Liste des communications
Correlation between structure and photoluminescence properties of thin films of TiO2 doped Er3+, obtained by the sol-gel process
In this work, we are interested to the study of the influence of structure on photoluminescence properties of Er3+ doped TiO2 thin films, dip-coated by the sol-gel method. TiO2 thin films and powders obtained are doped with different rates of Erbium (0.1, 0.5, 1, 3 at %) and have undergone an annealing at 450 ° C. Thin films and powders thus obtained were characterized by different techniques: differential scanning calorimetric (DSC), infrared spectroscopy FTIR, Raman spectroscopy and photoluminescence. (DSC) results show that the Erbium causes a shift of the transformation from amorphous TiO2 to anatase crystalline state to the low temperatures and the latter varies according to the percentage of erbium. While the FTIR shows strong absorption peaks around 438 cm-1 and 612 cm-1 corresponding respectively to the vibration Ti-O-Ti and Ti-O of TiO2. In contrast the Raman spectra show the presence of two phases’ anatase and brookite in the case of un-doped thin films and the disappearance of the brookite in those doped with Erbium and annealed at 450 °C. Finally, the photoluminescence curves show the green and red up-conversion emissions. Green emissions are positioned in the range of 520-570 nm (2H11 / 2, 4S3/2 4I15/2), and then for those of the red they are set in the range 640-690 nm (4F9/2, 4I15/2). We also note that the emission intensity of red and green gradually increased when the erbium rate increases. Voir les détails
Mots clés : TiO2 doped Er3+, sol-gel, photoluminescence properties
Etude Comparative des Techniques de Filtrage Actif Sélectif Par le Référentiel Synchrone de Park d-q et l’Approche FMV
Cet article, présente une étude comparative entre deux techniques de filtrage actif parallèle par action sélective des harmoniques, afin de minimiser le facteur de distorsion harmonique totale THD, et par conséquence améliorer, le facteur de puissance FP. Les deux techniques sont basées sur le FAP de certaines harmoniques de basses fréquences 5 et 7, dont l’identification des harmoniques de références de la première se fait par le référentiel synchrone de Park dq, et la deuxième se fait par l’approche du Filtre Multi-Variable FMV. Le filtrage actif sélectif des harmoniques du courant de la charge 5 et 7 prises simultanément. Les formes des signaux et les valeurs des THD issues des résultats de simulations numériques (Matlab-Simulink) élaborés mettent en évidence l’efficacité et la meilleure technique de ce type de filtrage. Voir les détails
Mots clés : FP, THD, harmoniques, FMV, référentiel synchrone de Park d-q, FAP
Combination between STFT and DWT for Fault Detection and Diagnosis in Rotating Machinery by Vibration Monitoring
Signal analysis with fixed time-frequency resolution, such as the Short-Time Fourier Transform(STFT), is a common tool for many industrial applications in rotating machinery condition monitoring allowing effective implementation via the Fast Fourier Transform (FFT).However, the fixed time-frequency resolution of the STFT can lead to the undesirable smearing of events in both timeand frequency. In this paper, we propose a combination between STFT and DWT for the faults detection and diagnosis in a rotating machine. An implementation procedure for the fault detection and diagnosis in rotating machinery at real-time has been presented out in this paper. The experimental results confirm that this procedure serves as a good tool to fault detection and diagnosis in rotating machinery. Voir les détails
Mots clés : I. Atoui, R. Boulkroune, A. Grid, and R. Saidi
Structural Characterization of TiO2 Thin Films on Aluminum Substrates Obtained by Sol-Gel Process
In this work, TiO2 thin films were prepared by dip-coating Sol-Gel process on aluminum substrates. The deposition process allows having layers of good quality (homogeneity, adhesion). The layers thus prepared have undergone annealing at 550 °C for 1\2h and 2h and characterized by different techniques: Differential scanning calorimetric (DSC), X-ray diffraction (XRD), Raman spectroscopy and scanning electronic microscopy (SEM). The DSC curve shows an exothermic peak corresponding to the crystallization of TiO2. XRD and Raman results indicate that TiO2 layers deposited on aluminum crystallize in tetragonal anatase phases of TiO2 by annealing at 550 °C, the grain size depend on the annealing time. Then observing the cavities of TiO2 randomly formed on aluminum by SEM. Voir les détails
Mots clés : Aluminum substrate, TiO2Thin films, anatase
Moment matching estimation method for an asymmetric generalized Gaussian mixture model
In this paper, the r-order moments of the asymmetric generalized Gaussian (AGG) distribution is originally computed. Then, the moment matching method associated to the expectation-maximization (EM) algorithm is used to estimate the AGG mixture model parameters. The obtained results are comparable to those of the maximum likelihood method which, however, manipulates high nonlinear equations (piece-wise function, log, etc.), contrarily to the proposed method where the calculus is less difficult. Voir les détails
Mots clés : Asymmetric generalized Gaussian distribution, finite mixture model, moment matching method, EM algorithm
Graphene: Material description, elaboration methods and main properties
Nanomaterials containing carbon have open new ways for the development of interesting and innovator applications. Among these materials, the mother of all graphite shapes, the graphene, is becoming a material of a great interest because of their remarkable properties (physical, chemical and electrical ones). Currently, the graphene presents a great promise for potential applications in many technological fields such as: sensors, composites, transparent conducting films, solar cells, storage medium of gas, saturable absorber for pulsed laser etc.The development of graphene is a technological challenge; the methods of current production are required with a balance between the facility of the production and the quality of materials. Our present work consist on a digest of the most significant works and protocols presented by the scientific community. It selects ones which ensure a graphene with optimal properties; it also discuss the main physical and chemical phenomenon responsible of the graphene formation. Solvothermal technique is an interesting way to synthesize graphene sheets. Firstly Graphene Oxide (GO) is elaborated, followed by its reduction in different solvents (for example: hydrazine, L-glutathione, Dimethylhydrazine, aluminum powder, etc.). This last approach is regarded as more suitable because of its simplicity, reliability, adequacy on a large scale and production at low cost. Voir les détails
Mots clés : Graphene, solvothermale technique, Chemical reduction
Modelling, Faults Detection and Diagnosis of Squirrel-Cage Self Excited Induction Generator for Isolated Wind Energy Conversion System
The condition monitoring of the Squirrel-cage Self-Excited Induction Generator (SEIG). can significantly reduce the costs of maintenance, prevent the unscheduled downtimes and make the best maintenance decisions for isolated Wind Energy Conversion Systems (WECS). On the other hand, growing attention has been paid to fractional calculus theory in practical control field for many industrial applications. In this paper, an on-line diagnostic procedure for stator and rotor faults in the squirrel SEIG of isolated wind energy conversion system is presented. This diagnostic procedure is based on stator current analysis by FFT. A generalized model of the squirrel-cage SEIG is developed to simulate both the rotor and stator faults taking iron loss, cross flux saturation into account. Additionally, a new control strategy is proposed for the fixed operation of the wind turbine, based on fractional PIλ controllers. Voir les détails
Mots clés : Issam Attoui, Amar Omeiri
FAULT DETECTION AND DIAGNOSIS IN ROTATING MACHINERY BY VIBRATION MONITORING USING FFT AND WAVELET TECHNIQUES
Rotor unbalance is the most cause of machine vibration that reduces the life of the rotating machine. On the other hand, vibration monitoring is reported as an interesting technique for the rotating machinery condition diagnosis.This paper considers the Wavelet Transform (WT) and FFT of vibration signals for detect and diagnose of unbalance faults in rotating machinery. The fault condition and location of faults are success fully detected by WT-FFT for non-stationary vibration measurements obtained from accelerometer sensors. Experimental studies on the rotating machine include faulty rotor with different rotational speeds has been carried out in this paper. These experimental results confirm that WT-FFT serves as a good tool to online faults detection and diagnosis of rotating machines. Voir les détails
Mots clés : Rotor unbalance, fault detection and diagnosis, Rotating machinery, WAVELET TECHNIQUES
Impact Majeur du Condensateur de Filtrage sur la Qualité d’un Filtre Actif Parallèle Contrôlépar l’Approche d’un FMV
Dans cet article, nous présentons l’impact majeurd’un condensateur de filtrage sur la qualité du filtrage d’unFiltre actif parallèle FAP contrôlé par une technique évoluéedénommée filtre multi-variable FMV, ce dernier se base sur latransformée de Concordia, et fait l’extraction sélective ou globaledes courants harmoniques de références, et par conséquencefaisant leur filtrage globale des ces harmoniques, par unecommande approprié de l’onduleur de tension, soit hystérésis ouMLI, on fait l’injection des courants harmonique au réseau à finde minimiser le taux de distorsion harmonique et parconséquences amélioré son facteur de puissance de réseauxélectrique. Les résultats de simulation numérique dansl’environnement Matab-Simulink d’un système de puissance PD3à diode débité sur une charge contient un grand condensateur defiltrage montrent bien l’impact majeur de cette condensateur surla qualité du courant du réseau filtré. Voir les détails
Mots clés : FAP, harmoniques, FMV, Système de Puissance PD3, Facteur de Puissance, MLI, Hystérises, Condensateur de Filtrage, Filtrage Globale
Modélisation d’une chaine de conversion d’énergie éolienne Basée sur une machine asynchrone à double alimentation.
Actuellement, les éoliennes utilisant une génératrice asynchrone à double alimentation « GADA » sont les plus utilisées pour production de l’énergie électrique. Notre travail consiste dans la première étape à la modélisation de la chaine de conversion de l’énergie éolienne où la génératrice asynchrone à double alimentation fonctionne à vitesse variable. Et, en seconde étape, on considère le réglage des puissances active et réactive afin d’assurer un fonctionnement optimal. A cet effet, une commande vectorielle est appliquée pour assurer un découplage entre ses grandeurs électromécaniques. Ces deux parties, sont développées et programmées sous Matlab/Simulink a fin d’analyser par simulation le comportement de la chaine dans les différant domaines de fonctionnement possibles. Les résultats de simulations obtenus seront présentés et analyser. Voir les détails
Mots clés : Aérogénérateur, Turbine éolienne, GADA, MLI à bande d’hystérésis.