1,720,959 research outputs found
Numerical Evaluation of the Effects of Inclusions on Solid Rocket Motor Performance
Full text linkThis work describes the application of original computer graphics methods to examine the effect of inclusionswithin the solid rocket motor thrust chamber. The adoptance of a dynamic three-dimensional triangular mesh with aself-intersection removal algorithm, as the core of the burning surface regression module, allows the aforementionedtargetto bereached.Manyphenomena notmeasurablein an analyticalclosed form, likedifferent-shapedvoidswithinthe grain, can be investigated. Indeed, both local heterogeneities and surface imperfections could generate unexpectedvariations in the combustion chamber pressure pattern and early thermal protections exposure. The aforementionedtechniques are developed and tested on a ballistic simulator developed using computer graphics methods to improvemesh handling. Simulation results are carried out and discussed
Impact of Thermal Protections Insulation Layer on Solid Rocket Motor Performance
No full textThe aim of the paper is to reproduce thermal protections ablation phenomenon in solid rocket motors focusing on its influence on rocket performance. A physical model able to predict thermal protections ablation behavior coupled with an internal ballistics simulator is outlined. The main outcome of the abovementioned model is the estimation of residual thrust occurring after burn-out at high altitudes whose evaluation is particularly important when solid rocket motors are used as upper stages and after burn-out operations take place in vacuum. During these phases residual thrust is generated by pyrolysis gases produced by case insulation layer due to ablation of thermal protections materials. The nozzle radiative power has been identified as the main source enabling thermal protections to ablate. An investigation of a commercial motor performance is obtained and discussed. Numerical methods are explained in detail
Influence of Nozzle Radiation on Solid Rocket Motors Tail-Off Thrust
Full text linkThe aims of this work are focused on the evaluation of the solid rocket motor residual thrust and
on the impact of thermal protection properties on such thrust. Indeed, tail-off thrust of solid rocket
motors upper stages can last tens of seconds after motor burn-out, affecting the performance of
the rocket on sequencing of stage separation. Hence, the knowledge of the tail-off thrust profile is
fundamental to properly design wait times and separation systems total impulse of a multi-stage
launcher. Therefore, although it has been shown in the past that pyrolysis gases responsible for the
residual thrust are mostly produced by alumina molten slag deposited next to the nozzle nose within
the combustion chamber, this study is aimed at suggesting that the portion of the nozzle within
the combustion chamber can act as the main radiative heat source leading to thermal protection
material ablation, and then to residual thrust production. An analysis of an actual solid rocket
motor has been performed in the direction of proving the effectiveness of the overall procedure. Then
a sensitivity analysis with respect to the quantities identifying the thermal protection properties has
been computed in order to evaluate the impact of such variations on the residual thrust profile
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
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