网格身份认证和细粒度访问控制模型的研究与设计

网格是继因特网(Internet)、万维网(Web)之后,互联网发展的第三个里程碑。网格系统具有数据量大、地理上分布、数据库结构异构、其应用环境网络化、用户人数众多、分散的特点。开放的网络环境对信息的传输没有足够的安全保证。网格系统的安全问题已经成为网格研究的热点问题,国内外研究机构正在对网格安全问题进行广泛的研究。身份认证和访问控制机制是网格安全的重要研究方面,产生了集中式层次认证模型、混合交叉认证模型等网络安全认证模型。这些方法都存在各种各样的缺陷,如证书管理复杂,路经选择困难,不能进行细粒度的访问控制等。探讨在网格环境中跨域身份认证和细粒度访问控制系统方面,提出了基于多种认证组合和资源代理的网格身份认证及访问控制模型,通过混合身份认证和票据交换达到身份认证的及时性、有效性和细粒度资源控制,在用户数量大、更新频繁的情况下,达到系统响应速度快的要求。     

CNGrid GOS安全:设计与实现

分析了网格计算环境中的安全问题,并提出了针对中国国家网格系统软件(CNGrid GOS)的安全框架,即使用证书来处理相互的认证,利用虚拟组织层次的访问控制决策和资源层次的访问控制实施进行处理授权.通信安全是通过在传输层使用安全套接字标准(SSL)、在消息层使用Web服务安全(WS-security)标准实现的.此安全框架已在CNGrid GOS中实现,且在中国国家网格环境中部署.     

P2P文件系统安全访问控制模型的研究

结合信任模型、激励机制和认证授权技术提出一种安全访问控制模型,将PGP信任模式和SPKI授权证书机制相结合,加入简单的激励机制,实现了基于信任表达和授权方式的灵活的访问控制机制,该机制在提高共享系统安全性的同时,实现了多种形式的访问控制策略.     

网格中通过认证密钥交换协议实现的权限管理系统

网格中的授权管理有多种结构形式,本文利用基于口令的三方认证密钥交换协议（GPAKE）,实现了基于口令的授权访问控制协议,完成用户向资源管理员提出访问请求,直至获得访问权限进行安全访问的过程．整个系统中不使用证书机制,完全基于用户口令,为用户提供了最大的使用便利．这样的系统提供的安全强度低于GSI等基于证书的架构,面临了字典攻击、猜测口令攻击等威胁,但由于系统的灵活性和便利性,可作为证书系统的补充应用于轻型网格等体系中．     

空间知识网格安全体系结构模型研究

阐述空间知识网格环境中的安全需求以及现有安全技术的不足,研究空间知识网格安全策略,建立空间知识网格安全体系结构模型.该模型基于属性证书和策略集,用XACML作为描述访问控制决策的语言,充分利用Web服务技术,集成权限管理基础设施和XACML,使自身适合空间知识网格的需求,可支持基于角色的访问控制,具有灵活性、适应性、可伸性和可扩展性等特点.     

一种基于缓存的快速PKI认证模型

在大规模PKI系统中跨域建立证书信任时,为提供高效的证书路径发现及认证算法,基于缓存机制提出了一种系统、灵活的认证框架.该框架模型对于短期缓存认证提出一次一密以提高安全性;对于较长时期的证书缓存提出证书可靠性指数概念,让用户可在安全和效率间权衡.扩展证书缓存及证书可靠性指数到CA间的认证,满足实际网络环境需要,提高了认证效率,消除了上层CA证书验证服务时存在的性能瓶颈问题.     

一种基于属性证书的分布式访问控制模型

在分布式环境中通常需要协同合作和共享资源,RBAC是安全系统中保护资源的有效手段之一。基于对面向对象RBAC模型的分析,引入PMI属性证书,提出一种面向对象的分布式多域访问控制模型AC-ORBAC,给出形式化描述,该模型通过属性证书实现角色授权访问控制,使对访问控制的管理更为灵活高效,并对职责分离和域问访问进行了讨论。结合PKI．给出了一个实现原型。     

面向服务的学习评价网格安全体系

安全问题是网格系统中一个极具挑战性的问题。为了解决面向e-L earn ing的学习评价网格(LAG rid)中的安全问题,该文提出了一种面向服务的网格安全体系。该体系基于对称密钥基础设施,实现了单次登录方式的系统用户认证和基于角色的访问控制,以及一种安全令牌发行服务,并在此基础上进一步实现了网格节点认证和基于W eb服务安全规范的消息加密和签名。这种安全体系已被成功用于构建LAG rid系统,实现了一种安全、透明的基于W eb的用户环境,支持广域资源共享和跨组织的大规模协同工作。     

基于群组-活动的制造网格访问控制模型研究

针对制造网格访问控制的需求,提出一种网格环境下基于群组-活动的访问控制模型.模型对RBAC模型进行扩展,用活动对角色和权限对象进行封装,增加了活动状态、活动层次和活动依赖,实现动态的权限控制和灵活的权限粒度;用群组和群组层次表示参与协同的组织中原有组织结构和访问控制机制,保持了参与组织原有结构的自治性及权限的分布式管理...     

网格计算环境下基于角色的细粒度协作访问控制

针对网格中大量协作访问资源的需求,提出了一种基于角色的细粒度协作访问控制方案.该方案将基于角色的访问控制方法用于网格计算环境,并修改了其中的权限配置规则,添加了时空属性以及细粒度的协作访问属性,可以更好地适应网格计算环境下协作访问控制共有资源的要求.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-