1,721,061 research outputs found
Numerical analysis of a spray combustion with nongray radiation using weighted sum of gray gases model
No full textIn this study, the effect of radiation has been considered in a liquid spray combustion chamber. The discrete ordinates method (DOM) was employed to solve the radiative transfer equation (RTE) and the weighted sum of gray gases model (WSGGM) was applied to model a nongray radiation effect by CO2 and H2O gases. The absorption coefficients derived from WSGGM were used with DOM by summing solutions of the RTE for each gray gas. Eulerian-Lagrangian scheme was adopted to alalyze the two phase combustion. The interactions between two phases are accounted for by using the particle source in cell (PSIC) model. The results have shown that the gasfication of the droplets is more quickly completed by radiation, which results in shorter droplet trajectories. The radiation also led to a broader high temperature zone inside the combustor. Therefore, it was found that the performance of the spray combustor was enhanced by the radiation effect
Investigation of droplet combustion with nongray gas radiation effects
No full textSingle droplet combustion processes including heating, evaporation, burning, soot formation and name radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE). n-Heptane was chosen as a fuel in the numerical calculation and the results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray gas radiation effect by CO2 and H2O while foot was assumed gay. Therefore, very detailed effects by nongray gases could be figured out in the results. The results have shown that the total burning time increases due to a decrease in total heat flux with the nongrey gas model. It is also found that for the nongray case the radiative loss to external environment is higher, thereby reducing the maximum gas temperature and the flame thickness. Consequently, a better agreement with experimental data could be obtained by using nongray gas model
INVESTIGATION OF A COAL-WATER SLURRY DROPLET EXPOSED TO HOT GAS-STREAM
No full textIn this study a refined theoretical model was devised to estimate the ignition delay of a suspended coal-water slurry (CWS) droplet exposed to hot gas stream. A very detailed temporal temperature variation inside the droplet is taken into account. The effect of the surface radiation was also included in the model. The governing equations are numerically solved and the results are corroborated in comparison with the experimental ones. The outer porous layer could be pyrolyzed as the evaporation front kept going inward to the center of the droplet. Even before the binary mixture in inner region of the droplet was thoroughly evaporated, the volatile gases generated could be ignited in the vicinity of droplet surface. The ignition delay time was primarily comprised of both the heating time and the mixing time. But the heating time, which is required for a droplet to be vaporized and then pyrolyzed, was found to be controlling one. Experimental results were used to validate the numerical results. A reasonable agreement was observed in ignition delays of droplets, only when the surface radiation was incorporated in the model
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
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