Liste des publications
DETERMINATION OF THE PARAMETERS THAT CONTROL THE LAMINAR MIXED CONVECTION IN A SQUARE CAVITY (Pr = 0.015)
This work consists to a parametric study of heat transfer in laminar mixed convection inside a square cavity. Our objective is the determination of a parameter that able to locate the transition between the forced, mixed and natural convection for a low Prandtl number fluid (Pr = 0.015). The proposed geometry is a cavity with moving left vertical wall which is maintained to cold temperature and with the right fixed wall at hot temperature. The horizontal walls are adiabatic. The governing equations of this problem are: the equation of conservation of mass, the Navier Stokes equations and energy conservation equation. These differential equations are discretized by the finite volume method on a staggered grid and the SIMPLE algorithm was used for the iterative procedure.The numerical simulations were made for a wide range of Reynolds numbers (1 ≤ Re ≤ 600), and Grashof (29.2 ≤ Gr ≤ 685800). The frontiers of transition from one regime to another regime of convection (forced-mixed and mixed-natural) were determined by a modified Richardson Number. Finally, we found that the parameter which specifies the natural convection regime is Gr/Re1, 58194 and for the forced convection regime is Gr/Re1, 50235. Voir les détails
Mots clés : square cavity, low Prandtl number, modified Richardson Number
Texture Analysis for Flaw Detection in Ultrasonic Images
In this paper, we present two approaches for flaw detection in TOFD (Time of Flight Diffraction) images based on texture features. Texture is one of the most important features used in recognizing patterns in an image. The paper describes texture features by two methods: Multiresolution analysis such as wavelet transforms and Gabor filters bank. The two-dimensional wavelet transform is used to decompose the input image into a multiresolution framework. The textural statistical parameters are used to allow the choice of the decomposition channel. The Gabor filter is a Gaussian kernel function modulated by a sinusoidal plane wave. All Gabor filters can be generated from one mother wavelet by dilation and rotation. These filters represent an appropriate choice for tasks requiring simultaneous measurement in both space and frequency domains. The most relevant features are optimized by Principal Components Analysis (PCA) and used as input data on a Fuzzy C-Mean clustering classifier. We use two classes: ‘defects’ or ‘no defects’. The proposed approach is tested on the TOFD image achieved in an industrial field. Voir les détails
Mots clés : Texture analysis, NDE, TOFD image, Wavelet transform, Gabor filters, Fuzzy logic, PCA
Multi-objective GA optimization of fuzzy penalty for image reconstruction from projections in X-ray tomography
This paper concerns X-ray tomography image reconstruction of an object function from few projections in Computed Tomography (CT). The problem is so ill-posed that no classical method can give satisfactory result. We have investigated a new combined method for penalized-likelihood image reconstruction that combines the fuzzy penalty function (FP) and GA (genetic algorithm) optimization. The proposed algorithm does not suffer from the same problem as that of ML EM (maximum likelihood expectation maximization) algorithm, and it converges rapidly to a low noisy solution even if the iteration number is high, and gives global estimation not a local one like in classical algorithm such as gradient, to the problem of determining object parameters. The method was tested and validated on datasets of synthetic and real image. Voir les détails
Mots clés : Computed tomography, Non-Destructive testing, Analytic estimation, Bayesian inference and estimation, Fuzzy inference, Genetic optimization
Investigation of InGaN/Si double junction tandem solar cells
In this work, the solar power conversion efficiency of InGaN/Si double junction tandem solar cells was investigated under 1-sun AM1.5 illumination, using realistic material parameters. With this intention, the current-voltage curves are calculated for different front recombination velocities and the influence of the bottom cell thickness on efficiency has been studied. The results show that a front recombination velocity value of 1e3cm/s is most advantageous and the use of relatively thick bottom cell is necessary to obtain conversion efficiency greater than 27%, at 300°k cell temperature. This efficiency will decrease as the operating temperature increase. Voir les détails
Mots clés : Photovoltaic, Efficiency, Carrier Lifetimes, Recombination Velocity, Temperature
F.MIS-SIM 1.0: A Program for Simulation of Metal - Insulating - Si(N) Photovoltaic Structures
A variety of numerical models are currently in use by scientists investigating different aspects of photovoltaic technologies. The fundamental physics associated with solar cells are often studied using programs that model electron-hole transport and carrier generation-recombination mechanisms. Modeling of individual cells has been done recently using several programs. Our simulation program «F. MIS-SIM 1.0» was designed to simulate the effects of changing physical and geometrical parameters of a MIS solar cell on the photovoltaic performance. We can also simulate the effect of solar spectrum irradiance and temperature on this structure. Voir les détails
Mots clés : MIS solar cell, Visual Basic, Model, Solar spectrum, I-V characteristics, Spectral response
Performance evaluation of a GaSb thermophotovoltaic converter
In recent years, Gallium Antimonide (GaSb), which has smallest bandgap among III-V semiconductors family, became the subject of extensive investigations in the field of thermophotovoltaic (TPV) converters, because of the recent improvements in optoelectronic technology. This paper describes an analytical process used to evaluatethe performance of a GaSb TPV converter under different levels of illumination, taking account of the photons with energy below the cells bandgap by considering the cell’s reflectance to this fraction of incident radiation. The results show that a radiator temperature near 2200 K is most advantageous and a reflectance of 0.98 is necessary for below-bandgap irradiations to obtain conversion efficiency greater than 28%, at 300 K cell temperature. This efficiency will decrease as the cell temperature increase. The obtained results are found to be in good agreement with the available data. Voir les détails
Mots clés : Thermophotovoltaic, GaSb, Reflectance, Emissivity, Temperature
Application of Wavelet Transform for Fault Diagnosis in Rotating Machinery
Vibration analysis is essential in improving condition monitoring and fault diagnostics of rotating machinery. Many signal analysis methods are able to extract useful information from vibration data. Currently, the most of these methods use spectral analysis based on Fourier Transform (FT). However, these methods present some limitations; it is the case of non-stationary signals. In the present work, we are interested to the vibration signal analysis by the Wavelet Transform (WT). The WT is one of the most important methods for signal processing; it is especially suitable for non-stationary vibration measurements obtained from accelerometer sensors. The monitoring results indicate that the WT can diagnose the abnormal change in the measured data. Voir les détails
Mots clés : Vibration analysis, Fault Diagnosis, Rotating machinery, Spectral analysis, Wavelet transform
Thermal oxidation of tin layers and study of the effect of their annealings on their structural and electrical properties
The main objective of this article is the control of tin dioxide preparation process onglass substrate. Layers of pure tin with thicknesses of 500 and 1000deposited. Their enrichment with oxygen is ensured by thermal annealing for 1 and2 h in a continuous tube furnace with temperatures varying between 300 and 500 1C.The tin film formed by vacuum evaporation has tetragonal crystalline structure, andis composed of grains of various sizes separated by grain boundaries. After annealing inoxygen, the formed phases consist of a mixture of SnO and SnOcrystalline mixturesand sometimes amorphous tin oxide. The more the time or the temperature ofannealing, the more the quantity of SnO22and SnO. For an annealing at 500 1C for10 h the size of grains increases more than annealing for 2 h. This is confirmed by thestudy of their micrographs.The electrical resistivity of these layers, measured by the 4 point method, iscorrelated to the size of the oxide particles: the smaller the particle size, the lowerthe electrical resistivity.˚ Voir les détails
Mots clés : vacuum evaporation, SnO2, Thermal oxidation, X-rays, Thin layers, SEM
Welding Quality Evaluation Using Residual – Based Reference Temperature Distribution Model and Fuzzy Reasoning
A method for welding quality evaluation, which combines model identification and fuzzy sets methods, is proposed. To account for welding quality variations, the proposed approach is based on an optimal reference Gauss distribution temperature along of the welding line in order to take into account the eventual process changes. Fuzzy analysis is then applied to the generated residual data to give an evaluation of the welding condition. This approach is applied to welding process for constructing a complementary condition monitoring system which permits an online quality evaluation. The temperature measurement is carried out using an infrared camera. Simulation results based on the measured surface temperature and generated residual data show that the new approach is easily implementable and gives good evaluation online. Voir les détails
Mots clés : Heat Affected zone of Welding Process, Infrared temperature measurement, Gauss distribution model, Residual generation, intelligent modeling, Fuzzy reasoning, Quality evaluation.
Neural network for modeling solar panel
In this paper, we present the results of the characterization and modeling of the electrical current-voltage and power-voltage of the photovoltaic (PV) panel BP 3160W, using a new approach based on artificial intelligence. We analyze the electrical parameters of solar cells and electrical parameters of the optimal PV panel (current, voltage and power) according to changes in weather (temperature, irradiation...) by the simulation programs carried out in MATLAB. These simulation results were compared with experimental data to be validated. Voir les détails
Mots clés : One diode model, Modeling and behavior, Photovoltaic panel, Neural Network