Dynamics of visual feedback in a laboratory simulation of a penalty kick

Sport scientists have devoted relatively little attention to soccer penalty kicks, despite their decisive role in important competitions such as the World Cup. Two possible kicker strategies have been described: ignoring the goalkeeper action (open loop) or trying to react to the goalkeeper action (closed loop). We used a paradigm simulating a penalty kick in the laboratory to investigate the dynamics of the closed-loop strategy in these controlled conditions. The probability of correctly responding to the simulated goalkeeper motion as a function of time available followed a logistic curve. Kickers on average reached perfect performance only if the goalkeeper committed him or herself to one side about 400 ms before ball contact and showed chance performance if the goalkeeper motion occurred less than 150 ms before ball contact. Interestingly, coincidence judgement?-?another aspect of the laboratory responses?-?appeared to be affected for a much longer time (>500 ms) than was needed to correctly determine laterality. The present study is meant as groundwork for experiments in more ecological conditions applicable to kickers and goalkeepers.     

How do technique and coordination change during learning of a whole-body task: Application to the upstart in gymnastics

ABSTRACT

When learning swinging skills on a bar there has been conflicting advice in the research literature regarding whether to coach the “gold standard” technique to novices. The present study aimed to determine how technique (joint angle time histories) and (inter-limb) coordination changed as novice gymnasts learned a fundamental gymnastics skill (the upstart). It was hypothesised that both technique and coordination would become more like an expert as learning progressed. Eight novice gymnasts, unable to perform an upstart, underwent four months of training, with the number of successful upstarts out of 10 recorded at the start and then every month subsequently. In the first and last sessions motion capture was used to determine joint kinematics. Root mean squared differences for the joint angle time histories and continuous relative phase at the shoulder and hip were calculated between the novices and an expert gymnast. As training progressed technique and coordination became more like the expert gymnast. The more successful novices were better able to time their actions within the swing than the less successful novices. Gymnastics coaches teach towards a “gold standard” technique since being successful at the skill is not the only goal, as considerations for future skill development are made.     

The effects of task constraints on the organization of interception movements

In the light of the intensity coupling effects reported in the literature, subjects' capacities for independently controlling the absolute velocity of their movement at the point of interception was evaluated by asking them to learn to propel orthogonally approaching balls, varying in their speed of approach, into target boxes placed at various distances from the interception point. As required for successful accomplishment of the task, movement velocity was found to be adapted to the distance to be covered, with the near target giving rise to lower velocities and the far target giving rise to higher velocities even when the conditions were presented in random order. Nevertheless, even though target distance accounted for a substantial proportion of the total variance, a small but significant effect of ball approach speed on movement velocity was found, suggesting that intensity coupling is a persistent but modulable phenomenon in interception tasks.     

基于单片机的智能遥控灯具升降器设计

在生活当中,对仓库、体育馆等高大建筑物中的高位灯进行清洁、维护保养,如果把每盏灯都取下来非常不方便,需要付出很大的代价。针对这个情况,设计了一套以STC89C52单片机为基础的智能吊灯升降器。系统以STC89C52为处理器,通过控制继电器达到使电机正反转的目的,从而使吊灯升降。本文详细地介绍了该系统的结构和工作原理以及系统的软件设计。     

根据球墨铸铁的理化特性 减少其铸件质量缺陷

针对电机的生产过程中经常出现的铸件质量问题,经技术攻关反复试验,探索出解决方法。     

冷却塔风机电机绕组烧毁及控制系统优化

绕组烧毁是电机常见故障。绕组烧毁前的迹象不容易发现,而烧毁后一些导致烧毁的直接原因又被掩盖,给事后分析增加了难度。文章就电机密封、绕组绝缘破坏等几方面进行了分析,同时阐述闭式冷却塔系统优化对于电机及时维修和避免循环水温度带来换热器温度变化。     

运用内部注意焦点促进初学者掌握开放式运动技能学习的研究

对"内部注意焦点是否促进初学者开放式运动技能的学习"及其生物力学基础进行研究。共21名北京体育大学教育学院非专选学生参加本研究。实验结果表明:内部注意焦点更有利于初学者学习开放式运动技能。图像解析数据表明,在技能掌握阶段接受内部注意焦点指导的学生,其保持测试时动作的协调模式与指导教师的更加一致,且不同动作间的协调模式一致性更高,说明内部注意焦点更能加速初学者开放式运动技能的学习。     

基于S3C44BOX的药物粒子硬度仪设计

本文是ARM及相关技术在智能化精密仪器生产领域中的一种应用,着重介绍嵌入式药物粒子硬度测定仪的系统设计。该仪器采用三星公司的ARM7芯片——S3C44B0X为微处理器,系统包括步进电机的细分驱动、传感器的数据采集、键盘菜单管理、LCD显示等。系统软件采用嵌入式实时操作系统(RTOS)ΜC/OS-II。     

一次绕线机低功率热丝改造

本文主要论述了公司为了满足市场对低功率热丝的需求,针对已有的日立一次绕线机只能生产单一产品的实际情况,通过大量实验和理论分析,逐层深入剖析一次绕线机控制原理,然后确定改造方案,终于成功完成了一次绕线机低功率热丝改造。     

交流调速模糊控制系统的设计及实现

介绍了采用8031微型单片机为控制核心,运用模糊控制技术解决交流电动机的调速控制问题的实现方案,该设计具有实用简单,效果良好等特点。