Billets of A356 aluminum alloy were treated using ultrasonic vibrations during solidification.The billets were reheated to the semisolid state at different routes to optimize the procedure.Billets were,then,thixocast ...Billets of A356 aluminum alloy were treated using ultrasonic vibrations during solidification.The billets were reheated to the semisolid state at different routes to optimize the procedure.Billets were,then,thixocast using a die casting machine.The results showed that the ultrasonic-treated billets exhibited finely distributed α（Al） globules after reheating and thixocasting.The thixocast ultrasonic-treated billets showed higher ultimate tensile strength and elongation compared with the untreated billets.Moreover,the thixocast parts showed a tendency to ductile fracture under tension when made from ultrasonic-treated billets,while those made of untreated billets showed brittle fracture with obvious straight facets.These results revealed the feasibility and competence of ultrasonic melt treatment as a potential route for preparing billets for thixocasting.展开更多
In this paper,we propose a novel spatial data index based on Hadoop:HQ-Tree.In HQ-Tree,we use PR QuadTrec to solve the problem of poor efficiency in parallel processing,which is caused by data insertion order and spac...In this paper,we propose a novel spatial data index based on Hadoop:HQ-Tree.In HQ-Tree,we use PR QuadTrec to solve the problem of poor efficiency in parallel processing,which is caused by data insertion order and space overlapping.For the problem that HDFS cannot support random write,we propose an updating mechanism,called "Copy Write",to support the index update.Additionally,HQ-Tree employs a two-level index caching mechanism to reduce the cost of network transferring and I/O operations.Finally,we develop MapReduce-based algorithms,which are able to significantly enhance the efficiency of index creation and query.Experimental results demonstrate the effectiveness of our methods.展开更多
文摘Billets of A356 aluminum alloy were treated using ultrasonic vibrations during solidification.The billets were reheated to the semisolid state at different routes to optimize the procedure.Billets were,then,thixocast using a die casting machine.The results showed that the ultrasonic-treated billets exhibited finely distributed α（Al） globules after reheating and thixocasting.The thixocast ultrasonic-treated billets showed higher ultimate tensile strength and elongation compared with the untreated billets.Moreover,the thixocast parts showed a tendency to ductile fracture under tension when made from ultrasonic-treated billets,while those made of untreated billets showed brittle fracture with obvious straight facets.These results revealed the feasibility and competence of ultrasonic melt treatment as a potential route for preparing billets for thixocasting.
基金This work is supported by the National Natural Science Foundation of China under Grant No.61370091and No.61170200, Jiangsu Province Science and Technology Support Program （industry） Project under Grant No.BE2012179, Program Sponsored for Scientific Innovation Research of College Graduate in Jiangsu Province under Grant No. CXZZ12_0229.
文摘In this paper,we propose a novel spatial data index based on Hadoop:HQ-Tree.In HQ-Tree,we use PR QuadTrec to solve the problem of poor efficiency in parallel processing,which is caused by data insertion order and space overlapping.For the problem that HDFS cannot support random write,we propose an updating mechanism,called "Copy Write",to support the index update.Additionally,HQ-Tree employs a two-level index caching mechanism to reduce the cost of network transferring and I/O operations.Finally,we develop MapReduce-based algorithms,which are able to significantly enhance the efficiency of index creation and query.Experimental results demonstrate the effectiveness of our methods.
