Liste des communications
Etude du Comportement Thermique des Fluides Non-Newtoniens en Ecoulement dans une Conduite à Section Elliptique soumise a un Flux Constant
Dans cette présente étude, nous analysons le comportement thermique d'un écoulement laminaire de fluide non-Newtonien qui obéit à la loi de puissance dansune conduite à section elliptique, soumise à un flux constant à la paroi. L’écoulement est supposé hydro-dynamiquement établi. La résolution numérique est baséesur la méthode dynamique des directions alternées (dADI). L’application de cette méthode nous permettra deréduire le temps de calcul tout en préservant l’affinité desrésultats. L’influence du rapport de forme géométrique sur les échanges thermiques a été étudiée pour trois types de fluide, Newtonien, pseudoplastique et dilatant. La température moyenne, le nombre de Nusselt sont présentés numériquement et graphiquement. Les résultats obtenus montrent une bonne concordance avec lalittérature. Voir les détails
Mots clés : Conduite elliptique, Fluide non-Newtonien, Loi de puissance, Flux constant, dADI
Effects of annealing on the structural and optical properties of ZnO thin films synthesis by spin-conting
Zinc oxide thin films were deposited on microscope glass substrate by spin-coating method,from a precursor solution containing zinc acetate dissolved in methanol. ZnO thin films were obtained after preheating the spin coated thin films at 300 °C for 3 min after each coating. The films, after the deposition of the 9-layer, were annealed in air at various temperatures of 400 °C, 500 °C and 600 °C for 2 h for complete oxidation. The structural and optical properties of ZnO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-visible and photoluminescence techniques in order to observe the influence of thermal annealing. XRD analysis revealed that the annealed ZnO thin films consist of single phase ZnO with wurtzite structure and show the c-axis grain orientation. Increasing annealing temperature increased the c-axis orientation and the crystallite size of the films. FESEM analysis of annealed thin films has shown a completely different surface morphology behavior. UV-vis has shown that the films were highly transparent with average transmission exceeding 80% in the visible range (400–800 nm). The measured optical band gap values of the ZnO thin films were around 3,24-3,28 eV. Photoluminescence spectra revealed the intensity of UV emission (NBE) increased with the annealing temperature. Voir les détails
Mots clés : Spin-coating, Zinc oxide, Annealing, optical properties
Merging discrepancy measures for region-based segmentation results evaluation and comparison: Application to thresholded weld defect radiographic images
This paper presents a new method for evaluating and comparing image segmentation results. This method consists of an association of measures that have the purpose to compute, in the sense of segmentation evaluation, the difference between two regions, one extracted from an ideal segmentation map and the same region obtained with a segmentation algorithm. Those measures take into account many aspects of the miss-segmented pixels as connectivity, compactness, location and their influence on the segmentation result. The new measure which rates the overall segmentation results, is easier to use comparatively to several measures, especially for a machine or an inexperienced user. Voir les détails
Mots clés : Image segmentation evaluation, Discrepancy measures, radiographic images
Impactdes rejets liquide sur les eaux de l’oued Meboudja, Annaba NE Algérie
L’eau est l’élément autour duquel ce maintien la vie, une expansion industrielle et unecroissance alarmante de la pollution des eaux entraîne des difficultés énormes d’alimentationce qui nous oblige à nous inquiéter d’avantage quant à notre santé et conditions de vie, carleurs répercussions s’avère très grave sur notre environnement.Dans ce contexte, nous avons essayé de donner un aperçu détaille sur la pollution de ouedMeboudja (N.E. Algérie) par des métaux toxiques (Fer, Manganèse, Plomb), des matières ensuspension et des huiles-graisses.Les résultats obtenus ont révélé que les eaux de l’oued Meboudja sont très turbides durant leshautes saisons et fortement huileuses pendant les basses saisons. La contamination métalliqueest plus importante vers les eaux avoisinant le complexe sidérurgique avec une dominanceflagrante en fer et à un degré moindre en manganèse.La présence de telle pollution dans ce site naturel est alarmante par le fait que ce dernier sesitue dans une zone urbaine, agricole et surmontant une nappe phréatique sub-affleurante. Deplus, les eaux de l’oued se déversent directement dans la mer méditerranée par le biais d’ouedSeybouse sans traitement préalable. Voir les détails
Mots clés : Oued Meboudja, eau, pollution, rejet, métaux toxiques
Calcul tridimensionnel par la MEF de l’effet des paramètres d’une source thermique lors le soudage TIG de l’acier 304L avec validation.
Le présent travail est porté sur la simulation du comportement thermique des soudures de l’acier 304L, à usage aéronautique. Le calcul est effectué par la méthode des éléments finis tridimensionnel. Le flux thermique du soudage est modélisé par une source de chaleur Gaussienne surfacique de forme bi-elliptique [1, 2]. Une recherche du maillage optimal du calcul est menée. L’effet des rayons du modèle source thermique est étudié sur le comportement des pics de température le long du cordon de soudure. La meilleure combinaison des valeurs de ces rayons est obtenue. Les résultats numériques sont aussi des cycles thermiques à quelques points et des champs thermiques à quelques instants. Une étude des soudures expérimentale de tôles minces bout à bout de cet acier est menée pour valider les calculs numériques effectués. La comparaison des cycles thermiques obtenus par le calcul numérique à ceux obtenus par l’expérience montre une bonne concordance et très bonne validation du modèle développé. Voir les détails
Mots clés : soudage TIG, source gaussienne de chaleur, MEF, 3D
Etude Comparative de la Compensation Active par Action Sélective par l’Approche FMV et Par la Théorie des Puissances Instantanées P-Q
This article presents a comparative study between two methods of active compensation by selective action of harmonics to minimize the total harmonic distortion factor (THD) of the current and voltage of the electric network, and consequently improve the power factor (PF). Both methods are based on the parallel active compensation of certain low frequency harmonics 5 and 7 which identification of the harmonics of references of the first method is through the approach the of Self Tuning Filter (STF) and the second is based on the theory of instantaneous power (P-Q). Selectively active compensation of harmonic current of the load 5 and 7 taken simultaneously Thereafter .The shapes of the signals and values of THD from the results of numerical simulations (Matlab/Simulink) developed demonstrates the efficiency and the best method of selectively active compensation. Voir les détails
Mots clés : PF, THD, Harmonics, Self Tuning Filter STF, Theory of Instantaneous Power PQ.
An Advanced Control Approach for a Shunt Selective Active Power Filter
This paper deals with the design, analysis andsimulation of a three phase three wire shunt selective active powerfilter. It compensates harmonic currents selectively underbalanced supply network. In order to improve, the factor ofpower of the network electric. An advanced control based on amulti-variable filter is adopted. The novelty with the controlapproach developed in this paper is to use a multi-variable filter,which can extract the harmonics of references of the load current,selectively according to the axis of Concordia (α-β). Generally theharmonic in questions are of low frequencies and order 5 and 7.The objective is that the current of the network doesn't containthe harmonics desired to filtered.The shapes of waves and thevalues of the THD of the network current before and after theselective active filtering of the harmonic 5 and 7 from of theresults of numerical simulations under the Matlab/Simulinkenvironment put in evidence the efficiency of this type of activefiltering elaborated. Voir les détails
Mots clés : harmonic, Shunt active power filter, multi-variable filter, THD
Reconstruction of Pulsed Ultrasonic Fields Received by a hydrophone of rectangular aperture by application of inverse methods.
In order to carry out reliable measurements of pulsed ultrasonic fields, the use of a piezoelectric hydrophone as receiver is recommended. However, due the finite size of the receiver aperture the measured acoustic pressure is affected by spatial averaging. The output signal may also be distorted because of the frequency variations of its transfer function. The aim of this work is to deconvolve the spatio-temporal effects of the receiving chain (hydrophone, cable, oscilloscope...) in order to reconstruct the pulsed ultrasonic field with higher spatial and temporal resolution. This constitutes an inverse problem, which has been encountered in various domains of physics. The possibility of deconvolving the spatial effects has been shown for harmonic ultrasonic fields. The present contribution is a generalization of the study to pulsed ultrasonic fields. For that, three methods allowing the inversion of the aperture effect are tested 1) Wiener’s method 2), the power spectral equalization method (PSE), and 3) the maximum a posteriori method (MAP). The obtained results show that the three methods are able to reconstruct the ultrasonic field from the spatially averaged values and the quality of the reconstruction depends strongly upon the SNR, the hydrophone dimensions and the axial distance to the source. Voir les détails
Mots clés : pulsed ultrasonic fields, Wiener’s method, the power spectral equalization method (PSE), the maximum a posteriori method (MAP).
ELECTRODEPOSTION OF ZnO NANOWIRES FOR ENERGY HARVESTING
Zinc oxide is a transparent n-type semiconductor with a direct bandgap ranging between 3.3 and 3.5 eV. Polycrystalline ZnO has found numerous interesting applications such as piezoelectric transducers varistors , phosphors, transparent conducting films, transparent windows or nanostructured electrode for solar cells. ZnO nanostructures such as nanowires (NWs) and nanorods (NRs) showed attractive characteristics for certain applications ZnO, is among the most interesting materials in terms of piezoelectric properties that are relatively large compared to other non-ceramic piezoelectric materials . It also has the advantage of being easily burn which is of great interest for microtechnolog.To get, the ZnO thin films and nanowire must present a good cristallinity with preferential orientation (002) direction. Also, films electrodeposited must have good morphological properties, and NW must show good alignment and have direction of growth perpendicular to the substrate. This work is related to the fabrication of ZnO nanowires and nanrcords at room temperature also we showed the influence of the concentration of ZnCl2 on the morphological and structural properties of the deposits made by electrochemical route (NW and thin films). We made these deposits in an aqueous solution at room temperature and without buffer layer. Voir les détails
Mots clés : ZnO, nanowires, thin film, electrodeposition.
Electrochemical synthesis of ZnO thin film and nanowire for piezoelectric applications
ZnO thin films and ZnO nanowire (NW) having piezoelectric qualities can be used in respectively SAW devices (Surface Acoustic Wave) and nanogenerators. In this work, we are interested in optimizing experimental conditions of ZnO electrodeposition to obtain thin films and nanowire with good piezoelectric performances. To achieve this goal, the ZnO thin films and nanowire must firstly present a good cristallinity with preferential orientation along (002) direction. Also, films electrodeposited must have good morphological properties (not porous and with insignificant surface rugosity), and NW must show good alignment and have direction of growth perpendicular to the substrate. The electrodeposition of ZnO was performed in a classical three electrodes electrochemical cell, under potentiostatic mode and at room temperature. The substrate was a molybdenum foil of 0.1 mm thick and with 99.95% purity. The electrolytic bath was initially composed of 5mM ZnCl2, 5mM H2O2 and 100 mM KCl (supporting electrolyte), pH value being about 6.8. The initial conditions which give a well aligned of ZnO-NW (see fig. 1) were progressively modified in order to obtain a ZnO thin film. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Electrochemical impedance spectroscopy (EIS), to obtain information about microstructure, morphology, composition and electronic properties of the films and nanostructures electrodeposited. Voir les détails
Mots clés : ZnO, nanowires, thin film, electrodeposition, piezoelectric.