Crystallized AlN thin films have been successfully prepared by pulsed laser deposition. In particular, the roughness on the film surface has been studied. The roughness has been found mainly due to the droplets and precipitates. It is found that droplets remain in the film and that precipitates grow from the film. With increasing substrate temperature, precipitates do not appear and the film surface becomes smoother. However, many precipitate nucleuses remain in the film. Relative dielectric constant of the film is typically 9.4 at 1 MHz.

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Presently the finite element method is widely used in the field analysis. It is easily applied to arbitrary mesh points and curved boundaries. On the other hand, it is believed that the finite difference method is applicable primarily to rectangular meshes and that it is difficult to fit the mesh points to curved boundaries. Most of simulation programs for field analysis are written by use of the finite element method. The finite difference method seems to be out of date. This evaluation is not fair to the finite difference method.
In this paper, the author likes to make it clear that the finite difference method is applicable to arbitrary mesh points with high accuracy. The finite difference equations of 4th and 3rd order approximation are derived. An example of coaxial electrodes is numerically solved and successfully demonstrates the feasibility.

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This paper describes experimental results of polarization charge density and residual charge density on PET-film/plane-electrode contact with a thin air layer by a pulsed electroacoustic method. In this method, the air layer has an important role as an acoustic barrier to separate the charge on the film from the charge on the electrode. When a dc applied voltage exceeded a critical level, the polarization charge density deviated from its theoretical value. The quantity of the deviation had a good agreement with the quantity of increase in the residual charge density after short-circuiting. These results suggested that some true charges were trapped at the surface states of PET by the voltage application and they could not be returned to the electrode by their own internal field. Critical field strength across the air layer for trapping was calculated from the results. True charge density on the electrode surface could be also measured by the use of this method.

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The novel features of electrochemical actuators fabricated using cylindrical polypyrrole (PPy) fibers prepared by electrochemical polymerization techniques are described. A Ni wire with a Teflon-made slender pipe was used as a working electrode. If the inner wall side (contacting surface with electrolyte when PPy was polymerized) was insulated and the redox was carried out, the PPy fiber bends toward the outer side, but the bending was not completely observed when the outer wall side was insulated. Although such an anomalous bending in PPy-fiber actuator can't be explained satisfactorily at this stage, we speculate that the bending phenomena are due to the difficulty of dopant transfer between the inner and outer wall sides.

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In this paper, a biological tri-medium spherical model which consists of tissue, its membrane and extra-tissue is employed, and detailed distributions and characteristics of the induced current in the modeled structure are calculated by using a semi-analytical solution developed for this model. It is demonstrated how both the change in the thickness and electrical properties of the bio-membrane and the difference in the conductivities between the inner and outer substances significantly affect the current passing through the membrane and the resultant profiles of the induced current. Those analytical results consist with the experimental ones suggesting the influence of the practical membrane, and point out the important role of the bio-membrane on the induced current characteristics under the specific membrane conditions.

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In nonlinear dielectric properties on cells, the harmonics of response waves have particular patterns for cell activity. In order to measure this activity, it is important to examine the difference of the responses in each growth phase of cells. In this paper, at first, for finding adequate condition in the measurement, we studied voltage and frequency characteristic in nonlinear dielectric properties. Based on this result, the activity of yeast cells was measured in each growth phase, and a particular pattern was shown in each growth phase. We also discussed the relationship between the number of cells and nonlinear dielectric properties in each growth phase.

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The higher order sampling of electron energy distribution function in Monte Carlo simulation (MCS) using Legendre polynomial and B-spline, called Legendre Polynomial Weighed Sampling (LPWS) developed by Ventzek and Kitamori(J. Appl. Phys., vol. 75, pp. 3785-8, 1994; one dimensional), is extended into two (2D) and three(3D) dimensional LPWS in this work. The spatio-temporal variations of energy and velocity distributions of electrons are respectively obtained by 2D and 3D LPWS. It is found that energy and velocity distributions of electrons obtained here are in excellent agreement with those obtained by conventional sampling method, namely, simple counting of electrons. It is also found that the energy and velocity distributions by LPWS give detailed information of electron behaviour in relaxation process and near electrodes and good statistics with smaller number of electrons sampled and with wider size of bin than the conventional sampling method.

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In conjunction with the previous experiments to study the effect of peroxide decomposition products and antioxidants (AOs) in XLPE insulation on electrical tree generation, authors conducted experiments to examine the tree suppression of phenolic AO. Experiments were conducted using XLPE slabs containing 4 kinds of phenolic AO. Among the specimens containing these AOs, the specimen containing 4, 4' thiobis (3-methyl-6-tert.-buthylphenol) was found to show the highest tree inception voltage. To examine the reasons of the significant increase of tree inception voltage of the specimen containing 4, 4' thiobis (3-methyl-6-tert.-buthylphenol), further experiments were carried out using XLPE specimen containing both phenolic AO and sulfur-containing AO. The result demonstrated that the tree inception voltages of specimens containing both phenolic and sulfur-containing AOs are higher than those of the specimens containing either only phenolic or sulfur-containing AO. Taking the schemes of auto-oxidation of polymeric materials into consideration, the roles of antioxidants in XLPE dielectrics was discussed. It was presumed that the great increase in the tree inception voltage of XLPE specimen containing 4, 4' thiobis (3-methyl-6-tert.-buthylphenol) could be due to the synergetic effect between the phelolic AO and the sulfur-containing AO.

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A new algorithm of the analysis of electron swarm parameters in gas based on the dispersion relation of the Boltzmann equation is presented. The hydrodynamic dispersion curve is obtained by solving the eigenvalue problem of the Boltzmann equation. It is shown that TOF parameters (both of α and ω parameters) of electron swarm can be easily and exactly derived by the least square curve fitting of the polynomial expansion of a dispersion curve. Some recent calculating results on SF₆ gas are presented.

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Pulsed high voltage with variable pulse duration was applied to a discharge reactor with a needle-plane electrodes, and the NOx removal performance in N2/NO was measured. Moreover the discharge luminous intensity of N2 2nd positive band (SPB) was measured as temporal and spatial distribution. The relationship between NOx removal performance and the luminous intensity of N2 SPB were analyzed with regard to pulse duration and applied voltage. The analyses show the following: (1) The NOx removal efficiency decreases in longer duration than 200ns because the energy injected after 200ns is not effectively used for N radical production. (2) The NOx removal efficiency decreases with increase of applied voltage from 16kV to 22kV. (3) The luminous quantity of N₂ SPB has a linear relationship with NOx removal in N2/NO. From this relationship, the temporal and spatial distribution of the NOx removal reaction can be estimated. For one of the application of this estimation, the effect of shortened pulse duration was analyzed.

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In order to improve the soft magnetic properties of SuperSendust I, [SS(I)], we tried to decrease the grain size by RF sputtering using an Ar+N₂ mixed gases. An SS(I) thin film prepared in pure Ar plasma shows the following magnetic properties; saturation magnetization, Ms=1.52T, coercive force, Hc=3.18×103A/m, in-plane magnetic anisotropy, K_//=5.4 ×10³J/m³, average grain size, t=16.6nm and exchange stiffness constant, A=12.2×10^-13J/m.
SS(I)-N thin films prepared in Ar+4%N₂ plasma show good soft magnetic properties such as H_C=0.16×10³A/m, μr=520, K_//=2.7×10³J/m³, t=10.7nm and A=4.96×10^-13J/m. And it was also found that coercive force, Hc of SS(I)-N films decrease with decreasing grain size, tand in-plane magnetic anisotropy, K_//, and Hc are related to tand K_// by following equations; Hc∝t6 and Hc∝K_//⁴. This suggests that RF sputtering in Ar+N₂ plasma can improve the soft magnetic properties of SS(I) thin films.

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We have observed a Coulomb crystal composed of the dust particles levitated in the plasma-sheath boundary region at a low gas pressure of less than 1.3Pa (10 mtorr). The dust particles form a crystal with the triangular structure above the electrode, making in one horizontal layer. The mean interparticle distance is about 500μm, and the Coulomb coupling parameter Γ is estimated to be about 500-1000. The vertical position of the Coulomb crystal can be controlled by changing the electron density ne and/or the biasing voltage V_b. A decrease in n_e and/or an increase in V_b result in moving the Coulomb crystal upward. In this paper, we will show the detailed analysis on the levitating position of the Coulomb crystal, by taking account of the gravity and the electrostatic force acting the dust particle, which was estimated precisely based on the sheath theory.

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We have been investigated NOx removal by superimposing barrier discharges for exhaust gases from diesel engine. Several superimposing barrier discharges reactors has been proposed, the superimposing barrier discharges methods are useful for NOx removal.
We proposed a reactor in which the gap area is filled as single layer of glass plates and spherical barrier beads. We expect that surface and silent discharges are generated simultaneously in the same space. In this paper, the effect of the barrier beads on the NOx removal in our reactor is experimentally investigated. Firstly, the condition with barrier beads is very effective of NOx removal. Secondly, the influences of some parameters show that the best condition of discharge reactor needs both barrier plates and one layer of barrier beads.

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In this work, the effect of blend on physical and electrical properties of low-density polyethylene has been investigated. The two kinds of low-density polyethylene (LDPE) whose densities were evaluated to be 0.9179g/cm' and 0.9192g/cm', respectively, were used and blended according to the different blend ratio. The five kinds of specimens were classified according to the blend ratio which was determined by the weight percentage (wt%) of the LDPE with 0.9192g/cm' to the total weight. In the X-ray diffraction patterns, two peaks appear at 2θ=21.4° and 36.2°. In the case of the (020) plane in the diffraction peak at 2θ=36.2°, the crystal size is enlarged according to blend up to the blend ratio of 50wt%. From these results, it is found that the crystal size which is perpendicular to the (020) plane has the largest one at the blend ratio of 50wt%. The blended LDPE of 50wt% shows the lowest impulse breakdown strength, F_olmp at 30°C. However, the F_olmp of the blended LDPE of 50wt% is higher than that of original LDPE-A and LDPE-B. The blended LDPE of 50wt% has the highest F_olmp at 90°C. It seems that the F_olmp is associated with the changes of crystal size. The DC breakdown strength, Fmx, of the blended LDPE little depends on the blend ratio at all temperature.

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Plasma etching characteristic of LiNbO₃ has been investigated. Etch rate increased in propotion to the atomic weight of inert gas in CF₄+inert gas(He, Ne, Ar) plasma. Etch rate increased by removing a mixing layer, such as LiF, by an ion bombardment effect in CF₄+Ar plasma. As etch rate was extremely low in Ar+H₂, it was understood that F radical is contributing to etching of LiNbO₃. Etching profile of the surface of crystal by CF₄+Ar+H₂ plasma was remarkably smooth similar to the non-etched surface. An anisotropic etching that had a high aspect ratio could be materialized in CF₄+Ar plasma. Futhermore, waveguide pattern that had a comparatively high aspect ratio and etching profile of the surface was smooth could be realized in CF₄+Ar+H₂ plasma.

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A new method for measuring the transient potential distribution of insulating material surface on which surface discharge propagates is developed. The measuring system consists of a BGO Pockels crystal, an Ar ion laser, a beam expander, a streak camera and a CCD camera. The potential profile on the BGO crystal plate along a linear path of 50mm in maximum length is measured with high space and time resolution: 50μm and 2ns in minimum resolution. From the measured potential profiles together with the electric field computation, the charge density of a surface discharge can be estimated. The experimental results obtained from the potential distribution measurement of positive surface discharge are summarized as follows: The propagating direction component of electric field in the stem of a positive surface streamer is 8-9kV/cm. The developing velocity of the streamer initially reaches 108cm/s just after its inception and decreases down to 10⁷cm/s while propagating.

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We developed a composite conductor-backed single layered electromagnetic wave absorbers of composite materials (spinel-type Ni-Zn ferrite, SiO₂) which can operate in the frequency region between 1 and 10 GHz. Both the complex permittivity and the complex permeability for the composite ferrite obeyed Lichtenecker's logarithm mixed law. A composite ferrite with a suitable thickness have the higher absorption frequency range than both Ni-Zn ferrites and Ba ferrite absorbers. The center absorbing frequency can be changed by changing the mixing ratio of SiO₂, the thickness, or the composition of Ni and Zn. The absorption band width is almost independent on the thickness of the composite ferrite in the wide frequency range. The range of absorbable thickness becomes wider than that of Ni-Zn ferrite. The density and the hardness is improved by adding B2O3. The conductance value, however, increases and the center absorbing frequency is shifted to the lower frequency in proportional to the density. The conductance value can be reduced by adding a small amount of CoO.

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Space charge electrons transport a considerable fraction of current in magnetically insulated transmission lines (MITLs). When MITL has geometrical discontinuity, the interaction between the disturbed electrons and non-linearly coupled electromagnetic field makes their behavior difficult to predict. In this paper, the power flow through those MITLs is discussed using a particle simulation code and an analytical model. The results show that the space-charge electrons tend to maintain the effective impedance of the transmission lines, by changing their distribution and boundary of the space charge flow. Although a fraction of the space charge flow shunts the gap when the discontinuity is larger than the critical value, the total current upstream the discontinuity is still preserved.

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Pulsed glow discharge is one of the candidates for the ion source plasma because it can easily generate large volume plasma even for a short time. This paper describes the characteristics of a transient glow discharge with high current using a low impedance circuit. A low inductance capacitor of 1.89μ F was used in this experiment. The voltage between electrodes and consumed energy were obtained by calculation of circuit equations and measurement of discharge current and static breakdown voltage. The gas used is dry air. As the experimental results, the transient glow discharge with high current above one hundred ampere was generated for several microseconds. It was clarified that cathode fall voltage under this experimental condition is approximately 320V which agrees with the value of normal glow discharge. The glow-to-arc transition occurs when the consumed energy in the cathode fall region reaches almost 35mJ in the present experimental conditions.

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To study the effect of additives on water tree generation, experiments of water tree generation in LDPE and XLPE containing nonionic surfactants were carried out. Among the materials studied some kinds of nonionic surfactant with small HLB value were discovered to have the effect of water tree suppression. In addition to the preliminary experiment of examining the effect of water tree suppression, two kinds of another nonionic surfactant with HLB value smaller than 6.5 were investigated. The result of the experiment demonstrated that the surfactants examined showed a significant decrease of bow-tie and vented type water tree generation. On the basis of the result of the experiments, the mechanism of water tree suppression of surfactants was discussed. It was presumed that the surfactant in hydrophobic polymeric materials form micelles, which could accept the excess moisture in the dielectric material under voltage stress and suppress the generation of water tree.

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The reconstruction theory that enables one accurately to estimate some sets of three parameters, such as an energetic depth of carrier trap E_t, an escape frequency factor v and the charge carrier density n_t, from thermally stimulated current curves without peak is applied to experimental data. The specimen of naphthacene doped anthracene single crystal was excited by Q-switched ruby laser pulses. Impurity naphthacene forms clear trap sites for both electron and hole, which has been partially replaced from the hole trap site observed mainly even in purified anthracene crystals. Coexistence of the hole trap sites from both materials has been confirmed. Additionally, the state to state transition process has been recognized. The v values of about 10⁷ s^-1 for hole and about 10³ s^-1 for electron were first evaluated from partial data without peak obtained experimentally.

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We describe for the first time the basic illumination characteristics of lighting source using 10cd-class InGaN-based LEDs (an efficacy of 151m/W) under a driving condition of AC 100V at 60Hz. Several hundred white LEDs with series connections were arrayed on a glass epoxy substrate and were driven by adjusting a current of less than 20mA under the AC 100V. The dependence of temperature and injection current on both the emission spectra and intensity were measured. The white LED array indicates distinct two electroluminescence peaks at 460 and 555nm at room temperature, which are related to the recombination emissions from the InGaN MQW blue LED and from the YAG: Ce phosphor, respectively. We have obtained a maximum luminous intensity of about 10000lx at a distance of 30cm from the LED array, which is sufficient for the practical application. After operating for 1 hr, a temperature of the LED array increased up to about 65°C without a cooling system.

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NOx removal technology by non-thermal plasma has been investigated so far, and many investigations have revealed the NOx removal performance of various type of discharge, energy efficiency, effect of additives, co-operative effect of selective catalyzer and so on. Now it is important to establish the design method of these NOx removal systems. This paper describes a design method of these systems for NOx removal in exhaust gas from diesel engine. The knowledges on exhaust gas of diesel engine, thermal conductivity of high speed gas flow and the efficiency of NO removal at various NO removal rate are necessary in the design procedure. A system was designed according to this design method and the system was constructed and tested.

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Recently, the usefulness of using parallelogram coil, has been reported in eddy current sensor or eddy current testing. This coil has the peculiar distribution of the magnetic field which can not be produced by a circular coil. Then, in this letter, the rhombic coil which is one of the parallelogram coils is taken up, and the singlelayer winding coil without hurting the accurate shape in the production, is noticed. And the exact calculation formula of the self-inductance of this coil is shown using the coefficient like Nagaoka's coefficient.

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