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- The effects of intrinsic spin of matter in relativistic cosmologyPublication . Luz, PauloWe discuss general solutions of the Einstein-Cartan theory sourced by a cosmological perfect fluid composed of particles with intrinsic spin. In the considered model, the metric tensor is described by a general FLRW solution, however, the Weyl tensor might not vanish. The coupling between the intrinsic spin and the Weyl tensor excludes spatially closed solutions, and the universe must either be flat or open. In the open case, it is shown that the magnetic part of the Weyl tensor verifies a wave equation, such that, in a dynamic universe, the intrinsic spin of matter leads to the generation and emission of gravitational waves. The properties of these waves are discussed, with an emphasis on their decay rate at late time. Lastly, we discuss that, in the considered cosmological model, the intrinsic spin of matter contributes to a positive accelerated expansion of the universe.
- Extended- Range Marine Unmanned Surface Vehicles for Border Surveillance MissionsPublication . Fernandes, J. F. P.; Branco, P. J. Costa; Marat-Mendes, R.; Póvoa, R.; Teodoro, P.; Neves, J.; Marques, H.; Pinheiro, P.; Afonso, P.; Serrano, D.; Assunção, M.This work focuses on the development of extended-range marine unmanned surface vehicles (USV) for border surveillance missions. USVs present many advantages for marine applications due to their energy-saving capabilities and lack of in-board pilot needs. Nevertheless, due to their small scales, USVs often present reduced mission ranges. In order to overcome this handicap, this work proposes the application of innovative energy management strategies to optimize the available energy during one mission. This solution is based on path and speed optimizations, taking into account the most probable weather and sea conditions, to define a mission plan. The proposed energy management optimization is supported by the USV simulation model. This model is calibrated and verified with two experimental tests: one in an indoor swimming pool and the other in an outdoor enclosed harbour. Applying the proposed optimization strategy results in energy savings between 10 and 35.9%, subject to the maximization of mission time. This work is carried out within the international project SEMS4USV, supported by Frontex.
- Real-time GPS indoor for USV tracking using lookup tablePublication . Vieira, Fábio; Teodoro, Pedro; Jorge, Pedro MendesThis study introduces an approach that utilizes Lookup Tables (LUT) to enable real-time tracking of an Unmanned Surface Vehicle (USV) in an indoor setting, using a fish-eye camera. The proposed method streamlines image processing and achieves O(1) complexity, significantly reducing application run time. The paper also outlines the process of calibrating the fish-eye camera to correct image distortion, computing the homography matrix for re-projection, and obtaining a virtual top view of the camera’s field of view. The paper provides a detailed explanation of the replacement of the undistortion and re-projection steps with the new LUT method. Experimental results demonstrate a significant enhancement in the process’s run time, making it feasible for real-time tracking, regardless of the image size.
- Instigating Maritime Studies via Rapid Prototyping and Robotics: A Case From the Smartboat InitiativePublication . Teodoro, Pedro; Marat-Mendes, R.; Assunção, Mário; Alves, Nuno; Sanguino, Beatriz; Gaspar, Henrique M.A case on rapid prototyping is presented in this work to exemplify the use of learn, make and share activities to promote maritime studies. SMARTBOAT is an initiative from the Escola Superior Náutica Infante D. Henrique, in Portugal, where students are invited to interact with computer-aided design modelling, additive manufacturing and programming. Such initiative is paramount to instigate and promote higher education studies in science, technology, engineering, art, and mathematics (STEAM). The initiative is presented and discussed, with its main steps and schemes. A step forward is later discussed by the ongoing collaboration with the Norwegian University of Science and Technology (NTNU, Norway), which intend to combine the Portuguese case with recent advancements in robotics and digital twin, such as remote operation via internet of things protocols and web-based tools. The work ends with a discussion on the results and future works on autonomous shipping, as well as a call for the development and sharing of similar initiatives.
- The impacts of higher education institutions on sustainable software developmentPublication . Chkoniya, Valentina; Batista, Maria Manuela Martins; Gonçalves, Fernando Cruz
- Accomplishing PROMISE, PROgrammable MIxed Signal ASIC Electronics FrameworkPublication . Berrojo, Luis; Veljkovic, Filip; Ayzac, Philippe; Maggioni-Mezzomo, Cecilia; Trouche, Christophe; Kakoulin, Michael; Franciscatto, Giancarlo; Berti, Laurent; Arslanov, Dmitry; Póvoa, Ricardo; Guilherme, Jorge; Roumkou, Anna; Tukkiniemi, KariThis paper presents the activities, current results and status of the PROMISE (PROgrammable MIxed Signal Electronics) project which started at the beginning of 2020 . The project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870358. It’s tailored to bring to the space community a flexible, cost competitive mixed-signal ASIC architecture design ecosystem built on a portfolio of silicon qualified hardened IP blocks. It includes analogue IPs such as ADC, DAC, PLL, LDO, BG, LO, POR and HV MOS transistors. A digital embedded FPGA core provides a flexible programmable element and an NVM permits reconfiguration abilities without the need of using an external memory. All these elements are included on the PILOT Circuit ASIC that will be submitted to electrical validation and radiation testing as part of the qualification process of these basic elements for their future use as building blocks.
- Radiation-Hardened Bandgap Voltage and Current Reference for Space Applications with 2.38 ppm/ºC Temperature CoefficientPublication . Lourenço, N.; Passos, F.; Vieira, R.; Horta, N.; Guilherme, J.; Póvoa, R.This paper describes a radiation-hardened bandgap voltage reference (BGR) for space applications. The BGR has a second-order curvature compensation and can deliver a stable output voltage and current for N-type and P-type loads through internal resistors or, optionally, through an external precision resistor. The circuit includes three 8-bit trimming resistive ladders for post-fabrication calibration of the temperature compensation slope, output voltage, and output current value. The circuit is designed for reliable performance in space application, considering process, voltage, and temperature variations and the impact of single-event transients and total ionizing dose. The BGR was designed in a 180 nm silicon-oninsulator CMOS technology, using radiation-hardened devices to provide a 1.25 V reference voltage and a 20 μA current reference, and occupies a 920×430 μm2 area. After trimming, the nominal post-layout simulation over the temperature range of -40 to 125°C shows the BGR achieving a 2.7 ppm/°C temperature coefficient, 6.13 ppm/°C in the worst case.
- Study on the Application of EfficientDet to Real-Time Classification of Infrared Images from Video SurveillancePublication . Mendes, Filipe; Fernades, Armando M.; Fernandes, Luis; Piedade, Fernando; Chaves, PauloThe monitoring of certain areas can be a tedious and non-interactive task that usually leads to some missed occurrences. With the development of object-detection models, this problem can be mitigated and reduced. In this paper, a rare application of EfficientDet model to the analysis of footage from an infrared camera in real-time is studied. The model will be used to detect deers, people and cars in images captured at the surroundings of a classified facility from where we do not yet have images available. Consequently, we show the process of creating the model and discuss the problems raised by the real-time performance limitations as well as by the available data limitations. The results obtained suggest that this kind of implementation has the potential to improve existing surveillance systems.
- Use of User Generated Content to Support the Creation of Smart Tourist DestinationsPublication . Sousa, M. C. P. Belchior; Fernandes, A. L.; Pequeno, V. M.The Covid-19 pandemic had an unprecedented impact on the tourism industry. It is believed that the recovery of the sector goes through a strong investment in technologies that allow creating and managing tourists' perception of the virtual image of tourist destinations. This article proposes a discussion about the relevance of User Generated Content (UGC) to reveal the virtual image of a tourist destination, in order to contribute to the creation of a Smart Tourism Destination (STD). The virtual image is studied from the perspective of the public transport system due to the fact that its improvement is one of the objectives of the Tourism of Portugal strategic plan for the creation of a STD in the decade 2017 - 2027. The methodology used was qualitative, through a bibliographical research, in which the key factors of this theme were addressed. After the study carried out it was concluded that the exploration of UGCs can allow managers and regulatory and tourism promoting entities to extract a lot of interesting information about how to take better advantage of the technologies adopted to create value for tourists.
- A Sub-1 µA Low-Power, LowNoise Amplifier with Tunable Gain and Bandwidth for EMG and EOG Biopotential SignalsPublication . Vieira, Rafael; Martins, Ricardo; Horta, Nuno; Lourenço, Nuno; Póvoa, RicardoThis paper presents the design of a low-power low-noise amplifier for biomedical and healthcare applications, focusing on lectromyography and electrooculography. The signals operate in different broad bands, yet follow an impulse-shape transmission, being suitable to be applied and detected by the same receiver. The biopotential sensing amplifiers usually have a major impact in power and noise performance of an analog front end; hence, the development of a low-noise amplifier with low-power consumption is of great importance. In this paper, the state-of-the-art amplifiers for biomedical applications are overviewed, and the proposed solution is presented. The proposed design has tunable cutoff frequency (FC) and gain, being adjustable for each type of signal. The circuit is designed in UMC 130 nm CMOS technology, supplied by 1.2 V, and consumes less than 1 μA. Post-layout simulation results show that, at the high FC of 2 kHz, the gain is 34 dB, presenting an input-referred noise of 1.476 μVrms corresponding to a noise efficiency factor (NEF) of 1.27. Whereas at the low FC of 20.91 Hz, the gain is 52.35 dB, the input-referred noise is 0.202 μVrms, and the NEF is 1.70.