This paper presents a cell-centered Godunov method based on staggered data distribu-tion in Eulerian framework.The motivation is to reduce the intrinsic entropy dissipation of classical Godunov methods in the calculat...This paper presents a cell-centered Godunov method based on staggered data distribu-tion in Eulerian framework.The motivation is to reduce the intrinsic entropy dissipation of classical Godunov methods in the calculation of an isentropic or rarefaction flow.At the same time,the property of accurate shock capturing is also retained.By analyzing the factors that cause nonphysical entropy in the conventional Godunov methods,we introduce two velocities rather than a single velocity in a cell to reduce kinetic energy dissipation.A series of redistribution strategies are adopted to update subcell quantities in order to improve accuracy.Numerical examples validate that the present method can dramatically reduce nonphysical entropy increase.Mathematics subject classification:35Q35,76N15,76M12.展开更多
Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis.The homogeneous catalyst,despite providing high conversion,can cause corrosion in reactors,...Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis.The homogeneous catalyst,despite providing high conversion,can cause corrosion in reactors,which is not observed with the use of heterogeneous catalysts.However,some of these catalysts require a high process temperature and may lose their catalytic activity with reuse.Thus,catalytic membranes have been proposed as a promising alternative.The combination of catalysis and separation in a single module provides greater conversion,reduction of excess reagents,compact industrial plant,making the process more efficient.Within this context,this work aims to present a literature review on the catalytic membrane for the synthesis of esters,improving the understanding of the production and development.This review examines the materials,catalysts used,and synthetic pathways.A comparison between the methods,as well as limitations and gaps in the literature,are highlighted.展开更多
Iron and Manganese contents and parameters including pH, conductivity, and organic matter contents were determined in the sediments of the Okpara dam in Northern Benin. Fifteen samples were collected during a one-mont...Iron and Manganese contents and parameters including pH, conductivity, and organic matter contents were determined in the sediments of the Okpara dam in Northern Benin. Fifteen samples were collected during a one-month period and analysed in laboratory using the method of sequential extraction of Tessier. The analyses indicated that sediments contained high concentrations in reducible fraction of Iron and relatively high contents of exchangeable fraction, acidhydrolysable fraction and residual fraction of Manganese. The findings of this study confirmed the hypotheses that the meal contents of the sediments were relatively high and varied according to the geochemical phases.展开更多
A one-dimensional quantum hydrodynamic model （or quantum Euler-Poisson system） for semiconductors with initial boundary conditions is considered for general pressure-density function. The existence and uniqueness of...A one-dimensional quantum hydrodynamic model （or quantum Euler-Poisson system） for semiconductors with initial boundary conditions is considered for general pressure-density function. The existence and uniqueness of the classical solution of the corresponding steady-state quantum hydrodynamic equations is proved. Furthermore, the global existence of classical solution, when the initial datum is a perturbation of t he steadystate solution, is obtained. This solution tends to the corresponding steady-state solution exponentially fast as the time tends to infinity.展开更多
We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the lo...We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.展开更多
In this article, the globally bounded in-time pointwise estimate of solutions to the simplified Keller-Segel system modelling chemotaxis are derived. Moreover, a local existence theorem is obtained.
We report the formation of jet-like long spike in the nonlinear evolution of the ablative Rayleigh-Taylor instability （ARTI） experiments by numerical simulations. A preheating model k（T） = KSH[1＋f（T）], where KS...We report the formation of jet-like long spike in the nonlinear evolution of the ablative Rayleigh-Taylor instability （ARTI） experiments by numerical simulations. A preheating model k（T） = KSH[1＋f（T）], where KSH is the Spitzer Harm （SH） electron conductivity and f（T） interprets the preheating tongue effect in the cold plasma ahead of the ablative front [Phys. Rev. E 65 （2002） 57401], is introduced in simulations. The simulation results of the nonlinear evolution of the ARTI are in general agreement with the experiment results. It is found that two factors, i.e., the suppressing of ablative Kelvin Helmholtz instability （AKHI） and the heat flow cone in the spike tips, contribute to the formation of jet-like long spike in the nonlinear evolution of the ARTI.展开更多
We prove the local in time existence and a blow up criterion of solution in the Holder spaces for the inviscid Boussinesq system in RN,N ≥ 2, under the assumptions that the initial values θo,uo ∈ Cr, with 1 〈 r ≠ 2.
In this paper, the decomposition of SU(2) gauge potential in terms of Pauli spinor is studied. Using this decomposition, the spinor structures of Chern Simons form and the Chern density are obtained. Furthermore, the ...In this paper, the decomposition of SU(2) gauge potential in terms of Pauli spinor is studied. Using this decomposition, the spinor structures of Chern Simons form and the Chern density are obtained. Furthermore, the knot quantum number of non-Abelian gauge theory can be expressed by the Chern-Simons spinor structure, and the second Chern number is characterized by the Hopf indices and the Brouwer degrees of Φ-mapping.展开更多
In this paper, we study the large time asymptotic behavior of solutions to both the Cauchy problem and the exterior problem of the Stokes approximation equations of two dimensional compressible flows.
The periodic Anderson model （PAM）, where local electron orbitals interplay with itinerant electronic carriers, plays an essential role in our understanding of heavy fermion materials. Motivated by recent proposals f...The periodic Anderson model （PAM）, where local electron orbitals interplay with itinerant electronic carriers, plays an essential role in our understanding of heavy fermion materials. Motivated by recent proposals for simulating the Kondo lattice model （KLM） in terms of alkaline-earth metal atoms, we take another step toward the simulation of PAM, which includes the crucial charge/valence fluctuation of local f-electrons beyond purely low-energy spin fluctuation in the KLM. To realize PAM, a transition induced by a suitable laser between the electronic excited and ground state of alkaline-earth metal atoms （^1S0←→^3P0） is introduced. This leads to effective hybridization between local electrons and conduction electrons in PAM. Generally, the SU（N） version of PAM can be realized by our proposal, which gives a unique opportunity to detect large-N physics without complexity in realistic materials. In the present work, high-temperature physical features of standard [SU（2）] PAM with harmonic trapping potential are analyzed by quantum Monte Carlo and dynamic mean-field theory, where the Mott/orbital-selective Mott state was found to coexist with metallic states. Indications for near-future experiments are provided. We expect our theoretical proposal and （hopefully） forthcoming experiments will deepen our understanding of heavy fermion systems. At the same time, we hope these will trigger further studies on related Mott physics, quantum criticality, and non-trivial topology in both the inhomogeneous and nonequilibrium realms.展开更多
It is well known that a linear complementarity problem (LCP) can be formulated as a system of nonsmooth equations F(x) = 0, where F is a map from Rninto itself. Using the aggregate function, we construct a smooth Newt...It is well known that a linear complementarity problem (LCP) can be formulated as a system of nonsmooth equations F(x) = 0, where F is a map from Rninto itself. Using the aggregate function, we construct a smooth Newton homotopy H(x,t) = 0. Under certain assumptions, we prove the existence of a smooth path defined by the Newton homotopy which leads to a solution of the original problem, and study limiting properties of the homotopy path.展开更多
In this article, we prove the local existence and uniqueness of the classical solution to the Cauchy problem of the 3-D compressible Navier-Stokes equations with large initial data and vacuum, if the shear viscosity ...In this article, we prove the local existence and uniqueness of the classical solution to the Cauchy problem of the 3-D compressible Navier-Stokes equations with large initial data and vacuum, if the shear viscosity μ is a positive constant and the bulk viscosity λ（ρ） = ρ^β with β≥0. Note that the initial data can be arbitrarily large to contain vacuum states.展开更多
In this paper, we analyze the bifurcation and the confluence of the Pacific western boundary currents by an analytical approach. Applying the conservation law, the geostrophic balance relation and the Bernoulli integr...In this paper, we analyze the bifurcation and the confluence of the Pacific western boundary currents by an analytical approach. Applying the conservation law, the geostrophic balance relation and the Bernoulli integral to a reduced gravity model, we get a quantitative relation for the outflow and the inflow, and establish the related formulae for the width and the veering angle of offshore currents under the inflow condition. Furthermore, a comparison between the volume transport based on the observation data and the analytical value for the Pacific western boundary currents is presented, which validates the theoretical analysis.展开更多
This paper is concerned with the numerical approximations of semi-linear stochastic partial differential equations of elliptic type in multi-dimensions.Convergence analysis and error estimates are presented for the n...This paper is concerned with the numerical approximations of semi-linear stochastic partial differential equations of elliptic type in multi-dimensions.Convergence analysis and error estimates are presented for the numerical solutions based on the spectral method.Numerical results demonstrate the good performance of the spectral method.展开更多
We perform a first-principles computational tensile test on PuO_(2)based on density-functional theory within a local density approximation(LDA)+U formalism to investigate its structural,mechanical,magnetic and intrins...We perform a first-principles computational tensile test on PuO_(2)based on density-functional theory within a local density approximation(LDA)+U formalism to investigate its structural,mechanical,magnetic and intrinsic bonding properties in four representative directions:[001],[100],[110]and[111].The stress-strain relations show that the ideal tensile strengths in the four directions are 81.2,80.5,28.3 and 16.8 GPa at strains of 0.36,0.36,0.22 and 0.18,respectively.The[001]and[100]directions are prominently stronger than the other two directions since more Pu-0 bonds participate in the pulling process.By charge and density of state analysis along the[001]direction,we find that the strong mixed ioni%ovalent character of the Pu-0 bond is weakened by tensile strain and PuO_(2)will exhibit an insulator-to-metal transition after tensile stresses exceeding about 79 GPa.展开更多
The elastic anisotropy and superconductivity upon hydrostatic compression ofα,ω,and β Hf are investigated using first-principle methods.The results of elastic anisotropies show that they increase with increasing pr...The elastic anisotropy and superconductivity upon hydrostatic compression ofα,ω,and β Hf are investigated using first-principle methods.The results of elastic anisotropies show that they increase with increasing pressure for α and ω phases,while decrease upon compression forβphase.The calculated superconducting transition temperatures are in excellent agreement with experiments.Electron-phonon coupling constants(λ)are increasing with pressure for α and ω phases,while decreasing for β phase.For β phase,the large values ofλare mainly due to the obvious TA1 soft mode.Under further compression,the TA1 soft vibrational mode will disappear gradually.展开更多
In this paper, we obtain the necessary and sufficient conditions on the global existence of all positive （weak） solutions to a nonlinear degenerate parabolic equation with nonlinear boundary condition.
Using first-principles calculations, we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg（0001） surface. It is found that during the dissociative adsorp...Using first-principles calculations, we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg（0001） surface. It is found that during the dissociative adsorption process with the minimum energy barrier, the hydrogen molecule first orients perpendicularly, and then rotates tobecome parallel to the surface. It is also found that the orientation of the hydrogen molecule in the transition state is neither perpendicular nor parallel to the surface. Most importantly we find that the rotation causes a reduction of the calculated dissociation energy barrier for the hydrogen molecule. The underlying electronic mechanism for the rotation of the hydrogen molecule is also discussed in the paper.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11971071,12302377)by the Foundation of LCP(Grant No.6142A05220201)by the China Postdoctoral Science Foundation(Grant No.2022M722185).
文摘This paper presents a cell-centered Godunov method based on staggered data distribu-tion in Eulerian framework.The motivation is to reduce the intrinsic entropy dissipation of classical Godunov methods in the calculation of an isentropic or rarefaction flow.At the same time,the property of accurate shock capturing is also retained.By analyzing the factors that cause nonphysical entropy in the conventional Godunov methods,we introduce two velocities rather than a single velocity in a cell to reduce kinetic energy dissipation.A series of redistribution strategies are adopted to update subcell quantities in order to improve accuracy.Numerical examples validate that the present method can dramatically reduce nonphysical entropy increase.Mathematics subject classification:35Q35,76N15,76M12.
基金support from CAPES-Coorde nação de Aperfeiçoamento de Pessoal de Nível Superior(PROEX and PrInt Programs)CNPq-Conselho Nacional de Desenvolvimento Científico e Tecnológico(307576/2018-3 and 420275/2018-5)and FAPESC-Fundação de AmparoàPesquisa do Estado de Santa Catarina.
文摘Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis.The homogeneous catalyst,despite providing high conversion,can cause corrosion in reactors,which is not observed with the use of heterogeneous catalysts.However,some of these catalysts require a high process temperature and may lose their catalytic activity with reuse.Thus,catalytic membranes have been proposed as a promising alternative.The combination of catalysis and separation in a single module provides greater conversion,reduction of excess reagents,compact industrial plant,making the process more efficient.Within this context,this work aims to present a literature review on the catalytic membrane for the synthesis of esters,improving the understanding of the production and development.This review examines the materials,catalysts used,and synthetic pathways.A comparison between the methods,as well as limitations and gaps in the literature,are highlighted.
文摘Iron and Manganese contents and parameters including pH, conductivity, and organic matter contents were determined in the sediments of the Okpara dam in Northern Benin. Fifteen samples were collected during a one-month period and analysed in laboratory using the method of sequential extraction of Tessier. The analyses indicated that sediments contained high concentrations in reducible fraction of Iron and relatively high contents of exchangeable fraction, acidhydrolysable fraction and residual fraction of Manganese. The findings of this study confirmed the hypotheses that the meal contents of the sediments were relatively high and varied according to the geochemical phases.
基金The first author was supported by the China Postdoctoral Science Foundation(2005037318)The second author acknowledges partial support from the Austrian-Chinese Scientific-Technical Collaboration Agreement, the CTS of Taiwanthe Wittgenstein Award 2000 of P.A. Markowich, funded by the Austrian FWF, the Grants-in-Aid of JSPS No.14-02036the NSFC(10431060)the Project-sponsored by SRF for ROCS, SEM
文摘A one-dimensional quantum hydrodynamic model （or quantum Euler-Poisson system） for semiconductors with initial boundary conditions is considered for general pressure-density function. The existence and uniqueness of the classical solution of the corresponding steady-state quantum hydrodynamic equations is proved. Furthermore, the global existence of classical solution, when the initial datum is a perturbation of t he steadystate solution, is obtained. This solution tends to the corresponding steady-state solution exponentially fast as the time tends to infinity.
基金supported by the China Postdoctoral Science Foundation (20090450333)supported by the National Basic Research Program (2005CB321700)NSFC (40890154)
文摘We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.
基金Supported by the NSF of Jiangxi Province, the NSFC (10225105, 10671023) and a CAEP grant
文摘In this article, the globally bounded in-time pointwise estimate of solutions to the simplified Keller-Segel system modelling chemotaxis are derived. Moreover, a local existence theorem is obtained.
基金Supported by the National Basic Research Program of China under Grant No 2007CB815103, and the National Natural Science Foundation of China under Grant Nos 10935003, 10775020 and 11075024.
文摘We report the formation of jet-like long spike in the nonlinear evolution of the ablative Rayleigh-Taylor instability （ARTI） experiments by numerical simulations. A preheating model k（T） = KSH[1＋f（T）], where KSH is the Spitzer Harm （SH） electron conductivity and f（T） interprets the preheating tongue effect in the cold plasma ahead of the ablative front [Phys. Rev. E 65 （2002） 57401], is introduced in simulations. The simulation results of the nonlinear evolution of the ARTI are in general agreement with the experiment results. It is found that two factors, i.e., the suppressing of ablative Kelvin Helmholtz instability （AKHI） and the heat flow cone in the spike tips, contribute to the formation of jet-like long spike in the nonlinear evolution of the ARTI.
文摘We prove the local in time existence and a blow up criterion of solution in the Holder spaces for the inviscid Boussinesq system in RN,N ≥ 2, under the assumptions that the initial values θo,uo ∈ Cr, with 1 〈 r ≠ 2.
文摘In this paper, the decomposition of SU(2) gauge potential in terms of Pauli spinor is studied. Using this decomposition, the spinor structures of Chern Simons form and the Chern density are obtained. Furthermore, the knot quantum number of non-Abelian gauge theory can be expressed by the Chern-Simons spinor structure, and the second Chern number is characterized by the Hopf indices and the Brouwer degrees of Φ-mapping.
基金A The research is supported in part by the National Natural Science Foundation of China （Grant No. 10401012） and The Project Sponsored by the Scientific Research Foundation for the Returned 0verseas Chinese Scholars, State Education Ministry.Acknowledgment This is a part of my Ph.D thesis at The Institute of Mathematical Sciences, The Chinese University of Hong Kong. I express my deep gratitude to my graduate advisor, Professor Zhouping Xin, for his guidance and encouragement.
文摘In this paper, we study the large time asymptotic behavior of solutions to both the Cauchy problem and the exterior problem of the Stokes approximation equations of two dimensional compressible flows.
基金Acknowledgements We thank Congjun Wu for helpful discussion on SU（N） physics, and Ren Zhang for discussions about orbital Feshbach Resonance. This research was supported in part by the National Natural Science Foundation of China under Grant Nos. 11325417, 11674139, and 11504061, the China Postdoctoral Science Foundation, and the Foundation of LCP.
文摘The periodic Anderson model （PAM）, where local electron orbitals interplay with itinerant electronic carriers, plays an essential role in our understanding of heavy fermion materials. Motivated by recent proposals for simulating the Kondo lattice model （KLM） in terms of alkaline-earth metal atoms, we take another step toward the simulation of PAM, which includes the crucial charge/valence fluctuation of local f-electrons beyond purely low-energy spin fluctuation in the KLM. To realize PAM, a transition induced by a suitable laser between the electronic excited and ground state of alkaline-earth metal atoms （^1S0←→^3P0） is introduced. This leads to effective hybridization between local electrons and conduction electrons in PAM. Generally, the SU（N） version of PAM can be realized by our proposal, which gives a unique opportunity to detect large-N physics without complexity in realistic materials. In the present work, high-temperature physical features of standard [SU（2）] PAM with harmonic trapping potential are analyzed by quantum Monte Carlo and dynamic mean-field theory, where the Mott/orbital-selective Mott state was found to coexist with metallic states. Indications for near-future experiments are provided. We expect our theoretical proposal and （hopefully） forthcoming experiments will deepen our understanding of heavy fermion systems. At the same time, we hope these will trigger further studies on related Mott physics, quantum criticality, and non-trivial topology in both the inhomogeneous and nonequilibrium realms.
文摘It is well known that a linear complementarity problem (LCP) can be formulated as a system of nonsmooth equations F(x) = 0, where F is a map from Rninto itself. Using the aggregate function, we construct a smooth Newton homotopy H(x,t) = 0. Under certain assumptions, we prove the existence of a smooth path defined by the Newton homotopy which leads to a solution of the original problem, and study limiting properties of the homotopy path.
基金supported by China Postdoctoral Science Foundation(2012M520205)supported by National Natural SciencesFoundation of China(11171229,11231006)Project of Beijing Chang Cheng Xue Zhe
文摘In this article, we prove the local existence and uniqueness of the classical solution to the Cauchy problem of the 3-D compressible Navier-Stokes equations with large initial data and vacuum, if the shear viscosity μ is a positive constant and the bulk viscosity λ（ρ） = ρ^β with β≥0. Note that the initial data can be arbitrarily large to contain vacuum states.
基金supported by the National Natural Science Foundation of China(Grant Nos.40890154,10971016,91130020)
文摘In this paper, we analyze the bifurcation and the confluence of the Pacific western boundary currents by an analytical approach. Applying the conservation law, the geostrophic balance relation and the Bernoulli integral to a reduced gravity model, we get a quantitative relation for the outflow and the inflow, and establish the related formulae for the width and the veering angle of offshore currents under the inflow condition. Furthermore, a comparison between the volume transport based on the observation data and the analytical value for the Pacific western boundary currents is presented, which validates the theoretical analysis.
基金This work is supported by the National Natural Science Foundation of China(10701014,10871029)a grant from the Laboratory of Computational Physics,and the Foundation of China Academy of Engineering PhysicsThe authors thank the anonymous referees for helpful comments which improve the presentation of the paper.
文摘This paper is concerned with the numerical approximations of semi-linear stochastic partial differential equations of elliptic type in multi-dimensions.Convergence analysis and error estimates are presented for the numerical solutions based on the spectral method.Numerical results demonstrate the good performance of the spectral method.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51071032 and 11074155the National Basic Security Research Program of China,and the Foundations for Development of Science and Technology of China Academy of Engineering Physics under Grant No 2009B0301037.
文摘We perform a first-principles computational tensile test on PuO_(2)based on density-functional theory within a local density approximation(LDA)+U formalism to investigate its structural,mechanical,magnetic and intrinsic bonding properties in four representative directions:[001],[100],[110]and[111].The stress-strain relations show that the ideal tensile strengths in the four directions are 81.2,80.5,28.3 and 16.8 GPa at strains of 0.36,0.36,0.22 and 0.18,respectively.The[001]and[100]directions are prominently stronger than the other two directions since more Pu-0 bonds participate in the pulling process.By charge and density of state analysis along the[001]direction,we find that the strong mixed ioni%ovalent character of the Pu-0 bond is weakened by tensile strain and PuO_(2)will exhibit an insulator-to-metal transition after tensile stresses exceeding about 79 GPa.
基金the National Natural Science Foundation of China(Grant Nos.11874247 and U1530258)the National Key R&D Program of China(Grant No.2017YFA0304500)+2 种基金the 111 Plan of China(Grant No.D18001)the Hundred Talent Program of the Shanxi Province(2018)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices of China(Grant Nos.KF201703 and KF201904).
文摘The elastic anisotropy and superconductivity upon hydrostatic compression ofα,ω,and β Hf are investigated using first-principle methods.The results of elastic anisotropies show that they increase with increasing pressure for α and ω phases,while decrease upon compression forβphase.The calculated superconducting transition temperatures are in excellent agreement with experiments.Electron-phonon coupling constants(λ)are increasing with pressure for α and ω phases,while decreasing for β phase.For β phase,the large values ofλare mainly due to the obvious TA1 soft mode.Under further compression,the TA1 soft vibrational mode will disappear gradually.
基金supported by the NSFC(Grant No.10471009)BSFC(Grant No.1052001)
文摘In this paper, we obtain the necessary and sufficient conditions on the global existence of all positive （weak） solutions to a nonlinear degenerate parabolic equation with nonlinear boundary condition.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10904004,10604010,60776063,50471070 and 50644041)
文摘Using first-principles calculations, we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg（0001） surface. It is found that during the dissociative adsorption process with the minimum energy barrier, the hydrogen molecule first orients perpendicularly, and then rotates tobecome parallel to the surface. It is also found that the orientation of the hydrogen molecule in the transition state is neither perpendicular nor parallel to the surface. Most importantly we find that the rotation causes a reduction of the calculated dissociation energy barrier for the hydrogen molecule. The underlying electronic mechanism for the rotation of the hydrogen molecule is also discussed in the paper.
