A dielectric disc with a thickness of 0.1 cm placed on the plane electrode in a rod to plane room air gap of 2 cm long is charged by DC corona discharges with the positive and negative polarities. The dielectric discs made of acryl PMMA have six kinds of radii from 2 to 16 cm. The surface potentials induced from the accumulated surface charges are measured by a vibrating capaciting voltage meter which can be controlled in the direction of X and Y, and the effect of surface potential on the corona onset voltage is also investigated from both the laser-induced measurement of electric field and the theoretical calculation of surface potential and electric field.
In order to make clear the effect of surface charge on the corona onset voltage under the same gap condition, we measure the onset voltage by using the applied voltage of same or inversed polarity to the polarity of surface charge just after the charge deposition was achieved on the dielectric disc. In the case of same polarity, the corona onset voltages increase with increasing the amount of surface charge. However, in the case of inverse polarity the corona onset voltages remarkably decrease in increase of the amount of the charge and are much lower than those without the surface charge. Also, it is surprising that in spite of short gap length 2 cm, the charging area spreads more than that with a radius of 16 cm around the disc center.

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A photochemical effect of vacuum ultra-violet light on NO removal was experimentally investigated. The light source was constructed as a discharge lamp of Xe gas enclosed into a cylindrical silica glass tube. Based on the dielectric barrier discharge, excimer light with 172 nm in wavelength was radiated from the Xe lamp. The photon energy exceeded the binding energy between N and O atoms for NO molecule. The experimental evaluation of photochemical NO removal was conducted by the Xe discharge lamp installed into a simple reactor. For NO/N₂ mixture gas under a referential condition with exception of O₂ molecules, the photochemical decomposition of NO molecules was confirmed from the presented experimental results. For NO/N₂/O₂ mixture gas with air, the photochemical effect of irradiation light on the NO removal was improved due to increasing NO₂ molecules as a secondary product with NO molecules and photochemically dissociated O atoms from surrounding O₂ molecules. The experimental results indicated that the photochemical effect enhanced the NO removal rather than the NO₂ product. This paper shows the radiation characteristics of 172 nm in wavelength from the constructed Xe discharge lamp, and discusses the NO removal characteristics in terms of the photochemical effect.

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The relationship between enhancement of H^- negative ion volume production and behaviors of fast primary electros are studied. Trajectories of fast primary electrons are calculated numerically, including collisional effects with hydrogen molecules. Taking into account our experimental study, following two main targets are discussed: (1) Effect of field intensity of the magnetic filter (MF) and a filament position on active region of fast primary electrons, and (2) combination effect of the field intensity of the MF and the filament position for controlling behaviors of fast electrons.
Active region of fast electrons depends strongly on the field intensity of the MF and filament position. Therefore, spatial distributions of ionization and vibrational excitation collision points are also changed in the same manner although number of vibrational excitation collision points is lower than that of ionization collision points due to longer mean free path. According to the results and discussions including transport of produced vibrationally excited molecules and H^- ions, for enhancement of H^- production, it is desired that fast electrons should approach the MF position and move into the downstream region as deep as possible without destruction of H^- ions. To realize these conditions, good combination between filament position and the intensity of the MF should be required.

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The melt-spun ribbons of Pr_xFe_90-x-y-zCo₈Ti_1.5Y_ySi_0.5B_z (x = 10.0 -13.0, y = 0.0 -1.2, z = 10.5 -14.0) alloy were prepared by signal roller liquid rapid-quenching method, and effects of composition, wheel velocity and annealing condition on the magnetic properties were studied. The optimum preparation conditions and some of the properties were as follows: Composition: Pr₁₁Fe_67.8Co₈Ti_1.5Y_0.7Si_0.5B_10.5; wheel velocity: 10.0 m/s; annealing condition: 625°C for 5 min in Ar atmosphere, magnetic properties J_r = 0.77 T (7.7 kG), H_cJ = 1.82 MA/m (22.9 kOe), H_cB = 0.54 MA/m (6.7 kOe), (BH)_max = 103.5 kJ/m³ (13.0 MGOe), H_k/H_cJ × 100 = 24.0 %, α(J_r) = -0.078 %/°C, α(H_cJ) = -0.420 %/°C and T_c = 380 °C. From TEM observation, average particle size of ribbon was found to be about 31 nm. The isotropic compression molding bonded magnets were prepared by using Pr₁₁Fe_67.8Co₈Ti_1.5Y_0.7Si_0.5B_10.5 ribbons annealed at 625°C for 5 min. Their magnetic properties of this magnet were J_r = 0.63 T (6.3 kG), H_cJ = 1.60 MA/m (20.1 kOe), H_cB = 0.43 MA/m (5.4 kOe), (BH)_max = 67.6 kJ/m³ (8.5 MGOe), H_k/H_cJ × 100 = 19.8 %. Irreversible loss of the bonded magnet is -2.1 % at 150°C.

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A chaotic region and stabilization method of domain-wall motion were examined by computer simulation. As a result, the chaotic domain-wall motion was distributed outside of (high frequency)-(large amplitude), and (low frequency)-(small amplitude) excitation region, and the bottom of region supported domain-wall resonance. In addition, the extended delayed feedback control (EDFC) method and Half-period-EDFC method that improved delayed feedback method were shown to be effective as a control method.

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The coaxial cone to rod electrode system was devised to generate a powerful electrohydrodynamic (EHD) liquid jet and the performance as a liquid pump was investigated using an isothermal weakly conducting liquid, HFC43-10. When a positive dc voltage was applied to the rod electrode, the liquid spouted forcibly from the glass tube outlet installed in the top of grounded conical electrode. The properties of liquid jet: pumping pressure, flow velocity and flow pattern were examined for the electrode systems with various cone angles (θ =40°∼90°) of the conical electrode. The potential distribution in the electrode gap and the conduction current also were measured as a function of applied voltage. In this paper, it is shown that the pumping pressure is almost independent of the cone angle of electrode systems as well as the flow velocity, but is raised effectively by a partial insulating coating of rod electrode surface and the current is reduced by a coating. The potential distribution in the gap revealed the existence of heterocharge layer in the vicinity of the electrode surfaces. It is considered that the EHD pumping in this study is attributed to a space charge layer with single ionic polarity near the rod electrode, which is formed by a non-uniform electric field.

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It is reported that nitrogen active species such as ions, metastable molecules and atoms affect the breakdown properties of nitrogen gas under low pressure. The purpose of this study is to clear the influence of nitrogen active species on the depression of insulation strength under high pressure and to offer the method for improvements. The results indicated that the nitrogen active species affects the breakdown properties under high pressure. To confirm the quenching properties, small amount of NO is mixed into nitrogen gas and the number of primary electrons was evaluated. The results showed that decreasing rate of primary electrons become fast depending on the mix rate. Therefore,the quenching phenomenon is confirmed. Also in the case of SF₆, the number of primary electron becomes very low. Consequently, the attachment effect is confirmed.

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