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Multigrid method for stability problems

Journal of Scientific Computing 1988年第3期3卷 261-274页

作者： Ta'asan Shlomo Department of Applied Mathematics and Computer Science The Weizmann Institute of Science Rehovot 76100 Israel Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton 23665 Virginia United States

The problem of calculating the stability of steady state solutions of differential equations is treated. Leading eigenvalues (i.e., having maximal real part) of large matrices that arise from discretization are to be calculated. An efficient multigrid method for solving these problems is presented. The method begins by obtaining an initial approximation for the dominant subspace on a coarse level using a damped Jacobi relaxation. This proceeds until enough accuracy for the dominant subspace has been obtained. The resulting grid functions are then used as an initial approximation for appropriate eigenvalue problems. These problems are solved first on coarse levels, followed by refinement until a desired accuracy for the eigenvalues has been achieved. The method employs local relaxation on all levels together with a global change on the coarsest level only, which is designed to separate the different eigenfunctions as well as to update their corresponding eigenvalues. Coarsening is done using the FAS formulation in a nonstandard way in which the right-hand side of the coarse grid equations involves unknown parameters to be solved for on the coarse grid. This in particular leads to a new multigrid method for calculating the eigenvalues of symmetric problems. Numerical experiments with a model problem that are presented demonstrate the effectiveness of the method proposed. Using an FMG algorithm a solution to the level of discretization errors is obtained in just a few work units (less than 10), where a work unit is the work involved in one Jacobi relaxation on the finest level. © 1988 Plenum Publishing Corporation.

关键词： Multigrid relaxation methods stability problems

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Wave envelope technique for multimode wave guide problems

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Journal of Scientific Computing 1987年第4期2卷 371-387页

作者： Hariharan, S.I. Sudharsanan, S.I. Department of Mathematical Sciences University of Akron Akron 44325 Ohio United States Institute for Computer Applications in Science and Engineering United States Applied Physics Group University of Tennessee Space Institute Tullahoma 37388 TN United States

In this paper we propose a fast method for solving wave guide problems. In particular, we consider the guide to be inhomogeneous, and allow propagation of waves of higher-order modes. Such techniques have been handled successfully for acoustic wave propagation problems with single mode and finite length. This paper extends this concept to electromagnetic wave guides with several modes and infinite in length. The method is shown and results of computations are presented. © 1987 Plenum Publishing Corporation.

关键词： acoustic waves electromagnetic waves multimode waveguides Wave envelope

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A Look at Internet Gateway Functional Requirements for Tactical Distributed C3 Systems

A Look at Internet Gateway Functional Requirements for Tacti...

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MILCOM, Military Communications Conference

作者： Don L. Bailey Ralph Martinez Science Applications International Corporation La Jolla CA USA Computer Engineering Research Laboratory Electrical & Computer Engineering Department University of Arizona Tucson Tucson AZ USA

This paper investigates the application of internet gateway technology to distributed C 3 systems. Internet gateway technology is in an infancy stage of development and currently applied to benign government and industry internetworking environments. This paper postulates a generic distributed C 3 system and describes the basic need for internet gateways in such a system to achieve interoperability. The relationship of the distributed C 3 system to an SDI networking environment is presented. The functional and operational requirements of internet gateways in a distributed C 3 system are described. A summary description of the current state-of-the-art in internet gateway technology and standards is also presented. Finally, a recommendation is made for further research into the specification and demonstration of internet gateways in distributed C 3 environments. The sponsor of this research work is the Defense Communications Agency, Center for Command and Control, and Communications.

关键词： Internet Command and control systems Distributed computing Application software Communication system control Control systems Mobile communication Management information systems Protocols Communication standards

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AN ALTERNATE SMOOTHING AND STRIPPING ALGORITHM FOR THINNING DIGITAL BINARY PATTERNS

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SIGNAL PROCESSING 1986年第3期11卷 207-222页

作者： CHU, YK SUEN, CY Department of Engineering and Computing Applications Pratt & Whitney P.O. Box 10 Longueil Quebec J4K 4X9 Canada Department of Computer Science Concordia University 1455 de Maisonneuve Bouleard West Montréal Quebec H3G 1M8 Canada

This paper presents an algorithm for thinning digital binary patterns (skeletonization). The algorithm consists of two phases. The first phase thins the input pattern to unit thickness by alternately smoothing of the pattern and stripping of the contour points. The second phase adjusts the resulting skeleton from phase one so that a medial skeleton can be obtained. The performance of this algorithm is first compared experimentally with recent results of two other research groups and then with nine other skeletonization algorithms proposed by other researchers. Results show that the alternate smoothing and stripping algorithm produces skeletons which are smooth and with least distortion and well-formed than the others. Dieser Beitrag beschreibt einen zweistufigen Algorithmus zur Ausdünnung (Skelettierung) digitaler binärer Muster. In der ersten Stufe wird das Eingangsmuster bis hinunter zu einer Strichstärke von einem Abtastwert ausgedünnt, indem es abwechselnd geglättet und von seinen Randpunkten befreit wird. In der 2. Stufe wird das verbleibende Skelett justiert, so daß sich ein nach der Mitte hinausgerichtetes Skelett ergibt. Die Wirkungsweise des Algorithmus wird zunächst mit neueren Ergebnissen zweier anderer Forschungsgruppen verglichen und sodann neun bekannten Skelettierungsalgorithmen gegenübergestellt. Wie die Ergebnisse zeigen, liefert die abwechselnde Glättung und Entfernung von Randpunkten Skelette, die glatt und wohlgeformt sind und im Vergleich zu anderen Verfahren die geringsten Verzerrungen aufweisen. Cet article présente un algorithme pour amincir des formes numériques binaires (extraction de squelette). L'algorithme consiste en deux phases. La première phase réduit la forme d'entrée à l'épaisseur unité, alternativement, en adoucissant et en enlevant les points de contour. La seconde phase ajuste la squelette resultant de la première phase pour obtenir une squelette médiane. Les performances de cet algorithme sont comparées d'abord expérimentalemen

关键词： Thinning thinning algorithm pattern processing skeletonization stripping

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A computer INTEGRATED engineering SYSTEM FOR DESIGN AND LIFE-CYCLE MANAGEMENT

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NAVAL ENGINEERS JOURNAL 1986年第3期98卷 115-121页

作者： NICKODEMUS, GH YANUS, ID Irwin D. Yanusgraduated from the University of Pennsylvania with a bachelor's degree in arts and science in 1960 and a bachelor of science degree in mechanical engineering in 1961. In 1963 he received a master of science degree in mechanical engineering from Carnegie-Mellon University. Mr. Yanus is presently the manager of naval systems engineering in the Computer Aided Engineering Department of the Plant Engineering Division of Westinghouse Electric Corporation. His prior experience includes 19 years at the Bettis Atomic Power Laboratory where he performed assignments of increasing responsibility in design analysis development and procurement of nuclear reactor components for naval applications. As the manager of reactor mechanical design he was responsible for the mechanical design of theNimitzclass reactor components and control drive mechanism technology development. Mr. Yanus is a member of the American Society of Mechanical Engineers and the Society of Naval Architects and Marine Engineers. Glen H. Nickodemusgraduated from Michigan State University in 1964 with a bachelor of science degree in civil engineering. He joined the Pittsburgh-Des Moines Corporation in July of the same year. A master of science degree in civil engineering was obtained from Carnegie-Mellon University in 1973. In 1969 Mr. Nickodemus joined the Advanced Reactors Division of the Westinghouse Electric Corporation where he performed design and structural analysis functions for the development of the Fast Flux Test Facility and Clinch River Breeder Reactor Plant (CRBRP). As manager of CRBRP reactor engineering stress analysis he was responsible for the reactor vessel internals closure head control rod drivelines and miscellaneous guard vessels and head access area components. He is currently the manager of software development for the Computer Aided Engineering Department of the Plant Engineering Division. Mr. Nickodemus is a member of the American Society of Mechanical Engineers and is a registered professional engineer in Penn

This paper describes a computer integrated engineering system for design and life cycle management of weapons systems, ships and other multidisciplined systems. All engineering data are stored in a central engineering database. Individual application databases define and process information necessary for specific discipline evaluations. Interface modules between the application databases and the engineering database ensure that the entered data are complete, consistent, compatible, and in compliance with requirements. Conflicts are immediately identified and efficiently resolved. Implementation of the system improves design quality and reduces costs by minimizing the number of design iterations, reducing the effort to implement changes, providing effective storage and retrieval, and reducing the need for ship checks prior to modifications and alterations.

关键词： MILITARY engineering

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1983 Design of Angle-Controlled Current Source Inverter-Fed Induction Motor Drive

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IEEE Transactions on Industry applications 1984年第4期IA-20卷 1104-1105页

作者： Krishnan, R. Lindsay, James F. Stefanovic, Victor R. Gould Research Center Rolling Meadows Faculty of Engineering and Computer Science Concordia University Industrial Power Conversion Systems Department Industry Applications Society

The current source inverter-fed induction motor drive (hereafter referred to as CSIM drive) is one of the widely used drives in the industry. Of the many strategies employed for the control of CSIM drive, angle control is the simplest scheme to incorporate the aspect of “frequency compensation,” thus paving the way for a fast response CSIM drive. A step-by-step design of the angle-controlled CSIM drive is described. A systematic design of inner current loop, slip speed loop, outer speed loop, and frequency compensation loop is given. The design incorporates a linear relationship between the reference input and output of electromagnetic torque and a strategy to obtain maximum torque per ampere. The commutation delay in the current source inverter is taken care of in the design of the frequency compensator. Experimental results are given in support of the design procedure. Copyright © 1984 by The Institute of Electrical and Electronics Engineers, Inc.

关键词： Induction motor drives Educational institutions Electrical equipment industry Electrical engineering Power electronics Frequency Torque Electronics industry Motor drives Education

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Evolution equations for Taylor vortices in the small-gap limit

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Physical Review A 1984年第5期29卷 2921-2921页

作者： Philip Hall Department of Mathematics Imperial College of Science of Technology University of London London SW7 2AZ United Kingdom Institute for Computer Applications in Science and Engineering NASA Langley Research Center National Aeronautics and Space Administration Hampton VA 23665 United States

We consider the centrifugal instability of the viscous fluid flow between concentric circular cylinders in the small-gap limit. The amplitude of the Taylor vortex is allowed to depend on a slow time variable, a slow axial variable, and the polar angle θ. It is shown that the amplitude of the vortex cannot, in general, be described by a single amplitude equation. In the absence of any slow axial variations it is shown that a Taylor vortex remains stable to wavy vortex perturbations.

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ARCTIC TRAFFICABILITY PROGRAM - A REVIEW

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NAVAL ENGINEERS JOURNAL 1984年第3期96卷 169-175页

作者： VOELKER, R GLEN, IF SEIBOLD, F BAYLY, I Richard Voelker:is Vice President of ARCTEC Incorporated a firm specializing in cold regions technology. He has been responsible for the management of thePolarClass Traffic-ability Program since its inception and annually participates in the field data collection in the Arctic. His prior experience includes positions with the U.S. Coast Guard in the icebreaker design project the Military Sealift Command and at Newport News Shipbuilding. He is a graduate of N. Y.S. Maritime College and has a MS degree from the University of Michigan. I.F. Glen:received his professional degrees in naval architecture from the Royal Naval Engineering College Manadon Plymouth and RN College Greenwich London entering the Royal Corps of Naval Constructors in 1967. After serving as a Constructor Lieutenant in the Royal Navy's Far East Fleet for a short period he joined the Polaris submarine project team in Bath England in 1968. In 1971 he was seconded to the Canadian Department of National Defense in Ottawa as a Constructor Lieutenant Commander under NATO exchange arrangements where he had responsibilities initially for conventional submarines and latterly for computer aided conceptual design. He ventured to Bath England in 1974 and joined Forward Design Group. In 1975 he took a position as a civilian engineer in the Canadian Defense Department and was Head of Hull Systems Engineering from 1977 to 1979. He joined ARCTEC CANADA LIMITED in 1980 and in addition to managing ice model testing projects and full scale trials has specialized in structural response of ships to ice impact. He headed ARCTEC's Kanata Laboratory from 1981 to 1983 when he was promoted to president. Frederick Seibold:is a research program manager with the Maritime Administration's Office of Advanced Ship Development and Technology. He is responsible for the marine science program which includes research in the areas of ship powering structures and propeller performance and Arctic technology. Mr. Seibold has been employed by Mar Ad since 1961 having hel

This paper describes a multiyear program to make an operational assessment on the feasibility of a year-round Arctic marine transportation system to serve Alaska. Specifically, the three objectives were to: collect meteorological and ice data along potential marine routes; instrument the hull and propulsion machinery to improve design critera for ice-worthy ships; and demonstrate that ships can operate in midwinter Alaskan Arctic ice conditions. The U.S. Coast Guard's Polar class icebreakers were used to make the operational assessment by annually extending the route northward and by operating throughout the winter season. This paper reviews some of the operational and technical achievements to date, as well as plans for future Arctic deployments.

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AN ADVANCED METHODOLOGY FOR PRELIMINARY HULL FORM DEVELOPMENT

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NAVAL ENGINEERS JOURNAL 1984年第4期96卷 147-161页

作者： LIN, WC DAY, WG HOUGH, JJ KEANE, RG WALDEN, DA KOH, IY Wen-Chin Lin:heads the Ship Powering Division at the David Taylor Naval Ship R&D Center (DTNSRDC). Dr. Lin received his B.S. degree in mechanical engineering from the National Taiwan University in 1957. He was awarded his M.S. degree in naval architecture and Ph.D. in engineering science from the University of California at Berkeley in 1963 and 1966 respectively. From 1966 to 1969 he was employed by ESSO Research and Engineering Company to conduct marine hydrodynamic research for oil tankers and offshore structures. Since joining DTNSRDC in 1969 he has actively conducted and directed hydrodynamic research to advance naval ship design technology and improve ship performance. Active in national and international symposia on ship hydrodynamic research he is recognized for contributions to the ship research community. For the past six years he has been a member of the Performance Committee of the ITTC and currently serves as secretary of the committee. He is a member of SNAME and the Society of Naval Architects of Japan. William G. Day Jr:. has been employed as a naval architect at the David Taylor Naval Ship R&D Center since receiving a B.E.S. degree from the Johns Hopkins University in 1966. He obtained an M.S. E. degree from George Washington University in 1971. As Head Design Evaluation Branch of the Ship Performance Department he is responsible for model experiments to evaluate the hydrodynamic performance of ships and propulsors. He is a member of ASNE and SNAME. In-Young Koh:received his B.S. and M.S. degrees in electrical engineering from Lowell University in 1969 and 1971 respectively and his Ph.D. in applied mechanics from Rensselaer Polytechnic Institute in 1976. Dr. Koh joined DTNSRDC as an electronic engineer specializing in the application of advanced instrumentation and computer techniques to ship research and design. He is currently engaged in research and development of active control systems for naval ship applications. Dr. Koh is a member of ASNE SNAME and IEEE. David Andrew Walden:is

A ship design methodology is presented for developing hull forms that attain improved performance in both seakeeping and resistance. Contrary to traditional practice, the methodology starts with developing a seakeeping-optimized hull form without making concessions to other performance considerations, such as resistance. The seakeeping-optimized hull is then modified to improve other performance characteristics without degrading the seakeeping. Presented is a point-design example produced by this methodology. Merits of the methodology and the point design are assessed on the basis of theoretical calculations and model experiments. This methodology is an integral part of the Hull Form Design System (HFDS) being developed for computer-supported naval ship design. The modularized character of HFDS and its application to hull form development are discussed.

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Reading Retardation or Linguistic Deficit? III: a Further Examination of Response Strategies in a Reading Test Completed by Hearing‐impaired Children

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Journal of Research in Reading 1983年第1期6卷 19-28页

作者： Beggs, W.D.A. Breslaw, P.I. W.D. Alan Beggs is a Research Fellow now working in the Blind Mobility Research Unit within the Department of Psychology at Nottingham. He obtained his first degree in Psychology from Queens University Belfast and holds a PhD from the University of Nottingham. His interests and publications have covered perceptual illusions the control of voluntary movement information processing in reading eye movements in reading clumsiness and auditory spatial knowledge in the deaf. Dr Beggs' address is Blind Mobility Research Unit Department of Psychology University of Nottingham University Park Nottingham NG7 2RD UK. W.D.A. BEGGS Blind Mobility Research Unit Department of Psychology University of Nottingham University Park Nottingham NG7 2RD UK. P.I. BRESLAW Department of Psychology University of Nottingham University Park Nottingham NG7 2RD UK. Paul I. Breslaw was a Research Assistant in the Department of Psychology at the University of Nottingham for a number of years until 1981. During that period he contributed to research projects in the automatic generation of variables in computer controlled experiments the study of on-line techniques for eye-movement recording during reading problem solving and paced aiming and the development of communicative competence in deaf children. He holds a BSc from the University of Sussex and an MPhil from Nottingham. He has recently turned his attention exclusively to computer science and runs his own software consultancy for real time and robot applications in psychology and engineering. He may be contacted at the Department of Psychology University of Nottingham University Park Nottingham NG7 2RD UK.

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