As estruturas tubulares, muitas vezes, têm sua aplicação restrita a construções onde a concepção arquitetônica determina o seu uso, no entanto há algumas vantagens do ponto de vista estrutural que podem justificar a sua aplicação. A reduzida área exposta ao fogo e aos ambientes agressivos, boa resistência a compressão axial com baixa tendência ao desenvolvimento de instabilidades localizadas, são algumas das vantagens da utilização destas estruturas. O objetivo principal deste trabalho é analisar numericamente o comportamento da ligação entre viga de seção I com coluna tubular circular, para tanto são consideradas configurações usuais de ligação com anéis externos transversais e chapa de alma. É ainda objetivo trazer um panorama das estruturas tubulares em geral, com o desenvolvimento histórico das pesquisas, e principalmente estabelecer uma compilação dos procedimentos analíticos de cálculo e classificação apresentados pelas normas Eurocode 3 e ANSI/AISC. A análise numérica foi realizada por meio dos pacotes comerciais TRUEGRID® e ANSYS®, os quais aplicam o método dos elementos finitos. Foram empregados modelos que consideram as características mecânicas do aço, como plastificação e encruamento, e ainda as não-linearidades geométricas e de contato. Os resultados numéricos apresentaram coerência razoável com os modelos analíticos normativos. Foi possível o conhecimento do comportamento M-\'fi\' (momento-rotação) das ligações, bem como a determinação dos parâmetros que caracterizam tal relação, como resistência, rigidez inicial e ductilidade. Os estudos comprovaram a eficácia dos anéis externos na distribuição dos esforços oriundos do engastamento parcial da viga, fazendo com que a coluna não seja comprometida. / The application of tubular structures is usually restricted to constructions on which the architectural conception demands them. However, there are also several structural advantages which justify their usage, such as a) reduced exposed area concerning fire and agressive environments; b) high axial compression resistance; c) high local buckling resistance. The aim of this work is the numerical analysis on the behavior of the I beam-circular hollow column connection, usually constituted by an external ring with single plate. It is presented a general view about the researchers development over the years on tubular structures focusing the compilation of the analytical design procedures and Eurocode 3 and ANSI/AISC classification as well. Finite element method softwares TRUEGRID and ANSYS are used for the numerical analysis in order to consider steel mechanical properties such as yielding, hardening and also geometric and contact nonlinearities. Numerical results present good agreement to codes\' analytical models. Analysis lead to understanding the connection\'s moment-rotation behavior and some of its parameters such as resistance, initial stiffness and ductility. It is shown external rings significantlly improve the semi-rigid connections stress distribution at the columns face.

Made available in DSpace on 2017-07-10T19:24:33Z (GMT). No. of bitstreams: 1 Elisabete Ferro Mendonca.pdf: 1930052 bytes, checksum: 772f421efdecf47a02c45460b7957433 (MD5) Previous issue date: 2009-07-13 / The wastewater resulting from milk production processes with animals at free stall barns has huge organic matter concentration and requires treatment before being disposed at the environment. At this study, the dairy cattle wastewater from free stall barns was treated in horizontal tubular anaerobic reactors with continuous flow and 9.6 liters volume each, made with polyvinyl chloride (PVC). The material was collected at Iguaçu Farm, with geographic coordinates latitude 25°02'43.07" south, longitude 53°46'51.85" west and 641 meters altitude, sieved at 2 mm mesh and stored at -18 °C, conditioned in polyethylene terephthalate (PET) packs. The material was put in room temperature before being added to the reactor each day. Different loads were used, resulting in retention times equals to were 8, 10, 15 and 20 days. Two temperatures were used: 30 and 35 °C; with 4 replications. Statistical data were evaluated by factorial crossover design 4 x 2 x 4, 4 factors of hydraulic retention time (HRT), 2 temperature factors and 4 replicates, with the average calculated by the Tukey method. They were evaluated the chemical oxygen demand (COD) removal, by colorimetric method, total solids (TS) and volatile solids (VS), by gravimetric methods. The best treatments were met with 20 days HRT and 30 °C, with average 83.30% 76.16% and 86.23% of COD, TS and VS removed. The biogas production was measured relatively to COD, TS and VS removals, resulting in 1.32 m³ of biogas kg-¹ DQO at 5 days of HRT and 35 ° C. At the 8 days HRT and 30 ° C, they resulted in 1.05 and 1.01 m³ of biogas · kg-¹ of TS and VS removed from the system, respectively. / A água residuária resultante dos processos das atividades de produção intensiva de leite com animais em regime de estabulação completa possui elevada concentração de matéria orgânica e necessita de tratamento antes de ser disposta no ambiente. Neste estudo, a água residuária da criação e produção de bovinos leiteiros em regime de estabulação completa foi tratada em reatores anaeróbios tubulares horizontais de fluxo contínuo, em escala laboratorial, de volume útil de 9,6 litros cada, construídos em cloreto de polivinila (PVC). O material foi coletado na Fazenda Iguaçu, com coordenadas geográficas latitude 25°02 43,07 sul, longitude 53°46 51,85 oeste e altitude 641 metros, sendo peneirado em malha de 2 milímetros e armazenado a 18 °C abaixo de zero, em embalagens de polietileno tereftalato (PET). O material foi levado à temperatura ambiente antes de ser acrescentado aos reatores a cada dia. Foram utilizadas diferentes cargas, de forma que os tempos de retenção do efluente foram de 8, 10, 15 e 20 dias. Foram empregadas 2 temperaturas: 30 e 35 °C; com 4 repetições. Os dados estatísticos foram avaliados através de delineamento fatorial cruzado 4 x 2 x 4, sendo 4 fatores de tempo de retenção hidráulica (TRH), 2 fatores temperatura e 4 repetições; com as médias calculadas pelo método de Tukey. Foram avaliados a remoção de demanda química de oxigênio (DQO), a partir da metodologia colorimétrica, sólidos totais (ST) e sólidos voláteis (SV), com métodos gravimétricos. Os melhores tratamentos ocorreram com 20 dias de TRH e 30 °C com médias de 83,30%, 76,16% e 86,23% de DQO, ST e SV removidos, respectivamente. A produção de biogás foi avaliada em relação à DQO removida e aos ST e SV retirados do sistema, com 1,32 m³ de biogás·kg-¹ DQO em 15 dias de TRH a 35 °C e 8 dias com 30 °C, 1,05 e 1,01 m³ de biogás·kg-¹de ST e SV retirados do sistema, respectivamente.

Made available in DSpace on 2017-05-12T14:47:55Z (GMT). No. of bitstreams: 1 Elisabete Ferro Mendonca.pdf: 1930052 bytes, checksum: 772f421efdecf47a02c45460b7957433 (MD5) Previous issue date: 2009-07-13 / The wastewater resulting from milk production processes with animals at free stall barns has huge organic matter concentration and requires treatment before being disposed at the environment. At this study, the dairy cattle wastewater from free stall barns was treated in horizontal tubular anaerobic reactors with continuous flow and 9.6 liters volume each, made with polyvinyl chloride (PVC). The material was collected at Iguaçu Farm, with geographic coordinates latitude 25°02'43.07" south, longitude 53°46'51.85" west and 641 meters altitude, sieved at 2 mm mesh and stored at -18 °C, conditioned in polyethylene terephthalate (PET) packs. The material was put in room temperature before being added to the reactor each day. Different loads were used, resulting in retention times equals to were 8, 10, 15 and 20 days. Two temperatures were used: 30 and 35 °C; with 4 replications. Statistical data were evaluated by factorial crossover design 4 x 2 x 4, 4 factors of hydraulic retention time (HRT), 2 temperature factors and 4 replicates, with the average calculated by the Tukey method. They were evaluated the chemical oxygen demand (COD) removal, by colorimetric method, total solids (TS) and volatile solids (VS), by gravimetric methods. The best treatments were met with 20 days HRT and 30 °C, with average 83.30% 76.16% and 86.23% of COD, TS and VS removed. The biogas production was measured relatively to COD, TS and VS removals, resulting in 1.32 m³ of biogas kg-¹ DQO at 5 days of HRT and 35 ° C. At the 8 days HRT and 30 ° C, they resulted in 1.05 and 1.01 m³ of biogas · kg-¹ of TS and VS removed from the system, respectively. / A água residuária resultante dos processos das atividades de produção intensiva de leite com animais em regime de estabulação completa possui elevada concentração de matéria orgânica e necessita de tratamento antes de ser disposta no ambiente. Neste estudo, a água residuária da criação e produção de bovinos leiteiros em regime de estabulação completa foi tratada em reatores anaeróbios tubulares horizontais de fluxo contínuo, em escala laboratorial, de volume útil de 9,6 litros cada, construídos em cloreto de polivinila (PVC). O material foi coletado na Fazenda Iguaçu, com coordenadas geográficas latitude 25°02 43,07 sul, longitude 53°46 51,85 oeste e altitude 641 metros, sendo peneirado em malha de 2 milímetros e armazenado a 18 °C abaixo de zero, em embalagens de polietileno tereftalato (PET). O material foi levado à temperatura ambiente antes de ser acrescentado aos reatores a cada dia. Foram utilizadas diferentes cargas, de forma que os tempos de retenção do efluente foram de 8, 10, 15 e 20 dias. Foram empregadas 2 temperaturas: 30 e 35 °C; com 4 repetições. Os dados estatísticos foram avaliados através de delineamento fatorial cruzado 4 x 2 x 4, sendo 4 fatores de tempo de retenção hidráulica (TRH), 2 fatores temperatura e 4 repetições; com as médias calculadas pelo método de Tukey. Foram avaliados a remoção de demanda química de oxigênio (DQO), a partir da metodologia colorimétrica, sólidos totais (ST) e sólidos voláteis (SV), com métodos gravimétricos. Os melhores tratamentos ocorreram com 20 dias de TRH e 30 °C com médias de 83,30%, 76,16% e 86,23% de DQO, ST e SV removidos, respectivamente. A produção de biogás foi avaliada em relação à DQO removida e aos ST e SV retirados do sistema, com 1,32 m³ de biogás·kg-¹ DQO em 15 dias de TRH a 35 °C e 8 dias com 30 °C, 1,05 e 1,01 m³ de biogás·kg-¹de ST e SV retirados do sistema, respectivamente.

O semiárido cearense apresenta um baixo potencial hídrico superficial, aumentando a dependência da população às águas subterrâneas. O Aquífero Fraturado, constituído pelo embasamento cristalino, é o de maior ocorrência na região e apresenta baixa produtividade e teores excessivos de sais. O presente trabalho propôs avaliar os condicionantes regionais que controlam as produtividades nos aquíferos no semiárido com base nas informações de mais de 6 mil poços tubulares. A correlação entre a litologia, clima e geomorfologia demonstrou que a primeira exerce o papel principal no controle das potencialidades hídricas, sendo o clima o seu segundo fator de influência. Os maiores valores de mediana da capacidade específica (Q/smed) de 15,32 m3/h/m e 0,83 m3/h/m foram verificados em rochas carbonáticas e sedimentares em clima úmido/subúmido, respectivamente. Desta forma, suas produtividades são mais evidentes em climas mais úmidos, logo que sua permeabilidade intrínseca e produtividade estabelecem uma relação diretamente proporcional com a disponibilidade de chuvas. De maneira geral, os metassedimentos (Q/smed 0,099 m3/h/m) se apresentaram mais produtivos quando comparados aos gnaisses e migmatitos (0,051 m3/h/m) e às rochas plutônicas (0,052 m3/h/m). Nos gnaisses e migmatitos o clima aparentou não ter uma influência efetiva na produtividade. As águas subterrâneas da região têm elevada salinidade, confirmada em 210 análises hidroquímicas. O mecanismo de salinização dos aquíferos no semiárido provavelmente está associado aos sais aerotransportados do mar, com predominância para o cloreto e sódio, e às elevadas taxas de evaporação, como pode ser confirmado pelas maiores concentrações de cloreto na água de poços localizados mais próximos à costa. O mecanismo de recarga em rochas mais permeáveis pode favorecer a redução de salinidade (maior infiltração), como o verificado em metassedimentos, quando comparadas às maiores concentrações verificadas em gnaisses e migmatitos. / The semi-arid region of Ceará has low surface-water availability, increasing the population\'s dependence on groundwater. The fractured aquifer, constituted by a crystalline basement, is the one with the highest occurrence in the region and presents low productivity and excessive levels of salinity. The present work proposed to evaluate the regional constraints that control the aquifer productivities in the semiarid region based on the information of more than 6 thousand tubular wells. The correlation between lithology, climate and geomorphology has shown that the former plays the main role in controlling the aquifer potentiality, with climate being its second influence factor. The highest values of specific capacity average (Q/s avg) were verified in carbonate (15.32 m3/h/m) and sedimentary (0.83 m3/h/m) rocks in humid/sub- humid climate. In this way, their productivities are more evident in more humid climates, once their intrinsic permeability and productivity establish a relationship directly proportional to the availability of rainfall. In general, metasediments (Q/s avg 0.099 m3/h/m) were more productive when compared to gneisses and migmatites (0,051 m3/h/m) and to plutonic rocks (0.052 m3/h/m). In the gneisses and migmatites, the climate appeared to have no effective influence on productivity. The groundwater of the region has high salinity, confirmed in 210 hydrochemical analyzes. The mechanism of salinization of aquifers is probably associated with salt seawater spray, predominantly for chloride and sodium, and high evaporation rates, as can be confirmed by the higher concentrations of chloride in the water of wells located closer to the coast. The mechanism of recharge in more permeable rocks may favor the reduction of salinity (greater infiltration), as verified in metasediments when compared to the higher concentrations observed in gneisses and migmatites.

Abstract not available

This work is focused on a state-of-the-art tubular micro-solid oxide fuel cell (TSOFC), ~3 millimeters in diameter and ~300 microns thick, with Ni/YSZ and LSM/YSZ composite electrodes and a YSZ electrolyte. A 2D axi-symmetric, multi-scale CFD model is developed which includes the fluid flow, mass transfer, and heat transfer within the gas channels and the porous electrodes. The electrochemical reactions are modeled within the volume of the electrodes, enabling the model to account for the extent of the reaction zone. Thermodynamic expressions are developed to estimate the single-electrode reversible heat generation and the single-electrode electromotive force of a non-isothermal electrochemical cell. The isothermal, non-isothermal, and transient models are each validated against the experimental results, and consistent with the physical reality of the TSOFC. A novel approach is used to estimate the kinetic parameters, enabling the simulations to be used as a diagnostic tool. The model is used to gain a thorough insight about the TSOFC. The cathode electrochemical activity and the anode support ohmic loss are identified as the two major performance bottlenecks for this cell. Including radiation is found to be essential for a physically meaningful heat transfer model. The thermoelectric effects on the cell overall electromotive force is found to be negligible. It is found that the anode reaction is always endothermic, while the cathode reaction is always exothermic, and that the temperature gradients across the cell layers are less than 0.05C The cell transient response is found to be fast, and dominated by the thermal transients. Several physical properties used in the model are measured experimentally, indicating that that the correlations used in the literature are not always suitable, especially when new fabrication techniques are used. The conductivity of the anode support was measured to be several orders of magnitude lower than expected and very sensitive to temperature, which explains the lower than expected and occasionally degrading cell performance. A hypothesis is proposed to explain this phenomenon based on the thermal expansion effects which result in the formation and disruption of particle to particle contacts within the composite electrode. / Chemical Engineering

Recently, active suspension has been applied to many commercial automobiles. To develop the control algorithm for active suspension, a quarter-car test bed was built by using a direct-drive tubular linear brushless permanent-magnet motor (LBPMM) as a force-generating component. Two accelerometers and a linear variable differential transformer (LVDT) are used in this quarter-car test bed. Three pulse-width-modulation (PWM) amplifiers supply the currents in three phases. Simulated road disturbance is generated by a rotating cam. Modified lead-lag control, linear-quadratic (LQ) servo control with a Kalman filter, and the fuzzy control methodologies were implemented for active-suspension control. In the case of fuzzy control, asymmetric membership functions were introduced. This controller could attenuate road disturbance by up to 78%. Additionally, a sliding-mode controller (SMC) is developed with a different approach from the other three control methodologies. While SMC is developed for the position control, the other three controllers are developed for the velocity control. SMC showed inferior performance due to the drawback of the implemented chattering-proof method. Both simulation and experimental results are presented to demonstrate the effectiveness of these four control methodologies.

<p>This thesis discusses the dress code during the Pitted Ware culture on the Swedish island of Gotland. Eight Pitted Ware grave-fields have been analyzed; only 74 skeletons have been identified with some sort of ornament that could have been attached to clothes. The grave-fields are rich in finds and in people nearly every age group is present. The analysis has shown that there are clear differences between the genders. The female always has some sort of seal tooth ornament around her waist and thighs. The man has sometimes tusks from wild boar and tubular bones as an ornament on his clothes. The children have all of the ornaments that the parents have but in smaller numbers. There are also other finds that appear on all of the individuals, but the tusks, seal tooth and tubular bones are the ones that appear on nearly every individual. The North American Indians clothing has been used as a reference to help understand the clothing of the Pitted Ware. So far all of the finds that have been found on the skeletons have shown great diversity in the Pitted Ware clothing.</p>

The novel method of this thesis work is based on using quadrature filters to estimate an orientation tensor and to use the advantage of tensor information to control 3D adaptive filters. The adaptive filters are applied to enhance the Magnetic Resonance Angiography (MRA) images. The tubular structures are extracted from the volume dataset by using the quadrature filters. The idea of developing adaptive filtering in this thesis work is to enhance the volume dataset and suppress the image noise. Then the output of the adaptive filtering can be a clean dataset for segmentation of blood vessel structures to get appropriate volume visualization. The local tensors are used to create the control tensor which is used to control adaptive filters. By evaluation of the tensor eigenvalues combination, the local structures like tubular structures and stenosis structures are extracted from the dataset. The method has been evaluated with synthetic objects, which are vessel models (for segmentation), and onion like synthetic object (for enhancement). The experimental results are shown on clinical images to validate the proposed method as well.

The goal of this work is to increase the current understanding of Controlled Radical Polymerizations (CRPs) in two areas. Progressing closer towards employing an aqueous system, specifically miniemulsion, to produce poly(vinyl acetate) via reversible addition fragmentation chain transfer (RAFT) chemistry constitutes the first part of this goal. Presented are the results of miniemulsion polymerizations using both water and oil-soluble initiators. Limiting conversions in both are examined and explained in terms of radical loss. The second part of the goal is to further the understanding of the nature of the RAFT/miniemulsion system when employed in continuous tubular reactors. The development of the recipe using mixed surfactants, the results of styrene homopolymerizations in batch and tube, and the results of a chain extension experiment demonstrating the living nature of the chains formed in the tubular reactor are presented. Kinetic anomalies are addressed, as well as polydispersity (PDI) differences between batch and tube. Flow phenomenon and their influence on residence time distribution and by implication the polydispersity of the polymer formed are offered as explanations for the variance in PDI and are subsequently quantified. A model of RAFT in laminar flow is presented and the results and implications are discussed in general terms. The flow profile of the reactor is examined using a tracer technique developed specifically for this system. Experiments are presented directly relating the residence time distribution to the polydispersity of the polymer. Transient behavior of the reactor in isolated plug flow is explained in terms of initiator loss. Both experimental data and a model are used to support this hypothesis. Finally, conclusions and implications are presented and unanswered questions and the ideas for future work that they generated are addressed.