Liste des communications
Investigation of Properties of ZnO Nanostructures by First- Principals Calculations
Structural and microstructural properties were investigated by first-principals computing. The ZnO powder as Transparent Ceramics exhibited a hexagonal crystal structure with space group p63mc of ZnO. We applied the present first-principals approach to the electronic structure of the ZnO structures. Band structure and density of states of the phase of crystal ZnO computed using first principal methods, confirmed that pure ZnO is a direct band gap semiconductor when obtained in the B4 type structure phase. Voir les détails
Mots clés : ZnO;DFT; FP-LAPW
Electronic Properties of Carbon Nanotubes
Theoretical calculations predicted that carbon nanotubes were to present a metal behavior or semiconductor following their diameter and their chirality, these properties of conduction have inherited the structure of a particular band of graphite. Consequently, a limited number of wave vectors are allowed in this direction, It depends on the diameter and the winding of the graphene sheet on itself. If the edge conditions include the corners of the Brillouin zone, the behavior of the nanotube is metallic, this is the case for all “chair” type nanotubes and a third of “chiral” and “zig-zag” nanotubes. In other cases, the band structure has a bandgap, as a first approximation, inversely proportional at the radius of the nanotube. In addition, STM makes it possible to image the atomic structure of nanotubes and therefore to determine their chirality and their diameter. The transport properties can thus be correlated with the structure of the nanotube, the nanotube would be thus a quantum prototype of wire to a dimension. The various measurements carried out by AFM and STM on nanotubes monofeuillets showed that they behave indeed like such. The possible applications of these properties come within the province of nanoelectronic, not only the use of the nanotube like a molecular discussion thread but also like an active electronic element. Voir les détails
Mots clés : Carbon Nanotubes;STM;AFM
Optimization of the number of layers for a fixed thickness of a composite material subjected to compression loading
In this paper, the effect of varying the number of layers for a fixed total thickness is investigated. In order to conserve the integrity and the safety of a multilayers composite structure, the search of the optimal number of layers in the cross section, induced the low stress-strain field intensity, is strongly recommended. Meanwhile, this study aims to show how the mechanical response of a multilayers composite plate loaded on a compression in the axial direction, changes when the number of layers increases from for a fixed total thickness. Voir les détails
Mots clés : security factor, stress-strain field, Composite material, Compression loading
The importance of using dual-channel heterostructure in strained P-MOSFETs
We present in this work a dual-channel heterostructure strained structure, introduce the high carrier mobility Awaited in heterostructure devices while using several models which are: CVT, SHIRAHATA, and WATT, we present a two-dimensional simulation of dual strained channel heterostructure P-MOSFETs. This study is accomplished usingSILVACO-TCAD simulation software, the comparison of the effect of using strain technique on P-MOSFET transistors will demonstrate the importance of using strain technique especially in dual channel heterostructure MOSFET. The simulation of fabrication steps and the extraction of the electronic proprieties in terms of transfer and output characteristics, transconductance, and the quasi-static capacitance allow understanding and interpreting these enhancements Voir les détails
Mots clés : Strained Silicon, SiGe layer, MOSFET; Heterostructure, simulation, Silvaco
Surface Flaw Classification Based on Dual Cross Pattern
The evaluation of flat steel surface quality is mainly concerned with detecting and identifying product surface defects. Although the variety of the implemented techniques, this type of control still presents a challenge. In this paper, we assess the Dual Cross Pattern technique, as a feature descriptor, that should be quite discriminative, to ease the steel surface defect classification. The histograms extracted from the captured DCP features are concatenated to represent the global image feature vector. The procedure parameters, as the DCP circle radius, the number of the training images and their choice, are considered to show their impact on the results. The experiment conducted on the NEU published defect database shows that, compared to the other used techniques, the proposed approach reveals not only interesting recognition rates but presents advantages in time coast too. Voir les détails
Mots clés : Image description, pattern recognition, Product quality, steel surface defects, hot rolling process
Tool combination for the description of steel surface image and defect classification
In industry, the automatic recognition of surface defects of flat steel products still represents a real challenge. Indeed, in addition to constraints such as the image noise or blur, there is neither an agreed standard of these defects nor a standard method that can ensure the defect identification, whatever are their size, shape, orientation and location. Thus, the complexity of the algorithm that deals with this matter always depends on specific needs of the application. In this paper, we give details on an approach that combines Gabor wavelets (GW) and the local phase quantization technique (LPQ), to describe the steel surface images, and uses the histogram to extract their characteristics. The defect classification is carried out by means of two classifiers, namely the nearest neighbors and the support vector machine. The method assessment is based on testing different parameter values of the used tools. The approach shows a good performance in terms of recognition rates and feature vector length, which impacts the computing time. Also, the study reveals its suitability for an online steel surface defect recognition application. Voir les détails
Mots clés : Quality control, Computer vision, metal surface imaging, Filter bank application, pattern analysis and recognition
Asymmetric Generalized Gaussian DistributionParameters Estimation based on MaximumLikelihood, Moments and Entropy
In this paper, we address the problem of estimatingthe parameters of Asymmetric Generalized Gaussian Distribution(AGGD) using three estimation mehods, namely, Maximum LikelihoodEstimation (MLE), Moment Matching Estimation (MME)and Entropy Matching Estimaion (EME). For this purpose, thesemethods are applied on an unimodal histogram fitting of animage corrupted with AGGD noise. Experiments show that theeffectiveness of each method comparatively to the other onedepends on the variation range of the shape factor. Voir les détails
Mots clés : Asymmetric generalized Gaussian distribution, Parameter estimation, maximum likelihood, Moments, Entropy.
Preparation and characteristics of synthesized hydroxyapatite from bovine bones and by co-precipitation method
Hydroxyapatite (HA, (Ca10(PO4)6(OH)2) is a widely studied bioceramic due to its biocompatibility, bioactivity, and chemical similarity to the mineral component of bone. Generally, hydroxyapatite can be made from several natural and synthetic sources.The objective of this study is to prepare hydroxyapatite powders from different precursors (natural or chemical). Hydroxyapatite was synthetized by Co-precipitation method, the chemical precursors of which are [Ca(NO3)2.4H2O, (NH4)2HPO4] and the natural source was bovine bone. Bovine hydroxyapatite (BHA) was extracted from the bovine bone bio-waste via thermal method and milling process. Synthesized HA (SHA) was prepared by co-precipitation method with the pH 10.0 of mother liquor. The prepared powders were characterized using various analytical techniques such as XRD, FTIR spectroscopy, thermogravimetry (ATG), and scanning electron microscope (SEM). These techniques provide information about the structural, chemical, morphological and physicochemical of each of the prepared powders. The use of co-precipitation method produced a low crystallinity of HA while the thermal method increased crystallinity. On the other hand, the results showed that the Ca / P ratio of synthetic hydroxyapatite (SHA) as well as that of bovine bone source (BHA) was also stoichiometric. Voir les détails
Mots clés : hydroxyapatite, Bovine bone, synthesis, Co-precipitation.
Synthesis and characterization of hydroxyapatite powder derived of eggshell by precipitation method
Hydroxyapatite is the inorganic material with formula Ca10(PO4)6(OH)2. It is one of bioceramic was used for one repairs, fixing defects of filing voids in biomedical fields. The use of chicken eggshell is one of the natural sources to obtain the calcium phosphate compounds. The main objective of this study is to synthesize the hydroxyapatite by precipitation method from eggshell. The raw eggshell was calcined at 850°C for 2 hours following by grinding for 16 hours. The HA powder was synthesized by wet chemical method, using eggshells and phosphoric acid (H3PO4). X-ray diffraction spectroscopy (XRD, Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR) were used to characterize the morphology, composition and distribution of the particles. The Thermos gravimetric analysis (TGA-DTA) was also carried out to evaluate the stability of the synthesized HA powder. The particle-size distribution (PSD) of the powder was determined by the laser scattering particle size distribution analyzer. The results showed that the sintered at 1000°C of HA powder resembles the feature of pure and single apatite phase having favorable Ca/P ratio. Voir les détails
Mots clés : hydroxyapatite, Bioceramics, synthesis, Eggshell, Precipitation