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A Chemical System that Recognizes the Shape of a Sphere

Giżyński K., Górecki J.

Computational Methods in Science and Technology

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2016

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Vol. 22, No. 4

167--177

EN

Unconventional computing devices operating on nonlinear chemical media offer an interesting alternative to standard, semiconductor-based computers. In this work we consider database classifiers formed of interacting droplets in which a photosensitive variant of Belousov-Zhabotinsky (BZ) reaction proceeds. We introduce an evolutionary algorithm that searches for optimal construction of a droplets-based classifier for a given problem. The algorithm is based on maximizing the mutual information between the database and the observed evolution of medium. As an example application of chemical database classifiers we apply the idea to the dataset of points belonging to a unit cube. The dataset contains two output classes: 1 for points belonging to a sphere with radius 0.5 located in the cube center, and 0 for points outside of the sphere. The reliability of optimized chemical classifiers of such database for different numbers of droplets involved in data processing is presented.

2

Regularities in Complex Asymptotic Oscillations in the Belousov-Zhabotinsky Reaction at Various Residence Times and Inflow Malonic Acid Concentration

Rachwalska M., Kawczyński A.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 1

135-143

EN

Simple and complex oscillations have been observed in an asymptotic regime of the Belousov-Zhabotinsky (BZ) system of bromate-malonic acid-ferroin in a continuously stirred tank reactor (CSTR). Changes of the residence time and the influx concentration of malonic acid induce the appearance of regularities in complex patterns which resemble the period adding bifurcation. All experimental results can be reproduced by a simple model suggested earlier for qualitative description of asymptotic and transient oscillations observed in the BZ system.

3

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

Darowicki K., Felisiak W.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 9

1269-1278

EN

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.

4

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

Darowicki K., Felisiak W.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 4

575-582

EN

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.

5

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

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1999

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Vol. 73, nr 12

2003-2012

EN

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.