Identifying profiles of actual and perceived motor competence among adolescents: associations with motivation,physical activity,and sports participation

The present study identified adolescents’ motor competence (MC)-based profiles (e.g., high actual and low perceived MC), and accordingly investigated differences in motivation for physical education (PE), physical activity (PA) levels, and sports participation between profiles by using regression analyses. Actual MC was measured with the Körperkoordinationstest für Kinder. Adolescents (n = 215; 66.0% boys; mean age = 13.64 ± .58 years) completed validated questionnaires to assess perceived MC, motivation for PE, PA-levels, and sports participation. Actual and perceived MC were only moderately correlated and cluster analyses identified four groups. Two groups of overestimators (low – overestimation, average – overestimation) were identified (51%), who particularly displayed better motivation for PE when compared to their peers who accurately estimated themselves (low – accurate, average – accurate). Moreover, adolescents with low actual MC, but high perceived MC were significantly more active than adolescents with low actual MC who accurately estimated themselves. Results pointed in the same direction for organised sports participation. Underestimators were not found in the current sample, which is positive as underestimation might negatively influence adolescents’ motivation to achieve and persist in PA and sports. In conclusion, results emphasise that developing perceived MC, especially among adolescents with low levels of actual MC, seems crucial to stimulate motivation for PE, and engagement in PA and sports.     

Natural nano-machines

In the first part of this article, we read about Alice’s guided tour through the cellular microfactory. In the second part, I introduce the methods of studying the materials and mechanisms of the molecular machines through dialogues. The three participants in this discussion are Alice, her elder brother Alex and her father Albert. The style of presentation here is adapted from Galileo’s Dialogue Concerning the Two Chief World Systems. Albert, a professor of biophysics, emphasizes the crucial differences between the mechanisms of the natural nano-machines and those of their macroscopic counterparts. He also points out some practical applications of this interdisciplinary research in biomedical science and nano-technology. Debashish Chowdhury is a professor of Physics at IIT Kanpur. He is a theoretical physicist and the areas of his research interest are statistical and biological physics. He plays with toy models using mathematical formulae and simulates nature with computers.     

单片机在智能软启动器中的应用

软启动器的出现解决了过大的电流对电网的冲击,提高了供电系统的质量,延长了供电设备的寿命。本文介绍了一种交流电机软启动器的硬件和软件程序设计,以AT89C52单片机为核心,通过电动机启动过程中的晶闸管调压调速,实现电动机的平滑启动。研究表明:该系统的结构简单,参数调整灵活,控制效果好,具有一定的使用价值。     

三相异步电动机的不对称运行

利用对称分量法对三相异步电动机不对称运行状态下电磁关系进行了分析，阐述了 不对称运行状态对电机性能的影响。     

人机界面与PLC在物料分拣系统中的应用

人机界面和PLC在工业控制中得到了广泛的应用,本文简要介绍将信捷TP系列TP460-T型触摸屏与三菱FX2N型PLC相结合,应用于物料分拣系统中。通过PLC及人机界面与机械手的通信,可在人机界面上直接控制机械手动作,实现现场控制的一种全新的图形操作界面,为人机友好交互提供有效和便捷的途径,大大简化操作过程,提高工作效率,降低生产成本。     

基于PC104与ADT-834运动控制卡的伺服电机控制系统

设计了一种通过嵌入式系统与运动控制卡来驱动伺服电机的控制系统。系统在DOS下用BorlandC++3.1语言实现,启动后系统根据接收到的不同的控制要求调用控制卡的运动函数库,以改变伺服电机的脉冲频率和方向信号,实现对伺服电机的运动控制。     

A New Inventory for Assessing Affordances in the Home Environment for Motor Development (AHEMD-SR)

A contemporary view of motor development considers environmental influences as critical factors in optimal growth and behavior, with the home being the primary agent. The intent of this communication is to introduce the Affordances in the Home Environment for Motor Development Self-Report (AHEMD-SR) to early childhood practitioners. The AHEMD-SR is a reliable and valid parental self-report assessment instrument that addresses the quality and quantity of factors (affordances and events) in the home that are conducive to enhancing motor development in children ages 18–42 months. The instrument could provide useful information in a wide variety of settings, including applications to intervention and remediation.     

On using wearable tri-axial accelerometers to examine the striking phase kinematics of expert specialist drag flickers on-field

Analysing player kinematics during a match using “gold-standard” 3D video-based motion analysis techniques is a difficult prospect indeed. The development of small, wireless, wearable sensors offers the potential to reduce the challenges of measuring kinematics during match-play without hindering performance. The present study examined the viability of using wireless tri-axial accelerometers to examine whether key performance measures of drag flicks executed by expert specialist drag-flickers are predicted by the kinematics of the striking phase. Linear mixed models were used to examine whether the speed and accuracy of players’ drag flicks were predicted by the duration of stick-ball contact, and the kinematics of the lead lower limb at stick-ball contact and ball release. Results revealed that stick and lead lower limb kinematics significantly predicted shot accuracy but not shot speed. Shorter drag-time predicted more accurate flicks (p = 0.03) as did a more vertical leg at stick-ball contact (p = 0.016) and a more horizontal thigh at ball release (p = 0.001). This may indicate that there are more ways to produce fast drag flicks than accurate ones. This study illustrates that wireless tri-axial accelerometers can be used on-field to measure the effects of kinematics on key performance measures.     

快速修复直流电动机电枢铁心松动故障

对本钢连轧厂精轧第七架2*2300kw直流轧钢电机电枢铁心松动故障,进行事故原因分析,找出快速修复的方法。     

运动技能教学中学生学习策略的培养

学习策略是学生进行自我学习的一种高级方式,学习策略的形成有其内在的规律性。就学习策略的基本特征以及在运动技术教学中如何培养学生运动技术的学习策略提出了一些基本的建议。