Share price returns on different time scales can be well modeled by a superstatistical dynamics. We provide an investigation which type of superstatistics is most suitable to properly describe share price dynamics on various time scales. It is shown that while chi-square-superstatistics works well on a time scale of days, on a much smaller time scale of minutes the price changes are better described by lognormal superstatistics. The system dynamics thus exhibits a transition from lognormal to chi-square-superstatistics as a function of time scale. We discuss a more general model interpolating between both statistics which fits the observed data very well. We also present results on correlation functions of the extracted superstatistical volatility parameter, which exhibits exponential decay for returns on large time scales, whereas for returns on small time scales there are long-range correlations and power-law decays. We also apply the symbolic dynamics technique from dynamical system theory to analyse the coarse-grained evolution of share price returns. A nontrivial spectrum of Renyi entropies is found. We study how the spectrum depends on the time scale of returns, the sector of stocks considered, as well as the number of symbols used for the symbolic description. Overall our analysis confirms that in the symbol space transition probabilities of observed share price returns depend on the entire history of previous symbols, thus emphasizing the need for a model of share price evolution based on non-Markovian stochastic processes. Our method allows for quantitative comparisons of entirely different complex systems, for example the statistics of coarse-grained share price returns using 4 symbols can be compared with that of other complex systems.

The incredible ability of human beings to quickly detect the prominent or salient regions in an image is often taken for granted. To be able to reproduce this intelligent ability in computer vision systems remains quite a challenge. This ability is of paramount importance to perception and image understanding since it accelerates the image analysis process, thereby allowing higher vision processes such as recognition to have a focus of attention. In addition to this, human eye fixation points occurring during the early stages of visual processing, often correspond to the loci of salient image regions. These regions provide us with assistance in determining the interesting parts of an image and they also lend support to our ability to discriminate between different objects in a scene. Salient regions attract our immediate attention without requiring an exhaustive scan of a scene. In essence, saliency can be defined as the quality of an image region that enables it to stand out in relation to its neighbors. Saliency is often approached in either one of two ways. The bottom-up saliency approach refers to mechanisms which are image-driven and independent of the knowledge in an image, whereas the top-down saliency approach refers to mechanisms which are task-oriented and make use of the prior knowledge about a scene. In this thesis, we present a bottom-up measure of saliency based on the relationships exhibited among image features. The perceived structure in an image is determined more by the relationships among features rather than the individual feature attributes. From this standpoint, we aim to capture the organization within an image by employing relational distributions derived from distance and gradient direction relationships exhibited between image primitives. The Rényi entropy of the relational distribution tends to be lower if saliency is exhibited for some image region in the local pixel neighborhood over which the distribution is defined. This notion forms the foundation of our measure. Correspondingly, results of our measure are presented in the form of a saliency map, highlighting salient image regions. We show results on a variety of real images from various datasets. We evaluate the performance of our measure in relation to a dominant saliency model and obtain comparable results. We also investigate the biological plausibility of our method by comparing our results to those captured by human fixation maps. In an effort to derive meaningful information from an image, we investigate the significance of scale relative to our saliency measure, and attempt to determine optimal scales for image analysis. In addition to this, we extend a perceptual grouping framework by using our measure as an optimization criterion for determining the organizational strength of edge groupings. As a result, the use of ground truth images is circumvented.

Située au carrefour de la didactique des langues et cultures et des sciences de l’éducation, la présente thèse porte sur l’appropriation, par les enseignants du cycle primaire au Bénin, de l’Initiative Francophone pour la Formation à Distance des Maîtres (IFADEM) en tant que dispositif de formation continue, en enseignement-apprentissage du FLES. L’objectif consiste à apporter des pistes pour améliorer l’appropriation du dispositif. A partir d’un modèle théorique d’appropriation, mis en place au regard d’une approche théorique transdisciplinaire et des spécificités du contexte d’étude, doublé d’une démarche de triangulation articulant enquêtes par questionnaires, par entretiens semi-directifs, d’auto-confrontation et par observations de pratiques effectives (situantes), nous nous sommes attachés à identifier les « indicateurs » d’appropriation ainsi que les « effets » du dispositif de formation sur les « pratiques pédagogiques effectives » des enseignants. Les théories holistiques de l’apprentissage des langues et spécifiquement l’éducation bilingue, le translanguaging et les théories sur l’enseignement-apprentissage de l’oral, ont constitué un socle pour l’analyse et la compréhension de la situation de recherche. La stabilité de nos analyses, offerte par le choix d’une méthodologie par triangulation, confirme que le parcours d’appropriation est déterminé par des relations d’interdépendance entre des facteurs situationnels (contextualisation), relationnels (relation avec les pairs) et individuels (self-system, réflexivité, recul épistémologique). Elle nous permet également d’aboutir aux conclusions suivantes : les enseignants bénéficiaires de la formation IFADEM font usage de la formation de façon instrumentale, et notamment des tâches qui leurs sont proposées pour améliorer l’enseignement oral du et en français afin de faire face au plurilinguisme. Ils sont exposés à plusieurs variations d’échelle, sources de contraintes et de tensions dans leurs activités pédagogiques, et ces dernières constituent un frein à l’appropriation du dispositif. L’analyse du processus d’appropriation au regard de l’émergentisme et des systèmes complexes d’activité permet d’aboutir au fait que les tensions générées par le déploiement du dispositif IFADEM font partie intégrante du processus de transformation de ce dernier. C’est l’absence de feed-back soutenu et institutionnalisé qui constitue une entrave à l’appropriation du dispositif. Afin de réagir positivement à ces écarts et de garantir l’appropriation du dispositif, le recours à la médiation ainsi qu’à une approche par tâches constituerait une voie intermédiaire. Elle permettrait notamment au dispositif de formation IFADEM, de s’inscrire dans une démarche co-évolutive, essentielle à l’équilibre des systèmes. C’est en tenant compte de l’ensemble de ces analyses et ajustements que cette recherche aboutit à l’élaboration d’un modèle d’appropriation. / This PhD thesis, situated at the crossroads of two domains – language and culture learning and teaching and learning sciences – deals with the way Beninese primary school teachers appropriated the IFADEM programme - « Initiative Francophone pour la Formation à Distance des Maîtres » (Francophone Initiative for Distance Education of Teachers), as a lifelong education environment in the teaching and learning of « French as Foreign/Second Language Learning ». Our purpose is to suggest new avenues aimed at improving the appropriation of this education environment. Our approach is based on a theoretical model of appropriation informed by a transdisciplinary theoretical stance and by the specifics of the context under study, but also on a triangulation method mixing questionnaire surveys, semi-directive interviews, self-confrontation interviews and observations of actual practises (situating). We try to identify the « indicators » of appropriation as well as the « effects » of the education environment on the « actual pedagogical practises » of teachers. Holistic theories of language learning – and more specifically bilingual education, translanguaging and the theories on oral skills development have given a foundation to the analysis and the comprehension of the research situation. The stability of our analyses, made possible by the choice of a triangulation methodology, confirms that the appropriation paths are determined by interdependency relations between factors of situational (contextualisation), relational (relationships with peers) and individual (self-system, reflexivity, epistemological distancing) natures. It also allows us to reach the following conclusions : the teachers who benefitted from the IFADEM training use it instrumentally and more specifically use the tasks they were proposed to improve the teaching of oral skills in and of French, in order to tackle the question of plurilingualism. These teachers are faced with several scale variations which engender constraints and tensions in their pedagogical activities, thus hindering the appropriation of the education environment. The analysis of the appropriation process in the light of emergentism and of complex systems of activity leads to the conclusion that the tensions generated by the implementation of the IFADEM progamm are part and parcel of its process of transformation. The absence of institutionalised and sustained feedback is the real hindrance to the appropriation of the education environment. In order to reduce these discrepancies in a positive way and to guarantee appropriation, turning to mediation and a task-based approach would constitute a middle way. In particular, it would allow the IFADEM environment to come within the scope of a co-evolutive approach, which is essential to the balance of systems. Taking into account all these analyses and adjustments helps this research to reach the elaboration of a model of appropriation.