产品方案设计与评价一体化系统集成技术

在产品设计过程中,方案设计与评价的系统集成是技术关键。以履带车辆设计评价集成为例,给出其设计方法,采用J2EE平台技术,实现基于Web的履带车辆设计评价一体化系统。管理员可通过web添加任意层次的评价指标和待评价的设计方案,Web服务器上集成了多种评价方法,专家可选择一种或几种方法对方案分别进行评价,采用VRML显示待评价的三维设计方案,专家可在线修改设计方案并加以评价。应用结果表明,使用本系统可有效提高设计效率。     

Web数据挖掘技术及其应用

Web数据挖掘是从海量Web信息资源中发现有价值信息的有效技术．本文就Web数据挖掘技术进行了简介,对Web数据挖掘中的关键技术、系统流程进行了阐述,指出Web数据挖掘的应用前景．     

When does an imperfect sampling frame produce more efficient estimators than a perfect frame?

The issue of when imperfect sampling frames can result in more efficient estimators of population totals than perfect frames is explored. Our analysis is based on an expression we call the difference score. We show how, when properly expanded it provides an illuminating basis for comparing a weighted estimator under an imperfect frame with that of a conventional estimator assuming the frame has been corrected. Specifically, the circumstances (i.e., population and frame characteristics) under which an imperfect frame results in estimates of population totals that are more precise than those from a perfect frame can in many cases be discerned by analytically examining the terms in the expansion of this difference score. In addition, a classification tree methodology was used to further explore circumstances under which imperfect frames result in more precise estimators. The results of this analytical study complement, strengthen, and in many cases explain those discovered in an earlier empirical investigation that lead to recommendations as to when to correct a frame or when to adjust for imperfection using a weighting methodology called the arc weight estimator.     

Patterns of practice: a reflection on the development of quantitative/mixed methodologies capturing everyday life related to water consumption in the UK

There is a growing body of research arguing the relevance of practice approaches to understand resource consumption, and to highlight alternative pathways to sustainability. These practice approaches offer an alternative conceptualisation of demand and have been demonstrated largely by qualitative research, particularly in the work on water and energy consumption in the home. However, these historical narratives and qualitative research have not, to date, lead to the development of quantitative or mixed methodologies that could potentially reflect the diversity of performances of practice across populations in a more systematic way. This paper reflects, critically, on one such attempt to scale a practice-based perspective into a quantitative survey on water consumption and practice in homes in the south and South-East of England. The use of quantitative and mixed methodology has substantial potential – from translating practice-based research to policy; developing indictors to track patterns of practices as they change over time; and the exploration of methodologies that reflect the bundling and coordination of practices associated with water use inside and outside the home. The benefits and utility of such a methodological approach are highlighted as cautions and future research directions.     

On the Problem of Compromise Allocation in Multi-Response Stratified Sample Surveys

In stratified sample surveys, the problem of determining the optimum allocation is well known due to articles published in 1923 by Tschuprow and in 1934 by Neyman. The articles suggest the optimum sample sizes to be selected from each stratum for which sampling variance of the estimator is minimum for fixed total cost of the survey or the cost is minimum for a fixed precision of the estimator. If in a sample survey more than one characteristic is to be measured on each selected unit of the sample, that is, the survey is a multi-response survey, then the problem of determining the optimum sample sizes to various strata becomes more complex because of the non-availability of a single optimality criterion that suits all the characteristics. Many authors discussed compromise criterion that provides a compromise allocation, which is optimum for all characteristics, at least in some sense. Almost all of these authors worked out the compromise allocation by minimizing some function of the sampling variances of the estimators under a single cost constraint. A serious objection to this approach is that the variances are not unit free so that minimizing any function of variances may not be an appropriate objective to obtain a compromise allocation. This fact suggests the use of coefficient of variations instead of variances. In the present article, the problem of compromise allocation is formulated as a multi-objective non-linear programming problem. By linearizing the non-linear objective functions at their individual optima, the problem is approximated to an integer linear programming problem. Goal programming technique is then used to obtain a solution to the approximated problem.     

An Analysis of the Game of Tennis

The American Statistical Association conducted a pilot study to develop methodology to conduct a nationwide evaluation of survey practices and the quality of survey data. This article is a report on the objectives and principal findings of that pilot study. In addition, the objectives of the nationwide study are presented.     

Measuring the impact of the Web: Rasch modelling for survey evaluation

In 2012, the World Wide Web Foundation launched for the first time the Web Index (WI), which combines the existing secondary data with new primary data to rank countries according to their progress and use of the Web. Primary data are gathered via a multi-country specifically designed questionnaire. The aim of our analysis is (1) to evaluate the measurement properties of the expert assessment survey and to provide survey designers with some insights into possible problematic questions and/or unexpectedly behaving countries and (2) to assess the experts’ perception of the state and the value of the Web. To do so the Rating Scale Rasch model is employed. Results show that about 10% of survey questions are detected as misfitting and need to be reworded. Possible reasons are: counter-orientation with respect to the WI polarity, difficulty in understanding the question's words or binary instead of the multiple response scale. Country analysis shows that no country can be considered as an outlier due to notable unexpected pattern of answers. Since the survey is to be expanded in future editions of the WI, the results of our analysis are very important in pin-pointing the questions most in need of refinement for the next edition of the Index.     

On Sample Allocation in Multivariate Surveys

The problem of a sample allocation between strata in the case of multiparameter surveys is considered in this article. There are several multivariate sample allocation methods and, moreover, several criteria to deal with in such a case. A maximum coefficient of variation of estimators of the population mean of characters under study is taken as the optimality criterion. This article contains a study on a group of the methods that are easy to implement and do not need complex numerical computation; however, they all are approximate. Five such methods are presented and compared using a simulation study. Finally, it is shown which methods should be considered when designing a survey in which the multivariate sample allocation is to be involved.