Submitted by DOUGLAS RICARDO DE ASSIS null (douglasnet9@hotmail.com) on 2016-03-10T00:50:50Z No. of bitstreams: 1 Dissertação de mestrado_Douglas Ricardo de Assis.pdf: 1652654 bytes, checksum: 93d244d8dfc88314c10a76a7d27326ef (MD5) / Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-03-10T19:37:31Z (GMT) No. of bitstreams: 1 assis_dr_me_araiq_par.pdf: 232607 bytes, checksum: 0428ae381482be9888a3bad4adaa01cc (MD5) / Made available in DSpace on 2016-03-10T19:37:31Z (GMT). No. of bitstreams: 1 assis_dr_me_araiq_par.pdf: 232607 bytes, checksum: 0428ae381482be9888a3bad4adaa01cc (MD5) Previous issue date: 2016-02-19 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A auto-organização é uma das ferramentas mais versáteis e mais poderosas para a estruturação de nanopartículas em duas ou três dimensões. A técnica de Langmuir - Blodgett é o método mais promissor para a produção de filmes bidimensionais organizados de tensoativos, polímeros e nanopartículas (NPs), porque proporciona um bom controle da espessura e a homogeneidade da monocamada e de multicamadas. Esse trabalho visa sintetizar nanopartículas de Ag na interface ar-água utilizando filmes de Langmuir-Blodgett de surfactantes como suportes. A síntese das NPs de Ag na interface ar/água foi realizada de acordo com a metodologia de Khomutov e colaboradores. Foi possível sintetizar as NPs de Ag através do espalhamento da mistura das soluções de sulfadiazina de prata e ácido esteárico com razão molar de 1:1. As imagens de microscopia eletrônica de varredura de alta resolução mostram que a ausência de ácido esteárico melhorou a organização das NPs durante a síntese na interface ar/água. A composição química das NPs de prata foi determinada através da espectroscopia de energia dispersiva de raios X acoplada ao microscópio eletrônico operando no modo de varredura. Um estudo comparativo foi feito preparando-se filmes de NPs de Ag. As nanopartículas de Ag recobertas com dodecil sulfato de sódio foram sintetizadas de acordo com o método descrito por Song. As nanopartículas de Ag recobertas com polietilenoglicol (MM ≈ 3400 g.mol-1) e com ácido oléico/oleilamina foram sintetizadas pelo método poliol. Os difratogramas de raios X confirmaram a composição e a fase obtida em cada amostra. Foi estudada a composição do recobrimento das NPs através da espectroscopia na região do infravermelho e quantificado através das análises termogravimétricas. A preparação dos filmes LB de todas as amostras foi feita de acordo com o método descrito por Shin. Através das imagens de microscopia eletrônica de varredura de alta resolução observa-se que somente os filmes LB das nanopartículas de Ag recobertas com ácido oléico e oleilamina apresentam uma organização a longo alcance. Durante a formação dos filmes das amostras recobertas com SDS e com PEG3400 as nanopartículas agregaram prejudicando a organização do sistema. Esse processo de agregação pode ser atribuído a falta de surfactante na superfície das NPs ou ao excesso de polímero que aprisiona as nanopartículas no meio de suas cadeias carbônicas interferindo na organização de NPs. / Self-assembly is one of the most powerful and versatile tools for structuring nanoparticles in two or three dimensions. The Langmuir–Blodgett (LB) technique is the most promising method for production of organized surfactants, polymers, and nanoparticles (NPs) two-dimensional films, because it provides good control of the thickness and homogeneity of the mono and multilayer. This paper aims to synthesize silver nanoparticles in the air-water interface using surfactants Langmuir-Blodgett films such as “templates”. The synthesis of Ag NPs in the air / water interface was performed according the Khomutov methodology [1] it was possible to synthesize Ag NPs by spreading the mixture of silver sulfadiazine solutions and stearic acid molar ratio 1: 1. Field emission gun scanning electron microscope (FEG-SEM) images show that the absence of stearic acid improved the arrangement of NPs during synthesis in the air / water interface. The chemical composition of silver NPs was determined by energy dispersive X-ray spectroscopy attached to the electron microscope operating in scan mode. A comparative study was made preparing Ag NPs films. The Ag nanoparticles coated with sodium dodecyl sulfate were synthesized according to the method described by Song. The Ag nanoparticles coated with polyethylene glycol (MW ≈ 3400 g / mol) and oleic acid / oleylamine was synthesized by the polyol method. The X-ray diffraction confirmed the composition and phase obtained in each sample. It studied the composition of the coating of NPs through spectroscopy in the infrared region and quantified through thermogravimetric analysis. The preparation of LB films of a silver nanoparticles covered with oleic acid and olelamine (Ag@AO/OL) was done according to the methodology described by Shin et al. The images obtained by electron microscopy high resolution scan can be observed that only the LB films of Ag nanoparticles coated with oleic acid and oleylamine have an organization-reaching. During the formation of the films of the other samples the aggregated nanoparticles damaging the system organization. This aggregation process may be attributed to the lack of surfactant on the surface of the NPs or excess polymer which entraps the nanoparticles in the middle of their carbon chains interfering with NPs organization. / CNPq: 139251/2013-8

O objetivo global deste trabalho foi fornecer subsídios para melhor compreender como as políticas públicas voltadas às emissões veiculares, incluindo o uso de etanol combustível, podem afetar a composição química da atmosfera. O peróxido de hidrogênio (H2O2) é um dos oxidantes mais importantes presentes na troposfera, podendo participar de reações com uma variedade de compostos orgânicos e inorgânicos. Neste trabalho, a determinação de H2O2, etanol, acetaldeído e outras espécies orgânicas e inorgânicas, foi realizada na fase gasosa, água de chuva e em águas superficiais. Foi utilizado de forma pioneira o método fluorimétrico baseado na formação do fluoróforo 2,7-diclorofluoresceína para determinar H2O2 em amostras de águas naturais (LD = 2 nmol L-1 e LQ = 7 nmol L-1). Enquanto outros métodos demandam a análise imediata da amostra, neste caso, o fluoróforo permanece estável por cerca de 48 h, facilitando as análises e o trabalho de campo. A concentração de H2O2 na água de chuva de Ribeirão Preto coletada de 2014 a 2017 variou entre 5,8 e 96 mol L1, com média ponderada pelo volume (MPV) de 28,9 ± 1,3 µmol L-1 (n = 88). Foi observado que a radiação solar foi um parâmetro mais importante na formação de H2O2 do que no seu consumo. Enquanto as concentrações MPV de sulfato (pH < 5) e nitrato na água de chuva decresceram em torno de 35% em 2017 com relação a 2014, as concentrações de H2O2 praticamente dobraram no mesmo período. A correlação negativa entre essas espécies evidencia que as políticas nacionais destinadas a reduzir as emissões veiculares podem alterar a capacidade oxidativa da atmosfera. As concentrações de H2O2, etanol e acetaldeído na fase gasosa em Ribeirão Preto (RP) e São Paulo (SP) foram determinadas, utilizando de forma pioneira no Brasil, o método de coleta do condensado. As concentrações de etanol na atmosfera de RP (15,0 ± 6,6 ppbv, n = 19) e SP (22,0 ± 9,4 ppbv, n = 10) foram relativamente próximas, apesar da frota veicular de SP ser ~ 16 vezes maior. Essas concentrações de etanol são cerca de 21 vezes maiores que aquelas relatadas nos Estados Unidos devido ao elevado uso de etanol combustível no Brasil. As médias das concentrações de H2O2 e acetaldeído na atmosfera foram, respectivamente, de 2,10 ± 1,46 e 16,3 ± 6,0 ppbv em RP; e 1,29 ± 0,62 e 14,4 ± 5,4 ppbv em SP. A avalição diurna mostrou que enquanto a concentração de H2O2 aumentou com a radiação solar, a concentração de etanol diminuiu numa taxa próxima da produção de acetaldeído. Esses resultados indicam que o H2O2 pode ser um oxidante importante de etanol a acetaldeído em fase gasosa, sendo este último de elevada toxicidade para o ser humano. Os fluxos na interface ar-água nos locais estudados em RP e SP mostram que o corpo dágua funcionou como um sumidouro de H2O2. Já o fluxo de etanol foi variável, isto é, ora invasivo e ora evasivo, com evidências de uma importante produção fotoquímica dessa espécie no meio aquático. / The main objective of this work was to provide insights to better understand how the public policies focused on vehicular emissions, including the use of ethanol fuel, can affect the chemical composition of the atmosphere. Hydrogen peroxide (H2O2) is one of the most important oxidants in the troposphere and it can participate in reactions with a variety of organic and inorganic compounds. In this work, determination of H2O2, ethanol, acetaldehyde and other organic and inorganic species was carried out in the gas phase, rainwater and surface water. The fluorimetric method based on the formation of the 2, 7-dichlorofluorescein fluorophore was applied for the first time to determine H2O2 in natural water samples (LOD = 2 nmol L-1 and LOQ = 7 nmol L-1). While other methods require the immediate analysis of the sample, in this case, the fluorophore remains stable for about 48 h, facilitating the analyzes and fieldwork. H2O2 concentrations in rainwater of Ribeirão Preto collected between 2014 and 2017 ranged from 5.8 to 96 mol L-1, with a volume-weighted mean (VWM) of 28.9 ± 1.3 mol L-1 (n = 88). The solar radiation was observed to be a more important parameter in the formation of H2O2 than in its consumption. While the VWM concentrations of sulfate (pH <5) and nitrate in rainwater declined by approximately 35% in 2017 compared to 2014, H2O2 concentrations virtually doubled over the same period. The negative correlation between these species shows that national policies aimed at reducing vehicle emissions may modify the oxidizing capacity of the atmosphere. Gas phase H2O2, ethanol and acetaldehyde concentrations in Ribeirão Preto (RP) and São Paulo (SP) were determined using, for the first time in Brazil, the method of condensate collection. Ethanol concentrations in the atmosphere of RP (15.0 ± 6.6 ppbv, n = 19) and SP (22.0 ± 9.4 ppbv, n = 10) were relatively close, although the SP vehicle fleet is ~ 16 times higher. These ethanol concentrations are about 21 times higher than those reported in the United States due to the high use of ethanol fuel in Brazil. The mean concentrations of H2O2 and acetaldehyde in the atmosphere were, respectively, 2.10 ± 1.46 and 16.3 ± 6.0 ppbv in RP; and 1.29 ± 0.62 and 14.4 ± 5.4 ppbv in SP. Daytime variation showed that while H2O2 concentration increased with solar radiation, ethanol concentration decreased at a rate close to the one of acetaldehyde production. These results indicate that H2O2 may be an important oxidant of ethanol to acetaldehyde in the gas phase, the latter being highly toxic to humans. Fluxes in the air-water interface at the studied sites in RP and SP show that the water body worked as an H2O2 sink. On the other hand, ethanol fluxes were variable, i.e., sometimes invasive and sometimes evasive, with evidence of an important photochemical production of this species in the aquatic environment.

O parâmetro que determina o processo de transferência de oxigênio através da interface ar-água em escoamentos com superficie livre é o coeficiente de reaeração superficial, \'K IND.2\'. Existe um grande número de equações na literatura científica que realizam a previsão do coeficiente de reaeração, no entanto, a maioria dessas equações considera apenas algumas características hidráulicas do corpo de água como a velocidade e a profundidade, e ainda, como em sua maioria são de natureza empírica, acabam sendo adequadas para corpos de água específicos. Além destes dois parâmetros (velocidade e profundidade do escoamento), existem outros doze que são considerados importantes para estudos de reoxigenação em águas superficiais. É neste contexto que o objetivo deste trabalho foi estudar em condições de laboratório a influência da rugosidade do leito de um canal sobre o coeficiente de reaeração superficial. Além da rugosidade, foram variadas as condições de velocidade média do escoamento e profundidade da lâmina de água. A variação da rugosidade foi realizada através da implementação de obstáculos com geometria conhecida, dispostos transversalmente ao escoamento, e denominados como macro-rugosidades. Os resultados demonstraram evidências de que o coeficiente de reaeração superficial é controlado de forma significativa pela rugosidade do leito do canal. Foram desenvolvidos dois modelos matemáticos de natureza semi-empírica para a previsão do \'K IND.2\', os quais incorporam variáveis hidrodinâmicas e geométricas consideradas relevantes para o processo de transferência de massa na interface ar-água. / The parameter that determines the process of oxygen transfer through the air-water interface in flows with free surface is the superficial reaeration coefficient, \'K IND.2\'. There are a large quantity of equations in the cientific literature that perform the prevision of the reaeration coefficient; however, most of them consider only some of the hydraulic characteristics of water body; for example, the velocity and the depth. Most of these equations have empirical origin and are adequate just for a specific water body. In addition to these two parameters (velocity and depth of flow), there are another twelve important parameters in reoxygenation studies in superficial waters. In this context, the aim of this work was to study the influence of bed roughness of a channel on the superficial reaeration coefficient, under laboratory conditions. Besides the roughness, the conditions of mean velocity of the flow and depth of water were varied. The variation of roughness was done with implementation of obstacles with known geometry, arranged transversely to the flow direction, and called macro-roughness. The results have shown evidences that the surface reaeration coefficient is controlled significantly by the roughness of the channel bed. Two mathematical models of semi-empirical origin for the \'K IND.2\' prevision were developed, which incorporate hydrodynamic and geometric variables considered relevant in the process of mass transfer in air-water interface.

This thesis deals with dependence of heat transfer coefficient on rate of air concentration in the water. Main idea appears from gas dissolvability in water depending on pressure, Henry's law and Newton's law of cooling. There had been an experiment made to verify the hypothesis.

This master`s thesis deals with low-temperature heating that employs a heat pump. The introduction gives reasons for utilization of the renewable heat sources for heating. The next part focuses on a practical application of renewables on the heating of a family house. It covers a detailed description of the building and the designed heating system which includes: the calculation of thermal losses, design of the low-temperature boiler, heat pump, safety devices, heating elements, sizing and control of the system. The last part is devoted to the assessment of the system performance.

Considérant une particule isolée, la différence principale entre un colloïde actif et un colloïde passif réside dans le temps de persistance du régime balistique. La transition du régime balistique vers le régime diffusif est déterminée dans les deux cas par des coefficients de friction ou de manière équivalente par des coefficients de diffusion. Le mouvement d’une particule colloïdale passive micrométrique est diffusif lorsqu’il est observé sur des intervalles de temps d’au moins une microseconde, suffisamment longs pour que la direction de la quantité de mouvement soit rendue aléatoire par des collisions avec les molécules de solvant. A l’échelle macroscopique ces collisions se traduisent par un coefficient de friction de translation. Pour une particule colloïdale active, un mouvement diffusif est observé pour des intervalles de temps de plusieurs secondes, suffisamment longs pour que la direction d’auto-propulsion soit rendue aléatoire par la diffusion rotationnelle de la particule.Dans cette thèse, nous étudions le mouvement d’une particule colloïdale active déposée à la surface de l’eau. Des particules Janus aux propriétés catalytiques ont été préparées par dépôt de platine métal à la surface de particules de silice. La profondeur d’immersion des particules ainsi que leur orientation par rapport à la surface de l’eau ont été caractérisées et discutées en tenant compte des propriétés de mouillage non-uniformes de la surface des particules Janus. Le mouvement de particules isolées en présence de quantités variables d’eau oxygénée utilisée comme source d’énergie, a été enregistré par vidéo-microscopie optique et les trajectoires analysées en termes de déplacement carré moyen et de fonction d’auto-corrélation des vitesses. L’observation de deux types de trajectoires, rectilignes et circulaires, révèle la force effective ainsi que le couple induit par la décomposition catalytique de l’eau oxygénée à la surface de la particule Janus. Le résultat principal de ce travail est que le mouvement des particules actives confinées à l’interface persiste plus longtemps dans le régime balistique que celui de particules actives totalement immergées en solution. Ceci est dû au confinement qui réduit le nombre de degrés de liberté de rotation mais aussi aux conditions de mouillage partiel qui font apparaître des contributions supplémentaires à la friction de rotation. / At the single-particle level, the main difference between active colloids and passive ones is the time scale over which the motion crosses over from ballistic to diffusive regime. In both cases, friction coefficients or equivalently diffusion coefficients determine this time scale. For instance, the motion of a passive colloid of 1m radius is diffusive when observed over lag times longer than a microsecond, once the direction of its momentum has been randomized by collisions with solvent molecules. At the macroscopic scale these collisions are accounted for by the translational friction coefficient. For an active colloid the effective diffusive behavior observed over lag times larger than few seconds results from the randomization of the direction of self-propulsion by rotational diffusion. In this thesis we investigated the motion of an active Janus colloid trapped at air-water interface. Spherical catalytic Janus colloids have been prepared through the deposition of platinum metal at the surface of silica particles. Immersion depth of the Janus colloid as well as their orientation with respect to the water surface, has been characterized and interpreted in terms of the non-uniform wetting properties of the Janus particles. The motion of the active Janus colloids in the presence of various concentration of hydrogen peroxide H2O2 as fuel was characterized by video microscopy and the trajectories analyzed through the mean square displacement and the velocity autocorrelation function. The types of trajectories, directional and circular ones that we observed in our experiments, revealed the effective force and torque induced by the catalytic decomposition of H2O2. At the water surface, active colloids perform more persistent directional motions as compared to the motions performed in the bulk. This has been interpreted as due to the loss of degrees of freedom resulting from the confinement at interface and also to the partial wetting conditions that possibly bring new contributions to the rotational friction at interface.

Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

Due to the high-speed flow in a chute spillway, cavitation damages often occur. This undesired phenomenon threatens the safety of the structure. For the purpose of eliminating the damages, an aerator is often installed in the spillway. To understand its characteristics, physical model tests are a popular method. To complement the model tests, computation fluid dynamics (CFD) simulations are used to study aerator flows. To represent the two-phase flows, multiphase models should be employed. This thesis examines two of them, namely, the Volume-Of-Fluid model (VOF) and Two-Fluid model. Based on the background of the Bergeforsen dam, the aerator flow is modelled by means of the VOF model. The simulated spillway discharge capacity is in accordance with the experimental data. Compared with the results, empirical formulas fail to evaluate the air supply capacity of aerator as it is wider than the conventional width. A hypothetical vent modification is proposed. For the original and proposed layouts, the study illustrates the difference in the air-flow conditions. The results show that a larger vent area is, for a large-width aerator, preferable in the middle of the chute. To study the flip bucket-shaped aerators in the Gallejaur dam, physical model tests and prototype observations are conducted. The results lead to contradicting conclusions in terms of jet breakup and air entrainment. A CFD model is, as an option, employed to explain the reason of the discrepancy. The numerical results coincide with the prototype observations. The jet breakup and air entrainment are evaluated from air cavity profiles; the air-pressure drops are small in the cavity. The discrepancy is due to overestimation of the surface-tension effect in the physical model tests. Based on the experimental data of an aerator rig at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, the Two-Fluid model is used to predict air concentration distributions in the aerated flow. The model includes relevant forces governing the motion of bubbles and considers the effects of air bubble size. The numerical results are conformable to the experiments in the air cavity zone. Downstream of the cavity, the air concentration near the chute bottom is higher, which is presumably caused by the fact that the interfacial forces in the Two-Fluid model are underestimated. / <p>QC 20170224</p>

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