Six coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are em-ployed for examining the full evolution of the North Pacific mode water and Subtropical Countercurrent (STCC...Six coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are em-ployed for examining the full evolution of the North Pacific mode water and Subtropical Countercurrent (STCC) under global warming over 400 years following the Representative Concentration Pathways (RCP) 4.5. The mode water and STCC first show a sharp weakening trend when the radiative forcing increases, but then reverse to a slow strengthening trend of smaller magnitude after the radiative forcing is stablized. As the radiative forcing increases during the 21st century, the ocean warming is surface-intensified and decreases with depth, strengthening the upper ocean's stratification and becoming unfavorable for the mode water formation. Moving southward in the subtropical gyre, the shrinking mode water decelerates the STCC to the south. After the radiative forcing is stabilized in the 2070s, the subsequent warming is greater at the subsurface than at the sea surface, destabilizing the upper ocean and becoming favorable for the mode water formation. As a result, the mode water and STCC recover gradually after the radiative forc-ing is stabilized.展开更多
Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete dur...Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete during the penetration process. Grid STCC system with square steel tubes is a potential solution to protective structures. In this paper, experiments of 9-cell grid STCC targets penetrated by 12.7 mm Armor Piercing Projectile(APP) were performed. The influence of side length and thickness of steel tube,steel ratio and impact velocity on anti-penetration performance were taken into account. Additionally,single-cell square STCC targets were also designed and tested for comparison with the 9-cell grid STCC targets. Damage modes and parameters of the tested targets were measured and discussed. Moreover,the stiffness of radial confinement of grid STCC targets is achieved according to the elastic solution of infinite cylindrical shell in Winkler medium. Furthermore, the penetration resistance and depth of penetration(DOP) for grid STCC targets are obtained on the basis of the dynamic finite spherical cavityexpansion(FSCE) models including radial confinement effect. It is shown that the 9-cell grid STCC targets with optimal dimension match of thickness and side length of steel tube can reduce the DOP by about17 % and 23 % in comparison with the SIC targets and single-cell square STCC targets, respectively, due to both the confinement of square steel tube to concrete in the impacted cell and the additional confinement of the surrounding cells to the impacted cell;the penetration resistance and DOP of the grid and cellular STCC targets with similar steel ratio is close, and thus the grid STCC targets with simpler manufacturing process and excellent in-plane expandability are preferred in engineering practice;moreover, the predicted results of DOP model based on the FSCE models agree well with the tested results with the maximum disparity less than 12 % and the proposed model is more applicable to the grid and cellular STCC targets with high radial confinement.展开更多
Observations indicated that in the region of the Subtropical Countercurrent(STCC) over the Pacific (140°E-170°W, 19°N-28°N), the eddy kinetic energy over the western sideis much higher than that ov...Observations indicated that in the region of the Subtropical Countercurrent(STCC) over the Pacific (140°E-170°W, 19°N-28°N), the eddy kinetic energy over the western sideis much higher than that over the eastern side. The cause of such a behavior was theoreticallyinvestigated in this paper. The calculation of geostrophic current in this region indicates thatthere are relatively strong meridional geostrophic currents in this region even though the zonalcurrent is dominant in most seasons. Using a 2. 5-layer reduced-gravity model, ba-roclinicinstability of non-zonal current was discussed. It is found that at the western side of STCC thevertical shear of the meridional geostrophic current will be in favor of the ba-roclinicinstability, but at its eastern side it will suppress ba-roclinic instability, thus causing thegrowth of eddies over the western side much faster than that over the eastern side.展开更多
基金supported by the National Basic Research Program of China(2012CB955602)National Key Program for Developing Basic Science(2010CB428904)Natural Science Foundation of China(41176006 and 40921004)
文摘Six coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are em-ployed for examining the full evolution of the North Pacific mode water and Subtropical Countercurrent (STCC) under global warming over 400 years following the Representative Concentration Pathways (RCP) 4.5. The mode water and STCC first show a sharp weakening trend when the radiative forcing increases, but then reverse to a slow strengthening trend of smaller magnitude after the radiative forcing is stablized. As the radiative forcing increases during the 21st century, the ocean warming is surface-intensified and decreases with depth, strengthening the upper ocean's stratification and becoming unfavorable for the mode water formation. Moving southward in the subtropical gyre, the shrinking mode water decelerates the STCC to the south. After the radiative forcing is stabilized in the 2070s, the subsequent warming is greater at the subsurface than at the sea surface, destabilizing the upper ocean and becoming favorable for the mode water formation. As a result, the mode water and STCC recover gradually after the radiative forc-ing is stabilized.
基金the projects supported by the Natural Science Foundation of Hunan Province, China (No. 2018JJ2470 and 2021JJ30776)。
文摘Steel-tube-confined concrete(STCC) targets are provided with excellent anti-penetration performance over semi-infinite concrete(SIC) targets since the steel tube imposes passive restraint on the in-filled concrete during the penetration process. Grid STCC system with square steel tubes is a potential solution to protective structures. In this paper, experiments of 9-cell grid STCC targets penetrated by 12.7 mm Armor Piercing Projectile(APP) were performed. The influence of side length and thickness of steel tube,steel ratio and impact velocity on anti-penetration performance were taken into account. Additionally,single-cell square STCC targets were also designed and tested for comparison with the 9-cell grid STCC targets. Damage modes and parameters of the tested targets were measured and discussed. Moreover,the stiffness of radial confinement of grid STCC targets is achieved according to the elastic solution of infinite cylindrical shell in Winkler medium. Furthermore, the penetration resistance and depth of penetration(DOP) for grid STCC targets are obtained on the basis of the dynamic finite spherical cavityexpansion(FSCE) models including radial confinement effect. It is shown that the 9-cell grid STCC targets with optimal dimension match of thickness and side length of steel tube can reduce the DOP by about17 % and 23 % in comparison with the SIC targets and single-cell square STCC targets, respectively, due to both the confinement of square steel tube to concrete in the impacted cell and the additional confinement of the surrounding cells to the impacted cell;the penetration resistance and DOP of the grid and cellular STCC targets with similar steel ratio is close, and thus the grid STCC targets with simpler manufacturing process and excellent in-plane expandability are preferred in engineering practice;moreover, the predicted results of DOP model based on the FSCE models agree well with the tested results with the maximum disparity less than 12 % and the proposed model is more applicable to the grid and cellular STCC targets with high radial confinement.
文摘Observations indicated that in the region of the Subtropical Countercurrent(STCC) over the Pacific (140°E-170°W, 19°N-28°N), the eddy kinetic energy over the western sideis much higher than that over the eastern side. The cause of such a behavior was theoreticallyinvestigated in this paper. The calculation of geostrophic current in this region indicates thatthere are relatively strong meridional geostrophic currents in this region even though the zonalcurrent is dominant in most seasons. Using a 2. 5-layer reduced-gravity model, ba-roclinicinstability of non-zonal current was discussed. It is found that at the western side of STCC thevertical shear of the meridional geostrophic current will be in favor of the ba-roclinicinstability, but at its eastern side it will suppress ba-roclinic instability, thus causing thegrowth of eddies over the western side much faster than that over the eastern side.
