In this paper signal processing using statistical algorithm for vibration measurement is reported. The algorithm uses a statistical feature of standard deviation for sinusoidal vibration and enables higher accuracy than Peak-to-Peak method. Additionally the algorithm achieves accuracy as well or better, with less hardware compared with the FFT method. This method gave good results in simulations and actual measurement values. The method is widely applied for a self-coupling effect sensor and other vibration sensors.

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Accurate measurement of low-frequency AC voltage using a digital multimeter at frequencies of 4-200Hz is a challenge in the mechanical engineering industry. At the National Metrology Institute of Japan, we developed a low-frequency AC voltage measurement system for calibrating digital multimeters operating at frequencies down to 1 Hz. The system uses a single-junction thermal converter and employs a theoretical model and a three-parameter sine wave fitting algorithm based on the least-square (LS) method. We calibrated the AC voltage down to 1Hz using our measurement system and reduced the measurement time compared with that using thin-film thermal converters. Our measurement results are verified by comparison with those of a digital sampling method using a high-resolution analog-to-digital converter; our data are in agreement to within a few parts in 10⁵. Our proposed method enables us to measure AC voltage with an uncertainty of 25 μV/V (k = 1) at frequencies down to 4 Hz and a voltage of 10 V.

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In ultra-low field MRI with optically pumped atomic magnetometer (OPAM), it is required for the direct detection of MR signals with high sensitivity to match the resonant frequency of potassium to that of proton. A ferrite shield box, which has high-permeability and high electric resistance, is able to be utilized to match the resonant frequencies. In this study, analyses of magnetic field distributions in the vicinities of sample and potassium vapor cell of OPAM were carried out. In addition, the uniformities of the magnetic fields in the areas of sample and potassium vapor cell of OPAM and the magnetic field caused by MR signals were evaluated. These analyses indicated that the resonant frequencies of proton and potassium were matched by using the ferrite shield box with a number of combinations of height and thickness. The uniformities of the magnetic fields applied to a sample were found to be improved by placing the ferrite shield box far from the sample. Furthermore, regardless of the height, the magnetic field caused by MR signals was able to be measured.

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Surface hardness of PMMA (poly methyl methacrylate) was improved by low energy nitrogen ion irradiation. It was confirmed that hardness on the surface was improved by increasing the acceleration voltage of ion irradiation. It was thought that this was because the projected range became long and region of cross-link formation became thick. However the depth of cross-link formation was not confirmed. Then, distribution of the cross-link structure in the direction of depth was measured by using XPS (X-ray Photoelectron Spectrometer).
As a result, it was confirmed that the surface hardness was improved on the formation depth of the C-N-C bonds. From this, it was suggested that the modification layer of the cross-link structure became thick the surface hardness became strong.

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Magnetic fluctuations with frequency lower than the local ion cyclotron frequency was observed associated with magnetic reconnection event in TS-3 plasma merging device. Counter helicity merging of spheromaks provides significant ion heating by magnetic reconnection to form high-β field-reversed configuration plasma. The magnitude of the fluctuation observed during and after the counter helicity merging has stronger dependency on ion mass than reconnection speed, indicating that fast ion outflow from X-point would bring about excitation of large amplitude low frequency magnetic fluctuations which may be responsible for direct ion heating.

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Transient effect of magnetic reconnection has been investigated in the TS-4 torus plasma merging device. The two loop merging with pull reconnection converts one common flux to two private fluxes. Under strongly driven inflow, the plasma and magnetic flux inflow exceeded the outflow ones, causing flux and density piled-up in the current sheet. This pile-up effect was found to increase the inflow speed without anomalous resistivity effect. Under strong guiding field, a plasmoid grew in the current sheet during plasma pile-up. When flux pile-up reached a critical value, the plasmoid was ejected from the reconnection region and the reconnection speed transiently increased. The plasmoid ejection made the reconnection rate maximum when its acceleration was maximized.

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The adhesive strength doesn't improve so much even if the surface is activated. It is known that PTFE (polytetra fluoroethylene) is one of the collapse type polymer since the binding energy of main chain is smaller than that of side chain. Accordingly, it is assumed that adhesive strength may improve by suppressing the collapse of structure. It is also expected that introduction of cross-linking structure may suppress the collapse of structure. It was confirmed that a lot of polar radicals were introduced at the surface by nitrogen ion irradiation around 30 eV. Thus, to introduce the cross-linking structure several 100 eV nitrogen ions were irradiated after irradiation of nitrogen with 30 eV ion. As a result, adhesive strength irradiated by 300 eV improved more than that of 1000 eV. From the result of XPS (X-ray-Photoelectron-Spectroscopy) analysis, many C-N-C bonds contributing cross-linking structure was detected at a shallow layer by irradiation of ions with 300 eV. From these results, it is concluded that the depth of cross-link formation is important to improve the adhesive strength.

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This paper describes the evaluations of the non-sinusoidal power measurement standard, including a wideband inductive voltage divider (IVD), shunt and sampling measurement system which are important components in the standard, at the National Metrology Institute of Japan (NMIJ). The power measurement standard measures harmonic voltages and currents up to 50th harmonic for calibrating power generators. In order to achieve uncertainties of less than 60ppm and 80ppm (k=2) for the harmonic voltage and current measurements, the wideband IVD and sampling measurement system in the standard are focused on. Its active power measurement capability has been also evaluated by intercomparison between the Japan Electric Meter Inspection Corporation (JEMIC) and NMIJ.

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Silicone rubber filled with nano-filler was prepared in laboratory-scale for outdoor insulators. Specimen preparation and property estimation were done to improve various properties of silicone rubber by mixing small amount of nano-fillers. This paper deals with the influence of particle type, particle size and dispersibility on various surface properties of silicone rubber filled with nano-scale aluminum hydroxide. Boehmite alumina (AlOOH) and alumina trihydrate (ATH) are used as nano-filler and micro-filler, respectively. Specimens were originally prepared using three kinds of mixing machines such as a planetary mixer, a triple roll mill, and a high-pressure-type mixer. Dispersion state of the fillers was analyzed with a scanning electron microscope (SEM). Hydrophobicity characteristics and tracking characteristics of the specimens were evaluated with a developed artificial acceleration pollution aging test system (AAPATS) and IEC-60112, respectively.

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The nanocomposite material based on polyamide-imide was not able to prevent nano-particles from aggregating up to now, therefore the development of this material was extremely difficult. However we prevented aggregation of nano-particles by developing the hygroscopicity solvent and copolyamide-imide, and commercialized the new partial discharge resistant enameled wire with nanocomposite polyamide-imide insulating material in 2010.
The lifetime of newly developed partial discharge resistant nanocomposite polyamide-imide enameled wire has 1000 or more times compared to general organic enameled wire. Moreover lifetime of new wire is also extremely excellent in the high temperature atmosphere.

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Surface treatment of GaN by pulsed atmospheric microplasma was experimentally investigated. Microplasma was generated with a pair of electrodes which covered with dielectric layer, at relatively low discharge voltage of around 1 kV, and advantage of reducing the power and downsizing the entire plasma system. Electrodes were faced each other with a spacer (thickness 100 um) in between. Streamers were generated between the electrodes, which generate various radicals and ions that could affect a target surface. Contact angles and an analysis by X-ray Photoelectron Spectroscopy (XPS) were measured before and after microplasma to refer GaN surface. Discharge voltage was -1.3 kV, frequency was 24 kHz, treatment time was 10s.

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