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Lisbon, Portugal

Caleiro C.,Institute Telecomunicaces | Goncalves R.,New University of Lisbon
Fundamenta Informaticae | Year: 2011

Logical matrices are widely accepted as the semantic structures that most naturally fit the traditional approach to algebraic logic. The behavioral approach to the algebraization of logics extends the applicability of the traditional methods of algebraic logic to a wider range of logical systems, possibly encompassing many-sorted languages and non-truth-functional phenomena. However, as one needs to work with behavioral congruences, matrix semantics are unsuited to the behavioral setting. In [5], a promising version of algebraic valuation semantics was proposed in order to fill in this gap. Herein, we define the class of valuations that should be canonically associated to a logic, and we show, by means of new meaningful bridge results, how it is related to the behaviorally equivalent algebraic semantics of a behaviorally algebraizable logic. Source


Cernigliaro G.,Technical University of Madrid | Naccari M.,Institute Telecomunicaces | Jaureguizar F.,Technical University of Madrid | Cabrera J.,Technical University of Madrid | Garcia N.,Technical University of Madrid
2012 Picture Coding Symposium, PCS 2012, Proceedings | Year: 2012

A novel scheme for depth sequences compression, based on a perceptual coding algorithm, is proposed. A depth sequence describes the object position in the 3D scene, and is used, in Free Viewpoint Video, for the generation of synthetic video sequences. In perceptual video coding the human visual system characteristics are exploited to improve the compression efficiency. As depth sequences are never shown, the perceptual video coding, assessed over them, is not effective. The proposed algorithm is based on a novel perceptual rate distortion optimization process, assessed over the perceptual distortion of the rendered views generated through the encoded depth sequences. The experimental results show the effectiveness of the proposed method, able to obtain a very considerable improvement of the rendered view perceptual quality. © 2012 IEEE. Source


Andre P.S.,Institute Telecomunicaces | Andre P.S.,University of Aveiro | Domingues F.,Institute Telecomunicaces | Granada M.,University of Aveiro
2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011 | Year: 2011

The effect of the maritime environment on the aging of optical fibers coatings was studied. The obtained stress decay rate was 29.05 days, however, this value is higher than for a pure water saturate environment. © 2011 OSA. Source


Oliveira R.A.,Federal University of Technology of Parana | Oliveira R.A.,University of Sydney | Possetti G.R.C.,Federal University of Technology of Parana | Marques C.A.F.,Institute Telecomunicaces | And 10 more authors.
Measurement Science and Technology | Year: 2011

We have shown experimental results of the excitation of long period fiber gratings by means of flexural acoustic waves with a wavelength larger than the grating period, validated by numerical simulations. The effect of the acoustic wave on the grating is modeled with the method of assumed modes, which delivers the strain field inside the grating, then used as the input to the transfer matrix method, needed for calculating the grating spectrum. The experimental and numerical results are found to be in good agreement, even though only the strain-optic effects are taken into account. © 2011 IOP Publishing Ltd. Source


Paiva C.R.,University of Lisbon | Matos S.A.,Institute Telecomunicaces
IEEE Transactions on Antennas and Propagation | Year: 2012

The perfect electromagnetic conductor (PEMC) was introduced as an observer-independent axion medium that generalizes the concepts of perfect electric conductor (PEC) and perfect magnetic conductor (PMC). Following the original boundary definition, its 3-D medium definition corresponds to a 4-D representation that is, actually, observer-dependent (i.e., it is not isotropic for the whole class of inertial observers), leading to a nonunique characterization of the electromagnetic field inside. This characterization of the PEMC, then, violates the boundary conditionsunless some extraneous waves, called metafields, are surgically extracted from the final solution. In this paper, using spacetime algebra, we define the PEMC as the unique limit of the most general class of isotropic media in Minkowskian spacetime, which we call Minkowskian isotropic media (MIM). An MIM is actually a dilaton-axion medium. Its isotropy is a Lorentz invariant characterization: It is an observer-independent property, contrary to isotropy in 3-D Gibbsian characterization. Hence, a more natural definition of a PEMC is herein presented: It leads to a unique electromagnetic field in its interior; it corresponds, though, to the same original boundary definition. This new approach is applied to the analysis of an air-MIM interface that, as a particular case, reduces to an air-PEMC interface. © 1963-2012 IEEE. Source

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