Liste des documents
Effect of the austenite hot deformation on the transformation microstructural mechanics parameters of a microalloyed steel
This study was established to optimize the heat treatments - mechanical and improve the mechanical properties of microalloyed steel with Nb-Ti-V for the production of hot rolled strip. A database of the main parameters of deformation of this steel was developed by dilatometer-plastometer tests. The cooling experiments were used to simulate sequences of the industrial process. The results of these investigations used to analyze the effect of deformation parameters on the evolution of the ferritic structure and mechanical properties of steel. The conditions of rolling deformation bands must be simulated by experimental investigations in order to find a favorable microstructure while choosing the appropriate technological parameters. The microstructural evolution during hot rolling is a dominant factor for achieving the optimal properties. The chemical composition can predict the limits of the desired properties, but these limits depend significantly thermomechanical conditions imposed. A good adaptation of these conditions with the performance of the material allows for a high quality finished product. These investigations will be the basis for determining in advance of the microstructure, mechanical properties for subsequent monitoring of the industrial process. Voir les détails
Mots clés : Microalloyed steel, Austenite, hot deformation, mechanical properties, structure
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
Uniaxial Anisotropic Substrate Effects on the Resonance of an Equitriangular Microstrip Patch Antenna
Using a new combined approach, the effect of the uniaxial anisotropic dielectrics on the resonant frequency and radiation field of an equi-triangular patch antenna is presented in this paper. The problem is analysed in the spectral domain using the moment method and an electric field integral equation combined with a mathematical approach. However, the dyadic Green's functions corresponding to the proposed structure are separately developed and the Fourier transform of the basis current components are calculated mathematically using 'the reference element' method. Numerical results show that the change in the resonant frequency and the radiation patterns of the antenna is due primarily to a small disturbance of the substrate's nature. Then the effect of the uniaxial anisotropic materials is a significant parameter and most essential on the microstrip antenna characterization. Voir les détails
Mots clés : Uniaxial anisotropic dielectric, moment method, spectral domain
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
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
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
Comparison and statistical validation of a model of a photovoltaic module
The study presented in this paper includes a comparison, and a statistical validation. The results that are obtained by a numerical simulation in MATLAB are compared with the experimental results that are taken from the Unit of Applied Researchin Renewable Energy "Ghardaïa" (URAERG) (Experience in the fieldof solar energy). The work is to exploit the experimental dataobtained by exposing the solar cells (panel BP3160W) to light(sunlight), wherever the place of use and the operating conditions. The purpose of this study was to evaluate the model of single diode proposed by Walker of University of Queensland, Australia, uses the electric model with moderate complexity. The numerical results are presented relating to the current-voltage characteristics and power-voltage; during a change of weather conditions such as light, and temperature. To compare, objectively, the performance of the model with the diode modeled using experimental data, statistical indicators proposed by Chang and Hanna (2004) were calculated for different measurement points of light and temperature; the analysis shows that the results for the current and the power reflect the physical reality. Note; however, that the model results are in a very good agreement with experimental measurements. Voir les détails
Mots clés : Model of single diode, solar panels, Matlab, statistical validation
Optical and Photo-Electrochemical Properties of Conducting Polymer/Inorganic Semiconductor Nanoparticle
Optical and photoelectrochemical properties of polybithiophene Poly(bTh) films electrochemically synthesized and modified with incorporation of silicon nanoparticles (n-Si or p-Si) dispersed in the electrolytic during polymerization were studied. The characterisation of these modified surface electrodes by Poly(bTh)+n-Sior Poly(bTh)+p-Si, was carried out by using the photocurrent measurements and UV-visible spectroscopy. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been used to investigate the electrochemical behaviour of theresulting materials. The results show that the photosensitive composite materials have good photoelectrochemical and optical properties, and it can be used as material for the photovoltaic cells applications. Voir les détails
Mots clés : Organic-inorganic composite, polybithiophene, Silicon, electroactivity, photoelectrochemistry.