1,720,967 research outputs found
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
General effects of pulsed wire feeding on GMAW process with globular metal transfer
No full textThe use of pulsed wire feeding has been a field of innovation on both GTAW and GMAW processes. The commercially available equipment, in general, require specific feeders and/or torches to implement such technique. Besides that, a wide comprehension of the phenomena involved in pulsed wire feeding still lacks deeper investigation. In this context, the present work aims to evaluate the effects of pulsed wire feeding on GMAW with globular metal transfer in order to contribute to the scientific background for further development of innovative applications of such technique. Exploratory tests were carried out to assess the effects of pulsing frequency and amplitude on the electric signals. Posteriorly, an analysis of the droplet dynamics on metallic transfer was made through high speed filming for a variety of wire feeding pulsing frequencies and power source on constant current and constant voltage operation modes. Moreover, the geometric characteristics of the weld beads were measured from the transverse sections. It was verified that the mechanical pulse affects the process, the voltage and current oscillograms assume frequencies and amplitudes directly related to the pulse parameters. It was found that, in most cases, pulsation promotes the detachment of smaller and faster droplets, when compared to the conventional case. The pulse frequency of 16 Hz resulted in a more stable and regular transfer. Besides that, it tends to reduce bead width and concentrates the penetration on its center.Trabalho de Conclusão de Curso (Graduação)A alimentação pulsada de material é um dos campos de aprimoramento tanto no processo TIG como no MIG/MAG. Os equipamentos comercialmente disponíveis, de modo geral, dependem de tochas e/ou alimentadores específicos para a aplicação deste tipo de técnica. Além disso, a ampla compreensão dos fenômenos associados à alimentação pulsada ainda carece de caracterizações mais profundas. Neste contexto, o presente trabalho tem como objetivo investigar os efeitos da alimentação pulsada de material no processo MIG/MAG com transferência metálica globular visando contribuir com o embasamento científico para a proposição de aplicações inovadoras da técnica. Foram realizados testes exploratórios para averiguar os efeitos da frequência e da amplitude de pulsação sobre os sinais elétricos no processo. A dinâmica das gotas na transferência metálica foi avaliada através de filmagens em alta velocidade com diferentes frequências de pulsação e fonte nos modos de corrente constante e tensão constante. As características geométricas dos cordões de solda foram medidas. Foi verificado que a pulsação mecânica afeta o desempenho do processo, os oscilogramas de tensão e corrente assumem frequências e amplitudes de oscilação diretamente relacionadas aos parâmetros de pulsação. Constatou-se que o emprego da pulsação promove, na maioria dos casos, o destacamento de gotas menores e com maior velocidade, quando comparados ao caso convencional. A frequência de pulsação de 16 Hz garantiu maior estabilidade e regularidade na transferência. A pulsação tende a reduzir a largura do cordão de solda, e concentrar a penetração no centro.2021-07-0
Wire arc additive manufacturing of super duplex stainless steel thin walls with near-immersion active cooling
No full textWithin the processes used for additive manufacturing of metals, Wire Arc Additive
Manufacturing (WAAM), which employs processes traditionally applied for welding, stands
out due to the lower costs and higher deposition rates achieved. Strategies to manufacture super
duplex stainless steels (SDSS) parts through WAAM should focus on guaranteeing a deposit
with proper geometry, free from defects, proper phase balance (ferrite and austenite) and
minimize the occurrence of deleterious phases. Given the importance of controlling cooling
rates in WAAM, different thermal management methods have been studied aiming at mitigating
problems related to heat accumulation, resultant from the energy input throughout the
deposition process. Thus, this work aims at assessing the use of Near-Immersion Active
Cooling (NIAC) in the deposition of SDSS thin walls in terms of geometry, microstructure and
deposition time. The operational modes CMT and Pulsed GMA were explored throughout the
work, with different travel speeds. During the first step clues that a higher tendency to form
porosity was caused by the shielding gas composition Ar + 2 % CO2. This was confirmed by
the fact that when Ar + 25% He was applied no indication of porosity was found in the walls.
In terms of cooling conditions, it was found that it is possible to achieve acceptable fractions of
austenite and ferrite with natural cooling (NC) with dwell times long enough so the wall reached
100 °C. With short dwell times and NC, heat accumulation resulted in a progressive increase in
width, unacceptable phase balance and indications of sigma phase presence. By using NIAC it
was possible to manufacture walls with no indications of defects, acceptable phase balance and
dwell times up to 89% shorter, compared to the NC condition. For a same wire feed speed,
when a travel speed two times higher was employed in relation to CMT, similar widths were
achieved. Comparing these two conditions, Pulsed mode resulted in better surface finish.
However, to reach the same wall height, the number of layers was twice greater with Pulsed
mode. Clues were found that a more pronounced nitogren loss occurs during the deposition onvi
Pulsed mode, resulting in ferrite contents higher than expected, but still within the limits. Except
in the conditions where heat accumulation occurred (NC with short times), secondary austenite
(γ2), which is considered also a deleterious phase although less critic than sigma, was commonly
observed. In general, the use of NIAC in WAAM of SDSS thin walls showed itself promising
with the potential of reducing the overall deposition time significantly, without causing defects
or metallurgical problems.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorPetrobrás - Petróleo Brasileiro S.ADissertação (Mestrado)Entre os processos aplicáveis à manufatura aditiva de metais a manufatura aditiva por
deposição a arco (MADA), que utiliza dos processos tradicionalmente empregados na
soldagem, se destaca pelo menor custo e pelas altas taxas de deposição atingidas. A fabricação
dos aços inoxidáveis super duplex (AISD) por MADA deve visar a deposição de peças com
geometria adequada, livre de defeitos, além de garantir o balanço adequado das fases (ferrita e
austenita) e a minimizar a formação de fases deletérias. Dada a importância do controle das
taxas de resfriamento em MADA, diferentes técnicas de gerenciamento térmico têm sido
estudadas no sentido de mitigar problemas relacionados ao acúmulo de calor, resultante da
energia imposta pelo processo de deposição. Assim, este trabalho tem como objetivo avaliar a
utilização do resfriamento ativo por quase-imersão (RAQI) na deposição de paredes finas de
AISD sob as perspectivas de geometria, microestrutura e tempo de deposição dessas pré-
formas. Ao longo do trabalho foram explorados os modos operacionais CMT e Pulsado,
variantes do processo GMA, com diferentes velocidades de deposição. Em um primeiro
momento foram identificados indícios de maior tendência à formação de poros quando uma
mistura Ar + 2% CO2 foi utilizada, diferentemente de deposições com Ar + 25% He nas quais
não foram encontrados indícios de porosidade. Quanto às condições de resfriamento,
identificou-se que é possível atingir níveis aceitáveis de ferrita e austenita quando se utiliza
resfriamento natural (RN) com tempos de espera entre as camadas tais que a temperatura atinja
100° C. Ao utilizar um tempo de espera curto com RN, o acúmulo de calor acarretou um
aumento progressivo da largura, balanço inadequado de fases e indícios da presença de fase
sigma. Comparando com as condições RN, a utilização da técnica RAQI permitiu a fabricação
de paredes sem indícios de defeitos, com níveis aceitáveis de ferrita e austenita e com temposiv
de espera até 89% curtos. Para uma mesma velocidade de alimentação, ao se utilizar uma
velocidade de deposição duas vezes maior no Pulsado em relação ao CMT, atingiram-se
larguras próximas. Comparadas essas condições, identificou-se melhor acabamento superficial
com Pulsado. No entanto, foram necessárias o dobro de camadas neste modo para atingir uma
mesma altura de parede, acarretando em tempos consideravelmente mais longos de deposição.
Também foram identificados indícios de que a perda de nitrogênio ocorre de forma mais
acentuada no modo Pulsado, resultando em teores de ferrita maiores que o esperado, mas ainda
dentro dos limites. Com exceção das condições em que houve acúmulo de calor (RN com
tempos de espera curtos), a austenita secundária intragranular (γ2), considerada também uma
fase deletéria, apesar de menos crítica que a sigma, foi comumente observada. De modo geral,
a aplicação da técnica RAQI se mostra promissora na deposição de paredes finas de AISD, com
o potencial de reduzir drasticamente o tempo de deposição, sem acarretar prejuízos em termos
de descontinuidades ou problemas metalúrgicos.2023-09-2
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
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