1,720,991 research outputs found
Instream generation using tethered kites in the carousel configuration
Full text linkIn recent years, kites are beginning to be considered as viable alternatives to oshore
wind turbines, due to the potential reduction in levelised cost of energy and the increase
in exploitable resource due to versatility of kite based generators. This thesis focuses
on the kite carousel design, which consists of a ground based vertical axis generator
with a number of kites attached. The kites are flown in a pattern that induces motion
in the generator and thus produces power. This method of energy harvesting allows
substantial scaling of devices. Device output depends not only on the available ow
and kite size, but is further influenced by the length of the kite tether, the radius of the
carousel structure, and the number of kites attached.
Although kites have been studied extensively in recent years, there is no consensus on
the optimum design and configuration of the carousel. The thesis presents a minimum
order model of a kite carousel. This numerical model is used to indicate the driving
principles of the carousel and the importance of flightpath design on output. The presented model can be applied to various ow conditions. However, due to the definition
of dimensionless power used, there is a scaling dependency of the model outputs regarding the kite tether length. An alternative method of describing the swept area of
the carousel, based on the swept area of the kite flightpath, is used to mitigate this and
indicate device efficiency in power extraction.
The flightpath optimisation and parameter study illustrate this scaling dependency and
highlight the effect of the carousel radius and tether length on the optimized flightpath.
These results then inform a case study for a carousel placed in a representative tidal
flow. The case study describes a device with 8 kites attached to a 5 m diameter carousel
that produces 64 kW over a representative tidal cycle with a peak flow of 2.2 m/s
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
Naval ship design-process analysis through dynamic social networks
Full text linkModern naval ship design is increasing in complexity as more and more systems are incorporated into the design process, leading to an increase in the number (and interdependence) of tasks that designers need to complete and progress through the design stages. This work develops a dynamic bipartite social network representation, separating the nodes in activities and individuals, with the aim to analyse and draw conclusions regarding the design process. A dynamic time-dependent graph (TDG) is constructed with the use of a presence function for the edges. Network properties (density, clustering, active tasks/designers) are expressed as functions of time, and node-wise metrics (centralities) reveal the key role of individuals in the naval ship design process, which is heavily-crowded with respect to tasks. Furthermore, application of the model to naval ship design data reveals interesting insights regarding the impact of COVID-19 and the design company’s adopted hiring policy
Concept design considerations for the next generation of mega-ships
No full textThe cruise industry represents one of the fastest growing shipping industries, supported by a 62% demand increase for the last decade, and an order-book in excess of $25bn. The sustained growth in demand is complemented by increasing vessel size, which represent investments in the order of billions. Megaships serve a specific market segment, with capacities in excess of 6,000 guests and crew. Increased capacities though lead to an increasing number of people at risk, hence safety considerations are key to these developments. By considering the current trends of the industry, a techno-economic feasibility for a 12,000 passenger mega-liner, with a significantly increased safety level, is investigated. The increased size of the cruise ship enables enhanced on-board guest experience, whilst ensuring an unparalleled safety level
From regional sensitivity to intra-sensitivity for parametric analysis of free-form shapes : application to ship design
Full text linkRobust Parametric Sensitivity Analysis (PSA) is a prerequisite for efficient shape optimisation via parametric modelling. A major challenge PSA has to handle is related to the fact that a parameter can be sensitive in certain local areas of the design space but become insensitive in others. Therefore, setting an applicable space for this analysis becomes a difficult task. In this paper, we introduce the concept of intra-sensitivity to identify parameters whose perturbation has a major impact on the sensitivity index of the remaining parameters. For this purpose, we firstly appeal to Active Subspace Method (ASM) and develop an ASM-based regional sensitivity analysis, which investigates parametric sensitivity in local regions of the design space and aids conducing to parameters' intra-sensitivity. This regional analysis is applied in conjunction with a Dynamic Propagation Sampling approach, for tackling the computational complexity arising when high-dimensional problems are concerned. Once sensitive and intra-sensitive parameters are identified, then free-form features, correlated to these parameters, are evaluated using a feature saliency map built with the aid of Hausdorff distance. The so resulting methodology has been validated in the area of computer-aided ship design using two parametric modellers: the first one is a Procedural Deformation (PD) modeller which is based on T-splines and involves 24 parameters while the second one is based on Free-Form Deformation (FFD) and involves 104 parameters. The corresponding design spaces have been generated using a parent hull close to the KCS container ship and are analysed against hull’s volume of displacement and total resistance. Finally, the convergence performance of the various components of this approach is compared with state-of-the-art techniques
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