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PARALLELIZATION OF A CLASS OF IMPLICIT FINITE DIFFERENCE SCHEMES IN COMPUTATIONAL FLUID DYNAMICS

International Journal of High Speed Computing 1993年第1期5卷 1-50页

作者： NAOMI H. NAIK VIJAY K. NAIK MICHEL NICOULES Lamont-Doherty Earth Observatory Columbia University Palisades NY 10964 USA Research supported by the National Aeronautics and Space Administration under NASA Contract No. NAS1-18605 while in residence at the Institute for Computer Applications in Science and Engineering (ICASE) NASA Langley Research Center Hampton VA 23665– 5225. IBM T.J. Watson Research Center P.O. Box 218 Yorktown Heights NY 10598 USA Current address: Institut National Des Telecommunications 91011 Evry France.

Implicit finite difference schemes are often the preferred numerical methods in computational fluid dynamics, requiring less stringent stability bounds than the explicit schemes. Each iteration in an implicit scheme, however, involves global data dependencies in the form of second and higher order recurrences. Efficient parallel implementations of such methods, therefore, are more difficult and can be non-intuitive. Moreover, in practical applications, some sections of the computations are explicit while other sections are implicit in nature. Developing techniques that extract maximum parallelism simultaneously from all sections of an application is considerably harder than extracting parallelism from just an implicit section or an explicit section of the computations. In this paper, we consider issues in the parallelization of techniques that are used for solving Euler and thin-layer Navier-Stokes equations and that require, as a part of the computation, solving large linear systems in the form of block tri-diagonal and/or scalar penta-diagonal matrices. We focus our attention on three-dimensional cases and present schemes that minimize the total execution time when implemented on a message passing system. We describe various partitioning and scheduling strategies for alleviating the effects of the global data dependencies. Analyses of the computation, the communication, and the memory requirements of these methods are presented. The ARC-3D code, developed at NASA Ames, is used as an example application. Performance of the proposed methods is verified on the Victor multiprocessor system, a message passing architecture developed at the IBM T.J. Watson Research center.

关键词： Parallel CFD implicit finite difference schemes partitioning methods for block tri-diagonal and scalar penta-diagonal solvers ARC-3D message passing systems

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UTILIZING RESERVE ASSETS - MUTUAL SUPPORT AT SUPSHIP BATH

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NAVAL ENGINEERS JOURNAL 1993年第6期105卷 39-42页

作者： GOLDA, EM PORPORA, GA Cdr. Eugene Michael Golda:is a Naval Reserve engineering duty officer and is commanding officer of NR NavSea PMS Det 302. He has developed and directed mutual support programs assisting the Supervisor of Shipbuilding Brooklyn and has participated in the training and mutual support programs at the Supervisor of Shipbuilding Bath. He received a Ph.D. and M.S. in materials science and engineering from Stevens Institute of Technology Hoboken N.J. A 1977 graduate of the United States Naval Academy Cdr. Golda has been a member of ASNE since 1974. Cdr. Golda is a materials engineer at the Annapolis Detachment Carderock Division Naval Surface Warfare Center working on naval applications of superconducting technology. LCdr. Gregory A. Porpora:is an IBM market support representative who provides technical consulting support in application development with computer aided software engineering (CASE) tools. Prior to joining IBM he was a senior design engineer for a defense contractor involved in design and development of radar and ASW systems including the AN/BSY-1 combat system trainer. LCdr. Porpora is a member of IEEE the Naval Institute and the Naval Reserve Association. He holds a BSEE and MSEE from the Polytechnic Institute of Technology New York. LCdr. Porpora is currently assigned to NR SupShip Det 502 which provides extensive mutual support for the Supervisor of Shipbuilding Bath and the resident office in Brooklyn New York.

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An approach to the direct analysis of transient stability

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European Transactions on Electrical Power 1993年第3期3卷 241-248页

作者： Djukanovic, M.B. Sobajic, D.J. Pao, Y.‐H. Miodrag B. Djukanovic (1959) received his B.S. M.Sc. and Ph.D. degrees in Electrical Engineering from the University of Belgrade/Yugoslavia in 1982 1985 and 1992 respectively specializing in electric power systems. In 1984 he joined the Electrical Engineering Institute “Nikola Tesla” in Belgrade where he was working on the scientific studies in the field of power systems planning operation and control. In 1985 and 1990 he was appointed as a research scholar at the Royal Institute of Technology Stockholm and Case Western Reserve University Cleveland Ohio. His major in- terests are in the area of power system analysis steady-state and dynamic security and application of neural networks in electric power systems. (Electrical Engineering Institute “Nicola Tesla” ul. Koste Glavinica 8A YU-11000 Belgrad T +3811/2351-619 Fax + 3811/2351-823) Dejan J. Sobajic (1949) received the B.S.E.E. and the M.S.E.E. degrees from the University of Belgrade/Yugoslavia in 1972 and 1976 respectively and the Ph.D. degree from Case Western Reserve University Cleveland Ohio in 1988. At present he is with the Department of Electrical Engineering and Applied Physics Case Western Reserve University Cleveland. He is also the Engineering Manager of A1 WARE Inc. Cleveland. His current research interests include power system operation and control neuralnet systems and adaptive control. He is a member of the IEEE Task Force on Neural-Network Applications in Power Systems and of the IEEE Intelligent Controls Committee. He is the Chairman of the International Neural-Networks Society Special Interest Group on Power Engineering. (Case Western Reserve University Department of Electrial Engineering and Computer Sciences Glennan Building Ohio 44 106 USA T + 1216/421-2380 Fax +1216/368-8776) Yoh-Han Pao (1922) has been a Professor of Electrical Engineering and Computer Science at Case Westem Reserve University (CWRU) Cleveland Ohio since 1967. He has served as chairman of the University's Electrical Engineering Department

The Transient Energy Function (TEF) method has been intensely investigated over the last decade as a reliable and accurate tool for transient stability assessment of multimachine power systems. In this paper we propose the Potential Energy Boundary Surface (PEBS) based method for direct analysis of transient stability. The critical value of transient energy and the Critical Clearing Time (T_CCT) are evaluated without the need for successive calculation and memorization of the system kinetic and potential energy values along the sustained fault trajectory. The method is used for determination of output features in the training phase of the neural‐net based transient security assessment. The proposed approach is tested on the well‐known ten‐generator New England test system demonstrating the validity and accuracy of obtained results. Copyright © 1993 John Wiley & Sons, Ltd.

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THE PRESSURE DILATION CORRELATION IN COMPRESSIBLE FLOWS

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PHYSICS OF FLUIDS A-FLUID DYNAMICS 1992年第12期4卷 2674-2682页

作者： SARKAR, S Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23665

Simulations of simple compressible flows have been performed to enable the direct estimation of the pressure-dilatation correlation. The generally accepted belief that this correlation may be important in high-speed flows has been verified by the simulations. The pressure-dilatation correlation is theoretically investigated by considering the equation for fluctuating pressure in an arbitrary compressible flow. This leads to the isolation of a component of the pressure-dilatation that exhibits temporal oscillations on a fast time scale. Direct numerical simulations of homogeneous shear turbulence and isotropic turbulence show that this fast component has a negligible contribution to the evolution of turbulent kinetic energy. Then, an analysis for the case of homogeneous turbulence is performed to obtain a formal solution for the nonoscillatory pressure-dilatation. Simplifications lead to a model that algebraically relates the pressure-dilatation to quantities traditionally obtained in incompressible turbulence closures. The model is validated by direct comparison with the simulations.

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A computer MODEL OF DERIVATIVE METHOD FOR POINT SOURCE GRAVITY WAVES IN ATMOSPHERE

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science China Mathematics 1992年第11期35卷 1374-1387页

作者：庄洪春 CHAO H.LIU MICHAEL C.KELLEY Research Center of Space Science and Applications Academia Sinica Beljing 100080 PRC Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign USA School of Electrical Engineering Cornell University Ithaca NY USA

Analytical Solutions of point source gravity wave s in an isothermal atmosphere are given.A computer model based on the analytical solutions is developed for point source gravity waves in a horizontally and isothermally stratified *** numerical calculation of the propagation of point source gravity waves in a tealistic atmosphere then becomes feasible. The propagation of point source acoustic waves in the atmosphere can also be numerically calculated using the same model.

关键词： atmospheric gravity waves atmospheric waves acoustic-gravity waves.

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Performance evaluation of local real-time schedulers

Performance evaluation of local real-time schedulers

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International Phoenix Conference on computers and Communications (IPCCC)

作者： H.A. Sholl P.J. Pia L.R. Lipsky Center for Computer Applications and Research University of Connecticut Storrs CT USA Department of Computer Science and Engineering University of Connecticut Storrs CT USA

Through the use of a simulation study, the authors show how the effectiveness of a scheduling algorithm varies depending on the metric of interest and the execution environment under which it runs. They describe the timing requirements of real-time jobs. Three measures of response time controls are described. The model of a scheduling algorithm's execution environment is described, followed by a discussion on the variations in execution environment necessary to investigate adequately the behavior of a given scheduling algorithm. A simulation case study is described. A description of the modeling and simulation of a single processor running M job classes is included. Two scheduling algorithms for controlling response times are described, the results of running three scheduling algorithms under varying execution environments are presented.< >

关键词： Scheduling algorithm Delay Processor scheduling Timing Real time systems Probability distribution computer science Upper bound Clustering algorithms Costs

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Comparison among three types of dynamic current distribution control strategies

Comparison among three types of dynamic current distribution...

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International Conference on Industrial Electronics, Control and Instrumentation

作者： T.-F. Wu K. Siri C.Q. Lee Illinois Power Applications Center Department of Electrical Engineering and Computer Science University of Illinois Chicago Chicago IL USA

The authors present comparisons of the performance of three types of dynamic current distribution control strategies for power converters connected in parallel. The controls considered are static ramp pulse width modulation (PWM) control (SRPWM), dynamic ramp PWM control (DRPWM), and peak current PWM control (PCPWM). All of these controls are capable of dynamically distributing the total output current among converters in the system, although there exist several different features in their performance characteristics. The comparison is concentrated primarily on the aspects of controller implementation, system stability, transient behavior, and deviation of current distribution from the desired value.< >

关键词： Current distribution Control systems Pulse width modulation Voltage control Stability Application software Power system reliability Collision mitigation computer simulation DC-DC power converters

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Complete exchange on a circuit switched mesh

Complete exchange on a circuit switched mesh

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Scalable High Performance Computing Conference

作者： S.H. Bokhari H. Berryman Department of Electrical Engineering University of Engineering and Technology Lahore Pakistan Institute for Computer Applications in Science & Engineering NASA-Langley Research Center Hampton VA USA

The complete exchange ('all-to-all personalized') communication pattern is at the heart of numerous important multicomputer algorithms. Recent research has shown how this pattern can efficiently be performed on circuit-switched hypercubes. However, on circuit-switched meshes, this pattern is difficult to perform efficiently because the sparsity of the mesh interconnect leads to severe link contention. The authors develop a family of algorithms that proceed by recursively carrying out a series of contention-free exchanges on subdivisions of the mesh. Each member of this family is useful for some range of the parameters: mesh size, message size, startup time, and data transmission and permutation rates. The authors describe the performance of their algorithms on the Touchstone Delta mesh.< >

关键词： Switching circuits Hypercubes Communication switching Programming profession Power engineering computing NASA Distributed computing Power engineering and energy Hardware Integrated circuit interconnections

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PERFORMANCE STUDY OF INGAAS/INALAS/INP MODFETS ON HETEROSTRUCTURES GROWN BY OMVPE AND MBE 4

PERFORMANCE STUDY OF INGAAS/INALAS/INP MODFETS ON HETEROSTRU...

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4TH INTERNATIONAL CONF ON INDIUM PHOSPHIDE AND RELATED MATERIALS

作者： ADESIDA, I TONG, M NUMMILA, K KETTERSON, AA AINA, L MATTINGLY, M Center for Compound Semiconductor Microelectronics Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois Urbana-Champaign 61801 IL United States Allied-Signal Aerospace Company 9140 Old Annapolis Road Columbia 21045 MD United States COMSAT Clarksburg MD United States

ISBN: (纸本)0780305221

Devices fabricated in InAlAs/InGaAs/InP heterostructures have demonstrated superior performance in comparison with GaAs-based heterostructures (1). In particular, InAlAs/InGaAs/InP modulation-doped field effect transistors (MODFETs) with submicron gates have demonstrated higher current drive, higher gain, and better frquency response than their corresponding GaAs-based MODFETs. This advantage is attributed to superior material properties in the form of larger conduction band discontinuity, higher room temperature electron mobility, and higher effective electron velocity. To date, the materials used for realizing these high performance submicron MODFETs have been grown largely by molecular beam epitaxy (MBE). It has recently been shown that excellent InAlAsAnGaAs/InP materials can also be grown using organometallic vapor phase epitaxy (OMVPE) (2). This has led to recent reports of OMVPE-grown InGaAs-channel and InP-channel MODFETs with performances similar to those grown using MBE (3, 4). The flexibility of OMVPE in growing both InP and InGaAs in contrast with conventional MBE makes it more versatile for the realization of materials for optoelectronic integrated circuits (OEICs). In this paper, we present our results on the DC and RF characteristics of OMVPE-grown InAlAs/InGaAs/InP MODFETs (OMVPE MODFETs) as a function of gatelength. These results are compared with results reported in literature for MBE-grown InAlAs/InGaAs/InP MODFETs (MBE MODFETs). © 1992 IEEE.

关键词： Molecular beam epitaxy

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SELECTIVE WET ETCHING FOR INGAAS/INALAS/INP HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS 4

SELECTIVE WET ETCHING FOR INGAAS/INALAS/INP HETEROSTRUCTURE ...

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4TH INTERNATIONAL CONF ON INDIUM PHOSPHIDE AND RELATED MATERIALS

作者： TONG, M KETTERSON, AA NUMMILA, K ADESIDA, I AINA, L MATTINGLY, M Center for Compound Semiconductor Microelectronics Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois Urbana-Champaign 61801 IL United States Allied-Signal Aerospace Company 9140 Old Annapolis Road Columbia 21045 MD United States COMSAT Clarksburg MD United States

ISBN: (纸本)0780305221

The fabrication procedure of heterostructure field-effect transistors (HFETs) such as modulation-doped field-effect transistors (MODFETs) typically includes two important etching steps. The first is the mesa etch for device isolation, and the second is the gate recess where the cap layer is removed to expose the underlying layer for the Schottky gate formation. The gate recess is also used to achieve the desired drain saturation current. Both etching steps require good etch depth control, although, the control needed for the mesa process is not as critical as that for the gate recess. However, the mesa should not be overetched since metal-gate discontinuity due to breakage can occur at the mesa edge, especially for devices with nanometerdimension gate lengths. It has been shown by Tiwari (1) that excellent etch depth control is imperative in the gate recess process for short-gate-length MODFETs in order to achieve uniform threshold voltages which in turn is essential to the realization of high performance integrated circuits. Therefore, a good selectivity in the etching of the cap layer with respect to the underlying high band-gap layer is required in the fabrication of HFETs. © 1992 IEEE.

关键词： Drain current

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