The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)feature intertwined Dirac fermions,topological flat bands,and van Hove singularities(vHS)near the Fermi level,which give rise to a range of exotic,strongly correlated phenomena...The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)feature intertwined Dirac fermions,topological flat bands,and van Hove singularities(vHS)near the Fermi level,which give rise to a range of exotic,strongly correlated phenomena such as charge density waves(CDW)and superconductivity.Although the vHS from V 3d states have been implicated in CDW formation,their three-dimensional nature and temperature evolution remain poorly understood.In this study,we used high-resolution angle-resolved photoemission spectroscopy and density functional theory to reveal pronounced out-of-plane dispersion of vHS and their temperature dependence in KV_(3)Sb_(5).The identified c-axis band folding and scattering channels were directly linked to the CDW order.These results demonstrate that the CDW transition in this family involves cooperative coupling between electron correlations and structural modulation along the c axis.This offers new insights into the interplay of topology,correlations,and lattice instabilities in kagome metals.展开更多
The spatial-temporal measurement of complex wave evolution is significant in studying wave-structure interactions.Current methods,such as that using wave probes,have shown limitations in measuring the wave evolution a...The spatial-temporal measurement of complex wave evolution is significant in studying wave-structure interactions.Current methods,such as that using wave probes,have shown limitations in measuring the wave evolution around structures in laboratories.In this study,an improved stereo imaging method is proposed for measuring the wave evolution around a fixed structure.Regular wave tests were conducted on a fixed surface-piercing square column in a wave flume to validate the reliability and accuracy of the proposed method.A flexible markernet made of foam particles was arranged around the column to pro-vide Lambertian features for the water surface.Two synchronized stereo imaging systems covered all the surrounding areas of the column and provided stereo pair sequences for wave evolution.Subsequently,image segmentation techniques were used to mask the low-confidence disparities in stereo matching,and finally,three-dimensional(3D)wave surfaces were reconstructed in the time sequence.The time histories of the wave elevations at particular locations were extracted and agreed well with the measurements of wave probes with an average bias of 2.4%.Subsequently,the reconstructed 3D wave field was sliced,exhibiting the instantaneous profiles that agreed with the measurements of wave probes.Moreover,the wave run-up height ratios were consistent with those of a previous study,thereby verifying the method’s accuracy from the perspective of spatial evolution.The results demonstrated that the proposed method was capable of precisely measuring the spatial-temporal evolution of the wave field around the square column and displayed potential for application in more studies on wave-structure interactions.展开更多
Based on the Navier-Stokes （N-S） equations for viscous, incompressible fluid and the VOF method, 2-D and 3-D Numerical Wave Tanks （NWT） for nonlinear shallow water waves are built. The dynamic mesh technique is ap...Based on the Navier-Stokes （N-S） equations for viscous, incompressible fluid and the VOF method, 2-D and 3-D Numerical Wave Tanks （NWT） for nonlinear shallow water waves are built. The dynamic mesh technique is applied, which can save computational resources dramatically for the simulation of solitary wave propagating at a constant depth. Higher order approximation for cnoidal wave is employed to generate high quality waves. Shoaling and breaking of solitary waves over different slopes are simulated and analyzed systematically. Wave runup on structures is also investigated. The results agree very well with experimental data or analytical solutions.展开更多
Research on the wave field evolution law is highly significant to the fields of offshore engineering and marine resource development.Numerical simulations have been conducted for high-precision wave field evolution,th...Research on the wave field evolution law is highly significant to the fields of offshore engineering and marine resource development.Numerical simulations have been conducted for high-precision wave field evolution,thus providing short-term wave field prediction.However,its evolution occurs over a long period of time,and its accuracy is difficult to improve.In recent years,the use of machine learning methods to study the evolution of wave field has received increasing attention from researchers.This paper proposes a wave field evolution method based on deep convolutional neural networks.This method can effectively correlate the spa-tiotemporal characteristics of wave data via convolution operation and directly obtain the offshore forecast results of the Bohai Sea and the Yellow Sea.The attention mechanism,multi-scale path design,and hard example mining training strategy are introduced to suppress the interference caused by Weibull distributed wave field data and improve the accuracy of the proposed wave field evolu-tion.The 72-and 480-h evolution experiment results in the Bohai Sea and the Yellow Sea show that the proposed method in this pa-per has excellent forecast accuracy and timeliness.展开更多
In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based ...In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution, we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries, where the viscous damping of the r-modes and its resultant effects are taken into account. The numerical results show that, for both kinds of NSs, the differential rotation can significantly prolong the duration of the r-modes. As a result, the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years. Moreover, the persistent radiation of a quasi-monochromatic gravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation. This increases the detectability of gravitational waves from both young isolated and old accreting NSs.展开更多
This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional l...This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.展开更多
The average variational principle was employed in this paper to study the evolution of large-scale and slowly varying Rossby wave packet with basic flow both in barotropic and baroclinic atmospheres. The evolution of ...The average variational principle was employed in this paper to study the evolution of large-scale and slowly varying Rossby wave packet with basic flow both in barotropic and baroclinic atmospheres. The evolution of the structure of Rossby wave packet with both time and space was studied. The results obtained in this paper are similar to the results of by WKBJ method. In addition, the dispersive process of the wave packet was analysed by taking Gaussian type wave packet as an initial disturbance. The valid time scale for application of wave packet theory in the atmosphere was obtained.展开更多
We present a fully time-dependent quantum wave packet evolution method for investigating molecular dynamics in intense laser fields.This approach enables the simultaneous treatment of interactions among multiple elect...We present a fully time-dependent quantum wave packet evolution method for investigating molecular dynamics in intense laser fields.This approach enables the simultaneous treatment of interactions among multiple electronic states while simultaneously tracking their time-dependent electronic,vibrational,and rotational dynamics.As an illustrative example,we consider neutral H_(2)molecules and simulate the laser-induced excitation dynamics of electronic and rotational states in strong laser fields,quantitatively distinguishing the respective contributions of electronic dipole transitions(within the classical-field approximation)and non-resonant Raman processes to the overall molecular dynamics.Furthermore,we precisely evaluate the relative contributions of direct tunneling ionization from the ground state and ionization following electronic excitation in the strong-field ionization of H_(2).The developed methodology shows strong potential for performing high-precision theoretical simulations of electronic-vibrational-rotational state excitations,ionization,and dissociation dynamics in molecules and their ions under intense laser fields.展开更多
Time evaluation of wave functions for any quantum mechanical system/particle is essential nevertheless quantum mechanical counterpart of the time dependant classical wave equation does simply not appear. Epistemologic...Time evaluation of wave functions for any quantum mechanical system/particle is essential nevertheless quantum mechanical counterpart of the time dependant classical wave equation does simply not appear. Epistemologically and ontologically considered time dependant momentum operator is initially defined and an Alternative Time Dependant Schrodinger Wave Equation (ATDSWE) is plainly derived. Consequent equation is primarily solved for the free particles, in a closed system, signifying a good agreement with the outcomes of the ordinary TDSWE. Free particle solution interestingly goes further possibly tracing some signs of new pathways to resolve the mysterious quantum world.展开更多
Spectral bandwidth is a relevant parameter of water wave evolution and is commonly used to represent the number of wave components involved in wave-wave interactions.However,whether these two parameters are equivalent...Spectral bandwidth is a relevant parameter of water wave evolution and is commonly used to represent the number of wave components involved in wave-wave interactions.However,whether these two parameters are equivalent is an open question.Following the high-order spectral method and taking the weakly modulated Stokes wave train as the initial condition,the relationship between the spectral bandwidth and the number of wave components is investigated in this work.The results showed that the number of wave components can vary with the same spectral bandwidth and that distinct wave profiles emerge from different numbers of wave components.With a new definition of significant wave components,the characteristics of this parameter in the long-time wave evolution are discussed,along with its relationship with common parameters,including the wave surface maximum and the wave height.The results reveal that the wave surface evolution trend of different numbers of significant wave components(Ns)is the same from a holistic perspective,while the difference between them also exists,mainly in locations where extreme waves occur.Furthermore,there is a negative correlation between r(aj/a_(0))and wave surface maximum(η_(max)/a_(0))and wave height(H_(max)and Hs).The evolution trends of the relative errors(RE)ofη_(max)/a_(0),H_(max),and Hs of different Ns show the periodic recurrence of modulation and demodulation in the early stage when the Benjamin-Feir instability is dominated.The difference is that in the later stage,the RE ofη_(max)/a_(0)and H_(max)is chaotic and irregular,while those of Hs gradually stabilize near an equilibrium value.Furthermore,we discuss the relationship between the mean relative error(MRE)and r.Forη_(max)/a_(0),MRE and r show a logarithmic relationship,while for H_(max)and Hs,a quadratic relationship exists between them.Therefore,the choice of Ns is also important for extreme waves and is particularly meaningful for wave generation experiments in the wave flume.展开更多
The evolution of the nonlinear wave groups in deep water is investigated through laboratory measurements and numerical analysis.Laboratory experiments are conducted in deep-water wave tank,focusing on the characterist...The evolution of the nonlinear wave groups in deep water is investigated through laboratory measurements and numerical analysis.Laboratory experiments are conducted in deep-water wave tank,focusing on the characteristics of breaking waves arising from the evolved wave train.Some quantitative results are obtained for the significant breaking wave train,including the surface elevation time series,the local geometry,and the energy dissipation.A nonlinear model for the evolution of the wave groups in deep water is developed by adding eddy viscosity dissipation terms in the High Level Irrotational Green-Naghdi(HLIGN)equations.The results of the simulation are compared with the laboratory measurements,and good agreement is observed for the evolved wave train.展开更多
The interaction between an atomic beam of two-level atoms and a standing wave light field has been studied by the exact solution of a time-dependent quantum system developed recently. When the initial atomic state is ...The interaction between an atomic beam of two-level atoms and a standing wave light field has been studied by the exact solution of a time-dependent quantum system developed recently. When the initial atomic state is choosen to be ground, we find that with the limit of zero detuning the atoms will oscillate between the upper and the lower levels with a decaying amplitude. The most interesting result obtained in this paper is when the initial atomic state is a particular superposition of the two levels, now the system does not oscillate at any time.展开更多
A water wave evolution equation is developed from the combinedrefraction-diffraction equation on non-uniform current in water of slowly varying topography byusing the perturbation method. A numerical model is presente...A water wave evolution equation is developed from the combinedrefraction-diffraction equation on non-uniform current in water of slowly varying topography byusing the perturbation method. A numerical model is presented with the governing equationdiscretized with an improved Alternating Direction Impicit (ADI) method involving a relaxationfactor which can improve convergent rate. The calculation results show that the model caneffectively reflect the effects of current on wave propagation.展开更多
The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an...The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an unusual double rainband structure.Using a wavenumber-frequency spectral filtering method,we unveil that this double rainband structure arises primarily from the Kelvin wave component.The zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean,being in the range of convectively coupled Kelvin wave phase speeds.The convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells,with low-level westerly（easterly）and high（low）pressure anomalies to the west（east）of the convective centers,and opposite wind and pressure anomalies in the upper troposphere.Such a zonal wind–pressure phase relationship is consistent with the equatorial free-wave dynamics.While the freeatmospheric circulation was dominated by the first baroclinic mode vertical structure,moisture and vertical motion in the boundary layer led the convection.The convection and circulation structures derived based on the conventional MJO filter show a different characteristic.For example,the phase speed is slower（about 5.9 degree per day）,and there were no double convective branches.This suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.展开更多
Almost everything I have done in the last twenty years is based on what I have discovered from studying ocean phenomena.Specifically,the waves on the surface of the ocean and their dynamics.Two items stand out:The fir...Almost everything I have done in the last twenty years is based on what I have discovered from studying ocean phenomena.Specifically,the waves on the surface of the ocean and their dynamics.Two items stand out:The first one is from studying the evolution of the waves from ripples to fully developed giant ocean waves.To quantify the changes,I found that frequency is very different from what had been defined traditionally through Fourier analysis.Ture frequency should be determined by difterentiation of the phase function defined by an adaptive method rather than by any form of integral transform.Therefore,it should have ever changing instantaneous values.The second discovery is from studying wave turbulence interactions.To reveal the detailed dynamics,I found that spectral representation should not be a single line on the frequency and energy plane.True spectrum should be a high dimensional manifold to cover all the possible dynamic interactions:additive and multiplicative ones.These discoveries have enabled me to develop a set of nonlinear and nonstationary data analysis tools to study many other phenomena,from turbulence to brain waves.They have led me to new wonders I have never even contemplated before.展开更多
Foreshock cavitons are transient phenomena observed in the terrestrial foreshock region.They are characterized by a simultaneous depression of magnetic field magnitude and plasma density,which are bounded with enhance...Foreshock cavitons are transient phenomena observed in the terrestrial foreshock region.They are characterized by a simultaneous depression of magnetic field magnitude and plasma density,which are bounded with enhancements of these two parameters and surrounded by ultralow frequency(ULF)waves.Previous studies focused on the interplanetary magnetic field(IMF)conditions,solar wind(SW)conditions,and the growth of the foreshock waves related to the generation of foreshock cavitons.Previously,a multipoint spacecraft analysis method using Cluster data was applied to analyze only two foreshock cavitons,and this method did not consider uncertainties.In this study,multipoint spacecraft analysis methods,including the timing method,the minimum directional derivative(MDD)method,and the spatiotemporal difference(STD)method are applied to determine the velocity in both spacecraft and solar wind frames.The propagation properties show good agreement with previous results from simulations and observations that most cavitons move sunward in the solar wind frame,with the velocities larger than the Alfvén speed.The propagation properties of foreshock cavitons support the formation mechanism of cavitons in previous simulations,which suggested that cavitons are formed due to the nonlinear evolution of compressive ULF waves.We find that there is clear decreasing trend between the size of cavitons and their velocity in the solar wind frame.In addition,the timing method considering errors has been applied to study the evolution properties by comparing the velocities with errors of the leading and trailing edges,and we identify three stable cavitons and one contracting caviton,which has not been studied before.Most cavitons should remain stable when they travel toward the Earth’s bow shock.The relationship between the size of foreshock cavitons and their distance from the bow shock is also discussed.展开更多
基金supported by the National Key R&D Program of China(Grant Nos.2023YFA1406304 and 2024YFA1408103)the National Science Foundation of China(Grant Nos.12494593 and 12004405)+5 种基金the Anhui Provincial Natural Science Foundation(Grant No.2408085J003)the National Key R&D Program of China(Grant No.2023YFA1406100)the open projects of the State Key Laboratory of Functional Materials for Informatics(Grant No.SKL2022)the China National Postdoctoral Program for Innovative Talents(BX20240348)support from the National Natural Science Foundation of China(Grant No.12404186)the Shanghai Sailing Program(Grant No.23YF1426900)。
文摘The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)feature intertwined Dirac fermions,topological flat bands,and van Hove singularities(vHS)near the Fermi level,which give rise to a range of exotic,strongly correlated phenomena such as charge density waves(CDW)and superconductivity.Although the vHS from V 3d states have been implicated in CDW formation,their three-dimensional nature and temperature evolution remain poorly understood.In this study,we used high-resolution angle-resolved photoemission spectroscopy and density functional theory to reveal pronounced out-of-plane dispersion of vHS and their temperature dependence in KV_(3)Sb_(5).The identified c-axis band folding and scattering channels were directly linked to the CDW order.These results demonstrate that the CDW transition in this family involves cooperative coupling between electron correlations and structural modulation along the c axis.This offers new insights into the interplay of topology,correlations,and lattice instabilities in kagome metals.
基金the support of the National Natural Science Foundation of China(Grant Nos.52031006 and 42206192)Shanghai Sailing Program,China(Grant No.20YF1419800).
文摘The spatial-temporal measurement of complex wave evolution is significant in studying wave-structure interactions.Current methods,such as that using wave probes,have shown limitations in measuring the wave evolution around structures in laboratories.In this study,an improved stereo imaging method is proposed for measuring the wave evolution around a fixed structure.Regular wave tests were conducted on a fixed surface-piercing square column in a wave flume to validate the reliability and accuracy of the proposed method.A flexible markernet made of foam particles was arranged around the column to pro-vide Lambertian features for the water surface.Two synchronized stereo imaging systems covered all the surrounding areas of the column and provided stereo pair sequences for wave evolution.Subsequently,image segmentation techniques were used to mask the low-confidence disparities in stereo matching,and finally,three-dimensional(3D)wave surfaces were reconstructed in the time sequence.The time histories of the wave elevations at particular locations were extracted and agreed well with the measurements of wave probes with an average bias of 2.4%.Subsequently,the reconstructed 3D wave field was sliced,exhibiting the instantaneous profiles that agreed with the measurements of wave probes.Moreover,the wave run-up height ratios were consistent with those of a previous study,thereby verifying the method’s accuracy from the perspective of spatial evolution.The results demonstrated that the proposed method was capable of precisely measuring the spatial-temporal evolution of the wave field around the square column and displayed potential for application in more studies on wave-structure interactions.
文摘Based on the Navier-Stokes （N-S） equations for viscous, incompressible fluid and the VOF method, 2-D and 3-D Numerical Wave Tanks （NWT） for nonlinear shallow water waves are built. The dynamic mesh technique is applied, which can save computational resources dramatically for the simulation of solitary wave propagating at a constant depth. Higher order approximation for cnoidal wave is employed to generate high quality waves. Shoaling and breaking of solitary waves over different slopes are simulated and analyzed systematically. Wave runup on structures is also investigated. The results agree very well with experimental data or analytical solutions.
基金supported by the National Key Research and Development Project(No.2018YFC1407001).
文摘Research on the wave field evolution law is highly significant to the fields of offshore engineering and marine resource development.Numerical simulations have been conducted for high-precision wave field evolution,thus providing short-term wave field prediction.However,its evolution occurs over a long period of time,and its accuracy is difficult to improve.In recent years,the use of machine learning methods to study the evolution of wave field has received increasing attention from researchers.This paper proposes a wave field evolution method based on deep convolutional neural networks.This method can effectively correlate the spa-tiotemporal characteristics of wave data via convolution operation and directly obtain the offshore forecast results of the Bohai Sea and the Yellow Sea.The attention mechanism,multi-scale path design,and hard example mining training strategy are introduced to suppress the interference caused by Weibull distributed wave field data and improve the accuracy of the proposed wave field evolu-tion.The 72-and 480-h evolution experiment results in the Bohai Sea and the Yellow Sea show that the proposed method in this pa-per has excellent forecast accuracy and timeliness.
基金Supported by the National Natural Science Foundation of China(Grant Nos.10603002 and 10773004)
文摘In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution, we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries, where the viscous damping of the r-modes and its resultant effects are taken into account. The numerical results show that, for both kinds of NSs, the differential rotation can significantly prolong the duration of the r-modes. As a result, the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years. Moreover, the persistent radiation of a quasi-monochromatic gravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation. This increases the detectability of gravitational waves from both young isolated and old accreting NSs.
文摘This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.
文摘The average variational principle was employed in this paper to study the evolution of large-scale and slowly varying Rossby wave packet with basic flow both in barotropic and baroclinic atmospheres. The evolution of the structure of Rossby wave packet with both time and space was studied. The results obtained in this paper are similar to the results of by WKBJ method. In addition, the dispersive process of the wave packet was analysed by taking Gaussian type wave packet as an initial disturbance. The valid time scale for application of wave packet theory in the atmosphere was obtained.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1602502)the National Natural Science Foundation of China(Grant No.12450404)。
文摘We present a fully time-dependent quantum wave packet evolution method for investigating molecular dynamics in intense laser fields.This approach enables the simultaneous treatment of interactions among multiple electronic states while simultaneously tracking their time-dependent electronic,vibrational,and rotational dynamics.As an illustrative example,we consider neutral H_(2)molecules and simulate the laser-induced excitation dynamics of electronic and rotational states in strong laser fields,quantitatively distinguishing the respective contributions of electronic dipole transitions(within the classical-field approximation)and non-resonant Raman processes to the overall molecular dynamics.Furthermore,we precisely evaluate the relative contributions of direct tunneling ionization from the ground state and ionization following electronic excitation in the strong-field ionization of H_(2).The developed methodology shows strong potential for performing high-precision theoretical simulations of electronic-vibrational-rotational state excitations,ionization,and dissociation dynamics in molecules and their ions under intense laser fields.
文摘Time evaluation of wave functions for any quantum mechanical system/particle is essential nevertheless quantum mechanical counterpart of the time dependant classical wave equation does simply not appear. Epistemologically and ontologically considered time dependant momentum operator is initially defined and an Alternative Time Dependant Schrodinger Wave Equation (ATDSWE) is plainly derived. Consequent equation is primarily solved for the free particles, in a closed system, signifying a good agreement with the outcomes of the ordinary TDSWE. Free particle solution interestingly goes further possibly tracing some signs of new pathways to resolve the mysterious quantum world.
基金the National Key Research and Development Program of China(Grant No.2022YFE0104500)the National Natural Science Foundation of China(Grant No.52271271)the Major Science and Technology Project of the Ministry of Water Resources of the People’s Republic of China(Grant No.SKS-2022025).
文摘Spectral bandwidth is a relevant parameter of water wave evolution and is commonly used to represent the number of wave components involved in wave-wave interactions.However,whether these two parameters are equivalent is an open question.Following the high-order spectral method and taking the weakly modulated Stokes wave train as the initial condition,the relationship between the spectral bandwidth and the number of wave components is investigated in this work.The results showed that the number of wave components can vary with the same spectral bandwidth and that distinct wave profiles emerge from different numbers of wave components.With a new definition of significant wave components,the characteristics of this parameter in the long-time wave evolution are discussed,along with its relationship with common parameters,including the wave surface maximum and the wave height.The results reveal that the wave surface evolution trend of different numbers of significant wave components(Ns)is the same from a holistic perspective,while the difference between them also exists,mainly in locations where extreme waves occur.Furthermore,there is a negative correlation between r(aj/a_(0))and wave surface maximum(η_(max)/a_(0))and wave height(H_(max)and Hs).The evolution trends of the relative errors(RE)ofη_(max)/a_(0),H_(max),and Hs of different Ns show the periodic recurrence of modulation and demodulation in the early stage when the Benjamin-Feir instability is dominated.The difference is that in the later stage,the RE ofη_(max)/a_(0)and H_(max)is chaotic and irregular,while those of Hs gradually stabilize near an equilibrium value.Furthermore,we discuss the relationship between the mean relative error(MRE)and r.Forη_(max)/a_(0),MRE and r show a logarithmic relationship,while for H_(max)and Hs,a quadratic relationship exists between them.Therefore,the choice of Ns is also important for extreme waves and is particularly meaningful for wave generation experiments in the wave flume.
基金Projects supported by the National Natural Science Foundation of China(Grant No.11772099)the Heilongjiang Touyan Innovation Team Program,China.
文摘The evolution of the nonlinear wave groups in deep water is investigated through laboratory measurements and numerical analysis.Laboratory experiments are conducted in deep-water wave tank,focusing on the characteristics of breaking waves arising from the evolved wave train.Some quantitative results are obtained for the significant breaking wave train,including the surface elevation time series,the local geometry,and the energy dissipation.A nonlinear model for the evolution of the wave groups in deep water is developed by adding eddy viscosity dissipation terms in the High Level Irrotational Green-Naghdi(HLIGN)equations.The results of the simulation are compared with the laboratory measurements,and good agreement is observed for the evolved wave train.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 10075302.
文摘The interaction between an atomic beam of two-level atoms and a standing wave light field has been studied by the exact solution of a time-dependent quantum system developed recently. When the initial atomic state is choosen to be ground, we find that with the limit of zero detuning the atoms will oscillate between the upper and the lower levels with a decaying amplitude. The most interesting result obtained in this paper is when the initial atomic state is a particular superposition of the two levels, now the system does not oscillate at any time.
文摘A water wave evolution equation is developed from the combinedrefraction-diffraction equation on non-uniform current in water of slowly varying topography byusing the perturbation method. A numerical model is presented with the governing equationdiscretized with an improved Alternating Direction Impicit (ADI) method involving a relaxationfactor which can improve convergent rate. The calculation results show that the model caneffectively reflect the effects of current on wave propagation.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB453200)National Natural Science Foundation of China(41475084,41630423,41575052,and 41375095)+7 种基金US National Science Foundation(AGS-1643297)US Office of Naval Research(N00014-16-12260)US Naval Research Laboratory(N00173-16-1-G906)Jiangsu Natural Science Foundation Key Project(BK20150062)of ChinaJiangsu Shuang-Chuang Team Fund(R2014SCT001)of ChinaSOEST contribution number 9819IPRC contribution number 1211ESMC number 126
文摘The second Madden–Julian Oscillation（MJO）event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011（DYNAMO/CINDY2011）exhibi ted an unusual double rainband structure.Using a wavenumber-frequency spectral filtering method,we unveil that this double rainband structure arises primarily from the Kelvin wave component.The zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean,being in the range of convectively coupled Kelvin wave phase speeds.The convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells,with low-level westerly（easterly）and high（low）pressure anomalies to the west（east）of the convective centers,and opposite wind and pressure anomalies in the upper troposphere.Such a zonal wind–pressure phase relationship is consistent with the equatorial free-wave dynamics.While the freeatmospheric circulation was dominated by the first baroclinic mode vertical structure,moisture and vertical motion in the boundary layer led the convection.The convection and circulation structures derived based on the conventional MJO filter show a different characteristic.For example,the phase speed is slower（about 5.9 degree per day）,and there were no double convective branches.This suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.
文摘Almost everything I have done in the last twenty years is based on what I have discovered from studying ocean phenomena.Specifically,the waves on the surface of the ocean and their dynamics.Two items stand out:The first one is from studying the evolution of the waves from ripples to fully developed giant ocean waves.To quantify the changes,I found that frequency is very different from what had been defined traditionally through Fourier analysis.Ture frequency should be determined by difterentiation of the phase function defined by an adaptive method rather than by any form of integral transform.Therefore,it should have ever changing instantaneous values.The second discovery is from studying wave turbulence interactions.To reveal the detailed dynamics,I found that spectral representation should not be a single line on the frequency and energy plane.True spectrum should be a high dimensional manifold to cover all the possible dynamic interactions:additive and multiplicative ones.These discoveries have enabled me to develop a set of nonlinear and nonstationary data analysis tools to study many other phenomena,from turbulence to brain waves.They have led me to new wonders I have never even contemplated before.
基金supported by the National Natural Science Foundation of China(Grant Nos.41574157,41628402&41774153)partially supported by National Science Foundation(Grant No.AGS-1352669)+1 种基金the International Space Science Institute-Beijing for supporting the international team “Dayside Transient Phenomena and Their Impact on the Magnetosphere-Ionosphere”supported by the specialized research fund for State Key Laboratories
文摘Foreshock cavitons are transient phenomena observed in the terrestrial foreshock region.They are characterized by a simultaneous depression of magnetic field magnitude and plasma density,which are bounded with enhancements of these two parameters and surrounded by ultralow frequency(ULF)waves.Previous studies focused on the interplanetary magnetic field(IMF)conditions,solar wind(SW)conditions,and the growth of the foreshock waves related to the generation of foreshock cavitons.Previously,a multipoint spacecraft analysis method using Cluster data was applied to analyze only two foreshock cavitons,and this method did not consider uncertainties.In this study,multipoint spacecraft analysis methods,including the timing method,the minimum directional derivative(MDD)method,and the spatiotemporal difference(STD)method are applied to determine the velocity in both spacecraft and solar wind frames.The propagation properties show good agreement with previous results from simulations and observations that most cavitons move sunward in the solar wind frame,with the velocities larger than the Alfvén speed.The propagation properties of foreshock cavitons support the formation mechanism of cavitons in previous simulations,which suggested that cavitons are formed due to the nonlinear evolution of compressive ULF waves.We find that there is clear decreasing trend between the size of cavitons and their velocity in the solar wind frame.In addition,the timing method considering errors has been applied to study the evolution properties by comparing the velocities with errors of the leading and trailing edges,and we identify three stable cavitons and one contracting caviton,which has not been studied before.Most cavitons should remain stable when they travel toward the Earth’s bow shock.The relationship between the size of foreshock cavitons and their distance from the bow shock is also discussed.
