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991.
准饱和土体中圆形衬砌对弹性波的散射 总被引:1,自引:0,他引:1
采用Vardoulakis和Beskos提出的准饱和土体的波动控制方程,根据Helmholtz矢量分解定理,得到了准饱和土中P1波(快压缩波)、P2波(慢压缩波)和S波(剪切波)的波数的势函数表达式.将准饱和土体和圆形衬砌视为各向同性的均质体,运用波函数展开法将入射波、散射波和折射波的势函数展开成Fourier-Bessel函数的级数形式,根据准饱和土体与衬砌边界处应力和位移连续及衬砌内完全自由的边界条件,得到了平面P1波入射下,准饱和土体内深埋圆形衬砌的散射系数和折射系数的理论解,通过数值计算分析了饱和度对准饱和土体和衬砌的DSCF(动应力集中因子)及准饱和土体的PPCF(孔压集中因子)的影响规律,结果表明:准饱和土体的DSCF随着饱和度的增大而减小,衬砌的DSCF基本不受饱和度的影响,而准饱和土体的PPCF则随着饱和度的增大而增大. 相似文献
992.
采用Somigiliana公式给出了三维横观各向同性压电材料中的非渗漏裂纹问题的一般解和超奇异积分方程,其中未知函数为裂纹面上的位移间断和电势间断.在此基础上,使用有限部积分和边界元结合的方法,建立了超奇异积分方程的数值求解方法,并给出了一些典型数值算例的应力强度因子和电位移强度因子的数值结果,结果令人满意. 相似文献
993.
Bounding the growth factor in Gaussian elimination for Buckley's class of complex symmetric matrices
A Buckley matrix is an n × n complex symmetric matrix A = I n + iC, where C is real symmetric positive definite. We prove that, for such A the growth factor in Gaussian elimination is not greater than $${1 + \sqrt{17} \over 4} \simeq 1.28078\ldots$$ Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
994.
建立了碰撞池-电感耦合等离子体质谱法测定芝麻中痕量的锗元素(germanium , Ge)。采用微波消解,碰撞池(KED模式)-电感耦合等离子体质谱检测,在线引入内标元素铑(Rh),同时消解液中加入3%正戊醇增敏。结果 3 % 正戊醇可使74Ge的上机检测信号强度提高2.85倍,74Ge校正曲线线性相关系数为1.00000,检出限为0.0555 μg/kg,加标回收率为92.0%~106%,相对标准偏差(relative standard deviation, RSD%)为2.6%~4.3%。采用建立的方法测定7种国家标准物质,检测结果均在认定值范围内,RSD%为2.5%~8.8%。结论 该方法灵敏度高、准确,可实现批量检测,适用于芝麻中痕量锗的检测。 相似文献
995.
We report a method for calculating the electronic factor in the superexchange rate equation of electron transfer theory; this method is a basis set independent, grid‐based numerical technique that utilizes fast Fourier transforms (FFTs) and a Lanczos recursion in a pseudospectral framework and is used to treat a three‐dimensional one‐electron model of the electronic factor. We compare eigenvalues calculated from the current method to eigenvalues from the literature for both one‐dimensional (1D) and three‐dimensional (3D) model problems and find that the current method provides excellent accuracy and efficiency. With respect to the superexchange electronic factor, we use model potentials to calculate the tunneling matrix elements with the present method to illustrate how the method can be used to address current issues in superexchange. In particular, we show how this method is useful in evaluating the effect of the bridge potential on the superexchange electronic factor when using repulsive‐core pseudopotentials to represent the bridge. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 1262–1273, 2000 相似文献
996.
Alejandro Saenz Tanja Asthalter Wolf Weyrich 《International journal of quantum chemistry》1997,65(3):213-223
For the first time, an analytical and efficient algorithm for the evaluation of spherically averaged reciprocal form factors B(s)=〈B( s )〉Ω using Gauss-type basis functions is presented. The spherically averaged Compton profile is available by Fourier transformation of the reciprocal form factor. The algorithm has been successfully implemented in connection with the quantum chemistry codes GAMESS and CRYSTAL92, which perform Hartree–Fock calculations for molecules and solids. In addition, an analytical algorithm for the direct evaluation of spherically averaged Compton profiles and the moments 〈pν〉 (ν≥−1) via the momentum density is proposed for Gauss-type basis functions. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65 : 213–223, 1997 相似文献
997.
Jodi M. Milhaupt Bryan R. Chapman Timothy P. Lodge Steven D. Smith 《Journal of polymer science. Part A, Polymer chemistry》1998,36(17):3079-3086
Monomeric friction factors, Ξ, for polystyrene (PS), polyisoprene (PI), and a polystyrene–polyisoprene (SI) diblock copolymer have been determined as a function of temperature in four poly(styrene-b-isoprene-b-styrene-b-isoprene) tetrablock copolymer matrices. The Rouse model has been used to calculate the friction factors from tracer diffusion coefficients measured by forced Rayleigh scattering. Within the experimental temperature range the tetrablock copolymers are disordered, allowing for measurement of the diffusion coefficient in matrices with average compositions determined by the tetrablock copolymers (23, 42, 60, and 80% styrene by volume). Remarkably, for a given matrix composition the styrene and isoprene friction factors are essentially equivalent. Furthermore, at a constant interval from the system glass transition temperature, Tg, all of the friction factors (obtained from homopolymer, diblock copolymer, and tetrablock copolymer dynamics) agree to within an order of magnitude. This is in marked contrast to results for miscible polymer blends, where the individual components generally have distinct composition dependences and magnitudes at constant T − Tg. The homopolymer friction factors in the tetrablock matrices were systematically slightly higher than those of the diblock, which in turn were slightly higher than those of the homopolymers in their respective melts, when all compared at constant T − Tg. This is attributed to the local spatial distribution of styrene and isoprene segments in the tetrablocks, which presents a nonuniform free energy surface to the tracer molecules. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3079–3086, 1998 相似文献
998.
中国战略性新兴产业国际竞争力评价 总被引:1,自引:0,他引:1
以"新钻石模型"为基础,从产业环境、产业支撑和产业创新等3个维度构建战略性新兴产业国际竞争力评价指标体系.运用2005~2014年的面板数据对战略性新兴产业进行因子分析.评价结果显示,电子及通信设备制造业与医药制造业国际竞争力明显高于计算机及办公设备制造业与医疗仪器设备及仪器仪表制造业.航空航天器及设备制造业国际竞争力有很大提升潜力.电子及通信设备制造业创新能力表现突出,但战略性新兴产业整体创新能力较低. 相似文献
999.
Traditional ligand-field theory has to be improved by taking into account
both “pure electronic” contribution and electron-phonon interaction one
(including lattice-vibrational relaxation energy). By means of improved
ligand-field theory, R1,
R2, R3',
R2', and R1'
lines, U band, ground-state zero-field-splitting (GSZFS), and ground-state g factors of ruby and/or
GSGG:Cr3+ as well as thermal shifts of GSZFS, R1 line and R2 line of ruby have been calculated. The results are
in very good agreement with the experimental data. Moreover, it is found
that the value of cubic-field parameter given by traditional ligand-field
theory is inappropriately large. For thermal shifts of GSZFS, R1 line and R2 line of ruby, several conclusions have also been obtained. 相似文献
1000.