Cette thèse s’intéresse à l’étude de la stabilité des systèmes à commutation qui évoluent sur un domaine de temps non uniforme en introduisant la théorie des échelles de temps. On s’intéresse essentiellement aux systèmes dynamiques linéaires à commutation définis sur une échelle de temps particulière T = P{tσk ,tk+1} = ∪∞k=0[tσk , tk+1]. Le système étudié commute entre un sous-système dynamique continu sur les intervalles ∪∞k=0[tσk , tk+1[ et un sous-système dynamique discret aux instants ∪∞k=0{tk+1} (à temps discret) avec un pas discret qui varie dans le temps. Dans une première partie, des conditions suffisantes sont données pour garantir la stabilité exponentielle de cette classe de systèmes à commutation. Ensuite, des conditions nécessaires et suffisantes de stabilité sont données en déterminant une région de stabilité exponentielle. Dans une deuxième partie, la stabilité de cette classe des systèmes à commutation avec des perturbations nonlinéaires a été traitée en utilisant des majorations de la solution, puis en introduisant l’approche de la fonction de Lyapunov commune. La troisième partie est consacrée au problème du consensus en présence d’interruptions de transmission d’informations où le système multi-agent en boucle fermée peut être représenté comme un système à commutation par une combinaison de modèles de systèmes linéaires à temps continu et de systèmes linéaires à temps discret. / This thesis deals with the stability analysis of switched systems that evolve on non uniform time domain by introducing the time scale theory. We are interested mainly in dynamical linear switched systems defined on particular time scale T = P{tσk ,tk+1} = ∪∞k=0[tσk, tk+1]. The studied system switches between a continuous-time dynamical subsystem on the intervals ∪∞k=0[tσk, tk+1[ and a discrete-time dynamical subsystem on instants ∪∞k=0{tk+1} (a discrete time) with a time-varying discrete step. In a first part, sufficient conditions are given to guarantee the exponential stability of this class of switched systems. Then necessary and sufficient conditions for stability are given by determining a region of exponential stability. In the second part, the stability of this class of switched systems with nonlinear uncertainties, is treated using majoration of the solution, and after that by introducing the approach of a common Lyapunov function. The third part is devoted to the consensus problem under intermittent information transmissions where the closed-loop multi-agent system can be represented as a switched system using a combination of linear continuous-time and linear discrete-time systems.

Si l’industrie aéronautique a fait l’objet d’investigations historiques poussées, le versant économique et social semble être resté dans l’ombre pour ce qui concerne l’après Seconde Guerre mondiale. Cette thèse de doctorat, à travers l’exemple d’un établissement de constructions aéronautiques nationalisé, s’intéresse au rôle joué par les salariés dans l’édification de l’entreprise sur une trentaine d’années, au moyen d’une micro-histoire socio-économique. L’analyse des trajectoires suivies par la négociation collective, ainsi qu’une attention portée au développement industriel et à l’activité productive, permettent de mettre en lumière comment se construisent, au quotidien, les relations professionnelles au sein d’une firme relevant de l’autorité de l’État. La politisation des rapports sociaux qui découle de son statut et de son rôle dans la Défense nationale, amène souvent ses acteurs à s’opposer sur les questions sociales, industrielles ou encore politiques tout au long des années 1950 et des années 1960. Dans le dernier tiers de cette décennie, une partie d’entre eux décide finalement de revenir à la table des négociations et de fonder leurs relations sur des pratiques contractuelles, ce qui contribue, au terme de discussions difficiles, à un apaisement durable des relations sociales.Ainsi, s’interroger sur les rapports qui prennent forme dans l’espace usinier, à une échelle multiscalaire – entre local, national et international et entre établissement, société, branche et interprofessionnel – permet de mettre en évidence la capacité qu’ont les protagonistes à réaliser ou non des compromis. Il s’agit de mieux comprendre le rôle des conflits et des consensus dans le développement industriel, afin de démontrer que de la santé de relations sociales peut dépendre, pour partie, son développement socio-économique. L’exemple démontre qu’à rebours des schémas communément admis, il existe une culture de la négociation dans les entreprises, lorsque le compromis est rendu possible par la coopération des diverses parties, et ce, même lorsque les relations professionnelles y sont fondées sur le rapport de forces, ou marquées par l’influence des thématiques politiques et par l’intrication des rôles de l’État. / Whilst the aviation industry has been the subject of extensive historical investigations, economic and social topics seem to have remained in the shadows as far as the post-World War II period is concerned. This PhD thesis, through the example of a state-owned aeronautical company, and using a socio-economic micro-history method, focuses on the role played by workers in the building of an aeronautics company over thirty years. By analysing the trajectories followed by collective bargaining, as well as paying attention to industrial development and productive activity, this thesis highlights how professional relationships were built, day after day, inside a firm under the authority of the State. The politicization of industrial relationships, that derived from the company’s status and role in National Defence, often led its actors to oppose each other on social, industrial or political issues throughout the 1950s and 1960s. In the last third of this decade, some of these actors finally decided to return to the bargaining table and base their relations on contractual practices, which contributed, after difficult discussions, to a lasting mollification of these industrial relations.Hence, using a multi-scalar approach to interrogate the relationships that emerged in the factory space, between local, national and international and between plant, firm, branch and inter-professional, makes it possible to evidence the capacity of the protagonists to either succeed or fail in coming to compromises and trade-offs. The aim is thus to understand the role of conflict and consensus in industrial development, in order to demonstrate that the health of industrial relations may depend, at least partly, on a company’s socio-economic development. This example also shows that, contrary to commonly accepted thought, there is a culture of bargaining in French companies, when trade-offs are made possible by the cooperation of the various protagonists, even when professional relationships are based on power dynamics, or influenced by political issues and by the complexities of State intervention. / Si la industria aeronáutica fue el objeto de numerosas investigaciones históricas, los aspectos económicos y sociales aun permanecen en la sombra, por el período posterior a la Segunda Guerra Mundial. Esta tesis doctoral, con el ejemplo de una empresa de construcción aeronáutica pública, y mediante una microhistoria socioeconómica, se centra en el papel de los trabajadores en su desarrollo industrial, durante más de treinta años. El análisis de las trayectorias seguidas por la negociación colectiva, así como la atención prestada al desarrollo industrial y a la actividad productiva, permiten destacar la construcción, a diario, de las relaciones profesionales dentro de una compañía que depende de la autoridad del estado. La politización de las relaciones sociales, que se deriva de su estatus y de su papel en la Defensa Nacional, acarrea a sus actores a menudo a oponerse en asuntos sociales, industriales o políticos, a lo largo de las décadas de 1950 y 1960. En el último tercio de esta década, parte de ellos decidieron finalmente volver a negociar y a basar sus relaciones en prácticas contractuales, lo cual contribuye, después de difíciles discusiones, a mejorar el entorno social.Así, preguntarse sobre las relaciones que se establecen en el espacio de la fábrica, con un enfoque multiescalar, – entre local, nacional e internacional, y entre fabrica, sociedad, rama profesional e interprofesional –, permite subrayar la habilidad de los protagonistas de conseguir o no acuerdos. Se trata de mejorar la comprensión del rol de los conflictos y de los consensos en el desarrollo industrial, con el fin de demostrar que de la salud de las relaciones sociales puede depender el desarrollo socioeconómico de las empresas. El ejemplo demuestra que, contrariamente a los patrones comúnmente aceptados, existe una cultura de negociación en el seno de las empresas francesas, cuando el consenso se hace posible gracias a la cooperación de las distintas partes, incluso cuando las relaciones profesionales se basan en el equilibrio de fuerzas, o están marcadas por la influencia de temas políticos y por los papeles intrincados del Estado.

Le clustering est le processus de partitionnement d’un ensemble de données en groupes, de sorte que les instances du même groupe sont plus semblables les unes aux autres qu’avec celles de tout autre groupe. De nombreux algorithmes de clustering ont été proposés, mais aucun d’entre eux ne s’avère fournir une partitiondes données pertinente dans toutes les situations. Le clustering par consensus vise à améliorer le processus de regroupement en combinant différentes partitions obtenues à partir de divers algorithmes afin d’obtenir une solution de consensus de meilleure qualité. Dans ce travail, une nouvelle méthode de clustering par consensus, appelée MultiCons, est proposée. Cette méthode utilise la technique d’extraction des itemsets fréquents fermés dans le but de découvrir les similitudes entre les différentes solutions de clustering dits de base. Les similitudes identifiées sont représentées sous une forme de motifs de clustering, chacun définissant un accord entre un ensemble de clusters de bases sur le regroupement d’un ensemble d’instances. En traitant ces motifs par groupes, en fonction du nombre de clusters de base qui définissent le motif, la méthode MultiCons génère une solution de consensus pour chaque groupe, générant par conséquence plusieurs consensus candidats. Ces différentes solutions sont ensuite représentées dans une structure arborescente appelée arbre de consensus, ouConsTree. Cette représentation graphique facilite la compréhension du processus de construction des multiples consensus, ainsi que les relations entre les instances et les structures d’instances dans l’espace de données / Clustering is the process of partitioning a dataset into groups, so that the instances in the same group are more similar to each other than to instances in any other group. Many clustering algorithms were proposed, but none of them proved to provide good quality partition in all situations. Consensus clustering aims to enhance the clustering process by combining different partitions obtained from different algorithms to yield a better quality consensus solution. In this work, a new consensus clustering method, called MultiCons, is proposed. It uses the frequent closed itemset mining technique in order to discover the similarities between the different base clustering solutions. The identified similarities are presented in a form of clustering patterns, that each defines the agreement between a set of base clusters in grouping a set of instances. By dividing these patterns into groups based on the number of base clusters that define the pattern, MultiCons generates a consensussolution from each group, resulting in having multiple consensus candidates. These different solutions are presented in a tree-like structure, called ConsTree, that facilitates understanding the process of building the multiple consensuses, and also the relationships between the data instances and their structuring in the data space. Five consensus functions are proposed in this work in order to build a consensus solution from the clustering patterns. Approach 1 is to just merge any intersecting clustering patterns. Approach 2 can either merge or split intersecting patterns based on a proposed measure, called intersection ratio

BACKGROUND: The need to create controlled vocabularies such as ontologies for knowledge organization and access has been widely recognized in various domains. Despite the indispensable need of thorough domain knowledge in ontology construction, most software tools for ontology construction are designed for knowledge engineers and not for domain experts to use. The differences in the opinions of different domain experts and in the terminology usages in source literature are rarely addressed by existing software. METHODS: OTO software was developed based on the Agile principles. Through iterations of software release and user feedback, new features are added and existing features modified to make the tool more intuitive and efficient to use for small and large data sets. The software is open source and built in Java. RESULTS: Ontology Term Organizer (OTO; http://biosemantics.arizona.edu/OTO/) is a user-friendly, web-based, consensus-promoting, open source application for organizing domain terms by dragging and dropping terms to appropriate locations. The application is designed for users with specific domain knowledge such as biology but not in-depth ontology construction skills. Specifically OTO can be used to establish is_a, part_of, synonym, and order relationships among terms in any domain that reflects the terminology usage in source literature and based on multiple experts' opinions. The organized terms may be fed into formal ontologies to boost their coverage. All datasets organized on OTO are publicly available. CONCLUSION: OTO has been used to organize the terms extracted from thirty volumes of Flora of North America and Flora of China combined, in addition to some smaller datasets of different taxon groups. User feedback indicates that the tool is efficient and user friendly. Being open source software, the application can be modified to fit varied term organization needs for different domains.

The applications for Unmanned Aerial Vehicles are numerous and cover a range of areas from military applications, scientific projects to commercial activities, but many of these applications require substantial human involvement. This work focuses on the problems and limitations in cooperative Unmanned Aircraft Systems to provide increasing realism for cooperative algorithms. The Consensus Based Bundle Algorithm is extended to remove single agent limits on the task allocation and consensus algorithm. Without this limitation the Consensus Based Grouping Algorithm is proposed that allows the allocation and consensus of multiple agents onto a single task. Solving these problems further increases the usability of cooperative Unmanned Aerial Vehicles groups and reduces the need for human involvement. Additional requirements are taken into consideration including equipment requirements of tasks and creating a specific order for task completion. The Consensus Based Grouping Algorithm provides a conflict free feasible solution to the multi-agent task assignment problem that provides a reasonable assignment without the limitations of previous algorithms. Further to this the new algorithm reduces the amount of communication required for consensus and provides a robust and dynamic data structure for a realistic application. Finally this thesis provides a biologically inspired improvement to the Consensus Based Grouping Algorithm that improves the algorithms performance and solves some of the difficulties it encountered with larger cooperative requirements.

published_or_final_version / abstract / Education / Master / Master of Education

published_or_final_version / Urban Planning / Master / Master of Science in Urban Planning

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This paper introduces a model framework for dynamic credit rating processes. Our framework aggregates ordinal rating information stemming from a variety of rating sources. The dynamic of the consensus rating captures systematic as well as idiosyncratic changes. In addition, our framework allows to validate the different rating sources by analyzing the mean/variance structure of the rating deviations. In an empirical study for the iTraxx Europe companies rated by the big three external rating agencies we use Bayesian techniques to estimate the consensus ratings for these companies. The advantages are illustrated by comparing our dynamic rating model to a naive benchmark model. (authors' abstract)

We study distributed estimation of dynamic random fields observed by a sparsely connected network of agents/sensors. The sensors are inexpensive, low power, and they communicate locally and perform computation tasks. In the era of large-scale systems and big data, distributed estimators, yielding robust and reliable field estimates, are capable of significantly reducing the large computation and communication load required by centralized estimators, by running local parallel inference algorithms. The distributed estimators have applications in estimation, for example, of temperature, rainfall or wind-speed over a large geographical area; dynamic states of a power grid; location of a group of cooperating vehicles; or beliefs in social networks. The thesis develops distributed estimators where each sensor reconstructs the estimate of the entire field. Since the local estimators have direct access to only local innovations, local observations or a local state, the agents need a consensus-type step to construct locally an estimate of their global versions. This is akin to what we refer to as distributed dynamic averaging. Dynamic averaged quantities, which we call pseudo-quantities, are then used by the distributed local estimators to yield at each sensor an estimate of the whole field. Using terminology from the literature, we refer to the distributed estimators presented in this thesis as Consensus+Innovations-type Kalman filters. We propose three distinct types of distributed estimators according to the quantity that is dynamically averaged: (1) Pseudo-Innovations Kalman Filter (PIKF), (2) Distributed Information Kalman Filter (DIKF), and (3) Consensus+Innovations Kalman Filter (CIKF). The thesis proves that under minimal assumptions the distributed estimators, PIKF, DIKF and CIKF converge to unbiased and bounded mean-squared error (MSE) distributed estimates of the field. These distributed algorithms exhibit a Network Tracking Capacity (NTC) behavior – the MSE is bounded if the degree of instability of the field dynamics is below a threshold. We derive the threshold for each of the filters. The thesis establishes trade-offs between these three distributed estimators. The NTC of the PIKF depends on the network connectivity only, while the NTC of the DIKF and of the CIKF depend also on the observation models. On the other hand, when all the three estimators converge, numerical simulations show that the DIKF improves 2dB over the PIKF. Since the DIKF uses scalar gains, it is simpler to implement than the CIKF. Of the three estimators, the CIKF provides the best MSE performance using optimized gain matrices, yielding an improvement of 3dB over the DIKF. Keywords: Kalman filter, distributed state estimation, multi-agent networks, sensor networks, distributed algorithms, consensus, innovation, asymptotic convergence, mean-squared error, dynamic averaging, Riccati equation, Lyapunov iterations, distributed signal processing, random dynamical systems.