Estudo de estratégias de controlo activo de vibrações para um edifício de dois andares

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Civil - Perfil de EstruturasAs estruturas podem ser sujeitas a acções dinâmicas capazes de provocar vibrações excessivas, comprometendo o conforto e, em casos extremos, a segurança dos seus utilizadores. Ao longo das últimas décadas têm sido desenvolvidos e aplicados diversos sistemas de controlo de vibrações em pontes e edifícios altos. Neste trabalho descrevem-se sucintamente alguns sistemas de controlo passíveis de serem aplicados em estruturas de engenharia civil e apresentam-se alguns casos de estudo. Esta dissertação exemplifica o dimensionamento de um sistema de controlo activo para um modelo de um edifício de dois andares. As vibrações são absorvidas por um amortecedor de massa activo (AMD) posicionado no topo do pórtico. As técnicas utilizadas para o dimensionamento do controlador fazem parte da teoria de controlo moderno. O primeiro método consiste na alocação de pólos que permite ao projectista mudar directamente as características dinâmicas da estrutura. A segunda metodologia consiste num problema de optimização em que o dimensionamento do controlador é feito de forma a minimizar um índice de desempenho quadrático. Além de introduzir os princípios básicos de dimensionamento de controladores, será referido o funcionamento de um observador e o seu papel no sistema de controlo. Na componente prática da tese foi desenvolvido um programa, em MATLAB e SIMULINK, que permite simular o comportamento do pórtico e avaliar a eficiência do sistema de controlo quando se aplicam acções externas

Reinforced dowel type connections: mechanical behaviour under cyclic tests

Dowel type joints are widely used in timber structures given their ease of construction and ability to dissipate energy when subjected to cyclic loading. The behaviour of these connections under cyclic loading depends on good detailing at the design phase, which is developed to guarantee ductile failure modes and avoid wood splitting through careful consideration of the dowel-to-edge and dowel-to-end distances. This conference paper presents the cyclic response of a dowel type connection that is reinforced with self-tapping screws (STS). The experimental campaign included unreinforced joints, with inadequate and adequate end distances as defined per Eurocode 5, and joints with self-tapping screws fastened perpendicular to the dowels to avoid premature splitting. To reduce the number of variables of the experimental design, dowel slenderness and position of the reinforcements were kept throughout the testing programme. Moreover, the laboratory tests only considered specimens loaded in the parallel-to-grain direction. The influence of timber species was evaluated by using specimens from Pinus pinaster and Pinus sylvestris. Laboratory testing results highlight the ability of dowel-type joints to withstand large displacement reversals without rupture. The reinforcement scheme proposed in this work achieved ductility values consistent with the Eurocode's Ductility Class High structures.This work was financed by FEDER funds through the Competitivity and Internationalization Operational Programme COMPETE, Portugal 2020, and by national funds through FCT – Foundation for Science and Technology within the scope of the Timquake project POCI-01-0145-FEDER-032031. Gratitude is extended towards Rothoblass, Portilame, and AOF for materials supplied

Monotonic tests on beam-to-column joint with steel link for timber seismic resistant structures

For the design of dissipative heavy timber frame structures, in the context of modern seismic design approach based on the mechanical triad of strength, stiffness and ductility, brittle timber failure modes can be avoided by integrating modern timber connection technology into hybrid timber-steel system. The overall seismic performance can be improved, entrusting the dissipation function to ad hoc conceived devices, as an alternative to connections. Steel links located at the ends of the beams are very promising solutions, which can develop plastic hinges, thus providing a ductile behaviour, with a significant dissipative capacity. Besides timber members, as well as connections, to be designed with an adequate over-strength, can remain in elastic field. In this perspective, the paper illustrates the mechanical characterisation through monotonic tests of two different configurations of timber beam-to-column joint with steel link for heavy timber frames, consisting of a timber element connected to a steel link by means of a steel end-plate and glued-in steel rods. The experimental results indicate a satisfactory agreement with the theoretical ones, therefore the suitability of the system and of the design criteria.The research project DPC–ReLUIS 2019-2021 and 2022-2024 - WP13 Contribution to standards for timber structures, and the Department of Civil Engineering (DECivil) laboratory of the Minho University, in Guimaraes (Portugal) are acknowledged

A list of land plants of Parque Nacional do Caparaó, Brazil, highlights the presence of sampling gaps within this protected area

Brazilian protected areas are essential for plant conservation in the Atlantic Forest domain, one of the 36 global biodiversity hotspots. A major challenge for improving conservation actions is to know the plant richness, protected by these areas. Online databases offer an accessible way to build plant species lists and to provide relevant information about biodiversity. A list of land plants of “Parque Nacional do Caparaó” (PNC) was previously built using online databases and published on the website "Catálogo de Plantas das Unidades de Conservação do Brasil." Here, we provide and discuss additional information about plant species richness, endemism and conservation in the PNC that could not be included in the List. We documented 1,791 species of land plants as occurring in PNC, of which 63 are cited as threatened (CR, EN or VU) by the Brazilian National Red List, seven as data deficient (DD) and five as priorities for conservation. Fifity-one species were possible new ocurrences for ES and MG states

ANÁLISE COMPARATIVA DO USO DA ESTATINA E DO ÁCIDO NICOTÍNICO NO TRATAMENTO DA SÍNDROME METABÓLICA

Considering metabolic syndrome (MS) as a pathophysiological condition characterized by arterial hypertension, central obesity, insulin resistance, dyslipidemia, and hyperglycemia, this study aims to compare the use of statins and nicotinic acid in the treatment of MS. To this end, a comparative analysis based on relevant clinical and epidemiological studies was conducted. Thus, it is observed that statins significantly reduce LDL cholesterol by about 50% and decrease the risk of cardiovascular events by 25% to 35%, with an odds ratio (OR) of improvement between 0.70 and 0.80. Statins are widely available and accessible, especially in generic versions, and have a relatively manageable adverse effect profile. In contrast, nicotinic acid reduces LDL cholesterol by 15% to 25%, increases HDL cholesterol, and reduces triglycerides, but with less consistent efficacy in preventing cardiovascular events (OR ranging from 0.90 to 1.10) and significant side effects, such as skin flushing and hepatotoxicity. The cost and availability of nicotinic acid are more limited compared to statins. It is concluded that statins are the preferred choice for the treatment of MS due to their robust efficacy and accessibility, while nicotinic acid may be considered in specific cases, with caution due to its adverse effects.Considerando a síndrome metabólica (SM) como uma condição fisiopatológica caracterizada por hipertensão arterial, obesidade central, resistência à insulina, dislipidemia e hiperglicemia, este estudo objetiva comparar o uso de estatinas e ácido nicotínico no tratamento da SM. Para tanto, procede-se a uma análise comparativa baseada em estudos clínicos e epidemiológicos relevantes. Desse modo, observa-se que as estatinas reduzem significativamente o LDL-colesterol em cerca de 50% e diminuem o risco de eventos cardiovasculares em 25% a 35%, com odds ratio (OR) de melhora entre 0,70 e 0,80. As estatinas são amplamente disponíveis e acessíveis, especialmente nas versões genéricas, e apresentam um perfil de efeitos adversos relativamente manejável. Em contraste, o ácido nicotínico reduz o LDL-colesterol em 15% a 25%, aumenta o HDL-colesterol e reduz os triglicerídeos, mas com uma eficácia menos consistente na prevenção de eventos cardiovasculares (OR variando de 0,90 a 1,10) e efeitos colaterais significativos, como rubor cutâneo e hepatotoxicidade. O custo e a disponibilidade do ácido nicotínico são mais limitados em comparação às estatinas. Conclui-se que as estatinas são a escolha preferida para o tratamento da SM devido à sua eficácia robusta e acessibilidade, enquanto o ácido nicotínico pode ser considerado em casos específicos, com precaução devido aos seus efeitos adversos

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost