1,720,953 research outputs found
New Techniques and Methods for In-Situ Orbital Debris Detectors
Full text linkThe rapidly increasing population of orbital debris in the near-Earth environment poses a significant hazard for operational spacecraft and future space missions. This has led to an increased need for in-situ detectors capable of observing, and distinguishing between, natural space dust and anthropogenic orbital debris, to both measure their flux and help quantify the threat that they pose. Accordingly, this thesis is concerned with the development of new techniques for in-situ orbital debris detection, with a focus on the development of acoustic thin film time of flight (TOF) detectors, specifically the Debris Resistive Acoustic Grid Orbital NASA-Navy Sensor (DRAGONS) developed by NASA, and my industrial partners AstroAcoustics. TOF detectors are valued for their impactor speed and direction measurement capabilities that allow the distinction between orbital debris and natural space dust particles. The development and successful implementation of thin film TOF detectors, which measure impactor speed via the passage of the impactor through successive thin films, requires that two key questions be answered: Firstly, what is the measurement accuracy of such a detector? Secondly, what effect does passage through the thin film have on the impactor and the resulting speed measurement, i.e. is the impactor decelerated upon passage through the first film? To address these questions prototype detectors based on the DRAGONS concept were constructed, one with two successive 12.5 µm Kapton films and the other with two successive 25 µm Kapton films. These were then impacted with stainless steel projectiles ranging from 0.2 mm to 1 mm in diameter at hypervelocity speeds of ~ 2 km s-1 and ~ 4 km s-1 using the University of Kent's two-stage Light Gas Gun. This range of projectile sizes provided a film thickness to projectile diameter ratio (f/dp) of between 1/80 ≤ f/dp ≤ 1/8. For the largest 1 mm projectiles impacting 12.5 µm Kapton films, no deceleration was observed, and the speed obtained from the detector was found to be accurate to less than 1% error. This confirms that acoustic thin film detectors can measure the speed of 1 mm-sized impactors to a high degree of accuracy and are thus suitable for use in space to measuring this size of orbital debris, which poses the greatest threat to space missions in low Earth orbit (LEO). As f/dp increases, the penetration hole morphology becomes more complex and with-it acoustic signal onset determination decreases in accuracy, resulting in a decrease in speed measurement accuracy. Deceleration was not observed for projectiles ≥ 0.4 mm impacting 12.5 µm Kapton films (f/dp = 1/32), however, as f/dp increased to f/dp = 1/16, deceleration started to occur. Broadly deceleration was found to have size dependent effects, with the absolute film thickness playing a role as well as f/dp. Furthermore, comparison to previous results in the literature would suggest that there is also a material dependence. During the investigation, non-acoustic noise was identified in some of the traces from the polyvinylidene fluoride (PVDF) acoustic sensors. This was observed to coincide with impact light flash produced during projectile impact and is the likely source of this noise. With the space industry moving towards using smaller spacecraft in favour of larger, more traditional spacecraft, a preliminary analysis of the feasibility of using small area detectors applied to small spacecraft (specifically CubeSats), to perform orbital debris flux measurements, was conducted. Traditionally large areas on single spacecraft are required for impact detectors to ensure they provide meaningful statistical data. Thus, the use of small area detectors that can be applied to CubeSats faces an important question: can the accumulation of data from detection areas split over multiple small detectors provide statistically meaningful results? Comparison between the accumulated flux from CubeSat sized surfaces that have previously been exposed to space and predictions from ESA's most up to date space environment modelling software - MASTER 8.0.3 - suggests that the accumulation of detection area does provide statistically meaningful data, with accumulated fluxes within or very close to the estimated minimum uncertainties for the predicted fluxes
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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