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Search Results: 1 - 10 of 461793 matches for " A. Lakhoua "
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Fractional Quantum Hall States in Fast Rotating Bose Gases
A. Lakhoua,T. Masson,J. C. Wallet
Physics , 2006,
Abstract: We use a Chern Simons Landau-Ginzburg (CSLG) framework related to hierarchies of composite bosons to describe 2D harmonically trapped fast rotating Bose gases in Fractional Quantum Hall Effect (FQHE) states. The predicted values for $\nu$ (ratio of particle to vortex numbers) are $\nu$$=$${{p}\over{q}}$ ($p$, $q$ are any integers) with even product $pq$, including numerically favored values previously found and predicting a richer set of values. We show that those values can be understood from a bosonic analog of the law of the corresponding states relevant to the electronic FQHE. A tentative global phase diagram for the bosonic system for $\nu$$<$1 is also proposed.
Anyonic Excitations in Fast Rotating Bose Gases Revisited
A. Lakhoua,M. Lassaut,T. Masson,J. C. Wallet
Physics , 2005, DOI: 10.1103/PhysRevA.73.023614
Abstract: The role of anyonic excitations in fast rotating harmonically trapped Bose gases in a fractional Quantum Hall state is examined. Standard Chern-Simons anyons as well as "non standard" anyons obtained from a statistical interaction having Maxwell-Chern-Simons dynamics and suitable non minimal coupling to matter are considered. Their respective ability to stabilize attractive Bose gases under fast rotation in the thermodynamical limit is studied. Stability can be obtained for standard anyons while for non standard anyons, stability requires that the range of the corresponding statistical interaction does not exceed the typical wavelenght of the atoms.
Application of Functional Analysis on a SCADA System of a Thermal Power Plant
LAKHOUA, M. N.
Advances in Electrical and Computer Engineering , 2009, DOI: 10.4316/aece.2009.02014
Abstract: The aim of this paper is to present firstly the functionality of a supervisory system for complex processes, and secondly to present the concepts of SCADA (supervisory control and data acquisition) systems. A functional analysis technique SADT (Structured Analysis and Design Technique) has been applied on an example of a SCADA system of a thermal power plant. This technique allows a functional description of a SCADA system. The paper briefly discusses the functions of a SCADA system and some advantages of the application of functional analysis for the design of a human centered supervisory system. Then the basic principles of the SADT technique applied on the SCADA system are presented. Finally, the different results obtained from the SADT technique are discussed.
Using fuzzy logic for automatic control: Case study of a problem of cereals samples classification
Lakhoua Najeh Mohamed
Serbian Journal of Electrical Engineering , 2009, DOI: 10.2298/sjee0902203l
Abstract: The aim of this paper is to present the use of fuzzy logic for automatic control of industrial systems particularly the way to approach a problem of classification. We present a case study of a grading system of cereals that allows us to determine the price of transactions of cereals in Tunisia. Our contribution in this work consists in proposing not only an application of the fuzzy logic on the grading system of cereals but also a methodology enabling the proposing of a new grading system based on the concept of 'Grade' while using the fuzzy logic techniques. .
Cyclosporine A and steroid therapy in childhood steroid-resistant nephrotic syndrome
Gargah Tahar, Lakhoua M Rachid
International Journal of Nephrology and Renovascular Disease , 2010, DOI: http://dx.doi.org/10.2147/IJNRD.S10168
Abstract: losporine A and steroid therapy in childhood steroid-resistant nephrotic syndrome Original Research (4326) Total Article Views Authors: Gargah Tahar, Lakhoua M Rachid Published Date August 2010 Volume 2010:3 Pages 117 - 121 DOI: http://dx.doi.org/10.2147/IJNRD.S10168 Gargah Tahar, Lakhoua M Rachid Department of Pediatric Nephrology, Charles Nicolle Hospital, Tunis, Tunisia Background: In children, idiopathic nephrotic syndrome (INS) is primarily treated using corticosteroids. When remission is not achieved, the coadministration of potent immunosuppressant therapy becomes imperative. Cyclosporine A (CsA) is reportedly associated with a higher incidence of remission in comparison with other immunosuppressive agents. Methods: The present study investigated the response of combination therapy using CsA and prednisolone in 30 Tunisian children with idiopathic steroid-resistant nephrotic syndrome (ISRNS). Renal histopathology was compatible with focal segmental glomerular sclerosis (FSGS) in 15 children, minimal change disease (MCD) in nine children, and diffuses mesangiale proliferation (DMP) in six children. Results: The therapy protocol produced a complete remission of proteinuria in 15 patients (50%) and a partial remission in nine patients (30%). Six patients (20%) showed no response to therapy. Progression to end stage renal disease occurred in five CsA-resistant children and in four CsA-responsive patients. CsA-related nephrotoxicity was detected by renal biopsy in one patient. Conclusions: CsA remains the primary cytotoxic treatment for childhood steroid-resistant nephrotic syndrome. Its use in combination with corticosteroids provides optimum efficiency without high risk of nephrotoxicity.
Cyclosporine A and steroid therapy in childhood steroid-resistant nephrotic syndrome
Gargah Tahar,Lakhoua M Rachid
International Journal of Nephrology and Renovascular Disease , 2010,
Abstract: Gargah Tahar, Lakhoua M RachidDepartment of Pediatric Nephrology, Charles Nicolle Hospital, Tunis, TunisiaBackground: In children, idiopathic nephrotic syndrome (INS) is primarily treated using corticosteroids. When remission is not achieved, the coadministration of potent immunosuppressant therapy becomes imperative. Cyclosporine A (CsA) is reportedly associated with a higher incidence of remission in comparison with other immunosuppressive agents.Methods: The present study investigated the response of combination therapy using CsA and prednisolone in 30 Tunisian children with idiopathic steroid-resistant nephrotic syndrome (ISRNS). Renal histopathology was compatible with focal segmental glomerular sclerosis (FSGS) in 15 children, minimal change disease (MCD) in nine children, and diffuses mesangiale proliferation (DMP) in six children.Results: The therapy protocol produced a complete remission of proteinuria in 15 patients (50%) and a partial remission in nine patients (30%). Six patients (20%) showed no response to therapy. Progression to end stage renal disease occurred in five CsA-resistant children and in four CsA-responsive patients. CsA-related nephrotoxicity was detected by renal biopsy in one patient.Conclusions: CsA remains the primary cytotoxic treatment for childhood steroid-resistant nephrotic syndrome. Its use in combination with corticosteroids provides optimum efficiency without high risk of nephrotoxicity.Keywords: children, corticosteroids, cyclosporine A, nephrotic syndrome
Project Management Phases of a SCADA System for Automation of Electrical Distribution Networks
Mohamed Najeh Lakhoua,Mohamed Kamel Jbira
International Journal of Computer Science Issues , 2012,
Abstract: The aim of this paper is, firstly, to recall the basic concepts of SCADA (Supervisory Control And Data Acquisition) systems, to present the project management phases of SCADA for real time implementation, and then to show the need of the automation for Electricity Distribution Companies (EDC) on their distribution networks and the importance of using computer based system towards sustainable development of their services. A proposed computer based power distribution automation system is then discussed. Finally, some projects of SCADA system implementation in electrical companies over the world are briefly presented.
The max-plus finite element method for solving deterministic optimal control problems: basic properties and convergence analysis
Marianne Akian,Stephane Gaubert,Asma Lakhoua
Mathematics , 2006, DOI: 10.1137/060655286
Abstract: We introduce a max-plus analogue of the Petrov-Galerkin finite element method to solve finite horizon deterministic optimal control problems. The method relies on a max-plus variational formulation. We show that the error in the sup norm can be bounded from the difference between the value function and its projections on max-plus and min-plus semimodules, when the max-plus analogue of the stiffness matrix is exactly known. In general, the stiffness matrix must be approximated: this requires approximating the operation of the Lax-Oleinik semigroup on finite elements. We consider two approximations relying on the Hamiltonian. We derive a convergence result, in arbitrary dimension, showing that for a class of problems, the error estimate is of order $\delta+\Delta x(\delta)^{-1}$ or $\sqrt{\delta}+\Delta x(\delta)^{-1}$, depending on the choice of the approximation, where $\delta$ and $\Delta x$ are respectively the time and space discretization steps. We compare our method with another max-plus based discretization method previously introduced by Fleming and McEneaney. We give numerical examples in dimension 1 and 2.
The max-plus finite element method for optimal control problems: further approximation results
Marianne Akian,Stephane Gaubert,Asma Lakhoua
Mathematics , 2005,
Abstract: We develop the max-plus finite element method to solve finite horizon deterministic optimal control problems. This method, that we introduced in a previous work, relies on a max-plus variational formulation, and exploits the properties of projectors on max-plus semimodules. We prove here a convergence result, in arbitrary dimension, showing that for a subclass of problems, the error estimate is of order $\delta+\Delta x(\delta)^{-1}$, where $\delta$ and $\Delta x$ are the time and space steps respectively. We also show how the max-plus analogues of the mass and stiffness matrices can be computed by convex optimization, even when the global problem is non convex. We illustrate the method by numerical examples in dimension 2.
A max-plus finite element method for solving finite horizon deterministic optimal control problems
Marianne Akian,Stephane Gaubert,Asma Lakhoua
Mathematics , 2004,
Abstract: We introduce a max-plus analogue of the Petrov-Galerkin finite element method, to solve finite horizon deterministic optimal control problems. The method relies on a max-plus variational formulation, and exploits the properties of projectors on max-plus semimodules. We obtain a nonlinear discretized semigroup, corresponding to a zero-sum two players game. We give an error estimate of order $(\Delta t)^{1/2}+\Delta x(\Delta t)^{-1}$, for a subclass of problems in dimension 1. We compare our method with a max-plus based discretization method previously introduced by Fleming and McEneaney.
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