WorldCat Identities

Institut national de recherche en informatique et en automatique (France) Centre de recherche Bordeaux - Sud-Ouest

Overview
Works: 66 works in 66 publications in 2 languages and 66 library holdings
Roles: Other
Publication Timeline
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Most widely held works by Institut national de recherche en informatique et en automatique (France)
Méthodes numériques de type Volumes Finis sur maillages non structurés pour la résolution de thermique anisotrope et des équations de Navier-Strokes compressibles by Pascal Jacq( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

Lors de la rentrée atmosphérique nous sommes amenés à modéliser trois phénomènes physiques différents. Tout d'abord, l'écoulement autour du véhicule entrant dans l'atmosphère est hypersonique,il est caractérisé par la présence d'un choc fort et provoque un fort échauffement du véhicule. Nous modélisons l'écoulement par les équations de Navier-Stokes compressibles et l'échauffement du véhicule au moyen de la thermique anisotrope. De plus le véhicule est protégé par un bouclier thermique siège de réactions chimiques que l'on nomme communément ablation.Dans le premier chapitre de cette thèse nous présentons le schéma numérique de diffusion CCLAD (Cell-Centered LAgrangian Diffusion) que nous utilisons pour résoudre la thermique anisotrope. Nous présentons l'extension en trois dimensions de ce schéma ainsi que sa parallélisation.Nous continuons le manuscrit en abordant l'extension de ce schéma à une équation de diffusion tensorielle. Cette équation est obtenue en supprimant les termes convectifs de l'équation de quantité de mouvement des équations de Navier-Stokes. Nous verrons qu'une pénalisation doit être introduite afin de pouvoir inverser la loi constitutive et ainsi appliquer la méthodologie CCLAD. Nous présentons les propriétés numériques du schéma ainsi obtenu et effectuons des validations numériques.Dans le dernier chapitre, nous présentons un schéma numérique de type Volumes Finis permettant de résoudre les équations de Navier-Stokes sur des maillages non-structurés obtenu en réutilisant les deux schémas de diffusion présentés précédemment
Optimization and parallelization of the boundary element method for the wave equation in time domain by Bérenger Bramas( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

The time-domain BEM for the wave equation in acoustics and electromagnetism is used to simulatethe propagation of a wave with a discretization in time. It allows to obtain several frequencydomainresults with one solve. In this thesis, we investigate the implementation of an efficientTD-BEM solver using different approaches. We describe the context of our study and the TD-BEMformulation expressed as a sparse linear system composed of multiple interaction/convolutionmatrices. This system is naturally computed using the sparse matrix-vector product (SpMV). Wework on the limits of the SpMV kernel by looking at the matrix reordering and the behavior of ourSpMV kernels using vectorization (SIMD) on CPUs and an advanced blocking-layout on NvidiaGPUs. We show that this operator is not appropriate for our problem, and we then propose toreorder the original computation to get a special matrix structure. This new structure is called aslice matrix and is computed with a custom matrix/vector product operator. We present an optimizedimplementation of this operator on CPUs and Nvidia GPUs for which we describe advancedblocking schemes. The resulting solver is parallelized with a hybrid strategy above heterogeneousnodes and relies on a new heuristic to balance the work among the processing units. Due tothe quadratic complexity of this matrix approach, we study the use of the fast multipole method(FMM) for our time-domain BEM solver. We investigate the parallelization of the general FMMalgorithm using several paradigms in both shared and distributed memory, and we explain howmodern runtime systems are well-suited to express the FMM computation. Finally, we investigatethe implementation and the parametrization of an FMM kernel specific to our TD-BEM, and weprovide preliminary results
Modélisation de l'électroperméabilisation à l'échelle cellulaire by Michael Leguebe( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

La perméabilisation des cellules à l'aide d'impulsions électriques intenses, appelée électroperméabilisation, est un phénomène biologique impliqué dans des thérapies anticancéreuses récentes. Elle permet, par exemple, d'améliorer l'efficacité d'une chimiothérapie en diminuant les effets secondaires, d'effectuer des transferts de gènes, ou encore de procéder à l'ablation de tumeurs. Les mécanismes de l'électroperméabilisation restent cependant encore méconnus, et l'hypothèse majoritairement admise par la communauté de formation de pores à la surface des membranes cellulaires est en contradiction avec certains résultats expérimentaux.Le travail de modélisation proposé dans cette thèse est basé sur une approche différente des modèles d'électroporation existants. Au lieu de proposer des lois sur les propriétés des membranes à partir d'hypothèses à l'échelle moléculaire, nous établissons des lois ad hoc pour les décrire, en se basant uniquement sur les informations expérimentales disponibles. Aussi, afin de rester au plus prèsde ces dernières et faciliter la phase de calibration à venir, nous avons ajouté un modèle de transport et de diffusion de molécules dans la cellule. Une autre spécificité de notre modèle est que nous faisons la distinction entre l'état conducteur et l'état perméable des membranes.Des méthodes numériques spécifiques ainsi qu'un code en 3D et parallèle en C++ ont été écrits et validés pour résoudre les équations aux dérivées partielles de ces différents modèles. Nous validons le travail de modélisation en montrant que les simulations reproduisent qualitativement les comportements observés in vitro
Modélisation multi-échelle de la diffraction des ondes électromagnétiques par de petits obstacles by Justine Labat( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

In this thesis, we develop fast, accurate and efficient numerical methods for solving the timeharmonicscattering problem of electromagnetic waves in 3D by a multitude of obstacles for low andmedium frequencies. Taking into account a large number of heterogeneities can be costly in terms ofcomputation time and memory usage, particularly in the construction process of the matrix. In thefirst part of our work, we consider a multi-scale diffraction problem in low-frequency regimes inwhich the characteristic length of the obstacles is small compared to the incident wavelength. We usethe matched asymptotic expansion method which allows for the model reduction. Two types ofapproximations are distinguished : near-field or quasi-static approximations that descibe thephenomenon at the microscopic scale and far-field approximations that describe the phenomenon ata long distance. In the latter one, small obstacles are no longer considered as geometric constraintsand can be modelled by equivalent point-sources which are interpreted in terms of electromagneticmultipoles. The second part of this thesis also deals with the multiple scattering of electromagneticwaves by multiple spheres, however, at medium-frequencies. Here, the domain of computation is afew tens of wavelengths and we implement a spectral method which is based on the discretization ofa boundary integral equation into local and tangential basis functions composed of the vectorialspherical harmonics. The reduced asymptotic models of the first problem can be adapted for thisregime by incorporating non-trivial corrections appearing in the Mie theory. Specifically, the gaugefunctions in the asymptotics are modified. We then present a comparison of these different methodsin terms of their accuracy. Finally, for both methods and to overcome difficulties related tocomputational cost, we solve the linear problems iteratively and implement a clever algorithm whichavoids the global assembling of the matrices associated with the discretizations
On the design of sparse hybrid linear solvers for modern parallel architectures by Stojce Nakov( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

In the context of this thesis, our focus is on numerical linear algebra, more precisely on solution of large sparse systems of linear equations. We focus on designing efficient parallel implementations of MaPHyS, an hybrid linear solver based on domain decomposition techniques. First we investigate the MPI+threads approach. In MaPHyS, the first level of parallelism arises from the independent treatment of the various subdomains. The second level is exploited thanks to the use of multi-threaded dense and sparse linear algebra kernels involved at the subdomain level. Such an hybrid implementation of an hybrid linear solver suitably matches the hierarchical structure of modern supercomputers and enables a trade-off between the numerical and parallel performances of the solver. We demonstrate the flexibility of our parallel implementation on a set of test examples. Secondly, we follow a more disruptive approach where the algorithms are described as sets of tasks with data inter-dependencies that leads to a directed acyclic graph (DAG) representation. The tasks are handled by a runtime system. We illustrate how a first task-based parallel implementation can be obtained by composing task-based parallel libraries within MPI processes throught a preliminary prototype implementation of our hybrid solver. We then show how a task-based approach fully abstracting the hardware architecture can successfully exploit a wide range of modern hardware architectures. We implemented a full task-based Conjugate Gradient algorithm and showed that the proposed approach leads to very high performance on multi-GPU, multicore and heterogeneous architectures
Simulation de la dynamique des dislocations à très grande échelle by Arnaud Etcheverry( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

This research work focuses on bringing performances in 3D dislocation dynamics simulation, to run efficiently on modern computers. First of all, we introduce some algorithmic technics, to reduce the complexity in order to target large scale simulations. Second of all, we focus on data structure to take into account both memory hierachie and algorithmic data access. On one side we build this adaptive data structure to handle dynamism of data and on the other side we use an Octree to combine hierachie decompostion and data locality in order to face intensive arithmetics with force field computation and collision detection. Finnaly, we introduce some parallel aspects of our simulation. We propose a classical hybrid parallelism, with task based openMP threads and domain decomposition technics for MPI
Unified system of code transformation and execution for heterogeneous multi-core architectures. by Pei Li( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Heterogeneous architectures have been widely used in the domain of high performance computing. However developing applications on heterogeneous architectures is time consuming and error-prone because going from a single accelerator to multiple ones indeed requires to deal with potentially non-uniform domain decomposition, inter-accelerator data movements, and dynamic load balancing. The aim of this thesis is to propose a solution of parallel programming for novice developers, to ease the complex coding process and guarantee the quality of code. We lighted and analysed the shortcomings of existing solutions and proposed a new programming tool called STEPOCL along with a new domain specific language designed to simplify the development of an application for heterogeneous architectures. We evaluated both the performance and the usefulness of STEPOCL. The result show that: (i) the performance of an application written with STEPOCL scales linearly with the number of accelerators, (ii) the performance of an application written using STEPOCL competes with an handwritten version, (iii) larger workloads run on multiple devices that do not fit in the memory of a single device, (iv) thanks to STEPOCL, the number of lines of code required to write an application for multiple accelerators is roughly divided by ten
Self Exploration of Sensorimotor Spaces in Robots. by Fabien Benureau( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

La robotique développementale a entrepris, au courant des quinze dernières années,d'étudier les processus développementaux, similaires à ceux des systèmes biologiques,chez les robots. Le but est de créer des robots qui ont une enfance--qui rampent avant d'essayer de courir, qui jouent avant de travailler--et qui basent leurs décisions sur l'expérience de toute une vie, incarnés dans le monde réel.Dans ce contexte, cette thèse étudie l'exploration sensorimotrice--la découverte pour un robot de son propre corps et de son environnement proche--pendant les premiers stage du développement, lorsque qu'aucune expérience préalable du monde n'est disponible. Plus spécifiquement, cette thèse se penche sur comment générer une diversité d'effets dans un environnement inconnu. Cette approche se distingue par son absence de fonction de récompense ou de fitness définie par un expert, la rendant particulièrement apte à être intégrée sur des robots auto-suffisants.Dans une première partie, l'approche est motivée et le problème de l'exploration est formalisé, avec la définition de mesures quantitatives pour évaluer le comportement des algorithmes et d'un cadre architectural pour la création de ces derniers. Via l'examen détaillé de l'exemple d'un bras robot à multiple degrés de liberté, la thèse explore quelques unes des problématiques fondamentales que l'exploration sensorimotrice pose, comme la haute dimensionnalité et la redondance sensorimotrice. Cela est fait en particulier via la comparaison entre deux stratégies d'exploration: le babillage moteur et le babillage dirigé par les objectifs. Plusieurs algorithmes sont proposés tour à tour et leur comportement est évalué empiriquement, étudiant les interactions qui naissent avec les contraintes développementales, les démonstrations externes et les synergies motrices. De plus, parce que même des algorithmes efficaces peuvent se révéler terriblement inefficaces lorsque leurs capacités d'apprentissage ne sont pas adaptés aux caractéristiques de leur environnement, une architecture est proposée qui peut dynamiquement choisir la stratégie d'exploration la plus adaptée parmi un ensemble de stratégies. Mais même avec de bons algorithmes, l'exploration sensorimotrice reste une entreprise coûteuse--un problème important, étant donné que les robots font face à des contraintes fortes sur la quantité de données qu'ils peuvent extraire de leur environnement;chaque observation prenant un temps non-négligeable à récupérer. [...] À travers cette thèse, les contributions les plus importantes sont les descriptions algorithmiques et les résultats expérimentaux. De manière à permettre la reproduction et la réexamination sans contrainte de tous les résultats, l'ensemble du code est mis à disposition. L'exploration sensorimotrice est un mécanisme fondamental du développement des systèmes biologiques. La séparer délibérément des mécanismes d'apprentissage et l'étudier pour elle-même dans cette thèse permet d'éclairer des problèmes importants que les robots se développant seuls seront amenés à affronter
Gestion hétérogène des données dans les hiérarchies mémoires pour l'optimisation énergétique des architectures multi-coeurs by Gregory Vaumourin( )

1 edition published in 2016 in French and held by 1 WorldCat member library worldwide

The energy consumption of the memory system in modern architectures is a major issue for embedded system limited by their battery or supercalculators limited by their Thermal Design Power. Using a classification information in the memory system allows a heterogeneous management of data, more specific to each kind of data. During this thesis, we focused on the specific management of read-only data into the memory system through a compilation/architecture codesign. It allows to explore new potentials in terms of data locality, scalability of the system or cache designs. Evaluated by simulation with multi-core architecture, the proposed solution others significant energy consumption reduction while keeping the performance stable
Neuroscience of decision making : from goal-directed actions to habits by Meropi Topalidou( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Les processus de type “action-conséquence” (orienté vers un but) et stimulus-réponse sont deux composants importants du comportement. Le premier évalue le bénéfice d'une action pour choisir la meilleure parmi celles disponibles (sélection d'action) alors que le deuxième est responsable du comportement automatique, suscitant une réponse dès qu'un stimulus connu est présent. De telles habitudes sont généralement associées (et surtout opposées) aux actions orientées vers un but qui nécessitent un processus délibératif pour évaluer la meilleure option à prendre pour atteindre un objectif donné. En utilisant un modèle computationnel, nous avons étudié l'hypothèse classique de la formation et de l'expression des habitudes au niveau des ganglions de la base et nous avons formulé une nouvelle hypothèse quant aux rôles respectifs des ganglions de la base et du cortex. Inspiré par les travaux théoriques et expérimentaux de Leblois et al. (2006) et Guthrie et al. (2013), nous avons conçu un modèle computationnel des ganglions de la base, du thalamus et du cortex qui utilise des boucles distinctes (moteur, cognitif et associatif) ce qui nous a permis de poser l'hypothèse selon laquelle les ganglions de la base ne sont nécessaires que pour l'acquisition d'habitudes alors que l'expression de telles habitudes peut être faite par le cortex seul. En outre, ce modèle a permis de prédire l'existence d'un apprentissage latent dans les ganglions de la base lorsque leurs sorties (GPi) sont inhibées. En utilisant une tâche de bandit manchot à 2 choix, cette hypothèse a été expérimentalement testée et confirmée chez le singe; suggérant au final de rejeter l'idée classique selon laquelle l'automatisme est un trait subcortical
Conception et réalisation d'un solveur pour les problèmes de dynamique des fluides pour les architectures many-core by Damien Genet( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

Numerical simulation is nowadays an essential part of engineering analysis, be it to design anew plane, or to detect underground oil reservoirs. Numerical simulations have indeed become an important complement to theoretical and experimental investigation, allowing one to reduce the cost of engineering design processes. In order to achieve a high level of precision, one need to increase the resolution of his computational domain. So to keep getting results in reasonable time, one shall nd a way to speed-up computations. To do this, we use high performance computing, HPC, to exploit the complex architecture of modern supercomputers. Under these two constraints, and some other like the genericity of finite elements, or the mesh dimension, we developed a new platform AeroSol. In this thesis, we present the mathematical background, and the two types of schemes that are implemented in the platform, the continuous finite elements method, and the discontinuous one. Then, we present the design choices made in the platform,then, we study a sub-problem, the assembly operation, which can be found in linear algebra multi-frontal methods
Interaction and introspection with tangible augmented objects by Renaud Gervais( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Most of our waking hours are now spent staring at a screen. While the advances in touch screens have enabled a more expressive interaction space with our devices, by using our fingers to interact with digital content, what we see and manipulate on screen is still being kept away from us, locked behind a glassy surface. The range of capabilities of the human senses is much richer than what screens can currently offer. In order to be sustainable in the future, interaction with the digital world should leverage these human capabilities instead of letting them atrophy. One way to provide richer interaction and visualization modalities is to rely on the physical world itself as a host for digital content. Spatial Augmented Reality provides a technical mean towards this idea, by using projectors to shed digitally controlled light onto real-world objects to augment them and their environment with features and content. This paves the way to a future where everyday objects will be embedded with rich and expressive capabilities, while still being anchored in the real world. In this thesis, we are interested in two main aspects related to these tangible augmented objects. In a first time, we are raising the question on how to interact with digital content when it is hosted on physical objects. As a basis for our investigation, we studied interaction modalities that leverage traditional input and output devices found in a typical desktop environment. Our rationale for this approach is to leverage the experience of users with traditional digital tools - tools which researchers and developers spent decades to make simpler and more efficient to use - while at the same time steering towards a physically enriched interaction space. In a second time, we go beyond theinteraction with the digital content of augmented objects and reflect on their potential as a humane medium support. We investigate how these augmented artifacts, combined with physiological computing, can be used to raise our awareness of the processes of our own bodies and minds and, eventually, foster introspection activities. This took the form of two different projects where we used tangible avatars to let users explore and customize real-time physiological feedback of their own inner states
Adaptive techniques for free surface flow simulations : Application to the study of the 2011 Tohoku Tsunami. by Luca Arpaia( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

In this thesis we implement the Shallow Water equations (SWEs) on unstructured grids in order to simulate free surface flow over irregular bathymetries, wetting/drying and other complex phenomena that typically occurs in hydrodynamic applications. In particular we would to accurately simulate tsunami events, from large scale wave propagation up to localized runup. To this aim we use two methods that are extensively compared along the manuscript: the Finite Volume method, which is very popular in the hydrodynamics and hydraulic community and a more recent technique called Residual Distribution which belongs to the class of multidimensional upwind schemes. To enhance the resolution of important flow feature such as bore development or small scale flooding, we use a dynamic mesh adaptation based on a redistribution of mesh nodes or r-adaptation (r stands for "relocation"). The proper combination of this method with the flow solver is usually referred to as Moving Mesh Method. Among the many different moving mesh algorithms available we propose an Arbitrary Lagrangian Eulerian (ALE) form of the SWEs which elegantly permit to evolve the flow variables from one mesh to the updated one
Free surface flow simulation in estuarine and coastal environments : numerical development and application on unstructured meshes by Andrea Gilberto Filippini( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Over the last decades, there has been considerable attention in the accurate mathematical modeling and numerical simulations of free surface wave propagation in near-shore environments. A physical correct description of the large scale phenomena, which take place in the shallow water region, must account for strong nonlinear and dispersive effects, along with the interaction with complex topographies. First, a study on the behavior in nonlinear regime of different Boussinesq-type models is proposed, showing the advantage of using fully-nonlinear models with respect to weakly-nonlinear and weakly dispersive models (commonly employed). Secondly, a new flexible strategy for solving the fully-nonlinear and weakly-dispersive Green-Naghdi equations is presented, which allows to enhance an existing shallow water code by simply adding an algebraic term to the momentum balance and is particularly adapted for the use of hybrid techniques for wave breaking. Moreover, the first discretization of the Green-Naghdi equations on unstructured meshes is proposed via hybrid finite volume/ finite element schemes. Finally, the models and the methods developed in the thesis are deployed to study the physical problem of bore formation in convergent alluvial estuary, providing the first characterization of natural estuaries in terms of bore inception
Towards Vygotskian Autotelic Agents : Learning Skills with Goals, Language and Intrinsically Motivated Deep Reinforcement Learning by Cédric Colas( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

Concevoir des machines autonomes qui explorent des environnements larges, découvrent des interactions pertinentes et développent des répertoires de comportements non-bornés est un des défis majeurs en intelligence artificielle. Inspiré par le remarquable apprentissage de l'humain, l'apprentissage machine développemental étudie les mécanismes permettant aux machines d'auto-organiser leurs trajectoires développementales et de développer des répertoires de comportements. Notre recherche progresse vers ce but.L'apprentissage par renforcement (RL) entraîne des agents à contrôler leur environnement de sorte à maximiser des récompenses et apparaît donc adapté à notre objectif. Malgré ses récent succès--battre l'humains à certains jeux vidéos, aux échecs, au go ou contrôler des robots--le RL ne saurait être suffisant : les agents RL sont peu autonomes et montrent des comportements bornés car ils s'attaquent à de (petits) sets de tâches pré-définies, caractérisées par des fonctions de récompenses pré-codées. Dans cette recherche, nous proposons de transférer, d'adapter et d'étendre des idées issues d'une approche de robotique développementale appelée processus d'exploration de buts intrinsèquement motivés (IMGEP) aux méthodes de RL. Notre nouveau cadre algorithmique étend les techniques de RL conditionné par des buts pour développer des agents RL autotéliques: des agents intrinsèquement motivés à représenter, générer, poursuivre et maîtriser leurs propres buts en vue de développer des répertoires de comportements.L'acquisition efficace de répertoires de comportements non-bornés nécessite une génération créative de buts en dehors de la distribution des effets connus (exploration créative), la généralisation de comportements connus à des comportements nouveaux (généralisation systématique) et la capacité à composer des comportements connus pour en former de nouveaux (composition). Inspiré par la psychologie développementale, nous proposons d'utiliser le langage comme un outil cognitif de sorte à soutenir ces propriétés.Ce manuscrit est construit autour de deux notions: les buts et le langage. La première partie se concentre sur les buts. Elle couvre les concepts fondamentaux et la littérature associée traitant des motivations intrinsèques, de l'apprentissage par renforcement et de la robotique développementale avant d'introduire notre framework: les processus d'exploration de buts intrinsèquement motivés avec des politiques conditionnées par des buts (GC-IMGEP). À partir de ce cadre, nous présentons trois études computationnelles des propriétés des agents autotéliques. Nous montrons d'abord que l'exploration autotélique peut être utilisée pour résoudre des tâches nécessitant une importante exploration (étude 1: GEP-PG et 2: ME-ES). Nous proposons ensuite CURIOUS dans un environnement sans récompense: un agent autotélique qui vise une diversité de buts, transfère de l'information entre compétences et organise sa trajectoire d'apprentissage en poursuivant les buts liés à de forts progrès (étude 3).La seconde partie se concentre sur le langage. Inspirés par les travaux de Vygostky et d'autres, nous discutons des utilisations des capacités communicatives et cognitives du langage dans le cadre d'agents dirigés par des buts. Le langage facilite les interactions humain-agent, l'abstraction, la généralisation systématique, le contrôle à long horizon temporel, mais aussi la créativité et la simulation mentale. Dans les deux études computationnelles qui suivent, nous implémentons ces deux dernières capacités. IMAGINE utilise le langage pour apprendre des représentations de buts (usage communicatif) et pour imaginer de nouveaux buts de sorte à diriger une exploration créative (usage cognitif). Dans notre dernière étude, LGB entraîne un modèle du monde à générer une diversité de futurs possibles à partir de descriptions linguistiques. Cela mène à une plus grande diversité comportementale et à des comportements de changement de stratégie
Fast hierarchical algorithms for the low-rank approximation of matrices, with applications to materials physics, geostatistics and data analysis by Pierre Blanchard( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Les techniques avancées pour l'approximation de rang faible des matrices sont des outils de réduction de dimension fondamentaux pour un grand nombre de domaines du calcul scientifique. Les approches hiérarchiques comme les matrices H2, en particulier la méthode multipôle rapide (FMM), bénéficient de la structure de rang faible par bloc de certaines matrices pour réduire le coût de calcul de problèmes d'interactions à n-corps en O(n) opérations au lieu de O(n2). Afin de mieux traiter des noyaux d'interaction complexes de plusieurs natures, des formulations FMM dites ”kernel-independent” ont récemment vu le jour, telles que les FMM basées sur l'interpolation polynomiale. Cependant elles deviennent très coûteuses pour les noyaux tensoriels à fortes dimensions, c'est pourquoi nous avons développé une nouvelle formulation FMM efficace basée sur l'interpolation polynomiale, appelée Uniform FMM. Cette méthode a été implémentée dans la bibliothèque parallèle ScalFMM et repose sur une grille d'interpolation régulière et la transformée de Fourier rapide (FFT). Ses performances et sa précision ont été comparées à celles de la FMM par interpolation de Chebyshev. Des simulations numériques sur des cas tests artificiels ont montré que la perte de précision induite par le schéma d'interpolation était largement compensées par le gain de performance apporté par la FFT. Dans un premier temps, nous avons étendu les FMM basées sur grille de Chebyshev et sur grille régulière au calcul des champs élastiques isotropes mis en jeu dans des simulations de Dynamique des Dislocations (DD). Dans un second temps, nous avons utilisé notre nouvelle FMM pour accélérer une factorisation SVD de rang r par projection aléatoire et ainsi permettre de générer efficacement des champs Gaussiens aléatoires sur de grandes grilles hétérogènes. Pour finir, nous avons développé un algorithme de réduction de dimension basé sur la projection aléatoire dense afin d'étudier de nouvelles façons de caractériser la biodiversité, à savoir d'un point de vue géométrique
Redefining and Adapting Feedback for Mental-Imagery based Brain-Computer Interface User Training to the Learners' Traits and States by Léa Pillette( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Mental-Imagery based Brain-Computer Interfaces (MI-BCIs) present new opportunities to interact with digital technologies, such as neuroprostheses or videogames, only by performing mental imagery tasks, such as imagining an object rotating. The recognition of the command for the system is based on the analysis of the brain activity of the user. The users must learn to produce brain activity patterns that are recognizable by the system in order to control BCIs. However, current training protocols do not enable 10 to 30% of persons to acquire the skills required to use BCIs. The lack of robustness of BCIs limit the development of the technology outside of research laboratories. This thesis aims at investigating how the feedback provided throughout the training can be improved and adapted to the traits and states of the users. First, we investigate the role that feedback is currently given in MI-BCI applications and training protocols. We also analyse the theories and experimental contributions discussing its role and usefulness. Then, we review the different feedback that have been used to train MI-BCI users. We focus on three main characteristics of feedback, i.e., its content, its modality of presentation and finally its timing. For each of these characteristics, we reviewed the literature to assess which types of feedback have been tested and what is their impact on the training. We also analysed which traits or states of the learners were shown to influence BCI training outcome. Based on these reviews of the literature, we hypothesised that different characteristics of feedback could be leveraged to improve the training of the learners depending on either traits or states. We reported the results of our experimental contributions for each of the characteristics of feedback. Finally, we presented different recommendations and challenges regarding each characteristic of feedback. Potential solutions were proposed to meet these recommendations in the future
Collaboration interactive 3D en réalité virtuelle pour supporter des scénarios aérospatiaux by Damien Clergeaud( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

The aerospace industry is no longer composed of local and individualbusinesses. Due to the complexity of the products (their size, the numberof components, the variety of systems, etc.), the design of an aircraft or alauncher involves a considerable number of engineers with various fields of expertise.Furthermore, aerospace companies often have industrial facilities allover the world. In such a complex setting, it is necessary to build virtual experimentsthat can be shared between different remote sites. Specific problemsthen arise, particularly in terms of the perception of other immersed users.We are working with Airbus Group in order to design efficient collaborativeinteraction methods. These collaborative sessions allow multiple sites to beconnected within the same virtual experiment and enable experts from differentfields to be immersed simultaneously. For instance, if a problem occurs duringthe final stages of a launcher assembly, it may be necessary to bring togetherexperts on different sites who were involved in previous steps ( initial design,manufacturing processes). In this thesis, we propose various interaction technique in order to ease thecollaboration at different moments of an industrial process. We contributedin the context of communication between immersed users, taking notes inthe virtual environment and sharing it outside virtual reality and asymmetriccollaboration between a physical meeting room and a virtual environment
A method of hp-adaptation for Residual Distribution schemes by Quentin Viville( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

This thesis presents the construction of a p-adaptive Residual Distribution scheme for the steady Euler equations and a hp-adaptive Residual Distribution scheme for the steady penalized Navier-Stokes equations in dimension two and three. The Euler and Navier-Stokes equations are recalled along with their non dimensional versions. The basis definitions and properties of the steady Residual Distribution schemes are presented. Then, the construction of a p-adaptive Residual Distribution scheme for the Euler equations is considered. The construction of the p-adaptive scheme is based upon the expression of the total residual of an element of a given degree k (in the Finite Element sense) into the total residuals of its linear sub-elements. The discrete solution obtained with the p-adaptive scheme is then a one degree polynomial in the divided elements and a k-th degree polynomial in the undivided ones. Therefore, the discrete solution is in general discontinuous at the interface between a divided element and an undivided one. This is in apparent contradiction with the continuity assumption used in general to demonstrate the discrete Lax-Wendroff theorem for Residual Distribution schemes. However, as we show in this work, this constrain can be relaxed. The consequence is that if special quadrature formulas are employed in the numerical implementation, the discrete Lax-Wendroff theorem can still be proved, which guaranties the convergence of the p-adaptive scheme to a weak solution of the governing equations. The formulas that express the total residual into the combination of the total residuals of the sub-elements are central to the method. In dimension two, the formula is obtained with the classical Lagrange basis in the quadratic case and with the Bézier basis in dimension three. These two formulas are then generalized to arbitrary polynomial degrees in dimension two and three with a Bézier basis. In the second part of the thesis the application of the p-adaptive scheme to the penalized Navier-Stokes equations with anisotropic mesh adaptation is presented. In practice, the p-adaptive scheme is used with the IBM-LS-AUM (Immersed Boundary Method with Level Sets and Adapted Unstructured Meshes) method. The IBM-LS-AUM allows to impose the boundary conditions with the penalization method and the mesh adaptation to the solution and to the level-set increases the accuracy of the representation of the surface and the solution around walls. When the IBM-LSAUM is combined with the p-adaptive scheme, it is possible to use high-order elements outside the zone where the penalization is applied. The method is robust as shown by the numerical applications at low to large Mach numbers and at different Reynolds in dimension two and three
Apprentissage simultané d'une tâche nouvelle et de l'interprétation de signaux sociaux d'un humain en robotique by Jonathan Grizou( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

This thesis investigates how a machine can be taught a new task from unlabeled humaninstructions, which is without knowing beforehand how to associate the human communicative signals withtheir meanings. The theoretical and empirical work presented in this thesis provides means to createcalibration free interactive systems, which allow humans to interact with machines, from scratch, using theirown preferred teaching signals. It therefore removes the need for an expert to tune the system for eachspecific user, which constitutes an important step towards flexible personalized teaching interfaces, a key forthe future of personal robotics.Our approach assumes the robot has access to a limited set of task hypotheses, which include the task theuser wants to solve. Our method consists of generating interpretation hypotheses of the teaching signalswith respect to each hypothetic task. By building a set of hypothetic interpretation, i.e. a set of signallabelpairs for each task, the task the user wants to solve is the one that explains better the history of interaction.We consider different scenarios, including a pick and place robotics experiment with speech as the modalityof interaction, and a navigation task in a brain computer interaction scenario. In these scenarios, a teacherinstructs a robot to perform a new task using initially unclassified signals, whose associated meaning can bea feedback (correct/incorrect) or a guidance (go left, right, up, ...). Our results show that a) it is possible tolearn the meaning of unlabeled and noisy teaching signals, as well as a new task at the same time, and b) itis possible to reuse the acquired knowledge about the teaching signals for learning new tasks faster. Wefurther introduce a planning strategy that exploits uncertainty from the task and the signals' meanings toallow more efficient learning sessions. We present a study where several real human subjects controlsuccessfully a virtual device using their brain and without relying on a calibration phase. Our system identifies, from scratch, the target intended by the user as well as the decoder of brain signals.Based on this work, but from another perspective, we introduce a new experimental setup to study howhumans behave in asymmetric collaborative tasks. In this setup, two humans have to collaborate to solve atask but the channels of communication they can use are constrained and force them to invent and agree ona shared interaction protocol in order to solve the task. These constraints allow analyzing how acommunication protocol is progressively established through the interplay and history of individual actions
 
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Alternative Names
Centre de recherche Inria Bordeaux - Sud-Ouest

Inria Bordeaux - Sud-Ouest

Inria Bordeaux - Sud-Ouest Research Centre

Languages
English (12)

French (8)