This paper describes the effect of antioxidants mixed in XLPE on electrical tree inception voltage by using the density functional theory (DFT) approach. It already has been demonstrated experimentally that among the four phenolic antioxidants, 3-methyl-6-tert-butylphenol has the highest tree inception voltage. First, it is shown DFT calculation results which are the energy levels, electric dipole moment and 3D electrostatic potential distributions of antioxidants. We could be confirmed that the electrical tree inception voltage increases with increasing the dipole moment of antioxidants, and the inhibitory effect becomes larger when the phenolic antioxidant contains sulfur. The DFT approach is very useful to consider the mechanism of the relationship between tree inception voltage and antioxidants mixed in XLPE.

Reliability in the insulating materials is necessary in order to supply stable power. However, the non-uniform electric field is caused by foreign matters or voids in the insulating material. The deterioration of insulating material is accelerated due to the non-uniform electric field and it finally leads to a dielectric breakdown. It is likely that the space charge distribution is related to the deterioration of the insulating material. The pulsed electro-acoustic (PEA) method can make it possible to detect the space charge distribution and to get the valuable information for the deterioration diagnosis. In this study, a line-plate electrodes system was used to bring non-uniform electric field and the epoxy resin was inserted as the insulating material between the line electrode and the plate electrode. The changes of space charge distribution were observed under non-uniform electric field before the dielectric breakdown. As a result, this study indicates that the charge is injected from the line electrode and the space charge distribution changes due to the deterioration of the epoxy resin.

Recently, as quantum chemical methods such as DFT method have widely investigated on the dielectric and insulating materials, electronic and orbital structures of the materials which contain aromatic groups in the molecular chain have been gradually becoming apparent. From the quantum chemical view points, the styrene group has higher HOMO and lower LUMO levels compared to those of polyethylene, and this means the styrene groups may form a new molecular orbital between the HOMO/LUMO levels of polyethylene as a trap site of electric charges. The influences of styrene groups on the molecule of polyethylene were investigated in 30 years ago as the ethylene-styrene random copolymer manufactured by high pressure method. The content of styrene in the copolymer was said to be less than 1 wt % which gave a most appropriate dielectric and insulating properties, but their properties which relate to molecular orbital such as space charge behavior were less studied then. We have obtained some of commercially available styrene modified polyethylene, and investigated the influences of styrene groups on dielectric and insulating properties theoretically and experimentally. As the results, even more contents of styrene than that of previous studies show a more excellent dielectric and insulating properties than polyethylene.

Cables used in nuclear power plants are required to be flame retardant as a measure of fire protection. Cables with polymer insulation, such as silicone rubber (SiR) insulated cables, flame-retardant ethylene propylene diene rubber (FR-EPDM) insulated cables and flame-retardant cross-linked polyethylene (FR-XLPE) insulated cables, are commonly used as safety-related low voltage cables in nuclear power plants. This paper describes results of flame-propagation tests conducted in accordance with IEEE Std 383-1974 and IEEE Std 1202-2006, and oxygen index measurement tests conducted in accordance with JIS K 7201-2:2007, which were carried out to investigate the effect of pre-aging on flame retardancy of the cables. The samples employed in the tests were un-aged cables and pre-aged cables by accelerated simultaneous thermal and radiation aging to simulate aging in their service life under normal operating environment in nuclear power plants. In addition, decomposition temperatures were measured by thermogravimetry for pre-aged insulation samples of SiR, FR-EPDM and FR-XLPE to evaluate the results of flame-propagation tests and oxygen index measurement tests. As a result of flame-propagation tests and oxygen index measurement tests, flame retardancy of the cables was not degraded by the pre-aging process of this study. From the thermogravimetry, the significant decrease in decomposition temperature due to pre-aging was not observed.

In recent years, understanding of the characteristic mechanism of electrical insulating materials using quantum chemical calculation has attracted increasing interest. Dielectric properties are one of the important properties in practical use of electrical insulating materials, but there is no precedent investigation for the dielectric properties using quantum chemical calculation. In this paper, the relative permittivity of dicyclopentadiene and tricyclopentadiene resin is estimated by mean of density functional theory and Clausius-Mossotti's, Onsager's or Kirkwood's equations. As a result, estimated values of the relative permittivity are in reasonable agreement with experimental ones. In addition, in order to investigate the dependency of estimated values on molecular modeling, the influence of the number of repeating units was examined. As a result, it was found that the estimated values is almost independent of the number of repeating units. In other words, the calculation model for the permittivity prediction may be sufficient for a small molecular chain as dealt with in this paper.

Spacecraft has been operatied in the radiation zone where it is directly exposed by electrons and protons. In such environment, a charging and a discharging phenomena occur in insulating materials on the surface of spacecraft. These phenomena may lead to the deterioration of the insulators and the malfunction of onboard equipments, and consequently they make the life time of spacecraft shorter. Therefore, for high reliability and long service life of the spacecraft, it is important to evaluate the characteristics of charging phenomena of insulating materials for spacecraft at the design stage. In previous research, we investigated electron beam irradiated ETFE (Ethylene-tetrafluoroethylene) and FEP (Fluorinatedethylene-propylenecopolymer), which are used for OSR (Optical Solar Reflector) and wire harness, to evaluate the charging properties of them by the irradiation of the electron. In the research, the space charge accumulation characteristics in the irradiated ETFE and FEP have been observed using PEA (pulsed electro-acoustic) method under high DC electric field. As the results, the generation of electron-hole pairs were confirmed in the electron beam irradiated materials. In this research, we tried to evaluate the dependences of the acceleration energy and irradiation time of the electron beam on the amount of electron-hole pair generated in the sample. As a result, we found that the amount of generated electron-hole pairs increased with increase of both acceleration energy and irradiation time.

As XLPE cable laid in duct is mainly degraded by water-tree, water-tree growth and its affection to breakdown voltage of aged XLPE cable has been investigated. For XLPE cables laid under dry condition (substation, tunnel, etc.) or with water barrier, the growth rate of water-tree is considered to be lower than those laid in duct because of little water invading into the insulating layer. However, few reports related to this issue have been published and the degradation of aged XLPE cable laid under dry condition or with water barrier is not revealed. From these view-points, we investigated the breakdown voltage and the condition of water-tree degradation on removed 33kV XLPE cables laid under dry condition and with water barrier.

Nano composite (NC) materials have a great potential to improve characteristics of electrical rotating machinery insulation systems. In order to understand the contribution of the NC materials on the insulation characteristics, a fundamental study which used semi-conductor field technologies is shown in this paper. The thin NC film is formed on a silicon substrate by a spin coating method. The silica particle dispersion in epoxy is analyzed by SEM. Furthermore, the insulation breakdown is measured and the nanoscale breakdown spots are investigated by STM. The results show that a NC which has a potential of actual application is developed and that the nanoscale method seems to be effective for evaluating NC materials.

In order to change the refractive index of polydimethylsiloxane (PDMS), TiO₂ nanoparticles were added to obtain a TiO₂/PDMS composite. The refractive index of the PDMS composite increased by up to 0.008 by adding 1.0 wt% TiO₂ nanoparticles to PDMS. By 1.0-MeV proton beam irradiation, the TiO₂/PDMS composite shows increased refractive index up to by 0.012 for 1.0 wt% TiO₂/PDMS composite with fluence of 100 nC/mm².

Evaluation method of the magnetic properties of electrical steels under compressive stress along magnetizing direction using single sheet samples was studied. In this measurement, the friction due to retainer plates for applying normal pressure to prevent buckling should be considered. Experimentally, influence of the friction tended to be stronger with the increase in the pressure onto the retainer plate, and with the decrease in the stress along the magnetizing direction. Numerical analysis of mechanical stress indicated that the effects of friction coefficient and sheet thickness were significant. The method to revise the influence of the friction covering wide range of stress along the magnetizing direction was proposed. Furthermore, the effect of the normal pressure on the magnetic properties was evaluated and correction method to obtain true stress in magnetizing direction was studied.

This study deals with structural coloration caused by a subwavelength periodic structure modeled on a tree-like structure that comprises a lamella and ridge on the scales of a Morpho butterfly wing. For a three-dimensional scattering problem of the structure for an unpolarized incident wave, we formulate a color specification procedure to calculate the reflection spectrum in visible wavelengths using the matrix eigenvalues method and obtain the tristimulus values of standard RGB or chromaticity coordinates (x, y) from the spectrum. Moreover, we obtain numerical results for the structural coloration observed from the azimuthal direction. Results show that by considering periodicity during analysis, coloration varies against the azimuthal direction. Therefore, a periodic structure is found to significantly affect iridescent color.

This paper describes the pasteurization of liquid whole egg using intense pulsed electric fields (PEF) combined with mild heat. Four kinds of liquids as solvents including carboxymetyl cellulose solution (CMC), CMC solution with adding lipoproteins extracted from liquid whole egg (CMC+), liquid whole egg (LWE), and centrifuged LWE for reducing lipoproteins (LWE-) were compared for the effectiveness of the PEF pasteurization. The liquids including enterobacter aerogenes (10⁷ /mL) were subjected to a number of PEF with an amplitude of 30 kV/cm or 50 kV/cm. Pre- and post-PEF thermal treatments with a temperature below 55℃ were used to enhance the killing effect. Our experiments show that the bacteria reduction ratios of the pasteurization using 30 kV/cm PEF for CMC, CMC+, LWE and LWE- were 6.6, 2.4, 1.4 and 1.6, respectively, whereas the reduction ratios were all more than 6 when the increased field of 50 kV/cm. Only bacteria in CMC solution were effectively killed compared to other liquids which includes lipoproteins more or less. Numerical analysis of the electric field indicates the presence of lipoproteins in the vicinity of bacteria lessens the bacterial membrane potential, which results in weakening the killing effect.

Solar irradiance is one of the important environmental parameters in agriculture and various other fields. Photovoltaic (PV) simple pyranometer has been developed as an inexpensive device measuring the solar irradiance. However, its output had slightly increased with increase of temperature due to temperature characteristics of PV cell. Therefore, it is desired that temperature compensation is given to the PV pyranometer.

To compensate the output of PV pyranometer, the output resistance with temperature dependence was designed with negative temperature coefficient (NTC) thermistor. The field test was indicated that the output of the PV pyranometer with temperature compensation function was comparably constant against the cell temperature.

This letter describes the comparison of education in electric circuits between Toyota College and Nagaoka College in National Institute of Technology. Textbooks that one of this letter's authors has written have been used for an education of electric circuits in both colleges. It was carried out that a survey how students to answer to questions of electric circuits by using same tests in both Toyota College and Nagaoka College. It is considered that correct ways to questions of electric circuits were mainly shown in answers of students who have had much syllabus time in electric circuits.