Trunk axial rotation in baseball pitching and batting

The purpose of this study was to quantify trunk axial rotation and angular acceleration in pitching and batting of elite baseball players. Healthy professional baseball pitchers (n = 40) and batters (n = 40) were studied. Reflective markers attached to each athlete were tracked at 240 Hz with an eight-camera automated digitizing system. Trunk axial rotation was computed as the angle between the pelvis and the upper trunk in the transverse plane. Trunk angular acceleration was the second derivative of axial rotation. Maximum trunk axial rotation (55 ± 6°) and angular acceleration (11,600 ± 3,100 °/s²) in pitching occurred before ball release, approximately at the instant the front foot landed. Maximum trunk axial rotation (46 ± 9°) and angular acceleration (7,200 ± 2,800 °/s²) in batting occurred in the follow-through after ball contact. Thus, the most demanding instant for the trunk and spine was near front foot contact for pitching and after ball contact for batting.     

基于动态研究的新课改后各类教材特点的比较

随着基础教育课程改革的逐步深入,教材多样化的趋势越来越明显,中小学教材的品种也越来越多,促进了中小学教材质量的提高,但也出现了重复编写同一水平、同一层次教材的现象。对国内各学科有代表性的教材从学生的学习和发展、对教师教学组织的影响、教师或学生对教材的评价三个维度进行动态比较研究发现,各版本新课标教材都能不同程度地体现新课标要求,追求以学生为本,重视探究活动,强调过程与方法等;各版本新课标教材各有优劣,都有修订和改进的空间,主要问题集中在内容容量不当,难度过大,对学生个体差异性、学校差异性以及地区差异性考虑得不够,各个学段之间缺乏有效衔接等方面,教材编制者应当互相借鉴。     

湖南媒介环境与长株潭"一体化"宣传策略探析

长、株、潭经济一体化(以下简称“一体化”)的宣传工作涉及到一个如何充分利用湖南媒介资源,最大限度地扩大“一体化”影响,创造良好的内外部环境的问题。根据以往“一体化”宣传工作的成效与不足,应当应用传播学和管理学的基本原理,针对湖南媒介资源的基本状况,探讨大众传播特征的变化趋势,加大“一体化”宣传的工作力度。从资源配置角度研究宣传工作的基本策略。     

从中都(燕京)到南京(汴京):金王朝的最终覆亡(续)

蒙古势力从13世纪初崛起于蒙古草原后,即开始南向进攻金的控制区,随着力量的不断增强而步步进逼.而此时的金朝,由于制度体系的变化、军事能力的衰退和官场习气的败坏等因素的作用,迅速步入衰微阶段.金宣宗贞祐三年(1215年)的中都沦陷和金哀宗天兴二年(1233年)的南京陷落,成为金朝衰亡过程中最后二十余年的重要界碑.