规范场论中引进协变导数的物理实质

一般认为粒子与场的相互作用是通过引进规范场实现的。其实，对自由粒子做局域规范变换，粒子就已被自动置于场的相互作用之中了。当使自由粒子整体规范变换向局域规范变换过渡时，场的相互作用发生了从“无”到“有”的变化，规范不变性遭到了破坏。通过协变导数引进规范场，虽然体现了粒子与场的作用，但那是让粒子恢复“自由状态”的抵消作用。     

网络信息流量测量仪技术研究

目前网络通信的计量计费主要采用基于电信运营商服务器端的软件集中计量计费方式。本文研究的“网络信息流量测量仪”,可适应用户端信息流量计费,连接在用户端计算机与电信网络之间,弥补了电信运营商统一后台计费方式存在的诸多缺陷。     

Validating the Implementation Climate Scale (ICS) in child welfare organizations

There is increasing emphasis on the use of evidence-based practices (EBPs) in child welfare settings and growing recognition of the importance of the organizational environment, and the organization's climate in particular, for how employees perceive and support EBP implementation. Recently, Ehrhart, Aarons, and Farahnak (2014) reported on the development and validation of a measure of EBP implementation climate, the Implementation Climate Scale (ICS), in a sample of mental health clinicians. The ICS consists of 18 items and measures six critical dimensions of implementation climate: focus on EBP, educational support for EBP, recognition for EBP, rewards for EBP, selection or EBP, and selection for openness. The goal of the current study is to extend this work by providing evidence for the factor structure, reliability, and validity of the ICS in a sample of child welfare service providers. Survey data were collected from 215 child welfare providers across three states, 12 organizations, and 43 teams. Confirmatory factor analysis demonstrated good fit to the six-factor model and the alpha reliabilities for the overall measure and its subscales was acceptable. In addition, there was general support for the invariance of the factor structure across the child welfare and mental health sectors. In conclusion, this study provides evidence for the factor structure, reliability, and validity of the ICS measure for use in child welfare service organizations.     

Phantom and big-fish-little-pond-effects on academic self-concept and academic achievement: Evidence from English early primary schools

The Big-Fish-Little-Pond Effect (BFLPE) suggests that school-average achievement has a negative effect on academic self-concept (ASC); some research has also verified a negative effect on students' academic achievement. Our study evaluates the compositional effects of school-average achievement on both outcomes, using a longitudinal sample of English early primary school students in Year 1 and Year 4. We provide evidence for BFLPEs in children as young as six to nine years of age. Further, we show that the BFLPE is a potential mechanism in the negative compositional effect of school average achievement in Year 1 on students' achievement in Year 4. Once adjustments for measurement error are made, the negative effect of school-average achievement on students' self-concept, and on their subsequent achievement, becomes even more negative. Our findings question previous research suggesting that attending a school with higher average achievement necessarily advances students’ outcomes.     

It Matters: Reference Indicator Selection in Measurement Invariance Tests

Conventional approaches for selecting a reference indicator (RI) could lead to misleading results in testing for measurement invariance (MI). Several newer quantitative methods have been available for more rigorous RI selection. However, it is still unknown how well these methods perform in terms of correctly identifying a truly invariant item to be an RI. Thus, Study 1 was designed to address this issue in various conditions using simulated data. As a follow-up, Study 2 further investigated the advantages/disadvantages of using RI-based approaches for MI testing in comparison with non-RI-based approaches. Altogether, the two studies provided a solid examination on how RI matters in MI tests. In addition, a large sample of real-world data was used to empirically compare the uses of the RI selection methods as well as the RI-based and non-RI-based approaches for MI testing. In the end, we offered a discussion on all these methods, followed by suggestions and recommendations for applied researchers.     

Getting Better All the Time? An Illustrative Investigation of Multilevel Longitudinal Measurement Invariance Based on School Climate Surveys

School climate surveys are central to school improvement and principal evaluation policies. The quality of school climate has been linked both to student achievement and to teacher retention. Oftentimes, policymakers and practitioners are concerned with monitoring change in school climate quality in each academic year. Such applications assume longitudinal factorial invariance—it is presupposed that the surveys are measuring the same things in the same metric at each time point. While there is considerable research examining the validity of inferences based on survey‐derived climate indicators, this research is almost exclusively based on cross‐sectional data. There is little literature describing procedures for gathering evidence of factorial invariance of school climate indicators. This study proposes to adapt existing methods for evaluating factorial invariance in longitudinal designs into multilevel frameworks, and in doing so, articulates a novel method for evaluating longitudinal measurement invariance in school climate research. This technique is illustrated on a widely used school climate survey.     

Self-concept in reading: Factor structure,cross-cultural invariance and relationships with reading achievement in an international context (PIRLS 2011)

Using data from 48 countries, this study investigated the factorial structure and tested the cross-cultural invariance of the PIRLS 2011 reading self-concept scale and its relationships with reading achievement. The study showed that a two-factorial structure of the self-concept scale in reading had the best fit with the data. Configural invariance and metric invariance were achieved, scalar invariance was not. The two dimensions ‘Perception of competence’ and ‘Perception of difficulty’ showed robust within-country correlations with reading achievement, especially the second one. At the country level, the ‘Perception of competence’ was negatively related with reading, illustrating the attitudes-achievement paradox: countries in which students on average reported a more positive self-concept performed lower. On the contrary, for the ‘Perception of difficulty’, the sign of the correlation remained the same at the within-country and at the country level.     

Multilevel Factorial Invariance in n-Level Structural Equation Modeling (nSEM)

We present a multigroup multilevel confirmatory factor analysis (CFA) model and a procedure for testing multilevel factorial invariance in n-level structural equation modeling (nSEM). Multigroup multilevel CFA introduces a complexity when the group membership at the lower level intersects the clustered structure, because the observations in different groups but in the same cluster are not independent of one another. nSEM provides a framework in which the multigroup multilevel data structure is represented with the dependency between groups at the lower level properly taken into account. The procedure for testing multilevel factorial invariance is illustrated with an empirical example using an R package xxm2.     

浅谈射影几何的优越性

从三个方面阐述了运用射影几何学中有关原理解决问题具有一定的优越性:可使证明过程简化;揭示内在联系;发现新结论,并举例说明该观点.     

300m跨栏跑丈量数据补缺

依据《田径竞赛规则》中栏架设置规定和相关田径理论,利用《标准田径场地十二点丈量法》中有关基准点计算出三种类型标准田径场地300m跨栏跑的放射丈量数据,弥补了目前该项目测量数据的空白,为体育教学、训练和竞赛场地测画工作提供参考依据.