1,727,545 research outputs found
Component Analysis of TBCC Propulsion for a Mach 4.5 Supersonic Cruise Airliner
No full textThis paper describes the status of the study on component analysis for the different Variable TBCC
cycle configurations. The paper investigates different Variable Cycle TBCC configurations and compares
them with an advanced turbojet for the generic configuration of a Mach 4.5 supersonic passenger
airliner.
One VCE engine variant and the turbojet are preliminarily designed and their mass including airintake
and nozzle is estimated. The air-intake has been preliminarily sized and pressure recovery and
mass flow in design and off-design conditions is estimated. The intake's dimension and airflow data
have been subsequently delivered for further analyses. Engine weight analysis is also conducted both
for existing engines and proposed LAPCAT turbo engines
Concentration probe measurements in a Mach 4 nonreacting hydrogen jet
No full textA new probe technique is introduced for the measurement of concentration in binary gas flows. The new technique is demonstrated through application of the probe in a Mach 4 nonreacting jet of hydrogen injected into a nominally quiescent air environment. Previous concentration probe devices have mostly used hot wires or hot films within an aspirating probe tip. However, the new technique relies on Pitot pressure and stagnation point transient thin film heat flux probe measurements. The transient thin film heat flux probes are operated at a number of different temperatures and thereby provide stagnation temperature and heat transfer coefficient measurements with an uncertainty of around ±5K and ±4% respectively. When the heat transfer coefficient measurements are combined with the Pitot pressure measurements, it is demonstrated that the concentration of hydrogen within the mixing jet can be deduced. The estimated uncertainty of the reported concentration measurements is approximately ±5% on a mass fraction basis
Transient temperature probe measurements in a Mach 4 nitrogen jet
No full textStagnation temperature measurements have been obtained in a Mach 4 free jet of nitrogen using a technique based on transient thin film heat flux probe measurements. The uncertainty in the stagnation temperature measurements depends on the probe location within the jet but is typically around ±5 K at the centre of the jet. The thin film heat flux probe technique also provides a measurement of the heat transfer coefficient of the thin film probes with an uncertainty of around ±4% at the centre of the jet. Pitot pressure measurements were also obtained within the jet. Analysis of the heat transfer coefficient results yields the Mach number and velocity profiles which are compared with results from the pitot probe measurements. Jet velocities identified using the thin film probe and the pitot probe techniques produce results with uncertainties of less than ±2% at the centre of the jet. Measurements of RMS stagnation temperature fluctuations indicate values of around 3 K at the centre of the jet to more than 10 K in the shear layer
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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