This paper introduces that iron losses of electrical steel sheets on inverter excitation are underestimated when insufficient sampling frequency, which is reciprocal of time interval of sampling, is chosen for magnetic characteristics evaluation. On low sampling frequency, minor loops on B-H plots (B: magnetic flux density, H: magnetic field intensity) are not constructed or becomes small, because sharp waveform of inverter voltage cannot be represented properly. Therefore, the iron losses corresponding to internal area of B-H curve become small. On the lowest sampling frequency used for this evaluation, the iron loss is underestimated about 20 %.

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This paper presents influence of angle of principal stress on vector magnetic properties of a non-oriented electrical steel sheet under alternating magnetic flux conditions. The magnetic flux density and magnetic field strength vector under alternating magnetic flux conditions are measured by changing the angle of the principal stress. From these results, it was clarified that amplitude and the angle of the loci of the magnetic field strength vector, and magnetic power loss differ by changing the angle of the principal stress. It is possible to improve the magnetic properties of the non-oriented electrical steel sheet by controlling the angle of the principal stress.

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Since the magnetic field of spherical symmetry does not exist in nature, it is understood that the electromagnetic field of spherical symmetry does not exist, either. This paper examines the electromagnetic field of the spherical symmetry which is produced by periodically changing the electric charge. It was found that the electromagnetic field of spherical symmetry was represented by a scalar potential of the spherical wave. It was also found that the scalar potential forms standing wave of spherical symmetry.

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“Iwami-kagura” is the traditional dance arts in the western Iwami district of Shimane. It is dance performance about many topics “The Izumo myth”. It is special dance with story characteristics and a dynamic movement. The crisis of the tradition by the local depopulation has become a serious problem these days. And young children tend to keep away from a physical science. Therefore we suggest “Iwami-kagura robot performance contest” in this study. This contest is that performance groups of handmade robots compete on the basis of the theme of the Iwami-kagura. In this way we can let young children show an interest in local traditional arts and technology through manufacturing.

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We have proposed a convenience fabrication technique of carbon nano-tubes (CNTs) transistor. Dip coating method using metallic solution was employed to deposit metal catalysts of CNTs on the source and drain electrodes on SiO₂ coated Si substrate at a low temperature. This method does not require vacuum system and a long process time. After the CNTs fabrication by chemical vapor deposition, we evaluated the morphology of CNTs by scanning electron microscopy and their electrical property as a CNT field-effect-transistor (FET). The CNTs formed suspended bridges between the source and drain electrodes. Field effect mobility of the CNT-FET was measured to be 3000 cm²/Vs from its transfer curve. On the basis of the electrical property, the CNT-FET with high field effect mobility can be obtained.

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The 3D vibration and 3D magnetostriction of a model transformer core made up of grain-oriented electrical steel sheets were studied by using laser Doppler vibrometry, an accelerometer and strain gauges. The following results were obtained. The magnetostriction of the transformer core at the T-joint and the corner area including the joint part displayed several times larger amplitude than that of a single sheet under sinusoidal excitation. The out-of-plane vibration of the transformer core showed a much larger amplitude than the in-plane vibration. It is considered that the out-of-plane vibration was the main cause of acoustic noise. The amplitude of in-plane vibration of the core can be explained for the magnetostriction amplitude in the in-plane direction. On the other hand, the out-of-plane vibration was tens of times larger than the vibration calculated from the magnetostriction amplitude in the out-of-plane direction. Furthermore, the same result, that out-of-plane vibration is larger than in-plane vibration, was also obtained by measuring a practical transformer core, and the frequency spectrum of acoustic noise presented a similar frequency spectrum to that of out-of-plane vibration.

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Water tree is a significant degradation mode of power cable with polymeric insulation. As those installed long time ago is supposed to be degraded with water trees, their diagnosing technique is being required for effective replacement. Especially locating the degraded region along the length would be helpful, since only a part of the cable line is usually degraded. As inside of the water tree is filled with trap sites, it is polarized with a certain distribution of relaxation time when a DC poling voltage is applied. Although its depolarization process after removing the poling voltage is determined by ambient temperature, applying a “depolarizing voltage” with the opposite polarity can accelerate the process. If a short pulse propagating through the cable is employed as a depolarization voltage, we may locate the water tree through looking at the time-resolved pulse response. This would lead to a diagnosing method with spatial resolution. In order to retain 100 m of spatial resolution, the response should be as sharp as 1 µs. As a preliminary study, a coaxial communication cable was employed as the specimen. An experiment using 405 m-long cable, with 5 m of degraded length in the middle, was performed. Two cables, one of which included degradation and the other did not, were oppositely coupled with a current transformer in order to cancel a rush current when the pulse voltage was applied. A sharp current response was observed, suggesting that a rapid depolarization took place. No such response was seen when the cable specimen was not applied with a poling bias voltage. The spatial resolution was equivalent to 50 m. We concluded that the technique is quite feasible.

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A new evaluation system of water purification by using photocatalyst has been developed and tested. The developed system, which uses a light-to-frequency converter photo IC, can solve the problems of dynamic range and precision, which are presented in a conventional evaluation system using an absorption spectrophotometer. In addition, the method of applied voltage to photocatalyst with light irradiation for water purification has been proposed.

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We have developed the secondary electron emission (SEE) with wide energy range for spacecraft thermal control materials. SEE yield measurement is very important for analyzing charge accumulation on the spacecraft surface. Therefore, we are developing the measurement system without the deceleration voltage and enable to obtain the characteristics of the SEE yield on those materials irradiated by an electron beam with energy of 200 eV to 10 keV. Furthermore, SEE yield on the aging materials is also important for determination of end of life of spacecraft. 50 keV electron gun for aging was attached on the developed chamber, we can create the seamless system form the aging to SEE measurement.

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An artificial underground coal gasification (UCG) gas, which is a mixture of N₂, CO₂, H₂ and H₂S, is decomposed using a packed-bed dielectric barrier discharge, and the desulfurization characteristics of the UCG gas are investigated. It is found that 81% of H₂S in the UCG gas is desulfurated at input energy of 46 Wh without H₂ decomposition. It is also found that CO, SO₂ COS and CS₂ are produced as by-products during the plasma desulfurization of the UCG gas.

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Influence of pulse width and water conductivity on decolorization of organic dye by discharge inside bubble in water was investigated. Two types of pulsed power generator, a magnetic pulse compression circuit and an inductive-energy storage system using semiconductor opening switch, were used to generate high voltage pulses with various pulse widths. Indigo carmine was employed as a specimen to evaluate decolorization efficiency. Argon gas was used to identify the influence of hydroxyl radicals produced by the discharge on decolorization efficiency. Energy efficiency for the decolorization increased with decreasing the pulse width owing to the reduction of ohmic loss.

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[in Japanese]

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