游泳运动员负荷后不同姿势放松游对血乳酸清除的影响

我们通过实验发现 :负荷后采用非主项姿势放松游血乳酸清除速率明显高于主项姿势放松游 (P <0 .0 5 -0 .0 1 ) ,说明负荷与放松之间姿势的转换 ,改变了原负荷肌群的负荷强度 ,并动员了非负荷肌参与活动 ,从而提高了放松活动效果。     

风速对划船运动成绩的影响

本文讨论了赛艇、皮划艇裸船的阻力构成,不同重量的运动员对阻力的影响,根据不同重量运动员的上体投影面积,在顺风或逆风下,不同风速对赛艇、皮划艇船速有较大影响。     

单人皮划艇500 m竞速结构与竞赛策略研究

通过对我国优秀皮划艇运动员测试数据的分析,提出了基于桨频曲线转折点的皮划艇500 m比赛竞速结构划分方法;根据全程桨频和船速的变化特点,对每个阶段重新命名,更准确地反映了皮划艇500 m竞速规律;冲刺阶段桨频的增加并不一定意味着船速的提高,船速是否增长取决于平均桨力,它才是船速的最终决定因素;对世界大赛中分段成绩的进行对比分析;以我国划艇运动员杨文军参加世界大赛成绩为例,说明了竞赛策略的重要性。     

论“加速度”式英语教学模式的理论与实践

在加速度存在的情况下,速度随着时间增加而加快。而在中国目前的英语教学中,每一个阶段和每一类语言知识讲授几乎都是采用同样的节奏和方式逐一进行,忽视了"加速度"的存在。针对英语课堂教学中的这些问题,构建一种全新"加速度"式的英语教学模式。在理论上,要明确"加速度"英语的本质和应用范围,要统一和明确教学目的,要建立"学而思,思而用"的教学方式,创造性地教与学。在教学实践中,典型例子法、数学模型法、逆向思维法、英汉对照法在一定程度上能促进学生创造性思维能力的发展。     

The influence of the hand’s acceleration and the relative contribution of drag and lift forces in front crawl swimming

The aim of this study was to assess the effect of the hand’s acceleration on the propulsive forces and the relative contribution of the drag and lift on their resultant force in the separate phases of the front crawl underwater arm stroke. Ten female swimmers swam one trial of all-out 25-m front crawl. The underwater motion of each swimmer’s right hand was recorded using four camcorders and four periscope systems. Anatomical landmarks were digitised, and the propulsive forces generated by the swimmer’s hand were estimated from the kinematic data in conjunction with hydrodynamic coefficients. When the hand’s acceleration was taken into account, the magnitude of the propulsive forces was greater, with the exception of the mean drag force during the final part of the underwater arm stroke. The mean drag force was greater than the mean lift force in the middle part, while the mean lift force was greater than the mean drag force in the final part of the underwater arm stroke. Thus, swimmers should accelerate their hands from the beginning of their backward motion, press the water with large pitch angles during the middle part and sweep with small pitch angles during the final part of their underwater arm stroke.     

三轴加速度传感器系统在运动技术分析领域的研究与应用

为满足在运动训练过程中的人体三维空间技术特征研究的需要,开发一套三轴向加速度传感器系统.该系统由下位机和上位机两部分组成,其中下位机部分由加速度传感器、传感器拾取单元、数据处理单元、电源监测与保护单元和无线传输单元组成,上位机部分由数据采集和分析软件组成.该系统具有四通道同步采集功能,结合同步视频,可对运动员的肢体关节、比赛训练器械等技术组成要素进行运动学和动力学参数进行实时采集与分析.以体育训练中常用的杠铃深蹲训练为实验性应用领域,对速滑和举重两种项目的杠铃深蹲训练进行技术分析,通过对三轴加速度传感器采集数据的分析,找出不同项目间杠铃深蹲动作技术的特征与差异,为今后深入开展加速度传感器系统的开发与相关应用提供研究基础.     

Knowledge of bout duration influences pacing strategies during small-sided games

This investigation examines pacing during intermittent team sports. Sixteen junior Rugby League players participated in eight different small-sided offside touch games. All games were 24 min, but bout durations differed in continuous (1 × 24 min) or repeated (2 × 12, 3 × 8, 4 × 6, 6 × 4, 8 × 3, 12 × 2 or 24 × 1 min) formats. Repeat bouts were interspersed by 2 min of passive rest, and participants were informed of the bout duration immediately prior to the game. Heart rates, ratings of perceived exertion and data gathered from global positioning system devices were used to investigate the pacing strategies employed within each game. No significant (P > 0.05) between-game differences were observed in total distance; however, during the 1-min bouts, high-speed movement was significantly (P < 0.05) increased, during the first and second quarters of the 24 × 1-min game compared to all other formats (effect size range: 0.75 ± 0.61–1.38 ± 0.47). Furthermore, the rate of decline in high-speed movement over-time was greatest during the 24 × 1-min game with large differences observed between the first and third quarters (effect size: 0.90 ± 0.58). Greater moderate-speed (effect size range: 0.62 ± 0.63–1.56 ± 0.40) and less low-speed (effect size range: 0.69 ± 0.62–1.54 ± 0.40) distances were also observed during the 1-min bouts, yet heart rates were higher during the continuous 1 × 24-min game. Pacing strategies during intermittent activities are influenced by the number and duration of exercise bouts. Practitioners should consider within-game bout durations when prescribing game-based activities to improve aerobic capacity.     

圆管分层两相流问题的解析方法

管道输运工程中经常遇到两相流问题,因此需要预测对流体施加的压力大小以指导运输。拟对圆直管道分层两相流-层流模型做研究,用解析方法计算出圆管任一截面处流体的速度分布,并验证两层流体交界面处的摩擦力与其平均速度差值呈近似线性关系的结论。以此为基础,可以通过计算截面速度分布得到流体与管壁的摩擦力,通过输运流体所需达到的速度得到分界面处摩擦力,最终反推出运输流体所需要施加的压力差大小。     

行人最大速度对行人流影响的研究

应用改进的格子气模型(即将行人的最大速度扩展到大于1)研究行人的最大速度对过道中单向和双向行人流的影响。模拟结果显示:最大速度为5时所对应基本图的临界密度跟实验值比较符合,说明该扩展是必要的;在一定范围内随着行人最大速度的增大道路的整体通行能力增强同时临界密度减小;双向行人流的时空斑图显示行人最大速度的增大加快了拥堵的形成过程(即缩短了行人从局部拥堵演化为完全拥堵的时间)。     

Dealing with Challenges of Energy and Climate Change:Policy-oriented Researches

<正>Rapid growth of total energy consumption and carbon emissions is a challenge to sustainable energy development In the first decade of the 21st century,along with the acceleration of industrialization and urbanization,especially the rapid development of heavy and chemical