Unsupervised classification of multivariate geostatistical data: Two algorithms

International audienceWith the increasing development of remote sensing platforms and the evolution of sampling facilities in mining and oil industry, spatial datasets are becoming increasingly large, inform a growing number of variables and cover wider and wider areas. Therefore, it is often necessary to split the domain of study to account for radically different behaviors of the natural phenomenon over the domain and to simplify the subsequent modeling step. The definition of these areas can be seen as a problem of unsupervised classification, or clustering, where we try to divide the domain into homogeneous domains with respect to the values taken by the variables in hand. The application of classical clustering methods, designed for independent observations, does not ensure the spatial coherence of the resulting classes. Image segmentation methods, based on e.g. Markov random fields, are not adapted to irregularly sampled data. Other existing approaches, based on mixtures of Gaussian random functions estimated via the expectation-maximization algorithm, are limited to reasonable sample sizes and a small number of variables. In this work, we propose two algorithms based on adaptations of classical algorithms to multivariate geostatistical data. Both algorithms are model free and can handle large volumes of multivariate, irregularly spaced data. The first one proceeds by agglomerative hierarchical clustering. The spatial coherence is ensured by a proximity condition imposed for two clusters to merge. This proximity condition relies on a graph organizing the data in the coordinates space. The hierarchical algorithm can then be seen as a graph-partitioning algorithm. Following this interpretation, a spatial version of the spectral clustering algorithm is also proposed. The performances of both algorithms are assessed on toy examples and a mining dataset

Domaining by clustering multivariate geostatistical data

International audienceDomaining is very often a complex and time-consuming process in mining assessment. Apart from the further delineation of envelopes, a significant number of parameters (lithology, alteration, grades?) are to be combined in order to characterize domains or sub domains. This rapidly leads to a huge combinatory. Hopefully the number of domains should be limited, while ensuring their connectivity as well as the stationarity of the variables within each domain. In order to achieve this goal, different methods for the spatial clustering of multivariate data are explored and compared. A particular emphasis is placed on the ways to modify existing procedures of clustering in non spatial settings to enforce the spatial connectivity of the resulting clusters. K-means, spectral methods and EM-based algorithms are reviewed. The methods are illustrated on mining data

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

[EN] A set of ancient Antoninianus silver coins, dating back between 249 and 274¿A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In the prosperous periods, Romans produced Ag-Cu alloys with relatively high silver content for the manufacture of both the external layers and inner nucleus of coins. This study also revealed that, although surface silvering processes were applied in different periods of crisis under the reign of Antoninii, even during crisis, Romans produced Antoninianus of high quality. Moreover, a first attempt to improve the silvering procedure using Hg-Ag amalgam has been identified.Financial support was provided by Sapienza University of Rome (Ateneo funding, 2014 15) and Spanish projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P, which are supported with Ministerio de Economía, Industria y Competitividad (MINECO) and Fondo Europeo de Desarrollo Regional (ERDF) funds, as well as project CTQ2017-85317-C2-1-P supported with funds from, MINECO, ERDF and Agencia Estatal de Investigación (AEI). PhD grants of the Department of Earth Sciences, Sapienza University of Rome, are gratefully acknowledgedDomenech Carbo, MT.; Di Turo, F.; Montoya, N.; Catalli, F.; Doménech Carbó, A.; De Vito, C. (2018). FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes. Scientific Reports. 8. https://doi.org/10.1038/s41598-018-28990-xS8Doménech-Carbó, A., del Hoyo-Meléndez, J. M., Doménech-Carbó, M. T. & Piquero-Cilla, J. Electrochemical analysis of the first Polish coins using voltammetry of immobilized particles. Microchem. J. 130, 47–55 (2017).Di Turo, F. et al. Archaeometric analysis of Roman bronze coins from the Magna Mater temple using solid-state voltammetry and electrochemical impedance spectroscopy. Anal. Chim. Acta 955, 36–47 (2017).Doménech-Carbó, A., Doménech-Carbó, M. T. & Peiró-Ronda, M. A. Dating Archeological Lead Artifacts from Measurement of the Corrosion Content Using the Voltammetry of Microparticles. Anal. Chem. 83, 5639–5644 (2011).Giumlia-Mair, A. et al. Surface characterisation techniques in the study and conservation of art and archaeological artefacts: a review. Materials Technology 25(5), 245–261 (2010).Robbiola, L. & Portier, R. A global approach to the authentication of ancient bronzes based on the characterization of the alloy–patina–environment system. Journal of Cultural Heritage 7, 1–12 (2006).Campbell, W. Greek and Roman plated coins, Numismatics Notes and Monographs 57, American Numismatic Society, New York (1933).Kallithrakas-Kontos, N., Katsanos, A. A. & Touratsoglou, J. Trace element analysis of Alexander the Great’s silver tetradrachms minted in Macedonia, Nuclear Instruments and Methods in Physics. Research B 171, 342–349 (2000).Catalli, F. Numismatica greca e romana. (Libreria dello Stato, 2003).Cope, L. H. The Metallurgical development of the Roman Imperial Coinage during the first five centuries. (Liverpool, 1974).Scriptores Historiae Augustae. Historia Augusta. (The Perfect Library, 2014).Vlachou-Mogire, C., Stern, B. & McDonnell, J. G. The application of LA-ICP-MS in the examination of the thin plating layers found in late Roman coins. Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms 265, 558–568 (2007).Keturakis, C. J. et al. Analysis of corrosion layers in ancient Roman silver coins with high resolution surface spectroscopic techniques. Appl. Surf. Sci. 376, 241–251 (2016).Ingo, G. M. et al. Roman sophisticated surface modification methods to manufacture silver counterfeited coins. Appl. Surf. Sci. 1–11, https://doi.org/10.1016/j.apsusc.2017.01.101 (2017).La Niece, S. In: La Niece S. & Craddock, P. (Eds), Metal, Plating and Platination, Butterworth–Heinemann, London, 1993, p. 201.Anheuser, K. & France, P. Silver plating technology of the late 3rd century Roman coinage. Historical Metallurgy 36(1), 17–23 (2002).Anheuser, K. & Northover, P. Silver plating on Roman and Celtic coins from Britain– A technical study. The British Numismatic Journal 64, 22–32 (1994).Anheuser, K. Where is all the amalgam silvering? Materials Issues1996 in Art and Archaeology - V proceedings, Boston.Beck, L. et al. In NIM 269, 2011 and in Counterfeit coinage of the Holy Roman Empire in the 16th century: silvering process and archaeometallurgical replications, Archaeometallurgy in Europe III.Deraisme, A., Beck, L., Pilon, F. & Barrandon, J. N. A study of the silvering process of the Gallo-Roman coins forged during the third century AD. Archaeometry 48, 469–480 (2006).Giumlia-Mair, A. On surface analysis and archaeometallurgy. Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms 239, 35–43 (2005).Tate, J. Some problems in analysing museum material by nondestructive surface sensitive techniques. Nuclear Inst. and Methods in Physics Research, B, 14 (1), pp. 20–23 (1986).Beck, L., Bosonnet, S., Réveillon, S., Eliot, D. & Pilon, F. Silver surface enrichment of silver-copper alloys: A limitation for the analysis of ancient silver coins by surface techniques. Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms 226, 153–162 (2004).Pardini, L. et al. X-ray fluorescence and laser-induced breakdown spectroscopy analysis of Roman silver denarii. Spectrochim. Acta - Part B At. Spectrosc. 74–75, 156–161 (2012).Klockenkämper, R., Bubert, H. & Hasler, K. Detection of near-surface silver enrichment on Roman imperial silver coins by x-ray spectral analysis. Archaeometry 41, 311–320 (1999).Ponting, M., Evans, J. A. & Pashley, V. Fingerprinting of roman mints using laser-amblation MC-ICP-MS lead isotope analysis.Del Hoyo-Meléndez, J. M. et al. Micro-XRF analysis of silver coins from medieval Poland. Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms 349, 6–16 (2015).Cesare Brandi. Il restauro. Teoria e pratica (1939–1986). (Editori Riuniti, 2009).Barberio, M., Veltri, S., Scisciò, M. & Antici, P. Laser-Accelerated Proton Beams as Diagnostics for Cultural Heritage. Sci. Rep. 7, 40415 (2017).Linke, R., Sehreiner, M., Demortier, G., Alram, M. & Winter, H. Non-Destructive Microanalysis of Cultural Heritage Materials. Comprehensive Analytical Chemistry 42, (Elsevier, 2004).Łojewska, J. et al. Recognizing ancient papyri by a combination of spectroscopic, diffractional and chromatographic analytical tools. Sci. Rep. 7, 46236 (2017).Meulebroeck, W., Wouters, H., Nys, K. & Thienpont, H. Authenticity screening of stained glass windows using optical spectroscopy. Nat. Sci. Reports 6 37726, 1–10 (2016).Martina, I., Wiesinger, R. & Schreiner, M. Micro-Raman Characterisation of Silver Corrosion Products: Instrumental Set Up and Reference. e-Preservation. Sci. Rep 9, 1–8 (2012).Rizzo, F. et al. Non-destructive determination of the silver content in Roman coins (nummi), dated to 308–311 A. D., by the combined use of PIXE-alpha, XRF and DPAA techniques. Microchem. J. 97, 286–290 (2011).Carl, M. & Young, M. L. Complementary analytical methods for analysis of Ag-plated cultural heritage objects. Microchem. J. 126, 307–315 (2016).Cepriá, G., Abadías, O., Pérez-Arantegui, J. & Castillo, J. R. Electrochemical Behavior of Silver-Copper Alloys in Voltammetry of Microparticles: A Simple Method for Screening Purposes. Electroanalysis 13, 477–483 (2001).Capelo, S., Homem, P. M., Cavalheiro, J. & Fonseca, I. T. E. Linear sweep voltammetry: a cheap and powerful technique for the identification of the silver tarnish layer constituents. J. Solid State Electrochem. 17, 223–234 (2013).Doménech-Carbó, A. et al. Detection of archaeological forgeries of Iberian lead plates using nanoelectrochemical techniques. The lot of fake plates from Bugarra (Spain). Forensic Sci. Int. 247, 79–88 (2015).Doménech-Carbó, A., Doménech-Carbó, M. T. & Peiró-Ronda, M. A. ‘One-Touch’ Voltammetry of Microparticles for the Identification of Corrosion Products in Archaeological Lead. Electroanalysis 23, 1391–1400 (2011).Doménech-Carbó, A., Doménech-Carbó, M. T., Montagna, E., Álvarez-Romero, C. & Lee, Y. Electrochemical discrimination of mints: The last Chinese emperors Kuang Hsü and Hsüan T’ung monetary unification. Talanta1 69, 50–56 (2017).Ager, F. J. et al. Combining XRF and GRT for the analysis of ancient silver coins. Microchem. J. 126, 149–154 (2016).Fawcett, T., Blanton, J., Blanton, T., Arias, L. & Suscavage, T. Non-destructive evaluation of Roman coin patinas from the 3rd and 4th century. Powder Diffraction, 1–10.Salvemini, F. et al. Neutron tomographic analysis: Material characterization of silver and electrum coins from the 6th and 5th centuries B.C. Mater. Charact. 118, 175–185 (2016).Ashkenazi, D., Gitler, H., Stern, A. & Tal, O. Metallurgical investigation on fourth century BCE silver jewellery of two hoards from Samaria. Sci. Rep. 7, 40659 (2017).Romano, F. P., Garraffo, S., Pappalardo, L. & Rizzo, F. In situ investigation of the surface silvering of late Roman coins by combined use of high energy broad-beam and low energy micro-beam X-ray fluorescence techniques. Spectrochim. Acta - Part B At. Spectrosc. 73, 13–19 (2012).Ingo, G. M. et al. Ancient Mercury-Based Plating Methods: Combined Use of Surface Analytical Techniques for the Study of Manufacturing Process and Degradation Phenomena. Accounts of Chemical Research 46(11), 2365–2375.Pouchou, J. L. & Pichoir, F.¨PAP¨ (ϕ–ρ–Z) procedure for improved quantitative microanalysis, in: Armstrong, J. T. (Ed.), Microbeam Analysis, San Francisco Press, San Francisco, pp. 104–106 (1985)

Karlhorst Stribrny, Funktionsanalyse barbarisierter, barbarischer Denare mittels numismatischer und metallurgischer Methoden. Hans-Gerd Bachmann und Peter Hammer, Vergleichende metallanalystische Untersuchungen an römischen Denaren aus der 2. Hälfte des 2. Jahrhunderts n. Chr.

Peter M., Deraisme Aurélie. Karlhorst Stribrny, Funktionsanalyse barbarisierter, barbarischer Denare mittels numismatischer und metallurgischer Methoden. Hans-Gerd Bachmann und Peter Hammer, Vergleichende metallanalystische Untersuchungen an römischen Denaren aus der 2. Hälfte des 2. Jahrhunderts n. Chr.. In: Revue numismatique, 6e série - Tome 161, année 2005 pp. 234-235

Invoice from E. Deraisme to Ogden Goelet

https://digitalcommons.salve.edu/goelet-personal-expenses/1096/thumbnail.jp

Recent and future developments in «downstream» geostatistics.

International audienc

Karlhorst Stribrny, Funktionsanalyse barbarisierter, barbarischer Denare mittels numismatischer und metallurgischer Methoden. Hans-Gerd Bachmann und Peter Hammer, Vergleichende metallanalystische Untersuchungen an römischen Denaren aus der 2. Hälfte des 2. Jahrhunderts n. Chr.

Peter M., Deraisme Aurélie. Karlhorst Stribrny, Funktionsanalyse barbarisierter, barbarischer Denare mittels numismatischer und metallurgischer Methoden. Hans-Gerd Bachmann und Peter Hammer, Vergleichende metallanalystische Untersuchungen an römischen Denaren aus der 2. Hälfte des 2. Jahrhunderts n. Chr.. In: Revue numismatique, 6e série - Tome 161, année 2005 pp. 234-235

L'hétérogénéité des teneurs en plomb dans les monnaies de bronze antiques

Summary. — The lead contents can vary greatly in a series of bronze coins belonging to a same type. This variation maybe due to changes in the bronze composition or to lead segregation during the casting process. A limestone mould for casting bronze blank was discovered at the Gallic-Roman site of Châteaubleau (France) and was used as a starting point to study lead segregation in bronze blanks. Bronze blanks were cast in a modern mould similar to the one found at Châteaubleau using ancient methods. Our experiments show that the variation in lead contents of the blanks is random.Deraisme Aurélie, Barrandon Jean-Noël. L'hétérogénéité des teneurs en plomb dans les monnaies de bronze antiques. In: Revue numismatique, 6e série - Tome 161, année 2005 pp. 5-15