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M. Dobson R. Rada C. Chen A. Michailidis A. Ulloa 《Journal of Computer Assisted Learning》1993,9(1):34-50
Abstract In an effort to reduce the expensive resource requirements in courseware production and to allow effective management of, and communication and collaboration between authors, a model is needed to harmonize the diverse theoretical backgrounds such a process requires. To this end we look at five abstract models which where chosen for their apparent appropriateness within the general area of collaborative authoring and reuse of multimedia courseware. These models consist of a functional model of hypertext, an infrastructure model for an open collaborative authoring system, two object-oriented communication models, and a courseware production model. We attempt a consolidation of these models and ultimately make several conclusions, which are exposed during a conceptual harmonisation. The principal conclusion is that a hypermedia logical model is not by itself adequate to support collaboration and reuse. Our modeling conclusions have driven the design of a system which will be implemented and tested. 相似文献
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We study in this paper the capacity of the downlink of OFDMA-based IEEE802.16 WiMAX system in the presence of two types of traffic, streaming and elastic. We focus in particular on the impact of Adaptive Modulation and Coding (AMC) as well as inter-cell interference resulting from different frequency reuse schemes. Several performance measures, namely blocking rates, mean transfer time and the mean number of collisions between two OFDMA WiMAX cells, are then derived and quantified. We show that reuse partitioning results in a higher blocking rate at the appreciable gain in terms of lower mean transfer time for users close to the base station as well as a lower number of collisions which implies a higher throughput. 相似文献
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While reuse is an effective lifecycle option in terms of reduction of environmental loads and value of reutilization, reuse has inherent difficulties. Our naive question is why component reuse of home appliances seems impossible while that of photocopiers succeeded. This paper clarifies an essential factor for successful reuse; that is, the balance between supply and demand of reusables, and proposes an index named ‘marginal reuse rate,’ which indicates upper limit of reusability. By using this index, reusability of several products is analyzed. The marginal reuse rate indicates that design of lifecycle, in addition to product design, is indispensable for successful reuse. 相似文献
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袁宝龙 《网络安全技术与应用》2014,(8):46-47
本文结合吉林电视台播出网络的建设,针对播出系统中光传输在系统中的重要组成部分。基于本台的特殊传输情况,以及所涉及到的系统中光传输构架加以简单介绍。 相似文献
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利用存储过程的预编译机制,将存储过程应用于COM组件模型,是本文讨论的一项关键技术。在该技术的基础上,提出了三种可重用的COM组件模型,并在VB6.0环境下对三种组件给出了详细设计和实现。 相似文献
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A reuse system for carwash water with a cellulose acetate (CA), hollow-fiber-type ultrafiltration membrane with the aid of flocculation and activated carbon treatments was proposed. The multi-blended flocculating agent containing bentonite, Al2(SO4)3, sodium alginic acid and a cationic polyacrylamide showed higher removals of COD and turbidity for carwash wastewater compared with Al2(SO4)3 or a water-soluble polymer individually. The effect of pure water permeability of the membrane on permeation flux in pretreated carwash wastewater by this agent was examined using three kinds of CA membranes whose molecular weight cut-offs were 150,000 Dalton. Permeation flux showed a higher value in the case of the membrane with higher pure water permeability. Practical scale experiments with a membrane area of 32 m2 and 48 m2 were conducted under a membrane pressure of 20 kPa. When carwash wastewater was pretreated with 50 mg/L of this multi-blended flocculating agent, permeation flux through the CA membrane with pure water permeability of 0.78 m3/(m2/h) at 100 kPa showed 1.0 m3/(m2/d) for more than 6 months. The COD, BOD and extract by n-hexane values of reuse water were 3.7-15.7 mg/L, 2.5-14.0 mg/L and below 0.5 mg/L, respectively. 相似文献
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代码重用攻击的实施过程较为繁杂,通常需要一些工具辅助人工来完成gadget序列的构建,但现有的自动化构建工具效率较低。在分析Ropper、angrop和BOPC等典型开源gadget工具语义分析内容的基础上,总结gadget语义分析应包含的要素,提出一种基于表达式树的gadget语义分析方法。通过表达式树变体描述寄存器和内存读写的表达式信息,提高gadget语义分析的效率。实现一个gadget搜索与语义分析工具SemExpr,针对现有gadget工具难以进行对比分析的问题,设计能对多种gadget工具进行效率和效能分析的实验系统gadgetAnalysis。基于该系统进行实验,结果表明,SemExpr工具能够权衡效率和效能,取得较好的语义分析效果。 相似文献
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