用PTA模型形式化分析基于Gossip 协议的发布/订阅系统

在研究传统的发布／订阅消息中间件系统的基础之上,结合Gossip协议的特点来研究发布／订阅消息中间件,最后运用形式化方法,通过PRISM仿真工具,对仿真的模型进行形式化分析．实验结果表明,发布／订阅消息中间件系统的实时性受消息产生速度的影响,在各个订阅者订阅相同消息和不同消息两种情况之下网络特性展现不同的变化,但最终都是随着消息产生速度的增加而减小．可靠性随着消息产生速度的增加而减小,并且订阅者的接收缓存越大可靠性越高,但增幅率会越来越小．该实验模型和实验方法对于发布／订阅消息中间件系统的研究,以及在现实环境中配置系统的相关参数有一定的帮助．     

多媒体在高等数学教学中的作用探讨

多媒体在高等数学教学中的作用一直以来倍受争议。本文从学习兴趣、数学美、数学建模以及留有思维空间等几个方面对多媒体在高等数学教学中的作用做一个初步的探讨。     

深层话语——城市设计的文化与美

随着我国城市的日益繁荣,城市形象成为令人关注的文化资本。为了改善形象,促进经济发展,城市设计作为城市规划与建筑设计衔接的重要阶段,也日趋成熟。但是,目前的设计似乎都存在重形式、轻本质的现象。本文从文化与美两个角度,结合实际案例阐述设计的本质,以求对城市设计的实践有所裨益。     

形式化攻击者能力描述的计算可靠性研究

研究在安全协议仅使用数据完整性算法时，形式化分析方法中形式化攻击者能力描述的计算可靠性，首先假设计算性攻击者的能力超过形式化攻击者的能力，然后构造攻击实验，进而论证攻击实验中计算攻击者的输出与签名算法或密钥杂凑函数的安全定义相矛盾。因此得出计算性攻击者所能生成的消息均属于形式化攻击者所能生成的消息闭集这一结论，基于该结论，可以构建或者改进形式化分析系统，使其具有计算可靠性。     

Roles of Sexual Objectification Experiences and Internalization of Standards of Beauty in Eating Disorder Symptomatology: A Test and Extension of Objectification Theory.

This study extends the literature on eating disorder symptomatology by testing, based on extant literature on objectification theory (B. L. Fredrickson & T. Roberts, 1997) and the role of sociocultural standards of beauty (e.g., L. J. Heinberg, J. K. Thompson, & S. Stormer, 1995), a model that examines (a) links of reported sexual objectification experiences to eating disorder-related variables and (b) the mediating roles of body surveillance, body shame, and internalization of sociocultural standards of beauty. Consistent with hypotheses, with a sample of 221 young women, support was found for a model in which (a) internalization of sociocultural standards of beauty mediated the links of sexual objectification experiences to body surveillance, body shame, and eating disorder symptoms, (b) body surveillance was an additional mediator of the link of reported sexual objectification experiences to body shame, and (c) body shame mediated the links of internalization and body surveillance to disordered eating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CSP和RSL应用于协议形式化描述的研究

文中用一种新的形式化描述语言RSL来描述网络协议，采用通信顺序进程CSP为模型。该模型基于进程代数，能用严密的代数演算方法验证协议性质，文中对CSP模型和RSL语言作了时间的扩充，并且给出了从CSP模型到RSL语言的转换步骤及规则，最后给出了一个TFTP的实例来说明RSL语言在协议描述上的适应性。     

Characterizing Grids: Attributes, Definitions, and Formalisms

Grid systems and technologies have evolved over nearly a decade; yet, there is still no widely accepted definition for Grids. In particular, the essential attributes that distinguish Grids from other distributed computing environments have not been articulated. Most approaches to definition adopt a static view and consider only the properties and components of, or the applications supported by, Grids. The definition proposed in this paper is based on the runtime semantics of distributed systems. Rather than attempt to simply compare static characteristics of Grids and other distributed computing environments, this paper analyzes operational differences, from the viewpoint of an application executing in both environments. Our definition is expressed formally as an Abstract State Machine that facilitates the analysis of existing Grid systems or the design of new ones with rigor and precision. This new, semantical approach proposes an alternative to the currently accepted models for determining whether or not a distributed system is a Grid.     

Structural Refinement of Systems Specified in Object-Z and CSP

This paper is concerned with methods for refinement of specifications written using a combination of Object-Z and CSP. Such a combination has proved to be a suitable vehicle for specifying complex systems which involve state and behaviour, and several proposals exist for integrating these two languages. The basis of the integration in this paper is a semantics of Object-Z classes identical to CSP processes. This allows classes specified in Object-Z to be combined using CSP operators. It has been shown that this semantic model allows state-based refinement relations to be used on the Object-Z components in an integrated Object-Z/CSP specification. However, the current refinement methodology does not allow the structure of a specification to be changed in a refinement, whereas a full methodology would, for example, allow concurrency to be introduced during the development life-cycle. In this paper, we tackle these concerns and discuss refinements of specifications written using Object-Z and CSP where we change the structure of the specification when performing the refinement. In particular, we develop a set of structural simulation rules which allow single components to be refined to more complex specifications involving CSP operators. The soundness of these rules is verified against the common semantic model and they are illustrated via a number of examples.     

Formal Verification Successes at Motorola

Formal tools are either too labor intensive or are completely impractical for industrial-size problems. This paper describes two formal verification tools used within Motorola, Versys2 and CBV, that challenge this assertion. The two tools are being used in current design verification flows and have shown that it is possible to seamlessly integrate formal tools into existing design flows.