The Oscillatory Failure Case (OFC) is the name given to a class of failures in the actuator servo loop that cause undesired oscillation of the control surface. The term undesired refers to the fact that these oscillations, even if they are extremely rare, could be coupled with a structural mode and thus must be taken into account for load computation. The structural design is influenced by the OFC amplitude and detection time and so, if we are able to detect quickly smaller and smaller OFC amplitudes we can reduce the overall structural weight with all the related benefits. The current Airbus servo loop principle is shown in Figure 1. The faulty behaviour of an electronic component or a mechanical failure inside the actuator control loop could lead to an OFC. In this study we simulated the OFC effects through the injection of a periodic signal at two specific points of the control loop: the …

Detecting skin lentigo in reflectance confocal microscopy images is an important and challenging problem. This imaging modality has not yet been widely investigated for this problem and there are a few automatic processing techniques. They are mostly based on machine learning approaches and rely on numerous classical image features that lead to high computational costs given the very large resolution of these images. This paper presents a detection method with very low computational complexity that is able to identify the skin depth at which the lentigo can be detected. The proposed method performs multiresolution decomposition of the image obtained at each skin depth. The distribution of image pixels at a given depth can be approximated accurately by a generalized Gaussian distribution whose parameters depend on the decomposition scale, resulting in a very-low-dimension parameter space. SVM classifiers are then investigated to classify the scale parameter of this distribution allowing real-time detection of lentigo. The method is applied to 45 healthy and lentigo patients from a clinical study, where sensitivity of 81.4% and specificity of 83.3% are achieved. Our results show that lentigo is identifiable at depths between 50μm and 60μm, corresponding to the average location of the the dermoepidermal junction. This result is in agreement with the clinical practices that characterize the lentigo by assessing the disorganization of the dermoepidermal junction.

This paper deals with the characterization and the classification of reflectance confocal microscopy images of human skin. The aim is to identify and characterize the skin lentigo, a phenomenon that originates at the dermo-epidermic junction. High resolution images are acquired at different depths of the skin. In this paper, an analysis of confocal images is performed for each depth and the histogram of pixel intensities in the image is determined. It is modeled by a generalized gamma distribution parameterized by a translation, scale and shape parameters ( , and ). These parameters are estimated using the natural gradient descent algorithm and used to achieve the classification between healthy and lentigo patients of clinical images. The obtained results show that the scale and shape parameters (beta and rho) are good features to identify and characterize the presence of lentigo in skin tissues.

This paper presents a fast approach for penalized least squares (LS) regression problems using a 2D Gaussian Markov random field (GMRF) prior. More precisely, the computationoftheproximityoperatoroftheLScriterionregularizedby different GMRF potentials is formulated as solving a Sylvesterlike matrix equation. By exploiting the structural properties of GMRFs, this matrix equation is solved column-wise in an analytical way. The proposed algorithm can be embedded into a wide range of proximal algorithms to solve LS regression problems including a convex penalty. Experiments carried out in the case of a constrained LS regression problem arising in a multichannel image processing application, provide evidence that an alternating direction method of multipliers performs quite efficiently in this context.

Satellite networks are easy-to-deploy solutions to connect rural un-served and underserved areas. But satellite latency has a significant negative impact on performance. Hybrid networks, combining high-throughput long-delay links (e.g. GEO satellites) and short-delay low-throughput links (e.g. poor ADSL), can improve user experience by the use of intelligent routing. Emerging solutions, such as MultiPath TCP (MPTCP), already optimize the throughput in these hybrid networks. However, this kind of solutions does not take into account QoE requirements by the lack of relevant flows information, leading to sub-optimal path selection. This paper proposes an architecture able to retrieve the content size through interconnection with Content Delivery Networks (CDNs). Then, we conduct an analytical study of a probabilistic and a size threshold based routing schemes with the Mean Value Analysis (MVA) method. This shows the great benefit brought by size information in terms of QoE. To solve the limitations due to the threshold configuration, we propose a third algorithm that takes into account the path delay and capacity. Finally, we develop a testbed in order to validate our model and to compare this third scheme to the previous ones. We obtain results equivalent to the size threshold scheme, without its disadvantages.

We are facing a steady increase in Internet usages and bandwidth requirements. However, many terrestrial infras-tructures remain unchanged due to exorbitant modernization costs, particularly in rural areas. In front of the aging of their infrastructures, concerned users are turning towards satellite internet access. Indeed, these solutions offer a high-throughput internet access at a moderate cost of deployment. Unfortunately, the long delay introduced by GEO satellite degrades significantly the user Quality of Experience (QoE) in many cases. In this paper, we consider a hybrid access, composed of a low data rate terrestrial path and a satellite path, within a Content Delivery Network (CDN) context. Thanks to the CDN, requested content size is known allowing to use this information in routing schemes to maximize the users' QoE. Then, we compare flow and packet based routing in this heterogeneous and size-aware context. We finally conclude on the limited interest in packet-based routing compared to flow-based routing, privileged by its simplicity and good performance from a QoE point of view.

Les produits d'intermodulation créés par les non-linéarités actives et passives ont des effets de plus en plus importants dans les charges utiles de satellites de télécommunications et dans les stations de base de téléphonie mobile à cause de l'augmentation du nombre de bandes utilisées, de la largeur de bande et de la puissance émise. Ils peuvent dans certains cas perturber gravement le fonctionnement des récepteurs. La modélisation de non-linéarités héritée de celle des amplificateurs donne de très mauvais résultats qualitativement et quantitativement, ce qui amène à des sur-spécifications d'équipements. Les modèles comportementaux non-analytiques (présentant une discontinuité en 0) proposés en 2010 donnent par contre de très bons résultats mais leur explication physique n'existait pas. La modélisation physique commence à donner des résultats que l'on peut comparer aux résultats de mesure et aux résultats des modèles comportementaux. La modélisation des non-linéarités des isolateurs et des circulateurs par le phénomène d'hystérésis magnétique rentre dans ce cas. Le modèle physique obtenu alors est non-analytique comme les bons modèles comportementaux. Il est correct qualitativement mais reste moins bon quantitativement qu'un modèle comportemental. Les modèles comportementaux prédisent mieux les résultats de mesure, on peut les rapprocher des modèles physiques mais ils nécessitent alors des modifications empiriques de certains paramètres cruciaux des modèles physiques non-analytiques. La compréhension de l'origine physique de ces différences permettra de proposer des modèles physiques plus proches de la réalité.

Face à la croissance du nombre d'utilisateurs par satellite, il devient nécessaire d'augmenter la bande passante disponible sur une région. Les systèmes satellites multi-faisceaux avec une répartition des fréquence en 4 couleurs ont déjà permis d'énormes progrès, mais limite la portion de la bande disponible dans chaque spot. Dans nos travaux, nous envisageons une utilisation plus agressive de la bande passante. L'interférence alors générée étant trop importante, nous nous sommes intéressés aux différentes techniques de coordination d'interférence. Pour cela, nous avons abordé plusieurs approches, d'une analyse des schémas de colorations à la formulation et résolution de problèmes d'optimisation permettant d'approcher la borne supérieure de la capacité d'un système.