Modeling of Free Surface Flows with Elastic Bodies Interactions

In this paper, a series of new fluid and structure interactions test cases with strong free surface effects are presented and computations of such flows with the Particle Finite Element Method (PFEM) (Idelsohn, Oiiate, Del Pin and Calvo, 2006) are documented. The structures object of study are elastic cantilever bars clamped inside sloshing tanks subjected ro roll motion. The possibilities of PFEM for the coupled simulation of moderately violent free surface flows interacting with elastic bodies are investigated. The problem can be described as the coupling of a sloshing flow with an easily deformable elastic body. A series of experiments designed and executed specifically for these tests are also described. The experiments comprise cases with different liquid height and liquids of different viscosity. The aim is to identify canonical benchmark problems in FSI (Fluid and Structure Interactions), including free surfaces, for future comparisons between different numerical approaches

Usos de la microscopía electroquímica de barrido (SECM) para la investigación de procesos localizados de corrosión

La microscopía electroquímica de barrido (SECM) es una técnica muy apropiada para el estudio local de los procesos de corrosión debido a que suministra información  insitu, a escalas micrométrica y submicrométrica, relativa a la topografía y a la actividad electroquímica de superficies reactivas en disolución acuosa. La resolución espacial se obtiene en base a desplazar una sonda colocada en la proximidad de la superficie activa, permitiendo la comparación de las respuestas locales en diferentes regiones. En esta comunicación se presentan los modos de operación de la técnica que encuentran aplicación para la investigación de procesos localizados de corrosión, ilustrándose cada uno de ellos con un ejemplo de su aplicación en el laboratorio de corrosión

Fuga de radiação de unidades de radiologia pediátrica

Em radiologia pediátrica, é necessário que uma pessoa segure os pacientes durante a exposição, já gue os pacientes são crianças e recém-nascidos. Portanto, torna-se importante uma apropriada determinação e minimização da radiação de fuga das unidades de radiodiagnóstico. Fez-se medidas de radiação de fugas em cinco unidades de raios X, sendo quatro unidades produzidas pela mesma companhia. Três das quatro unidades produzidas pela mesma companhia apresentaram uma contribuição anormal da radiação de fuga. Discute-se a não-adequação dos atuais cabeçotes para radiologia pediátrica e apresenta-se sugestões para um novo enfoque em radiação pediátrica.In pediatric radiology, it is necessary that a person stay with the patients, as they are children and newly bom, during radiation exposure. Therefore, the proper evaluation and minimization of radiation leakage from radiodiagnostic units becomes important. Measurements of leakage radiation were carried out in five X-ray units, where four of which are manufactured by the same company. Three of the four units produced by the same company, showed an abnormal contribution of the leakage radiation. The inadequacy of the presently available housing tubes for pediatric radiology is discussed. Suggestions regarding new approach in pediatric radiology are presented

Equação de estado para a materia de neutrons Super-densa

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciencias Fisicas e MatematicasNeste trabalho, a equação de estado para a matéria de nêutrons é estudada no contexto da aproximação não perturbativa Expansão d, e comparada a aproximação Relativística de Hartree (RHA). Esta expansão é uma aproximação não perturbativa para modelos de teoria de campo, que combina técnicas de teoria de perturbação e cálculo variacional. Utilizando este método para o modelo de Walecka, encontramos um novo ponto de saturação para a matéria de nêutrons em uma densidade 30 vezes superior a usual , além do resultado conhecido de saturação em 1.42 fm-1. Do ponto de vista astrofísico analisamos a equação de estado para as duas soluções e integramos a equação de Oppenheimer-Volkoff-Tolman simulando uma estrela de nêutrons

Diversidades geográficas e construção de um conhecimento crítico para participar em rede. A experiência do Geoforo Iberoamericano. Balanço inicial

La diversidad de pueblos, culturas y situaciones sociales en países de Iberoamérica no impide el diálogo crítico y honesto en torno a la investigación que se realiza sobre el aprendizaje de los problemas del mundo. A este reto puede contribuir la Geografía como ciencia, pero necesita, entonces, abandonar los obstáculos intelectuales, corporativos y académicos que dificultan su estudio por parte de los alumnos. En este trabajo damos cuenta de las iniciativas llevadas a cabo por un grupo de profesores a través del Geoforo, que aprovecha las facilidades del ciberespacio, a partir del portal Geocrítica de la Universidad de BarcelonaThe diversity of people, cultures and social situations in Latin America countries does not obstruct the critical and honest dialogue concerning the research carried out on the learning of world problems. Geography, as a science, can contribute to this challenge, but it needs, then, to leave the intellectual, corporate and academic obstacles that prevent its study by the pupils. In this work we communicate the initiatives developed by a group of teachers by means of the Geoforo, which takes advantage of the facilities of the cyberspace, from the Geocrítica portal of the University of Barcelona

Interaction between an elastic structure and free-surface flows: experimental versus numerical comparisons using the PFEM.

The paper aims to introduce new fluid–structure interaction (FSI) tests to compare experimental results with numerical ones. The examples have been chosen for a particular case for which experimental results are not much reported. This is the case of FSI including free surface flows. The possibilities of the Particle Finite Element Method (PFEM) [1] for the simulation of free surface flows is also tested. The simulations are run using the same scale as the experiment in order to minimize errors due to scale effects. Different scenarios are simulated by changing the boundary conditions for reproducing flows with the desired characteristics. Details of the input data for all the examples studied are given. The aim is to identifying benchmark problems for FSI including free surface flows for future comparisons between different numerical approaches

Estudo da homogeneidade e determinação de parâmetros básicos do experimento de leito fluidizado den-01

Neste trabalho foi feito um estudo hidráulico de um experimento a leito fluidizado onde aplicou-se a técnica de absorção gama para a determinação da porosidade do leito. Verificou-se a influência da colocação de uma tela para limitação da altura do leito bem como do comportamento do mesmo com a introdução de um anel metálico de diâmetro próximo do diâmetro do tubo de fluidização. As medidas foram realizadas em um modelo hidráulico especialmente construído para esta finalidade. No modelo foram utilizadas esferas de aço com diâmetro de 8 mm que fluidizaram em água à temperatura ambiente em circuito fechado. Foram feitos testes com 20 kg, 30 kg e 40 kg de esferas. Para as medidas utilizou-se a radiação gama proveniente de uma fonte de cobalto 60 com atividade de 700 mCi colimada com chumbo. O detector utilizado foi um cristal de NaI (Tl). Os resultados obtidos mostram que tanto a tela como o anel provocam a divisão do leito fluidizado em duas partes. A tela faz formar um leito fixo invertido na sua superfície inferior. O anel faz com que o leito seja transportado para a parte de cima do mesmo a medida em que ele é introduzido no leito. Verificou-se que a maior expansão do leito se dá para uma relação entre a altura do leito compactado e o diâmetro do tubo de fluidização de 0,55, correspondendo ao teste com 30 kg de esferas. A formação de jorro acontece sempre para a mesma vazão, em torno de 16 l/s, independente da relação entre a altura do leito compactado e o diâmetro do tubo de fluidização. Na fase de leito particulado a porosidade é menor no centro do leito e aumenta nas camadas superiores e inferiores.In this work an experimental hydraulical study of the fluidized bed reactor concept was performed, where the absorption gamma ray technique was applied for the determination of bed porosity. The influence of the use of a screen for the limitation of the bed height was investigated as well as the behavior of the bed by introducing a metal ring with a diameter close to the diameter of the fluidization tube. Measurements were performed in a hydraulical model built with this purpose. In the model, steel spheres with 8 mm diameter were fluidized in water at room temperature in a closed loop. Tests with 20, 30 and 40 kg of spheres were made. Bed porosity was measured with a cobalt-60 gamma ray source, with 700 mCi activity, and a NaI (Tl) crystal detector. Results show that both screen and ring split the bed in two parts. The screen leads to the formation of a fixed bed in the top of the test section. By moving the ring downwards, the bed is displaced upwards. It was observed that the largest bed expansion occurs for a value of 0.55 ofthe ratio between the height ofthe compacted bed and the tube diameter, which corresponds to a mass of 30 kg of spheres. Jet formation occurred always for the same flow rate, about 16 l/h, without dependence on the ratio between the height ofthe fixed bed and tube diameter. For the particulate bed regime, porosity is lower at the center o f the bed, increasing at the upper and lower layers

Comparison of the qCON and qNOX indices for the assessment of unconsciousness level and noxious stimulation response during surgery

The objective of this work is to compare the performances of two electroencephalogram based indices for detecting loss of consciousness and loss of response to nociceptive stimulation. Specifically, their behaviour after drug induction and during recovery of consciousness was pointed out. Data was recorded from 140 patients scheduled for general anaesthesia with a combination of propofol and remifentanil. The qCON 2000 monitor (Quantium Medical, Barcelona, Spain) was used to calculate the qCON and qNOX. Loss of response to verbal command and loss of eye-lash reflex were assessed during the transition from awake to anesthetized, defining the state of loss of consciousness. Movement as a response to laryngeal mask (LMA) insertion was interpreted as the response to the nociceptive stimuli. The patients were classified as movers or non-movers. The values of qCON and qNOX were statistically compared. Their fall times and rise times defined at the start and at the end of the surgery were calculated and compared. The results showed that the qCON was able to predict loss of consciousness such as loss of verbal command and eyelash reflex better than qNOX, while the qNOX has a better predictive value for response to noxious stimulation such as LMA insertion. From the analysis of the fall and rise times, it was found that the qNOX fall time (median: 217 s) was significantly longer (p value <0.05) than the qCON fall time (median: 150 s). At the end of the surgery, the qNOX started to increase in median at 45 s before the first annotation related to response to stimuli or recovery of consciousness, while the qCON at 88 s after the first annotation related to response to stimuli or recovery of consciousness (p value <0.05). The indices qCON and qNOX showed different performances in the detection of loss of consciousness and loss of response to stimuli during induction and recovery of consciousness. Furthermore, the qCON showed faster decrease during induction. This behaviour is associated with the hypothesis that the loss of response to stimuli (analgesic effect) might be reached after the loss of consciousness (hypnotic effect). On the contrary, the qNOX showed a faster increase at the end of the surgery, associated with the hypothesis that a higher probability of response to stimuli might be reached before the recovery of consciousness.Postprint (author's final draft

Kinetics of copper passivation and pitting corrosion in Na2SO4 containing dilute NaOH aqueous solution

The electrochemical behaviour of Cu in alkaline solutions containing Na2SO4 was studied using potentiodynamic and potentiostatic techniques complemented by scanning electron microscopy. The presence of Na2SO4 enhances Cu electrodissolution through the passive layer and decreases the breakdown potential. There is a critical OH-/sulphate concentration ratio for the onset of localized corrosion. The competitive interaction between OH- and sulphate ions at the passive layer can explain the experimental data. Pit initiation fits the point defect model for passivity breakdown. Pit growth involves a number of current contributions which can be distinguished through the analysis of current transients at constant potential by using nucleation and growth models.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

The long-term evolution of intergenerational transfers in Spain (1958-2012)

National Transfer Accounts (NTA) aim at disentangling how people produce, consume and save along the lifecycle, and how resources move among generations through the different resource allocation devices available (family, market and government). This paper extends the available Spanish NTA estimates (2000 -2012) to the past until 1958, to analyse changes in intergenerational transfers associated to long-term processes such as the demographic transition and the welfare state development. For 1980 and 1990, we provide new estimates based on the Spanish Household Budget Surveys (HBS) while, for previous periods in which HBS do not provide enough information, we resort to the available evidence on demography, national accounts and public finance. The long-term evolution of Spanish NTA shows the increasing weight of government transfers as a device to reallocate resources across generations and the growing importance of the elderly in the system of intergenerational transfers as a result of population ageing