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951.
The powder-infrared spectra of different crystalline compounds containing the tetrahedral Cro3- 4, anion have been recorded and analyzed with the aid of the site symmetry rules. In some cases Raman data are also reported. The effect of the different crystalline environments is discussed in detail and comparisons with isostructural phases are also made. A definitive assignment for the internal vibrations of the CrO3- 4, ion is proposed and a new set of force constants has been calculated fron a modified valence force field. 相似文献
952.
Abstract The top part of the coexistence curve of methyl fluoride in the critical region has been determined first by direct observation of the disappearance of the meniscus of the fluid situated in a high-pressure light scattering cell and subsequently from the measured maximum depolarization ratio of an appreciable number of isochores close to the critical point. The experimental data obtained from direct observations yield a coexistence curve which nearly coincides with that found recently from pVT measurements. However, the data obtained from light scattering experiments describe a gravity induced coexistence curve which lies above the previous one and which shows a minimum at the critical point. The complete experimental data have been used to evaluate the critical parameters pc, ρc and Tc and the critical exponent β. 相似文献
953.
利用第一原理研究了过渡金属元素 Cr 或 Ni 在 Fe3Al合金中的优先占位行为及其合金化效应. 计算结果表明: Cr 或 Ni 的取代有助于Fe3Al 合金体系更稳定, Cr 优先占据 FeI 位, Ni 优先占据 FeII位. Fe2NiAl-II 具有最小的剪切模量G, 杨氏模量E和G/B值, 因此Fe2NiAl-II合金的韧性、延展性最佳. 态密度和电荷密度图表明, 过渡金属元素的取代提高了它们与近邻基体原子之间的相互作用, 削弱了Al和Fe的相互作用. 相似文献
954.
Dong Zhengchao 《中国科学G辑(英文版)》2006,49(5):597-605
We study the Zeeman effect on the d-wave superconductor and tunneling spectrum in normal-metal(N)/d-wave superconductor(S) junction by applying a Zeeman magnetic field to the S. It is shown that: (1) the Zeeman magnetic field
can lead to the S gap decreasing, and with the increase in Zeeman energy, the superconducting state is changed to the normal
state, exhibiting a first-order phase transition; (2) the Zeeman magnetic field may make the zero-bias conductance peak split
into two peaks, and the energy difference between the two splitting peaks in the conductance spectrum is equal to 2h
0 (h
0 is the Zeeman energy); (3) both the barrier strength of interface scattering and the temperature can lower the magnitudes
of splitting peaks, of which the barrier strength can lead to the splitting peaks becoming sharp and the temperature can smear
out the peaks, however, neither of them can influence the Zeeman effect. 相似文献
955.
956.
Y. Turki-Ben Ali G. Bastard R. Bennaceur 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):222
The aim of this work is to analyze theoretically the correlation energies, for neutral, positive and negative excitons and bi-excitons in the III–V nitride InxGa1−xN/GaN quantum dot; where x=17.5% denotes the indium concentration. So, we propose a model consistent with experimental observations that is small InxGa1−xN truncated pyramids with circular base lying on wetting layer, both buried into GaN matrix. The correlation energies of many-body complexes X, X−, X+ and XX are investigated as a function of the quantum dot radius rc and the intrinsic electric field. 相似文献
957.
The purpose of this study was to investigate if there was an effect of duration of speaking on determination of habitual pitch. Five speaking periods commonly used to elicit habitual pitch in clinical voice evaluations were compared (1, 5, 15, 30, and 60 seconds). Thirty female speakers with normal voices participated. Results of a within-subject univariate F-test revealed a statistically significant (p < 0.001) difference in habitual pitch among the speaking periods. Habitual pitch for the 1-second and 60-second speaking periods were found to be statistically significantly (p < 0.05) different than all remaining speaking periods, and the habitual pitch for the 30-second speaking period was found to be statistically significantly (p < 0.05) different than 60-second speaking period. Implications for the use of various speaking durations when determining habitual pitch are discussed, as is the possibility of a speaking duration effect on determination of other pitch-related voice parameters. 相似文献
958.
C.F. Lo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):93-95
Based upon the hidden Lie SU(1,1) symmetry, we have constructed the unitary decoupling transformation which diagonalizes the
multimode two-quantum Jaynes-Cummings model and provides us with an extremely convenient basis to gain a deeper understanding
of the dressing processes present in the matter-field interaction. This canonical transformation approach is very simple and
can be easily extended to other generalized Jaynes-Cummings models.
Received: 5 July 1997 / Revised: 3 November 1997 / Accepted: 14 November 1997 相似文献
959.
Summary It is shown that in the presence of a crossed electric and magnetic field the electronic states of a semiconductor in the
effective-mass approximation are described by a Hamiltonian containing a non-local potential. In order to preserve the gauge
invariance of the two-photon interband transition rate, the interaction Hamiltonian between the electrons and the incident
radiation has to be generalized. For GaAs, the transition rate between two particular levels is evaluated in both length and
velocity gauges demonstrating the correctness of our approach.
Work partially supported by the European Community Programme ESPRIT, Basic research, action n. 6878, EASI. 相似文献
960.
Rudolf Beran 《Annals of the Institute of Statistical Mathematics》1993,45(4):639-654
Linear regression models with random coefficients express the idea that each individual sampled may have a different linear response function. Technically speaking, random coefficient regression encompasses a rich variety of submodels. These include deconvolution or affine-mixture models as well as certain classical linear regression models that have heteroscedastic errors, or errors-in-variables, or random effects. This paper studies minimum distance estimates for the coefficient distributions in a general, semiparametric, random coefficient regression model. The analysis yields goodness-of-fit tests for the semiparametric model, prediction regions for future responses, and confidence regions for the distribution of the random coefficients.This research was supported in part by NSF Grant DMS 9001710. 相似文献