在线协作学习对感知学习的影响

在线学习环境缺乏人际交互的缺点在一定程度上决定了在线学习需要依靠学习者之间的交流和协作才能维持。对于在线学习的实际成效,研究者已经开发了不同的测量工具和评价方法来对其进行测量,但由于这些工具和方法之间缺乏内在一致性,使得针对学习的直接测量十分困难,因而感知学习常被用作反映学习的指标,也被视为衡量网络教学成功的重要标志之一。影响感知学习的变量很多,既有个体层面的,也有小组层面的。以天津职业技术师范大学本科生参与的网络课程“远程教育学”为例,运用逐步回归方法进行的实证研究表明：个体层面的变量——个体的协作学习态度、与熟人的交流能力,小组层面的变量——小组任务的相互依赖、小组任务的有效分配以及社会临场感都会显著影响学习者的感知学习。     

氧化还原滴定中等当点电位及在突跃线上位置的讨论

本文探讨氧化还原滴定中,两个半反应得失电子数n值对等当点在滴定曲线上位置的影响。     

广义回归神经网络在全国高技能人才需求中的应用研究

广义回归神经网络(GRNN)克服了BP神经网络运行中收敛速度慢且局部极小的不足,正逐渐被应用到货运量、农业需求及煤炭需求方面。引入GRNN对全国高技能人才需求进行预测检验,并从5个角度将其与GM(1,1)模型的输出结果做对比分析。结果表明GRNN模型具有优异的预测性能,验证了把该模型引入高技能人才需求这一新领域是有效可行的。为今后进一步定量研究有关高技能人才需求方面提供一种新方法。     

社会科学背景下因果推论的统计方法

如何根据非随机数据估计变量间的因果关系是社会科学研究中一个迫切的方法论问题。上世纪70年代,Rubin等人指出因果问题本质上是一个反事实的问题,认为某些统计方法可保证混淆变量和分组安排独立,并将这种方法推广到观察数据的分析中。倾向分数、工具变量和回归间断点是三种常用的方法,其中倾向分数居核心地位。以实际数据为例建立计算倾向分数的logistic模型,报告了模型的整体检验、预测变量的显著性检验和多重共线性检验、建立匹配组和分析结果报告。     

How can we evaluate the effectiveness of grammar schools in England? A regression discontinuity approach

Previous research evaluating grammar school effectiveness has generally relied on snapshot or longitudinal regression models to deal with pre-existing differences between grammar school pupils and those in non-selective schools. These passive designs are based on correlations, and cannot demonstrate clear positive causal relationships between grammar school attendance and subsequent attainment. After accounting for the variables available for the analysis, pupils in different schools might still have distinct and unmeasured characteristics which threaten the validity of any conclusions drawn. Given that a randomised trial is not feasible under current conditions, this study addresses the limitations of previous research, using a regression discontinuity design (RDD) approach. This is the first use of RDD to attempt to make a robust causal inference about the effectiveness of grammar schools in one local authority in England. However, the authority, the Department for Education and the schools would not provide the individual data on pupils’ 11+ entry test scores, and the scores obtained could not be uniquely matched to Key Stage 4 outcomes. While the model presented suggests that there is an advantage to grammar school attendance, the incomplete data means that the study is more a feasibility trial of this strong design than any kind of definitive test intended to settle the debate on grammar school effectiveness. Conducting this design with national data on grammar school selection would create the most powerful evidence so far. To promote an effective and equitable education system for generations to come, those advocating the expansion of grammar schools should make the responsible decision to disclose all grammar school selection data for the purposes of research.     

生命发展的非连续性及其教育--兼论博尔诺夫的非连续性教育思想

生命的发展是连续性和非连续性的统一,但以往教育学对人的发展的研究,注重的是发展的连续性,忽视了发展的非连续性.针对这一缺陷,本文论述了生命发展非连续性的原因以及它的教育形式,重点评述了博尔诺夫的非连续性教育思想.     

走出困境:中学教育研究的路径选择

中学教育研究要根据教育的实践本性,意识到当前教育研究在理论研究、实践研究和方法论研究方面的困境,用生成性思维深入探究新课改中为什么教、怎样教和怎样评的问题,在实践研究中建构新课程的教学模式.     

Dynamic instability of tunnel in blocky rock mass

The displacements and geometry of the rock blocks and the properties of the rock struc-ture play an important role in the stability of tunnels.Based on the key block model,the dynamic instability analysis of underground tunnel subjected to intensive short-time compressional wave was conducted.The instability of the tunnel caused by the spallation and the inertial effect was distin-guished.And the influence of the roof contour curvature of tunnel was also determined.     

Constitutive Laws of the Underground Opening Collapse due to Dynamic Load

The constitutive laws of the collapse of underground openings in a rock massif were in-vestigated based on the results of laboratory and field experiments, and computations using ana-lytical and numerical models. It is shown that the principal mechanism of failure of underground openings over important for practice peak particle velocity amplitude range of 1 to 10 m/s is the roof and wall breakage due to the fall of key blocks. Over this load range the material crushing is of considerably less importance. The geometry of discontinuities influences mainly the stability of key blocks. Further caving depends weakly on block structure of near-tunnel zone. The mean volume of fall material is a rather stable quantity for rock massifs of different structures. Lower tunnel sta-bility in the zones of high fracturing is caused by a higher probability of the presence of the unsta-ble key blocks and the decrease of strength characteristics of fractured bounding blocks. The de-crease of average block size is a less important accompanying factor.     

一类污染数据回归模型参数的最大似然估计及若干不变性

摘要 本文研究一般的线性回归模型的观测向量受到一种污染时未知参数的最大似然估计,并讨论了若干用于统计推论的统计量在污染下的不变性。不变性的研究提示我们,在何种统计推断中可无视污染的影响。