• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1724-1726
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• 2002

A novel ozonizer has been developed using a high-frequency surface discharge and a high purity alumina ceramic as its dielectric component. A thin ceramic layer, cylindrical in form, is adhered by a film-like induction electrode. An ac exciting voltage of frequency to 0.6 kHz from 1.0 kHz and $6{\sim}9kV$ peak-to-peak is applied between the electrodes to produce a stable high-frequency silent discharge for generation of ozone. A substantial reduction of the exciting voltage is also enabled by using a thin alumina ceramic layer. As a result, the ozonizer can easily produce ozone concentration($128g/m^2$ for oxygen) and power efficiency(360g/kWh for oxygen) without using a special enrichment means.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1794-1797
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• 1997

The preflashover light emission of the $SiO_2$-dielectric system behavior under high electric field is discussed. Time dependence of the voltage drop, electrical current, and light emission, are analyzed for high-purity $SiO_2$-vacuum systems under impulse voltage stress. We will summarize the experimental results showing the main feature of the time-dependent system response up to breakdown.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1041-1042
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• 2006

High heat-resistant Al-Fe-V-Si and Al-Fe-V-Si-X rapidly solidified powder metallurgy (RS P/M) alloys have been developed under well-controlled high purity argon gas atmosphere. The $Al_{90.49}Fe_{6.45}V_{0.68}Si_{2.38}$ (at. %) RS P/M alloy exhibited high elevated-temperature strength exceeding 300 MPa and good ductility with elongation of 6 % at 573 K. Reduction of $H_2O$ partical pressure in P/M processing atmosphere led to improvement in mechanical properties of the powder-consolidated alloys under elevated-temperature service conditions. Ti addition to the Al-Fe-V-Si conduced to enhancement of the strength at room temperature. The tensile yeild strength and ultimate strenght were 545 MPa and 722 MPa, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1284-1285
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• 2006

We reported a P/M soft magnetic material with core loss value of $W_{10/1k}=68W/kg$, which is lower than that of 0.35mm-thick laminated material, by using high purity gas-atomized iron powder. Lack of mechanical strength and high cost of powder production are significant issues for industrial use. In order to achieve both low core loss and high strength by using inexpencive powder, the improvement of powder shape and surface morphology and binder strength was conducted. As the result, the material based on water-atomized powder with 80 MPa of TRS and 108 W/kg of core loss (W10/1k) was achieved.

• Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.191-195
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• 2012

We report here the use of high-speed countercurrent chromatography (HSCCC) in the preparative isolation and purification of the bioactive component, fucosterol, from Pelvetia siliquosa. A crude extract was obtained by ultrasonic extraction of powdered P. siliquosa using methylene chloride and was then subjected to separation and purification by HSCCC, coupled with evaporative light-scattering detection. Preparative HSCCC was performed successfully using a two-phase solvent system, n-heptane:methanol (3:2, v/v), to obtain 10.96 mg fucosterol with 96.8% purity from 50 mg of crude extract; the recovery rate was approximately 90.5%.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.111-117
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• 2002

The high quality and a nearly stoichometric growth of $Cd_{1-y} Zn_y$/Te(y＝0.04) epilayers have been successfully grown on GaAs substrate by hot wall epitaxy (HWE) by optimizing the growth condition including the preheating treatment and Cd reservoir temperature. The relationship between quality and thickness was examined and best value of FWHM from X-ray rocking curve of 121 arcsec are obtained. Also, emission peaks related to the recombination of free excitons such as the ground state and the first excited state were observed in the PL spectrum at 4.2K. The ($A^0$, X) emission related to Cd vacancy and deep level emission was not measured. These results indicated that the grown CZT/GaAs epilayer was high qualify and purity.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.206-208
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• 2002

A novel ozonizer has been developed using a high frequence surface discharge and a high purity ceramic as its dielectric component. And A cylindrical thin compound ceramic catalyst in reactor is adhered to inside of the film-like outside electrode. An ac exciting voltage with frequency to 0.6 kHz from 1.0 kHz and $4{\sim}6$ kV of peak-to-peak is applied between the electrodes to produce a stable high-frequency silent discharge for generation of ozone. A substantial reduction of the exciting voltage is also enabled by using a thin ceramic. As a result, the ozonizer can easily produce ozone concentration(50 $g/m^3$ for oxygen) and power efficiency(240 g/kWh for oxygen) without using a special enrichment means.

• Journal of Powder Materials
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• v.26 no.3
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• pp.195-200
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• 2019

Whisker-type magnesium hydroxide sulfate hydrate ($5Mg(OH)_2{\cdot}MgSO_4{\cdot}3H_2O$, abbreviated 513 MHSH), is used in filler and flame-retardant composites based on its hydrate phase and its ability to undergo endothermic dehydration in fire conditions, respectively. In general, the length of whiskers is determined according to various synthetic conditions in a hydrothermal reaction with high temperature (${\sim}180^{\circ}C$). In this work, high-quality 513 MHSH whiskers are synthesized by controlling the concentration of the raw material in ambient conditions without high pressure. Particularly, the concentration of the starting material is closely related to the length, width, and purity of MHSH. In addition, a ceramic-coating system is adopted to enhance the mechanical properties and thermal stability of the MHSH whiskers. The physical properties of the silica-coated MHSH are characterized by an abrasion test, thermogravimetric analysis, and transmission electron microscopy.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.238-243
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• 2005

Mg and Mg-based alloys are most important hydrogen storage materials. It is a lightweight and low-cost materials with high hydrogen storage capacity. However, the formation of hydride at high temperature, the deterioration effect, the hydriding and dehydriding kinetics are bad factor for application. In this study, Mg and Ni have been produced by hydrogen induced mechanical alloying(HIMA) process. The raw materials, Mg(purity 99.9%) chip and Ni(purity 99.95%) chip was prepared by using a planetary ball mill apparatus(FRITSCH pulverisette 5). The balls to chips mass ratio(BCR) are 30:1. The hydrogen pressure induced 2.0MPa and milling times were 12, 24, 48, 72, 96 hours with a rotating speed of 200rpm. X-ray diffraction(XRD) analysis was made to characterize the crystallite size and misfit strain. The crystallite size measured by laser particle size analysis(PSA). Microstructure changes were investigated by scanning electron microscopy(SEM) and the transmission electron microscopy(TEM). The hydrogen storage properties were evaluated by using an Sivert's type automatic pressure-composition-therm(PCT) apparatus.

• Journal of the Korean Society of Radiology
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• v.7 no.1
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• pp.31-36
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• 2013

The radioactive gas radon ($^{222}Rn$), which is generated from the decay process of uranium ($^{238}U$) originating from the soil of more than 85 percent higher the porosity of the soil, the soil can radiate out the possibility that many isotopes. In order to protect the human body from radon, above all, the development of accurate measurement techniques to formulate appropriate measures should be followed. This study Gamma-ray spectrometry using a high purity germanium (HPGe) detector, if you want to measure radon unstable the nature radiation of the background problems can be reduced, radium and radon daughter nuclides after radioactive equilibrium leads to Radon concentration was measured, the soil samples from the Gamma-ray emitting nuclides, and the energy spectrum is analyzed.