1,721,514 research outputs found
Unsteady disturbances in a swept wing boundary layer due to plasma forcing
Full text linkThis work investigates the response of a transitional boundary layer to spanwise-invariant dielectric barrier discharge plasma actuator (PA) forcing on a 45 ° swept wing at a chord Reynolds number of 2.17 × 10 6. Two important parameters of the PA operation are scrutinized, namely, the forcing frequency and the streamwise location of forcing. An array of passive discrete roughness elements is installed near the leading edge to promote and condition a set of critical stationary crossflow (CF) instability modes. Numerical solutions of the boundary layer equations and linear stability theory are used in combination with the experimental pressure distribution to provide predictions of critical stationary and traveling CF instabilities. The laminar-turbulent transition front is visualized and quantified by means of infrared thermography. Measurements of velocity fields are performed using hotwire anemometry scans at specific chordwise locations. The results demonstrate the inherent introduction of unsteady velocity disturbances by the plasma forcing. It is shown that, depending on actuator frequency and location, these disturbances can evolve into typical CF instabilities. Positive traveling low-frequency type III modes are generally amplified by PA in all tested cases, while the occurrence of negative traveling high-frequency type I secondary modes is favored when PA is operating at high frequency and at relatively downstream locations, with respect to the leading edge. </p
Does liquidity information matter? A view from fixed income dealers
No full textBoth the inventory theory and the asymmetric information theory assume that dealers possess no information advantage compared to other market participants. However, dealers can observe market liquidity from more aspects than any other participants do, and therefore have better information on market liquidity. Does this liquidity information advantage lead to profit? Using a detailed 3-month transaction data from London Stock Exchange, I examined dealer’s information advantage by analyzing dealers’ trading revenue and the components. The results strongly support that liquidity information does matter to dealers
Crossflow instabilities under plasma actuation: Design, commissioning and preliminary results of a new experimental facility
No full textPlasma-based flow control poses a simple and robust technique for transition delay on swept wings. However, a clear understanding of how plasma actuators affect crossflow instabilities is necessary to develop and mature crossflow control based on plasma actuators. In this paper, the design of a new swept wing model optimised for the study of crossflow receptivity and stability under plasma actuator is described in detail. First, a 2D wing shape is designed, to match the nearing leading edge pressure distribution of a reference high-Reynolds number swept wing model (M3J) which has been used extensively in past investigations. The aerodynamic performance of this new shape is investigated using CFD simulations and the results show a good agreement for the pressure coefficient. In manufacturing design, the wing model features provisions to accept plasma actuators, such as non-conductive material as well as an appropriately designed recess for the actuator assembly. The new model in conjunction with a recently refurbished low turbulence windtunnel facility are characterized in a preliminary experiment. The uniformity and quality of the flow is identified using pressure measurements and the results confirm the new model achieved near-invariant spanwise conditions until 40% of the chord. Infrared thermography is used to capture the surface footprint of stationary primary crossflow vortices. Clear formations of stationary vortices created by discrete roughness are captured and no visible transition is observed. Finally, the effects of plasma actuation on crossflow instabilities are inspected by Infrared Thermography and PIV scanning. The results validate the prediction of Linear Stability Theory with respect to the most unstable stationary mode and traveling mode. The appearance of secondary crossflow instabilities is observed at relatively upstream chord locations even without transition detected. The outcome positively confirms the ability of this new model to reproduce receptivity and initial growth of crossflow instabilities of the reference model (M3J) under plasma actuation.Virtual/online event due to COVID-19AerodynamicsWind Energ
Time-varying beta and the asian financial crisis: evidence from the asian industrial sectors.
No full textGoing 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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