Browsing by Issue Date, starting with "1997"
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- Contribuição para o conhecimento dos ácaros fitoseídeos (Acari: Phytoseiidae) da Vinha em Trás-os-Montes.Publication . Pereira, J.A.; Espiñha, Isabel; Torres, L.Os fitoseídeos incluem-se entre os mais importantes componentes da fauna auxiliar relativa à vinha e fruteiras, frequentemente limitando de forma eficaz as flutuações populacionais de ácaras fitófagos. Contudo, estes auxiliares estão ausentes de muitas parcelas comerciais, devido ao uso de práticas culturais inadequadas, nomeadamente de pesticidas de largo espectro de acção. Nestas condições poderá assumir interesse a sua introdução a partir de parcelas colonizadas. Relativamente aos pomares de macieira é aconselhável recorrer, para o efeito, a parcelas de vinha, por forma a evitar a disseminação de organismos nocivos à fruteira.
- Acid leaching of alloys within the quaternary system Fe-Si-Ca-AlPublication . Margarido, Fernanda; Figueiredo, Maria Ondina; Queiroz, Ana; Martins, João Pedro de AlmeidaSilicon with high purity and fine particle size can be produced by acid leaching of Fe-Si industrial alloys under the condition that they have adequate chemical composition and structural constitution. Such alloys contain phases that fall within the system Fe-Si-Ca-Al, where the quaternary phase Caalsifer, with aproximate formula (Fe0.8Al0.1 0.1) (Si0.8Ca0.2)2, is found along with several binary and ternary phases (Fe-Si, Ca-Si, Al-Fe-Si, Ca-Al-Si). With the purpose of optimizing the phase, constitution alloys were synthesized within the system Fe-Si-Ca-Al. The results of leaching experiments performed using HCl (150 and 220g/L) at constant temperature (T=102 1 C) and ordinary atmosphere indicate that the Caalsifer plus Al-Fe-Si phases should be maximized whereas the FeSi2 phases should be minimized, by controlling Al/Ca and Fe/Si concentration ratios in the synthesis process.
- Measurement and modeling of solubilities of D-glucose in water/alcohol and alcohol/alcohol systemsPublication . Peres, António M.; Macedo, Eugénia A.In this work, the solubilities of D-glucose in water/methanol and ethanol/methanol mixtures are measured at 40 and 60 °C, using a simple and accurate analytical method. A modified UNIQUAC model is used for the correlation of the experimental solubility data. New UNIQUAC interaction parameters for the pairs D-glucose/alcohol, water/alcohol, and alcohol/alcohol are estimated based on the ternary solubility data presented in this work together with those available in the literature for D-glucose in water/ethanol. The solubility calculations were performed using an equation based on enthalpy of fusion data for D-glucose. The model describes satisfactorily the experimental solubility data of D-glucose in water/ethanol, water/methanol, and ethanol/methanol mixtures at both temperatures.
- Effect of composted sewage sludge amendment on soil nitrogen and phosphorus availabilityPublication . Coutinho, João; Arrobas, Margarida; Rodrigues, OlgaMunicipal sewage sludge previously composted with sawdust (CSS) was applied to an eutric sandy cambisol at rates of 7.5, 15.0, 22.5, and 30 g·kg-1. Incubation and pot experiments were conducted to evaluate CSS effectiveness on nitrogen (N) and phosphorus (P) soil availability and on plant nutrition. The CSS rates did not increase soil mineral N and had little effect on organic P and on labile forms of P. Efficiency of total applied P was 17% for the soil labile forms and 4.8% for the resin extractable fraction. In contrast, CSS significantly increased hydroxide extractable inorganic P and nonextractable soil P fraction. The major portion of the increment on nonextractable forms was at the expense of HC1 extractable P fraction [calcium (Ca)-bounded], dominant on the original CSS. Thus, chemical rather than biological reactions lead to the redistribution of CSS-borne P to more firmly held forms after its application to the soil. Ryegrass dry matter yield, N content, and N uptake did not increase in CSS-treated soils. Plant P content increased at the second harvest, but the effect was nil in the subsequent harvest. Total P uptake increased from 14.1 to 20.2 mg·pot-1, but percentage P recovery by ryegrass was modest, averaging 2.5% of the CSS-borne P. Results suggest that moderate application of CSS to agricultural systems are inadequate for crop growth but may contribute to nutrient recycling without environmental risks related to N and P loss.
- Modeling, simulation and operation of a simulated moving bed for continuous chromatographic separation of 1,1'-bi-2-naphthol enantiomersPublication . Pais, Luís S.; Loureiro, José M.; Rodrigues, AlírioThe objective of this paper is to study the separation of enantiomers of 1,1′-bi-2-naphthol in 3,5-dinitrobenzoyl phenylglycine bonded to silica gel, using heptane–isopropanol (72:28) as eluent by simulated moving bed chromatography (SMB). A model for the prediction of the cyclic steady state performance of the SMB, based on the analogy with the true moving bed, is developed assuming axial dispersion flow, linear driving force approximation for intraparticle mass transfer and multicomponent adsorption equilibria. The SMB package allows the simulation of the pilot unit. The effect of several operating parameters on the SMB performance is analyzed. The performance is characterized by purity, recovery, solvent consumption and adsorbent productivity. The package is an important tool for learning and training operators, allowing the choice of best operating conditions. The operation of the SMB pilot unit was carried out for the separation of racemic mixtures using a 8-column configuration. Purities and recoveries higher than 95% in the extract and raffinate were obtained. Model and experimental results are compared and the package is also used to predict the steady state internal profiles for the SMB operation in good agreement with experimental results.
- Aglomeração não hierárquica em sistemas distribuídos de recuperação de informaçãoPublication . Exposto, JoséA procura de documentos relevantes em colecções de grandes dimensões é um processo que envolve uma carga computacional muito elevada e uma enorme necessidade em termos de capacidade de armazenamento de dados. Apesar de toda a investigação feita, no sentido de minimizar o espaço físico ocupado pelos documentos, através de técnicas de filtragem, eliminação de palavras comuns e radicalização, são ainda exigidas grandes necessidades de armazenamento devido ao grande número de documentos das colecções. Se aliarmos as técnicas de aglomeração à distribuição de cada um dos aglomerados, por máquinas ligadas por uma rede de grande velocidade, podemos repartir o espaço ocupado pela totalidade da colecção e tirar ainda partido da utilização concorrente do poder computacional de várias máquinas, quer no processo de classificação, quer no processo de selecção de documentos relevantes a pedidos de utilizadores. A investigação apresentada nesta tese tem por objectivo verificar as potencialidades reais da distribuição dos aglomerados de documentos e fazer uma estudo comparativo do desempenho de um sistema de Recuperação de Informação variando o número de aglomerados nos modos local e distribuído. The search for relevant documents in huge collections requires very high computer load and storage overhead. Although, many research has been made towards the minimization of the document overall space overhead through stoplist techniques and stemming, the storage needed to support 60 big collections is still very high. Putting together the decomposition of big collections using clustering algorithms, and their distribution in a high speed network, it would be possible to divide the total document space by each of the network machines, and yet to get concurrent computational processing resources from those same machines. It is the goal of this thesis to verify the real potentialities of clustering distribution making a comparative study of the performance of an Information Retrieval system changing the number of clusters and confronting a local and distributed mode of that system.
- A influência da temperatura e da radiação solar na capacidade de armazenamento térmico de elementos construtivosPublication . Almeida, Manuela; Garcia, Valdemar; Maldonado, Eduardo; Bragança, LuisA capacidade de armazenamento térmica dos diversos elementos construtivos depende de vários factores, sendo a radiação solar incidente e as amplitudes térmicas verificadas nos espaços adjacentes, dois dos factores que mais fortemente a afectam e que não têm sido levadas directamente em conta na sua quantificação. Neste trabalho apresenta-se a metodologia que foi usada para o cálculo da quantidade de calor armazenada diariamente por esses elementos, QARM, descrevendo-se a forma como foram estabelecidas as dependências deste parâmetro com a radiação solar incidente e com a amplitude térmica diária dos perfis das temperaturas ambientes dos espaços confinantes com o elemento. Mostra-se como foram desenvolvidas correlações entre estes parâmetros e apresentam-se os resultados obtidos para alguns dos elementos construtivos mais utilizados nos edifícios em Portugal.
- Separation of 1,1'-bi-2-naphthol enantiomers by continuous chromatography in simulated moving bedPublication . Pais, Luís S.; Loureiro, José M.; Rodrigues, AlírioThe chromatographic separation of 1,1′-bi-2-naphthol enantiomers with 3,5-dinitrobenzoyl phenylglycine bonded to silica gel stationary phases is studied. Continuous chromatography in simulated moving bed (SMB) is analyzed by modeling, simulation and operation of a SMB pilot unit Licosep 12–26 from Separex (France). A model for the prediction of the cyclic steady-state performance of the SMB is developed based on the analogy with the true moving bed (TMB). The model assumes axial dispersion flow for the liquid phase, linear driving force (LDF) approximation for intraparticle mass transfer rate and takes into account multicomponent adsorption equilibria. The SMB package allows the simulation of the pilot unit. The effect of operating variables (switching time, extract and feed flow rates, section length) and number of mass transfer units on the SMB performance is analyzed. The SMB performance is characterized by purity, recovery, solvent consumption and adsorbent productivity. The package also allows the simulation of the dynamic evolution of internal profiles for the transient operation of a TMB. The operation of the SMB pilot unit was carried out for the separation of racemic mixtures of bi-naphthol enantiomers. Using a 8-column configuration purities as high as 94.5% of the more retained species in the extract and 98.9% of the less retained species in the raffinate were obtained.
- Ácaros fitoseidos asociados a la viña en el interior del Norte de Portugal.Publication . Pereira, J.A.; Espiñha, Isabel; Ferragut, F.; Torres, L.La importancia de los fitoseidos en la protección de los cultivos contra las plagas causadas por ácaros fitófagos está ampliamente reconocida. Por otro lado, se conoce también que las especies de esta familia existentes en cada región pueden ser diferentes. Este hecho confiere un gran interés a la realización de estudios regionales cuyo objetivo sea conocer tales especies.
- Efeitos do ácido acético e do etanol na respiração e na fermentação da glucose em Zygosaccharomyces bailiiPublication . Estevinho, Leticia M.; Côrte-Real, Manuela; Leão, CecíliaAnexo