Made available in DSpace on 2016-04-26T20:48:52Z (GMT). No. of bitstreams: 1 Yim Kyu Lee.pdf: 844652 bytes, checksum: 4c191989a678bd58df27a6ae41c712ad (MD5) Previous issue date: 2008-09-30 / This dissertation analyses the period of weakening of the U.S. dollar in the 2001-2007 period and the three possible scenarios: (i) the maintenance and adjustment of the freefloating currency system, through the prolonged effects of the devaluation of the dollar, (ii) the protracted decline of the dollar as world currency, with the transfer of all or part of its role to another currency, with the Euro as most likely candidate, (iii) U.S. reaction in the style of the Volcker s shock in 1979-1980. It discusses whether there are limits to the setting in which the dollar, in the role of main reserve currency, is issued in large quantities to cover the U.S. current account deficits and whether the world will keep financing these deficits and paying significant margins of contribution to the United States, the so-called "exorbitant privilege" of the country issuing the world currency. The dissertation studies the formation of the freefloating dollar standard after the collapse of the Bretton Woods system in 1971-73 and the stages of its development, highlighting the period from 2001, which was marked by a sharp decline in the value the dollar. We draw attention to the similarities with the period of weakening of 1974-1980, which led to strong reaction from the United States with the high increase of interest and the imposition of credit controls, a process known as "Volcker s shock" / A dissertação analisa o período de enfraquecimento do dólar nos anos 2001-2007 e as alternativas colocadas no momento: (i) sustentação e ajustamento do sistema dólar flexível, por meio dos efeitos da desvalorização prolongada do dólar; (ii) declínio prolongado da posição do dólar como moeda mundial, com a transferência total ou parcial de seu papel para outra moeda, tendo o euro como candidato óbvio; (iii) reação dos EUA no estilo do choque de Volcker de 1979-1980. Discute-se se há limites para a configuração em que o dólar, no papel de moeda de reserva principal, é emitido em grandes quantidades em razão dos déficits em transações correntes norte-americanos, e se o mundo manterá o financiamento destes déficits pagando uma margem de contribuição expressiva para os Estados Unidos, o chamado "privilégio exorbitante" do país emissor da moeda mundial. A dissertação analisa a formação do padrão dólar-flexível, após a ruptura do sistema de Bretton Woods, em 1971-73, e as etapas de seu desenvolvimento, com destaque para os anos recentes, a partir de 2001, período marcado pelo declínio acentuado do valor do dólar. Destacam-se as semelhanças com o período de enfraquecimento de 1974-1980 que conduziu à forte reação dos Estados Unidos, com a forte elevação dos juros e a imposição de controles de crédito, processo conhecido como "choques de Volcker"

Globulettes have recently been found in the Rosette Nebula, the Carina Nebula and other nebulæ. They are expected to be seeds of brown dwarfs and free-floating planetary-mass objects. The size distribution in the Carina Nebula was found to follow a power-law, and the same power-function resulted in 880 +- 250 globulettes in total in the Rosette Nebula. Compared to the 145 observed objects in this nebula, many globulettes are beneath the resolution limit of the Nordic Optical Telescope, which was used to explore the Rosette Nebula. A simulation that arranged all these globulettes randomly in the nebula determined that some globulettes are captured by stars. They are believed to form into one or more planets, orbiting the star thereafter. The possibility that globulettes result into the formation of planets, orbiting a star, is some 4.75·10^2 per cent. According to this simulation, about 3.35·10^3 per cent of the stars with spectral type A to M host one or more planets that once have been globulettes. / <p>Validerat; 20101217 (root)</p>

Como tópico de fundamental importância na robótica, o planejamento de rotas tem encontrado excelentes resultados nos últimos anos através da utilização de algoritmos baseados no conceito de árvore de exploração rápida, RRT. No entanto, a aplicação desses métodos em sistemas robóticos espaciais revela um cenário ainda a ser explorado. O comportamento não-holonômico e a presença de singularidades dinâmicas são alguns fatores que dificultam a consideração de obstáculos no planejamento de rotas desses sistemas. Além disso, os trabalhos relacionados ao planejamento de movimento para manipuladores espaciais mostram-se concentrados na estratégia ponto-a-ponto, com interesse especial nos aspectos particulares da dinâmica desses sistemas. De modo geral, para manipuladores espaciais, o planejamento de trajetória envolvendo o desvio de obstáculos depende de uma rota previamente computada. Contudo, essa tarefa carece de formulações ou técnicas solidificadas, sobretudo para manipuladores espaciais de base livre flutuante. Com esta motivação, o trabalho proposto nesta dissertação de mestrado cria um planejador de rotas com suporte a desvio de obstáculos para um manipulador espacial planar de base livre flutuante. O modelo dinâmico utilizado é baseado no conceito de manipulador dinamicamente equivalente e incorporado a um algoritmo baseado no conceito de RRT. / As major challenge in the field of robotics, path planning has experienced successful results in recent years by means of the RRT algorithm. However, the application of such algorithms in space manipulators reveals a scenario yet to be explored. The non-holonomic behavior, added to the presence of dynamic singularities are only a few factors that make collision-avoidance path planning of these systems such a hard task. Besides, works in the field of motion planning of space manipulators often concentrate in the strategy pointto- point, with particular interest in the complex dynamics of such systems. As a rule of thumb, collision-avoidance for space manipulators depends on a previous computed path. However, this task still lacks robust formulations, specially in the case of free-floating manipulators. With this motivation, the proposed work creates a collision-avoiding path planning for a free-floating planar manipulator. The dynamic model is based on the Dynamically Equivalent Manipulator and the concept of Rapidly-Exploring Random Trees serves as a frame for the developed algorithm.

Neste trabalho, o equacionamento dinâmico de um manipulador espacial de base livre flutuante é descrito a partir do conceito do manipulador dinamicamente equivalente para que as técnicas de controle desenvolvidas sejam experimentalmente validadas em um manipulador convencional de base fixa. Dois tipos de controle de movimento são considerados. O primeiro foi desenvolvido no espaço das juntas e realiza o comando direto de posicionamento das juntas do manipulador; o segundo foi desenvolvido no espaço inercial e o controle é direcionado para o posicionamento do efetuador no espaço Cartesiano. Nos dois casos, o problema de acompanhamento de trajetória de um manipulador espacial com base livre flutuante sujeito a incertezas na planta e perturbações externas é proposto e solucionado sob o ponto de vista do critério de desempenho H \'INFINITO\'. Considerando métodos de controle para sistemas subatuados, três técnicas adaptativas foram desenvolvidas a partir de um controlador H \'INFINITO\' não-linear baseado na teoria dos jogos. A primeira técnica foi proposta considerando a estrutura do modelo bem definida, porém calculada com base em parâmetros incertos. Uma lei adaptativa foi aplicada para estimar esses parâmetros utilizando parametrização linear. Redes neurais artificiais são aplicadas nas outras duas abordagens adaptativas. A primeira utiliza uma rede neural para aprender o comportamento dinâmico do sistema robótico, considerado totalmente desconhecido. Nenhum dado cinemático ou dinâmico da base é utilizado neste caso. A segunda abordagem considera a estrutura do modelo nominal do manipulador bem definida e a rede neural é aplicada para estimar o comportamento das incertezas paramétricas e da dinâmica não-modelada da base. O critério H \'INFINITO\' é aplicado nas três técnicas para atenuar o efeito dos erros de estimativa. Resultados experimentais foram obtidos com um robô manipulador de base fixa subatuado (UArmII) e apresentaram melhor desempenho no acompanhamento da trajetória e no consumo de energia para as abordagens baseadas em redes neurais. / In the present work, the dynamics of a free-floating space manipulator is described through the dynamically equivalent manipulator approach in order to obtain experimental results in a planar fixed base manipulator. Control in joint and Cartesian spaces are considered. The first acts directly on joints positioning; the second control scheme acts on positioning the end-effector in some inertially fixed position. In both cases, the problem of tracking control with a guaranteed H-infinity performance for free-floating manipulator systems with plant uncertainties and external disturbances is proposed and solved. Considering control methods for underactuated systems, three adaptive techniques were developed from a nonlinear H-infinity controller based on game theory. The first approach was proposed considering a well defined structure for the plant, however it was computed based on uncertain parameters. An adaptive law was applied to estimate these parameters using linear parametrization. Artificial neural networks were applied in the two other approaches. The first one uses a neural network to learn the dynamic behavior from the robotic system, which is considered totally unknown. No kinematics or dynamics data from the spacecraft are necessary in this case. The second approach considers the nominal model structure well defined and the neural network is applied to estimate the behavior of the parametric uncertainties and of the spacecraft non-modeled dynamics. The H-infinity criterion was applied to attenuate the effect of estimation errors in the three techniques. Experimental results were obtained with an underactuated fixed-base planar manipulator (UArmII) and presented better performance in tracking and energy consumption for the neural based approaches.

Free floating electric scooters is a relatively new phenomena in many cities across the world and despite the Covid-19-pandemic, electric scooters are growing in popularity. There are however mixed opinions on whether electric scooters are environmentally friendly or not and if they are an option for municipalities to utilize in their planning towards more sustainable cities or not. Laws are also lacking for regulating this new means of transport. This study aims to examine how municipalities can plan for electric scooters in their traffic planning as well as examining if electric scooters work according to the municipalities’ visions for their future traffic planning. This study also aims to map out what Swedish cities have electric scooters today and examine what characteristics these cities have. The study has been conducted through interviews with two Swedish municipalities, one Norwegian municipality and one provider of free floating electric scooters. A literature review of several municipalities’ planning and strategy documents has been carried out as well. Findings show that free floating electric scooters exist in the most populous municipalities in Sweden. The municipalities have a high share of students and young people in the ages 18-35, which is the age group that tend to use electric scooters the most. The municipalities have a lower amount of days with snow-cover than the national average. Findings also show that municipalities are positive towards free floating electric scooters and think that they fit in with the overall visions for the municipalities’ planning.

Les marais filtrants artificiels sont des écosystèmes recréés par l’homme dans le but d’optimiser l’épuration des eaux usées. Lors de la sélection d’espèces végétales pour la mise en place de ces marais filtrants, l’utilisation d’une polyculture ainsi que d’espèces indigènes non invasives est de plus en plus recommandée. Néanmoins, la plupart des marais filtrants existants sont des monocultures utilisant des plantes envahissantes, probablement à cause du manque d’évidences scientifiques sur les avantages de la diversité végétale et de la performance des espèces locales. Ainsi, les questions de recherche autour desquelles s’oriente ma thèse sont: Les polycultures présentent-elles un potentiel épuratoire aussi ou plus grand que les monocultures, et une espèce indigène est-elle aussi efficace et performante qu’une espèce exotique envahissante dans des marais filtrants ? Trois expériences ont été conduites afin de répondre à ces questions. J’ai d’abord testé l’influence de la richesse végétale sur l’élimination des polluants en deux dispositifs expérimentaux: 1) comparant deux espèces de plantes émergentes en monoculture ou combinées séquentiellement, et 2) évaluant la performance de quatre espèces flottantes plantées en monoculture par rapport à des associations de deux (avec toutes les combinaisons possibles) et de quatre espèces. Une troisième expérience a été réalisée afin de comparer l’efficacité épuratoire de l’haplotype européen envahissant du roseau commun (Phragmites australis) et de la sous-espèce locale non-invasive (P. australis subsp. americanus). La composition en espèces végétales a produit un effet notable sur la performance des marais filtrants. La comparaison des performances en mono- et en polyculture n’a pas permis de démontrer clairement les avantages de la diversité végétale pour l’élimination des polluants dans les marais filtrants. Toutefois, les marais filtrants plantés avec une combinaison d’espèces étaient aussi efficaces que les monocultures des espèces les plus performantes. La comparaison entre les deux sous-espèces de P. australis indiquent que la sous-espèce indigène pourrait remplacer le roseau exotique envahissant, évitant ainsi les potentiels risques environnementaux sans toutefois compromettre l’efficacité du traitement. Les résultats prometteurs de la sous-espèce indigène de P. australis doivent encore être testés dans des expériences à grande échelle avant d’utiliser largement cette espèce dans les marais filtrants. Nos résultats suggèrent que, dans des conditions où la performance des macrophytes disponibles est inconnue ou ne peut être déterminée, l’utilisation d’une combinaison d’espèces présente les meilleures chances d’accomplir le plus haut niveau possible d’élimination de polluants. De plus, même si la diversité végétale ne présente pas un avantage mesurable en termes d’efficacité épuratoire, celle-ci améliore la résilience des marais filtrants et leur résistance aux stress et aux maladies. / Treatment wetlands (TWs) are complex engineered ecosystems designed to remove pollutants from wastewater. In selecting plant species for TWs, the use of polycultures as well as the choice of local non-invasive species is increasingly recommended. However, to date, the majority of TWs have been planted in monoculture using invasive species, probably because the performance of native species and the possible advantages associated with plant diversity have not been clearly demonstrated. The research questions of my thesis are: Are polycultures as good as or better than monocultures for pollutant removal, and could a native species be as efficient as an exotic invasive species in TWs? Three experiments were performed to answer this question. The influence of plant richness on pollutant removal was tested in two mesocosm experiments: 1) comparing two emergent plant species in monoculture and planted in sequence, and 2) evaluating four free-floating species, each in monoculture versus pairs of species (all possible combinations) and the four species planted together. A third experiment was carried out to compare the removal efficiency of the invasive European haplotype of common reed (Phragmites australis) and the native non-invasive subspecies (P. australis subsp. americanus). Plant species composition influenced the performance of TWs. The comparison of the performance of monocultures versus polycultures showed that, overall, TWs planted with a combination of species were as efficient as monocultures of the best performing species. Comparing the performance of native and invasive P. australis strongly suggests that the native could replace the invasive species in TWs, thereby avoiding possible environmental risks without compromising treatment efficiency. The promising results of the native P. australis subspecies need to be further tested in full-scale experiments in order to encourage the use of this species in TWs. The results obtained comparing plant species combinations suggest that under circumstances in which the performance of available macrophytes is unknown or cannot be determined, using a mixture of species offers the best chances of achieving the highest possible level of pollutant removal. Furthermore, it has been suggested that plant diversity contributes to TWs in terms of their resilience to stress and disease.