1,720,958 research outputs found
On the Interaction of Capillary Shapes with Solid Surfaces
No full textControl over the interaction of droplets with solid surfaces is commonplace in nature. Famous examples are the water-shedding capabilities of the lotus leaf and the water-harvesting skin of certain types of beetles. To date, this type of control remains a challenge in engineering applications. Consider, for example, droplets on the windscreen of a car that need to be wiped off because they unwantedly stick to the glass, or the dripping of droplets from fog harvesting devices, where one actually wants the droplets to stick. In this thesis, we address the interaction of droplets with solid surfaces that underlies the sticking behavior. In particular, we investigate how droplets stick to chemically and physically heterogeneous surfaces, and what shape droplets take when squeezed by various confining geometries. The results of these investigations can be used to predict the force needed to set a droplet on a given surface into motion, and to calculate the volume of droplets in confining geometries. An important tool in our studies is the principle of energy minimization, by which we determine the (local) equilibrium shape of a droplet under the influence of surface tension, gravity and solid boundaries. It turns out that the interaction of droplets with solid surfaces can largely be captured in terms of two aspects of the system. The first is the contact line of the droplet, the line where the fluid-fluid interface meets the solid surface. The second is the contact angle distribution around this line, where the contact angle is defined as the angle at which the fluid-fluid interface meets the solid surface. A core question in our work is how to predict the shape and sticking force of a droplet on a realistic, thus physically or chemically heterogeneous, inclined surface. The answer to this question constitutes an important step towards a model for the sticking force. We resolve this question by studying the model system of a droplet on an incline, using 2D analytical and 3D numerical energy minimization. An important conclusion from our work is that the maximum sticking force of the droplet is determined by local constraints on repositioning of the contact line, originating from a range of possible contact angles within which the droplet can deform while the contact line remains static. The possible, i.e. accessible, shapes of the droplet during the inclination process are then also determined by constraints on repositioning, which causes the initial shape and deformation history of the droplet to influence the shape of the droplet at roll off and thereby the maximum sticking force. Accounting for inaccessible shapes and droplet shape history hence results in accurate predictions of the sticking force, in contrast to currently available models that allow all shapes and are thus bound to yield incorrect predictions. Based on the insight that local constraints control the global shape of the droplet we developed an approach to analytically predict the deformation of 3D droplets upon inclination and the maximum sticking force of these droplets. This prediction can be used for a number of engineering applications where the sticking force of droplets is an important factor. Examples include the design and positioning of solar panels and windscreens, as well as more industrial applications such as condensors and chemical reactors with small flow channels. The analytical model for 3D droplets builds on the findings on the role of local constraints by explicitly modelling the deformation process of the contact line, in contrast to the current state-of-the-art where contact line shapes are either assumed or predicted without regard for the constraints. To keep the model analytically tractable, we parameterize the deformation of the droplet in terms of the contact line shape and the contact angle distribution around the contact line. In combination with a few physically sound assumptions, based on our earlier findings, this model accurately predicts the deformation and maximum sticking force of a droplet, as compared with experiments and numerical simulations. Unlike currently available models, this model also accounts for the history of the droplet in the prediction of the maximum sticking force. Apart from droplets sticking to surfaces we also use energy minimization to determine the shape of bubbles and droplets in straight microchannels of various cross-sectional geometries. With this, we develop a model to calculate the volume of a droplet on the basis of only the channel geometry and the droplet length as observed from a top view. This determination of volume is for example important to accurately determine the concentration of gaseous species or nutrients in studies of mass transfer rates or growth of cells. The model is based on a physical description of the central part of the droplet, where we calculate the shape of a cross-sectional slice of the droplet based on energy minimization. The volume calculation is completed with two caps on the droplet that smoothly fit onto the central part and mimick the physically realistic shape. We compare our analytical model with 3D numerical energy minimization calculations and find excellent agreement for a large range of droplet lengths and channel geometries, thus validating the model for use in quantitative research. The findings of this research can, with small adaptations, be applied in related systems, such as pinned gas bubbles or droplets in a shear flow. We discuss the necessary adaptations and what open questions remain in the field of droplet pinning, specifically related to cases where assumptions made in our work do not apply. This results in a series of recommendations for future research on the role of viscous and inertial effects and heterogeneities with sizes on the order of the droplet.Chemical EngineeringApplied Science
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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