关于Pro/E环境变量设置的探讨

在运用Pro/E设计软件将三维模型转换为工程图时,正确设置系统环境变量和工程图环境变量,可以快速绘制出符合我国国家标准的工程图。运用举例方法探讨Pro/E中由三维模型转化工程图时有关变量的具体设置,并使设置的变量在启动Pro/E的同时生效,从而提高绘制工程图的效率。     

四连杆变幅机构平衡重系统的优化设计

本文介绍了一种四连杆变幅机构平衡重系统的优化设计方法。它将该系统的设计归结为五维、5个目标函教、9个约束条件的数学模型,应用改进的随机方向法求该数学模型的最优解。经改进的随机方向法,对于解决机构类优化设计中经常出现的反正弦、反余弦函数变量值大于1的问题提出了笔者的看法。 文中进行了实例计算,其结果较用传统方法得出的结果有显著进步,可直接应用于实际生产。     

Effectiveness during ball screens in elite basketball games

Ball screens are one of the most frequently used tactical behaviour in elite basketball games. The aim of the present study was to identify their predictors of success related to time, space, players, and tasks performed. The sample was composed of 818 ball screens corresponding to 20 close games (mean differences in score of 3.1 ± 0.8 points) randomly selected from the playoff games of the Spanish Basketball League (2008–2011). Classification tree analysis (CHAID) was used to analyse which variable or combination of variables, better predicts effectiveness during ball screens. The main results allowed identifying interactions with dribbler actions after the screen and the orientation of the screen on the ball. The results showed no interaction with game quarter and quarter minute temporal-related variables in both analyses. The present findings allow improving coaches’ strategic plans that involve selecting the most appropriate offensive approach when performing ball screens.     

概率论中事件独立性的几个命题

为了充分应用概率论中事件独立性概念及相关性质,简化实际解题过程,文章采用随机变量的有关独立性性质,构造指示变量研究了事件的独立性,得到事件独立性的几个命题,并给予了数学证明,完善了教材中的独立性理论,方便了实际问题的解决。最后通过举例阐述了概率计算中事件独立性的重要性。     

A multi-criteria approach for the group assessment of an academic course: A case study

The present paper aims at proposing a structured methodology to evaluate the results of an academic training course addressed to postgraduate students. The evaluation process intends to identify the efficacy of an education course by means of a comparison between the general objectives and the results expected by the students. Since the evaluated aspects by the students, detected by means of questionnaires, are both quantitative and qualitative, the proposed methodology is based on the analytic hierarchy process (AHP). In order to facilitate the evaluation process, answers have been modelled by means of linguistic variables. In particular, different evaluation scales have been used and each one is characterized by different levels associated to different fuzzy numbers.     

学生个体差异:研究方法与基本结构

对课堂教学中学生个体差异的研究主要有两种方法:一是类型化研究,二是差异变量分析。其中差异变量分析是全面动态把握学生个体差异的较好方法。从影响学生学习的主体因素角度来分析,课堂教学中学生的个体差异主要包括基础性差异、动力性差异、操作性差异和方向性差异等四个方面,它们共同构成了课堂教学中学生个体差异变量的分析框架,为我们全面检视课堂教学中学生个体差异的真实状况提供了有效的检视工具。     

An NCME Instructional Module on Data Mining Methods for Classification and Regression

Data mining methods for classification and regression are becoming increasingly popular in various scientific fields. However, these methods have not been explored much in educational measurement. This module first provides a review, which should be accessible to a wide audience in education measurement, of some of these methods. The module then demonstrates using three real‐data examples that these methods may lead to an improvement over traditionally used methods such as linear and logistic regression in educational measurement.     

考虑遮挡的视频车辆跟踪

为了对遮挡情况下的运动车辆进行跟踪,提出一种基于分块的车辆跟踪算法。该算法将目标车辆以可重叠的方式划分为若干大小一致的子块。在分块的基础上估计所有子块的运动矢量,检测噪声运动矢量并进行调整,以减少运动矢量估计的误差,然后对子块进行移位以实现车辆跟踪。为了处理车辆间的遮挡现象建立了马尔可夫随机场描述子块之间的关系,利用欧氏距离定义块的邻域,并基于块的直方图构建能量函数,最后利用模拟退火法对能量函数进行优化,以对遮挡区域进行分割。实验结果表明,该算法能够对遮挡车辆进行准确跟踪。     

The effect of toxicity on COVID-19 news network formation in political subcommunities on Reddit: An affiliation network approach

Political polarization remains perhaps the “greatest barrier” to effective COVID-19 pandemic mitigation measures in the United States. Social media has been implicated in fueling this polarization. In this paper, we uncover the network of COVID-19 related news sources shared to 30 politically biased and 2 neutral subcommunities on Reddit. We find, using exponential random graph modeling, that news sources associated with highly toxic – “rude, disrespectful” – content are more likely to be shared across political subreddits. We also find homophily according to toxicity levels in the network of online news sources. Our findings suggest that news sources associated with high toxicity are rewarded with prominent positions in the resultant network. The toxicity in COVID-19 discussions may fuel political polarization by denigrating ideological opponents and politicizing responses to the COVID-19 pandemic, all to the detriment of mitigation measures. Public health practitioners should monitor toxicity in public online discussions to familiarize themselves with emerging political arguments that threaten adherence to public health crises management. We also recommend, based on our findings, that social media platforms algorithmically promote neutral and scientific news sources to reduce toxic discussion in subcommunities and encourage compliance with public health recommendations in the fight against COVID-19.     

基于口令的高效语义安全群密钥交换协议

现有的基于口令的群密钥交换协议大都借助分组密码算法和Hash函数确保协议的安全性. 本文仅借助Hash函数,构造了一种高效、可证明安全的协议. 该协议在随机预言模型下是语义安全的,并能对抗离线字典攻击. 与相关工作比较,本文设计的协议具有更高的计算效率.