Influence of technique on upper body force and power production during medicine ball throws

ABSTRACT

This project examined the interrelationships between power production and upper body kinematics during a series of medicine ball push-press (MBP-P) throws. Twenty-five regular weight trainers (body mass = 86 ± 10 kg) performed a series of ballistic vertical MBP-P throws at loads representing 5% and 10% of their assessed 5RM bench press. Throws were performed lying supine on a force platform (1 kHz) with upper body kinematics assessed using standard infra-red motion capture techniques (0.5 kHz). Gross measures of performance and power production such as peak vertical ball velocity (Vel_peak), peak force (F_peak) and power (P_peak) were recorded during the propulsive phase of the movement. Comparative analyses indicated that despite significant reductions in Vel_peak from the 5% to 10% loads (P < 0.001), F_peak remained largely unchanged (P = 0.167). Analysis of inter-trial variability showed that the gross measures of performance and power were relatively stable (Coefficient of Variation [CV%] <13%), while most upper limb segmental kinematics varied considerably between trials (CV% up to 70%). This project highlights the complexity of the relationships between power production and upper body kinematics during light load ballistic MBP-P throwing. Additionally, it shows how trained athletes can achieve similar outcomes during ballistic movements using a variety of movement strategies.     

Teacher evaluation: Are principals’ classroom observations accurate at the conclusion of training?

Teacher evaluation commonly includes classroom observations conducted by principals. Despite widespread use, little is known about the quality of principal ratings. We investigated 1,324 principals’ rating accuracy of six teaching practices at the conclusion of training within an authentic teacher evaluation system. Data are from a video-based exam of four 10-minute classroom observations. Many-Facet Rasch modeling revealed that (1) overall principals had high accuracy, but individuals varied substantially, and (2) some teaching episodes and practices were easier to rate accurately. For example, promotes critical thinking was rated more accurately than uses formative assessment. Because Many-Facet Rasch modeling estimates individuals’ accuracy patterns across teaching episodes and practices, it is a useful tool for identifying areas that individual principals, or groups, may need additional training (e.g., evaluating formative assessment). Implications for improving training of principals to conduct classroom observations for teacher evaluation are discussed.     

基于小波分析的GPS基线向量精化技术

基线解算是GPS数据处理中的重要环节。文章针对GPS双差观测序列中难以消除的非模型化误差,应用小波变换进行去噪,以提高GPS双差观测值的信噪比和精度;并提出了基线精化技术,有效解决了基线解算的关键问题,即模糊度解的快速固定和有效性,提高了基线解算的可靠性和平差结果的精度。     

普通高校电子注册学籍学历管理网络全程动态监控体系的构建

以普通高校的电子注册基本内容和构成系统阐述为起点,剖析其内部监控管理系统和外部服务监督系统。在外部服务监督系统引入学生信息档案,构建出普通高校电子注册学籍学历管理网络全程动态监控体系。     

谈多功能行为观察实验室的设计与应用

介绍了多功能行为观察室的基本配置和建设方案,在心理实验和心理咨询中的重要作用.依据不同的心理实验,介绍如何利用多功能行为观察室在儿童发展心理学实验、生理心理学实验和心理咨询进行教学和科研.     

动态视觉化技术及其对数学概念教学的作用——以椭圆概念的教学为例

动态视觉化技术具有数学原理与数学视觉化两大特点,依据数学概念的学习心理因素,动态视觉化技术对数学概念教学的作用主要体现在5方面:丰富对概念的感知,增强对概念的操作,促使对概念的抽象,促进对概念的概括,凸显概念符号的意义。     

痰热清注射液治疗儿童急性呼吸道感染的疗效观察

目的：观察痰热清注射液在儿童急性呼吸道感染中的疗效。方法：140例急性呼吸道感染患儿,随机分为治疗组（痰热清组）和对照组（氨溴索组）,观察两组治疗7天的治疗评价,包括发热、咳嗽、咳痰难易程度的临床变化。结果：痰热清治疗组治疗后临床症状明显改善及其临床疗效优于对照组（P〈0.01）。结论：痰热清注射液具有明显的退热、止咳、祛痰作用,安全性好。     

An overview of structure-soil-structure dynamic interaction research

The concept of structure-soil-structure dynamic interaction was introduced and the research methods were summarized. Based on lots of documents, a systematic summary of the history and current situation of structure-soil-structure dynamic interaction research considering adjacent structures was proposed as reference for researchers. The existing matter and the prospect of future research trend in this field was also examined.     

A Comment on Two Chinese Versions Of little Women

The differences between English and Chinese in terms of the adoption of subject,voice,and stative & dynamic styles are shown in this paper through a contrastive study between the two Chinese versions of Little Women.The discussion aims to deepen our understanding of the differences between the two languages so as to facilitate the formation of a creative method for English teaching and help students solve problems they encounter in the process of second language acquisition.     

新型混联式输送机构的有限时间收敛滑模控制研究

针对一种新型混联式汽车电泳涂装输送机构控制方法存在收敛时间较长问题,提出一种有限时间收敛滑模控制方法。首先采用解析法对机构进行运动学分析,并基于拉格朗日法建立输送机构动力学模型;提出一种快速终端滑模有限时间收敛控制方法,实现新型混联式输送机构控制的有限时间收敛;然后设计有限时间滑模观测器,实时观测被控对象模型中的不确定参数以及外部随机干扰并加以前馈补偿,以进一步提高系统鲁棒性,同时解决快速终端滑模控制存在的抖振问题;最后运用Lyapunov稳定性理论证明该控制方法的稳定性,利用MATLAB对控制方法进行仿真,并将其应用于新型混联式输送机构样机进行实验,结果表明该控制器具有跟踪误差小、稳态精度高、响应速度快、鲁棒性好的特点。