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Publications

2025

Normalized temperature sensitivity of fiber Bragg gratings inscribed under different conditions

Authors
Preizal, J; Cosme, M; Pota, M; Caldas, P; Araujo, FM; Oliveira, R; Nogueira, R; Rego, GM;

Publication
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS

Abstract
In this paper we present results on the normalized temperature sensitivity of UV- and fs-induced fiber Bragg gratings in a singlemode fiber with similar to 4.7 mol% GeO2 and having an Ormocer coating. In the 1500-1600 nm wavelength range, the former shows an almost constant value of 6.165x10(-6) K-1, whilst the fs-induced present some variation not related with the strength of the grating but probably due to induced birefringence. The average value obtained was 6.191x10(-6) K-1 which is higher than the former. For the UV-induced gratings in the Corning SMF-28 fiber (3.67 mol% GeO2) the value obtained was 6.143x10(-6) K-1. The achieved values are compatible with the use of Corning 7980 silica-based cladding fiber. Preliminary results also show no measurable impact of the hydrogenation process or the strength of the grating on the normalized temperature sensitivity.

2025

Analysis of the New Portuguese and Spanish Necps Using Cevesa Market Model

Authors
De Oliveira A.R.; Martinez S.D.; Collado J.V.; Bessa T.F.; Saraiva J.T.; Campos F.A.; Goncalves De Morais R.; Davila-Isidoro B.;

Publication
International Conference on the European Energy Market Eem

Abstract
The recent updates of the National Energy and Climate Plans (NECPs) for Portugal and Spain have some significant changes compared to the previous 2019 versions, especially for the Portuguese side where a greater demand and renewable generation capacity are foreseen. This work assesses the impact of these new plans on the Iberian electricity market (MIBEL) main outcomes using CEVESA market model. Simulation results allow the analysis of the expected generation mix and prices, CO2 emissions, system cost, system adequacy, interconnections capacity usage, H2 demand impact and its contribution to provide balancing flexibility, under different simulation scenarios.

2025

Fairness Analysis in Causal Models: An Application to Public Procurement

Authors
Teixeira, S; Nogueira, AR; Gama, J;

Publication
MACHINE LEARNING AND PRINCIPLES AND PRACTICE OF KNOWLEDGE DISCOVERY IN DATABASES, ECML PKDD 2023, PT II

Abstract
Data-driven decision models based on Artificial Intelligence (AI) have been widely used in the public and private sectors. These models present challenges and are intended to be fair, effective and transparent in public interest areas. Bias, fairness and government transparency are aspects that significantly impact the functioning of a democratic society. They shape the government's and its citizens' relationship, influencing trust, accountability, and the equitable treatment of individuals and groups. Data-driven decision models can be biased at several process stages, contributing to injustices. Our research purpose is to understand fairness in the use of causal discovery for public procurement. By analysing Portuguese public contracts data, we aim i) to predict the place of execution of public contracts using the PC algorithm with sp-mi, smc-chi(2) and mc-chi(2) conditional independence tests; ii) to analyse and compare the fairness in those scenarios using Predictive Parity Rate, Proportional Parity, Demographic Parity and Accuracy Parity metrics. By addressing fairness concerns, we pursue to enhance responsible data-driven decision models. We conclude that, in our case, fairness metrics make an assessment more local than global due to causality pathways. We also observe that the Proportional Parity metric is the one with the lowest variance among all metrics and one with the highest precision, and this reinforces the observation that the Agency category is the one that is furthest apart in terms of the proportion of the groups.

2025

Semi-distributed optical fiber bending extensometer system for precision landslide monitoring based on OTDR

Authors
Lorenzo Santini; Paulo Caldas; Luís C. Coelho;

Publication
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS

Abstract
A semi-distributed optical fiber bending extensometer system based on OTDR is proposed, consisting of N-loops designed to enable different maximum extension measurements and sensitivities. This system offers a low-cost solution for monitoring landslides and similar civil structures. Tests conducted at 1625 nm demonstrate that different series of sensors can be independently measured with elongation errors typically within +/- 0.25 cm across a range from 0 to 9 cm.

2025

Assesing the Role of Fuel Cell Vehicles in the Iberia Energy Transition

Authors
Mahou J.; Castanon R.; Campos F.A.; Oliveira A.; Villar J.;

Publication
International Conference on the European Energy Market Eem

Abstract
The mobility sector is expected to significantly impact the power system by deploying battery electric vehicles (BEV) and fuel cell vehicles (FCEV). This work improves CEVESA, a market model for the long-term planning and operation of the Iberian Electricity Market, by modelling FCEV as an alternative to BEV and internal combustion vehicles (ICEV), and its impact on the H2demand and storage. The mobility and H2economy models interact with the power system through the electricity needs and price. CEVESA is then applied to estimate potential expansion paths of ICEV, BEV and FCEV mobility alternatives considering the total system costs and the EU decarbonization strategy. The findings suggest that if FCEVs technology matures, it could rival BEVs, offering greater system flexibility via electrolyzers and extended driving ranges for users.

2025

CapyMOA: Efficient Machine Learning for Data Streams in Python

Authors
Gomes, HM; Lee, A; Gunasekara, N; Sun, Y; Cassales, GW; Liu, J; Heyden, M; Cerqueira, V; Bahri, M; Koh, YS; Pfahringer, B; Bifet, A;

Publication
CoRR

Abstract

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