Previously, we have proposed the sampled pattern matching method in order to search for the current distributions in biological systems from local magnetic field measurements. This method is now applied to defect estimation problems in conducting materials. In the present paper, defects are. regarded as equivalent potential sources due to discontinuity of the conductivity at defect positions. The equivalent potentials depend on the externally applied potential source so that this functional relationship between the equivalent and applied potential sources leads to a modified sample pattern matching method named the projective sampled pattern matching method. This new method provides a fairly good result even in the case of multi-defect problems.

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Large scale superconducting magnets are planned to be used in diverse areas of science projects which need high. magnetic field level around 10T. As superfluid helium (HeII) near atmospheric pressure can reach a lower temperature near 2K and has far better thermal conductivity and larger heat capacity, it would improve the performance of the magnets considerably. As the coolant of superconducting magnets serves also as an electrical insulation medium, it is necessary to study the dielectric strength of HeII. In this study, breakdown characteristics of pressurized superfluid HeII were investigated experimentally in uniform and non-uniform electric fields. The breakdown field strength mea sured under uniform field condition increases with a shorter gap length and pressure. With a positive point electrode, glow corona discharge is observed beyond a critical gap length. At a lower temperature, the positive corona appears with a shorter gap length and the breakdown voltage increases. No corona discharge is observed with a negative point electrode. The breakdown voltage is always higher with the negative point than positive one. No apparent change in the breakdown characteristics is observed during phase transition from normal liquid helium to superfluid helium.

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When a high pressure argon gas from 3 to 150 ata was irradiated by afocused XeCl excimer laser light with the maximum power of 15MW, a hot and dense plasma was produced. The dense plasma produced at the focal spot developed not only backward but also forward to the focal spot, which differed from one produced by visible laser light. The backward plasma length was calculated on basis of the breakdown wave and the radiation supported shock wave mechanisms, and agreed with the experimental one. At high pressures, the breakdown wave is dominant, while the radiation supported shock wave is predominant at low pressure. The backward plasma length produced by ultraviolet laser light was nearly equal to that produced by visible laser light. However, the total plasma length including the forward plasma length became to be about twice than that by visible laser light.

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The leakage current and the surface flashover characteristics of silicon bulk in a vacuum ambient are discussed for two kinds of sample with the distinct surface treatments: the etched surface sample, and the unetched surface sample. The experimental results show that the surface conditions of sample are a main factor to determine these characteristics. The ohmic current is only observed for the unetched surface sample due to the presence of the defect levels at the surface. The surface flashover phenomena can be explained by Joule heating during the earlier stages of a flashover event and by current filament during the later stages of a flashover event, respectively. There is a evidence to show that the current filament flows from the bulk of contacts with a depth longer than the Debye length toward the surface of a specimen.

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The relative intensities of the emission spectra from a local discharge on an electrolytic solution surface, which simulates the surface of wet polluted insulators, set in the chamber were measured. The air pressure in the chamber was changed in the range of 53-101kPa to simulate the environment of wet polluted insulators of overhead lines in mountains. The resistivity of electrolytic solution was changed from about 80 to 700Ω• cm. At first, 50% flashover voltage of the solutlon surface was measured. Subsequently, the gas temperature in the local discharge under an impulse voltage of positive polarity was estimated from the comparison of the experimental values with calculated values of the relative intensities of the emission spectra. As a result, it was found that the flashover voltage is in direct proportion to the 0.13-0.34 power of the air pressure and as the resistivity of electrolytic solution drops the influence of the air pressure on the flashover voltage are reduced, and the gas temperature in the local discharge rises with a reduction of the air pressure, regardless of the resistivity of electrolytic solution.

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This experiment was carried out to investigate the effect of Mg²⁺ substitution for Zn²⁺ on the magnetic and physical properties of anisotropic Pb-Zn system W-Type hexagonal ferrite magnets. It was found that magnetic properties of Pb-Zn W-type compounds substituted Mg²⁺ for Zn²⁺ were improved, especially, anisotropy field HA of Pb-Zn-Mg magnet increased as compared to that of Pb-Zn-ones. The optimum condition of making magnets and some properties of typical specimens are as follows: chemical analysis composition-Pb1.21 Zn1.43Mg0.49Fe²⁺0.02Fe³⁺15.9O27;semisinteringcondition1, 200°C×2hinair;sinteringcondition1, 100°C×0.5h in air; Magnetic and physical properties are Jm=0.364T, Jr=0.335T, HcJ=92.31kA/m, HcB=91.51kA/m, (BH)max=17.8kJ/m³, Tc=332°C, HA=966.6kA/m, KA=1.76×10⁵J/m³, and ηB=34.2μB.

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Optical and electrical properties for LB films of Spiropyran (SP) dyes (SP 98 and SP 1822) and their structure are investigated. SP dyes change from SP to photomerocyanine (PMC) forms as a result of UV irradiation. The UV-irradiated SP dyes change from PMC to SP forms again by visible irradiation or heattreatment. Polarized reflection spectra of SP Langmuir films and absorption spectra for the SP LB films are measured. The structure is investigated from their results and the surface pressure-area isotherms. Thermally stimulated current (TSC) measurements are used to examine the electrical properties of the SP LB films. The TSC for the SP films is found to be due to the dipolar depolarization. The TSC of the SP 98 LB films strongly depends on their structure, and exhibits reversible changes caused by the isomerization. The TSC for the SP1822 LB films, however, dose not change clearly by the isomerization. It is estimated that the TSC due to the dipolar depolarization depends on how the molecules are packed in the LB films, and that the microscopic behavior of the molecule may be influenced by its surrounding space.

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