The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Anne Jaffrezic - One of the best experts on this subject based on the ideXlab platform.
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PUB in Quebec: A robust geomorphology-based Deconvolution-reconvolution framework for the spatial transposition of hydrographs
Journal of Hydrology, 2019Co-Authors: Stéphane Ecrepont, Christophe Cudennec, Francois Anctil, Anne JaffrezicAbstract:The flexibility and parsimony of transpositioning hydrographs using geomorphology-based Deconvolution-reconvolution frameworks is particularly adapted to prediction in ungauged basins. Although already tested in semi-arid and oceanic-temperate hydro-climates, its predictions must be reproducible in a variety of hydrological contexts. The present study explores the nivo-pluvial hydrological regime using geomorphology-based hydrograph transposition between 21 gauged catchments ranging from 1.1 to 4466.4 km(2) in Quebec, Canada, and constitutes a case study in prediction in ungauged basins. Three metrics were used to assess model performance for each donor-target pair: Nash Sutcliffe Efficiency (NSE), NSE calculated for the square root of discharge (NSEsqrt), and Volumetric Efficiency (VE). The classic transposition of hydrographs using the specific discharge ratio, used as a reference, was almost always outperformed by the geomorphology-based approach. Good but seasonally variable performance values were obtained for several pairs of catchments, revealing simultaneous structural and circumstancial effects. The difference in size, the physical distance between the gauged donor and its target ungauged catchment, and the season influenced the performance of the geomorphology-based transposition.
Victoria E. Hamilton - One of the best experts on this subject based on the ideXlab platform.
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Discrimination of glass and phyllosilicate minerals in thermal infrared data
Journal of Geophysical Research: Planets, 2005Co-Authors: William C. Koeppen, Victoria E. HamiltonAbstract:[1] Thermal infrared spectra of glasses and phyllosilicates have similar shapes leading to a proposed ambiguity in Deconvolution results. We quantify the spectral separability of these two classes using discriminant analysis and linear Deconvolution. We apply the Deconvolution technique to single spectra, and two- and four-component mixtures. Missing end-members result in quantifiable uncertainties between modeled abundances of glasses and phyllosilicates. Mixtures containing silica-K2O glass are susceptible to overestimating phyllosilicates with minimal increases in root-mean-square error if the silica-K2O glass spectrum is not present in the end-member set. Missing phyllosilicate end-members are likely to be modeled as combinations of other phyllosilicates rather than glasses, with saponite, nontronite, and halloysite showing the highest uncertainties. Empirically, ±15% of the total glass plus phyllosilicate abundance incorporates all uncertainties in derived glass abundance if the glass in the mixture is in the end-member set. If the glass in the mixture is excluded from the end-member set, these uncertainties increase to ±65%. Four-component mixtures show that glasses and phyllosilicates act as a two-component mixing system but can induce small uncertainties in other components. Applying the maximum derived uncertainties to Deconvolutions of surface type 2, measured by the Mars Global Surveyor Thermal Emission Spectrometer, we find that silica-K2O glass abundance is above the instrument detection limit and a likely component of the surface. Pure silica glass, a proposed amorphous weathering product, is the least likely candidate for confusion with phyllosilicates and its noninclusion in models of Martian spectra suggests it likely is not a component of the Martian surface.
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analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 2 application to martian surface spectra from the mars global surveyor thermal emission spectrometer
Journal of Geophysical Research, 2001Co-Authors: Victoria E. Hamilton, M B Wyatt, H Y Mcsween, Philip R ChristensenAbstract:Atmospherically corrected thermal infrared spectra of large regions of the Martian surface from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) previously have been interpreted to represent two general spectral classes. One class represents a basalt to basaltic andesite composition, and the other class represents a basaltic andesite to andesite composition. We have performed new linear Deconvolutions of the two Martian surface type spectra with an end-member set tailored to represent volcanic rock types. Our preparatory study of laboratory spectra of terrestrial volcanic rocks (acquired at 2 cm 21 sampling), convolved to TES spectral sampling (10 cm 21 ), shows little degradation in Deconvolution results when compared to results acquired using the higher spectral resolution data, indicating that the Deconvolution technique is valid for analyzing data at TES resolution. Our spectral fits to the Martian data agree well with previous models and do not exhibit any notable deviations from the Martian spectra that would indicate the absence of any significant end-members in our model. Modal mineralogies obtained with these new spectral fits also compare favorably (within the previously stated uncertainties) to prior results. The newly derived modal mineralogies are used with new and traditional classification schemes for volcanic igneous rocks (introduced in a companion paper (Wyatt et al., this issue)) to classify the Martian compositions. Our results substantiate the previously proposed hypothesis that these two spectral classes on the Martian surface represent volcanic compositions with distinguishable differences in silica content ranging from basalt to andesite.
Stéphane Ecrepont - One of the best experts on this subject based on the ideXlab platform.
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PUB in Quebec: A robust geomorphology-based Deconvolution-reconvolution framework for the spatial transposition of hydrographs
Journal of Hydrology, 2019Co-Authors: Stéphane Ecrepont, Christophe Cudennec, Francois Anctil, Anne JaffrezicAbstract:The flexibility and parsimony of transpositioning hydrographs using geomorphology-based Deconvolution-reconvolution frameworks is particularly adapted to prediction in ungauged basins. Although already tested in semi-arid and oceanic-temperate hydro-climates, its predictions must be reproducible in a variety of hydrological contexts. The present study explores the nivo-pluvial hydrological regime using geomorphology-based hydrograph transposition between 21 gauged catchments ranging from 1.1 to 4466.4 km(2) in Quebec, Canada, and constitutes a case study in prediction in ungauged basins. Three metrics were used to assess model performance for each donor-target pair: Nash Sutcliffe Efficiency (NSE), NSE calculated for the square root of discharge (NSEsqrt), and Volumetric Efficiency (VE). The classic transposition of hydrographs using the specific discharge ratio, used as a reference, was almost always outperformed by the geomorphology-based approach. Good but seasonally variable performance values were obtained for several pairs of catchments, revealing simultaneous structural and circumstancial effects. The difference in size, the physical distance between the gauged donor and its target ungauged catchment, and the season influenced the performance of the geomorphology-based transposition.
Philip R Christensen - One of the best experts on this subject based on the ideXlab platform.
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analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 2 application to martian surface spectra from the mars global surveyor thermal emission spectrometer
Journal of Geophysical Research, 2001Co-Authors: Victoria E. Hamilton, M B Wyatt, H Y Mcsween, Philip R ChristensenAbstract:Atmospherically corrected thermal infrared spectra of large regions of the Martian surface from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) previously have been interpreted to represent two general spectral classes. One class represents a basalt to basaltic andesite composition, and the other class represents a basaltic andesite to andesite composition. We have performed new linear Deconvolutions of the two Martian surface type spectra with an end-member set tailored to represent volcanic rock types. Our preparatory study of laboratory spectra of terrestrial volcanic rocks (acquired at 2 cm 21 sampling), convolved to TES spectral sampling (10 cm 21 ), shows little degradation in Deconvolution results when compared to results acquired using the higher spectral resolution data, indicating that the Deconvolution technique is valid for analyzing data at TES resolution. Our spectral fits to the Martian data agree well with previous models and do not exhibit any notable deviations from the Martian spectra that would indicate the absence of any significant end-members in our model. Modal mineralogies obtained with these new spectral fits also compare favorably (within the previously stated uncertainties) to prior results. The newly derived modal mineralogies are used with new and traditional classification schemes for volcanic igneous rocks (introduced in a companion paper (Wyatt et al., this issue)) to classify the Martian compositions. Our results substantiate the previously proposed hypothesis that these two spectral classes on the Martian surface represent volcanic compositions with distinguishable differences in silica content ranging from basalt to andesite.
Laura Marcu - One of the best experts on this subject based on the ideXlab platform.
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laguerre nonparametric Deconvolution technique of time resolved fluorescence data application to the prediction of concentrations in a mixture of biochemical components
Biomedical optics, 2004Co-Authors: Qiyin Fang, Thanasis Papaioannou, Laura MarcuAbstract:To estimate the intrinsic fluorescence intensity decay of a compound, the excitation light pulse must be deconvolved from the measured fluorescence pulse trace. The most commonly used Deconvolution method is the multiexponential least-square iterative reconvolution (LSIR) technique. A variant of LSIR in which the intrinsic fluorescence intensity decay is expressed as an expansion on the discrete time Laguerre basis, was recently introduced. In this study, the performance of the Laguerre Deconvolution technique was successfully tested with simulated and fluorescence standard data. It was also demonstrated that the Laguerre Deconvolution presents a number of advantages over the classical multiexponential LSIR, including less expensive computational resolution, and the property to generate a unique set of expansion coefficients highly correlated with the intrinsic lifetimes. A novel method for concentration estimation based on the analysis of the Laguerre expansion coefficients was also proposed and successfully applied to different fluorescence standard mixtures, performing even better (error<2%) than more traditional methods of spectral analysis, such as PCR (error<7%) and PLS (error<10%). These findings suggest that the use of Laguerre expansion coefficients represents an alternative nonparametric approach to characterize and discriminate biological systems, in terms of their spectral and lifetime characteristics.
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nonparametric analysis of time resolved fluorescence data based on the laguerre expansion technique
International Conference of the IEEE Engineering in Medicine and Biology Society, 2003Co-Authors: Qiyin Fang, Thanassis Papaioannou, Laura MarcuAbstract:To estimate the intrinsic fluorescence intensity decay of a compound, the excitation light pulse must be deconvolved from the measured fluorescence pulse trace. The most commonly used Deconvolution method is the multiexponential least-square iterative reconvolution (LSIR) technique. A variant of LSIR in which the intrinsic fluorescence intensity decay is expressed as an expansion on the discrete time Laguerre basis, was recently introduced. In this study, the performance of the Laguerre Deconvolution technique was successfully tested with simulated and fluorescence standard data. It was also demonstrated that the Laguerre Deconvolution presents a number of advantages over the classical multiexponential LSIR, including less expensive computational resolution, and the property to generate a unique set of expansion coefficients highly correlated with the intrinsic lifetimes. A novel method for concentration estimation based on the analysis of the Laguerre expansion coefficients was also proposed and successfully applied to different fluorescence standard mixtures, performing even better (error<2%) than more traditional methods of spectral analysis, such as PCR (error<7%) and PLS (error<10%). These findings suggest that the use of Laguerre expansion coefficients represents an alternative nonparametric approach to characterize and discriminate biological systems, in terms of their spectral and lifetime characteristics.
