2-D Prony-Huang Transform: A New Tool for 2-D Spectral Analysis

This work proposes an extension of the 1-D Hilbert Huang transform for the analysis of images. The proposed method consists in (i) adaptively decomposing an image into oscillating parts called intrinsic mode functions (IMFs) using a mode decomposition procedure, and (ii) providing a local spectral analysis of the obtained IMFs in order to get the local amplitudes, frequencies, and orientations. For the decomposition step, we propose two robust 2-D mode decompositions based on non-smooth convex optimization: a "Genuine 2-D" approach, that constrains the local extrema of the IMFs, and a "Pseudo 2-D" approach, which constrains separately the extrema of lines, columns, and diagonals. The spectral analysis step is based on Prony annihilation property that is applied on small square patches of the IMFs. The resulting 2-D Prony-Huang transform is validated on simulated and real data.Comment: 24 pages, 7 figure

A Multicomponent proximal algorithm for Empirical Mode Decomposition

International audienceThe Empirical Mode Decomposition (EMD) is known to be a powerful tool adapted to the decomposition of a signal into a collection of intrinsic mode functions (IMF). A key procedure in the extraction of the IMFs is the sifting process whose main drawback is to depend on the choice of an interpolation method and to have no clear convergence guarantees. We propose a convex optimization procedure in order to replace the sifting process in the EMD. The considered method is based on proximal tools, which allow us to deal with a large class of constraints such as quasi-orthogonality or extrema-based constraints

A Primal-Dual Algorithm for Link Dependent Origin Destination Matrix Estimation

Origin-Destination Matrix (ODM) estimation is a classical problem in transport engineering aiming to recover flows from every Origin to every Destination from measured traffic counts and a priori model information. In addition to traffic counts, the present contribution takes advantage of probe trajectories, whose capture is made possible by new measurement technologies. It extends the concept of ODM to that of Link dependent ODM (LODM), keeping the information about the flow distribution on links and containing inherently the ODM assignment. Further, an original formulation of LODM estimation, from traffic counts and probe trajectories is presented as an optimisation problem, where the functional to be minimized consists of five convex functions, each modelling a constraint or property of the transport problem: consistency with traffic counts, consistency with sampled probe trajectories, consistency with traffic conservation (Kirchhoff's law), similarity of flows having close origins and destinations, positivity of traffic flows. A primal-dual algorithm is devised to minimize the designed functional, as the corresponding objective functions are not necessarily differentiable. A case study, on a simulated network and traffic, validates the feasibility of the procedure and details its benefits for the estimation of an LODM matching real-network constraints and observations

How to retrieve the normal modes using the POD

International audienceProper orthogonal decomposition (POD) is an increasingly popular way to analyze data, and to obtain either a low- dimensional approximated description of a high-dimensional process, or useful information for damage assessment. In the case of a dynamic system with n degrees of freedom, the purpose of POD is to retrieve the modal properties from the measured response. Until now, POD has been used for systems with a diagonal mass matrix. The aim of this presentation is double: first, to demonstrate that POD can also be used for a non-diagonal symmetric mass matrix; and second, to present sufficient conditions on the response sampling, in order to retrieve the modal characteristics with a prescribed accuracy. The conditions to obtain this approximation with a given accuracy are first explicitly given for the case without damping. Then the case of proportional damping is addressed and similar conditions are shown. The critical case of two modal frequencies close together is also studied, given that it requires particular conditions. The obtained conditions show that the expected accuracy is explicitly limited by the damping ratio. Some numerical tests illustrate the accuracy evolution of the approximated normal modes obtained by this method, with respect to the variation of the observation time and the damping ratio. This careful analysis can be useful for finding the cause of poor approximation properties in more complex cases, such as analysis of variation in nonlinear normal modes

Relative importance of location and period of banana bunch growth in carbohydrate content and mineral composition of fruit

Les relations entre les conditions naturelles de production (sol, climat) et les caractéristiques chimiques des bananes ont été étudiées en Martinique, afin d'alimenter une réflexion sur la mise en place d'un label de qualité basé sur l'origine et d'aider la gestion de la qualité. Matériel et méthodes. Les fruits produits sur six sites, les plus divers possibles, et pendant trois périodes distinctes de l'année, ont été récoltés à la même somme thermique et mûris dans les mêmes conditions. Résultats. Les différences de poids sec et de composition minérale de la pulpe des fruits à la récolte ont été plus fortes entre les sites qu'entre les périodes. Le poids sec de la pulpe a été plus élevé dans les fruits récoltés sur le site en altitude que dans les fruits récoltés en plaine. Les fruits produits sur des sols de type vertisol ont été plus riches en calcium et magnésium que ceux produits sur des sols de type andosol. Les fruits produits sur des sols bruns rouille à halloysite ont été les plus riches en manganèse. Les différences de teneurs en matière sèche, extrait sec soluble et acide citrique dans la pulpe des fruits mûrs ont été plus fortes entre les périodes qu'entre les sites. Les bananes récoltées pendant la saison chaude et humide ont présenté les plus faibles teneurs en extrait sec soluble et total. Les bananes récoltées pendant la saison fraîche et sèche ont été les plus riches en acide citrique. Le poids sec de la pulpe, la teneur en matière sèche des fruits verts, l'extrait sec soluble et les concentrations en glucose et fructose dans les fruits mûrs ont diminué avec l'augmentation, pendant la croissance des fruits, de la température moyenne journalière. À l'inverse, les teneurs en phosphore, magnésium et calcium de la pulpe des fruits verts ont augmenté en même temps que l'augmentation de la température. Conclusion. Ces données devraient être prises en compte pour une meilleure compréhension de l'élaboration de la qualité des bananes. Les conditions environnementales spécifiques en altitude justifient la mise en place d'une dénomination " Montagne " pour la banane. (Résumé d'auteur

The effect of nocturnal wear of dentures on the sleep quality: A systematic review and meta-analysis

Purpose The effect of nocturnal wear of denture on sleep quality and integrity is still not well understood. Therefore, this systematic review was conducted to provide evidence on this topic. Methods Electronic searches were conducted from 1964 up to September 2015, using MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials. Only publications in English or French, in which sleep quality of edentate adult individuals wearing dentures at night was compared to those not wearing were included in the review. Random effects models were used to pool the effect sizes. Results A total of 10 studies were included in the systematic review and 5 in the meta-analysis. No statistically significant difference between sleeping with denture and without denture was found for the Apnea-Hypopnea Index (AHI; Standard Mean Difference = −0.60, 95 % CI −1.67–0.47; Z = −1.10; p = 0.27). However, there was considerable heterogeneity in the studies included in the meta-analysis (Tau2 = 1.34; Q-value = 59.32, df = 4 (P < 0.0001); I2 = 93.3 %). When results from randomized controlled trials (RCTs) were pooled in subgroup analyses of AHI, there was a tendency towards favoring sleeping without dentures (P = 0.059) and no evidence of heterogeneity between studies (Tau2 = 0.000; Q-value = 0.06, df = 1 (P = 0.80); I2 = 0.000 %). Conclusion The current evidence suggests that there is no difference in the sleep quality and integrity of individuals wearing or not wearing their denture during sleep. However, the results of randomized controlled trials favoring sleeping without dentures and the likely presence of bias in the previous studies indicate the need for further randomized controlled trials for the development of clinical guideline

Damage assessment of pre-stressed structures: A SVD-based approach to deal with time-varying loading

International audienceVibration-based methods are well-established and effective tools to assess the health state of civil, mechanical and aerospace engineering structures. However, their reliability is still affected by the variability of the features commonly used for damage detection. Environmental effects and changes in operational conditions are the main sources of variability in the structural response. As a consequence, the modal identification used to extract damage sensitive features has to face constricting requirements in terms of signals stationarity and performance accuracy. Moreover, with reference to the damage assessment, large variations of monitored features mask subtle effects due to damage, which remain undetected. This study is conceived to address both these issues by focusing, in particular, on the non-stationarity of the loading conditions of tensioned structures, such as cables and pre-stressed beams. The capability of spectral methods to deal with the modal identification of non-stationary systems is enhanced by a curve-fitting procedure based on nonlinear least squares optimization. Wavelet analysis is applied for comparison and validation of the FFT-based technique. Identified natural frequencies are then used for the damage detection, exploiting the capacity of singular values decomposition to discriminate between damage-related events and the intrinsic non-stationary nature of the structural response. A reduced-order realization of the features set is performed to amplify changes not belonging to measurement variability but deriving from exogenous events, such as damage. The proposed methodology is validated by experimental analyses carried out on beams subjected to time-varying loading conditions in order to simulate the health monitoring of quasi and non-stationary systems