1,720,970 research outputs found
Electrohydrodynamics of charge injection atomization: regimes and fundamental limits
No full textThe dynamics and controlling mechanisms of a charge injection electrostatic atomization method for insulating liquids have been investigated using a sharp electrode as a current source, which is placed inside the atomizer and held at a high electrical potential. The method is applicable to highly insulating liquids such as hydrocarbon oils and oil-based solutions, and potential uses of this technology include combustion systems and high-quality spray coating/deposition applications. Subcritical and supercritical flow regimes of atomizer operation are delineated by different types of electrical breakdown. The subcritical flow regime is limited by an insulation failure of the liquid hydrocarbon itself and occurs inside the atomizer. This regime, although of interest to understand the fundamental nature of the electrohydromechanics, does not produce finely atomized sprays. Atomization performance in the supercritical flow regime is characterized by the maximum spray specific charge being limited by a partial discharge in the gas outside the nozzle, around the liquid jet as it emerges from the nozzle. In this case, finely atomized sprays are possible, and with no electrical limitation on the upper flow rate limit. The maximum spray specific charge achievable in the supercritical regime has been found to increase at larger nozzle exit velocities and also for smaller orifice diameters. These two factors, combined with the increased aerodynamic shear acting on the charged liquid jet as it emerges from the orifice at higher velocities, enhances the destabilization of the charged liquid jet to produce finely atomized and well-dispersed sprays of insulating liquids
Design issues concerning charge injection atomizers
No full textTwo versions of a charge injection electrostatic atomizer design, useful for producing charged sprays of highly insulating liquids, have been subjected to systematic changes of their physical and electrical characteristics. The aim is to enhance the atomization of these liquids by maximizing the amount of charge that can be introduced into the spray. Spray current measurements showed that atomizer internal geometry is the key parameter and a "point-plane" geometry was found to be optimum. The "point" is the charge injection site, the tip of a needle electrode, coaxial with the "plane," conceptually a disk which contains the atomizer orifice. An important requirement is to place the electrode tip as near as possible to this "plane," while maintaining sufficient current. A ratio of unity of the distance between the tip and the plane, and the orifice diameter, was found to be optimum, and independent of orifice diameter. The orifice length-to-diameter ratio was varied and was found to have little measurable effect on the electrical performance of the atomizer. An investigation of the atomizer electrical characteristics was also performed, by placing large resistances between the metal nozzle body and ground and also placing a ring electrode around the liquid jet as it emerged from the orifice. We found that electrical modifications to the atomizer can provide significant improvements in the spray current and hence the atomization quality
Atomization, combustion and control of charged hydrocarbon sprays
No full textThe atomization of electrically insulating liquid fuels has been investigated using the charge injection method with consideration of its usefulness as a spray combustion technique. This requires electrostatic spraying systems that atomize unadulterated commercial grades of fuel oil sufficiently finely while being able to operate robustly in the ionized combustion environment. As a natural consequence of the liquid charging mechanism, the atomization quality improves with flow rate because of the dual action of aerodynamic shear and the higher specific charge that can be achieved in the liquid jet. At moderate charging conditions, sprays of insulating liquids are similar to those of semiconducting liquids, with a core of larger drops surrounded by a sheath of much smaller companions. More highly charged sprays are more homogeneous, and stable combustion of kerosene and diesel oil has been achieved for the first time at practically useful flow rates. Flame stability improves with atomization quality and a stable flame seat is formed without the need for a pilot flame for an atomizer of 150-mm orifice diameter for a kerosene flow rate of 0.5 ml/s and a specific charge of 3.0 C/m3. Spray manipulation of both cold and combusting sprays using DC electric fields has been demonstrated, and the effectiveness of the technique suggests that optimization of the combustion process is possible by applying AC electric fields
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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