RELIABILITY OF LIGHT-FRAME WOOD ROOF CONSTRUCTION UNDER EXTREME WIND LOADS

Light-frame wood construction is frequently used in the U.S. High wind events, such as hurricanes, may cause severe damage to these structures by breaking the roof envelope. This study focuses on computing reliability indices of roof sheathing panels exposed to high wind events while considering a time and spatially varying wind load. A procedure is developed that links probabilistic and dynamic finite element analysis codes. The results show that a few critical panels are most susceptible to damage, while most panels have significantly higher reliability indices than previous studies based on simplified analyses have shown. By setting a target reliability index, panel nail spacing can be adjusted to provide a more uniform level of safety over the entire roof

O aluguel de ações no mercado financeiro brasileiro e os efeitos da proibição da venda a descoberto

Esta monografia pretende explicar o funcionamento do mercado de aluguel de ações, através da análise de sua regulamentação, assim como do comportamento dos investidores no atual cenário brasileiro e a íntima relação da operação de aluguel de ações com as operações de venda a descoberto - amplamente realizadas no mercado financeiro. O presente trabalho se propõe, também, a identificar os impactos gerados pelas operações de venda a descoberto no mercado financeiro como um todo, e as consequências ocasionadas por restrições impostas à realização deste tipo de operação em determinados cenários macroeconômicos

Knowledge and Use of PEP and PrEP Among Key Populations Tested in Community Centers in Portugal

Background: Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) have been increasingly available in Europe. Due to the high burden of HIV in key populations, these could benefit from their use. In 2016, in Portugal, an open, non-interval, prospective cohort study was established in a network of 26 community-based voluntary HIV/STI counseling and testing centers. Data collected included questions on PEP and PrEP knowledge and use. We aimed to estimate the proportion of PEP and PrEP knowledge and its use among key populations, visiting the centers between 2016 and 2019. Method and results: Individuals who self-identify as being among at least one key population for HIV, men who have sex with men (MSM), people who inject drugs (PWID), sex workers (SW), migrants, and male-to-female transgender individuals (MTF), responded to questions on PEP and PrEP knowledge and use while waiting for their test results between 2016 and 2019 (n = 12,893 for PEP; n = 10,973 for PrEP). Reported knowledge was low in all key populations for both tools: 15.7% of respondents reported knowing about PEP and 10.9% about PrEP over the course of 4 years. PEP was used by 1.8% and PrEP by 0.4% of the respondents, MSM being 88.9% of PrEP users, and 52.8% of PEP users. Multivariate logistic regression showed multiple factors associated with knowing the tools, including age, education, country of birth, gender, year of test, having a reactive HIV test in the same visit, reporting an STI or condomless sex in the last 12 months, and identifying with being MSM or SW. Conclusions: Knowledge and use of PEP and PrEP remain low among key populations in Portugal. The need remains to increase knowledge and use among those at risk for HIV infection.DS was the recipient of PhD Grant PD/BD/128008/2016 from Fundação para a Ciência e Tecnologia (FCT), co-funded by POCH/FSE. AA was the recipient of PhD Grant 2020.09390.BD co-funded by the FCT and the POCH/FSE Program. Project development and implementation was supported by Iceland, Liechtenstein and Norway Grants (EEA Grants), grant identification 00200DT1. Grupo de Activistas em Tratamentos received unrestricted grants from Abbvie, Abbott, Gilead, Janssen and ViiV to support project implementation

Caracterização elétrica de barramentos laminados para DC-links

Dissertação de mestrado integrado em Engenharia Eletrónica, Industrial e ComputadoresO crescente desenvolvimento de soluções para mobilidade elétrica e para a geração distribuída de energia elétrica, como a fotovoltaica, leva à procura por circuitos de eletrónica mais baratos, mais leves, mais eficientes e mais robustos. Os transístores de potência com tecnologias baseadas em Silicon Carbide (SiC) e Gallium Nitride (GaN) são resultado dessa evolução, suportando condições mais severas e alcançando níveis mais altos de eficiência através de perdas reduzidas durante a sua comutação, sendo esta mais rápida, de muitas dezenas a centenas de kHz. O aumento da frequência de operação torna ainda mais rigorosos os requisitos sobre elementos parasitas, em particular a indutância parasita inerente ao banco de condensadores que constitui o DC-link dos inversores. Em aplicações atualmente em desenvolvimento, esses requisitos têm sido geralmente abaixo de 10 nH e até “sub-nano” para aplicações específicas. Ao longo deste documento, será discutida em profundidade a indutância parasita de condensadores de filme implantados como DC-links, como descrevê-los através de um modelo matemático (melhorando o tempo de desenvolvimento de novos produtos) e soluções de desenho para minimizar a sua indutância equivalente. Estas soluções são validadas com a construção de amostras reais testadas em laboratório. No decurso da dissertação, na Vishay Eletrónica Portugal (VEP), foi elaborado um estudo relativo aos DC-links com condensadores de filme de baixa indutância. Foi criado um modelo de cálculo de indutância de acordo com a geometria dos conjuntos de condensadores, e ainda um conjunto de diretivas para orientar a futura construção dos conjuntos de condensadores. Foram desenhados oito protótipos de DC-link, através dos ferramentas de software SolidWorks e Paint3D que foram posteriormente construídos na Vishay, com o objetivo de verificar a influência da utilização dos princípios de mitigação de indutância e a fiabilidade do modelo de cálculo elaborado. Foram obtidos resultados experimentais que permitiram elaborar um artigo que descreve o trabalho realizado pelo autor ao longo da dissertação de mestrado.The increasing adoption of electric vehicles and distributed generation, such as photovoltaic, lead to the demand of cheaper, lighter, more efficient, and robust circuits. Power switches based on Silicon Carbide (SiC) and Gallium Nitride (GaN) are a result of this evolution, withstanding harsher conditions and reaching higher levels of efficiency through a faster switching, from many dozens to hundreds of kHz. Increasing the operation frequency turns the requisites over parasitic elements even more strict, in particular the stray inductance inherent to the capacitor bank that constitutes the inverters’ DC link. In applications currently under development, these requisites have been usually below 10 nH and even “sub-nano” for specific applications. In this text, it will be discussed in depth the parasitic inductance of film capacitors deployed as DC links, how to mathematically describe them (improving new products development time) and design solutions to minimize the total inductance of the set. These solutions are validated with the construction of real samples tested in laboratory. During the dissertation, at Vishay Eletrónica Portugal (VEP), a study was carried out on DC-links with low inductance film capacitors. An inductance calculation model was created according to the geometry of the capacitor sets, as well as a set of directives to guide the future construction of the capacitor sets. Eight DC-link prototypes were modeled, using Paint3D and SolidWorks software, which were later built at Vishay, to verify the influence of the use of inductance mitigation principles and the reliability of the calculated calculation model. Through the obtained experimental results, an article was prepared that describes the work carried out by the author throughout his master's dissertation

Structural dynamic updating using a global optimization methodology

In this article, we present the application of a global optimization technique, in particular the GlobalSearch command from MatLab®, in the updating of structural dynamic models. For comparative purposes, we evaluate the efficiency of the global method relatively to the local search method previously used in the Finite Element Model Updating program. The Finite Element Model Updating programs are designed with the primary purpose of validating and optimizing structural numerical models. The first step for structural optimization process is to idealize the desired behavior of the dynamic model to develop, or collect experimental data of a physical model considered as the reference model. The process begins with the construction, on a finite element program, of a numerical model with initial physical parameters, preferably close to the reference model parameters. The numerical model is then submitted, through a Finite Element Model Updating program, to a successive parametric updating until improving its dynamic behavior described by their natural frequencies, mode shapes and damping properties, be similar to the dynamic behavior of the reference model. The Sequential Quadratic Programming algorithm was already used in the optimization of the Finite Element Model Updating program, and the obtained solutions showed that it can’t achieve the global optimal value of the objective function. This kind of methods, used for nonlinear constrained optimization problems, have, generally, difficulties to achieve the global optimum, since they are local optimization methods.Centre for Mechanical and Materials Technologies (CT2M) and Algoritmi R&D Centreinfo:eu-repo/semantics/publishedVersio

Dimensionamento de sistemas de isolamento de base em estruturasde edificios de acordo com o eurocódigo 8

Mestrado Integrado. Engenharia Civil - Especialização em Estruturas. Faculdade de Engenharia. Universidade do Porto. 201