The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Antonios Giannopoulos - One of the best experts on this subject based on the ideXlab platform.

  • An Improved New Implementation of Complex Frequency Shifted PML for the FDTD Method
    IEEE Transactions on Antennas and Propagation, 2008
    Co-Authors: Antonios Giannopoulos
    Abstract:

    A new implementation of the perfectly matched layer absorbing boundary for finite-difference time-domain grids is presented. The approach which is based on the Complex co-ordinate stretching perfectly matched layer (PML) formulation uses the Complex Frequency shifted stretching function and is based on the simple concept of the recursive evaluation of an integral avoiding the calculation of time derivatives. This recursive integration PML is simple to implement, efficient and exhibits a modest gain in performance over the convolutional PML without requiring any extra computational resources or an increase in the algorithmic Complexity of the PML implementation.

  • Complex Frequency shifted convolution pml for fdtd modelling of elastic waves
    Wave Motion, 2007
    Co-Authors: F Drossaert, Antonios Giannopoulos
    Abstract:

    The perfectly matched layer (PML) is nowadays considered as the best optimum absorbing boundary condition available. However, the PML with the classical stretching tensor has certain limitations. Strangely, these limitations have rarely been addressed in elastic wave modelling. For example, substantial reflections occur when strong evanescent waves are propagating parallel to the interface. To circumvent problems like this, the Complex Frequency shifted stretching tensor has been introduced in electromagnetic modelling. In this paper we show that the convolution PML with this stretching tensor as used in electromagnetic modelling can be adapted for elastic wave modelling. Numerical results of a model where the presence of evanescent waves is predominant show that the PML based on the Complex Frequency shifted stretching tensor can improve the performance of the absorbing boundary layer considerably.

  • a nonsplit Complex Frequency shifted pml based on recursive integration for fdtd modeling of elastic waves
    Geophysics, 2007
    Co-Authors: F Drossaert, Antonios Giannopoulos
    Abstract:

    In finite-difference time-domain FDTD modeling of elastic waves, absorbing boundary conditions are used to mitigate un- fields — it is difficult to adopt a Complex Frequency--shifted stretching function. We present an alternative implemen-tation of a PML that is based on recursive integration and does not re- quire splitting of the velocity and stress fields. Modeling re-sults show that the performance of our implementation using a stan- dard stretching function is identical to that of the convention-al split-field PML. Then we show that the new PML can be modi- fied easily to include the Complex Frequency-shifted stretching function. Results of models with an elongated domain show that this modification can substantially improve the performance of

Xun Li - One of the best experts on this subject based on the ideXlab platform.

  • A digital filter approach for Complex Frequency-shifted perfectly matched layer in semivectorial FDTD
    IEEE Photonics Technology Letters, 2003
    Co-Authors: Gui-rong Zhou, Ning-ning Feng, Xun Li
    Abstract:

    A new formulation of the perfectly matched layer (PML) for the semivectorial finite-difference time-domain (FDTD) method in optical waveguide simulation is presented by incorporating the infinite-impulse response (IIR) digital filter technique. The Complex Frequency-shifted PML is implemented through Z transformation, where the second-order derivatives in semivectorial FDTD are realized by two cascaded first-order recursive IIR digital filters. The numerical examples indicate that the new scheme has better performance compared with the normal PML.

Bo Zhao - One of the best experts on this subject based on the ideXlab platform.

  • An Auxiliary Differential Equation Formulation for the Complex-Frequency Shifted PML
    IEEE Transactions on Antennas and Propagation, 2010
    Co-Authors: Stephen D. Gedney, Bo Zhao
    Abstract:

    An efficient auxiliary-differential equation (ADE) form of the Complex Frequency shifted perfectly matched layer (CPML) absorbing media derived from a stretched coordinate PML formulation is presented. It is shown that a unit step response of the ADE-CPML equations leads to a discrete form that is identical to Roden's convolutional PML method for FDTD implementations. The derivation of discrete difference operators for the ADE-CPML equations for FDTD is also presented. The ADE-CPML method is also extended in a compact form to a multiple-pole PML formulation. The advantage of the ADE-CPML method is that it provides a more flexible representation that can be extended to higher-order methods. In this paper, it is applied to the discontinuous Galerkin finite element time-domain (DGFETD) method. It is demonstrated that the ADE-CPML maintains the exponential convergence of the DGFETD method.

  • Complex-Frequency shifted PML for high-order solution methods
    2009 IEEE Antennas and Propagation Society International Symposium, 2009
    Co-Authors: Stephen D. Gedney, Bo Zhao
    Abstract:

    A novel stretched-coordinate form of the CFS-PML has been introduced based on the introduction of auxiliary terms that satisfy distinct auxiliary differential equations (ADE). The formulation provides a more general form for representing the CFS-PML for time-dependent solutions of Maxwell's equations. It is found that the method is equal in effectiveness and efficiency as the CPML for FDTD simulations, and provides an efficient foundation for high-order time-dependent solutions of Maxwell's equations.

Magdalena Kaniewska - One of the best experts on this subject based on the ideXlab platform.

  • ECCTD - Online pitch estimation using instantaneous Complex Frequency
    2011 20th European Conference on Circuit Theory and Design (ECCTD), 2011
    Co-Authors: Magdalena Kaniewska
    Abstract:

    The paper presents new results of pitch estimation for speech signals obtained using a pipeline algorithm. The algorithm uses instantaneous Complex Frequency to perform voiced/unvoiced classification and estimate the fundamental Frequency for each sample of the speech signal. Its performance is evaluated using two databases containing utterances spoken by male and female English speakers.

  • Online pitch estimation using instantaneous Complex Frequency
    2011 20th European Conference on Circuit Theory and Design (ECCTD), 2011
    Co-Authors: Magdalena Kaniewska
    Abstract:

    The paper presents new results of pitch estimation for speech signals obtained using a pipeline algorithm. The algorithm uses instantaneous Complex Frequency to perform voiced/unvoiced classification and estimate the fundamental Frequency for each sample of the speech signal. Its performance is evaluated using two databases containing utterances spoken by male and female English speakers.

  • EUSIPCO - Voice transformations through instantaneous Complex Frequency modifications
    2010
    Co-Authors: Magdalena Kaniewska
    Abstract:

    The paper presents the possibilities of altering human voice by modifying instantaneous Complex Frequency (ICF) of the speech signal. The proposed algorithm is based on the factorization of a band-limited, analytic signal into two factors: one fully characterized by its envelope and the other with positive instantaneous Frequency (PIF). ICFs of both factors are estimated and modified for different sound effects. The algorithm is tested on short speech utterances and the results of these experiments are presented in the paper.

  • Voice transformations through instantaneous Complex Frequency modifications
    2010 18th European Signal Processing Conference, 2010
    Co-Authors: Magdalena Kaniewska
    Abstract:

    The paper presents the possibilities of altering human voice by modifying instantaneous Complex Frequency (ICF) of the speech signal. The proposed algorithm is based on the factorization of a band-limited, analytic signal into two factors: one fully characterized by its envelope and the other with positive instantaneous Frequency (PIF). ICFs of both factors are estimated and modified for different sound effects. The algorithm is tested on short speech utterances and the results of these experiments are presented in the paper.

  • Instantaneous Complex Frequency for pipeline pitch estimation
    Signal Processing Algorithms Architectures Arrangements and Applications SPA 2010, 2010
    Co-Authors: Magdalena Kaniewska
    Abstract:

    In the paper a pipeline algorithm for estimating the pitch of speech signal is proposed. The algorithm uses instantaneous Complex frequencies estimated for four waveforms obtained by filtering the original speech signal through four bandpass Complex Hilbert filters. The imaginary parts of ICFs from each channel give four candidates for pitch estimates. The decision regarding the final estimate is made based on the real parts of ICFs.

Gui-rong Zhou - One of the best experts on this subject based on the ideXlab platform.

  • A digital filter approach for Complex Frequency-shifted perfectly matched layer in semivectorial FDTD
    IEEE Photonics Technology Letters, 2003
    Co-Authors: Gui-rong Zhou, Ning-ning Feng, Xun Li
    Abstract:

    A new formulation of the perfectly matched layer (PML) for the semivectorial finite-difference time-domain (FDTD) method in optical waveguide simulation is presented by incorporating the infinite-impulse response (IIR) digital filter technique. The Complex Frequency-shifted PML is implemented through Z transformation, where the second-order derivatives in semivectorial FDTD are realized by two cascaded first-order recursive IIR digital filters. The numerical examples indicate that the new scheme has better performance compared with the normal PML.