Damages on the surfaces of concrete buildings can easily be detected by visual inspection and can be repaired. However, damages inside walls need non-destructive inspection techniques to be detected, located, and identified. There has been a great demand for such techniques particularly after the 3.11 Great East Japan Earthquake. Ground-based synthetic aperture radar (GB-SAR) is a technique that can potentially inspect concrete walls in a non-destructive and non-contacting manner. The paper reports a fundamental experiment with a polarimetric GB-SAR system to detect internal damages of a concrete specimen, which was caused by horizontal loading simulating earthquakes. The results shows that the system does not have enough resolution to visualize individual defects, and the effect of steel rebars installed inside the concrete is so strong that masks week responses. However, polarimetric analysis showed the capability to minimize the effect of rebars by re-arranging polarization basis and to extract week responses. In particular, internal damages could be detected by observing volume scattering component in this experiment.

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Simulation models of magnetic sheets are proposed. The partial fraction decomposition for trigonometric functions is used to obtain the models in the form of Foster I and II realizations, while the formulas for Bessel functions are used to obtain the models in the form of Cauer I. It is shown that the convergence speed of Cauer realization is much faster than that of Foster's. It implies that the circuit behaviors with wide frequency range can be evaluated by using small number of circuits components. Cauer II realization is obtained by transforming impedance functions given by Cauer I. It is shown that the flux behaviors in the magnetic sheets can be properly estimated by Cauer II models. Simulation models for magnetic wires are also presented by the methods mentioned above. The proposed method is applied to the analysis of inverter surge voltage. The results show that the proposed method is adequate for practical use.

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During winter, at the Shonai Airport located at the northern part of Japan, some low-level turbulences caused by tornadoes and downbursts often interrupt takeoff and landing, which is the main source of economic loss. It is well-known that weather radar system is one of the most useful devices for observing various weather phenomena. However, it is difficult for conventional radar systems (range resolution of several hundred meters and temporal resolution of about 5 min.) to detect small scale phenomena (horizontal scale of several hundred meters and duration of several minutes). We have been developing a meteorological Ku-band broadband radar (BBR) which can detect small scale phenomena with high resolution (range resolution of several meters and temporal resolution of about one minute). We construct the advisory system with the BBR for supporting aircraft operation at this airport, and have a comparison between the BBR data and the Flight Data Recorder (FDR) data.

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A 3D lightning mapper consisting of multi LF sensors has been developed to monitor the thunderstorms and charge structure of thunderstorms. We have been conducting observation campaign with the 3D lightning mapper in Kansai, Japan, from October 2012. In this paper, we show 3D source locations of cloud-to-cloud (CC) and cloud-to-ground (CG) flashes and compare with radar reflectivity estimated by a phased array radar with quite high temporal and spatial resolution. Most LF sources are located in high radar reflectivity regions, indicating that the 3D lightning mapper can monitor thunderstorms. It is found that a lightning flash with heavily branches is clearly imaged. With bi-directional leader theory that negative and positive ends of a lightning leader develop simultaneously, we estimate positive and negative charge regions in a thundercloud from LF source locations. Radar reflectivity estimated by the phased array radar support the charge structure estimated by LF source locations.

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We have been developing the Phased Array Weather Radar (PAR) which detects small scale phenomena such as tornadoes and downbursts. PAR is installed on the 13^th floor rooftop of a building in Suita Campus, Osaka University, Osaka, Japan. In this paper, we compare Beam Former method (BF), which is a conventional method in Digital Beam Forming signal processing of array antenna, with Minimum Mean Square Error method (MMSE), which is our proposed method, and discuss simulation results and observation results estimated by each method. In BF, antenna pattern is uniform and unique in the radar system, and its sidelobe level is high. As a result, if there are obstacles, for example high building, or very heavy rain area, the observation results of array antenna are imprecision in the region near them. In contrast, we can turn the null-point to interference wave direction at the same time we turn the mainlobe to the desired signal direction in MMSE. As a result of estimating observation results by each method and comparing each result, we can reduce the influence of clutter by almost 20dBZ.

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Meteorological disasters are caused by the severe weather phenomena like tornadoes or heavy rains. Weather radar is helpful to observe those phenomena. The conventional radar, which has about 500m spatial resolution and about 5 minutes temporal resolution, is not able to catch the detailed cloud growths and movements spatially or temporally. The PAR developed by our research group, which has 100m spatial resolution, can scan over the whole sky within the range of 30km every 10 seconds or within the range of 60km every 30 seconds by applying Digital Beam Forming (DBF). This paper discusses about the evaluation on the observation accuracy of PAR by comparing with other radars and a disdrometer. At first, PAR's reflectivities are compared with reflectivities derived from a disdrometer for the calibration. PAR reflectivities are highly correlated with disdromter reflectivities. Next, PAR reflectivities are compared with those of other radars. In this comparison, PAR reflectivities are also highly correlated with those of other radars. Therefore, it appears that PAR can observe precipitation accurately in high temporal resolution.

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In this paper, we miniaturize the capacitor charger for pulsed power applications. The capacitor charger circuit is constructed by a single chopper circuit using a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). A single chopper circuit has many advantages. However, due to operate by single switching device, operating power per switching device is higher than other topology. Then, a SiC (Silicon Carbide)-MOSFET is used for switching device, and compared to a single chopper circuit using a Si (Silicon)-MOSFET. In this research, we simulated a single chopper circuit concisely and developed the miniature capacitor charger for repetitive pulsed power generator. Charging time of Si-MOSFET charger and SiC-MOSFET charger are 310µs and 300µs respectively.

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Magnetic properties of motor cores are deteriorated due to residual stress occurred during manufacturing process. Therefore, it is necessary to reduce the residual stress in motor cores through stress-relied annealing. As a conventional method, electric furnaces have been used to anneal motor cores. However it takes a long annealing time and requires high running cost for annealing with electric furnaces. In order to improve this method, we have developed a new stress-relied annealing technique with the usage of a low frequency induction heating. This paper presents the effect of the stress-relied annealing on the magnetic properties of ring cores. The low frequency induction heating can be extended the skin depth of eddy currents and achieved uniform heating in annealing.

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Perfluorooctane sulfonate is persistent and useful substance; however energy efficient decomposing methods are urgent needs due to the toxicity of prolonged exposure of PFOS. PFOS in solution cannot be decomposed by hydroxyl radicals but easily decomposed by plasma generated on or in the solution. The voltage polarity is one of the unknown parameters for PFOS decomposition using plasma. Experimental results showed that the plasma sustaining voltages and the decomposition rate of PFOS were not affected by the voltage polarity; however the decomposition energy efficiency and by-product generation quantity was affected by the voltage polarity. Two types of decomposing processes was proposed according to the voltage polarity.

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In recent years, the precise magnetic properties of electrical steel sheet are needed to develop high efficiency electromagnetic devices. An IEC standard single sheet tester is often used for the magnetic property measurement, especially for commercial transactions. But it is not accurate, so is not proper for the material evaluation based on its precise properties data. Therefore, we developed the measurement technique for the precise magnetic properties of electrical steel sheet. In this paper, two single sheet testers are shown. One is according to IEC standard (IEC-SST), and the other, the Stress load type-Single Sheet Tester (S-SST) is originally designed with our measurement technique for the precise magnetic properties. The key technology for evaluation of electrical steel sheet is proposed, using the S-SST and the IEC-SST. In particular, magnetic field strength distribution in measurement area inside exciting coil and solution of H coil specification difference are studied. And the magnetic properties of the S-SST and the IEC-SST are compared.

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Polylactic acid (PLA) is a bioplastic and a biomass material that is made from corn starch, etc. Having studied the potential of PLA as an electrical insulation material, the authors have demonstrated that PLA has high resistivity, high dielectric breakdown strength and other outstanding electrical insulation properties equivalent to those of low-density polyethylene (LDPE) and other petroleum-based plastics within a temperature range from room temperature to approximately 70°C. The degree of crystallinity of PLA was increased by heat treatment, and the dielectric breakdown strength (E_B) and mechanical properties of the obtained PLA of different spherulite sizes were studied. PLA heat-treated at a temperature of 120°C or higher showed rapid increases in spherulite size. At both measurement temperatures of 25°C and 80°C, the E_B showed rapid falls when the heat treatment temperature was 120°C or higher. At a measurement temperature of 25°C, the tensile strength at break and breaking elongation showed rapid falls when the heat treatment temperature was 120°C or higher.

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Quantitative estimation of core loss considering magnetic hysteresis property is strongly required to develop high-efficient electrical machines. This paper presents a novel magnetic circuit model considering magnetic hysteresis. In the proposed model, dc hysteresis loss is calculated by the LLG equation, while classical and anomalous eddy current losses are calculated in the magnetic circuit. It is demonstrated that hysteresis loop under PWM wave excitation can be expressed by the proposed model. The validity and availability are proved by comparing with measured values.

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The LDPE impregnated with acetophenone, one of cross-linking by-products in XLPE, under a high electrical stress of 150kV/mm caused a breakdown with the consumption electric power of κE²=2.3W/cm² which was measured by using the advanced technique combined with the space charge measurement (PEA system) and the external current measurement. This paper discusses on the thermal breakdown model which is occurred when an intrinsic energy, m_dC_v(T_m-T_o)=220J/cm³, required to impulse breakdown of LDPE equals to the supplying electric power, kE²Δt, where m_d is a density of material, C_v a specific heat, T_m a melting point of LDPE and T_o a room temperature, κ a conductivity, E an electric field, Δt a formation time of breakdown. It is found that when the thermal breakdown was occurred, the measured electric power, κE²=2.3W/cm², was consumed in a filamentary higher conductivity path (size; a thickness of specimen of a=100µm, and a cross section of filament of ΔS=100µm×100µm).

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The LDPE impregnated with acetophenone (AP), one of cross linking byproducts, under a high electrical stress of E=150kV/mm caused a breakdown by the consumption electric power density of κE²=2.5W/cm², which was measured by using the advanced technique combined with the space charge measurement (PEA system) and the terminal current measurement. The consumption electric power (κE²) leads to a thermal breakdown of LDPE specimen, where κ is an electric conductivity. The conductivity of LDPE with AP is much increased because the injection barrier of electron carrier from cathode decrease 4.25eV to 2.60eV and the injection barrier of hole carrier from anode also decrease 3.37eV to 2.54eV. These injection barrier height were calculated by Gaussian 09 software of Quantum Chemical Calculation. It is proposed the thermal breakdown mechanism that the conductivity (κ) of LDPE with AP increases, the consumption electric power (κE²) also increases, the temperature of filamentary conductivity path increases to a melting temperature, and then the breakdown is occurred.

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For the diagnosis of cancer metastasis, lymph nodes are selectively removed. In this study, we developed a magnetic probe for intraoperatively detecting accumulation of magnetic fluid. We manufactured a magnetic probe consisting of a permanent magnet and a Hall-effect sensor, and investigated the sensitivity. The results agreed well with the numerical results. In addition, a prototype probe detected 1.6 mL magnetic fluid located at 30 mm from the probe head.

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We have investigated characteristics of radiated electromagnetic (EM) waves from positive and negative partial discharge (PD) in epoxy resin and cross-linked polyethylene. As a result, we found that there is correlation among EM level from PD, positive PD current and electrical tree. Therefore, growth of an electrical tree makes up a lot of positive PD.  Also, we have investigated characteristics of frequency region of radiated EM waves from PD in air, insulating oil and liquid epoxy in addition to above insulators. EM waves were detected in the frequency region of 40-300 MHz from positive and negative PD in epoxy resin and cross-linked polyethylene. Also, EM waves were detected in the frequency region of 40-150 MHz from positive and negative PD in air. And in the case of insulating oil and liquid epoxy, EM waves were detected in the frequency region of 40-150 MHz from positive PD, and 40-250 MHz from negative PD. Frequency region was different depending on materials or polarity of discharge. Results of the study, we considered that the cause is difference of the electric field strength at partial discharge occurring.

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Ozone generators of dielectric barrier discharge (DBD) are mainly used for water and waste water treatment. Recently, they are also used for cleaning of food product machines, semiconductors processes, pulp bleaching field and so on. It is well-known that ozone concentration composed by DBD type ozone generator decreases with time when high purity oxygen used for feed gas. This is named by us, ozone zero phenomenon (OZP). The causes of the phenomena have been investigated experimentally in the world wide industries us. One of the causes is considered as an electrode material by discharge in the generator metal oxides formed from stainless steel electrode.  We have studied the ozone generation characteristics using high purity oxygen as a feed gas and ozone generator of which both electrodes covered with dielectrics. It was found that using only high purity oxygen as a feed gas, ozone concentration decreased from 200g/m³(N) to 54g/m³(N) during about 5 hours. However, adding 0.1vol% of nitrogen into oxygen, ozone concentration increased rapidly over the initial maximum ozone concentration of 216g/m³(N). After that, the concentration of ozone gradually decreased with time. Therefore, adding nitrogen into oxygen has the effect of recovery of ozone concentration in the same generator. The maximum ozone concentration was obtained when 0.1-0.6vol% of nitrogen gas was added to oxygen gas.  OZP is caused by ozone generator even when both electrodes are covered with dielectrics. The metal oxide is produced on electrode is not the cause of OZP. Ozone concentration can be increased by adding nitrogen into oxygen.

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Covering the electrode with a dielectric layer improves SF₆ gas insulation systems. To raise the reliability of this method for application to high voltage power equipment, a mechanism was studied in which the coated electrode has higher breakdown field than a bare electrode by observing the discharge light. By observing the discharge inception point, two things became clear. First, if the harmfulness of micro protrusions on the electrode surface is small, discharges start from a position in the gas space away from the coated electrode surface. Second, the position of the discharge inception point shifts from the electrode surface to the gas space by covering it with a thick dielectric layer.

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