The effects of baseball bat mass properties on swing mechanics,ground reaction forces,and swing timing

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.     

背越式跳高弧线段助跑的生物力学分析及其技术特点

背越式的助跑速度突飞猛进提高的当今,使人体在弧线助跑过程中,获得一个既合理又适宜的内倾角度,从而加大腾起角,加快助跑速度,获得良好的起跳效果,以达到更理想的跳高成绩尤为重要。运用生物力学理论,对弧线助跑人体内倾角及其动作特点与助跑速度和圆弧半径等相关因素进行了分析和探讨,找出相关因素的内在联系,避免实践中片面地去追求内倾和加速,用于实践意义重大。     

论体操制动技术

本文研究了体操制动技术概念和分类,阐述了制动动作的技术原理、制动效果和训练原则,为体操基础理论的建设和制动技术的训练提供参考。     

修正的q-Stancu—Beta算子的加权统计逼近性质

基于q-整数的定义,引入了一类修正的q-Stancu—Beta算子,由算子的各阶矩量、中心矩量及加权光滑模结合统计逼近的概念,得到了算子的加权统计收敛定理,并研究了算子的局部逼近性质,得到了算子的局部逼近定理．     

飞碟双向“快打”技术探讨

射击飞碟双向项目曾是我国拿过奥运会金牌的拳头项目，但随着国际射联不断修改规则增加难，加上我国的飞碟双向缺少一整套先进技术理论的支持，与世界先进水平距离逐渐拉大。要改变现状，迎状赶上，必须实践快打技术，培养“快打型”选手，形成快速、简捷、流畅的技术风格，实践证明：“快打型”技术能更有效地发挥弹丸的效能；有利于克服变化靶、不规则靶的不利因素；有利于射手整体动作程序的完成，防止击发瞬间注意力分散，在实际训练中则要强调人枪结合的质量，将发展速度与提高命中率有效地结合起来，注意发射速度规律性的培养，大胆实践飞碟射击概略瞄准的概念。     

"陌生化"瞬间与摄影构图

“陌生化“是将熟悉的事物或景象,用人们不太熟悉的面孔呈现在观者面前,从而引起注意和思考,提高影像的传播效果;在当前摄影创作中这一技巧正被广泛采用,成为获胜的一大法宝.     

掷标枪最后用力过程中左腿技术的运动学分析

用高速摄影机现场拍摄,并通过用影片运动分析系统进行解析对掷标枪最后用力过程中左腿技术进行了运动学分析。研究结果认为,“交叉步”后加快左腿的前摆速度可以形成牢固的双支撑,对重心水平速度的保持与提高有重要作用,并能缩短最后用力的时间。左侧支撑技术是保证最后用力时动量传递和“鞭打”技术有效完成的重要技术环节,并影响着出手高度。     

对影响掷标枪最后用力阶段左侧支撑技术的因素分析

左侧支撑技术是掷标枪最后用力过程中的关键性技术,其重要作用和意义已在标枪教学和训练中引起广泛关注和足够重视.为此,着重从左腿支撑、左肩制动和左腿蹬伸三个阶段七个方面,对影响左侧支撑技术的因素进行全面分析和阐述,以期能为标枪教学和训练提供一些帮助和建议.     

基于边信息抗仿射变换的数字图像水印算法

设计抗几何攻击的图像水印算法是数字水印技术研究中的难点。仿射变换是典型的几何攻击,能够使目前大多数数字水印算法失效。基于带边信息的水印模型,本文提出了一种利用Zernike矩的抗仿射变换多比特图像水印算法。该算法将归一化图像的Zernike矩作为边信息,利用量化技术对的水印信息进行编码和嵌入。实验证明,本文提出的算法不仅具有很好的抗仿射变换和抗JPEG压缩的鲁棒性,而且具有较小的嵌入失真和较大的水印容量。     

The creative use of companion values in environmental education and education for sustainable development: exploring the educative moment

Our paper addresses the emergence and evolution of values in educational settings. It builds upon and extends earlier work on companion meanings to develop a theory of the creative use of companion values and meanings in education. The recognition of companion values in educational practices highlight epistemological, ethical, and aesthetic transactions that occur in ways we characterize as ‘other than modern.’ Introducing the idea of educative moments allows us to identify situations where value spheres interpenetrate and interrogate each other in the meaning-making of students and teachers. These moments occur when students suddenly experience companion meanings and values such that teacher and student must deliberate together rather than the teacher dictating some dominating epistemological, ethical, or aesthetic value. This way, it is possible to accommodate critical and creative reflection in education where new values can emerge or evolve. We illustrate the theory by empirical examples from classroom conversations.