A research topic of great interest to the space physics community is the observation of plasmas flowing at hundreds of kilometers per second in the Earth’s plasma sheet. Although considerable effort has been made to ...A research topic of great interest to the space physics community is the observation of plasmas flowing at hundreds of kilometers per second in the Earth’s plasma sheet. Although considerable effort has been made to understand the source of fast-flowing plasmas, many questions remain unanswered about the mechanisms that produce high-speed flows and the effects they have on magnetospheric disturbances, especially their contributions to magnetospheric convection and substorms. In this paper, we discuss briefly the history of high-speed flows and review the proposed mechanisms, signatures of high-speed flows in auroras and their interaction with the background plasma. We then summarize the relationships between high-speed flows and magnetic structures, discuss questions associated with substorms, and finally pose several important scientific questions that need to be addressed.展开更多
By applying the reinforcing and toughening effect of calcium carbonate （CaCO3） nanoparticles on polypropylene, foam sheets of good performance were successfully fabricated by extrusion. The equipment and conditions ...By applying the reinforcing and toughening effect of calcium carbonate （CaCO3） nanoparticles on polypropylene, foam sheets of good performance were successfully fabricated by extrusion. The equipment and conditions of the extrusion were explored. The mechanical properties of the produced foam sheets were tested. The effect of CaCO3 nano-particles on the mechanical properties and the cellular structure of the sheets was comprehensively studied. The experimental results show that the optimum content of CaCO3 nano-particles in the composite material was -4wt%. At this content, the nano-particles were well dispersed in the substrate, and the composite material had maximum tensile strength and impact strength. Surface treatment of the nano-particles only affected the impact strength of the composite material. CaCO3 micro-particles, on the other hand, showed little effect on the properties of the composite material when the micro-particles content was less than 5 wt%. At a content higher than 5wt%, the properties of the composite material significantly worsened.展开更多
The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection...The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories,including A-type horizontal-vertical elbow with an upstream flow,B-type horizontal-vertical elbow with a downstream flow,C-type vertical-horizontal elbow with an upstream flow,D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow.Compared with the C/D-type elbow,where particles were injected uniformly,the A-type elbow and E-type elbow were found to increase erosion rate,while the B-type elbow decreases erosion rate.An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow.Based on the observation,a novel preceding rotating sheet structure was developed to regulate the particle injection position.It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50,100,and 200μm by 23%,35%,and 43%,respectively.展开更多
To provide a new idea to reduce anisotropy for sheets in the thickness direction by microstructure modification and,mean-while,maintain or even enhance tensile performance,the in-situ ZrB2 particle/AA7085 composite sh...To provide a new idea to reduce anisotropy for sheets in the thickness direction by microstructure modification and,mean-while,maintain or even enhance tensile performance,the in-situ ZrB2 particle/AA7085 composite sheets with thicknesses of 1,2,3,and 6 mm were investigated.The as-cast grain size was significantly refined by the heterogeneous nucleus of the ZrB2 particle.The microstructure results show that severe hot deformation converts as-cast disordered microstructure into a sequential microstructure by crushing the remanent phases and matrix into a fiber structure.After the solid solution and aging heat treatment,the composite sheets exhibit largely recrystallized grains compared with partially recrystallized grains in the matrix sheets,and weak or even free texture exists in the composite.The grain size in the composite sheets decreases with the increase in thickness reductions.For the thickness range of 1-3 mm,the composite sheets maintain a similar tensile per-formance as that in matrix sheets,while the strength and ductility in the 6-mm-thick composite sheet are improved.展开更多
基金supported by the National Natural Science Foundation of China (40874086 and 41031065)the Specialized Research Fund for State Key Laboratories (08262DAA4S)
文摘A research topic of great interest to the space physics community is the observation of plasmas flowing at hundreds of kilometers per second in the Earth’s plasma sheet. Although considerable effort has been made to understand the source of fast-flowing plasmas, many questions remain unanswered about the mechanisms that produce high-speed flows and the effects they have on magnetospheric disturbances, especially their contributions to magnetospheric convection and substorms. In this paper, we discuss briefly the history of high-speed flows and review the proposed mechanisms, signatures of high-speed flows in auroras and their interaction with the background plasma. We then summarize the relationships between high-speed flows and magnetic structures, discuss questions associated with substorms, and finally pose several important scientific questions that need to be addressed.
基金the National Natural Science Foundation of China(No.19632004 and 10172074)
文摘By applying the reinforcing and toughening effect of calcium carbonate （CaCO3） nanoparticles on polypropylene, foam sheets of good performance were successfully fabricated by extrusion. The equipment and conditions of the extrusion were explored. The mechanical properties of the produced foam sheets were tested. The effect of CaCO3 nano-particles on the mechanical properties and the cellular structure of the sheets was comprehensively studied. The experimental results show that the optimum content of CaCO3 nano-particles in the composite material was -4wt%. At this content, the nano-particles were well dispersed in the substrate, and the composite material had maximum tensile strength and impact strength. Surface treatment of the nano-particles only affected the impact strength of the composite material. CaCO3 micro-particles, on the other hand, showed little effect on the properties of the composite material when the micro-particles content was less than 5 wt%. At a content higher than 5wt%, the properties of the composite material significantly worsened.
基金the National Natural Science Foundation of China(grant No.22278332)Shaanxi Province's Key Research and Development Plan(grant No.2023-YBGY-317,2023-YBGY-175)+1 种基金Natural Science Basic Research Program of Shaanxi(grant No.2020JQ-597)Natural Science Foundation of Shaanxi Provincial Department of Education(grant No.23JK0723).
文摘The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories,including A-type horizontal-vertical elbow with an upstream flow,B-type horizontal-vertical elbow with a downstream flow,C-type vertical-horizontal elbow with an upstream flow,D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow.Compared with the C/D-type elbow,where particles were injected uniformly,the A-type elbow and E-type elbow were found to increase erosion rate,while the B-type elbow decreases erosion rate.An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow.Based on the observation,a novel preceding rotating sheet structure was developed to regulate the particle injection position.It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50,100,and 200μm by 23%,35%,and 43%,respectively.
基金financial support of the National Natural Science Foundation of China (Nos.U20A20274,52071158,51701085,and U1664254)the Six Talents Peak Project of Jiangsu Province (2018-XCL-202)+1 种基金the Open Funds of SKLMMC of SJTU (MMC-KF18-16)the Jiangsu Provincial Key Laboratory of High-End Structural Materials (HSM1803,1902).
文摘To provide a new idea to reduce anisotropy for sheets in the thickness direction by microstructure modification and,mean-while,maintain or even enhance tensile performance,the in-situ ZrB2 particle/AA7085 composite sheets with thicknesses of 1,2,3,and 6 mm were investigated.The as-cast grain size was significantly refined by the heterogeneous nucleus of the ZrB2 particle.The microstructure results show that severe hot deformation converts as-cast disordered microstructure into a sequential microstructure by crushing the remanent phases and matrix into a fiber structure.After the solid solution and aging heat treatment,the composite sheets exhibit largely recrystallized grains compared with partially recrystallized grains in the matrix sheets,and weak or even free texture exists in the composite.The grain size in the composite sheets decreases with the increase in thickness reductions.For the thickness range of 1-3 mm,the composite sheets maintain a similar tensile per-formance as that in matrix sheets,while the strength and ductility in the 6-mm-thick composite sheet are improved.
