In this paper, an intelligent control of the single-phase shunt active filter (SP-SAF) for power quality improvement is proposed. The developed approach is essentially composed of two controllers based on the fuzzy logic theory. The first fuzzy proportional derivative (PD) controller with integral (I) action replacing the standard PI regulator, intervenes in the DC voltage regulation loop of the depollution device. In addition, it effectively participates in the delivery of the reference source current. The second controller represented by a fuzzy hysteresis regulator ensures better control of the filter current. Moreover, it acts as an intelligent governance decision maker of the (DC/AC) converter constituting the filtering system. The strategy offers a source current of sinusoidal shape respecting the imposed international standards and the operation of the treated system under a power factor very close to unity. The effectiveness of the new proposed control strategy has been tested through MATLAB/Simulink software and practically validated via the dSPACE 1104 card under various operating conditions. Finally, the experimental results show that the proposed control paradigm outperformed the existing control schemes.
This work aims to evaluate the adsorption capacity of an abundant natural diatomite (ND) to remove the azo dye carmoisine, known as a harmful emerging organic pollutant. Indeed, to the best of our knowledge, no results were reported on this subject. The ND was characterized by FTIR, XRD, and SEM/EDX analyses. The experimental study of adsorption was carried out in batch mode. Results showed that ND adsorbent is mainly composed of silica. A fraction of calcite and ankerite was also identified. It is a porous material with a specific surface of about 41 m2.g-1 and with a hydroxyl surface functional group -OH. Adsorption results showed that adsorption process on ND is found to be effective in removing the carmoisine colorant. The adsorption capacity is strongly affected by the adsorbent and adsorbate contents, the solution pH, the work temperature, and the water hardness and mineralization. At room temperature, optimal experimental conditions for the highest adsorption capacity (12 mg.g-1) were colorant concentration 50mg.L-1, pH 2, contact time 30min, and ND content 1 g.L-1. Modeling study has showed that experimental results are well modeled by the Freundlich isotherm in multilayer adsorption. The reaction kinetics are pseudo-second order, and the thermodynamic parameters indicated that the nature of the adsorption process is endothermic and spontaneous.
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.
Alfa grass is one of the most abundant and renewable natural fiber resources in North Africa. In this regard, this work aimed to valorize this plant by preparing a sandwich panel composed of Alfa fiber-based core and a hybrid polymer matrix composite (jute and metallic mesh) as skin. The mechanic properties of the parts (the core, skin and whole sandwich composite) were evaluated by bending, tensile and non-destructive tests. Thanks to Alfa fiber-based core, the resulting sandwich performance was higher compared to other bio-based ones such as cork-based sandwiches but had higher density. The hybridization of the jute improves the rigidity of the skin (about 65% of Young and flexural modulus, respectively) but decries the tensile strength by about 23%. The sandwich breaking was strongly influenced by the stacking sequence of the skin, the presence of metallic mesh at the interface core/skin led to delamination, which reduces the mechanical properties of the sandwich. Overall, this sandwich could find useful application as a non-structural component in building materials (separation or roofs panels).
In this work, we describe a simple strategy for the preparation of a low-cost electrode material based on polypyrrole (PPy) film grown on an insulating cellulosic paper substrate via in-situ oxidative polymerisation technique and functionalised by silver nanoparticles (AgNPs) uniformly dispersed on its surface. The properties of the obtained AgNPs-PPy composites were characterised using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis. The electrocatalytic activity of the prepared electrode was investigated for the electroreduction of nitrate using cyclic voltammetry in 0.1 M KOH solution. Results demonstrated that the incorporation of AgNPs into the PPy matrix improves significantly the catalytic behaviour of this film. The effect on the electrode response of the amount of the incorporated AgNPs was also investigated. This paper highlights a simple procedure for the making of low-cost paper electrodes for the efficient reduction of nitrates.
This article presents a robust adaptive dynamic surface control using σ‐modification adaptation laws for a class of single‐input and single‐output (SISO) uncertain nonlinear systems in strict‐feedback form with parametric uncertainties and external disturbances. The proposed scheme is developed by employing dynamic surface control based robust adaptive control technique. The key features of the approach are that, first, the problem of explosion of complexity inherent in the conventional adaptive backstepping control method is avoided, second, the proposed approach of σ‐modification adaptation laws gives fast and accurate parameter estimation performance, and, third, the closed‐loop signals of the system are proven to be uniformly ultimately bounded (UUB) by using the Lyapunov stability theory. We show the effectiveness of our approach by simulating an electromechanical system.
The aim of this work is to study the effect of solid particle impact erosion parameters of sand on the isotropy parameter "Std" which presents the direction of surface texture. The experimental methodology adopted for this experimental work is the Box Behnken plan with three factors, each at three levels (-1, 0 and +1), the parameters considered are: time "t", pressure "P" and angle of impact "θ". 3D roughness measurements were carried out using a laser source profilometer type Cyper- Technologie-CT100, in order to characterize the different surfaces after erosion test. The statistical analysis was carried out using the Mini Tab software, where a mathematical model was established showing the relationship between the input parameters (t, P, 0) and the output parameter "Std". This model predicts the "Std" response in the field of study as well as the parameters of the sandblasting regime. The results show the significant effect of the impact angle on "Std" and the interaction between the different parameters in the study domain, of which the highest value of "Std" is equal to 130 ° for an average time combined with low pressure and impact angle.
The investigation presented in this paper focuses on the effect of surface texture on the adhesion of a paint coating as well as the influence of shot peening regime parameters on the surface isotropy indicator "Str" and on the fractal dimension "Df". The tests have been organized according to full factorial designs 2³, where three parameters have been examined, at their two levels (min, max), namely the pressure (P), the angle of attack (0) and the time (t). 3D roughness measurements have been carried out to characterize the different surfaces after a shot peening operation. A mathematical model linking the input parameters (P, 0, t) and the output parameter "Str", in the study area has been established, and the fractal dimension (Df) has been used for the surface characterization. Paint deposit has been applied to surfaces and adhesion tests have been carried out. The results show the significant effect of the impact angle on "Str", and the interaction between the different parameters in the studied area. Furthermore, the greatest bond strength has been obtained with the sample 3 (F=4.25 N / mm2), whose the isotropy indicator "Str" is equal to 0.6438 and the fractal dimension Df=is about 1.768.
Using stationary electrochemical, polarization resistance, cathodic charging, transient electro-chemical impedance spectroscopy, and theoretical and molecular mechanics studies, epoxy polymer-coated carbon steel specimens' ability to protect metals from corrosion in various soil extracts was examined. According to the results of the polarization resistance tests, the polymer coating remained stable for 60 days in all three soil extracts, with a 90% efficiency for the steel coated in soil extract A, indicating that the sandy soil is less aggressive than the other two. The aggressiveness of clay soil is confirmed by the fact that a polymer-coated steel rod in the clay soil extract experiences a corrosion current density of 97 µA/cm2. In contrast, the same rod in sandy soil participates a current density of 58 µA/cm2. The coating's good adsorption contact with the metal surface is further guaranteed by molecular dynamics simulations, which provide atomic-level evidence of the epoxy molecule's adsorption behavior (geometry) and adsorption energy on the carbon steel surface.
Differential scanning calorimetric (DSC) is a good tool for invetsigating the phases transformation, since it permits the determination of the kinetic parameters such as activation energy and reaction order. The hardening phase precipitation in the Al–Mg–Si alloy was investigated by using DSC and isothermal and non-isothermal calculation models. All specimens were treated up to 550 °C with heating rates (ν) of 5, 10, 20 and 30 °C/min. The shift from the temperature peak to a higher for high heating rate indicates that the precipitation reactions are thermally activated. The results showed that the activation energy and the reaction orders, obtained from both methods are similar. The decreased activation energy is attributed to the saturation of the previous phase, which acts as precursor for the metastable phases. The pre-exponential factor (ko) calculated by the isothermal calculation method is equal to 8.36×10⁷ s⁻¹. On the other hand, the corrosion resistance of the alloy is significantly enhanced by photoelectrochemical cathodic protection. This was achieved by short-circuiting the alloy to n-CdS under visible irradiation where the corrosion current decreases by 88%.
In the world, the enormous usage of fossil fuels, e.g., coal, oil, and gas, is the source of both air pollutants and greenhouse gases, thus provoking serious problems for air quality, public health, and climate. Renewable energy sources can provide a good solution to overcoming these problems. However, the renewable energies are one of the energy sources that their energy production are unpredictable in changing climate conditions, which provoke a real problem of limited rate of penetration when this energy is injected in the electrical network. Nevertheless, the penetration of renewable energy in the grid can be enhanced by the improvement of the energy management and control techniques. This chapter presents modeling, simulation and control of grid‐connected hybrid solar–wind system with two level energy storage under different climatic conditions. The system proposed in this paper includes wind turbine system equipped by a Doubly Fed Induction Generator DFIG, photovoltaic (PV) system, hybrid supercapacitors‐battery energy storage system and controlled power electronics converters. The hybrid system is connected to the grid using a three‐level inverter with hybrid supercapacitors‐batteries energy storage. In order to maximize the power of PV system, the Particle Swarm Optimization PSO algorithm that generates the optimal current of the PV system is applied. The results of simulation are demonstrated using MatLab‐Simulink through different climatic conditions.
Photovoltaic energy generation systems are characterized by the dependence of their energy conversion efficiency on the operating point in its nonlinear Power‐Voltage. Maximum power point tracking algorithms have been proposed to adjust the operating point of PV systems using power converters to correspond to the optimal energy conversion efficiency. Conventional approaches include true seeking (or direct) methods designed based on gradual perturbation of the operating point and the calculation of mathematical quantities to decide the next direction of the perturbation of the P‐V curve. The indirect methods are based on approximations of the maximum power point using known values, such as open‐circuit voltage or short circuit current. Modern MPPT techniques have been introduced as a result to solve issues found in conventional approaches, such as steady‐state oscillations, rapid change in climatic conditions, or presence an irradiation mismatch along with PV panels. Artificial intelligence‐based techniques use approximate reasoning and human brain processing architectures in order to construct trained structures able to estimate the optimal operating point at the actual climatic conditions. Bioinspired MPPT algorithms have known increasing use to solve mismatching issues in PV arrays, which adds the functionality of using multiagents searching strategy that allows the convergence to the global MPP in the presence of multi‐peak P‐V characteristic curve. Hybrid MPPT strategies have been proposed to combine modern techniques global search with incremental perturbation and seek conventional approaches.
In this paper, a C0 simple and efficient isoparametric eight-node displacement-model based on higher order shear deformation theory is proposed for the bending behavior study of multilayer composites sandwich plates. Difficult C1-continuity requirement is overcome by extracting the seven degrees of freedom from strain relations for each element node: two displacements for in-plane behavior and five bending unknowns namely: a transverse displacement, two rotations and two shear angles, which results in a kinematic approximation formulation having only first order derivative requirement. The governing equations of the element (constitutive, virtual work and equilibrium equations) are implemented for the prediction of approximate solutions of deflections and stresses of sandwich plates linear elastic problems. Thereby, the formulation element is able to present a cubic in-plane displacement along both core and faces sandwich thickness, as well as, the shear stresses are found to vary as quadratic field without requiring shear correction factors and independent from any transverse shear locking problems. The accuracy and validity of the proposed formulation is verified through the numerical evaluation of displacements and stresses and their comparison with the available analytical 3D elasticity solutions and other published finite element results.
TiO2 thin films were deposited by reactive magnetron sputtering with increasing thickness T1, T2, T3 and T4. The μ-Raman spectra showed the presence of anatase TiO2 in all films. The phonon confinement model revealed the crystallite size ranging between 5.1 and 6.1 nm. The optical gap energy was found to decrease from 3.45 eV to 3.37 eV. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis showed enhancement of crystallinity and stoichiometry over the films’ thickness in accordance with the μ-Raman measurements. The m-lines spectroscopy confirmed the normal behavior of the films as multimode waveguides by the increase of propagation modes’ number with the films’ thickness for each transverse electric and transverse magnetic polarization. Both ordinary and extraordinary refractive indices decreased over the films’ thickness. The birefringence however had an opposite behavior. The cut-off thickness experienced an increment as a function of thickness. In comparison, m-lines and Swanepoel’s method were relatively compatible.
Introduction. A wind energy conversion system needs a maximum power point tracking algorithm. In the literature, several works have interested in the search for a maximum power point wind energy conversion system. Generally, their goals are to optimize the mechanical rotation or the generator torque and the direct current or the duty cycle switchers. The power output of a wind energy conversion system depends on the accuracy of the maximum power tracking controller, as wind speed changes constantly throughout the day. Maximum power point tracking systems that do not require mechanical sensors to measure the wind speed offer several advantages over systems using mechanical sensors. The novelty. The proposed work introduces an intelligent maximum power point tracking technique based on a fuzzy model and multivariable predictive controller to extract the maximum energy for a small-scale wind energy conversion system coupled to the electrical network. The suggested algorithm does not need the measurement of the wind velocity or the knowledge of turbine parameters. Purpose. Building an intelligent maximum power point tracking algorithm that does not use mechanical sensors to measure the wind speed and extracts the maximum possible power from the wind generator, and is simple and easy to implement. Methods. In this control approach, a fuzzy system is mainly utilized to generate the reference DC-current corresponding to the maximum power point based on the changes in the DC-power and the rectified DC-voltage. In contrast, the fuzzy model-based multivariable predictive regulator follows the resultant reference current with minimum steady-state error. The significant issues of the suggested maximum power point tracking method, such as the detailed design process and implementation of the two controllers, have been thoroughly investigated and presented. The considered maximum power point tracking approach has been applied to a wind system driving a 5 kW permanent magnet synchronous generator in variable speed mode through the simulation tests. Practical value. A practical implementation has been executed on a 5 kW test bench consisting of a dSPACEds1104 controller board, permanent magnet synchronous generator, and DC-motor drives to confirm the simulation results. Comparative experimental results under varying wind speed have confirmed the achievable significant performance enhancements on the maximum wind energy generation and overall system response by using the suggested control method compared with a traditional proportional integral maximum power point tracking controller. References 24, tables 3, figures 15. Key words: small-scale wind generator, maximum power point tracking, fuzzy system, fuzzy model based multivariable predictive control, linear matrix inequalities approach. Вступ. Система перетворення енергії вітру потребує алгоритму відстеження точки максимальної потужності. У літературі є кілька робіт, присвячених пошуку системи перетворення енергії вітру із точкою максимальної потужності. Як правило, їх метою є оптимізація механічного обертання або моменту, що крутить, генератора і перемикачів постійного струму або робочого циклу. Вихідна потужність системи перетворення енергії вітру залежить від точності контролера стеження за максимальною потужністю, оскільки швидкість вітру постійно змінюється протягом дня. Системи стеження за точками з максимальною потужністю, яким не потрібні механічні датчики для вимірювання швидкості вітру, мають ряд переваг у порівнянні з системами, що використовують механічні датчики. Новизна. Пропонована робота представляє інтелектуальний метод відстеження точки максимальної потужності, заснований на нечіткій моделі та багатопараметричному прогнозуючому контролері, для отримання максимальної енергії для маломасштабної системи перетворення енергії вітру, підключеної до електричної мережі. Пропонований алгоритм не вимагає вимірювання швидкості вітру або знання параметрів турбіни. Мета. Побудова інтелектуального алгоритму відстеження точки максимальної потужності, який не використовує механічні датчики для вимірювання швидкості вітру та витягує максимально можливу потужність з вітрогенератора, а також простий та зручний у реалізації. Методи. У цьому підході до управління нечітка система в основному використовується для генерування еталонного постійного струму, що відповідає точці максимальної потужності, на основі змін потужності постійного струму та постійної випрямленої напруги. Навпаки, багатопараметричний прогнозуючий регулятор на основі нечіткої моделі слідує за результуючим еталонним струмом з мінімальною помилкою, що встановилася. Істотні проблеми запропонованого методу відстеження точки максимальної потужності, такі як процес детального проектування та реалізація двох контролерів, були ретельно досліджені та представлені. Розглянутий підхід до відстеження точки максимальної потужності був застосований до вітрової системи, що приводить у дію синхронний генератор з постійними магнітами потужністю 5 кВт у режимі змінної швидкості за допомогою моделювання. Практична цінність. Для підтвердження результатів моделювання було виконано практичну реалізацію на випробувальному стенді потужністю 5 кВт, що складається з плати контролера dSPACEds1104, синхронного генератора з постійними магнітами та електроприводів з двигунами постійного струму. Порівняльні експериментальні результати при різній швидкості вітру підтвердили значні поліпшення продуктивності з максимального вироблення енергії вітру і загального відгуку системи при використанні запропонованого методу управління в порівнянні з традиційним пропорційно-інтегральним контролером спостереження за точкою максимальної потужності. Бібл. 24, табл. 3, рис. 15. Ключові слова: малогабаритний вітрогенератор, відстеження точки максимальної потужності, нечітка система, багатопараметричне прогностичне управління на основі нечіткої моделі, метод лінійних матричних нерівностей.
Adsorption and corrosion inhibitionof Cactus cladode(CC) extract collectedin eastern Algeria from areas of Chetaibi in Annaba on mild steel (MS) in 0.5 MH2SO4 solution were studied with potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical stability of surface inhibitor film was investigated by chronoamperometry (CA) technique. The MS surface exposed to thecorrosive medium in the absence and presence of CC extract was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. The potential of zero charge(Epzc) of MS in the presence of CC extract was determined by EIS methodand excess surface scharge of the metal surface was determined. It was found that CC extract has a high inhibition effeciency on the corrosion of MS. The thermodynamic examinations indicated that Kads was 20.88 L g⁻¹ and ▵G⁰ads was −24.64 kJ mol⁻¹.Thevalue of Epzc confirmed excess positive charge atthe MS surface. The adsorption of extract molecules obeys to Langmuir isotherm. The inhibition efficiency was 91.8 % at 1000 ppm CC extract concentration, while it iscreased to 97.7 % when 1000 ppm KI was added to this solution.The inhibitor film formed over the metal surface has a hydrophobic character.The addition of KI to the inhibited solution stabilizes the surface film and enhances inhibition efficiency.
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.
The contributions of the GP zones and the matrix to the alloy hardening have been studied in the alloy Al-5% at. Ag aging at 150 °C. They were determined separately using a method based on the hardness measurement which obeys the relation ΔHvSS = 19.72x2/3 + 0.218 (Gpa), where x is the means atomic concentration of the matrix. The GP zones follows the relationship (ΔHv GP = 18.4 fv0.94 kg/mm²), fv is the volume fraction of GP zones. In a second part, the photo-electrochemical properties of n-CdS were exploited for the cathodic protection of the alloy Al-5% at.Ag in one of the most corrosive environments namely seawater. The corroded surface was rough and the corrosion product contains divided particles. However, the corrosion was significantly hindered by contacting the alloy to n-CdS (Eg = 2.40 eV) irradiated by visible light with different intensities (42–103 mW cm⁻²). Under illumination, the electrode potential of the alloy is catholically shifted when short-circuited to n-CdS, indicating a photo cathodic protection while the corrosion current falls from 2.67 (in the dark) down to 1.73 mA cm⁻² under a light flux of 103 mW cm⁻². Conversely, when the alloy is short-circuited to p-type CuO (Eg = 1.46 eV), the corrosion current increased by 26% under illumination, due to the activated dissolution by photoholes.
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