This paper investigates the oscillatory and nonoscillatory behaviour of solu- tions of a class of third order nonlinear differential equations. Results extend and improve some known results in the literature.
The dynamics of the reshocked multi-mode Richtmyer-Meshkov instability is investigated using 513 × 257^2 three-dimensional ninth-order weighted essentially nonoscil- latory shock-capturing simulations. A two-mode...The dynamics of the reshocked multi-mode Richtmyer-Meshkov instability is investigated using 513 × 257^2 three-dimensional ninth-order weighted essentially nonoscil- latory shock-capturing simulations. A two-mode initial perturbation with superposed ran- dom noise is used to model the Mach 1.5 air/SF6 Vetter-Sturtevant shock tube experiment. The mass fraction and enstrophy isosurfaces, and density cross-sections are utilized to show the detailed flow structure before, during, and after reshock. It is shown that the mixing layer growth agrees well with the experimentally measured growth rate before and after reshock. The post-reshock growth rate is also in good agreement with the prediction of the Mikaelian model. A parametric study of the sensitivity of the layer growth to the choice of amplitudes of the short and long wavelength initial interfacial perturbation is also pre- sented. Finally, the amplification effects of reshock are quantified using the evolution of the turbulent kinetic energy and turbulent enstrophy spectra, as well as the evolution of the baroclinic enstrophy production, buoyancy production, and shear production terms in the enstrophy and turbulent kinetic transport equations.展开更多
This paper deals with oscillatory /nonoscillatory behaviour of solutions of thirdorder nonlinear differential equations of the formwhere a,b,c E C([a,oo),R) such that a(t) does not change sign, b(t) 5 0, c(t) > 0,f...This paper deals with oscillatory /nonoscillatory behaviour of solutions of thirdorder nonlinear differential equations of the formwhere a,b,c E C([a,oo),R) such that a(t) does not change sign, b(t) 5 0, c(t) > 0,f∈C(R, R) such that (f(y)/y) ≥ β > 0 for y ≠ 0 and γ > 0 is a quotient of odd integers.It has been shown, under certain conditions on coefficient functions, that a solution of (1)and (2) which Las a zero is oscillatory and the nonoscillatory solutions of these equationstend to zero as t → ∞. The motivation for this work came from the observation that thewhere al b, c are constants such that b≤ 0, c > 0, has an oscillatory solution if and only ifand all nonoscillatory solutions of (3) tend to zero if and only if the equation has anoscillatory solution.展开更多
Consider the nonlinear delay difference equation x<sub>n+1</sub>-x<sub>n</sub>+sum j=1 to m p<sub>j</sub>f<sub>j</sub>（x<sub>n</sub>-k<sub>j</sub&...Consider the nonlinear delay difference equation x<sub>n+1</sub>-x<sub>n</sub>+sum j=1 to m p<sub>j</sub>f<sub>j</sub>（x<sub>n</sub>-k<sub>j</sub>）=0. We establish a linearized oscillation result of this equation,which is the extension of the result in the paper [1].展开更多
In this paper, a general high-order multi-domain hybrid DG/WENO-FD method, which couples a p^th-order （p ≥ 3） DG method and a q^th-order （q ≥ 3） WENO-FD scheme, is developed. There are two possible coupling appr...In this paper, a general high-order multi-domain hybrid DG/WENO-FD method, which couples a p^th-order （p ≥ 3） DG method and a q^th-order （q ≥ 3） WENO-FD scheme, is developed. There are two possible coupling approaches at the domain interface, one is non-conservative, the other is conservative. The non-conservative coupling approach can preserve optimal order of accuracy and the local conservative error is proved to be upmost third order. As for the conservative coupling approach, accuracy analysis shows the forced conservation strategy at the coupling interface deteriorates the accuracy locally to first- order accuracy at the ＇coupling cell＇. A numerical experiments of numerical stability is also presented for the non-conservative and conservative coupling approaches. Several numerical results are presented to verify the theoretical analysis results and demonstrate the performance of the hybrid DG/WENO-FD solver.展开更多
By using Banach contraction principle, we obtain the global results （with respect to ｜｜A｜｜≠1） on the sufficient conditions for the existence of nonoscillatory solutions to a system of nonlinear neutral delay di...By using Banach contraction principle, we obtain the global results （with respect to ｜｜A｜｜≠1） on the sufficient conditions for the existence of nonoscillatory solutions to a system of nonlinear neutral delay difference equations with matrix coefficients.展开更多
The boundary-layer method is used to study a wide moving jam to a class of higher-order viscous models. The equations for characteristic parameters are derived to determine the asymptotic solution. The sufficient and ...The boundary-layer method is used to study a wide moving jam to a class of higher-order viscous models. The equations for characteristic parameters are derived to determine the asymptotic solution. The sufficient and essential conditions for the wide moving jam formation are discussed in detail, respectively, and then used to prove or disprove the existence of the wide moving jam solutions to many well-known higher-order models. It is shown that the numerical results agree with the analytical results.展开更多
This paper is concerned with the study of asymptotic behavior of nonoscillatory solutions of second order neutral nonlinear difference equations of theformwhere λ∈ {-1,1},△ is the forword difference operator define...This paper is concerned with the study of asymptotic behavior of nonoscillatory solutions of second order neutral nonlinear difference equations of theformwhere λ∈ {-1,1},△ is the forword difference operator defined by △x_n=x_n+1 x+n.展开更多
In this paper, we first consider differential equations with several delays inthe neutral term of the formstudy various cases of coefficients in the neutral term and obtain the asymptoticbehavior for nonoscillatory so...In this paper, we first consider differential equations with several delays inthe neutral term of the formstudy various cases of coefficients in the neutral term and obtain the asymptoticbehavior for nonoscillatory solution of (1~*) under some hypotheses. Moreover,we consider reaction-diffusion differential equations with several delays in theneutral term of the formfor (t, x)∈ R^+ ×Ω. We also study various cases of coefficients in the neutralterm and obtain the asymptotic behavior for nonoscillatory solution of (2~*)under some hypotheses.展开更多
In this paper necessary and sufficient conditions for the existence of nonoscillatory solutions of a class of higher order nonlinear functional differential systems are obtained.
In this paper, we obtain some nonoscillatory theories of the functional differential equation (r(t)ψ(x(t))x (t)) + f(t, x(t), x(σ(t))) = 0, t ≥ t 0 , where r ∈ C 1 ([t 0 , ∞); (0, ∞)), ψ∈ C 1 (R, R) and f ∈ C...In this paper, we obtain some nonoscillatory theories of the functional differential equation (r(t)ψ(x(t))x (t)) + f(t, x(t), x(σ(t))) = 0, t ≥ t 0 , where r ∈ C 1 ([t 0 , ∞); (0, ∞)), ψ∈ C 1 (R, R) and f ∈ C([t 0 , ∞) × R × R, R).展开更多
In this paper, we establish a few existence results of nonoscillatory solutions to second-order nonlinear neutral delay differential equations, construct several Manntype iterative approximation schemes for these nono...In this paper, we establish a few existence results of nonoscillatory solutions to second-order nonlinear neutral delay differential equations, construct several Manntype iterative approximation schemes for these nonoscillatory solutions, and give some error estimates between the approximate solutions and the nonoscillatory solutions. And finally we give an example to illustrate our results.展开更多
The aim of this paper is to show that the following difference equation：Xn＋1=α＋（xn-k/xn-m）^p, n=0,1,2,…,where α 〉 -1, p 〉 O, k,m ∈ N are fixed, 0 ≤ m 〈 k, x-k, x-k＋1,…,x-m,…,X-1, x0 are positive, has p...The aim of this paper is to show that the following difference equation：Xn＋1=α＋（xn-k/xn-m）^p, n=0,1,2,…,where α 〉 -1, p 〉 O, k,m ∈ N are fixed, 0 ≤ m 〈 k, x-k, x-k＋1,…,x-m,…,X-1, x0 are positive, has positive nonoscillatory solutions which converge to the positive equilibrium x=α＋1. It is interesting that the method described in the paper, in some cases can also be applied when the parameter α is variable.展开更多
The main objective of this article is to study the oscillatory behavior of the solutions of the following nonlinear functional differential equations（a（t）x＇（t））＇＋δ1p（t）x＇（t） ＋δ2q（t）f（x（g（t））） ...The main objective of this article is to study the oscillatory behavior of the solutions of the following nonlinear functional differential equations（a（t）x＇（t））＇＋δ1p（t）x＇（t） ＋δ2q（t）f（x（g（t））） = 0,for 0 ≤ to≤ t, where 51 = ：El and δ±1. The functions p,q,g ： [t0, ∞） → R, f ： R → are continuous, a（t） 〉 0,p（t） ≥0,q（t） 〉 0 for t ≥ to,lirn g（t） = ∞, and q is not identically zero on any subinterval of [to, ∞）. Moreover, the functions q（t）, g（t）, and a（t） are continuously differentiable.展开更多
A new second-order nonlinear neutral delay differential equation r（t） x（t） ＋ P（t）x（t-τ） ＋ cr（t） x（t）-x（t-τ） ＋ F t,x（t-σ1）,x（t-σ2）,...,x（t-σn） = G（t）,t ≥ t0,where τ 0,σ1,σ2,...,σn ≥ ...A new second-order nonlinear neutral delay differential equation r（t） x（t） ＋ P（t）x（t-τ） ＋ cr（t） x（t）-x（t-τ） ＋ F t,x（t-σ1）,x（t-σ2）,...,x（t-σn） = G（t）,t ≥ t0,where τ 0,σ1,σ2,...,σn ≥ 0,P,r ∈ C（[t0,＋∞）,R）,F ∈ C（[t0,＋∞）×Rn,R）,G ∈ C（[t0,＋∞）,R） and c is a constant,is studied in this paper,and some sufficient conditions for existence of nonoscillatory solutions for this equation are established and expatiated through five theorems according to the range of value of function P（t）.Two examples are presented to illustrate that our works are proper generalizations of the other corresponding results.Furthermore,our results omit the restriction of Q1（t） dominating Q2（t）（See condition C in the text）.展开更多
This paper studies the first order nonlinear retarded differential equations. By discussing the behavior of solutions of the equations, 'sharp' conditions are established for all solutions of the equations to...This paper studies the first order nonlinear retarded differential equations. By discussing the behavior of solutions of the equations, 'sharp' conditions are established for all solutions of the equations to be oscillatory, and sufficient conditions for the existence of a nonoscillatory solution of the equations are also given.展开更多
For the second-order charachteristics schemes of hyperbolic convection e-quations, an analysis of the occurring factors of overshoots and undershoots is made, and the nonoscillatory conditions are found. Either the La...For the second-order charachteristics schemes of hyperbolic convection e-quations, an analysis of the occurring factors of overshoots and undershoots is made, and the nonoscillatory conditions are found. Either the Lax-Wendroff scheme or the second-order upwind scheme is employed according to the value of the smooth parameter rj+-1/2 of the slope ratio of the solution. Numerical results show that the oscillation can be avoided and the high-order accuracy can be preserved. It is verified by a lot of numerical tests on typical examples of scalar convection equations. Further study is required for its extension to the system of hyperbolic equations.展开更多
In this paper, we are concerned with the existence of convergent or divergent solutions of two-dimensional nonlinear difference system of the form{xn＋1=αnxn＋bnf（yn）,yn=cnyn-1＋dng（xn）.We＇ classify their soluti...In this paper, we are concerned with the existence of convergent or divergent solutions of two-dimensional nonlinear difference system of the form{xn＋1=αnxn＋bnf（yn）,yn=cnyn-1＋dng（xn）.We＇ classify their solutions according to asymptotic behavior and give some sufficient and necessary conditions for the existence of solutions of such classes by using the method of the fixed point theorem. We also give an example and show how the results can be applied to certain difference systems.展开更多
文摘This paper investigates the oscillatory and nonoscillatory behaviour of solu- tions of a class of third order nonlinear differential equations. Results extend and improve some known results in the literature.
基金performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
文摘The dynamics of the reshocked multi-mode Richtmyer-Meshkov instability is investigated using 513 × 257^2 three-dimensional ninth-order weighted essentially nonoscil- latory shock-capturing simulations. A two-mode initial perturbation with superposed ran- dom noise is used to model the Mach 1.5 air/SF6 Vetter-Sturtevant shock tube experiment. The mass fraction and enstrophy isosurfaces, and density cross-sections are utilized to show the detailed flow structure before, during, and after reshock. It is shown that the mixing layer growth agrees well with the experimentally measured growth rate before and after reshock. The post-reshock growth rate is also in good agreement with the prediction of the Mikaelian model. A parametric study of the sensitivity of the layer growth to the choice of amplitudes of the short and long wavelength initial interfacial perturbation is also pre- sented. Finally, the amplification effects of reshock are quantified using the evolution of the turbulent kinetic energy and turbulent enstrophy spectra, as well as the evolution of the baroclinic enstrophy production, buoyancy production, and shear production terms in the enstrophy and turbulent kinetic transport equations.
文摘This paper deals with oscillatory /nonoscillatory behaviour of solutions of thirdorder nonlinear differential equations of the formwhere a,b,c E C([a,oo),R) such that a(t) does not change sign, b(t) 5 0, c(t) > 0,f∈C(R, R) such that (f(y)/y) ≥ β > 0 for y ≠ 0 and γ > 0 is a quotient of odd integers.It has been shown, under certain conditions on coefficient functions, that a solution of (1)and (2) which Las a zero is oscillatory and the nonoscillatory solutions of these equationstend to zero as t → ∞. The motivation for this work came from the observation that thewhere al b, c are constants such that b≤ 0, c > 0, has an oscillatory solution if and only ifand all nonoscillatory solutions of (3) tend to zero if and only if the equation has anoscillatory solution.
基金Supported by the National Natural Science Foundation of China
文摘Consider the nonlinear delay difference equation x<sub>n+1</sub>-x<sub>n</sub>+sum j=1 to m p<sub>j</sub>f<sub>j</sub>（x<sub>n</sub>-k<sub>j</sub>）=0. We establish a linearized oscillation result of this equation,which is the extension of the result in the paper [1].
基金This work is supported by the Innovation Foundation of BUAA for PhD Graduates, the National Natural Science Foundation of China （Nos. 91130019 and 10931004）, the International Cooperation Project （No. 2010DFR00700）, the State Key Laboratory of Software Development Environment （No. SKLSDE-2011ZX-14） and the National 973 Project （No. 2012CB720205）.
文摘In this paper, a general high-order multi-domain hybrid DG/WENO-FD method, which couples a p^th-order （p ≥ 3） DG method and a q^th-order （q ≥ 3） WENO-FD scheme, is developed. There are two possible coupling approaches at the domain interface, one is non-conservative, the other is conservative. The non-conservative coupling approach can preserve optimal order of accuracy and the local conservative error is proved to be upmost third order. As for the conservative coupling approach, accuracy analysis shows the forced conservation strategy at the coupling interface deteriorates the accuracy locally to first- order accuracy at the ＇coupling cell＇. A numerical experiments of numerical stability is also presented for the non-conservative and conservative coupling approaches. Several numerical results are presented to verify the theoretical analysis results and demonstrate the performance of the hybrid DG/WENO-FD solver.
基金This work is supported by the National Natural Sciences Foundation of China under Grant 10361006the Natural Sciences Foundation of Yunnan Province under Grant 2003A0001MYouth Natural Sciences Foundation of Yunnan University under Grant 2003Q032C and Sciences Foundation of Yunnan Educational Community under Grant 04Y239A.
文摘By using Banach contraction principle, we obtain the global results （with respect to ｜｜A｜｜≠1） on the sufficient conditions for the existence of nonoscillatory solutions to a system of nonlinear neutral delay difference equations with matrix coefficients.
基金Project supported by the National Natural Science Foundation of China(No.11602128)the Natural Science Foundation of Fujian Province of China(No.2016J01679)
文摘The boundary-layer method is used to study a wide moving jam to a class of higher-order viscous models. The equations for characteristic parameters are derived to determine the asymptotic solution. The sufficient and essential conditions for the wide moving jam formation are discussed in detail, respectively, and then used to prove or disprove the existence of the wide moving jam solutions to many well-known higher-order models. It is shown that the numerical results agree with the analytical results.
文摘This paper is concerned with the study of asymptotic behavior of nonoscillatory solutions of second order neutral nonlinear difference equations of theformwhere λ∈ {-1,1},△ is the forword difference operator defined by △x_n=x_n+1 x+n.
文摘In this paper, we first consider differential equations with several delays inthe neutral term of the formstudy various cases of coefficients in the neutral term and obtain the asymptoticbehavior for nonoscillatory solution of (1~*) under some hypotheses. Moreover,we consider reaction-diffusion differential equations with several delays in theneutral term of the formfor (t, x)∈ R^+ ×Ω. We also study various cases of coefficients in the neutralterm and obtain the asymptotic behavior for nonoscillatory solution of (2~*)under some hypotheses.
文摘In this paper necessary and sufficient conditions for the existence of nonoscillatory solutions of a class of higher order nonlinear functional differential systems are obtained.
基金Supported by the Key NSF of China(40333031)Supported by the NSF of Education Department of Hunan Province(04C646)
文摘In this paper, we obtain some nonoscillatory theories of the functional differential equation (r(t)ψ(x(t))x (t)) + f(t, x(t), x(σ(t))) = 0, t ≥ t 0 , where r ∈ C 1 ([t 0 , ∞); (0, ∞)), ψ∈ C 1 (R, R) and f ∈ C([t 0 , ∞) × R × R, R).
基金supported by the National Natural Science Foundation of China(No.10771001)Doctoral Fund of Ministry of Education of China(No.20093401110001)Nature Science Foundation of Anhui Province(No.KJ2013B276)
文摘In this paper, we establish a few existence results of nonoscillatory solutions to second-order nonlinear neutral delay differential equations, construct several Manntype iterative approximation schemes for these nonoscillatory solutions, and give some error estimates between the approximate solutions and the nonoscillatory solutions. And finally we give an example to illustrate our results.
文摘The aim of this paper is to show that the following difference equation：Xn＋1=α＋（xn-k/xn-m）^p, n=0,1,2,…,where α 〉 -1, p 〉 O, k,m ∈ N are fixed, 0 ≤ m 〈 k, x-k, x-k＋1,…,x-m,…,X-1, x0 are positive, has positive nonoscillatory solutions which converge to the positive equilibrium x=α＋1. It is interesting that the method described in the paper, in some cases can also be applied when the parameter α is variable.
文摘The main objective of this article is to study the oscillatory behavior of the solutions of the following nonlinear functional differential equations（a（t）x＇（t））＇＋δ1p（t）x＇（t） ＋δ2q（t）f（x（g（t））） = 0,for 0 ≤ to≤ t, where 51 = ：El and δ±1. The functions p,q,g ： [t0, ∞） → R, f ： R → are continuous, a（t） 〉 0,p（t） ≥0,q（t） 〉 0 for t ≥ to,lirn g（t） = ∞, and q is not identically zero on any subinterval of [to, ∞）. Moreover, the functions q（t）, g（t）, and a（t） are continuously differentiable.
文摘A new second-order nonlinear neutral delay differential equation r（t） x（t） ＋ P（t）x（t-τ） ＋ cr（t） x（t）-x（t-τ） ＋ F t,x（t-σ1）,x（t-σ2）,...,x（t-σn） = G（t）,t ≥ t0,where τ 0,σ1,σ2,...,σn ≥ 0,P,r ∈ C（[t0,＋∞）,R）,F ∈ C（[t0,＋∞）×Rn,R）,G ∈ C（[t0,＋∞）,R） and c is a constant,is studied in this paper,and some sufficient conditions for existence of nonoscillatory solutions for this equation are established and expatiated through five theorems according to the range of value of function P（t）.Two examples are presented to illustrate that our works are proper generalizations of the other corresponding results.Furthermore,our results omit the restriction of Q1（t） dominating Q2（t）（See condition C in the text）.
文摘This paper studies the first order nonlinear retarded differential equations. By discussing the behavior of solutions of the equations, 'sharp' conditions are established for all solutions of the equations to be oscillatory, and sufficient conditions for the existence of a nonoscillatory solution of the equations are also given.
文摘For the second-order charachteristics schemes of hyperbolic convection e-quations, an analysis of the occurring factors of overshoots and undershoots is made, and the nonoscillatory conditions are found. Either the Lax-Wendroff scheme or the second-order upwind scheme is employed according to the value of the smooth parameter rj+-1/2 of the slope ratio of the solution. Numerical results show that the oscillation can be avoided and the high-order accuracy can be preserved. It is verified by a lot of numerical tests on typical examples of scalar convection equations. Further study is required for its extension to the system of hyperbolic equations.
文摘In this paper, we are concerned with the existence of convergent or divergent solutions of two-dimensional nonlinear difference system of the form{xn＋1=αnxn＋bnf（yn）,yn=cnyn-1＋dng（xn）.We＇ classify their solutions according to asymptotic behavior and give some sufficient and necessary conditions for the existence of solutions of such classes by using the method of the fixed point theorem. We also give an example and show how the results can be applied to certain difference systems.
