Search results for "SPECTRA"
showing 10 items of 3542 documents
Regression Wavelet Analysis for Lossless Coding of Remote-Sensing Data
2016
A novel wavelet-based scheme to increase coefficient independence in hyperspectral images is introduced for lossless coding. The proposed regression wavelet analysis (RWA) uses multivariate regression to exploit the relationships among wavelet-transformed components. It builds on our previous nonlinear schemes that estimate each coefficient from neighbor coefficients. Specifically, RWA performs a pyramidal estimation in the wavelet domain, thus reducing the statistical relations in the residuals and the energy of the representation compared to existing wavelet-based schemes. We propose three regression models to address the issues concerning estimation accuracy, component scalability, and c…
Discrete wavelet transform based multispectral filter array demosaicking
2013
International audience; The idea of colour filter array may be adapted to multi-spectral image acquisition by integrating more filter types into the array, and developing associated demosaicking algorithms. Several methods employing discrete wavelet transform (DWT) have been proposed for CFA demosaicking. In this work, we put forward an extended use of DWT for mul-tispectral filter array demosaicking. The extension seemed straightforward, however we observed striking results. This work contributes to better understanding of the issue by demonstrating that spectral correlation and spatial resolution of the images exerts a crucial influence on the performance of DWT based demosaicking.
Advanced Ultrasonic Structural Monitoring of Waveguides
2008
Ultrasonic Guided Waves (UGWs) are a useful tool in those structural health monitoring applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes two methods, based on linear and nonlinear acoustics for structural damage detection based on UGWs. The linear method combine the advantages of UGW inspection with the outcomes of the Discrete Wavelet Transform (DWT) that is used for extracting defect-sensitive features that can be combined to perform a multivariate diagnosis of damage. In particular, the DWT is exploited to generate a set of relevant wavelet coefficients to construct a uni-dimensional or m…
NIR and Visible Image Fusion for Improving Face Recognition at Long Distance
2014
Face recognition performance achieves high accuracy in close proximity. However, great challenges still exist in recognizing human face at long distance. In fact, the rapidly increasing need for long range surveillance requires a passage from close-up distances to long distances which affects strongly the human face image quality and causes degradation in recognition accuracy. To address this problem, we propose in this paper, a multispectral pixel level fusion approach to improve the performance of automatic face recognition at long distance. The main objective of the proposed approach is to formulate a method to enhance the face image quality as well as the face recognition rate. First, v…
Controllability method for acoustic scattering with spectral elements
2007
We formulate the Helmholtz equation as an exact controllability problem for the time-dependent wave equation. The problem is then discretized in time domain with central finite difference scheme and in space domain with spectral elements. This approach leads to high accuracy in spatial discretization. Moreover, the spectral element method results in diagonal mass matrices, which makes the time integration of the wave equation highly efficient. After discretization, the exact controllability problem is reformulated as a least-squares problem, which is solved by the conjugate gradient method. We illustrate the method with some numerical experiments, which demonstrate the significant improveme…
Performance of Spectral Fitting Methods for vegetation fluorescence quantification
2010
The Fraunhofer Line Discriminator (FLD) principle has long been considered as the reference method to quantify solar-induced chlorophyll fluorescence (F) from passive remote sensing measurements. Recently, alternative retrieval algorithms based on the spectral fitting of hyperspectral radiance observations, Spectral Fitting Methods (SFMs), have been proposed. The aim of this manuscript is to investigate the performance of such algorithms and to provide relevant information regarding their use. FLD and SFMs were used to estimate F starting from Top Of Canopy (TOC) fluxes at very high spectral resolution (0.12 nm) and sampling interval (0.1 nm), exploiting the O2-B (687.0 nm) and O2-A (760.6 …
EPR studies of the oxyfluoride glass ceramics using Mn2+as a paramagnetic probe
2010
In this work, we used Mn2+ as a dopant in the oxyfluoride glasses with various fluoride compounds. Electron paramagnetic resonance (EPR) measurements were carried out before and after a heat treatment of the material. In both cases, a well pronounced hyperfine (hf) structure of the EPR spectra characteristic to the Mn2+ ion have been observed. EPR measurements have also been studied for the separate fluoride counterparts of the oxyfluoride glasses. EPR spectra of the LaF3:Mn2+ and CaF2:Mn2+ powders show that Mn2+ ion has a strong superhyperfine (shf) interaction with surrounding fluorine nuclei, and this shf structure could be observed also in the heat treated glass samples.
Multispectral Photophletysmography for Evaluation of Cutaneous Flowmotions
2021
Human skin may reflect health conditions. Important and possibly diagnostically potent components of microcirculation are slow flow oscillations-flowmotions, however there is a lack of studies in this field. The present pilot study was devoted to evaluation of multispectral imaging photoplethysmography in determination of different components of flowmotions. Eight subjects were enrolled for the study. During resting conditions video was captured from dorsal aspect of hand at seven different wavelength and flowmotion analysis performed. Results indicate that at the resting conditions neurogenic component along with endothelial are dominant regardless of wavelength, while myogenic has the low…
Determination of New Radical Species in Ammonium Tartrate Dosimeters by CW- and Pulsed-EPR Techniques
2015
Samples of ammonium tartrate irradiated with doses of about 0.1–1 kGy by different beams of ionizing radiation (60Co–γ, 19 MeV protons and 62 MeV per nucleon carbon ions) were studied by continuous-wave electron paramagnetic resonance (cw-EPR) and by pulse-EPR techniques. Careful analysis of the cw-EPR and of the echo-detected EPR spectra allowed the identification of a second radical in the system besides the already known radical formed at high temperature by an hydrogen elimination at C(2) position [M. Brustolon et al., Res. Chem. Int 4:359, 1996]. The spectrum of the radical is compatible with that of a radical obtained by hydroxyl elimination.
Two-Photon Transitions in CW-ENDOR Spectra of Radicals in Fluid Solution
2002
The radical anion of duroquinone (2,3,5,6-tetramethyl-1,4-benzoquinone) was used as a model compound to describe the low-frequency (LF) ENDOR lines observed in many radical systems. These LF lines ...