ENIDH – EEM - Engenharia Eletrotécnica Marítima
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- A 1.1 µA voltage reference circuit with high PSRR and temperature compensationPublication . Pereira, M. Silva; Costa, João E. N.; Santos, M.; Vaz, J. CaldinhasThis paper presents a low-power and a low output voltage CMOS Bandgap Reference Generator topology with high PSRR and a novel temperature curvature compensation method. The proposed design was implemented in a standard 0.13 μm CMOS process. The main circuit is based in an opamp based β-multiplier bandgap circuit with resistive division. The compensation method cancels out up to 2nd order non-linear terms of the BJT voltage by using the MOSFET leakage current effect. The performance of the circuit was verified by post-layout simulations. Simulated results have shown temperature coefficients as low as -4.4 ppm/°C over a temperature range of 140°C (-40°C to 100°C). In addition the circuit demonstrated a PSSR of -100 dB at low frequencies and -73 dB at 1 MHz. The current consumption is 1.1 μA at 27°C.
- Advanced sensing and information technologies for timely artefact diagnosisPublication . Chaves Ferreira, Paulo; Utkin, Andrei Borissovitch; Argyriou, Lemonia; Bexiga, Vasco; Boldrighini, Francesca; Cantoro, Gianluca; Drygiannakis, Myronas; Giapitsoglou, Kostas; Governatori, Giulia; Manataki, Meropi; Marsella, Stefano; Marzoli, Marcello; Oikonomou, Dimitris; Papadopoylos, Nikos G.; Santamaria, Ulderico; Sarris, Apostolos; Tzigounaki, Anastasia; Uckan, Eren; Vlachakis, Georgios; Williamson, Robert James; Akbas, Bulent; Cakir, Ferit
- Análise Qualitativa e Quantitativa do Cluster do Mar PortuguêsPublication . Simões, Abel; Ferreira, Ana Maria; Salvador, Regina; Soares, Carlos GuedesReconhecendo-se a importância de um Cluster do Mar para Portugal, procura-se identificar e analisar as principais relações intersetoriais que se processam no seu interior. Assim, na primeira parte é feita uma análise de carácter mais qualitativo, através da aplicação de inquéritos a empresas de transporte marítimo, estaleiros navais, portos, associações empresariais e instituições de ensino e investigação. Na segunda parte, utilizando a análise de input-output procede-se à quantificação das ligações existentes entre setores do Cluster marítimo português, ao cálculo dos coeficientes de interdependência e apresentam-se alguns dos efeitos multiplicadores das atividades marítimas. Algumas debilidades estruturais, que são comuns a outras áreas, como sejam a fraca cooperação e competição entre setores económicos e incipientes relações intersetoriais, refletem-se ao nível deste Cluster como uma das suas principais fragilidades, a ponto de comprometer o reconhecimento da sua existência na economia marítima nacional.
- Analysis and Design of Current Mode Class-D Power Amplifiers With Finite Feeding InductorsPublication . Silva-Pereira, M.; Assunção, Mário; Vaz, João CaldinhasCurrent-mode class-D (CMCD) power amplifiers (PAs) may not achieve a switching efficiency as good as class-E PAs, but they require fewer inductances and deliver almost five times more power for the same load and supply voltage when compared with the ideal push–pull class-E PA. Furthermore, CMCD PAs can easily use bondwires as the only circuit inductors, a precious feature that Internet-of-Things (IoT) wireless interfaces can exploit. For this reason, we analyze the voltage and current waveforms in CMCD PAs without assuming infinite value feeding inductors (i.e., without choke inductors). It is shown that the current stress on the switching device is significantly higher than in the conventional topology, especially in bondwire-based designs where relatively small feeding induc tances are presented. Finally, we propose a design procedure for a given feeding inductance that maximizes energy efficiency while delivering a compact-size solution. A 2.4-GHz PA capable of delivering 19.8 dBm to a 100-Ω differential load with a power added-efficiency (PAE) of 58% is presented. Three-dimensional electromagnetic (3-D EM) simulations combined with postlayout simulations were used to evaluate the PA performance in a quad-flat nonlead (QFN)-type package. The circuit is designed in a 0.13-μm process and only occupies a silicon area of 0.025 mm2.
- Buckling and nonlinear response of functionally graded plates under thermo-mechanical loadingPublication . Moita, José S.; Araújo, Aurélio L.; Correia, Victor Franco; Soares, C. M. Mota; Herskovits, Josén this work, a formulation for buckling and geometrically nonlinear analysis of functionally graded plates under thermo-mechanical loading is presented. The influence of high temperature environment on deflections due to mechanical loading as well the deflections produced by thermal loads acting alone or combined with mechanical loads is analysed. The implemented finite element model is based on a non-conforming triangular flat plate/shell element, with three nodes and eight degrees of freedom per node, associated with a higher order shear deformation theory. The solutions of some illustrative examples are evaluated involving the variation of volume fractions of constituent materials, temperature range and material combinations, which have significant impact on the deflections of plates. The numerical results obtained with the present model are presented and compared with alternative solutions.
- Coefficient of Voltage Energy EfficiencyPublication . Gnaciński, P.; Mindykowski, J.; Pepliński, M.; Tarasiuk, T.; Costa, J. D.; Assunção, M.; Silveira, L.; Zakharchenko, V.; Drankova, A.; Mukha, M.; Xu, XThe reduction of greenhouse gas emissions is a major contemporary challenge. This has prompted the requirements concerning energy efficiency for ships, among other things. Improvement in eficiency of ship operations could be achieved by reducing unnecessary power consumption by induction motors. Specifically, the occurrence of power quality disturbances, such as frequency and voltage deviations, voltage unbalances, and voltage harmonics, can cause an extraordinary increase in the power losses occurring in induction motors, as well as an unnecessary increase in the output power. Furthermore, excessive power quality disturbances are often interconnected with failures of on-board equipment, and in extreme cases, these may even pose a threat to safety at sea. Consequently, strict power quality monitoring of on-board microgrids can also contribute to improving safety while afloat. In this study, a dedicated tool for power quality monitoring is proposed, namely the coeficient of voltage energy efficiency, which has a value proportional to the power losses occurring in induction motors under power quality disturbances.
- Computing Repairs from Active Integrity ConstraintsPublication . Cruz-Filipe, L.; Engrácia, P.; Nunes, I.; Gaspar, G.Repairing an inconsistent knowledge base is a well known problem for which several solutions have been proposed and implemented in the past. In this paper, we start by looking at databases with active integrity constraints - consistency requirements that also indicate how the database should be updated when they are not met - as introduced by Caroprese et al.We show that the different kinds of repairs considered by those authors can be effectively computed by searching for leaves of specific kinds of trees. Although these computations are in general not very efficient (deciding the existence of a repair for a given database with active integrity constraints is NP-complete), on average the algorithms we present make significant reductions on the number of nodes in the search tree. Finally, these algorithms also give an operational characterization of different kinds of repairs that can be used when we extend the concept of active integrity constraints to the more general setting of knowledge bases.
- DeepPlacer: A Custom Integrated OpAmp Placement Tool using Deep ModelsPublication . Gusmão, António; Póvoa, Ricardo; Horta, Nuno; Lourenço, Nuno; Martins, RicardoMechanisms towards the automatic analog integrated circuit layout design have been an intensive research topic in the past few decades. Still, the industrial environment has no automatic approach established. The advances of machine learning applications in electronic design automation come with the promise to change this reality. This paper proposes a deep learning generative model for the placement ‘‘optimization’’ of analog integrated circuit basic blocks. The model behaves as an argmin operator for the placement cost function and can provide placement solutions instantly. Moreover, the model can be fed with unlabeled data, greatly facilitating data collection. A generic and innovative circuits’ representation at the network’s input layer is proposed, encoding the devices’ dimensions, connectivity, and topological constraints. Besides, the randomness found in generative models is embedded directly into the feature vector, as the order of the features per device is shuffled in the input vector. Shuffling the order of the devices’ features in the input not only brings multi-modality but also solves a generalization problem, as there is not any natural order defined to place devices in the feature vector. As a proof of concept, a deep artificial neural network capable of proposing different placement solutions, in less than 150 ms each, for six amplifier topologies and, in multiple technology nodes ranging from 350 nm down to 65 nm, is demonstrated. DeepPlacer was capable of producing correct solutions for topologies and technology nodes not present in the training set, showing good generalization while not hindering circuit performance due to the placement
- Desafios actuais e futuros para o ensino náuticoPublication . Costa, José Dores
- Description logics, rules and multi‐context systemsPublication . L. Cruz‐Filipe, l.; Henriques, R.; Nunes, I.The combination of rules and ontologies has been a fertile topic of research in the last years, with the proposal of several different systems that achieve this goal. In this paper, we look at two of these formalisms, Mdl-programs and multi-context systems, which address different aspects of this combination, and include different, incomparable programming constructs. Despite this, we show that every Mdl-program can be transformed in a multi-context system, and this transformation relates the different semantics for each paradigm in a natural way. As an application, we show how a set of design patterns for multi-context systems can be obtained from previous work on Mdl-programs.