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以通用有限元程序ABAQUS为平台,基于混凝土损伤塑性本构模型,充分考虑材料非线性和几何非线性,分析大跨建筑结构中钢-混凝土组合梁受分布荷载作用全过程内力变化、内力重分布、应力分布等复杂特性,深入揭示组合梁的受力机理和特点。为钢-混凝土组合梁在大跨建筑结构中的推广应用提供参考。 相似文献
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为研究杭州软黏土地区不规则深基坑开挖过程中围护结构受力、变形规律及其对周围环境的影响,并论述隧道注浆纠偏技术的变形控制效果,本文采用施工全过程系统监测方法,以杭州某临近隧道群的基坑B3-1-2分坑施工为例开展系列分析。结果表明：由于受力状态不同,各挡墙墙身位移随深度呈现不同的变化趋势,最大位移受注浆纠偏施工影响且大多向坑外发展;北侧挡墙墙顶位移变化均较小,其余挡墙墙顶水平位移向坑内发展而竖向位移先发生隆起再下沉的变形;支撑轴力与墙顶水平位移呈正相关变化关系;受场地空间制约,地表监测沉降值随基坑边距离增大而逐渐增大;得益于分坑开挖施工策略和MJS (metro jet system)桩隔离作用,分坑B3-1-2开挖对1号线影响较小;隧道注浆纠偏技术能有效控制隧道沉降和侧移发展。研究成果可为相关深基坑工程的设计、施工、监测提供工程借鉴。 相似文献
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利用三维地震数据体进行东湾背斜区域的构造解释工作,通过生长地层分析得到其发育时间为古近纪安集海河组时期,形成机制为翼部旋转机制滑脱褶皱.面积-深度-应变法分析结果显示滑脱层位于深度为～9 km的下侏罗统八道湾组中,褶皱主要受平行层纯剪切控制以及部分地层弯曲调节变形.背斜带核部位移量可达1239 m,且构造带位移量的分配主要有两种方式,为滑脱褶皱的生长以及褶皱调节断层的发育.东湾背斜两翼发育有丰富的褶皱调节断层,构造带不同位置处为褶皱调节断层发育的不同阶段,且调节断层随褶皱生长会向上及向下传播,传播方向取决于软弱层的发育和其厚度.此外,褶皱调节断层的发育可能为东湾1井没有钻获到油气资源的重要原因. 相似文献
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本文通过将电动水源热泵与传统锅炉房区域供热系统相比较,在国家建筑节能设计标准中的耗电输热比EHR的基础上结合一次能耗率和火用分析方法引申得到一次能源消耗输热比法PEHR和火用比法ER的能耗比较标准,分别推导计算了两种不同标准下当电动水源热泵区域供热系统比传统的锅炉房区域供热系统节能时,水源热泵机细制热性能系数的下限值表达式。结果表明,热泵的制热系数的下限值不仅随锅炉热效率的提高而升高,而且随区域供热作用范围的增加而增大,因而小规模的热泵区域耳燃系统有利于系统节能的体现。 相似文献
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在分析国内外钢-混凝土组合梁各种剪切连接件形式的基础上,着重阐述了钢-轻骨料混凝土组合梁中栓钉连接件的受力性能和刚度计算方法,提出了有待完善的地方。 相似文献
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热拌沥青薄层罩面是目前高等级沥青路面常用的预防性养护技术之一,而新旧沥青路面是性质不完全相同的两种材料,若在旧沥青面层上直接加铺新的混合料,面面之间就会出现层间结合力不足的问题。工程中一般要在新旧沥青层之间设置粘层,以增强面面之间的连结。文本在分析新旧沥青路面层间状态的基础上对沥青加铺作业中的粘层设计和施工技术开展研究。 相似文献
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既有建筑下增层开挖对群桩基础的影响不同于基坑开挖对待建建筑桩基的影响,采用HARDENING-SOIL弹塑性模型模拟土体及接触面单元模拟桩土相互作用,分别就摩擦型桩和端承型桩,建立桩筏基础-地基-增层开挖三维有限元模型,分析增层开挖后桩顶反力、桩身轴力、桩侧摩阻力、桩体水平位移和桩身弯矩分布规律,并对比分析桩顶Q-S曲线和桩侧摩阻力在开挖前后变化规律,通过研究,取得了增层开挖对既有建筑群桩基础影响的基本认识,揭示了开挖后摩擦型桩和端承型桩不同变化规律,这些规律有助于类似工程的设计施工。 相似文献
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A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 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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Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 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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Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 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