1,721,015 research outputs found
The thermal environment encountered in space by a multifunctional solar array
No full textThe design concept of multifunctional structures allows spacecraft to be more efficient. By creating structural components that can fulfil extra subsystem functions in addition to meeting structural requirements, mass and volume can be saved. The presented example of this is a wing solar array that contains the spacecraft's batteries. The batteries are commercial off the shelf components, used for their lower costs. The paper focuses on understanding the thermal environment and the response of the multifunctional structure to that environment. With this information, it is shown that the concept can be implemented in many orbits without any particular thermal control and that many more orbits could be used with thermal control of a suitable authority. Possible thermal control solutions are reviewed and recommendations for a passive system are made
Thermal control of multifunctional power structures using phase change materials
No full textA structure becomes a multifunctional power structure when in addition to meeting structural requirements it also performs functions associated with the electrical power system. With the structure performing these functions, some separate discreet components may no longer be required. Thus the parasitic structures that support them and the bus volume for these components are no longer required, reducing both mass and volume of the spacecraft. This paper focuses on the inclusion of commercial lithium polymer batteries into a sandwich panel which comprises the structure of a wing mounted solar array. It is shown that the thermal environment in earth orbit is hostile to the batteries. As such, a local thermal control system is required; with its authority targeted at preventing overcooling during eclipse. Phase change materials are proposed as a method to increase the thermal inertia of the structure by exploiting the latent heat. Through numerical simulation, it is shown that phase change materials are a relatively heavy solution. It is demonstrated that as the transition temperature rises, the amount of phase change material increases and that the optical properties of the structure can be altered to reduce the mass of phase change material required to more feasible levels
Multifunctional power structures and related thermal issues
No full textMultifunctional spacecraft power structures are an incorporation of energy storage and generation into structures on a spacecraft. For the mass and volume saving benefits to be realised, the technology must be shown to be viable throughout the spacecraft's lifetime. Firstly, commercially available batteries where built into a structural panel and tested to determine the battery's capability to withstand the manufacturing cycle and the effect upon the mechanical characteristics of the panel. Secondly, a mathematical model was created to determine the temperatures a battery would experience in various earth orbits. It was found that spacecraft in most low earth orbits will require thermal control and that the addition of a phase change material is a feasible control solution. Copyright © 2008 by ASME
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
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