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Gerald Samba - One of the best experts on this subject based on the ideXlab platform.

  • Resolution of the time dependent Pn equations by a Godunov type scheme having the diffusion limit
    ESAIM: Mathematical Modelling and Numerical Analysis, 2010
    Co-Authors: Patricia Cargo, Gerald Samba
    Abstract:

    We consider the P n model to approximate the time dependent transport equation in one dimension of space. In a diffusive regime, the solution of this system is solution of a diffusion equation. We are looking for a numerical scheme having the diffusion limit property: in a diffusive regime, it has to give the solution of the limiting diffusion equation on a mesh at the diffusion scale. The numerical scheme proposed is an extension of the Godunov type scheme proposed by Gosse to solve the P 1 model without absorption term. It requires the computation of the solution of the steady state P n equations. This is made by one Monte-Carlo simulation performed outside the time loop. Using formal expansions with respect to a small parameter representing the inverse of the number of mean free path in each cell, the resulting scheme is proved to have the diffusion limit. In order to avoid the CFL constraint on the time step, we give an implicit version of the scheme which preserves the positivity of the Zeroth Moment.

  • Resolution of the time dependent Pn equations by a Godunov type scheme having the diffusion limit. Part 1 : The case of the time dependent P1 equations
    2008
    Co-Authors: Patricia Cargo, Gerald Samba
    Abstract:

    We consider the P1 model to approximate the time dependent transport equation in one dimension of space. In a diffusive regime, the solution of this system is solution of a diffusion equation. We are looking for a numerical scheme having the diffusion limit property: in a diffusive regime, it has to give the solution of the limiting diffusion equation on a mesh at the diffusion scale. The numerical scheme is an extension of the Godunov type scheme proposed by L.Gosse to solve the P1 model without absorption term. It requires the computation of the solution of the steady P1 equations. Using formal expansions with respect to a small parameter representing the inverse of the number of mean free path in each cell, the resulting scheme is proved to have the diffusion limit. In order to avoid the CFL constraint on the time step, we give an implicit version of the scheme which preserves the positiveness of the Zeroth Moment.

Winyu Rattanapitikon - One of the best experts on this subject based on the ideXlab platform.

  • empirical formula for computing representative wave heights from Zeroth Moment of wave spectrum
    2013
    Co-Authors: P Nuntakomol, Winyu Rattanapitikon
    Abstract:

    The present study focuses on conversion formulas for estimating four common statistical-based representative wave heights (i.e. mean wave height, root-mean-square wave height, average of the highest one-third wave height, and average of the highest one-tenth wave height) from Zeroth Moment of wave spectrum. The existing conversion formulas are usually derived from given probability density functions of wave heights. There seems to be no literature that proposes an empirical formula for estimating the representative wave heights from Zeroth Moment of wave spectrum. Hence, the objective of this study is to develop an empirical formula for computing the representative wave heights. Based on the existing conversion formulas, the representative wave heights are assumed to be proportional to square root of Zeroth Moment of wave spectrum. The influence of depth-limited wave breaking is empirically incorporated into the proportional coefficients. The empirical formula is calibrated and examined based on field experiments (13,456 wave records collected from 4 sources). Reasonable good agreements are obtained between the measured and computed representative wave heights. The applicability of five sets of existing conversion formulas is also examined. The present formula gives better estimation than those of existing conversion formulas.

  • Verification and Modification of Conversion Formulas for Estimating Statistical-Based Representative Wave Heights from Zeroth Moment of Wave Spectrum Based on Field Data
    2013
    Co-Authors: Winyu Rattanapitikon
    Abstract:

    Conversion formulas were studied for estimating statistical-based representative wave heights (the mean wave height (Hm), root-mean-square wave height (Hrms ), average of the highest one-third wave height (H1/3) and average of the highest one-tenth wave height (H1/10)) from the Zeroth Moment of the wave spectrum (m0). The applicability of five sets of existing conversion formulas was examined based on two field experiments of the COAST3D project (using 13,430 wave records). The examination showed that the conversion formulas derived from the Weibull distribution with a constant shape parameter gave the best prediction. The best set of conversion formulas was modified by reformulating the shape parameter in the formulas. The modified formulas gave slightly better predictions at Hm , Hrms and H1/3 , and considerably better prediction at H1/10 than those of existing formulas. The modified formulas can be applied from shallow water to deepwater.

Marcello Lissia - One of the best experts on this subject based on the ideXlab platform.

  • Constraining spectral functions at finite temperature and chemical potential with exact sum rules in asymptotically free theories.
    Physical Review D, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure in an asymptotically free theory, and in particular in QCD. Logarithmic corrections are found to play an essential role in the derivation. This exact result constrains the shape of SF’s, and implies striking effects near phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density must satisfy these constraints. We also explicitly illustrate in detail the exact sum rule in the Gross-Neveu model.

  • Exact sum rules at finite temperature and chemical potential and their application to QCD
    Physics Letters B, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Abstract Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure of an asymptotically free theory. This exact result constrains the shape of SF's, and implies a highly non-trivial functional form for the SF near second order, or weak first order, phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density, must satisfy these constraints.

  • Exact sum rules at finite temperature and chemical potential and their application to QCD
    Physics Letters B, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure of an asymptotically free theory. This exact result constrains the shape of SF's, and implies a highly non-trivial functional form for the SF near second order, or weak first order, phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density, must satisfy these constraints.Comment: 8 pages, no figures, uses RevTeX 3.0. No major changes. Typos fixed and text sharpened. To appear in Phys. Lett. B. Postscript file available at ftp://risc0.ca.infn.it/pub/private/lissia/infnca-th-94-1.p

Patricia Cargo - One of the best experts on this subject based on the ideXlab platform.

  • Resolution of the time dependent Pn equations by a Godunov type scheme having the diffusion limit
    ESAIM: Mathematical Modelling and Numerical Analysis, 2010
    Co-Authors: Patricia Cargo, Gerald Samba
    Abstract:

    We consider the P n model to approximate the time dependent transport equation in one dimension of space. In a diffusive regime, the solution of this system is solution of a diffusion equation. We are looking for a numerical scheme having the diffusion limit property: in a diffusive regime, it has to give the solution of the limiting diffusion equation on a mesh at the diffusion scale. The numerical scheme proposed is an extension of the Godunov type scheme proposed by Gosse to solve the P 1 model without absorption term. It requires the computation of the solution of the steady state P n equations. This is made by one Monte-Carlo simulation performed outside the time loop. Using formal expansions with respect to a small parameter representing the inverse of the number of mean free path in each cell, the resulting scheme is proved to have the diffusion limit. In order to avoid the CFL constraint on the time step, we give an implicit version of the scheme which preserves the positivity of the Zeroth Moment.

  • Resolution of the time dependent Pn equations by a Godunov type scheme having the diffusion limit. Part 1 : The case of the time dependent P1 equations
    2008
    Co-Authors: Patricia Cargo, Gerald Samba
    Abstract:

    We consider the P1 model to approximate the time dependent transport equation in one dimension of space. In a diffusive regime, the solution of this system is solution of a diffusion equation. We are looking for a numerical scheme having the diffusion limit property: in a diffusive regime, it has to give the solution of the limiting diffusion equation on a mesh at the diffusion scale. The numerical scheme is an extension of the Godunov type scheme proposed by L.Gosse to solve the P1 model without absorption term. It requires the computation of the solution of the steady P1 equations. Using formal expansions with respect to a small parameter representing the inverse of the number of mean free path in each cell, the resulting scheme is proved to have the diffusion limit. In order to avoid the CFL constraint on the time step, we give an implicit version of the scheme which preserves the positiveness of the Zeroth Moment.

Suzhou Huang - One of the best experts on this subject based on the ideXlab platform.

  • Constraining spectral functions at finite temperature and chemical potential with exact sum rules in asymptotically free theories.
    Physical Review D, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure in an asymptotically free theory, and in particular in QCD. Logarithmic corrections are found to play an essential role in the derivation. This exact result constrains the shape of SF’s, and implies striking effects near phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density must satisfy these constraints. We also explicitly illustrate in detail the exact sum rule in the Gross-Neveu model.

  • Exact sum rules at finite temperature and chemical potential and their application to QCD
    Physics Letters B, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Abstract Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure of an asymptotically free theory. This exact result constrains the shape of SF's, and implies a highly non-trivial functional form for the SF near second order, or weak first order, phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density, must satisfy these constraints.

  • Exact sum rules at finite temperature and chemical potential and their application to QCD
    Physics Letters B, 1995
    Co-Authors: Suzhou Huang, Marcello Lissia
    Abstract:

    Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the Zeroth Moment of a spectral function (SF) is completely determined by the one-loop structure of an asymptotically free theory. This exact result constrains the shape of SF's, and implies a highly non-trivial functional form for the SF near second order, or weak first order, phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density, must satisfy these constraints.Comment: 8 pages, no figures, uses RevTeX 3.0. No major changes. Typos fixed and text sharpened. To appear in Phys. Lett. B. Postscript file available at ftp://risc0.ca.infn.it/pub/private/lissia/infnca-th-94-1.p