1,720,971 research outputs found
Aero-Acoustic Studies and Innovative Noise Control with Application to Modern Automotive Gas Exchange System. Kaasaegse automootori gaasivahetuss\ufcsteemide aeroakustilised uuringud ja m\ufcra v\ue4hendamise innovaatilised meetodid
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The effect of high temperatures and grazing flow on the acoustic properties of liners
No full textAcoustic liners are used to reduce fan noise in aircraft engine intakes but also in hot stream parts of the engine. To gain confidence in liner impedance models which are used for design it is important to make experimental tests under realistic conditions as possible. This paper present results of hot stream impedance eduction tests for single degree of freedom Helmholtz resonator liners with different configurations. These types of liners consist of a perforate top sheet backed by a honeycomb cavity to give a locally reacting wall treatment which can be characterized by an acoustic impedance. In the present case a number of different perforate sheet geometries were tested under varying grazing flow and temperature conditions. In some cases the liner test samples also included a thin layer of metallic foam. These types of liners are used for aircraft engine applications but are also of interest for IC-engine applications. It could be argued that the main effect of high temperatures is a change of medium properties such as: density, viscosity and speed of sound. If this is true the high temperature impedance could be predicted by scaling from the result at cold conditions. This is investigated in the paper by comparing measured results from liner impedance models available in the literature.</p
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
Investigation of flow-acoustic interaction in automotive turbocharger
No full textIn IC engine design, the surge condition of a turbocharger is a well-recognized phenomena. As the resulting global fluctuation of mass flux in the intake system is hazardous, the implemented safety margins are large. In order to, reduce such safety margins and employ turbochargers more efficiently, it is of interest to investigate acoustic fields as a possible surge triggering mechanism. Regardless the increasing relevance of this topic today, only few publications exist addressing the acoustics of turbochargers from the perspective of surge prediction and triggering. In the present paper acoustical properties of an automotive turbocharger are experimentally studied at the limit of stable operation as well as under normal operating conditions in the unique CCGEx test rig at KTH. The full two-port data including passive and active parts is determined and utilized to investigate the possible coupling effects between unstable flow and acoustic fields. The local flow instabilities, occurring at the limit of globally stable operation, can interact with the acoustic field and amplify incident sound waves which eventually can lead to an unstable situation and surge. This effect can be studied from the passive two-port data. In addition the active data can be used to find the occurrence of compact correlated sources in the compressor such as rotating stall a pre-cursor of surge.</p
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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