基于PWM双闭环的检测仪器开关电源设计

介绍了一套基于PWM的双闭环的检测仪器开关电源系统,叙述了双闭环电源系统的构建方法 ,该设计中,开关电源属于大电流低电压,控制核心为脉宽调制控制电路。本开关电源的核心技术部分是PWM脉冲宽制调制,采用国外先进的直流-直流变换处理器,能够保证电压和电流的稳定输出。根据开关电源的设计要求,列出电路结构、核心控制部分、电流电压等重要参数。试验结果表明,该电源工作稳定,能够使检测仪器稳定可靠的工作。     

USB2.0技术在便携式测试系统中的应用

介绍了一种基于USB技术的便携式石油测井测试系统的设计,详细阐述了该测试系统的USB接口开发的方法数据通信过程。该系统使用DSP和FPGA的硬件架构,完成了测井数据的获取和格式转换,并利用USB控制芯片FT245BL实现了测井仪器与PC机之间的通信,实验结果表明该测试系统很好的满足了实验室仪器调试的需要。     

基于全寿命成本的输电线路设计方法

伴随着科学技术的快速发展和社会的进步,推动了输电系统的发展进程,为确保输电线路系统的稳步发展,应延长输电线路寿命,只有这样,才能真正实现稳步、持续发展的目的。因此,我们应加强对输电线路系统全寿命的管理,节省输电线路资源,切实保障输电线路的安全运行,进而促进我国电网的健康发展。本文先对基于全寿命成本的输电线路设计进行概述,然后分析了基于全寿命成本的输电线路设计的影响因素,最后提出了设计的具体方法,希望能为输电线路设计提供一定的参考。     

基于Labwindows CVI的仪器测试系统

为降低测井仪器的研发和测试成本,实现仪器的控制和数据采集,该设计是基于LabWindows/CVI的数据采集系统。通过LabWindows/CVI的交互式C语言开发平台,设计了上位机的测试界面,实现上位机与仪器间的通讯控制和数据采集。实验结果表明,该界面完成采集仪器数据的功能,很好地满足了仪器调试的需要,可广泛应用于测井领域。     

基于单片机的按法测试仪的设计

按法是中医按摩手法中一个重要手法,作者设计一个基于单片机的中医按法测试仪。该仪器通过阵列式压力传感器,将按摩过程中的力度进行采集并显示,同时记录力度到达峰值所需的时间。     

基于图像识别技术的输电线路智能监控技术应用分析

本文介绍了一种基于图像识别技术的输电线路智能监控技术,该技术利用4G无线通讯将现场实际情况传送到后台服务器进行智能识别,当识别出可能发生对输电线路破坏的情况时,后台服务器自动发出预警信号通知相应的管理人员,并启动现场的报警装置警示,以此来减少停电次数,提升输电线路可靠性。     

浅谈变电站电气二次系统的设计

电流、电压和电力需要经过变电站的综合处理,经过汇集电流、分配电压和电力来为用户提供服务,变电站是用户与电厂之间的重要桥梁,起到调度分配的作用,而变电站电气二次系统的设计可以为电力系统提供更好的保护和监控服务。论文结合笔者的研究经验,在研究变电站电气主接线设计参数的前提下,提出电气二次系统的设计,对于有效的保护、监控一次仪器的运行具有重要的作用,也为电力系统的稳定可靠提供了支持。     

一起大电流雷击故障跳闸分析

本文针对一起大电流雷击故障跳闸事故的分析,在调研了现场情况的前提下,结合雷电定位系统数据,采用基于电磁暂态仿真分析程序的ATP-EMTP法,分别建立雷电电流波形和雷电通道波阻抗模型、输电线路模型、杆塔模型、绝缘子串闪络模型、接地电阻模型及感应电压模型,对其耐雷水平进行了计算,分析了跳闸原因,并针对本次事故的特点,提出了整改措施,预防类似事故再次发生,并为其线路的防雷提供经验。     

浅议电力GIS中的空间分析

空间分析在电力GIS中的应用非常广泛,本文主要针时空间分析在输电线路选线方法和输电线路线损分析两个方面的应用进行阐述.在研究输电线路选线原则的基础上,利用空间建模方法,基于DEM和GIS确定最佳路径位置,为输电线路选线提供科学依据.线损分析是众多电力专业分析功能之一,是供电部门一项必不可少的工作.     

500kV过载保护金具安全销失效分析及设计

近些年来由自然灾害、覆冰、风振等引起的倒塔、断线事故逐年增多,而输电塔在线路总投资中约占40%左右,并且输电塔的构造复杂,以致于在输电线路的抢修过程中,倒塔重建的花费和困难最多。本文基于过载保护金具的思想,利用安全销、碗头挂板和联板整体有限元模型,对安全销的应力分布情况进行分析,得出了弯矩对安全销的破坏起主要作用的结论;最后对安全销的尺寸设计进行了分析及建议。本文的研究完善了输电线路防灾减灾金具的设计,对输电线路过载保护金具的研发具有一定的参考价值。     

Indirect Measurement of Leaf Area Index in Sagebrush-Steppe Rangelands

Leaf area index (LAI) is defined as the one-sided area of leaves above a unit area of ground. It is a fundamental ecosystem parameter that is a required input of process-based plant growth and biogeochemical models. Direct measurement of LAI is the most accurate method, but is destructive, time-consuming, and labor-intensive. LAI is highly variable in time and space on sagebrush-steppe rangelands, and a rapid, nondestructive method is desirable to understand ecosystem processes. The point-intercept method is nondestructive and has been demonstrated to provide accurate LAI estimates, but the method is time-consuming. LAI measurement with the Accupar ceptometer (Decagon Devices, Pullman, WA) is nondestructive and faster than the point-intercept method, but has not been evaluated on sagebrush-steppe rangelands. The objective of this study was to evaluate the ceptometer for measurement of LAI in sagebrush-steppe rangelands. Ceptometer and point-intercept LAI data were collected at six sites in sagebrush-steppe rangelands and the values were compared. We found that 1) ceptometer LAI data were consistently greater than point-intercept LAI data, 2) ceptometer data were much more variable than the point-intercept data based on standard deviations, and 3) the overall correlation between the two methods was very weak (r² = 0.15). The much greater ceptometer LAI values were, at least partly, due to the large woody component of the vegetative cover. We attribute the high variability of ceptometer-measured LAI to high instrument sensitivity of the angle of the instrument relative to the sun.     

The effects of stray voltage on turkey poults

Three successive flocks of turkey poults experienced cumulative mortality of 10% to 26% through the fifth week of brooding. Stray electrical voltage was suspected after no definitive laboratory diagnosis could be made and no evidence of management deficiency was found. Alternating current voltages of 0.2 to 2.5 volts were detected between waterers and the floor and between the water line and gas line. When the water line was equipment-grounded to the electrical service entrance, the subsequent flock had no mortality problem. A series of experiments was conducted to determine the sensitivity of turkey poults to alternating current. Based on these experiments, the voltage levels measured at the farm probably did not cause the mortality experienced in the three flocks. The reason for the farm problem could have been 1) the poults experienced higher voltage than was present when measurements were taken, 2) the voltage may have been intermittent, or 3) there was a difference between the farm environment and the cage battery environment in the experiments.     

Constitution and evaluation of a long-lived productive rabbit line

An evaluation of a new maternal line (LP) of rabbits was carried out. This new line was founded following a scheme similar to that applied in the selection for hyperprolificacy in rabbits or pigs. In this case, the selection criteria were hyperlongevity and an independent culling level near the average for prolificacy. Evaluation was carried out by comparison of the reproductive and longevity performance of the LP line with another maternal line recognized for good reproductive performance and standard longevity (V line). The results indicate that the LP line could be a valuable resource for inclusion in the current 3-way cross schema used in rabbit production, because females showed better survival ability and nearly the same prolificacy as the well-reputed V line. A V doe was 1.3 times more likely to leave the herd than an LP doe, and the probability of the differences in prolificacy between lines being greater than 0 was not extreme (no more than 0.22). Differences in relative performance of the lines were observed across farms for prolificacy, longevity, cumulative production, and fertility; however, based on deviance information criterion results, the data supported the hypothesis of only these differences being generated under a genotype x environment interaction for prolificacy traits. The longer productive life of LP females could partially be understood as an indication of success of the selection procedure during the foundation of this line.     

Studies on the determination of optimal insemination time using electrometric resistance measurements in heifers and young cows after estrus synchronization

Studies were conducted on how to use under the conditions of industrialised production in the GDR an electrometric method proposed by Soviet scientists to determine oestrus and ovulation date in oestric-synchronised heifers and cows. "Oestrometer-2", an instrument developed in the USSR, was used for 4,818 measurements of electric resistance in 700 oestric-synchronised heifers and 39 oestric-synchronised cows. The typical course of the resistence curve was confirmed by the results. Individual data variation together with unsatisfactory data reliability of the instrument, when applied to measurement at vaginovestibular mucosa, were likely to suggest that the method could not be used with good effect for high-accuracy determination of the ovulation date and therefore, was not useful in helping to save semen pellets after oestric synchronisation.     

The detection and measurement of stray electrical leakages on dairy farms: effects on performance

Sources of stray electrical leakage from Power Supply Authority alternating current (AC), fence energiser pulses and randomly generated pulses and spikes on 55 dairy farms in the Waikato area were identified between December 1986 and March 1988. The electrical measurements were made using a specifically designed voltmeter able to detect voltages between 0.1V and 1500V, from single voltage spikes of two microseconds or greater duration from direct current (DC) as well as 50 Hz AC. Ninety-five sources of stray voltage were identified, and 53 per cent of properties had more than one source of >0.5V. The major source was from electric fence energisers. Rotary platform parlours were among the commonest sources of random or transient voltage spikes. Leakage of AC into one or other of the components of the milk transport system such as vat, plate cooler, milk lift pump and milk line was common. Owners acknowledged the improvements in milk production, reproductive performance and growth rate of calves after reduction of the exposure of dairy cattle to stray electrical leakage. A representative summary of five case records helps define the range of improvements that may possibly be achieved.     

超高频电子耳标物理层及标签识别层测试方法研究

基于RFID技术的电子耳标追溯体系可进行动物出生后、屠宰前的精准定位,实现畜产品的可追溯性管理。超高频电子耳标测试系统具有较远的读取距离及较高的传输速率,广泛应用于畜产品的可追溯性领域。该类标签的存储地址依据空中接口协议标准ISO18000-63定义,测试项目依据18047-6测试方法进行。对测试项目的测试方法和判定依据进行了详细介绍,并对链接时间T1进行10次测试,计算其测量不确定度,测量结果显示符合标准要求。     

The detection and measurement of stray electrical leakages on dairy farms: effects on performance

Sources of stray electrical leakage from Power Supply Authority alternating current (AC), fence energiser pulses and randomly generated pulses and spikes on 55 dairy farms in the Waikato area were identified between December 1986 and March 1988.

The electrical measurements were made using a specifically designed voltmeter able to detect voltages between 0.1V and 1500V, from single voltage spikes of two microseconds oi- greater duration from direct current (DC) as well as 50 Hz AC. Ninety-five sources of stray voltage were identified, and 53 per cent of properties had more than one source of >0.5V. The major source was from electric fence energisers. Rotary platform parlours were among the commonest sources of random or transient voltage spikes. Leakage of AC into one or other of the components of the milk transport system such as vat, plate cooler, milk lift pump and milk line was common.

Owners acknowledged the improvements in milk production, reproductive performance and growth rate of calves after reduction of the exposure of dairy cattle to stray electrical leakage. A representative summary of five case records helps define the range of improvement that may possibly be achieved.     

两种细度测量仪对羊毛纤维直径测定的对比分析

为了检验国产动物纤维细度自动测量仪奥达2000的稳定性和准确性,分别用进口的OFDA100细度仪和国产动物纤维细度自动测量仪对来自314只细毛羊的毛样进行测定,再对两者测得的数据作配对性t检验。检验结果表明,二者间差异不显著（P>0.05）。因此,国产动物纤维细度自动测量仪奥达2000性能与OFDA100细度仪没有差异,可以代替进口细度仪OFDA100。     

Effect of chewing rawhide and cereal biscuit on removal of dental calculus in dogs

The effect of chewing rawhide and cereal biscuit on removal of dental calculus was studied in 67 dogs. Two methods were used to measure supragingival calculus and calculus removal as a function of time and acceptability. Trial 1 used a quantitative method based on actual measurement of the area of calculus on a tooth, and trial 2 used a quantitative method based on an arbitrary grading system to establish a supragingival calculus index. Analysis was performed, using 2-factor (trial 1) and a 3-factor (trial 2) analysis of variance. Results indicated that dogs removed calculus from their teeth by chewing rawhide; some teeth were cleaned better than others. The optimal amount or frequency of rawhide treatment was not necessarily determined. It was determined that regular consumption of up to 3 rawhide strips/d for 3 weeks was safe. Processed biscuits were sometimes effective in removing calculus from dog's teeth; however, biscuits were not as effective as the rawhide in removing supragingival calculus.     

禽网状内皮组织增生症病毒单抗制备及在外源病毒检测中的应用

将禽网状内皮组织增生症病毒(REV)囊膜蛋白gp90(SU)的基因合成后连接至原核表达载体中进行表达,获得REV-SU蛋白,通过Ni柱亲和层析获得纯化的重组蛋白,免疫BALB/c小鼠,应用杂交瘤技术获得1株分泌特异性抗REV-SU蛋白的单克隆抗体杂交瘤细胞系(2A2株),该细胞株制备的腹水与不同REV毒株具有良好的反应性,荧光效价可达1∶51200,与不同禽白血病病毒毒株和其他常见禽的病原均没有交叉反应,特异性良好。应用该单克隆抗体建立的间接免疫荧光法能检出至少5 TCID₅₀REV感染,与多克隆抗体作为检测一抗具有同等的效力,且检测背景更加纯净,适用于外源性REV检验。