ESTG - Comunicações em conferências e congressos internacionais
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- Frame loss concealment for 3D video decoders based on disparity-compensated motion fieldPublication . Carreira, J.; Assunção, P.; Rodrigues, N.; Faria, S.This paper addresses the problem of frame loss concealment in 3D video decoders capable of handling stereoscopic views compliant with H.264/MVC. A joint motion-disparity compensation method is proposed to fully recover an estimated motion field for the lost frame in stereoscopic video, by using a combination of inter-view disparity-compensated motion vectors and intra-view motion extrapolation. The overall motion field is estimated from both the motion information of the co-located view, through disparity compensation, and neighboring frames of the same view, through motion vector extrapolation. The results show that the proposed method outperforms currently used methods such as frame-copy and motion-copy. In video sequences, average PSNR gains up to 1.6 dB are obtained over motion-copy, while for individual frames a maximum of 5 dB is achieved.
- A deconvolution method to remove distortion caused by antenna radiation pattern from measurementPublication . Cui, Huajian; Caldeirinha, Rafael; Richter, JuergenThe influence of vegetation on radiowave signals has become an important aspect of the design of wireless communication links. In recent years the theory of Radiative Energy Transfer has been adopted as a reliable tool to predict the radiowave propagation through and near vegetation. However one major factor influencing accuracy of the measurement is the radiation pattern of the receiver antenna. The measured pattern will be the convolution product of the antenna radiation pattern and the phase function of the vegetation medium. The measured pattern therefore needs to undergo a deconvolution process before enable to provide reliable information. This paper presents a deconvolution method developed using optimum compensation filtering to remove the distortion caused by the receiver antenna radiation pattern. A pre-filtering technique using auto/cross-correlation is utilised to improve the deconvolution results, as well as an error function is deployed to determine the optimal parameter in the iterative filter.
- Influence of a SVC on AC Arc furnaces harmonics, flicker and unbalance. Measurement and analysis.Publication . Donsión, M. P.; Güemes, J. A.; Oliveira, F.An AC arc furnace is an unbalanced, nonlinear and time varying load, which can cause many problems to power system quality. Different studies on arc furnaces harmonics analysis can be found in the bibliography on the topic; however, it is very difficult obtain an exact model that takes into account all the parameters that have influence on the process, therefore it is necessary to take measurements under different conditions. In this paper we'll present the harmonic distortion, flicker and unbalance results and conclusions on three different measurement campaigns in an iron and steel industry (SNL) with an AC arc furnace of 83 MW (170 TM) with a transformer of 120 MVA connected with a dedicated power line of 220 kV (55 km) to the Carregado Substation, where there are another other branches that connect industrial and domestic consumers.
- Using Uncertainty Information to Combine Soft ClassificationsPublication . Gonçalves, Luisa M. S.; Fonte, Cidália C.; Caetano, MarioThe classification of remote sensing images performed with different classifiers usually produces different results. The aim of this paper is to investigate whether the outputs of different soft classifications may be combined to increase the classification accuracy, using the uncertainty information to choose the best class to assign to each pixel. If there is disagreement between the outputs obtained with the several classifiers, the proposed method selects the class to assign to the pixel choosing the one that presents less uncertainty. The proposed approach was applied to an IKONOS image, which was classified using two supervised soft classifiers, the Multi-layer Perceptron neural network classifier and a fuzzy classifier based on the underlying logic of the Minimum-Distance-to-Means. The overall accuracy of the classification obtained with the combination of both classifications with the proposed methodology was higher than the overall accuracy of the original classifications, which shows that the methodology is promising and may be used to increase classification accuracy.
- Extension of the dRET Model to Include Scattering from Tree Trunks in Microcell Urban Mobile ScenariosPublication . Caldeirinha, R. F. S.; Fernandes, T. R.; Leonor, N.; Ferreira, D.This paper proposes a framework for extending the applicability of the discrete RET (dRET) model to accommodate radiowave scattering from tree trunks, particularly in microcell urban mobile scenarios, at micro- and millimetre wave frequencies. This framework aims to provide accurate modelling of the signal emanated inside and around isolated blocks of tree trunks, for instances, in raised canopy forests or in urban street canyons like scenarios. Model validation against measurement results inside an anechoic chamber for a double line of regularly spaced metallic and dielectric trunks at 18.8 GHz, as well as recommendations for a more encompassing model, are presented.
- Goals for an IoT Context-Based Process Modelling Language Regarding LogisticsPublication . Ferreira, Pedro Henrique; Martinho, Ricardo; Domingos, DulceThe Internet of Things (IoT) aims at bridging the gap between real-world business processes and information systems. When attached to physical items, the IoT technologies such as sensor networks transform objects of the supply chain into smart items. These items have the ability to capture context data and provide business process management systems (BPMSs) with a representation of things. To adequately describe a business process, process engineers commonly use Business Process Modelling Languages (BPMLs). However, in a larger scope, BPMLs differ according to the application area they are used in, and there is no current language solution to represent IoT context data within a process model. In this paper we introduce the goals for a BPML to represent these data. The language will enable process engineers to model business process behaviour taking into account IoT context data.
- Survey on Anti-spam Single and Multi-objective OptimizationPublication . Yevseyeva, Iryna; Basto-Fernandes, Vitor; Méndez, José R.In this paper anti-spam filtering is presented as a cumbersome service, as opposing to a software product perspective. The human effort for setting up, adaptation, maintenance and tuning of filters for spam detection is stressed. Because choosing the proper scores (relevance) for the spam filters is essential to the accuracy of the anti-spam system and one of the biggest challenges for the Apache SpamAssassin project (the most widely adopted anti-spam open-source software), we present a survey on single and multi-objective optimization studies for this purpose. Our survey constitutes a contribution and a stimulus for further research on this open research topic, with particular emphasis on evolutionary multi-objective approaches.
- Multidimensional fractional Schrödinger equationPublication . Rodrigues, M. M.; Vieira, NelsonThis work is intended to investigate the multi-dimensional space-time fractional Schrödinger equation of the form ħ𝛻 , with ħ the Planck's constant divided by 2π, m is the mass and u(t,x) is a wave function of the particle. Here 𝛻 are operators of the Caputo fractional derivatives, where α ∈]0,1] and β ∈]1,2]. The wave function is obtained using Laplace and Fourier transforms methods and a symbolic operational form of solutions in terms of the Mittag-Leffler functions is exhibited. It is presented an expression for the wave function and for the quantum mechanical probability density. Using Banach fixed point theorem, the existence and uniqueness of solutions is studied for this kind of fractional differential equations.
- Development and performance assessment of a real time high-resolution RF channel sounderPublication . Ferreira, D.; Caldeirinha, RafaelThis paper presents a swept time delayed cross-correlation (STDCC) channel sounder. The proposed topology employs the real-time sliding correlation technique of pseudo-random (PN) sequences, enabling amplitude and Doppler spectrum measurements and analysis of individual multipath components. It makes use of recent technologies, specifically in the generation and transmission of PN sequences, which allows for an easy adjustment of the main specifications of the sounder. The intermediate frequency (IF) stage of the system presented here has been bench-tested and validated by using a PN sequence at 1GHz chip rate, which allows for a time-delay resolution of consecutive multipath components of 2ns. The radio frequency (RF) stage as also been bench-tested, and will be followed by rigorous measurements in an anechoic chamber. The dynamic range of the system was measured to be better than 40dB.
- Phase Diagram and Critical Properties within an Effective Model of QCD: The Nambu–Jona-Lasinio Model Coupled to the Polyakov LoopPublication . Costa, Pedro; Ruivo, Maria C.; Sousa, Célia A. de; Hansen, HubertWe investigate the phase diagram of the so-called Polyakov-Nambu-Jona-Lasinio model at finite temperature and non-zero chemical potential with three quark flavors. Chiral and deconfinement phase transitions are discussed and the relevant order-like parameters are analyzed. The results are compared with simple thermodynamic expectations and lattice data. We present the phase diagram in the (T, μB) plane, paying special attention to the critical end point: as the strength of the flavor-mixing interaction becomes weaker, the critical end point moves to low temperatures and can even disappear.