ESTG - Comunicações em conferências e congressos internacionais
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- Energy Efficiency and Sustainability in an Aquaponic Greenhouse Supported by IoTPublication . Galvão, João; Santos, Pedro; Aires, Luis; Ribeiro, Vânia; Neves, FilipeThe increasing demand for agricultural crops and the necessity to reduce environmental impacts from traditional agriculture have led to the emergence of sustainable production systems such as hydroponics and aquaponics. These soil and pesticide-free systems require less water and fertilizers but need electrical energy and controlled greenhouse environmental conditions to be highly productive. This work presents a monitoring and management system for environmental parameters inside an aquaponic greenhouse, that allows the manager to assess in real-time the working status of the aquaponic system, helping in the detection of critical conditions that require a quick decision. This system was developed to measure, through IoT sensors network, the temperature and the relative humidity of the air, the temperature, pH and the electrical conductivity of the water that contains the dissolved nutrients that feed the growth of the plants. It is possible to visualize the measured parameters via the Internet, on a dashboard, in a mobile application and store these variables in a database. To further increase the sustainability of the aquaponic greenhouse, the electricity consumed during its activity will be produced locally by photovoltaic technology. The technologies proposed in this work may promote the emergence of small models of greenhouses, implemented by communities and populations, reducing production energy costs and transportation resources.
- Recycling of PET fines waste by density separation: a way to circularity of plasticPublication . Heleno, M. L.; Oliveira, N. S.; Gaspar, M.; Silveira, A.; Vasco, J.Plastic is one of the most used materials due to its specific characteristics such as high flexibility and impact resistance, low cost, formability, light weight and recyclability. In this set, polyethylene terephthalate (PET) based materials are among of the most used plastics on the packaging market worldwide. The European strategy for plastics aims to modify the processes of design, production, use and recycling of plastics. It becomes crucial to study solutions to enhance the circularity of plastics in recycling processes. Therefore, it is mandatory to evaluate the potential separation of PET fines resulting from the recycling process of PET bottles (post-consumer waste), which are still contaminated by other polymers and other materials. The recovery of PET fines was successfully achieved with a multistage density plastics separation process, consisting on the use of solutions of different densities and ensuring the adequate wettability of the residues in the solutions. The addition of this multistage separation process by plastics density, improves PET fines recovery, by achieving 91.7% of pure PET fines from plastic material waste.
- Radiowave Propagation Modelling of Dual Wildfire Front Spreading over Hilly Terrain at 700 MHzPublication . Faria, Stefânia; Vala, Mário; Coimbra, Pedro; Leonor, Nuno; Felício, João; Fernandes, Carlos A.; Salema, Carlos; Caldeirinha, Rafael F. S.In this paper, a study of a fire front spreading over flat and sloped terrains and how these fire fronts may have impact on radiowave communications are presented. The phenomenon is modelled using Fire Dynamics Simulator (FDS) and the Cold Plasma Model (CPM), using pine needles as fuel heap. Fire parameters such as Heat Release Rate (HRR), Mass Loss Rate (MLR) and fuel consumption are presented and analysed. Attenuation effects at 700 MHz are calculated considering the Full-Stack Model (FSM) and Transmission Line Model (TLM). Simulation results clearly demonstrate that the slope of the terrain profile in the presence of a dual fire front spreading up the hill has significant impact on the additional excess loss of around 2.5 dB, yielding an overall excess loss of 3.5 dB for such a small-scale fire simulation.
- Sustainability study of limestone quarry waste into value-added products: PCC and GCCPublication . Monteiro, S. M. C. S.; Jorge, Muanassa; Heleno, M. L.; Oliveira, N. S.; Alves, M. L.; Veiga, A.; Silva, A.Calcium carbonate can be obtained naturally from limestone, chalk, marble, and other sedimentary rock forms. Ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC) are two materials that can be produced from natural calcium carbonate. The future of GCC and PCC is promising since they are linked to industries with high demand, such as packaging, building & construction, transportation, and industrial applications, with an expected compound annual growth rate higher than 4% until 2027. This research focuses on the production of GCC and PCC through a comparative analysis that identifies the macro conditions that become advantageous to produce and commercialising PCC in a quarry context. This allows a valorisation of the limestone waste resulting from the extraction operations, converting it into by-products of the process. Not all existing limestone quarries in the Serra de Aire e Candeeiros region are suitable sources of raw material to produce PCC. The five extraction poles were identified with the potential for extracting suitable raw materials, associated with several companies dedicated to the extraction operation in these quarries.
- Qualitative analysis of the limestone waste potential from the Serra de Aire e Candeeiros quarriesPublication . Monteiro, S. M. C. S.; Jorge, Muanassa; Oliveira, N. S.; Alves, M.L.; Veiga, A.; Silva, A.The mountains of Aires and Candeeiros are part of the Maciço Calcário Estremenho where the landscape is predominantly made up of limestone. The limestone explored in the region has been the driver of social and cultural development, contributing significantly to the local economy. This emerging concern has motivated public and private organisations to develop solutions to improve the sector's sustainability. The present work aims to evaluate the limestone waste potential to produce precipitated (PCC) and ground (GCC) calcium carbonate in the region by surveying the local extraction industries that fulfil the defined minimum requirements to produce high quality PCC and GCC. The results allowed to stablish an estimate of the amount of waste resulting from the extraction process. The conversion of these wastes into PCC or GCC constitutes a possibility of recovery into by-products, allowing use in noble and profitable applications and contributing to the circular economy and the sustainability of the sector.
- Keeping track of UWP application changes for digital forensic purposesPublication . Andrade, Luis Miguel; Domingues, Patricio; Frade, MiguelDigital forensics aims to collect and interpret artifacts that can help in the understanding of the action performed by a given individual or organization. The forensic artifacts are highly dependent on the inner working of the operating system (OS) and applications. This is the case for applications of the Universal Windows Platform (UWP), with digital forensic practitioners often depending on the data kept in the private database(s) of the application. However, some of these applications evolve rapidly, with new versions bringing changes that sometimes involve their inner databases and thus might impact digital forensic artifacts. In this paper, we present UWPscanner, an open source system that we have developed. The UWPscanner system allows to track the changes of internal databases used by UWP applications, aiming to ease the task of not only digital practitioners, but also of digital forensic tool developers. The paper is complemented with the case-study of tracking Microsoft Skype (SkypeApp) and Your Phone evolution with UWPscanner.
- Automatic visual inspection system for solder paste deposition in PCBsPublication . Paulo, Guilherme B. F.; Perdigoto, Luís M. R.; Faria, Sergio M. M.The growth of the electronics industry led to a need for efficient methods of testing and validation of printed circuit boards (PCB). It is necessary to identify defects that might appear in a component in early production stages. This task may be performed by automatic inspection systems, showing advantages in speed, accuracy and repeatability, over human inspection. This paper describes a visual inspection system that is able to detect solder paste deposition defects on a PCB. The PCB image is analysed to segment the areas with solder paste and then, by comparing with reference data from the PCB design files, defects are identified, either because of missing or excess solder. The system is based on low cost components, namely a Raspberry Pi Compute Module and two Raspberry Pi v2 cameras. Experimental tests performed with the prototype, regarding the PCB defect detection and execution time, allowed to conclude the system can aid human visual inspection in a production line.
- Building Information Modelling Conversion for Radiowave Propagation StudiesPublication . Louro, João; Fernandes, Telmo Rui; Rodrigues, Hugo; Caldeirinha, RafaelThis paper presents a Building Information Modelling (BIM) data conversion algorithm for radio wave propagation studies in indoor and outdoor environments. The tool presented here allows to extract the geometrical and physical information of BIM models present in IFC2×3 files. The first conversion step is done using the IFCOpenSHell library through a Python interface and the second one is done using MatLab. Following MatLab results extraction, studies of propagation will proceed. The extracted information allows ray tracing simulations and/or radiowave propagation studies through a real-scale simulation scenarios, spending less computational time. The results presented refer to a small wooden house for a frequency of 3.6 GHz, for 5G, using a directional transmitter antenna and an omnidirectional receiving antenna. It is possible to check the result for the direct component and first, second and third order reflections.
- On the Practical Limitations of Scalable Electronic 2D Beamsteering Using Metamaterials at Micro and Millimetre-wave FrequenciesPublication . Vala, Mário; Reis, Joao R.; Caldeirinha, Rafael F. S.In this paper, the practical limitations of scalable electronic two-dimensional (2D) beamsteering using metamaterials at Micro- and Millimetre-wave frequencies, are addressed. In particular, the practical effects of using varactor diodes on a metamaterial-based beamsteering transmitarray, are studied and characterised, at four different frequencies of interest: 5, 14, 28 and 60 GHz. The parasitic effects intrinsic to such components, namely the internal resistance and internal inductance, are being studied. A thorough parametric analysis in CST Microwave Studio is conducted, in order to ascertain how the varactor's parasitics affect the frequency response, insertion loss, bandwidth and maximum achieved phase shift and consequent beamsteering resolution, at the proposed frequencies. The parametric study targets the parasitic resistance and inductance values of varactor diodes commercially available, making this study useful for any RF transmitarray implementation.
- Perfect Periodic Sequences with Low PAPRPublication . Ferreira, M.; Gasparovic, M.; Manjunath, G.; Priem-Mendes, S.; Pereira, J. S.Different coding sequences have huge effects on the performance of Code Division Multiple Access and Orthogonal Frequency Division Multiple Access communication systems. We propose new perfect sequences, derived from an Inverse Discrete Fourier Transform of Golay codes, and present both a mathematical and hardware-based direct/inverse generator for these new sequences. Our analysis reveals that these new sequences, named Orthogonal Perfect DFT Golay (OPDG) codes, have better autocorrelation and cross-correlation properties than the Golay codes. High Peak-to-Average Power Ratio (PAPR) is identified as one of the main practical problems involving Orthogonal Frequency Division Multiple Access power transmission. To minimize this problem, we introduce a bipolar decomposition of our new perfect sequences that permit the lowest PAPR (equal to 1) for each of the new bipolar codes. Additionally, this paper shows that the new bipolar codes derived from OPDG sequences outperform orthogonal Gold codes regarding error transmission probabilities.