1,720,953 research outputs found
Óleos básicos vegetais biodegradáveis como potencial alternativa aos óleos básicos convencionais : comparação das propriedades físico-químicas e tribológicas e viabilidade econômica na formulação de biolubrificantes automotivos e industriais.
No full textA demanda de energia global apresenta uma projeção de crescimento entre os anos de 2010
e 2030 de 33,5%. Esta expectativa impacta diretamente no consumo do petróleo, fonte principal dos
óleos básicos utilizados na formulação de óleos lubrificantes. Atualmente, estima-se que estes óleos
minerais são usados em 95% do volume global de lubrificantes. A grande preocupação sobre este tipo
de produto é a sua disposição incorreta no meio ambiente, uma vez que de 40% a 55% do volume
total não possuem uma logística reversa apropriada. Diante desta necessidade por fontes renováveis
de energia, preocupações com políticas ambientais como o ESG, depreciação das reservas de óleos
brutos, criação de normas internacionais como a MARPOL 73/78 e crescimento da participação dos
biolubrificantes nos setores de transporte e equipamentos pesados, os óleos básicos biodegradáveis
têm se mostrado fortes candidatos a substituírem as bases convencionais nas formulações dos
lubrificantes, total ou parcialmente. Estes produtos são, em sua maioria, polialfaolefinas (PAOs)
polialquilenoglicois (PAGs), ésteres sintéticos e ésteres naturais provenientes de fontes animais e/ou
vegetais. Para o presente trabalho, os principais óleos vegetais foram mapeados aplicando equações
de busca (bibliometria) nas bases de dados Web of Science e Scopus a fim de definir suas fontes bem
como a frequência com que eles são discutidos nas produções científicas. O Brasil produziu em 2019
cerca 35.000 m3
de lubrificantes biodegradáveis, volume que corresponde a, aproximadamente 2,65%
da produção total nacional neste mesmo ano. As bases biodegradáveis utilizadas nestas formulações,
quando comparadas físico-quimicamente com os óleos básicos minerais, apresentam baixa
toxicidade, boa lubricidade, elevado ponto de fulgor, elevado índice de viscosidade, baixa volatilidade
e boa resistência ao cisalhamento. Por outro lado, a pouca eficiência na resistência à oxidação e a
fluidez limitada em baixas temperaturas geram necessidade de modificar quimicamente estas bases
para que elas sejam utilizadas na formulação dos biolubrificantes. Quando se avalia os custos das
bases sustentáveis, nota-se que elas se tornam competitivas à medida que as comparações são feitas
com óleos convencionais mais refinados, como os de Grupo III e PAOs, por exemplo. No entanto,
óleos minerais, principalmente no cenário nacional devido ao refino local, ainda se posicionam mais
competitivos. Frente a estes expostos, um caminho interessante a ser seguido é avaliar o uso conjunto
das bases convencionais e biodegradáveis a fim de se obter um custo atrativo e desempenho adequado
para o lubrificante final, além de contribuir com a descarbonização do setor e reduzir a sua pegada de
carbono.
Palavras-chave: biolubrificantes, óleos vegetais, sustentabilidade, pegada de carbono, ESG,
bibliometria.he global energy demand presents a growth projection of 33.5% between the years
2010 and 2030. This expectation directly impacts the consumption of oil, the primary source of
base oils used in lubricating oil formulations. Currently, it is estimated that these mineral oils
are used in 95% of the global lubricant volume. The major concern regarding this type of
product is its improper disposal into the environment, as from 40% to 55% of the total volume
lack proper reverse logistics. In the face of the need for renewable energy sources,
environmental policy concerns such as ESG, depreciation of crude oil reserves, the
establishment of international standards like MARPOL 73/78, and the increasing role of
biolubricants in transportation and heavy equipment sectors, biodegradable base oils have
emerged as strong candidates to replace conventional bases in lubricant formulations, either
entirely or partially. These products are primarily composed of polyalphaolefins (PAOs),
polyalkylene glycols (PAGs), synthetic esters, and natural esters derived from animal and/or
vegetable sources. For this study, the primary vegetable oils were mapped using search
equations (bibliometrics) in the Web of Science and Scopus databases to determine their
sources and frequency of discussion in scientific literature. In 2019, Brazil produced
approximately 35,000 m3
of biodegradable lubricants, which corresponds to approximately
2.65% of the total national production in the same year. The biodegradable bases used in these
formulations, when compared to the physicochemical parameters of mineral base oils, exhibit
low toxicity, good lubricity, high flash point, high viscosity index, low volatility, and good
shear stability. On the other hand, their limited oxidation resistance and restricted fluidity at
low temperatures necessitate chemical modifications to make these bases suitable for
biolubricant formulations. When evaluating the costs of sustainable bases, they become
competitive when comparisons are made with more refined conventional oils, such as Group
III and PAOs, for example. However, mineral oils, especially in the Brazilian context due to
local refining, still maintain a competitive position. Given these factors, an interesting approach
to consider is the joint use of conventional and biodegradable bases to achieve an attractive cost
and suitable performance for the final lubricant, in addition to contributing to the decarbonization
of the sector as well as reducing its carbon footprint
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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