Liste des publications
Computer aided weld defect delineation using statistical parametric active contours in radiographic inspection
A perfect knowledge of a defect shape is determinant for the analysis step in automatic radiographic inspection. Image segmentation is carried out on radiographic images and extract defects indications. This paper deals with weld defect delineation in radiographic images. The proposed method is based on a new statistics-based explicit active contour. An association of local and global modeling of the image pixels intensities is used to push the model to the desired boundaries. Furthermore, other strategies are proposed to accelerate its evolution and make the convergence speed depending only on the defect size as selecting a band around the active contour curve. The experimental results are very promising, since experiments on synthetic and radiographic images show the ability of the proposed model to extract a piece-wise homogenous object from very inhomogeneous background, even in a bad quality image. Voir les détails
Mots clés : Welded joint, Radiographic inspection, Active contours, local statistics-based model, band region selection
Optimization of Optical Gain in Inx Ga1-xSb/GaSb unstrained quantum well structures
In this paper we study the effects of In concentration, temperature, quantum well width and carrier density on optical gain for GaSb/InxGa1-xSb/GaSb untrained quantum well structures. This system was chosen as it is useful in infrared emission, finally, we introduce the optimum structure of quantum well to obtain the maximum optical gain, at room temperature and infrared emission particularly 2.3 (μm), for the use this structure in application of spectroscopic analysis of the gases specially CH4. This structure can be used for light absorption to increase the solar cell efficiency a based on a quantum well and multi-junction. Voir les détails
Mots clés : Quantum well, In1-x Gax Sb, optical gain, laser, Detection
Bayesian Networks-Based Defects ClassesDiscrimination in Weld Radiographic Images
Bayesian (also called Belief) Networks (BN) is a powerfulknowledge representation and reasoning mechanism. Based on probabilitytheory involving a graphical structure and random variables, BN iswidely used for classification tasks and in this paper, BN is used as aclass discrimination tool for a set of weld defects radiographic imagesusing suitable attributes based on invariant geometric descriptors. Testsare performed on a database of few hundred elements where the resultsare outstanding and very promising, since they outperform those givenby powerful SVM classifiers. Voir les détails
Mots clés : Bayesian networks, weld defects, Geometric descriptors, radiography
Joining Ti3SiC2 MAX Phase with 308 Stainless Steel and Aluminum Fillers by Tungsten Inert Gas (TIG)-Brazing Process
Herein we report on the Tungsten Inert Gas (TIG) brazing of Ti3SiC2 to 308 stainless steel and Al brazing fillers materials. The microstructures of the interfaces were investigated by scanning electron microscopy and energy dispersive spectrometry. Intensive interactions including dissolution and diffusion simultaneously occurred within the Ti3SiC2 and at the Ti3SiC2/308 stainless steel interface during TIG-Brazing. The interfacial region between Ti3SiC2 and 308 stainless steel filler is comprised of a decomposed Ti3SiC2 zone, an interaction layer zone and a modified 308 stainless steel zone. When the Ti3SiC2 comes into contact with the 308 SS molten filler during TIG-brazing, it starts decomposing into a TiCx+SiLiquid +Sigas, and simultaneously, deep penetration of the molten 308 SS into the Ti3SiC2 occurred to form a complex bright phase containing [Fe, Cr, Ni, Ti, C, Si] and TiCxphase. The loss of Si is attributed to its evaporation during the TIG-brazing process. Thermally induced residual stress due to thermal expansion mismatches create interfacial cracks between the decomposed Ti3SiC2 and the interaction layer zone. The phases that most likely form when Ti3SiC2 is joined with Al brazed filler material are Al in which some Si is dissolved, TiAl3 and Ti4AlC3. No cracks were observed during TIG joining of Ti3SiC2 with Al brazing filler material. Voir les détails
Mots clés : Tungsten Inert Gas (TIG) brazing, Ti3SiC2
Phenol photodegradation process assisted with Wells–Dawson heteropolyacids
This work aims to investigate the catalytic properties of the heteropolyacids (HPAs) withinphotocatalytic process. Photocatalytic degradation of phenol in aqueous solution was performedusing Wells–Dawson HPAs as catalysts under UV-illuminated condition at 254 nm.The effects of various parameters such as, concentration of catalyst, initial pH, and initialphenol concentration on the performance of photocatalytic process have been investigatedto obtain the efficient and durable catalysts and determine the better reaction conditions.The kinetics and the efficiency of phenol degradation were determined by various analyticaltechniques, such as HPLC and TOC. The results show that the photocatalytic degradationefficiency increases with decreasing pH and the optimum pH is 2 for both catalysts. Thephotodegradation follows pseudo-first-order kinetics with rate constants k = 8.56 × 10−2 and 9.94 × 10−2 min−1 for iron- and vanadium-substituted HPAs, respectively. Voir les détails
Mots clés : Well-Dawson HPA, Homogeneous catalysis, Phenol photodegradation, UV irradiation
Pillared clays as catalysts for methyl parathion removal by advanced oxidation processes
A natural bentonite from Mostaganem in Algeria was modified by intercalation with polyoxocationic solutions (Al•Fe, Al•Co, Al•Cu, Al•Fe•Cu or Al•Fe•La). The modification of the bentonite occurred via pillaring by ionic exchange with these solutions. The addition of these solutions led to the formation of pillared clays with important catalytic properties in environmental impact reactions. The structural and textural properties of materials calcined at 500 °C were determined by several techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and N2 adsorption–desorption analysis. The pillared clays were then used as a Fenton-type heterogeneous catalyst for the heterogeneous sono-Fenton process for the oxidation of methyl parathion in water. The catalytic tests revealed the activity of the introduced iron species and the promoter effect of lanthanide or copper on the catalytic activity of these species. The sono-Fenton method showed promising results for the degradation of methyl parathion when compared with the Fenton method. Therefore, the sono-Fenton method can be a viable alternative technology to the existing methods for treating methyl parathion in wastewater. Voir les détails
Mots clés : Advanced oxidation process, Pillared clay, Sono-Fenton, Methyl parathion pesticide, Wastewater treatment
Head Pose Classification Using a BidimensionalCorrelation Filter
Correlation filters have been extensively used in face recognition but surprisingly underused in head pose classification. In this paper,we present a correlation filter that ensures the tradeoff between three criteria: peak distinctiveness, discrimination power and noise robustness.Such a filter is derived through a variational formulation of these threecriteria. The closed form obtained intrinsically considers multiclass information and preserves the bidimensional structure of the image. The filterproposed is combined with a face image descriptor in order to deal withpose classification problem. It is shown that our approach improves poseclassification accuracy, especially for non-frontal poses, when comparedwith other methods. Voir les détails
Mots clés : Head pose classification, Bidimensional correlation filter
Enhancement of phased array ultrasonic signal in compositematerials using TMST algorithm
In this paper, we apply a new technique for the ultrasonic phased array signal enhancement. It is based on the threshold modifiedS-transform (TMST). The signal processing algorithms generally give very satisfactory results on synthetic signals verifying theimplicit or explicit hypotheses on which they are constructed. The obtained performances on the real signals can be howeverdifferent radically. Time–frequency analysis methods are mainly used to improve the defects detection resolution. Significantperformance enhancement is confirmed when the proposed approach is tested with the simulation of the B-scan signals contain acloser delamination to the front face. The experimental results show that the TMST Algorithm can enhance the quality of imageprovided by composite materials contained delamination defect. Voir les détails
Mots clés : Ultrasonic Phased Array, composite materials, S-transform, TMST Algorithm
On-Off control based particle swarm optimization for maximum power point tracking of wind turbine equipped by DFIG connected to the grid with energy storage
In this paper, particle swarm optimization (PSO) is proposed to generate an On-Off Controller. On-Off Control scheme based maximum power point tracking is proposed to control the rotor side converter of wind turbine equipped with doubly fed induction generator connected to the grid with battery storage. The Grid Side Converter (GSC) is controlled in such a way to guarantee a smooth DC voltage and ensure sinusoidal current in the grid side. Simulation results show that the wind turbine can operate at its optimum power point for variable speed and power quality can be improved. Voir les détails
Mots clés : DFIG, Energy storage, Maximum Power Point Tracking, On-Off Control, Particle Swarm Optimization (PSO)
Phenol photodegradation process assisted with Wells- Dawson heteropolyacids
This work aims to investigate the catalytic properties of the heteropolyacids (HPAs) within photocatlytic process. Photocatalytic degradation of phenol in aqueous solution was performed using Wells-Dawson HPAs as catalysts under UV-illuminated condition at 254 nm. The effects of various parameters such as, concentration of catalyst, initial pH and initial phenol concentration on the performance of photocatalytic process have been investigated to obtain the efficient and durable catalysts and determine the better reaction conditions. The kinetics and the efficiency of phenol degradation were determined by various analytical techniques, such as HPLC and TOC. The results show that the photocatalytic degradation efficiency increases with decreasing pH and the optimum pH is 2 for both catalysts. The photodegradation follows pseudo first-order kinetics with rate constants k = 8.56×10−2 min-1 and 9.94x10-2 min-1 for iron and vanadium substituted - HPAs, respectively. Voir les détails
Mots clés : Wells-Dawson HPA, Homogeneous catalysis, Phenol photodegradation, UV irradiation