Biomedical subjects

Christophe Bourlier

Publications and source records attributed to Christophe Bourlier.

4 recordsLinked to original sources

PubMed2006

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

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PubMed2006

Fast numerical method for electromagnetic scattering by rough layered interfaces: propagation-inside-layer expansion method.

Electromagnetic scattering from a stack of two one-dimensional rough surfaces separating homogeneous media is modeled with a rigorous integral formulation solved by the method of moments. We present an efficient numerical method for computing the field scattered by such rough layers, in reflection as well as in transmission. We call this method propagation-inside-layer expansion (PILE) due to its straightforward physical interpretation. To our knowledge, it is the first method able to handle problems for this configuration with a huge number of unknowns. We study the convergence of this method versus a coupling condition and validate it by comparison with results from the literature.

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PubMed2005

Energy conservation of the scattering from one-dimensional random rough surfaces in the high-frequency limit.

Energy conservation of the scattering from one-dimensional strongly rough dielectric surfaces is investigated using the Kirchhoff approximation with single reflection and by taking the shadowing phenomenon into account, both in reflection and transmission. In addition, because no shadowing function in transmission exists in the literature, this function is presented here in detail. The model is reduced to the high-frequency limit (or geometric optics). The energy conservation criterion is investigated versus the incidence angle, the permittivity of the lower medium, and the surface rms slope.

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PubMed2005

Unpolarized infrared emissivity with shadow from anisotropic rough sea surfaces with non-Gaussian statistics.

The emissivity of two-dimensional anisotropic rough sea surfaces with non-Gaussian statistics is investigated. The emissivity derivation is of importance for retrieval of the sea-surface temperature or equivalent temperature of a rough sea surface by infrared thermal imaging. The well-known Cox-Munk slope probability-density function, considered non-Gaussian, is used for the emissivity derivation, in which the skewness and the kurtosis (related to the third- and fourth-order statistics, respectively) are included. The shadowing effect, which is significant for grazing angles, is also taken into account. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In addition, multiple reflections are ignored. Numerical results of the emissivity are presented for Gaussian and non-Gaussian statistics, for moderate wind speeds, for near-infrared wavelengths, for emission angles ranging from 0 degrees (nadir) to 90 degrees (horizon), and according to the wind direction. In addition, the emissivity is compared with both measurements and a Monte Carlo ray-tracing method.

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