应用SIP构建IPv6安全移动组播系统

以RFC3740提出的安全组播架构为基础,利用会话初始化协议（Session Initiation Protocol, SIP）作为信令协议,构建IPv6下的安全移动组播系统.系统提供用户访问控制和安全通信功能.此外,由于采用分布式结构,系统不存在单一故障点,易于部署和扩展.     

IP组播网络安全威胁与积极测试

基于IP组播路由协议存在的安全问题,深入剖析了多种针对组播网络的DoS攻击行为,总结了三类组播DoS攻击模式,进而设计并实现了一个组播安全的主动测试框架以评估IP组播网络安全. 通过主动测试,可以发现组播路由协议以及组播部署中存在的安全隐患,帮助运营商及早发现和解决组播安全问题.     

基于SIP的组播接入控制

组播业务的实施离不开组播安全,而组播接入控制是组播安全中非常重要的一部分. 提出了一种使用会话初始化协议(SIP)进行组播接入控制的方法. 该方法利用SIP协议身份验证机制、S/MIME加密与签名方法提供了组播用户身份验证、鉴权和安全通信. 该方法具有安全性高、运行稳定、扩展性好的优点,能轻松移植到IPv6下运行.     

一种新的组播安全通信密钥管理协议

在分析群组通信安全问题的基础上,采用一种折中的方法,提出一种混合的分组分层的组播群组密钥管理协议,以解决组规模较大的安全组播应用中存在的问题.新的组播安全通信协议有效地降低了协议通信带宽、解密和加密计算等负载,具有较好的可扩展性,适合大型动态组播.     

基于NAK压缩的可靠组播协议研究

随着组播应用范围的不断扩大,人们对组播的可靠性尤其在应用于不稳定的无线网络时有了更高的要求,提出了基于否定确认(NAK) 的可靠组播传输协议.文章在分析典型的组播网络系统模型的基础上,对基于NAK的可靠组播传输协议进行了改进;通过NS仿真结果证明,改进的协议有效压缩了NAK,减少了所需带宽,增强了系统的实时性和可扩展性,并提高了组播的可靠性.     

基于TCL的PIM—SM协议一致性测试系统设计

针对PIM-SM组播协议,提出了一种协议一致性测试系统的设计方法.其核心思想是通过创建虚拟测试体,用简单的PC机模拟复杂的网络环境和协议行为,并针对协议测试过程中同时要求报文高效处理和网络场景频繁修改的问题,进行了系统层次的划分,实现了模拟配置灵活性和运行效率的统一,具有良好的扩展性.基于该方法实现的系统,成功地对多个不同的PIM-SM组播协议实现进行了一致性测试.     

基于SSALMP的应用层组播的研究与实现

应用层组播将组播功能从路由器转移到端系统,由端系统完成所有组播组通讯的功能.文章主要研究了面向单源流媒体非交互式应用的应用层组播系统.研究并实现了基于SSALMP协议的原型系统,该系统实现了组播组的创建,组播组的加入和退出以及节点失效的处理,同时对其性能在局域网中进行了测试.     

一个组播密钥分发协议的密码学分析

分析了由Molva提出的一个可扩展的基于RSA的组播密钥分发协议，说明此协议对密钥泄漏攻击和共谋攻击是不安全的.     

流媒体应用层组播系统的实现

设计和实现了一个流媒体应用层组播系统.系统中节点之间使用RTP协议传播数据,并对系统的整体传输和大规模组播下的可扩展性进行了仿真评测,结果显示该系统能够比较好地支持实时的流媒体组播应用.     

无线多跳网络中基于声誉机制的可靠组播协议

为了提高无线多跳网络中组播树的可靠性和提高组播效率,提出了一种基于声誉机制的组播协议.该协议在构建组播树时考虑了节点的声誉值,从而将自私性节点排除在组播树之外,使得构建的组播路径比较可靠.仿真实验表明该协议可以用较低的代价有效地提高组播效率.     

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.     

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.     

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)

正~~     

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).     

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.