2020
Authors
Costa, J; Silva, C; Antunes, M; Ribeiro, B;
Publication
NEURAL COMPUTING & APPLICATIONS
Abstract
Many text classification problems in social networks, and other contexts, are also dynamic problems, where concepts drift through time, and meaningful labels are dynamic. In Twitter-based applications in particular, ensembles are often applied to problems that fit this description, for example sentiment analysis or adapting to drifting circumstances. While it can be straightforward to request different classifiers' input on such ensembles, our goal is to boost dynamic ensembles by combining performance metrics as efficiently as possible. We present a twofold performance-based framework to classify incoming tweets based on recent tweets. On the one hand, individual ensemble classifiers' performance is paramount in defining their contribution to the ensemble. On the other hand, examples are actively selected based on their ability to effectively contribute to the performance in classifying drifting concepts. The main step of the algorithm uses different performance metrics to determine both each classifier strength in the ensemble and each example importance, and hence lifetime, in the learning process. We demonstrate, on a drifted benchmark dataset, that our framework drives the classification performance considerably up for it to make a difference in a variety of applications.
2020
Authors
Machado, M; Ferreira, CA; Pedrosa, J; Negrao, E; Rebelo, J; Leitao, P; Carvalho, AS; Rodrigues, MC; Ramos, I; Cunha, A; Campilho, A;
Publication
XV MEDITERRANEAN CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING AND COMPUTING - MEDICON 2019
Abstract
The lung cancer diagnosis is based on the search of lung nodules. Besides its characterization, it is also common to register the anatomical position of these findings. Even though computed-aided diagnosis systems tend to help in these tasks, there is still lacking a complete system that can qualitatively label the nodules in lung regions. In this way, this paper proposes an automatic lung reference model to facilitate the report of nodules between computed-aided diagnosis systems and the radiologist, and among radiologists. The model was applied to 115 computed tomography scans with manually and automatically segmented lobes, and the obtained sectors' variability was evaluated. As the sectors average variability within lobes is less or equal to 0.14, the model can be a good way to promote the report of lung nodules.
2020
Authors
Ferreira, ML; Ferreira, JC;
Publication
JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY
Abstract
In future wireless communication systems, several radio access technologies will coexist and interwork to provide a great variety of services with different requirements. Thus, the design of flexible and reconfigurable hardware is a relevant topic in wireless communications. The combination of high performance, programmability and flexibility makes Field-programmable gate array a convenient platform to design such systems, especially for base stations. This paper describes a dynamically reconfigurable baseband modulator for Orthogonal Frequency Division Multiplexing and Filter-bank Multicarrier modulation waveforms implemented on a Virtex-7 board. The design features Dynamic Partial Reconfiguration (DPR) capabilities to adapt its mode of operation at run-time and is compared with a functionally equivalent static multi-mode design regarding processing throughput, resource utilization, functional density and power consumption. The DPR-based design implementation reserves about half the resources used by static multi-mode counterpart. Consequently, the baseband processing dynamic power consumption observed in the DPR-based design is between 26 mW to 90 mW lower than in the static multi-mode design, representing a dynamic power reduction between 13% to 52%. The worst-case DPR latency measured was 1.051 ms, while the DPR energy overhead is below 1.5 mJ. Considering latency requirements for modern wireless standards and power consumption constraints for commercial base stations, the DPR application is shown to be valuable in multi-standard and multi-mode systems, as well as in scenarios such as multiple-input and multiple-output or dynamic spectrum aggregation.
2020
Authors
Sekerinski, E; Moreira, N; Oliveira, JN; Ratiu, D; Guidotti, R; Farrell, M; Luckcuck, M; Marmsoler, D; Campos, J; Astarte, T; Gonnord, L; Cerone, A; Couto, L; Dongol, B; Kutrib, M; Monteiro, P; Delmas, D;
Publication
FM Workshops (1)
Abstract
2020
Authors
Crispim, J; Fernandes, J; Rego, N;
Publication
RELIABILITY ENGINEERING & SYSTEM SAFETY
Abstract
This paper describes a customized risk assessment framework to be applied in military shipbuilding projects. The framework incorporates the Delphi method with visual diagrams, Bayesian Networks (BN) and the expression of expert opinions through linguistic variables. Noisy-OR and Leak Canonical models are used to determine the conditional probabilities of the BN model. The approach can easily be adapted for other shipbuilding construction projects. The visual diagrams that support the Delphi questionnaire favor the comprehensive visualization of the interdependencies between risks, causes, risks and causes, and risks and effects. The applicability of the framework is illustrated through the assessment of risk of two real military shipbuilding projects. This assessment includes a sensitivity analysis that is useful to prioritize mitigation actions. In the two cases studies, the risks with higher probability of occurrence were failures or errors in production, of the contracted, in the requirements, and in planning. The results of the sensitivity analysis showed that a set of mitigation actions directed at relatively easily controllable causes would have achieved important reductions in risk probabilities.
2020
Authors
Caratti o Garatti, A; Fedriani, R; Garcia Lopez, R; Koutoulaki, M; Perraut, K; Linz, H; Brandner, W; Garcia, P; Klarmann, L; Henning, T; Labadie, L; Sanchez-Bermudez, J; Lazareff, B; van Dishoeck, EF; Caselli, P; de Zeeuw, PT; Bik, A; Benisty, M; Dougados, C; Ray, TP; Amorim, A; Berger, J; Clénet, Y; Coudé du Foresto, V; Duvert, G; Eckart, A; Eisenhauer, F; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Gordo, P; Jocou, L; Horrobin, M; Kervella, P; Lacour, S; Le Bouquin, J; Léna, P; Grellmann, R; Ott, T; Paumard, T; Perrin, G; Rousset, G; Scheithauer, S; Shangguan, J; Stadler, J; Straub, O; Straubmeier, C; Sturm, E; Thi, WF; Vincent, FH; Widmann, F;
Publication
ASTRONOMY & ASTROPHYSICS
Abstract
Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved.Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 mu m).Methods. We present the first GRAVITY/VLTI observations at high spectral (R=4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS 2.Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (<= 8 degrees). Our best ellipsoid model provides a disc inclination of 34 degrees +/- 1 degrees, a disc major axis position angle (PA) of 166 degrees +/- 1 degrees, and a disc diameter of 3.99 +/- 0.09 mas (or 1.69 +/- 0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74 +/-(0.08)(0.07) +/- 0.07 0.08 mas (1.16 +/- 0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M-* similar to 14.7(-3.6)(+2)M(circle dot) M * similar to 14 . 7 - 3.6 + 2 M circle dot by combining our interferometric and spectral modelling results.
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