焊接史

本文追溯了19世纪末发明的电弧焊接的历史。当Oscar Kjellberg成立伊萨公司以探索他发明的涂层焊条时，伊萨从一开始就和电弧焊的发展结下了不解之缘。     

A force modulation study on crystallization process in ferroelectric vinylidene fluoride and trifluoroethylene copolymer films

This paper introduces the Force Modulation technique to the study of crystallization process in ferroelectric vinylidene fluoride and trifluoroethylene copolymer films. Using this technique we have successfully visualized ferroelectric crystalline domains and observed that these ferroelectric domains grow out from amorphous phase, unite into strip-like structures, and finally congregate into a union. Force Modulation can weaken the influence of topography on imaging of ferroelectric domains, and reveal more details, which are difficult to be observed in topographical image.     

电子商务中信息传输与共享

电子商务中信息传输与共享技术是电子商务的核心技术 ,电子商务是以Internet为基础的新兴产业 ,保护信息的安全无疑是十分重要的 ,人们越来越多地使用计算机网络来传送对安全敏感的信息 ,所以在信息传输域共享中 ,认证业务、保密业务、数据完整性业务、不可否认业务是当前电子商务急需解决的关键技术 ,本文对这方面做了一些探讨并提出自己的看法     

食品工厂设计方案多级模糊评价方法的研究

食品工厂设计方案的评价受众多因素影响,采用模糊评价和层次分析法,不仅考虑了所有因素的影响,而且保留了各级评价的全部信息,减少了评价过程中人为因素的影响,提高食品工厂设计方案评价的科学性和准确性.     

XML在机械CAD系统中的应用

分析了Internet上最新的XML技术的特点，通过实例用XML技术对机械CAD产生的各种文档信息进行了描述，并且构造了基于XML文档交换的分布式支持环境的体系结构。     

Surface charge accumulation and decay on a spacer stressed with DC voltages at atmospheric conditions

Contents Surface charge accumulation and its decay at a GIS spacer are studied at atmospheric conditions employing a two step-calibration method. The results show that the accumulation saturates within 30 minutes; the dominant mechanism of surface charge accumulation is the drift of charged particles via air, while that of the decay is surface conduction. The characteristics are similar at both polarities.

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Sättigungskonzentration und Abklingverhalten der Oberflächenladung an einem mit Gleichspannung beanspruchten Abstandshalter unter atmosphärischen Bedingungen

Übersicht Die Konzentration und das Abklingen von Oberflächenladungen an einem GIS Abstandshalter wurden unter atmosphärischen Bedingungen mit Hilfe eines zweistufigen Kalibrierungsverfahrens untersucht. Die Ergebnisse zeigen eine Sättigung der Ladungskonzentration innerhalb von 30 Minuten. Als Hauptursache der Ladungskonzentration ist die Drift geladener Teilchen in Luft anzusehen, während das Abklingen auf die Oberflächenleitung zurückzuführen ist. Ähnliche Charakteristiken ergeben sich mit beiden Polaritäten.

     

镁质瓷泥浆流变性能的改进

滑石质瓷是一种高性能瓷的材料，但由于其泥浆的稠化性及泥料塑性差，阻碍了滑石质瓷的大量生产。实验表明：引入长石作助熔剂并加入适量粘土，可以改进泥料塑性及泥浆流变性能，使烧成变形度小，机械强度提高，能较好地满足制品成型的工艺要求。实验中设计了多组配料，分析比较烧后试样的性能测试结果，确定最佳配方及烧结温度。     

长输管道外防护层的选择与应用

文章介绍了目前国内外长输管道外防护技术的特点和防护层应用的现状,分析了常用防腐蚀材料的防腐蚀性能。指出在山区复杂地形条件下,应考虑环境条件和施工条件,并通过技术经济分析对管道外防腐蚀层进行合理选择。     

Speed–accuracy tradeoff in Fitts’ law tasks—on the equivalency of actual and nominal pointing precision

Pointing tasks in human–computer interaction obey certain speed–accuracy tradeoff rules. In general, the more accurate the task to be accomplished, the longer it takes and vice versa. Fitts’ law models the speed–accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts’ index of difficulty (I_d) based on the ratio of the nominal movement distance and the size of the target. Operating with different speed or accuracy biases, performers may utilize more or less area than the target specifies, introducing another subjective layer of speed–accuracy tradeoff relative to the task specification. A conventional approach to overcome the impact of the subjective layer of speed–accuracy tradeoff is to use the a posteriori “effective” pointing precision W_e in lieu of the nominal target width W. Such an approach has lacked a theoretical or empirical foundation. This study investigates the nature and the relationship of the two layers of speed–accuracy tradeoff by systematically controlling both I_d and the index of target utilization I_u in a set of four experiments. Their results show that the impacts of the two layers of speed–accuracy tradeoff are not fundamentally equivalent. The use of W_e could indeed compensate for the difference in target utilization, but not completely. More logical Fitts’ law parameter estimates can be obtained by the W_e adjustment, although its use also lowers the correlation between pointing time and the index of difficulty. The study also shows the complex interaction effect between I_d and I_u, suggesting that a simple and complete model accommodating both layers of speed–accuracy tradeoff may not exist.     

CdSe量子点的制备与荧光特性研究

主要讨论了CdSe量子点的制备及荧光特性。CdSe量子点由化学方法制备，通过选择不同的反应时间得到不同尺度的量子点样品。用荧光方法研究了量子点样品在石英衬底和有机溶剂中的荧光特性。实验表明，这些量子点都有良好的荧光特性。还用无限深球方势阱模型分析了量子点样品的电子态，并根据荧光参数估算了量子点的尺度．各样品荧光峰具有一致的半峰宽，表明CdSe量子点的成核过程在反应开始时同时完成。