A review of the effect of a／W ratio on fracture toughness （Ⅰ）—experimental investigation in EPFM

Many experimental investigations have previously been performed and recently done on different shipbuilding structural steels where the specimens size and crack depth/specimen width (a/W) were varied. A series of interesting results have been gained. It is worthwhile to have a review on the effect of a/W ratio on fracture toughness, and further theoretical analysis is necessary. In this paper, experimental work in elasticplastic fracture mechanics (EPFM) was discussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J _i and δ₁ values increased with decreasing a/W when a/W<0.3 for three-point bend specimens and that shallow crack specimens which have less constrained flow field give markedly higher values of toughness than deeply notched specimens. However, for a/W>0.3, the toughness was found to be independent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stress is lower than that from standard deeply cracked bend specimen which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structure defects especially if initiation values of COD/J-integral are used.     

Determinants of crew injuries in vessel accidents

This study investigates determinants of the number of non-fatal crew injuries, fatal crew injuries and missing crew in freight ship, tanker and tugboat vessel accidents based upon individual accidents investigated by the US Coast Guard for the 1991-2001 period. Poisson and negative binomial regression estimates suggest that: (1) freight ship and tanker non-fatal injuries are higher when the vessel is moored or docked and during high winds and cold temperatures; (2) tugboat non-fatal injuries are higher during poor visibility; (3) freight ship fatal injuries increase with vessel age and tanker and tugboat fatal injuries are higher for fire and capsize accidents, respectively; and (4) freight ship missing crew increase with vessel age and tugboat missing crew are higher for fire and lake accidents.     

钢筋混凝土烟囱定向爆破倒塌运动解析

从力学原理推导分析钢筋混凝土烟囱定向爆破倾倒运动过程中的时程、下墩和后坐问题,得到有关计算公式,计算结果与烟囱爆破的实际情况相符合。     

疲劳试验在橡胶减振制品寿命预测中的应用

橡胶减振制品的耐疲劳特性严重影响其使用寿命。文章阐述了橡胶减振制品疲劳失效的判断准则和疲劳试验在使用寿命预测中的应用，以及国内外在橡胶减振制品寿命预测方面的研究进展情况。     

《工程估价》课程整合与创新——信息化电算化在《工程估价》的应用

《工程估价》课程教学改革是一项教学实践的创新活动。本文从工程估价课程整合的角度,就如何有效利用现有教学资源,结合学科热点,提出了自己的方案,同时对课程整合的教改实践进行了分析和探讨。     

行星齿轮变速箱最佳传动方案设计

根据给定的各档传动比，利用传动转速关系式，对行星排的各种组合进行综合分析，找出全部可能实现的方案，然后根据结构性能、传动效率、操纵力矩和制造工艺等因素挑选最佳的传动方案并确定各行星排参数。     

120例孕妇心理分析

对我院产前检查的１２０例健康孕妇进行了心理问卷调查，结果显示多数孕妇心理健康状况良好，认为生育是妇女的特权，因妊娠而心情愉快，全心期待执行优生优育政策而对胎儿性别无所谓，积极准备承担母亲角色。但有一些孕妇却存在不同程度的消极心理反应：忧虑、感情脆弱、依赖性强，为胎儿的健康与性别以及分娩痛苦而担心。针对目前孕妇的心理需求，提出了加强孕妇心理保健的措施。     

尾滑道式工作艇收放装置控制系统PLC应用技术研究

本文分析了尾滑道式工作艇收放装置采用的继电器控制技术所存在的问题，介绍了可编程控制器（PLC）的优点，并结合实例介绍了将PLC应用于工作艇收放控制系统的研制过程和最终实现的功能。     

淬火钢轨应力研究

沈阳局淬火线从最初建立喷雾淬火到最后改造为喷风淬火,期间由于淬火轨应力不均匀而造成施工中的种种困难,文章介绍为解决施工难题而采取的各种措施和试验方法。     

移动输入装置评估模型

目前移动输入装置种类繁多,在人机交互方式、性能和效率等方面存在着很大的差异。国外对输入装置性能评估的研究起步比较早,形成相应的评估模型。针对移动输入装置的评估和测试模型做一个综述性的介绍和分析。