电力线通信自动抄表系统中的电能表捕获算法

针对目前电力公司按照面向人工抄表的习惯组织划分用户资料,致使理清配电台区与用电户的关系需要耗费很大的精力,现场排查困难等问题,提出了集中器自动获取表号的线性时间算法。该算法基于报文冲突和快速二分搜索技术,为抄表系统实现即插即用奠定了基础。     

WLAN时变信道下链路性能改进

在IEEE802.11n的MIMO信道模型基础上研究了时变信道下链路性能,提出了一种基于SNR动态调整调制编码方案(MCS)链路自适应方法。多普勒频移下利用基于长训练序列估计SNR动态调整MCS的方法来提高链路性能。仿真表明,该方法根据信道状况动态调整MCS,在数据吞吐率上有很大的提高。     

基于C8051F120和CPLD的多功能望远镜控制系统设计

基于C8051F120和大规模CPLD(EPM570T144)设计的多功能望远镜大型转台两轴控制系统,包括两轴直流电机伺服控制器、GPS时统系统、增量式编码器采样读数、PWM功能模块、LCD显示功能、通信功能、AD采样功能等。功能齐全,结构紧凑,外部接口丰富且具有保护功能,可靠性高。     

Zigbee通信技术在配电线路安全监测中的应用

介绍了在配电线路安全监测温度数据传输中应用Zigbee通信技术,即使用一种以太阳能为能源、超级电容为储能装置、超低功耗的Zigbee芯片发送数据的传感器装置实现温度数据的无线传输。由于该装置无需外供电源且采用无线通信,因而使配电线路的安全监测变得更加方便可靠。     

基于功率MOSFET的激光器外触发系统研制

采用功率MOSFET及其驱动器和光纤收发器件,研究了激光触发开关脉冲功率源控制技术中的快上升沿(≤5ns)触发信号产生、驱动、传输及光纤隔离、高耐压脉冲变压器使用等关键技术。给出了激光器外触发控制电路的设计及测试结果,并对其应用特点进行了分析和讨论。     

Nonlocal and multiple-point boundary value problem for fractional differential equations

In the light of the fixed point theorems, we analytically establish the conditions for the uniqueness of solutions as well as the existence of at least one solution in the nonlocal boundary value problem for a specific kind of nonlinear fractional differential equation. Furthermore, we provide a representative example to illustrate a possible application of the established analytical results.     

全仿真污水处理实训平台的建设

在研究污水处理自动控制系统工艺流程和过程控制的基础上,设计了全仿真污水处理实训平台。该平台由上位机、工业以太网、PLC、变频器、Profibus DP总线等组成。分别介绍了实训平台控制系统的构成、功能以及上位机监控软件WinCC的设计方法。经过实际应用证明,系统设计先进可靠,运行稳定。     

基于Web日志的数据挖掘初探

Web日志挖掘是Web数据挖掘研究领域中一个最重要的应用方面。该文首先介绍了Web日志挖掘产生的背景,然后介绍了Web日志挖掘的基本概念,着重阐述了Web日志挖掘的预处理和日志挖掘算法两个关键技术,最后介绍了Web日志挖掘的应用,提出了其发展方向。     

Array SSL VPN如何保障番禺有线办公网的安全运行

企业办公自动化系统的应用十分广泛,随着互联网的高速发展,WEB应用成为主流,OA系统在互联网上的延伸成为大趋势,本文阐述在WEB应用中如何保障数据和系统安全的手段和方法。     

Structures and spectroscopic properties of nonperipherally and peripherally substituted metal-free phthalocyanines: a substitution effect study based on density functional theory calculations

The molecular structures, molecular orbitals, atomic charges, electronic absorption spectra, and infrared (IR) and Raman spectra of a series of substituted metal-free phthalocyanine compounds with four (1, 3, 5, 7) or eight (2, 4, 6, 8) methoxyl (1, 2, 5, 6) or methylthio groups (3, 4, 7, 8) on the nonperipheral (1-4) or peripheral positions (5-8) of the phthalocyanine ring are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The calculated structural parameters and simulated electronic absorption and IR spectra are compared with the X-ray crystallography structures and the experimentally observed electronic absorption and IR spectra of the similar molecules, and good agreement between the calculated and experimental results is found. The substitution of the methoxyl or methylthio groups at the nonperipheral positions of the phthalocyanine ring has obvious effects on the molecular structure and spectroscopic properties of the metal-free phthalocyanine. Nonperipheral substitution has a more significant influence than peripheral substitution. The substitution effect increases with an increase in the number of substituents. The methylthio group shows more significant influence than the methoxyl group, despite the stronger electron-donating property of the methoxyl group than the methylthio group. The octa-methylthio-substituted metal-free phthalocyanine compounds have nonplanar structures whose low-lying occupied molecular orbitals and electronic absorption spectra are significantly changed by the substituents. The present systematical study will be helpful for understanding the relationship between structures and properties in phthalocyanine compounds and designing phthalocyanines with typical properties.