Entity

Time filter

Source Type

Pardubice, Czech Republic

University of Pardubice is a university in Pardubice, the Czech Republic. In 2005 it had nearly 8,000 students. It is the only university in Pardubice Region. Wikipedia.


Svoboda R.,University of Pardubice
Journal of Thermal Analysis and Calorimetry | Year: 2014

The article critically reviews the current methodologies for determination of apparent activation energy of structural relaxation, Δh×, in the glass transition range. Tool-Narayanaswamy-Moynihan phenomenological model was used to simulate data for all major types of relaxation behavior, which were consequently evaluated in terms of the tested methodologies (curve-fitting, evaluation of Δh×from intrinsic cycles and evaluation of Δh×from constant heating rate cycles). Advantages and disadvantages of particular methodologies are demonstrated and thoroughly discussed. In addition, effects of various data-distortive effects influencing determination of glass transition activation energy are demonstrated and described. The discussed data-distortive effects include presence thermal gradients, improperly designed temperature programs, incorrectly applied subtractions of the thermokinetic background, or inability of the DSC instrument to perform high cooling/heating rates. Detailed guide for correct determination of Δh×from DSC measurements is introduced. © 2014 Akadémiai Kiadó, Budapest, Hungary. Source


Svoboda R.,University of Pardubice
Acta Materialia | Year: 2013

Structural relaxation processes were studied by means of differential scanning calorimetry for a number of compositions belonging to the Se-rich sides of Se-Te, Ge-Se and As-Se chalcogenide systems. Based on the results of fitting and non-fitting methods, the relaxation behavior of these selenide glasses is described in terms of the Tool-Narayanaswamy-Moynihan (TNM) equations. The goal of this paper is to introduce an advanced model describing the relationship between the macroscopic relaxation behavior and molecular structure of the glass. Special attention is paid to differences between the particular structural units and molecular arrangements characteristic for each system studied. The TNM parameters as well as their changes are discussed with respect to both the increasing content of dopant in the Se matrix within each chalcogenide system and different structural units employed in the respective systems. A unique novel conception is suggested, showing a connection between the values of TNM parameters and respective molecular structures and their changes during structural relaxation. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Bures F.,University of Pardubice
RSC Advances | Year: 2014

Property tuning in selected examples of D-π-A molecules has been discussed and summarized in this review article. The tuning and structure-property relationships have been demonstrated on the particular A, π and D parts of the push-pull molecule. Special emphasis has been put on the tuning of the FMO levels and optical properties. Further prospective applications of the given chromophore have also been considered. This journal is © 2014 The Royal Society of Chemistry. Source


Hajek P.,University of Pardubice
Decision Support Systems | Year: 2011

The paper presents the modelling possibilities of neural networks on a complex real-world problem, i.e. municipal credit rating modelling. First, current approaches in credit rating modelling are introduced. Second, previous studies on municipal credit rating modelling are analyzed. Based on this analysis, the model is designed to classify US municipalities (located in the State of Connecticut) into rating classes. The model includes data pre-processing, the selection process of input variables, and the design of various neural networks' structures for classification. The selection of input variables is realized using genetic algorithms. The input variables are extracted from financial statements and statistical reports in line with previous studies. These variables represent the inputs of neural networks, while the rating classes from Moody's rating agency stand for the outputs. In addition to exact rating classes, data are also labelled by four basic rating classes. As a result, the classification accuracies and the contributions of input variables are studied for the different number of classes. The results show that the rating classes assigned to bond issuers can be classified with a high accuracy rate using a limited subset of input variables. © 2010 Elsevier B.V. All rights reserved. Source


Svoboda R.,University of Pardubice
European Polymer Journal | Year: 2014

The utilization of the constant ratio cyclic temperature history, where q+/q- = const., was examined with respect to physical aging studies. In particular, determination of the apparent activation energy of enthalpy relaxation from constant ratio (CR) cycles was discussed. A novel equation fully utilizing the advantages of CR cycles was derived - it is based on shift of temperature corresponding to the maximum of relaxation peak T p with the applied heating rate: -Δh*/R = dln(q+)/dTp -1. The equation was extensively tested for all types of structural relaxation behavior; it was proven to be highly accurate and independent from most data-distortive effects. In addition, it was shown that the unique shape of CR cycles curves can be utilized for the identification of certain data-distortive effects - thermal lags, imprecise heating/cooling rates or incomplete achievement of a true glassy state during cooling. Correspondingly, corrections for these data-distortive effects can be applied to other physical aging measurements performed for the given glassy material and DSC instrument. © 2014 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations