Browsing by Issue Date, starting with "2021-05-19"
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- As Redes Sociais como plataforma para os outsiders políticos: Uma investigação empírica sobre os três novos partidos na Assembleia da República com a XIV legislaturaPublication . Lopes, Rafael Humberto Pinheiro; Pereira, Sandra Cristina MartinsO presente trabalho de investigação procura entender qual o papel que a comunicação digital poderá ter representado na emergência de novos partidos políticos, no âmbito do recente processo eleitoral que em 2019 levou três organizações políticas de curta história a obter assento na Assembleia da República Portuguesa na mesma legislatura. Enquadrando esta temática no campo disciplinar das Relações Públicas na Política, procura-se apurar a aplicação de princípios e de objetivos de RP nas práticas destas entidades, que se prendem com a gestão de relacionamentos mutuamente benéficos e o recurso a ferramentas digitais como uma ponte de compreensão e colaboração entre uma organização política e os seus stakeholders. Com a massificação do uso da internet e das redes sociais, cabe às Relações Públicas apurarem quais as melhores práticas no uso das tecnologias de informação e comunicação aplicadas à esfera política. Esta temática prende-se ainda com a necessidade de desenvolvimento e consolidação conceptual da disciplina das RP na Política e da monitorização de outcomes no âmbito da comunicação digital. A metodologia seguida tem um caráter misto assente na condução de entrevistas semi estruturadas aos assessores de comunicação dos partidos e uma análise quantitativa das suas publicações na rede social Facebook durante o período de campanha eleitoral antecedente às eleições legislativas de 2019.
- Backstepping predictive control of hybrid microgrids interconnected by neutral point clamped convertersPublication . Barros, J. Dionísio; Rocha, Luis Lamy; Silva, J. FernandoIn this work, DC and AC parts of hybrid microgrids are interconnected by a neutral point clamped-NPC converter controlled using a new backstepping predictive (BP) method. The NPC converter is controlled to operate in the DC microgrid voltage control mode or in the AC microgrid power control mode. The novel backstepping predictive controller is designed using the dq state space dynamic model of the NPC converter connected to the hybrid microgrid. The designed BP controller regulates the DC voltage or AC injected power, balances the capacitor voltages, controls the AC currents, and enforces the near unity power factor. Simulation (MATLAB/Simulink) and experimental (laboratory prototype) results show that the converter can regulate the DC voltage in the DC microgrid interconnection point, by adjusting the AC power conversion to compensate variations on the loads or on the distributed renewable energy sources in the DC microgrid. AC currents are sinusoidal with low harmonic distortion. The obtained BP controller is faster at balancing capacitor voltages than PWM (pulse width modulation) control with carrier offset. The fast AC power response allows the converter to be used as a primary frequency regulator of the AC microgrid. This research is appropriate for power and voltage control in hybrid microgrids with renewable energy.
- A full featured configurable accelerator for object detection with YOLOPublication . Pestana, Daniel; Miranda, Pedro R.; Lopes, João D.; Duarte, Rui; Véstias, Mário; Neto, Horácio C; De Sousa, JoseObject detection and classification is an essential task of computer vision. A very efficient algorithm for detection and classification is YOLO (You Look Only Once). We consider hardware architectures to run YOLO in real-time on embedded platforms. Designing a new dedicated accelerator for each new version of YOLO is not feasible given the fast delivery of new versions. This work's primary goal is to design a configurable and scalable core for creating specific object detection and classification systems based on YOLO, targeting embedded platforms. The core accelerates the execution of all the algorithm steps, including pre-processing, model inference and post-processing. It considers a fixed-point format, linearised activation functions, batch-normalisation, folding, and a hardware structure that exploits most of the available parallelism in CNN processing. The proposed core is configured for real-time execution of YOLOv3-Tiny and YOLOv4-Tiny, integrated into a RISC-V-based system-on-chip architecture and prototyped in an UltraScale XCKU040 FPGA (Field Programmable Gate Array). The solution achieves a performance of 32 and 31 frames per second for YOLOv3-Tiny and YOLOv4-Tiny, respectively, with a 16-bit fixed-point format. Compared to previous proposals, it improves the frame rate at a higher performance efficiency. The performance, area efficiency and configurability of the proposed core enable the fast development of real-time YOLO-based object detectors on embedded systems.
- Planning of aircraft fleet maintenance teamsPublication . Pereira, Duarte P.; Gomes, Isaías; Melício, Rui; Mendes, VictorThis paper addresses a support information system for the planning of aircraft mainte nance teams, assisting maintenance managers in delivering an aircraft on time. The developed planning of aircraft maintenance teams is a computer application based on a mathematical pro gramming problem written as a minimization one. The initial decision variables are positive inte ger variables specifying the allocation of available technicians by skills to maintenance teams. The objective function is a nonlinear function balancing the time spent and costs incurred with aircraft fleet maintenance. The data involve technicians’ skills, hours of work to perform maintenance tasks, costs related to facilities, and the aircraft downtime cost. The realism of this planning entails random possibilities associated with maintenance workload data, and the inference by a procedure of Monte Carlo simulation provides a proper set of workloads, instead of going through all the possibilities. The based formalization is a nonlinear integer programming problem, converted into an equivalent pure linear integer programming problem, using a transformation from initial posi tive integer variables to Boolean ones. A case study addresses the use of this support information system to plan a team for aircraft maintenance of three lines under the uncertainty of workloads, and a discussion of results shows the serviceableness of the proposed support information system.