The widely distributed red clay sediment underlying the Chinese Loess Plateau truly records the Neogene environmental evolution, and its genesis and development are intrinsically related to the uplift processes of the...The widely distributed red clay sediment underlying the Chinese Loess Plateau truly records the Neogene environmental evolution, and its genesis and development are intrinsically related to the uplift processes of the Tibetan Plateau and the evolution of East Asia monsoon system. In this paper, a detailed magnetostratigraphy of a loess-red clay section （107°13′E, 35°02′N） from the central Loess Plateau is reported. The loess-red clay sequence is composed of 175 m Quaternary loess-paleosol sequence and 128 m Neogene red clay sediments. Based on the correlation with the standard geomagnetic polarity time scale, the paleomagnetic results indicate that the age of Chaona red clay sequence extends to 08.1 Ma, which is the older red clay deposition in the central Chinese Loess Plateau. The commencement of red clay at -8.1 Ma may imply that the Ordos planation surface was broken by the movement of the Haiyuan-Liupanshan Faults, which was related to the uplift of the Tibetan Plateau induced by the collision of India Plate and Eurasian Plate. And the western part adjacent to the Tibetan Plateau was uplifted to form the embryo of the Liupan Shan （Mts.） and the eastern part was down-faulted to receive red clay deposition. We link this faulting to an initial uplift of the Tibetan Plateau. The undulating nature of the broken Ordos planation surface may explain the chronological differences and depth discrepancies among various cross-sections of red clay.展开更多
The growth of mixing zone on an interface induced by Richtmyer-Meshkov(RM)instability occurs frequently in natural phenomena and in engineering applications.Usually,the medium on which the RM instability happens is in...The growth of mixing zone on an interface induced by Richtmyer-Meshkov(RM)instability occurs frequently in natural phenomena and in engineering applications.Usually,the medium on which the RM instability happens is inhomogeneous,the effect of medium inhomogeneity on the growth of the mixing zone during the RM instability is still not clear.Therefore,it is necessary to investigate the RM instability in inhomogeneous medium.Based on a high-order computational scheme,the interactions of a density interface with an incident shock wave(ISW)in inhomogeneous medium are numerically simulated by solving the compressible Navier-Stokes equations.The effect of the inhomogeneity on the interface evolution after the passage of ISW through the interface is investigated.The results show that the interface morphology develops in a distinctive "spike-spike"structure in inhomogeneous medium.Particularly,the spike structure on the bottom of the interface is due to the reverse induction of RM instability by curved ISW or reflected shock wave.With the increase of inhomogeneity,the growth rate of the mixing zone width on interface increases,and the wave patterns caused by interaction between the shock wave and interface are more complex.Compared with RM instability in homogeneous medium,the inhomogeneous distribution of the density in medium further enhances the baroclinic effect and induces larger vorticity in flow field.Therefore,the interface is stretched much more significantly under the induction of enhanced vorticity in inhomogeneous medium.Based on above analyses,a model for predicting the growth of mixing zone width on the interface after the passage of ISW is proposed,in order to provide a useful method for evaluations of perturbation growth behavior during the RM instability in inhomogeneous medium.展开更多
β-decay properties of N=18-22,Z=10-14 nuclei are analyzed with a new shell-model Hamiltonian using the Gogny densitydependent interaction.The Gogny force which has been widely and successfully used in mean-field theo...β-decay properties of N=18-22,Z=10-14 nuclei are analyzed with a new shell-model Hamiltonian using the Gogny densitydependent interaction.The Gogny force which has been widely and successfully used in mean-field theory can provide reasonable two-body matrix elements for cross-shell calculations.The log f t values andβ-decay level schemes are systematically studied using the D1S-Gogny interaction and compared with the SDPF-M results and experimental data.It is shown that the new Hamiltonian provides reliable results forβ-decay along with subtle level schemes for this region.Shell-model calculations with Gogny interaction can lead to a successful description of nuclei in and around the N=20 island of inversion and supplements experiment where sufficient data are not available.展开更多
Our objective is a better understanding of the role of physical properties of real fluids in the thermodynamics of cavitation in impure water. An extension to the classical homogenous nucleation theory suitable for mi...Our objective is a better understanding of the role of physical properties of real fluids in the thermodynamics of cavitation in impure water. An extension to the classical homogenous nucleation theory suitable for mixtures is presented in attempt to address the discrepancy between the theoretical predictions and practical observations of cavitation rates in water at normal temperatures. The extension takes into account the non-equilibrium (dissipative) effects involved in nuclei formation through a substance dependent correction coefficient to be determined experimentally. The theory of thermodynamic fluctuations is applied to derive the work of formation of a bubble nucleus. The value of the correction coefficient is estimated using preliminary experimental data from a convergent-divergent nozzle. An application of the results to the numerical prediction of the cavitation zones in a radial-flow water pump is shown.展开更多
A U-Pb-He double-dating method is applied to detrital zircons with core-rim structure from the Ganges River in order to de- termine average short and long-term exhumation rates for the Himalayas. Long-term rates are c...A U-Pb-He double-dating method is applied to detrital zircons with core-rim structure from the Ganges River in order to de- termine average short and long-term exhumation rates for the Himalayas. Long-term rates are calculated from the U/Pb ages of metamorphic rims of the grains that formed during the Himalayan orogeny and their crystallization temperatures, which are calculated from the Ti-in-zircon thermometer. Short-term rates are calculated from （U-Th）/He ages of the grains with appro- priate closure temperatures. The results show that short-term rates for the Himalayas, which range from 0.70 ± 0.09 to 2.67 ± 0.40 km/Myr and average 1.75 ± 0.59 （1δ） km/Myr, are higher and more varied than the long-term rates, which range from 0.84 ±0.16 to 1.85 ± 0.35 km/Myr and average 1.26 ±0.25 （let） km/Myr. The differences between the long-term and short-term rates can be attributed to continuous exhumation of the host rocks in different mechanisms in continental collision orogen. The U/Pb ages of 44.0 ± 3.7 to 18.3 ±0.5 Ma for the zircon rims indicate a protracted episode of -：25 Myr for regional metamorphism of the host rocks at deeper crust, whereas the （U-Th）/He ages of 42.2 ± 1.8 to 1.3 ± 0.2 Ma for the zircon grains represent a protracted period of -40 Myr for exposure of the host rocks to shallower crustal level. In particular, the oldest （U-Th）/He ages of the zircon grains are close to the oldest U/Pb ages for the rims, indicating that some parcels of the rocks that contain zircons were rapidly exhumed from deep to shallow levels in the stage of collisional orogeny. On the other hand, some parcels of the rocks may have been carried upwards by thrust faults in the post-collisional stage. The parcels could be carried upwards by the thrust faults that steepen as they near the surface, or by transient movement faults so that areas of rapid exhu- mation became areas of slow exhumation and visa versa on a time scale of a few Myr in order to maintain the continuous ex- humation. In this regard, the Ganges River must be preferentially sampling areas that are currently undergoing above average rates of uplift.展开更多
基金supported by the National Natural Science Foundation of China(NO:40202019,90102017,40121303)National Basic Research Program of China(2004CB720202)China Postdoctoral Fund
文摘The widely distributed red clay sediment underlying the Chinese Loess Plateau truly records the Neogene environmental evolution, and its genesis and development are intrinsically related to the uplift processes of the Tibetan Plateau and the evolution of East Asia monsoon system. In this paper, a detailed magnetostratigraphy of a loess-red clay section （107°13′E, 35°02′N） from the central Loess Plateau is reported. The loess-red clay sequence is composed of 175 m Quaternary loess-paleosol sequence and 128 m Neogene red clay sediments. Based on the correlation with the standard geomagnetic polarity time scale, the paleomagnetic results indicate that the age of Chaona red clay sequence extends to 08.1 Ma, which is the older red clay deposition in the central Chinese Loess Plateau. The commencement of red clay at -8.1 Ma may imply that the Ordos planation surface was broken by the movement of the Haiyuan-Liupanshan Faults, which was related to the uplift of the Tibetan Plateau induced by the collision of India Plate and Eurasian Plate. And the western part adjacent to the Tibetan Plateau was uplifted to form the embryo of the Liupan Shan （Mts.） and the eastern part was down-faulted to receive red clay deposition. We link this faulting to an initial uplift of the Tibetan Plateau. The undulating nature of the broken Ordos planation surface may explain the chronological differences and depth discrepancies among various cross-sections of red clay.
文摘The growth of mixing zone on an interface induced by Richtmyer-Meshkov(RM)instability occurs frequently in natural phenomena and in engineering applications.Usually,the medium on which the RM instability happens is inhomogeneous,the effect of medium inhomogeneity on the growth of the mixing zone during the RM instability is still not clear.Therefore,it is necessary to investigate the RM instability in inhomogeneous medium.Based on a high-order computational scheme,the interactions of a density interface with an incident shock wave(ISW)in inhomogeneous medium are numerically simulated by solving the compressible Navier-Stokes equations.The effect of the inhomogeneity on the interface evolution after the passage of ISW through the interface is investigated.The results show that the interface morphology develops in a distinctive "spike-spike"structure in inhomogeneous medium.Particularly,the spike structure on the bottom of the interface is due to the reverse induction of RM instability by curved ISW or reflected shock wave.With the increase of inhomogeneity,the growth rate of the mixing zone width on interface increases,and the wave patterns caused by interaction between the shock wave and interface are more complex.Compared with RM instability in homogeneous medium,the inhomogeneous distribution of the density in medium further enhances the baroclinic effect and induces larger vorticity in flow field.Therefore,the interface is stretched much more significantly under the induction of enhanced vorticity in inhomogeneous medium.Based on above analyses,a model for predicting the growth of mixing zone width on the interface after the passage of ISW is proposed,in order to provide a useful method for evaluations of perturbation growth behavior during the RM instability in inhomogeneous medium.
基金supported by the National Key Basic Research Program of China(Grant No.2013CB834402)the National Natural Science Foundation of China(Grant Nos.11235001,11320101004,and 11575007)the China-U.S.Theory Institute for Physics with Exotic Nuclei(CUSTIPEN)funded by the U.S.Department of Energy,Office of Science(Grant No.DESC0009971)
文摘β-decay properties of N=18-22,Z=10-14 nuclei are analyzed with a new shell-model Hamiltonian using the Gogny densitydependent interaction.The Gogny force which has been widely and successfully used in mean-field theory can provide reasonable two-body matrix elements for cross-shell calculations.The log f t values andβ-decay level schemes are systematically studied using the D1S-Gogny interaction and compared with the SDPF-M results and experimental data.It is shown that the new Hamiltonian provides reliable results forβ-decay along with subtle level schemes for this region.Shell-model calculations with Gogny interaction can lead to a successful description of nuclei in and around the N=20 island of inversion and supplements experiment where sufficient data are not available.
文摘Our objective is a better understanding of the role of physical properties of real fluids in the thermodynamics of cavitation in impure water. An extension to the classical homogenous nucleation theory suitable for mixtures is presented in attempt to address the discrepancy between the theoretical predictions and practical observations of cavitation rates in water at normal temperatures. The extension takes into account the non-equilibrium (dissipative) effects involved in nuclei formation through a substance dependent correction coefficient to be determined experimentally. The theory of thermodynamic fluctuations is applied to derive the work of formation of a bubble nucleus. The value of the correction coefficient is estimated using preliminary experimental data from a convergent-divergent nozzle. An application of the results to the numerical prediction of the cavitation zones in a radial-flow water pump is shown.
基金supported by the Australian Research Council Discovery Project(Grant No.DP 0556923)the Chinese Academy of Sciences Distinguished ProfessorshipGuangzhou Institute of Geochemistry,Chinese Academy of Sciences(Grant No.Y234041001)
文摘A U-Pb-He double-dating method is applied to detrital zircons with core-rim structure from the Ganges River in order to de- termine average short and long-term exhumation rates for the Himalayas. Long-term rates are calculated from the U/Pb ages of metamorphic rims of the grains that formed during the Himalayan orogeny and their crystallization temperatures, which are calculated from the Ti-in-zircon thermometer. Short-term rates are calculated from （U-Th）/He ages of the grains with appro- priate closure temperatures. The results show that short-term rates for the Himalayas, which range from 0.70 ± 0.09 to 2.67 ± 0.40 km/Myr and average 1.75 ± 0.59 （1δ） km/Myr, are higher and more varied than the long-term rates, which range from 0.84 ±0.16 to 1.85 ± 0.35 km/Myr and average 1.26 ±0.25 （let） km/Myr. The differences between the long-term and short-term rates can be attributed to continuous exhumation of the host rocks in different mechanisms in continental collision orogen. The U/Pb ages of 44.0 ± 3.7 to 18.3 ±0.5 Ma for the zircon rims indicate a protracted episode of -：25 Myr for regional metamorphism of the host rocks at deeper crust, whereas the （U-Th）/He ages of 42.2 ± 1.8 to 1.3 ± 0.2 Ma for the zircon grains represent a protracted period of -40 Myr for exposure of the host rocks to shallower crustal level. In particular, the oldest （U-Th）/He ages of the zircon grains are close to the oldest U/Pb ages for the rims, indicating that some parcels of the rocks that contain zircons were rapidly exhumed from deep to shallow levels in the stage of collisional orogeny. On the other hand, some parcels of the rocks may have been carried upwards by thrust faults in the post-collisional stage. The parcels could be carried upwards by the thrust faults that steepen as they near the surface, or by transient movement faults so that areas of rapid exhu- mation became areas of slow exhumation and visa versa on a time scale of a few Myr in order to maintain the continuous ex- humation. In this regard, the Ganges River must be preferentially sampling areas that are currently undergoing above average rates of uplift.
