Life Tests Under Dependent Competing Causes of Failure

In a life testing situation the failure of an individual, either a living organism or an inanimate object, may be classified into one of k(< 1) mutually exclusive classes, usually causes of failure. One often has dependent causes of failure in actual physical situations, i.e., the theoretical lifetime of an individual failing from one cause may be correlated with the theoretical lifetime of the same individual failing from a different cause. This paper i) discusses some properties of a bivariate Weibull distribution and ii) is concerned with estimating, by the method of maximum likelihood, the unknown parameters of life distributions belonging to two particular parametric families, viz., bivariate normal and bivariate Weibull, when the causes of failure are dependent. An example involving the failure of small electrical appliances is analyzed and compared with an analysis which assumes the causes of failure to be independent.     

Problem solving through digital game design: A quantitative content analysis

Project Tech engages secondary students (ages 14 to 17) in the process of digital game design in a variety of in-school, after-school, and secure settings. The goal of Project Tech is to leverage students’ interests in games and design to foster their problem-solving in a supportive environment where they learn to create games about a social issue they have experienced personally. The present study compares the in-school special needs version of Project Tech (n = 11) to examine problem solving. Students enrolled in Project Tech were guided in the process of designing digital games aimed at teaching younger students (ages 12–15) about social issues facing teenagers. A quantitative content analysis was conducted on 35 iterations of a directed design game and 35 iterations of a free design game created by special needs young people and director notes. The purpose of the study was to draw from the game iterations a list of empirically grounded problem solving attributes that are associated with digital game design in a special needs classroom. The findings of the study resulted in the understanding of problem solving with special needs young people in four areas: representative characteristics, planning characteristics, executing characteristics and evaluation characteristics.     

地铁车站通信机房使用机房专用空调下送风方式的探讨

通过对地铁车站通信机房空调系统运行时间、负荷特点的分析,结合地铁车站通信机房现有空调系统形式存在的缺点,分析了在地铁车站中使用下送风机房专用空调方式的可行性,为减少地铁建设投资及地铁车站空调系统设计提供一种新思路。     

五轴联动数控工具磨床的开发

随着现代制造技术的发展,对特型刀具的品种和刃形的要求越来越高。而用普通工具磨床和传统生产工艺方法很难加工这些刃形复杂的刀具。针对这一现状自主开发一种五轴联动数控工具磨床,该五轴联动数控工具磨床能实现对球头立铣刀等多种硬度高、刃形复杂刀具的磨削加工,且一次装夹能完成所有的精加工。     

异型深盲孔结构的展开式刀具设计

异型深盲孔结构的加工是深盲孔结构加工领域的难题。针对一种具有异型深盲孔结构的零件,设计了一种具有导向功能的展开式刀具。详细叙述了展开式刀具的运动原理、结构特点、装配方法,并进行了工艺切削实验,表明展开式刀具设计合理,能够满足这类异型深盲孔结构的加工需求。     

灯具罩旋压机专用数控系统的设计与实现

在灯具罩生产行业至今没有由专用数控系统组成的旋压机床,大部分由通用数控机床改造而成,故数控系统功能浪费、数控旋压机床成本高。因此,采用工控机、伺服驱动器和变频器等硬件设备,设计了灯具罩数控旋压机床的电气控制系统,并根据灯具罩的几何形状和旋压加工工艺,开发了灯具罩旋压轨迹控制模型,在此基础上研制了灯具罩数控旋压机床的专用数控系统。该系统只要将模具参数、加工轨迹外轮廓参数和灯具罩加工参数输入专用数控系统,就可以按照设定算法自动生成加工轨迹图,滚刀按照轨迹图自动进行旋压加工,从而实现加工过程的全自动控制。     

矿区专用铁路开采沉陷预计及治理系统研究

在矿区铁路下进行放顶煤开采所引起的地表及铁路的变形量大，变形速度快，从而导致矿区铁路维护困难。如果在开采前及开采过程中对地表及铁路的变形预计不准确，维修措施不当，将无法保证矿区铁路的正常运输，甚至出现安全行车事故。为此，研究开发了综采放顶煤条件下铁路开采沉陷预计及其治理系统，该系统通过对地表及铁路的变形进行较为准确的预计，可提出铁路线路及道岔的维修治理措施。     

养老保险基金管理中需加强的几个问题

养老保险基金工作是建立健全社会保障体系，发展市场经济、维护社会稳定的需要。因此，党中央、国务院高度重视养老保险基金的管理工作，文章从六个方面论述了养老保险基金管理中应需加强的问题。     

特种冶金生产流程的发展趋势

特种冶金是生产高端特殊钢和特种合金的主要手段,代表了一个国家的工业化发展水平,一直是国内外冶金技术竞争的制高点.本文首先回顾和总结了传统特种冶金技术的种类和主要生产流程;其次,概述了典型特殊钢品种的特种冶金生产流程;再次,对典型特钢企业的特种冶金生产流程进行了介绍;最后,对特种冶金生产流程的未来发展趋势作出预测.新技术将进一步促进特种冶金生产流程的变革与发展.