Accelerated test system strength models based on Birnbaum–Saunders distribution: a complete Bayesian analysis and comparison

Several models for studies related to tensile strength of materials are proposed in the literature where the size or length component has been taken to be an important factor for studying the specimens’ failure behaviour. An important model, developed on the basis of cumulative damage approach, is the three-parameter extension of the Birnbaum–Saunders fatigue model that incorporates size of the specimen as an additional variable. This model is a strong competitor of the commonly used Weibull model and stands better than the traditional models, which do not incorporate the size effect. The paper considers two such cumulative damage models, checks their compatibility with a real dataset, compares them with some of the recent toolkits, and finally recommends a model, which appears an appropriate one. Throughout the study is Bayesian based on Markov chain Monte Carlo simulation.     

Missing item imputation for quality-of-life instruments with application to asthma quality-of-life questionnaires

There has been increasing use of quality-of-life (QoL) instruments in drug development. Missing item values often occur in QoL data. A common approach to solve this problem is to impute the missing values before scoring. Several imputation procedures, such as imputing with the most correlated item and imputing with a row/column model or an item response model, have been proposed. We examine these procedures using data from two clinical trials, in which the original asthma quality-of-life questionnaire (AQLQ) and the miniAQLQ were used. We propose two modifications to existing procedures: truncating the imputed values to eliminate outliers and using the proportional odds model as the item response model for imputation. We also propose a novel imputation method based on a semi-parametric beta regression so that the imputed value is always in the correct range and illustrate how this approach can easily be implemented in commonly used statistical software. To compare these approaches, we deleted 5% of item values in the data according to three different missingness mechanisms, imputed them using these approaches and compared the imputed values with the true values. Our comparison showed that the row/column-model-based imputation with truncation generally performed better, whereas our new approach had better performance under a number scenarios.     

The generalized log-gamma mixture model with covariates: local influence and residual analysis

In a sample of censored survival times, the presence of an immune proportion of individuals who are not subject to death, failure or relapse, may be indicated by a relatively high number of individuals with large censored survival times. In this paper the generalized log-gamma model is modified for the possibility that long-term survivors may be present in the data. The model attempts to separately estimate the effects of covariates on the surviving fraction, that is, the proportion of the population for which the event never occurs. The logistic function is used for the regression model of the surviving fraction. Inference for the model parameters is considered via maximum likelihood. Some influence methods, such as the local influence and total local influence of an individual are derived, analyzed and discussed. Finally, a data set from the medical area is analyzed under the log-gamma generalized mixture model. A residual analysis is performed in order to select an appropriate model. The authors would like to thank the editor and referees for their helpful comments. This work was supported by CNPq, Brazil.     

基于Logit模型的区域集镇系统需求分析及规模确定研究

集镇迁建并非简单的将集镇按照原规模从一个地方搬到另一个地方,集镇迁建规模的大小．应该根据迁入区的实际需求（需求规模）来确定,需求的大小主要取决于村民对集镇的选择行为,即越多的人选择到某个集镇进行活动,该集镇的需求规模越大,反之越小。影响集镇需求的因素很多,包括交通时间、交通费用、集镇服务种类、服务质量等,本文将其概括为广义费用和集镇效用（服务能力）,建立反映村民选择行为的Logit模型分析集镇需求情况,并将其应用于区域集镇系统布局优化中,以我国西部某地为例进行实证分析,反映搬迁前后一定区域内各榘镇需求规模的变化,同时计算出新集镇的需求规模,为集镇迁建规模的确定及其布局优化提供科学的参考。     

中国工业化进程中农村劳动力转移“中间力量模型”的构建

文章在借鉴“推一拉”理论的基础上,结合中国的实际情况,从影响劳动力转移的全过程出发．着眼劳动力转移的中间环节,构建农村劳动力转移的“中间力量模型”,时中国工业化进程中农村劳动力转移的影响因素进行了解释,并提出相应的对策建议。     

民族共生理论:散杂居民族关系及目标范示研究

本文以生物学中的共生理论为参照,基于生物共生理论的理念范畴和分析方法,结合生物共生理论在其他领域的研究成果,重点考察了我国散杂居民族的共生关系,并提供了民族共生目标范式以及实现途径.     

传统节日文化生存发展策略——写在传统节日法定化之后

当前,中国传统节日文化要得以生存与发展,有三个方面的工作是紧迫和重要的:提升对传统节日的"文化自觉",这是中国传统节日文化的生存之本,这方面媒体、学校教育、家庭、社区均有着重要的责任;重建传统节日的符号体系,在这方面,企业、商家和政府肩负着重要的使命;转换传统节日的参与模式,将封闭型的"血缘共同体参与模式"转换为适应现代生活的开放型的"业缘共同体参与模式",这对中国传统节日文化的生存与发展有着现实而又长远的意义,这方面,各类社会组织起着重要的作用.     

Evaluation of the impact of intervention programmes on education organisations: Application to a Quality Management System

This paper analyses the importance of evaluating the various components of the programmes or actions carried out by education organisations. It highlights the need to assess the impact of the intervention on the organisation and consider how changes are consolidated over time in interaction with the context. We propose an impact evaluation model and as an example have chosen the implementation of Quality Management Systems in schools. The paper analyses the results obtained in 40 schools in three regions (Spanish Autonomous Communities) with varying levels of implementation. The results show overall impact on these education centres as the teachers and management teams of the centres perceive it. This impact is more evident in some of the dimensions considered in the study than in others. The results also confirm the differences between regional contexts.     

Trajectory of problem behaviours of Korean adopted children: using piecewise hierarchical linear growth modelling

This study examined the trajectory of problem behaviours in domestically adopted children in South Korea as they aged. This study used the Panel Study on Korean Adopted Children's longitudinal, three‐wave data (2006, 2008 and 2010). Although data were collected at three time points, our data consisted of six time points, which covered the 5–10 years age range of the adopted children at the time of survey. One hundred sixty‐four children were included in the analysis, 75 of whom contributed to one time point, 74 to two time points and 15 to three time points. The trajectory of the problem behaviours of adopted children was examined using a piecewise hierarchical linear growth model. Because the initial exploration of the data suggested non‐linear changes in behaviour problems over time, we split the growth trajectory into two time periods: Time 1 (5–7 years) and Time 2 (7–10 years). A two‐rate model was used to estimate separate slopes for the two time periods. Results showed that the externalizing and internalizing problems of adopted children have different trajectories. Internalizing problems did not show significant changes after 5 years of age, while externalizing problems increased until 7 years of age and decreased significantly thereafter.     

Employee communication,job engagement,and organizational commitment: A study of members of the Millennial Generation

The purpose of this study was to explore the relationship between job engagement and two key components of employee-organization relationships (EOR). Findings from a survey of members of the Millennial Generation (N = 539) in the United States indicate that job engagement mediates the relationship between employee communication and organizational commitment. It is concluded that when employees are engaged in their work, their commitment to the organization is strengthened and the likelihood of them leaving the organization decreases. Furthermore, an argument is made in light of the study’s findings that engagement and commitment work in concert to strengthen EORs overall. To foster engagement, organizations should remove obstacles to internal information flow and provide ongoing feedback to employees about individual and organizational issues.