非自治随机时滞微分方程概周期解的存在唯一性

讨论以下非自治时滞随机微分方程: \begin{align*} \left\{\!\!\!\begin{array}{l} \rmd[x(t)-h(t,x_t)]=[A(t)x(t)+f(t,x_t)]\rmd t+g(t,x_t)\rmd W(t), \quad t\geq t_0,\ x_{t_0}=\xi(\theta),\quad \theta\in[-r,0], \quad r\geq0. \end{array}\right. \end{align*} 如果非自治线性算子$A(t)$满足Acquistapace-Terreni (简称为AT)条件,则能找到算子$\{U(t,s),t\geq s;t,s\in \mathbb R\}$与其存在某种对应关系, 然后根据算子$ \{U(t,s),t\geq s;t,s\in \mathbb R\}$的性质和Banach不动点定理,证明了以上方程存在唯一的均方概周期mild解.     

非线性随机微分方程终值问题的适应解和连续依赖性

本文讨论了一般形式非线性随机微分方程的终值问题$x(t)+\int_t^Tf(s,x(s),y(s))\mbox{d}s+\int_t^Tg(s,x(s),y(s))\mbox{d}W(s)=\xi,\qq 0\leq t\leq T,$这里$W$为$d$\,-维标准Wiener过程\bd 证明了在某种弱于Lipschitz条件下方程存在唯一适应解, 并给出了解的估计和非线性随机微分方程的解关于终值的连续依赖性     

Initial Boundary Value Problem for One Class of System of Multi- Dimensional Inhomogeneous GBBM Equations

This paper studies the following initial-boundary value problem for the system of multidimensional inhomogeneous GBBM equations $[\begin{array}{l} {u_r} - \Delta {u_i} + \sum\limits_{i = 1}^n {\frac{\partial }{{\partial {x_i}}}} grad\varphi (u) = f(u),{\rm{ (1}}{\rm{.1)}}\u{|_{t = 0}} = {u_0}(x),x \in \Omega ,{\rm{ (1}}{\rm{.2)}}\u{|_{\partial \Omega }} = 0,t \ge 0,{\rm{ (1}}{\rm{.3)}} \end{array}\]$ The existence and uniqueness of the global solution for the problem(l.l) (1.2) (1.3) are proved. The asymptotic behavior and “blow up” phenomenon of the solution for the problem (1.1) (1.2) (1.3) are investigated under certain conditions.     

由H\"{o}rmander向量场构成的抛物方程的 $W_{\ast}^{1,p}$ 正则性

设 $X_{1},\cdots ,X_{q}\ (q相似文献   

Some Remarks on Burton''s Asymptotic Stable Theorem (in English)

讨论泛函微分方程$\[\dot x = f(t,{x_t})\]$的解的渐近稳定性理论，往往需要假定f的某种全连续性.Burton在他的论文中讨论了f是一般$\[R \times C \to {R^n}\]$的连续泛函的情况.本文的目的是改进Burton的工作.证明方法釆取更简单的直接证法，证明结果不但同样获得有关解的一致渐近稳定性的结论，而且得到一个有趣的不等式，从中能够导出解的收敛于0的估计式. 设f是$\[R \times C \to {R^n}\]$连续泛函.$$是严格上升的连续函数,$$.设u,v,w是单调不减的连续函数u(0)=v(0)=w(0)=0,且对s>0有u(s),v(s),w(s)>0, 又设$\[|\phi {|_\eta } = \eta (|\phi (0)|) + \frac{1}{r}\int_{ - r}^0 {\eta (|\phi (\theta )|)d} \theta \]$,$\[{w_1}(s) = w({\eta ^{ - 1}}(s))\]$,$\[h(s) = \int_0^s {{w_1}(s)ds} \]$,$\[k(s) = v(s) + \frac{{{w_1}(1)}}{2}rs\]$，那么有如下定理： 定理1 设$\[V:R \times C \to R\]$是连续泛函，使得 $\[u(|\phi (0)|) \le V(t,\phi ) \le v(||\phi |{|_\eta })\]$ $\[V(t,\phi ) \le - w(|\phi (0)|)\]$ 那么必有另一个连续泛函$\[G:R \times C \to R\]$,使得对$ \[\eta (|\mu |) < 1\]$有 $\[G(t,\phi ) \le - g(G(t,\phi )),V(t,\phi ) \le G(t,\phi )\]$, 其中$\[g:{R^ + } \to {R^ + }\]$定义为$\[g(s) = h(\frac{1}{2}{k^{ - 1}}(s))\]$ 定理2 设定理1的条件均满足，设$\[F(y) = \int_1^y {\frac{{dz}}{{g(z)}}} \]$,那么存在s>0使得对于$\[|{\phi _0}| < s\]$有 $\[|x(t;{t_0},{\phi _0})| \le {u^{ - 1}}({F^{ - 1}}(F(G({t_0},{\phi _0})) + {t_0} - t))\]$ 且x=0—致渐近稳定 文章最后给出两个实例说明以上定理的应用.     

具有退化粘性的非齐次双曲守恒律方程的Cauchy问题

该文讨论了如下具有退化粘性的非齐次双曲守恒律方程的Cauchy问题$\left\{\begin{array}{l} u_t+f(u)_x=a^2t^\alpha u_{xx}+g(u),\ \ \ x\in{\bf R},\ \ \ t>0,\\u(x,0)=u_0(x) \in L^\infty({\bf R}).\end{array}\right.\eqno{({\rm I})}$其中$f(u), g(u)$是${\bf R}$上的光滑函数, $a>0, 0<\alpha<1$均为常数.在此条件下, 作者首先给出了Cauchy问题(I)的局部解的存在性, 再利用极值原理获得了解的$L^{\infty}$估计, 从而证明了Cauchy问题(I)整体光滑解的存在性.     

具有脉冲的Dirichlet边值问题的Lyapunov不等式及其应用

该文首先研究具有脉冲的线性Dirichlet边值问题 $\left\{ \begin{array}{ll} x'(t)+a(t)x(t)=0, t\neq \tau_{k}, \ \Delta x(\tau_{k})=c_{k}x(\tau_{k}),\ \Delta x'(\tau_{k})=d_{k}x(\tau_{k}), \ x(0)=x(T)=0, \end{array} \right. (k=1,2\cdots,m) $ 给出该Dirichlet边值问题仅有零解的两个充分条件, 其中$a:[0,T]\rightarrow R$, $c_{k}, d_{k}, k=1,2,$ $\cdots,m$是常数, 该文首先研究具有脉冲的线性Dirichlet边值问题 $$\left\{ \begin{array}{ll} x'(t)+a(t)x(t)=0, t\neq \tau_{k}, \ \Delta x(\tau_{k})=c_{k}x(\tau_{k}),\ \Delta x'(\tau_{k})=d_{k}x(\tau_{k}), \ x(0)=x(T)=0, \end{array} \right. (k=1,2\cdots,m) $$ 给出该Dirichlet边值问题仅有零解的两个充分条件, 其中$a:[0,T]\rightarrow R$, $c_{k}, d_{k}, k=1,2,$ $\cdots,m$是常数, $0<\tau_{1}<\tau_{2}\cdots<\tau_{m}<T$为脉冲时刻. 其次利用上面的线性边值问题仅有零解这个性质和Leray-Schauder度理论, 研究具有脉冲的非线性Dirichlet边值问题 $$\left\{ \begin{array}{ll} x'(t)+f(t,x(t))=0, t\neq \tau_{k}, \ \Delta x(\tau_{k})=I_{k}(x(\tau_{k})), \ \Delta x'(\tau_{k})=M_{k}(x(\tau_{k})), \ x(0)=x(T)=0 \end{array} \right. (k=1,2\cdots,m) $$ 解的存在性和唯一性, 其中 $f\in C([0,T]\times R,R)$, $I_{k},M_{k}\in C(R, R),k=1,2,\cdots,m$. 该文主要定理的一个推论将经典的Lyaponov不等式比较完美地推广到脉冲系统.     

具有偏差变元的Li\''{e}nard型方程的周期解

本文利用重合度理论研究了一类具偏差变元的Li\'{e}nard型方程$x'(t)+f_1(t,x(t))|x'(t)|^2+f_2(t,x(t),x(t-\tau_{0}(t)))x'(t)+g(t,x(t-\tau_{1} (t)))=p(t).$获得了该方程存在$\omega$-周期解的若干新结论, 改进和推广了已有文献中的相关结果.     

On the Uniqueness Solutions of Nonlinear Degenerate Parabolic Equations (in English)

本文证明，在条件$a(s)>0(s>0),a(0)=0,b(s)=O(a(s)^\lambda)(s \geq 0,0 \leq \lambda \geq 1/2),s^\mu=O(a(s))(s \geq 0, \mu >0$之下，混合问题 ${u_t} = {(a(u){u_x})_x} + b(u){u_x},(x,t) \in R = \{ (x,t)| - 1 < x < 1,0 < t < T\} $ $u(x,0)=u_0(x)(\geq0),-1 \leqx \leq 1$ $u(-1,0)=\psi_1(t)(\geq0),u(1,t)=\psi _w(t)(\geq 0),0 \leq t \leq T$ 当$\mu<1,\lambda \geq0$或$\mu \geq1,2\lambda+1/ \mu>1$时，解为唯一的，这改善了[1,2]的结果。     

含有Sobolev-Hardy临界指标的奇异椭圆方程Neumann问题无穷多解的存在性

该文研究了如下的奇异椭圆方程Neumann问题$\left\{\begin{array}{ll}\disp -\Delta u-\frac{\mu u}{|x|^2}=\frac{|u|^{2^{*}(s)-2}u}{|x|^s}+\lambda|u|^{q-2}u,\ \ &;x\in\Omega,\\D_\gamma{u}+\alpha(x)u=0,&;x\in\partial\Omega\backslash\{0\},\end{array}\right.$其中$\Omega $ 是 $ R^N$ 中具有 $ C^1$边界的有界区域, $ 0\in\partial\Omega$, $N\ge5$. $2^{*}(s)=\frac{2(N-s)}{N-2}$ (该文研究了如下的奇异椭圆方程Neumann问题$\left\{\begin{array}{ll}\disp -\Delta u-\frac{\mu u}{|x|^2}=\frac{|u|^{2^{*}(s)-2}u}{|x|^s}+\lambda|u|^{q-2}u,\ \ &;x\in\Omega,\\D_\gamma{u}+\alpha(x)u=0,&;x\in\partial\Omega\backslash\{0\},\end{array}\right.$其中$\Omega $ 是 $ R^N$ 中具有 $ C^1$边界的有界区域, $ 0\in\partial\Omega$, $N\ge5$. $2^{*}(s)=\frac{2(N-s)}{N-2}$ (该文研究了如下的奇异椭圆方程Neumann问题其中Ω是RN中具有C1边界的有界区域,0∈■Ω,N≥5.2*(s)=2(N-s)/N-2(0≤s≤2)是临界Sobolev-Hardy指标, 10.利用变分方法和对偶喷泉定理,证明了这个方程无穷多解的存在性.     

一类中立型积分微分方程周期解的存在性和唯一性

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.     

多时滞中立型微分积分方程的周期解

研究了一类具有多个时滞的中立型微分积分方程x'(t)=∫tt-σ9(t,s,x(s))ds f(t,x(t-τ0),x'(t-τ1))周期解的存在性,得到了方程周期解存在的充分条件.所得结果体现了滞量σ对周期解存在性的影响.     

多维非退化扩散过程的象集与图集的一致Packing维数

设B(t)=(B(t))=(B1(t),B2(t),…,BN(t))为N维Brown运动,设α(x)=(αij(x),1(≤)I(≤)d,1(≤)j(≤)N),β(x)=(βi(x),1(≤)I(≤)d),x∈Rd,1(≤)d(≤)N,α(x)和β(x)有界连续和满足Lipchitz条件,且存在常数c0＞0,使得对每个x∈Rd,a(x)=α(x)α(x)*的每个特征根都不小于c0.设dX(t)=α(X(t))dB(t) β(X(t))dt,设d(≥)3.可以证明P(ωDimX(E,ω)=DimGRX(E,ω)=2DimE,(A)E∈B[0,∞))=1.这里X(E,ω)={X(t,ω)t∈E},GRX(E,ω)={(t,X(t,ω))t∈E},DimF表示F的Packing维数.     

关于Banach空间一阶非线性脉冲积分-微分方程初值问题解存在性的注记

设m(t)∈C[Jk,R ](k=1,2,…,m),且满足不等式m(t)<(L1 L2t)∫tn(s)ds L3t∫a m(s)ds ∑o0满足KaLs(eδ(L1 aL2)-1)相似文献   

An Existence Result for a Class of Chemically Reacting Systems with Sign-Changing Weights

We prove the existence of positive solutions for the system$$\begin{align*}\begin{cases}-\Delta_{p} u =\lambda a(x){f(v)}{u^{-\alpha}},\qquad x\in \Omega,\\-\Delta_{q} v = \lambda b(x){g(u)}{v^{-\beta}},\qquad x\in \Omega,\\u = v =0, \qquad x\in\partial \Omega,\end{cases}\end{align*}$$where $\Delta_{r}z={\rm div}(|\nabla z|^{r-2}\nabla z)$, for $r>1$ denotes the r-Laplacian operator and $\lambda$ is a positive parameter, $\Omega$ is a bounded domain in $\mathbb{R}^{n}$, $n\geq1$ with sufficiently smooth boundary and $\alpha, \beta \in (0,1).$ Here $ a(x)$ and $ b(x)$ are $C^{1}$ sign-changingfunctions that maybe negative near the boundary and $f,g $ are $C^{1}$ nondecreasing functions, such that $f, g :\ [0,\infty)\to [0,\infty);$ $f(s)>0,$ $g(s)>0$ for $s> 0$, $\lim_{s\to\infty}g(s)=\infty$ and$$\lim_{s\to\infty}\frac{f(Mg(s)^{\frac{1}{q-1}})}{s^{p-1+\alpha}}=0,\qquad \forall M>0.$$We discuss the existence of positive weak solutions when $f$, $g$, $a(x)$ and $b(x)$ satisfy certain additional conditions. We employ the method of sub-supersolution to obtain our results.     

Elliptic Systems with a Partially Sublinear Local Term

Let $1 0.$ This is in sharp contrast to D'Aprile and Mugnai's non-existence results.     

An Inverse Coefficient Problem for an Integro-differential Equation

In this article we consider the inverse coefficient problem of recovering the function { ( x ) system of partial differential equations that can be reduced to a second order integro-differential equation $ -u_{xx} + c(x)u_{x} + d\phi (x)u-\gamma d\phi (x)\int _{0}^{t}e^{-\gamma (t-\tau )}u(x,\tau )\, d\tau = 0 $ with boundary conditions. We prove the existence and uniqueness of solutions to the inverse problem and develop a numerical algorithm for solving this problem. Computational results for some examples are presented.     

Positive periodic solutions for a nonlinear differential system with two parameters

In this article, we investigate a nonlinear system of differential equations with two parameters $$\left\{ \begin{array}{l} x"(t)=a(t)x(t)-\lambda f(t, x(t), y(t)),\y"(t)=-b(t)y(t)+\mu g(t, x(t), y(t)),\end{array}\right.$$ where $a,b \in C(\textbf{R},\textbf{R}_+)$ are $\omega-$periodic for some period $\omega > 0$, $a,b \not\equiv 0$, $f,g \in C(\textbf{R} \times \textbf{R}_+ \times \textbf{R}_+ ,\textbf{R}_+)$ are $\omega-$periodic functions in $t$, $\lambda$ and $\mu$ are positive parameters. Based upon a new fixed point theorem, we establish sufficient conditions for the existence and uniqueness of positive periodic solutions to this system for any fixed $\lambda,\mu>0$. Finally, we give a simple example to illustrate our main result.     

Periodic solution of a higher dimensional ecological system

The main purpose of this article is to study the periodicity of a Lotka-Volterra''s competition system with feedback controls. Some new and interesting sufficient conditions are obtained for the global existence of positive periodic solutions. Our method is base on combining matrix''s spectral theory and inequality $|x(t)|\leq x(t_{0})+\int_{0}^{\omega }|\dot{x}(t)|{\rm d}t$. Some examples and their simulations show the feasibility of our main result.     

Study on a kind of $p$-Laplacian neutral differential equation with multiple variable coefficients

In this paper, we first discuss some properties of the neutral operator with multiple variable coefficients $(Ax)(t):=x(t)-\sum\limits_{i=1}^{n}c_i(t)x(t-\delta_i)$. Afterwards, by using an extension of Mawhin''s continuation theorem, a kind of second order $p$-Laplacian neutral differential equation with multiple variable coefficients as follows $$\left(\phi_p\left(x(t)-\sum\limits_{i=1}^{n}c_i(t)x(t-\delta_i)\right)''\right)''=\tilde{f}(t,x(t),x''(t))$$ is studied. Finally, we consider the existence of periodic solutions for two kinds of second-order $p$-Laplacian neutral Rayleigh equations with singularity and without singularity. Some new results on the existence of periodic solutions are obtained. It is worth noting that $c_i$ ($i=1,\cdots,n$) are no longer constants which are different from the corresponding ones of past work.