Liste des documents
Power control strategy of a photovoltaic system with battery storage system
In this paper, an intelligent approach based on fuzzy logic has been developed to ensure operation at the maximum power point of a PV system under dynamic climatic conditions. The current distortion due to the use of static converters in photovoltaic production systems involves the consumption of reactive energy. For this, separate control of active and reactive powers using a proportional-integral controller is applied. Using batteries for energy storage in the photovoltaic system has become an increasingly promising solution to improve energy quality: current and voltage. For this purpose, the energy management of batteries for regulating the charge level under dynamic climatic conditions has been studied. The research presented in this paper provides an important contribution to the application of fuzzy theory to improve the power and performance of a hybrid system comprising a grid-connected PV, battery, and energy management strategy. Therefore, to highlight the advantage of the FL-MPPT studied in this paper, its performance has been compared and analyzed with conventional P&O and NNT algorithms. Simulation results are carried out in MatLab/Simulink tools. According to the analysis of the results, a better energy quality has been proven. Voir les détails
Mots clés : Battery storage, Energy management, Energy storage, MPPT control, Performance, photovoltaic System
A0 Lamb Mode Tracking to Monitor Crack Evolution in Thin Aluminum Plates Using Acoustic Emission Sensors
This paper presents a real time monitoring methodology to identify the location of acoustic emission (AE) sources generated by microcracks created within an aluminum plate when submitted to a tensile load. The real time detection of the AE hits was performed by means of a network of piezoelectric sensors distributed on the surface of the plate. The proposed localization approach is based on the combination of the time-frequency analysis of the detected AE hits with an extended Kalman filter (EKF). The spatial coordinates of the AE sources were determined by solving a set of nonlinear equations, where the extended Kalman filter is based on an iterative calculation. By considering the statistics related to the estimation of the coordinates’ errors, results show that the proposed method is in agreement with the experimental observations related to the propagation of the crack when the aluminum plate is under load. Voir les détails
Mots clés : Acoustic Emission (AE), AE events localization, Continuous Wavelet Transform (CWT), crack propagation, Extended Kalman Filter (EKF), Lamb waves, tensile test
Argon flow rate effects on the optical waveguide properties of DC sputtered TiO2 thin films
TiO2 thin films were successfully prepared by DC sputtering using pure titanium target in mixed gases (Argon, Oxygen) plasma on glass substrates. The films were deposited at a constant substrate temperature (350 °C) with different Argon flow rate values (15, 30, 45, and 60 sccm). Raman spectroscopy analysis shows that all films crystallized in the Anatase phase. The crystallinity was found to improve with increasing Argon flow rate up to 45 sccm and then deteriorate sharply at 60 sccm. The crystallite size varied between 9.1 and 9.7 nm. Atomic force microscopy (AFM) revealed that the roughness fluctuated between 1.30 and 6.01 nm with an overall increase. The grain shape went from sharp needles like shape to dome like shape with an enlargement in their size by up to 60 nm. The UV–Vis spectrophotometer displayed that the films were highly transparent. The optical band gap ranged from 3.65 to 3.49 eV. Prism coupler analysis exhibited single guided modes in both transverse electric and transverse magnetic polarizations for the sample prepared at 15 sccm Argon flow rate and bi-guided modes in both polarizations for the rest of the samples. Both ordinary and extraordinary refractive indices decreased over Argon flow by 9.912% and 6.441% respectively. The thickness, porosity as well as the birefringence where found to increase by 155 nm, 16.16% and 0.0832 respectively as Argon flow rate went from 15 to 60 sccm. Voir les détails
Mots clés : Ar flow rate, DC sputtering, Prism coupler, Refractive indices, TiO2, waveguides
Antibacterial activity of intermetallic NixMgy and NiO–MgO phases in nickel-magnesium oxide nanocomposites
This work focuses on Ni–Mg metallic nanomaterials and NiO–MgO composites, especially on their antibacterial activity against Escherichia coli (E. coli (G-)) and Staphylococcus aureus (S. aureus (G+)) in relation with their size and structure. They are generated by impregnation of nickel formate, followed by either calcination (T = 100–600 °C) or gamma-irradiation at room temperature. In samples prepared by calcination at temperatures T ≤ 300 °C or irradiation, the structural study by XRD and HRTEM reveals the presence of nanoscaled Ni–Mg intermetallic phases: NiMg2, Ni2Mg and NiMg6.33 (2–4 nm diameter) and magnesium hydroxide Mg(OH)2. At T > 300 °C, only the NiO–MgO solid solution is formed. Bare MgO and NiO–MgO nanoparticles exhibit a bacterial activity only against E. coli and S. aureus, respectively. In contrast, the Ni–Mg intermetallic phases of high specific area, that are present in irradiated (T = 20 °C) or calcined (T ≤ 300 °C) samples, exhibit a significant antibacterial activity against both E. coli and S. aureus. Voir les détails
Mots clés : Antibacterial Activity, Gamma radiolysis, intermetallic Compounds, NiO–MgO, Ni–Mg
Effects of Erbium Incorporation on Structural, Surface Morphology, and Degradation of Methylene Blue Dye of Magnesium Oxide Nanoparticles
This paper reports the chemical synthesis of MgO and Er-doped MgO nanoparticles (NPs) by the sol–gel method. Their microstructural, optical characterization and the evaluation of their photocatalytic activity are presented. The synthesized NPs were characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Environmental Scanning Electron Microscopy (ESEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX), UV–Visible and Photoluminescence (PL) spectroscopy. The effective synthesis of cubic MgO compound is attested by XRD, FTIR and electron diffraction in TEM. Er2O3 cubic secondary phase is found in the 2 and 3 wt% Er-doped MgO samples. The average size of the roundish cuboid-shaped crystallites decreases from 50 to 32 nm upon the incorporation of the rare earth element (TEM, XRD). Concomitantly, the size of flakes in which the NPs do agglomerate follows the same trend (ESEM). UV–Visible results show that the calculated band-gap energy of the NPs was in the 5.23 to 5.35 eV range. PL analysis showed that all samples have visible emissions owing to the formation of defects in the MgO band-gap. The photocatalytic activity against methylene blue dye was evaluated under UV light irradiation. The photocatalytic results showed an improvement in degradation efficiency with the addition of erbium in samples, with a maximal MB dye removal for the 3 wt% Er-doped MgO sample after 90 min irradiation. The performance is ascribed to a higher separation of the photo-generated (electron–hole) and larger surface area. Voir les détails
Mots clés : Erbium, methylene blue, MgO, Photocatalytic activity, X-ray diffraction
Enhanced the modeling accuracy by the design of new photovoltaic models including the proposed nonlinear thermal resistors
This article proposes new photovoltaic (PV) models, with which the modeling accuracies are much improved, regardless of wide absolute temperature variations. The desired PV models are designed by an equivalent electrical circuit consisting of a single diode and two proposed nonlinear thermal resistors. The realization of such resistors is therefore the key contribution of this article since they significantly increase the degrees of freedom of similar circuits, including fixed resistors. As a result, the given modeling accuracies are clearly improved not only under standard test conditions but also in more severe climatic environments, characterized by high absolute temperatures. To achieve this goal, the parameters of the two proposed PV models were optimized using the gnetic algorithm, where a fitness function for each PV model is well minimized. Each fitness function was previously formulated from comparing actual output currents, prerecorded from the existing ISOFOTON I-50 PV panel, by predicted output currents, computed using the Lambert-W function. The given performances by the proposed PV models were compared with those provided by the standard PV ones where the given simulation results reveal the superiority of the proposed PV models under different weather conditions. Voir les détails
Mots clés : Genetic algorithm, Lambert-W function, Photovoltaic, Resistance-based metallic conductor, Resistance-based thermistance material, standard climatic condition
Robust adaptive sliding mode control strategy of uncertain nonlinear systems
This paper presents a robust adaptive sliding mode controller scheme as applied to a class of uncertain nonlinear systems with parametric uncertainties and external disturbances. First, a sliding mode control technique is designed. Then, the proposed robust adaptive control schemes are applied to estimate the parametric uncertainties and the upper bound value of the external disturbances by using adaptive laws, ensure robustness in presence of parametric uncertainties and external disturbances, and reduce chattering problem by introducing an hyperbolic tangent function. Lyapunov stability theory is used to analyze the stability of the closed-loop system. As an exemplar, the schemes have been applied to a quadrotor unmanned aerial vehicle (QUAV) model. Simulation results for the control of the QUAV model are provided to illustrate the performance of the proposed robust adaptive sliding mode control scheme and demonstrate that the proposed method has good tracking performance. The simulation results clearly prove the effectiveness of our approach. Voir les détails
Mots clés : adaptive control, Robust control, Sliding mode control, uncertain nonlinear systems, parametric uncertainties, external disturbances, adaptive laws, Lyapunov stability theory, quadrotor unmanned aerial vehicle
Microstructural Investigation and Oxidation Performance of Nickel‑Based Superalloys
An as-received IN738LC blade root material has been firstly characterized, in order to appreciate its structural, micro- structural and morphological properties. Different observations and analysis (OM, XRD, SEM/EDS, etc.) showed that our sample is mainly constituted of γ´ precipitates in a Ni-rich matrix (γ solution), a γ/γ´ eutectic and some carbides. After that, the oxidation behavior of IN738LC superalloy has been investigated to assess the oxidized formed layers. For this purpose, isothermal oxidation experiences have been carried out at 950 and 1150 °C for various times (24h, 48h and 72h). The differ- ent microstructures of oxides and substrate obtained after oxidation tests were observed and analyzed by scanning electron microscopy (SEM/EDS). The oxidation kinetics were monitored by samples weight change with time. Composition and phase evolutions, mean crystallite size and strain appeared in this superalloy, were determined by X-ray diffraction (XRD) patterns. Last, the adhesion of the growing oxides onto the substrate was evaluated by the scratch test. The main results of these investigations reveal that microstructure parameters strongly depend on temperature and durations of the process. Moreover, the oxidation kinetics of the alloys follows a parabolic rate law both at 950 °C and at 1150 °C. From XRD and EDS analysis, the major phases seen are Cr2O3, TiO2, Al2O3, NiO and NiCr2O4, which contribute to a better oxidation resistance. The oxide scales increase with time and temperature, they are compact, dense, distributed uniformly and adherent at 950°C/72h, while they are relatively larger and non-uniform at 1150 °C. On the other hand, the adhesion of the oxides at 1150°C is fairly weak, and oxidation products flake off quite easily, which indicated weakening of the protection. Voir les détails
Mots clés : Turbine blade, Inconel 738LC, Oxidation kinetics, microstructure, Strain, Adhesion
Etude D’efficacité D’inhibiteur NALCO E1154A Sur L’acier A36 Utilisé Dans Les Bacs De Stockage Des Hydrocarbures Du Site GTFT-ILIZI
The corrosion of the condensate and LPG storage tanks in the GTFT zone presents a major problem that leads to a degradation of the storage tanks where huge sums are spent annually to protect the structures against corrosion, The maintenance and repair of the storage tanks. storage systems go through a detailed inspection program in order toobtain the data necessary to be properly adapted, today corrosion protection includes treatments such as cathodic protection, surface treatments or even the modification of the corrosive environment by addition of corrosion inhibitors. These constitute an original means of combating corrosion.In order to test the effectiveness of NALCO 115 EC 1154A inhibitor on A36 steel for use in the protection against corrosion of storage facilities for hydrocarbon products inthe GTFT zone, we were interested in this study to seek the optimal concentration in order to perform electrochemical tests. Voir les détails
Mots clés : corrosion, storage bins, inhibitors, A36 steel
Elaboration et Caractérisation des Cuprates Supraconducteurs de type YBCO
In this work, we prepared YBCO samples by sol-gel process and the gel decomposition studied by TG/DSC, which shows the X-ray diffraction due to the fact that the samples contained a preponderant phase (YBa2Cu3O7). SEM images showed the polycrystalline structure of samples with grain size between 2 and 3 µm and high porosity rate. Longitudinal and transverse ultrasonic velocity and attenuation measurements were performed on 3 mm thick samples. The experiments were performed at room temperature (300 K). The objective of this technique is ultrasonic characterization. Voir les détails
Mots clés : YBCO, sol-gel, XRD, DTA, Ultrasound