随着大数据应用日益增多,NoSQL(not only structured query language)数据库管理系统得到了快速发展。如何对NoSQL数据库和关系型数据库进行有效集成成为研究热点之一。在现有研究成果中,在这些异构的多数据库之间进行联接(join)操作时...随着大数据应用日益增多,NoSQL(not only structured query language)数据库管理系统得到了快速发展。如何对NoSQL数据库和关系型数据库进行有效集成成为研究热点之一。在现有研究成果中,在这些异构的多数据库之间进行联接(join)操作时,所采用的分页查询方法产生的延迟较大。针对这一问题,提出了一种分页预取的模型,并重点研究了其基本构成、预取方式以及运行机制。基于该模型,设计开发了原型系统,对其效果进行了验证,达到了预期目标。与无预取的分页查询方法相比,所建模型可以减少分页查询延迟,从而提升跨数据库联接操作的效率。展开更多
For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscop...For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscope (SEM) demonstrates the wear mechanism of the drum, and the test data of the influence coefficient of the normal pressure, relative sliding speed and surface lubrication conditions acted on the linear rate of the wear could be obtained by the regression method. A calculation model, which considers the factors of the structure of the drum, coiling tension and coiling strip specifications, was established by the combination method to predict the wear life of the drum. Then the practical production data was applied into this model and the analysis result was in good accordance with that of actual production.展开更多
文摘随着大数据应用日益增多,NoSQL(not only structured query language)数据库管理系统得到了快速发展。如何对NoSQL数据库和关系型数据库进行有效集成成为研究热点之一。在现有研究成果中,在这些异构的多数据库之间进行联接(join)操作时,所采用的分页查询方法产生的延迟较大。针对这一问题,提出了一种分页预取的模型,并重点研究了其基本构成、预取方式以及运行机制。基于该模型,设计开发了原型系统,对其效果进行了验证,达到了预期目标。与无预取的分页查询方法相比,所建模型可以减少分页查询延迟,从而提升跨数据库联接操作的效率。
基金Project(2009AA04Z143) supported by the National High Technology Research and Development Program of ChinaProject(E2006001038) supported by the Major Program of the Natural Science Foundation of Hebei Province, China
文摘For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscope (SEM) demonstrates the wear mechanism of the drum, and the test data of the influence coefficient of the normal pressure, relative sliding speed and surface lubrication conditions acted on the linear rate of the wear could be obtained by the regression method. A calculation model, which considers the factors of the structure of the drum, coiling tension and coiling strip specifications, was established by the combination method to predict the wear life of the drum. Then the practical production data was applied into this model and the analysis result was in good accordance with that of actual production.
