Liste des publications

Nombre total de résultats : 646
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Improved cross pattern approach for steel surface defect recognition

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

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

Modeling and Simulation of Biaxial Strained P-MOSFETs: Application to a Single and Dual Channel Heterostructure

Amine Mohammed TABERKIT, Ahlam GUEN-BOUAZZA, Benyounes Bouazza  (2018)
Publication

The objectives of this work are focused on the application of strained silicon on MOSFET transistor. To do this, the impact and benefits obtained with the use of strained silicon technology on p-channel MOSFETs are presented. This research attempt to create conventional and two-strained silicon MOSFETsfabricated from the use of TCAD, which is a simulation tool from Silvaco. In our research, two-dimensional simulation of conventional MOSFET, biaxial strained PMOSFET, and dual-channel strained P-MOSFET has been achieved to extract their characteristics. ATHENA and ATLAS have been used to simulate the process and validate the electronic characteristics. Our results allow showing improvements obtained by comparing the three structures and their characteristics. The maximum of carrier mobility improvement is achieved with the percentage of 35.29 % and 70.59 % respectively, by result an improvement in drive current with the percentage of 36.54 % and 236.71 %, and reduction of leakage current with the percentage of 59.45 % and 82.75 %, the threshold voltage is also enhanced with the percentage of 60 % and 61.4%. Our simulation results highlight the importance of incorporating strain technology MOSFET transistors. Voir les détails

Mots clés : Biaxial strain, CMOS technology, SILVACO-TCAD, Strained silicon layers

Heat Transfer Mode and Effect of Fluid Flow on the Morphology of the Weld Pool

Abdel Halim ZITOUNI, Pierre SPITERI, Mouloud Aissani, Younes Benkheda  (2021)
Publication

In this work, the heat transfer by conduction and convection mode, effect of the fluid flow on the morphology of the weld pool and the welding properties are investigated during Tungsten Inert Gas (TIG) process. In the first part, a computation code under Fortran was elaborated to solve the equations resulting from the finite difference discretization of the heat equation, taking into account the liquid-solid phase change with the associated boundary conditions. In order to calculate the velocity field during welding, the Navier-Stokes equations in the melt zone were simplified and solved considering their stream-vorticity formulation. A mathematical model was developed to study the effect of the melted liquid movement on the weld pool. The evolution of the fraction volume of the liquid and the thermal fields promoted the determination of the molten zone (MZ) and the Heat Affected Zone (HAT) dimensions, which seems to be in good agreement with literature. Voir les détails

Mots clés : Thermal and flow modeling, TIG welding, Heat affected zone, molten zone

Slug length and frequency upstream a sudden expansion in gas– liquid intermittent flow

A. H. Zitouni, A. Arabi, Y. Salhi, Y. Zenati, E. K. Si-Ahmed, J. Legrand  (2021)
Publication

The purpose of this work is to analyze the influence of a sudden expansion on the upstream behavior of the horizontal gas–liquid slug flow. Measurements were made on a 40 mm ID pipe with and without a sudden enlargement of aspect ratio σ = 0.444. The experiments were carried out with two-phase air–water mixture. The slug lengths and frequencies were measured using a non-intrusive video technique. Upstream the sudden enlargement, it was observed that the mixture velocity has no influence on slug length. The variation of slug frequency is found proportional to the liquid superficial velocity for the two cases within this study. It was also observed that the behavior of the slug length and frequency was affected by the presence of the sudden enlargement. The comparison of the results obtained with various empirical correlations available in the literature showed that the latter are not worthwhile in the case where singularity is installed. Voir les détails

Mots clés : slug flow, sudden expansion, slug length, slug frequency

Structural, Magnetic, Dielectric and Piezoelectric Properties of Multiferroic PbTi1−xFexO3−δ Ceramics

Khiat Abd elmadjid, Felicia Gheorghiu, Mokhtar Zerdali, Ina Turcan, Saad Hamzaoui  (2021)
Publication

PbTi1−xFexO3−δ (x = 0, 0.3, 0.5, and 0.7) ceramics were prepared using the classical solid-state reaction method. The investigated system presented properties that were derived from composition, microstructure, and oxygen deficiency. The phase investigations indicated that all of the samples were well crystallized, and the formation of a cubic structure with small traces of impurities was promoted, in addition to a tetragonal structure, as Fe3+ concentration increased. The scanning electron microscopy (SEM) images for PbTi1−xFexO3−δ ceramics revealed microstructures that were inhomogeneous with an intergranular porosity. The dielectric permittivity increased systematically with Fe3+ concentration, increasing up to x = 0.7. A complex impedance analysis revealed the presence of multiple semicircles in the spectra, demonstrating a local electrical inhomogeneity due the different microstructures and amounts of oxygen vacancies distributed within the sample. The increase of the substitution with Fe3+ ions onto Ti4+ sites led to the improvement of the magnetic properties due to the gradual increase in the interactions between Fe3+ ions, which were mediated by the presence of oxygen vacancies. The PbTi1−xFexO3−δ became a multifunctional system with reasonable dielectric, piezoelectric, and magnetic characteristics, making it suitable for application in magnetoelectric devices. Voir les détails

Mots clés : dielectric response, Fe-doped PbTiO3, Magnetic Properties, multiferroic ceramics, piezo- electric properties

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

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

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

Magnetic and structural Behavior of Fe-CoO NanocompositesMechanically Milled

A.Younes, M.Khorchef, A.BOUAMER, H.Amar  (2019)
Publication

The Fe60(CoO)40 nanostructured alloys have been prepared from pure iron and cobaltoxide powders by mechanical alloying technique within a high energy planetary ball-mill.Morphology, microstructural and magnetic properties of this powder were investigated by a Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM). The effect of time of milling on magnetic behaviour of Fe(CoO) nanostructured composite has been investigated. Apparition of new phase polycrystallinesample having a size in the range of 12 and 26 nm, it is confirmed by X-ray diffraction testing.The enhanced magnetic properties and structural behaviour of the nanoparticle are due by the diminution of size of crystallite. After 40 hours of milling, the appearance of spinel structureof CoFe2O4. The reduction in particle size leads to a significant increase in magnetic hardening, the coercive field at room temperature increases from 6 Oe to 208 Oe Voir les détails

Mots clés : FeCoO nanostructured, Magnetic Properties

The influence of vacuum pressure on the electrical properties of PbTiO3-δ ceramics

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

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

Mechanical and structural behaviour of TiAlV nanocrystalline elaborated bymechanical milling technique

A.ABADA, S.Bergheul, A.Younes  (2020)
Publication

The aim of this study is to fabricate the Ti50Al40X1 0 nanostructured alloy (X: V) from pure titanium,aluminium, and vanadium powders by using a high-energy planetary ball mill with increasingmilling time from 10 to 80 h. Morphology, structural, and mechanical properties of this alloy wereinvestigated by a SEM, XRD, and nano-indentation testing. The effect of milling time on structural,morphological, and mechanical properties has been investigated. Microstructural characterisationshowed a decrease of average particle size during milling time. Crystallite size decreased from 49to 6.02 nm and lattice strain increased from 0.15% to about 0.89% during mechanical alloying. Inaddition, the mechanical properties of Ti50Al40V1 0 nanostructured materials were stronglydepended on the microstructure and crystallite size of new phases that appear during mechanicalmilling. Microhardness of the Ti50Al40V1 0 alloy increases with milling time from 261 to 738 Hv.These changes could be attributed to the crystallite size and the strain variations during milling. Voir les détails

Mots clés : crystal microstructure, Mechanical milling, Microstructural properties, nanostructured alloy, hardness testing

THE EFFECT OF Ti ADDITION ON MICROSTRUCTUREAND MAGNETIC PROPERTIES OF NANOCRYSTALLINEFeAl40 ALLOY POWDERS PREPAREDBY MECHANICAL ALLOYING

N.METIDJI, N-E.Bacha, A.Younes  (2020)
Publication

Recent research on nanocrystalline FeAl alloys has shown that these alloys are of high importancedue to their promising structural and mechanical properties, particularly magnetic behavior. Thiswork aims at studying the synthesis, structural and magnetic characterization of nanocrystallineFeAl alloy powders, prepared by a mechanical alloying process (MA), as well as the effect of Tiaddition on the magnetic properties of a compound. The powder morphology, phase transformation,crystallite size, micro-stress evolution, and magnetic properties were investigated by X-raydiffraction (XRD), scanning electronic microscopy (SEM), and vibrating samples magnetometer(VSM). It has been found that at the final stage of mechanical alloying the bcc-disordered FeAlphase and nanocrystalline Fe(Al, Ti) solid solution occurred for the FeAl40 and FeAl40Ti3 alloys,respectively. The milling time and the addition of titanium affect the powder morphology anddecrease the size of the particles. The average crystallites size of 17.2 and 11.2 nm was reached atthe end of 30 h of milling, and the lattice strain increased up to 0.3 and 0.21% for the FeAl40 andFeAl40Ti3 alloys, respectively. Also, the magnetic properties attributed to microstructural changeswere investigated. It has been established that the change in magnetic behavior occurs mainly due tothe formation of a supersaturated Fe(Al, Ti) solid solution. Magnetic properties of the samples arehighly influenced by the addition of the Ti element into FeAl40 alloy, as well. The magnetism of theFeAl40Ti3 compound is reported to be higher than that of FeAl40. Voir les détails

Mots clés : Mechanical Alloying, nanocrystalline materials, lattice strain, crystallite size, magnetic behavior.