A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method （AAM） tha...A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method （AAM） that yields the surface distribution of transferred mass by analyzing the color distribution on a filter paper with the results of the color chemical reaction. A digital image processing technology is applied for data visualiza-tion. The three-dimensional plot of the local mass transfer coefficients shows that there exist three peak values on different positions of a unit cell of structured packing. In order to improve mass transfer efficiency of the structured packing, one piece of baffle is added between packing sheets. As a result, the average mass transfer coefficient increases by （10 20）% and the pressure drop decreases by （15-55）%.展开更多
In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The varia...In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO2,NO2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution.展开更多
The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Grou...The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Group using the high mass-resolution hydrodynamic APOSTLE simulation.The simulated HI mass function agrees with the ALFALFA survey very well above 10~6M_⊙,although there is a discrepancy below this scale because of the observed flux limit.After carefully checking various systematic elements in the observations,including fitting of line width,sky coverage,integration time and frequency drift due to uncertainty in a galaxy’s distance,we predicted the abundance of HI in galaxies in a future survey that will be conducted by FAST.FAST has a larger aperture and higher sensitivity than the Arecibo telescope.We found that the HI mass function could be estimated well around 10~5M_⊙ if the integration time is 40 minutes.Our results indicate that there are 61 HI satellites in the Local Group and 36 in the FAST field above 10~5M_⊙.This estimation is one order of magnitude better than the current data,and will put a strong constraint on the formation history of the Local Group.Also more high resolution simulated samples are needed to achieve this target.展开更多
The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differenti...The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differential equations: an elliptic equation for electric potential, two convection-diffusion equations for electron concentration and hole concentration, and a heat conduction equation for temperature. The first equation is solved by the conservative block-centered method. The concentrations and temperature are computed by the block-centered upwind difference method on a changing mesh, where the block-centered method and upwind approximation are used to discretize the diffusion and convection, respectively. The computations on a changing mesh show very well the local special properties nearby the P-N junction. The upwind scheme is applied to approximate the convection, and numerical dispersion and nonphysical oscillation are avoided. The block-centered difference computes concentrations, temperature, and their adjoint vector functions simultaneously.The local conservation of mass, an important rule in the numerical simulation of a semiconductor device, is preserved during the computations. An optimal order convergence is obtained. Numerical examples are provided to show efficiency and application.展开更多
The physical model is described by a seepage coupled system for simulating numerically three-dimensional chemical oil recovery, whose mathematical description includes three equations to interpret main concepts. The p...The physical model is described by a seepage coupled system for simulating numerically three-dimensional chemical oil recovery, whose mathematical description includes three equations to interpret main concepts. The pressure equation is a nonlinear parabolic equation, the concentration is defined by a convection-diffusion equation and the saturations of different components are stated by nonlinear convection-diffusion equations. The transport pressure appears in the concentration equation and saturation equations in the form of Darcy velocity, and controls their processes. The flow equation is solved by the conservative mixed volume element and the accuracy is improved one order for approximating Darcy velocity. The method of characteristic mixed volume element is applied to solve the concentration, where the diffusion is discretized by a mixed volume element method and the convection is treated by the method of characteristics. The characteristics can confirm strong computational stability at sharp fronts and it can avoid numerical dispersion and nonphysical oscillation. The scheme can adopt a large step while its numerical results have small time-truncation error and high order of accuracy. The mixed volume element method has the law of conservation on every element for the diffusion and it can obtain numerical solutions of the concentration and adjoint vectors. It is most important in numerical simulation to ensure the physical conservative nature. The saturation different components are obtained by the method of characteristic fractional step difference. The computational work is shortened greatly by decomposing a three-dimensional problem into three successive one-dimensional problems and it is completed easily by using the algorithm of speedup. Using the theory and technique of a priori estimates of differential equations, we derive an optimal second order estimates in 12 norm. Numerical examples are given to show the effectiveness and practicability and the method is testified as a powerful tool to solve the important problems.展开更多
In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and t...In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and the approximation accuracy of Darch-Forchheimer velocity is improved one order.The concentration equation is solved by the method of mixed finite element,where the convection is discretized along the characteristic direction and the diffusion is discretized by the zero-order mixed finite element method.The characteristics can confirm strong stability at sharp fronts and avoids numerical dispersion and nonphysical oscillation.In actual computations the characteristics adopts a large time step without any loss of accuracy.The scalar unknowns and its adjoint vector function are obtained simultaneously and the law of mass conservation holds in every element by the zero-order mixed finite element discretization of diffusion flux.In order to derive the optimal 3/2-order error estimate in L^(2) norm,a post-processing technique is included in the approximation to the scalar unknowns.Numerical experiments are illustrated finally to validate theoretical analysis and efficiency.This method can be used to solve such an important problem.展开更多
In this study,a feedforward neural network(FNN)approach is employed to optimize three local mass models(GK,GKs,and GK+J).We find that adding physical quantities related to the pairing effect in the input layer can eff...In this study,a feedforward neural network(FNN)approach is employed to optimize three local mass models(GK,GKs,and GK+J).We find that adding physical quantities related to the pairing effect in the input layer can effectively improve the prediction accuracy of local models.For the known masses in AME2012,the FNN reduces the root-mean-square deviation between theory and experiment for the three mass models by 11 keV,32 keV,and 623 keV.Among them,the improvement effect of the light mass region with mass number between 16 and 60 is better than that of medium and heavy mass regions.The approach also has good optimization results when extrapolating AME2012 to AME2020 and the latest measured masses after AME2020.Based on the improved mass data,the separation energies for single-and two-proton(neutron)emissions andα-decay energies are obtained,which agree well with the experiment.展开更多
Numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science.The mathematical model is defined by a nonlinear system of initial-boundary problem including four parti...Numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science.The mathematical model is defined by a nonlinear system of initial-boundary problem including four partial differential equations:an elliptic equation for electrostatic potential,two convection-diffusion equations for electron concentration and hole concentration,a heat conduction equation for temperature.The electrostatic potential appears within the concentration equations and heat conduction equation,and the electric field strength controls the concentrations and the temperature.The electric field potential is solved by the conservative block-centered method,and the order of the accuracy is improved by the electric potential.The concentrations and temperature are computed by the upwind blockcentered multistep method,where three different numerical methods are involved.The multistep method is adopted to approximate the time derivative.The blockcentered method is used to discretize the diffusion.The upwind scheme is applied to approximate the convection to avoid numerical dispersion and nonphysical oscillation.The block-centered difference simulates diffusion,concentrations,temperature,and the adjoint vector functions simultaneously.It has the local conservation of mass,which is an important nature in numerical simulation of a semiconductor device.By using the variation,energy estimates,induction hypothesis,embedding theorem and the technique of a priori estimates of differential equations,convergence of the optimal order is obtained.Numerical examples are provided to show the effectiveness and viability.This method provides a powerful tool for solving the challenging benchmark problem.展开更多
VOF method which consists in transporting a discontinuous marker variable is widely used to capture the free surface in computational fluid dynamics.There is numerical dissipation in simulations involving the transpor...VOF method which consists in transporting a discontinuous marker variable is widely used to capture the free surface in computational fluid dynamics.There is numerical dissipation in simulations involving the transport of the marker.Numerical dissipation makes the free surface lose its physical nature.A free surface sharpening strategy based on optimization method is presented in the paper.The strategy can keep the location of the free surface and local mass conservation at both time,and can also keep free surface in a constant width.It is independent on the types of solvers and meshes.Two famous cases were chosen for verifying the free surface sharpening strategy performance.Results show that the strategy has a very good performance on keeping local mass conservation.The efficiency of prediction of the free surface is improved by applying the strategy.Accurate modeling of flow details such as drops can also be captured by this method.展开更多
We develop a locally mass-conservative enriched Petrov-Galerkin(EPG)method without any penalty term for the simulation of Darcy flow in fractured porous media.The discrete fracture model is applied to model the fractu...We develop a locally mass-conservative enriched Petrov-Galerkin(EPG)method without any penalty term for the simulation of Darcy flow in fractured porous media.The discrete fracture model is applied to model the fractures as the lower dimensional fracture interfaces.The new method enriches the approximation trial space of the conforming continuous Galerkin(CG)method with bubble functions and enriches the approximation test space of the CG method with piecewise constant functions in the fractures and the surrounding porous media.We propose a framework for constructing the bubble functions and consider a decoupled algorithm for the EPG method.The solution of the pressure can be decoupled into two steps with a standard CG method and a post-processing correction.The post-processing correction based on the bubble functions in the matrix and the fractures can be solved separately,which is useful for parallel computing.We derive a priori and a posteriori error estimates for the problem.Numerical examples are presented to illustrate the performance of the proposed method.展开更多
文摘A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method （AAM） that yields the surface distribution of transferred mass by analyzing the color distribution on a filter paper with the results of the color chemical reaction. A digital image processing technology is applied for data visualiza-tion. The three-dimensional plot of the local mass transfer coefficients shows that there exist three peak values on different positions of a unit cell of structured packing. In order to improve mass transfer efficiency of the structured packing, one piece of baffle is added between packing sheets. As a result, the average mass transfer coefficient increases by （10 20）% and the pressure drop decreases by （15-55）%.
基金supported by the Key Research Program of Chinese Academy of Sciences (No. KJZD-EW-TZ-G06-01-15)the National Natural Science Foundation of China (No. 21407158)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (No. XDB05010300)
文摘In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO2,NO2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution.
基金support by China Program of International S&T Cooperation(2016YFE0100300)support by the National Natural Science Foundation of China(NSFC,Grant Nos.11633004,11390372,11303008 and 11773034)+1 种基金the 973 program grant 2015CB857005the NSFC(No.11373029)
文摘The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Group using the high mass-resolution hydrodynamic APOSTLE simulation.The simulated HI mass function agrees with the ALFALFA survey very well above 10~6M_⊙,although there is a discrepancy below this scale because of the observed flux limit.After carefully checking various systematic elements in the observations,including fitting of line width,sky coverage,integration time and frequency drift due to uncertainty in a galaxy’s distance,we predicted the abundance of HI in galaxies in a future survey that will be conducted by FAST.FAST has a larger aperture and higher sensitivity than the Arecibo telescope.We found that the HI mass function could be estimated well around 10~5M_⊙ if the integration time is 40 minutes.Our results indicate that there are 61 HI satellites in the Local Group and 36 in the FAST field above 10~5M_⊙.This estimation is one order of magnitude better than the current data,and will put a strong constraint on the formation history of the Local Group.Also more high resolution simulated samples are needed to achieve this target.
基金supported the Natural Science Foundation of Shandong Province(ZR2016AM08)Natural Science Foundation of Hunan Province(2018JJ2028)National Natural Science Foundation of China(11871312).
文摘The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differential equations: an elliptic equation for electric potential, two convection-diffusion equations for electron concentration and hole concentration, and a heat conduction equation for temperature. The first equation is solved by the conservative block-centered method. The concentrations and temperature are computed by the block-centered upwind difference method on a changing mesh, where the block-centered method and upwind approximation are used to discretize the diffusion and convection, respectively. The computations on a changing mesh show very well the local special properties nearby the P-N junction. The upwind scheme is applied to approximate the convection, and numerical dispersion and nonphysical oscillation are avoided. The block-centered difference computes concentrations, temperature, and their adjoint vector functions simultaneously.The local conservation of mass, an important rule in the numerical simulation of a semiconductor device, is preserved during the computations. An optimal order convergence is obtained. Numerical examples are provided to show efficiency and application.
基金Supported by the National Natural Science Foundation of China(11101124 and 11271231)Natural Science Foundation of Shandong Province(ZR2016AM08)National Tackling Key Problems Program(2011ZX05052,2011ZX05011-004)
文摘The physical model is described by a seepage coupled system for simulating numerically three-dimensional chemical oil recovery, whose mathematical description includes three equations to interpret main concepts. The pressure equation is a nonlinear parabolic equation, the concentration is defined by a convection-diffusion equation and the saturations of different components are stated by nonlinear convection-diffusion equations. The transport pressure appears in the concentration equation and saturation equations in the form of Darcy velocity, and controls their processes. The flow equation is solved by the conservative mixed volume element and the accuracy is improved one order for approximating Darcy velocity. The method of characteristic mixed volume element is applied to solve the concentration, where the diffusion is discretized by a mixed volume element method and the convection is treated by the method of characteristics. The characteristics can confirm strong computational stability at sharp fronts and it can avoid numerical dispersion and nonphysical oscillation. The scheme can adopt a large step while its numerical results have small time-truncation error and high order of accuracy. The mixed volume element method has the law of conservation on every element for the diffusion and it can obtain numerical solutions of the concentration and adjoint vectors. It is most important in numerical simulation to ensure the physical conservative nature. The saturation different components are obtained by the method of characteristic fractional step difference. The computational work is shortened greatly by decomposing a three-dimensional problem into three successive one-dimensional problems and it is completed easily by using the algorithm of speedup. Using the theory and technique of a priori estimates of differential equations, we derive an optimal second order estimates in 12 norm. Numerical examples are given to show the effectiveness and practicability and the method is testified as a powerful tool to solve the important problems.
基金supported by the Natural ScienceFoundation of Shandong Province(ZR2021MA019)。
文摘In this paper a mixed finite element-characteristic mixed finite element method is discussed to simulate an incompressible miscible Darcy-Forchheimer problem.The flow equation is solved by a mixed finite element and the approximation accuracy of Darch-Forchheimer velocity is improved one order.The concentration equation is solved by the method of mixed finite element,where the convection is discretized along the characteristic direction and the diffusion is discretized by the zero-order mixed finite element method.The characteristics can confirm strong stability at sharp fronts and avoids numerical dispersion and nonphysical oscillation.In actual computations the characteristics adopts a large time step without any loss of accuracy.The scalar unknowns and its adjoint vector function are obtained simultaneously and the law of mass conservation holds in every element by the zero-order mixed finite element discretization of diffusion flux.In order to derive the optimal 3/2-order error estimate in L^(2) norm,a post-processing technique is included in the approximation to the scalar unknowns.Numerical experiments are illustrated finally to validate theoretical analysis and efficiency.This method can be used to solve such an important problem.
基金Supported by National Natural Science Foundation of China(11875188)China Scholarship Council(202409390020)。
文摘In this study,a feedforward neural network(FNN)approach is employed to optimize three local mass models(GK,GKs,and GK+J).We find that adding physical quantities related to the pairing effect in the input layer can effectively improve the prediction accuracy of local models.For the known masses in AME2012,the FNN reduces the root-mean-square deviation between theory and experiment for the three mass models by 11 keV,32 keV,and 623 keV.Among them,the improvement effect of the light mass region with mass number between 16 and 60 is better than that of medium and heavy mass regions.The approach also has good optimization results when extrapolating AME2012 to AME2020 and the latest measured masses after AME2020.Based on the improved mass data,the separation energies for single-and two-proton(neutron)emissions andα-decay energies are obtained,which agree well with the experiment.
基金supported by National Natural Science Foundation of China(Grant No.11871312)Natural Science Foundation of Shandong Province(Grant No.ZR2021MA019).
文摘Numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science.The mathematical model is defined by a nonlinear system of initial-boundary problem including four partial differential equations:an elliptic equation for electrostatic potential,two convection-diffusion equations for electron concentration and hole concentration,a heat conduction equation for temperature.The electrostatic potential appears within the concentration equations and heat conduction equation,and the electric field strength controls the concentrations and the temperature.The electric field potential is solved by the conservative block-centered method,and the order of the accuracy is improved by the electric potential.The concentrations and temperature are computed by the upwind blockcentered multistep method,where three different numerical methods are involved.The multistep method is adopted to approximate the time derivative.The blockcentered method is used to discretize the diffusion.The upwind scheme is applied to approximate the convection to avoid numerical dispersion and nonphysical oscillation.The block-centered difference simulates diffusion,concentrations,temperature,and the adjoint vector functions simultaneously.It has the local conservation of mass,which is an important nature in numerical simulation of a semiconductor device.By using the variation,energy estimates,induction hypothesis,embedding theorem and the technique of a priori estimates of differential equations,convergence of the optimal order is obtained.Numerical examples are provided to show the effectiveness and viability.This method provides a powerful tool for solving the challenging benchmark problem.
基金funded by National Natural Science Foundation of China,Grant number:51176012
文摘VOF method which consists in transporting a discontinuous marker variable is widely used to capture the free surface in computational fluid dynamics.There is numerical dissipation in simulations involving the transport of the marker.Numerical dissipation makes the free surface lose its physical nature.A free surface sharpening strategy based on optimization method is presented in the paper.The strategy can keep the location of the free surface and local mass conservation at both time,and can also keep free surface in a constant width.It is independent on the types of solvers and meshes.Two famous cases were chosen for verifying the free surface sharpening strategy performance.Results show that the strategy has a very good performance on keeping local mass conservation.The efficiency of prediction of the free surface is improved by applying the strategy.Accurate modeling of flow details such as drops can also be captured by this method.
基金supported by the National Key Research and Development Project of China(Grant No.2023YFA1011702)the NSF of China(Grant No.12122115)。
文摘We develop a locally mass-conservative enriched Petrov-Galerkin(EPG)method without any penalty term for the simulation of Darcy flow in fractured porous media.The discrete fracture model is applied to model the fractures as the lower dimensional fracture interfaces.The new method enriches the approximation trial space of the conforming continuous Galerkin(CG)method with bubble functions and enriches the approximation test space of the CG method with piecewise constant functions in the fractures and the surrounding porous media.We propose a framework for constructing the bubble functions and consider a decoupled algorithm for the EPG method.The solution of the pressure can be decoupled into two steps with a standard CG method and a post-processing correction.The post-processing correction based on the bubble functions in the matrix and the fractures can be solved separately,which is useful for parallel computing.We derive a priori and a posteriori error estimates for the problem.Numerical examples are presented to illustrate the performance of the proposed method.
