Factors influencing enrolment: A case study from Birth to Twenty, the 1990 birth cohort in Soweto–Johannesburg

Longitudinal studies offer significant advantages in rendering data commensurate with the complexity of human development. However, incomplete enrolment and attrition over time can introduce bias. Furthermore, there is a scarcity of evaluative information on cohorts in developing countries. This paper documents various strategies adopted to minimize loss to follow up and describes a retrospective analysis of a small group of families who were missed during initial enrolment and through several subsequent rounds of data collection of the Birth to Twenty (BT20) birth cohort in Soweto–Johannesburg, South Africa that began in 1990. A purposive case study approach was used, and 10 of the 119 families missed at enrolment were interviewed to investigate why these families were not enrolled into the study. The findings demonstrate that high mobility, both within urban areas and between urban and rural areas, are a major challenge for longitudinal studies in densely populated urban areas. In addition, enrolment was also affected by individuals changing their names, largely motivated to facilitate access to employment under Apartheid, as well as varying motivations for participating in research. Longitudinal studies in the developing country context must be mindful of the political, social and economic climate that influences enrolment and ongoing cohort maintenance.     

青年知识分子精神文化生活的困境与出路

成长起来的青年知识分子正处在中国社会的转型期,他们承受着比以往更大的生存与发展压力,其精神文化生活也因此出现了种种困境。对1312名青年知识分子的问卷调查表明,当代青年知识分子群体的精神文化生活存在对精神文化产品利用有限,精神文化活动内容单一,精神文化生活满意度低等问题。因此,完善公共文化服务体系,提升青年知识分子精神文化生活的地位非常重要。     

“蚁族”的群体特征、诉求与风险

在社会转型、城市化加速、高等教育改革的浪潮中,"蚁族"成为了新兴弱势群体。该群体失落、挫败感强,容易引发许多社会问题,成为社会和谐稳定的风险隐患。因此,应该高度重视"蚁族"问题,将其纳入社会援助范围,要对他们加强文化引导和人文关怀。同时,高校要加强对弱势学生的教育和培养,提升其综合竞争力。     

Post model-fitting exploration via a “Next-Door” analysis

We propose a simple method for evaluating the model that has been chosen by an adaptive regression procedure, our main focus being the lasso. This procedure deletes each chosen predictor and refits the lasso to get a set of models that are “close” to the chosen “base model,” and compares the error rates of the base model with that of nearby models. If the deletion of a predictor leads to significant deterioration in the model's predictive power, the predictor is called indispensable; otherwise, the nearby model is called acceptable and can serve as a good alternative to the base model. This provides both an assessment of the predictive contribution of each variable and a set of alternative models that may be used in place of the chosen model. We call this procedure “Next-Door analysis” since it examines models “next” to the base model. It can be applied to supervised learning problems with ℓ₁ penalization and stepwise procedures. We have implemented it in the R language as a library to accompany the well-known glmnet library. The Canadian Journal of Statistics 48: 447–470; 2020 © 2020 Statistical Society of Canada     

论新历史小说的话语意义与审美特征

本文从历史观念、导向、叙述形态三个方面切入文本,全面论证了新历史小说与传统小说的不同,从而总结出新历史小说的话语意义和审美特征。     

The burden of acting wise: sanctioned success and ambivalence about hard work at an elite school in the Netherlands

Sam and his classmates despise ‘nerds’: they say working hard in school makes a student unpopular, and that they purposefully do only the minimum to pass. Research suggests that such ‘oppositional’ attitudes are prevalent among working class students and/or ethnoracial minorities. Like most of his classmates, however, Sam is white, hails from a privileged background, and attends a selective school in the Netherlands. Deeply ambivalent about working hard and ‘acting wise’, Sam and the others constituting his adolescent society are thoroughly caught up in peer dynamics which sanction success and promote mediocrity. We link these anti-school peer dynamics to the institutional configuration of education in the Netherlands, characterized by rigid tracking at the end of primary school and non-selective universities: state structures and policies contribute to these privileged students’ rationale for ‘taking it easy’ and doing poorly in school.     

RFID技术在钢材质量追溯系统中的应用

文章首先简要介绍了无线射频识别RFID技术,探讨了现有的追溯方法在钢材质量管理中的局限性;然后．依据RFID的存储、跟踪、自动识别特性,在生产、运输、仓储、加工和使用等关键节点采集钢材质量属性信息,按操作顺序存储在RFID中;最后建立了一个贯穿于完整钢材供应链的质量安全控制体系,以支持从上游到下游的钢材质量追踪和从下游到上游的质量溯源。系统能有效实现钢材质量信息透明化管理,提升钢材使用工程质量。     

2000年以来天山北坡经济带县市经济差异时空特征分析

文章以天山北坡经济带内25个县（市）为研究对象,利用传统统计分析与GeoDa、Arc view软件相结合的方法,通过计算人均GDP的绝对差异和相对差异,探讨了天山北坡经济带区内经济差异的时间以及空间特征。研究表明：2000年以来天山北坡经济带区内县（市）经济绝对差异不断扩大,但相对差异在逐步缩小;总体经济差异在波动中下降,并且2008年以后主要是由三大区域之间的经济差异所造成;中部区域的经济差异在三大区域中最大,其差异主要是由乌鲁木齐市和克拉玛依市这两个地级市的经济发展水平远高于其他县市所引起;经济发达地区和经济落后地区的空间分异特征明显,经济发展水平高的地区基本分布在天山北坡经济带的中部,而经济发展滞后的县域大多集中在伊犁河谷地区;区内各县域经济在空间上呈现集聚性,空间经济差异在缩小。     

汉语报纸报道语体有标记主位研究

语体的功能是由语体的语言特征实现的。有标记主位作为小句信息结构的成分,具有实现报道语体的报道功能的作用。汉语报纸报道语体的有标记主位在词语类别、充当的语法成分以及功能类型上都有其自身的特点,这些特点体现了报道语体时效性、准确性、客观性的要求。CF有标记主位是值得重点关注的对象,它句法成分单一,下位语境功能类型与词语类别、新闻内容都有一定的相关性,具有突出焦点信息和语篇衔接与连贯的语用功能。     

Mixture Kalman filters

In treating dynamic systems, sequential Monte Carlo methods use discrete samples to represent a complicated probability distribution and use rejection sampling, importance sampling and weighted resampling to complete the on-line 'filtering' task. We propose a special sequential Monte Carlo method, the mixture Kalman filter, which uses a random mixture of the Gaussian distributions to approximate a target distribution. It is designed for on-line estimation and prediction of conditional and partial conditional dynamic linear models, which are themselves a class of widely used non-linear systems and also serve to approximate many others. Compared with a few available filtering methods including Monte Carlo methods, the gain in efficiency that is provided by the mixture Kalman filter can be very substantial. Another contribution of the paper is the formulation of many non-linear systems into conditional or partial conditional linear form, to which the mixture Kalman filter can be applied. Examples in target tracking and digital communications are given to demonstrate the procedures proposed.