Liste des publications
A Comparative Study of Various Methodsof Bearing Faults Diagnosis Using the CaseWestern Reserve University Data.
Bearing is probably one of the most criticalcomponents of rotating machinery. They are employed toguide and support the shafts in rotating machinery.Therefore, any fault in the bearings can lead to losses onthe level of production and equipments as well as potentiallyunsafe. For these reasons, the bearing fault diagnosishas received considerable attention from the research andengineering communities in recent years. The purpose ofthis study is to review the vibration analysis techniques andto explore their capabilities, advantages, and disadvantagein monitoring rolling element bearings. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Temporal analysis, Cepstrum analysis
Full-potential calculations of structural and optoelectronic properties of cubic indium gallium arsenide semiconductor alloys
In this work, the first-principle calculations have been performed to predict the structural,electronic and optical properties of cubic InxGa1−xAs for 0≤x≤1, using 16-atom within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method based on Density Functional Theory (DFT) as implemented in WIEN2k computational code. The Local Density Approximation (LDA) and Wu–Cohen Generalized Gradient Approximation (WC–GGA)were employed as the exchange–correlation term to calculate the structural and electronic properties. Moreover, the Engel–Vosko GGA (EV-GGA) and the recently modified semi–local Becke–Johnson (mBJ) functional were also used to compute the electronic and optical properties in order to get some better degree of precision. The real and the imaginary parts ofthe dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient and optical conductivity were calculated to discuss the linear optical properties ofInxGa1−xAs alloys. The achieved results show a great potential utilization in optoelectronic devices especially in infrared applications. Voir les détails
Mots clés : Ab inition, DFT, Cubic, InxGa1-xAs alloys, structural parameters, Optoelectronic properties
Structural, electronic, optical and elastic properties of the complex K2PtCl6-structure hydrides ARuH6 (A = Mg, Ca, Sr and Ba): first-principles study
We report a systematic study of the structural, electronic, optical and elastic properties of the ternary ruthenium-based hydrides A2RuH6 (A = Mg, Ca, Sr and Ba) within two complementary first-principles approaches. We describe the properties of the A2RuH6 systems looking for trends on different properties as a function of the A sublattice. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gaps are about 3.53, 3.11, 2.99 and 2.68 eV for Mg2RuH6, Ca2RuH6, Sr2RuH6 and Ba2RuH6, respectively. Calculated density of states spectra demonstrates that the topmost valence bands consist of d orbitals of the Ru atoms, classifying these materials as d-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. Optical spectra in a wide energy range from 0 to 30 eV have been provided and the origin of the observed peaks and structures has been assigned. Optical spectra in the visible range of solar spectrum suggest these hydrides for use as antireflection coatings. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time. Voir les détails
Mots clés : Ruthenium-based hydrides; first-principles calculations; elastic constants; optical properties; electronic
Spatially Varying Weighting Function-BasedGlobal and Local Statistical Active Contours.Application to X-Ray Images
Image segmentation is a crucial task in the image processingfield. This paper presents a new region-based active contour whichhandles global information as well as local one, both based on the pixelsintensities. The trade-off between these information is achieved by aspatially varying function computed for each contour node location. Theapplication preliminary results of this method on computed tomographyand X-ray images show outstanding and efficient object extraction Voir les détails
Mots clés : image segmentation, Active contour, Averaged Shifted, histogram, pressure forces, statistics, Spatially varying function
Adsorption of the copper in solution by the kaolin
The physico-chemical characterization showed that this adsorbent is mostly silica and alumina and. The specific surface area measured is more important for purified. The proposed disposal is in batch system. The results of investigations carried out show that the equilibrium is reached after 30 minutes. This sorption is maximum at 20°C, for stirring speed of 200 tr/min a size of between 150 and 200 µm and at pH 4. The maximum amount adsorbed at equilibrium per gram is 46.18 mg/g. The model of adsorption obeys to the Langmuir equation. The plot of the sorption isotherm is confirmed by the presence of a slow landing. The kinetics is pseudo first order. The external transport of metal ions considered in the solution towards the adsorbent seems a step controlling the overall speed of the process. Therefore internal transport in the pores is not the only mechanism limiting the kinetics of sorption. The probably other mechanisms involved. This adsorption is divided into two zones: a diffusion region and a kinetic area controlled by the reaction. The thermodynamic parameters show that the sorption is spontaneous (ΔG <0), exothermic (ΔH <0) and no changes have been made in its structure (ΔS <0). Measured activation energy is 24.45 kj/mol Voir les détails
Mots clés : Kaolin, copper, adsorption, water, depollution
An experimental analysis of fracture mechanisms by acousticemission of woven composite bolted assembly
This work is focused on the study of the evolution of damage mode and failure mechanisms of woven composite bolted assembly carbon fiber/epoxy. In the present paper three configurations are studied [0°,45°,0°,45°], [0°,45°,0°,45°]s and [0°,45°,0°,45,0°]s. In order to analyze a global mechanical behavior of the assembly, monotonous tensile tests are performed. The damage evolution is followed simultaneously by acoustic emission (A.E) and digital image correlation (D.I.C). Acoustic signatures of four modes of damage are identified, matrix cracking, fiber-matrix debonding, delaminating and fiber breakage, then confirmed by microscopic observations in scanning electron microscopy (SEM).Composite woven, émission acoustique, assemblage boulonné, corrélation d'image numérique, endommagement. Voir les détails
Mots clés : Woven composite, acoustic emission, bolted assembly, digital image correlation, Damage.
Computer Code for Materials Diagnosis Using Monte CarloMethod and Neural Networks
Non-destructive testing (NDT) is a highlyvaluable technique in evaluation and evolution of materialsand products. X-ray imaging is an important NDT techniquethat is used widely in the metal industry in order tocontrol the quality of materials. Sometimes it may be difficultto get a measurement. The simulation of X-rayimaging is often performed using computer codes. Thispaper presents a new simulation method for materialsdiagnosis. The simulation is based primarily on the X-rayattenuation law and it is performed using a combinationbetween Monte Carlo method and multi-layer perceptronneural network. The main goal of the proposed method isto obtain more detailed information about the state of thematerials. Voir les détails
Mots clés : Non-Destructive testing, X-ray imaging, Materials diagnosis, Monte Carlo, Neural Network
Diagnosis and Detection of Eccentricity Faults in a Doubly-Fed Induction Generator
Doubly-fed induction generators are being used extensively in wind energy conversion systems. Efforts are being made to effectively adopt existing condition monitoring and fault diagnostic techniques for these systems. We consider in this paper to take account of the specificities and characteristics of the doubly-fed induction generator, for develop an analytical model that describes as precisely as possible the machine performance in healthy and machine with different eccentricity faults types. In this paper, we propose a method for the eccentricity diagnosis fault based on the stator current analysis during the start-up using this wavelet method enables faults eccentricity detection and isolation of this fault in rotor by analysing the frequency spectrum. This study showed that the application of this technique offered reliable and acceptable results for diagnosis detection and faults. Voir les détails
Mots clés : diagnosis, Detection, faults, doubly-fed indduction generator, eccentricity, modeling, simulation
Metallic Coating for Carbon Fiber Reinforced Polymer Matrix Composite Substrate
This paper investigates the application of metallic coatings on high fiber volume fraction polymer matrix composites. For the grip of the metallic layer, a method of modifying the surface of the composite by introducing a mixture of copper and steel powder filler powders which can reduce the impact of thermal spray particles. The powder was introduced to the surface at the time of the forming. Arc spray was used to project the zinc coating layer.The substrate was grit blasted to avoid poor adherence. The porosity, microstructure, and morphology of layers are characterized by optical microscopy, SEM and image analysis. The samples were studied also in terms of hardness and erosion resistance. This investigation did not reveal any visible evidence damage to the substrates. The hardness of zinc layer was about 25.94 MPa and the porosity was around 6.70 percent. The erosion test showed that the zinc coating improves the resistance to erosion. Based on the results obtained, we can conclude that thermal spraying allows the production of protective coating on PMC. Zinc coating has been identified as acompatible material with the substrate. The filler powders layer protects the substrate from the impact of hot particles and allows avoiding the rupture of brittle carbon fibers. Voir les détails
Mots clés : Arc spray, coating, composite, erosion
On-Line Monitoring and Classification of Stator windings Faults inInduction Machine Using Fuzzy Logic and ANFIS Approach
the induction machines drives becomes moreand more important used in many industrial applications.Their attractiveness is largely due to their simplicity,ruggedness and low cost manufacture, easy maint00enance,high power efficiency and high reliability, are susceptible tovarious types of electrical and/or mechanical faults that canlead to unexpected motor failure and consequently impulsivedowntime. This made necessary the monitoring functioncondition of these machines types for improved anexploitation of the industrial processes. The aim of this taskis the proposal of a monitoring strategy based on the fuzzylogic inference system (FIS) and the neuro-fuzzy inferencesystem (ANFIS) for monitoring and classification ofelectrical faults types, especially the open phase and interturnsshort-circuit in the stator windings. The principleadopted for the strategy suggested is based on monitoring ofthe average root mean square value of stator current (RMS).Mathematical models and simulations results are presentedto validate the efficiency of this approach. Voir les détails
Mots clés : Monitoring, classification, Fis, INFIS, RMS