Liste des documents
CORROSION RESISTANCE EVALUATION OF DUPLEX STAINLESS STEEL 2205 INACIDIC AND CHLORIDE ENVIRONMENT
This work is mainly devoted to the study ofelectrochemical performance anticorrosive of stainless steel,2205 duplex by immersion in different study at roomtemperature and different concentrations of corrosive speciesenvironments. The chemical composition and morphologicalstructure of the stainless steel material, respectively, arecharacterized by X-ray fluorescence and by optical microscopy.Electrochemical tests are performed in three electrolytes,namely sodium chloride (NaCl) at 3 %, hydrochloric acid (HCl)3% and hydrochloric acid (HCl) 5%. The techniques used inthis study are potentiometric open circuit (OCP), linearpolarization (LP) and electrochemical impedance spectroscopy(EIS). The impedance spectra and the current - potential curvesobtained allowed the estimation of the rate of corrosion indifferent electrolytes and showed a change of the polarizationresistance (Rp) and the degradation kinetics of this materialdepending on the composition of the study areas. Voir les détails
Mots clés : duplex stainless steel, Pitting corrosion, PREN, Electrochemical impedance spectroscopy
Room temperature and seed layer free electrochemicalo elaboration of ZnO-nanowires and thin films highly c-axis oriented
In this present work we report the electrodeposition at room-temperature and without seed-layer of well-aligned and highly c-axis oriented ZnO nanowires and ZnO thin films.The electrodeposition was performed in a classical three electrodes electrochemical cell, under potentiostatic mode and without stiring. The substrates used were molybdenum foil, ITO-glass and aluminium foil.The electrolytic bath was initially composed of 5mM ZnCl2, 5mM H2O2 and 100 mM KCl as supporting electrolyte, the pH value being about 6.8. The ZnCl2 concentration was progressively modified, and this gives morphological modification of the deposits.Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy to give information about microstructure, morpholohy and crystalline phases.The morphology observed by SEM showed that the increasing of ZnCl2concentration will increase the average diameter of the ZnO-nanowires, until obtaining thin films. DRX spectra confirm the elaboration of ZnO-deposits with highly c-axis orientation.These important result will promote the facile use of electrodeposition to elaborate ZnO nanostructures and thin films for several technological applications as nanogenerators, SAW devices, DSSC, ETA solar-cells, water-splitting, sensing, etc. Voir les détails
Mots clés : ZnO, nanowires, thin film, electrodeposition
Efficient Detection Criteria for Model Order Selection of Interferometric SAR signal corrupted by multiplicative noise with a new penalty function
In this paper the problem of estimating the number of components in a multibaseline interferometric synthetic aperture radar (InSAR) signal, corrupted by complex correlated multiplicative noise in the presence of the layover phenomenon, is addressed. Research tasks were carried out by using the information theoretic criteria (ITC). It has been shown that among the ITC, one of the efficient detection criteria (EDC) achieves generally the best performance. We propose then a new penalty function for EDC. Voir les détails
Mots clés : Model order estimation, information theoretic criteria, multiplicative noise, SAR interferometry
STRUCTURAL AND MAGNETIC PROPRIETIES OF NANOSTRUCTURED Fe80CO20 POWDERS ELABORATED BY MECHANICAL ALLOYING PROCESS.
Nanostructured disordered iron–cobalt alloy of Fe–80% Co–20% composition was prepared by mechanical alloying of the elemental powders in a high-energy ball milling. The transformations occurring in the material during milling were studied with the Eddy current characterization for having the relationship with impedance, lattice parameters and crystallite size. The transformation of the phase depends upon the milling time. With the increase of milling time all Co atoms became dissolved in the bcc Fe and the final product of the MA process was the nanocrystalline Fe (Co) solid solution with a mean crystallite size of about 15 nm. Scanning electron microscopy (SEM) was employed to examine the morphology of the samples as a function of milling times. Magnetic properties were investigated and related to the microstructural changes. Voir les détails
Mots clés : Mechanical Alloying, Nanostructure materials, Eddy Current, Magnetic and mechanical properties
Elaboration Et Caractérisation D’un Multi-Matériaux (WC/W2C-W-Ni) Infiltre Par Un Bronze Industriel (Cu-Sn-Ni): Application Aux Outils de Forage Imprégnés.
L’élaboration et la mise en œuvre de nouveaux matériaux plus performants, possédant une très grande résistance à l’usure et à l’érosion (compromis dureté-ténacité) nous mènent à penser au procédé d’infiltration qui offre une grande possibilité de formes pour les géométries complexes. Notre travail consiste à élaborer un multi matériaux issu d’un mélange de poudres libres (sans compactage) matrice (W2C/WC-20W-20Ni) avec les infiltrant (Cu-15Sn-5Ni) par le procédé d’infiltration industriel SILP et la caractérisation de ce multi-matériau par les différentes techniques de caractérisation disponible au laboratoire LSGM seront utilisées. Dont Nous Citons Particulièrement, l’ATD, la microscopie optique (métallographie-analyse d’image), le MEB couplé à l’EDS (analyse Ponctuelle, profils de concentration et cartographies) et la caractérisation mécanique (Dureté HRA et micro-dureté HV0.1). Afin de mettre évidence essentiellement l’influence des différentes proportions de nickel et sa réactivité avec l’infiltrant. Voir les détails
Mots clés : procédé SILP, matrice, poudres libres, frittage, multi-matériau, infiltration spontanée.
Support Vector Machine Based on Firefly Algorithm For Bearing Fault Diagnosis
The fault diagnostics and identification of rolling element bearings have been the subject of extensive research. It consists of two major parts: vibration signal feature extraction and condition classification for the extracted features. In this paper, feature extraction from faulty bearing vibration signals is performed by signal’s time-varying statistical parameters. In this way, a 7-dimensional vector of the vibration signal feature is obtained. After feature extraction from vibration signal, the support vector machine (SVM) was applied to automate the fault diagnosis procedure. To improve the classification accuracy for bearing fault prediction, Firefly Algorithm (FFA) is employed to simultaneously optimize the SVM kernel function parameter and the penalty parameter. The results have shown feasibility and effectiveness of the proposed approach. Voir les détails
Mots clés : Condition monitoring, Firefly Algorithm, Roller Bearing, Statistical parameters, Support Vector Machine.
Autoregressive Modeling and PCA Preprocessing to Support Vector Machines Based on PSO for Bearing Fault Diagnosis
In this paper a method for fault diagnosis of rolling bearings is presented. It consists of two major parts: vibration signal feature extraction and condition classification for the extracted features. In this paper Autoregressive Modeling followed by Principal Components Analysis (PCA) was introduced for feature extraction from faulty bearing vibration signals. After extracting feature vectors by AR-PCA, the support vector machine (SVM) was applied to automate the fault diagnosis procedure. To improve the classification accuracy for bearing fault prediction, particle swarm optimization (PSO) is employed to simultaneously optimize the SVM kernel function parameter and the penalty parameter. The results have shown feasibility and effectiveness of the proposed approach. Voir les détails
Mots clés : Autoregressive Modeling, Principal Components Analysis, Support vector machine, Particle Swarm Optimization, Wavelet Packet, Fault Diagnosis, Roller Bearing.
Feature Extraction and SOM for Bearing Fault Diagnosis
In this paper a method for fault diagnosis of rolling bearings is presented. It consists of two parts: vibration signal feature extraction and condition classification. The aim of the first step is the extraction of the relevant parameters; the proposed technique consists of preprocessing the bearing fault vibration signal using a combination of the signal’s Kurtosis and discrete wavelet transform (DWT). The Self-organization Map (SOM) is used to accomplish the classification step and automate the fault diagnosis procedure. The results have shown feasibility and effectiveness of the proposed approach. Voir les détails
Mots clés : Condition monitoring, Discrete wavelet transform, Fault Diagnosis, Kurtosis, Roller Bearing, Rotating machines, Self-organization Map, Vibration measurement.
Direct adaptive backstepping control with tuning functions for a single-link flexible-joint robot
In this paper, direct adaptive backstepping control with tuning functions approach for a single-link flexible-joint robot model is proposed. The proposed approach of adaptation is based on the tracking error based parameter adaptation law. First, the direct adaptive backstepping control with tuning functions is applied for a class of nonlinear systems in parametric strict-feedback form to avoid overparametrization. Next, the main steps of the controller design for a single-link flexible-joint robot manipulator model are described. The stability of the proposed controller is studied by using the Lyapunov functions. Finally, the simulation results are given to demonstrate the performance of the proposed approach. Voir les détails
Mots clés : Single-link flexible-joint robot, Backstepping control, direct adaptive control, tuning functions, direct adaptation
Indirect adaptive backstepping control by using the virtual controls filtering
In this paper, by using the dynamic surface control technique, an indirect adaptive backstepping controller based x-swapping identifier with a gradient-type update law is proposed for a class of parametric strict-feedback nonlinear systems. The main steps of the controller design for a class of nonlinear systems in parametric strict-feedback form are described. Then, the closed-loop error dynamics is shown to be globally stable by using the Lyapunov stability approach. Simulation results for a single-link flexible-joint robot manipulator are given to illustrate the performance of the proposed controller. Voir les détails
Mots clés : Backstepping control, adaptive control, dynamic surface control, Lyapunov stability, Single-link flexible-joint robot