Reutilização direta de termoplásticos em máquinas de Modelagem por Deposição de Material Fundido

Cada vez mais a acumulação de plástico nas lixeiras é um problema. A sua composição não biodegradável e produção geralmente feita a partir de combustíveis fósseis fazem com que seja de extrema importância que este plástico se mantenha no ciclo da reciclagem. Políticas de incentivo á reciclagem, ou punição à má separação de resíduos têm-se provado eficazes para combater o problema, no entanto a contínua e crescente utilização de plásticos requer o desenvolvimento de novas abordagens que contribuam também a este fim. Viemos também numa era em que o crescimento da tecnologia de modelação por deposição de material fundido (comumente referida como impressão 3D) está a atingir uma escala exponencial, podendo num futuro muito próximo ser um eletrodoméstico comum de encontrar em habitações domésticas, pondo em causa o funcionamento da produção de bens tal como a conhecemos. Na presente dissertação apresenta-se o dimensionamento e etapas de construção de uma extrusora de termoplástico com dimensões reduzidas, especificamente construída para extrudir resina termoplástica politereftalato de etileno e todas as suas componentes, assente no estudo de termoplásticos, máquinas de fabricação aditiva e da extrusão. Esta proposta pretende contribuir para a redução do desperdício de termoplásticos, permitindo que a reciclagem seja feita em ambiente doméstico e o produto desta utilizado em máquinas de modelação por deposição de material fundido. Assim, é possibilitada a criação de novos bens a partir de plásticos que seriam descartados, trazendo assim os lucros da reciclagem para o utilizador, diminuindo o desperdício e custos associados ao transporte.Now more than ever the accumulation of plastic in dumpsters is a problem we are facing. Its non-degradable composition and production generally from fossil fuels make it of extreme importance that this plastic is maintained in the recycling cycle. Policies that incite the population to recycle, or punish a bad waste separation have proven effective to fight this problem, nonetheless the continuous growth of plastics usage requires the development of new approaches that contribute to this end. We also live at a time in which the growth of the fluid deposition modeling (usually known as 3D printing) is at an exponential scale, bringing the possibility of being a common domestic appliance in a few years, jeopardizing the functionality of production of goods, as we know it today. In the present thesis, the design and construction of a small-scale thermoplastic extruder machine, specifically built for the thermoplastic resin Polyethylene Terephthalate and all its components is presented, based on the study of thermoplastics, fluid deposition modeling machines and extrusion. This proposal aims to contribute to the reduction of the waste of thermoplastics, allowing the recycling to be done in a domestic environment and its product used in fluid deposition modeling machines. This way the creation of new goods from plastic that would carelessly be thrown to waste is allowed, bringing the profit obtained from recycling directly to the user, diminishing the waste and costs associated with transport

Standalone docking station with combined charging methods for agricultural mobile robots

One of the biggest concerns in the field of agriculture is around the energy efficiency of robots that will perform agriculture’s activity and their charging methods. In this paper, two different charging methods for agricultural standalone docking stations are shown that will take into account various variants as field size and its irregularities, work’s nature to which the robot will perform, deadlines that have to be respected, among others. Its features also are dependent on the orchard, season, battery type and its technical specifications and cost. First charging base method focuses on wireless charging, presenting more benefits for small field. The second charging base method relies on battery replacement being more suitable for large fields, thus avoiding the robot stop for recharge. Existing many methods to charge a battery, the CC CV was considered the most appropriate for either simplicity or effectiveness. The choice of the battery for agricultural purposes is if most importance. While the most common battery used is Li-ion battery, this study also discusses the use of graphene-based new type of batteries with 45% over capacity to the Li-ion one. A Battery Management Systems (BMS) is applied for battery balancing. All these approaches combined showed to be a promising method to improve a lot of technical agricultural work, not just in terms of plantation and harvesting but also about every technique to prevent harmful events like plagues and weeds or even to reduce crop time and cost.Project PrunusBotinfo:eu-repo/semantics/publishedVersio

Image recognition method for frost sensing applications

Frost formation in the heat exchangers of refrigeration systems is a well-documented phenomenon. This frost accumulation creates a thermally insulating barrier that can restrict, or even block, the airflow between fins, resulting in decreased efficiency and degradation of the food products. Several methods of frost detection and defrosting have been developed, although there is not an efficient mainstream method to measure and control frost formation. In previous works, the results of a small low-cost resistive sensor for frost detection were shown to be promising. This paper extends that research using computer vision to compare the results of this sensor with the frost formed on the heat exchanger, allowing for a better study of the sensor. This method allowed to trace and plot a frost formation curve of the sensor detected values.This work has been supported by the project Centro-01-0145-FEDER000017 -EMaDeS -Energy, Materials and Sustainable Development, co-funded by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the EU through the European Regional Development Fund (ERDF). The authors thank the opportunity and financial support to carry on this project to Fundac¸ao para a Ci ˜ encia e ˆ Tecnologia (FCT) and R&D Unit “Centre for Mechanical and Aerospace Science and Technologies” (C-MAST), under project UIDB/00151/2020. This study is within the activities of project “PrunusPos - Optimization of processes for the storage, cold ´ conservation, active and/or intelligent packaging and food quality traceability in post-harvested fruit products”, project n. ◦ PDR2020-101-031695, Partnership n◦ 87, initiative n.◦ 175, promoted by PDR 2020 and co-funded by EAFRD within Portugal 2020.info:eu-repo/semantics/publishedVersio

Fast return path planning for agricultural autonomous terrestrial robot in a known field

The agricultural sector is becoming more critical than ever in view of the expected overpopulation of the Earth. The introduction of robotic solutions in this field is an increasingly researched topic to make the most of the Earth's resources, thus going to avoid the problems of wear and tear of the human body due to the harsh agricultural work, and open the possibility of a constant careful processing 24 hours a day. This project is realized for a terrestrial autonomous robot aimed to navigate in an orchard collecting fallen peaches below the trees. When it receives the signal indicating the low battery, it has to return to the docking station where it will replace its battery and then return to the last work point and resume its routine. Considering a preset path in orchards with tree rows with variable length by which the robot goes iteratively using the algorithm D*. In case of low battery, the D* algorithm is still used to determine the fastest return path to the docking station as well as to come back from the docking station to the last work point. MATLAB simulations were performed to analyze the flexibility and adaptability of the developed algorithm. The simulation results show an enormous potential for adaptability, particularly in view of the irregularity of orchard field, since it is not flat and undergoes modifications over time from fallen branch as well as from other obstacles and constraints. The D* algorithm determines the best route in spite of the irregularity of the terrain. Moreover, in this work, it will be shown a possible solution to improve the initial points tracking and reduce time between movements.Project PrunusBot - Sistema robótico aéreo autónomo de pulverização controlada e previsão de produção frutícola (autonomous unmanned aerial robotic system for controlled spraying and prediction of fruit production), Operation n.º PDR2020-101-031358 (leader), Consortium n.º 340, Initiative n.º 140 promoted by PDR2020 and co-financed by FEADER under the Portugal 2020 initiative.info:eu-repo/semantics/publishedVersio

Low-Cost IoT Remote Sensor Mesh for Large-Scale Orchard Monitorization

Population growth and climate change lead agricultural cultures to face environmental degradation and rising of resistant diseases and pests. These conditions result in reduced product quality and increasing risk of harmful toxicity to human health. Thus, the prediction of the occurrence of diseases and pests and the consequent avoidance of the erroneous use of phytosanitary products will contribute to improving food quality and safety and environmental land protection. This study presents the design and construction of a low-cost IoT sensor mesh that enables the remote measurement of parameters of large-scale orchards. The developed remote monitoring system transmits all monitored data to a central node via LoRaWAN technology. To make the system nodes fully autonomous, the individual nodes were designed to be solar-powered and to require low energy consumption. To improve the user experience, a web interface and a mobile application were developed, which allow the monitored information to be viewed in real-time. Several experimental tests were performed in an olive orchard under di erent environmental conditions. The results indicate an adequate precision and reliability of the system and show that the system is fully adequate to be placed in remote orchards located at a considerable distance from networks, being able to provide real-time parameters monitoring of both tree and the surrounding environment.info:eu-repo/semantics/publishedVersio

Testing of a resistive sensor with fabric medium for monitoring frost formation in refrigeration systems

Refrigeration is one of the key elements for food preservation. With global temperatures increasing due to global warming, the efficiency in refrigerated storage systems must be improved. One of the problems that is yet to be solved in these systems is the efficient and accurate removal of the frost formed on the heat exchanger surface. In previous works, a low-cost resistive sensor has been developed to detect frost formation for accurate removal. This paper shows the results of an experimental study carried out to increase the accuracy, by placing different configurations of a fabric medium in between the sensor electrodes.This study is within the activities of project “Pack2Life – High performance packaging”, project IDT in consortium No.33792, call No.03/SI/2017, Ref. POCI-01-0247-FEDER-033792, promoted by COMPETE 2020 and co-funded by FEDER within Portugal 2020. This work has been supported by the project Centro-01-0145-FEDER000017 - EMaDeS - Energy, Materials and Sustainable Development, co-funded by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors thank the opportunity and financial support to carry on this project to Fundação para a Ciência e Tecnologia (FCT) and R&D Unit "Centre for Mechanical and Aerospace Science and Technologies" (C-MAST), under project UIDB/00151/2020.info:eu-repo/semantics/publishedVersio

Modeling the heat transfer and the pressure loss in flat fin-and-tube compact heat exchangers

This work has been supported by the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors wish to thank the opportunity and financial support that permitted to carry on this project.Fin-and-tube heat exchangers (HX) have wide application in the industry. The study of HXs with reduced tube diameter has allowed the development of more compact and equally efficient equipment. Most of the HXs of this type are composed of flat fins, not only due to the ease of construction but also to their reliability in long-term operation and reduced friction characteristics. The formulation of mathematical equations that predict the effect of the geometric characteristics on the heat transfer and friction factors of the HXs lead many researchers to try to establish correlations that approximate the experimental results. In this paper is developed a computational tool based on literature correlations is used to evaluate the Colburn and friction factors for flat fin-and-tube compact HXs. The results of predictions show the Colburn and friction factors behavior for different geometrical parameters (fin pitch, tube diameter, tube number) and typical Reynolds number.info:eu-repo/semantics/publishedVersio

A review

It is widely known that defrosting operation on commercial refrigerators is one of the main causes of inefficiency on these systems. Several defrosting methods are used nowadays, but the most commonly used are still time-controlled defrosting, usually by either electric resistive heating or reverse cycle, as most demand defrost methods are usually complex, expensive or unreliable. Demand defrost can work by either predicting frost formation by processing measured conditions (fin surface temperature, air humidity and air velocity) and/or frost accumulation symptoms such as pressure drop and refrigerant properties. Other way of knowing when to defrost is to directly measure the frost formation using sensors such as photoelectric, capacitive or resistive. This review gathers some of the methods that can be used for directly measuring frost accumulation on the evaporator fin surface.info:eu-repo/semantics/publishedVersio

Further development and experimental testing of a resistive sensor for monitoring frost formation in refrigeration systems

This work has been supported by the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors wish to thank the opportunity and financial support that permitted to carry on this project.Refrigeration systems are widely accepted as a mean to prevent food degradation. These systems usually rely on fin-and-tube heat exchangers to lower the air temperature. Due to long operation times and surface temperatures below dew point, frost may form and accumulate on the evaporators fin surface. This frost accumulation reduces and may clog the airflow, decreasing the system efficiency. Usually, most systems use a time-controlled system (stopping the compressor with or without powering a heating resistor inserted among fins to heat) to melt the ice. This method does not measure or predict the amount of frost formed, thus it is not reliable. Ice sensors that are cheap, reliable and easy to implement in commercial systems are studied. A resistive sensor is purposed, that measures the voltage between two electrodes with the water phase change (condensation and solidification -freezing-), as these states have different resistive values. Different electrode materials, morphologies and configurations are studied in order to obtain the best design.info:eu-repo/semantics/publishedVersio