The elementary and systematic binary Bell polynomials method is applied to the generalized NizhnikNovikov-Veselov (GNNV) equation.The bilinear representation,bilinear B&cklund transformation,Lax pair and infinitec...The elementary and systematic binary Bell polynomials method is applied to the generalized NizhnikNovikov-Veselov (GNNV) equation.The bilinear representation,bilinear B&cklund transformation,Lax pair and infiniteconservation laws of the GNNV equation are obtained directly,without too much trick like Hirota’s bilinear method.展开更多
The symmetries and non-Noether conservation laws of Birkhoffian system with unilateral constraints are studied. The differential equations of motion of the system are established, and the criterions of Noether symmetr...The symmetries and non-Noether conservation laws of Birkhoffian system with unilateral constraints are studied. The differential equations of motion of the system are established, and the criterions of Noether symmetry, Lie symmetry and Mei symmetry of the system are given. Two types of new conservation laws, called the Hojman conservation law and the Mei conservation law respectively, are obtained, and the intrinsic relations among the symmetries and the new conservation laws are researched. At the end of the paper, an example is given to illustrate the application of the results.展开更多
In this paper, we introduce the notion of a (2+1)-dimenslonal differential equation describing three-dimensional hyperbolic spaces (3-h.s.). The (2+1)-dimensional coupled nonlinear Schrodinger equation and its...In this paper, we introduce the notion of a (2+1)-dimenslonal differential equation describing three-dimensional hyperbolic spaces (3-h.s.). The (2+1)-dimensional coupled nonlinear Schrodinger equation and its sister equation, the (2+1)-dimensional coupled derivative nonlinear Schrodinger equation, are shown to describe 3-h.s, The (2 + 1 )-dimensional generalized HF model:St=(1/2i[S,Sy]+2iσS)x,σx=-1/4i tr(SSxSy), in which S ∈ GLc(2)/GLc(1)×GLc(1),provides another example of (2+1)-dimensional differential equations describing 3-h.s. As a direct con-sequence, the geometric construction of an infinire number of conservation lairs of such equations is illustrated. Furthermore we display a new infinite number of conservation lairs of the (2+1)-dimensional nonlinear Schrodinger equation and the (2+1)-dimensional derivative nonlinear Schrodinger equation by a geometric way.展开更多
An improved algorithm for symbolic computations of polynomial-type conservation laws (PCLaws) of ageneral polynomial nonlinear system is presented.The algorithm is implemented in Maple and can be successfully usedfor ...An improved algorithm for symbolic computations of polynomial-type conservation laws (PCLaws) of ageneral polynomial nonlinear system is presented.The algorithm is implemented in Maple and can be successfully usedfor high-dimensional models.Furthermore,the algorithm discards the restriction to evolution equations.The programcan also be used to determine the preferences for a given parameterized nonlinear systems.The code is tested on severalknown nonlinear equations from the soliton theory.展开更多
In this paper, we investigate conservation laws of a class of partial differential equations, which combines the nonlinear telegraph equations and the nonlinear diffusion-convection equations. Moreover, some special c...In this paper, we investigate conservation laws of a class of partial differential equations, which combines the nonlinear telegraph equations and the nonlinear diffusion-convection equations. Moreover, some special conservation laws of the combined equations are obtained by means of symmetry classifications of wave equations uxx = H (x)utt.展开更多
The authors give the first convergence proof for the Lax-Friedrichs finite differencescheme for non-convex genuinely nonlinear scalar conservation laws of the formu_t + f(k(x, t), u)_x = 0,where the coefficient k(x, t...The authors give the first convergence proof for the Lax-Friedrichs finite differencescheme for non-convex genuinely nonlinear scalar conservation laws of the formu_t + f(k(x, t), u)_x = 0,where the coefficient k(x, t) is allowed to be discontinuous along curves in the (x, t)plane. In contrast to most of the existing literature on problems with discontinuouscoefficients, here the convergence proof is not based on the singular mapping approach,but rather on the div-curl lemma (but not the Young measure) and a Lax type en-tropy estimate that is robust with respect to the regularity of k(x, t). Following [14],the authors propose a definition of entropy solution that extends the classical Kruzkovdefinition to the situation where k(x, t) is piecewise Lipschitz continuous in the (x, t)plane, and prove the stability (uniqueness) of such entropy solutions, provided that theflux function satisfies a so-called crossng condition, and that strong traces of the solu-tion exist along the curves where k(x, t) is discontinuous. It is shown that a convergentsubsequence of approximations produced by the Lax-Friedrichs scheme converges tosuch an entropy solution, implying that the entire computed sequence converges.展开更多
Derivatives of discontinuities being Dirac singularities, it is usually not possible to multiply them by discontinuous functions. However in the context of conservation laws we have shown in a recent paper that it can...Derivatives of discontinuities being Dirac singularities, it is usually not possible to multiply them by discontinuous functions. However in the context of conservation laws we have shown in a recent paper that it can be done. We shall make use of this new framework to revisit some upwind methods, mostly characteristic schemes, and show that they can be corrected to be conservative and to work on difficult problems such as Euler's equations for fluids. Numerous numerical results are given.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
Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514] Nilsson state of the odd-Z nucleus 255Lr are studied by the cranked shell model (CSM) w...Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514] Nilsson state of the odd-Z nucleus 255Lr are studied by the cranked shell model (CSM) with the paring correlations treated by the particle-number-conserving (PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia (f^(1) and ,f^(2) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia f(1) with the experimental ones extracted from different spin assignments, the spin 17/2- →13/2- is assigned to the lowest-lying 196.6(5) keV transition of the 1/2- [521 ] band, and 15/2→11/2- to the 189(1) keV transition of the 7/2- [514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high-j low→lj15/2 (1/2-[770]) orbital at the high spin leads to band-crossings at hω = 0.20 (hω~=0.25) MeV for the 7/2-[514]ω= -1/2 (ω= +1/2) band, and at hω=0.175 MeV for the 1/2- [521 ] ω= - 1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.展开更多
This paper obtains the 1-soliton solution by the ansatz method for the proposed model that governs the propagation of solitons through the neurons. This model is an improved one that describes the solitons in neurosci...This paper obtains the 1-soliton solution by the ansatz method for the proposed model that governs the propagation of solitons through the neurons. This model is an improved one that describes the solitons in neurosciences more accurately. The ansatz method is applied to obtain the 1-soliton solution to the model. The Lie symmetry analysis is subsequently applied to obtain the conservation laws for the model.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.10735030,11075055,61021004,90718041,Shanghai Leading Academic Discipline Project (No. B412)Program for Changjiang Scholars and Innovative Research Team in University (IRT0734)
文摘The elementary and systematic binary Bell polynomials method is applied to the generalized NizhnikNovikov-Veselov (GNNV) equation.The bilinear representation,bilinear B&cklund transformation,Lax pair and infiniteconservation laws of the GNNV equation are obtained directly,without too much trick like Hirota’s bilinear method.
基金The project supported by the Natural Science Foundation of High Education of Jiangsu Province of China under Grant No. 04KJA130135 and the "Qing Lan" Project Foundation of Jiangsu Province of China
文摘The symmetries and non-Noether conservation laws of Birkhoffian system with unilateral constraints are studied. The differential equations of motion of the system are established, and the criterions of Noether symmetry, Lie symmetry and Mei symmetry of the system are given. Two types of new conservation laws, called the Hojman conservation law and the Mei conservation law respectively, are obtained, and the intrinsic relations among the symmetries and the new conservation laws are researched. At the end of the paper, an example is given to illustrate the application of the results.
基金The project partially supported by National Natural Science Foundation of China
文摘In this paper, we introduce the notion of a (2+1)-dimenslonal differential equation describing three-dimensional hyperbolic spaces (3-h.s.). The (2+1)-dimensional coupled nonlinear Schrodinger equation and its sister equation, the (2+1)-dimensional coupled derivative nonlinear Schrodinger equation, are shown to describe 3-h.s, The (2 + 1 )-dimensional generalized HF model:St=(1/2i[S,Sy]+2iσS)x,σx=-1/4i tr(SSxSy), in which S ∈ GLc(2)/GLc(1)×GLc(1),provides another example of (2+1)-dimensional differential equations describing 3-h.s. As a direct con-sequence, the geometric construction of an infinire number of conservation lairs of such equations is illustrated. Furthermore we display a new infinite number of conservation lairs of the (2+1)-dimensional nonlinear Schrodinger equation and the (2+1)-dimensional derivative nonlinear Schrodinger equation by a geometric way.
基金the Scientific Fund of Education Department of Zhejiang Province of China under Grant No.20070979the National Natural Science Foundations of China under Grant Nos.10675065,90503006,and 10735030+1 种基金the State Basic Research Program of China (973 Program) under Grant No.2007CB814800the K.C.Wong Magna Fund in Ningbo University
文摘An improved algorithm for symbolic computations of polynomial-type conservation laws (PCLaws) of ageneral polynomial nonlinear system is presented.The algorithm is implemented in Maple and can be successfully usedfor high-dimensional models.Furthermore,the algorithm discards the restriction to evolution equations.The programcan also be used to determine the preferences for a given parameterized nonlinear systems.The code is tested on severalknown nonlinear equations from the soliton theory.
文摘In this paper, we investigate conservation laws of a class of partial differential equations, which combines the nonlinear telegraph equations and the nonlinear diffusion-convection equations. Moreover, some special conservation laws of the combined equations are obtained by means of symmetry classifications of wave equations uxx = H (x)utt.
基金Project supported by the BeMatA Program of the Research Council of Norway and the European network HYKE, funded by the EC as contract HPRN-CT-2002-00282
文摘The authors give the first convergence proof for the Lax-Friedrichs finite differencescheme for non-convex genuinely nonlinear scalar conservation laws of the formu_t + f(k(x, t), u)_x = 0,where the coefficient k(x, t) is allowed to be discontinuous along curves in the (x, t)plane. In contrast to most of the existing literature on problems with discontinuouscoefficients, here the convergence proof is not based on the singular mapping approach,but rather on the div-curl lemma (but not the Young measure) and a Lax type en-tropy estimate that is robust with respect to the regularity of k(x, t). Following [14],the authors propose a definition of entropy solution that extends the classical Kruzkovdefinition to the situation where k(x, t) is piecewise Lipschitz continuous in the (x, t)plane, and prove the stability (uniqueness) of such entropy solutions, provided that theflux function satisfies a so-called crossng condition, and that strong traces of the solu-tion exist along the curves where k(x, t) is discontinuous. It is shown that a convergentsubsequence of approximations produced by the Lax-Friedrichs scheme converges tosuch an entropy solution, implying that the entire computed sequence converges.
文摘Derivatives of discontinuities being Dirac singularities, it is usually not possible to multiply them by discontinuous functions. However in the context of conservation laws we have shown in a recent paper that it can be done. We shall make use of this new framework to revisit some upwind methods, mostly characteristic schemes, and show that they can be corrected to be conservative and to work on difficult problems such as Euler's equations for fluids. Numerous numerical results are given.
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 Natural Science Foundation of China(Grant Nos.11275098 and 11275067)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514] Nilsson state of the odd-Z nucleus 255Lr are studied by the cranked shell model (CSM) with the paring correlations treated by the particle-number-conserving (PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia (f^(1) and ,f^(2) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia f(1) with the experimental ones extracted from different spin assignments, the spin 17/2- →13/2- is assigned to the lowest-lying 196.6(5) keV transition of the 1/2- [521 ] band, and 15/2→11/2- to the 189(1) keV transition of the 7/2- [514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high-j low→lj15/2 (1/2-[770]) orbital at the high spin leads to band-crossings at hω = 0.20 (hω~=0.25) MeV for the 7/2-[514]ω= -1/2 (ω= +1/2) band, and at hω=0.175 MeV for the 1/2- [521 ] ω= - 1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.
文摘This paper obtains the 1-soliton solution by the ansatz method for the proposed model that governs the propagation of solitons through the neurons. This model is an improved one that describes the solitons in neurosciences more accurately. The ansatz method is applied to obtain the 1-soliton solution to the model. The Lie symmetry analysis is subsequently applied to obtain the conservation laws for the model.