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大型ORACLE数据库系统的优化设计方案 总被引:1,自引:0,他引:1
ORACLE数据库技术在各类船舶管理系统中应用广泛,提供综合的船舶管理、人事管理、设备管理、交易管理、保养管理以及故障查询分析等各种业务应用,以保障船舶行驶安全,降低事故发生率、提高企业管理水平、提高服务水平、加强管理力度、增加管理效率,减少人力、物力、财力上的浪费.本文主要从大型数据库ORACLE环境4个不同级别(操作系统级包括硬件平台、ORACLE关系管理系统级、数据库系统设计级、数据库开发范畴的结构化查询语句分析级)的调整分析入手,分析ORACLE的系统结构和数据存取工作机理,从9个方面分析ORACLE数据库的优化调整方案. 相似文献
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Chorng-Shern Horng Chih-An Huh Kuo-Hang Chen Pin-Ru Huang Kan-Hsi Hsiung Hui-Ling Lin 《Journal of Marine Systems》2009,76(4):468
Kaohsiung City and its neighborhood in the southwestern coastal plain of Taiwan have suffered serious air pollution since the region became the largest center for heavy-industry on the island. In order to unravel the air pollution history of the region, four 210Pb- and 137Cs-dated sediment box cores recovered in 2006 from offshore of this area were chosen for magnetic and petrographic analyses. The data were used to distinguish changes in concentration, composition and grain size of magnetic particles in the sediments due to inputs of anthropogenic magnetic spherules. Sedimentation rates have been reasonably constant for the last one hundred years, except at the core tops which were affected by a turbidite layer induced by a typhoon in 2005. Down-core profiles of mass-specific magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM) are similar among the cores, and reflect similar trends to magnetic spherule counts. This reveals that χ and SIRM of modern marine sediments can be used as air pollution indicators for nearby industrialized upwind areas. The studied record indicates that industrialization of the area was gradual during 1950–1980 and boomed afterward, resulting in a high production of airborne magnetic spherules, which is consistent with evidence for poor air quality at that time. Optical and scanning electron microscopic (SEM) surveys of magnetic extracts indicate that the magnetic spherules have grain sizes ranging from a few micrometers up to 50 μm and consist mainly of iron oxides with variable Si, Al, and Ca contents. X-ray diffraction analysis on magnetic extracts from different depths in the cores further indicates that magnetite and pyrrhotite, which are derived from terrigenous detritus, form the magnetic constituents of the sediments before the area was industrialized. In contrast, during the industrial boom, anthropogenic magnetite and hematite spherules became the dominant magnetic particles in the sediments. Down-core profiles of hard isothermal remanent magnetization (HIRM) below the turbidite layer also reveal similar trends to the corresponding magnetic spherule counts, which indicate that the concentration of hematite in the sediments is also closely related to the extent of air pollution. In addition, relatively low values of χARM/χ, which are indicative of coarse magnetic grains, started to occur when large magnetite spherules became significant during the industrialized period. The air pollution history elucidated from our sediment core data not only reflects the development of Kaohsiung from a small village to a highly industrialized metropolitan area in the 20th century, but it is also consistent with the most recent air pollution trends revealed by real time air quality measurements of PM10. Our results demonstrate the usefulness of magnetic parameters for delineating the air pollution history of coastal marine sediments down-wind of nearby industrialized regions. 相似文献
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为充分利用信道信息(Channel State Information,CSI)来改善准正交空时码(Quasi Orthogonal Space-Time Block Code,QSTBC)系统的性能,提出基于天线选择的QSTBC系统自适应设计方案,对QSTBC的编码结构添加自适应系数,使信道矩阵正交化,消除码间串扰.推导了系统的瞬时输出信噪比,以此作为天线选择准则.仿真结果表明,相对于未经过自适应编码设计的天线选择QSTBC系统,新系统的误码率性能有明显改善. 相似文献
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为加强恶劣海况下深水防波堤护面稳定性和结构安全性,根据最新规范规定和试验研究结果,对防波堤原设计方案的护面结构形式进行优化调整。采用双层扭王字块护面结构,利用人工块体代替超大质量规格的块石,并提出实施过程中保证深水防波堤工程护面块体质量的施工控制要点。结果表明,双层扭王字块护面既解决了大规格石料供应问题,又提高了深水防波堤护面结构的稳定性。 相似文献
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针对工程环抱形防波堤平面布置方案,利用整体物理模型试验手段进行了验证。结果表明:1)掩护后传入港内波峰线发生了偏转和波能集中,致使码头局部泊稳条件不满足标准要求。将位轴线顺时针旋转15°,与波峰线平行优化布置后,则满足。2)根据越堤波浪是否冲击港内码头轴线标准,论证10.0、10.5、11.0 m共3个防波提高程掩护体,得出11.0 m是可行的。3)防波堤外侧质量6 t护面块体失稳,经多次优化后采用质量10 t则稳定,弧形转弯处勾连性护面块体受侧向波浪力作用比受正向波浪力偏于危险。4)将试验结果与规范公式计算值进行对比,前者均大,因此对于弧形转弯段的处理应给予关注,尽量遵循规范要求轴线夹角的相关规定。5)试验再次验证了三维港池整体物理模型试验在防波堤稳定性、越浪量和优化设计方面的必要性。 相似文献