1,721,007 research outputs found
Nonlinear filtering with application to the bearings only measurement problem
No full textThe general nonlinear filtering problem, and the application to bearings only measurements is considered. The problem may be formulated from a variety of perspectives: the discrete state space approach utilised for this research is set in context. The basic methods of solution then involve either modal filtering, or linearising the system by approximation. The methods are compared and contrasted, and the algorithms derived, including a novel implementation of the modal filter for a noisy process. This method circumvents the two point boundary value problem, and the consequent approximation schemes, usually associated with modal estimation of a random vector. As the modal filters carry a high computational cost, and the linearised approximation methods are prone to unstable, even divergent behaviour, many variants on the basic filters have been developed. These are reviewed, and derived where appropriate. Another source of practical difficulty in filtering applications is that it is often not possible to define the system as fully as the filter requires. Methods for coping with inaccuracy and uncertainty in the filter's model of the system are reviewed and algorithms derived. As these methods predominantly assume linearity, attention is paid in particular to their potential for extension to the nonlinear environment. A novel method for minimising the effect on the estimation error of the sudden onset of uncertainty in the process is presented. The application of these methods to, and bounds on their performance in the bearings only measurement problem is then discussed, together with filters developed specifically for this case. Addressed are both the standard formulation of the problem, in which the target is unaccelerated, and the case where the target is capable of manoeuvre, inducing error in the filter's model of the process. Extensive simulation studies of a selection of these filters and bounds, over a wide range of dynamical and filter initialisation parameter values, are presented and analysed.</p
The Theban harbours and waterscapes survey. Recent fieldwork to investigate the canals and harbours on the west and east banks at ancient Thebes (Luxor), Egypt
No full text
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
- …
