The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

Alfred Fettweis - One of the best experts on this subject based on the ideXlab platform.

  • Skew Symmetry and orthogonality in the equivalent representation problem of a time-varying multiport inductor
    IEEE Transactions on Circuits and Systems I: Regular Papers, 2004
    Co-Authors: N.k. Bose, Alfred Fettweis
    Abstract:

    This paper considers the fundamental problem of passive multidimensional Kirchhoff networks for linear time-varying systems that are suitable for wave digital filter discretization. An explicit solution, subject to the validity of a commutativity condition, is given in the linear time-varying case for the feasibility of representation of the coupled inductor, the crucial dynamic multiport in the network, in two equivalent forms so that the property of losslessness of the coupled inductor, and therefore, passivity of the entire network, is assured by the nonnegative definiteness of the inductance matrix for all space and time variables. The commutativity condition is expressed in an equivalent form that requires the product of two Skew-symmetric matrices to be symmetric. An isomorphism is developed and proved between the spaces of Skew-symmetric and orthogonal matrices of a common order. The feasibility of generalization of these results to the case of nonlinear current-controlled coupled inductor matrix is briefly explored and illustrative examples are provided throughout to facilitate comprehension of the concepts.

  • Skew-Symmetry in the equivalent representation problem of a time-varying multiport inductor
    Proceedings of the 2003 International Symposium on Circuits and Systems 2003. ISCAS '03., 2003
    Co-Authors: N. Bose, Alfred Fettweis
    Abstract:

    This paper considers the fundamental problem of passive multidimensional Kirchhoff networks for linear time-varying systems that are suitable for wave digital filter discretization. An explicit solution, subject to the validity of a commutativity condition, is given in the linear time-varying case for the feasibility of representation of the coupled inductor, the crucial dynamic multiport in the network, in two equivalent forms so that the property of losslessness of the coupled inductor, and therefore passivity of the entire network, is assured by the nonnegative definiteness of the inductance matrix for all space and time variables.

Juan Vicente Gutierrezsantacreu - One of the best experts on this subject based on the ideXlab platform.

  • unconditionally stable operator splitting algorithms for the incompressible magnetohydrodynamics system discretized by a stabilized finite element formulation based on projections
    International Journal for Numerical Methods in Engineering, 2013
    Co-Authors: Santiago Badia, Ramon Planas, Juan Vicente Gutierrezsantacreu
    Abstract:

    SUMMARY In this article, we propose different splitting procedures for the transient incompressible magnetohydrodynamics (MHD) system that are unconditionally stable. We consider two levels of splitting, on one side we perform the segregation of the fluid pressure and magnetic pseudo-pressure from the vectorial fields computation. At the second level, the fluid velocity and induction fields are also decoupled. This way, we transform a fully coupled indefinite multi-physics system into a set of smaller definite ones, clearly reducing the CPU cost. With regard to the finite element approximation, we stick to an unconditionally convergent stabilized finite element formulation because it introduces convection stabilization, allows to circumvent inf-sup conditions (clearly simplifying implementation issues), and is able to capture non-smooth solutions of the magnetic subproblem. However, residual-based finite element formulations are not suitable for segregation, because they lose the Skew-Symmetry of the off-diagonal blocks. Therefore, in this work, we have proposed a novel term-by-term stabilization of the MHD system based on projections that is still unconditionally convergent. Copyright © 2012 John Wiley & Sons, Ltd.

Richard A Sundheim - One of the best experts on this subject based on the ideXlab platform.

  • generating factor variables for aSymmetry non independence and Skew Symmetry models in square contingency tables using sas
    Journal of Statistical Software, 2002
    Co-Authors: Bayo H Lawal, Richard A Sundheim
    Abstract:

    In this paper, a SAS program (macro) is written to generate factor and regression variables required for implementing aSymmetry, non-independence, non-Symmetry + independence models as well as Skew-Symmetry models in discussed in square a x a contingency tables having nominal or ordinal categories. While several authors have developed similar factor variables for use with GLIM, we have extended this to the non-independence and the non-Symmetry+independence models. The former includes both the fixed and variable distance models as well as the quasi-ordinal Symmetry model. Further, our implementation of the aSymmetry model in terms of the required factor variable is different from those defined for implementation of same in GLIM. Most of the models described in this paper however assume ordinal categories for the contingency table. The SAS macro developed can be applied to any square table of dimension a. We apply the models discussed in this paper to the 5 x 5 Danish mobility data that have been widely analyzed in various literatures.

Santiago Badia - One of the best experts on this subject based on the ideXlab platform.

  • unconditionally stable operator splitting algorithms for the incompressible magnetohydrodynamics system discretized by a stabilized finite element formulation based on projections
    International Journal for Numerical Methods in Engineering, 2013
    Co-Authors: Santiago Badia, Ramon Planas, Juan Vicente Gutierrezsantacreu
    Abstract:

    SUMMARY In this article, we propose different splitting procedures for the transient incompressible magnetohydrodynamics (MHD) system that are unconditionally stable. We consider two levels of splitting, on one side we perform the segregation of the fluid pressure and magnetic pseudo-pressure from the vectorial fields computation. At the second level, the fluid velocity and induction fields are also decoupled. This way, we transform a fully coupled indefinite multi-physics system into a set of smaller definite ones, clearly reducing the CPU cost. With regard to the finite element approximation, we stick to an unconditionally convergent stabilized finite element formulation because it introduces convection stabilization, allows to circumvent inf-sup conditions (clearly simplifying implementation issues), and is able to capture non-smooth solutions of the magnetic subproblem. However, residual-based finite element formulations are not suitable for segregation, because they lose the Skew-Symmetry of the off-diagonal blocks. Therefore, in this work, we have proposed a novel term-by-term stabilization of the MHD system based on projections that is still unconditionally convergent. Copyright © 2012 John Wiley & Sons, Ltd.

N. Bose - One of the best experts on this subject based on the ideXlab platform.

  • Skew-Symmetry in the equivalent representation problem of a time-varying multiport inductor
    Proceedings of the 2003 International Symposium on Circuits and Systems 2003. ISCAS '03., 2003
    Co-Authors: N. Bose, Alfred Fettweis
    Abstract:

    This paper considers the fundamental problem of passive multidimensional Kirchhoff networks for linear time-varying systems that are suitable for wave digital filter discretization. An explicit solution, subject to the validity of a commutativity condition, is given in the linear time-varying case for the feasibility of representation of the coupled inductor, the crucial dynamic multiport in the network, in two equivalent forms so that the property of losslessness of the coupled inductor, and therefore passivity of the entire network, is assured by the nonnegative definiteness of the inductance matrix for all space and time variables.