Percorrer por data de Publicação, começado por "2024-09"
A mostrar 1 - 10 de 16
Resultados por página
Opções de ordenação
- Intelligent PPG-based Heart Rate Signal Analysis for Car Drivers MonitoringPublication . Baiense, João Pedro; Eerdekens, Anniek; Schampheleer, Jorn; Deruyck, Margot; Pires, Ivan Miguel; Velez, Fernando JoséThis research aims to contribute to enhancing road safety through the development and exploration of an intelligent wristbandbased health monitoring solution for car drivers. It focuses on using various sensors, such as the photoplethysmogram (PPG) and an accelerometer, to accurately estimate the drivers’ heart rate. The primary goal was to create a robust and accurate model capable of real-time heart rate estimation from PPG signals, with the potential to improve the effectiveness of Internet of Medical Things (IoMT) applications in the healthcare sector. The study delves into the multiple processing steps involved in improving the quality of data to make it suitable for efficient processing by the deep learning model, encompassing data analysis, signal interpretation, and applying diverse techniques such as filters, data shifting, and data manipulation. The research integrated the leave-one-session-out (LOSO) cross-validation technique for model training and evaluation alongside fine-tuning hyperparameters to optimize model performance and efficiency. The achieved Mean Absolute Error (MAE) of 3.450 ± 1.324 bpm and Mean Squared Error (MSE) of 69.50 ± 93.57 bpm2 represent notable outcomes, resulting in a 54.9% improvement in MAE from the original study. Additionally, the research integrated the model into a user-friendly mobile application, visually presenting the results and enabling users to examine their health status in real-time. These findings highlight the significance of eticulous data analysis and processing in wearable device applications and the high accuracy of the proposed model.
- Segurança, Defesa e a Paz: Educação para a Cidadania no Currículo Escolar em PortugalPublication . Albernaz, V. B.O presente estudo tem como objetivo refletir sobre quais as estratégias educativas para a educação e para a cidadania dos jovens voltadas para a segurança, defesa e a paz no ensino secundário em Portugal. Buscamos debater sobre as diferenças de adoção pedagógica entre um Estabelecimento Militar de Educação e um Estabelecimento Regular de ensino e refletir sobre a importância na adoção de uma Unidade Curricular-UC voltada para o ensino de Segurança, Defesa e Paz nos estabelecimentos regulares de ensino. Metodologicamente, a pesquisa resulta de uma pesquisa bibliográfica e documental, visando delimitar os referenciais teóricos. Em seguida aborda as leis e diretrizes que legitimam a educação para a cidadania voltada para a segurança, defesa e a paz. Por último realiza a comparação dos planos curriculares das seguintes escolas: Colégio Militar em Lisboa e Escola Secundária Campos Melo, na Covilhã.
- Towards a Framework for System and Attack Modelling and Mapping of Requirements and Technology for the Internet of ThingsPublication . Sequeiros, João Bernardo Ferreira; Inácio, Pedro Ricardo MoraisThe proliferation of Internet of Things (IoT) devices has been expanding several domains, offering unprecedented connectivity and convenience. However, this surge in interconnected devices has brought forth significant security challenges, as constrained budgets and development time leave security in a secondary role, or even non-existent. This is compounded upon by small design and development teams, where security expertise is reduced and lacking, creating a landscape of IoT systems that are unsecured and ripe for attack by malicious actors. The data gathered by these devices, their general lack of security, and the possibility of serving ans entry points to otherwise more secure systems, makes them increasingly tempting targets for exploration and exploitation. This thesis attempts to bridge the gap of aiding in the secure IoT system development, by approaching the issue of security in IoT from a standpoint of low knowledge and/or low expertise in IoT security. The first step towards the main goal is the extensive survey of existing IoT architectures and modeling tools, to aid in identifying the main challenges in secure IoT development and what can be improved or built upon. The second phase advances upon what was surveyed, by proposing an IoT system model that encompasses a large set of IoT ecosystems, and that embeds security in its essence, by identifying, for each system component, what are its critical security requirements, and what are the most attractive targets for an attacker on the given component. This model is complemented by the creation of an attack taxonomy, that attempts to take the most common attacks on IoT, and identifying where in the system those attacks may occur. To further aid the development process and provide a practical substrate to the Doctor of Philosophy (degree) (Ph.D.) work, an attack modeling tool named Attack Trees for IoT (ATIoT) is presented as a means to identify, starting from a system description given through a direct answer questionnaire, the attacks the system may be more susceptible to, providing the user with a set of attack trees, together with detailed node descriptions, of the identified attacks for the described system. Joining ATIoT, other existing tools are mapped to the proposed model, to further aid in identifying where security requirements, best practices, guidelines, security mechanisms and potential threats in an IoT system should be applied or can be found, further enhancing the usefulness of such tools. Motivated by the profound transformation that Artificial Intelligence (AI) is causing in the technological world, and the always fast advancing security area, a series of experiments of applying different AI mechanisms to the developed tools are also detailed herein. They specifically concern the application of classification models to the elicitation of security requirements, and the use of Large Language Models (LLMs) for identifying potential attacks from a textual system description. The thesis presents the results of these experiments, which show the promise of applying such methodologies to the process of security engineering. Main conclusions include achieving the goal of creating a panoply of mechanisms and tools that aid the development of secure IoT systems, that were designed towards being used by developers with low or no security background and expertise. It was also concluded that AI methods can aid in the maintaining of such tools and mechanisms, ensuring their validity in a longer time period, a challenge always present in fast-paced, always evolving areas.
- Influence of aluminum nanoparticles in alternative fuel: Single droplet combustion experiments and modelingPublication . Ferrão, Inês; Mendes, Tomás; Mendes, Miguel; Moita, A. S.; Silva, A. R. R.In this work, the effect of adding aluminum nanoparticles on hydrotreated vegetable oil was investigated experimentally and numerically in terms of nanofuel stability and single droplet combustion. The purpose is to understand the phenomena related to isolated droplet combustion when metallic particles are added to a liquid biofuel. Falling droplet combustion experiments were conducted in a drop tube furnace at two different furnace temperatures (800 C and 1000 C) using a high-speed camera coupled with a high magnification lens to investigate the droplet size evolution as disruptive burning phenomena. In numerical terms, a simplified macroscopic model was developed to predict the burning behavior of isolated nanofuel droplets, considering hexadecane as a surrogate fuel for the biofuel. The results reveal that adding nanoparticles resulted in a departure from the -law. Moreover, an increase in the overall droplet burning rate was observed, and according to the numerical results, nanoparticle radiation absorption is the responsible mechanism. Micro-explosions occurred for all nanofuels, and this disruptive burning behavior substantially influenced the droplet lifetime.
- Mitigating Dynamic Stall with a Movable Leading-Edge: the NACA0012-IK30 WingPublication . Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.One major problem that affects rotor blade aerodynamics is dynamic stall, characterized by a series of events where transient vortex shedding negatively affects drag and lift, leading to abrupt changes in the wing’s pitching moment. The present work focuses on the mitigation of such effects by using a modified NACA0012 airfoil: the NACA0012-IK30 airfoil, used previously for thrust enhancement in flapping propulsion. An experimental rig is designed and built to study the advantages of a time-varying pitching leading edge on a plunging wing, more specifically its influence on the aerodynamic coefficients over time. Results indicate that when the wing is not experiencing significant stall, the movable leading edge does not hold considerable influence on drag or lift. However, it can reduce the pitching moment intensity by indirectly shifting the pressure center. Contrarily, when the wing is under proper dynamic stall, the movable leading edge truly improves the aerodynamic characteristics while operating at smaller effective angles of attack. This study contributes to the long-standing discussion on how to mitigate the adverse effects of dynamic stall by providing an innovative yet simple solution.
- E-Kerosene Potential for Commercial Aviation DecarbonizationPublication . Quaresma, Guilherme da Silva Nheu; Magalhães, Leandro; Ferreira, Ana Filipa; Silva, André Resende Rodrigues daReducing greenhouse gas emissions from aircraft transport is crucial to achieving climate goals. In this sense, the present study looks into the suitability of e-fuels such as e-kerosene in reducing CO2 emissions. The Fleet System Dynamic Model is employed to examine data and predict future trends in line with the Committee on Aviation Environmental Protection. While the findings suggest that achieving carbon-neutral growth is possible, it might take longer than current forecasts indicate. For instance, considering an e-fuel production rate of 15%, it is possible to cut emissions by half around 2060 concerning 2005 levels.
- Modelling Asteroid Trajectory in Earth’s AtmospherePublication . Morais, Renato Henriques; Santos, Luis; Silva, André Resende Rodrigues da ; Melício, RuiEarth’s atmosphere is humanity’s last defence against the potential threat of asteroid impacts. To assess the impact risk and devise effective mitigation strategies, it is essential to understand the interaction between asteroids and the atmosphere. This paper presents a comprehensive study that employs a system of differential-algebraic equations (DAEs) to model the trajectory and associated physical processes involved in an atmospheric entry and the consequent impact of an asteroid. The Apophis asteroid is utilized as a case study to compare and evaluate the performance of two numerical methods for solving these equations. The findings from this research contribute to advancing our understanding of asteroid entry dynamics and provide valuable insights for enhancing asteroid impact mitigation strategies. The Apophis asteroid, represented as a 340 m diameter sphere with a density of 3190 kg.m−3, enters the atmosphere at a velocity of 30759 m.s−1 and a 45-degree angle from an altitude of 81 km. The first method employed is the 4th-order Runge-Kutta method (RK4) with a constant time-step, commonly used for solving highly non-linear problems like this. The second method is based on the Dormand-Prince method, which utilizes a dynamic time step and provides a 4th-order solution with error estimation using a 5th-order solution. Computational efficiency and the resulting solutions are compared between the two methods. The study finds that the Dormand-Prince method offers a more accurate numerical solution with less computational effort. However, both approaches demonstrate a correspondence of at least three significant digits, confirming their validity. Overall, during its traversal through the atmosphere, the Apophis asteroid experiences a decrease in initial velocity by 0.83%, a loss of 22% of its initial mass, and a variation in its angle with the horizontal by 1.5%.
- Thermal properties of electrical arc furnace slag based materials obtained by accelerated carbonationPublication . Cristino, Luciana Sucupira; Gomes, João Paulo de CastroReducing dependence on fossil fuels and harnessing renewable energy are imperative to facing the current climate emergency and mitigating problems related to pollutants. This thesis focuses on the analysis of the microstructure and thermal properties of mortars manufactured with 100% electric arc furnace slag (EAF-slag) for passive solar energy capture, aiming to contribute to sustainable energy solutions. The first phase involved a comprehensive review of recent civil engineering research on solar thermal energy storage, highlighting the potential of energy harvesting devices. In addition, it delved deeper into the investigation of accelerated carbonation materials used both in research environments and in the construction sector. The subsequent step evaluated the thermal capacity of the EAF-slag through differential scanning calorimetry (DSC). The results indicated that the EAF-slag binders exhibited consistent and minimal changes in heat flux responses at various temperature rates, contrasting with the irregular and more significant variations observed in the Portland cement-based binders. The DSC results emphasized the potential of EAF-slag in developing materials with thermal properties. The third stage analyzed the thermal properties, microstructure and compressive strength of 100% EAF-slag mortars, with and without biochar. The incorporation of biochar led to a reduction in the thermal conductivity of the specimens. However, all EAF-slag specimens obtained results that surpass conventional Portland cement specimens in thermal conductivity. EAF-slag mortars demonstrated favorable thermal properties in all tests carried out. The thermal expansion of EAF-slag mortars was slightly more than twice that of Portland cement (PC) mortars. The EAF-slag mortar sample maintained a higher temperature than the PC mortar sample. The material with particle size composition ranging from 1 mm to 2 mm and 100% EAF slag without biochar showed the most promising results of all tests of passive solar energy utilization in the construction industry. These findings highlight a potential for 100% EAF-slag materials in passive solar thermal applications. Their superior thermal conductivity, substantial thermal capacitance, gradual heat absorption and heat release characteristics, and resilience to the effects of thermal energy position them as materials that perform well in maintaining mechanical stability even under extreme summer conditions. This research highlights the feasibility of 100% EAF-slag carbonated materials for construction, offering a sustainable solution that mitigates the environmental impacts associated with waste and conventional passive solar thermal energy storage. This study represents an advancement toward innovative and sustainable practices in civil engineering and construction. The analyzed material can be applied to facades, roofs, and pavements in areas with high solar exposure and elevated temperatures.
- Essays on electricity market price dynamics: the effects of restructuring the generation mix and energy transition policiesPublication . Macedo, Daniela Pereira; Marques, António Manuel CardosoProducing energy from fossil energy sources is the giant behind the climate change. The energy transition is fostering the massive integration of intermittent Renewable Energy Sources (RES-I) to reduce carbon dioxide and other greenhouse gas emissions. The integration of RES-I, such as wind and solar photovoltaic (PV) power, in electricity markets entails great challenges mainly because of (i) intermittent production levels; and (ii) nearly zero marginal production costs. The inherent features of RES-I are being claimed of decreasing the wholesale electricity price, also known as the Merit-Order Effect (MOE). Meanwhile, the volatility of the wholesale electricity prices was also found to be strongly affected by electricity production levels from RES-I. This thesis is focused on analyzing the electricity market price dynamics in European countries and is divided in two parts. The first part consists of four essays, where the MOE and the behaviour of the wholesale electricity price is assessed in detail. The second part is composed by two essays, that discuss the potential consequences of energy transition policies aiming the reduction of the dependency in fossil fuels. The first part assesses, in the first essay, the impact in behaviour of the volatility of the Portuguese wholesale electricity price of the electricity produced from wind and solar PV power, by analysing two different samples. The long-sample covers a period where both wind and solar PV power incurred significant development levels, although the deployment of wind power stands out. Meanwhile, the small sample is focused in analysing the significant deployment of solar PV power. The main findings of this essay suggest that the the behaviour of the volatility of the electricity price, per-si, is less persistent in short-sample. This could be related to the knowledge acquired by market participants regarding the ramp-up phase of wind power, which makes them less susceptible of making short-sighted decisions in the speed-up period of the solar PV power. Furthermore, the electricity produced from wind and solar PV power revealed to increase and decrease the volatility of the wholesale electricity price, respectively. The differing production patterns of wind and solar PV power could be behind the reasoning for their divergent impacts on the volatility of the wholesale electricity price. Therefore, in the second and third essays, the behaviour of the wholesale electricity price is analysed for each hour of the day, by also considering the role of external factors, namely electricity imports and exports. Two different electricity markets, i.e., the Nord Pool and the Iberian, namely by focusing on Sweden and Spain, respectively, were analysed. The results of these two electricity systems, which have different pricing mechanisms (namely, zonal and uniform) and generation mix structures, were critically compared. The results of essay 2 revealed that the magnitude of the MOE was stable in Sweden during the 24 hours of the day. Meanwhile, in Spain, the behaviour of the MOE was found to vary significantly during the day. In fact, the differing behaviours of the MOE are related with the baseload and backup strategies used in each electricity system. The Swedish electricity system, has high production levels from nuclear power – with low production costs - and it belongs to an electricity market with great production levels of hydro power. However, in the Spanish electricity system, natural gas is the major backup energy source, which entails higher production costs. Another revealing finding of these two essays is the impact of the electricity flow in the behaviour of the wholesale electricity price. In Spain, electricity imports and exports reduce both the mean and volatility of the electricity price, in most hours of the day, as evidenced in the third essay. Meanwhile, in Sweden, the electricity flow, with neighbouring countries, appear to augment the volatility of electricity prices, mainly during peak hours of electricity consumption. This could be related with congestion in transmission lines. In fact, both zonal and uniform pricing mechanism reveal inneficiencies. In the fourth essay, where the main advantages and disadvantages of pricing mechanisms – zonal, uniform and nodal - are discussed, the potential inefficiencies in the redispatch mechanism, in the zonal and uniform pricing mechanisms, are warned. Backup strategies seem to have a prominent role in ensuring energy security. However, recent energy policies appear to underestimate the flexibility needs in electricity markets by strongly betting on displacing fossil energy sources. The second part of this thesis analyses, in the fifth essay, the role of the natural gas in the pre- and post-decommission period of coal power plants, in Portugal. The results revealed that the electricity produced from natural gas explains a greater percentage of the variance in electricity price after the decommissioning of coal power plants. In fact, the energy transition seems not to be ready to displace fossil energy sources from the electricity markets. In the last essay of this thesis, the impact of investment in research, development and demonstration (RD&D) in fossil energy sources and RES in retail electricity prices (both industrial and household) is analysed for 10 European countries. Additional investments RD&D in fossil energy sources is likely to decrease retail electricity prices (both industrial and households), while RD&D investments in RES increase household electricity prices. In short, this thesis provides insightful guidelines for designing energy policies considering the sustainable diversification of the electricity generation mix during the energy transition. The role of the electricity flow and resilient backup strategies were identified as potential strategies to ensure the resilience, as well as the reliability of electricity markets.
- Aplicação de Patient-Reported Outcome Measures (PROMs) em pacientes com Hipertensão Arterial – Revisão SistemáticaPublication . Fonseca, Daniel Filipe Silva; Almeida, Anabela Antunes de; Sousa, Miguel Castelo Branco Craveiro deIntrodução: A Hipertensão Arterial (HTA) é uma doença com elevada prevalência a nível mundial, sendo que para o seu tratamento é essencial a adesão do paciente às alterações de estilo de vida e à terapêutica farmacológica. Neste contexto de cuidados centrados no paciente, os Patient-Reported Outcome Measures (PROMs) têm particular interesse, por obter informações sobre vários resultados da saúde da perspetiva do paciente (PRO), o que permite melhorar os seus cuidados de saúde. Objetivo: Identificar quais os PROMs genéricos ou específicos de HTA que estão a ser aplicados para estudar doentes de HTA. Métodos: Para esta revisão sistemática da literatura foram utilizadas as bases de dados PubMed, B-on e Web of Science. Foram selecionados artigos escritos em inglês, espanhol e português, com publicação entre 23 de março de 2019 e 23 de março de 2024. A data da última pesquisa foi 23 de março de 2024. Foram incluídos artigos que aplicassem PROMs genéricos ou específicos de HTA a adultos com HTA, e excluídos protocolos de ensaios clínicos e estudos de desenvolvimento e/ou validação de PROMs. Para sintetizar os dados extraídos dos estudos foi elaborada uma tabela no Excel. Resultados: Foram obtidos 728 artigos da pesquisa nas bases de dados. Após remoção de duplicados (n=503), foram submetidos a triagem do título e resumo 225 artigos, com exclusão de 118 artigos nesta fase. Foram procurados 107 artigos para recuperação integral, resultando em 85 artigos. Deste número foram excluídos 77 artigos, por não cumprirem os critérios de elegibilidade, resultando num número final de 8 artigos. Estes artigos foram publicados em países diferentes, com tipos de estudos diferentes e tamanhos de amostra variáveis entre 140 a 1225. Foi identificado um total de 19 PROMs, incluindo um PROMs específico da HTA, o MINICHAL, e os seguintes PROMs genéricos: 6 domínios do PROMIS; EQ-5D-3L e EQ-5D-5L, com o EQ-VAS aplicado isoladamente também; SF-36 e SF-12; MMAS-8; TSQM 1.4; PHQ-8; GHQ-12; PSS; STAI; BDI-II; HADS. Quanto aos domínios avaliados, houve um foco na saúde mental, seguido da QVRS e da adesão à medicação. Conclusão: Esta revisão sistemática da literatura identificou um número variado de PROMs que avaliam diversos domínios, com destaque para o MINICHAL e os questionários dos grupos PROMIS, EuroQOL e SF-36/SF-12. Tendo em conta o número de estudos incluídos, é necessária mais investigação nesta área para esclarecer quais os instrumentos mais adequados, com desenvolvimento, validação e aplicação de mais PROMs específicos de HTA.