表面安装技术与表面安装元件发展面面观

本文综合性地介绍了国内外表面安装技术与表面安装元件的发展现状、技术水平、市场动向,以及今后尚需开发的主要课题。     

河南省嵩山风景区旅游资源评价与可持续发展研究

本文针对河南嵩山风景区旅游资源的特点,采用层次分析法,选取资源价值、景观市场和旅游条件3个综合指标,建立旅游资源评价模型树,计算出各评价因子的权重值。并在此基础上,通过问卷调查对各景区因子进行打分,对嵩山各景区旅游资源进行了总体评价,最后提出了嵩山风景区可持续发展的策略。     

Rapid location of mount points

‘Mount points’ allow more storage to be grafted into tree-structured hierarchical file systems. Administrative tasks use their locations, which are tabulated in a file. In our System V Unix environment, this file was occasionally removed. Getmnt was written to recover the information. Getmnt has had three significant versions. The original version (getmnt1) was a highly optimized naive tree traversal. Getmnt3 improved the real time performance by a mean factor of 7 by pruning unnecessary branches from the traversal. Getmnt3 doubled getmnt2's speed, with a change from depth-first to breadth-first search. On our development system, getmnt1 required 647.6 s to run, whereas getmnt3 required 42.53 s.     

Head Banging: Engineering Neutrality + the Parametric Ceiling

Through the work of Unit 15 at the Architectural Association in London, Francesca Hughes and Noam Andrews have been exploring the limits of parametric systems. Here Francesca Hughes questions whether parametricism has now hit a ‘developmental ceiling’. What are the full cultural implications of the promised instantaneity of completed components in architectural production? Where does the ‘strange engineered neutrality’ of ‘optimisation’ take us? Is there a real danger that an ambivalence to context is returning us to the tabula rasa of Modernism?. Copyright © 2009 John Wiley & Sons, Ltd.     

挤压铸造A356.2铝合金发动机悬置支架的组织与性能

以挤压铸造A356.2铝合金发动机悬置支架为研究对象,对支架铸态组织、不同固溶时效热处理后的显微组织与力学性能,以及内部缺陷进行了分析研究。结果表明,挤压铸造A356.2铝合金铸态组织由α-Al相和Al-Si共晶组成,晶粒尺寸约为148μm,二次枝晶间距约为20μm;经固溶时效处理后,共晶Si一部分溶入α-Al相中,一部分以粒状、球状形式分布在α-Al晶界;固溶时间、时效温度和时效时间对A356.2合金的力学性能有一定影响。试样经过535℃×6h固溶+8min水淬+170℃×6h时效处理后,抗拉强度为340.5MPa,屈服强度为274.5MPa,伸长率为10%,满足支架整体力学性能要求。     

发动机隔振橡胶元件的有限元分析

有限元分析是发动机隔振橡胶元件设计开发的现代分析方法.橡胶元件的形状系数对其外在弹性特性影响的复杂性、动一静刚度比的多样性及黏弹性阻尼特性是其工程应用方面的难点.系统研究了橡胶有限元分析在工程应用上需要明确回答的问题,指出橡胶有限元分析的材料数据应是消除端部摩擦后的圆柱压缩试验数据,超弹性本构模型能够反映橡胶元件的静特性以及橡胶作为有质量弹性体对其动特性的影响规律,黏弹性本构模型能够反映橡胶元件的阻尼特性,但两种本构模型均不能反映其动一静比特性.如何准确反映橡胶元件的动-静比特性是橡胶有限元分析的重要课题.     

从郊天与封禅看玉器在古代国家宗法政治中的地位

为了进一步了解中国远古玉文化在古代国家宗法政治中的作用和地位，从历代礼祭活动中遴选出两个重要礼典——郊天和封禅，详细阐述了郊天与封禅礼祭中的用玉礼制，并分析了玉器在宗法政治中发挥的重要作用．指出中国远古玉文化与中国古代国家统治理论有着不可分割的依存关系，在中华民族文化中占有重要的历史地位。     

一种观察细胞骨架的简易整装电镜制样方法

本文介绍一种显示细胞骨架的简易有效的整装电镜制样方法。24孔培养板上钻以直径为2.5mm的圆孔,覆上0.25%的Formvar膜后,成为培养细胞的良好支撑物,然后在原位对培养的细胞进行抽提、固定和二氧化碳临界点干燥,相差显微镜下观察、选择和定位,再以浸湿的单目铜网置于圆孔上,自然干燥后取上已覆有Formvar膜的铜网,即可进行标本的观察。该方法材料来源容易、经济,操作简便,成功率较高,并可减少盲目的电镜观察及人工假象,所得的细胞骨架图像清晰。     

Escalating commitment in the death zone: New insights from the 1996 Mount Everest disaster

The procession of people and organisations that pour resources into evidently failing causes is surprising and seemingly never-ending. This phenomenon, which is called “escalating commitment” (Staw, 1976), refers to situations in which people are incapable of turning future disasters into sound current decisions. The purpose of this paper is to use the, in project management literature (Kloppenborg and Opfer, 2002), non-traditional case of the 1996 Mt Everest disaster to explain and analyse escalating commitment determinants and processes. Not only does the paper identify and add a determinant to escalation but it also treats determinants and processes in a novel and intertwined fashion. The conceptual developments and findings suggest that escalating commitment strives on conditions that are inherent to any project, which consequently project managers should be aware of. Based on the results project failures could be better explained and understood by examining several explanatory levels simultaneously.     

基子产品特征和知识的SMA制造信息描述技术

针对采用电子电路表面组装技术(SMT)组装制造而成的表面组装组件(SMA)这一特定制造产品,以及SMA制造信息的特点,研究和探讨了基于产品特征和知识的SMA制造信息描述技术与方法,提出了一种综合信息描述方法的构思和框架,并对其中的关键技术进行了研究探讨.