共查询到20条相似文献，搜索用时 750 毫秒
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利用有限元软件ABAQUS对桶形基础受水平荷载进行数值模拟,并与模型试验结果进行对比.通过数值计算,分析饱和软黏土中单个斜壁桶形基础受水平荷载后的破坏模式.通过变动参数,分别探讨研究了土体有效重度、土体不排水抗剪强度、桶体等效长度和宽度、荷载作用高度对饱和软黏土中单个斜壁桶形基础水平承载力的影响及相对敏感性. 相似文献
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以斯里兰卡南部铁路部分挡土墙为例,采用英国规范,介绍截面假定和计算公式以及结构材料与中国规范的差异,详细论述挡土墙计算过程,进行了正截面承载能力分析、斜截面抗剪能力分析和裂缝宽度验算,并对英国规范计算结果与中国公路规范计算结果对比。 相似文献
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本文对横向荷载作用下受弯构件临界弯矩设计公式理论根据进行分析,提出根据能量法推导过程中存在两种计算总势能的计算方法,其区别在于是否考虑非线性剪切应变能。文中分别对两种不同假定的方法进行推导并分析比较,提出对于横向荷载形式不同时,单轴对称截面修正系数的推导不应考虑非线性剪切应变能。为了验证分析的正确性,采用两种不同计算方法计算了具体横向荷载下受弯构件的算例,并使用通用有限元程序ANSYS进行验证对比。 相似文献
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钢筋混凝土结构是《建筑结构》中一门主要学科 ,而钢筋混凝土结构的主要内容是基本受力构件的教学。其中“受弯构件”承载力计算是重点 ,“单筋矩形截面受弯构件正截面承载力计算”是重点之重点。那么只要解决了这个主要矛盾 ,对以后“双筋矩形”、“T形”截面受弯构件、“偏压”、“偏拉”构件的学习就迎刃而解了。据“大纲”要求 ,中专学校只讲授“拉、压、弯”三种基本受力构件 ,总结其教学步骤 ,则归纳为以下“五部曲”:1实验 ;2构造 ;3公式 ;4设计 ;5复核。即通过分析实验 ,了解各类基本构件破坏特征 ,从而采取积极措施 ,控制构件破坏… 相似文献
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随着数值模拟的发展,有限单元法已成为当今工程分析中最广泛应用的数值计算方法。本文采用有限元分析了变截面压杆的稳定问题,并用ANSYS分析结果与解析分析结果进行对比,分析表明杆剪应力对杆受荷的影响,使荷载偏小。 相似文献
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一、墙梁的适用范围墙梁广泛应用于工业建筑的围护结构之中,如基础梁、联系墙,民用上层为住宅,下层为商店的多层砌体结构建筑中,采用墙梁结构以解决底层为大空间,上层为小空间的矛盾,与框架结构相比。它具有节约三大主材、缩短工期、施工方便等优点,因此得到广泛的应用。二、墙梁的主要特征和破坏模式墙粱试件基本上是单跨;梁的高跨比则自l/3到1,分为有门洞与无门洞两种。墙梁在试验过程中发现有三种破坏模式。1、弯曲破坏。当托梁配筋较少时,随着荷载的增加,托梁跨中的垂直裂缝产生,贯通托梁并进入上部墙体,发生正截面受弯破坏。2、支座墙体局部受压破坏。当墙体高跨比较大时,正截面弯曲承载力增大很快,此时往往发生支座上边砌体的局压破坏。3、墙体剪切破坏和托梁剪切破坏。当墙体高跨比不高时,随荷载的增加,墙体产生斜裂缝,此斜裂缝由小到大,发展和延伸到全部墙体而使墙梁失去承载能力。墙梁的设计将根据上述的三种破坏模式进行。三、墙梁的计算简图,荷载取值和计算高度 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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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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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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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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《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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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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《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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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