Papers by mahfoud Elfagrich
Applied Optics
This paper proposes an algorithm for phase demodulating fringe patterns using a two-dimensional c... more This paper proposes an algorithm for phase demodulating fringe patterns using a two-dimensional continuous wavelet transform (2D-CWT). This algorithm exploits the isotropy property of the fan mother wavelet conjugated to Shannon entropy to perform the ridge extraction process by using only 2D-CWT arguments. The proposed algorithm’s performance is shown through simulated fringe patterns corrupted by speckle noise. Also, to evaluate the accuracy of the ridge extracted from the modulus to that obtained from the arguments of 2D-CWT, the developed algorithm is compared to the maximum ridge extraction algorithm for 2D-CWT and cost function ridge extraction algorithm for 2D-CWT, which extract the ridge from the 2D-CWT modulus. Furthermore, we demonstrate the ability of the proposed algorithm to demodulate real fringe patterns derived from optical metrology for temperature measurement. The most important result of the proposed method is that it is provably optimal in estimating the 2D-CWT r...
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Abel inversion method using Chebyshev wavelets for tomographic reconstruction of an axisymmetric medium, 2021
We describe an Abel inversion method for tomographic reconstruction of an axisymmetric medium. Th... more We describe an Abel inversion method for tomographic reconstruction of an axisymmetric medium. The essence of this method is the approximation of data by Chebyshev wavelets. A numerical method and operational matrices are proposed. The accuracy of the method is tested in terms of the noise coefficient. The studied method is compared with the Legendre wavelets method. The results show that the proposed method is less sensitive to noise. We also demonstrate the efficiency of the developed method by obtaining good and expected results for the inversion of interferometric data.
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Applied Optics, 2013
In this work, we describe an adaptation of Fourier-Hankel method to Abel inversion for the deflec... more In this work, we describe an adaptation of Fourier-Hankel method to Abel inversion for the deflection tomographic reconstruction of axisymmetric temperature field. This technique is compared with existing methods to test the accuracy and error propagation using simulated Moiré stripes of natural convection flow above a heated horizontal disk in air. Simpson's 1/3rd rule and one-point and two-point formulas are used in this comparison. The results showed that the proposed technique for Abel inversion is accurate and has the powerful capacity to control the smoothing degree of noise in the inversion process.
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Objectives: The purposes of this work are to investigate the free convective heat transfer in an ... more Objectives: The purposes of this work are to investigate the free convective heat transfer in an axis-symmetric open-ended cavity heated from below and to propose useful correlations of Nusselt number. Methods: The governing equations that model the fluid flow and the temperature field are solved using a control volume-based finite differences method. Under steady state condition, the natural convective flow is considered to be laminar, incompressible and axisymmetric. The Boussinesq approximation with constant thermophysical properties is adopted. Numerical experimentations are performed to deduce the optimum sizes of the calculation domain and the mesh grid. Findings: the obtained results indicate that when Rayleigh number (Ra) and aspect ratio (A) are low the heat transfer is weak and mainly conductive. The increase of Ra and A enhances the convective heat transfer mode thereby the heat transfer is ameliorated. Unlike the Rayleigh Benard convection, the transition from conduction...
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The tomography of temperature fields is the cornerstone of every thermal metrology. Being an area... more The tomography of temperature fields is the cornerstone of every thermal metrology. Being an area of large scale activity, it requires a new control tools that are more powerful and efficient with a low cost. The use of holographic interferometry and moiré deflectometry have simplified to the maximum the needed equipments and transmitted the task to the smart and accurate image processing algorithms offered by these techniques.
The main objective of this thesis is to develop chaining algorithms that allow the tomographic reconstruction of the temperature field of a transparent axis-symmetric medium. The realized work consists on providing at least three classes of algorithms which lead to the necessary information for the temperature field tomography. The first class includes the phase demodulation algorithms. The second represents the unwrapping phase algorithms. The last and the third class gather the algorithms used for solving the inverse Abel transform. To contribute to the problem solving, a phase demodulation by wavelet transform implementation has been performed. In this way, we have examined four versions of implementation of the wavelet transform, developed and compared three algorithms of estimation of the wavelet ridge. Concerning the unwrapping process, we have dissected four algorithms to surround and overcome some of the inherent problems involved in the unwrapping phase operation. In the same context, we have highlighted the resolution of the Abel inverse transform for which we have tested four algorithms for the moiré deflectometry and three algorithms for the holographic interferometry.
The performance of all of these algorithms has been tested in both simulated images and profiles, as well as in real images and profiles. The obtained results reveal the weakness of some of these algorithms and attest the insured and fast convergence for others. We have also examined their ability to overcome some of the critical and inherent problems to the tomography of axis-symmetric mediums. To give practical and applied aspects to this work, we have conducted an experimental research using the holographic interferometry technique. Interferograms have been the subject of processing algorithms studied and found to be adequate for reconstruction of axisymmetric field temperature
Keywords : Tomography, Phase demodulation, Phase unwrapping, Wavelet transform, Abel inverse transform, holographic interferometry, moiré déflectométrie
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Applied optics, 2021
We describe an Abel inversion method for tomographic reconstruction of an axisymmetric medium. Th... more We describe an Abel inversion method for tomographic reconstruction of an axisymmetric medium. The essence of this method is the approximation of data by Chebyshev wavelets. A numerical method and operational matrices are proposed. The accuracy of the method is tested in terms of the noise coefficient. The studied method is compared with the Legendre wavelets method. The results show that the proposed method is less sensitive to noise. We also demonstrate the efficiency of the developed method by obtaining good and expected results for the inversion of interferometric data.
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Experimental Thermal and Fluid Science, 2015
ABSTRACT
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Optics and Lasers in Engineering, 2012
In this work, we describe a simple method of Abel inversion for temperature measurement in a natu... more In this work, we describe a simple method of Abel inversion for temperature measurement in a natural convection axisymmetric flow. The essence of the method is that the measured lateral fringe shift profile is fitted with a polynomial with only even powers and then Abel inverse integral is evaluated analytically. This technique is compared with recent existing methods to test the accuracy and error propagation using a simulated interferogram of natural convection flow below a downward-facing heated horizontal disk in air. For this comparison, lateral fringe profiles are simulated using temperature fields computed by solving Navier Stokes and energy equations. Through random-number generation, noise profile is artificially added to the simulated noise-free lateral fringe shift profile. The results showed that the proposed technique for Abel inversion leads to accurate temperature profiles when the lateral fringe shift profile is fitted with even-power polynomials having degrees ranging from 20 to 30.
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Conference Presentations by mahfoud Elfagrich
conference, 2010
Flow visualization and numerical study of natural convection under a heated horizontal disk facin... more Flow visualization and numerical study of natural convection under a heated horizontal disk facing downward
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Numerical and experimental study of natural convection under a heated horizontal disk facing down... more Numerical and experimental study of natural convection under a heated horizontal disk facing downward
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Teaching Documents by mahfoud Elfagrich
chapitre, 2024
Dans le domaine scientifique, le stockage et la gestion efficaces des données sont cruciaux pour ... more Dans le domaine scientifique, le stockage et la gestion efficaces des données sont cruciaux pour la recherche, l'analyse et la collaboration. Différents formats de fichiers ont été développés pour répondre aux besoins spécifiques des diverses disciplines scientifiques. Voici une introduction aux cinq formats de stockage de données les plus couramment utilisés : DICOM, NetCDF, HDF5, FITS et CSV.
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Papers by mahfoud Elfagrich
The main objective of this thesis is to develop chaining algorithms that allow the tomographic reconstruction of the temperature field of a transparent axis-symmetric medium. The realized work consists on providing at least three classes of algorithms which lead to the necessary information for the temperature field tomography. The first class includes the phase demodulation algorithms. The second represents the unwrapping phase algorithms. The last and the third class gather the algorithms used for solving the inverse Abel transform. To contribute to the problem solving, a phase demodulation by wavelet transform implementation has been performed. In this way, we have examined four versions of implementation of the wavelet transform, developed and compared three algorithms of estimation of the wavelet ridge. Concerning the unwrapping process, we have dissected four algorithms to surround and overcome some of the inherent problems involved in the unwrapping phase operation. In the same context, we have highlighted the resolution of the Abel inverse transform for which we have tested four algorithms for the moiré deflectometry and three algorithms for the holographic interferometry.
The performance of all of these algorithms has been tested in both simulated images and profiles, as well as in real images and profiles. The obtained results reveal the weakness of some of these algorithms and attest the insured and fast convergence for others. We have also examined their ability to overcome some of the critical and inherent problems to the tomography of axis-symmetric mediums. To give practical and applied aspects to this work, we have conducted an experimental research using the holographic interferometry technique. Interferograms have been the subject of processing algorithms studied and found to be adequate for reconstruction of axisymmetric field temperature
Keywords : Tomography, Phase demodulation, Phase unwrapping, Wavelet transform, Abel inverse transform, holographic interferometry, moiré déflectométrie
Conference Presentations by mahfoud Elfagrich
Teaching Documents by mahfoud Elfagrich
The main objective of this thesis is to develop chaining algorithms that allow the tomographic reconstruction of the temperature field of a transparent axis-symmetric medium. The realized work consists on providing at least three classes of algorithms which lead to the necessary information for the temperature field tomography. The first class includes the phase demodulation algorithms. The second represents the unwrapping phase algorithms. The last and the third class gather the algorithms used for solving the inverse Abel transform. To contribute to the problem solving, a phase demodulation by wavelet transform implementation has been performed. In this way, we have examined four versions of implementation of the wavelet transform, developed and compared three algorithms of estimation of the wavelet ridge. Concerning the unwrapping process, we have dissected four algorithms to surround and overcome some of the inherent problems involved in the unwrapping phase operation. In the same context, we have highlighted the resolution of the Abel inverse transform for which we have tested four algorithms for the moiré deflectometry and three algorithms for the holographic interferometry.
The performance of all of these algorithms has been tested in both simulated images and profiles, as well as in real images and profiles. The obtained results reveal the weakness of some of these algorithms and attest the insured and fast convergence for others. We have also examined their ability to overcome some of the critical and inherent problems to the tomography of axis-symmetric mediums. To give practical and applied aspects to this work, we have conducted an experimental research using the holographic interferometry technique. Interferograms have been the subject of processing algorithms studied and found to be adequate for reconstruction of axisymmetric field temperature
Keywords : Tomography, Phase demodulation, Phase unwrapping, Wavelet transform, Abel inverse transform, holographic interferometry, moiré déflectométrie