均匀各向同性湍流的频率波数能量谱

对均匀各向同性湍流的频率波数能量谱进行了初步研究，得出均匀各向同性湍流中能量随时间、空间尺度分布的解析表达式，并运用直接数值模拟的方法对理论预测进行验证．数值结果很好地支持了理论预测：横扫速度是决定频率波数能量谱的特征量．

A Study on the Microstructure Characteristic of the Cold-Rolled Deformed Nanocrystalline Nickel

In this paper the microstructure characteristic of the cold-rolled deformed nanocrystalline Nickel metal has been studied by transmission electron microscopy (TEM). The results show that there were step structures near by grain boundary (GB), and the contrast of stress field in front of the step corresponds to the step in the shape. It indicates that the interaction between twins and dislocations is not a necessary condition to realizing the deformation. In the later stage of the deformation when the grain size became about 100 nm, the deformation occurs only depend upon the moving of the boundary of the stack faults (SFs) which result from the imperfection dislocations emitted from GBs. In the other word, the movement of the boundary dislocations of SFs results to growing-up of the size of the SFs, therefore realizes deformation. However, when the size of stack faults grows up, the local internal stress which is in front of the step gradually becomes higher. When this stress reach a critical value stopping the gliding of the partial dislocations, the SFs will stop growing up and leave a step structure behind.

A movable-cavity cold atom space clock

We present an experimental scheme of a cold atom space clock with a movable cavity. By using a single microwave cavity, we find that the clock has a significant advantage, i.e. the longitudinal cavity phase shift is eliminated. A theoretical analysis has been carried out in terms of the relation between the atomic transition probability and the velocity of the moving cavity by taking into account the velocity distribution of cold atoms. The requirements for the microwave power and its stability for atomic pi/2 excitation at different moving velocities of the cavity lead to the determination of the proper working parameters of the rubidium clock in frequency accuracy 10(-17). Finally, the mechanical stability for the scheme is analysed and the ways of solving the possible mechanical instability of the device are proposed.

Ultra-slow atomic beam generation by velocity selective resonance

We describe a method to generate an ultra-slow atomic beam by velocity selective resonance (VSR). A VSR experiment on a metastable helium beam in a magnetic field is presented and the results show that the transverse velocity of the defected beam can be cooled and precisely controlled to less than the recoil velocity, depending on the magnitude of the magnetic field. We extend this idea to a cold atomic cloud to produce an ultra-slow Rb-87 beam that can be used as a source of an atomic fountain clock or a space clock.

Grating-encoded multichannel photorefractive incoherent-to-coherent optical conversion

A dynamic multichannel incoherent-to-coherent optical converter based on the photorefractive effect of SBN:Ce is described. A number of grating-encoded input images, illuminated by incoherent light, are projected onto the crystal to yield photoinduced phase gratings. Coherent positive replicas of these images are simultaneously reconstructed by a coherent read beam. A simple theoretical description of this converter and corresponding experimental results are presented.

光折变局域体全息柱透镜变波长读出下的波前转换

研究了用波长为632．8nm的柱面波与平面波记录形成的体全息柱透镜用波长为800nm的平面波重现下的波前转换情况。结合二维耦合波理论，推导了形成于LiNbO3双掺杂晶体中该全息柱透镜的耦合波方程，并求出了其积分形式的解析解，分析了改变读出波长下该透镜的布拉格失配因子的分布情况，讨论了它的几何尺寸和记录柱面光波对其衍射效率的影响，以及柱面衍射光振幅在出射口径上的分布情况。结果表明，记录所形成的全息柱透镜的焦距越长它的衍射效率越高；该透镜厚度的增加会使它的衍射效率增加，但是透镜的衍射口径增加它的衍射效率会降低

脉冲压缩光栅光路调节新方法研究

介绍了一种简单而实用的大口径脉冲压缩光栅光路调节方法，有效解决了普通光路调节方法中轴向调节精度不高的问题。首先由全息透镜（光栅）成像公式出发，推导出了该光路调节的基本原理。并从光栅记录系统与光栅衍射波像差的关系，结合初级像差理论推导得出叠栅条纹像差为0．4786λ，大约是光栅衍射波像差（0．25λ）的两倍，利用此关系也可对光栅衍射波像差进行实时监测。从数值模拟结果可知，利用叠栅条纹法调节光路可将光栅波像差减至0．06λ，相应的轴向误差量为0．007mm，可有效提高了轴向调节精度。