Science & Mathematics

Generating a valid high-quality mesh representing geological interfaces is a difficult task due to the complexity of the geometrical configurations encountered in geosciences. Furthermore, uncertainties regarding the locations or even the existence of geological discontinuities call for mesh updating techniques, operating on a local scale, in a fast and robust manner. To address these challenges, we introduce a novel mesh-update method that enables the insertion of finite surfaces such as faults in existing multi-material tetrahedral meshes. In this approach, the surface to be inserted is defined as the intersection of the zero level sets of two distinct level set functions: one that defines an extension of the surface across the domain into a closed surface, while the second extends its boundary. The level set functions can be obtained via interpolation, subject to a smoothness criterion or by using the fast marching algorithm.

La polyculture-élevage est citée dans un large consensus comme étant un système de production vertueux tant au niveau environnemental qu’économique. Notre objectif est d’analyser les différences de structures, de résultats techniques, économiques et environnementaux entre les exploitations spécialisées élevage et les exploitations dites polyculture-élevage (agriculture conventionnelle et biologique) issues d’un réseau de 66 élevages bovins allaitants du bassin Charolais. Les 21 exploitations polyculture-élevage conventionnelles s’avèrent être moins efficientes quant à l’utilisation des intrants et, par ce fait, pas plus (voire même moins) performantes au niveau économique et environnemental. Aucune économie de gamme n’a pu être démontrée pour ces 21 exploitations. Les 7 exploitations en agriculture biologique exploitent de façon plus efficiente la diversité des ressources alimentaires pour les troupeaux (fourrages, céréales), les positionnant ainsi comme un prototype possible d’exploitation polyculture-élevage répondant au concept d’agro-écologie.

Les califes Fatimides (909-1171) mirent en place une marine active et efficace dès les premières décennies de leur règne en Ifrîqiyya – Tunisie actuelle. Si la documentation relative à cette première phase ne permet guère de comprendre comment la flotte fut financée, à partir du milieu du XI e siècle, alors que les califes se trouvaient désormais en Égypte, les textes – documents administratifs, manuels d'administration et traités fiscaux – témoignent de la mise en place d'un système de plus en plus complexe d'administration et de financement de la flotte. Ce système trouva sa pleine mesure avec les croisades, lorsque la marine devint la principale force de résistance des Fatimides à l'avancée franque. Ainsi, les sources attestent avant tout d'une activité croissante de la marine de guerre durant toute la période considérée ici. Au-delà des exploits des flottes fatimides, célébrés dès le X e siècle, quelques documents permettent de comprendre que ces succès n'étaient pas dus qu'au seul hasard. C'est en effet l'image d'une flotte professionnelle, à l'organisation et au commandement rationnalisés, et soucieuse d'innovation qui se dessine progressivement. Autant d'éléments qui invitent à s'interroger sur le financement de la marine de guerre fatimide. Les sources témoignent du développement d'un système complexe d'achats de matières premières stratégiques qui s'appuyait sur les services douaniers. Ce système, atypique pour la période, permit aux Fatimides de concevoir une marine qui constituait l'outil essentiel de légitimation des prétentions universalistes de la dynastie ismaélienne face à ses concurrentes sunnites.

Quantitative methods have been adopted by more and more individual investors for investment activities. Many third party platforms have been developed to help users complete the process of backtesting, which fills the gap between the trading strategy code and the trading strategy model. However, using a quantitative platform for backtesting has a high threshold for users who do not have programming experience. There is still a huge gap between the description and the code of trading strategy. Code generation allows developers to focus more on business related design and implementation, thereby increasing the efficiency of software development. The import of domain knowledge can improve the accuracy of requirement parsing to improve the quality of constructed code model. The general knowledge base is often incomplete in terms of domain specific terms and relationships, and the construction of domain knowledge graphs requires more domain related data. In this paper, encyclopedia data and the financial report data are used to extract domain terms and relations. And then a domain knowledge graph for quantitative trading is constructed to realize the automatic generation of quantitative trading strategy code.

The non-smooth contact dynamics method was selected to investigate the damage occurred to typical masonry churches (namely Apennine churches) belonging to Central Italy areas affected by the seismic activity started in 2016. The investigated buildings show discontin-uous dynamics since the optioned method gave the chance to properly model the temples as multi rigid body systems using the Signorini's impenetrability condition and the dry-friction Coulomb's law, achieving a thoughtful response to ground seismic solicitations. The results provided by the assessment grant an overview of the most common damages and failure mechanisms, giving the guidelines to restoration projects that fully respond to structural needs.

We revisit some problems arising in the context of multiallelic discrete-time evolutionary dynamics driven by fitness. We consider both the deterministic and the stochastic setups and for the latter both the Wright-Fisher and the Moran approaches. In the deterministic formulation, we construct a Markov process whose Master equation identifies with the nonlinear deterministic evolutionary equation. Then, we draw the attention on a class of fitness matrices that plays some role in the important matter of polymorphism: the class of strictly ultrametric fitness matrices. In the random cases, we focus on fixation probabilities, on various conditionings on non-fixation and on (quasi-)stationary distributions.

We introduce new classes of weighted automata on words. Equipped with pebbles, they go beyond the class of recognizable formal power series: they capture weighted first-order logic enriched with a quantitative version of transitive closure. In contrast to previous work, this calculus allows for unrestricted use of existential and universal quantifications over positions of the input word. We actually consider both two-way and one-way pebble weighted automata. The latter class constrains the head of the automaton to walk left-to-right, resetting it each time a pebble is dropped. Such automata have already been considered in the Boolean setting, in the context of data words. Our main result states that two-way pebble weighted automata, one- way pebble weighted automata, and our weighted logic are expressively equivalent. We also give new logical characterizations of standard recognizable series.

ReaderBench is an automated software framework designed to support both students and tutors by making use of text mining techniques, advanced natural language processing, and social network analysis tools. Read‐ erBench is centered on comprehension prediction and assessment based on a cohesion-based representation of the discourse applied on different sources (e.g., textual materials, behavior tracks, metacognitive explanations, Computer Supported Collaborative Learning – CSCL – conversations). Therefore, Reader‐ Bench can act as a Personal Learning Environment (PLE) which incorporates both individual and collaborative assessments. Besides the a priori evaluation of textual materials' complexity presented to learners, our system supports the iden‐ tification of reading strategies evident within the learners' self-explanations or summaries. Moreover, ReaderBench integrates a dedicated cohesion-based module to assess participation and collaboration in CSCL conversations.

Modigliani et la question de l'existence d'un équilibre dans un modèle à prix flexibles Résumé. En 1955, Franco Modigliani rédigea les notes du cours qu'il donnait au Carnegie Institute of Technology. Ce document, qui porte le titre de Preliminary Notes on the Theory of Money and Interest in the Framework of General Equilibrium Analysis, est resté inédit. Travaillant dans le cadre d'un modèle d'équilibre temporaire voisin de celui que Hicks avait développé dans Value and Capital, Modigliani proposait une reconstruction de la théorie monétaire voisine mais différente de celle que Patinkin développera dans Money, Interest and Prices. Il établit que ce modèle n'a pas nécessairement un équilibre si les prix et les salaires sont flexibles. Il montre que les propositions habituellement associées à la théorie quantitative-la dichotomie entre secteur monétaire et secteur réel, la neutralité de la monnaie, le parallélisme de l'évolution des prix et de la monnaie-ne sont pas généralement vérifiées. Il introduit dans le modèle d'équilibre général la rigidité des salaires et des prix pour construire un cadre approprié pour l'étude des politiques monétaires. Ce texte novateur est important pour comprendre la façon dont la théorie monétaire était conçue et enseignée aux États-Unis dans les années 1950.

We shall first consider the classical neutral Moran model with two alleles whose fate is either to become extinct or to reach fixation. We will study an ergodic version of the Moran model obtained by conditioning it to never hit the boundaries, making use of a Doob transform. We shall call it the recurrent Moran model. We will show that the Siegmund dual of the recurrent Moran process exists and is a substochastic birth and death chain. Conditioning this process to exit in its natural absorbing state, we construct a process with a unique absorbing state which is intertwined to the original recurrent Moran process. The time needed for the intertwined process to first hit its absorbing state is related to the time to reach stationarity for the recurrent Moran process. Using spectral information on the intertwined chain, we extract limiting information on this first hitting time that shows that there is no abrupt relaxation to equilibrium for the recurrent Moran chain. This makes use of the relation between duality and intertwining and strong stationary times. Other related transition times of the recurrent Moran chain are also briefly investigated, namely: the first return time to the ground state and the expected time needed to move from one end to the other end of the state-space.

Networked 3D virtual environments allow multiple users to interact with each other over the Internet. Users can share some sense of telepresence by remotely animating an avatar that represents them. However, avatar control may be tedious and still render user gestures poorly. This work aims at animating a user‟s avatar from real time 3D motion capture by monoscopic computer vision, thus allowing virtual telepresence to anyone using a personal computer with a webcam. The approach followed consists of registering a 3D articulated upper-body model to a video sequence. This involves searching iteratively for the best match between features extracted from the 3D model and from the image. A two-step registration process matches regions and then edges. The first contribution of this thesis is a method of allocating computing iterations under real-time constrain that achieves optimal robustness and accuracy. The major issue for robust 3D tracking from monocular images is the 3D/2D ambiguities that result from the lack of depth information. Particle filtering has become a popular framework for propagating multiple hypotheses between frames. As a second contribution, this thesis enhances particle filtering for 3D/2D registration under limited computation constrains with a number of heuristics, the contribution of which is demonstrated experimentally. A parameterization of the arm pose based on their end-effector is proposed to better model uncertainty in the depth direction. Finally, evaluation is accelerated by computation on GPU. In conclusion, the proposed algorithm is demonstrated to provide robust real-time 3D body tracking from a single webcam for a large variety of gestures including partial occlusions and motion in the depth direction.

Si un métal est soumis à un chargement cyclique autour d'une contrainte moyenne non nulle, de la déformation plastique peut s'accumuler au cours des cycles, généralement dans la direction de la contrainte moyenne : c'est le phénomène de déformation progressive ou phénomène dit de rochet. Le contexte de cette thèse était l'amélioration de la description de ce phénomène dans les structures métalliques. Pour cela, nous avons choisi d'axer nos efforts sur les modèles macroscopiques phénoménologiques qui décrivent le comportement de matériaux dans des calculs de structure. Comme cela était suggéré dans plusieurs articles récents, une voie d'amélioration de ces modèles était de prendre en compte la distorsion du domaine d'élasticité, phénomène maintes fois observé expérimentalement, mais jusqu'alors négligé par soucis de simplicité. Pour introduire convenablement ce nouvel ingrédient dans la modélisation, nous nous sommes appuyés sur un dialogue entre un modèle micro-macro d'une part (plus pertinent mais aussi plus coûteux en temps de calcul) et le modèle macroscopique à construire d'autre part. Nous avons sû tirer profit des informations données par le modèle micro-macro pour constuire un modèle macroscopique capable de décrire à la fois le phénomène de rochet multiaxial et la distorsion du domaine d'élasticité prévus par le modèle micro-macro, et ce sur une large base d'"essais virtuels". Ensuite, le modèle développé a été identifié et validé avec succès sur plusieurs résultats d'essais complexes obtenus sur un élément de volume d'un matériau réel. Une validation finale du modèle sur un essai non-homogène (de structure) est en cours d'étude.

We consider models of block-weighted random planar maps in which possibly decorated maps are decomposed canonically into blocks, each block receiving the weight u. These maps present a transition at some critical value u = u_cr above which the maps degenerate into Brownian trees. We show that the enumerative properties and critical exponents of the maps at u = u_cr and those for u < u_cr are connected by duality relations which are precisely those expected in the context of the Liouville quantum gravity description of random surfaces. We illustrate this result by various instances of blockweighted maps: random planar quadrangulations decomposed into simple blocks, Hamiltonian cycles on cubic or bicubic planar maps decomposed into irreducible blocks, and meandric systems.