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1.
方程 dx/dt=f(x(t-1))具有周期量的4/3周期解的条件   总被引:1,自引:0,他引:1  
孙纪方 《数学学报》1990,33(5):694-711
本文证明了滞后型泛函微分方程(dx)/(dt)=f(x(t-1)) (E)存在4/3-周期解的两个定理.一个主要结果如下:假如f(x)是[a-1,a+1]上连续函数,且满足:(i)-f(x)=f(y),y=2a-x,(?)x∈[a-1,a]:(ii):f(x)=f(y),y=2a+1-x,(?)x∈[a,a+1]:(iii)f(x)>0,(?)x∈(a,a+1)和(?).则方程(E)存在4/3-周期解x(t),且x(-1+k4/3)=a+1,x(-2/3+k(4/3))=a,x(-1/3+k(4/3))=a-1,x(k(4/3))=a,k=0,1,2,….  相似文献   

2.
一类二阶n-维中立型微分系统周期解问题   总被引:8,自引:0,他引:8  
鲁世平  葛渭高 《数学学报》2003,46(3):601-610
笔者利用重合度原理研究一类二阶n-维中立型微分系统(d2)/(dt2)(x(t)-Cx(t- ))+d/(dt)gradF(x(t))+gradG(x(t-τ(t)))=p(t)的周期解问题,得到了周期解存在性的新结果,推广了已有工作中相应的结论.  相似文献   

3.
本文研究含有n 个滞量的三维微分差分方程组x(t)=sum from i=1 to ∞(1/i)f[x(t),x(t-τ_i),y(t),y(t-τ_i),z(t),z(t-τ_i)]y(t)=sum from i=1 to ∞(1/i)g[x(t),x(t-τ_i),y(t),y(t-τ_i),z(t),z(t-τ_i)](τ_i>0)z(t)=sum from i=1 to ∞(1/i)h[x(t),x(t-τ_i),y(t),y(t-τ_i),z(t),z(t-τ_i)]周期解的存在性,给出了方程组周期解周期的取值范围.推广并改进了文[1]的结果.  相似文献   

4.
本文证明了滞后型泛函微分方程(dx)/(dt)=f(x(t-1)) (E)存在4/3-周期解的两个定理.一个主要结果如下:假如f(x)是[a-1,a+1]上连续函数,且满足:(i)-f(x)=f(y),y=2a-x,(?)x∈[a-1,a]:(ii):f(x)=f(y),y=2a+1-x,(?)x∈[a,a+1]:(iii)f(x)>0,(?)x∈(a,a+1)和(?).则方程(E)存在4/3-周期解x(t),且x(-1+k4/3)=a+1,x(-2/3+k(4/3))=a,x(-1/3+k(4/3))=a-1,x(k(4/3))=a,k=0,1,2,….  相似文献   

5.
研究一个描述血吸虫病的周期微分方程模型dx/dt=-rx+A/S(t)y,dy/dt=-δ(t)y+B(S(t)-y) x2/1+ x.数值计算发现该系统同时具有渐近稳定的零解和一个正周期解.通过证明该系统解的有界性,并在一个函数空间上构造单调有界序列,进而证明了在一定条件下正周期解的存在性.  相似文献   

6.
利用重合度理论和一些分析技巧,研究了一类Lienard型p-Laplacian方程(φ_p(x((n-1))(t)))'+f(t,x(t),x((n-1))(t)))'+f(t,x(t),x((n-1))(t))+(?)gk(t,x(t),x(t-τ_k(t))=e(t)获得其存在周期解的充分条件,并给出了在p≥2,n=2,f(t,u,v)=h(t,v)情形下存在唯一周期解的充分条件.所用方法与已有文献不同,结果是新的且与时滞τ_k(t)有关.  相似文献   

7.
利用Fourier级数理论和重合度理论研究了一类二阶n-维中立型泛函微分系统d2/dt2(x(t)-Cx(t-r))+d/dt gradF(x(t))+gradG(x(t-τ(t)))=p(t)的周期解问题,得到了周期解存在性的新结论,有意义的是本文的矩阵C仅为一般的实方阵,不必为实对称阵,因而本文的结果改进和推广了已有工作.此外,本文周期解先验界估计方法与已有工作也不同.  相似文献   

8.
运用k-集压缩算子的拓扑度抽象连续定理,研究了如下一类高阶微分方程的周期解存在性问题x(m)(t)= r(t)-a(t)x(t-σ)-b(t)x(m)(t-τ).并将其应用于研究一类中立型对数种群模型dN/dt= N(t) [r(t)-a(t) In N(t-σ-b(t)d/(dt)In N(t-τ)]的正周期解存在性...  相似文献   

9.
考虑具连续时滞和离散时滞的中立型积分微分方程d/dt[x(t) q∑j=1ej(t)x(t-δj(t))]=A(t,x(t))x(t ∫t-∞ C(t,s)x(s)ds 1∑i=1gi(t,x(t-Υi(t))) b(t)和d/dt[x(t) q∑j=1ej(t)x(t-δj(t))]=A(t)x(t) ∫t-∞C(t,s)x(s)ds 1∑j=1gi(t,x(t-Υi(t))) b(t)周期解的存在性和唯一性问题,利用线性系统指数型二分性理论和泛函分析方法,并通过技巧性代换获得了保证中立型系统周期解存在性和唯一性的充分性条件,从而避开了在研究中立型系统时x(t-δ)时滞项的导数x1(t-δ)的出现,推广了相关文献的主要结果.  相似文献   

10.
本文运用了比较新的手法,证明了非线性微分系统(dx)/(dt)=1/(a(x))[c(y)-b(x)];(dy)/(dt)=-a(x)[h(x)-e(t)](1)(其中a(x),b(x),h(x),c(y),e(t)为连续可微函数,x,y∈R,t∈[0,+∞),且a(x)>0)解的有界性及周期解的存在性,并应用该结论讨论了强迫振动方程:x+(f(x)+g(x)x)x+h(x)=e(t)(2)(其中f(x),g(x)为连续可微函数,x∈R,h(x),e(t)同上)解的有界性及周期解的存在性.  相似文献   

11.
We provide existence results for almost periodic solutions of nonlinear second order ordinary differential equations. The results extend existence results for periodic solutions of periodic equations, where the existence of periodic sub and supersolutions implied the existence of periodic solutions.  相似文献   

12.
中立型泛函微分方程的周期解   总被引:1,自引:1,他引:0  
对于中立型泛函微分方程,证明了解的毕竟有界性蕴含周期解的存在性,把常微分方程中著名的Yoshizawa周期解存在定理推广到中立型泛函微分方程,然后利用所得结果给出一类产生于电力系统的中立型时滞泛函微分方程周期解存在惟一与吸引的条件。  相似文献   

13.
The method of upper and lower solutions is a classical tool in the theory of periodic differential equations of the second order. We show that this method does not have a direct extension to almost periodic equations. To do this we construct equations of this type without almost periodic solutions but having two constants as ordered upper and lower solutions.  相似文献   

14.
In this paper, we propose a new method to find the periodic solutions of differential equations. The key technique is to convert the problem of finding periodic solutions of differential equations into an optimization problem. Then by solving the corresponding optimization problem, we can find the periodic solutions of differential equations. Finally, some numerical results are presented to illustrate the utility of the technique.  相似文献   

15.
A translation along trajectories approach together with averaging procedure and topological degree are used to derive effective criteria for existence of periodic solutions for nonautonomous evolution equations with periodic perturbations. It is shown that a topologically nontrivial zero of the averaged right hand side is a source of periodic solutions for the equations with increased frequencies. Our setting involves equations on closed convex cones, therefore it enables us to study positive solutions of nonlinear parabolic partial differential equations.  相似文献   

16.
时标上具有阶段结构的三种群捕食系统的周期解   总被引:1,自引:0,他引:1  
徐昌进 《经济数学》2013,30(1):5-11
研究了时标上具有阶段结构的三种群捕食系统.运用时标上连续拓扑度定理,得到了系统存在周期解的充分条件.其研究方法使系统的连续时间情形和离散时间情形的周期解问题得到了统一,被广泛地应用来研究微分方程和差分方程的周期解的存在问题.  相似文献   

17.
We study the twist periodic solutions of second order singular differential equations. Such twist periodic solutions are stable in the sense of Lyapunov and present much interesting dynamical features around them. The proof is based on the third-order approximation method. The estimates of periodic solutions of Ermakov-Pinney equations and the estimates on rotation numbers of Hill equations play an important role in the analysis.  相似文献   

18.
This article is devoted to the study of bifurcations of periodic solutions for discontinuous autonomous systems from single periodic solutions of unperturbed discontinuous equations. In addition, local asymptotic properties of derived perturbed periodic solutions are also investigated. An example of planar discontinuous ordinary differential equations is given to illustrate the theory.  相似文献   

19.
考查了周期边界条件下的磁流体方程,证明了它的解关于时间是解析的,由此得到了磁流体方程的解的向后惟一性.对于周期解,证明了当周期小于某个常数时,周期的弱解是强解,进一步地这样的强解是定常解.  相似文献   

20.
In this paper, we use the bifurcation method of dynamical systems to study the periodic wave solutions and their limits for the modified Kd V–KP equations. Some explicit periodic wave solutions are obtained. These solutions contain smooth periodic wave solutions and periodic blow-up solutions. Their limits contain solitary wave solutions, periodic wave solutions, kink wave solutions and unbounded solutions.  相似文献   

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