Measuring Career Mobility: An Empirical Comparison of Six Mobility Indexes

The current paper presents six indexes that can be used to characterize the course of a career during a particular time interval, respectively, (1) the total number of transitions during that interval; (2) the number of positive transitions; (3) the number of negative transitions; (4) the subtraction of the number of negative transitions from the number of positive transitions; (5) the relative uncommonness of the transitions; and (6) the subtraction of the number of negative transitions from the number of positive transitions, weighted by their uncommonness. Advantages and disadvantages of these six indexes are discussed. Further, an empirical example is presented that draws on data from a sample of 357 employed Dutch youth. Finally, our approach is compared to previous approaches (event-centered methods, such as survival analysis, and career-centered methods, such as clustering techniques). It is concluded that our simple approach complements these other approaches well.     

中外合资企业合资模型选择的案例研究

随着经济发展的全球化,合资企业这一组织形式逐渐备受瞩目。经验证据表明,合资企业的失败率相当高,其中一个重要的原因就是合资模型的选择不当。本文首先阐述了Killing合资模型的三种类型,然后回顾了管理控制权与合资企业绩效关系的有关理论,最后以乐山—菲尼克斯公司为例,分析了其优势方管理合资模型的选择背景和过程,并阐明了该合资模型的优越性。     

Multilevel Analysis of Repeated Measures Data

Hierarchically structured data are common in many areas of scientific research. Such data are characterized by nested membership relations among the units of observation. Multilevel analysis is a class of methods that explicitly takes the hierarchical structure into account. Repeated measures data can be considered as having a hierarchical structure as well: measurements are nested within, for instance, individuals. In this paper, an overview is given of the multilevel analysis approach to repeated measures data. A simple application to growth curves is provided as an illustration. It is argued that multilevel analysis of repeated measures data is a powerful and attractive approach for several reasons, such as flexibility, and the emphasis on individual development.     

Longitudinal Surveys and the Study of Occupational Mobility: Panel and Retrospective Design in Comparison

The paper discusses the extent to which longitudinal surveys are able to expose occupational mobility and the dynamics of these processes. It compares two survey designs: the repeated panel design and the retrospective life history design. This comparison details the strength and the weaknesses of the two designs. The paper particularly calls attention to the unique features of the two designs with respect to the exploration of occupational mobility – pointing to three general problems of quantitative social research: item-nonresponse, design effects of single and multi-measurement occasion, and the strong assumption that researchers and respondents share the same definition of concepts. The main conclusion of the paper is that both designs offer unique opportunities to study social change, yet the differences between the two should be kept in mind when choosing the data set for particular research questions.     

Discrete Response Multilevel Models for Repeated Measures: An Application to Voting Intentions Data

Repeated measures data can be modelled as a two-levelmodel where occasions (level one units) are grouped byindividuals (level two units). Goldstein et al. (1994)proposed a multilevel time series model when theresponse variable follows a Normal distribution andthe measurements are taken with unequal timeintervals. This paper extends the methodology todiscrete response variables. The models are applied toBritish Election Study data consisting of repeatedmeasures of voting intention.     

Occupational Careers and Longitudinal Data: Tools and Perspectives of Research

Over the last years, the start of an increasing number of longitudinal researches and the development of suitable techniques of analysis have made possible the study of an increasing number of questions about social mobility and individual careers. Yet there is not just one way to face the study of careers. For the richness of the information they contain, longitudinal data offer the possibility to carry out different types of analysis according to the different questions of research. In this article four different approaches to the study of work-life careers will be introduced. The objective is twofold. On one hand, the study intends to offer a brief introduction to the most recent and sophisticated techniques that can be used for the analysis of careers. On the other hand, the article aims to point out the theoretical contribution that each technique can give to the debate on social mobility. The main potentialities and limits of the techniques will be stressed too.The techniques introduced in this article represent a fruitful approach for the study of work-life histories and occupational careers. Nevertheless they can be used for the analysis of all kinds of social careers.     

汽车电脑检修方案浅析

汽车电脑在目前和未来汽车维修中所占比例逐渐扩大,介绍汽车电脑的工作原理,分析并制定正确的维修方案,应做到从电脑硬件和电脑软件分开检修,电脑本体到外围电路分开检修,综合分析故障原因并把握正确的检修思路,提高工作效率。     

基于Excel的金属电子逸出功测量数据分析和管理系统设计

结合金属电子逸出功的测量实例,设计了一套基于Excel数据分析和管理系统.实践表明,该系统快捷、简明、直观,完全可以比拟常见的实验教学仪器随机附带的处理软件.此种设计方法具有推广价值。     

Testing a linear dynamic panel data model against nonlinear alternatives

The most popular econometric models in the panel data literature are the class of linear panel data models with unobserved individual- and/or time-specific effects. The consistency of parameter estimators and the validity of their economic interpretations as marginal effects depend crucially on the correct functional form specification of the linear panel data model. In this paper, a new class of residual-based tests is proposed for checking the validity of dynamic panel data models with both large cross-sectional units and time series dimensions. The individual and time effects can be fixed or random, and panel data can be balanced or unbalanced. The tests can detect a wide range of model misspecifications in the conditional mean of a dynamic panel data model, including functional form and lag misspecification. They check a large number of lags so that they can capture misspecification at any lag order asymptotically. No common alternative is assumed, thus allowing for heterogeneity in the degrees and directions of functional form misspecification across individuals. Thanks to the use of panel data with large $N$ and $T$, the proposed nonparametric tests have an asymptotic normal distribution under the null hypothesis without requiring the smoothing parameters to grow with the sample sizes. This suggests better nonparametric asymptotic approximation for the panel data than for time series or cross sectional data. This is confirmed in a simulation study. We apply the new tests to test linear specification of cross-country growth equations and found significant nonlinearities in mean for OECD countries’ growth equation for annual and quintannual panel data.     

浅谈基于Web环境的系统软件数据安全

在信息化时代,种类丰富和功能日益强大的系统软件能够满足人们个性化、全方位的需求,但是系统软件的极大丰富,使其安全性面临着极大的威胁和挑战。数据安全问题直接影响着软件的性能以及软件用户的信息安全。本文简要分析了基于web环境的系统软件所面临的几个安全问题,对系统的数据安全进行了较深入的需求分析,并探讨系统软件数据安全的具体防护策略。应用数据加密技术和理论能够更好地保证数据的安全性。     

合约变异在测试数据优化中的研究及应用

软件测试是保证Web服务质量的重要技术手段,测试数据生成是Web服务测试的重要内容,而生成的初始测试数据量大,数据冗余,为了减少初始测试数据数量,提高测试数据的有效性,本文在变异测试方法的基础上,使用合约变异方法对初始测试数据进行优化,据此可以生成一批达到一定变异充分度的有效测试数据,并通过实验验证了方法的有效性。