1,720,963 research outputs found
Three-dimensional visual mapping of underwater ship hull surface using image stitching geometry
No full textThis paper presents a method for three-dimensional (3D) visual mapping of underwater ship hulls using monocular vision. Visual inspection of underwater ship hulls using unmanned underwater vehicles needs to be conducted at very close range to the target surface because of the limited visibility in underwater environments. These environmental challenges can result in ineffective photometric and geometric information in hull surface images. Therefore, the performance of conventional 3D reconstruction techniques based on monocular vision is often unsatisfactory. To address these challenges and generate a precise 3D global map of the surveyed hull surface, the proposed visual mapping method adopts a two-step approach comprising global registration in two-dimensional space and 3D reconstruction using the information of the stitching geometry drawn by the registered images. Experimental results are shown to demonstrate the feasibility of the proposed method using image datasets obtained in field experiments with two different full-scale ships in real sea environments.
Robust Loop Closure Method for Multi-Robot Map Fusion by Integration of Consistency and Data Similarity
No full textFor an efficient collaboration of multi-robot system during missions, it is essential for the system to create a global map and localize the robots in it. However, the relative poses among robots may be unknown, preventing the system from generating the reference map. In such cases, the necessary information must be inferred through inter-robot loop closures, which are mainly perception-derived measurements obtained when robots observe the same place. However, as perception-derived measurements rely on the similarity of sensor data, different places could be wrongly identified as the same location if they exhibit similar appearances. This phenomenon, called perceptual aliasing, produces inaccurate loop closures that can severely distort the global map. This study presents a robust inter-robot loop closure selection for map fusion that utilizes the degrees of both consistency and data similarity of the loop closures for accurate measurement determination. We define the coalition of these information as the measurement pair score and employ it as weights in the objective function of the combinatorial optimization problem that can be solved as maximum edge weight clique from graph theory. The algorithm is tested on an experimental dataset for performance evaluation and the result is discussed in comparison to a state-of-the-art method.
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
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