Calibrage de caméra fisheye et estimation de la profondeur pour la navigation autonome

Ce mémoire s’intéresse aux problématiques du calibrage de caméras grand angles et de l’estimation de la profondeur à partir d’une caméra unique, immobile ou en mouvement. Les travaux effectués se situent à l’intersection entre la vision 3D classique et les nouvelles méthodes par apprentissage profond dans le domaine de la navigation autonome. Ils visent à permettre la détection d’obstacles par un drone en mouvement muni d’une seule caméra à très grand angle de vue. D’abord, une nouvelle méthode de calibrage est proposée pour les caméras fisheyes à très grand angle de vue par calibrage planaire à correspondances denses obtenues par lumière structurée qui peuvent être modélisée par un ensemble de caméras génériques virtuelles centrales. Nous démontrons que cette approche permet de modéliser directement des caméras axiales, et validons sur des données synthétiques et réelles. Ensuite, une méthode est proposée pour estimer la profondeur à partir d’une seule image, à partir uniquement des indices de profondeurs forts, les jonctions en T. Nous démontrons que les méthodes par apprentissage profond sont susceptibles d’apprendre les biais de leurs ensembles de données et présentent des lacunes d’invariance. Finalement, nous proposons une méthode pour estimer la profondeur à partir d’une caméra en mouvement libre à 6 degrés de liberté. Ceci passe par le calibrage de la caméra fisheye sur le drone, l’odométrie visuelle et la résolution de la profondeur. Les méthodes proposées permettent la détection d’obstacle pour un drone.This thesis focuses on the problems of calibrating wide-angle cameras and estimating depth from a single camera, stationary or in motion. The work carried out is at the intersection between traditional 3D vision and new deep learning methods in the field of autonomous navigation. They are designed to allow the detection of obstacles by a moving drone equipped with a single camera with a very wide field of view. First, a new calibration method is proposed for fisheye cameras with very large field of view by planar calibration with dense correspondences obtained by structured light that can be modelled by a set of central virtual generic cameras. We demonstrate that this approach allows direct modeling of axial cameras, and validate it on synthetic and real data. Then, a method is proposed to estimate the depth from a single image, using only the strong depth cues, the T-junctions. We demonstrate that deep learning methods are likely to learn from the biases of their data sets and have weaknesses to invariance. Finally, we propose a method to estimate the depth from a camera in free 6 DoF motion. This involves calibrating the fisheye camera on the drone, visual odometry and depth resolution. The proposed methods allow the detection of obstacles for a drone

Global Environmental Commons: Analatycal and Political Challenges in Building Governance Mechanisms

Environmental challenges, and the potential solutions to address them, have a direct effect on living standards, the organization of economies, major infrastructures, and modes of urbanization. Since the publication of path-breaking contributions on the governance of environmental resources in the early 1990s, many political initiatives have been taken, numerous governance experiments have been conducted, and a large multi-disciplinary field of research has opened up. This interdisciplinary book takes stock of the knowledge that has accumulated to date, and addresses new challenges in the provision of environmental goods. It focuses on three essential dimensions with respect to governance. First, it addresses the issue of designing governance solutions through analyzing systems of rules, and levels of organization, in the governance and management of environmental issues. Second, it draws renewed attention to the negotiation processes among stakeholders playing a crucial role in reaching agreements over issues and solutions, and in choosing and implementing particular policy instruments. Finally, it shows that compliance depends on a combination of formal rules, enforced by recognized authorities, and informal obligations, such as social and individual norms. The evolution of the research frontiers on environmental governance shows that more legitimate and informed processes of collective decision, and more subtle and effective ways of managing compliance, can contribute to more effective policy. However, this book also illustrates that more democratic and effective governance should rely on more direct and pluralistic forms of involvement of citizens and stakeholders in the collective decision making processe

Introduction : Global Environmental Commons: Analytical and Political Challenges in Building Governance Mechanisms

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Évaluation d’un programme d’aide au succès de sevrage des benzodiazépines

L’efficacité d’un nouveau programme de sevrage des BZD basé sur l’approche cognitivo-comportementale (PASSE) a été évaluée en le comparant à une autre condition où les participants ne reçoivent que du soutien social. Le programme d’une durée de 20 semaines débute par une préparation de quatre semaines suivie d’un sevrage standard pendant les 16 semaines suivantes. Quarante-huit participants (24 dans chaque condition) ayant un diagnostic de trouble anxieux ont participé à cette étude. Les deux conditions de traitement actif ont été comparées avec une condition contrôle de sevrage standard comprenant 41 participants. Les résultats au post-traitement permettent d’affirmer que les participants dans les deux conditions de traitement actif ont un taux de succès supérieur au sevrage. Parmi ceux qui ont complété le programme, il n’y avait aucune différence en terme de succès au sevrage entre les résultats de la condition soutien social et de l’intervention PASSE, mais lorsque les abandons étaient pris en considération, l’intervention PASSE démontrait des résultats supérieurs comparativement à la condition soutien social. Les résultats suggèrent que l’approche béhaviorale-cognitive peut aider l’individu qui désire débuter un sevrage des BZD à mieux en tolérer les effets immédiats.The efficacy of a new cognitive-behavioral group program to help discontinuation of benzodiazepines (PASSE) was evaluated by comparison to a group receiving only social support. Both programs lasted 20 weeks commencing with a preparatory period of one month and then tapering continually during 16 subsequent weeks until discontinuation. Forty-eight participants (24 in each condition) with a diagnosis of anxiety disorder took part in the study. These two active conditions were compared with a separate group of 41 people receiving standard tapering with physician counselling only. The results post-treatment supported the hypothesis that those receiving either of the two active treatments succeeded better in discontinuing benzodiazepines than those receiving the standard treatment. Among those completing the two active programs there was no difference in outcome between the social support and the cognitive behavioral (PASSE) group. However, when the rate of dropout was considered, the cognitive-behavioral group proved significantly superior than the social support group. The results suggest that a cognitive-behavioral program can help people wishing to discontinue benzodiazepines to psychologically tolerate the immediate effects of discontinuation.La eficacia de un nuevo programa de abstinencia de las BZD, basado en el enfoque cognitivo-comportamental (PASSE), fue evaluado al compararlo con otra condición en la que los participantes no reciben más que apoyo social. El programa de una duración de 20 semanas inicia con una preparación de cuatro semanas, seguidas de una abstinencia estándar durante las 16 semanas siguientes. Cuarenta y ocho participantes (24 de cada condición) con un diagnóstico de trastorno de ansiedad participaron en este estudio. Las dos condiciones de tratamiento activo fueron comparadas con una condición de control de abstinencia estándar que comprendía 41 participantes. Los resultados posteriores al tratamiento permiten afirmar que los participantes de las dos condiciones de tratamiento activo tienen una tasa de éxito superior a la abstinencia. Entre aquellos que completaron el programa no hubo ninguna diferencia en términos de éxito en la abstinencia, entre los resultados de la condición de apoyo social y de la intervención PASSE. Pero en el momento de tomar en consideración el abandono del medicamento, la intervención PASSE demostró resultados comparativamente superiores a la condición de apoyo social. Los resultados sugieren que el enfoque cognitivo-comportamental puede ayudar al individuo que desea iniciar la abstinencia de las BZD para tolerar mejor los efectos inmediatos.A eficácia de um novo programa de desabituação no uso das BZD, baseado na abordagem cognitivo-comportamental (PASSE) foi avaliada em comparação a uma outra condição na qual os participantes recebem apenas um apoio social. O programa de 20 semanas de duração inicia-se com uma preparação de quatro semanas, seguida de um programa de desabituação comum durante as próximas 16 semanas. Participaram deste estudo 48 pessoas (24 em cada condição) tendo um diagnóstico de transtorno de ansiedade. As duas condições de tratamento ativo foram comparadas a uma condição de controle do processo de desabituação comum, que contou com 41 participantes. Os resultados no pós-tratamento permitem-nos afirmar que os participantes nas duas condições de tratamento ativo têm uma taxa de sucesso superior à desabituação. Entre os que concluíram o programa, não havia nenhuma diferença em relação ao sucesso na desabituação entre os resultados da condição de apoio social e da intervenção PASSE, mas quando os abandonos eram levados em consideração, a intervenção PASSE demonstrava resultados superiores em relação à condição de apoio social. Os resultados sugerem que a abordagem cognitivo-comportamental pode ajudar o indivíduo, que deseja iniciar um processo de desabituação do uso das BZD, a melhor tolerar os efeitos imediatos

Geographic scale and disturbance influence intraspecific trait variability in leaves and roots of North American understorey plants

International audienceConsidering intraspecific trait variability (ITV) in ecological studies has improved our understanding of species persistence and coexistence. These advances are based on the growing number of leaf ITV studies over local gradients, but logistical constraints have prevented a solid examination of ITV in root traits or at scales reflecting species' geographic ranges. We compared the magnitude of ITV in above- and below-ground plant organs across three spatial scales (biophysical region, locality and plot). We focused on six understorey species (four herbs and two shrubs) that occur both in disturbed and undisturbed habitats across boreal and temperate Canadian forests. We aimed to document ITV structure over broad ecological and geographical scales by asking: (a) What is the breadth of ITV across species range-scale? (b) What proportion of ITV is captured at different spatial scales, particularly when local scale disturbances are considered? and (c) Is the variance structure consistent between analogous leaf and root traits, and between morphological and chemical traits? Following standardized methods, we sampled 818 populations across 79 forest plots simultaneously, including disturbed and undisturbed stands, spanning four biophysical regions (similar to 5,200 km). Traits measured included specific leaf area (SLA), specific root length (SRL) and leaf and root nutrient concentrations (N, P, K, Mg, Ca). We used variance decomposition techniques to characterize ITV structure across scales. Our results show that an important proportion of ITV occurred at the local scale when sampling included contrasting environmental conditions resulting from local disturbance. A certain proportion of the variability in both leaf and root traits remained unaccounted for by the three sampling scales included in the design (36% on average), with the largest amount for SRL (54%). Substantial differences in magnitude of ITV were found among the six species, and between analogous traits, suggesting that trait distribution was influenced by species strategy and reflects the extent of understorey environment heterogeneity. Even for species with broad geographical distributions, a large proportion of within-species trait variability can be captured by sampling locally across ecological gradients. This has practical implications for sampling design and trait selection for both local studies and continental-scale modelling. A plain language summary is available for this article