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Browsing by Issue Date, starting with "2023-05-10"

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  • Valorisation of Leather Wastes from the Footwear Industry via Pyrolysis: Product Yields and Characterisation
    Publication . Silva, F.; Direito, D.; Pilão, R.; Ribeiro, A.M.; Silva, Felipe; Direito, Daniel; Pilão, Rosa Maria; Ribeiro, Albina
    The footwear industry, although contributing positively to the Portuguese economy, generates a lot of residues including chromium tanned leather wastes. This study presents results on the slow pyrolysis of these residues at particle sizes between 5 and 6.3 mm and temperatures inside the reactor ranging from 444 to 875 °C. For this range of temperatures, char yield decreased from 36.2 to 28.1% and gas yield increased between 33.2 and 47.6%. The liquid phase yield was highest at 444 °C (30.6%) and then decreased to 24.3% at 875 °C. As the operating temperature increased, there was an increase in the ash content (15.8 to 21.6%) and a decrease in volatiles content (20.9–3.7%) of biochars. The higher heating values (HHV) of the chars were between 21.9 and 23.1 MJ/kg. Preliminary results show that an increase in particle size leads to a rise in char yield. The infrared analysis of the liquid phase indicated the presence of water, alcohols, phenols, carboxylic acids, alkanes, alkenes, and aromatics. The liquid phases had an average water content of 43%, densities between 1110 and 1120 kg/m3 and the HHV between 12.7 and 15.1 MJ/kg. The gases produced were analysed by gas chromatography. For 538 °C, the production of H2, CO, CH4 and CO2 was, respectively, 1.00, 0.37, 0.18 and 1.37 mol/kg of leather. At 875 °C, H2 was the most produced gas (2.74 mol/kg leather), followed by CO, CO2 and CH4 with quantities of 1.40, 1.26 and 0.42 mol/kg leather.
    2023-05-10Conference paper Open access Show more
  • A WSSL Implementation for Critical Cyber-Physical Systems Applications
    Publication . Rocha, Márcia; Vasconcelos Filho, Ênio; Alves, Fernando; Penna, Sergio; Santos, Pedro Miguel; Tovar, Eduardo
    The advancements in wireless communication technologies have enabled unprecedented pervasiveness and ubiquity of Cyber-Physical Systems (CPS). Such technologies can now empower true Systemsof-Systems, which cooperate to achieve more complex and efficient functionalities. However, for CPS applications to become a reality, safety and security must be guaranteed, particularly in critical systems, since they rely on open communication systems prone to intentional and non-intentional interferences. We propose designing a Wireless Safety and Security Layer (WSSL) architecture to be implemented in critical CPS applications to address these issues. WSSL increases the reliability of these critical communications by enabling the detection of communication errors. Furthermore, it increases the CPS security using a message signature process that uniquely identifies the sender. So, we present the WSSL architecture and its implementation over an MQTT protocol. We prove that WSSL does not significantly increase the system transmission costs and demonstrate its capability to ensure safety and security, allowing it to be used in any general or critical CPS.
    2023-05-10Journal article Open access Show more