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  • Open Access


    A Study of Boundary Conditions in the Meshless Local Petrov-Galerkin (MLPG) Method for Electromagnetic Field Computations

    Meiling Zhao1, Yufeng Nie2

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.2, pp. 97-112, 2008, DOI:10.3970/cmes.2008.037.097

    Abstract Meshless local Petrov-Galerkin (MLPG) method is successfully applied for electromagnetic field computations. The moving least square technique is used to interpolate the trial and test functions. More attention is paid to imposing the essential boundary conditions of electromagnetic equations. A new coupled meshless local Petrov-Galerkin and finite element (MLPG-FE) method is presented to enforce the essential boundary conditions. Unlike the conventional coupled technique, this approach can ensure the smooth blending of the potential variables as well as their derivatives in the transition region between the meshless and finite element domains. Then the boundary singular weight method is proposed to enforce… More >

  • Open Access


    Analytical Solution for Estimation of Temperature-Dependent Material Properties of Metals Using Modified Morse Potential

    Kuo-Ning Chiang1, Chan-Yen Chou2, Chung-Jung Wu2,Chao-Jen Huang2, Ming-Chih Yew2

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 85-96, 2008, DOI:10.3970/cmes.2008.037.085

    Abstract An atomic-level analytical solution, together with a modified Morse potential, has been developed to estimate temperature-dependent thermal expansion coefficients (CTE) and elastic characteristics of bulk metals. In this study, inter-atomic forces are considered as a set of anharmonic oscillator networks which can be described by Morse potential, while the material properties can be defined by these inter-atomic forces; when temperature increases, the vibration of the anharmonic oscillator causes the phenomenon of temperature-dependent material properties. The results of analysis showed that the original Morse potential can give a reasonable prediction of the thermal expansion coefficients and elastic constants of metals at… More >

  • Open Access


    Steady-state Response of the Wave Propagation in a Magneto-Electro-Elastic Square Column

    Jianping Wei1, Xianyue Su1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 65-84, 2008, DOI:10.3970/cmes.2008.037.065

    Abstract The steady-state response of the wave propagation in a magneto-electro-elastic square column (MEESC) was studied. Some new characteristics were discovered: the guided waves are classified in the forms of the Quasi-P, Quasi-SV and Quasi-SH waves and ordered by the standing wave number, and the three type guided waves are corresponding to the extension, twist and shear modes of the body vibration; the induced electric and magnetic fields can be aroused by the propagating stress wave. We proposed a self-adjoint method, by which the guided-wave restriction condition was derived. After finding the corresponding orthogonal sets, the analytic dispersion equation was obtained.… More >

  • Open Access


    Efficient Numerical Solution of the 3-D Semiconductor Poisson Equation for Monte Carlo Device Simulation

    Z. Aksamija1,2, U. Ravaioli3

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 45-64, 2008, DOI:10.3970/cmes.2008.037.045

    Abstract Finding the scalar potential from the Poisson equation is a common, yet challenging problem in semiconductor modeling. One of the central problems in traditional mesh-based methods is the assignment of charge to the regular mesh imposed for the discretisation. In order to avoid this problem, we create a mesh-free algorithm which starts by assigning each mesh point to each particle present in the problem. This algorithm is based on a Fourier series expansion coupled with point matching. An efficient algorithm for repeatedly solving the Poisson problem for moving charge distributions is presented. We demonstate that this approach is accurate and… More >

  • Open Access


    Insight into High-quality Aerodynamic Design Spaces through Multi-objective Optimization

    T. Kipouros1, D.M. Jaeggi2, W.N. Dawes3, G.T. Parks2,A.M. Savill1, P.J. Clarkson2

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 1-44, 2008, DOI:10.3970/cmes.2008.037.001

    Abstract An approach to support the computational aerodynamic design process is presented and demonstrated through the application of a novel multi-objective variant of the Tabu Search optimization algorithm for continuous problems to the aerodynamic design optimization of turbomachinery blades. The aim is to improve the performance of a specific stage and ultimately of the whole engine. The integrated system developed for this purpose is described. This combines the optimizer with an existing geometry parameterization scheme and a well-established CFD package. The system's performance is illustrated through case studies -- one two-dimensional, one three-dimensional -- in which flow characteristics important to the… More >

  • Open Access


    A Novel Fictitious Time Integration Method for Solving the Discretized Inverse Sturm-Liouville Problems, For Specified Eigenvalues

    Chein-Shan Liu1, Satya N. Atluri2

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 261-286, 2008, DOI:10.3970/cmes.2008.036.261

    Abstract The inverse Sturm-Liouville problem finds its applications in the identification of mechanical properties and/or geometrical configurations of a vibrating continuous medium; however, this problem is hard to solve, either theoretically or numerically. Previously, Liu (2008a) has constructed a Lie-group shooting method to determine the eigenvalues, and the corresponding eigenfunctions, for the direct Sturm-Liouville problem. In this study, we are concerned with solving the inverse Sturm-Liouville problem, by developing a Lie-group of SL(2,R) to construct nonlinear algebraic equations (NAEs), when discrete eigenvalues are specified. Our purpose here is to use these NAEs to solve the unknown function in the Sturm-Liouville operator.… More >

  • Open Access


    A Parameter Free Cost Function for Multi-Point Low Speed Airfoil Design

    G. Veble1,2,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 243-260, 2008, DOI:10.3970/cmes.2008.036.243

    Abstract A simple cost function is proposed that depends on the inviscid pressure distribution around an airfoil and that, when minimized, results in airfoils that promote laminar flow. Additional constraints specify the design point of the airfoil. The method allows for straightforward inclusion of multiple design points. The resulting airfoils are quantitatively similar to those already successfully used in practice. More >

  • Open Access


    Methods to Automatically Build Point Distribution Models for Objects like Hand Palms and Faces Represented in Images

    Maria João M. Vasconcelos1, João Manuel R. S. Tavares1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 213-242, 2008, DOI:10.3970/cmes.2008.036.213

    Abstract In this work we developed methods to automatically extract significant points of objects like hand palms and faces represented in images that can be used to build Point Distribution Models automatically. These models are further used to segment the modelled objects in new images, through the use of Active Shape Models or Active Appearance Models. These models showed to be efficient in the segmentation of objects, but had as drawback the fact that the labelling of the landmark points was usually manually made and consequently time consuming. Thus, in this paper we describe some methods capable to extract significant points… More >

  • Open Access


    Probabilistic Collocation used in a Two-Step approach for \\efficient uncertainty quantification in computational fluid dynamics.

    G.J.A. Loeven1,2, H. Bijl3

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 193-212, 2008, DOI:10.3970/cmes.2008.036.193

    Abstract In this paper a Two-Step approach is presented for uncertainty quantification for expensive problems with multiple uncertain parameters. Both steps are performed using the Probabilistic Collocation method. The first step consists of a sensitivity analysis to identify the most important parameters of the problem. The sensitivity derivatives are obtained using a first or second order Probabilistic Collocation approximation. For the most important parameters the probability distribution functions are propagated using the Probabilistic Collocation method using higher order approximations. The Two-Step approach is demonstrated for flow around a NACA0012 airfoil with eight uncertain parameters in the free stream conditions and geometry.… More >

  • Open Access


    Meshless Analysis of Ductile Failure

    L. Li, S. Liu, H. Wang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.2, pp. 173-192, 2008, DOI:10.3970/cmes.2008.036.173

    Abstract We study ductile fracture using Reproducing Kernel Particle Interpolation and the Gurson-Tvergaard-Needleman (GTN) model. The meshless simulations are compared with the available experimental results and previous finite element simulations for crack propagation. The results agree well with experimental results, and it is confirmed that the proposed method provides a convenient and yet accurate means for simulation of ductile fracture. More >

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