Liste des publications
Fault detection and diagnosis using principal component analysis. Application to low pressure lost foam casting process
Process fault detection and diagnosis plays a very important role in the production security and the product quality. In this paper, in order to improve the accuracy for fault detection and diagnosis, a new method based on Principal Component Analysis (PCA) is proposed in low pressure lost foam casting process. PCA method reduces the dimensionality of the original data set by the projection of the data set onto a smaller subspace defined by the principal components, the aim of this method is to establish the normal statistical correlation among the coefficients of the data set to detect and diagnose the faults. The process faults are detected and diagnosed using Multivariate Statistical Process Control (MSPC) parameters such as: Hotelling’s T2-statistic, Q-statistic or Squared Prediction Error (SPE) and Q-residual contribution. The monitoring results indicates that the proposed method can be detect and diagnose the abnormal change of the process. Voir les détails
Mots clés : fault detection and diagnosis, principal component analysis, multivariate statistical process control, T2-statistic, Q-statistic, squared prediction error, Q-residual contribution.
CARACTERISATION DES MATERIAUX BIOLOGIQUES ISSUS D’UNECOSYSTEME NATUREL« PNEK » SITUE AU NORD-EST DE L’ALGERIE
Notre étude a pour objectif de caractériser la composition et le degré de contaminationdes sédiments superficiels de trois lacs de la région d’El Kala situé au Nord Est de l’Algérie(Tonga, Oubeira, El Mellah), et de distinguer les sources de cette composition (naturelle ouanthropique).Le dosage des métaux, fer, cuivre, zinc, nickel, chrome, plomb et cadmium, estobtenu dans le sédiment superficiel de chaque site et durant quatre saisons. Les résultatsd’analyses montrent que les sédiments analysés se caractérisent par une abondance de certainsmétaux lourds surtout pour le fer, le plomb, le nickel et le chrome. En effet, en se référant auxnormes la lagune El Mellah est contaminée par le fer, le nickel et le chrome, lac Oubeira estcontaminé par le fer et le nickel, et lac Tonga est contaminé par le fer et le cadmium. Lesautres éléments cuivre et zinc, ne présentent aucune nuisance à l’environnement. Ces résultatssont appuyés par les valeurs des indices de contamination, Voir les détails
Mots clés : sédiment métaux lourds, contamination, lacs, indice de contamination.
Theoretical model and experimental investigation of current density boundary condition for welding arc study
This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm’s law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ∼21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 Am−2 for a 1.2 mm diameter welding electrode. Voir les détails
Mots clés : Gas Tungsten Arc Welding, GTAW, Gas Metal Arc Welding, GMAW, spectroscopie
LTE Experimental Validation in a Gas Metal Arc Welding Plasma Column
During gas metal arc welding (GMAW), the plasma obtained has a rich composition and some hypothesis are often made for modelling, in particular the local thermodynamical equilibrium (LTE) state of the plasma. It is then important to study its validity domain, as it is also needed for plasma parameters determination.The plasma was investigated using optical emission spectroscopy. The electron temperature and density were determined from Stark width measurements, independently of the plasma equilibrium state, and compared to the excitation temperature obtained using the Boltzmann plot (BP) method. The welding experiments were made at arc current of 330 A, with pure argon as shielding gases. The LTE is verified in the core region of the plasma, for about one half of the column radius in the arc lower part. Voir les détails
Mots clés : GMAW, Optical Emission Spectroscopy, Boltzmann Plot, Sola method, LTE
Texture, microstructure and anisotropic properties in annealed 2205 duplex stainless steel welds
The effect of welding and subsequent annealing on the evolution of the crystallographic texture and the anisotropic properties in a 2205 duplex stainless steel was studied. A strong texture was found in the base metal for both austenite and ferrite phases. The austenite texture is composed of rolling (copper and brass) and recrystallization (cube) components whereas the ferrite texture contains mainly a marked < 001>//RD α fibre with a major rotated cube component. The texture evolution during welding and annealing was characterized in the base metal, heat affected zone and weld metal; the corresponding phase proportions and misorientation values were also calculated. The analysis of all these data allows improving the understanding of the recovery, recrystallization and grain growth mechanisms occurring during the various steps of the treatment. Finally, a micromechanical model was used to calculate some mechanical properties from the measured texture, and to confirm that the optimal annealing treatment is about 1050 °C. Voir les détails
Mots clés : duplex stainless steel, TIG welding, texture, anisotropy of mechanical properties, EBSD
Elimination du plomb en solution par la sciure de bois
Cette étude présente les résultats obtenus lors de l’utilisation de la sciure debois pour l’élimination du plomb contenu dans les eaux usées. Les propriétés de sorptionont été déterminées en régime discontinu. Les résultats des essais montrent qu’un grammede sciure de bois activé peut fixer 40,04 mg/g de plomb selon le modèle de Langmuir, 1erversion, avec une cinétique du pseudo premier ordre, où le temps d’équilibre est de 10minutes. Les mesures réalisées révèlent aussi, que la diffusion externe contrôle la vitessedu processus globale de la sorption. La diffusion dans les pores ne présente pas l’uniquemécanisme réactionnel limitant cette cinétique, ce mécanisme est basé aussi sur l’échangecationique, où les ions de bases jouent un rôle très important. En dernier, on montre quecette sorption est spontanée (ΔG < 0) jusqu'à 40 °C, exothermique (ΔH < 0) et aucunchangement n’a été effectué au niveau de la structure de la sciure de bois (ΔS < 0). Voir les détails
Mots clés : Plomb Sportion, Sciure de bois, eau, pollution
Dual-Frequency Behavior of Stacked High Tc Superconducting Microstrip Patches
The dual-frequency behavior of stacked high Tc superconducting rectangular microstrip patches fabricated on a two-layered substrate is investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. Using a matrix representation of each layer, the dyadic Green's functions of the problem are efficiently determined in the vector Fourier transform domain. The stationary phase method is used for computing the radiation electric field of the antenna. The proposed approach is validated by comparison of the computed results with previously published data. Variations of the lower and upper resonant frequencies, bandwidth and quality factor with the operating temperature are given. Results showing the effects of the bottom patch thickness as well as the top patch thickness on the dual-frequency behavior of the stacked configuration are also presented and discussed. Finally, for a better comprehension of the dual-frequency operation, a comparison between the characteristics of the lower and upper resonances is given Voir les détails
Mots clés : Dual-frequency operation, Stacked patches, Superconducting microstrip patches
Effect of textured area on the performances of a hydrodynamic journal bearing
A growing interest is given to the textured hydrodynamic lubricated contacts. The use of textured surfaceswith different shapes of microcavities (textures) and at different locations of the texture zone can be aneffective approach to improve the performance of bearings. The present study examines the texturelocation influence on the hydrodynamic journal bearing performance. A numerical modelling is used toanalyze the cylindrical texture shape effect on the characteristics of a hydrodynamic journal bearing. Thetheoretical results show that the most important characteristics can be improved through an appropriatearrangement of the textured area on the contact surface. Voir les détails
Mots clés : textures, Hydrodynamic lubrication, journal bearing, Finite difference method
Correlation between structural and optical propertiesof TiO2:ZnO thin films prepared by sol–gel method
We have studied structural and optical properties of thin films of TiO2, doped with 5% ZnO and deposited on glass substrate (by the sol–gel method). Dip-coated thin films have been examined at different annealing temperatures (350–450 °C) and for various layer thicknesses (89–289 nm). Refractive index, porosity and energy band gap were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.97–2.44, the porosity is in the range of 0.07–0.46 and the energy band gap is in the range of 3.32–3.43. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO2, doped with 5% ZnO, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 20.23 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 of 8.61–29.48 nm. Voir les détails
Mots clés : Thin films, TiO2–ZnO, Sol–gel, anatase, Brookite, optical properties, Structural properties, Thermal Properties
Elimination du plomb par la sciure de bois
Cette étude présente les résultats obtenus lors de l’utilisation de la sciure de bois pourl’élimination du plomb contenu dans les eaux usées. Les propriétés de sorption ont étédéterminées en régime discontinu. Les résultats des essaies montrent qu’un gramme de sciurede bois activé peut fixer 40,04 mg/g de plomb selon le modèle de Langmuir 1er version avecune cinétique du pseudo premier ordre, où le temps d’équilibre est de 10 minutes. Lesmesurés réalisées révèlent aussi, que la diffusion externe contrôle la vitesse du processusglobale de la sorption, la diffusion dans les pores n’est pas le seul mécanisme limitant cettecinétique et le mécanisme réactionnel est basé sur l’échange cationique, où les ions de basesjouent un rôle très important. A la fin, on montre que cette sorption est spontanée (ΔG<0)jusqu'à 40°C, exothermique (ΔH<0) et qu’aucun changement n’a été effectué au niveau de lastructure du la sciure de bois (ΔS<0). Voir les détails
Mots clés : Plomb – Sportion – Sciure de bois – Eau – Pollution