1,720,963 research outputs found
A Comparative Analysis of GPS-based Algorithms for Real-Time Navigation of Small Satellites
No full textImplementation and tuning of LEO satellites real-time navigation algorithm based on single frequency GPS measurements
No full textSince its origin, the navigation services provided by the GNSS system have been applied to a variety of field, some of which are beyond the original scope of the infrastructure. LEO satellites autonomous orbit determination by means of on board GNSS receiver is one of the cases. The achievable position accuracy, in the order of 10 m 3d rms, satisfies most of the mission requirements and can be implemented with a simple navigation algorithm based on loose constraining of observations. For those missions that require better real time accuracies, sub meter positioning is achievable, by means of reduced dynamic filtering, which provides strong constraining of observations thanks to a detailed orbit force model. The algorithm general architecture is well covered in literature, although its real world implementation is still limited to few cases, partially because few are the missions that require such accuracy in real time, and partially because of its implementation complexity. This paper addresses one aspect of this complexity, which is related to filter tuning, or in other words to the effective definition of a statistical description of observations and process errors. Being the filter tuning a process of trial and error in most cases, and a delicate implementation step at the same time which may lead to instability and divergence, this paper proposes a procedure to achieve stable sub meter positioning from the reduced dynamic algorithm implementation
Development and test campaign of a GPS-based navigation sub-system for the ESEO mission
No full textThis paper deals with the presentation of the contribution provided by the University of Bologna to the ESA ESEO mission. Since 2013 the University of Bologna is developing one of the payloads that will operate on board of the ESEO spacecraft: a GPS receiver for small satellites, able to provide real time high quality position fixes with reduced manufacturing time and costs. This is possible thanks to the navigation filter, hosted on board of the payload, that processes together the GPS observables provided by the COTS front-end, OEM615 receiver from Novatel, with an accurate model of the orbit dynamics. This paper presents the work done so far on the design and development of the GPS Payload: the whole architecture of the device and the navigation algorithm will be briefly described, while particular focus is given to the update status of the project and on the test campaign carried out at a sub-system level on the device. The current state of the design is between CDR and TRR and the manufacturing of the PFM is already started. Also the firmware is entering the final development phase, with the filter design and verification foreseen to be completed by the end of June 2016
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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