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146 results on '"Charles, Gérard"'

1. Demons registration for 2D empirical wavelet transforms

Author

Lucas, Charles-Gérard and Gilles, Jérôme

Subjects
Electrical Engineering and Systems Science - Image and Video Processing
Abstract

The empirical wavelet transform is a fully adaptive time-scale representation that has been widely used in the last decade. Inspired by the empirical mode decomposition, it consists of filter banks based on harmonic mode supports. Recently, it has been generalized to build the filter banks from any generating function using mappings. In practice, the harmonic mode supports can have low constrained shape in 2D, leading to numerical difficulties to compute the mappings and therefore the related wavelet filters. This work aims to propose an efficient numerical scheme to compute empirical wavelet coefficients using the demons registration algorithm. Results show that the proposed approach gives a numerically robust wavelet transform. An application to texture segmentation of scanning tunnelling microscope images is also presented.

Published
2024

2. Multidimensional empirical wavelet transform

Author

Lucas, Charles-Gérard and Gilles, Jérôme

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, 42C15, 42C40, 68U10
Abstract

The empirical wavelet transform is a data-driven time-scale representation consisting of an adaptive filter bank. Its robustness to data has made it the subject of intense developments and an increasing number of applications in the last decade. However, it has been mostly studied theoretically for signals and its extension to images is limited to a particular generating function. This work presents a general framework for multidimensional empirical wavelet transform based on any wavelet kernel. It also provides conditions to build wavelet frames for both continuous and discrete transforms. Moreover, numerical simulations of transforms are given.

Published
2024

3. Demon Registration for 2D Empirical Wavelet Transforms

Author

Charles-Gérard Lucas and Jérôme Gilles

Subjects
empirical wavelet, adaptive representation, demon algorithm, texture segmentation, Mathematics, QA1-939
Abstract

The empirical wavelet transform is a fully adaptive time-scale representation that has been widely used in the last decade. Inspired by the empirical mode decomposition, it consists of filter banks based on harmonic mode supports. Recently, it has been generalized to build the filter banks from any generating function using mappings. In practice, the harmonic mode supports can have a low-constrained shape in 2D, leading to numerical difficulties to estimate mappings adapted to the construction of empirical wavelet filters. This work aims to propose an efficient numerical scheme to compute empirical wavelet coefficients using the demons registration algorithm. Results show that the proposed approach is robust, accurate, and continuous wavelet filters permitting reconstruction with a low signal-to-noise ratio. An application for texture segmentation of scanning tunneling microscope images is also presented.

Published
2024
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4. Multivariate selfsimilarity: Multiscale eigen-structures for selfsimilarity parameter estimation

Author

Lucas, Charles-Gérard, Didier, Gustavo, Wendt, Herwig, and Abry, Patrice

Subjects
Statistics - Methodology, Electrical Engineering and Systems Science - Signal Processing
Abstract

Scale-free dynamics, formalized by selfsimilarity, provides a versatile paradigm massively and ubiquitously used to model temporal dynamics in real-world data. However, its practical use has mostly remained univariate so far. By contrast, modern applications often demand multivariate data analysis. Accordingly, models for multivariate selfsimilarity were recently proposed. Nevertheless, they have remained rarely used in practice because of a lack of available robust estimation procedures for the vector of selfsimilarity parameters. Building upon recent mathematical developments, the present work puts forth an efficient estimation procedure based on the theoretical study of the multiscale eigenstructure of the wavelet spectrum of multivariate selfsimilar processes. The estimation performance is studied theoretically in the asymptotic limits of large scale and sample sizes, and computationally for finite-size samples. As a practical outcome, a fully operational and documented multivariate signal processing estimation toolbox is made freely available and is ready for practical use on real-world data. Its potential benefits are illustrated in epileptic seizure prediction from multi-channel EEG data., Comment: 14 pages, 8 figures

Published
2023

8. Hyperparameter selection for Discrete Mumford-Shah

Author

Lucas, Charles-Gérard, Pascal, Barbara, Pustelnik, Nelly, and Abry, Patrice

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Mathematics - Optimization and Control
Abstract

This work focuses on a parameter-free joint piecewise smooth image denoising and contour detection. Formulated as the minimization of a discrete Mumford-Shah functional and estimated via a theoretically grounded alternating minimization scheme, the bottleneck of such a variational approach lies in the need to fine-tune their hyperparameters, while not having access to ground truth data. To that aim, a Stein-like strategy providing optimal hyperparameters is designed, based on the minimization of an unbiased estimate of the quadratic risk. Efficient and automated minimization of the estimate of the risk crucially relies on an unbiased estimate of the gradient of the risk with respect to hyperparameters. Its practical implementation is performed using a forward differentiation of the alternating scheme minimizing the Mumford-Shah functional, requiring exact differentiation of the proximity operators involved. Intensive numerical experiments are performed on synthetic images with different geometry and noise levels, assessing the accuracy and the robustness of the proposed procedure. The resulting parameter-free piecewise-smooth estimation and contour detection procedure, not requiring prior image processing expertise nor annotated data, can then be applied to real-world images.

Published
2021
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10. Comparison of Earthquake and Moisture Effects on Rockfall-Runouts Using 3D Models and Orthorectified Aerial Photos

Author

Mohammad Al-Shaar, Pierre-Charles Gérard, Ghaleb Faour, Walid Al-Shaar, and Jocelyne Adjizian-Gérard

Subjects
rockfall hazard, mapping, runout, orthorectification, aerial photos, Geography (General), G1-922
Abstract

Rockfall hazard gains popularity nowadays among researchers in different scientific fields, decision-makers and urban planners. The assessment of rockfall hazard requires detection, mapping and estimating the maximum travel distance that rock boulders may reach, commonly known as “rockfall runout”. This latter can change significantly under the effects of different triggering factors such as soil conditions, chemical, physical and geological rock properties. However, comparing and analyzing these different effects represents, to the best of our knowledge, one of the newest scientific challenges that need to be addressed. This paper presents a complete methodologic approach aiming to assess the rockfall hazard through runout estimation in three different conditions: (i) gravity, (ii) earthquakes, and (iii) the presence of moisture along the slope. The “Mtein” Village and its surrounding areas in the Mount Lebanon region were chosen as the study area because there have been numerous historic rockfalls and various-sized rocks, such as cobbles and boulders, scattered throughout the area. Thus, three-dimensional simulations were conducted using the Rockyfor3D software and aerial photos for the year 1999 to assess the rockfall runout, the energy curves, and the number of deposited rocks. The results reveal that earthquakes have the highest triggering effect on rockfall and that moisture has a damping effect on RFs by decreasing the kinetic energy. The study shows the importance of taking into consideration the influence of triggering factors as well as rock density on rockfall runout and hazard.

Published
2023
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16. Spatial and temporal regularization to estimate COVID-19 reproduction number R(t): Promoting piecewise smoothness via convex optimization.

Author

Patrice Abry, Nelly Pustelnik, Stéphane Roux, Pablo Jensen, Patrick Flandrin, Rémi Gribonval, Charles-Gérard Lucas, Éric Guichard, Pierre Borgnat, and Nicolas Garnier

Subjects
Medicine, Science
Abstract

Among the different indicators that quantify the spread of an epidemic such as the on-going COVID-19, stands first the reproduction number which measures how many people can be contaminated by an infected person. In order to permit the monitoring of the evolution of this number, a new estimation procedure is proposed here, assuming a well-accepted model for current incidence data, based on past observations. The novelty of the proposed approach is twofold: 1) the estimation of the reproduction number is achieved by convex optimization within a proximal-based inverse problem formulation, with constraints aimed at promoting piecewise smoothness; 2) the approach is developed in a multivariate setting, allowing for the simultaneous handling of multiple time series attached to different geographical regions, together with a spatial (graph-based) regularization of their evolutions in time. The effectiveness of the approach is first supported by simulations, and two main applications to real COVID-19 data are then discussed. The first one refers to the comparative evolution of the reproduction number for a number of countries, while the second one focuses on French departments and their joint analysis, leading to dynamic maps revealing the temporal co-evolution of their reproduction numbers.

Published
2020
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20. Multivariate time-scale bootstrap for testing the equality of selfsimilarity parameters

Author

Lucas, Charles-Gérard, Wendt, Herwig, Abry, Patrice, Didier, Gustavo, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), CoMputational imagINg anD viSion (IRIT-MINDS), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Tulane University, Wendt, Herwig, École normale supérieure de Lyon (ENS de Lyon)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), and Université de Toulouse (UT)

Subjects
[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [INFO.INFO-TS] Computer Science [cs]/Signal and Image Processing, [INFO]Computer Science [cs]
Abstract

Monitoring one system from multivariate data collected on multiple sensors often entails counting how many actually different selfsimilarity parameters drive their temporal dynamics. Making use of a multivariate fractional Brownian motion model, of multivariate eigen-wavelet estimations, and of a multivariate time-scale block bootstrap procedure, a test for equality between pairs of sorted estimated selfsimilarity parameters is devised. The procedure permits the estimation of the test p-value and power from a single finite-size data observation. Test performance are quantified from large size Monte Carlo simulations performed under several scenarios., La surveillance d'un système à partir de données multivariées enregistrées par un ensemble de capteurs implique souvent de compter combien de paramètres d'autosimilarité effectivement différents pilotent leurs dynamiques temporelles. En utilisant un modèle de mouvement brownien fractionnaire multivarié, des procédures d'estimations construites sur les valeurs propres de représentations en ondelettes et une technique de bootstrap par bloc dans le domaine temps-échelle, un test d'égalité entre paires triées de paramètres d'auto-similarité estimés est construit. La procédure permet, à partir d'une seule observation de taille finie des données, d'estimer la p-valeur et la puissance du test. Les performances de la procédure sont quantifiées au moyen de simulations Monte Carlo de grandes tailles, conduites sous différents scénarios.

Published
2022

21. Drowsiness detection from polysomnographic data using multivariate selfsimilarity and eigen-wavelet analysis

Author

Lucas, Charles-Gérard, Abry, Patrice, Wendt, Herwig, Didier, Gustavo, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon, Tulane University, École normale supérieure de Lyon (ENS de Lyon)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), CoMputational imagINg anD viSion (IRIT-MINDS), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), IEEE Engineering in Medicine & Biology Society, Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, Heart Rate, Wavelet Analysis, [INFO]Computer Science [cs], Electroencephalography, Sleep Stages, Sleep
Abstract

International audience; Because drowsiness is a major cause in vehicle accidents, its automated detection is critical. Scale-free temporal dynamics is known to be typical of physiological and body rhythms. The present work quantifies the benefits of applying a recent and original multivariate selfsimilarity analysis to several modalities of polysomnographic measurements (heart rate, blood pressure, electroencephalogram and respiration), from the MIT-BIH Polysomnographic Database, to better classify drowsiness-related sleep stages. Clinical relevance-This study shows that probing jointly temporal dynamics amongst polysomnographic measurements, with a proposed original multivariate multiscale approach, yields a gain of above 5% in the Area-under-Curve quantifying drowsiness-related sleep stage classification performance compared to univariate analysis.

Published
2022
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22. Hyperparameter selection for Discrete Mumford–Shah.

Author

Lucas, Charles-Gérard, Pascal, Barbara, Pustelnik, Nelly, and Abry, Patrice

Abstract

This work focuses on a parameter-free joint piecewise smooth image denoising and contour detection. Formulated as the minimization of a discrete Mumford–Shah functional and estimated via a theoretically grounded alternating minimization scheme, the bottleneck of such a variational approach lies in the need to fine-tune their hyperparameters, while not having access to ground truth data. To that aim, a Stein-like strategy providing optimal hyperparameters is designed, based on the minimization of an unbiased estimate of the quadratic risk. Efficient and automated minimization of the estimate of the risk crucially relies on an unbiased estimate of the gradient of the risk with respect to hyperparameters. Its practical implementation is performed using a forward differentiation of the alternating scheme minimizing the Mumford–Shah functional, requiring exact differentiation of the proximity operators involved. Intensive numerical experiments are performed on synthetic images with different geometry and noise levels, assessing the accuracy and the robustness of the proposed procedure. The resulting parameter-free piecewise-smooth estimation and contour detection procedure, not requiring prior image processing expertise nor annotated data, can then be applied to real-world images. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Counting the Number of Different Scaling Exponents in Multivariate Scale-Free Dynamics: Clustering by Bootstrap in the Wavelet Domain

Author

Lucas, Charles-Gérard, Abry, Patrice, Wendt, Herwig, Didier, Gustavo, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), CoMputational imagINg anD viSion (IRIT-MINDS), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Centre National de la Recherche Scientifique (CNRS), Tulane University, IEEE Signal Processing Society, École normale supérieure de Lyon (ENS de Lyon)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), ANR-16-CE33-0020,MULTIFRACS,Théories et méthodes multifractales multivariées pour les systèmes de grande taille - Applications à l'analyse des propriétés d'invariance d'échelle dans la dynamique de l'activité cérébrale(2016), and ANR-18-CE45-0007,MUTATION,Analyse multifractale multidimensionnelle : Théorie et applications en imagerie échographique du cancer de pancréas(2018)

Subjects
[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, multivariate wavelet transform, multivariate scaling exponents, multivariate selfsimilarity, bootstrap
Abstract

International audience; Multivariate selfsimilarity has become a classical tool to analyze collections of time series recorded jointly on one same system. Often, it amounts to estimating as many scaling exponents as time series. However, this leaves open the important question how many such scaling exponents are actually different. Elaborating on earlier work aiming to test the hypothesis that all exponents are equal, we intend here to count the number of different scaling exponents from a single finite size multivariate time series. To this end, we devise an original clustering procedure that combines a wavelet domain block multivariate bootstrap scheme with a test strategy for a reduced set of multiple hypotheses on the pairwise equality of scaling exponents that are relevant to clustering. Monte Carlo simulations, making use of synthetic multivariate selfsimilar processes, assess the relevance and performance of the proposed procedure under different scenarios and demonstrate that the proposed method yields practically satisfactory cluster number and size estimations.

Published
2022
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25. Antología del pensamiento crítico haitiano contemporáneo

Author

León, Camila Valdés, Voltaire, Frantz, Trouillot, Michel-Rolph, Castor, Suzy, Pierre-Charles, Gérard, Casimir, Jean, Depestre, René, Hurbon, Laënnec, Moïse, Claude, Ollivier, Émile, Manigat, Leslie F., Anglade, Mireille Neptune, Bellande, Alex, Dominique, Max, Alexis, Jacques Stephene, Danticat, Edwidge, León, Camila Valdés, Voltaire, Frantz, Trouillot, Michel-Rolph, Castor, Suzy, Pierre-Charles, Gérard, Casimir, Jean, Depestre, René, Hurbon, Laënnec, Moïse, Claude, Ollivier, Émile, Manigat, Leslie F., Anglade, Mireille Neptune, Bellande, Alex, Dominique, Max, Alexis, Jacques Stephene, and Danticat, Edwidge

Published
2018

27. Hyperparameter selection for the Discrete Mumford-Shah functional

Author

Lucas, Charles-Gérard, Pascal, Barbara, Pustelnik, Nelly, Abry, Patrice, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)

Subjects
non-convex minimization, contour detection, Stein Unbiased Risk Estimate, [INFO.INFO-TI]Computer Science [cs]/Image Processing [eess.IV], Mumford-Shah functional, [MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC]
Abstract

This work focuses on joint piecewise smooth image reconstruction and contour detection, formulated as the minimization of a discrete Mumford-Shah functional, performed via a theoretically grounded alternating minimization scheme. The bottleneck of such variational approaches lies in the need to finetune their hyperparameters, while not having access to ground truth data. To that aim, a Stein-like strategy providing optimal hyperparameters is designed, based on the minimization of an unbiased estimate of the quadratic risk. Efficient and automated minimization of the estimate of the risk crucially relies on an unbiased estimate of the gradient of the risk with respect to hyperparameters, whose practical implementation is performed thanks to a forward differentiation of the alternating scheme minimizing the Mumford-Shah functional, requiring exact differentiation of the proximity operators involved. Intensive numerical experiments are performed on synthetic images with different geometries and noise levels, assessing the accuracy and the robustness of the proposed procedure. The resulting parameterfree piecewise-smooth reconstruction and contour detection procedure, not requiring prior image processing expertise, is thus amenable to real-world applications.

Published
2021

28. Bootstrap for testing the equality of selfsimilarity exponents across multivariate time series

Author

Herwig Wendt, Charles-Gérard Lucas, Patrice Abry, Gustavo Didier, CoMputational imagINg anD viSion (IRIT-MINDS), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure de Lyon (ENS de Lyon)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Tulane University, PhD Grant DGA/AID (n° 01D20019023), ANR-18-CE45-0007,MUTATION,Analyse multifractale multidimensionnelle : Théorie et applications en imagerie échographique du cancer de pancréas(2018), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon

Subjects
010104 statistics & probability, 0202 electrical engineering, electronic engineering, information engineering, Statistics::Methodology, 020206 networking & telecommunications, [INFO]Computer Science [cs], 02 engineering and technology, 0101 mathematics, 16. Peace & justice, 01 natural sciences
Abstract

International audience; Because of the ever-increasing collections of multivariate data, multivariate selfsimilarity has become a widely used model for scale-free dynamics, with successful applications in numerous different fields. Multivariate selfsimilarity exponent estimation has therefore received considerable attention, with notably an original procedure recently proposed and based on the eigenvalues of the covariance random matrices of the wavelet coefficients at fixed scales. Expanding on preliminary work aiming to test for the equality of the selfsimilarity exponents in bivariate time series, we propose and study here a truly multivariate procedure that permits, from a single observation of multivariate time series, to test for the equality of several, possibly many, selfsimilarity exponents. It is based on an original bootstrap procedure, applied in a multivariate timescale domain and designed to effectively capture the scale-dependent joint covariance structure of multivariate wavelet coefficients as well as the associated wavelet eigenvalue structures. Extensive simulations conducted on synthetic data, modeled by operator fractional Brownian motions, the reference multivariate selfsimilarity model, permit to show that the proposed multivariate timescale domain bootstrap based test yields the targeted significance level under the null hypothesis (all selfsimilarity exponents are equal) and to assess the power of the test for several alternative hypotheses. This analysis leads us to conclude that the proposed test for the equality of multivariate selfsimilarity exponents is effective and ready for use on (a single time series of) real data.

Published
2021

39. COVID-19 Reproduction Number Estimation: Spatial and Temporal in Convex Optimization to Promote Piecewise Smoothness

Author

Patrice Abry, Nelly Pustelnik, Stéphane Roux, Pablo Jensen, Patrick Flandrin, Rémi Gribonval, Charles-Gérard Lucas, Éric Guichard, Pierre Borgnat, Nicolas Garnier, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Dynamic Networks : Temporal and Structural Capture Approach (DANTE), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de l'Informatique du Parallélisme (LIP), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut Rhône-Alpin des systèmes complexes (IXXI), École normale supérieure de Lyon (ENS de Lyon)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Triangle : action, discours, pensée politique et économique (TRIANGLE), École normale supérieure de Lyon (ENS de Lyon)-Université Lumière - Lyon 2 (UL2)-Sciences Po Lyon - Institut d'études politiques de Lyon (IEP Lyon), Université de Lyon-Université de Lyon-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université Grenoble Alpes (UGA)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Université Grenoble Alpes (UGA)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon, Centre National de la Recherche Scientifique (CNRS)-Sciences Po Lyon - Institut d'études politiques de Lyon (IEP Lyon), and Université de Lyon-Université de Lyon-Université Jean Monnet [Saint-Étienne] (UJM)-Université Lumière - Lyon 2 (UL2)-École normale supérieure - Lyon (ENS Lyon)

Subjects
[SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

40. Spatial and temporal regularization to estimate COVID-19 reproduction number R(t): Promoting piecewise smoothness via convex optimization

Author

Pablo Jensen, Eric Guichard, Pierre Borgnat, Patrick Flandrin, Stéphane Roux, Nicolas Garnier, Rémi Gribonval, Nelly Pustelnik, Charles-Gérard Lucas, Patrice Abry, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Institut Rhône-Alpin des systèmes complexes (IXXI), Université Grenoble Alpes (UGA)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Dynamic Networks : Temporal and Structural Capture Approach (DANTE), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire de l'Informatique du Parallélisme (LIP), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut Rhône-Alpin des systèmes complexes (IXXI), Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Université Grenoble Alpes (UGA)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon, Triangle : action, discours, pensée politique et économique (TRIANGLE), Centre National de la Recherche Scientifique (CNRS)-Sciences Po Lyon - Institut d'études politiques de Lyon (IEP Lyon), Université de Lyon-Université de Lyon-Université Jean Monnet [Saint-Étienne] (UJM)-Université Lumière - Lyon 2 (UL2)-École normale supérieure - Lyon (ENS Lyon), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), École normale supérieure de Lyon (ENS de Lyon)-Université Lumière - Lyon 2 (UL2)-Sciences Po Lyon - Institut d'études politiques de Lyon (IEP Lyon), Université de Lyon-Université de Lyon-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut Rhône-Alpin des systèmes complexes (IXXI), École normale supérieure - Lyon (ENS Lyon)-Université Lumière - Lyon 2 (UL2)-Sciences Po Lyon - Institut d'études politiques de Lyon (IEP Lyon), and Université de Lyon-Université de Lyon-Université Jean Monnet [Saint-Étienne] (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Multivariate statistics, Viral Diseases, Databases, Factual, Computer science, Epidemiology, Poisson distribution, Geographical Regions, Regularization (mathematics), Geographical locations, 0302 clinical medicine, Medical Conditions, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, Medicine and Health Sciences, 030212 general & internal medicine, Poisson Distribution, 0303 health sciences, Multidisciplinary, Geography, Applied Mathematics, Simulation and Modeling, Software Engineering, Inverse problem, Europe, Infectious Diseases, Convex optimization, Physical Sciences, symbols, Engineering and Technology, Medicine, France, Coronavirus Infections, Algorithms, Research Article, Optimization, Mathematical optimization, Computer and Information Sciences, Science, Pneumonia, Viral, Research and Analysis Methods, 03 medical and health sciences, symbols.namesake, Betacoronavirus, Spatio-Temporal Analysis, Disease Transmission, Infectious, Humans, European Union, Pandemics, Preprocessing, 030304 developmental biology, COVID-19, Geographical regions, Models, Statistical, Series (mathematics), SARS-CoV-2, Covid 19, Regional Geography, Earth Sciences, People and places, Mathematics, Software
Abstract

International audience; Among the different indicators that quantify the spread of an epidemic such as the on-going COVID-19, stands first the reproduction number which measures how many people can be contaminated by an infected person. In order to permit the monitoring of the evolution of this number, a new estimation procedure is proposed here, assuming a well-accepted model for current incidence data, based on past observations. The novelty of the proposed approach is twofold: 1) the estimation of the reproduction number is achieved by convex optimization within a proximal-based inverse problem formulation, with constraints aimed at promoting piecewise smoothness; 2) the approach is developed in a multivariate setting, allowing for the simultaneous handling of multiple time series attached to different geographical regions, together with a spatial (graph-based) regularization of their evolutions in time. The effectiveness of the approach is first supported by simulations, and two main applications to real COVID-19 data are then discussed. The first one refers to the comparative evolution of the reproduction number for a number of countries, while the second one focuses on French departments and their joint analysis, leading to dynamic maps revealing the temporal co-evolution of their reproduction numbers.

Published
2020
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42. Controlled comparison of milnacipran and fluoxetine in major depression

Author

Ansseau, Marc, Papart, Patrick, Troisfontaines, Benoît, Bartholomé, Franz, Bataille, Michel, Charles, Gérard, Schittecatte, Michel, Darimont, Philippe, Devoitille, Jean-Michel, De Wilde, Jules, Dufrasne, Michel, Gilson, Henri, Evrard, Jean-Luc, De Nayer, André, Krémer, Pierre, Mertens, Claudine, and Serre, Christiane

Published
1994
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45. Antología del pensamiento crítico haitiano contemporáneo

Author

Trouillot, Michel-Rolph, primary, Castor, Suzy, additional, Pierre-Charles, Gérard, additional, Casimir, Jean, additional, Depestre, René, additional, Hurbon, Laënnec, additional, Moïse, Claude, additional, Ollivier, Émile, additional, Manigat, Leslie F., additional, Anglade, Mireille Neptune, additional, Bellande, Alex, additional, Dominique, Max, additional, Alexis, Jacques Stephene, additional, and Danticat, Edwidge, additional

Published
2018
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46. Beirut faced with climatic aridification

Author

Myriam Traboulsi, Naji Kehdy, Rita Zaarour, Pierre-Charles Gérard, Christelle Bakhache, Jocelyne Adjizian-Gérard, Firas El Ess, and Nada Badaro-Saliba

Subjects
021110 strategic, defence & security studies, Global and Planetary Change, 010504 meteorology & atmospheric sciences, Ecology, 13. Climate action, 0211 other engineering and technologies, 02 engineering and technology, 15. Life on land, Management, Monitoring, Policy and Law, 01 natural sciences, 0105 earth and related environmental sciences
Abstract

Beyrouth, capitale du Liban, est aujourd'hui confrontee a une nette degradation de la qualite de son air. Dans le meme temps, elle doit faire face au defi majeur de la penurie hydrique, specialement en fin de periode estivale. Ces deux problemes environnementaux, imputables a la fois aux caracteristiques du climat de la region, aux modalites d'amenagement de la ville et aux activites humaines, risquent a moyen terme de s'aggraver. En effet, le pays commence a subir les consequences de l'evolution climatique qui touche le Proche et le Moyen-Orient : la desertification s'etend, la saison seche s'allonge, le regime pluviometrique est modifie, les temperatures s'elevent de maniere significative. Or, jusqu'a present, aucune politique de gestion n'a reellement ete mise en œuvre pour repondre a de telles contraintes. Bien au contraire, on assiste au developpement des initiatives privees qui accentuent la pression anthropique sur les ressources : l'urbanisation se densifie, verticalement aussi bien qu'horizontalement, les puits illegaux proliferent pour pallier la penurie hydrique, la ville est asphyxiee par la circulation automobile... Finalement, on est en presence de signes avant-coureurs de l'aridification du climat qui, conjugues a l'absence de gestion de l'environnement, sont susceptibles de mettre en peril, notamment du point de vue hydrique, la situation jusqu'ici privilegiee du Liban au sein des milieux arides ou semi-arides.

Published
2013
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