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37th Aerospace sciences Meeting and Exhibit, 1999

作者： Mavriplis, D.J. Pirzadeh, S. Institute for Computer Applications in Science and Engineering NASA Langley Research Center HamptonVA23681-0001 United States Configuration Aerodynamics Branch NASA Langley Research Center HamptonVA23681-0001 United States

A complete "geometry to drag-polar" analysis capability for three-dimensional high-lift configurations is described. The approach is based on the use of unstructured meshes in order to enable rapid turnaround for complicated geomtries which arise in high-lift configurations. Special attention is devoted to creating a capability for enabling analyses on highly resolved grids. Unstructured meshes of several million vertices are initially generated on a work-station, and subsequently refined on a supercomputer. The flow is solved on these refined meshes on large parallel computers using an unstructured agglomeration multigrid algorithm. Good prediction of lift and drag throughout the range of incidences is demonstrated on a transport take-off configuration using up to 24.7 million grid points. The feasibility of using this approach in a production environment on existing parallel machines is demonstrated, as well as the scalability of the solver on machines using up to 1450 processors. © 1999 by tlie American Inatibute of Aeronáutica and ABtro-nautics, Inc.

关键词： Supercomputers

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X-band photoinjector for a chirped-pulse FEL

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AIP Conference Proceedings 1999年第1期474卷 433-451页

作者： E. C. Landahl R. M. Alvis A. L. Troha F. V. Hartemann G. P. Le Sage W. E. White H. A. Baldis C. V. Bennett K. Li J. P. Heritage C. H. Ho N. C. Luhmann, Jr. 1Applied Science Department University of California Davis California 95616 2Institute for Laser Science and Applications LLNL Livermore California 94550 3Lawrence Livermore National Laboratory Livermore California 94550 4Electrical Engineering Department University of California Los Angeles California 90024 5Electrical and Computer Engineering Department University of California Davis California 6Synchrotron Radiation Research Center Taiwan

The phase noise and jitter characteristics of the laser and rf systems of a high gradient X-band photoinjector have been measured experimentally. The laser oscillator is a self-modelocked Titanium:Sapphire system operating at the 108th subharmonic of the rf gun. The X-band signal is produced from the laser by a phase-locked dielectric resonance oscillator, and amplified by a pulsed TWT and klystron. A comparison between the klystron and TWT amplifier phase noise and the fields excited in the rf gun demonstrates the filtering effect of the high Q structure, thus indicating that the rf gun can be used as a master oscillator, and could be energized by either a rf oscillator such as a magnetron or a compact source such as a cross-field amplifier. In particular, the rf gun can play the role of a pulsed rf clock to synchronize the photocathode laser system: direct drive of a synchronously modelocked AlGaAs quantum well laser has been achieved using the X-band gun rf fields. This novel, GHz repetition rate, laser system is being developed to replace the more conventional femtosecond Ti:Al2O3 system. Some advantages include pumping this laser with a stabilized current source instead of a costly, low efficiency pump laser. Finally, dark current measurements and initial photoelectron measurements are reported.

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On convergence acceleration techniques for unstructured meshes 29

On convergence acceleration techniques for unstructured mesh...

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29th AIAA Fluid Dynamics Conference

作者： Mavriplis, D.J. Institute for Computer Applications in Science and Engineering MS 403 NASA Langley Research Center HamptonVA23681-0001 United States

A discussion of convergence acceleration techniques as they relate to computational fluid dynamics problems on unstructured meshes is given. Rather than providing a detailed description of particular methods, the various different building blocks of current solution techniques are discussed and examples of solution strategies using one or several of these ideas are given. Issues relating to unstructured grid CFD problems are given additional consideration, including suitability of algorithms to current hardware trends, memory and cpu tradeoffs, treatment of non-linearities, and the development of efficient strategies for handling anisotropy-induced stiffness. The outlook for future potential improvements is also discussed. © 1998 by the American institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Computational fluid dynamics

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Three-dimensional high-lift analysis using a parallel unstructured multigrid solver 16th

Three-dimensional high-lift analysis using a parallel unstru...

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16th AIAA Applied Aerodynamics Conference, 1998

作者： Mavriplis, D.J. Institute for Computer Applications in Science and Engineering MS 403 NASA Langley Research Center HamptonVA23681-0001 United States

A directional implicit unstructured agglomeration multigrid solver is ported to shared and distributed memory massively parallel machines using the explicit domain-decomposition and message-passing approach. Because the algorithm operates on local implicit lines in the unstructured mesh, special care is required in partitioning the problem for parallel computing. A weighted partitioning strategy is described which avoids breaking the implicit lines across processor boundaries, while incurring minimal additional communication overhead. Good sealability is demonstrated on a 128 processor SGI Origin 2000 machine and on a 512 processor CRAY T3E machine for reasonably fine grids. The feasibility of performing large-scale unstructured grid calculations with the parallel multigrid algorithm is demonstrated by computing the flow over a partialspan flap wing high-lift geometry on a highly resolved grid of 13.5 million points in approximately 4 hours of wall clock time on the CRAY T3E. © 1998 by the American institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Message passing

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Effect of finite computational domain on turbulence scaling law in both physical and spectral spaces

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Physical Review E 1998年第5期58卷 5841-5841页

作者： Thomas Y. Hou Xiao-Hui Wu Shiyi Chen Ye Zhou Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23681

The well-known translation between the power law of the energy spectrum and that of the correlation function or the second order structure function has been widely used in analyzing random data. Here, we show that the translation is valid only in proper scaling regimes. The regimes of valid translation are different for the correlation function and the structure function. Indeed, they do not overlap. Furthermore, in practice, the power laws exist only for a finite range of scales. We show that this finite range makes the translation inexact even in the proper scaling regime. The error depends on the scaling exponent. The current findings are applicable to data analysis in fluid turbulence and other stochastic systems.

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Everything you ever wanted to know about software engineering education, but were afraid to ask 98

Everything you ever wanted to know about software engineerin...

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3rd Annual Conference on Integrating Technology into computer science Education, ITiCSE 1998

作者： Mead, Nancy R. Hilburn, Thomas B. Bagert, Donald J. Ryan, Michael Benediktsson, Oddur Van Scoy, Frances Software Engineering Institute Carnegie Mellon University 5000 Forbes Ave. PittsburghPA15213 United States Department of Computer Science Embry-Riddle Aeronautical University United States Department of Computer Science Texas Tech University LubbockTX79409-3104 United States School of Computer Applications Dublin City University Glasnevin Dublin 9 Ireland University of Iceland Dunhaga 5 Reykjavik Iceland Computer Science West Virginia University MorgantownWV26506-0209 United States

ISBN: (纸本)1581130007

In this panel, we will address questions on software engineering education that are voted on by the conference attendees in advance of the session. A sample set of questions will be posted. Conference attendees who will then vote on the questions to be addressed by the panel will augment these. After the panellists provide answers to a given question, the discussion will be opened up for follow-up questions or comments by the conference attendees. © 1998 ACM.

关键词： Software engineering

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Training environment for inferior vena caval filter placement

Training environment for inferior vena caval filter placemen...

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6th Conferenc on Medicine Meets Virtual Reality, MMVR 1998

作者： Hahn, James K. Kaufman, Roger Winick, Adam B. Carleton, Thurston Park, Youngser Lindeman, Rob Oh, Kwang-Man Ai-Ghreimil, Nadia Walsh, Raymond J. Loew, Murray Gerber, Joanne Sankar, Siddarth Laboratory for Advanced Computer Applications in Medicine Institute for Computer Graphics George Washington University Washington DC 20052 United States Department of Electrical Engineering and Computer Science George Washington University Washington DC 20052 United States Department of Radiology George Washington University Washington DC 20052 United States Department of Civil and Mechanical Engineering George Washington University Washington DC 20052 United States Department of Anatomy and Cell Biology George Washington University Washington DC 20052 United States Institute for Medical Imaging and Image Analysis George Washington University Washington DC 20052 United States

ISBN: (纸本)9051993862

This paper describes a Virtual Environment system designed to aid in training interventional radiologists in inferior vena cava filter placement. It is being developed as part of a VE simulator for a number of surgical and interventional radiology procedures at the Laboratory for Advanced computer applications in Medicine at the George Washington University. In this procedure a filter is placed in the inferior vena cava to prevent blood clots from the lower portion of the body from reaching the lungs and causing a pulmonary embolus. The simulation is designed to provide both tutorial and testing modes for the filter placement procedure.

关键词： Virtual reality

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Energy spectra of strongly stratified and rotating turbulence

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Physical Review E 1998年第5期57卷 6187-6187页

作者： Alex Mahalov Basil Nicolaenko Ye Zhou Department of Mathematics Arizona State University Tempe Arizona 85287 IBM Research Division T.J. Watson Research Center P.O. Box 218 Yorktown Heights New York 10598 Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23681

Turbulence under strong stratification and rotation is usually characterized as quasi-two-dimensional turbulence. We develop a “quasi-two-dimensional” energy spectrum which changes smoothly between the Kolmogorov −53 law (no stratification), the −2 scalings of Zhou [Phys. Fluids 7, 2092 (1995)] for the case of strong rotation, as well as the −2 scalings for the case of strong rotation and stratification. For strongly stratified turbulence, the model may give the −2 scaling predicted by Herring [Meteorol. Atmos. Phys. 38, 106 1988], and the −53 scaling indicated by some mesoscale observations.

关键词： Turbulence

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TOPOLOGICAL PROPERTIES OF THE (n,k)-STAR GRAPH

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International Journal of Foundations of computer science 1998年第2期9卷 235-248页

作者： WEI-KUO CHIANG RONG-JAYE CHEN Computer Telephony Applications Department Computer and Communication Research Laboratories Industrial Technology Research Institute K200 CCL Bldg. 51 195-11 Sec. 4 Chung Hsing Road Chutung Hsinchu Taiwan 310 Republic of China Department of Computer Science and Information Engineering National Chiao Tung University 1001 Ta Hsueh Road Hsinchu Taiwan 300 Republic of China

The star graph, though an attractive alternative to the hypercube, has a major drawback in that the number of nodes for an n-star graph must be n!, and thus considerably limits the choice of the number of nodes in the graph. In order to alleviate this drawback, the arrangement graph was recently proposed as a generalization of the star graph topology. The arrangement graph provides more flexibility than the star graph in choosing the number of nodes, but the degree of the resulting network may be very high. To overcome that disadvantage, this paper presents another generalization of the star graph, called the (n,k)-star graph. We examine some topological properties of the (n,k)-star graph from the graph-theory point of view. It is shown that two different types of edges in the (n,k)-star prevent it from being edge-symmetric, but edges in each class are essentially symmetric with respect to each other. Also, the diameter and the exact average distance of the (n,k)-star graph are derived. In addition, the fault-diameter for the (n,k)-star graph is shown to be at most the fault-free diameter plus three.

关键词： Interconnection networks star graphs symmetry average distance fault diameter

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A Region-Based Representation of Images in MARS

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Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology 1998年第1-2期20卷 137-150页

作者： Servetto, Sergio D. Rui, Yong Ramchandran, Kannan Huang, Thomas S. Beckman Inst. Adv. Sci. and Technol. Univ. Illinois at Urbana-Champaign Urbana IL 61801 United States Universidad Nacional de La Plata Argentina Univ. Illinois at Urbana-Champaign United States Comp. Res. Adv. Applications Group IBM Argentina Argentina Image Formation and Processing Group Beckman Institute UIUC United States Department of Computer Science UNLP Argentina Dept. of Elec. and Comp. Engineering UIUC United States Multimedia Commun. Res. Department Bell Laboratories Murray Hill NJ United States Info. Sciences Research Department AT and T Labs. Florham Park NJ United States Department of Computer Science UIUC United States Southeast University China Tsinghua University China University of Illinois Urbana-Champaign IL United States Image Formation and Processing Group Beckman Inst. Advance Sci. Technol. UIUC United States Vis. Technol. Grp. of Microsoft Res. Redmond WA United States City College of New York United States Columbia University United States AT and T Bell Labs. United States Ctr. for Telecommunications Research Columbia University United States Elec. and Comp. Eng. Department United States Beckman Institute Coordinated Science Laboratory IL United States IEEE Signal Processing Society United States IEEE IMDSP Technical Committee United States IEEE Transactions on Image Proc. United States National Taiwan University Taipei Taiwan Massachusetts Inst. of Technology Cambridge MA United States Department of Electrical Engineering MIT United States School of Electrical Engineering United States Lab. for Info. and Signal Processing Purdue University United States Dept. of Elec. and Comp. Engineering United States Coordinated Science Laboratory United States Image Formation and Processing Group Beckman Inst. Adv. Sci. and Technol. United States MIT Lincoln Laboratory IBM Thomas J. Watson Research Center Rheinishes Landes Museum Bonn Germany Swiss Institutes of Technology Zurich Switzerland Swiss Institutes of Technology Lausanne S

We study the problem of representing images within a multimedia Database Management System (DBMS), in order to support fast retrieval operations without compromising storage efficiency. To achieve this goal, we propose new image coding techniques which combine a wavelet representation, embedded coding of the wavelet coefficients, and segmentation of image-domain regions in the wavelet domain. A bitstream is generated in which each image region is encoded independently of other regions, without having to explicitly store information describing the regions. Simulation results show that our proposed algorithms achieve coding performance which compares favorably, both perceptually and objectively, to that achieved using state-of-the-art image/video coding techniques while additionally providing region-based support.

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