Currently,in the automotive industry,joining of the aluminum alloys with the steel is a crucial problem to be solved.Conventional joining techniques including resistance spot and gas metal arc welding are not acceptab...Currently,in the automotive industry,joining of the aluminum alloys with the steel is a crucial problem to be solved.Conventional joining techniques including resistance spot and gas metal arc welding are not acceptable for those applications due to a number of metallurgical problems.The investigation was carried out to develop the hybrid joining process combining the resistance spot welding and brazing.In this study,an attempt was made to apply hybrid process to the joining of dissimilar sheet metals,Al-Mg-Si（6000 series） alloy and low carbon steel sheet.Hybrid process（resistance spot weld/brazing） using filler metal was found to be effective to overcome the incompatibility between aluminum alloy and steel.Although hybrid joining process of Al alloy sheet and steel sheet did not produce acceptable bond strength,it was proved to have reasonable interfacial bond layer if the optimal process condition was applied.展开更多
The Ramsar Convention on Wetlands is an international framework through which countries identify and protect important wetlands.Yet Ramsar wetlands are under substantial anthropogenic pressure worldwide,and tracking e...The Ramsar Convention on Wetlands is an international framework through which countries identify and protect important wetlands.Yet Ramsar wetlands are under substantial anthropogenic pressure worldwide,and tracking ecological change relies on multitemporal data sets.Here,we evaluated the spatial extent,temporal change,and anthropogenic threat to Ramsar wetlands at a national scale across China to determine whether their management is currently sustainable.We analyzed Landsat data to examine wetland dynamics and anthropogenic threats at the 57 Ramsar wetlands in China between 1980 and 2018.Results reveal that Ramsar sites play important roles in preventing wetland loss compared to the dramatic decline of wetlands in the surrounding areas.However,there are declines in wetland area at 18 Ramsar sites.Among those,six lost a wetland area greater than 100 km^(2),primarily caused by agricultural activities.Consistent expansion of anthropogenic land covers occurred within 43(75%)Ramsar sites,and anthropogenic threats from land cover change were particularly notable in eastern China.Aquaculture pond expansion and Spartina alterniflora invasion were prominent threats to coastal Ramsar wetlands.The observations within China’s Ramsar sites,which in management regulations have higher levels of protection than other wetlands,can help track progress towards achieving United Nations Sustainable Development Goals(SDGs).The study findings suggest that further and timely actions are required to control the loss and degradation of wetland ecosystems.展开更多
文摘Currently,in the automotive industry,joining of the aluminum alloys with the steel is a crucial problem to be solved.Conventional joining techniques including resistance spot and gas metal arc welding are not acceptable for those applications due to a number of metallurgical problems.The investigation was carried out to develop the hybrid joining process combining the resistance spot welding and brazing.In this study,an attempt was made to apply hybrid process to the joining of dissimilar sheet metals,Al-Mg-Si（6000 series） alloy and low carbon steel sheet.Hybrid process（resistance spot weld/brazing） using filler metal was found to be effective to overcome the incompatibility between aluminum alloy and steel.Although hybrid joining process of Al alloy sheet and steel sheet did not produce acceptable bond strength,it was proved to have reasonable interfacial bond layer if the optimal process condition was applied.
基金supported by the National Key R&D Program of China(grant numbers 2016YFC0500201 and 2016YFA0602301)the National Natural Science Foundation of China(grant numbers 41771383 and 41730643)+1 种基金the Science and Technology Development Program of Jilin Prov-ince(grant number 20200301014RQ)the funding from the Youth Innovation Promotion Association of Chinese Academy of Sciences(grant numbers 2017277 and 2012178)。
文摘The Ramsar Convention on Wetlands is an international framework through which countries identify and protect important wetlands.Yet Ramsar wetlands are under substantial anthropogenic pressure worldwide,and tracking ecological change relies on multitemporal data sets.Here,we evaluated the spatial extent,temporal change,and anthropogenic threat to Ramsar wetlands at a national scale across China to determine whether their management is currently sustainable.We analyzed Landsat data to examine wetland dynamics and anthropogenic threats at the 57 Ramsar wetlands in China between 1980 and 2018.Results reveal that Ramsar sites play important roles in preventing wetland loss compared to the dramatic decline of wetlands in the surrounding areas.However,there are declines in wetland area at 18 Ramsar sites.Among those,six lost a wetland area greater than 100 km^(2),primarily caused by agricultural activities.Consistent expansion of anthropogenic land covers occurred within 43(75%)Ramsar sites,and anthropogenic threats from land cover change were particularly notable in eastern China.Aquaculture pond expansion and Spartina alterniflora invasion were prominent threats to coastal Ramsar wetlands.The observations within China’s Ramsar sites,which in management regulations have higher levels of protection than other wetlands,can help track progress towards achieving United Nations Sustainable Development Goals(SDGs).The study findings suggest that further and timely actions are required to control the loss and degradation of wetland ecosystems.
