Embeddings ofPSL(2, 41) andPSL(2, 49) inE8(C)

We classify embeddings of the finite simple groups PSL(2, 41) andPSL (2, 49) into algebraic groups of type E₈in characteristic not dividing the orders of these respective groups. Lie theory and finite group theory point to families of elements in a group of typeE₈ over a finite field which might satisfy a presentation for our finite simple group. Techniques from computational representation theory identify all suitable systems of generators. We describe a number of methods of computation in Chevalley groups of type E₈.     

入侵检测综述(二)

研究现状 从Denning和Neumann提出具有划时代意义的IDES系统至今,入侵检测系统已经经历了十多年的发展历程,目前国外著名的入侵检测研究机构包括Stanford Research Institute的Computer Science Laboratory (SRI/CSL),Purdue Uni-versity的COAST (Computer Operations Audit and Se-curity Technology)研究小组,美国国家能源部的 LawrenceLivermore National Laboratory,UC Davis的Computer Se-curity Lab等。对于入侵检测的研究,从早期的审计跟踪数据     

GF(2)上周期为2pn序列的m(s)

给出多项式的若干引理,并对引理进行证明。在此基础上,给出GF(2)上周期序列线性复杂度的表达形式,应用该表达式得出周期N=2pn的二元序列线性复杂度和m(s)之间的关系,其中p是个奇素数,并且2是一个模p2的本源根。结合魏算法,给出2个实例进行证明,结果表明该结果的正确性。     

Partial (set) 2-structures

Summary The notion of a labeled partial 2-structure is introduced and studied. It generalizes the notion of a (labeled) 2-structure studied in [1] and [2] and it provides a convenient mathematical framework for studying graphs. In particular, a subclass of labeled partial 2-structures, the so-called labeled partial set 2-structures corresponds very closely to those graphs that are state spaces of concurrent systems. Part I of this paper investigates the basic theory of labeled partial 2-structures and it considers the problem of representing partial 2-structures as partial set 2-structures.     

MediaSpace 7 (part 2)

This article describes a simple and easy to use framework for web jamming using the OpenSound Control (OSC) protocol (2002) and SuperCollider (2002) by James McCartney. The word ‘web jamming’ refers to playing music together over the Internet. This kind of musical collaboration over networks has been around for a while and has already been implemented in a number of applications. Even though much of the recent development in this field is very impressive and provides the players with all sorts of customisation for sound and graphics, I still feel some very important things are lacking. Most of all I would like to see personality reflected throughout the system, and by providing a framework suitable for connecting musicians together rather than a fixed set of musical instruments for them to use, I think this can be achieved. So, by handing over the complete design of the virtual instruments, what parameters to control, how they will sound, what they will look like etc., to the players themselves, I wish to open up web jamming for individual and creative use to all kinds of musicians. If the players can express their ‘sound’ more freely, this can compensate somewhat for delayed reactions, lack of eye contact, gestures and atmospheres lost due to physical displacement and technological limitations.     

New (n, r)-arcs in PG(2, 17), PG(2, 19), and PG(2, 23)

An (n, r)-arc is a set of n points of a projective plane such that some r but no r+1 of them are collinear. The maximum size of an (n, r)-arc in PG(2, q) is denoted by m _r (2, q). In this paper a new (95, 7)-arc, (183, 12)-arc, and (205, 13)-arc in PG(2, 17) are constructed, as well as a (243, 14)-arc and (264, 15)-arc in PG(2, 19). Likewise, good large (n, r)-arcs in PG(2, 23) are constructed and a table with bounds on m _r (2, 23) is presented. In this way many new 3-dimensional Griesmer codes are obtained. The results are obtained by nonexhaustive local computer search.     

光学液位传感器(下)

文章描述了三种光学液位和传感器的结构，工作原理和信号处理技术第一种已在上期介绍。本期介绍后两种。第二种光纤晚爆爆燃料液位传感器又分吸收和数字编码两种类型，前者由LED光源和多模光纤组成，后者利用光纤与光波导间的耦合。第三种荧光液位传感器利用掺杂玻璃或塑料中产生的荧光辐射来探测液位。     

信息和网络安全(二)

Bruce Schneier在《Secrets and Lies:DigitalSecurity in a Networked World》回顾了信息安全技术、产品和策略的实用性和局限性,并且站在较高的层次上俯视了信息和网络安全的全貌。他指出:安全问题实际上是人的问题。 他的观点并没有排斥信息安全技术和产品的重要性,只是强调了人的因素在信息安全领域里所起的作用比其它领域要重要一些。     

Time-optimal decompositions in SU(2)

A connected Lie group G is generated by its two 1-parametric subgroups exp(tX), exp(tY) if and only if the Lie algebra of G is generated by {X, Y}. We consider decompositions of elements of G into a product of such exponentials with times t > 0 and study the problem of minimizing the total time of the decompositions for a fixed element of G. We solve this problem for the group SU ₂ and describe the structure of the time-optimal decompositions.     

透视数字化关键技术(二)

数字化音／视频处理技术数字视频处理技术可以大大提高传输和存储性能、图像的清晰度和质量以及交互功能，这些都是模拟视频无法做到的。因此目前模拟视频正逐步被数字视频所取代，而发展最为迅速的两大视频产品是亚洲的ＶＣＤ和美国的ＤＳＳ（数字卫星系统）。数字视频技...     

Contents of Volume 2 (1998)

Multibody System Dynamics -     

L_(1/2) regularization

In this paper we propose an L1 /2 regularizer which has a nonconvex penalty.The L 1/2 regularizer is shown to have many promising properties such as unbiasedness, sparsity and oracle properties.A reweighed iterative algorithm is proposed so that the solution of the L 1/2 regularizer can be solved through transforming it into the solution of a series of L 1 regularizers.The solution of the L 1/2 regularizer is more sparse than that of the L 1 regularizer, while solving the L 1/2 regularizer is much simpler t...     

基于J2EE的多层、分布式企业应用软件系统

通过分析企业对应用软件系统的要求,介绍J2EE平台及相关技术的特点,提出基于J2EE的企业应用软件系统架构及实现方法。     

基于二阶(2D)2PCA的人脸识别

研究光照变化条件下的人脸识别问题。基于最近提出的二阶特征脸方法和（2D）^2PCA方法,提出了二阶（2D）^2PCA方法。该方法将（2D）^2PCA技术分别应用到原始图像矩阵集和剩余图像矩阵集。在extended Yale人脸库上的实验表明,在光照变化条件下,二阶（2D）^2PCA方法是一种有效的人脸识别方法。该方法与传统的特征脸、二阶特征脸方法和（2D）^2PCA相比,具有更高的识别精度;且比特征脸和二阶特征脸方法节省计算时间。