A fractal approximation algorithm for inverse initial-value problems of nonlinear differential equations

1. Introduction Initial-value problems (IVP) for the differential equations are often confronted with in many fields of science, and are particularly common in engineering. These problems are characterized by a governing differential equation and its associated initial conditions. Methods for solving direct IVP have been known for many decades in the area of differential equation. A few of the more popular methods of solution have proven to provide sufficient and even efficient mechanisms …     

Hip joint kinetics in the table tennis topspin forehand: relationship to racket velocity

The purpose of this study was to determine hip joint kinetics during a table tennis topspin forehand, and to investigate the relationship between the relevant kinematic and kinetic variables and the racket horizontal and vertical velocities at ball impact. Eighteen male advanced table tennis players hit cross-court topspin forehands against backspin balls. The hip joint torque and force components around the pelvis coordinate system were determined using inverse dynamics. Furthermore, the work done on the pelvis by these components was also determined. The peak pelvis axial rotation velocity and the work done by the playing side hip pelvis axial rotation torque were positively related to the racket horizontal velocity at impact. The sum of the work done on the pelvis by the backward tilt torques and the upward joint forces was positively related to the racket vertical velocity at impact. The results suggest that the playing side hip pelvis axial rotation torque exertion is important for acquiring a high racket horizontal velocity at impact. The pelvis backward tilt torques and upward joint forces at both hip joints collectively contribute to the generation of the racket vertical velocity, and the mechanism for acquiring the vertical velocity may vary among players.     

我国体育科学研究地图——基于知识图谱的CSSCI（2009年）文献计量分析

运用词频分析法、社会网络分析法和知识图谱等方法,对CSSCI（2009年）数据库体育科学来源期刊的2 319篇文献,从期刊载文量及出版周期、各地区的发文量及合作关系、研究机构、作者发文量及合作网络、关键词及研究热点、基金分布、引文状况等方面进行了全面系统的统计和分析,绘制出了中国体育科学研究一系列的地图。从可视化的角度揭示了中国体育科学研究的现状。     

国内数字化作品版权保护的研究态势——基于文献计量的科学知识图谱分析

通过文献计量分析方法对中国学术期刊网络出版总库1996年至2011年的数字化作品版权保护论文进行研究,分析了论文的年代分布、期刊分布、学科分布、基金分布、高影响力论文等,利用文献可视化工具画图探讨了我国数字化作品版权保护的研究热点,并得出该领域的研究前沿.     

基于网络共链分析和共词分析的国际银行业竞争态势研究

网络共链分析和共词分析是网络时代探讨企业竞争关系结构的有效方法。以国际顶尖的银行企业为实证对象,综合应用两种方法研究国际银行业的竞争态势。并利用共词分析获取高质量的博客信息源,通过深层次的内容分析探讨竞争格局变化的原因和走向。研究结果表明,检索词的选择、数据源的覆盖范围、检索工具的语言种类等因素均对分析结果有显著的影响。与共链分析相比,共词分析具有数据来源丰富,研究数据具有时序性,可进行深度的内容挖掘等显著优势,但在基本原理和方法论的研究上亟待加强。网络共链分析和共词分析是互补的关系,应当结合起来使用。     

线性映射的零空间与值域的若干性质

本文讨论了数域F上向量空间上线性映射的零空间和值域的一些性质,证明了秩与零度定理,并研究了n维向量空间V上的两个线性变换的零空间和值域之间的关系。     

从读者感兴趣区域看当前国内测绘期刊的发展趋势

以测绘期刊<武汉大学学报·信息科学版>为例,从读者感兴趣区域出发,对读者信息和读者需求进行分析,并根据测绘期刊现状讨论测绘类刊物要真正实现为读者办刊的理念,占领国内外市场,必须做好的工作,以及测绘期刊的发展趋势.     

Estimation of Controlled Direct Effects in the Presence of Exposure-Induced Confounding and Latent Variables

Estimation of the direct effect of an exposure on an outcome requires adjustment for confounders of the exposure–outcome and mediator–outcome relationships. When some of the latter confounders have been affected by the exposure, then standard regression adjustment is prone to possibly severe bias. The use of inverse probability weighting under so-called marginal structural models has recently been suggested as a solution in the psychological literature. In this article, we show how progress can alternatively be made via G-estimation. We show that this estimation method can be easily embedded within the structural equation modeling framework and could in particular be used for estimating direct effects in the presence of latent variables. Moreover, by avoiding inverse probability weighting, it accommodates the typical problem of unstable weights in the alternative estimation approaches based on marginal structural models. We illustrate the approach both by simulations and by the analysis of a longitudinal study in individiduals who ended a romantic relationship. In this example we explore whether the effect of attachment anxiety during the relationship on mental distress 2 years after the breakup is mediated by rumination or not.     

解析PKS背诵模式的认知优势——基于思维导图和词块的应用

PKS背诵模式从语言学和认知心理学的角度对背诵重新解析.该模式以词块为关键词作为背诵的基本单位,以图片表达词块帮助学习者形成视觉映像,利用思维导图管理词块,再辅助以视听读结合的输入方式,寓背诵于娱乐,激发学习者的学习动机,提高背诵效率.PKS背诵有着强大的认知优势,词块可以清除理解障碍,思维导图可以促进背诵图式的建构,二者结合拥有强大的助记功能.该模式的应用有利于培养学习者的想象力和自主学习能力.     

基于SNA的我国期刊论文客家研究主题分析

社会网络分析方法为学科和领域的综述研究提供了一个新的研究方法,通过社会网络分析进行分析,可以从社会网络的视角了解我国客家研究类期刊论文在研究主题的现状和特点。研究结果揭示,我国期刊论文中的客家研究主题较松散,研究不是非常成熟和深入;客家山歌、客家文化等研究主题是我国期刊论文中客家研究的热点;高频词共词网络存在126个1-派系众多但规模小,表明期刊论文中的客家研究广度还不够,但在客家山歌、客家文化、赣南客家、客家民系、客家人等方面的研究比较深入。