Mg-Gd based alloys are an important class of high-performance Mg alloys.In this study,three Mg-Gd alloys with different gadolinium(Gd)contents:Mg-9.54Gd-0.40Zr(wt.%,G10 K),Mg-15.11Gd-0.35Zr(wt.%,G15 K)and Mg-19.67Gd-0...Mg-Gd based alloys are an important class of high-performance Mg alloys.In this study,three Mg-Gd alloys with different gadolinium(Gd)contents:Mg-9.54Gd-0.40Zr(wt.%,G10 K),Mg-15.11Gd-0.35Zr(wt.%,G15 K)and Mg-19.67Gd-0.33Zr(wt.%,G20 K)were prepared by semicontinuous casting and subsequent solution and aging heat treatments.The role of Gd content on microstructures and mechanical properties of the Mg-Gd-Zr alloy is studied.All three as-cast alloys exhibit eutectic phases of Mg_(5)Gd,with the amount increasing as the Gd content rises.Mg_(5)Gd disappears after the solution heat treatment(the G10 K alloy solution-treated at 480℃ for 4 h,the G15 K alloy at 500℃ for 12 h and the G20 K alloy at 520℃ for 24 h,respectively).Aging heat treatment at 200℃ for 64 h after solution introduces numerous prismatic β' precipitates,with a significant increase in their area number density corresponding to increased Gd content.Additionally,the morphology of the β' precipitates exhibits distinct variations:the G10 K alloy is characterized by an enhanced aspect ratio.Consequently,the peak-aged G10 K alloy demonstrates superior strength-ductility synergy,with a yield strength(YS)of 216±1 MPa,an ultimate tensile strength(UTS)of 363±1 MPa,and an elongation(EL)of 8.7±0.6%.This study suggests that plasticity diminishes and precipitation strengthening is limited when the gadolinium content exceeds 15 wt.%.展开更多
Urban parks are essential habitats for birds in densely built environments.However,most studies focus only on horizontal features,overlooking the role of integrated vertical structures.Using bird records from the Chin...Urban parks are essential habitats for birds in densely built environments.However,most studies focus only on horizontal features,overlooking the role of integrated vertical structures.Using bird records from the China Bird Report(CBR) collected between 2020 and 2024,this study focused on major urban parks in Harbin,a cold highlatitude city in Northeast China.Using interpretable machine learning models,we assessed the impact of threedimensional(3D) park features on bird species richness and identified key variables along with their nonlinear relationships.Subsequently,we grouped bird species by ecological traits and applied ordination analysis to assess their differential abundance responses to the 3D environmental characteristics of urban parks.Results showed that:(1) urban park 3D environmental features had a certain influence on bird richness,among which disturbance from built-up land and the coverage of commercial buildings were the most important factors;(2) different bird groups responded differently to the urban park 3D environmental features.Specifically,waterbirds and generalist birds preferred mixed habitats dominated by water,wetlands,and tall vegetation,and exhibited significant edge effects caused by built-up land disturbance.In contrast,forest birds were mainly affected by greenspace configuration.Although they showed tolerance to human disturbance,this trend may increase the risk of biotic homogenization.The study used a 3D environmental framework integrating horizontal and vertical dimensions to explore how bird diversity is shaped,providing detailed recommendations for biodiversitysensitive park planning in Harbin.展开更多
基金supported by the National Key Research and Development Program of China (No.2021YFB3701000)the National Natural Science Foundation of China (Nos. 52401158, U21A2047, 52201129, 51821001,U2037601)+1 种基金the China Postdoctoral Science Foundation (No.2023M742219)the Postdoctoral Fellowship Program(Grade B) of CPSF (No. GZB20240419)
文摘Mg-Gd based alloys are an important class of high-performance Mg alloys.In this study,three Mg-Gd alloys with different gadolinium(Gd)contents:Mg-9.54Gd-0.40Zr(wt.%,G10 K),Mg-15.11Gd-0.35Zr(wt.%,G15 K)and Mg-19.67Gd-0.33Zr(wt.%,G20 K)were prepared by semicontinuous casting and subsequent solution and aging heat treatments.The role of Gd content on microstructures and mechanical properties of the Mg-Gd-Zr alloy is studied.All three as-cast alloys exhibit eutectic phases of Mg_(5)Gd,with the amount increasing as the Gd content rises.Mg_(5)Gd disappears after the solution heat treatment(the G10 K alloy solution-treated at 480℃ for 4 h,the G15 K alloy at 500℃ for 12 h and the G20 K alloy at 520℃ for 24 h,respectively).Aging heat treatment at 200℃ for 64 h after solution introduces numerous prismatic β' precipitates,with a significant increase in their area number density corresponding to increased Gd content.Additionally,the morphology of the β' precipitates exhibits distinct variations:the G10 K alloy is characterized by an enhanced aspect ratio.Consequently,the peak-aged G10 K alloy demonstrates superior strength-ductility synergy,with a yield strength(YS)of 216±1 MPa,an ultimate tensile strength(UTS)of 363±1 MPa,and an elongation(EL)of 8.7±0.6%.This study suggests that plasticity diminishes and precipitation strengthening is limited when the gadolinium content exceeds 15 wt.%.
基金supported by Natural Science Foundation of Heilongjiang Province of China [Grant number LH2023E007]。
文摘Urban parks are essential habitats for birds in densely built environments.However,most studies focus only on horizontal features,overlooking the role of integrated vertical structures.Using bird records from the China Bird Report(CBR) collected between 2020 and 2024,this study focused on major urban parks in Harbin,a cold highlatitude city in Northeast China.Using interpretable machine learning models,we assessed the impact of threedimensional(3D) park features on bird species richness and identified key variables along with their nonlinear relationships.Subsequently,we grouped bird species by ecological traits and applied ordination analysis to assess their differential abundance responses to the 3D environmental characteristics of urban parks.Results showed that:(1) urban park 3D environmental features had a certain influence on bird richness,among which disturbance from built-up land and the coverage of commercial buildings were the most important factors;(2) different bird groups responded differently to the urban park 3D environmental features.Specifically,waterbirds and generalist birds preferred mixed habitats dominated by water,wetlands,and tall vegetation,and exhibited significant edge effects caused by built-up land disturbance.In contrast,forest birds were mainly affected by greenspace configuration.Although they showed tolerance to human disturbance,this trend may increase the risk of biotic homogenization.The study used a 3D environmental framework integrating horizontal and vertical dimensions to explore how bird diversity is shaped,providing detailed recommendations for biodiversitysensitive park planning in Harbin.
