• The Korean Journal of Zoology
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• v.16 no.3
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• pp.193-201
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• 1973

A cellulose acetate electrophoretic survey of Korean Anura has revealed the presence of diverse lactate and malate dehydrogenase isozymes. The LDH and MDH isozymes in the tissues of the brain, heart, stomach, skeletal muscle and liver of the six species of Anura examined show the species specific patterns which differ from those of mammals and birds. Two isozymic forms of LDH and MDH exist in both Rana nigromaculata and Rana nigromaculata coreana, respectively, with almost the same pattern. LDH of Bombina orientalis has five isozymic forms, and that of Rana temporaria ornativentris contains four isozymes. Bufo sp. has 3 to 5, and Rana rugosa has 3 to 4 isozymic bands according to the tissues. MDH's of all animals have two isozymic forms with different spacing on the zymograms.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.351-352
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• 2011

그래핀(Graphene)은 2차원 평면구조의 $sp^2$ 탄소 결합으로 이루어진 물질이다. 일반적으로 그래핀은 탄소 원자 한층 정도의 얇은 두께를 가지면서 강철의 100배 이상 높은 강도, 다이아몬드보다 2배 이상 뛰어난 열 전도성, 그리고 규소보다 100배 이상 빠른 전자이동도 등의 매우 우수한 특성을 지닌다. 그래핀을 합성하거나 얻는 방법에는, 기계적 박리법(Micro mechanical exfoliation), 산화흑연(graphite oxide)을 이용한 reduced graphene oxide(RGO)방법과 탄화 규소(SiC)를 이용한 epitaxial growth 방법 등이 있지만, 대 면적화가 어렵거나 구조적 결함이 큰 문제점이 있다. 반면, 탄화수소(hydrocarbon)를 탄소 공급원으로 하는 열화학 기상 증착법(Thermal chemical vapor deposition, TCVD)은 구조적 결함이 상대적으로 적으면서 대 면적화가 가능하다는 이점 때문에 최근 가장 많이 이용되고 있는 방법이다. TCVD를 이용, 니켈, 몰리브덴, 금, 코발트 등의 금속에서 그래핀 합성연구가 보고되었지만, 대부분 수 층(fewlayer)의 그래핀이 합성되었다. 하지만, 구리 촉매를 이용하는 것이 단층 그래핀 합성에 매우 효율적이라는 연구결과가 보고되었다. 구리의 경우, 낮은 탄소융해도(solubility of carbon) 때문에 표면에서 self limiting 과정을 통하여 단층 그래핀이 합성된다. 그러나 단층 그래핀 일지라도 면저항(sheet resistance)이 매우 높고, 이론적 계산값에 비해 전자이동도(electron mobility)가 낮게 측정된다. 이러한 원인은 구조적 결함에서 기인된 것으로써 산업으로의 응용을 어렵게 만들기 때문에 양질의 단층 그래핀 합성연구는 필수적이다[1,2]. 본 연구에서는 TCVD를 이용하여 구리 포일(25 ${\mu}m$, Alfa Aeser) 위에 메탄가스를 탄소공급원으로 하여 수소를 함께 주입하고, 메탄가스의 양과 합성시간, 열처리 시간을 조절하면서 균일한 단층 그래핀을 합성하였다. 합성된 그래핀을 $SiO_2$ (300 nm)기판위에 전사(transfer)후 라만 분광법(raman spectroscopy)과 광학 현미경(optical microscope)을 통하여 분석하였다. 그 결과, 열처리 시간이 증가할수록 촉매로 사용된 구리 포일의 grain size가 커짐을 확인하였으며, 구리 포일 위에 합성된 그래핀의 grain size는, 구리 포일의 grain size에 의존하여 커짐을 확인하였다. 또한 동일한 grain 내의 그래핀은 균일한 층으로 합성되었다. 이는 기계적 박리법, RGO 방법, epitaxial growth 방법으로 얻은 그래핀과 비교하여 매우 뛰어난 결정성을 지님이 확인되었다. 본 연구를 통하여 면적이 넓으면서도 결정성이 매우 뛰어난 양질의 단층 그래핀 합성 방법을 확립하였다.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.4-21
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• 2019

In this paper, 23 Silla gold earrings from the sixth and seventhand centuries, excavated from the Yeongnam region, were analyzed. Based on the silver content of the gold plate, they were classified into three types. The classifications included type I(20-50wt%), type II(10-20wt%) and type III (less than 10wt%). In the analysis process, the composition and morphological differences were identified on the surface of the gold plate. In the case of type I and II earrings, it was observed that the fine holes were concentrated in a relatively higher part of the gold content. The causes of the difference in the surface composition of the gold plate were divided into four categories: 1) surface treatment, 2) thermal diffusivity in the manufacturing process, 3) differences in composition of alluvial gold, and 4) the refining method of gold. It is possible that depletion gilding was attempted to increase the gold content while intentionally removing the other metals from the surface of the gold alloy in the portion where the gold deposit is relatively concentrated on the surface of the gold plating. The highest copper content was detected in the earring with the highest gold content of the analyzed earrings, and it was assumed that thermal diffusion had occurred between the gold plate and the metal rod during the manufacturing process rather than intentional addition. Copper was detected only in the thin ring earring type, and copper was not detected in the thick ring earring type or pendant type. It also proves that this earring has a high degree of tightness at higher temperatures, as there was an invisible edge finish on other earrings and horizontal wrinkles on the gold plate surface. In terms of the material of the gold plate, we examined whether the silver content of the gold plate was natural gold or added by alloy through analyzing the alluvial gold collected in the region. As a result of the analysis, it was found that on average about 13wt% of silver is included. This suggests that type II is natural gold, type III is refined gold, and type I seems to have been alloyed with natural gold. Here, we investigated the refining method introduced in the ancient literature, both at home and abroad, about the possibility of alloying silver after the refining process of type III earrings and then making pure gold. It was found that from ancient refining methods, silver which had been present in the natural gold was removed by reacting and combining with silver chloride or silver sulfide, and long-term efforts and techniques were required to obtain pure gold through this method. Therefore, it was concluded that the possibility of adding a small amount of silver in order to increase strength after making pure gold through a refining process is low.

• Korean Journal of Ecology and Environment
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• v.52 no.4
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• pp.366-377
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• 2019

Paddy wetlands are a critical habitat for a variety of wild animals, and their rapid development and environmental changes pose a threat to the conservation of agrobiodiversity. The objectives of this study were to evaluate the habitat characteristics of anuran inhabiting paddy wetlands and identify major environmental variables affecting their distributions. The study was conducted in the Daeho reclaimed area in Dangjin, from March to October 2018. In this study, we found three anuran species (Pelophylax nigromaculatus, Hyla japonica and Pelophylax chosenicus). The environmental factors affecting the three species were identified as air temperature, humidity, water-depth, and micro-habitats. H. japonica were affected by water temperature, and P. chosenicus were affected by rice height and types of farming practices. All the three species richness was correlated with air temperature, humidity, and water-depth positively, and the three species used rice transplanted paddy fields the most. It was also found that paddy is the most preferred of the micro-habitats during the breeding season, so the survey area is considered to be used as the major breeding sites for the three species. P. chosenicus were more observed on environmental-friendly paddy fields than conventional paddy fields, which appears to be differences in their surroundings environment caused by predators and weeding. It will be needed to identify their relationship with predators, their preferred food resources and the richness and diversity of wild vegetation around paddy wetlands.

• Journal of Conservation Science
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• v.28 no.2
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• pp.175-184
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• 2012

A purpose of this research is to find out characteristic of bronze artifacts and gold ornaments excavated from Xiongnu tombs No. 2~4 at Duurlig Nars in Mongolia through scientific analysis of them. The Tombs are comparatively small. There were still lots of relics remaining although the tombs had been already robbed. Also the tombs are evaluated important since the origin of them show coexisting of chinese and northern style. First of all, an analysis result about bronze vessels found in this site, they have high lead(Pb) content and relatively low tin(Sn) content, as compared with the Bronze Han Mirror and End-fittings of Bronze Parasol Rib. Especially in case of bronze tray and bronze lamp from the no. 2 tomb and also bronze cauldron from the no. 4 tomb contain only 1wt% of tin which means binary alloy composition(Cu-Pb). Also, in the case of gold ornaments found in the no. 2 tomb, they have comparatively high purity. And the research suppose that the high possibility of that they were used soldering using alloy of Au-Cu or diffused bonding(using malachite and copper oxide) for joining gold grains of gold granulation ornament. Further scientific research and analysis in Mongolia and other countries will provide more clues to solve mystery of Xiongnu culture.

• Journal of Wetlands Research
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• v.17 no.4
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• pp.407-413
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• 2015

As the number of applications containing nanomaterials increase, aquatic ecosystem exposure to nanoparticles (NPs) is unavoidable. In this study, we carried out toxicity assessment to Au-nanoparticles(NPs) of Rana dybowskii eggs and tadpoles. Toxicity was recorded hatching rate, body condition(Snout-tail length, STL), and behavioral sensitivity. Behavioral sensitivity was analyzed to anti-predator behavior using Ethovision XT 9. Au-NPs did not show any toxicity of hatching rate and STL. But, Tadpoles exposed to Au-NPs decrease behavioral sensitivity of stimuli. This study has value of environmental toxicity evaluation because these results show the new way of toxicity assessment.

• Conservation Science in Museum
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• v.12
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• pp.59-69
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• 2011

The conservation treatment and production technique of Yongmuntujoeunpanpi-Angyo(Saddle Ornament) at Hwangnamdaechong were: The conservation treatment removed foreign material by using both chemical method and physical method to reinforce and to recover area by jointing that was destroyed and weakened. Not only Angyogeumgu but also Jwamokseongeumgu was made of 99wt% or more silver (Ag), and Wondujeong, Naeyeongeumgu and Bokryung were produced by amalgam gold plaiting. Not only Angyogeumgu but also Jwamokseongeumgu that was cast with silver plate was jointed by folding both and putting Naeyeongeumgu on it and then nailing gild ofwondujeong at specific interval. A tree that grew up in curve was used, and it was adhered by plain weave fabric of hemp cloth and wool.

• Conservation Science in Museum
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• v.3
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• pp.65-69
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• 2001

Scientific analysis are carried on gilded ornamental shoes, which have been excavated from tomb No 1. and No 4. in Beopcheon-ri, Wonju dated from Baekje Period. This object is a very important because it provides valuable information on the development of metal-making techniques of that period. Thus, this article illustrates the investigation conducted to reveal how the object was created using what materials and techniques. Instead of the spikes-attached to the bottom plate of the object-that couldn't be sampled, a sample of a decorative rivet showing a similar structure to the spikes-attached to the other parts of the shoes-was prepared for a cross-section examination. Using radiography and microscopes, it was found that the head of a spike was placed and then punched to the gilded plate, so it can be held to the shoes. Under the SEM-EDS, the cross-section of the rivet shows that the gilding layer was applied before the attachment of the rivets. It also shows that the gilding layer is distributed unevenly and there are empty spaces indicating amalgam gilding was employed. This was confirmed as Mercury was detected on the SEM-EDS analysis of the object. The examination of the microstructure of the plate using the SEM-EDS revealed that the object is made of a single copper alloy plate with recrystallized twining and non-metallic white inclusions, which found to be lead in this case.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.37-37
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• 2013

무전해도금법 (electroless plating)은 Brenner와 Riddell이 1946년에 처음으로 환원제를 이용한 금속의 침적을 electroless plating이라고 명명한 뒤 전기를 이용하지 않고 금속막을 얻을 수 있는 방법으로 인지되어왔다. 초기에는 용액이 불안정하였으나 용액의 안정성을 향상시키면서 꾸준히 산업체에 쓰여왔다. 무전해도금의 응용이 처음에는 니켈에 국한되었으나 구리의 무전해도금이 PCB에 사용되면서 80년대부터 전자산업에서 많이 쓰이게 되었다. 최근에는 무전해도금을 이용한 전자산업뿐만 아니라 MEMS와 같이 전기도금을 위한 전기접촉이 어려우면서 정밀한 균일도를 요구하는 분야에도 많이 쓰이고 있다. 본 발표에서는 무전해도금법의 일반적인 원리와 이를 이용한 IT 산업에서의 응용에 대하여 알아본다.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.29-50
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• 2003

Physicochemical Properties of acid mine water of the Chonam-ri Creek and the Sagok-ri Creek in the Kwangyang Au-Ag mine area were determined using geochemical approaches. Metal contamination (Cd, Cu, Pb, Zn) is more serious in the Chonam-ri Creek than in the Sagok-ri Creek. However, the contents of Al and Fe is higher in the Sagok-ri Creek. Such differences between the two creeks probably reflect the abundance and composition of ore minerals. The attenuation processes for acid mine water in both creeks were investigated. In the Chonam-ri Creek, a small retention pond which contains limestone plays an important role in the removal of heavy metals by adsorption or coprecipitation due to increase of pH. The capacity of metal scavenging in this pond depends on the seasonal variation of inflow volume. Reddish yellow precipitates sampled in the Chonam-ri Creek were analyzed by XRD, SEM-EDS, EPMA, and chemical decomposition. The precipitates mainly consist of goethite and are also enriched in Al, Mn, Cu and Zn. This inditates that precipitation of goethite is important for scavenging those trace elements, possibly due to adsorption or coprecipitation. In the Sagok-ri Creek, on the other hand, hydrologic mixing of uncontaminated tributaries results in removal of heavy metals with iron hydroxides precipitation due to the pH increase. The mechanisms proposed for metal attenuation at the confluence between contaminated mine water and uncontaminated tributary water are also explained by the property-property plots.