Liste des publications

Nombre total de résultats :688
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The influence of vacuum pressure on the electrical properties of PbTiO3-δ ceramics

Khiat Abd elmadjid, Felicia Gheorghiu, Mokhtar Zerdali, Saad Hamzaoui  (2020)

PbTiO3-δ ceramics were successfully prepared by the traditional solid state reaction method using different vacuum pressures during calcinations step and then sintered at 1150 °C/2h. The present study was focused on the influence of vacuum pressure variation on the electrical properties of PbTiO3-δ ceramics. The room temperature XRD patterns indicate the crystallization of the perovskite structure for all the ceramics. The dielectric permittivity is increasing with decreasing of vacuum pressure due to the increasing of oxygen vacancies with reaching the high vacuum. Resistivity decreased with temperature increasing which proves the semiconductor character of present PbTiO3-δ ceramics. The electrical characterization indicates that PbTiO3-δ ceramics prepared using three different vacuum pressures during calcinations step are suitable for room temperature applications in microelectronics. Voir les détails

Mots clés : PbTiO3-δ ceramics, vacuum pressure, oxygen vacancies, Electrical properties, resistivity

Thermal andlfuid fow modeling oflthelmolten pool behavior duringlTIG welding bylstream vorticity method

Abdel Halim ZITOUNI, Pierre SPITERI, Mouloud Aissani, Younes Benkheda  (2020)

The present paper deals with the numerical simulation of weld pool development in Tungsten Inert Gas (TIG) process. A mathematical model is developed in order to solve the Navier–Stokes equations expressed in the stream–vorticity formulation coupled with heat equation taking into account the liquid solid phase change. Using the stream–vorticity formulation in incompressible fuid fow, the same problem is solved with reducing the number of transport equations. Therefore, only one transport equation (vorticity) and one Poisson equation (stream) are considered in this model. The FORTRAN programming and the numerical simulation are then achieved using appropriate discretization that ensures the convergence of the numerical methods to solve a large and sparse linear algebraic systems. Furthermore, to solve the radiation phenomena during welding described by the Stefen law, another method is proposed. Thefobtained numerical results are discussed and validate with experimental. Voir les détails

Mots clés : Thermal and fuid modeling, TIG welding, Stream vorticity, 304L steel, Numerical simulation

Improved cross pattern approach for steel surface defect recognition

Zoheir MENTOURI, Hakim DOGHMANE, Abdelkrim Moussaoui, Hocine Bourouba  (2020)

In steel-making processes, different methods are used for online surface product monitoring. Such a control has become anecessity to avoid additional costs resulting from the poor quality of the final product. With the reported performance that variesfrom one application to another, all the applied methods have to meet a minimum of criteria as accuracy and speed. Thiseffectiveness is assured thanks to a relevant image description and efficient defect classification algorithms. The Dual CrossPattern technique, successfully applied in face recognition, is a concept that relies on coding pixels to provide such a discriminatingdescription of the image. Its principle can perfectly be used in industrial vision applications for surface defect recognition.In this study, the relevance of this method of describing defect images is evaluated, and improvements are proposed to increase itsefficiency. The experimental study shows that the pixel coding that considers the variations of the intensity in several directionsand captures the information from more than one pixel-neighborhood level makes it possible to better detect the variability in thedefect image and helps to increase the defect recognition rate. The experiments are carried out with the use of the publishedNortheastern University (NEU) database for the comparison and with a new constructed database to better show the improvementsbrought by the proposed approach. Voir les détails

Mots clés : Computer vision, Image description, Surface defect classification, Steel process

Steel Strip Surface Defect Identi?cation using MultiresolutionBinarized Image Features

Zoheir MENTOURI, Abdelkrim Moussaou, Djalil BOUDJEHEM, Hakim DOGHMANE  (2020)

The shaped steel strip, in the hot rolling process,may exhibit some surface ?aws. Their origin could bethe internal discontinuities in the input product or thethermomechanical transformation of the material, duringthe shaping process. Such defects are of a random occurrenceand may lead to costly rework operations or to adowngrading of the ?nal product. So, they should bedetected and identi?ed as soon as possible, to allow atimely decision-making. For such a quality monitoring, theused vision systems are mainly based on an imagedescription and a reliable classi?cation. In this paper, weexplore pre-de?ned image ?lters and work on a procedureto extract a discriminant image feature, while realizing thebest trade-off between the improved recognition rate of thesurface defects and the computing time. The proposedmethod is a multiresolution approach, based on theBinarized Statistical Image Features method, employed todate in biometrics. The ?lters, pre-learnt from naturalimages, are applied to steel defect images as a new surfacestructure indicator. They provide a quite discriminating image description. A relevant data reduction is used togetherwith a classi?er to allow an ef?cient recognition rate ofthe defective hot rolled products. Voir les détails

Mots clés : Computer vision, statistical features, Classi?cation, strip surface defects, hot rolling process

Unraveling the effect of Bi2S3 on the optical, electrical and magnetic properties of γ-MnS-based composite thin films

Z.Amara, M.Khadraoui, R.Miloua, A.Boukhachem, A. ZIOUCHE  (2020)

(Bi2S3)x (γ-MnS)1-x composite thin films have been deposited onto glass substrates using spray pyrolysis method. The structural and compositional investigations confirmed the co-existence of Bi2S3 and γ-MnS binary compounds in the thin films. The surface morphology indicated that the increase in Bi2S3 concentration influences both the shape and the size of γ-MnS crystallites. The optical analysis via transmittance and reflectance measurements revealed that the band gap energy Eg decreased from 3.29 eV to 1.5 eV in terms of Bi2S3 content. The electrical parameters such as resistivity ρ, mobility μ, carrier concentrations and Hall coefficient have been obtained by Hall Effect measurements. It is found than incorporation of Bi2S3 enhances the conductivity, and p-type conduction of γ-MnS could be converted to n-type at x = 0.5. The vibrating sample magnetometer measurement has revealed that (Bi2S3)x (γ-MnS)1-x composite thin films have a ferromagnetic behavior at room temperature. Voir les détails

Mots clés : γ-MnS, Bi2S3, Spray pyrolysis, Magnetic Properties

First principal investigation of structural, morphological, optoelectronic and magnetic characteristics of sprayed Zn: Fe2O3 thin films

Rihab BenAyed, MejdaAjili, Jorge M.Garcia, AichaZiouche, Jose Luis CostaKramer, Najoua KamounTurki  (2020)

Undoped and Zn-doped Fe2O3 thin films were grown through spray pyrolysis. Zinc doping effect on the physical properties was investigated in detail. X-ray diffraction analysis confirms that all the Fe2O3 thin films showed a rhombohedral structure. The surface morphological study shows an interesting dendrite structure. The estimated band gaps energies were increased from 2.13 to 2.21 eV for indirect transition and from 1.80 to 1.85 eV for direct transition as function of doping ratio which was increased from 2 to 8 at. % Zn. The resistivity value (ρ) of un-doped Fe2O3 thin film is 6.06 × 104 Ω. cm and as adding Zn ions, ρ consequently decreased to 52 Ω. cm for 6 at. % Zn-doped Fe2O3 thin films. Vibrating sample magnetometer (VSM) measurements showed an increase of the saturation magnetization with the Zn2+ insertion. Further, a ferromagnetic behavior was observed. Voir les détails

Mots clés : Ferromagnetic, semiconductor, Fe2O3, Zinc doping, Low resistivity

Optimal Tuning of Fractional Order Proportional-Integral-Derivative Controller for WireFeeder System Using Ant Colony Optimization

Noureddine Hamouda, Badreddine BABES, Cherif Hamouda, Sami KAHLA, Thomas Ellinger, Jürgen Petzoldt  (2020)

The goal of this work is to present a robust optimal control approach, in order to improve the speed error-tracking and control capability of a permanent magnet DC Motor (PMDC)driven wire-feeder systems (WFSs) of gas metal arc welding (GMAW) process. The proposed speed controller employs an optimized fractional-order proportional + integral+ derivative (FOPID) controller that serves to eliminate oscillations, overshoots, undershoots and steady state fluctuations of the PMDC motor and makes the wire-feeder unit (WFU) has fast and stable starting process as well as excellent dynamic characteristics. The fixed controller parameters are meta-heuristically selected via an ant colony optimization (ACO) algorithm. Numerical simulations are performed in Matlab/Simulink environment and the performance of the proposed ACO-FOPID controller is validated. The simulation results clearly demonstrate the significantimprovement rendered by the proposed approach in the wire-feeder system's reference tracking performance, torque disturbance rejection capability, and transient recovery time. Voir les détails

Mots clés : gas metal arc welding process, wire-feeder system, fractional-order-proportionalintegral-derivative controller, ant colony optimization algorithm

CoSoTIA Project: Decision Supportfor the Choice of Concentrated SolarTechnologies for Electricity Generation

M. AISSANI, K. Mohammedi, A. ZITOUNI, M. BOUKRAA, T. Cheki?  (2020)

The CoSoTIA (Concentrated Solar Technologies for Industrial Applications)project initiated by the CRTI center in collaboration with the URMPEunit concerns the study and development of CSP solar concentrators for industrialapplications. In the present work, we present decision support tools for thechoice of a solar concentration technology for sites in Algeria. They will be usedfor the comparison between different technologies of solar concentration e.g.:cylindro-parabolic, parabolic, solar tower, etc. The models used include projectcosts and site characteristics; they incorporate also engineering knowledge (economic,social, technical and environmental). The information needed for decisionmakingproduced by these tools is: the total cost of the project, indicators witheconomic, social, technical and environmental aspects. The case studies presentedwere conducted under the SAM Advisor environment, which was developed toevaluate the capacities to implement CSP project in order to produce expertisefor the different actors through an application on a given site (by the client). Fourcase sites in Algeria and for two types of solar concentrator plant are studied andpresented. A comparative study was conducted and for each site the best CSP wasdeduced and commented. Voir les détails

Mots clés : Decision support, Multicriteria analysis, Solar concentration

Auto-control technique using gradient method based on radial basis function neural networks to control of an activated sludge process of wastewater treatment

A.Lemita, S. Boulahbel, S.KAHLA, M. Sedraoui  (2020)

Dissolved oxygen (DO) concentration is a key variable in the activated sludge wastewater treatment processes. In this paper, an auto control strategy based on Euler method and gradient method with radial basis function (RBF) neural networks (NNs) is proposed to solve the DO concentration control problem in an activated sludge process of wastewater treatment. The control purpose is to maintain the dissolved oxygen concentration in the aerated tank for having the substrate concentration within the standard limits established by legislation of wastewater treatment. For that reason, a new proposed control strategy based on gradient descent method and RBF neural network has been used. Compared with RBF neural network PI control, the obtained results show the effectiveness in terms of both transient and steady performances of proposed control method for dissolved oxygen control in the activated sludge wastewater treatment processes. Voir les détails

Mots clés : activated sludge process, Wastewater treatment, Gradient descent algorithm, RBF neural network, PI control

New Optimal Control of Permanent Magnet DC Motor for Photovoltaic Wire Feeder Systems

Badreddine BABES, Amar BOUTAGHANE, Noureddine Hamouda, Sami KAHLA, Ahmed KELLAI, Thomas Ellinger, Jürgen Petzoldt  (2020)

This article aims to improve the permanent magnet DC (PMDC) motor performance for photovoltaic (PV) wire-feeder systems (PVWFSs) of arc welding machines. The considered technique is designed by direct speed control based on optimal Fractional-order Fuzzy PID FO-Fuzzy-PID controller. The purpose is to ensure optimal control of wire feed speed reference to reduce torque ripples and hence, the performance of the WFS is improved. The dynamic reaction of the proposed solar PVWFS relies upon the scaling factors of FO-Fuzzy-PID controller, which are optimized by using teaching-learning algorithm based on Particle Swarm Optimization (PSO) method. The maximum power point tracking (MPPT) is achieved using an intelligent FO-Fuzzy-PID current controller based Perturb and Observe (P&O) MPPT algorithm. The PVWFS system incorporating the proposed method is tested and compared with the conventional PID control scheme under different weather conditions. The simulation of the proposed system by MATLAB\SIMULINK is carried out. The simulation results indicate the effectiveness of the considered control strategy in terms of the reduction in torque oscillations, optimizing electrical power and wire feed speed. Voir les détails

Mots clés : Solar photovoltaic (PV) module, wire feeder systems (WFSs), DC-DC buck converter, MPPT control, FO-Fuzzy PID controller, Particle Swarm Optimization (PSO) algorithm