网络入侵危险性评估的云理论实现

由于任何网络安全手段都无法完全阻止网络攻击,保护网络的绝对安全,因此对网络入侵危险性进行评估,进而采取相应的防御手段就非常重要。传统的评估方法都无法同时评估网络入侵的不确定性(模糊性和随机性),基于此,利用云模型理论把模糊性和随机性有效集成在一起的优点,提出了一种基于云理论的网络入侵风险评估方法。本文给出了方法的理论基础、设计思想和关键实现技术及评估过程,并提出了一种改进的逆向云生成算法。该模型通过对系统资源监控,并对得到的数据进行处理,然后输入到云控制器,云控制器根据设定的规则做出评估结果。实验结果表明,该方法最大限度地保留了网络入侵评估过程中固有的不确定性,提高了评估结果的科学性和准确性。     

基于猜测概率和失误概率的学习诊断模型

受测者在测试过程中存在猜测和失误的可能,然而现有的诊断模型并未考虑这两个因素,因此无法在这种情况下对受测者的知识状态进行有效诊断。本文提出了一种知识空间理论中基于猜测概率和失误概率的学习诊断模型,当受测者出现猜测或失误时,该模型仍可对受测者的知识状态进行有效的诊断。模型依据试题的猜测概率和失误概率对答题状态进行转移,以诊断受测者的真实知识状态,并重点分析了这两种概率的计算方法。该模型在实用性、诊断的准确性等方面具有较好的效果。     

Ehrenfeucht-Fraïssé games in finite set theory

In this article, with Ehrenfeucht-Fraïssé games we prove that Δ₁≠Δ₀ on BFR, which implies Δ≠Δ₀ on BFR, and thus solve an open problem raised by Albert Atserias in his dissertation (Δ₀,Δ₁,Δ are fragments of first order logic and BFR is a class of finite sets which in essence is equivalent to a class of finite pure arithmetic structures with built-in BIT predicate).     

Static Bayesian games with finite fuzzy types and the existence of equilibrium

This paper studies a special game with incomplete information, in which the payoffs of the players are both random and fuzzy. Such a game is considered in the context of a Bayesian game with the uncertain types characterized as fuzzy variables. A static fuzzy Bayesian game is then introduced and the decision rules for players are given based on credibility theory. We further prove the existence of the equilibrium of the game. Finally, a Cournot competition model with fuzzy efficiency under asymmetric information is investigated as an application and some results are presented.     

Fault tolerance in cellular automata at high fault rates

A commonly used model for fault-tolerant computation is that of cellular automata. The essential difficulty of fault-tolerant computation is present in the special case of simply remembering a bit in the presence of faults, and that is the case we treat in this paper. We are concerned with the degree (the number of neighboring cells on which the state transition function depends) needed to achieve fault tolerance when the fault rate is high (nearly 1/2). We consider both the traditional transient fault model (where faults occur independently in time and space) and a recently introduced combined fault model which also includes manufacturing faults (which occur independently in space, but which affect cells for all time). We also consider both a purely probabilistic fault model (in which the states of cells are perturbed at exactly the fault rate) and an adversarial model (in which the occurrence of a fault gives control of the state to an omniscient adversary). We show that there are cellular automata that can tolerate a fault rate 1/2−ξ (with ξ>0) with degree O((1/ξ²)log(1/ξ)), even with adversarial combined faults. The simplest such automata are based on infinite regular trees, but our results also apply to other structures (such as hyperbolic tessellations) that contain infinite regular trees. We also obtain a lower bound of Ω(1/ξ²), even with only purely probabilistic transient faults.     

Queueing analysis of a server node in transaction processing middleware systems

Quantitative performance modeling of complex information systems is of immense importance for designing enterprise e-business infrastructures and applications. In this paper, we present a traffic model of a server node in a typical transaction processing middleware system as well as a quantitative framework to model and analyze its performance. A multi-class open queueing network model is presented in which multi-class jobs are admitted to a number of server processes sharing hardware resources including the CPU and the disk. We have developed a viable approximation method, which decomposes the dependent components into their independent counterparts while preserving their relevant characteristics. We have conducted queueing-theoretic delay analyses and verified the approach using simulation. Results demonstrate the strength of our approach in predicting delays, elapsed times and other system performance measures.     

Application of system dynamics in analyzing the carrying capacity of water resources in Yiwu City,China

A risk assessment model for water shortage is constructed using a risk analysis method based on the information diffusion theory. The application of this model is demonstrated in the city of Yiwu in Zhejiang Province, China. Based on the analytical results from a small sample, this study indicates that the present model is more stable and effective than the traditional model. Risk assessment results are used to analyze the carrying capacity of water resources from an ecological angle. For this study, the carrying capacity of water resources is defined as the maximum volume of water suitable for supporting human activity in certain stages of social development that can be borne by water resources under favorable ecological conditions. Further study on Yiwu is also performed, with results indicating that water shortages in this city are not related to types of water source, but can be classified in terms of water quality and conservation. To verify the results of theoretical investigation in this paper, the authors simulate changes in the carrying capacity of water resources under the conditions of future water management policies. This simulation uses the system dynamics (SD) model, based on the historical data collected by the city over the past 20 years and governmental plans to raise inhabitants’ living standards between the present and 2020. The paper simultaneously indicates that both singularly pursuing fast economic development at the expense of the environment and promoting environmental protection via reduced economic development are undesirable for Yiwu. Simultaneously giving consideration to both the economic development and environmental protection is likely to produce better overall results. However, if the present water supply level is maintained but does not increase in the near future, Yiwu's water supply will be unable to satisfy requirements even under this scheme. In this case, the carrying capacity of water resources in the region can only be effectively improved by promoting more efficient use of water and water conservation schemes, as well as strengthening long-term investment in environmental protection.     

High-order compact boundary value method for the solution of unsteady convection–diffusion problems

In this paper, we propose a new class of high-order accurate methods for solving the two-dimensional unsteady convection–diffusion equation. These techniques are based on the method of lines approach. We apply a compact finite difference approximation of fourth order for discretizing spatial derivatives and a boundary value method of fourth order for the time integration of the resulted linear system of ordinary differential equations. The proposed method has fourth-order accuracy in both space and time variables. Also this method is unconditionally stable due to the favorable stability property of boundary value methods. Numerical results obtained from solving several problems include problems encounter in many transport phenomena, problems with Gaussian pulse initial condition and problems with sharp discontinuity near the boundary, show that the compact finite difference approximation of fourth order and a boundary value method of fourth order give an efficient algorithm for solving such problems.