1,720,991 research outputs found
Experiments on aircraft flight parameter detection by on-skin sensors
No full textAir speed and flight attitude angles are fundamental parameters for manual of automatic control of flying bodies. Conventional measuremen methods rely on probes (e.g. Pitot tubes or vanes) having a one-to-one correspondence with the physical quantities of interest and requiring specific placements. Here, a novel measurement approach is proposed, relying on indirect measurement and on a plurality of pressure readings made by thin capacitive sensors directly placed on the aircraft skin. A redundant number of probes relaxes the accuracy requirements posed on the individual units and helps achieving fault detection or fault tolerance. A strategy for efficiently processing/combining sensor data is herein presented together with an error propagation analysis, and experimental data
Progress in Turbulence VII - Proceedings of the iTi Conference in Turbulence 2016
No full textThis volume collects the edited and reviewed contribution presented in the 7th iTi Conference in Bertinoro, covering fundamental and applied aspects in turbulence. In the spirit of the iTi conference, the volume is produced after the conference so that the authors had the opportunity to incorporate comments and discussions raised during the meeting.
In the present book, the contributions have been structured according to the topics:
I Theory
II Wall bounded flows
III Pipe flow
IV Modelling
V Experiments
VII Miscellaneous topic
An Experimental Study on a Wind Turbine Rotor Affected by Pitch Imbalance
Full text linkAn experimental and numerical investigation about the pitch imbalance effect on a wind turbine model is performed. The characterization of the power losses and loads generated on a small-scale model and the validation of an analytical framework for the performance of unbalanced rotors are proposed. Starting from the optimal collective pitch assessment (performed to identify the condition with the maximum power coefficient), the pitch of just one blade was systematically changed: it is seen that the presence of a pitch misalignment is associated with a degradation of the turbine performance, visible both from experiments and from Blade Element Momentum (BEM) calculations (modified to account for the load asymmetry). Up to 30% power losses and a 15% thrust increase are achievable when an imbalanced rotor operates at tip speed ratios around five, clearly highlighting the importance of avoiding this phenomenon when dealing with industrial applications. The numerical model predicts this result within 5% accuracy. Additional numerical simulations showed that, away from the optimal collective pitch, the blade imbalance can provide a power increase or a power decrease with respect to the balanced case, suggesting how an operator can maximise the production of an unbalanced rotor. An analysis of the axial and lateral forces showed a sensitivity of the loads’ standard deviation when imbalance is present. An increase of the lateral loads was observed in all unbalanced cases
The attached reverse and detached forward cascades in wall-turbulent flows
No full textThe present work describes the multidimensional behaviour of wall-bounded turbulence in the space of cross-scales (spanwise and wall-normal) and distances from the wall. This approach allows us to understand the cascade mechanisms by which scale-energy is transmitted scale-by-scale away from the wall, through the overlap layer, and into the bulk flow. Two distinct cascades are identified involving the attached and detached scales of motion, respectively. From the near-wall region, scale-energy is transferred towards the bulk, flowing through the attached scales of motion, while among the detached scales it converges towards small scales, ascending again to the channel centre. It is then argued that the attached scales of wall-bounded turbulence are involved in a reverse cascade process that starts from the wall and ends in the bulk flow. On the other hand, the detached scales belong to a direct forward cascade process towards dissipation. Hence, at a given distance from the wall the attached motion is fed by smaller attached scales located closer to the wall. In turn this attached motion is responsible for creating the scale-energy that sustains larger attached scales farther from the wall and smaller detached scales that are responsible for connecting the scale-energy at large scales to the dissipation at small scales through a forward cascade. © Published under licence by IOP Publishing Ltd
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
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