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SVD-based principal component analysis of geochemical data

100%

Praus P.

Open Chemistry

2005

vol. 3

issue 4

731-741

Principal Component Analysis (PCA) was used for the mapping of geochemical data. A testing data matrix was prepared from the chemical and physical analyses of the coals altered by thermal and oxidation effects. PCA based on Singular Value Decomposition (SVD) of the standardized (centered and scaled by the standard deviation) data matrix revealed three principal components explaining 85.2% of the variance. Combining the scatter and components weights plots with knowledge of the composition of tested samples, the coal samples were divided into seven groups depending on the degree of their oxidation and thermal alteration. The PCA findings were verified by other multivariate methods. The relationships among geochemical variables were successfully confirmed by Factor Analysis (FA). The data structure was also described by the Average Group dendrogram using Euclidean distance. The found sample clusters were not defined so clearly as in the case of PCA. It can be explained by the PCA filtration of the data noise.

Agglomeration of ZnS nanoparticles without capping additives at different temperatures

51%

Praus P., Dvorský R., Kovář P., Svoboda L.

Open Chemistry

2014

vol. 12

issue 3

312-317

ZnS nanoparticles were precipitated in diluted aqueous solutions of zinc and sulphide ions without capping additives at a temperature interval of 0.5–20°C. ZnS nanoparticles were arranged in large flocs that were disaggregated into smaller agglomerates with hydrodynamic sizes of 70–150 nm depending on temperature. A linear relationship between hydrodynamic radius (R a) and temperature (T) was theoretically derived as R a =652 - 2.11 T. The radii of 1.9–2.2 nm of individual ZnS nanoparticles were calculated on the basis of gap energies estimated from their UV absorption spectra. Low zeta potentials of these dispersions of −5.0 mV to −6.3 mV did not depend on temperature. Interactions between individual ZnS nanoparticles were modelled in the Material Studio environment. Water molecules were found to stabilize ZnS nanoparticles via electrostatic interactions.

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2 Open Chemistry

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2 Praus P.

1 Dvorský R.

1 Kovář P.

1 Svoboda L.

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SVD-based principal component analysis of geochemical data

Agglomeration of ZnS nanoparticles without capping additives at different temperatures