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1.
K. L. Janssens B. Partoens F. M. Peeters 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):349
We investigated theoretically the influence of strain on the exciton in both single and three vertically coupled self-assembled quantum dot systems in the presence of a perpendicular magnetic field. For the single disk, we find that the heavy-hole exciton is the ground state, while for the system of three stacked disks, the light hole state was found to be lower in energy. Results for the diamagnetic shift were compared with experimental results. 相似文献
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R. Broda P. J. Daly J. McNeill R. V. F. Janssens D. C. Radford 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(4):403-408
The level structure of theN=81 nucleus149Er has been studied by γ-ray spectroscopy following the reaction92Mo+255 MeV60Ni. Yrast levels in149Er are established up to ~3.3 MeV, including 0.61 and 4.8 μs isomeric states. Most of the observed levels are interpreted as seniority-three states arising from the coupling of s1/2, d3/2 and h11/2 neutron holes with πh 11 2/n . Isomers identified in the reaction96Ru+255 MeV58Ni are tentatively assigned to151Yb. TheB (E2) values of high-spin isomers inZ=66?70,N=81?83 nuclei are surveyed. 相似文献
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The implementation of an expert system for the automated qualitative interpretation of energy-dispersive x-ray spectra is discussed. The first step in the interpretation process is the extraction of the relevant data from the spectrum, which is done by a preprocessor program, written in FORTRAN. The expert system itself consists of three parts. The knowledge base contains specific information on energy-dispersive x-ray fluorescence spectrometry presented in the form of IF/THEN rules. The data base contains the reduced spectral data and an array of certainty factors associated with each element; the certainty factor for an element represents the probability of its being present in the sample from which the spectrum was taken. Finally, the inference engine performs manipulation of the knowledge. For a particular state of the data base, the certainty factors for all the elements are iteratively modified until convergence is reached by using the rules from the knowledge base. During each cycle, the inference engine selects one rule from the knowledge base and executes it. Rules are selected on the basis of the chemical elements contained in their IF part and according to their previously assigned focus levels. Execution of the THEN part of the selected rule modifies the certainty factors of a number of elements. At the end of the interpretation session, the system lists the elements which have a high probability of being present in the sample. Optionally, the user can be provided with explanations of the reasoning steps taken during the interpretation. Application of the expert system to a particular spectrum shows that it is useful for the reliable interpretation of spectral data obtained from electron microprobe analysis of industrial aerosol particles. 相似文献
5.
A procedure for the determination of atmospheric particulate lead by flameless atomic absorption spectrometry is described. Aerosols are collected on 10-cm Whatman 41 filters with high-volume pumps. The lead is removed from a one-eighth sector of the filter by two ultrasonic treatments in 0.1 M nitric acid for 10 and 5 min, respectively. Investigations, including comparison with samples pre-ashed at low temperature, indicated that the lead was completely recovered. Routinely 20-μ1 amounts of the solution are injected into a graphite tube and the % absorption at 283.3 nm is measured. The elements normally encountered in atmospheric aerosols do not interfere. The sensitivity for 24-h samples is 0.01 μg m?3 of air. Sampling time can be reduced to a few minutes in urban air when a larger segment of the filter is used and a larger volume is injected. The reproducibility of the complete procedure is 3% for a typical lead concentration of 0.35 μg m?3. The method was applied to short-period variations of the lead concentration in urban air. 相似文献
6.
Lopez-Martens A Hannachi F Dossing T Schück C Collatz R Gueorguieva E Vieu C Leoni S Herskind B Khoo TL Lauritsen T Ahmad I Blumenthal DJ Carpenter MP Gassmann D Janssens RV Nisius D Korichi A Bourgeois C Astier A Ducroux L Le Coz Y Meyer M Redon N Sharpey-Schafer JF Wilson AN Korten W Bracco A Lucas R 《Physical review letters》1996,77(9):1707-1710
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K. D. Sen T. V. Gayatri R. Krishnaveni M. Kakkar Helge Toufar Geert O. A. Janssens Bart G. Baekelandt Robert A. Schoonheydt Wilfried J. Mortier 《International journal of quantum chemistry》1995,56(4):399-408
The average local electrostatic potential function, V(r)/ ρ(r), is calculated for 87 atoms, Li-Ac, in the ground state using the nonrelativistic average-over-configuration numerical Hartree-Fock density. It is found empirically that in a given atom the shell boundaries are expressed as the successively increasing maxima in V(r)/ ρ(r) and the outermost maximum presents good approximate estimates of the core-valence separation in atoms. The likeness in behavior of V(r)/ ρ(r) at each shell boundary with the maximum hardness principle is discussed. The single-exponent-fit parameters for the electron density in the valency region are provided for all atoms. © 1995 John Wiley & Sons, Inc. 相似文献
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