Complex Boundary Value Problems of Nonlinear Differential Equations 2014View this Special Issue
Research Article | Open Access
Stability of a Class of Coupled Systems
We consider a class of coupled systems with damping terms. By using multiplier method and the estimation techniques of the energy, we show that even if the kernel function is nonincreasing and integrable without additional conditions, the energy of the system decays also to zero in a good rate.
This work is motivated by the recent researches on the Cauchy problem for the coupled evolution equations with memory (e.g., Alabau-Boussouira et al. , Cannarsa and Sforza , Wan and Xiao , and Xiao and Liang ).
We study the following abstract Cauchy problem for coupled systems with damping terms: where is a positive self-adjoint linear operator in a Hilbert space ; and are two nonnegative functions on and denote the memory kernel, which will be specified later. The problem arises in the theory of viscoelasticity.
We are concerned with the delay behavior of the energy of the systems. In the real world, for the viscoelastic material, the kernel function is almost all nonincreasing and nonnegative. Therefore, we are more interested in decay behavior when the kernel is nonnegative and nonincreasing. In this case, is a strongly positive definite kernel (as in [2, 5]). By using multiplier method and the estimation techniques of the energy, we show that even if the kernel function is nonincreasing and integrable without additional conditions, the energy of the system decays also to zero in a good rate.
Let us recall the following assumptions which were used in related literature:(I1) is a positive self-adjoint linear operator in , satisfying for a constant .(I2) is a nonincreasing and integrable function such that where .
Proof. The existence and uniqueness of solution can be obtained by the standard operator theory. Here, we omit it.
Multiplying (1) by and (2) by , respectively, and summing-up, we obtained the equality (21).
Remark 2. From assumption and (21), we have
Definition 3. Set ; is called positive definite kernel if, for any , Also, is said to be a strongly positive definite kernel if there exists a constant such that is positive definite, for any .
2. Result and Proof
Theorem 4. Let hold, and let , and be as in Theorem 1. Then, the energy satisfies where is a positive constant and depends on the initial data. Moreover,
To prove Theorem 4, we need the following lemmas.
From now on, we write Then, is a strongly positive definite kernel; see [2, Theorem 2.1].
Lemma 5. Let hold, , and . Then, for any , where depends only on the initial data.
Proof. It follows from (1) that Moreover, taking the inner product of (2) with and integrating over , we obtain Combining the above two equations and using integration by parts, we get Applying Lemma 3.4 and in  to the two integral terms on the left-hand side, we have Noticing and Remark 2, we obtain (16).
Lemma 6. Let hold, , and . Then, for any , where depends only on the initial data.
Moreover, in view of (23) and , we have where depends only on the initial data.
Lemma 7. Let hold, , and . Then, for any , where depends only on the initial data.
Proof. It follow from (1) and (2) that Note that we have used (24)-(25) in the above calculation. Hence, we have On the other hand, we see that By Young’s inequality, we obtain Putting (31)-(32) into (29), we obtain Noticing assumption , we obtain the desired estimates (26)-(27).
Proof of Theorem 4. First, we estimate the two memory energy terms.
By a direct calculation, we have Hence, by (26), we obtain Similarly, we have Thus, (24)–(27) and (35)-(36) yield for a positive constant . As , we have Accordingly, (37) means that Hence, the estimate (13) follows. Furthermore, since the integral is convergent, it follows that via the Cauchy convergence principle. Then, the proof of Theorem 4 is completed.
Conflict of Interests
The author declares that there is no conflict of interests regarding the publication of this paper.
The work was supported partly by the NSF of China (nos. 11371095 and 11271082).
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Copyright © 2014 Kun-Peng Jin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.