Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top ...Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top surface of the joint was characterized by scanning electron microscopy and transmission electron microscopy.The corrosion behaviors of different regions in the joint were investigated by an electrochemistry method and an alternating salt spray exposure.The corrosion was mainly dependent on the nature of precipitates in each region of the joint.The shoulder affected zone had the worst corrosion resistance as a result of the re-dissolved ofθ′(Al2Cu),T1(Al2CuLi)andδ′(Al3Li)phases,the formation of intergranular precipitates and precipitate-free zones.However,the thermomechanically affected zone had a slightly improved corrosion resistance because it had no intergranular precipitates.The heat affected zone and base metal had the best corrosion resistance.展开更多
The lorentz force-type magnetic bearing(LFTMB)with good linearity is suitable for the high-precision deflection control of the magnetically suspended gyrowheel(MSGW). Two kinds of novel implicit LFTMBs are proposed in...The lorentz force-type magnetic bearing(LFTMB)with good linearity is suitable for the high-precision deflection control of the magnetically suspended gyrowheel(MSGW). Two kinds of novel implicit LFTMBs are proposed in allusion to the poor magnetic flux density uniformity of the existing explicit LFTMB. The improvement of uniformity is realized under the paramagnetic contribution of magnetic ring. Their structures are introduced,the mathematical models are established based on the equivalent magnetic circuit method and the magnetic fields are analyzed by the finite element method based on the design parameters. Simulation results indicate that the magnetic flux density uniformity of implicit LFTMBs is superior to the traditional explicit LFTMB. Furthermore,the implicit trapezoid LFTMB with double magnetic circuits is better than that of those with single magnetic circuit,in terms of the magnetic flux density uniformity and the magnetic flux density. The magnetic flux density of implicit trapezoid double magnetic circuits LFTMB is verified by the experiment. The error between the experimental results and the simulation results is within 5%,which shows that the implicit trapezoid double magnetic circuits LFTMB is promising to meet the high-precision agile maneuver requirement of the magnetically suspended gyrowheel.展开更多
Tourism-oriented revitalization of historic districts has been identified as a form of sustainability which is believed to contribute to both conservation and development.Comprehensive assessments of the effects of su...Tourism-oriented revitalization of historic districts has been identified as a form of sustainability which is believed to contribute to both conservation and development.Comprehensive assessments of the effects of such tourism-oriented revitalizations in historic districts are thus a great challenge,and are needed to support sustainable development and management efforts.In this study criteria and indicators were identified by using the AHP method with experts scoring four aspects on two levels.We assess a case in China using this system and outputs indicated infrastructure and environment performed best,while the score for residents’living condition and participation was the lowest.Finally,we offer some suggestions to improve the relatively poor status in order to assist historic districts in achieving sustained revitalization.展开更多
基金Beijing Natural Science Foundation (Grant No. 3194048)China Friction Stir Welding Center and to Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development (Grant No. BIPT2018006) for the financial support
文摘Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top surface of the joint was characterized by scanning electron microscopy and transmission electron microscopy.The corrosion behaviors of different regions in the joint were investigated by an electrochemistry method and an alternating salt spray exposure.The corrosion was mainly dependent on the nature of precipitates in each region of the joint.The shoulder affected zone had the worst corrosion resistance as a result of the re-dissolved ofθ′(Al2Cu),T1(Al2CuLi)andδ′(Al3Li)phases,the formation of intergranular precipitates and precipitate-free zones.However,the thermomechanically affected zone had a slightly improved corrosion resistance because it had no intergranular precipitates.The heat affected zone and base metal had the best corrosion resistance.
基金supported by Beijing Municipal Natural Science Foundation (General Program) (No. 3212004)Cultivation Project of Important Scientific Research Achievements of Beijing Institute of Petrochemical Technology(No. BIPTACF-007)
文摘The lorentz force-type magnetic bearing(LFTMB)with good linearity is suitable for the high-precision deflection control of the magnetically suspended gyrowheel(MSGW). Two kinds of novel implicit LFTMBs are proposed in allusion to the poor magnetic flux density uniformity of the existing explicit LFTMB. The improvement of uniformity is realized under the paramagnetic contribution of magnetic ring. Their structures are introduced,the mathematical models are established based on the equivalent magnetic circuit method and the magnetic fields are analyzed by the finite element method based on the design parameters. Simulation results indicate that the magnetic flux density uniformity of implicit LFTMBs is superior to the traditional explicit LFTMB. Furthermore,the implicit trapezoid LFTMB with double magnetic circuits is better than that of those with single magnetic circuit,in terms of the magnetic flux density uniformity and the magnetic flux density. The magnetic flux density of implicit trapezoid double magnetic circuits LFTMB is verified by the experiment. The error between the experimental results and the simulation results is within 5%,which shows that the implicit trapezoid double magnetic circuits LFTMB is promising to meet the high-precision agile maneuver requirement of the magnetically suspended gyrowheel.
基金National Natural Science Foundation of China(41801139)Science and Technology Support Program of the Institute of Geographic Sciences & Natural Resources Research,CAS(Y8V80105YZ)+1 种基金Social Science Planning Project of Beijing Municipal Education Commission(SM201810017002)The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23100302)
文摘Tourism-oriented revitalization of historic districts has been identified as a form of sustainability which is believed to contribute to both conservation and development.Comprehensive assessments of the effects of such tourism-oriented revitalizations in historic districts are thus a great challenge,and are needed to support sustainable development and management efforts.In this study criteria and indicators were identified by using the AHP method with experts scoring four aspects on two levels.We assess a case in China using this system and outputs indicated infrastructure and environment performed best,while the score for residents’living condition and participation was the lowest.Finally,we offer some suggestions to improve the relatively poor status in order to assist historic districts in achieving sustained revitalization.
