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We consider the problem of controlling the model of one-dimensional fluid flow through a soil packed tube in which a contaminant is initially distributed. A fluid is pumped through a tube to remove the contaminant. The control problem is to determine the optimal convective velocity due to the fluid being pumped by minimizing a given performance criterion. The performance criterion is chosen to be a combination of the total contaminant at the final time and the cost of the control. The set of orthogonal Fourier trigonometry series is used as a basis function of the Galerkin procedure to lump the distributed parameter system. A Legendre wavelet operational matrix of derivative is used to approximate the control and modal state variables. The main characteristics of this technique is that it reduces these problems to those of solving a system of algebraic equations, thus greatly simplifying the problem. The effectiveness of the proposed approach is illustrated numerically and the results are quite satisfactory. 相似文献
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Nicolas Faysse Mohamed Taher Sraïri Mostafa Errahj 《The Journal of Agricultural Education and Extension》2013,19(3):285-299
Abstract Purpose: The study investigated to what extent local farmers' organisations are spaces where farmers discuss, learn and innovate. Design/methodology/approach: Two milk collection cooperatives in Morocco were studied. The study analysed the discussion networks, their impacts on farmers' knowledge and innovation, and the performance of collective action at cooperative level. Findings: In both cooperatives, only two-thirds of the farmers regularly discussed dairy practices with other farmers. Most leaders of one cooperative were acknowledged to be experienced farmers and played key roles as advisors on dairy farming. Farmers' involvement in dialogue networks in this cooperative improved their capacity to innovate in dairy farming, even though their knowledge on some issues related to cattle, health and nutrition was not improved. In the other cooperative, experienced farmers did not share their knowledge and farmers' involvement in dialogue networks at cooperative level had no impact on their knowledge and practices. Dialogue networks and collective action were found to influence each other, since in the first cooperative, collective action was considered by members to be efficient, whereas in the second collective action was limited to milk collection. Practical implications: The study enabled identification of stumbling blocks which need to be addressed to get local farmers’ organisations involved in farmer capacity-building. Originality/value: While the importance of local discussion networks for knowledge creation and diffusion is widely acknowledged, taking such networks into account in farmers' capacity-building programmes in developing countries has been hindered by their informality. Combining the analysis of dialogue networks and collective action proved to be a productive way to assess the potentialities of working with farmers' organisations with the aim of establishing a connection with local discussion networks. 相似文献
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Application of honey-bee mating optimization on state estimation of a power distribution system including distributed generators 总被引：1，自引：0，他引：1
Taher Niknam 《浙江大学学报(A卷英文版)》2008,9(12):1753-1764
We present a new approach based on honey-bee mating optimization to estimate the state variables in distribution networks including distributed generators. The proposed method considers practical models of electrical equipments such as static var compensators, voltage regulators, and under-load tap changer transformers, which have usually nonlinear and discrete characteristics. The feasibility of the proposed approach is demonstrated by comparison with the methods based on neural networks, ant colony optimization, and genetic algorithms for two test systems, a network with 34-bus radial test feeders and a realistic 80-bus 20 kV network. 相似文献
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Taher A. Razik Patrick J. Nalbone 《Educational technology research and development : ETR & D》1990,38(1):65-76
Technological change and social change are viewed as interdependent in this paper. At the same time technology's push is seen as outpacing the capability of social institutions to respond. Consequently, America risks losing its competitive edge economically and, further, is rapidly evolving toward a two-tiered occupational and social structure. This paper examines the relationship between technological and social change, the nature and significance of technological innovation and dissemination, and impacts on organizational life. Finally, the paper explores the role of higher education as well as strategies the university must adopt if it is to participate effectively in addressing the changes that are emerging as society moves from being production-and-material based to an information-based system. 相似文献
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亚斯 《南京晓庄学院学报》2009,25(2)
该文比较的是巴林王国教育部2003年颁布的<基础教育科学课程文件>与中华人民共和国教育部2001年制订的<全日制义务教育物理课程标准(实验稿)>.比较内容涉及到文件的设计框架、文件中的课程改革的原则与理念的比较、课程目标的比较、课程内容的比较等方面. 相似文献
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Mohamed Taher Amin Ahmed Khan Muhammed Burhanuddin 《International Information and Library Review》2013,45(4):337-345
This paper relates to the difficulty in retrieving precise information from big repositories of magazine articles in full text, and proposes an Extended Markup Language (XML) vocabulary for improving retrieval rates. The hypothesis tested was as follows: Magazine articles marked up with an XML vocabulary, indexed only by selected parts, give more precise search results than the same search using full text index.The study was exploratory with the following characteristics: 29 magazine articles were tested for results, 8 scholars were interviewed for defining 23 search strategies and evaluating results. The data showed that precision improved from 40.72% with full text search to 62.84% using XML markup and searching only in specific labels.Revision of the vocabulary and more testing has to be done by the library and information science community in order to obtain a valid vocabulary and provide more research results. Cultural characteristics and politics of librarians and information managers’ community are as important as technical issues in order to consider any technical proposal to be implemented successfully to achieve interoperability. 相似文献
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This article analyzes patterns of expenditure on higher education in Jordan, explores the current system??s adequacy, efficiency, and equity, and identifies its strengths and weaknesses in light of current constraints and future challenges. Among the constraints are the relatively low public expenditure on higher education, leaving households to compensate through private expenditure. Moreover, despite more spending on university education, the quickly rising volume of students has required compromises in quality. Meanwhile, gradually falling subsidies have pressured public universities to reconsider their financing mechanisms and become more efficient. Cost-sharing mechanisms have been introduced through commercial private universities and ??parallel programmes?? at public universities. This generates much-needed income, but raises two critical issues. Students from poorer backgrounds find it even more difficult to enter university, and quality is constrained because universities must compromise on tasks that are essential but not profitable such as research and development. Among the suggested solutions are promoting the culture of charitable endowments, perhaps through a revision of the Islamic awqaf system, and developing innovative financial mechanisms to tap private savings without incurring the hazards of profit maximization. 相似文献
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Globally, universities are currently facing increased external demands to strengthen and develop their learning environments. The article examines how a sample of Norwegian universities responds to governmental demands concerning establishing good learning environments. Based on document analysis and interviews, the article demonstrates that the concept of the learning environment seems to be interpreted and implemented in a standardised way and that institutional work in this area might suffer from a decoupling between ‘administrative’ and ‘academic’ responsibilities. Furthermore, the analysis shows that the universities studied to a great extent seem to rely on copying and imitating understandings of the concept instead of using it to develop more specific and uniquely local practices. In conclusion, the article calls for more attention to the consequences of specific organisational solutions, and it is argued that more attention should be given to identifying factors that enable or constrain how universities handle external pressure for change. 相似文献