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91.
Haohai Yu Dawei Hu Huaijin Zhang Zhengping Wang Wenwei Ge Xinguang Xu Jiyang Wang Zongshu Shao Minhua Jiang 《Optics & Laser Technology》2007,39(6):1239-1242
In single-pass configuration, a picosecond pulse laser was used to investigate the stimulated Raman scattering in different BaWO4 crystals. Using the thresholds for the first Stokes line along the a- and c-axis, the Raman gain coefficients of the BaWO4 crystals were calculated along their respective direction. The higher Stokes (fourth) and anti-Stokes (third) lines were observed. Compared with other well-known Raman crystals, such as KGd(WO4)2 and Ba(NO3)2, BaWO4 has favorable properties for scattering the pump radiation with picosecond pulse duration. The Raman gain coefficients of BaWO4 are different, but do not vary for different transmission directions, which means that this Raman material can be selected more freely. 相似文献
92.
Previous calculations of transport coefficients of particle systems in two or more dimensions have used computer simulations or various approximations, like those implicit in the Boltzmann equation or in the standard probability theory of diffusion. Here an exactly solved model of crystal growth in three dimensions is transformed into a 2D model of steady particle transport. Then the exact, many-body stationary distribution and exact transport coefficients can be found as well as correlation functions. The model is highly asymmetric. In the transverse direction, particles are strongly attracted, so that long transverse rows of particles tend to form at low temperature. Kinks in these rows are rare, so the transverse positions of kinks effectively move continuously on a large distance scale. 相似文献
93.
Holstein P Bender M Galvosas P Geschke D Karger J 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,143(2):427-430
The access to self-diffusion coefficients in anisotropic systems such as thermotropic liquid crystals by means of PFG NMR is complicated by strong dipolar interactions. Additionally, problems arise due to the immediate orientation of low-molar-mass nematic liquid crystals in an external field. The director orientation can be changed by the application of an additional electric field. This can be exploited in order to reduce the dipolar interaction to such an extent that the NMR linewidths change from a solid-state to a liquid-like situation enabling PFG NMR experiments. 相似文献
94.
X射线荧光分析中谢尔曼方程逆问题的求解(理论影响系数法 … 总被引:1,自引:0,他引:1
本文首先在理论分析基础上,建立多元素样品的重量分数Ci、X射线荧光相对强度Ri与基体效应因子Fi的代数关系。然后,按照此关系导出两种求解谢尔曼方程逆问题的方法,即理论影响系数法和基本参数法。并用这两种方法分析了6个耐热钢标样,主量、常量元素的平均相对分析误差〈0.5%,对低含量轻元素Si、P、S的分析也取得良好的结果。 相似文献
95.
96.
A.A. Yaremchenko A.V. Kovalevsky E.N. NaumovichV.V. Kharton J.R. Frade 《Solid State Ionics》2011,192(1):252-258
Phase relationships, thermal expansion and electrical properties of Mg1 − xFexO (x = 0.1-0.45) cubic solid solutions and Fe3 − x − yMgxCryO4 ± δ (x = 0.7-0.95; y = 0 or 0.5) spinels were studied at 300-1770 K in the oxygen partial pressure range from 10 Pa to 21 kPa. Increasing iron content enlarges the spinel phase stability domain at reduced oxygen pressures and elevated temperatures. The total conductivity of the spinel ceramics is predominantly n-type electronic and is essentially p(O2)-independent within the stability domain. The computer simulations using molecular dynamics technique confirmed that overall level of ion diffusion remains low even at high temperatures close to the melting point. Temperature dependencies of the total conductivity in air exhibit a complex behavior associated with changing the dominant defect-chemistry mechanism from prevailing formation of the interstitial cations above 1370-1470 K to the generation of cation vacancies at lower temperatures, and with kinetically frozen cation redistribution in spinel lattice below 700-800 K. The average thermal expansion coefficients of the spinel ceramics calculated from dilatometric data in air vary in the range (9.6-10.0) × 10− 6 K− 1 at 300-500 K and (13.2-16.1) × 10− 6 K− 1 at 1050-1370 K. Mg1 − xFexO solid solutions undergo partial decomposition on heating under oxidizing and mildly reducing conditions, resulting in the segregation of spinel phase and conductivity decrease. 相似文献
97.
《Physics letters. A》2014,378(30-31):1992-1996
Due to quantum size effects (QSEs), the isobaric thermal expansion coefficient and isothermal compressibility well defined for macroscopic systems are invalid for finite-size systems. The two parameters are redefined and calculated for a finite-size ideal Fermi gas confined in a rectangular container. It is found that the isobaric thermal expansion coefficient and isothermal compressibility are generally anisotropic, i.e., they are generally different in different directions. Moreover, it is found the thermal expansion coefficient may be negative in some directions under the condition that the pressures in all directions are kept constant. 相似文献
98.
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100.
本文在传统的力学量测定的实验基础上,利用电学量参数变化测定杨氏模量,达到研究应力与应变的规律。 相似文献