Analytical Model for the Performance Curves of a Family of Propellers based on Wind Tunnel Tests

The main objective of the work done in this dissertation is the construction and validation of an analytical model for the performance curves of a family of propellers tested at low Reynolds numbers. This kind of propellers is more commonly used in Unmanned Aerial Vehicles (UAVs). The model was designed in MATLAB® using a variety of regression techniques, such as the Least Squares Method (LSQ), via experimental data acquired at University of Illinois at Urbana-Champaign (UIUC), of measurements of seventeen APC Thin Electric propellers. The experimental data went through a reduction process for easier analysis. In order to further develop this model, tests were run at the Department of Aerospace Sciences (DCA) of University of Beira Interior (UBI) for ten more APC Thin Electric propellers. The analytical model will predict power coefficient and propeller efficiency accurately for the propellers with dimensions close to those that were used for its development. This model will be useful to achieve optimal design, providing a faster and more efficient propeller selection phase. The propeller performance obtained during the experimental tests will also be catalogued to further increase the documentation on propellers tested at LRN.O principal objetivo do trabalho levado a cabo nesta dissertação é a construção e validação de um modelo analítico para o desempenho de uma família de hélices com base em dados experimentais em condições de baixo número de Reynolds. Este tipo de hélices é mais utilizado em Veículos Aéreos Não Tripulados (VANTs). O modelo foi projetado em MATLAB® utilizando vários métodos de regressão, tal como o método dos mínimos quadrados (MMQ), baseado em dados experimentais obtidos na Universidade de Illinois em Urbana-Champaign (UIUC), de dezassete hélices testadas da APC Thin Electric. Os dados experimentais passaram por um processo de redução para um tratamento de dados mais facilitado. No âmbito do desenvolvimento deste modelo, foram feitos testes no Departamento de Ciências Aerospaciais (DCA), na Universidade da Beira Interior (UBI) a mais dez hélices da APC Thin Electric. O modelo analítico permite calcular os valores para o coeficiente de potência e para a eficiência propulsiva para hélices com dimensões próximas ou iguais das que foram utilizadas para a sua construção. Este modelo será útil para proporcionar uma melhor fase de projeto, providenciando uma mais rápida e eficiente seleção de hélice. Os dados dos testes ao desempenho das hélices obtidos durante o processo experimental foram catalogados para aumentar a documentação existente sobre hélices testadas em condições de baixo número de Reynolds

Analytical Model for the Performance Curves of a Family of Propellers Based on Wind Tunnel Tests

Propeller aircraft performance is greatly influenced by the performance of the propeller it uses. Thus, proper selection of a propeller for a given aircraft design at the early stages of the design process is fundamental. During the design of a new aircraft, simple yet accurate performance models are required to properly optimize the design. Significant experimental performance data of low speed, small propellers is available. The main objective of this work is to create and validate an analytical model for     the performance curves of a family of propellers tested at low Reynolds numbers, which can be used in selecting a propeller for a given existing aircraft design or during its design optimization process. This kind of propellers is more commonly used in Unmanned Aerial Vehicles (UAVs). The model is designed in MATLAB® using a variety of regression techniques, such as the Least Squares Method (LSQ), applied to experimental data acquired at University of Illinois at Urbana-Champaign (UIUC), for seventeen APC Thin Electric propellers, and at the Department of Aerospace Sciences (DCA) of University of Beira Interior (UBI), for ten more APC Thin Electric propellers. The analytical model predicts propeller power coefficient and propulsive efficiency accurately for the family of propellers tested and can also be used for the propellers with dimensions close to those used for its development. The propeller performance data obtained during the experimental tests are made available the community to further increase the documentation on propellers tested at low Reynolds numbers. Keywords: Propeller, Low Reynolds propeller performance, Propeller tests, Wind tunne

Práticas artísticas no ensino básico e secundário

Sobre a Matéria-Prima, há novidades e perigos. O tempo vivido na Europa e no contexto global tem vindo a acentuar a urgência das prioridades quantificadas, com um discurso dominante onde há menos política (pessoas) e mais representação económica (coisas). O correlato entre pessoas e coisas é, como sabemos, o dinheiro, ou trabalho reificado. A crise europeia, em torno da dívida soberana e dos maiores orçamentos do mundo, da capacidade da sua gestão na linguagem dura dos mercados e das taxas de juro veio modificar os objetivos imediatos da Europa, que em 2000 eram ambiciosos — “a sociedade mais competitiva do mundo em 2010” — para uma estratégia de emergência, agora chamada horizonte 2020. Este é o panorama ideal para colocar o ensino artístico em risco. Os fóruns internacionais passaram a valorizar os resultados da educação em rankings e sondagens de aproveitamento, cuja principal estratégia e preocupação é a mensurabilidade e comparabilidade, como são exemplo os relatórios PISA: avaliam-se em todos os países, as competências em Ciências, Matemática e Língua Materna. A matéria-prima de amanhã corre riscos de desaparecer gradualmente, pelos cortes de carga horária, pela concepção extracurricular da educação artística, pela sua perceção menorizada em função das concepções competitivas da sociedade contemporânea globalizada.info:eu-repo/semantics/publishedVersio

Outcomes after perioperative SARS-CoV-2 infection in patients with proximal femoral fractures: an international cohort study

Objectives Studies have demonstrated high rates of mortality in people with proximal femoral fracture and SARS-CoV-2, but there is limited published data on the factors that influence mortality for clinicians to make informed treatment decisions. This study aims to report the 30-day mortality associated with perioperative infection of patients undergoing surgery for proximal femoral fractures and to examine the factors that influence mortality in a multivariate analysis. Setting Prospective, international, multicentre, observational cohort study. Participants Patients undergoing any operation for a proximal femoral fracture from 1 February to 30 April 2020 and with perioperative SARS-CoV-2 infection (either 7 days prior or 30-day postoperative). Primary outcome 30-day mortality. Multivariate modelling was performed to identify factors associated with 30-day mortality. Results This study reports included 1063 patients from 174 hospitals in 19 countries. Overall 30-day mortality was 29.4% (313/1063). In an adjusted model, 30-day mortality was associated with male gender (OR 2.29, 95% CI 1.68 to 3.13, p80 years (OR 1.60, 95% CI 1.1 to 2.31, p=0.013), preoperative diagnosis of dementia (OR 1.57, 95% CI 1.15 to 2.16, p=0.005), kidney disease (OR 1.73, 95% CI 1.18 to 2.55, p=0.005) and congestive heart failure (OR 1.62, 95% CI 1.06 to 2.48, p=0.025). Mortality at 30 days was lower in patients with a preoperative diagnosis of SARS-CoV-2 (OR 0.6, 95% CI 0.6 (0.42 to 0.85), p=0.004). There was no difference in mortality in patients with an increase to delay in surgery (p=0.220) or type of anaesthetic given (p=0.787). Conclusions Patients undergoing surgery for a proximal femoral fracture with a perioperative infection of SARS-CoV-2 have a high rate of mortality. This study would support the need for providing these patients with individualised medical and anaesthetic care, including medical optimisation before theatre. Careful preoperative counselling is needed for those with a proximal femoral fracture and SARS-CoV-2, especially those in the highest risk groups. Trial registration number NCT0432364