Identificação de parâmetros elásticos e piezoelétricos em estruturas activas tipo placa : técnicas de optimização clássica versus redes neuronais artificiais

Neste trabalho são apresentados dois métodos não destrutivos para a identificação de parâmetros elásticos e piezoeléctricos em estruturas laminadas activas do tipo placa, com sensores/actuadores de superfície. O primeiro destes métodos resolve o problema inverso através de métodos de optimização clássica, minimizando a diferença entre frequências naturais experimentais e as fornecidas por um modelo de elementos finitos. O segundo método baseia-se na construção de um “meta-modelo” do problema inverso, recorrendo a Redes Neuronais Artificiais. Os dois métodos são comparados recorrendo a resultados experimentais de uma placa em vibração livre

A numerical-experimental method for damage location based on rotation fields spatial differentiation

This paper presents a structural damage location method that decreases the number of spatial differentiations needed to compute modal curvature fields. The method is numerically and experimentally applied to isotropic and laminated rectangular plates, respectively. A speckle shear interferometer is used to measure the rotation fields of the laminated plate, while the isotropic plate is analysed by finite elements. It was found that the Gaussian differentiation is the most suited technique to compute the curvature fields. It is also demonstrated the superior performance of the curvature method using measured rotation fields instead of measured displacement fields

Damage localization in laminated composite plates using mode shapes measured by pulsed TV holography

Three methods for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, are presented in this paper. These methods use double pulse TV holography with acoustic excitation for mode shapes acquisition and the differences in translations, rotations and curvatures. The rotations and curvatures are obtained by numerical differentiation of mode shapes translations using a differentiation/smoothing technique. The methods are applied to a carbon fiber reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows the localization of both cases of damage, which can be undetected by visual, X-ray or C-scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode.Three methods for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, are presented in this paper. These methods use double pulse TV holography with acoustic excitation for mode shapes acquisition and the differences in translations, rotations and curvatures. The rotations and curvatures are obtained by numerical differentiation of mode shapes translations using a differentiation/smoothing technique. The methods are applied to a carbon fiber reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows the localization of both cases of damage, which can be undetected by visual, X-ray or C-scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode

Damage localization in laminated composite plates using double pulse-electronic holographic interferometry

One method for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, is presented in this paper. This method uses double pulse-electronic holographic interferometry for mode shapes acquisition and the differences in curvatures. The rotations and curvatures are numerically obtained. The method is applied to a carbon fibre reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows for the localization of both cases of damage, which can be undetected by visual, X-ray or C-Scan inspections. The best localizations are achieved by selecting and applying the method to the most changed mode

Water as a critical issue for viticulture in southern Europe: sustainability vs competiveness

Sourced from the research article “Modern viticulture in southern Europe: vulnerabilities and strategies for adaptation to water scarcity” (Agricultural Water Management, 2016)Water is a vulnerable resource in the Mediterranean region, but irrigation demands have been increasing to mitigate effects of environmental stress. Sustainable wine production involves the precise use of water in the vineyard and winery. Improved knowledge on grapevine ecophysiology and genetics, the use of sensors for soil and canopy monitoring, plant phenotyping and improved crop management can help save water. In the winery, best management practices and improved water metrics will promote water savings and decrease wastewater productioninfo:eu-repo/semantics/publishedVersio

Suivi de l'évolution de la température du couvert végétal de deux variétés soumises a une irrigation déficitaire: un outil pour optimiser la géstion de l'eau ?

A better understanding of grapevine responses to drought and high air temperatures can help to optimize vineyard management to improve water use efficiency, yield and berry quality. Faster and robust field phenotyping tools are needed in modern precision viticulture, in particular in dry and hot regions such as the Mediterranean. Canopy temperature (Tc) is commonly used to monitor water stress in plants/crops and to characterize stomatal physiology in different woody species including Vitis vinifera. Thermography permits remote determination of leaf surface or canopy temperature in the field and also to assess the range and spatial distribution of temperature from different parts of the canopies. Our hypothesis is that grapevine genotypes may show different Tc patterns along the day due to different stomatal behaviour and heat dissipation strategies. We have monitored the diurnal and seasonal course of Tc in two grapevine genotypes, Aragonez (syn. Tempranillo) and Touriga Nacional subjected to deficit irrigation under typical Mediterranean climate conditions. Temperature measurements were complemented by determination of the diurnal course of leaf water potential (ψleaf) and leaf gas exchange. Measurements were done in two seasons (2013 and 2014) at different phenological stages: i) mid-June (green berry stage), ii) mid-July (veraison), iii) early August (early ripening) and iv) before harvest (late ripening). Correlations between Tc and minimal stomatal conductance will be presented for the two genotypes along the day. Results are discussed over the use of thermal imagery to derive information on genotype physiology in response to changing environmental conditions and to mild water stress induced by deficit irrigation. Strategies to optimize the use of thermal imaging in field conditions are also propose

Sorologia pareada por imunofluorescência e excreção de antígeno de rotavirus na diarréia aguda infantil

A serological study was carried out to evaluate the causal relationship of acute diarrhoea and rotavirus in children under five years of age. The rotaviral infection was demonstrated in paired sera by determining the antibody titers by immunofluorescence test (IF). Bovine rotavirus-infected MA-104 cell culture was used as substratum for IF. Out of 80 paired sera it was shown that 23 (28.75%) presented seroconversion, 19 (23.75%) samples showed a twofold increase in their titers and 38 (47.5%) had no increase in rotavirus antibody. This result is discussed on the light of previously obtained results on viral antigen detection by counterimmunoelectrosmophoresis (CIEOP).Realizamos este estudo para avaliar a relação causai diarréia aguda e rotavirus em crianças abaixo de cinco anos de idade. A infecção viral foi caracterizada pela sorologia pareada, por meio de titulação de anticorpos anti-rotavírus pela reação de imunofluorescência indireta (IF) nos soros dos pacientes. Utilizamos como substrato para a reação células MA-104 infectadas com o rotavirus bovino cepa UK. De 80 amostras de soros pareados, verificamos que 23 amostras (28,75%) apresentaram soroconversão, 19 amostras (23,75%) tiveram elevação no título de 2 vezes e em 38 amostras (47,5%) não observamos elevação no título de anticorpos anti-rotavírus. Estes resultados são confrontados com os resultados previamente obtidos na detecção do antígeno de rotavírus nas fezes, dos mesmos pacientes, pela técnica de contraimunoeletroforese (CIEOP)

Monitorização da temperatura do coberto em duas castas de videira: uma ferramenta para comparar genótipos e optimizar a rega deficitária ?

A viticultura mediterrânica enfrenta desafios crescentes relacionados com as alterações climáticas, com recursos hídricos escassos ou de menor qualidade e com maiores exigências de sustentabilidade por parte dos “stakeholders”. Neste domínio, o uso sustentável da água deverá ser uma prioridade nas regiões semi-áridas. Para tal é necessário compreender melhor a fisiologia da videira e a sua resposta ao stress hídrico e térmico, e assegurar a monitorização rápida e eficiente da condição das culturas. A temperatura do coberto (Tc) é um indicador do estado hídrico e do comportamento estomático das plantas. A termografia permite a determinação remota de Tc no campo e visualizar a distribuição das temperaturas em diferentes zonas do coberto (e do solo). A nossa hipótese é a de que padrões diurnos de Tc podem revelar diferenças entre castas em termos das estratégias de controlo estomático/regulação da perda de água e calor. Desta forma monitorizámos o curso diário e sazonal da Tc em duas castas de V. vinifera Aragonez (syn. Tempranillo) (ARA) e Touriga Nacional (TOU) sujeitas a rega deficitária em condições Mediterrânicas (Reguengos de Monsaraz, Alentejo). As medições de Tc foram complementadas pela medição do potencial hídrico, fotossíntese e transpiração, clorofila e parâmetros agronómicos. As medições decorreram ao longo de diferentes estados fenológicos: i) Maio/meados de Junho (vingamento-bago ervilha), ii) meados de Julho (pintor), iii) início de Agosto (meia maturação) e iv) meados e fim de Agosto (antes da colheita). As correlações da Tc (14-17h) com a conductância estomática (gs) e o potencial hídrico (ψ) foram mais robustas em condições/anos de maior stress. A ARA revelou a tendência para potenciais mais negativos, que pode estar relacionado com uma maior área foliar comparativamente à TOU. Todavia as correlações entre parâmetros ecofisiológicos (ψ, gs) e a Tc mantiveram-se idênticas nas duas castas sugerindo que, para os níveis de stress hídrico imposto não se observaram diferenças entre castas na Tc e nas trocas gasosas. Estratégias de optimização do uso da termografia para monitorizar plantas e solo em condições de campo são discutidas numa perspectiva de optimização do uso sustentável da águainfo:eu-repo/semantics/publishedVersio

Chaotic multigrid methods for the solution of elliptic equations

Supercomputer power has been doubling approximately every 14 months for several decades, increasing the capabilities of scientific modelling at a similar rate. However, to utilize these machines effectively for applications such as computational fluid dynamics, improvements to strong scalability are required. Here, the particular focus is on semi-implicit, viscous-flow CFD, where the largest bottleneck to strong scalability is the parallel solution of the linear pressure-correction equation — an elliptic Poisson equation. State-of-the-art linear solvers, such as Krylov subspace or multigrid methods, provide excellent numerical performance for elliptic equations, but do not scale efficiently due to frequent synchronization between processes. Complete desynchronization is possible for basic, Jacobi-like solvers using the theory of ‘chaotic relaxations’. These non-deterministic, chaotic solvers scale superbly, as demonstrated herein, but lack the numerical performance to converge elliptic equations — even with the relatively lax convergence requirements of the example CFD application. However, these chaotic principles can also be applied to multigrid solvers. In this paper, a ‘chaotic-cycle’ algebraic multigrid method is described and implemented as an open-source library. It is tested on a model Poisson equation, and also within the context of CFD. Two CFD test cases are used: the canonical lid-driven cavity flow and the flow simulation of a ship (KVLCC2). The chaotic-cycle multigrid shows good scalability and numerical performance compared to classical V-, W- and F-cycles. On 2048 cores the chaotic-cycle multigrid solver performs up to faster than Flexible-GMRES and faster than classical V-cycle multigrid. Further improvements to chaotic-cycle multigrid can be made, relating to coarse-grid communications and desynchronized residual computations. It is expected that the chaotic-cycle multigrid could be applied to other scientific fields, wherever a scalable elliptic-equation solver is required