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水工构筑物由于性能要求和工况条件的特殊性,致使水工混凝土耐久性问题突出,如何考量乃至延长水工混凝土的耐久性问题,需要从多个方向研究探讨予以解决。 相似文献
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水泥混凝土路面因其高强度和来源的广泛而得到广泛应用,然而,目前的交通频繁的出现超载、重载等情况,加之自然环境的侵蚀,水泥路面的耐久性就变得十分日趋下降,因此耐久性设计就成了建设混凝土道路的时候的关键技术。本文就是在这个研究方向的基础上,借鉴了国内外先进的研究成果,对氯盐环境、碳化环境和冻融环境侵蚀的状态下的混凝土耐久性能的进行了评价,有利于增强道路混凝土在设计过程中的耐久性。 相似文献
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跟踪当前国内外纤维混凝土发展的最新进展,阐述了纤维材料改善混凝土受力性能的基本原理,详细给出了三种应用广泛的纤维材料对混凝土的受力性能以及耐久性的影响程度,并提出了当前纤维增强混凝土研究中存在的问题和今后研究的方向。 相似文献
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高性能混凝土(HPC)是20世纪80年代末基于混凝土结构耐久性设计提出的一种全新概念的混凝土,它以耐久性为首要设计指标,具有高耐久性、高工作性、高强度和高体积稳定性等许多优良特性,至今已在不少重要工程中应用,特别是在使用环境恶劣的桥梁等重要结构工程中显示出其独特的优越性,是今后混凝土技术的发展方向。本文结合《结构混凝土耐久性设计与施工指南》的要求,在某公路桥梁施工中部分混凝土进行了应用,通过对混凝土配合比进行优化,加强了现场混凝土拌和的控制,在混凝土强度、弹性模量、抗渗性能、外观、经济性等方面均取得了较好的效果。 相似文献
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本文主要针对钢铁项目中混凝土结构的耐久性设计进行了详细分析。文章以某钢铁厂为例,阐述了混凝土结构耐久性的研究背景与意义,指出了该钢铁厂项目工程中存在的结构耐久性问题。继而简要说明了高性能混凝土耐久性的试验研究,就该钢铁项目的混凝土结构耐久性的设计方案进行了探讨,并分析了其经济效益,以确保该设计方案能够达到预期的安全性、耐久性与经济性。 相似文献
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《内蒙古科技与经济》2021,(3)
混凝土应用广泛,但由于服役环境不同会导致其未到使用年限就提前失效,导致严重损失,可靠有效的混凝土防腐涂层可提高混凝土的耐久性,因此,混凝土防腐涂层是混凝土应用研究方向的热点问题,文章就混凝土防腐涂层进行综述,并对混凝土防腐涂层进行了展望。 相似文献
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本文探讨了混凝土坏化的模式和引起坏化的各种成因,分析了改善混凝土结构耐久性的各种技术,归纳总结了提高混凝土耐久性方法的特点,并对混凝土耐久性研究给出一些初步建议,指出了应改变混凝土耐久性设计中的错误观念。 相似文献
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混凝土结构的耐久性是指混凝土结构对化学的、生物的以及其它使结构材料性能恶化的各种侵蚀的掘抗能力.今后,在研究混凝土结构耐久性方面仍需做大量的工作来满足工程建设的需要,这样才能使混凝土的耐久性问题得到较好的解决. 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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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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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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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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Elke Duncker 《The Information Society》2000,16(3):187-199
Electronic computers in information systems are often seen as "ready-to-use" technology, which simply becomes applied to certain domains. This article explores the sociotechnical processes involved in the development of information systems by studying two cases of medical informatics, the Laboratory Instrument Computer (LINC) and a medical information system at a hospital. They show that information systems have from the beginning been a result of multiple alignment processes between the relevant actors, among which are users, developers, and the technology itself. The first case reveals that information systems are successful when actors become aligned and coordinated across boundaries. This alignment includes user interfaces as well as parts and components of the computer. The second case exhibits disalignment between relevant actors, which leads to an unstable information system. The two mechanisms are found coexisting in medical informatics. 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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This study illustrates design optimization for multiple wind towers located at different villages in Alaska. The towers are supported by two different types of foundations: large mat or deep piles foundations. Initially, a reinforced concrete (RC) mat foundation was proposed. Where soil conditions required it, a pile foundation solution was devised utilizing a 30 in thick RC mat containing an embedded steel grillage of W18 beams and supported by 20-24 in grouted or un-grouted piles. For faster installation and lower construction cost, all-steel foundations were proposed for these remote Alaska sites. The new all-steel design was found to reduce the natural frequencies of the structural system due to softening the foundation. Thus, the tower-foundation system could potentially become near-resonant with the operational frequencies of the wind turbine. Consequently, the likelihood of structural damage or even the collapse is increased.A detailed 3D finite-element model of the tower-foundation-pile system with RC foundation was created using SAP2000. Soil springs were included in the model based on soil properties obtained from the geotechnical investigation. The natural frequency from the model was verified against the tower manufacturer analytical and experimental values. When piles were used, numerous iterations were carried out to eliminate the need for the RC and optimize the design. An optimized design was achieved with enough separation between the natural and operational frequencies. The design successfully avoids damage to the structural system, while eliminating the need for any RC in most cases. 相似文献
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李丽 《科学．经济．社会》2008,26(4)
文明是文化的静态表现形式,文明之忧思的实质是文化之困惑.两种典型的哲学文化理解都有其局限和不足.由对文化定义和功能的分析可见,有序是文化的基本特征,文化是社会秩序之源.社会生活中的各种无序现象和行为从性质上看不是文化现象而是反文化现象.反文化现象的发生有其内在根据.思想史上,对反文化的警惕与质疑作为文化之困惑由来已久,当下更是有深入思考的必要与可能. 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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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