排球发旋转球的分析和研究

运用生物力学理论对排球发球中旋转球的几种现象及发旋转球的击球和抛球进行了分析，提出采用抛旋转球的方法来发旋转球，以丰富发球方法和提供一定的理论参考价值。     

浅析排球运动员发球效能的影响因素

发球是排球主动得发技术之一，对比赛胜起着举足轻重的作用，本文试图通过对影响运动员发球效能因素的分析，从而能给运动员在提高发球成功率方面带来一些有益的启示。     

我国排球发球技战术现状与对策研究

]发球是排球运动的一项重要的基本技术。它是比赛的开始,也是排球比赛的重要进攻手段。有威力、攻击性强的发球,不但可以直接得分,起着先发制人的作用,而且还可以破坏对方组织进攻战术,减轻本方防守压力,为防守反攻提供有利条件。此外,威力大的发球还能振奋精神,鼓舞士气,打乱对方的阵脚和部署。反之,发球失误过多,不但会失去发球权或为对方加分,而且还会给本方造成很大的心理压力和防守的困难局面。因此,发球首先要有稳定性,然后增加其攻击性和准确性。随着排球技术和战术的不断发展,发球也在不断的改进和提高。目前,各国排球队都在寻找新的具有较强攻击性的发球技术,以求打破发垫平衡的局面。主要是采用远或近距离发平冲的重飘球和跳起发大力球,提高发球的命中率和破攻能力。     

基于旋量理论的排球发球机器人挡板模块的运动学和动力学方程

排球发球机器人是一新兴的产品,对其进行运动学和动力学的分析是对其进行运动控制的基础.排球发球机器人的挡板模块是一开链式机构,基于旋量理论的运动学和动力学的分析方法是利用运动螺旋和指数积等数学工具建立其运动学和动力学方程,求驱动力矩,比采用传统的D-H方法建立局部坐标系简化了对机器人运动学和动力学的分析,从而为建立控制策略、控制方法、轨迹规划做好必要的准备.     

运动感知觉对排球发球落点效果的探讨

发球是排球比赛中一项重要技术,利用专门运动感知觉方面的教学练习,进行排球发球落点和辨别能力两方面对比实验。结果表明,运动感知觉与排球发球落点效果之间有着高度相关性,能有效地提高排球发球落点的准确性。     

现代排球的典型发球技术及其运用

文章概述了现代排球发球的现状，分析了“每球得分制”实施后，发球对排球比赛的影响，阐述了三种典型的排球发球技术，提出了如何在比赛中运用典型发球，将三种发球特点有机结合。     

浅论排球发球技战术及心理训练

论述了发球在排球训练中的重要性,并从技术、战术、心理三个方面具体探讨了排球的发球训练,以期从整体上提高排球训练的质量和水平。     

排球比赛中运动员发球心理分析

本文从影响排球发球的因素入手,说明了心理因素对发球成功与否,质量好坏的影响效果,提出了在排球训练中,在不断加强和提高身体素质,技术和战术的同时,应重视运动员发球心理的问题探讨,分析产生不稳定型消极发球的原因,加强运动员心理训练。     

基于全概率思想的排球发球技术水平的评价与分析

简要分析了传统的排球发球技术水平评价方法存在的不足,给出了排球发球质量等级划分办法,在此基础上,提出了排球发球技术水平的全概率评价方法.分别用2种方法对中国女排队员在北京奥运会上的发球技术水平进行了评价,并对2种评价结果进行了比较和分析,得出了全概率评价方法优于传统评价方法的结论.定义了发球威力的概念,计算了中国女排队员的发球威力值,并进行了2种评价方法评价结果与威力值的斯皮尔曼等级相关分析,得出全概率评价方法的评价结果与威力值具有较高一致性等结论.     

浅谈发球在排球比赛中的重要性

从排球运动理论上说,发球、扣球和拦网是比赛得分的三大手段。发球是排球比赛中的进攻手段之一。发球是比赛的开始,有威力的发球可以破坏对方战术起到先发制人的、争取主动的作用。从近年来的世界排球发展趋势来看,发球这一得分手段又有新的发展、新的认识,使世界排坛发球与接发球的平衡格局产生了较大的变化。国际排联从1999年开始实行每球得分制,由此带来的对排球攻防体系的一系列改变非常大。这对所有球队来说都是一个机会,同时也是一个挑战。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to