Liste des documents
Head Pose Classification Using a BidimensionalCorrelation Filter
Correlation filters have been extensively used in face recognition but surprisingly underused in head pose classification. In this paper,we present a correlation filter that ensures the tradeoff between three criteria: peak distinctiveness, discrimination power and noise robustness.Such a filter is derived through a variational formulation of these threecriteria. The closed form obtained intrinsically considers multiclass information and preserves the bidimensional structure of the image. The filterproposed is combined with a face image descriptor in order to deal withpose classification problem. It is shown that our approach improves poseclassification accuracy, especially for non-frontal poses, when comparedwith other methods. Voir les détails
Mots clés : Head pose classification, Bidimensional correlation filter
Adaptive Fuzzy Gain Scheduling of PI Controller for control of theWind Energy Conversion Systems
In this work, the Wind Energy Conversion Systems (WECS) based on doubly fed induction generator (DFIG) model is built.First, we consider the vector control strategy of the active and reactive powers in order to ensure an optimum operation. Thewhole system is presented in d-q-synchronous reference frame. After, the design of Adaptive Fuzzy Gain Scheduling ofProportional Integral Controller (AFGPI) for WECS is described, where the optimization by Fuzzy rules is utilized online toadjust the parameters of PI controller based on the error and its first derivative. Finally, the control of the active and reactivepower using fuzzy-PI controller is simulated using software Matlab/Simulink, studies on a 1.5 MW DFIG wind generationsystem compared with conventional proportional integral controller. Performance and robustness results obtained are presentedand analyzed. Voir les détails
Mots clés : wind systems, doubly fed induction generator, fuzzy control, fuzzy gain scheduling control, fuzzy PI control, PI controller.
Robust Control of Doubly Fed Induction Generator for WindTurbine Under Sub-Synchronous Operation Mode
This paper presents a modeling and a robust control of doubly fed induction generator for wind generation system. The wholesystem is presented in d-q-synchronous reference frame. The regulation of the electromagnetic torque , stator reactive powercontrol and neuronal controller are applied in order to control the rotor currents of the DFIG. For to improve the controllerrobustness, the study is validated through simulation using software Matlab/Simulink, studies on a 1.5 MW DFIG windgeneration system compared with conventional proportional integral controller. Performance and robustness results obtained willbe presented and analyzed. Voir les détails
Mots clés : wind power generation, modeling, Control, doubly fed induction generator, Neuronal controller, performances.
Fault Diagnosis of an Induction Generator ina Wind Energy Conversion System Using SignalProcessing Techniques
In this article, a contribution to fault diagnosis of an in-duction machine in a wind energy conversion system in closed-loopoperation using a combination between short-time Fourier transformand discrete wavelet transform algorithms is proposed. An on-linefault diagnostic technique based on stator currents analysis of thesquirrel-cage induction generator is proposed to detect and localizeabnormal electrical conditions that indicate, or may lead to, a statoror rotor failure in a squirrel-cage induction generator. This techniquealso permits identification of a fault severity factor and consequentlyhelps to determine the best choice of correctivemaintenance. Further-more, a generalized model of the squirrel-cage induction generatoris used to simulate both the rotor and stator faults, taking iron losses,main flux, and cross-flux saturation into account. The efficiency ofdiagnostic procedure in closed-loop operation of the wind energyconversion system under non-stationary operating conditions is illus-trated with simulation results. Voir les détails
Mots clés : fault diagnosis;, Induction Generator;, Wind Energy Conversion System;, Signal Processing Techniques
Three-dimensional simulation of 304L steel TIG welding process: contribution of the thermal flux
In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Gas welding (TIG) problem combining an experimental and a three-dimensional simulation approaches. Optimal conditions are used to weld stainless steel (304L) sheets in butt configuration. Both instrumental monitoring and metallographic investigation of the welded material are carried out. The modelling of the heat source is performed by a mobile Gaussian surface source exhibiting a bi-elliptical shape. This source is implemented in a three-dimensional finite element model to compute heat flux and temperature fields. The comparison between the experimental and numerical thermal cycles shows a fair agreement. Predicted temperature fields and heat flux distributions are discussed. Conversion of isotherms into microstructural information shows that the size of the fusion zone is four times smaller than the heat affected zone dimension. The metallographic analysis confirms the expected microstructural evolutions but highlights differences between observed and predicted extents of the heat affected zone. Voir les détails
Mots clés : Finite elements method, Three-dimensional heat fluxAjout mot clé, TIG welding, 304L steel, Heat affected zone, Fusion Zone
EDDY CURRENT CHARACTERIZATION OF NANOMATERIALS
NDT Magnetic measurements as impedance in Eddy currents, corecitif and residual field in hysteresis loop are used to study the different stages of mechanical alloying in the Fe–Co system. In this paper, we changed the electromagnetic properties of Fe-Co, by developing their metallurgical parameters such as grain size. For this we are used a planetary ball mill, we are milled the FeCo alloy for different milling times until to obtain nanostructure, the lamellar structure with some small particles embedded inthem was observed during the first stage of mechanical alloying. XRD patterns show after 10 h of milling the formation of a disordered solid solution having a body-centered cubic (bcc) structure. After40h of milling, morphological studies indicated that the average crystallites size is around 15 nm. Voir les détails
Mots clés : nanostructured materialsx, powder metallurgy, NDT, Eddy Current, Magnetic measurement
Etude du comportement structural et mécanique d’un alliage aéronautique 2024 T3 par procédé de soudage.
Vu leurs propriétés mécaniques importantes, l’aluminium et ses alliages ont suscité beaucoup d’intérêt au cours de ces dernières années, notamment dans le domaine de la recherche et plus particulièrement pour des applications aéronautiques et aérospatiales. Néanmoins, l’assemblage de ces matériaux reste encore difficile à cause de l’existence de la couche d’alumine jouant le rôle d’une barrière empêchant ainsi leurs soudabilités. Ce travail a pour but l’étude du comportement structurale et mécanique d’un alliage aéronautique 2024 T3 obtenus par le procédé de soudage sous atmosphère protectrice TIG pulsé, cela, en optimisant les paramètres de travail afin d’avoir un bon cordon de soudure. Une étude métallographique est faite sur les différentes zones du joint soudé (Métal de base MB, Zone Affectée Thermiquement ZAT et la Zone Fondue ZF) en utilisant la microscopie optique. De plus, l’évolution des propriétés mécaniques le long du joint soudé est suivie par un profil de microdureté sur les différentes zones (MB, ZAT et ZF). Voir les détails
Mots clés : Aluminium, soudage TIG, TIG pulsé, Aluminium à durcissement structural
Evaluation of the Effect of Citronellol Group on Functionalized Mesogenic Materials by Capillary GC
In this paper, the effects of functionalization with terpenes on two new liquid-crystalline stationary phases for gas chromatography (GC) are described. Citronellol was used as the terminal group in the first material, and tetrahydrogeraniol was used with a second material. Inverse GC showed that the new materials have wide liquid-crystalline ranges (mesophases), 371–500 and 395–501 K, respectively. Moreover, they show good thermal stability up to 523 K and good potential as stationary phases for capillary GC. To clarify the effects of the liquid crystal structures and functional groups on retention and separation, the chromatographic behaviors of the two stationary phases were compared by eluting alkylbenzenes, polycyclic aromatic hydrocarbons, aromatic compounds, and terpenoids. The selectivities for a wide range of analytes achieved using the citronellol column were significantly better than those obtained using the tetrahydrogeraniol column. The columns showed different retention behaviors and fine resolutions for some of the main constituents of essential oils. Introduction of the double bond of citronellol greatly improved the polarization interactions involved in the shape recognition of the liquid-crystalline state for isomers. The new citronellol liquid-crystalline stationary phase, therefore, has a high affinity for natural compounds. Voir les détails
Mots clés : Capillary gas chromatography, Terpenoid liquid crystal, Stationary phase
Microstructure and mechanical behavior in dissimilar 13Cr/2205stainless steel welded pipes
Thiswork aims to investigate the microstructure and themechanical behavior of dissimilar 13Cr Supermartensitic/2205 Duplex stainless steelwelded pipes. A wide variety ofmicrostructures resulting fromboth solidification andsolid state transformation is induced by the fusion welding process across the weld joint. The tensile tests showthat the deformation process of the dissimilarweld joint ismainly controlled by the two basematerials: the duplexsteel at the beginning of the deformation and the supermartensitic one at its end. This is confirmed by the microtensiletests showing the overmatching effect of the weld metal. The fatigue tests conducted on dissimilar weldedspecimens led us to conclude that the weld metal is considered as a weak link of the weld joint in the high cyclefatigue regime. This is supported by its lower fatigue limit compared to the two basematerials that exhibit a similarfatigue behavior. Voir les détails
Mots clés : Dissimilar welding, microstructure, Tensile testing, High cycle fatigue
Degradation of plastic pipe surfaces in contact with an aggressive acidic environment
olyethylene (PE) pipes transporting water are vulnerable to aggressive agents which are able to diffuse through buried plasticpipes causing oxidative degradation. The latter may occur as a result of a spontaneous chemical reaction with atmospheric oxygen or as an induced oxidizing reaction with disinfectant agents (i.e. chlorine or hypochlorous acid ions) which are commonly added to municipal water supplies for public health reasons. Basically, PE pipes surfaces undergo undesired oxidation reactionswhenever they are in contact with adverse external environments and/or when conveying fluids which tend to modify internal pipe wall structure. In this work, the effects of distilled water and diluted hydrochloric acid at different concentrations on the external and internal surfaces of a high density polyethylene (HDPE-100) pipe are studied. The measured parameters are roughness and hardness in order to appreciate surface quality variances in as-received and degraded materials. Initially the outer surface is rougher than the inner’s one but in contact with distilled water, the external surface roughness increased by 6% although the internal face of the tube revealed a small decrease (<5%). When exposed to hydrochloric acid, pipe roughness (μm) showed a substantial increase as a function of increasing medium concentration. Crystallinity (χ in %) measurements confirmed the gap between outer (51.55%) and inner (61.31%) surfaces indicating that degradation has taken place at the structural level when HDPE was in contact with such aggressive agents. On the other hand, it is revealed that after exposure to oxidizing environments, crystallinity dropped by approximately one third when compared to as-received material; therefore reducing resistance to fracture and subsequently pipe lifetime. Voir les détails
Mots clés : polyethylene pipe; environment; distilled water; diluted hydrochloric acid; degradation; surface roughness; hardness; crystallinity.