Liste des documents
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
One-dimensional Parametric Study of Damage Detection in a Solid Material using a Nonlinear Wave Modulation Spectroscopy (NWMS) Technique.
Nonlinear Wave Modulation Spectroscopy (NWMS) is one of the most powerful techniques used to detect damage in materials. It consists in simultaneously applying two continuous waves with different frequencies, the one high, f2, and the other low, f1. When the material is damaged, the frequency spectrum exhibits harmonics and sidebands which are located at (f2 + f1) and (f2 - f1). This paper presents a parametric simulation study of the nonlinear propagation of elastic waves in solid media, which can be represented by a one dimensional mass-spring system. The system of motion equations is resolved by a fourth order Runge-Kutta iterative method. A quadratic nonlinearity can be introduced locally in the system at any spring. The objective of the paper is to highlight the ability of the nonlinear acoustic methods, especially the NWMS (Nonlinear Wave Modulation Spectroscopy), to detect damages in solid material. The study of the evolution of the sidebands amplitude, according to the low frequency of the wave (pump wave), f1, in cracked and intact material will be presented. It is shown that this amplitude reaches a maximum when the pump frequency corresponds to a resonance frequency of the system. In addition, the study shows the strong dependency of the resulting frequency spectrum of the received signal upon the nonlinearity magnitude as well as the rigidity of the simulating crack spring. Voir les détails
Mots clés : Nonlinear Modulation Spectroscopy, Damage detection, nonlinear wave propagation simulation
Stady and analysis of mechanical and viscoelastic behavior in flexure of laminated composites
In the present paper, seven laminated composites were thesubject of an experimental study to determine their mechanical and viscoelastic properties by means of dynamic mechanical analysis in a bending configuration. The influenceof the frequency, fiber type and fiber orientation on dynamic mechanical properties of different system composites were investigated. Carbon/epoxy laminates exhibit agreat stiffness when fibers are oriented along the axis ofthe clamps, and the maximum modulus was reported forunidirectional carbon/epoxy laminate [08 plies] with56.4 GPa. The glass transition temperature was found to decrease with the incorporation of fibers and increase with increased frequency. For the Kevlar/epoxy laminate, an increase of 12.5 8C in glass transition temperature wasobserved. This is related to a better interfacial adhesion between epoxy matrix and Kevlar fibers. Voir les détails
Mots clés : Composite laminate; Dynamic mechanical analysis; Fiber/matrice interface; Glass transition temperature
Poly Chlorure de Vinyle (PVC) Plastifié par des Mélanges des Plastifiants d’origineBiosourcés : Synthèse et Caractérisation
L’huile de tournesol époxydée (HTE) avec un indice d’oxyrane de 4,5 a été synthétisée à partir de l’huile de tournesol vierge et l’eau oxygénée (H2O2) en présence de l’acide formique. L’HTE est utilisée avec le di esters isosorbide (DEI) comme un système plastifiant biosourcé dans le PVC en combinaison avec un plastifiant classique soit le di-éthyle-2-hexyle phthalates (DEHP).Après fabrication des films (0,5 mm d’épaisseurs) de différents pourcentages des plastifiants dans un mélangeur à deux cylindres, on a réalisé les essais de la migration et d’excudation des plastifiants des formulations obtenues. La migration des plastifiants biosourcés (DEI ou HTE) en combinaison avec le DEHP est suivie par les tests de volatilité, d’extraction et de lessivage. Les pertes des masses des formulations plastifiées réalisées obtenues par les différents modes de caractérisation à savoir: la volatilité, l’extraction dans l’eau distillée et dans la gazoline et le lessivage dépendent de la pression devapeur, de la masse moléculaire, de la solubilité, de la compatibilité et de la structure chimique du plastifiant. Voir les détails
Mots clés : PVC, Biosourcé, Epoxydation, plastifiants
Cr(VI) photocatalytic reduction under sunlight followed by Cr(III) extraction from TiO2 surface
The main objective of this work was the extraction of Cr(III) from TiO2 surface deposited after Cr(VI) reduction by TiO2 solar photocatalysis. The results show that the reduction of Cr(VI) to Cr(III) by TiO2 under natural sunlight is total after 2 h using tartaric acid (A.T) as a hole scavenger under the following conditions: [Cr(VI)]: 20 ppm, [TiO2]: 2 g/L, [A.T]: 60 ppm and pH: 2.2. The produced Cr(III) is divided between deposited onto TiO2 surface (39.75%) and in the solution (60.25%). The Cr(III) removal from TiO2 surface by the sequential extraction after three washing were 90.13% and 42.62% using citric acid and EDTA respectively. Voir les détails
Mots clés : Chromium, Reduction, Deposition, Solar light, extraction, TiO2 surface
Particle swarm optimization based sliding mode control of variable speed wind energy conversion system
This paper proposes a particle swarm optimization based sliding mode control of squirrel cage induction generator of a variable speed wind energy conversion system. The key feature of sliding mode control is a wisely chosen sliding surface which allows the turbine to operate more or less close to the optimal regimes characteristic. Optimal control parameters which are the convergence speed to the sliding-mode, the slope of the surface and the switching component amplitude of SMC are determined using particle swarm optimization approach. The simulation results prove the viability of the proposed control structure. Voir les détails
Mots clés : Squirrel Cage Induction Generator (SCIG), Wind Energy Conversion System (WECS), Sliding Mode Control (SMC), Particle Swarm Optimization (PSO)
Feedback linearization control based particle swarm optimization for maximum power point tracking of wind turbine equipped by PMSG connected to the grid
The main problem regarding wind power systems is the major discrepancy between the irregular character of the primary source (wind speed is a random, strongly non-stationary process) and the exigent demands regarding the electrical energy quality. This paper presents a feedback linearization controller based particle swarm optimization for maximum power point tracking of wind turbine equipped by PMSG connected to the grid, the proposed method which aims at maximizing the power captured by WECS. In order to drive the system to the optimal operating point using the selection of the controller parameters with particle swarm optimization. The obtained simulation results with a variable wind profile show an adequate dynamic of the conversion system using the proposed approach. Voir les détails
Mots clés : Wind turbine, Maximum Power Point Tracking, Feedback linearization control, Particle Swarm Optimization (PSO), Wind Energy Conversion System (WECS)
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
Study and analysis of mechanical and viscoelasticbehavior in flexure of laminated composites
In the present paper, seven laminated composites were thesubject of an experimental study to determine their mechanical and viscoelastic properties by means of dynamic mechanical analysis in a bending configuration. The influenceof the frequency, fiber type and fiber orientation on dynamic mechanical properties of different system composites were investigated. Carbon/epoxy laminates exhibit agreat stiffness when fibers are oriented along the axis ofthe clamps, and the maximum modulus was reported forunidirectional carbon/epoxy laminate [08 plies] with56.4 GPa. The glass transition temperature was found to decrease with the incorporation of fibers and increase with increased frequency. For the Kevlar/epoxy laminate, an increase of 12.5 8C in glass transition temperature wasobserved. This is related to a better interfacial adhesion between epoxy matrix and Kevlar fibers Voir les détails
Mots clés : Composite laminate, Dynamic mechanical analysis, Fiber/matrice interface, glass transition temperature
Numerical and Experimental Investigation of FluidicMicrodrops Manipulation by Fluidic Mono-Stable Oscillator
A numerical and experimental study of passive microdrops manipulation hasbeen presented. This paper focuses on the modeling of micro-oscillators systemswhich are composed by passive amplifier without moving part. The characteristicsize of the channels is generally about 35 ¹mof depth. The numerical results indicatethat the production and manipulation of microdrops are possible with passivedevice within a typical oscillators chamber of 2:25 mm diameter and 0:20 mmlength when the Reynolds number is Re = 490. The novel microdrops methodthat is presented in this study provides a simple solution about the production ofmicrodrops problems in micro system. We undertake an experimental step. Thefirst part is based on realization of sample oscillator; the second part is consistedof visualization of the microdrops production and its manipulation. Voir les détails
Mots clés : microdrop, fluidic oscillator, CFD