高精度保偏光纤偏振测试系统的设计

介绍了保偏光纤的偏振串音和h参数以及它们的相互关系。给出了高精度起偏系统和检偏系统的光路结构。对影响测试精度的各种因素进行了详细分析,并使用自制的测试系统对国内几个单位生产的保偏光纤进行了测试,得到了理想的测试结果。其中,2m长的保偏光纤的偏振串音达到了-50dB以下,其测试精度达到了国际先进水平。     

Rb原子饱和吸收稳频半导体激光器系统

用饱和吸收光谱法对半导体激光器进行稳频，通过对反馈回路的优化设计，得到具有高信噪比的饱和吸收光谱微分误差信号，从而大大提高了半导体激光器的频率锁定灵敏度及长期稳定性，该中用于Rb原子的激光冷却与囚禁。     

Convergence Rate of the Distributions of Normalized Maximum Likelihood Estimators for Irregular Parametric Families

We study the convergence rate of the distributions of normalized maximum likelihood estimators defined by a parametric family of discontinuous multidimensional densities in the case of a vector parameter.     

Growth of epitaxial Si1-xGex layers at 750° C by VLPCVD

Silicon-germanium epitaxial layers have been grown on (100) silicon at 750° C by very low pressure chemical vapor deposition (VLPCVD). Pure SiH₄ and GeH₄ were used as the processing gases. Commensurate films of Si_1-x withx < 0.13 have been deposited up to a critical thickness about 2-4 times larger than the equilibrium value. Interrupted growth, controlled by gas switching, was employed to improve interfacial abruptness. The films have been characterized as a function of SiH₄ and GeH₄ flow rates and germanium content. Growth rate and germanium incorporation as a function of GeH₄:SiH₄ input ratio and total gas flow rate have been studied. We observed that the growth rate of the Si_1-x Ge _x layer decreases as the germanium content in the film or the GeH₄:SiH₄ ratio increases at 750° C using VLPCVD. We also found that, for a given GeH₄:SiH₄ ratio, the germanium incorporated in the solid is independent of the total gas flow rate.     

光电检测系统的带宽选择

本文分析光电检测系统的带宽与系统响应时间及信噪比之间的关系。提出在方案设计时根据所要求的响应时间和最佳信噪比初步确定带宽的方法。     

抽样调查的设计与分析(Ⅱ)

本文讨论抽样调查实践中有关设计和数据分析中的若干问题．第二部分主要涉及数据处理与统计分析问题．     

一种应用于无线监控网的图像压缩及重建法

采用降低分辨率的方式进一步地降低无线监控图像存储和传输的比特数,然后,在接收端采用垂直瞬间3场调节内插法进行处理,将图像还原,在不损害图像质量的情况下重建原始图像,使得接收端能够获得较清晰的监控图像。该方法比一般的线性内插法具有更好的图像质量,与自适应运动检测控制内插法、基于小波变换的自适应内插法等方法相比,方法更简便易行。     

Contrast manipulation in NMR imaging

The past few years have shown rapid growth of NMR imaging in both image quality and diagnostic usefulness. It has become apparent, as the images have been published, that both inter- and intra-group imaging of the same underlying pathology produces images which can have vastly differing appearance. This effect is mainly due to imaging techniques which use different pulse sequence types and timings thus varying the relative contribution of the protpn density, T1, and T2 properties of the tissues. In this paper we investigate the contrast manipulation effects and methods for SNR optimization for the saturation recovery, inversion recovery, spin echo, and inversion recovery spin echo pulse sequences when applied to three clinically relevant imaging tasks.     

A new look at Theodorsen's method in aerofoil theory

Theodorsen's method for calculating the incompressible potential flow past an aerofoil is viewed afresh. It is found that some simple modifications to the computational process make the computations relatively faster, easier and more accurate. The new modifications are applicable to the analysis of conventional aerofoils with up to moderate thickness and camber ratios. Several examples are presented to show the effectiveness of the modifications.     

激光表面硬化效果的计算与实验

本文从求解高能激光束加热工件产生的温度场入手，给出由于温度场引起的金属结构变化的计算模型，并求出处理后的表层硬度。利用这些计算公式对不同含碳量钢的热处理进行计算，得出了最终处理硬度与激光功率，钢含碳量等参数之间的关系，计算结果与实验数据吻合。