Os objetivos desta pesquisa incluem: (i) estudar as características de compactação dos resíduos sólidos urbanos (RSU); (ii) avaliar os mecanismos de compressão dos RSU e o efeito de sobrecarga (aterro experimental) em maciço sanitário existente; (iii) desenvolver programa computacional para previsão de recalques em aterros sanitários. Um aterro experimental com cerca de 24.400 \'M POT.3\' de RSU e altura de até 4 m, distribuído em área aproximada de 8.400 \'M POT.2\', foi construído em São Paulo para estudar os procedimentos de compactação de aterros sanitários. Ensaios in situ de grande dimensão foram executados para avaliar o peso específico do resíduo, após a compactação, em diferentes posições e camadas do experimento. Ensaios de umidade e composição dos resíduos foram realizados, assim como o levantamento das espessuras das camadas para cada etapa construtiva. O aterro experimental foi construído sobre aterro existente, criando a oportunidade para estudar a compressão do resíduo novo e antigo. Rigoroso programa de monitoração de recalques foi implantado, de forma que as deformações do aterro experimental pudessem ser isoladas das do aterro existente. Marcos superficiais foram posicionados interna e externamente à área do experimento, e placas de recalque instaladas na base do aterro experimental. O período de monitoramento envolveu cerca de 3 anos de medidas. A pesquisa resultou em: (i) novos subsídios e relações para a compactação dos RSU, incluindo as influências do equipamento de compactação, número de passadas, espessura das camadas, plano de compactação e teor de umidade, mostrando ser este último o parâmetro de maior impacto no processo de compactação; (ii) dados de peso específico e de sua relação com a profundidade, assim como do efeito da compactação na compressibilidade dos RSU e na geração de líquidos percolados em aterros sanitários; (iii) avaliação do desempenho de modelos de compressibilidade existentes na literatura; (iv) desenvolvimento de modelo compósito para compressibilidade dos RSU, considerando a compressão mecânica primária e secundária e a parcela devido a biodegradação dos resíduos; (v) desenvolvimento do programa MSWSET usando o modelo compósito para cálculo dos recalques de aterros como função do tempo. O modelo e programa desenvolvidos apresentaram elevado desempenho, constituindo importante ferramenta para previsão de recalques de aterros sanitários. / The objectives of this research were to: (i) study the compaction characteristics of municipal solid waste (MSW); (ii) evaluate the compression mechanisms of MSW and its response to a surcharge (waste test fill) over an existing landfill; (iii) develop a computer program for landfill settlement predictions. A waste test fill with a volume of about 24,400 \'M POT.3\' and a height up to 4 m, distributed over an area of approximately 8,400 \'M POT.2\', was constructed in Sao Paulo, to study compaction procedures for sanitary landfills. Large in situ tests were performed to evaluate the unit weight of waste immediately after compaction at several locations for each lift. Water content measurements and composition determinations were carried out, as well as thickness measurements of the waste layers after each construction (compaction) phase. The test fill was constructed over an existing landfill. Thus, the test fill provided opportunities to study the compression of the new and the old waste. A rigorous program of deformation monitoring was implemented in order to separate compression of the test fill from settlement of the underlying landfill. Benchmarks were located inside and outside of the experimental area, and settlement plates were installed at the bottom of the test fill. The monitoring period encompasses around 3 years of measurements. The research provided: (i) new guidelines and relationships for compaction of municipal solid waste, including the influences of compaction equipment, number of passes, lift thickness, water content, and compaction plane. The water content has presented larger response on the compaction process than the other variables; (ii) quantitative data regarding unit weight, the influence of depth on unit weight, water content, compressibility of MSW, and leachate generation; (iii) assessment of the performance of existing MSW compressibility models described in the literature; (iv) development of a composite model of MSW compressibility that considers primary compression, secondary mechanical compression, and compression from biodegradation; (v) development of the computer program MSWSET using the composite model of MSW compressibility to calculate landfill settlement as a function of time. The developed model and program has presented a high performance, being a powerful tool for landfill settlement prediction.

A utilização de sistemas semi-ativos no controle de movimento e vibração vem crescendo muito nos últimos anos, e está se firmando como a opção mais econômica em muitas aplicações. Os sistemas de controle semi-ativos baseados em fluidos magneto-reológicos (MR) já são empregados no controle de vibrações desde máquinas de lavar a grandes pontes suspensas, e até mesmo no controle de vibração de edifícios sujeitos a abalos sísmicos. No controle de movimento, eles têm sido aplicados em aparelhos de fisioterapia, próteses de joelho humano e embreagens. No setor automobilístico, os sistemas semi-ativos são empregados em sistemas de controle da suspensão e sistemas anti-rolagem, e também no controle de sistemas de torque e tração. Visto a crescente importância dos sistemas de controle semi-ativo, este trabalho aborda este assunto dividindo-o em duas partes: a primeira, apresentada no volume 1, trata do projeto de atuadores magneto-reológicos e do seu modelamento dinâmico voltado para projetos de controle; e a segunda parte, apresentada no volume 2, trata de projeto de controladores para sistemas semi-ativos, mais especificamente voltados para o controle de suspensão veicular semi-ativa, buscando a melhoria do desempenho em conforto, segurança e dirigibilidade do veículo. Na primeira parte, a maior contribuição deste trabalho está em preencher uma lacuna na literatura no que diz respeito a uma técnica sistemática de projeto de atuadores magneto-reológicos e da forma mais adequada de sua representação dinâmica para projetos de controle, que é feita a partir de dados experimentais. Na segunda parte deste trabalho buscou-se desenvolver um sistema de controle economicamente viável para veículos utilitários (caminhonetes principalmente). Estes são os veículos que mais carecem de sistemas de suspensão capazes de atender a uma grande variedade de situações (variação de pista, variação de carga), e cujo mercado exige uma relação custo/benefício melhor que aquela dos mercados de carros de luxo, onde estes sistemas são empregados atualmente. Como resultados mais importantes deste trabalho têmse: uma proposição para o uso da lei de controle LQG/LTR em sistemas não estritamente próprios; um modelo de um veículo utilitário completo com sete graus de liberdade e capaz de representar as situações mais importantes do comportamento dinâmico deste tipo de veículo; o desenvolvimento de uma estratégia de controle robusto baseado na técnica LQG/LTR, adequada para trabalhar com atuadores semi-ativos, e que utiliza sensores de custo compatível com a aplicação. O sistema de controle proposto foi capaz de melhorar o desempenho em conforto e segurança, evitando situações de perda de aderência dos pneus e comportamentos dinâmicos indesejáveis destes veículos, que foi verificado experimentalmente e através de simulações em computador. / The application of semi-active systems to motion and vibration control has significantly grown during the last years, and it is becoming an economically viable option for several applications. Semi-active systems based on magneto-rheological (MR) fluids were applied to vibration control ranging from washing machines to suspended bridges, and also in vibration control of buildings under seismic tremors. Regarding the movement control, they have been used in gym apparati, human knee prosthesis and clutches. More specifically in the automotive industry, semi-active systems have been applied in suspension and anti-roll systems, and also in torque and traction control systems. This work treats this subject dividing it into two parts: the first one, presented in volume 1, deals with the design of semi-active actuators based on magneto-rheological fluids and dynamic modeling; and the second one, presented in volume 2, deals with the design of semi-active control for vehicular suspension systems. The control main objective is the performance improvement in comfort, safety and handling features of a vehicle. In the first part, the main contribution of this work is to fulfill a literature gap regarding a systematic procedure for design of magneto-rheological actuators and to find a better representation for the dynamic behavior regarding the control system development, which is done based on experimental data analysis. The second part of this work leaded with the development of a vehicular suspension system for utility vehicles (for SUVs, and mainly for light trucks), which need suspension systems able to face a great number of situations (road variation, load variation, etc.), and which present stability problems due to its high gravity center height. Important results of this work are: the development of a robust control strategy based on LQG/LTR techniques for non-strictly proper systems, the development of a dynamic model for light trucks and SUVs with seven degrees of freedom; the development of a robust control strategy based on the LQG/LTR synthesis, suit to work with semi-active actuators, and using sensors with costs compatible to the application. The proposed control system was able to improve the performance of comfort and safety, avoiding the loss of adherence between tires and the ground and other undesirable dynamic behaviors of these vehicles, that was verified experimentally and through computer simulations.

Made available in DSpace on 2017-07-21T20:42:44Z (GMT). No. of bitstreams: 1 Volnei Patel.pdf: 2182418 bytes, checksum: 0c02f090d39438a33dbc14bd153a4062 (MD5) Previous issue date: 2011-12-09 / In this work, blends of PEBD/m-PELBD with typical applications in the area of packaging films were studied. Thermal and rheological properties of blends of PEBD/m-PELBD were analyzed in the proportions of 80/20; 75/25; 70/30; 65/35;60/40, as well as the pure polymers. The samples were processed in single and twin screw extruders, thus allowing the evaluation of the influence of homogenization on the thermal and rheological properties. The effect of variations of the compositions of the blends on thermal properties was analyzed using the Differential Scanning Calorimetry technique (DSC), and the effect of variation in the rheology of the blends was analyzed in parallel plate and capillary rheometer for the various compositions and at different temperatures. The results obtained from the thermal analysis showed no variations in the melting and crystallization temperatures with variation of the composition, and the pure m-PELBD presented a melting temperature of 108ºC and PEBD 105ºC. The rheological analysis showed the high influence of PEBD in viscosity at low shear rates, presenting high viscosity. However, as of 100 1/s the reversal of the viscosity curves is observed,where m-PELBD has more influence. By means of rheological analysis, the phase behavior of the blends was investigated, which proved insoluble in all compositions in the molten state. However, due to the close proximity of the values of the melting temperature of the pure components, it was not possible to identify the expected second melting peak in the thermal analysis. Comparing the thermal and rheological results of the processed blends in the extruders of single and twin screws, no significant variations were observed. The thermal and rheological results obtained in this study show that possible small variations in composition during the feed dispensing process in the extruder would not generate significant instabilities in the process. / No presente trabalho foram estudadas blendas de PEBD/m-PELBD com aplicações típicas na área de filmes para embalagens. Foram analisadas as propriedades térmicas e reológicas das blendas de PEBD/m-PELBD nas proporções 80/20; 75/25; 70/30; 65/35; 60/40, bem como dos polímeros puros. As amostras foram processadas em extrusoras mono e dupla rosca, desta forma possibilitando avaliar a influencia da homogeneização nas propriedades térmicas e reológicas. O efeito das variações das composições das blendas nas propriedades térmicas foi analisado através da técnica de calorimetria exploratória diferencial (DSC), e os efeitos das variações na reologia da blenda foram analisados em reômetro de placa paralelas e capilar para as diversas composições e em diferentes temperaturas. Os resultados obtidos nas analises térmicas não apresentaram variações nas temperaturas de fusão e cristalização, com variação da composição, sendo que o m-PELBD puro apresentou uma temperatura de fusão de 108ºC, e o PEBD 105ºC. As analises reológicas demonstraram à alta influência do PEBD na viscosidade em baixas taxas de cisalhamento, apresentando viscosidade elevada. Porém, a partir de 100 1/s observa-se inversão das curvas de viscosidade, onde o m-PELBD influencia mais. Através de análises reológicas foi investigado o comportamento de fase das blendas, a qual se mostrou imiscível em todas as composições no estado fundido. Entretanto, devido à grande proximidade dos valores de temperatura de fusão dos componentes puros, na analise térmica não foi possível identificar o segundo pico de fusão esperado. Comparando os resultados reológicos e térmicos das blendas processadas em extrusora de rosca simples e dupla rosca, não foram observadas variações significativas. Os resultados térmicos e reológicos obtidos no presente estudos mostram que possíveis pequenas oscilações de composição durante o processo de dosagem na alimentação da extrusora não gerariam instabilidades significativas no processo.

Les cavités salines représentent une technique prometteuse de stockage massif d’énergie, notamment pour les énergies renouvelables dont la production est par nature intermittente et imprévisible. Historiquement utilisées pour le stockage saisonnier d’hydrocarbures (méthane, pétrole...), les cavités salines sont aujourd’hui sollicitées pour le stockage de nouveaux fluides (hydrogène, dioxyde de carbone...) avec des scenarii plus exigeants. Les méthodes de dimensionnement des cavités doivent être mises à jour pour répondre aux nouveaux défis de la transition énergétique.Cette thèse propose une nouvelle méthodologie de dimensionnement des cavités salines, basée sur le développement d’un nouveau modèle constitutif pour le sel gemme incluant des critères de dilatance et de traction. Ce nouveau modèle permet d’ajuster avec un unique jeu de paramètres de nombreux essais de laboratoire différents, en particulier courts et longs.Des simulations couplées thermo-mécaniques de cavités, remplies de méthane ou d’hydrogène, et du sel gemme environnant sont réalisées pour différents scenarii d’exploitation, classiques ou se rapprochant des nouveaux besoins liés à la transition énergétique. On étudie en particulier les effets de la durée et de l’amplitude des cycles, du débit d’injection ou de soutirage. Les résultats obtenus avec la nouvelle méthodologie sont comparés avec ceux de la méthodologie classique. / Salt caverns are a promising technique for massive energy storage, especially in the case of the intermittent and unpredictable renewable energy. Historically used for seasonal storage of hydrocarbons (methane, oil...), they are potentially operated with increasingly demanding scenarios for the storage of other fluids (hydrogen, carbon dioxide...). Design methods need to be updated to rise to the new challenges of the energy transition.This thesis proposes a new methodology for salt cavern design, based on the development of a new rheological model including a dilatancy and a tensile criteria. This new model allows to fit numerous different laboratory tests with a single parameter set, in particular short- and long-term tests.Thermo-mechanical numerical simulations of caverns, filled with either methane or hydrogen, and the surrounding rock salt are performed under various cycling scenarios which are classical or closer to the needs associated with the energy transition. Effects of cycle duration, amplitude and mass flow are especially investigated. Results obtained with the new and the classical methodologies are compared.

Made available in DSpace on 2014-12-17T15:41:41Z (GMT). No. of bitstreams: 1 OldemarRC.pdf: 2134736 bytes, checksum: bf80e72f9b5d1ebc0b3148367e30383f (MD5) Previous issue date: 2007-10-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The aim of this work was the preparation of polyols from reactions between castor oil and dietanolamine to increase the hydroxyl content and the network degree in the products to application in electronic devices. The polyols and the mixtures obtained were characterized by nuclear magnetic ressonance. Castor oil (CO) is a natural triglyceride - based polyol possessing hydroxyl groups, which allow several reactions that produce many different products. Among them are the polyurethanes (PU), which have been considered an ideal product for the covering of electricelectronic circuits, due to their excellent electrical, shock-absorbing, solvents resistance and hydrolytic stability properties. About 90% of the fatty acids present in the castor oil are ricinoleic acid (12-hydroxyoleic acid), while the remaining 10% correspond to non-hydroxylated fatty acids, mainly linoleic and oleic acids. The chemical analysis of castor oil indicates a hydroxyl number of 2.7. In this work, a polyol was obtained by the reaction of the CO with diethanolamine (DEA), in order to elevate the hydroxyl value from 160 to 230 or to 280 mgKOH/g, and characterized by nuclear magnetic resonance (NMR) 1H and 13C (Mercury 200). The polyadition of the resulting polyol with isophorone diisocianate (IPDI) was carried out at 60?C, and the reaction kinetics was followed by rheological measurements in a Haake RS150 rheometer. The electrical properties were determined in a HP LCR Meter 4262A, at 1.0 Hz and 10.0 KHz. The chemical analysis showed that the polyols obtained presented hydroxyl number from 230 to 280 mgKOH/g. The polyadition reaction with IPDI produced polyurethane resins with the following properties: hardness in the range from 45 shore A to 65 shore D (ASTM D2240); a dielectric constant of 3.0, at 25?C (ASTM D150). Those results indicate that the obtained resins present compatible properties to the similar products of fossil origin, which are used nowadays for covering electric-electronic circuits. Therefore, the PUs from castor oil can be considered as alternative materials of renewable source, free from the highly harmful petroleum - derived solvents / O presente trabalho teve como objetivo a obten??o de poli?is a partir das rea??es do ?leo de mamona (OM) com dietanolamina (DEA), visando elevar o ?ndice de hidroxila e consequentemente o grau de reticula??o dos produtos finais, cuja aplica??o se destinou ao encapsulamento de circuitos eletroeletr?nicos. A caracteriza??o desses poli?is e respectivas misturas foram feitas utilizando-se a t?cnica da resson?ncia magn?tica nuclear (NMR). O OM (triglicer?deo do ?cido ricinoleico) ? um poliol vegetal natural por apresentar grupo funcional hidroxila que permite v?rias rea??es e produ??o de diferentes produtos. Entre eles est?o as poliuretanas (PU) que t?m sido consideradas como produtos ideais para encapsulamento de componentes de circuitos eletro-eletr?nicos, devido as suas excelentes propriedades com rela??o ? resist?ncia mec?nica e qu?mica. As poliuretanas derivadas do ?leo de mamona podem ser consideradas materiais alternativos de fonte renov?vel e, para as produzidas neste trabalho, n?o foram empregados nenhum tipo de solvente. Cerca de 90% dos ?cidos graxos que comp?em o ?leo de mamona s?o ?cido ricinoleico (?cido 12-hidroxioleico), enquanto os outros 10% s?o ?cidos graxos n?o hidroxilados (?cidos linoleico e oleico). As an?lises qu?micas do ?leo de mamona indicam uma funcionalidade m?dia de 2,7, em rela??o aos grupos hidroxila. A poliadi??o entre o poliol resultante e o isocianato de isoforona (IPDI) teve sua cin?tica aco mpanhada com o aux?lio do re?metro Haake RS 150 ? temperatura de 60 ?C. As propriedades el?tricas foram determinadas em uma ponte HP LCR Meter 4262 A a 1,0 Hz e 10,0 KHz. As an?lises qu?micas mostraram que os poli?is obtidos apresentaram ?ndice de hidroxila entre 230 e 280 mgKOH/g. A rea??o de poliadi??o com IPDI produziu resinas de poliuretana com as seguintes propriedades: dureza entre 45 e 65 shore D (ASTM D2240); constante diel?trica de 3,0 a 25 ?C (ASTM D150). Os resultados, de um modo geral, indicaram que as resinas, cujo extensor de cadeia foi a DEA, apresentaram propriedades compat?veis e em muitos casos superiores, quando comparadas ?s dos produtos atualmente dispon?veis no mercado, sintetizados ? base de trietanolamina (TEA)

<p>Prema najnovijim istraživanjima modifikovanim skrobovima može se pripisati jo&scaron; jedna uloga &ndash; aditivi u pekarstvu, s obzirom da utiču na pobolj&scaron;anje kvaliteta hleba i<br />usporavaju proces starenja. Međutim, prema saznanjima autora ove disertacije, ne<br />postoje istraživanja na temu uticaja emulgujućih skrobova (skrob-natrijum<br />oktenilsukcinata, OSA skrobova) na kvalitet testa i hleba od p&scaron;eničnog bra&scaron;na.<br />Uzimajući u obzir činjenicu da druge vrste modifikovanih skrobova ispoljavaju dobre<br />osobine u smislu pobolj&scaron;anja kvaliteta hleba i da je OSA skrob nutritivno vredna<br />sirovina, s obzirom da se u organiznu pona&scaron;a kao prehrambeno vlakno, od velike je<br />važnosti ispitati ulogu OSA skroba kao aditiva u pekarstvu.<br />Međutim, usled kompleksne prirode testa kao sistema, bilo je te&scaron;ko odrediti relativni<br />uticaj pojedinačnih komponenti (proteina, p&scaron;eničnog skroba, OSA skroba) i njihovih<br />međusobnih interakcija na osobine testa. Stoga je, u cilju rasvetljavanja uticaja različitih OSA skrobova na viskoelastične osobine testa i retrogradaciju skrobne komponente (fenomen povezan sa starenjem hleba), p&scaron;enično bra&scaron;no frakcionisano na gluten i skrob, i vr&scaron;ena su ispitivanja strukturnih, reolo&scaron;kih i termičkih osobina hidratisanog glutena i skrobnih gelova sa dodatkom OSA skroba. Takođe su pripremani i model sistemi testa.<br />Ispitivanja na realnim sistemima (testo i hleb) izvođena su zamenom 2,5; 5 i 10%<br />p&scaron;eničnog bra&scaron;na, jednim od tri vrste OSA skroba: skrob-natrijum oktenilsukcinatom<br />(OSA-ST), preželatiniziranim skrob-natrijum oktenilsukcinatom (Pregel OSA-ST) i<br />hidrolizovanim su&scaron;enim u spreju skrob-natrijum oktenilsukcinatom (Hydrol OSA-ST).<br />Cilj je bio da se ispita uticaj dodatka OSA skrobova na strukturu testa (SEM), empirijske (miksolab, alveograf i reofermentometar) i fundamentalne (oscilatorna merenja i testovi puzanja i deformacije) reolo&scaron;ke osobine, kao i parametre kvaliteta hleba (specifična zapremina, boja kore i sredine hleba, vlaga sredine hleba, parametri raspodele veličine pora i tekstura sredine). Pored pomenutog, praćena je i promena kvaliteta hleba tokom skladi&scaron;tenja, kako bi se dobio uvid u kinetiku starenja hleba.<br />Rezultati dobijeni u ovoj disertaciji ukazali su da reolo&scaron;ko pona&scaron;anje testa sa dodatkom OSA skrobova zavisi od strukture skrobnih granula, tj. od stepena dezintegracije i depolimerizacije granule tokom procesa modifikacije. Stoga je dodatak OSA-ST doveo do ojačavanja glutenske mreže &scaron;to se odrazilo na porast modula elastičnosti i testa i glutena. Nasuprot tome, Pregel and Hydrol OSA-ST uticali su na kontinualnost glutenske mreže koja je u njihovom prisustvu bila poroznija, a time su i dobijena testa bila mek&scaron;a i rastegljivija. Istraživanja na realnim i model sistemima (p&scaron;enični skrob sa dodatkom OSA skroba) ukazala su da sva tri OSA skroba usporavaju retrogradaciju p&scaron;eničnog skroba. Takođe je dokazano da svi ispitivani emulgujući skrobovi povećavaju specifičnu zapreminu hleba u poređenju sa kontrolnim, pri čemu je Pregel OSA ispoljio najjači efekat. To se odrazilo i na strukturne osobine sredine hleba, a posledično i na mehaničke osobine sredine, čija promena je praćena u cilju određivanja kinetike starenja hleba. Prema dobijenim rezultatima, vrednosti čvrstoće sredine hleba koji je sadržao OSA-ST i Pregel OSA-ST su i nakon 24 h bile slične ili značajno niže od vrednosti čvrstoće kontrolnog uzorka određene 2 h nakon pečenja.</p> / <p>Recent studies have demonstrated that modified starches can be used as novel additives in breadmaking since they improve bread quality and retard stalling. However, up to the author&#39;s knowledge, there are no investigations concerning the influence of emulsifying starches (starch sodium octenyl succinates - OSA starches) on wheat flour dough and bread quality. Taking into account the fact that other modified starches have exhibited significant bread improving properties and that OSA starch has special nutritional value since it can act as functional fibre, it is of a great importance to investigate the feasibility of OSA starch as bread improver.<br />However, due to the complex nature of dough, it was difficult to determine the relative contributions of protein, native and modified starch components and their interactions on dough properties. Therefore, in order to resolve the influence of different OSA starches on dough viscoelastic properties and starch retrogradation (the phenomenon related to bread stalling), wheat flour was fractionated into gluten and starch; and the structural, rheological and thermal behaviour of the hydrated gluten samples and starch gels supplemented with emulsifying starches was also studied. Dough model systems were also prepared.<br />Experiments on real systems (dough and bread) were performed by incorporating<br />starch sodium octenyl succinate (OSA-ST), pregelatinized OSA starch (Pregel OSA-ST) and hydrolysed spray-dried OSA starch (Hydrol OSA-ST) at 2.5, 5 and 10 % into wheat flour. The aim was to investigate the effect of incorporating OSA starches on dough structural (SEM imaging), empirical (Mixolab, Alveograph, Rheofermentometre) and fundamental (oscillatory and creep measurements) rheological properties as well as bread quality parameters (specific loaf volume, crust and crumb colour, crumb moisture, crumb grain features, crumb texture). In addition, the bread quality attributes during storage were also monitored in order to get insight into bread stalling kinetics.<br />The results obtained in this thesis revealed that the rheological behaviour of OSA starch supplemented dough depended on the OSA starch granule rigidity, i.e. extent of OSA starch granule disintegration and polysaccharide degradation during modification. OSA-ST starch caused a reinforcement of the gluten network, as shown by the increase in storage modulus of doughs and gluten. On contrary, Pregel and Hydrol OSA-ST affected the continuity of gluten network which became porous and thus produced softer and stickier doughs in comparison to control. Investigations on real dough and model systems containing wheat and OSA starches revealed that all three types of OSA starches reduced starch retrogradation.<br />In general, all the examined emulsifying starches increased bread loaf volume in comparison to control bread with no added polymers, while Pregel OSA starch has expressed the greatest impact. It also reflected on bread crumb structural features and consequently on the crumb mechanical properties which were used for bread stalling monitoring. Firmness values of OSA-ST and Pregel OSA-ST starch supplemented bread crumbs, after 24 h of storage, were similar to or significantly lower than those of control determined 2 h after baking.</p>

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-11-17T15:28:54Z No. of bitstreams: 1 Márcio Lembi Teles_.pdf: 1859021 bytes, checksum: 5dc2746be44c5f2b865c68ec0b4c0db0 (MD5) / Made available in DSpace on 2016-11-17T15:28:54Z (GMT). No. of bitstreams: 1 Márcio Lembi Teles_.pdf: 1859021 bytes, checksum: 5dc2746be44c5f2b865c68ec0b4c0db0 (MD5) Previous issue date: 2016-09-16 / Nenhuma / Este trabalho apresenta uma análise fatorial, através de fluidodinâmica computacional, do escoamento e transferência de calor para fluidos viscoplásticos a partir de um cilindro confinado entre paredes paralelas. Considera-se que as propriedades reológicas sensíveis à temperatura, o que acopla os problemas térmico e fluidodinâmico de forma bilateral. Foi desenvolvida uma formulação baseada no método estabilizado de elementos finitos Galerkin Mínimos Quadrados (GLS – Galerkin Leart-Squares) para a aproximação de escoamentos não newtonianos com transferência de calor e propriedades reológicas termodependentes. Esta formulação foi implementada em um código computacional próprio. Para a modelagem das tensões viscosa, foi utilizado um modelo de líquido newtoniano generalizado, com função viscosidade dada pelo modelo de Herschel-Bulkley regularizado conforme Papanastasiou e propriedades termodependentes – a tensão inicial de escoamento e o índice de consistência. Os resultados numéricos foram investigados utilizando os adimensionais: número de Reynolds (Re), número de Herschel-Bulkley (Hb), número de Prandtl (Pr), índice de potência (n) e coeficientes de dependência térmica (a* e b*). Foi realizado um planejamento experimental fatorial completo 2K, com objetivo de avaliar a influência destes parâmetros na taxa de transferência de calor, através do número de Nusselt (Nu), e na perda de carga localizada devido à obstrução do canal pelo cilindro. / This paper presents a factor analysis using computational fluid dynamics, flow and heat transfer for viscoplastic fluids from a cylinder confined between parallel walls. It is considered that the rheological properties sensitive to temperature, which couples the thermal and fluid dynamic problems bilaterally. It was developed a formulation based on stabilized finite element method Galerkin Least Squares (GLS - Galerkin Leart-Squares) for approaching non-Newtonian flow with heat transfer and rheological properties dependent terms. This formulation has been implemented in a proper computer code. For the modeling of viscous stresses, a generalized Newtonian fluid model was used, with viscosity function given by the Herschel-Bulkley regularized model as Papanastasiou and properties dependent terms – the initial yield stress and consistency index. The numerical results were investigated using the dimensionless: Reynolds number (Re), Herschel-Bulkley number (Hb), Prandtl number (Pr), potency index (n) and temperature dependence coefficients (a* and b*). It conducted a full factorial experimental design 2K, with objective to evaluate the influence of these parameters on the heat transfer rate, through the Nusselt number (Nu), and localized head loss due to the cylinder by duct obstruction.

As nanocomposites provide considerable improvements in material properties, scientists and engineers are focussing on biodegradable nanocomposites having superior material properties as well as degradability. This thesis has investigated the properties of biodegradable nanocomposites of the aliphatic thermoplastic polyester, poly (lactide acid) (PLA) and the synthetic biodegradable polyester, poly (butylene succinate) (PBS). To enhance the properties of this blend, nanometer-sized clay particles, have been added to produce tertiary nanocomposite. High aspect ratio and surface area of clay provide significant improvement in structural, mechanical, thermal and barrier properties in comparison to the base polymer. In this study, a series of PLA/PBS/layered silicate nanocomposites were produced by using a simple twin-screw extruder. PLA/PBS/Cloisite 30BX nanocomposites were prepared containing 1, 3, 5, 7 and 10 wt% of C30BX clay, while PLA and PBS polymers compositions were fixed at a ratio of 80 to 20. This study also included the validation of a gas barrier model for these biodegradable nanocomposites. WAXD indicated an exfoliated structure for nanocomposites having 1 and 3 wt% of clay, while predominantly development of intercalated structures was noticed for nanocomposites higher than 5 wt% of clay. However, TEM images confirmed a mixed morphology of intercalated and exfoliated structure for nanocomposite having 1 wt% of clay, while some clusters or agglomerated tactoids were detected for nanocomposites having more than 3 wt% of clay contents. The percolation threshold region for these nanocomposites lied between 3-5 wt% of clay loadings. Liquid-like behaviour of PLA/PBS blends gradually changed to solid-like behaviour with the increase in concentration of clay. Shear viscosity for the nanocomposites decreased as shear rate increased, exhibiting shear thinning non-Newtonian behaviour. Tensile strength and Young's modulus initially increased for nanocomposites of up to 3 wt% of clay but then decreased with the introduction of more clay. At high clay content (more than 3 wt%), clay particles tend to aggregate which causes microcracks at the interface of clay-polymer by lowering the polymer-clay interaction. Percentage elongation at break did not show any improvement with the addition of clay. PLA/PBS blends were considered as immiscible with each other as two separate glass transition and melting temperatures were observed in modulated differential scanning calorimetry (MDSC) thermograms. MDSC showed that crystallinity of the nanocomposites was not much affected by the addition of clay and hence some compatibilizer is required. Thermogravimetric analysis showed that the nanocomposite containing 3 wt% of clay demonstrated highest thermal stability compared to other nanocomposites. Decrease in thermal stability was noticed above 3 wt% clay; however the initial degradation temperature of nanocomposites with 5, 7 and 10 wt% of clay was higher than that of PLA/PBS blend alone. Gas barrier property measurements were undertaken to investigate the transmission of oxygen gas and water vapours. Oxygen barrier properties showed significant improvement with these nanocomposites, while that for water vapour modest improvement was observed. By comparing the relative permeabilities obtained from the experiments and the model, it was concluded that PLA/PBS/clay nanocomposites validated the Bharadwaj model for up to 3 wt% of clay concentration.

Chemical modification is an important way to improve the properties of existing polymers, and one of the important examples is the hydrogenation of nitrile butadiene rubber (NBR) in organic solvent by homogeneous catalysis in order to extend its application. This process has been industrialized for many years to provide high performance elastomers (HNBR) for the automotive industry, especially those used to produce components in engine compartments. In the current commercial process, a batch reactor is employed for the hydrogenation step, which is labor intensive and not suitable for large volume of production. Thus, novel hydrogenation devices such as a continuous process are being developed in our research group to overcome these drawbacks. In order to make the process more practical for industrial application, high concentration polymer solutions should be targeted for the continuous hydrogenation. However, many problems are encountered due to the viscosity of the high concentration polymer solution, which increases tremendously as the reaction goes on, resulting in severe mass transfer and heat transfer problems. So, hydrogenation kinetics in high concentration NBR solution, as well as the rheological properties of this viscous solution are very essential and fundamental for the design of novel hydrogenation processes and reactor scale up. In the present work, hydrogenation of NBR in high concentration solution was carried out in a batch reactor. A commercial rhodium catalyst, Wilkinson’s catalyst, was used with triphenylphosphine as the co-catalyst and chlorobenzene as the solvent. The reactor was modified and a PID controller was tuned to fit this strong exothermic reaction. It was observed that when NBR solution is in a high concentration the kinetic behavior was greatly affected by mass transfer processes, especially the gas-liquid mass transfer. Reactor internals were designed and various agitators were investigated to improve the mechanical mixing. Experimental results show that the turbine-anchor combined agitator could provide superior mixing for this viscous reaction system. The kinetic behavior of NBR hydrogenation under low catalyst concentration was also studied. It was observed that the hydrogenation degree of the polymer could not reach 95% if less than 0.1%wt catalyst (based on polymer mass) was used, deviating from the behavior under a normal catalyst concentration. The viscosity of the NBR-MCB solutions was measured in a rotational rheometer that has a cylinder sensor under both room conditions and reaction conditions. Parameters that might affect the viscosity of the solutions were studied, especially the hydrogenation degree of polymer. Rheological properties of NBR-MEK solutions, as well as NBR melts were also studied for relevant information. It is concluded that the hydrogenation kinetics deviates from that reported by Parent et al. [6] when polymer is in high concentration and/or catalyst is in low concentration; and that the reaction solution (HNBR/NBR-MCB solution) deviates from Newtonian behavior when polymer concentration and hydrogenation degree are high.

In several applications of casting, dendritic microstructure is not desirable as it results in poor mechanical properties. Enhancing the fluid flow in the mushy zone by stirring is one of the means to suppress this dendritic growth. The strong fluid flow detaches the dendrites from the solid-liquid interface and carries them into the mold to form slurry. The detached dendrites coarsen in the slurry and form into rosette or globular particles based on processing conditions. This slurry offers less resistance to flow even at a high solid fraction and easily flow into the die-cavity. The above principle is the basis of a new manufacturing technology called “semi-sold forming” (SSF), in which metal alloys are cast in the semi-solid state. This technique has several advantages over other existing commercial casting processes, such as reduction of macrosegregation, reduction of porosity and low forming efforts. A major challenge existing in semisolid manufacturing is the production of metallic slurry in a consistent manner. The main difficulty arises because of the presence of a wide range of process parameters affecting the quality of the final product. An established method of producing slurry is by stirring the alloy using an electromagnetic stirrer. From an elaborate review of literature, it is apparent that solidification in presence of electromagnetic stirring involves a wide range of shear and cooling rates variation. However, the CFD models found in the literature are generally not based on accurate rheological properties, which are known to be functions of the relevant process parameters. Hence, there is a clear need for a comprehensive numerical model for such a solidification process, involving accurate rheological data for the semisolid slurry subjected to a range of processing conditions. The objective of the present work is to develop a numerical model for studying the transport phenomena during solidification with linear electromagnetic stirring. The study is presented in the context of a billet making process in a cylindrical mould using linear electromagnetic stirring. The mould consists of two parts: the upper part of the mould is surrounded by a linear electromagnetic stirrer forming the zone of active stirring, and the lower part of the mould is used to cool the liquid metal. The material chosen for the study is Al-7.32%Si (A356) alloy, commonly used for die casting applications. A complete numerical model will therefore have two major components: one dealing with rheological behavior of the semisolid slurry, and the other involving macroscopic modeling of the process using computational fluid dynamics (CFD) techniques. For the latter part of the model, determination of rheological behavior of the slurry is a pre-requisite. The rheological characteristics of the stirred slurry, as a function of shear rate and cooling rate, is determined experimentally using a concentric cylinder viscometer. Two different series of experiments are performed. In the first series, the liquid metal is cooled at a constant cooling rate and sheared with different shear rates to get the effect of shear rate on viscosity. In the second series of experiments, the liquid metal is cooled at different cooling rates and sheared at a constant shear rate to obtain the effect of cooling rate on viscosity. During all these experiments, the shear rate is calculated from the measured angular velocity of spindle using inductive position sensor; viscosity of the slurry is calculated based on the torque applied to the slurry and angular velocity of the spindle; and the solid fraction is calculated from measured temperature of the slurry based on Schiel equation. From these data, a constitutive relation for variable viscosity is established, which is subsequently used in a numerical model for simulating the transport phenomena associated with the solidification process. The numerical model uses a set of single-phase governing equations of mass, momentum, energy and species conservation. The set of governing equations is solved using a pressure based finite volume technique, along with an enthalpy based phase change algorithm. The numerical simulation of this process also involves modeling of Lorentz force field. The numerical study involves prediction of temperature, velocity, species and solid fraction distribution. First, studies are performed for a base case with a moderate stirring intensity of 250A primary current and 50 Hz frequency. It is found that the electromagnetic forces have maximum values near the mould periphery, which results in an ascending movement of the slurry near the mould periphery. Because of continuity, this slurry comes down along the axis of the mould. Stirring produces a strong fluid flow which results good mixing in the melt. Correspondingly, a homogenized temperature distribution is found in the domain. Because of strong stirring, the solid fraction in the slurry is found to be distributed almost uniformly. It is also found that fragmentation of dendrites increases solid fraction in the slurry with processing time. During processing, the continuous rejection of solute makes the liquid progressively solute enriched. It is predicted from the present study that the remaining liquid surrounding the primary solid phase finally solidifies with a near-eutectic composition, which is desirable from the point of view of semisolid casting. Correspondingly, a set of experiments are performed to validate the numerically predicted results. The numerical predictions of temperature variations are in good agreement with experiments, and the predicted flow field evolution correlate well with the microstructures obtained through experiments at various locations, as observed in the numerical results. Subsequently the study is extended to predict the effect of process parameters such as stirring intensity and cooling rate on the distributions of solid fraction and solute in the domain. It is found, from the simulation, that the solidification process is significantly affected by stirring intensity. At increasing primary excitation current, the magnitude of Lorentz force increases and results in increase of slurry velocity. Correspondingly, the fragmentation of dendrites from the solid/liquid is more during solidification at higher stirring intensity, which increases the fraction of solid in the slurry to a high value. It is also found that the solute and fraction of solid in the liquid mixes well under stirring action. Thus, a near uniform distribution of solute and solid fraction is found in the domain. It is found that stirring at high currents produces high solid fraction in the liquid. Also, at very low cooling rate, the solid fraction in the liquid increases. The present study focuses on the model development and experimental validation for solidification with linear electromagnetic stirring for producing a rheocast billet. Further studies highlighting the effects of various process parameters on the thermal history and microstructure formation are also presented.