The cooling rate during vitrification is critical for determining the mechanical properties of metallic glasses.However,the structural origin of the cooling rate effect on mechanical behaviors is unclear.In this work,...The cooling rate during vitrification is critical for determining the mechanical properties of metallic glasses.However,the structural origin of the cooling rate effect on mechanical behaviors is unclear.In this work,a systematical investigation of the cooling rate effect on the deformation mode,shear band nucleation,and nanoscale heterogeneous structure was conducted in three Fe-based metallic glasses.The brittle to ductile deformation transition was observed when increasing the cooling rate.Meanwhile,the governing shear band nucleation site from high load site to low load site appears the synchronous tran-sition.By studying the corresponding nanoscale heterogeneous structure,it was found that nanoscale viscoelastic transition from solid-like to liquid-like as increasing cooling rate enables ductile deformation.The current work not only reveals the nanoscale structural origin of the cooling rate effect on the de-formation behaviors,but also provides a new route to design ductile metallic glasses by freezing more nanoscale liquid-like regions during cooling.展开更多
Three representative types of houses in Beijing were selected and, in each type, smoking and nonsmoking households were compared. IP, RP. and CO concentrations in the living room and kitchen were monitored during each...Three representative types of houses in Beijing were selected and, in each type, smoking and nonsmoking households were compared. IP, RP. and CO concentrations in the living room and kitchen were monitored during each season. and the level of COHb in the heads of the households were measured. The study showed that indoor air pollution was rather severe, especially during winter. when paniculate concentrations markedly exceeded the standard and CO concentration was as high as 47 ppm. Indoor air pollution was closely related to the type of house, particularly to the mode of heating. In houses. of the same type, pollution improved greatly after central heating facilities were installed. Analysis of 30 elements revealed that pollution was typically caused by coal burning. aggravated by dusty wind, but high indoor Pb levels were probably due to the use of LPG for cooking. In our study the effect of cigarette smoking was sometimes masked by the severe indoor pollution. (C)1990 Academic Press, Inc.展开更多
基金supported by the National Natural Science Foun-dation of China(Nos.52201194,52222105,52261028,52001269,92163108,52231006)the 3315 Innovation Youth Talent in Ningbo City(No.2021A123G)+3 种基金the Youth Innovation Promotion Association CAS(No.2019296)the Zhejiang Provincial Natural Science Foun-dation of China(No.LR22E010004)the Zhejiang Provincial Natu-ral Science Foundation Regional Innovation and Development Joint Foundation with Quzhou City(No.LZY23E010002)the Nat-ural Science Foundation of Xinjiang Uygur Autonomous Region of China(No.2022D01C383).
文摘The cooling rate during vitrification is critical for determining the mechanical properties of metallic glasses.However,the structural origin of the cooling rate effect on mechanical behaviors is unclear.In this work,a systematical investigation of the cooling rate effect on the deformation mode,shear band nucleation,and nanoscale heterogeneous structure was conducted in three Fe-based metallic glasses.The brittle to ductile deformation transition was observed when increasing the cooling rate.Meanwhile,the governing shear band nucleation site from high load site to low load site appears the synchronous tran-sition.By studying the corresponding nanoscale heterogeneous structure,it was found that nanoscale viscoelastic transition from solid-like to liquid-like as increasing cooling rate enables ductile deformation.The current work not only reveals the nanoscale structural origin of the cooling rate effect on the de-formation behaviors,but also provides a new route to design ductile metallic glasses by freezing more nanoscale liquid-like regions during cooling.
文摘Three representative types of houses in Beijing were selected and, in each type, smoking and nonsmoking households were compared. IP, RP. and CO concentrations in the living room and kitchen were monitored during each season. and the level of COHb in the heads of the households were measured. The study showed that indoor air pollution was rather severe, especially during winter. when paniculate concentrations markedly exceeded the standard and CO concentration was as high as 47 ppm. Indoor air pollution was closely related to the type of house, particularly to the mode of heating. In houses. of the same type, pollution improved greatly after central heating facilities were installed. Analysis of 30 elements revealed that pollution was typically caused by coal burning. aggravated by dusty wind, but high indoor Pb levels were probably due to the use of LPG for cooking. In our study the effect of cigarette smoking was sometimes masked by the severe indoor pollution. (C)1990 Academic Press, Inc.
