Liste des publications
Investigation of some physical properties of pure and Co-doped MoO3 synthesized on glass substrates by the spray pyrolysis method
Pristine and Cobalt (Co)-doped MoO3 nanofilms were synthesized on glass substrates using the spray pyrolysis method. The nanometric pristine MoO3 films were prepared from the 10−2 M.L-1 solution of ammonium molybdate tetrahydrate [(NH4)6Mo7O24,4H2O] in distilled water. Co-doping at 0.5, 0.75 and 1% was achieved by adding cobalt (II) chloride hexahydrate (Cl2CoH12O6) in the pristine solution. The structure and the morphology of the films were investigated by means of X-ray diffraction and atomic force microscopy: two pronounced (020) and (040) peaks corresponding to the orthorhombic structure phase of α-MoO3 were detected. The AFM observations revealed the formation of micro-plates, parallel to the surface plane, with a roughness ranging from 33?nm to 54?nm. Optical properties were investigated through reflectance, transmittance and photoluminescence measurements. The optical band gap, the Urbach energy and the refractive index were deduced from these measurements. The presence of oxygen vacancies was revealed from the interband transitions in the blue and green domains. Co-doped MoO3 nanofilms showed ferromagnetic behavior. The photocatalytic degradation of an aqueous solution of methylene blue (MB) under UV irradiation, in the presence of Co-MoO3 nanomfilms, has been carried out using UV–vis spectrometery: the intensity of the absorption peak recorded at 660?nm decreased with the increase of the UV-illumination time while the color of the initial MB solution was drastically waned. Voir les détails
Mots clés : Spray pyrolysis method, MoO3 nanofilms, optical properties, Magnetic Properties
A novel correlation filter based on variational calculus
Correlation filters have been a popular technique for tackling image classification problems. The traditionalcriteria used to design correlation filters overlook some properties that can improve their discriminative power.Therefore, new criteria are proposed to design a novel correlation filter. Such criteria take advantage ofnegative samples, spatial information and the smoothness of the correlation output space. A closed formis derived from the criteria proposed using variational calculus. Moreover, it is shown that the resultingcorrelation filter is a bandpass filter. Experiments are conducted for face identification under illuminationvariation for a single training image per subject and head pose classification. The correlation filter proposeddelivers favorable scores when compared to other correlation filters and state-of-the-art approaches Voir les détails
Mots clés : Correlation filter, Variational calculus, Face identification, Illumination variation, Single training image, Pose classification
Video Processing and Analysisfor Endoscopy-Based InternalPipeline Inspection
Because of the increasing requirements in regards to the pipeline transport regulations, the operators take care to the rigorous application of checking routines that ensure nonoccurrence of leaks and failures. In situ pipe inspection systems such as endoscopy, remains a reliable mean to diagnose possible abnormalities in the interior of a pipe such as corrosion. Through digital video processing, the acquired videos and images are analyzed and interpreted to detect the damaged and the risky pipeline areas. Thus, the objective of this work is to bring a powerful analysis tool for a rigorous pipeline inspection through the implementation of specific algorithms dedicated to this application for a precise delimitation of the defective zones and a reliable interpretation of the defect implicated, in spite of the drastic conditions inherent to the evolution of the endoscope inside the pipeline and the quality of the acquired images and videos. Voir les détails
Mots clés : video processing, endoscopy, Pipeline inspection
Unsupervised weld defect classification in radiographic images usingmultivariate generalized Gaussian mixture model with exactcomputation 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 themanufacturing process in order to prevent unfair harm to the industrial plant in construction. For thispurpose, in this paper, a software specially conceived for computer-aided diagnosis in weld radiographictesting is presented, where a succession of operations of preprocessing, image segmentation, featureextraction andfinally defects classification is carried out on radiographic images. The last operationwhich is the main contribution in this paper consists in an unsupervised classifier based on afinitemixture model using the multivariate generalized Gaussian distribution (MGGD). This classifier is newlyapplied on a dataset of weld defect radiographic images. The parameters of the nonzero-mean MGGDbasedmixture model are estimated using the Expectation-Maximization algorithm where, exactcomputations of mean and shape parameters are originally provided. The weld defect database representfour weld defect types (crack, lack of penetration, porosity and solid inclusion) which are indexed by ashape geometric descriptor composed of geometric measures. An outstanding performance of theproposed 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%. Theefficiency of the proposed classifier is mainly due to theflexiblefitting of the input data, thanks to theMGGD shape parameter. Voir les détails
Mots clés : Mixture model, Multivariate GGD, radiography, weld defect, classification
Thermodynamic investigation on the adhesion and corrosion inhibitionproperties of a non-steroidal anti-inflammatory drug in HCl electrolyteapplied on mild steel material
In this paper, the inhibition mechanism of a pharmaceutical agent, piroxicam, on the corrosion behavior of carbon steel in HCl (1M) solution was investigated. The weight loss technique and quantum chemical calculations were carried out. The determined inhibition efficiency at 298 K was 86.90 % for a concentration of 600 ppm. The adsorption mode of the drug obeys to the Langmuir isotherm model. The free energy of adsorption (ΔGads = −32.84 kJ mol?¹) revealed a spontaneous process with a mixed interaction type, physical and chemical. The thermodynamic parameters (ΔHads and ΔSads) governing the adsorption phenomenon and metal dissolution were investigated and discussed through thermodynamic and kinetic principles. The ΔHads and ΔSads were respectively −17.86 kJ mol?¹ and 50.27 J mol?¹ K?¹ which indicates an exothermic process and an increased disorder at the interface. The DFT method was used to determine the adsorption centers of the chemical structure of the drug. EHOMO (−6.448 eV) reveals a high tendency of the drug to share its electrons with the metal. In addition, the SEM analysis was carried out for the surface characterization of the carbon steel after immersion into the aggressive medium in the absence and presence of the drug substance. Voir les détails
Mots clés : Mild steel, Weight loss, adsorption, DFT
Prediction of the Friction Coefficient of 13Cr5Ni2Mo Steel Using Experiments Plans-Study of Wear Behavior
Metal materials used in industrial applications deteriorate under the effect mechanical and chemical phenomena occurring under operating conditions, such as pipes carrying gas or fluid that are subject to internal wall wear. From where an experimental study was conducted through friction tests on supermartensitic stainless steel Cr13Ni5Mo2, in order to estimate the effect of test parameters on friction coefficient and wear behavior of this steel by adopting the factorial plans 22 methodology at two factors (Load "P" and linear sliding "V"), each at two levels (-1, +1). The results have been demonstrated using a mathematical model predicting the coefficient of friction "f" in every point of the study field. The factorial plans make it possible to establish a modeling of the studied phenomenon with a maximum of efficiency and a minimum of experiences. The experimental results showed that the friction coefficient "f" reaches a max value for an applied load P=10N combined with a linear speed V=5cm/s. In addition, the wear morphology of surfaces after the friction test indicates that for 2N and at all speeds, friction is dominated by an abrasive wear mechanism. However, for 10N, it is observed the predominance of adhesive wear with a higher wear rate. Voir les détails
Mots clés : friction, factorial design, Mathematical model, wear mechanism
Experimental study of chemically aged HDPE pipe material in toluene-methanol mixture and distilled water
Studying the aging phenomenon of plastic pipes presents simultaneously an economic achievement and a technical challenge for water and natural gas transportation systems. Ver y often, they are exposed to aggressive environmental agents such as UV rays, ambient oxygen, acids, bases and some other so lvents, altering the material microstructure, its physical and chemical properties. The high density polyethylene (HDPE) material degradation and loss of performance are usually the consequence of unwanted changes in mechanical behaviors leading to lower resistance. In this s tudy, we examine the effects of distilled water (DW) and a mixture of toluene-methanol (TM) in contact with an HDPE pipe. Morphological properties such as crystallinity and oxidation induction time (OIT) are in vestigated using DSC method. Tensile tests and thermal analysis show that the TM mixture is much more absorbed by the resin as compared to DW. An increase in crystallinity is observed as established from literature for other organic solutions. Finally, the study gives an idea about property variances and their evolution as a function of the pipe thickness which c an be used as an estimation of the structural heterogeneity of the product. Voir les détails
Mots clés : Pipe; HDPE; Aging; Distilled Water; Toluene-Methanol Mixture; Crystallinity; OIT
Study of The Reliability of A Composite Used In The Knee Prosthesis
In orthopedic surgery, the effectiveness of the implants used, such as hip and knee prostheses, depends mainly on their geometries and the type of loading to which they are subjected. In this work a probabilistic approach is chosen to study the reliability of a composite structure used in the manufacture of knee prostheses. The purpose of integrating reliability concepts is to consider uncertainty in several aspects including loading and material properties. The reliability index β is an excellent indication of durability and safety for given operating conditions. β is obtained using failure probability and a mechanical model. The critical stress intensity factor (Kc) is adopted as a criterion to the maximum limit of a numerically calculated KI. The results presented are discussed according to the length of the crack (a), and the limit load used. Voir les détails
Mots clés : Reliability analysis, critical stress intensity factor, crack length, load, reliability index
Magnetic and structural Behavior of Fe-CoO Nanocomposites Mechanically Milled
The Fe60(CoO)40 nanostructured alloys have been prepared from pure iron and cobaltoxide powders by mechanical alloying technique within a high energy planetary ball-mill.Morphology, microstructural and magnetic properties of this powder were investigated by aScanning Electron Microscope (SEM), X-ray diffraction (XRD) and Vibrating samplemagnetometer (VSM). The effect of time of milling on magnetic behaviour of Fe(CoO)nanostructured composite has been investigated. Apparition of new phase polycrystallinesample having a size in the range of 12 and 26 nm, it is confirmed by X-ray diffraction testing.The enhanced magnetic properties and structural behaviour of the nanoparticle are due by thediminution of size of crystallite. After 40 hours of milling, the appearance of spinel structureof CoFe2O4. The reduction in particle size leads to a significant increase in magnetichardening, the coercive field at room temperature increases from 6 Oe to 208 Oe Voir les détails
Mots clés : Fe60(CoO)40 nanostructured alloys, Mechanical Alloying, Magnetic Properties
Theoreticalmodelling for calculation of the energydensities of adsorption sites using inverse gaschromatography
The inverse gas chromatography is used to determine the energy densities of theadsorption sites of the stationary solid phase. The use of this technique is old anddates back to the 1940s. The many possibilities offered by this method are describedin several works. This work is an attempt to explore some adsorption local isothermmodels in order to determine the energy density of the adsorption sites. It involves theuse of integral equations of the first kind which are known to be numerically instable.These integral equations were solved by two different methods of solution. One isbased on the use of Taylor series expansions and the other uses the Stieltjes transform.Some interesting theoretical and numerical results are presented. Voir les détails
Mots clés : adsorption, Integral equations, Adsorption isotherms, energy