基于GPS和CDMA的物流车辆监控终端的设计

近年来物流行业发展迅速,提出了一种基于GPS(全球定位系统)和CDMA(码分多址)技术的物流车辆监控终端的设计方案。采用S3C2440A ARM芯片作为主控芯片,选取合适的GPS模块和CDMA模块进行硬件设计。研究分析了GPS和CDMA技术。在WinCE 5.0平台上设计了GPS串口接收程序,以及终端与监控中心的无线通信程序。结果表明,本系统运行稳定,数据刷新时间小于3 s,GPS位置漂移值小于20 m。     

软件无线电中OFDM的IFFT仿真设计

基于软件无线电的思想,阐述了第四代移动通信核心技术OFDM的原理及其IFFT/FFT实现的数学模型,并且提出了OFDM调制的核心部分IFFT的软件实现方法,即采用XILINX公司的System Generator这一高性能DSP系统的快速建模和实现工具,在MATLAB/Simulink的环境下构造OFDM技术中的IFF...     

电子政务信息安全体系的研究与构建

电子政务是全面提升政府机构管理与服务质量的重要技术手段,电子政务的安全性问题已成为各国政府普遍关注和研究的重要问题.本文对电子政务信息安全进行了分析,并从安全组织管理、安全技术、安全服务体系及安全法律保障四个维度对电子政务安全体系进行构建,为我国电子政务信息安全的防范提供了一定的思路.     

基于nRF24LE1的抗干扰无线视频监控系统的设计

为提高无线视频监控系统的抗干扰能力,采用频率捷变技术,完成了基于nRF24LE1的星形无线视频监控系统的设计,并做了相应的抗干扰测试,根据测试数据计算出丢包率和吞吐率,并且分析了测试数据。在保障整个无线系统性能的前提下,该设计实现了抗干扰的设计要求,可广泛应用于家居、工厂视频监控等多种场合。     

交直流隔离的分布式MEMS移相器设计

设计了一种五位分布式微电子机械系统（MEMS）移相器,通过分析对比传统分布式MEMS移相器加载直流偏置的两种方式,提出了一种新的直流偏置的加载方式,能解决传统方式带来的交直流干扰和引线繁杂问题,同时工艺容易实现。采用ADS软件对移相器进行级联仿真,优化了微波性能参数,仿真得出移相器在35 GHz时移相精确度小于3°,移相器的插入损耗小于0.5 dB,回波损耗大于23 dB。给出了五位分布式MEMS移相器的工艺流程,同时验证了所设计加载直流偏置方式工艺简单的优势。     

基于XML技术的武器控制系统交联信息解析

将可扩展标记语言(XML)技术应用到武器控制系统交联信息解析中.首先,根据采集的交联信息格式和逻辑关系,建立XML文件,采用位运算方法,从导弹发射控制逻辑层面解析交联信息码,解决了多种弹型多种工作状态下信息检索的难题;其次,通过分析比较两种典型的XML文档解析技术,选择基于DOM的解析技术,并给出XML解析过程;最后,...     

β-( N -Acylamino)vinylphosphonium Salts--Synthesis and Properties

A reaction of g -carbonyl phosphorus ylides with imidoyl halides gives hitherto unknown g -( N -acylamino)vinylphosphonium salts. The same product can be obtained using the N-monosubtituted amide/Ph 3 PBr 2 /Et 3 N system instead of imidoyl halide. The key step of the reaction probably involves an intramolecular [1,3] O-to-N migration of the vinyl group, converting the primary O -imidoylation product into g -( N -acylamino)vinylphosphonium salt.     

AQUEOUS POLYMERIZATION OF METHYL METHACRYLATE INITIATED BY TITANIUM(III)—SALICYLALDOXIME REDOX SYSTEM: A KINETIC STUDY

The polymerization of methyl methacrylate initiated by the titanium(III)-salicylaldoxime redox system was studied in an aqueous sulfuric acid-ethanol medium in the temperature range of 20–30°C. The rates of polymerization were investigated at various concentrations of reductant, oxidant, ethanol, sulfuric acid, and monomer. Cyclic voltammetric sensing of salicylaldoxime kinetic conditions demonstrated its reduction behavior. From the results obtained, it was inferred that the polymerization reaction was initiated by an organic free radical arising from the titanium(III)-salicylaldoxime redox system and termination took place predominantly by mutual coupling and small fraction by chain transfer mechanism involving solvent molecules. The effects of some water-miscible organic solvents and surfactants on the rate of polymerization were investigated. The temperature dependence of the rate was studied and the activation parameters were computed using Arrhenius and Eyring plots. A suitable kinetic scheme has been proposed on the basis of experimental observations.     

SURFACTANT MEDIATED POLYMERIZATION KINETICS OF ACRYLAMIDE USING CR(VI)-CYCLOHEXANONE REDOX SYSTEM

The effect of organized surfactants on the kinetics of acrylamide (AM) polymerization have been studied over a temperature range of 25–45°C using Cr (VI)-cyclohexanone (CH) redox system as initiator. The rate of polymerization, R_p(obs), as well as, the percentage of the monomer conversio were found to be increased with increasing the concentration of the anionic surfactant (SDS), above its CMC. But the cationic surfactant (CTAB) reduced the rate considerably at higher concentration, while non-ionic surfactant (TX-100) played no role on the rate. The effect of [Cr(VI)], [CH], [AM], [H+], and ionic strength on the rates have also been examined. The presence of 0.015M SDS decreased the overall activation energy of the polymerization by 6.28 k.Cal/ mole as compared to that in the absence of a surfactant. On increasing the SDS concentration, the viscosity average molecular weight was also found to increase. For the polymerization process, a mutable mechanistic scheme has been pro-posed.     

基于LT-GaAs外延片的THz片上系统

太赫兹（THz）波在物质检测方面发挥着巨大的作用,是一种非常有潜力的生化传感工具。但是传统的太赫兹时域光谱系统（TDS）结构复杂,系统的集成度低,占用空间较大。所以,如何对THz波进行有效引导、实现集成化传输并得到高质量光谱就成为太赫兹光谱系统的研究热点。太赫兹片上系统是将THz的产生、传输以及探测都集成到同一芯片上,然后通过相干探测的方法获得THz时域光谱。它可以实现对多种样品的检测,尤其在对难于取样的微量样品探测方面具有广泛的应用价值。它无需光路准直,操作简便,成品率高。两个研究工作都是基于低温砷化镓(LT-GaAs)外延片开展的。首先将一根直径为200 μm的铜线固定在LT-GaAs外延片的上方,通过真空蒸镀的方法制备出天线电极,同时得到天线间隙,研制出基于LT-GaAs外延片的THz天线。利用波长为800 nm的飞秒激光对其进行测试,得到了质量较高的THz信号,验证了天线的实用性。然后在另一外延片上利用光刻微加工工艺制作出传输线和微电极,得到了集成的THz片上系统。使用波长为1 550 nm的飞秒激光分别激发片上系统的太赫兹产生天线和探测天线,天线产生的太赫兹波在传输线上传播,在探测端同样得到了质量较高的THz时域信号,证实了THz片上系统的可行性。该方法省去了腐蚀牺牲层以及LT-GaAs薄膜的转移、键合等步骤,极大地提高了片上系统的成品率,避免了薄膜转移过程中易破碎及腐蚀液存在毒性的问题。最后,研究了外加电压对从片上系统中获得的THz波性能的影响,结果为电压越高,THz波的信号强度越强;另外,通过在传输线上方垂直放置铜箔的方法验证了THz波沿着传输线传播的事实。该研究中采用的基于LT-GaAs外延片的片上系统的制备方法简单,制作周期短,制作过程安全,应用领域广泛,这为将来与微流控芯片相结合实现对液体样品的探测打下了基础。