1,720,971 research outputs found
From HPC to HPSS: The use of superplasticizers for the improvement of S/S technology
No full textThis paper presents an S/S treatment which is based on the principles of High Performance Concrete (HPC). By using superplasticizers and hydrophobic additives, the proposed process allows the transformation of contaminated soils and sediments into low water to cement ratio (W/C) granular materials. These grains are characterized by lower porosity,
lower leaching rate of inorganic contaminants and lower water absorption as well as higher mechanical properties and improved durability compared to solidified products obtained without additives. Moreover, the mixing water may be reduced more than 25%. The results of X-ray microtomography and mercury intrusion porosimetry measurements carried out on samples prepared with and without additives are illustrated here. Volatile and/or semi-volatile organic pollutants, if present, can be removed from the granular material by a steam distillation step, at relatively low temperature (max 250°C) and under vacuum (P < 0.1 bar) in excellent yield. The resulting aggregates are suitable for the re-utilization as backfilling, concrete aggregates or may be employed for covering landfills and in other civil engineering projects
The pigments of the frigidarium in the Sarno Baths, Pompeii: Identification, stratigraphy and weathering
No full textIn the present research is used a multi-analytical approach to study the wall paintings from the Sarno Baths, located in the southern part of Pompeii. In particular the investigation is focused on the frescos of the frigidarium, though a few samples from other rooms were also analysed. Twenty wallpaintings fragments were analysed by laser scanning confocal microscopy (LSCM), optical microscopy (OM), micro-Raman, scanning electron microscope with energy dispersive spectrometry (SEM-EDS), portable X-ray fluorescence spectrometry (p-XRF) and X-ray powder diffraction (XRPD). The XRPD data were used for the mineralogical semi-quantitative phase analyses (SQPA) and the estimation of the hematite crystals size. The obtained data allow the identification of the pigments and the techniques used, and address new question such as whether talc and aragonite were used routinely in the formulation of pigments. The chemical composition of red and yellow pigments is also discussed and compared with data available from the recent literature. The wall paintings are badly preserved and weathering products occur on the pictorial surface. Eight samples of efflorescence salts and patinas were analysed by XRPD: all the samples are composed mainly by alkali sulphates. The systematic difference between the salts present on the northern and the western walls is likely related to the materials inserted during the 19th century restauration
Mineralogical interpretation of multispectral images: The case study of the pigments in the frigidarium of the Sarno Baths, Pompeii
No full textWall paintings are invaluable archives of pigments, techniques, and artistic expressions of past civilizations, and Pompeii is an excellent example of such archives for Roman art from mid-first century AD. Assessing wall paintings’ state of preservation requires characterizing the pigments on a large scale and documenting alteration processes which will influence conservation interventions. The problem is that large scale characterization requires delicate high resolution chemical and spectral instrumentation that is limited to the museum environment. Here, we present a new methodology for non-invasive characterization of wall paintings on-site, based on analyzing stacked photos as multi-spectral data. The photos were imaged using a portable modified digital camera that registers the ultraviolet, visible, and infrared spectral regions through external band-pass filters. Combined with portable X-ray fluorescence and fiber optic reflectance spectrometers, predetermined mineral-specific band ratios were developed on fragments found below the wall paintings, and large scale mineralogical maps were constructed. The mineralogical maps show the distribution of hematite, goethite and Egyptian blue in a wall painting of the frigidarium of the Sarno Baths complex of Pompeii, documenting iconographic figurines of plants, pygmy people, and animals from a degraded depiction of a river scene. The applications are in conservation and archaeological sciences, showing the ancient technology of the wall paintings using non-invasive measurements, and developing restoration strategies that are matching the ancient materials
Towards three-dimensional quantitative reconstruction of cement microstructure by X-ray diffraction microtomography
No full textQuantitative characterization of the microstructure of cement-based materials is of fundamental importance for assessing the performance and durability of the final products. However, accessing the three-dimensional microstructural information of hydrating cement pastes without introducing any perturbation is not trivial. Recently, a novel non-invasive method based on X-ray diffraction computed microtomography (XRD-CT) has been applied to cement-based materials, with the aim of describing the three-dimensional spatial distribution of selected phases during the hydration of the cement paste. This paper illustrates a method based on XRD-CT, combined with Rietveld-based quantitative phase analysis and image processing, which provides quantitative information relative to the distribution of the various phases present in the studied samples. In particular, it is shown how this method allows the estimation of the local volume fraction of the phase ettringite within a hydrating cement paste, and construction of a three-dimensional distribution map. Application of this method to the various constituents of a cementitious material, or, more generally, of a composite polycrystalline material, may provide a non-invasive tool for three-dimensional microstructural quantitative characterization
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Combining multispectral images with X-ray fluorescence to quantify the distribution of pigments in the frigidarium of the Sarno Baths, Pompeii
No full textMultispectral imaging is used to identify and semi-quantify the distribution of pigments in wall paintings based on mineral-specific band ratios. The western wall in the frigidarium of the Sarno baths in Pompeii was imaged using VIS-IR band-pass filters, stacked as multispectral data, and different pigments were measured using portable X-ray fluorescence (pXRF) and fiber optic reflected spectroscopy (FORS) to determine their chemical composition and spectral signature. Cuprorivaite and hematite were found to be the main minerals in blue and red pigments, with higher amounts of copper and iron respectively. Proportional relations were found between cuprorivaite specific band ratios from multispectral and FORS data and the intensity of copper in pXRF spectra, allowing to map the mineral content on a large scale and determine their relative concentrations. These results were confirmed by X-ray powder diffraction (XRD) and thin section analysis on painted fragments that were detached from the wall paintings and found below. This contribute indicates that on-site portable instrumentation could identify specific pigments and determine their 2D distributions based on non-invasive diagnostics of chemical composition and spectral reflectance in wall paintings
Variations on the Author
Get PDF“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
Get PDFWe 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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