S. Venkatesha¹, R. Rajender², C. S. Manohar³

CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.2, pp. 113-152, 2008, DOI:10.3970/cmes.2008.037.113

Abstract The problem of structural damage detection based on measured frequency response functions of the structure in its damaged and undamaged states is considered. A novel procedure that is based on inverse sensitivity of the singular solutions of the system FRF matrix is proposed. The treatment of possibly ill-conditioned set of equations via regularization scheme and questions on spatial incompleteness of measurements are considered. The application of the method in dealing with systems with repeated natural frequencies and (or) packets of closely spaced modes is demonstrated. The relationship between the proposed method and the methods based More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.16, No.3, pp. 157-176, 2006, DOI:10.3970/cmes.2006.016.157

Abstract To characterize largely deformed spin-free reference configuration of materials, we have to construct an orthogonal transformation tensor Q relative to the fixed frame, such that the tensorial equation Q^˙ = WQ holds for a given spin history W. This paper addresses some interesting issues about this equation. The Euler's angles representation, and the (modified) Rodrigues parameters representation of the rotation group SO(3) unavoidably suffer certain singularity, and at the same time the governing equations are nonlinear three-dimensional ODEs. A decomposition Q = FQ₁ is first derived here, which is amenable to a simpler treatment of Q₁ than Q, and… More >

F. Han¹, E. Pan¹, A.K. Roy², Z.Q. Yue³

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.1, pp. 15-30, 2006, DOI:10.3970/cmes.2006.014.015

Abstract In this paper, an analytical solution is presented to study the response of piezoelectric, transversely isotropic, functionally graded, and multilayered half spaces to uniform circular surface loadings (pressure or negative electric charge). The inhomogeneous material is exponentially graded in the vertical direction and can have multiple discrete layers. The propagator matrix method and cylindrical system of vector functions are used to first derive the solution in the transformed domain. In order to find the responses in the physical-domain, which are expressed in one-dimensional infinite integrals of the Bessel function products, we introduced and adopted an… More >

A. N. Guz, V. A. Dekret¹

CMES-Computer Modeling in Engineering & Sciences, Vol.13, No.3, pp. 165-170, 2006, DOI:10.3970/cmes.2006.013.165

Abstract Stability problem of composite material reinforced by two parallel short fibers is solved. The problem is formulated with application of equations of linearized three-dimensional theory of stability. The composite is modeled as piecewise-homogeneous medium. The influence of geometrical and mechanical parameters of the material on critical strain is investigated. More >

Y.F. Nie^1,2, S.N. Atluri², C.W. Zuo¹

CMES-Computer Modeling in Engineering & Sciences, Vol.12, No.2, pp. 137-148, 2006, DOI:10.3970/cmes.2006.012.137

Abstract Owing to the meshless and local characteristics, moving least squares (MLS) methods have been used extensively to approximate the unknown function of partial differential equation initial boundary value problem. In this paper, based on matrix analysis, a sufficient and necessary condition for the existence of inverse of coefficient matrix used in MLS methods is developed firstly. Then in the light of approximate theory, a practical mathematics model is posed to obtain the optimal radius of support of radial weights used in MLS methods. As an example, while uniform distributed particles and the 4^th order spline weight More >

Gerhard Klimeck^1,2, Fabiano Oyafuso², Timothy B. Boykin³, R. Chris Bowen², Paul von Allmen⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 601-642, 2002, DOI:10.3970/cmes.2002.003.601

Abstract Material layers with a thickness of a few nanometers are common-place in today's semiconductor devices. Before long, device fabrication methods will reach a point at which the other two device dimensions are scaled down to few tens of nanometers. The total atom count in such deca-nano devices is reduced to a few million. Only a small finite number of "free'' electrons will operate such nano-scale devices due to quantized electron energies and electron charge. This work demonstrates that the simulation of electronic structure and electron transport on these length scales must not only be fundamentally… More >

Biao Zhou^1,2,3, Xiong yao Xie^1,2, Yeong Bin Yang⁴, Jing Cai Jiang³

CMES-Computer Modeling in Engineering & Sciences, Vol.86, No.4, pp. 321-348, 2012, DOI:10.3970/cmes.2012.086.321

Abstract The vibration-based SHM (Structure Health Monitoring) system has been successfully used in bridge and other surface civil infrastructure. However, its application in operation tunnels remains a big challenge. The reasons are discussed in this paper by comparing the vibration characteristics of the free tunnel structure and tunnel-soil coupled system. It is revealed that all the correlation characteristics of the free tunnel FRFs (Frequency Response Function spectrum) will vanish and be replaced by a coupled resonance frequency when the tunnel is surrounded by soil. The above statement is validated by field measurements. Moreover, the origin of More >

Gusein Sh. Guseinov¹

CMES-Computer Modeling in Engineering & Sciences, Vol.86, No.4, pp. 301-320, 2012, DOI:10.3970/cmes.2012.086.301

Abstract This paper deals with the inverse spectral problem for two spectra of finite order complex Jacobi matrices (tri-diagonal symmetric matrices with complex entries). The problem is to reconstruct the matrix using two sets of eigenvalues, one for the original Jacobi matrix and one for the matrix obtained by replacing the first diagonal element of the Jacobi matrix by some another number. The uniqueness and existence results for solution of the inverse problem are established and an explicit algorithm of reconstruction of the matrix from the two spectra is given. More >

Huimin Song¹, Dewey H. Hodges¹

CMES-Computer Modeling in Engineering & Sciences, Vol.85, No.3, pp. 239-278, 2012, DOI:10.3970/cmes.2012.085.239

Abstract The present paper presents a rigorous approach that can accurately and efficiently capture the linear, static and free-vibration behaviors of a beam-like structure by the rigorous combination of a one-dimensional beam model with a three-dimensional continuum model. This study focuses on coupling these disparate finite element types, putting them both into a single finite element model while making use of the asymptotically exact information available as part of the beam model, which itself is obtained by asymptotic dimensional reduction. The coupling is undertaken by use of appropriate transformation matrices at the interface together with stress More >

Gusein Sh. Guseinov¹

CMES-Computer Modeling in Engineering & Sciences, Vol.84, No.5, pp. 405-422, 2012, DOI:10.3970/cmes.2012.084.405

Abstract In this work we study the inverse spectral problem for two spectra of finite order real Jacobi matrices (tri-diagonal matrices). The problem is to reconstruct the matrix using two sets of eigenvalues, one for the original Jacobi matrix and one for the matrix obtained by replacing the first diagonal element of the Jacobi matrix by some another number. The uniqueness and existence results for solution of the inverse problem are established and an explicit procedure of reconstruction of the matrix from the two spectra is given. More >