Liste des documents
A Lossless hybrid wavelet-fractal compression for welding radiographic images
In this work a lossless wavelet-fractal image coder is proposed. The process starts by compressing and decompressing the original image using wavelet transformation and fractal coding algorithm. The decompressed image is removed from the original one to obtain a residual image which is coded by using Huffman algorithm. Simulation results show that with the proposed scheme, we achieve an infinite peak signal to noise ratio (PSNR) with higher compression ratio compared to typical lossless method. Moreover, the use of wavelet transform speeds up the fractal compression algorithm by reducing the size of the domain pool. The compression results of several welding radiographic images using the proposed scheme are evaluated quantitatively and compared with the results of Huffman coding algo-rithm. Voir les détails
Mots clés : Fractal image compression, Wavelet-Fractal coder, lossless wavelet-fractal compression, Huffman algorithm, Radiographic images of weld defects
Study of Composite with Metallic Matrix WC/W2C–20W–20Ni Realized by Spontaneous Infiltration ofthe Bronze Alloy Cu–30Mn–3P
The improved performance and duration of an impregnated tool for the mineral drilling requires thoroughunderstanding of the mechanisms involved in the consolidation of powder mixtures in the liquid phasesintering cycle (FPL). The elements used for the manufacture of the active parts of these tools are usuallymade from mixtures of loose powders based on WC/W–Ni. The spontaneous infiltration process is themost appropriate method offers a big possibility of shapes due to molding. It lets to have considerabledensity of the metal matrix composite (MMC) constituting the active head and increase its resistance toerosion and abrasion. This work consists to develop a metal matrix composite which can constitute theactive part of a drilling tool impregnated by the infiltration of industrial process SILP (Sintering byInfiltration of an appropriate mixture of Loose Powders). The mixture of loose powders (WC/W2C–W–Ni)is infiltrated under hydrogen by a manganese bronze (Cu–30Mn–3P) and then characterized by DTA,optical microscopy, SEM coupled with EDS, HRA hardness and micro-hardness Hv0.1. Voir les détails
Mots clés : Applied Mechanics, Behavior of Materials, Engineering Systems
Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsedTIG welds
Increasing the pulse frequency in pulsed Tungsten Inert Gas arc welding refines the prior- grain size in the fusion zoneof Ti-6Al-4V compared to unpulsed arc welding. The microhardness increases in the fusion zones obtained with pulsed welding mode, with respect to this microstructural evolution. The increase of the pulse frequency contributes to the formation of a more important amount of residual phase in the fusion zone which is accompanied by a decrease of microhardness. The tensile residual stress (RS) level in the pulsed process is lower than the one of the unpulsed process. The tensile RS induced by both welding processes in the HAZ are found to decrease when increasing the pulse frequency. In the fusion zone, the transversal RS are of compressive type for both processes whereas the longitudinal ones change from tensile to compressive type when increasing the pulse frequency. Voir les détails
Mots clés : Ti-6Al-4V alloy, welding, pulsed current, microstructure, residual stress.
Monitoring of Stator windings Faults in Induction Machine Using Fuzzy Logic
the monitoring and fault detection of theinduction machines drives becomes more and moreimportant. This made necessary the monitoringfunction condition of these machines for improved anexploitation of the industrial processessing. The aim ofthis task is the proposal of a monitoring strategy basedon the fuzzy logic inference system, that informs usabout the healthy function and stator fault condition,especially the open circuit and short-circuit inter-turnsof the stator windings. The principle adopted for thestrategy suggested is based on monitoring of theaverage root mean square value of stator current(RMS).Theoretical analysis, simulations results arepresentes to validate the effectiveness of the proposesdmethod. Voir les détails
Mots clés : Induction machine, Monitoring, diagnosis, Detection, Fuzzy logic, RMS
On-Line Monitoring and Classification of Stator windings Faults inInduction Machine Using Fuzzy Logic and ANFIS Approach
the induction machines drives becomes moreand more important used in many industrial applications.Their attractiveness is largely due to their simplicity,ruggedness and low cost manufacture, easy maint00enance,high power efficiency and high reliability, are susceptible tovarious types of electrical and/or mechanical faults that canlead to unexpected motor failure and consequently impulsivedowntime. This made necessary the monitoring functioncondition of these machines types for improved anexploitation of the industrial processes. The aim of this taskis the proposal of a monitoring strategy based on the fuzzylogic inference system (FIS) and the neuro-fuzzy inferencesystem (ANFIS) for monitoring and classification ofelectrical faults types, especially the open phase and interturnsshort-circuit in the stator windings. The principleadopted for the strategy suggested is based on monitoring ofthe average root mean square value of stator current (RMS).Mathematical models and simulations results are presentedto validate the efficiency of this approach. Voir les détails
Mots clés : Monitoring, classification, Fis, INFIS, RMS
Comparative Study of Wind Energy Conversion SystemDriven by Matrix Converter and AC/DC/AC Converter
In this work we presents comparative study of avariable speed wind energy conversion system (WECS) basedon the doubly fed induction generator (DFIG) driven by twoAC/DC/AC converters and WECS driven by matrix converter(MC). The whole system is presented in d-q-synchronousreference frame. For this purpose, the control of the activeand reactive power using PI controller is verified usingsoftware Matlab/Simulink, studies on a 1.5 MW DFIG windgeneration system. Simulation results obtained are presentedand analyzed. The results show the high performance andimprove the electric energy of the control strategy adopted inthe WECS based on a DFIG driven by a MC. Voir les détails
Mots clés : wind systems, doubly fed induction generator, matrix converter, simulation
Assessment and analysis of wind energy generation and power control ofwind turbine system
This study concerns the evaluation of wind power potential and the choice of a wind turbine to be installed nearRabah Bitat international airport of Annaba. Furthermore, the performances of power control of this turbine aredeveloped. For this, the wind speed data measured by meteorological station of the airport are used. At the firsttime, a statistical analysis of wind characteristics and the extrapolation of weibull parameters are presented.Otherwise, the analysis of the power produced and the capacity factor led to the choice of the wind turbineEnercon E-82/2000 whose characteristics: Rated wind speed (13m / s), the cut-in wind speed (2.5m / s) and arated power of 2000kW. Finally, the control of the active and reactive power, by adaptive fuzzy gain schedulingof proportional integral controller is simulated using software Matlab/Simulink, studies on a 2 MW DFIG windgeneration system. Performance and robustness results obtained are presented and analyzed. Voir les détails
Mots clés : Wind energy, wind speed, weibull distribution, capacity factor, power output.
Evaluation of surface quality by Fractal Dimension and VolumeParameters
This study aims, the evaluation of the surface quality by the fractal dimension "D" and volume settings (Vmp,Vmc, Vvv). Experimental work was conducted by process of surface mechanical treatment; in this case ballburnishing was applied on a commercial aluminum alloy material. Three parameters of regime were considered:"burnishing feed f", "burnishing force Py" and "burnishing ball diameter Db". Mathematical models wereidentified using the plans of multifactorial experiments "Box-Behnken" for prediction of fractal dimension "D"and volume parameters. Experimental and simulation results have enabled to show than the large diameter ballunder low loads and medium feed speeds, favors the elimination of peaks and reduction of fractal dimensionwhence quality improvement of surface. Voir les détails
Mots clés : burnishing, volume parameters, fractal dimension, experimental designs
Improvement of surface finish by ball burnishing:approach by fractal dimension
The surface roughness significantly affects the quality of parts and their functional properties suchas contact surface, as well as coating adhesion. The machined surface quality is evaluated byarithmetic deviation Ra which does not suffice to describe the surface irregularities. In order toapprehend these deficiencies a new technique based on fractal geometry was introduced. Toapply this concept an experimental work was carried out to characterise surface quality byfractal dimension ‘D’. The operations of burnishing ball were performed according to plans ofexperiments of ‘Box–Behnken’, an optimal regime was obtained and a mathematical model wascleared for predicting the fractal dimension ‘D’ as a function of treatment regime parameters.Furthermore, the application of optimal regime under several passes ‘i’ has enabled to examinethe evolution of ‘D’. The results confirm that fractal dimension ‘D’ has impact on surface qualityand tribological parameters. Voir les détails
Mots clés : roughness, fractal dimension, Burnishing process, Designs of experiments
THE CONTRIBUTION OF DIRECT TORQUE CONTROL WITH APPLICATION OFFUZZY LOGIC ON THE PERFORMANCE OF A MULTI-LEVEL INVERTER FED INDUCTION MACHINEWITH A FAULT TOLERANCE
Today it is possible to obtain induction machine performances similar to those of dc machines through the mastering of power electronics and control.Moreover, there are new methods of control for sensorless speed traction-type applications already studied particularly those related to the Direct Torque Control technique (DTC). This study consists at optimizing the three-level DTC algorithm fed from an NPC structure multilevel inverter with fault tolerant using are the configurable redundant spare arm to increase the average value of the torque. The results obtained in the DTC are further improved by applying the technique of fuzzy logic Voir les détails
Mots clés : Multilevel Inverter, DTC, NPC, Fault tolerance, Fuzzy logic.