SF₆ is used as a main insulation gas for gas-insulated switchgears (GIS), but it has recently become a gas to be restricted because of its greenhouse effect. Up to now, we have studied the insulation characteristics of compressed N₂ and CO₂ as a possible SF₆-alternative gas. As GIS are subjected to very fast transient voltage due to incoming lightning surges or at disconnector switching operation, it is necessary to clarify the sparkover voltage-time (V-t) characteristics in the short time region. In this report, we describe the V-t curves ranging from 30ns to 10μs for high pressure (0.6 and 1.0MPa) N₂ and CO₂ obtained by applying square impulse voltage. We next studied the V-t curves for standard lightning and oscillating impulses for the same experimental conditions. Based on these results, we investigated the possibility of quantitatively estimating of the V-t curves for these waveforms by applying the “equal-area criterion”. The minimum sparkover voltage estimated by the criterion very well agreed with the measured characteristic in all conditions studied, and thus it has become clear that the quantitative estimation of the sparkover characteristics is possible for high pressure N₂ and CO₂.

抄録全体を表示

The decomposition characteristics of phenol in an aqueous solution by the exposure of a pulsed-discharge plasma are investigated for different electrode configuration, applied voltage, and the humidity and composition of a background gas. It is likely that OH radicals are responsible for the decomposition of phenol in the solution for all kind of background gases. In pure O₂, the decomposition rate of phenol increases due to the generation of O and O₃, and in pure N₂, OH radicals, produced by N₂ excited in metastable state, contribute to the phenol decomposition. In N₂-O₂, the decomposition rate of phenol stays lower values, since NO_x, produced by the pulsed plasma, reduces O₃ concentration and the production of the NO_x inhibits O₃ production. In Ar-O₂, the decomposition rate of phenol rises with an increase in the mixture ratio of Ar. It is likely that excited Ar atoms are responsible for the decomposition of phenol in the solution at higher mixture ratio of Ar. Further, no significant difference in the decomposition rate is found between the pulsed discharge and a DC corona discharge.

抄録全体を表示

We have investigated the estimation of dielectrics location based on the measured capacitance using long distance measurement electrodes with a shield and additional electrodes. In order to investigate the estimation method, the numerical technique was developed for calculating the capacitance between long distance measurement electrodes using finite element analysis. In the paper, we will discuss and propose the estimation method of the location of two dielectrics using a capacitor of long distance parallel electrodes with additional electrodes.

抄録全体を表示

Possibility of the deep etching using plasma reactive ion etching (RIE) without an etching-mask (mask-less) for -Z and +Z parts formed on the same surface by partially polarization reversing LiNbO₃ single crystal polarized in the direction of c-axis is investigated. NF₃/H₂ mixture gas was used. The etching rates, depths and the profiles of etched surfaces were evaluated by atomic force microscopy (AFM) and optical microscope. The etching rate for -Z surface was larger than that for +Z surface. The extension of +Z domain by the partially polarization-reversing was observed. Applying the high voltage quickly for the partially polarization-reversing, the area of +Z domain was extended compared with applying voltage slowly. Apparent step at the boundary between -Z and +Z parts formed on the same surface was observed. Using NF₃/H₂ mixture gas, segments are removed efficiently. It is concluded that RIE etching using NF₃/H₂ mixture gas is suitable for processing of LiNbO₃ crystal surface without a etching-mask compared with CF₄/H₂ mixture gas.

抄録全体を表示

The purpose of this study is to prepare high-quality TiO₂ thin films suitable for dye-sensitized solar cells using the electrophoresis method. A high-quality TiO₂ thin film without crack could be deposited by using highly dispersed colloidal solution of TiO₂ fine particles. Highly dispersed colloidal solution was prepared using mechanical milling (MM). Two electrodes of electrophoresis were set perpendicular or parallel to horizontal plane. Optimum preparing condition to disperse TiO₂ fine particles using MM could be found. Under this condition, homogeneous TiO₂ thin film was deposited on ITO glass. The open-electromotive force and short-circuit current of dye-sensitized solar cell show excellent reproducibility.

抄録全体を表示

It is reported that metastable excited particles affect the breakdown properties of nitrogen gas under low pressure extended over a long period. The purpose of this study is to confirm the influence of metastable excited particles with the high pressure condition and to reduce the influence by metastable excited particles. In the experiment, the delay time was measured and number of primary electron was evaluated. The test was carried out in N₂/NO, N₂/CO₂, N₂/SF₆ and N₂/NO/SF₆. The decrease rate of primary electron number supplied by metastable excited particles is higher in N₂/NO than in N₂/CO₂. In N₂/NO/SF₆, it was more effective than two mixture gases.

抄録全体を表示

For electrical insulation diagnosis, it is necessary to obtain information about the electric field distribution and the space charge distribution in insulation materials. We have investigated the measurement of nonuniform electric field vector distributions in liquid dielectrics using an original method based on electrooptic Kerr effect and CT method. We developed a optical system that could measure electric field distributions in about 1 ms. In this study, when the DC voltage pulse of 50 ms width was applied to a sphere-to-plane electrode system, electric field vector distributions on some measured planes were measured at intervals of 1 ms. The distribution after a while from applying the voltage pulse seemed to be disturbed. It was considered that the “disturbance” was caused by the change of the density of the liquid due to moving of the liquid with certain carriers. The observation of the time that started the disturbance would be able to give the behaviour and electric characteristic of the liquid.

抄録全体を表示

Generation of space charges in polymeric dielectric materials is known to be affected by such inclusions as cross-linking byproducts, antioxidants and moisture. Authors reported previously that the negative heterocharges in XLPE are generated under the existence of acetophenone and sulfur-containing antioxidants. In this research the authors performed further experiments using samples containing DCP and three kinds of antioxidants to examine the mechanism. Negative heterocharges near the positive electrode were detected in samples containing both DCP and the antioxidants when those samples were soaked in acetophenone. The negative heterocharges were not detected in samples containing either DCP or the antioxidant, even when the sample was soaked in acetophenone. These results demonstrate that the heterocharge is generated by the combined effect between acetophenone and substance produced by interaction between DCP and antioxidant. Considering results of experiments measuring the amount of heterocharges in samples that had been heat-pressed at different temperatures, the mechanism of negative heterocharge generation in polymeric dielectric material is inferred.

抄録全体を表示

This paper describes an accuracy estimation of low frequency electric fields induced in a human head model calculated by the FMM-SCM-V (fast-multipole surface-charge-simulation method for voxel data) by comparing them with the true fields calculated by the EMMM-PT (equivalent multipole moment method with polar-coordinates translations). The head model is composed of seven spheres and the spheres are composed of cubic voxels having 2, 1, 0.5, or 0.34mm side length. A square-coil current (1A, 50Hz) induces eddy field in the model. The number of voxels, the number of elements, and calculation time were 106,575,801, 4,936,874, and 82 minutes, respectively, when 0.34mm size voxel model was analyzed. In this case, the maximum value and the standard deviation of the electric field error vector in gray matter region were less than 19% and 0.89% , respectively. In addition, they were less than 2.9% and 0.33%, respectively, when we intended to estimate spatially averaged field strength in a (0.34x11)³ mm³ volume region.

抄録全体を表示

The effect of momentum addition by a dielectric-barrier discharge was experimentally investigated. At first, flow induced by the discharge on a flat plate was investigated. Velocity profile was visualized by the smoke-wire technique and measured by a hot-wire anemometer. Maximum velocity was several meters per second at 1mm above the plate. Induced flow affect the velocity profile of boundary layer on the plate. Secondary, separation control for wing surface flow was investigated using a 9cm chord NACA0015 in a wind tunnel at 20m/s of air stream velocity (Re˜10⁵). Barrier discharge electrode was set on the leading edge of the wing. Separation angle was increased by 4 degrees and the maximum of the lift coefficient was improved by 17% with discharge power of 0.4W.

抄録全体を表示

We developed composite electromagnetic wave absorbers dispersed aluminum fine particles in polystyrene medium and evaluated those properties in order to realize single layer electromagnetic wave absorbers with the good absorption property in the GHz region. Polystyrene particles with two kind of diameters (approximately 200 μm or 1 μm) and aluminum fine particles were mixed by mechanical milling. Mixture was heated above the melting point of polystyrene and then cooled naturally in the air. The frequency characteristics of the complex relative permeability, the complex relative permittivity were calculated from values of the scattering parameters of the coaxial line loaded with a sample of a toroidal-core shape. Both the magnetization and the magnetic loss increased proportional to the volume mixing ratio of aluminum particles up to approximately 34 vol% for samples made of polystyrene particles with approximately 200 μm or 1 μm diameter. The diamagnetism was almost frequency independent and the magnetic loss decreased with increasing frequency for all samples. These results were in agreement with qualitative theoretical prediction.

抄録全体を表示

Liquid medicines like organic solvents are mainly used for conventional surface modification technologies. They change the characteristic of surface by removing particles or changing bonding by oxidizing and inducing functional groups. High reactivity oxidants are easily produced by atmospheric pressure non-equilibrium discharge. Oxidants produced in discharge are selected intentionally to select the feed gas, applications for various materials are expected.
Gas dependence for polyimide film treatment was estimated by using atmospheric pressure non-equilibrium discharge constituted blades to plate electrode with dielectric. It was clarified that the condition of high humidity condition of feed gas had good effect for decreasing the contact angle after treatment, depending on the experimental condition, addition of 3 % H₂O had effect as same as applying about 3.5 times of electric power. And more, highly electric power discharge using N₂ gas or humid gas had effect for decreasing the contact angle.

抄録全体を表示

We developed a cloud profiling radar, named FALCON-I, transmitting frequency-modulated continuous wave (FM-CW) at 95 GHz for high sensitivity and high spatial resolution ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith at this moment. The radar can observe clouds up to 20 km in height with a resolution of 9 m. Beam size of the antenna is as small as 0.2 degree of arc, which corresponds to 15 m at the range of 5 km. Observation results showed that the sensitivity of -34 dBZ is realized at 5 km in range, and good spatial resolutions.

抄録全体を表示

The development mode of the AC tree can be classified into three modes; (i) straight mode, (ii) isotropic mode and (iii) selected branch mode. The development of the tree in diffusion mode means that an envelope of the tips of the branches spreads as diffusion. This development has been considered. An AC tree in silicone rubber sample has disappeared after applied voltage. Behavior of the disappearance of trees is different in 2-dimensional (2-D) and 3-dimensional (3-D) sample in which needle electrode system was set up. The branches of 2-D tree are survived longer than the branches of the 3-D tree.

抄録全体を表示

Plasma CVD is a candidate technology to fabricate an optical polymer waveguide. It can deposit a film on any surface geometry and any material of substrate at temperature under 200 deg.C in vacuum process. Also, it provides good thickness controllability and uniformity of the deposition film. In the present study the effects of deposition temperature on film properties, those are refractive index, deposition rate, and molecular structure, are discussed. The refractive index decreases with elevating deposition temperature. The logarithm of deposition rare increases proportionally with the reciprocal temperature and the gradient of that depends on the ratio of double bond in monomer sources. The gradient does not change by using CF₄ instead of Ar as gas mixed in plasma, though the deposition rate increases about 5 times. Langmuir adsorption isotherm explains the temperature dependency of deposition rate. We speculate that the deposition rate increase due to precursor increasing by mixing CF₄ to plasma and due to dangling bonds increasing in the surface of deposition film by F radicals. And we also speculate that the precursors incorporated into the polymer are selected on a substrate by absorbed sites and absorption energy.

抄録全体を表示

We have designed and implemented the “Virtual Laboratory” on the computer systems. Some of the implemented systems are Web-based learning environments where server/client model and Java technologies are adopted. The subject of electronic circuits is the most essential one in the department of electrical and electronic engineering. However, it is a difficult subject for students to understand the basic therory, technical term and electronic circuits design. In this paper, we will describe the study support system for the electronic circuits with observable V-I characteristics using Java.

抄録全体を表示

This paper shows the new driving method for self turn-off devices of high power. The driving circuit by this method consists of mainly three transformers, switching circuits at these primary side and passive components like as diode, capacitors at these secondary side. Because all soft circuits of low power like as switching controller, signal receivers can be set at these primary side, conventional measures at the grounded side against outer noises and surges come to be much effective. This new method makes use of diodes as passive switches to prevent outputs of d. c. circuit from shorting through those secondary windings.

抄録全体を表示

The output voltage of an eddy current displacement sensor (EC displacement sensor) depends on the heat treatment of the measuring object. The EC displacement sensor must detect a displacement of several tens of μm to allow the examination of the change in output voltage due to the heat treatment of the measuring object. Thus, we measure the relative permeability and resistivity of four objects made of chromium molybdenum steel that have undergone different heat treatments (initial condition (INT), salt quenching (SAQ), annealing (ANL), and vacuum furnace cooling (VFC)). In addition, we examine the relationship between the heat treatment of the measuring objects and the output voltage characteristics of the sensor at a displacement between the measuring object and the sensor of 1 mm. The result shows that the relative permeability of measuring object varies between 35 and 80, and resistivity varies between 0.18 μΩm and 0.35 μΩm due to different heat treatment conditions. The sensitivities of the sensor after SAQ and VFC treatments of the measuring object are 82.0 V/m and 73.0 V/m, respectively; thus, the difference is -11%.

抄録全体を表示

When steep-fronted surge voltages are generated and applied to a motor by an inverter drive, higher voltages are distributed at turn-to-turn insulations than those of a motor supplied by line voltage. In addition, the voltage waveforms are quite different, especially pulse widths of them are narrower than those of a motor supplied by line voltage. This paper describes partial discharge and electrical lifetime characteristics of turn-to-turn insulation when pulse voltages are applied. As a result, it is found that partial discharge inception voltage increases, the number of partial discharges decreases and lifetime of insulations increases when pulse widths of applied voltages decrease as narrow as those of turn-to-turn voltages of motors fed by inverter drives. These results can probably improve a present design and a quality assurance of materials and motor insulations for inverter drives in the future.

抄録全体を表示

Igneous rocks generally involve positive hole pairs (PHPs), a kind of lattice defects also known as peroxy links: O₃X-OO-YO₃ with X, Y = Si⁴⁺, Al³⁺ etc. When a portion of such a rock block is stressed or heated, PHPs are deformed and positive holes (p-holes) are activated. They are defect electrons corresponding to the O^- electronic state in the O^2- sublattice and can spread away into unstressed portion. Currents and positive surface electrifications detected in laboratory stressed igneous rocks can be explained by the p-holes. When the p-holes are activated in the Earth's crust accompanied with seismic or volcanic events, they would lead to anomalous electromagnetic phenomena and could affect our electronic communication.

抄録全体を表示

In this paper, the evaluation method of anisotropic absorber panels is discussed. Linearly polarized wave incidence - circular polarized wave reflection measurement to evaluate the anisotropy of absorber panels is proposed. The reflection characteristics of the anisotropic absorber panels is described.

抄録全体を表示

Recently, correct value of the spin-magnetic moment of the electron due to electric current was obtained by the present authors. The current was expressed as transition matrix element between positive energy and negative energy solutions of Dirac equation. The possibility of the change of the spin-magnetic moment in the semiconductor was also pointed out. Following that results, we roughly estimete the rate of the change for the InSb-type semiconductor.

抄録全体を表示

In this paper, the spatial distribution of the reflectivity of an one layered type wave absorber is analyzed by using FDTD method. The reflectivity from the near field to the far field is examined in the case of changing the distance from the surface of the absorber and the size of it. As a result, it is confirmed that the tendency of the reflectivity converges to a steady value in the far field though it shows intricate behavior in the near field. Moreover, the reflectivity is decreased and the difference between the near field and the far field is increased as the size of the absorber becomes smaller.

抄録全体を表示

We study sterilization of bacteria in water using pulsed streamer discharge of gas phase. This method enhances efficiency of water treatment by spraying pretreatment water in a streamer discharge area. In this paper, yeast was sterilized because we assumed a case that fungus like mold existed in wastewater. As a result, colony forming units decreased rapidly for 2 minutes of the processing time, and all yeast sterilized by 45 minutes of the processing time.

抄録全体を表示

Novel plasma acceleration method using transverse rotating magnetic field (RMF) was proposed and investigated using small pre-experimental setup. Interaction between the steady azimuthal current driven by the RMF and the radial bias field will generate axial electromagnetic force, which is expected to provide effective plasma acceletation. Plasma with density of n_e > 3 × 10¹⁸[m^-3] generated by the RMF was observed to have axial internal magnetic field, which is considered to be generated by the azimuthal current of electrons rotating synchronously with the RMF.

抄録全体を表示