Liste des documents
Tomographic Image Reconstruction Using Filtered Back Projection (FBP) And Algebraic Reconstruction Technique (ART)
This paper presents comparative study and experimentation of Algebraic Reconstruction Technique (ART) and Filter Back Projection (FBP). The ART and FBP methods are used to reconstruct the object from the X-ray projection. The process of creating back the object image from the Radon Transform of the object is known as Image Reconstruction. Image reconstruction is a famous and interesting field which comes under computed tomography. Computed Tomography is used for identifying the hidden or inner defects of objects. In this paper Algebraic Reconstruction technique and Filter Back Projection methods are implemented and the experimented results are compared using performance parameters for various test cases. Projections for the image reconstruction are calculated analytically by defining two phantoms: Shepp-Logan phantom head model and the standard medical image of abdomen. The original images are grayscale images of size 128 × 128, 256 × 256, respectively. Voir les détails
Mots clés : Computed tomography, X-ray projection, Filter Back Projection, Algebraic Reconstruction Technique
Density functional approach to study structural and electronic properties of III-Sb semi-conductors by modified Becke-Johnson Potential
In this work, we present the structure and electronic properties of the semiconductors III-Sb binaries, using a first principles calculations have been performed, using the FullPotential Linearized Augmented Plane Wave (FP-LAPW) calculations based on Density Functional Theory (DFT) [1-2].The local density approximation (LDA) and the revised Perdew-Burke-Ernzerhof generalized gradient approximation (GGA-PBEsol) were used only in calculating structural properties, the modified Becke–Johnson (mBJ-GGA) approach were used to calculate the electronic properties. Our calculations are in good agreement with the theoretical works and experimental data, deducing the possibility of these materials to be used in the optoelectronics devices. Voir les détails
Mots clés : FP-LAPW, mBJ-GGA, wien2k, structural parameters, electronic properties
Theoretical investigation of optical properties of zinc blende III-Antimony materials
A first-principles calculations have been performed, using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) calculations based on Density Functional Theory (DFT) method as implemented in Wien2k code, to evaluate the optical properties of III-Antimony binary compounds AlSb, GaSb and InSb, using the new semi-local modified Becke–Johnson potential (TB-mBJ) developed by Tran and Blaha. The real and the imaginary parts of the dielectric function, absorption coefficient, reflectivity and optical conductivity versus photon energy were presented to discuss optical properties of III-Sb. The results obtained were compared with experimental data and other computational works, suggesting our compounds as suitable materials for optoelectronic device applications. Voir les détails
Mots clés : FP-LAPW, DFT, mBJ-BT, Optical parameters.
Study and control of PWM arc welding inverter based on a microcontroller
This paper presents an arc welding inverter, based on a microcontroller device for generate PWM pulse. An IGBT inverter was established by applying several control techniques. This system improves the power factor of welding machine and reduce the harmonics. Simulations results are presented to show the operation of proposed system. Voir les détails
Mots clés : are welding inverter, microcontroller, PWM, IGBT inverter
Microstructure and mechanical behavior of TIG bimetallic joints
Bimetallic weld techniques have progressed a great deal in the last decade. In this work, the effect of the filler metal composition on microstructure and mechanical behavior of dissimilar HSLA-X70/304L stainless steels weld joint is investigated. The dissimilar weld joints are fabricated using austenitic, duplex and low Carbone filler metal. The mechanical behavior is investigated through microhardness, charpy impact and tensile test.The results show that, the weld metal composition has a great influence on mechanical properties and microstructure of weldments, in particular the grain size and phases nature, changes with filler metal composition. In addition presence of martensitic slats in the FZ when using the low Carbone filler metal, detailed microstructure examination is carried out and related to the mechanical behavior of the dissimilar joints. Voir les détails
Mots clés : TIG welding, Bimetallic weld, HSLA, DSS, HAZ, microstructure, Microhardness
Solid state synthesis of ZnO nanostructures: effect of temperature on the structural and Optical properties
Among the different approaches to synthesize nanostructured ZnO, the solid state synthesis isone of the simplest methods to elaborate the ZnO nanoparticles. In this work we obtainednanostructured ZnO by aforesaid method using zinc nitrate tetrahydrate ZnO(NO3)2 asprecursor. The influence of calcination temperatures as 300, 400, 500 and 600°C, on thecrystallite size and the optical properties was investigated by X-Ray diffraction and UV–visible spectroscopy, respectively. The results obtained by XRD confirm that the diameter ofnanocrystallites was affected by the calcinations temperature. The UV–visible absorbancespectra of the synthesized samples reveals that the calcinations temperature plays a significantrole in the absorption characteristics, and influences the optical band-gap of the samples.Raman and FT-IR spectroscopy were performed to investigate the structural, vibrational andchemical properties of the ZnO nanostructures. Voir les détails
Mots clés : ZnO nanostructure, FTIR, UV-Vis, solid state synthesis
Structural and microstructural characterization of Algerian diatomite
Diatomite is a sedimentary rock composed of fossilized skeletons of diatoms which are microscopic unicellular alga. Due to its useful physical and chemical characteristics, it is used in a wide range of industrial applications. Raw diatomite samples were taken from SIG region of Algeria. Chemical composition, morphology, structure and specific surface area are determined by X-ray fluorescence, scanning electron microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and N2-adsorption-desorption analysis, respectively. The XRF results indicate that the raw diatomite is mainly composed of silica (>60%) and CaO (>14%). The XRD pattern reveals a mixture of amorphous silica and crystalline phases such as quartz and tridimite. The surface area, pore volume and pore size are 26.4 m2/g, 0.204cm3/g and 30.82 nm, respectively. Voir les détails
Mots clés : diatomite, characterization, pore, FTIR
Study of composite with metallic matrix WC/W2C- 20W-20Ni realized by spontaneous infiltration of the bronze alloy Cu-30Mn-3P.
The improved performance and duration of an impregnated tool for the mineral drilling requires thorough understanding of the mechanisms involved in the consolidation of powder mixtures in the liquid phase sintering cycle (FPL). The elements used for the manufacture of the active parts of these tools are usually made from mixtures of loose powders based on WC / W-Ni. The spontaneous infiltration process is the most appropriate method offers a big possibility of shapes due to molding. It lets to have considerable density of the metal matrix composite (MMC) constituting the active head and increase its resistance to erosion and abrasion.This work consists to develop a metal matrix composite which can constitute the active part of a drilling tool impregnated by the infiltration of industrial process SILP (Sintering by Infiltration of an appropriate mixture of Loose Powders). The mixture of loose powders (WC/W2C-W-Ni) is infiltrated under hydrogen by a manganese bronze (Cu-30Mn-3P) and then characterized by DTA, optical microscopy, SEM coupled with EDS, HRA hardness and micro-hardness Hv0.1. Voir les détails
Mots clés : Matrix Composite Material (MMC), SILP process, Matrix, Powder Free, alloying element, sintering in liquid phase (FPL), multi-material, physical chemistry.
Analyse Par LA Technique TSDC et la Spectroscopie Infrarouge (FTIR) DU Polactic acid (PLA) au Voisinage de la Transition Vitreuse
Résumé :L'acide polylactique (PLA) se présente comme une alternative viable aux plastiques pétrochimiques pour de nombreuses applications [1]. Il est produit à partir de ressources renouvelables et est biodégradable, se décompose en donnant du H2O, CO2 et de l'humus, la matière organique noire dans le sol. En outre, il possède des propriétés physiques uniques qui le rendent utile dans diverses applications, y compris dans le domaine biomédical mais aussi dans l’industrie comme la fabrication des fibres, des films d’emballages [2]. Dans ce travail nous nous sommes intéressés aux propriétés physico-thermiques de ce matériau et ses propriétés de relaxation en présence de champs électriques. Ce type de travaux reste jusqu’à présent peu développé. L’analyse des courants thermiquement stimulés TSDC ainsi que la spectroscopie infrarouge à transformée de Fourier FTIR ont été utilisées dans notre investigation dans la zone de transition vitreuse de ce matériaux. Les résultats obtenus nous suggèrent dans le cas des renforts de chaines, des applications très intéressantes dans le domaine de l’isolation électrique et l’encapsulation des composants électronique. Ceci offre une alternative écologique dans ce domaine. Voir les détails
Mots clés : Polylactic acid, TSDC, Spectroscopie infrarouge
Vibration-based bearing fault diagnosis by an integrated DWT-FFT approach and an adaptive neuro-fuzzy inference system
The rotating machine, which can be subject to breakdowns or dysfunctions in its time-of-use, represents an essential part in the majority of industrial applications. Hence, their reliability, productivity, safety and availability are very important issues that are imposed to increase production with quality assurance as per given specification at a reasonable cost. Furthermore, because the bearing faults are the most frequent and critical defects in rotating machinery that may have a direct influence on the availability of the machine itself and also on those of the surrounding systems, a particular interest is carried in this paper to the analysis and diagnosis of these defects which can appear in the bearing's ball, inner race and outer race with various fault severity and rotating speed. This paper consists of the application of the Discrete Wavelet Transform DWT and Fast Fourier Transform FFT theories to extract the amplitude of the fundamental bearing defect frequencies in the vibration signal from a rotating machine. These parameters will be used by the Adaptive Neural Fuzzy Inference System ANFIS to automate the fault detection and diagnosis process. Experimental results show that the proposed procedure can classify with precision various types of bearing faults according to the fault location and severity. Voir les détails
Mots clés : bearing faults, vibration signal, Fault Diagnosis, ANFIS, DWT, FFT