788 resultados para Permeabilidade da dentina


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Reservoirs that present highly viscous oils require methods to aid in their recovery to the surface. The elev ated oil viscosity hinders its flow through porous media and conventional recovery methods have not obtained significant efficiency. As such, the injection of steam into the reservoir through an injection well has been the most widely used method of therma l recovery, for it allows elevated volumes of recovery due to the viscosity reduction of the oil, facilitating the oil’s mobility within the rock formation and consequently into the production well where it will be exploited. On the other hand, the injecti on of vapor not only affects the fluids found in the rock pores, but the entire structure that composes the well where it is injected due to the high temperatures used in the process. This temperature increment is conducted to the cement, found in the annu lus, responsible for the isolation of the well and the well casing. Temperatures above 110 ̊C create new fazes rich in calcium in the cement matrix, resulting in the reduction of its permeability and the consequential phenomenon of mechanical resistance ret rogression. These alterations generate faults in the cement, reducing the well’s hydraulic isolation, creating insecurity in the operations in which the well will be submitted as well as the reduction of its economic life span. As a way of reducing this re trograde effect, this study has the objective of evaluating the incorporation of rice husk ash as a mineral additive substitute of silica flour , commercially utilized as a source of silica to reduce the CaO/SiO 2 ratio in the cement pastes submitted to high temperatures in thermal recovery. Cement pastes were formulated containing 20 and 30% levels of ash, apart from the basic paste (water + cement) and a reference paste (water + cement + 40% silica flour) for comparison purposes. The tests were executed th rough compression resistance tests, X - Ray diffraction (XRD) techniques, thermogravimetry (TG), scanning electron microscopy (SEM) and chemical anal ysis BY X - ray fluorescence (EDS) on the pastes submitted to cure at low temperatures (45 ̊C) for 28 days following a cure at 280 ̊C and a pressure of 2,000 PSI for 3 days, simulating vapor injection. The results obtained show that the paste containing 30% r ice shell ash is satisfactory, obtaining mechanical resistance desired and equivalent to that of the paste containing 40% silica flour, since the products obtained were hydrated with low CaO/SiO 2 ratio, like the Tobermorita and Xonotlita fases, proving its applicability in well subject to vapor injection.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This work deals with the analytical, computational and experimental study of phenomena related to the Eddy current induction in low permeability means for embedded electromagnetic braking systems applications. The phenomena of forces generation in opposing to the variation of stationary magnetic flux produced by DC power supplies, set in motion by the application of an external propulsive force are addressed. The study is motivated by search for solving the problem of speed control of PIGs used to verifying and maintaining pipelines, and is led based on the analytical models synthesis, validated by means of computer simulations in Finite Elements environment, provided by engineering support software; and with experimental tests conducted under controlled laboratory conditions. Finally, a damping systems design methodology based on analyzes results conducted throughout the study is presented

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Inúmeras estruturas de concreto no Brasil e no mundo estão atingindo o limite de sua vida útil projetada, completando um ciclo de cinco ou mais décadas de uso e operação. Além das estruturas mais antigas, existem ainda estruturas com reduzido tempo de serviço, e qualidade discutível, que já apresentam patologias em estado tão avançado que chegam a comprometer o seu desempenho. Vindo ao encontro dessas necessidades e no sentido de contribuir para o avanço científico e tecnológico do setor, este trabalho apresenta um método para dosagem, preparo e aplicação de argamassas de alto desempenho para recuperação de estruturas deterioradas, além de sugerir procedimentos para a realização desses reparos, fomentando a cultura das manutenções preventivas e desmistificando a complexidade atribuída a tais operações. Para tanto, foram realizados ensaios mecânicos, microestruturais e relacionados à durabilidade em corpos-de-prova moldados com sílica ativa e látex de estireno-butadieno. Os resultados indicaram que a adoção desses ingredientes, na composição da argamassa de reparo, provocou uma redução significativa da permeabilidade total e descontinuidade de poros, assim como promoveu uma melhor integridade dos constituintes da argamassa, traduzindo-se em uma ampliação, expressiva, das suas capacidades mecânicas. Quando comparada aos produtos industrializados da construção civil, com padrões similares, proporcionou uma economia da ordem de 85%, que permitiria recuperar, com os mesmos custos, quase cinco vezes mais estruturas comprometidas. Este estudo, de viés altamente tecnológico, vem oferecer à construção civil uma argamassa polimérica de alto desempenho, com função reparadora e custo mais acessível, que pode ser adotada em canteiros de obras, implementando ações de natureza sustentável e ainda atendendo às atuais exigências elencadas pela literatura, relacionadas à desempenho, vida útil e durabilidade das estruturas reparadas.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The understanding of the occurrence and flow of groundwater in the subsurface is of fundamental importance in the exploitation of water, just like knowledge of all associated hydrogeological context. These factors are primarily controlled by geometry of a certain pore system, given the nature of sedimentary aquifers. Thus, the microstructural characterization, as the interconnectivity of the system, it is essential to know the macro properties porosity and permeability of reservoir rock, in which can be done on a statistical characterization by twodimensional analysis. The latter is being held on a computing platform, using image thin sections of reservoir rock, allowing the prediction of the properties effective porosity and hydraulic conductivity. For Barreiras Aquifer to obtain such parameters derived primarily from the interpretation of tests of aquifers, a practice that usually involves a fairly complex logistics in terms of equipment and personnel required in addition to high cost of operation. Thus, the analysis and digital image processing is presented as an alternative tool for the characterization of hydraulic parameters, showing up as a practical and inexpensive method. This methodology is based on a flowchart work involving sampling, preparation of thin sections and their respective images, segmentation and geometric characterization, three-dimensional reconstruction and flow simulation. In this research, computational image analysis of thin sections of rocks has shown that aquifer storage coefficients ranging from 0,035 to 0,12 with an average of 0,076, while its hydrogeological substrate (associated with the top of the carbonate sequence outcropping not region) presents effective porosities of the order of 2%. For the transport regime, it is evidenced that the methodology presents results below of those found in the bibliographic data relating to hydraulic conductivity, mean values of 1,04 x10-6 m/s, with fluctuations between 2,94 x10-6 m/s and 3,61x10-8 m/s, probably due to the larger scale study and the heterogeneity of the medium studied.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Nanoemulsions are emulsified systems, characterized for reduced droplet size (50- 500nm), which the main characteristic are kinect stability and thermodynamic instability. These are promising systems on cosmetic area due to their droplet size that provide different advantages when compared to conventional systems, among others, larger surface area and better permeability. The Opuntia ficus-indica (L.) Mill is a plant cultivated on Caatinga Brazilian biome, which has great socioeconomic importance to region. This plant shows carbohydrates utilized for cosmetic industry as moisturizing active in their chemical composition. The aim of study was to develop, characterize, evaluate stability and moisturizing efficacy of cosmetic nanoemulsions added to Opuntia ficus-indica (L.) Mill extract. Nanoemulsions preparation was made using a low energy method. Different nanoemulsions were formulated varying the ratio of oil, water and surfactant phases beyond xanthan gum (0.5% e 1%) and Opuntia ficus-indica (L.) Mill hydroglycolic extract addition on 1% and 3%. Obtained nanoemulsions were submitted to preliminary and accelerated stability tests. The evaluated parameters monitored were: macroscopic aspect, pH value, droplet size, zeta potential and polydispersion index, during 60 days on different temperatures. Stable formulations were submitted to moisturizing efficacy assessment by capacitance and transepidermal water loss methodologies during 5 hours. Stable samples were white and showed homogeneous and fluid aspect, pH value was inside ideal range (4,5-6,0) to topical application and droplet size under 200nm characterizing these system as nanoemulsions. Developed nanoemulsions did not decrease transepidermal water loss, however increased the water content on stratum corneum, highlighting the nanoemulsions containing 0.5% of xanthan gum and 1% of hydroglycolic extract. This work presents cosmetic moisturizing nanoemulsions composed to vegetal raw material from Brazilian Caatinga with potential to be used on cosmetic area.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The distribution of diagenetic alterations in Late Cenomanian siliciclastic reservoirs from Potiguar Basin was influenced by the stratigraphic framework and the depositional system. Seismic sections and geophysical logs of two wells drilled in the SW portion of the mentioned basin above register regional stratigraphic surfaces representing maximum floods related to a transgressive event. The sequential analysis of 80 m of drill core (~450 m deep) recognized nine depositional facies with an upwards granodecrescent standard piling that limits cycles with an erosional conglomeratic base (lag) overlain by intercalations of medium to very fine sandstones showing cross bedding (channel, planar and low angled) and horizontal bedding (plane-parallel , wave and flaser). The top of the cycles is marked by the deposition of pelites and the development of paleosoils and lagoons. The correlation of genetically related facies reveals associations of channel fillings, crevasse, and flood plains deposited in a transgressive system. Detailed descriptions of seventy nine thin sections aided by MEV-EBSD/EDS, DRX and stable isotope analyses in sandstones revealed an arcosian composition and complex textural arrays with abundant smectite fringes continuously covering primary components, mechanically infiltrated cuticles and moldic and intragrain pores. K-feldspar epitaxial overgrowth covers microcline and orthoclase grains before any other phase. Abundant pseudomatrix due to the compactation of mud intraclasts concentrate along the stratification planes, locally replaced by macrocristalline calcite and microcrystalline and framboidal pyrite. Kaolinite (booklets and vermicular), microcrystalline smectite, microcrystalline titanium minerals and pyrite replace the primary components. The intergrain porosity prevails over the moldic, intragrain and contraction porosities. The pores are poorly connected due to the presence of intergranular smectite, k-feldspar overgrowth, infiltrated mud and pseudomatrix. The sandstones were subjected to eodiagenetic conditions next to the surface and shallow burial mesodiagenetic conditions. The diagenetic alterations reduced the porosity and the permeability mainly due to the precipitation of smectite fringes, compactation of mud intraclasts onto the pseudomatrix and cementing by poikilotopic calcite characterizing different reservoir petrofacies. These diagenetic products acted as barriers and detours to the flow of fluids thus reducing the quality of the reservoir.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The recognition of karst reservoirs in carbonate rocks has become increasingly common. However, most karst features are small to be recognized in seismic sections or larger than expected to be investigated with borehole data. One way forward has been the study of analogue outcrops and caves. The present study investigates lithofacies and karst processes, which lead to the generation of the largest system of caves in South America. The study area is located in the Neoproterozoic Una Group in central-eastern Brazil. This province comprises several systems of carbonate caves (Karmann and Sanchéz, 1979), which include the Toca da Boa Vista and Barriguda caves, considered the largest caves in South America (Auler and Smart, 2003). These caves were formed mainly in dolomites of the Salitre Formation, which was deposited in a shallow marine environment in an epicontinental sea (Medeiros and Pereira, 1994). The Salitre Formation in the cave area comprises laminated mud/wakestones, intraclastic grainstones, oncolitic grainstones, oolitic grainstones, microbial laminites, colunar stromatolites, trombolites and fine siliciclastic rocks (marls, shales, and siltites). A thin layer and chert nodules also occur at the top of the carbonate unit. Phosphate deposits are also found. Our preliminary data indicate that folds and associated joints control the main karstification event at the end of the Brasiliano orogeny (740-540 Ma). We recognized five lithofacies in the cave system: (1) Bottom layers of grainstone with cross bedding comprise the main unit affected by speleogenesis, (2) thin grainstone layers with thin siltite layers, (3) microbial laminites layers, (4) layers of columnar stromatolites, and a (5) top layer of siltite. Levels (1) to (3) are affected by intense fracturing, whereas levels (4) and (5) seal the caves and have little fracturing. Chert, calcite and gipsite veins cut across the carbonate units and play a major role in diagenesis. Our preliminary study indicate that hypogenic spelogenesis is the main process of karst development and contributed significantly to the generation of secondary porosity and permeability in the carbonate units.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A constante busca da indústria de petróleo pelo aumento de produção à um baixo custo operacional faz necessário o desenvolvimento de tecnologias que una as duas necessidades. A Acidificação de matriz é um método de estimulação frequentemente empregado para aumentar produção de um poço de petróleo com um custo menor se comparado a um fraturamento. O objetivo deste trabalho é estudar a obtenção de nanoemulsões ácidas para aplicação em acidificação de matriz. As nanoemulsões são capazes de retardar reações, por diminuir a difusão do ácido no meio, possibilitando a acidificação em reservatórios com baixa permeabilidade. Os reagentes utilizados para formar os sistemas nanoemulsionados foram UNT L90/OMS e RNX 110 como tensoativos, Sec-butanol como cotensoativo, Xileno e Querosene como fase óleo e Solução de HCl como fase aquosa. As nanoemulsões foram obtidas a partir da diluição de microemulsões com água ou solução de HCl. Foi realizado estudo das tensões superficiais, estudo das cinéticas de reação, avaliação da injeção em rocha carbonática e remoção de borra asfáltica. As nanoemulsões apresentaram tensão superficial menor que suas microemulsões de origem. As nanoemulsões tiveram êxito em retardar a reação entre CaCO3 e HCl, onde o sistema mais eficiente é composto por UNT L90/OMS, Secbutanol, Querosene e solução de HCl. As nanoemulsões foram eficientes em formar wormholes em plugs de carbonato calcitico com baixa permeabilidade natural. As wormholes proporcionaram incremento de permeabilidade alcançando valores de até 390 mD. O sistema ácido apresentou bom resultado de remoção de borra asfáltica, mostrando o potencial das nanoemulsões em remover esse tipo de dano. Conclui-se que os sistemas nanoemulsionados têm grande potencial de aplicação em acidificação de matriz.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The microstrip antennas in your simplest form consist of a ground plane and a dielectric substrate which supports a conductive tape. As these antennas have some limitations, this work presents a study of anisotropic substrates, as well as some results in microstrip antennas with circular patch, aiming to overcome these limitations, especially in applications at 4G technology. These anisotropic substrates are those in which electrical permittivity and magnetic permeability are represented by tensors of second order. The study consists of a theoretical analysis of substrates and development of a mathematical formalism, the Transverse Transmission Line Method, aimed the application of these substrates in microstrip antennas. Among the substrates used in this study, there are the ferrimagnetic and metamaterials, in which some miniaturizations of the antennas are achieved. For antennas with circular patch, are considered arrays and modified ground planes in order to achieve improvement in parameters, in particular, gain and bandwidth. Several simulations have been made and antennas were constructed so that the measured values could be compared with the simulated values.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Natal, como outras cidades metropolitanas brasileiras, sofreu nas últimas décadas uma forte transformação impulsionada pelo mercado imobiliário e pela indústria da construção civil. A produção de apartamentos em condomínios fechados vem crescendo e tornando cada vez mais comum, no cenário urbano, a presença de torres residenciais (com extensos muros e grades, fachadas cegas e guaritas) que favorecem o “desurbanismo”. Por outro lado, este tipo de empreendimento, o edifício multifamiliar, apresenta plantas baixas padronizadas as quais frequentemente são incoerentes com a diversidade de perfis dos usuários. A consequência disso são reformas e adequações nos apartamentos após a entrega da obra. Diante deste contexto, elaborei uma proposta arquitetônica, que é apresentada nesta dissertação, como alternativa a essa modalidade de produção que está se tornando dominante no Brasil e em outros países. Dois conceitos nortearam esta proposta: a) o conceito de urbanidade cujo objetivo no projeto arquitetônico é favorecer a percepção do outro (por copresença e/ou cociência) através da permeabilidade, acessos e passagens entre o edifício e o entorno. A maneira como os cheios (barreiras) se estruturam com os vazios foi trabalhada de modo que definissem propriedades espaciais cuja intenção é facilitar o encontro e a diversidade entre moradores e entre estes e os de fora, no entanto sem desconsiderar o problema da violência urbana e, consequentemente a importância da promoção de segurança para os usuários. b) o conceito de flexibilidade a fim de possibilitar ao consumidor final o desmembramento da unidade habitacional em duas e, em especial, a participação e ou escolha na concepção do arranjo interno e da definição dos acabamentos do seu apartamento. Tudo isto durante a construção do empreendimento e ao longo da sua vida útil, favorecendo assim o potencial de diversidade (grupos sociais), adaptabilidade a fases distintas da vida e durabilidade do edifício.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this work it is assessed the performance of Portland cement-based mortar to the grouting of type II ceramic plates with the addition of unusable tire rubber powder. It is presented a bibliographical review about the subject in which is done the theoretical and methodological foundation of the whole investigative process. The analyzed universe comprises a sample of mortar to the grouting of conventional ceramic plates type II (reference sample) and five more samples to the grouting of ceramic plates type II, which were made up of the addition of unusable tire rubber powder in the respective proportion (in mass) of 4%, 8%, 12%, 16% and 20%. These mortar samples were subject to the trials of determination of the consistency index (Brazilian Standard NBR 13276:2005), water retention ( Brazilian Standard NBR 14992 Attachment B:2003), permeability in 240 minutes (Brazilian Standard NBR 14992 Attachment G:2003), absorption of water by immersion (Brazilian Standard NBR 9781:2013), resistance to compression (Brazilian Standard NBR14992 Attachment D: 2003), resistance to traction in the flexion (Brazilian Standard NBR 13279:2005), resistance of traction adherence (Brazilian Standard NBR 14081 part 4:2012) and hardened mass density (Brazilian Standard NBR 13280: 2005). It has been found out from the analyzes of the results in the trial the following situation: the reference mortar used met the established requirements in the norms of specifications corresponding to only six from the eight parameters assessed in the research; the mortar with addition of 4,0% of tire rubber powder met the established requirements corresponding to only the resistance to compression and the resistance of adherence to traction. Thus, the other kinds of mortar with addition of 8,0 %, 12,0 %, 16,0 % and 20,0 % of tire rubber powder met the requirements of specifications corresponding to only the resistance to compression and the resistance of adherence to traction. This result concludes that the adding of tire rubber powder does not grant improvement to the mortar of type II grouting to the laying of ceramic plates.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this work it is assessed the performance of Portland cement-based mortar to the grouting of type II ceramic plates with the addition of unusable tire rubber powder. It is presented a bibliographical review about the subject in which is done the theoretical and methodological foundation of the whole investigative process. The analyzed universe comprises a sample of mortar to the grouting of conventional ceramic plates type II (reference sample) and five more samples to the grouting of ceramic plates type II, which were made up of the addition of unusable tire rubber powder in the respective proportion (in mass) of 4%, 8%, 12%, 16% and 20%. These mortar samples were subject to the trials of determination of the consistency index (Brazilian Standard NBR 13276:2005), water retention ( Brazilian Standard NBR 14992 Attachment B:2003), permeability in 240 minutes (Brazilian Standard NBR 14992 Attachment G:2003), absorption of water by immersion (Brazilian Standard NBR 9781:2013), resistance to compression (Brazilian Standard NBR14992 Attachment D: 2003), resistance to traction in the flexion (Brazilian Standard NBR 13279:2005), resistance of traction adherence (Brazilian Standard NBR 14081 part 4:2012) and hardened mass density (Brazilian Standard NBR 13280: 2005). It has been found out from the analyzes of the results in the trial the following situation: the reference mortar used met the established requirements in the norms of specifications corresponding to only six from the eight parameters assessed in the research; the mortar with addition of 4,0% of tire rubber powder met the established requirements corresponding to only the resistance to compression and the resistance of adherence to traction. Thus, the other kinds of mortar with addition of 8,0 %, 12,0 %, 16,0 % and 20,0 % of tire rubber powder met the requirements of specifications corresponding to only the resistance to compression and the resistance of adherence to traction. This result concludes that the adding of tire rubber powder does not grant improvement to the mortar of type II grouting to the laying of ceramic plates.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Esse trabalho tem como objetivo apresentar configurações de substratos dielétricos inovadores projetados e fabricados a partir de estruturas metamateriais. Para isso, são avaliados diversos fatores que podem influenciar no seu desempenho. A princípio, foi feito um levantamento bibliográfico a respeito dos temas, que estão relacionados com as pesquisas sobre: materiais dielétricos, metamateriais e interferometria óptica. São estudados, pesquisados e desenvolvidos dois projetos experimentais propostos, que comprovam a eficiência de métodos, para se alcançar a permeabilidade magnética negativa na formação de metamateriais. O primeiro projeto é a produção de uma nova estrutura, com u anel ressoador triangular equilateral (Split Equilateral Triangle Resonator - SETR). O segundo projeto: aplica os princípios da interferometria óptica, especialmente, com o interferômetro de Fabry-Perot. Técnicas para obtenção dos dispositivos que complementam a placa metamaterial como substrato foram pesquisadas na literatura e exemplificadas principalmente por meio de simulações e medições. Foram feitas comparações, simulações e medições de estruturas convencionais e especiais. As experiências se concentram nas evoluções e modelagens de substratos metamateriais com aplicações em antenas de microfita. As melhorias de alguns parâmetros de desempenho de antenas também são relatadas. As simulações das antenas foram feitas nos programas computacionais comerciais. Os resultados medidos foram obtidos com um analisador vetorial de redes da Rhode and Schwarz modelo ZVB 14.