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从面向对象的程序设计的角度,剖析了CLIENT/SERVER环境下的通用数据库开发工具POWERBUILDER(PB)的特点、基本结构及其开发数据库应用系统的方法。 相似文献
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In the past several decades, many ranking‐and‐selection (R&S) procedures have been developed to select the best simulated system with the largest (or smallest) mean performance measure from a finite number of alternatives. A major issue to address in these R&S problems is to balance the trade‐off between the effectiveness (ie, making a correct selection with a high probability) and the efficiency (ie, using a small total number of observations). In this paper, we take a frequentist's point of view by setting a predetermined probability of correct selection while trying to reduce the total sample size, that is, to improve the efficiency but also maintain the effectiveness. In particular, in order to achieve this goal, we investigate combining various variance reduction techniques into the fully sequential framework, resulting in different R&S procedures with either finite‐time or asymptotic statistical validity. Extensive numerical experiments show great improvement in the efficiency of our proposed procedures as compared with several existing procedures. 相似文献
244.
Ranking is a common task for selecting and evaluating alternatives. In the past few decades, combining rankings results from various sources into a consensus ranking has become an increasingly active research topic. In this study, we focus on the evaluation of rank aggregation methods. We first develop an experimental data generation method, which can provide ground truth ranking for alternatives based on their “inherent ability.” This experimental data generation method can generate the required individual synthetic rankings with adjustable accuracy and length. We propose characterizing the effectiveness of rank aggregation methods by calculating the Kendall tau distance between the aggregated ranking and the ground truth ranking. We then compare four classical rank aggregation methods and present some useful findings on the relative performances of the four methods. The results reveal that both the accuracy and length of individual rankings have a remarkable effect on the comparison results between rank aggregation methods. Our methods and results may be helpful to both researchers and decision‐makers. 相似文献
245.
王鸿 《中国人民武装警察部队学院学报》2004,20(3):59-61
鉴于目前农村的社会阶层有了新的变化 ,必须加强农村社会保障工作的针对性 ,区别国内外不同国情 ,根据国内不同地区的情况采取因地制宜的政策 ,并在税收和慈善工作等方面做相应的调整 相似文献
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He-yang Xu Wei-bing Li Wen-bin Li Qing Zhang Ya-jun Wang Xiao-wen Hong Ying Yang 《防务技术》2021,17(5):1650-1659
The failure mechanism of a cylindrical shell cut into fragments by circumferential detonation collision was experimentally and numerically investigated. A self-designed detonation wave regulator was used to control the detonation and cut the shell. It was found that the self-designed regulator controlled the fragment shape. The macrostructure and micro-characteristics of fragments revealed that shear fracture was a prior mechanism, the shell fractured not only at the position of detonation collision, but the crack also penetrated the shell at the first contact position of the Chapmen-Jouguet (C-J) wave. The effects of groove number and outer layer thickness on the fracture behavior were tested by simulations. When the thickness of the outer layer was 5–18 mm, it has little effect on fragmentation of the shell, and shells all fractured at similar positions. The increase of the groove number reduced the fracture possibility of the first contact position of the C-J wave. When the groove number reached 7 with a 10 mm outer layer (1/4 model), the fracture only occurred at the position of detonation collision and the fragment width rebounded. 相似文献
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基于HLA/RTI的炮兵指挥系统仿真设计与开发 总被引:1,自引:0,他引:1
HLA高级体系结构作为新一代分布式仿真技术标准,解决了仿真系统中的可重用和互操作性问题,在C3I系统仿真领域有着十分广泛的应用。分析了C3I系统仿真的可行性和必要性,简要介绍了HLA高级体系结构的技术规范,提出了一种基于HLA/RTI的能与实践相接的、易于扩展的炮兵指挥系统仿真框架,并依据联邦开发与执行过程模型(FEDEP)给出了该系统的设计与开发过程。 相似文献