中、外优秀女子三级跳远运动员助跑步长与速度研究

通过文献资料调研、现场拍摄法、视频图像解析法等对国内、外优秀女子三级跳远运动员的助跑步长和速度进行了纵向的整体性研究及横向的层次性研究。研究发现,助跑速度是运动成绩提高的源动力;国外优秀运动员水平越高,助跑最后10m的速度与比赛成绩的相关性就越大;最后两步步长随着竞技水平的提高有增加的趋势,并具有明显的个体差异性;在横向上,国外优秀运动员助跑最后两步的速度,随着竞技水平的不断提高而增加,呈加速攻板状态,国内优秀运动员在上板瞬间整体呈减速状态;国外优秀运动员的比赛成绩与助跑最后两步步长呈负相关关系,与最后两步助跑速度呈正相关关系,国内优秀运动员助跑最后两步步长与速度匹配的实效性不如国外优秀运动员。     

S_5的子群

小阶数对称群在有限群论研究中具有重要的作用,但随着n的增大,结构也越复杂。文章利用传递与正规性计算出了S5的所有子群,并给出了严格的证明。     

公法线长度测量的应用

测量公法线长度是齿轮精度检验常用的方法之一,在齿轮设计、齿轮精度检验及齿轮测绘中应用广泛.测量公法线长度的工具简单,测量技术易掌握且能保证测量精度,基本可以满足普通齿轮的精度测量与测绘计算.     

天然肠衣搭配组装算法

天然肠衣原料长短不一,按要求搭配组装成品,运算量很大。采用迭代算法并基于平均值变动规律的研究,建立起用于肠衣成品搭配组装的4个算法模型,其特点是：先行剔除剩余原料,随机应变安排次序,均匀调节长短搭配,即时检验约束条件,可同时保障可行性与最优性,得到了最好的结果,且优于整数规划模型。     

Simulation of droplet topography on super-hydrophobic surface

We established a novel droplet model (with-gravity model) to show the gravity effect of the droplet in the contact angle experiment.By using with-gravity model, we obtained a three-dimensional topography of the droplet including the height of the droplet, the shape of the baseline and the circumference of the baseline.Comparing the with-gravity model with the ideal spherical model, our model considered the measurement error caused by gravity effect in the contact angle experiment which is a key point to influence the three-dimension topography of the droplet.From the calculation of our model, we found that there were two important points to enhance the measurement error: the size of the droplet and the contact angle.With the droplet and the contact angle became larger, measurement error was obviously increased.     

基于贝叶斯估计的Context量化器设计方法

介绍了一种基于贝叶斯估计的Context量化器设计方法.通过将自适应码长增量与贝叶斯估计中的先验概率估计进行结合,使得该量化器在不需要先验知识的情况下,既考虑到Context量化本身的特点,又使得编码后信源的自适应码长最短,最终保证了Context量化的自适应性.实验结果表明,该Context量化器设计方法能获得最优量化结果,达到设计目标.     

An analysis on document length retrieval trends in language modeling smoothing

Document length is widely recognized as an important factor for adjusting retrieval systems. Many models tend to favor the retrieval of either short or long documents and, thus, a length-based correction needs to be applied for avoiding any length bias. In Language Modeling for Information Retrieval, smoothing methods are applied to move probability mass from document terms to unseen words, which is often dependant upon document length. In this article, we perform an in-depth study of this behavior, characterized by the document length retrieval trends, of three popular smoothing methods across a number of factors, and its impact on the length of documents retrieved and retrieval performance. First, we theoretically analyze the Jelinek–Mercer, Dirichlet prior and two-stage smoothing strategies and, then, conduct an empirical analysis. In our analysis we show how Dirichlet prior smoothing caters for document length more appropriately than Jelinek–Mercer smoothing which leads to its superior retrieval performance. In a follow up analysis, we posit that length-based priors can be used to offset any bias in the length retrieval trends stemming from the retrieval formula derived by the smoothing technique. We show that the performance of Jelinek–Mercer smoothing can be significantly improved by using such a prior, which provides a natural and simple alternative to decouple the query and document modeling roles of smoothing. With the analysis of retrieval behavior conducted in this article, it is possible to understand why the Dirichlet Prior smoothing performs better than the Jelinek–Mercer, and why the performance of the Jelinek–Mercer method is improved by including a length-based prior.

词族现象探微

词族的大量出现,有其独特的语言学价值。它说明了附加构词法表现非常突出,汉语的最佳词音长度受到挑战,某些外来悟睚成为汉语中能产性极强的构词语素。词族现象也为我们提供了透视社会变革,考察人们思想观念变化等方面的认识价值。     

t重n阶同余数的性质与应用

本文对t重n阶同余数的性质进行了初步探讨并应用这些性质给出了任意数同余初阶的简易求法,并提出一类循环小数的循环节等长问题供讨论。     

A Simple Model to Determine the Efficient Duration of Exams

This study develops a theoretical model for the costs of an exam as a function of its duration. Two kind of costs are distinguished: (1) the costs of measurement errors and (2) the costs of the measurement. Both costs are expressed in time of the student. Based on a classical test theory model, enriched with assumptions on the context, the costs of the exam can be expressed as a function of various parameters, including the duration of the exam. It is shown that these costs can be minimized in time. Applied in a real example with reliability .80, the outcome is that the optimal exam time would be much shorter and would have reliability .675. The consequences of the model are investigated and discussed. One of the consequences is that optimal exam duration depends on the study load of the course, all other things being equal. It is argued that it is worthwhile to investigate empirically how much time students spend on preparing for resits. Six variants of the model are distinguished, which differ in their weights of the errors and in the way grades affect how much time students study for the resit.