Bouakba M.,University of Ouargla |
Bouakba M.,University 08 Mai 1945 |
Bezazi A.,University 08 Mai 1945 |
Scarpa F.,University of Bristol
International Journal of Solids and Structures | Year: 2012
This work presents a novel formulation for a Voronoi-type cellular material with in-plane anisotropic behaviour, showing global positive and negative Poisson's ratio effects under uniaxial tensile loading. The effects of the cell geometry and relative density over the global stiffness, equivalent in-plane Poisson's ratios and shear modulus of the Voronoi-type structure are evaluated with a parametric analysis. Empirical formulas are identified to reproduce the mechanical trends of the equivalent homogeneous orthotropic material representing the Voronoi-type structure and its geometry parameters. © 2012 Elsevier Ltd. All rights reserved.
Meraoumia A.,University of Ouargla |
Chitroub S.,Signal Sciences |
Bouridane A.,Northumbria University
Integrated Computer-Aided Engineering | Year: 2013
Biometric systems based on a single source of information suffer from limitations such as the lack of uniqueness, non-universality of the chosen biometric trait, noisy data and spoof attacks. Multimodal biometrics are relatively new systems that overcome those problems. These systems fuse information from multiple sources in order to achieve the better person recognition performance. In this paper, the 2D and 3D information of palmprint are integrated in order to construct an efficient multimodal biometric system based on fusion at matching score level and at feature extraction level. The observation vectors are created independently either from the original data of the two modalities (2D and 3D palmprint) or from their rotation invariant variance measures applied on textures. On each modality (or its corresponding invariant texture), we have applied the Principal Component Analysis (PCA) for reducing dimension of the feature vector. We have also used the multi-scale wavelet decomposition for each modality and the results of decomposition are combined and compressed using PCA for selecting the feature vectors. Subsequently, we have used the Hidden Markov Model (HMM) for modeling the feature vectors. Finally, Log-likelihood scores are used for palmprint evaluation. We note that the selected principal components of two modalities are fused at feature level and at matching score level. The proposed scheme is tested and evaluated using PolyU 2D and 3D palmprint database of 250 persons. Our experimental results show the effectiveness and reliability of the proposed system, which brings high identification accuracy rate. © 2013 - IOS Press and the author(s). All rights reserved.
Benmir A.,University of Ouargla |
Aida M.S.,University of Mentouri Constantine
Energy Procedia | Year: 2013
This paper deals with the development of an analytical model for simulating a polycrystalline Cu(In,Ga)Se2(CIGS)-based thin film solar cells by a CdS(n)/CIGS(p) heterojunction structure. Consequently, a link between the characteristics of this cell and the material parameters is established. This procedure would help improving the performances of the cell. We have been investigating over this work the contribution of the space charge region in the photocurrent density which seemed to be dominant in comparison to the neutral regions. However, the increases of the buffer layer thickness only reduce the cell performances. The optimum thickness of the absorber layer was about 3 μm, a value from which the efficiency has no significant increase. The increase of the absorber bandgap reduces the optical absorption, which is reflected in the reduction of the photocurrent density. Accordingly the open circuit voltage increases as a result to the linear variation with the band gap. The compromise between these two phenomena would be a band gap of 1.55 eV which is the optimum value for obtaining a high efficiency of about 25%. All these optimization results give helpful indication for a feasible fabrication process. © 2010 Published by Elsevier Ltd.
Touchan R.,University of Arizona |
Anchukaitis K.J.,Lamont Doherty Earth Observatory |
Meko D.M.,University of Arizona |
Attalah S.,University of Ouargla |
Aloui A.,Institute of Sylvo pastoral of Tabarka
Climate Dynamics | Year: 2011
Changes in precipitation patterns and the frequency and duration of drought are likely to be the feature of anthropogenic climate change that will have the most direct and most immediate consequences for human populations. The latest generation of state-of-the-art climate models project future widespread drying in the subtropics. Here, we reconstruct spatially-complete gridded Palmer drought severity index values back to A. D. 1179 over Morocco, Algeria, and Tunisia. The reconstructions provide long-term context for northwest African hydroclimatology, revealing large-scale regional droughts prior to the sixteenth century, as well as more heterogeneous patterns in sixteenth, eighteenth, and twentieth century. Over the most recent decades a shift toward dry conditions over the region is observed, which is consistent with general circulation model projections of greenhouse gas forced enhanced regional subtropical drought. © 2010 Springer-Verlag.
Merzougui A.,University Mohamed Khider of Biskra |
Hasseine A.,University Mohamed Khider of Biskra |
Kabouche A.,University of Oum El Bouaghi |
Korichi M.,University of Ouargla
Fluid Phase Equilibria | Year: 2011
Experimental liquid-liquid equilibrium (LLE) data for the extraction of methanol, ethanol and 1-propanol from water by diethyl ether and dichloromethane at 293.15. K and at ambient pressure were investigated. Data for the binodal curves have been determined by cloud-point titration method and conjugate points on tie-line were obtained by correlating the refractive index of the binodal curves as a function of composition. The experimental ternary (liquid. +. liquid) equilibrium data have been estimated using the NRTL and UNIQUAC activity coefficient models to obtain the binary interaction parameters of these components by a combination of Levenberg-Marquardt method and the genetic algorithm based method. The distribution coefficients and the selectivity factor of the solvent used were calculated and presented. From our experimental and calculated results, we conclude that for the extraction of alcohol from aqueous solutions with dichloromethane solvent has a higher selectivity factor than the diethyl ether solvent. © 2011 Elsevier B.V.