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Kjell Eriksson - One of the best experts on this subject based on the ideXlab platform.

  • a domain independent Integral Expression for the crack extension force of a curved crack in three dimensions
    Journal of The Mechanics and Physics of Solids, 2002
    Co-Authors: Kjell Eriksson
    Abstract:

    An Integral Expression that is domain independent in curvilinear coordinates and compatible with zero divergence of Eshelby's (Phil. Trans. Roy. Soc. (London) 244 (1951) 87.) energy momentum tensor was obtained from the principle of virtual work. By applying Eshelby's definition of the force on a material defect a general Expression of the crack extension force for a curved crack in three dimensions, here called the F-Integral, was derived from the domain independent Integral Expression. The F-Integral is given explicitly for a number of curved cracks and found to be in agreement with previously known solutions, when available. The influence of crack surface and crack front curvature upon the various forms of the F-Integral is discussed. The F-Integral presented in this work is a generalisation of the J-Integral (Rice, J. Appl. Mech. 35 (1968) 379.) to curved cracks in orthogonal curvilinear coordinates.

  • a path independent Integral for the crack extension force of the circular arc crack
    Engineering Fracture Mechanics, 2000
    Co-Authors: Maria Lorentzon, Kjell Eriksson
    Abstract:

    Abstract A path independent Integral Expression for the crack extension force of a two-dimensional circular arc crack is presented. The Integral Expression, which consists of a contour and an area Integral, is derived from the principle of virtual work. It is implemented into a FEM post-processing program and the crack extension force is calculated for a circular arc crack in a linear elastic material. Comparison with exact solutions by Cotterell and Rice [10] for the effective elastic stress intensity factor shows acceptable accuracy for the numerical procedure used.

Tibor K. Pogány - One of the best experts on this subject based on the ideXlab platform.

Jerry A Hausman - One of the best experts on this subject based on the ideXlab platform.

  • using a laplace approximation to estimate the random coefficients logit model by nonlinear least squares laplace approximation of the random coefficients logit model
    International Economic Review, 2007
    Co-Authors: Matthew Harding, Jerry A Hausman
    Abstract:

    Current methods of estimating the random coefficients logit model employ simulations of the distribution of the taste parameters through pseudo-random sequences. These methods suffer from difficulties in estimating correlations between parameters and computational limitations such as the curse of dimensionality. This article provides a solution to these problems by approximating the Integral Expression of the expected choice probability using a multivariate extension of the Laplace approximation. Simulation results reveal that our method performs very well, in terms of both accuracy and computational time.

  • using a laplace approximation to estimate the random coefficients logit model by nonlinear least squares
    International Economic Review, 2006
    Co-Authors: Matthew Harding, Jerry A Hausman
    Abstract:

    Current methods of estimating the random coefficients logit model employ simulations of the distribution of the taste parameters through pseudo-random sequences. These methods suffer from difficulties in estimating correlations between parameters and computational limitations such as the curse of dimensionality. This article provides a solution to these problems by approximating the Integral Expression of the expected choice probability using a multivariate extension of the Laplace approximation. Simulation results reveal that our method performs very well, in terms of both accuracy and computational time.

Guy A E Vandenbosch - One of the best experts on this subject based on the ideXlab platform.

  • the expansion wave concept i efficient calculation of spatial green s functions in a stratified dielectric medium
    IEEE Transactions on Antennas and Propagation, 1998
    Co-Authors: Filip Demuynck, Guy A E Vandenbosch, A Van De Capelle
    Abstract:

    A procedure is given to perform the inverse Fourier transformation relating a spatial Green's function to its spectral equivalent. The procedure is applied to the spectral Green's functions of the double scalar mixed-potential Integral Expression formulation of the electromagnetic field in a stratified dielectric medium. The extraction technique is used to annihilate every type of "problematic" behavior of the spectral Green's functions. Every annihilating function is inverse Fourier transformed analytically. It is shown that the annihilation of both the surface wave poles and the singularities at the branch point results in a set of analytical spatial functions, which are a very good approximation of the exact spatial Green's function down to relatively small lateral distances.

  • mixed potential Integral Expression formulation of the electric field in a stratified dielectric medium application to the case of a probe current source
    IEEE Transactions on Antennas and Propagation, 1992
    Co-Authors: Guy A E Vandenbosch, A Van De Capelle
    Abstract:

    The well-known procedure for determining the electric field in a structure consisting of an arbitrary number of planar dielectric layers is modified in order to obtain a form specially suited for the analysis of multiprobe multipath configurations. In general, the field is generated by arbitrary currents in the layers and arbitrary sheet currents in the transitions between the layers. The currents may be electric as well as magnetic, and the dielectric layers are isotropic, homogeneous, and lossy. The procedure results in Green's functions especially suited for the analysis of multiprobe multipatch configurations. They can be used in an efficient mixed-potential Integral Expression formulation. The theoretical procedure is applied in the case of a probe current source situated in one of the dielectric layers of the structure. For this probe current a highly efficient attachment current distribution is derived. Comparison of measured and calculated results for example structures proves the accuracy of both the approach and the attachment mode. >

A Van De Capelle - One of the best experts on this subject based on the ideXlab platform.

  • the expansion wave concept i efficient calculation of spatial green s functions in a stratified dielectric medium
    IEEE Transactions on Antennas and Propagation, 1998
    Co-Authors: Filip Demuynck, Guy A E Vandenbosch, A Van De Capelle
    Abstract:

    A procedure is given to perform the inverse Fourier transformation relating a spatial Green's function to its spectral equivalent. The procedure is applied to the spectral Green's functions of the double scalar mixed-potential Integral Expression formulation of the electromagnetic field in a stratified dielectric medium. The extraction technique is used to annihilate every type of "problematic" behavior of the spectral Green's functions. Every annihilating function is inverse Fourier transformed analytically. It is shown that the annihilation of both the surface wave poles and the singularities at the branch point results in a set of analytical spatial functions, which are a very good approximation of the exact spatial Green's function down to relatively small lateral distances.