Šiame darbe nagrinėjami fraktalų – iteruoųjų funkcijų sistemų (IFS) atraktorių – sintezės algoritmai. Pagrindinis dėmesys skiriamas pabėgimo laiko (PL)-algoritmui. PL-algoritmas yra pakankamai universalus. Pagrindinės šio algoritmo panaudojimo sričitys – netiesinių dinaminių sistemų, veikiančių kompleksinėje plokštumoje, analizė, kompleksinių daugianarių šaknų pritraukimo baseinų vizualizavimas ir kt. Geometrinių fraktalų (IFS atraktorių) sintezei šis algoritmas iki šiol nebuvo naudojamas, nors tokia galimybė, kaip teorinis rezultatas, yra žinoma. Pagrindinė to priežastis – IFS sudarančių afiniųjų transformacijų veikimo zonų atskyrimo kriterijaus nebuvimas. Tokio kriterijaus paieškai ir realizacijai darbe skiriamas didžiausias dėmesys. Rezultatas – nauja adaptyvi IFS sudarančių afiniųjų transformacijų veikimo zonų atskyrimo procedūra. Lygegrečiai spendžiama tolygaus spalvinio sintezuojamo (PL-algoritmo pagalba) fraktalinio vaizdo užpildymo problema. Pasiūlytas originalus sprendimas – problemiškai oriantuota iteracij�� skaičiaus (sintezės metu) korekcija. Darbe pristatomi ir preliminarūs su fraktalinių vaizdų (IFS atraktorių) sinteze susijusių eksperimentų rezultatai. / The contribution of this work is a new version of the escape time algoritm adapted for synthesizing fractal images, indentified with atractors of iterated functions systems (IFS). The proposesd synthesis algorithm is based on the use of shift dynamics, associated with one or another IFS. The strategy for the seperation of extended domains of the inverse affine transformations, specified by IFS, is developed. In the field of computerized real word image models (digital images) the fractal approach is of outmost importance, because it facilitates perception and understanding of the information content of an image. To say more, it provides us with a powerful means to catch sight of a fundamental real word image property generally known as self-similarity. Due to this property, the research and development of algorithms („fractal techniques“) to extract imortant fractal parameters from appropriate digital data has received significant attention in recent years. In this work, the basic concepts and ideas that are needed to describe, state and solve the problem of synthesizing fractal images, identified with attractors of IFS, are introduced and explored. A new original approach (idea), leading to practical implementation of the shift dynamical system, associated with a particular IFS, is proposed (part 3). Some experimental results are given (Part 4).

Nous nous intéressons à la modélisation de formes complexes de type structures arborescences, formes lacunaires ou surfaces rugueuses. Ces formes sont intéressantes de par leurs propriétés physiques particulières :objets légers, économie de matière, résistance mécanique, absorption acoustique importante. Les modèles basés sur le concept de la géométrie fractale permettent de générer de telles formes et notamment les formes auto-similaires. A partir des travaux de Barnsley sur les systèmes itérés de fonctions, Tosan et al, ont proposé une extension, Boundary Controled Iterated Funcions Systems (BCIFS) pour contrôler plus facilement les formes et faciliter leur description. Nous nous intéressons aux propriétés différentielles des formes décrites par BCIFS. Nous proposons une définition plus générale d'espace tangent qui permet de caractériser le comportement de cas non-classiquement différentiables.Nous montrons que l'étude du comportement différentiel peut alors se faire simplement par analyse des valeurs propres et vecteurs propres généralisés des opérateurs de subdivision. Il devient alors possible de contrôler ces propriétés différentielles. Nous présentons une application de nos résultats, en proposant une méthode pour construire des raccords entre deux structures définies par des processus de subdivision différents. Cette méthode est appliquée pour la construction d'un raccord entre une surface de subdivision de Doo-Sabin(schéma dual) et une surface de subdivision de Catmull-Clark (schéma primal) / The fractal geometry is a relatively new branch of mathematics that studies complex objects of non-integer dimensions. It finds applications in many branches of science as objects of such complex structure often poses interesting properties. In 1988 Barnsley presented the Iterative Func-tion System (IFS) model that allows modelling complex fractal shapes with only a limited set of contractive transformations. Later many other models were based on the IFS model such as Language-Restricted IFS,Projective IFS, Controlled IFS and Boundary Controlled IFS. The lastto allow modelling complex shapes with control points and specific topol-ogy. These models cover classical geometric models such as B-splines and subdivision surfaces as well as fractal shapes.This thesis focuses on the analysis of the differential behaviour of the shapes described with Controlled IFS and Boundary Controlled IFS. Wederive the necessary and sufficient conditions for differentiability for ev-erywhere dense set of points. Our study is based on the study of the eigenvalues and eigenvectors of the transformations composing the IFS. We apply the obtained conditions to modelling curves in surfaces. We describe different examples of differential behaviour presented in shapes modelled with Controlled IFS and Boundary Controlled IFS. We also use the Boundary Controlled IFS to solve the problem of connecting different subdivision schemes. We construct a junction between Doo-Sabin and Catmull-Clark subdivision surfaces and analyse the differential behaviour of the intermediate surface

The purpose of this thesis is to generalize the growing theory of iterated function systems (IFSs). Earlier, hyperbolic IFSs with finitely many functions have been studied extensively. Also, hyperbolic IFSs with infinitely many functions have been studied. In this thesis, more general IFSs are studied. The Hausdorff pseudometric is studied. This is a generalization of the Hausdorff metric. Wide and narrow limit sets are studied. These are two types of limits of sequences of sets in a complete pseudometric space. Stable Iterated Function Systems, a kind of generalization of hyperbolic IFSs, are defined. Some different, but closely related, types of stability for the IFSs are considered. It is proved that the IFSs with the most general type of stability have unique attractors. Also, invariant sets, addressing, and periodic points for stable IFSs are studied. Hutchinson’s metric (also called Vaserhstein’s metric) is generalized from being defined on a space of probability measures, into a class of norms, the £-norms, on a space of real measures (on certain metric spaces). Under rather general conditions, it is proved that these norms, when they are restricted to positive measures, give rise to complete metric spaces with the metric topology coinciding with the weak*-topology. Then, IFSs with probabilities (IFSPs) are studied, in particular, stable IFSPs. The £-norm-results are used to prove that, as in the case of hyperbolic IFSPs, IFSPs with the most general kind of stability have unique invariant measures. These measures are ”attractive”. Also, an invariant measure is constructed by first ”lifting” the IFSP to the code space. Finally, it is proved that the Random Iteration Algorithm in a sense will ”work” for some stable IFSPs. / <p>Diss. Umeå : Umeå universitet, 1992</p> / digitalisering@umu

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-07-26T15:02:31Z No. of bitstreams: 1 arquivototal.pdf: 2908745 bytes, checksum: 430a29a1552b3b5cdeda3dfa52afa524 (MD5) / Made available in DSpace on 2017-07-26T15:02:31Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2908745 bytes, checksum: 430a29a1552b3b5cdeda3dfa52afa524 (MD5) Previous issue date: 2017-02-24 / The Brazilian public institutions have adopted sustainable policies with socio-educational measures, green biddings are examples of promotion to sustainable development, through the use of social, environmental and economic criteria in the acquisition of goods, contracting of services and execution of works. The Federal Institute of Sergipe (IFS) Campus Legato makes small sustainable purchases, such as recycled paper, but it does not have a practice of sustainable purchases, given the lack of a facilitating method for sustainable bidding. The small purchases are made by the Rectory of the IFS, by adhesion of the Act of licitation (ride). This study, therefore, proposes the creation of a methodology of sustainable purchases in this Federal autarchy. This qualitative-descriptive research uses a semi-structured questionnaire to capture information from IFS employees about the use of sustainable biddings within the Institute, environmental perception and the main obstacles to sustainable procurement. The results point to the need to propose a sustainable purchasing methodology to guide the acquisition of goods and services. The purpose of this proposal is to streamline the purchasing process in the IFS, streamlining procurement steps and procedures. Thus, in line with the Sustainable Procurement Laws, the IFS is expected to exercise its purchasing power, which will lead to a socioenvironmental gain, the promotion of sustainable development. / As instituições públicas brasileiras têm adotado políticas sustentáveis com medidas socioeducativas. As licitações verdes são exemplos de promoção ao desenvolvimento sustentável, mediante a utilização de critérios sociais, ambientais e econômicos nas aquisições de bens, contratações de serviços e execução de obras. O Instituto Federal de Sergipe (IFS) Campus Lagarto, de maneira geral faz pequenas compras sustentáveis, a exemplo do papel reciclado, mas, não tem como prática as compras sustentáveis, dada a não existência de um método facilitador para a realização das licitações sustentáveis. As compras sustentáveis na maioria das vezes são realizadas pela Reitoria do IFS, por adesão de Ata de licitação (carona). Este estudo, portanto, propõe a criação de uma metodologia de compras sustentáveis nesta autarquia Federal. Esta pesquisa de caráter qualitativo-descritiva, utiliza-se de questionário semiestruturado com o objetivo de captar informações dos servidores do IFS acerca da utilização de licitações sustentáveis no âmbito do Instituto, da percepção ambiental e dos principais entraves das compras sustentáveis. Os resultados apontaram a necessidade da proposição de uma metodologia de compras sustentáveis que norteei as aquisições de bens e serviços. Pretende-se com esta proposição dinamizar o processo de compras no IFS, agilizando as etapas e procedimentos das compras. Assim, em conformidade com as Leis de compras sustentáveis, espera-se que o IFS exerça seu poder de compras, o que leve a um ganho socioambiental, a promoção do desenvolvimento sustentável.

Aujourd’hui, plus de 1800 planètes qui orbitent autour d’étoiles en dehors du système solaire ont été découvertes. La plupart des planètes découvertes actuellement a été révélée grâce aux méthodes indirectes. Par contre, avec ce type de techniques, la caractérisation des planètes ne peut pas être complète si on n’utilise pas plusieurs techniques simultanément. Aussi, pour obtenir le spectre de la planète, il doit y avoir un transit et même dans ce cas là,le signal est très faible par rapport au signal de l’étoile. L’observation directe de ces objets, appellée imagerie directe, est maintenant possible grâce à des systèmes très avancés d’optique adaptative installés sur des télescopes de classe 8m. L’imagerie directe permet l’observation des planètes sufisamment lumineuses et éloignées de l’étoile principale en utilisant un masque qui cache la lumière de la dernière. Cette technique est donc efficace en particulier pour des systèmes jeunes et voisins car la luminosité intrinsèque de la planète diminue avec l’âge et la séparation réelle de la planète dépend de la distance du système. Dans le VLT au Paranal (Chili), deux instruments sont dédiés à ce type de recherche : NACO et SPHERE. SPHERE a vu sa première lumière en Mai 2014, et est maintenant prêt à commencer une enquête consacrée à la découverte de planètes autour de systèmes jeunes et voisins, NIRSUR. Cet instrument se compose de trois sous-systèmes : IRDIS, IFS et ZIMPOL. / In the year of the 20th anniversary of the discovery of the first extrasolar planet we can count more than 1800 companions found with different techniques. The majority of them are indirect methods that infer the presence of an orbiting body by observing the parent star (radial velocity, transits, astrometry). In this work we explore the technique that permits to directly observe planets and retrieve their spectra, under the conditions that they are bright and far enough from their host star. Direct imaging is a new technique became possible thanks to a new generation of extreme adaptive optics instruments mounted on 8m class telescopes. On the Very Large Telescope two instruments dedicated to the research for exoplanets with direct imaging are now operative: NACO and SPHERE. This thesis will describe the development and results of SPHERE from its predecessor NACO to its integration in laboratory and the final on sky results.

Arctic climate is changing fast, but weather forecast and climate models have serious deficiencies in representing the Arctic atmosphere, because of the special conditions that occur in this region. The cold ice surface and the advection of warm air aloft from the south result in a semi-continuous presence of a temperature inversion, known as the “Arctic inversion”, which is governed by interacting large-scale and local processes, such as surface fluxes and cloud formation. In this thesis these poorly understood interactions are investigated using observations from field campaigns on the Swedish icebreaker Oden: The Arctic Summer Cloud Ocean Study (ASCOS) in 2008 and the Arctic Clouds in Summer Experiment (ACSE) in 2014. Two numerical models are also used to explore these data: the IFS global weather forecast model from the European Center for Medium-range Weather Forecasts and the MIMICA LES from Stockholm University. Arctic clouds can persist for a long time, days to weeks, and are usually mixed-phase; a difficult to model mixture of super-cooled cloud droplets and ice crystals. Their persistence has been attributed to several mechanisms, such as large-scale advection, surface evaporation and microphysical processes. ASCOS observations indicate that these clouds are most frequently decoupled from the surface; hence, surface evaporation plays a minor role. The determining factor for cloud-surface decoupling is the altitude of the clouds. Turbulent mixing is generated in the cloud layer, forced by cloud-top radiative cooling, but with a high cloud this cannot penetrate down to the surface mixed layer, which is forced primarily by mechanical turbulence. A special category of clouds is also found: optically thin liquid-only clouds with stable stratification, hence insignificant in-cloud mixing, which occur in low-aerosol conditions. IFS model fails to reproduce the cloud-surface decoupling observed during ASCOS. A new prognostic cloud physics scheme in IFS improves simulation of mixed-phase clouds, but does not improve the warm bias in the model, mostly because IFS fails to disperse low surface-warming clouds when observations indicate cloud-free conditions. With increasing summer open-water areas in a warming Arctic, there is a growing interest in processes related to the ice marginal zones and the summer-to-autumn seasonal transition. ACSE included measurements over both open-water and sea-ice surfaces, during melt and early freeze. The seasonal transition was abrupt, not gradual as would have been expected if it was primarily driven by the gradual changes in net solar radiation. After the transition, the ocean surface remained warmer than the atmosphere, enhancing surface cooling and facilitating sea-ice formation. Observations in melt season showed distinct differences in atmospheric structure between the two surface types; during freeze-up these largely disappear. In summer, large-scale advection of warm and moist air over melting sea ice had large impacts on atmospheric stability and the surface. This is explored with an LES; results indicate that while vertical structure of the lowest atmosphere is primarily sensitive to heat advection, cloud formation, which is of great importance to the surface energy budget, is primarily sensitive to moisture advection. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

Dans le cadre d’une collaboration avec la société PHYTOREM, nous avons élaboré un prototype de distribution autorégulé afin d’épandre des Eaux Usées après un simple dégrillage et via la Phytorémédiation (dépollution par les plantes).La première approche du projet de thèse a été de comprendre les comportements rhéologiques des effluents, mis à disposition par Phytorem, et mécaniques du matériau élastomère de type EPDM. Nous avons exposé les différentes façons de retrouver leurs propriétés rhéologiques et mécaniques par le biais de divers tests de rhéométrie, concernant les effluents, et de traction uni-, bi- et équibi-axiale, pour la partie matériau. Ceci nous a permis d’obtenir d’une part, la viscosité de nos effluents, et d’autre part, la loi de comportement la mieux adaptée à notre matériau.La deuxième et dernière approche porte sur les interactions entre un fluide et une membrane hyperélastique ayant pour fonction de réguler un écoulement. Le comportement de la membrane contrainte par la pression a été simulé sous Abaqus. Ces résultats ont permis de modéliser l’écoulement (code CFD commercial) lorsque la membrane est déformée et de déterminer numériquement la loi débit/pression du dispositif. Ces développements numériques s’appuient sur la méthode des éléments finis et un couplage partitionné simple en une étape pour une première approche entre le fluide, la membrane et la structure. Les modèles numériques sont validés expérimentalement. Ces travaux participent à l’élaboration d’un prototype de distributeur auto-régulé. / In collaboration with PHYTOREM, we have developed a prototype of self-regulated drip emitter to spread the Wastewater after a simple screening using phytoremediation (remediation by plants).The first approach of the thesis project was to understand the rheological behaviour of waste provided by PHYTOREM, and mechanical properties behaviour of EPDM elastomer type. We have explained the different ways to find their rheological and mechanical properties through various rheometry tests on waste, and tension uni-, biand equibi-axiale, for the material part. This allowed us to obtain first, the viscosity of our waste, and secondly, the behaviour law of best suited to our material.The second and final approach focuses on the interactions between a fluid and a hyperelastic membrane whose function is to regulate flow. The membrane behaviour under pressure stress was simulated using Abaqus. These results were used to model the flow (commercial CFD) when the membrane is distorted and to determine numerically its flow versus pressure law. These developments are relying on numerical finite element method and partitionned into a single coupling step for a first approach between fluid, membrane and structure. The numerical models are validated experimentally. This work contributes to the development of a prototype of self-regulated drip emitter.

La thèse s'intéresse aux deux écoulements présents en aviron, autour du bateau et de la palette, et aux interactions avec le système bateau-avirons-rameur. Le premier est inhabituel en hydrodynamique, à cause du cavalement important et des mouvements secondaires. La complexité du second provient de l'instationnarité et de la déformation de la surface libre. L'objectif consiste à mettre en oeuvre des méthodes numériques performantes et précises puis à les valider pour, à plus long terme, les réutiliser à des fins d'analyse et d’optimisation de la performance en aviron.Ces simulations instationnaires à surface libre sont coûteuses en ressources pour les codes RANS. Un algorithme de sub-cycling a été développé et validé sur plusieurs cas test, diminuant les temps CPU d'un facteur 3 à 4, sans perte de précision. Il est compatible avec la déformation et le raffinement automatique de maillage. Deux bases de données expérimentales sont exploitées pour chaque écoulement afin de valider le cadre de simulation. Pour celui autour de la palette, une campagne in situ et une autre en laboratoire sont utilisées. Dans les deux cas, les profils d'efforts sont bien capturés, compte tenu des incertitudes cumulées liées à la mesure indirecte de la cinématique de la palette par rapport à l'eau. Pour le skiff en configuration instationnaire, les efforts fluctuants sont bien capturés, en amplitude et en phase, pour des fréquences typiques. Des écarts inattendus (de l'ordre de 10%) sont constatés sur la valeur moyenne et restent pour le moment sans réponse probante. La structure d'une co-simulation entre les résolutions des écoulements et celle de la dynamique du système multicorps est initiée. / The thesis focuses on the two flows occurring in rowing,around the boat and the blade, and on interactions with theboat-oars-rower system. The first flow is unusual in hydrodynamics because of the large surge and secondary motions. The complexity of the second one comes from the unsteadiness and the free surface deformation. The goal is to set up efficient and accurate numerical methods to reproduce these flows and then to validate them for the purpose of analysis and optimisation of the performance in rowing.Those unsteady computations with free surface are cost lyin resources for RANS codes. A sub-cycling algorithm was developed and validated on several test cases, allowing to decrease the CPU time by a factor of 3 to 4, without loss of accuracy. It is compatible with mesh deformation and automatic grid refinement. Two experimental databases are exploited for each flow in order to validate the frame of simulation. For the flow around the blade, an in-situ campaign and a more controlled one conducted in laboratory, are used. In both cases, the profiles of the efforts are well captured, considering the cumulative uncertainties linked to the indirect measurement of the blade kinematics relative to the water. For the skiff in unsteady state, the fluctuating forces are well captured, in terms of amplitudes and phases, for typical frequencies. Unexpected errors (around10%) are observed for the mean value and remain unexplained for now. The structure of a co-simulation between the resolutions of the flows and the resolution of the dynamics of the multibody system is initiated.

The complex and diverse populations of galaxies observed today form hierarchically through past galactic mergers. Interactions between galaxies of similar masses will drastically alter the morphology, chemical composition, star-formation activity, and central black-hole accretion of their constituents. Though we can see the components and byproducts of galaxy mergers, these events endure over a timescale of hundreds of millions of years. Thus to understand the merging process from observations, astronomers are reliant on large spectroscopic surveys which will contain galaxy mergers at various stages of interaction, and those which have just experienced coalescence. Until recently, such surveys were limited to the global properties of each galaxy, constraining the global changes in chemical composition and star-formation activity, but overlooking how such changes vary across a galaxy. The advent of Integral Field Unit (IFU) spectroscopy surveys provides spatially resolved spectroscopic properties for thousands of galaxies for the first time. This thesis presents analysis of galaxy mergers from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) IFU spectroscopy survey. Enhancements and deficits in star-formation rate and metallicity, as a result of the interaction, are determined for each spatial pixel containing a spectrum (spaxel) based on well established relationships with stellar mass density. These offsets are then compressed into radial profiles to quantify how the effects of an interaction vary as a function of radius. A sample of 36 post-mergers are, on average, enhanced out to ~2 effective radii, though individual galaxies can be enhanced or suppressed in the outskirts depending on the global star-formation rate of the galaxy. The metallicity is uniformly suppressed in post-merger galaxies, in concordance with the global SFR enhancement. A sample of galaxy pairs is identified with cuts in the projected separation, the line of sight velocity difference, and the mass ratio of the interaction. I develop a method to deblend close galaxy pairs that are on the same IFU observation, and remove contribution from the companion galaxy in the radial profile. Radial profiles of SFR and metallicity offsets for the pairs sample, binned by projected separation, confirm that central enhancements in SFR increase as separation decreases. Behaviour in the outskirts is more varied, and does not appear to correlate with the projected separation or the mass ratio of the interaction. Metallicity offsets display a similar issue, showing no clear correlation with separation or mass ratio. Such ambiguity implies that multiple characteristics of the interaction and its components are required to predict the spatial changes in a galaxy merger. I propose projects that could shed light on these ambiguities. The most recent release of MaNGA will double the sample size of mergers, possibly homogenizing projected separation and mass ratio bins that may be dominated by a particular population. An analysis of interacting galaxies that do not have mass ratio measurements, but very small projected separations and highly disturbed morphologies, could provide understanding of the transition between the very end of an interaction and the state of the galaxy post-coalescence. I also propose a more complex analysis of the asymmetry of IFU spectroscopy data products, which until now have been simplified with radial profiles. Lastly, I emphasize the importance of follow up studies of the resolved molecular gas properties of merging galaxies to discern whether gas reservoir, depletion time, or both are driving the change in star-formation rate. / Graduate

L'approximation des objets naturels (courbes, surfaces ou images) par des formes fractales constitue aujourd'hui un important centre d'intérêt pour la recherche. Sous le nom générique de problème inverse, cette problématique intéresse en effet des domaines d'applications aussi divers que la représentation synthétique de l'information pour la transmission et la compression d'images, la reconstruction 3D pour la visualisation ou la CAO. Diverses études ont été menées pour répondre à ce problème inverse fractal. La plus connue est certainement la méthode dite de compression fractale d'images introduite par Jacquin. D'une manière générale, ces techniques existentes souffrent aujourd'hui d'un manque de souplesse en terme de contrôle sur la forme utilisée pour l'approximation. De plus, l'espace d'itération utilisé se limite à l'espace de visualisation, c'est à dire R². Des travaux antérieurs ont permis de dégager un modèle générique fractal : les formes fractales à pôles. Ce modèle, par l'intermédiaire d'une projection, permet de définir les auto-similarités d'un objet dans un espace de dimension supérieure. Nous proposons une résolution du problème inverse basée sur ce modèle et sur un algorithme de régression non-linéaire. Cette méthode générale permet d'approximer des courbes et des surfaces, aussi bien lisses que rugueuses, ainsi que des images en niveaux de gris. Une extension hiérarchique du modèle est introduite pour la modélisation d'objets hétérogènes dont les caractéristiques varient dans l'espace. Deux algorithmes sont proposés pour résoudre le problème d'approximation associé. Le premier calcule, à partir d'une image et d'un critère de distorsion, le modèle qui uniformise cette distorsion. Le deuxième décrit une méthode complète d'optimisation du codage du modèle en vue de comprimer les images à partir d'un critère de débit. Les résultats montrent l'avantage de ce type de modèle dans le domaine de la compression à faible débit.