Project of a bandgap voltage reference and a temperature sensor for "energy harvest" systems

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e ComputadoresThe objective of this thesis is to study the behaviour of a bandgap voltage reference and develop it in order to be more efficient than the existing ones. In this case having applicability in energy harvest, the main approach for this circuit is to reduce the power dissipation and at the same time guarantee a stable of the reference voltage. This can be achieved through the utilization of MOS transistors which can work with a lower voltage then bipolar transistors. The reference voltage circuit present in this thesis can work with a supply voltage as low as 500 mV. In energy harvest systems besides the need to work with extremely low voltages, the sensitivity of the signals is very high, to temperature variation. So it was also important to work with an extended ranges of temperature. For this work it was also developed a temperature sensor so that it has applicability in various fields. The sensor works by currents generated by the bandgap voltage reference, having similar results to a dual slope integrating analogue-to-digital converter, although its operation and logic are quite different. The proposed solution is to implement a reference voltage generator powered by a voltage source of 500 mV, with a consumption of about 7 W. Having a temperature coefficient slightly below 74 ppm/ C and a temperature sensor with linearity quite satisfactory

Recheio : growing through a declining channel : a case on wholesale food private labels and its competitiveness

The Portuguese wholesale food market is in a mature phase where the space to grow seems to be limited. In the end of 2008 economic and business environment were expected to deteriorate intensely making this growth even more difficult wholesale food companies. Recheio, the market leader in this sector, had been growing sustainably and regardless the situation they wanted to keep their pace. As so Mr. Antunes challenged the Marketing Director Rita Silva, to develop a strategy to boost the Traditional Retail channel sales since it was the one with the one decreasing the most. Due to its lack of capacity to compete with Modern Retail chains Mrs. Silva and her team worked to understand the gap between these two channels in order to build the necessary management tools to increase traditional retailers´ competitiveness and Recheio sales. These management tools could be as simple as more competitive prices or as complex as developing a Private Label but one thing was clear, waiting to see the exact evolution without any of these actions was not an option

Home-Advantage during COVID-19: An Analysis in Portuguese Football League

Covid-19 pandemic forced, at the final rounds of 2019–2020 season, in many different sports leagues worldwide, teams to play without an audience. Therefore, the present paper aims to compare the home advantage score in the last ten rounds in the 2019–2020 season with the first 24 rounds in the same season using Pollard’s (1986) and Matos et al.’s (2020) methods. In addition, comparisons across different seasons (2016–2017; 2017–2018; 2018–2019 and 2019–2020) using the same methods were also analyzed. Results showed no differences (p > 0.05) between first 24 rounds and the last 10 in 2019–2020 season as well as in the 3 previous seasons. With Pollard’s method, no differences (p > 0.05) were also found among those four seasons on global (all 34 rounds) home advantage. However, a significance difference between 2017–2018 and 2019–2020 (p < 0.05) was founded using Matos et al.’s (2020) method, which is an indicator of the importance of using complementary methods when analyzing the same realities. Overall, despite what might be expectable from recent findings, the lack of an audience in the last 10 rounds of Portuguese Football League 2019–2020 season, due to COVID-19 pandemic, did not affect home advantage. Therefore, future studies could try to analyze other different variables in Portuguese Football League, such as referees’ behaviors, rules changing (e.g., the possibility of making five substitutions, instead of three), crowd dimension and density as well as include variables about odds as forecasts in football being played without crowds.info:eu-repo/semantics/publishedVersio

Algoritmos eficientes para gestão energética das estações base de sistemas de comunicação móveis

Com o crescimento exponencial de consumo de dados e a subsequente expansão de infraestruturas das redes de comunicação móveis, é crucial criar estratégias que reduzam o consumo energético. Na verdade, 80% da energia total consumida é utilizada pelas estações base. As fortes variações espaciais e temporais do tráfego oferecido exigem uma implementação heterogénea de estações base, recorrendo a diferentes tamanhos associados a tecnologias distintas (GSM, UMTS e LTE), que respondem aos requisitos de capacidade e cobertura. Tipicamente, as macro-células utilizam frequências inferiores para garantir a cobertura numa maior área de serviço (as chamadas células de cobertura). As micro-células recorrem a frequências superiores e têm uma cobertura menor, sendo utilizadas para aumentar a capacidade do sistema em zonas específicas (chamadas de células de capacidade). É proposta uma estratégia de gestão de estações base, consciente do tráfego da rede. Usando medições do tráfego e da estimativa da área de cobertura das células, são identificados pares de células de cobertura e capacidade. Foram identificados pares de células de cobertura e capacidade, onde a célula de cobertura cobre a área servida pela outra. Uma análise de tráfego permite identificar períodos do dia em que a célula de capacidade poderá ser desligada, ou seja, quando o tráfego agregado das duas células é suficientemente baixo para ser entregue à célula de cobertura.With the exponential growth of data consumption and the subsequent expansion of the infrastructures of mobile communication networks, it is crucial to devise strategies that reduce energy consumption. In fact 80% of the total spent power is used by the base stations. The strong spatial and temporal variations of offered traffic require heterogeneous deployment of base stations, by recurring to different sizes associated with distinct technologies (GSM, UMTS and LTE), to address coverage and capacity requirements. Typically, macro-cells use lower frequencies to guarantee coverage in larger areas of service (so-called coverage-cells). Micro-cells use higher frequencies and have a lower coverage and are used to increase the system capacity in specific zones (so-called capacity-cells). A traffic aware strategy for the management of base stations’ activity is proposed. Using traffic load measurements and estimating cells’ coverage areas, it identifies coverage and capacity cells pairs, where the coverage-cell covers the area served by the other. A traffic analysis identifies periods in the day where capacitycells may be switched-off, when aggregate traffic of both cells is sufficiently low to be handed-over to the coverage-cell

Configuração de sistema de monitorização

O presente trabalho enquadra-se na área das redes de computadores, fazendo referência aos protocolos e ao conjunto de equipamentos e softwares necessários para a administração, controlo e monitorização desse tipo de infra-estruturas. Para a gestão de uma rede de dados, é essencial dispor de conhecimentos e documentação de nível técnico para representar da forma mais fiel possível a configuração da rede, seguindo passo a passo a interligação entre equipamentos existentes e oferecendo assim uma visão o mais fidedigna possível das instalações. O protocolo SNMP é utilizado em larga escala sendo praticamente um standard para a administração de redes baseadas na tecnologia TCP/IP. Este protocolo define a comunicação entre um administrador e um agente, estabelecendo o formato e o significado das mensagens trocadas entre ambos. Tem a capacidade de suportar produtos de diferentes fabricantes, permitindo ao administrador manter uma base de dados com informações relevantes da monitorização de vários equipamentos, que pode ser consultada e analisada por softwares NMS concebidos especialmente para a gestão de redes de computadores. O trabalho apresentado nesta dissertação teve como objectivo utilizar uma ferramenta NMS, para fazer a monitorização e a gestão da infra-estrutura de comunicações de forma que permitisse conhecer em tempo real o estado dos elementos de rede, ajudar no diagnóstico de possíveis problemas, instalados pela Nonius nos diversos navios da frota Douro Azul. O software NMS escolhido utiliza as potencialidades do protocolo SNMP para adquirir dados de monitorização de equipamentos de rede presentes na rede, bem como monitorizar redes remotas.The work presented in this thesis fits in the area of computer networks, more precisely in the set of protocols, equipment and software required for the administration, control and monitoring of this type of infrastructure. Efficient management of a data network, requires knowlodge and technical documentation to represent as faithfully as possible the network architecture and configuration, enabling a real view about the facilities. The SNMP protocol is used on a large scale and is practically a standart for managing networks based on the TCP/IP technology. This protocol defines the communication between a manager and an agent, establishing the format and meaning of messages exchanged between them. It has the ability to support products from different manufacturers, allowing the administrator to maintain a database of relevant information from various monitoring equipment’s, which can be viewed and analysed using an NMS software designed especially for the management of computer networks. The work presented in this thesis aimed to use a NMS tool, to make the monitoring and management of communications infrastructure in a way that allows to know in real time the status of network elements installed by Nonius, to help diagnoses possible problems, in several ships on the fleet Douro Azul. The NMS software chosen uses SNMP capabilities to acquire monitoring data network equipment in the network, and monitor remote networks