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  • Boundary Element Analysis of Three-Dimensional Exponentially Graded Isotropic Elastic Solids
  • Abstract A numerical implementation of the Somigliana identity in displacements for the solution of 3D elastic problems in exponentially graded isotropic solids is presented. An expression for the fundamental solution in displacements, Ujl, was deduced by Martin et al. (Proc. R. Soc. Lond. A, 458, pp. 1931--1947, 2002). This expression was recently corrected and implemented in a Galerkin indirect 3D BEM code by Criado et al. (Int. J. Numer. Meth. Engng., 2008). Starting from this expression of Ujl, a new expression for the fundamental solution in tractions Tjl has been deduced in the present work. These quite complex expressions of the…
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  • Envelope frequency Response Function Analysis of Mechanical Structures with Uncertain Modal Damping Characteristics
  • Abstract Recently, an interval finite element methodology has been developed to calculate envelope frequency response functions of uncertain structures with interval parameters. The methodology is based on a hybrid interval implementation of the modal superposition principle. This hybrid procedure consists of a preliminary optimization step, followed by an interval arithmetic procedure. The final envelope frequency response functions have been proved to give a very good approximation of the actual response range of the interval problem. Initially, this method was developed for undamped structures. Based on the theoretical principles of this approach, this paper introduces a new method for the analysis of…
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  • A New Uncertain Optimization Method Based on Intervals and An Approximation Management Model
  • Abstract A new uncertain optimization method is developed based on intervals and an approximation management model. A general uncertain optimization problem is considered in which the objective function and constraints are both nonlinear and uncertain, and intervals are used to model the uncertainty existing in the system. Based on a possibility degree of interval,anonlinear interval number programming (NINP) method is proposed. A deterministic objective function is constructed to maximize the possibility degree of the uncertain objective function, and the uncertain constraints are changed into deterministic ones by introducing some possibility degree levels. If the optimal possibility degree of the objective function…
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  • A Comparative Study of Non-separable Wavelet and Tensor-product Wavelet in Image Compression
  • Abstract The most commonly used wavelets for image processing are the tensor-product of univariate wavelets, which have a disadvantage of giving a particular importance to the horizontal and vertical directions. In this paper, a new class of wavelet, non-separable wavelet, is investigated for image compression applications. The comparative results of image compression preprocessed with two different kinds of wavelet transform are presented: (1) non-separable wavelet transform; (2) tensor-product wavelet transform. The results of our experiments show that in the same vanishing moment, the non-separable wavelets perform better than the tensor-product wavelets in dealing with still images.
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  • Modeling of Degraded Composite Beam Due to Moisture Absorption For Wave Based Detection.
  • Abstract In this paper, wave propagation is studied in degraded composite beam due to moisture absorption. The obtained wave responses are then used for diagnosis of the degraded zone. Moisture absorption causes an irreversible hygrothermal deterioration of the material. The change in temperature and moisture absorption changes the mechanical properties. Thus this affects the structure in dimensional stability as well as material degradation due to reduction in mechanical properties. Here, the composite beam is modeled as Timoshenko beam using wavelet based spectral finite element (WSFE) method. The WSFE technique is especially tailored for simulation of wave propagation. It involves Daubechies scaling…
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  • Meshless Local Petrov-Galerkin Collocation Method for Two-dimensional Heat Conduction Problems
  • Abstract Meshless local Petrov-Galerkin collocation method is applied to compute two-dimensional heat conduction problems in irregular domain. By taking the Dirac's Delta function as the test function, the local domain integration is avoided. The essential boundary conditions can be implemented easily in this method. A case that has analytical solution shows the present method can obtain desired accuracy and efficient. Two cases in engineering are computed to validate the approach by comparing the present method with the finite volume method (FVM) solutions obtained from a commercial CFD package FLUENT 6.3. The results show that the present method is in good agreement…
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  • Fictitious Domain with Least-Squares Spectral Element Method to Explore Geometric Uncertainties by Non-Intrusive Polynomial Chaos Method
  • Abstract In this paper the Non-Intrusive Polynomial Chaos Method coupled to a Fictitious Domain approach has been applied to one- and two-dimensional elliptic problems with geometric uncertainties, in order to demonstrate the accuracy and convergence of the methodology. The main advantage of non-intrusive formulation is that existing deterministic solvers can be used. A new Least-Squares Spectral Element method has been employed for the analysis of deterministic differential problems obtained by Non-Intrusive Polynomial Chaos. This algorithm employs a Fictitious Domain approach and for this reason its main advantage lies in the fact that only a Cartesian mesh needs to be generated. Excellent…
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  • Non-Equilibrium Molecular Dynamics Simulation of Water Flow around a Carbon Nanotube
  • Abstract In this paper, non-equilibrium molecular dynamics (MD) simulations were performed to investigate water flow around a single-walled carbon nanotube. In the simulation, the nanotube was modeled as a rigid cylinder of carbon atoms. Water molecules were described with the extended simple point charge (SPC/E) model. The nanotube-water interactions were calculated with a Lennard-Jones potential between carbon-oxygen pairs. The water-water interactions comprised a Lennard-Jones potential between the oxygen-oxygen pairs and a Coulomb potential between all charge sites on interactive water molecules. It was shown that classical continuum mechanics does not hold when the drag forces on the nanotube are considered. In…
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  • Structural Analysis of the Right Rear Lug of American Airlines Flight 587*
  • Abstract A detailed finite element analysis of the right rear lug of the American Airlines Flight 587 - Airbus A300-600R was performed as part of the National Transportation Safety Board's failure investigation of the accident that occurred on November 12, 2001. The loads experienced by the right rear lug were evaluated using global models of the vertical tail, local models near the right rear lug, and a global-local analysis procedure. The right rear lug was analyzed using two modeling approaches. In the first approach, solid-shell type modeling was used, and in the second approach, layered-shell type modeling was used. The solid-shell…
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