建筑结构地震响应混沌特性及影响因素分析

采用混沌时间序列分析方法分别对以经典混沌信号和地震动为激励的结构响应进行混沌特性分析,从关联维数、Kolmogorov熵及最大Lyapunov指数等定量指标的角度,考察结构自振周期、地震动的类型和幅值等因素对结构地震响应的非线性特性的影响。研究结果表明:在经典混沌信号和地震动作用下,经过结构的放大和滤波作用,结构加速度响应仍然保留了混沌特性,且通过混沌参数的变化程度能够判断结构是否进入弹塑性状态。结构自振周期为结构加速度响应的混沌特性的主要影响因素;幅值对经典混沌信号作用结构下加速度响应的混沌特性影响较为显著;而地震动的类型、幅值等因素对地震动作用下响应的混沌特性影响更为显著。     

The influence of the hand’s acceleration and the relative contribution of drag and lift forces in front crawl swimming

The aim of this study was to assess the effect of the hand’s acceleration on the propulsive forces and the relative contribution of the drag and lift on their resultant force in the separate phases of the front crawl underwater arm stroke. Ten female swimmers swam one trial of all-out 25-m front crawl. The underwater motion of each swimmer’s right hand was recorded using four camcorders and four periscope systems. Anatomical landmarks were digitised, and the propulsive forces generated by the swimmer’s hand were estimated from the kinematic data in conjunction with hydrodynamic coefficients. When the hand’s acceleration was taken into account, the magnitude of the propulsive forces was greater, with the exception of the mean drag force during the final part of the underwater arm stroke. The mean drag force was greater than the mean lift force in the middle part, while the mean lift force was greater than the mean drag force in the final part of the underwater arm stroke. Thus, swimmers should accelerate their hands from the beginning of their backward motion, press the water with large pitch angles during the middle part and sweep with small pitch angles during the final part of their underwater arm stroke.     

提高学校田径接力项目成绩的初探

接力比赛是一项团体项目，由于竞争激烈．可观赏性很强。在各级田径运动会的比赛中起着举足轻重的作用。一个接力队成绩的好坏也反映出一个学校(团体)的教学与训练的水平。成绩的优劣除了取决于几名运动员的个人短跑成绩外，每个运动员之间的传接棒水平，传接棒成功率的高低，也直接影响着接力队的成绩。     

王怡的单脚背飞扣球技术特征

本文通过摄影、测试、解析得出：单脚背飞和球的球速比正面扣球球速快的优势．３名单脚背飞扣球队员中，王怡助跑速度适宜，腾起角合理，较好地利用身体的前冲力量，使空中位移增长，有较充分时间做空中转体击球动作．从而使她转体利落、连贯、完整、协调．能运用转体的惯性．增加击球时手指掌的加速度，通过比较，王怡的单脚背飞扣球技术、动作合理完整、协调，可称为优秀的单脚背飞和球手．     

球坐标系中速度与加速度的转动参考系求法

应用转动参考系 ,给出了一种求解球坐标系中速度和加速度的简捷方法。该方法不仅图像清晰 ,简明直观 ,而且可应用到矢量力学教学中去     

催陈白酒回生现象对策

综述了现行人工催陈白酒技术的种类和弊端，认为回生现象是催陈技术不可避免的方法缺陷，单一的催陈方法无法实现理想的陈酿效果。以内部催陈法配合外部低能量处理的组合催陈技术是科学的方法，能够最大限度地克服回生现象的不良影响。应注意因采用新科技手段使白酒出现的异常成分对人体健康的影响；主张生产优质白酒应以自然陈酿为主要方法，适当的科学催陈处理只应该是辅助手段。     

半导体物理中电子的运动与有效质量的关系

当研究半导体中的电子在外力作用下的运动时,引入了有效质量这个概念,其概括了半导体内部势场的作用,使得在研究半导体中电子在外力作用下的运动规律时,可以不涉及到半导体内部势场的作用,有效质量将量子力学结果与经典力学牛顿第二定律联系起来了,本文主要研究半导体中电子在外力作用下的运动状态,并讨论有效质量与E-k图、平均速度和加速度的关系。     

电控SASS的结构分析与检测

通过对汽车安全气囊系统(Car Safety Airsac System)的组成结构、工作原理和控制方法进行分析．研究其故障显示检修方法。     

基于SSL加速的电子商务安全机制

电子商务是互联网应用和发展的重点方向。如何在保证系统安全的前提下提高在线交换的处理速度,是电子商务服务的重要保障。本文就如何利用SSL加速服务来实现电子商务的安全保障问题进行了讨论。     

Jump Distance Increases While Carrying Handheld Weights: Impulse, History, and Jump Performance in a Simple Lab Exercise

This laboratory exercise is designed to provide an understanding of the mechanical concept of impulse as it applies to human movement and athletic performance. Students compare jumps performed with and without handheld weights. Contrary to initial expectation, jump distance is increased with moderate additional weights. This was familiar to Ancient Greek athletes where halteres were a part of the original Olympic jumping sports. The effectiveness of this laboratory was assessed with a prelab questionnaire evaluating understanding of the concepts relevant to jumping mechanics and a postlab questionnaire assessing understanding of the same principles in the context of a different but mechanically analogous circumstance, that of throwing. Results indicate that understanding improved significantly as a result of participation in the laboratory exercise.