1,720,963 research outputs found
Determination of 3-D weld seams in ship blocks using a laser vision sensor and a neural network
No full textIn automatic welding of a 3-D weld seam, a vision sensor is applied to acquire image patterns at various sensor positions and orientations. To extract the proper features from the image data, it is required to identify the pattern categories. In this paper, typical image patterns acquired in the sensing of the 3-D weld seam are classified. To identify the pattern categories, several parameters of the 2-D image data were tested, and a neural network using two input parameters and two hidden layers was developed to find the pattern type as output. A laser vision sensor attached to a conceptual mobile platform-manipulator was considered for sensing simulations, and a back-propagation algorithm was adopted to teach the neural network by using the geometrical patterns acquired from those simulations. The classified image data are processed using the line segmentation method to determine the distinctive features, and these features can then be used to find the weld seam or its end position for the automatic welding system. Experimental results of sensing are also presented
Development of an arc sensor with mechanized rotation of electrode
No full textIn order to develop an arc sensor using the mechanically rotating arc, a theoretical modeling and experiments were carried out to investigate the sensitivity and the accuracy of the "rotating arc sensor". The automatic seam tracking sensor was successfully developed for steel and Al alloy welding. The increase of the sensitivity and the responsiveness guaranteed an accurate seam tracking, and the way in which the welding and rotating parameters affect the accuracy of seam tracking was clarified from the experimental results. With the increase of responsiveness, the rotating arc sensor was able to be effectively applied to detecting the end-point due to the decrease of the influence of molten pool shape when the welding arc is on the preceding half circle
A study on a vision sensor based laser welding system for bellows
No full textWelded metal bellows are commonly manufactured by welding pairs of washer-shaped diaphragms of thin sheet metal. Two types of welding operations are required: inner edge welding to make pairs of diaphragms, and outer edge welding to form a bellows by welding the number of pairs. In this study, the inner and outer edges of bellows were welded by using a CW Nd:YAG laser. For the inner edge welding, the Nd:YAG laser beam was directed at an angle of 45 degrees to the edge because of the limited accessibility. In the outer edge welding, welded pairs were fixed on a jig and compressed axially. The difference between the center of the bellows and that of a jig shaft causes an eccentricity, while the tolerance between a motor shaft and a jig shaft causes a wobble-type motion. A vision sensor based on the optical triangulation was used for seam tracking. Two image processing algorithms that can find a bellows edge were developed for inner and outer edge welding. A geometrical modeling that describes the difference between the position of the Nd:YAG laser spot on a bellows edge and that of the laser diode stripe of the vision sensor was established. The seam tracking by a two-axis Cartesian robot was performed after the vision sensor determined the positional deviation in each sampling. Experiments were performed with 0.1 mm thick stainless steel bellows and 0.5 mm outer edges pitch. The seam tracking by the sensed positional deviation and geometrical modeling was performed successfully with an acceptable error
A study on a mobile platform-manipulator welding system for horizontal fillet joints
No full textThe mobile platform-manipulator welding system discussed in this paper is a three-link manipulator mounted on a mobile platform. This system uses laser range sensors to guide the mobile platform and a vision sensor to guide the manipulator end-effector to the weld seam line accurately. The task is to track the horizontal fillet seam in the grillage assembling method, which is one of the conventional procedures for assembling the flat hull blocks in shipbuilding and consists of only the horizontal fillet seam. In this paper, the path planning for the combined motion of the mobile platform and the manipulator was presented concerning manipulability measure and characteristics of the welding process. A control method for the mobile manipulator was presented, and simulation results were also presented to demonstrate the effectiveness of the control method for horizontal fillet welding. (C) 2001 Published by Elsevier Science Ltd.This work was supported in part by the Brain Korea 21 Project
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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