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Lars Døvling Andersen 《Discrete Mathematics》1979,25(3):199-210
In this paper we give some new lower bounds for the cover-index of graphs with multiple edges permitted. The results are analogous to upper bounds for the chromatic index. We show that a simple graph with cover-index different from the minimum degree has at least three vertices of minimum degree. This implies that almost all simple graphs have cover-index equal to the minimum degree. 相似文献
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T. Andersen O. Poulsen P.S. Ramanujam 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(6):521-527
The zero-field level-crossing technique has been used to determine radiative lifetimes of excited states in singly ionized zinc, cadmium, and mercury. The excited levels in Zn(II), Cd(II) and Hg(II) were populated by collisions between fast ions and helium gas. Particular attention has been paid to the systematic errors occurring in radiative lifetimes by this technique. The results are compared with the lifetimes obtained by beam-foil, phase-shift, delayed-coincidence techniques and theoretical calculations. 相似文献
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The angular distribution of copper and platinum sputtered by argon ions from polycrystalline CuPt targets at 77 K has been measured by a collection technique. The argon-ion energy has been varied from 1.25 to 320 keV. For bombardment energies above 20 keV, differences in the angular distributions for the two elements indicate a strong copper segregation to the surface during bombardment. 相似文献
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Kirsti Andersen 《Historia Mathematica》1983,10(1):48-62
This article attempts to explain Fermat's not quite obvious calculations connected with his deduction of the law of refraction in Analysis ad refractiones (1662), and to describe the development which led to these calculations. In 1657 Fermat tried to deduce a law of refraction based on the principle that light follows the quickest path between two given points. He did not succeed because he found that the calculations were too long and tedious. The calculations are indeed complicated, but if Fermat, in 1657, had been willing to accept Descartes' law of refraction he would probably also have seen that it solved his problem. However, Fermat was of the opinion that Descartes' law was wrong and, therefore, he did not expect that solution. Only in 1662, when he succeeded in reducing the calculations substantially, did he realize that they led to the sine law of Descartes. 相似文献
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T. Andersen 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,19(2):169-171
The three second-order partial differential equations of the Voigt function are presented, leading to a powerful and accurate method of determining the Voigt function in the calculation of a line profile in a stellar atmosphere. 相似文献
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