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LATEF Mohamed, Pr. AΪAD Abedelkarime (2016)

La connaissance des caractéristiques modales est primordiale dans l’étude du comportement dynamique des structures. L’application de l’analyse modale a été souvent réservée au domaine linéaire. Cependant, la plupart des structures mécaniques, rencontrées dans la pratique, présentent un comportement plus ou moins non linéaire. L’aspect non linéaire est d’origines diverses, dépend de plusieurs facteurs et peut se manifester globalement (géométrie, propriétés mécaniques,…) ou localement (conditions aux limites, joints, …).Dans ce travail, nous avons applique l’analyse modale a des systèmes vibratoires discrets (masse-ressort) non linéaires d’aspect géométrique.Plusieurs méthodes ont été utilisées pour déterminer les paramètres modaux, a savoir :- Balance harmonique (analytique).- Variété de l’invariant de Shaw-Pierre (numérique).- Range Kutta d’ordre 4.Des programmes ont été établis sous matlab pour exploiter ces méthodes. Les résultats obtenus nous ont permis de préciser :- la limite entre les systèmes linéaires et non linéaires.- l’effet des conditions initiales et le paramètre non linéaire.- domaine d’application des méthodes permettant l’étude des systèmes non linéaires.Voir les détails

Mots clés : vibration, Analyse modale, non linéarité géometrique

Electronic Properties Study, of Ni/MgO Nanoparticles by (XPS)

N. Ouafek, N. Keghouche, H. Dehdouh, C.Untidt (2017)

A lot of knowledge has been accumulated on the metal clusters supported on oxide surfaces because of their multiple applications in microelectronics, heterogeneous catalysis and magnetic devices.In this work, the surface state of Ni / MgO has been studied by XPS (X-ray Photoemission Spectroscopy). The samples were prepared by impregnation with ion exchange Ni2+ / MgO, followed by either a thermal treatment in air (T = 100 -350 ° C) or a gamma irradiation (dose 100 kGy, 25 kGy dose rate h -1). The obtained samples are named after impregnation NMI, NMR after irradiation, and finally NMC(T) after calcination at the temperature T (T = 100-600 °C). A structural study by XRD and HRTEM reveals the presence of nanoscaled Ni-Mg intermetallic phases (Mg2Ni, MgNi2 and Mg6Ni) and magnesium hydroxide. Mg(OH)2 in nanometric range (2- 4 nm). Mg-Ni compounds are of great interest in energy filds (hydrogen storage…).XPS spectra show two Ni2p peaks at energies of about 856.1 and 861.9 eV, indicating that the nickel is primarily in an oxidized state on the surface. The shift of the main peak relative to the pure NiO (856.1 instead of 854.0 eV) suggests that in addition to oxygen, nickel is engaged in another link with magnesium. This is in agreement with the O1s spectra which present an overlap of peaks corresponds to NiO and MgO, at a calcination temperature T ≤ 300 ° C.Voir les détails

Mots clés : nanoparticles, Ni-MgO, XPS, XRD

Influence of manufacturing process on wear resistance Of grinding balls

BOUREBIA.MOUNIRA, BOUHAMLA Khedidja, MAOUCHE Hichem, Gherbi Amel, Chaour Mouhamed, Laouar.Lakhder (2017)

Abstract The grinding balls are widely used in cement works, they are often manufactured by the molding process, but the problem faced by major cement plants in Algeria is that these balls wear out quickly and broken. The objective of this work is to test wear resistance of grinding balls made by molding and grinding balls produced by forging. The tests of characterization of samples will be made thus that wear tests. The results indicate that grinding balls made by forging resist longer than molded balls by fact this method offers by fiber-forming phenomenon a solid texture which allows increases service life, wear resistance and impact strength.Voir les détails

Mots clés : Grinding ball, forging, molding, texture, wear


A.Younes, N.Dilmi, A.BOUAMER, H.Amar, Z.GUEZOUI, M.amir, M.Zergoug (2016)

Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength [1], good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear [1,2]. In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well-known methods for depositing such [3] coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet [4], nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress [5-6]. Voir les détails

Mots clés : Nanostructured materials, alumina, Mechanical Alloying, MEB, EDX, DRX, VSM

Love wave sensor based on PMMA/ZnO/glass structure for liquids sensing

Muhammad Hamidullah, Cinzia Caliendo, Farouk LAIDOUDI (2016)

PMMA/ZnO/glass structure was investigated to enhance Love mode sensor sentivities. The phase velocities and the attenuation of the acoustic wave propagating along the PMMA /30° tilted c-axis ZnO/glass structure contacting a viscous non-conductive liquid were calculated for different PMMA and ZnO guiding layer thicknesses, added mass thicknesses, and liquid viscosity and density. The sensor velocity and attenuation sensitivities were also calculated for different environmental parameters. The resulted sensitivities to liquid viscosity and added mass were optimized by adjusting the ZnO and PMMA guiding layer thickness corresponding to a sensitivity peak. The present analysis is of importance in manufacturing and applications of the PMMA-ZnO-glass structure Love wave sensors for the detection of liquids properties, such as viscosity, density and mass anchored to the sensor surface.Voir les détails

Mots clés : Love wave sensor, surface acoustic waves, ZnO-PMMA

Amorphous SiC/c-ZnO-based Lamb mode sensor for liquid environments

Cinzia Caliendo, Muhammad Hamidullah, Farouk LAIDOUDI (2016)

The propagation of the first symmetric Lamb mode S0 along ZnO/a-SiC thin composite plates was modeled and analysed aimed at the design of a sensor able to detect the changes of the environmental parameters, such as added mass in vacuum and the liquid viscosity changes in a viscous liquid medium. The Lamb mode propagation was modeled by numerically solving the system of coupled electro-mechanical field equations in the two media. The S0 acoustic field profile was calculated aimed at finding the proper plate thickness suitable for the propagation of longitudinally polarized modes. The phase velocity and electroacoustic coupling efficiency dispersion curves of the S0 mode were calculated aimed at the design of enhanced coupling efficiency devices. The gravimetric sensitivity in vacuum, and the attenuation that the S0 mode soffers when contacting a liquid viscous Newtonian environment were finally calculated for different ZnO layer thicknesses. Recently obtained results on the sputtering deposition of the a-SiC and ZnO thin and thick layers on Si substrates are also reported.Voir les détails

Mots clés : Lamb S0 mode, Amorphous SiC-ZnO, sensors, viscous liquids

Structural, Mechanical, Electronic, Elastic and Chemical Bonding Properties of the Complex K2PtCl6-Structure Hydrides Sr2RuH6 First-Principles Study

O.Boudrifa, A.Bouhemadou (2016)

We report a systematic study of the structural, electronic and elastic properties of the ternary ruthenium-based hydrides Sr2RuH6 within two complementary first-principles approaches. We describe the properties of the Sr2RuH6 systems looking for trends on different properties. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gap is about 2.99eV. Calculated density of states spectra demonstrate that the topmost valence bands consist of d orbitals of the Ru atoms, classifying these materials as d-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time.Voir les détails

Mots clés : Ruthenium-based hydrides; first-principles calculations; elastic constants; electronic structure

Fundamental properties of the rocksalt ZnO and MgO: an ab-initio prediction

Moufdi Hadjab, Smail BERRAH, Hamza ABID (2016)

The one of the most accurate first-principales methods is the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism, based on Density Functional Theory (DFT), has been exploited to study theatrically, the fundamental properties of the both ZnO and MgO rocksalt binary compound using 16 atoms rocksalt supercell which corresponds to (1×1×2) conventional cell. The Local Density Approximation (LDA) was used only for the structural properties, to treat the exchange-correlation terms. In order to explore the wanted properties. The recently modified semi-local Becke-Johnson potential within LDA correlation in the form of (mBJ) was used to predict the optoelectronic properties of ZnO and MgO binary materials. As results, our computed lattices parameters equal to: 4.22 Å and 4.16 Å respectively, showed satisfactory agreements with experimental values (4.27 Å and 4.2 Å) for ZnO and MgO respectively again. in order to understand the changeability between relaxed and un-relaxed of the electronic structures, The calculated band structures reveal that ZnO posses indirect band gap (Г-M) while for MgO have an indirect band gap (Г-Г) which agree well with the experiment and other theoretical calculations. Optical dielectric function, refractive index, absorption coefficient and optical conductivity, are well described in a wide range of the incident photon energy. The acquired results are used to give an significant guideline to the material's design for optoelectronic applications.Voir les détails

Mots clés : ZnO, MgO, FP-LAPW, Electronic materials, Optical parameters, ab initio calculations.


Abdeldjalil BENFOUGHAL, Khaled BOUBENDIRA, Nasira SASSANE, Mohamed BOULKRA, Skander Boukhezar, Noureddine BOUGHDIR, Nihel HAMZAOUI (2016)

The tribological and thermal behavior of dry sliding contact steel composite carbone/carbone and steel-organic matrix composites are studied according to the parameters normal load, sliding speed, friction coefficient and test time. In the case of automotive braking, using a mathematical model, the surface temperature of contact was determined. Four normal forces, four sliding speeds and four friction coefficients were applied in this study. These parameters have a significant influence on the variation of average contact temperature. The results illustrate the evolution of the contact temperature according to the braking time.Voir les détails

Mots clés : Temperature, friction, steel, composite, Disc, Trim.

Modélisation et simulation numérique du reformage catalytique du n-hexane sur un catalyseur bi-fonctionnel en régime transitoire


Ce travail est une tentative de modéliser et simuler mathématiquement le comportement, en régime transitoire, d’un réacteur catalytique isotherme a lit fixe avec résistance au transfert et dispersion axiale.Le modèle est appliqué à la réaction de reformage catalytique du n-hexane sur un catalyseur bi-fonctionnel (métal - acide). Cette réaction est d’une grande importance à l’échelle industrielle pour avoir des essences de haute qualité, ces calculs ont été faits en régime transitoire. L’objectif du travail était de suivre l’influence sur l’installation du régime stationnaire d’un certain nombre de paramètres à savoir : temps de séjour, concentration moyenne des sites actifs, la position des particules catalytique dans le lit. Les résultats obtenus nous ont éclairés sur le mécanisme d’installation du régime stationnaire dans le réacteur.Voir les détails

Mots clés : Reformage catalytique, réacteur a lit fixe, catalyseur bifonctionnel, résistance au transfert, Régime transitoire