Liste des documents
Local and Global Statistics-Based Explicit Active Contour for Weld Defect Extraction in Radiographic Inspection
Welding is a process of utmost importance in the metal industry. With the advances in computer science and artificial intelligence techniques, the opportunity to develop computer aided technique for radiographic inspection in Non Destructive Testing arose. This paper deals with the weld defects detection in radiographic films. A greedy active contour model is used exploiting global and local statistics to drive the model to the boundaries. Moreover, and to decrease the computation cost, the local statistics computation is done only for pixels in a selected band. Results seem to be promising ones. Voir les détails
Mots clés : Radiographic inspection, weld defects, Active contours
Investigation properties of Au – Porous a-Si0.60C0.40as Humidity sensor
In this letter, we report the study of a humidity sensor based on porous amorphous silicon carbide (PASiC) as a function of exposure time and relative humidity (RH). Resistive humidity sensors Au–PASiC/Si(p) were fabricated through evaporating coplanar interdigital gold electrodes. The PASiC was formed by anodization of a-Si0.70C0.30 in HF/ethylene glycol (ETG) solution at current density of 50 mA/cm2 for 30 s. The structural properties of a-Si0.70C0.30 thin films deposited by DC magnetron co-sputtering using single silicon crystal, 6H-SiC targets and the PASiC films were investigated by FT-IR and Raman spectroscopy. Hygroscopicity was studied by measuring the resistance of the PASiC under various RH. The results show that the measured resistance highly depends on the applied bias voltage. Moreover, the response signal against RH is found linear for an applied voltage of 2 V. Finally, the response and recovery times were determined around 13 s and 20 min, respectively. Voir les détails
Mots clés : Porous SiC, Electrochemical etching, RH sensors, Au electrodes
Dynamic Response of a Stand Alone AC Side Wind Energy Conversion System
This Paper consists on the study of one part of wind energy system conversion, its ACside. Renewable resources are in constant fluctuation. This situation could put in peril the energizing efficiency towards a given demand requirement. Therefore, in order to maximize the efficiency of the renewable energy system, it is necessary to track the maximum powerpoint of the input source, a study established under MATLAB/Simulink platform. For the wind system, the maximizing is assured while considering the optimal power curve as load characteristic, with the knowledge of the turbine characteristic C_p (λ).Then, this work elaboratesthe analysis and simulation of a low speed Permanent Magnet Synchronous Generator (PMSG) driven by a vertical wind turbine through a Pulse-Width Modulation (PWM) voltage inverter, independently of the DC components of the wind system conversion, usingMATLAB computer simulation. Voir les détails
Mots clés : Wind, Optimal load characteristic, Compensation decoupling, IP regulator, Permanent Magnet Synchronous Generator.
Extraction of weld defects dimension from radiographic images using the level set segmentation without re-initialization
Radiographic images segmentation is the major interest for the weld defect diagnosis and monitoring in the field of industry. In this work we present a method that takes ownership of local segmentation geodesic active contours. The goal of the method presented in this paper is to automate the process of extracting dimension of weld defects from radiographic images using level set segmentation. The information would be used in the area of nondestructive testing (NDT). This method is found to be effective and robust. Voir les détails
Mots clés : radiographic method, weld inspection, defect dimensions, Signal processing
Real Time Implementation of Shunt Active PowerFilter (SAPF)for Harmonic suppression and PowerQuality Improvement
In this paper, A Shunt Active Power Filter (SAPF) is implemented using a dSPACEDS1104 processor to compensate harmonics and reactive power produced by nonlinearload. The reference source current is computed based on the measurement of harmonicsin the supply voltage and load current. A hysteresis based current controller has beenimplemented in a DSP processor for injecting the compensating current into the powersystem, so that SAPF allows suppression of the harmonics and reactive power componentof load current, resulting in a supply current that is purely sinusoidal. Simulation andexperimental results of the proposed SAPF to meet the IEEE-519 standards are presented. Voir les détails
Mots clés : Harmonics, Power quality, Active power filter, hystérisis comparator, real time control
Guided Wave Sensitivity for De- Bond Defects in Aluminum Skin Honeycomb Core
Sandwich plates are finding an increasing range ofapplication in the aircraft industry. The inspection of honeycomb composite structure by conventional ultrasonic technique is complexand very time consuming. The present study demonstrates a technique using guided Lamb waves at low frequencies to predict de-bond defects in aluminum skin_honeycomb core sandwich structure used in aeronautics. The numerical method was investigated for drawing the dispersion and displacement curves of ultrasonic Lamb wave propagated in Aluminum plate. An experimental study was carried out to check the theoretical prediction. The detection of unsticking between the skin and the core was tested by the two first modes for a low frequency. It was found that A0 mode is more sensitive to delamination defect compared to S0 mode. Voir les détails
Mots clés : Damage detection, delamination, guided waves, Sandwich structure
A numerical study of viscous dissipation effect on non-Newtonian fluid flow inside elliptical duct
Laminar heat transfer inside duct with elliptical cross section, subjected to uniform wall temperature is studied by taking into account the viscous dissipation. The temperatures distributions are evaluated numerically by using a dynamic Alternating Direction Implicit method (dADI). Nusselt number (Nu) is presented graphically for various Brinkman number (Br) and aspect ratio for a non-Newtonian fluid described by the power law model. The results obtained showed a good agreement with those found in the literature for fluid flow in circular cross section ducts and in elliptical cross section without viscous dissipation effects. It is shown that in the fully developed region and for Br ≠ 0, Nusselt number has a fixed asymptotic value independent of Brinkman number (Br). In the thermally developing region, it is observed a single fixed point independent of heating or cooling condition which the numerical value is equal to the asymptotic Nusselt number. Another relevant feature is that in the fully developed region, the Nusselt number increases with the aspect ratio. Voir les détails
Mots clés : Elliptical duct section, Viscous dissipation, Non-Newtonian fluids, Power law model, Laminar forced convection
Petroleum quaternary ammonium surfactants mixture synthesized from light naphtha as corrosion inhibitors for carbon steel in 1 m HCl
A quaternary ammonium cationic surfactants mixture was synthesized from light naphtha, petroleum fraction. The mixture was analyzed by Fourier transform infrared spectroscopy and UV/Visible spectroscopy and was evaluated as a corrosion inhibitor for carbon steel in 1 m HCl, by gravimetry, potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that inhibiting efficiency increased with inhibitor concentration and temperature, and was independent of pH (in the range of 0 – 4) and immersion time; its optimal value was up to 84% for 560 mg/l at 25 ° C. Experimental data showed that the cationic surfactants mixture acts as a mixed (anodic and cathodic) inhibitor and conformed to the Langmuir adsorption isotherm. Scanning electron microscopy images revealed the inhibiting capacity of the mixture against carbon steel acid corrosion. Voir les détails
Mots clés : adsorption; carbon steel; cationic surfactants mixture; corrosion inhibition; surfactants synthesis.
Study of the inhibiting effect of a quaternaryammonium surfactants mixture synthesizedfrom petroleum fraction (reformate) againstthe carbon steel corrosion in HCl 1 M
Quaternary ammonium cationic surfactants were synthesized fromreformate, a liquid mixture of hydrocarbons (aromatics, naphthenes and paraffins),via chloromethylation/quaternization sequences. The petroleum surfactants thusobtained were evaluated as corrosion inhibitors for carbon steel in 1 M HCl, bygravimetry, potentiodynamic polarization and electrochemical impedance spectroscopy.The corrosion inhibiting efficiency was assessed as functions of surfactantconcentration. The results showed that the inhibiting efficiency increased withsurfactant concentration; its optimal value of 70 % was for a surfactant concentrationof 320 mg/L at 25 C. Potentiodynamic polarization measurements showedthat the mixture acts as a mixed type inhibitor. The corrosion inhibiting mechanismis thought to proceed via an adsorption of the surfactant molecules on the steelsurface, generating a film and hindering the active sites. Our experimentaladsorption data were found to obey the Langmuir adsorption isotherm. SEM imagesof the treated specimens, revealing the likely formation of a protective film, demonstratedthe inhibiting capacity of the petroleum quaternary ammonium surfactantsagainst the carbon steel corrosion. Voir les détails
Mots clés : Corrosion inhibition Carbon steel Petroleum quaternary ammonium Cationic surfactants mixture
Notch detection in copper tubes immersed in water by a compressional guided waves
Tube- or pipe-like structures are used to convey fluids such as gas, oil or water. These fluids can be transported on land, in sea or in industrial buildings. Hence, tubes can suffer from mechanical, thermal and chemical stresses. The latter, can severely damage these structures due to the oxidation phenomena. This damage weakens the structure and reveals cracks and inhomogeneities. The objective of this work is to detect and characterise damage in tubes immersed in water by a non-destructive method. This research work is devoted to the development of an experimental device. This device can detect and locate axy- and nonaxy-symmetric circumferential small notches located on the outer surface of a filled tube and immersed in water using guided waves. Different sizes of notches are milled into copper tubes with a thin wall are considered. A single transducer is used for emission and reception of leaky guided waves by using the pulse-echo technique. The compressional L(0,2)mode is launched at relatively high frequency using oblique incidence of the transducer into the fluid. By using the wave leakages, notches of small sizes are detected and located. In addition, the sensitivity of the L(0,2) mode to the radial depth and circumferential extent of notches is evaluated. A roughly linear behaviour of the amplitude reflection coefficients is revealed which is in accordance with research works found in the literature. Voir les détails
Mots clés : guided waves, Immersed tubes, Circumferential notches, Experimental device