Liste des publications
Rational Function Approximationof a Fundamental Fractional OrderTransfer Function
This paper introduces a rational function approximation of thefractional order transfer function ; for 0 to 0:5. Thisfractional order transfer function is one of the fundamental functions of thelinear fractional system of commensurate order corresponding to pure complexconjugate poles or eigenvalues, in sa. Hence, the proposed approximation willbe used in the solution of the linear fractional systems of commensurate order.Illustrative examples are given to show the exactitude and the efficiency of theapproximation method. Voir les détails
Mots clés : Fractional power zero Linear fractional system Irrational transfer function Rational transfer function
The solution of state space linear fractionalsystem of commensurate order withcomplex eigenvalues using regularexponential and trigonometric functions
In a previous work, we have derived the generalsolution of the state space linear fractional system of commensurate order for real simple and multiple eigenvalues ofthe state space matrix. The obtained solutions of the homogeneous and non-homogeneous cases have been expressed as alinear combination of introduced fundamental functions. Inthis paper, the above work has been extended to solve thestate space linear fractional system of commensurate orderfor complex eigenvalues of the state space matrix. First, suitable fundamental functions corresponding to the differenttypes of complex eigenvalues of the state space matrix areintroduced. Then, the derived formulations of the resolutionapproach are presented for the homogeneous and the nonhomogeneous cases. The solutions are expressed in terms ofa linear combination of the proposed fundamental functionswhich are in the form of exponentials, sine, cosine, dampedsine and damped cosine functions depending on the commensurate fractional order. The results are validated by solving anillustrative example to demonstrate the effectiveness of theproposed analytical tool for the solution of the state spacelinear fractional system of commensurate order. Voir les détails
Mots clés : Complex eigenvalues · Fractional differential equation · Fundamental functions · Modal decomposition · Rational function · State space representation
Study of physico-chemical properties of diatomiteAlgeria: Application to the thermal insulation ofliquid steel bath
The purpose of this paper is to characterize and to evaluate the diatomite powder of Sig region (West Algeria) withoutfluorine by powder generally used in tundish to thermal insulation of steel bath contain fluorine, that affecting the environment andhealth of workers. Thermal and physicochemical characterization showed different endothermic and exothermic peaks. Thescanning microscopy method was used and a large porosity was observed, which is very beneficial for improving the thermalconductivity of the product. The trial industrial in steelwork with diatomite powder, showed a weak loss temperature of steel (10 °Cmax), and filled fully function in thermal insulation of the steel bath. Voir les détails
Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC
Fuzzy monitoring of stator and rotor winding faultsfor DFIG used in wind energy conversion system
According to its high robustness, the use of doubly-fed induction generators in thewind energy conversion takes an important place in the world of production of electrical energy.This type of conversion became very attractive because of its manufacturing environments,low cost and operation with an easily available power supply. The increase interest in windenergy conversion has been accompanied by efforts to improve reliability, effective conditionmonitoring and better efficiency. In this work, a new technique is proposed for monitoring anddetection of inter-turn short-circuit ITSC and open phase circuits in the stator or rotor windingsof wind turbines based on doubly-fed induction generator The principle of the suggestedtechnique is based on the acquisition of the stator and the rotor currents of a doubly-fed inductiongenerator with the aim to calculate the values of root mean square amplitude, in addition to theknowledge expressed in rules and membership function. This technique is verified usingsimulations performed via the model of doubly-fed induction generators built in MATLAB ®Simulink. Voir les détails
Mots clés : doubly-fed induction generator, DFIG, Fuzzy logic, Monitoring, Detection, faults, RMS
Spatio-temporal aspects of the domain propagation in a spin-crossover lattice with defect
the collective spatiotemporal dynamics of the metastable high-spin state (HS) upon relaxation towards the low-spin (LS) is investigated using an electro-elastic model which includes the change of the spin states and the lattice volume at the transition. The present work focusses on the case of a lattice in which is embedded a structural defect in the center, represented here by a hole with a fixed size. The simulations are made on a 2D rectangular-shaped and compared to those of an ideal system. To account for the volume change, we set the distances between the sites as spin-dependent which requires the use of Monte Carlo simulations on spin states and atomic positions to solve the present problem. It is found that the presence of the defect affects the dynamics of the spin-crossover transformations which starts stochastically from a corner of the lattice, then propagates in the first stage along the width (shortest distance to the surface), before to proceed via a second longitudinal regime whose velocity slows down significantly at the vicinity of the defect, which plays the role of a pining center. After a while, the interface leaves the defect, and accelerates when it approaches the lattice's border. We have also investigated the spatial dependence of the displacement field, from which we derived the distribution of the divergence and rotational of the displacement field, which directly connects to the trace of the strain tensor and to shear strains respectively. Valuable information on the relaxation process of the elastic field are derived and discussed in direct relation with the presence of the defect. Voir les détails
Mots clés : Spin Crossover, Phase transition;, Interface propagation;, Spatiotemporal effects, elasticity
RF magnetron sputtering deposition of NiO/Ni bilayer and approach of the Magnetic behavior using the Preisach model
Bilayer of nickel and nickel oxide were deposited on glass substrates using RF magnetron sputtering technique. The magnetic properties of the prepared thin films were carried out at room temperature in both parallel and perpendicular magnetic field to the sample. The Preisach model was applied to provide a mathematical model of the magnetic hysteresis loop in the case of parallel geometry, along the easy axis of the bi-layer NiO / Ni. Good agreement was obtained between the theoretical and experimental results. Voir les détails
Mots clés : Ni/NiO bilayer;, Magnetic properties;, Preisach Model
Microstructural Study of Thin Films CuFe Obtained by Thermal Evaporation of Nanostructured Milled Powder
Commercial copper and iron powders were used as starting materials. These powders were mechanically alloyed to obtain Cu(100-x) Fex supersaturated mixture. The milling duration was chosen in such a way as to obtain a nanostructured mixture and to form a supersaturated solid solution 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 vapor deposition) under 1 × 10-6 mbar vacuum from an electrically heated tungsten boat, using the supersaturated solid solution Cu(100-x) Fex powder obtained by mechanical alloying. The films deposition has been done on glass substrates. In this study, we present the composition effect on the structural and magnetic proprieties of Cu(100-x) Fex powder and thin films. The chemical composition, structural and magnetic proprieties of milled powders and thin films were examined by SEM, TEM, XRD, XRF and VSM. Voir les détails
Mots clés : CuFe Solid Solution, DRX, MET, microstructure, thin film, VSM
Structure and Magnetic Properties of Ternary Nanosized FeAlSn and CuFeCo Powders Synthesized by Mechanical Milling
Ternary Fe72Al26Sn2 and Cu70Fe18Co12 alloys were obtained by mechanical alloying of pure Fe, Al, Sn, Cu and Co powders using a high energy ball mill. X-ray diffraction and electron microscopy supported by magnetic measurements have been applied to follow changes in the microstructure, phase composition and magnetic properties in dependence on milling time. With the increase of milling time all Al and Sn atoms dissolved in the bcc Fe and the final product of the MA process was the nanocrystalline Fe (Al, Sn) solid solution in a metastable state with a large amount of defects and mean crystallite size of 5 nm. However, the obtained crystallite size value is about 10 nm for the ball milled Cu70Fe18Co12 powders. The electron microscope observations show the morphology of powder particles. Magnetic properties of the nanocrystalline mechanically alloyed FeAlSn and CuFeCo were also investigated and were related to the microstructural changes. Voir les détails
Mots clés : CuFe Solid Solution, DRX, FeAl, Mechanical Alloying, SEM, VSM
Method for diagnosis of the effect of AC on the X70 pipeline due to an inductive coupling caused by HVPL
The inductive coupling between high-voltage power lines (HVPL) and buried pipelines has been an important research subject over the last decades. This coupling may result in alternating current (AC) on pipelines that may pose a serious threat to the pipelines due to corrosive effects and the cathodic protection (CP) performance. A method to investigate the effects of the induced AC density on the corrosion and the CP performances of the X70 steel buried pipeline due to the inductive interference caused by HVPL is proposed in this study. The method is based on the corrosion parameters of the X70 steel pipeline obtained by electrochemical measurements such as Tafel slopes, corrosion current densities, and corrosion potentials. These parameters were used as boundary conditions in the elaborated CP model. The results showed that, firstly, the induced AC density affects the electrochemical characteristic of the X70 steel and accelerates the corrosion of the pipeline. On the other hand, the impressed current cathodic protection is incapable of maintaining the CP potential level. However, some technical solutions were proposed to prevent the pipelines from AC corrosion and maintain the CP potential to an acceptable level. Voir les détails
Mots clés : electrochemical analysis, interference, chemical variables measurement, power cables, steel, electric current measurement, Corrosion protection, pipelines
Prediction of thermal and mass loss behavior of mineral mixture using inferential stochastic modeling and thermal analysis measurement data
Abstract:Characterization methods of material are widely used in different steps of quality control in material sciences and engineering. Such methods are relatively complex according to the considered case. This paper is concerned by a characterization method for mineral material analysis using thermal analysis i.e. Differential Scanning Calorimetric. The thermal analysis is a physical method based on the heating; the sample is heated using a ramped set point of the input temperature, according to its properties, the sample gives a thermal response qualified by endothermic and exothermic reactions: Such responses are fundamental for phase’s identification.In mineral industry, different material mixture is used in different stage of manufacturing process; the thermal behavior prediction of mixture between two or more materials is very interesting. The thermal mixture behavior is predicted in basis of individual thermal behavior of each input element and the mixture ratio.A mathematical modeling based on artificial neural network is designed to have a soft sensor for predicting the thermal and mass behavior of the mixture, validation using measurement and prediction uncertainties is also considered.Using such approach, the prediction of the mineral mixture characteristics is given by an implementation of the obtained model using the individual behavior and the mixture proportion of the inputs elements. Voir les détails
Mots clés : • Modeling and identification; • Artificial neural network (ANN); • Monte Carlo Simulation (MTCS); • Thermal analysis; • Material/mineral mixture; • Uncertainty of measurement