Thèses de Doctorat
http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/130
2024-03-29T00:38:03ZContribution to chaotic and fractional data cryptography
http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11358
Contribution to chaotic and fractional data cryptography
Bouridah, Mohamed salah; Bouden, Toufik (encadreur)
With the rapid development of network technology and multimedia, digital information can be transported in different form conveniently. People can exchange information and trade online easily. The internet does not just bring convenience to people's lives but also involves risks. Some sensitive information can be stolen and even distributed illegally. It is linked to political, diplomatic and military life, economic, social and commercial security. Since chaos has good cryptography properties such as randomness, aperiodicity, extremely sensitive to initial conditions and parameters, forcing the robustness of data cryptography. This thesis revolves around two main objectives. The first is to design chaotic and fractional order synchronization systems. The development of new chaos based cryptography and transmission schemes is the second objective of this thesis.
2022-03-17T00:00:00ZContribution to the conception of chaotic systems for secure data transmission
http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11307
Contribution to the conception of chaotic systems for secure data transmission
Benkouider, Khaled; Bouden, Toufik (encadreur)
Since the main characteristics of chaos, such as sensitivity to initial conditions, randomness, unpredictability and complexity can be attached with the well-known confusion and diffusion properties of cryptography, there has been tremendous interest world-wide in the possibility of using chaos in communication systems. Therefore, it is of significant interest to design suitable chaotic systems for secure, cost-effective and robust communications.
The first contribution of this thesis is to design a new chaotic system with high complexity and large bandwidth compared with the existing chaotic systems. The second contribution is to develop a new n-dimensional multistable hyperchaotic system with (n>7) and multiple coexisting attractors. The third contribution is to construct new n-dimensional hyperchaotic systems with (n>7) and (n-2) positive Lyapunov exponents. The last contribution is to construct a new delayed discrete-time hyperchaotic system and propose a new approach for delay estimation and information recovery for delayed discrete-time chaos-based secure communication.
2021-07-15T00:00:00ZContributions to Adaptive Control of Multivariable Nonlinear Systems With and Without Observers
http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11306
Contributions to Adaptive Control of Multivariable Nonlinear Systems With and Without Observers
Merazka, Loubna; Boulkroune, Abdesselem (encadreur)
The work of this thesis deals with two types of problems in adaptive fuzzy control for nonlinear multivariable systems: state-feedback control and output-feedback control. In all proposed adaptive control schemes, fuzzy logic systems are used to appropriately approximate uncertain nonlinear functions. A Lyapunov-based analysis is carried out to conclude about the stability of the closed-loop system as well as the convergence of the underlying (tracking and observation) errors. Numerical simulations are presented to demonstrate the effectiveness of theoretical results.
2019-12-08T00:00:00ZContribution a la commande des systèmes non lineaires incertains avec contraintes
http://dspace.univ-jijel.dz:8080/xmlui/handle/123456789/11305
Contribution a la commande des systèmes non lineaires incertains avec contraintes
Haddad, Mohammed; Boulkroune, Abdesselem (encadreur)
L’objectif de cette thèse est principalement porté sur deux thèmes majeurs. Dans le premier thème, deux schémas de commande adaptative floue par backstepping, pour une classe de systèmes non linéaires monovariables incertains avec des contraintes sur les états (ou sur la sortie) et l’entrée et avec des perturbations externes, sont développés. Dans l’autre thème, un schéma de commande adaptative floue par backstepping, pour une classe de systèmes non linéaires multivariables incertains avec des non-linéarités de l’actionneur et des matrices des gains de commande étant asymétriques, est conçu. Dans tous les schémas de commande, les systèmes flous sont utilisés pour approximer les fonctions non linéaires inconnues du système. De plus, l’analyse de la stabilité est effectuée par une approche de Lyapunov. Les résultats théoriques sont validés par des exemples de simulation numériques
2021-10-28T00:00:00Z