对起重机断错相保护设置的探讨

GB/T 3811—2008《起重机设计规范》增加了起重机断错相保护的要求,通过对起重机电气图的分析,说明了起重机断错相保护设置的必要性,同时结合起重机实际使用工况,指出了当前该保护装置设置存在的问题,最后通过对控制回路进行改进,提出了解决方法,这对当前起重机断错相保护装置的安装具有一定的参考价值。     

我国线接触股钢丝绳渊源及结构参数计算程序

介绍我国线接触股钢丝绳的由来、发展过程和品种范围。鉴于钢丝绳增加品种和需用7.0以下的低捻距倍数捻股等要求,编制了线接触股程序,该程序可自动生成捻距倍数为6～10的多种结构。以西鲁式股为例,在某一捻距倍数时,给出线接触股钢丝绳技术参数的关系和相应的计算公式,计算精度达小数点后4位有效数字。介绍所应用的编程软件和代表品种计算程序的模式,使用该程序能输出所列线接触股全系列的基本参数和捻制参数。     

Scanning the Melting Curve of Tungsten by a Submicrosecond Wire-Explosion Experiment

Measurements of temperature and density during a wire-explosion experiment at atmospheric pressure are described. The measurements encompass a parameter range from the solid to near the critical point. The influence of a polytetrafluoroethylene coating of the wire, necessary to prevent surface discharges, on the temperature and density measurements is investigated. The melting curve of tungsten up to 4000 K is detemined.     

In situ synthesis of ammonia by catalytic hydrolysis of urea in the presence of aluminium oxide for safe use of ammonia in power plants for flue gas conditioning

BACKGROUND: Ammonia is applied to increase the efficiency of an electrostatic precipitator for fly ash removal from a flue gas stream from a boiler using fossil fuel. In the present work, the hydrolysis of urea to generate ammonia for flue gas conditioning, with the help of aluminium oxide catalyst, has been studied. RESULTS: The effect of temperature, catalyst and initial concentration on the conversion was studied. Conversion was found to increase exponentially with temperature. Addition of catalyst resulted in an increase in conversion. Experiments were conducted with different doses of catalyst, and the optimum dosage of catalyst for a particular feed concentration was determined. A decrease in conversion was observed when the initial concentration of ammonia was increased. CONCLUSION: A study of reaction kinetics showed the effect of reaction time on conversion of urea to ammonia. The catalytic hydrolysis of urea, using aluminium oxide behaved as a first‐order reaction; the rate constant at different temperatures was found, and the activation energy determined. Copyright © 2011 Society of Chemical Industry     

pcb电源布线设计-印制导线温升与导线宽度和负载电流的关系

本文阐述了PCB电源分配网络布线需要关注的几个方面,提供了量化设计的方法和工具.结合案例,介绍了电源通流能力可靠性设计的方法.     

Properties of welded joints made of Weldox 1100 steel

This study evaluated both the joint strength of copper wire on a copper substrate with tin plating and the joint reliability of copper wire bonding after heat treatment. The suitable tin thickness and bonding conditions, which are stage temperature, wire bonding power and bonding time, were chosen by the peel test after copper wire bonding. Tin thickness of 10 m showed a high bonding rate under the conditions of stage temperature 373 K, bonding power 500–700 mW and bonding time 30 50 ms. Before heat treatment, the peel strength of the copper wire on the copper substrate with tin plating conditions was weaker than that of gold wire on a gold substrate. After heat treatment for more than 70 h at 298 K, the peel strength of the copper wire became higher than that of the gold wire and twice as high as the initial bonding strength. The tin layer remained between the copper wire and copper substrate before heat treatment. When the samples were held at 298 K, tin reacted with copper and turned into a Cu–Sn intermetallic compound. Upon completion of this reaction at 298 K for over 70 h, the soft tin layer between the copper wire and copper substrate disappeared. Therefore, the peel strength of copper wire after heat treatment increased. These results were observed by scanning electron microscope images of the interface between the copper wire and copper substrate before and after heat treatment.     

Metallurgical aspects of corrosion resistance of aluminium alloys

Aluminium is the second most often used metal after steel. In this paper, the most current uses of aluminium alloys are first summarised. Then, their different corrosion modes, i.e. pitting, crevice, filiform, galvanic and structural corrosion (including inter‐granular, exfoliation and stress corrosion cracking) are reviewed, with particular attention paid to metallurgical factors controlling the corrosion process. For each mode, some instances of possible in‐service failure are given, followed by the discussion of the involved mechanisms and the presentation of appropriate solutions to prevent corrosion. Last, passivity and polarisation behaviour are discussed with reference to stainless steels.     

Study of shunt type SFCL equipped with electromagnetic repulsion switch for large capacity

Using a high‐temperature superconductor, we constructed and tested a model Superconducting Fault Current Limiter (SFCL). The SFCL that we proposed has a vacuum interrupter with electromagnetic repulsion mechanism. We set out to construct a high‐voltage‐class SFCL. We produced an electromagnetic repulsion switch equipped with a 24‐kV vacuum interrupter (VI). However, the opening speed becomes slower, because the larger vacuum interrupter needs a heavier‐weight contact. For this reason, the current which flows in a superconductor may not be interruptible within a half cycle of current. In order to solve this problem, it is necessary to change the design of the coil connected in parallel and to strengthen the electromagnetic repulsion force at the time of opening the vacuum interrupter. Thus, the design of the coil was changed, and in order to examine whether the problem is solvable, a current limiting test was conducted. We carried out a current limiting test using second‐generation (2G) HTS wire. The element used in this experiment has a stainless steel stabilizer on both sides of the wire. In the experiment we succeeded in interrupting the current of a superconductor within a half cycle. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(4): 20–27, 2010; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21039     

一种基于免换装绳牵引卡轨车的设计

煤矿生产过程中必然要使用到轨道运输系统,该系统的性能和安全性与矿井本身的生产效益和工作人员的人身安全有直接关系。现阶段免换装绳牵引卡轨式轨道运输系统还存在一定的弊端,在此基础上通过对制动系统和张紧系统进行改造,帮助运输车辆安全有效的实现运行和停止,方案中提出的张紧系统给予钢丝绳足够的牵引力,保证车辆运输的安全性。     

捞油作业用钢丝绳

介绍油田捞油作业的基本情况,分析捞油作业用钢丝绳的工作状况。国内捞油作业曾先后使用6×7+FC,6×19S+FC,18×7+FC等结构钢丝绳,均未取得满意的使用效果。针对捞油用钢丝绳作业时由于频繁卸载、加载,使钢丝绳产生灯笼状、绳芯散出或钢丝绳扭结现象,研制、开发新型捞油用钢丝绳。重点介绍咸阳宝石钢管钢绳有限公司研发的K5×7+FC,K4V×39+5FC,K5×19S+FC结构捞油用钢丝绳,在油田的实际应用中,该类结构钢丝绳的使用寿命与国外同类产品相比没有大的差异。