Electronique
Mean Scatterer Spacing For Human Liver Tissue Characterization Using Backscattered Ultrasound Signals
We studied the periodicity of in vitro healthy and pathological liver tissue using the backscattered ultrasound signals. Lot of signal processing methods are used to mean scatterer spacing (MSS) as a parameter of tissue characterization, we cite: Spectral Auto-Correlation (SAC), Spectral Correlation of the autoregressive model (AR-SAC) and others. We used the Discrete Wavelet Technique (DWT) to MSS estimate, in comparison, the DWT with Fourier Transform together (DWT with FT) can provide a very effective tool to extract the MSS from such structure and characterize the tissue Voir les détails
Mots clés : Periodicity, Liver tissue, Mean scatterer spacing, Backscattered Ultrasound Signals
Low-profile U-shaped DRA for ultra-wideband applications
In this paper, a microstrip-fed U-shaped dielectric resonator antenna (DRA) is simulated, designed, and fabricated. This antenna, in its simple configuration, operates from 5.45 to 10.8 GHz. To enhance its impedance bandwidth, the ground plane is first modified, which leads to an extended bandwidth from 4 to 10.8 GHz. Then by inserting a rectangular metallic patch inside the U-shaped DRA, the bandwidth is increased more to achieve an operating band from 2.65 to 10.9 GHz. To validate these results, an experimental antenna prototype is fabricated and measured. The obtained measurement results show that the proposed antenna can provide an ultra-wide bandwidth and a symmetric bidirectional radiation patterns. With these features, the proposed antenna is suitable for ultra-wideband applications. Voir les détails
Mots clés : Ultra-wideband applications, Dielectric resonator antenna, Low-profile antenna, Measurements
A Hybrid Integrated Ultra-Wideband/Dual-Band Antenna with High Isolation
In this paper, we propose a novel integrated ultra-wideband (UWB) monopole antenna with dual-band antenna. The antenna consists of planar rectangular with semi-elliptical base and a rectangular dielectric resonator antenna (DRA) with dual-band operation. Both of them are excited via coplanar waveguide (CPW) lines. The experimental measurements show that the planar monopole provides an impedance bandwidth between 2.44 and 11.9 GHz which largely covers the entire UWB spectrum, and the rectangular DRA operates at two bands; 5.3–6.2 and 8.5–9.4 GHz. Additionally, the proposed structure ensures low mutual coupling between the two ports (with S21 less than 22 dB in the whole operating frequency band). Voir les détails
Mots clés : CPW-fed line, Dielectric resonator antenna, Dual-band antenna, Integrated antennas, isolation, UWB antenna
High/Low Gain Rectangular Dielectric Resonator Antenna for WLAN Applications
In this paper, a novel integrated dual-port rectangular dielectric resonator antenna (DRA) is presented for 802.11a WLAN system applications. The antenna structure is formed by integrating the concept of antenna array with a single DRA element to produce a radiation characteristic necessity. The array is composed of four identical rectangular DRA elements placed on a horizontal ground plane and separated by a distance of 0.54λ at design frequency of 5.97 GHz, excited through rectangular shaped aperture slots by a microstrip transmission line from port 1. The central element fed from port 2 by 50 Ohm microstrip line via a slot etched on the ground plane. The designed proposed antenna sized of 60×80×0.672 mm3 operates over the frequency band between 5 and 6 GHz for VSWR. Voir les détails
Mots clés : High/Low Gain antenna, dielectric resonator antenna (DRA)
Nonlinear predictive control of a mobile robot: asolution using metaheuristcs
The basic features of model-based predictive control (MBPC) make it an interesting candidate for the control of mobile robots. However, fast solution procedures remain a challenge for nonlinear MBPC problems such as the one arising in mobile robot control. Metaheuristics are general purpose heuristics which have been successful in solving difficult optimization problems in a reasonable computation time. In this work, we present a comparison between the uses of three different heuristics, namely particle swarm optimization (PSO), ant colony optimization, and gravitational search algorithm for the solution of the nonlinear MBPC for a mobile robot tracking trajectory with dynamic obstacle avoidance. The computation times obtained show that PSO is a feasible alternative for real-time applications. The MBPC based on the PSO is applied to controlling a LEGO mobile robot with encouraged results. Voir les détails
Mots clés : nonlinear predictive control, Metaheuristcis, mobile robots, optimization
Asymmetric Generalized Gaussian Mixturesfor Radiographic Image Segmentation
In this paper, a parametric histogram-based image segmentation methodis used where the gray level histogram is considered as a finite mixture of asymmetricgeneralized Gaussian distribution (AGGD). The choice of AGGD is motivated byits flexibility to adapt the shape of the data including the asymmetry. Here, themethod of moment estimation combined to the expectation–maximization algorithm(MME/EM) is originally used to estimate the mixture parameters. The proposedimage segmentation approach is achieved in radiographic imaging where the imageoften presents an histogram with a complex shape. The experimental results providedin terms of histogram fitting error and region uniformity measure are comparableto those of the maximum likelihood method (MLE/EM) with the advantage thatMME/EM method reveals to be more robust to the EM initialization than MLE/EM. Voir les détails
Mots clés : AGGD, radiography, MLE/EM, MME/EM, image segmentation
First-principles investigation of the optical properties for rocksalt mixed metal oxide MgxZn1-xO
In this paper, we have presented a theoretical study of the optical properties for the cubic MgxZn1-xO(x = 0.0, 0.125, 0.375, 0.625, 0.875 and 1.0) alloys using the full-potential linearized augmented planewave (FP-LAPW) method based on the density functional theory (DFT). The local density approximation(LDA) was applied to calculate the structural properties. In order to explore the desired properties, the MgxZn1-xO alloys were modeled at various x compositions from 0.0 to 1.0 by step of 0.125. The recentlymodified semi-local Becke-Johnson potential with LDA correlation in the form of mBJ-LDA was used topredict the energy band gap, optical dielectric function, refractive index, absorption coefficient, reflectivity,optical conductivity and the electron energy loss of MgxZn1-xO alloys. The obtained results show good agreement with the experimental data, which indicate that the investigated ternary alloys areamong promising material for the fabrication of electronic, optoelectronic devices and their applications. Voir les détails
Mots clés : alloys, Electronic materials, Optical materials, Ab initio calculations, Band-structure
Full-potential calculations of structural and optoelectronic properties of cubic indium gallium arsenide semiconductor alloys
In this work, the first-principle calculations have been performed to predict the structural,electronic and optical properties of cubic InxGa1−xAs for 0≤x≤1, using 16-atom within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method based on Density Functional Theory (DFT) as implemented in WIEN2k computational code. The Local Density Approximation (LDA) and Wu–Cohen Generalized Gradient Approximation (WC–GGA)were employed as the exchange–correlation term to calculate the structural and electronic properties. Moreover, the Engel–Vosko GGA (EV-GGA) and the recently modified semi–local Becke–Johnson (mBJ) functional were also used to compute the electronic and optical properties in order to get some better degree of precision. The real and the imaginary parts ofthe dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient and optical conductivity were calculated to discuss the linear optical properties ofInxGa1−xAs alloys. The achieved results show a great potential utilization in optoelectronic devices especially in infrared applications. Voir les détails
Mots clés : Ab inition, DFT, Cubic, InxGa1-xAs alloys, structural parameters, Optoelectronic properties
Computer Code for Materials Diagnosis Using Monte CarloMethod and Neural Networks
Non-destructive testing (NDT) is a highlyvaluable technique in evaluation and evolution of materialsand products. X-ray imaging is an important NDT techniquethat is used widely in the metal industry in order tocontrol the quality of materials. Sometimes it may be difficultto get a measurement. The simulation of X-rayimaging is often performed using computer codes. Thispaper presents a new simulation method for materialsdiagnosis. The simulation is based primarily on the X-rayattenuation law and it is performed using a combinationbetween Monte Carlo method and multi-layer perceptronneural network. The main goal of the proposed method isto obtain more detailed information about the state of thematerials. Voir les détails
Mots clés : Non-Destructive testing, X-ray imaging, Materials diagnosis, Monte Carlo, Neural Network
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