Sensores ópticos para monitorização dinâmica de estruturas

O presente trabalho centra-se no desenvolvimento e aplicação de sensores de aceleração ópticos, baseados em redes de Bragg gravadas em fibras ópticas, para monitorização da integridade estrutural de estruturas de engenharia civil. Foram implementados dois acelerómetros uniaxiais e um acelerómetro biaxial. Recorreu-se a uma ferramenta de simulação baseada no método dos elementos finitos que permitiu optimizar, sem custos de produção, as características dos sensores, nomeadamente a sua frequência de ressonância. A caracterização dos sensores foi realizada em ambiente laboratorial e a sua resposta comparada com os resultados de simulação, de modo a validar os modelos numéricos. A aplicabilidade e demonstração de conceito foram realizadas na monitorização de estruturas com testes de campo. Foi monitorizado um teste destrutivo de uma parede de adobe, construída à escala real no Departamento de Engenharia Civil da Universidade de Aveiro, onde foram utilizados sensores estáticos e dinâmicos baseados em redes de Bragg gravadas em fibra óptica. Foram realizadas medidas dinâmicas na ponte pedonal do Campus Universitário da Universidade de Aveiro, onde se compararam os resultados obtidos com os sensores ópticos com resultados de sensores electrónicos comerciais. O acelerómetro biaxial foi testado na monitorização de estruturas esbeltas, nomeadamente na monitorização de duas torres de telecomunicações móveis, onde se demonstrou a possibilidade da utilização de sensores ópticos na caracterização dinâmica deste tipo de estruturas. Outro tipo de estruturas de engenharia civil onde foi demonstrada a aplicabilidade dos sensores ópticos desenvolvidos na monitorização estrutural foram os reservatórios de água elevados. Foi realizada a monitorização dinâmica de um exemplo deste tipo de estruturas, localizado no Campus Universitário da Universidade de Aveiro. A monitorização foi realizada recorrendo ao sensor biaxial desenvolvido e a um sismógrafo, ficando o sensor óptico instalado na estrutura de modo a permitir futuras leituras e assim a monitorização periódica da estrutura. Foi ainda desenvolvido um sensor de humidade relativa do ar, com um material sol-gel, que permitiu registar o nível de humidade relativa no interior de blocos de betão, durante um ano. Este sensor pode ser incluído numa rede de sensores multiplexados, na caracterização e monitorização da integridade estrutural de certas estruturas de engenharia civil.

Secagem convectiva de produtos alimentares: otimização e controlo

O presente trabalho tem como objetivo analisar a cinética de secagem do bacalhau salgado verde (Gadus morhua) em secador convectivo. É apresentada a análise da composição físico-química dos bacalhaus utilizados nos ensaios experimentais, bem como o estudo das isotermas de sorção do produto, através de experiências e modelação matemática. Dos modelos usados para o ajuste das isotermas de sorção do bacalhau salgado verde, o que melhor se adaptou aos resultados experimentais foi o modelo de GAB Modificado, com coeficientes de correlação variando entre 0,992 e 0,998. Para o controlo do processo de secagem (nomeadamente os parâmetros temperatura, humidade relativa e velocidade do ar) foi utilizada lógica difusa, através do desenvolvimento de controladores difusos para o humidificador, desumidificador, resistências de aquecimento e ventilador. A modelação do processo de secagem foi realizada através de redes neuronais artificiais (RNA), modelo semi-empírico de Page e modelo difusivo de Fick. A comparação entre dados experimentais e simulados, para cada modelo, apresentou os seguintes erros: entre 1,43 e 11,58 para o modelo de Page, 0,34 e 4,59 para o modelo de Fick e entre 1,13 e 6,99 para a RNA, com médias de 4,38, 1,67 e 2,93 respectivamente. O modelo obtido pelas redes neuronais artificiais foi submetido a um algoritmo de otimização, a fim de buscar os parâmetros ideais de secagem, de forma a minimizar o tempo do processo e maximizar a perda de água do bacalhau. Os parâmetros ótimos obtidos para o processo de secagem, após otimização realizada, para obter-se uma humidade adimensional final de 0,65 foram: tempo de 68,6h, temperatura de 21,45°C, humidade relativa de 51,6% e velocidade de 1,5m/s. Foram também determinados os custos de secagem para as diferentes condições operacionais na instalação experimental. Os consumos por hora de secagem variaram entre 1,15 kWh e 2,87kWh, com uma média de 1,94kWh.

Revestimentos compatíveis para alvenarias antigas sujeitas a ação severa da água

Uma das maiores causas de degradação dos revestimentos é a presença de sais solúveis, tanto nas zonas costeiras como nas zonas continentais. Estes sais podem ter origens distintas, tais como: humidade ascensional, nevoeiro salino, inundações ou ainda estarem presentes nos próprios materiais, como é o caso da utilização de areias mal lavadas. O local onde os sais cristalizam é dependente do tipo de transporte entre a alvenaria e o revestimento, assim como da severidade da envolvente ambiental (temperatura e humidade relativa). Com esta tese pretende-se desenvolver revestimentos de substituição compatíveis, eficazes e duráveis para alvenarias antigas sujeitas à ação severa da água (humidade ascensional através das fundações com elevada concentração de NaCl); desenvolver ensaios de envelhecimento acelerado baseados em ciclos de dissolução e cristalização que permitam simular a ação severa da água; perceber a influência de revestimentos com caraterísticas extremas de permeabilidade ao vapor de água aplicados nas duas faces do mesmo suporte (argamassas de cimento e resina versus argamassas de cal), e sujeitos à ação severa da água; perceber a influência de vários fatores, tais como : rasgos verticais contínuos executados no emboço e a utilização de hidrófugo no reboco no desempenho dos vários sistemas de revestimento desenvolvidos, quando sujeitos à ação severa da água;; utilizar a remoção eletrocinética de sais, em provetes simulando a influência da alvenaria e dos revestimentos, com o objetivo de reduzir a sua concentração de NaCl, para que no futuro possa ser aplicado de forma eficaz em paredes de edifícios antigos, enquanto ação de manutenção, e desta forma aumentar a durabilidade dos revestimentos. Para atingir os objetivos descritos, foram considerados: i) o desenvolvimento de provetes que permitam considerar os sistemas de revestimento desenvolvidos nesta tese e o suporte, e que simulem uma alvenaria revestida em ambas as faces, e com os quais seja possível a simulação da ação severa da água em laboratório e, ii) o desenvolvimento ciclos de dissolução e cristalização numa parede de grandes dimensões existente em laboratório, que permitam simular a ação severa da água em condições tão reais quanto possível. O objetivo final deste estudo é o desenvolvimento de um revestimento de substituição denominado “emboço ventilado” para paredes de edifícios antigos com revestimentos degradados devido à presença de humidade ascensional e sais solúveis. Pretende-se que este sistema de revestimento, composto por duas camadas de revestimento (camada base e reboco), seja compatível, durável e eficaz, e que funcione como um sistema de acumulação no qual os sais cristalizem na camada base do sistema de revestimento (executada com rasgos verticais) e não na alvenaria ou na camada exterior.

Hygrothermal performance of wood-hemp insulation in timber frame wall panels with and without a vapour barrier

An in situ experiment on a full-scale timber frame test building was carried out to study the hygrothermal performance of wood-hemp composite insulation in timber frame wall panels with and without a vapour barrier. The heat transfer properties and the likelihood of mould growth and condensation in the panels were compared. Step changes in the internal relative humidity were performed to explore the effects of high, normal and low internal moisture loads on the wall panels. No significant difference in the average equivalent thermal transmittance (U-values) between the panels with and without a vapour barrier was observed. The average equivalent U-values of the panels were close to the U-values calculated from the manufacturers’ declared thermal conductivity values of the insulation. The likelihood of condensation was higher at the interface of the wood-hemp insulation and the oriented strand board (OSB) in the panel without a vapour barrier. In terms of the parametric assessment of the mould germination potential, the relative humidity, the temperature and the exposure conditions in the insulation-OSB interfaces of the panel without a vapour barrier were found to be more favourable to the germination of mould spores. Nonetheless, when the insulations were dismantled, no mould was visually detected.

The comparative in situ hygrothermal performance of Hemp and Stone Wool insulations in vapour open timber frame wall panels

An in situ experiment in a full scale timber frame test building was carried out to compare the hygrothermal performance of Hemp and Stone Wool insulations of identical thermal conductivity. Hemp and Stone Wool insulations were installed in timber frame wall panels without vapour barrier. The comparison was made in terms of heat transfer properties, likelihood of mould growth and condensation. Step changes in internal relative humidity were performed to explore the effect of high and normal internal moisture load on the wall panels. No significant difference between the average equivalent thermal transmittance (U-values) of the panels incorporating Hemp and Stone Wool insulations was observed. The average equivalent U-values of the panels were closer to the calculated U-values of the panels based on the manufacturers’ declared thermal conductivity of Hemp and Stone Wool insulations. It was observed that the placement of heat flux sensor along the depth of the insulation had significant influence on the measured equivalent U-value of the panels during high internal moisture load. The frequency and likelihood of condensation was higher in the interface of Stone Wool and Oriented Strand Board (OSB). In terms of the parametric assessment of mould germination potential, relative humidity, temperature and exposure conditions in the insulation-OSB interfaces were found to be favourable to germination of mould spore. However, when the insulations were dismantled, no mould was visually detected.

Quasi steady state and dynamic hygrothermal performance of fibrous Hemp and Stone Wool insulations: Two innovative laboratory based investigations

Moisture and heat management properties of Hemp and Stone Wool insulations were studied by mounting them between a hot and a cold climate chamber. Both insulations were exposed to identical hygrothermal boundary conditions. Quasi steady state and dynamic tests were carried out at a range of relative humidity exposures. The likelihood of interstitial condensation was assessed and equivalent thermal conductivity values of the insulations were determined. The adsorption-desorption isotherms of the insulations were also determined in a dynamic vapour sorption (DVS) instrument. It was observed that the likelihood of condensation was higher in Stone Wool insulation than in Hemp insulation. Hemp insulation performed better in managing moisture due to its high hygric inertia and water absorption capacity. It was observed that the equivalent thermal conductivity of Stone Wool insulation was dependent on enthalpy flow and phase change of moisture. The equivalent thermal conductivity of Hemp insulation was close to its declared thermal conductivity in dynamic conditions when high relative humidity exposures were transient. In quasi steady state boundary conditions, when the insulation was allowed to reach the equilibrium moisture content at ranges of relative humidity, there was a moisture dependent increase of thermal conductivity in Hemp insulation.

Application of radial basis function neural networks to a greenhouse inside air temperature model

The problem with the adequacy of radial basis function neural networks to model the inside air temperature as a function of the outside air temperature and solar radiation, and the inside relative humidity in an hydroponic greenhouse is addressed.

Comparison of on-line learning algorithms for RBF models in greenhouse environmental control problems

The problem with the adequacy of radial basis function neural networks to model the inside air temperature as a function of the outside air temperature and solar radiation, and the inside relative humidity in an hydroponic greenhouse is addressed.

Dynamic temperature models of a soiless greenhouse

In this paper climate discrete-time dynamic models for the inside air temperature of a soilless greenhouse are identified, using data acquired during two different periods of the year. These models employ data from air temperature and relative humidity.

Identification of greenhouse climate dynamic models

In this paper climate discrete-time dynamic models for the inside air temperature of two different greenhouses are identified, using data acquired during two different periods of the year. These models employ data from air temperature and relative humidity (both outside and inside the greenhouse), solar radiation, wind speed, and control inputs (ventialtion, etc.).

Predicting the greenhouse inside air temperature with RBF neural networks

The application of the Radial Basis Function (RBF) Neural Network (NN) to greenhouse inside air temperature modelling has been previously investigated (Ferreira et al., 2000a). In those studies, the inside air temperature is modelled as a function of the inside relative humidity and of the outside temperature and solar radiation. A second-order model structure previously selected (Cunha et al., 1996) in the context of dynamic temperature models identification, is used.

In vitro spore germination of Polystichum drepanum, a threatened fern from Madeira Island

Polystichum drepanum (Sw) C. Presl is a threatened fern endemic to a few forest areas in the north-west of Madeira Island. The aims of this work were to establish suitable culture conditions for in vitro germination of spores, and to evaluate short-term storage conditions for P drepanum spores. The highest frequency of germination was obtained in Murishage and Skoog (MS) liquid medium, without agitation. However, gametophytes maintained in MS liquid medium did not grow and, after 4 weeks, became anoxic and died. Thus, after germination in liquid medium, gametophytes were transferred to an MS double-phase culture system for further growth. The effects of storage period, temperature, and relative humidity during storage on in vitro spore germination were studied. Spore viability was assessed after 2, 4 and 6 months, and high viability (> 94%) was observed in all the assays. However, germination capability decreased with increased storage periods. The number of sporophytes obtained also decreased with prolonged storage periods. The results indicate that spores of R drepanum stored for 4 months at 21 degrees C maintain high viability and high germination frequency. ne sporophytes obtained were acclimatised in a mixture of peat and vermiculite [2:1 (v/v)] under high relative humidity (90-95%). Seventy-five sporophytes were successfully acclimatised to ex vitro conditions and showed active growth in the glasshouse.

Prevalence of Artemisia Species Pollinosis in Western Poland: Impact of Climate Change on Aerobiological Trends, 1995-2004

Background: Artemisia species pollen represents a major cause of allergy in Central Europe. Variations in the pollen season, the influence of climate variables and the prevalence of pollinosis to it were analyzed in Poznan, in western Poland between 1995 and 2004. Methods: A Hirst volumetric spore trap was used for atmospheric sampling. Pollination date trend analysis and Spearman correlation tests were performed. Skin prick tests (SPT) and allergen specific immunoglobulin (Ig)E antibody measurements were performed in 676 and 524 patients, respectively. Results: The Artemisia species pollen season grew longer due to a clear advance in the starting day and only a slightly earlier end point; the peak day also came slightly earlier. Rainfall in the fi rst fortnight of July highly influenced pollen season severity. Temperature was directly correlated with daily Artemisia species pollen levels; relative humidity was inversely correlated. Twelve percent of patients had a positive SPT reaction to Artemisia species. Their symptoms were rhinitis and conjunctivitis (15%), atopic dermatitis (15%), chronic urticaria (14.3%), bronchial asthma (2.4%), and facial and disseminated dermatitis (1.3%). Elevated specifi c IgE concentrations were detected in the sera of 10.1% of patients. Conclusions: Artemisia species pollen is an important cause of pollinosis in western Poland. Pollen season intensity is highly influenced by rainfall in the previous weeks. Trends towards earlier season starts and longer duration, possibly caused by climate change, may have an impact on the allergic population.

Do Urban Canyons Influence Street Level Grass Pollen Concentrations

In epidemiological studies, outdoor exposure to pollen is typically estimated using rooftop monitoring station data, whilst exposure overwhelmingly occurs at street level. In this study the relationship between street level and roof level grass pollen concentrations was investigated for city centre street canyon environments in Aarhus, Denmark, and London, UK, during the grass pollen seasons of 2010 and 2011 respectively. For the period mid-day to late evening, street level concentrations in both cities tended to be lower than roof-level concentrations, though this difference was found to be statistically significant only in London. The ratio of street/roof level concentrations was compared with temperature, relative humidity, wind speed and direction, and solar radiation. Results indicated that the concentration ratio responds to wind direction with respect to relative canyon orientation and local source distribution. In the London study, an increase in relative humidity was linked to a significant decrease in street/roof level concentration ratio, and a possible causative mechanism involving moisture mediated pollen grain buoyancy is proposed. Relationships with the other weather variables were not found to be significant in either location. These results suggest a tendency for monitoring station data to overestimate exposure in the canyon environment.

Application of Redundancy Analysis for Aerobiological Data

An aerobiological survey was conducted through five consecutive years (2006–2010) at Worcester (England).The concentration of 20 allergenic fungal spore types was measured using a 7-day volumetric spore trap. The relationship between investigated fungal spore genera and selected meteorological parameters (maximum, minimum, mean and dew point temperatures, rainfall, relative humidity, air pressure,wind direction) was examined using an ordination method(redundancy analysis) to determine which environmental factors favoured their most abundance in the air and whether it would be possible to detect similarities between different genera in their distribution pattern. Redundancy analysis provided additional information about the biology of the studied fungi through the results of the Spearman’s rank correlation. Application of the variance inflation factor in canonical correspondence analysis indicated which explanatory variables were auto-correlated and needed to be excluded from further analyses. Obtained information will be consequently implemented in the selection of factors that will be a foundation for forecasting models for allergenic fungal spores in the future.