Based on the daily rainfall datasets from 740 stations in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, the relationship between the north-south anti-phase distribution(APD) of rainfall during Meiyu perio...Based on the daily rainfall datasets from 740 stations in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, the relationship between the north-south anti-phase distribution(APD) of rainfall during Meiyu periods and the Quasi-Biweekly Oscillation(QBWO) in the atmosphere was analyzed. Diagnostic results are as follows:(1) there was significant north-south oscillation of Meiyu rainfall during the 16 years from 1954 to 2005. Since the 1990 s, the APD enhanced significantly and showed 2- and 4-6-year period. In the region with more rainfall, the QBWO was always more active.(2) The APD of Meiyu and north-south movements of precipitation in eastern China belong to the same phase.(3) The 10-25 day filtered water vapor flux could spread to the area north of 30°N in 1991. The divergence of the water vapor flux which propagated from middle- and higher- latitudes to the of Yangtze-Huaihe River Basins(YHRB) was significant in 1991, but the latitudes that the water vapor flux could reach were further southward and there was no southward propagation of divergence in 1993.(4) The locations of Western Pacific Subtropical High(WPSH) and 10-25 day anti-cyclone, which modulated WPSH's advancement in and out of the South China Sea, were relatively northward in 1991. Furthermore, the vertical circulation showed north-south deviation between 1991 and 1993, just as other elements of the circulation did.展开更多
In this paper, we consider a model system with two identical time-delayed coupled layers. Synchronization and anti-phase synchronization are exhibited in the reactive system without diffusion term. New segmented spira...In this paper, we consider a model system with two identical time-delayed coupled layers. Synchronization and anti-phase synchronization are exhibited in the reactive system without diffusion term. New segmented spiral waves, which are constituted by many thin trips, are found in each layer of two identical time-delayed coupled layers, and are different from the segmented spiral waves in a water-in-oil aerosol sodium bis（2-ethylhexyl） sulfosuccinate （AOT） microemulsion （ME） （BZ-AOT system）, which consists of many small segments. ＂Anti-phase spiral wave synchronization＂ can be realized between the first layer and the second one. For different excitable parameters, we also give the minimum values of the coupling strength to generate segmented spiral waves and the tip orbits of spiral waves in the whole bilayer.展开更多
This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chiral...This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.展开更多
Transition of flows past a pair of side-by-side circular cylinders are investigated by numerical simulations and the bifurcation analysis of the numerical results. Various flow patterns behind the cylinder-pair have b...Transition of flows past a pair of side-by-side circular cylinders are investigated by numerical simulations and the bifurcation analysis of the numerical results. Various flow patterns behind the cylinder-pair have been identified by the gap ratio (G) and Reynolds number (Re). This study focus on transition of in-phase and anti-phase vortex shedding synchronized forms. A nested Cartesian-grid formulation, in combination with an effective immersed boundary method and a two-step fractional-step procedure, has been adopted to simulate the flows. Numerical results reveal that the in-phase and anti-phase vortex shedding flows at Re = 100 can co-exist at 2.08 ≤G≤ 2.58. Hysteresis loop with increasing/decreasing G at constant Reynolds number Re = 100 is reported.展开更多
Single crystal(SX)superalloys are required for full-operating-temperature mechanical properties.How-ever,the quest for intermediate temperature(IT)resistance often encounters a perplexing phenomenon:anomalous yielding...Single crystal(SX)superalloys are required for full-operating-temperature mechanical properties.How-ever,the quest for intermediate temperature(IT)resistance often encounters a perplexing phenomenon:anomalous yielding behavior coupled with an unexpected loss of ductility.This study delved into the tensile behavior of a[111]-oriented SX superalloy from room temperature(RT)to 1150℃,uncover-ing temperature-dependent tensile mechanisms where the interplay among phases and deferent de-fects governs plastic deformation.Desirable high strength-ductility properties were observed at IT,show-casing comparable strength with increased ductility.Microstructural evidences show that the primary strengthening effects stem from coupled interface boundary strengthening and anti-phase boundary(APB)strengthening,while the plasticity arises from planer defects transitioning from the stacking fault(SF)withinγphase at small strains,to superlattice SFs,ultimately to the erasure of superlattice SFs,leaving cutting dislocation pairs inγʹphase.Energy analysis of APB and SF,along with adherence to Schmid laws,reinforce the plausibility of such intricate defect interactions.The strength-ductility balance can be ascribed to the collective effect of preferentially generated dislocations and prompt formation of SF.This strategy of sequential defects’competition provides a new route for solving the strength-ductility trade-offof alloys.展开更多
基金Beijing Excellent Talents Cultivation ProjectOceanography Science Foundation for Youth Scholars of State Oceanic Administration(2013256)
文摘Based on the daily rainfall datasets from 740 stations in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, the relationship between the north-south anti-phase distribution(APD) of rainfall during Meiyu periods and the Quasi-Biweekly Oscillation(QBWO) in the atmosphere was analyzed. Diagnostic results are as follows:(1) there was significant north-south oscillation of Meiyu rainfall during the 16 years from 1954 to 2005. Since the 1990 s, the APD enhanced significantly and showed 2- and 4-6-year period. In the region with more rainfall, the QBWO was always more active.(2) The APD of Meiyu and north-south movements of precipitation in eastern China belong to the same phase.(3) The 10-25 day filtered water vapor flux could spread to the area north of 30°N in 1991. The divergence of the water vapor flux which propagated from middle- and higher- latitudes to the of Yangtze-Huaihe River Basins(YHRB) was significant in 1991, but the latitudes that the water vapor flux could reach were further southward and there was no southward propagation of divergence in 1993.(4) The locations of Western Pacific Subtropical High(WPSH) and 10-25 day anti-cyclone, which modulated WPSH's advancement in and out of the South China Sea, were relatively northward in 1991. Furthermore, the vertical circulation showed north-south deviation between 1991 and 1993, just as other elements of the circulation did.
基金The project supported by National Natural Science Foundation of China under Grant No.10647127National Natural Science Foundation of China for Major Projects under Grant No.10335010the Natural Science Foundation of Hebei Province of China under Grant No.A2006000128
文摘In this paper, we consider a model system with two identical time-delayed coupled layers. Synchronization and anti-phase synchronization are exhibited in the reactive system without diffusion term. New segmented spiral waves, which are constituted by many thin trips, are found in each layer of two identical time-delayed coupled layers, and are different from the segmented spiral waves in a water-in-oil aerosol sodium bis（2-ethylhexyl） sulfosuccinate （AOT） microemulsion （ME） （BZ-AOT system）, which consists of many small segments. ＂Anti-phase spiral wave synchronization＂ can be realized between the first layer and the second one. For different excitable parameters, we also give the minimum values of the coupling strength to generate segmented spiral waves and the tip orbits of spiral waves in the whole bilayer.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60768001 and 10464002)
文摘This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.
文摘Transition of flows past a pair of side-by-side circular cylinders are investigated by numerical simulations and the bifurcation analysis of the numerical results. Various flow patterns behind the cylinder-pair have been identified by the gap ratio (G) and Reynolds number (Re). This study focus on transition of in-phase and anti-phase vortex shedding synchronized forms. A nested Cartesian-grid formulation, in combination with an effective immersed boundary method and a two-step fractional-step procedure, has been adopted to simulate the flows. Numerical results reveal that the in-phase and anti-phase vortex shedding flows at Re = 100 can co-exist at 2.08 ≤G≤ 2.58. Hysteresis loop with increasing/decreasing G at constant Reynolds number Re = 100 is reported.
基金sponsored by the National Natural Science Foundations of China(Nos.52101116,52301126,and 92360302)the Science Center for Gas Turbine Project(Nos.P2022-A-I-001-001 and P2022-A-Ⅰ-002-002)+2 种基金the National Science and Technology Major Project(No.2019-Ⅵ-0016-0131)the Beijing Nova Program(No.20230484318)the Key R&D Program of Zhejiang(No.2024SSYS0076).
文摘Single crystal(SX)superalloys are required for full-operating-temperature mechanical properties.How-ever,the quest for intermediate temperature(IT)resistance often encounters a perplexing phenomenon:anomalous yielding behavior coupled with an unexpected loss of ductility.This study delved into the tensile behavior of a[111]-oriented SX superalloy from room temperature(RT)to 1150℃,uncover-ing temperature-dependent tensile mechanisms where the interplay among phases and deferent de-fects governs plastic deformation.Desirable high strength-ductility properties were observed at IT,show-casing comparable strength with increased ductility.Microstructural evidences show that the primary strengthening effects stem from coupled interface boundary strengthening and anti-phase boundary(APB)strengthening,while the plasticity arises from planer defects transitioning from the stacking fault(SF)withinγphase at small strains,to superlattice SFs,ultimately to the erasure of superlattice SFs,leaving cutting dislocation pairs inγʹphase.Energy analysis of APB and SF,along with adherence to Schmid laws,reinforce the plausibility of such intricate defect interactions.The strength-ductility balance can be ascribed to the collective effect of preferentially generated dislocations and prompt formation of SF.This strategy of sequential defects’competition provides a new route for solving the strength-ductility trade-offof alloys.
