Liste des publications

Nombre total de résultats : 666
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Characteristics of Al-doped TiO2 thin films grown bypulsed laser deposition

Faouzi HANINI, Yacine BOUACHIBA, Fouad KERMICHE, Adel TAABOUCHE, Abderrahmane BOUABELLOU, Tahar KERDJA, Kamel Boukheddaden  (2013)

Al-doped TiO2 (TiO2:Al) thin films were deposited at 450ºC ontoglass substrates using pulsed laser deposition method. X-rays diffractionspectra showed that the obtained films are polycrystalline of anatase structurewith preferential orientation of (101) direction. AFM images, nanoparticles sizeand surface roughness mean square values showed that the surfaces of TiO2:Alfilms are smoother than that of undoped TiO2 films. A blue shift in theabsorption edge of TiO2 with increasing Al concentration in the film isnoteworthy as it leads to increase in the width of the optical transmission. Theoptical waveguiding performances of the TiO2:Al films were demonstrated byusing the m-lines spectroscopy technique and the results were correlated to thestructural properties. Spectroscopic ellipsometry was used to extract the opticalconstants of the films. The determined band gap of undoped and Al doped filmsvaries from 3.43 to 3.61 eV, which is in accordance to Burstein-Moss shift. Voir les détails

Mots clés : Al-doped TiO2, structure, morphology, optical properties, waveguide, nanoparticles

Extraction of weld defects dimension from radiographic images using the level set segmentation without re-initialization

Mohammed Halimi, Naim Ramou  (2013)

Radiographic images segmentation is the major interest for the weld defect diagnosis and monitoring in the field of industry. In this work  we present a method that takes ownership of local segmentation geodesic active contours. The goal of the method presented in this paper is to automate the process of extracting dimension of weld defects from radiographic images using level set segmentation. The information would be used in the area of nondestructive testing (NDT). This method is found to be effective and robust. Voir les détails

Mots clés : radiographic method, weld inspection, defect dimensions, Signal processing

Etude Comparative des Techniques de Filtrage Actif Sélectif par le Référentiel Synchrone de Park d-q et l’Approche FMV

Noureddine Hamouda, Kamel Eddine Hemsas, Hocine Benalla  (2014)

To minimize the total harmonic distortion (THD) and improve the power factor (PF), this paper presents a comparative study between two techniques of shunt power active filter (SPAF) by a selective action of harmonics. These two techniques are based on the SAPF of certain low frequency harmonics (5th and 7th) whose identification of the harmonics of references of the first is made by the axis synchronous d-q of the Park, and the second is done by the approach of self-tuning filter (STF) Thereafter, The active simultaneously filtering of the 5th and 7th harmonics of the current of load catches. The shapes of the signals and the THD values resulting from the results of digital simulations (Matlab-Simulink) elaborate the effectiveness and the best technique of this type of filtering. Voir les détails

Mots clés : PF, THD, Harmonics, SAPF, STF, d-q Park Synchronous Axis

Segmentation of welding defects using level set methods

HALIMI Mohammed, RAMOU Naim  (2012)

Non-destructive testing (NDT) is a technique used in science and industry to evaluate the properties of a material without causing damage. In this paper we propose a method for segmenting radiographic images of welding in order to extract the welding defects which may occur during the welding process. We study different methods of level set and choose the model adapted to our application. The methods presented here take the property of local segmentation geodesic active contours and have the ability to change the topology automatically. The computation time is considerably reduced after taking into account a new level set function which eliminates the re-initialisation procedure. Satisfactory results are obtained after applying this algorithm both on synthetic and real images. Voir les détails

Mots clés : image segmentation, Level set, weld defects, Radiographic image

Acoustic emission signal denoising to improve damage analysis in glass fibre reinforced composites

Abida Satour, Silvio Montrésor, Mourad Bentahar, Rachid Elguerjouma and Fouad Boubenider  (2014)

In this contribution, continuous wavelet denoising technique is developed to enhancethe signal to noise ratio of acoustic emission (AE) signals. The time– frequency characteristics of the recorded noise are first determined by calculating the noisewavelet coefficients. Then, an algorithm able to proceed denoising by extracting noise features from those corresponding to AE signals is developed. The denoising procedure is applied to get meaningful signals when the detection threshold is decreased from 30 dB to 25 dB. Furthermore, the spectral flatness measure was applied to eliminate signals originating from noise. Experiments were conducted on cross-ply composite specimens [±45°]6S to examine the efficacy of the proposed technique. The denoised signals were analysed using the continuous wavelet transform and were also analysed in terms of the dominant frequency band which was processed by a fast Fouriertransform. Results show that denoised low-amplitude AE hits are well correlated withhigh-amplitude AE hits (A≥30 dB) in terms of damage characterisation. Voir les détails

Mots clés : acoustic emission, polymer-based composite, Denoising, Signal processing, damage characterisation

Use of Guided Waves for Inspection of Composite Skin-Honeycomb Core

A. Satour, F. Boubenider, A. Badidibouda, R.Halimi  (2010)

Sandwich plates, made of two aluminum layers and a metal honey comb core are used inthe aircraft industry. The purpose of this study is to show the ultrasonic guided waves sensibility to discover delamination in skin-honeycomb sandwich structures used in aeronautics. Separation between the skin and the core can appear during the manufacture or after use. In this work, Lamb's waves are used to control this kind of plane structure. Indeed, these waves have the advantage to putin vibration the totality of the plate that we want to control and they propagate on long distances without too much attenuation. The revealing, by the guided waves, of the unsticking which canmeet on such sandwiches, between the plate and the honeycomb core is studied and commented. Voir les détails

Mots clés : Lamb waves, Sandwich structure, Dispersion curves, Displacements.