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991.
建立在模方程近似解的基础上,考虑LiNbO3材料的色散特性,提出了一种用可见激光测量红外介质波导主要参数的方法,给出了实验测量结果,并对结果进行了分析讨论,本文提出的方法方便而且可靠,特别是较好地解决了单模波导的参数测量问题,具有较大的实用意义。 相似文献
992.
A. Kyritsis P. Pissis J. Grammatikakis 《Journal of Polymer Science.Polymer Physics》1995,33(12):1737-1750
The electrical and dielectric properties of poly(hydroxyethyl acrylate), PHEA, hydrogels were studied by means of dielectric relaxation spectroscopy in wide ranges of frequencies (5–2 × 109 Hz), temperatures (173–363 K) and water contents (0.065–0.46, g of water per gram of dry material). The secondary dipolar mechanisms (γ and βsw) and the dc conductivity mechanism were studied in detail by analyzing the dielectric susceptibility data within the complex permittivity formalism, the modulus formalism, and the complex impedance formalism. For both mechanisms molecular mobility was found to increase with increasing temperature or increasing water content (T-f-h superposition principle). The energy parameters and the shape parameters of the response were determined for both mechanisms at several water contents and temperatures. The temperature dependence of dc conductivity was found to change from Vogel-Tamman-Fulcher (VTF) type to Arrhenius type at water contents of ca. 0.30. At water contents lower than about 0.30 the hydrogels are homogeneous whereas at higher water contents a separate water phase appears. In terms of the strong/fragile classification scheme our results suggest that the PHEA hydrogels are fragile systems. ©1995 John Wiley & Sons, Inc. 相似文献
993.
The ASED-MO method has been used to gather electronic and energetic information on Pd deposits on Ni(111) and Pd atom inclusion in the first Ni layer since these model catalysts exhibit a striking catalytic efficiency towards butadiene hydrogenation. The electronic structure of Pd atoms is strongly altered compared with pure Pd. A Pd(4d)→Pd(5s) electronic transfer occurs in the case of the deposit when a slight similar transfer and a charge transfer from Pd to surrounding Ni takes place in the case of the inclusion. Those results are consistent with XPS experimental data. A low density of states, near the Fermi level, is also observed. The optimal geometrical situation for Pd deposits is found to be 2D-aggregates (in pseudoepitaxy or pseudomorphy with the underlying Ni surface, depending on the aggregate size). Small aggregates (part of the first Ni layer) are found to be the most stable in the case of a Pd inclusion in the Ni with a Pd---Pd distance of 2.64 Å, in agreement with available EXAFS experimental data. 相似文献
994.
995.
We show that the temperature of plasma produced by exposure of copper-zinc alloy specimens to laser radiation changes little
(within the limits of random errors) with a change in the conditions of the laser effect and chemical composition of the specimens.
With use of electric discharges (a low-voltage spark), systematic changes in the temperature of the plasma are observed when
the chemical composition of copper-zinc alloys changes.
Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 319–321, May–June, 1998. 相似文献
996.
997.
Measuring efficiency and productivity in professional football teams: evidence from the English Premier League 总被引:1,自引:0,他引:1
Professional football clubs are unusual businesses, their performance judged on and off the field of play. This study is concerned
with measuring the efficiency of clubs in the English Premier League. Information from clubs’ financial statements is used
as a measure of corporate performance. To measure changes in efficiency and productivity the Malmquist non-parametric technique
has been used. This is derived from the Data Envelopment Analysis (DEA) linear programming approach, with Canonical Correlation
Analysis (CCA) being used to ensure the cohesion of the input–output variables. The study concludes that while clubs operate
close to efficient levels for the assessed models, there is limited technological advance in their performance in terms of
the displacement of the technological frontier.
The research was supported by the Investigation Program of the Technical University of Cartagena (Spain) and by the Department
of Sports Studies at the University of Stirling (Scotland, UK). 相似文献
998.
提出一种用积分形式的高斯定理、环路定理(电场线的主要性质是它们的具体体现)和叠加原理来有有导体存在时的唯一性定理的方法。 相似文献
999.
本文对三阶非线性极化率的多种测量方法进行了比较研究,分析了每种方法的优缺点,对于实际情况下各类光学材料非线性性质的测量具有一定的指导意义。 相似文献
1000.
蒋志民 《新疆大学学报(理工版)》1991,8(4):37-44
本文推广应用[2~4]的方法,讨论向量微分算子在一般情况下的自拌扩张问题,给出了形式对称向量微分表达式一切自拌扩张的直接而完全的描述,完善了[1]中的的结果。 相似文献