1,720,972 research outputs found
Aerothermodynamic analysis of high-altitude space launcher with direct-simulation Monte Carlo method
No full textAerothermodynamics of space launchers operating at high altitudes (above 100 km) is characterized by complex physical processes that are related to the substantially higher air rarefaction with respect to lower altitudes. Consequently, the use of continuum methods to numerically simulate such flow conditions is questionable. In this study, the problem of proper assessment of the aerothermodynamic behavior of space launchers operating at high altitudes is analyzed considering Vega in its ascent flight, an actual space launcher that has already performed a number of successful flights. The direct simulation Monte Carlo molecular method is used to carry out the simulations. After a convergence analysis of the adopted numerical approach, a comparison of different air models is presented to highlight the effect of chemical reactions and molecules vibrational excitation. Then, a comparison of the flowfield around the Vega launcher is reported at two altitudes (113 and 127 km), where the third stage of the space launcher is not propelled. The analysis describes the effects of the atmospheric air rarefaction, which has significant repercussions on the bow-shock structure and the drag coefficient. Finally, the achieved solutions are compared with computational fluid dynamics (CFD) continuum solutions to show that a standard CFD approach is not able to represent the physical phenomenon under examination, due to the model’s breakdown caused by the effects of rarefaction
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
CFD analysis of the lateral sloshing phenomenon inside an aerospace lh2 cryogenic tank
No full textIn this work, we propose to perform unsteady 3D numerical simulations by means of the VOF methodology to understand the behavior of the lateral sloshing inside an aerospace LH2 cryogenic tank. The first geometry considered is a simple laboratory-scale cylindrical tank model, designed to investigate the sloshing phenomenon with the presence of a single baffle ring. The case is used to assess the capability of the adopted method to predict the correct sloshing damping. The second geometry under study is instead inspired to a typical common bulkhead cryogenic tank used in space launchers. Simulations investigate sloshing inside the tank under normal gravity conditions. The unsteady lateral force on the tank wall, as well as the center of gravity position, obtained from the simulations are used to obtain and validate a reduced-order model (ROM) that takes into account the non-linear nature of the damping. Lateral loads are then analyzed through Fourier spectral analysis and through wavelet analysis, decomposing the time series into the time-frequency domain, to determine the time evolution of the energy of the excited mode
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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