Relationship between accuracy and complexity when learning underarm precision throwing

Learning precision ball throwing was mostly studied to explore the early rapid improvement of accuracy, with poor attention on possible adaptive processes occurring later when the rate of improvement is reduced. Here, we tried to demonstrate that the strategy to select angle, speed and height at ball release can be managed during the learning periods following the performance stabilization. To this aim, we used a multivariate linear model with angle, speed and height as predictors of changes in accuracy. Participants performed underarm throws of a tennis ball to hit a target on the floor, 3.42 m away. Two training sessions (S1, S2) and one retention test were executed. Performance accuracy increased over the S1 and stabilized during the S2, with a rate of changes along the throwing axis slower than along the orthogonal axis. However, both the axes contributed to the performance changes over the learning and consolidation time. A stable relationship between the accuracy and the release parameters was observed only during S2, with a good fraction of the performance variance explained by the combination of speed and height. All the variations were maintained during the retention test. Overall, accuracy improvements and reduction in throwing complexity at the ball release followed separate timing over the course of learning and consolidation.     

Perception-action coupling in complex game play: Exploring the quiet eye in contested basketball jump shots

The duration of the final fixation before movement initiation – a gaze strategy labelled quiet eye – has been found to explain differences in motor expertise and performance in precision tasks. To date, research only addressed this phenomenon in situations without adversarial constraints. In the present study, we compared the quiet-eye behaviour of intermediately-skilled and highly-skilled basketball players in defended vs. undefended game situations. We predicted differences in quiet-eye duration as a function of skill and performance particularly resulting from late quiet-eye offsets. Results indicated performance-enhancing effects of long quiet-eye durations in the defended but not in the undefended game situation. Furthermore, in line with our prediction, later quiet-eye offsets were associated with superior performance elucidating the phenomenon’s relevance in online-demanding motor tasks. Further, earlier quiet-eye onsets were linked to successful performance supporting earlier suggestions that it is not only the duration but also the timing that matters. These findings not only extend the positive effects of the quiet eye in motor performance to dynamic game-play situations but also support the role of the quiet eye in response to programming and information processing respectively.     

Effect of a pilot multi-component intervention on motor performance and metabolic risks in overweight/obese youth

This study evaluated the effect of a multi-component intervention on motor performance (MP) and metabolic risk markers (MRM) in overweight/obese youth. A secondary aim was to examine whether changes in MP are associated to changes in MRM. A 3-month multi-component intervention was performed, consisting of physical exercise sessions (twice/week;1h), nutritional education sessions (once/month), and parental support (twice/week). The sample included 35 volunteers (7–13 y.o), allocated to intervention (INT, n = 17) and control (CONT, n = 18) group. Variables were measured pre (T0) and post intervention (T1). Fasting blood samples were analyzed for MRM. MP tests included the measurement of health related physical fitness components and motor coordination performance (KTK battery). To assess food intake, a 24-hour recall diary was used. GLM-ANCOVA was performed. Standardized scores were calculated for the outcome variables, and multilinear regressions were applied to analyze associations between the key variables. INT group showed improvements in MP, glycolytic and hepatic profiles. After adjustments for MVPA, SB, total intake and maturational stage, negative associations between %ΔMP and %Δglycolytic (β = -.424; 95%CI:-0.343:-0.022), and %Δhepatic scores (β = -.382 95%CI:-0.001:-0.009) were observed. The intervention produced a moderate-to-high effect on the MP and some MRM. Changes in MP were inversely associated with changes in glycolytic and hepatic markers.     

船舶永磁同步推进电动机的基于滑模变结构的SVM-DTC方法

为解决船舶电力推进系统在螺旋桨负载受到风浪干扰时的稳定性问题,采用永磁同步电动机(Permanent Magnet Synchronous Motor,PMSM)作为推进电动机,在空间矢量调制(Space Vector Modulation,SVM)方法和直接转矩控制(Direct Torque Control,DTC)方法的基础上,提出一种基于滑模变结构的SVM-DTC方法.通过Simulink搭建模型进行船舶工况仿真,对推进电动机的转速和电磁转矩进行分析.仿真结果表明采用滑模控制的船舶电力推进系统具有很好的静态、动态特性和鲁棒性.     

基于ARM的直流电机模糊控制系统设计与研究

本文介绍了ARM嵌入式微处理器芯片的架构,直流电机的PWM控制,以及利用模糊算法建立直流电机控制系统。通过对直流电机同轴光学码盘的测速实现闭环反馈,在ARM嵌入式微处理器中调用模糊控制算法实现电机速度的控制。本课题着重介绍了模糊控制在嵌入式ARM微处理器中的实现,以及两者在直流电机控制中的优越表现。     

96单片机实现的直流电机H型PWM调速控制器设计与实现

本文详细介绍了调速控制系统的工作原理、接口电路、PWM驱动接口电路和相应的控制软件设计。所设计的整个调速控制器具有结构简单、驱动能力强、功耗低的特点。     

电机实践课程的改革与创新

“电机学”是电气工程专业一门重要的专业技术基础课程,是一门教师难教、学生难学的课程,其理论性强、抽象概念多、涉及的基础理论知识广;因此,研究如何通过丰富实践教学环节来加深学生对课程的理解变得尤为重要。为丰富电机实践课程教学环节,弥补以往该课程实践教学环节存在的诸多问题,对当前实践教学现状及存在的问题进行了分析,从丰富完善教学内容、设计电机拆装与维修实训软件、探索与分析电机实践课程教学规律、“电机实验与实践”课程教材建设等方面提出了具体的改革举措。     

Implementing a Physical Activity Curriculum into the School Day: Helping Early Childhood Teachers Meet the Challenge

In Fall 2006, North Carolina kindergarten teachers were charged with the task of meeting the NASPE guidelines for providing daily physical activity to their kindergarten students. In turn, the teachers researched resources and consulted experts to design and develop a developmentally appropriate physical activity and physical play environment for their students. The purpose of this article is to disseminate useful information one group of kindergarten teachers believed would help other teachers in similar situations. The article discusses the planning process, suggestions for activities and necessary equipment for program implementation, and vignettes regarding the experiences the teachers and students have had during the physical activity and physical play program’s inaugural year.

内隐学习在运动技能学习中的优势效应

通过对内隐学习的基本特征的分析,认为内隐学习比外显学习更具有可持续发展运动技能的优越性;同时指出了内隐学习和外显学习在运动技能学习中的相互协同作用,两者在一定条件下可以相互转化.     

电动机保护装置的发展展望

电动机是工农业生产的主要动力,我国在保护电动机的安全上取得了很大进展．本文分析和总结了几代电动机保护装置的原理和特点,提出了产品研究和发展的方向．