1,720,960 research outputs found
Evaluating the potential of thermoplastic polymers for cryogenic sealing applications: strain rate and temperature effects
No full textHydrogen in liquid or cryogenic compressed form is revolutionising various industries as fuel, and thermoplastic polymers can be a suitable alternative to metal seals in cryogenic hydrogen fuel systems. This paper measured the tensile properties and coefficient of thermal expansion of three thermoplastics: PTFE, PEEK and UHMWPE at room temperature (RT), 77 Kelvin (K) and 20 K at four strain rates. Further microscopic analysis was conducted to understand the failure mechanisms under the above conditions. The tensile strength of each polymer increased when the temperature was reduced from RT to 77 K and decreased from 77 K to 20 K. Young's modulus increased, and the strain at failure decreased with decreasing temperature. Finally, PEEK was found less contraction than PTFE and UHMWPE at 20 K, in agreement with its highest glass transition temperature of the three polymers, which is normally a good indicator in selecting suitable sealing materials in cryogenic hydrogen fuel systems.</p
Thermal fatigue effects on the gas leakage characterisation of thin-ply carbon fibre composites
No full textCarbon fibre reinforced polymers (CFRPs) stand out as a preferred material for liquid hydrogen storage in the future. However, the hydrogen leakage caused by micro-cracking is limiting their application. In this study, thin-ply CFRP laminates with different ply thickness were selected due to their potential of high cracking resistance. The leak rate tests with helium after 0, 2, 5, 10, 15 times of thermal cycling were conducted. The results indicate that there was no explicit leak rate increase after 15 times of thermal cycling between 77 K and room temperature. It may suggest that the selected thin-ply materials shown promising leakage resistance
Effects of hydrogen-rich environment on the tensile properties of thermoplastics for liquid hydrogen service
No full textThermoplastic polymers can provide solutions for many liquid hydrogen storage and distribution applications, especially for weight sensitive applications. However, it remains unclear whether thermoplastics can operateconsistently at cryogenic temperatures particularly after long term exposure to hydrogen-rich environments. This study measured the mechanical behaviours of three thermoplastics at room and cryogenic temperatures (77 K and 20 K), andcompared the results of hydrogen charged and uncharged samples. All materials showed increased ultimate tensile strengths and reduced ductility at cryogenic temperatures compared to results at room temperature. The amount of hydrogen absorbed may have a positive correlation to their molecular weight. However, the method of hydrogen charging applied in this work appear to have marginal effects on the thermoplastics. Further chemical examinations is in progress to reinforce
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
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