The smart grid has caught great attentions in recent years, which is poised to transform a centralized, producer-controlled network to a decentralized, consumer- interactive network that＇s supported by fine-grained m...The smart grid has caught great attentions in recent years, which is poised to transform a centralized, producer-controlled network to a decentralized, consumer- interactive network that＇s supported by fine-grained monitoring. Large-scale WSNs （Wireless Sensor Networks） have been considered one of the very promising technologies to support the implementation of smart grid. WSNs are applied in almost every aspect of smart grid, including power generation, power transmission, power distribution, power utilization and power dispatch, and the data query processing of ＇WSNs in power grid＇ become an hotspot issue due to the amount of data of power grid is very large and the requirement of response time is very high. To meet the demands, top-k query processing is a good choice, which performs the cooperative query by aggregating the database objects＇ degree of match for each different query predicate and returning the best k matching objects. In this paper, a framework that can effectively apply top-k query to wireless sensor network in smart grid is proposed, which is based on the cluster-topology sensor network. In the new method, local indices are used to optimize the necessary query routing and process intermediate results inside the cluster to cut down the data traffic, and the hierarchical join query is executed based on the local results.Besides, top-k query results are verified by the clean-up process, and two schemes are taken to deal with the problem of node＇s dynamicity, which further reduce communication cost. Case studies and experimental results show that our algorithm has outperformed the current existing one with higher quality results and better efficiently.展开更多
Carbon emissions embodied in international trade of China during 1997-2007 are accounted by input-output method based on Chinese input-output table and global trade analysis project database.It is revealed that carbon...Carbon emissions embodied in international trade of China during 1997-2007 are accounted by input-output method based on Chinese input-output table and global trade analysis project database.It is revealed that carbon emissions embodied in imports and exports both increased during 1997-2007,but carbon emissions embodied in exports are greater than those embodied in imports,China is a net export nation in embodied carbon.The net exports of embodied carbon account for about 10.82%of the total carbon emissions in 1997,dropped to 7.15%in 2002,increased to 13.13%in 2006,and slightly dropped to 12.64%in 2007.Low-end position of international industry division is an objective factor of being a net exporter of embodied carbon for China,and usage of a large amount of obsolete energy-using equipments wasted much energy and increased carbon emissions embodied in exports. Importers should take more responsibilities for carbon emissions embodied in trade,and China should take a certain responsibility for unreasonable energy dissipations too.展开更多
Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. O...Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. On the basis of a comprehensive grasp of the concepts and principles, combined with the actual applications, the students will understand the development trend, and unceasingly enhance the level of the database knowledge, which has great benefits for training the comprehensive talents. In this paper, by analyzing the problems existing in the database courses, the author of this paper put forward the ideas and measures for the reform of the relevant curriculums.展开更多
Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. O...Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. On the basis of a comprehensive grasp of the concepts and principles, combined with the actual applications, the students will understand the development trend, and unceasingly enhance the level of the database knowledge, which has great benefits for training the comprehensive talents. In this paper, by analyzing the problems existing in the database courses, the author of this paper put forward the ideas and measures for the reform of the relevant curriculums.展开更多
文摘The smart grid has caught great attentions in recent years, which is poised to transform a centralized, producer-controlled network to a decentralized, consumer- interactive network that＇s supported by fine-grained monitoring. Large-scale WSNs （Wireless Sensor Networks） have been considered one of the very promising technologies to support the implementation of smart grid. WSNs are applied in almost every aspect of smart grid, including power generation, power transmission, power distribution, power utilization and power dispatch, and the data query processing of ＇WSNs in power grid＇ become an hotspot issue due to the amount of data of power grid is very large and the requirement of response time is very high. To meet the demands, top-k query processing is a good choice, which performs the cooperative query by aggregating the database objects＇ degree of match for each different query predicate and returning the best k matching objects. In this paper, a framework that can effectively apply top-k query to wireless sensor network in smart grid is proposed, which is based on the cluster-topology sensor network. In the new method, local indices are used to optimize the necessary query routing and process intermediate results inside the cluster to cut down the data traffic, and the hierarchical join query is executed based on the local results.Besides, top-k query results are verified by the clean-up process, and two schemes are taken to deal with the problem of node＇s dynamicity, which further reduce communication cost. Case studies and experimental results show that our algorithm has outperformed the current existing one with higher quality results and better efficiently.
文摘Carbon emissions embodied in international trade of China during 1997-2007 are accounted by input-output method based on Chinese input-output table and global trade analysis project database.It is revealed that carbon emissions embodied in imports and exports both increased during 1997-2007,but carbon emissions embodied in exports are greater than those embodied in imports,China is a net export nation in embodied carbon.The net exports of embodied carbon account for about 10.82%of the total carbon emissions in 1997,dropped to 7.15%in 2002,increased to 13.13%in 2006,and slightly dropped to 12.64%in 2007.Low-end position of international industry division is an objective factor of being a net exporter of embodied carbon for China,and usage of a large amount of obsolete energy-using equipments wasted much energy and increased carbon emissions embodied in exports. Importers should take more responsibilities for carbon emissions embodied in trade,and China should take a certain responsibility for unreasonable energy dissipations too.
文摘Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. On the basis of a comprehensive grasp of the concepts and principles, combined with the actual applications, the students will understand the development trend, and unceasingly enhance the level of the database knowledge, which has great benefits for training the comprehensive talents. In this paper, by analyzing the problems existing in the database courses, the author of this paper put forward the ideas and measures for the reform of the relevant curriculums.
文摘Along with the wide application and the rapid development of the database technology, the teaching of the database principle will focus on developing the students＇ innovative abilities and their application skills. On the basis of a comprehensive grasp of the concepts and principles, combined with the actual applications, the students will understand the development trend, and unceasingly enhance the level of the database knowledge, which has great benefits for training the comprehensive talents. In this paper, by analyzing the problems existing in the database courses, the author of this paper put forward the ideas and measures for the reform of the relevant curriculums.
