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CONCURRENT BOUNDARY-ELEMENT COMPUTATION

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS 1993年第2期6卷 83-98页

作者： MCDOWALL, DS LEE, TW FUSCO, VF Microwave Research Group Department of Electrical and Electronic Engineering The Queen's University of Belfast Ashby Building Stranmillis Road Belfast BT9 5AH Northern Ireland U.K. D. Stewart McDowall was born in Dublin epublic of Ireland in 1967. He received the M. Eng. degree in Electrical and Electronic Engineering from the Queen's University of Belfast in 1990. In the same year he was presented with a Distinction Award from the Department of Education of Northern Ireland and he is currently pursuing his Ph.D. in the Microwave Research Group at Q.U.B. His principal research area is the electromagnetic field mapping of microwave systems using concurrient programming. He is an Associate Member of the Institute of Electrical Engineers. Lee Thaim Wee was awarded the degree of B. Eng. in Electronics from the Queen's University of Belfast in July 1991. He is currently serving in the Malaysian Armed Forces. Vincent F. Fusco was educated at the Queen's Univeristy of Belfast where he obtained the degree of Ph.D. in 1982. He has worked as a research engineer on short-range radar and radio telementry systems. Currently he is a reader in Microwave Communications in the School of Electrical Engineering and Computer Science the Queen's Univeristy of Belfast. His current research interests include non-linear microwave circuit simulation and concurrent programming techniques for electromagnetic field problems with particular emphasis on EMC applications. He has published numerous research papers in these areas. He is the author of the bookMicrowave Circuits Analysis and Computer Aided Design Prentice-Hall 1987. Dr Fusco is a Chartered Electrical Engineer and a Member of the Institute of Electrical Engineers.

A major limitation of the boundary element method (BEM) for the solution of electrical potential problems is the long computational time required. However, a large portion of the calculations involved can be viewed as being parallel in nature and can therefore be computed concurrently. This paper makes an effort to increase the efficiency of the BEM process using transputer-based multiprocessor computing techniques. The algorithms developed may equally well be applied to any multiprocessor system. The application selected to demonstrate the technique is the solution of an electrostatic problem governed by a two-dimensional Laplace equation. A parallel algorithm for problem setup and field extraction using BEM is designed and implemented on a transputer array. Special attention is directed to the utilization of the parallel processors to achieve maximum efficiency. The analysis in this work concentrates on the communication strategies for passing data between processors as well as a consideration of the workload attributed to each processor. The parallel algorithms were implemented using 3L Parallel Fortran;however, the choice of topology for the overall BEM implementation was limited by the fact that certain parts of the algorithm could only utilize a pipeline configuration of processors. Comprehensive results for the parallel BEM algorithm are given and they are encouraging, indicating that parallel processing has much to offer when applied to the boundary element method.

关键词： Boundary element method

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Stabilizers enhancing the frequency regulation action of HVDC links supplying weak AC systems

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European Transactions on Electrical Power 1993年第3期3卷 201-212页

作者： Maris, T.I. Lygdis, A.D. Vovos, N.A. Giannakopoulos, G.B. Theodoros I. Maris (1961) received the Diploma in Electrical Engineering from the University of Patras/Greece in 1984. In 1985 he joined the Power Systems Laboratory at the Electrical Engineering Department of the University of Patras as research assistant where he is currently working for his Ph.D. degree. His area of interest is HVDC transmission. (University of Patras Dep. of Electrical Engineering Power Systems Laboratory GR-26 500 Rion. Patras/Greece T +3061/997350 Fax +3061/997362) Athanassios D. Lygdis (1954) received the Diploma in Electrical Engineering from the University of Patras/Greece in 1979. From 1979 until 1982 he worked at the Nuclear Technology Laboratory of the University of Patras as research assistant. In 1983 he joined the Power Systems Laboratory at the Electrical Engineering Department of the University of Patras as scientific collaborator. He is now working for his Ph.D. degree in this Department. His main field of interest is power transmission by HVDC systems. (University of Patras Dep. of Electrical Engineering Power Systems Labora- tory GR-26 500 Rion Patras/Greece T + 3061/997350 Fax + 3061/997361) Nickolas A. Vovos (1951) received the Diploma degree from the University of Patras/Greece the M.Sc. degree from the University of Manchester/England Institute of Science and Technology. and the Ph.D. degree from the University of Patras in 1974 1975 1978 respectively all in Electrical Engineering. In 1976 he joined the Power Systems Laboratory at the Electrical Engineering Department of the University of Patras where he is now Associate Professor. His main fields of interest are the modeiling and the transient stability study of integrated AC/DC systems. He is a member of the IEEE Power Engineering Society and CIGRE and a registered professional Engineer and member of the Technical Chamber of Greece (University of Patras Dep. of Electrical Engineering Power Systems laboratory GR-26500 Rion Patras/Greece. T +3061/997369 Fax +3061/997362) Gabriel B. Giannakopoulos (1

Power System Stabilizers (PSS) superimposed to the basic control system of an HVDC link supplying a weak AC system, in order to enhance its frequency regulation action, are proposed. To decrease the AC voltage sensitivity at the inverter side, the basic control system of the HVDC link is proposed to operate with the rectifier under Minimum Ignition Angle (MIA) control and the inverter under Constant Current (CC) control. Inputs to the PSS are the frequency and the AC voltage deviations at the inverter side and their constant parameters are calculated using modal control technique. Detailed simulation results for a practical integrated AC/DC system are presented to evaluate the performance of the proposed control scheme. Copyright © 1993 John Wiley & Sons, Ltd.

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HIGH INDEX PLANE SELECTIVITY OF SILICON ANISOTROPIC ETCHING IN AQUEOUS POTASSIUM HYDROXIDE AND CESIUM HYDROXIDE

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THIN SOLID FILMS 1992年第1期215卷 58-64页

作者： JU, CS HESKETH, PJ Microfabrication Applications Laboratory Department of Electrical Engineering and Computer Science (M/C 154) University of Illinois at Chicago Box 4348 Chicago IL 60680 USA

Mechanically fabricated single-crystal silicon spheres with diameters of 0.25 in were etched in 40 wt.% aqueous potassium hydroxide at 75-degrees-C and 50 wt.% aqueous cesium hydroxide at 50-degrees-C. The post-etching shapes of both etched spheres show that the [111] and [100] directions were the slowest etching directions in both cases. The characteristic structures formed on the surface of these etched spheres were examined under the scanning electron microscope to study the high index plane selectivity. The [311] directions were found to be the most significant among the higher order crystal planes in both cases. Directions close to [023] were concluded to be the fastest etching in aqueous KOH;however, the [110] directions were the fastest in aqueous CsOH.

关键词： Silicon

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MEASUREMENTS OF THE ANISOTROPIC ETCHING OF A SINGLE-CRYSTAL SILICON SPHERE IN AQUEOUS CESIUM HYDROXIDE

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SENSORS AND ACTUATORS A-PHYSICAL 1992年第3期33卷 191-196页

作者： JU, CS HESKETH, PJ Microfabrication Applications Laboratory University of Illinois at Chicago Department of Electrical Engineering and Computer Science (M/C 154) Box 4348 Chicago IL 60680 USA

A mechanically polished single-crystalline silicon sphere with a diameter of 0.25 in is etched in 40% cesium hydroxide solution to study the orientation dependence of the anisotropic etching of silicon in three dimensions. The characteristic structures formed on the surface of the sphere after etching are examined under the scanning electron microscope. The slow-etching planes, {111} and {100}, as well as fast-etching planes, {110}, are identified from the micrographs. Most importantly, the {311} planes are found to be the most significant amongst the higher-order crystal planes.

关键词： Etching

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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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LOWER BOUNDS TO THE EXTERNAL PATHLENGTH OF A LOPSIDED BINARY TREE

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International Journal of High Speed Computing 1992年第3期4卷 169-178页

作者： C. V. SASTRY J. PRADHAN Department of Computer Science Engineering and Applications Regional Engineering College Rourkela Orissa India - 769008 India

Binary search trees with costs α and β on the left and right edges (lopsided binary search trees) are important in the construction of optimum prefix codes. In this paper we derive lower bounds for the external pathlengths of lopsided binary trees. It is found that the lower bound is tight if the cost difference (the difference in maximum cost and the minimum cost) is small but quite sharp when the cost difference is large. We suggest alternative ways to construct the lopsided binary tree when the cost difference is high to improve the lower bound.

关键词： Lopsided binary search tree pathlength lower bound fringe thickness

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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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A fully Sinc‐Galerkin method for Euler–Bernoulli beam models

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Numerical Methods for Partial Differential Equations 1992年第2期8卷 171-202页

作者： Smith, Ralph C. Bowers, Kenneth L. Lund, John Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23665 United States Department of Mathematical Sciences Montana State University Bozeman Montana 59717 United States

A fully Sinc‐Galerkin method in both space and time is presented for fourth‐order time‐dependent partial differential equations with fixed and cantilever boundary conditions. The sine discretizations for the second‐order temporal problem and the fourth‐order spatial problems are presented. Alternate formulations for variable parameter fourth‐order problems are given, which prove to be especially useful when applying the forward techniques of this article to parameter recovery problems. The discrete system that corresponds to the time‐dependent partial differential equations of interest are then formulated. Computational issues are discussed and an accurate and efficient algorithm for solving the resulting matrix system is outlined. Numerical results that highlight the method are given for problems with both analytic and singular solutions as well as fixed and cantilever boundary conditions. Copyright © 1992 Wiley Periodicals, Inc.

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