http://hdl.handle.net/10256/635 2013-05-23T14:16:01Z 2013-05-23T14:16:01Z Schwedt, A. Buxeda i Garrigós, Jaume Madrid Fernández, Marisol http://hdl.handle.net/10256/691 2012-11-30T07:34:04Z 2005-10-01T00:00:00Z

Grain size analyses in tin-lead glazes based on 2d-sections Schwedt, A.; Buxeda i Garrigós, Jaume; Madrid Fernández, Marisol Mateu i Figueras, Glòria; Barceló i Vidal, Carles A problem in the archaeometric classification of Catalan Renaissance pottery is the fact, that the clay supply of the pottery workshops was centrally organized by guilds, and therefore usually all potters of a single production centre produced chemically similar ceramics. However, analysing the glazes of the ware usually a large number of inclusions in the glaze is found, which reveal technological differences between single workshops. These inclusions have been used by the potters in order to opacify the transparent glaze and to achieve a white background for further decoration. In order to distinguish different technological preparation procedures of the single workshops, at a Scanning Electron Microscope the chemical composition of those inclusions as well as their size in the two-dimensional cut is recorded. Based on the latter, a frequency distribution of the apparent diameters is estimated for each sample and type of inclusion. Following an approach by S.D. Wicksell (1925), it is principally possible to transform the distributions of the apparent 2D-diameters back to those of the true three-dimensional bodies. The applicability of this approach and its practical problems are examined using different ways of kernel density estimation and Monte-Carlo tests of the methodology. Finally, it is tested in how far the obtained frequency distributions can be used to classify the pottery

2005-10-01T00:00:00Z Buenestado Caballero, Pablo Jarauta Bragulat, Eusebio Hervada i Sala, Carme http://hdl.handle.net/10256/690 2012-06-28T12:30:36Z 2005-10-01T00:00:00Z

Interpretation of wind components as compositional variables Buenestado Caballero, Pablo; Jarauta Bragulat, Eusebio; Hervada i Sala, Carme Mateu i Figueras, Glòria; Barceló i Vidal, Carles The classical statistical study of the wind speed in the atmospheric surface layer is made generally from the analysis of the three habitual components that perform the wind data, that is, the component W-E, the component S-N and the vertical component, considering these components independent. When the goal of the study of these data is the Aeolian energy, so is when wind is studied from an energetic point of view and the squares of wind components can be considered as compositional variables. To do so, each component has to be divided by the module of the corresponding vector. In this work the theoretical analysis of the components of the wind as compositional data is presented and also the conclusions that can be obtained from the point of view of the practical applications as well as those that can be derived from the application of this technique in different conditions of weather

2005-10-01T00:00:00Z Baxter, M.J. Beardah, C.C. Freestone, I.C. http://hdl.handle.net/10256/688 2012-06-28T12:30:36Z 2005-10-01T00:00:00Z

Compositional analysis of archaeological glasses Baxter, M.J.; Beardah, C.C.; Freestone, I.C. Mateu i Figueras, Glòria; Barceló i Vidal, Carles At CoDaWork'03 we presented work on the analysis of archaeological glass composi- tional data. Such data typically consist of geochemical compositions involving 10-12 variables and approximates completely compositional data if the main component, sil- ica, is included. We suggested that what has been termed `crude' principal component analysis (PCA) of standardized data often identi ed interpretable pattern in the data more readily than analyses based on log-ratio transformed data (LRA). The funda- mental problem is that, in LRA, minor oxides with high relative variation, that may not be structure carrying, can dominate an analysis and obscure pattern associated with variables present at higher absolute levels. We investigate this further using sub- compositional data relating to archaeological glasses found on Israeli sites. A simple model for glass-making is that it is based on a `recipe' consisting of two `ingredients', sand and a source of soda. Our analysis focuses on the sub-composition of components associated with the sand source. A `crude' PCA of standardized data shows two clear compositional groups that can be interpreted in terms of di erent recipes being used at di erent periods, re ected in absolute di erences in the composition. LRA analysis can be undertaken either by normalizing the data or de ning a `residual'. In either case, after some `tuning', these groups are recovered. The results from the normalized LRA are di erently interpreted as showing that the source of sand used to make the glass di ered. These results are complementary. One relates to the recipe used. The other relates to the composition (and presumed sources) of one of the ingredients. It seems to be axiomatic in some expositions of LRA that statistical analysis of compositional data should focus on relative variation via the use of ratios. Our analysis suggests that absolute di erences can also be informative

2005-10-01T00:00:00Z