex and weakening its strength. When applied to the blade vortex interaction phenomena, this enlarged and weak vortex can produce a lower pressure gradient on the blade surface, which means that the jet flow can effectively reduce blade vortex interaction noise.

  7. Parallel interacting edge cracks under pure bending

    E-print Network

    Moran, Ivan

    1991-01-01

    . When the fracture mode is pure mode I, equation 2. 5 gives ( Nfp ) I p Kgop? t 2zr +r Nf If op?2() (a) can be approximate to Nf ~2zr ( ? ') =K, +op?/nr Normal i z ing f or o~ma=Kp and defining Nf K~=~2xr ( ? ') t results in 16 &a &z sod l r...

  8. Parallel Adaptive Mesh Refinement

    SciTech Connect

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

    2005-03-04

    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.

  9. Bilingual parallel programming

    SciTech Connect

    Foster, I.; Overbeek, R.

    1990-01-01

    Numerous experiments have demonstrated that computationally intensive algorithms support adequate parallelism to exploit the potential of large parallel machines. Yet successful parallel implementations of serious applications are rare. The limiting factor is clearly programming technology. None of the approaches to parallel programming that have been proposed to date -- whether parallelizing compilers, language extensions, or new concurrent languages -- seem to adequately address the central problems of portability, expressiveness, efficiency, and compatibility with existing software. In this paper, we advocate an alternative approach to parallel programming based on what we call bilingual programming. We present evidence that this approach provides and effective solution to parallel programming problems. The key idea in bilingual programming is to construct the upper levels of applications in a high-level language while coding selected low-level components in low-level languages. This approach permits the advantages of a high-level notation (expressiveness, elegance, conciseness) to be obtained without the cost in performance normally associated with high-level approaches. In addition, it provides a natural framework for reusing existing code.

  10. Programming parallel architectures - The BLAZE family of languages

    NASA Technical Reports Server (NTRS)

    Mehrotra, Piyush

    1989-01-01

    This paper gives an overview of the various approaches to programming multiprocessor 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. This paper also describes recent work in the design of parallel languages. Research on languages for both shared and nonshared memory multiprocessors is described.

  11. DPL : Data Parallel Library Manual

    Microsoft Academic Search

    Daniel W. Palmer

    1994-01-01

    IntroductionIn [PP93] we described a transformational approach to realizing architecture independent parallel executionof a high-level parallel language. Detailed in that document is a series of steps that when applied to highlevel,data-parallel programs written in the Proteus programming language yield parallel execution on avariety of different parallel architectures. The Data Parallel Library (DPL) directly supports Proteus bysupplying a vital link in

  12. Parallel programming with PCN

    SciTech Connect

    Foster, I.; Tuecke, S.

    1991-12-01

    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).

  13. Parallels with nature

    NASA Astrophysics Data System (ADS)

    2014-10-01

    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.

  14. Series/Parallel Batteries

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    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

  15. Methodological Approach Parallel Computation

    E-print Network

    Paciorek, Chris

    and intensity (hurricanes, tornados, storm surges, etc.) are of great general interest. Chris Paciorek Parallel (levels) A 100-year flood is the size of flood expected to occur once every 100 years on average, also

  16. Scalable parallel communications

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  17. Scalable parallel communications

    NASA Astrophysics Data System (ADS)

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

    1992-06-01

    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.

  18. Parallelization: Binary Tree Traversal

    NSDL National Science Digital Library

    Aaron Weeden

    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.

  19. Artificial intelligence in parallel

    SciTech Connect

    Waldrop, M.M.

    1984-08-10

    The current rage in the Artificial Intelligence (AI) community is parallelism: the idea is to build machines with many independent processors doing many things at once. The upshot is that about a dozen parallel machines are now under development for AI alone. As might be expected, the approaches are diverse yet there are a number of fundamental issues in common: granularity, topology, control, and algorithms.

  20. A Scalable Process-Management Environment for Parallel Programs

    Microsoft Academic Search

    Ralph Butler; William Gropp; Ewing L. Lusk

    2000-01-01

    We present a process management system for parallel programssuch as those written using MPI. A primary goal of the system,which we call MPD (for multipurpose daemon), is to be scalable. By thiswe mean that startup of interactive parallel jobs comprising a thousandprocesses is quick, that signals can be quickly delivered to processes, andthat stdin, stdout, and stderr are managed intuitively.

  1. Volcano - An Extensible and Parallel Query Evaluation System

    Microsoft Academic Search

    Goetz Graefe

    1994-01-01

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

  2. Parallel computing: at the interface of high school and industry

    Microsoft Academic Search

    Robert A. Chesebrough; Ivan Turner

    2010-01-01

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

  3. Parallelizing Quantum Circuits

    E-print Network

    Anne Broadbent; Elham Kashefi

    2007-04-13

    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.

  4. Parallel optical sampler

    SciTech Connect

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

    2014-05-20

    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.

  5. Is quantum parallelism real?

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco; Uhlmann, Jeffrey

    2008-04-01

    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.

  6. Parallel Magnetic Resonance Imaging

    E-print Network

    Uecker, Martin

    2015-01-01

    The main disadvantage of Magnetic Resonance Imaging (MRI) are its long scan times and, in consequence, its sensitivity to motion. Exploiting the complementary information from multiple receive coils, parallel imaging is able to recover images from under-sampled k-space data and to accelerate the measurement. Because parallel magnetic resonance imaging can be used to accelerate basically any imaging sequence it has many important applications. Parallel imaging brought a fundamental shift in image reconstruction: Image reconstruction changed from a simple direct Fourier transform to the solution of an ill-conditioned inverse problem. This work gives an overview of image reconstruction from the perspective of inverse problems. After introducing basic concepts such as regularization, discretization, and iterative reconstruction, advanced topics are discussed including algorithms for auto-calibration, the connection to approximation theory, and the combination with compressed sensing.

  7. Adaptive parallel logic networks

    NASA Technical Reports Server (NTRS)

    Martinez, Tony R.; Vidal, Jacques J.

    1988-01-01

    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.

  8. Module 12: Parallel Circuits

    NSDL National Science Digital Library

    This module on parallel circuits contains a set of notes and a link to allaboutcircuits.com. The module was created by the California Regional Consortium for Engineering Advances in Technological Education (CREATE) which is “a joint effort between seven community colleges and over 30 large high tech engineering/technology employers.” This collection of study modules encourages students to learn about the basics of DC electronics and circuits. Module 12 teaches students about parallel circuits through a study guide and worked annotated sample problems.

  9. Parallel programming with PCN

    SciTech Connect

    Foster, I.; Tuecke, S.

    1993-01-01

    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.

  10. Parallel Spectral Numerical Methods

    NSDL National Science Digital Library

    Gong Chen

    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.

  11. Parallel hierarchical radiosity rendering

    SciTech Connect

    Carter, M.

    1993-07-01

    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.

  12. Massively parallel processor computer

    NASA Technical Reports Server (NTRS)

    Fung, L. W. (inventor)

    1983-01-01

    An apparatus for processing multidimensional data with strong spatial characteristics, such as raw image data, characterized by a large number of parallel data streams in an ordered array is described. It comprises a large number (e.g., 16,384 in a 128 x 128 array) of parallel processing elements operating simultaneously and independently on single bit slices of a corresponding array of incoming data streams under control of a single set of instructions. Each of the processing elements comprises a bidirectional data bus in communication with a register for storing single bit slices together with a random access memory unit and associated circuitry, including a binary counter/shift register device, for performing logical and arithmetical computations on the bit slices, and an I/O unit for interfacing the bidirectional data bus with the data stream source. The massively parallel processor architecture enables very high speed processing of large amounts of ordered parallel data, including spatial translation by shifting or sliding of bits vertically or horizontally to neighboring processing elements.

  13. High performance parallel architectures

    SciTech Connect

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

    1989-09-01

    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.

  14. Optimizing parallel reduction operations

    SciTech Connect

    Denton, S.M.

    1995-06-01

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

  15. Parallel hierarchical global illumination

    SciTech Connect

    Snell, Q.O.

    1997-10-08

    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.

  16. Parallel Circuits Lab

    NSDL National Science Digital Library

    This in-class lab exercise will give students a familiarity with basic series and parallel circuits as well as measuring voltage, current and resistance. The worksheet provided leads students through the experiment step by step. Spaces for student measurements and conclusions are provided on the sheet. This document may be downloaded in PDF file format.

  17. Parallel Traveling Salesman Problem

    NSDL National Science Digital Library

    David Joiner

    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.

  18. NAS Parallel Benchmarks Results

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  19. Parallelism for imaging applications

    Microsoft Academic Search

    M. P. Battaglia

    1993-01-01

    Numerous image processing functions involve repetitive operations and therefore can benefit from parallel processing, where performance may be significantly improved as a function of the number of processors applied to the task. One such application that requires processing to be as near to real-time as possible is vision processing and, in particular, low level vision processing. A system developed by

  20. Components and Interfaces of a Process Management System for Parallel Programs

    Microsoft Academic Search

    Ralph Butler; William Gropp; Ewing L. Lusk

    2001-01-01

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

  1. Time sharing massively parallel machines. Draft

    SciTech Connect

    Gorda, B.; Wolski, R.

    1995-03-01

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

  2. A parallel world in the dark

    SciTech Connect

    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

    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.

  3. Darwinian Evolution in Parallel Universes: A Parallel Genetic Algorithm for

    E-print Network

    Zhu, Mu

    Darwinian Evolution in Parallel Universes: A Parallel Genetic Algorithm for Variable Selection Mu outcome of interest commonly arises in various industrial engineering applications. The genetic algorithm modification. Our idea is to run a number of GAs in parallel without allowing each GA to fully converge

  4. ZAMBEZI: a parallel pattern parallel fault sequential circuit fault simulator

    Microsoft Academic Search

    Minesh B. Amin; Bapiraju Vinnakota

    1996-01-01

    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

  5. A parallel, portable and versatile treecode

    SciTech Connect

    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

    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.

  6. Parallelization: Sieve of Eratosthenes

    NSDL National Science Digital Library

    Aaron Weeden

    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.

  7. Parallel Subconvolution Filtering Architectures

    NASA Technical Reports Server (NTRS)

    Gray, Andrew A.

    2003-01-01

    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.

  8. Parallel multilevel preconditioners

    SciTech Connect

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

    1989-01-01

    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.

  9. Parallel Anisotropic Tetrahedral Adaptation

    NASA Technical Reports Server (NTRS)

    Park, Michael A.; Darmofal, David L.

    2008-01-01

    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.

  10. Parallel Consensual Neural Networks

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  11. Resistor Combinations for Parallel Circuits.

    ERIC Educational Resources Information Center

    McTernan, James P.

    1978-01-01

    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)

  12. The Galley Parallel File System

    NASA Technical Reports Server (NTRS)

    Nieuwejaar, Nils; Kotz, David

    1996-01-01

    As the I/O needs of parallel scientific applications increase, file systems for multiprocessors are being designed to provide applications with parallel access to multiple disks. Many parallel file systems present applications with a conventional Unix-like interface that allows the application to access multiple disks transparently. The interface conceals the parallelism within the file system, which increases the ease of programmability, but makes it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. Furthermore, most current parallel file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic parallel workloads. We discuss Galley's file structure and application interface, as well as an application that has been implemented using that interface.

  13. Laws for Communicating Parallel Processes

    E-print Network

    Baker, Henry

    1977-05-10

    This paper presents some laws that must be satisfied by computations involving communicating parallel processes. The laws are stated in the context of the actor theory, a model for distributed parallel computation, and ...

  14. Parallelization: Infectious Disease

    NSDL National Science Digital Library

    Aaron Weeden

    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.

  15. Xyce parallel electronic simulator.

    SciTech Connect

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

    2010-05-01

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

  16. Parallel sphere rendering

    SciTech Connect

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

    1996-10-01

    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.

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

    E-print Network

    Deiterding, Ralf

    with local velocity w, treat interface as moving rigid wall Construction of values in embedded boundary cells by interpolation / extrapolation Interpolate / constant value ex- trapolate values at ~x = x + 2n Velocity in ghost cells u = (2w · n - u · n)n + (u · t)t = 2 ((w - u) · n) n + u j-1 j j j-1 uj-1 uj 2w - uj 2w - uj-1 pj

  18. The Vesta parallel file system

    Microsoft Academic Search

    Peter F. Corbett; Dror G. Feitelson

    1996-01-01

    The Vesta parallel file system is designed to provide parallel file access to application programs running on multicomputers with parallel I\\/O subsystems. Vesta uses a new abstraction of files: a file is not a sequence of bytes, but rather it can be partitioned into multiple disjoint sequences that are accessed in parallel. The partitioning—which can also be changed dynamically—reduces the

  19. Using Motivational Interviewing Techniques to Address Parallel Process in Supervision

    ERIC Educational Resources Information Center

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

    2013-01-01

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

  20. Roo: A parallel theorem prover

    SciTech Connect

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

    1991-11-01

    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.

  1. A taxonomy of parallel sorting

    Microsoft Academic Search

    Dina Bitton; David J. DeWitt; David K. Hsaio; Jaishankar Menon

    1984-01-01

    We propose a taxonomy of parallel sorting that encompasses a broad range of array- and file-sorting algorithms. We analyze how research on parallel sorting has evolved, from the earliest sorting networks to shared memory algorithms and VLSI sorters. In the context of sorting networks, we describe two fundamental parallel merging schemes: the odd-even and the bitonic merge. We discuss sorting

  2. Synchronous Parallel Kinetic Monte Carlo

    SciTech Connect

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

    2006-12-14

    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.

  3. Parallel Job Scheduling and Workloads

    E-print Network

    Segall, Adrian

    Parallel Job Scheduling and Workloads Dror Feitelson Hebrew University #12;Parallel Jobs · A set · On multicores: probably more dynamic #12;MPP Parallel Job Scheduling · Each job is a rectangle in processorsXtime space · Given many jobs, we must schedule them to run on available processors · This is like packing

  4. Computer Assisted Parallel Program Generation

    E-print Network

    Kawata, Shigeo

    2015-01-01

    Parallel computation is widely employed in scientific researches, engineering activities and product development. Parallel program writing itself is not always a simple task depending on problems solved. Large-scale scientific computing, huge data analyses and precise visualizations, for example, would require parallel computations, and the parallel computing needs the parallelization techniques. In this Chapter a parallel program generation support is discussed, and a computer-assisted parallel program generation system P-NCAS is introduced. Computer assisted problem solving is one of key methods to promote innovations in science and engineering, and contributes to enrich our society and our life toward a programming-free environment in computing science. Problem solving environments (PSE) research activities had started to enhance the programming power in 1970's. The P-NCAS is one of the PSEs; The PSE concept provides an integrated human-friendly computational software and hardware system to solve a target ...

  5. Parallelized nested sampling

    NASA Astrophysics Data System (ADS)

    Henderson, R. Wesley; Goggans, Paul M.

    2014-12-01

    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.

  6. DPL: a data parallel language for the expression and execution of general parallel algorithm

    Microsoft Academic Search

    Robert Gordon Willhoft

    1995-01-01

    T a powerful, easy to use, parallel language continues despite very significant advances in the area of parallel processing. Many parallel languages are simply old sequential languages with parallel constructs added. This research describes the Data Parallel Language (DPL), a parallel language built from its foundations on parallel concepts. DPL bases much of its expression on data parallelism found in

  7. DPL: a data parallel language for the expression and execution of general parallel algorithm

    Microsoft Academic Search

    Robert Gordon Willhoft

    1995-01-01

    THE NEED FOR a powerful, easy to use, parallel language continues despite very significant advances in the area of parallel processing. Many parallel languages are simply old sequential languages with parallel constructs added. This research describes the Data Parallel Language (DPL), a parallel language built from its foundations on parallel concepts. DPL bases much of its expression on data parallelism

  8. Parallel flows with Soret effect in tilted cylinders

    NASA Technical Reports Server (NTRS)

    Jacqmin, David

    1990-01-01

    Henry and Roux (1986, 1987, 1988) have conducted extensive numerical studies on the interaction of Soret separation with convection in cylindrical geometry. Many of their solutions exhibit parallel flow away from end walls. Their parallel flow results can be matched by closed-form solutions. Solutions are nonunique in some parameter regions. Disappearance of one branch of solutions correlates with a sudden transition of Henry and Roux's results from a separated to a well-mixed flow.

  9. Parallel Eclipse Project Checkout

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  10. Highly parallel computation

    NASA Technical Reports Server (NTRS)

    Denning, Peter J.; Tichy, Walter F.

    1990-01-01

    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.

  11. Parallel sphere rendering

    SciTech Connect

    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

    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.

  12. Parallel Lines and Transversals

    NSDL National Science Digital Library

    Mrs. Sonntag

    2010-10-07

    In this lab you will review the names of angles formed by transversals. In addition you will discover the unique relationship that these pairs of anlges have when the transversal cuts through two parallel lines. picture We have already discussed many angle relationships in class. For example, we have learned to identify vertical angles and linear pairs. Each of the angles have a special relationship. Vertical angles are congruent, and Linear angles are supplementary. In the following lesson you will review the names of angle pairs ...

  13. Rotary wing aerodynamically generated noise

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  14. Principle and applications of the background oriented schlieren (BOS) method

    Microsoft Academic Search

    H. Richard; M. Raffel

    2001-01-01

    The practical aspects of an advanced schlieren technique, which has been presented by Meier (1999) and Richard et al (2000) and in a similar form by Dalziel et al (2000), are described in this paper. The application of the technique is demonstrated by three experimental investigations on compressible vortices. These vortices play a major role in the blade vortex interaction

  15. Detection, classification, and extraction of helicopter-radiated noise

    Microsoft Academic Search

    R. F. Dwyer

    1984-01-01

    Surface ships operating in conjunction with supporting helicopters may experience sonar performance degradation due to the accompanying interference from helicopter-radiated noise. The interference manifests itself in the time domain as impulses due to blade vortex interactions and in the frequency domain as harmonic components from both the main and tail rotors. But these components are not pure sinusoids. In addition,

  16. Structural integrity design for an active helicopter rotor blade with piezoelectric flap actuators

    Microsoft Academic Search

    Jaehwan Lee; Sangjoon Shin

    2011-01-01

    Helicopter uses a rotor system to generate lift, thrust and forces, and its aerodynamic environment is generally complex. Unsteady aerodynamic environment arises such as blade vortex interaction. This unsteady aerodynamic environment induces vibratory aerodynamic loads and high aeroacoustic noise. The aerodynamic load and aeroacoustic noise is at N times the rotor blade revolutions (N\\/rev). But conventional rotor control system composed

  17. JOURNAL DE PHYSIQUE IV Colloque C5, supplement au Journal de Physique III, Volume 4, mai 1994 C5-989

    E-print Network

    Paris-Sud XI, Université de

    potential Rotor blade/vortex interaction. Since three years we have developed an aerodynamic code named ROTAR, in order to compute the loads on the rotor blades [1,2,3,4] which serve as input data for an acoustic code named ROTAC for the noise

  18. Fluid Dynamics Conference and Exhibit AIAA-2004-2432 28 June-1 July, 2004/ Portland, OR.

    E-print Network

    Mittal, Rajat

    , location and orientation of the tip vortices have a direct impact on rotor performance and blade loading-tip vortex is one of the most important aerodynamic features of a helicopter rotor wake. The strength, size. In addition, in some flight configurations, blade-vortex interaction (BVI) can result in rotor noise

  19. Programming parallel architectures: The BLAZE family of languages

    NASA Technical Reports Server (NTRS)

    Mehrotra, Piyush

    1988-01-01

    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.

  20. Tile-based Level of Detail for the Parallel Age

    SciTech Connect

    Niski, K; Cohen, J D

    2007-08-15

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

  1. Tolerant (parallel) Programming

    NASA Technical Reports Server (NTRS)

    DiNucci, David C.; Bailey, David H. (Technical Monitor)

    1997-01-01

    In order to be truly portable, a program must be tolerant of a wide range of development and execution environments, and a parallel program is just one which must be tolerant of a very wide range. This paper first defines the term "tolerant programming", then describes many layers of tools to accomplish it. The primary focus is on F-Nets, a formal model for expressing computation as a folded partial-ordering of operations, thereby providing an architecture-independent expression of tolerant parallel algorithms. For implementing F-Nets, Cooperative Data Sharing (CDS) is a subroutine package for implementing communication efficiently in a large number of environments (e.g. shared memory and message passing). Software Cabling (SC), a very-high-level graphical programming language for building large F-Nets, possesses many of the features normally expected from today's computer languages (e.g. data abstraction, array operations). Finally, L2(sup 3) is a CASE tool which facilitates the construction, compilation, execution, and debugging of SC programs.

  2. Parallel ptychographic reconstruction.

    PubMed

    Nashed, Youssef S G; Vine, David J; Peterka, Tom; Deng, Junjing; Ross, Rob; Jacobsen, Chris

    2014-12-29

    Ptychography is an imaging method whereby a coherent beam is scanned across an object, and an image is obtained by iterative phasing of the set of diffraction patterns. It is able to be used to image extended objects at a resolution limited by scattering strength of the object and detector geometry, rather than at an optics-imposed limit. As technical advances allow larger fields to be imaged, computational challenges arise for reconstructing the correspondingly larger data volumes, yet at the same time there is also a need to deliver reconstructed images immediately so that one can evaluate the next steps to take in an experiment. Here we present a parallel method for real-time ptychographic phase retrieval. It uses a hybrid parallel strategy to divide the computation between multiple graphics processing units (GPUs) and then employs novel techniques to merge sub-datasets into a single complex phase and amplitude image. Results are shown on a simulated specimen and a real dataset from an X-ray experiment conducted at a synchrotron light source. PMID:25607174

  3. Performance characteristics of a parallel treecode

    E-print Network

    R. Valdarnini

    2002-12-11

    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.

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

    SciTech Connect

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

    1999-06-10

    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.

  5. Parallel Computing in SCALE

    SciTech Connect

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

    2010-01-01

    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.

  6. Parallel Grid Manipulations in Earth Science Calculations

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  7. PARLOG: parallel programming in logic

    Microsoft Academic Search

    Keith L. Clark; Steve Gregory

    1986-01-01

    PARLOG is a logic programming language in the sense that nearly every definition and query can be read as a sentence of predicate logic. It differs from PROLOG in incorporating parallel modes of evaluation. For reasons of efficient implementation, it distinguishes and separates and-parallel and or-parallel evaluation.PARLOG relations are divided into two types: single-solution relations and all-solutions relations. A conjunction

  8. Toward Parallel Document Clustering

    SciTech Connect

    Mogill, Jace A.; Haglin, David J.

    2011-09-01

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

  9. Parallel processing and expert systems

    NASA Technical Reports Server (NTRS)

    Yan, Jerry C.; Lau, Sonie

    1991-01-01

    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 90's cannot enjoy an increased level of autonomy without the efficient use of expert systems. Merely increasing the computational speed of uniprocessors may not be able to guarantee that real time demands are met for large expert systems. Speed-up via parallel processing must be pursued alongside the optimization of sequential implementations. Prototypes of parallel expert systems have been built at universities and industrial labs in the U.S. and Japan. The state-of-the-art research in progress related to parallel execution of expert systems was surveyed. The survey is divided into three major sections: (1) multiprocessors for parallel expert systems; (2) parallel languages for symbolic computations; and (3) measurements of parallelism of expert system. Results to date indicate that the parallelism achieved for these systems is small. In order to obtain greater speed-ups, data parallelism and application parallelism must be exploited.

  10. Parallel processor engine model program

    NASA Technical Reports Server (NTRS)

    Mclaughlin, P.

    1984-01-01

    The Parallel Processor Engine Model Program is a generalized engineering tool intended to aid in the design of parallel processing real-time simulations of turbofan engines. It is written in the FORTRAN programming language and executes as a subset of the SOAPP simulation system. Input/output and execution control are provided by SOAPP; however, the analysis, emulation and simulation functions are completely self-contained. A framework in which a wide variety of parallel processing architectures could be evaluated and tools with which the parallel implementation of a real-time simulation technique could be assessed are provided.

  11. Parallel Programming in the Age of Ubiquitous Parallelism

    NASA Astrophysics Data System (ADS)

    Pingali, Keshav

    2014-04-01

    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

  12. Fast Parallel Particle Methods: Angstroms to Gigaparsecs

    NASA Astrophysics Data System (ADS)

    Warren, Michael

    2006-03-01

    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 flows with vortex-particle methods, electromagnetic scattering and aerodynamics. Several these simulations were recognized with Gordon Bell prizes for significant achievement in parallel processing. We will discuss some recent work which used a series of 1-billion particle dark matter simulations to accurately determine the mass function of galaxy halos. These simulations required over 4x10^18 floating point operations (4 exaflops). Another focus of our current research is extending the HOT framework to biological systems, with the goal of simulating systems using over ten times as many atoms as the current state-of-the-art. This requires addressing several issues with current multipole algorithms, such as spatially-correlated errors and the ability to handle disparate time scales efficiently.

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

    NASA Astrophysics Data System (ADS)

    Guo, Zehua; Tang, Xian-Zhu

    2012-06-01

    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.

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

    SciTech Connect

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

    2012-06-15

    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.

  15. Parallel execution of logic programs

    SciTech Connect

    Conery, J.S.

    1987-01-01

    This work is about the AND/OR Process Model, an abstract model for parallel execution of logic programs. This book defines a framework for implementing parallel interpreters. The research presented here provides an intermediate level of abstraction between hardware and semantics, a set of requirements for a parallel interpreter running on a multiprocessor architecture. Contents. LIST OF FIGURES. 1. INTRODUCTION. 2. LOGIC PROGRAMMING. 2.1 Syntax. 2.2 Semantics. 2.3 Control. 2.4 Prolog. 2.5 Alternate Control Strategies. 2.6 Chapter Summary. 3. PARALLELISM IN LOGIC PROGRAMS. 3.1 Models for OR Parallelism. 3.2 Models for AND Parallelism. 3.3 Low Level Parallelism 3.4 Chapter Summary. 4. THE AND/OR PROCESS MODEL. 4.1 Oracle. 4.2 Messages. 4.3 OR Processes. 4.4 AND Processes. 4.5 Interpreter. 4.6 Programming Language. 4.7 Chapter Summary. 5. PARALLEL OR PROCESSES. 5.1 Operating Modes. 5.2 Execution. 5.3 Example. 5.4 Chapter Summary.

  16. Applications Parallel computing for chromosome

    E-print Network

    Bhandarkar, Suchendra "Suchi" M.

    Applications Parallel computing for chromosome reconstruction via ordering of DNA sequences and implementation of a suite of parallel algorithms called PARODS, for chromosome reconstruction via ordering of DNA.V. All rights reserved. Keywords: Clone ordering; DNA sequencing; Chromosome reconstruction; Simulated

  17. Limited width parallel prefix circuits

    Microsoft Academic Search

    David A. Carlson; Binay Sugla

    1990-01-01

    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

  18. Parallel Matlab MIT Lincoln Laboratory

    E-print Network

    Kepner, Jeremy

    by the Department of Defense under Air Force Contract F19628-00-C-0002. Opinions, interpretations, conclusions development, testing and system integration · MatlabMPI allows any Matlab program to become a high performance parallel program · MatlabMPI allows any Matlab program to become a high performance parallel program #12

  19. Patterns for Parallel Application Programs

    Microsoft Academic Search

    Berna L. Massingill

    1999-01-01

    We are involved in an ongoing effort to design a pattern language for parallel application programs. The pattern language consists of a set of patterns that guide the programmer through the entire process of developing a parallel program, including patterns that help find the concurrency in the problem, patterns that help find the appropriate algorithm structure to exploit the concurrency

  20. Interference effects on scattering by parallel fibers

    NASA Technical Reports Server (NTRS)

    White, Susan M.; Kumar, Sunil

    1989-01-01

    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.

  1. Parallel contingency statistics with Titan.

    SciTech Connect

    Thompson, David C.; Pebay, Philippe Pierre

    2009-09-01

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

  2. Optimal parallel quantum query algorithms

    E-print Network

    Stacey Jeffery; Frederic Magniez; Ronald de Wolf

    2015-02-20

    We study the complexity of quantum query algorithms that make p queries in parallel in each timestep. This model is in part motivated by the fact that decoherence times of qubits are typically small, so it makes sense to parallelize quantum algorithms as much as possible. We show tight bounds for a number of problems, specifically Theta((n/p)^{2/3}) p-parallel queries for element distinctness and Theta((n/p)^{k/(k+1)} for k-sum. Our upper bounds are obtained by parallelized quantum walk algorithms, and our lower bounds are based on a relatively small modification of the adversary lower bound method, combined with recent results of Belovs et al. on learning graphs. We also prove some general bounds, in particular that quantum and classical p-parallel complexity are polynomially related for all total functions f when p is small compared to f's block sensitivity.

  3. The Galley Parallel File System

    NASA Technical Reports Server (NTRS)

    Nieuwejaar, Nils; Kotz, David

    1996-01-01

    Most current multiprocessor file systems are designed to use multiple disks in parallel, using the high aggregate bandwidth to meet the growing I/0 requirements of parallel scientific applications. Many multiprocessor file systems provide applications with a conventional Unix-like interface, allowing the application to access multiple disks transparently. This interface conceals the parallelism within the file system, increasing the ease of programmability, but making it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. In addition to providing an insufficient interface, most current multiprocessor file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic scientific multiprocessor workloads. We discuss Galley's file structure and application interface, as well as the performance advantages offered by that interface.

  4. The science of computing - The evolution of parallel processing

    NASA Technical Reports Server (NTRS)

    Denning, P. J.

    1985-01-01

    The present paper is concerned with the approaches to be employed to overcome the set of limitations in software technology which impedes currently an effective use of parallel hardware technology. The process required to solve the arising problems is found to involve four different stages. At the present time, Stage One is nearly finished, while Stage Two is under way. Tentative explorations are beginning on Stage Three, and Stage Four is more distant. In Stage One, parallelism is introduced into the hardware of a single computer, which consists of one or more processors, a main storage system, a secondary storage system, and various peripheral devices. In Stage Two, parallel execution of cooperating programs on different machines becomes explicit, while in Stage Three, new languages will make parallelism implicit. In Stage Four, there will be very high level user interfaces capable of interacting with scientists at the same level of abstraction as scientists do with each other.

  5. Revisiting parallel catadioptric goniophotometers

    NASA Astrophysics Data System (ADS)

    Karamata, Boris; Andersen, Marilyne

    2013-04-01

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

  6. Trajectories in parallel optics.

    PubMed

    Klapp, Iftach; Sochen, Nir; Mendlovic, David

    2011-10-01

    In our previous work we showed the ability to improve the optical system's matrix condition by optical design, thereby improving its robustness to noise. It was shown that by using singular value decomposition, a target point-spread function (PSF) matrix can be defined for an auxiliary optical system, which works parallel to the original system to achieve such an improvement. In this paper, after briefly introducing the all optics implementation of the auxiliary system, we show a method to decompose the target PSF matrix. This is done through a series of shifted responses of auxiliary optics (named trajectories), where a complicated hardware filter is replaced by postprocessing. This process manipulates the pixel confined PSF response of simple auxiliary optics, which in turn creates an auxiliary system with the required PSF matrix. This method is simulated on two space variant systems and reduces their system condition number from 18,598 to 197 and from 87,640 to 5.75, respectively. We perform a study of the latter result and show significant improvement in image restoration performance, in comparison to a system without auxiliary optics and to other previously suggested hybrid solutions. Image restoration results show that in a range of low signal-to-noise ratio values, the trajectories method gives a significant advantage over alternative approaches. A third space invariant study case is explored only briefly, and we present a significant improvement in the matrix condition number from 1.9160e+013 to 34,526. PMID:21979506

  7. High Performance Parallel Architectures

    NASA Technical Reports Server (NTRS)

    El-Ghazawi, Tarek; Kaewpijit, Sinthop

    1998-01-01

    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.

  8. Parallel Strategies for Crash and Impact Simulations

    SciTech Connect

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

    1998-12-07

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

  9. Parallel node placement method by bubble simulation

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  10. 1998Second InternationalConferenceon Knowledge-Based IntelligentElectronicSystems, 21-23April 1998,Adelaide, Australia. Editors, L.C. Jain and R.KJain InteractiveAnimation for Visualisationof Mapping of Parallel

    E-print Network

    Thomas, Bruce

    and Ungar [51 supports cartoon-style animation techniques. They describe three principles (solidity,Adelaide, Australia. Editors, L.C. Jain and R.KJain InteractiveAnimation for Visualisationof Mapping programming environment. Extending the use of animation techniques will have a two fold effect

  11. Overview of the Vesta parallel file system

    Microsoft Academic Search

    Peter F. Corbett; Sandra Johnson Baylor; Dror G. Feitelson

    1993-01-01

    The Vesta parallel file system provides parallel access from compute nodes to files distributed across I\\/O nodes in a massively parallel computer. Vesta is intended to solve the I\\/O problems of massively parallel computers executing numerically intensive scientific applications. Vesta has three interesting characteristics: First, it provides a user defined parallel view of file data, and allows user defined partitioning

  12. Parallel processing and expert systems

    NASA Technical Reports Server (NTRS)

    Lau, Sonie; Yan, Jerry C.

    1991-01-01

    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.

  13. Parallel processing for control applications

    SciTech Connect

    Telford, J. W. (John W.)

    2001-01-01

    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.

  14. Ternary SNARE complexes in parallel versus anti-parallel orientation: examination of their disassembly using single-molecule force spectroscopy.

    PubMed

    Liu, Wei; Stout, Randy F; Parpura, Vladimir

    2012-01-01

    Interactions between the proteins of the ternary soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptor (SNARE) complex, synaptobrevin 2 (Sb2), syntaxin 1A (Sx1A) and synaptosome-associated protein of 25 kDa (SNAP25) can be readily assessed using force spectroscopy single-molecule measurements. We studied interactions during the disassembly of the ternary SNARE complex pre-formed by binding Sb2 in parallel or anti-parallel orientations to the binary Sx1A-SNAP25B acceptor complex. We determined the spontaneous dissociation lifetimes and found that the stability of the anti-parallel ternary SNARE complex is ?1/3 less than that of the parallel complex. While the free energies were very similar, within 0.5 k(B)T, for both orientations, the enthalpy changes (42.1 k(B)T and 39.8 k(B)T, for parallel and anti-parallel orientations, respectively) indicate that the parallel ternary complex is energetically advantageous by 2.3 k(B)T. Indeed, both ternary SNARE complex orientations were much more stable (by ?4-13 times) and energetically favorable (by ?9-13 k(B)T) than selected binary complexes, constituents of the ternary complex, in both orientations. We propose a model which considers the geometry for the vesicle approach to the plasma membrane with favorable energies and stability as the basis for preferential usage of the parallel ternary SNARE complex in exocytosis. PMID:22525946

  15. Parallel integer sorting with medium and fine-scale parallelism

    NASA Technical Reports Server (NTRS)

    Dagum, Leonardo

    1993-01-01

    Two new parallel integer sorting algorithms, queue-sort and barrel-sort, are presented and analyzed in detail. These algorithms do not have optimal parallel complexity, yet they show very good performance in practice. Queue-sort designed for fine-scale parallel architectures which allow the queueing of multiple messages to the same destination. Barrel-sort is designed for medium-scale parallel architectures with a high message passing overhead. The performance results from the implementation of queue-sort on a Connection Machine CM-2 and barrel-sort on a 128 processor iPSC/860 are given. The two implementations are found to be comparable in performance but not as good as a fully vectorized bucket sort on the Cray YMP.

  16. Template based parallel checkpointing in a massively parallel computer system

    DOEpatents

    Archer, Charles Jens (Rochester, MN); Inglett, Todd Alan (Rochester, MN)

    2009-01-13

    A method and apparatus for a template based parallel checkpoint save for a massively parallel super computer system using a parallel variation of the rsync protocol, and network broadcast. In preferred embodiments, the checkpoint data for each node is compared to a template checkpoint file that resides in the storage and that was previously produced. Embodiments herein greatly decrease the amount of data that must be transmitted and stored for faster checkpointing and increased efficiency of the computer system. Embodiments are directed to a parallel computer system with nodes arranged in a cluster with a high speed interconnect that can perform broadcast communication. The checkpoint contains a set of actual small data blocks with their corresponding checksums from all nodes in the system. The data blocks may be compressed using conventional non-lossy data compression algorithms to further reduce the overall checkpoint size.

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

    Microsoft Academic Search

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

    1993-01-01

    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.

  18. Software for parallel processing applications

    SciTech Connect

    Wolbers, S.

    1992-10-01

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

  19. Realtime Ray Tracing on a Hibrid Parallel Architecture

    Microsoft Academic Search

    Xin Yang; Duan-qing Xu; Wen-zhi Chen

    2009-01-01

    Octrees are attractive data structures for rendering of volumes, as they provide simultaneously uniform and hierarchical data encapsulation. We present a simple and efficient algorithm for interactive ray tracing on a hybrid architectures, which takes advantage of the parallelism present by heavily exploiting the hardware for the CPU and GPU, which has been observed to give superior performance in ray

  20. Massively parallel visualization on linux clusters with Rocketeer Voyager

    Microsoft Academic Search

    Robert A. Fiedler; John C. Norris

    This paper describes Rocketeer Voyager, a versatile 3-D scientific visualization tool which processes in parallel a series of HDF output dumps from a large scale simulation. Rocketeer reads data defined on many types of grids and displays translucent surfaces and isosurfaces, vectors as glyphs, surface and 3-D meshes, etc. An interactive version is first used to view a few snapshots,

  1. Molecular dynamics in arbitrary geometries: Parallel evaluation of pair forces

    Microsoft Academic Search

    Graham B. Macpherson; Jason M. Reese

    2008-01-01

    A new algorithm for calculating intermolecular pair forces in molecular dynamics (MD) simulations on a distributed parallel computer is presented. The arbitrary interacting cells algorithm (AICA) is designed to operate on geometrical domains defined by an unstructured, arbitrary polyhedral mesh that has been spatially decomposed into irregular portions for parallelisation. It is intended for nano scale fluid mechanics simulation by

  2. Learning and evaluating response prediction models using parallel listener consensus

    Microsoft Academic Search

    Iwan de Kok; Derya Ozkan; Dirk Heylen; Louis-Philippe Morency

    2010-01-01

    Traditionally listener response prediction models are learned from pre-recorded dyadic interactions. Because of individual differences in behavior, these recordings do not capture the complete ground truth. Where the recorded listener did not respond to an opportunity provided by the speaker, another listener would have responded or vice versa. In this paper, we introduce the concept of parallel listener consensus where

  3. PARALLEL IMPLEMENTATION OF VLSI HED CIRCUIT SIMULATION

    E-print Network

    Silc, Jurij

    14 PARALLEL IMPLEMENTATION OF VLSI HED CIRCUIT SIMULATION INFORMATICA 2/91 Keywords: circuit simulation, direct method, vvaveform relaxation, parallel algorithm, parallel computer architecture Srilata, India Junj Sile Marjan Spegel Jozef Stefan Institute, Ljubljana, Slovenia The importance of circuit

  4. Automatic Generation of Parallel CRC Circuits

    Microsoft Academic Search

    Michael Sprachmann

    2001-01-01

    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

  5. A Parallel Logic Programming Language for PEPSys

    Microsoft Academic Search

    Michael Rate

    This paper describes a new parallel Logic Programming language designed to exploit the OR- and Independent AND- parallelisms. The language is based on conventional Prolog but with natural extensions to support handling of multiple solutions and expression of parallelism.

  6. Uhlmann's parallelism Nagaoka's quantum information geometry

    E-print Network

    Yamamoto, Hirosuke

    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

  7. Load Balancing of Parallelized Information Filters

    E-print Network

    Rowe, Neil C.

    Load Balancing of Parallelized Information Filters Neil C. Rowe, Member, IEEE Computer Society develop an analytic model for the costs and advantages of load rebalancing the parallel filtering, data parallelism, load balancing, information retrieval, conjunctions, optimality, and Monte Carlo

  8. Parallel stochastic systems biology in the cloud.

    PubMed

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

    2014-09-01

    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

  9. Designing and Building Parallel Programs

    NSDL National Science Digital Library

    Designing and Building Parallel Programs [Online] is an innovative traditional print and online resource publishing project. It incorporates the content of a textbook published by Addison-Wesley into an evolving online resource.

  10. Debugging Serial and Parallel Codes

    NSDL National Science Digital Library

    NCSA

    Introduction to debugger software. Serial debugging of array indexing, arguments mismatch, infinite loops, pointer misuse, and memory allocation. Parallel debugging of process count, shared memory, MPI I/O, collective communications, and OpenMP scope.

  11. Demonstrating Forces between Parallel Wires.

    ERIC Educational Resources Information Center

    Baker, Blane

    2000-01-01

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

  12. Parallel algorithms for message decomposition

    SciTech Connect

    Teng, S.H.; Wang, B.

    1987-06-01

    The authors consider the deterministic and random parallel complexity (time and processor) of message decoding: an essential problem in communications systems and translation systems. They present an optimal parallel algorithm to decompose prefix-coded messages and uniquely decipherable-coded messages in O(n/P) time, using O(P) processors (for all P:1 less than or equal toPless than or equal ton/log n) deterministically as well as randomly on the weakest version of parallel random access machines in which concurrent read and concurrent write to a cell in the common memory are not allowed. This is done by reducing decoding to parallel finite-state automata simulation and the prefix sums.

  13. Turbomachinery CFD on parallel computers

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  14. Interpreting Quantum Parallelism by Sequents

    NASA Astrophysics Data System (ADS)

    Battilotti, Giulia

    2010-12-01

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

  15. New NAS Parallel Benchmarks Results

    NASA Technical Reports Server (NTRS)

    Yarrow, Maurice; Saphir, William; VanderWijngaart, Rob; Woo, Alex; Kutler, Paul (Technical Monitor)

    1997-01-01

    NPB2 (NAS (NASA Advanced Supercomputing) Parallel Benchmarks 2) is an implementation, based on Fortran and the MPI (message passing interface) message passing standard, of the original NAS Parallel Benchmark specifications. NPB2 programs are run with little or no tuning, in contrast to NPB vendor implementations, which are highly optimized for specific architectures. NPB2 results complement, rather than replace, NPB results. Because they have not been optimized by vendors, NPB2 implementations approximate the performance a typical user can expect for a portable parallel program on distributed memory parallel computers. Together these results provide an insightful comparison of the real-world performance of high-performance computers. New NPB2 features: New implementation (CG), new workstation class problem sizes, new serial sample versions, more performance statistics.

  16. "Feeling" Series and Parallel Resistances.

    ERIC Educational Resources Information Center

    Morse, Robert A.

    1993-01-01

    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)

  17. Parallel computation and computers for artificial intelligence

    SciTech Connect

    Kowalik, J.S. (Boeing Computer Services, Bellevue, WA (US))

    1988-01-01

    This book discusses Parallel Processing in Artificial Intelligence; Parallel Computing using Multilisp; Execution of Common Lisp in a Parallel Environment; Qlisp; Restricted AND-Parallel Execution of Logic Programs; PARLOG: Parallel Programming in Logic; and Data-driven Processing of Semantic Nets. Attention is also given to: Application of the Butterfly Parallel Processor in Artificial Intelligence; On the Range of Applicability of an Artificial Intelligence Machine; Low-level Vision on Warp and the Apply Programming Mode; AHR: A Parallel Computer for Pure Lisp; FAIM-1: An Architecture for Symbolic Multi-processing; and Overview of Al Application Oriented Parallel Processing Research in Japan.

  18. PMI: A Scalable Parallel Process-Management Interface for Extreme-Scale Systems

    E-print Network

    Buntinas, Darius

    PMI: A Scalable Parallel Process-Management Interface for Extreme-Scale Systems Pavan Balaji1 the processes that make up the execution of a parallel program. The process-management system must be able different process managers to interact with the MPI library in a standardized way. In this paper, we

  19. Exploiting Parallelism to Accelerate Keyword Search On Deep-web Sources

    E-print Network

    Agrawal, Gagan

    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

  20. Web based parallel/distributed medical data mining using software agents

    SciTech Connect

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

    1997-12-31

    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.

  1. Efficiency of parallel direct optimization

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  2. Parallel asynchronous particle swarm optimization

    PubMed Central

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

    2006-01-01

    SUMMARY The high computational cost of complex engineering optimization problems has motivated the development of parallel optimization algorithms. A recent example is the parallel particle swarm optimization (PSO) algorithm, which is valuable due to its global search capabilities. Unfortunately, because existing parallel implementations are synchronous (PSPSO), they do not make efficient use of computational resources when a load imbalance exists. In this study, we introduce a parallel asynchronous PSO (PAPSO) algorithm to enhance computational efficiency. The performance of the PAPSO algorithm was compared to that of a PSPSO algorithm in homogeneous and heterogeneous computing environments for small- to medium-scale analytical test problems and a medium-scale biomechanical test problem. For all problems, the robustness and convergence rate of PAPSO were comparable to those of PSPSO. However, the parallel performance of PAPSO was significantly better than that of PSPSO for heterogeneous computing environments or heterogeneous computational tasks. For example, PAPSO was 3.5 times faster than was PSPSO for the biomechanical test problem executed on a heterogeneous cluster with 20 processors. Overall, PAPSO exhibits excellent parallel performance when a large number of processors (more than about 15) is utilized and either (1) heterogeneity exists in the computational task or environment, or (2) the computation-to-communication time ratio is relatively small. PMID:17224972

  3. Parallel processing of natural language

    SciTech Connect

    Chang, H.O.

    1986-01-01

    Two types of parallel natural language processing are studied in this work: (1) the parallelism between syntactic and nonsyntactic processing and (2) the parallelism within syntactic processing. It is recognized that a syntactic category can potentially be attached to more than one node in the syntactic tree of a sentence. Even if all the attachments are syntactically well-formed, nonsyntactic factors such as semantic and pragmatic consideration may require one particular attachment. Syntactic processing must synchronize and communicate with nonsyntactic processing. Two syntactic processing algorithms are proposed for use in a parallel environment: Early's algorithm and the LR(k) algorithm. Conditions are identified to detect the syntactic ambiguity and the algorithms are augmented accordingly. It is shown that by using nonsyntactic information during syntactic processing, backtracking can be reduced, and the performance of the syntactic processor is improved. For the second type of parallelism, it is recognized that one portion of a grammar can be isolated from the rest of the grammar and be processed by a separate processor. A partial grammar of a larger grammar is defined. Parallel syntactic processing is achieved by using two processors concurrently: the main processor (mp) and the two processors concurrently: the main processor (mp) and the auxiliary processor (ap).

  4. Parallel Performance Optimization of the Direct Simulation Monte Carlo Method

    NASA Astrophysics Data System (ADS)

    Gao, Da; Zhang, Chonglin; Schwartzentruber, Thomas

    2009-11-01

    Although the direct simulation Monte Carlo (DSMC) particle method is more computationally intensive compared to continuum methods, it is accurate for conditions ranging from continuum to free-molecular, accurate in highly non-equilibrium flow regions, and holds potential for incorporating advanced molecular-based models for gas-phase and gas-surface interactions. As available computer resources continue their rapid growth, the DSMC method is continually being applied to increasingly complex flow problems. Although processor clock speed continues to increase, a trend of increasing multi-core-per-node parallel architectures is emerging. To effectively utilize such current and future parallel computing systems, a combined shared/distributed memory parallel implementation (using both Open Multi-Processing (OpenMP) and Message Passing Interface (MPI)) of the DSMC method is under development. The parallel implementation of a new state-of-the-art 3D DSMC code employing an embedded 3-level Cartesian mesh will be outlined. The presentation will focus on performance optimization strategies for DSMC, which includes, but is not limited to, modified algorithm designs, practical code-tuning techniques, and parallel performance optimization. Specifically, key issues important to the DSMC shared memory (OpenMP) parallel performance are identified as (1) granularity (2) load balancing (3) locality and (4) synchronization. Challenges and solutions associated with these issues as they pertain to the DSMC method will be discussed.

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

    DOEpatents

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

    2014-08-12

    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.

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

    DOEpatents

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

    2014-02-11

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  9. Parallelizing Timed Petri Net simulations

    NASA Technical Reports Server (NTRS)

    Nicol, David M.

    1993-01-01

    The possibility of using parallel processing to accelerate the simulation of Timed Petri Nets (TPN's) was studied. It was recognized that complex system development tools often transform system descriptions into TPN's or TPN-like models, which are then simulated to obtain information about system behavior. Viewed this way, it was important that the parallelization of TPN's be as automatic as possible, to admit the possibility of the parallelization being embedded in the system design tool. Later years of the grant were devoted to examining the problem of joint performance and reliability analysis, to explore whether both types of analysis could be accomplished within a single framework. In this final report, the results of our studies are summarized. We believe that the problem of parallelizing TPN's automatically for MIMD architectures has been almost completely solved for a large and important class of problems. Our initial investigations into joint performance/reliability analysis are two-fold; it was shown that Monte Carlo simulation, with importance sampling, offers promise of joint analysis in the context of a single tool, and methods for the parallel simulation of general Continuous Time Markov Chains, a model framework within which joint performance/reliability models can be cast, were developed. However, very much more work is needed to determine the scope and generality of these approaches. The results obtained in our two studies, future directions for this type of work, and a list of publications are included.

  10. Parallel object-oriented programming in SYMPAL

    Microsoft Academic Search

    I. Danieli; S. Cohen

    1988-01-01

    An object-oriented programming model in a parallel system is presented. It is designed for modelling, describing and solving a wide variety of AI problems. AI applications, in particular, deal with knowledge-bases and a lot of problems have parallel solutions. Therefore, while parallel computers are becoming widespread, there is a need for a rich language that enables the exploitation of parallelism

  11. Dynamic parallel complexity of computational circuits

    Microsoft Academic Search

    Gary L. Miller; Shang-Hua Teng

    1987-01-01

    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

  12. Refinement Transformation Using Abstract Parallel Machines

    E-print Network

    Goodman, Joy

    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

  13. File concepts for parallel I/O

    NASA Technical Reports Server (NTRS)

    Crockett, Thomas W.

    1989-01-01

    The subject of input/output (I/O) was often neglected in the design of parallel computer systems, although for many problems I/O rates will limit the speedup attainable. The I/O problem is addressed by considering the role of files in parallel systems. The notion of parallel files is introduced. Parallel files provide for concurrent access by multiple processes, and utilize parallelism in the I/O system to improve performance. Parallel files can also be used conventionally by sequential programs. A set of standard parallel file organizations is proposed, organizations are suggested, using multiple storage devices. Problem areas are also identified and discussed.

  14. Parallel Adaptive Mesh Refinement Library

    NASA Technical Reports Server (NTRS)

    Mac-Neice, Peter; Olson, Kevin

    2005-01-01

    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.

  15. Parallel integrated frame synchronizer chip

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  16. Performance Issues in Parallelized Network Protocols

    Microsoft Academic Search

    Erich M. Nahum; David J. Yates; James F. Kurose; Donald F. Towsley

    1994-01-01

    Parallel processing has been proposed as a means of improving network protocol throughput. Several different strategies have been taken towards parallelizing protocol s. A relatively popular approach is packet-level parallelism, where packets are distributed across processors. This paper provides an experimental performance study of packet-level parallelism on a contemporary shared- memory multiprocessor. We examine several unexplored areas in packet-level parallelism

  17. Parallels plane projection and its geometric features

    Microsoft Academic Search

    ChengHu Zhou; Ting Ma; Liao Yang; Biao Qin

    2007-01-01

    A new equivalent map projection called the parallels plane projection is proposed in this paper. The transverse axis of the\\u000a parallels plane projection is the expansion of the equator and its vertical axis equals half the length of the central meridian.\\u000a On the parallels plane projection, meridians are projected as sine curves and parallels are a series of straight, parallel

  18. Gang scheduling a parallel machine

    SciTech Connect

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

    1991-12-01

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

  19. Gang scheduling a parallel machine

    SciTech Connect

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

    1991-03-01

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

  20. Parallelization of the SIR code

    NASA Astrophysics Data System (ADS)

    Thonhofer, S.; Bellot Rubio, L. R.; Utz, D.; Jur?ak, J.; Hanslmeier, A.; Piantschitsch, I.; Pauritsch, J.; Lemmerer, B.; Guttenbrunner, S.

    A high-resolution 3-dimensional model of the photospheric magnetic field is essential for the investigation of small-scale solar magnetic phenomena. The SIR code is an advanced Stokes-inversion code that deduces physical quantities, e.g. magnetic field vector, temperature, and LOS velocity, from spectropolarimetric data. We extended this code by the capability of directly using large data sets and inverting the pixels in parallel. Due to this parallelization it is now feasible to apply the code directly on extensive data sets. Besides, we included the possibility to use different initial model atmospheres for the inversion, which enhances the quality of the results.

  1. Nerve-pulse interactions

    SciTech Connect

    Scott, A.C.

    1982-01-01

    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.

  2. Parallel-processing techniques for production systems

    SciTech Connect

    da Mota Tenorio, M.F.

    1987-01-01

    Production systems static and dynamic characteristics are modeled with the use of graph grammar, in order to create means to increase the processing efficiency and the use of parallel computation through compile-time analysis. The model is used to explicate rule interaction, so that proofs of equivalence between knowledge bases can be attempted. Solely relying on program static characteristics shown by the model, a series of observations are made to determine the system dynamic characteristics and modifications to the original knowledge base are suggested as a means of increasing efficiency and decreasing overall search and computational effort. Dependencies between the rules are analyzed and different approaches for automatic detection are presented. From rule dependences, tools for programming environments,logical evaluation of search spaces and Petri net models of production systems are shown. An algorithm for the allocation and partitioning of a production system into a multiprocessor system is also shown, and addresses the problems of communication and execution of these systems in parallel. Finally, the results of a simulator constructed to test several strategies, networks, and algorithms are presented.

  3. A vestibular prosthesis with highly-isolated parallel multichannel stimulation.

    PubMed

    Jiang, Dai; Cirmirakis, Dominik; Demosthenous, Andreas

    2015-02-01

    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

  4. Parallel computation of seismic analysis of high arch dam

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    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.

  5. Parallelization: Area Under a Curve

    NSDL National Science Digital Library

    Aaron Weeden

    This module teaches: 1) How to approximate the area under a curve using a Riemann sum, 2) how approximating the area under a curve is used in solutions to scientific problems, 3) how to implement parallel code for Area Under a Curve (including versions that use shared memory via OpenMP, distributed memory via the Message Passing Interface (MPI), and hybrid via a combination of MPI and OpenMP), 4) how to measure the performance and scaling of a parallel application in multicore and manycore environments, and 5) how Area Under a Curve falls into the MapReduce "dwarf" (a class of algorithms that have similar communication and computation patterns). Upon completion of this module, students should be able to: 1) Understand the importance of approximating the area under a curve in modeling scientific problems, 2) Design a parallel algorithm and implement it using MPI and/or OpenMP, 3) Measure the scalability of a parallel code over multiple or many cores, and 4) Explain the communication and computation patterns of the MapReduce dwarf. It is assumed that students will have prerequisite experience with C or Fortran 90, *nix systems, and modular arithmetic.

  6. Parallelization: Conway's Game of Life

    NSDL National Science Digital Library

    Aaron Weeden

    This module teaches: 1) Conway's Game of Life as an example of a cellular automaton, 2) how cellular automata are used in solutions to scientific problems, 3) how to implement parallel code for Conway's Game of Life (including versions that use shared memory via OpenMP, distributed memory via the Message Passing Interface (MPI), and hybrid via a combination of OpenMP and MPI), 4) how to measure the performance and scaling of a parallel application in multicore and manycore environments, and 5) how cellular automata fall into the Structured Grid "dwarf" (a class of algorithms that have similar communication and computation patterns). Upon completion of this module, students should be able to: 1) Understand the importance of cellular automata in modeling scientific problems, 2) Design a parallel algorithm and implement it using OpenMP and/or MPI, 3) Measure the scalability of a parallel code over multiple or many cores, and 4) Explain the communication and computation patterns of the Structured Grid dwarf. It is assumed that students will have prerequisite experience with C or Fortran 90, *nix systems, and modular arithmetic.

  7. Parallel, Distributed Scripting with Python

    SciTech Connect

    Miller, P J

    2002-05-24

    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.

  8. Where are the parallel algorithms?

    NASA Technical Reports Server (NTRS)

    Voigt, R. G.

    1985-01-01

    Four paradigms that can be useful in developing parallel algorithms are discussed. These include computational complexity analysis, changing the order of computation, asynchronous computation, and divide and conquer. Each is illustrated with an example from scientific computation, and it is shown that computational complexity must be used with great care or an inefficient algorithm may be selected.

  9. Parallel Programming Models and Paradigms

    E-print Network

    Melbourne, University of

    /workstations and networks. These technologies are making a network/cluster of computers an appealing vehicle for cost­effective, HPVM, Beowulf, Solaris­MC, which have been discussed in Volume 1 of this book [8]. Clusters use clusters to support multiuser, time­sharing parallel execu­ tion environments, where it is necessary

  10. Spectral analysis in parallel structures

    Microsoft Academic Search

    V. Zagursky; V. Zorin

    2001-01-01

    Experimental studies of large class applications are needed of spectral analysis in real time. The possibility is shown to form computer algorithm for the model of signal representation in stochastic realization. A possible variant of parallel structures algorithm for crosspectral and spectral density function of signal estimation is considered

  11. Parallel Programming Examples using MPI

    NSDL National Science Digital Library

    David Joiner

    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.

  12. The Tau Parallel Performance System

    Microsoft Academic Search

    Sameer S. Shende; Allen D. Malony

    2006-01-01

    The ability of performance technology to keep pace with the growing complexity of parallel and distributed systems depends on robust performance frameworks that can at once provide system-specific performance capabilities and support high-level performance problem solving. Flexibility and portability in empirical methods and processes are influenced primarily by the strategies available for instru- mentation and measurement, and how effectively they

  13. Fast Parallel Absolute Irreducibility Testing

    Microsoft Academic Search

    Erich Kaltofen

    1985-01-01

    e present a fast parallel deterministic algorithm for testing multivariate integral polyno- - c mials for absolute irreducibility, that is irreducibility over the complex numbers. More pre isely, we establish that the set of absolutely irreducible integral polynomials belongs to the e i complexity class NC of Boolean circuits of polynomial size and logarithmic depth. Therefor t also belongs to

  14. THE PARALLEL PLATE PLASMA PROBLEM

    Microsoft Academic Search

    Hall

    1962-01-01

    The parallel plate plasma problem is considered under the assumption of ; uniform density and a specular reflection boundary condition at the plates. The ; impedance of the device is derived for several different models of the plasma ; medium. The impedance of a hydromagnetic medium exhibits resonances whenever the ; plate separation is an odd multiple of a half

  15. Parallel circuit simulation on supercomputers

    Microsoft Academic Search

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

    1989-01-01

    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

  16. Parallel Data Mining - Case Study

    Microsoft Academic Search

    Firat Tekiner; Mike Pettipher; Larry Bull; Mathew Studley; Ian Whittley; Tony Bagnall

    The continuing rapid growth of data and knowledge in scientific domain has spurred huge interest in distributed\\/parallel data and text mining. This paper reports the investigation of a large scale data mining application to supercomputing environment. The aim is to explore some of the issues that may arise in porting and working with the C++\\/MPI implementation of the ensemble knn

  17. The Everett axiom of parallelism

    E-print Network

    Lebedev, Yury A; Dulphan, Anna Ya

    2013-01-01

    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.

  18. Parallel reconstruction using null operations.

    PubMed

    Zhang, Jian; Liu, Chunlei; Moseley, Michael E

    2011-11-01

    A novel iterative k-space data-driven technique, namely parallel reconstruction using null operations (PRUNO), is presented for parallel imaging reconstruction. In PRUNO, both data calibration and image reconstruction are formulated into linear algebra problems based on a generalized system model. An optimal data calibration strategy is demonstrated by using singular value decomposition, and an iterative conjugate-gradient approach is proposed to efficiently solve missing k-space samples during reconstruction. With its generalized formulation and precise mathematical model, PRUNO reconstruction yields good accuracy, flexibility, and stability. Both computer simulation and in vivo studies have shown that PRUNO produces much better reconstruction quality than generalized autocalibrating partially parallel acquisition (GRAPPA), especially under high accelerating rates. With the aid of PRUNO reconstruction, ultra-high accelerating parallel imaging can be performed with decent image quality. For example, we have done successful PRUNO reconstruction at a reduction factor of 6 (effective factor of 4.44) with eight coils and only a few autocalibration signal lines. PMID:21604290

  19. Multiband Phase Constrained Parallel MRI

    PubMed Central

    Blaimer, Martin; Choli, Morwan; Jakob, Peter M.; Griswold, Mark A.; Breuer, Felix A.

    2013-01-01

    Purpose Parallel MRI methods are typically associated with a degradation of the signal-to-noise ratio (SNR). High scan time reduction factors are therefore restricted to applications with high intrinsic SNR. One possibility to increase the intrinsic SNR is to simultaneously excite several slices by means of multiband radio-frequency (RF) pulses and subsequently separate the slices by parallel MRI reconstruction algorithms. However, the separation of closely spaced slices may suffer from severe noise amplification when there is insufficient coil sensitivity variation along the slice direction. The purpose of this work is to apply a phase-constrained reconstruction for multiband experiments in order to minimize the noise amplification. Methods Pre-defined phase differences between neighboring slices are induced and slice separation is performed by a phase-constrained parallel MRI reconstruction. Phase differences between neighboring slices are tailored to achieve optimal slice separation with minimized noise amplification. The potential of the method is demonstrated through multiband in-vivo experiments. Results Noise amplification in multiband phase-constrained reconstructions is significantly reduced in comparison to standard multiband reconstruction when the phase difference between neighboring slices (distance = 12 mm) is 90°. Conclusions Multiband phase constrained parallel MRI has the potential for accelerated multi-slice imaging with an improved SNR performance. PMID:23440994

  20. Efficient schemes for parallel communication

    Microsoft Academic Search

    Eli Upfal

    1982-01-01

    A fundamental problem in the theory of parallel computation is to find an efficient interconnection pattern between N processors that minimizes the number of lines entering or leaving each processor while enabling fast communication between the processors. A family of Balanced communication schemes for connecting N processors with only a constant number of lines entering or leaving each processor is

  1. Tutorial: Parallel Simulation on Supercomputers

    SciTech Connect

    Perumalla, Kalyan S [ORNL

    2012-01-01

    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.

  2. The physics of parallel machines

    NASA Technical Reports Server (NTRS)

    Chan, Tony F.

    1988-01-01

    The idea is considered that architectures for massively parallel computers must be designed to go beyond supporting a particular class of algorithms to supporting the underlying physical processes being modelled. Physical processes modelled by partial differential equations (PDEs) are discussed. Also discussed is the idea that an efficient architecture must go beyond nearest neighbor mesh interconnections and support global and hierarchical communications.

  3. 1 Introduction re nement parallel

    E-print Network

    Sekerinski, Emil

    the Steam Boiler Control Dept. of Electronics and Computer Science, University of Southampton, Southampton and distributed systems [7, 6, 5]. Action systems are similarto the UNITY programs of Chandy and Misra [11] which? ? 1 2 3 1 2 3 Abstract. 1 Introduction re#12;nement parallel decomposition An Action System

  4. The plane with parallel coordinates

    Microsoft Academic Search

    Alfred Inselberg

    1985-01-01

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

  5. Intermediate language extensions for parallelism

    Microsoft Academic Search

    Jisheng Zhao; Vivek Sarkar

    2011-01-01

    An Intermediate Language (IL) specifies a program at a level of abstraction that includes precise semantics for state updates and control flow, but leaves unspecified the low-level software and hardware mechanisms that will be used to implement the semantics. Past ILs have followed the Von Neumann execution model by making sequential execution the default, and by supporting parallelism with runtime

  6. Task parallelism and high-performance languages

    SciTech Connect

    Foster, I.

    1996-03-01

    The definition of High Performance Fortran (HPF) is a significant event in the maturation of parallel computing: it represents the first parallel language that has gained widespread support from vendors and users. The subject of this paper is to incorporate support for task parallelism. The term task parallelism refers to the explicit creation of multiple threads of control, or tasks, which synchronize and communicate under programmer control. Task and data parallelism are complementary rather than competing programming models. While task parallelism is more general and can be used to implement algorithms that are not amenable to data-parallel solutions, many problems can benefit from a mixed approach, with for example a task-parallel coordination layer integrating multiple data-parallel computations. Other problems admit to both data- and task-parallel solutions, with the better solution depending on machine characteristics, compiler performance, or personal taste. For these reasons, we believe that a general-purpose high-performance language should integrate both task- and data-parallel constructs. The challenge is to do so in a way that provides the expressivity needed for applications, while preserving the flexibility and portability of a high-level language. In this paper, we examine and illustrate the considerations that motivate the use of task parallelism. We also describe one particular approach to task parallelism in Fortran, namely the Fortran M extensions. Finally, we contrast Fortran M with other proposed approaches and discuss the implications of this work for task parallelism and high-performance languages.

  7. Extensive parallel processing on scale-free networks.

    PubMed

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

    2014-12-01

    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

  8. Blade-mounted trailing edge flap control for BVI noise reduction

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  9. Beyond vector processing: parallel programming on the CRAY APP

    Microsoft Academic Search

    Douglas Miles

    1993-01-01

    The CRAY APP is a highly parallel network compute server designed to accelerate Fortran and C programs in a UNIX environment. It can run complete programs in a simple shared memory environment, including support for UNIX system calls. A very efficient HiPPI interface makes the CRAY APP cluster-capable and well-suited to interact with other programs running on a network in

  10. Parallel play in medical anthropology and medical sociology

    Microsoft Academic Search

    Peter Conrad

    1997-01-01

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

  11. Segmented ray casting for data parallel volume rendering

    Microsoft Academic Search

    William M. Hsu

    1993-01-01

    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

  12. Parallel supercomputing with commodity components

    SciTech Connect

    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

    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.

  13. Parallel processing spacecraft communication system

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

  14. Merlin - Massively parallel heterogeneous computing

    NASA Technical Reports Server (NTRS)

    Wittie, Larry; Maples, Creve

    1989-01-01

    Hardware and software for Merlin, a new kind of massively parallel computing system, are described. Eight computers are linked as a 300-MIPS prototype to develop system software for a larger Merlin network with 16 to 64 nodes, totaling 600 to 3000 MIPS. These working prototypes help refine a mapped reflective memory technique that offers a new, very general way of linking many types of computer to form supercomputers. Processors share data selectively and rapidly on a word-by-word basis. Fast firmware virtual circuits are reconfigured to match topological needs of individual application programs. Merlin's low-latency memory-sharing interfaces solve many problems in the design of high-performance computing systems. The Merlin prototypes are intended to run parallel programs for scientific applications and to determine hardware and software needs for a future Teraflops Merlin network.

  15. A Parallel Plug-in Programming Paradigm

    SciTech Connect

    Baumann, Ronald [ORNL; Engelmann, Christian [ORNL; Geist, Al [ORNL

    2006-01-01

    Software component architectures allow assembly of applications from individual software modules based on clearly defined programming interfaces, thus improving the reuse of existing solutions and simplifying application development. Furthermore, the plug-in programming paradigm additionally enables runtime reconfigurability, making it possible to adapt to changing application needs, such as different application phases, and system properties, like resource availability, by loading/unloading appropriate software modules. Similar to parallel programs, parallel plug-ins are an abstraction for a set of cooperating individual plug-ins within a parallel application utilizing a software component architecture. Parallel programming paradigms apply to parallel plug-ins in the same way they apply to parallel programs. The research presented in this paper targets the clear definition of parallel plug-ins and the development of a parallel plug-in programming paradigm.

  16. On-the-fly pipeline parallelism

    E-print Network

    Lee, I-Ting Angelina

    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 ...

  17. Parallelizing Sequential Programs with Statistical Accuracy Tests

    E-print Network

    Misailovic, Sasa

    We present QuickStep, a novel system for parallelizing sequential programs. Unlike standard parallelizing compilers (which are designed to preserve the semantics of the original sequential computation), QuickStep is instead ...

  18. Parallel Scalability of Video Technical Report

    E-print Network

    Kuzmanov, Georgi

    - level parallelism in H.264. Using real movie sequences we find a maximum MB parallelism ranging from . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 #12;1 Introduction 3 1 Introduction We are witnessing a paradigm shift in computer architecture

  19. Adaptively Parallel Processor Allocation for Cilk Jobs

    E-print Network

    Sen, Siddhartha

    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 ...

  20. Parallel Rendering of Large Time-Varying Volume Data

    NASA Technical Reports Server (NTRS)

    Garbutt, Alexander E.

    2005-01-01

    Interactive visualization of large time-varying 3D volume datasets has been and still is a great challenge to the modem computational world. It stretches the limits of the memory capacity, the disk space, the network bandwidth and the CPU speed of a conventional computer. In this SURF project, we propose to develop a parallel volume rendering program on SGI's Prism, a cluster computer equipped with state-of-the-art graphic hardware. The proposed program combines both parallel computing and hardware rendering in order to achieve an interactive rendering rate. We use 3D texture mapping and a hardware shader to implement 3D volume rendering on each workstation. We use SGI's VisServer to enable remote rendering using Prism's graphic hardware. And last, we will integrate this new program with ParVox, a parallel distributed visualization system developed at JPL. At the end of the project, we Will demonstrate remote interactive visualization using this new hardware volume renderer on JPL's Prism System using a time-varying dataset from selected JPL applications.

  1. Automated Instrumentation and Monitoring of Data Movement for Parallel Programs

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  2. LES Applications on Parallel Systems

    Microsoft Academic Search

    L. Temmerman; M. A. Leschziner; M. Ashworth; D. R. Emerson

    A Large Eddy Simulation code based on a non-orthogonal, multiblock, finite volume approach with co-located variable storage, was ported to three different parallel architectures: a Cray T3E\\/1200E, an Alpha cluster and a PC Beowulf cluster. Scalability and parallelisation issues have been investigated, and merits as well as limitations of the three implementations are reported. Representative LES results for three flows

  3. Parallel strategies for SAR processing

    NASA Astrophysics Data System (ADS)

    Segoviano, Jesus A.

    2004-12-01

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

  4. Parallel Simulation of Multicomponent Systems

    Microsoft Academic Search

    Michael T. Heath; Xiangmin Jiao

    2004-01-01

    \\u000a Simulation of multicomponent systems poses many critical challenges in science and engineering. We overview some software\\u000a and algorithmic issues in developing high-performance simulation tools for such systems, based on our experience in developing\\u000a a large-scale, fully-coupled code for detailed simulation of solid propellant rockets. We briefly sketch some of our solutions\\u000a to these issues, with focus on parallel and performance

  5. Resource-efficient parallel algorithms

    SciTech Connect

    Hochschild, P.H.

    1986-01-01

    This thesis concerns the problem of exploiting the possibilities of parallel computation. To that end, several paradigms for the construction of efficient parallel algorithms were developed. These paradigms are effective in designing algorithms for solving a variety of combinatorial and pattern-matching problems. The resulting space and time-efficient programs operate on simple and regular parallel architectures that are suitable for VLSI implementation. Many of the algorithms owe their efficiency to filtration. A filter is a device used to discard rapidly input data that is irrelevant. Filtration reduces the storage, time, and communication requirements of a wide variety of problems. Filter construction demands balancing two opposing goals. On the one hand, a filter must operate quickly enough to avoid becoming a bottleneck. On the other hand, it must be thorough enough to discard a significant portion of the data. Thus, in general, a filter performs a kind of approximation to the desired computation. This approximation is later refined to yield the correct result. By implementing the paradigm of cascaded filtration, using the funnelled pipeline architecture, efficient solutions to several classical problems were developed.

  6. Parallelism in integrated fluidic circuits

    NASA Astrophysics Data System (ADS)

    Bousse, Luc J.; Kopf-Sill, Anne R.; Parce, J. W.

    1998-04-01

    Many research groups around the world are working on integrated microfluidics. The goal of these projects is to automate and integrate the handling of liquid samples and reagents for measurement and assay procedures in chemistry and biology. Ultimately, it is hoped that this will lead to a revolution in chemical and biological procedures similar to that caused in electronics by the invention of the integrated circuit. The optimal size scale of channels for liquid flow is determined by basic constraints to be somewhere between 10 and 100 micrometers . In larger channels, mixing by diffusion takes too long; in smaller channels, the number of molecules present is so low it makes detection difficult. At Caliper, we are making fluidic systems in glass chips with channels in this size range, based on electroosmotic flow, and fluorescence detection. One application of this technology is rapid assays for drug screening, such as enzyme assays and binding assays. A further challenge in this area is to perform multiple functions on a chip in parallel, without a large increase in the number of inputs and outputs. A first step in this direction is a fluidic serial-to-parallel converter. Fluidic circuits will be shown with the ability to distribute an incoming serial sample stream to multiple parallel channels.

  7. 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.

  8. Highly parallel sparse Cholesky factorization

    NASA Technical Reports Server (NTRS)

    Gilbert, John R.; Schreiber, Robert

    1990-01-01

    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.

  9. Parallel multi-computers and artificial intelligence

    SciTech Connect

    Uhr, L.

    1986-01-01

    This book examines the present state and future direction of multicomputer parallel architectures for artificial intelligence research and development of artificial intelligence applications. The book provides a survey of the large variety of parallel architectures, describing the current state of the art and suggesting promising architectures to produce artificial intelligence systems such as intelligence systems such as intelligent robots. This book integrates artificial intelligence and parallel processing research areas and discusses parallel processing from the viewpoint of artificial intelligence.

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

    E-print Network

    Voldman, Joel

    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

  11. Parallel Search Algorithm for Geometric Constraints Solving

    Microsoft Academic Search

    Kong Zhao; Hua Yuan; Wenhui Li; Rongqin Yi

    2007-01-01

    In this paper, we propose a hybrid algorithm -(parallel search algorithm) to solve geometric constraint problems. First, particle swarm optimization is employed to gain parallelization while solution diversity is maintained. Second, simplex method reduces the number of infeasible solutions while solution quality is improved with an operation order search. Performance results on geometric constraint problems show that parallel search algorithm

  12. Identifying, Quantifying, Extracting and Enhancing Implicit Parallelism

    ERIC Educational Resources Information Center

    Agarwal, Mayank

    2009-01-01

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

  13. Developing Parallel Finite Element Software Using MPI

    Microsoft Academic Search

    P. k. Jimack; N. Touheed

    2000-01-01

    : 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

  14. The RISAM Storage Manager for Parallel Architectures

    Microsoft Academic Search

    Atul Tulshibagwale; Sujal Parikh; Sameer Mahajan; Tushar Tambay; K. C. Pravin; R. Talashikar; R. Pande

    1994-01-01

    The use of massively parallel processors for high performance data management is moving rapidly into the commercial mainstream. This paper describes key features of the RISAM (replicated ISAM) parallel data manager, which is currently available on the C-DAC PARAM 8000 series of parallel supercomputers and on the Unisys U6000 symmetric multiprocessors, and which can be readily ported to other platforms.

  15. A Message Ordering Problem in Parallel Programs

    Microsoft Academic Search

    Bora Uçar; Cevdet Aykanat

    2004-01-01

    We consider a certain class of parallel program segments in which the order of messages sent affects the completion time. We give characterization of these parallel program segments and propose a solu- tion to minimize the completion time. With a sample parallel program, we experimentally evaluate the effect of the solution on a PC cluster.

  16. PARALLEL ALGORITHM DESIGN FOR BRANCH AND BOUND

    E-print Network

    Bader, David A.

    /or computationally expensive optimization problems some- times require parallel or high-performance computing systems to achieve reasonable running times. This chapter gives an introduction to parallel computing for those of multi-processor workstations and Beowulf-style clusters has made parallel computing resources avail

  17. Parallel Computing Using Web Servers and "Servlets".

    ERIC Educational Resources Information Center

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

    2000-01-01

    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…

  18. Morphing Polyhedra with Parallel Faces: Counterexamples

    E-print Network

    Biedl, Therese

    Morphing Polyhedra with Parallel Faces: Counterexamples Therese Biedl and Anna Lubiw and Michael J. {biedl,alubiw}@uwaterloo.ca, michael.spriggs@rogers.com Abstract Two simple polyhedra P and Q (not-facing unit normal as the corresponding face in Q. Parallel polyhedra P and Q admit a parallel morph

  19. Structured Hardware Compilation of Parallel Programs

    E-print Network

    Luk, Wayne

    implementation. A circuit module is developed for each control structure, such as sequential or parallelStructured Hardware Compilation of Parallel Programs Wayne Luk, David Ferguson and Ian Page. The potential of this approach is evaluated. INTRODUCTION Recent work has shown how parallel programs

  20. Simple Randomized Mergesorting on Parallel Disks

    E-print Network

    Barve, Rakesh; Grove, Edward F.; Vitter, Jeffrey Scott

    1997-01-01

    R. D. Barve, E. F. Grove, and J. S. Vitter. “Simple Randomized Mergesorting on Parallel Disks,” special issue on parallel I/O in Parallel Computing, 23(4), 1997, 601–631. An extended abstract appears in Proceedings of the 8th Annual ACM Symposium...

  1. Parallel genotypic adaptation: when evolution repeats itself

    Microsoft Academic Search

    Troy E. Wood; John M. Burke; Loren H. Rieseberg

    Until recently, parallel genotypic adaptation was considered unlikely because phenotypic differences were thought to be controlled by many genes. There is increasing evidence, however, that phenotypic variation sometimes has a simple genetic basis and that parallel adaptation at the genotypic level may be more frequent than previously believed. Here, we review evidence for parallel genotypic adaptation derived from a survey

  2. Parallel genotypic adaptation: when evolution repeats itself

    Microsoft Academic Search

    Troy E. Wood; John M. Burke; Loren H. Rieseberg

    2005-01-01

    Until recently, parallel genotypic adaptation was considered unlikely because phenotypic differences were thought to be controlled by many genes. There is increasing evidence, however, that phenotypic variation sometimes has a simple genetic basis and that parallel adaptation at the genotypic level may be more frequent than previously believed. Here, we review evidence for parallel genotypic adaptation derived from a survey

  3. The recognition of Series Parallel digraphs

    Microsoft Academic Search

    Jacobo Valdes; Robert Endre Tarjan; Eugene L. Lawler

    1979-01-01

    We present an algorithm that recognizes the class of General Series Parallel digraphs and runs in time proportional to the size of its input. To perform this recognition task it is necessary to compute the transitive reduction and transitive closure of any General Series Parallel digraph. Our analysis is based on the relationship between General Series Parallel digraphs and a

  4. ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION

    E-print Network

    Kolda, Tamara G.

    ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION PATRICIA D. HOUGH, TAMARA G. KOLDA. 1, pp. 134­156 Abstract. We introduce a new asynchronous parallel pattern search (APPS). Parallel pattern search can be quite useful for engineering optimization problems characterized by a small number

  5. ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION #

    E-print Network

    Kolda, Tamara G.

    ASYNCHRONOUS PARALLEL PATTERN SEARCH FOR NONLINEAR OPTIMIZATION # PATRICIA D. HOUGH + , TAMARA G Mathematics Vol. 23, No. 1, pp. 134--156 Abstract. We introduce a new asynchronous parallel pattern search (APPS). Parallel pattern search can be quite useful for engineering optimization problems characterized

  6. Singularity analysis of redundant parallel manipulators

    Microsoft Academic Search

    Hengbin Liao; Tiemin Li; Xiaoqiang Tang

    2004-01-01

    The general methods of singularity analysis of a general parallel manipulator are not suitable for that of a redundant parallel manipulator, thereby This work presents a method for the identification of the singularities of redundant parallel manipulators. Firstly, the theory of singular value decomposition is employed to analyze the velocity equation of a mechanism, and the relationship between the generalized

  7. Perfect Pipelining: A New Loop Parallelization Technique

    Microsoft Academic Search

    Alexander Aiken; Alexandru Nicolau

    1988-01-01

    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

  8. Robotenis: parallel robot with visual control

    Microsoft Academic Search

    L. Angel; R. Saltaren; J. M. Sebastian; A. Hansson; R. Aracil

    2004-01-01

    RoboTenis is an experimental innovation platform with high performance for visual control of a parallel robot with four degrees of freedom (DOF). The platform is an open parallel structure for the implementation of different strategies of visual control that allow the robot to play table tennis. The design of the platform consists of the construction of the parallel robot, the

  9. Parallel Processing at the High School Level.

    ERIC Educational Resources Information Center

    Sheary, Kathryn Anne

    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…

  10. MAPS: multi-algorithm parallel circuit simulation

    Microsoft Academic Search

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

    2008-01-01

    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

  11. NWChem: scalable parallel computational chemistry

    SciTech Connect

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

    2011-11-01

    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.

  12. A Parallel Algorithm for Clustering Protein-Protein Interaction Networks

    E-print Network

    Lonardi, Stefano

    in proteomics such as yeast two- hybrid, phage display and mass spectrometry have re- sulted in several genome. With the availability of PPI networks from sev- eral model organisms, recent research on identifying functional related

  13. Parallel and Adaptive Methods for FluidStructureInteractions

    E-print Network

    Institut f¨ur Geometrie und Praktische Mathematik RWTH Aachen Templergraben 55, D­52056 Aachen (Germany) K. Brix, W. Dahmen, S. Melian, S. M¨uller Institut f¨ur Geometrie und Praktische Mathematik, RWTH Aachen University, Templergraben 55, D­52056 Aachen, e-mail: dahmen, melian, brix, mueller@igpm.rwth-aachen.de M

  14. Interacting Parallel Constructions of Knowledge in a CAS Context

    ERIC Educational Resources Information Center

    Kidron, Ivy; Dreyfus, Tommy

    2010-01-01

    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…

  15. Collective Interaction of a Compressible Periodic Parallel Jet Flow

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1997-01-01

    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.

  16. Theoretical and experimental correlation of low-speed model helicopter blade slap

    NASA Astrophysics Data System (ADS)

    Chan, Daniel Chin-Leung; Hubbard, James E., Jr.

    1985-09-01

    The operating conditions under which the assumptions made in the Widnall and Wolf (1980) model of low-speed helicopter blade slap are correct are investigated. Using a limited number of miniature pressure transducers on a scale model helicopter rotor blade, the load distribution near the tip is estimated and used as input to the Widnall and Wolf model to determine the structure of the trailing vortex. The geometry of the blade-vortex interaction is determined by smoke visualization techniques. The unsteady load on the blade resulting from the blade-gust interaction is modeled as a distribution of acoustic dipoles. The predicted sound pressure level is compared with the experimentally obtained far-field acoustic signature. Good agreement is found between the Widnall and Wolf model and the experimental results for the blade-vortex interactions in the region outside the vortex core.

  17. A flight investigation of blade section aerodynamics for a helicopter main rotor having NLR-1T airfoil sections

    NASA Technical Reports Server (NTRS)

    Morris, C. E. K., Jr.; Stevens, D. D.; Tomaine, R. L.

    1980-01-01

    A flight investigation was conducted using a teetering-rotor AH-1G helicopter to obtain data on the aerodynamic behavior of main-rotor blades with the NLR-1T blade section. The data system recorded blade-section aerodynamic pressures at 90 percent rotor radius as well as vehicle flight state, performance, and loads. The test envelope included hover, forward flight, and collective-fixed maneuvers. Data were obtained on apparent blade-vortex interactions, negative lift on the advancing blade in high-speed flight and wake interactions in hover. In many cases, good agreement was achieved between chordwise pressure distributions predicted by airfoil theory and flight data with no apparent indications of blade-vortex interactions.

  18. Parallel multiscale simulations of a brain aneurysm

    PubMed Central

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

    2012-01-01

    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

  19. Parallel multiscale simulations of a brain aneurysm

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  20. Parallel multiscale simulations of a brain aneurysm.

    PubMed

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

    2013-07-01

    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

  1. Parallel multiscale simulations of a brain aneurysm

    SciTech Connect

    Grinberg, Leopold [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)] [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Fedosov, Dmitry A. [Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich 52425 (Germany)] [Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich 52425 (Germany); Karniadakis, George Em, E-mail: george_karniadakis@brown.edu [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)

    2013-07-01

    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.

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

    E-print Network

    Scott, Michael L.

    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

  3. Parallel ecological networks in ecosystems

    PubMed Central

    Olff, Han; Alonso, David; Berg, Matty P.; Eriksson, B. Klemens; Loreau, Michel; Piersma, Theunis; Rooney, Neil

    2009-01-01

    In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator–prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal ‘ecological stoichiometry’ axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah. PMID:19451126

  4. Parallel Lines Cut By A Transversal

    NSDL National Science Digital Library

    Mrs. Neubert

    2010-09-28

    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 ...

  5. On the dimensionally correct kinetic theory of turbulence for parallel propagation

    NASA Astrophysics Data System (ADS)

    Gaelzer, R.; Yoon, P. H.; Kim, Sunjung; Ziebell, L. F.

    2015-03-01

    Yoon and Fang [Phys. Plasmas 15, 122312 (2008)] formulated a second-order nonlinear kinetic theory that describes the turbulence propagating in directions parallel/anti-parallel to the ambient magnetic field. Their theory also includes discrete-particle effects, or the effects due to spontaneously emitted thermal fluctuations. However, terms associated with the spontaneous fluctuations in particle and wave kinetic equations in their theory contain proper dimensionality only for an artificial one-dimensional situation. The present paper extends the analysis and re-derives the dimensionally correct kinetic equations for three-dimensional case. The new formalism properly describes the effects of spontaneous fluctuations emitted in three-dimensional space, while the collectively emitted turbulence propagates predominantly in directions parallel/anti-parallel to the ambient magnetic field. As a first step, the present investigation focuses on linear wave-particle interaction terms only. A subsequent paper will include the dimensionally correct nonlinear wave-particle interaction terms.

  6. Partitioning in parallel processing of production systems

    SciTech Connect

    Oflazer, K.

    1987-01-01

    This thesis presents research on certain issues related to parallel processing of production systems. It first presents a parallel production system interpreter that has been implemented on a four-processor multiprocessor. This parallel interpreter is based on Forgy's OPS5 interpreter and exploits production-level parallelism in production systems. Runs on the multiprocessor system indicate that it is possible to obtain speed-up of around 1.7 in the match computation for certain production systems when productions are split into three sets that are processed in parallel. The next issue addressed is that of partitioning a set of rules to processors in a parallel interpreter with production-level parallelism, and the extent of additional improvement in performance. The partitioning problem is formulated and an algorithm for approximate solutions is presented. The thesis next presents a parallel processing scheme for OPS5 production systems that allows some redundancy in the match computation. This redundancy enables the processing of a production to be divided into units of medium granularity each of which can be processed in parallel. Subsequently, a parallel processor architecture for implementing the parallel processing algorithm is presented.

  7. Toward an automated parallel computing environment for geosciences

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

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

  8. Instant well-log inversion with a parallel computer

    SciTech Connect

    Kimminau, S.J.; Trivedi, H.

    1993-08-01

    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.

  9. 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.

  10. Superconducting fluctuations and magnetoconductance measurements of thin films in parallel magnetic fields

    Microsoft Academic Search

    Ralph Rosenbaum

    1985-01-01

    Parallel magnetoconductance measurements have been made on thin Cu-Pb films having different spin-orbit interactions. A theory of parallel magnetoconductance, first proposed by Al'tshuler and Aronov and expanded by Gershenzon, Gubankov, and Zhuravlev gives a qualitative description of the experimental results. However, this theory fails to account for the low-temperature dependence of the magnetoconductance data at low temperatures. The temperature dependence

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

    Microsoft Academic Search

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

    2005-01-01

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

  12. Parallel Assembly of LIGA Components

    SciTech Connect

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

    1999-03-04

    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.

  13. Series-Parallel Combination Circuits

    NSDL National Science Digital Library

    Kuphaldt, Tony R.

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

  14. On Parallelism in Turing Machines

    Microsoft Academic Search

    Dexter Kozen

    1976-01-01

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

  15. Parallel execution of portfolio optimization

    E-print Network

    Nuriyev, R

    2008-01-01

    Analysis of asset liability management (ALM) strategies especially for long term horizon is a crucial issue for banks, funds and insurance companies. Modern economic models, investment strategies and optimization criteria make ALM studies computationally very intensive task. It attracts attention to multiprocessor system and especially to the cheapest one: multi core PCs and PC clusters. In this article we are analyzing problem of parallel organization of portfolio optimization, results of using clusters for optimization and the most efficient cluster architecture for these kinds of tasks.

  16. Experimental and Numerical Investigation of Rarefied Interacting Plumes

    NASA Astrophysics Data System (ADS)

    Chirokov, Ivan A.; Elizarova, Tatiana G.; Lengrand, Jean-Claude; Gibek, Isabelle; Graur, Irina A.

    2003-05-01

    Experimental and numerical investigations of the interaction of two rarefied underexpanded parallel plumes and of the interaction of a plume with a parallel plate are presented. Numerical results are in a reasonable agreement with the experimental ones including the low-density far field. Results obtained give access to flow features not available from the measurements.

  17. Generic implementations of parallel prefix sums and its applications

    E-print Network

    Huang, Tao

    2009-05-15

    synchronization as the number of processors increases. As part of the applications for parallel prefix sums, parallel radix sort and four parallel tree applications are built on top of the implementation. These applications are also fundamental parallel algorithms...

  18. Helicopter impulsive noise - Theoretical and experimental status

    NASA Astrophysics Data System (ADS)

    Schmitz, F. H.; Yu, Y. H.

    1986-09-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  19. Helicopter impulsive noise - Theoretical and experimental status

    NASA Astrophysics Data System (ADS)

    Schmitz, F. H.; Yu, Y. H.

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory/experiment are suggested.

  20. Helicopter impulsive noise: Theoretical and experimental status

    NASA Astrophysics Data System (ADS)

    Schmitz, F. H.; Yu, Y. H.

    1983-11-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  2. The prediction of transonic loading advancing helicopter rotors

    NASA Technical Reports Server (NTRS)

    Strawn, R.; Tung, C.

    1986-01-01

    Two different schemes are presented for including the effect of rotor wakes on the finite-difference prediction of rotor loads. The first formulation includes wake effects by means of a blade-surface inflow specification. This approach is sufficiently simple to permit coupling of a full-potential finite-difference rotor code to a comprehensive integral model for the rotor wake and blade motion. The coupling involves a transfer of appropriate loads and inflow data between the two computer codes. Results are compared with experimental data for two advancing rotor cases. The second rotor wake modeling scheme in this paper is a split potential formulation for computing unsteady blade-vortex interactions. Discrete vortex fields are introduced into a three-dimensional, conservative, full-potential rotor code. Computer predictions are compared with two experimental blade-vortex interaction cases.

  3. Helicopter impulsive noise: Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1983-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  4. Xyce parallel electronic simulator design.

    SciTech Connect

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

    2010-09-01

    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.

  5. Integrated Task and Data Parallel Programming

    NASA Technical Reports Server (NTRS)

    Grimshaw, A. S.

    1998-01-01

    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.

  6. Parallel processing considerations for image recognition tasks

    NASA Astrophysics Data System (ADS)

    Simske, Steven J.

    2011-01-01

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

  7. Reducing neural network training time with parallel processing

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  8. Parallel line analysis: multifunctional software for the biomedical sciences

    NASA Technical Reports Server (NTRS)

    Swank, P. R.; Lewis, M. L.; Damron, K. L.; Morrison, D. R.

    1990-01-01

    An easy to use, interactive FORTRAN program for analyzing the results of parallel line assays is described. The program is menu driven and consists of five major components: data entry, data editing, manual analysis, manual plotting, and automatic analysis and plotting. Data can be entered from the terminal or from previously created data files. The data editing portion of the program is used to inspect and modify data and to statistically identify outliers. The manual analysis component is used to test the assumptions necessary for parallel line assays using analysis of covariance techniques and to determine potency ratios with confidence limits. The manual plotting component provides a graphic display of the data on the terminal screen or on a standard line printer. The automatic portion runs through multiple analyses without operator input. Data may be saved in a special file to expedite input at a future time.

  9. Airloads, wakes, and aeroelasticity

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    1990-01-01

    Fundamental considerations regarding the theory of modeling of rotary wing airloads, wakes, and aeroelasticity are presented. The topics covered are: airloads and wakes, including lifting-line theory, wake models and nonuniform inflow, free wake geometry, and blade-vortex interaction; aerodynamic and wake models for aeroelasticity, including two-dimensional unsteady aerodynamics and dynamic inflow; and airloads and structural dynamics, including comprehensive airload prediction programs. Results of calculations and correlations are presented.

  10. GOTPM: a parallel hybrid particle-mesh treecode

    NASA Astrophysics Data System (ADS)

    Dubinski, John; Kim, Juhan; Park, Changbom; Humble, Robin

    2004-02-01

    We describe a parallel, cosmological N-body code based on a hybrid scheme using the particle-mesh (PM) and Barnes-Hut (BH) oct-tree algorithm. We call the algorithm GOTPM for Grid-of-Oct-Trees-Particle-Mesh. The code is parallelized using the Message Passing Interface (MPI) library and is optimized to run on Beowulf clusters as well as symmetric multi-processors. The gravitational potential is determined on a mesh using a standard PM method with particle forces determined through interpolation. The softened PM force is corrected for short range interactions using a grid of localized BH trees throughout the entire simulation volume in a completely analogous way to P3M methods. This method makes no assumptions about the local density for short range force corrections and so is consistent with the results of the P3M method in the limit that the treecode opening angle parameter, ??0. The PM method is parallelized using one-dimensional slice domain decomposition. Particles are distributed in slices of equal width to allow mass assignment onto mesh points. The Fourier transforms in the PM method are done in parallel using the MPI implementation of the FFTW package. Parallelization for the tree force corrections is achieved again using one-dimensional slices but the width of each slice is allowed to vary according to the amount of computational work required by the particles within each slice to achieve load balance. The tree force corrections dominate the computational load and so imbalances in the PM density assignment step do not impact the overall load balance and performance significantly. The code performance scales well to 128 processors and is significantly better than competing methods. We present preliminary results from simulations run on different platforms containing up to N=1 G particles to verify the code.

  11. Parallel pivoting combined with parallel reduction and fill-in control

    NASA Technical Reports Server (NTRS)

    Alaghband, Gita

    1989-01-01

    Parallel algorithms for triangularization of large, sparse, and unsymmetric matrices are presented. The method combines the parallel reduction with a new parallel pivoting technique, control over generation of fill-ins and check for numerical stability, all done in parallel with the work being distributed over the active processes. The parallel pivoting technique uses the compatibility relation between pivots to identify parallel pivot candidates and uses the Markowitz number of pivots to minimize fill-in. This technique is not a preordering of the sparse matrix and is applied dynamically as the decomposition proceeds.

  12. Parallel automated adaptive procedures for unstructured meshes

    NASA Technical Reports Server (NTRS)

    Shephard, M. S.; Flaherty, J. E.; Decougny, H. L.; Ozturan, C.; Bottasso, C. L.; Beall, M. W.

    1995-01-01

    Consideration is given to the techniques required to support adaptive analysis of automatically generated unstructured meshes on distributed memory MIMD parallel computers. The key areas of new development are focused on the support of effective parallel computations when the structure of the numerical discretization, the mesh, is evolving, and in fact constructed, during the computation. All the procedures presented operate in parallel on already distributed mesh information. Starting from a mesh definition in terms of a topological hierarchy, techniques to support the distribution, redistribution and communication among the mesh entities over the processors is given, and algorithms to dynamically balance processor workload based on the migration of mesh entities are given. A procedure to automatically generate meshes in parallel, starting from CAD geometric models, is given. Parallel procedures to enrich the mesh through local mesh modifications are also given. Finally, the combination of these techniques to produce a parallel automated finite element analysis procedure for rotorcraft aerodynamics calculations is discussed and demonstrated.

  13. Design considerations for parallel graphics libraries

    NASA Technical Reports Server (NTRS)

    Crockett, Thomas W.

    1994-01-01

    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.

  14. Parallel computing for probabilistic fatigue analysis

    NASA Technical Reports Server (NTRS)

    Sues, Robert H.; Lua, Yuan J.; Smith, Mark D.

    1993-01-01

    This paper presents the results of Phase I research to investigate the most effective parallel processing software strategies and hardware configurations for probabilistic structural analysis. We investigate the efficiency of both shared and distributed-memory architectures via a probabilistic fatigue life analysis problem. We also present a parallel programming approach, the virtual shared-memory paradigm, that is applicable across both types of hardware. Using this approach, problems can be solved on a variety of parallel configurations, including networks of single or multiprocessor workstations. We conclude that it is possible to effectively parallelize probabilistic fatigue analysis codes; however, special strategies will be needed to achieve large-scale parallelism to keep large number of processors busy and to treat problems with the large memory requirements encountered in practice. We also conclude that distributed-memory architecture is preferable to shared-memory for achieving large scale parallelism; however, in the future, the currently emerging hybrid-memory architectures will likely be optimal.

  15. Linearly exact parallel closures for slab geometry

    SciTech Connect

    Ji, Jeong-Young; Held, Eric D. [Department of Physics, Utah State University, Logan, Utah 84322 (United States)] [Department of Physics, Utah State University, Logan, Utah 84322 (United States); Jhang, Hogun [National Fusion Research Institute, 52 Yeoeun-dong, Yusung-Gu, Daejon (Korea, Republic of)] [National Fusion Research Institute, 52 Yeoeun-dong, Yusung-Gu, Daejon (Korea, Republic of)

    2013-08-15

    Parallel closures are obtained by solving a linearized kinetic equation with a model collision operator using the Fourier transform method. The closures expressed in wave number space are exact for time-dependent linear problems to within the limits of the model collision operator. In the adiabatic, collisionless limit, an inverse Fourier transform is performed to obtain integral (nonlocal) parallel closures in real space; parallel heat flow and viscosity closures for density, temperature, and flow velocity equations replace Braginskii's parallel closure relations, and parallel flow velocity and heat flow closures for density and temperature equations replace Spitzer's parallel transport relations. It is verified that the closures reproduce the exact linear response function of Hammett and Perkins [Phys. Rev. Lett. 64, 3019 (1990)] for Landau damping given a temperature gradient. In contrast to their approximate closures where the vanishing viscosity coefficient numerically gives an exact response, our closures relate the heat flow and nonvanishing viscosity to temperature and flow velocity (gradients)

  16. Towards Distributed Memory Parallel Program Analysis

    SciTech Connect

    Quinlan, D; Barany, G; Panas, T

    2008-06-17

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

  17. Multipactor saturation in parallel-plate waveguides

    SciTech Connect

    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

    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.

  18. Six-Degree-Of-Freedom Parallel Minimanipulator

    NASA Technical Reports Server (NTRS)

    Tahmasebi, Farhad; Tsai, Lung-Wen

    1994-01-01

    Six-degree-of-freedom parallel minimanipulator stiffer and simpler than earlier six-degree-of-freedom manipulators. Includes only three inextensible limbs with universal joints at ends. Limbs have equal lengths and act in parallel as they share load on manipulated platform. Designed to provide high resolution and high stiffness for fine control of position and force in hybrid serial/parallel-manipulator system.

  19. Conservation of writhe helicity under anti-parallel reconnection

    PubMed Central

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

    2015-01-01

    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. PMID:25820408

  20. Conservation of writhe helicity under anti-parallel reconnection.

    PubMed

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

    2015-01-01

    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. PMID:25820408

  1. Information hiding in parallel programs

    SciTech Connect

    Foster, I.

    1992-01-30

    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.

  2. Parallel network simulations with NEURON.

    PubMed

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

    2006-10-01

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

  3. Parallel discovery of Alzheimer's therapeutics.

    PubMed

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

    2014-06-18

    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

  4. A parallel dipole line system

    NASA Astrophysics Data System (ADS)

    Gunawan, Oki; Virgus, Yudistira; Tai, Kong Fai

    2015-02-01

    We present a study of a parallel linear distribution of dipole system, which can be realized using a pair of cylindrical diametric magnets and yields several interesting properties and applications. The system serves as a trap for cylindrical diamagnetic object, produces a fascinating one-dimensional camelback potential profile at its center plane, yields a technique for measuring magnetic susceptibility of the trapped object and serves as an ideal system to implement highly sensitive Hall measurement utilizing rotating magnetic field and lock-in detection. The latter application enables extraction of low carrier mobility in several materials of high interest such as the world-record-quality, earth abundant kesterite solar cell, and helps elucidate its fundamental performance limitation.

  5. Parallel computing in enterprise modeling.

    SciTech Connect

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

    2008-08-01

    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.

  6. Parallel execution model of logic programs

    SciTech Connect

    Umeyama, S.; Tamura, K.

    1983-01-01

    A logic programming language offers several kinds of parallelism for its execution. Among these, this paper concentrates on or-parallelism which is an alternative to the backtracking mechanism of a serial interpreter, and proposes an abstract model of or-parallel interpretation. It consists of tokens and five kinds of function units mutually connected as a process graph. The overall processing is done by the flows of tokens among these units. The authors also present a mechanism for token labeling, which makes this process graph reentrant. A simulation result is given to show how efficiently the model works in terms of parallelism. 12 references.

  7. Parallel Genetic Algorithm for Alpha Spectra Fitting

    NASA Astrophysics Data System (ADS)

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

    2005-01-01

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

  8. Parallel auto-correlative statistics with VTK.

    SciTech Connect

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

    2013-08-01

    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.

  9. The Uses and Abuses of the Acoustic Analogy in Helicopter Rotor Noise Prediction

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Brentner, Kenneth S.

    1987-01-01

    This paper is theoretical in nature and addresses applications of the acoustic analogy in helicopter rotor noise prediction. It is argued that in many instances the acoustic analogy has not been used with care in rotor noise studies. By this it is meant that approximate or inappropriate formulations have been used. By considering various mechanisms of noise generation, such abuses are identified and the remedy is suggested. The mechanisms discussed are thickness, loading, quadrupole, and blade-vortex interaction noise. The quadrupole term of the Ffowcs Williams-Hawkings equation is written in a new form which separates the contributions of regions of high gradients such as shock surfaces. It is shown by order of magnitude studies that such regions are capable of producing noise with the same directivity as the thickness noise. The inclusion of this part of quadrupole sources in current acoustic codes is quite practical. Some of the difficulties with the use of loading noise formulations of the first author in predictions of blade-vortex interaction noise are discussed. It appears that there is a need for development of new theoretical results based on the acoustic analogy in this area. Because of the impulsive character of the blade surface pressure, a time scale of integration different from that used in loading and thickness computations must he used in a computer code for prediction of blade-vortex interaction noise.

  10. Parallel genotypic adaptation: when evolution repeats itself

    PubMed Central

    Wood, Troy E.; Burke, John M.; Rieseberg, Loren H.

    2008-01-01

    Until recently, parallel genotypic adaptation was considered unlikely because phenotypic differences were thought to be controlled by many genes. There is increasing evidence, however, that phenotypic variation sometimes has a simple genetic basis and that parallel adaptation at the genotypic level may be more frequent than previously believed. Here, we review evidence for parallel genotypic adaptation derived from a survey of the experimental evolution, phylogenetic, and quantitative genetic literature. The most convincing evidence of parallel genotypic adaptation comes from artificial selection experiments involving microbial populations. In some experiments, up to half of the nucleotide substitutions found in independent lineages under uniform selection are the same. Phylogenetic studies provide a means for studying parallel genotypic adaptation in non-experimental systems, but conclusive evidence may be difficult to obtain because homoplasy can arise for other reasons. Nonetheless, phylogenetic approaches have provided evidence of parallel genotypic adaptation across all taxonomic levels, not just microbes. Quantitative genetic approaches also suggest parallel genotypic evolution across both closely and distantly related taxa, but it is important to note that this approach cannot distinguish between parallel changes at homologous loci versus convergent changes at closely linked non-homologous loci. The finding that parallel genotypic adaptation appears to be frequent and occurs at all taxonomic levels has important implications for phylogenetic and evolutionary studies. With respect to phylogenetic analyses, parallel genotypic changes, if common, may result in faulty estimates of phylogenetic relationships. From an evolutionary perspective, the occurrence of parallel genotypic adaptation provides increasing support for determinism in evolution and may provide a partial explanation for how species with low levels of gene flow are held together. PMID:15881688

  11. Recent Improvements to HST Parallel Scheduling

    NASA Astrophysics Data System (ADS)

    Henry, Ronald; Butschky, Mike

    The Hubble Space Telescope (HST) has several scientific instruments (SIs) that may be used at any given time. Most primary visits submitted by HST observers only use one SI, leaving the other SIs free to be requested by ``pure parallel'' observing programs. In order to accomplish this, separate scheduling units (SUs) for each parallel SI must be created and then scheduled by the Science Planning and Scheduling System (SPSS), taking into account numerous orbital and scientific constraints. The Parallel Observation Matching System (POMS) has the task of matching parallel visits to primary observations and ``crafting'' appropriate parallel SUs at each opportunity, taking scientific criteria and orbital constraints into account. The process for planning and scheduling parallel observations is thus quite different from the process for primary science. In the past, custom crafting rules for each parallel program were necessary, requiring full-time support from a software developer. In addition, because POMS ran as a standalone system, its ability to model how long parallel SUs would take was limited, especially with the flexible buffer-management schemes used for the second-generation SIs. A new version of POMS was developed in 1997. This version uses a formal proposal syntax (the same used for primary observations) for parallels, so that different proposals can be handled uniformly and without the need for customized ``crafting rules.'' In addition, POMS is integrated with the Transformation (TRANS) planning system in order to give it full knowledge of overheads within an SU, eliminating the need for ad hoc modeling. The power and versatility of this approach has paid off in improved utilization of parallel opportunities, greatly reduced maintenance costs, and an ability to gracefully handle new parallel proposals and new SIs with minimal software effort. This paper discusses the requirements, design, and operational results of the new POMS.

  12. Parallel methods for the flight simulation model

    SciTech Connect

    Xiong, Wei Zhong; Swietlik, C.

    1994-06-01

    The Advanced Computer Applications Center (ACAC) has been involved in evaluating advanced parallel architecture computers and the applicability of these machines to computer simulation models. The advanced systems investigated include parallel machines with shared. memory and distributed architectures consisting of an eight processor Alliant FX/8, a twenty four processor sor Sequent Symmetry, Cray XMP, IBM RISC 6000 model 550, and the Intel Touchstone eight processor Gamma and 512 processor Delta machines. Since parallelizing a truly efficient application program for the parallel machine is a difficult task, the implementation for these machines in a realistic setting has been largely overlooked. The ACAC has developed considerable expertise in optimizing and parallelizing application models on a collection of advanced multiprocessor systems. One of aspect of such an application model is the Flight Simulation Model, which used a set of differential equations to describe the flight characteristics of a launched missile by means of a trajectory. The Flight Simulation Model was written in the FORTRAN language with approximately 29,000 lines of source code. Depending on the number of trajectories, the computation can require several hours to full day of CPU time on DEC/VAX 8650 system. There is an impetus to reduce the execution time and utilize the advanced parallel architecture computing environment available. ACAC researchers developed a parallel method that allows the Flight Simulation Model to be able to run in parallel on the multiprocessor system. For the benchmark data tested, the parallel Flight Simulation Model implemented on the Alliant FX/8 has achieved nearly linear speedup. In this paper, we describe a parallel method for the Flight Simulation Model. We believe the method presented in this paper provides a general concept for the design of parallel applications. This concept, in most cases, can be adapted to many other sequential application programs.

  13. High-Throughput parallel blind Virtual Screening using BINDSURF

    PubMed Central

    2012-01-01

    Background Virtual Screening (VS) methods can considerably aid clinical research, predicting how ligands interact with drug targets. Most VS methods suppose a unique binding site for the target, usually derived from the interpretation of the protein crystal structure. However, it has been demonstrated that in many cases, diverse ligands interact with unrelated parts of the target and many VS methods do not take into account this relevant fact. Results We present BINDSURF, a novel VS methodology that scans the whole protein surface in order to find new hotspots, where ligands might potentially interact with, and which is implemented in last generation massively parallel GPU hardware, allowing fast processing of large ligand databases. Conclusions BINDSURF is an efficient and fast blind methodology for the determination of protein binding sites depending on the ligand, that uses the massively parallel architecture of GPUs for fast pre-screening of large ligand databases. Its results can also guide posterior application of more detailed VS methods in concrete binding sites of proteins, and its utilization can aid in drug discovery, design, repurposing and therefore help considerably in clinical research. PMID:23095663

  14. Sequential and parallel algorithms for minimum cost parallel decomposition of finite state machines

    E-print Network

    Shelke, Rajendra Ram

    1992-01-01

    SEQUENTIAL AND PARALLEL ALGORITHMS FOR MINIMUM COST PARALLEL DECOMPOSITION OF FINITE STATE MACHINES A Thesis by RAJENDRA RAM SHELKE Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1992 Major Subject: Electrical Engineering SEQUENTIAL AND PARALLEL ALGORITHMS FOR IvIINIMUM COST PARALLEL DECOMPOSITION OF FINITE STATE MACHINES A Thesis by RAJENDRA RAM SHELKE Approved as to style and content by...

  15. 3: Parallelism in Microprocessors Course on "Scalable Computing". Vittorio Scarano 3: Parallelism in Microprocessors

    E-print Network

    Scarano, Vittorio

    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

  16. Hybrid Scheduling for Parallel Ray Tracing Hybrid Scheduling for Parallel Ray Tracing

    E-print Network

    Reinhard, Erik

    Hybrid Scheduling for Parallel Ray Tracing #12;#12;Hybrid Scheduling for Parallel Ray Tracing Katwijk #12;#12;Preface Ray tracing is an easy algorithm to explain, but difficult to implement ray tracer to evolve into a system for parallel ray tracing and is the result of a two-year (TWAIO

  17. Parallel three dimensional perspective rendering

    NASA Astrophysics Data System (ADS)

    Li, P. Peggy; Curkendall, David W.

    1993-08-01

    The three dimensional rendering of imaging data using co-registered elevation data is an increasingly important tool for science data visualization and presentation. Computation time becomes a key issue when considering the feasibility of using this technique in conjunction with either film animation or interactive data base exploration.

  18. Uhlmann's parallelity in quantum estimation theory

    E-print Network

    Yamamoto, Hirosuke

    Uhlmann's parallelity in quantum estimation theory Keiji Matsumoto METR 97-03 February 1997 #12;Uhlmann's parallelity in quantum estimation theory Keiji Matsumoto Department of Mathematical Engineering estimation theory of quantum states. He called the matrix LS t (t) symmetrized logarithmic derivative (SLD

  19. Parallel Programming with Matrix Distributed Processing

    E-print Network

    Massimo Di Pierro

    2005-05-09

    Matrix Distributed Processing (MDP) is a C++ library for fast development of efficient parallel algorithms. It constitues the core of FermiQCD. MDP enables programmers to focus on algorithms, while parallelization is dealt with automatically and transparently. Here we present a brief overview of MDP and examples of applications in Computer Science (Cellular Automata), Engineering (PDE Solver) and Physics (Ising Model).

  20. GPU Parallelization of Algebraic Dynamic Programming

    E-print Network

    Boyer, Edmond

    GPU Parallelization of Algebraic Dynamic Programming Peter Steffen1,2 , Robert Giegerich1 mathieu.giraud@lifl.fr Abstract. Algebraic Dynamic Programming (ADP) is a framework to encode a broad similar data dependencies in the dynamic programming tables, a generic parallelization is possible. We