1,720,963 research outputs found
Average beamforming in reverberant fields: application on helicopter and airplane cockpits
No full textThe aim of this paper is to present the applicability of the Average Beamforming (ABF) as a helpful technique to map acoustic emission for interior noise in which we can assume that sources exist only on the wall, but not in the internal volume.
In these conditions conventional Beamforming measurements show disturbing pseudo images in the acoustic maps due to internal reflections that are erroneously interpreted by the algorithm: these pseudo sources are in many cases also stronger than the real one.
The proposed procedure consists in carrying out subsequent conventional beamforming measurements from different known locations and combining the relative results statistically: through both the wider “virtual” array obtained and the map of sample standard deviation of single measurement a great improvement both in the resolution and in the map quality is achieved, with a very good accuracy and robustness.
The uncertainty of the proposed strategy is also analyzed
Ultrasonography in follow-up of soft tissue augmentation of the face with synthetic materials: a pilot study
No full textPurpose: To assess ultrasonography in the evaluation of reactions after soft tissue augmentation of the face with synthetic materials. Material and Methods: Six female patients (mean age 39+/-8 years) treated for facial tissue augmentation noticed unpleasant or painful effects in the intervention site after a mean of 24 months were evaluated with ultrasonography. Two patients had been treated with injections of microparticles, two with Gore-Tex implants, and two had been injected with liquid silicone. Fifteen female patients (age 27-55 years, mean 41+/-14 years) who had received the same treatment 14-48 months before without any complications were also evaluated and used as controls. Biopsy was performed in all patients, while four underwent re-intervention. Results: In all patients with Gore-Tex implants, a thick, homogeneous hypoechoic halo was seen surrounding the implants. Small hypoechoic nodules were noticed in the patients who had been treated with microparticles and with liquid silicone. In two cases treated with liquid silicone the subcutaneous tissue was invaded by an irregular area of marked inhomogeneity. Conclusion: Sonography must be considered the method of choice for producing instrumental evidence of foreign body reactions after soft tissue augmentation of the face with synthetic materials
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
Sensitivity Investigation of Aircraft Engine Noise to Operational Parameters
No full textAircraft noise is associated to two main groups of acoustic sources: those which produce airframe noise and the other ones which produce engine noise. Airframe noise can be numerically simulated once defined aircraft geometry and its intensity depends on aerodynamic configuration of aircraft. Engine noise is due to contribution of several sources according to engine’s type: in several cases these sources are not all well theoretically defined for the difficulty of performing experimental campaigns, and this does not allow a general validation of numerical simulation tools. Sound pressure levels associated to fans, compressors, jets, propellers can be numerically evaluated through commercial codes that require a big amount of input parameters concerning the geometric description of the different engine parts and the engine operational conditions that are well known from a physical standpoint but can be difficult to manage in a preliminary assessment of the noise emission due to a typical civil aircraft engine. The numerical definition of all these parameters requires a deep knowledge of the mechanism of the engine part subject of investigation and, often, also having a clear view of how this part works, the values of operational parameters, during the aircraft engine working, can be not available. For this reason an investigation of the sensitivity of the overall sound pressure levels associated to the different noise sources to the engine operational parameters can be useful to understand how much the noise can change if the working conditions change and to rank the variables from an acoustic standpoint fixing the most influential parameters. The present paper focuses on some of the acoustic sources acting on a typical civil aircraft engine and is based on the use of commercial codes able to simulate numerically the sound pressure levels associated to these sources
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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