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Publicações

2017

Entropy and Compression Capture Different Complexity Features: The Case of Fetal Heart Rate

Autores
Monteiro Santos, J; Goncalves, H; Bernardes, J; Antunes, L; Nozari, M; Costa Santos, C;

Publicação
ENTROPY

Abstract
Entropy and compression have been used to distinguish fetuses at risk of hypoxia from their healthy counterparts through the analysis of Fetal Heart Rate (FHR). Low correlation that was observed between these two approaches suggests that they capture different complexity features. This study aims at characterizing the complexity of FHR features captured by entropy and compression, using as reference international guidelines. Single and multi-scale approaches were considered in the computation of entropy and compression. The following physiologic-based features were considered: FHR baseline; percentage of abnormal long (% abLTV) and short (% abSTV) term variability; average short term variability; and, number of acceleration and decelerations. All of the features were computed on a set of 68 intrapartum FHR tracings, divided as normal, mildly, and moderately-severely acidemic born fetuses. The correlation between entropy/compression features and the physiologic-based features was assessed. There were correlations between compressions and accelerations and decelerations, but neither accelerations nor decelerations were significantly correlated with entropies. The % abSTV was significantly correlated with entropies (ranging between 0.54 and 0.62), and to a higher extent with compression (ranging between 0.80 and 0.94). Distinction between groups was clearer in the lower scales using entropy and in the higher scales using compression. Entropy and compression are complementary complexity measures.

2017

A New DG Planning Approach to Maximize Renewable - Based DG Penetration Level and Minimize Annual Loss

Autores
Najafi, S; Shafie khah, M; Hajibandeh, N; Osorio, GJ; Catalao, JPS;

Publicação
TECHNOLOGICAL INNOVATION FOR SMART SYSTEMS

Abstract
Distributed Generation (DG) using renewable technologies is increasing due to their benefits including energy security and emission reduction. However, installing new DGs in distributed networks is limited due to network constraints such as feeder capacity and short circuit level, as well as higher investment costs. In this paper, network reconfiguration and reactive power planning are used to maximize DG penetration level and to minimize annual loss for DGs with biomass technologies. In order to model the problem uncertainties, 96 scenarios considering ten different network load levels are studied. A multi objective method is applied for solving this optimization problem by using Pareto front. The numerical results indicate the positive impacts of the proposed approach on improving the network security.

2017

Biomass in the generation of electricity in Portugal: A review

Autores
Nunes, LJR; Matias, JCO; Catalao, JPS;

Publicação
RENEWABLE & SUSTAINABLE ENERGY REVIEWS

Abstract
The quality and composition of biomass as used in Portugal's thermal power plants is highly variable. The biomass consists mainly of residual forest biomass derived from forestry operations and wood waste from industrial processes, in particular paper and pulp industry. Its quality and composition is influenced by the presence of moisture and inert fragments, the latter being incorporated during collection or as a consequence of adherence to the biomass prior to collection. This variability presents difficulties for the thermal power plants; besides being an additional operational cost, the presence of large amounts of water and inerts in biomass used as a fuel, can result in problems related to the instability of the combustion and the accumulation of ash or rock that have to be removed and discarded. The objective of this paper is to review the main parameters that influence the quality of biomass, while analysing the current state-of-the-art power generation from the biomass sector in Portugal, as a new contribution to earlier studies.

2017

Microfiber Knot With Taper Interferometer for Temperature and Refractive Index Discrimination

Autores
Gomes, AD; Frazao, O;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A compact sensing structure using two distinct optical devices, a microfiber knot resonator and an abrupt taper-based Mach-Zehnder interferometer (MZI), is presented. The device was fabricated using only CO2 laser processing. The transmission spectrum presents two different components with different sensitivities to different physical and chemical parameters. The sensor was characterized in temperature and refractive index. For temperature sensing in water, the MZI component presents a sensitivity of -196 +/- 2 pm/degrees C while the microfiber knot resonator (MKR) component shows a sensitivity of 25.1 +/- 0.9 pm/degrees C, for water temperature variations of 12 degrees C. Sensitivities of 1354 +/- 14 nm/RIU and -43 +/- 4 nm/RIU were achieved for refractive index sensing for the MZI and the MKR components, respectively, in a refractive index range from 1.32823 to 1.33001. The matrix method was used for the simultaneous measurement of temperature and refractive index.

2017

Fiber Bragg grating sensor based on cantilever structure embedded in polymer 3D printed material

Autores
Lima, R; Tavares, R; Silva, SO; Abreu, P; Restivo, MT; Frazao, O;

Publicação
2017 25TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS (OFS)

Abstract
A cantilever structure in 3D printed based on a fiber Bragg grating (FBG) sensor embedded in polymer material is proposed. The FBG sensor was embedded in 3D printed coating and was tested under three physical parameters: displacement, temperature and vibration. The sensor was tested in displacement in two different regions of the cantilever, namely, on its midpoint and end point. The maximum displacement sensitivity achieved was (3 +/- 0.1) pm/mm for end point displacement, and a temperature sensitivity of (30 +/- 1) pm/degrees C was also attained. In the case of vibration measurements it was possible to obtain a 10.23Hz-low frequency oscillation.

2017

Using low-voltage surge protection devices for lightning protection of 15/0.4 kV pole-mounted distribution transformer

Autores
Resende, FO; Peças Lopes, JA;

Publicação
CIRED - Open Access Proceedings Journal

Abstract

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