Inferences on the Means of Two Log-Normal Distributions: A Computational Approach Test

In this article, we propose a novel approach for testing the equality of two log-normal populations using a computational approach test (CAT) that does not require explicit knowledge of the sampling distribution of the test statistic. Simulation studies demonstrate that the proposed approach can perform hypothesis testing with satisfying actual size even at small sample sizes. Overall, it is superior to other existing methods. Also, a CAT is proposed for testing about reliability of two log-normal populations when the means are the same. Simulations show that the actual size of this new approach is close to nominal level and better than the score test. At the end, the proposed methods are illustrated using two examples.     

Testing equality of two normal covariance matrices with monotone missing data

Abstract

The problem of testing equality of two multivariate normal covariance matrices is considered. Assuming that the incomplete data are of monotone pattern, a quantity similar to the Likelihood Ratio Test Statistic is proposed. A satisfactory approximation to the distribution of the quantity is derived. Hypothesis testing based on the approximate distribution is outlined. The merits of the test are investigated using Monte Carlo simulation. Monte Carlo studies indicate that the test is very satisfactory even for moderately small samples. The proposed methods are illustrated using an example.     

疲劳裂纹扩展试验裂纹图像采集系统

针对目前金属疲劳裂纹扩展检测方法存在效率低、操作繁琐、精度不高，不能实现实时性等缺点，文章提出了基 于机器视觉的裂纹检测方法。根据金属疲劳裂纹扩展试验过程中裂纹图像的采集要求，设计了摄像头位置可自动调整 的疲劳裂纹图像采集系统，包括摄像头安装运动装置，裂纹图像采集装置以及摄像头运动控制系统。图像采集装置由高 分辨率黑白面阵CCD摄像头、光学镜头，光源照明装置和图像采集卡组成，前3者安装在摄像头支架上，与摄像头运动 装置相连。摄像头运动装置中的X，Y，，Z轴运动机构由步进电机带动滚珠导轨机构。在基于ARM技术的运动控制系统 的控制下摄像头可沿X，Y，，Z轴作高精度直线运动，实现和试件之间精确位置的调整。实验结果表明，所设计的系统可 采集到疲劳裂纹扩展试验过程中高清晰度、高分辨率的试件裂纹图像，满足下一步裂绞尺寸计算的要求；摄像头运动定 位精度可达到0. 02 mm，满足精确的系统聚焦、位置调整、跟踪采集的要求。     

Random effects regression mixtures for analyzing infant habituation

Random effects regression mixture models are a way to classify longitudinal data (or trajectories) having possibly varying lengths. The mixture structure of the traditional random effects regression mixture model arises through the distribution of the random regression coefficients, which is assumed to be a mixture of multivariate normals. An extension of this standard model is presented that accounts for various levels of heterogeneity among the trajectories, depending on their assumed error structure. A standard likelihood ratio test is presented for testing this error structure assumption. Full details of an expectation-conditional maximization algorithm for maximum likelihood estimation are also presented. This model is used to analyze data from an infant habituation experiment, where it is desirable to assess whether infants comprise different populations in terms of their habituation time.     

Tests for time series of counts based on the probability-generating function

We propose testing procedures for the hypothesis that a given set of discrete observations may be formulated as a particular time series of counts with a specific conditional law. The new test statistics incorporate the empirical probability-generating function computed from the observations. Special emphasis is given to the popular models of integer autoregression and Poisson autoregression. The asymptotic properties of the proposed test statistics are studied under the null hypothesis as well as under alternatives. A Monte Carlo power study on bootstrap versions of the new methods is included as well as real-data examples.     

谈多媒体环境下的英语教学策略

依据教育学、心理学有关理论,从教学环节入手,探讨了英语教学在多媒体环境下的教学策略选择原则及相应英语教学策略,提出英语教学的整体筹划策略、信息输入策略、全息评价策略和重现巩固策略。     

网络环境下图书馆服务的变革

本文针对当前的网络环境,论述了图书馆读者工作在服务理念、服务方式、服务手段和内容方面的变革     

高新技术园区社会创新环境的系统整合

今天的高新技术园区在发展的意义上 ,已经成为现实的社会实体。从这一理念出发 ,思考园区的建设和发展 ,其创新环境是个非常重要的问题 ,也可以说它是各类高新技术园区得以发展的基本条件。创新环境状况的好坏直接关系到园区内高新技术产业的发展。从严格意义上讲 ,缺少这个基本条件 ,高新技术园区难以形成 ,创新环境不完善 ,即便是已经建立起来的园区 ,也难以得到真正的发展。由此决定了建设高新技术园区必须重视对园区社会创新环境的研究 ,通过精心培育创新环境 ,推动我国高新技术园区在 2 1世纪得到健康、持续的发展。     

风险投资与地方政府财政的作用定位

发展风险投资是推动高新技术产业加快发展、实现产业结构优化升级的重要途径。鉴于风险投资业在我国刚刚起步的现实 ,强调地方政府介入风险投资意义重大。近期地方政府介入风险投资应在资本配置中发挥重要作用 ;从长远来讲 ,地方政府应致力于相关制度环境建设 ,这方面的内容包括政策引导、制度环境支持以及法律保障等 ,以此创造有利于风险投资业大发展的社会环境     

中国区域投资环境评估指标系统的构建及综合评价方法

中国区域投资环境评估指标系统的主要缺陷和不足之处在于 ,对区域投资环境研究选择的指标太少 ,更难以建立一个科学的评价指标系统 ,评价方法也显得较为单一。目前应采取(专家 )综合评分法、层次分析法、因子 (素 )分析法、灰色关联法、信息熵法、聚类分析法等投资环境评估方法。从而实现对中国区域投资环境的科学认识