Various periodic plasma structures have been obtained by nonlinear self-organization in dielectric barrier discharge
with two water electrodes. The spatio-temporal evolvement of these plasma structures has been studied when changing
the discharge parameters. Based on the experimental results, a potential tunable plasma photonic crystal for microwave
to THz wave control is suggested. In addition, a special superlattice plasma structure is observed, in which three
disparate refractive indexes are modulated periodically.
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.
The electron excited temperature in dielectric barrier discharge under argon at atmospheric pressure is diagnosed by
photoelectric method. The electron excited temperature Texc can be estimated by using spectral lines intensity ratio
method. The spectral lines 763.72nm (2P6→1S5) and 772.63nm (2P2→1S3) in the spectrum range from 690nm to 800nm
are chosen to estimate the electron excite temperature. The power of the discharge gap is calculated by analyzing the
waveform of the apply voltage and the voltage of the test capacitance. The experimental results show that the electron
excited temperature is in the range of 0.19-0.31eV and the discharge power in the gas gap is in the range of 35.7-51.0W
under different discharge gap 0.9-3.0mm. In addition, it is found that the variation tendency of the electron excited
temperature with the discharge gap increasing is similar to that of discharge power, and the electron excited temperature
and discharge power has a minimum value at d=1.1mm. The discharge operates in glow-like mode when the discharge
gap d<1.3mm, and the discharge operates in patterned mode when d>1.3mm. As the discharge gap increase from 1.3mm
to 3.0mm, the streamer channels became brighter, and move faster. The self-organized behavior is also found in the
experiment.
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.
KEYWORDS: Dielectrics, Liquids, Oscilloscopes, Electrodes, Digital cameras, Imaging systems, Glasses, Power supplies, Signal detection, Fluctuations and noise
A dielectric barrier discharge system is specially designed with two liquid electrodes and a corresponding
photoelectricity detection system. The detection system is composed of lens, apertures, multiplier-tube, digital camera,
and an oscilloscope. A rich variety of emission patterns are obtained in the system as the voltage is increased. The
wavelength characteristic of the emission patterns in dielectric barrier discharge is investigated. It is found that the
wavelength of the emission patterns displays a non-monotonic variation as the applied voltage is increased. When the
applied voltage is relatively low, the wavelength of the emission patterns decreases as the applied voltage increases.
When the applied voltage is increased over a critical value, the wavelength of the patterns becomes larger as the voltage
is increased. The wavelength of the emission pattern may maintain approximately invariable when the voltage is
increased within some particular voltage range.
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.
The transition among three discharge modes, glow-like discharge, filamentary discharge and diffuse discharge, has been obtained in air dielectric barrier discharge at 0.1atm pressure. To get the transition conditions, the electric waveforms and optical emission spectroscopy (OES) of the discharge have been measured. The results show that the wall charges and the ion concentration in the discharge are important to the transition of discharge modes.
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.
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