The mean-variance ratio test—A complement to the coefficient of variation test and the Sharpe ratio test

To circumvent the limitations of the tests for coefficients of variation and Sharpe ratios, we develop the mean-variance ratio statistic for testing the equality of mean-variance ratios, and prove that our proposed statistic is the uniformly most powerful unbiased statistic. In addition, we illustrate the applicability of our proposed test for comparing the performances of stock indices.     

Some new kinds of pseudoprimes

We define some new kinds of pseudoprimes to several bases, which generalize strong pseudoprimes. We call them Sylow -pseudoprimes and elementary Abelian -pseudoprimes. It turns out that every which is a strong pseudoprime to bases 2, 3 and 5, is not a Sylow -pseudoprime to two of these bases for an appropriate prime

We also give examples of strong pseudoprimes to many bases which are not Sylow -pseudoprimes to two bases only, where or

     

Density of Carmichael numbers with three prime factors

We get an upper bound of on the number of Carmichael numbers with exactly three prime factors.

     

月尘被动防护技术的最新研究进展

月球的特殊环境使月尘具有导电等特殊的性质,极易黏附在探测仪器上造成设备的失效,给探月工程带来极大的危害,因此国内外众多研究组针对月尘危害展开深入研究.本文从黏附机理、防护方法和实验测试几方面对月尘的被动防护技术进行综述和展望.首先,阐述了月尘对探测设备造成的不利影响及影响因素,进而具体论述月尘黏附的机理,详细介绍造成黏附的两种主要作用力的理论基础.然后,针对不同作用机理系统阐述了降低月尘颗粒黏附力的主要方法,对月尘被动防护技术的最新进展进行了总结.最后,结合防护方式的不同,总结了测试月尘黏附力的方法,从而为有效实现探测设备表面月尘防护奠定基础.     

大型光学惯性稳定跟踪仪器稳像精度测试系统原理方案探讨

本文主要探讨大型光学惯性稳定跟踪仪器稳像精度或瞄准线稳定精度测试原理方案设想及其框图、稳像精度计算公式及本测试系统的关键技术。     

Integrated photoelasticity for nondestructive residual stress measurement in glass

The paper gives a review of integrated photoelasticity and of its application for residual stress measurement in glass. By considering the basic theory of the method, two particular cases, the case of weak birefringence and that of constant principal stress axes, are picked up. It is shown that integrated photoelasticity is actually optical tensor field tomography. Its peculiarities in comparison with scalar field tomography are considered. Since directly integrated photoelasticity allows for the measurement of only some of the stress components, analytical or numerical methods are to be used for complete determination of the stress field. Nonlinear optical phenomena, interference blots and fringe bifurcation, are briefly considered. Several examples illustrate the application of the method.     

Excess thermal-noise in the electrical breakdown of random resistor networks

We discuss a new type of excess noise strongly sensitive to non-homogeneous Joule heating of random resistor network and associated with local sources of thermal noise. The evolution of the network towards an electrical breakdown of conductor-insulator type is then studied by using a biased percolation model and it is analysed in terms of an excess-noise temperature. Monte Carlo simulation results show a significant increase of the excess-noise temperature over the average temperature of the network. Remarkably the excess-noise temperature scales with the resistance with an exponent of about 3. The predictivity of the model can be tested on thin film resistors where the determination of the excess noise temperature should provide a valuable indicator of the defectiveness of the film. Received 13 April 1999 and Received in final form 7 May 1999     

点衍射干涉仪中小孔衍射波面误差分析

针孔或光纤直径的大小是影响点衍射干涉仪检测精度的重要因素,在实际检测中须根据检测任务的精度要求来选择小孔的尺寸.基于标量衍射理论,仿真计算了小孔尺寸引起的衍射波面相对标准球面偏离的误差.结果表明,当小孔直径为2.5μm,数值孔径(NA)为0.3时,与小孔有关的光学系统误差峰值(PV)约为0.07 nm.仿真方法和计算结果为针对各种高精度面形检测任务而设计点衍射干涉仪和分析其精度提供了理论和数据参考.     

阴影检验中的气流排除技术与方法

介绍利用微机图象处理技术消除气流有天文镜面检测中的干扰，提高天文镜面检测质量，达到大幅度缩短天文镜面加工周期的目的。     

玩具油漆涂层中有机锡检测能力验证样品研制及应用分析

制备了用于可迁移有机锡检测能力验证的玩具油漆涂层样品,并开展了相关测定能力验证计划,采用迭代法、四分位法和敏感分析法3种不同统计方法对23家实验室数据进行统计分析,并对不满意结果的原因进行了分析。结果表明所研制样品的均匀性和稳定性良好,能满足能力验证要求。不同统计方法对实验室能力评定结果存在差异,但指定值差异很小,而能力评定标准差差异较大,运用卡方检验能选择出更合理的统计方法。