O desempenho final das argamassas depende das matérias-primas e de suas proporções na formulação, pois estas determinam o comportamento do material na etapa de aplicação e a microestrutura final do material endurecido. Entre as patologias de revestimentos, a falha de aderência é um dos fenômenos mais freqüentes, sendo originada pela incompatibilidade entre o comportamento reológico da argamassa e a energia de lançamento utilizada, resultando em defeitos na interface argamassa substrato. A adequação das características reológicas das argamassas às solicitações envolvidas na aplicação fornece condições de processamento mais favoráveis para a obtenção das máximas propriedades finais do revestimento. Assim, o objetivo do trabalho é desenvolver critérios de formulação, baseados nas características das matérias-primas, nos modelos de empacotamento de partículas e nos comportamentos reológicos, de modo a obter um método de formulação de argamassas. O método de squeeze-flow foi desenvolvido com sucesso para avaliação reológica de argamassas, sendo as principais variáveis experimentais foram estudadas, assim como o efeito do tipo de mistura no comportamento reológico. Procedimento para quantificação da segregação pasta-agregado foi criado, tendo em vista o intenso efeito que este fenômeno exerce sobre o comportamento reológico em squeeze-flow, especialmente em baixas velocidades. Foi ainda comprovado que o squeeze-flow tem boa relação com a percepção do pedreiro, principalmente, nas etapas de lançamento e aperto. Diversas argamassas nacionais e européias foram caracterizadas, resultando em um mapeamento das características de formulação, do comportamento reológico e das propriedades no estado endurecido. Através da aplicação de conceitos de empacotamento e distância de separação de partículas, foi verificado que a otimização do empacotamento de agregados permite um melhor aproveitamento da pasta para promover argamassas com comportamento reológico mais adequado à aplicação ou com menor consumo de finos e água. As correlações estabelecidas entre as características no estado fluido e as propriedades no estado endurecido permitem prever o comportamento das propriedades no estado endurecido com boa confiabilidade. Por fim, são descritas diretrizes sistemáticas para a formulação de argamassas considerando requisitos de desempenho tanto no estado fresco quanto no endurecido. / The in-use performance of rendering mortars depends on the raw materials features and their content in the formulation, since they have major influence on the material behavior during emplacement, as well as, on its final properties. Adherence failure is one of the most frequent problems of this class of building materials, caused by the incompatibility between rheological behavior and the application process, generating mortar/substrate interface flaws. A rheological behavior more suitable to the application demands, provides appropriate conditions to obtain maximum final rendering properties. Therefore, the main goal of this work is to develop mix-design parameters based on raw materials features, particle packing models and rheological behavior, in order to create a mix-design method for mortars. Squeeze-flow technique was successfully adapted for the rheological evaluation of rendering mortars, and the most important experimental parameters were studied. The method is sensitive enough to measure rheological changes as a function of the mixing process applied. Considering that phase segregation plays an important role on the rheological behavior of concentrated suspensions especially at low speeds, a method was developed to measure paste-aggregate segregation. It was also established that the squeeze-flow agrees well with the workers perception during manual emplacement. Several Brazilian and European products were evaluated, and significant differences were determined on the formulation features, rheological behavior and hardened properties. Using models of particle packing and particle distance, it was verified that optimized packing of aggregates enhances rheological behavior and can also allow the reduction of water and fine particles consumption. The experimental relationships established between fresh characteristics, rheological behavior and final properties can be used to predict hardened features and properties with fair confidence. Lastly, mix-design suggestions are made considering both fresh and hardened performance.

This work detailed the physical and chemical characterization of oil water mixtures prepared using fresh and weathered Macondo related oils under different conditions of mixing energy/time and in the presence/absence of chemical dispersants. The results indicated that WAFs produced consistent, droplet free solutions for both source and weathered oils with concentration ranges that represented the soluble components of the oil used. Chemically enhanced WAFs prepared with the source oil generated a large amount of micron-size droplets; however the viscosity of the weathered oils were a limiting factor for the preparation of CEWAFs with weathered oils. Droplet size distributions were influenced by the amount of energy in the system and the oil weathering stage, when high energy WAFs were made the increase in weathering of the oil resulted in the formation of smaller droplets that were more stable over time.

Earth's species are disappearing at a rate unprecedented in human history, yet whether this loss will make the ecosystem "services" that support our civilisation more vulnerable to environmental change is poorly understood. This thesis investigates two different aspects of land surface modelling. It firstly models the role of biodiversity in ecosystem resilience using the Lotka-Volterra and single resource models to model diversity using competition coeffcients, stochastic noise and evolution inspired trait diffusion and then examines if higher diversity makes these simple models more resistant to temperature increases. It secondly develops a theoretical plant demography model, based on the continuity equation, to robustly represent forest size diversity. This avoids both the complexity and maintainability issues seen in Forest Gap models and improves the representation of land use and land cover change and of regrowth time-scales after disturbance, which can be unrealistic in some of the previous generation of Dynamic Global Vegetation Models (DGVMs), such as TRIFFID (Cox et al., 2001). While the Lotka-Volterra with competition coeffcients and the single resource with stochastic noise approaches are found to be impractical, the single resource model with trait diffusion successfully shows that higher diversity requires a faster critical rate of temperature change before system net primary productivity (NPP) collapses. The continuity equation model of vegetation demography is solved analytically with the size dependence of the growth rate approximated first by a power law and then with a quadratic. The power law solution can be reduced to a "self-thinning" trajectory, and the quadratic solution gives either a rotated sigmoid or 'U-shape' distribution of plant sizes, depending on the ratio of mortality to maximum growth gradient. The model is then extended to produce the basis of a new Dynamic Global Vegetation Model (DGVM) called "Robust Ecosystem Demography" (RED), adapting the plant physiology from TRIFFID DGVM to generate a size-dependent growth function. A proportion of the NPP from this growth is used for reproduction and the shading is modelled simply by random overlap. The model is found to better represent regrowth time-scales compared to TRIFFID and is also found to demonstrate an optimum proportion of NPP to reproduction which decreases with plant lifetime.

The structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar.

We address the problem of stochastic simulation of soil particle-size curves (PSCs) in heterogeneous aquifer systems. Unlike traditional approaches that focus solely on a few selected features of PSCs (e.g., selected quantiles), our approach considers the entire particle-size curves and can optionally include conditioning on available data. We rely on our prior work to model PSCs as cumulative distribution functions and interpret their density functions as functional compositions. We thus approximate the latter through an expansion over an appropriate basis of functions. This enables us to (a) effectively deal with the data dimensionality and constraints and (b) to develop a simulation method for PSCs based upon a suitable and well defined projection procedure. The new theoretical framework allows representing and reproducing the complete information content embedded in PSC data. As a first field application, we demonstrate the quality of unconditional and conditional simulations obtained with our methodology by considering a set of particle-size curves collected within a shallow alluvial aquifer in the Neckar river valley, Germany.

Superhydrophobic surfaces have gained attention as a potential mechanism for increasing condensation heat transfer rates. Various aspects related to condensation heat transfer are explored. Adiabatic, air-water mixtures are used to explore the influence of hydrophobicity on two-phase flows and the hydrodynamics which might be present in flow condensation environments. Pressure drop measurements in a rectangular channel with one superhydrophobic wall (cross-section approximately 0.37 X 10 mm) are obtained, revealing a reduction in the pressure drop for two-phase flow compared to a control scenario. The observed reduction is approximately 10% greater than the reduction that is observed for single-phase flow (relative to a classical channel). Carbon nanotubes have been used to create superhydrophobic coatings due to their ability to offer a relatively uniform nanostructure. However, as-grown carbon nanotubes often require the addition of a thin-film hydrophobic coating to render them superhydrophobic, and fine control of the overall nanostructure is difficult. This work demonstrates the utility of using carbon infiltration to layer amorphous carbon on multi-walled nanotubes to achieve superhydrophobic behavior with tunable geometry. The native surface can be rendered superhydrophobic with a vacuum pyrolysis treatment, with contact angles as high as 160 degrees and contact angle hysteresis less than 2-3 degrees. Drop-size distribution is an important aspect of heat transfer modeling that is difficult to measure for small drop sizes. The present work uses a numerical simulation of condensation to explore the influence of nucleation site distribution approach, nucleation site density, contact angle, maximum drop size, heat transfer modeling to individual drops, and minimum jumping size on the distribution function and overall heat transfer rate. The simulation incorporates the possibility of coalescence-induced jumping over a range of sizes. Results of the simulation are compared with previous theoretical models and the impact of the assumptions used in those models is explored. Results from the simulation suggest that when the contact angle is large, as on superhydrophobic surfaces, the heat transfer may not be as sensitive to the maximum drop-size as previously supposed. Furthermore, previous drop-size distribution models may under-predict the heat transfer rate at high contact angles. Condensate drop behavior (jumping, non-jumping, and flooding) and size distribution are shown to be dependent on the degree of subcooling and nanostructure size. Drop-size distributions for surfaces experiencing coalescence-induced jumping are obtained experimentally. Understanding the drop-size distribution in the departure region is important since drops in this size are expected to contribute significantly to the overall heat transfer rate.

No description available.

This study aims to find a relationship between the distribution of locals inside of Sweden and the municipalities’ relative concentration of foreigners. With the usage of data found in the website Statistics Sweden, we aim to investigate the existence of any relationship between the local population size of a municipality against the number of foreigners present in said municipalities, and see whether foreigners and immigrants are more concentrated in more populated municipalities rather than less populated ones. We aim to do this by utilizing multiple regression and dummy variables to identify whether there is a significant extra negative or positive effect on foreigners. The answer seems to be that foreigners are in fact more concentrated in more locally populated municipalities, rather than less populated ones

Emulsions constitute a wide range of natural as well as processed products. Pharmaceutical applications of emulsions include oral administration, parenteral delivery, ophthalmic medicine, topical and transdermal creams, and fluorocarbon-in-water emulsions for blood oxygenation. In the foods area many of the products like mayonnaise, margarine, ice-creams are emulsions by nature and some products can also be used for delivery of active ingredients (e.g. nutraceuticals) with potential health benefits. Emulsions are also encountered at many stages of petroleum recovery, transportation, and processing. Typically, emulsions are manufactured in a two-step process. First a coarse emulsion called a premix is made which is passed through a high-pressure homogenizer. Intense energy supplied in the high pressure homogenizer causes breakage of the coarse emulsion to a fine one with a tighter distribution. Population balance equation (PBE) models are useful for emulsions since they allow prediction of the evolution of the drop size distribution on specification of the two rate processes i.e., breakage of drops due to the flow field and coalescence of colliding drops. In our work, we developed a PBE model to describe emulsion breakage in a high pressure homogenizer. The focus of the work was breakage and conditions to keep coalescence to minimum were implemented. Two breakage rates representing two mechanisms i.e., turbulent inertial and turbulent viscous breakage were necessary for reproducing the bimodal nature of the distributions. We used mechanistic functions in the PBE model to develop a predictive model which could be extended to changes in formulation variables as well as process variables. Starting with the assumption of binary breakage, the model was refined to include multiple drop breakage. The developed model was found to be extensible to reasonable changes in oil concentration, surfactant concentration, continuous phase viscosity and constant ratio of oil to surfactant. Anomalies in pressure prediction encountered earlier were also corrected for by including some additional features like heating, maximum stable diameter, and number of daughter drops. A preliminary attempt was also made to use the developed model for designing experiments for making target emulsions with pre-specified properties.

No description available.