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以金相、X射线衍射和拉伸试验研究Si 对Fe-Mn-C合金显微结构和拉伸性能的影响。实验结果表明,Si有助于Fe-Mn-C合金在固溶状态形成退火孪晶,在形变中促使发生形变感生γ→ε马氏体转变和孪生切变。拉伸形变中形成的形变ε-马氏体相变强化和形变孪晶平和退火孪晶的应变强化,他Fe-Mn-C合金强度提高和塑性降低。 相似文献
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利用单辊熔体旋转法制备了近等原子比的Ti-Ni形状记忆合金,利用DSC与XRD分析了快速凝固对合金相变点的影响以及相变产物马氏体的结构。实验表明,快速凝固可使Ti-Ni形状记忆合金马氏体相变点降低。并确定了具体的快速凝固Ti-Ni合金中马氏体的结构。 相似文献
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综述作者在马氏体相变研究中的一些新进展,包括:无扩散相变中存在间隙原子的扩散,铁基合金马氏体相变热力学,奥氏体状态对马氏体相变的影响,淬火钢中等温马氏体的形成,回火马氏体致脆的新机制,热弹性马氏体相变热力学,以及马氏体相变晶体学等。其中部分工作得到国家自然科学基金委员会的资助。 相似文献
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一、磨削烧伤的本质磨削烧伤是淬火处理后的钢材在磨削加工中一种常见的缺陷。磨削烧伤可分为三种类型:裂纹、二次淬火烧伤及回火烧伤。尤以回火烧伤最为常见。众所周知,钢材磨削时,磨削接触区的温度是很高的,例如磨削区表层最高温度可达1000°C。由于温度升高,必然引起钢材表层组织的变化。当温度超过相变温度时,珠光体向奥氏体转变,随后就被钢材心部较冷的基体淬硬,得到淬火马氏体,这就形成钢材表层的二次淬火烧伤。即使温度在相变温度以下,也会使回火马氏体向屈氏体或者索氏体转变,使表层软化,就形成回火烧伤。必须指出,磨削区内瞬间高… 相似文献
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应用JEM-2100电镜、QUANTA-400环扫电镜对钢中马氏体相变的形核进行了观察,发现马氏体不仅可在奥氏体晶内形核,而且可在晶界、相界面等处形核。认为马氏体是在缺陷处依靠结构涨落、能量涨落形核,是晶格重构的过程,不是切变过程。研究计算了马氏体晶核的临界尺寸和形核功。 相似文献
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<正>激光淬火是用高功率密度（1×104-1×105W/cm2）的激光光束快速扫描工件,在其表面极薄一层的区域内,温度以极快速度（1×105-1×106℃/s）上升到奥氏体温度（高于相变点而低于熔化温度）,而工件基本温度基本保持不变。当激光光束移开时,由于热传导的作用,处于冷态的基体使其迅速冷却得到马氏体组织,实现自冷淬火（冷却速度可达1×105℃/s）,进而实现工件表面的相变硬化。 相似文献
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高硬度不锈钢的使用需求在快速增长.尽管析出硬化不锈钢具有高强度,但在粉末冶金(PM)中使用的并不多.可通过加入在时效过程形成金属问沉淀的成份如铜、铌对这些合金进行强化.析出硬化级不锈钢的耐腐蚀性能可与铬镍级(300系列)相媲美.本文提出了两种析出硬化不锈钢粉末的物理性质和微观结构:17-4PH,一种高铬马氏体析出硬化不锈钢,优化条件后应用于粉末冶金中;另一种是在析出反应中使用铜的新型低铬(12w/o)合金.这种新型合金(410LCu)被视为满足高强度和中等耐腐蚀性的要求的低成本选择. 相似文献
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浙江大学材料系记忆合金课题组 《科技通报》1988,(2)
形状记忆合金是一种具有广泛用途的新型功能材料,可以用于宇宙飞船的张开天线、机械紧固及连接件、热机、温度调节器(如暖房窗户)等。NiTi和Cu基合金是具有实用价值的两类主要合金,后者由于价格低廉,易于加工,正日渐为人们重视。但因为如何去除使记忆性能衰减的马氏体稳定化现象,如何提高记忆性能,如何增加使用寿命等问题尚缺乏深入研究,从而使该类合金的推广使用受到限制。我们以Cu Zn Al合金为材料深入研究了与实际使用有密切关系的性能。表明经过合适的热处理,该材料即具有良好的性能。 相似文献
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《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献