Proposta de modelos individual e agregado no domínio do tempo para estimação de correntes harmônicas em usinas eólicas e fotovoltaicas

Tese (doutorado) — Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2021.Nas análises das distorções harmônicas causadas por fontes renováveis de energia, modelos computacionais são frequentemente empregados para a reprodução de impactos que emergem da interação entre a operação do conversor, as distorções pré-existentes na rede e a impedância harmônica do sistema. De acordo com a literatura atinente, poucos modelos individuais simplificados desenvolvidos no domínio do tempo são capazes de ao mesmo tempo i) estimar com precisão as distorções harmônicas e ii) reduzir o tempo de simulação demandado por modelos detalhados. Além disso, é possível observar na literatura uma lacuna no tocante a modelos equivalentes capazes de representar o comportamento harmônico de múltiplos inversores em usinas renováveis de grande porte. Nesse contexto, este trabalho apresenta uma proposta de modelo average harmônico (HM – do inglês harmonic average model) para a reprodução de unidades inversoras, e uma proposta de modelo harmônico agregado (AHM – do inglês aggregated harmonic model) para a estimação de correntes harmônicas geradas por múltiplos inversores em plantas eólicas e fotovoltaicas. No processo de concepção do HM, o princípio da superposição é aplicado em um modelo médio para a inclusão dos efeitos do tempo morto e do chaveamento dos conversores. No processo de montagem do AHM, emprega-se o HM para a representação da usina por meio de um único gerador e, em seguida, aplica-se o método de agregação de circuitos coletores desenvolvido pelo National Renewable Energy Laboratory (NREL). Da análise dos resultados das simulações computacionais executadas, é possível constatar que as formas de onda e os espectros harmônicos produzidos pelo HM e pelo AHM são aderentes àqueles proporcionados por modelos detalhados e medições reais. Cabe ressaltar que os métodos propostos são modelos genéricos rápidos e relativamente simples de serem implementados. Com isso, conclui-se que estes modelos podem ser empregados por operadores de sistemas elétricos para estimar as correntes harmônicas produzidas por inversores e, paralelamente, para analisar os impactos das fontes renováveis na qualidade e estabilidade da energia elétrica.In the analyses of harmonic distortions caused by renewable energy sources, computational models are required to reproduce the impacts that emerge from the interaction between the converter operation, background distortions, and harmonic grid impedance. According to the literature, few simplified time-domain individual models can simultaneously i) estimate harmonic currents and ii) reduce the computation time demanded by detailed models. Further, it is possible to observe a gap in the literature regarding equivalent models used to represent the harmonic behavior of multiple inverters in large-scale power plants. This work proposes a harmonic average model (HM) to represent individual inverters and an aggregated harmonic model (AHM) to estimate the harmonic currents generated by multiple converters in wind power plants and photovoltaic systems. For the HM, we apply the superposition principle in an average model to include dead time and switching effects. For the AHM, we use the HM to reproduce the entire plant as a single-machine topology and employ the National Renewable Energy Laboratory (NREL) method for equivalencing the collector system. Based on the simulation results, we verify that the waveforms and harmonic spectra produced by the HM and AHM are in accordance to those generated by detailed models and real-world measurements. It is worth mentioning that the proposed method provides generic models that are fast and relatively simple to deploy. These results show that the HM and AHM are suitable to predict harmonic currents of inverters. Further, these models investigate the impacts of renewable energy sources on power quality and system stability

Reconditioning in synchronous operation with one parallel induction generator

The purpose of this paper is to compare mathematical modeling and practical bench in order to validate the electrical interactions between an induction generator and a synchronous generator. Two generators was connected to a common bus in steady state, subject to non-linear load. The results comparing modeling and bench tests show that the induction generator besides the active power increasing, has a better way for harmonic currents flowing in common bus. It was concluded that the induction generator repowering and attenuates current harmonic components present at the connection point, improving the network voltage profile

Activity of scorpion venom-derived antifungal peptides against planktonic cells of Candida spp. and Cryptococcus neoformans and Candida albicans Biofilms

The incidence of fungal infections has been increasing in the last decades, while the number of available antifungal classes remains the same. The natural and acquired resistance of some fungal species to available therapies, associated with the high toxicity of these drugs on the present scenario and makes an imperative of the search for new, more efficient and less toxic therapeutic choices. Antimicrobial peptides (AMPs) are a potential class of antimicrobial drugs consisting of evolutionarily conserved multifunctional molecules with both microbicidal and immunomodulatory properties being part of the innate immune response of diverse organisms. In this study, we evaluated 11 scorpion-venom derived non-disulfide-bridged peptides against Cryptococcus neoformans and Candida spp., which are important human pathogens. Seven of them, including two novel molecules, showed activity against both genera with minimum inhibitory concentration values ranging from 3.12 to 200 μM and an analogous activity against Candida albicans biofilms. Most of the peptides presented low hemolytic and cytotoxic activity against mammalian cells. Modifications in the primary peptide sequence, as revealed by in silico and circular dichroism analyses of the most promising peptides, underscored the importance of cationicity for their antimicrobial activity as well as the amphipathicity of these molecules and their tendency to form alpha helices. This is the first report of scorpion-derived AMPs against C. neoformans and our results underline the potential of scorpion venom as a source of antimicrobials. Further characterization of their mechanism of action, followed by molecular optimization to decrease their cytotoxicity and increase antimicrobial activity, is needed to fully clarify their real potential as antifungals

A sexualidade na opinião de adolescentes residentes na área de abrangência Dr. Fábio em Cuiabá MT

Estudo quantitativo que objetivou conhecer o entendimento dos adolescentes a respeito da própria sexualidade e o modo como a exerce, para posterior intervenção da equipe de saúde. Foi aplicado um questionário estruturado em uma amostra de 43 adolescentes com idades entre 12 a 19 anos, residentes na área de abrangência da Unidade de Saúde da Família Dr. Fábio I e II. Os dados encontrados foram tabulados em planilhas do programa Microsoft Office Excel 2007, possibilitando um tratamento descritivo, mantendo-se um intervalo de confiança de 95%. Os resultados revelam que 32,5% dos participantes tiveram a primeira relação sexual entre 12 a 16 anos, e 50% deles admitem não ter usado preservativo na última relação sexual. Além disso, 4,6% já tiveram algum tipo de doença sexualmente transmissível. O estudo indica a necessidade de ações educativas em saúde sexual e reprodutiva voltada aos adolescentes dos bairros estudados, com vistas a promoção da saúde

Tomografia de corpo todo no trauma e seus desfechos na mortalidade: uma revisão sistemática: Whole body tomography in trauma and its outcomes in mortality: a systematic review

A tomografia computadorizada de corpo inteiro é altamente sensível e representa o padrão-ouro no cenário de diagnóstico da sala de trauma. WBCT fornece uma ferramenta de diagnóstico rápido, que reduz a mortalidade em pacientes gravemente feridos. A lesão traumática é a terceira principal causa de morte em geral. Para otimizar os resultados nesses pacientes, os hospitais empregam imagens de tomografia computadorizada de corpo inteiro (WBCT) devido ao alto rendimento diagnóstico e potencial para identificar lesões perdidas. No entanto, isso atrasa intervenções de tempo crítico. Atualmente, há uma ausência de qualquer evidência de alto nível para apoiar ou refutar qualquer visão. Uma busca sistemática da literatura foi realizada nas bases de dados MEDLINE, Embase, Web of Science, Cochrane Library e demais bases dedados eletrônicas. As publicações eram elegíveis se contivessem dados originais comparando TC de corpo total imediata em pacientes com trauma e associação com a mortalidade. A análise mostra que a TC está associada a melhores resultados, incluindo uma menor taxa de mortalidade geral, entretanto estudos randomizados e controlados merecem ser realizados para que se possa estabelecer de forma fidedigna essa relação

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

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI