Thermal curve interpretation method

It is known that the response to a Dirac heat pulse S(t) of unit amplitude is the pulse response HaO). For stationary linear systems, the response to a heat pulse AjS (t - tj) generated at time moment tj is 

In the method [237, 248], it is assumed that the heat effect P(t) generated can be approximated by the function 

The aim of the spectrum method is to find the values of coefficients Pj. The scheme of searching for the values of these coefficients can be shown as follows. Let us transform the set of functions Hj into the set 

Using the basis of orthonormal functions Hj and curve T, the coefficients P are calculated as 

Applying the inverse transformation to transformation (3.117), we obtain the values of coefficients Pj as 

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The computer realization of this scheme is very simple under the condition that the orthonormalization does not give problems. The thermal curve interpretation method was proposed by Adamowicz [237-239]. 

For correct interpretation of DSC curves usually, complementary methods (such as TG, TOA, XRPD, Raman, or IR spectroscopy) must be applied, for example, to recognize decomposition effects and to correctly assign a thermal event to the phases present... 

In most laboratory experiments dealing with the properties of a material or a system the properties are measured under isothermal conditions. Separate experiments are required to measure these same property at different temperatures. In thermal analysis the specified property is measured under a controlled temperature regime. The simplest temperature regime would be that of an isothermal experiment, but in most cases the temperature is raised at a predetermined rate, for example, 10°C per minute. The interpretation then involves the variation of a particular property with both temperature and time. There is, however, a decrease in labor and time which makes such studies especially interesting for industrial applications. With more complicated temperature regimes there is an ability inherent in the method to mimic industrial processes. Industries utilizing thermoanalytical methods are listed in Table 1. The plot of the physical property of the sample recorded as a function of the temperature is said to be a thermal analysis curve. There is still some confusion in the literature about this name, as it was initially applied to the specific technique in which the temperature of a sample was recorded against time as it was cooled down from a particular value. The use of the name in this way persists in physical chemistry textbooks where the name thermal analysis is used for this specific purpose. Other conditions that have to be satisfied in the practice of thermal analysis are as follows. 

Many cable sheaths are mamrfactured from heavily filled polymers, and TGA has been foimd to be of immeasurable value in studies of such materials and some of their ingredients. The combination of the weight-loss curve, for quantitative analysis, with the derivative, for a qualitative interpretation, has been found to be particularly powerful for these applications particularly when taken together with data obtained by the other thermal methods already discussed but also with that obtained by FTIR spectroscopy. In addition the vinyl acetate content of ethylene-vinyl acetate (EVA) copolymer used in the preparation of some sheathing formulations has been measured and used as a confirmation of grade. 

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