The Experts below are selected from a list of 113103 Experts worldwide ranked by ideXlab platform

Xinqing Sheng - One of the best experts on this subject based on the ideXlab platform.

  • a discontinuous galerkin surface Integral Solution for scattering from homogeneous objects with high dielectric constant
    IEEE Transactions on Antennas and Propagation, 2020
    Co-Authors: Beibei Kong, Xiaowei Huang, Xinqing Sheng
    Abstract:

    The discontinuous Galerkin (DG) method for homogeneous bodies has been studied and shown to be an efficient tool for multiscale homogeneous bodies. However, the slow convergence of DG with the block diagonal preconditioner (BDP) is still observed in solving high contrast homogeneous bodies. An efficient preconditioning approach is designed for the DG method in this communication by using the sparsing approach on the near-field matrix of the whole region. The iteration convergence speed of the DG method is improved while the computing resources for constructing the preconditioner are effectively reduced. Numerical experiments demonstrate the capability of the presented DG method for multiscale homogeneous bodies, especially for those with a high dielectric constant.

Hermann Grabert - One of the best experts on this subject based on the ideXlab platform.

  • exact time evolution and master equations for the damped harmonic oscillator
    Physical Review E, 1997
    Co-Authors: Robert Karrlein, Hermann Grabert
    Abstract:

    Using the exact path Integral Solution for the damped harmonic oscillator it is shown that in general there does not exist an exact dissipative Liouville operator describing the dynamics of the oscillator for arbitrary initial bath preparations. Exact nonstationary Liouville operators can be found only for particular preparations. Three physically meaningful examples are examined. An exact master equation is derived for thermal initial conditions. Second, the Liouville operator governing the time evolution of equilibrium correlations is obtained. Third, factorizing initial conditions are studied. Additionally, one can show that there are approximate Liouville operators independent of the initial preparation describing the long-time dynamics under appropriate conditions. The general form of these approximate master equations is derived and the coefficients are determined for special cases of the bath spectral density including the Ohmic, Drude, and weak coupling cases. The connection with earlier work is discussed.

Liénardy Jean - One of the best experts on this subject based on the ideXlab platform.

  • The open XXZ chain at Δ=−1/2 and the boundary quantum Knizhnik-Zamolodchikov equations
    'IOP Publishing', 2021
    Co-Authors: Hagendorf Christian, Liénardy Jean
    Abstract:

    The open XXZ spin chain with the anisotropy parameter Δ=−12 and diagonal boundary magnetic fields that depend on a parameter x is studied. For real x>0, the exact finite-size ground-state eigenvalue of the spin-chain Hamiltonian is explicitly computed. In a suitable normalisation, the ground-state components are characterised as polynomials in x with integer coefficients. Linear sum rules and special components of this eigenvector are explicitly computed in terms of determinant formulas. These results follow from the construction of a contour-Integral Solution to the boundary quantum Knizhnik-Zamolodchikov equations associated with the R-matrix and diagonal K-matrices of the six-vertex model. A relation between this Solution and a weighted enumeration of totally-symmetric alternating sign matrices is conjectured

  • The open XXZ chain at $\Delta=-1/2$ and the boundary quantum Knizhnik-Zamolodchikov equations
    'IOP Publishing', 2020
    Co-Authors: Hagendorf Christian, Liénardy Jean
    Abstract:

    The open XXZ spin chain with the anisotropy parameter $\Delta=-\frac12$ and diagonal boundary magnetic fields that depend on a parameter $x$ is studied. For real $x>0$, the exact finite-size ground-state eigenvalue of the spin-chain Hamiltonian is explicitly computed. In a suitable normalisation, the ground-state components are characterised as polynomials in $x$ with integer coefficients. Linear sum rules and special components of this eigenvector are explicitly computed in terms of determinant formulas. These results follow from the construction of a contour-Integral Solution to the boundary quantum Knizhnik-Zamolodchikov equations associated with the $R$-matrix and diagonal $K$-matrices of the six-vertex model. A relation between this Solution and a weighted enumeration of totally-symmetric alternating sign matrices is conjectured.Comment: 36 pages, no figure

Beibei Kong - One of the best experts on this subject based on the ideXlab platform.

  • a discontinuous galerkin surface Integral Solution for scattering from homogeneous objects with high dielectric constant
    IEEE Transactions on Antennas and Propagation, 2020
    Co-Authors: Beibei Kong, Xiaowei Huang, Xinqing Sheng
    Abstract:

    The discontinuous Galerkin (DG) method for homogeneous bodies has been studied and shown to be an efficient tool for multiscale homogeneous bodies. However, the slow convergence of DG with the block diagonal preconditioner (BDP) is still observed in solving high contrast homogeneous bodies. An efficient preconditioning approach is designed for the DG method in this communication by using the sparsing approach on the near-field matrix of the whole region. The iteration convergence speed of the DG method is improved while the computing resources for constructing the preconditioner are effectively reduced. Numerical experiments demonstrate the capability of the presented DG method for multiscale homogeneous bodies, especially for those with a high dielectric constant.

Gaetano Sequenzia - One of the best experts on this subject based on the ideXlab platform.

  • Alternative elliptic Integral Solution to the beam deflection equations for the design of compliant mechanisms
    International Journal on Interactive Design and Manufacturing (IJIDeM), 2019
    Co-Authors: Alessandro Cammarata, Michele Lacagnina, Gaetano Sequenzia
    Abstract:

    The interactive design for industrial applications is today carried out through methods and tools, with different level of accuracy and simulation times. Consequently, the time necessary for virtual prototyping and analysis phases are often long and may be definitely reduced by means of optimization of tools and methodologies. Compliant mechanisms are increasingly used in the industrial field and the design methods are the subject of several studies, to improve their performance and reliability. This paper provides the reader with reliable numerical expressions to describe flexural beams with large deflections in case of combined end loads and without inflection points. Most of the numerical expressions describing beam deflection already existing in the literature are based on elliptic Integrals that take into account strict limitations on the maximum slope angle. Here, we go beyond these limitations at the same time trying to give an order to the most relevant formulations used for determining large deflections of beams subject to combined tip loads. The proposed method provides the same results of the comprehensive elliptic Integral Solution described in a recent study.