Liste des documents
Characterization of The Structure, Microstructure of ZnO Powder Nanostructures as Transparent Ceramic for Optical Applications
ZnO powder nanoparticles have been studied to investigate their structural and microstructural properties using X-ray diffraction (XRD)and optical microscope for examined ZnO pure powder. The ZnO powder exhibited a hexagonal crystal structure with space group p63mc of ZnO, XRD patterns of powder ZnO were obtained from the full pattern XRD using the MATCH program. For the applications of Zinc oxide as transparent ceramic for optical applications, ZnO is a potential candidate material for optics applications, which has attracted considerable attention over past decades due to its wide potential applications. Voir les détails
Mots clés : ZnO, microstructure, XRD, Optical Microscope.
RELATIONSHIP BETWEEN AE PARAMETERS AND FRACTURE OF COMPOSITE MATERIALS UNDER SOLICITATIONS
Abstract: Acoustic emission (AE) techniques have been extensively studied in concrete engineering. There has been much research in relating AE parameters, such as energy, amplitude, count number, rise time to physical properties such as crack area delaminating, pull out, break down. Our work is performed using of carbon fiber reinforced polymer to study the evolution of AE parameters under solicitations. Meanwhile the waveforms created by the failure were monitored by AE sensors attached to the concrete beam.Examination of the waveforms produced by a range of four sensors with different frequency responses reveals that the fracture depth affects the AE parameters detected during failure. Relationship between fracture area and AE parameters was examined. These results can be used to aid the quantification of damage size based on energy release from concrete structures in the field. Voir les détails
Mots clés : acoustic emission, carbon fiber, sollicitation, quantifi
Structural and Thermal Characterization of 1% Fe-doped ZnO Powder Nanostructures Prepared by Mechanical Alloying as Transparent Ceramic for Optical Applications
ZnO powder nanoparticles mechanically alloyed were doped with iron to investigate their structural and microstructural properties using X-ray diffraction (XRD) for examined 1% Fe doped ZnO. The ZnO starting pure powder exhibited a hexagonal crystal structure with space group p63mc of ZnO, however with the introduction of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains are found milling time dependent. For the applications of Zinc oxide, Zinc oxide (ZnO) is a potential candidate material for optics applications which has attracted considerable attention over past decades due to its wide potential applications such as ZnO photonic crystal slab ,photo catalyst, antibacterial treatment,UV absorption, light emitting diodes, photo detectors, solar cells, gas sensors and so on. Voir les détails
Mots clés : ZnO, XRD, microstructure, Optics applications
Modélisation de l’élaboration d’un biomatériau (hydroxyapatite)
Résumé / Abstract : L’hydroxyapatite (HA) Ca10 (PO4) 6 (OH) 2est élément major dans le corps humain, dans notre travail on a fait une élaboration du ce biomatériau avec la variation de six facteur nécessaire a la fabrication de ce dernier et ce la selon un plan d’expérience Plackett-Burman et ainsi on a calculé le rendement de la réaction on se basant sur un model mathématique avec l’utilisation du minitab14. Les paramètres qui ont été suivi sont : le rapport molaire Ca/P, le temps de la réaction, la vitesse d’agitation, le débit d’ajout des phosphates, la température de la réaction et la température de calcination du produit final. Ainsi, à la fin du processus, les produits solides susceptibles qui sont obtenus sont CaCl2, 2H2O, Na2HP04, 12H2O et Ca3 (PO4) 2, les autres NaCl et HCl sont éliminés avec l'eau de rinçage.Les résultats obtenus montrent que le paramètre rapport Ca/P semble être le plus important et que le produit obtenu est un mélange de phosphate tricalcique avec les réactifs initiaux de la réaction à savoir le chlorure de calcium hydraté et le di-sodium hydrogénophosphate hydraté. Cela fait en tout un mélange d’hydroxyapatite, de phosphate tricalcique et aussi des produits de départ, le chlorure de calcium et le sel de phosphate les deux hydratés. Voir les détails
Mots clés : hydroxyapatite, plan d’expérience, élaboration, Plackett-Burman, Biomatériau
Inhibition Efficiency of Cinnamon Oil as a Green Corrosion Inhibitor
The corrosion inhibition efficiency of cinnamon oil for stainless steel 304 L in 0.1 and 1.0 M HCl solutions was investigatedusing electrochemical study and surface electronic observation. The potentiodynamic polarization curves showed that, independentlyof the time of immersion in 1.0% HCl, a reaction to the anode occurred, which was explained by the dissolutionof the metal due to the strong aggressiveness of the medium; the addition of 1% cinnamon oil led to a corrosion efficiencyof 84%. Furthermore, in 0.1 M aggressive medium the tests with addition of inhibitor showed that the inhibition efficiencyincreases (86.6–96.0%) with an increase in the cinnamon oil concentration from 0.5 to 5%. Scanning electron microscopeobservations of metal surface confirmed the existence of a protective adsorbed film of the inhibitor on the steel surface. Cinnamonoil can be proposed as an efficient green inhibitor of corrosion of stainless steel exposed to hydrochloric acid mediums. Voir les détails
Mots clés : Aggressive medium · Cinnamon oil · Corrosion inhibitor · Stainless steel
Fast Adapting Mixture Parameters Schemes for Probability Density Difference-Based Deformable Model
This paper presents a new region-driven active contour using the pdf difference to evolve. The pdf estimation is done via a new and fast Gaussian mixture model (GMM) parameters updating scheme. The experiments performed on synthetic and X-ray images have shown not only an accurate contour delineation but also outstanding performance in terms of execution speed compared to the GMM estimation based on EM algorithm and to non-parametric pdf estimations. Voir les détails
Mots clés : Active contour, Adaptive mixture, GMM parameters update
Unsupervised weld defect classification in radiographic images using multivariate generalized Gaussian mixture model with exact computation of mean and shape parameters
In industry, the welding inspection is considered as a mandatory stage in the process of quality assurance/quality control. This inspection should satisfy the requirements of the standards and codes governing the manufacturing process in order to prevent unfair harm to the industrial plant in construction. For this purpose, in this paper, a software specially conceived for computer-aided diagnosis in weld radiographic testing is presented, where a succession of operations of preprocessing, image segmentation, feature extraction and finally defects classification is carried out on radiographic images. The last operation which is the main contribution in this paper consists in an unsupervised classifier based on a finite mixture model using the multivariate generalized Gaussian distribution (MGGD). This classifier is newly applied on a dataset of weld defect radiographic images. The parameters of the nonzero-mean MGGD-based mixture model are estimated using the Expectation-Maximization algorithm where, exact computations of mean and shape parameters are originally provided. The weld defect database represent four weld defect types (crack, lack of penetration, porosity and solid inclusion) which are indexed by a shape geometric descriptor composed of geometric measures. An outstanding performance of the proposed mixture model, compared to the one using the multivariate Gaussian distribution, is shown, where the classification rate is improved by 3.2% for the whole database, to reach more than 96%. The efficiency of the proposed classifier is mainly due to the flexible fitting of the input data, thanks to the MGGD shape parameter. Voir les détails
Mots clés : Mixture model, Multivariate GGD, radiography, weld defect, classification
Effect of zinc/cadmium proportion in CdS layers deposited by CBD method
Cadmium poisoning and the cost of panel recovery which is very expensive and difficult in the buffer layers of CdS in solar cell, for these two drawbacks, we do a search on the effect of proportion of zinc/cadmium in the properties layers of CdS. For this, our studies study the properties of CdxZn1-xS layers deposited by chemical bath (CBD). CdZnS thin films were synthesized by chemical bath deposition (CBD) with different deposition protocols to optimize deposition parameters such as temperature, deposition time, ion concentrations and pH. The surface morphology, structural, optical and chemical properties of the CdZnS thin films were studied by SEM, XRD, Raman and UV-visible spectrophotometer. The transmittance is 80% in the visible region 300 nm - 800 nm; the crystalline structure is hexagonal and cubic, the grain size is between 9.95 to 25.82 nm. It is observed that the transmittance and the shape change with the concentration of zinc in the solution; this result favors the application of these films in solar cells application. Voir les détails
Mots clés : CdZnS, chemical bath, SEM, Raman, solar cells, Thin films
Preparation, structural and functional properties of PbTiO3-δ ceramics
In the present study, oxygen deficient PbTiO3-δ ceramics were prepared by solid state-reaction method. The formation of the pure perovskite phase with tetragonal structure was confirmed for the 800 °C/2 h calcined sample by using X-ray diffraction analysis at room temperature. Energy dispersive X-ray spectroscopy analyses confirm the creation of oxygen vacancies in the system for charge compensations, as demonstrated by the percentage of O atoms of ∼53%. The complex impedance data reveals important contributions of the oxygen vacancies to the total dielectric response that are homogeneous distributed within the sample. The room temperature magnetic properties show a weak ferromagnetic character in all the samples that might be attributed to the oxygen vacancies defects and to surface effects. Voir les détails
Mots clés : Ceramics, oxygen vacancies, EDX spectra, Dielectric properties, Magnetic Properties
Optimal Stochastic Excitation for Linear Flaw Detection in a Solid Material.
The field of ultrasonic nondestructive testing has known a great development during the recent years. In order to increase the faw detection sensitivity, many improvements have been made in the equipment and the sensors technology. In the present work, the optimal command which maximizes the flaw detection is investigated experimentally. A parametric optimization consisting of finding the optimal excitation frequency which maximizes the Euclidean distance between a reference medium and a medium with a linear faw has been obtained automatically by using the gradient descent algorithm. Moreover, the waveform excitation optimization has been considered. A set of stochastic signals have been transmitted to the medium. A closed loop optimization process based on a genetic algorithm allowed to find the optimal excitation without a priori knowledge on the shape of the signal. This optimal excitation converged to a sinusoidal pulse with the optimal frequency found by the parametric optimization. Voir les détails
Mots clés : Optimal command, nondestructive testing, Gradient descent algorithm, Genetic algorithm, Ultrasound