Subdivision of work on construction projects

In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure.     

30CrMnsi联接环断裂失效分析

对断裂的联接环进行了化学成分、机械性能、显微组织核验，指出回火工艺不当、锻造缺陷以及原材料化学成分不合格，是造成断裂事故的主要原因．在此基础上．提出了改进措施．     

预测宾汉流体中最大下套管速度的实用方法

波动压力的大小与井眼系统稳定密切相关,而管柱下放速度又是影响波动压力的主要因素。因此,基于平衡压力钻井和井控要求而确定合理的管柱下放速度,对确保安全快速钻井具有重要意义。文中以宾汉流体为例,从理论上推导了控制管柱最大下放速度的非线性方程组,并在地层破裂压力梯度给定的情况下分析了影响管柱最大下放速度的主要因素。计算结果表明:随钻井液屈服值、塑性粘度增加,最大下放速度应该减小;随环空内外管径比增加,最大下放速度应该减小;随地层破裂压力梯度增加,最大下放速度可以增大。文中还给出了计算实例。     

覆铜板设备的发展及现状

本文主要就生产覆铜板的主要设备的发展过程和现状作一简要论述。     

橡胶挤出机螺旋旋转轴断裂分析

本文通过对“橡胶挤出机螺旋旋转轴的断裂分析”找出了断裂原因,并提出改进意见,经厂方的应用,取得了满意的效果。     

有机、无机复合膜在电致发光器件中的应用

主要介绍了一种将有机材料[1]和无机介质层进行复合,以提高电致发光显示器中介质层绝缘性能的方法,通过这种复合方法提高了器件中介质层的耐压可靠性,减少甚至消除了器件在工作时出现的漏电、打火、击穿等现象。     

开坯轧机大压下量对大棒材芯部的影响

基于有限元仿真对比分析了大棒材在开坯轧制前两道次中不同变形程度对轧件芯部的影响.仿真结果表明:两道次压下量在90m m和70mm时的轧件等效应力比两道次压下量都在65mm时大200 MPa;轧件等效应力随道次增加而增加,变形程度增加使得轧件轧后残余应力增加;等效塑性应变随着道次变形程度增加而增大,而大的变形程度会促使等效应变渗透至轧件芯部,为消除或减小轧件芯部组织缺陷提供解决措施,从而提高材料的使用寿命.     

CCD多晶硅层间绝缘介质对器件可靠性的影响

采用扫描电子显微镜和电学分析技术研究了电荷耦合器件(CCD)多晶硅层间绝缘介质对器件可靠性的影响.研究结果表明,常规热氧化工艺制作的多晶硅介质层,在台阶侧壁存在薄弱区,多晶硅层间击穿电压仅20 V,器件在可靠性试验后容易因多晶硅层间击穿而失效.采用LPCVD淀积二氧化硅技术消除了多晶硅台阶侧壁氧化层薄弱区,其层间击穿电压大于129 V,明显改善了器件可靠性.     

几起电缆击穿故障的原因分析与对策

长治市近年来在城网建设与改造工程中,对主城区实施了几项电缆入地工程。该文章通过电缆入地后,发生的几起电缆击穿故障,从现场发生故障到原因分析和今后应采取的防范措施等方面,进行了简要的阐述。     

Methods for overcoming breakdown problems in the Unsymmetric Lanczos Reduction method

The Unsymmetric Lanczos Reduction (ULR) method is developed to solve the finite-element-based solution to the contaminant transport problem. The method sometimes suffers from breakdown when at some step division by a pivot which is zero or near zero, causes numerical instability. In this paper, the Maximum-Pivot New-Start Vector method is developed to overcome such breakdowns by constructing a new starting vector with the possible maximum pivot. Some cases of instability cannot be remedied by this approach (pathological breakdowns) and the Switch method is developed to complete the solution by changing the algorithm to an Arnoldi reduction approach. Investigation of some two-dimensional examples and field problems illustrates the efficiency of the methods and substantial time savings over other existing solution methods. © 1998 John Wiley & Sons, Ltd.