Limit cycles obtained by perturbing a degenerate center

OMA-Vol. 7 (2023), Issue 1, pp. 56 – 70 Open Access Full-Text PDF
Nabil Rezaiki and Amel Boulfoul

Abstract: This paper deals with the maximum number of limit cycles bifurcating from the degenerate centre
\[ \dot{x}=-y(3x^2+y^2),\: \dot{y}=x(x^2-y^2), \]
when we perturb it inside a class of all homogeneous polynomial differential systems of degree \(5\). Using averaging theory of second order, we show that, at most, five limit cycles are produced from the periodic orbits surrounding the degenerate centre under quintic perturbation. In addition, we provide six examples that give rise to exactly \(5, 4, 3, 2, 1\) and \(0\) limit cycles.

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Expansion of the Jensen \((\Gamma_{1},\Gamma_{2})\)-functional inequatities based on Jensen type \((\eta,\lambda)\)-functional equation with \(3k\)-Variables in complex Banach space

OMA-Vol. 7 (2023), Issue 1, pp. 56 – 70 Open Access Full-Text PDF
Ly Van An

Abstract: In this paper, we work on expanding the Jensen \((\Gamma_{1},\Gamma_{2})\)-function inequalities by relying on the general Jensen \((\eta,\lambda)\)-functional equation with \(3k\)-variables on the complex Banach space. That is the main result of this.

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On norms of derivations implemented by self-adjoint operators

OMA-Vol. 7 (2023), Issue 1, pp. 42 – 55 Open Access Full-Text PDF
Obogi Robert Karieko

Abstract:In this paper, we concentrate on norms of derivations implemented by self-adjoint operators. We determine the upper and lower norm estimates of derivations implemented by self-adjoint operators. The results show that the knowledge of self-adjoint governs the quantum chemical system in which the eigenvalue and eigenvector of a self-adjoint operator represents the ground state energy and the ground state wave function of the system respectively.

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A class of power series based modified newton method with high precision for solving nonlinear models

OMA-Vol. 7 (2023), Issue 1, pp. 32 – 41 Open Access Full-Text PDF
Oghovese Ogbereyivwe and Salisu Shehu Umar

Abstract:This manuscript proposed high-precision methods for obtaining solutions for nonlinear models. The method uses the Newton method as its predictor and an iterative function that involves the perturbed Newton method with the quotient of two power series as the corrector function. The theoretical analysis of convergence indicates that the methods class is of convergence order four, requiring three functions evaluation per cycle. The computation performance comparison with some existing methods shows that the developed methods class has perfect precision.

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Identification of parameters in parabolic partial differential equation from final observations using deep learning

OMA-Vol. 7 (2023), Issue 1, pp. 10 – 31 Open Access Full-Text PDF
Khalid Atif, El-Hassan Essouf and Khadija Rizki

Abstract:In this work, we propose a deep learning approach for identifying parameters (initial condition, a coefficient in the diffusion term and source function) in parabolic partial differential equations (PDEs) from scattered final observations in space and noisy a priori knowledge. In Particular, we approximate the unknown solution and parameters by four deep neural networks trained to satisfy the differential operator, boundary conditions, a priori knowledge and observations. The proposed algorithm is mesh-free, which is key since meshes become infeasible in higher dimensions due to the number of grid points explosion. Instead of forming a mesh, the neural networks are trained on batches of randomly sampled time and space points. This work is devoted to the identification of several parameters of PDEs at the same time. The classical methods require a total a priori knowledge which is not feasible.
While they cannot solve this inverse problem given such partial data, the deep learning method allows them to resolve it using minimal a priori knowledge.

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The local fractional natural transform and its applications to differential equations on Cantor sets

OMA-Vol. 7 (2023), Issue 1, pp. 01 – 09 Open Access Full-Text PDF
Djelloul Ziane, and Mountassir Hamdi Cherif

Abstract:The work that we have done in this paper is the coupling method between the local fractional derivative and the Natural transform (we can call it the local fractional Natural transform), where we have provided some essential results and properties. We have applied this method to some linear local fractional differential equations on Cantor sets to get nondifferentiable solutions. The results show this transform’s effectiveness when we combine it with this operator.

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