Mobile Ad Hoc网络覆盖组播路由协议

移动自组网(Mobile Ad Hoc Networks)是一种特殊的、应用前景广阔的新型移动无线网络.在Ad Hoc网络体系中,路由技术至关重要.覆盖组播(Overlay multicast)路由协议是解决组播路由协议的一种有效的方案,是在物理链路上构建一个虚拟或者是逻辑的网络,其中的每个虚拟连接都是下层的物理链路的单播通道.主要是从如何构建一个覆盖组播的角度系统地描述了当前典型的覆盖组播路由算法,并比较和分析了这些算法的特点和适应情况.最后结合该领域当前研究现状,指出覆盖组播路由算法未来的研究重点.     

一种考虑节点剩余能量及其消耗率的Ad Hoc组播路由算法

基于移动Ad Hoc组播路由协议ODMRP,提出一种考虑节点剩余能量的同时加入节点消耗率的Ad Hoc组播路由算法(EDRODMRP算法),并使用NS-2.28模拟器对EDRODMRP算法和ODMRP协议进行仿真实验.相对于ODMRP协议,EDRODMRP算法提高了网络吞吐量和网络投递率,延长了网络的生存时间,使网络的整体性能得到了提高.     

基于NS2的移动无线Ad Hoc网路由协议的仿真

Ad Hoc网是由一组具有路由和转发功能的移动节点组成的临时性自组织网络，是一种没有集中控制管理中心的无线移动网络.在研究Ad Hoc网的路由协议和设计Ad Hoc网时，对其进行有效的仿真是一个重要且必须的步骤.本文首先对Ad Hoc网和NS2进行了介绍，给出了在NS2下进行Ad Hoc网仿真的方法和步骤，最后对Ad Hoc网的路由协议AODV和DSR进行了仿真，并得出了相应的路由协议性能参数图.     

利用链路预测实现的抢先式路由算法

提出了一种将反应式路由协议和先应式路由协议结合在一起的抢先式Ad Hoc网络的路由算法.如果接收分组的能量小于危险阈值，则计算该链路的有效时间.如果估算的链路有效时间小于反应时间，则在链路失效前寻找局部替换路由，并用发现的局部路由替代当前即将失效的链路，保证节点的数据传送不受影响.将该算法应用于AODV协议，通过ns-2仿真，并将仿真结果和AODV协议比较，本算法在网络中负载较重的情况下明显降低了报文的传输时延，减少了路由失效数，提高了Ad Hoc网络的性能.     

微功率移动无线Ad Hoc网络

无线Ad Hoc网络是一个自组织、拓扑动态变化的网络，具有构建迅速、无需预设的通信基础设施等特点.提出一个微功率移动无线Ad Hoc网络的实现方案.研制的2.4 GHz微功率无线通信模块，符合IEEE 802.15.4标准，成功实现了多跳通信和自组织功能.研究了适合于低功耗低成本硬件系统上实现的Ad Hoc网络协议栈方案，新的协议方案可以显著减少网络的开销，延长节点寿命.提出一个考虑单向链路的路由协议和一种基于LAN的无线Ad Hoc网络仿真系统.设计并实现了基于μC/OS II实时操作系统的无线Ad Hoc网络通信协议.     

基于 MIMO 技术和“双环”技术的 Ad Hoc 网络路由协议

针对以往的 Ad Hoc 网络的缺陷,提出了一种基于 MIMO 技术和“双环”技术的 Ad Hoc 网络路由协议方案。在MIMO 技术、“双环”技术的支持下,新的 Ad Hoc 网络路由协议中采用了分集链路与复用链路,发挥了 DZR 协议与 ZRP协议的优势,以 OPNET 仿真工具为平台,从而实现了新 Ad Hoc 网络路由协议的最优化。     

基于NS2的Ad Hoc网络DRMR协议计算机仿真

针对现存多种Ad Hoc组播路由协议的有效性差、控制开销大等问题,设计并实现了一种基于动态广播环的组播路由（DRMR：Dynamic Ring based Multicast Routing)协议,确定了DRMR协议的实现框架,定义了各功能模块。在该协议中,组播路由建立和维护每个组成员广播环所构成的连通环图,当组成员广播环离开连通环图时,采用逐步扩大广播环的半径恢复其连通性。仿真结果表明,DRMR协议具有较高的数据分组递交率和较低的路由维护开销,其总体控制开销比基于需求的多播路由协议节省,能满足Ad Hoc网络对组播应用的要求,对研究Ad Hoc网络人员具有实际参考价值。     

移动Ad Hoc路由协议分析

移动Ad Hoc网络是一组带有无线收发装置的移动节点所组成的一个多珧临时性自治系统.作为无需基础设施的网络,移动Ad Hoc网络在军事和民用方面具有广阔的应用前景,是目前网络研究中的热点问题.文章描述了移动Ad Hoc网络的特征,对移动Ad Hoc网络的路由协议进行了分类、对比和分析.     

移动AdHoc网络及其路由协议剖析

移动Ad Hoc网络是一种不需要任何基础设施的临时性自治系统,本文主要介绍了移动Ad Hoc网络的概念、特点及其路由协议的设计要求,并且分析比较了目前现有的路由协议,进一步指出了移动Ad Hoc网络的发展前景.     

Ad Hoc网络路由协议研究

Ad Hoc网络是目前国际上前沿和热点的研究领域,具有分布式的体系结构。其组网简单灵活,支持随时随地通信。本文介绍了移动Ad Hoc的特点以及网络路由协议目前的研究现状,重点综述了移动Ad Hoc网路由协议,对它们进行了分类、对比和分析。最后提出了关于移动Ad Hoc网络路由协议的研究热点和展望。     

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。