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961.
麻晓刚 《科技情报开发与经济》2007,17(20):294-294,F0004
介绍了直放站的应用特点以及工作原理,阐述了在设计过程中直放站站址选择、前期勘测及理论测算方法,指出了设计中需要注意的几个问题。 相似文献
962.
周绮雯 《科技情报开发与经济》2007,17(27):173-174
通过对《核心期刊与期刊评价》一书的解读,提出了现行的核心期刊和期刊评价体系已经发生扭曲的论点,并探讨如何建立科学完善的核心期刊遴选和评价制度。 相似文献
963.
提出了一种新的人工免疫系统算法——免疫克隆选择算法,描述了算法的操作过程.采用函数优化仿真实验与进化算法进行比较,结果表明免疫克隆选择算法收敛速度快,求解精度高,稳定性好,并能有效地克服早熟问题和骗问题. 相似文献
964.
介绍了煤矿井下无线通信现状,分析了技术上存在的问题——巷道条件对无线传输的影响、弱信号接收困难和井下环境噪声的干扰,对解决方案进行了探讨。同时指出,借鉴陆地移动通信技术解决方案可以解决煤矿井下移动通信难题。 相似文献
965.
966.
This paper studies roto spinning blended yarn producedof spun silk and cashmere. Nine samples were spun, from threedifferent opening rollers and different navels.According to theUster test results of yarn quality prioerties, optimum selection isdane by using analysis method of combining fuzzy decision-makingand fuzzy pattern classification.Expermental plan is designedbased on universal rotated experitmental design, and the method ofconfined optimization is used to optimize the speed of openingtaller, the speed of rotor and twist factor, according to the resultsof yarn quality test by Uster. 相似文献
967.
WU Ming YAN Puliu 《武汉大学学报:自然科学英文版》2007,12(3):467-470
Feature selection is the pretreatment of data mining. Heuristic search algorithms are often used for this subject. Many heuristic search algorithms are based on discernibility matrices, which only consider the difference in information system. Because the similar characteristics are not revealed in discernibility matrix, the result may not be the simplest rules. Although differencesimilitude(DS) methods take both of the difference and the similitude into account, the existing search strategy will cause some important features to be ignored. An improved DS based algorithm is proposed to solve this problem in this paper. An attribute rank function, which considers both of the difference and similitude in feature selection, is defined in the improved algorithm. Experiments show that it is an effective algorithm, especially for large-scale databases. The time complexity of the algorithm is O(| C |^2|U |^2). 相似文献
968.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying. 相似文献
969.
类比是一种在科学研究中有重要作用的逻辑思维方法。本文就类比方法在证明生物进化、生命起源、生物进化、人类起源以及生物进化原因研究中的作用予以了论述。 相似文献
970.
针对稠油开采 ,推广应用浅层稠油选层开采技术这项新的增产措施 .利用热胀式封隔器 ,可诱导蒸汽进入注蒸汽开采目的层 ,提高油藏动用程度 .单井平均增产原油 2 31 t,比措施前吞吐周期产油量提高 30 %~ 84% .该项技术施工方便 ,投资少 ,降低了油田污染 ,经济效益明显 . 相似文献