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Time-Frequency Characteristics of Chemical Oscillations. Experimental and Model Studies

Darowicki K., Felisiak W.

Polish Journal of Chemistry

2004

Vol. 78 / nr 9

1269-1278

Chemical oscillations exhibit nonlinear, and nonstationary features and their complete characterization cannot be accomplished via classical Fourier transform. That is why there is a need for another analysis framework in joint time-frequency domain. In this paper the authors propose a proper methodology of spectral analysis of Belousov-Zhabotinsky (BZ) reaction. The short time Fourier transformation (STFT) has been applied to the analysis of potential registers of BZ reaction in a batch reactor. The method allowed finding the frequency and energy distribution of chemical oscillations in the function of time. The similarities and the differences between the spectrograms generated for the experimental data and simulated time series, based on the modified Oregonator model, are briefly discussed.

Frequency Distribution of Chemical Oscillations in the Closed belousov-Zhabotinsky Reaction

Darowicki K., Felisiak W.

Polish Journal of Chemistry

2004

Vol. 78 / nr 4

575-582

The potential registers of chemical oscillations, generated in the closed Belousov- Zhabotinsky reaction, have been submitted to detail spectral analysis using two algorithms based on the Fourier transform. It has been found that for selected stationary fragments of this signal the FFT algorithm distinctly reflects the strength of the spectral components contained in an exemplary potential register of BZ reaction. The temporal localization of these components is hidden in the phase of the spectrum, what makes the drawing of correct conclusions about the process investigated impossible. The cone-shape distribution, belonging to the group of joint time-frequency transformations, has been proposed as a proper method of nonstationary signals analysis. Spectrograms obtained by the above method have been presented, showing frequency evolution of chemical oscillations in time domain and their energy distribution simultaneously. Good reproducibility of spectrograms for potential registers of different time courses has been found. On the basis of harmonic components analysis the linear dependency between the frequency of harmonics and the composition of BZ reacting mixture has been noticed.

Transient Period Adding Phenomena in the Belousov-Zhabotinsky Reaction at Low Flow rates in a CSTR

Didenko O., Strizhak P., Kawczyński A.

Polish Journal of Chemistry

1999

Vol. 73, nr 12

2003-2012

Period adding phenomena in transient dynamics of the Belousov-Zhabotinsky reaction (bromate-malonic acid-ferroin) in a CSTR have been observed for decreasing residence time at various inflow concentrations of malonic acid. Oscillations showing similar transient patterns are obtained in a simple model proposed recently for a qualitative description of transient and asymptotic oscillations observed in the BZ system.