Liste des documents
Electrochemical and spectroscopic characterization of poly (bithiophene + 2-methylfuran) copolymer.
In this work, Poly(bithiophene + 2-methylfuran) copolymer is successfully achieved by an electrochemical polymerization of two monomers, bithiophene and 2-methylfuran in acetonitrile containing lithium perchlorate. The resultant copolymer was characterized via cyclic voltammetry, impedance spectroscopy, UV-visible, scanning electron microscope, conductivity and photocurrent measurements. The cyclic voltammetry study showed two redox couples characteristic of Poly (bithiophene + 2-methylfuran) copolymer. The impedance spectroscopy study revealed that the resistance of the copolymer ?lm increases with the addition of 2-methylfuran. The photocurrent measurement showed good photoelectrochemical properties, making this copolymer an ideal candidate for photovoltaic cell applications. Voir les détails
Mots clés : Electrochemical polymerization, copolymer, polybithiophene, poly2-methylfuran, morphology, photo-electrochemical properties.
Computational Investigation of Droplets Behaviour inside Passive Microfluidic Oscillator
Recently, modeling immiscible fluids such as oil and water have been a classical research topic. Droplet-based microfluidics presents a unique platform for mixing, reaction, separation, dispersion of drops and many other functions. In this paper, we suggest a numerical CFD study of microfluidic oscillator with two different lengths of feedback loop. In order to produce simultaneous droplets of gasoil on water, a typical geometry that includes double T-junction is connected to the fluidic oscillator. Droplets production is computed by volume-of-fluid method (VOF). Flow oscillations of droplets were triggered by the Coanda effect of jet flow. The aim of work is to get a high oscillation frequency in the output of this passive device, the influence of hydrodynamics and physics parameters on the droplets frequency in the output of our microsystem is also investigated, the computational results show that, the length of feedback loop, operating pressure and interfacial tension have a significant effect on the droplets dynamic inside microfluidic oscillator. Across the range of low Reynold number, the droplets generation and its dynamics have been accurately controlled by adjusting applying pressure ratio of two phases. Voir les détails
Mots clés : Droplet, microfluidics, fluidic oscillator, CFD and VOF (volume of fluid method).
Structural modification, photoluminescence, andmagnetic property enhancement with Er3+ doping,of sol–gel TiO2 thin films
Nanocrystalline undoped and Er3+ doped TiO2 thin films were prepared by sol–gel dip-coatingtechnique onto glass substrates. Post-deposited films were annealed at 450 °C for 1 h. Differentialscanning calorimetric analysis showed that undoped film crystallization occurred at 339 °C, whileit appears at lower temperature for Er:TiO2. X-ray diffraction and Raman spectroscopy resultsindicate that the films crystallize only into anatase phase, and the crystallite size decreases from24.3 to 21.16 nm with increasing Er3+ doping ratio. The photoluminescence (PL) spectra arecomposed of two broad peaks at 520–570 nm and 640–680 nm assigned to (2H11/2, 4S3/2)–4I15/2 and4F9/2–4I15/2 transitions of Er3+ ions, respectively. PL emission intensities increase gradually raisingthe erbium doping ratio. Vibrating sample magnetometer results of undoped TiO2 thin films reveala ferromagnetic behavior at room temperature and erbium doping leads to an enhancement of thesaturated magnetic moment (Ms). Voir les détails
Mots clés : TiO2 doped Er3+, Sol–gel, Photoluminescence, Magnetic Properties
Adaptive backstepping control using combined direct and indirect σ-modification adaptation
In this paper, by using the dynamic surface control technique, an adaptive backstepping controller using combined direct and indirect σ-modification adaptation is proposed for a class of parametric strict-feedback systems. In this approach, a σ-modification parameter adaptation law that combines direct and indirect update laws is proposed. At first, the x-swapping identifier with a gradient-type update law is presented for a class of parametric strict-feedback nonlinear systems. Next, the main steps of the controller design for a class of nonlinear systems in parametric strict-feedback form are described. The closed-loop error dynamics is shown to be globally stable by using the Lyapunov stability approach. Finally, simulation results for a single-link flexible-joint robot manipulator are given to illustrate the tracking performance of the proposed adaptive control scheme. Voir les détails
Mots clés : Backstepping control, direct and indirect adaptive control, adaptive dynamic surface control, Lyapunov stability, flexible joint manipulators
Microstructural Study of Thin Films CuFe Obtained by ThermalEvaporation of Nanostructured Milled Powde
Commercial copper and iron powders were used as starting materials. These powderswere mechanically alloyed to obtain Cu(100-x) Fex supersaturated mixture. The milling duration waschosen in such a way as to obtain a nanostructured mixture and to form a supersaturated solidsolution of CuFe; the powder mixture was used to deposit CuFe on a glass substrate.The elaboration of our films has been carried out using thermal evaporation process (physical vapordeposition) under 1 × 10-6 mbar vacuum from an electrically heated tungsten boat, using thesupersaturated solid solution Cu(100-x) Fex powder obtained by mechanical alloying. The filmsdeposition has been done on glass substrates. In this study, we present the composition effect on thestructural and magnetic proprieties of Cu(100-x) Fex powder and thin films. The chemicalcomposition, structural and magnetic proprieties of milled powders and thin films were examinedby SEM, TEM, XRD, XRF and VSM. Voir les détails
Mots clés : thin film, CuFe Solid Solution, microstructure, DRX, MET, VSM
Structural, microstructural and thermal characterization of Fe- doped ZnO powder nanostructures prepared by mechanical alloying
ZnO powder nanoparticles mechanically alloyed were doped with iron to investigate their structural and microstructural properties using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) for examined 1% Fe doped ZnO. The ZnO starting pure powder exhibited a hexagonal crystal structure with space group p63mc of ZnO, however with the introduction of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains are found milling time dependent. Voir les détails
Mots clés : ZnO, XRD, DSC
Conception, Réalisation, Modélisation et Caractérisation Expérimentale d'un Transformateur de Tension de Type Rosen
Les travaux de recherche entrepris dans ce mémoire s'inscrivent dans le cadre de la modélisation et la caractérisation expérimentale des transformateurs de tension piézoélectriques. A partir de la théorie linéaire de la piézoélectricité, une modélisation analytique unidimensionnelle du transformateur de Rosen basée sur un circuit électrique équivalent inspiré des schémas de Mason des résonateurs piézoélectriques est menée. Les caractéristiques électriques obtenues après exploitation de ce circuit sont validées d'une part par une modélisation numérique 3D issue d'un logiciel de calcul par éléments finis (Comsol- multiphysiques) et d'autre part par une caractérisation expérimentale montrant un bon accord entre eux. De ces études, il ressort que les principales caractéristiques du transformateur (gain, puissance, rendement, etc...) sont fortement dépendantes de la fréquence, donc du mode de vibration, des dimensions, de la charge électrique et des constantes du matériau utilisé. Un écart de 30% entre la théorie et l'expérimental est toutefois constaté. Cet écart a été réduit en utilisant deux méthodes d'optimisation : l'algorithme simplexe qui permet d'ajuster les constantes du matériau et la méthode d'impédancemetrie qui permet de déterminer expérimentalement les valeurs des éléments du circuit équivalent dont les capacités du primaire et du secondaire du transformateur. Ainsi, pour certains résultats, l'écart a pu être réduit à 1%. Mots clés : transformateur de Rosen, modélisation 1D, modélisation 3D, caractérisation expérimentale. Voir les détails
Mots clés : Piezoelectricité, Transformateur de Rosen, Modèle 1D, Modèle 3D, caractérisation expérimentale
Extraction des colorants par membrane liquide émulsionnée et Application des plans d’expériences
Our work is based on the study of an extraction method for the treatment of water contaminated with cationic and anionic dyes (methylene blue, yellow99 acid and orange10 acid), using an emulsified liquid membrane. This method, which noted as a new separation technique, powerful booming and seems to open great prospects of technological achievements. An optimization of the different parameters which influence the stability of the membrane and the BM extraction was examinated. We also used the test planning technique that is a design of experiments to achieve the method of extraction by emulsified liquid membrane giving better extraction efficiency. To conduct this study we used initially screened plan Plakett-Burman, made to select the most influential factors on the dye extraction yield of AY 99 AO 10 in an aqueous solution. These factors are then studied by the response surface methodology Box Benken. The extractants used are: HDEHP and l’aliquat336, SPAN 80 as surfactant, hexane and cyclohexane as solvent. The extraction yields obtained for the dyes (BM, AY99 and AO10) are respectively: 99.9%, 99.98% and 99.9% higher, using an internal solution of H2SO4. Voir les détails
Mots clés : extraction, stabilité, membrane liquide émulsionnée, Colorants, plans d’expériences.
Modélisation et Commande d’une Chaine de Conversion d’Energie Renouvelable.
The imminent exhaustion and uncontested from fossil resources has motivated researchers worldwide to find alternatives to such resources in order to ensure equilibrium in energy requirements, which continues to grow. So it is in this context fits the work presented in this thesis. It concerns the modeling and the control of wind energy conversion chain based on a double fed induction machine (DFIG). An indirect control of active and reactive power ensuring optimal functioning is presented. Furthermore, because of inevitable variations of the parameters a fuzzy adaptive control and neural control have been proposed to evaluate the performance and robustness of the control overlooked the parametric variations. Voir les détails
Mots clés : éolienne, MADA, Commande adaptative, réseau de neurone, logique floue, performances.
DIAGNOSTIC DES DEFAUTS MECANIQUES ETELECTROMAGNETIQUES SUR LES AEROGENERATEURS ÀBASE DE MACHINE ASYNCHRONE À DOUBLE ALIMENTATION
The use of doubly-fed induction machine in wind conversion systems occupies a verysignificant place. Therefore, the diagnosis of potential faults in these machines is nowadays a majorpriority for the industrialists in particular and for the scientists in general.Currently, the requirements of renewable energy, in terms of wind conversion system, is growingup due to the availability of the industrial processes became an economic argument than a meremarketing. However, the monitoring and the diagnosis require at the same time a better functionaland behavioral knowledge of the system in order to highlight, in an early stage, the conditionsleading to a failure situation.In this thesis, we are interested of the fault of the doubly-fed induction machine. Firstly, we willdevelop the doubly-fed induction machine model that can to represent the machine behavior invarious function modes and structural imbalances. Among the faults, the fault of static, dynamic andmixed eccentricity, and the phases openings faults, and the stator or rotor inter-turns short-circuit areconsidered.A spectral analysis of stator currents of the doubly-fed induction machine taken at the time ofthese faults will be presented subsequently.In the last part, we will develop an approach of monitoring allowing to obtain information on themachine state, the detection and the localization of the faults. Voir les détails
Mots clés : défauts mécaniques, électromagnétique, aérogénérateurs, GADA, modélisations