Liste des communications
STUDY OF ALLOY Zn-Fe ELECTRODEPOSITION FROM CHLORIDE ELECTROLYTE
This study show that of the alloy zinc-iron electrodeposited on steel by electrodeposition from chloride acid electrolytes, the chloride electrolyte more advantages than the electrolyte sulphate. Furthermore the influence of various parameters(current densities, [Zn(II)]/[(Fe(II)] concentration ratio in electrolyte and the nature of additives: saccharin Na(S) and glycerol (J) …) on the morphology and the structure of the deposits is discussed. EDS Analysis making it possible to determine the composition of alloysobtained gives an increase in Fe content with the density of current.For high [Zn(II)]/[(Fe(II)]~1/9 concentration ratio in solution, Fe content remains constant independently of current densities. In the presence of brightener "J.S", the deposit contains a weaker content iron, which is in agreement with measurements of the cyclic voltammetry showing that the " J.S " inhibits the electroreduction of iron. X-ray diffractograms realized for Zn-Fe alloys, lead to thepresence of the three phases of the alloy Zn-Fe: η, ζ and Γ. Voir les détails
Mots clés : electrodeposition, Alloy, Zn-Fe, micrograohy, XRD, additive, chloride, electrolyte
Numerical Analysis of a Microstrip MIMO Antenna Array
In this paper, we present a simulation anddesign of a microstrip MIMO antenna array. The basic configuration is a microstrip patch antennas consist of ametallic patch on one side of the dielectric substrate with aground plane on the other side. The antenna system consists of2x4 radiating elements of similar geometry printed on asubstrate. The designed antenna is excited using the microstripfeeding .The theoretical analysis is based on the finitedifferencetime-domain (FDTD) method. In these analyses thecharacteristics of the MIMO antenna arrays are presented interms of return loss, mutual coupling, gain and radiationpatterns. The proposed antenna is simulated by using HighFrequency Structure Simulator (HFSS). The designed antennais suitable for MIMO systems operating for several WLANapplications. Voir les détails
Mots clés : Microstrip antenna, MIMO system, Resonant Frequency, Radiation Pattern, FDTD Method.
Numerical simulation of the fracture behavior of aluminum alloy welds: Al6061-T6
Welding is used to realize permanent assembly in mechanical structures to assure the continuity of the parts to be assembled contrary to the other assembly techniques which have physical or chemical discontinuities. Generally, crack evolution depends on several intrinsic and extrinsic parameters of material. The aim of this work is to analyze the severity of crack defects on the mechanical behavior of Welded joints. The cracks are considered located in the weld metal. The J-integral method was used to analyze the fracture behavior of these structures by the two-dimensional finite element method using Cast3M code. The effect of the mechanical properties, the mismatching and the crack size on the J-integral values was highlighted. A good correlation between the FEM simulations and the literature analysis results was observed. We note that the loading mode affects directly the J-integral value and consequently on the mechanical behavior of the welded joint. Voir les détails
Mots clés : J-integral, welding, fracture, plastic behavior, finite element analysis.
Ultra-Wideband Antenna Integrated with Dual-Band Dielectric Resonator
In this paper, we proposed a novel integrated ultrawideband(UWB) monopole antenna with dual-band antenna.The antenna consists of planar rectangular with semi-ellipticalbase and a rectangular dielectric resonator (DRA) with dualbandoperation. Both of them are excited via coplanar waveguide(CPW) lines. The numerical results show that the planarmonopole provides a -10dB impedance bandwidth between 2GHzand 12 GHz which largely covers the entire UWB spectrum, andthe rectangular DRA operates at two bands; 5.7-6.2 GHz and 8.2-9.7 GHz. The electromagnetic analysis is carried out using CSTmicrowave studio and HFSS software. The numerical results,obtained from simulation, are given and compared in terms of Sparameters and radiation patterns. Voir les détails
Mots clés : CPW-fed line, dielectric resonator antenna (DRA), Dual-band antenna, Integrated antennas, UWB antenna.
Comportement de la recristallisation statique de l’acier inoxydable ferritique type 430
Le comportement de la recristallisation statique d’un acier inoxydable type 430 a été examiné en utilisant des essais de laminage à chaud à une seule passe. Les essais de laminage à chaud étaient réalisés à des températures de C0870, C0950 et C01000 avec des réductions de 25 à 50% à une vitesse de déformation de 3,3S -1. Le volume recristallisé augmente avec l’augmentation de la réduction par laminage à chaud et le temps de maintien après laminage. Le processus de la restauration dynamique qui opère pendant le travail à chaud à une vitesse de déformation constante égale à 13 , 3Set à des températures égales à C0870et C01000est la restauration dynamique. Le microscope électronique à transmission montre que les basses températures de déformation (C0870) produisent des sous-joints irréguliers avec un intérieur de sous-grain très dense par les dislocations. La nucléation des nouveaux grains semble être associée avec les joints de grain initial principalement les bords de grain. Les équations empirique précises liant les variables de déformation et la taille de grain initial aux temps de recristallisation et la taille de grain recristallisé ont été développées avec succès et peuvent être utilisé pour la simulation de laminage à chaud. Voir les détails
Mots clés : Acier inoxydable type 430, laminage à chaud, restauration dynamique, restauration statique, recristallisation statique
Contrôle des fissures des placages des bois Algériens
En Algérie, une partie non négligeable du bois utilisé actuellement dans l’industrie provient de l’importation. Ce fait est regrettable car l’Algérie pourrait couvrir une partie de ses besoins et ce notamment grâce à de fortes ressources en chênes Zéen et Afarès disponibles en Kabylie. Ceci aurait l’avantage d’utiliser et de gérer une ressource alors laissée à l’abandon. Le but de ce travail, d’étudier l’influence de la température d’étuvage sur les efforts de coup et sur la qualité de placage leur de déroulage pour la fabrication de contreplaqué et LVL. Des expériences ont été réalisés sur la microdérouleuse pour déterminer l’évolution des efforts de déroulage en fonction du la température du bois. Et aussi, des essais sur le SMOF (Système de Mesure de l'Ouverture des fissures) effectués, afin de mesurer la profondeur et la fréquence des fissures par rapport à l’augmentation de la température Voir les détails
Mots clés : Chêne zéen, Chêne Aferés, étuvage, efforts de coupe, fissures, fréquence
Performance Evaluation of Omni-Directional Circular UWB Disc Antenna Conformed on a Cylindrical Surface
The cylindrical geometry can offer certain desirable antenna characteristics that are not provided by planar elements. In this paper a conformal omni-directional circular disc antenna which is mounted on a cylindrical surface feeding by a microstrip line is presented and proven to operate equally well compared to its planar rival. The return losses and the radiation pattern characteristics of the proposed antenna are studied using the commercially available electromagnetic software CST studio suiteTM , and high frequency structure simulator HFSS. Compared with the planar shape and the cylindrical conformal antenna existing, the proposed structure possesses an important wideband which is needed for many wearable electronics applications. Voir les détails
Mots clés : Conformal antenna, UWB antenna, CST simulator, HFSS simulator.
Etude comparative entre la cinétique de l’oxydation du phénol par la tyrosinase libre et immobilisée dans le gel d’alginate de calcium
Phenol is known as a toxic compound; therefore, it is necessary to develop an efficiency method to remove phenol from wastewater of industrial effluent. Removing of phenol and its derivatives can be made by different biological and physico-chemical processes. The biological treatment of water containing phenol is currently made by enzymes such as tyrosinase, laccase and peroxidase. The objective of our work is to study the kinetics oxidation of phenol by free tyrosinase (EC: 1.14.18.1) and encapsulated tyrosinase in calcium alginate gel. First of all, tyrosinase is extracted from mushroom (Agaricus bisporus) and its phenolase activity was measured sprectrophotometrically at 400 nm. Mushroom tyrosinase catalyzes efficiently phenol oxidation in solution. A comparative study is made between the different kinetic parameters of free and immobilized tyrosinase. The Michaelis-Menten constant (Km) for the immobilized enzyme (0.9 mM) is approximately twice higher than that of the free enzyme (0.55 mM), suggesting that alginate matrix limits the rate diffusion of substrate and product. In contrary, the maximal velocity (Vmax) of the enzyme immobilized is 20-fold lower than that of the free enzyme. The effects of pH, temperature, enzyme and substrate concentration, alginate beads size and operational stability on the initial rate of phenol oxidation were studied. The pH and temperature optima are shifts from 7.6 to 5.6 and from 45 to 55°C, for free and immobilized tyrosinase, respectively. The immobilized enzyme seems to be more thermostable than the free enzyme and its activity is maximal when immobilized in alginate beads with a diameter of 2.6 mm. Voir les détails
Mots clés : Agaricus bisporus, Tyrosinase, Kinetics, Phenol, Oxidation, alginate, Immobilization.
Interaction des ondes acoustiques guidées avec la corrosion dans des structures tubulaires
Dans ce travail, un modèle hybride qui combine la méthode des éléments finis et la décomposition modale est utilisé pour décrire l’interaction des ondes acoustiques guidées avec des défauts sous forme de points disposés de façon aléatoire sur des structures tubulaires. La méthode des éléments finis est utilisée pour décrire la région entourant le défaut, alors que la décomposition modale est utilisée pour la mise en évidence des ondes transmises par la zone endommagée et la confirmation du phénomène de la conversion du mode Voir les détails
Mots clés : Ondes guides, Structures tubulaires, Eléments finis, Décomposition modale
Experimental Investigations of an Omni-directional Dielectric Resonator Antenna for UWB Systems
In this paper, a new dielectric resonator antenna(DRA) is presented and investigated for ultra wideband (UWB)applications. The UWB antenna has a U-shape and excited by amicrostip fed monopole. The proposed antenna was simulatedand designed using two electromagnetic simulators. To validateour design, a prototype antenna was fabricated and measured.From the measurements, the U-shaped DRA has a 117.6 %impedance bandwidth (from 2.94 GHz to 11.34 GHz, for returnloss below -10 dB, largely covering the UWB spectrum band).Moreover, the proposed antenna provides an omni-directionalradiation pattern. With these features, the present antenna canbe used in ultra-wideband wireless systems. Voir les détails
Mots clés : Dielectric Resonator Antennas, Measurements, Radition Pattern, UWB applications.