Liste des documents
FINITE ELEMENT MODELING OF GROUND MOVEMENT ON THE ROADCW16 SÉRAIDI -CHÉTAIBI (ANNABA, ALGERIA)
Grounds movements are considered a natural hazard, some of which have, over time, significant slow movements.Significance of these dynamic effects involves a risk which generates human and material damage. Policymakers musttake this issue into account in their permanent security organization program. Some landslides exhibit a function of time,significant slow movements. They are assigned to a behavior of clay materials mechanism caused by the variation ofgeotechnical properties. The effects of water seepage in wet periods generally linked to the viscous nature of claymaterials are causes primarily .They can also be related to the variation modeling parameters. The land slip site is locatedat the road CW16 Seraidi -Chétaibi, (Annaba, Algeria) area with an annual rainfall of more than 700mm. Analysis of theslope stability is carried out using several methods of deformation calculation of the natural ground state. In our case weuse a plastic Mohr Coulomb from supported models. The project proposes to examine the different causes using theexample of Cam Clay. The project will examine the different causes using the example of Cam Clay; elasticvisco plasticmodel with time (SSCM: Soft Soil Creep Model) set in a finite element program Plaxis. This technique can show us howdifferent behavioral assumptions can describe the slow movements of a slope. A comparison will be made with the MohrCoulomb (MC). Voir les détails
Mots clés : Mohr Coulomb, slip, numerical modeling, plaxis, cam clay, elasticvisco plastic model
Numerical simulations of the electrical transport characteristics of a Pt/n-GaN Schottky diode
In this paper, using a numerical simulator, we investigated the current-voltage characteristics of a Pt/n-GaN thin Schottky diode on the basis of the thermionic emission (TE) theory in the 300 to 500 K temperature range. During the simulations, the effect of different defect states within the n-GaN bulk with different densities and spatial locations is considered. The results show that the diode ideality factor and the threshold voltage decrease with increasing temperature, while at the same time, the zero-bias Schottky barrier height (Φb0) extracted from the forward current density-voltage (J-V) characteristics increases. The observed behaviors of the ideality factor and zero-bias barrier height are analyzed on the basis of spatial barrier height inhomogeneities at the Pt/GaN interface by assuming a Gaussian distribution (GD). The plot of apparent barrier height (Φb,App) as a function of q/2kT gives a straight line, where the mean zero-bias barrier height ( ) and the standard deviation (σ0) are 1.48 eV and 0.047 V, respectively. The plot of the modified activation energy against q/kT gives an almost the same value of and an effective Richardson constant A* of 28.22 Acm-2K-2, which is very close to the theoretical value for n-type GaN/Pt contacts. As expected, the presence of defect states with different trap energy levels has a noticeable impact on the device electrical characteristics. Voir les détails
Mots clés : Gallium nitride, Schottky barrier, diode, Temperature
Waveguide Filter Modeling and Simulation using Mode-matching, FullwaveNetwork Analysis and Swarm Optimization
This paper presents the modeling ofwaveguide bandpass filter synthesis. It consists of acombination of the most appropriate and reliablemethods and techniques of analysis, simulation andoptimization used in determined order and leading to afast and accurate method of filter synthesis. An exampleof a forth-order filter synthesis is given, employing asymmetric configuration and symmetric response. Theobtained results, reference measurement and commercialsoftware simulator results are compared for validation. Voir les détails
Mots clés : filter, waveguide, Coupling matrix, Mode-matching, Segmentation method, Optimization techniques.
An Automated Microemboli Detection and Classification System using Backscatter RF Signals and Differential Evolution
Embolic phenomena, whether air or particulate emboli, can induce immediate damages like heart attack or ischemic stroke. Embolus composition (gaseous or particulate matter) is vital in predicting clinically significant complications. Embolus detection using Doppler methods have shown their limits to differentiate solid and gaseous embolus. Radio-Frequency (RF) ultrasound signals backscattered by the emboli contain additional information on the embolus in comparison to the traditionally used Doppler signals. Gaseous bubbles show a nonlinear behavior under specific conditions of the ultrasound excitation wave, this nonlinear behavior is exploited to differentiate solid from gaseous microemboli. In order to verify the usefulness of RF ultrasound signal processing in the detection and classification of microemboli, an in vitro set-up is developed. Sonovue micro bubbles are exploited to mimic the acoustic behavior of gaseous emboli. They are injected at two different concentrations (0.025µl/ml and 0.05µl/ml) in a nonrecirculating flow phantom containing a tube of 0.8 mm in diameter. The tissue mimicking material surrounding the tube is chosen to imitate the acoustic behavior of solid emboli. Both gaseous and solid emboli are imaged using an Anthares ultrasound scanner with a probe emitting at a transmit frequency of 1.82 MHz and at two mechanical indices (MI) 0.2 and 0.6.We propose in this experimental study to exploit discrete wavelet transform (DWT) and a dimensionality reduction algorithm based on differential evolution (DE) technique in the analysis and the characterization of the backscattered RF ultrasound signals from the emboli.Several features are evaluated from the detail coefficients. It should be noted that the features used in this study are the same used in the paper by N. Aydin et al. These all features are used as inputs to the classification models without using feature selection method. Then we perform feature selection using differential evolution algorithm with support vector machines (SVM) classifier. The experimental results show clearly that our proposed method achieves better average classification rates compared to the results obtained in a previous study using also the same backscatter RF signals. Voir les détails
Mots clés : Embolic phenomena, whether air or particulate emboli
Performance analysis of a Pt/n-GaN Schottky barrier UV detector
The electrical and optical characteristics of an n-type gallium nitride (GaN) based Schottky barrier ultraviolet (UV) detector, where a platinum (Pt) metal layer forms the anode contact, have been evaluated by means of detailed numerical simulations considering a wide range of incident light intensities. By modeling the GaN physical properties, the detector current density-voltage characteristics and spectral responsivity for different (forward and reverse) bias voltages and temperatures are presented, assuming incident optical power ranging from 0.001 to 1 Wcm-2. The effect of defect states in the GaN substrate is also investigated. The results show that, at room temperature and under reverse bias voltage of -300 V, the dark current density is in the limit of 2.18×10-19 Acm-2. On illumination by a 0.36-µm UV uniform beam with intensity of 1 Wcm-2, the photocurrent significantly increased to 2.33 Acm-2 and the detector spectral responsivity reached a maximum value of 0.2 AW-1 at zero-bias voltage. Deep acceptor trap states and high temperature strongly affected the spectral responsivity curve in the considered 0.2 µm to 0.4 µm UV spectral range. Voir les détails
Mots clés : Gallium nitride, Schottky barrier, ultraviolet detector, photocurrent, responsivity, Temperature
Infiltration behavior of Cu and Ti fillers into Ti2AlC/Ti3AlC2 compositesduring tungsten inert gas (TIG)brazing
Herein we study the infiltration behavior of Ti and Cu fillers into a Ti2AlC/Ti3AlC2MAX phase composites using aTIG-brazing process. The microstructures of the interfaces were investigated by scanning electron microscopyand energy dispersive spectrometry. When Ti2AlC/Ti3AlC2 comes into contact with molten Ti, it starts decomposinginto TiCx, a Ti-richandTi3AlC; when in contact with molten Cu, the resulting phases are Ti2Al(Cu)C, Cu(Al), AlCu2Ti and TiC. In the presence of Cu at approximately 1630 °C, a defective Ti2Al(Cu)C phase was formedhaving a P63/mmc structure. Ti3AlC2 MAX phase was completely decomposed in presence of Cu or Ti fillermaterials.The decomposition of Ti2AlC to Ti3AlC2 was observed in the heat-affected zone of the composite.Notably, no cracks were observed during TIG-brazing of Ti2AlC/Ti3AlC2 composite with Ti or Cu filler materials. Voir les détails
Mots clés : MAX phase, Joining, microstructure, hardness, Brazing, TIG process
Type-2 Fuzzy Logic Predictive Control of a Grid Connected Wind Power Systems with Integrated Active Power Filter Capabilities
This paper proposes a real-time implementation of an optimal operation of a double stage grid connected wind power system incorporating an active power filter (APF). The system is used to supply the nonlinear loads with harmonics and reactive power compensation. On the generator side, a new adaptive neuro fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) control is proposed to track the maximum wind power point regardless of wind speed fluctuations. Whereas on the grid side, a modified predictive current control (PCC) algorithm is used to control the APF, and allow to ensure both compensating harmonic currents and injecting the generated power into the grid. Also a type 2 fuzzy logic controller is used to control the DC-link capacitor in order to improve the dynamic response of the APF, and to ensure a well-smoothed DC-Link capacitor voltage. The gained benefits from these proposed control algorithms are the main contribution in this work. The proposed control scheme is implemented on a small-scale wind energy conversion system (WECS) controlled by a dSPACE 1104 card. Experimental results show that the proposed T2FLC maintains the DC-Link capacitor voltage within the limit for injecting the power into the grid. In addition, the PCC of the APF guarantees a flexible settlement of real power exchanges from the WECS to the grid with a high power factor operation. Voir les détails
Mots clés : Active power filter (APF), Adaptive neuro fuzzy inference system (ANFIS), Maximum Power Point Tracking (MPPT), Predictive current control (PCC), Type-2 fuzzy logic controller (T2FLC)
Analysis and experimental evaluation of shunt active power filter for power quality improvement based on predictive direct power control
This paper discusses the use of the concept of classical and predictive direct power control for shunt active power filter function. These strategies are used to improve the active power filter performance by compensation of the reactive power and the elimination of the harmonic currents drawn by non-linear loads. A theoretical analysis followed by a simulation using MATLAB/Simulink software for the studied techniques has been established. Moreover, two test benches have been carried out using the dSPACE card 1104 for the classic and predictive DPC control to evaluate the studied methods in real time. Obtained results are presented and compared in this paper to confirm the superiority of the predictive technique. To overcome the pollution problems caused by the consumption of fossil fuels, renewable energies are the alternatives recommended to ensure green energy. In the same context, the tested predictive filter can easily be supplied by a renewable energy source that will give its impact to enhance the power quality. Voir les détails
Mots clés : Harmonic pollution, Power quality, Direct power control, Predictive direct power control, Shunt active filter, Renewable energy source, power factor
Design and Experimental Validation of a Digital Predictive Controller for Variable-Speed Wind Turbine Systems
Advanced control algorithms must be used to make wind power generation truly cost effective and reliable. In this study, we develop a new and simple control scheme that employs model predictive control (MPC), which is used in permanent magnet synchronous generators and grid-connected inverters. The proposed control law is based on two points, namely, MPC-based torque?current control loop is used for the generator-side converter to reach the maximum power point of the wind turbine, and MPC-based direct power control loop is used for the grid-side converter to satisfy the grid code and help improve system stability. Moreover, a simple prediction scheme is developed for the direct-drive wind energy conversion system (WECS) to reduce the computation burden for real-time applications. A small-scale WECS laboratory prototype is built and evaluated to verify the validity of the developed control methods. Acceptable results are obtained from the real-time implementation of the proposed MPC methods for WECS. Voir les détails
Mots clés : Maximum Power Point Tracking (MPPT), Model predictive control (MPC), Permanent Magnet Synchronous Generator (PMSG), Wind Energy Conversion System (WECS)
The Performance of Some Implicit Region-Based ActiveContours in Segmenting and Restoring WeldingRadiographic Images
Several domains are based on image processing and analysis. One of them is the radiographicinspection which is used in Non Destructive Testing (NDT). Active contours, snakes ordeformable models are powerful techniques in image segmentation and restoration. According to theterm related to the input data (image to be treated) those functionals are ranked on two categories:edge-based models and region-based models. Previous studies point out the advantages of the regionbasedmodels over edge-based models. In this paper, we discuss and we summarize the strengths andweaknesses of four implicit region-based active contour models named: Piecewise Constant PC,Piecewise Smooth PS, Local Binary Fitting LBF and Global Local fitting energy GLF. After performingseveral experiments, we have concluded that all the models perform well with homogeneousimages. On the contrary when images are strongly inhomogeneous, the models based on global (PC)or local (LBF) statistic intensity fail to segment such images. The PS model with its great advantage inpreserving the contours has, as a drawback, the high CPU time consuming. The combination of localand global statistic image intensity gives to the GLF model the ability to better deal with such imagesin less CPU time. Voir les détails
Mots clés : segmentation, radiographic images, Level set, region-based active contour, PC, PS, LBF, GLF