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Últimos itens adicionados do Acervo: Laboratório Nacional de Energia e Geologia

O Laboratório Nacional de Energia e Geologia (LNEG) é uma instituição de I&D orientada para responder às necessidades da sociedade e das empresas. Apostando numa investigação sustentável e para a sustentabilidade através da geração do conhecimento em Portugal.

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Indium in the Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal

Oliveira, Daniel P. S.; Rosa, Diogo R. N.; Matos, João Xavier; Guimarães, Fernanda; Figueiredo, M. Ondina; Silva, Teresa Pereira
Tipo: info:eu-repo/semantics/bookpart
Publicado em //2009 Português
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The Iberian Pyrite Belt (IPB) is one of the most outstanding ore provinces in Europe hosting some of the largest concentrations of massive sulphides and 22% of the world-class (> 32 Mt) VMS orebodies. A significant number of (pyrite) mines are now inactive but some orebodies still remain unexploited; this is the case of Lagoa Salgada. It is the most NW orebody known and occurs beneath approximately 130 m of Cenozoic sediments which limits interpretation solely to borehole intersection data. The orebody is folded and interpreted to occur on the subvertical-overturned and intensely faulted limb of a SW verging anticline. It is hosted within a thick IPB volcanic sedimentary sequence and is made uo of a centralstockwork and a massive sulphide lens. An electron microprobe study revealed consistent trace amounts of indium in sphalerite, thus contrasting with the neighbouring Neves Corvo mine where indium is known to occur associated with stannite and stanoidite. The occurrence of elevated trace amounts of indium in sphalerite from Lagoa Salgada could make this orebody an attractive economic target beyond the traditional tin-base metal suite so far extracted in the Iberian Pyrite Belt.

Recent changes in lead isotopic signature of the Cascais Canyon (Portugal)

Mil-Homens, Mário; Caetano, M.; Costa, A. M.; Lebreiro, S. M.; Stigter, H. de; Richter, T.; Cesário, R.; Brito, Pedro; Boer, Wim; Trancoso, Maria Ascensão; Mouro, Filomena C.
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em 05/12/2009 Português
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Geochemistry of garnets from a tonalite and granitic aplite-pegmatite veins from Ciborro-Aldeia da Serra, Ossa-Morena Zone, Southern Portugal

Lima, S. S. M.; Neiva, Ana Margarida R.; Ramos, João Farinha
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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Electron-microprobe analysis of garnet from a tonalite and aplite-pegmatite and pegmatite veins cutting different lithologies from an area located in the Ossa-Morena Zone, southern Portugal, show distinct compositions, mainly andradite with a subordinate grossular component in tonalite, and predominantly spessartine with a subordinate almandine component [and rarely, of mainly almandine with a subordinate spessartine component] in the veins. In general, single crystals of garnet are unzoned in tonalite, but commonly show a Mn-enriched core in veins, as the ratio Mn/(Mn + Fe) in the melt is controlled by garnet. However, reverse zoning also occurs owing to resorption of garnet at lower temperatures. A fractionation trend involving a decrease of Mn/(Mn + Fe) occurs in garnet from a complex aplite-pegmatite vein with 22 alternating layers cutting schists; values decrease toward the hanging wall because garnet is the sole host of Mn, which is depleted in the granitic magma.

Utilização de macrófitas aquáticas no tratamento de efluentes de suinicultura

Maia, Anabela; Catarino, Justina; Rodrigues, Fátima; Mendonça, E.; Trancoso, Maria Ascensão
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em 18/04/2007 Português
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Em contraste com anteriores abordagens, actualmente as tecnologias ambientais tendem a utilizar um menor consumo de recursos energéticos e materiais. No que respeita ao tratamento de efluentes a utilização de macrófitas aquáticas tem tido um interesse crescente revelando-se como um método simples e energicamente eficiente na remoção de nutrientes e contaminantes com aplicação no tratamento de efluentes urbanos, industriais e agrícolas. Este sistema baseia-se nas interações entre as plantas, essencialmente através do sistema radicular, as diferentes espécies de microorganismos, o substrato , o ar, o sol e a água (Wood & McAtanney, 1996). Os efluentes agro-pecuários em particular os resultantes de suinicultura, apresentam elevada concentração em nutrientes, essencialmente azoto e fósforo, constituindo um problema agrícola e ambiental, na medida em que contaminam solos, águas superficiais e subterrâneas. O tratamento destes efluentes em leitos de macrófitas, parece ser uma tecnologia fiável, robusta e menos intensiva em recursos que os sistemas tradicionais. Efectivamente estes leitos constituem sistemas biológicos de tratamento de efluentes, nos quais as plantas podem remover directamente os constituintes dos efluentes e/ou promover a sua degradação...

Hemicellulose biorefineries: a review on biomass pretreatments

Carvalheiro, Florbela; Duarte, Luís C.; Gírio, Francisco M.
Tipo: Artigo de Revista Científica
Publicado em /11/2008 Português
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Biomass pretreatment (BP) plays a crucial role in a lignocellulose feedstock-based biorefinery (LCFBR) for processing of three major output streams (cellulose, hemicelluloses and lignin) into chemicals and biofuels. BP includes processing of lignocellulosic material (LCM) under aqueous, dilute acid or alkaline media to obtain a cellulosic fraction, which is then fermented to produce bioethanol. Hemicellulose is usually treated as a secondary stream due to lack of efficient fermentation of hemicellulosic sugars to ethanol. This review provides BPs assuming that hemicellulose stream should be integrated in LCFBR as a primary fraction for converting into value-added compounds other than bioethanol. Different LCM treatments are analyzed foreseeing bio-based products possible to obtain from hemicellulose path.

Alunite veins versus supergene kaolinite-halloysite alteration in the Lagoa Salgada, Algares and S. João, Aljustrel, and S. Domingos massive sulphide deposits, Iberian Pyrite Belt, Portugal

Matos, João Xavier; Barriga, Fernando; Oliveira, Vítor M. J.
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em /06/2003 Português
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Contributo para o conhecimento da falha de Pinhal Novo-Alcochete, no âmbito da neotectónica do Vale Inferior do Tejo

Moniz, Catarina
Tipo: info:eu-repo/semantics/masterthesis
Publicado em //2010 Português
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Influência da resistência ao gelo de rochas silicatadas portuguesas na utilização como elemento construtivo exterior

Borges, Maria Isabel; Simão, Joaquim; Carvalho, Cristina; Pires, Vera
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em /04/2012 Português
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Three dimensional model of a high temperature PEMFC. Study of the flow field effect on performance

Sousa, T.; Mamlouk, M.; Scott, K.; Rangel, C. M.
Fonte: WILEY Publicador: WILEY
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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A three-dimensional isothermal model of a high temperature polymer membrane fuel cell equipped with polybenzimidazole membrane is described. All major transport phenomena were taken into account except the species crossover through the membrane. The cathode catalyst layer was treated as spherical catalyst agglomerates with porous inter-agglomerate spaces. The inter-agglomerate spaces were filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). This approach proved to be an essential requirement for accurate simulation. In this particular paper, the influence of different flow field designs and dimensions on performance was intensely study. Traditional configurations were tested (straight, serpentine, pin-in, and interdigitated), and new designs were proposed. With these new designs, we tried to maximize performance by providing homogeneous reactants distribution over the active area keeping low-pressure drop and relatively high velocity. The dimension and position of the inlet and outlet manifolds were also analyzed. From the obtained results a massive influence of the manifolds position and dimension on performance was observed. This fact can provide important guidelines for future bipolar plates optimization.

Guia de projecto elétrico de centrais eólicas: Projecto elétrico básico e impacto de Centrais Eólicas na rede Elétrica

Rosas, Pedro A. Carvalho; Estanqueiro, Ana
Fonte: Centro Brasileiro de Energia Eólica Publicador: Centro Brasileiro de Energia Eólica
Tipo: info:eu-repo/semantics/book
Publicado em //2003 Português
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Síntese de ácidos e ésteres mono- e bisfosfónicos derivados do indazole

Afonso, S. S.; Teixeira, A. P. S.; Martins, M. R.; Teixeira, Fátima C.
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em //2013 Português
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Os bisfosfonatos (BPs) constituem um grupo de compostos derivados do ácido bisfosfónico e dos seus sais, onde o grupo P-O-P foi substituído por um bioisoster, resultando na estrutura P-C-P, que lhe confere maior estabilidade química e metabólica. Os bisfosfonatos (BPs) constituem uma classe importante de fármacos, com aplicações terapêuticas no tratamento de doenças do metabolismo mineral do osso, como a osteoporose e a doença de Paget. Estes compostos também têm mostrado atividade em outras áreas, como o demonstram os estudos sobre a atividade antitumoral de bisfosfonatos ao nível das metástases ósseas, e no cancro da próstata e da mama, e também atividade antiparasitária, nomeadamente contra diversos microrganismos e protozoários, incluindo o Trypanosoma cruzi e o Plasmodium falciparum.[1-4] A utilização destes compostos na terapêutica é dificultada pela sua reduzida biodisponibilidade por via oral devida à baixa lipofilicidade e à presença de cargas a pH fisiológico. A melhoria das suas propriedades farmacocinéticas pode ser obtida pela utilização dos derivados ésteres como prófármacos.[5] Neste trabalho apresenta-se a síntese e caraterização de diversos derivados do indazole com grupos ácidos mono- e bisfosfónicos...

Soda and aluminum recovery from spent etching baths by aqueous precipitation

Berto, Andrea; Nogueira, C. A.; Margarido, F.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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The aluminum anodising industry is an important industrial sector that produces great amounts of polluted effluents, which after treatment generate sludge. This fact brings environmental and economical concerns to the companies. Best way to deal with the problem, according to the “prevention strategy” set by the European Directive on Integrated Pollution Prevention and Control, is to implement preventive techniques and technologies to optimise the use of resources and minimise losses, and in turn waste. Among the operations of an anodising line, the etching/satinising stage is responsible for the production of a huge quantity of wastewater neutralisation sludge and for the wrong use of caustic soda. “Caustic etch recovery” technology is claimed to drastically reduce the generation of neutralisation sludge and the purchasing of fresh caustic soda by regenerating the exhausted etching/satinising solution, through an aqueous precipitation reaction. This paper presents the capability of the technology to effectively regenerate the exhausted caustic solution, and investigated the parameters with major effect on the process yield, in order to optimise it. It was demonstrated that the technology effectively recovers the solution, increases its soda content and diminishes the dissolved aluminum content by precipitation. Moreover the conditions that optimise the process are simple and inexpensive. After treatment the solution present the properties to be recycled in the etching/satinising operation.

Bassin versant urbaine Ribeira do Poço das Patas

Pereira, Ana Paula Teixeira; Santos, Reanta
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em /05/2011 Português
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Optimization of a seasonal storage solar system using Genetic Algorithms

Durão, Bruno; Joyce, António; Mendes, J. Farinha
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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Seasonal storage solar systems are capable of storing thermal energy, from one season to another (typically a few months). In the present paper solar thermal energy generated during summer time, is stored for use in winter time (typically 120 days). The analyzed system consists of solar thermal collectors and a sensible heat storage device using water as storing media. The area of solar collector and the capacity of the storage tank are the basic sizing parameters, which have to meet the requirements of the load. The present case study considers the utilization of the seasonal storage solar system for heating greenhouses, with a 50 kW heating load. The whole system was modeled using a dynamic modeling tool and the sizing parameters were optimized through a Genetic Algorithm process. This optimization process was compared with other optimization methods by a pattern search, and the results showed the benefits of the Genetic Algorithm process.

Reactive scheduling in a make-to-order flexible job shop with re-entrant process and assembly: a mathematical programming approach 

Gomes, Marta C.; Barbosa-Póvoa, Ana Paula; Novais, Augusto Q.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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A mixed-integer linear programming model is presented for the scheduling of flexible job shops, a production mode characteristic of make-to-order industries. Re-entrant process (multiple visits to the same machine group) and a final assembly stage are simultaneously considered in the model. The formulation uses a continuous time representation and optimises an objective function that is a weighted sum of order earliness, order tardiness and in-process inventory. An algorithm for predictive-reactive scheduling is derived from the proposed model to deal with the arrival of new orders. This is illustrated with a realistic example based on data from the mould making industry. Different reactive scheduling scenarios, ranging from unchanged schedule to full re-scheduling, are optimally generated for order insertion in a predictive schedule. Since choosing the most suitable scenario requires balancing criteria of scheduling efficiency and stability, measures of schedule changes were computed for each re-scheduling solution. The short computational times obtained are promising regarding future application of this approach in the manufacturing environment studied.

Bacia de Chaves : estudo prospectivo dos seus corpos argilosos

Grade, José; Moura, A. Casal
Tipo: Artigo de Revista Científica
Publicado em /06/1982 Português
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No âmbito do estudo das potencialidades dos depósitos argilosos de Trás-os-Montes como fontes de matéria-prima para a cerâmica de construção, os autores realizam o estudo da bacia de Chaves cujo depósito sedimentar é controlado por acidentes tectónicos. O estudo geológico-estrutural efectuado revelou-se indispensável à correcta avaliação das reservas de barro existentes, sua salvaguarda e exploração racional.

Climatic variability of the last five isotopic interglacials : direct land-sea correlation from multiproxy analyses of northwestern Iberian margin deep-sea cores

Desprat, Stéphanie; Sánchez Goñi, María Fernanda; Naughton, Filipa; Turon, Jean-Louis; Duprat, Josette; Malaizé, Bruno; Peypouquet, Jean-Pierre; Pujol, Claude
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em /09/2004 Português
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Integrated conversion of agroindustrial residue with high pressure CO2 within the biorefinery concept

Morais, Ana Rita; Mata, Ana C.; Bogel-Lukasik, R.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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Sustainable production of energy and other added-value products from biomass-derived polysaccharides is a key challenge of an efficient biorefinery facility. Most technologies for biomass processing are energy demanding and use significant amounts of chemicals and catalysts. The need to develop a process which is devoid of all these shortcomings associated with conventional processes is emphasized. A new approach is demonstrated for an integrated wheat straw biorefinery using a green technology, highpressure CO2–H2O, to produce oligosaccharides from hemicellulose fraction and to enhance the cellulose digestibility for the enzymatic hydrolysis. Over the range of reaction conditions (130, 215, 225 °C and 0 to 54 bar of CO2), CO2 adds value to the process by in situ formation of carbonic acid that leads to higher dissolution of hemicellulose into xylo-oligosaccharides and xylose and to the use of less energy in comparison with water-only technologies. Without an additional chemical catalyst, high-pressure CO2–H2O out performed hydrothermal reactions and gave much higher total sugars yield for wheat straw (as high as 84% in comparison with 67.4% with auto-hydrolysis at a 10 °C higher temperature). Apart from the results obtained for valorisation of hemicellulose fraction...

Corrosão e protecção em estruturas offshore: projecto WIND_ENERMAR

Marques, Maria João F.; Alves, Isabel Nascimento; Gonçalves, Rita; Diamantino, Teresa C.
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em //2014 Português
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A Falha de Pinhal Novo-Alcochete no contexto da neotectónica do Vale Inferior do Tejo

Moniz, Catarina; Cabral, João; Madeira, J.
Tipo: info:eu-repo/semantics/conferenceobject
Publicado em /07/2011 Português
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