1,721,040 research outputs found
A study on vision sensors for seam tracking of height-varying weldment. Part 2: Applications
No full textMany efforts have been made to develop an automatic welding system in order to improve the quality and productivity in welding shipping containers and LNG (Liquefied Natural Gas) storage tanks which consist of many sheet metals having linear weldments with height variation. A vision sensor which can provide 3D geometry information about objects is investigated primarily, because it is difficult to apply the are sensor to automatic welding of thin plates. However it is difficult to determine the proper configuration of sensory system including a CCD camera and diode laser to specific weldments because of the interference and relative motion among vision sensor, welding torch and weldment. Therefore, to develop a vision sensor with high performance for a specific workpiece, the sensory system should be analyzed for various configurations of sensors and weldment shapes by using a mathematical model. In this study, the measuring efficiency of vision sensor predicted by its model and the criterion for data deficiency was in significant agreement with experiments for typical corrugations of shipping containers and LNG tanks. It was found that the results obtained from the mathematical model were very useful in designing the vision sensor for automatic welding of linear weldments with height variation. (C) 1998 Elsevier Science Ltd
A study on vision sensors for seam tracking of height-varying weldment. Part 1: Mathematical model
No full textAmong the various types of sensors used in welding automation, are and vision sensors are widely used for automatic seam tracking and quality control of are welding processes. The development of a vision sensor which can provide 3D geometry information is needed especially for robot guidance in automatic welding of thin plates, because it is difficult to apply an are sensor to the welding of thin plates. Vision sensors using optical triangulation have been widely used in various ways for automatic welding systems. The separation angle between the camera and the laser axis has been mainly considered in previous studies of the vision sensor with structured light. Their measuring efficiency is, however, considerably influenced by the different arrangements of the weldment, the CCD camera, and a diode laser of a vision sensor in three-dimensional space. Therefore to enhance the effectiveness of a vision sensor for height-varying workpieces, other geometrical parameters such as diagonal and tilt angles should also be investigated. In the present study, the data deficiency in the vision sensor falls into two classifications: the shadow effect and the missing field of view (FOV), and a mathematical model is proposed to estimate the occurrence of data deficiency. (C) 1997 Elsevier Science Ltd
Influence of reflected arc light on vision sensors for automatic GTAW systems
No full textBecause of the difficulty in applying arc sensors to the welding of thin corrugated plates, vision sensors that provide three-dimensional geometry information by optical triangulation have been widely used for robot guidance in automatic welding of plates. The reliability of vision sensors, however, is influenced considerably by arc light reflected from the base metal surface in spite of blocking the direct arc light with a light isolator. A reflectance model of a welding arc was developed to estimate arc noise for various configurations of sensors, base metals, and welding arcs in three-dimensional space by assuming the welding arc as a point and extended light source. Various experiments were conducted to determine the bidirectional reflectance distribution function (BRDF) parameters of the model, and to verify the validity of the proposed model. Two proposed models, the point source model and the extended source model, were compared with, the gray level of the reflected arc caught by a CCD camera. The experimental data of the gray level of the reflected arc generally agreed well with. calculated results obtained by the two models, while the model with a point light source resulted in a greater discrepancy for short distances between the welding arc and reflecting surface of the base metal. The proposed models and experimental results can be effectively used for optimal design of the configuration and the moving path of vision sensors according to base metal shape, which improves the measuring efficiency of vision sensors (Refs. 1, 2) and reduces the effect of arc noise on them (Ref. 3), thus enhancing the performance of the vision sensor in automatic joint tracking of the arc welding process
TMRCC: A Congestion Control Mechanism for Tree-based Many-to-many Reliable Multicast Protocols
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Cloning of the cDNA for thyroid stimulating hormone subunit and changes in activity of the pituitary–thyroid axis during silvering of the Japanese eel, Anguilla japonica
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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
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