Uniqueness to Some Inverse Source Problems for the Wave Equation in Unbounded Domains

This paper is concerned with inverse acoustic source problems in an unbounded domain with dynamical boundary surface data of Dirichlet kind. The measurement data are taken at a surface far away from the source support. We prove uniqueness in recovering source terms of the form f(x)g(t) and f(x1, x2, t)h(x3),where g(t) and h(x3) are given and x =(x1, x2, x3) is the spatial variable in three dimensions. Without these a priori information, we prove that the boundary data of a family of solutions ca...     

分数阶R-L微分方程初值问题解的存在唯一性

研究了R-L导数定义下的分数维微分方程初值问题解的存在性及其唯一性,给出了方程的Peano存在定理和不等式定理,基于逐次逼近的方法,利用对分数阶R-L微夯方程构造的Tonelli序列和Ascoli引理证明分数阶R-L微分方程解的存在性,根据分数阶不等式定理证明了分数阶R-L微分方程解的唯一性.     

An Inverse Problem for the Burgers Equation

In this paper the Generalized Pulse-Spectrum Technique (GPST) is extended to solve an inverse problem for the Burgers equation. We prove that the GPST is equivalent in some sense to the Newton-Kantorovich iteration method. A feasible numerical implementation is presented in the paper and some examples are executed. The numerical results show that this procedure works quite well.     

Inverse Obstacle Problem for the Non-Stationary Wave Equation with an Unknown Background

We consider boundary measurements for the wave equation on a bounded domain M ? ?² or on a compact Riemannian surface, and introduce a method to locate a discontinuity in the wave speed. Assuming that the wave speed consist of an inclusion in a known smooth background, the method can determine the distance from any boundary point to the inclusion. In the case of a known constant background wave speed, the method reconstructs a set contained in the convex hull of the inclusion and containing the inclusion. Even if the background wave speed is unknown, the method can reconstruct the distance from each boundary point to the inclusion assuming that the Riemannian metric tensor determined by the wave speed gives simple geometry in M. The method is based on reconstruction of volumes of domains of influence by solving a sequence of linear equations. For τ ∈C(?M) the domain of influence M(τ) is the set of those points on the manifold from which the distance to some boundary point x is less than τ(x).     

Initial Boundary Value Problems for Scalar and Vector Burgers Equations

In this article we study Burgers equation and vector Burgers equation with initial and boundary conditions. First we consider the Burgers equation in the quarter plane x >0, t >0 with Riemann type of initial and boundary conditions and use the Hopf–Cole transformation to linearize the problems and explicitly solve them. We study two limits, the small viscosity limit and the large time behavior of solutions. Next, we study the vector Burgers equation and solve the initial value problem for it when the initial data are gradient of a scalar function. We investigate the asymptotic behavior of this solution as time tends to infinity and generalize a result of Hopf to the vector case. Then we construct the exact N-wave solution as an asymptote of solution of an initial value problem extending the previous work of Sachdev et al. (1994). We also study the limit as viscosity parameter goes to 0.Finally, we get an explicit solution for a boundary value problem in a cylinder.     

KdV-KSV方程的初边值问题

本文证明了KdV－KSV方程的周期边值问题和Cauchy问题广义解和古典解的整体存在性、正则性及唯一性．     

Numerical Solution of the Positional Boundary Control Problem for the Wave Equation with Unknown Initial Data

The problem of one-sided boundary Neumann control is considered for the onedimensional wave equation. Information about the initial state of the process is absent. Instead, the values of Dirichlet observations are received in real time at the controlled boundary. The aim is to bring the process to a complete rest by means of positional boundary controls. To solve this problem, we propose an efficient numerical algorithm with an optimal guaranteed damping time. Some results of numerical experiments are presented.     

Distributed Control Problems for the Burgers Equation

In this work a distributed optimal control problem for time-dependent Burgers equation is analyzed. To solve the nonlinear control problems the augmented Lagrangian-SQP technique is used depending upon a second-order sufficient optimality condition. Numerical test examples are presented.     

Uniqueness for Inverse Boundary Value Problems by Dirichlet-to-Neumann Map on Subboundaries

We consider inverse boundary value problems for elliptic equations of second order of determining coefficients by Dirichlet-to-Neumann map on subboundaries, that is, the mapping from Dirichlet data supported on subboundary ${\partial \Omega \setminus \Gamma_{-}}$ to Neumann data on subboundary ${\partial \Omega \setminus \Gamma_{+}}$ . First we prove uniqueness results in three dimensions under some conditions such as ${\overline{\Gamma_{+}\cup\Gamma_{-}}= \partial\Omega}$ Next we survey uniqueness results in two dimensions for various elliptic systems for arbitrarily given ${\Gamma_{-} = \Gamma_{+}}$ Our proof is based on complex geometric optics solutions which are constructed by a Carleman estimate.     

一类非线性双曲型方程初边值问题解的爆破

该文给出一类非线性双曲型方程初边值问题解爆破的充分条件, 并证明问题局部解的存在性与唯一性     

Derivative swift-Hohenberg方程的初边值问题解的存在性

运用压缩影射原理证明了DS-H方程的初边值问题的局部解的存在性和唯一性.     

一类带有源项的拟线性波动方程的初边值问题

考虑一类带有源项的拟线性波动方程的初边值问题,利用G a lerk in方法和单调算子方法讨论在混合边界条件下,该问题整体广义解的存在性及衰减性.     

Approximation of an Inverse Initial Problem for a Biparabolic Equation

In this paper, we consider the problem of finding the initial distribution for the linear inhomogeneous and nonlinear biparabolic equation. The problem is severely ill-posed in the sense of Hadamard. First, we apply a general filter method to regularize the linear nonhomogeneous problem. Then, we also give a regularized solution and consider the convergence between the regularized solution and the sought solution. Under the a priori assumption on the exact solution belonging to a Gevrey space, we consider a generalized nonlinear problem by using the Fourier truncation method to obtain rigorous convergence estimates in the norms on Hilbert space and Hilbert scale space.     

Euler-Bernoulli粘弹性方程初边值问题整体解的存在性

本文利用 Faedo- Galerkin方法证明了一类具记忆项的 Euler- Bernoulli粘弹性方程初边值问题整体解的存在性 .     

Inverse Problem of Determining an Unknown Coefficient in the Beam Vibration Equation

Differential Equations - We consider the direct initial–boundary value problem for the equation of transverse vibrations of a homogeneous beam freely supported at the ends and study the...     

Uniqueness of the Solution of a Nonlocal Problem for an Elliptic-Hyperbolic Equation with Singular Coefficients

Mathematical Notes - A boundary-value problem with nonlocal integral condition of Samarskii–Ionkin type is studied for a mixed-type equation with singular coefficients in a rectangular...