Dynamics of the martial arts high front kick

Fast unloaded movements (i.e. striking, throwing and kicking) are typically performed in a proximo‐distal sequence, where initially high proximal segments accelerate while distal segments lag behind, after which proximal segments decelerate while distal segments accelerate. The aims of this study were to examine whether proximal segment deceleration is performed actively by antagonist muscles or is a passive consequence of distal segment movement, and whether distal segment acceleration is enhanced by proximal segment deceleration. Seventeen skilled taekwon‐do practitioners were filmed using a high‐speed camera while performing a high front kick. During kicking, EMG recordings were obtained from five major lower extremity muscles. Based on the kinematic data, inverse dynamics computations were performed yielding muscle moments and motion‐dependent moments. The results indicated that thigh deceleration was caused by motion‐dependent moments arising from lower leg motion and not by active deceleration. This was supported by the EMG recordings. Lower leg acceleration was caused partly by a knee extensor muscle moment and partly by a motion‐dependent moment arising from thigh angular velocity. Thus, lower leg acceleration was not enhanced by thigh deceleration. On the contrary, thigh deceleration, although not desirable, is unavoidable because of lower leg acceleration.     

CH2N+HONO反应的动力学研究

用直接从头算动态学方法对CH2N＋HONO→CH2NH＋NO2反应进行了研究.用BH＆HLYP/6-31＋G（d,p）方法对所有稳定结构和过渡态的几何结构进行了优化,并用内禀反应坐标方法计算了最小能量路径（MEP）.在QCISD（T）/6-311＋G（2df,2pd）理论水平上对所有结构的能量进行了进一步校正.用变分过渡态理论（CVT）在考虑小曲率隧道（SCT）校正的水平上计算了200～2500K温度范围内标题反应的热速率常数,计算结果表明,上述温度范围内热速率常数有正的温度效应,计算结果与文献数据能够很好地吻合.     

珠江三角洲农田黄毛鼠种群动态分析

根据1987～1990年和1992～1993年虎门镇农田调查的数据为依据．全面系统地研究和分析了黄毛鼠种群动态的基本特征，包括性比、年龄组成、繁殖强度等．同时，研究了种群季节迁移和季节变化．研究表明．黄毛鼠种群每年有两个繁殖高峰期和一个数量高峰期．     

基于群体动力学理论的基础教育数字资源USGC四方联动共建共享模式的构建与实现

在前期研究构建“基于资源分类的基础教育数字资源共享机制”的基础上,文章采用行动研究法,进一步深入分析现实问题,以群体动力学为理论基础,构建基础教育数字资源USGC四方联动共建共享模式。在该模式中,高校(U)、中小学(S)、政府(G)、企业(C)这四大主体各司其职而又互联互动。高校的主要职能为师资培训、政策建议、促进联动、实践推进,中小学的主要职能为质量审核、评价反馈、资源建设、创新生成,政府的主要职能为系统规划、政策驱动、经费保障、评估激励,企业的主要职能为资源(软硬件)供给、标准化共享平台、技术保障、管理服务。研究选取三所学校分别开展持续四年的基于校情的分阶段、分层次、有步骤的USGC四方联动共建共享模式的实践:A中学基于电子书包开展校内数字资源共建共享、B中学开展校际数字资源共建共享、C中学依托河南省“互联网+教育”精准扶贫计划开展区域数字资源共建共享。结果表明,此模式切实可行,对实践具有一定的指导意义。     

《结构动力学》本科课程中数值计算内容调研:国际研究型高校土木工程专业比较

动力响应数值计算是分析结构动力学中“三非”(非线性、非稳态、非定常)问题的重要理论方法和技术手段。本文调研了十余所国际著名研究型高校土木工程专业本、硕、博阶段《结构动力学》课程教学计划,比较了《结构动力学》本科初级课程中单自由度系统动力响应数值计算和响应谱的相关内容设置,通过比较相关内容的知识点设置等方面对我国土木工程专业《结构动力学》课程的教学改革提供了若干有意义的建议。     

Design optimization on the front wheel orientation parameters of a vehicle

1. Introduction In order to improve the driving operation performance, the front suspension of a vehicle is generally of McPherson independent style, which can simplify the structure, lighten the unsprung mass, and conveniently arrange the engine and steering system. Moreover, it can adapt to many types of springs and is of advantage to adjust the height of the vehicle. In such a system, the axis of the kingpin is the line between the upper damper end and the intersection of the transverse ar…     

The challenge of fluid flow

You look up at the sky, and see a lovely cloud; you look down, and may see lovely ripples on a rivulet (or river). On a hot summer afternoon you see dancing dust devils; on a cold winter evening you can see smoke rising lazily from achulah, and hang up there as if it has given up. You peer at a telescope, and see intense supersonic jets, or vast whirling galaxies; you measure in a wind tunnel, and sense powerful tornadoes behind an aircraft wing. The universe is full of fluid that flows in crazy, beautiful or fearsome ways. In our machines and in the lab, as in terrestrial nature, one sees this amazing diversity in the flow of such a simple liquid like water or a simple gas like air. What is it that makes fluid flows so rich, so complex-some times so highly ordered that their patterns can adorn a saree border, sometimes so chaotic as to defy analysis? Do thesame laws governall that extraordinary variety? We begin with a picture gallery of a number of visible or visualized flows, and consider which ones we understand and which ones we do not, which ones we can compute and which ones we cannot; and it will be argued that behind those all-too-common but lovely flows lie deep problems in physics and mathematics that still remain mysteries.     

体内医疗微型机器人的外磁场驱动与控制系统研究

本文以胶囊状体内医疗微型机器人为研究对象,着眼于无线胶囊内窥镜的外磁场主动驱动,在分析人体消化道能动性特点的基础上,设计了一种外磁场驱动方案,建立了胶囊状微机器人外磁场驱动的动力学模型,同时给出了驱动控制系统方案设计,为微型机器人在人体消化道内进行无损检查和微创手术提供了一种设计思路。     

浅谈莫扎特钢琴奏鸣曲的演奏特点

莫扎特的钢琴奏鸣曲在西方钢琴艺术发展史上占有极其重要的地位。文章将从音色与触键、力度与速度、装饰音和阿尔贝蒂低音的弹奏三方面来探讨莫扎特钢琴奏鸣曲的演奏特点,以便能完美地表现莫扎特作品的自然、典雅、质朴的风格特征。     

一类多全方位移动机器人动力学系统的镇定

本文考虑了由 2个全方位移动机器人组成的混合动力学系统的协调拟镇定问题 .利用机器人位置之间的向量与机器人目标之间向量的内积 ,设计了多步拟镇定律 ,该控制律能够在避碰后按指数速率运动到目标点 ,且在整个过程中两机器人之间的距离不小于避碰的安全距离 .最后对 2个全方位移动机器人进行了仿真 ,验证了所给方法的有效性