Liste des communications
Solid state synthesis of ZnO nanostructures: effect of temperature on the structural and Optical properties
Among the different approaches to synthesize nanostructured ZnO, the solid state synthesis isone of the simplest methods to elaborate the ZnO nanoparticles. In this work we obtainednanostructured ZnO by aforesaid method using zinc nitrate tetrahydrate ZnO(NO3)2 asprecursor. The influence of calcination temperatures as 300, 400, 500 and 600°C, on thecrystallite size and the optical properties was investigated by X-Ray diffraction and UV–visible spectroscopy, respectively. The results obtained by XRD confirm that the diameter ofnanocrystallites was affected by the calcinations temperature. The UV–visible absorbancespectra of the synthesized samples reveals that the calcinations temperature plays a significantrole in the absorption characteristics, and influences the optical band-gap of the samples.Raman and FT-IR spectroscopy were performed to investigate the structural, vibrational andchemical properties of the ZnO nanostructures. Voir les détails
Mots clés : ZnO nanostructure, FTIR, UV-Vis, solid state synthesis
Bayesian Networks-Based Defects Classes Discrimination in Weld Radiographic Images
Bayesian (also called Belief) Networks (BN) is a powerful knowledge representation and reasoningmechanism. Based on probability theory involving a graphical structure and random variables, BN iswidely used for classification tasks and in this paper, BN is used as a class discrimination tool for a set ofweld defects radiographic images using suitable attributes based on invariant geometric descriptors. Testsare performed on a database of few hundred elements where the results are outstanding and verypromising, since they outperform those given by powerful SVM classifiers. Voir les détails
Mots clés : Bayesian networks, weld defects, Geometric descriptors, radiography
Structural and microstructural characterization of Algerian diatomite
Diatomite is a sedimentary rock composed of fossilized skeletons of diatoms which are microscopic unicellular alga. Due to its useful physical and chemical characteristics, it is used in a wide range of industrial applications. Raw diatomite samples were taken from SIG region of Algeria. Chemical composition, morphology, structure and specific surface area are determined by X-ray fluorescence, scanning electron microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and N2-adsorption-desorption analysis, respectively. The XRF results indicate that the raw diatomite is mainly composed of silica (>60%) and CaO (>14%). The XRD pattern reveals a mixture of amorphous silica and crystalline phases such as quartz and tridimite. The surface area, pore volume and pore size are 26.4 m2/g, 0.204cm3/g and 30.82 nm, respectively. Voir les détails
Mots clés : diatomite, characterization, pore, FTIR
FINITE ELEMENT ANALYSIS OF AlN/Si THIN FILM RESONATOR
This paper aim to study the influence of thin film thickness on the surface acoustic wave and reflectivity in AlN/Si resonator with Al electrodes, using finite element analysis. Mode shapes of the device as a function of frequency thickness were presented and results were obtained to optimize the design of SAW thin film devices that can work in high frequency. Voir les détails
Mots clés : Surface acoustic wave, thin film resonator, FEM analysis
Study of composite with metallic matrix WC/W2C- 20W-20Ni realized by spontaneous infiltration of the bronze alloy Cu-30Mn-3P.
The improved performance and duration of an impregnated tool for the mineral drilling requires thorough understanding of the mechanisms involved in the consolidation of powder mixtures in the liquid phase sintering cycle (FPL). The elements used for the manufacture of the active parts of these tools are usually made from mixtures of loose powders based on WC / W-Ni. The spontaneous infiltration process is the most appropriate method offers a big possibility of shapes due to molding. It lets to have considerable density of the metal matrix composite (MMC) constituting the active head and increase its resistance to erosion and abrasion.This work consists to develop a metal matrix composite which can constitute the active part of a drilling tool impregnated by the infiltration of industrial process SILP (Sintering by Infiltration of an appropriate mixture of Loose Powders). The mixture of loose powders (WC/W2C-W-Ni) is infiltrated under hydrogen by a manganese bronze (Cu-30Mn-3P) and then characterized by DTA, optical microscopy, SEM coupled with EDS, HRA hardness and micro-hardness Hv0.1. Voir les détails
Mots clés : Matrix Composite Material (MMC), SILP process, Matrix, Powder Free, alloying element, sintering in liquid phase (FPL), multi-material, physical chemistry.
Analyse Par LA Technique TSDC et la Spectroscopie Infrarouge (FTIR) DU Polactic acid (PLA) au Voisinage de la Transition Vitreuse
Résumé :L'acide polylactique (PLA) se présente comme une alternative viable aux plastiques pétrochimiques pour de nombreuses applications [1]. Il est produit à partir de ressources renouvelables et est biodégradable, se décompose en donnant du H2O, CO2 et de l'humus, la matière organique noire dans le sol. En outre, il possède des propriétés physiques uniques qui le rendent utile dans diverses applications, y compris dans le domaine biomédical mais aussi dans l’industrie comme la fabrication des fibres, des films d’emballages [2]. Dans ce travail nous nous sommes intéressés aux propriétés physico-thermiques de ce matériau et ses propriétés de relaxation en présence de champs électriques. Ce type de travaux reste jusqu’à présent peu développé. L’analyse des courants thermiquement stimulés TSDC ainsi que la spectroscopie infrarouge à transformée de Fourier FTIR ont été utilisées dans notre investigation dans la zone de transition vitreuse de ce matériaux. Les résultats obtenus nous suggèrent dans le cas des renforts de chaines, des applications très intéressantes dans le domaine de l’isolation électrique et l’encapsulation des composants électronique. Ceci offre une alternative écologique dans ce domaine. Voir les détails
Mots clés : Polylactic acid, TSDC, Spectroscopie infrarouge
Commande Predictive non Lineaire d’une Station de Production d’eau Froide à Base de Reseaux de Neurones Artificiels
Cet article présente la commande prédictive non linéaire (CPNL) avec une application sur une station de production d’eau froide . La modélisation de la station a été réalisée à l’aide des Réseaux de Neurones Artificielles (RNA). Le développement des modèles RNA des différents composants de la station à savoir compresseur, évaporateur, condenseur et détendeur ont été réalisés séparément et regroupés par la suite pour donner le modèle complet de la station. L’objectif principal de ce travail est de maintenir les sorties de la commande du système de production proches d’une valeur désirée ou alors de poursuivre une référence donnée par la température d’un produit. Pour cela la commande prédictive non linéaire a été implémenté avec comme modèle interne. Le modèle neuronal développé est validé à l’aide de données entrées/sorties de la station. La commande a été réalisée en utilisant comme variable de commande la température et/ou le débit du fluide frigorigène. Voir les détails
Mots clés : Commande prédictive non linéaire (CPNL), station de production d’eau froide, Réseaux de Neurones Artificielles (RNA)
Vibration-based bearing fault diagnosis by an integrated DWT-FFT approach and an adaptive neuro-fuzzy inference system
The rotating machine, which can be subject to breakdowns or dysfunctions in its time-of-use, represents an essential part in the majority of industrial applications. Hence, their reliability, productivity, safety and availability are very important issues that are imposed to increase production with quality assurance as per given specification at a reasonable cost. Furthermore, because the bearing faults are the most frequent and critical defects in rotating machinery that may have a direct influence on the availability of the machine itself and also on those of the surrounding systems, a particular interest is carried in this paper to the analysis and diagnosis of these defects which can appear in the bearing's ball, inner race and outer race with various fault severity and rotating speed. This paper consists of the application of the Discrete Wavelet Transform DWT and Fast Fourier Transform FFT theories to extract the amplitude of the fundamental bearing defect frequencies in the vibration signal from a rotating machine. These parameters will be used by the Adaptive Neural Fuzzy Inference System ANFIS to automate the fault detection and diagnosis process. Experimental results show that the proposed procedure can classify with precision various types of bearing faults according to the fault location and severity. Voir les détails
Mots clés : bearing faults, vibration signal, Fault Diagnosis, ANFIS, DWT, FFT
NDT CHARACTERIZATION OF NANO-OXIDE
Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength, good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear . In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well known methods for depositing such coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet , nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress . Voir les détails
Mots clés : Nanostructured materials, EDX, MEB, DRX, VSM
Optical characterization of FeCo nanostructured
Fe–Co alloys are important optical and magnetic materials that have been widely used in industry. The material nanostructured has showed a superior magnetic and optic properties Compared to polycrystalline materials. However, optical and magnetic properties of materials nanostructured are affected by their microstructure such as grain size, internal strain and crystal structure. This, studies on synthesis of materials nanostructured with controlled microstructure are obligatory for a significant improvement. MA is a method with a lot of advantage that it can be simply and fabricate large amounts of nanostructured powders in small time. In the present work, starting with two powder mixtures of Fe and Co produced by Mechanical alloying. Voir les détails
Mots clés : optical and magnetic properties, Fe–Co alloys nanostructured