表面改性纳米Al2O3电流变液的制备及性能     

邹云玲  李酽  吕莹  郑文旭 《通化师范学院学报》2008,29(2):43-45

在水热反应条件下,采用十二烷基苯磺酸钠（SDBS）对纳米Al2O3进行表面改性处理,通过红外光谱（FT-IR）、X射线衍射（XRD）等手段对表面改性的纳米Al2O3进行了表征;探讨了pH值、十二烷基苯磺酸钠（SDBS）用量对表面修饰效果的影响;对改性纳米Al2O3电流变液进行了性能测试．结果表明,采用SDBS对纳米Al2O3进行表面改性处理,要在中性环境下进行;SDBS含量占纳米Al2O3质量的2．0％左右时,可以获得表面修饰效果理想的纳米Al2O3粒子;SDBS的加入影响了纳米Al2O3颗粒的表面性质,使其与甲基硅油的润湿性大大提高,改性纳米Al2O3含量为30％的电流变液在2kV／mm的电场作用下静态剪切应力可达1．04kPa．  相似文献   

As2O3对人体外宫颈癌细胞的影响     

陈慧  陈惕 《常熟理工学院学报》2008,22(8)

采用光镜及荧光显微镜观察、溴化二甲噻唑二苯四氮唑(MTT)还原法、流式细胞仪检测法检测As2O3对人HeLa细胞的影响.HeLa细胞经As2O3作用后,出现凋亡的形态学改变,细胞增殖受到浓度依赖性抑制,流式细胞仪检测结果显示细胞凋亡率呈浓度依赖性增高.As2O3具有诱导HeLa细胞发生凋亡的生物活性.  相似文献   

土地利用纹理样本数据库的建立     

周秀华  霍宏  方涛  李钢 《中国科技信息》2007,(9):28-30

本文概述了多种数据源,多时相的所有类别的不同表现形式的土地利用纹理样本数据的采集、建库等一系列工作,介绍了土地利用纹理样本库德体系结构,主要功能以及设计方法,并分析了XML、OO4O等关键技术。  相似文献   

The birth of a new industry: entry by start-ups and the drivers of firm growth: The case of encryption software     

Marco S Giarratana 《Research Policy》2004,33(5):787-806

The paper analyses the birth of the encryption software industry (ESI), a new niche in the software industry. Using a Chandlerian perspective, this work reports the main facts about firm entry and growth, with a particular focus on start-up strategies and actions.Since scale economies do not play a major role in ESI, the paper investigates the different sources of firm competitive advantages.This work shows that innovation and product differentiation, along with investments in co-specialised assets, are variables strongly correlated to young firm probability to survive and grow. In doing so, we have collected highly detailed information on product introduction, US patents granted, worldwide alliances and biographical data of firm founders.  相似文献   

Innovation, regional knowledge spillovers and R&D cooperation     

Michael Fritsch  Grit Franke 《Research Policy》2004,33(2):245-255

We investigate the impact of knowledge spillovers and R&D cooperation on innovation activities in three German regions. We begin by estimating the knowledge-production function in order to test for interregional difference with regard to the efficiency of innovation activities. In a second step, we analyze the contribution of spillovers from R&D effort of other private firms and of public research institutions to explain these differences. The inclusion of variables for R&D cooperation in the model indicates that R&D cooperation is only of relatively minor importance as a medium for knowledge spillover.  相似文献   

The structure and evolution of industrial clusters: Transactions, technology and knowledge spillovers   总被引：2，自引：0，他引：2  

Simona Iammarino  Philip McCann 《Research Policy》2006,35(7):1018-1036

In this paper, we investigate the relationship between location patterns, innovation processes and industrial clusters. In order to do this we extend a transactions costs-based classification into a knowledge-based taxonomy of clusters, along the lines suggested by a critical revision of the main assumptions underlying most of the existing literature on spatial clusters. Our arguments show that the transactions costs approach and the innovation and technological regimes framework are broadly consistent, and that real insights into the microfoundations, nature, and evolution of clusters can be provided by these classification systems.  相似文献   

The impact of cognitive communities on the diffusion of academic knowledge: Evidence from the networks of inventors of a French university     

Caroline Hussler  Patrick Rondé 《Research Policy》2007,36(2):288-302

Looking at micro-data on the networks of inventors of a French science university, we investigate whether the kind of cognitive relationships between researchers influences the geography of their collaborations.The hypothesis we test (and confirm empirically) is that academic knowledge diffuses in a restricted geographic area when the connected researchers belong to epistemic communities, whereas communities of practice entail less localised effects. We also show that institutionally mixed research teams do not impede large knowledge diffusion.  相似文献   

Investigating the interaction and mutual dependence between science and technology     

Catari Vilela Chaves  Sueli Moro 《Research Policy》2007,36(8):1204-1220

Literature on the economics of science and technology (S&T) suggests not only that technological innovation demands the expansion of the institutional borders between universities, research institutes, industrial companies and the financial system, but also that science leads as well as follows technology. Medical innovation in particular is very dependent on scientific research, which represents a source of information that impels the productive sector. The latter introduces a series of questions that motivate the researchers in their attempt to understand how the human body reacts to certain products and therapies. This paper analyses the pattern of S&T interaction for both the national system of innovation (NSI) and the health innovation system. The panel data and simultaneous equations models analyze the interaction between S&T. The theory about the existence of a mutual dependence between them has been confirmed, which means that science moves technology and technology also influences scientific development. The estimated models, which use data from scientific papers and patents as proxies of science and technology, represent just the tip of the iceberg called NSI, known as a multifaceted and complex institutional arrangement.  相似文献   

Scientific teams and institutional collaborations: Evidence from U.S. universities, 1981-1999     

James D. Adams  Grant C. Black  Paula E. Stephan 《Research Policy》2005,34(3):259-285

This paper explores recent trends in the size of scientific teams and in institutional collaborations. The data derive from 2.4 million scientific papers written in 110 top U.S. research universities over the period 1981-1999. The top 110 account for a large share of published basic research conducted in the U.S. during this time.We measure team size by the number of authors on a scientific paper. Using this measure we find that team size increases by 50% over the 19-year period. We supplement team size with measures of domestic and foreign institutional collaborations, which capture the geographic dispersion of team workers. The time series evidence suggests that the trend towards more geographically dispersed scientific teams accelerates beginning with papers published at the start of the 1990s. This acceleration suggests a sharp decline in the cost of collaboration. Our hypothesis is that the decline is due to the deployment of the National Science Foundation's NSFNET and its connection to networks in Europe and Japan after 1987.Using a panel of top university departments we also find that private universities and departments whose scientists have earned prestigious awards participate in larger teams, as do departments that have larger amounts of federal funding. Placement of former graduate students is a key determinant of institutional collaborations, especially collaborations with firms and with foreign scientific institutions. Finally, the evidence suggests that scientific output and influence increase with team size and that influence rises along with institutional collaborations. Since increasing team size implies an increase in the division of labor, these results suggest that scientific productivity increases with the scientific division of labor.  相似文献   

Intellectual property protection mechanisms in research partnerships   总被引：1，自引：0，他引：1  

Henry R. Hertzfeld  Nicholas S. Vonortas 《Research Policy》2006,35(6):825-838

A set of US-based companies is investigated regarding the effectiveness of intellectual property protection mechanisms (IPPMs) in the formation of research partnerships. Patents are the most frequently used IPPM to protect both background and foreground knowledge in partnerships. Other IPPMs are used to protect know-how, especially in the early, forming stages of a partnership. Existing IP titles are quite useful when negotiating new partnerships. IPR negotiations are reported to be more complex in horizontal partnerships and when universities are involved.  相似文献