Use of the Extreme Groups Approach: A Critical Reexamination and New Recommendations.

Analysis of continuous variables sometimes proceeds by selecting individuals on the basis of extreme scores of a sample distribution and submitting only those extreme scores to further analysis. This sampling method is known as the extreme groups approach (EGA). EGA is often used to achieve greater statistical power in subsequent hypothesis tests. However, there are several largely unrecognized costs associated with EGA that must be considered. The authors illustrate the effects EGA can have on power, standardized effect size, reliability, model specification, and the interpretability of results. Finally, the authors discuss alternative procedures, as well as possible legitimate uses of EGA. The authors urge researchers, editors, reviewers, and consumers to carefully assess the extent to which EGA is an appropriate tool in their own research and in that of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于TS101型DSP链路口的多通道高精度数据采集电路设计

介绍一种基于数字信号处理器(DSP)TS101链路口的多通道高精度数据采集电路的设计方法,详细阐述利用多个ADS8361型A/D转换器进行数据采集,并经TS101链路口传输数据的FP-GA和DSP设计实现,讨论如何提高A/D转换精度的问题.     

Comparison of finite element reliability methods

The spectral stochastic finite element method (SSFEM) aims at constructing a probabilistic representation of the response of a mechanical system, whose material properties are random fields. The response quantities, e.g. the nodal displacements, are represented by a polynomial series expansion in terms of standard normal random variables. This expansion is usually post-processed to obtain the second-order statistical moments of the response quantities. However, in the literature, the SSFEM has also been suggested as a method for reliability analysis. No careful examination of this potential has been made yet. In this paper, the SSFEM is considered in conjunction with the first-order reliability method (FORM) and with importance sampling for finite element reliability analysis. This approach is compared with the direct coupling of a FORM reliability code and a finite element code. The two procedures are applied to the reliability analysis of the settlement of a foundation lying on a randomly heterogeneous soil layer. The results are used to make a comprehensive comparison of the two methods in terms of their relative accuracies and efficiencies.     

基于二阶矩阵微分方程的机械振动系统线性二次型调节器设计

本文讨论机械振动系统线性二次型状态调节器（LQR）问题，直接针对系统二阶运动微分方程，性能指标为一个依赖于二阶导数的泛函。由欧拉-拉格朗日方程得出一个系统矩阵增广的二阶线性微分方程，指出该方程稳定的特征对就是最优控制振动系统闭环特征对，并给出求解最优控制状态反馈矩阵的方法，另外，由本文方法还可得出基于速度和加速度反馈的最优控制反馈矩阵。这里不涉及求解代数矩阵Riccati方程。     

调谐质量阻尼器参数设计中的两个问题

本文以单自由度系统安装一个调谐质量阻尼器（简称TMD）为例，对抗风和抗震两类不同激励工况下TMD的参数设计问题进行了理论研究与对比分析。通过给出相对误差系数的概念，定量评价了不同的参数方法对TMD减振性能的影响程度。本文的研究为TMD的参数设计提供了理论指导。     

提高检测数据准确性 促进选钼生产稳定高效

本文从6个方面对选钼2个作业段的取样方式进行了校验,通过对检测数据的比对分析,找出了选钼2个作业段数据存在矛盾的原因,并针对原因采取了有效的措施,保证了检测数据的准确性,促进了选钼生产的稳定高效。     

Effect-Size Indices for Dichotomized Outcomes in Meta-Analysis.

It is very common to find meta-analyses in which some of the studies compare 2 groups on continuous dependent variables and others compare groups on dichotomized variables. Integrating all of them in a meta-analysis requires an effect-size index in the same metric that can be applied to both types of outcomes. In this article, the performance in terms of bias and sampling variance of 7 different effect-size indices for estimating the population standardized mean difference from a 2 × 2 table is examined by Monte Carlo simulation, assuming normal and nonnormal distributions. The results show good performance for 2 indices, one based on the probit transformation and the other based on the logistic distribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基坑支护工程的优化设计研究

通过基坑工程实例,对深基坑支护结构的优化设计进行了探讨,结果表明,在基坑支护设计中综合利用各方面因素,因地制宜,将具有良好的社会效益和经济效益。     

Fisher最优分割法在星星哨水库汛期分期划分中的应用

Fisher最优分割法是对有序样本进行最优化分段的一种数学方法。本文利用该方法对星星哨水库汛期进行相应的划分,结果表明该方法是可行的。因此,可利用该结果对分期实施不同的汛限水位,使水库的防洪和兴利效益达到最大。     

Reliability of structures in high dimensions, part I: algorithms and applications

The present paper is concerned with the estimation of structural reliability when a large number of random variables is present. A sampling technique which uses lines in order to probe the failure domain, is presented. The latter is employed in conjunction with a stepwise procedure which makes use of Markov Chains. The resulting algorithm exhibits accelerated convergence.