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Publicações

2018

Twitter as a Source for Time- and Domain-Dependent Sentiment Lexicons

Autores
Guimaraes, N; Torgo, L; Figueira, A;

Publicação
SOCIAL NETWORK BASED BIG DATA ANALYSIS AND APPLICATIONS

Abstract
Sentiment lexicons are an essential component on most state-of-the-art sentiment analysis methods. However, the terms included are usually restricted to verbs and adjectives because they (1) usually have similar meanings among different domains and (2) are the main indicators of subjectivity in the text. This can lead to a problem in the classification of short informal texts since sometimes the absence of these types of parts of speech does not mean an absence of sentiment. Therefore, our hypothesis states that knowledge of terms regarding certain events and respective sentiment (public opinion) can improve the task of sentiment analysis. Consequently, to complement traditional sentiment dictionaries, we present a system for lexicon expansion that extracts the most relevant terms from news and assesses their positive or negative score through Twitter. Preliminary results on a labelled dataset show that our complementary lexicons increase the performance of three state-of-the-art sentiment systems, therefore proving the effectiveness of our approach.

2018

Skinfolds compressibility and calliper's time response in male athletes

Autores
Bini, A; Amaral, TF; Oliveira, BMPM; Carvalho, P; Teixeira, VH;

Publicação
PROGRESS IN NUTRITION

Abstract
Introduction: The body skinfolds compressibility is an individual characteristic determined by tissues properties. Compressibility could affect the skinfold thicknesses inducing error in the assessment of subcutaneous adipose tissue and in the estimation of body composition. Objectives: This study aims to firstly describe the time behaviour of eight body skinfolds' physical response to the skinfold calliper pressure during measurement. Methods: Using a digital skinfold calliper that gathers 60 measurements per second, the dynamic response of height skinfolds to pressure was characterized in 36 adult male athletes. To assess the skinfolds compressibility, two points were defined L and H: the S-L corresponds to the lowest value within the 120 measurement the time when it was obtained was defined as T-L. The T-H corresponds to the first moment where the 110% of of the value S-L was measured. The equations of the average of each skinfold as a function of time were obtained from a non-linear fitting. Results: Skinfold compressibility varied according subjects (p< 0.05). Significant differences were found among skinfold sites within S-H, S-L, T-H and T-L, confirming that each skinfold compressibility is different from the other, even within a homogeneous study group. Biceps was the first skinfold to reach the minimum thickness value (T-L= 1.08 +/- 0.38s), while iliac crest was the last one (T-L= 1.63 +/- 0.27s). Given the very good fits that were obtained for all skinfolds (R-2 >= 0.997), it was postulated that the skinfold thickness y changes with time t according to the equation: y = y0 + a/(b + t(n)). Conclusions: Inter and intraindividual skinfolds' variation in compressibility was documented, supporting a reduction in protocolled time during evaluations.

2018

Experimental Evaluation of Resonant Tunnelling Diode Oscillators Employing Advanced Modulation Formats

Autores
Tavares, JS; Pessoa, LM; Salgado, HM;

Publicação
2018 20TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
The performance of Resonant Tunnelling Diode (RTD) oscillators with an optical window is evaluated experimentally, in the transmission of advanced modulation formats using electrical and optical modulation, for the first time. Additionally, the impact of phase noise in the transmission performance is also assessed.

2018

Microgrid protection schemes

Autores
Gomes, M; Coelho, P; Moreira, C;

Publicação
Microgrids Design and Implementation

Abstract
A microgrid embraces a low-voltage (LV) distribution grid with distributed energy resources (DER) and controllable loads. In the last years, there has been a growing awareness in exploiting microgrids to facilitate DER integration in electric power systems as well as to improve reliability and power quality in distribution grids. A microgrid can operate connected to the upstream medium voltage (MV) grid-utility grid-or islanded (disconnected from the MV grid) in a controlled and coordinated way. A major challenge associated with the implementation of microgrids is to design a suitable protection system scheme for different operating conditions. To overcome this challenge, different approaches have been proposed in the literature. The protection systems applied at microgrids must work both in utility grid faults and microgrid faults. Faults on the utility grid could lead to a protection response that isolates the microgrid from the utility grid as fast as required to keep the microgrid safety. On the other hand, faults in the own microgrid require the smallest sector removal of the microgrid to isolate the fault. Due to the presence of several DER in microgrids, the protection systems are also needed to cope with the bidirectional energy flows. Thus, the traditional protection devices (fuses and electromechanical switches) and standard solid-state relays are designed for selectivity purposes, making them inapt to ensure the protection of microgrids. These protection devices do not provide flexibility for setting the tripping characteristics neither the current direction sensitivity feature. Some problems related to protections sensitivity and selectivity arises when a microgrid is in islanded operation (DER generation). Thus, this new paradigm of distribution facilities requires a protection system based on microprocessor relaying and communications. Protecting microgrids in both modes (grid-connected and islanded) can be achieved by using different communication architectures associated with protections. Using centralized or distributed architectures means that the relay protection settings are modified centrally or locally regarding microgrid operating conditions. This chapter aims to provide the key highlights of the available protection schemes used to address microgrid protection issues.

2018

Joint capsule segmentation in ultrasound images of the metacarpophalangeal joint using a split and merge approach

Autores
Martins, N; Sultan, MS; Veiga, D; Ferreira, M; Coimbra, MT;

Publicação
BHI

Abstract
This work presents a new approach for the identification of the joint capsule in ultrasound images of the metacarpophalangeal joint. These images are used to diagnose rheumatic diseases which are one of the main causes of impairment and pain in developed countries. The early diagnosis of these conditions is crucial to a proper treatment and follow-up and so, this work contributes to the automatic extraction of relevant information from the resulting images. The algorithm uses the metacarpus, phalange and extensor tendon positions to create a region of interest. Next, a split and merge approach is used to identify the joint capsule, where the split is done using the Simple Linear Iterative Clustering algorithm and the merge is achieved with a special region growing with shape constraints. After that, the results are refined using a Localizing Active Contours method. Results shown that the segmentation is possible with 60% of the joint capsules identified with a Dice Coefficient higher than 0.7.

2018

Stay true, but innovate!

Autores
Mention, AL; Pinto Ferreira, JJ; Torkkeli, M;

Publicação
Journal of Innovation Management

Abstract
Were you ever asked by a manager to ‘do what you want’, where you felt free to innovate? Did it feel like freedom? Maybe you felt encouraged since you could now experiment your idea, but did it mean that your performance was now on the radar? Could you then stay true to your vision or did you feel the need to compromise so that the ‘numbers lined up’? Either way, you should know that you are not alone. Arguably, we are in an age of paradox1 where simultaneous contradic- tions are all too common. Innovation paradox arises when “the aggressive pursuit of operational excellence and incremental innovation crowds out the possibility of creating ground-breaking innovations” (Davila & Epstein, 2014, p.2). Often these contradictions are meaningful on their own merit but when interdependent on each other, they create tensions in economic, social, environmental and ethical decision-making. In previous editorials, we have shared how digital innovations and societal disparity across the world are influencing strategic decision-making and shifting the innovation mindset. We now stretch the boundaries by suggesting that paradigms relying on economic trade-offs and shared-value that have shaped conventional organisational strategies are no longer sufficient to guide paradoxical tensions in decision-making. (...)

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