Search results for "Spectral"

Photoionization of adsorbates on sites with non-axial local symmetry. An example of the symmetry group

1996

We present an analysis of the influence of the local adsorption site symmetry on the angular distribution of photoelectrons ejected from adsorbed atoms or molecules. This analysis applies to photoelectron spectra obtained with photons of any energy in the VUV (photoelectron spectroscopy) or x-ray (XPS) regions, provided that the associated wave of the electron `sees' the neighbouring surface atoms. The adsorbate - substrate system is modelled by a cluster of symmetry group consisting of an adsorbate and several atoms of the substrate. The analysis applies also to clean surfaces of symmetry and to molecules of the symmetry group fixed in space. This local symmetry analysis is an alternative …

The oxidation state of iron in silicic melt at 500 MPa water pressure

2002

Abstract The dependence of the ferric–ferrous ratio in silicate melts on oxygen fugacity was studied in the system SiO2(Qz)–NaAlSi3O8(Ab)–CaAl2Si2O8(An)–H2O using Mossbauer spectroscopy. Experiments were performed under water-saturated conditions at 500 MPa, and at temperatures of 850 and 950 °C, covering a range typical for magmatic processes. The oxygen fugacity was varied in the fO2 range from Cu–Cu2O buffer to slightly more reducing conditions than the wustite–magnetite buffer. The iron redox ratio was determined by analyzing the Mossbauer parameter distribution that was modeled based on experimental spectra collected at room temperature on the quenched samples. The obtained iron redox …

Lossless coding of hyperspectral images with principal polynomial analysis

2014

The transform in image coding aims to remove redundancy among data coefficients so that they can be independently coded, and to capture most of the image information in few coefficients. While the second goal ensures that discarding coefficients will not lead to large errors, the first goal ensures that simple (point-wise) coding schemes can be applied to the retained coefficients with optimal results. Principal Component Analysis (PCA) provides the best independence and data compaction for Gaussian sources. Yet, non-linear generalizations of PCA may provide better performance for more realistic non-Gaussian sources. Principal Polynomial Analysis (PPA) generalizes PCA by removing the non-li…

Spectral analysis and orbital evolution of Low Mass X-ray Binaries at high inclination

X-Ray binaries are gravitationally bound systems consisting of a compact object that accretes matter from a companion star; they are the most interesting objects of the sky, infact they allow to study the physics of matter in very extreme conditions of density, temperature or magnetic eld. So the determination of spectral and temporal properties of X-ray binaries plays an important role in understanding the processes involved in these systems. This project aims to understand the properties of binary systems, at high inclination (dipping and eclips- ing sources), containing neutron stars weakly magnetized. In the light curves of these systems it is possible to identify a variety of modulatio…

Perturbation of the Lyapunov spectra of periodic orbits

2012

We describe all Lyapunov spectra that can be obtained by perturbing the derivatives along periodic orbits of a diffeomorphism. The description is expressed in terms of the finest dominated splitting and Lyapunov exponents that appear in the limit of a sequence of periodic orbits, and involves the majorization partial order. Among the applications, we give a simple criterion for the occurrence of universal dynamics.

Software Framework for Hyperspectral Data Exploration and Processing in MATLAB

2017

This paper presents a user introduction and a general overview of the MATLAB software package hsicube developed by the author for simplifying the data manipulation and visualization tasks often encountered in hyperspectral analysis work, and the design principles and software development methods used by the author. The framework implements methods for slicing, masking, visualization and application of existing functions to hyperspectral data cubes without the need to use explicit indexing or reshaping, as well as enabling expressive syntax for combining these operations on the command line for highly efficient data analysis workflows. It also includes utilities for interfacing with existing…

The Hamburg/ESO R-process Enhanced Star survey (HERES):XI. The highly r-process-enhanced star CS 29497-004

2017

We report an abundance analysis for the highly r-process-enhanced (r-II) star CS 29497-004, a very metal-poor giant with Teff = 5013K and [Fe/H]=-2.85, whose nature was initially discovered in the course of the HERES project. Our analysis is based on high signal-to-noise, high-resolution (R~75000) VLT/UVES spectra and MARCS model atmospheres under the assumption of local thermodynamic equilibrium, and obtains abundance measurements for a total of 46 elements, 31 of which are neutron-capture elements. As is the case for the other 25 r-II stars currently known, the heavy-element abundance pattern of CS 29497-004 well-matches a scaled Solar System second peak r-process-element abundance patter…

Validation of temperature-emissivity separation and split-window methods from TIMS data and ground measurements

2003

Abstract Land surface temperature retrieved with temperature-emissivity separation (TES) and split-window (SW) algorithms from six-channel Thermal Infrared Multispectral Scanner (TIMS) data in the HAPEX-Sahel experiment agreed with contemporaneous ground temperature measurements to within ±1 °C (TES and SW with channels at 10.8 and 11.7 μm, or SW-56). The SW algorithm used with TIMS channels at 8.4 and 8.7 μm (SW-12) underestimated ground temperatures by 2–5 °C. The TES method required atmospheric correction of at-sensor radiances, which was done with local radiosonde data and MODTRAN 4, and an empirical relationship between the spectral range of emissivity and its minimum value. Emissivity…

In-scene atmospheric correction of hyperspectral thermal infrared images with nadir, horizontal, and oblique view angles

2012

Atmospheric corrections for hyperspectral thermal images acquired with nadir, horizontal, and oblique views have typically relied on atmospheric modelling software, such as Moderate Resolution Atmospheric Transmission MODTRAN, to estimate atmospheric parameters. Data-only corrections, which require only information from the scene, are more versatile and less labour intensive, but do not yet seem to have been applied to horizontal and oblique views. Here, we apply, and modify where necessary, one published data-only algorithm in-scene atmospheric correction ISAC to nadir, horizontal, and slanted views The Aerospace Corporation's Spatially Enhanced Broadband Array Spectrograph System SEBASS a…

Comparison of line-by-line and band models of near-IR methane absorption applied to outer planet atmospheres

2012

Import OPTIWOS; International audience; Recent improvements in high spectral resolution measurements of methane absorption at wavenumbers between 4800 cm(-1) and 7919 cm(-1) have greatly increased the number of lines with known lower state energies, the number of weak lines, and the number of lines observed at low temperatures (Campargue, A., Wang, L, Kassi, S., Masat, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1141-1151; Campargue, A., Wang, L, Liu, A.W., Hu, S.M., Kassi, S. [2010]. Chem. Phys. 373, 203-210; Mondelain, D., Kassi, S., Wang, L.C. [2011]. Phys. Chem. Chem. Phys. 13, 7985-7996; Nikitin, A.V. et al. [2011a]. J. Mol. Spectrosc. 268, 93-106; Nikitin, A.V. et …