个体风险模型总理赔额的数字特征、分布及其近似

研究了个体风险模型总理赔额的数字特征,利用矩母函数及母函数求其精确分布,给出了总理赔额的多种近似方法,并举例比较分析近似方法的优劣,给出了模拟程序.     

The influence of variable resistance moment arm on knee extensor performance

Abstract

To enhance muscular strength, resistance training machines with a cam, incorporating a variable resistance moment arm, are widely used. However, little information is available about the influence of the variable resistance moment arm on torque, velocity, and power during muscle contraction. To address this, a knee extensor machine was equipped with a cam or with a semi-circular pulley that imposed a variable or a constant resistance moment arm, respectively. Fourteen physically active men performed two full knee extensions against loads of 40–80 kg in both conditions. Participants developed significantly higher torque with the pulley than with the cam (P < 0.001). The relative differences between pulley and cam conditions across all loads ranged from 8.72% to 19.87% (P < 0.001). Average knee extension velocity was significantly higher in the cam condition than in the pulley condition. No differences were observed in average and peak power, except at 50 and 55 kg. Torque–velocity and power–velocity relationships were modified when the resistance moment arm was changed. In conclusion, whatever the link, namely cam or pulley, the participants produced similar power at each load. However, the torque–velocity and power–velocity relationships were different in the cam and pulley conditions. The results further suggest that the influence of the machine's mechanism on muscular performance has to be known when prescribing resistance exercises.     

Segmental dynamics of soccer instep kicking with the preferred and non-preferred leg

Abstract

Detailed time-series of the resultant joint moments and segmental interactions during soccer instep kicking were compared between the preferred and non-preferred kicking leg. The kicking motions of both legs were captured for five highly skilled players using a three-dimensional cinematographic technique at 200 Hz. The resultant joint moment (muscle moment) and moment due to segmental interactions (interaction moment) were computed using a two-link kinetic chain model composed of the thigh and lower leg (including shank and foot). The mechanical functioning of the muscle and interaction moments during kicking were clearly illustrated. Significantly greater ball velocity (32.1 vs. 27.1 m · s^?1), shank angular velocity (39.4 vs. 31.8 rad · s^?1) and final foot velocity (22.7 vs. 19.6 m · s^?1) were observed for the preferred leg. The preferred leg showed a significantly greater knee muscle moment (129.9 N · m) than the non-preferred leg (93.5 N · m), while no substantial differences were found for the interaction moment between the two legs (79.3 vs. 55.7 N · m). These results indicate that the highly skilled soccer players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg. The faster leg swing observed for the preferred leg was most likely the result of the larger muscle moment.     

三线摆测量刚体转动惯量及其误差分析

本文研究了三线摆法测量刚体转动惯量的误差影响因素并对误差的来源和原因进行了分析,在此基础上对实验操作提出了一些改进的方法,以提高实验的精度。     

定轴转动刚体轴承附加压力的计算

机器飞轮转动时,轴承可能受到一定的附加压力。文章通过均质圆盘转动实例,根据质心运动定理和对固定点的角动量定理,给出一种较为简单的计算这种压力的方法,在此基础上指出了改变这种压力的方法。     

楔形体在楔面受一段均布弯矩作用的弹性应力解

用应力函数及其导数在弹性体边界上的力学意义和海维谷函数的方法，对棋形体在楔面承受一段均布湾知作用的问题进行了受力分析，并得出了其弹性应力解．     

“類”与“禷”祭

《诗经》、《尚书》、《周礼》、《礼记》等经籍提到的“禷”祭(又作“類”祭),是上古中国一项有着深厚民俗文化背景和深远历史影响的祭仪。不幸其礼早亡,汉儒已经难究其详。影响及今的《尚书》古文家说和郑玄《礼记》注等,将“禷”祭解为祭天之礼。但根据经籍中的记载来看,“禷”祭指的是当国有大事时,向上帝或社稷宗庙祈福禳灾的一种“祷祈”仪式,与祭天之礼并不是一回事。据《说文解字》等书,“類”字本义是一种犬,可能是白犬。“禷”祭应是指特以“類”为牺牲的祭仪。《山海经》等说“類”具有“自为牝牡”的神奇特性,这与该书所记“白犬有牝牡,是生犬戎”的传说非常相似。在先秦文献中,“類”字常用来指出自同一祖先的子孙后代。这些材料表明“類”与古代中国某些族群的祖先神话有着密切的关系。“禷”祭之形成,正植根于此种观念之上。“禷”祭当属于曾广为流行于上古中国北方地区的犬祭礼俗中某种特定的类型,它的消亡可能与周人颇具理性色彩的的礼制改革有关。     

The political dimension in ESE: the construction of a political moment model for analyzing bodily anchored political emotions in teaching and learning of the political dimension

This article departures from the understanding of environmental sustainable education (ESE) as a political project that consists of dissonant and conflicting voices. The aim of the article is to understand how affection, i.e. bodily sensations, transform into political emotions in teaching and learning settings. The article offers a philosophical and empirically based model called the ‘political moment model’ for analyzing bodily anchored political emotions in teaching and learning of the political dimension. The model was developed in response to an empirical case study where the data were somewhat confusing. In order understand the empirical data, we used parts of Mouffe’s theory of the political and various scholars’ work on political emotions and placed these aspects in a pragmatist standpoint of experience, emotions and meaning making. The model helped to investigate students’ experiences of the political dimension in situations where they experienced affection, i.e. bodily sensation, and emotions in connection with reflections and discussions about how to handle public issues of sustainable development. The article ends with a theoretical discussion of the findings in order to understand the political dimension in teaching and learning activities and to discern possible directions for future research on political moments in ESE.     

刚体转动惯量测量的研究

在刚体转动惯量测量实验中,利用数字毫秒计时器计时,改进测量角加速度的原理和方法,大大提高实验的精确度和效率.     

力矩在刚体平衡问题中的作用

本文从刚体平动的实例出发，指出在高中物理教学中将刚体简化成质点所带来的种种弊端，进一步说明新编高中物理教材中引进力矩概念的重要性。