1,720,964 research outputs found
Application of hyperspectral imaging for the study of pigments in paintings
No full textHyperSpectral Imaging (HSI) can be considered as the evolution of classical spectroscopy, where “only” punctual analyses are carried out. The obtained 2D information (i.e. one spectrum for each pixel of the target image) can be thus used to characterize, map and monitor the materials constituting cultural heritage. Such non-invasive diagnostic technique can be applied by mobile devices directly in situ. The adoption of HSI techniques allows the acquisition of the spectra without a direct physical contact and/or sampling of material objects under investigations. This research aims at the development of a methodology to classify different pigments through HSI. Reference samples were prepared using six pigments (i.e. red ocher, yellow ocher, chrome yellow, mineral blue, cobalt green, and malachite) mixed with egg tempera. The obtained products were then applied on two different supports (i.e. canvas and wood) in order to obtain different combinations among pigment/support. The spectral changes of each pigment with different supports were evaluated with reference to the spectrum of the original pigment in powder. The samples were acquired in the SWIR (1000-2500 nm) range by HSI. Results showed as it is possible to identify a pigment on the surface of painting using a reference database of pigments in powder and also to obtain information on the binder and the support from the spectral signature
Hyperspectral imaging-based approach for the in-situ characterization of ancient Roman wall paintings.
No full textA diagnostic study was recently carried out on fragments of wall paintings belonging to the decorations of an ancient Roman residential villa of the Ager Gabinus, in the locality Pratolungo (Rome, Italy). The study was organized as follows: a first phase, in which small splinters of these painted specimens were embedded in resin and characterized by optical microscopy on polished cross-sections and thin sections; a second phase, in which the specimens were analyzed by Raman spectroscopy and hyperspectral imaging (HSI). The aim of the present work is to verify the potential use in situ of HSI technique in the range of SWIR (1000 nm - 2500 nm), presenting many advantages to punctual techniques of analysis as, i.e., Raman spectroscopy. In particular, the results obtainable by classical methods, such as optical microscopy, were compared to information resulting from non-destructive investigation techniques, as precisely the HSI. The acquired hyperspectral images were processed applying chemometric methods which allow not only the exploration of the data but also their recognition and their distribution over the whole specimen, without sampling. In fact, the use of HSI as a diagnostic tool in the field of cultural heritage is of great interest and it presents high potentialities, being this analysis non-destructive, non-invasive and almost portable. Furthermore, the possibility to couple hyperspectral data with chemometric techniques allows getting qualitative and/or quantitative information on the nature and physical-chemical characteristics of the investigated materials. Combining the results obtained on the samples by HSI and the results by Raman spectroscopy, it is possible to obtain information comparable with optical microscopy, allowing the identification of pigments and the constituent materials, confirming the potential use of this technique as a portable one
HYPERSPECTRAL IMAGING FOR EARLY DETECTION OF ALTERATION PHENOMENA IN PAINT LAYERS
No full textHyperspectral imaging (HSI) is a technique that can be applied in various fields of science and recent developments in hardware and software allow to increase its power and to decrease the costs of the analysis based on reflectance spectrum in the visible and near infrared wavelength range. This monitoring technique is particularly suitable for pigment classification and for the monitoring of pictorial materials without the need of sampling [1]. In order to study the alteration of paint layers by solar aging , samples were prepared with different pigments, binders and supports and artificially aged using solar box. The results obtained for a sample composed by yellow ocher mixed with Arabic gum and applied to a canvas support are presented in this work [2].The sample was acquired in the VIS-NIR (400-1000 nm) and SWIR (1000-2500 nm) ranges by HSI after196 hours and 400 hours. Besides, for comparison, color measurements were carried out before and after aging the sample to monitor color changes during the two steps. The goal of this study is to verify the possibility to detect alteration phenomena before they become macroscopically visible by HSI in the VIS-NIR and SWIR ranges.Hyperspectral imaging (HSI) is a technique that can be applied in various fields of science and recent developments in hardware and software allow to increase its power and to decrease the costs of the analysis based on reflectance spectrum in the visible and near infrared wavelength range. This monitoring technique is particularly suitable for pigment classification and for the monitoring of pictorial materials without the need of sampling [1]. In order to study the alteration of paint layers by solar aging , samples were prepared with different pigments, binders and supports and artificially aged using solar box. The results obtained for a sample composed by yellow ocher mixed with Arabic gum and applied to a canvas support are presented in this work [2].The sample was acquired in the VIS-NIR (400-1000 nm) and SWIR (1000-2500 nm) ranges by HSI after196 hours and 400 hours. Besides, for comparison, color measurements were carried out before and after aging the sample to monitor colo
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
Microstructural consolidation of historic surfaces by di-ammonium hydrogen phosphate (DAP). First in situ applications - results' evaluation
No full textDispelling 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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