Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-08T21:26:33Z No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-07-12T21:45:11Z (GMT) No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) / Made available in DSpace on 2016-07-12T21:45:11Z (GMT). No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) Previous issue date: 2014-10-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O fraturamento em rochas carbon?ticas vem atra?ndo aten??o devido as novas descobertas de petr?leo em reservat?rios carbon?ticos. Este estudo investiga como fraturas (falhas e juntas) submetidas a diferentes campos de tens?es se comportam e como seu comportamento pode estar associado ? gera??o de carste e, consequentemente, ao aumento da porosidade secund?ria em carbonatos. Neste estudo usei imagens de sat?lite e imagens de ve?culos a?reos n?o tripulado, al?m de dados de campo para identificar e mapear falhas e juntas no lajedo de rochas carbon?ticas, que considero ser um bom an?logo para reservat?rio carbonat?co. O lajedo est? localizado na Forma??o Janda?ra, Bacia Potiguar. Os dados de campo foram modelados utilizando o software TECTOS, que usa an?lise de elementos finitos para fraturas 2D. Formam identificados tr?s sets de juntas NS, EW e NW-SE, que foram reativadas como falhas. Os maiores valores de Ratio of Failure by Stress (RFS) obtido na modelagem representam o qu?o perto a rocha est? de tocar a envolt?ria Mohr-Coulomb, que indica a concentra??o da tens?o. Os resultados indicam que as tens?es tect?nicas est?o concentradas em zonas estruturais preferenciais, que s?o locais ideais para a gera??o de dissolu??o nos carbonatos. Observei dissolu??o ao longo de fraturas e planos de estratifica??o em todo o lajedo. No entanto, concluo que os maiores valores de RFS ocorrem no cruzamento e termina??es das fraturas. Estes s?o lugares de concentra??o do carste. Finalmente sugiro que existe uma rela??o direta entre a concentra??o da tens?o e a localiza??o da dissolu??o em rochas carbon?ticas. ABSTRACT The fracturing in carbonate rocks has been attracting increasing attention. This study investigates how the fractures (faults and joints) behaves subjected to the stress field and how their behavior may be associated with the generation of karst and consequently to increased secondary porosity in these rocks. We use satellite imagery and VANT image and field data to identify and map the faults and joints, analogous outcrop carbonate rock reservoir in the Janda?ra Formation, Potiguar Basin. Then, we modeled our data using the TECTOS software, which uses finite element analysis for 2D fractures. The results indicate that the tectonic stresses are concentrated in preferred structural zones, which are ideal places for the generation of dissolution in carbonates. The highest values of Ratio of Failure by Stress (RFS) obtained in modeling represents how close the rock is touching the envelopment Morh-Coulomb. We conclude that the highest values of RFS occur at the intersection of fractures and termination thereof. These sites are places of concentration of karst. From the data collected in the field there were three sets of fractures with NS, EW and NW-SE directions. In all cases, the regular pattern of fractures indicates that the system of lineaments 80 ? and 340 ? direction are sets of joints that were reactivated as faults. The joints and faults are shown consistent with the extracted lineaments in the GoogleEarth image. However, it is observed that, in marioria cases, both sets are reactivated as strike-slip faults. Tectonic stylolites occur mainly found in Lajedo showing shortening parallel to the joints (stylolites NS direction), formed in the same tectonic event. In every part of the flagstone we observed dissolution along fractures and bedding planes of the rock. Combining field data with numerical modeling we suggest that there is a direct relationship between stress concentration and location of dissolution. / The fracturing in carbonate rocks has been attracting increasingly attention due to new oil discoveries in carbonate reservoirs. This study investigates how the fractures (faults and joints) behave when subjected to different stress fields and how their behavior may be associated with the generation of karst and consequently to increased secondary porosity in these rocks. In this study I used satellite imagery and unmanned aerial vehicle UAV images and field data to identify and map faults and joints in a carbonate outcrop, which I consider a good analogue of carbonate reservoir. The outcrop comprises rocks of the Janda?ra Formation, Potiguar Basin. Field data were modeled using the TECTOS software, which uses finite element analysis for 2D fracture modeling. I identified three sets of fractures were identified: NS, EW and NW-SE. They correspond to faults that reactivate joint sets. The Ratio of Failure by Stress (RFS) represents stress concentration and how close the rock is to failure and reach the Mohr-Coulomb envelopment. The results indicate that the tectonic stresses are concentrated in preferred structural zones, which are ideal places for carbonate dissolution. Dissolution was observed along sedimentary bedding and fractures throughout the outcrop. However, I observed that the highest values of RFS occur in fracture intersections and terminations. These are site of karst concentration. I finally suggest that there is a relationship between stress concentration and location of karst dissolution in carbonate rocks.

Made available in DSpace on 2014-12-17T14:57:38Z (GMT). No. of bitstreams: 1 AdrianoSB.pdf: 1824941 bytes, checksum: 9594a533193a54f04b78499b7820f209 (MD5) Previous issue date: 2007-07-30 / The processing of materials through plasma has been growing enough in the last times in several technological applications, more specifically in surfaces treatment. That growth is due, mainly, to the great applicability of plasmas as energy source, where it assumes behavior thermal, chemical and/or physical. On the other hand, the multiplicity of simultaneous physical effects (thermal, chemical and physical interactions) present in plasmas increases the complexity for understanding their interaction with solids. In that sense, as an initial step for the development of that subject, the present work treats of the computational simulation of the heating and cooling processes of steel and copper samples immersed in a plasma atmosphere, by considering two experimental geometric configurations: hollow and plane cathode. In order to reach such goal, three computational models were developed in Fortran 90 language: an one-dimensional transient model (1D, t), a two-dimensional transient model (2D, t) and a two-dimensional transient model (2D, t) which take into account the presence of a sample holder in the experimental assembly. The models were developed based on the finite volume method and, for the two-dimensional configurations, the effect of hollow cathode on the sample was considered as a lateral external heat source. The main results obtained with the three computational models, as temperature distribution and thermal gradients in the samples and in the holder, were compared with those developed by the Laboratory of Plasma, LabPlasma/UFRN, and with experiments available in the literature. The behavior showed indicates the validity of the developed codes and illustrate the need of the use of such computational tool in that process type, due to the great easiness of obtaining thermal information of interest / O processamento de materiais por plasmas tem crescido bastante nos ?ltimos tempos em diversas aplica??es tecnol?gicas, mais especificamente no tratamento de superf?cies. Esse crescimento se deve, principalmente, pela grande aplicabilidade do plasma como fonte energ?tica. Por outro lado, a multiplicidade de efeitos simult?neos presentes no plasma, (intera??es t?rmicas, qu?micas e f?sicas) aumenta a complexidade para entendimento da sua intera??o com s?lidos. Nesse sentido, como um passo inicial para o desenvolvimento desse tema, o presente trabalho trata da simula??o computacional de aquecimento e resfriamento de amostras de a?o e cobre em ambientes de plasma, considerando-se duas configura??es geom?tricas: catodo oco e catodo planar. Para tal, tr?s modelos computacionais foram desenvolvidos na linguagem Fortran 90: um modelo unidimensional transiente sem suporte (1D,t), um modelo bidimensional transiente sem suporte (2D,t) e um modelo bidimensional transiente (2D,t) que considera a presen?a de um suporte na montagem experimental. Os modelos foram desenvolvidos utilizando-se o m?todo dos volumes finitos e, para as situa??es bidimensionais, o efeito de catodo oco sobre a amostra foi considerado como uma fonte externa de calor lateral. Os resultados obtidos com os tr?s modelos computacionais, como a distribui??o de temperatura nas amostras e nos suportes, os seus gradientes t?rmicos, em fun??o de alguns experimentos de aquecimento e resfriamento desenvolvidos pelo Laborat?rio de Plasma, LabPlasma/UFRN, e de experimentos reportados na literatura, apontam para a validade dos c?digos desenvolvidos e ilustram a necessidade da utiliza??o dessa ferramenta nesse tipo de processo, pela sua facilidade de disponibiliza??o de informa??es t?rmicas de interesse

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-08-01T12:12:38Z No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-08-03T19:57:19Z (GMT) No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) / Made available in DSpace on 2017-08-03T19:57:19Z (GMT). No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) Previous issue date: 2017-03-27 / Canais compostos s?o caracterizados por possu?rem canais principais, regi?es mais largas onde o fluido escoa axialmente com maior facilidade, e canais secund?rios (fendas) que s?o regi?es mais estreitas onde o fluido ? desacelerado devido aos efeitos viscosos. Para determinar os coeficientes de transfer?ncia de calor e de atrito nos canais compostos ? necess?rio entender o comportamento dos escoamentos turbulentos que ocorrem neles, por?m isto continua sendo um desafio para a engenharia. Estes canais apresentam, al?m do fluxo axial paralelo ao canal, flutua??es na velocidade transversal que est?o associadas a estruturas de grande escala denominadas de estruturas coerentes. Assim, neste trabalho buscou-se analisar os efeitos do aparecimento dessas estruturas e as suas consequ?ncias para o escoamento, tanto na parte din?mica como na t?rmica. Para isto foi utilizado uma geometria empregada em trabalhos experimentais, que ? composta por um canal retangular com um tubo interno, de di?metro D, que est? a uma dist?ncia W/D da parede inferior do canal. O fluido escoa axialmente apenas na parte externa do tubo. No total foram analisados cinco casos, modificando apenas a rela??o W/D (espa?amento da fenda). Para examinar as caracter?sticas do escoamento turbulento no interior deste canal, empregou-se o pacote ANSYS CFX 13 com o modelo de turbul?ncia SAS-SST. Os resultados mostraram que quanto maior a rela??o W/D, mais elevados foram os valores do Fator de Desempenho T?rmico. Este fator ? uma rela??o entre o n?mero de Nusselt e o fator de atrito e, quanto maior seu valor, melhor ? o desempenho t?rmico do canal. Em rela??o as estruturas coerentes, nos canais em que surgiram, elas t?m uma grande influ?ncia sobre os escoamentos, j? que essas estruturas acabam elevando os valores locais dos coeficientes de transfer?ncia de calor e de atrito superficial, o que torna esse fen?meno indispens?vel nos projetos e an?lises de seguran?a de equipamentos que possuem fendas. / Compound channels are characterized by having main channels, wider regions where the fluid flows axially more easily, and narrower regions (gaps) where the fluid is decelerated due to the viscous effects. In order to determine the heat transfer coefficients in these channels it is necessary to understand the behavior of the turbulent flows in them, but this remains a challenge for engineering. These channels have, in addition to axial flow parallel to the channel, a cross flow velocity in the gap region that are associated with large scale structures called coherent structures. Thus, the goal of this work is to compare the effects on the appearance of coherent structures of large scale and its consequences for the flow in dynamic and thermal characteristics. To accomplish this, the same geometry used in the experimental works was applied, which is composed of a rectangular channel with an internal tube of diameter D and it is located at a distance W/D from the lower wall of the channel. The fluid flows axially only on the outside of the tube. In total, five different cases were analyzed, modifying only the W/D ratio (gap distance). To examine the characteristics of the turbulent flow inside this channel, ANSYS CFX13 with SASSST turbulence model was applied. The results showed that the W/D ratio increase also caused an increase in the values of the Thermal Performance Factor. This factor is a relationship between the Nusselt number and the friction factor, and the higher its value, better is the thermal performance of the channel. In relation to the coherent structures, in the channels in which they arise, they have a great influence on the flows, since these structures end up raising the local values of heat transfer and friction coefficients, making this phenomenon indispensable in projects and safety analyzes of equipment with gap.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-08-29T12:36:36Z No. of bitstreams: 1 2017 - Iris Cristiane Magistrali.pdf: 5586295 bytes, checksum: cf90d85c09628780240eede5db4ec99e (MD5) / Made available in DSpace on 2017-08-29T12:36:36Z (GMT). No. of bitstreams: 1 2017 - Iris Cristiane Magistrali.pdf: 5586295 bytes, checksum: cf90d85c09628780240eede5db4ec99e (MD5) Previous issue date: 2017-02-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The Intergovernmental Panel on Climate Change (IPCC) has published reports on issues related to global climate changes. As a result, the climatic suitability of various agricultural crops in different regions of the world may change. Sugarcane is an important agricultural species and it is grown in several regions of the world, mainly for the generation of sugar and ethanol. Given this, there is a need for studies that assess the consequences of climate change in this crop in future scenarios. Therefore, the present work has as objectives: 1) to evaluate the performance of two climatic models CCCma (Canadian Center for Climate Modeling and Analysis) and GFDL (Geophysical Fluid Dynamic Laboratory) in the baseline period (1961-2000), and in the Future scenario A1B (2046-2065); 2) to elaborate the zoning of sugarcane for the State of Rio de Janeiro due to the A1B scenario considered intermediate. For the evaluation of the models performance, descriptive statistical analysis and spatial interpolation (Kriging and Co- Kriging ordinary) was used based on temperature and rainfall variables in water balance of the crop for the elaboration of agro climatic zoning, calculated by Thornthwaite & Mather?s (1955) method. The zoning was elaborated based on the reclassified thematic maps of water deficit and temperature. We used images from SRTM (Shuttle Radar Topography Mission) radar for altimetry, and map of use and ground cover. The results referring to the descriptive measures in the different points of the model showed the average rainfall ranged from 1118.02 mm to 1447.47 mm for the CCCma model. However, for the GFDL model average rainfall was lower than the CCCma, ranging from 804.82 mm to 1013.72 mm. The temperature averages presented similar behaviour and presented little oscillation during the year, when compared with the rainfall. For the CCCma model, the minimum average temperature was 21.02 ?C and the maximum was 22.99 ?C. For the GFDL model, the mean minimum temperature was 20.62 ?C and the maximum was 23.47 ?C. The CCCma model presented the data closest to the National Oceanic & Atmospheric Administration (NOOA) reanalysis data, and the GFDL model underestimated most rainfall and temperature data. The average rainfall of the NOOA data ranged from a minimum to a maximum of 947.74 mm at 1689.77 mm, respectively, and the minimum and maximum average temperature of 19.62 ? C and 21.62 ? C, respectively. Through geostatistics, it was possible to verify that, for the past and future scenarios, the exponential transitive model presented in the majority of cases the least degree of spatial dependence (GDE), being therefore considered the best. When comparing the GDE of the two climate models, noticed that the CCCma presented the best geostatistical performance. Due to the high GDE values, it was not possible to interpolate the GFDL model data regarding temperature for the future scenario. Through the product MCD12Q1, it was possible to register relevant differences in rainfall and temperature. Urban areas in general have lower amounts of rainfall and higher temperatures compared to areas with forest occurrence. In relation to the zoning, the results showed that for the past conditions, as well as for future projections, there is no water restriction for the development of the sugarcane crop. The temperature showed an increase in the future scenario adopted and, consequently, expansion of areas suitable for cultivation / O Painel Intergovernamental sobre Mudan?as Clim?ticas (IPCC) tem publicado relat?rios sobre quest?es ligadas as altera??es no clima global. Em fun??o disso, a aptid?o clim?tica de diversas culturas agr?colas em diferentes regi?es do mundo pode sofrer altera??es. A cana-de-a??car ? uma esp?cie agr?cola importante e, ? cultivada em v?rias regi?es do mundo, principalmente para a gera??o de a??car e etanol. Diante disso, existe a necessidade de estudos que avaliem as consequ?ncias das mudan?as clim?ticas nessa cultura em cen?rios futuros. Portanto, o presente trabalho tem como objetivos: 1) avaliar o desempenho de dois modelos clim?ticos CCCma (Canadian Centre for Climate Modelling and Analysis) e GFDL (Geophysical Fluid Dynamic Laboratory) no per?odo ?baseline? (1961-2000), e no cen?rio futuro A1B (2046-2065); 2) elaborar o zoneamento da cana-de-a??car para o Estado do Rio de Janeiro em fun??o do cen?rio de emiss?o A1B considerado intermedi?rio. Para a avalia??o do desempenho dos modelos foi utilizado an?lise estat?stica descritiva e interpola??o espacial (Krigagem e Co-Krigagem ordin?ria) para as vari?veis temperatura e chuva. Para a etapa da elabora??o do zoneamento agroclim?tico procedeu-se o c?lculo dos balan?os h?dricos da cultura, pelo m?todo de Thornthwaite e Mather (1955). Baseados nos mapas tem?ticos reclassificados de defici?ncia h?drica e temperatura elaborou-se o zoneamento. Utilizou-se imagens provenientes do radar SRTM (Shuttle Radar Topography Mission) para a altimetria, e, mapa de uso e cobertura do solo. Os resultados referentes as medidas descritivas nos diferentes pontos do modelo, mostraram que a m?dia da chuva variou de 1118,02 mm ? 1447,47 mm, para o modelo CCCma. Entretanto, para o modelo GFDL a m?dia da chuva foi inferior ao CCCma, variando de 804,82 mm ? 1013,72 mm. As m?dias de temperatura apresentaram comportamento semelhante e apresentaram pouca oscila??o durante o ano, se comparada a chuva. Para o modelo CCCma a temperatura m?dia m?nima foi de 21,02 ?C e a m?xima de 22,99 ?C. Para o modelo GFDL temperatura m?dia m?nima foi de 20,62 ?C e a m?xima de 23,47 ?C. O modelo CCCma apresentou os dados mais pr?ximos aos dados de rean?lise do National Oceanic & Atmospheric Administration (NOOA), sendo que o modelo GFDL subestimou a maioria dos dados de chuva e temperatura. A chuva m?dia dos dados do NOOA variou entre a m?nima e m?xima de 947,74 mm ? 1689,77 mm, respectivamente, e a temperatura m?dia m?nima e m?xima de 19,62 ?C e 21,62 ?C, respectivamente. Atrav?s da geoestat?stica, foi poss?vel constatar que tanto para o cen?rio passado quanto o futuro, o modelo transitivo exponencial apresentou na maioria dos casos o menor grau de depend?ncia espacial (GDE), sendo portanto, considerado o melhor. Ao comparar o GDE dos dois modelos clim?ticos, verifica-se que o CCCma apresentou o melhor desempenho geoestat?stico. Devido ao altos valores de GDE n?o foi poss?vel interpolar os dados do modelo GFDL referente a temperatura para o cen?rio futuro. Atrav?s do produto MCD12Q1 foi poss?vel registrar diferen?as relevantes em rela??o a chuva e a temperatura. ?reas urbanas em geral apresentam menores quantidades de chuvas e maiores temperaturas se comparadas ? ?reas com ocorr?ncia de floresta. Em rela??o ao zoneamento os resultados mostraram que tanto para as condi??es do passado, quanto para proje??es futuras, n?o h? restri??o h?drica para o desenvolvimento da cultura da cana-de-a??car. A temperatura apresentou um aumento no cen?rio futuro adotado e consequentemente expans?o de ?reas aptas ao cultivo. Praticamente todo o estado apresenta ?reas aptas em rela??o a topografia, exceto as regi?es serranas. Atrav?s do zoneamento final, ix foi poss?vel constatar que no cen?rio futuro adotado haver? uma expans?o da cana-de-a??car em torno de 58%, podendo esse resultado estar aliado ao aumento da temperatura.

Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2012

Network Utility Maximization (NUM) provides a key conceptual framework to study reward allocation amongst a collection of users/entities in disciplines as diverse as economics, law and engineering. However when the available resources and/or users' utilities vary over time, reward allocations will tend to vary, which in turn may have a detrimental impact on the users' overall satisfaction or quality of experience. In this thesis, we introduce a generalization of the NUM framework which incorporates the detrimental impact of temporal variability in a user's allocated rewards and explicitly incorporates Mean-Variability-Fairness tradeoffs, i.e., tradeoffs amongst the mean and variability in users' reward allocations, as well as fairness across users. We propose a simple online algorithm to realize these tradeoffs, which, under stationary ergodic assumptions, is shown to be asymptotically optimal, i.e., achieves a long term performance equal to that of an offline algorithm with knowledge of the future variability in the system. This substantially extends work on NUM to an interesting class of relevant problems where users/entities are sensitive to temporal variability in their service or allocated rewards. We extend the theoretical framework and tools developed for realizing Mean-Variability-Fairness tradeoffs to develop a simple online algorithm to solve the problem of optimizing video delivery in networks. The tremendous increase in mobile video traffic projected for the future along with insufficiency of available wireless network capacity makes this one of the most important networking problems today. Specifically, we consider a network supporting video clients streaming stored video, and focus on the problem of jointly optimizing network resource allocation and video clients' video quality adaptation. Our objective is to fairly maximize video clients' video Quality of Experience (QoE) realizing Mean-Variability-Fairness tradeoffs, incorporating client preferences on rebuffering time and the cost of video delivery. We present a simple asymptotically optimal online algorithm NOVA (Network Optimization for Video Adaptation) to solve the problem. Our algorithm uses minimal communication, 'distributes' the tasks of network resource allocation to a centralized network controller, and video clients' video quality adaptation to the respective video clients. Further, the quality adaptation is also optimal for standalone video clients, and is an asynchronous algorithm well suited for use in the Dynamic Adaptive Streaming over HTTP (DASH) framework. We also extend NOVA for use with more general video QoE models, and study NOVA accounting for practical considerations like time varying number of video clients, sharing with other types of traffic, performance under legacy resource allocation policies, videos with variable sized segments etc. / text

Made available in DSpace on 2014-12-17T14:08:43Z (GMT). No. of bitstreams: 1 TiagoPC_DISSERT.pdf: 1471839 bytes, checksum: 916c40a19572e874803d077f6852a370 (MD5) Previous issue date: 2010-09-18 / In Brazilian Northeast there are reservoirs with heavy oil, which use steam flooding as a recovery method. This process allows to reduce oil viscosity, increasing its mobility and consequently its oil recovery. Steam injection is a thermal method and can occurs in continues or cyclic form. Cyclic steam stimulation (CSS) can be repeated several times. Each cycle consisting of three stages: steam injection, soaking time and production phase. CSS becomes less efficient with an increase of number of cycles. Thus, this work aims to study the influence of compositional models in cyclic steam injection and the effects of some parameters, such like: flow injection, steam quality and temperature of steam injected, analyzing the influence of pseudocomponents numbers on oil rate, cumulative oil, oil recovery and simulation time. In the situations analyzed was compared the model of fluid of three phases and three components known as Blackoil . Simulations were done using commercial software (CMG), it was analyzed a homogeneous reservoir with characteristics similar to those found in Brazilian Northeast. It was observed that an increase of components number, increase the time spent in simulation. As for analyzed parameters, it appears that the steam rate, and steam quality has influence on cumulative oil and oil recovery. The number of components did not a lot influenced on oil recovery, however it has influenced on gas production / No Nordeste brasileiro existem reservat?rios de ?leos pesados, nos quais se utiliza a inje??o de vapor como m?todo de recupera??o. Este processo permite diminuir a viscosidade do ?leo, aumentando a sua mobilidade e melhorando o volume de ?leo a ser recuperado. A inje??o de vapor ? um m?todo t?rmico e ocorre na forma cont?nua ou c?clica. A inje??o c?clica de vapor pode ser repetida diversas vezes. Cada ciclo consiste de tr?s etapas distintas: a fase de inje??o, fase de fechamento (soaking) e fase de produ??o. A inje??o c?clica se torna menos eficiente ? medida que o n?mero de ciclos aumenta. Neste sentido, este trabalho visa estudar a influ?ncia de modelos composicionais na inje??o c?clica de vapor e os efeitos de alguns par?metros, tais como: vaz?o de inje??o, qualidade do vapor e temperatura do vapor injetado; analisando a influ?ncia do n?mero de pseudocomponentes, no que diz respeito ? vaz?o de ?leo, produ??o acumulada de ?leo, fator de recupera??o e tempo de simula??o. Nas situa??es analisadas foi comparado o modelo de fluido de tr?s fases e tr?s componentes conhecido como Black-oil . Foram realizadas simula??es, utilizando um simulador comercial a partir de um modelo de reservat?rio homog?neo com caracter?sticas similares ?s encontradas no Nordeste brasileiro. Observou-se que quanto maior o n?mero de componentes, maior ? o tempo gasto na simula??o. J? para os par?metros analisados, verifica-se que a vaz?o de inje??o de vapor e a qualidade do vapor influenciam na produ??o acumulada de ?leo e no fator de recupera??o. O n?mero de componentes n?o exerceu muita influ?ncia na produ??o acumulada, nem no fator de recupera??o de ?leo, por?m foi significativa na produ??o de g?s do sistema

Made available in DSpace on 2014-12-17T14:48:12Z (GMT). No. of bitstreams: 1 JohnGBG_DISSERT.pdf: 5632038 bytes, checksum: eabbd6743af14f648742650469c3d48f (MD5) Previous issue date: 2012-07-02 / A numerical study on the behavior of tied-back retaining walls in sand, using the finite element method (FEM) is presented. The analyses were performed using the software Plaxis 2D, and were focused on the development of horizontal displacements, horizontal stresses, shear forces and bending moments in the structure during the construction process. Emphasis was placed on the evaluation of wall embedment, tie-back horizontal spacing, wall thickness, and free anchor length on wall behavior. A representative soil profile of a specific region at the City of Natal, Brazil, was used in the numerical analyses. New facilities built on this region often include retaining structures of the same type studied herein. Soil behavior was modeled using the Mohr-Coulomb constitutive model, whereas the structural elements were modeled using the linear elastic model. Shear strength parameters of the soil layers were obtained from direct shear test results conducted with samples collected at the studied site. Deformation parameters were obtained from empirical correlations from SPT test results carried out on the studied site. The results of the numerical analyses revealed that the effect of wall embedment on the investigated parameters is virtually negligible. Conversely, the tie-back horizontal spacing plays an important role on the investigated parameters. The results also demonstrated that the wall thickness significantly affects the wall horizontal displacements, and the shear forces and bending moments within the retaining structure. However, wall thickness was not found to influence horizontal stresses in the structure / O presente trabalho apresenta um estudo num?rico atrav?s do m?todo dos elementos finitos (MEF) utilizando-se o aplicativo computacional Plaxis 2D, com o objetivo de verificar aspectos do comportamento de estruturas de conten??o atirantadas em areia. As an?lises foram dirigidas ao desenvolvimento dos deslocamentos horizontais, das tens?es horizontais e dos esfor?os internos (esfor?o cortante e momento fletor) durante o processo construtivo da estrutura. As simula??es num?ricas inclu?ram avalia??es da influ?ncia do comprimento da ficha, do espa?amento horizontal entre os tirantes, da espessura da parede e do comprimento do trecho livre. O perfil de solo utilizado nas simula??es num?ricas ? representativo de uma determinada regi?o da Cidade de Natal RN, na qual s?o constru?das com frequ?ncia conten??es do tipo analisado no presente trabalho. Utilizou-se o modelo constitutivo de Mohr-Coulomb para simular o comportamento do solo e o modelo el?stico linear para simular o comportamento dos elementos estruturais. Os par?metros de resist?ncia do solo foram determinados por meio de ensaios de cisalhamento direto e os par?metros de deformabilidade foram estimados atrav?s de correla??es emp?ricas obtidas de resultados de ensaios SPT executados na regi?o em estudo. Os resultados obtidos mostraram que varia??es no comprimento da ficha praticamente n?o influenciam o comportamento da estrutura, no ?mbito dos par?metros avaliados, ao passo que o espa?amento horizontal entre os tirantes apresenta forte influ?ncia sobre essas grandezas. Verificou-se tamb?m que a espessura da parede apresenta consider?vel influ?ncia sobre os deslocamentos horizontais e sobre os esfor?os internos e pouca influ?ncia sobre as tens?es horizontais

Made available in DSpace on 2014-12-17T14:48:17Z (GMT). No. of bitstreams: 1 GilvanBSJ_DISSERT.pdf: 3763149 bytes, checksum: 74cfc52e8eaadf3e1722a2a37d52aca9 (MD5) Previous issue date: 2014-03-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Usually masonry structures has low tension strength, hence the design to flexural efforts can results in high reinforcement ratio, specification of high unit and prism strength, structural members with larger section dimensions and modification in structural arrangement to be possible to use masonry members. The main objective of this study is to evaluate the stiffness, the efforts distribution and the effect of horizontal elements (girders) and vertical elements (counterforts) distribution on the behavior of masonry blocks retaining walls. For this purpose, numerical modeling was performed on typical retaining wall arrangements by varying the amount and placement of horizontal and vertical elements, beyond includes elements simulating the reactions of the soil supporting the foundation of the wall. The numerical modeling also include the macro modeling strategy in which the units, mortar and grout are discretized by a standard volume that represents the masonry elastic behavior. Also, numerical model results were compared with those ones of simplified models usually adopted in bending design of masonry elements. The results show horizontal displacements, principal and shear stresses distribution, and bending moments diagrams. From the analysis it was concluded that quantity and manner of distribution of the girders are both important factors to the panel flexural behavior, the inclusion of the foundation changed significantly the behavior of the wall, especially the horizontal displacements, and has been proposed a new way of considering the flanges section of the counterforts / As estruturas de alvenaria solicitadas por elevados esfor?os de flex?o podem necessitar, dada a baixa resist?ncia ? tra??o, de elevadas taxas de armadura; de maior resist?ncia ? compress?o da alvenaria; de elementos estruturais com maiores dimens?es ou mesmo um rearranjo desses elementos para possibilitar o emprego da alvenaria. O estudo ora apresentado tem por objetivo avaliar a rigidez, a distribui??o de esfor?os e o efeito da distribui??o de cintas e de elementos verticais (contrafortes) no caso de muros de arrimo de alvenaria estrutural de blocos. Para tanto, foram realizadas modelagens num?ricas de arranjos t?picos de muro, variando a quantidade e o posicionamento de cintas horizontais, o espa?amento entre os contrafortes, al?m de incluir elementos simulando as rea??es do solo de apoio na funda??o do muro. A modelagem num?rica realizada empregou a estrat?gia de macromodelagem em que os blocos, a argamassa e o graute s?o discretizados pelo volume padr?o representativo do comportamento el?stico da alvenaria. Alternativamente, os resultados do modelo num?rico foram comparados com os de modelos simplificados comumente adotados nos projetos desse tipo de elemento estrutural. A an?lise dos resultados consistiu na verifica??o dos deslocamentos transversais, na distribui??o das tens?es principais (para balizar um futuro modelo de bielas e tirantes e os modos de ruptura), na distribui??o das tens?es de cisalhamento, e na obten??o de diagramas de momento fletor. A partir das an?lises foi poss?vel concluir que n?o apenas a quantidade, mas tamb?m a forma de distribui??o das cintas ? um fator relevante para a distribui??o dos esfor?os no painel fletido (pano de alvenaria), a inclus?o dos elementos de funda??o alterou significativamente o comportamento do muro, principalmente os deslocamentos transversais, al?m de ter sido proposta uma nova forma de considera??o de flanges na se??o resistente do contraforte

Made available in DSpace on 2014-12-17T14:48:17Z (GMT). No. of bitstreams: 1 EdmilsonCR_DISSERT.pdf: 2891870 bytes, checksum: f918eb51bee8f43b778a96c5fd23f003 (MD5) Previous issue date: 2014-04-07 / The aim of this work is the numerical simulation of the mechanical performance of concrete affected by Alkali-Aggregate Reaction or RAA, reported by Stanton in 1940. The RAA has aroused attention in the context of Civil Engineering from the early 80, when they were reported consequences of his swelling effect in concrete structures, including cracking, failure and loss of serviceability. Despite the availability of experimental results the problem formulation still lacks refinement so that your solution remains doubtful. The numerical simulation is important resource for the assessment of damages in structures caused by the reaction, and their recoveries The tasks of support of this work were performed by means of the finite element approach, about orthotropic non-linear formulation, and, thermodynamic model of deformation by RAA. The results obtained revealed that the swelling effect of RAA induced decline of the mechanical performance of concrete by decreasing the margin of safety prior to the material failure. They showed that the temperature influences, exclusively, the kinetics of the reaction, so that the failure was the more precocious the higher the temperature of the solid mass of concrete / O objetivo deste trabalho ? a simula??o num?rica do desempenho Mec?nico de membros de concreto afetados pela Rea??o ?lcali-Agregado ou RAA, reportada por Stanton em 1940. A RAA despertou a aten??o no ?mbito da Engenharia Civil a partir da d?cada de 80, quando foram relatadas consequ?ncias de seu efeito expansivo em estruturas de concreto, incluindo fissura??o, ru?na e perda de funcionalidade. Apesar da disponibilidade de resultados experimentais a formula??o do problema ainda carece de aperfei?oamento de modo que sua solu??o permanece duvidosa. A simula??o num?rica ? recurso importante para a avalia??o de danos em estruturas provocados pela rea??o, e suas recupera??es. As tarefas de suporte desse trabalho foram realizadas mediante a aproxima??o por elementos finitos, sobre formula??o ortotr?pica n?o linear, e, modelo termodin?mico de deforma??es por RAA. Os resultados obtidos revelaram que o efeito expansivo da RAA induziu o decl?nio do desempenho mec?nico do concreto diminuindo a margem de seguran?a pr?via ? ru?na do material. Ficou evidente que a temperatura influencia, exclusivamente, a cin?tica da rea??o, de modo que a ru?na foi tanto mais precoce quanto maior a temperatura da massa s?lida do concreto