1,720,967 research outputs found
Thickness determination of the gilding on brass materials by XRF technique
No full textThe gold coating layer of the gold-plated brass objects was estimated using calibration curves obtained with a handheld X-ray fluorescence spectrometer (XRF). Calibration curves were obtained using reference materials (Au and brass) and intensity ratios of the X-ray fluorescence peaks generated in both the gold coating and the brass substrate. In addition, a calibration was also performed with the PLS (Partial Least Squares) multivariate analysis method. Good agreement was obtained by comparing the results of the different methods. The calibrations were successfully applied to gold-plated brass jewels and samples
Coating thickness of plated objects using XRF technique concentrations
No full textThe coating layer thickness of the double-layer objects was estimated using the concentration value of an element of the covering layer or of the substrate after obtaining suitable calibration curves using reference materials. The x-ray fluorescence technique was used with a handheld instrument to determine the concentration of elements. Various experimental configurations were built using gold- and silver-plated materials. The concentration calibrations curve as a function of coating layer thickness were successfully applied to gold-plated brass and copper jewelry, gold-plated samples and an ancient silver coin. The results obtained using the concentrations are in good agreement with those of other more elaborate methods
Gli Incusi della Collezione Numismatica del Museo Campano: presentazione preliminare
No full textGli esemplari inediti delle serie incuse di Magna Grecia, attestate nella gamma di emissioni tra seconda metà del VI sec. a.C. e prima metà del V sec. a.C., nella collezione del Museo Campano Provinciale di Capua, rappresentano una presenza inconsueta in ambito campano: la questione si innesta sulla genesi e sui processi di formazione della raccolta. Inoltre, i materiali esaminati si segnalano per l’ apporto di nuovi elementi allo studio delle monetazioni di pertinenza. L’analisi condotta mediante ED-XRF ha consentito di puntualizzare la composizione elementale degli esemplare e di escludere, nella maggioranza dei casi, il fenomeno dell’arricchimento in superficie (Vedi anche articolo, pag. 75)
Estimation of Ag coating thickness by different methods using a handheld XRF instrument
No full textPrecious objects are often made from a thin layer of metal (gold or silver) superimposed on another metal or alloy. Non-invasive XRF analysis is widely used on these objects to determine the composition and thickness of the surface layer. Here, silver surface thickness of two-layered metal samples using an ED-XRF handheld spectrometer is estimated by different methods whose results are compared. These methods involved the relationships between the intensities of the characteristic lines of Kα, Kβ, Lα and Lβ of Ag and of elements present in the substrate (Cu, Fe, Pb) and some of their combinations, as well as the PLS regression. Reference layers were used to derive the calibration curves of each methodology. PLS method was the most accurate, but the other methods were also found suitable for the purpose. Applications have been successfully made on an ancient Roman coin and a modern silver-plated object
Gold-coating thickness determination on Ag, Cu, Fe, and Pb using a handheld X-ray instrument
No full textHere, the X-ray fluorescence technique is used to determine the thickness of a coating layer as well as to analyze the surface of objects. Four metals (Ag, Cu, Fe, Pb) were covered with increasing thicknesses of gold. The measurements were performed with a commercial handheld instrument, X-SORT (Spectro). In double layers, the thickness of the covering layer was assessed by (a) the ratio between the most intense fluorescence lines of the covered element, (b) a cross-ratio between two lines of the elements in the two layers, and (c) the ordinary partial least squares (PLS) regression method. In all cases, the curves obtained could be used for the quantitative determination of the thickness. The experimental data followed the theoretical trend even though the values of the attenuation parameters were not always in agreement with the theoretical ones. Comparisons and discussion of the results of the different approaches and also with models in the literature are made. The methods studied were applied to determine the nature of the coating layers of some gilded objects and proved to be suitable for estimating the thickness of gold by providing results that were in good agreement with each other
Ag X-ray fluorescence on different thickness and concentration layers
No full textThis work derives from the requirement to investigate on the silver surface enrichment of objects of historical and artistic interest using the X-ray fluorescence non-destructive technique (XRF). The aim is the thickness estimation through the experimental relationship between K-alpha/K-beta and K-alpha/L-alpha of Ag as a function of the thickness. Measurements on silver sheets of different thicknesses and three concentrations are carried out using a XRF spectrometer with a maximum voltage of 50 kV. The results allow to analyse the plating layer of silver objects also to make other interesting considerations
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
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