Concentration dependence of gas discharge around drops of inorganic electrolyte
JOURNAL OF APPLIED PHYSICS VOLUME 89, NUMBER 9 1 MAY 2001
Concentration dependence of gas discharge around drops of inorganic electrolytes
K. G. Korotkov
Institute of Fine Mechanics and Optics, Sablinskaya 14, St. Petersburg 190000, Russia
D. A. Korotkin
Department of Mathematics and Statistics, Concordia University, Sherbrook West 7141, Montreal, H4B 1R6 Quebec, Canada
Received 14 September 2000; accepted for publication 6 February 2001
This article is devoted to the study of image formation in gas discharge, initiated by a strong impulsive electromagnetic field around drops of four different nonorganic electrolytes. To describe the image mathematically we propose several parameters: the form coefficient fractality, the entropy, and the average streamer width. We study the dependence of these parameters on concentration. The form coefficient turns out to have the best combination of stability and sensitivity in the whole range of concentrations. Statistically significant difference between the solutions and distilled water disappears at concentrations of about 220 N. © 2001 American Institute of Physics. DOI: 10.1063/1.1360700
I. INTRODUCTION
Image formation in gas discharge around objects of a different nature initiated by strong impulsive electromagnetic essentially different from the images obtained by use of stan- dard photographic tools. Computerized gas discharge cam- eras have many obvious advantages, although it turns out to be difficult to directly apply the mathematical description of Ref. 6 to computer images of gas discharge. Ideally, ad- equate mathematical tools should be stable with respect to the method of measurement, and, in particular, to the type of device used to obtain a gas discharge image of the given object. However, they should also be sensitive enough to reveal small fluctuations of the object.
As far as water solutions of different salts are concerned, in our opinion, this is an excellent laboratory for testing the methodology of gas discharge visualization before trying to further apply rigorous mathematical tools to gas discharge images of more complicated objects.
Therefore, the purpose of this article is twofold. First, we introduce several mathematical parameters characterizing the gas discharge image the form coefficient, entropy, average streamer width. All these parameters are borrowed from the theory of signal and image processing, and appropriately ad- justed to describe the gas discharge images. Second, we test the applicability of these parameters to explicit description of gas discharge images around drops of different electrolytes: NaCl, NaNO3 , KCl, KNO3 . In particular, we evaluate the average error resulting from the stochastic nature of the gas discharge process itself. The main focus will be on the de- pendence of these parameters on concentration.
II. BASIC PRINCIPLES OF GASEOUS DISCHARGE VISUALIZATION TECHNIQUE: EXPERIMENTAL SCHEME
The scheme of the experiment is shown in Fig. 1. By a vacuum photogalvanoplastic process a thin metal grid with 10 mkm wires is evaporated onto the bottom surface of the glass plate. A train of duration 0.1 s of triangular 10 mks electrical impulses of amplitude 3 kV, steep rate 106 V/s and repetition frequency 103 Hz is applied to this grid. This gen-
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lems is finding an adequate quantitative description of the process. The main obstacle to an effective mathematical de- scription is the high nonlinearity of gas discharge. Moreover, this nonlinearity comes on top of extreme complexity of the biological objects themselves.
The authors of Ref. 6 compared gas discharge images around drops of water solutions of several nonorganic salts using the traditional method of gas discharge photography. The authors introduced several numerical parameters charac- terizing gas discharge around solution drops, which in par- ticular correspond to size and shape of separate streamers. Using these parameters they were able to demonstrate essen- tial quantitative differences between gas discharge pictures around drops of solutions of different salts at different con- centrations.
However, there are several reasons which led us to at-
tempt to further understand gas discharge around drops of
different inorganic electrolytes. First, traditional gas dis-
charge photography is largely replaced by computer image
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