电多极矩与取矩点无关的条件

论述了电多极矩与取矩点选择的关系,给出了其与取矩点无关条件的证明。     

当代篮球比赛决胜时刻攻防技战术结构分析

篮球比赛中,最后决胜时刻攻守战术的选择和运动员技术的合理运用决定着比赛的胜负,也最终决定着球队成绩。最后决胜时刻的攻防技战术不仅仅是简单的战术配合和技术的运用,更是球队平时训练水平的真实写照。不仅是运动员在场上的较量,更是教练员智慧的角力。运用调查访问、录像观察、逻辑分析和实验设计等方法,通过对最后时刻攻防战术案例的分析,总结出了最后时刻攻防战术的规律和特征,形成了决胜时刻攻防战术理论,确定了时间和比分因素是影响篮球比赛最后关键时刻技战术运用的关键因素,暂停、掷界外球地点等因素为重要因素。对辅助中国男女篮比赛决胜时刻攻防技战术的运用,促进中国男女篮备战奥运和丰富篮球技战术理论具有重要的意义。     

基于Gaussian-Hermite矩和HVS的图像质量评价

提出一种基于Gaussian-Hermite矩和人类视觉系统（HVS）特性融合的图像全参考质量评价方法。正交矩在图像处理和模式识别方面有很重要的作用。图像的低阶矩能很好地表征图像的特征,可用于图像质量的准确评价。该方法首先通过计算两幅图像间连续正交矩能量差异获得低阶矩特征;然后,结合HVS的掩盖效应对图像的不同区域分配不同权重;最后,对图像所有分区的连续正交矩能量差进行加权平均得到图像质量分数。在国际通用的图像质量评价数据集中,对所提出的方法进行测试。实验结果对比表明,该方法具有很好的效果。     

女子单人蹦床着网技术的生物力学分析

对2000年全国蹦床冠军赛女子单人决赛前3名运动员完成自选动作的着网技术进行了详尽的分析。结果表明冠军运动员每次跳着网前身体姿势较好、着网缓冲与蹬伸压网时间比例较合理、对“最佳蹬伸瞬刻”的把握较恰当，且其压网深度曲线呈现高、低、高的总体变化趋势，这与硼床女子网上单人世界水平相一致；与冠军相比，亚、季军蹬伸压网与着网缓冲时间曲线存有较大波动，说明其着网技术有待于进一步改进；入网缓冲阶段3名运动员普遍存有蹬伸压网过早的毛病。     

动量矩定理及动量矩守恒定律在篮球投篮技术动作中的应用

本文运用运动生物力学分析法，对篮球投篮技术动作，特别是对投篮技术动作中投篮异侧手、腹部及下肢动作与投篮稳定性之间的关系进行了研究，得出了动量矩定理及动量矩守恒定律运用到篮球投篮技术中的一些规律，并对这些规律的具体动作方式进行了实例分析研究，其目的是规范投篮技术动作、丰富篮球教学与训练的理论和方法，促进篮球专项技术的发展。     

跳远起跳技术的动力学模拟

跳远起跳技术的运用在学界一直存有争议,为探讨跳远起跳技术的生物力学原理,选取跳远起跳动作作为研究对象,建立起跳动作的数学模型并在计算机上实施基于肌肉动力学层面的运动模拟。模拟结果表明:在增大人体重心垂直速度和重心的腾起角方面,膝关节肌较之髋关节肌都有更为显著的作用;在相同的着地距离下,增大小腿环节角与增大大腿环节角相比明显有利。     

Shoe collar height and heel counter-stiffness for shoe cushioning and joint stability in landing

ABSTRACT

This study examined the effects of shoe collar-height and counter-stiffness on ground reaction force (GRF), ankle and knee mechanics in landing. Eighteen university basketball players performed drop landing when wearing shoes in different collar height (high vs. low) and counter-stiffness (stiffer vs. less stiff). Biomechanical variables were measured with force platform and motion capturing systems. Two-way repeated measures ANOVA was performed with α = 0.05. Wearing high collar shoes exhibited smaller peak ankle dorsiflexion and total sagittal RoM, peak knee extension moment, but larger peak knee varus moment than the low collar shoes. Stiffer counter-stiffness shoes related to smaller ankle inversion at touchdown and total coronal RoM, but larger peak knee flexion and increased total ankle and knee sagittal RoM than the less stiff counter-stiffness. Furthermore, wearing stiffer counter-stiffness shoes increased forefoot GRF peak at high collar condition, while no significant differences between counter-stiffness at low collar condition. These results suggest that although higher collar height and/or stiffness heel counter used can reduce ankle motion in coronal plane, it would increase the motion and loading at knee joint, which is susceptible to knee injuries. These findings could be insightful for training and footwear development in basketball.     

Dynamics of submaximal effort soccer instep kicking

During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.     

110m栏攻栏腿最佳下压时机探讨

用文献参阅、录象资料观察和理论分析的方法研究了优秀运动员和普通水平运动员110m栏中蹬地腿和攻栏腿下压时机的配合,并将配合分为三种情况：1.蹬地腿离地瞬间攻栏腿继续上摆;2.蹬地腿离地前攻栏腿开始下压;3.蹬地腿离地的瞬间攻栏腿开始下压。结果表明：蹬地腿离地瞬间攻栏腿继续上摆,拉长了过栏时间,造成压栏过晚;蹬地腿离地前攻栏腿开始下压,造成跳栏,影响了水平速度;蹬地腿离地的瞬间攻栏腿开始下压是最佳的下压时机。希望通过该研究能给跨栏训练者提供一些理论参考。     

综合法快速绘制静定梁的剪力图和弯矩图

剪力图和弯矩图是工程力学中材料力学部分基本计算的重要内容之一,是准确确定梁危险截面的重要手段。综合法绘制剪力图弯矩图与其它方法相比,快速准确,易被学生掌握,值得推广．