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Centre of Technology and Systems
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Decomposition of a Petri Net-Based Cyber-Physical System toward Implementation as an Integrated System within FPGA
Publication . Wiśniewski, Remigiusz; Costa, Anikó; Wojnakowski, Marcin; Maliński, Maxim; CTS - Centro de Tecnologia e Sistemas; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; MDPI - Multidisciplinary Digital Publishing Institute
Featured Application: The proposed technique is strictly oriented on practical application. The decomposed Petri net-based cyber-physical system can be easily implemented within the integrated device such as FPGA. An exemplary decomposition of a real-life CPS—beverage production and distribution machine—is shown in the paper. The system is modelled by a Petri net, decomposed with the proposed technique, and finally implemented within an FPGA device. Decomposition is one of the commonly used techniques applied in the design of Petri net-based cyber-physical systems. Such an operation permits the splitting of the initial system into sequential components that can be further implemented as an integrated or distributed system. This paper is focused on the decomposition of the modelled CPS toward its further implementation as an integrated system, namely an FPGA device. The adequate decomposition method is presented and explained in detail. Moreover, the proposed idea is explained by the real-life example of the beverage production and distribution system. The results of the experiments are presented and discussed.
A Brief on Nano-Based Hydrogen Energy Transition
Publication . Lobo, Rui F. M.; CTS - Centro de Tecnologia e Sistemas; DF – Departamento de Física; MDPI - Multidisciplinary Digital Publishing Institute
Considering the clean, renewable, and ecologically friendly characteristics of hydrogen gas, as well as its high energy density, hydrogen energy is thought to be the most potent contender to locally replace fossil fuels. The creation of a sustainable energy system is currently one of the critical industrial challenges, and electrocatalytic hydrogen evolution associated with appropriate safe storage techniques are key strategies to implement systems based on hydrogen technologies. The recent progress made possible through nanotechnology incorporation, either in terms of innovative methods of hydrogen storage or production methods, is a guarantee of future breakthroughs in energy sustainability. This manuscript addresses concisely and originally the importance of including nanotechnology in both green electroproduction of hydrogen and hydrogen storage in solid media. This work is mainly focused on these issues and eventually intends to change beliefs that hydrogen technologies are being imposed only for reasons of sustainability and not for the intrinsic value of the technology itself. Moreover, nanophysics and nano-engineering have the potential to significantly change the paradigm of conventional hydrogen technologies.
Impacts of Generative Artificial Intelligence in Higher Education
Publication . Saúde, Sandra; Barros, João Paulo; Almeida, Inês; Centro Interdisciplinar de Ciências Sociais (CICS.NOVA - NOVA FCSH); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CTS - Centro de Tecnologia e Sistemas; MDPI - Multidisciplinary Digital Publishing Institute
In this paper, the effects of the rapid advancement of generative artificial intelligence (Gen AI) in higher education (HE) are discussed. A mixed exploratory research approach was employed to understand these impacts, combining analysis of current research trends and students’ perceptions of the effects of Gen AI tools in academia. Through bibliometric analysis and systematic literature review, 64 publications (indexed in the SCOPUS and Web of Science databases) were examined, highlighting Gen AI’s disruptive effect on the pedagogical aspects of HE. The impacts identified by the literature were compared with the perceptions held by computer science students of two different HE institutions (HEIs) on the topic. An exploratory study was developed based on the application of a questionnaire to a group of 112 students. The results suggest that while Gen AI can enhance academic work and learning feedback, it requires appropriate pedagogical support to foster critical, ethical, and digital literacy competencies. Students demonstrate awareness of both the risks and benefits associated with Gen AI in academic settings. The research concludes that failing to recognize and effectively use Gen AI in HE impedes educational progress and the adequate preparation of citizens and workers to think and act in an AI-mediated world.
Analog Flat-Level Circuit Synthesis With Genetic Algorithms
Publication . Campilho-Gomes, Miguel; Tavares, Rui; Goes, Joao; DEE - Departamento de Engenharia Electrotécnica e de Computadores; CTS - Centro de Tecnologia e Sistemas; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; Faculdade de Ciências e Tecnologia (FCT); Institute of Electrical and Electronics Engineers (IEEE)
This paper proposes new techniques for automatic simulation-based analog circuit synthesis using genetic algorithms. This is intended to contribute to the set of electronic design automation tools that use genetic algorithms in circuit synthesis, especially those that use the simulator-in-the-loop paradigm. In this study, a genetic algorithm was employed as the generation engine for analog circuits, and variable-length chromosomes were used to describe circuit topology. The entire process is carried out on a flat level (device level), i.e. using the transistor and other elementary devices (e.g. resistors) as the basic elementary blocks. Circuit synthesis is accomplished without any knowledge of previously defined topologies (or analog block cells). Three techniques are presented for analog circuit synthesis that are incorporated in the genetic algorithm, which contribute to its robustness, leading to better and faster results. These techniques can be summarized as follows: 1) adaptive probability of chromosome acceptance, 2) removal of redundant or useless components, and 3) segmented evolution. The automatic process starts with the circuit input and output specifications and proceeds with the evolution of both circuit topology and component sizing. The results shown in this paper include a 40 dB DC gain amplifier, which, when evaluated with SPECTRE/CADENCE 6.0, using a standard 130 nm technology, with a load capacitor of 10 pF, has a gain of 102 V/V, a GBW product of 70 MHz, and a figure of merit of 1436 MHz.pF/mW.
A Reconfigurable 1x2 Photonic Digital Switch Controlled by an Externally Induced Metasurface
Publication . Fantoni, Alessandro; Di Giamberardino, Paolo; CTS - Centro de Tecnologia e Sistemas; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; MDPI - Multidisciplinary Digital Publishing Institute
This work reports the design of a 1x2 photonic digital switch controlled by an electrically induced metasurface, configurated by a rectangular array of points where the refractive index is locally changed through the application of an external bias. The device is simulated using the Beam Propagation Method (BPM) and Finite Difference Time Domain (FDTD) algorithms and the structure under evaluation is an amorphous silicon 1x2 multimode interference (MMI), joined to an arrayed Metal Oxide Semiconductor (MOS) structure Al/SiNx/a-Si:H/ITO to be used in active-matrix pixel fashion to control the output of the switch. MMI couplers, based on self-imaging multimode waveguides, are very compact integrated optical components that can perform many different splitting and recombining functions. The input–output model has been defined using a machine learning approach; a high number of images have been generated through simulations, based on the beam propagation algorithm, obtaining a large dataset for an MMI structure under different activation maps of the MOS pixels. This dataset has been used for training and testing of a machine learning algorithm for the classification of the MMI configuration in terms of binary digital output for a 1x2 switch. Also, a statistical analysis has been produced, targeting the definition of the most incident-activated pixel for each switch operation. An optimal configuration is proposed and applied to demonstrate the operation of a digital cascaded switch. This proof of concept paves the way to a more complex device class, supporting the recent advances in programmable photonic integrated circuits.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDP/00066/2020