The objective of the present study was to investigate deformational behavior and functional adaptation of articular cartilage by comparing the changes of biochemical osteoarthritis markers&rsquo / concentrations due to 30-min exercise after 12-weeks of regular high impact, impact or non-impact exercise. Blood samples were drawn from 44 healthy sedentary males immediately before, immediately after and 0.5 h after a 30-min moderate walking exercise. Osteoarthritis biomarkers&rsquo / (Serum COMP and CTX-I) concentrations were determined with enzyme-linked immunosorbent assay. After the first measurements, participants were randomly assigned to running, cycling, swimming, and control groups. All groups except for control group trained for 12 weeks. After 12-weeks, post tests were applied. Multivariate tests indicated a significant fatigue and resting effect on serum COMP concentration in all groups at pre- and post-tests. Therefore, pair wise comparisons were conducted in order to assess the differences across all groups and conditions. Results indicated significant differences in post-test measurements among phases of groups except for running group. However, fatigue or resting did not change the concentration of serum CTX-I in any groups during the tests. According to results, moderate walking activity has an influence on the increase of serum COMP concentrations of young sedentary men. However, 12 weeks regular weight-bearing high impact physical exercise decreases the deformational effect of walking activity by functional adaptation of articular cartilage to specific environmental requirements.

The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks. The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. Measurements were conducted in a GSM/GPRS testbed. The results indicate that TCP interact efficiently with the GSM link layer protocol in most cases. From experiments of queuing in GPRS, we conclude that with a smaller buffer delay is reduced significantly, but that TCP throughput is about the same as with a larger buffer. Furthermore, we propose an improved buffer management when a connection loses all its resources to traffic with higher priority. We also propose a scheme for data forwarding to avoid negative impact on TCP during handover for WINNER, a research system that was used to test ideas for LTE. The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of users for CoMP that is based on user experience. Simulation results indicate that user experience, represented with application utility,  and fairness are improved compared to if only rate is considered in the user selection. / The Internet has grown enormously since the introduction of the World Wide Web in the early 90's. The evolution and wide spread deployment of cellular networks have contributed to make the Internet accessible to more people in more places. The cellular networks of today offer data rates high enough for most Internet services. Even so, the service quality experienced by the users is often lower than in wired networks. The performance of TCP has a large impact on user experience. Therefore, we investigate TCP in cellular networks and propose functionality to improve the situation for TCP. We have studied sources of delay and data loss, such as link layer retransmissions, queuing, and handover. The achievable data rates in cellular networks are limited by inter-cell interference that vary over the cell area. Inter-cell interference can be mitigated with Coordinated Multipoint techniques (CoMP), techniques that currently are being standardized for LTE-Advanced. System wide CoMP is, however, not an option, since it would be too resource consuming. In order to limit the required resources for CoMP, we propose an approach to select a subset of the users for CoMP that is based on user experience.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-01-15T21:40:49Z No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-01-17T15:55:28Z (GMT) No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) / Made available in DSpace on 2018-01-17T15:55:28Z (GMT). No. of bitstreams: 1 VirginiaBezerraOliveiraCampos_DISSERT.pdf: 3793113 bytes, checksum: 4435d7d3c46fc8d73615a9b23cd0e5f4 (MD5) Previous issue date: 2017-08-10 / A constante busca de materiais mais eficientes e com alto desempenho mec?nico, contribue efetivamente para a crescente demanda na utiliza??o de comp?sitos h?bridos. O processo de hibridiza??o pode propiciar melhoria significativa na combina??o global de propriedades, possibilitando assim aplica??es espec?ficas em elementos estruturais que requerem excel?ncia em suas propriedades mec?nicas e baixa massa espec?fica. Atrelado ? gradativa utiliza??o destes materiais, estudos que incidem nas previs?es de falha e, consequentemente, an?lises das cargas m?ximas que estes materiais podem suportar tornam-se essenciais para garantia da confiabilidade quanto a sua aplica??o. Neste sentido, a presente pesquisa buscou analisar o comportamento mec?nico de uma l?mina constitu?da ? base de tecido h?brido bidirecional (vidro/carbono) e resina ep?xi ?ster-vin?lica. Bem como, avaliar a representatividade de crit?rios de falhas desenvolvidos para comp?sitos unidirecionais quando aplicados em comp?sito h?brido de natureza bidirecional. A l?mina estudada foi caracterizada mecanicamente com base nos resultados obtidos pelos ensaios de tra??o e cisalhamento realizados em amostras com fibras de carbono orientadas a 0?, 30?, 45?, 60? e 90?. Observou-se a partir destes ensaios que materiais com fibras em ?ngulos fora do eixo (off-axis) de aplica??o de carga apresentam resist?ncia menor, embora apresentem maiores alongamentos, quando comparados a amostras com fibras alinhadas na dire??o principal do carregamento. Os dados experimentais referentes ?s propriedades cisalhantes, normatizados pela ASTM D3518M-13 (ensaio de cisalhamento por tra??o ?45?) e ASTM D5379-12 (ensaio de Iosipescu), apresentaram diferen?as significativas para a resist?ncia ao cisalhamento e similaridade nos valores do m?dulo de cisalhamento. O ensaio de tra??o ?45?, conforme an?lise macromec?nica, mostrou-se como o mais adequado para comp?sito com caracter?sticas similares ao analisado. Ao inserir os dados dos ensaios nas equa??es te?ricas que definem os crit?rios de falhas da M?xima Tens?o, Tsai-Hill, Tsai-Wu e Hashin e, analis?-los estatisticamente, contatou-se que estas teorias de falhas descrevem satisfatoriamente o comportamento experimental da l?mina, e, portanto, podem ser utilizados para predizer a resist?ncia mec?nica em comp?sitos como o avaliado, embora se tenha observado ?ndices de representatividade maiores quando se utiliza o ensaio de cisalhamento por tra??o ?45?. / The constant search for more efficient materials and with high mechanical performance, contributes effectively to the growing demand in the use of hybrid composites. The hybridization process can provide significant improvement in the overall combination of properties, thus enabling specific applications in structural elements that require excellence in their mechanical properties and low specific mass. Coupled with the gradual use of these materials, studies that focus on fault predictions and, consequently, analyzes of the maximum loads that these materials can withstand become essential to guarantee the reliability of their application. In this sense, the present research sought to analyze the mechanical behavior of laminae composed of two-way hybrid fabric (glass/carbon) and epoxy resin vinyl ester. As well as evaluating the representativeness of failure criteria developed for unidirectional composites when applied in hybrid composites of a bidirectional nature. The laminas studied were mechanically characterized based on the results obtained by tensile and shear tests performed on samples with carbon fibers orientated at 0?, 30?, 45?, 60? and 90?. It was observed from these tests that materials with fibers at off-axis loading angles exhibit lower strength, although they exhibit greater elongations when compared to samples with fibers aligned in the main direction of loading. Experimental data on shear properties, standardized by ASTM D3518M-13 (tensile shear test ?45?) and ASTM D5379-12 (Iosipescu's test), showed significant differences for shear strength and similarity in the modulus values of Shear. The tensile test ? 45?, according to macromechanical analysis, proved to be the most suitable for composite with characteristics similar to the one analyzed. By inserting test data into the theoretical equations defining Tsai-Hill, Tsai-Wu, and Hashin fault criteria, and statistically analyzing them, it was found that these fault theories satisfactorily describe the experimental behavior of the blade , and therefore can be used to predict mechanical strength in composites as evaluated, although higher representativity indices were observed when using the ? 45? traction shear test.

Made available in DSpace on 2014-12-17T14:06:53Z (GMT). No. of bitstreams: 1 CarlosRG.pdf: 3095179 bytes, checksum: 8f85422621006a6dd669bfabb5747ac9 (MD5) Previous issue date: 2009-08-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Although already to exist alternative technique and economically viable for destination of used tires, quantitative data on properties of constructive elements that use the rubber waste as aggregate still are restricted. In the present work, the waste proceeding from industry of retreading as material for manufacture of composite destined to the production of constructive elements was considered. Mechanical and thermal properties of mortar had been analyzed Portland cement with addition of waste without treatment, in the ratios of 10%, 20% and 30% in mass in relation to the mass of the cement, substituting the aggregate in the trace in mortar 1:5 mass cement and sand. The size of the used residue varied between 0,30mm and 4,8mm (passing in the bolter 4,8mm and being restrained in the one of 0,30mm), being it in the formats fibers and granular. The influences of the size and the percentage of residue added to the mortar (in substitution to the aggregate) in the thermal and mechanical properties had been considered. Assays of body-of-test in thestates had been become fullfilled cool (consistency index) and hardened (absorption of water for capillarity, strength the compression, traction and strength flexural). The work is centralized in the problem of the relation thermal performance /strength mechanics of used constructive systems in regions of low latitudes (Been of the Piau?), characterized for raised indices of solar radiation. / Apesar de j? existirem alternativas t?cnica e economicamente vi?veis para destina??o de pneum?ticos usados, dados quantitativos sobre propriedades de elementos construtivos que utilizam o res?duo de borracha como agregado ainda s?o restritos. No presente trabalho, considerou-se o res?duo proveniente de ind?stria de recauchutagem como material para fabrica??o de comp?sito destinado ? produ??o de elementos construtivos. Foram analisadas propriedades mec?nicas e t?rmicas de argamassa de cimento Portland com adi??o de res?duo sem tratamento, nas propor??es de 10%, 20% e 30% em massa em rela??o ? massa do cimento, substituindo o agregado no tra?o em massa 1:5 de argamassa cimento e areia. A granulometria do res?duo utilizado variou entre 0,30mm e 4,8mm (passando na peneira 4,8mm e ficando retido na de 0,30mm), sendo ele nos formatos fibroso e granular. Consideraram-se as influ?ncias da granulometria e do percentual de res?duo adicionado ? argamassa (em substitui??o ao agregado) nas propriedades t?rmicas e mec?nicas. Realizaram-se ensaios de corpos-deprova nos estados fresco (?ndice de consist?ncia) e endurecido (absor??o de ?gua por capilaridade, resist?ncia a compress?o e tra??o). O trabalho est? focado no problema da rela??o desempenho t?rmico /resist?ncia mec?nica de sistemas construtivos utilizados em regi?es de baixas latitudes (Estado do Piau?), caracterizadas por elevados ?ndices de radia??o solar.

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 AntonioCSC_DISSERT.pdf: 3611638 bytes, checksum: 66d2009e96e503fa1be4ca56924e34a1 (MD5) Previous issue date: 2011-03-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The clay mineral attapulgite is a group of hormitas, which has its structures formed by microchannels, which give superior technological properties classified the industrial clays, clays of this group has a very versatile range of applications, ranging from the drilling fluid for wells oil has applications in the pharmaceutical industry. Such properties can be improved by activating acid and / or thermal activation. The attapulgite when activated can improve by up to 5-8 times some of its properties. The clay was characterized by X-ray diffraction, fluorescence, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and transmission electron microscopy before and after chemical activation. It can be seen through the results the efficiency of chemical treatment, which modified the clay without damaging its structure, as well as production of polymer matrix composites with particles dispersed atapugita / A atapulgita ? um argilomineral do grupo das hormitas, que tem suas estruturas formadas por microcanais, que lhe conferem propriedades tecnol?gicas superiores a argilas classificadas industriais, esse grupo de argilas tem um leque de aplica??es muito vers?til, que vai de fluido de perfura??o para po?os de petr?leo at? aplica??es na ind?stria farmac?utica. Tais propriedades podem ser melhoradas por ativa??o acida e/ou ativa??o t?rmica. A atapulgita quando ativada pode melhorar em at? de 5 a 8 vezes algumas de suas propriedades. A argila foi caracterizada por difra??o de raios X, fluoresc?ncia, an?lise termogravim?trica, an?lise t?rmica diferencial, microscopia eletr?nica de varredura e microscopia eletr?nica de transmiss?o antes e depois da ativa??o qu?mica. ? poss?vel observar, atrav?s dos resultados a efici?ncia do tratamento qu?mico, que modificou a argila sem danificar sua estrutura, assim como produ??o de composito de matriz polim?rica com part?culas dispersas de atapugita

Made available in DSpace on 2014-12-17T14:07:02Z (GMT). No. of bitstreams: 1 FabioSCPpdf.pdf: 1533458 bytes, checksum: 0df903e6bea6c66d762b8b1bbe3c6937 (MD5) Previous issue date: 2009-11-30 / Due to the occurrence of diseases in the use of structural reinforcements in composites, with presentation of concrete blanket detachment, has been identified the need to evaluate the performance of concrete reinforced with glass fiber. This study aims to evaluate these concretes by means of testing methodologies, using concrete with low resistance with structural reinforcement for confinement by preimpregnated glass fiber and traditional fiberglass blanket. The first stage of work was the development of methodologies for analysis, opting for four types, such as the acoustic survey, strength to compressive, the pull-off and ultrasound. Next, tests were carried out using the four selected methodologies in 30 of proof-of-specimens by 5x10 cm, 15 were reinforced with the traditional fiberglass blanket with 5specimens exposed to test a marine environment of marine coastline of Natal-RN and 15 were reinforced with a pre-impregnated glass fiber blanket, as well as 5specimens exposed to a test environment of the marine coastline of Natal-RN. After conducting the acoustic survey, it has been verified a lack of delaminating and air bubbles in the samples, confirming the absence of gross shortcomings in the implementation of the ribs both the traditional fiberglass blanket and in the preimpregnated fiber glass blanket. After carrying out methods of pull-off and compressive strengthening test it was observed that the reinforced proof-bodies with pre-impregnated glass blanket showed maximum stresses higher than the traditional fiberglass blanket; consequently a greater grip with the formation of a smaller area of . fracture, unlike traditional glass mat, which showed lower maximum stresses, with a greater area of fracture. It was also found that the traditional fiberglass blanket presented detachment of blanket-concrete interface, unlike the pre-impregnated fiberglass blanket, which showed a better grip on the blanket-concrete interface. In the trial of ultrasound there was no presence of cracks in the blanket-concrete interface, yielding to both blankets good compactness of the concrete. At the end of this work, they were developed and proposed two methods of testing for evaluation of reinforced concrete structures with composites, for standardization, the acoustic survey and pull-off / Em virtude da ocorr?ncia de patologias na utiliza??o de refor?os estruturais com comp?sitos, com apresenta??o de descolamento da manta do concreto, foi identificada a necessidade de se avaliar o desempenho dos concretos refor?ados com a fibra de vidro. Sendo o objetivo principal deste trabalho, avaliar estes concretos, atrav?s de metodologias de ensaios, utilizando concretos com resist?ncias baixas com refor?o estrutural por confinamento por fibra de vidro pr?impregnada e por manta de fibra de vidro tradicional. A primeira etapa do trabalho consistiu na elabora??o das metodologias de an?lise, optando-se por quatro tipos, a sondagem ac?stica, resist?ncia ? compress?o,o pull-off e o ultra-som. Em seguida, foram realizados os ensaios utilizando as quatro metodologias escolhidas em 30 corpos-de-prova de 5x10 cm, sendo 15 refor?ados com a manta de fibra de vidro tradicional, com 5 corpos-de-prova expostos a um ambiente marinho da orla mar?tima de Natal-RN e sendo 15 refor?ados com a manta de fibra de vidro pr?impregnada, tamb?m com 5 corpos-de-prova expostos a um ambiente marinho da orla mar?tima de Natal-RN. Ap?s a realiza??o dos ensaios de sondagem ac?stica, verificou-se a inexist?ncia de delamina??es e bolhas de ar nas amostras analisadas, comprovando a inexist?ncia de falhas grosseiras na aplica??o dos refor?os tanto na manta de fibra de vidro tradicional, como na da manta de fibra de vidro pr?impregnada. Depois de executadas as metodologias de ensaios de resist?ncia ? compress?o e pull-off, observou-se que os corpos-de-prova refor?ados com a manta de vidro pr?-impregnada apresentaram tens?es m?ximas superiores ?s obtidas com a manta de fibra de vidro tradicional, consequentemente uma ader?ncia maior, com a forma??o de uma menor ?rea de fratura, ao contr?rio da manta de vi dro tradicional, que apresentou tens?es m?ximas inferiores, com uma maior ?rea de fratura. Verificou-se ainda que a manta de fibra de vidro tradicional apresentou descolamento da interface manta/concreto, ao contr?rio da manta de fibra de vidro pr?-impregnada, que apresentou uma maior ader?ncia na interface manta/concreto. No ensaio de ultra-som n?o se observou presen?a de fissuras na interface manta/concreto, obtendo-se para ambas as mantas, boas compacidades do concreto. Ao final do trabalho foram elaboradas e propostas duas metodologias de ensaios para avalia??o das estruturas de concreto armado refor?adas com comp?sitos, para normaliza??o, a sondagem ac?stica e o pull-off

Made available in DSpace on 2014-12-17T14:07:08Z (GMT). No. of bitstreams: 1 ErikSS_DISSERT.pdf: 3248804 bytes, checksum: 7241bc799da79c157edae8da7a7966cc (MD5) Previous issue date: 2013-04-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Currently the search for new materials with properties suitable for specific applications has increased the number of researches that aim to address market needs. The poly (methyl methacrylate) (PMMA) is one of the most important polymers of the family of polyacrylates and polymethacrylates, especially for its unique optical properties and weathering resistance, and exceptional hardness and gloss. The development of polymer composites by the addition of inorganic fillers to the PMMA matrix increases the potential use of this polymer in various fields of application. The most commonly used inorganic fillers are particles of silica (SiO2), modified clays, graphite and carbon nanotubes. The main objective of this work is the development of PMMA/SiO2 composites at different concentrations of SiO2, for new applications as engineering plastics. The composites were produced by extrusion of tubular film, and obtained via solution for application to commercial PMMA plates, and also by injection molding, for improved the abrasion and scratch resistance of PMMA without compromising transparency. The effects of the addition of silica particles in the polymer matrix properties were evaluated by the maximum tensile strength, hardness, abrasion and scratch resistance, in addition to preliminary characterization by torque rheometry and melt flow rate. The results indicated that it is possible to use silica particles in a PMMA matrix, and a higher silica concentration produced an increase of the abrasion and scratch resistance, hardness, and reduced tensile strength / Atualmente a busca por novos materiais com propriedades adequadas para aplica??es espec?ficas vem aumentando o n?mero de pesquisas que visam suprir as necessidades do mercado. O poli(metacrilato de metila) (PMMA) ? um dos pol?meros mais importantes da fam?lia dos poliacrilatos e polimetacrilatos, principalmente pelas suas inigual?veis propriedades ?pticas e resist?ncia ?s intemp?ries, al?m de excepcional dureza e brilho. O desenvolvimento de comp?sitos polim?ricos por meio da adi??o de cargas inorg?nicas ? matriz de PMMA aumenta o potencial de uso deste pol?mero em diferentes ?reas de aplica??o. Dentre as cargas inorg?nicas mais utilizadas, podem-se destacar as part?culas de s?lica (SiO2), argilas modificadas, grafite e nanotubos de carbono. O objetivo principal deste trabalho ? o desenvolvimento de comp?sitos PMMA/SiO2, em diferentes concentra??es, para novas aplica??es como pl?stico de engenharia. Os comp?sitos foram produzidos por meio de extrus?o de filme tubular, e obtidos via solu??o, para aplica??o em chapas de PMMA comercial, e tamb?m por moldagem por inje??o, buscando o aumento da resist?ncia ? abras?o e ao risco do PMMA, sem comprometer a transpar?ncia. Os efeitos causados pela adi??o das part?culas de s?lica nas propriedades da matriz polim?rica foram avaliados atrav?s da resist?ncia m?xima ? tra??o, dureza, resist?ncia ? abras?o e ao risco, al?m das caracteriza??es preliminares por reometria de torque e ?ndice de fluidez. Os resultados indicaram que ? poss?vel utilizar part?culas de s?lica em uma matriz de PMMA, e que uma maior concentra??o de s?lica promoveu um aumento da resist?ncia ? abras?o e ao risco, dureza, e reduziu a resist?ncia m?xima ? tra??o

Made available in DSpace on 2014-12-17T14:07:24Z (GMT). No. of bitstreams: 1 MarcusAlexandreD.pdf: 2205651 bytes, checksum: 56cca2e578c0f1071a36ad849c8f80ca (MD5) Previous issue date: 2007-10-01 / Ceramic composites produced with polymerics precursors have been studied for many years, due to the facility of obtaining a complex shape, at low temperature and reduces cost. The main objective of this work is to study the process of sintering of composites of ceramic base consisting of Al2O3 and silicates, reinforced for NbC, through the technique of processing AFCOP, as well as the influence of the addition of LZSA, ICZ and Al as materials infiltration in the physical and mechanical properties of the ceramic composite. Were produced ceramic matrix composites based SiCxOy e Al2O3 reinforced with NbC, by hidrosilylation reaction between D4Vi and D1107 mixtured with Al2O3 as inert filler, Nb and Al as reactive filler. The specimens produced were pyrolised at 1200, 1250 and 1400?C and infiltred with Al, ICZ and LZSA, respectively. Density, porosity, flexural mechanical strength and fracture surface by scanning electron microscopy were evaluated. The microstructure of the composites was investigated by X-ray diffraction to identify the presence of crystalline phases. The composites presented apparent porosity varying of 31 up to 49% and mechanical flexural strength of 14 up to 34 MPa. The infiltration process improviment of the densification and reduction of the porosity, as well as increased the values of mechanical flexural strength. The obtained phases had been identified as being Al3Nb, NbSi2, Nb5S3, Nb3Si and NbC. The samples that were submitted the infiltration process presented a layer next surface with reduced pores number in relation to the total volume / Os comp?sitos cer?micos produzidos atrav?s de precursores polim?ricos v?m sendo estudados h? v?rios anos, tendo em vista a facilidade de moldagem em formas complexas, menores temperaturas de sinteriza??o e custo reduzido. O principal objetivo deste trabalho ? estudar o processo de sinteriza??o de comp?sitos de base cer?mica constitu?da de alumina e silicatos, refor?ados por carbetos de ni?bio, atrav?s da t?cnica de processamento AFCOP, bem como a influ?ncia da adi??o de LZSA, ICZ, e Al como materiais infiltrantes nas propriedades f?sicas e mec?nicas do comp?sito cer?mico. Foram produzidos comp?sitos de matriz cer?mica baseados em SiCxOy e Al2O3 refor?ados com carbeto de ni?bio, a partir da rea??o de hidrossila??o entre os olig?meros D4Vi (1,3,5,7 tetrametil 1,3,5,7 tetravinilciclotetrasiloxano) e D1107 Poli (metilhidrogeniosiloxano), misturados com alumina como carga inerte, ni?bio e alum?nio como aditivos reativos. As amostras produzidas foram pirolisadas a 1200?C, 1250?C e 1400?C e infiltradas com Al, ICZ e LZSA, respectivamente. Foram realizados ensaios de densidade, porosidade, resist?ncia mec?nica ? flex?o e an?lises da superf?cie de fratura por microscopia eletr?nica de varredura. A microestrutura dos comp?sitos foi investigada pela an?lise de difra??o de raios-x para identifica??o das fases cristalinas presentes. Os comp?sitos apresentaram porosidade aparente variando de 31 a 49 por cento e resist?ncia mec?nica ? flex?o de 14 a 34 MPa. Os resultados mostraram que o processo de infiltra??o promoveu uma melhoria na densifica??o e redu??o da porosidade, bem como um incremento nos valores de resist?ncia mec?nica do comp?sito. As fases formadas ap?s a pir?lise foram identificadas como sendo Al3Nb, NbSi2, Nb5Si3, Nb3Si e NbC. As amostras que foram submetidas ao processo de infiltra??o apresentaram uma camada superficial com reduzido n?mero de poros em rela??o ao volume total

In order to support the new paradigm shift in fifth generation (5G) mobile communication, radically different network architectures, associated technologies and network operation algorithms, need to be developed compared to existing fourth generation (4G) cellular solutions. The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. To realise the dramatic increase in data rates in particular, research is focused on improving the capacity of current, Long Term Evolution (LTE)-based, 4G network standards, before radical changes are exploited which could include acquiring additional spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell-edge users vulnerable to heavy inter cell interference in addition to the other factors such as fading and path-loss. In this direction, this thesis focuses on improving the performance of cell-edge users in LTE and LTE-Advanced networks by initially implementing a new Coordinated Multi-Point (CoMP) technique to support future 5G networks using smart antennas to mitigate cell-edge user interference in uplink. Successively a novel cooperative uplink inter-cell interference mitigation algorithm based on joint reception at the base station using receiver adaptive beamforming is investigated. Subsequently interference mitigation in a heterogeneous environment for inter Device-to-Device (D2D) communication underlaying cellular network is investigated as the enabling technology for maximising resource block (RB) utilisation in emerging 5G networks. The proximity of users in a network, achieving higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the evolved Node B (eNodeB) i.e. by direct communication between User Equipment (UE), has been explored. Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for D2D receivers, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNodeB in the network. It is finally demonstrated that the application, as an extension to the above, of a novel receiver beamforming technique to reduce interference from D2D users, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond the-state-of-the-art LTE system-level-simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-14T18:45:29Z No. of bitstreams: 1 HerikDantasDeLima_DISSERT.pdf: 4131924 bytes, checksum: 277ee7a89b9043637734f077d15e5432 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-15T18:02:24Z (GMT) No. of bitstreams: 1 HerikDantasDeLima_DISSERT.pdf: 4131924 bytes, checksum: 277ee7a89b9043637734f077d15e5432 (MD5) / Made available in DSpace on 2016-01-15T18:02:24Z (GMT). No. of bitstreams: 1 HerikDantasDeLima_DISSERT.pdf: 4131924 bytes, checksum: 277ee7a89b9043637734f077d15e5432 (MD5) Previous issue date: 2014-12-19 / Existe uma grande dificuldade na forma??o de um comp?sito do metal refrat?rio de ni?bio com o cobre. Isto se deve ao fato de que o sistema Nb-Cu ? quase mutuamente imisc?vel, podendo ser desprezada a solubilidade entre eles. Estas propriedades dificultam ou impedem a obten??o de estruturas homog?neas e de alta densidade, convencionalmente preparadas. Este trabalho tem por objetivo analisar a utiliza??o do processo de moagem de alta energia (MAE) para transpor estas dificuldades naturais, no que se refere ? densifica??o dos corpos sinterizados. A MAE e a prensagem foram utilizadas na prepara??o dos p?s, para a obten??o de uma fina e homog?nea distribui??o do tamanho dos gr?os. Quatro cargas de p?s de Nb e Cu contendo 15% em massa de Cu foram ent?o mo?dos por MAE em um moinho de bolas tipo planet?rio, sob diferentes per?odos e velocidades de moagem. Os resultados obtidos pela MAE foram analisados atrav?s da microscopia eletr?nica de varredura (MEV), de acordo com os par?metros de tempo e velocidade de moagem. As amostras foram compactadas sob press?o de 200 MPa, em seguida foram sinterizadas por fase l?quida em um forno ? v?cuo nas temperaturas de 1100?C/60 min e 1200?C/60 min. Depois foi utilizada a t?cnica de caracteriza??o de difra??o de raios-X para a identifica??o das fases. As microestruturas das amostras sinterizadas foram observadas e avaliadas atrav?s de microscopia eletr?nica de varredura (MEV). Ensaios de Microdureza Vickers foram realizados, obtendo maiores valores para os corpos sinterizados nos maiores tempos de moagem dos p?s e para as maiores velocidades de moagem. Foi verificado que a sinteriza??o por fase l?quida das amostras que foram processadas por MAE, produziu no final uma estrutura homog?nea e densificada em 77,4% em rela??o ao valor da densidade te?rica do comp?sito / There is great difficulty in forming a composite refractory metal niobium with copper. This is due to the fact that Nb-Cu system is almost mutually immiscible and may be neglected solubility between them. These properties hinder or prevent obtaining homogeneous and high-density structures, conventionally prepared. This study aims to analyze the use of high-energy milling process (MAE) to implement these natural difficulties, with regard to the densification of the sintered bodies. The MAE and the press were used in the preparation of powders, to obtain a fine and homogeneous distribution of the grain size. Four loads Nb and Cu powders containing 15% by weight of Cu were then milled for MAE in a planetary type ball mill under various milling times and speeds. The results obtained by MAE were analyzed by scanning electron microscopy (SEM), according to the parameters of time and grinding speed. The samples were compacted under pressure of 200 MPa, were then sintered in liquid phase in a vacuum furnace at temperatures of 1100 ? C / 60 min and 1200 ? C / 60 min. Then it was used to characterize diffraction of X-rays to identify the phases. The microstructures of the sintered samples were observed and evaluated using scanning electron microscopy (SEM). Vickers Microhardness tests were performed, obtaining higher values for the sintered bodies in the largest of the post milling times and the larger grinding speeds. It was found that the liquid phase sintering of the samples that were processed by MAE produced at the end of a homogeneous and densified structure in 77,4% relative to the value of the theoretical density of the composite