1,721,023 research outputs found
Optical fibre sensors coated with carbon nanotubes, tin dioxide, and nanoporous polymers for cryogenic detection of hydrogen
No full textRecently, preliminary measurements carried out by using optical fibre sensors coated with Langmuir–Blodgett (LB) multilayers of closed-end (CeSWCNTs) and opened-end single-walled carbon nanotubes (OeSWCNTs) demonstrated their capability of detecting hydrogen at cryogenic temperatures. In this paper, a comparative study between different sensitive materials for the cryogenic H2 detection is presented. To achieve this aim, tin dioxide (SnO2) particle layers and syndiotactic polystyrene (sPS) thin films have also been used as sensitive fibre coatings and their performances have been compared to the ones obtained with the SWCNTs-based overlays. Their integration with optical fibres has been carried out by using the electrostatic spray pyrolysis (ESP) and the dip-coating techniques, which allow thin films at micro and nano scale to be obtained and the sensitive coatings features to be tailored by properly changing the deposition parameters. A time division multiplexing (TDM) approach has been employed in order to simultaneously perform the interrogation of all the fabricated sensors. The results obtained from the experimental measurements demonstrate the capability of the proposed configuration to sense very low concentrations of hydrogen (< 4 per cent) at the very low temperatures of 113 K. CeSWCNTs-based sensors, especially, have demonstrated to be the most interesting materials to be used for the detection of cryogenic hydrogen, with good sensitivity, fast response times, and good recovery features. © 2007, Institution of Mechanical Engineers. All rights reserved
Ultrasonic analysis and lock-in thermography for debonding evaluation of composite adhesive joints
No full textGlass-fiber reinforced thermosetting plastic adhesive joints were characterized through ultrasonic imaging and lock-in thermographic analysis for assessing the adhesion quality before being subjected to static tensile mechanical tests and to accelerated aging cycles. The mapping of each sample has been obtained. Visual testing were performed on all specimens after the mechanical tests in order to obtain a comparison with ultrasonic and lock-in thermography technique. A quantitative analysis has been carried out to evaluate the ability of lock-in thermography in investigating inadequate bonding and obtaining the validation of the technique by the consistency of the results with the well-established ultrasonic testing. © 2015 Published by Elsevier Ltd
Infrared thermography for the investigation of dynamic thermal behaviour of opaque building elements: Comparison between empty and filled with hemp fibres prototype walls
No full textThe analysis of the thermal dynamic behaviour of buildings is an important tool for reducing inefficiencies and then wasted energy. In this field, European Standards specify the procedures to obtain information about the thermal behaviour of building in terms of decrement factor and time lag. However, these procedures are based on a theoretical approach that does not take into account the real factors involved in the heat exchange phenomena such as the correct knowledge of thermo-physical parameters and the presence of non-homogeneous materials or defects in the investigated walls. In this work, we propose an innovative experimental procedure based on the application of stimulated thermography with the aim of investigate the thermal dynamic behaviour of walls. In particular, two prototype walls were compared: an empty wall and one made with an insulating filler of vegetable nature (hemp fibre). The results were then compared with those obtained with a numerical simulation and with the Standard procedure EN ISO 13786:2007, highlighting the differences between the three approaches. © 2017 Elsevier B.V
Set-up of an experimental procedure for the measurement of thermal transmittances via infrared thermography on lab-made prototype walls
No full textIn this paper an experimental set-up measurement for the evaluation of the thermal transmittance of opaque elements has been developed. It is based on infrared thermography and it is suggested as alternative to the standard approach set by the ISO 9869:1994 based on heat flow meter (HFM) measurement which is widely accepted by scientific audience. The proposed method has been designed in order to overcome the following restrictions of HFM method: long measuring times (about 72 h), weather conditions as constant as possible and at least a difference of 10–15 °C between the temperatures of internal and external sides of walls. In this work, the alternative method proposed is widely described and applied on lab-made prototype walls: the results are encouraging, showing discrepancies with theoretical U-values, determined in accordance with international standard ISO 6946:2007, in the range −3.5 to 2.9%. The thermal transmittances were also calculated with a commercial software based on finite element analysis; the obtained results were in good agreement with the experimental ones. Moreover, the simulations pointed out that the values obtained on lab-made prototype walls are similar to those associated with partition walls which separate rooms with different environmental conditions. © 2016 Elsevier B.V
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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