2020
Authors
Martins, A; Almeida, C; Lima, P; Viegas, D; Silva, J; Almeida, JM; Almeida, C; Ramos, S; Silva, E;
Publication
GLOBAL OCEANS 2020: SINGAPORE - U.S. GULF COAST
Abstract
This paper presents an autonomous robotic system, IRIS, designed for lost fishing gear recovery. The vehicle was developed in the context of the NetTag project. This is a European Union project funded by EASME the Executive Agency for Small and Medium Enterprises addressing marine litter, and the reduction of quantity and impact of lost fishing gears in the ocean. NetTag intends to produce new technological devices for location and recovery of fishing gear and educational material about marine litter, raise awareness of fisheries industry and other stakeholders about the urgent need to combat marine litter and increase scientific knowledge on marine litter problematic, guaranteeing the engagement of fishers to adopt better practices to reduce and prevent marine litter derived from fisheries. The design of IRIS is presented in detail, addressing the mechanical design, hardware architecture, sensor system and navigation and control. Preliminary tests in tank and in controlled sea conditions are presented and ongoing developments on the recovery system are discussed.
2020
Authors
Pereira, J; Silva, FJG; Sá, JC; Bastos, JA;
Publication
Lecture Notes in Networks and Systems
Abstract
The automotive industry is one of the most demanding sectors of the global market. The response capacity and flexibility of companies represent a key factor for their success. Applying Six Sigma, it was carried out an improvement project aiming at reducing the quantity of scrap on the most critical sector of a automotive components’ manufacturer achieving a better comprehension of the flows, process characteristics and different variables associated to the scrap generation, identifying the equipment responsible for that scrap and its type. Brain- storming sessions were performed, as well as the application of 5 Why’s and 5W2H techniques in order to fulfill the Ishikawa diagrams aiming at understanding possible root-causes for the scrap generation. A definition of the improvement actions has been developed. A reduction of 15% was achieve just in the machine identified as the main generator of scrap in these processes. © 2020, Springer Nature Switzerland AG.
2020
Authors
da Silva, I; Jacobina, CB; de Freitas, IS; Sousa, RPR; Maia, ACN; de Freitas, NB;
Publication
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS
Abstract
In this article, two new unidirectional multilevel six-phase power rectifier topologies are proposed and investigated. Such topologies may be applied to ac-dc systems such as wind energy conversions systems, aerospace generator drives, telecommunications or any other application where regenerative operation is either not required or prohibited. The first topology is composed of two three-level neutral-point-clamped (NPC) converters connected to the open-end windings of a six-phase permanent magnet synchronous generator, and a three-phase noncontrolled diode bridge converter. The second topology is composed of three modified NPC converters with the substitution of two controlled switches by diodes in each leg. The use of a noncontrolled converter with diodes aims to reduce the controlled switches count, the system complexity, and the costs. However, it makes both systems nonreversible. The system models, operating principles, the space vector pulsewidth modulation strategies, the dc-links balance, and the control system to ensure the elimination of the zero-crossover distortion caused by the use of the diodes are presented. Due to the high number of levels generated, the systems are suitable for high power applications with voltage and current ratings restrictions. A study concerning harmonic distortion and semiconductor losses for both systems is performed, in order to be compared with a standard configuration. The feasibility of the system is demonstrated by simulation and experimental results.
2020
Authors
Ribeiro Robalinho, PMR; Gomes, AD; Frazao, O;
Publication
IEEE PHOTONICS TECHNOLOGY LETTERS
Abstract
In this letter, a strain sensor with high sensitivity enhancement using a special case of Vernier effect is presented. The sensor configuration is composed of two-fiber loop mirrors in a cascaded configuration with opposite strain responses when individually characterized. Thus, the enhanced Vernier effect is explored, which is the most sensitive of three possible cases Vernier effect. Here, the Vernier response depends on the difference between the sensitivities of each Hi-Bi optical fiber. In addition to this, the fundamental and the first harmonic were also explored. The results obtained are a strain sensitivity of (13.3 +/- 0.3) pm/mu epsilon for the carrier, (80.0 +/- 0.3) pm/mu epsilon or the Vernier envelope of the fundamental case and (120 +/- 1) pm/mu epsilon for the Vernier envelope of the first harmonic. The first harmonic could achieve a magnification factor of 8. Considering that the optical interrogation system allows a minimum resolution of 0.02 nm, the minimum measurement step achievable is 0.2 mu epsilon. This work proves the possibility of applying the concept of enhanced Vernier effect to fiber loop mirrors, obtaining higher sensitivity than a standard fiber loop mirror alone. Besides, the sensitivity can be increased through the usage of harmonics of the Vernier effect. Moreover, the use of large interferometers allows a better discretization of the envelope, which implies a greater ease of analysis.
2020
Authors
Teymourifar, A; Rodrigues, AM; Ferreira, JS;
Publication
Proceedings - 24th International Conference on Circuits, Systems, Communications and Computers, CSCC 2020
Abstract
This paper compares the non-dominated sorting genetic algorithm (NSGA-II) and NSGA-III to solve multiobjective sectorization problems (MO-SPs). We focus on the effects of the parameters of the algorithms on their performance and we use statistical experimental design to find more effective parameters. For this purpose, the analysis of variance (ANOVA), Taguchi design and response surface method (RSM) are used. The criterion of the comparison is the number of obtained nondominated solutions by the algorithms. The aim of the problem is to divide a region that contains distribution centres (DCs) and customers into smaller and balanced regions in terms of demands and distances, for which we generate benchmarks. The results show that the performance of algorithms improves with appropriate parameter definition. With the parameters defined based on the experiments, NSGA-III outperforms NSGA-II. © 2020 IEEE.
2020
Authors
Putnik, GD; Rodrigues, D; Alves, C; Avila, P; Castro, H; Cruz Cunha, MM;
Publication
FME TRANSACTIONS
Abstract
Various companies choose to outsource the delivery of part of their services, so as not to deviate from its core business and improve the service level. This approach leads to a new type of organizations, so-called networked and virtual enterprises, where possibly a great number of companies work together without having direct contact but through a broker, as an intermediary, that streamlines the relationships between them. To enable high level efficiency, as well as some other functional requirements, the meta-organizations and brokering services are conceived as environments and services for networked and virtual enterprises operation and dynamic reconfigurations, representing a model of organizations-of-organizations, as an implementation of one of the Industry 4.0 models and ecosystem for networked and virtual enterprises dynamic reconfiguration. In this paper, the meta-organizations with embedded brokering services, modelled as call centres, are analyzed. Various simulations are presented, based on Erlangs formulas for some of design and performance measures parameters evaluation, such as service level, average waiting time, agent occupancy and service traffic intensity.
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