Electronique
The Bayesian formulation for radiographic image segmentation of welding defect using Mumford and Shah model
In this paper, we propose to use the method ofpiecewise constant level set with the Mumford-Shah model. For imagesegmentation, the Mumford-Shah model needs to find regions andconstant values of the regions, for it we use a variational approachbased on the extraction regional information (mean and variance) forthe process segmentation in an adaptive manner, . Finally, we validate the proposed models by numerical results for radiographic image segmentation Voir les détails
Mots clés : Level set, Mumford shah model, image segmentation
Comparative study of optical properties of In0.25Ga0.75As and In0.75Ga0.25As in zinc-blende phase by first-principles calculations
The full-potential linearized augmented plane wave method (FP-LAPW) within Density Functional Theory (DFT) framework as implemented in the WIEN2K computational code is used in order to study the structural, electronic and optical properties of In0.25Ga0.75As and In0.75Ga0.25As ternaries alloys. The structural parameters such as lattice parameters, bulk modulus, and its pressure derivative were extracted using the Local Density Approximation (LDA)3, and the one of Wu and Cohen (GGA-WC) for the exchange-correlation (XC) functional. In addition, the electronic and the optical properties of our compounds were obtained by using the new semi-local modified Becke–Johnson potential (TB-mBJ) developed by Tran and Blaha. The performed results were compared with experimental data and other computational works. Consequently, our computations of the equilibrium lattice parameter and bulk modulus generally give a good agreement with the experimental measurements. For electronic and optical properties, we deduced that the TB-mBJ approach is relatively more suitable for the properties of our both ternaries alloys. Voir les détails
Mots clés : DFT, FP-LAPW, InGaAs, Optical parameters
Faults Diagnosis of Rolling Bearing Based on Empirical Mode Decomposition: Optimized Threshold De-noising Method
The faults of rolling bearings frequently occur in rotary machinery, therefore the rolling bearings fault diagnosis is a very important research project. The vibration signal is usually noisy and the information about the fault in the early stage of its development can be lost. A threshold de-noising method based on Empirical Mode Decomposition (EMD) is presented in this paper. Firstly, the signal is decomposed into a number of IMFs using the EMD decomposition .Secondly the algorithm based on the energy to determine the trip point is designed for IMF selection, then, by comparing the energy of the selected IMFs with excluded IMFs, singular selected IMFs are dealt with soft threshold function, and finally the de-noised signal is obtained by summing up the selected IMFs, it is proved that the best IMFs can be summed up and properly de-noised by the proposed method .The results show the effectiveness of the proposed technique in revealing the bearing fault impulses and its periodicity for both simulated and real rolling bearing vibration signals. Voir les détails
Mots clés : bearing fault detection, EMD, threshold De-noising, IMF selection, Singular IMF
Condition Monitoring and Fault Diagnosis of Bearing Using Hybrid Method Based on EEMD and Minimum Entropy Deconvolution
The application of vibration signals is power tool for diagnostic of bearing defect, however this signal is usually noisy and the information about the fault can be lost.This paper presents a novel method based on ensemble empirical mode decomposition EEMD and the minimum entropy deconvolution (MED) . MED technique is used to denoise the vibration signals, and the filtered signal is decomposed into a number of IMFs using the EEMD decomposition. The selection of the relevant modes is dependent on the correlation coefficient between the IMFs and the filtered signal. The experimental results show that the roller bearing fault features can be extracted effectively by this method Voir les détails
Mots clés : Empirical Mode Decomposition, minimum entropy deconvolution, bearing faults, correlation coefficient
Application of Diagonally Relaxed Orthogonal Projections (DROP)- conjugate gradient and Kaczmarz method for X Rays reconstruction image
In this work, we present the application of algorithms based on algebraic methods, ray tomography image reconstruction X. So DROP algorithms with quadratic regularization (orthogonal projections Relaxes diagonal), conjugate gradient and Kaczmarz will be implemented and applied to real images obtained by an X-ray tomography, a comparative study was made in order to examine the reconstruction algorithms results Voir les détails
Mots clés : DROP method, regularization, Tomography, Kaczmarz method
ETUDE ET DÉVELOPPEMENT D’UNE TECHNIQUE DEFILTRAGE BASÉE SUR L’ACPAPPLICATION SUR LES INTERFÉROGRAMMES INSAR
Les interférogrammes dans un processus interférométrique sont souvent bruités, ils présentent desdiscontinuités au niveau des franges ; qui sont due principalement à la décorelation spatiale,temporelle, et thermique, en plus des erreurs de recalage des couples interférométriques. Plusieursméthodes de filtrage ont été développées. Dans ce travail nous sommes particulièrement intéressé auxtechniques de filtrage interférométrique basées sur la décomposition en sous espaces dont nous avonsproposé une méthode de sélection de sous espace optimal afin de conserver l’information physiqueparticulièrement au niveau des zones de transitions des franges. La méthode a été testée sur desinterférogrammes de zones accidentées. Les résultats obtenus sont comparés aux résultats de filtragepar les algorithmes de Goldstein et vecteur Voir les détails
Mots clés : processus interférométrique, interférogrammes, décorrélation spatiale, sous espace optimal, transitions des franges
APPLICATION DES TECHNIQUES MICRO-ONDES DANS LE DOMAINE DE CND : APPLICATION SUR LES ANTENNES IMPRIMES
Résumé : Dans ce travail nous avons effectué une analyse numérique d’une antenne imprimée en utilisant le logiciel de simulation électromagnétique HFFS (High Frequency Structure Simulation). On s'est intéressé à l’excitation d’un matériau par la technique Micro-ondes, En outre la détermination des paramètres hyperfréquences de cette antenne (fréquence de résonance, bande passante, diagramme de rayonnement, gain, etc.), les paramétres diélectriques du matériau (la permittivité diélectrique et la tangente des pertes), L’analyse par le logiciel est basée sur la méthode des éléments finis. Nous avons caractérisé les antennes imprimées à l’aide du logiciel d’Ansoft-HFSS pour les structures 3D ou Ansoft Designer pour les structures planaires 2D. La représentation de tous les éléments de base dans la structure est appelée « maillage ». Le logiciel calcule une solution à certaines positions du maillage puis reconstitue une solution globale sous forme de matrice. Le logiciel HFSS a été conçu pour étudier l’évolution des champs électromagnétiques dans des structures 3D. Les éléments de base de ce logiciel sont des tétraèdres. Dans notre travail on a effectué deux applications, la première à l’aide d’une antenne à patch rectangulaire alimentée par une sonde coaxiale à l’entrée d’un micro ruban fonctionnant à une fréquence de 2.35 GHz et la seconde est alimentée par une sonde coaxiale au milieu du patch fonctionnant à 2.4 GHz. Les résultats de simulation numérique obtenus concernent le champ électrique, la densité de courant, le coefficient de réflexion, le diagramme de rayonnement. Ils sont en général en bon accord avec ceux trouvés dans la littérature. Voir les détails
Mots clés : Antennes imprimées, Caractérisation micro ondes, matériaux, hfss.
Fundamental properties of the rocksalt ZnO and MgO: an ab-initio prediction
The one of the most accurate first-principales methods is the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism, based on Density Functional Theory (DFT), has been exploited to study theatrically, the fundamental properties of the both ZnO and MgO rocksalt binary compound using 16 atoms rocksalt supercell which corresponds to (1×1×2) conventional cell. The Local Density Approximation (LDA) was used only for the structural properties, to treat the exchange-correlation terms. In order to explore the wanted properties. The recently modified semi-local Becke-Johnson potential within LDA correlation in the form of (mBJ) was used to predict the optoelectronic properties of ZnO and MgO binary materials. As results, our computed lattices parameters equal to: 4.22 Å and 4.16 Å respectively, showed satisfactory agreements with experimental values (4.27 Å and 4.2 Å) for ZnO and MgO respectively again. in order to understand the changeability between relaxed and un-relaxed of the electronic structures, The calculated band structures reveal that ZnO posses indirect band gap (Г-M) while for MgO have an indirect band gap (Г-Г) which agree well with the experiment and other theoretical calculations. Optical dielectric function, refractive index, absorption coefficient and optical conductivity, are well described in a wide range of the incident photon energy. The acquired results are used to give an significant guideline to the material's design for optoelectronic applications. Voir les détails
Mots clés : ZnO, MgO, FP-LAPW, Electronic materials, Optical parameters, ab initio calculations.
Segmentation of the Weld Radiographic Images by the Level Set Method using the Kernel Fuzzy C-Means Clustering.
In this paper, we are interested to segment weld radiographic images using the level set method (LSM) based on kernel fuzzy c-means clustering (KFCM) in order to extract the region of interest (weld defects) and to improve the precision of segmentation. The proposed approach contains two successive necessary stages. The first one consists in the application of kernel fuzzy c-means algorithm to get a clustered image. The second stage is based on the using of the appropriate class of the clustered image as an initial contour of the level set method to extract the defects boundaries. The experimental results have shown that the proposed model can extract successfully the interest region from image and confirm its efficiency for welding defects segmentation. Voir les détails
Mots clés : Level set, kernel fuzzy c-means, weld defects, weld radiographic images, image segmentation
Numerical Simulation of CdTe thin films solar cells using AMPS
The numerical modeling and simulation is much needed for the realization of thin films solar cells before that device is in fact produced. In this study we have simulated a theoretical configuration based on SnO2/CdS/CdTe/MoTe heterojunction solar cell under AM 1.5 illumination using the Analysis of Microelectronic and Photonic Structures (AMPS-1D) software tool in one dimension. The effect of physical properties variations is well thought-out on the evaluation of performance (VOC, JSC, FF and Efficiency) in CdTe thin films solar cells Voir les détails
Mots clés : AMPS, Numerical simulation, CdTe, Thin-films solar cells