The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repea...The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.展开更多
Appropriate vibration can promote the feeding capacity of gravity casting, but the effect of vibration on the feeding of low-pressure casting is not clear. The effect of vibration on the seepage feeding of ZL205A allo...Appropriate vibration can promote the feeding capacity of gravity casting, but the effect of vibration on the feeding of low-pressure casting is not clear. The effect of vibration on the seepage feeding of ZL205A alloy was investigated by vibration casting experiment and physical simulation. The aqueous solution of sodium carboxymethyl cellulose(CMC) with the same rheological characteristic of metal melt was used. The results show that vibration can improve the feeding capacity and reduce shrinkage defects of ZL205A alloy in lowpressure casting. The orthogonal physical simulation experiments indicate that vibration with low frequency and great exerted force can significantly improve the seepage velocity of non-Newtonian fluid with solid particles in porous medium. The seepage phenomenon in CMC solution shows that vibration can change the structure of accumulated particles at the seepage entrance, and thus open the blocked feeding channel. The numerical simulation of one-dimensional semisolid fluid seepage reveals that vibration can form a wave field in the porous medium, which can reduce the adhesion force between fluid and capillary wall and destroy the boundary layer of fluid, and thus promote the seepage velocity.展开更多
A novel method to improve the feeding capacity of ZL205 A alloy castings by pressure fluctuation during its solidification process under gravity field was proposed. The experiments were done in the graphite mould by a...A novel method to improve the feeding capacity of ZL205 A alloy castings by pressure fluctuation during its solidification process under gravity field was proposed. The experiments were done in the graphite mould by applying the fluctuation pressure at the top of the riser. Results of the X-ray inspection of castings and simulations of flow velocity of alloy melt and temperature field show that the new method can effectively improve the feeding capacity and significantly reduce the shrinkage in the castings. The mechanism of improving the feeding capacity by pressure fluctuation is that the fluctuating pressure can make the ZL205 A alloy melt form a vibration wave in the melt. The vibration wave can intensify the convection of the melt, and therefore, break down the barrage from the feeding channel which forms during the solidification process of the ZL205 A alloy, improving the feeding capacity.展开更多
Graph processing is a vital component of many AI and big data applications.However,due to its poor locality and complex data access patterns,graph processing is also a known performance killer of AI and big data appli...Graph processing is a vital component of many AI and big data applications.However,due to its poor locality and complex data access patterns,graph processing is also a known performance killer of AI and big data applications.In this work,we propose to enhance graph processing applications by leveraging fine-grained memory access patterns with a dual-path architecture on top of existing software-based graph optimizations.We first identify that memory accesses to the offset,edge,and state array have distinct locality and impact on performance.We then introduce the Skyway architecture,which consists of two primary components:1)a dedicated direct data path between the core and memory to transfer state array elements efficiently,and 2)a data-type aware fine-grained memory-side row buffer hardware for both the newly designed direct data path and the regular memory hierarchy data path.The proposed Skyway architecture is able to improve the overall performance by reducing the memory access interference and improving data access efficiency with a minimal overhead.We evaluate Skyway on a set of diverse algorithms using large real-world graphs.On a simulated fourcore system,Skyway improves the performance by 23%on average over the best-performing graph-specialized hardware optimizations.展开更多
基金Projects(51475120,U1537201) supported by the National Natural Science Foundation of China
文摘The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.
基金financially supported by the National Natural Science Foundation of China(No.51475120)the Joint Fund of Research of Advanced Manufacturing Technology in Aerospace(No.U1537201)
文摘Appropriate vibration can promote the feeding capacity of gravity casting, but the effect of vibration on the feeding of low-pressure casting is not clear. The effect of vibration on the seepage feeding of ZL205A alloy was investigated by vibration casting experiment and physical simulation. The aqueous solution of sodium carboxymethyl cellulose(CMC) with the same rheological characteristic of metal melt was used. The results show that vibration can improve the feeding capacity and reduce shrinkage defects of ZL205A alloy in lowpressure casting. The orthogonal physical simulation experiments indicate that vibration with low frequency and great exerted force can significantly improve the seepage velocity of non-Newtonian fluid with solid particles in porous medium. The seepage phenomenon in CMC solution shows that vibration can change the structure of accumulated particles at the seepage entrance, and thus open the blocked feeding channel. The numerical simulation of one-dimensional semisolid fluid seepage reveals that vibration can form a wave field in the porous medium, which can reduce the adhesion force between fluid and capillary wall and destroy the boundary layer of fluid, and thus promote the seepage velocity.
基金financially supported by the National Natural Science Foundation of China(No.51475120)the Joint Fund of Research of Advanced Manufacturing Technology in Aerospace(No.U1537201)
文摘A novel method to improve the feeding capacity of ZL205 A alloy castings by pressure fluctuation during its solidification process under gravity field was proposed. The experiments were done in the graphite mould by applying the fluctuation pressure at the top of the riser. Results of the X-ray inspection of castings and simulations of flow velocity of alloy melt and temperature field show that the new method can effectively improve the feeding capacity and significantly reduce the shrinkage in the castings. The mechanism of improving the feeding capacity by pressure fluctuation is that the fluctuating pressure can make the ZL205 A alloy melt form a vibration wave in the melt. The vibration wave can intensify the convection of the melt, and therefore, break down the barrage from the feeding channel which forms during the solidification process of the ZL205 A alloy, improving the feeding capacity.
基金supported in part by the U.S.National Science Foundation under Grant Nos.CCF-2008907 and CCF-2029014the Chinese Academy of Sciences Project for Young Scientists in Basic Research under Grant No.YSBR-029the Chinese Academy of Sciences Project for Youth Innovation Promotion Association.
文摘Graph processing is a vital component of many AI and big data applications.However,due to its poor locality and complex data access patterns,graph processing is also a known performance killer of AI and big data applications.In this work,we propose to enhance graph processing applications by leveraging fine-grained memory access patterns with a dual-path architecture on top of existing software-based graph optimizations.We first identify that memory accesses to the offset,edge,and state array have distinct locality and impact on performance.We then introduce the Skyway architecture,which consists of two primary components:1)a dedicated direct data path between the core and memory to transfer state array elements efficiently,and 2)a data-type aware fine-grained memory-side row buffer hardware for both the newly designed direct data path and the regular memory hierarchy data path.The proposed Skyway architecture is able to improve the overall performance by reducing the memory access interference and improving data access efficiency with a minimal overhead.We evaluate Skyway on a set of diverse algorithms using large real-world graphs.On a simulated fourcore system,Skyway improves the performance by 23%on average over the best-performing graph-specialized hardware optimizations.
