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据我校畜牧场2×35m~3沼气池用奶牛粪作原料,所测得的沼气成份是CH_4含68.3％、CO_2含31.3％,其他还有少量的O_2、N_2、H_2和极少量的H_2S等。由此可见,CH_4是沼气的主要成份,也是供燃烧的主要原料。但由于CH_4是一种热稳定性很高的烷族碳氢化合物,常压下要到900℃以上才有显著的分解。它虽具有良好的抗暴性能,且在多种燃烧器中易于均匀燃烧,不会稀释润滑剂。但由于其临界温度很低(-82.5℃),临界压力又很高(45.8kg/cm~2),故在一般条件下,要使沼气液化是相当困难的。这就给沼气的储藏和运输等带来了很大的麻 相似文献
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本文研究了 PbO_2与多元醇(乙二醇、丙三醇、木糖醇、甘露醇)的氧化还原反应。测定了在氢氧化钠碱性溶液中 Pb(Ⅱ)与多元醇反应所形成的1:1络合物。此络合物为带负电荷的阴络离子,其稳定性按多元醇配位体乙二醇——丙三醇——甘露醇——木糖醇的顺序递增。添加多元醇于碱性溶液中可以增大 PbO 的溶解速率和溶解量。根据实验结果,对在氢氧化钠碱性溶液中铅氧化物与多元醇的反应机理进行了初步探讨。 相似文献
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对地球科学的研究目前已经成为一个热门的话题,其中对源区示踪以及地质测温的研究尤为重要,在这个领域中发展相对成熟的就是对地球化学示踪以及稳定同位素测温。在自然界之中分析每种矿物之间的各种分馏系数,来计算其在热力平衡条件下所产生的相应的温度函数,这是地球化学理论在稳定同位素研究的基础上,对同位素分馏系数的最为准确、精准的确定。将对同位素交换原理、热液交换实验、碳酸盐交换实验、CO2交换实验、矿物流体交换实验以及化学合成等方面进行具体的分析。 相似文献
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固体聚合物电解池分离氚的理论分析 总被引：1，自引：0，他引：1
水电解是氢同位素分离的一种有效方式,固体聚合物电解池(SPE)因具有高电流密度、低液体滞留等特点而备受青睐.为了完成SPE氚分离系统的工程设计与建造,本文针对由氢和不同阴极材料组成的SPE,在其分离氚的机理上,对水与二元氢化物之间的氢同位素交换反应进行了分析,利用归一配分函数和同位素两相分布理论计算了同位素交换反应的平衡常数和分离因子.结果表明:采用316L不锈钢和镍作为阴极的SPE,其分离因子的计算值与文献实验值较为符合,而碳阴极SPE分离因子的计算值远小于文献实验值. 相似文献
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孟庆龙 《内蒙古科技与经济》2002,(6):99-99
1 问题的提出有这样一道习题 :判断镁与硝酸铵溶液反应的产物。答案是硝酸镁、氨气和氢气。不少学生提出疑问 :1 .NH4 NO3 水解有 HNO3 生成 ,Mg与 HNO3 反应怎么能产生 H2 呢 ?2 .既然有 NH3 生成 ,说明溶液中氨水已饱和 ,Mg2 应生成 Mg(OH) 2 ,怎能是Mg(NO3 ) 2呢 ?2 实验 相似文献
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以热重分析(TGA)、电阻测量和X射线衍射分析等方法,研究了CO_2与NH_3对YBa_2Cu_3O_(7-x)超导体结构稳定性及超导,电性的影响。当温度低于373K时,CO_2对YBa_2Cu_3O(7-x)的结构和超导电性无影响;当温度为523K时,CO_2使YBa_2Cu_3O_(7-x)的Tc下降;温度高于703K时,CO_2将很快破坏YBa_2Cu_3O_(7-x)的结构,并产生化学反应,生成新的化合物,在CO_2中存在的O_2与N_2对YBa_2Cu_3O(7-x)与CO_2的反应及反应产物的影响有较大差异。NH_3对YBa_2Cu_3O(7-x)结构稳定性的影响不大。 相似文献
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报道了浙江7个地开石粘土矿床的氢和氧同位素分析数据。应用水-岩石同位素交换作用的基本原理和方法,探讨这些矿床的同位素地球化学特征及其形成条件。同位素交换平衡曲线表明,成矿热液流体起源于中生代大气降水,在300℃的较高温下与围岩发生同位素交换后形成环流地热水;而地开石粘土是在250～100℃的中低温阶段酸性火山岩的热液蚀变产物。此外,还概述了地开石粘土的成矿热液体系从酸性偏还原环境到微酸性氧化环境的演化过程。 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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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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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