1,720,952 research outputs found
Power to the airborne wind energy performance model: Estimating long-term energy production with an emphasis on pumping flexible-kite systems
No full textThe potential of utility-scale airborne wind energy (AWE) systems to contribute significantly to the energy transition hinges on their large-scale deployment, which depends on the cost-competitiveness and complementarity with conventional wind turbines. Central to the assessment of these metrics is understanding long-term energy production, which is influenced by the variability of wind profiles. This thesis investigates the significance of wind profile variability on annual energy production estimation for AWE systems. The study establishes the climatology of vertical wind profiles and expands flight operation models of AWE systems. By synthesising these aspects, a new energy production estimation framework is developed to incorporate variations in the wind profile shape. This framework is utilised to assess the impact of different wind profile shapes on the energy production estimation. The research underlines the need to move away from conventional wind energy calculation methods and offers a more suitable alternative for AWE systems. The framework offers a valuable tool for increasing the understanding of the viability of large-scale deployment of AWE systems.Wind Energ
Validation of the quasi-steady performance model for pumping airborne wind energy systems
No full textThe quasi-steady performance model (QSM) has been developed specifically for pumping airborne wind energy systems using flexible membrane wings. In this study, we validate this model using a comprehensive set of flight data that includes 87 consecutive pumping cycles and is acquired with the development platform of Kitepower B.V. The aerodynamic properties of the kite are determined using onboard measurements of the relative flow velocity. We found that neglecting the vertical wind component and straightening and slacking motion of the tether lead to substantial errors in the kite velocity calculated using the system model. A reasonable agreement between the QSM simulations and flight data can be obtained by multiplying the kite's drag coefficient by a fudge factor and thereby turning the QSM into a grey-box model. The model accuracy is statistically evaluated as opposed to only evaluating a single pumping cycle per system configuration as done in earlier research.Wind Energ
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
Structural Optimization of Multi-Megawatt, Offshore Vertical Axis Wind Turbine Rotors: Identifying Structural Design Drivers and Scaling up of Vertical Axis Wind Turbine Rotors
No full textThe knowledge about Vertical Axis Wind Turbines (VAWT) lags behind the knowledge about Horizontal AxisWind Turbines (HAWT), since most of the development of VAWT’s ceased after the 80’s. A lack of insight exists about how certain design parameters affect the rotor design of a modern VAWT. The objective of this thesis is to gain knowledge about the influence of the size (power capacity) of the turbine on the structural rotor performance of multi-megawatt VAWT’s by optimizing the rotor design. The influence of the size is expressed by scaling trends. The scope is limited to the structural design of the rotor blade and struts. The major loads on the rotor structure are aerodynamic, gravitational, and centrifugal loads. Fatigue, buckling, and resonance are the failure modes driving the design of the VAWT rotor. Modern manufacturing techniques of composite materials are believed to have a significant effect on the VAWT rotor design, since they offer more flexibility in the blade geometry. The mass increase of the blades is identified as a limiting factor for upscaling wind turbines. Gradient-based optimizations are performed to find the optimum 3-bladed H-rotor and Darrieus rotor designs for different rotor sizes and heights. The structural rotor performance is assessed by the ratio of the rotor mass over projected area. The laminate thicknesses and the shape of the rotor structure are varied in search of the optimum performance. A constant tip speed ratio and blade solidity is imposed on the optimization. Furthermore, constraints are imposed to prevent failure of the rotor structure. Optimizations of the VAWT rotor are performed for rotor sizes ranging from 3 MW to 20 MW. Rotor mass reductions for the carbon-fiber 20 MW H-VAWT and Darrieus VAWT of respectively 35% and 44% are obtained with respect to the fiberglass HAWT rotors. Despite this mass reduction, the material cost of the HAWT rotor will be significantly smaller. The optimized VAWT rotors are rough approximations of the best design solutions because of restrictions on the design space. In general, expanding the design space of the optimization yields better design solutions. In future VAWT rotor design optimization, the design space should allow for a variable diameter-to-height ratio of the rotor, since this parameter is driving the structural rotor performance.Aerospace EngineeringWind Energ
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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