无线局域网安全漏洞剖析

概述了无线局域网的通信特点,剖析了IEEE802.11的安全机制,重点对无线局域网安全方面的隐患进行了分析,最后提出了提高安全性的对策.     

General exponential smoothing and the equivalent arma process

Although the basic principles of exponential smoothing and discounted least squares are easily understood, the full power of the technique is only rarely exploited. The reason for this failure lies in the complexity of the standard procedures. Often they require fairly complex mathematical models and use a variety of cumbersome algebraic manipulations. An alternative formulation for exponential smoothing is presented. It simplifies these procedures and allows an easier use of the full range of models. This new formulation is obtained by considering the relationship between general exponential smoothing (GES) and the well-known ARMA process of Box and Jenkins. The three commonest seasonal models have only recently been considered for GES systems. They are discussed in some detail here. The computational requirements of the GES and equivalent ARMA procedures are reviewed and some recommendations for their application are made. The initialization of GES forecasting systems and the important problem of model selection is also discussed. A brief illustrative example is given.     

高阶Lagrange函数的同位变换

本文将Lagrange函数的同位变换推广到广义力学中,并举例说明这种变换。     

Learning Bayesian networks using genetic algorithm

A new method to evaluate the fitness of the Bayesian networks according to the observed data is provided. The main advantage of this criterion is that it is suitable for both the complete and incomplete cases while the others not. Moreover it facilitates the computation greatly. In order to reduce the search space, the notation of equivalent class proposed by David Chickering is adopted. Instead of using the method directly, the novel criterion, variable ordering, and equivalent class are combined,moreover the proposed mthod avoids some problems caused by the previous one. Later, the genetic algorithm which allows global convergence, lack in the most of the methods searching for Bayesian network is applied to search for a good model in this space. To speed up the convergence, the genetic algorithm is combined with the greedy algorithm. Finally, the simulation shows the validity of the proposed approach.     

循环加载后饱和软粘土退化性状的试验研究

基于上海地区淤泥质饱和粘土的循环加载试验,总结了正常固结下淤泥质饱和粘土的孔压发展规律,在前人工作的基础上,引入等效超团结比的概念,描述了循环加载后饱和粘土的强度及模量的退化规律,从而确定了循环加载后其应力应变双曲线模型中的参数．为动载后计算上体附加沉降提供了一种方法     

等效阻抗（导纳）的几何解法

利用两个建立在基尔荷夫定则之上的定理,可以得到无源线性两端网络等效阻抗（导纳）的几何解法．这种方法只需对网络图的结构进行分析,找出网络图在特定条件下所有的树和余树,并计算出所有树的支路导纳之积或余树的支路阻抗之积,就能方便地计算出网络等效阻抗（导纳）．     

柔性垫梁下砌体局部受压问题的讨论

为了考虑柔性垫梁下砌体局部受压问题，ＧＢＪ３－８８给出了具体的计算公式，但这一公式给设计者造成一个误会，即当垫梁宽为定值时，砌体的局部受压承载力随墙厚的增加而减小。本文针对这一问题，从理论上推导了计算公式。修正了垫梁折算高度。     

对“置换法测定金属的当量”实验的改进

本文从原理上对该实验进行了部分改进,用“原子量”取代了“当量”,并建议将实验题目改为“置换法测定金属的原子量”。克服了实验教学中的疑难问题,有利于更好地达到实验目的。     

等势凝聚集

本文给出等势凝聚集的概念，得到了有别于导集的若干结果，由此产生了几个新概念，并讨论了它们的基本性质。     

对电源模型等效变换理解存在的歧义

根据对两种电源模型在内阻趋于零和无穷大时伏安特性变化趋势的分析,指出通常对电源模型等效变换理解存在的歧义,全面、准确的理解应是理想电压源不能等效变换为电流源,理想电流源不能等效变换为电压源。