1,720,986 research outputs found
STUDI PER LA MODELLIZZAZIONE DELLA RIFLETTANZA SPETTRALE NEGLI STRATI PITTORICI
Full text linkNowadays a lot of physical techniques are available in order to have information about an historical painting. They are able to know which chemical elements are present in the paint layer, or they are also able to show the pattern under the colored layer, but there is not a non-destructive technique able to study the artist technique of painting or the historical pigments used in order to obtain the particular nuance we can observe.
In this thesis we study an evolution of the VIS-NIR-spectroscopic technique with these goals. In particular we start from a preliminary historical study of the artist’s pigments available for paintings and, starting from the colorimetric technique till the spectrophotometetric technique we create a representative pigments Database and we study a new method for pigment grindings identification, pigment’s mixture recognition and pigments layer technique studies.
The international method for color measurements provides the use of colorimeter but the sizes of these instruments don’t allow to perform measurements in any cases. Applications in the field of cultural heritage like as pigment characterizations on statues or ceramic and sometimes paintings don’t allow the use of integrating sphere. So we study the applicability of optical fiber for the realization of optical fiber remote probes. The use of optical fibre is consolidated for spectroscopy measurements (in particular for UV-VIS-NIR spectroscopy), but it may introduce an error in the detection of the spectra and, in consequence, a further error in the definition of the color of the sample analyzed. The first goal of this work was therefore the evaluation of compatibility of CIE colorimetric results obtained using Fiber Optic Reflectance Spectroscopy (FORS) and those values obtained with a standard colorimeter and then we extend the use of remote probe in NIR range for the measure of the pigments reflectance spectra.
After the test of the remote probe setup we have studied spectra obtained for well-defined mixtures of the most important artist’s pigments with the barium sulphate white pigment, the same used like standard sample for color measurements. These mixture simulate the different desaturation degree of the main color like in the earlier paintings techniques before Renaissance age. In order to have the best numerical characterization we fit the main behavior of the spectra using two analytical models: the Gaussian function (with 4 free parameters) and the sigmoidal function (with 4 free parameters): the comparison of their parameters allow to define the change of the spectra for different concentration of each colored pigment in the white one when thy were mixed in oil or without oil (as in oil renaissance paint technique and in the tipical affresco Middleage paint technique). Determination of weight mixture Pigment to white were: pigment pure, 1:1, 1:2, 1:5, 1:10, 1:20, 1:50. The pigments analyzed with sigmoidal fit were: Cadmium Red , Lacca rossa (Red Laquel), Chromium Orange, Cadmium Yellow, Naple Yellow (with Lead), Green Chromium oxide, Cobalt Blue, Cobalt Violet and Ultramarine Green. Pigments studied using Gaussian fit were: Green Chromium oxide, Cobalt Violet, Ultramarine Green, Verderame (Copper Green), Azurite, Ultramarine blue (artificial), Lapislazuli, Green earth, Malachite Green, Zinc Yellow and Cinabrum.
The next step is the research of a model able to study mixtures of two different colored pigments. The best historical model able to describe the interaction light-pigment was the Kubelka-Munk theory. In this model the Absorbtion (K) and Scattering (S) coefficients are needed. Here we study a method to obtain this coefficient from the reflectance spectra of the pigments and the spectra of their mixtures with barium sulphate and we use the same method in order to obtain the spectra of a mixture of two different colored pigment in an oil-paint layer.
The change of the color due to the presence of the oil is finest and the normal remote probes (optical fiber) setup is not enough to solve the differences, like it is not able for study the effect of the different grindings of the pigment’s powders. We realized an high-definition setup for reflectance measurements without optical fibers and a Fianium white LASER source (collaboration wit AMOLF-Fom institute, Amsterdam) creating also samples with characteristics nearest the Kubelka-Munk request. Using this high sensitivity setup we obtain the reflectance spectra for all the selected pigments and we study the difference of color due to the different grindings of the powder for the azurite and verderame pigments.
We were able also to study color differences of specific paint techniques of ancient painters: the “Italian” Renaissance technique based on the mixtures of color pigments and the “Flamish” technique based on the overlapping of translucent glaze of different color in order to obtain the deep in the paint and the famous sfumato
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
Power Supply Selective Mapping for Accurate Timing Analysis
No full textIn Deep Sub-Micron technologies post-layout timing analysis has become the most critical phase in the verification of large System-on-Chip (SoC) designs with several power-hungry blocks. The impact of coupling capacitances has been adequately analyzed, and modern signal integrity analysis tools can effectively consider the crosstalk-induced delay. However, an increasingly important factor that can introduce a severe performance loss is the power supply noise. As technology advances into the nanometer regime, the operating frequencies increase, and clock gating has emerged as an effective technique to limit the power consumption in block-based designs. As a consequence, the amplitude of the supply voltage fluctuations has reached values where techniques to include the effect of power supply noise into timing analysis based on linear models are no longer adequate, and the non-linear dependence of cell delay from supply voltage must be considered. In this work we present a practical methodology that accurately takes into account the power supply noise effects in static timing analysis, which can be seamlessly included into an industrial sign-off design flow. The experimental results obtained from the timing verification of an industrial SoC design have demonstrated the effectiveness of our approach
A Fast Heuristic for Extending Standard Cell Libraries with Regular Macro Cells
No full textNowadays, design issues related to physical design and scalability are becoming the main bottlenecks of modern tools for technology mapping, limiting the usage of large cells. On the other hand, the generation of regular macro cells, such as compound gates, are becoming interesting from the manufacturing point of view, but they need to be properly integrated into the existing industrial design flows. In this paper, we present an efficient methodology for identifying the cells that can extend an existing standard-cell library. We validated our approach on different benchmarks targeting area minimization and we also analyzed timing, power consumption and routing effects for the final circuit implementation
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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