A microfluídica atua em áreas como controle de fluxo, e \"química e ciências da vida\". Nesta última área encontram-se dispositivos como micro-agulhas, micro-separadores, microdispensadores, micro-reatores e micromisturadores. Em particular, micromisturadores podem estar presentes nas mais variadas aplicações na industria e na ciência, que necessitam de mistura de fluidos. Uma dessas aplicações é a encapsulação de ativos por uma matriz polimérica (micro-esferas poliméricas) para sistemas de liberação controlada. Nos processos convencionais de encapsulação uma das etapas cruciais é a produção de emulsões simples e múltiplas, que é o resultado do processo de mistura de dois líquidos imiscíveis. A introdução de micromisturadores para formação de emulsões é uma alternativa tecnológica que foi explorada neste trabalho. Portanto, foi realizado um estudo de pré-formulação, no qual foram produzidas micro-esferas poliméricas sem nenhum ativo encapsulado através de n misturadores microfluídicos diferentes. Os dispositivos mais eficientes foram identificados através das características das micro-esferas produzidas, tais como: diâmetro médio de partícula, índice de dispersão da distrib uição de partículas e morfologia (forma geométrica). Identificados os dispositivos, parâmetros de processo foram estudados, tais como: vazão e formulação. Os resultados obtidos indicaram que é possível produzir micro-esferas poliméricas com suas principais características controladas: tamanho e índice de dispersão. / Microfluidics actuates in areas as flow control, and \"chemistry and life sciences\". In this latter area appear devices as microneedles, microseparators, microdispensers, micro-reactors and micromixers. In particular, micromixers can be found in several applications in industry and science where it is needed fluid mixing. One of these applications is the asset encapsulation of a polymeric matrix (polymeric microspheres) for controlled release systems. In conventional processes of encapsulation one of crucial steps is the production of simple or multiple emulsions, which is the result of the mixing process of two immiscible liquids. Utilization of micromixers for emulsion preparation is a technological alternative that is explored in this work. Therefore, it was realized a pre-formulation study, for production of polymeric microspheres without any asset encapsulated, through several microfluidic mixers. The more efficient devices were ident ified through characteristic parameters of produced microspheres, such as: particle average diameter, dispersion index of particle size distribution and morphology (geometric shape). After device identification, process parameters were studied, such as: flow rate and formulation. Obtained results indicated that it is possible to produce polymeric microspheres with its main controlled characteristics: size and dispersion index.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-03-06T15:55:06Z No. of bitstreams: 1 annapaulaguidaferreira.pdf: 5817854 bytes, checksum: 306e931a0420692a140c4efe990dcec9 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-06T20:26:02Z (GMT) No. of bitstreams: 1 annapaulaguidaferreira.pdf: 5817854 bytes, checksum: 306e931a0420692a140c4efe990dcec9 (MD5) / Made available in DSpace on 2017-03-06T20:26:02Z (GMT). No. of bitstreams: 1 annapaulaguidaferreira.pdf: 5817854 bytes, checksum: 306e931a0420692a140c4efe990dcec9 (MD5) Previous issue date: 2011-08-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O concreto é um meio extremamente complexo, cujas propriedades ainda não são totalmente compreendidas. As dificuldades encontradas na descrição e previsão do comportamento de estruturas de concreto devem-se a aspectos relacionados à heterogeneidade do meio - que é poroso e multifásico - podendo conter em seu interior fluidos na forma líquida e gasosa. Quando exposto a condições de temperatura elevada, tais dificuldades são ainda maiores, devido à ocorrência de fenômenos físicos e químicos, que alteram a estrutura porosa e as propriedades do meio. Como a reação de hidratação do cimento é reversível e termoativada, a exposição do concreto a temperaturas elevadas pode ter efeitos deletérios, com a ocorrência de desidratação da matriz a base de cimento, fissuração devido a pressões internas geradas pela evaporação da àgua de amassamento remanescente da mistura e ao desplacamento superficial (\spalling"). Este trabalho consiste no estudo do comportamento termo-hídrico de estruturas compostas por bicamadas rocha-concreto - comumente encontradas em túneis e repositórios subterrâneos. Foi desenvolvido um programa experimental consistindo em análises térmicas no qual corpos-de-prova bicamada feitos com dois tipos de concreto - convencional e de alto desempenho - foram submetidos a temperaturas de até 750ºC. Tais ensaios forneceram dados para a implementação de um modelo termo-hídrico desenvolvido no código Cast3m - que foi empregado para simular os mesmos experimentos desenvolvidos em laboratório. Os resultados numéricos permitem avaliar a qualidade do modelo proposto, e servem de base para futuros desenvolvimentos que levem em conta o acoplamento termo-hidro-mecânico na descrição do comportamento do material. / Concrete is an extremely complex material, whose properties are not yet fully understood. The difficulties in describing and predicting the behavior of concrete structures are due to aspects related to the heterogeneity of medium - which is porous and multiphase - presenting fluids in liquid and gas forms. When exposed to high temperature conditions, such difficulties are even increased because of the occurrence of physical and chemical phenomena, which alters the porous structure and properties of the material. As the cement hydration reaction is reversible and thermo-activated, exposure of concrete to elevated temperatures causes deleterious effects, such as dehydration of the cement-based matrix, cracking due to internal pressures generated by evaporation of free water and spalling. This work aims the study of the hygro-thermal behavior of structures composed of bilayers rock-concrete - commonly found in tunnels and underground repositories. It was developed an experimental program consisting of thermal analysis in which bilayer samples made of two types of concrete - conventional and high performance - were submitted to temperatures up to 750ºC. These tests provided data for the implementation of a hygrothermal model on the Cast3m code - which was used to simulate the same experiments developed in the laboratory. The numerical results allowed the evaluation of the quality of the proposed model, and serve as a basis for future developments that take into account the thermo-hydro-mechanical coupling to describe the material behavior.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-04-18T12:11:58Z No. of bitstreams: 1 thaisrossilopessoares.pdf: 4963413 bytes, checksum: 4bda9f5f51bc1fdb665a92c88b066713 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-04-20T11:51:33Z (GMT) No. of bitstreams: 1 thaisrossilopessoares.pdf: 4963413 bytes, checksum: 4bda9f5f51bc1fdb665a92c88b066713 (MD5) / Made available in DSpace on 2018-04-20T11:51:33Z (GMT). No. of bitstreams: 1 thaisrossilopessoares.pdf: 4963413 bytes, checksum: 4bda9f5f51bc1fdb665a92c88b066713 (MD5) Previous issue date: 2018-02-26 / O concreto é um dos materiais mais utilizados na construção civil. As três razões principais que justificam tamanha utilização são: a ótima resistência à água, a plasticidade do material quando fresco que facilita a sua moldagem e o preço e acessibilidade na maioria dos canteiros de obras. O concreto é um material heterogêneo e poroso cujo comportamento é extremamente complexo e cujas características não são totalmente compreendidas. Quando sujeito a condições ambientais extremas, como é o caso da exposição a temperaturas elevadas, esse material está suscetível a alterações físicas e químicas que podem influenciar no seu desempenho estrutural. Portanto, a previsão do comportamento deste material é complicada, pois o concreto, quando submetido a carregamentos térmicos, sofre alterações na sua estrutura porosa e nas propriedades do meio que podem influenciar seu desempenho macroestrutural térmico e mecânico. Dada a relevância do tema em estudo, o objetivo do presente trabalho é aprimorar o modelo em estudo, através da realização de análises paramétricas e da comparação entre os resultados obtidos e informações disponíveis na literatura. Especial atenção será dada aos resultados da saturação, uma vez que trabalhos anteriores denotaram a ocorrência de alguma discrepância relacionada a esta grandeza. O modelo estudado é um modelo termohídrico que descreve o comportamento do concreto submetido a carregamentos térmicos. Sua formulação matemática foi desenvolvida a partir do estudo acoplado das transferências de calor e massa no interior do concreto, quando exposto a altas temperaturas. O concreto é descrito como um sistema multifásico cujos vazios do esqueleto sólido são preenchidos com água no estado líquido e vapor de água. Quando exposto a temperaturas mais elevadas que a ambiente, diversos fenômenos, tais como condução de calor, difusão de vapor e fluxo de água no estado líquido, desidratação e evaporação são considerados. Esse modelo é discretizado utilizando o método das diferenças finitas e o método dos elementos finitos, e em seguida implementado no programa livre de cálculo por elementos finitos, o Cast3M – programa desenvolvido pelo DMT-CEA (Département de Mécanique et Technologie du Commissariat à l’ Énergie Atomique). A sua aplicação gera resultados numéricos de temperatura, saturação e pressão de vapor, os quais são utilizados para avaliar o desempenho do modelo. / Concrete is one of the most used material in construction. The three main reasons for such are: its excellent water resistance; its plastic consistency when fresh, which facilitates molding; its price and accessibility at most construction sites. Concrete is a heterogeneous and porous material whose behavior is extremely complex and whose characteristics are not fully understood. When subjected to extreme environmental conditions, such as exposure to high temperatures, this material is susceptible to physical and chemical changes that may influence its structural performance. Therefore, the prediction of this material behavior is complicated, since the concrete, when submitted to thermal loads, undergoes changes in its porous structure and in the properties of the medium, which may influence its macro-structural thermal and mechanical performance. Given the relevance of the subject under study, the objective of the present research is to improve the studied model by performing parametric analyzes and comparations with the results obtained with the information available in the literature. Special attention will be given to the saturation results, since previous work has indicated the occurrence of some discrepancy related to its magnitude. The model studied, is a thermohydric model that describes the behavior of the concrete submitted to thermal loads. Its mathematical formulation was developed applying the coupled study of heat and mass transfers in the interior of the concrete when exposed to high temperatures. The concrete is described as a multiphase system whose voids of the solid skeleton are filled with liquid water and water vapor. When exposed to higher temperatures than the environmental ones, several phenomena, such as heat, vapor diffusion and water flow in the liquid state, dehydration and evaporation are considered. The model is discretized using the finite difference method and the finite element method, and then implemented in the free finite element calculation program, Cast3M - a program developed by DMT-CEA (Département de Mécanique et Technologie du Commissariat à l’Energy Atomique). Its application generates numerical results of temperature, saturation and vapor pressure, which are used to evaluate the performance of the material.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23450号 / 理博第4744号 / 新制||理||1680(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 早川 尚男, 教授 佐々 真一, 教授 川上 則雄 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Separation technologies with polymeric membranes are widely studied and have a wide range of applications. The membrane's heart is a dense selective layer whose permeability should strongly depend on the permeating species' properties. In turn, permeability depends on the diffusivity and solubility of the permeating species in the selective layer, which are considered intrinsic properties of the polymer forming the selective layer. When developing new membrane materials, the ultimate objective is to exceed the famous "upper bound" limit by achieving simultaneously higher selectivity and higher permeability. This objective is impossible without a reliable and accurate characterization method to determine the selective layer's intrinsic transport properties. The time-lag method is the most common membrane characterization technique, initially developed for polymeric membranes. However, as the membrane technology and material science advance, the selective layer structure becomes more complex and not limited to organic polymers. As a result, the time-lag method needs to be reviewed and adapted to these more complicated cases, which was the main objective of this thesis. Numerical simulation of dynamic gas permeation experiments is a powerful tool to examine different aspects of the time-lag method. Therefore, we have established a comprehensive variable-mesh finite-difference scheme, which was used throughout the thesis. It allowed us to investigate the effect of different random and resolution errors and an extrapolation error on the resulting time lag of an ideal membrane. We then considered more complex systems, particularly those of glassy polymers and mixed matrix membranes, to investigate the effect of different transport mechanisms on the results of dynamic and steady-state gas permeation experiments. In parallel, we also focused on developing a novel gas permeation system that would monitor dynamic gas permeation experiments based on pressure decay at the feed side. All the existing constant-volume gas permeation systems rely on monitoring pressure to rise at the membrane's permeate side. Although this work is still ongoing, we have made considerable progress. Among the numerous contributions made through this thesis, there are three of particular significance. We have developed an analytical model to predict mixed matrix membranes' relative permeability with the uniformly dispersed non-permeable fillers of different shapes. The model requires three structural parameters arising from the filler's shape and size, and it is superior to all existing analytical models, including the famous Maxwell model. We have also demonstrated that the diffusivity of mixed matrix membranes determined by the time-lag method depends on the number of layers of dispersed particles. In the limiting case of a single layer of uniformly impermeable fillers, it is possible for the diffusivity determined by the time-lag method to be greater than that of the host polymer, which might appear as counterintuitive in the absence of defects at the polymer-particle interface. In the case of glassy polymers, it is possible to observe an upward deviation from the steady-state flux, resulting from a non-instantaneous equilibrium between permeating species in Henry's and Langmuir adsorption sites.

A numerical simulation of electrowetting on a dielectric was performed in COMSOL to grant insight on various parameters that play a critical role in system performance. The specific system being simulated was the Open Drop experiment and the parameters being investigated were the applied voltage, contact angle at the advancing triple point, and droplet overlap onto neighboring actuated electrodes. These parameters were investigated with respect to their effect on droplet locomotion performance. This performance was quantified by the droplets velocity and the dielectrophortic (DEP) force’s magnitude; the DEP force was calculated from integration of the Maxwell Stress Tensor, however, the force was not integrated into the simulation to assist with droplet movement. It was found that as the droplet overlap onto the neighboring electrode, or droplet radius to electrode size ratio, decreased, the droplet velocity increased. As the applied potential increased, and induced contact angle at the advancing triple point decreased, droplet velocity also increased. Both the decreasing overlap and increasing voltage had a linear effect on droplet velocity. As the droplet overlap increased, the rate of change of droplet velocity decreased as increasing voltages were considered. A 2D DEP calculation illustrated that an increase in voltage induced a tenfold increase in the corresponding DEP force; a linear relationship was found between droplet overlap and DEP force for the Open Drop size regime.

<p>  </p> <p>Laser powder bed fusion (L-PBF) is a relatively young metallurgical processing method which has many advantages over traditional casting and wrought based methods. Alloy systems suitable for this additive manufacturing (AM) process include Ti-6Al-4V, 316 stainless steel, Inconel 718 and 625 making it attractive for automotive, aerospace, and biomedical applications. Despite the potential, L-PBF is plagued by defects and inconsistent build qualities which make certification of critical components onerous. Additionally, experimental studies are difficult due to the cost of laser systems and feedstock material. Many researchers have turned to computational modeling as this allows for rigorous examination and isolation of the underlying physics to better understand where problems may arise, and where improvements can be made. However, models often fail to consider the role of systematic and statistical uncertainty while also relying heavily on assumptions and simplifications for computational efficiency. As such, there is no quantifiable metric for how reliable these models are. This work applies an uncertainty quantification (UQ) framework to computational models for L-PBF to understand the role of uncertainty and assumptions on model reliability as this provides insight into their limitations and potential areas of improvement.</p> <p>First, the UQ framework is applied to a finite volume melt pool transport model to evaluate the role of uncertainty and model assumptions on melt pool shapes and solidification dynamics. This includes the role of simulating the powder bed thermophysical properties, surface tension driven Marangoni convection, and the thermodynamic relation dictating latent heat release. The transport model is then weakly coupled to a cellular automata (CA) grain evolution model to propagate and quantify the uncertainty in the as-built microstructure including crystallographic texture formation. Further propagation of melt pool and microstructure uncertainty to the resulting mechanical properties to close the process-microstructure-property relations are discussed. Lastly, recommendations for future model development and research are presented. </p>

Spatiotemporal metabolic modeling of microbial metabolism is a step closer to achieving higher dimensionalities in numerical studies (in silico) of biofilm maturation. Dynamic Flux Balance Analysis (DFBA) is an advanced modeling technique because this method incorporates Genome Scale Metabolic Modeling (GSMM) to compute the biomass growth rate and metabolite fluxes. Biofilm thickness is pertinent because this variable of biofilm maturation can be measured in a laboratory (in vitro). Pseudomonas aeruginosa (P. aeruginosa) is the model bacterium used in this computational model based on previous research conducted by Dr. Michael Henson, available GSMMs, and the societal significance of patients suffering from P. aeruginosa airway infections. Spatiotemporal Flux Balance Analysis (SFBA) will be the computational method used in this thesis to simulate biofilm growth. Another level of accuracy will be introduced to SFBA which is a dynamic finite difference grid that will vary relative to the biofilm’s velocity of expansion/contraction. This novel idea is governed by a differential equation that defines the biofilm’s velocity and updates the spatial dependency of the finite difference grid which has never been done while utilizing GSMM. Environmental conditions (bulk concentrations of metabolites) are altered to investigate how varying nutrients (glucose, oxygen, lactate, nitrate) affected biofilm maturation.

No description available.

Hamnefjärden är ett havsområde utanför Oskarshamns kärnkraftverk som har en förhöjd temperatur jämfört med vad som har varit naturligt innan Oskarshamnsverket togs i bruk. Sedan dess har kylvattnet från anläggningen påverkat ekologin med konstanta plymer av varmvattentillförsel med hög temperatur. I och med detta har påverkan av dessa utsläpp undersökts med hjälp av en sammanställning av litteratur gällande de fysikaliska och biologiska påverkningarna som skett på Hamnefjärden. Mätningar där Hamnefjärden jämförts med ett referensområde, visar att den lokala ekologin har påverkats av varmvattnet till en grad. Stora temperaturskillnader i mynningen för kylvattnet visar på stor fysikalisk påverkan men de biologiska verkar mindre påtagliga. / Hamnefjärden is a sea area outside of Oskarshamn nuclear powerplant which has an increased temperature compared to what was natural before the powerplant was started. Ever since the cooling water from the powerplant has been affecting the ecology with constant plumes of inflow with heated water. This discharge has thus been investigated by compiling literature about the physical and biological effects on Hamnefjärden. Surveys, in which Hamnefjärden has been compared to a reference area, shows that the local ecology has been affected by the heated water somewhat. Large differences in temperature in the estuary of the coolingwater indicates large physical effects but the biological effects seem smaller.