https://dspace.univ-guelma.dz/jspui/handle/123456789/2 2026-06-09T22:30:12Z 2026-06-09T22:30:12Z GHOUL, Wissam https://dspace.univ-guelma.dz/jspui/handle/123456789/19030 2026-06-09T09:38:16Z 2026-04-09T00:00:00Z

Titre: Stability and controllability of fractional deterministic and stochastic systems Auteur(s): GHOUL, Wissam Résumé: The present work establishes new finite-time stability results for Hadamard fractional stochastic delay systems. These systems combine the memory effects of the Hadamard fractional derivative with the influence of discrete time delays, making them suitable for modeling complex dynamical processes. Using recent advances in fractional calculus and stochastic analysis, the study derives explicit sufficient conditions ensuring finite-time stability under general stochastic perturbations. The methodology relies on analytical estimates for fractional kernels together with inequalities adapted to delay-dependent stochastic dynamics. The obtained criteria extend classical results for Itô stochastic differential equations and fractional systems without delay. Overall, the work provides a unified framework for understanding the transient behavior of stochastic systems with both memory and delay, with potential applications in engineering, physics, biology, and control theory.

2026-04-09T00:00:00Z LESLOUS, Aymen https://dspace.univ-guelma.dz/jspui/handle/123456789/19005 2026-05-10T13:30:44Z 2026-04-30T00:00:00Z

Titre: Stochastic Differential Equations: Controllability and Almost Periodicity Auteur(s): LESLOUS, Aymen Résumé: This dissertation presents fundamental contributions to the theory of infinite-dimensional stochastic differential equations and their optimal control, with particular emphasis on hyperbolic-type systems and almost periodic phenomena. The research establishes profound connections among functional analysis, stochastic analysis, and control theory, thereby addressing long-standing challenges in the study of systems governed by stochastic partial differential equations. In the first part, we develop a comprehensive framework for second-order neutral stochastic differential equations in Hilbert spaces. We establish the existence, uniqueness, and almost periodicity in distribution of mild solutions for a broad class of such equations over the entire real line. The methodology relies on innovative fixed-point arguments in suitable path spaces and introduces a novel generalisation of Grönwall’s inequality capable of treating convolutions on unbounded temporal domains. The second major contribution provides a complete resolution of the stochastic linear– quadratic optimal control problem for hyperbolic systems with multiplicative noise, representing a significant extension beyond classical theory restricted to deterministic systems. We prove the well-posedness, boundedness, and uniqueness of solutions to the associated operator-valued Riccati equation by means of original techniques that combine chronological calculus with a generalised Grönwall–Bihari inequality. The effectiveness of these theoretical developments is demonstrated through applications to almost periodic second-order stochastic differential equations and stochastic wave equations with random forcing, thereby confirming the relevance of the proposed framework to problems in mathematical physics and engineering. By integrating tools from operator theory, stochastic analysis, and harmonic analysis, this work provides a unified analytical toolkit that advances our understanding of infinite-dimensional stochastic dynamics.

2026-04-30T00:00:00Z AGGOUNE, Aicha https://dspace.univ-guelma.dz/jspui/handle/123456789/19001 2026-05-03T08:51:36Z 2026-03-17T00:00:00Z

Titre: DATA MINING Auteur(s): AGGOUNE, Aicha

2026-03-17T00:00:00Z KOUARTA, AYA https://dspace.univ-guelma.dz/jspui/handle/123456789/18984 2026-04-08T21:22:58Z 2025-01-01T00:00:00Z

Titre: " Évaluation théorique des effets inhibiteurs de corrosion des composés organiques " Auteur(s): KOUARTA, AYA Résumé: Including The capacity of a series of derivatives of the thiadiazole molecule 2-amino-1,3,4-thiadiazole (ATD), 5-amino-1,3,4-thiadiazole-2-thiol (ATDT), 2-amino-5-ethyl-1,3,4 thiadiazole (AETD) and 2-amino-5-tert-butyl-1,3,4-thiadiazole (ATBTD), to inhibit the corrosion of an iron substrate in 1 M HCl was investigated. An extensive theoretical study was carried out to examine adsorption modes and electronic structures, and to identify and quantify the nature of interactions at the inhibitor/substrate interface, using density functional theory (DFT/B3LYP) calculations based on Grimme's method for DFT-D correction, in combination with a dual digital plus polarisation (DNP) basis set, and Monte Carlo simulations based on the simulated annealing algorithm via automated temperature control using the DMol3 and Adsorption Locator modules implemented in Material studio 17 software. 0. The effect of the solvent was represented by the implicit solvation model COSMO. The inhibitors studied show spontaneous and favorable adsorption, but the expected order of effectiveness is: ATDT > ATBTD > AETD > ATD. ATDT was the most effective of the inhibitors studied.

2025-01-01T00:00:00Z