Influence of service loading and the resulting micro-cracks on chloride resistance of concrete

Chloride-induced corrosion of steel in reinforced concrete structures is one of the main problems affecting their durability, but most previous research projects and case studies have focused on concretes without cracks or not subjected to any structural load. Although it has been recognised that structural cracks do influence the chloride transport and chloride induced corrosion in reinforced concrete structures, there is little published work on the influence of micro-cracks due to service loads on these properties. Therefore the effect of micro-cracks caused by loading on chloride transport into concrete was studied. Four different stress levels (0%, 25%, 50% and 75% of the stress at ultimate load – fu) were applied to 100 mm diameter concrete discs and chloride migration was measured using a bespoke test setup based on the NT BUILD 492 test. The effects of replacing Portland cement CEMI by ground granulated blast-furnace slag (GGBS), pulverised fuel ash (PFA) and silica fume (SF) on chloride transport in concrete under sustained loading were studied. The results have indicated that chloride migration coefficients changed little when the stress level was below 50% of the fu; however, it is desirable to keep concrete stress less than 25% fu if this is practical. The effect of removing the load on the change of chloride migration coefficient was also studied. A recovery of around 50% of the increased chloride migration coefficient was found in the case of concretes subjected to 75% of the fu when the load was removed.

Multilayered micro/nanocrystalline CVD diamond coatings for biotribology

In the present work multilayered micro/nanocrystalline (MCD/NCD) diamond coatings were developed by Hot Filament Chemical Vapour Deposition (HFCVD). The aim was to minimize the surface roughness with a top NCD layer, to maximize adhesion onto the Si3N4 ceramic substrates with a starting MCD coating and to improve the mechanical resistance by the presence of MCD/NCD interfaces in these composite coatings. This set of features assures high wear resistance and low friction coefficients which, combined to diamond biocompatibility, set this material as ideal for biotribological applications. The deposition parameters of MCD were optimized using the Taguchi method, and two varieties of NCD were used: NCD-1, grown in a methane rich gas phase, and NCD-2 where a third gas, Argon, was added to the gas mixture. The best combination of surface pre-treatments in the Si3N4 substrates is obtained by polishing the substrates with a 15 μm diamond slurry, further dry etching with CF4 plasma for 10 minutes and final ultrasonic seeding in a diamond powder suspension in ethanol for 1 hour. The interfaces of the multilayered CVD diamond films were characterized with high detail using HRTEM, STEM-EDX and EELS. The results show that at the transition from MCD to NCD a thin precursor graphitic film is formed. On the contrary, the transition of the NCD to MCD grade is free of carbon structures other than diamond, as a result of the richer atomic hydrogen content and of the higher substrate temperature for MCD deposition. At those transitions, WC nanoparticles were found due to contamination from the filament, being also present at the first interface of the MCD layer with the silicon nitride substrate. In order to study the adhesion and mechanical resistance of the diamond coatings, indentation and particle jet blasting tests were conducted, as well as tribological experiments with homologous pairs. Indentation tests proved the superior behaviour of the multilayered coatings that attained a load of 800 N without delamination, when compared to the mono and bilayered ones. The multilayered diamond coatings also reveal the best solid particle erosion resistance, due to the MCD/NCD interfaces that act as crack deflectors. These results were confirmed by an analytical model on the stress field distribution based on the von Mises criterion. Regarding the tribological testing under dry sliding, multilayered coatings also exhibit the highest critical load values (200N for Multilayers with NCD-2). Low friction coefficient values in the range μ=0.02- 0.09 and wear coefficient values in the order of ~10-7 mm3 N-1 m-1 were obtained for the ball and flat specimens indicating a mild wear regime. Under lubrication with physiological fluids (HBSS e FBS), lower wear coefficient values ~10-9-10-8 mm3 N-1 m-1) were achieved, governed by the initial surface roughness and the effective contact pressure.

Micro/nanoreservoirs for controlled release of active species in smart functional coatings

This work reports one possible way to develop new functional coatings used to increase the life time of metallic structures. The functionalities selected and attributed to model coatings in the frame of this work were corrosion protection, self-sensing and prevention of fouling (antifouling). The way used to confer those functionalities to coatings was based on the encapsulation of active compounds (corrosion inhibitors, pH indicators and biocides) in micro and nanocontainers followed by their incorporation into the coating matrices. To confer active corrosion protection, one corrosion inhibitor (2-mercaptobenzothiazole, MBT) was encapsulated in two different containers, firstly in silica nanocapsules (SiNC) and in polyurea microcapsules (PU-MC). The incorporation of both containers in different models coatings shows a significant improvement in the corrosion protection of aluminum alloy 2024 (AA2024). Following the same approach, SiNC and PU-MC were also used for the encapsulation of phenolphthalein (one well known pH indicator) to introduce sensing properties in polymeric coatings. SiNC and PU-MC containing phenolphthalein acted as corrosion sensor, showing a pink coloration due to the beginning of cathodic reaction, resulting in a pH increase identified by those capsules. Their sensing performance was proved in suspension and when integrated in coatings for aluminium alloy 2024 and magnesium alloy AZ31. In a similar way, the biocide activity (antifouling) was assigned to two polymeric matrices using SiNC for encapsulation of one biocide (Dichloro-2-octyl-2H-isothiazol-3-one, DCOIT) and also SiNC-MBT was tested as biocide. The antifouling activity of those two encapsulated compounds was assessed through inhibition and consequent decrease in the bioluminescence of modified E. coli. That effect was verified in suspension and when incorporated in coatings for AISI 1008 carbon steel. The developed micro and nanocontainers presented the desired performance, allowing the introduction of new functionalities to model coatings, showing potential to be used as functional additives in the next generation of multifunctional coatings.

Exploring the micro-politics of place: lifestyle migrants, collective identities and modes of belonging

Taking up Hopkins and Dixon’s (2006) call to attend to the micro-politics of everyday constructions of space and place, which necessarily involves psychological concepts such as identity, belonging and attachment, this paper aims to show how a critical socio-cognitive approach to discourse analysis is an effective means of unpacking the ways in which versions of place are (re)produced and negotiated through discursive practices, and in particular the ways in which ‘legitimate’ collective identities are constructed in relation to place. I focus on the contemporary social phenomenon of lifestyle migration. Within Europe, this typically involves relatively affluent northern Europeans moving to destinations in southern Europe that are strongly linked to tourism. Although lifestyle migrants are generally viewed by their hosts as ‘desirable’ migrants due to their perceived economic and socio-cultural capital, their integration into destination communities is often minimal. The question arises as to how these migrants construct modes of belonging in relation to their adopted home-place and how they relate to the other social groups with whom they share it. Using texts from a variety of sources, including in-depth interviews with British migrants in Portugal, I explore not only how migrants position themselves (and others) discursively in relation to places, but also how they are already positioned by discursive practices in the public sphere. I also examine to what extent the construction of a ‘legitimate’ mode of belonging involves the construction of intergroup cooperation within that place.

Des polyphonies sauves des eaux: les représentations de la "Tradition" dans une micro-localité de la Serra de Gerês

A região montanhosa do noroeste de Portugal é conhecida há muito pelos seus cantos polifónicos femininos, que apresentam microvariações duma aldeia para outra e estavam tradicionalmente ligados à cultura dos cereais (centeio e milho). Há muito que a aldeia de São João do Campo (concelho de Terras de Bouro, distrito de Braga) não pratica a agricultura, mas as suas mulheres continuam a cantar em polifonia de modo perfeito, usando as vozes como actividade recreativa e transmitindo às filhas a arte de cantar. Uma das razões para a idealização dos seus cantos poderia ser a desaparição da aldeia vizinha, Vilarinho da Furna, engolida pelas águas duma barragem. Em São João do Campo convergem, no entanto, outras “tradições” musicais: a dos antigos habitantes de Vilarinho da Furna, que comemoram musicalmente todos os anos a sua aldeia desaparecida; e a dos habitantes duma localidade vizinha, Aboim da Nóbrega, que à aldeia de São João do Campo vêm entoar cantos petitórios de chuva, dedicados a São João. O amor pela terra é aqui propício a práticas musicais que, todas elas, se reclamam da “tradição”, embora sendo radicalmente diferentes,mesmo, heteróclitas. Em São João do Campo convergiram também diversas experiências “de campo”: a de Virgílio Pereira, a de Michel Giacometti e a minha, através das quais a noção de “tradição” é vista de modo diferente. Além de determinar as diversas funções dos cantos polifónicos femininos (ceifa, malha do centeio, monda, desfolhada do milho, secagem do linho, artesanato, festas...), este artigo levanta também a questão de como definir “a tradição”.

Central micro-hídrica incorporada em conduta adutora

No presente Trabalho foi efectivado um Estudo sobre a viabilidade técnico-económica sobre o aproveitamento eficiente da energia hídrica excedentária nas condutas adutoras dos sistemas de captação, tratamento e distribuição de águas, através da implementação, imediatamente a montante das Estações de Tratamento de Águas, de miniturbinas hidráulicas incorporadas nas condutas e acopladas a geradores de energia eléctrica assíncronos. Esta energia excedentária integra-se no duplo conceito de energia renovável e de energia alternativa – renovável porque a fonte primária é a água acumulada nas albufeiras das barragens; alternativa porque a produção de energia eléctrica é utilizada em consumo nas Instalações de Tratamento de Águas (ETA) em alternância ou/e em simultâneo com a energia da rede. Este Estudo resultou de uma proposta dirigia a Águas do Algarve, S.A. cuja aceitação culminou na elaboração do Projecto Base da Central Mini-Hídrica (CMH) do Beliche, localizada na ETA do Beliche (Sistema Multimunicipal de Abastecimento de Águas do Algarve). A construção da CMH foi da responsabilidade da empresa Electrolagos, CRL, e foi concluída nos fins de 2010, encontrando-se actualmente em plena exploração. Os resultados já obtidos permitem concluir que a instalação é eficiente, energética e economicamente, excedendo, nesta primeira fase, as expectativas relativamente à excelente integração no sistema de auto-regulação do caudal de entrada. O Projecto é inovador, não só porque aplica diversos equipamentos standards de utilizações convencionalmente diferentes, mas também porque congrega essa diversidade num único modelo. As inovações fundamentais consistem em: -Utilização de bombas hidráulicas tradicionais a funcionar como miniturbinas, sistema PaT (Pumb as Turtine) de recente aplicação e em plena investigação; -Utilização de Máquinas Assíncronas a funcionar como geradores de energia eléctrica a 50Hz; -Injecção directa da energia produzida na Instalação e/ou na Rede de Distribuição sem sistema de conversão. A integração directa da MCH na adutora também constitui uma inovação pois, tradicionalmente, estas instalações são isoladas (sistema ‘ilha’) ou em paralelo ou ainda em derivação relativamente a condutas. Esta inovadora integração implicou testes pormenorizados das canalizações de adução e de impulsão, assim como a escolha de equipamentos e acessórios adequados, de modo a não interferir e perturbar significativamente os parâmetros nominais do funcionamento normal da ETA (caudais; velocidades; pressões). O Trabalho aqui apresentado está totalmente em linha com a Estratégia Nacional para a Energia (Resolução 29/2010 do concelho de Ministros) no sentido que contribui para a redução da dependência energética externa através do uso de energias renováveis e para a redução das emissões de CO2.

Multi-agent simulation of continental, regional, and micro electricity markets

Renewable based power generation has significantly increased over the last years. However, this process has evolved separately from electricity markets, leading to an inadequacy of the present market models to cope with huge quantities of renewable energy resources, and to take full advantage of the presently existing and the increasing envisaged renewable based and distributed energy resources. This paper proposes the modelling of electricity markets at several levels (continental, regional and micro), taking into account the specific characteristics of the players and resources involved in each level and ensuring that the proposed models accommodate adequate business models able to support the contribution of all the resources in the system, from the largest to the smaller ones. The proposed market models are integrated in MASCEM (Multi- Agent Simulator of Competitive Electricity Markets), using the multi agent approach advantages for overcoming the current inadequacy and significant limitations of the presently existing electricity market simulators to deal with the complex electricity market models that must be adopted.

Optimal scheduling of a renewable micro-grid in an isolated load area using mixed-integer linear programming

In the energy management of the isolated operation of small power system, the economic scheduling of the generation units is a crucial problem. Applying right timing can maximize the performance of the supply. The optimal operation of a wind turbine, a solar unit, a fuel cell and a storage battery is searched by a mixed-integer linear programming implemented in General Algebraic Modeling Systems (GAMS). A Virtual Power Producer (VPP) can optimal operate the generation units, assured the good functioning of equipment, including the maintenance, operation cost and the generation measurement and control. A central control at system allows a VPP to manage the optimal generation and their load control. The application of methodology to a real case study in Budapest Tech, demonstrates the effectiveness of this method to solve the optimal isolated dispatch of the DC micro-grid renewable energy park. The problem has been converged in 0.09 s and 30 iterations.

Self-mated tribological systems based on multilayer micro/nanocrystalline CVD diamond coatings

The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried out with a reciprocating sliding configuration without lubrication. Such composite coatings exhibit a superior critical load before delamination (130–200 N), when compared to the mono- (60–100 N) and bilayer coatings (110 N), considering ∼10 µm thick films. Regarding the friction behaviour, a short-lived initial high friction coefficient was followed by low friction regimes (friction coefficients between 0.02 and 0.09) as a result of the polished surfaces tailored by the tribological solicitation. Very mild to mild wear regimes (wear coefficient values between 4.1×10−8 and 7.7×10−7 mm3 N−1 m−1) governed the wear performance of the self-mated multilayer coatings when subjected to high-load short-term tests (60–200 N; 2 h; 86 m) and medium-load endurance tests (60 N; 16 h; 691 m).

Increasing the wear resistance of molds for injection of glass fiber reinforced plastics

Abrasion by glass fibers during injection molding of fiber reinforced plastics raises new challenges to the wear performance of the molds. In the last few decades, a large number of PVD and CVD coatings have been developed with the aim of minimizing abrasion problems. In this work, two different coatings were tested in order to increase the wear resistance of the surface of a mold used for glass fiber reinforced plastics: TiAlSiN and CrN/CrCN/DLC. TiAlSiN was deposited as a graded monolayer coating while CrN/CrCN/DLC was a nanostructured coating consisting of three distinct layers. Both coatings were produced by PVD unbalanced magnetron sputtering and were characterized using scanning electron microscopy (SEM) provided with energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), micro hardness (MH) and scratch test analysis. Coating morphology, thickness, roughness, chemical composition and structure, hardness and adhesion to the substrate were investigated. Wear resistance was characterized through industrial tests with coated samples and an uncoated reference sample inserted in a feed channel of a plastic injection mold working with 30 wt.% glass fiber reinforced polypropylene. Results after 45,000 injection cycles indicate that the wear resistance of the mold was increased by a factor of 25 and 58, by the TiAlSiN and CrN/CrCN/DLC coatings, respectively, over the uncoated mold steel.

Business micro-location: factors, preferences and indicators to assess the influence factors

The paper presents a study on business micro-location behaviour as well as corresponding factors of influence, conducted in two metropolitan areas, Bucharest-Ilfov (Romania) and Greater Porto (Portugal). By business micro-location we refer to a specific site such as a building or facility, accommodating a business within a small, compact geographical area (e.g. metropolitan area). At this geographical scale, the macroeconomic layer factors were excluded, applicable when discern between regions or countries. The factors derived from location theory and previous empirical studies were surveyed, completing a cross-sectional analysis in order to find out the specific weights of the location factors and preferences, by region and by industry. Based on already established firms’ feedback on location, the specific weights were granted by each industry to the main location factors, types of areas, and types of accommodation facilities. The authors also suggested a model to integrate these results into a Geographical Information System (GIS).

A construção da comunidade lusófona apartir do antigo centro. Micro-comunidades e práticas da lusofonia

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Doutor em Sociologia.

A importância das consultoras no processo de internacionalização das micro, pequenas e médias empresas em Portugal

Relatório de Estágio Apresentado ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Empreendedorismo e Internacionalização, sob orientação da Mestre Inês Veiga Pereira

Intelligent Micro Grid Management using a Multi-Agent approach

Recent changes in electricity markets (EMs) have been potentiating the globalization of distributed generation. With distributed generation the number of players acting in the EMs and connected to the main grid has grown, increasing the market complexity. Multi-agent simulation arises as an interesting way of analysing players’ behaviour and interactions, namely coalitions of players, as well as their effects on the market. MASCEM was developed to allow studying the market operation of several different players and MASGriP is being developed to allow the simulation of the micro and smart grid concepts in very different scenarios This paper presents a methodology based on artificial intelligence techniques (AI) for the management of a micro grid. The use of fuzzy logic is proposed for the analysis of the agent consumption elasticity, while a case based reasoning, used to predict agents’ reaction to price changes, is an interesting tool for the micro grid operator.