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The triadjoint of an orthosymmetric bimorphism

Mohamed Ali Toumi — 2010

Czechoslovak Mathematical Journal

Let A and B be two Archimedean vector lattices and let ( A ' ) n ' and ( B ' ) n ' be their order continuous order biduals. If Ψ : A × A B is a positive orthosymmetric bimorphism, then the triadjoint Ψ * * * : ( A ' ) n ' × ( A ' ) n ' ( B ' ) n ' of Ψ is inevitably orthosymmetric. This leads to a new and short proof of the commutativity of almost f -algebras.

On the state observation and stability for uncertain nonlinear systems

Mohamed Ali Hammami — 2000

Kybernetika

In this paper, we treat the class of nonlinear uncertain dynamic systems that was considered in [3,2,1,4]. We consider continuous-time dynamical systems whose nominal part is linear and whose uncertain part is norm-bounded. We study the problems of state observation and obtaining stabilizing controller for uncertain nonlinear systems, where the uncertainties are characterized by known bounds.

On extensions of orthosymmetric lattice bimorphisms

Mohamed Ali Toumi — 2013

Mathematica Bohemica

In the paper we prove that every orthosymmetric lattice bilinear map on the cartesian product of a vector lattice with itself can be extended to an orthosymmetric lattice bilinear map on the cartesian product of the Dedekind completion with itself. The main tool used in our proof is the technique associated with extension to a vector subspace generated by adjoining one element. As an application, we prove that if ( A , * ) is a commutative d -algebra and A 𝔡 its Dedekind completion, then, A 𝔡 can be equipped...

Growth conditions for the stability of a class of time-varying perturbed singular systems

Faten EzzineMohamed Ali Hammami — 2022

Kybernetika

In this paper, we investigate the problem of stability of linear time-varying singular systems, which are transferable into a standard canonical form. Sufficient conditions on exponential stability and practical exponential stability of solutions of linear perturbed singular systems are obtained based on generalized Gronwall inequalities and Lyapunov techniques. Moreover, we study the problem of stability and stabilization for some classes of singular systems. Finally, we present a numerical example...

The existence of limit cycle for perturbed bilinear systems

Hanen DamakMohamed Ali HammamiYeong-Jeu Sun — 2012

Kybernetika

In this paper, the feedback control for a class of bilinear control systems with a small parameter is proposed to guarantee the existence of limit cycle. We use the perturbation method of seeking in approximate solution as a finite Taylor expansion of the exact solution. This perturbation method is to exploit the “smallness” of the perturbation parameter ε to construct an approximate periodic solution. Furthermore, some simulation results are given to illustrate the existence of a limit cycle for...

New criterion for asymptotic stability of time-varying dynamical systems

In this paper, we establish some new sufficient conditions for uniform global asymptotic stability for certain classes of nonlinear systems. Lyapunov approach is applied to study exponential stability and stabilization of time-varying systems. Sufficient conditions are obtained based on new nonlinear differential inequalities. Moreover, some examples are treated and an application to control systems is given.

Converse theorem for practical stability of nonlinear impulsive systems and applications

Boulbaba GhanmiMohsen DlalaMohamed Ali Hammami — 2018

Kybernetika

The Lyapunov's second method is one of the most famous techniques for studying the stability properties of dynamic systems. This technique uses an auxiliary function, called Lyapunov function, which checks the stability properties of a specific system without the need to generate system solutions. An important question is about the reversibility or converse of Lyapunov's second method; i. e., given a specific stability property does there exist an appropriate Lyapunov function? The main result of...

Practical h -stability behavior of time-varying nonlinear systems

Abir KichaHanen DamakMohamed Ali Hammami — 2023

Commentationes Mathematicae Universitatis Carolinae

We deal with the problem of practical uniform h -stability for nonlinear time-varying perturbed differential equations. The main aim is to give sufficient conditions on the linear and perturbed terms to guarantee the global existence and the practical uniform h -stability of the solutions based on Gronwall’s type integral inequalities. Several numerical examples and an application to control systems with simulations are presented to illustrate the applicability of the obtained results.

Evaluating flexible solutions in single machine scheduling via objective function maximization: the study of computational complexity

Mohamed Ali AloulouMikhail Y. KovalyovMarie-Claude Portmann — 2007

RAIRO - Operations Research

We study a deterministic problem of evaluating the worst case performance of flexible solutions in the single machine scheduling. A flexible solution is a set of schedules following a given structure determined by a partial order of jobs and a type of the schedules. In this paper, the schedules of active and non-delay type are considered. A flexible solution can be used on-line to absorb the impact of data disturbances related to, for example, job arrival, tool availability or machine breakdowns....

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