1,721,055 research outputs found
Impact of Different Liquid Drops on Micro/Nano-Structured Superhydrophobic Surfaces
No full textOne of the most fascinating natural phenomena is the ability of some surfaces to repel water drops. Since the discovery of lotus leaf surface structure, several attempts of artificial, biomimetic superhydrophobic surfaces (SHS) have been made. Nowadays, we know that superhydrophobicity arises from a combination of surface morphology and chemical composition. However, different surfaces can display analogous wetting properties in static conditions (e.g. similar contact angles) but radically divergent drop impact output. Thus, drop impact studies provide enhanced insight on surface wetting properties in dynamic conditions.
We fabricated SHS with different morphology and/or chemical composition. Namely, surface S had a flower-like alumina structure with nanoscale cavities (as observed with FESEM), chemically modified with fluorosilanes; surfaces LAU and FAS had a terrace-like alumina structure with micro-cavities, modified with lauric acid or fluorosilanes, respectively. Then, we assessed their quasi-static wetting properties (e.g. advancing contact angle θA, receding contact angle θR and contact angle hysteresis Δθ) and drop impact behavior in a range of Weber number 1135°, Δθ120° with hexadecane, LAU was oleophilic (θR≈0).
In water drop impacts, S surfaces always produced a rebound, indicating a stable Cassie-Baxter wetting state. Meanwhile, for LAU and FAS a Cassie-to-Wenzel transition (CWT) was observed at high We, with partial rebound as an output. Such behavior is consistent with results in literature: nano-cavities on S surface cause high capillary pressure PC against wetting, while micro-cavities on LAU and FAS were penetrated by drops when wetting pressures (i.e. effective water hammer pressure PEWH and gas layer pressure PGL) exceeded PC. Significantly, CWT occurred at higher We for LAU than for FAS, notwithstanding their identical surface structure and water contact angles. This result hints at a role of surface chemistry in drop impact behavior, a phenomenon that has never been reported before and certainly deserves further studies.
On the other hand, hexadecane drops never rebounded, even on S and FAS surfaces. Antonini et al. (Langmuir 2013) defined θR>100° as a criterion for water drop rebound. However, this does not hold for hexadecane: PC is lower when s is smaller, thus causing CWT even if the surface is oleophobic in static conditions.
In conclusion, the results highlight that it is not possible to easily correlate contact angles and drop impact dynamics of low- and high-surface-tension liquids on different surfaces, as CWT can be observed even on statically repellent surfaces. Thus, an accurate design of surface properties must be pursued in the future research towards dynamically amphiphobic, biomimetic surfaces
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
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
Mitral valve finite element modelling from ultrasound data: a pilot study for a new approach to understand mitral function and clinical scenarios
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