1,720,962 research outputs found
Nonlinear dynamic analysis of gas turbine combustor leaf seal
Full text linkThe leaf seals are one of the typical sealing systems in gas turbine and jet engines. In Baker Hughes LT family gas turbines, they are used to create sealing between the combustion chamber and the first stage nozzle. The leaf seals are thin metallic plates and subjected to dynamic loads and high temperatures. They have curved contacts, and depending on the inclination, they can experience partial contact. Furthermore, when excited by dynamic loads, the leaf seal can be subject to intermittent contact, possibly triggering wear out or vibratory phenomena. Due to its flexibility and its partial seating, it exhibits a complex nonlinear dynamic behaviour, strongly variable with the operating conditions. This study presents a numerical investigation using coupled static/dynamic harmonic balance method (HBM) frequency-based solution technique. The reported solutions include nonlinear forced response and contact studies for various operating and kinematic conditions along with brief insights
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
Experimental Investigation of the Simultaneous Firing of Two FEEP Thrusters
No full textThe first ever experimental characterization of a two-emitter 150 μN FEEP thruster assembly is described in this paper. The envisaged arrangement of FEEP thrusters in all of the near-term missions is in “clusters” of two or three ion emitters. Due to constraints on thrust vector orientation and available room, very close packing of emitters is foreseen. While several test results are available on the behaviour and performance of single ion sources and prototype thruster units, the design and testing issues arising from the combined operation of a multi-thruster assembly were never thoroughly addressed, nor was the assessment of potential interaction effects that may impair the thruster performance.
A two-emitters test was therefore recently carried out to assess possible interactions between incident ion beams from adjacent thrusters. A pair of identical, 5-mm linear slit FEEP emitters, was integrated in Alta’s IV1 vacuum facility. The two emitters’ slits were mounted parallel to each other at a distance of 10 cm. The ion beam density was evaluated using a set of single-filament Langmuir probes immersed in the thrusters’ plume. It was observed that the beam profile resulting from combined operation is essentially coincident with the sum of the individual profiles, as indicated by a numerical plume simulation of the test configuration run using Alta’s proprietary 3-D code. The experiment shows that there is no significant interaction between the overlapping plumes, thus demonstrating the feasibility of closely-packed clusters of FEEP emitters
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
- …
