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Publications

2016

A Realistic Evaluation of Iris Presentation Attack Detection

Authors
Sequeira, AF; Thavalengal, S; Ferryman, J; Corcoran, P; Cardoso, JS;

Publication
2016 39TH INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS AND SIGNAL PROCESSING (TSP)

Abstract
Iris liveness detection methods have been developed to overcome the vulnerability of iris biometric systems to spoofing attacks. In the literature, it is typically assumed that a known attack modality will be perpetrated. Then liveness models are designed using labelled samples from both real/live and fake/spoof distributions, the latter derived from the assumed attack modality. In this work it is argued that a comprehensive modelling of the spoof samples is not possible in a real-world scenario where the attack modality cannot be known with a high degree of certainty. In fact making this assumption will render the liveness detection system more vulnerable to attacks that were not included in the original training. To provide a more realistic evaluation, this work proposes: a) testing the binary models with unknown spoof samples that were not present in the training step; b) the use of a single-class classification designing the classifier by modelling only the distribution of live samples. The results obtained support the assertion that many evaluation methods from the literature are misleading and may lead to optimistic estimates of the robustness of liveness detection in practical use cases.

2016

Hybrid Automata as Coalgebras

Authors
Neves, R; Barbosa, LS;

Publication
THEORETICAL ASPECTS OF COMPUTING - ICTAC 2016

Abstract
Able to simultaneously encode discrete transitions and continuous behaviour, hybrid automata are the de facto framework for the formal specification and analysis of hybrid systems. The current paper revisits hybrid automata from a coalgebraic point of view. This allows to interpret them as state-based components, and provides a uniform theory to address variability in their definition, as well as the corresponding notions of behaviour, bisimulation, and observational semantics.

2016

Rewritting Data Cleaning Operations Defined at a Conceptual Level

Authors
Almeida, Ricardo; Oliveira, Paulo; Barroso, Joao;

Publication
Proceedings of the 21st International Conference on Information Quality, ICIQ 2016, Ciudad Real, Spain, June 22-23, 2016.

Abstract

2016

A remote monitoring and control system for ecosystem replication experiments

Authors
Ventura, JP; Cruz, NA; Lima, FP;

Publication
OCEANS 2016 MTS/IEEE MONTEREY

Abstract
In this article we describe the implementation of remote monitoring and control for multiple and independent experiments, namely, ecosystem replication experiments. First by presenting the main concepts behind the system architecture, and ultimately its design, and secondly by discussing its implementation. The system makes use of IEEE 802.15.4 Standard for Wireless Communications, a BeagleBone Black as the central coordinator for the experiments, and Arduino Mega as the monitoring and control device for each experiment. Data is stored on a PostgreSQL RDBMS, and the user interfaces with the system through a Website.

2016

EvolvDSO grid management tools to support TSO-DSO cooperation

Authors
Fonseca, N; Silva, J; Silva, A; Sumaili, J; Seca, L; Bessa, R; Pereira, J; Matos, M; Matos, P; Morais, AC; Caujolle, M; Sebastian Viana, M;

Publication
IET Conference Publications

Abstract
This paper presents two contributions developed in the framework of evolvDSO Project to support TSO-DSO cooperation. The Interval Constrained Interval Power Flow (ICPF) tool estimates the flexibility range at primary substations by aggregating the distribution network flexibility. The Sequential Optimal Power Flow (SOPF) tool defines a set of control actions that keep the active and reactive power flow within pre-agreed limits at primary substations level, by integrating different types of flexibility levers. Several study test cases were simulated using data of four real distribution networks from France and Portugal, with different demand/generation profiles and several degrees of flexibility.

2016

Noveloptical current sensor for metering and protection in high power applications

Authors
Nascimento, IM; Brigida, ACS; Baptista, JM; Costa, JCWA; Martinez, MAG; Jorge, PAS;

Publication
INSTRUMENTATION SCIENCE & TECHNOLOGY

Abstract
A clamp-on optical current sensor prototype for metering and protection applications in high power systems was developed and characterized. The system is based on the Faraday effect in a low birefringence, high Verdet constant, 8cm long SF57 Schott glass prism. It was incorporated in a nylon casing suitable for clamp-on applications in the power line. The sensor operation was tested at 630nm, 830nm, and 1550nm to access its applicability in remote interrogation via fiber links. Optimal operation at 830nm is reported with a linear response up to 65.28kA, with 0.1 or 0.2 accuracy class considering a nominal currents of 1.2 and 0.3 kA (root mean square), respectively. Twelve calibrations procedures performed over six days showed an estimated maximum error of 11m A. Preliminary measurements were made from 40 to 400Hz. The sensor was exposed to transient signals less than 10 mu s that demonstrated its use in protection applications.

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