1,720,981 research outputs found
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
Metallic materials in Solid Oxide Fuel Cells: Oxidation and chromium evaporation properties
Full text linkSolid oxide fuel cells (SOFCs) are high-temperature energy conversion devices which have great potential due to their high efficiency, low operating costs and flexibility in using conventional hydrocarbon based fuels. However, system cost, durability and performance stability in long-term operation are barriers to the widespread commercialization of SOFC technology.Due to the high-temperature operation and aggressive environment in SOFCs, metallic materials - used for interconnects and balance of plant (BOP) - are subject to corrosion. Interconnects are typically made of ferritic stainless steel, which forms a protective chromia scale at high temperatures. This results in two main degradation mechanisms: 1) chromium evaporation, which leads to cathode poisoning and 2) chromia scale growth, which leads to increased electrical resistance. To date, research into metallic materials in SOFC has focused mostly on interconnects. However, metallic materials used inBOP components can be a significant source of volatile chromium species and are often overlooked. The aim of this thesis is to find high performance, cost-effective metallic materials for SOFC systems. Five metallic materials AISI 441, AISI 444, A197/Kanthal\uae EF101, alloy 800H and alloy 600, were studied for potential use in BOP components. Lowcost steels, AISI 441 and AISI 444, and tailor-made Crofer 22 APU in combination with different coatings were evaluated for the interconnect application. Chromium evaporation and oxide-scale growth of the materials are investigated, and the oxide scale is studied further, using XRD, SEM, EDX and ASR.The alumina former, A197, showed the lowest chromium evaporation and oxidation in all exposure conditions. Alloy 800H showed poor oxidation behaviour at lower temperatures but its performance improved significantly after pre-oxidation. Alloy 800H has higher chromium evaporation than A197 but significantly lower than 441 and 444. This low chromium evaporation is due to the formation of an Fe, Ni-rich oxide cap layer. Alloy 600 showed intermediate performance. 441 and 444 showed the highest oxidation and chromium evaporation of the selected alloys, making them a poor choice for BOP components.The uncoated low-cost steels, 441 and 444, showed higher chromium evaporation and/or oxide scale growth than the tailor-made Crofer 22 APU. The oxide scale structure was similar for all the steels, with (Cr, Mn)3O4 spinel on top and Cr2O3 scale underneath after 500 hours. The Ce/Co coated steels showed lower oxide scale growth and a chromium evaporation at least 60 times lower than the uncoated steels. In addition, all the coated steels showed similar chromium evaporation, oxide scale structure ((Co, Mn)3O4 spinel on top and Cr2O3 scale underneath), oxide scale thickness and area specific resistance after 1,000 hours
Metallic materials for solid oxide fuel cells and electrolysers - Mitigating high temperature corrosion [Elektronisk resurs]
No full textSolid oxide cells (SOCs) are high-temperature energy conversion devices that have great potential due to their high efficiency, low operating costs, and flexibility. SOCs can produce electricity from a variety of fuels as solid oxide fuel cells (SOFCs), and they can convert electricity to fuels as solid oxide electrolyser cells (SOECs). However, the wide-spread commercialisation of this technology is hindered by high system cost, lack of durability, and poor performance stability during long-term operation. Owing to the high-temperature operation and aggressive environment of SOCs, metallic materials used for interconnects and balance of plant (BOP) components are subject to corrosion. Interconnects are typically made of ferritic stainless steel (FSS), which forms a protective chromia scale at high temperatures. The degradation mechanisms, such as Cr (VI) evaporation and chromia scale growth, lead to electrode poisoning and increased electrical resistance, which degrade cell performance. The primary objective of this thesis is to develop alternative materials and understand the degradative mechanisms so as to effectively reduce the costs and improve the performances of metallic materials in SOC systems. The Cr evaporation, oxide scale growth, the microstructural evolution of the oxide scale, and the area-specific resistances are investigated for the selected materials. The majority of the thesis is focused on Ce/Co coatings. Ce/Co-coated, low-cost, commercial FSS (AISI 441, AISI 430, and AISI 444) are compared to tailor-made Crofer 22 APU in air-side atmospheres. Ce/Co-coated steels are further investigated under dual-atmosphere conditions. The Ce/Co coating is compared to various coatings from research laboratories and universities world-wide. Furthermore, the underlying causes for the improvement in the oxidation resistances of FSS that occur in the presence of the reactive element Ce (in the Ce/Co coating) are investigated, and a new mechanism is proposed. Finally, a model to predict the lifetimes of the coated steels is proposed. Moreover, a new coating system, the Ce/FeNi coating, is proposed as an alternative to the Ce/Co coating. The Ce/FeNi coating is found to be more effective than Ce/Co coating in reducing chromia scale growth. While research on metallic materials for SOC has centred on the interconnects, the metallic materials used in BOP components, which can be a significant source of volatile chromium species, have been largely neglected. Five metallic materials (AISI 441, AISI 444, A197/Kanthal® EF101, alloy 800H, and alloy 600) are examined for potential usage in BOP components. The oxidation and Cr evaporation behaviours of these materials are discussed and correlated to the observed microstructures
Metallic materials for solid oxide fuel cells and electrolysers - Mitigating high temperature corrosion
Full text linkSolid oxide cells (SOCs) are high-temperature energy conversion devices that have great potential due to their high efficiency, low operating costs, and flexibility. SOCs can produce electricity from a variety of fuels as solid oxide fuel cells (SOFCs), and they can convert electricity to fuels as solid oxide electrolyser cells (SOECs). However, the wide-spread commercialisation of this technology is hindered by high system cost, lack of durability, and poor performance stability during long-term operation. Owing to the high-temperature operation and aggressive environment of SOCs, metallic materials used for interconnects and balance of plant (BOP) components are subject to corrosion. Interconnects are typically made of ferritic stainless steel (FSS), which forms a protective chromia scale at high temperatures. The degradation mechanisms, such as Cr (VI) evaporation and chromia scale growth, lead to electrode poisoning and increased electrical resistance, which degrade cell performance.The primary objective of this thesis is to develop alternative materials and understand the degradative mechanisms so as to effectively reduce the costs and improve the performances of metallic materials in SOC systems. The Cr evaporation, oxide scale growth, the microstructural evolution of the oxide scale, and the area-specific resistances are investigated for the selected materials. The majority of the thesis is focused on Ce/Co coatings. Ce/Co-coated, low-cost, commercial FSS (AISI 441, AISI 430, and AISI 444) are compared to tailor-made Crofer 22 APU in air-side atmospheres. Ce/Co-coated steels are further investigated under dual-atmosphere conditions. The Ce/Co coating is compared to various coatings from research laboratories and universities world-wide. Furthermore, the underlying causes for the improvement in the oxidation resistances of FSS that occur in the presence of the reactive element Ce (in the Ce/Co coating) are investigated, and a new mechanism is proposed. Finally, a model to predict the lifetimes of the coated steels is proposed. Moreover, a new coating system, the Ce/FeNi coating, is proposed as an alternative to the Ce/Co coating. The Ce/FeNi coating is found to be more effective than Ce/Co coating in reducing chromia scale growth.While research on metallic materials for SOC has centred on the interconnects, the metallic materials used in BOP components, which can be a significant source of volatile chromium species, have been largely neglected. Five metallic materials (AISI 441, AISI 444, A197/Kanthal\uae EF101, alloy 800H, and alloy 600) are examined for potential usage in BOP components. The oxidation and Cr evaporation behaviours of these materials are discussed and correlated to the observed microstructures
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
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