Yahi H.,8 May 1945 University of Guelma |
Meddour A.,8 May 1945 University of Guelma
Journal of Magnetism and Magnetic Materials | Year: 2017
In this study, we investigated the structural, electronic and magnetic properties of Cd0.9375TM0.0625S (TM=Ni, Co and Fe) compounds in zinc blende (B3) ferromagnetic phase using all-electron full-potential linear muffin tin orbital (FP-LMTO) calculations within the frame work of the density functional theory and the generalized gradient approximation. The analysis of electronic structures shows that Cd0.9375Ni0.0625S, Cd0.9375Co0.0625S and Cd0.9375Fe0.0625S compounds are half-metallic ferromagnets with 100% spin polarization at the Fermi level. This half-metallic behavior is confirmed by the total calculated magnetic moment per Ni, Co and Fe substituted transition metal (TM) atom, which is found to be 2 µB, 3 µB and 4 µB for Cd0.9375TM0.0625S (TM=Ni, Co and Fe) compounds, respectively. Furthermore, we found that the TM-3d states are responsible for generating spin-polarization and magnetic moment in these compounds and we establish that the p-d hybridization reduces the local magnetic moment of TM atoms from its free space charge value and produces small local magnetic moments on nonmagnetic Cd and S host sites. Also, we predicted exchange splitting energy Δx(pd) and exchange constants N0α and N0β. The calculated values validate the ferromagnetic nature of these compounds. © 2017 Elsevier B.V.
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.
Abdelhalim C.,8 May 1945 University of Guelma |
Farid D.,Ferhat Abbas University Setif
International Journal of Antennas and Propagation | Year: 2014
A modified compact planar ultrawideband (UWB) monopole antenna with triple controllable band-notched characteristics is presented in this paper. The proposed antenna consists of a modified stair cased V-shaped radiating element and partial ground plane. The triple band-notched characteristics are achieved by embedding two different vertical up C-shaped slots with a vertical down C-shaped slot in the radiating patch and in the ground plane, respectively. Besides, the bandwidth of each rejected band can be independently controlled by adjusting the dimensions of the corresponding band notched structure. The proposed antenna with rejected bands characteristics is successfully simulated, prototyped, and measured. The measured results show that the antenna operates until upper 11 GHz for voltage standing wave ratio (VSWR) is less than 2, and exhibits bands rejection of 1.6-2.66 GHz (49.76%), 3-4 GHz (28.57%), and 5.13-6.03 GHz (16.12%). Moreover, the proposed antenna shows a near omnidirectional radiation patterns, stable peak gain, and with small group delay and transfer function variation on the whole UWB frequency range except in the notched frequency bands, which makes it suitable for being used in the future UWB applications. © 2014 Chaabane Abdelhalim and Djahli Farid.
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
Himeur M.,8 May 1945 University of Guelma |
Guenfoud M.,8 May 1945 University of Guelma
European Journal of Computational Mechanics | Year: 2011
We present a new plate bending triangular finite element. It is developed in perspective to building shell elements. Its formulation uses concepts related to the deformation approach, the fourth fictitious node, the static condensation and analytic integration. It is based on the assumptions of the theory of thin plates (Kirchhoff theory). The approach has resulted in a bending plate finite element (HIMEUR) competitive, robust and efficient. © 2011 Lavoisier, Paris.
Nacef M.,8 May 1945 University of Guelma |
Affoune A.M.,8 May 1945 University of Guelma
International Journal of Hydrogen Energy | Year: 2011
In this paper, direct alcohol fuel cells' thermodynamics parameters were calculated by means of analytical formulas using thermodynamic data. The effect of temperature on reversible efficiency, electromotive force and specific energy for fuel cells supplied with alcohols having from one to five carbons was studied in the range between 298.15 and 1300 K. All parameters were also compared with those of hydrogen fuel cell. It was found that reversible efficiency, electromotive force and specific energy are a function of the amount of carbon atoms in the fuel and a function of temperature. In addition, alcohol's structure influences fuel cells' parameters too. We have found that there is a competition between hydrogen, ethanol and methanol at standard conditions, while methanol, ethanol, propanol isomers, 2-methylpropan-1-ol and butan-2-ol, as classified, appear more indicated than hydrogen at more elevated temperature. Therefore, the approach presented here can be considered as sufficient enough for a primary choice of an alcohol that could be used in fuel cells in the future. © 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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.
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.
Seridi L.,8 May 1945 University of Guelma |
Boufelfel A.,8 May 1945 University of Guelma
Journal of Molecular Liquids | Year: 2011
We investigated the inclusion process of Lamotrigine (LMN) in beta cyclodextrin (β-CD) with 1:1 stoichiometry using empirical, semi-empirical and quantum mechanical calculations models. We have found that the quantum and hybrid ONIOM2 methods gave the most favorable orientation in which the guest molecule is totally sequestered in the hydrophobic cavity of the cyclodextrin with the tiazine ring located near the primary hydroxyls of the β-CD and the dichloro phenyl moiety near the secondary hydroxyls with no hydrogen bonding formation. Moreover, the statistical thermodynamic calculations at 1 atm and 298.15 K demonstrate that 1:1 LMN/β-CD complexation is an exothermic process, enthalpically favorable in nature and that non bonded Van der Waals interactions represent the mainly driving forces leading to complex stability. While, HOMO and LUMO orbital investigations confirm on one hand the better stability of 'A' orientation and on the other hand prove that no significant change will be observed in the electronic structure of LMN after complexation. © 2010 Elsevier B.V.
Bourouis C.,8 May 1945 University of Guelma |
Meddour A.,8 May 1945 University of Guelma
Journal of Magnetism and Magnetic Materials | Year: 2012
In this paper, we report theoretical investigations of structural, electronic and magnetic properties of ordered dilute ferromagnetic semiconductors Cd 1-xFe xS with x=0.25, 0.5 and 0.75 in zinc blende (B3) phase using all-electron full-potential linear muffin tin orbital (FP-LMTO) calculations within the density functional theory and the generalized gradient approximation. The analysis of band structures, density of states, total energy, exchange interactions and magnetic moments reveals that both the alloys may exhibit a half-metallic ferromagnetism character. The value of calculated magnetic moment per Fe impurity atom is found to be 4 μ B. Moreover, we found that pd hybridization reduces the local magnetic moment of Fe from its free space charge value of 4 μ B and produces small local magnetic moments on Cd and S sites. © 2011 Elsevier B.V. All rights reserved.