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.     

跨栏教学中使用"软式跨栏架"的实践性研究

根据在跨栏跑教学中学生对跨栏跑学习普遍存在的恐惧心理现象,作者采用具有针对性地"软式跨栏架"的辅助教学法,结果表明:"软式跨栏架"教法能有效地克服跨栏跑教学过程中学生对跨栏跑存在的恐惧心理,提高学习兴趣和效率;有助于学生掌握跨栏跑技术和提高运动成绩.     

当前世界女子高低杠项目成套动作难度特征分析

以第39届世界体操锦标赛的女选手为研究对象，对新规则实施后世界女子高低杠发展特点进行研究。结果显示：成套动作的平均难度为6．638分，位居4项之首，仍有继续提高的空间；其中飞行动作的难度变化不大，连接价值提高；从低杠换握高杠大多以B组动作为主，从高杠换握低杠则以D组为主；上法开发了挺身跳起成低杠手倒立的D组难度，且有连接动作加难的趋势；下法动作继续呈现多样化特征：今后的主要任务是提高完成动作的成功率和动作质量，重点提高动作细节和下法的稳定性。     

第40 届世界体操锦标赛女子高低杠技术特征研究

采用文献资料法、录像观察与数理统计等方法,系统分析当今世界女子高低杠技术发展的新特征.发现:使用D组以上难度的两个或两个以上更多动作构成"两串以上"具有高连接价值的"直接"来获取连接加分,并促使高、低两杠动作完成更加紧凑、流畅和具有观赏性将是女子高低杠技术发展的主要趋向.其中,由低杠换握高杠的动作将加难,"扭掏"系列的高难度也将增多,而增加高难度的单动作和完成高连接价值的"四连接"还将是女子高低杠A分动作编排的新动态.     

背越式跳高过杆技术训练方法的研究

文章根据运动生物力学原理,揭示背越式跳高过杆技术的内在规律,引导和启发挖掘过杆技术的潜力。并通过对基层跳高运动员背越式过杆技术训练前后的对比研究,探讨提高跳高过杆技术的途径与方法。     

筋条部分开裂复合材料加筋板后屈曲性态的有限元分析

采用参考面单元技术并引入虚拟杆单元,建立筋条局部脱胶开裂复合材料梁／板结构后屈曲分析的有限元简化模型。着重研究不同开裂尺寸和位SLM置对复合材料层合加筋板后屈曲承载能力的影响。计算表明：开裂位置相同,开裂尺寸增加会导致后屈曲承载能力降低;开裂尺寸相同,随着其位置由筋条中心向端部移动,加筋板的后屈曲承载能力逐渐上升;值得注意的是,筋条端部开裂使加筋板的后屈曲承栽能力显著降低,其影响远大于筋条中心位置开裂。     

Bluebells and Bias,Stitchwort and Statistics

Infants are not too young to engage in real, useful statistical work. This activity allowed comparisons between distributions of two species of flowers in three different habitats.     

关于混凝土结构耐久性的探讨

本文通过总结影响混凝土结构耐久性的多种因素,提出了降低各因素影响的措施,强调了混凝土结构耐久性的重要性。     

单杠上人体摆动的凯恩动力学模型

理论建模是人们定量地认识客观事物的一种重要方法,通过动用多体动力学的凯恩方法,建立一个单杠上人体摆动的５环节多刚体系统模型,并以隐式方法推导出运动方程。该模型较国内外其他模型能够更加细致地分析单杠上人体摆动技术,并为其数值仿真奠定基础。     

男子体操三个单项成套动作起评分加分技巧的比较研究

国际体操联合会正酝酿不久的将来实行起评分突破 10分的做法。起评分的争夺将要进一步升级 ,在研究各种加分途径的基础上 ,对中外男子高水平运动员在自由体操、双杠、单杠三个项目上获得加分、提高起评分的途径和方法进行了比较研究 ,认为自由体操和双杠我国达到世界先进水平 ,单杠项目总体实力仍存在差距 ;我国选手一般采取同类动作的难度变化的办法加分 ,而外国选手采用的多样少量的办法有利于适应未来的变化发展