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Publications

2016

On the Quality of the Gaussian Copula for Multi-temporal Decision-making Problems

Authors
Bessa, RJ;

Publication
2016 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)

Abstract
Multi-temporal decision-making problems require information about the potential temporal trajectories of wind generation for a given time horizon. Typically, the Gaussian copula is used for modelling the dependency between probabilistic forecasts from different lead-times. This paper explores the vine copula framework as a benchmark model since it captures complex multivariate dependence structures with mixed types of dependencies. The results show that a Gaussian copula with a suitable covariance matrix suffice to generate high quality temporal trajectories.

2016

Immersive Learning Research Network - Second International Conference, iLRN 2016, Santa Barbara, CA, USA, June 27 - July 1, 2016, Proceedings

Authors
Allison, C; Morgado, L; Pirker, J; Beck, D; Richter, J; Gütl, C;

Publication
iLRN

Abstract

2016

Collaboration in a Hyperconnected World - 17th IFIP WG 5.5 Working Conference on Virtual Enterprises, PRO-VE 2016, Porto, Portugal, October 3-5, 2016, Proceedings

Authors
Afsarmanesh, Hamideh; Matos, LuisM.Camarinha; Soares, AntonioLucas;

Publication
PRO-VE

Abstract

2016

BLUECOM plus : Cost-effective Broadband Communications at Remote Ocean Areas

Authors
Campos, R; Oliveira, T; Cruz, N; Matos, A; Almeida, JM;

Publication
OCEANS 2016 - SHANGHAI

Abstract
The ocean and the Blue Economy are increasingly top priorities worldwide. The immense ocean territory in the planet and its huge associated economical potential is envisioned to increase the activity at the ocean in the forthcoming years. The support of these activities, and the convergence to the Internet of Things paradigm, will demand wireless and mobile communications to connect humans and systems at remote ocean areas. Currently, there is no communications solution enabling cost-effective broadband Internet access at remote ocean areas in alternative to expensive, narrowband satellite communications. This paper presents the maritime communications solution being developed in the BLUECOM+ project. The BLUECOM+ solution enables cost-effective broadband Internet access at remote ocean areas using standard wireless access technologies, e.g., GPRS/UMTS/LTE and Wi-Fi. Its novelty lies on the joint use of TV white spaces for long range radio communications, tethered balloons for lifting communications nodes high above the ocean surface, multi-hop relaying techniques for radio range extension, and standard access networks at the ocean. Simulation results prove it is possible to reach radio ranges beyond 100 km and bitrates in excess of 3 Mbit/s using a two-hop land-sea communications chain.

2016

Detection of Fraud Symptoms in the Retail Industry

Authors
Ribeiro, RP; Oliveira, R; Gama, J;

Publication
ADVANCES IN ARTIFICIAL INTELLIGENCE - IBERAMIA 2016

Abstract
Data mining is one of the most effective methods for fraud detection. This is highlighted by 25% of organizations that have suffered from economic crimes [1]. This paper presents a case study using real-world data from a large retail company. We identify symptoms of fraud by looking for outliers. To identify the outliers and the context where outliers appear, we learn a regression tree. For a given node, we identify the outliers using the set of examples covered at that node, and the context as the conjunction of the conditions in the path from the root to the node. Surprisingly, at different nodes of the tree, we observe that some outliers disappear and new ones appear. From the business point of view, the outliers that are detected near the leaves of the tree are the most suspicious ones. These are cases of difficult detection, being observed only in a given context, defined by a set of rules associated with the node.

2016

Effect of anion type in the performance of ionic liquid/poly(vinylidene fluoride) electromechanical actuators

Authors
Mejri, R; Dias, JC; Hentati, SB; Martins, MS; Costa, CM; Lanceros Mendez, S;

Publication
JOURNAL OF NON-CRYSTALLINE SOLIDS

Abstract
Low voltage actuators based on poly(vinylidene fluoride) (PVDF) with 10, 25 and 40% 1-hexyl-3-methylimidazolium chloride ([C(6)mim][Cl]) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(6)mim][NTf2]) are prepared by solvent casting in order to evaluate the effect of anion size in the bending properties. Independently of the ionic liquid type and content, its presence leads to the crystallization of PVDF in the beta-phase. The addition of ionic liquid into the polymer matrix decreases significantly its degree of crystallinity and the elastic modulus. It is also confirmed the good miscibility between PVDF and IL, determined by the interaction of the CF2 groups from the PVDF chains with the imidazolium ring in the ionic liquid (IL). The AC conductivity of the composites depends both on the amount of ionic liquid content and anion size. The bending movement of the IL/PVDF composites is correlated to their degree of crystallinity, mechanical properties and ionic conductivity value and the best value of bending response (0.53%) being found for IL/PVDF composite with 40 wt of [C(6)min][Cl] at an applied voltage of 10 V square signal.

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