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Análise termoeconômica de uma central de ciclo combinado de 826 mw - estudo de caso utilizando um simulador full-scope
Full text linkCombined cycle power plants are increasing their role in the electricity generation
worldwide. These plants stand out for their higher efficiency, lower electricity production costs
and relatively low greenhouse gas emissions. In Brazil, a country with mostly renewable energy
generation, these plants have been increasing their participation in electricity production. It is
noteworthy that combined cycle power plants can show off as an alternative to diversify the
Brazilian energy matrix and increase the reliability of the system, preventing supply crisis just
like happened in the past. In this context, this works performs an energetic, exergetic and
exergoeconomic analysis of a combined cycle power plant, using a full-scope simulator, which
digitally and faithfully reproduces the operation of the EDF Norte Fluminense Power Plant,
located in Macaé-RJ. Briefly, the simulator presents an exact duplicate of the real power plant
and its operation is identical to the operation of the EDF Norte Fluminense Power Plant.
The results show that the energy efficiency of the studied plant is equal to 51.47% and
the exergetic efficiency is equal to 49.25%. In addition, it was found that the equipment parts
that are responsible for the main irreversibilities are: combustion chamber, gas turbines and
heat recovery steam generators. From the exergoeconomic analysis, it was found that the cost
of electricity production, for the base case, was calculated to be 0.3891 R/MWh, o que é 10%
inferior ao CVU calculado pela ANEEL para a usina em questão. Por fim, verificou-se que,
quanto maior o tempo de operação anual da usina, menor o custo de produção de eletricidade,
o que pode motivar a construção de novas usinas de ciclo combinado para operar na base do
sistema elétrico brasileiro, reduzindo a dependência de hidrelétricas e proporcionando ao
consumidor tarifas inferiores àquelas observadas nas operações de térmicas convencionais
Estudo experimental do desempenho, combustão e emissões de um motor de ignição por compressão operando com HVO em modo dual-fuel com hidrogênio ou gás natural
Full text linkHVO and green hydrogen are highly promising alternative fuels with great potential to meet increasingly stringent environmental regulations regarding greenhouse gases emissions. In this context, this study presents an experimental analysis of the performance, combustion, and emissions of a compression ignition engine operating with HVO in dual-fuel mode, using port-fuel injection of hydrogen or compressed natural gas (CNG). For this purpose, a fully instrumented test bench was developed, and a compression ignition engine, model FPT NEF 67, was adapted to operate in dual-fuel mode, by using pilot injection of HVO or diesel and port-fuel injection of hydrogen or CNG. The experimental tests were divided into three stages: conventional operation tests with diesel and HVO separately; dual-fuel operation with diesel as the pilot fuel and injections of hydrogen or CNG separately; and dual-fuel tests with HVO as the pilot fuel and the same gaseous fuels. The results indicated that single-fuel operation with HVO presented significant advantages over diesel, such as higher combustion efficiency and fuel conversion efficiency, even without adjustments to the engine’s injection parameters. Additionally, there were reductions in CO2 emissions (an average of 3.16 %), NOx (an average of 6.63 %), as well as lower formation of HC, CO, and particulate matter. In dual-fuel operation, an increase in in-cylinder pressure was observed with the injection of H2 or CNG, regardless of the pilot fuel used. Nevertheless, both the pressure rise rate and the IMEP covariance remained close to the values observed in single-fuel operation. Increases were also observed in the maximum heat release rate and the maximum temperature in the combustion chamber, along with a longer ignition delay, longer combustion duration, and a reduction in fuel conversion efficiency. Even so, the HVO-hydrogen combination showed potential for reducing NOx and CO2 emissions, representing a viable alternative to replace diesel. Finally, implementing a programmable system to optimize injection conditions may be a strategy to mitigate efficiency losses.HVO e hidrogênio verde são combustíveis alternativos bastante promissores, com potencial para atender às legislações ambientais cada vez mais rigorosas quanto a descarbonização do setor de transportes. Nesse contexto, este trabalho apresenta uma análise experimental de desempenho, combustão e emissões de um motor de ignição por compressão operando com HVO, em modo dual-fuel, utilizando injeção port-fuel de hidrogênio ou gás natural veicular (GNV). Para isso, foi desenvolvida uma bancada de testes com instrumentação completa, e um motor de ignição por compressão, modelo FPT NEF 67, foi adaptado para operar em modo dual-fuel, com injeção piloto de HVO ou diesel e injeção port-fuel de hidrogênio ou GNV. Os ensaios experimentais foram divididos em três etapas: testes em modo convencional com diesel e HVO separadamente; operação em modo dual-fuel com diesel como combustível piloto e injeções de hidrogênio ou GNV, separadamente; e ensaios em modo dual-fuel com HVO como combustível piloto e com os mesmos combustíveis gasosos. Os resultados indicaram que a operação com HVO em modo single-fuel apresentou vantagens significativas em relação ao diesel, como maior eficiência de combustão e de conversão de combustível, mesmo sem ajustes nos parâmetros de injeção. Além disso, houve reduções nas emissões de CO2 (em média 3,16 %), NOx (média de 6,63 %), além de menor formação de HC, CO e material particulado. Na operação dual-fuel, verificou-se um aumento na pressão no interior do cilindro com a injeção de H2 ou GNV, independentemente do combustível piloto utilizado. Apesar disso, tanto a taxa de aumento de pressão, quanto a covariância do IMEP permaneceram próximas aos valores observados na operação single-fuel. Também foram verificados aumentos na taxa máxima de liberação de calor e na temperatura máxima na câmara de combustão, além de maior atraso de ignição, maior duração da combustão e redução na eficiência de conversão de combustível. Ainda assim, a combinação HVO-hidrogênio demonstrou potencial para reduzir as emissões de NOx e CO2, representando uma alternativa com potencial de substituir o diesel. Por fim, a implementação de um sistema programável para otimizar as condições de injeção pode ser uma estratégia para mitigar a redução da eficiência
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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