http://localhost:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2026-03-05T22:56:04Z http://dspace.univ-chlef.dz/handle/123456789/2401 Analyse de l'effet du confinement transversal sur les éléments structuraux avec matériaux composites BERRADIA, MOHAMMED L’utilisation de l’enveloppe externe en polymères renforcés de fibres de carbone est l’une des techniques les plus efficaces existante, pour le confinement des colonnes circulaires en béton armé. L’objectif de ce travail consiste à proposer deux nouveaux modèles contraintedéformation, pour prédire le comportement des colonnes circulaires confinées par des polymères renforcés de fibres de carbone (PRFC) sans aciers transversaux (RAT) et sous l’effet combiné de l’enveloppe PRFC externe et des aciers transversaux interne, sur la base d’une analyse de régression de plus de 340 de données expérimentales. Deux indicateurs statistiques sont utilisés, pour illustrer la performance, à savoir : le coefficient de détermination R² et la racine carrée du carré moyen des résidus RMSE. D’après ces deux indicateurs les deux nouveaux modèles proposés présentent une bonne performance comparés aux modèles existants. De plus, la comparaison des deux modèles proposés avec les résultats expérimentaux a montré une bonne concordance par rapport aux modèles existants. En outre, les expressions d’estimations de la résistance ultime et la déformation correspondante sont simples et concises qui les rendent plus facile à utiliser pour des applications de conception. Enfin, une étude paramétrique des facteurs, à savoir le diamètre de la colonne, l’épaisseur, la résistance en traction du PRFC, la limite élastique et le pourcentage volumique des aciers transversaux influençant le confinement par PRFC a été réalisé. Cette analyse a montré la variation de l’effet propice du confinement par PRFC que par l’effet combiné PRFC-RAT. THÈSE Présentée pour l’obtention du diplôme de DOCTORAT EN SCIENCES Spécialité : Génie Civil 2017-10-05T00:00:00Z http://dspace.univ-chlef.dz/handle/123456789/2400 Applications of bifurcation theory in biomathematics DJILALI, Salih Bifurcation theory is a powerful mathematical tool used to study the qualitative changes in the dynamics of a system as a parameter is varied. In the context of biomathematics, bifurcation analysis provides critical insights into the behavior of biological and ecological models, such as predator-prey interactions, epidemiological spread, and pattern formation in biological tissues. The techniques of bifurcation theory allow us to understand how small changes in parameters can lead to significant changes in the system’s dynamics—such as the transition from steady states to oscillatory behavior (Hopf bifurcation), the sudden appearance or disappearance of equilibria (saddle-node bifurcation), or the onset of spatial patterns (Turing instability). This course is designed for first-year Master’s students in Biomathematics and is structured to cover a broad spectrum of topics in bifurcation theory applied to systems of ordinary and partial differential equations, as well as delay differential equations. The applications include ecological and epidemiological models, where spatial diffusion and time delays are critical in reproducing realistic dynamics observed in nature. The course is organized as follows: – 1. Applications of Bifurcation Theory on Systems of Equations: This section introduces the fundamental notions of bifurcation theory, starting with onedimensional ordinary differential equations. We study classic bifurcations such as saddle-node, pitchfork, and transcritical bifurcations, and extend these concepts to two-dimensional systems. Later, we discuss bifurcations in delay differential equations. – 2. Bifurcation Analysis for Ecological Models: In this section, the focus shifts to ecological models such as predator-prey systems. We examine both delay differential equations (DDEs) and ordinary differential equations (ODEs) in the context of population dynamics. Detailed analysis of the delayed Volterra predatorprey model is presented, including exercises to reinforce the concepts. – 3. Bifurcation Analysis for Epidemiological Models: Here, we apply bifurcation theory to models arising in epidemiology. The course covers topics such as Hopf bifurcation in delayed epidemiological SIS models, and includes several exercises to enhance understanding. – 4. Bifurcation Theory for Partial Differential Equations (PDEs): This section extends the bifurcation analysis to spatially extended systems governed by partial differential equations. We cover the existence and uniqueness of solutions for parabolic problems, the spectral analysis of the Laplacian operator, and methods of separation of variables. Finally, the course discusses Hopf and Turing bifurcations in spatial models. Exercises: Each section is supplemented with exercises that challenge the students to apply the theory to various models, thereby deepening their understanding of both the mathematical techniques and their biological applications. Throughout the course, our aim is to not only present the theoretical framework but also to provide practical examples and computational techniques that reveal how bifurcation theory can be used to predict and analyze complex spatiotemporal dynamics in biological systems. The interplay between delay, diffusion, and nonlinear interactions is central to these analyses, and this course equips students with the necessary tools to explore these phenomena in dept Intended for students of First Year Master in Biomathematics (M1) 2025-01-01T00:00:00Z http://dspace.univ-chlef.dz/handle/123456789/2399 Methods for Mathematical Modeling I DJILALI, Salih Mathematical modeling has become an essential component of research and studies in ecology. This book is intended for undergraduate and master’s level students who wish to acquire mathematical modeling techniques in ecology and epidemiology. It introduces fundamental concepts of mathematical modeling, focusing on deterministic dynamic systems, particularly ordinary differential equations. The book also presents a series of classical models in population dynamics and ecology. It aims to provide a rigorous yet accessible introduction to these methods, making them understandable not only for mathematicians but also for students from various scientific backgrounds, including life sciences, who may not have prior training in dynamic systems. Numerous examples and exercises illustrate the techniques presented, allowing students to practice and apply them to real ecological problems. We hope that students with a mathematical background will find clear explanations of qualitative analysis methods for dynamic systems—methods they may already be familiar with—along with numerous applications in ecology. Likewise, we hope that students with a biological background will find a comprehensive and accessible introduction to the main techniques used to study dynamic systems, as well as their implementation in classical ecological models such as the Lotka-Volterra model, Holling’s model, and many others. This book is a synthesis of the authors’ teaching experience in mathematical modeling applied to ecology. While primarily intended for students, doctoral candidates, postdoctoral researchers, and academics looking to acquire or deepen their knowledge in this field will also find it useful. Many researchers in both public and private institutions study complex natural and social systems, and mathematical modeling has become an indispensable tool in modern research to understand the mechanisms governing these systems’ dynamics. Although several books cover similar topics, most of them are written in English. This book aims to make mathematical modeling methods in ecology more accessible to a wider audience. It brings together a broad range of classical mathematical models in ecology, some of which are traditionally scattered across different sources, while also introducing some original models. Students will find a comprehensive collection of commonly used models in ecology, while researchers will have a fundamental reference for constructing and analyzing mathematical models relevant to their work. The book is organized into chapters that are either methodological or applied. The methodological chapters introduce techniques for analyzing mathematical models which includes the continuous-time models. The applied chapters use these techniques to study population and community dynamics. We provide an overview of population growth models and interaction models between two species (e.g., predator-prey, host-parasitoid, competition, mutualism). We also discuss models of multi-species interactions within trophic networks and structured population models incorporating age classes. Intended for students of First Year Master in Biomathematics (M1) - Hassiba Benbouali University of Chlef (UHBC) Faculty of Exact Sciences And Informatics Department of Mathematics 2025-01-01T00:00:00Z http://dspace.univ-chlef.dz/handle/123456789/2398 Commande robuste d'une GADA intégrée dans un système éolien (mode local, mode connecté au réseau stable et déséquilibré) L’HADJ, SAID MOHAMMED Voici le texte extrait de l’image : --- Dans le cadre de la transition énergétique et de la promotion des énergies renouvelables, cette thèse s’intéresse à la modélisation, à la commande et à l’optimisation d’un système de conversion d’énergie éolienne basé sur une génératrice asynchrone à double alimentation (GADA). Après une étude approfondie des différentes architectures d’éoliennes et des types de génératrices existantes, la GADA a été retenue pour ses avantages en termes de fonctionnement en vitesse variable, de rendement énergétique et de réduction de la taille du convertisseur. La première partie du travail a porté sur la modélisation électromécanique complète de la chaîne de conversion et sur l’implémentation d’une commande vectorielle des puissances active et réactive. Ensuite, deux approches avancées de commande non linéaire, basées sur la théorie des modes glissants d’ordre 1 et d’ordre 2, ont été développées pour améliorer la robustesse du système face aux perturbations et réduire l’effet de chattering. Une architecture hybride autonome, composée d’une GADA et d’une machine synchrone à aimants permanents (MSAP), a été étudiée pour l’alimentation de charges isolées. Des simulations numériques ont été réalisées sous MATLAB/Simulink pour évaluer le comportement du système en présence de charges linéaires et non linéaires. L’introduction d’un filtre LC a permis de corriger les distorsions harmoniques et d’assurer une tension stable. Ce travail démontre la pertinence des stratégies de commande avancées pour améliorer les performances, la fiabilité et la qualité de l’énergie dans les systèmes éoliens modernes. Des perspectives de recherche sont proposées, incluant l’intégration de stratégies sans capteurs, la prise en compte des phénomènes non linéaires de la machine, et l’ajout de dispositifs de stockage d’énergie. --- Si tu veux, je peux aussi te faire un **résumé ultra structuré (type examen ou soutenance)** ou une version **en anglais académique**. 2025-01-01T00:00:00Z