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DYNAMIC EVOLUTION OF THE PARTICLE SIZE DISTRIBUTION IN PARTICULATE PROCESSES.

IFAC Proceedings Volumes 2006年第2期39卷 661-666页

作者： D. Meimaroglou A.I. Roussos C. Kiparissides Department of Chemical Engineering Aristotle University of Thessaloniki and Chemical Process Engineering Research Institute P.O. Box 472 540 06 Thessaloniki Greece

The present wok provides a comparative study on the numerical solution of the dynamic population balance equation (PBE) in batch particulate processes undergoing simultaneous particle aggregation, growth and nucleation. The general PBE was numerically solved using three different techniques namely, the Galerkin on finite elements method (GFEM), the generalized method of moments (GMOM) and stochastic Monte Carlo simulations (MC). numerical simulations were carried out over a wide range of variation of particle aggregation and growth rate models.

关键词： Monte Carlo method moments method finite element method numerical algorithms distribution

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OPTIMAL MODE-SWITCHING FOR HYBRID SYSTEMS WITH UNKNOWN INITIAL STATE

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IFAC Proceedings Volumes 2006年第5期39卷 95-100页

作者： Henrik Axelsson Mauro Boccadoro Yorai Wardi Magnus Egerstedt Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332 Dipartimento di Ingegneria Elettronica e dell'Informazione Universita di Perugia 06125 Perugia — Italy

This paper concerns an optimal control problem defined on a class of switched mode hybrid dynamical systems. Such systems change modes whenever the state intersects certain surfaces that are defined in the state space. These switching surfaces are parameterized by a finite dimensional vector called the switching parameter. The optimization problem we consider is to minimize a given cost-functional with respect to the switching parameter under the assumption that the initial state of the system is not completely known. Instead, we assume that the initial state can be anywhere in a given set. We will approach this problem by minimizing the worst possible cost over the given set of initial states using results from minimax optimization. The results are then applied in order to solve a navigation problem in mobile robotics.

关键词： Hybrid Systems Switching Modes Optimal Control Gradient Descent numerical algorithms Minimax Techniques Mobile Robotics

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MODEL WEIGHT AND STATE ESTIMATION FOR MULTIPLE MODEL SYSTEMS APPLIED TO FAULT DETECTION AND IDENTIFICATION

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IFAC Proceedings Volumes 2006年第1期39卷 648-653页

作者： Redouane Hallouzi Michel Verhaegen Robert Babuška Stoyan Kanev Delft Center for Systems and Control Delft University of Technology Mekelweg 2 2628CD Delft The Netherlands

A method is proposed for estimating both the weights and the state of a multiple model system with one common state vector. In this system, the weights are related to the activation of each individual model. For the resulting nonlinear estimation problem a method is developed that efficiently decomposes the total problem into two separate parts, one for estimating the model weights and one for estimating the state. The method has been validated on a component, actuator and sensor fault detection and identification problem for a linearized model of an aircraft.

关键词： Fault detection and identification state-space methods recursive estimation filtering theory numerical algorithms

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Publish and perish: definition and analysis of an n-person publication impact game 06

Publish and perish: definition and analysis of an n-person p...

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Proceedings of the eighteenth annual ACM symposium on Parallelism in algorithms and architectures

作者： Zvi Lotker Boaz Patt-Shamir Mark R. Tuttle CWI Tel Aviv University Intel

ISBN: (纸本)9781595934529

We consider the following abstraction of competing publications. There are n players vying for the attention of the audience. The attention of the audience is abstracted by a single slot which holds, at any given time, the name of the latest release. Each player needs to choose, ahead of time, when to release its product, and the goal is to maximize the amount of time its product is the latest release. Formally, each player i chooses a point xi ∈ [0,1], and its payoff is the distance from its point xi to the next larger point, or to 1 if xi is the largest. For this game, we give a complete characterization of the Nash equilibrium for the two-player, continuous-action game, and, more important, we give an efficient approximation algorithm to compute numerically the symmetric Nash equilibrium for the n-player game. The approximation is computed via a discrete-action version of the game. In both cases, we show that the (symmetric) equilibrium is unique. Our algorithmic approach to the n-player game is non-standard in that it does not involve solving a system of differential equations. We believe that our techniques can be useful in the analysis of other timing games.

关键词： numerical algorithms nash equilibrium timing games

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numerical algorithms for spatial registration of line fiducials from cross-sectional images

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MEDICAL PHYSICS 2002年第8期29卷 1881-1891页

作者： Lee, S Fichtinger, G Chirikjian, GS Johns Hopkins Univ Dept Mech Engn Baltimore MD 21218 USA Johns Hopkins Univ Ctr Comp Integrated Surg Syst & Technol Baltimore MD 21218 USA

We present several numerical algorithms for six-degree-of-freedom rigid-body registration of line fiducial objects to their marks in cross-sectional planar images, such as those obtained in CT and MRI, given the correspondence between the marks and line fiducials. The area of immediate application is frame-based stereotactic procedures, such as radiosurgery and functional neurosurgery. The algorithms are also suitable to problems where the fiducial pattern moves inside the imager, as is the case in robot-assisted image-guided surgical applications. We demonstrate the numerical methods on clinical CT images and computer-generated data and compare their performance in terms of robustness to missing data, robustness to noise, and speed. The methods show two unique strengths: (1) They provide reliable registration of incomplete fiducial patterns when up to two-thirds of the total fiducials are missing from the image;and (2) they are applicable to an arbitrary combination of line fiducials without algorithmic modification. The average speed of the fastest algorithm is 0.3236 s for six fiducial lines in real CT data in a Matlab implementation. (C) 2002 American Association of Physicists in Medicine.

关键词： stereotactic registration line fiducials numerical algorithms robustness

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numerical PROBLEMS AND THEIR SUPPORT IN THE JMSL LIBRARY 4

NUMERICAL PROBLEMS AND THEIR SUPPORT IN THE JMSL LIBRARY

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4th International Conference on APLIMAT

作者： Lukas, Ladislav Univ W Bohemia Fac Econ Dept Stat & Operat Res Plzen 30614 Czech Republic

ISBN: (纸本)9788096926428

An overview of the JMSL 2.5 numerical library, the software product of the Visual Numerics, Inc., is given. There is a package of Java classes developed especially to support scientific computations. The package offers well-known numerical algorithms of linear algebra, optimization, statistics, and lot of other ones covering various fields including 2-D graphics. The paper discusses the JMSL numerical capabilities in general overview and provides some issues focused on possibilities of that package to solve problems in computational economics particularly.

关键词： Computational economics Java numerical algorithms

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Simulating time-dependent energy transfer between crossed laser beams in an expanding plasma

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JOURNAL OF COMPUTATIONAL PHYSICS 2005年第2期209卷 695-729页

作者： Hittinger, JAF Dorr, MR Berger, RL Williams, EA Ctr Appl Sci Comp Lawrence Livermore Natl Lab Livermore CA 94551 USA Lawrence Livermore Natl Lab AX Div Livermore CA 94551 USA

A coupled mode system is derived to investigate a three-wave parametric instability leading to energy transfer between co-propagating laser beams crossing in a plasma flow. The model includes beams of finite width refracting in a prescribed transverse plasma flow with spatial and temporal gradients in velocity and density. The resulting paraxial light equations are discretized spatially with a Crank-Nicholson-type scheme, and these algebraic constraints are nonlinearly coupled with ordinary differential equations in time that describe the ion acoustic response. The entire nonlinear differential-algebraic system is solved using an adaptive, backward-differencing method coupled with Newton's method. A numerical study is conducted in two dimensions that compares the intensity gain of the fully time-dependent coupled mode system with the gain computed under the further assumption of a strongly damped ion acoustic response. The results demonstrate a time-dependent gain suppression when the beam diameter is commensurate with the velocity gradient scale length. The gain suppression is shown to depend on time-dependent beam refraction and is interpreted as a time-dependent frequency shift. (c) 2005 Elsevier Inc. All rights reserved.

关键词： laser plasma interaction forward Brillouin scattering numerical algorithms paraxial wave equation coupled mode equations differential-algebraic systems

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Effective elasto-plastic properties of inclusion-reinforced composites. Study of shape, orientation and cyclic response

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MECHANICS OF MATERIALS 2005年第1期37卷 45-68页

作者： Doghri, I Friebel, C Univ Catholique Louvain CESAME B-1348 Louvain Belgium

A Hill-type incremental formulation for two-phase composites was recently proposed by Doghri and Ouaar [Int. J. Solids Struct. 40(7) (2003) 168 1]. We present a slightly improved version of the formulation and test it for non-spherical inclusions. The formulation enables the simulation of unloading and cyclic loadings. Two homogenization schemes are implemented: Mori-Tanaka (M-T) and an interpolative double-inclusion model (D-I). Two plasticity models which can be used for any phase are implemented: classical J(2) elasto-plasticity and Chaboche's model with non-linear kinematic and isotropic hardenings. All rate equations are discretized in time using implicit generalized mid-point schemes. A two-scale procedure for the simulation of composite structures is developed: a finite element (FE) program at macro-scale linked to the homogenization module at micro-scale. An extensive validation of the homogenization predictions against experimental data and direct unit cell FE simulations is conducted for several composite systems. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： composites micromechanics homogenization plasticity numerical algorithms finite elements

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Estimation of multiple heat sources in two-dimensional heat conduction problems

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2005年第3期19卷 388-394页

作者： Yang, CY Natl Kaohsiung Univ Appl Sci Dept Mold & Die Engn Kaohsiung 807 Taiwan

There have been some recent restrictions in the estimation of location and strength in inverse problems. One of the restrictions is that the problem is limited to the fixed number of heat sources. In other words, the moving sources cannot coincide in the moving path. Therefore, it is necessary to develop a method to estimate the location and the strength of various numbers of moving heat sources. A numerical algorithm combined with simplex method is proposed to determine the problem sequentially. A special feature of this method is that no prior knowledge of the number, the location, and the strength of the heat sources is necessary and that no sensitivity analysis is needed in the algorithm. Two examples are used to demonstrate the characteristics of the proposed method. The examples enable the investigation of the multiple moving sources with some coincided paths that lead to the number of sources varied with respect to the temporal coordinate. The numerical results show that the proposed method is an accurate and efficient method to determine the location and the strength of multiple moving sources in the inverse heat conduction problem.

关键词： Transient Heat Conduction Inverse Problems Dirac Delta Function numerical algorithms Finite Element Modeling Temperature Fields Conjugate Gradient Method Heat Transfer Coefficients Thermal Conductivity Finite Difference Method

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A visco-damage model for brittle materials under monotonic and sustained stresses

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INTERNATIONAL JOURNAL FOR numerical AND ANALYTICAL METHODS IN GEOMECHANICS 2005年第3期29卷 287-310页

作者： Papa, E Taliercio, A Politecn Milan Dept Struct Engn I-20133 Milan Italy

A theoretical model is proposed to describe the evolution of damage in brittle materials, such as concrete and masonry, subjected to increasing or sustained stresses of relatively high intensity. The model is based on the introduction of suitable damage variables in a rheological model. In this way, it is possible to describe the material behaviour under stresses either increasing or constant in time. The capabilities of the model in describing the mechanical response of material elements subjected to different stress histories are illustrated. Some correlations with experimental data from tests performed on masonry and concrete specimens are presented, to assess the reliability of the theoretical predictions. The results of some numerical applications to non-proportional stress paths are also illustrated. Finally, the limitations of the proposal are discussed and possible further improvements are envisaged. Copyright (C) 2005 John Wiley Sons, Ltd.

关键词： creep damage concrete anisotropy numerical algorithms

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