用倾斜气轨系统与Spss测定重力加速度

用垫块调整气轨的倾斜角,使滑行器在自身重力作用下沿气轨表面直接做功,使用智能计时系统精准测出滑块在气轨斜面定点位置的速度。由测量原理及不确定度分析,对照测量数据,引入Spss的曲线估计功能分析得到速长综合量与垫块高度的定标曲线,并验证出速长综合量与垫块高度存在线性关系,由此标定出重力加速度,并用置信概率为95%的不确定度对其进行了合理的分析和评定,得到更加合理的实验结果。     

基于虚拟仪器的减振效果分析系统设计

该文采用自行设计的三维加速度传感器和虚拟仪器技术开发了减振效果分析系统,具有在线实时分析、离线分析、加速数据流回放、一键生成减振效果分析报表等功能,具有界面直观、操作简单、易于扩展的特点,系统测量分析准确,运行稳定,为检验减振装置的减振效果提供了依据。     

不同屈膝角度与g值全身振动刺激对下肢肌肉影响的研究

摘要：目的：探讨在不同半蹲屈膝角度情况下接受不同重力加速度（g）的全身振动训练（Whole-body vibration,WBV）,下肢股内侧肌（Vastus medium,VM）与股二头肌（Bicepes femoris,BF）激活表现以及两者共同收缩变化。方法：46名健康男性大学生,以表面肌电仪监测惯用腿VM与BF肌电反应。先以3种角度（90、60、45°）半蹲姿势进行无振动刺激（Non-Vibration,NV）测试,再以相同3种屈膝角度接受WBV,振动刺激为随机采用0.98、2.52、3.72、5.61 等4种g值。统计学显著性水平为P<0.05,以配对样本T检验比较NV与WBV的肌电信号。因变量为NV与WBV的标准化肌电比例（%MVC）,自变量为g值与屈膝角度。以双因素方差分析比较不同g 值、角度的肌电反应差异以及共同收缩比例,主效应检验g值与屈膝角度对肌电信号的影响,交互作用检验不同g值振动刺激下屈膝角度差异对肌电信号的影响。结果：BF%MVC在屈膝60 °搭配0.98~3.72g 与45°搭配0.98~5.61g 的振动刺激情况下,显著高于NV,而VM在屈膝45°搭配0.98和2.52 g 时有显著提升肌肉激活的效果。结论：BF与VM的激活程度受半蹲屈膝角度影响较大,而屈膝45°搭配0.98、2.52等2种g 值对于BF与VM有较佳激活效果。     

短跑跨栏摆动训练的运动传感器监测和能力评价研究

田径短跨运动是许多竞技运动的基础,是典型的周期性运动.运动员肢体的高速摆动能力是一个重要的专项能力.训练现场的实时定量化的测试评价和监控,对当前高水平运动训练有迫切需求.运动传感器检测技术的发展为运动训练的测试分析提供了有效的工具.本研究探讨了力学传感器对短跨运动员摆动训练的定量检测方法,建立了训练过程的专项能力与力学参数之间的联系,实现了运动能力的定量评价和训练效果的实时反馈,初步创建了“信号回馈”式辅助训练的方法.     

Acute effects of static stretching on characteristics of the isokinetic angle – torque relationship,surface electromyography,and mechanomyography

Abstract

The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad · s^?1 in men and women. Ten women (mean ± s: age 23.0 ± 2.9 years, stature 1.61 ± 0.12 m, mass 63.3 ± 9.9 kg) and eight men (age 21.4 ± 3.0 years, stature 1.83 ± 0.11 m, mass 83.1 ± 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad · s^?1. Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P≤ 0.05) from pre- to post-stretching at 1.04 and 5.23 rad · s^?1; there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle – torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a “flattening” of the angle – torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle – torque relationship and/or sarcomere shortening velocity.     

Validity of a trunk-mounted accelerometer to assess peak accelerations during walking,jogging and running

Abstract

The purpose of this study was to validate peak acceleration data from an accelerometer contained within a wearable tracking device while walking, jogging and running. Thirty-nine participants walked, jogged and ran on a treadmill while 10 peak accelerations per movement were obtained (n = 390). A single triaxial accelerometer measured resultant acceleration during all movements. To provide a criterion measure of acceleration, a 12-camera motion analysis (MA) system tracked the position of a retro-reflective marker affixed to the wearable tracking device. Peak raw acceleration recorded by the accelerometer significantly overestimated peak MA acceleration (P < 0.01). Filtering accelerometer data improved the relationship with the MA system (P < 0.01). However, only the 10 Hz and 8 Hz cut-off frequencies significantly reduced the errors found. The walk movement demonstrated the highest accuracy, agreement and precision and the lowest relative errors. Linear increases in error were observed for jog compared with walk and for run compared to both other movements. As the magnitude of acceleration increased, the strength of the relationship between the accelerometer and the criterion measure decreased. These results indicate that filtered accelerometer data provide an acceptable means of assessing peak accelerations, in particular for walking and jogging.     

Acceleration sensing based on piezoresistive effect of carbon nanotube films

1 Introduction a Carbon nanotubes have attracted much attention due to their remarkable properties [1, 2]. One of their most important applications is to take advantage of their outstanding mechanical properties for their extreme flexibility and strength …     

面向单元内加速的可重构算法设计

为了能够在可编辑逻辑器件上设计更高速度的功能单元,提出了一种面向单元内加速的可重构算法。通过该算法能够对目标逻辑功能单元进行功能重构,并以缩短单元内部逻辑门的层数,以及单元内逻辑门的控制结构,实现单元内加速。选取了典型的可重构计算单元,分析了应用本文所设计的可重构算法对逻辑功能单元进行重构设计。测试中,经过重构设计后的计算单元,运行时间最多减少了30%。     

谈一道力学题的解

纠正了文献^[1]中的一个错误，用计算机作图求得一个力学难题的近似解。     

健康中国行动背景下我国青少年体育生活化促进方略探究

倡导青少年形成积极健康的生活方式,提高青少年健康水平。研究方法:文献资料法、问卷调查法、数理统计法等。研究结论:青少年体育生活化情况有喜有忧,每周进行体育锻炼频率较高,每次进行体育锻炼时间处于中等水平,但参与体育活动强度较小,进行体育活动的时间分布比较均匀;体育锻炼项目选择多样,体育锻炼场所选择倾向于免费的场地;青少年参加体育锻炼的动机有个人生活习惯、强身健体、预防疾病和减肥塑形等;影响青少年参加体育锻炼的原因主要包括个人惰性、对体育锻炼不感兴趣、课余时间少、设施及场地不足等。促进策略:强化青少年主导因素的作用,转变自身的健康价值观念;拓宽体育知识,增强体育意识,充分发挥青少年的主观能动作用;营造积极健康的家庭体育环境;营造以生活化为目标的学校体育环境;优化体育社会环境,促进青少年体育生活化。