Search results for "Spectral"
showing 10 items of 3116 documents
Spectral properties of a variable period Bragg grating including a segment isolated of external deformations
2017
In this work the behavior of a Bragg grating of variable period (usually called a linearly chirped fiber Bragg grating — CFBG) is analyzed when a small portion of it is fixed so that its properties remain unchanged, while the rest of the grating is affected by a longitudinal deformation. The system was simulated using the Transfer Matrix Method to obtain its behavior under different levels of deformation and it was observed the appearance of negative peaks in the spectral response (transmission peaks). The analysis allowed characterizing the system with different sizes of the fixed portion (defects) (0.5 to 6 mm), for a grating with 10 cm long and 3 nm spectral width.
N2-, O2- and air-broadened half-widths and line shifts for transitions in the nu3 band of methane in the 2726- to 3200-cm-1 spectral region
2008
International audience; Complex Robert-Bonamy calculations of the pressure-broadened half-width and the pressure-induced line shift are made for some 4000 transitions in the [nu]3 band of methane with N2, O2, and air as the perturbing gases. This work focuses on A and F symmetry transitions in the spectral range 2726 to 3200 cm-1. More work is needed on the intermolecular potential before calculations can be made for the E-symmetry transitions. The calculations are made at 225 and 296 K in order to determine the temperature dependence of the half-width. The calculations are compared with measurements. These data are to support remote sensing of the Earth and Titan atmospheres.
Spectral and temperature sensitivity of area de-coupled tandem modules
2015
- Area de-coupling is a recently suggested method for current- or voltage-matching two-terminal tandem modules. It has previously been shown that under standard conditions, area de-coupled modules have the same theoretical efficiency as four-terminal tandem cells for any combinations of band gaps. In this work, the spectral and temperature sensitivity of ideal area de-coupled modules is investigated by detailed balance modeling. Voltage-matched area de-coupled modules are found to be considerably less sensitive to changes in the spectrum than current-matched modules. Current-matched modules are, on the other hand, found to be less sensitive to changes in the temperature. Under normal condit…
Spectroscopic studies of Tl containing high frequency electrodeless lamps
2014
In this work we estimate gas temperature from OH rotational spectrum at 306.4 nm and C 2 Swan band at 516.5 nm in thallium containing lamps during two working regimes: stable generation and self-modulation regime. The usage of both molecules allowed us to estimate gas temperature in different zones of the discharge. The measurement results show that the central part of discharge has temperature higher for about 400 K than in vicinity of lamp inner walls. The measurement results of self-modulation regime showed that rotational temperature variations are similar to that of atomic and molecular spectral line intensities with period being around 1 minute. More detailed analysis of temporal beha…
Hyperspectral imaging in perfusion and wound diagnostics – methods and algorithms for the determination of tissue parameters
2018
Abstract Blood perfusion is the supply of tissue with blood, and oxygen is a key factor in the field of minor and major wound healing. Reduced perfusion of a wound bed or transplant often causes various complications. Reliable methods for an objective evaluation of perfusion status are still lacking, and insufficient perfusion may remain undiscovered, resulting in chronic processes and failing transplants. Hyperspectral imaging (HSI) represents a novel method with increasing importance for clinical practice. Therefore, methods, software and algorithms for a new HSI system are presented which can be used to observe tissue oxygenation and other parameters that are of importance in supervising…
Photon Energy Dependent Hard X-ray Photoemission Spectroscopy of YbCu2Si2
2012
We have performed photon energy ( h ν) dependent hard X-ray photoemission spectroscopy (HAXPES) for YbCu 2 Si 2 , which is a heavy Fermion compound with intermediate Yb valence. We identified that the bulk components in the Si 1 s and Yb 3 d spectra develop with increasing h ν from 2.5 to 6 keV. Moreover, the temperature dependence of the Yb 3 d spectra measured at h ν= 8 keV has shown a valence fluctuation behavior. These results suggest that high h ν HAXPES is essential to determine the mean valence of the Yb compounds.
XIPE: the x-ray imaging polarimetry explorer
2016
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror bu…
B-MINE, the balloon-borne microcalorimeter nuclear line explorer
2001
B-MINE is a concept for a balloon mission designed to probe the deepest regions of a supernova explosion by detecting Ti-44 emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the extent and velocity distribution of the Ti-44 emitting region. The payload introduces the concept of focusing optics and microcalorimeter spectroscopy to nuclear line emission astrophysics. B-MINE has a thin, plastic foil telescope multilayered to maximize the reflectivity in a 20 keV band centered at 68 keV and a microcalorimeter array optimized for the same energy band. This combination provides a reduced background, an energy resolution of 50 eV and a 3sigma sensitivity in …
Formation of nanostructures in Eu3+ doped glass-ceramics: an XAS study.
2012
We describe the results of x-ray absorption experiments carried out to deduce structural and chemical information in Eu(3+) doped, transparent, oxyfluoride glass and nanostructured glass-ceramic samples. The spectra were measured at the Pb and Eu-L(III) edges. The Eu environment in the glass samples is observed to be similar to that of EuF(3). Complementary x-ray diffraction experiments show that thermal annealing creates β-PbF(2) type nanocrystals. X-ray absorption indicates that Eu ions act as seeds in the nanocrystal formation. There is evidence of interstitial fluorine atoms around Eu ions as well as Eu dimers. X-ray absorption at the Pb-L(III) edge shows that after the thermal treatmen…
A Study Using Sulfur K-Edge XAS of Bitumens, Asphaltenes, Maltenes and their Oxidation Products by Comparison with Model Compounds
1997
High resolution Sulfur K-edge XANES spectra have been recorded at the ESRF on test samples of bitumen, asphaltene and maltene fractions and various model compounds. All these fractions were found to have a low content of sulfidic species as opposed to thiophenic species and it is therefore not surprising that thermally oxidized samples (RTFOT) had also a low content (1%) of sulfoxides. This is indeed consistent with the absence of any detectable S=O signature in the EXAFS spectra which were recorded over more than 1300 eV using the undulator gap scan technique.