Geometric Properties of Central Catadioptric Line Images and Their Application in Calibration

In central catadioptric systems, lines in a scene are projected to conic curves in the image. This work studies the geometry of the central catadioptric projection of lines and its use in calibration. It is shown that the conic curves where the lines are mapped possess several projective invariant properties. From these properties, it follows that any central catadioptric system can be fully calibrated from an image of three or more lines. The image of the absolute conic, the relative pose between the camera and the mirror, and the shape of the reflective surface can be recovered using a geometric construction based on the conic loci where the lines are projected. This result is valid for any central catadioptric system and generalizes previous results for paracatadioptric sensors. Moreover, it is proven that systems with a hyperbolic/elliptical mirror can be calibrated from the image of two lines. If both the shape and the pose of the mirror are known, then two line images are enough to determine the image of the absolute conic encoding the camera’s intrinsic parameters. The sensitivity to errors is evaluated and the approach is used to calibrate a real camer

Lateral resistance of log timber walls subjected to horizontal loads

The present works intends to represent a further step in the knowledge of timber log-houses through an experimental approach, from which only few information is available. The main part of the experimental work is based on in-plane static tests conducted on timber log walls with distinct transversal stiffness, two vertical compression levels and two values of slenderness. Monotonic and cyclic tests were performed according to EN 12512:2001. The formers were performed to define the elastic slip values and assessment of the failure mechanisms while the lasts allowed evaluating impairment of strength, to measure the ductility and to quantify the energy dissipation. In a first step research, an extensive characterization of the timber logs was made. The connection between the first timber log and the basement was also evaluated.(undefined

Comportamento sísmico de um sistema log-house

O presente trabalho pretende contribuir para o conhecimento do sistema construtivo “Log-house” através de uma vasta análise experimental e de análises numéricas. A campanha experimental, realizada previamente, teve por objectivo de estudar o comportamento no plano das paredes em troncos de madeira quando sujeitas a acções monotónicas e cíclicas, de acordo com a EN 12512:2001. Apresenta-se ainda um caso de estudo, relativo a uma moradia produzida e comercializada pela empresa “Rusticasa”, no qual se considera a distribuição das forças sísmicas em função: a) da área de influência de cada parede e, b) da rigidez de cada parede. As análises efectuadas contemplam algumas verificações de resistência, nomeadamente ao nível da ligação à fundação e no cruzamento entre paredes ortogonais, as quais não são verificadas na totalidade pelo que se apresentam algumas sugestões a implementar no sistema construtivo com vista à verificação da segurança.This paper aims to contribute to the knowledge of the building system "Log-house” through an extensive experimental analysis and numerical analysis. The experimental campaign, performed previously, aimed of studying the in-plane behavior of log walls when subjected to monotonic and cyclic loads, in accordance with EN 12512:2001. Moreover, a case study concerning a house characteristic of the "Rusticasa" system was analyzed considering the distribution of seismic forces according to: a) the area of influence of each wall, and b) the stiffness of each wall. Analyses carried out include some resistance checks, particularly in terms of the connection to the foundation and at the crossing between orthogonal walls, which are not checked for all walls and, therefore, some suggestions are presented to improve the safety of the structural system.Rusticas

Structural behaviour of log timber walls under lateral in-plane loads

The present works intends to represent a further step in the knowledge of timber loghouses through an experimental approach, from which only few information is available. The main part of the experimental work is based on in-plane static tests conducted on timber log walls with distinct transversal stiffness, two vertical compression levels and different values of slenderness. Monotonic and cyclic tests were performed according to EN 12512:2001. The former were performed to define the elastic slip values and assessment of the failure mechanisms while the latter allowed for the evaluation of the impairment of strength, the measurement of the ductility and the quantification the energy dissipation. Previously to the full-scale tests of walls, an extensive characterization of the timber logs was made. Due to its importance, the connection between the first timber log and the basement was also evaluated through tests. In a second step of the research, a case study was used to develop a numeric analysis. Using FEM, the in-plane stiffness of timber logs walls was quantified, thus allowing to compare the result of distributing the horizontal loads by the walls according to their area of influence or their in-plane stiffness. Finally, improvements to the log system analyzed were suggested

Comportamento sísmico de um sistema log-house

Dissertação de mestrado (ciclo de estudos integrado em Engenharia Civil)A madeira, enquanto material de construção, já ocupou no passado um lugar de destaque. Contudo, o aparecimento de outros materiais, como o aço e o betão, levou quase ao seu abandono total para fins estruturais. Excepção a esta tendência viveu-se nos países do Norte e Centro da Europa, sendo exemplo o sistema construtivo “Log-house”. Este sistema construtivo consiste na construção de paredes através da sobreposição de troncos de secção circular ou rectangular, geralmente possuindo nas faces superior e inferior um entalhe de forma a aumentar a superfície de contacto e a estabilidade. As paredes que constituem este sistema construtivo conferem-lhe resistência estrutural e estabilidade face às acções verticais e horizontais, quer no seu plano, quer no plano perpendicular. A resistência às acções verticais depende da área de contacto entre os toros e da resistência à compressão perpendicular às fibras da madeira, enquanto as acções horizontais perpendiculares ao plano da parede serão suportadas pelas paredes transversais, dependendo a estabilidade das paredes a acções horizontais no seu plano do atrito desenvolvido nos entalhes que cada toro possui e da resistência oferecida pelas paredes ortogonais. Face à falta de conhecimento do comportamento destas construções em caso de ocorrência de um sismo, pretende-se, com o presente trabalho, avaliar numericamente o seu comportamento face à acção sísmica, recorrendo-se para tal a modelos simplificados. Estas análises baseiam-se nos resultados e conclusões de uma campanha de ensaios experimentais realizada previamente, com o objectivo de estudar o comportamento no plano das paredes comercializadas pela empresa Rusticasa, quando sujeitas a acções monotónicas e cíclicas.Timber as building material has held in the past a prominent importance. However, with the emergence of new materials such as steel and concrete, its structural use becomes limited. Exception to this trend happened in North and Central Europe, where the timber system "Log-house”, which involves the construction of walls by overlapping logs of circular or rectangular, usually having the faces upper and lower a notch in order to increase the surface contact and stability, was never abandoned. The walls that make up this building system give its structural strength and stability with respect to the vertical and horizontal actions, both in its plan and in the perpendicular. The resistance to vertical actions depends on the contact area between the logs and on the timber compressive strength perpendicular to grain. Horizontal loads perpendicular to the wall will be supported by the transverse walls while, the horizontal in-plane loads will be carried out by friction and by the resistance offered by the orthogonal walls. Given the lack of understanding of the behavior of the log-house system under earthquakes, this study aims to evaluate numerically its behavior under seismic actions. Such analysis will be based on the findings and conclusions achieved throughout monotonic and cyclic full-scale tests of timber log walls, performed previously, with the aim to have the European Technical Approval

Simulação computacional do contágio da gripe pessoa a pessoa

Neste trabalho estuda-se a propagação do vírus da gripe numa comunidade escoar com 2000 pessoas recorrendo ao modelo matemático SIR em que se considera que a população está dividida em três grupos independentes: os Suscetíveis (S), os Infecciosos (l) e os Recuperados (R). 'O estudo è feito do" ponto" de"vista determinístico e estocástico.info:eu-repo/semantics/publishedVersio

On the nature of the (de)coupling of the magnetostructural transition in Er5_5Si4_4

In this report, a successful thermodynamical model was employed to understand the structural transition in Er$_5$Si$_4$, able to explain the decoupling of the magnetic and structural transition. This was achieved by the DFT calculations which were used to determine the energy differences at 0 K, using a LSDA+U approximation. It was found that the M structure as the stable phase at low temperatures as verified experimentally with a $\Delta F_0 = -$0.262 eV. Finally, it was achieved a variation of Seebeck coefficient ($\sim$ 6 $\mu$V) at the structural transition which allow to conclude that the electronic entropy variation is negligible in the transition.Comment: 17 pages, 3 figures, 1 tabl

Avaliação da influência da camada de desgaste na sustentabilidade dos pavimentos rodoviários

A noção de que os recursos que a humanidade tem usado não são ilimitados tem levado à implementação de práticas mais sustentáveis. Sendo os pavimentos rodoviários infraestruturas cuja construção, utilização e reabilitação provoca impactes ambientais consideráveis, torna-se indispensável a procura de novas técnicas e processos construtivos, com vista à mitigação das suas consequências. No presente artigo, para além de uma Análise do Ciclo de Vida dos pavimentos rodoviários, apresentam-se os resultados de um estudo laboratorial no qual se pretende avaliar a influência do tipo de camada de desgaste utilizada num pavimento, na variação do consumo de energia necessária à circulação.Financiado por fundos FEDER através do Programa Operacional de Competitividade - COMPETE e por fundos nacionais através da FCT - Fundação para a Ciência e a Tecnologia - no âmbito do Projeto PLASTIROADS - PTDC/ECM/119179/2010 e do Projeto Estratégico - UI 4047 - 2011-201