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Publications

2011

Summarising changes in air temperature over Central Europe by quantile regression and clustering

Authors
Barbosa, SM; Scotto, MG; Alonso, AM;

Publication
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES

Abstract
The analysis of trends in air temperature observations is one of the most common activities in climate change studies. This work examines the changes in daily mean air temperature over Central Europe using quantile regression, which allows the estimation of trends, not only in the mean but in all parts of the data distribution. A bootstrap procedure is applied for assessing uncertainty on the derived slopes and the resulting distributions are summarised via clustering. The results show considerable spatial diversity over the central European region. A distinct behaviour is found for lower (5%) and upper (95%) quantiles, with higher trends around 0.15 degrees C decade(-1) at the 5% quantile and around 0.20 degrees C decade(-1) at the 95% quantile, the largest trends (>0.2 degrees C decade(-1)) occurring in the Alps.

2011

Human-Machine Interface for the control of a climbing robot

Authors
Oliveira, ALC; Silva, MF; Barbosa, RS;

Publication
Proceedings of the IASTED International Conference on Modelling, Identification and Control

Abstract
This paper presents the Human-Machine Interface developed for the manual and automatic control of a wheeled climbing robot, with adhesion through permanent magnets. This machine has been developed with the intention of being used in the inspection of ferromagnetic structures, in order to, for instance, detect weaknesses due to corrosion. Although it can be manually controlled, the vehicle is designed to have a semi-autonomous behavior, allowing a remote inspection process controlled by a technician, this way reducing the risks associated with the human inspection of tall structures and ATEX places. The distinguishing characteristic of this robot is its dynamic adjustment system of the permanent magnets in order to assure the machine adhesion to the surfaces, even while crossing irregular and curved surfaces.

2011

An epidemic approach to dependable key-value substrates

Authors
Matos, M; Vilaca, R; Pereira, J; Oliveira, R;

Publication
Proceedings of the International Conference on Dependable Systems and Networks

Abstract
The sheer volumes of data handled by today's Internet services demand uncompromising scalability from the persistence substrates. Such demands have been successfully addressed by highly decentralized key-value stores invariably governed by a distributed hash table. The availability of these structured overlays rests on the assumption of a moderately stable environment. However, as scale grows with unprecedented numbers of nodes the occurrence of faults and churn becomes the norm rather than the exception, precluding the adoption of rigid control over the network's organization. In this position paper we outline the major ideas of a novel architecture designed to handle today's very large scale demand and its inherent dynamism. The approach rests on the well-known reliability and scalability properties of epidemic protocols to minimize the impact of churn. We identify several challenges that such an approach implies and speculate on possible solutions to ensure data availability and adequate access performance. © 2011 IEEE.

2011

NUVE

Authors
Martinho Moura, J; Barros, N; Branco, P; Marcos, AF;

Publication
Proceedings of the fifth international conference on Tangible, embedded, and embodied interaction - TEI '11

Abstract

2011

Soil-gas radon monitoring in an active granite quarry from central Portugal

Authors
Pereira, AJSC; Barbosa, SM; Neves, LJPF; Aumento, F;

Publication
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES

Abstract
Seven soil-gas radon monitoring stations were placed along the active front of a granite quarry in Canas de senhorim, Central Portugal, recording continuously for 81 days. Important differences in the radon concentration were found between stations, with average values comprised between 102 and 2982 Bq m(-3), which can be explained by the local presence of uranium anomalies in the regional late-orogenic Hercynian granite, usually associated with faults. One of the boreholes exhibits large radon anomalies lasting for several days, and two, contrary to the others, show a clear daily periodic behaviour, with minima around 19:00 LT and maxima around 07:00 LT. The different patterns observed in stations placed at such a short distance (< 100 m) has no clear explanation and deserves further investigation. Data analysis shows no evidence of soil-gas radon concentration changes during explosions carried out at the quarry. This is likely to result from the absence of a progressive stress field affecting the rock, as typically occurs before an earthquake.

2011

Knowledge Discovery and Multimodal Inputs for Driving an Intelligent Wheelchair

Authors
Faria, BM; Reis, LP; Lau, N;

Publication
IJKDB

Abstract

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