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Abdelbaki Choucha, Salah Mahmoud Boulaaras, Djamel Ouchenane, Ali Allahem, "Global Existence for Two Singular One-Dimensional Nonlinear Viscoelastic Equations with respect to Distributed Delay Term", Journal of Function Spaces, vol. 2021, Article ID 6683465, 18 pages, 2021. https://doi.org/10.1155/2021/6683465
Global Existence for Two Singular One-Dimensional Nonlinear Viscoelastic Equations with respect to Distributed Delay Term
In this current work, we are interested in a system of two singular one-dimensional nonlinear equations with a viscoelastic, general source and distributed delay terms. The existence of a global solution is established by the theory of potential well, and by using the energy method with the function of Lyapunov, we prove the general decay result of our system.
We are interested in the following system: with where , , , , , , the second integral represents the distributed delay and are bounded functions, where are two real numbers satisfying , and , are defined functions later.
Three decades ago, these problems that arise in one-dimensional elasticity have been studied and developed with regard to viscosity with long-term memory. And it has been studied in many fields of science, engineering, medical sciences, and chemistry, as well as population and other matters; see, for example, [1–24]. Recently, in the absence of delay (), problem (1) was studied in , and also later in , the authors considered problem (1) with localized frictional damping term. We also know that delay, especially distributed delay, is a phenomenon in our life and is almost found in various fields, and its inclusion in any problem makes it more important. The distributed delay in many works has been studied and many authors have taken care of it, for example, [5, 9, 27, 28]. Based on all this and the results of the research papers [14, 15, 17, 28–30, 31], the introduction of the term distributed delay as a damping mechanism in problem (1) makes it a new problem from what has been previously studied.
And we have divided this paper into the following. We present in the second section the definitions, basics, and theories of function spaces that are required throughout the rest of the paper. In Section 3, we present the energy function while proving to be decreasing. And in the final section, the general decay is obtained by applying the energy method and the function of Lyapunov.
Let be the weighted Banach space equipped with the norm
be the Hilbert space of square integral functions having the finite norm and be the Hilbert space equipped with the norm
is the Hilbert space equipped with the norm
Theorem 1 . For and in , we have where is a constant depending on and only.
As in , introducing the new variables yields
Problem (1) arrives at where
With the initial data and boundary conditions
We have the following assumptions:
(G1) are , nonincreasing functions satisfying
(G2) a differentiable function, such that and satisfies for some
And also, where , fixed, , such that
(G3) we take where and .
We have where
Lemma 3. For , such that , we have
Lemma 4. such that
Proof. We prove inequality for and the same result also holds for .
It is clear that By Young’s inequality, with we get Therefore, Hence, by Poincaré’s inequality and (11), we obtain The proof of lemma is complete.
Lemma 5. Let be the solution of system (11); then, is a nonincreasing function, that is, where
Proof. Multiplying equation (11)1,2 by , and integrating over , we find Using integration by parts, we get Now, multiplying equation (11)3 by and integrating over , we get Similarly, by multiplying equation (11)4 by and integrating over , we get Using Young’s and Cauchy-Schwartz inequalities, we have Similarly, we get By combining (39), (40), (41), (42), (43), (45), (46), (47), (48), (49), and (50) in (38), we get (34) and (36).
3. Global Existence
In this section, we showed the global existence of the solutions of the system (11).
First, introducing the following notation note that
Then, such that where
Proof. As , then by continuity of , such that , ; this implies that we have a maximum time value noting such that This, with (51), (52), and (14), we have Hence, By (24) and (54), we get Hence, This proves that . By repeating the procedure, is extended to .
Proof. To prove that is bounded independently of , using (36) yields Using (52), we find By using (62) in (63), we get and using (14), (15), and (54) in (64), we get So where Hence, the solution of system (11) is bounded and global.
4. Decay of Solutions
In this section, the decay result is showed by using several lemmas.
As, we let where , and
Lemma 8. There exist , such that for , , and small enough.
Proof. Using the inequality of Young and the Poincaré-type inequality and , we find
A combination of (73), (74), (75), (76), and (77) in (68) gives Then, , for , , and small enough, such that Similarly, thanks to the inequalities of Young and Poincaré-type and using gives