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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
TL;DR: In this article, the rational homotopy of groups of symplectomorphisms of S 2 S 2 and one point blow-up CP 2 # CP 2 of CP 2 was analyzed.
Abstract: Let M be either S 2 S 2 or the one point blow-up CP 2 # CP 2 of CP 2 . In both cases M carries a family of symplectic forms ! , where > 1 determines the cohomology class [! ]. This paper calculates the rational (co)homology of the group G of symplectomorphisms of (M; ! ) as well as the rational homotopy type of its classifying space BG . It turns out that each group G contains a nite collection Kk; k = 0; : : : ; ‘ = ‘( ), of nite dimensional Lie subgroups that generate its homotopy. We show that these subgroups \asymptotically commute", i.e. all the higher Whitehead products that they generate vanish as ! 1. However, for each xed there is essentially one nonvanishing product that gives rise to a \jumping generator" w in H (G ) and to a single relation in the rational cohomology ring H (BG ). An analog of this generator w was also seen by Kronheimer in his study of families of symplectic forms on 4-manifolds using Seiberg{Witten theory. Our methods involve a close study of the space of ! -compatible almost complex structures on M.

130 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the fundamental, technical, environmental, and economic aspects associated with the use of pure ammonia as a transportation fuel are broadly addressed, focusing on pure ammonia and ammonia fuel blends operation, NOx emissions control, current challenges related to the detailed and accurate understanding of the ammonia chemistry, and the lack of high-fidelity numerical models.

129 citations

Journal ArticleDOI
TL;DR: It was proven that the proportion of residual silanol groups, and the fraction of siloxane 6-rings (which correlates with porosity) may be tailored by adequate catalytic conditions, mostly by the hydrolysis pH.
Abstract: Monolithic porous silica xerogels were synthesized by the sol-gel process, and their local structure was analysed by vibrational spectroscopy. The silica alcogels were prepared by a two-step hydrolytic polycondensation of tetraethoxysilane (TEOS) in isopropanol, with a water/TEOS molar ratio of 4. The hydrolysis step was catalysed by hydrochloric acid (HCl), with different HCl/TEOS molar ratios (ranging from 0.0005 to 0.009), and the condensation step was catalysed by ammonia (NH(3)), with different NH(3)/HCl molar ratios (ranging from 0.7 to 1.7). After appropriate ageing, the alcogels were washed with isopropanol and subcritically dried at atmospheric pressure. The diffuse reflectance infrared Fourier transform (DRIFT) spectra were analysed in terms of the main siloxane rings that form the silica particles, taking into account the splitting of the nu(as)Sibond;Obond;Si mode into pairs of longitudinal and transverse optic components, by long-range Coulomb interactions. It was proven that the proportion of residual silanol groups (which correlates with hydrophilicity), and the fraction of siloxane 6-rings (which correlates with porosity) may be tailored by adequate catalytic conditions, mostly by the hydrolysis pH. This was explained in terms of the reactions' mechanisms taking place in the two-step sol-gel process followed.

129 citations

Proceedings Article
01 Dec 2004
TL;DR: A graph-based prior is proposed for parametric semi-supervised classification that utilizes both labelled and unlabelled data and integrates features from multiple views of a given sample, thus implementing a Bayesian form of co-training.
Abstract: A graph-based prior is proposed for parametric semi-supervised classification. The prior utilizes both labelled and unlabelled data; it also integrates features from multiple views of a given sample (e.g., multiple sensors), thus implementing a Bayesian form of co-training. An EM algorithm for training the classifier automatically adjusts the tradeoff between the contributions of: (a) the labelled data; (b) the unlabelled data; and (c) the co-training information. Active label query selection is performed using a mutual information based criterion that explicitly uses the unlabelled data and the co-training information. Encouraging results are presented on public benchmarks and on measured data from single and multiple sensors.

129 citations

Proceedings ArticleDOI
22 Jun 1997
TL;DR: In this article, the authors presented the control circuit of a shunt active power filter based on the instantaneous active and reactive current i/sub d/-i/sub q/ method.
Abstract: This paper presents the control circuit of a shunt active power filter based on the instantaneous active and reactive current i/sub d/-i/sub q/ method The presented method is compared with the instantaneous active and reactive power p-q method under several mains voltage conditions and for different harmonic injection highpass filters The i/sub d/-i/sub q/ method as an excellent harmonic compensation performance and presents the advantage of being frequency-independent The DC voltage regulation system is analysed and its synthesis is performed Extensive simulation results are used to show the stability of the voltage regulation system and to establish the superior performance of i/sub d/-i/sub q/ method based compensator

129 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