1,720,964 research outputs found
Thermal load effects on side plates of superyachts
No full textFrom the commercial point of view the aesthetics of large luxury yachts has the same importance of their technical performances and reliability. In this perspective the first impact that a new construction can exert on a potential owner takes place through the overall appearance of the hull and superstructures. The hull colour, in particular, is becoming more and more determinant to make a yacht more attractive. After a long, undisturbed supremacy of white and cream colours, now an increasing number of owners are opting for dark colours, like blue, green or black. For a perfect painting output these colours needs a perfectly smooth surface as they have the tendency to emphasize every small defect of the hull surface. This aspect can be further amplified by those shape defects affecting hull sides, such as bump and hollows, coming from welding plates each other and plates to frames. For this reason, in case of steel and aluminium vessels, the surface finishing must be achieved by a long and delicate process of filling and fairing. Notwithstanding very accurate preparation, hull surfaces can undergo undesired alteration because of long expositions to solar radiation. This phenomenon is amplified when the surface is painted with dark colours which have the tendency of absorbing much greater solar heat. As stated by a previous investigation carried out on superyachts painted with dark colours, the surface of hull sides after a long exposition to solar radiation can reach temperatures close to 70–80°. In order to evaluate possible distortions of hull sides caused by thermal loads, an investigation has been carried out on the influence of temperature on the mechanical behaviour of steel plates coated by epoxy filler. The study has been developed by FEM structural analyses on a portion of a superyacht hull in the region of aft sides where the flatness of shell makes more visible possible distortions. Both steel and aluminium material have been considered covered by filler layers of different kind and thickness. A preliminary experimental investigation has been performed on a number of steel and aluminium specimens in order to calibrate the numerical models
Experimental Analysis of Cavitation Erosion on Blade Root of Controllable Pitch Propeller
No full textThe aim of this study is to experimentally investigate the cavitation
erosion on the blade root of a model scale controllable pitch propeller. Tests are
carried out in a cavitation tunnel, using the soft paint technique to study cavitation
erosion, exploiting also two standard cameras and one high speed camera to study
the damage patterns and cavitation dynamics, respectively. Standard cameras are
placed on the top of test section in order to periodically monitor the occurrence of
damages on the layer of paint. The high-speed camera has been used instead to
analyse bubble dynamics and identify potentially erosive phenomena. Three
different cavitation bubble structures on the blade root have been identified in the
present study: streak cavitation, spherical bubble cavitation, and twisting bubble
cavitation. The paint tests results have been analysed together with high-speed
videos, showing a remarkable agreement between the occurrence of damage and
cavitation collapse phenomena. The results demonstrated two regions on the
propeller blade root with high risk of erosion: (1) suction side blade root showed
significant damage pattern due to single bubble as well as bubble assembly collapse,
and (2) pressure side blade root showed slight damage pattern due to spherical
bubble collapse
Rheological, Mechanical and Morphological Characterization of Fillers in the Nautical Field: The Role of Dispersing Agents on Composite Materials
No full textCoatings have a fundamental role in covering the external surface of yachts by acting both as protective and aesthetic layers. In particular, fillers represent the essential layer from the point of view of mechanical properties and consist of a polymeric matrix, different extenders and additives, and dispersing agents, with the latter having the role to provide good extender-matrix compatibility. In the present work, the effects of dispersing agents with an ionic or steric action on the interactions between hollow glass microspheres and an epoxy-polyamide resin are evaluated. Un-crosslinked filler materials are studied via rheological tests, whereas the mechanical and morphological properties of the crosslinked samples are assessed. The results clearly indicate that steric dispersing agents provide a much greater compatibility effect compared to ionic ones, owing to their steric hindrance capability, thus leading to better-performing filler materials with a less-marked Payne effect, which is here proved to be an efficient tool to provide information concerning the extent of component interactions in nautical fillers. To the best of our knowledge, this work represents the first attempt to deeply understand the role of dispersing agents, which are until now empirically used in the preparation of fillers
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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