Exact controllability for some degenerate wave equations

In this paper, we study one-dimensional linear degenerate wave equations with a distributed controller. We establish observability inequalities for degenerate wave equation by multiplier method. We also deduce the exact controllability for degenerate wave equation by Hilbert uniqueness method when the control acts on the nondegenerate boundary. Moreover, an explicit expression for the controllability time is given.     

Persistent regional null controllability of some degenerate wave equations

This paper is addressed to a study of the persistent regional null controllability problems for one‐dimensional linear degenerate wave equations through a distributed controller. Different from non‐degenerate wave equations, the classical null controllability results do not hold for some degenerate wave equations. Thus, persistent regional null controllability is introduced, which means finding a control such that the corresponding state of the degenerate wave equation may vanish in a suitable subset of the space domain in a period of time. In order to solve this problem, we need to establish the regional null controllability for degenerate wave equations. This problem is reduced to a suitable observability problem of a linear degenerate wave equation. The key point is to choose a suitable multiplier in order to establish this observability inequality. Copyright © 2017 John Wiley & Sons, Ltd.     

Null controllability of a class of systems governed by coupled degenerate equations

This paper concerns the null controllability of the system governed by coupled degenerate equations. By the Carleman estimate for the case of a single degenerate equation, the Carleman estimate and the observability inequality are established. Then, the system with two controls and the system with one control are shown to be null controllable.     

Observability and Controllability of the 1-D Wave Equation in Domains with Moving Boundary

By mean of generalized Fourier series and Parseval’s equality in weighted \(L^{2}\)-spaces, we derive a sharp energy estimate for the wave equation in a bounded interval with a moving endpoint. Then, we show the observability, in a sharp time, at each of the endpoints of the interval. The observability constants are explicitly given. Using the Hilbert Uniqueness Method we deduce the exact boundary controllability of the wave equation.     

Simultaneous observability and stabilization of some uncoupled wave equations

We consider uncoupled wave equations with different speed of propagation in a bounded domain. Using a combination of the Bardos–Lebeau–Rauch observability result for a single wave equation and a new unique continuation result for uncoupled wave equations, we prove an observability estimate for that system. Applying Lions? Hilbert uniqueness method (HUM), one may derive simultaneous exact controllability results for the uncoupled system; the controls being locally distributed, with their supports satisfying the geometric control condition of Bardos, Lebeau and Rauch. Afterwards, we discuss the related simultaneous stabilization problem; this latter problem is solved by a combination of the new observability inequality, and a result of Haraux establishing an equivalence between observability and stabilization for second order evolution equations with bounded damping operators. Our observability and stabilization results generalize to higher space dimensions some earlier results of Haraux established in the one-dimensional setting.     

Observability Inequalities by Internal Observation and Their Applications

By means of a Carleman estimate, we obtain several observability inequalities by internal observation for hyperbolic equations with lower-order terms. Also, we apply our observability results to an exact controllability problem and an inverse wave source problem.     

Controllability and observability of a heat equation with hyperbolic memory kernel

The exact controllability and observability for a heat equation with hyperbolic memory kernel in anisotropic and nonhomogeneous media are considered. Due to the appearance of such a kind of memory, the speed of propagation for solutions to the heat equation is finite and the corresponding controllability property has a certain nature similar to hyperbolic equations, and is significantly different from that of the usual parabolic equations. By means of Carleman estimate, we establish a positive controllability and observability result under some geometric condition. On the other hand, by a careful construction of highly concentrated approximate solutions to hyperbolic equations with memory, we present a negative controllability and observability result when the geometric condition is not satisfied.     

Inverse problem on a tree-shaped network: unified approach for uniqueness

In this article, we prove uniqueness results for coefficient inverse problems regarding wave, heat or Schrödinger equation on a tree-shaped network, as well as the corresponding stability result of the inverse problem for the wave equation. The objective is the determination of the potential on each edge of the network from the additional measurement of the solution at all but one external end points. Several results have already been obtained in this precise setting or in similar cases, and our main goal is to propose a unified and simpler method of proof of some of these results. The idea which we will develop for proving the uniqueness is to use a more traditional approach in coefficient inverse problems by Carleman estimates. Afterwards, using an observability estimate on the whole network, we apply a compactness–uniqueness argument and prove the stability for the wave inverse problem.     

Global Uniqueness and Stability for an Inverse Plate Problem

This paper deals with the global uniqueness and stability of an inverse problem for the plate equation. By means of a suitable transformation, the problem is reduced to the observability estimate for the plate equations with memory. The main tool that we employ is a global Carleman-type estimate. This work was supported by FANEDD of China Project 200119 and by NSFC under Grant 10371084. The author thanks Professor X. Zhang for help.     

一类退化半导体方程弱解的唯一性

本文研究了一类退化漂移-扩散模型的混合边值问题.利用能量估计的方法,在边界数据和初始数据是严格正的条件下获得了此问题弱解的唯一性.     

Global Uniqueness and Stability for a Class of Multidimensional Inverse Hyperbolic Problems with Two Unknowns

In this paper we obtain the global uniqueness and stability estimate for a class of multidimensional inverse hyperbolic problems of determining a source term and an initial value from a single measurement of boundary values or interior values. By means of a suitable transformation, we reduce the problem to the observability inequalities for nonconservative hyperbolic equations with memory. Then, using a compactness/uniqueness argument, we can prove the uniqueness and the stability by a new kind of unique continuation property of a nonlocal hyperbolic equation.     

Uniform observability estimates for the 1-D discretized wave equation and the random choice method

In this Note, we consider the 1-dimensional wave equation, discretized by means of Glimm's random choice method. We prove that for almost every choice of the random parameter, the observability estimate is true asymptotically, uniformly with respect to the discretization parameters. To cite this article: J.-M. Coron et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

RAPID EXACT CONTROLLABILITY OF THE SEMILINEAR WAVE EQUATION

1.IntroductionConsiderthefollowingsemilinearwaveequationwithalocallydistributedcofltroller:whereI~g,11~$,nCR"isaboundeddomainwithaboundaryoffECI)andforeachtE[0,co),G(t)isasubdomainoffi.Intheabove,y(t,x)isthestateandXG(t)(x)u(t,x)isthecolltrol.Thus,u(t,x)istheintensityofthecontrolactionandG(t)isthelocationandtheshapeofthecontroller.Wewillallowthelocationandtheshapeofthecontrollertochange.LetU=Lfo.(0'co;L'(fl))andletQbeafamilyofset--valuedfunctionsG(t)definedon[0,co)takingsubdomainsoffias…     

Constructive observability inequalities for weak generalized solutions of the wave equation with elastic restraint

Problems with one-sided boundary controls and a homogeneous Robin boundary condition set on the uncontrolled end are considered in the class of strong generalized solutions of the variable coefficient wave equation. In the adjoint class of weak generalized solutions of the dual problems with one-sided observations, new constructive observability inequalities are obtained that differ from previously known ones by an optimal threshold time. It is shown that, in the considered functional classes, the estimated constants degenerate as the time interval length approaches the threshold. Numerical illustrations are given showing that the stability of approximate solutions to control problems can be substantially enhanced by taking into account a priori information contained in the resulting observability inequalities.     

Existence and regularity of the solution of a mixed boundary value problem for the Keldysh equation with a nonlinear absorption term

The Keldysh equation is a more general form of the classic Tricomi equation from fluid dynamics. Its well-posedness and the regularity of its solution are interesting and important. The Keldysh equation is elliptic in y>0 and is degenerate at the line y=0 in R². Adding a special nonlinear absorption term, we study a nonlinear degenerate elliptic equation with mixed boundary conditions in a piecewise smooth domain—similar to the potential fluid shock reflection problem. By means of an elliptic regularization technique, a delicate a priori estimate and compact argument, we show that the solution of a mixed boundary value problem of the Keldysh equation is smooth in the interior and Lipschitz continuous up to the degenerate boundary under some conditions. We believe that this kind of regularity result for the solution will be rather useful.     

由退化抛物方程支配串联系统的零能控性

该文讨论了由一个半线性退化抛物方程与半线性热方程构成的串联系统的零能控性. 这里控制函数仅施加在一个方程上. 证明的关键是建立适当的能观性不等式.     

Null controllability of degenerate parabolic equations

Motivated by a boundary layer problem, we are interested in the controllability properties of parabolic equations degenerating at the boundary of the space domain. We derive new Carleman estimates for a class of degenerate parabolic equation; the proof is based in particular on Hardytype inequalities. Then we deduce observability and null controllability results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

非线性退化波方程的Riemann问题

研究了弹性力学中一退化波方程的Riemann问题．其应力函数非凸非凹,从而使得激波条件退化．通过引入广义激波条件下的退化激波,构造性地得到了各种情形下Riemann问题的整体解．     

在Radon测度给定下的一类退化椭圆型方程

此文研究一类在Ｒａｄｏｎ测度给定下二阶退化拟线性椭圆型方程．通过引入逼近子问题列并求解、先验估计和收敛性研究，证明了该方程广义解在带权Ｓｏｂｏｌｅｖ空间的存在性．     

Observability Inequality for the Kirchhoff-Rayleigh Plate Like Equation in a Short Time

In this paper, for any given observation time and suitable moving observation domains, the author establishes a sharp observability inequality for the Kirchhoff-Rayleigh plate like equation with a suitable potential in any space dimension. The approach is based on a delicate energy estimate. Moreover, the observability constant is estimated by means of an explicit function of the norm of the coefficient involved in the equation.