汇川H2U系列PLC之间RS-485通信的实现

主要研究了汇川公司H2U可编程控制器(PLC)的通信技术,实现了两个H2U系列PLC之间基于RS-485的通信,并详细介绍了PLC之间通信的硬件连接方式、通信串口参数配置、触摸屏画面的设计以及程序实现。所讨论的方法已在采用H2U PLC及辅助设备组建的"运动控制系统"课程的教学实验平台上进行了验证,可以拓展应用于多台H2U PLC之间以及其他设备与H2U PLC之间的RS-485通信实现,对工程应用具有一定的借鉴意义。     

当今世界男子鞍马成套加分动作结构编排特征与发展趋向

依据第28届奥运会体操比赛实况录像及2005年国际男子体操新评分规则变化的相关信息，采用调研访问法、录像统计法和文献资料法，分析世界男子鞍马成套加分动作结构编排的特征及发展趋向。采用纵向移位动作为主体，以多个高难动作的直接连接构成加分主干，并结合D组难度的下法，是鞍马成套动作结构编排的主要特征；而使用“D＋E”难度以上的多个动作“直接”和发展新“Flops规则”内容的单环高难度动作，将是未来大赛鞍马成套加分动作竞争的新内容。     

怎样求数列前n项的和

数列是高中数学的重要内容之一,也是高考必须的知识点,本文就数列前 n 项的求和问题作了较细的分类讨论。对掌握数列前 n 项求和问题有较大帮助。     

特殊级数↑∞∑↓（n=1） （-1）^（n-1）/（2n-1）^（2k-1）与π^（2k-1）的关系

根据傅立叶级数的性质，得到并运用数学归纳法证明了某一类特殊级数与π之间的关系。     

构建中国大型古籍书库——论四库类丛书的互补性

文章从内容、时间、版本和学术性诸方面阐述了《四库全书》、《续修四库全书》、《四库全书存目丛书》、《四库禁毁书丛刊》、《四库未收书辑刊》相互之间的互补性。     

国外常用实时软件系统比较

比较分析了国外9种实时软件系统的功能,包括交流功能、特有功能、用户界面、咨 询员界面、系统及培训信息等。     

红色经典与民族精神

一大批以红色经典小说改编的电视剧问世,引起人们的浓厚兴趣.其实,红色经典出现的新的热潮,绝对不是偶然的,因为,红色经典小说中贯穿着我们当今这个社会人们最需要的民族精神,蕴含着我们的民族魂.     

Proximal advantage in knowledge diffusion: The time dimension

This paper intends to explore the impact of geographic proximity on the diffusion of knowledge in the form of publication citations, and argues that codified knowledge is transmitted faster in proximity and is subject to similar geographic constraints as tacit knowledge. The geographic proximity advantage would be particularly relevant in the early stage of dissemination. We collected three sets of research articles published in 1990, 2000 and 2010 and compared the longitudinal citations they received domestically and from abroad. The study found that domestic citations accumulate faster and reach their peak much earlier than foreign citations, and the difference is most evident in the first few years after publication. The result shows that geographic proximity does play a role in the speed of knowledge diffusion and points to the network effect for citations. Those located closer to the knowledge origin would be exposed and react to publications faster due to the additional opportunities of research exchange and network.     

College course scarcity and time to degree

College students are taking longer to earn baccalaureate degrees now than ever before, but little is known about institutional factors that may contribute to this trend. In this paper we investigate an important institutional constraint—course scarcity—that we hypothesize may be associated with increased time to degree. We employ a unique administrative dataset from a large, moderately selective, public institution and use an instrumental variables approach, identifying off the random registration times assigned to students. Results suggest that course scarcity does not delay students’ graduation. We explore alternative explanations for our findings and discuss a variety of other factors correlated with time to baccalaureate completion.