NO2与NO气体制备演示一体化微型实验探究

实验室制取NO2、NO的反应,由于其毒性,实验装置的改良备受关注,笔者进行了进一步的改进,旨在减少试剂用量、减轻尾气毒害,人人有机会动手实践,这一点符合绿色化学的发展理念。     

皮划艇运动员冬训水上多级递增负荷测试分析

通过实验法等研究方法对某省皮划艇队6名运动员进行冬季水上多级递增负荷测试,对测试结果进行了统计分析,研究认为该队的基本能力和专项技术还有待提高,并提出了改进的建议。     

世界优秀男子乒乓球运动员特长技术分析

采用文献资料等方法,对世界优秀男子乒乓球运动员特长技术进行研究,旨在提升我国乒乓球项目特长技术创新与发展。结果表明：世界优秀男子乒乓球运动员特长技术主要有8项,分别为,瓦尔德内尔横拍直握式发球技术和晃接技术、科贝尔反手侧拧技术、金泽洙步法技术、蒋澎龙加力推挡技术、格林卡反手横向拉球技术、马琳加转摆短技术和正手前冲弧圈球技术、朱世赫削中反攻技术、王皓直板横打技术。     

Reliabilities of leg and vertical stiffness during treadmill running

The aim of this study was to determine the intra-participant variabilities (i.e. intra-day and inter-day reliabilities) in leg and vertical stiffness, as well as related kinematic parameters, during treadmill running using the sine-wave method. Twenty-two healthy men ran on a treadmill at 4.44 m/s, and the flight and contact times were measured with a high-speed video camera. Three 30-s running bouts with 2-min inter-bout rests were performed to examine the intra-day reliability, and single 30-s running bouts on three separate days with 24- to 48-h inter-bout intervals were performed to examine the inter-day reliability. The reliability statistics included repeated-measure analyses of variance, average inter-trial correlations, intra-class correlation coefficients (ICCs), Cronbach's α reliability coefficient, and the coefficient of variation. Both leg and vertical stiffness produced high ICCs within 0.972 and 0.982, respectively, and between 0.922 and 0.873 days, respectively. High values were also observed for all of the reliability coefficients. Similar results were found regarding contact time, flight time, step length, and step rate. It was concluded that the measurements of leg and vertical stiffness, as well as related kinematic parameters, obtained using the sine-wave method during treadmill running at 4.44 m/s, were highly reliable, both within and across days.     

Anticipatory postural adjustments during cutting manoeuvres in football and their consequences for knee injury risk

Abstract

Anticipatory postural adjustments (APAs), i.e. preparatory positioning of the head, the trunk and the foot, are essential to initiate cutting manoeuvres during football games. The aim of the present study was to determine how APA strategies during cutting manoeuvres are influenced by a reduction of the time available to prepare the movement.

Thirteen football players performed different cutting tasks, with directions of cutting either known prior to the task or indicated by a light signal occurring 850, 600 or 500 ms before ground contact.

With less time available to prepare the cutting manoeuvre, the head was less orientated towards the cutting direction (P = 0.033) and the trunk was even more rotated in the opposite direction (P = 0.002), while the foot placement was not significantly influenced. Moreover, the induced higher lateral trunk flexion correlated with the increased knee abduction moment (r = 0.41; P = 0.009).

Increasing lateral trunk flexion is the main strategy used to successfully perform a cutting manoeuvre when less time is available to prepare the movement. However, higher lateral trunk flexion was associated with an increased knee abduction moment and therefore an increased knee injury risk. Reducing lateral trunk flexion during cutting manoeuvres should be part of training programs seeking the optimisation of APAs.     

乒乓球运动员应加强快速、准确、灵活的步法训练

论述了乒乓球运动员在短时间内,根据来球方向、速度、落点以及旋转等快速作出判断时步法移动的重要意义,并提出一些训练措施。     

加强数学思想在交变电流教学中的渗透

在交变电流的知识体系中 ,一些物理量的制约关系 ,与数学中一些数量制约有着相似之处。正弦式交流电的图象与正弦曲线完全吻合 ,它们满足相同的规律。研究数学的思维方法 ,在交变电流中体现出来 ,在教学中渗透这种思想 ,可开阔学生思维 ,提高其解题能力     

台阶无氧功率实验方法新探

应用身高百分比对每步跨台阶垂直高度进行标定的方法，对２１名运动员和４３名学生的台阶无氧功率实验进行了方法学研究。结果证明，以不同每步跨台阶垂直高度所测得的个体无氧功率有明显差异；认为个体最大台阶无氧功率与个体最佳用力幅度有密切关系，后者可以反映受试的训练水平和技术水平，对选材和机能评定有参考价值。     

对纵箱支撑跳越教学步骤的实验研究

根据人类跳越障碍的自然活动能力，设计了一套纵箱支撑跳越教学步骤，经实验证明，此教学步骤可有效地预防教学中学生不良心理、生理状态的产生     

改进的求和生成器的密码分析

利用分别征服攻击、Chepyzhov提出的快速相关攻击以及代数攻击等3种算法对改进的求和生成器进行了密码分析,并分别给出了攻击算法的计算复杂度和所需要的密钥流的长度