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In real life, immediately after joint replacement, the artificial joint is actually bathed in blood (and clotted blood) instead of synovial fluid. Blood contains large molecules and cells of size ~ 5 to 20 μm suspended in plasma and considered to be a non-Newtonian (pseudoplastic) fluid with density of 1060 Kg/m³ and viscosity ~ 0.01 Pas at shear rates of 3000 s⁻¹ (as obtained in this work). The effect of these properties on friction and lubrication is not fully understood and, so far to our knowledge, hardly any studies have been carried out regarding friction of metal-on-metal bearings with various clearances in the presence of lubricants such as blood or a fluid containing macromolecules such as hyaluronic acid (HA) which is a major component of synovial fluid increasing its viscosity and lubricating properties. In this work, therefore, we have investigated the frictional behaviour of a group of Smith and Nephew Birmingham Hip Resurfacing implants with a nominal diameter of 50mm and diametral clearances in the range ~ 80 μm to 300 μm, in the presence of blood (clotted and whole blood), a combination of bovine serum (BS) with hyaluronic acid (HA) and carboxymethyl cellulose (CMC, as gelling agent) adjusted to a range of viscosities (~0.001-0.2 Pas), and bovine serum with CMC adjusted to a similar range of viscosities. These results suggested that reduced clearance bearings have the potential to generate high friction especially in the presence of blood which is indeed the in vivo lubricant in the early weeks after implantation. Friction factors in higher clearance bearings were found to be lower than those of the lower clearance bearings using blood as the lubricant. Similar trends, i.e. increase in friction factor with reduction in diametral clearance, were found to be also the case using a combination of BS+CMC or BS+HA+CMC as lubricants having viscosities in the range 0.1-0.2 and 0.03-0.14 Pas, respectively. On the other hand, all the lubricants with lower viscosities in the range 0.001-0.0013 and 0.001-0.013 Pas for both BS+CMC and BS+HA+CMC, respectively, showed the opposite effect, i.e. caused an increase in friction factor with increase in diametral clearance. Another six large diameter (50mm nominal) BHR deflected prostheses with various clearances (~ 50-280μm after cup deflection) were friction tested in vitro in the presence of blood and clotted blood to study the effect of cup deflection on friction. It was found that the biological lubricants caused higher friction factors at the lower diametral clearances for blood and clotted blood as clearance decreased from 280μm to 50μm (after deflection). The result of this investigation has suggested strongly that the optimum clearance for the 50 mm diameter MOM BHR implants to be ≥150μm and <235μm when blood lubricant used, so as to avoid high frictions (i.e. avoid friction factors >0.2) and be able to accommodate a mixed lubrication mode and hence lower the risk of micro- or even macro-motion specially immediately after hip implantation. These suggested optimum clearances will also allow for low friction (i.e. friction factors of <0.2-0.07) and reasonable lubrication (dominantly mixed regime) for the likely cup deflection occurring as a result of press-fit fixation.

Esta pesquisa tem como objetivo a descrição e a análise do funcionamento de debates veiculados pela rede mundial de computadores. O corpus compreende três discussões coletadas na internet que abrangem gêneros discursivos distintos (a lista de discussão, o chat com convidados e o fórum eletrônico), desenvolvidas por dois provedores de grande circulação nacional: América on-line (AOL) e Universo on-line (UOL). O foco da pesquisa se concentra na observação de como interagem os internautas e quais estratégias utilizam no momento em que debatem um tópico específico, também na descrição dos três gêneros digitais selecionados. Dentro desse universo, pouco sabemos sobre o funcionamento do ato argumentativo - peça essencial no mundo da comunicação. Uma vez que a interação se processa através de um canal eletrônico e os falantes não estão diretamente em contato, o jogo argumentativo assume características específicas. Por apresentar uma condição de produção peculiar, o discurso no meio virtual prescinde, muitas vezes, de elementos não-lingüísticos - tão essenciais para influir sobre o outro, dar mais emotividade aos enunciados, para convencer e persuadir, etc. Como todo processo interacional não pode ser apartado de seu contexto específico de produção, este trabalho também investiga a rede digital, para conhecer essa mediadora dos processos de comunicação e conseqüente \"fundadora\" de diversos gêneros discursivos, os chamados gêneros digitais. / This investigation aims to describing and analysing how debates carried out by means of the worldwide computer web operate. The corpus encompasses three discussions collected at the Internet, covering different discursive genres (the discussion list, the chat with invited guests and the electronic forum), developed by two large providers used in Brazil, i.e. America On-line (AOL) and Universo On-line (UOL). Besides focusing on the description of the three digital genres selected, the research is centered on the observation of how internet users interact and which strategies are employed by them while debating a specific topic. Within this universe, little do we know of how the argumentative act - essential in the realm of communication - operates. Since interaction is processed via an electronic channel, and speakers are not actually in contact, the argumentative game takes up specific characteristics. Because it presents peculiar production conditions, the speech within the virtual media often requires non-linguistic elements - rather essential in utterances whose functions might be to influence others, show emotion, convince, persuade, etc As is the case in every interactional process, the ones described here cannot be parted from their specific production contexts, thus, this research\'s investigation of the digital network, in order to be familiar with this mediator of communication processes and consequent \"founder\" of several discursive genres - called digital genres.

No description available.

Made available in DSpace on 2014-12-17T15:01:13Z (GMT). No. of bitstreams: 1 ValdirCRN.pdf: 131656 bytes, checksum: 4153e21d4042d68f4cdd2a9f2c14b5e9 (MD5) Previous issue date: 2007-08-31 / Petroleum is a complex combination of various classes of hydrocarbons, with paraffinic, naphtenic and aromatic compounds being those more commonly found in its composition. The recent changes in the world scenario, the large reserves of heavy oils and also the lack of new discoveries of large petroleum fields are indications that, in the near future, the oil recovery by conventional methods will be limited. In order to increase the efficiency of the extraction process, enhanced recovery methods are cited in applications where conventional techniques have proven to be little effective. The injection of surfactant solutions as an enhanced recovery method is advantageous in that surfactants are able to reduce the interfacial tensions between water and oil, thus augmenting the displacement efficiency and, as a consequence, increasing the recovery factor. This work aims to investigate the effects of some parameters that influence the surfactant behavior in solution, namely the type of surfactant, the critical micelle concentration (CMC) and the surface and interface tensions between fluids. Seawater solutions containing the surfactants PAN, PHN and PJN have been prepared for presenting lower interfacial tensions with petroleum and higher stability under increasing temperature and salinity. They were examined in an experimental apparatus designed to assess the recovery factor. Botucatu (Brazil) sandstone plug samples were submitted to assay steps comprising saturation with seawater and petroleum, conventional recovery with seawater and enhanced recovery with surfactant solutions. The plugs had porosity between 29.6 and 32.0%, with average effective permeability to water of 83 mD. The PJN surfactant, at a concentration 1000% above CMC in water, had a higher recovery factor, causing the original oil in place to be recovered by an extra 20.97%, after conventional recovery with seawater / O petr?leo ? uma combina??o complexa de v?rias s?ries de hidrocarbonetos, sendo as mais comumente encontradas as parafinicas, naft?nicas e arom?ticas. As recentes mudan?as no cen?rio mundial, as grandes reservas de ?leos pesados, bem como a escassez de descobertas de grandes campos de petr?leo, indicam que em um futuro pr?ximo a recupera??o de ?leo por m?todos convencionais ser? limitada. Para aumentar a efici?ncia do processo de extra??o, faz-se uso dos m?todos avan?ados de recupera??o para agir nos pontos onde o processo convencional mostrou-se pouco eficiente. A inje??o de solu??o de tensoativo, como um m?todo avan?ado de recupera??o mostra-se vantajosa, pois os tensoativos t?m a finalidade de reduzir as tens?es interfaciais entre a ?gua e o ?leo, ampliando a efici?ncia de deslocamento e, conseq?entemente, aumentando o fator de recupera??o. Este trabalho se prop?s a estudar os efeitos dos par?metros que influenciam as solu??es de tensoativos, como: tipo de tensoativo, concentra??o micelar cr?tica e tens?o superficial e interfacial entre os fluidos. As solu??es com ?gua do mar dos tensoativos PAN, PHN e PJN, por apresentarem menores tens?es interfaciais com o petr?leo e maior estabilidade com o aumento da temperatura e salinidade, foram estudadas em um aparato experimental para avalia??o do fator de recupera??o. Os testemunhos de arenito Botucatu foram submetidos a etapas de satura??o com ?gua do mar e petr?leo, recupera??o convencional com ?gua do mar e recupera??o avan?ada com solu??es de tensoativos. Os testemunhos apresentaram porosidade entre 29,6 e 32,0%, com permeabilidade m?dia efetiva ? ?gua de 83 mD. O tensoativo PJN, com concentra??o de 1000% acima da CMC apresentou maior fator de recupera??o, aumentando em 20,97% a recupera??o do ?leo original in place ap?s a recupera??o convencional com ?gua do mar

Pour réduire les nuisances et pollutions émises par le transport aérien, une solution consisterait à remplacer les matériaux des pièces chaudes des moteurs d'avions par des composites à matrice céramique (CMC). Pour intégrer ces matériaux dans les moteurs, il est nécessaire de les adapter aux contraintes imposées par ce milieu (température≥1400°C, oxydation/corrosion), tout en garantissant des propriétés égales à celles des superalliages actuels (conductivité thermique, résistance mécanique). L'objectif de la thèse était de proposer une architecture de matériau présentant l'ensemble des propriétés demandées par le cahier des charges, d'élaborer ce composite et de le caractériser. Ce travail a permis d'identifier les phénomènes mis en jeu lors de l'élaboration des composites. L'optimisation du procédé, de l'architecture et de la composition du matériau a permis de fournir un CMC dense. Les caractérisations réalisées ont montré l'intérêt de ces matériaux pour l'application visée. / To reduce pollution emitted by air transport, high temperature materials used in hot parts of aircraft engines could be replaced by ceramic matrix composites (CMC). To integrate these materials, they must support the harsh environment encountered inside the engine (temperature ≥ 1400 ° C, oxidation / corrosion), while having properties equivalent to current superalloys (thermal conductivity, mechanical strength). This work was aimed to establish a material architecture presenting all properties required, and to develop and characterize this composite. This procedure has helped to identify the phenomena involved in the development of composites. Various optimizations, as process, material architecture and composition, have lead to the establishment of a dense CMC. Measured properties have proved that these materials can be used for the intended application.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Nesta tese, provamos estimativas para o volume e Ãrea do bordo de hipersuperficies estÃveis &#8721;n-1 com invariante de Yamabe nÃo positivo satisfazendo à condiÃÃo de bordo livre em uma variedade Riemanniana de dimensÃo n com limitaÃÃo na curvatura escalar e curvatura mÃdia do bordo. Supondo ainda que &#8721; à localmente minimizante de volume em uma variedade M com curvatura escalar limitada inferiormente por uma constante nÃo positiva, concluÃmos que localmente M divide-se ao longo &#8721; como (-&#1028;, &#1028;)x &#8721;, para algum &#1028; > 0. No caso em que &#8721; localmente minimiza um funcional adequado inspirado pelo trabalho de Yau (2001), uma vizinhanÃa de &#8721; em M à isomÃtrica a ((-&#1028;, &#1028;) x &#8721;, dt2 +e2tg), onde g à Ricci plana. Na segunda parte, estudamos outro fenÃmeno de rigidez pela curvatura escalar adaptando a tÃcnica desenvolvida por MÃximo e Nunes (2013) para mostrar um resultado local de rigidez para uma variedade Riemanniana tridimensional M3 cuja curvatura escalar à limitada inferiormente por um constante negativa. Provamos o seguinte resultado: Seja &#8721;2 &#8834; M3 uma superfÃcie mÃnima estritamente estÃvel que localmente maximiza a massa Hawking em M. EntÃo M perto de &#8721; à um pedaÃo de um dos espaÃos de Kottler. / In this thesis, we prove estimates for the volume and boundary area of stable hypersurfaces &#8721;n-1 with nonpositive Yamabe invariant satisfying the free boundary condition in a Riemannian manifold Mn with bounds for the scalar curvature and the mean curvature of the boundary. Assuming further that &#8721; is locally volume-minimizing in a manifold M with scalar curvature bounded below by a nonpositive constant, we conclude that locally M splits along &#8721; as (-&#1028;, &#1028;)x &#8721;, for some &#1028; > 0. In the case that &#8721; locally minimizes a certain functional inspired by the work of Yau (2001), a neighborhood of &#8721; in M is isometric to ((-&#1028;, &#1028;) x &#8721;, dt2 + e2tg), where g is Ricci at. In the second part, we study other scalar curvature rigidity phenomena adapting a technique developed by MÃximo e Nunes (2013) to show a local rigidity result for three-dimensional Riemannian manifold M3 whose scalar curvature is bounded from below by a negative constant. We prove the following result: Let &#8721;2 &#8834; M3 be a stable minimal surface which locally maximizes the Hawking mass on M. Then M near &#8721; is a piece of one the Kottler space.

Esta pesquisa tem como objetivo a descrição e a análise do funcionamento de debates veiculados pela rede mundial de computadores. O corpus compreende três discussões coletadas na internet que abrangem gêneros discursivos distintos (a lista de discussão, o chat com convidados e o fórum eletrônico), desenvolvidas por dois provedores de grande circulação nacional: América on-line (AOL) e Universo on-line (UOL). O foco da pesquisa se concentra na observação de como interagem os internautas e quais estratégias utilizam no momento em que debatem um tópico específico, também na descrição dos três gêneros digitais selecionados. Dentro desse universo, pouco sabemos sobre o funcionamento do ato argumentativo - peça essencial no mundo da comunicação. Uma vez que a interação se processa através de um canal eletrônico e os falantes não estão diretamente em contato, o jogo argumentativo assume características específicas. Por apresentar uma condição de produção peculiar, o discurso no meio virtual prescinde, muitas vezes, de elementos não-lingüísticos - tão essenciais para influir sobre o outro, dar mais emotividade aos enunciados, para convencer e persuadir, etc. Como todo processo interacional não pode ser apartado de seu contexto específico de produção, este trabalho também investiga a rede digital, para conhecer essa mediadora dos processos de comunicação e conseqüente \"fundadora\" de diversos gêneros discursivos, os chamados gêneros digitais. / This investigation aims to describing and analysing how debates carried out by means of the worldwide computer web operate. The corpus encompasses three discussions collected at the Internet, covering different discursive genres (the discussion list, the chat with invited guests and the electronic forum), developed by two large providers used in Brazil, i.e. America On-line (AOL) and Universo On-line (UOL). Besides focusing on the description of the three digital genres selected, the research is centered on the observation of how internet users interact and which strategies are employed by them while debating a specific topic. Within this universe, little do we know of how the argumentative act - essential in the realm of communication - operates. Since interaction is processed via an electronic channel, and speakers are not actually in contact, the argumentative game takes up specific characteristics. Because it presents peculiar production conditions, the speech within the virtual media often requires non-linguistic elements - rather essential in utterances whose functions might be to influence others, show emotion, convince, persuade, etc As is the case in every interactional process, the ones described here cannot be parted from their specific production contexts, thus, this research\'s investigation of the digital network, in order to be familiar with this mediator of communication processes and consequent \"founder\" of several discursive genres - called digital genres.

This master thesis deals with stress-strain analysis of carpometacarpal (CMC) thumb joint. It is a preliminary study, which was not analysed on BUT Mechanical and biomechanical institute yet. There is a comparative stress-strain analysis of CMC with applied total endoprosthesis and physiological condition. The model of geometry was created based on CT images and processed with using software Catia and Solidworks. The problem was solved in numerical FEM (finite element method) in software Ansys 13.0

Les composites SiC/SiC à renfort fibreux à base de SiC, et à matrice SiC sont développés pour applications aéronautiques. En vue d’améliorer leur durée de vie en atmosphère oxydante à haute température, l’utilisation d’interphase BN est préconisée,puisque l’oxyde de bore liquide permet de protéger le matériau. Cependant, sous atmosphère humide, la volatilisation de B2O3 sous forme d’hydroxyde HxByOz est non négligeable. L’objectif de ce travail est d’optimiser l’organisation structurale de BN élaboré par CVD/CVI, pour améliorer sa résistance à l’oxydation, et d’évaluer l’intérêt de l’ajout d’élément(s) au nitrure de bore permettant la stabilisation thermodynamique de B2O3 à haute température, en présence d’humidité. Ce travail a permis d’établir des liens entre composition chimique de la phase gazeuse, cinétique et mécanisme de dépôt, et degré d’organisation du nitrure de bore. Malheureusement, si la résistance à l’oxydation de BN augmente perpendiculairement à ses plans (002) avec son organisation structurale, elle est à peine améliorée le long des plans (002). Néanmoins, l’intérêt de l’ajout d’aluminium à l’interphase BN pour améliorer la stabilité chimique de B2O3 en présence d’humidité a été démontré à une température suffisamment élevée pour permettre la formation de cristauxAl4B2O9. Ainsi, il semble que ces cristaux permettent une cicatrisation efficace des fissures matricielles dans des composites SiC/SiC. Des essais supplémentaires d’oxydation dans des conditions plus complexes, comme sous cyclage thermique, sont nécessaires pour conclure catégoriquement en faveur de l’amélioration de la durée de vie de ces matériaux. / SiC/SiC composites with SiC-based fibres and SiC matrix are developed for aeronautic applications. In order to improve their life time in an oxidizing atmosphere at high temperature, the use of BN interphase is recommended, as far as liquid boron oxide can protect the material. However, this glassy material is known to be very sensitive to moisture because boron oxide volatilizes quickly under high temperature. The aims of this work are (i) to maximise the structural organization of BN deposited by CVD/CVI to improve its oxidation resistance and (ii) to assess the interest of elemental addition to boron nitride allowing thermodynamic retention for B2O3 under wet air. Relationships between gas phase composition, deposition rates, and microstructure have been established in this work. Unfortunately, if the oxidation resistance of BN perpendicular to its (002) crystal planes increases with its structural organization, it appears to be hardly improved along the (002) planes. Nevertheless, aluminium addition to BN has led to Al4B2O9 crystals generation, asAl2O3 reacts together with B2O3 under high temperature. These materials therefore appear tobe able to seal SiC matrix cracks. As a result, the global oxidation resistance under wet air of SiC/SiC composites with B(Al)N interphases can been significantly improved. Additional oxidation tests, especially under thermal cycling, are needed to definitively conclude about this point.