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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‣ Peças de Adolphe D'Archiac no núcleo inicial de colecções da Commissão Geológica do Reino, Portugal [Resumo]

Brandão, José Manuel
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /06/2009 Português

‣ Cattle fat valorisation through biofuel production by hydrogenation in supercritical carbon dioxide

Morais, Ana Rita; Lopes, André; Costa, Paula; Fonseca, I.; Nogueira, Isabel N.; Oliveira, A. C.; Bogel-Lukasik, R.
Fonte: The Royal Society of Chemistry Publicador: The Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
The use of residues or wastes in biofuel production is a potential solution to the questioned increase of the food market price. The hydrogenation (more specifically hydrodeoxygenation) of residues or wastes rich in free fatty acids seems to be an interesting option for the valorisation of this type of feedstock. The major obstacle of this process is the high temperature and high H2 pressure process requirement. The way to reduce it is the use of a co-solvent e.g. supercritical fluids. At supercritical conditions, CO2 is completely miscible with H2 and at the same time is also a great solvent for non-polar liquids allowing enhanced efficiency of the hydrogenation leading to the ability to perform reactions at milder conditions. This work deals with the heterogeneous hydrogenation of cattle fat in the presence of CO2. Total reaction pressures up to 140 bar at 340 C and the residence time from 1 to 6 hours as well as the reuse of catalyst were examined. Depending on the chosen reaction conditions a diverse end products can be obtained. The CO2 presence influences positively the concentration of hydrocarbons minimising the presence of glycerides' content in the final product mixture. At elevated CO2 pressure, a high concentration of hydrocarbons simultaneously with a low presence of free fatty acids and glycerides' content in the mixture was obtained. A similar effect was observed for reaction carried out for 6 hours...

‣ Building innovation networks in science-based young firms: the selection of knowledge sources

Sousa, Cristina; Fontes, Margarida
Fonte: Inderscience Publishers Publicador: Inderscience Publishers
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
The paper investigates the strategic choices made by young science-based firms regarding the selection of knowledge sources. Data collected on Portuguese biotechnology firms are analysed with a view to answer to two research questions: whether, to what extent and in which conditions science-based entrepreneurs activate their social capital and/or build new knowledge relationships at start-up; whether and to what extent the knowledge relationships established at start-up persist and/or the firm builds relationships with new organisations. The results confirm the importance attributed to tie persistence but they also show that science-based firms need to search for new knowledge sources from the very early stages. Thus, their start-up behaviour departs from the one often depicted by the entrepreneurship literature, that emphasises the mobilisation of the entrepreneurs' social capital. Results also show that persistence of ties established at start-up is lower than would be expected.

‣ Roles of unstable chemical species and non-equilibrium reaction routes on properties of reaction product: a review

Shohoji, Nobumitsu
Fonte: American Scientific Publishers Publicador: American Scientific Publishers
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Chemical species might be held in a state being away from equilibrium state, at least temporarily, as represented by non-graphitic carbon and gaseous ammonia NH3 with suppressed extent of dissociation by flowing. Such chemical species X in unstable state would possess chemical activity a(X) considerably higher than that of the same element in equilibrium (reference) state. In case of carbon, a(C) of amorphous carbon is higher than that of graphite (equilibrium state of C; a(C) = 1). Thus, when metal M is reacted with excess C, carbon content x' in carbide MC x' in equilibrium with amorphous carbon becomes higher than x in MC x in equilibrium with graphite. In case of uranium carbo-nitride UC x N1–x in equilibrium with excess free C under given conditions of temperature T and N2 gas partial pressure p(N2), x' in UC x' N1–x' in equilibrium with amorphous carbon was experimentally demonstrated to be higher than x in UC x N1–x in equilibrium with graphite. Gaseous ammonia NH3 with suppressed extent of dissociation by flowing would yield very high nitrogen activity a(N) and modestly high hydrogen activity a(H) while NH3 dissociated to N2 and H2 to reach equilibrium state in closed reaction chamber would yield a(N) and a(H) to be represented by respective partial pressures...

‣ Life cycle in practice: capacity building aiming European SME’s

Pasquet, V.; Roy, A.; Adibi, N.; Coppee, S.; Echard, P.; Rocha, Cristina; Martins, Paulo; Alexandre, Jorge; Atin, E.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2014 Português
The application of life cycle approaches – including life cycle assessment, ecodesign and environmental labelling – is becoming an increasing reality for business, and a growing challenge in many economic sectors. Businesses are facing increasing legal and market requirements to enhance resource efficiency and reduce the environmental impact of their products & services. To significantly address this challenge, the Life Cycle in Practice (LCiP) project was conceived, aiming to promote the uptake of LC approaches particularly in SMEs. The LCiP project helps SMEs in France, Belgium, Portugal and Spain reduce the environmental impacts of their products and services across the entire Life Cycle in three sectors: Buildings & Construction, Waste Management and Energy Equipment. LCiP’s specific objectives are to foster the widespread uptake of these approaches by SMEs beyond the duration of the project, by (i) Demonstrating the environmental and business benefits of applying LC Approaches through practical application in 32 businesses; (ii) Providing physical and online resource centres to support regional application of LC approaches; (iii) Building capacity for on-going implementation of LC approaches through a network of Life Cycle Champions and (iv) (Re)designing practical tools & methods tailored to the needs of the three industrial sectors. This paper presents the project's activities and expected results...

‣ Avaliação da transformação de contaminantes organoclorados em águas subterrâneas

Amaral, Helena; Aeppli, Christoph; Berg, Michael; Schwarzenbach, René P.; Kipfer, Rolf
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 Português

‣ Utilização de metodologias integradas na produção da carta ambiental da cidade da Beira, Moçambique : resultados preliminares

Fernandes, Judite; Batista, Maria João; Ramalho, Elsa Cristina; Quental, Lídia Maria; Dias, Ruben P.; Oliveira, José Tomás; Cune, Grácio; Daudi, Elias Félix; Melisse, Dino; Ussene, Ussene Vasco; Manhiça, Vítor
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 Português
Comunicação apresentada em powerpoint, com 20 slides.

‣ Dispersion of quarry's dust - pilot study

Campos, A.; Matos, Maria Luísa Ferreira; Góis, J.; Vila, M. C.; Dinis, M. L.; Baptista, João Santos
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /02/2014 Português

‣ Cork: a strategic material

Gil, Luís
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Cork is a material whose applications have been known since Antiquity, especially in floating devices and as stopper for beverages, mainly wine, whose market, from the early twentieth century, had a massive expansion, particularly due to the development of several cork based agglomerates. Cork is closely related to the maintenance of biodiversity, the heart of sustainable development, and the reduction of emissions and sequestration of CO2, aspects that, additionally to the environmental importance, are also economically very important (Gil, 2011). Other services such as the formation of the landscape, soil protection, regulation of hydrological cycle, are also very sound (Pereira, 2007). Cork regenerates after each stripping, and the cork tree survives the lost of an important quantity, often more than 50% of the total trunk and branches' surface. The fact that corks are made of the bark harvested from living trees has lead environmentalists to encourage the use of cork over other, less natural, alternatives.

‣ Slurry preparation methods affect dental porcelain reliability

Pelaez-Vargas, Alejandro; Dussán, Jaime A.; Restrepo, Luís F.; Paucar, Carlos; Ferreira, Jorge Amaral; Monteiro, Fernando J.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em /05/2011 Português
One-step and incremental mixing procedures are currently used to produce dental ceramic pastes. In the ceramic industry, high quality is obtained using one-step mixing, but in dentistry, the best method has not been yet determined. The purpose of this study is to evaluate the effects of 2 mixing techniques on the biaxial flexural strength and microstructure of dental porcelain. Feldspathic porcelain discs (2 × 15 mm in diameter) were produced and divided according to the ceramic paste preparation method, powder-liquid incremental mixing group (n=50) or one-step mixing, as a control group (n=50). Specimens were tested for biaxial flexural strength and characterized using porosimetry, relative humidity, SEM/EDS, XRD, and FT-IR analyses. Statistical analysis was conducted using Weibull statistics. The Weibull modulus, characteristic strength and relative humidity were compared between groups, using Student's t-test and Mann-Whitney U test (a=.05). The powder-liquid incremental mixing group showed significantly higher values (SD) of Weibull modulus (6.74 (0.70), P<.001) and characteristic strength (79.87 (2.01) MPa, P<.001) when compared to the one-step mixing group (4.94 (0.94) and 75.95 (2.61) MPa). Significantly lower mean (SD) relative humidity values (P=.009) were found for powder-liquid incremental mixing group (20% (0.5%)) compared to one-step mixing group (22% (1%)). XRD spectra showed that the one-step mixing group produced higher amounts of the amorphous phase. Specimens produced by the incremental mixing technique showed higher biaxial flexural strength than one-step mixing.

‣ Improving gap flow simulations near coastal areas of continental Portugal

Costa, P.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2014 Português

‣ Reservas estratégicas de água subterrânea na Região Centro (Projecto Images)

Melo, Maria Teresa Condesso de; Fernandes, Judite; Midões, Carla; Almeida, Carlos Costa; Amaral, Helena; Gomes, Ana Rita; Madruga, Maria José; Silva, Manuel Marques da; Mendonça, João Lopo
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 Português
Comunicação apresentada em Powerpoint, composta por 12 slides

‣ Permeabilities of the Lower Cretaceous porous aquifers of Portugal - prompt estimations

Sampaio, José Eduardo; Amaral, Helena
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2011 Português

‣ Elemental characterization of the airborne pollen surface using Electron Probe Microanalysis (EPMA)

Duque, Laura; Guimarães, Fernanda M. G.; Ribeiro, Helena; Sousa, Raquel; Abreu, Ilda
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em /08/2013 Português
Recent worldwide increase in pollinoses has been attributed to the synergy between pollen and pollutants. We used EPMA for the elemental characterization of the airborne pollen surface in order to find out what occurs to the wall of pollen grains when they are together with other atmospheric pollutants. Analyses were performed both to airborne pollen and to pollen that was collected from Acer spp., Platanus spp. and Pinus spp. trees. Airborne samples were assembled using a Hirst-type volumetric spore sampler set in the coastal city of Porto, Portugal. Airborne pollen samples showed major elemental differences when compared to the control pollen sample of the same species, namely in the amounts of Cl, Na and Mg, which very significantly increased on airborne samples, revealing an important influence of the ocean. Mineral dust also contributed to modify the pollen surface, by increasing Si contents on Acer spp. and Platanus spp. airborne pollen. Our results revealed consistent positive effects of the relative humidity and the precipitation in the increase of Cl, Na and Mg relative amounts on the pollen surface. This study shows that pollen grains have the ability to adsorb and/or absorb other materials, which may contribute to enhance pollen's harmful effects on people's health.

‣ Gold in the Lousal mine, Iberian Pyrite Belt, Portugal

Oliveira, Daniel P. S.; Guimarães, Fernanda M. G.; Matos, João Xavier; Rosa, Diogo R. N.; Rosa, Carlos J. P.; Castelo-Branco, José Mário
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2011 Português
Recent exploration boreholes in the Lousal Mine, located within the Portuguese sector of the Iberian Pyrite Belt (IPB) yielded marked concentrations in gold/electrum in a section of core consisting of banded metasediments with massive pyrite. Preliminary research indicates that the gold is associated with native bismuth and bismuthinite and is clearly late in the paragenetic sequence occurring in fine chalcopyrite (± covellite)-bismuthinite-gold filled veinlets within the dominant and more massive pyrite. The pale yellow gold grains are fine, seldom reaching more than 6 ..m in length and half of that in thickness. EPMA results indicate that silver concentrations in gold grains can be as high as 27 wt.%. The results show similarities with conclusions drawn from the IPB on the Spanish side where gold of Co-Bi geochemical association is found as electrum with abundant to common Co and Bi minerals. These associated with pyrite and/or chalcopyrite are characterized by an abundance of sedimentary facies and show that the gold association formed at high temperature (>300 °C) during the initial phases of massive sulphide formation.

‣ Treatment of groundwater contaminated by arsenic using iron oxides/hydroxides

Azevedo, Irene; Silva, Maria Aurora Soares; Freitas, Olga; Figueiredo, Sónia; Ferreira, Adelaide; Fiúza, António M. Antunes
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /02/2011 Português

‣ Characterization of placer gold deposits from central Portugal : preliminary results

Ehser, Anja; Borg, Gregor; Oliveira, Daniel P. S.; Rosa, Diogo R. N.; Salgueiro, Rute
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2011 Português

‣ Frequency and Stochastic Domain Models for Two Geometries of the IPS Wave Power Buoy

Cândido, J.; Justino, Paulo Alexandre; Henriques, J.C.C.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 Português
Frequency-domain analysis is applied to a geometry of the original IPS buoy device concept. The analysis is particularly useful in the early development stages to establish the response of power take-off mechanism characteristic parameters to different frequencies of the wave spectrum. Optimal mechanical damping and spring coefficients are computed for some parameters restrictions. Absorbed power, capture width and other variables, such as relative displacement,are computed for regular waves and these optimal mechanical coefficients. A stochastic model is developed in order to evaluate the IPS buoy behaviour for irregular waves’ conditions. This allows defining probability density functions for parameters that characterize the device’s behaviour. Assuming that the overall system behaviour is linear and that the surface elevation for irregular waves may be regarded as a stochastic process with a Gaussian probability density function, the variables that define the system behaviour, such as bodies’ displacements and velocities, will also hold a Gaussian probability density function. The average power extraction is computed for different sea state conditions.Aiming to enhance the device’s hydrodynamic performance, a new non-axisymmetric IPS geometry is conceived. Using the stochastic modelling approach...

‣ The 'mica sandwich'; a remarkable new genus of Foraminifera (Protista, Rhizaria) from the Nazaré Canyon (Portuguese margin, NE Atlantic)

Gooday, Andrew J.; Silva, Ana Aranda; Koho, Karoliina A.; Lecroq, Béatrice; Pearce, Richard B.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2010 Português

‣ Analysis of processing systems involving reaction and distillation : the synthesis of ethyl acetate

Filipe, Rui M.; Castro, Pedro; Matos, Henrique A.; Novais, Augusto Q.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 21/09/2005 Português
The integration of reaction and separation into a single process unit, i. e., reactive destillation, may offer several advantages over conventional systems that use a reactor followed by a distillation column. In this paper we explore the operational characteristics of reactive distillation and highlight some of this potential benefits, using the production of ethyl acetate as an illustrative example. With this aim, the two types of system are compared employing different reactor types and a number of performance indicators, such as yield, conversion, purity, specific energy consumption and residence time. A sensitivity analysis is carried out on some variables and parameters, in order to explore and define the distillation columns operating conditions. As expected, results point to a clear advantage of reactive distillation allowing for the azeotrope to be surpassed and for the overcoming of chemical equilibrium, favouring an increase in conversion and product purity, along with reduced operating costs.