• Journal of Conservation Science
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• v.32 no.3
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• pp.313-320
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• 2016

The aim of this study was to obtain information on the ancient material of cast bronze through an investigation of the microstructure and impurity characteristics of the casting. Three Koryo bronze coins were analyzed using an optical microscope, scanning electron microscope, and electron dispersive X-ray analyses were used to determine the composition of the specimens. The three coins had 4 phases: ${\alpha}phase$, ${\delta}phase$, Pb, and impurities ($Cu_2S$). $Cu_2S$ was found to exist near Pb or in ${\delta}phase$. $Cu_2S$ is the inter mediate product of copper ore refining. Therefore, the copper ore was not completely refined. To find out the characteristic of $Cu_2S$, we melt 1)Koryo bronze coin and 2)$Cu_2S$ and Pb powder at 1273 K. The reaction between $Cu_2S$ and Pb at 1273 K yielded fine Cu and black gas, which was identified to be PbS and is presented below: $Cu_2S+Pb{\rightarrow}PbS{\uparrow}+2Cu$.

• Journal of Life Science
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• v.24 no.10
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• pp.1046-1054
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• 2014

Beta-1,3-glucanase is widely used in various biotechnological and industrial processes, with over-production required to enable versatile utilization. We examined the overexpression of ${\beta}$-1,3-glucanase (EXGA) from Aspergillus oryzae using ${\delta}$-sequence-mediated integration. We constructed $pRS{\delta}$-exgA and $pRS{\delta}K$-exgA plasmids for integration of the EXGA gene into various chromosomes of Saccharomyces cerevisiae. These plasmids contain the ADH1 promoter for constitutive expression, a signal sequence (exoinulinase signal sequence [INU1 s.s]) for secretory production, and a ${\delta}$-sequence for integration of ${\beta}$-1,3-glucanase. The $pRS{\delta}$-exgA plasmid was transformed into the S. cerevisiae $BY4742{\Delta}exg1$ strain, and ${\beta}$-1.3-glucanase was stably overexpressed and secreted. Another plasmid, $pRS{\delta}K$-exgA, was introduced into the S. cerevisiae $BY4742{\Delta}exg1$ (YKY082) strain, and overexpression of ${\beta}$-1,3-glucanase was examined by inducible integration under geneticin selection. The activity of ${\beta}$-1,3-glucanase increased in accordance with a rise in the geneticin concentration, with 0.8 mg/ml of geneticin suitable for overexpression of ${\beta}$-1,3-glucanase. Subsequently, $pRS{\delta}K$-exgA was repeatedly transformed for sequential ${\delta}$-integration. The activity of ${\beta}$-1,3-glucanase reached about 0.063 unit/ml/$OD_{600}$, 0.095 unit/ml/$OD_{600}$, 0.131 unit/ml/$OD_{600}$ and 0.165 unit/ml/$OD_{600}$ by the first, second, third, and fourth round of integration, respectively. According to the increase in the activity of ${\beta}$-1,3-glucanase by sequential ${\delta}$-integration, the copy number (integration rate) of the EXGA gene also increased in various chromosomes. These results suggest that recombinant ${\beta}$-1,3-glucanase activity can be sequentially increased by repeated ${\delta}$-sequence integration.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.59-64
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• 2003

We fabricated mixed ionic-electronic conducting membranes, $CH_4\;Using\;{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$, by solid state reaction method for solid oxide fuel cell. The membranes consisted of single perovskite phase and exhibited high relative density, $>95\%$. We coated $La_{0.6}Sr_{0.4}CoO_{3-\delta}$ layer using screen printing method in order to improve surface reactivity of the $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$. As a result, the oxygen permeation flux of the coated $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$ showed higher value, $0.5ml/min{\cdot}cm^2\;at\;950^{\circ}C$ than the uncoated one. Higher oxygen permeation was observed in the porously coated Lao $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$membranes with larger grain sizes. Syngas, $CO+H_2$, was successfully obtained from methane gas, $CH_4$, using the $La_{0.6}Sr_{0.4}CoO_{3-\delta}$ coated $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$, with over $40\%\;of\;CH_4$ conversion and syngas yield. $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_{3-\delta}$ membrane was stable even when it was exposed to the reducing environment, methane, for 600 hrs at $950^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.1
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• pp.17-24
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• 1994

The evaluation and analysis of diffusivity of lithium for coarsening and coarsening kinetics of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy aged at $170^{\circ}C$ have been investigated by transmission electron microscopy. With ageing time, ${\delta}^{\prime}$ precipitate coaesened to followed $\bar{\gamma}{\propto}t^{1/3}$ and coarsening kinetics was found to be obeyed to the Lifshitz-Slyozov-Wagner(LSW) theory and diffusivity of lithium for coarsening of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy was obtained to be $5.85{\times}10^{-17}{\sim}1.53{\times}10^{-16}$ by experimental coarsening rate constant and various coarsening kinetic theory. Diffusivity of lithium measured by using various model but MLSW and Tsumuraya (VI) et al. model in Al-Li-Cu-Mg-Zr alloy is similar to that calculated by the Costas's diffusivity equation. It was, therefore, suggested that additing to the Cu, Mg and Zr element in Al-Li system have no great effect on diiffusivity of lithium for coarsening of ${\delta}^{\prime}$ This suggest that in matrix.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.231-239
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• 1999

An improved version of current-regulated delta modulator (CRDM) is investigated for the output cunent control of v voltage-source inverters that have transformer-coupled series resonant load and are operated at the resonant frequency. Conventional CRDM has not only CUlTent offset problem but also transformer flux saturation problem when i it is applied to induction heating systems that have transformel-coupled loads. To cope with these problems, the effect of flux saturation is analysed, and simple method to av이d the problem is proposed. And integral type of CRDM is a adopted to remove the cunent offset. The boundaries of integrator gain for stable operation is calculated using the c concept of sliding mode controL The validity of proposed strategy is vel퍼ed through simulations and prototype e experiments.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.270.2-270.2
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• 2013

직선운동하는 하전입자의 진행방향에 수직한 평면상에 서로 직교하는 전기장과 자기장을 걸어주면, 하전입자에는 전기장에 의한 힘 FE와 자기장과 속도 v에 의한 로렌츠력 $F_B=q(v{\times}B)$가 동시에 작용하게 된다. 이때 Wien 조건 FB=-FE를 만족하는 질량 mA과, 에너지 EA를 가지는 하전입자 A는 휘지 않고 직선운동을 계속하나, 하전입자 A와 다른 에너지 $E_B\;(=E_A+{\delta}E)$나 질량 $m_B\;(=m_A+{\delta}m)$을 가지는 하전입자는 휘게 되며, 그 휘는 정도는 ${\delta}E$나 ${\delta}m$에 비례하게 된다. 이 현상을 이용하여 다양한 종류의 에너지 또는 질량 분석기가 독일, 미국, 일본 등의 분석기기 선진국에서 개발되어 왔고, 전자현미경의 이미지 필터로도 활용되고 있으며, 통상 EXB 필터 또는 발명자의 이름을 딴 Wien 필터로 불리어지고 있다. $E{\times}B$ 필터는 일반적인 하전입자빔 렌즈와 다른 광학특성을 가지며, 지난 발표에서는 $E{\times}B$ 필터의 기본 궤도 방정식 및 다양한 2차 기하 수차 방정식의 유도과정 및 결과를 보여주었다. 본 발표에서는 EXB 필터의 전후에 배치시켜, 초점거리 등의 조정을 수행할 4극자와, $E{\times}B$ 필터에서 발생하는 2차 수차의 보정을 수행할 6극자의 광학특성의 계산 결과를 보여준다. 4극자-6극자-EXB필터-6극자-4극자 조합의 기본 광학궤도 계산 결과는 빔 다이어그램으로 보여준다. 6극자에 의해 수차를 줄여서 향상되는 에너지 분해능 값은 수치적으로 추정한다. 실제 제작이 된 각 부품의 외형 및 사진을 보여주어 에너지 필터의 제작 진행 상황을 보고한다.

• Korean Journal of Remote Sensing
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• v.25 no.1
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• pp.85-94
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• 2009

This paper presents the capability to use QuickBird imagery for effects of forest disturbance in Okgye burned area. Particular attention of this paper deals with the NBR-derived mapping burn severity on QuickBird imagery to locate reliable rehabilitation(namely, secondary succession) over postfire surface. Comparisons of the mapping forest disturbance derived from QuickBird NBR data and the mapping burn severity derived from Landsat ${\Delta}NBR$ data show substantial agreement (KHAT value =0.7886). The method calculated from the correlation between QuickBird wetness and Landsat ETM+ band7 may have application to forest harvest disturbance.

• Economic and Environmental Geology
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• v.35 no.5
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• pp.379-393
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• 2002

Within the Boseong-Jangheung area of Korea, five hydrothermal gold (-silver) quartz vein deposits occur. They have the characteristic features as follows: the relatively gold-rich nature of e1ectrurns; the absence of Ag-Sb( -As) sulfosalt mineral; the massive and simple mineralogy of veins. They suggest that gold mineralization in this area is correlated with late Jurassic to Early Cretaceous, mesothermal-type gold deposits in Korea. Fluid inclusion data show that fluid inclusions in stage I quartz of the mine area homogenize over a wide temperature range of 200$^{\circ}$ to 460$^{\circ}$C with salinities of 0.0 to 13.8 equiv. wt. % NaCI. The homogenization temperature of fluid inclusions in stage II calcite of the mine area ranges from 150$^{\circ}$ to 254$^{\circ}$C with salinities of 1.2 to 7.9 equiv. wt. % NaCI. This indicates a cooling of the hydrothermal fluid with time towards the waning of hydrothermal activity. Evidence of fluid boiling including CO2 effervescence indicates that pressures during entrapment of auriferous fluids in this area range up to 770 bars. Calculated sulfur isotope composition of auriferous fluids in this mine area (${\delta}^34S$_{{\Sigma}S}$$\textperthousand$) indicates an igneous source of sulfur in auriferous hydrothermal fluids. Within the Sobaegsan Massif, two representative mesothermal-type gold mine areas (Youngdong and Boseong-Jangheung areas) occur. The ${\delta}^34S values of sulfide minerals from Youngdong area range from -6.6 to 2.3$\textperthousand$ (average=-1.4$\textperthousand$, N=66), and those from BoseongJangheung area range from -0.7 to 3.6$\textperthousand$ (average=1.6$\textperthousand$, N=39). These i)34S values of both areas are comparatively lower than those of most Korean metallic ore deposits (3 to 7TEX>$\textperthousand$). And, within the Sobaegsan Massif, the ${\delta}^34S values of Youngdong area are lower than those of Boseong-Jangheung area. It is inferred that the difference of ${\delta}^34S values within the Sobaegsan Massif can be caused by either of the following mechanisms: (1) the presence of at least two distinct reservoirs (both igneous, with ${\delta}^34S values of < -6 $\textperthousand$ and 2$\pm$2 %0) for Jurassic mesothermal-type gold deposits in both areas; (2) different degrees of the mixing (assimilation) of 32S-enriched sulfur (possibly sulfur in Precambrian pelitic basement rocks) during the generation and/or subsequent ascent of magma; and/or (3) different degrees of the oxidation of an H2S-rich, magmatically derived sulfur source ${\delta}^34S = 2$\pm$2$\textperthousand$) during the ascent to mineralization sites. According to the observed differences in ore mineralogy (especially, iron-bearing ore minerals) and fluid inclusions of quartz from the mesothermal-type deposits in both areas, we conclude that pyrrhotite-rich, mesothermal-type deposits in the Youngdong area formed from higher temperatures and more reducing fluids than did pyrite(-arsenopyrite)-rich mesothermal-type deposits in the Boseong-Jangheung area. Therefore, we prefer the third mechanism than others because the ${\delta}^34S values of the Precambrian gneisses and Paleozoic sedimentary rocks occurring in both areas were not known to the present. In future, in order to elucidate the provenance of ore sulfur more systematically, we need to determine ${\delta}^34S values of the Precambrian metamorphic rocks and Paleozoic sedimentary rocks consisting the basement of the Korean Peninsula including the Sobaegsan Massif.

• Journal of the Korean Chemical Society
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• v.25 no.3
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• pp.190-198
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• 1981

In contrast with pmr (only multiplets at ${\delta}6.6$∼7.8 ppm) spectrum of triphenyl-9-thioxanthenylphosphonium perchlorate and tri-o-methoxyphenyl-9-thioxanthenylphosphonium perchlorate, tri-n-butyl-9-thioxanthenylphosphonium perchlorate and tribenzyl-9-thioxanthenylphosphonium perchlorate showed a doublet at ${\delta}5.58$ and 5.70ppm, respectively, assigned to a methine proton. This value is slightly larger than the corresponding values (${\delta}5.05$~5.30) of 9-arylthioxanthenes but clearly differentiated from those of aromatic protons. This result implys that the downfield shift of a methine proton of triaryl-9-thioxanthenylphosphonium perchlorate is not due to inductive effects of an electron deficient phosphorus atom but paramagnetic deshielding effects by three aryl groups on phosphorus.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.456-460
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• 1999

Rates of 1-adamantyl fluoroformate with substituted pyridines ($3-CH_3,\;4-CH_3,\;H,\;3-Cl,\;3,4-(CH_3)_2,\;3,5-(CH_3)_2$) in methanol have been measured by conductometric method at various temperatures and concentrations. The activation parameters (${\Delta}H^{\neq},\;{\Delta}S^{\neq}$) and Hammett reaction constant (${\rho}$) or Bronsted coefficient (${\beta}$) were evaluated from rate constants. The activation entropies are large and negative, and the activation enthalpies are small and positive. The Hammett reaction constant (${\rho}$) and Bronsted coefficient (${\beta}$) values were -4.15 and 0.63, respectively. From the above results, it may be concluded that this reaction proceeds to a concerted displacement mechanism in methanol.