This paper deals with the blow-up properties of solutions to semilinear heat equation ut-uxx= up in (0, 1) × (0, T) with the Neumann boundary condition ux(0, t) = 0, u:x1, t) = 1 on [0, T). The necessary and suff...This paper deals with the blow-up properties of solutions to semilinear heat equation ut-uxx= up in (0, 1) × (0, T) with the Neumann boundary condition ux(0, t) = 0, u:x1, t) = 1 on [0, T). The necessary and sufficient conditions under which all solutions to have a finite time blow-up and the exact blow-up rates are established. It is proved that the blow-up will occur only at the boundary x = 1. The asymptotic behavior near the blow-up time is also studied.展开更多
We consider the semilinear heat equation with globally Lipschitz non-linearity involving gradient terms in a bounded domain of R^n. In this paper, we obtain explicit bounds of the cost of approximate controllability, ...We consider the semilinear heat equation with globally Lipschitz non-linearity involving gradient terms in a bounded domain of R^n. In this paper, we obtain explicit bounds of the cost of approximate controllability, i.e., of the minimal norm of a control needed to control the system approximately. The methods we used combine global Carleman estimates, the variational approach to approximate controllability and Schauder＇s fixed point theorem.展开更多
This paper deals with the blow up properties of solutions to semilinear heat equation u t- Δ u=u p in R N +×(0,T) with the nonlinear boundary condition -ο u ο x 1 = u q for x 1=0,t∈(0,T) ....This paper deals with the blow up properties of solutions to semilinear heat equation u t- Δ u=u p in R N +×(0,T) with the nonlinear boundary condition -ο u ο x 1 = u q for x 1=0,t∈(0,T) .It has been proved that if max( p,q) ≤1,every nonnegative solution is global.When min (p,q) >1 by letting α=1p-1 and β=12(q-1) it follows that if max (α,β)≥N2 ,all nontrivial nonnegative solutions are nonglobal,whereas if max (α,β)<N2 ,there exist both global and nonglobal solutions.Moreover,the exact blow up rates are established.展开更多
We prove the approxomate controllability and finite dimensional exact controllability of semilinear heat equation in R <SUP>N </SUP>with the same control by introducing the weighted Soblev spaces.
It is shown that any solution to the semilinear problem{u（x,0=）u0（x）〈1,x∈[-1,1] u（±1,t）=0,t∈（0,T）, ut=uxx＋δ（1-u）^-p（x,t）∈（-1,1） ×（0,T）either touches 1 in finite time or converges smooth...It is shown that any solution to the semilinear problem{u（x,0=）u0（x）〈1,x∈[-1,1] u（±1,t）=0,t∈（0,T）, ut=uxx＋δ（1-u）^-p（x,t）∈（-1,1） ×（0,T）either touches 1 in finite time or converges smoothly to a steady state as t -~ ~e. Some extensions of this result to higher dimensions are also discussed.展开更多
文摘This paper deals with the blow-up properties of solutions to semilinear heat equation ut-uxx= up in (0, 1) × (0, T) with the Neumann boundary condition ux(0, t) = 0, u:x1, t) = 1 on [0, T). The necessary and sufficient conditions under which all solutions to have a finite time blow-up and the exact blow-up rates are established. It is proved that the blow-up will occur only at the boundary x = 1. The asymptotic behavior near the blow-up time is also studied.
基金supported by the Natural Science Foundation of China (No.10371136,10771222)
文摘We consider the semilinear heat equation with globally Lipschitz non-linearity involving gradient terms in a bounded domain of R^n. In this paper, we obtain explicit bounds of the cost of approximate controllability, i.e., of the minimal norm of a control needed to control the system approximately. The methods we used combine global Carleman estimates, the variational approach to approximate controllability and Schauder＇s fixed point theorem.
文摘This paper deals with the blow up properties of solutions to semilinear heat equation u t- Δ u=u p in R N +×(0,T) with the nonlinear boundary condition -ο u ο x 1 = u q for x 1=0,t∈(0,T) .It has been proved that if max( p,q) ≤1,every nonnegative solution is global.When min (p,q) >1 by letting α=1p-1 and β=12(q-1) it follows that if max (α,β)≥N2 ,all nontrivial nonnegative solutions are nonglobal,whereas if max (α,β)<N2 ,there exist both global and nonglobal solutions.Moreover,the exact blow up rates are established.
基金the National Natural Science Foundation of ChinaGuangdong Province Natural Science Foundation of China (No.021765).
文摘We prove the approxomate controllability and finite dimensional exact controllability of semilinear heat equation in R <SUP>N </SUP>with the same control by introducing the weighted Soblev spaces.
基金Supported by National Natural Science Foundation of China (Grant No. 10801058)an Earmarked Grant for Research, Hong Kong and a self-determined Research Fund of CCNU from the Colleges’ Basic Research and Operation of MOE
文摘It is shown that any solution to the semilinear problem{u（x,0=）u0（x）〈1,x∈[-1,1] u（±1,t）=0,t∈（0,T）, ut=uxx＋δ（1-u）^-p（x,t）∈（-1,1） ×（0,T）either touches 1 in finite time or converges smoothly to a steady state as t -~ ~e. Some extensions of this result to higher dimensions are also discussed.
