Estimation of reaction forces in high bar swinging

Reaction forces experienced by gymnasts swinging on the high bar may be determined indirectly using inverse dynamics analysis or may be measured using strain gauges. The accuracy of inverse dynamics analysis may be poor because of errors in the estimated inertia parameters and in the accelerations obtained from digitized data. On the other hand the use of strain gauges is not always possible in elite competition. This paper presents a method for estimating the reaction forces based on the linear displacements of the bar. The bar was modelled as a point mass attached to horizontal and vertical linear springs (obeying Hooke’s law) with stiffness coefficients determined from static loading. The stiffness coefficients of the bar were determined with three different tensions in the stabilizing cables of the high bar. A force and video analysis of backward giant circles was performed. Estimates for the reaction forces were obtained by multiplying the bar displacements from the video analysis by the stiffness coefficients determined from the static loadings. Comparisons were made between the estimated reaction forces and the reaction forces recorded using strain gauges attached to the high bar. Varying the tension in the stabilizing cables of the high bar did not effect the stiffness of the bar. Root mean squared differences between estimated and recorded reaction forces were on average within 99 N for three ‘regular’ and three ‘accelerated’ giant circles. This was less than 3.5% of the range of forces recorded. The bar displacement method was able to estimate the peak reaction forces to within 7% on average, which compares favourably with 24% reported by Gervais (1993) using inverse dynamics.     

身体锻炼方式与中老年人信息加工能力的关系

182名受试者被分为3个锻炼组和1个对照组。3个锻炼组是:大极拳/剑组、导引养生功组和慢跑锻炼组。结果表明:1,积极锻炼者的心理健康指标明显优于不积极锻炼者;2,各积极锻炼组之间心理健康指标的差异不大;3,太极拳/剑锻炼对于中老年人数字广度的保持具有更积极的意义,表现为它见效快,所有负荷小,但如果坚持锻炼时间在6 a以上,则慢跑锻炼比太极和导引对数字广度的保持更为有效;4,身体锻炼对延缓心理衰老的积极作用,可能在于其对参与者注意和意识状态的有效调整。     

DZW-A型起跑反应时测定仪的研制及其在运动实践中的应用

反应时在运动实践中应用极为广泛,有经验的教师和教练员都用手动控制测定学生和运动员的反应时。根据心理学实验室中反应时测定仪的原理,研制出能在运动场上直接测定起跑反应时的DZW—A型起跑反应时测定仪。本仪器主要用于测定运动员起跑反应时和起跑教学中的反应时测定,测定的数据对于提高短跑速度专门训练效果、创造优异成绩和体育选材及改进体育专业起跑教学质量等提供了科学依据。     

离子反应的定量分析

通过对多种离子参加氧化—还原反应、多元弱酸(或酸式盐)与可溶性强碱反应的定量分析.归纳出离子反应方程式的正确书写与反应物的用量之间的对应关系.     

TiO_2/Al_2O_3复相催化酯化合成邻苯二甲酸二异辛酯

以苯酐和2-乙基己醇为原料,在自制的TiO_2/Al_2O_3复合型催化剂上合成邻苯二甲酸二异辛酯;确定了反应中催化剂的最佳配比及催化剂制备温度。考察了原料配比、催化剂用量、反应温度等工艺条件对酯化反应的影响。结果表明,该催化剂体系具有较好的催化活性,合成的DOP产品色相较好。     

配合物亲核取代的机理

配合物的亲核取代是常见的一类取代反应,通过亲核取代仅应的三种机理,即离解机理(D机理),缔合机理(A机理),交换机理(I机理)揭示亲核取代反应的本质。     

葡萄糖电还原反应机理的研究进展

综合论述了葡萄糖电还原反应机理的研究进展,着重介绍了Tse-chuan Chou建立的葡萄糖电还原反应机理及数学模型。     

起跑反应时对短跑成绩的影响

起跑反应时直接影响短跑比赛成绩,在短跑比赛中有许多运动员由于起跑不顺利,反应时过长而导致比赛失利。起跑反应迅速的运动员在枪声瞬间即刻起动就占了很大的优势,为比赛取得优异成绩奠定基础。起跑反应时的快慢除先天反应素质外,与起跑技术、机体状态、比赛环境密切相关,经过教学训练起跑反应时就能缩短。     

羽毛球运动员动作前情境的预判绩效及其差异性研究

选取16名羽毛球专业运动员和8名大学生初学者为被试,以羽毛球专项情境中对手即将回球的动作前情境为反应任务,来探讨运动员的预判绩效及其差异性问题.结果显示:(1)在动作前情境中,运动员存在明显的预判现象,预判能力随水平的提高而提高;(2)不同水平运动员的预判绩效差异主要表现在准确性上,反应速度差异不显著;(3)运动员的预判自信心和选择反应时对专项情境预判绩效没有显著性影响.     

浅谈运动训练中疲劳与恢复的运动生理过程

采用文献资料法,分析了人体疲劳产生的生理过程,提出了相应的恢复人体疲劳过程的方法与手段。研究表明,消除与恢复疲劳,对于提高运动成绩,增进健康有着十分重要的意义。