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Theory of the lattice Boltzmann method: Lattice Boltzmann models for nonideal gases

Physical Review E 2000年第4期62卷 4982-4982页

作者： Li-Shi Luo Institute for Computer Applications in Science and Engineering MS 132C NASA Langley Research Center Hampton VA 23681-2199 3 West Reid Street Building 1152 United States

In this paper a procedure for systematic a priori derivation of the lattice Boltzmann models for nonideal gases from the Enskog equation (the modified Boltzmann equation for dense gases) is presented. This treatment provides a unified theory of lattice Boltzmann models for nonideal gases. The lattice Boltzmann equation is systematically obtained by discretizing the Enskog equation in phase space and time. The lattice Boltzmann model derived in this paper is thermodynamically consistent up to the order of discretization error. Existing lattice Boltzmann models for nonideal gases are analyzed and compared in detail. An evaluation of these models is made in light of the general procedure to construct the lattice Boltzmann model for nonideal gases presented in this work.

关键词： Gases

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Stochastic matched field array processing for detection and nulling in uncertain ocean environments

Stochastic matched field array processing for detection and ...

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Asilomar Conference on Signals, Systems & computers

作者： A.B. Baggeroer P.M. Daly Departments of Electrical Engineering and Computer Science and Ocean Engineering Massachusetts Institute of Technology Cambridge MA USA Ocean Sciences Division of Science Applications International Corporation McLean VA USA

ISBN: (纸本)0780365143

In current matched field processing (MFP) methods all the algorithms concentrate on generating a single high fidelity replica for matching the received signals. Several well known sources of mismatch limit this, so one must accept some degree of signal gain degradation in most experiments. Generally, less than 5 dB is acceptable, but beyond this the power leaks into too many other resolution cells and MFP usually does not "focus" on the target even when the "in bin" signal to noise ratio at a single sensor is large. Here we accept that the ocean is an uncertain environment and use a stochastic representation for the signal which spans more than one spatial dimension. We first examine the covariance structure of signals propagating In a random medium. This can be done both analytically using results in the acoustics literature or by simulations which incorporate the ocean physics of random fluctuations. Next, we consider a generalization of MFP, which we term stochastic matched field processing (SMFP) which attempts to focus the power from all the signal dimensions. Finally, we consider the deeper question of when does an uncertain ocean medium randomize the spatial structure so much that localization cannot be done. Probably a more important application of stochastic signal models is for robust nulling techniques. Many existing arrays do not achieve their full potential for nulling because the environment is not stationary over the time scales required for adaptive methods, commonly termed the "snap-shot deficient" situation. If one attempts parametric methods, the spatial signals leading to the array manifold do not span the space of the interfering signals because the ocean has randomized them. Higher dimensional nulling such as adjacent resolution cells has been done, but it is not clear if this is the appropriate physical model for spanning the interference. Here we use acoustic propagation models for this and examine nulling techniques which are robust to the u

关键词： Stochastic processes Array signal processing Oceans Signal processing Spatial resolution Signal resolution Acoustic propagation Robustness Signal generators Degradation

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On AUV control architecture

On AUV control architecture

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IEEE International Workshop on Intelligent Robots and Systems (IROS)

作者： P. Ridao J. Yuh J. Batlle K. Sugihara Informatics and Applications Institute University of Girona Spain Mechanical Engineering Department University of Girona Honolulu HI USA University of Girona Spain Information and Computer Science Department University of Hawaii Manoa Honolulu HI USA

This paper surveys control architectures proposed in the literature and describes a control architecture that is being developed for a semi-autonomous underwater vehicle for intervention missions (SAUVIM) at the University of Hawaii. Conceived as hybrid, this architecture has been organized in three layers: planning, control and execution. The mission is planned with a sequence of subgoals. Each subgoal has a related task supervisor responsible for arranging a set of pre-programmed task modules in order to achieve the subgoal. Task modules are the key concept of the architecture. They are the main building blocks and can be dynamically re-arranged by the task supervisor. In our architecture, deliberation takes place at the planning layer while reaction is dealt through the parallel execution of the task modules. Hence, the system presents both a hierarchical and an heterarchical decomposition, being able to show a predictable response while keeping rapid reactivity to the dynamic environment.

关键词： Robot sensing systems Mobile robots computer architecture Control systems Actuators Underwater vehicles Vehicle dynamics Communication system control Delay Fault tolerance

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Multiscale Coherent Structures and Broadband Waves due to Parallel Inhomogeneous Flows

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Physical Review Letters 2000年第20期85卷 4285-4285页

作者： Valeriy V. Gavrishchaka Gurudas I. Ganguli Wayne A. Scales Steven P. Slinker Christopher C. Chaston James P. McFadden Robert E. Ergun Charles W. Carlson Science Applications International Corporation McLean Virginia Plasma Physics Division Naval Research Laboratory Washington D.C. Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Blacksburg Virginia Space Sciences Laboratory University of California Berkeley California Department of Astrophysical and Planetary Science Laboratory for Atmospheric and Space Physics Colorado University Boulder Colorado

Linear theory analysis and particle-in-cell simulations show that a spatial transverse gradient in the ion drift parallel to the magnetic field, dVdi/dx≤Ωi, where Ωi is the ion cyclotron frequency, can generate a broadband multimode spectrum extending from ω≪Ωi to ω≫Ωi. Nonlinearly, these waves lead to multiscale spatially coherent structures, substantial cross-field transport, ion energization, and phase-space diffusion. Large spikes are formed in the parallel electric field time series. These signatures are similar to the Fast Auroral Snapshot satellite observations in the upward current region.

关键词： Plasma flow

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Higher-order dynamics in lattice-based models using the Chapman-Enskog method

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Physical Review E 2000年第2期61卷 2103-2103页

作者： Yue-Hong Qian Ye Zhou Department of Applied Physics and Applied Mathematics Columbia University New York New York 10027 IBM Research Division Thomas 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

In this paper, we investigate the existence of higher-order dynamics in lattice-based models. We have identified two conditions that determine whether a model would allow some Burnett-like equations when the Chapman-Enskog expansion is used. These two conditions are the number of the conserved quantity as well as the space and time discretization. We shall demonstrate these conditions by discussing (1) pure diffusion equation and (2) hydrodynamic equations. While the fact that diffusion equation allows the higher-order dynamics can be shown easily, we will illustrate that care must be taken when deriving Burnett-like equations for lattice-based hydrodynamics models using the Chapman-Enskog method.

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Higher-order dynamics in lattice-based models using the Chapman-Enskog method

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Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2000年第2期61卷 2103-2106页

作者： Qian, Yue-Hong Zhou, Ye Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States IBM Research Division Thomas J. Watson Research Center P.O. Box 218 Yorktown HeightsNY10598 United States Institute for Computer Applications in Science and Engineering NASA Langley Research Center HamptonVA23681 United States Exa Corp 450 Bedford Street LexingtonMA02420 United States

关键词： Hydrodynamics

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On the implementation of the Opus coordination language

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Concurrency and Computation: Practice and Experience 2000年第4期12卷

作者： Erwin Laure Matthew Haines Piyush Mehrotra Hans Zima Institute for Software Technology and Parallel Systems University of Vienna Liechtensteinstrasse 22 A-1090 Vienna Austria Department of Computer Science University of Wyoming Laramie WY 82071-3682 U.S.A. Institute for Computer Applications in Science and Engineering NASA Langley Research Center Mail Stop 132C Hampton VA 23681-0001 U.S.A.

Opus is a new programming language designed to assist in coordinating the execution of multiple, independent program modules. With the help of Opus, coarse grained task parallelism between data parallel modules can be expressed in a clean and structured way. In this paper we address the problems of how to build a compilation and runtime support system that can efficiently implement the Opus constructs. Our design considers the often-conflicting goals of efficiency and modular construction through software re-use. In particular, we present the system requirements for an efficient Opus implementation, the Opus runtime system, and describe how they work together to provide the underlying services that the Opus compiler needs for a broad class of machines. Copyright © 2000 John Wiley & Sons, Ltd.

关键词： Opus task parallelism data parallelism coordination

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Parallel visualization of large-scale aerodynamics calculations: a case study on the Cray T3E

Parallel visualization of large-scale aerodynamics calculati...

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IEEE Parallel Visualization and Graphics Symposium

作者： Kwan-Liu Ma T.W. Crockett University of California Davis USA Institute of Computer Applications in Science and Engineering USA

ISBN: (纸本)0780359011

This paper reports the performance of a parallel volume rendering algorithm for visualizing a large-scale unstructured-grid dataset produced by a three-dimensional aerodynamics simulation. This dataset, containing over 18 million tetrahedra, allows us to extend our performance results to a problem which is more than 30 times larger than the one we examined previously. This high resolution dataset also allows us to see fine, three-dimensional features in the flow field. All our tests were performed on the SGI/Cray T3E operated by NASA's Goddard Space Flight Center. Using 511 processors, a rendering rate of almost 9 million tetrahedra/second was achieved with a parallel overhead of 26%.

关键词： Large-scale systems Aerodynamics computer aided software engineering Rendering (computer graphics) Testing Parallel programming Concurrent computing Data visualization computer graphics Supercomputers

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Parallel compact multi-dimensional numerical algorithm with application to aeroacoustics 14th

Parallel compact multi-dimensional numerical algorithm with ...

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14th Computational Fluid Dynamics Conference, 1999

作者： Povitsky, Alex Morris, Philip J. Institute for Computer Applications in Science and Engineering NASA Langley Research Center MS 132C HamptonVA23681 United States Department of Aerospace Engineering The Pennsylvania State University University ParkPA16802 United States

In this study we propose an efficient method to parallelize high-order compact numerical algorithms for the solution of three-dimensional PDEs in a spacetime domain. The proposed parallelization method includes 3-D partitioning and the solution of sets of linear banded systems that split onto processors. Efficient. parallelization of the Thomas algorithm is difficult due to its pipelined nature. We use processors for either non-local data independent computations, solving lines in the next spatial direction, or local datadependent computations by the Runge-Kutta method while processors are idle due to the forward and backward recurrences of the Thomas algorithm. Control of processor communication and computations by a static schedule is adopted in this study. The obtained parallelization speed-up of the novel algorithm is about twice as much as that for the standard pipelined algorithm and close to that for the explicit algorithm. © 1999 by Alex Povitsky & Philip J. Morris. Published by the American institute of Aeronautics and Astronautics, Inc.

关键词： Runge Kutta methods

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Parallel rendering of 3D AMR data on the SGI/Cray T3E

Parallel rendering of 3D AMR data on the SGI/Cray T3E

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Frontiers of Massively Parallel Computation

作者： Kwan-Liu Ma Institute for Computer Applications in Science and Engineering NASA-Langley Research Center Hampton VA USA

ISBN: (纸本)0769500870

This paper describes work-in-progress on developing parallel visualization strategies for 3D Adaptive Mesh Refinement (AMR) data. AMR is a simple and powerful tool for modeling many important scientific and engineering problems. However visualization tools for 3D AMR data are not generally available. Converting AMR data onto a uniform mesh would result in high storage requirements, and rendering the uniform-mesh data on an average graphics workstation can be painfully slow if not impossible. The adaptive nature of the embedded mesh demands sophisticated visualization calculations. In this work, we compare the performance and storage requirements of a parallel volume renderer for regular-mesh data with a new parallel renderer based on adaptive sampling. While both renderers can achieve interactive visualization, the new approach offers significant performance gains, as indicated by our experiments on the SGI/Cray T3E.

关键词： Adaptive mesh refinement Data visualization Supercomputers Rendering (computer graphics) Power engineering and energy Runtime NASA Graphics Packaging computer applications

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