1,720,969 research outputs found
Dyadic Cooperation in Code Acquisition: a Theoretical Framework
No full textThis paper presents a general framework for the analysis of dyadic cooperation of finite-state machines (FSMs)
performing code acquisition, as applied to navigation and communication spread-spectrum systems. Our aim is to show how code acquisition performance can be improved by relying on the unidirectional or bidirectional exchange of timing information between two FSMs. We develop an analytical framework based on the flow-graph approach to derive closed forms for the mean and variance of the acquisition time of various cooperating structures. An approximate form of the cumulative distribution function (CDF) is also provided. This framework is suitable for multiple applications, including peer-to-peer navigation, hierarchical codes, assisted global navigation satellite systems (GNSS), multiple navigation signals, and others. As a study case, we provide quantitative results for a dual-band Galileo receiver, which demonstrate the superiority of dyadic cooperation approaches in acquiring synchronization in both the E1 and E5 bands
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Enabling Techniques and Algorithms for Integrated Communication and Navigation Satellite Systems
No full textThis thesis presents the outcomes of my Ph.D. course in telecommunications engineering. The focus of my research has been on Global Navigation Satellite Systems (GNSS) and in particular on the design of aiding schemes operating both at position and physical level and the evaluation of their feasibility and advantages.
Assistance techniques at the position level are considered to enhance receiver availability in challenging scenarios where satellite visibility is limited. Novel positioning techniques relying on peer-to-peer interaction and exchange of information are thus introduced. More specifically two different techniques are proposed: the Pseudorange Sharing Algorithm (PSA), based on the exchange of GNSS data, that allows to obtain coarse positioning where the user has scarce satellite visibility, and the Hybrid approach, which also permits to improve the accuracy of the positioning solution.
At the physical level, aiding schemes are investigated to improve the receiver’s ability to synchronize with satellite signals. An innovative code acquisition strategy for dual-band receivers, the Cross-Band Aiding (CBA) technique, is introduced to speed-up initial synchronization by exploiting the exchange of time references between the two bands. In addition vector configurations for code tracking are analyzed and their feedback generation process thoroughly investigated
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
Vector tracking aiding for carrier phase estimation in the presence of ionospheric scintillation
No full texthttp://www.ion.org/publications/abstract.cfm?jp=p&articleID=10856International audienceIn GNSS receivers, the ability of guaranteeing continuous position, velocity and time (PVT) solutions is linked with their capacity of maintaining lock with the satellite signals. However, this is not always possible and in degraded environments the received signals can be strongly attenuated or affected by errors that cause the tracking loops to lose lock and the navigation processor to be unable to produce a useful positioning solution. A particularly challenging environment is represented by the presence of ionospheric scintillations that combine signal fading and fast phase variations. These effects can severely test receiver tracking loops and their capacity to follow the received signal changes. Carrier tracking through phase lock loops (PLL) is especially susceptible to losing lock. Amplitude scintillations may in fact generate deep fades in the received signal power that in worst cases can cause the signal to drop below the lock threshold; on the other hand, phase scintillations cause rapid carrier phase changes that might produce cycle slips and even cause loss of lock. This lack of robustness strongly impacts receiver performance as it reduces carrier phase measurements availability, the capability to demodulate the navigation message data and the ability to perform carrier-smoothing. This is the motivation behind the study of innovative architectures to improve receiver robustness and aid the phase tracking process. Ionospheric scintillation mitigation can in fact be achieved by improving carrier tracking ability to sustain rapidly changing received signals. Different tracking schemes could be envisaged; in this paper a Vector Frequency Lock Loop (VFLL) assisted PLL is described. Vector tracking loops are interesting as they allow implementing cross-channel aiding by linking together all received signals through the receiver position and velocity. The aim of this paper is therefore to present the VFLL-assisted PLL receiver architecture describing the system model and feedback generation process and to test its feasibility in scintillation scenarios. To reproduce the scintillation effect, the Cornell Scintillation Model (CSM) has been used and simulations that quantify the performance in terms of phase tracking error variance, cycle slips and loss of lock are conducted
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