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Radiation Problem (radiation + problem)

Distribution by Scientific Domains

Engineering	83%

Selected Abstracts

A model for the 3D kinematic interaction analysis of pile groups in layered soils

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2009
Francesca Dezi
Abstract The paper presents a numerical model for the analysis of the soil,structure kinematic interaction of single piles and pile groups embedded in layered soil deposits during seismic actions. A finite element model is considered for the pile group and the soil is assumed to be a Winkler-type medium. The pile,soil,pile interaction and the radiation problem are accounted for by means of elastodynamic Green's functions. Condensation of the problem permits a consistent and straightforward derivation of both the impedance functions and the foundation input motion, which are necessary to perform the inertial soil,structure interaction analyses. The model proposed allows calculating the internal forces induced by soil,pile and pile-to-pile interactions. Comparisons with data available in literature are made to study the convergence and validate the model. An application to a realistic pile foundation is given to demonstrate the potential of the model to catch the dynamic behaviour of the soil,foundation system and the stress resultants in each pile. Copyright © 2009 John Wiley & Sons, Ltd. [source]

An inverse radiation problem of simultaneous estimation of heat transfer coefficient and absorption coefficient in participating media

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2003
H. M. Park
Abstract An inverse radiation problem is investigated where the spatially varying heat transfer coefficient h(z) and the absorption coefficient , in the radiant cooler are estimated simultaneously from temperature measurements. The inverse radiation problem is solved through the minimization of a performance function, which is expressed by the sum of square residuals between calculated and observed temperature, using the conjugate gradient method. The gradient of the performance function is evaluated by means of the improved adjoint variable method that can take care of both the function estimation and the parameter estimation efficiently. The present method is found to estimate h(z) and , with reasonable accuracy even with noisy temperature measurements. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Analysis of the radiation properties of a planar antenna on a photonic crystal substrate

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 13 2001
Habib Ammari
Abstract This paper is concerned with the rigorous investigation of the radiation properties of a planar patch antenna on a photonic crystal substrate. Under the assumptions that the driving frequency of the antenna lies within the band gap of the photonic crystal substrate and that the crystal satisfies a symmetry condition, we prove that the power radiated into the substrate decays exponentially. To do this, we reduce the radiation problem to the study of the well-posedness of a weakly singular integral equation on the patch antenna, and to the study of the asymptotic behaviour of the corresponding Green's function. We also provide a mathematical justification of the use of a photonic crystal substrate as a perfect mirror at any incidence angle. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The lattice Boltzmann method and the finite volume method applied to conduction,radiation problems with heat flux boundary conditions

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2009
Bittagopal Mondal
Abstract This article deals with the implementation of the lattice Boltzmann method (LBM) in conjunction with the finite volume method (FVM) for the solution of conduction,radiation problems with heat flux and temperature boundary conditions. Problems in 1-D planar and 2-D rectangular geometries have been considered. The radiating,conducting participating medium is absorbing, emitting and scattering. In the 1-D planar geometry, the south boundary is subjected to constant heat flux, while in the 2-D geometry the south and/or the north boundary is at constant heat flux condition. The remaining boundaries are at prescribed temperatures. The energy equation is solved using the LBM and the radiative information for the same is computed using the FVM. In the direct method, by prescribing temperatures at the boundaries, the temperature profile and heat flux are calculated. The computed heat flux values are imposed at the boundaries to establish the correctness of the numerical code in the inverse method. Effects of various parameters such as the extinction coefficient, the scattering albedo, the conduction,radiation parameter, the boundary emissivity and the total heat flux and boundary temperatures are studied on the distributions of temperature, radiative and conductive heat fluxes. The results of the LBM in conjunction with the FVM have been found to compare very well with those available in the literature. Copyright © 2008 John Wiley & Sons, Ltd. [source]