酸度计示值误差的测定不确度

<正>0概述1)测量依据:JJG119-2005《实验室pH(酸度)计检定规程》2)环境条件:温度(23±10)℃,相对湿度≤85%3)测量标准:pHC——1C型酸度计检定仪。4)被测对象:酸度计5)测量过程:采用直接比较法进行检定,即用规程规定的直流电位差计、pH计检定仪作为标准器,检定的环境温度为(23±10)℃。检定时用电位差计、pH计检定仪或标准溶液值向被检pH计(简称电计)     

电阻箱组装电位差计直流电路测量电动势与电阻

本文设计了一种用电阻箱代替十一米线电位差计板组装电位差计的直流电路的方法 ,并介绍了如何使用这种直流电路测量电动势和电阻。     

UJ36电位差计与铜-康铜热电偶测温接线方法

<正> 在建筑工程中,用UJ36电位差计与铜-康铜热电偶组合的测温法比较简单、可靠、迅速、准确,可实现多点测量,得出所要求观测的温度场的变化过程。现将这套测温系统的接线方法介绍如下。一、接线方法及仪表 UJ36电位差计与铜一康铜热电偶测温系统,一般需要如下的设备和材料:UJ36     

紫外辐照计探头的新标定方法

紫外辐照计是检测紫外线强度的一种检测仪表。它的探头的光敏感元件是紫外敏感光纤。入射的紫外线由探头中的紫外敏感光纤接收，并将其换为电信号，然后再经过IIV及Afl3转换，最后在LCD上显示出来。一、原来的标定方法为保证辐照计的测量精度、辐照计的探头标定工作非常重要。探头标定的好坏直接影响到辐照计的产品质量。辐照计的探头是集光电转换和W电流电压转换于一体的关键部份。原来的标定方法如图1所示：R；和R。为2个可调电阻器。在设定紫外强度照射下，调节2个可调电阻器，使被标定的探头在显示表上所显示出的测量值与标准探头的…     

直读式测钙仪电计电位校准方法研究

介绍了直读式测钙仪电计电位的校准方法,包括电计电位示值误差和重复性测量方法,以及对仪器电计电位示值误差测量不确定度的评定等。     

惠斯登电桥测量灵敏度分析

分析了惠斯登电桥测量电阻的灵敏度问题,推导出电桥灵敏度与电源电压、检流计灵敏度、总阻值和比例臂电阻有关。并针对传统的惠斯登电桥测电阻实验装置存在的不足,研制出了立体式电桥实验仪,实验结果表明能够有效提高测量精度。     

热电偶测温在建筑施工中的应用

在建筑工程施工中有很多施工过程对温度的变化有一些具体要求,诸如以温度变化情况掌握工程进程,以温度条件为前提确定施工方法,或以控制一定温度变化范围来确保工程质量等等,所以在建筑施工过程中有很多时候要及时对温度进行测量,而且往往需要准确地了解一些物体内部的温度变化或温度场的分布情况。应用UJ36电位差计与铜-     

PWM 逆变器的一种控制算法

设计了一种单相工频逆变电源的实现方案和控制算法，该电源可产生幅度可调的单相工频电压、电流，并且电压和电流的相位可在０。到３６０。间调节，很适合作为测试继电器时的供给电源．     

基于MSP430的AD采样直流电子负载系统的设计

针对目前电源负载测试一般都采用静态负载耗放电的方法来实现,整个测试过程的安全保护以及精准度方面有很多不足之处。为了实现了电子负载的恒流控制,能够检测被测电源的电流、电压并由液晶进行实时显示。此系统设计一种采用高精度的AD采样芯片并结合单片机实现可调电子负载。系统中利用键盘预置电流值及单片机控制外部D/A模块输出改变其电子负载功率器件参数,来实现电源输出电流大小的改变;同时,系统中采用闭环负反馈电路来保持电流值恒定不变。     

基于杂散电流监测技术的轨道交通安全监测设备

对地铁杂散电流的成因以及破坏机理进行论述,并利用测量杂散电流参考电位差以及环境因素进行分析和测量杂散电流的发生趋势,并及时做好防护工作。     

An evaluation of the benefits of source control measures at the regional scale

Source control measures include rainwater tanks, infiltration trenches, grassed swales, detention basins and constructed wetlands that can be used in housing allotments and subdivisions. A methodology for evaluating the regional economic benefits due to implementation of source control measures is presented and illustrated for two case studies in the Lower Hunter and Central Coast regions of New South Wales, Australia. It is demonstrated that use of rainwater tanks to supplement mains water supply for toilet, hot water and outdoor uses can very significantly reduce demand on mains water supply. Reductions in regional water demand will enable deferment of water supply headworks augmentation, while reductions in peak mains water demand will extend the life of water supply distribution infrastructure. In addition, substantial reduction of stormwater discharge from allotments can be realised. For the Lower Hunter region with an urban population of about 450,000 it is shown that construction of new water supply headworks infrastructure can be delayed by up to 34 years. Compared with the traditional provision of mains water and stormwater disposal, the use of rainwater tanks along with other source control measures can produce present worth savings to the Lower Hunter region conservatively estimated to be up to $67 million. Similar results were found for the Central Coast region.     

Pre‐insulated pipe mains for district heating

A method developed by co‐operative research in Hungary differs from many other ‘pipe‐in‐the‐pipe’ systems; it uses a special joint to couple the prefabricated insulated pipe sections and includes many sub‐systems which can be built into the pipe casing, such as a separate mains line for high‐temperature media. A built‐in electric indicator precisely locates any possible fault area in service.     

高效非逆变光伏技术理论基础

关于光伏应用形式的主要争论之一,是光伏电力的逆变应用与非逆变应用之争。其实"逆变"只是电力技术中一种直流变交流的方法,逆变与非逆变的本质区别,并不在于采用该方法与否。在逆变应用中也有直流线路,非逆变应用中也有逆变装置。关键问题是,被统称为"逆变并网"的逆变应用,是推崇用光伏电力取代市电的一种思潮,并长期以来作为主流观点在光伏应用领域占统治地位。而非逆变应用就不赞成这种应用形式,并且有针对性地提出了许多不同意见,归结起来有3条:第一,不必要,因为直流电、交流电都可以应用,将直流低压的光伏电力变成高压交流电去适应普通电气应用是多余而又降低效率的环节;第二,问题复杂化,因为光伏电力的输出功率不稳定,又不采用储能装置,依附电网上的负载卸载,势必给网电造成影响,从而发生一系列技术问题和与电力部门的协调问题,人为增加了光伏电力应用的困难;第三,经济上不合算,无论如何,光伏电力成本的价格还是远高于市电。而逆变应用反驳得不太有说服力,除了第一条所说的应用方便之外,其余2条对于实际问题的解决,至今没有实质性的进展。     

Sampling and quantifying invertebrates from drinking water distribution mains

Water utilities in the Netherlands aim at controlling the multiplication of (micro-) organisms by distributing biologically stable water through biologically stable materials. Disinfectant residuals are absent or very low. To be able to assess invertebrate abundance, methods for sampling and quantifying these animals from distribution mains were optimised and evaluated. The presented method for collecting invertebrates consists of unidirectionally flushing a mains section with a flow rate of 1 ms(-1) and filtering the flushed water in two separate flows with 500 microm and 100 microm mesh plankton gauze filters. Removal efficiency from mains was evaluated in nine experiments by collecting the invertebrates removed from the mains section by intensive cleaning immediately subsequent to sampling. Of 12 taxa distinguished, all except case-building Chironomidae larvae (2%) and Oligochaeta (30%) were removed well (51-75%). Retention of invertebrates in 100 microm filters was evaluated by filtering 39 filtrates using 30 microm filters. Except for flexible and small invertebrates such as Turbellaria (13%), Nematoda (11%) and Copepoda larvae (24%), most taxa were well retained in the 100 microm filters (53-100%). During sample processing, the method for taking sub-samples with a 10 ml pipette from the suspension of samples with high sediment concentrations was found to perform well in 75% of the samples. During a 2-year national survey in the Netherlands and consecutive investigations, the method appeared to be very suitable to assess the abundance of most invertebrate taxa in drinking water distribution systems and to be practicable for relatively inexperienced sampling and lab technicians. Although the numbers of small, less abundant or sessile taxa were not accurately assessed using the method, these taxa probably should not be the primary focus of monitoring by water utilities, as consumer complaints are not likely to be caused by these invertebrates. The accuracy of quantifying small invertebrates was further improved, however, by filtering the 100microm filtrate with a 30microm mesh plankton gauze filter.     

Cost-Effective Water-Quality Modelling of Potable Water Distribution Systems

Before privatization of the water authorities in England and Wales in 1989, future water companies were instructed to provide auditable proof of their investment requirements by the production of asset management plans.
With respect to distribution systems for potable water, asset management plan studies have established that unlined ferrous mains are often the main cause of complaints about discoloured water. It has also been found that the investment in water mains rehabilitation, which is driven by water quality problems, overshadows similar investment requirements driven by high burst rates and poor hydraulic performance.
This paper describes how certain techniques of water quality modelling have been developed and refined to provide a rapid, cost-effective method for identifying requirements for water-main rehabilitation.     

Accounting for Polycyclic Aromatic Hydrocarbons in Public Water Supplies

Asset management plans were prepared in 1989 and 1994 by water companies in England and Wales for submission to the Office of Water Services. These plans constituted the financial programming required by water companies to meet specified standards of service, particularly with respect to water quality. Detailed studies have previously established that problems associated with iron from unlined ferrous mains, particularly in soft water areas, is often the main cost 'driver'for water distribution investment. However, many of the so-called unlined iron mains were treated with a coal-tar pitch lining for corrosion protection before installation, and residues of this painted lining can give rise to unsatisfactory levels of polycyclic aromatic hydrocarbons in drinking water.
The paper describes how desk-study research, followed by the development and application of a modified 'focused downstream series sampling'water-quality modelling technique allowed polycyclic aromatic hydrocarbons to be accounted for in two water company asset management plan submissions. The paper also raises a number of fundamental implications with respect to the occurrence of these carcinogenic compounds in drinking water.     

Decision support model for selection of rehabilitation methods of water mains

The deteriorating condition of water mains in Canada and US calls for rehabilitation strategies that accounts mainly for budget and level of service constraints. These water mains have received ‘D’ grade in the two countries. Decision support models can assist decision makers regarding when to rehabilitate and whether to repair, renovate or replace section(s) of water mains. The literature indicates that decision models should account for life cycle cost, uncertainty, long-term planning, targeted levels of service and budget constraints. The objectives of this paper are to: identify and group rehabilitation methods, present decision support model to rank and select most suitable rehabilitation method(s), and study the impact of rehabilitation methods on the functional and structural performance of water mains. The developed decision support model accounts for life cycle cost of each competing scenario along with the associated uncertainty. The model, unlike available models, can effectively account for vagueness, qualitative assessments and human judgment associated with input data. A case study of a water main network was analysed in order to demonstrate the use of the developed model and to illustrate its essential features. The results obtained indicate that the model can support the generation of well-informed decisions in a timely manner.     

纸质地图的作用及对策研究

纸质地图作为人们出行的助手,受到电子地图越来越多的冲击,有人质疑纸质地图即将被电子地图所取代。本文结合纸质地图和电子地图的优劣对比,阐述了纸质地图在现代社会生活中应该发挥的作用,强调了其在辅助出行、普及地理知识、军事价值、专题图应用和文史价值方面的意义。同时结合工作实践重点介绍了纸质地图面临冲击所采取的应对措施。