• 보존과학연구
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• s.8
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• pp.1-12
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• 1987

Fifty ancient Korean coins originated in Choson dynasty have been determined for 9 elements such as Sn, Fe, As, Ag, Co, Sb, Ir, Ru and Ni by instrumental neutron activation analysis and for 3 elements such as Cu, Pb, and Zn by atomicalsorption spectrometry. Bronze coins originated in early days of the dynasty contain as major constituents Cu, Pb and Sn approximately in the ratio 90 : 4 : 3, where as, those in latter days contain in the ratio 7 : 2 : 0. Brass coins which had begun in 17century contain as major constituents Cu, Zn and Pb approximately in the ratio 7 : 1: 1. The multivariate date have been analyzed for the relation among elemental contents through the variance-covariance matrix. The data have been fur theranalyzed by a principal component mapping method. As the results training set of 8class have been chosen, based on the spread of sample points in an eigenvector plotand archaeolgical data such as age and the office of minting.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1345-1348
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• 1997

$YBa_2Cu_3O_x$ samples were fabricated by MPMG(Melt Powder Melt Growth). The effects of the $Y_2BaCuO_5$ and Ag addition on $YBa_2Cu_3O_x$ were studied throuth the Jc, Tc and magnetization. For the application of the bulk HTSC to current limiter, fly wheel and current lead and so on, the critical charateristics were investigated and compared with the solid sintering method.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.5
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• pp.99-106
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• 2008

Metal ions such as Cu and Cr were extracted from the Cu, Cr and Ag impregnated active carbon by contacting the solid surfaces with supercritical carbon dioxide(Sc-$CO_2$) containing chelating agents. About 10g of the active carbon sample were loaded in a vertical tube extractor contacting with $CO_2$ flowing from the bottom of the tube for 6hrs. The ligands used were acetyl acetone(AA) and Cyanex-302(C-302). Water and methanol were used as entrainers to study the effect of co-solvent to $CO_2$. Experimental results showed that C-302 was more effective than AA in removing Cu with the maximum extraction of 42.0wt%, while 57.6wt% of Cr was extracted with AA from the sample.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.20-23
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• 2005

The objective of this study is to examine a stabilized efficiency of heavy metals including Cd, Cu, Pb and Zn using slaked lime. Tailings from the Janggun Pb-Zn mine, the second Yeonhwa Pb-Zn mine, the Jisi Au-Ag mine and the Sangdong W mine were sampled and measured heavy metal concentrations contents using AAS as various extraction methods. During 156 hours, column test were undertaken to evaluate the possibility of stabilization by slaked lime. The result shows that $Ca(OH)_2$ has a good efficiency in heavy metal stabilization, especially at the Jisi mine with stabilized efficiencies of 97%(Cd), 99%(Cu), 86%(Pb) and 99%(Zn), respectively.

• Journal of Korea Foundry Society
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• v.21 no.4
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• pp.232-238
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• 2001

Experimental study on the twin roll strip casting of BCuP-5(Cu-15wt%Ag-wt5%P) alloy was carried out using laboratory scale horizontal type twin roll caster. In this study, among the various operating parameters, such as tundish angle, contact angle, pouring temperature, roll speed, presetting gap of the rolls and kinds of roll and tundish materials, effect of pouring temperature for strip casting of BCuP-5 alloy which has long freezing range of about $170^{\circ}C$ was mainly investigated. BCuP-5 alloy strip was successfully produced when pouring molten metal at lower temperature than its liquidus temperature. Microstructure of the cast strip consists of primary Cu and eutectic. Especially the size of primary Cu phase increased with decreasing of pouring temperature.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.35-41
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• 2002

To improve the reliability of solder joints, a composite solder which consists of solder matrix and intermetallic reinforcements was manufactured by a new method. The cast ingot of Sn-6.9Cu-2.9Ag alloy had primary Cu6Sn5 intermetallics in the form of dendrites. After rolling the ingot, the intermetallic dendrites were crushed into fine particles and distributed uniformly throughout the solder matrix. As the rolled strips became thinner, the average size of the crushed particles reached a critical size which did not decrease any more by further rolling. The critical size was nearly the same as the average width of intermetallic dendrite trunk. The crushed intermetallic particles did not melt and remained in solid state during reflow soldering due to their high meltingterm-perature. The coarsening and gravitational segregation of the particles were observed during reflow soldering.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.7
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• pp.364-366
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• 2006

In order to realize the commercial application of HTSC materials, it is necessary to develop the fabrication process of high Tc oxide superconductor materials with desired shape and for practical application and high critical current density as well as good mechanical strength which can withstand high lorenz force generated at high magnetic field. Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of HTSC materials at liquid nitrogen temperature. Recently some new fabrication techniques have been developed for YBaCuO bulk superconductor with high mechanical strength and critical current density. In this project, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of YBaCuO superconductor, and we reported the production of the YBaCuO high Tc superconductor by the pyrolysis method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.12-15
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• 2003

The YBaCuO thick film was deposited by the electrophoresis in the solution with different dimension particles. The morphology of the films deposited from different particles size was compared. The powder made by sol-gel method has the submicron particles, which deposit the most smooth film, and without microcracks after sintering. After sintering of the deposited film, the zone-melting process was carried out in low oxygen partial pressure (100 Pa) and Ag was used as substrate. And the zone-melted YBaCuO was studied by XRD.

• Korean Journal of Materials Research
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• v.7 no.7
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• pp.571-575
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• 1997

급냉온도에 따른 전기 저항 측정으로 Cu-17, 25Zn-15AI 및 Cu-17.25Zn-15AI-1Ag형상기억합금의 열처리에 의한 마르텐사이트 변태온도의 영향을 연구하였다. DSC 측정으로 고온 모상에서의 상전이 온도롸 종류를 구별하였고 XRD측정으로 구조 변화를 연구하였다. 그리고 열처리에 의한 온도 변화의 원인을 연구하였17.25Zn-15AI 합금에서 고온 모상의 규칙-불규칙 전이온도인 $T_{2}$, $T_{L21}$은 각각 809K와 610K였다. CuZnAI의 경우 $T_{2}$근방에서의 급냉은 마르텐사이트 변태온도를 높이지만 $T_{L21}$ 근방에서의 급냉은 마르텐사이트 변태온도를 낮춘다. 실험결과 열처리에 따른 상전이온도 변화의 원인은 석출물의 형성이라기 보다는 급냉전의 모상의 구조에 가장 큰 영향을 받는다.받는다.

• Economic and Environmental Geology
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• v.46 no.3
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• pp.267-278
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• 2013

The East African Rift System(EARS) is known to be hosted epithermal Au-Ag deposits, and the best-known example is Main Ethiopian Rift Valley(MER) related to Quaternary bimodal volcanism. Large horst-graben system during rifting provides open space for emplacement of bimodal magmas and flow channel of geothermal fluids. In recent, large hydrothermally altered zones(Shala, Langano, and Allalobeda) and hot spring related to deeply circulating geothermal water have been increasing their importance due to new discoveries in MER and Danakil depression. The hot springs in Shala and Allalobeda occur as boiling pool and geyser on the surface, whereas some areas didn't observe them due to decreasing ground water table. The host rocks are altered to quartz, kaolinite, illite, smectite, and chlorite due to interaction with rising geothermal water. The hot springs in MER are neutral to slightly alkaline pH(7.88~8.83) and mostly classified into $HCO_3{^-}$ type geothermal water. They are strongly depleted in Au, and Ag, but show a higher Se concentration of up to 26.7 ppm. In contrast, siliceous altered rocks around hot springs are strongly enriched in Pb(up to 33 ppm, Shala), Zn(up to 313 ppm, Shala), Cu(up to 53.1 ppm, Demaegona), and Mn(up to 0.18 wt%t, Shala). In conclusion, anomalous Se in hot spring water, Pb, Zn, Cu, and Mn in siliceous altered rocks, and new discoveries in MER have been increasing potential for epithermal gold mineralization.