1,721,021 research outputs found
Linear quadratic control of service rate allocation in a satellite network
No full textThe real-time control of multiple queues handling traffic of different nature is obtaining increasing
relevance in both the uplink and downlink of wireless telecommunication networks, characterised by the
presence of a central access point. Such is the case of satellite networks, with either on-board processing or
double-hop configuration, besides a number of terrestrial local and metropolitan wireless networks. Given a
certain amount of available bandwidth, the problem is that of deciding, within a certain time frame, the
allocation of bandwidth partitions for each traffic queue, whose packets are awaiting transmission; eventually,
this determines the transmission rates to be passed to the scheduler and to the physical layer adaptive
coding and modulation devices. In a satellite network, where this task is accomplished by a master station,
residing at the access point, it is possible to take such decisions by means of a centralised controller, based
on real-time instantaneous (in the downstream direction) or delayed (in the upstream) information on the
queues’ state. The study derives a control law to be used in this task, by adopting an approach based on
optimal linear quadratic regulation. Both cases of un-delayed and delayed information are considered. The
control laws are tested in a geo-stationary satellite scenario of digital video broadcasting – return channel via
satellite (DVB-RCS), and the queues are considered at the medium access control level. Simulation results
under real-traffic traces are also presented to highlight the effectiveness of the control and to compare
alternative solutions
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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