• YAKHAK HOEJI
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• v.56 no.2
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• pp.74-79
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• 2012

Citrate-capped silver nanoparticles (AgNPs) are widely used in industry, consumer products and medical appliances. However, information on the toxicity, environmental fate and toxicokinetics are not enough. In this study, stability of citrate-capped AgNPs was investigated using different types of isotonic solution, which is important in the toxicokinetic study by the exposure route of intravenous injection. Size, morphology, zeta potential and ion formation were investigated in isotonic solutions for the physico-chemical characterization of AgNPs. Aggregation and precipitation of AgNPs were observed in saline or phosphate-buffered saline while they were stable without precipitation in 2% glycerol of isotonic solution. The average size of AgNPs in 2% glycerol was 6~10 nm, which was almost same as that in water-based suspension of AgNPs. Zeta potential was ranged from -30 mV to -60 mV, which was in the range of original stock AgNPs. The stability was maintained during the whole experimental period of 48 hours. Furthermore, the stability was not changed in different temperature (10~36$^{\circ}C$) and at different concentrations (10~1,000 ppm). The osmolarity of the AgNPs suspension was $299{\pm}1$ mOsm/kg which was in isotonic range. These data suggest that AgNPs in 2% glycerol solution can be used for the preparations of intravenous injection for toxicokinetic study without undesired disturbance of blood isotonicity.

• The Korean Journal of Mycology
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• v.49 no.3
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• pp.413-416
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• 2021

In July 2019, damping-off symptoms of young Fischer's ragwort (Ligularia fischeri) plants were observed in four vinyl greenhouses of a farmer located in Taebaek, Gangwon Province, Korea. This disease occurred in 20-30% of plants in the vinyl greenhouses investigated. Nine isolates of Rhizoctonia sp. were obtained from the diseased plants. All the isolates were identified as Rhizoctonia solani AG-2-2 (IIIB), based on morphological, cultural characteristics, and anastomosis test. Three isolates were used for artificial inoculation test on Fischer's ragwort. Pathogenicity of these isolates was confirmed on the plants with the inoculation tests. Damping-off symptoms observed on the inoculated plants were similar to those observed in the diseased plants in the vinyl greenhouses. This is the first report of R. solani AG-2-2 (IIIB) being the causative agent in damping-off in Fischer's ragwort.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.162-167
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• 1987

Four component $Ag_2S$-PbS-$PbHAsO_4-Cu_2S$ and three component $Ag_2S$-PbS-$PbHAsO_4$ electrodes have been prepared and evaluated for the direct measurement of monohydrogen arsenate. The 3.0 : 0.5 : 1.0 : 0.25 (mole ratio, $Ag_2S$:PbS:$PbHAsO_4:Cu_2S$) composition is superior in terms of potentiometric response, stability, rapidity of response and reproducibility. Testing was done over the concentration range $10^{-1}$~$10^{-4}M\;HA_SO_4^{2-}$in 0.1F NH4Ac-NH4OH buffer solution at pH 8.50 with constant ionic strength. Interfering ions were $CN^-,\;I^-,\;S^{-2}$ and $Cl^-$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.84-91
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• 2002

The stochiometric composition of $AgGaS_2$/GaAs polycrystal source materials for the $AgGaS_2$/GaAs epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal $AgGaS_2$/GaAs has tetragonal structure of which lattice constant an and Co were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$/GaAs epilayer was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$/GaAs by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively. The crystallinity of the grown $AgGaS_2$/GaAs epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$/GaAs epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by $\alpha=8.695{\times}10^{-4}$ eV/K, and $\beta=332K$. From the photocurrent spectra by illumination of polarized light of the $AgGaS_2$/GaAs epilayer, we have found that crystal field splitting ${\Delta}Cr$ was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.133-136
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• 2001

In this paper, we investigated the diffraction efficiency of polarization holography using by amorphous $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ multi-layer thin films by He-Ne laser. Multi-layer structures were formed by alternating a layer of meta1(Ag) and chalcogenide( $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ ). The holographic grating in these thin flims has been formed using a linealy polarized He-Ne laser light (633nm). The diffraction efficiency was investigated the two sample of $Ag/As_{40}Ge_{10}Se_{15}S_{35}-7$ layers and $Ag/As_{40}Ge_{10}Se_{15}S_{35}-15$ layers. As the results, we found that the diffraction efficiency of $Ag/As_{40}Ge_{10}Se_{15}S_{35}-7$ layers and $Ag/As_{40}Ge_{10}Se_{15}S_{35}-15$ layers were 1.7% and 2.5% respectively.

• Proceedings of the KIEE Conference
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• 2004.07e
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• pp.134-136
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• 2004

The results of investigations of $Ag_2Te$ crystal is presented. $Ag_2Te$ crystal was grown by the Bridgman method. The $Ag_2Te$ crystal was an monoclinic structure with lattice constance a = 8.1686 A, b = 9.0425 ${{\AA}}$, c = 8.0065 ${{\AA}}$. Hall effect shows a n-type conductivity in the $Ag_2Te$ crystal. The electrical resistivity values was $1.080e^{-3}{\Omega}cm$ and electron mobility was $-5.48{\times}10^3cm^2/V{\cdot}sec$ at room temperature(RT).

• Economic and Environmental Geology
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• v.24 no.4
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• pp.347-361
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• 1991

The Sangeun ore deposit is located in a volcanic belt within the Gyeongsang Basin in south western Korea. The ore deposit is of representative epithermal Au-Ag quartz vein type developed in lapilli tuff. This paper presents the mineralization with special emphasis on mineral zoning of the deposits. Principal points are summarized as follows: (1) Four stages of mineralization are recognized based on macrostructures. From ealier to later they are stage I(arsenopyrite-pyrite-quartz), stage II(Au-Ag bearing Pb-Zn-quartz), stage III(barren quartz), and stage IV(dickite-quartz). (2) Electrum principally occurs with arsenopyrite and galena in stage II, and has chemical compositions of 72.9-67.1 Ag atom %, and has Ag/Au ratio of 2.69-2.04. (3) Sphalerite varies in its FeS content according to the mineralization stages; 22.03-18.60 mole % FeS and 1.33-0.23 mole % MnS in stage IB, 16.11-8.64 mole % FeS and 1.33-0.23 mole % MnS in stage II. (4) Alteration zones of mineral assemblage, from the vein to the wall-rock, consist of sericite - quartz - pyrite, sericite - quartz - dickite, sericite - chlorite plagioclase respectively.

• Asian Journal of Turfgrass Science
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• v.12 no.4
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• pp.211-220
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• 1998

Cellulose-degrading fungi were idenfied as Rhizoctonia solani AG2-2(IV), T. harzianum and C. cochliodes. Rhizoctonia solani AG2-2(IV) grows better in the acidified media of pH 4 and 5 than pH 6 and 7. Mycelial growth of T. harzianum and C. cochliodes was also higher in pH 4 and 5 than in pH 6 and 7. In order to relate the above findings to nutrient utilization, mycelial growth of R. solani AG2-2(IV) are evaluated with various carbon sources. R. solani AG2-2(IV) grows well in the order of mannose, cellobiose, glucose, xylose and arabinose. However, mycelial dry weights of T. harzianum were 98.7, 78.0, 72.3, 43.7 and 32.3mg in glucose, mannose, cellobiose, xylose, and arabinose, respectively. Mycelial dry weight of C. cochilodes was 118, 65, 57, 49, and 16mg in mannose, cellobiose, xylose, glucose, and arabinose, respectively. Result of cellulase assay of R. solani AG2-2(IV) and soil fungi was reffered as, R. solani AG2-2(IV) produced more cellulase on CMC substrate than on CEL and secretes more enzyme in floated condition than in water-immersed condition. T. harzianum secreted less amount of cellulase than R. solani AG2-2 and C. cochliodes. T. harzianum produced no enzyme on CEL under water-immersed condition. C. cochliodes produced similar amounts of cellulase on either CMC or CEL under both water-immersed and floated condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.632-635
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• 2004

The purpose of this paper is to investigate the effect of arc current and contact velocity on the erosion of silver-based contact materials to be used in low voltage circuit breakers. The opening velocity during breaking, which is constant, ranges between 2m/s to 6m/s in the 415V $25kA_{rms}$. Contact erosion is evaluated by measuring the mass change of the cathode and anode. The results show that the increase in opening velocity from 2m/s to 6m/s leads to a decrease in the contact erosion. It is shown that the material transfer from one electrode to another depends on the transfer charge and the opening velocity of the contacts. The contact pairs of AgWC/AgCdO are superior to $AgWC/AgSnO_2In_2O_3$ or AgWC/AgC contact pairs in the contact erosion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.561-565
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• 1999

We measured the optical properties in Ag/chalcogenide films with the exposure of 325nm-Held laser In addition we have investigated the Ag doping mechanism as considering the changes of Ag-concentration distribution and optical energy gap ( $E_{op}$ ) with Photon-dose. The "windows" characteristics of Ag thin film occur around the wavelength of 325 nm and the Ag is evaluated to be transparent, without an absorption, in the region. While the $E_{op}$ of S $b_2$ $S_3$ thin film was changed largely by an exposure of HeNe laser(632.8 nm) an exposure of HeCd laser resulted in relatively small variation of $E_{op}$ . Therefore it is thought that photon absorption at the metal layer plays an important role in Ag photodoping.on at the metal layer plays an important role in Ag photodoping.