Search results for "Spectral"
showing 10 items of 3116 documents
Numerical procedures and their practical application in PV modules’ analyses. Part II: Useful fractions and APE
2019
Abstract The article regards aspects of PV modules tested with the use of natural sunlight. The analysis of spectral structure of solar energy resources in southern Poland, carried out on the basis of meteorological data originating from SolarLab PW Wroclaw and AGH Krakow, Poland [ 1 ] was used in the article. It is a continuation of the article: Analysis of solar energy resources in southern Poland for photovoltaic applications [ 1 ], describing the method to determine spectral parameters of average photon energy (APE) and useful fraction (UF) with the use of a solar radiation spectrum simulator. This article, however, includes an experimental presentation of their impact on PV conversion …
Stark broadening of the hydrogen Paschen ? transition at electron densities of the order of $ \mathsf {10^{15}}$ cm $ \mathsf {^{-3}}$
2003
Stark broadening measurements and calculations of the Paschen γ spectral line of hydrogen ( λ = 1.094[: MU :] m) are reported. Investigations have been performed at plasma electron densities between 1.4×10 15 cm -3 and 3.7×10 15 cm -3 . As the light source a wall-stabilized arc operated in a helium-hydrogen gas mixture at atmospheric pressure has been applied. The radiation of the plasma emitted from nearly homogeneous plasma layers in end-on direction, was measured with the use of a grating spectrometer equipped with a charge coupled device (CCD) detector. The radiance calibration was carried out against light outputs originating from a tungsten strip radiation standard. The measured FWHM …
A small spherical liquid: A DFT molecular dynamics study of WAu12
2009
The finite-temperature dynamics of WAu12, incorporating both electronic and structural effects, is studied using a density-functional-based Born-Oppenheimer molecular dynamics method. Molecular dynamics simulations for monomolecular WAu12 suggest a surface-melting-type behaviour of the angular degrees of freedom between 366 and 512 K. Thermally averaged electron density-of-states of WAu12 are compared to the experimental photoelectron spectra of WAu12(-).
Calibration of the width of the NI spectral line at for electron density determination
2002
Abstract The Stark broadening of a NI spectral line at 7915.42 A has been calibrated for electron density determination of low temperature plasmas. The determined simple formula based on measured FWHM is applicable in the electron density range from 3×1015 to 10 16 cm −3 .
Computational modeling of isotropic electron paramagnetic resonance spectra of doublet state main group radicals
2007
The combined use of theoretical and mathematical methods in the analysis of electron paramagnetic resonance data has greatly increased the ability to interpret even the most complex spectra reported for doublet state inorganic main group radicals. This personal account summarizes the theoretical basis of such an approach and provides an in-depth discussion of some recent illustrative examples of the utilization of this methodology in practical applications. The emphasis is on displaying the enormous potential embodied within the approach. peerReviewed
Electron correlation effects on the calculated 13C NMR spectra of vinyl cations
1997
Abstract A study of calculated 13C NMR chemical shifts in vinyl cations is presented. The sensitivity of predicted isotropic shifts to correlation, basis set and geometry effects is explored. In order to obtain accurate estimates that are reasonably well converged with respect to further improvements in theory, it appears that the CCSD(T) method must be used with a basis of triple-zeta plus polarization quality on the carbon atoms. Second-order many-body perturbation theory performs adequately for all carbons except for that bearing the formal positive charge, while the self-consistent field approximation cannot be relied upon to predict even the correct qualitative ordering in the spectrum…
Above-bandgap ordinary optical properties of GaSe single crystal
2009
We report above-bandgap ordinary optical properties of ε-phase GaSe single crystal. Reference-quality pseudodielectric function 〈ε(E)〉 = 〈ε1(E)〉+i〈ε2(E)〉 and pseudorefractive index 〈N(E)〉 = 〈n(E)〉+i〈k(E)〉 spectra were measured by spectroscopic ellipsometry from 0.73 to 6.45 eV at room temperature for the light polarization perpendicular to the optic axis (math⊥math). The 〈ε〉 spectrum exhibited several interband-transition critical-point structures. Analysis of second-energy derivatives calculated numerically from the measured data yielded the critical-point energy values. Carmen.Martinez-Tomas@uv.es
Approximating Empirical Surface Reflectance Data through Emulation: Opportunities for Synthetic Scene Generation
2019
Collection of spectroradiometric measurements with associated biophysical variables is an essential part of the development and validation of optical remote sensing vegetation products. However, their quality can only be assessed in the subsequent analysis, and often there is a need for collecting extra data, e.g., to fill in gaps. To generate empirical-like surface reflectance data of vegetated surfaces, we propose to exploit emulation, i.e., reconstruction of spectral measurements through statistical learning. We evaluated emulation against classical interpolation methods using an empirical field dataset with associated hyperspectral spaceborne CHRIS and airborne HyMap reflectance spectra…
Comparison Between Fractional Vegetation Cover Retrievals from Vegetation Indices and Spectral Mixture Analysis: Case Study of PROBA/CHRIS Data Over …
2009
Abstract: In this paper we compare two different methodologies for Fractional Vegetation Cover (FVC) retrieval from Compact High Resolution Imaging Spectrometer (CHRIS) data onboard the European Space Agency (ESA) Project for On-Board Autonomy (PROBA) platform. The first methodology is based on empirical approaches using Vegetation Indices (VIs), in particular the Normalized Difference Vegetation Index (NDVI) and the Variable Atmospherically Resistant Index (VARI). The second methodology is based on the Spectral Mixture Analysis (SMA) technique, in which a Linear Spectral Unmixing model has been considered in order to retrieve the abundance of the different constituent materials within pixe…
Linear spectral mixture modelling to estimate vegetation amount from optical spectral data
1996
Abstract Spectral mixture modelling has developed in recent years as a suitable remote sensing tool for analysing the biophysical and compositional character of ground surfaces. In this paper the potentiality of the linear spectral mixture model to extract vegetation related parameters from 0·4-2·5 μm reflectance data has been tested. High spectral resolution reflectance measurements of soil-plant mixtures with different soil colour and plant densities were carried out in a laboratory experiment. The constrained least-squares and the factor analysis unmixing procedures were applied to generate endmember fractions of the components present in the mixtures and to test the validity of the mode…