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Teaching module for laminar and turbulent forced convection on a flat plate

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION 1998年第2期6卷 115-125页

作者： Ribando, RJ Coyne, KA O'Leary, GW Univ Virginia Sch Engn & Appl Sci Dept Mech Aerosp & Nucl Engn Charlottesville VA 22903 USA

This article describes a PC-based teaching module for the classical problem of forced convection over a heated flat plate. The transformed boundary layer equations for an incompressible fluid are solved using a finite-difference numerical procedure on a grid that grows along with the boundary layer. Simple transition and mixing length turbulence models allow the algorithm to be used across a wide range of Reynolds numbers. The program returns a colored contour plot of the thermal boundary layer on the screen and shows the edge of the velocity boundary layer. The effects of the Reynolds number and Prandtl numbers are dramatically demonstrated. The user can use a slider mechanism to take local measurements of the plate temperature and surface temperature gradient, and from these data develop local and overall "virtual" convection correlations. (C) 1998 John Wiley & Sons, Inc.

关键词： heat transfer engineering education forced convection numerical algorithms graphical user interface

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Crack nucleation and growth as strain localization in a virtual-bond continuum

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ENGINEERING FRACTURE MECHANICS 1998年第1期61卷 21-48页

作者： Klein, P Gao, H Stanford Univ Div Mech & Computat Stanford CA 94305 USA

We have recently proposed a virtual internal bond (VIB) model with cohesive interactions between material particles as an alternative approach to modeling fracture. This approach differs from atomistic methods in that a phenomenological "cohesive force law" is assumed to act between "material particles" which are not necessarily atoms;it also differs from "cohesive surface" models in that, rather than imposing a cohesive law along a prescribed set of discrete surfaces, a network of cohesive bonds is statistically incorporated into the constitutive law of the material via the Cauchy-Born rule, i.e. by equating the strain energy density on the continuum level to the potential energy stored in the cohesive bonds due to an imposed deformation. With this approach, crack initiation and growth occur spontaneously when the classical condition for the loss of ellipticity in the elastic governing equations is satisfied. We demonstrate the application of the VIE model to failure detection, dynamic crack propagation, and fracture toughening with combined fracture and constrained plasticity in a multilayered structure. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词： crack nucleation-growth and branching finite strain cohesive models numerical algorithms

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Direct computation of lower-bound dynamic buckling loads of imperfection-sensitive systems

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AIAA JOURNAL 1998年第12期36卷 2257-2261页

作者： Wu, BS Jilin Univ Technol Dept Math Changchun 130023 Peoples R China

The computation of lower-bound dynamic buckling loads of imperfection sensitive systems is examined under step load of infinite duration. An extended system based on the energy criterion for establishing the lower-bound dynamic buckling loads without solving the highly nonlinear initial-value problems is proposed. The newly introduced scaling parameters are nonsingular solutions to the extended system;thus, standard methods can be used to compute them. Using the extended system, one can directly obtain the lower-bound dynamic buckling loads without tracing the postbuckling equilibrium paths. An efficient implementation of Newton's method for solving the extended system is presented, and numerical examples are given.

关键词： Buckling Newton's Method Stiffness Matrices Structural System Simply Supported Beams numerical Simulation numerical algorithms Gaussian Elimination Structural Design Structural Modeling

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Global one-dimensional optimization using smooth auxiliary functions

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MATHEMATICAL PROGRAMMING 1998年第1期81卷 127-146页

作者： Sergeyev, YD Univ Calabria DEIS Natl Res Council Inst Syst Sci & Informat I-87036 Arcavacata Di Rende Italy Nizhnii Novgorod State Univ Nizhnii Novgorod Russia

In this paper new global optimization algorithms are proposed for solving problems where the objective function is univariate and has Lipschitzean first derivatives. To solve this problem, smooth auxiliary functions, which are adaptively improved during the course of the search, are constructed. Three new algorithms are introduced: the first used the exact a priori known Lipschitz constant for derivatives;the second, when this constant is unknown, estimates it during the course of the search and finally, the last method uses neither the exact global Lipschitz constant nor its estimate but instead adaptively estimates the local Lipschitz constants in different sectors of the search region during the course of optimization. Convergence conditions of the methods are investigated from a general viewpoint and some numerical results are also given. (C) 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.

关键词： global optimization Lipschitzean first derivatives numerical algorithms convergence

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New principle and algorithms of stable parallel real-time processing for distributed processor

New principle and algorithms of stable parallel real-time pr...

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Conference on Real-Time Imaging III

作者： Khlebnikov, WA Softjoys Corp Digital Signal Proc Div St Petersburg 196235 Russia

ISBN: (纸本)0819427438

The paper presents the novel principle on constructing a new class of highly parallel fast stable numerical algorithms of linear algebra. In accordance with suggested principle the parallel modifications of classic Gran-Shmidt algorithm and the conjugate directions' algorithm are developed. The modified algorithms have super-linear convergence rate: the sufficient number of iterations is proportional to effective rank of linear algebraic system. Also they have high numerical stability supported by easy controlled parallel cross-feedbacks. The new algorithms provide for high computing density in distributed processors and proposed for using in area of multidimensional data stream real-time processing.

关键词： parallel processing linear algebra numerical algorithms distributed processor

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Compile time symbolic derivation with C++ templates 4

Compile time symbolic derivation with C++ templates

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4th USENIX Conference on Object-Oriented Technologies and Systems

作者： Gil, J Gutterman, Z IBM Corp Thomas J Watson Res Ctr Yorktown Heights NY 10598 USA

ISBN: (纸本)1880446936

C++ templates are already recognized as a powerful linguistic mechanism, whose usefulness transcends the realization of traditional generic containers. In the same venue, this paper reports on a somewhat surprising application of templates-for computing the symbolic derivative of expression. Specifically, we describe a software package based on templates, called SEMT, which allows the programmer to create symbolic expressions, substitute variables in them, and compute their derivatives. SEMT is unique in that these manipulations are all done at compile time. In other words, SEMT effectively coerces the compiler to do symbolic computation as part of the compilation process. Beyond the theoretical interest, SEMT can be practically applied in the efficient, generic and easy to use implementation of many numerical algorithms.

关键词： Generic programming numerical algorithms Scientific computing Symbolic derivation

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numerical Methods For Polynomial Matrix Rank Evaluation ⋆

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IFAC Proceedings Volumes 1998年第18期31卷 369-374页

作者： Didier Henrion Michael Šebek LAAS-CNRS 7 Avenue du Colonel Roche 31 077 Toulouse Cedex 4 France Trnka Laboratory of Automatic Control Faculty of Electrical Engineering Czech University of Technology Prague Czech Republic Institute of Information Theory and Automation Academy of Sciences of the Czech Republic 182 08 Prague 8 Czech Republic

Two algorithms are proposed for evaluating the rank of an arbitrary polynomial matrix. They rely upon constant matrix rank evaluations and therefore are more reliable than already existing elementary polynomial operations techniques. Some applications are mentioned, such as polynomial null-space extraction or conditions of existence of solutions to matrix polynomial equations arising in control problems. Deux algorithmes sont proposés pour évaluer le rang d'une matrice polynomiale quelconque. Ils sont basés sur des évaluations de rangs de matrices constantes et sont donc plus fiables que les techniques déjà existantes d'opérations polynomiales élémentaires. Quelques applications sont mentionnées, comme l'extraction du noyau polynomial ou des conditions d'existence de solutions aux équations polynomiales matricielles provenant de problèmes de commande.

关键词： numerical algorithms Matrix polynomial equations

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The hardware configuration and field experiment of GPS-Based for online parameter tester for transmission lines with mutual inductance

The hardware configuration and field experiment of GPS-Based...

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International Conference on Energy Management and Power Delivery (EMPD 98)

作者： Chen, YP Zhang, CX Hu, ZJ Wuhan Univ Hydraul & Elect Engn Sch Elect Engn Wuhan 430072 Hubei Peoples R China

ISBN: (纸本)0780344952

A GPS-based power transmission line tester, in which the time tag of GPS is used as the synchronization signal, is developed practically to realize the online measurement of power system parameters. The principles of the new measurement scheme are reviewed in the first part of the paper. The hardware and numerical algorithms are then presented in details, followed by experimental results.

关键词： power transmission lines power system measurement Global Positioning System power transmission line online parameter tester hardware configuration field experiment GPS synchronization signal power system parameters measurement numerical algorithms mutual inductance

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Control-Oriented Model Simplification Application to Active Suspension Design

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IFAC Proceedings Volumes 1998年第20期31卷 853-858页

作者： Thierry Cambois Philippe de Larminat PSA Peugeot Citroën Information Technologies Department 18 rue des Fauvelles 92250 La Garenne Colombes FRANCE Institut de Recherche en Cybernétique de Nantes UMR 6597 1 rue de la Noë 44072 Nantes Cedex FRANCE

A pragmatic approach is proposed in order to perform simplification of a complex non-linear model of a full-vehicle with the purpose of active suspension design. It relies upon two stages : numerical linearisation of the non-linear model around an equilibrium point, and order reduction of the linear representation. The emphasis is put on the fact that, as the objective is control design, it is necessary to involve the control law into the simplification process. This is done in an iterative way, since, initially, no controller is available.

关键词： active vehicle suspension linearisation modelling model reduction numerical algorithms

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A Structure Based Synthesis Method for Disturbance Rejection

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IFAC Proceedings Volumes 1998年第18期31卷 691-696页

作者： Jean-François Camart Basilio Del-Muro-Cuellar Michel Malabre Institut de Recherche en Cybernétique de Nantes UMR GNRS 6597 1 rue de la Noë B.P. 92101 44321 Nantes Gedex 03 France. Phone: (+33) 2 40 37 16 51. Fax: (+33) 2 40 37 25 22. ITESM-GEM Depto. de Ingeniera Mécanica Apdo. Postal 6-3 Atizapan Estado de México GP 52926 México

A new method for the synthesis of compensators which solve the disturbance rejection problem (either by state feedback or by output feedback) is presented. This method, based on structural and geometric approaches, provides solutions to the problem with the minimal number of unassignable poles (i.e. poles that are fixed due to the fact that this particular problem is been solved). Moreover, all the poles that remain assignable are relocated to values selected by a non expert user, without any required knowledge of the proposed programs. Une nouvelle méthode de synthèse de compensateurs solutions du problème du rejet de perturbation, soit par retour d'état soit par retour de mesure, est proposée. Cette méthode, basée sur les approches géométrique et structurelle, permet de résoudre le problème (s'il est soluble) avec le minimum de pôles imposés par cette résolution. De plus tous les autres pôles sont placés aux valeurs indiquées par un utilisateur non expert de ces méthodes.

关键词： Linear Systems Disturbance Rejection Dynamic Output Feedback State Feedback Geometric Approach Fixed Poles Pole Assignment numerical algorithms

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