Liste des publications

Nombre total de résultats : 423
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Simplified Modelling of Tandem Cold Rolling

K. SLIMANI, M. ZAAF, H.Bendjama (2018)
Article de journal

In this paper, a calculation technique for solving the problem of regulatinginter-stand tension in a tandem cold rolling is proposed. Based on the slicesmethod, the proposed technique develops a computational model for a singlestand, and then generalizes it for five stands. The effectiveness of this technique is evaluated using experimental data acquired from tandem rolling millof IMittal steel complex of El-Hadjar-Algeria. By taking into account theelasticity of the rolls and using Newton’s method; the developed model can beused to calculate, successfully, the tensions correction of the five stands.Compared with the LAM3 software, the obtained results indicated that theproposed technique is effective and can be used to produce better performance of tandem cold rolling.Voir les détails

Mots clés : modelling, tandem cold rolling, slices method, elasticity, Newton’s method.

DETECTION OF BROKEN ROTOR BAR FAULT IN THE SQUIRREL CAGE INDUCTION MOTOR USING WAVELET PACKET ANALYSIS

DRICI Djalel, Merabet hichem, Aouabdi Salim, Boudiaf Adel (2018)
Article de journal

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. Tghe energy of wavelet components appear to be useful for detecting different electrical faults. In this paper we will study the problem of broken rotor barsVoir les détails

Mots clés : Wavelet Packet, Analysis, diagnosis fault, induction motor, broken bar

Sensor Monitoring of the Concentrations of Different Gases Present in Synthesis of Ammonia Based On Multi-Scale Entropy and Multivariate Statistics

Aouabdi Salim, Taibi Mahmoud (2015)
Article de journal

This paper presents powerful techniques for the development of a new monitoring method based on multi-scale entropy (MSE) in order to characterize the behaviour of the concentrations of different gases present in the synthesis of Ammonia and soft-sensor based on Principal Component Analysis (PCA).Voir les détails

Mots clés : Ammonia synthesis, Concentrations of different gases, Soft sensor, Multi-scale entropy, multivariate statistics.

Preparation and characterization of spinel type Zn2TiO4 nanocomposite.

Alima MEBREK, Safia ALLEG, Sihem BENAYACHE, Mohamed BENABDSLEM (2018)
Article de journal

Zinc orthotitanate Zn2TiO4 spinel structures have been prepared by solid state reaction in two stages. First, a mixture of ZnO and TiO2 (67% anatase+33% rutile) in a molar ratio of 2:1 was mechanically milled for 6 and 18 h, at room temperature, in a high energy planetary ball mill under argon atmosphere. Next, the ball milled powders were calcined at 900°C for 2 h, pressed into pellets and then sintered for 4 h at 1100°C in air. Phase formation, microstructure, surface morphology and optical properties were characterized by X-ray di?raction, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and UV–visible spectro- photometery. The mechanical milling process for 6 h gives rise to the formation of nanocrystalline orthotitanate Zn2TiO4 (15.5%, =13.2 nm) in addition to unreacted rutile TiO2, anatase TiO2 and ZnO structures. As the milling process progresses up to 18 h, the volume fraction of Zn2TiO4 increases to about 44.5%. The sintered pellets exhibit a composite structure where about a small amount of rutile nanograins are dispersed into the Zn2TiO4 matrix. FT-IR and Raman results con?rm the biphasic character of the sintered pellets. The band gap energy is milling time dependent. It varies from 3.22 for pellet 6 h to 3.45 for pellet 18 h.Voir les détails

Mots clés : Mechanical Alloying, ZnO−TiO2 system, XRD, Raman spectroscopy, SEM

SIMULATION STUDY OF SUPER-RESOLUTION IN HYDROPHONE MEASUREMENTS OF PULSED ULTRASONIC FIELDS

Wahiba Djerir, Tarek Boutkedjirt (2018)
Article de journal

In order to carry out reliable measurements of pulsed ultrasonic fields, the use of a piezoelectric hydrophone as receiver is recommended. However, due the finite size of the receiver aperture the measured acoustic pressure is affected by spatial averaging on the surface active face. The aim of this work is to deconvolve the spatial effects of the receiver hydrophone in order to reconstruct the pulsed ultrasonic field with a better spatial resolution. Hereby, the linear pulsed pressure field radiated in water by wideband planar transducers of 19 mm diameter, with central frequencies fc=2.25 MHz and fc=15 MHz are considered. The receivers are PVDF membrane hydrophones of 25 µm - thickness with rectangular and circular apertures. The results of this study show the strong dependency of the reconstruction quality upon the signal-to-noise ratio (SNR). Generally, the quality of the reconstruction decreases with decreasing SNR. Good reconstruction quality has been obtained with correlation coefficient larger than 0.9936 when the “acquired” signals are not too much noisy (SNR=60dB). In this case, improvement of the spatial resolution by a factor of 5 and 9 respectively could be reached. The reconstruction quality depends also upon the hydrophone dimensions, the axial distance to the source, the central frequency and the spectral frequency bandwidth of the pressure pulse.Voir les détails

Mots clés : Super-resolution, spatial inverse filter, spatial Wiener filter, PVDF hydrophone, pulsed ultrasonic field, ultrasonic field reconstruction.

Spatially Varying Weighting Function-BasedGlobal and Local Statistical Active Contours.Application to X-Ray Images

Aicha Baya Goumeidane, Nafaa Nacereddine (2016)
Article de journal

Image segmentation is a crucial task in the image processingfield. This paper presents a new region-based active contour whichhandles global information as well as local one, both based on the pixelsintensities. The trade-off between these information is achieved by aspatially varying function computed for each contour node location. Theapplication preliminary results of this method on computed tomographyand X-ray images show outstanding and efficient object extractionVoir les détails

Mots clés : image segmentation, Active contour, Averaged Shifted, histogram, pressure forces, statistics, Spatially varying function

Electroless copper deposition on epoxy glass substrate for electrocatalysis of formaldehyde

C. Dehchar, I. CHIKOUCHE, R. KHERRAT, A. Sahari, A. Zouaoui, A. MERATI (2018)
Article de journal

In this paper, we investigated the characteristics of a structured copper (Cu) ?lm deposited on the surface of an insulating epoxy glass (EG) substrate via a facile electroless plating process. The ?lm produced by this method was found to be of high purity and has a homogeneous microstructure consisting of an assembly of numerous aggregates that vary in size from 1 to 5 mm depending on the electroless deposition time. The electrocatalytic activity of the prepared electrode was investigated for the electrooxidation of formaldehyde using cyclic voltammetry in 0.1 M NaOH solution. Results show that formaldehyde oxidation takes place at a low potential of -0.34 V with large anodic current densities.Voir les détails

Mots clés : copper, electroless plating, Formaldehyde, Oxidation, Thin films

Numerical simulation study of a high efficient AlGaN-based ultraviolet photodetector

F. Bouzid, L. Dehimi, F. Pezzimenti, M. HADJAB, A. HADJ LARBI (2018)
Article de journal

In this paper, a two-dimensional (2D) numerical simulation study of a p+-n-n+ AlGaN-based ultraviolet (UV) photodetector, which is designed to achieve true solar blindness with a cutoff wavelength of 0.31 µm, is presented. The device performance is evaluated by investigating both the current density-voltage characteristics and the spectral response (SR). The proposed structure is optimized in terms of the fundamental geometrical and doping parameters. During the simulations, it was found that the detector is sensitive to the UV rays in the 0.155-0.37 µm wavelength range and the spectral response can reach 0.156 AW-1 under a light intensity of 1 Wcm-2 at zero-bias voltage and room temperature. This SR peak value increases further under reverse bias conditions. The temperature effect on the detector SR and the impact of an explicit trap concentration located into the p+ and n-region are also investigated. The spectral response decreases for a temperature exceeding 420 K. At the same time, the SR reference values begin to be affected only for acceptor and donor trap densities that are much higher than the local (total) doping concentration.Voir les détails

Mots clés : AlGaN, Numerical simulation, Photodetector, Spectral response, Trap Density

Correlation between defect depth and defect length through a reliability index when evaluating of the remaining life of steel pipeline under corrosion and crack defects.

Djamel Zelmati, Oualid GHELLOUDJ, Abdelaziz AMIRAT (2017)
Article de journal

Despite the various engineering models existing for lifetime investigation of hydrocarbon steel pipelines under localized corrosion and crack defects there is still a lack of information about the correlation between the two main parameters characterizing the geometrical defect model, depth and length. So the aim of the present work is a contribution in evaluating the remaining life of the pipeline using reliability analysis in order to correlate the two parameters through one common parameter, the reliability index. As a first step, the investigation is carried out on four standard and well established engineering models; Irwin, SINTAP, ASME B31G and Modified ASME B31G methods, aiming to coordinate results given by each of the four models. The potential defect depth and length correlation through a reliability index can be used as a decision-making tool to give realistic answers for replacing and/or repairing a tube subjected to internal pressure and on which flaws of different depths and lengths have been detected from inspection of a pipeline after few years of service.Voir les détails

Mots clés : corrosion, Defect, Reliability, Correlation, Sensitivity

Reliability estimation of pressurized API 5L X70 pipeline steel under longitudinal elliptical corrosion defect.

Djamel Zelmati, Oualid GHELLOUDJ, Abdelaziz AMIRAT (2017)
Article de journal

The probabilistic approach is the best way to give realistic answers for design and maintenance and it is considered as a powerful decision-making tool. In the present paper, assessment of the failure probability of corroded pipeline subjected to internal pressure is estimated by using the first order reliability method (FORM). Measurements of defect dimensions have been achieved changed into collected by using ultra sound inspection probe through a 75-km pipeline portion on one of the main Algerian high pressure gas transportation that has been in service for 30 years. The sensitivity analyses have been carried out on random variables to identify the importance of the parameters within the reliability mechanical model. The modified B31G code has been coupled as a mechanical model, with Rackwitz optimization algorithm by using PHIMECA Software. The limit state function resumes the difference between the pipeline burst pressure and the pipeline operating pressure. The aim of the present work is to make in evidence the competitive importance of pressure service, wall thickness and the defect depth with regards to defect length and to determine the influence of the coefficients of variation on the failure probability and the remaining life of the pipeline. A diagram based on the reliability index results is proposed to predict the pipeline degradation and it can be used as a decision tool for maintenance program.Voir les détails

Mots clés : corrosion, Failure probability, Coefficient of variation, Modified ASME B31G