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48 results on '"Boudraa, Bachir"'

5. A Dynamic FEC for Improved Robustness of CELP-Based Codec

Author

Benamirouche, Nadir, Boudraa, Bachir, Gomez, Angel M., Pérez-Córdoba, José L., López-Espejo, Iván, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Abad, Alberto, editor, Ortega, Alfonso, editor, Teixeira, António, editor, García Mateo, Carmen, editor, Martínez Hinarejos, Carlos D., editor, Perdigão, Fernando, editor, Batista, Fernando, editor, and Mamede, Nuno, editor

Published
2016
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7. Ultrasonic Data Compression and Analysis During Material Inspection

Author

Merazi-Meksen, Thouraya, Boudraa, Malika, Boudraa, Bachir, Rannenberg, Kai, Editor-in-chief, Sakarovitch, Jacques, Series editor, Goedicke, Michael, Series editor, Tatnall, Arthur, Series editor, Neuhold, Erich J., Series editor, Pras, Aiko, Series editor, Tröltzsch, Fredi, Series editor, Pries-Heje, Jan, Series editor, Whitehouse, Diane, Series editor, Reis, Ricardo, Series editor, Furnell, Steven, Series editor, Furbach, Ulrich, Series editor, Winckler, Marco, Series editor, Rauterberg, Matthias, Series editor, Chbeir, Richard, editor, Manolopoulos, Yannis, editor, Maglogiannis, Ilias, editor, and Alhajj, Reda, editor

Published
2015
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16. Ultrasonic Image Enhancement to Internal Defect Detection during Material Inspection

Author

Merazi-Meksen Thouraya, Boudraa Malika, and Boudraa Bachir

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

Ultrasonic waves are efficiently exploited to detect internal defects such as cracks and occlusions in non-destructive testing (NDT) of materials. In some automated procedures, emitter and receiver probes are displaced step by step and signals are displayed to form images that make diagnosis easier to interpret. However, too much images are unnecessarily stored when they correspond to safe zones (without presented defects). In this paper, we propose a method that enhances ultrasonic images quality in order to improve the discrimination between images containing or not a shape regarding a detected defect. The method is based on the adapted histogram equalization technique followed by morphological operations that erase all useless shapes on processed images.

Published
2018
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31. Fixed sound source localization in reverberant environments using a multimicrophone set

Author

Meraoubi, Hamid, Boudraa, Bachir, System, HAL, and Société Française d'Acoustique

Subjects
[SPI.ACOU] Engineering Sciences [physics]/Acoustics [physics.class-ph], MICROPHONES ARRAY, CSP, REVERBERATION, treatment times
Abstract

The aim of this study is the implementation of algorithms for locating a fixed sound source using a set of 4 microphones, arranged in a linear geometry and whose inter-microphone distances are known. The first results concern the duration of treatments to detect the arrival direction of the incident wave in reverberant environments. In the series of tests conducted in this work, we keep constant both the sampling frequency (Fe= 44100Hz) as soon as the distance d between microphones. Then, we vary the angle of incidence of the sound signal. The tests were repeated for different lengths of analysis windows. The tests were carried out in a reverberant room and with a significant background noise. As the most applications are conducted in reverberant rooms, the signals received by a sensor are the sum signals provided by both the direct path and the reflected ones through walls or other obstacles. The present study helps us to rapidly locate a fixed source for treatment times of 1*N to 20*N ( N=1024 samples ). So, the good detection of a sound source in a reverberating room is obtained by taking only the beginning of the recording files corresponding to the 4 microphones of the array.

Published
2012

48. Defects Clustering using Kohonen Networks during Ultrasonic Inspection.

Author

Meksen, Thouraya Merazi, Boudraa, Bachir, and Boudraa, Malika

Subjects
ULTRASONIC waves, ULTRASONICS, SELF-organizing maps, SIGNAL theory, HUMAN-machine systems, WELDING
Abstract

In Non Destructive Testing (NDT) of materials, the ultrasonic waves propagating in a structure are reflected or refracted from the presented discontinuities. The reached waves are received and converted to electrical signals containing informations about the internal defects. The characterization of those defects is an important task and the use of tools of signal processing gives an appreciated help in the decision making for the human operators. This work is a contribution for the defect characterization. The Neural Networks are used in order to classify reached signals allowing to distinguish between signals reflected from two different defects (cracks and inclusions) included in a welding. [ABSTRACT FROM AUTHOR]

Published
2009

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