1,720,957 research outputs found
Solid oxide fuel cells for aviation: A comparative evaluation against alternative propulsion technologies
Get PDFConventional aircraft emit high greenhouse gases, hindering aviation decarbonization. Among sustainable so-
lutions, battery-electric planes face range limitations, while renewable fuels can cut emissions without sacrificing
endurance. Fuel cells enable full electrification, powering propulsion and auxiliary systems. Although they have
lower power density than combustion engines, their promising efficiency can potentially reduce overall weight.
This study compares fuel cell and conventional propulsion systems, focusing on Solid Oxide Fuel Cells (SOFCs)
and Proton-Exchange Membrane Fuel Cells (PEMFCs). The initial literature review emphasizes the potential of
SOFCs for aviation and discusses ongoing projects, forming the basis for the subsequent technical analysis. A
break-even analysis examines flight durations in which fuel cell systems match the weight of conventional al-
ternatives. Additionally, various fuels and storage methods, including jet fuel and hydrogen, are assessed. Results
show that jet fuel SOFCs are currently the lightest fuel cell option, while PEMFCs with liquid hydrogen require
higher power density and lighter storage to compete. Looking ahead, liquid hydrogen storage appears most
viable, with PEMFCs better for short-range and SOFCs for long-range flights. An environmental analysis evaluates
CO2 emissions across European countries, identifying break-even grid carbon intensities for jet fuel and hydrogen
SOFCs. These findings highlight fuel cells’ potential to reduce aviation’s environmental footprint
Design space exploration through liquid H2 tank preliminary sizing and design of experiments analysis
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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
Potential of ammonia as hydrogen storage for future electrified aircraft
Get PDFThe implementation of hydrogen as a clean aviation energy vector faces challenges in onboard storage and transportation due to its low volumetric energy density and the strict weight and space constraints of aircraft. This study introduces a breakthrough approach, leveraging liquid ammonia as a hydrogen carrier for electrified aircraft propulsion, an area largely unexplored compared to land and maritime applications. Ammonia’s high hydrogen content, ease of storage, and existing infrastructure make it a compelling alternative to conventional hydrogen storage methods.An integrated system design is presented, combining ammonia storage, a high-efficiency cracking reactor for on-demand hydrogen release, and a purification unit ensuring compatibility with the conversion system, which consists of proton exchange membrane fuel cells (PEMFCs) and their associated balance-of-plant components. To optimize performance and reduce the overall system footprint, a thermal integration strategy is implemented.The paper provides a quantitative assessment of the system’s feasibility in a regional aircraft, demonstrating a gravimetric hydrogen storage index of 9.1%, rivaling state-of-the-art physical storage solutions, and identifying key technological gaps that must be overcome to enhance system performance and competitiveness with conventional kerosene-based propulsion.By addressing the specific challenges of hydrogen storage in aviation, this work provides new insights into the potential of ammonia-based systems and their role in advancing sustainable airborne propulsion technologies
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
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