1,720,960 research outputs found
Effects of fabrication imperfections on fully developed flow in rectangular micro-channels
No full textOver the past few decades, the microfluidics field has been established itself as an emerging technology, serving as a tool for many areas both in science and in industry. As a result, research involving the analysis of micro-flows has been growing dramatically and is acting in the advancement of new technologies and microfluidic devices. As small diameters are considered, on most occasion laminar flow occurs, which allows simpler numerical solution of the problem to be carried-out. In fact, for fully developed velocity profiles the advective terms become unimportant and the problem becomes linear, which allows analytical solutions to be carried out if regular geometries are considered. While for macro-channel flows, the fabrication of channels with regular geometries such as circular or rectangular is fairly simple, when micro-fabrication is considered the resulting channels geometry in many occasions cannot be treated as regular, even if the nominal profile is so. On such example is seen channels with rectangular nominal geometries. For this type of channels, on many occasions the resulting cross-section geometry is somewhat trapezoidal with slightly rounded corners. While for large scale channels these imperfections can be neglected, in micro channels they may be of notable influence on the flow field. In this context, the purpose of the paper is to analyze the influence that the aforementioned fabrication imperfections has on the fully developed flow field in nominally rectangular microchannels. The solution methodology is based on the Generalized Integral Transform Technique applied to irregular geometries
Laminar forced convection in circular microchannels with slip-flow: Analysis of randomly distributed roughness
No full textThis paper investigates the sensitivity of heat transfer and fluid flow to geometric uncertainties caused by roughness in microchannels. The study considers laminar, fully developed slip flow and temperature jump conditions in the momentum and energy equations, controlled by velocity slip (λ) and temperature jump (λT) parameters, under traditional H1 and H2 heating conditions. Microchannels with nominally circular geometries are analyzed, incorporating random boundary variations defined by a roughness parameter, δrmax∗. These variations generate unique geometries for each δrmax∗, grouped into samples for numerical simulation and statistical analysis. The analysis shows that for every configuration, a normal distribution of Poiseuille and Nusselt numbers values is obtained for each δrmax∗. An examination of the median and standard deviation of each sample reveals that increasing δrmax∗ leads to higher Poiseuille numbers and lower Nusselt numbers, indicating greater pressure drop and reduced heat transfer, respectively. The influence of slip length and temperature jump parameters was also assessed, revealing that while higher λ values reduce the friction factor, these cases are more impacted by roughness. Conversely, although an increase in λT significantly reduces the Nusselt number due to added thermal resistance, cases with lower λT are more sensitive to roughness effects
Shape uncertainty analysis of laminar forced convection in a round microchannel with viscous dissipation
Full text linkThis paper is aimed at analysing the effects of roughness caused by random geometric uncertainties in microchannels and how these can influence heat transfer and pressure drop in fluid flow within such geometries. The shape of a microchannel is typically affected by significant uncertainty due to the small size of the cross-section, which is comparable to the typical wall-roughness length scale. While this uncertainty exists at any scale, it becomes amplified and critically important when the hydraulic diameter is smaller than a few tens of micrometer. The analysis is performed numerically, considering a nominally circular channel with random variations in its cross-section within a prefixed maximum extent, effectively representing roughness at the micro-scale. The adopted mathematical model considers fully developed heat and fluid flow by taking into account the effect of viscous dissipation and an irregular cross-section is generated by random geometric variations. The effects of an increasing wall roughness generally lead to an increase in the Fanning friction factor and a decrease in the wall heat transfer rate, as expressed by the Nusselt number
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
- …
