Liste des publications
CARACTÉRISATION ET TRAITEMENT PARCOAGULATION-FLOCULATION D’UN EFFLUENT DE LAITERIE
L’objectif de cette étude est de clarifier les eaux usées de la laiterie "EDOUGH" parun traitement physico-chimique en procédant à une coagulation-floculation douce ; à l’aide dedeux coagulants communément utilisés dans le traitement des eaux. Dans ce cas ; le sulfated’aluminium Al2(SO4)3 et la chaux Ca(OH)2 ont été testé en présence d’un floculant PE14.Les essais de traitement ont montré que les deux coagulants utilisés permettraient deréduire : les matières en suspension (MES), la charge organique, les éléments azotée etphosphorée. Le meilleur résultat a été enregistré par la chaux avec un abattement de 92 % desMES et 83 % de Pt (phosphate totale), ce qui garantit le respect des normes algérienne envigueur pour ces deux paramètres. Voir les détails
Mots clés : coagulation-floculation, Effluent laitier, Matière organique, Eau usée, pollution
Theory of solids/gas mixtures multi-interfaces: Application to the steady state interactions between a sensor array based on metal oxide semiconductor detectors and a mixture of vapours
The aim of this paper is to find useful relationships in differential form that describe the isothermal steady state interactions between a sensor array based on metal oxide sensors and a mixture of vapours. These equations of state relate the variation of partial molar intensive quantities (as the change of the sensor molar partial sensitivity or molar adsorptions enthalpy), to gas mixture components concentrations and sensor array parameters. This kind of equalities is known in the thermodynamic of miscellaneous as Gibbs–Duhem equations. Voir les détails
Mots clés : Metal oxide sensors, Gas mixtures, Freundlich adsorptions isotherm, Sensitivity, Selectivity, Gibbs–Duhém equations, Adsorptions enthalpy change
Region-based active contour with adaptive B-spline. Application in radiographic weld inspection
This paper describes a probabilistic region-based deformable model using a new adaptive scheme for B-spline representation. The idea is to adapt the number of spline control points which are necessary to describe an object with complex shape. For this purpose, the curve segment length (CSL) is used as criterion. The proposed split and merge strategy on the spline model consists in : adding a new control point when CSL is greater than a certain splitting threshold so that the contour tracks all the concavities and, removing a control point when CSL is less to a certain merging threshold so that the contour aspect maintains its smoothness. Noise on synthetic and real weld radiographic images is assumed following Gaussian or Rayleigh distribution. The experiments carried out confirm the adequacy of this approach, especially in tracking pronounced concavities contained in images. Voir les détails
Mots clés : radiography, weld defect, region-based active contour, B-spline, adaptive control point number
Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared bysol–gel method
We have studied the structural and optical properties of thin films of TiO2, doped with 5% ZrO2 and deposited on glass substrate (by the sol–gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450 °C) and for various layer thicknesses (63–286 nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62–2.29 and the porosity is in the range of 0.21–0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO2, doped with 5% ZrO2, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm grains). However, the un-doped TiO2 exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58–20.56 nm). Voir les détails
Mots clés : Thin films, TiO2–ZrO2, Sol–gel, anatase, Brookite, Optical properties Structural properties, Thermal Properties
Automatic Crack Detection and Characterization During Ultrasonic Inspection
The creation of a non-destructive technique that enables the automatic detection of defects is desirable, and TOFD (Time-Of-Flight Diffraction) technique is gaining rapid prominence due to its high accuracy in detecting, positioning and sizing flaws in steel structures. In this type of imaging, cracks are characterized using sets of hyperbolas, where summit positions correspond to crack tip positions.However, ultrasonic diffracted signals are often too low and difficult to distinguish from noise, and when large structures are inspected, the quantity of data can be extremely large, with the area of interest being very small in comparison to the image size. This paper describes a method that avoids the image formation, replacing it with a sparse matrix (as there is no reason to store and operate on an excessive number of zeros), and automates crack detection by analyzing the curve formed by the sparse matrix elements.The sparse matrix is formed using Split-Spectrum Processing, which enhances the signal-to-noise ratio. The Randomized Hough transform is then applied on the sparse matrix elements to detect the hyperbolas that characterize the crack defects. Voir les détails
Mots clés : Automated inspection, Ultrasonic imagery, Sparse matrix, Defect characterization
VIBRATION SIGNAL ANALYSIS USING WAVELET-PCA-NN TECHNIQUE FOR FAULT DIAGNOSIS IN ROTATING MACHINERY
Condition monitoring and fault diagnostics are useful for ensuring the safe running of machines. The demand for monitoring and fault diagnosis of processes and sensors in industrial systems has increased the efforts to develop new analysis techniques. In this paper, a new combined fault diagnosis method that uses Wavelet Transform (WT), Principal Component Analysis (PCA) and Neural Networks (NN) is proposed for rotating machinery vibration monitoring and analysis. In this proposed method, WT is employed to decompose the vibration signal of the sensor measurements into approximations and details coefficients at different levels. These coefficients are then used as inputs to the PCA algorithm in order to perform fault detection and feature extraction using Q-statistic or Squared Prediction Error (SPE) and Q-residual contribution, respectively. After that, NN are applied to further improve the separation between fault classes. The measurements from the vibration process are used to verify the WT-PCA-NN method for detecting and diagnosing faults under typical operating conditions. Simulation results using real sensor measurements from a pilot scale are presented and discussed. Voir les détails
Mots clés : Vibration Signal; Fault Diagnosis; Wavelet Transform; Principal Component Analysis; Neural Networks.
Application of Inverse Methods for Spatial Deconvolution of Pulsed Ultrasound Fields Radiated in Solids
When measuring the ultrasound field, the signal provided by the receiving transducer is affected by its spatial properties. Particularly, the displacement normal to its surface is spatially averaged because of the receiver finite size. In this study, we show using a numerical simulation, the effectiveness of the spatial deconvolution of these effects for a rectangular transducer. For that, three methods allowing the inversion of the aperture effect are tested 1) Wiener’s method; 2) the power spectral equalization (PSE) method, and 3) the maximum a posteriori (MAP) method. The obtained results show that the three methods are able to reconstruct the ultrasound field from the spatially averaged values and the quality of the reconstruction depends strongly upon the signal to noise ratio (SNR) and the spatial frequencies of the ultrasound field investigated. Voir les détails
Mots clés : Deconvolution, Spatial filter, Wiener filter, Power spectral equalization method, Maximum a posteriori method.
Effet du titane, manganèse et molybdène sur le comportement à l’usure des fontes au chrome traitées
Les fontes à haute teneur en chrome sont largement utilisées dans les domaines où la résistance à l’usure est recommandée. Elles constituent la troisième génération d’alliage après les fontes ordinaires et les fontes au nickel. Le présent travail étudie l’effet de l’addition des éléments carburigènes sur le comportement à l’usure d’une fonte au chrome légèrement hypoeutectique. L’objectif visé est un compromis entre les propriétés de la matrice et des phases eutectiques constituant la microstructure de la fonte étudiée en vue d’atteindre un comportement optimal en cours d’usure caractérisé par de faibles pertes de masse en cours d’exploitation. La méthodologie utilisée consiste à introduire des éléments fortement carburigènes tel que le titane, le manganèse et le molybdène. L’utilisation du titane a été variée entre 0 et 3% par contre le manganèse et le molybdène ont été introduits à des proportions de l’ordre de 0,5% combinés avec le titane (Ti+Mn ; Ti+Mo et Ti+Mn+Mo). La microscopie optique et électronique à balayage ainsi la diffraction des rayons X complétée par affinement Rietveld du diffractogramme expérimental ont été utilisées pour mettre en évidence les précipitations secondaires ainsi que les principales phases microstructurales de cette fonte. Les résultats discutés en terme de comportement à l’usure montrent que la plus faible perte de masse a été obtenue pour l’alliage titrant 3% de titane. Ceci est justifié par le fait que la microstructure de la fonte est composée d’une fine martensite renforcée par des carbures du type MC (TiC) et des carbures secondaires du type M7C3 et d’un carbure eutectique allié. Voir les détails
Mots clés : fonte au chrome, carbures, usure, eutectique
Monitoring of metal powder by eddy current
Nanocrystalline Fe(1−x)Cox, Fe, Fe80N120,Cu70Fe18Co12 mixtures have been prepared by mechanical alloying using a planetary ball mill under several milling conditions. Their structures and magnetic properties were investigated. Mechanical alloying is a non-balanced process for synthesis materials. The structural effects of mechanical alloying of powders were investigated by scanning X-ray diffraction analysis. In this report, we examine the applicability of eddy current techniques in-process for monitoring of powder density particle size and the time necessary to structure variation. An eddy current based monitoring system developed to measure metal powder density is expanded for monitoring metal powder diameter in metal compounds. Experimental sensor readings were gathered using four different metal powders with known particle sizes Fe(1−x)Cox, Fe, Fe80N120 and Cu70Fe18Co12. Analysis of the data showed that the sensor output was in relation with different parameter of powder (diameter, density and structure) that the sensitivity of the sensor differed with the type of metal powder. The merit of this technique is its reliance on a simple and inexpensive sensor probe. Voir les détails
Mots clés : metal powders, Mechanical Alloying, Magnetic Properties, Eddy Current, NDT, nondestructive testing, process monitoring, nanocrystalline materials, planetary ball milling, powder density, particle size, structure variation, sensors, sensor probes, nanostructures, nanotechnology.
Adaptive B-Spline Model Based Probabilistic Active Contour for Weld Defect Detection in Radiographic Imaging
This paper describes a probabilistic region-based deformable model using a new adaptive scheme for B-spline representation. The idea is to adapt the number of spline control points which are necessary to describe an object with complex shape. For this purpose, the curve segment length (CSL) is used as criterion. The proposed split and merge strategy on the spline model consists in: adding a new control point when CSL is greater than a certain splitting threshold so that the contour tracks all the concavities and, removing a control point when CSL is less to a certain merging threshold so that the contour aspect maintains its smoothness. Noise on synthetic and real weld radiographic images is assumed following Gaussian or Rayleigh distribution. The experiments carried out confirm the adequacy of this approach, especially in tracking pronounced concavities contained in images. Voir les détails
Mots clés : weld defect, Active contour, adaptive B-spline, split and merge operations