银币模压加工过程中表面发蓝的发生机理及克服方法

在银币的生产过程中,硬币表面发蓝是非常普遍的现象.许多硬币收藏者用放大镜,甚至是显微镜去观察硬币发蓝.如果不满意硬币的外观,收藏者将退还硬币给造币厂.为了清除银币表面的发蓝,造币生产线必须被中断,以抛光或清洗压印的模具.如果毛胚没有处于良好的准备状态,抛光一副冲模的时间就超过了压印硬币的时间.文中分析了硬币表面发蓝的原因,揭示了在模压过程中值得注意的摩擦学现象,并且提出了无需人工抛光冲模去除发蓝的方法,实现了银币的高效生产,清洗模具周期由冲压80次,提高到800次以上.     

Editorial: Manufacturing in the ’90s

Vendor Industries—original material and component manufacturers— must incorporate process design as a key part of their manufacturing function to improve quality, delivery, cost and competitiveness in the ’90s.     

防止我国由无缝钢管大国变成无缝钢管“穷”国的思考

介绍了当前我国无缝钢管行业的基本情况,指出我国无缝钢管行业由大国走向强国的同时,正在变成无缝钢管“穷”国.分析了我国无缝钢管行业经济效益下滑的主要原因,提出了通过控制投资规模淘汰落后产能,加快企业重组提高产业集中度,依靠技术进步、加强企业管理,降低钢管制造成本以及调整品种结构,提高产品附加值和探索“走出去”道路,避免反...     

原生铝与再生铝缘何一热一冷两重天

中国作为有色金属生产第一大国正在受到世界的高度关注.2003年,中国有色金属总产量达到了1205万吨,铝产量达到了556万吨,位居世界第一.但是中国作为铝生产和消费大国,再生铝的产量却并没有同步增长,再生铝在整个铝消费中所占比例仍然不高,据业内人士估计,我国再生铝的产量一直徘徊在120-130万吨,而且再生铝的质量、企业规模、环境保护状况都远远不能令人满意.     

守望与超越:中国大学文化建设反思

大学文化是大学组织主体实践活动的结晶,揭示着大学的本质、塑造着大学形象、凸显着大学的职能。当前,中国大学发展中所出现的诸多问题与大学应然价值的偏离与迷失有着内在联系。为此,中国大学应借由文化的内省与反思,捍卫其在人才培养、科学研究及价值导向方面的使命与角色。应将大学文化建设放置在中国高等教育现代性构建的历史进程中,正确处理好中国高等教育现代性与传统性、民族性和后现代性问题。     

史学理论对教育史研究方法论影响的实证分析

国际史学理论经历了从传统史学理论到法国年鉴学派理论,再到新文化史学理论的转向。通过对国际教育史领域三种社会科学引文索引期刊论文(1982年至2020年)的实证分析,发现教育史研究深受史学理论两次转向的影响。三种史学理论并非互相替代,而是以统整形式渐进融入教育史研究的主题、史料来源、理论构建、研究方法、表述方式等各环节中。这对中国的教育史学科走出困境,促进自身发展,具有如下启示:既要重视宏观的总体史、问题史考察,又要坚持微观的个案分析;要不断拓展研究领域,丰富史料来源,加强跨学科研究;在研究过程中需秉承传统史学求真纪实的实证主义精神;要密切关注国际史学的发展趋势,及时借鉴历史学科的新理论、新方法。     

铸造企业如何建立和实施质量管理体系

介绍铸造企业如何建立ISO9001：2000质量管理体系，并提出实施过程中应注意的问题，对铸造行业在质量控制方面，具有一定的指导作用。     

Oligo(phenylenevinylene)s with increased electron affinity: 1,3,4-oxadiazoles in the main chain

Stilbenoid chromophores and 2,5-diaryl-1,3,4-oxadiazoles are compounds with wide technical importance. Their intense fluorescence is used in szintillators and optical whiteners and their semiconducting properties makes them valuable emissive or electron conducting layers in organic light emitting diodes (OLED). The synthesis and the electronic spectra of soluble oligo(phenylenevinylene)s with 1,3,4-oxadiazoles in the main chain are presented. The Huisgen reaction of tetrazole-terminated stilbenoid compounds with aromatic acyl chlorides yields model compounds, isophthalic acid dichlorides lead to soluble polymers with well-defined conjugated segments, as can be seen in the electronic spectra. Besides connection of the stilbenoid sections, the electron deficient heterocycles promise to increase the electron affinity of the chromophore.     

Generation of micropatterns in poly(3-methylthiophene) films using microlithography: A first step in the design of an all-organic thin-film transistor

A thin-film transistor structure was designed using poly(3-methylthiophene) in its oxidized (highly conducting: σ ≈ × 10⁴ S/m) state as source and drain contacts, and the same material in its reduced (semiconducting: δ ≈ 10⁻⁷ S/m) state as channel. The source, drain and channel zones can be defined by means of electrochemical and microlithographic procedures. The ultimate resolution is in the submicron range.     

The mechanisms of bell mouth formation in gundrilling when the drill rotates and the workpiece is stationary. Part I: the first stage of drill entrance

The reliability of the gundrilling process in the automotive industry is greatly affected by tool stability. This stability is defined as a complex issue consisting of the following sub-items: entrance, static, and dynamic stabilities. Entrance stability plays the chief role when the rotational speed and feed rate are high, which is the common case in the automotive industry where engine heads made of aluminum alloys are drilled. Entrance instability is the prime cause for the so-called ‘unpredicted’ drills’ failure, which often appears as a fatigue crack(s) on the drill shank and cannot be explained when only stable drilling is considered. This paper reveals the main design and technological factors affecting entrance stability and provides practical recommendations on the design of gundrills. This subject is covered in two parts. Part one deals with the first stage of drill entrance, which begins when the gundrill touches the face of the workpiece and ends when the gundrill’s cutting edges are fully engaged in cutting. The role of the clearance in the starting bush and the design of the gundrill’s supporting area are analyzed.