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Physics in Higher-Dimensional ManifoldsSeahra, Sanjeev January 2003 (has links)
In this thesis, we study various aspects of physics in higher-dimensional manifolds involving a single extra dimension. After giving some historical perspective on the motivation for studying higher-dimensional theories of physics, we describe classical tests for a non-compact extra dimension utilizing test particles and pointlike gyroscopes. We then turn our attention to the problem of embedding any given <i>n</i>-dimensional spacetime within an (<i>n</i>+1)-dimensional manifold, paying special attention to how any structure from the extra dimension modifies the standard <i>n</i>-dimensional Einstein equations. Using results derived from this investigation and the formalism derived for test particles and gyroscopes, we systematically introduce three specific higher-dimensional models and classify their properties; including the Space-Time-Matter and two types of braneworld models. The remainder of the thesis concentrates on specific higher-dimensional cosmological models drawn from the above mentioned scenarios; including an analysis of the embedding of Friedmann-Lemaitre-Robertson-Walker submanifolds in 5-dimensional Minkowski and topological Schwarzschild spaces, and an investigation of the dynamics of a <i>d</i>-brane that takes the form of a thin shell encircling a (<i>d</i>+2)-dimensional topological black hole in anti-deSitter space. The latter is derived from a finite-dimensional action principle, which allows us to consider the canonical quantization of the model and the solutions of the resulting Wheeler-DeWitt equation.
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Des modèles et des indicateurs pour évaluer la performance d'aires marines protégées pour la gestion des zones côtières. Application à la Réserve Naturelle des Bouches de Bonifacio (Corse) / Models and indicators to assess the marine protected areas performance for coastal ecosystems management : application to the Bonifacio Strait Natural Reserve (Corsica)Rocklin, Delphine 12 April 2010 (has links)
Les dernières décennies ont été marquées la surexploitation de nombreux stocks de ressources marines. Po ur limiter ce déclin et restaurer les communautés impactées, l'instauration de mesures de gestion s'est révélée nécessaire. Les Aires Marines Protégées (AMP), initialement développées pour protéger les habitats remarquables et la biodiversité associée, sont de plus en plus utilisées en tant qu'outil de gestion spatialisée des activités de pêche.L'objectif de cette thèse était d'évaluer à l'aide d'indicateurs et de modèles prédictifs (i) l'impact de la mise en place de la Réserve Naturelle des Bouches de Bonifacio (Corse) sur les communautés de poissons et (ii) les bénéfices de ce type de gestion pour l'activité de pêche artisanale locale. Nous avons ensuite développé un modèle et testé (iii) les scénarios de gestion les mieux adaptés au maintien de la ressource de langouste rouge, en déclin dans la réserve, et à son exploitation durable. Les données de captures de la pêche artisanale du sud de la Corse nous ont permis de mettre en évidence l'impact de la pêche plaisancière sur la structure et la biomasse des communautés exploitées. Bien que la forte diminution de l'effort de pêche ait pu contribuer à une augmentation des captures par unité d'effort, l'analyse sous forme de groupes de réponse nous a permis de mettre en évidence une augmentation différenciée des captures de la pêche artisanale en fonction de l'intérêt des espèces pour la chasse au harpon. De plus, nous avons remarqué que la réglementation de la RNBB ne semble pas suffire à la protection d'une espèce emblématique, la langouste rouge. Les indicateurs issus de l'outil de modélisation ISIS-Fish nous ont permis de constater la nécessité d'une restriction plus importante de l'accès à cette ressource dans l'objectif d'une pêche durable. / These last decades have been characterized by a great development of fishing techniques, contributing to the overexploitation of numerous marine fish stocks. In order to limit this collapse and to restore impacted communities, the implementation of management measures was necessary. Marine Protected Areas (MPAs), initially developed to protect remarkable habitats and associated biodiversity, are more and more used as a tool for spatial management of fishing activities, by adult export and/or larvae migrations from protected zones to surrounding fisheries.The aim of this PhD was to evaluate using indicators and predictive models (i) the impact of the Bonifacio Strait Natural Reserve (Corse) implementation on fish communities and (ii) the benefits of such management measures for the local artisanal fishery. We then developed a model and tested (iii) management scenarios for maintaining the spiny lobster resource, en decline in the reserve, into a sustainable exploitation way.Artisanal fishery catch data from south Corsica has permitted to highlight the indirect impact of recreational fishing on exploited fish communities structure and biomass. Whereas a decrease of the fishing effort may contribute to increasing catches per unit effort (CPUE), the analysis using response groups helped us to reveal differentiated increase of the artisanal fishery catches considering the interest of species to spearfishing. Moreover, we noticed than even if the BSNR legislation represents a benefit for many species, it is not sufficient for the emblematic red spiny lobster recover. Indicators issued from the ISIS-Fish model showed that higher restrictions on this resource access are necessary in the objective of sustainable fisheries.
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Biomass Potential for Heat, Electricity and Vehicle Fuel in SwedenHagström, Peter January 2006 (has links)
The main objective of this thesis was to determine how far a biomass quantity, equal to the potential produced within the Swedish borders, could cover the present energy needs inSwedenwith respect to economic and ecological circumstances. Three scenarios were studied where the available biomass was converted to heat, electricity and vehicle fuel. Three different amounts of biomass supply were studied for each scenario: 1) potential biomass amounts derived from forestry, non-forest land, forest industry and community; 2) the same amounts as in Case 1, plus the potential biomass amounts derived from agriculture; 3) the same amounts as in Case 1, plus 50% of the potential pulpwood quantity. For evaluating the economic and ecological circumstances of using biomass in the Swedish energy system, the scenarios were complemented with energy, cost and emergy analysis. The scenarios indicated that it may be possible to produce 170.2 PJ (47.3 TWh) per year of electricity from the biomass amounts in Case 2. From the same amount of biomass, the maximum annual production of hydrogen was 241.5 PJ (67.1 TWh) per year or 197.2 PJ (54.8 TWh) per year of methanol. The energy analysis showed that the ratio of energy output to energy input for large-scale applications ranged from 1.9 at electric power generation by gasification of straw to 40 at district heating generation by combustion of recovered wood. The cost of electricity at gasification ranged from 7.95 to 22.58 €/GJ. The cost of vehicle work generated by using hydrogen produced from forestry biomass in novel fuel cells was economically competitive compared to today’s propulsion systems. However, the cost of vehicle work generated by using methanol produced from forestry biomass in combustion engines was rather higher compared to use of petrol in petrol engines. The emergy analysis indicated that the only biomass assortment studied with a larger emergy flow from the local environment, in relation to the emergy flow invested from society after conversion, was fuel wood from non-forest land. However, even use of this biomass assortment for production of heat, electricity or vehicle fuels had smaller yields of emergy output in relation to emergy invested from society compared to alternative conversion processes; thus, the net contribution of emergy generated to the economy was smaller compared to these alternative conversion processes. / <p>QC 20120217</p>
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Environnement et mobilité 2050 : des scénarios sous contrainte du facteur 4 (-75% de CO2 en 2050) / Environment and mobility 2050 : scenarios for a 75% reduction in CO2 emissionsLopez-Ruiz, Hector G. 21 October 2009 (has links)
Afin de limiter les impacts du changement climatique sur la planète, les experts du Groupe Intergouvernemental d’experts sur l’Evolution du Climat (GIEC) préconisent une division par deux des émissions mondiales de gaz à effet de serre à l’horizon 2050. Cet objectif impose une division par quatre (i.e. facteur 4) des émissions de gaz à effet de serre des pays industrialisés comme la France. Le secteur des transports peut-il se plier à cette exigence ?A l’aide du modèle TILT (Transport Issues in the Long Term), centré sur les relations macroéconomiques entre croissance économique, technologies, mobilité et émissions de CO2, cette thèse recherche les conditions à réunir pour que soit atteint, en France, le « facteur 4 ». Si les progrès techniques annoncés par les ingénieurs sont au rendez-vous, nous pouvons atteindre un facteur 2. L’autre moitié du chemin doit donc être réalisée par une modification des comportements des individus et des entreprises. Trois familles de scénarios sont proposées pour en illustrer le contenu de ces évolutions. / In France an objective of dividing greenhouse gas emissions by four, from the 1990 level, by 2050 has been set. Are these ambitions out of our reach? What will the price to pay for this objective be?We have built a long-term backcasting transport demand model (TILT, Transport Issues in the Long Term). This model is centered on defined behavior types -in which the speed-GDP elasticity plays a key role- in order to determine demand estimations. This model lets us understand past tendencies -the coupling between growth and personal and freight mobility and adapt behavioral hypothesis -linked to the evolution of public policies- in order to show how a 75% reduction objective can be attained.The main results are an estimation of CO2 emissions for the transport sector taking into account technical progress and demand. These results are presented as three scenario families named: Pegasus, Chronos and Hestia. Each family corresponds to a growing degree of constraint on mobility.It is possible to divide greenhouse gas emissions in the transport sector by four. Technical progress is able to lead to more than half of these reductions. The interest of these scenarios is to show that there exist different paths –through organizational change- to getting the other half of the reductions.
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Impacts du changement global sur la biodiversité en mer Méditerranée : une approche par modélisation End-to-End / Impacts of global change on biodiversity in the Mediterranean Sea : and End-to-End modelling approachMoullec, Fabien 10 July 2019 (has links)
Sous les effets combinés de la surexploitation des ressources marines et du changement climatique la mer Méditerranée se transforme progressivement en un point chaud du changement global. En dépit d’un grand nombre de modèles développés localement ou régionalement en mer Méditerranée, aucun ne s’est encore attelé aux modifications d'assemblages d’espèces à l’échelle du bassin avec une modélisation intégrée des écosystèmes de la physique jusqu’aux prédateurs et représentant explicitement les dimensions à la fois multi-spécifique, spatiale, et trophique. Ces travaux de thèse présentent donc un triple enjeu : (i) mettre en œuvre une telle modélisation de la richesse spécifique en Méditerranée basée sur les traits de vie et représentant l'intégralité du cycle de vie d’espèces en interaction ; (ii) projeter les conséquences des changements physiques et biogéochimiques induits par le changement climatique sur la distribution spatiale des espèces et sur la structure et le fonctionnement trophique de l'écosystème méditerranéen ; (iii) explorer des scénarios de gestion des pêches visant à reconstituer certains stocks d'intérêts commerciaux dans un contexte de changement climatique. Pour répondre à ces enjeux, un modèle end-to-end, OSMOSE-MED, s’appuyant sur le couplage d’un modèle de hauts niveaux trophiques OSMOSE à des modèles de physique et de biogéochimie NEMOMED12 et ECO3M-S, a été développé. Avec cent espèces modélisées, représentant près de 95 % des captures effectuées en Méditerranée, il s’agit du premier modèle trophique de ce type intégrant une aussi grande richesse spécifique, sur une échelle spatiale aussi vaste (la mer Méditerranée dans son ensemble) et à fine résolution (20x20 km²). Selon le scénario d'émissions de gaz à effet de serre RCP8.5, les projections réalisées avec le modèle OSMOSE-MED mettent en évidence une augmentation globale de la biomasse et des captures, respectivement de 22% et 7% d'ici la fin du siècle. Ces augmentations masquent néanmoins de grandes disparités géographiques. Le bassin oriental se démarque par une augmentation globale de la biomasse associée aux espèces exotiques. Au regard des captures, le modèle prévoit des augmentations dans le bassin oriental et une diminution importante dans la partie occidentale. Un changement de la composition spécifique des captures pourrait apparaître au cours du 21ème siècle avec l'apparition d'espèces gagnantes (e.g. anchois) et perdantes (e.g. merlu). Les espèces gagnantes seraient principalement les espèces de petits pélagiques, thermophiles et/ou exotiques, de plus petites tailles et de plus bas niveaux trophiques tandis que les espèces perdantes seraient généralement les grands démersaux et pélagiques, pouvant pâtir d'un décalage spatial avec leurs proies potentielles à la suite d'une contraction ou d'un déplacement de leur aire de répartition géographique. Dans ce contexte, les projections de scénarios de gestion des pêches mettent en évidence les avantages d'une plus grande sélectivité ou d'une réduction de la mortalité par pêche pour reconstituer certains stocks d'intérêts commerciaux, en particulier parmi les organismes appartenant au groupe des démersaux, benthiques et grands pélagiques. Une réduction de la mortalité par pêche pourrait en outre inverser les tendances projetées à la baisse de la biomasse et des captures totales en Méditerrannée occidentale. / Under the combined effects of overexploitation of marine resources and climate change the Mediterranean Sea is gradually becoming a hotspot of global change. Despite a large number of models developed locally or regionally in the Mediterranean Sea, no previous studies have addressed changes in species assemblages at the basin scale with an integrated ecosystem modelling from physics to predators and explicitly representing the multi-species, spatial, and trophic dimensions. This thesis work presents a threefold challenge: (i) implementing such a model of the species richness in the Mediterranean Sea based on life history traits and representing the entire life cycle of interacting species; (ii) projecting the consequences of physical and biogeochemical changes induced by climate change on the spatial distribution of species and on the structure and trophic functioning of the Mediterranean ecosystem; (iii) exploring fisheries management scenarios aiming at rebuilding some stocks of commercial interest in a climate change context. To address these challenges, an end-to-end model, OSMOSE-MED, based on the coupling of a high trophic level OSMOSE model with NEMOMED12 and ECO3M-S physical and biogeochemical models, has been developed. With 100 modelled species, representing nearly 95% of the catches made in the Mediterranean Sea, it is the first trophic model of this type to integrate such a large diversity of species, on such a large spatial scale (the Mediterranean Sea as a whole) and at fine resolution (20x20 km²). According to the greenhouse gas emissions scenario RCP8.5, projections made with the OSMOSE-MED model show an overall increase in biomass and catches of 22% and 7% respectively by the end of the century. However, these increases mask large geographical disparities. The eastern basin is characterized by an overall increase in biomass associated with exotic species. With regard to catches, the model projects increase in the eastern basin and a significant decrease in the western part. A change in the species composition of catches could appear during the 21st century with winner (e.g. anchovy) and loser (e.g. hake) species. Winner species would mainly belong to the small pelagics group, are thermophilic and/or exotic, of smaller sizes and of low trophic level while loser species are generally large-sized, some of them of great commercial interest, and could suffer from a spatial mismatch with potential prey subsequent to a contraction or shift of their geographic range. Fisheries management scenario projections highlight the benefits of greater selectivity or reduced fishing mortality for the recovery of certain stocks of commercial interest, particularly among organisms belonging to the demersal, benthic and large pelagic groups. A reduction in fishing mortality could also reverse the projected decline in biomass and total catches in the Western Mediterranean.
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LONG RUN FOOD SECURITY IN NIGER: AGRICULTURAL PRODUCTIVITY, CLIMATE CHANGE AND POPULATION GROWTHKayenat Kabir (7152716) 14 August 2019 (has links)
<div>
<p>This dissertation examines long-run food security in Niger
in an era of climate change and comprises three interlinked essays. The first
essay investigates the socio-economic projections for Niger in the current
climate change literature in a growth accounting framework and provides a
critical assessment to evaluate global projections in the context of
a low-income developing country. The second essay quantifies the combined and
individual impacts of income, population growth, agricultural productivity,
and climate change on food security outcomes by mid-century in rural and
urban Niger. Finally, the third essay assesses three policy scenarios
considering accelerated investments in agricultural research and dissemination
(R&D), reductions in fertility rates, and regional market integration.</p>
</div>
<br>
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Mudanças climáticas e seus impactos na produtividade da cultura de milho e estratégias de manejo para minimização de perdas em diferentes regiões brasileiras / Climate change and its impacts on maize yield and crop management strategies to minimize yield losses in different Brazilian regionsBender, Fabiani Denise 01 August 2017 (has links)
O clima é um dos fatores ambientais que impõe os maiores riscos para a atividade agrícola, sendo responsável pelas oscilações e frustrações das safras no Brasil. Em cenário de mudanças climáticas, os atuais níveis de produtividade do milho de 1ª e de 2ª safra deverão ser alterados. Para se avaliar tais impactos, os modelos de simulação de culturas possibilitam estimar o crescimento, o desenvolvimento fenológico e a produtividade das culturas sob ampla gama de condições ambientais e de manejo, sendo, portanto, ferramentas eficientes para esse tipo de estudo. Considerando os possíveis impactos das mudanças climáticas na produtividade da cultura do milho, o presente estudo teve por objetivos: i) realizar preenchimento de falhas em séries de dados meteorológicos e, gerar séries sob projeções futuras do clima a curto (2010- 2039), médio (2040-2069) e longo (2070-2099) prazos, para os cenários de emissão intermediária (RCP4.5) e de alta emissão (RCP8.5); ii) calibrar e validar os modelos DSSAT/CERES-Maize e MONICA para simular a produtividade do milho de 1ª e de 2ª safra, e analisar a sensibilidade desses modelos, identificando os fatores de maior influência na produtividade do milho; iii) aplicar o modelo DSSAT/CERES-Maize, para determinar a produtividade do milho de 1ª e de 2ª safra, em condições de clima atual e futuro, e avaliar possíveis estratégias de manejo, de forma individual e combinada, como épocas de semeadura, ciclo da cultivar, irrigação e adubação nitrogenada, para minimização dos possíveis impactos. Para o preenchimento de falhas em séries de dados meteorológicos, o método de Bristow- Campbell (estimação da radiação solar), e a base em ponto de grade XAVIER foram as que apresentaram melhor desempenho. As projeções de clima futuro evidenciaram condições de clima mais quente, com redução no total acumulado de chuva nas regiões Norte-Nordeste e aumento no Sul do país, e as regiões Sudeste e Centro-Oeste configurando como áreas de transição. Os modelos DSSAT/CERES-Maize e MONICA apresentaram índice de desempenho (c) muito bom para ambas as safras, na estimação da produtividade do milho, com EAM inferior a 450 e 350 kg ha-1 na 1ª e na 2ª safra, respectivamente. Para as estimativas por conjunto, os valores de c foram avaliados como ótimos para as duas safras, com EAM caindo para 276 e 194 kg ha-1, na 1ª e na 2ª safra, respectivamente. Ambos os modelos mostraram sensibilidade às alterações climáticas e de adubação, porém com o modelo DSSAT/CERES-Maize se mostrando mais adequado para estudos de impactos de mudanças climáticas na cultura do milho. As simulações sob clima futuro com o modelo DSSAT/CERES-Maize, mostraram perdas de produtividade em relação aos atuais níveis, variando de 41 a 63% para milho da 1ª safra, e de 58 a 65% para o milho da 2ª safra, com as estratégias de manejo quanto a data de semeadura, ciclo da cultivar, irrigação e adubação nitrogenada mostrando redução das perdas e até mesmo ganhos de produtividade quando adotadas em condições de clima futuro. / Climate is one of the major environmental factors that impose the greatest risks for the agricultural activity, being responsible for the oscillations and frustrations of the crops in Brazil. In a scenario of climate change, the current yield levels of maize growing in-season and offseason should be impacted. In order to evaluate such impacts, crop simulation models allow estimating the growth, phenological development and yield under a wide range of environmental and crop management conditions, being efficient tools for applying to this kind of study. Considering the possible impacts of climate change on maize crop yield, the present study had as objectives: i) to fill gaps in meteorological data series and to generate series under future climate projections in the short (2010-2039), medium (2040-2069) and long (2070-2099) terms periods, for the intermediate emission (RCP4.5) and high emission (RCP8.5) scenarios; ii) to calibrate and validate the DSSAT/CERES-Maize and MONICA models to simulate inseason and off-season maize yield and to analyze the sensitivity of these models, identifying the factors that have the major influence on yield; (iii) to apply the DSSAT/CERES-Maize model to determine maize yield in the in-season and off-season, under current and future climate conditions, and evaluate possible crop management strategies, individually and in combination, such as sowing dates, crop cycle, irrigation and nitrogen fertilization, to minimize possible negative impacts. In order to fill the gaps in meteorological data series, the Bristow- Campbell method (for solar radiation estimation) and the XAVIER daily gridded database were the ones that presented the best performance. The projections of future climate showed warmer climate conditions, with a reduction in the rainfall amounts in the North-Northeast and an increase in the South of the country, with the Southeast and Center-West regions representing transition areas. Both DSSAT/CERES-Maize and MONICA models showed very good performance index (c) in the estimation of maize yield for both seasons, with MAE lower than 450 and 350 kg ha-1 during the in-season and off-season, respectively. For the ensemble estimation, the estimation improve, with optimal performance index, with MAE falling to 276 and 194 kg ha-1, for in-season and off-season maize growing, respectively. Both models showed sensitivity to climate change and fertilization, but with the DSSAT/CERES-Maize model being more suitable for studies of climate change impacts on maize crop. The simulations under future climate with DSSAT/CERES-Maize model showed a yield loss in relation to current levels, ranging from 41 to 63% for in-season, and from 58 to 65% for off-season, with management strategies regarding sowing date, cultivar cycle, irrigation and nitrogen fertilization, showing reduction of losses and even yield gains when adopted in the future climate conditions.
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Análise de processos de cenarização na geração hidroenergética. / Analysis of scenario processes in hydropower generation.Vilhena, Frederico Abdo de 25 September 2014 (has links)
O planejamento de médio e longo prazo da operação hidrelétrica brasileira consiste em um problema de grande porte e que envolve muitas variáveis, onde, dentre estas, se destacam as vazões afluentes aos reservatórios. Estas vazões devem assim ser estimadas, com o objetivo de caracterizar a oferta futura de eletricidade em um horizonte de planejamento. Dentre as possíveis abordagens existentes para estimar estas vazões, se destaca a abordagem estocástica, que permite considerar variáveis em função de sua distribuição probabilística, e busca considerar o universo mais provável de manifestações. A abordagem estocástica pode se utilizar de modelos estocásticos, que costumam ser caracterizados através de árvores de cenários, que representam o universo de possibilidades de ocorrências. No entanto, devido à elevada dimensionalidade que o processo estocástico pode resultar ao se considerar árvores muito grandes, torna-se necessária a utilização de técnicas complementares, que visem a redução do número de cenários. Com base nesta contextualização, esta dissertação aborda de modo geral o processo de otimização estocástica do planejamento da geração hidrelétrica, considerando árvores de cenários e técnicas de redução de cenários, e utilizando como meio a modelagem de otimização da geração desenvolvida no SSD HIDROTERM, em linguagem GAMS. Como estudo de caso, foram desenvolvidos e adaptados algoritmos de otimização estocástica que consideram árvores com elevado número de cenários, gerados por meio de modelos estocásticos autorregressivos do tipo PAR e, sobre estas árvores, foi ainda aplicada a ferramenta de redução de cenários por agrupamento - SCENRED, desenvolvida em GAMS. As análises de sensibilidade realizadas visaram: validar o processo proposto de otimização estocástica; analisar os efeitos da utilização de diferentes árvores reduzidas de cenários de vazões, o impacto da consideração de diferentes horizontes de planejamento e a influência do regime hidrológico nos principais resultados do processo de otimização; além de estudar as vantagens e desvantagens deste processo para o planejamento da operação hidrelétrica. Os resultados indicam que o processo de otimização estocástica é eficaz ao considerar as aleatoriedades envolvidas na previsão de vazões afluentes. Estes também confirmaram tendências já esperadas no processo de otimização estocástica, como o fato de que quanto maior a árvore de cenários, mais precisos e estáveis tendem os resultados; assim como que quanto mais cenários envolvidos, maior o tempo de processamento requerido. Neste contexto, a utilização da ferramenta de redução SCENRED permitiu reduções significativas no tamanho da árvore de cenários, sem, contudo, ocasionar em perdas na qualidade e estabilidade da solução, além de viabilizar a aplicação do algoritmo de otimização estocástica proposto. / The medium and long-term planning of the Brazilian electric system consists of a complex problem with many uncertainties and variables, where, among these the inflows to the reservoirs highlight. These inflows need to be estimated in order to characterize the future availability of electricity in a planning horizon. Among the existing approaches to estimate these inflows, highlights the stochastic approach, which consider these variables according to their probability distribution, and aims to consider the most likely universe of manifestations. The stochastic approach can be developed through stochastic models, which are often characterized by scenarios trees that represent the possible universe. However, due to the high dimensionality that stochastic analyses can result when considering very large trees, it becomes necessary to use complementary tools, aimed at reducing the number of scenarios. Based on this context, this dissertation discusses in general the process of stochastic optimization of the hydroelectric generation planning, considering scenarios trees and scenario reduction tools, through the optimization modeling developed in the DSS HIDROTERM, developed in GAMS language. As a case study, it was generated and adapted stochastic optimization algorithms that consider trees with large number of scenarios, generated by autoregressive stochastic models PAR. Based on these trees it was applied the scenario reduction tool SCENRED, developed in GAMS language. The sensitivity analyzes developed intended to: validate the stochastic optimization process; analyze the effects of using different reduced scenarios trees of inflows; analyze the impacts of considering different planning horizons, analyze the hydrological influence on the main results of the optimization process, and the benefits and disadvantages of this process in the hydroelectric operation planning. The results indicate that the stochastic optimization process is effective to consider the randomness involved in the prediction of inflow to the reservoirs. These results have also confirmed some well-known trends in the stochastic optimization process, such as the fact that the larger the tree scenarios, more accurate and stable tend the results but also greater the processing time required. In this context, the use of the reduction tool SCENRED allowed significant reductions in the size of scenarios tree, without causing losses in quality and solution stability, enabling the application of the stochastic optimization algorithm proposed.
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Instrumentalização do planejamento estratégico: aplicação no setor aeroviário comercial brasileiro / Strategic planning´s instrumentation: application in the commercial air transportation sectorSilva, Luiz Mauricio de Andrade da 14 February 2001 (has links)
Esta tese dá continuidade aos trabalhos de Vianna (1982, 1989), que discute o uso da subjetividade em previsões. A partir de uma crítica da visão objetivista preponderante na teoria administrativa, apresenta um método híbrido de análise do ambiente empresarial. Ainda como instrumento de análise é formulada uma matriz de confronto entre as expectativas dos administradores, declaradas em relatórios a acionistas, e as reais possibilidades circunstanciais indicadas pelo método híbrido. O confronto contribui para evidenciar possíveis conflitos de agência. Em seguida, o método híbrido proposto é aplicado por meio de um estudo de caso no setor aeroviário comercial brasileiro. / This thesis draws upon extends Viannas (1982, 1989) work on the use of subjectivity in administrative forecasts. Taking as a starting point a critical stance on objectivist conceptions in administrative theories, this thesis offers a hybrid method for the analysis of managerial environments. It also introduces a novel analytical category - a matrix which allows one to contrast, on the one hand, managerial expectations, declared in reports to the stockholders, and, on the other hand, actual circumstantial possibilities, such as revealed by the hybrid method. The contrast contributes to the identification of agency conflicts. Next, after description and discussion of the analytical categories adopted, the hybrid methodology is applied, through one case study, to the analysis of aspects of the Brazilian commercial air transportation sector.
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Perspectivas de integração modal rodo-hidro-ferroviária na exportação de produtos agrícolas e minerais no estado de Mato Grosso do Sul / Prospects for modal integration among hydro-road-rail in the export of agricultural products and minerals in Mato Grosso do SulGonçalves, Gilmerson Inácio 27 June 2008 (has links)
O Brasil tem como principal base econômica a exportação de commodities agrícolas e minerais. Esses produtos se caracterizam por possuírem grandes volumes de produção e baixo valor agregado. Diante desses fatos, as economias geradas ao longo da cadeia logística têm papel fundamental para o sucesso da comercialização destes produtos. Nesse contexto, este trabalho teve como objetivo encontrar as rotas de transportes mais econômicas para o escoamento da soja e minérios de ferro e manganês oriundos do estado do Mato Grosso do Sul com destino à exportação. Para tal foram identificados os pólos de geração destas cargas, assim como os modais de transportes existentes e futuros, terminais de transbordos e portos marítimos para exportação. Os métodos utilizados para esta análise foram a geração de cenários, modelos de custo de transporte para os modos rodoviário, ferroviário e fluvial; e sistema de informação geográfica. Os resultados obtidos neste trabalho indicam que opções de rotas com uso do modal hidroviário são as que possuem menores custos, com forte participação da hidrovia Paraguai-Paraná. Sugere-se para futuros trabalhos, a investigação da rede de transporte estudada com o uso de restrições de capacidade e também a inclusão dos custos portuários praticados nos portos marítimos de exportação. / Brazil has as the main economic base the exportation of agricultural and mineral commodities. These products are characterized by having a large quantity of production and low price. Given these facts, the saving generated along the supply chain are fundamental role in the marketing success of these products. In that context, this study aimed to find the most economic transport routes to the disposal of soybeans and iron ore and manganese from the state of Mato Grosso do Sul destined to exportation. For that were identified the places that generate as, and the transportation ways that exist up to now and the future ones, the terminals, transshipments and harbor for export. The methods used for this analysis were the generation of scenarios, models of cost of transport to the modes transport to road, rail and river, and geographic information system. The results obtained in this study indicate that options trades with the use of the waterway are those that have lower costs, with strong participation of the waterway Paraguay-Parana. It is suggested to future researches investigation of the transportation system studied the use of restrictions on capability and the inclusion of costs charged at seaports of exportation.
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