1,720,956 research outputs found
Assessment of flutter prediction and trends in the design of large-scale wind turbine rotor blades
No full textWith the progression of novel design, material and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the levelized cost of energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to instabilities due to their long and slender nature, and one of the concerning aero-elastic instabilities of these blades is classical flutter. In this work we assess classical flutter prediction tools for predicting flutter speeds in the design of large blades. Flutter predictions are benchmarked against predictions of previous studies. Then, we turn to the main focus of the study, which is design to mitigate flutter. Trends in flutter speeds and flutter mode shapes are examined for a series of 100-meter blade designs. Then, a sensitivity study is performed to assess the impacts of blade design choices (e.g. materials choice and material placement) on flutter speed in a redesign study of a lightweight 100-meter blade with small flutter margin. A new design is developed to demonstrate the ability to increase the flutter speed while reducing blade mass through structural design.Erik Jonsson School of Engineering and Computer Scienc
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
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
Design of Large Wind Turbine Rotors Through Passive and Active Load Mitigation Strategies
No full textWind energy over the years has positioned itself to become a primary source of renewable
energy and this is attributed to the reduction in the Levelized Cost of Energy (LCOE).
Historically, this is accomplished by an increase in tower heights which allow access to higher
wind speeds, and also by increasing rotor diameters which allow for more power capture.
However, there are significant challenges that come with these large turbines like aeroelastic
instabilities of the blades due to their long and slender nature, and the need for more robust
turbine components that can withstand the larger loads associated with large turbines. This
has motivated the development of design strategies that incorporate different methods of load
alleviation to achieve optimized wind turbine designs that can result in lower LCOE. This
dissertation presents various methods of designing wind turbine rotors that take advantage
of passive and active load reduction strategies.
First, classical flutter is addressed for the design of large blades. Flutter is an aeroelastic
instability that contributes to fatigue damage, or in the worst case can least to sudden catastrophic turbine failure. A comprehensive evaluation of flutter behavior including classical
flutter, edgewise vibration, and flutter mode characteristics for two- and three-bladed wind
turbine blade designs is carried out. Further, a study is performed to evaluate mitigation
of flutter in the design process via structural redesign by evaluating the effect of leadingvi
edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to
increase the flutter speed and satisfy structural design requirements (such as fatigue) while
maintaining or even reducing blade mass. This flutter structural mitigation study is conducted for two wind turbine designs, one a two-bladed rotor and the other a three-bladed
rotor.
Second, a new rotor design methodology is developed to integrate active load control in the
form of controllable gurney flaps. A comprehensive sequential iterative design procedure
is developed that integrates aerodynamics, structural, and baseline turbine control system
design with advanced active load control into a design process. This procedure also takes into
account the contribution of loads on all major components of the turbine. To realize the best
LCOE reduction solution, new methods to evaluate blade structural properties are developed
wherein, the reductions in damage equivalent loads (i.e.; fatigue loads) due to a generic active
load control system are mapped to structural design improvements in terms of blade mass
reduction, cost reduction in other major turbine components, and LCOE reductions that
result from integration and redesign of the turbine with the active load control system.
Third, using the design methodologies established, newer rotor designs with a larger rotor
radius are explored to examine the impacts of the active load control system. These rotors
take advantage of the fatigue load reductions due to the controllable gurney flaps integrated
into the design. The effect of the controllable gurney flaps is evaluated for various blade and
non-blade component loads on the turbine. This methodology results in larger rotors that
have increased energy capture and reduced LCOE’s. For this study, two different turbine
operating strategies are followed, one limits the turbine power to that of the baseline while
the other allows the turbine to extract more power at higher wind speeds.
Finally, a method is introduced to support the realization of new passive and active load
mitigation strategies by improving prototype wind turbine development. A novel method
of developing a multi-fidelity digital twin structural model of a wind turbine blade is presented. The digital twin model development methodology, presented herein, involves a novel
calibration process to integrate a wide range of information including design specifications,
manufacturing information, and structural testing data (modal and static) to produce a
multi-fidelity digital twin structural model: a detailed high-fidelity model (i.e., 3D FEA)
and consistent beam-type models for aeroelastic simulation. Digital twin models are useful to cost-effectively evaluate the performance of new technologies in the field like novel
downwind rotors and controllable gurney flaps. Finally, the new methodology is demonstrated for an as-built two-bladed downwind prototype rotor resulting in a multi-fidelity
digital twin model which has a 1% match in mass properties, 3.2% in blade frequencies,
and 6% in deflection to the as-built blade. The rotor examined is the SUMR – Demonstrator (SUMR-D), which was installed on the Controls Advanced Research Testbed (CART-2)
wind turbine at the National Wind Technology Center. The digital twin model developed
here was utilized to design controllers to safely operate SUMR-D in field tests, which are
providing additional data for further evaluation and development of the multi-fidelity digital
twin structural model
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
