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971.
A laminate weakened by multiple elliptical holes of arbitrary distribution, arbitrary orientation and arbitrary dimensions, is treated as an anisotropic, infinite, multiple connected thin plate. By Faber series expansion [1–6] and a complex potential method in the plane theory of thermo-elasticity of an anisotropic body, the general step to deduce the thermostress concentration in the laminate subjected to arbitrary mechanical and thermal loads is obtained.Supported by The Chinese Science Foundation of Aeronautics 相似文献
972.
973.
浓度边界层中成长汽泡的界面特性 总被引:1,自引:0,他引:1
对于双组分池内核态沸腾,热边界层中生成的汽泡,同时也处于浓度边界层中.本文建立了边界展中汽泡表面张力模型,对温度和浓度引起的表面张力变化进行分析.结果表明,表面张力从汽泡顶部到底部是递增的,从而形成液体沿界面自上而下的Marangoni流.通过汽泡底部微层相界面方程的求解,探讨了微层变形特征,由此分析汽泡脱离机理.微层变形与文献[1]中指出的接触线的变化从本质上是一致的. 相似文献
974.
Ti^3+离子浓度对掺钛蓝宝石激光器输出特性的影响 总被引:3,自引:0,他引:3
首次从理论上研究了掺钛蓝宝石晶体中Ti^3+离子浓度对脉冲式激光泵浦的掺钛蓝宝石激光器的输出特性的影响,并用五种不同Ti^3+离子浓度的掺钛蓝宝石晶体进行了实验研究,实验结果与理论符合得较好。 相似文献
975.
Yu-Zhi Wang 《Optics & Laser Technology》1993,25(6):367-370
An in situ mass-spectrometric sampling technique has been developed for lifetime studies of TEA CO2 lasers. Using the new technique, an analysis of the gas components of a TEA CO2 laser during its lifetime has been performed. The results show that the laser output pulse energy was strongly influenced by the oxygen concentration inside the device. 相似文献
976.
R. Kotsilkova D. Fragiadakis P. Pissis 《Journal of Polymer Science.Polymer Physics》2005,43(5):522-533
The reinforcing effect of carbon nanoparticles in an epoxy resin has been estimated with different approaches based on rheology, molecular dynamics (evaluated by differential scanning calorimetry, dielectric relaxation spectroscopy, and thermally stimulated depolarization current), and dynamic mechanical analysis. Carbon particles aggregate as the volume increases and form a fractal structure in the matrix polymer. The dispersion microstructure has been characterized by its viscoelastic properties and relaxation time spectrum. The scaling of the storage modulus and yield stress with the volume fraction of carbon shows two distinct exponents and has thus been used to determine the critical carbon volume fraction of the network formation (Φ*) for the carbon/epoxy dispersions. At nanofiller concentrations greater than Φ*, the overall mobility of the polymer chains is restricted in both dispersions and solid nanocomposites. Therefore, (1) the relaxation spectrum of the dispersions is strongly shifted toward longer times, (2) the glass‐transition temperature is increased and (3) the relaxation strength of both the secondary (β) and primary (α) relaxations increases in the nanocomposites, with respect to the pure polymer matrix. The dispersion microstructure, consisting of fractal flocs and formed above Φ*, is proposed to play the main role in the reinforcement of nanocomposites. Moreover, the network structure and the interface polymer layer (bond layer), surrounding nanoparticles, increases the relaxation strength and slows the cooperative α relaxation, and this results in an improvement of the mechanical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 522–533, 2005 相似文献
977.
Parameters G
ij
in the Kirkwood-Buff theory of solution were calculated for binary fluid mixtures of Lennard-Jones (LJ) 6–12 molecules by using the Percus-Yevick theory. Calculations were carried out for various parameters in the LJ potential. Under the Lorentz-Berthelot rules, G
11
and/or G
22
-composition curves do not show a maximum for any parameters in the LJ potential. When the intermolecular interaction between different species becomes much weaker than that expected from the Berthelot rule, G
11
and G
22
show a maximum and G
12
a minimum. The pressure effect on G
ij
was examined and calculations at constant pressure were also carried out. G
ij
is almost independent of the pressure when the ratio of the molecular volume of two components is in the range 1.0 to 2.5. Comparison was made between experimental and calculated G
ij
for cyclohexane-2,3-dimethylbutane and acetonitrile-toluene systems. For the latter system, the quantitative agreement between the calculated and experimental could not be obtained but showed that the characteristics of G
ij
-composition curves can be explained qualitatively by using the PY theory.Adjunct Associate Professor of Institute for Molecular Science (April 1982–March 1984) 相似文献
978.
979.
Alexander Barvinok 《Mathematical Programming》1997,79(1-3):33-53
We discuss some consequences of the measure concentration phenomenon for optimization and computational problems. Topics include
average case analysis in optimization, efficient approximate counting, computation of mixed discriminants and permanents,
and semidefinite relaxation in quadratic programming. 相似文献
980.
本文研究了Pr1.85Ce0.15CuO4-δ(PCZA))中V^4+离子替代Cu^2+离子后对其超导电性的影响.Pr1.85Ce0.15Cu1-xVxO4-δ(x=0~0.10)电阻率测量结果显示:微量(x≤0.04)V^4+离子替代Cu^2+离子可以改善样品的超导电性;随着替代量的增加,体系的超导电性逐渐被抑制,x=0.08时超导电性消失.我们主要从样品的微观结构和载流子浓度两个方面的变化分析了V^4+替代Cu^2+对PCCO超导电性的影响机制.霍尔系数实验结果表明,替代量较少时,体系中载流子浓度随着x的增加而增加,有助于超导电性的改善,但是当替代量增加到一定程度时,晶格畸变程度的增大和顶点氧的出现,抑制了超导电性. 相似文献