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Institution

Instituto Superior Técnico

Education
About: Instituto Superior Técnico is a based out in . It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 10085 authors who have published 30226 publications receiving 667524 citations. The organization is also known as: IST & Instituto Superior Tecnico.


Papers
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Journal ArticleDOI
01 Apr 2004
TL;DR: This paper proposes a novel objective criterion for enhancement, and attempts finding the best image according to the respective criterion, using an evolutionary algorithm as a global search strategy for the best enhancement.
Abstract: Image enhancement is the task of applying certain transformations to an input image such as to obtain a visually more pleasant, more detailed, or less noisy output image. The transformation usually requires interpretation and feedback from a human evaluator of the output result image. Therefore, image enhancement is considered a difficult task when attempting to automate the analysis process and eliminate the human intervention. This paper introduces a new automatic image enhancement technique driven by an evolutionary optimization process. We propose a novel objective criterion for enhancement, and attempt finding the best image according to the respective criterion. Due to the high complexity of the enhancement criterion proposed, we employ an evolutionary algorithm (EA) as a global search strategy for the best enhancement. We compared our method with other automatic enhancement techniques, like contrast stretching and histogram equalization. Results obtained, both in terms of subjective and objective evaluation, show the superiority of our method.

162 citations

Journal ArticleDOI
TL;DR: In this article, solvent extraction is investigated as a promising alternative for the recovery of iron from leach solutions, which is usually carried out by precipitation as jarosite, goethite or hematite.

162 citations

Journal ArticleDOI
TL;DR: In this article, the effects of pressure, temperature, extractor capacity and superficial velocity on the extraction rate of olive husk oil were studied and the relative merits of the models were compared with those obtained in the literature.
Abstract: Olive husk oil was extracted from olive husk under pressures of 12.0 to 18.0 MPa and temperatures of 308 to 330 K with supercritical carbon dioxide. Olive husk was supplied by an olive oil factory. The effects of pressure, temperature, extractor capacity and superficial velocity on the extraction rate of olive husk oil were studied. Extraction curves were evaluated by an empirical model, a ‘hot sphere’ model and by the extended Lack's plug-flow model and the relative merits of the models are demonstrated. The results are compared with those obtained in the literature. Good agreement between the extended Lack's plug-flow model and our experimental measurements was obtained. The empirical model (in which only one adjustable parameter varied with extraction conditions) also fitted the data well. The ‘hot sphere’ model, as currently applied, gave acceptable results at the higher superficial velocities studied but gave a very poor fit at the lowest velocities. The effects on the parameters in this model of allowing rapid equilibration to occur between the pore fluid and adjacent adsorbed solute are examined and discussed in the light of the experimental findings.

162 citations

Journal ArticleDOI
01 Apr 2006-Planta
TL;DR: The results show that only plants that are able to maintain high levels of GS activity in the dark (either in leaves or in roots) and high root GDH activities accumulate equal amounts of biomass independently of the nitrogen source available to the root medium and thus are ammonium tolerant.
Abstract: The wide range of plant responses to ammonium nutrition can be used to study the way ammonium interferes with plant metabolism and to assess some characteristics related with ammonium tolerance by plants. In this work we investigated the hypothesis of plant tolerance to ammonium being related with the plants' capacity to maintain high levels of inorganic nitrogen assimilation in the roots. Plants of several species (Spinacia oleracea L., Lycopersicon esculentum L., Lactuca sativa L., Pisum sativum L. and Lupinus albus L.) were grown in the presence of distinct concentrations (0.5, 1.5, 3 and 6 mM) of nitrate and ammonium. The relative contributions of the activity of the key enzymes glutamine synthetase (GS; under light and dark conditions) and glutamate dehydrogenase (GDH) were determined. The main plant organs of nitrogen assimilation (root or shoot) to plant tolerance to ammonium were assessed. The results show that only plants that are able to maintain high levels of GS activity in the dark (either in leaves or in roots) and high root GDH activities accumulate equal amounts of biomass independently of the nitrogen source available to the root medium and thus are ammonium tolerant. Plant species with high GS activities in the dark coincide with those displaying a high capacity for nitrogen metabolism in the roots. Therefore, the main location of nitrogen metabolism (shoots or roots) and the levels of GS activity in the dark are an important strategy for plant ammonium tolerance. The relative contribution of each of these parameters to species tolerance to ammonium is assessed. The efficient sequestration of ammonium in roots, presumably in the vacuoles, is considered as an additional mechanism contributing to plant tolerance to ammonium nutrition.

162 citations

Journal ArticleDOI
TL;DR: The main goal was to quantify the trade‐offs in ecosystem services associated to different vegetation types, using a spatially detailed approach, and took a more ecologically oriented approach, by explicitly considering different units of vegetation structure and composition.

162 citations


Authors

Showing all 10288 results

NameH-indexPapersCitations
Joao Seixas1531538115070
A. Gomes1501862113951
Amartya Sen149689141907
António Amorim136147796519
Joao Varela133141192438
Pietro Faccioli132137889795
João Carvalho126127877017
Pedro Jorge12477668658
Pedro Silva12496174015
A. De Angelis11853454469
Hermine Katharina Wöhri11662955540
Helena Santos114105854286
P. Conde Muiño10955856133
Joao Saraiva10751953340
J. N. Reddy10692666940
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202341
2022354
20212,263
20202,433
20192,327
20182,190