• Korean Journal of Heritage: History & Science
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• v.46 no.1
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• pp.208-227
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• 2013

Twenty-seven bronze bowls excavated from the Goryo burial complex at Deobu-gol were examined for their microstructure and chemical composition to characterize the bronze technology practiced by commoners at the time. Results showed that the objects examined can be classified into four groups: 1) objects forged out of Cu-near 22%Sn alloys and then quenched; 2) objects cast from Cu-below 10% Sn alloys containing lead; 3) objects cast from Cu-10%~20% Sn alloys containing lead and then quenched; 4) objects forged out of Cu-10~20% Sn alloys containing lead and then quenched. This study revealed that the fabrication technique as determined by alloy compositions plays an important role in bronze technology. The use of lead was clearly associated with the selection of quenching temperatures, the character of inclusions and the color characteristics of bronze surfaces. It was found that the objects containing lead were quenched at temperatures of $520^{\circ}{\sim}586^{\circ}C$ while those without lead were quenched at the range of $586^{\circ}{\sim}799^{\circ}C$. The presence of selenium in impurity inclusions was detected only in alloys containing lead, suggesting that the raw materials, Cu and Sn, used in making the lead-free alloys for the first group were carefully selected from those smelted using ores without lead contamination. Furthermore, the addition of lead was found to have significant effects on the color characteristics of the surface of bronze alloys when they are subjected to corrosion during interment. In leaded alloys, corrosion turns the surface light green or dark green while in unleaded alloys, corrosion turns the surface dark brown or black. It was found that in fabrication, the wall thickness of the bronze bowls varies depending on the application of quenching; most of the quenched objects have walls 1mm thick or below while those without quenching have walls 1mm thick or above. Fabrication techniques in bronze making usually reflect social environments of a community. It is likely that in the late Goryo period, experiencing lack of skilled bronze workers, the increased demand for bronze was met in two ways; by the use of chief lead instead of expensive tin and by the use of casting suitable for mass production. The above results show that the Goryo bronze workers tried to overcome such a resource-limited environment through technological innovations as apparent in the use of varying fabrication techniques for different alloys. Recently, numerous bronze objects are excavated and available for investigation. This study shows that with the use of proper analytical techniques they can serve as a valuable source of information required for the characterization of the associated technology as well as the social environment leading to the establishment of such technology.

• The Korean Journal of Quaternary Research
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• v.14 no.1
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• pp.33-48
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• 2000

Vegetation disturbance history of the Korean Peninsula from the Palaeolithic Age to the Koryo Dynasty (1392) has reconstructed by the use of various data sources. Active vegetation disturbance, which has begun during the Neolithic Age, seems to be more widespread on lowland and coastal areas in the early stages, but later expanded into inland areas. The ploughing of a field and the selective cutting of certain trees, such as oak trees, nettle trees and pine trees are noticeable, and eventually caused deforestation during the Bronze Age. The use of iron tools of the Iron Age has enabled the forest clearing to develope the dry fields. During the Three Kingdoms period (BC 57∼AD 918) extensive deforestation has maintained for the development of cultivated fields, as well as other activities, such as timber, lumbering, production of iron farm implement, ploughing by cattle. The encouragement of disafforestation on mountain slope and creation of terraced field during the Koryo Dynasty (918∼1392) has caused the deforestation over the country, along with the consumption of large amount of wood and timber for fire-wood, ship-building, mining, xylography and so on.

• Journal of Conservation Science
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• v.30 no.2
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• pp.111-122
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• 2014

In Bongseon-ri site, the central type and the local type of the Baekje tombs co-exist together. Many swords with ring pommel which to regional leaders in Seocheon the Beekje government granted are excavated from these tombs. These represent that the regional leaders were controlled by the Baekje government gradually. Four swords with ring pommel and one simple sword are investigated metallurgically and we seek what swords have a function of weapon or what sword produce for grave goods. The simple sword is made by solid carburizing technology and quenching of heat treatment so it's possibly used as a weapon. In contrast, four swords with ring pommel has little chance of weapon because the blade of swords consists of microstructure that have low hardness and the back of swords don't have microstructure can absorb the shock. The most identical characteristic of the simple sword and swords with ring pommel is that they are possible to classify clearly into practical/non-practical tools. Additionally, according to non-metallic inclusion analysis result of these swords, w$\ddot{u}$stite and glass phase are found together. Thus, it is able to say that reduction method in low temperature is applied during smelting process.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.1
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• pp.23-29
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• 2013

LCC (Liquid cadmium cathode) is used for electrowinning in pyroprocessing to recover uranium and transuranic elements simultaneously. It is one of the core technologies in pyroprocessing with higher proliferation resistance than a wet reprocessing because LCC-cell does not separate TRU from uranium. The crucible which holds the LCC is technically important because it should be nonconducting material to prevent deposition of metallic elements on the crucible outer surface. The chemical stability is also crucial factor to choose crucible material due to the strong reactivities of TRU and possible incorporation of Li metal during the operation. In this study, the chemical stabilities of four kinds of representative ceramic materials such as $Al_2O_3$, MgO, $Yl_2O_3$ and BeO were thermodynamically and experimentally evaluated at $500^{\circ}C$ with simulated LCC. The contact angle of LCC on ceramic materials was measured as function of time to predict chemical reactivity. $All_2O_3$ showed poorest chemical stability and the pores in BeO contributed to a decreases in contact angle. MgO and $Y_2O_3$ have superior chemical stability among the materials.

• Resources Recycling
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• v.19 no.5
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• pp.25-30
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• 2010

Leaching of CMSX-4 superalloy was done in hydrochloric acid solutions. The leaching behaviors of main alloy components, such as Ni, Co, Cr, Al, was investigated by controlling acid concentration, temperature, leaching time and pulp density. Increasing acid concentration enhanced the leaching rate till the rate decreased over 3 M acid concentration. Raising temperature increased the leaching amount of the metal components. After the leaching for 60 minutes at $90^{\circ}C$ and 10 g/L pulp density in 4 M acid solution, 93.2% nickel, 89.9% aluminum, 80.4% cobalt, and 79.1% chromium were leached. Nickel and aluminum were preferentially leached out, while the leaching rate of cobalt and chromium were relatively high only after 60 minutes, Increasing pulp density lowered the leaching rate and especially serious on cobalt and chromium, The optimum leaching condition for CMSX-4 was obtained at $90^{\circ}C$, 120 minutes, and less than 125 g/L in 4 M hydrochloric acid solution.

• Journal of Environmental Impact Assessment
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• v.24 no.6
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• pp.549-560
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• 2015

The priorities of siting restriction was derived from quantification of environmental hazard according to industrial classification based on 'Chemical Ranking and Scoring System(CRS)' which is handling the discharge characteristics of 31 industrial classifications regulated from locating at 'Industrial Complex in Rural Area(ICRA)'. CRS that is utilizing the data of 'Pollutant Release and Transfer Registers(PRTR)' is applied to determine human health risk and ecological risk which are calculated by discharged amount and materials $LC_{50}$ according to water, soil and air media based on industrial classification. From this process, exposure assessment and toxicity assessment for integrating the adverse environmental impact and the mitigation effect of environmental risk according to the development of environmental technologies into establishing the rational landuse management method for the 31 industrial classifications regulated from locating at ICRA was analyzed. From the assessment result of the siting restriction removal at ICRA for 31 industrial classifications, based on 2012 year reference 6 industries that includes Manufacture of Guilt Coloration Surface Processing Steel Materials, Manufacture of Biological Product, Manufacture of Smelting Refining and Alloys of Copper, Dyeing and Finishing of Fibers and Yarns, Manufacture of Other Basic Iron and Steel n.e.c., Rolling Drawing and Extruding of Non-ferrous Metals n.e.c. are calculated as having relatively lower environmental hazards, thus it is judged that the siting restriction mitigation at ICRA is possible for the 6 industrial classifications that are not discharging the specific hazardous water contaminants during manufacturing process.

• Resources Recycling
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• v.24 no.4
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• pp.32-37
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• 2015

Cobalt is abundant only in some countries including Democratic Republic of the Congo. It would be necessary to secure overseas Co ores and Co extraction technology. Two kinds of matte varying the sulfur content were manufactured by smelting reduction of Co concentrate containing ~8 wt% Co, ~19 wt% Cu, and ~3 wt% Fe. The amount of Co, Cu and Fe was concentrated to 19~21 wt%, 39~41 wt%, and 7~9 wt% respectively in the resulting matte. High-pressure leaching of matte was performed in an autoclave with considering the effect of oxidizing agent, $H_2SO_4$ concentration as a lixiviant, and the amount of sulfur added to the matte. An oxidizing agent (oxygen) is necessary to improve Co leaching efficiency enabling usage of a dilute $H_2SO_4$ leaching agent. An increase in $H_2SO_4$ concentration prevents selective leaching of Co, and the sulfur content in matte has a minor influence on the Co leaching efficiency.