This paper presents the "virtual eddy current method" for coil shape optimization. In this method, optimum coil shapes are determined as paths of eddy currents induced in a virtual thin metallic plate. To get the eddy currents, which produce target fields within a specific region, the distribution of the magnetic flux density impressed on the plate is optimized. The general formulation of this method based on the FEM by current vector potential method (T-method) is shown. The validity of the virtual eddy current method is demonstrated by shape optimizing of a z field gradient coil of the MRI with the formulation on the four node isoparametric line element of the FEM.

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Reduction of Carbondioxide by AC Glow Discharge has been studied. Main product is Carbonmonoxide and the maximum efficiency of Carbondioxide reduction is about 160 nmol/secW. It has been shown that the simple simulation model based on rate equations can reproduce the experimental results.

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Theory of formerly proposed "flight time integral method" for the rigorous analyses of transport property of charged particles in gas under electric and magnetic fields is derived using the path integral formulation of the Boltzmann equation. Fundamental formulae in the FTI procedure to obtain the velocity distribution and transport coefficients are presented in comparison with those of the path integral method. Under arbitrary conditions of fields and cross sections, this method is quite stable and accurate, due to the procedure based on the normalized starting rate distribution from which the flight behavior is calculated through the time.

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The synergistic behaviour in dielectric gas mixtures containing SF₆ has been shown from (E/N)_lim, that is the E/N at which the net ionization coefficient is equal to zero, and investigated by a Boltzmann equation method. In this paper, the difference between SF₆ and nitrogen, and SF₆ and c-C₄F₈ mixtures, in dielectric strength has been explained by the calculated electron energy distributions and the respective sets of electron collision cross-sections. The dielectric characteristics in SF₆, N₂ and c-C₄F₈ mixtures has been also calculated and discussed in detail.

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Capacitive humidity sensors using polyphenol resin (PPR) were fabricated. Then, the humidity characteristics of PPR were compared with that of cellulose acetate butyrate (CAB).
It is reported by several researchers that CAB is suitable to a humidity sensitizer of the capacitive humidity sensor.
Relative humidity (RH) vs. capacitance (C) curves are almost linear for PPR 72 (phenylene content of 72%), and are non-linear for CAB and PPR 66 (phenylene content of 66%). For all materials, temperature coefficient of C-RH curve is less than 1%/°C. Especially the temperature coefficient is negligibly small for PPR 66. Hysteresis width against humidity cycles are 0.5%, 1.5%, 3% and 2% at maximum in RH equivalent for PPR 72, PPR 66, CAB 38 (butyryl content of 38%) and CAB 50 (butyryl content of 50%), respectively. The response duration time against humidity change is short enough at a relatively low humidity range for all materials. However, it takes 4 min, 4 min, 33 min and 28 min for -1% response in RH equivalent by increasing humidity from RH of 81.2% to RH of 90.7% for PPR 72, PPR 66, CAB 38 and CAB 50, respectively. The humidity sensors of PPR 72 and PPR 66 work stable in 3%. accuracy after kept in 90% RH of 80°C for 100 days. Furthermore, the sensors of PPR 66 can be used even after kept in 150°C for 100 days.

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Statistical calculating programs simulating partial discharge appearance are developed and applied to evaluations of criteria for descrimination of the partial discharges from noises. According to the simulation, clusters of sequential pulses appear at the partial discharge inception voltage, which have never been utilized at an usual pattern recognition of the partial discharges. Two original indexes those are a pair pulse rate and a maximum sequential pulse rate are defined to describe the time sequential features of the partial discharge and their signal distinguishable capabilities from noises are evaluated. A new logical index describing the signal distinguishable capability of an usual φ-q pattern of the partial discharges from the noises is also proposed and compared with those of cluster pulses. The maximum sequential pulse rate gives most sensitive criteria in the bounds of calculating conditions.
A 66kV cross-linked polyethylene cable with an artificial defect is used to detect cluster pulses. By adding noise pulses twice as much as measured partial discharge pulses the usual φ-q pattern criteria becomes powerless but cluster pulse criteria still infomative on the recognition of the partial discharges.

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Relationships of the current-voltage (I-V) characteristic and the flow velocity U in transformer oil have been studied under DG stresses using needle- and blade-plane geometries. Linear plots of V vs. I^1/n (n=2 for the needle and n=3 for the blade) and of U vs. I/V are obtained respectively whatever the polarity of the applied voltage. However, in the case of negative applied voltage, the slope of these linear plots in both geometries changes when V and I exceed their critical values. The change is explained by Kolmogoroff's turbulence theorem both with experimental distribution of flow velocities and with the observation of flow patterns.

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The contributions of the electrohydrodynamic (EHD) motion to the DC electric conduction in insulating oils are presented. The effects of solid/liquid interfaces on the EHD motion has been studied with a mineral oil-polypropylene mixed dielectric and a mineral oil single dielectric. We have observed time dependence of current, schlieren images of EHD motion induced in the oil layer and responce signals of density change in the vicinity of the electrode/oil interfaces after application of step voltage.
The results are as follows: (1) The EHD motion occurs at the positive electrode/oil interfaces when a voltage above critical voltage is applied. (2) A time delay exists between application of step voltage and the onset of EHD motion. The time is inversely proportional to the applied voltage. (3) The EHD motion increases current and produces a peak phenomena in the current waveform. (4) The time difference between peak current time and the delay time is inversely proportional to applied voltage.

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