丝绸之路五大城市群公路通达性空间格局研究

以丝绸之路经济带上5个城市群为研究对象,城市群内部城市为研究单位,采用基于城市综合发展水平评价指标体系的加权平均旅行时间为研究手段,对5座城市群内部公路通达性水平和空间格局进行研究.结果显示,各城市群受到经济发展水平、城市空间分布、公路交通网络基本形态等因素影响,通达性水平和空间格局呈现明显差异.宁夏沿黄城市群、关中平原城市群、中原城市群公路通达性总体呈同心圆空间结构且通达性较好;兰西城市群和天山北坡城市群呈单侧放射状空间结构且通达性水平较差.     

世界主要旅游国家和地区航空通达性对比分析

运用距离度量法和社会网络分析法对30个世界主要旅游国家和地区之间的航空通达性进行对比研究.以30个世界主要旅游国家和地区的航空枢纽机场所在城市为节点,以航空枢纽机场所在城市之间的直达航班为连接,构建世界主要旅游国家和地区航空通达性计算网络,从便利程度、旅行时间成本和旅行经济成本3个方面对比研究主要旅游国家和地区的航空通达性.得出这30个世界主要旅游国家和地区的航空便利通达性、时间通达性、费用通达性的排名以及综合这3个通达性之后的最终通达性水平排名情况.另外,研究认为,便利通达性应与时间通达性、费用通达性共同作为衡量旅游交通通达性的重要指标.     

基于GIS的佛山市禅城区路网空间通达性分析Ⅱ——通达性分析

以佛山市掸城区为研究区域．基于GIS建立道路网络．求算出道路网络的各个通达性指标。从通达性水平、空间距离、时间距离和绕行系数几个方面分析了禅城区道路网络的通达性。研究结果表明：祖庙街道的道路网络密度明显高于其他镇街．石湾街道道路结点的通达程度高．南庄镇的各项指标均最低。总体来说掸城区的3个街道通达性水平比南庄镇高。     

基于空间句法和网络分析的武汉市城郊休闲农业点空间可达性研究

休闲农业是乡村旅游发展的重要载体，其可达性水平直接影响着乡村旅游的可持续发展.基于此，论文以武汉市城郊368个休闲农业点作为研究对象，在空间句法方法的基础上，借助网络分析方法，构建空间句法模型和空间关联性网络模型，从全局通达性、局部关联性两个方面对武汉市城郊休闲农业点的空间可达性进行研究，以揭示武汉市城郊休闲农业点的布局特征与空间关联性.结果发现： 1) 武汉市城郊休闲农业点整体密度核心分布较为分散，空间呈现群聚式非均匀分布在武汉市绕城高速周边，形成了绕城高速休闲农业点分布带； 2) 从路网全局通达性来看，武汉市城郊休闲农业点多分布在2级可达性道路300 m缓冲区范围内，且此道路等级缓冲区范围内的农庄经济型休闲农业点可进入性较好，对外通达性一般； 3) 从路网局部关联性来看，区域间休闲农业点内部联系“西密东疏”，东西湖区与黄陂区、蔡甸区休闲农业点联系较为密切；区域内休闲农业点内部关联性差异明显，高速公路、国道沿线区域的休闲农业点关联性普遍较强.     

基于FLD算法的南昌市老城区公交网络的优化研究

为了研究城市道路遭受攻击而出现拥堵时所呈现的特性,把现实中的城市道路抽象成复杂网络,利用FLD算法对其体现的特征进行仿真分析,结果表明:公交路网在遭受针对性和随机性攻击时均具有一定的稳定性,但当网络中的失效节点达到一定比例时,遭受针对性攻击时的路网会在极短时间内断裂所有连边从而导致网络迅速崩溃。在此研究的基础上,分析了南昌市老城区交通路网的几个拓扑特征并相应地提出了四点可行性的优化建议,结果表明优化后的路网具有更高的通达性和抗毁性,对保持城市交通的畅通性具有一定的现实意义。     

构建合理配置的青海综合交通运输网络

根据青海省交通网基本特征、结构,分析制约青海省综合交通网络因素,依照交通需求特点,构建合理配置的青海交通运输网络,形成西部大通道,完善路网结构,提高公路的通达深度和通行能力.     

包含立交匝道信息的高速公路网络复杂拓扑结构研究

在以往的路网拓扑研究中,立交和出入口一般都只被看成一个节点来处理,没有涉及具体的匝道信息,但随着路网规模的扩大及基于路网拓扑的安全性分析、通达性研究、交通标志设置、紧急情况处置、模拟仿真和车辆导航等需求的不断增加,原来单层结构的拓扑关系已经不能满足这些应用要求,另一方面,由于原来路网拓扑结构相对比较简单,导致相应的最佳路径搜寻算法都很复杂.在总结已完成项目的基础上,从交通工程角度研究了一种包含具体匝道信息的多层次高速公路路网复杂拓扑结构,包含路段/节点、匝道/出入口、方向节点等内容,满足地理数据文件(GDF)标准格式要求,可支持新一代基于复杂路网结构的多种应用,采用双向链表建立的数据结构,方便增减高速公路、立交或者出入口等对象,在此基础上研究了一种适应复杂路网架构的路径搜索算法,为基于所提出的复杂路网拓扑应用提供了可能.     

基于GIS的佛山市禅城区路网空间通达性分析Ⅰ——通达性指标的选取与计算

以佛山市禅城区为研究对象,基于GIS建立道路网络,求算出道路网络的各个通达性指标.从网络密度、连通度、可达性、空间距离、时间距离和绕行系数几个方面分析了禅城区道路网络的通达性.研究结果表明：祖庙街道的网络密度明显高于其他镇街,石湾街道的道路结点的通达程度较高,南庄镇的各项指标均最低.总体来说禅城区的3个街道通达性水平比南庄镇高.     

包含立交匝道信息的高速公路网络复杂拓扑结构

在以往的路网拓扑研究中,立交和出入口一般都只被看成一个节点来处理,没有涉及具体的匝道信息,但随着路网规模的扩大及基于路网拓扑的安全性分析、通达性研究、交通标志设置、紧急情况处置、模拟仿真和车辆导航等需求的不断增加,原来单层结构的拓扑关系已经不能满足这些应用要求,另一方面,由于原来路网拓扑结构相对比较简单,导致相应的最佳路径搜寻算法都很复杂.在总结已完成项目的基础上,从交通工程角度研究了一种包含具体匝道信息的多层次高速公路路网复杂拓扑结构,包含路段/节点、匝道/出入口、方向节点等内容,满足地理数据文件(GDF)标准格式要求,可支持新一代基于复杂路网结构的多种应用,采用双向链表建立的数据结构,方便增减高速公路、立交或者出入口等对象,在此基础上研究了一种适应复杂路网架构的路径搜索算法,为基于所提出的复杂路网拓扑应用提供了可能.     

湘江流域综合交通优势度测度与分析

以湘江流域为研究区域,选取县级及以上城市为评价单元,运用GIS分析技术从公路网密度、邻近度、通达性3方面分别对各评价单元的差异进行分析,并利用以上3个指标构建区域交通优势度综合评价模型。分析湘江流域交通优势度的空间分布格局和特征以及其形成成因．研究表明：湘江流域路网密度整体较低,城市间差异较大;邻近度和通达性以地级市为中心呈圈层分布;城市间交通优势度极化严重,交通优势度较高的地区主要在长株潭城市圈、衡阳市及周边地区：整个流域交通优势度成“H”字型分布格局．     

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。