2014
Autores
Barros, A; Pinho, LM;
Publicação
ARCS
Abstract
Recent embedded processor architectures containing multiple heterogeneous cores and non-coherent caches, bring renewed attention to the use of Software Transactional Memory (STM) as a building block for developing parallel applications. STM promises to ease concurrent and parallel software development, but relies on the possibility of abort conflicting transactions to maintain data consistency, which affects the execution time of tasks carrying transactions. Thus, execution time overheads resulting from aborts must be limited, otherwise the timing behaviour of the task set will not be predictable. In this paper we formalise a FIFO-based algorithm to order the sequence of commits of concurrent transactions. Furthermore, we propose and evaluate two non-preemptive scheduling strategies, in order to avoid transaction starvation. © 2014 Springer International Publishing Switzerland.
2014
Autores
Delaere, S; Goncalves, V; Marques, P;
Publicação
2014 IEEE Globecom Workshops, GC Wkshps 2014
Abstract
This paper investigates the gap between research into Dynamic Spectrum Access (DSA), and the standardization of these technologies, as well as ways in which coordination of standardization activities between EU funded research projects might help bridge this gap. Concretely, it first discusses the current state of standardization in CR and DSA, as well as the need for a coordinated approach to DSA standardization among European projects. It subsequently provides a short overview of the DSA and CR research landscape in Europe and briefly describes the objectives of the Cognitive Radio Standardization Initiative (CRS-i). The following sections on the paper then focus on a survey which was conducted among the 26 currently funded, Radio Access and Spectrum related EU projects, with specific analysis also performed for the CR and DSA related sub-cluster of projects. This survey provides insight into projects' current standardization activities and collaboration methods, as well as opportunities and bottlenecks for collaboration in standardization. The paper concludes that the coordination of standardization efforts, as well as specific instruments to enable the standardization of research results beyond the project lifetime, are desirable if Europe is to play a role in the global standardization of CR and DSA. Based on the survey and on close interactions with RAS cluster projects, the paper finally proposes a number of concrete coordination trajectories. © 2014 IEEE.
2014
Autores
Ribeiro, J; Carmona, J; Misir, M; Sebag, M;
Publicação
Business Process Management - 12th International Conference, BPM 2014, Haifa, Israel, September 7-11, 2014. Proceedings
Abstract
Over the last decade, several algorithms for process discovery and process conformance have been proposed. Still, it is well-accepted that there is no dominant algorithm in any of these two disciplines, and then it is often difficult to apply them successfully. Most of these algorithms need a close-to expert knowledge in order to be applied satisfactorily. In this paper, we present a recommender system that uses portfolio-based algorithm selection strategies to face the following problems: to find the best discovery algorithm for the data at hand, and to allow bridging the gap between general users and process mining algorithms. Experiments performed with the developed tool witness the usefulness of the approach for a variety of instances. © 2014 Springer International Publishing Switzerland.
2014
Autores
Oliveira, JMB; Pessoa, LM; Coelho, D; Tavares, JS; Salgado, HM;
Publicação
2014 16TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)
Abstract
In this paper we present a comprehensive analysis and a performance assessment on the transmission of digitised RF signals over optical fibre (DRoF). Specifically, a study of the impact of the ADC/DAC quantization, jitter noise and the signal attenuation caused by the sub-sampling technique and DAC frequency roll-off are addressed by means of simulation, considering the transmission of RF signals conveying QAM symbols. Additionally, an experimental evaluation of DRoF links using vertical-cavity surface-emitting lasers (VCSEL) for different optical fibre attenuation levels is also conducted. Finally, a new paradigm of DRoF systems based on well-known sigma-delta modulators (SDM) is also presented. Results show that it is possible to digitally transmit signals through a digital optical-based network and to distribute them wirelessly at the receiver side without the need for local oscillators (LO) and/or frequency up-converters. Results also show that the new sigma-delta-over-fibre concept performs similarly to conventional DRoF schemes, whilst being more competitive for either upgrading installed systems as well as for new deployments.
2014
Autores
Guimaraes, D; Santos, JP; Carvalho, ML; Diniz, MS; House, B; Miller, VM;
Publicação
NEUROTOXICOLOGY
Abstract
Lead is a potent toxicant associated with adverse cardiovascular effects and hypertension in children. Yet, few studies have determined if autonomic dysfunction associated with lead exposure involves brain regions which regulate autonomic responses. Central autonomic nuclei such as the nucleus tractus solitarius (NTS) and hypothalamic defence area (HDA) may be particularly sensitive to lead infiltration because they are adjacent to ventricles and areas with semi-permeable blood-brain-barriers. To understand if autonomic nuclei are sensitive to lead accumulation Wistar rats were exposed to lead from the gestational period and lead levels were quantified in brain regions that regulate arterial pressure: the NTS and the HDA. Energy dispersive X-ray fluorescence (EDXRF) was used to quantify total brain lead levels and revealed no differences between exposed and control tissues; measured values were close to the detection limit (2 mu g/g). Electrothermal atomic absorption spectrometry (ETAAS) was also used, which has a greater sensitivity, to quantify lead. There was similar to 2.1 mu g/g lead in the NTS and similar to 3.1 mu g/g lead in the HDA of exposed rats, and no lead in the control rats. There were greater lead levels in the HDA (similar to 50%) as compared with the NTS. Pathology studies revealed more prominent lead granules in the HDA as compared with the NTS. Increased microglia and astrocyte activation was also noted in the NTS of lead exposed rats as compared with the HDA. Regional differences in neuro-inflammatory responses likely contribute to heterogeneous lead accumulation, with enhanced clearance of lead in the NTS. Future studies will resolve the mechanisms underpinning tissue-specific lead accumulation.
2014
Autores
Trigueiros, P; Ribeiro, F; Reis, LP;
Publicação
RoboCup 2013: Robot World Cup XVII
Abstract
In RoboCup Middle Size league (MSL) the main referee uses assisting technology, controlled by a second referee, to support him, in particular for conveying referee decisions for robot players with the help of a wireless communication system. In this paper a vision-based system is introduced, able to interpret dynamic and static gestures of the referee, thus eliminating the need for a second one. The referee's gestures are interpreted by the system and sent directly to the Referee Box, which sends the proper commands to the robots. The system is divided into four modules: a real time hand tracking and feature extraction, a SVM (Support Vector Machine) for static hand posture identification, an HMM (Hidden Markov Model) for dynamic unistroke hand gesture recognition, and a FSM (Finite State Machine) to control the various system states transitions. The experimental results showed that the system works very reliably, being able to recognize the combination of gestures and hand postures in real-time. For the hand posture recognition, with the SVM model trained with the selected features, an accuracy of 98,2% was achieved. Also, the system has many advantages over the current implemented one, like avoiding the necessity of a second referee, working on noisy environments, working on wireless jammed situations. This system is easy to implement and train and may be an inexpensive solution.
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