In this study, the variations of the important characteristics of solenoid-type RF chip inductors utilizing a low-loss A1203 core material on inductor dimensions were investigated systematically. Four dimensions of the chip inductors fabricated in this work were $1.0\times0.5\times0.5mm^3,\;1.5\times1.0\times0.7mm^3,\;2.1\times1.5\times1.0mm^3,\;and\;2.4\times2.0\times1.4mm^3$ and copper (Cu) wire with $40{\mu}m$ diameter was used as the coils. High frequency characteristics of the inductance, quality factor, and impedance of developed inductors as a function of inductor dimensions were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 6 have the inductance (L) of 12 to 82 nH and exhibit the self-resonant frequency (SRE) of 3.6 to 1.2 GHz. The SRF of inductors decreases with increasing the inductor size while the L increases with the inductor size. The smallest inductors of $1.0\times0.5\times0.5mm^3$ exhibited the L of 12 nH, SRF of 3.6 GHz, and the quality factor of 67 near the frequency of 1.1 GHz. The calculated data predicted the high-frequency data of the L, and Q of the developed inductors well.

The effect of x on microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics for microwave components were investigated. All spcecimens prepared by the conventional mixed oxied method and sintered at $1450^{\circ}C$. Microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-xTiO_2$ ceramics were influenced by $MgTi_2O_5$ phase. Also the microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were dominated with an addition of $CaTiO_3\;and\;SrTiO_3$. The dielectric constant $(\varepsilon_r)$, quality factor $(Q{\times}f_r)$ and temperature coefficient of the resonant frequency $(TCRF,\;\tau_f)$ of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were $12.96\sim70.98,\;5,132\sim186,410GHZ$ and $-35.82\sim+75.96ppm/^{\circ}C$, respectively, and depend on x and addition materials.

[ $TiO_2-Nb_2O_5$ ] sol was prepared using sol-gel method. Crystalline properties of gel powder changed from rutile phase to anatase phase with increasing $Nb_2O_5$ additives at $800^{\circ}C$, while they retained rutile phase regardless of $Nb_2O_5$ additives at $900^{\circ}C,\;1,000^{\circ}C$. They retained amorphous phase from $50^{\circ}C\;to\;400^{\circ}C$, retained anatase phase from $500^{\circ}C\;to\;600^{\circ}C$ and had rutile phase over $700^{\circ}C$ at 1mole% $Nb_2O_5$ additive. After $TiO_2-Nb_2O_5$ sol retained low viscosity with normal chain structure for a long time, its viscosity increased fast with network structure. DTA properties of gel powder had endothermic reaction due to evaporation of propanol and water about $78^{\circ}C$, had exothermic reaction due to propanol combustion about $290^{\circ}C$ and had exothermic reaction due to changing of $TiO_2$ phase about $640^{\circ}C$.

In this paper, we investigated the selective etching rate of amorphous As-Ge-Se-S thin film due to the photoexpansion effect and fabricated the 2-dimensional embossing type diffraction grating hologram. We measured the thickness change with the etching time among NaOH solution after forming 1-dimension diffraction grating. As a results, we found that the selective etching rate were $2.5\AA/s,\;3.3\AA/s,\;3.9\AA/s$ where NaOH solution concentration were 0.26N, 0.33N, 0.36N, respectively. Also after the formation of 2-dimensional diffraction grating by the $90^{\circ}$ degree of circulation on the formed 1-dimensional diffraction grating, we etched selectively during 60sec, among 0.26N NaOH solution and obtained 2-dimensional embossing diffraction grating. As the results of AFM (Atomic Force Microscopy), we confirmed the formation of distinct embossing type 2-dimensional diffraction grating hologram, successfully.

Single-walled carbon nanotubes (SWCNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of methane in $H_2$ over well-dispersed metal particles supported on MgO. The yield of SWCNTs was estimated to be 88.5% and the purities of SWCNTs thus obtained were more than 90%. Peak of the radial breathing mode in the Raman spectrum demonstrated that the diameters of synthesized CNTs are in the range 0.4-2.0 nm. Our results also indicated that MgO support materials are useful to a large-scale synthesis of high-quality SWCNTs. Increasing temperature could remarkably increase the yield and also improve the quality of SWCNTs from catalytic decomposition of methane. The morphologies and microstructures of the synthesized carbon materials were characterized by scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction (XRD).

In order to realize the commercial application of HTSC materials, it is necessary to develop the fabrication process of high Tc oxide superconductor materials with desired shape and for practical application and high critical current density as well as good mechanical strength which can withstand high lorenz force generated at high magnetic field. Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of HTSC materials at liquid nitrogen temperature. Recently some new fabrication techniques have been developed for YBaCuO bulk superconductor with high mechanical strength and critical current density. In this project, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of YBaCuO superconductor, and we reported the production of the YBaCuO high Tc superconductor by the pyrolysis method.

A novel coil gun type actuator has been proposed and tested for its possibility as an actuator for a high voltage circuit breaker by experimental method. The 20kJ capacitor bank with the electrolytic condensers was charged up to 500V and discharged to a couple of 100 turn coils connected with parallel through a thyristor switch. The repulsive force between coil and the actuator made by copper conductor of 20kg reached up to 23,000 N, and over 800J of energy was transferred to the kinetic energy of the conductor. The experimental results showed that the coil gun type actuator has a good possibility for the high voltage circuit breaker.

The low-voltage induction motors have been widely driven by IGBT PWM inverters, ever since it was used to apply variable speed drives. Recently, the insulation failures of the stator windings become critical problems due to the high ratio of dv/dt in IGBT PWM inverters. In this paper, the detailed insulation tests on the IGBT PWM inverter fed induction motor are carried out. Five different types of insulation techniques are used to ti induction motors. The change of the insulation characteristics such as partial discharge, AC current, capacitance, and dissipation factor are compared. respectively In addition, insulation breakdown tests using the high voltage pulse are performed, and corresponding breakdown voltages are analyzed.