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A numerical study of some modified differential evolution algorithms

european JOURNAL OF OPERATIONAL RESEARCH 2006年第3期169卷 1176-1184页

作者： Kaelo, P Ali, MM Univ Witwatersrand Sch Computat & Appl Math ZA-2050 Johannesburg Johannesburg South Africa

Modifications in mutation and localization in acceptance rule are suggested to the differential evolution algorithm for global optimization. numerical experiments indicate that the resulting algorithms are considerably better than the original differential evolution algorithm. therefore, they offer a reasonable alternative to many currently available stochastic algorithms, especially for problems requiring 'direct search type' methods. numerical study is carried out using a set of 50 test problems many of which are inspired by practical applications. (c) 2005 Elsevier B.V. All rights reserved.

关键词： global optimization population set based method modified differential evolution continuous variable

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A numerical study of some modified differential evolution algorithms

A numerical study of some modified differential evolution al...

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6th International conference on Industrial engineering and Production Management

作者： Kaelo, P Ali, MM Univ Witwatersrand Sch Computat & Appl Math ZA-2050 Johannesburg Johannesburg South Africa

关键词： global optimization population set based method modified differential evolution continuous variable

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Use of the finite element method for the optimum selection of ANC sensors and actuators locations

Use of the finite element method for the optimum selection o...

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6th european conference on Noise Control: Advanced Solutions for Noise Control, EURONOISE 2006

作者： Mouzakitis, Spiridon Provatidis, Christopher National Technical University of Athens School of Mechanical Engineering Zografou Campus 9 Iroon Polytechnioy str 157 73 Athens Greece

the present work is concerned with the optimization of the physical components of an active noise control system installed in an enclosure. Specifically, a numerical procedure for calculating the optimum positions of the sensors and the actuators is described, which incorporates the finite element method. this procedure neither uses modal analysis nor simplified damping models and is therefore not restrained for use in enclosures with uniform and light acoustical damping, which used to be shortcomings of the existing numerical methods. Instead, the finite element method is used for the direct calculation of the primary and the controlled sound fields, a fact that improves the accuracy of the procedure in trade of slightly more computational effort. Furthermore, this work demonstrates how the problem of optimum selection of sensors and actuators locations using discrete optimization related to the FEM mesh (rather than continuous optimization of their positions in space) is better treated using the proposed procedure. Specifically, an improvement technique is presented, in which the computational bottleneck is transferred in the pre-optimization part of the method, resulting in substantial computational speed increase while retaining the numerical accuracy gained by the use of the finite element method.

关键词： Finite element method

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Field study on nighttime sleep disturbance from railway noise

Field study on nighttime sleep disturbance from railway nois...

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6th european conference on Noise Control: Advanced Solutions for Noise Control, EURONOISE 2006

作者： Lee, Soogab Kim, Jaehwan Lim, Changwoo Hong, Jiyoung Kim, Kyutae Sung, Dongwon Lee, Edward Center for Environmental Noise and Vibration Research School of Mechanical and Aerospace Engineering Seoul National University San 56-1 Shillim Dong Gwanak Gu 151-744 Seoul Korea Republic of School of Mechanical and Aerospace Engineering Seoul National University Seoul Korea Republic of Sehwa High School Seoul Korea Republic of

In this paper, the results of research on sleep disturbance in residential community around railway are introduced. For evaluation of sleep disturbance from railway noise, two methods were adopted. One is using questionnaire, and the other is measuring body movement of 12 subjects. At first, field survey was conducted in the 18 areas. numerical scale from 0 to 10 for evaluating sleep disturbance was used in questionnaire and equivalent sound pressure level during the nighttime was adopted as a noise metric. then, 12 subjects near the railway were tested the extent of their body movement during the sleep period time. For relating environmental noise events and subjects' body movement, noise measurement was conducted indoors and outdoors. Environmental noises were controlled using measured data and trains time table acquired from Korea Railroad Corporation. the statistical analysis using data collected from respondents in 18 areas around railway was conducted. the highly sleep disturbed population was examined to identify the relation between their subjective scale and their corresponding environmental noise levels. Percentage of motility, which is probability of sleep disturbance from railway noise event, was investigated and related to each sound exposure levels.

关键词： Railroads

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the influence of spatial correlation on the performance of earth structures and foundations

The influence of spatial correlation on the performance of e...

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GeoCongress 2006

作者： Baecher, Gregory B. Christian, John T. Department of Civil and Environmental Engineering University of Maryland College Park MD 20742 United States 23 Fredana Road Waban MA 02468 United States ASCE

ISBN: (纸本)0784408033

the concept of autocorrelation is central to geostatistics and other stochastic representations of the spatial variability of soil properties, but little has been made in the literature about the practical implications of such spatial correlation for design. Much of the literature focuses on abstract statistical methods and theoretical modeling. However, analytical and field research over many years has demonstrated that spatial correlation dramatically affects the performance of earth structures and foundations, and in particular sheds light on aspects of geotechnical performance that are otherwise difficult to predict. Examples include differential movements, size effects, and extent of failures. Spatial correlation also has important implications for the selection of engineering design parameters from field test data and measurements. All of these things have practical usefulness in day-by-day practice and provide new insights into the behavior of facilities built on or in the ground. Copyright ASCE 2006.

关键词： geotechnical engineering

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UNCERTAINTY ESTIMATION FOR numerical SOLUTIONS OF WALL BOUNDED TURBULENT FLOWS

UNCERTAINTY ESTIMATION FOR NUMERICAL SOLUTIONS OF WALL BOUND...

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2nd US-european Fluids engineering Division Summer Meeting/14th International conference on Nuclear engineering

作者： Elizalde-Blancas, Francisco Celik, Ismail Pakalapati, Suryanarayana W Virginia Univ Dept Mech & Aerosp Engn Morgantown WV 26506 USA

ISBN: (纸本)9780791847510

In this study numerical solutions are presented for a steady state, incompressible, 2-D turbulent flow near a wall. For this specific problem a manufactured (exact) solution was provided by the organizers of the 2006 Lisbon Workshop [6]. With the help of manufactured solution, assessment of the true error and other relevant uncertainty measures are possible. the calculations were performed using the commercial flow solver FLUENT along with some user defined functions to define source terms and velocity profiles at boundaries. though the flow regime is turbulent;the numerical solution is carried out for pseudo-laminar flow. this was done in order to avoid the errors implicit in turbulence models. the transformation from turbulent to laminar flow was done by defining a momentum source term which precludes the pressure gradient term. A detailed grid convergence analysis was performed. Using three-grid triplets the limiting values of the variables solved as the grid size tends to zero were calculated using different extrapolations. the L(2) norms of the true error obtained from various extrapolations are assessed. these results exhibit solution convergence as the grid size decreases. It was also shown that cubic spline extrapolation perform the best among the methods considered.

关键词： Turbulent flow

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the MUSE network: Sharing research expertise on unsaturated soils across Europe

The MUSE network: Sharing research expertise on unsaturated ...

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4th International conference on Unsaturated Soils

作者： Gallipoli, Domenico Toll, David Augarde, Charles Tarantino, Alessandro De Gennaro, Vincenzo Vaunat, Jean Wheeler, Simon Mancuso, Claudio School of Engineering Durham University South Road Durham DH1 3LE United Kingdom Dipartimento di Ingegneria Meccanica e Strutturale Università degli Studi di Trento Via Mesiano 77 Trento-Povo 38050 Italy Centre d'Enseignement et de Recherche en Mécanique des Sols Ecole Nationale des Ponts et Chaussées 6/8 Avenue Blaise Pascal Champs-sur-Marne Cedex 2 77455 France Departament d'Enginyeria del Terreny Cartogràfica i Geoffísica Mòdul D2 Universitat Politècnica de Catalunya c/ J.Girona 1-3 Barcelona 08034 Spain Department of Civil Engineering University of Glasgow Oakfield Avenue Glasgow G12 3LT United Kingdom Dipartimento di Ingegneria Geotecnica Università degli Studi di Napoli Federico II Via Claudio 21 Napoli 80125 Italy

ISBN: (纸本)0784408025

the paper presents the MUSE project to academics and practitioners who have an interest in the area of unsaturated soil mechanics. the MUSE ("Mechanics of Unsaturated Soils for engineering") project is a major research and training network funded by the european Union involving six european universities and five industrial partners. Further details can be obtained visiting the MUSE website (2005). the project started in December 2004 with a planned duration of four years. It aims at undertaking a comprehensive programme of research on unsaturated soils divided in the following four main tasks: laboratory testing, constitutive modelling, numerical analysis and application to practical problems. Copyright ASCE 2006.

关键词： Soils

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Formulation of continuous/discontinuous galerkin methods for strain gradient-dependent damage

Formulation of continuous/discontinuous galerkin methods for...

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11th International conference on Fracture 2005, ICF11

作者： Molari, L. Garikipati, K. Wells, G.N. DISTART Università di Bologna V.le Risorgimento 2 40136 Bologna Italy Department of Mechanical Engineering University of Michigan Ann Arbor MI 48109 United States Faculty of Civil Engineering and Geosciences Delft University of Technology Stevinweg 1 2628CN Delft Netherlands

ISBN: (纸本)9781617820632

Continuum damage models are widely used to represent the development of microscopic defects that coalesce into a macroscopic crack. the microscopic defects cause a progressive weakening or softening of the material (damage). Strain gradient-dependent terms have been included in some damage theories to regularize them, and thereby avoid a pathological mesh-dependence in the solution. A strain gradient-dependent damage model is considered here for the simulation of this feature in quasi-brittle materials. In the model considered, the damage parameter depends upon a regularized equivalent strain. the regularization is introduced through a dependency on the Laplacian of an equivalent strain measure. the introduction of the Laplacian of the strain leads to numerical difficulties as the governing differential equations are fourth-order, and additional boundary conditions must be specified. the application of such a model in a standard finite element framework requires C1 continuity of the shape functions. Here, a continuous/ discontinuous mixed Galerkin method is presented which avoids the need for high-order continuity. the formulation allows the use of C0 or C -1 interpolations for the regularized strain field and a 6C 0 interpolation of the displacement field. numerical examples are presented to validate the formulation in one and two dimensions. Several interpolations are tested extensively in one dimension in order to provide guidance for the most appropriate formulations in two dimensions. the formulation is applied to crack propagation in a three-point bending test, with the computed result being independent of the discretization.

关键词： Interpolation

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the boundary finite element method for the semi-analytical computation of 3D stress singularities in fracture mechanics

The boundary finite element method for the semi-analytical c...

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11th International conference on Fracture 2005, ICF11

作者： Mittelstedt, C. Becker, W. Siegen University Department of Mechanical Engineering Paul-Bonatz-Str. 9-11 D-57068 Siegen Germany Darmstadt University of Technology Department of Mechanics Hochschulstr. 1 D-64289 Darmstadt Germany

ISBN: (纸本)9781617820632

the numerical analysis of singular elasticity problems by means of standard finite element analyses usually requires significant computational effort, hence there is a particular interest in introducing new and efficient analysis methods like e.g. the boundary finite element method (BFEM, [1]), especially when detailed information on the asymptotic behaviour of the state variables - displacements, strains and stresses - in the vicinity of the singularity is sought. the BFEM combines the advantages of the finite element method and the boundary element method to a new and efficient procedure. As a prerequisite the BFEM assumes a certain scalability of the given structure with respect to a similarity center. In analogy to the boundary element method, only the boundary of the structure needs to be discretized, wherein standard isoparametric displacement based finite element formulations are sufficient. thus, no fundamental solution is required. Hence, the BFEM can be characterized as a fundamental-solution-less boundary element method solely based on finite elements. In the course of the finite element based derivation of the governing equations, the similarity or scalability characteristics enable a separation of coordinates such that in the scaling direction the method yields simple systems of differential equations that can be solved in an analytical way. In the directions perpendicular to the scaling direction the method converges in the FEM sense. the BFEM thus exhibits semi-analytical characteristics. In the present contribution the BFEM is employed for the investigation of the order of stress singularities for several classes of three-dimensional singular stress concentration problems, e.g. for three-dimensional crack [2-4] or notch [5] situations as well as for free edges [6] and corners [7,8] of layered structures. In all cases, the BFEM results agree excellently with reference results. the required computational effort is considerably lower compared to e.g. st

关键词： Boundary element method

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Inelastic behaviour of I-shaped aluminium beams: numerical analysis and cross-sectional classification

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COMPUTERS & STRUCTURES 2004年第23-26期82卷 2157-2171页

作者： De Matteis, G Landolfo, R Manganiello, M Mazzolani, FM Univ Naples Federico II Dept Struct Anal & Design I-80125 Naples Italy Univ Naples Federico II Dept Construct & Math Methods Arcitecture I-80134 Naples Italy

In this paper, the results of an extensive numerical analysis program devoted to the evaluation of the inelastic response of I-shaped aluminium alloy beams in non-uniform bending are presented. By using a numerical model implemented in the implicit FE code ABAQUS/Standard and largely calibrated with experimental tests, the main geometrical and mechanical parameters influencing the plastic behaviour of such beams are investigated. the results obtained in this study confirm the important role of the material hardening which, in addition to the local slenderness of compressed elements, has a strong influence on both ultimate moment and rotational capacity of the member. Moreover, it is shown that the influence of the other parameters, namely flange-to-web slenderness ratio, moment gradient, web slenderness and sectional area ratio, on the plastic capacity of the considered beams in terms of strength and deformability is of a secondary importance even if it is not negligible. On the whole, the results, which are obtained for two different tempers, emphasize the need to improve the present guidelines provided by the european code for aluminium structures relating to cross-sectional classification. More accurate class limits for outstand elements, which are able to account for the most important influential parameters on the plastic behaviour, are therefore proposed. (C) 2004 Civil-Comp Ltd. and Elsevier Ltd. All rights re served.

关键词： aluminium alloys cross-sectional classification Eurocode 9 inelastic capacity local buckling local slenderness rotational capacity strain hardening ultimate moment

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