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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‣ Geofísica aplicada à gestão da água subterrânea e ao ordenamento do território da cidade da Beira

Daudi, Elias Félix; Ramalho, Elsa Cristina; Fernandes, Judite; Batista, Maria João; Quental, Lídia Maria; Dias, Ruben P.; Milisse, Dino; Ussene, Ussene Vasco; Oliveira, José Tomás; Cune, Grácio; Balate, Gabriel; Manhiça, Vítor
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2014 Português

‣ Repositório de falhas activas de Portugal Continental, base de dados da Ibéria (QAFI) - vantagens e dificuldades

Moniz, Catarina; Cabral, João; Dias, Ruben P.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /10/2014 Português

‣ Proposal of a classification scheme for rating the credibility of fault seismic parameters in active faults databases

García-Mayordomo, Julián; Cabral, João; Martín-Banda, R.; Insua-Arévalo, J. M.; Álvarez-Gómez, J. A.; Martínez-Díaz, José J.; Moniz, Catarina; Dias, Ruben P.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /10/2014 Português

‣ A Falha de Pinhal Novo-Alcochete no contexto da neotectónica do Vale Inferior do Tejo

Moniz, Catarina; Cabral, João
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /10/2014 Português

‣ MED parallel system powered by concentrating solar power (CSP): model and case study: Trapani, Sicily

Casimiro, Sergio; Cardoso, João P.; Ioakimidis, C.; Mendes, J. Farinha; Mineo, Carmelo; Cipollina, Andrea
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
This work presents an overlook on a new model that simulates the physical operation in steady state of a multi-effect distillation (MED) plant with parallel-feed (P) configuration. This model includes the consumption of steam with steam ejectors, and its validation was done using data from a real MED industrial plant using a thermal vapor compressor (TVC) operating in Italy, in the Sicilian city of Trapani. Results show that the MED model returns accurate predictions of the plant behavior, very useful for a first analysis on such type of investments. This MED model was also integrated into the system advisor model developed by the US National Renewable Energy Laboratory. Simulations with this new tool were run using the location of Trapani as case study for a concentrating solar power (CSP) plant working in cogeneration with a low-temperature MED-P plant vs. other cooling options available for CSP plants (wet cooling, dry cooling, and a once through seawater cooling circuit). These results were compared with the existing TVC-MED plant, and indicate that CSP+MED has the potential to be economically attractive.

‣ Identification and characterisation of xylanolytic yeasts isolated from decaying wood and sugarcane bagasse in Brazil

Lara, Carla A.; Santos, Renata O.; Cadete, Raquel, M.; Ferreira, Carla; Marques, Susana
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
In this study, yeasts associated with lignocellulosic materials in Brazil, including decaying wood and sugarcane bagasse, were isolated, and their ability to produce xylanolytic enzymes was investigated. A total of 358 yeast isolates were obtained, with 198 strains isolated from decaying wood and 160 strains isolated from decaying sugarcane bagasse samples. Seventy-five isolates possessed xylanase activity in solid medium and were identified as belonging to nine species: Candida intermedia, C. tropicalis, Meyerozyma guilliermondii, Scheffersomyces shehatae, Sugiyamaella smithiae, Cryptococcus diffluens, Cr. heveanensis, Cr. laurentii and Trichosporon mycotoxinivorans. Twenty-one isolates were further screened for total xylanase activity in liquid medium with xylan, and five xylanolytic yeasts were selected for further characterization, which included quantitative analysis of growth in xylan and xylose and xylanase and ß-d-xylosidase activities. The yeasts showing the highest growth rate and cell density in xylan, Cr. laurentii UFMG-HB-48, Su. smithiae UFMG-HM-80.1 and Sc. shehatae UFMG-HM-9.1a, were, simultaneously, those exhibiting higher xylanase activity. Xylan induced the highest level of (extracellular) xylanase activity in Cr. laurentii UFMG-HB-48 and the highest level of (intracellular...

‣ A hybrid scheduling approach for automated flowshops with material handling and time constraints

Aguirre, Adrian M.; Mendez, Carlos A.; Castro, Pedro
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Flowshop scheduling problems have been extensively studied by several authors using different approaches. A typical flowshop process consists of successive manufacturing stages arranged in a single production line where different jobs have to be processed following a predefined production recipe. In this work, the scheduling of a complex flowshop process involving automated wet-etch station from semiconductor manufacturing systems requires a proper synchronisation of processing and transport operations, due to stringent storage policies and fixed transfer times between stages. Robust hybrid solution strategies based on mixed integer linear programming formulations and heuristic-based approaches, such as aggregation and decomposition methods, are proposed and illustrated on industrial-scale problems. The results show significant improvements in solution quality coupled with a reduced computational effort compared to other existing methodologies.

‣ Testing of solar thermal collectors under transient conditions

Osório, Tiago; Carvalho, M. J.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
The most important standard for collector testing in Europe is the EN 12975:2006 which is applied in all the major laboratories and is the reference for the Solar Keymark certification. Besides the steady-state method, the EN 12975 allows the application of the quasi-dynamic method performed outdoors in natural conditions with variable radiation and ambient temperature. The available number of days for each test was investigated by analyzing meteorological data series acquired in the Solar Energy Laboratory (LES) in Lisbon since 2008 showing the advantage of the quasi-dynamic test. Both the steady-state and the quasi-dynamic methods were applied to five collectors of different types (two flat plate collectors, one evacuated tube collector with a back reflector and direct flow circulation, one evacuated tube collector with heat pipes, and a CPC collector). The results were compared and a good agreement between the steady-state and the quasi-dynamic test results was observed. Issues concerning the incidence angle modifiers and the effective thermal capacity of the collectors were analyzed in detail, which resulted in the identification of model and test limitations. Suggestions are given to improve the test methodology and the data analysis of quasi-dynamic test.

‣ Review on micro-direct methanol fuel cells

Falcão, D. S.; Oliveira, V. B.; Rangel, C. M.; Pinto, A. M. F. R.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Fuel cells have unique technological attributes: efficiency, minimization of moving parts and low emissions. The Direct Methanol Fuel Cell (DMFC) has attracted much attention due to its potential applications as a power source for transportation and portable electronic devices. With the advance of micromachining technologies, miniaturization of power sources became one of the trends of evolution of research in this area. Based on the advantages of the scaling laws, miniaturization promises higher efficiency and performance of power generating devices, therefore, Micro-DMFC is an emergent technology. There has been a growing interest in the development of this type of micro cells in the last years, resulting both in experimental studies (operating conditions, cell design and new materials) and in modeling studies. Despite the increase in the knowledge acquired, many challenges are still to be reached. This book provides a detailed comprehensive review both on fundamental and technological aspects of Micro-DMFC. Special attention is devoted to systematization of published results on experimental area and also to a special section dedicated to modeling studies.

‣ Optimality-based bound contraction with multiparametric disaggregation for the global optimization of mixed-integer bilinear problems

Castro, Pedro; Grossmann, Ignacio E.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
We address nonconvex mixed-integer bilinear problems where the main challenge is the computation of a tight upper bound for the objective function to be maximized. This can be obtained by using the recently developed concept of multiparametric disaggregation following the solution of a mixed-integer linear relaxation of the bilinear problem. Besides showing that it can provide tighter bounds than a commercial global optimization solver within a given computational time, we propose to also take advantage of the relaxed formulation for contracting the variables domain and further reduce the optimality gap. Through the solution of a real-life case study from a hydroelectric power system, we show that this can be an efficient approach depending on the problem size. The relaxed formulation from multiparametric formulation is provided for a generic numeric representation system featuring a base between 2 (binary) and 10 (decimal).

‣ Microalgal symbiosis in biotechnology

Santos, Carla A.; Reis, Alberto
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
This review provides an analysis of recent published work on interactions between microorganisms, especially the ones involving mainly nutrient exchanges and at least with one microalga species. Examples of microbial partners are given, with a remark to the potential application of cultures of an autotroph and a heterotroph, which grow simultaneously, taking advantage of the complementary metabolisms. These are particularly interesting, either due to economic or sustainable aspects, and some applications have already reached the commercial stage of development. The added advantages of these symbiotic cultures are biomass, lipid, and other products productivity enhancement a better utilization of resources and the reduction or even elimination of process residues (including carbon dioxide and other greenhouse gases) to conduct an increasingly greener biotechnology. Among the several symbiotic partners referred, the microalgae and yeast cultures are the most used. The interaction between these two microorganisms shows how to enhance the lipid production for biodiesel purposes compared with separated (stand-alone) cultures.

‣ Spectrometric differentiation of yeast strains using minimum volume increase and minimum direction change clustering criteria

Fachada, Nuno; Figueiredo, Mário A.T.; Lopes, Vitor V.; Martins, Rui C.; Rosa, Agostinho
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
This paper proposes new clustering criteria for distinguishing Saccharomyces cerevisiae (yeast) strains using their spectrometric signature. These criteria are introduced in an agglomerative hierarchical clustering context, and consist of: (a) minimizing the total volume of clusters, as given by their respective convex hulls; and, (b) minimizing the global variance in cluster directionality. The method is deterministic and produces dendrograms, which are important features for microbiologists. A set of experiments, performed on yeast spectrometric data and on synthetic data, show the new approach outperforms several well-known clustering algorithms, including techniques commonly used for microorganism differentiation.

‣ Rare Earth Elements fractionation in native vegetation from the Moncorvo iron mines, NE Portugal

Durães, Nuno; Silva, Eduardo Ferreira da; Bobos, Iuliu; Ávila, Paula Freire
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Fractionation of Rare Earth Elements (REE) and the accumulation and translocation indexes were measured and determined in the native vegetation [Halimium lasianthum (Lam.) Spach subsp. alyssoides (Lam.) Greuter; Cytisus multiflorus (L’Hér.) Sweet; and Cistus monspeliensis L.; Cistus ladanifer subsp. ladanifer; Lavandula stoechas L.] from the iron mining area of Moncorvo (NE Portugal). There is no correlation between the amounts of REE in rhizosphere and in plants. The REE concentration as the fractionation follows roots>leaves>stems in plants. A slightly enrichment in HREE were found in rhizosphere and plants (roots and stems), whereas the leaves are enriched in LREE. The accumulation and translocation depend of internal complexes ligands. The redox and pH conditions of the rhizosphere conditioned the REE uptake. Greatest bioaccumulation ability of heavy REE (HREE) was found in C. monspeliensis, followed by H. lasianthum that also, has a high capacity of the REE translocation to the aerial parts, contrary to C. monspeliensis. An M-type tetrad effect was determined mainly for HREE (Gd-Ho series) indicating a complexation of REE. The greatest differences in the REE fractionation patterns (mainly for HREE) are observed in stems...

‣ Crystallinity and microchemistry of Nassarius reticulatus (Caenogastropoda) statoliths : towards their structure stability and homogeneity

Oliveira, Susana Galante; Marçal, Raquel; Guimarães, Fernanda M. G.; Soares, Jorge; Lopes, José Carlos; Machado, Jorge; Barroso, Carlos
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em /05/2014 Português
Gastropod statoliths are spherical biocarbonates formed during their lifespan. The stability and homogeneity of these structures’ mineral matrix was characterised along their radiuses, using Nassarius reticulatus as a model. Generally, they were proved to be bimineralic. Two of the three CaCO3 crystalline polymorphs occurring in biocarbonates – aragonite and calcite – coexist along statolith radiuses, aragonite being unequivocally the most abundant phase. The presence of a diffuse organic matrix was also perceived by the detection of a weak Raman band between 2800 and 3000 cm-1 consistently observed along radiuses. Beyond the apparent stability and homogeneity, different crystalline orientations were disclosed by Raman spectroscopy. A change in the intensity pattern of the features related to the lattice and bending modes of aragonite between different radiuses give new insights for a possible spherulitic-like growth of these structures. As expected from the relative homogeneity of both mineral and organic signals, there was no pattern on the distribution of Ca, O, Na and S along radiuses. However, a higher concentration of Sr occurs in growth rings (known as winter tags), corroborating the already described negative correlation between the concentration of this element in statoliths and temperature. Despite the apparent stability and homogeneity of the matrix during its lifespan...

‣ Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal) : genetic implications of crystal-chemical and isotopic features

Costa, Isabel Ribeiro da; Mourão, C.; Récio, C.; Guimarães, Fernanda M. G.; Antunes, I. M.; Ramos, João Farinha; Barriga, Fernando; Palmer, Martin R.; Milton, J. A.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em /04/2014 Português
Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (d18O, dD, d11B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl–oxyschorl tourmalines from granitic rocks have variable foititic component (X? = 17–57 %) and Mg/(Mg + Fe) ratios (0.19–0.50 in two-mica granitic rocks, and 0.05–0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant d18O values (12.1 ± 0.1 ‰), with wider-ranging dD (-78.2 ± 4.7 ‰) and d11B (-10.7 to -9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31–0.44] results from late...

‣ Pulp properties resulting from different pretreatments of wheat straw and their influence on enzymatic hydrolysis rate

Rosseberg, Christine; Steffien, Doreen; Bremer, Martina; Koening, Swetlana; Carvalheiro, Florbela; Duarte, Luís C.; Moniz, Patrícia; Hoernicke, Max; Bertau, Martin; Fischer, Steffen
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Wheat straw was subjected to three different processes prior to saccharification, namely alkaline pulping, natural pulping and autohydrolysis, in order to study their effect on the rate of enzymatic hydrolysis. Parameters like medium concentration, temperature and time have been varied in order to optimize each method. Milling the raw material to a length of 4 mm beforehand showed the best cost–value-ratio compared to other grinding methods studied. Before saccharification the pulp can be stored in dried form, leading to a high yield of glucose. Furthermore the relation of pulp properties (i.e. intrinsic viscosity, KLASON-lignin and hemicelluloses content, crystallinity, morphology) to cellulose hydrolysis is discussed.

‣ Hot treatment and upgrading of syngas obtained by co-gasification of coal and wastes

Pinto, Filomena; André, Rui Neto; Carolino, Carlos; Miranda, Miguel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Nowadays there is a great interest in producing energy through co-gasification of low grade coals and waste blends to increase the use of alternative feedstocks with low prices. The experimental results showed that the viability of co-gasification to process such blends and that by the right manipulation of coal and biomass or waste blends, syngas treatment and upgrading may be simplified and the cost of the overall process may be reduced. Blends of three different coal grades (sub-bituminous coal from Puertollano mines, South African bituminous coal and German brown coal) with two different types of biomass (pine and olive oil bagasse) or polyethylene (PE) were co-gasified. Blend co-gasification showed to be beneficial to reduce the negative characteristics of some coals, such as the high ash and sulphur contents, especially of Puertollano coal. Syngas obtained by these blends was hot cleaned and undesirable syngas components (tar, NH3 and H2S) were measured along the hot treatment tested, which proved to be suitable to treat syngas produced by a wide range of feedstocks. Different routes for syngas cleaning were analysed to reduce unsuitable components to values required by most common end-uses. The results obtained showed that the type of feedstock to be gasified is a key outcome on initial syngas composition...

‣ Co-gasification of rice production wastes

André, Rui Neto; Pinto, Filomena; Miranda, Miguel; Carolino, Carlos; Costa, Paula
Fonte: Italian Association of Chemical Engineering - AIDIC Publicador: Italian Association of Chemical Engineering - AIDIC
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Rice production is one of the major food sources in the world and unavoidably generates large amounts of wastes, mainly husk and straw that must be dealt in an environmentally sound and sustainable way. Traditional solutions, like burning in open fields or soil incorporation, may contribute for local pollution. Even the use of these wastes as animal food is not an appropriate solution. Plastics are also an additional waste arising from the life cycle of rice production, manufacturing and distribution. The co-gasification of these wastes was easily accomplished in a fluidized bed installation using steam mixed with air or oxygen as gasifying and fluidisation agents. By changing the gasifying agent composition it is possible to select the best conditions to co-gasify rice husks and PE wastes blends. For rice husks gasification, highest H2/hydrocarbons molar ratios were obtained using a mixture of air and steam and an equivalent ratio of 0.2. These conditions correspond to low tar emissions and very good gas yields and gas higher heating values (HHV). Co-gasification of rice husk mixed with PE enables to increase gas HHV, but also generates more tar. Nevertheless using up to 20 % of PE can be considered a promising solution to deal with this kind of wastes. Pollutants like H2S and NH3 were formed in the gasification process in acceptable amounts. Co-gasification with PE enables to decrease these pollutants. Depending on the gas end-use...

‣ Study of the experimental conditions of the co-pyrolysis of rice husk and plastic wastes

Costa, Paula; Pinto, Filomena; Miranda, Miguel; André, Rui Neto
Fonte: Italian Association of Chemical Engineering - AIDIC Publicador: Italian Association of Chemical Engineering - AIDIC
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
The main objective of this study is to access the technical and economical viability of using pyrolysis technology applied to the rice production main wastes to produce bio-fuels to substitute fossil fuels and electricity consumption during rice milling processes. Therefore, it was studied the effect of operating conditions (reaction temperature, initial pressure and reaction time) on products yields and quality, as well as the possible synergetic effects that may occur during the pyrolysis of these wastes. The pyrolysis experiments were performed in 1 L capacity batch reactor made of Hastelloy C276 and built by Parr Instruments. According to previous studies, the range of operational conditions studied was: 350-430 ºC for reaction temperature, 2-10 bar for initial pressure and 10-60 min for reaction time. So far, the results obtained showed that these two wastes can be processed together. The presence of PE seems to favour the biomass conversion, as PE is easily converted into liquids by pyrolysis, which increases heat and mass transfer in the reaction medium.

‣ The phase equilibrium phenomenon in model hydrogenation of oleic acid

Morais, Ana Rita; Lopes, André; Bogel-Lukasik, R.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Hydrogenation is one of the most commonly practised types of reaction in industry. The processing of low or null price feedstock to produce energy through hydrogenation is an interesting solution for waste valorisation. The hydrogenation in CO2 atmosphere offers a series of advantages and facilitates the process by the dramatic reduction of normally harsh reaction conditions. The hydrogenation of natural feedstock with complex matrix is a challenging task and the examination of the phase equilibrium of this system is crucial to understand the phenomena driving the kinetics of the hydrogenation reaction. High pressure phase equilibrium modelling is a key method to design and to analyse the obtained data and helps to understand the hydrogenation reaction outcome. The increase of H2 pressure does not translate to the increase of hydrogen solubility in the liquid phase due to the significant decrease of CO2 solubility in oleic acid. The obtained data confirm that both thermodynamics and kinetics play an important role in the hydrogenation of cattle fat in the presence of CO2.