Le problème de Zolotarev pour des ensembles discrets apparaît pour décrire le taux de convergence de la méthode ADI, dans l'approximation de certaines fonctions matricielles ou encore pour quantifier le taux de décroissance des valeurs singulières de certaines matrices structurées. De plus, la réduction de modèle constitue un enjeu important en théorie du contrôle linéaire, et on peut prédire la qualité de l'approximation d'un système dynamique linéaire continu stationnaire de grande dimension donné grâce à la résolution approchée d'une équation de Sylvester. Après avoir prouvé l'existence d'un minimiseur pour le troisième problème de Zolotarev pour des ensembles discrets, on détermine dans cette thèse le comportement asymptotique faible de ce problème sous certaines hypothèses de régularité. Pour mener cette étude, on considère un problème de minimisation d'énergie sous contraintes pour des mesures signées en théorie du potentiel logarithmique. On discute également la précision de nos résultats asymptotiques pour des ensembles discrets généraux du plan complexe, et une formule intégrale explicite est établie dans le cas particulier de deux sous-ensembles discrets de l'axe réel symétriques par rapport à l'origine. L'impact de nos résultats théoriques pour l'analyse du taux de convergence de la méthode ADI appliquée pour la résolution approchée d'une équation de Lyapounov est estimé à l'aide de plusieurs exemples numériques après avoir exposé l'algorithme nous permettant d'obtenir les paramètres utilisés.

The Finite-Difference Time Domain (FDTD) method is a very useful numerical simulation technique for solving problems related to electromagnetism. However, as the traditional FDTD method is based on an explicit finite-difference algorithm, the Courant-Friedrich-Levy(CFL) stability condition must be satisfied when this method is used. Therefore, a maximum time-step size is limited by minimum cell size in a computational domain, which means that if an object of analysis has fine scale dimensions, a small time-step size creates a significant increase in calculation time. Alternating-Direction Implicit (ADI) method is based on an implicit finite-difference algorithm. Since this method is unconditionally stable, it can improve calculation time by choosing time-step arbitrarily. The ADI-FDTD is based on an Alternating direction implicit technique and the traditional FDTD algorithm. The new method can circumvent the stability constraint. In this thesis, we incorporate Lumped Element and Equivalent Current Source method into the ADI-FDTD. By using them to simulate active or passive device, the application of method will be more widely.

The numerical treatment of linear-quadratic regulator problems for parabolic partial differential equations (PDEs) on infinite time horizons requires the solution of large scale algebraic Riccati equations (ARE). The Newton-ADI iteration is an efficient numerical method for this task. It includes the solution of a Lyapunov equation by the alternating directions implicit (ADI) algorithm in each iteration step. On finite time intervals the solution of a large scale differential Riccati equation is required. This can be solved by a backward differentiation formula (BDF) method, which needs to solve an ARE in each time step. Here, we study the selection of shift parameters for the ADI method. This leads to a rational min-max-problem which has been considered by many authors. Since knowledge about the complete complex spectrum is crucial for computing the optimal solution, this is infeasible for the large scale systems arising from finite element discretization of PDEs. Therefore several alternatives for computing suboptimal parameters are discussed and compared for numerical examples.

Made available in DSpace on 2014-12-17T14:48:16Z (GMT). No. of bitstreams: 1 JefferssonFL_DISSERT.pdf: 8770410 bytes, checksum: 43aa967e35d51daf5e4ede35d14faf86 (MD5) Previous issue date: 2013-10-18 / O desenvolvimento das grandes cidades tem gerado um dos maiores desafios ambientais enfrentados na atualidade, que ? a gest?o eficaz de res?duos s?lidos. A grande variedade e quantidade dos res?duos produzidos diariamente, tem tornado a destina??o ecologicamente correta e sustent?vel destes materiais cada vez mais dif?cil. Dentre os v?rios res?duos produzidos diariamente destacam-se os lodos oriundos de esta??es de tratamento de esgotos, denominados de lodos de esgoto, cuja destina??o final segura tem sido discutida mundialmente em diversos estudos, tendo em vista que a tend?ncia de gera??o deste tipo de res?duo tende a crescer com o aumento do saneamento das cidades. Uma forma amplamente difundida nos pa?ses desenvolvidos para destina??o dos lodos de esgoto ? a incinera??o destes materiais para posterior envio das cinzas geradas neste processo a aterros sanit?rios. Por?m, tem-se estudado formas alternativas de disposi??o, destacando-se a utiliza??o destas cinzas como adi??o mineral em concretos e argamassas de cimento Portland. Sabe-se que o desempenho de res?duos de incinera??o como adi??o mineral em matrizes ciment?cias, depende em grande parte da capacidade de atua??o destes materiais como elementos pozol?nicos ou como fileres, podendo estas caracter?sticas serem influenciadas pela temperatura de queima ao qual estes res?duos foram submetidos. Neste sentido, verificou-se com esta pesquisa a influ?ncia da temperatura empregada na queima dos lodos s?pticos no ?ndice de atividade pozol?nica (IAP) das cinzas geradas como res?duo deste processo, aqui denominadas de cinzas de lodo s?ptico (CLS), sendo em seguida, avaliadas as implica??es t?cnicas e microestruturais da utiliza??o deste res?duo em teores de 10%, 20% e 30% como adi??o mineral em concretos de cimento Portland. Os resultados obtidos demonstraram n?o haver altera??es significativas no IAP das CLS em decorr?ncia da temperatura utilizada durante o processo de queima dos lodos de esgoto. Al?m disso, verificou-se que embora a utiliza??o das CLS tenham provocado diminui??o da trabalhabilidade dos concretos para todos os teores de incorpora??o, estas melhoraram a resist?ncia mec?nica ? compress?o, o ?ndice de vazios, a absor??o de ?gua e o comportamento microestrutural dos concretos contendo 10% e 20% de res?duo

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-06-15T00:30:07Z No. of bitstreams: 1 JoseDanielJalesSilva_DISSERT.pdf: 2654477 bytes, checksum: 95ea07b4f227c6359f14ec087c4ad54c (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-20T19:11:26Z (GMT) No. of bitstreams: 1 JoseDanielJalesSilva_DISSERT.pdf: 2654477 bytes, checksum: 95ea07b4f227c6359f14ec087c4ad54c (MD5) / Made available in DSpace on 2016-06-20T19:11:26Z (GMT). No. of bitstreams: 1 JoseDanielJalesSilva_DISSERT.pdf: 2654477 bytes, checksum: 95ea07b4f227c6359f14ec087c4ad54c (MD5) Previous issue date: 2015-11-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A gera??o de res?duos industriais tem aumentado cada vez mais nas ?ltimas d?cadas, motivando estudos sobre uma destina??o ambientalmente correta e sustent?vel e que tamb?m represente vantagens para seus geradores. Neste contexto est?o inseridas duas empresas do nicho de produtos de limpeza que est?o localizadas no munic?pio de S?o Jos? do Mipibu e produzem um lodo industrial em esta??o de tratamento de efluentes, constituindo a abordagem principal desta pesquisa. Diante disto, verificou-se o potencial de incorpora??o do referido lodo em matriz de cimento Portland como adi??o mineral para a fabrica??o de concretos, dado o elevado potencial de imobiliza??o de res?duos na matriz endurecida desse material, sendo estes utilizados posteriormente na pr?pria empresa para confec??o de artigos pr?-moldados. Foram adicionados diferentes teores de lodo (5, 10, 15 e 20%) em um tra?o comum (1:2:3), sendo avaliadas suas implica??es t?cnicas e microestruturais por meio de ensaios de trabalhabilidade no estado fresco e resist?ncia ? compress?o, porosidade total e microscopia eletr?nica de varredura (MEV) no estado endurecido. Os resultados obtidos demonstraram a viabilidade do processo tanto do ponto de vista t?cnico e ambiental quanto econ?mico. Todos os concretos produzidos com res?duo apresentaram uma aumento de trabalhabilidade atribu?do a natureza do res?duo que possu?a subst?ncias surfactantes capazes de adsorver min?sculas part?culas de ar na massa. Em contrapartida, para todos os teores foram obtidas resist?ncias ? compress?o inferiores ao concreto padr?o, com uma redu??o de 39%, para as amostras com 20% de lodo. Isso se deve, principalmente a um aumento de porosidade na zona de transi??o desses materiais, resultante de maior forma??o de etringita em detrimento a forma??o de CSH, principal composto cimentante, mas que, ainda assim, permite o uso desses concretos para a fabrica??o de artigos com car?ter n?o estrutural, como pisos pr?-moldados. Ademais, a absor??o de ?gua e ?ndice de vazios aumentaram levemente para todas as amostras, com exce??o do concreto com 20% de res?duo que apresentou redu??o para os dois par?metros. Diante deste contexto, o teor m?ximo recomendado ? de 20%, constituindo uma propor??o significativa e capaz de destinar sustentavelmente todo o res?duo gerado na ind?stria. / The generation of industrial wastes has been increased more and more in recent decades, motivating studies about a correct sustainable allocation and that also represents advantages for their generators. In this context, are included two companies of cleaning products niche, located in S?o Jos? do Mipibu/RN, that produces industrial sludge at a sewage treatment plant, and that is the main approach of this research. Given this, it was studied the incorporation potentiality of this sludge as a mineral addition in cement matrix for concrete production due it high capacity of wastes immobilization inside this material, which are subsequently used in the company for making precast articles. Were added different sludge concentrations (5, 10, 15 and 20%) in a common trait (1: 2: 3), and evaluated their techniques and microstructural implications via workability test in fresh state and compressive strength, full porosity and scanning electron microscopy (SEM) in the hardened state. The results demonstrated the feasibility of the process both from a technical and environmental view as economical. All concretes produced with residue showed an increase of workability given the nature of the waste that had surfactants substances capable of adsorbing tiny particles of air into the batter. However, for all concentrations were obtained lower compressive resistances than standard concrete, with a reduction of 39% for samples with 20% of sludge. This are attributed mainly to an increase of porosity in the transition zone of these material, resulting from increased formation of ettringite at the detriment to the formation of other compounds, but which still allows the use of these for the manufacture of concrete articles with non-structural nature, such as precast floor. In addition, the water absorption and void ratio increased slightly for all samples, except the concrete with 20% of waste that has a reduction for the last parameter. Given this context, the recommended maximum level is 20%, constituting a significant proportion and able to allocate sustainably all waste generated in the industry.

Made available in DSpace on 2014-12-17T15:37:15Z (GMT). No. of bitstreams: 1 DianaMMC_DISSERT.pdf: 1035496 bytes, checksum: 142ca5f441bb6233e304c45b39c59301 (MD5) Previous issue date: 2013-02-28 / Excessive alcohol consumption is responsible for many harmful effects on individuals and society. Despite years of research, the mechanisms by which alcohol affects neurological functions and the exact causes of cognitive impairment related to long-term use are unknown. In this sense, this master study proposed to observe how different doses of alcohol affect the addiction response and the learning ability of two fish species: Betta splendens and Danio rerio, the latter a commonly model due to organizational and functional characteristics shared with mammals. For this, different concentrations of ethanol (0%, 0.1%, 0.25%, 1% and 1.5%) were used in acute, chronic and withdrawal treatments. We tested the fish in three experimental protocols: 1) alcohol addiction potential using conditioned place preference, 2) associative conditioning using light as unconditioned stimulus and food as conditioned stimulus and 3) spatial learning using a maze without cues. For the alcohol addiction potential, preference between two different places in a shuttle box was tested before and after alcohol exposure (chronic and acute). In this test, the animals intoxicated by 0.1% did not change behavior, while animals receiving 1% and 1.5% alcohol changed the initial preference to the side where they received alcohol For the associative conditioning, the results show that the groups undergoing low dose (0.1%), both in chronic and withdrawal treatment, learned the task faster than control; groups under 0.25 and 1% alcohol withdrawal learned the task after control; groups chronically intoxicated with these doses did not learn the task. For the spatial learning test, fish submitted to acute and chronic treatments decreased the time to exit the maze; there were significant differences in the animal s performance in a dose-dependent pattern. This difference was not observed for the withdrawal treatment. Given these results, we conclude that the effects of alcohol on learning are dependent on the dosage. Furthermore, low doses of alcohol seem to maximize animal performance on learning tasks and do not alter their seeking behavior, while higher doses induced addition and hinder learning / O consumo excessivo de bebidas alco?licas ? respons?vel por in?meros efeitos prejudiciais aos indiv?duos e ? sociedade. Apesar de anos de pesquisa, ainda ? pouco o conhecimento sobre os mecanismos pelos quais o ?lcool afeta as fun??es neurol?gicas e quais seriam as causas exatas das defici?ncias cognitivas e de mem?ria relacionadas ao seu uso em longo prazo. Neste sentido, este trabalho prop?s observar como diferentes doses de ?lcool interferem na capacidade de aprendizagem de duas esp?cies de peixes: Betta splendens e Danio rerio, este ?ltimo um modelo bastante utilizado devido ?s caracter?sticas organizacionais e funcionais que compartilha com mam?feros. Para isto, diferentes concentra??es de ?lcool (0%, 0,1%, 0,25%, 1% e 1,5%) foram usadas em doses agudas e cr?nicas e os animais, alcoolizados ou em fase de abstin?ncia, foram testados em tr?s protocolos experimentais: 1) Condicionamento associativo apetitivo os resultados encontrados mostram que os grupos submetidos ? dose baixa (0,1%), tanto em tratamento cr?nico quanto em abstin?ncia, aprendem a tarefa mais rapidamente que o controle; os grupos em abstin?ncia das doses 0,25 e 1% de ?lcool apresentaram aprendizagem ap?s o controle; e os grupos alcoolizados cronicamente nestas doses n?o aprendem a tarefa. 2) Aprendizagem espacial - nesta tarefa o peixe foi testado quanto ao desempenho em um labirinto sem dicas ambientais. Os resultados obtidos demonstram que, embora todos os grupos submetidos ao tratamento agudo e cr?nico diminu?ram o tempo de sa?da do labirinto ao longo dos dias, houve diferen?as significativas no desempenho dos animais de forma dose-dependente. Tal diferen?a n?o foi observada no tratamento abstin?ncia. 3) Prefer?ncia ambiental foi testada a prefer?ncia por dois ambientes (base quadriculada X base branca) em um aqu?rio do tipo shuttle box, e posteriormente ? alcooliza??o no ambiente n?o preferido, foi observada novamente a prefer?ncia do animal. Neste teste, os animais alcoolizados em 0,1% n?o tiveram altera??o comportamental, enquanto animais que receberam 1% e 1,5% de ?lcool alteraram sua prefer?ncia para o lado onde haviam sido alcoolizados, mantido por todo o per?odo experimental. Tendo em vista os resultados encontrados, podemos concluir que os efeitos do ?lcool na aprendizagem s?o dependentes da dosagem. Alem disso, doses baixas de ?lcool parecem maximizar o desempenho do animal em tarefas de aprendizagem, mesmo n?o alterando sua prefer?ncia, enquanto as doses mais elevadas produzem efeito de adi??o e prejudicam a aprendizagem dos animais

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-14T22:33:05Z No. of bitstreams: 1 ThiagoVieiraFonseca_DISSERT.pdf: 2958142 bytes, checksum: c66f334f99f3044869ebf39752984389 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-03-16T19:54:31Z (GMT) No. of bitstreams: 1 ThiagoVieiraFonseca_DISSERT.pdf: 2958142 bytes, checksum: c66f334f99f3044869ebf39752984389 (MD5) / Made available in DSpace on 2017-03-16T19:54:31Z (GMT). No. of bitstreams: 1 ThiagoVieiraFonseca_DISSERT.pdf: 2958142 bytes, checksum: c66f334f99f3044869ebf39752984389 (MD5) Previous issue date: 2016-12-15 / O concreto autoadens?vel (CAA) possui elevado teor de materiais finos e vem sendo bastante utilizado devido as suas caracter?sticas de alta fluidez e coes?o. Os finos provindos de res?duos ou subprodutos industriais podem vir a ser usados em prol da sustentabilidade, minimizando consideravelmente o consumo de cimento associado ? possibilidade de manter, ou melhorar, as propriedades mec?nicas ou de durabilidade. Desta forma, o presente trabalho investigou a viabilidade do desenvolvimento de CAA?s confeccionados com elevados teores de adi??es minerais e cal hidratada. Para isso, o cimento foi substitu?do por adi??es minerais (pozolana da casca do arroz, metacaulim e f?ler calc?rio) no teor de 60%, com base no tra?o de refer?ncia com consumo de 451,1 kg/m? de cimento, originando novos tra?os com consumos de cimento entre 167,7 kg/m? e 173,3 kg/m?. A cal hidratada foi incorporada como adi??o em tr?s tra?os no teor de 5% sobre a massa total dos materiais finos. Os CAA?s foram caracterizados no estado fresco pelos ensaios de espalhamento, T500, anel-J, funil-V e caixa-L. Para avalia??o do desempenho mec?nico dos CAA?s foram realizados ensaios de resist?ncia ? compress?o, velocidade do pulso ultrass?nico e m?dulo de elasticidade est?tico, bem como propriedades de transporte relacionadas ? durabilidade: absor??o por capilaridade, difus?o de ?ons cloreto, resistividade el?trica e carbonata??o. Os CAA?s com adi??es minerais apresentaram desempenho mec?nico satisfat?rio, embora inferiores ao do tra?o de refer?ncia. As resist?ncias ? compress?o aos 28 dias dos concretos com adi??es minerais apresentaram redu??o de 15 a 60% em rela??o ao tra?o de refer?ncia, mas todos os resultados foram compat?veis com concretos estruturais de acordo com os requisitos da NBR 6118 (ABNT, 2014). Com rela??o a durabilidade, os concretos com adi??es minerais apresentaram redu??o do coeficiente de difus?o de ?ons cloreto que variaram entre 25,4% e 74,8%. As resistividades el?tricas do concreto de refer?ncia foram bastante inferiores ?s dos concretos com adi??es minerais, mas todas as composi??es estudadas foram classificadas como prov?vel taxa de corros?o desprez?vel. As resistividades el?tricas sofreram grande redu??o quando analisadas em amostras carbonatadas. J? a an?lise da carbonata??o acelerada mostrou que a substitui??o do cimento por adi??es minerais em elevados teores torna os CAA?s bastante suscet?veis a carbonata??o. Quanto a adi??o de cal hidratada, n?o foi verificada influ?ncia positiva no desempenho mec?nico dos CAA?s estudados, mas observou-se que sua utiliza??o proporcionou redu??o da profundidade de carbonata??o nos CAA?s devido a reposi??o da reserva alcalina. / Self-compacting concrete (SCC) has a high content of fine materials and has been widely used due to its characteristics of high fluidity and cohesion. Fines from industrial waste or by-products may be used for the sake of sustainability, considerably reducing the consumption of cement associated with the possibility of maintaining or improving mechanical or durability properties. In this way, the present work investigated the feasibility of the development of SCC's made with high levels of mineral additions and hydrated lime. For this purpose, the cement was replaced by mineral additives (rice husk pozzolan, metakaolin and limestone filer) in the 60% content, based on the reference mixture with consumption of 451.1 kg / m? of cement, giving rise to new mixtures with consumption of cement between 167.7 kg / m? and 173.3 kg / m?. The hydrated lime was incorporated as an addition in three mixtures in the content of 5% on the total mass of the fine materials. The SCC's were characterized in the fresh state by the slump flow test, T500, J-ring, V-funnel and L-box. To evaluate the mechanical performance of the SCC's, tests of compressive strength, ultrasonic pulse velocity and static modulus of elasticity, as well as transport properties related to durability were performed: capillary absorption, chloride ion diffusion, electrical resistivity and carbonation. The SCC's with mineral additions presented satisfactory mechanical performance, although lower than the reference mixture. The compressive strength at 28 days of the concretes with mineral additions showed a reduction of 15 to 60% in relation to the reference mixture, but all the results were compatible with structural concretes according to the requirements of NBR 6118 (ABNT, 2014). Regarding the durability, the concrete with mineral additions presented reduction of the diffusion coefficient of chloride ions that varied between 25.4% and 74.8%. The electrical resistivities of the reference concrete were much lower than those of the concretes with mineral additions, but all the studied compositions were classified as probable negligible corrosion rates. The electrical resistivities suffered great reduction when analyzed in carbonated samples. The analysis of the accelerated carbonation showed that the substitution of cement by mineral additions at high levels makes the SCC very susceptible to carbonation. As for the addition of hydrated lime, there was no positive influence on the mechanical performance of the SCC's studied, but it was observed that its use provided a reduction of the carbonation depth in the SCC's due to the alkaline reserve.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-20T23:06:42Z No. of bitstreams: 1 WesleyFeuDosSantos_DISSERT.pdf: 2488767 bytes, checksum: 54fa9201753bfbbe0b0ff0a295b2a4ac (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-03-24T21:53:11Z (GMT) No. of bitstreams: 1 WesleyFeuDosSantos_DISSERT.pdf: 2488767 bytes, checksum: 54fa9201753bfbbe0b0ff0a295b2a4ac (MD5) / Made available in DSpace on 2017-03-24T21:53:11Z (GMT). No. of bitstreams: 1 WesleyFeuDosSantos_DISSERT.pdf: 2488767 bytes, checksum: 54fa9201753bfbbe0b0ff0a295b2a4ac (MD5) Previous issue date: 2016-09-09 / A fabrica??o do Cimento Portland ? uma atividade que causa grande impacto ambiental devido ? sua elevada taxa de emiss?o de CO2 na atmosfera. Visando reduzir esse impacto, a viabilidade t?cnica de materiais alternativos em substitui??o ao Cimento Portland tem sido cada vez mais analisada. J? s?o conhecidos os benef?cios que as adi??es minerais infere ao concreto convencional (CV), no entanto, existe a necessidade de compreender melhor seus benef?cios quando utilizadas em CAA e verificar o comportamento deste quando curado termicamente. Assim, este trabalho avalia os efeitos da incorpora??o de f?ler calc?rio (Fc) e metacaulim (Mk) na hidrata??o do concreto autoadens?vel, quando submetido ? cura t?rmica. Para tanto, foram produzidos seis composi??es de CAA, sendo uma de refer?ncia, sem adi??o mineral, quatro misturas bin?rias com substitui??o do cimento por 10% de Mk, 10% Fc, 20% de Mk e 20% Fc e uma terci?ria com substitui??o do cimento por 10% de Mk e 10% de Fc. Os concretos foram dosados e realizados os ensaios realizados para os concretos dosados foram: slump flow, T500, L-box, V-test e J-ring para caracteriza??o do CAA no estado fresco. Ap?s iniciada a pega (aproximadamente 3 horas), intervalo chamado de pr?-cura, os corpos de prova moldados foram curados atrav?s de imers?o total em banho aquecido. A taxa de aquecimento utilizada foi de 20 ?C/h, chegando ?s temperaturas m?ximas de 50, 60 e 70 ?C, com posterior resfriamento de 10 ?C/h. O tempo total do ciclo (pr?-cura, aquecimento, patamar isot?rmico e resfriamento), foi de 18 a 20 horas. Tamb?m foram confeccionados corpos de prova de CAA que foram curados por imers?o em ?gua a temperatura ambiente. As propriedades analisadas no estado endurecido de todas as composi??es foram: resist?ncia ? compress?o nas idades de 1, 3, 7 e 28 dias, com m?dulo de elasticidade din?mico, absor??o de ?gua por capilaridade, massa espec?fica e absor??o total aos 28 dias de idade. A an?lise da microestrutura dos diferentes concretos se deu por microscopia eletr?nica de varredura e difra??o de raios X aos 3 e 28 dias de idade. As adi??es de metacaulim e filer calc?rio podem substituir o cimento Portland, nos percentuais de 10% e 20%, de maneira satisfat?ria em misturas bin?rias e terci?rias. Aos 28 dias de idade, os CAA curados termicamente em geral n?o apresentaram resist?ncias ? compress?o inferiores aos curados a 28 ?C. A cura t?rmica ?mida por imers?o propicia um aumento na resist?ncia ? compress?o nas primeiras idades, exceto para os concretos contendo 20% de f?ler calc?rio em substitui??o ao cimento Portland. Para cada tra?o estudado, houve um temperatura que se mostrou mais eficaz, ou seja, uma temperatura patamar mais adequada. Na an?lise da microestrutura dos CAA pode se observar que a elevada resist?ncia obtida a 1 dia de idade, deve-se a r?pida forma??o de CSH para os CAA tratados termicamente. / The manufacture of Portland cement is an activity that causes great environmental impact due to its high CO2 emission rate in the atmosphere. In order to reduce this impact, technical feasibility of alternative materials to replace Portland cement has been increasingly analyzed. It is already known the benefits that mineral additions infers to conventional concrete (CV), however, little is known of their use in self-compacting concrete (SCC) subjected to heat treatment. This work evaluates the effects of the incorporation of limestone fillers (LP) and metakaolin (MK) in the hydration of self-compacting concrete, when subjected to thermal curing. For this purpose six SCC compositions were produced, as a reference without mineral addition, four binary mixtures with replacement of cement with 10% MK, 10% LP, 20% MK and 20% LP and a tertiary with substitution of cement by 10% MK and 10% LP. The concrete were measured and made the tests slump flow, T500, L-box, V-test and J-ring to characterize the SCC fresh. After started the crystallization reactions (about 3 hours), range called pre-curing, the molded specimens were cured through total immersion in a warm bath. The heating rate used was 20 ?C/hr, reaching the maximum temperatures 50, 60 and 70 ?C, with subsequent cooling 10 ?C/hr. The total cycle time (pre-curing, heating, cooling and isothermal level) was 18 to 20 hours. Also, specimens were prepared which were cured by immersion in water at room temperature. The analyzed properties in the hardened state of all compositions were compressive strength at ages of 1, 3, 7 and 28 days at modulus, water absorption by capillarity, density, and total absorption to 28 days of age. The analysis of the microstructure of different concrete was given by scanning electron microscopy and X-ray diffraction at 1 and 28 days of age. The CAA thermally cured obtained a high increase in compressive strength at 1 day old, when compared to CAA cured at room temperature. For each dosage analyzed, there is a maximum temperature within the thermal cycle, which provides better mechanical performance to the CAA. The thermal curing causes changes in the microstructure, including, promote the rapid formation of calcium silicate hydrate (CSH). The additions of metakaolin and lime filer can replace Portland cement in percentages of 10% and 20%, satisfactorily in binary and tertiary mixtures. After 28 days the CAA cured thermally groups showed no resistance to compression to lower cured at 28 ? C. The wet thermal curing dip provides an increase in compressive strength at early ages, except for the concrete containing 20% filler limestone to replace Portland cement. For each studied trait, there was a temperature that was more effective, i.e., a temperature most suitable level. The analysis of the microstructure of the CAA can be seen that the high strength obtained at 1 day old, due to rapid formation of the CSH to the heat-treated CAA.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-05-24T17:45:39Z No. of bitstreams: 1 texto completo.pdf: 3441417 bytes, checksum: a795290bb5f3cf798dc2cf4939b636d7 (MD5) / Approved for entry into archive by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-05-24T17:45:53Z (GMT) No. of bitstreams: 1 texto completo.pdf: 3441417 bytes, checksum: a795290bb5f3cf798dc2cf4939b636d7 (MD5) / Approved for entry into archive by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-05-24T17:46:03Z (GMT) No. of bitstreams: 1 texto completo.pdf: 3441417 bytes, checksum: a795290bb5f3cf798dc2cf4939b636d7 (MD5) / Made available in DSpace on 2018-05-24T17:46:13Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3441417 bytes, checksum: a795290bb5f3cf798dc2cf4939b636d7 (MD5) Previous issue date: 2017-02-23 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Na retificação de pequenas séries ou na retificação de geometrias complexas os rebolos de óxido de alumínio (Al2O3) podem ser uma alternativa competitiva em várias aplicações e apresentar um melhor desempenho, quando comparadas aos rebolos superabrasivos, no que tange a qualidade da superfície usinada para grandes taxas de remoção de material. Nesta pesquisa é avaliada a influência de rebolos de Al2O3 com diferentes composições de grãos abrasivos microcristalinos sinterizados e grãos monocristalino eletrofundidos no resultado de retificação do ADI Classe 3. São correlacionadas as variáveis de entrada com as características do processo, como as componentes de forças de retificação, do desgaste radial dos rebolos e o ruído magnético de Barkhausen (RMB), bem como pelo resultado de trabalho, como a rugosidade e a textura das superfícies retificadas. Os resultados mostraram que na retificação com os rebolos com menores porcentagens de grãos microcristalinos sinterizados são gerados as menores rugosidades e menor desgaste radial, e revelaram que para todos os rebolos convencionais ensaiados não se verificam danos de retificação (queima de retificação) com os parâmetros de entrada de processo estabelecidos. Verificou-se uma correlação das amplitudes dos sinais do RMB com os perfis de microdureza geradas pelos diferentes rebolos nas amostras de ADI Classe 3. Os resultados desta pesquisa permitem uma especificação mais adequada de rebolos convencionais para a retificação do ADI, uma vez que há poucas informações sobre a usinabilidade deste material no processo de retificação. / The grinding of low-size inventories or complex geometries with conventional sintered grinding wheels can be a competitive alternative in many applications and has a better performance in compare with superabrasive grinding wheels, regarding the machined surface quality for high material removal rates. In this research is evaluated the Al2O3 grinding wheels influence with different compositions of sintered microcrystalline and monocrystalline electrofused abrasive grains in the ADI Class 3 grinding result. The input variables are correlated with the process characteristics, such as the grinding forces components, the grinding wheels radial wear and the magnetic Barkhausen noise (MBN), as well as the work result, such as the roughness and texture of the ground surfaces. The results showed the grinding wheels with lower sintered abrasive grains percentages generated the lower roughness values and lower radial wear, and revealed that all conventional grinding wheels evaluated caused no thermal damages (grinding burns) with the established input parameters process. It was verified amplitudes MBN correlation with the microhardness profiles generated by different grinding wheels on the ADI samples. The results of this research will contribute to the most appropriate specification of conventional grinding wheels to the ADI grinding, since there is a few information available about the ADI machinability in the grinding process.

We present new results on absolute stability for BDF-ADI (Backward differentiation formula Alternating Direction Implicit) methods applied to a linear advection and diffusion equations. Unconditional absolute stability of the BDF2-ADI method is proven for advection and diffusion separately, as well as to the BDF3-ADI method for the purely-diffusive case. Conditional absolute stability of the BDF4-ADI is also proven for the purely-diffusive case, and stability regions for BDF3-ADI and BDF4- ADI are given in terms of the PDE coefficients and numerical parameters. Lastly, numerical experiments are presented to support the theoretical results and conjectures. These experiments also suggest future work.