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Haddadi S.,8 May 1945 University of Guelma
Journal of Combinatorial Optimization | Year: 2015

This paper describes Benders decomposition approaches to optimally solve set covering problems “ almost” satisfying the consecutive ones property. The decompositions are based on the fact that set covering problems with consecutive ones property have totally unimodular coefficient matrices. Given a binary matrix, a totally unimodular matrix is enforced by filling up every row with ones between its first and its last non-zero entries. The resulting mistake is handled by introducing additional integer variables whose number depends on the reordering of the columns of the given matrix. This leads us to consider the consecutive block minimization problem. Two cutting plane algorithms are proposed and run on a large set of benchmark instances. The results obtained show that the cutting plane algorithms outperform an existing tree search method designed exclusively for such instances. © 2015 Springer Science+Business Media New York Source

Debbouche A.,8 May 1945 University of Guelma | Debbouche A.,University of Aveiro | Torres D.F.M.,University of Aveiro
International Journal of Control | Year: 2013

We study the existence and approximate controllability of a class of fractional nonlocal delay semilinear differential systems in a Hilbert space. The results are obtained by using semigroup theory, fractional calculus and Schauders fixed point theorem. Multi-delay controls and a fractional nonlocal condition are introduced. Furthermore, we present an appropriate set of sufficient conditions for the considered fractional nonlocal multi-delay control system to be approximately controllable. An example to illustrate the abstract results is given. © 2013 Taylor & Francis. Source

Debbouche A.,8 May 1945 University of Guelma | Baleanu D.,Cankaya University | Baleanu D.,Romanian Space Science Institute
Computers and Mathematics with Applications | Year: 2011

In this work, the controllability result of a class of fractional evolution nonlocal impulsive quasilinear delay integro-differential systems in a Banach space has been established by using the theory of fractional calculus, fixed point technique and also we introduced a new concept called (α,u)- resolvent family. As an application that illustrates the abstract results, an example is given. © 2011 Elsevier Ltd. All rights reserved. Source

Hamel A.,8 May 1945 University of Guelma
Physics of Particles and Nuclei Letters | Year: 2016

The work presented in this paper is concerned a detailed study about the light transmission through textured surfaces in a surface made up of pyramids [1, 2]. We investigate to what extent and under what conditions we want to take advantage of ray incidence five times and more [3, 4]. It is found that these analyses can be used to determine the optimal surface texture which provides the best light trapping for solar cells in terms of the total internal reflection occurring in the high-index medium at incidence angles larger than the nominal critical angle [5–11]. One of the main contributions of this paper is the analysis and quantification of the influence of the opening between the heads of the two closest pyramids in textured surface for solar cells and its application on the photovoltaic parameters such as the quantum efficiency. In this model we show that the material can have five and more successive incident ray absorptions instead of three currently, where we changed the direction of the reflected ray, by varying the angle between the two neighbouring pyramids, the incidence angle, the opening between the heads of the two closest pyramids and their height. Thus, with an angle between the two neighbouring pyramid varying between 20° and 12° and for angle of incidence varying between 80° and 84°. For these values of the angle between the two neighbouring pyramids and incidence angle, the opening between the heads of the two closest pyramids varied respectively from 3.53 to 2.10 µm for a pyramid height of 10 µm. This lead to a substantial increase of the quantum efficiency thus the photovoltaic efficiency. © 2016, Pleiades Publishing, Ltd. Source

Kachi M.,8 May 1945 University of Guelma | Dascalescu L.,University of Poitiers
Journal of Electrostatics | Year: 2014

The dual electrode, which consists of an ionizing wire in parallel with a metallic cylindrical support, both connected at same high voltage supply, has been extensively studied in relation with various electrostatic applications. In practical situations, the dual electrode may be installed in the proximity of metallic objects that will affect the electric field repartition and, hence, the development of the discharge. The aim of the present work is to analyze the operating conditions of such electrodes in the presence of metallic rods or plates connected at fixed or floating potentials. The Superficial Charge Simulation Method was then employed for the numerical analysis of several electrode arrangements involving a dual corona electrode and a metallic rod parallel to it. The paper also reports the results of current-voltage characteristics and current density repartition measurements for the dual corona electrode alone or in the presence of other bodies at same or floating potential. The proximity of metallic objects leads to the increase of corona inception threshold and shifts the I-V characteristics to higher voltages. The objects at floating potential may reduce the discharge current to very low values, while those energized at the same voltage as the ionizing wire may simply anneal the discharge. © 2013 Elsevier B.V. Source

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