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Publications

2010

Electromagnetic Transients Analysis of Lightning Overvoltages on Wind Power Plants

Authors
Rodrigues, RB; Mendes, VMF; Catalao, JPS;

Publication
INTERNATIONAL REVIEW OF ELECTRICAL ENGINEERING-IREE

Abstract
As wind power generation undergoes rapid growth, lightning and overvoltage incidents involving wind power plants have come to be regarded as a serious problem. Firstly, lightning location systems are discussed, as well as important parameters regarding lightning protection. Also, this paper presents a case study, based on a wind turbine with an interconnecting transformer, for the study of adequate lightning and overvoltage protection measures. The electromagnetic transients circuit under study is described, and computational results are presented Copyright

2010

How about an app store?" enablers and constraints in platform strategies for mobile network operators

Authors
Gonçalves, V; Walravens, N; Ballon, P;

Publication
ICMB and GMR 2010 - 2010 9th International Conference on Mobile Business/2010 9th Global Mobility Roundtable

Abstract
This paper describes the platformisation of the mobile services domain, which in recent years has become a successful strategy for some hardware manufacturers and software companies. While pursuing diverging platform strategies and business models, they have succeeded in creating a demand for mobile software and content with end-users. Mobile network operators have lagged behind in this area and are now attempting to keep up with other initiatives. This paper explores the question which platform type an operator should adopt if he wants to play a meaningful role in the mobile service domain. It describes advantages and disadvantages of different platform types and lists some core competences an operator should have, or develop, in order to successful adopt a certain platform type. © 2010 IEEE.

2010

Ensembles of jittered association rule classifiers

Authors
Azevedo, PJ; Jorge, AM;

Publication
DATA MINING AND KNOWLEDGE DISCOVERY

Abstract
The ensembling of classifiers tends to improve predictive accuracy. To obtain an ensemble with N classifiers, one typically needs to run N learning processes. In this paper we introduce and explore Model Jittering Ensembling, where one single model is perturbed in order to obtain variants that can be used as an ensemble. We use as base classifiers sets of classification association rules. The two methods of jittering ensembling we propose are Iterative Reordering Ensembling (IRE) and Post Bagging (PB). Both methods start by learning one rule set over a single run, and then produce multiple rule sets without relearning. Empirical results on 36 data sets are positive and show that both strategies tend to reduce error with respect to the single model association rule classifier. A bias-variance analysis reveals that while both IRE and PB are able to reduce the variance component of the error, IRE is particularly effective in reducing the bias component. We show that Model Jittering Ensembling can represent a very good speed-up w.r.t. multiple model learning ensembling. We also compare Model Jittering with various state of the art classifiers in terms of predictive accuracy and computational efficiency.

2010

Moderate electric fields can inactivate Escherichia coli at room temperature

Authors
Machado, LF; Pereira, RN; Martins, RC; Teixeira, JA; Vicente, AA;

Publication
JOURNAL OF FOOD ENGINEERING

Abstract
The inactivation of Escherichia coli using moderate electric fields (MEF) below 25 degrees C, was investigated. Keeping the temperature always below 25 degrees C demonstrated that electric fields are involved in the inactivation of E call, without possible synergistic temperature effects. Electric fields above 220 V cm(-1) promoted death rates of 3 log(10) cycles of E coli in less than 6 min, and even higher rates at greater electric fields, while presumably overcoming the thermal degradation caused by conventional high temperature treatments. A non-thermal model was proposed that successfully describes the E. coli death kinetics under this treatment. SEM observations of E. coli cells after the exposure to the MEF treatment, revealed changes at the cell membrane level, indicating a possible cause for the cell death rates. These results show that this treatment holds potential for sterilization of thermolabile products (e.g. serum and other physiological fluids, food products), by itself or as a complement of the traditional heat-dependent techniques.

2010

A QUEST FOR THE RIGHT WORD ENHANCING REFLEXIVITY AND TECHNOLOGY IN TERMINOLOGY TRAINING

Authors
Silva, M; Albuquerque, A;

Publication
4TH INTERNATIONAL TECHNOLOGY, EDUCATION AND DEVELOPMENT CONFERENCE (INTED 2010)

Abstract
When it comes to translators training, the acquisition of indexing and terminological competences (both at retrieval and management stage) has a major role in the performance of future translators. A good terminological database, as a result of an accurate research, along with computer assisted translation tools (CAT tools) can improve translation's speed and quality and also reduce revision costs, bringing in benefits for all the players in the translation industry: language service providers and clients. That process (analysis, selection, retrieval and storage of terminology) takes place mostly in the pre-translation stage, but underlies the whole translation work and can be a determining factor to the quality of the final product and to its homogeneity, especially when carried out in a collaborative environment. The development of terminological databases is an essential step in the training of translators and the efficient search for the right word a necessary skill in today's globalised translation market. Moreover being the quest for the right word almost entirely run over the Internet, data diversity can greatly increase the noise. This search poses several questions, mainly (1) how and where to retrieve information and (2) how to manage it efficiently, especially to students who are neither experts in terminology nor in translation. To ease some of these problems, students were assigned a project in terminology (a database) and, in order to accomplish it, both a Webquest and an ePortfolio were proposed as guidance tools. Along the process, students were expected to build up their thematic and communicative competence and, in parallel, widen their skills in computer-assisted translation tools as well as standard office-automation software. This paper aims at discussing how these two tools helped students guide their research, structure the problem solving activities, develop critical thinking and terminological competencies.

2010

A Facade Tracking System for Outdoor Augmented Reality

Authors
Martins, JF; Silva, JA; Augusto de Sousa, AA;

Publication
WSCG 2010: FULL PAPERS PROCEEDINGS

Abstract
We describe a real-time facade tracking system that uses, as setup information, only two images of a facade, captured on the moment. No more previous information is needed, such as a facade 3D model, dimensions or aspect ratio. Feature points and their local descriptors are extracted from that pair of images and used during the detection and tracking of the facade. Additionally, parallax and topological information is also used in order to increase the overall robustness of the tracking process. Experiments show that the system can detect and track a wide variety of facades, including those that are not entirely planar, partially occluded or have few distinguishable visual landmarks. The reliance on on-the-spot information, alone, makes this system useful for Outdoor Augmented Reality applications, in an Anywhere Augmentation urban context.

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