1,720,961 research outputs found
Acoustical optimization of a roller blind box
No full textRoller blind boxes, also know as blind boxes or roller casings, are quite popular elements in Italian buildings, as total enclosures for the roller blinds. The boxes quite frequently show a removable face, for reasons of access, and in some cases air ventilation vents. The peculiar acoustical behaviour of the boxes is due to the presence of apertures and leaks and for this reason manufacturers are focusing their attention on the improvement of their sound insulation performances. An experimental investigation was carried out by sound intensity measurements in a reverberation room to determine the sound insulation of various steel blind boxes. The initial design showed not satisfying sound insulation ratings. A light, sound absorbing inner lining of the casing demonstrated to be even more efficient than a traditional, denser sound insulating treatment, particularly when noticeable leaks were present at the access faces of the box. Suitable absorbing materials such as mineralized wood fibres and polymeric foams were chosen and compared achieving up to 5 dB of improvement for Rw. Analyses of the frequency behaviour of the sound insulation and of the intensity maps were performed. The influence of leaks was finally estimated, demonstrating that a proper sealing could lead up to a further 10 dB performance rise
Properties of transparent sound-absorbing panels for use in noise barriers
No full textSound absorption and optical transparency are among the most useful properties of noise barriers.
While the latter is required to reduce visual impact and for aesthetical reasons, the former is required
whenever conditions of multiple reflections and presence of close, high receivers occur. The
technical feasibility of a transparent, sound-absorbing panel for outdoor antinoise devices is
investigated in this paper. An analysis of acoustical performance of multiple perforated plates is
performed employing an existing theory for microperforated absorbers under normal incidence and
diffused sound field. An optimization of the geometrical parameters is carried out on the basis of the
European classification criteria of noise barriers for roadways. An optimized three-layer
configuration can achieve sound-absorption properties similar to nontransparent products with only
a limited loss of visual transparency and appropriate mechanical strength. Experimental data
obtained with an impedance tube on small test samples made of transparent polycarbonate and in a
reverberation room on full-scale prototypes are reported, showing a rather good agreement with the
theoretical predictions. The optical performance of a multilayered configuration is evaluated also
Acoustic intrinsic performances of novel sustainable noise barriers: laboratory and in situ measurement techniques
No full textLaboratory and in situ methods have been used for measuring intrinsic performances of noise barriers, as prescribed by the European standard series EN 1793. The use of in situ techniques is promising, but their accuracy has to be duly verified, even in comparison with well-known standardized procedures. Sound insulation and reflection properties have been measured through a MLS-based technique in an outdoor test field. The paper analyzes the procedures that mainly influence the accuracy: correction for wave spreading and time windowing. Repeatability of the in situ method for sound insulation is satisfying and its results look consistent with simple prediction models. Nevertheless, in situ data can be overestimated at low frequencies, due to the overlapping of the transmitted and diffracted components. The method has to be carefully employed when the sample shows apertures as slits or holes, unless a different kind of sound propagation is assumed at the receiving side. A good agreement was found between in situ and laboratory sound insulation data, while in situ and laboratory absorption properties show poorer correlation
Prestazioni acustiche intrinseche di barriere di tipo innovativo: metodi di valutazione in laboratorio e in campo libero simulato
No full textNell’ambito di un Accordo di Programma tra CIRIAF e Ministero dell’Ambiente, inerente la sperimentazione di sistemi innovativi integrati di abbattimento del rumore e sfruttamento delle fonti rinnovabili di energia, si sono misurate le proprietà acustiche intrinseche di campioni di barriere antirumore ed elementi antidiffrazione; le misure sono state eseguite sia nelle camere riverberanti del Laboratorio di Acustica dell’Università di Perugia che in campo libero simulato, in un sito appositamente predisposto. Si sono valutate, ai sensi degli standard EN 1793, le seguenti grandezze: S, R, RI, SI e DI.
Il lavoro riporta i risultati ottenuti e alcune osservazioni sulle metodologie di misura in situ. In particolare, le misure in situ di Reflection Index RI presentano una maggiore difficoltà di caratterizzazione per i campioni aventi geometria complessa e superfici composite. In tali casi, solo un maggior numero di posizioni di misura sembra adeguato al fine di ottenere risultati rappresentativi. La ripetibilità dei metodi in situ appare soddisfacente per SI, inferiore per RI. I valori di Sound Insulation Index SI appaiono congruenti con quelli forniti da modelli teorici di fonoisolamento; si osserva una discreta correlazione tra grandezze omologhe misurate in laboratorio e in situ. Sono infine riportati i risultati di misure preliminari per la caratterizzazione di un elemento antidiffrazione
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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