Suggestion of a new dimensionless number for dynamic plastic response of beams and plates

A dimensionless number, termed response number in the present paper, is suggested for the dynamic plastic response of beams and plates made of rigid-perfectly plastic materials subjected to dynamic loading. It is obtained at dimensional reduction of the basic governing equations of beams and plates. The number is defined as the product of the Johnson's damage number and the square of the half of the slenderness ratio for a beam; the product of the damage number and the square of the half of the aspect ratio for a plate or membrane loaded dynamically. Response number can also be considered as the ratio of the inertia force at the impulsive loading to the plastic limit load of the structure. Three aspects are reflected in this dimensionless number: the inertia of the applied dynamic loading, the resistance ability of the material to the deformation caused by the loading and the geometrical influence of the structure on the dynamic response. For an impulsively loaded beam or plate, the final dimensionless deflection is solely dependent upon the response number. When the secondary effects of finite deflections, strain-rate sensitivity or transverse shear are taken into account, the response number is as useful as in the case of simple bending theory. Finally, the number is not only suitable to idealized dynamic loads but also applicable to dynamic loads of general shape.

Direct Numerical Simulation of Supersonic Turbulent Boundary Layer Flow

Direct numerical simulations of a spatially evolving supersonic flat-plate turbulent boundary layer flow with free Mach number M = 2.25 and Reynolds number Re = 365000/in are performed. The transition process from laminar to turbulent flow is obtained by solving the three-dimensional compressible Navier-Stokes, equations, using high-order accurate difference schemes. The obtained statistical results agree well with the experimental and theoretical data. From the numerical results it can be seen that the transition process under the considered conditions is the process which skips the Tolimien-Schlichting instability and the second instability through the instability of high gradient shear layer and becomes of laminar flow breakdown. This means that the transition process is a bypass-type transition process. The spanwise asymmetry of the disturbance locally upstream imposed is important to induce the bypass-type transition. Furthermore, with increasing the time disturbance frequency the transition will delay. When the time disturbance frequency is large enough, the transition will disappear.

自由空间激光远距离传输的地面模拟研究

根据透镜的傅里叶变换性质，提出了采用光学傅里叶变换加级联光学成像放大并结合有限口径接收的方法来实现自由空间激光光束远距离传输的实验室模拟。由此原理设计了自由空间激光远距离传输模拟装置，该装置主要由大口径、长焦距的傅里叶变换平行光管和三级成像放大镜所组成，最大等效传输距离达2.4×10^5km，可用于星间激光通信终端综合通信性能的评估，在设定的误码率下测量终端可能的通信距离，或者在设定的作用通信距离下检测通信的误码率。

Hit-or-miss representation of a pattern spectrum and its optical implementation

We demonstrate that a pattern spectrum can be decomposed into the union of hit-or-miss transforms with respect to a series of structure-element pairs. Moreover we use a Boolean-logic function to express the pattern spectrum and show that the Boolean-logic representation of a pattern spectrum is composed of hit-or-miss min terms. The optical implementation of a pattern spectrum is based on an incoherent optical correlator with a feedback operation. (C) 1996 Optical Society of America

电控径向滤波器的横向超分辨与轴向焦移

提出一种光瞳滤波器来同时实现横向超分辨和轴向焦移效应的电控制．该光瞳滤波器由两偏光镜及包含有径向双折射元件的任意偏振态的电控旋光器组成。利用径向双折射元件对光偏振态的空间调制作用，结合旋光器对任意偏振态光的旋光作用，与两个偏光镜结合，实现了空间偏振态的重新分布．利用庞加莱球及琼斯理论进行了分析，结果表明，借助这种电致位相延迟来实现的偏振态调制效应，可同时实现横向超分辨与轴向焦移效应。对能够同时获得横向超分辨与轴向焦移的情况进行了分析，得到了系统各组成参量及电光调制范围。

基于基频分量消光的1/4波片快轴标定方法

提出了一种基于基频分量消光的波片快轴标定方法,并利用琼斯矩阵对其标定原理进行了分析。激光器、起偏器、相位调制器、待标定1/4波片、检偏器和光电探测器构成标定光路,起偏器、检偏器的透光轴与相位调制器的振动轴分别成+45°和0°夹角。准直激光束依次经过起偏器、相位调制器、待标定1/4波片和检偏器,由光电探测器接收。理论分析表明该标定方法标定精度主要取决于检偏器的定位误差。实验验证了该标定方法的有效性,1/4波片快轴标定结果的最大偏差为0.043°,标准差为0.012°,标定精度为0.05°。

Polarizing beam splitter of deep-etched triangular-groove fused-silica gratings

We investigated the use of a deep-etched fused-silica grating with triangular-shaped grooves as a highly efficient polarizing beam splitter (PBS). A triangular-groove PBS grating is designed at a wavelength of 1550 nm to be used in optical communication. When it is illuminated in Littrow mounting, the transmitted TE- and TM-polarized waves are mainly diffracted in the minus-first and zeroth orders, respectively. The design condition is based on the average differences of the grating mode indices, which is verified by using rigorous coupled-wave analysis. The designed PBS grating is highly efficient over the C+L band range for both TE and TM polarizations (> 97.68 %). It is shown that such a triangular-groove PBS grating can exhibit a higher diffraction efficiency, a larger extinction ratio, and less reflection loss than the binary-phase fused-silica PBS grating. (C) 2008 Optical Society of America.

掺镱双包层光纤放大器的放大特性

从掺镱(Yb)光纤放大器的功率传输方程出发,利用有限差分法对小模场面积(SMA)和大模场面积(LMA)掺镱双包层光纤放大器的放大特性进行了分析比较。采用模场直径(MFD)6.5 μm和20 μm的双包层掺镱光纤作为放大器增益介质进行窄线宽连续信号的放大,在915 nm激光抽运下模拟计算了大、小模场面积输出功率随输入信号功率、抽运光功率和光纤长度的变化特性,特别是对于大模场面积光纤放大器,最优光纤长度的选择至关重要;讨论了模场直径不同时的最优抽运功率和光纤长度的选择,得出4 m光纤放大时的临界抽运功率为4

Influences of radiation trapping on spectroscopic properties of Er3+-doped fluorophosphate glasses

Fluorophosphate glasses with different contents of ErF3 were prepared. Due to the radiation trapping of Er, concentration dependence of the fluorescence lifetime is subject to distortion, and the stimulated-emission cross section calculated by the Fuchtbauer-Ladenburg equation is underestimated. The influence of radiation trapping on the measured fluorescence lifetime and width are investigated quantitatively. By comparing the intensity ratio of the 1556-1532 nm peak in the fluorescence spectrum with that in the stimulated-emission cross-section spectrum obtained according to the McCumber theory, the distortion ratio of fluorescence spectrum due to radiation trapping is obtained. An empirical way to quantitatively evaluate the influences of radiation trapping on fluorescence lifetime and width is proposed. (c) 2007 Optical Society of America.

复方昆明山海棠颗粒对小鼠淋巴细胞体外增殖活化影响的研究

目的:研究复方昆明山海棠颗粒(composite tripterygium hypoglaucum hutch, CTHH)对小鼠脾淋巴细胞增殖、活化标志CD69和CD25及细胞因子IL-4及γ-IFN的影响,为阐明其免疫抑制作用提供分子药理学依据.方法:无菌分离小鼠脾淋巴细胞,加入不同浓度的复方昆明山海棠颗粒溶液,MTT法检测ConA刺激的小鼠脾淋巴细胞增殖;流式细胞仪检测活化标志CD69及CD25;酶联免疫法检测细胞因子IL-4及γ-IFN.结果: CTHH对脾淋巴细胞增殖活化及分泌均有抑制作用.