CDMA匹配滤波器设计

从数字匹配滤波器的理论出发,拟采用PN码同步捕获技术,在此基础上完成基于FPGA的扩频通信基带系统的具体实现,并通过仿真和硬件验证证明该设计的正确性,大部分工作都采用了FPGA器件结合相应的EDA工具来设计完成的。     

无线同频同播系统在森林防火中的应用

介绍了目前我国森林防火无线通信的组网方式、优缺点,以及存在的主要问题.阐述了无线同频同播系统的原理,并与现有无线通信系统进行了性能和价格的比较.论证了同频同播系统以无线链路方式组网符合森林防火无线通信系统应用环境.     

基于FPGA和LwIP协议的嵌入式以太网通信平台的设计

面对使用越来越广泛的嵌入式以太网通信，提出了一种FPGA为核心芯片，利用MicroBlaze微处理器软核，基于嵌入式操作系统Xilkernel，采用LwIP协议的功能函数的设计方法。本设计给出了系统的软硬件各个模块以及整体设计的实现。     

基于虚拟仪器技术的电力系统频率测量

虚拟仪器技术在工程测试、远程控制等越来越多的领域得到了广泛的应用。本文将虚拟仪器技术应用到电力系统频率测量中。在频率测量算法方面，本文通过在CVI中对两种测频算法进行仿真，讨论了两种测频算法的优缺点，并阐述了提高算法精度的措施。     

林业行业门户网站的设计与构建技术

阐述了河南林业信息网的建设目标、设计原则和网站系统硬件平台、系统软件平台、应用软件平台的设计要求,系统介绍了该网站的功能区划、网页栏目与美工设计及网站构建技术。     

复杂山地森林固定大样地测设方法

简述了森林固定大样地测设基本要求;以南方地形复杂、森林茂密、通视性差的山地为例,从坐标原点确定、建立闭合导线和全站仪放样等方面介绍了复杂山地森林固定大样地闭合导线测设方法。     

基于GPS的森林防火无线电通讯同频同播系统

文章详细介绍了基于GPS的广东省森林防火无线电通讯同频同播系统的组网规模、系统结构和网络配置等总体设计,以及系统功能和特点,最后归纳了系统建立之后对森林防火产生的意义。     

地铁探伤机车轮对驱动装置的设计开发

介绍了地铁探伤机车轮对驱动装置的基本结构、技术参数、设计要求,对箱体、齿轮、轴承、润滑系统等重要零部件的设计过程进行了简要阐述。经试验和装车运行考核,该轮对驱动装置运行平稳,无泄漏、无异音、无噪音等,满足设计要求。     

某燃机电站SCR烟气脱硝系统流场优化及分析

流场分析是验证和保证脱硝系统达到设计要求的重要手段。特别是对于脱硝要求高、烟道本身流场条件差的项目，流场的优化设计及分析必不可少。以某燃机电站SCR烟气脱硝系统为例，主要介绍了该项目脱硝设计的特点和难点、流场优化设计的具体措施以及CFD流场模拟分析的具体过程。经CFD流场模拟结果分析验证，该流场优化设计措施切实有效，达到了设计要求，成功解决了该项目烟道流场条件差的问题。     

GIS辅助苗圃规划设计初探——以哈尔滨永和苗圃为例

GIS具有量测面积和长度的优势,在苗圃规划设计中,综合运用GIS和AutoCAD可提高工作效率和质量。以哈尔滨永和苗圃为例,介绍了在AutoCAD设计的基础上,在GIS中量测和统计功能分区、用地布局等的方法。     

频率法测短吊杆索力测量方法的比较分析

以湖南益阳康富南路跨线桥为实例,对其吊杆索力分别采用DASP动态采集分析系统和JMM-268索力动测仪进行测试,从而比较两种频率测量方法用于短吊杆索力测量的优劣。通过实例比较得知,DASP动态采集分析系统更适宜短吊杆索力的测量,其精度比JMM-268索力动测仪高。以弦振动理论为基础的振动频率法是桥梁健康检测中检测索力的一种常用间接方法。由于系杆拱桥的吊杆比较短,且吊杆索力受两端约束条件影响比较大,根据本例实际考虑了短粗拉索的抗弯刚度,采用边界条件为两端铰接拉索的自由振动进行分析,建立由频率识别拉索索力的近似公式。     

Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy

The use of an effective medium theory is important when accurately measuring wood density using millimeter and terahertz wave techniques. To confirm the applicability of this theory to the evaluation of wood density, the relative permittivity and dielectric loss of oven-dry flat-sawn specimens of 11 different wood species were measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for terahertz time-domain spectroscopy. A mixture model based on the effective medium theory well explained the density dependence of relative permittivity over the entire frequency range, while it did not fully explain that of dielectric loss, especially for higher frequencies. This indicates that wood scatters the terahertz wave with a wavelength close to the transverse sectional dimensions of the pores in wood in the same way as Mie scattering. It was found from the dielectric loss spectrum of wood substance that the frequency around 0.23 THz was preferable for the nondestructive evaluation of wood.     

New impedance measurement system estimating cross-sectional moisture distribution in cylindrical bodies and electric network modeling

This work aimed to measure the cross-sectional moisture distribution in a cylindrical body using a double-glass-tube model filled with water and to construct an electric network model that explains the effects of moisture distribution. A new impedance measurement system introducing an intermediate electrode was exploited. The electrode was used to segregate the target local current from the whole current in a cross section of a specimen. Three model cylinders with different moisture distributions were used, and absolute values of impedance and phase were measured over the frequency range 1 kHz to 1 MHz. By introducing an intermediate electrode, frequency responses of the impedance and the phase showed characteristic changes in the high-frequency range associated with the moisture distributions. The trends were simulated numerically by using electric network analysis. The proposed method enabled measurement of a selective current path in the cross section of a cylindrical body.     

基于微波技术的温室作物含水量检测

为适应现代温室大棚灌溉系统科学化与精量化的需求,提出一种基于微波谐振技术测量温室作物含水量的方法。论述利用微波谐振法测量作物含水量的原理,将温室蔬菜叶片作为检测对象,提出并论证作物叶片水分含量不受叶片密度影响的算法。通过作物叶片介电常数作为桥梁,建立起作物含水量与谐振腔谐振频率f0与品质因数Q的函数关系,得出关系曲线,为建立温室大棚含水量检测系统打下基础,也为精量灌溉系统水分指标的获取提供一种新的技术手段。     

基于磁弹性的扭矩测量方法及特性分析

基于磁弹性原理组建扭矩测量系统;归纳出"扭矩与磁感应强度之间存在线性正比例关系"的规律;提出以扭矩与磁感应强度之间的线性正比例关系为基础,利用具有巨磁阻效应的特斯拉计先测量磁感应强度值,再计算出相应扭矩值的扭矩测量新方法,为研发汽车扭矩传感器提供一种新的思路;利用SPSS软件进行数据分析,扭矩测量系统的线性度误差小于0.1%,重复性误差均小于0.1%,符合测量系统的误差要求,验证这种扭矩测量新方法的可行性;总结出扭矩测量系统的主要技术指标有:量程为0～100 N.m、线性度和重复性两个误差指标均为0.1%。     

Measuring tree-ring increments on tree bole sections with a video-based robotic positioner

We report on the design and performance of a system that speeds measurement of radial tree-ring increments on tree stem disks; this method replaces the usual binocular microscope with a video image, and automates the measuring and recording processes. The system was used to measure bole sections cut from stems at various heights to determine volume growth of representative trees in an old-growth ponderosa pine stand. The objective of the measurement system was to speed acquisition of annual growth increments from a large number of disks. A personal computer controls the location of a video camera in a 3-axis positioning system. The operator views the sample on a video monitor and positions the camera over each ring by selecting it with a computer-driven mouse. The computer measures and records the distance that the camera moves between each ring. Task selection is facilitated by menu-driven software that also formats, checks and organizes data files. Measurements have a resolution of 0.026 mm; however, finer resolution could be obtained with a different camera lens. Tests of measurement variability (repeated measurements by individual operators on a single radius) indicated standard errors of 0.006 mm or less for the first measurement sets for four operators. Correlation coefficients among four radii per bole section were as low as 0.66 for a whole tree, suggesting that measurements on single radii may provide poor estimates of radial growth for old trees. This system also offers the potential for automatic ring detection and measurement.     

生物质导热系数测量系统设计

随着不可再生能源的日渐枯竭,生物质能源的研究工作受到越来越多的关注。想要充分了解和利用生物质能源,生物质材料的热物性分析必不可少。其中,导热系数表征就是研究的重点内容之一,设计出可靠便捷的测量系统至关重要。笔者以LabVIEW平台为基础,依靠其强大的测控功能,结合3ω法测量原理及具体的实验步骤,设计出一种固液相样品都适用的导热系数测量系统。实验中测量端的铂丝将产生电信号,经前置放大电路被锁相放大器SR830采集,然后通过GPIB接口卡与PC机通讯。其中,上位机LabVIEW的程控交互界面包括了前期准备、信息记录、数据采集和曲线显示4个部分,为研究人员提供了直观、便捷、高效的实验进程帮助。还从测量对象的性质和实验台搭建过程两个方面,分析了可能存在的误差来源。为了验证该导热系数测量系统的可靠性,对常见的生物质液体,包括存在固液相变化的样品,进行了测量实验。测量值与文献参考值比较显示,系统误差小于5%,说明该测量系统具有较高的可靠性和稳定性。     

Damping loss in wood at mid kilohertz frequencies

Summary The dynamic moduli and logarithmic decrement of Rimu (Dacrydium cupressinum) were measured along the grain and perpendicular to it in the frequency range 45–85 kHz using a Marx regenerative oscillator system. The moduli and decrement were observed to exhibit strong dispersions between-20°C and-80°C, the actual temperature being dependent on measurement frequency and moisture content of the sample. The activation enthalpy of the dispersion mechanism varied from 3.9 kcal/mole at moisture contents in excess of 7 % to 6 kcal/mole at lower (1%) moisture content. Impregnation of the wood with solvents produced dispersion effects different from those associated with water impregnation. It is postulated that this mechanical dispersion observed in moisture-bearing wood results from the motion of the adsorbed water molecules.The author wishes to thank the Head of the Princes Risborough Laboratory, Building Research Establishment, for the hospitality and facilities provided during his year's residence, and also the Council of the University of New South Wales for their generous allowance of sabbatical leave.     

农药喷雾全过程性能分析及其测试技术研究进展

农林植物受生物及非生物胁迫的发生面积居高不下,化学农药防治是消灭或控制病虫草害等有害生物胁迫的最主要方法,而农药喷雾性能直接影响着病虫草害防治效果.通过农药喷雾全过程性能综合分析图,归纳了农药喷雾过程中的雾化性能、输运沉降性能和沉积性能.其中,雾化性能包括雾流锥角形状、射流贯穿长度、液膜破碎距离以及药液在线混合等喷雾宏...     

木工榫槽铣刀的固有频率测试研究

分别采用随机激励功率谱和声学测量法测试木工榫槽铣刀的固有频率。结果表明，两种测试方法皆可行且安全可靠。对木工榫槽铣刀固有频率的测试研究可为木工榫槽铣刀设计与优化提供借鉴。