• Korean Journal of Veterinary Research
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• v.32 no.2
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• pp.239-243
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• 1992

In the present experiment, the blue-green algae, the principal food of the vector snail of Fasciola hepatica were cultured. Mud from good natural habitats was sterilized, made slopes, inoculated with algae from the habitats and maintained in a saturated atmosphere. Under the fluorescent-mercury lamp(100W) at about $20^{\circ}C$ the algal growth was optimal, taking 8 days to fully grow and to be ready for feeding the snails. The algae collected from the habitats and cultured in the laboratory were mainly green.

• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.45-59
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• 1996

Ultrafine powders(UFPs) of aluminum nitride(AlN) have been synthesized by chemical reactions in the nitrogen atmosphere and the gaseous aluminum evaporated from Al powders in thermal plasmas produced by a DC plasma torch. A synthesis system consisting of a plasma torch, a finely-controllable powder feeder, a reaction chamber, and a quenching-collection chamber have been designed and manufactured, and a filter for gathering AlN UFPs produced by the quenching process subsequent to the synthesis is set up. The synthesis process is interpreted by numerical analyses of the plasma-particle interaction and the chemical equilibrium state, respectively, and a fully-saturated fractional factorial test is used to find the optimum process conditions. The degrees and ultrafineness of synthesis are evaluated by means of SEM, TEM, XRD, and ESCA analyses. AlN UFPs synthesized in the optimum process conditions have polygonal shapes of the size of 5-100 nm, and their purities differ depending on collecting positions and filter types, and the maximum purity obtained is 72 wt% at the filter.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.105-106
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• 2008

Nanotube morphology change of Ti-Ta-Zr alloy as Zr content increase has been researched using various experimental methods. Ti-Ta-Zr(3, 7 and 15 wt%) alloys were prepared by arc melting and nano-structure controlled for 24 hr at $1000^{\circ}C$ in argon atmosphere. Formation of oxide nanotubes are conducted by anodizing a Ti-Ta-Zr alloy in $H_3PO_4$ electrolytes with small amounts of fluoride ions at room temperature. Electrochemical experiments were carried out with conventional three-electrode configuration with a platinum counter electrode and a saturated calomel reference electrode. The samples were embedded with epoxy resin, leaving a square surface area of $10mm^2$ exposed to the anodizing electrolyte, 1.0M $H_3PO_4$ containing 0.8wt% NaF.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.486-496
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• 2018

Bimetallic Pd@Ni nanostructure exhibited enhanced co-catalytic activity for the selective hydrogenation of benzaldehyde compare to their monometallic counterparts. Impregnation of these mono/bimetallic nanostructures on mesoporous $TiO_2$ leads to several surface modifications. The bimetallic PNT-3 ($Pd_3@Ni_1/mTiO_2$) exhibited large surface area ($212m^2g^{-1}$), and low recombination rate of the charge carriers ($e^--h^+$). The hydrogenation reaction was analyzed under controlled experiments. It was observed that under UV-light irradiations and saturated hydrogen atmosphere the bimetallic PNT-3 photocatalyst display higher rate constant $k=5.31{\times}10^{-1}h^{-1}$ owing to reduction in the barrier height which leads to efficiently transfer of electron at bimetallic/$mTiO_2$ interface.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.212-216
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• 2021

We investigated the feasibility of hydrogen storage with electrochemically formed VO₂ nanotubes. The VO₂ nanotubes were fabricated through the anodization of vanadium metal in fluoride ion-containing organic electrolyte followed by an annealing process in an Ar-saturated atmosphere at 673 K for 3 h at a heating rate of 3 K /min. During anodization, the current density significantly increased up to 7.93 mA/cm² for approximately 500 s owing to heat generation, which led to a fast-electrochemical etching reaction of the outermost part of the nanotubes. By controlling the anodization temperature, highly ordered VO₂ nanotubes were grown on the metal substrate without using any binders or adhesives. Furthermore, we demonstrated the hydrogen sorption properties of the anodic VO₂ nanotubes.

• Atmosphere
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• v.22 no.2
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• pp.209-219
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• 2012

Extreme heavy snowfall episodes have been investigated in case of accumulated snowfall amount larger than 50 cm during the past ten years, in order to understand the association of low-level stability with heavy snowfall in the Yeongdong region. In general, the selected 4 events have similar synoptic setting such as the Siberian High extended to East Sea along with the Low passing by the southern Korean Peninsula, eventually inducing easterly in the Yeongdong region. Specifically moist-adiabatically neutral layer has been observed during the heavy snowfall period, which was easily identified using vertical profiles of equivalent potential temperature observed at Sokcho, whereas convective unstable layer has been formed over the East sea due to relatively warm sea surface temperature (SST) about $8{\sim}10^{\circ}C$ and lower temperature around 1~2 km above the surface, obtained from RDAPS. Difference of equivalent potential temperature between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually increased before the snowfall period. Instability-induced moisture supply to the atmosphere from the East sea, being cooled and saturated by the upper cold surge, would make low-level ice cloud, and eventually move inland by the easterly flow. Heavy snowfall will be enhanced in association with low-level convergence by surface friction and upslope wind against Taebaek mountains. This study emphasizes the importance of low level stability in the Yeongdong region using the radiosonde sounding and RDAPS data, which should quantitatively be examined through numerical model as well as heat and moisture supply from the ocean.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.12-16
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• 2004

In this study, we have investigated the development of the crystal growth stability and reproducibility for large and high-quality DAST. DAST crystal were grown from a saturated methanol solution by a slow cooling method and DAST was synthesized by the condensation of 4-methyl-n-methyl pyridinum tosylate, which was prepared from 4-pocoline and methyl toluenesulponate and 4-N-dimethyl amino-bezaldehyde in the presence of piperidine. We had synthesized DAST crystals in dry Argon atmosphere in order to avoid the formation of hydride organge co-crystals, DAST$.$$H_2O$. Since DAST molecules crystallize in a humid atmosphere, crystal structure become centrosymmetric, and then second order NLO (nonlinear optical) properties would be disappeared. We fixed the growth orientation of DAST crystal (001) surface. The crystal growth was proceeded at a cooling rate of $H_2O$/day and the cooling period is for 4 days. The dimensions of seed crystal was $2.5\times 3.6\times0.4\textrm{mm}^3$ and we have obtained a DAST crystal with the dimension of $10\times 10.5\times3.0\textrm{mm}^3$. The color of grown DAST crystal is red and it's surface appears to be metallic green.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.29-30
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• 2001

This paper presents some results of plasma nitriding on hard chromium deposit. The substrates were C45 steel and $30~50{\;}\mu\textrm{m}$ of chromium deposit by electroplating was formed. Plasma nitriding was carried out in a plasma nitriding system with $95NH_3{\;}+{\;}SCH_4$ atmosphere at the pressure about 600 Pa and different temperature from $450^{\circ}C{\;}to{\;}720^{\circ}C$ for various time. Optical microscopy and X-ray diffraction were used to evaluate the characteristics of surface nitride layer formed by nitrogen diffusion from plasma atmosphere inward iCr coating and interface carbide layer formed by carbon diffusion from substrate outward Cr coating. The microhardness was measured using microhareness tester at the load of 100 gf. Corrosion resistance was evaluated using the potentiodynamic measurement in 3.5% NaG solution. A saturated calomel electrode (SiCE) was used as the reference electrode. Fig.1 shows the typical microstructures of top surface and cross-section for nitrided and unnitrided samples. Aaer plasma nitriding a sandwich structure was formed consisting of surface nitride layer, center chromium layer and interface carbide layer. The thickness of nitride and carbide layers was increased with the increase of processing temperature and time. Hardness reached about 1000Hv after nitriding while 900Hv for unnitrided hard chromium deposit. X-ray diffraction indicated that surface nitrided layer was a mixture of $Cr_2N$ and CrN at low temperature and erN at high temperature (Fig.2). Anodic polarization curves showed that plasma nitriding can greatly improve the corrosion resistance of chromium e1ectrodeposit. After plasma nitriding, the corrosion potential moved to noble direction and passive current density was lower by 1 to 4 orders of magnitude compared with chromium deposit(Fig.3).

• The Journal of the Korea Contents Association
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• v.14 no.4
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• pp.237-242
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• 2014

In this study, surface characteristics and corrosion behaviors have been investigated in addition to Zr elements on the low elastic modulus Ti-30Ta alloy. Low elastic modulus Ti-30Ta-xZr(x : 3, 7 and 15 wt %) alloys were prepared by arc melting and then heat treated at $1000^{\circ}C$ for 24 hrs in an argon atmosphere. Microstructures of the alloys were examined by field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). Electrochemical experiments were performed using a conventional three-electrode configuration with a sample working electrode, a high density carbon counter electrode and a saturated calomel reference electrode. According to the result of polarization behavior in the Ti-30Ta-xZr alloys, the current density of homogenized Ti-30Ta-15Zr in the passive region was lower than the other alloys.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.161-166
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• 2004

In this research, TiN films has been grown to the stainless steel substrate by ion beam assisted deposition. TiN film was grown to the nitrogen atmosphere of around $10^{-15}$ Torr with Arion bombardment. The chemical composition, color and adhesion of TiN films were examined as a variation of En(ion energy per atom). The N/Ti ratio increased linearly as the increase of En and saturated around 1.2 at high En. As a results, the bright golden color was obtained when En reached a certain value of Ecn. As a results, the N/Ti ratio is about 0.9.