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Publicações

2014

Analysis of FLOSS Communities as Learning Contexts

Autores
Fernandes, S; Cerone, A; Barbosa, LS;

Publicação
SOFTWARE ENGINEERING AND FORMAL METHODS

Abstract
It can be argued that participating in Free/Libre Open Source Software (FLOSS) projects can have a positive effect in the contributor's learning process. The need to collaborate with other contributors and to contribute to a project can motivate and implicitly foster learning. In order to validate such statements, it is necessary to (1) study the interactions between FLOSS projects' participants, and (2) explore the didactical value of participating in FLOSS projects, designing an appropriate questionnaire asking FLOSS contributors about their experience in FLOSS projects. In this paper, we illustrate how this questionnaire was designed and disseminated. We conclude the paper with results from 27 FLOSS projects contributors, determining that, not only they contribute and collaborate to the project and its community, but also that FLOSS contributors see that this type of activity can be regarded as a complement to formal education.

2014

Enhancing the performance of quota managed fisheries using seasonality information: The case of the Portuguese artisanal dredge fleet

Autores
Oliveira, MM; Camanho, AS; Gaspar, MB;

Publicação
MARINE POLICY

Abstract
Several fisheries across the world are managed by a quota regime. These quotas can be set yearly, monthly, weekly or daily. However, for some fish species demand seasonality may occur, which should be taken into consideration in the establishment of the quota (especially in those fisheries managed by daily or monthly quotas). This would allow fishermen to catch more fish at times of the year with higher demand in detriment of periods when demand is low. The present work investigates the existence of demand seasonality for bivalves from the artisanal dredge fleet. This fleet operates along the entire coast of the Portugal mainland. The analysis of fleets' revenue efficiency is assessed with Data Envelopment Analysis models, and the monthly seasonality effects on the revenue efficiency were tested using a Tobit regression. The results revealed that on the South coast there is a strong demand in the summer whereas on the western coast (northwest and southwest fishing areas) demand increases during Christmas and New Year festivities. Since this fishery is managed by weekly/daily quotas, it is proposed that these quotas should be redistributed in order to adjust them to periods of higher demand, thereby increasing the profitability of the vessels. The approach followed could be applied to similar fisheries worldwide.

2014

Outlier Detection in 802.11 Wireless Access Points Using Hidden Markov Models

Autores
Allahdadi, A; Morla, R; Cardoso, JS;

Publicação
2014 7TH IFIP WIRELESS AND MOBILE NETWORKING CONFERENCE (WMNC)

Abstract
In 802.11 Wireless Networks, detecting faulty equipment, poor radio conditions, and changes in user behavior through anomaly detection techniques is of great importance in network management. The traffic load and user movement on different access points (APs) in a wireless covered area vary with time, making these network management tasks harder. We intend to inspect the evolving structure of wireless networks and their inherent dynamics in order to provide models for anomaly detection. For this purpose we explore the temporal usage behavior of the network by applying various types of Hidden Markov Models. We observe the usage pattern of up to 100 APs in one week period in 2011 at the Faculty of Engineering of the University of Porto. The first step of this study consists of constructing various Hidden Markov Models from 802.11 AP usage data. We then apply statistical techniques for outlier detection and justify the presented outliers by inspecting the models' parameters and a set of HMM indicators. We finally introduce examples of wireless networks anomalous patterns based on the transitions between HMM states and provide an analysis of the entire set of APs under study.

2014

Syncopation as Transformation

Autores
Sioros, G; Guedes, C;

Publicação
SOUND, MUSIC, AND MOTION

Abstract
Syncopation is a rhythmic phenomenon present in various musical styles and cultures. We present here a set of simple rhythmic transformations that can serve as a formalized model for syncopation. The transformations are based on fundamental features of the musical meter and syncopation, as seen from a cognitive and a musical perspective. Based on this model, rhythmic patterns can be organized in tree structures where patterns are interconnected through simple transformations. A Max4Live device is presented as a creative application of the model. It manipulates the syncopation of midi "clips" by automatically de-syncopating and syncopating the midi notes.

2014

Guaranteeing replica determinism on IEC 61499

Autores
De Sousa, M;

Publicação
19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014

Abstract
Being distributed in nature, IEC 61499 industrial control applications are subject to partial failures. Building applications that are tolerant of these failures (i.e. a fault-tolerant application) may be achieved through the use of replication. In this paper we present a framework to support replicated IEC 61499 applications, and study how replica determinism may be achieved in this framework. © 2014 IEEE.

2014

Connectivity patterns of pallidal DBS electrodes in focal dystonia: A diffusion tensor tractography study

Autores
Rozanski, VE; Vollmar, C; Cunha, JP; Neves Tafula, SMN; Ahmadi, SA; Patzig, M; Mehrkens, JH; Boetzel, K;

Publicação
NEUROIMAGE

Abstract
Deep brain stimulation (DBS) of the internal pallidal segment (GPi: globus pallidus internus) is gold standard treatment for medically intractable dystonia, but detailed knowledge of mechanisms of action is still not available. There is evidence that stimulation of ventral and dorsal GPi produces opposite motor effects. The aim of this study was to analyse connectivity profiles of ventral and dorsal GPi. Probabilistic tractography was initiated from DBS electrode contacts in 8 patients with focal dystonia and connectivity patterns compared. We found a considerable difference in anterior-posterior distribution of fibres along the mesial cortical sensorimotor areas between the ventral and dorsal GPi connectivity. This finding of distinct GPi connectivity profiles further confirms the clinical evidence that the ventral and dorsal GPi belong to different functional and anatomic motor subsystems. Their involvement could play an important role in promoting clinical DBS effects in dystonia.

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