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采用共沉淀法合成Li Ni1/3Co1/3Mn1/3O2,对材料的结构和电化学性能进行了表征,结果表明Li Ni1/3Co1/3Mn1/3O2材料具有层状结构,在2.8~4.4V(vs Li/Li+)条件下进行充放电测试,首次放电比容量可达174.0 m Ah·g-1。 相似文献
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以聚丙烯酸来络合碳酸盐的方法来制备合成LiNi0.5Mn1.5O4,用X射线衍射、DSC-TGA、SEM和恒电流充放电技术研究了工艺条件对材料的结构、微观形貌和电化学性的影响,并针对所制备的单相尖晶石结构LiNi0.5Mn1.5O4在大电流0.5C下充放电循环性不稳定,进行了掺杂改性,结果共掺杂体LiCo0.09Ni0.41Mn1.5O3.85F0.15初始容量为131mAh/g,15次循环后的容量为130mAh/g,比容量损失仅为0.6%. 相似文献
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本文使用简单的一步水热法合成了由纳米棒自组装而成的纺锤状Co(CO_3)_(0.5)(OH)·0.11H_2O。由于该锂离子电池负极材料自身的多级结构,有效的缓解了电极材料在反复充放电过程中的体积膨胀,以及缩短了锂离子的传输距离,使得Co(CO_3)_(0.5)(OH)·0.11H_2O在200 mAg~(-1)的电流密度下展现了优异的循环性能,即循环600圈后仍具有1329 mAh g~(-1)的可逆比容量。 相似文献
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随着电动汽车的快速发展,对锂离子电池的负极材料有了越来越高的要求。目前商用锂离子电池的负极材料还是以石墨为主,但是石墨负极的理论比容量较低(为372 mAh/g),严重限制了锂离子电池的能量密度。硅的理论比容量高达4 200 mAh/g,被认为是最有前途的锂离子电池负极材料之一。然而,硅负极材料在锂化的过程中会伴随着巨大的体积膨胀效应,导致电极材料破裂和粉碎,从而大幅度降低电池的循环稳定性,并且硅的电导率不理想,也限制了其倍率性能和循环性能。用石墨烯对硅负极材料进行改性,有望缓解其电极材料的体积膨胀以及导电性差的难题。本文重点阐述了石墨烯对于硅基负极材料的性能提升机理,期望对未来石墨烯改性硅基负极材料的制备和研究提供思路。 相似文献
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以嵌段共聚物F127为模板剂,Ni(NO3)2·6H2O为Ni源,低分子量的戊二醛和木质素为碳源,KOH为扩孔剂,通过溶胶凝胶法合成以无定形碳或者聚合物为骨架的具有高分散性的NiO纳米粒子。通过XRD,TEM和BET表征其结构和形貌。结果表明复合材料中纯的NiO纳米粒子被无定形碳包围,BET比表面积最高为802 m2/g并且具有窄的孔径分布。通过循环伏安和恒流充放电来表征复合材料的电化学性能。结果表明复合材料具有高的比电容和在1000次循环中具有很好的循环稳定性。在1 A/g到10 A/g的恒流充放电实验中,复合材料的比电容保持率为90%。因此,介孔NiO/C复合材料具有很好的做超级电容器电极材料的前景。 相似文献
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超级电容器的性能研究 总被引：1，自引：0，他引：1
本工作对超级电容器性能进行了研究。电化学测试发现有机体系超级电容器拥有良好的电化学性能。其能量密度可达6．8Wh／Kg，最高功率密度超过1000W／Kg，2．5万次充放电循环后容量保持率在70％以上，循环性能良好，充放电效率高，且内阻小。 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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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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《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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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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《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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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