1,720,956 research outputs found
Simulations of Dynamic Interaction Between a Bluff Body and Installation Vessel During Launch and Recovery in Rough Seas
No full textSimulation of marine operations for launch and recovery of bluff bodies such as autonomous underwater vehicles (AUV), remotely operated vehicles (ROV) or subsea templates is traditionally performed in calm to moderate sea conditions. The reason for doing so is partly due to the interaction between the complex dynamic response of an installation vessel, a moving bluff body and the wave kinematics of the rough sea condition. This is in addition to the need for accurate hydrodynamic coefficients that would enable proper simulation and modelling of the launch and recovery process. The key objective of the current methodology is to minimize risks of damage to the vessel and total loss of assets during the deployment and recovery process for marine operations in rough sea conditions.
The aim of this paper is to present the results of experimental and numerical investigation on the prediction of dynamic response of a bluff body during launch and recovery from a surface vessel in rough sea condition. Experimental measurements of hydrodynamic coefficients and responses of a large scale bluff body using a scaled model were completed. Further studies using a time-domain numerical tool have been undertaken to measure the response characteristic of bluff bodies in rough seas. The study also predicted the contributions of vessel motion in rough seas to the dynamic response of the bluff bodies. The results obtained have shown that simulation of launch and recovery operations in rough seas can be carried out efficiently if their hydrodynamic coefficients through the wave active regions of the rough seas are predicted and then adequately implemented in the simulations.</jats:p
Hydrodynamic Characteristics of ROVs During Deployment Through Wave-Affected Zones
No full textThe prediction of wave-induced loads on Remotely Operated Vehicles (ROVs) during deployment through the splash zone is an important requirement to the design of a launch and recovery system. This paper presents the results of numerical and experimental hydrodynamic analysis of the motion response and wave-induced loads on a subsea trencher ROV during its deployment through the splash zone. The main focus of the study is to determine the maximum wave-induced loads and also to establish the maximum range of sea conditions in which the ROV can be operated safely. The numerical measurement of the hydrodynamic responses is completed using a 3D potential theory-based solver. The results obtained are compared with the predicted experimental responses measured using a 1/12 scale model of the ROV in a wave tank. A further comparison of the numerical responses with a box-shaped model of approximately similar overall dimensions to the ROV is performed in order to establish the validity of using a simplified shape to represent the actual ROV in various modelling scenarios. The result of this comparison shows that using a box-shaped model grossly over-predicts the responses and can lead to overly conservative load prediction.</p
The Dynamic Behaviour of an ROV in Wave Affected Zones
No full textWe present a method to directly predict the hydrodynamic response of a Remotely Operated Vehicle (ROV) as it transitions through the wave-affected splash zone during launch or recovery. ROVs are commonly used in offshore operations and for many different purposes. They are usually deployed from a purpose built Launch and Recovery System (LARS) located on the open deck of a surface ship. Current industry practice used for LARS design is to use a pre-defined dynamic amplification factor (DAF) together with high factors of safety. However, this does not properly account for the influence of different sea states and operational profiles. We therefore propose an improved method to directly predict the hydrodynamic response of an ROV as it transitions through the wave-affected splash zone.We apply the approach to a trencher ROV and validate using physical experiments completed in a wave tank. We demonstrate the need to for an accurate definition of the added mass and damping characteristics of the ROV. The method is incorporated into OrcaFlex for direct use within the design and analysis of a LARS system.</p
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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