1,720,975 research outputs found
Random set particle filter for bearings-only multitarget tracking
No full textThe random set approach to multitarget tracking is a theoretically sound framework that covers joint estimation of the number of targets and the state of the targets. This paper describes a particle filter implementation of the random set multitarget filter. The contribution of this paper to the random set tracking framework is the formulation of a measurement model where each sensor report is assumed to contain at most one measurement. The implemented filter was tested in synthetic bearings-only tracking scenarios containing up to two targets in the presence of false alarms and missed measurements. The estimated target state consisted of 2D position and velocity components. The filter was capable to track the targets fairly well despite of the missing measurements and the relatively high false alarm rates. In addition, the filter showed robustness against wrong parameter values of false alarm rates. The results that were obtained during the limited tests of the filter show that the random set framework has potential for challenging tracking situations. On the other hand, the computational burden of the described implementation is quite high and increases approximately linearly with respect to the expected number of targets. Keywords: Bearings-only tracking, finite set statistics, multitarget tracking, particle filter 1
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
Random Sets for Multitarget Tracking and Data Fusion
No full textThis thesis is a background study of the theory of finite random sets, and their application to target tracking. The main purpose is to provide a solid theoretical basis for further research and development of random set tracking methods. The random set approach to multitarget tracking is a theoretically sound framework, that covers the joint estimation of the number of targets, and the state of the targets. In addition to the theory of random sets, the thesis provides a review of related subjects, such as general probability theory and recursive Bayesian estimation. Sequential Monte Carlo (SMC) is selected as an approximative computational strategy, so a summary of SMC methods is included. In addition, a literature review on Bayesian target tracking methods is given. The random set tracking model that is considered in this thesis includes a model for such sensors that produce at most one measurement per report. A SMC implementation for the random set tracking model is derived. The results that were obtained during the limited tests of the SMC algorithm serve as a ``proof-of-concept''. Based on the results, the practical usability of the algorithm cannot be assessed. Merely, the results in this thesis show that the random set framework has potential for challenging tracking situations. The tests consisted of synthetic bearings-only tracking scenarios with up to four targets, in the presence of false alarms, and missed measurements. The algorithm was capable to track up to two targets quite reliably. In addition, the algorithm showed robustness against relatively high false alarm rates. Moreover, the performance of the algorithm degraded gradually with respect to an increasing mismatch in the false alarm rate parameter value and the parameter value in the tracking environment
PREPRINT, ACCEPTED FOR PUBLICATION IN IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 1 Rao-Blackwellised Particle Filtering in Random Set Multitarget Tracking
No full textAbstract — This article introduces a Rao-Blackwellised particle filtering (RBPF) approach in the finite set statistics (FISST) multitarget tracking framework. The RBPF approach is proposed in such a case, where each sensor is assumed to produce a sequence of detection reports each containing either one single-target measurement, or a “no detection” report. The tests cover two different measurement models: a linear-Gaussian measurement model, and a nonlinear model linearised in the extended Kalman filter (EKF) scheme. In the tests, Rao-Blackwellisation resulted in a significant reduction of the errors of the FISST estimators when compared to a previously proposed direct particle implementation. In addition, the RBPF approach was shown to be applicable in nonlinear bearings-only multitarget tracking. Index Terms — Finite set statistics, multitarget tracking, Rao-Blackwellised particle filte
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
- …
