Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.3, pp. 241-269, 2013, DOI:10.32604/cmes.2013.092.241

Abstract In order to solve an ill-posed linear problem, we propose an innovative Jacobian type iterative method by presetting a conditioner before the steepest descent direction. The preconditioner is derived from an invariant manifold approach, which includes two parameters α and γ to be determined. When the weighting parameter α is optimized by minimizing a properly defined objective function, the relaxation parameter γ can be derived to accelerate the convergence speed under a switching criterion. When the switch is turned-on, by using the derived value of γ it can pull back the iterative orbit to the fast manifold. More >

Chein-Shan Liu¹, Satya N. Atluri²

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 213-239, 2013, DOI:10.3970/cmes.2013.092.213

Abstract We show that the problem "real-time numerical differentiation" of a given noisy signal in time, by supplementing a compensated controller in the second-order robust exact differentiator, the tracking differentiator or the continuous hybrid differentiator, can be viewed as a set of differential algebraic equations (DAEs) to enhance a precise tracking of the given noisy signal. Thus, we are able to solve the highly ill-posed problem of numerical differentiation of noisy signal by using the Lie-group differential algebraic differentiators (LGDADs) based on the Lie-group GL(n,R), whose accuracy and tracking performance are better than before. The "index-two" differentiators More >

Zichun Yang^1,2,3, Wencai Sun²

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 193-212, 2013, DOI:10.3970/cmes.2013.092.193

Abstract The set-based structural eigenvalue problem is defined, by expressing the uncertainties of the structural parameters in terms of various convex sets. A new method based on Kriging model and Particle Swarm Optimization (PSO) is proposed for solving this problem. The introduction of the Kriging model into this approach can effectively reduce the computational burden especially for largescale structures. The solutions of the non-linear and non-monotonic problems are more accurate than those obtained by other methods in the literature with the PSO algorithm. The experimental points for Kriging model are sampled according to Latin hypercube sampling More >

S. Liu¹, X. Liu², X. F. Guan³, P.F. He¹, Y. Yuan²

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 173-191, 2013, DOI:10.3970/cmes.2013.092.173

Abstract Early performance of mass concrete structures is very sensitive to the thermal expansion characteristics of concrete. As a kind of multi-phase composite, concrete has different material composition and microscopic configuration in different scales. Its thermal expansion coefficient (CTE) depends not only on the physical and mechanical properties of the constituents, but also on their distribution. What’s more, CTE is also time-dependent with the procedure of hydration. This research proposes a stochastic multi-scale model for analyzing CTE of concrete. In the developed model, concrete macro-scale is divided into three different levels: cement paste scale, mortar scale… More >

Smitha Gopinath¹, C.K. Madheswaran¹, A. Rama Ch,ra Murthy¹, Nagesh. R. Iyer², Barkavi.T³

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 151-172, 2013, DOI:10.3970/cmes.2013.092.151

Abstract This paper presents the details of experimental and numerical investigations performed on fabric reinforced concrete (FABcrete) panels under impact loading. Experimental investigations have been carried out using drop weight impact on a square FABcrete panel to study the damage, failure mode and acceleration. The drop weight of 20 kg is used for the study and drop heights have been varied as 100mm, 200mm and 300mm. Numerical simulation of the drop weight impact tests on FABcrete panels have been carried out and observed that there is a good correlation between experimental and numerical predictions. It is More >

Shengzhong Li¹, Feng Zhao¹, Qi-Jun Ni¹

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 123-149, 2013, DOI:10.3970/cmes.2013.092.123

Abstract With the rapid development of computer technology and the continuous improvement of optimization theory, optimization techniques have been introduced into the field of ship design. Optimization algorithms and advanced CFD techniques are successfully integrated together into what is known as Simulation- Based Design (SBD) techniques, which opens a new situation for hull-form optimization design and configuration innovation. In this paper, fundamental elements of the SBD techniques are described and crucial components are analyzed profoundly. Focus is on breaking through key technologies as hull geometry modification and reconstruction, global optimization algorithms, and codes integration. Combined with More >

C. Gáspár¹

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 103-121, 2013, DOI:10.3970/cmes.2013.092.103

Abstract Some regularized versions of the Method of Fundamental Solutions are investigated. The problem of singularity of the applied method is circumvented in various ways using truncated or modified fundamental solutions, or higher order fundamental solutions which are continuous at the origin. For pure Dirichlet problems, these techniques seem to be applicable without special additional tools. In the presence of Neumann boundary condition, however, they need some desingularization techniques to eliminate the appearing strong singularity. Using fundamental solutions concentrated to lines instead of points, the desingularization can be omitted. The method is illustrated via numerical examples. More >

K.Y. Volokh^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 87-101, 2013, DOI:10.3970/cmes.2013.092.087

Abstract In the laminar mode interactions among molecules generate friction between layers of water that slide with respect to each other. This friction triggers the shear stress, which is traditionally presumed to be linearly proportional to the velocity gradient. The proportionality coefficient characterizes the viscosity of water. Remarkably, the standard Navier-Stokes model surmises that materials never fail – the transition to turbulence can only be triggered by some kinematic instability of the flow. This premise is probably the reason why the Navier-Stokes theory fails to explain the so-called subcritical transition to turbulence with the help of… More >

Y.C. Cai^1,2,3, J. Wu², S.N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 63-85, 2013, DOI:10.3970/cmes.2013.092.063

Abstract The numerical manifold method (NMM), based on the finite covers, unifies the continuum analyses and discontinuum analyses without changing a predefined mathematical mesh of the uncracked solid, and has the advantages of being concise in theory as well as being clear in concept. It provides a natural method to analyze complex shaped strong discontinuities as well as weak discontinuities such as multiple cracks, intersecting cracks, and branched cracks. However, the absence of an effective algorithm for cover generation, to date, is still a bottle neck in the research and application in the NMM. To address… More >

N Pimprikar¹, J Teresa², D Roy^1,3, R M Vasu⁴, K Rajan⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 33-61, 2013, DOI:10.3970/cmes.2013.092.033

Abstract Nearly pollution-free solutions of the Helmholtz equation for k-values corresponding to visible light are demonstrated and verified through experimentally measured forward scattered intensity from an optical fiber. Numerically accurate solutions are, in particular, obtained through a novel reformulation of the H1 optimal Petrov-Galerkin weak form of the Helmholtz equation. Specifically, within a globally smooth polynomial reproducing framework, the compact and smooth test functions are so designed that their normal derivatives are zero everywhere on the local boundaries of their compact supports. This circumvents the need for a priori knowledge of the true solution on the More >