1,720,971 research outputs found
Power Fluctuations caused by Wind Turbulence on a 15MW Floating Offshore Wind Turbine
Get PDFThis study informs about power fluctuations caused by wind turbulence that should be expected from a 15MW floating offshore wind turbine in the context of power supply to an isolated grid with energy storage. To this end, appropriate engineering models are used to screen through normal wind conditions to be encountered during the system's lifetime. The impact of the various modelling assumptions is then assessed through sensitivity studies. Power fluctuations are then translated into size requirements for energy storage, when its objective is to filter fluctuations over a selected time horizon to provide stable power to the isolated grid.Power Fluctuations caused by Wind Turbulence on a 15MW Floating Offshore Wind TurbinepublishedVersio
Synthetic turbulence modelling for offshore wind farm engineering models using coherence aggregation
Get PDFTurbulent wind fields are known to be a major driver for structural loads and power fluctuations on offshore wind turbines. At the single-turbine scale, there exist well-established design standards based on wind spectra and coherence functions calibrated from years of measurements, which are used to generate multiple 10-min wind field realisations known as synthetic turbulence boxes, themselves used as input to turbine-scale aero-hydro-servo elastic codes. These methods are however not directly applicable at farm scale. When analysing the dynamics of large offshore wind farms, measurements reveal the importance of large, low-frequency turbulent vortices for power fluctuations and hence for wind farm control and grid integration. Also, farm-scale wind fields are needed as input to farm-scale aero-servo-elastic codes for the modelling of wake dynamics, affecting structural loads. These new concerns motivate an upgrade in the original turbine-scale wind field representation: (1) spectral models need to be based on farm-scale measurements, (2) the frozen-turbulence assumption merging temporal and along-wind coherence must be lifted, (3) simplifications are needed to reduce the number of degrees of freedom as the domain becomes excessively large. This paper suggests models and algorithms for aggregated farm-wide corrrelated synthetic turbulence generation—lumping the wind field into space-averaged quantities—adapted to the aero-hydro-servo elastic modelling of large offshore wind farms. Starting from the work of Sørensen et al. in the early 2000s for grid integration purposes, methods for structural load modelling (through wake meandering and high-resolution wind field reconstruction) are introduced. Implementation and efficiency matters involving mathematical subtleties are then presented. Finally, numerical experiments are carried out to (1) verify the approach and implementation against a state-of-the-art point-based—as opposite to aggregated—synthetic turbulence generation code and (2) illustrate the benefit of turbulence aggregation for the modelling of large offshore wind farms.Synthetic turbulence modelling for offshore wind farm engineering models using coherence aggregationpublishedVersio
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
Rotor‐integrated modeling of wind turbine aerodynamics
Get PDFA novel approach for the modeling of rotor-integrated aerodynamic loads is suggested to answer the need for a comprehensive, insightful, and analytical actuator disc model. All the six degrees of freedom (including tangential components) are considered. It is shown that loads may be written as a quadratic form of a reduced six-component velocity vector at the hub. The individual contributions of lift and drag, azimuthal variations, as well as blade pitching and tip losses are isolated. Errors introduced by the necessary approximations are discussed, and parametric corrections are considered. Parameter identification methods are then suggested, and the performance of the resulting calibrated analytical models is assessed. Results show that the new modeling approach is able to accurately model both the mean values of the thrust and power coefficients and their derivatives with respect to tip-speed ratio and pitch angle across the full range of operating wind speeds. Furthermore, it is able to reconstruct the general rotor behavior with a minimal amount of information available. Tangential components are also well modeled, although they require the knowledge of airfoil properties. The model's architecture leaves room for extensions to dyna
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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