Search results for "SPECTRA"
showing 10 items of 3542 documents
Etude numérique d'équations aux dérivées partielles non linéaires et dispersives
2011
Numerical analysis becomes a powerful resource in the study of partial differential equations (PDEs), allowing to illustrate existing theorems and find conjectures. By using sophisticated methods, questions which seem inaccessible before, like rapid oscillations or blow-up of solutions can be addressed in an approached way. Rapid oscillations in solutions are observed in dispersive PDEs without dissipation where solutions of the corresponding PDEs without dispersion present shocks. To solve numerically these oscillations, the use of efficient methods without using artificial numerical dissipation is necessary, in particular in the study of PDEs in some dimensions, done in this work. As stud…
Optical calibration of a multispectral imaging system based on interference filters
2005
We present a new approach to optically calibrate a multispectral imaging system based on interference filters. Such a system typically suffers from some blurring of its channel images. Because the effectiveness of spectrum reconstruction depends heavily on the quality of the acquired channel images, and because this blurring negatively affects them, a method for deblurring and denoising them is required. The blur is modeled as a uniform intensity distribution within a circular disk. It allows us to characterize, quantitatively, the degradation for each channel image. In terms of global reduction of the blur, it consists of the choice of the best channel for the focus adjustment according to…
Perovskite CH3NH3PbI3–XClx Solar Cells. Experimental Study of Initial Degradation Kinetics and Fill Factor Spectral Dependence
2021
The main drawback of the methylammonium lead halide perovskite solar cells is their degradation in ambient atmosphere. To investigate ambient-air-induced cell degradation, spec-tral dependencies of open-circuit voltage (VOC), fill factor (FF) and the power conversion effi-ciency (PCE) have been acquired (for the first time reported in literature). Our custom-made measurement system allowed us to perform measurements of the above-mentioned entities in situ directly in vacuum during and after thermal deposition of the elec-trode. We also studied how these parameters in vacuum changed after cell exposure to ambient air for 85 min (50 nm top electrode) and for 180 min (100 nm top Ag electrode).…
Optimal extension of multispectral image demosaicking algorithms for setting up a one-shot camera video acquisition system
2022
Multispectral images are acquired using multispectral cameras equipped with CCD or CMOS sensors which sample the visible or near infrared spectrum according to specific spectral bands. A mosaic of multispectral MSFA filters is superimposed on the surface of the sensors to acquire a raw image called an MSFA image. In the MSFA image, only one spectral band is available per pixel, the demosaicking process is necessary to estimate the multispectral image at full spatio-spectral resolution. Motivated by the success of single-sensor cameras capturing the image in a single exposure that use CFA filters, we performed a comparative study of a few recent color image demosaicking algorithms and experi…
Multispectral imaging and its use for face recognition : sensory data enhancement
2015
In this thesis, we focus on multispectral image for face recognition. With such application,the quality of the image is an important factor that affects the accuracy of therecognition. However, the sensory data are in general corrupted by noise. Thus, wepropose several denoising algorithms that are able to ensure a good tradeoff betweennoise removal and details preservation. Furthermore, characterizing regions and detailsof the face can improve recognition. We focus also in this thesis on multispectral imagesegmentation particularly clustering techniques and cluster analysis. The effectiveness ofthe proposed algorithms is illustrated by comparing them with state-of-the-art methodsusing both…
Multiple scattering theory for non-local and multichannel potentials.
2012
International audience; Methodological advances in multiple scattering theory (MST) in both wave and Green's function versions are reported for the calculation of electronic ground and excited state properties of condensed matter systems with an emphasis on core-level photoemission and absorption spectra. Full-potential MST is reviewed and extended to non-local potentials. Multichannel MST is reformulated in terms of the multichannel density matrix whereby strong electron correlation of atomic multiplet type can be accounted for in both ground and excited states.
Gravity modelling of the lower crust in Sardinia (Italy)
1997
In this paper an example is given of an application of statistical techniques to the Bouguer anomalies analysis in order to design a simple crustal model using few a priori assumptions. All gravity measurements carried out in Sardinia have been collected and processed. The Bouguer anomalies have been calculated according to local density estimates. Spectral analysis of the Bouguer anomalies has been carried out along selected profiles in order to estimate the mean depth of the Moho discontinuity and that of an infracrustal discontinuity. The use of this technique inferred the presence of a discontinuity at a mean depth of ~ 28 km, interpreted as Moho and the likely presence of an infracrust…
Red emitting [Ir(C^N)2(N^N)]+ complexes employing bidentate 2,2':6,2''-terpyridine ligands for light-emitting electrochemical cells
2014
2,2':6',2''-Terpyridine (tpy), 4'-(4-HOC6H4)-2,2':6',2''-terpyridine (1), 4'-(4-MeOC6H4)-2,2':6',2''-terpyridine (2), 4'-(4-MeSC6H4)-2,2':6',2''-terpyridine (3), 4'-(4-H2NC6H4)-2,2':6',2''-terpyridine (4) and 4'-(4-pyridyl)-2,2':6',2''-terpyridine (4) act as N^N chelates in complexes of the type [Ir(C^N)2(N^N)][PF6] in which the cyclometallating ligand, C^N, is derived from 2-phenylpyridine (Hppy) or 3,5-dimethyl-1-phenyl-1H-pyrazole (Hdmppz). The single crystal structures of eight complexes have been determined, and in each iridium(III) complex cation, the non-coordinated pyridine ring of the tpy unit is involved in a face-to-face π-stacking interaction with the cyclometallated ring of an …
Characterization of complexes formed between [Me2Sn(IV)]2+ and carboxymethylcelluloses.
2006
Complexes formed between carboxymethylcellulose (CMC) and the [Me(2)Sn(IV)]2+ cation have been prepared in the solid state and characterized by FTIR and Mossbauer spectroscopy. The complexes contained CMC with varying molar weight and degree of carboxylation, and the complexes were isolated both from acidic and from neutral solutions at varying metal-to-ligand ratios. The characteristic vibration bands of the ligands were identified from their pH-dependent FTIR spectra. In the organotin(IV) complexes obtained at pH approximately 2, the -COO- moieties were found to be coordinated in a monodentate manner, and the band characteristic of the protonated (unbound) -COO- group(s) was also identifi…
Trimethylplatinum(IV) complexes with ON bidentate ligands
1972
Abstract Complexes of the trimethylplatinum(IV) moiety with bidentate monobasic salicylaldimines C 6 H 5 (OH)CHNR (R = ethyl, propyl, phenyl) have been prepared and characterized by IR, UV and NMR spectra and magnetic susceptibility measurements. The complexes are dimeric with double PtOPt bridges, and the metal appears to be pseudo-octahedrally hexacoordinated.