The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Patrick Carlier - One of the best experts on this subject based on the ideXlab platform.
-
Transformation of Irradiance Measurements into Spectral Actinic Flux for Photolysis Rates Determination
Journal of Atmospheric Chemistry, 1997Co-Authors: HÉlÈne Cotte, Claude Devaux, Patrick CarlierAbstract:The actinic flux is the only Radiometric Quantity suitable for photolysisfrequency determination. It is derived from solar spectral irradiancemeasurements performed by a portable spectroradiometer in the 300–850nm wavelength range. The spectral irradiance is first divided into a directpart and a diffuse part, according to the atmospheric conditions, and thenconverted into the corresponding actinic flux Quantity. As an intermediary,the ratio $$r_{dd} $$ of diffuse actinic flux to diffuseirradiance is calculated by the spherical harmonics radiative code withrespect to wavelength, solar zenith angle, surface albedo, and aerosolproperties.The results of extensive sensitivity studies of $$r_{dd} $$ asa function of the main atmospheric parameters are discussed and lead to theconclusion that aerosol optical depth is the major critical value for aprecise $$r_{dd} $$ determination. The global algorithm totransform spectral irradiance into actinic flux is finally applied forphotodissociation rate calculations by convolution of the obtained actinicflux spectra with the absorption cross-sections and quantum yields of themolecule studied. Photolysis rates of different atmospheric photooxidants havebeen measured with this spectroRadiometric method during the summers of 1993and 1994 in Brittany and in Portugal. The ozone and nitrogen dioxidephotodissociation rates obtained present a good agreement with the j (O_3) and j (NO_2) actinometerresults, for the same experimental conditions in Brittany.
HÉlÈne Cotte - One of the best experts on this subject based on the ideXlab platform.
-
Transformation of Irradiance Measurements into Spectral Actinic Flux for Photolysis Rates Determination
Journal of Atmospheric Chemistry, 1997Co-Authors: HÉlÈne Cotte, Claude Devaux, Patrick CarlierAbstract:The actinic flux is the only Radiometric Quantity suitable for photolysisfrequency determination. It is derived from solar spectral irradiancemeasurements performed by a portable spectroradiometer in the 300–850nm wavelength range. The spectral irradiance is first divided into a directpart and a diffuse part, according to the atmospheric conditions, and thenconverted into the corresponding actinic flux Quantity. As an intermediary,the ratio $$r_{dd} $$ of diffuse actinic flux to diffuseirradiance is calculated by the spherical harmonics radiative code withrespect to wavelength, solar zenith angle, surface albedo, and aerosolproperties.The results of extensive sensitivity studies of $$r_{dd} $$ asa function of the main atmospheric parameters are discussed and lead to theconclusion that aerosol optical depth is the major critical value for aprecise $$r_{dd} $$ determination. The global algorithm totransform spectral irradiance into actinic flux is finally applied forphotodissociation rate calculations by convolution of the obtained actinicflux spectra with the absorption cross-sections and quantum yields of themolecule studied. Photolysis rates of different atmospheric photooxidants havebeen measured with this spectroRadiometric method during the summers of 1993and 1994 in Brittany and in Portugal. The ozone and nitrogen dioxidephotodissociation rates obtained present a good agreement with the j (O_3) and j (NO_2) actinometerresults, for the same experimental conditions in Brittany.
Yannick Boucher - One of the best experts on this subject based on the ideXlab platform.
-
A wavelet-based framework for acquired Radiometric Quantity representation and accurate physical rendering
The Visual Computer, 2006Co-Authors: Luc Claustres, Mathias Paulin, Yannick BoucherAbstract:In this paper, we present a framework based on a generic representation, which is able to handle most of the Radiometric quantities required by global illumination software. A sparse representation in the wavelet space is built using the separation between the directional and the wavelength dependencies of such Radiometric quantities. Particularly, we show how to use this representation for spectral power distribution, spectral reflectance and phase function measurements modeling. Then, we explain how the representation is useful for performing spectral rendering. On the one hand, it speeds up spectral path tracing by importance sampling to generate reflected directions and by avoiding expensive computations usually done on-the-fly. On the other hand, it allows efficient spectral photon mapping, both in terms of memory and speed. We also show how complex light emission from real luminaires can be efficiently sampled to emit photons with our numerical model.
Boucheryannick - One of the best experts on this subject based on the ideXlab platform.
-
A wavelet-based framework for acquired Radiometric Quantity representation and accurate physical rendering
The Visual Computer, 2006Co-Authors: Claustresluc, Paulinmathias, BoucheryannickAbstract:In this paper, we present a framework based on a generic representation, which is able to handle most of the Radiometric quantities required by global illumination software. A sparse representation...
Claude Devaux - One of the best experts on this subject based on the ideXlab platform.
-
Transformation of Irradiance Measurements into Spectral Actinic Flux for Photolysis Rates Determination
Journal of Atmospheric Chemistry, 1997Co-Authors: HÉlÈne Cotte, Claude Devaux, Patrick CarlierAbstract:The actinic flux is the only Radiometric Quantity suitable for photolysisfrequency determination. It is derived from solar spectral irradiancemeasurements performed by a portable spectroradiometer in the 300–850nm wavelength range. The spectral irradiance is first divided into a directpart and a diffuse part, according to the atmospheric conditions, and thenconverted into the corresponding actinic flux Quantity. As an intermediary,the ratio $$r_{dd} $$ of diffuse actinic flux to diffuseirradiance is calculated by the spherical harmonics radiative code withrespect to wavelength, solar zenith angle, surface albedo, and aerosolproperties.The results of extensive sensitivity studies of $$r_{dd} $$ asa function of the main atmospheric parameters are discussed and lead to theconclusion that aerosol optical depth is the major critical value for aprecise $$r_{dd} $$ determination. The global algorithm totransform spectral irradiance into actinic flux is finally applied forphotodissociation rate calculations by convolution of the obtained actinicflux spectra with the absorption cross-sections and quantum yields of themolecule studied. Photolysis rates of different atmospheric photooxidants havebeen measured with this spectroRadiometric method during the summers of 1993and 1994 in Brittany and in Portugal. The ozone and nitrogen dioxidephotodissociation rates obtained present a good agreement with the j (O_3) and j (NO_2) actinometerresults, for the same experimental conditions in Brittany.