Liste des documents
Vibration for detection and diagnosis bearing faults using adaptive neurofuzzy inference system
The fault diagnosis of electrical machines is a primordial and necessary task in industry. Thefailure is unbearable because it causes, incontestably, decrease in production and increases costrepair. Induction motors are the most important equipment in industry, where reliability andsafe operation is desirable, for maintenance, such as detection, and diagnosis of mechanical andelectrical defects of electric drives. The several techniques are adopted and frequency analysis isthe most widely used. Artificial intelligence techniques was gained popularity last decay’s innumerous applications. The presented results show the detected and diagnosed, of the bearingfaults of the induction motor, based on Adaptive Neuro-Fuzzy Inference System. The vibrationsanalysis of the induction machine using the Artificial Intelligence Techniques, combining neuralnetworks and fuzzy logic has been applied successfully. The designed ANFIS network showsabout 99% accurate results as validated by Mat lab / Simulink simulation Voir les détails
Mots clés : diagnosis, fault, vibration, bearing
Structural and magnetic properties of FeCuNi nanostructured produced by mechanical alloying
We investigated the magnetic, morphological, and structural properties of FeCuNi. The powder alloy iselaborated by mechanical alloying process for 10 h with varying the Cu content. The aims of this workare to study the effect of Ni/Cu ratio on the magnetic and microstructure properties. The crystallite sizedecreases with the increase of Ni. The reduction of crystallite size proceeds slowly until 17 nm for 30% ofNi. Coercivity and saturation magnetization increases from 105.4 Oe, 122.568 emu/g to 156.77 Oe,140.679 emu/g respectively caused by the increase of the concentration of Cu and dislocation densityas well as the decrease of the crystallite size Voir les détails
Mots clés : FeCuNi nanostructured, Mechanical Alloying, MEB, DRX, VSM
Optoelectronic properties of the new quaternary chalcogenides Zn2CuInTe4 & Cd2CuInTe4: ab-initio study.
In order to exploit the fundamental properties of the new tellurides quaternary diamond-like structure Zn2CuInTe4 and Cd2CuInTe4, first principles investigation in the frameworkof the Full-Potential LAPW scheme have been carried out for that purpose. We used theWu and Cohen generalized gradient approximation (GGA-WC) to calculate the optimizedstructure that corresponds to the global minima of the energy. Enthalpy of formation showsthat the most stable structures are the relaxed ones. The EV-GGA and the TB-mBJ approx-imations were also used for electronic and optical properties. The equilibrium electronicparameters found are in good agreement with the previous results. The real and thecient, theopt imaginary parts of the dielectric function, the refractive index, the extinction coeffiicalconductivity, the absorption coefficient, the loss function and the reflectivity are reviewedin the large spectral range of photon energy. The present study demonstrates a variety ofnovel electronic and optical properties, which make these compounds highly promising foroptoelectronic materials. Voir les détails
Mots clés : DFT, Quaternary tellurides, Enthalpy of formation, band gap, Absorption coefficient
First principles investigation of optoelectronic properties ofZnXP2 (X = Si, Ge) lattice matched with silicon for tandemsolar cells applications using the mBJ exchange potential
II-IV-V2 materials are attractive compounds for optoelectronic, photonic and photovoltaicapplications due to their valuable ternary chemistry. A primary technological challengein photovoltaics is to find and develop a lattice matched efficient material to be usedin combination with silicon for tandem solar cells. ZnSiP2 and ZnGeP2 chalcopyrites arepromising semiconductors that could satisfy these criteria. Particularly, ZnSiP2 is known tohave bandgap energy of∼2 eV and a lattice mismatch with silicon of 0.5%. In this work, thefirst principle calculations have been performed to investigate the structural, electronic andoptical properties of ZnSiP2 and ZnGeP2 in chalcopyrite structure within the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method based on the Density FunctionalTheory (DFT) as implemented in WIEN2K code. The local Density approximation (LDA) ofPerdew and Wang was used as exchange-correlation potential to calculate the structuralproprieties. Furthermore, the recently modified Becke-Johnson (mBJ) functional of Tranand Blaha was also employed to compute the electronic and optical properties in order toget best values of the band gap energy and some better degree of precision. The complexdielectric function, the complex refractive index, reflectivity, absorption coefficient, and theoptical conductivity were calculated to illustrate the linear optical properties of both compoundsZnSiP2 and ZnGeP2. At last, the obtained results indicate that ZnSiP2 and ZnGeP2are attractive materials in optoelectronic devices especially as a lattice matched materialwith silicon for tandem solar cells applications. Voir les détails
Mots clés : FP-LAPW, mBJ, Chalcopyrite, Electronic band structure, Linear optical properties
Optical study of cubic, and orthorhombic structures of XCaCl3 (X = K, Rb) compounds: Comparative Ab initio calculations
The study predicts the optical properties of cubic and orthorhombic structures of XCaCl3 (X = K, Rb) perovskite compounds through electronic band structure computation within the framework of density functional theory (DFT). The ground state functions are computed employing full potential linearized augmented plane wave (FP-LAPW) method. Improved band gap values and the electronic as well as optical properties were calculated by Tran and Blaha modified Becke–Johnson (mBJ) functional. The studied compounds’ density of states reveals that Cl-p states dominate the valence band. To understand the optical properties, and predicting the optically isotropic nature of these materials, the real and imaginary parts of dielectric function, refractive index, absorption coefficient, and energy loss spectra are plotted. The present study shows a great potential utilization in ceramic scintillators. Voir les détails
Mots clés : DFT, FP-LAPW, Perovskites, Optical parameters, Scintillators
Theoretical design and performance of InxGa1-xN single junction solar cell
The insertion of optimized Window and a back surface field (BSF) layers on an InxGa1-xN p-n basic single junction (BSJ) solar cell is the chief reason behind the reduction of front and back recombination. In this context, this work is focused on the selection of the suitable parameters including the indium (In) content, thickness and doping concentration for the InxGa1-xN inserted layers, that gives the best photovoltaic performances. At this aim, numerical simulations were performed using the computational numerical modeling TCAD Silvaco-Atlas to design, optimize the InxGa1-xN BSJ and extract the above Window and BSF parameters that enhance the BSJ performances. A short circuit current density ?(J?_sc) of 26.15 mA⁄?cm?^2 , an open circuit voltage ?(V?_oc) value of 0.904 V and a fill factor (FF) value of 79.67 % are obtained under AM1.5G illumination, exhibiting a maximum conversion efficiency (η) of 19.62 %. Other parameters like the external quantum efficiency (EQE), electric field developed, the current density-voltage (J-V) and the power density-voltage (P-V) characteristics are also calculated and plotted for the designed solar cell. Voir les détails
Mots clés : InGaN, solar cell, BSF layer, Window layer, simulation, Silvaco
Detection of Broken Rotor Bar Fault in Squirrel Cage Induction Motor using Wavelet Packet Analysis
The fault of broken rotor bars in a three-phase induction motor is diagnosed by using the wavelet Packet analysis. In this paper Daubechies wavelet is selected as the wavelet base and the wavelet coefficient is obtained from the wavelet transform of current signal of the faulty induction motor. The Energy of Wavelet components appear to be useful for detecting different electrical faults. In this paper we will study the problem of broken rotor bars. Voir les détails
Mots clés : Wavelet Packet, Analysis, diagnosis fault, induction motor, broken bar, wavelet paket, analyses
Structural, electronic and optical properties for chalcopyrite semiconducting materials: ab-initio computational study
Investigation of the physical properties of chalcopyrite materials using ab-initio methods have been carried out to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. The Density Functional Theory calculations have been performed using Wien2k computational package by employing the full-potential linearized augmented plane wave method. Structural and electronic properties of chalcopyrite semiconducting material Copper–Indium–Gallium–Selenium i.e. CuIn1-xGaxSe2 have been investigated using local density approximation for the exchange-correlation potential. The electronic structures and linear optical properties have been studied using both the semi-local Becke-Johnson potential and its modified form i.e. mBJ and TB-mBJ. Computational results are in good agreement with those acquired experimentally. The viability of alloys in realization of ultra-thin-film based (CIGS) solar cells with high performance has been proposed after simulation and analysis study using one of solar cell simulation tools. The studied material exhibits capability to become a promising candidate for fabrication of optoelectronic and photovoltaic devices. Voir les détails
Mots clés : Chalcopyrite, FP-LAPW, optical properties, Thin-films solar cells, wien2k
Effect of root pass filler metal on microstructure and mechanicalproperties in the multi-pass welding of duplex stainless steels
This paper is focused on the estimation of the effect of root pass chemical composition, in multi-pass GTA Weldments, onmicrostructure and mechanical properties of duplex stainless steel welds.We used two different fillermetals, the super duplex ER2594 and duplex ER 2209. Microstructures of different passes of welded joints are investigated using optical microscope andscanning electron microscope. The relationship between mechanical properties, corrosion resistance, and microstructure ofwelded joints is evaluated. It is found that the tensile and toughness properties of the first weldment, employing the combinationof ER 2594 in the root pass and ER 2209 in the remaining, are better than that of the second weldment employing ER 2209 allpasses, due to the root pass grains refinement and its alloy elements content as chromium Cr and nitrogen N. The microstructureindicates the presence of austenite in different forms on the weld zone of ER 2209, same in the case of ER 2594, but with highercontent and finer grains size, in particularWidmanstätten austeniteWA. Potentiodynamic polarization tests of the first weld metalevaluated in 3.5% NaCl solution at room temperature have been demonstrated a corrosion resistance higher than that of thesecond weld metal. This work addressed the improvement of the corrosion resistance using appropriate filler metal withoutgetting any structural heterogeneity and detrimental changes in the mechanical properties. Voir les détails
Mots clés : Gas tungsten arc welding (GTAW), duplex stainless steel, Root pass, Filler metal, Microstructure and mechanical properties
Design and real time implementation of sliding mode supervised fractionalcontroller for wind energy conversion system under sever working conditions
Wind energy conversion system (WECS) is increasingly taking the place to be the most promised renewablesource of energy, which obliges researchers to look for e?ective control with low cost. Thus, this paper proposesto build a suitable controller for speed control loop to reach the maximum power point of the wind turbine undersever conditions and to ensure the stability of the outer voltage regulation loop to meet high range of loadvariations. In literature, a major defect of the well-used conventional PI controller is the slow response time andthe high damping. Nowadays, intelligent controllers have been used to solve the drawbacks of the conventionalones but they demand high speed calculators and expensive cost. Moreover, many solutions proposed thefractional order PI controller (FO-PI) by extending the order of integration from integer to real order. The FO-PIcontroller presents also some weakness in steady state caused by the approximation methods. The idea of thispaper is to propose a Sliding Mode Supervised Fractional order controller (SMSF) which consists of conventionalPI controller, FO-PI controller and sliding mode supervisor (SMS) that employs one of the controllers to ensuregood steady and transient states. WECS laboratory prototype is built around real-time dSPACE cards andevaluated to verify the validity of the developed SMSF. The results clearly ful?ll the requirements, con?rm itshigh performance in steady and transient states and demonstrate its feasibility and e?ectiveness. Voir les détails
Mots clés : Maximum Power Point Tracking (MPPT), Wind Energy Conversion System (WECS), PI controller, Fractional order PI controller, Sliding mode control, Direct power control