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  • Open Access


    Dynamic Instability of Straight Bars Subjected to Impulsive Axial Loads Using the DEM

    Letícia Fleck Fadel Miguel1, Leandro Fleck Fadel Miguel2, João Kaminski Jr.3

    CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.2, pp. 87-104, 2015, DOI:10.3970/cmes.2015.104.086

    Abstract Since the half of the XX century, attention was given to the instability of structures under parametric excitation, especially under periodic loads. On the other hand, the instability of bars subjected to axial loads of impulsive type has been little studied, in spite of the practical importance of the topic. Thus, in Engineering Design it is frequently supposed, without tests or additional verifications, that an axial load of short duration can exceed the Euler critical load of the bar without inducing damage in the same.
    Within this context, this paper proposes the use of the truss-like Discrete Element Method… More >

  • Open Access


    Numerical Study for a Class of Variable Order Fractional Integral-differential Equation in Terms of Bernstein Polynomials

    Jinsheng Wang1, Liqing Liu2, Yiming Chen2, Lechun Liu2, Dayan Liu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.1, pp. 69-85, 2015, DOI:10.3970/cmes.2015.104.069

    Abstract The aim of this paper is to seek the numerical solution of a class of variable order fractional integral-differential equation in terms of Bernstein polynomials. The fractional derivative is described in the Caputo sense. Four kinds of operational matrixes of Bernstein polynomials are introduced and are utilized to reduce the initial equation to the solution of algebraic equations after dispersing the variable. By solving the algebraic equations, the numerical solutions are acquired. The method in general is easy to implement and yields good results. Numerical examples are provided to demonstrate the validity and applicability of the method. More >

  • Open Access


    Numerical Simulation of Bubble Formation at a Single Orifice in Gas-fluidized Beds with Smoothed Particle Hydrodynamics and Finite Volume Coupled Method

    F.Z. Chen1,2, H.F. Qiang1, W.R. Gao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.1, pp. 41-68, 2015, DOI:10.3970/cmes.2015.104.041

    Abstract A coupled method describing gas-solid two-phase flow has been proposed to numerically study the bubble formation at a single orifice in gas-fluidized beds. Solid particles are traced with smoothed particle hydrodynamics, whereas gas phase is discretized by finite volume method. Drag force, gas pressure gradient, and volume fraction are used to couple the two methods. The effect of injection velocities, particle sizes, and particle densities on bubble growth is analyzed using the coupled method. The simulation results, obtained for two-dimensional geometries, include the shape and diameter size of a bubble as a function of time; such results are compared with… More >

  • Open Access


    Double Optimal Regularization Algorithms for Solving Ill-Posed Linear Problems under Large Noise

    Chein-Shan Liu1, Satya N. Atluri2

    CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.1, pp. 1-39, 2015, DOI:10.3970/cmes.2015.104.001

    Abstract A double optimal solution of an n-dimensional system of linear equations Ax = b has been derived in an affine m « n. We further develop a double optimal iterative algorithm (DOIA), with the descent direction z being solved from the residual equation Az = r0 by using its double optimal solution, to solve ill-posed linear problem under large noise. The DOIA is proven to be absolutely convergent step-by-step with the square residual error ||r||2 = ||b - Ax||2 being reduced by a positive quantity ||Azk||2 at each iteration step, which is found to be better than those algorithms based… More >

  • Open Access


    3D Echo-Based Patient-Specific Computational Left Ventricle Models to Quantify Material Properties and Stress/Strain Differences between Ventricles with and without Infarct

    Rui Fan1, Dalin Tang2,3, Jing Yao4, Chun Yang5, Di Xu4

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.6, pp. 491-508, 2014, DOI:10.3970/cmes.2014.099.491

    Abstract Identifying ventricle material properties and its infarct area after heart attack noninvasively is of great important in clinical applications. An echo-based computational modeling approach was proposed to investigate left ventricle (LV) mechanical properties and stress conditions using patient-specific data. Echo data was acquired from one healthy volunteer (male, age: 58) and a male patient (age: 60) who had an acute inferior myocardial infarction one week before echo image acquisition. Standard echocardiograms were obtained using an ultrasound machine (E9, GE Mechanical Systems, Milwaukee, Wisconsin) with a 3V probe and data were segmented for model construction. Finite element models were constructed to… More >

  • Open Access


    A Precise Integration Method for Modeling GPR Wave Propagation in Layered Pavement Structure

    H. Y. Fang1,2,3, J. Liu4, F. M. Wang1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.6, pp. 473-490, 2014, DOI:10.32604/cmes.2014.099.473

    Abstract Construction of electromagnetic wave propagation model in layered pavement structure is a key step in back analysis of ground penetrating radar (GPR) echo signal. The precise integration method (PIM) is a highly accurate, efficient, and unconditionally stable algorithm for solving 1-order ordinary differential equations. It is quite suitable for dealing with problems of wave propagation in layered media. In this paper, forward simulation of GPR electromagnetic wave propagating in homogeneous layered pavement structure is developed by employing PIM. To verify the performance of the proposed algorithm, simulated GPR signal is compared with the measured one. Excellent agreement is achieved. More >

  • Open Access


    Ambarzumyan Type Theorem For a Matrix Valued Quadratic Sturm-Liouville Problem

    Emrah Yilmaz1, Hikmet Koyunbakan2

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.6, pp. 463-471, 2014, DOI:10.3970/cmes.2014.099.463

    Abstract In this study, Ambarzumyan’s theorem for quadratic Sturm-Liouville problem is extended to second order differential systems of dimension d ≥ 2. It is shown that if the spectrum is the same as the spectrum belonging to the zero potential, then the matrix valued functions both P(x) and Q(x) are zero by imposing a condition on P(x). In scaler case, this problem was solved in [Koyunbakan, Lesnic and Panakhov (2013)]. More >

  • Open Access


    Local Defect Correction for Boundary Integral Equation Methods

    G. Kakuba1, M. J. H. Anthonissen2

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.6, pp. 445-462, 2014, DOI:10.3970/cmes.2014.099.445

    Abstract The aim in this paper is to develop a new local defect correction approach to gridding for problems with localised regions of high activity in the boundary element method. The technique of local defect correction has been studied for other methods as finite difference methods and finite volume methods. The initial attempts to developing such a technique by the authors for the boundary element method was based on block decomposition and manipulation of the coefficient matrix and right hand side of the system of equations in three dimension. It ignored the inherent global nature of the boundary integral equation, that… More >

  • Open Access


    Singular Boundary Method: Three Regularization Approaches and Exterior Wave Applications

    Zhuo-Jia Fu1, Wen Chen1,2, Jeng-Tzong Chen3, Wen-Zhen Qu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.5, pp. 417-443, 2014, DOI:10.3970/cmes.2014.099.417

    Abstract This study investigates the singular boundary method (SBM) with three regularization approaches for solving 2D and 3D exterior wave problems. The singular boundary method is a recent meshless boundary collocation method, which introduces the concept of source intensity factors to eliminate the singularity of the fundamental solutions. Recently, three approaches, the inverse interpolation technique (IIT), the semi-analytical technique with boundary IIT (SAT1) and the semi-analytical technique with integral mean value (SAT2), have been proposed to determine the source intensity factors for removing the singularities of Helmholtz fundamental solutions at origin. This study compares numerical accuracy and stability of these three… More >

  • Open Access


    An LGDAE Method to Solve Nonlinear Cauchy Problem Without Initial Temperature

    Chein-Shan Liu 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.5, pp. 371-391, 2014, DOI:10.3970/cmes.2014.099.371

    Abstract We recover an unknown initial temperature for a nonlinear heat conduction equation ut(x,t) = uxx(x,t) + H(x,t,u,ux), under the Cauchy boundary conditions specified on the left-boundary. The method in the present paper transforms the Cauchy problem into an inverse heat source problem to find F(x) in Tt(x,t) = Txx(x,t) + H + F(x). By using the GL(N,R) Lie-group differential algebraic equations (LGDAE) algorithm to integrate the numerical method of lines discretized equations from sideways heat equation, we can fast recover the initial temperature and two boundary conditions on the right-boundary. The accuracy and efficiency are confirmed by comparing the exact… More >

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