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基于行存储模型的模拟列存储策略研究 被引量:10
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作者 于利胜 张延松 +1 位作者 王珊 张倩 《计算机研究与发展》 EI CSCD 北大核心 2010年第5期878-885,共8页
列存储模型在只读的数据仓库应用中表现出非常好的性能,很多研究表明对于典型的OLAP查询,列存储数据库的性能大大优于行存储数据库.根据列存储模型的特性及数据处理特点,在传统的行存储模型关系数据库中模拟列存储的存储模式及数据处理... 列存储模型在只读的数据仓库应用中表现出非常好的性能,很多研究表明对于典型的OLAP查询,列存储数据库的性能大大优于行存储数据库.根据列存储模型的特性及数据处理特点,在传统的行存储模型关系数据库中模拟列存储的存储模式及数据处理过程,并通过优化的基于聚类的列存储模型、全索引模型与典型的行存储方式进行类比性能测试.实验结果显示,采用传统行存储模型模拟的列存储模型针对OLAP类查询具有很高的数据访问速度及查询性能,整体性能介于行存储数据库与列存储数据库之间.对于实际应用系统来说,该方案减少了整体系统部署代价,而且无需为提高OLAP查询的性能增加额外系统(列存储)投入,从而为OLAP应用提供了良好的性能支持. 展开更多
关键词 列存储 OLAPDB 聚集列模型 全索引模型 行存储
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Comprehensive Characterization Model of Integrated Cotton Fiber Quality Index 被引量:1
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作者 刘贵 杨瑜榕 +2 位作者 王明葵 YANG Shouren 于伟东 《Journal of Donghua University(English Edition)》 EI CAS 2011年第4期379-383,共5页
An integrated cotton fiber quality index (ICFQI) model with cotton fiber qualities which can directly express cotton fiber integrated quality and spinning yarn quality was studied. The fiber length, strength, Micron... An integrated cotton fiber quality index (ICFQI) model with cotton fiber qualities which can directly express cotton fiber integrated quality and spinning yarn quality was studied. The fiber length, strength, Micronalre (fiber fineness and fiber maturity), uniformity of fiber length, and short fiber content are the pivotal indexes expressing ICFQI. All of the results above are the basic knowledge to build up the models of ICFQI. According to spinning consistency index (SCI), spinning strength and spinning yarn integrated quality, ICFQI was the best choice. As the methods of ICFQI had quite a lot of advantages like explicit mechanism, few independent variables. The integrated fiber quality index had a significant positive correlation with yarn strength and spinning consistency, significant negative correlation with yarn evenness and yarn thin places. In additional, the model of the relationship between ICFQI and SCI was established as: SCI=0. 235 6·ICFQI +56.153. It was concluded that ICFQI value was the shared reference index for the testing of fiber inspection agency and the selection and distribution of raw cotton bales by textile mills. 展开更多
关键词 fiber quality integrated cotton fiber quality index(ICFQ1) comprehensive characterization model
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Projections of the impacts of climate change on the water deficit and on the precipitation erosive indexes in Mantaro River Basin, Peru 被引量:1
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作者 Sly C.WONGCHUIG Carlos R.MELLO Sin C.CHOU 《Journal of Mountain Science》 SCIE CSCD 2018年第2期264-279,共16页
Projections of climate change are essential to guide sustainable development plans in the tropical Andean countries such as Peru. This study assessed the projections of precipitation and potential evaporation, rain er... Projections of climate change are essential to guide sustainable development plans in the tropical Andean countries such as Peru. This study assessed the projections of precipitation and potential evaporation, rain erosive potential, and precipitation concentration in the Mantaro River Basin, in the Peruvian Andes, which is important for agriculture and energy production in Peru. We assumed the Intergovernmental Panel on Climate Change (IPCC) AIB greenhouse gas emission scenario and simulated the global climate change by the HadCM3 global climate model. Due to the steepness of the mountain slopes and the narrowness of the river valley, this study uses the downscaling of the global model simulations by the regional Eta model down to 2o-km resolution. The downscaling projections show decrease in the monthly precipitation with respect to the baseline period, especially during the rainy season, between February and April, until the end of the 21st century. Meanwhile, a progressive increase in the monthly evaporation from the baseline period is projected. The Modified Fournier Index (MFI) shows a statistically significant downward trend in the Mantaro River Basin, whieh suggests a possible reduction in the rain erosive potential. The Precipitation Concentration Index (PCI) shows a statistically significant increasing trend, which indicates increasingly more irregular temporal distribution of precipitation towards the end of the century. The results of this study allow us to conclude that there should be a gradual increase in water deficit and precipitation concentration. Both changes can be negative for agriculture, power generation, and water supply in the Mantaro River Basin in Peru. 展开更多
关键词 PRECIPITATION EVAPORATION PrecipitationConcentration Index (PCI) Modified Fournier Index(MFI) Climate change Tropical Andes
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