Browsing by Issue Date, starting with "2018-11-01"
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- Three-phase multilevel inverter for grid-connected distributed photovoltaic systems based in three three-phase two-level invertersPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, D.; Silva, J. FernandoA multilevel three-phase voltage source inverter (VSI) for distributed grid-connected photovoltaic system is proposed in this paper. This multilevel inverter is based on a new topology using three three-phase two-level VSIs ((TVSI)-V-3) with isolation transformer. The photovoltaic panels are connected at the DC side of each three-phase VSI. The three-phase VSIs AC sides are connected to the three-phase isolation transformer with primary open-end windings, ensuring multilevel operation. The (TVSI)-V-3 can be modulated using existing multilevel Pulse Width Modulation (PWM) schemes. A control system designed to ensure the transfer of the energy generated by the PV generators to the grid is also presented, together with a Phase Disposition PWM (PDPWM) adapted for the multilevel (TVSI)-V-3. Tests of the grid-connected PV multilevel (TVSI)-V-3 will be shown through simulation and experimental results. Several results obtained from experiments confirm the expected characteristics of the multilevel (TVSI)-V-3 photovoltaic system.
- Robust control of a Thermal Unstable PDE systemPublication . Igreja, José; Lemos, João M.Some distributed parameter systems with irrational transfer function can be written into an infinite factorized quotient for dynamic analysis and control design purposes. Hence, high accuracy approximate time solutions and frequency uncertainty bounds can be computed exactly, enabling early lumping in robust controller design. In this paper the focus is on finding a block factorization for a thermal unstable solid propellant rocket model, and design a near optimal robust finite dimensional controller.
- Application of the Mott-Schottky model to select potentials for EIS studies on electrodes for electrochemical charge storagePublication . Adan-Mas, Alberto; Moura E Silva, Teresa; Guerlou-Demourgues, Liliane; MONTEMOR, MARIAElectrochemical Impedance Spectroscopy (EIS) is a powerful technique to understand the electrode-electrolyte interaction and to evaluate degradation, resistive behaviour and electrochemical activity of energy storage materials used in batteries, pseudocapacitors and supercapacitors among others. However, it can sometimes be misused or under-interpreted. To effectively acquire EIS results, the voltages imposed to the working electrode at which EIS spectra are obtained, shall be critically selected. This work follows a previous study on the EIS response of Nickel-Cobalt hydroxide, and highlights how the Mott-Schottky model can be used as a complementary tool to explain EIS results obtained at different potentials. The Mott-Schottky model is used to understand further the fundamental processes occurring at the electrode-electrolyte interface of nickel-cobalt hydroxide in alkali media and to explain the changes in conductivity of the material that ultimately determine the electrode electrochemical activity. The applicability of the model to assist in the potential selection for EIS studies on other important charge storage materials such as MnOx and MoOx is discussed too.
- The news among youngsters: a journalistic literacy projectPublication . Bonacho, Fernanda; Alpuim, MargaridaThe main objective of this poster is to present the first findings of the project TJAME – Transliteracia Jornalística: até que o mundo fique tal como é (Journalitic Transliteracy: until the world becomes itself). Developed between March and May of 2018, the pilot experience was part of a new journalistic literacy research plan hosted at ESCS/Lisbon Polytechnic Institute. Counting with researchers and professionals with a solid experience in the field of journalism and communication sciences, TJAME focused on journalistic literacy among youngsters finishing their high school and journalism undergraduate studies. The working period included a wide range of immersive journalistic practices for more than 50 students from the area of Lisbon. The poster will tell the story of this literacy project, standing out the facts and numbers of the experience, the differences between participants' expectations and practices, wishing to trigger a different journalistic literacy debate based on clear awareness.
- What about the news? A journalistic transliteracy projectPublication . Bonacho, Fernanda; Mata, Maria J.; Sena Santos, FranciscoThe main objective of this roundtable is to enhance the importance of journalism transliteracy in today's world and present the first conclusions of a pilot experience, which is part of the The project TJAME – Transliteracia Jornalística: até que o mundo fique tal como é (Journalitic Transliteracy: until the world becomes itself), developed between March and May of 2018, in Escola Superior de Comunicação Social (School of Communication and Media Studies). This experience included a wide range of planned activities, monitored by professors and journalists, and participated by undergraduate journalism students and high school students from the area of L isbon. TJAME established as its strategic agenda for 2017-2018 the issue of journalistic literacy among those students finishing their general high school studies and journalism students finishing their undergraduate studies. The roundtable aims to stand out the ground-breaking findings of this experience, which triggered an agenda in weekly sessions, which included collaborative work between university and high school students throughout multimedia and press laboratories work, debates prompted by news and movies, press reviews meetings, planned visits to RTP (Rádio e Televisão de Portugal – the national broadcasting radio and television network) and Lusa (the national news agency), among others. Meanwhile, during this ten weeks' time, participants have simultaneously been creating a news piece to be published in the online university newspaper platform, and all processes have been monitored and analysed by researchers through participant observation, enquiries and interviews. Thus, the roundtable will also comment all key issues related to observed processes and we will try to demonstrate how important it is to open original and creative ground to discuss the importance of transliteracy news through the eyes of our young contemporary generation.