Nombre total de résultats : 482
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Reconnaissance hors ligne des mots arabes manuscrits par les réseaux de neurones

Rachid Zaghdoudi (2008)
Mémoire de magister

Le traitement de l'écrit est un domaine en pleine expansion qui commenceaujourd'hui à voir aboutir certaines réalisations industrielles importantes. Dans cecadre, la reconnaissance hors ligne de l'écriture arabe manuscrite reste cependant undes sujets les plus difficiles et les plus actifs au niveau de la recherche.La difficulté majeure rencontrée lors de la conception d'un système dereconnaissance des mots arabes manuscrits, est le problème de la segmentation de cesmots en caractères en vue de leur reconnaissance, pour remédier à ce problème, nousproposons une méthode globale pour la reconnaissance des mots arabes manuscritsdans un vocabulaire limité. Le système développé s’articule autour de cinq modulesdistincts : Acquisition, prétraitements, segmentation en parties connexes, extractiondes primitives les plus pertinentes et reconnaissance (classification et décision). Cedernier est basé sur les réseaux de neurones de type PMC.Pour tester la fiabilité de ce système de reconnaissance, des expériences ontété effectuées sur une base de données représentant les noms des 48 WilayasAlgériennes. Qui ont montré que l'approche proposée semble une solution intéressanteau problème de la reconnaissance des mots arabes manuscrits. Voir les détails

Mots clés : Reconnaissance d'écriture arabe manuscrite ; approche globale ; extractions des caractéristiques ; réseaux de neurones.

Structural, electronic and optical properties for chalcopyrite semiconducting materials: ab-initio computational study

Moufdi Hadjab, Miloud IBRIR, Smail BERRAH, Hamza ABID, Mohammad Alam Saeed  (2018)

Investigation of the physical properties of chalcopyrite materials using ab-initio methods have been carried out to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. The Density Functional Theory calculations have been performed using Wien2k computational package by employing the full-potential linearized augmented plane wave method. Structural and electronic properties of chalcopyrite semiconducting material Copper–Indium–Gallium–Selenium i.e. CuIn1-xGaxSe2 have been investigated using local density approximation for the exchange-correlation potential. The electronic structures and linear optical properties have been studied using both the semi-local Becke-Johnson potential and its modified form i.e. mBJ and TB-mBJ. Computational results are in good agreement with those acquired experimentally. The viability of alloys in realization of ultra-thin-film based (CIGS) solar cells with high performance has been proposed after simulation and analysis study using one of solar cell simulation tools. The studied material exhibits capability to become a promising candidate for fabrication of optoelectronic and photovoltaic devices. Voir les détails

Mots clés : Chalcopyrite, FP-LAPW, optical properties, Thin-films solar cells, wien2k

Optical study of cubic, and orthorhombic structures of XCaCl3 (X = K, Rb) compounds: Comparative Ab initio calculations

A.HADJ LARBI, S. Hiadsi, M. HADJAB, M. A. SAEED  (2018)

The study predicts the optical properties of cubic and orthorhombic structures of XCaCl3 (X = K, Rb) perovskite compounds through electronic band structure computation within the framework of density functional theory (DFT). The ground state functions are computed employing full potential linearized augmented plane wave (FP-LAPW) method. Improved band gap values and the electronic as well as optical properties were calculated by Tran and Blaha modified Becke–Johnson (mBJ) functional. The studied compounds’ density of states reveals that Cl-p states dominate the valence band. To understand the optical properties, and predicting the optically isotropic nature of these materials, the real and imaginary parts of dielectric function, refractive index, absorption coefficient, and energy loss spectra are plotted. The present study shows a great potential utilization in ceramic scintillators. Voir les détails

Mots clés : DFT, FP-LAPW, Perovskites, Optical parameters, Scintillators

First principles investigation of optoelectronic properties ofZnXP2 (X = Si, Ge) lattice matched with silicon for tandemsolar cells applications using the mBJ exchange potential


II-IV-V2 materials are attractive compounds for optoelectronic, photonic and photovoltaicapplications due to their valuable ternary chemistry. A primary technological challengein photovoltaics is to find and develop a lattice matched efficient material to be usedin combination with silicon for tandem solar cells. ZnSiP2 and ZnGeP2 chalcopyrites arepromising semiconductors that could satisfy these criteria. Particularly, ZnSiP2 is known tohave bandgap energy of∼2 eV and a lattice mismatch with silicon of 0.5%. In this work, thefirst principle calculations have been performed to investigate the structural, electronic andoptical properties of ZnSiP2 and ZnGeP2 in chalcopyrite structure within the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method based on the Density FunctionalTheory (DFT) as implemented in WIEN2K code. The local Density approximation (LDA) ofPerdew and Wang was used as exchange-correlation potential to calculate the structuralproprieties. Furthermore, the recently modified Becke-Johnson (mBJ) functional of Tranand Blaha was also employed to compute the electronic and optical properties in order toget best values of the band gap energy and some better degree of precision. The complexdielectric function, the complex refractive index, reflectivity, absorption coefficient, and theoptical conductivity were calculated to illustrate the linear optical properties of both compoundsZnSiP2 and ZnGeP2. At last, the obtained results indicate that ZnSiP2 and ZnGeP2are attractive materials in optoelectronic devices especially as a lattice matched materialwith silicon for tandem solar cells applications. Voir les détails

Mots clés : FP-LAPW, mBJ, Chalcopyrite, Electronic band structure, Linear optical properties

Optoelectronic properties of the new quaternary chalcogenides Zn2CuInTe4 & Cd2CuInTe4: ab-initio study.


In order to exploit the fundamental properties of the new tellurides quaternary diamond-like structure Zn2CuInTe4 and Cd2CuInTe4, first principles investigation in the frameworkof the Full-Potential LAPW scheme have been carried out for that purpose. We used theWu and Cohen generalized gradient approximation (GGA-WC) to calculate the optimizedstructure that corresponds to the global minima of the energy. Enthalpy of formation showsthat the most stable structures are the relaxed ones. The EV-GGA and the TB-mBJ approx-imations were also used for electronic and optical properties. The equilibrium electronicparameters found are in good agreement with the previous results. The real and thecient, theopt imaginary parts of the dielectric function, the refractive index, the extinction coeffiicalconductivity, the absorption coefficient, the loss function and the reflectivity are reviewedin the large spectral range of photon energy. The present study demonstrates a variety ofnovel electronic and optical properties, which make these compounds highly promising foroptoelectronic materials. Voir les détails

Mots clés : DFT, Quaternary tellurides, Enthalpy of formation, band gap, Absorption coefficient

Study of Substrate Temperatures effects on Optical TiO2 Nano-films Properties deposited by RF Magnetron Sputtering for Gas Sensor application

Khouloud BEDOUD, R. Graine, H. MERABET, I. Rahmani, D. ZELMATI, N. Sehab, L. Alimi.  (2018)
Article de conférence

Titanium dioxide (TiO2) is a non-toxic material and chemically stable. It hase a high optical transmittance, electrical conductivity and high refractive index. It is widely used in many fields such as photo catalysis, electro catalysis. It can be used serves as self-cleaning coatings. Similarly, TiO2 can be used as bio-sensor coatings, biomedical materials, antibacterial applications. Furthermore, it can be used in water purification, solar cells and gas sensors. This work deals with deposition of TiO2 onto heated glass substrates in a temperature range of 200 to 450 ° C via radio frequency (RF) reactive magnetron sputtering. We used a metal target of pure Ti of 3" diameter and 0.250" thickness with a purity of 99.99%. Optical properties of TiO2 are substrate temperature dependent. Those are investigated in the UV–Visible range of the specter. Transmission characterization confirmed the transparent character of the films. The highest transparency was achieved for deposition temperature of 300 °C. The yielded gaps varied in the range 3.75–3.92 eV. Voir les détails

Mots clés : Thin films, sputtering, semiconductor, TiO2films, gas sensors, carbon dioxide, Optical properties.

Vibration for detection and diagnosis bearing faults using adaptive neurofuzzy inference system

Djamila Bouneb, Tahar Bahi, Hichem MERABET  (2018)

The fault diagnosis of electrical machines is a primordial and necessary task in industry. Thefailure is unbearable because it causes, incontestably, decrease in production and increases costrepair. Induction motors are the most important equipment in industry, where reliability andsafe operation is desirable, for maintenance, such as detection, and diagnosis of mechanical andelectrical defects of electric drives. The several techniques are adopted and frequency analysis isthe most widely used. Artificial intelligence techniques was gained popularity last decay’s innumerous applications. The presented results show the detected and diagnosed, of the bearingfaults of the induction motor, based on Adaptive Neuro-Fuzzy Inference System. The vibrationsanalysis of the induction machine using the Artificial Intelligence Techniques, combining neuralnetworks and fuzzy logic has been applied successfully. The designed ANFIS network showsabout 99% accurate results as validated by Mat lab / Simulink simulation Voir les détails

Mots clés : diagnosis, fault, vibration, bearing

Investigation of Polycrystalline silicon TFT’s electrical characteristics

Hadjira Tayoub, Baya Zebentout, Zineb Benamara  (2017)
Article de conférence

Low-temperature polycrystalline silicon thin film transistors (poly-Si TFT’s) on plastic substrate have been studied because of their high performance in Active Matrix Liquid Crystal Displays (AMLCD’s) and Active Matrix Organic Light-Emitting Diode (AMOLED) applications. The purpose of this work is to simulate the impact of varying the electrical and physical parameters (the interface states, active layer’s thickness and BBT model) in the transfer characteristics of poly-Si TFT to extract the electrical parameters like threshold voltage, mobility and to evaluate the device performance. The device was simulated using the ATLAS software from Silvaco. The results show that the electrical and physical parameters of poly-Si TFT affect significantly its transfer characteristics. Voir les détails

Mots clés : Poly-Si TFT, TCAD-ATLAS, electrical characteristics

Detection and classification of steel defects using machine vision and SVM classifier

Rachid Zaghdoudi, Hamid Seridi, Adel BOUDIAF  (2017)
Article de conférence

the importance of quality control of steel products is increasing day by day in the manufacturing industrial systems because it offers the possibility of knowing the state of the products without stopping the production line which allows the control of a defect before it becomes a complex problem and avoiding production losses. Human quality control of steel products remains tedious, fatiguing, bit fast, bit robust, dangerous or impossible, therefore the use of automated vision system can significantly improve the quality inspection process, because the machine vision technology can overcomes the majority of manual inspection problems cited above and provide an interesting solution especially, with the impressive increasing of computing power of today's computers and the good quality of images that offer the current cameras.The main objective of this research is to propose an efficient control system based on machine vision technology and SVM classifier to classify different types of steel defects. Voir les détails

Mots clés : Defects steel, machine vision, pattern recognition, HOG, GLCM, SVM classifier

Développement d'algorithmes de traitement des signaux pour la détection et la localisation des défauts. Application au contrôle des matériaux par ultrasons multiéléments.

Ahmed Benyahia (En préparation)
Thèse de doctorat

Le contrôle non destructif (CND) par ultrasons vise à détecter et/ou localiser des défauts dans des pièces en phase de production, d’utilisation ou de maintenance. Pour s’adapter aux cadences de production industrielle de nouvelles méthodes se sont beaucoup développées depuis quelques années. Elles se basent sur une nouvelle technologie des équipements et des algorithmes de traitement plus puissants. Les techniques classiques par ultrasons, ne font plus l’objet de travaux de recherche. En effet, nous assistons à une émergence d’outils très utilisés dans le domaine médical qui commencent à voir une adaptation dans le contrôle industriel des matériaux et de leurs assemblages. La possibilité d’acquérir une information permettant de caractériser les défauts en nature, en taille et en orientation a nécessité le développement de nouvelles techniques basées sur les sondes multiéléments (Phased arrays).L'objectif du travail est donc le développement de nouvelles méthodes de traitement du signal permettant la détection et la localisation des imperfections présentes dans les matériaux. Voir les détails

Mots clés : contrôle non destructif (CND), ultrasons multiéléments, traitement du signal, détection, localisation