Search results for "reflectance"
showing 10 items of 161 documents
Prototype for Surface Albedo Retrieval Based on Sentinel-3 OLCI and SLSTR Data in the Framework of Copernicus Climate Change
2021
This work describes the different algorithmic steps used to retrieve the first Surface Albedo (SA) product based on Sentinel-3 (S-3) data in the framework of the Copernicus Climate Change Service (C3S). The atmospherically corrected Top-Of-Atmosphere (TOA) reflectances into Top-Of-Canopy (TOC) reflectances are brokered from the Copernicus Global Land Service (CGLS). The TOC reflectances are used to obtain a BRDF model. Next, the spectral and angular integration steps are implemented, which take the latter coefficients as input to produce spectral and broadband albedo quantities. The preliminary quality assessment of BSA broadband albedo for the total shortwave shows good overall spatiotempo…
<title>Methodology for quantitative analysis of scaling effects in multiresolution datasets acquired with airborne sensors flying at different …
2001
Scaling issues are always playing a critical role in most studies based on remote sensing data. The process of getting quantitative scaling information from raw multi-resolution images is not trivial, and many aspects must be taken very carefully into consideration. To get a better picture about the role of spatial resolution, we conducted a series of flights in summer 1997, in several test sites over Spain and Portugal. In order to minimize the time of acquisition (to get minimal changes in atmospheric status and solar illumination) we used three flight altitude levels, that produced images with 1.25 m, 3 m and 12 m resolutions. The main steps in our methodology are: a) Geometrical registr…
Improved detection limit for ammonium/ammonia achieved by Berthelot's reaction by use of solid-phase extraction coupled to diffuse reflectance spectr…
2005
Abstract The proposed procedure is based on the extraction of the indothylmol blue into C 18 solid-phase extraction (SPE) membranes and direct quantification on the membrane surface by diffuse reflectance spectroscopy. The analytical performance of the proposed method has been evaluated for standard solutions of ammonium using reflectance values, R , as well as the Kubelka–Munk function, F ( R ). The results have been compared with those obtained by the conventional method, which uses UV–vis absorption spectroscopy with a sensor-based method. The described methodology provided satisfactory linearity and reproducibility within the ammonium concentration intervals 25–250 μg L −1 and 25–500 μg…
Contact and contactless diffuse reflectance spectroscopy: potential for recovery monitoring of vascular lesions after intense pulsed light treatment.
2011
Optical fiber contact probe diffuse reflectance spectroscopy and remote multispectral imaging methods in the spectral range of 400 to 1100 nm were used for skin vascular malformation assessment and recovery tracing after treatment by intense pulsed light. The results confirmed that oxy-hemoglobin relative changes and the optical density difference between lesion and healthy skin in the spectral region 500 to 600 nm may be successfully used for objective appraisal of the therapy effect. Color redness parameter a* = 2 is suggested as a diagnostic border to distinguish healthy skin and vascular lesions, and as the indicator of phototreatment efficiency. Valuable diagnostic information on large…
Keggin heteropolyacid H3PW12O40 supported on different oxides for catalytic and catalytic photo-assisted propene hydration
2013
Catalytic and catalytic photo-assisted hydration of propene to form 2-propanol in gas–solid regime at atmospheric pressure and 85 1C were carried out by using a heteropolyacid (POM) supported on different oxides. Binary materials were prepared by impregnation of H3PW12O40 on different commercial and home prepared supports (TiO2, SiO2, WO3, ZrO2, ZnO, Al2O3). Some of the composites were active both for catalytic and catalytic photo-assisted reactions. The Keggin type POM was completely and partially degraded, when supported on ZnO and Al2O3, respectively, and these binary solids always resulted as inactive for both catalytic and catalytic photo-assisted reactions. The supported Keggin POM sp…
Detection of H. pylori induced gastric inflammation by diffuse reflectance analysis
2018
International audience; Spectral acquisitions contain rich information and thus, are promising modalities for early detection of gastric diseases. In this study, we analyze the diffuse reflectance of the gastric inflammatory lesions induced by the bacterium H. pylori in the mouse stomach. A pipeline has been designed to characterize and classify spectra acquired on mice. The pipeline is based on a band clustering algorithm followed by the computation of meaningful division and subtraction features and by classification with a linear SVM classifier. Currently, the pipeline is able to recognize inflamed stomachs spectra with an accuracy of 98%. These results are promising and the same pipelin…
Inorganic gels as precursors of TiO2 photocatalysts prepared by low temperature microwave or thermal treatment
2008
Abstract A simple procedure for preparing active TiO2 photocatalysts is presented. The starting materials were unusual TiO2 gels formed from TiCl4. The use of microwaves for a very short time enhanced the TiO2 crystallinity preventing an increase of particle size and minimizing the decrease of specific surface area. This result makes this preparation very attractive. The formation of the gels was monitored through measurements of viscosity. All the samples were characterized by means of X-ray diffraction, diffuse reflectance spectroscopy and BET specific surface area measurements. The photoactivity of the samples was evaluated using the photodegradation of 4-nitrophenol in liquid–solid regi…
Sol-gel synthesis and photocatalytic activity of ZnO-SnO2 nanocomposites
2014
Abstract ZnO–SnO 2 nanocomposites were synthesized by a facile sol–gel synthesis route and characterized through X-ray diffraction, BET specific surface area analysis, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy. The photocatalytic activity of the samples was tested using the degradation of 4-nitrophenol under UV light as model reaction. The ZnO/SnO 2 molar ratio was varied in order to study its influence on the photoefficiency of the samples. The ZnO–SnO 2 nanocomposites showed higher photoactivity than the pure oxides and in particular the sample with ZnO/SnO 2 mol…
Photocatalytic behaviour of metal-loaded TiO2 aqueous dispersions and films
2007
Abstract Titanium dioxide nanoparticles loaded with Ce, Co, Eu, Sm, W and Yb species were prepared by coprecipitation in mild conditions using TiCl 4 as precursor with the aim to enhance the photocatalytic activity, especially under visible light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the powders of pure and loaded TiO 2 was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid–solid system. Loading with suitable amounts of W, Co and Sm resulted in a significan…
Peracetylated β‐cyclodextrin as solubilizer of arylphosphines in supercritical carbon dioxide
2006
Abstract Effect of peracetylated β-cyclodextrin on the solubility of diphenyl(4-phenylphenyl)phosphine in supercritical carbon dioxide medium has been investigated. As shown by gravimetric measurements, the presence of cyclodextrin (CD) (1 equivalent) allows to increase the solubility of phosphine (P) in supercritical carbon dioxide (scCO 2 ) (40 °C, 35.2 MPa, nominal system density 0.89 g/mL). This solubility enhancement was attributed to host–guest interactions in scCO 2 as the P was recovered in the form of an inclusion complex. Furthermore, a diffuse reflectance spectroscopy study on the samples recovered after the experiments and on various CD/P solid mixtures obtained by co-grinding i…