基于平均度与平均聚类系数的RWP模型的研究

RWP模型作为节点仿真移动模型被广泛应用在传统移动自组织网络研究中,而机会网络作为移动自组织网络的一个分支,具有不保证连通的网络拓扑特性,这种特殊性可能导致RWP模型不适合作为仿真机会网络的节点移动模型.结合复杂网络理论中平均度与平均聚类系数的概念,对RWP模型仿真数据与实验数据进行了对比分析.分析结论指出,在平均度相近的条件下RWP模型的平均聚类系数与实验数据有明显的差异,因此RWP模型不适合作为描述机会网络的移动模型.     

基于掌形积分的路由协议仿真与性能分析

现有基于RWM移动模型的自组织网络路由协议仿真经常会引起一些问题,如平均运动速率衰减、移动节点分布不均匀等,使得路由协议的仿真不准确.针对这些问题,本文应用掌形积分对RWM移动模型的初始化重新进行了设计,该设计方法简单、易于实现.在此基础上,作者仿真了自组织网络常用的路由协议并进行性能分析.仿真结果表明,在RWM移动模型和修改后RWM移动模型下的路由协议性能存在差别.RWM移动模型的平稳性会对路由协议性能产生显著的影响.     

无线网络中节点移动性对病毒传播行为的影响

结合无线网络上病毒传播的实际特点,以蓝牙网络为载体,通过在SIS传播模型上引入移动的网络节点,分析和研究节点的移动速率对病毒传播的影响.数值仿真采用类似于蜂窝网络的拓扑结构,使网络中的节点按照指定的角度和速度在指定的网络区域内朝任意方向移动以建模实际网络拓扑的动态变化.结果表明节点移动越活跃,网络病毒感染速率越快,网络中被感染的节点数就越多.因此,通过控制网络中节点的移动速度来抑制无线网络中病毒的传播,进而为网络管理部门部署病毒的预警和控制措施等提供一些有意义的理论指导.     

一种基于节点运动范围自感知的路由方法

针对传统的路由协议不能适应移动网络中由于节点稀疏分布、频繁断开或周期性移动造成的节点间歇性连接的情况,文中在网络状态未知的情况下,提出了基于节点运动范围自感知的路由协议MSAR.它不需要地理位置定位等硬件的支持,利用节点历史相遇信息来分析节点的运动范围,选择运动范围重叠较小的节点来转发消息.仿真实验结果表明,MSAR路由协议能够保证较高的消息交付比率和相对较低的平均延时,并能够大量减少消息在网络中的分发数量,减小网络开销.     

节点移动速率对Epidemic协议性能影响分析

当容迟网络DTN中的传感器部署于城市环境下, 携带传感器的移动对象存在多种选择的问题. 文章在城市场景下分别设置传感器部署于较低移动速率节点组与较高移动速率节点组, 并基于工作日模型仿真Epidemic传染路由协议. 实验结果表明, 传输覆盖半径为10米时, 传感器携带于较高平均速率的移动节点组可以提高数据投递成功率与降低DTN的网络负载.     

战术Ad hoc网单元群组移动模型研究

提出以指挥员节点为参考点且更加接近真实战术的战术Ad hoc网单元群组移动模型.分析模型中战士节点运行特点和不同参数设置对节点路径有效性的影响.通过模型仿真与网络实际情况对照分析,证实了新的群组移动模型的可用性.     

基于真实场景下的DT-MSN性能分析

由于DT-MSN中节点的移动规律对网络性能起着关键的作用,本文采用真实场景中节点移动轨迹的样本,提取节点的移动规律,从而建立了容延迟移动传感器网络中移动节点间可通信概率的模型,并应用通用分析模型对网络进行了性能的分析,最后基于Randomized Routing下用仿真检验了该模型的可行性.它能在布置网络前提供技术参考,具有重要的实际应用价值.     

基于RPGM模型的Ad hoc路由协议的构建与仿真

为了改善无线Ad hoc网络中由于无线节点的移动所导致的网络性能下降,根据移动节点群体的特征,利用LANMAR作为簇间路由协议和AODV作为群组内的平面路由协议,提出一种基于参照点的群移动模型(RPGM)网络协议 MAG-Lanmar,并采用Ns2网络仿真工具进行了模拟测试.仿真结果表明,MAG-Lanmar无线网络协议在路由负载、响应时间、网络平均吞吐量方面,均有良好的性能.     

应用粒子群优化算法的航空自组网移动模型设计

为解决目前在航空自组网的研究过程中没有适用的移动模型问题,采用理论分析和实验仿真的方法,先对常用移动模型进行综述分析,在粒子群优化算法的基础上,结合AANET拓扑特点,提出一种基于PSO路径优化的移动模型,并在NS2平台上进行实验论证.研究结果表明:在节点高速运动情况下PSO模型比RWP模型更加稳定,网络吞吐量更大.该研究结果为航空自组网的研究提供模型参考与使用价值。     

基于节点通信监听机制的高效感知消息传输机会网络路由研究

针对采用社区划分策略的机会网络路由算法在消息传输过程中存在冗余转发的问题,设计节点通信监听机制,构建了新的消息传输策略,以高效感知邻居节点社区属性信息;并充分考虑携带移动设备的人的移动轨迹特点,设计了社区移动模型;嵌入时间片轮回机制,对网络节点进行动态划分社区;最终提出了基于节点通信监听机制的高效感知消息分发机会网络路由算法。在社区内转发消息时,选取与目的节点通信范围重叠区域内的邻居节点作为下一跳,若不存在这样的节点则将消息转发给与目的节点相遇概率较大的邻居节点或目的节点;在社区间转发消息时,算法选取与目的社区通信概率较大的中继社区节点转发消息,通过充分利用通信重叠区域内的节点转发消息,优化转发节点判定机制,重设消息传输条件,降低消息转发次数,从而提高消息传输成功率,降低传输时延。理论分析和仿真结果显示:与当前机会路由算法相比,新算法的传输成功率以及转发效率更高、平均端到端时延与平均存储时间更低。     

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…     

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。     

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     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

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.     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.