Physique

Nombre total de résultats : 255
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Eddy current characterization and Magnetic properties of iron alumina nanostructured alloy

Ahmed Benyahia, Abderrahmane YOUNES, Mohammed Khorchef, Rabah ABDELKADER, Mourad ZERGOUG  (2017)
Article de conférence

The mechanical alloying technique has been used to synthesis iron alumina nanostructred powder in a high energy planetary ball-mill PM400. Electromagnetic and magnetic characterizations of the powders was investigated by eddy current and vibrating sample magnetometer, the impedance, the coercivity and saturation magnetization of the iron alumina mixtures changes in function of x% (wt). Voir les détails

Mots clés : iron alumina, electromagnetic and magnetic properties, Eddy Current, VSM.

Etude de l’effet des conditions de polarisation sur le mode de relaxation principale (α) du PLA par la technique des courants thermostimulés (CTS)

A.BOUAMER, N. Benrekaa  (2017)
Article de conférence

Dans ce travail nous nous sommes intéressé à l’étude de l’influence des conditions de polarisation (champ et température), sur le mode de relaxation principal(α) du polylactic acide (PLA) par la technique des courants thermo-stimulés (CTS). L’influence du champ électrique se traduit parune augmentation linéaire de l’intensité du thermocourant relatif au mode α ainsi que celle de la polarisation totale de ce pic, affirmant ainsi le caractère dipolaire de la relaxation. L’élévation de la température de polarisation conduit à une augmentation progressive de l’intensité et de la polarisation jusqu’à saturation au voisinage de la transition vitreuse. Les énergies d’activations évaluées par la méthode des demi-hauteurs, augmentent pour des températures de polarisation inférieures à 70°C, puis rejoignes un palier de saturation. Un tel résultat est dû à un processus thermiquement activé et à une distribution du temps de relaxation. La température de transition vitreuse Tgaugmente avec la vitesse de chauffage. Ce résultat confirme la nature cinétique de la transition vitreuse. Voir les détails

Mots clés : Transition vitreuse, relaxation, PLA, CTS.

Amorphous SiC/c-ZnO-Based Quasi-Lamb ModeSensor for Liquid Environments

Cinzia Caliendo, Muhammad Hamidullah, Farouk LAIDOUDI  (2017)
Publication

The propagation of the quasi-Lamb modes along a-SiC/ZnO thin composite plates wasmodeled and analysed with the aim to design a sensor able to detect the changes in parametersof a liquid environment, such as added mass and viscosity changes. The modes propagation wasmodeled by numerically solving the system of coupled electro-mechanical ?eld equations in threemedia. The mode shape, the power ?ow, the phase velocity, and the electroacoustic couplingef?ciency (K2) of the modes were calculated, speci?cally addressing the design of enhanced-coupling,microwave frequency sensors for applications in probing the solid/liquid interface. Three modeswere identi?ed that have predominant longitudinal polarization, high phase velocity, and quitegood K2: the fundamental quasi symmetric mode (qS0) and two higher order quasi-longitudinalmodes (qL1 and qL2) with a dominantly longitudinal displacement component in one plate side.The velocity and attenuation of these modes were calculated for different liquid viscosities andadded mass, and the gravimetric and viscosity sensitivities of both the phase velocity and attenuationwere theoretically calculated. The present study highlights the feasibility of the a-SiC/ZnO acousticwaveguides for the development of high-frequency, integrated-circuit compatible electroacousticdevices suitable for working in a liquid environment. Voir les détails

Mots clés : Lamb Modes, Amorphous SiC, Coupling configurations, sensors, viscous liquids

ULTRASONIC DETERMINATION OF CARBON CONTENT

A. Badidi Bouda, R. Halimi, A. Mebtouche, W. Djerir  (2011)
Article de conférence

In this paper we are proposing an experimental study of the effect of low alloy steels carboncontent on the velocity and propagation attenuation coefficient of the ultrasonic waves inthese materials. We have observed simple relations between the velocities and theattenuations according to the carbon content. The same observations can be made for theYoung modulus. These results, in conformity with the theory, show the possibility ofcharacterizing the carbon content by a nondestructive method: ultrasounds. In parallel wehave studied the effect of some heat treatments such as hardening, annealing andquenching on velocities and attenuations. The results obtained show a correlation betweenheat treatments and ultrasonic parameters. This opens ways to a more complete and nondestructive characterization of steels by ultrasonic methods. Voir les détails

Mots clés : carbon content, velocity propagation, attenuation coefficient, ultrasonic methods, steel.

GRAINS SIZE CHARACTERIZATION BY WAVES ULTRASONICFREQUENCY

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)
Publication

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)
Publication

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)
Publication

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)
Publication

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