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Girum Admasu Nadew Zebene Lakew Tefera 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(3):357-364
Multivariate statistical analysis is very important to classify waters of different hydrochemical groups. Statistical techniques, such as cluster analysis, can provide a powerful tool for analyzing water chemistry data. This method is used to test water quality data and determine if samples can be grouped into distinct populations that may be significant in the geologic context, as well as from a statistical point of view. Multivariate statistical analysis method is applied to the geochemical data in combination with δ 18O and δ 2H isotopes with the objective to understand the dynamics of groundwater using hierarchical clustering and isotope analyses. The geochemical and isotope data of the central and southern rift valley lakes have been collected and analyzed from different works. Isotope analysis shows that most springs and boreholes are recharged by July and August rainfalls. The different hydrochemical groups that resulted from the multivariate analysis are described and correlated with the geology of the area and whether it has any interaction with a system or not. 相似文献
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Davide Tranchida Zebene Kiflie Stefano Piccarolo 《Macromolecular rapid communications》2006,27(18):1584-1589
Summary: Nanometer scale morphological order of macroscopically amorphous polyesters, obtained from the melt at moderate cooling rates, was observed in the past. The effect of such order on mechanical properties of a PET/PEN blend, evaluated by AFM nanoindentations, is reported in this study. Results show that nanoindentations conducted at relatively high load, with penetration depths of the order of 100 nm, confirm the information obtained from mechanical tests at micrometer scale, i.e., microhardness. On the other hand, true nanometer scale indentations (<40 nm) are seen to discriminate between the mechanical properties of the nanophases formed during solidification.
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Physical cross-links arise in amorphous PET upon solidification from the melt, their size distribution depending on the cooling rate adopted during a CCT (Continuous Cooling Transformation). They form a fading network structure. Above the Tg, their stability decreases with temperature. Physical cross-links stable above the Tg can influence the nucleation rate. Ageing, below Tg, is also affected by cooling rate and therefore by physical cross-links. However upon ageing new physical cross-links arise although their size and stability continue to depend on cooling rate. 相似文献
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