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Problem Consisting (problem + consisting)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Three-dimensional finite element analysis of lined tunnels

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2001
C. E. Augarde
Abstract This paper describes finite element procedures that have been developed to model the ground movements that occur when a shallow tunnel is installed in a clay soil. This study is part of a wider project concerned with the development of new methods to predict the likely extent of damage to surface structures caused by nearby shallow tunnelling. This particular paper, however, is concerned only with the numerical model of tunnel installation. The structural liner is an important component of this tunnel installation model; two different ways of modelling the liner (based on continuum elements and shell elements) are discussed in the paper. A test problem consisting of the installation of a lined tunnel in an elastic continuum is used to investigate the merits of these different approaches. When continuum elements are used to model the liner, the numerical results agree well with an analytical solution to the problem. When shell elements are used to model the liner, however, the results were found to be significantly influenced by the particular formulation adopted for the shell elements. Example analyses, involving incremental tunnel construction in a clay soil where the soil is modelled using a kinematic hardening plasticity model, are described. These analyses confirm that a thin layer of continuum elements may be used, satisfactorily, to model tunnel linings in a soil,structure interaction analysis of this sort. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Predictive adaptive control of plants with online structural changes based on multiple models

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2008
J. M. Lourenço
Abstract The objective of this paper is to present a new algorithm to improve the adaptation rate of a predictive adaptive controller. For that sake, the possible plant dynamic outcomes are covered by a bank of models. Each model is used to re-initialize the adaptive controller every time there is a large change in dynamics. The contribution of the paper consists in the development of a procedure that includes additional models in the bank when found suitable according to defined criteria. The algorithm is demonstrated in a benchmark problem consisting of the position control of two masses coupled by a spring of varying stiffness. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Reference and probability-matching priors in Bayesian analysis of mixed linear models

JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 5 2002
A. L. Pretorius
Summary Determination of reasonable non-informative priors in multiparameter problems is not easy; common non-informative priors, such as Jeffrey's prior, can have features that have an unexpectedly dramatic effect on the posterior. In recognition of this problem Berger and Bernardo (Bayesian Statistics IV. Oxford University Press, Oxford, UK, pp. 35,70, 1992), proposed the Reference Prior approach to the development of non-informative priors. In the present paper the reference priors of Berger and Bernardo (1992) are derived for the mixed linear model. In spite of these difficulties, there is growing evidence, mainly through examples that reference priors provide ,sensible' answers from a Bayesian point of view. We also examine whether the reference priors satisfy the probability-matching criterion. The theory and results are applied to a real problem consisting of 879 weaning weight records, from the progeny of 17 sires. These important aspects are explored via Monte Carlo simulations. Zusammenfassung Reference und Probability-Matching Priors in Bayesian Analysen von gemischten linearen Modellen Die Festlegung von vernünftigen Non-Informative Priors in Multi-Paramter Analysen ist nicht leicht; gewöhnliche Non-Informative Priors, wie beispielsweise Jeffrey's Priors, können unerwartete dramatische Effekte auf die Lösungen haben. Zur Lösung dieses Problems schlagen Berger and Bernardo (Bayesian Statistics IV. Oxford University Press, Oxford, UK, pp. 35,70, 1992) den Reference Prior Ansatz zur Entwicklung von Non-Informative Priors vor. In der vorliegenden Untersuchung werden die von Berger and Bernardo (1992) vorgeschlagenen Reference Priors in linearen gemischten Modellen angewandt. Trotz der bekannten Schwierigkeiten gibt es hauptsächlich anhand von Beispielen mehr und mehr Anhaltspunkte, dass die Reference Priors aus der Sicht von Bayesians zu brauchbaren Antworten führen. Es wurde auch untersucht, ob diese Reference Priors den Probability-Matching Kriterien genügen. Die Theorie und die Ergebnisse sind an einem Beispiel mit 879 Datensätzen mit Absatzgewichten von Schafen, die von 17 Böcken abstammen, verifiziert worden. Die wichtigen Aspekte sind mittels Monte Carlo Simulation untersucht worden. [source]

Study on Enzymatic Hydrolysis of Polylactic Acid by Endogenous Depolymerizaion Model

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2007
Masaji Watanabe
Abstract Enzymatic degradation of polylactic acid is studied experimentally and analytically. Gel permeation chromatography profiles obtained before and after the enzymatic degradation of polylactic acid (PLA) were introduced into the analysis based on a mathematical model. Previously developed techniques were successfully adapted to the analysis of an initial value problem consisting of an endogenous depolymerization model and an initial condition, and an inverse problem to determine the degradation rate for which the solution of the initial value problem also satisfies a final condition. Those problems were solved numerically and numerical results are introduced. Degradabilities of PLA and polyvinyl alcohol are compared. [source]