Os poliuretanos provavelmente são os mais versáteis dentre os polímeros de maior uso industrial por ser possível serem produzidos em uma ampla faixa de densidade, dureza, propriedades mecânicas e por meio de diferentes processos de conversão. Sua síntese envolve uma grande variedade de matérias-primas e proporções entre elas. Um modelo matemático que descreve o processo de formação do poliuretano é bastante útil no desenvolvimento de formulações e definição das condições de processamento, evitando grande consumo de tempo e erros no desenvolvimento e em experimentos. Neste trabalho foi proposta uma modelagem matemática que considera o conhecimento dos parâmetros cinéticos da reação de formação do poliuretano e o equilíbrio líquido-vapor do sistema. Os parâmetros cinéticos da reação entre poliol com isocianato foram determinados utilizando o método de temperatura adiabático, obtendo-se os valores de energia de ativação Ea (kJ/g-eq) e entalpia de reação ?H (kJ/g-eq) de 24,1 e 39,2 respectivamente mostrando-se como uma adequada. O modelo de Flory-Huggins foi utilizado para o estudo do equilíbrio líquido-vapor do agente expansor hidrofluorolefina em mistura binária com poliol, por meio de experimentos realizados para medir as temperaturas e composição da mistura na condição de equilíbrio, evidenciando a não idealidade do sistema e mostrando-se satisfatório com desvio de 1,6% em relação aos dados de atividade a experimental. O modelo matemático foi satisfatório para descrever o processo, entretanto a metodologia para obtenção dos dados cinéticos para a reação de poliol-isocianato não permitiu a obtenção de um conjunto de parâmetros que ajustasse simultaneamente os dados experimentais do sistema com e sem agente expansor HFO. / Polyurethanes are probably the most versatile among polymers of greater industrial use due to the possibility of being produced in a wide range of density, hardness, mechanical properties and through different conversion processes. Its synthesis involves a great variety of raw materials and proportions between them. A mathematical model that describes the formation process of polyurethane can be very useful for the development of formulations and in the definition of the processing conditions, avoiding great consumption of time and errors in the development and experiments. The present work proposes a mathematical modeling that considers the knowledge of the kinetic parameters of the polyurethane reaction and the liquid-vapor equilibrium of the system. The kinetic parameters of the reaction between polyol with isocyanate were determined using the adiabatic temperature rise method, obtaining the values of activation energy Ea (kJ/g-eq) and heat of reaction ?H (kJ/g-eq) of 24.1 and 39.2 respectively. The methodology employed to estimate the kinetic data was adequate. The Flory-Huggins model was used for the study of the liquid-vapor equilibrium of the hydrofluorolefin blowing agent in binary polyol mixture, through experiments carried out to measure the temperature and composition of the mixture in the equilibrium condition, verifying the non-ideality of the system and in good agreement with experimental data of activity a with deviation of 1.6%. The mathematical model was satisfatory to describe the process however the methodology used to obtain the kinetic data for a polyol isocyanate reaction did not allow to obtain a set of parameters that simultaneously adjusted the experimental data of the system with and without HFO blowing agent.

Os poliuretanos provavelmente são os mais versáteis dentre os polímeros de maior uso industrial por ser possível serem produzidos em uma ampla faixa de densidade, dureza, propriedades mecânicas e por meio de diferentes processos de conversão. Sua síntese envolve uma grande variedade de matérias-primas e proporções entre elas. Um modelo matemático que descreve o processo de formação do poliuretano é bastante útil no desenvolvimento de formulações e definição das condições de processamento, evitando grande consumo de tempo e erros no desenvolvimento e em experimentos. Neste trabalho foi proposta uma modelagem matemática que considera o conhecimento dos parâmetros cinéticos da reação de formação do poliuretano e o equilíbrio líquido-vapor do sistema. Os parâmetros cinéticos da reação entre poliol com isocianato foram determinados utilizando o método de temperatura adiabático, obtendo-se os valores de energia de ativação Ea (kJ/g-eq) e entalpia de reação ?H (kJ/g-eq) de 24,1 e 39,2 respectivamente mostrando-se como uma adequada. O modelo de Flory-Huggins foi utilizado para o estudo do equilíbrio líquido-vapor do agente expansor hidrofluorolefina em mistura binária com poliol, por meio de experimentos realizados para medir as temperaturas e composição da mistura na condição de equilíbrio, evidenciando a não idealidade do sistema e mostrando-se satisfatório com desvio de 1,6% em relação aos dados de atividade a experimental. O modelo matemático foi satisfatório para descrever o processo, entretanto a metodologia para obtenção dos dados cinéticos para a reação de poliol-isocianato não permitiu a obtenção de um conjunto de parâmetros que ajustasse simultaneamente os dados experimentais do sistema com e sem agente expansor HFO. / Polyurethanes are probably the most versatile among polymers of greater industrial use due to the possibility of being produced in a wide range of density, hardness, mechanical properties and through different conversion processes. Its synthesis involves a great variety of raw materials and proportions between them. A mathematical model that describes the formation process of polyurethane can be very useful for the development of formulations and in the definition of the processing conditions, avoiding great consumption of time and errors in the development and experiments. The present work proposes a mathematical modeling that considers the knowledge of the kinetic parameters of the polyurethane reaction and the liquid-vapor equilibrium of the system. The kinetic parameters of the reaction between polyol with isocyanate were determined using the adiabatic temperature rise method, obtaining the values of activation energy Ea (kJ/g-eq) and heat of reaction ?H (kJ/g-eq) of 24.1 and 39.2 respectively. The methodology employed to estimate the kinetic data was adequate. The Flory-Huggins model was used for the study of the liquid-vapor equilibrium of the hydrofluorolefin blowing agent in binary polyol mixture, through experiments carried out to measure the temperature and composition of the mixture in the equilibrium condition, verifying the non-ideality of the system and in good agreement with experimental data of activity a with deviation of 1.6%. The mathematical model was satisfatory to describe the process however the methodology used to obtain the kinetic data for a polyol isocyanate reaction did not allow to obtain a set of parameters that simultaneously adjusted the experimental data of the system with and without HFO blowing agent.

This Master’s thesis deals with investigation of high-frequency oscillations in intracranial electroencephalography in patients with pharmacoresistant epilepsy. It describes individual types of oscillations with respect to their frequency definition, examines their physiological differences and occurrence. In addition to conventional high-frequency oscillations (up to about 600 Hz), it also focuses on oscillations with a frequency component above 1kHz. According to recent studies, these oscillations could have higherspecificity for the determination of pathological tissue in the epileptic brain. The data for this work was obtained by manual labeling and categorization of approximately 1500 sections of the stereoencephalographic record signals of patients undergoing surgical removal of the epileptic foci and subsequently monitored for success in the operation. Differences between individual groups of oscillations and resected or unresected tissues are investigated in this work by methods using calculations of entropy signals or cross frequency coupling. The most significant results were achieved for the classification group (FR + vFR) vs. uFR, methods frequency-amplitude coupling and sample entropy 1. When categorizing according to information about channel resection, the Shannon entropy is the most successful classification parameter.

L'objectif de cette thèse est de caractériser les phénomènes d'oxydation de lubrifiants pétroliers et les produits lourds du pétrole. Dans les deux thématiques « lubrifiants » et «lourds pétroliers », une étude de veille stratégique a été effectuée en préalable des études analytiques et chimométriques dans ce cadre le paramètre temps est important. Il nous permet de comprendre les évolutions des domaines, leurs actualités et leur(s) pertinence(s) en précisant si ces domaines sont déjà en phase technologique et utilisation industrielle ou encore en phase de développement. Les huiles lubrifiantes doivent répondre à certaines exigences afin d'optimiser leur performance lors de l'utilisation dans le moteur. Dans ce travail, divers composés soufrés sont testés afin de déterminer le potentiel antioxydant. Deux huiles de base et sept additifs sont testés. Il apparaît que les composés soufrés avec des longues chaînes aliphatiques augmentent la résistance de l'huile, quelle que soit sa nature. Les fiouls lourds utilisés pour les moteurs de bateau peuvent être considérés comme un déchet de raffinage. Néanmoins, la spécification de ces produits est très stricte notamment pour la combustion, la stabilité et la teneur en soufre. Leurs caractérisations nécessitent l'analyse de diverses propriétés, qui sont essentielles pour le contrôle et le développement de technologies de moteurs d'entraînement. L'utilisation d'un support de diffusion permet de s'affranchir des problèmes de nettoyage de cuve couramment rencontrées. / The objective of this thesis is to characterize the phenomena of oxidation of oil lubricants and the heavy products of petroleum. In both themes « lubricating » and « Heavy Fuel Oil », a study of strategic monitoring was performed before analytical and chemometrics studies in this frame the parameter time is important. It helps us to understand changes domains, their news and their relevance and whether these domains are already in industrial use and technological phase or development stage scientific research. Lubricating oils must meet certain requirements in order to optimize their performance when operating in the engine. In this work various types of sulfur compounds are tested to identify the antioxidant potential. Two base oils and seven additives are tested. It appears that sulfur compounds with long aliphatic chains increases resistance of oil, whatever its nature. Heavy fuel oil used for boat motors can be considered as refining waste. Nevertheless the most stringent specification as burning, stability and sulfur content. Their characterizations require the analysis of various properties, which are essential for driving control and the development of engine technologies. The use of a diffusing support allows to free itself from problems of tank cleaning usually met. The aim of this work is to analyze fuel on the boat at the entrance of the engine in order to increase the motor performances and decrease the pollutants by a near infrared miniaturized sensor.

Depuis quelques années, le domaine de l’extraction végétale est en pleine mutation, avec à la fois un intérêt croissant des consommateurs pour des ingrédients d’origine naturelle, combiné à des préoccupations environnementales. Il apparaît dès lors indispensable de remplacer les procédés actuels utilisant des solvants pétrochimiques nocifs par de nouveaux procédés d’extraction réduisant le besoin énergétique, la toxicité du solvant et la quantité de déchets tout en s’assurant du rendement et de la qualité de l’extrait obtenu. L’objectif de cette thèse a donc consisté à développer un nouveau procédé d’extraction mettant en œuvre des gaz liquéfiés comme solvants. Ce manuscrit présentera tout d’abord l’état de l’art sur les gaz liquéfiés existants et leur mise en œuvre pour l’extraction des produits naturels. A l’issue de cette présentation, 3 gaz liquéfiés ont été sélectionnés (n-butane, HFO-1234ze et le DME) comme solvants pour mener des essais au laboratoire, grâce à un prototype dont la conception est détaillée dans le chapitre II. Dans un second temps, les essais réalisés à l’aide de ces gaz liquéfiés pour l’extraction de composés lipophiles ont été décrits. L’approche expérimentale a été couplée à une approche prédictive par l’utilisation d’outils d’aide à la décision : les paramètres de solubilité de Hansen et le modèle COSMO-RS. La prédiction théorique ainsi que les essais expérimentaux ont confirmé l’intérêt des gaz liquéfiés pour la solubilisation et l’extraction de composés lipophiles d’intérêt biologique et à haute valeur ajoutée. Parallèlement l’étude des impacts du procédé sur l’environnement, la qualité, la réglementation et la sécurité ont montré que l’extraction par gaz liquéfié était un procédé facilement transposable à l’échelle industrielle. / In recent years, the industrial sector of vegetable extraction has been evolving due to the growing interest of consumers for natural food ingredients combined with growing environmental concerns. Therefore, it seems essential to replace existing processes using toxic petroleum bases solvents with greener extraction processes with lower energy consumption, less wastes but higher extract quality. The objective of this thesis has consisted in the research and development of a new extraction process using liquefied gases as liquid solvents. First, this manuscript will outline the state of the art on the liquefied gases and how they are used for extraction of natural products. After this survey, 3 liquefied gases (n-butane, HFO-1234ze and DME) have been selected for laboratory scale experiments performed using a dedicated extraction unit whose design is detailed in chapter II. Then, the tests performed with these 3 gases for extraction of lipophilic compounds from several plant materials has been described. The experimental approach has been combined with a predictive one using decision tools: Hansen Solubility Parameters and COSMO-RS model. This survey demonstrated that liquefied gases are interesting solvents for solubilization and extraction of lipophilic compounds of interest. In parallel, the impacts of the process on environment, safety regulation and quality showed that liquefied gas extraction could be easily transposed at industrial scale.

With the discovery of the ferroelectric (FE) properties within HfO₂, the scaling gap between state-of-the-art technology nodes and non-volatile memories based on FE materials can be bridged. In addition to non-volatility, new memory concepts should guarantee sufficient endurance and operation stability. However, in contrast to optimized perovskite based FEs, binary oxide based FE memories still show changes in the memory window (MW) followed by either hard breakdown or closure of the MW. Recently, we have shown that anti-FE (AFE) materials exhibit very stable and significantly higher endurance with respect to the FE counterparts. Inspired by the robustness and remarkable cycling performance of the AFE materials, we analyze the remaining reliability aspects of these devices. By characterizing the pure film properties of capacitor stacks and switching performance when integrated into devices, we compare and investigate temperature stability, imprint, retention, and variability of both FE and AFE memories. We investigate if the lower energetic barrier to be overcome together with partial switching and lower switching induced stress are responsible for the higher endurance of the AFE with respect to the FE based memories. By utilizing charge trapping and charge pumping tests together with leakage current spectroscopy in combination with comprehensive modeling we check that assumption. Moreover, we identify the interfacial buffer layer as the weakest link of these devices.

The bio-enabled syntheses of functional nano-structured metal oxide thin films is of importance for a range of applications, in photonics, electronics, sensing, cell engineering, and biochemical devices. This type of novel syntheses method can overcome problems common in conventional oxide processing. In general, conventional oxide processes often require thermal treatment, caustic chemicals, and mechanical processing when producing shape-controlled inorganic materials. In contrast, biological processes are usually carried out under mild conditions (low temperature, neutral pH, and atmospheric pressure) and are therefore promising for the development of benign processes. Functional materials synthesized at room temperature using biomolecules are promising due to their expediency. During recent years, significant discoveries and progress have been made in discovering, and finding new applications for such biomimetic oxide-based minerals. However, much of the research has focused on SiO- and TiO-bearing organic-inorganic hybrid materials, of which a significant limitation is that, there are relatively few water-soluble inorganic oxide precursors commercially available for such biological syntheses. Two common compounds that are used in the biomimetic syntheses of SiO₂ and TiO₂ are tetramethoxisilane (TMOS) and Ti(IV) -bis(ammonium lactato) dihydroxide ( TiBALDH ). As a result, approaches to synthesize new water-soluble transitional metal complexes for use as precursors in the biomineralization of the corresponding functional metal oxide thin films were explored in this work, in order to expand the range of functional oxide chemistries formed via bio-enabled methods. A Ti-containing compound was synthesized to compare the behavior of commercially-available and as-synthesized TiBALDH. Another titanium-containing complex with citrate ligands, instead of lactate, was also synthesized to investigate the influence of the ligand type on the deposition behavior of the precursors. Zirconium- and hafnium-containing complexes were also synthesized to demonstrate the feasibility and versatility of the idea of applying bio-enabled syntheses to the fabrication of functional mineral oxides other than the reported SiO₂ and TiO₂. The second part of this thesis focuses on developing a novel way to fabricate porous functional mineral oxide thin films with controlled pore size, which can be used in a variety of applications, such as dye loading for optical, photochemical, or electrochemical purposes. Commercially-available, carboxyl-group-terminated polystyrene spheres of different sizes were utilized as pore-size controllers in the bio-enabled syntheses of TiO₂ by protamine. This approach has been found to be an effective means of creating uniform pores in inorganic mineral oxide coatings. The accomplishments of this work have the potential to be integrated so as to expand the boundaries of biomineralization in materials science and engineering fields.

Certain types of fuel used for combustion in land-based gas turbines can contain traces of ash when introduced into a gas turbine. Examples include synfuel, from the gasification of coal, and heavy fuel oil. When these ash particles travel through the hot gas path of the gas turbine they can deposit on turbine vanes and blades. As deposits grow, they can reduce turbine efficiency and damage turbine hardware. As turbine inlet temperatures increase, ash deposition rates increase as well.Experiments were conducted in the Turbine Accelerated Deposition Facility (TADF) at Brigham Young University to better understand ash deposition behavior at modern turbine inlet temperatures. Experiments were conducted that varied deposition duration, gas temperature, surface temperature, ash type and characteristics, and film-cooling blowing ratio. Analysis included measuring and calculating the capture efficiency, deposit surface roughness, deposit density, and deposit surface temperature. Test results indicate that capture efficiency increases with time and as the gas temperature increases. Previous studies have shown that the capture efficiency increases with increasing surface temperature as well, but the results from this study show that at a gas temperature of 1400°C, the capture efficiency of the ash used in these tests initially increased but then began to decrease with increasing surface temperature. It was also shown that different ashes, with differing ash chemistries and densities, deposit at very different rates and produce different surface structures. The film-cooling tests showed that film cooling does reduce the capture efficiency at modern turbine temperatures, but has a smaller relative effect than at lower temperatures. Tests performed with heavy fuel oil ash and increased SO2 levels (similar to those found in heavy fuel oil combustion environments) indicate that the increased sulfur levels result in the formation of more sulfur compounds in the deposit and change which elements are dissolved by water, but has little effect on the amount of deposit that dissolves. CFD simulations were performed to model the fluid dynamics and particle trajectories in the TADF. The resulting particle impact data (particle impact velocity, temperature, diameter, etc.) were used in sticking models to evaluate the models' performance at high temperatures. Results indicate that while the models can be fit fairly well to specific data, they need to be able to better account for changing surface conditions and high temperature particle behavior to accurately model deposition at high temperatures.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-07-17T13:25:04Z No. of bitstreams: 1 RobsonSchefferTeixeira_TESE.pdf: 28541390 bytes, checksum: 963c2c435bf67ce018fa618617a1a0a6 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-07-19T14:26:40Z (GMT) No. of bitstreams: 1 RobsonSchefferTeixeira_TESE.pdf: 28541390 bytes, checksum: 963c2c435bf67ce018fa618617a1a0a6 (MD5) / Made available in DSpace on 2017-07-19T14:26:40Z (GMT). No. of bitstreams: 1 RobsonSchefferTeixeira_TESE.pdf: 28541390 bytes, checksum: 963c2c435bf67ce018fa618617a1a0a6 (MD5) Previous issue date: 2016-04-07 / An?lises espectrais de registros eletrofisiol?gicos extracelulares t?m revelado que a atividade el?trica produzida pelo c?rebro ? comumente organizada em padr?es r?tmicos, conhecidos como oscila??es neuronais. Mais recentemente, descobriu-se que as oscila??es neuronais de frequ?ncias distintas n?o s?o independentes, mas podem interagir entre si. Ao longo das ?ltimas duas d?cadas, diversas ferramentas de an?lises foram desenvolvidas, amadurecidas e incorporadas de outras ?reas para se estudar os chamados acoplamentos entre frequ?ncias de oscila??es neuronais observadas nestes registros. Oscila??es neuronais s?o ditas acopladas se houver uma rela??o de depend?ncia entre suas caracter?sticas, como fase, amplitude ou frequ?ncia instant?neas. Dentre elas, o acoplamento fase-amplitude ? caracterizado por um aumento da amplitude instant?nea de uma banda de frequ?ncia condicionado a uma fase instant?nea de uma oscila??o de outra banda, enquanto que o acoplamento fase-fase do tipo n:m ? caracterizado pela rela??o fixa entre m ciclos de uma frequ?ncia em nciclos de outra. O hipocampo ? uma regi?o cerebral envolvida na forma??o de mem?rias e navega??o espacial. Assim como em outras estruturas, as redes neuronais do hipocampo produzem diversos padr?es oscilat?rios, que variam de acordo com os estados do ciclo sono-vig?lia. Entre estes padr?es, classicamente destacam-se os ritmos teta (4-12 Hz) e gama (30-100 Hz), que caracterizam estados comportamentais de locomo??o e sono REM. No entanto, o estudo dos padr?es de acoplamento oscilat?rio no hipocampo tem revelado subtipos oscilat?rios distintos dentro da defini??o tradicional da banda gama. Mais ainda, trabalhos recentes t?m mostrado a exist?ncia de oscila??es acopladas ao ritmo teta em frequ?ncias mais altas (>100 Hz), embora haja uma diverg?ncia na literatura atual sobre at? aonde estas oscila??es de altas frequ?ncias representariam atividade oscilat?ria genu?na de redes neuronais ou se seriam derivadas de efeitos esp?rios oriundos de contamina??es por resqu?cios de potencias de a??o registrados extracelularmente. A presente tese de doutorado visa contribuir para o maior entendimento dos padr?es oscilat?rios produzidos por redes neuronais do hipocampo, com particular foco nas rela??es de acoplamento entre oscila??es de diferentes frequ?ncias. Atrav?s de dados pr?prios e compartilhados de terceiros de animais implantados cronicamente com matrizes de m?ltiplos eletrodos, obtivemos registros da atividade el?trica da regi?o CA1 de ratos durante a explora??o de ambientes familiares e per?odos de sono. Investigamos a exist?ncia conjunta de distintos padr?es oscilat?rios do hipocampo em diferentes frequ?ncias atrav?s de marcadores eletrofisiol?gicos, anat?micos e comportamentais de cada oscila??o neuronal que, quando combinados, levaram a um perfil ?nico para cada banda de frequ?ncia. Nossos resultados mostram a exist?ncia de m?ltiplas bandas de frequ?ncia moduladas pelo ritmo teta hipocampal. As modula??es s?o dotadas de diversos mecanismos separat?rios, provavelmente de forma a minimizar interfer?ncias. Demonstramos ainda que padr?es oscilat?rios esp?rios e genu?nos podem co-existir numa mesma faixa de frequ?ncia, e que, ao contr?rio de trabalhos recentes, n?o h? evid?ncia para acoplamentos do tipo fase-fase n:m no hipocampo. A capacidade de uma oscila??o neural interagir com outras oscila??es, aparentemente independentes, levanta questionamentos naturais sobre sua signific?ncia biol?gica, que, apesar de diversos avan?os na ?rea, ainda permanece um mist?rio na sua ess?ncia. / Spectral analysis of extracellular electrophysiological recordings revealed that the brain electrical activity is often organized in rhythmic patterns, known as neuronal oscillations. Recently, it was discovered that oscillations of distinct frequencies are not independent, but can interact to each other. In the last two decades, several analysis tools were developed or incorporated from other fields to study cross-frequency coupling between neural oscillations. Neural oscillations are said to be coupled if there is a dependency between their features, such as phase, amplitude or frequency. Among them, phase ? amplitude coupling is characterized by an increase in the instantaneous amplitude of one frequency band conditioned to the instantaneous phase of another frequency band, whereas n:m phase ? phase coupling is characterized by a fixed relation between m cycles of one frequency to n cycles of another one. The hippocampus is a brain region involved in memory formation and spatial navigation. As in other brain structures, hippocampal neural networks generate several oscillatory patterns, which vary according to the stage of the sleep-waking cycle. Among these patterns, theta (4 ? 12 Hz) and gamma (30 ? 100 Hz) oscillations are prominent during active waking and REM sleep. However, the study of coupling patterns in the hippocampus has revealed distinct sub-types of oscillatory activity inside the traditional gamma band. Moreover, recent studies have shown the existence of even faster oscillations coupled to theta in the hippocampus (> 100 Hz), although there is a current divergence in the literature about whether they represent genuine network activity or spurious by-products from incomplete filtering of extracellular spikes. This thesis investigates oscillatory patterns generated by hippocampal neural networks, focusing in the coupling relation among oscillations of different frequencies. Using our own data and shared third-party ones of chronically implanted animals with multisite electrodes, we recorded electrical activity in the CA1 region of rats while exploring a familiar environment and during sleep stages. We investigated the existence of simultaneous but distinct oscillatory patterns in the hippocampus separated by electrophysiological, anatomic and behavioral markers, which, once taken together, can lead to a unique profile for each frequency band. Our results point to the existence of several frequency bands coupled to the hippocampal theta rhythm. All modulations are found to be separated by mechanisms that can potentially avoid interferences. We also demonstrate that a spurious oscillatory patterns can emerge and co-exist in the same frequency band of genuine oscillations and, contrary to recent work, we show that there is lack of evidence for n:m phase ? phase coupling in the hippocampus. The capacity of neural oscillations to interact with one another raises questions about the biological significance of such phenomenon; despite recent progress in the field, however, its essence remains a mystery.

No description available.