网络演算的矩阵解释

网络演算是离散事件动态系统理论在计算机网络中的应用,网络演算通过到达曲线和服务曲线计算网络的性能参数,这两个概念封装了复杂的理论背景,从而易于在实际中应用,但对到达曲线和服务曲线概念的理论研究比较缺乏.文中采用幂等矩阵的角度描述到达曲线和服务曲线,演算的过程成为矩阵运算,通过结合矩阵双子理论和余理论的研究结果,得出了由矩阵表演算的基本定理.研究表明,幂等矩阵理论为网络演算提供了很好的理论解释.文中还提出一种基于变换矩阵的方法求某些网络元素的服务曲线.     

Towards Optimal Use of Multi-Precision Arithmetic: A Remark

If standard-precision computations do not lead to the desired accuracy, then it is reasonable to increase precision until we reach this accuracy. What is the optimal way of increasing precision? One possibility is to choose a constant q > 1, so that if the precision which requires the time t did not lead to a success, we select the next precision that requires time q ˙ t˙ It was shown that among such strategies, the optimal (worst-case) overhead is attained when q = 2. In this paper, we show that this “time-doubling” strategy is optimal among all possible strategies, not only among the ones in which we always increase time by a constant q > 1.     

具有几乎完美代数免疫的偶数元弹性函数构造

完美代数免疫(PAI)的布尔函数能够抵御代数攻击和快速代数攻击。PAI函数的构造是目前布尔函数研究最具挑战性的问题之一。利用布尔函数的双变元表达式和有限域理论,基于Carlet-Feng函数提出一种新的偶数元布尔函数的一般性构造。证明由该构造得到的函数具有一阶弹性和至少次优代数免疫度等密码学性质,给出其代数免疫度达到最优时的充分条件,并比较该类函数、Carlet-Feng函数和由一阶级联方式构造的函数在6~16之间的所有偶数变元下抵抗快速代数攻击能力。实验结果表明,该类函数能更好地抵抗快速代数攻击,且具有几乎完美的代数免疫性能。     

U.S. College Students' Internet Use: Race, Gender and Digital Divides

The goal of this study was to learn about whether race and gender make a difference in Internet use among U.S. college students. A survey of college students at 40 U.S. higher education institutions was conducted, along with observations and interviews at several Midwestern U.S. universities. For comparison to the general U.S. population a nationwide telephone survey was undertaken. The study presents new data on Internet use among male and female college students, as well as trends in use across racial lines. Data on non-White Hispanic college student users of the Internet provides insight into Internet use among a group that appears to be underrepresented in the literature on college students and Internet use. The data analysis presents a complex picture of differential Internet use along gender lines, one that is generally consistent with the existing scholarly literature. Differential use based on race is a bit more complex. Stronger points of contrast emerge amongst White non-Hispanic, Hispanic, and Black non-Hispanic college students than they do when the respondents are grouped by gender.     

浅谈程序设计中绑定变量的使用

本文分析了ORACLE数据库中硬解析的缺点,引出绑定变量的必要性。并以C#语言为例,介绍了应用系统程序设计中绑定变量的使用。     

Algebraic Interpretation of a Microprogram Finite-State Machine with Datapath of Transitions

A new principle is proposed for the representation of functions of a microprogram finite state machine with datapath of transitions in the form of a set of some algebras. The principle consists of partitioning the set of tuples forming transition and output functions into subsets each of which is interpreted as a partial function from the signature of the corresponding algebra.     

Estimating and Validating the Cumulative Distribution of a Function of Random Variables: Toward the Development of Distribution Arithmetic

A method for estimating and validating the cumulative distribution of a function of random variables (independent or dependent) is presented and examined. The method creates a sequence of bounds that will converge to the distribution function in the limit for functions of independent random variables or of random variables of known dependencies. Moreover, an approximation is constructed from and contained in these bounds. Preliminary numerical experiments indicate that this approximation is close to the actual distribution after a few iterations. Several examples are given to illustrate the method.     

Bounding the Results of Arithmetic Operations on Random Variables of Unknown Dependency Using Intervals

Many real problems involve calculations on random variables, yet precise details about the correlations or other dependency relationships among those variables are often unknown.For example consider analyzing the cancer risk associated with an environmental contaminant. The dependency of an individual's cumulative exposure on the less useful (but more obtainable) current exposure level will be uncertain. In this and many other cases, data points from which to derive such dependencies are sparse, and obtaining additional data is prohibitively expensive or difficult. Thus manipulating variables whose dependencies are unspecified is a problem of significance.This paper describes a new approach to bounding the results of arithmetic operations on random variables when the dependency relationship between the variables is unspecified. The bounds enclose the space in which the result's distribution function can be.     

深入思考如何提高学生程序设计应用能力

本文通过总结<计算机软件技术基础>课程的讲授,在如何提高学生程序设计应用能力方面作者提出了自己的观点,并从"帮助学生认清C语言的重要性"、"提高学生学习程序设计的兴趣"、"注重培养学生逻辑思维能力"、"课堂上充分调动学生的积极性"、"帮助学生学会自主学习"、"开展课外讲座,帮助学生建立正确的学习观"等六个方面具体详细地阐述了提高学生程序设计应用能力的方法.     

长项优先的产生算法——改进的Apriori算法

Apriori算法是一种最有影响的挖掘布尔关联规则频繁项集的算法.本文简单介绍了Apriori算法,提出了Apriori算法的改进方案--长项优先的产生算法,它基于传统Apriori算法,通过改变候选项集的产生顺序来减少数据库访问,从而提高效率.     

Asymmetric Code-Theoretical Schemes Constructed with the Use of Algebraic Geometric Codes

Asymmetric coding schemes are developed that are constructed with the use of algebraic geometric codes. Basic analytical expressions are obtained that connect the parameters of algebraic geometric codes with the parameters of asymmetric coding schemes based on these codes. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 47–57, May–June 2005.     

Algebraic Algorithmics: Theory and Applications

This article is a review of works on the algebra of algorithms, which is a new promising line of investigation in the field of algebraic algorithmics and is progressing rapidly in Ukraine and abroad. To this line belong explorations into a multilevel structural software design method developed at the Automatic Programming Department at the V. M. Glushkov Cybernetics Institute of the Academy of Sciences of Ukraine.     

Ordinal Arithmetic: Algorithms and Mechanization

Termination proofs are of critical importance for establishing the correct behavior of both transformational and reactive computing systems. A general setting for establishing termination proofs involves the use of the ordinal numbers, an extension of the natural numbers into the transfinite that were introduced by Cantor in the nineteenth century and are at the core of modern set theory. We present the first comprehensive treatment of ordinal arithmetic on compact ordinal notations and give efficient algorithms for various operations, including addition, subtraction, multiplication, and exponentiation. Using the ACL2 theorem proving system, we implemented our ordinal arithmetic algorithms, mechanically verified their correctness, and developed a library of theorems that can be used to significantly automate reasoning involving the ordinals. To enable users of the ACL2 system to fully utilize our work required that we modify ACL2, e.g., we replaced the underlying representation of the ordinals and added a large library of definitions and theorems. Our modifications are available starting with ACL2 version 2.8.     

基于netflow数据流的蠕虫探测算法

随着网络的迅速发展,随之而来的网络安全事件日益突出,特别是以网络蠕虫为代表的异常流量。由于网络蠕虫能够在数分钟内感染网络上绝大多数有漏洞的机器,因此蠕虫探测系统必须能快速鉴别和隔离已感染蠕虫病毒的机器,特别是对感染新型的未知的蠕虫病毒的机器。鉴于此,我们提出了一种基于Netflow数据流的蠕虫探测算法,该算法能够探测出大部分蠕虫扫描,而且拥有非常高的效率和非常低的误报率。     

基于PID型Adaline网络的升降台控制方法

针对传统PID控制方法在剪叉升降台的非线性时变系统中表现出一定的局限性,通过分析升降台剪叉机构的运动模型后,结合神经网络控制技术,把Adaline网络应用在舞台升降台控制系统的PID控制中,构造PID型Adaline网络参数自整定控制器,MATLAB仿真结果表明,该算法简单实用,能保证升降台速度均匀稳定,准确定位。