平面上有噪音散乱点集的参数化

散乱点集曲线重建关键步骤是参数化.提出了一种对平面上有噪音散乱点集参数化的新算法.算法中,首先求出点集的Delaunay三角化的最小生成树,继而对最小生成树的最长路径进行参数化.通过把其他点投影到最长路径上,对最长路径以外的点进行参数化.还给出了提高参数化的准确度的方法.以圆盘控制顶点B样条拟合为例展示了该算法的应用.     

平面凸轮廓线实测数据的光顺及拟合

本文分析了凸轮廓线二阶导数连续的必要性,提出了以凸轮廓线一阶差商、二阶差商、法线倾角和曲率的差商为判据,修正凸轮廓线型值点,并保证其满足光顺条件的方法。文中还给出了可用于凸轮廓线拟合的三次样条和圆弧样条的求解方法。     

目标组织轮廓的三次非均匀B样条逼近

提出断层医学图像中目标组织轮廓最少数据点描述的样条曲线建模方法．首先采用多边形逼近将图像分割和轮廓跟踪所获得的目标组织轮廓线上几乎共线的部分离散数据点去除；再以剩下的轮廓数据点作为型值点，采用周期B样条曲线逼近的方法，得到控制误差条件下最少数据点描述的目标组织轮廓曲线，并依照IGES标准，输出医学内植物设计和骨组织有限元分析所需的目标组织样条曲线几何模型．     

用B样条曲线构造几何物体模型的方法

根据Ｂ样条曲线原理,提出了先用若干个截平面去切割几何物体,得到一组与几何物体轮廓线相交的点。根据这些点,再用Ｂ样条曲线去构造几何物体的近似轮廓线,从而得到几何物体模型。该方法方便、精确,便于在计算机几何造型系统中应用。     

曲面投影轮廓线在奇点光滑时的曲线特征

对凹回转面可见轮廓线的投影在奇点附近仍光滑的情况下,分析了可见轮廓线本身与奇点对应点处的曲线特征以及可见轮廓线在其对称平面的投影图上与奇点对应的点的特征. 对凹回转面可见轮廓线在奇点附近形状作了进一步的分析与研究.     

机载激光扫描中复杂建筑物轮廓线平差提取模型

建筑物轮廓线提取与规则化是房屋3维重建等处理中的重要步骤,目前大多方法面向多边形规则建筑物轮廓线的提取,而无法适用于包含圆弧轮廓线的不规则建筑物轮廓线提取.针对城市中这一类复杂不规则建筑物,提出一种结构化提取特征点的方法,并判断特征点的属性,对直角处的特征点进行条件平差,优化特征点的位置,而对圆弧处的特征点之间的边界点分段拟合圆弧,以得到平滑的符合实际情况的轮廓线.该方法可有效提取包含圆弧的建筑物轮廓线,最后通过上海陆家嘴地区的建筑物LiDAR(机械激光扫描)数据验证该方法的可行性和提取精度.     

密集三维散乱点数据的拓扑矩形网格自组织压缩重建

探讨了曲面密集三维散乱点数据的拓扑矩形网格自组织压缩重建方法。建立了基于自组织特征映射神经网络的三维散乱点数据的拓扑矩形网格自组织压缩重建模型。该模型利用神经元对曲面散乱点的学习和训练来模拟曲面上的点与点之间的内在关系，结点连接权矢量集作为对散乱点集的工程近似化并重构曲面样本点的内在拓扑关系，实现曲面密集三维散乱点数据的自组织压缩。按矩形阵列侧抑制邻区训练调整网络神经元权重矢量，使网络输出层结点呈矩形阵列分布，可生成测量点集压缩后的拓扑矩形网格，可用于NURBS曲面重构。计算机仿真实验表明，所建模型可以实现三维密集散乱点数据自组织压缩，生成期望疏密程度和精度的双有序点列，重建矩形拓扑网格。     

基于状态空间理论的多变量样条元法

本文提出一种基于状态空间理论的多变量样条元法。文中根据弹性理论的控制方程和二类变量广义变分原理导出状态方程．应用基样条函数构造二类场变量函数，建立了以样条结点参数为未知量的状态方程组，由现代控制论中的状态空间法来求解．文中给出平面应力问题的数值算例，计算结果表明，与材料力学方法十分接近．本文方法计算量小、精度好、效率高，可推广应用于板壳结构等问题     

可视化类库VTK在三维建模中的应用

采用VC＋＋6．0作为开发平台，引入三维可视化类库VTK，实现了散乱数据和体数据的建模．通过数据压缩、平面分割来减少数据量，分别采用不同的建模方法，如Delaunay三角化建模、轮廓线建模、MarchingCubes建模，实现了三维数据的建模．     

基于B-样条表示的物体轮廓曲线匹配

目的研究利用破碎物体的轮廓曲线进行形状复原。方法提出了3D曲线的表示和匹配方法。曲线的表示用B-样条曲线逼近到从碎片物体的轮廓线上提取的数据点，在弧长参数化下，曲率和挠率是空间曲线在旋转和平移下的不变量，且具有局部性和稳定性，因此将其选择为特征集。3D曲线的匹配就转化为1D字符串的匹配，并采用对于特征集排序方法。结果提高了匹配速度，匹配算法的时间复杂度为O（n）。实验结果表明该匹配算法有效。结论对于物体形状复原有应用价值。     

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.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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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.     

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     

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.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。