非同质保单组合赔付额分布的迭代算法

保单组合的赔付次数及赔付额在非寿险精算的研究中是一项基本的内容，对于非同质保单而言，迭代算法是比较有效的，我们在已有结果的基础上，得到了更一般情形下非同质保单组合的赔付额分布的迭代算法，并就一个具体例子进行了讨论。     

武术跳跃动作落地稳定性探讨

针对学生在武术套路演练中容易出现跳跃动作落地不稳，造成附加支撑或摔倒等问题，结合从事武术专业教学的经验，进行调查、分析，从技术、心理和体能方面探讨造成学生跳跃动作落地不稳定的原因。     

现代三级跳远的最佳三跳比例的探讨

本文以具有当今世界水平的三级跳远选手的30组测试成绩为依据,运用二次响应面回归模型,研究了三级跳远成绩与三跳远度的关系。并用冷嵴分析的方法,给出了使三级跳远成绩达到最大值的最佳三跳组合(比例)模式。     

Generalized Linear Factor Score Regression: A Comparison of Four Methods

Factor score regression has recently received growing interest as an alternative for structural equation modeling. However, many applications are left without guidance because of the focus on normally distributed outcomes in the literature. We perform a simulation study to examine how a selection of factor scoring methods compare when estimating regression coefficients in generalized linear factor score regression. The current study evaluates the regression method and the correlation-preserving method as well as two sum score methods in ordinary, logistic, and Poisson factor score regression. Our results show that scoring method performance can differ notably across the considered regression models. In addition, the results indicate that the choice of scoring method can substantially influence research conclusions. The regression method generally performs the best in terms of coefficient and standard error bias, accuracy, and empirical Type I error rates. Moreover, the regression method and the correlation-preserving method mostly outperform the sum score methods.     

The effects of vibration on explosive and reactive strength when applying individualized vibration frequencies

Abstract

The aim of this study was to assess the effects of 8 weeks of whole-body vibrations on explosive and reactive leg strength. Thirty-three physically active students took part in the study and were randomly assigned to an individualized-vibration group, a fixed-vibration group or a control group. The frequency of vibration was set to 30 Hz for the fixed-vibration group, whereas the frequency for the individualized-vibration group was determined by monitoring the participants' EMG_rms activity. The participants in the two vibration groups were exposed three times a week for 8 weeks to a series of 10 × 1-min whole-body vibrations with a 1-min pause between series of vibrations and a 4-min pause after the first five series of vibrations. Jump height in the squat jump increased significantly in all three groups (by 11% for the individualized-vibration group, p = 0.001; by 3% for the fixed-vibration group, p = 0.011; and by 2% for the control group, p = 0.006), but countermovement jump height was not affected. In continuous rebound jumps by the individualized-vibration group, jumping height increased by 22% (p = 0.006) and power increased by 18% (p = 0.002). The results of this study suggest that the use of an individualized vibration frequency produces a greater response from the neuromuscular system and is more beneficial than vibrations at a fixed pre-selected frequency.     

Explosive force production during isometric squats correlates with athletic performance in rugby union players

Abstract

This study investigated the association between explosive force production during isometric squats and athletic performance (sprint time and countermovement jump height). Sprint time (5 and 20 m) and jump height were recorded in 18 male elite-standard varsity rugby union players. Participants also completed a series of maximal- and explosive-isometric squats to measure maximal force and explosive force at 50-ms intervals up to 250 ms from force onset. Sprint performance was related to early phase (≤100 ms) explosive force normalised to maximal force (5 m, r = ?0.63, P = 0.005; and 20 m, r = ?0.54, P = 0.020), but jump height was related to later phase (>100 ms) absolute explosive force (0.51 < r < 0.61; 0.006 < P < 0.035). When participants were separated for 5-m sprint time (< or ≥ 1s), the faster group had greater normalised explosive force in the first 150 ms of explosive-isometric squats (33–67%; 0.001 < P < 0.017). The results suggest that explosive force production during isometric squats was associated with athletic performance. Specifically, sprint performance was most strongly related to the proportion of maximal force achieved in the initial phase of explosive-isometric squats, whilst jump height was most strongly related to absolute force in the later phase of the explosive-isometric squats.     

各向异性介质中的电磁场

阐述了近些年来研究各向异性介质的电磁场、磁各向异性介质中稳恒电流的磁场及磁各向异性介质中的辐射电磁场等基本情况.     

Implementing technical refinement in high-level athletics: exploring the knowledge schemas of coaches

This paper explores the approaches adopted by high-level field athletics coaches when attempting to refine an athlete’s already well-established technique (long and triple jump and javelin throwing). Six coaches, who had all coached multiple athletes to multiple major championships, took part in semi-structured interviews focused upon a recent example of technique refinement. Data were analysed using a thematic content analysis. The coaching tools reported were generally consistent with those advised by the existing literature, focusing on attaining “buy-in”, utilising part-practice, restoring movement automaticity and securing performance under pressure. Five of the six coaches reported using a systematic sequence of stages to implement the refinement, although the number and content of these stages varied between them. Notably, however, there were no formal sources of knowledge (e.g., coach education or training) provided to inform coaches’ decision making. Instead, coaches’ decisions were largely based on experience both within and outside the sporting domain. Data offer a useful stimulus for reflection amongst sport practitioners confronted by the problem of technique refinement. Certainly the limited awareness of existing guidelines on technique refinement expressed by the coaches emphasises a need for further collaborative work by researchers and coach educators to disseminate best practice.     

复合泊松过程可加性的一种证明

首先用概率母函数的方法证明了广义齐次泊松过程的可加性.由于给定了参数λ和Pk的广义齐次泊松过程是一个复合泊松过程,从而运用广义齐次泊松过程的证明思路,证明了复合泊松过程也具有与广义齐次泊松过程相似的性质--可加性.