断裂力学中的相似方法

不论是材料的断裂强度还是结构的承载能力均存在着明显的“尺度效应”。该文旨在总结断裂力学中的相似方法、无量纲数及其断裂力学中有关的尺度率，并给出作者自己对某些问题的看法和认识。

Ocean Waves Propagating over a Porous Seabed: Residual and Oscillatory Mechanisms

Two mechanisms for the wave-induced pore pressures in a porous seabed, i.e. oscillatory and residual excess pore pressures, have been observed in laboratory experiments and field measurements. Most previous investigations have focused on one of the mechanisms individually. In this paper, an analytical solution for the wave-induced residual pore pressure, which is not available yet, is derived, and compared with the existing experimental data. With the new solution, a parametric analysis is performed to clarify the applicable ranges of two mechanisms. Then, a simplified approximation for the prediction of wave-induced liquefaction potential is proposed for engineering practice.

Prescription for optimizing holograms in LiNbO3 : Fe : Mn

The photorefractive holographic dynamics of grating formation in photochromic doubly doped LiNbO3:Fe:Mn crystal is studied numerically and analytically in terms of the two-center model of Kukhtarev Et al. [Ferroelectrics 22, 949 (1979)]. The relations among the recorded and fixed space-charge fields and the doping densities, the oxidation-reduction states of the fields, and the intensities of UV-sensitizing and red recording beams are studied. Important conditions and effects are feued, and an optimal prescription for material doping and oxidation-reduction processing is suggested in which the crystal can be strongly oxidized and the Mn-doping density is smaller than the Fe-doping density. (C) 2000 Optical Society of America. OCIS codes: 050.7330, 190.5330, 090.2900.

磷酸盐激光玻璃聚（CH3）2Si（OC2H5）2防潮膜

以（CH3）2Si（OC2H5）2为前驱体，采用溶胶-凝胶与有机合成相结合的方法，制得稳定性良好的涂膜液。采用旋转涂膜法在掺钕磷酸盐激光玻璃棒端面涂制防潮膜，膜层固化后透过率达96．5％，获得的膜层表面粗糙度优良，均方根表面粗糙度（RMS）为1．659nm，平均粗糙度（RA）平均为1．321nm；在激光波长1053nm，脉冲宽度1 ns条件下膜层的激光破坏闽值可达10～14 J／cm^2。经过“神光Ⅱ”高功率激光器物理实验运行，膜层使用期为五年，并且已经在我国“神光Ⅲ”原型装置上试用。