ICA Mixtures Applied to Ultrasonic Nondestructive Classification of Archaeological Ceramics
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Research Article ICA Mixtures Applied to Ultrasonic Nondestructive Classification of Archaeological Ceramics Addisson Salazar and Luis Vergara Grupo de Tratamiento de Se˜nal, Instituto de Telecomunicaciones y Aplicaciones Multimedia, iTEAM, Universidad Polit´ecnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain Correspondence should be addressed to Luis Vergara, [email protected] Received 23 December 2009; Revised 7 May 2010; Accepted 7 June 2010 Academic Editor: Jo˜ao Manuel R. S. Tavares Copyright © 2010 A. Salazar and L. Vergara. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We consider a classifier based on Independent Component Analysis Mixture Modelling (ICAMM) to model the feature jointprobability density. This classifier is applied to a challenging novel application: classification of archaeological ceramics. ICAMM gathers relevant characteristics that have general interest for material classification. It can deal with arbitrary forms of the underlying probability densities in the feature vector space as nonparametric methods can do. Mutual dependences among the features are modelled in a parametric form so that ICAMM can achieve good performance even with a training set of relatively small size, which is characteristic of parametric methods. Moreover, in the training stage, ICAMM can incorporate probabilistic semisupervision (PSS): labelling by an expert of a portion of the whole available training set of samples. These properties of ICAMM are well-suited for the problem considered: classification of ceramic pieces coming from four different periods, namely, Bronze Age, Iberian, Roman, and Middle Ages. A feature set is obtained from the processing of the ultrasonic signal that is recorded in through-transmission mode using an ad hoc device. A physical explanation of the results is obtained with comparison with classical methods used in archaeology. The results obtained demonstrate the promising potential of ICAMM for material classification.
1. Introduction Determining the historical period of archaeological ceramic shards is important for many archaeological applications, particularly to reconstruct human activities of the past. In fact, the standardization of an efficient and nondestructive testing (NDT) method for ceramic characterization could become an important contribution for archaeologists. Chemical, thermoluminescence, and other analyses have shown to measure the age of ceramics accurately, but they are expensive, time-consuming and involve some destruction of the analyzed pieces [1]. Relative dating by comparison with ceramic collections is nondestructive but very inaccurate [1]. Ultrasound has been used in archaeological applications such as ocean exploration to detect wrecks, imaging of archaeological sites, and cleaning archaeological objects [2– 4]. In this paper, we consider a method to sort archaeological
ceramic
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