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An inverse problem for a quasilinear parabolic equation with nonlocal boundary and overdetermination conditions
Journal of Inequalities and Applications volume 2014, Article number: 76 (2014)
Abstract
In this paper the inverse problem of finding the time-dependent coefficient of heat capacity together with the solution of heat equation with nonlocal boundary conditions is considered. Under some natural regularity and consistency conditions on the input data, the existence, uniqueness and continuous dependence upon the data of the solution are shown. Some considerations on the numerical solution for this inverse problem are presented with an example.
1 Introduction
Denote the domain D by
Consider the equation
with the initial condition
the nonlocal boundary condition
and the integral overdetermination data
for a quasilinear parabolic equation with the nonlinear source term .
The functions and are given functions on and , respectively.
The problem of finding the pair in (1)-(4) will be called an inverse problem.
Definition 1 The pair from the class , for which conditions (1)-(4) are satisfied and on the interval , is called the classical solution of inverse problem (1)-(4).
The problem of identifying a coefficient in a nonlinear parabolic equation is an interesting problem for many scientists [1–3].
Inverse problems for parabolic equations with nonlocal boundary conditions are investigated in [4, 5]. This kind of conditions arise from many important applications in heat transfer, life sciences, etc. In [6], also the nature of (3) type boundary conditions is demonstrated.
These kind of conditions such as (4) arise from many important applications in heat transfer, thermoelasticity, control theory, life sciences, etc. For example, in heat propagation in a thin rod, in which the law of variation of the total quantity of heat in the rod is given in [7].
The paper organized as follows.
In Section 2, the existence and uniqueness of the solution of inverse problem (1)-(4) are proved by using the Fourier method and the iteration method. In Section 3, continuous dependence upon the data of the inverse problem is shown. In Section 4, the numerical procedure for the solution of the inverse problem is given.
2 Existence and uniqueness of the solution of the inverse problem
Consider the following system of functions on the interval :
The systems of these functions arise in [8] for the solution of a nonlocal boundary value problem in heat conduction. It is easy to verify that the systems of functions and ,  , are biorthonormal on . They are also Riesz bases in (see [5, 9]).
The main result on the existence and uniqueness of the solution of inverse problem (1)-(4) is presented as follows.
We have the following assumptions on the data of problem (1)-(4):
(A1) , , .
(A2)
(A2)1 ,
(A2)2 , , .
(A3)
(A3)1 Let the function be continuous with respect to all arguments in and satisfy the following condition:
where , .
(A3)2 , ,
(A3)3 , , ,
(A3)4 , ,
where
By applying the standard procedure of the Fourier method, we obtain the following representation for the solution of (1)-(3) for arbitrary :
Under conditions (A2)1 and (A3)2, the series (5) and converge uniformly in since their majorizing sums are absolutely convergent. Therefore their sums and are continuous in . In addition, the series and are uniformly convergent for (ε is an arbitrary positive number). In addition, is continuous in because the majorizing sum of is absolutely convergent under conditions (A2)2 and (A3)3. Differentiating (4) under condition (A1), we obtain
Definition 2 Denote the set
of continuous on functions satisfying the condition
by . Let
be the norm in .
Let us denote
be the norm in .
It can be shown that and are the Banach spaces.
Theorem 3 Let assumptions (A1)-(A3) be satisfied. Then inverse problem (1)-(4) has a unique solution.
Proof An iteration for (5) is defined as follows:
where and
From the conditions of the theorem, we have and .
Let us write in (8).
Adding and subtracting to and from both sides of the last equation, we obtain
Applying the Cauchy inequality and the Lipschitz condition to the last equation and taking the maximum of both sides of the last inequality yields the following:
Applying the Cauchy inequality, the Hölder inequality, the Bessel inequality, the Lipschitz condition and taking maximum of both sides of the last inequality yields the following:
Applying the same estimations, we obtain
Finally, we have the following inequality:
Hence . In the same way, for a general value of N, we have
Since , we have
An iteration for (7) is defined as follows:
where  .
Applying the Cauchy inequality,
Hence . In the same way, for a general value of N, we have
we deduce that .
Now we prove that the iterations and converge as in and , respectively.
Applying the Cauchy inequality, the Hölder inequality, the Lipschitz condition and the Bessel inequality to the last equation, we obtain
Applying the Cauchy inequality, the Hölder inequality, the Lipschitz condition and the Bessel inequality to the last equation, we obtain
Applying the Cauchy inequality and the Lipschitz condition to the last equation, we obtain
Applying the Cauchy inequality, the Hölder inequality, the Lipschitz condition and the Bessel inequality to the last equation, we obtain
By the same way, we obtain
For N, we have
Using (A1)-(A3) and the comparison test, we deduce from (9) that the series is uniformly convergent to an element of . However, the general term of the sequence may be written as
So the sequence is uniformly convergent to an element of because the sum on the right-hand side is the N th partial sum of the aforementioned uniformly convergent series.
It is easy to see that if , , then , .
Therefore and converge in and , respectively.
Now let us show that there exist u and p such that
In the same way, we have
Applying Gronwall’s inequality to (10) and using inequalities (9) and (11), we have
Here
When , we obtain . Hence .
For the uniqueness, we assume that problem (1)-(4) has two solution pairs , . Applying the Cauchy inequality, the Hölder inequality, the Lipschitz condition and the Bessel inequality to and , we obtain
Applying the Gronwall inequality to (13), we have . Hence .
The theorem is proved. □
3 Continuous dependence of upon the data
Theorem 4 Under assumptions (A1)-(A3), the solution of problem (1)-(4) depends continuously upon the data φ, E.
Proof Let and be two sets of the data, which satisfy the assumptions (A1)-(A3). Suppose that there exist positive constants , , such that
Let us denote . Let and be solutions of inverse problem (1)-(4) corresponding to the data and , respectively. According to (5), we have
Now let us estimate the difference .
Applying the Cauchy equation, we have
where , , are constants that are determined by , and . Finally, we obtain
If we take this estimation in (14), we get
Applying the Gronwall inequality, we obtain
Taking the maximum of the inequality, we have
If , then . Hence . □
4 Numerical procedure for nonlinear problem (1)-(4)
We construct an iteration algorithm for the linearization of problem (1)-(4) as follows.
Let and . Then problem (15)-(18) can be written as a linear problem:
We use the finite difference method to solve (19)-(22) with a predictor-corrector type approach which was explained in [10].
We subdivide the intervals and into subintervals and of equal lengths and , respectively. Then we add two lines and to generate the fictitious points needed for dealing with the boundary conditions. We choose the implicit scheme that is absolutely stable and has a second-order accuracy in h and a first-order accuracy in Ï„ [11]. The implicit scheme for (1)-(4) is as follows:
where and are the indices for the spatial and time steps, respectively, , , , , . At the level , adjustment should be made according to the initial condition and the compatibility requirements.
The system of equations (17)-(19) can be solved by the Gauss elimination method, and is determined.
5 Numerical example
Example 1 Consider inverse problem (1)-(4) with
It is easy to check that the analytical solution of this problem is
Let us apply the scheme which was explained in the previous section to the step sizes , .
In the case when , the comparisons between the analytical solution (23) and the numerical finite difference solution are shown in Figures 1 and 2.
It is clear from these results that this method has been shown to produce stable and reasonably accurate results for these examples.
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FK conceived the study, participated in its design and coordination and prepared computing section. IB participated in the sequence alignment and achieved the estimation. All authors read and approved the final manuscript.
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Kanca, F., Baglan, I. An inverse problem for a quasilinear parabolic equation with nonlocal boundary and overdetermination conditions. J Inequal Appl 2014, 76 (2014). https://doi.org/10.1186/1029-242X-2014-76
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DOI: https://doi.org/10.1186/1029-242X-2014-76