Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-05-08T17:34:51Z No. of bitstreams: 1 AntonioRobsonGurgel_TESE.pdf: 19778169 bytes, checksum: d9084d105aa006a9e3b12128107398f8 (MD5) / Approved for entry into archive by Monica Paiva (monicalpaiva@hotmail.com) on 2017-05-08T17:40:17Z (GMT) No. of bitstreams: 1 AntonioRobsonGurgel_TESE.pdf: 19778169 bytes, checksum: d9084d105aa006a9e3b12128107398f8 (MD5) / Made available in DSpace on 2017-05-08T17:40:17Z (GMT). No. of bitstreams: 1 AntonioRobsonGurgel_TESE.pdf: 19778169 bytes, checksum: d9084d105aa006a9e3b12128107398f8 (MD5) Previous issue date: 2015-12-04 / Nos m?todos t?rmicos de recupera??o de petr?leo, o calor transferido para a rocha-reservat?rio pode ser proveniente da inje??o de fluidos quentes (?gua quente ou vapor), por meio da combust?o in situ ou de aquecimento eletromagn?tico. Do ponto de vista energ?tico, apenas uma fra??o do calor injetado ir? aquecer efetivamente o meio poroso e assim auxiliar no aumento do fator de recupera??o final do ?leo, pois parte desse calor se perde nas linhas de inje??o, forma??es adjacentes ? zona produtora e nos po?os injetores e produtores. Uma das formas de se medir a quantidade de calor presente no meio poroso ? atrav?s da efici?ncia t?rmica, que pode ser definida como a raz?o entre o calor remanescente do reservat?rio e o calor l?quido injetado. A an?lise desta vari?vel pode auxiliar no gerenciamento da quantidade de energia necess?ria e que est? sendo gasta para recupera??o de ?leo. Para a realiza??o deste estudo, foi desenvolvido um modelo num?rico, semissint?tico, em um sistema cartesiano de malhas, com um padr?o de ? de five spot invertido, utilizando o programa STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator), do grupo CMG (Computer Modelling Group Ltd.). Os par?metros de reservat?rios e operacionais analisados neste estudo foram a espessura da zona produtora de ?leo, a condutividade t?rmica da rocha e a capacidade calor?fica das forma??es adjacentes (topo e base), a vaz?o de inje??o de vapor, o t?tulo e a completa??o dos po?os injetores e produtores. J? as vari?veis avaliadas foram a efici?ncia t?rmica, o fator de recupera??o e o valor presente l?quido, durante o per?odo de 15 anos. A forma??o portadora de hidrocarbonetos possui caracter?sticas de rocha-reservat?rio similares ?s encontradas no Nordeste Brasileiro, mais especificamente da Bacia Potiguar, contendo ?leo de alta viscosidade. A partir dos resultados obtidos nas simula??es num?ricas, verificou-se que o comportamento da efici?ncia t?rmica foi fortemente dependente das espessuras da zona produtora, da condutividade t?rmica e capacidade calor?fica das forma??es adjacentes, das taxas de inje??o de vapor, do t?tulo e da completa??o dos po?os. Em rela??o ? espessura, maiores valores deste par?metro melhoraram a fra??o de calor remanescente do ?leo. Por outro lado, o incremento no t?tulo do vapor e na vaz?o de inje??o favoreceram o aumento da efici?ncia t?rmica apenas antes da ocorr?ncia da erup??o de calor no po?o produtor, mas passaram a reduzir a efici?ncia t?rmica ap?s o referido evento. Isto n?o havia sido predito nos modelos cl?ssicos encontrados na literatura. / Nos m?todos t?rmicos de recupera??o de petr?leo, o calor transferido para a rocha-reservat?rio pode ser proveniente da inje??o de fluidos quentes (?gua quente ou vapor), por meio da combust?o in situ ou de aquecimento eletromagn?tico. Do ponto de vista energ?tico, apenas uma fra??o do calor injetado ir? aquecer efetivamente o meio poroso e assim auxiliar no aumento do fator de recupera??o final do ?leo, pois parte desse calor se perde nas linhas de inje??o, forma??es adjacentes ? zona produtora e nos po?os injetores e produtores. Uma das formas de se medir a quantidade de calor presente no meio poroso ? atrav?s da efici?ncia t?rmica, que pode ser definida como a raz?o entre o calor remanescente do reservat?rio e o calor l?quido injetado. A an?lise desta vari?vel pode auxiliar no gerenciamento da quantidade de energia necess?ria e que est? sendo gasta para recupera??o de ?leo. Para a realiza??o deste estudo, foi desenvolvido um modelo num?rico, semissint?tico, em um sistema cartesiano de malhas, com um padr?o de ? de five spot invertido, utilizando o programa STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator), do grupo CMG (Computer Modelling Group Ltd.). Os par?metros de reservat?rios e operacionais analisados neste estudo foram a espessura da zona produtora de ?leo, a condutividade t?rmica da rocha e a capacidade calor?fica das forma??es adjacentes (topo e base), a vaz?o de inje??o de vapor, o t?tulo e a completa??o dos po?os injetores e produtores. J? as vari?veis avaliadas foram a efici?ncia t?rmica, o fator de recupera??o e o valor presente l?quido, durante o per?odo de 15 anos. A forma??o portadora de hidrocarbonetos possui caracter?sticas de rocha-reservat?rio similares ?s encontradas no Nordeste Brasileiro, mais especificamente da Bacia Potiguar, contendo ?leo de alta viscosidade. A partir dos resultados obtidos nas simula??es num?ricas, verificou-se que o comportamento da efici?ncia t?rmica foi fortemente dependente das espessuras da zona produtora, da condutividade t?rmica e capacidade calor?fica das forma??es adjacentes, das taxas de inje??o de vapor, do t?tulo e da completa??o dos po?os. Em rela??o ? espessura, maiores valores deste par?metro melhoraram a fra??o de calor remanescente do ?leo. Por outro lado, o incremento no t?tulo do vapor e na vaz?o de inje??o favoreceram o aumento da efici?ncia t?rmica apenas antes da ocorr?ncia da erup??o de calor no po?o produtor, mas passaram a reduzir a efici?ncia t?rmica ap?s o referido evento. Isto n?o havia sido predito nos modelos cl?ssicos encontrados na literatura.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-07-04T13:29:17Z No. of bitstreams: 1 AndersonAlbinoFerreira_DISSERT.pdf: 5315680 bytes, checksum: 999fe3e6c74df532dc49b7549ac68b2f (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-07-12T13:47:03Z (GMT) No. of bitstreams: 1 AndersonAlbinoFerreira_DISSERT.pdf: 5315680 bytes, checksum: 999fe3e6c74df532dc49b7549ac68b2f (MD5) / Made available in DSpace on 2017-07-12T13:47:03Z (GMT). No. of bitstreams: 1 AndersonAlbinoFerreira_DISSERT.pdf: 5315680 bytes, checksum: 999fe3e6c74df532dc49b7549ac68b2f (MD5) Previous issue date: 2017-03-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A alvenaria ? um material comp?sito, constitu?do basicamente por unidades e juntas de argamassa (vertical e horizontal), podendo estar associada tamb?m a outros materiais, como o a?o e o graute. No Brasil, a partir da d?cada de 80, a alvenaria estrutural acabou se consolidando como um sistema construtivo altamente produtivo, racional e econ?mico devido a caracter?sticas como: simplifica??o das t?cnicas de execu??o, menor diversidade de materiais empregados, redu??o da m?o de obra e rapidez na execu??o. Em alvenaria estrutural, uma das possibilidades de execu??o que pode ser explorada ? o n?o preenchimento das juntas verticais, tamb?m chamada de juntas secas. A ado??o desta pr?tica gera certas vantagens como a diminui??o no tempo de execu??o da obra, a redu??o do consumo de materiais e a minimiza??o da fissura??o provocada pelas deforma??es intr?nsecas, como retra??o e deforma??es t?rmicas. No entanto, apesar de ser empregada a alguns anos no pa?s, as implica??es decorrentes de seu uso muitas vezes n?o t?m sido consideradas de forma apropriada nos projetos, isto se deve ao fato de existirem poucas pesquisas que tratam deste assunto. Al?m disso, as pesquisas existentes, por vezes, apresentam resultados que divergem entre si, principalmente no que se refere ? resist?ncia ? compress?o e ao cisalhamento. Neste trabalho foram efetuadas simula??es num?ricas de pequenas paredes de unidades cer?micas e de concreto, com e sem juntas verticais, ensaiadas com as prescri??es da NBR 15812-2 (ABNT, 2010), NBR 15961-2 (ABNT, 2011) e NBR 14321 (ABNT, 1999), com a finalidade de avaliar a influ?ncia do n?o preenchimento das juntas verticais na resist?ncia ? compress?o e ao cisalhamento da alvenaria. Para a realiza??o das an?lises num?ricas foi utilizado o M?todo dos Elementos Finitos a partir do software DIANA?. De acordo com os resultados num?ricos obtidos nos modelos em compress?o, e da compara??o entre estes e os resultados experimentais, foi poss?vel concluir que a aus?ncia das juntas verticais n?o influenciou na resist?ncia ? compress?o da alvenaria. Contudo, a partir dos resultados obtidos nos modelos em cisalhamento, conclui-se que n?o foi poss?vel avaliar quantitativamente a influ?ncia das juntas verticais na resist?ncia ao cisalhamento da alvenaria. / Masonry is a composite material, consisting basically of units and mortar joints (vertical and horizontal), and may also be associated with other materials, such as steel and grout. In Brazil, from the 1980s, structural masonry consolidated itself as a highly productive, rational and economical construction system due to characteristics as: simplification of execution techniques, less diversity of materials employed, reduction of labor and speed execution. In structural masonry, one of the execution possibilities that can be explored is the non-filling of vertical joints, also called dry joints. The adoption of this practice generates certain advantages as the reduction in the execution time of the construction, the reduction of the consumption of materials and the minimization of the cracking caused by the intrinsic deformations, such as retraction and thermal deformations. However, despite be employed to some years in country, the implications of its use often has been not properly considered in the projects, this is due to the fact that there is few research that deals with this subject. Moreover, the existing researches sometimes present results that diverge from each other, mainly with respect to the resistance to compression and shear. In this work, numerical simulations of small walls of ceramic and concrete units, with and without vertical joints, tested with the requirements of NBR 15812-2 (ABNT, 2010), NBR 15961-2 (ABNT, 2011) and NBR 14321 (ABNT, 1999). The purpose of this work was to evaluate the influence of non-filling of vertical joints on the compressive strength and shear strength of the masonry. For the numerical analyzes, the Finite Element Method was used from DIANA? software. According to the numerical results obtained in the models in compression, and the comparison between these and the experimental results, it was possible to conclude that the absence of the vertical joints did not influence the compressive strength of the masonry. However, from the results obtained in the shear models, it was concluded that it was not possible to quantitatively evaluate the influence of the vertical joints on the shear strength of the masonry.

Network utility maximization has emerged as a powerful tool in studying flow control, resource allocation and other cross-layer optimization problems. In this work, we study a flow control problem in the optimization framework. The objective is to maximize the sum utility of the users subject to the flow constraints of the network. The utility maximization is solved in a distributed setting; the network operator does not know the user utility functions and the users know neither the rate choices of other users nor the flow constraints of the network. We build upon a popular decomposition technique proposed by Kelly [Eur. Trans. Telecommun., 8(1), 1997] to solve the utility maximization problem in the aforementioned distributed setting. The technique decomposes the utility maximization problem into a user problem, solved by each user and a network problem solved by the network. We propose an iterative algorithm based on this decomposition technique. In each iteration, the users communicate to the network their willingness to pay for the network resources. The network allocates rates in a proportionally fair manner based on the prices communicated by the users. The new feature of the proposed algorithm is that the rates allocated by the network remains feasible at all times. We show that the iterates put out by the algorithm asymptotically tracks a differential inclusion. We also show that the solution to the differential inclusion converges to the system optimal point via Lyapunov theory. We use a popular benchmark algorithm due to Kelly et al. [J. of the Oper. Res. Soc., 49(3), 1998] that involves fast user updates coupled with slow network updates in the form of additive increase and multiplicative decrease of the user flows. The proposed algorithm may be viewed as one with fast user update and fast network update that keeps the iterates feasible at all times. Simulations suggest that our proposed algorithm converges faster than the aforementioned benchmark algorithm. When the flows originate or terminate at a single node, the network problem is the maximization of a so-called d-separable objective function over the bases of a polymatroid. The solution is the lexicographically optimal base of the polymatroid. We map the problem of finding the lexicographically optimal base of a polymatroid to the geometrical problem of finding the concave cover of a set of points on a two-dimensional plane. We also describe an algorithm that finds the concave cover in linear time. Next, we consider the minimization of a more general objective function, i.e., a separable convex function, over the bases of a polymatroid with a special structure. We propose a novel decomposition algorithm and show the proof of correctness and optimality of the algorithm via the theory of polymatroids. Further, motivated by the need to handle piece-wise linear concave utility functions, we extend the decomposition algorithm to handle the case when the separable convex functions are not continuously differentiable or not strictly convex. We then provide a proof of its correctness and optimality.

New algorithms for the matrix exponential and its Fréchet derivative are presented. First, we derive a new scaling and squaring algorithm (denoted expm[new]) for computing eA, where A is any square matrix, that mitigates the overscaling problem. The algorithm is built on the algorithm of Higham [SIAM J.Matrix Anal. Appl., 26(4): 1179-1193, 2005] but improves on it by two key features. The first, specific to triangular matrices, is to compute the diagonal elements in the squaring phase as exponentials instead of powering them. The second is to base the backward error analysis that underlies the algorithm on members of the sequence {||Ak||1/k} instead of ||A||. The terms ||Ak||1/k are estimated without computing powers of A by using a matrix 1-norm estimator. Second, a new algorithm is developed for computing the action of the matrix exponential on a matrix, etAB, where A is an n x n matrix and B is n x n₀ with n₀ << n. The algorithm works for any A, its computational cost is dominated by the formation of products of A with n x n₀ matrices, and the only input parameter is a backward error tolerance. The algorithm can return a single matrix etAB or a sequence etkAB on an equally spaced grid of points tk. It uses the scaling part of the scaling and squaring method together with a truncated Taylor series approximation to the exponential. It determines the amount of scaling and the Taylor degree using the strategy of expm[new].Preprocessing steps are used to reduce the cost of the algorithm. An important application of the algorithm is to exponential integrators for ordinary differential equations. It is shown that the sums of the form $\sum_{k=0}^p\varphi_k(A)u_k$ that arise in exponential integrators, where the $\varphi_k$ are related to the exponential function, can be expressed in terms of a single exponential of a matrix of dimension $n+p$ built by augmenting $A$ with additional rows and columns. Third, a general framework for simultaneously computing a matrix function, $f(A)$, and its Fréchet derivative in the direction $E$, $L_f(A,E)$, is established for a wide range of matrix functions. In particular, we extend the algorithm of Higham and $\mathrm{expm_{new}}$ to two algorithms that intertwine the evaluation of both $e^A$ and $L(A,E)$ at a cost about three times that for computing $e^A$ alone. These two extended algorithms are then adapted to algorithms that simultaneously calculate $e^A$ together with an estimate of its condition number. Finally, we show that $L_f(A,E)$, where $f$ is a real-valued matrix function and $A$ and $E$ are real matrices, can be approximated by $\Im f(A+ihE)/h$ for some suitably small $h$. This approximation generalizes the complex step approximation known in the scalar case, and is proved to be of second order in $h$ for analytic functions $f$ and also for the matrix sign function. It is shown that it does not suffer the inherent cancellation that limits the accuracy of finite difference approximations in floating point arithmetic. However, cancellation does nevertheless vitiate the approximation when the underlying method for evaluating $f$ employs complex arithmetic. The complex step approximation is attractive when specialized methods for evaluating the Fréchet derivative are not available.

Cette étude a été effectuée pour améliorer l'efficacité des mesures de stockage de carbone par des techniques de télédétection dans les plantations de Para rubber (Hevea brasiliensis) en Thaïlande. Les estimations des méthodes actuelles de stockage de carbone s’opèrent à l’aide de la classification classique basée sur le système des pixels basée sur des images de moyenne résolution et produit donc des résultats d’une grande incertitude. En revanche, dans cette étude, la méthode utilisée est basée sur des images de très haute résolution provenant du satellite THAICHOTE, associés à des mesures sur le terrain, dans le bassin de Mae num Prasae. L’utilisation de l'objet en fonction des classifications, les plantations cartographiées, leur âge et leur circonférence ont été estimées à partir d'un modèle paramétrique dérivé de données spectrales, de texture et 3D. L'étude propose une information de texture plus utile que l'information spectrale pour capturer l’architecture des arbres du couvert et donc l'âge de la canopée. Un spectrale de Global Environment Monitoring (GEMI) et quatre texturales de Homogeneity, Dissimilarity, Contrast et Variance ont été utilisées dans l'ajustement du modèle (régression R2 = 0,87) pour estimer la circonférence et l'âge des arbres tandis que le Canopy Height Model (CHM) de 3D n’était pas autorisée pour construire l'information de classement d'images. Environ 154 km2 des 232 km2 de la zone étudiée sont couverts par des plantations. La quantité totale de la biomasse et des stocks de carbone s’élève à 2,23 mégatonnes et 0,99 mégatonnes C, respectivement avec une incertitude de 11%. En 2011, la superficie totale séquestrée était de 121 tCO2 par des plantations. / This study explored to the improve efficiency of measurements of carbon stock by remote sensing techniques on Para rubber (Hevea brasiliensis) plantations in East Thailand. Current methods of carbon stock estimations use classical pixel based classification on middle-resolution images and thus produce results with a large uncertainty. In this study, the method use very high resolution images from the THAICHOTE satellite, associated to field measurements to estimates the carbon stock and its evolution in the Mae num Prasae watershed. Using object based classifications, the plantations have been mapped and their age and girth have been estimated from a parametric model derived from spectral, textural, 3D information and field data. The results of this study show that these data can be used to map Para rubber plantation and distinguish age classes of trees in the plantations. The study propose that textural information is more useful than spectral information to capture tree canopy architecture and thus the age of the canopy. One spectral of Global Environment Monitoring (GEMI) and four textural information of Homogeneity, Dissimilarity, Contrast and Variance were used in the fit model (multiple linear regression R2=0.87) for estimating the Para rubber tree girth and age while the 3D information (canopy height model: CHM) was not appropriated to build the image classification information. Around 154 km2 of the 232 km2 of the studied area are covered by Para rubber plantations. The total amount of biomass and carbon stocks are 2.23 Megatons and 0.99 Megatons C respectively with uncertainty of 11%. In 2011, the total area sequestered 121 tCO2 by Para rubber plantations.

University of the Witwatersrand Discipline of Psychology MASTERS RESEARCH REPORT / This study conducted a thematic content analysis qualitative methods approach to explore the perceptions of the “Impact of the 2012 Marikana labour unrest on labour and industrial relations in South Africa”. Perceptions of industrial relations stakeholder role efficacy; causes and consequences of labour-management conflict, intra-union conflict and inter-union conflict are discussed. Economic, political, sociological factors as well as the influence of group dynamics are discussed to frame the impact of the 2012 Marikana incident on labour and industrial relations in South Africa.

Made available in DSpace on 2014-12-17T15:14:52Z (GMT). No. of bitstreams: 1 LucioMSA.pdf: 2791852 bytes, checksum: 5cba560727621c49e5fc8f6cc80083c9 (MD5) Previous issue date: 1999-12-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / We use a finite diference eulerian numerical code, called ZEUS 3D, to do simulations involving the collision between two magnetized molecular clouds, aiming to evaluate the rate of star formation triggered by the collision and to analyse how that rate varies depending on the relative orientations between the cloud magnetic fields before the shock. The ZEUS 3D code is not an easy code to handle. We had to create two subroutines, one to study the cloud-cloud collision and the other for the data output. ZEUS is a modular code. Its hierarchical way of working is explained as well as the way our subroutines work. We adopt two sets of different initial values for density, temperature and magnetic field of the clouds and of the external medium in order to study the collision between two molecular clouds. For each set, we analyse in detail six cases with different directions and orientations of the cloud magnetic field relative to direction of motion of the clouds. The analysis of these twelve cases allowed us to conform analytical-theoretical proposals found in the literature, and to obtain several original results. Previous works indicate that, if the cloud magnetic fields before the collision are orthogonal to the direction of motion, then a strong inhibition of star formation will occur during a cloud-cloud shock, whereas if those magnetic fields are parallel to the direction of motion, star formation will be stimulated. Our treatment of the problem confirmed numerically those results, and further allowed us to quantify the relative star forming efficiencies in each case. Moreover, we propose and analyse an intermediate case where the field of one of the clouds is orthogonal to the motion and the field of the other one is parallel to the motion. We conclude that, in this case, the rate at which the star formation occurs has a value also intermediate between the two extreme cases we mentioned above. Besides that we study the case in which the fields are orthogonal to the direction of the motion but, instead of being parallel to each other, they are anti-parallel, and we obtained for this case the corresponding variation of the star formation rate due to this alteration of the field configuration. This last case has not been studied in the literature before. Our study allows us to obtain, from the simulations, the rate of star formation in each case, as well as the temporal dependence of that rate as each collision evolves, what we do in detail for one of the cases in particular. The values we obtain for the rate of star formation are in accordance with those expected from the presently existing observational data / Usamos um c?digo num?rico euleriano de diferen?as finitas, chamado ZEUS 3D, para fazer simula??es envolvendo a colis?o entre duas nuvens moleculares magnetizadas, visando avaliar a taxa de forma??o estelar desencadeada pela colis?o e analisar como essa taxa varia, dependendo das orienta??es relativas entre os campos magn?ticos das nuvens antes do choque. O c?digo ZEUS 3D n?o ? um c?digo de f?cil tratamento. Tivemos de criar duas subrotinas, uma para estudar a colis?o nuvem-nuvem e outra para a sa?da dos dados. O ZEUS ? um c?digo baseado em m?dulos. Seu funcionamento hier?rquico ? explicado, assim como o funcionamento de nossas subrotinas. Estudamos a colis?o entre duas nuvens moleculares, empregando dois conjuntos diferentes de valores iniciais para densidade, temperatura e campo magn?tico das nuvens e do meio. Para cada conjunto desses valores, analisamos detalhadamente seis casos com diferentes dire??es e sentidos do campo magn?tico das nuvens em rela??o ? dire??o do seu movimento. A an?lise desses doze casos nos permitiu comprovar previs?es te?rico-anal?ticas propostas na literatura e nos possibilitou a obten??o de v?rios resultados originais. Trabalhos anteriores indicaram que, se os campos magn?ticos das nuvens antes da colis?o forem ortogonais ? dire??o do movimento, ocorre forte inibi??o da forma??o de estrelas durante um choque nuvem-nuvem, enquanto que se esses campos magn?ticos forem paralelos ao movimento haver? indu??o da forma??o estelar. Nosso tratamento do problema comprovou numericamente essas previs?es, permitindo inclusive quantificar as relativas efici?ncias de forma??o estelar em cada caso. E mais: propusemos e analisamos um caso intermedi?rio, onde uma nuvem teria campo ortogonal ao movimento e a outra teria campo paralelo a este. Conclu?mos que neste caso ocorre forma??o estelar com uma taxa tamb?m intermedi?ria entre os dois casos extremos mencionados. Al?m disso, estudamos o caso onde os campos s?o ortogonais ? dire??o do movimento mas, em vez de serem paralelos um ao outro, eles s?o anti-paralelos, o que tampouco havia sido feito na literatura, e obtivemos a correspondente varia??o da taxa de forma??o de estrelas devido a essa altera??o de configura??o. Nosso estudo permite extrair das simula??es a taxa de forma??o estelar em cada caso, assim como a depend?ncia temporal dessa taxa conforme cada uma das colis?es estudadas evolui, o que fazemos em detalhe para um dos casos em particular. Os valores que obtivemos para a taxa de forma??o de estrelas est? em acordo com os dados observacionais existentes at? o presente momento

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-04-27T17:37:56Z No. of bitstreams: 1 main_old.pdf: 8825994 bytes, checksum: 363343ed7cc0b9cad81c747d8ce8c193 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-05-10T12:31:20Z (GMT) No. of bitstreams: 1 main_old.pdf: 8825994 bytes, checksum: 363343ed7cc0b9cad81c747d8ce8c193 (MD5) / Made available in DSpace on 2018-05-10T12:49:59Z (GMT). No. of bitstreams: 1 main_old.pdf: 8825994 bytes, checksum: 363343ed7cc0b9cad81c747d8ce8c193 (MD5) Previous issue date: 2018-03-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The present work uses a numerical computational methodology and the concept of gravity current to determine the effect of the variable properties on a sediment flow. Through two different numerical approaches, it compares the advantages of using an ILES or DNS in order to reduce computational time and still keep physics of the problem. Four different cases are compared, with and without variable properties, totaling eight simulations. To verify the code a case (CASE 0) was simulated based on the article of cite espath13 by varying the coefficient of dynamic viscosity and the fall velocity using a DNS methodology. For CASE I, the effect of the ILES methodology was verified with the same parameters of CASE 0. Finally, to increase the concentration and the Reynolds number, CASES II and III use sediment parameters such as coal and pume in Boussinesq approach. It was observed that the effect of the variable fall velocity helps to reduce the velocity of the front and maintains more material in suspension for longer time periods, being this effect observed in experimental cases, which demonstrates the even greater approximation of numerical simulations with cases real. / Com o objetivo de determinar qual o efeito do da varia??o do coeficiente de viscosidade din?mica e da velocidade de queda num escoamento com sedimentos, o presente trabalho faz uso de uma metodologia num?rica computacional e do conceito de corrente de gravidade. Por meio de duas abordagens num?ricas distintas, compara as vantagens de utilizar uma abordagem do tipo ILES com DNS, afim de reduzir o tempo computacional e ainda manter grande parte do efeito da f?sica no problema. S?o comparados quatro casos distintos, com e sem propriedades vari?veis, totalizando oito simula??es. Para verificar o c?digo, foi simulado um caso (CASO 0) baseado no artigo de Espath et al. (2013) variando o coeficiente de viscosidade din?mica e a velocidade de queda utilizando uma metodologia DNS. Para o CASO I, foi verificado o efeito da metodologia ILES, com os mesmos par?metros do CASO 0. Por fim, para aumentar a concentra??o e, por consequ?ncia, o n?mero de Reynolds, os CASOS II e III utilizaram par?metros de sedimentos como carv?o e pume na aproxima??o de Boussinesq. Foi observado que o efeito da velocidade de queda vari?vel auxilia na redu??o da velocidade da posi??o da frente e mant?m mais material em suspens?o por mais tempo, sendo tal efeito observado em casos experimentais, o que demonstra a aproxima??o ainda maior das simula??es num?ricas com casos reais.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-06-05T13:28:29Z No. of bitstreams: 1 frantz2018simulacoes.pdf: 23131075 bytes, checksum: e748910d1820968a07c86be9461b7489 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-06-12T12:40:17Z (GMT) No. of bitstreams: 1 frantz2018simulacoes.pdf: 23131075 bytes, checksum: e748910d1820968a07c86be9461b7489 (MD5) / Made available in DSpace on 2018-06-12T12:49:08Z (GMT). No. of bitstreams: 1 frantz2018simulacoes.pdf: 23131075 bytes, checksum: e748910d1820968a07c86be9461b7489 (MD5) Previous issue date: 2018-03-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This work investigates the method of large-eddy simulation (LES) in the context of gravity currents, which is found necessary since it allows a substantial increase in the order of magnitude of the characteristic Reynolds number used in numerical simulations, approaching them with natural scales, in addition to significantly reducing the computational cost. The implicit large eddy simulation (ILES) methodology, based on the spectral vanishing viscosity model, is unprecedentedly employed in the context of gravity currents, is compared against with explicit methods such as the static and dynamic Smagorisnky. The evaluation of the models is performed based on statistics from a direct numerical simulation (DNS). Results demonstrate that the first model based purely on numerical dissipation, introduced by means of the second order derivative, generates better correlations with the direct simulation. Finally, experimental cases of the literature, in different flow configurations, are reproduced numerically showing good agreement in terms of the front position evolution. / Este trabalho investiga o m?todo de simula??o de grandes escalas (LES) no contexto de correntes gravitacionais. O mesmo se faz necess?rio, visto que possibilita um aumento substancial da ordem de grandeza do n?mero de Reynolds caracter?stico utilizado em simula??es num?ricas, aproximando os mesmos de escalas naturais, al?m de reduzir significativamente o custo computacional dos c?lculos. A avalia??o dos modelos ? realizada utilizando uma base de dados de simula??o num?rica direta (DNS). A metodologia de simula??o de grandes escalas impl?cita (ILES), baseada no modelo de viscosidade turbulenta espectral, ? colocado a prova de maneira in?dita no contexto de correntes de gravidade com m?todos expl?citos dispon?veis na literatura. Resultados demonstram que o mesmo, baseado puramente em dissipa??o num?rica introduzida por meio do comportamento dos esquemas de derivada de segunda ordem, gera melhores correla??es com as estat?sticas baseadas em campos m?dios da simula??o direta. Por fim, casos experimentais da literatura, em diferentes configura??es de escoamento, s?o reproduzidos numericamente.

Made available in DSpace on 2014-12-17T14:55:47Z (GMT). No. of bitstreams: 1 EmanueleSRM_DISSERT.pdf: 2423953 bytes, checksum: 516a98f7f1136b2e57265165c2a43b20 (MD5) Previous issue date: 2010-12-21 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Frequency Selective Surfaces (FSS) are periodic structures in one or two dimensions that act as spatial filters, can be formed by elements of type conductors patches or apertures, functioning as filters band-stop or band-pass respectively. The interest in the study of FSS has grown through the years, because such structures meet specific requirements as low-cost, reduced dimensions and weighs, beyond the possibility to integrate with other microwave circuits. The most varied applications for such structures have been investigated, as for example, radomes, antennas systems for airplanes, electromagnetic filters for reflective antennas, absorbers structures, etc. Several methods have been used for the analysis of FSS, among them, the Wave Method (WCIP). Are various shapes of elements that can be used in FSS, as for example, fractal type, which presents a relative geometric complexity. This work has as main objective to propose a simplification geometric procedure a fractal FSS, from the analysis of influence of details (gaps) of geometry of the same in behavior of the resonance frequency. Complementarily is shown a simple method to adjust the frequency resonance through analysis of a FSS, which uses a square basic cell, in which are inserted two reentrance and dimensions these reentrance are varied, making it possible to adjust the frequency. For this, the structures are analyzed numerically, using WCIP, and later are characterized experimentally comparing the results obtained. For the two cases is evaluated, the influence of electric and magnetic fields, the latter through the electric current density vector. Is realized a bibliographic study about the theme and are presented suggestions for the continuation of this work / As Superf?cies Seletivas de Frequ?ncia (FSS) s?o estruturas peri?dicas em uma ou duas dimens?es que atuam como filtros espaciais, podendo ser formadas por elementos do tipo patches condutores ou aberturas, funcionando como filtros rejeita-faixa ou passa-faixa, respectivamente. O interesse no estudo das FSS tem crescido atrav?s dos anos, pois tais estruturas atendem a requisitos espec?ficos como baixo custo, dimens?es e pesos reduzidos, al?m da possibilidade de se integrar com outros circuitos de micro-ondas. As mais variadas aplica??es para tais estruturas t?m sido investigadas, como por exemplo, radomes, sistemas de antenas para avi?es, filtros eletromagn?ticos para antenas refletoras, estruturas absorvedoras, etc. V?rios m?todos t?m sido utilizados para a an?lise de FSS, dentre eles, o M?todo das Ondas (WCIP). S?o diversas as formas de elementos que podem ser utilizados em FSS, como por exemplo, os do tipo fractal, que apresenta uma relativa complexidade geom?trica. Este trabalho tem como objetivo principal propor um procedimento de simplifica??o geom?trica de uma FSS fractal, a partir da an?lise da influ?ncia dos detalhes (fendas) da geometria da mesma no comportamento da frequ?ncia de resson?ncia. De forma complementar ? mostrado um m?todo simples de ajustar a frequ?ncia de resson?ncia atrav?s da an?lise de uma FSS, que utiliza uma c?lula b?sica retangular, na qual s?o inseridas duas reentr?ncias e as dimens?es dessas reentr?ncias s?o variadas, tornando poss?vel o ajuste da frequ?ncia. Para isso, as estruturas s?o analisadas numericamente, utilizando o WCIP, e posteriormente s?o caracterizadas experimentalmente, comparando-se os resultados obtidos. Para os dois casos ? avaliada, a influ?ncia dos campos el?trico e magn?tico, este ?ltimo atrav?s do vetor densidade de corrente el?trica. ? realizado um estudo bibliogr?fico a cerca do tema e s?o apresentadas sugest?es para a continuidade deste trabalho