嵌入式操作系统VxWorks下PPPoE的实现

PPPoE是一种很常用的拨号协议,介绍PPPoE Discovery阶段的基本流程和帧封装格式,同时介绍PPP的连接控制协议(LCP)、认证协议(CHAP、PAP)、IP控制协议I(PCP)各协议子层之间的关系和PPP的数据包封装格式.讨论PPPoE、PPP协议在嵌入式操作系统VxWorks的TCP/IP协议栈体系中的具体位置和PPP、PPPoE数据包收发二个方向的处理流程,同时给出VxWorks下PPPoE实现的具体的软件模块设计,具有一定的工程应用价值.     

基于单片机的嵌入式SNMP代理器设计与实现

将SNMP(简单网络管理协议)用于控制,使监控现场的信号通过SNMP传输。给出了在51单片机上实现SNMP代理器的方案。阐述了网络接口、A/D采集以及串口的设计,软件采用实时多任务操作系统M icro-C/OS,用人机交互任务、数据采集任务、SNMP处理任务实现所需要的功能。     

基于uClinux的嵌入式系统在通信用高频开关组合电源监控中的应用

uClinux操作系统和ARM微处理器的结合是工业控制领域的有效方案,该方案实现了对通信高频开关组合电源的监控,不仅使嵌入式电源监控系统具有丰富的网络功能、灵活的软硬件扩展性能,而且使通信电源具有良好通用性、稳定性和可靠性。     

Sampling and Analysis of Odorous Compounds in Water Treatment Plants

Abstract

The following analytical method has been used to identify some odorous compounds in the air of the water treatment plant Werdholzli, Zurich: sampling of contaminated air with the help of activated carbon, desorption by the solvents carbon disulphide and methylene chloride, separation of the carbon disulfide extract into a polar and a nonpolar fraction by adsorption column chromatography on silica. Hereafter gaschromatographic analysis of the polar fraction on glass capillary column (Ucon HB 5100); detection and identification were achieved by flame ionisation, thermoionic nitrogen selective detector and computerized mass spectrometry (Finnigan 3200 F, data system 6110).

The results show the presence of sulfur compounds: thiophenes, thiazoles; nitrogen compounds: pyrazines; oxygen compounds: phenols, alcohols and some unsatured hydrocarbons. The malodorous compounds were sulfur and nitrogen compounds in the range of 0.01-0.1 ppm.     

Arsenic Speciation in Marine Sediments: Effects of Redox Potential and Reducing conditions

Abstract

The speciation of arsenic in the environment is among others controlled by reduction, methylation and oxidation processes and therefore influenced by the prevailing redox conditions. In this study we have analyzed sediments taken from La Coruña estuary in the north west of Spain. Inorganic (trivalent and pentavalent) and the organic (MMA and DMA) arsenic speciation is related to Eh, Fe and Mn load. The various of the arsenic species concentration and other parameters was analyzed at different depths in some of the sampling points. Low arsenic concentrations (1–10 μg·g^–1) were found. In spite of oxidising conditions (Eh values between 31–96 mV), most of the samples showed a higher As(V) percentage than As (III). Principal component analysis was made to see a sample groups and the results showed that speciation depends on reducing conditions (Eh and Mn).     

Molecular Constants of the NbN Molecule

Absorption spectrum of NbN has been obtained in the 560–670 nm region by intracavity laser spectroscopy. Vibrational and rotational analyses of ³φ - ³Δ transition has been caried out. Molecular constants for the upper (³φ) and ground (³Δ) states have been determined.     

多元统计分析方法的理论研究及应用分析

多元统计分析在多指标实际问题的研究中起着重要的作用.以往文献中,一般采用某一种多元统计方法对一个多指标实际问题进行研究,但其结果存在一定的偏差性.采用四种典型的多元统计方法:主成分分析法、因子分析法、分层聚类和K-均值聚类方法对同一个多指标银行问题进行研究,并对四种方法的不同结果进行比较综合分析,这样可以避免单一方法的偏差性,以便得到的结果更合理、更具有说服力.     

基于LPC2378的天调匹配性能检测仪的设计及实现

为了解决生产中短波天调配谐过程存在的劳动强度大,统计不够准确等问题,设计了一种检测仪。该检测仪以嵌入式技术为基础,利用短波电台所提供的遥控命令,实现短波天调自动配谐功能,并根据统计得到的配谐数据判断天调匹配性能是否合格。经生产验证,该测试仪在提高劳动效率的同时,还能减少人工统计数据可能带来的误差。     

误差合成空间固定系数模型的多阶段广义最小二乘估计

本文对时变系数的空间面板数据模型进行了研究,所研究的模型利用扰动项中的空间个体成分将不同时期的方程联系起来,同时,自变量系数和空间自回归系数是时变的,但不会随着观测个体的变动而变动。本文利用基于可行的广义最小二乘估计的多阶段方法对模型参数进行了估计,研究了估计量的大样本性质,并利用Monte Carlo方法模拟了其小样本性质。模拟结果表明,估计量的渐近性质随着样本容量的增加而改善。对中国省级地区间财税策略互动行为的实证案例也体现了本文理论模型的应用价值。     

多层PCB中内埋电阻的特性分析及应用

计算、分析了多层PCB内埋平面电阻的特性，并将其应用于一种多层射频板威尔金森功分器的设计，研究并分析了平面电阻尺寸对该功分器射频性能的影响。