Search results for "Infrared"
showing 10 items of 2110 documents
Young, active radio stars in the AB Doradus moving group
2017
Context. Precise determination of stellar masses is necessary to test the validity of pre-main-sequence (PMS) stellar evolutionary models, whose predictions are in disagreement with measurements for masses below 1.2 M. To improve such a test, and based on our previous studies, we selected the AB Doradus moving group (AB Dor-MG) as the best-suited association on which to apply radio-based high-precision astrometric techniques to study binary systems. Aims. We seek to determine precise estimates of the masses of a set of stars belonging to the AB Dor-MG using radio and infrared observations. Methods. We observed in phase-reference mode with the Very Large Array (VLA) at 5 GHz and with the Eur…
Infrared evolved gas analysis during thermal investigation of lanthanum, europium and samarium carbonates
2003
Abstract The characterisation of rare earth elements carbonates (REECs) was performed by thermal analysis (TG–DTG) combined with simultaneous infrared evolved gas analysis–Fourier transform infrared (EGA–FTIR) spectroscopy. The TG–DTG curves were obtained using the Perkin-Elmer PC series TGA-7 thermogravimetric analyser in the temperature range 25–800 °C both in dynamic air and nitrogen atmosphere. La 2 (CO 3 ) 3 · n H 2 O, Eu 2 (CO 3 ) 3 · n H 2 O and Sm 2 (CO 3 ) 3 · n H 2 O were analysed, the dehydration and decarbonation steps were investigated and the water content was calculated. The trace rare earth elements in lanthanum, europium and samarium carbonates were determined by Philips PU…
Crucial dependence of excimer laser toughness of “wet” silica on excess oxygen
2011
Creation of point defects by ArF (6.4 eV) and F2 laser (7.9 eV) irradiation in synthetic “wet” silica glass thermally loaded with interstitial O2 molecules was studied by optical absorption, electron paramagnetic resonance and infrared absorption. The presence of excess oxygen caused a significant increase of laser-induced ultraviolet (UV) absorption, which was 4 times (7.9 eV-irradiation) and > 20 times stronger (ArF irradiation) as compared to O2-free samples. The spectral shape of photoinduced absorption nearly completely coincided with the spectral shape of oxygen dangling bonds (NBOHC) in 3 to 6.5 eV regions. The contribution of Si dangling bonds (E' centers) was less than few % and wa…
Infrared image processing and its application to forest fire surveillance
2007
This paper describes an scheme for automatic forest surveillance. A complete system for forest fire detection is firstly presented although we focus on infrared image processing. The proposed scheme based on infrared image processing performs early detection of any fire threat. With the aim of determining the presence or absence of fire, the proposed algorithms performs the fusion of different detectors which exploit different expected characteristics of a real fire, like persistence and increase. Theoretical results and practical simulations are presented to corroborate the control of the system related with probability of false alarm (PFA). Probability of detection (PD) dependence on sign…
Hydrate Networks under Mechanical Stress – A Case Study for Co 3 (PO 4 ) 2 ·8H 2 O
2016
The nature of the bound water in solids with hydrogen-bonded networks depends not only on temperature and pressure but also on the nature of the constituents. The collapse and reorientation of these network structures determines the stability of hydrated solids and transitions to other crystalline or amorphous phases. Here, we study the mechanochemically induced loss of bound water in Co₃(PO₄)₂·8H₂O and compare this process to the behavior under hydrostatic pressure. The associated phase transition and its kinetics were monitored by X-ray powder diffraction with Synchrotron radiation and quantitative IR spectroscopy. High shearing forces are responsible for the degradation of the hydrogen-b…
Extension of the MIRS computer package for the modeling of molecular spectra : from effective to full ab initio ro-vibrational hamiltonians in irredu…
2012
The MIRS software for the modeling of ro-vibrational spectra of polyatomic molecules was considerably extended and improved. The original version (Nikitin, et al. JQSRT, 2003, pp. 239--249) was especially designed for separate or simultaneous treatments of complex band systems of polyatomic molecules. It was set up in the frame of effective polyad models by using algorithms based on advanced group theory algebra to take full account of symmetry properties. It has been successfully used for predictions and data fitting (positions and intensities) of numerous spectra of symmetric and spherical top molecules within the vibration extrapolation scheme. The new version offers more advanced possib…
Macroscopic and Molecular Insights from CO Adsorption on NaY Zeolite: A Combined FTIR and Manometric Study
2012
International audience; This survey combines both quantitative and IR molecular descriptions and aims to provide new insights for the description of CO adsorption on NaY zeolite at 77 K. Quantitative measurements of the number of CO molecules trapped in the microporous super cage are compared to the corresponding IR spectra of CO as adsorbed species. We demonstrate that polycarbonyls formed during the completion of the accessible S-II Na+ coordinative vacancies result in the formation of mono-, di- and tricarbonyls but not consecutively. Quantitative analysis and measurements of the CO molecules that are adsorbed prove that polycarbonyls coexist with different proportions over the adsorptio…
Gas-Phase Vibrational Spectroscopy of the Hydrocarbon Cations l-C3H+, HC3H+, and c-C3H2+: Structures, Isomers, and the Influence of Ne-Tagging
2019
We report the first gas-phase vibrational spectra of the hydrocarbon ions C3H+ and C3H2+. The ions were produced by electron impact ionization of allene. Vibrational spectra of the mass-selected ions tagged with Ne were recorded using infrared predissociation spectroscopy in a cryogenic ion trap instrument using the intense and widely tunable radiation of a free electron laser. Comparison of high-level quantum chemical calculations and resonant depletion measurements revealed that the C3H+ ion is exclusively formed in its most stable linear isomeric form, whereas two isomers were observed for C3H2+. Bands of the energetically favored cyclic c-C3H2+ are in excellent agreement with calculated…
Transfer Learning with Convolutional Networks for Atmospheric Parameter Retrieval
2018
The Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp satellite series provides important measurements for Numerical Weather Prediction (NWP). Retrieving accurate atmospheric parameters from the raw data provided by IASI is a large challenge, but necessary in order to use the data in NWP models. Statistical models performance is compromised because of the extremely high spectral dimensionality and the high number of variables to be predicted simultaneously across the atmospheric column. All this poses a challenge for selecting and studying optimal models and processing schemes. Earlier work has shown non-linear models such as kernel methods and neural networks perform w…
Observation of Geometric Parametric Instability Induced by the Periodic Spatial Self-Imaging of Multimode Waves
2016
Spatio-temporal mode coupling in highly multimode physical systems permits new routes for exploring complex instabilities and forming coherent wave structures. We present here the first experimental demonstration of multiple geometric parametric instability sidebands, generated in the frequency domain through resonant space-time coupling, owing to the natural periodic spatial self-imaging of a multimode quasi-continuous-wave beam in a standard graded-index multimode fiber. The input beam was launched in the fiber by means of an amplified microchip laser emitting sub-nanosecond pulses at 1064 nm. The experimentally observed frequency spacing among sidebands agrees well with analytical predic…