TEM Studies of High Temperature Corrosion Behaviour of TiAl Intermetallics with Surface Modifications

The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl₃ diffusion coating was studied in an environment of H₂/H₂S/H₂O at 850^oC. The kinetic results demonstrate that the TiAl₃ coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al₂O₃ scale on the surface of the TiAl₃‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800^oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate.     

雷达电子战自适应捷变频对抗技术研究

介绍了雷达自适应变频抗干扰技术,分析了与之相对应的干扰技术,并对雷达自适应变频对抗效果度量问题进行了研究。     

基于FPGA的ASI信号接收与发送的实现

提出了一种用FPGA芯片代替Cypress公司的CY78933和CY78923芯片来实现ASI信号接收与发送的方案，详细阐述了DVB—ASI接口的硬件组成与FPGA实现，该接口符合DVB—ASI的接口规范，可实现270Mbps的信号传输，已经得到实际运用。     

典型电子现金系统的分析及其安全需求

文章设计了一种电子现金系统,关键是对安全性、效率、成本等进行综合考虑。从这些方面入手,论文分析了三种典型的电子现金系统—D.Chaum方案、S.Brands方案和T.okamoto方案。然后,结合匿名通信协议,提出如何更好地满足顾客利用公开网络进行安全通信的需求。     

An Improved Immune Genetic Algorithm for Solving the Optimization Problems of Computer Communication Networks

1　IntroductionIndesigningacomputercommunicationnet work ,thenetworkaveragedelayisanimportantpa rameterinthenetworkperformance .Inthispaper,weonlyconsiderM /M/1networks,whichmeansthatthemessageprocessingtimeisaprobabilisticdensityfunctionwithnegativepower,thegroupar rivalandsendingisofPoissiondistributionwithasinglequeue .Supposethatthenetworktopologicalstructureandtheestimatesoftheexternaltrafficrequirementsaregiven ,howtoselecttheoptimalroutestobeusedbythecommunicatingnodesinthenetworksoast…     

Segmented polymer networks containing amino‐dendrimers

Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry     

流量比对等离子体基团分布和薄膜结构的影响

使用光强标定的发射光谱(AOES)测量了CHF3／C6H6混合气体的微波电子回旋共振(ECR)放电等离子体中基团的分布状态。实验发现随着CHF3流量的增加，成膜基团CF、CF2、CH等的相对密度增大，而刻蚀基团F的密度也会增加，从而使得a—C：F薄膜的沉积速率降低。同时红外吸收谱(IR)分析表明，在高CHF3流量下沉积的a—C：F薄膜中含有更高的C—F键成分。可见在a—C：F薄膜的制备中CHF3／(CHF3 C6H6)流量比是重要的控制参量。     

GMSK无线接收终端设计

设计了GMSK(Gauss Minimum Shift Keying，高斯最小频移键控)无线接收终端的硬件与软件系统。硬件的射频电路对空中信号进行接收与滤波，再由以MX589构成的解调模块解调，输出数字信号；数字硬件以单片机GMS97L5为核心。软件系统设计了对IC卡AT88SCl608加密卡的认证以及对串行数据的接收与处理的中断程序。终端系统接收数据快、性能稳定。     

An optimization model for placement of wavelength converters to minimize blocking probability in WDM networks

The introduction of wavelength converters in wavelength division multiplexing (WDM) networks can reduce the blocking probabilities of calls. In this paper, we study the problem of placing a given number of converters in a general topology WDM network such that the overall system blocking probability is minimized. The original contributions of this work are the following: 1) formulation of success probability in a network as a polynomial function of the locations of converters; 2) proposal of an optimization model of the converter placement problem as the minimization of a polynomial function of 0-1 variables under a linear constraint, so that standard optimization tools can be employed to solve the problem; and 3) design of a search algorithm that can efficiently find the optimal solution to the converter placement problem. Experiments have been conducted to demonstrate the effectiveness of the proposed model and the efficiency of the algorithm.     

Contact stresses in an infinite plate containing a smooth circular insert under thermal load

Summary. A solution is presented for the contact problem with a smooth circular elastic insert in an infinite, linearly elastic plate under thermal load. The thermal load considered here includes the temperature gradient applied at infinity and a uniform temperature change. One of the major difficult parts in solving the present problem is that separation may occur between an insert or inclusion and the surrounding matrix under a nonuniform expansion of the matrix and the insert due to a temperature change. Based on the complex potential theory and the method of analytical continuation, the problem is reduced to a singular integro-differential equation which is solved numerically. Results are presented for the contact angle and for the normal and circumferential stresses at the plate-insert interface. Exact solutions are found for the current problem for a special case when the material properties of the plate and the insert are identical.