G. R. Venkatakrishnan^1,*, R. Rengaraj², S. Salivahanan³

CMES-Computer Modeling in Engineering & Sciences, Vol.115, No.1, pp. 25-45, 2018, DOI:10.3970/cmes.2018.115.025

Abstract A new and efficient Grey Wolf Optimization (GWO) algorithm is implemented to solve real power economic dispatch (RPED) problems in this paper. The nonlinear RPED problem is one the most important and fundamental optimization problem which reduces the total cost in generating real power without violating the constraints. Conventional methods can solve the ELD problem with good solution quality with assumptions assigned to fuel cost curves without which these methods lead to suboptimal or infeasible solutions. The behavior of grey wolves which is mimicked in the GWO algorithm are leadership hierarchy and hunting mechanism. The More >

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 ||Az_k||² at each iteration step, which is found to be better than those algorithms based More >

Zichun Yang^1,2,3, Lei Zhang^1,4, Yueyun Cao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.97, No.2, pp. 101-130, 2014, DOI:10.3970/cmes.2014.097.101

Abstract Discretization of inverse problems often leads to systems of linear equations with a highly ill-conditioned coefficient matrix. To find meaningful solutions of such systems, one kind of prevailing and representative approaches is the so-called regularized total least squares (TLS) method when both the system matrix and the observation term are contaminated by some noises. We will survey two such regularization methods in the TLS setting. One is the iterative truncated TLS (TTLS) method which can solve a convergent sequence of projected linear systems generated by Lanczos bidiagonalization. The other one is to convert the Tikhonov… More >

S,erson L. Gonzaga de Oliveira¹, Jéssica Renata Nogueira¹, João Manuel R. S. Tavares²

CMES-Computer Modeling in Engineering & Sciences, Vol.100, No.1, pp. 31-57, 2014, DOI:10.3970/cmes.2014.100.031

Abstract Triangulations and tetrahedrizations are important geometrical discretization procedures applied to several areas, such as the reconstruction of surfaces and data visualization. Delaunay and Voronoi tessellations are discretization structures of domains with desirable geometrical properties. In this work, a systematic review of algorithms with linear-time behaviour to generate 2D/3D Delaunay and/or Voronoi tessellations is presented. More >

Chein-Shan Liu¹, Su-Ying Zhang², Satya N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.1, pp. 29-48, 2012, DOI:10.3970/cmes.2012.088.029

Abstract With a detailed investigation of n linear algebraic equations Bx=b, we find that the scaled residual dynamics for y∈Sⁿ⁻¹ is equipped with four structures: the Jordan dynamics, the rotation group SO(n), a generalized Hamiltonian formulation, as well as a metric bracket system. Therefore, it is the first time that we can compute the steplength used in the iterative method by a novel algorithm based on the Jordan structure. The algorithms preserving the length of y are developed as the structure preserving algorithms (SPAs), which can significantly accelerate the convergence speed and are robust enough against the noise More >

A.E. Martínez-Castro¹, I.H. Faris¹, R. Gallego¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.3, pp. 177-206, 2012, DOI:10.3970/cmes.2012.087.177

Abstract In this paper, the identification of hidden defects inside a three-dimen -sional layer is set as an Identification Inverse Problem. This problem is solved by minimizing a cost functional which is linearized with respect to the volume defects, leading to a procedure that requires only computations at the host domain free of defects. The cost functional is stated as the misfit between experimental and computed displacements and spherical and/or ellipsoidal cavities are the defects to locate. The identification of these cavities is based on the measured displacements at a set of points due to time-harmonic… More >

Peter J. Ireman, Anders Klarbring¹, Niclas Strömberg

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 125-158, 2009, DOI:10.3970/cmes.2009.052.125

Abstract In this paper finite element approaches for fretting fatigue are proposed on the basis of a non-local model of continuum damage coupled to friction and wear. The model is formulated in the frame-work of a standard material. In a previous paper this was done in the spirit of Maugin, where an extra entropy flux is introduced in the second law in order to include the gradient of the internal variable in a proper manner. In this paper we follow instead the ideas of Frémond and others, where this extra entropy flux is no longer needed,… More >

C.E. Majorana¹, V.A. Salomoni

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.1, pp. 49-84, 2008, DOI:10.3970/cmes.2008.033.049

Abstract A dynamic analysis of a thin shell finite element undergoing large displacements and rotations is here presented. The constitutive model adopted derives from the coupling of an hyperelastic basic model fulfilling a De Saint Venant-Kirchhoff criterion with a scalar damage function depending on the maximum value of a suitable strain measure attained through the deformation history; then plastic effects are included using an isotropic/kinematic hardening law. A conservative time integration scheme for the non-linear dynamics of the hyperelastic damaged-plastic thin shell is applied. The main characteristic of the scheme is to be conservative, since it More >

E. Bleszynski¹, M. Bleszynski¹, T. Jaroszewicz¹

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.4, pp. 295-318, 2004, DOI:10.3970/cmes.2004.005.295

Abstract We describe elements of our current work on the development of new methods for high frequency electromagnetic scattering, based on the wavefront (WF) representation of propagating fields and on the asymptotic but rigorous solution of integral equations for surface currents. In the wavefront evolution technique, surfaces of constant phase are constructed and treated not merely as collections of independent rays, but as well defined geometrical objects endowed with the full connectivity information. Hence, a precise determination of shadow and reflection boundaries, a construction of (multiply) diffracted wavefronts, a dynamic adjustment of the number of rays,… More >

W.J. Santos¹ , J.A.F. Santiago¹, J.C.F Telles¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.1, pp. 23-40, 2012, DOI:10.3970/cmes.2012.087.023

Abstract The aim of this paper is to present numerical simulations of Cathodic Protection (CP) Systems using a Genetic Algorithm (GA) and the Method of Fundamental Solutions (MFS). MFS is used to obtain the solution of the associated homogeneous equation with the non-homogeneous equation subject to nonlinear boundary conditions defined as polarization curves. The adopted GA minimizes a nonlinear error function, whose design variables are the coefficients of the linear superposition of fundamental solutions and the positions of the source points, located outside the problem domain. In this work, the anodes added to the CP system More >