1,720,968 research outputs found
Research and development of polyurethane icephobic composite coatings
Get PDFIce accretion over critical engineering structures could lead to costly hazards, and ice prevention is an energy-intensive activity, thus making the applications complicated and inefficient. A more promising and specific strategy is to deploy passive ice protection approaches such as durable coatings that allow the super-cooled droplets to slide off before icing (anti-icing), or that detaches the developed ice completely (de-icing). The main aim of this project was to research and develop new types of polyurethane-based icephobic coatings for potential applications in the aerospace and wind energy industries. The experimental work was planned to offer balanced research outputs on the fundamental aspects of icephobicity studies and to impart the acquired knowledge for the fabrication and investigation of novel durable icephobic materials/surfaces.
At first, fundamental studies relating to surface icephobicity and icephobicity were carried out. A systematic reduction of ice adhesion with the decrease in surface roughness was demonstrated across all the studied material types, i.e. metallic surfaces and polymeric coatings with different surface wettability. If the surface bears a similar surface roughness, then wettability plays a deciding role in reducing the ice adhesion. A surface with higher roughness provides an increased number of possible ice anchoring points and the ice anchoring mechanism was further validated under in-situ icing observation. Furthermore, the variation in response to surface characteristics in icephobicity evaluation methods was also investigated. Centrifugal and horizontal push (shear) methods suggested a linear relationship of ice adhesion strength with surface roughness, whereas the tensile (normal) method indicated an inverse curvilinear relationship with contact angle hysteresis. Apart from the de-icing evaluation, water droplet freezing delay suggested a direct correlation with surface roughness and the visual examination of frost accumulated samples suggested a reduction in ice densification on the smoothened surfaces, indicating a weakened bond between the ice/solid interfaces. The results offer crucial information on the pre-selection of testing regimes to accurately measure the performance of icephobic materials.
In the second part, several polyurethane-based nanocomposite, fibre-reinforced, and liquid-infused coatings were developed and investigated to understand the deteriorating behaviour of the coatings under impinging erosion tests and the subsequent impact on ice adhesion. The durability analysis on polyurethane composite coatings indicated that the incorporation of fillers was effective in reducing the number of possible ice anchoring points, and after the impingement, the icephobic performance was retained by either lowering surface roughness or by minimising surface deterioration. The reinforcement was effective such that the change in surface roughness was reduced by a factor of 4, compared to the pure polyurethane coatings under erosion impact. To provide an exceptional icephobic response, glycerol-infused fibre-reinforced polyurethane (GIFRP) coatings was proposed by mimicking the fibrous structure of cetacean skin. Instead of hosting the lipid proteins, the coatings were infused with glycerol, a known cryoprotectant to induce the supercooling of water, a strategy inspired by chionophiles, to prevent freezing. The inclusion of glycerol delayed water droplet freezing duration by 659%, while negligible frost accumulated on the fabricated coatings in the anti-icing tests. In addition to the promising anti-icing performance, the incorporation of fibrous structure has proven to be beneficial for infused-liquid replenishment and the slow-releasing capabilities of GIFRP coatings. Minimised surface deterioration and the continued presence of glycerol on GIFRP coatings demonstrated a small increase in ice adhesion from 0.22 kPa to 0.77 kPa after the erosion tests, one of the lowest values reported in literature after substantial surface damage. The concept inspired by cetacean skin and the cryoprotective features of chionophiles was instrumental in keeping the ice adhesion under 1 kPa after erosion impact
Research and development of polyurethane icephobic composite coatings
Get PDFIce accretion over critical engineering structures could lead to costly hazards, and ice prevention is an energy-intensive activity, thus making the applications complicated and inefficient. A more promising and specific strategy is to deploy passive ice protection approaches such as durable coatings that allow the super-cooled droplets to slide off before icing (anti-icing), or that detaches the developed ice completely (de-icing). The main aim of this project was to research and develop new types of polyurethane-based icephobic coatings for potential applications in the aerospace and wind energy industries. The experimental work was planned to offer balanced research outputs on the fundamental aspects of icephobicity studies and to impart the acquired knowledge for the fabrication and investigation of novel durable icephobic materials/surfaces.
At first, fundamental studies relating to surface icephobicity and icephobicity were carried out. A systematic reduction of ice adhesion with the decrease in surface roughness was demonstrated across all the studied material types, i.e. metallic surfaces and polymeric coatings with different surface wettability. If the surface bears a similar surface roughness, then wettability plays a deciding role in reducing the ice adhesion. A surface with higher roughness provides an increased number of possible ice anchoring points and the ice anchoring mechanism was further validated under in-situ icing observation. Furthermore, the variation in response to surface characteristics in icephobicity evaluation methods was also investigated. Centrifugal and horizontal push (shear) methods suggested a linear relationship of ice adhesion strength with surface roughness, whereas the tensile (normal) method indicated an inverse curvilinear relationship with contact angle hysteresis. Apart from the de-icing evaluation, water droplet freezing delay suggested a direct correlation with surface roughness and the visual examination of frost accumulated samples suggested a reduction in ice densification on the smoothened surfaces, indicating a weakened bond between the ice/solid interfaces. The results offer crucial information on the pre-selection of testing regimes to accurately measure the performance of icephobic materials.
In the second part, several polyurethane-based nanocomposite, fibre-reinforced, and liquid-infused coatings were developed and investigated to understand the deteriorating behaviour of the coatings under impinging erosion tests and the subsequent impact on ice adhesion. The durability analysis on polyurethane composite coatings indicated that the incorporation of fillers was effective in reducing the number of possible ice anchoring points, and after the impingement, the icephobic performance was retained by either lowering surface roughness or by minimising surface deterioration. The reinforcement was effective such that the change in surface roughness was reduced by a factor of 4, compared to the pure polyurethane coatings under erosion impact. To provide an exceptional icephobic response, glycerol-infused fibre-reinforced polyurethane (GIFRP) coatings was proposed by mimicking the fibrous structure of cetacean skin. Instead of hosting the lipid proteins, the coatings were infused with glycerol, a known cryoprotectant to induce the supercooling of water, a strategy inspired by chionophiles, to prevent freezing. The inclusion of glycerol delayed water droplet freezing duration by 659%, while negligible frost accumulated on the fabricated coatings in the anti-icing tests. In addition to the promising anti-icing performance, the incorporation of fibrous structure has proven to be beneficial for infused-liquid replenishment and the slow-releasing capabilities of GIFRP coatings. Minimised surface deterioration and the continued presence of glycerol on GIFRP coatings demonstrated a small increase in ice adhesion from 0.22 kPa to 0.77 kPa after the erosion tests, one of the lowest values reported in literature after substantial surface damage. The concept inspired by cetacean skin and the cryoprotective features of chionophiles was instrumental in keeping the ice adhesion under 1 kPa after erosion impact
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
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