In this study we use a boundary integral element-based numerical technique to solve the generalized Burger-Fisher equation. The essential feature of this method is the fundamental integral representation of the soluti...In this study we use a boundary integral element-based numerical technique to solve the generalized Burger-Fisher equation. The essential feature of this method is the fundamental integral representation of the solution inside the problem domain by means of both the boundary and domain values. The occurrences of domain integrals within the problem arising from nonlinearity as well as the temporal derivative are not avoided or transferred to the boundary. However, unlike the classical boundary element approach, they are resolved within a finite-element-type discrete domain. The utility and correctness of this formulation are proved by comparing the results obtained herein with closed form solutions.展开更多
Finite Element Method (FEM), based on p and h versions approach, and the Adomians decomposition algorithm (ADM) are introduced for solving the Emden-Fowler Equation. A number of special cases of p and h versions of FE...Finite Element Method (FEM), based on p and h versions approach, and the Adomians decomposition algorithm (ADM) are introduced for solving the Emden-Fowler Equation. A number of special cases of p and h versions of FEM are introduced. Several iterated forms of the ADM are considered also. To demonstrate the efficiency of both methods, the numerical solutions of different examples are compared for both methods with the analytical solutions. It is observed that the results obtained by FEM are quite satisfactory and more accurate than ADM. Moreover, the FEM method is applicable for a wide range of classes including the singularity cases with the given special treatments by the FEM. Comparing the results with the existing true solutions shows that the FEM approach is highly accurate and converges rapidly.展开更多
The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-...The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-fluid numerical model including electrochemical reactions and water-gas-shift(WGS)reaction for a single channel solid oxide fuel cell was developed to study the steady-state characteristics,which include distributions of the temperature(T),temperature gradient((35)T/(35)x),and fuel utilization.It was shown that the maximum temperature(Tmax)changed with operating voltage and the maximum temperature gradient(((35)T/(35)x)max)occurred at the inlet of the channel of a solid oxide fuel cell by simulation.Moreover,the natural convection condition had a great influence on T and(35)T/(35)x.The thermal stress generated by temperature differences was the key parameter and increasing the convection heat-transfer coefficient can greatly reduce the thermal stress.In addition,the results also showed that there were lower temperature gradients and lower current density at high working voltage;therefore,choosing the proper operating voltage can obtain better cell performance.展开更多
Flat subduction refers to low-angle(<10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ~10% of present-day subduction zones, but its impact on the behavior of the overri...Flat subduction refers to low-angle(<10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ~10% of present-day subduction zones, but its impact on the behavior of the overriding plate is particularly strong.For example, flat subduction zones are typically associated with stronger earthquakes. The deformation caused by typical flat subduction will transfer from the trench to the overriding continental interior and form a broad magma belt. The formation mechanism of flat subduction has been linked to the relative buoyancy of subducted oceanic plateaus, overthrusting of the overriding plate, hydrodynamic suction, and trench retreat. However, these mechanisms remain debated. This paper systematically analyzes and summarizes previous studies on flat subduction, and outlines the possible geological effects of flat subduction, such as intracontinental orogeny and magmatism. Using examples from numerical modeling, we discuss the possible formation mechanisms. The most important factors that control the formation of flat subduction are associated with overthrusting of the overriding plate and the arrival of an oceanic plateau at the subduction zone. In addition, trench retreat is necessary to enable flat subduction. Hydrodynamic suction contributes to the reduction of the slab dip angle, but is insufficient to form flat subduction. Future numerical modeling of flat subduction should carry out three-dimensional high-resolution thermo-mechanical simulation, considering the influence of crustal eclogitization(negative buoyancy) and mantle serpentinization(positive buoyancy) of oceanic lithosphere, in combination with geological and geophysical data.展开更多
Aiming at the interaction and coalescence of bubbles in gas–liquid two-phase flow, a multi-field coupling model was established to simulate deformation and dynamics of multi-bubble in gas–liquid two-phase flow by co...Aiming at the interaction and coalescence of bubbles in gas–liquid two-phase flow, a multi-field coupling model was established to simulate deformation and dynamics of multi-bubble in gas–liquid two-phase flow by coupling magnetic field, phase field, continuity equation, and momentum equation. Using the phase field method to capture the interface of two phases, the geometric deformation and dynamics of a pair of coaxial vertical rising bubbles under the applied uniform magnetic field in the vertical direction were investigated. The correctness of results is verified by mass conservation method and the comparison of the existing results. The results show that the applied uniform magnetic field can effectively shorten the distance between the leading bubble and the trailing bubble, the time of bubbles coalescence, and increase the velocity of bubbles coalescence. Within a certain range, as the intensity of the applied uniform magnetic field increases, the velocity of bubbles coalescence is proportional to the intensity of the magnetic field, and the time of bubbles coalescence is inversely proportional to the intensity of the magnetic field.展开更多
Taking the Rayleigh–Taylor instability with double interfaces as the research object,the interface coupling effects in the weakly nonlinear regime are studied numerically.The variation of Atwood numbers on the two in...Taking the Rayleigh–Taylor instability with double interfaces as the research object,the interface coupling effects in the weakly nonlinear regime are studied numerically.The variation of Atwood numbers on the two interfaces and the variation of the thickness between them are taken into consideration.It is shown that,when the Atwood number on the lower interface is small,the amplitude of perturbation growth on the lower interface is positively related with the Atwood number on the upper interface.However,it is negatively related when the Atwood number on the lower interface is large.The above phenomenon is quantitatively studied using an analytical formula and the underlying physical mechanism is presented.展开更多
Injecting CO2 into oil reservoirs can improve the oil recovery,meanwhile achieve CO2 storage.The diffusion of CO2 in oil-water systems has a substantial impact on this process.The interface significantly affects the m...Injecting CO2 into oil reservoirs can improve the oil recovery,meanwhile achieve CO2 storage.The diffusion of CO2 in oil-water systems has a substantial impact on this process.The interface significantly affects the mass transfer of CO2 between oil and water phase.In this paper,based on the determination of the CO2 diffusion coefficient in oil or water phases,the diffusion processes of CO2 from oil to water were experimentally investigated under different pressures.A numerical method was proposed to calculate the pressure drop and the diffusion coefficient in the process of CO2 diffusion from oil to water.The experimental results indicated that the CO2 diffusion coefficient in oil or water increased rapidly with pressure up to the critical pressure of CO2 and gradually slowed down thereafter.The CO2 diffusion from oil to water was much slower than that in oil or water.The diffusion coefficient of CO2 from oil to water was one magnitude lower than that in the single liquid phase of oil or water,and the effect of pressure was not significant.Based on the diffusion coefficient of CO2 in a single liquid phase and the proposed numerical method,the pressure drop and the numerical diffusion coefficient in the process of CO2 diffusion from oil to water were calculated.The relative errors between the experimental and numerical results were within 9%.Therefore,the numerical method proposed herein can be used to predict the diffusion process of CO2 from oil to water and the diffusion coefficient associated with this process.展开更多
Our article discusses a class of Jump-diffusion stochastic differential system under Markovian switching(JD-SDS-MS).This model is generated by introducing Poisson process and Markovian switching based on a normal stoc...Our article discusses a class of Jump-diffusion stochastic differential system under Markovian switching(JD-SDS-MS).This model is generated by introducing Poisson process and Markovian switching based on a normal stochastic differential equation.Our work dedicates to analytical properties of solutions to this model.First,we give some properties of the solution,including existence,uniqueness,non-negative and global nature.Next,boundedness of first moment of the solution to this model is considered.Third,properties about coefficients of JD-SDS-MS is proved by using a right continuous markov chain.Last,we study the convergence of Euler-Maruyama numerical solutions and apply it to pricing bonds.展开更多
The time-dependent Schr?dinger equation(TDSE)is usually treated in the real space in the textbook.However,it makes the numerical simulations of strong-field processes difficult due to the wide dispersion and fast osci...The time-dependent Schr?dinger equation(TDSE)is usually treated in the real space in the textbook.However,it makes the numerical simulations of strong-field processes difficult due to the wide dispersion and fast oscillation of the electron wave packets under the interaction of intense laser fields.Here we demonstrate that the TDSE can be efficiently solved in the momentum space.The high-order harmonic generation and above-threshold ionization spectra obtained by numerical solutions of TDSE in momentum space agree well with previous studies in real space,but significantly reducing the computation cost.展开更多
The advection step in Eulerian fluid simulation is prone to numerical dissipation[1],resulting in the loss of fluid details.Among the various attempts to develop accurate advection solvers,high-order advection schemes...The advection step in Eulerian fluid simulation is prone to numerical dissipation[1],resulting in the loss of fluid details.Among the various attempts to develop accurate advection solvers,high-order advection schemes such as back and forth error compensation and correction(BFECC)[2]and MacCormack[3]are effective solutions.展开更多
The generalized Born approximation is an approximation method that represents the scattering term by the error between the exact Green's function and the approximate Green's function,mainly for the gradient sc...The generalized Born approximation is an approximation method that represents the scattering term by the error between the exact Green's function and the approximate Green's function,mainly for the gradient scattering problem.However,so far,the research on the generalized Born approximation has only stayed in theory,and its implementation techniques are rarely reported.In order to fill this gap,the basic theory of generalized Born approximation is reviewed,and the implementation method of generalized Born approximation is discussed in this paper.In particular,the problem of calculating boundary effect elimination is discussed in detail.Finally,through model trial calculation,the calculation of gradient scattering,by comparing Born approximation and finite difference method,shows that using the generalized Born approximation to calculate gradient scattering achieves higher computational accuracy.展开更多
The solar power conversion efficiency of a gallium indium phosphide(GaInP)/silicon(Si)tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithi...The solar power conversion efficiency of a gallium indium phosphide(GaInP)/silicon(Si)tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithic structures.In particular,to interconnect the bottom and top sub-cells of the monolithic tandem,a gallium arsenide(GaAs)-based tunnel-junction,i.e.GaAs(n+)/GaAs(p+),which assures a low electrical resistance and an optically low-loss connection,has been considered.The J–V characteristics of the single junction cells,monolithic tandem,and mechanically stacked structure have been calculated extracting the main photovoltaic parameters.An analysis of the tunnel-junction behaviour has been also developed.The mechanically stacked cell achieves an efficiency of 24.27%whereas the monolithic tandem reaches an efficiency of 31.11%under AM1.5 spectral conditions.External quantum efficiency simulations have evaluated the useful wavelength range.The results and discussion could be helpful in designing high efficiency monolithic multijunction GaInP/Si solar cells involving a thin GaAs(n+)/GaAs(p+)tunnel junction.展开更多
The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twod...The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twodimensional morphodynamics numerical model of the Yangtze Estuary is established to verify the morphological evolution of the North-South Passage under the influence of the DNCP and to predict the future evolution in the next 40 years.Data analysis shows that the North Passage has experienced rapid adjustment stages and adaptive stages after the construction of the DNCP.Slow erosion occurred along the main channel,and slow siltation could be observed in the area between the groins.The South Passage showed a state of upper section erosion and down section deposition.At present,the whole South Passage is in a slight erosion state.According to the numerical model,the eroding and silting speed of the North Passage will slow down in the future.The present state that erosion occurs in the main channel and siltation occurs between the groins will continue.The South Passage will still maintain upper section erosion and down section deposition in the future.Due to the main channel erosion of the North Passage and siltation of the South Passage,the sediment division ratio of the North Passage will increase in the future but still be smaller than 50%.After morphological evolution of 40 years,the direction of residual sediment transport caused by M2 and M4 tidal components in the North Passage has not changed,but the transport rate will decrease.It is considered that the morphological evolution of the North-South Passage could reach a relatively stable state after 40 years.展开更多
The thermophysical properties of bone cement are important parameters for its application in the orthopedic treatment. This article focused on the thermal evaluation of the low-melting-point metal(Bi In Sn alloy), whi...The thermophysical properties of bone cement are important parameters for its application in the orthopedic treatment. This article focused on the thermal evaluation of the low-melting-point metal(Bi In Sn alloy), which has been proved to be an excellent bone cement. Firstly, the basic thermophysical properties of Bi In Sn alloys with different melting points were measured.Secondly, 15 fresh porcine femurs placed in the saline bath, bone cements with different melting points and amounts were injected into the bone cavities, respectively. Thermocouples were used to measure the temperature changes of the bone-cement interface and peripheral bone tissue. The possibility of thermal necrosis was evaluated. Moreover, a three-dimensional human knee model was built to numerically assess the effects of thermal parameters, such as melting point and latent heat on tissue temperature distribution. All the experimental and numerical results implied the heat distribution in the tissue depended on the thermal performances of liquid metal bone cement(LMBC). For LMBC of the same melting point, with increased amounts, the damage to the bone tissue is more severe, while for the same amount of different melting point LMBCs, with the higher melting point, which will lead to more serious damage to the tissue. Also, higher latent heat of LMBC has distinct longer solidification process, which may cause irreversible damage to surrounding tissues. Therefore, in the future, for different clinical surgery needs, the appropriate liquid metal bone cement can be obtained by adjusting the thermal parameters.展开更多
The effects of spring soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China(YRNC) and El Ni?o on the East Asian summer monsoon(EASM) and precipitation in easte...The effects of spring soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China(YRNC) and El Ni?o on the East Asian summer monsoon(EASM) and precipitation in eastern China, as well as the relevant mechanisms, are investigated using the modified atmospheric model ECHAM5 coupled with the Common Land Model. These models are the atmospheric and land components of the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM). The simulations show that both soil moisture anomalies in eastern China and El Ni?o sea surface temperature(SST) anomalies have significant influences on the EASM, with the effect of soil moisture being slightly greater than that of the El Ni?o. However, the impacts of soil moisture on EASM and rainfall in eastern China are markedly different from those of the El Ni?o. Wetter(drier) soil over the YRNC corresponds to less(more) precipitation over northern and southeastern China, and more(less) precipitation over the Yangtze River basin and northeastern China, as well as a strengthened(weakened) and westward-shifted(eastward-shifted) West Pacific Subtropical High and a deepened(shallower) East Asian trough, representing a weakened(strengthened) EASM pattern. During El Ni?o developing summers, an anomalous anticyclone extends from northeastern to northern China, and an anomalous cyclone occupies the middle and lower reaches of the Yangtze River and southern China. Concurrently, the West Pacific Subtropical High is anomalously weaker than normal. As a result,rainfall anomalously increases over the lower reaches of the Yangtze River and southern China, and decreases over northern and northeastern China. In El Ni?o decaying summers, there is an anomalous cyclone over northeastern China and an anomalous anticyclone over southern China. The convergence of southerly airflow and northerly winds leads to enhanced rainfall around northern China and the middle reaches of the Yangtze River, and reduced rainfall over other re展开更多
Iron corrosion in acidic media is a natural phenomenon that converts elemental iron to a more chemically-stable form,i.e.its oxide and hydroxide.In this study,the iron corrosion process is modeled as a completely impl...Iron corrosion in acidic media is a natural phenomenon that converts elemental iron to a more chemically-stable form,i.e.its oxide and hydroxide.In this study,the iron corrosion process is modeled as a completely implicit problem,solved by a novel finite difference model to provide insight into the ionic aspects of corrosion behavior.This new mathematical model eliminates the chemical potential parameters from the corrosion process equations,thereby reducing the need for experimental determination of chemical potentials.The eliminatedchemical-potential-parameters model predicts and quantifies key parameters(concentrations of conjugate base ion,iron(Ⅱ)ion,hydrogen ion,anodic and cathodic potentials,and the electrical current density)associated with the iron corrosion process in acidic solutions.The rigorous derivation and novel application of the eliminated-chemical-potential-parameters model and its results provide new insights into the iron corrosion process.The present model is also applicable in any industrial process which is associated with metal corrosion.The model helps to guide the design of future corrosion resistant systems,and various experimental studies pertaining to corrosion inhibition techniques.展开更多
One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collecte...One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collected from the beginning of the Chang’E-3 lunar mission in 2013.These observation data,taken together with the existing lunar laser ranging data,provide a new approach to extend research on the Earth-Moon system.The high precision of current observation data imposes exacting demands,making it necessary to include previously neglected factors.In this paper,motivated by progress of the Chinese lunar exploration project and to use its data in the near future,two lunar models:a one-layer model and a two-layer model with a fluid core,were applied to the rotational equations based on our implemented algorithm of the Moon’s motion.There was a difference of about 0.5′′in φ and ψ,but 0.2′′in θ between the two models.This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data.We also added precise Earth rotation parameters in our model;the results show that this factor is negligible at present,due to the limited precision of the existing data.These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.展开更多
According to the characteristics of submerged floating tunnel anchored by tension legs,simplifying the tube as point mass and assuming that the tension leg is a nonlinear beam model hinged at both ends,the nonlinear v...According to the characteristics of submerged floating tunnel anchored by tension legs,simplifying the tube as point mass and assuming that the tension leg is a nonlinear beam model hinged at both ends,the nonlinear vibration equation of the tension leg is derived.The equation is solved by the Galerkin method and Runge Kutta method.Subsequently,numerical analysis of typical submerged floating tunnel tension leg is carried out.It is shown that,the parametric vibration response of the submerged floating tunnel tension leg is related to the amplitude and frequency of the end excitation.Without considering axial resonance and transverse resonance,it is reasonable that higher order modes are abandoned and only the first three modes are considered.The axial resonance amplitude of the second or third order mode is equivalent to the first order mode axial resonance amplitude,which should not be ignored.展开更多
The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity,i.e.,the projectile is forced to flow radially on the surface of ceramic plates for a peri...The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity,i.e.,the projectile is forced to flow radially on the surface of ceramic plates for a period of time without significant penetration.Interface defeat has a direct effect upon the ballistic performance of the armor piercing projectile,which is studied numerically and theoretically at present.Firstly,by modeling the projectiles and ceramic targets with the SPH(Smoothed Particle Hydrodynamics)particles and Lagrange finite elements,the systematic numerical simulations on interface defeat are performed with the commercial finite element program AUTODYN.Three different responses,i.e.,complete interface defeat,dwell and direct penetration,are reproduced in different types of ceramic targets(bare,buffered,radially confined and oblique).Furthermore,by adopting the validated numerical algorithms,constitutive models and the corresponding material parameters,the influences of projectile(material,diameter,nose shape),constitutive models of ceramic(JH-1 and JH-2 models),buffer and cover plate(thickness,constraints,material),as well as the prestress acted on the target(radial and hydrostatic) on the interface defeat(transition velocity and dwell time) are syste matically investigated.Finally,based on the energy conservation approach and taking the strain rate effect of ceramic material into account,a modified model for predicting the upper limit of transition velocity is proposed and validated.The present work and derived conclusions can provide helpful reference for the design and optimization of both the long-rod projectile and ceramic armor.展开更多
文摘In this study we use a boundary integral element-based numerical technique to solve the generalized Burger-Fisher equation. The essential feature of this method is the fundamental integral representation of the solution inside the problem domain by means of both the boundary and domain values. The occurrences of domain integrals within the problem arising from nonlinearity as well as the temporal derivative are not avoided or transferred to the boundary. However, unlike the classical boundary element approach, they are resolved within a finite-element-type discrete domain. The utility and correctness of this formulation are proved by comparing the results obtained herein with closed form solutions.
文摘Finite Element Method (FEM), based on p and h versions approach, and the Adomians decomposition algorithm (ADM) are introduced for solving the Emden-Fowler Equation. A number of special cases of p and h versions of FEM are introduced. Several iterated forms of the ADM are considered also. To demonstrate the efficiency of both methods, the numerical solutions of different examples are compared for both methods with the analytical solutions. It is observed that the results obtained by FEM are quite satisfactory and more accurate than ADM. Moreover, the FEM method is applicable for a wide range of classes including the singularity cases with the given special treatments by the FEM. Comparing the results with the existing true solutions shows that the FEM approach is highly accurate and converges rapidly.
基金National Natural Science Foundation of China(No.51376018)。
文摘The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-fluid numerical model including electrochemical reactions and water-gas-shift(WGS)reaction for a single channel solid oxide fuel cell was developed to study the steady-state characteristics,which include distributions of the temperature(T),temperature gradient((35)T/(35)x),and fuel utilization.It was shown that the maximum temperature(Tmax)changed with operating voltage and the maximum temperature gradient(((35)T/(35)x)max)occurred at the inlet of the channel of a solid oxide fuel cell by simulation.Moreover,the natural convection condition had a great influence on T and(35)T/(35)x.The thermal stress generated by temperature differences was the key parameter and increasing the convection heat-transfer coefficient can greatly reduce the thermal stress.In addition,the results also showed that there were lower temperature gradients and lower current density at high working voltage;therefore,choosing the proper operating voltage can obtain better cell performance.
基金supported by the National Key Research and Development of China (Grant No. 2016YFC0600406)the National Natural Science Foundation of China (Grant Nos. 41731072, 41574095)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB18000000)。
文摘Flat subduction refers to low-angle(<10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ~10% of present-day subduction zones, but its impact on the behavior of the overriding plate is particularly strong.For example, flat subduction zones are typically associated with stronger earthquakes. The deformation caused by typical flat subduction will transfer from the trench to the overriding continental interior and form a broad magma belt. The formation mechanism of flat subduction has been linked to the relative buoyancy of subducted oceanic plateaus, overthrusting of the overriding plate, hydrodynamic suction, and trench retreat. However, these mechanisms remain debated. This paper systematically analyzes and summarizes previous studies on flat subduction, and outlines the possible geological effects of flat subduction, such as intracontinental orogeny and magmatism. Using examples from numerical modeling, we discuss the possible formation mechanisms. The most important factors that control the formation of flat subduction are associated with overthrusting of the overriding plate and the arrival of an oceanic plateau at the subduction zone. In addition, trench retreat is necessary to enable flat subduction. Hydrodynamic suction contributes to the reduction of the slab dip angle, but is insufficient to form flat subduction. Future numerical modeling of flat subduction should carry out three-dimensional high-resolution thermo-mechanical simulation, considering the influence of crustal eclogitization(negative buoyancy) and mantle serpentinization(positive buoyancy) of oceanic lithosphere, in combination with geological and geophysical data.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51661020,11504149,and 11364024)the Postdoctoral Science Foundation of China(Grant No.2014M560371)the Funds for Distinguished Young Scientists of Lanzhou University of Technology(Grant No.J201304)。
文摘Aiming at the interaction and coalescence of bubbles in gas–liquid two-phase flow, a multi-field coupling model was established to simulate deformation and dynamics of multi-bubble in gas–liquid two-phase flow by coupling magnetic field, phase field, continuity equation, and momentum equation. Using the phase field method to capture the interface of two phases, the geometric deformation and dynamics of a pair of coaxial vertical rising bubbles under the applied uniform magnetic field in the vertical direction were investigated. The correctness of results is verified by mass conservation method and the comparison of the existing results. The results show that the applied uniform magnetic field can effectively shorten the distance between the leading bubble and the trailing bubble, the time of bubbles coalescence, and increase the velocity of bubbles coalescence. Within a certain range, as the intensity of the applied uniform magnetic field increases, the velocity of bubbles coalescence is proportional to the intensity of the magnetic field, and the time of bubbles coalescence is inversely proportional to the intensity of the magnetic field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575033,11675026,and 11975053)the Science Foundation from China Academy of Engineering Physics(Grant No.CX2019033)。
文摘Taking the Rayleigh–Taylor instability with double interfaces as the research object,the interface coupling effects in the weakly nonlinear regime are studied numerically.The variation of Atwood numbers on the two interfaces and the variation of the thickness between them are taken into consideration.It is shown that,when the Atwood number on the lower interface is small,the amplitude of perturbation growth on the lower interface is positively related with the Atwood number on the upper interface.However,it is negatively related when the Atwood number on the lower interface is large.The above phenomenon is quantitatively studied using an analytical formula and the underlying physical mechanism is presented.
基金National Natural Science Foundation of China(No.51574264)National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05056-001)Shandong Provincial Natural Science Foundation,China(ZR2015EL015).
文摘Injecting CO2 into oil reservoirs can improve the oil recovery,meanwhile achieve CO2 storage.The diffusion of CO2 in oil-water systems has a substantial impact on this process.The interface significantly affects the mass transfer of CO2 between oil and water phase.In this paper,based on the determination of the CO2 diffusion coefficient in oil or water phases,the diffusion processes of CO2 from oil to water were experimentally investigated under different pressures.A numerical method was proposed to calculate the pressure drop and the diffusion coefficient in the process of CO2 diffusion from oil to water.The experimental results indicated that the CO2 diffusion coefficient in oil or water increased rapidly with pressure up to the critical pressure of CO2 and gradually slowed down thereafter.The CO2 diffusion from oil to water was much slower than that in oil or water.The diffusion coefficient of CO2 from oil to water was one magnitude lower than that in the single liquid phase of oil or water,and the effect of pressure was not significant.Based on the diffusion coefficient of CO2 in a single liquid phase and the proposed numerical method,the pressure drop and the numerical diffusion coefficient in the process of CO2 diffusion from oil to water were calculated.The relative errors between the experimental and numerical results were within 9%.Therefore,the numerical method proposed herein can be used to predict the diffusion process of CO2 from oil to water and the diffusion coefficient associated with this process.
基金Supported by the National Natural Science Foundation of China(71471075)Fundamental Research Funds for the Central University(19JNLH09)Humanities and Social Sciences Foundation of Ministry of Education,China(14YJAZH052).
文摘Our article discusses a class of Jump-diffusion stochastic differential system under Markovian switching(JD-SDS-MS).This model is generated by introducing Poisson process and Markovian switching based on a normal stochastic differential equation.Our work dedicates to analytical properties of solutions to this model.First,we give some properties of the solution,including existence,uniqueness,non-negative and global nature.Next,boundedness of first moment of the solution to this model is considered.Third,properties about coefficients of JD-SDS-MS is proved by using a right continuous markov chain.Last,we study the convergence of Euler-Maruyama numerical solutions and apply it to pricing bonds.
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFA0307702)the National Natural Science Foundation of China(Grants Nos.91850121 and 11674363)+1 种基金the Science Fund of Educational Department of Henan Province of China(Grant No.2011C140001)the Ninth Group of Key Disciplines in Henan Province,China(Grant No.2018119).
文摘The time-dependent Schr?dinger equation(TDSE)is usually treated in the real space in the textbook.However,it makes the numerical simulations of strong-field processes difficult due to the wide dispersion and fast oscillation of the electron wave packets under the interaction of intense laser fields.Here we demonstrate that the TDSE can be efficiently solved in the momentum space.The high-order harmonic generation and above-threshold ionization spectra obtained by numerical solutions of TDSE in momentum space agree well with previous studies in real space,but significantly reducing the computation cost.
基金supported by National Natural Science Foundation of China(Grant Nos.61502109,61672502,61402038)Natural Science Foundation of Guangdong Province(Grant Nos.2016A030310342,2018A030313802)+2 种基金National Key R&D Program of China(Grant No.2017YFB1002701)Science and Technology Planning Project of Guangdong Province(Grant Nos.2017B010110015,2017B010110007)Open Research Fund of Guangdong Provincial Key Laboratory of CyberPhysical System(Grant No.2016B030301008)。
文摘The advection step in Eulerian fluid simulation is prone to numerical dissipation[1],resulting in the loss of fluid details.Among the various attempts to develop accurate advection solvers,high-order advection schemes such as back and forth error compensation and correction(BFECC)[2]and MacCormack[3]are effective solutions.
基金Supported by Project of the National Natural Science Foundation of China(No.41974135).
文摘The generalized Born approximation is an approximation method that represents the scattering term by the error between the exact Green's function and the approximate Green's function,mainly for the gradient scattering problem.However,so far,the research on the generalized Born approximation has only stayed in theory,and its implementation techniques are rarely reported.In order to fill this gap,the basic theory of generalized Born approximation is reviewed,and the implementation method of generalized Born approximation is discussed in this paper.In particular,the problem of calculating boundary effect elimination is discussed in detail.Finally,through model trial calculation,the calculation of gradient scattering,by comparing Born approximation and finite difference method,shows that using the generalized Born approximation to calculate gradient scattering achieves higher computational accuracy.
文摘The solar power conversion efficiency of a gallium indium phosphide(GaInP)/silicon(Si)tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithic structures.In particular,to interconnect the bottom and top sub-cells of the monolithic tandem,a gallium arsenide(GaAs)-based tunnel-junction,i.e.GaAs(n+)/GaAs(p+),which assures a low electrical resistance and an optically low-loss connection,has been considered.The J–V characteristics of the single junction cells,monolithic tandem,and mechanically stacked structure have been calculated extracting the main photovoltaic parameters.An analysis of the tunnel-junction behaviour has been also developed.The mechanically stacked cell achieves an efficiency of 24.27%whereas the monolithic tandem reaches an efficiency of 31.11%under AM1.5 spectral conditions.External quantum efficiency simulations have evaluated the useful wavelength range.The results and discussion could be helpful in designing high efficiency monolithic multijunction GaInP/Si solar cells involving a thin GaAs(n+)/GaAs(p+)tunnel junction.
基金the National Key R&D Program of China(Grant No.2017YFC0405400)the National Natural Science Foundation of China(Grant No.51979172)Innovation Team Project of Estuarine and Coastal Protection and Management(Grant No.Y220013).
文摘The morphological evolution characteristics of the North-South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project(DNCP)are analyzed on the basis of the measured data.A twodimensional morphodynamics numerical model of the Yangtze Estuary is established to verify the morphological evolution of the North-South Passage under the influence of the DNCP and to predict the future evolution in the next 40 years.Data analysis shows that the North Passage has experienced rapid adjustment stages and adaptive stages after the construction of the DNCP.Slow erosion occurred along the main channel,and slow siltation could be observed in the area between the groins.The South Passage showed a state of upper section erosion and down section deposition.At present,the whole South Passage is in a slight erosion state.According to the numerical model,the eroding and silting speed of the North Passage will slow down in the future.The present state that erosion occurs in the main channel and siltation occurs between the groins will continue.The South Passage will still maintain upper section erosion and down section deposition in the future.Due to the main channel erosion of the North Passage and siltation of the South Passage,the sediment division ratio of the North Passage will increase in the future but still be smaller than 50%.After morphological evolution of 40 years,the direction of residual sediment transport caused by M2 and M4 tidal components in the North Passage has not changed,but the transport rate will decrease.It is considered that the morphological evolution of the North-South Passage could reach a relatively stable state after 40 years.
基金This work was supported by the Science and Technology Service Network Initiative of the Chinese Academy of Sciences(Grant No.KFJ-STS-QYZD-078)the National Natural Science Foundation of China(Grant No.51890893)。
文摘The thermophysical properties of bone cement are important parameters for its application in the orthopedic treatment. This article focused on the thermal evaluation of the low-melting-point metal(Bi In Sn alloy), which has been proved to be an excellent bone cement. Firstly, the basic thermophysical properties of Bi In Sn alloys with different melting points were measured.Secondly, 15 fresh porcine femurs placed in the saline bath, bone cements with different melting points and amounts were injected into the bone cavities, respectively. Thermocouples were used to measure the temperature changes of the bone-cement interface and peripheral bone tissue. The possibility of thermal necrosis was evaluated. Moreover, a three-dimensional human knee model was built to numerically assess the effects of thermal parameters, such as melting point and latent heat on tissue temperature distribution. All the experimental and numerical results implied the heat distribution in the tissue depended on the thermal performances of liquid metal bone cement(LMBC). For LMBC of the same melting point, with increased amounts, the damage to the bone tissue is more severe, while for the same amount of different melting point LMBCs, with the higher melting point, which will lead to more serious damage to the tissue. Also, higher latent heat of LMBC has distinct longer solidification process, which may cause irreversible damage to surrounding tissues. Therefore, in the future, for different clinical surgery needs, the appropriate liquid metal bone cement can be obtained by adjusting the thermal parameters.
基金supported by the National Natural Science Foundation of China(Grant Nos.41822503&41375092)the National Key Research and Development Program(Grant No.2016YFA0601502)。
文摘The effects of spring soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China(YRNC) and El Ni?o on the East Asian summer monsoon(EASM) and precipitation in eastern China, as well as the relevant mechanisms, are investigated using the modified atmospheric model ECHAM5 coupled with the Common Land Model. These models are the atmospheric and land components of the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM). The simulations show that both soil moisture anomalies in eastern China and El Ni?o sea surface temperature(SST) anomalies have significant influences on the EASM, with the effect of soil moisture being slightly greater than that of the El Ni?o. However, the impacts of soil moisture on EASM and rainfall in eastern China are markedly different from those of the El Ni?o. Wetter(drier) soil over the YRNC corresponds to less(more) precipitation over northern and southeastern China, and more(less) precipitation over the Yangtze River basin and northeastern China, as well as a strengthened(weakened) and westward-shifted(eastward-shifted) West Pacific Subtropical High and a deepened(shallower) East Asian trough, representing a weakened(strengthened) EASM pattern. During El Ni?o developing summers, an anomalous anticyclone extends from northeastern to northern China, and an anomalous cyclone occupies the middle and lower reaches of the Yangtze River and southern China. Concurrently, the West Pacific Subtropical High is anomalously weaker than normal. As a result,rainfall anomalously increases over the lower reaches of the Yangtze River and southern China, and decreases over northern and northeastern China. In El Ni?o decaying summers, there is an anomalous cyclone over northeastern China and an anomalous anticyclone over southern China. The convergence of southerly airflow and northerly winds leads to enhanced rainfall around northern China and the middle reaches of the Yangtze River, and reduced rainfall over other re
文摘Iron corrosion in acidic media is a natural phenomenon that converts elemental iron to a more chemically-stable form,i.e.its oxide and hydroxide.In this study,the iron corrosion process is modeled as a completely implicit problem,solved by a novel finite difference model to provide insight into the ionic aspects of corrosion behavior.This new mathematical model eliminates the chemical potential parameters from the corrosion process equations,thereby reducing the need for experimental determination of chemical potentials.The eliminatedchemical-potential-parameters model predicts and quantifies key parameters(concentrations of conjugate base ion,iron(Ⅱ)ion,hydrogen ion,anodic and cathodic potentials,and the electrical current density)associated with the iron corrosion process in acidic solutions.The rigorous derivation and novel application of the eliminated-chemical-potential-parameters model and its results provide new insights into the iron corrosion process.The present model is also applicable in any industrial process which is associated with metal corrosion.The model helps to guide the design of future corrosion resistant systems,and various experimental studies pertaining to corrosion inhibition techniques.
基金supported by LIESMARS Special Research Fundingthe National Natural Science Foundation of China(U1831132,41590851,11373060,10973030 and 10778635)+3 种基金the State Key Project for Science and Technology(2015CB857101)National Astronomical Observatories,Chinese Academy of Sciences,a grant from the Hubei Province Natural Science(2018CFA087)Open Project of Lunar and Planetary Science Laboratory,Macau University of Science and Technology(FDCT 119/2017/A3)Open Funding of Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing(KF201813).
文摘One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collected from the beginning of the Chang’E-3 lunar mission in 2013.These observation data,taken together with the existing lunar laser ranging data,provide a new approach to extend research on the Earth-Moon system.The high precision of current observation data imposes exacting demands,making it necessary to include previously neglected factors.In this paper,motivated by progress of the Chinese lunar exploration project and to use its data in the near future,two lunar models:a one-layer model and a two-layer model with a fluid core,were applied to the rotational equations based on our implemented algorithm of the Moon’s motion.There was a difference of about 0.5′′in φ and ψ,but 0.2′′in θ between the two models.This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data.We also added precise Earth rotation parameters in our model;the results show that this factor is negligible at present,due to the limited precision of the existing data.These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.
基金This work was financially supported by the Research Fund of Liaocheng University(Grant No.318011916)the Natural Science Foundation of Shandong Province(Grant No.ZR2018BEE046).
文摘According to the characteristics of submerged floating tunnel anchored by tension legs,simplifying the tube as point mass and assuming that the tension leg is a nonlinear beam model hinged at both ends,the nonlinear vibration equation of the tension leg is derived.The equation is solved by the Galerkin method and Runge Kutta method.Subsequently,numerical analysis of typical submerged floating tunnel tension leg is carried out.It is shown that,the parametric vibration response of the submerged floating tunnel tension leg is related to the amplitude and frequency of the end excitation.Without considering axial resonance and transverse resonance,it is reasonable that higher order modes are abandoned and only the first three modes are considered.The axial resonance amplitude of the second or third order mode is equivalent to the first order mode axial resonance amplitude,which should not be ignored.
基金supported by the National Natural Science Foundation of China(51878507)。
文摘The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity,i.e.,the projectile is forced to flow radially on the surface of ceramic plates for a period of time without significant penetration.Interface defeat has a direct effect upon the ballistic performance of the armor piercing projectile,which is studied numerically and theoretically at present.Firstly,by modeling the projectiles and ceramic targets with the SPH(Smoothed Particle Hydrodynamics)particles and Lagrange finite elements,the systematic numerical simulations on interface defeat are performed with the commercial finite element program AUTODYN.Three different responses,i.e.,complete interface defeat,dwell and direct penetration,are reproduced in different types of ceramic targets(bare,buffered,radially confined and oblique).Furthermore,by adopting the validated numerical algorithms,constitutive models and the corresponding material parameters,the influences of projectile(material,diameter,nose shape),constitutive models of ceramic(JH-1 and JH-2 models),buffer and cover plate(thickness,constraints,material),as well as the prestress acted on the target(radial and hydrostatic) on the interface defeat(transition velocity and dwell time) are syste matically investigated.Finally,based on the energy conservation approach and taking the strain rate effect of ceramic material into account,a modified model for predicting the upper limit of transition velocity is proposed and validated.The present work and derived conclusions can provide helpful reference for the design and optimization of both the long-rod projectile and ceramic armor.