A particle-pair of filaments is obtained by using liquid electrodes in a dielectric barrier discharge system. It travels in the
direction of the larger filaments and rebound at the boundary of discharge area. By using image processing and image
analyzing of the recorded pictures and video, the traveling velocity of particle-pair is calculated to be about 1.2 cm/s.
Moreover, the interparticle distance of particle-pair changes periodically with a period about 0.5 s.
A dielectric barrier discharge system with two liquid electrodes and a photoelectric detection system are specially
designed to study the spatiotemporal dynamics of square superlattice pattern. Two different types of square superlattice
patterns are observed for the first time. They are both composed of the square arranged large and small spots (filaments),
while one is without the glow background (type I), and the other one has (type II). The photoelectric measurements
indicate that they have the same spatial-temporal behaviors, which are an interleaving of two transient square
sublattices - the small-spot square sublattice (S) and the large-spot square sublattice (L). The emerging sequence of the
two sublattices in a one cycle of the applied voltage is S-L-L-S-L-L, which is harmonic with the forcing frequency. The
dynamic of the glow background of the type II square superlattice pattern is also studied. It is found that the glow
background discharge three times in each half cycle of the applied voltage, going with the emergence of each sublattice.
The photoelectric measurement of the hexagon pattern in dielectric barrier discharge is performed. By measuring the
current signals and the light signals of the hexagon pattern, it is found that there are three main pulses in both of the total
current signal and the total light signal. The light signal of a fixed filament in hexagon pattern is also measured. It is
found that the spatial location of the filament is unchanged, while its discharge moment is changed with the time, which
is probably corresponding to the first pulse, the second pulse or the third pulse of the total light signal. However, no
matter when it discharges, the light pulse width for one filament is almost 30 ns, and the ratio of the rising edge to the
falling edge of the pulse is about 1:1.88. In addition, the properties of hexagon patterns with the increased gas pressure
are investigated. The pattern bifurcation sequence is changed accordingly, and pulse widths of the light signals of the
hexagon pattern rises with increasing the gas pressure, which changes from 30ns (at 0.3atm) to 107ns (at 1atm), and the
ratio changes from 1:1.88 to 1:3.
Diverse stable localized states respectively with hexagonal, heptagonal and enneahedral symmetry have been
observed in a dielectric barrier discharge system with two water electrodes. The interacting process of different localized
clusters due to the attractive interaction is shown. The spatiotemporal dynamics of the localized hexagonal states are
measured by photoelectric method. It is found that the seven filaments composing a hexagonal cell discharge nearly at
the same time, with the light intensity of the central filament much stronger than its neighboring six ones. Magnifying the
light signal, however, it is found that the discharge moment of the central filament always precedes that of others
actually.
The images of square pattern, square superlattice pattern, and hexagonal pattern observed in dielectric barrier
discharge are processed to get the exactitude binary images for further investigation. By using spatial correlation function,
it is found that both of square and hexagonal patterns show perfect structures, and the square superlattice pattern exhibits
an interleaving of two perfect squares with the same wavelength including large and small spots respectively.
Furthermore, angular spectral distribution is used to study pattern development. It shows that, square and hexagonal
patterns are formed with single modes respectively, while square superlattice pattern is governed by a three wave
resonance.
Spatiotemporal patterns are obtained in gas discharge with increasing the voltage with the evolvement as following:
random spots, quasihexagonal pattern, hexagonal pattern with large spot, hexagonal pattern with small spot, white-eye
pattern, and chaos state. The structures of patterns are studied by analyzing the spatial correlation functions, Fourier
spectrum and angular spectral distributions of patterns after the image processing to the images of patterns. Furthermore,
the mechanism of the pattern formation is investigated, which indicates that hexagonal patterns both large and small spot
are selected by the single mode, while the white-eye pattern results from a three wave resonance.
The influence of different water temperatures on temporal behavior of dielectric barrier discharge in argon at
atmospheric pressure is studied by using an experimental device with water electrodes. It is found that, as the applied
voltage increasing, the evolvement of discharge with different water temperatures shows similar behavior spatially if
argon concentrations are same. The corresponding Fourier transformation is obtained by processing patterns images
with computer program based on the Matlab software. The discharge duration of the first current pulse in half cycle of
different voltage polarity is same in discharge if the two electrodes temperatures are same. But it becomes different if
the two electrodes have different temperatures. The discharge moment is always ahead when the low temperature
electrode is an instantaneous cathode. The analysis shows that the water temperature affects the accumulation of wall
charges, resulting in the differences of temporal behavior of discharge.
In this work, a rich variety of emission spiral patterns have been obtained in dielectric argon/air barrier discharge (DBD) system with a special designed water electrodes setup. We investigate the characteristics of spiral patterns with two kinds of different sidewall materials. By analyzing the image and the light signals of the patterns, it is found that spiral patterns with different sidewall material have different characteristics. The profile of the intensity distribution curve under the glass sidewall appears as a sinusoidal oscillation, while displays in relaxation oscillation mode under plastic sidewall. The space frequency spectrum of spirals under glass sidewall contains only one order spectrum, while the space spectrum of spirals under plastic sidewall contains more than two orders of space frequency spectrum. The experiment results indicate that the sidewall material may affect the excited property of the discharge system.
Edge detection is one of the most demanding tasks in optical image processing for artificial vision and image matching works. In this paper, the self organization theory is used for edge detection. A new algorithm based on a two variable reaction-diffusion equations is proposed. A stable edge pattern can be obtained by choosing suitable control parameters. Compared with the conventional methods, such as Soble, Prewitt and Robert detectors, the new algorithm indicates a higher accuracy and continuity for the image. Moreover, it can also extract exactly the edge of the human face image.
A special dielectric barrier discharge system with two liquid electrodes and a special optical system are designed to study the spatiotemporal dynamics of nonlinear patterns. A rich variety of patterns including square pattern, hexagon pattern, spiral and square superlattice pattern have been obtained. The spatio-temporal dynamics of square superlattice pattern is investigated. Results show that it is an interleaving of two different transient square sublattices with the emerging sequence of S-L-L-S-L-L in one cycle of the applied voltage. The light signals of the two sublattices indicate that the interval of the emergence of each sublattice is at an order of 0.1 μs.
KEYWORDS: Image processing, Dielectrics, Spatial frequencies, MATLAB, Physics, Digital imaging, Digital cameras, Electrodes, Analytical research, Control systems
Pattern formation is a process by which a spatially uniform state loses stability to a non-uniform state. A usual effective method for studying the property of patterns is to take pictures or record images of the patterns with digital cameras and get useful information from them. In this work, the structure, the spatial frequency spectrum of the patterns, the precise location of the discharge filaments center and the distribution of the light emission density of filaments are analyzed with Matlab6.1. This work can provide a beneficial reference for researchers who study pattern dynamics in DBD system or other systems.
Dielectric barrier discharge is a novel system for studying the pattern formation. In this system, spiral pattern has been observed for the first time. For the element of the pattern emits itself, the image can be obtained to give some information about the behavior of the spiral pattern. The image of spiral pattern is analyzed based on the software Matlab6.1. The spatial distribution of the intensity in the image gives a normal spiral structure. The temporal distribution of the intensity shows that the spiral pattern has a periodical behavior in a second time scale. All of the results are consistent with the theoretical simulations.
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