We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin ...We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.展开更多
When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seawa...When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seaway of shallow water.In this paper,a numerical analysis of the shallow-water effect on the hydrodynamic forces and wake characteristics of an international ship model,KVLCC2,in oblique flows is conducted.Numerical simulations are performed based on the Reynolds Averaged NavierStokes equation in conjunction with the shear stress transport(SST)k-ωturbulence model.Four relative water depths(h=1.2T,1.5T,3.0T,and 24T;T is the ship draft)and five different drift angles(β=0°,5°,10°,15°,and 20°)are considered.Results reveal the following:i)The shallow-water effect is strong and leads to nonlinear increases in the longitudinal force regardless of drift angles and on the transverse force and yaw moment whenever the drift angle increases.ii)In shallow water,the mean wake fraction is sensitive to the drift angle,and the strength of the aft-body vortex on the leeward side increases.展开更多
Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static ...Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.展开更多
The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with ...The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with different isolating layers were identified experimentally and a vehicle-track coupled dynamic model considering track bed broadband vibrations(TBBVs)was established.The WRL and its VET were investigated,and the contribution law as well as the influence mechanism of TBBVs on them was determined.The results showed the WRL and track bed vibration energy exhibited significant resonances,with more prominent high-frequency resonance peaks in the track bed vibration energy.TBBVs had a significant effect on low-frequency WRLs,and markedly influenced the VET across various frequency bands.Intense low-frequency and weak high-frequency intermodulation effects between the wheel-rail and track beds were observed.The effect of track bed vibrations can be disregarded when focusing on high-frequency WRLs above 200 Hz.Variations in the isolating layer stiffness have more significant effects on the track bed vibration energy than the WRL.Rational stiffness of the isolating layer should be selected to avoid mode-coupling resonance from track beds to the wheel-rail subsystem.展开更多
Based on the structural characteristics of the high-speed loading tester,a four-point bending test device was designed to carry out the four-point bending strength test of glass under the action of static load and dif...Based on the structural characteristics of the high-speed loading tester,a four-point bending test device was designed to carry out the four-point bending strength test of glass under the action of static load and different impact velocities,and the formulae for calculating the maximum dynamic stress and strain rate of glass specimens under the action of impact loads were derived.The experimental results show that the bending strength values of the glass under dynamic impact loading are all higher than those under static loading.With the increase of impact speed,the bending strength value of glass specimens generally tends to increase,and the bending strength value increases more obviously when the impact speed exceeds 0.5 m/s or higher.By increasing the impact velocity,higher tensile strain rate of glass specimens can be obtained because the load action time becomes shorter.The bending strength of the glass material increases with its tensile strain rate,and when the tensile strain rate is between 0 and 2 s^(-1),the bending strength of the glass specimen grows more obviously with the strain rate,indicating that the glass bending strength is particularly sensitive to the tensile strain rate in this interval.As the strain rate increases,the number of cracks formed after glass breakage increases significantly,thus requiring more energy to drive the crack formation and expansion,and showing the strain rate effect of bending strength at the macroscopic level.The results of the study can provide a reference for the load bearing and structural design of glass materials under dynamic loading.展开更多
Iron(Fe)-based alloys,which have been widely used as structural materials in nuclear reactors,can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation dur...Iron(Fe)-based alloys,which have been widely used as structural materials in nuclear reactors,can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation during operation,thus,the problems associated with the safe operation of nuclear reactors have been put forward naturally.In this work,a molecular dynamics simulation approach combined with electronic effects is developed for investigating the primary radiation damage process inα-Fe.Specifically,the influence of electronic effects on the collision cascade in Fe is systematically evaluated based on two commonly used interatomic potentials for Fe.The simulation results reveal that both electronic stopping(ES)and electron-phonon coupling(EPC)can contribute to the decrease of the number of defects in the thermal spike phase.The application of ES reduces the number of residual defects after the cascade evolution,whereas EPC has a reverse effect.The introduction of electronic effects promotes the formation of the dispersive subcascade:ES significantly changes the geometry of the damaged region in the thermal spike phase,whereas EPC mainly reduces the extent of the damaged region.Furthermore,the incorporation of electronic effects effectively mitigates discrepancies in simulation outcomes when using different interatomic potentials.展开更多
Ducted fans have been extensively used in Unmanned Aerial Vehicles(UAVs)for a variety of missions because of high efficiency,high safety and low noise.Wind,as a kind of typical meteorological condition,brings signific...Ducted fans have been extensively used in Unmanned Aerial Vehicles(UAVs)for a variety of missions because of high efficiency,high safety and low noise.Wind,as a kind of typical meteorological condition,brings significant aerodynamic interference to the ducted fan,which seriously threatens flight stability and safety.In this work,the numerical simulation with the Unsteady Reynolds Averaged Navier-Stokes(URANS)method and the sliding mesh technique is performed to evaluate the steady wind effect.The results show that the wind will lead to serious unsteady effects in the flow field,and the thrust fluctuates at the blade passing frequency of 200 Hz.As the wind speed increases,the rotor thrust increases,the duct thrust decreases,and the total thrust changes little.Flow instability may occur when the wind speed exceeds 8 m/s.As the angle of low-speed wind increases,the rotor thrust changes little,the duct thrust increases,and the total thrust increases.In addition,we figure out that cases with the same crosswind ratio are similar in results,and increasing the rotating speed or fan radius is beneficial to performance improvement in wind.The findings are essential to the ducted fan design and UAV flight control design for stable and safe operations in wind conditions.展开更多
Understanding the dynamic responses of hard rocks is crucial during deep mining and tunneling activities and when constructing nuclear waste repositories. However, the response of deep massive rocks with openings of d...Understanding the dynamic responses of hard rocks is crucial during deep mining and tunneling activities and when constructing nuclear waste repositories. However, the response of deep massive rocks with openings of different shapes and orientations to dynamic loading is not well understood. Therefore, this study investigates the dynamic responses of hard rocks of deep underground excavation activities. Split Hopkins Pressure Bar (SHPB) tests on granite with holes of different shapes (rectangle, circle, vertical ellipse (elliptical short (ES) axis parallel to the impact load direction), and horizontal ellipse (elliptical long (EL) axis parallel to the impact load direction)) were carried out. The influence of hole shape and location on the dynamic responses was analyzed to reveal the rocks' dynamic strengths and cracking characteristics. We used the ResNet18 (convolutional neural network-based) network to recognize crack types using high-speed photographs. Moreover, a prediction model for the stress-strain response of rocks with different openings was established using Deep Neural Network (DNN). The results show that the dynamic strengths of the granite with EL and ES holes are the highest and lowest, respectively. The strength-weakening coefficient decreases first and then increases with an increase of thickness-span ratio (h/L). The weakening of the granite with ES holes is the most obvious. The ResNet18 network can improve the analyzing efficiency of the cracking mechanism, and the trained model's recognition accuracy reaches 99%. Finally, the dynamic stress-strain prediction model can predict the complete stress-strain curve well, with an accuracy above 85%.展开更多
The dynamic effect is a very important issue widely debated by scholars when studying the genetic and disaster-causing mechanisms of earthquake-triggered landslides.First,the dynamic effect mechanism and phenomena of ...The dynamic effect is a very important issue widely debated by scholars when studying the genetic and disaster-causing mechanisms of earthquake-triggered landslides.First,the dynamic effect mechanism and phenomena of earthquake-triggered landslides were summarized in this paper.Then,the primary types of dynamic effects were further used to interpret the Mogangling landslide in Moxi Town of Luding County,China.A field investigation,remote sensing,numerical calculation and theoretical analysis were carried out to illustrate the failure mechanism of slope rock masses affected by earthquakes.The interaction between seismic waves and slope rock masses and the induced dynamic effect of slope rock masses were primarily accounted for in the analysis.The slope topography,rock mass weathering and unloading characteristics,river erosion,regional seismogenic structure,and rock mass structure characteristics were also discussed.The results showed that the formation of the Mogangling landslide was mainly related to the high amplification effect of seismic acceleration and back slope effects,interface dynamic stress effects,and double-sided slope effects of seismic waves caused by the catastrophic Ms 7.75 Moxi Earthquake in 1786.The principles for the site and route selection of large-scale infrastructure in the planning stage and the scientific prevention of seismic geological disasters were proposed on the basis of the dynamic effect of earthquake-induced landslides.展开更多
Nuclear magnetic resonance(NMR)spectroscopy is a powerful and broadly used spectroscopic technique for characterizing molecular structures and dynamics.Yet the power of NMR is restricted by its inherently low sensitiv...Nuclear magnetic resonance(NMR)spectroscopy is a powerful and broadly used spectroscopic technique for characterizing molecular structures and dynamics.Yet the power of NMR is restricted by its inherently low sensitivity due to the weak polarization of nuclear spins under conventional experiment conditions.Dynamic nuclear polarization(DNP)and chemically induced dynamic nuclear polarization(CIDNP)have been emerging as powerful in-situ hyperpolarization methods to boost NMR sensitivity.This review provides a brief overview of DNP mechanisms in the context of both solid-state and liquidstate.We delve into the molecular features of different polarizing agents and their impacts on DNP applications,which are now steadily progressing towards modern NMR magnetic field strengths and ambient temperatures.Furthermore,the progress of CIDNP,particularly photo-CIDNP as a potential alternative hyperpolarization technique of DNP,in studying protein dynamics and chemical reaction mechanisms,will be covered.This review also highlights the chemical diversity and experimental strategies crucial for these hyperpolarization techniques,showcasing their transformative role in NMR spectroscopy.展开更多
The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic re...The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.展开更多
Multi-electron and multi-orbital effects play a crucial role in the interaction of strong laser fields with complex molecules.Here,multi-electron effects encompass not only electron-electron Coulomb interactions and e...Multi-electron and multi-orbital effects play a crucial role in the interaction of strong laser fields with complex molecules.Here,multi-electron effects encompass not only electron-electron Coulomb interactions and exchangecorrelation effects but also the interference between the dynamics of different electron wave packets.展开更多
High-performance alumina-magnesia castables were developed with the addition of nano-CacO_(3) and nano-hydromagnesite.To further understand their dynamic failure mechanism,the quantitative investigation via the employ...High-performance alumina-magnesia castables were developed with the addition of nano-CacO_(3) and nano-hydromagnesite.To further understand their dynamic failure mechanism,the quantitative investigation via the employment of the Split-Hopkinson pressure bar(SHPB)method was adopted to test the dynamic failure behavior of alumina-magnesia castables under various impact velocities.The results demonstrate that the greater the impact velocity,the more intense the sample damage.The dynamic compressive stress,the ultimate strain,and the strain energy of all samples display a strain rate hardening effect,and this phenomenon is more conspicuous in the samples incorporating nano-additives.The nano-additives show a positive influence on the dynamic mechanical properties of the castables.展开更多
Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states an...Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states and use the non-Markovian stochastic Schrödinger equation(NMSSE)to simulate the photo-in-duced dynamics processes.The re-sults show that aggregation effects have a significant impact on the interfacial exciton dissociation process.After photo-excita-tion,the excitons first preferentially delocalize and perform the charge transfer(CT)states in the pure ZnPc or F_(8)ZnPc aggregates within 100 fs.These‘intramolecular’CT states can easi-ly evolve into interfacial CT states by hopping electrons and holes in the intramolecular CT states across the interface.Compared with these exciton dissociation processes,the direct ex-citon dissociation into interfacial CT state is relatively slow due to the small electronic cou-pling and vibrational coherence between the locally excited state and the interfacial CT state.As the temperature rises and the vibronic coherence weakens,the direct dissociation rates are significantly enhanced.This investigation provides valuable insights for the design and opti-mization of high-performance organic photovoltaic devices.展开更多
The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,...The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,this paper develops a three-dimensional discretized dynamic radiation transfer model based on the blade shape of the turbine.The relationship between the radiation angle coefficient of the surrounding blades and the rotation angle of the blade under test is analyzed.The radiation angle coefficient is calculated using the triangular element method,and temperature inversion is performed based on the effective emissivity to compute the measurement error.The results show that under dynamic high temperature conditions,the temperature measurement error caused by reflection at the selected 60%leaf height point varies with the rotation angle,and the maximum reaches 25.58K.The angular coefficient exhibits periodic fluctuations with changes in rotation angle,and the maximum effective emissivity increases as the rotation angle increases.As the blade height increases,the impact of reflected radiation on radiometric temperature measurement errors shows a decreasing trend.This study provides a reference for radiation thermometry in dynamic high-temperature environments.展开更多
We investigate the inertial domain wall(DW)dynamics driven by spin-polarized current in ferromagnets.The exact solutions reveal an upper limit for DW velocity,given by V≤1/√ατ.This indicates that damping and inert...We investigate the inertial domain wall(DW)dynamics driven by spin-polarized current in ferromagnets.The exact solutions reveal an upper limit for DW velocity,given by V≤1/√ατ.This indicates that damping and inertia become the key factors in achieving higher DW speeds.For the case of uniaxial anisotropy,we analyze the effects of inertia and current on DW dynamics.Due to inertia,the DW velocity,width,rotation frequency,and wave number are mutually coupled.When the DW width varies slightly,the velocity decreases rapidly while the magnetization precession frequency increases sharply with the inertia term.However,once the rotation frequency exceeds its maximum value,both the DW velocity and rotation frequency gradually decline.Regarding current-driven dynamics,we identify a critical current j1cthat directly triggers the Walker breakdown.For currents below this threshold j_(1)<j_(1c),the absolute DW velocity increases with current,whereas it decreases for j_(1)>j_(1c).During this process,the DW velocity rapidly peaks under current drive,accompanied by the magnetization rotation frequency nearing its maximum and minimal variation in DW width.These results suggest that the DW behaves like a classical rigid body,reaching its maximum velocity as it approaches peak rotational speed.For biaxial anisotropy,we derive analytical solutions.The competition between hard-axis anisotropy and inertia causes the DW magnetization to lose its spiral structure and rotational symmetry.The inertia effect leads to a slow initial decrease followed by a rapid increase in DW width,whereas current modulation gradually widens the DW.The analytical solution also reveals another critical current,j_(1 max)=√(α/τ)/β,which scales with the square root of the inertia-to-damping ratio and is inversely proportional to the nonadiabatic spin-transfer torque parameterβ.展开更多
The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and propos...The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.展开更多
Bit patterned recording(BPR)has attracted much attention due to its promising potential in achieving high densities in magnetic storage devices.The materials with strong perpendicular magnetic anisotropy(PMA)are alway...Bit patterned recording(BPR)has attracted much attention due to its promising potential in achieving high densities in magnetic storage devices.The materials with strong perpendicular magnetic anisotropy(PMA)are always preferred in designing the BPR.Here,the patterned Co/Ni multilayers showing d-d hybridization induced PMA was studied.In particular,we record the ultrafast spin dynamics by means of time-resolved scanning magneto-optical Kerr effect(TRMOKE)microscopy.We are able to acquire the“snapshot”magnetic maps of the sample surface because of both the femtosecond temporal and submicrometer spatial resolution in our TRMOKE microscopy.Furthermore,the spatially inhomogeneous ultrafast demagnetization was observed in experiment,and this has been evidenced by simulations.展开更多
The two-body fragmentation dynamics of water isotopologues dications(H_(2)O^(2+),HOD^(2+),and D_(2)O^(2+))induced by200 eV electron impact is investigated.Two fragment ions and an emitted electron are detected in coin...The two-body fragmentation dynamics of water isotopologues dications(H_(2)O^(2+),HOD^(2+),and D_(2)O^(2+))induced by200 eV electron impact is investigated.Two fragment ions and an emitted electron are detected in coincidence,and their momentum vectors are determined by employing a reaction microscope.The complete kinematical information of four two-body fragmentation channels of H^(+)+OH+,H^(+)+OD^(+),D^(+)+OH^(+),and D^(+)+OD+is obtained.By analyzing the projectile energy-loss spectrum,the initial electronic state of the two-body dissociation channel is determined.Upon examining the kinetic energy release(KER)distributions of the four fragmentation channels,a clear difference is found between the two-body fragmentation channel H^(+)+OD+and the other three channels.The isotopic effect in the two-body fragmentation is demonstrated by the analysis of the relative yields of the two-body fragmentation channels originating from different isotopologues,which shows preferential cleavage of the O-H bond over the O-D bond.These results provide deeper insight into the microscopic dynamic mechanisms in water radiolysis.展开更多
We design dynamical Casimir arrays(DCA)consisting of giant atoms and coupled resonator waveguides(CRWs)to investigate the Einstein–Podolsky–Rosen(EPR)steering at finite temperatures.Our designed system exhibits an a...We design dynamical Casimir arrays(DCA)consisting of giant atoms and coupled resonator waveguides(CRWs)to investigate the Einstein–Podolsky–Rosen(EPR)steering at finite temperatures.Our designed system exhibits an asymmetry in its structure,which is caused by the differences in the sizes and the coupling positions of the giant atoms.The system achieves different types of EPR steering and the reversal of one-way EPR steering by modulating parameters.Furthermore,the symmetry and asymmetry of the system structure,in their responses to parameter modulation,both reveal the asymmetry of EPR steering.In this process,we discover that with the increase in temperature,different types of steering can be transferred from Casimir photons to giant atoms.We also achieve the monogamy of the multipartite system.These results provide important assistance for secure quantum communication,and further intuitively validating the asymmetry of EPR steering from multiple perspectives.展开更多
文摘We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.
基金supported by the National Key R&D Plan Project(No.2019YFD0901003)。
文摘When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seaway of shallow water.In this paper,a numerical analysis of the shallow-water effect on the hydrodynamic forces and wake characteristics of an international ship model,KVLCC2,in oblique flows is conducted.Numerical simulations are performed based on the Reynolds Averaged NavierStokes equation in conjunction with the shear stress transport(SST)k-ωturbulence model.Four relative water depths(h=1.2T,1.5T,3.0T,and 24T;T is the ship draft)and five different drift angles(β=0°,5°,10°,15°,and 20°)are considered.Results reveal the following:i)The shallow-water effect is strong and leads to nonlinear increases in the longitudinal force regardless of drift angles and on the transverse force and yaw moment whenever the drift angle increases.ii)In shallow water,the mean wake fraction is sensitive to the drift angle,and the strength of the aft-body vortex on the leeward side increases.
基金National Natural Science Foundation of China-NSAF(Grant No.U2330202)the National Natural Science Foundation of China(Grant Nos.52175162 and 51805086)+1 种基金Fujian Provincial Technological Innovation Key Research and Industrialization Projects(Grant Nos.2023XQ005 and 2024XQ010)The National Independent Innovation Demonstration Platform Project of Fujian Province(2024QZFX07)。
文摘Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.
基金supported by the National Natural Science Foundation of China(No.52308468)the China Postdoctoral Science Foundation(No.2022M723390)the Jiangsu Provincial Excellent Postdoctoral Program(No.2023ZB020),China.
文摘The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with different isolating layers were identified experimentally and a vehicle-track coupled dynamic model considering track bed broadband vibrations(TBBVs)was established.The WRL and its VET were investigated,and the contribution law as well as the influence mechanism of TBBVs on them was determined.The results showed the WRL and track bed vibration energy exhibited significant resonances,with more prominent high-frequency resonance peaks in the track bed vibration energy.TBBVs had a significant effect on low-frequency WRLs,and markedly influenced the VET across various frequency bands.Intense low-frequency and weak high-frequency intermodulation effects between the wheel-rail and track beds were observed.The effect of track bed vibrations can be disregarded when focusing on high-frequency WRLs above 200 Hz.Variations in the isolating layer stiffness have more significant effects on the track bed vibration energy than the WRL.Rational stiffness of the isolating layer should be selected to avoid mode-coupling resonance from track beds to the wheel-rail subsystem.
基金Found by the National Natural Science Foundation of China(Nos.52072356 and 52032011)the Shandong Province Science and Technology Small and Medium-sized Enterprises Innovation Ability Improvement Project(No.2022TSGC1194)。
文摘Based on the structural characteristics of the high-speed loading tester,a four-point bending test device was designed to carry out the four-point bending strength test of glass under the action of static load and different impact velocities,and the formulae for calculating the maximum dynamic stress and strain rate of glass specimens under the action of impact loads were derived.The experimental results show that the bending strength values of the glass under dynamic impact loading are all higher than those under static loading.With the increase of impact speed,the bending strength value of glass specimens generally tends to increase,and the bending strength value increases more obviously when the impact speed exceeds 0.5 m/s or higher.By increasing the impact velocity,higher tensile strain rate of glass specimens can be obtained because the load action time becomes shorter.The bending strength of the glass material increases with its tensile strain rate,and when the tensile strain rate is between 0 and 2 s^(-1),the bending strength of the glass specimen grows more obviously with the strain rate,indicating that the glass bending strength is particularly sensitive to the tensile strain rate in this interval.As the strain rate increases,the number of cracks formed after glass breakage increases significantly,thus requiring more energy to drive the crack formation and expansion,and showing the strain rate effect of bending strength at the macroscopic level.The results of the study can provide a reference for the load bearing and structural design of glass materials under dynamic loading.
基金Project supported by the National MCF Energy Research and Development Program of China(Grant Nos.2022YFE03200200 and 2018YFE0308101)the National Natural Science Foundation of China(Grant No.12105194)the Natural Science Foundation of Sichuan Province,China(Grant Nos.2022NSFSC1265 and 2022NSFSC1251).
文摘Iron(Fe)-based alloys,which have been widely used as structural materials in nuclear reactors,can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation during operation,thus,the problems associated with the safe operation of nuclear reactors have been put forward naturally.In this work,a molecular dynamics simulation approach combined with electronic effects is developed for investigating the primary radiation damage process inα-Fe.Specifically,the influence of electronic effects on the collision cascade in Fe is systematically evaluated based on two commonly used interatomic potentials for Fe.The simulation results reveal that both electronic stopping(ES)and electron-phonon coupling(EPC)can contribute to the decrease of the number of defects in the thermal spike phase.The application of ES reduces the number of residual defects after the cascade evolution,whereas EPC has a reverse effect.The introduction of electronic effects promotes the formation of the dispersive subcascade:ES significantly changes the geometry of the damaged region in the thermal spike phase,whereas EPC mainly reduces the extent of the damaged region.Furthermore,the incorporation of electronic effects effectively mitigates discrepancies in simulation outcomes when using different interatomic potentials.
基金This study was co-supported by the National Key Research and Development Program of China(No.2020YFC1512500),The Advanced Aviation Power Innovation institution,The Aero Engine Academy of China,and Tsinghua University Initiative Scientific Research Program,China.
文摘Ducted fans have been extensively used in Unmanned Aerial Vehicles(UAVs)for a variety of missions because of high efficiency,high safety and low noise.Wind,as a kind of typical meteorological condition,brings significant aerodynamic interference to the ducted fan,which seriously threatens flight stability and safety.In this work,the numerical simulation with the Unsteady Reynolds Averaged Navier-Stokes(URANS)method and the sliding mesh technique is performed to evaluate the steady wind effect.The results show that the wind will lead to serious unsteady effects in the flow field,and the thrust fluctuates at the blade passing frequency of 200 Hz.As the wind speed increases,the rotor thrust increases,the duct thrust decreases,and the total thrust changes little.Flow instability may occur when the wind speed exceeds 8 m/s.As the angle of low-speed wind increases,the rotor thrust changes little,the duct thrust increases,and the total thrust increases.In addition,we figure out that cases with the same crosswind ratio are similar in results,and increasing the rotating speed or fan radius is beneficial to performance improvement in wind.The findings are essential to the ducted fan design and UAV flight control design for stable and safe operations in wind conditions.
基金funding support from the National Natural Science Foundation of China(Grant No.52374119)the opening fund of State Key Laboratory of Coal Mine Disaster Dynamics and Control(Grant No.2011DA105827-FW202209)the opening fund of State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure,East China Jiaotong University(Grant No.HJGZ2023103).
文摘Understanding the dynamic responses of hard rocks is crucial during deep mining and tunneling activities and when constructing nuclear waste repositories. However, the response of deep massive rocks with openings of different shapes and orientations to dynamic loading is not well understood. Therefore, this study investigates the dynamic responses of hard rocks of deep underground excavation activities. Split Hopkins Pressure Bar (SHPB) tests on granite with holes of different shapes (rectangle, circle, vertical ellipse (elliptical short (ES) axis parallel to the impact load direction), and horizontal ellipse (elliptical long (EL) axis parallel to the impact load direction)) were carried out. The influence of hole shape and location on the dynamic responses was analyzed to reveal the rocks' dynamic strengths and cracking characteristics. We used the ResNet18 (convolutional neural network-based) network to recognize crack types using high-speed photographs. Moreover, a prediction model for the stress-strain response of rocks with different openings was established using Deep Neural Network (DNN). The results show that the dynamic strengths of the granite with EL and ES holes are the highest and lowest, respectively. The strength-weakening coefficient decreases first and then increases with an increase of thickness-span ratio (h/L). The weakening of the granite with ES holes is the most obvious. The ResNet18 network can improve the analyzing efficiency of the cracking mechanism, and the trained model's recognition accuracy reaches 99%. Finally, the dynamic stress-strain prediction model can predict the complete stress-strain curve well, with an accuracy above 85%.
基金supported by the China Geological Survey Projects(Nos.20160272,20211379)the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0904)。
文摘The dynamic effect is a very important issue widely debated by scholars when studying the genetic and disaster-causing mechanisms of earthquake-triggered landslides.First,the dynamic effect mechanism and phenomena of earthquake-triggered landslides were summarized in this paper.Then,the primary types of dynamic effects were further used to interpret the Mogangling landslide in Moxi Town of Luding County,China.A field investigation,remote sensing,numerical calculation and theoretical analysis were carried out to illustrate the failure mechanism of slope rock masses affected by earthquakes.The interaction between seismic waves and slope rock masses and the induced dynamic effect of slope rock masses were primarily accounted for in the analysis.The slope topography,rock mass weathering and unloading characteristics,river erosion,regional seismogenic structure,and rock mass structure characteristics were also discussed.The results showed that the formation of the Mogangling landslide was mainly related to the high amplification effect of seismic acceleration and back slope effects,interface dynamic stress effects,and double-sided slope effects of seismic waves caused by the catastrophic Ms 7.75 Moxi Earthquake in 1786.The principles for the site and route selection of large-scale infrastructure in the planning stage and the scientific prevention of seismic geological disasters were proposed on the basis of the dynamic effect of earthquake-induced landslides.
基金supported by the National Natural Science Foundation of China(Grant No.22403029)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(Grant No.GZC20240475,2024M760922)+5 种基金supported by National Natural Science Foundation of China(Grant No.22174099)supported by the National Natural Science Foundation of China(Grant No.22273023)the National Key R&D Program of China(Grant No.2019YFA0905200)Shanghai Municipal Natural Science Foundation(Grant No.23ZR1418200)Natural Science Foundation of Chongqing,China(Grant No.CSTB2023NSCQ-MSX0616)Shanghai Frontiers Science Center of Molecule Intelligent Syntheses,and the Fundamental Research Funds for the Central Universities.
文摘Nuclear magnetic resonance(NMR)spectroscopy is a powerful and broadly used spectroscopic technique for characterizing molecular structures and dynamics.Yet the power of NMR is restricted by its inherently low sensitivity due to the weak polarization of nuclear spins under conventional experiment conditions.Dynamic nuclear polarization(DNP)and chemically induced dynamic nuclear polarization(CIDNP)have been emerging as powerful in-situ hyperpolarization methods to boost NMR sensitivity.This review provides a brief overview of DNP mechanisms in the context of both solid-state and liquidstate.We delve into the molecular features of different polarizing agents and their impacts on DNP applications,which are now steadily progressing towards modern NMR magnetic field strengths and ambient temperatures.Furthermore,the progress of CIDNP,particularly photo-CIDNP as a potential alternative hyperpolarization technique of DNP,in studying protein dynamics and chemical reaction mechanisms,will be covered.This review also highlights the chemical diversity and experimental strategies crucial for these hyperpolarization techniques,showcasing their transformative role in NMR spectroscopy.
基金financially supported by the National Natural Science Foundation of China (Grant No. 52278504)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220141)。
文摘The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0134200)the National Natural Science Foundation of China(Grant No.12204214)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.GK202207012)QCYRCXM-2022-241。
文摘Multi-electron and multi-orbital effects play a crucial role in the interaction of strong laser fields with complex molecules.Here,multi-electron effects encompass not only electron-electron Coulomb interactions and exchangecorrelation effects but also the interference between the dynamics of different electron wave packets.
基金National Natural Science Foundation of China(52472303 and 52304356).
文摘High-performance alumina-magnesia castables were developed with the addition of nano-CacO_(3) and nano-hydromagnesite.To further understand their dynamic failure mechanism,the quantitative investigation via the employment of the Split-Hopkinson pressure bar(SHPB)method was adopted to test the dynamic failure behavior of alumina-magnesia castables under various impact velocities.The results demonstrate that the greater the impact velocity,the more intense the sample damage.The dynamic compressive stress,the ultimate strain,and the strain energy of all samples display a strain rate hardening effect,and this phenomenon is more conspicuous in the samples incorporating nano-additives.The nano-additives show a positive influence on the dynamic mechanical properties of the castables.
基金supported by the National Natural Science Foundation of China(Nos.22033006,22173074,22473091, 92372105).
文摘Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states and use the non-Markovian stochastic Schrödinger equation(NMSSE)to simulate the photo-in-duced dynamics processes.The re-sults show that aggregation effects have a significant impact on the interfacial exciton dissociation process.After photo-excita-tion,the excitons first preferentially delocalize and perform the charge transfer(CT)states in the pure ZnPc or F_(8)ZnPc aggregates within 100 fs.These‘intramolecular’CT states can easi-ly evolve into interfacial CT states by hopping electrons and holes in the intramolecular CT states across the interface.Compared with these exciton dissociation processes,the direct ex-citon dissociation into interfacial CT state is relatively slow due to the small electronic cou-pling and vibrational coherence between the locally excited state and the interfacial CT state.As the temperature rises and the vibronic coherence weakens,the direct dissociation rates are significantly enhanced.This investigation provides valuable insights for the design and opti-mization of high-performance organic photovoltaic devices.
文摘The turbine blades operate under high temperature and high pressure conditions,and when using radiation thermometry,the influence of radiation from surrounding blades leads to measurement errors.To address this issue,this paper develops a three-dimensional discretized dynamic radiation transfer model based on the blade shape of the turbine.The relationship between the radiation angle coefficient of the surrounding blades and the rotation angle of the blade under test is analyzed.The radiation angle coefficient is calculated using the triangular element method,and temperature inversion is performed based on the effective emissivity to compute the measurement error.The results show that under dynamic high temperature conditions,the temperature measurement error caused by reflection at the selected 60%leaf height point varies with the rotation angle,and the maximum reaches 25.58K.The angular coefficient exhibits periodic fluctuations with changes in rotation angle,and the maximum effective emissivity increases as the rotation angle increases.As the blade height increases,the impact of reflected radiation on radiometric temperature measurement errors shows a decreasing trend.This study provides a reference for radiation thermometry in dynamic high-temperature environments.
基金supported by the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University,China(Grant No.KF202203)the Tianjin Natural Science(Grant No.25JCQNJC00990)。
文摘We investigate the inertial domain wall(DW)dynamics driven by spin-polarized current in ferromagnets.The exact solutions reveal an upper limit for DW velocity,given by V≤1/√ατ.This indicates that damping and inertia become the key factors in achieving higher DW speeds.For the case of uniaxial anisotropy,we analyze the effects of inertia and current on DW dynamics.Due to inertia,the DW velocity,width,rotation frequency,and wave number are mutually coupled.When the DW width varies slightly,the velocity decreases rapidly while the magnetization precession frequency increases sharply with the inertia term.However,once the rotation frequency exceeds its maximum value,both the DW velocity and rotation frequency gradually decline.Regarding current-driven dynamics,we identify a critical current j1cthat directly triggers the Walker breakdown.For currents below this threshold j_(1)<j_(1c),the absolute DW velocity increases with current,whereas it decreases for j_(1)>j_(1c).During this process,the DW velocity rapidly peaks under current drive,accompanied by the magnetization rotation frequency nearing its maximum and minimal variation in DW width.These results suggest that the DW behaves like a classical rigid body,reaching its maximum velocity as it approaches peak rotational speed.For biaxial anisotropy,we derive analytical solutions.The competition between hard-axis anisotropy and inertia causes the DW magnetization to lose its spiral structure and rotational symmetry.The inertia effect leads to a slow initial decrease followed by a rapid increase in DW width,whereas current modulation gradually widens the DW.The analytical solution also reveals another critical current,j_(1 max)=√(α/τ)/β,which scales with the square root of the inertia-to-damping ratio and is inversely proportional to the nonadiabatic spin-transfer torque parameterβ.
基金Supported by the Sichuan Science and Technology Program(Grant No.2023ZDZX0008)the National Natural Science Foundation of China(Grant No.52388102)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘The interaction between the airflow and train influences the aerodynamic characteristics and dynamic performance of high-speed trains.This study focused on the fluid-solid coupling effect of airflow and HST,and proposed a co-simulation(CS)approach between computational fluid dynamics and multi-body dynamics.Firstly,the aerodynamic model was developed by employing overset mesh technology and the finite volume method,and the detailed train-track coupled dynamic model was established.Then the User Data Protocol was adopted to build data communication channels.Moreover,the proposed CS method was validated by comparison with a reported field test result.Finally,a case study of the HST exiting a tunnel subjected to crosswind was conducted to compare differences between CS and offline simulation(OS)methods.In terms of the presented case,the changing trends of aerodynamic forces and car-body displacements calculated by the two methods were similar.Differences mainly lie in aerodynamic moments and transient wheel-rail impacts.Maximum pitching and yawing moments on the head vehicle in the two methods differ by 21.1 kN∙m and 29.6 kN∙m,respectively.And wheel-rail impacts caused by sudden changes in aerodynamic loads are significantly severer in CS.Wheel-rail safety indices obtained by CS are slightly greater than those by OS.This research proposes a CS method for aerodynamic characteristics and dynamic performance of the HST in complex scenarios,which has superiority in computational efficiency and stability.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1403302)the National Natural Science Foundation of China(Grant Nos.52031015,U22A20115,and 12104030)+1 种基金the Natural Science Foundation of Zhejiang Province,China(Grant No.LZ25A040007)the Natural Science Foundation of Beijing(Grant No.1252026).
文摘Bit patterned recording(BPR)has attracted much attention due to its promising potential in achieving high densities in magnetic storage devices.The materials with strong perpendicular magnetic anisotropy(PMA)are always preferred in designing the BPR.Here,the patterned Co/Ni multilayers showing d-d hybridization induced PMA was studied.In particular,we record the ultrafast spin dynamics by means of time-resolved scanning magneto-optical Kerr effect(TRMOKE)microscopy.We are able to acquire the“snapshot”magnetic maps of the sample surface because of both the femtosecond temporal and submicrometer spatial resolution in our TRMOKE microscopy.Furthermore,the spatially inhomogeneous ultrafast demagnetization was observed in experiment,and this has been evidenced by simulations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12325406,92261201,12404305,11974272)the Shannxi Province Natural Science Fundamental Research Project(Grant Nos.2023JC-XJ-03 and 23JSQ013)the Fundamental Research Funds for the Central Universities(Grant No.xzy022024040)。
文摘The two-body fragmentation dynamics of water isotopologues dications(H_(2)O^(2+),HOD^(2+),and D_(2)O^(2+))induced by200 eV electron impact is investigated.Two fragment ions and an emitted electron are detected in coincidence,and their momentum vectors are determined by employing a reaction microscope.The complete kinematical information of four two-body fragmentation channels of H^(+)+OH+,H^(+)+OD^(+),D^(+)+OH^(+),and D^(+)+OD+is obtained.By analyzing the projectile energy-loss spectrum,the initial electronic state of the two-body dissociation channel is determined.Upon examining the kinetic energy release(KER)distributions of the four fragmentation channels,a clear difference is found between the two-body fragmentation channel H^(+)+OD+and the other three channels.The isotopic effect in the two-body fragmentation is demonstrated by the analysis of the relative yields of the two-body fragmentation channels originating from different isotopologues,which shows preferential cleavage of the O-H bond over the O-D bond.These results provide deeper insight into the microscopic dynamic mechanisms in water radiolysis.
基金Project supported by the Education Department of Jilin Province,China(Grant No.JJKH20231291KJ)。
文摘We design dynamical Casimir arrays(DCA)consisting of giant atoms and coupled resonator waveguides(CRWs)to investigate the Einstein–Podolsky–Rosen(EPR)steering at finite temperatures.Our designed system exhibits an asymmetry in its structure,which is caused by the differences in the sizes and the coupling positions of the giant atoms.The system achieves different types of EPR steering and the reversal of one-way EPR steering by modulating parameters.Furthermore,the symmetry and asymmetry of the system structure,in their responses to parameter modulation,both reveal the asymmetry of EPR steering.In this process,we discover that with the increase in temperature,different types of steering can be transferred from Casimir photons to giant atoms.We also achieve the monogamy of the multipartite system.These results provide important assistance for secure quantum communication,and further intuitively validating the asymmetry of EPR steering from multiple perspectives.
