Nombre total de résultats : 279
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A. Badidi Bouda, R. Halimi, A. Mebtouche, W. Djerir  (2008)
Article de conférence

In this paper we propose an experimental study of the steel grains size effect on the shiftfrequency of the ultrasonic waves being propagated in this material. By suitable heat treatment on samples resulting from the same bar, we have obtained identical samples butwith different mean grains sizes. We have then measured the ultrasonic shifts frequency after propagation in the material. The results obtained show a direct effect on the meangrains sizes on the ultrasonic frequency. These results, in conformity with the theory, showthe possibility of characterizing a material grains size by a nondestructive method:ultrasounds.It is known that a material characterization is possible through the measurement of someultrasonic parameters such as propagation velocities and attenuation coefficients. Wepropose a method which exploits the frequency and whose measurement is easy. Theseresults open way to a more inclusive and nondestructive characterization of materials byultrasounds. Voir les détails

Mots clés : ultrasonic frequency, propagation velocities, attenuation coefficients, nondestructive characterization

Deconvolution of the transducer aperture effect in steel

Wahiba Djerir, Tarek Boutkedjirt and Ali Badidi Bouda  (2009)
Article de conférence

When measuring the ultrasonic field, the signal provided by the receiving transducer isaffected by its spatial properties. Particularly, the displacement normal to its surface isspatially averaged because of the receiver finite size. In this study, we show, using anumerical simulation, the effectiveness of the spatial deconvolution of these effects for arectangular transducer. For that, three methods allowing the inversion of the aperture effectare tested 1) Wiener’s method 2) The power spectral equalization method (PSE) and 3) themaximum a-posteriori method (MAP).The obtained results show that the three methods areable to reconstruct the ultrasonic field from the spatially averaged values and that the qualityof the reconstruction depends strongly upon the SNR and the spatial frequencies bandwidth ofthe ultrasonic field investigated. Voir les détails

Mots clés : Deconvolution, Spatial filter, Wiener filter, power spectral equalization method (PSE), maximum a posteriori method (MAP).

Modeling and simulation of ZnxCd1-xTe/ZnTe quantum well structure for laser applications

S.Dehimi L.Dehimi, T.Asarcd B.Mebarkie S.Özçelikcd  (2017)

In this work, we modeled and simulated aZnxCd1-xTe/ZnTe based single quantum well structure. We have taken into account the effect of carrier density, alloy composition, temperature and wells width on the optical gain as well as threshold current density. The use of ZnTe as a barrier leads to the improvement of the carrier confinement such as Qc (83%)/Qv (17%). Then, we have optimized the quantum well structure that allows obtaining a threshold current density Jth = 500 A/cm2. This study allowed us to achieve laser diodes VCSEL quantum well reliable and emitting around 0.740 μm. Voir les détails

Mots clés : Quantum well Semiconductor laser Gain ZnCdTe Optoelectronics

Modelling of a Cd1−xZnxTe/ZnTe Single Quantum Well for Laser Diodes

S.Dehimi L.Dehimi T.Asar S.Özçelik  (2017)

In this paper, the carrier density, temperature and quantum well width effect have been investigated for the optical gain for a Cd1−xZnxTe/ZnTe Zinc-blend strained quantum well structure. The device emits laser radiations in green–yellow–orange. Our results showed that the optical gain significantly increases with the increasing of the carrier density. It also increases with the decreasing of the Zn concentration, the well width and the temperature. In addition, the optimal threshold current density values were determined for three alloy compositions as 0.7, 0.8 and 0.9. Voir les détails

Mots clés : Quantum wells diode laser gain CdZnTe optoelectronics

Effect Of Thickness On The Structural, Microstructural, Electrical And Magnetic Properties Of Ni Films Elaborated By Pulsed Electrodeposition On Si Substrate

T. KACEL, A. Guittoum, M. Hemmous, E. DIRICAN, R. M. ÖKSÜZOGLU, A. Azizi, A. LAGGOUN, M. Zergoug  (2017)

We have studied the effect of thickness on the structural, microstructural, electrical and magnetic properties of Ni films electrodeposited onto nn-Si (100) substrates. A series of Ni films have been prepared for different potentials ranging from −−1.6V to −−2.6V. Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), four point probe technique, atomic force microscopy (AFM) and vibrating sample magnetometry (VSM) have been used to investigate the physical properties of elaborated Ni thin films. From the analysis of RBS spectra, we have extracted the films thickness tt (tt ranges from 83nm to 422nm). We found that the Ni thickness, tt (nm), linearly increases with the applied potential. The Ni thin films are polycrystalline and grow with the ?111??111? texture. The lattice parameter aa (Å) monotonously decreases with increasing thickness. However, a positive strain was noted indicating that all the samples are subjected to a tensile stress. The mean grain sizes DD (nm) and the strain εhklεhkl decrease with increasing thickness. The electrical resistivity ρρ (μΩ.μΩ.cm) increases with tt for tt less than 328nm. The diffusion at the grain boundaries may be the important factor in the electrical resistivity. From AFM images, we have shown that the Ni surface roughness decreases with increasing thickness. The coercive field HCHC, the squareness factor SS, the saturation field HSHS and the effective anisotropy constant K1effK1eff are investigated as a function of Ni thickness and grain sizes. The correlation between the magnetic and the structural properties is discussed Voir les détails

Mots clés : Ni thin films; pulsed electrodeposition; structural properties; microstructure; magnetization curves; magnetic anisotropy.

Modelling of thermodynamics of adsorption on sensor array films : application to the generalized multicomponent adsorption model of Langmuir

abbas abdelaziz  (2017)

In the present study, by using of Gibbs Duhem formalism and simple mathematics, new models, which describe the response of the elements of a sensor array , have been developed .In addition , the thermodynamic ehavior of the interfaces sensor array fims gas mixture has been treated . Finally, the derived models were used for the generalized model of adsorption of Langmuir. Voir les détails

Mots clés : adsorption of Langmuir, Gibbs Duhem equations, intrinsic conducting polymers, modeling, sensor array

Correlation between structural and optical properties of SiO2/TiO2multibilayers processed by sol-gel technique and applied toBragg reflectors

H.Sedrati, R.Bensaha, M.Brahimi, H.DEHDOUH, H.Bensouyad, F.Abbas, B.Toubal  (2013)

SiO2 and TiO2 thin layers processed by sol-gel technique have been deposited,alternatively, on glass substrates and Si (111) wafer. Dip-coatedmultibilayerswere characterized by different experimental techniques:XRD,SEM, FTIRandUV-VIS-NIR. The obtainedX-ray diffraction patterns analysishave shown that our films crystallize in anatase and rutile phases whateveris the number of bilayers and the corresponding grain sizes increasefrom 5.48 nmto 16.11 nm. The SEMmicrograph shows that our layers arehomogeneous without any visual cracks. The FTIR spectra have shownthat the vibration of Si-O-Ti bonds becomes intense by the increase in thenumber of bilayers. This increase, on the on hand, decreases the transmissioncoefficient from 4.58% to 0.55% and increases the width of the stopband shown in UV-VIS-NIR spectra. On the other hand, the band-gap decreasesfrom3.73 eV to 3.59 eV. In addition, a pseudo band-gap is locatedbetween 300 nmand 400 increasing from1.76 eVto 2.29 eV.? 2013 Trade Science Inc. - INDIA Voir les détails

Mots clés : Sol-gel;, Anatase;, Rutile;, Stop band;, Si-O-Ti;, Band-gap.

Simulation du L’implantation ionique du phosphore dans la matrice de ZnO

Article de conférence

Le matériau ZnO montre de manière quasi-naturelle un dopage de type n [1]. Son dopage de type p représente une importante problématique récurrente depuis plus d'une quinzaine d'années. Dans ce travail nous avons fait une simulation numérique du dopage de ZnO en type p. Pour cela, nous avons utilisé le code dénommée TRIM (Transport and Range of Ions in Matter) et SRIM (Stopping and range of Ions in Matter) développé par Ziegler et al [2].C’est une simulation faite pour caractériser l'interaction des ions avec des cibles échantillons en gaz ou en solides. Les résultats numériques visent à étudier l'interaction d'un faisceau d'ions avec la surface semi-conductrice du ZnO. Dans notre étude le bombardement des ions du phosphore P tombe sur la cible ZnO selon une incidence normale au plan de la surface du matériau avec la possibilité de former des postes vacants sur la zone irradiée le composé de type II-VI ZnO Voir les détails

Mots clés : ZnO, SRIM, TRIM


M. T. AbedGhars; M. Ghers; S. Bouhouche; B. Bezzina  (2017)
Article de conférence

Abstract.This work has a double objective. On the one hand, the valorization of natural raw materials, in particular, the oolithic iron ores which do not find their use in iron and steel because of their high phosphorus content and on the other hand the recycling of steel by-products.. The ultimate goal is to synthesize an anti-corrosion paint.In this first part, we will study the characterization of these two components by their chemical analysis, their grinding (fineness) and their thermal analysis (TGA, DSC).Chemical analysis showed that the pigment contains 53.18% of total iron and gangue dominated by silica. Calamine in turn contains 73.83% of iron in the form of iron oxides (FeO, Fe3O4 and Fe2O3).Iron pigment is composed mainly of hematite with a little of goethite.Grinding tests showed that the scale is much more suitable for grinding than pigment. The granulometric analysis measured by a laser granulometer (Hydro 2000MU) gave us a volume distribution of the particles with a size between 0.7 and 32 microns for scale and between 0.6 and 40 microns for the pigment and Their specific areas are 1.6 and 1.5 m2 / g..Thermogravimetric analysis (TGA) and the thermal variation of flow (DSC) showed that the iron pigment loses weight with phase dissolution by consuming energy when the temperature increases. Scale gains weight by the formation of new phase with heat.Exploration picture by scanning electron microscope of red iron pigment shows a grain aggregate formed rounded over at least iron oxide and gangue. The analysis by EDS shows a predominance of iron with a relatively large matrix containing the four predominant oxides in the case of iron ore deposits. Chemical elements forming these four oxides are silicon, calcium, aluminum and magnesium.The observation scale milled for 5 min SEM showed a homogeneous structure composed of sizes of iron oxide grains and shapes ranging from 1 µm to 10 µm. Voir les détails

Mots clés : Pigment iron, scale (calamine), iron oxides, grinding, Simultaneous thermal analysis.

Prediction of thermal and mass loss behavior of mineral mixture using inferential stochastic modeling and thermal analysis measurement data

M.T. AbedGhars, S. Bouhouche, M. Ghers  (2017)

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