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for presenting stress relaxation data in soft solid food s. Journal of Food Engineering 92 : 29 – 36 . Csima , Gy. , Dénes , L. D. , Vozáry , E. ( 2014 ) A possible

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Abstract  

Thermally stimulated depolarization currents and differential scanning calorimetry are performed on thermoplastic polyesters to characterize both a and b relaxations. The influence on the different relaxations phenomena of the chemical structure (size of the naphthalene groups, presence of cyclohexane, length of the aliphatic group, ...) as well as the influence of the crystallinity are discussed. The three phases model with a crystalline part, a rigid amorphous part unable to relax and an amorphous phase able to relax at various temperatures depending on the distribution of the relaxation times is used to explain the evolution of the main α relaxation while the standard two-phases model is sufficient to explain the variations of the β relaxation mode. Elementary analysis of both α and β relaxations show that the β relaxation characterized by a continuous variation of activation energies as a function of temperature follows the activated state equation with a zero activation entropy while the cooperative a relaxation exhibits a prominent maximum of the activation energies at the glass transition temperature.

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Abstract  

A new method of calculation of parameters of enthalpy relaxation models is proposed. Regression analysis treatment compares the experimental and calculated values of relaxation enthalpy. The experimental values of relaxation enthalpy are obtained by numerical integration of the difference between the two DSC curves. Contrary to the overall shape of the DSC curve the integral values are not affected by particular heat flow conditions during the DSC experiment. The Narayanaswamy's numerical model based on the Kohlrausch—William—Watts relaxation function was used to calculate the theoretical values of relaxation enthalpy. The application of the proposed method on the DSC experimental data of enthalpy relaxation of As2Se3 is shown.

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The amplitudes of the relaxation curves, as obtained by the Temperature-jump method have been used to measure simultaneously equilibrium constant and enthalpy for the reaction of complex formation of Ni2+ ion by 2,6-dihydroxobenzoic acid in the presence of a buffer. The experiments have been performed by changing the concentration of metal ion at constant ligand concentration andpH as in a complexometric titration. The points of such ‘dynamic titrations’ have been analysed by means of the concept of ‘normal reactions’ which enabled us to transform a set of coupled individual steps into a set of kinetically independent reactions. The potentialities of the dynamic titrations are discussed.

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The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity. The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO2 role near a TiO2 content of 3–4 mol%.

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In this paper we study the relaxation of optimal control problems monitored by subdifferential evolution inclusions. First under appropriate convexity conditions, we establish an existence result. Then we introduce the relaxed problem and show that it always has a solution under fairly general hypotheses on the data. Subsequently we examine when the relaxation is admissible. So we show that every relaxed trajectory can be approximated by extremal original ones (i.e. original trajectories generated by bang-bang controls) and that the values of the original and relaxed problems are equal. Some examples are also presented.

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Abstract  

Complex heat capacity, C p *=C p 'iC p '', of lithium borate glasses xLi2O(1–x)B2O3 (molar fraction x=0.00–0.30) has been investigated by Modulated DSC. We have analyzed the shape of C p * by the Cole-Cole plot, performed fitting by the Havriliak-Negami equation, and then determined the parameters related to the non-Debye nature of thermal relaxation. Moreover, the concentration dependence of the thermal properties has been investigated. Glass transition temperatures become higher with the increase of molar fraction of Li2O and shows the board peak around x=0.26. Temperature ranges of glass transitions become narrower with the increase of Li2O concentration.

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Simultaneous volume and enthalpy relaxation

The effect of experimental conditions

Journal of Thermal Analysis and Calorimetry
Authors: M. Liška and M. Chromčíková
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Introduction Glasses prepared by quenching of the melt do not reach any equilibrium state but they seek to attain it. The process the glass undergoes to reach this state is called structural relaxation and it is connected with

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crystalline solids, polymer nanocomposites, bio material, cells, tissues, [ 13 ] etc. The effects of dipolar, direct current (dc), and space charge relaxations are closely linked to the temperature-dependent mobility of molecules, their fragments, protons

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