混沌序列在3G安全通信中的应用研究

混沌映像生成的混沌序列具有不规则和对初值敏感等优点，特别适合应用于保密通信。本文在3G安全结构的基础上．提出了一种改进的安全通信方法．它利用混沌序列来定时改变3G通信中的初始密钥，以提高资料的安全性。通过计算机模拟分析得出，在合理选择改变密钥的频率时，该方法具有在不明显增加计算时间的基础上“一次一密”的优点。     

基于移动Agent的IP网络拓扑发现

随着现代网络规模不断扩大和结构日趋复杂,网络管理成为网络系统正常运行的关键,其中网络拓扑自动发现是网管系统的基本要求和重要功能。通过网络拓扑发现,可反映某些重要服务器、路由器和交换机的布局状况,并提供可视化管理界面,如系统配置、节点状态和流量监控、异常告警等,对网络系统正常运行、防范网络攻击具有重要意义。本文提出一种基于移动Agent的网络拓扑发现改进算法,降低了拓扑生成的复杂度,提高了拓扑发现的自动化程度,网络管理员只需指定子网搜索深度,算法即可由近及远逐层自动发现子网、路由器及拓扑,减少了管理上的支持。     

Automated adaptive 3D forming simulation processes

In this study, an automated adaptive mesh control scheme, based on local mesh modifications, is developed for the finite element simulations of 3D metal-forming processes. Error indicators are used to control the mesh discretization errors, and an h-adaptive procedure is conducted. The mesh size field used in the h-adaptive procedure is processed to control the discretization and geometric approximation errors of the evolving workpiece mesh. Industrial problems are investigated to demonstrate the capabilities of the developed scheme.     

A simple micro-mixer prototyped in polycarbonate

In this paper, we report on first stage results on our work on the design and prototyping of a simple polycarbonate micro-mixer. CFD simulations indicate that the elliptical shape of the mixer appears to eliminate dead volumes and to result in more uniform flow and hence more uniform mixing. The mixer has also been characterised spectrophotometrically in a simple way. A simple design may be advantageous in that it may be more reliable in the micro-scale. It is certainly easier to manufacture.The authors would like to thank Drs Jason Pickering and Hu Banghong for their valuable and constructive criticisms during the preparation of this short communication.     

Asymptotic distribution of the number of isolated nodes in wireless ad hoc networks with Bernoulli nodes

Nodes in wireless ad hoc networks may become inactive or unavailable due to, for example, internal breakdown or being in the sleeping state. The inactive nodes cannot take part in routing/relaying, and thus may affect the connectivity. A wireless ad hoc network containing inactive nodes is then said to be connected, if each inactive node is adjacent to at least one active node and all active nodes form a connected network. This paper is the first installment of our probabilistic study of the connectivity of wireless ad hoc networks containing inactive nodes. We assume that the wireless ad hoc network consists of n nodes which are distributed independently and uniformly in a unit-area disk, and are active (or available) independently with probability p for some constant 0

相似文献   

基于POS算法的结构模型修正与损伤检测

结构模型修正与损伤检测是结构健康监测过程中必须解决的多学科研究课题，常常转化为求解约束优化问题。介绍粒子群优化（PSO）算法，并在此基础上利用带惯性权重因子的全局版PSO算法对结构模型修正和损伤检测等约束优化问题进行研究。通过两层刚架单损伤和多损伤数值仿真以及三层建筑框架结构四种损伤试验研究，结果表明PSO算法对结构模型修正能够起到非常好的效果，采用PSO算法对结构损伤进行检测不仅能够准确定位结构损伤而且能够有效识别损伤程度。由此可见，PSO算法应用于该领域的效果是显而易见的。     

A Large Deformation Model for the Elastic Moduli of Two-dimensional Cellular Materials

1Introduction Themechanicalbehaviorofcellularmaterialsde pendsontheirrelativedensity,cellgeometryandthema terialpropertiesofthesolidfromwhichtheyaremade.Theelasticmoduliofcellularmaterialscanbederived fromananalysisofthedeformationmechanismofthecell members.Thesimplegeometryofanidealizedunitcell allowsthederivationofrelationsbetweenmicro structural featuresandeffectivemechanicalproperties.Manytheoreticalmodelshavebeendevelopedtopre dicttheelasticmoduliofcellularmaterials[14].AbdEl Sayedetal[…     

Exploration of Reactivity of Eu(TTA)2(phen)(MA)

The reactivity of Eu(TTA)2(phen)(MA) (HTTA=2-thenoyltrifluoroacetone, MA=maleic anhydride) was studied. A series of products were prepared by direct polymerization, suspension polymerization, and alternate suspension and solution copolymerization with the styrene. And then we reactivity of these products were studied. The complexes were investigated and characterized by X-ray Diffraction (XRD), gel permeation chromatography (GPC) and fluorescence spectrophotometer. Although high polymerization degree is not found in the exploration of reactivity, it is found that the fluorescent intensity of complexes prepared by suspension polymerization increases significantly compared with the original particles, which is five times higher than that of the pure rare earth complex.     

Effect of Rare Earths on Electronic Structure of (110) Twin Martensite Boundary for Ni2MnGa Alloy

The doping effect of rare earth elements (Tb and Sm) on the electronic structure of (110) martensitic twin boundary in Ni2MnGa alloys was investigated by using ab initio method within the DFT and the supercell implementation. The calculated results show that the atomic relaxation lowers the boundary energy and the segregation energy. Sm seems easier to segregate to the boundary and has a greater doping effect compared with Tb due to its lower segregation energy and bigger bonder order with neighboring atoms. Tb makes a greater contribution to the magnetic properties of the twin boundary than Sm.     

一种新颖的具有带隙结构运算放大器设计

本文提出了带隙结构的运算放大器，把带隙基准和运算放大器有机的结合到一起，有效的节省了芯片面积，并有很好的精度和动态响应特性。本文阐述了该结构的工作原理，对整体结构进行分析，重点阐述了带隙结构的特点。采用0.8μm BiCMOS工艺，通过HSPICE进行仿真验证，得到其开环增益为63.4dB，电源抑制比为106.4dB。