The effects of a calf pump device on second half performance of a simulated soccer match in competitive youth players     

S. Béliard  J. Cassirame  G. Ennequin  G. Coratella  N. Tordi 《Journal of sports sciences》2019,37(6):708-716

During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT⁹⁰). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters.  相似文献   

细长轴车削动特性的研究   总被引：9，自引：0，他引：9  

黄跃华  张景勘  李德滋 《科技通报》2001,17(4):41-45,49

对细长轴车削的动特性进行了分析、试验和研究，为保证细长轴车削的稳定性以提高加工质量，提出了转速与进量的合理计算公式，计算与实验结果基本一致。  相似文献   

加速度共振现象及其特征   总被引：2，自引：0，他引：2  

孟振庭 《渭南师范学院学报》2001,16(6):88-91

在受迫振动中，振动加速度达到最大值时的共振现象，称为“加速度共振”，其共振条件为Ω=ω^2/√ω^2-2β^2,振幅比通常的位移共振的振幅小，初位相比通常的位移共振的初位相大，其共振特征明显，物理意义明确。  相似文献   

旋转梁在横向铰支纵向自由约束下的耦合振动     

王树勇 《海南师范学院学报》2007,20(4):331-334

研究绕一端旋转的弹性梁产生的拉压与弯曲的复合振动，采用分离变量法，求出旋转梁在横向受两端固定铰链约束、纵向两端自由弯曲和拉压耦合振动的微分方程通解．  相似文献   

基于LabVIEW的二自由度及动力减振实验系统   总被引：1，自引：2，他引：1  

张茂华  姚恩涛  胡明敏  方义庆 《实验室研究与探索》2005,24(3):36-38

简要介绍了虚拟仪器概念及其软件开发平台LABVIEW。在建立振动模型的基础上，采用了LabVIEW图形编程语言以及数据采集卡组建了两自由度的振动及动力减振实验系统，利用“软件就是仪器”的技术方法，减少了测试系统中的硬件设备，实现了对振动信号进行实时采集、频谱分析的目的。  相似文献   

Pathways from parental stimulation of children’s curiosity to high school science course accomplishments and science career interest and skill     

Adele Eskeles Gottfried  Kathleen Suzanne Johnson Preston  Allen W. Gottfried  Pamella H. Oliver  Danielle E. Delany  Sirena M. Ibrahim 《International Journal of Science Education》2016,38(12):1972-1995

Curiosity is fundamental to scientific inquiry and pursuance. Parents are important in encouraging children’s involvement in science. This longitudinal study examined pathways from parental stimulation of children’s curiosity per se to their science acquisition (SA). A latent variable of SA was indicated by the inter-related variables of high school science course accomplishments, career interest, and skill. A conceptual model investigated parental stimulation of children’s curiosity as related to SA via science intrinsic motivation and science achievement. The Fullerton Longitudinal Study provided data spanning school entry through high school (N?=?118). Parental stimulation of curiosity at age 8 years comprised exposing children to new experiences, promoting curiosity, encouraging asking questions, and taking children to a museum. Intrinsic motivation was measured at ages 9, 10, and 13 years, and achievement at ages 9, 10, and 11 years. Structural equation modelling was used for analyses. Controlling for socio-economic status, parental stimulation of curiosity bore positive and significant relations to science intrinsic motivation and achievement, which in turn related to SA. Gender neither related to stimulation of curiosity nor contributed to the model. Findings highlight the importance of parental stimulation of children’s curiosity in facilitating trajectories into science, and relevance to science education is discussed.  相似文献   

基于小波去噪的快速定点ICA及其在振源识别中的应用     

武志勇  陈茜 《顺德职业技术学院学报》2006,4(1):6-8,12

在多源激励情况下,从传感器阵列输出的高维响应中分离、识别不同振源的性质,对于大型结构振动分析以及对其状态监测与健康评价有着重要的意义.本文结合大型结构振动的性质,介绍了小波阈值去噪原理,使用其改进的快速定点算法实现了多源激励情况下振源信息分离的方法.文中通过实例给出了这种方法的应用效果.  相似文献   

某型直升机总桨距操纵杆振动故障研究     

袁凯 《成都航空职业技术学院学报》2021,37(1):39-41

振动是直升机飞行中常发生的故障之一,严重影响直升机的飞行安全。某型直升机在试飞过程中,连续出现多架左座总桨距操纵杆振动偏大的故障,给正在开展的试飞工作带来了极大的困难。针对该故障通过测振分析、试验和对比其它同型号直升机,准确判断出导致问题发生的原因,从而采取相应的改进措施并进行试飞验证,最终使得直升机总桨距操纵杆振动水平大大降低,消除了质量安全隐患,确保了该型直升机的操纵可靠性,并为后续类似问题提供了解决思路。  相似文献   

基于心理需求的志愿者激励研究   总被引：2，自引：0，他引：2  

张向群 《科学学研究》2007,25(Z2):414-418

通过对志愿者参与志愿活动的心理需求和动机进行分析,将志愿者按不同的心理需求分为六大类。然后,利用模糊数学的方法建立了不同心理需求志愿者的效用函数,并结合志愿者激励方法和手段的指标体系,分析和探讨了志愿者效用最大化的激励方法。  相似文献   

弹性管束换热器传热与阻力特性的实验研究     

程菲  田茂诚 《实验室研究与探索》2007,26(11):23-25,41

对弹性管束水-水换热器的传热与阻力特性进行了研究。主要分析了换热器在不同工况下的传热系数的变化规律;研究了弹性管束在管外流体和管内流体的共同诱导作用下,管外和管内对流换热的情况;并对管程和壳程的流动阻力损失进行了实验测量,得出了管程和壳程的阻力损失变化的规律,以及换热器管程阻力损失的计算方法。  相似文献