Análise de tensões e deformações em fios de cabos condutores de linhas de transmissão

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2016.Este trabalho apresenta uma análise das tensões e deformações observadas nos fios do cabo condutor de linhas de transmissão de energia elétrica, na vizinhança de grampos de suspensão. O estudo considera um cabo IBIS submetido a condições de pré carga (EDS), carga de aperto no grampo e carregamento vibratório tipicamente associado a forças do vento. As simulações numéricas adotaram condições de carregamento consideradas em análises experimentais. O problema se mostra complexo em diversos aspectos, incluindo: (i) deformações plásticas de grande amplitude, (ii) centenas de regiões de contato, mesmo em pequenos trechos do cabo, (iii) necessidade de refinamento elevado da malha em cada região de contato, que levam a desafios como a solução de problemas envolvendo milhões de equações não lineares e estratégias de simulação numérica que evitem simultaneamente o travamento e os modos espúrios de deformação.This work aims to present an analysis of stresses and strains observed on the threads of electric transmission line conductors, in the neighborhood of suspension clamps. The study focuses on the IBIS cable submitted to conditions of Every Day Stress (EDS), clamp load and bending loads associated to aeolian forces. The numerical simulations adopted loading conditions typically considered in experimental analyses. The problem exhibits many complex features, including: (i) large plastic strains, (ii) hundreds of contact regions, even in small portions of cable, (iii) the need of highly refined mesh in the neighborhood of each contact region, which lead to challenges as the solution of problems involving millions of nonlinear equations as well as strategies of numerical simulations which tackle simultaneously the locking and hourglass modes often present when isochoric strains are involved

Estudo de contato elasto-plástico entre fios de cabos de linhas de transmissão

Monografia (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2014.O presente relatório apresenta o estudo de contato de Hertz entre cilindros simulando o contato de fios, de caso sobre atrito estático e de plasticidade. A teoria presente aqui será posta à prova com a análise de elementos finitos com o Abaqus CAE para os tópicos estudados. O caso de contato será dividido em contato bidimensional e tridimensional elástico, sendo este último com cilindros com eixos paralelos e rotacionados por ângulos de 30° e 90° em relações ao seus eixos. Será, ainda, apresentado a simulação de obtenção da curva de plasticidade do Al 7075-T651 bem como a aplicação do contato elasto-plástico para o contato entre fios rotacionados por 30°. _____________________________________________________________________________ ABSTRACTThis report presents the study of Hertz’ contact between cylinders simulating the contact of wires under influences of static friction and plasticity. The theory here presented will be tested using the finite element analysis with Abaqus CAE to the topics studied. The case of contact will be divided into two-dimensional and three-dimensional elastic contact situations, the latter with cylinders arranged according its parallel axes and being rotated by angles of 30 ° and 90 ° in relationship to their axes. The simulation of the plasticity curve of Al 7075-T651 is also presented and the application of elastic-plastic contact between wires rotated by 30°

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)