The zonal width of the Ural blocking(UB)is a potentially crucial characteristic related to cold events in Eurasia.While most studies focus on the intensity,duration,frequency,and mobility of blocking events,the import...The zonal width of the Ural blocking(UB)is a potentially crucial characteristic related to cold events in Eurasia.While most studies focus on the intensity,duration,frequency,and mobility of blocking events,the importance of UB zonal width has often been overlooked.Against the backdrop of the declining Arctic sea ice concentration(SIC),the changes in UB zonal width and their association with winter extreme cold events in China remain unclear and require further investigation.This study defines the UB zonal width as the longitude difference between the easternmost and westernmost points of the 120-gpm contour line in the 500-hPa geopotential height(Z500)anomaly field.Based on the NCEP/NCA Rreanalysis data and SIC observations during 1970–2020,the UB width and coldair events under varied SIC conditions are examined.It is found that as SIC decreases in the Barents–Kara Sea(BKS),the UB extends zonally,coinciding with the transition of the North Atlantic Oscillation(NAO)from its positive to negative phase.Additionally,linear baroclinic model(LBM)simulations indicate that as the BKS warms,the zonal width of the UB broadens.Concurrently,warming sea surface temperatures(SST)in the BKS lead to decreased 500-hPa zonal wind(U500)and meridional potential vorticity gradient(PVy)over mid–high latitudes in Eurasia.As a result,energy dispersion weakens and nonlinearity strengthens in the Ural region,resulting in a more zonal extension of the UB.Consequently,the frequency of winter cold events of varying intensities in China increases,such as high-tolow latitude(H–L)and middle-to-low latitude(M–L)cold events.For H–L cold events,both intensity and frequency are higher during low SIC years when the UB widens.Conversely,for M–L events,there is no significant difference in the relationship of UB and cold air intrusion between high and low SIC years.Overall,reduced BKS SIC leads to a more zonal extension of the UB,facilitating the southward movement of cold air and influencing southern China.展开更多
An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treat...An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treatment processes. The result shows that with decreasing prior austenite grain size, both the packet size and block width decrease, while the lath width has virtually no change. Accordingly, both strength and toughness increase, while total elongation decreases. The yield strength has a Hall Petch type relationship with the prior austenite grain size, packet size and block width, and the block width may be regarded as a key factor influencing strength. On the other hand, the ductile to brittle transition temperature （DBTT） is found to be more related lo the packet size, which may be considered as a dominant factor influencing toughness.展开更多
基金Supported by the National Natural Science Foundation of China(42375061)National Key Research and Development Program of China(2023YFF0805101).
文摘The zonal width of the Ural blocking(UB)is a potentially crucial characteristic related to cold events in Eurasia.While most studies focus on the intensity,duration,frequency,and mobility of blocking events,the importance of UB zonal width has often been overlooked.Against the backdrop of the declining Arctic sea ice concentration(SIC),the changes in UB zonal width and their association with winter extreme cold events in China remain unclear and require further investigation.This study defines the UB zonal width as the longitude difference between the easternmost and westernmost points of the 120-gpm contour line in the 500-hPa geopotential height(Z500)anomaly field.Based on the NCEP/NCA Rreanalysis data and SIC observations during 1970–2020,the UB width and coldair events under varied SIC conditions are examined.It is found that as SIC decreases in the Barents–Kara Sea(BKS),the UB extends zonally,coinciding with the transition of the North Atlantic Oscillation(NAO)from its positive to negative phase.Additionally,linear baroclinic model(LBM)simulations indicate that as the BKS warms,the zonal width of the UB broadens.Concurrently,warming sea surface temperatures(SST)in the BKS lead to decreased 500-hPa zonal wind(U500)and meridional potential vorticity gradient(PVy)over mid–high latitudes in Eurasia.As a result,energy dispersion weakens and nonlinearity strengthens in the Ural region,resulting in a more zonal extension of the UB.Consequently,the frequency of winter cold events of varying intensities in China increases,such as high-tolow latitude(H–L)and middle-to-low latitude(M–L)cold events.For H–L cold events,both intensity and frequency are higher during low SIC years when the UB widens.Conversely,for M–L events,there is no significant difference in the relationship of UB and cold air intrusion between high and low SIC years.Overall,reduced BKS SIC leads to a more zonal extension of the UB,facilitating the southward movement of cold air and influencing southern China.
文摘An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treatment processes. The result shows that with decreasing prior austenite grain size, both the packet size and block width decrease, while the lath width has virtually no change. Accordingly, both strength and toughness increase, while total elongation decreases. The yield strength has a Hall Petch type relationship with the prior austenite grain size, packet size and block width, and the block width may be regarded as a key factor influencing strength. On the other hand, the ductile to brittle transition temperature （DBTT） is found to be more related lo the packet size, which may be considered as a dominant factor influencing toughness.
