This thesis investigates physical processes in Lake Erie, a large, shallow mid-latitude lake, from two perspectives: climate change impacts on the thermal structure and dissolved oxygen concentration and small-scale eddy dynamics generated by internal Kelvin wave propagation. A three-dimensional hydrodynamic and aquatic ecological coupled model ELCOM-CAEDYM, validated by the field data collected in 2008, is first used to investigate the responses of the thermal structure and dissolved oxygen concentration in Lake Erie to potential changes in air temperature and wind speed. A new method is presented to define spatially and temporally varying regions for the epilimnion, thermocline, and hypolimnion. Four metrics are selected to quantify the characteristics of the thermal structure: mean epilimnion temperature, mean hypolimnion temperature, onset and breakdown of stratification, and thermocline depth. Exploiting the power of the three dimensional model to provide a more authentic characterization of thermal structure in such large lakes, it is shown that patterns inferred from simple isotherm dynamics, as typically done with one dimensional models, are not always accurate. In the dissolved oxygen studies similar analyses are presented. Three factors related to lake hydrodynamics have strong influences on hypolimnetic hypoxia: water temperature, stratification duration, and hypolimnion thickness. The present results show the potential for complicated and interactive effects of climate forcing on important biogeochemical processes in Lake Erie as well as other large mid-latitude lakes. Taking advantage of high performance computing, the generation of eddies when a baroclinic Kelvin wave propagates past a peninsula is studied using the MITgcm. The grid resolution can be refined from 2 km to 200 m in the parallel computing environment. With the finer resolution small-scale processes which cannot be resolved in the coarse resolution applied previously are able to be explored. The eddy dynamics are studied in detail in both an idealized lake and in Lake Erie. This work presents a first attempt at simulating small-scale hydrodynamic processes in large lakes and contributes to our understanding of how energy is moved from large scales (the scale of the basins in Lake Erie) to smaller scales (the scale of the peninsula or Point Pelee).

This thesis investigates physical processes in Lake Erie, a large, shallow mid-latitude lake, from two perspectives: climate change impacts on the thermal structure and dissolved oxygen concentration and small-scale eddy dynamics generated by internal Kelvin wave propagation. A three-dimensional hydrodynamic and aquatic ecological coupled model ELCOM-CAEDYM, validated by the field data collected in 2008, is first used to investigate the responses of the thermal structure and dissolved oxygen concentration in Lake Erie to potential changes in air temperature and wind speed. A new method is presented to define spatially and temporally varying regions for the epilimnion, thermocline, and hypolimnion. Four metrics are selected to quantify the characteristics of the thermal structure: mean epilimnion temperature, mean hypolimnion temperature, onset and breakdown of stratification, and thermocline depth. Exploiting the power of the three dimensional model to provide a more authentic characterization of thermal structure in such large lakes, it is shown that patterns inferred from simple isotherm dynamics, as typically done with one dimensional models, are not always accurate. In the dissolved oxygen studies similar analyses are presented. Three factors related to lake hydrodynamics have strong influences on hypolimnetic hypoxia: water temperature, stratification duration, and hypolimnion thickness. The present results show the potential for complicated and interactive effects of climate forcing on important biogeochemical processes in Lake Erie as well as other large mid-latitude lakes. Taking advantage of high performance computing, the generation of eddies when a baroclinic Kelvin wave propagates past a peninsula is studied using the MITgcm. The grid resolution can be refined from 2 km to 200 m in the parallel computing environment. With the finer resolution small-scale processes which cannot be resolved in the coarse resolution applied previously are able to be explored. The eddy dynamics are studied in detail in both an idealized lake and in Lake Erie. This work presents a first attempt at simulating small-scale hydrodynamic processes in large lakes and contributes to our understanding of how energy is moved from large scales (the scale of the basins in Lake Erie) to smaller scales (the scale of the peninsula or Point Pelee).

Mechanisms controlling the productivity, abundançe and taxonomic composition of phytoplankton in tropical Lake Malawi were examined by monitoring phytoplankton dynamics in 8 regions covering the length of the lake (560 km) over a 10-12 month period, and relating these dynamics to spatio-temporal changes in thermal structure, nutrient availability, and meteorological conditions. In addition, nearshore benthic photosynthetic rates were measured in 7 different months.Spatial and temporal changes in areal photosynthetic rates were due almost entirely to changes in the efficiency of light utilization by the phyroplankton community. An evaluation of potential factors which might influence tight utilization indicates that nutrient availabitity is the most important. Most of the photosynthetic N and P demand is met by internal recycling within the upper 200 m, and therefore spatio-temporal variation of phytoplankton photosynthetic rate is closely related to changes in mixing regime. It is shown that the dominant meteorological factors responsible for changes in the mixing regime were solar radiation and windspeed. A comparison with previous photosynthesis data for Lake Malawi indicates that windspeed is a dominant factor controlling interannual variability. Shallow areas of the lake were more productive than deep areas, due to more intense upwelling and more efficient internal nutrient recycling in shallow waters. Within the littoral zone, benthic photosynthetic rates were very high, accounting for 14% to 28% of total net photosynthesis within the shallow southeast arm. Phytoplankton biomass was not correlated with photosynthetic rate, indicating that biomass loss processes were important in controlling biomass variability. Changes in phytoplankton taxonomic composition were related to changes in mixing regime. Cyanobacteria and chlorophytes were dominant throughout much of the study period, but diatoms made up a significant proportion of total biomass during periods of increased turbulence and nutrient availability. An analysis of phytoplankton surface area : volume ratios revealed that organism shape and size are important determinants in species succession. Previous studies have emphasized the low variability of phytoplankton biomass and photosynthetic rates in tropical lakes, relative to temperate lakes. An inter-lake comparison reveals that this tenet does not apply to large lakes. Fluctuations in the mixing regime of large tropical lakes have an effect on phytoplankton variability similar in magnitude to the effect of fluctuating solar irradiance in large temperate lakes.

Mechanisms controlling the productivity, abundançe and taxonomic composition of phytoplankton in tropical Lake Malawi were examined by monitoring phytoplankton dynamics in 8 regions covering the length of the lake (560 km) over a 10-12 month period, and relating these dynamics to spatio-temporal changes in thermal structure, nutrient availability, and meteorological conditions. In addition, nearshore benthic photosynthetic rates were measured in 7 different months.Spatial and temporal changes in areal photosynthetic rates were due almost entirely to changes in the efficiency of light utilization by the phyroplankton community. An evaluation of potential factors which might influence tight utilization indicates that nutrient availabitity is the most important. Most of the photosynthetic N and P demand is met by internal recycling within the upper 200 m, and therefore spatio-temporal variation of phytoplankton photosynthetic rate is closely related to changes in mixing regime. It is shown that the dominant meteorological factors responsible for changes in the mixing regime were solar radiation and windspeed. A comparison with previous photosynthesis data for Lake Malawi indicates that windspeed is a dominant factor controlling interannual variability. Shallow areas of the lake were more productive than deep areas, due to more intense upwelling and more efficient internal nutrient recycling in shallow waters. Within the littoral zone, benthic photosynthetic rates were very high, accounting for 14% to 28% of total net photosynthesis within the shallow southeast arm. Phytoplankton biomass was not correlated with photosynthetic rate, indicating that biomass loss processes were important in controlling biomass variability. Changes in phytoplankton taxonomic composition were related to changes in mixing regime. Cyanobacteria and chlorophytes were dominant throughout much of the study period, but diatoms made up a significant proportion of total biomass during periods of increased turbulence and nutrient availability. An analysis of phytoplankton surface area : volume ratios revealed that organism shape and size are important determinants in species succession. Previous studies have emphasized the low variability of phytoplankton biomass and photosynthetic rates in tropical lakes, relative to temperate lakes. An inter-lake comparison reveals that this tenet does not apply to large lakes. Fluctuations in the mixing regime of large tropical lakes have an effect on phytoplankton variability similar in magnitude to the effect of fluctuating solar irradiance in large temperate lakes.

The accessibility of the Martian atmosphere to spacecraft provides an opportunity to study an ionosphere that differs from our own. Yet, despite the half century of measurements made at Mars, the current state of the neutral atmosphere and its embedded plasma (ionosphere) remains largely uncharacterized. In situ measurements of the neutral and ionized constituents versus height exist only from the two Viking Landers from the 1970s. Subsequent satellite and remote sensing data offer sparse global coverage of the ionosphere. Thermal characteristics of the plasma environment are not well understood. Patchy crustal magnetic fields interact with the Martian plasma in a way that has not been fully studied. Hence, investigating the coupled compositional, thermal and crustal-field-affected properties of the ionosphere can provide insight into comparative systems at Earth and other planets, as well as to atypical processes such as the solar wind interaction with topside ionospheric plasma and associated pathways to escape. Ionospheric models are fundamental tools that advance our understanding of complex plasma systems. A pre-existing one-dimensional model of the Martian ionosphere has been upgraded to include more comprehensive chemistry and transport physics. This new BU Mars Ionosphere Model has been used to study the composition, thermal structure and dynamics of the Martian ionosphere. Specifically: the sensitivity of the abundance of ions to neutral atmospheric composition has been quantified, diurnal patterns of ion and electron temperatures have been derived self-consistently using supra-thermal electron heating rates, and the behavior of ionospheric plasma in crustal field regions was simulated by constructing a two-dimensional ionospheric model. Results from these studies were compared with measurements and show that (1) ion composition at Mars is highly sensitive to the abundance of neutral molecular and atomic hydrogen, (2) lighter ions heat up more efficiently than heavier ones and provide additional heating sources for cooler plasma, and (3) crustal field morphology affects plasma dynamics and structure at Mars in a way that is consistent with observations. Finally, model predictions of ion composition and plasma temperatures are provided for observations to be made by several instruments on board the upcoming 2013 MAVEN orbiter.

Na Dissertação de Mestrado foi realizado um estudo sobre o comportamento de vigas mistas de aço e concreto biapoiadas sob iteração completa, compostas por perfis classificados como compactos em situação de incêndio. Apesar de ditas biapoiadas, a ideia principal da Dissertação é considerar, na análise em situação de incêndio, a reserva de capacidade existente nas extremidades dessas vigas, usualmente desprezada no dimensionamento à temperatura ambiente, provinda da continuidade da armadura longitudinal negativa presente na laje de concreto, sendo possível dispensar o revestimento contra fogo nesses elementos. Serão abordados, de início, os métodos de dimensionamento ao Estado-Limite Último de vigas mistas à temperatura ambiente, a fim de explicar o comportamento estrutural desse tipo de elemento, dando base para a posterior análise térmica. A análise térmica foi realizada, em uma primeira etapa, por métodos simplificados segundo normas vigentes e tomando hipóteses simplificadoras em que se desprezam esforços indiretos provocados pela dilatação térmica e gradiente térmico, sendo possível aplicar os conceitos no dia a dia de projeto. Numa segunda etapa foi realizada análise termestrutural com modelos numéricos para estudar o comportamento e colapso da viga, sendo os resultados suficientes para validar os valores de TRF encontrados por análise simplificada seguindo métodos normativos. Como conclusão, o ganho de capacidade estrutural da viga, proporcionado pela adoção da ligação mista no apoio, foi suficiente para situações de TRRFs entre 15 min e 21 min, no caso de perfis mais leves, com geometria própria para serem utilizados como vigas de piso de edifícios. Análises mostraram que não é possível justificar a ausência de revestimento contra incêndio para TRRFs de 30 min ou superiores. Tempos inferiores podem ser adotados de acordo com o denominado método do tempo equivalente, limitado a 15 min e são mais usuais para edificações de pequeno porte. / A study will be carried out on the behavior of simply supported, full interaction composite steel and concrete beams composed by compact profiles in fire situation. Despite being designed as simply supported, the main idea is to consider, in the fire situation analysis, the moment resistance capacity reserve on the beam supports, usually neglected during room temperature design, due to the upper longitudinal reinforcement present in the concrete slab, being possible to dispense fireproof coating in these elements. First, room temperature design procedures of composite beams will be approached in order to explain the structural behavior of this type of elements, providing a basis for subsequent thermal analysis. The thermal analysis will be carried out, in a first stage, by simplified methods according to design procedures and adopting simplifying hypotheses in which indirect stresses caused by thermal expansion and thermal gradient are neglected, being possible to apply those concepts in structural design offices. In a second step, thermal stress analyses were performed with aid of numerical models to study the structural behavior and collapse time of the beam. The results were sufficient to validate the fire resistance time values found by the simplified analysis following design methods. As a conclusion, the structural capacity increase of the beam, provided by the adoption of the composite connection at the support in case of lighter steel profiles usually chosen to be used as buildings floor beams, was sufficient for situations of standard fire resistance requirements between 15 min and 21 min. Analyzes have shown that it is not possible to justify the absence of fire resistant coating for standard fire resistance requirements of 30 min or higher. Lower times can be adopted according to the so-called equivalent time method, limited to 15 min, which are more common for small buildings.

The thermal structure of subduction zones depends on the age-controlled thermal state of the subducting slab and mantle wedge flow. Observations indicate that the shallow part of the forearc mantle wedge is stagnant and the slab-mantle interface is weakened. In this dissertation, the role of the interface strength in controlling mantle wedge flow, thermal structure, and a wide range of subduction zone processes is investigated through two-dimensional finite-element modelling and a global synthesis of geological and geophysical observations. The model reveals that the strong temperature-dependence of the mantle strength always results in full slab-mantle decoupling along the weakened part of the interface and hence complete stagnation of the overlying mantle. The interface immediately downdip of the zone of decoupling is fully coupled, and the overlying mantle is driven to flow at a rate compatible with the subduction rate. The sharpness of the transition from decoupling to coupling depends on the rheology assumed and increases with the nonlinearity of the flow system. This bimodal behaviour of the wedge flow gives rise to a strong thermal contrast between the cold stagnant and hot flowing parts of the mantle wedge. The maximum depth of decoupling (MDD) thus dictates the thermal regime of the forearc. Observed surface heat flow patterns and petrologically and geochemically estimated mantle wedge temperatures beneath the volcanic arc require an MDD of 70-80 km in most, if not all, subduction zones regardless of their thermal regime of the slab. The common MDD of 70-80 km explains the observed systematic variations of the petrologic, seismological, and volcanic processes with the thermal state of the slab and thus explains the rich diversity of subduction zones in a unified fashion. Models for warm-slab subduction zones such as Cascadia and Nankai predict shallow dehydration of the slab beneath the cold stagnant part of the mantle wedge, which provides ample fluid for mantle wedge serpentinization in the forearc but little fluid for melt generation beneath the arc. In contrast, models for colder-slab subduction zones such as NE Japan and Kamchatka predict deeper dehydration, which provides greater fluid supply for melt generation beneath the arc and allows deeper occurrence of intraslab earthquakes but less fluid for forearc mantle wedge serpentinization. The common MDD also explains the intriguing uniform configuration of subduction zones, that is, the volcanic arc always tends to be situated where the slab is at about 100 km depth. The sudden onset of mantle wedge flow downdip of the common MDD overshadows the thermal effect of the slab, and the resultant thermal field and slab dehydration control the location of the volcanic arc. The recognition of the fundamental importance of the MDD has important implications to the study of geodynamics and earthquake hazard in subduction zones.

Na Dissertação de Mestrado foi realizado um estudo sobre o comportamento de vigas mistas de aço e concreto biapoiadas sob iteração completa, compostas por perfis classificados como compactos em situação de incêndio. Apesar de ditas biapoiadas, a ideia principal da Dissertação é considerar, na análise em situação de incêndio, a reserva de capacidade existente nas extremidades dessas vigas, usualmente desprezada no dimensionamento à temperatura ambiente, provinda da continuidade da armadura longitudinal negativa presente na laje de concreto, sendo possível dispensar o revestimento contra fogo nesses elementos. Serão abordados, de início, os métodos de dimensionamento ao Estado-Limite Último de vigas mistas à temperatura ambiente, a fim de explicar o comportamento estrutural desse tipo de elemento, dando base para a posterior análise térmica. A análise térmica foi realizada, em uma primeira etapa, por métodos simplificados segundo normas vigentes e tomando hipóteses simplificadoras em que se desprezam esforços indiretos provocados pela dilatação térmica e gradiente térmico, sendo possível aplicar os conceitos no dia a dia de projeto. Numa segunda etapa foi realizada análise termestrutural com modelos numéricos para estudar o comportamento e colapso da viga, sendo os resultados suficientes para validar os valores de TRF encontrados por análise simplificada seguindo métodos normativos. Como conclusão, o ganho de capacidade estrutural da viga, proporcionado pela adoção da ligação mista no apoio, foi suficiente para situações de TRRFs entre 15 min e 21 min, no caso de perfis mais leves, com geometria própria para serem utilizados como vigas de piso de edifícios. Análises mostraram que não é possível justificar a ausência de revestimento contra incêndio para TRRFs de 30 min ou superiores. Tempos inferiores podem ser adotados de acordo com o denominado método do tempo equivalente, limitado a 15 min e são mais usuais para edificações de pequeno porte. / A study will be carried out on the behavior of simply supported, full interaction composite steel and concrete beams composed by compact profiles in fire situation. Despite being designed as simply supported, the main idea is to consider, in the fire situation analysis, the moment resistance capacity reserve on the beam supports, usually neglected during room temperature design, due to the upper longitudinal reinforcement present in the concrete slab, being possible to dispense fireproof coating in these elements. First, room temperature design procedures of composite beams will be approached in order to explain the structural behavior of this type of elements, providing a basis for subsequent thermal analysis. The thermal analysis will be carried out, in a first stage, by simplified methods according to design procedures and adopting simplifying hypotheses in which indirect stresses caused by thermal expansion and thermal gradient are neglected, being possible to apply those concepts in structural design offices. In a second step, thermal stress analyses were performed with aid of numerical models to study the structural behavior and collapse time of the beam. The results were sufficient to validate the fire resistance time values found by the simplified analysis following design methods. As a conclusion, the structural capacity increase of the beam, provided by the adoption of the composite connection at the support in case of lighter steel profiles usually chosen to be used as buildings floor beams, was sufficient for situations of standard fire resistance requirements between 15 min and 21 min. Analyzes have shown that it is not possible to justify the absence of fire resistant coating for standard fire resistance requirements of 30 min or higher. Lower times can be adopted according to the so-called equivalent time method, limited to 15 min, which are more common for small buildings.

This diploma thesis evaluates the influence of a thermal insulation of a structure on expenses related to its operation. It addresses the issues of a thermal insulation, energy loss, energy consumption, and evaluates the recovery of investments considering the insulation costs. It also monitors the insulation price projection on the total cost of the property.

This thesis focuses on the comparison of numerical simulation and optical measurement of deformation of the turbinehousing made by Honeywell company. The numerical calculation performed by finite element method to simulate transient thermal load on the measured entity. Numerical result of the strain state of the body caused by temperature gradients. To verify the simulation is used an experimental digital correlation method VIC-3D. The thesis also mentioned the theoretical foundations of digital correlation methods and thermal analysis.