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混凝土联锁块路面服务性能更接近于柔性路面而不是刚性路面,锁块路面的这种柔性意味着在一定的荷载作用下所需的泥凝土块厚度要比刚性路面的小,因此可以节省路面造价。锁块路面对基础变形的适应能力强,适用于车速不高、载重量很大和地基不均匀的路面铺设。 相似文献
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由于混凝土内在原因及温度变形、湿度变化、地基不均匀沉陷变形的影响,在水泥混凝土路面上难免发生各种类型的裂缝,在施工中通过改善混凝土的质量和路面结构并采取有效的浇注后的防治措施,水泥混凝土路面的裂缝现象是可以避免的。 相似文献
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由于工期紧张,哈尔滨火车站北广场站改造的主体结构工程面临着不间断冬季施工问题。由于造价低、施工简单,在混凝土中掺入防冻剂是冬季施工冬中经常采用的工程措施,在我国有着广泛的应用。防冻剂的作用实质是保证混凝±在负温下不冻结或部分冻结,从而使水泥在负温下不断水化、硬化获得强度增长。但是目前对低温环境下的防冻混凝土水化热发展规律研究较少,对水泥混凝土内部温度的发展变化规律尚不清楚,尤其是冬季施工时的大体积混凝土,温度场变化,水泥混凝土强度与水化程度具有较好的相关性。因此,本论文针对低温下水泥混凝土水化过程,通过理论分析,选择合理的计算模型,防冻水泥混凝土的水化热进行了计算,得到了冬季不同施工环境时,水泥混凝土的水化人热量和水化程度,提出了保证入模温度是控制混凝土工程质量的重要措施,在实际施工中应当进行严格控制。 相似文献
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在现今建筑行业中,屋面防水不仅是建筑物必须具备的功能,而且涉及居民安居乐业和生产安全的敏感问题,由于屋面受温湿变化影响很大,大多采用变形能力较强的柔性卷材或深层作防水层,但由于施工管理和材料质量与老化问题,屋面渗水是个大通病。以水泥混凝土为基材浇筑的屋面统称刚性屋面,其施工简易、造价较低,易于维修和耐久性好,但这种刚性屋面变形能力小,易引起温差裂缝,导致渗漏。所以长期以来,设计施工界对刚性屋面持怀疑 相似文献
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混凝土质量的好坏,即对结构物的安全,也对结构物的造价有很大影响,因此在施工中我们必须对混凝土的施工质量有足够的重视。 1、混凝土强度及主要影响因素。混凝土质量的主要指标之一是抗压强度,从混凝土强度表达式不难看出,混凝土抗压强度与混凝土用水泥的强度成正比,按公式计算,当水灰比相等时,高标号水泥比低标号水泥配制出的混凝土抗压强度高许多。所以混凝土施 相似文献
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水泥混凝土路面维修策略及技术研究 总被引：1，自引：0，他引：1
我国公路绝大多数都是水泥混凝土公路,水泥混凝土公路具有造价低、持久性强、耐热性优良、抗磨损性能优良、使用强度高等优良特性。但是,在对水泥混凝土公路进行维修工作的时候,一般会消耗很高的维修成本,而且维修工作所带来的水泥混凝土路面养护的时间也相对较长。如果水泥混凝土公路在维修期间受到交通运输的影响,就很有可能给水泥混凝土公路带来很大的伤害。针对这样的情况,本文将对水泥混凝土路面维修策略以及维修技术进行系统的分析介绍。 相似文献
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作为道路的主要结构物,路面分为柔性路面和刚性路面两种类型.前者主要包括各类沥青混凝土路面,后者指水泥混凝土路面,其强度高,刚度大,寿命长但施工工艺较为复杂,为质量控制增加难度.本文全面分析比较了两种路面的物理性能、施工工艺、造价等不同的特点,为如何选择路面类型提供了有效参考 相似文献
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垫层蜗壳混凝土回填灌浆时机对座环、蜗壳的抬动变形存在影响,是工程中必须考虑的重要设计环节。本文建立了垫层蜗壳轴对称有限元模型,通过数值模拟手段研究了上述影响,分析了灌浆压力及蜗壳与混凝土间接触滑移对座环、蜗壳的抬动变形的影响,并与实际的抬动变形监测数据做了对比分析。结果表明,蜗壳底部回填灌浆前外包混凝土已浇筑层数对座环、蜗壳抬动变形有较大影响;座环、蜗壳抬动变形对回填灌浆压力较为敏感,灌浆压力越大,抬动变形值也越大;接触滑移对计算结果影响很小;数值计算结果与实际的抬动变形监测数据较为吻合。 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