We present the first analysis of a type of special lightning discharge event, called “isolated large bipolar pulse” (ILBP), produced in winter thunderstorm. ILBP produces single bipolar electric field change waveforms with pulse widths mainly in the range of 7 to 19μs. The initial positive half cycle and the negative cycle of the bipolar pulse are symmetrical with each other to some extent. ILBP is also a very energetic discharge process, producing very large electric field changes even larger than that produced by positive return strokes. Most of ILBPs are found to be isolated with other discharge processes on a time scale of 1 second, but a few ILBPs also seem to be the initiation of other discharge processes. Based on the similarities and differences between ILBP, narrow bipolar pulse (NBP) and negative return stroke (RS) in winter thunderstorm, we discuss the possibility of ILBP as a special version of NBP in winter thunderstorm and as a special type of negative RS.

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Laser Thomson scattering (LTS) has been applied to arc discharges generated in the atmospheric air to measure electron density (n_e) and electron temperature (T_e). As electrode materials, tungsten and tungsten-copper (30%) were used. The electrode gap was 0.8mm and its diameter was 1mm. The applied voltage was 6kV, the peak current was 600A and the decay time of the voltage and the current was 25μs. Spatiotemporal evolutions of n_e and T_e were measured at 10μs, 30μs and 50μs after the discharge initiation. At these times, obtained values of n_e and T_e were estimated to be in the ranges of (0.8-2.0)×10²³m^-3 and 1.0-2.2eV, respectively. These values were consistent with those evaluated from Saha's thermodynamic equation at 1 atm. It was also found that the decay of the arc discharge produced using the tungsten-copper electrodes was much faster than that produced using the tungsten electrodes.

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Investigation on ozone effective lifetimes in ozone-oxygen gas mixtures contained in a cylindrical cell as a function of pressure and temperature is carried out. Effective lifetimes are determined by tracking the time decay of the ozone density in the cell which is measured by the HgI photo-absorption method. The decay curves were measured over long periods of time reaching 10⁵s, while the ozone densities varied in the range 10¹⁶-10¹⁴cm^-3. Variation of the decay rate with time and ozone density along single decay curves as well as gradual change of the effective lifetimes of ozone in successively repeated measurements was observed, likely due to variations of the wall surface properties. The loss rate of ozone was attributed to two processes: sticking and decomposition of ozone molecules at the cell wall surface and decomposition in reactions with oxygen in the gas phase. In this work, we obtained results on the temperature dependence of ozone loss rate in the range of 293-353K. From the measured data, the reaction rate coefficient of ozone molecules with oxygen in the gas phase is determined as k_p = 2.33×10^-23 exp (-1700/T) cm³/s.

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Ozone has many applications in various fields with an advantage of low environmental load, i.e., water treatment, sterilization, deodorization, bleaching, etc. While the dielectric barrier discharge (DBD) is mainly used for practical ozone generator, the various discharge methods have been studied to achieve higher yield and higher concentration of ozone generation in recent years. This study is carried out to compose ozone using a Blumlein type pulse forming network (B-PFN) as a discharge power source combined with the ordinary DBD type ozone generator. The ozone generator is equipped a pair of coaxial cylinder electrodes. The inner electrode is stainless steel cylinder and is applied pulsed voltage. The outer electrode is covered by glass lining of inner surface of electrode and is act as earthed electrode. This generator gives maximum ozone concentration of about 57g/Nm³ by negative polarity and maximum ozone yield of about 900g/kWh by positive polarity. These results are compared with other results using pulsed power discharges. We also investigated temporal variation of ozone concentration, related to “Ozone zero phenomena”.

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We investigated the effects of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) on the mu wave. The power of the mu wave decreases with the imagination of movement or actual movement. This phenomenon is described as the desynchronization (ERD) of the mu wave. The aim of our study was to investigate the effects of different rTMS and tDCS stimulation parameters on the mu wave. We used rTMS and tDCS to either facilitate or inhibit cortical excitability. EEG was measured over the sensorimotor cortex before and after stimulation. We performed four stimulation trials with different stimulus conditions: (1) 1Hz rTMS stimulation at 90% of the resting motor threshold (RMT), (2) 1Hz rTMS stimulation at 110% RMT,; (3) anodal tDCS,; and (4) cathodal tDCS over the motor area of the thumb in the left hemisphere. During EEG recording, participants were asked to (1) maintain a resting state, (2) imagine moving their right hand, or (3) actually move their right hand. We assessed the power difference and the amount of relative ERD before and after stimulation. We found no significant change in the power of the mu wave before or after rTMS or tDCS. Anodal tDCS, which produces facilitation, produced a significant increase in ERD. Both 1Hz rTMS at 110% of the RMT and cathodal tDCS, which produce inhibition, produced a significant decrease in ERD. We found no significant difference in ERD resulting from 1Hz rTMS at 90% of the RMT.

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Fe₃O₄ spinel ferrite nano-particles, promising electrode materials for redox capacitors, were prepared with chemical coprecipitation technique. In this research, the effects of electrical reduction on electrochemical properties of Fe₃O₄ spinel ferrite electrodes were studied. The results show that the pseudo-capacity of Fe₃O₄ electrodes was increased after the electrochemical reduction at -0.7V vs. Ag/AgCl reference electrode. Moreover, it was found that crystal structure of Fe₃O₄ electrodes remained almost unchanged even after the electrochemical reduction.

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Motions of magnetic domain walls are trapped at pinning points. The Barkhausen effect occurs at such pinning point break down inducing drastic transitions in flux structures. The domain energies are calculated from magnetic dipole moment interactions, which determine domain structures in the system. The flux structure transition occurs between loop and open domains with added field ΔH, which changes drastically the domain energy system and makes the lower energy states. The retarded trace method is based on the mechanisms of the domain system requiring the increased field steps for the changes, which nicely explains the experimental data of Fe nano-particles. This method can analyze B-H characteristics in various materials.

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