• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.45-52
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• 2010

This study has been carried out to estimate carbon contents in an average 40-years-old Pinus koraiensis plantations and an average 37-years-old Larix leptolepis plantations in Gongju, Chungnam Province. Average carbon concentration in stemwood, stembark, branches, needles, and root were 54.31% in Pinus koraiensis and 53.49% in Larix leptolepis stands. Carbon contents was estimated by the equation model logWt=A+BlogD where Wt is oven-dry weight in kg and D is DBH in cm. Total carbon contents was 103.38tC/ha in Pinus koraiensis stands and 96.59tC/ha in Larix leptolepis stands. Net primary carbon production was estimated at 8.79tC/ha/yr in Pinus koraiensis stands and 11.42tC/ha/yr in Larix leptolepis stands.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.6
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• pp.143-152
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• 2009

This study has been carried out to estimate carbon contents in an average 37-years-old Pinus densiflora plantations and an average 42-years-old natural Quercus acutissima stands in Gongju, Chungnam Province. Average carbon concentration in stemwood, stembark, branch, foliage, and root were 54.59% in Pinus densiflora and 53.73% in Quercus acutissima stands. Aboveground carbon contents was estimated by the equation model logWt = A + BlogD where Wt is oven-dry weight in kg and D is DBH in cm. Total carbon contents was 79.28t/ha in Pinus densiflora stands and 71.52t/ha in Quercus acutissima stands. Net primary carbon production was estimated at 9.79tC/ha/yr in Pinus densiflora stands and 5.52tC/ha/yr in Quercus acutissima stands.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1521-1524
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• 2004

The effect of $H_2$ gas on the carbon nanotubes (CNTs) synthesis with CO-$H_2$ gas mixture was investigated using mass measurements and scanning electron microscopy (SEM). The maximum weight and yield of the synthesized carbon were obtained when the mixture ratio of $H_2$: CO was 3 : 7 and 9 : 1, respectively. In case of 100% carbon monoxide (CO) without hydrogen ($H_2$) addition, the weight of carbon increased, but CNTs were not observed. The CNTs began to be made when the contents of $H_2$ reaches at least 10%, their structures became more distinct with an increase of $H_2$ addition, and then the shapes of CNTs were more thin and straight. When the contents of $H_2$ was 80% ($H_2$ : CO = 8 : 2), the shapes and growth of CNTs showed an optimal condition. On the other hand, when the contents of $H_2$ was higher than the critical value, the shapes of CNTs became worse due to transition into inactive surface of catalyst. It was considered that the inactive surface of catalyst resulted from decrease of carbon (C) and $H_2$ concentration by facilitation of methane ($CH_4$) gasification reaction (C + 2$H_2$ ${\rightarrow}$ $CH_4$) between C and $H_2$ gases. It was also found that H2 addition had an influence considerably on the shape and structure of CNTs.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.2
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• pp.80-87
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• 2009

Effects of retained austenite contents on ductility of medium carbon spring steels according to steel alloy compositions and heat treatment conditions were studied. Contents of retained austenite varied with steel compositions and heat treatment conditions, and some retained austenite were found to transform to martensite on stress. Reduction of area (RA) increased with contents of retained austenite, then saturated through its maximum, and subsequently decreased. Increase in RA with retained austenite contents could be due to crack blunting effect by retained austenite on stress, however, more contents of martensite transformed from retained austenite in its higher contents could cause decrease in RA.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.242-245
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• 2003

The purpose of this study is to investigate the shear modulus, the shear strength at failure and the failure process of QLS(quadruple-lap shear) Test specimen were made of two different fiber contents CFRR and HTPB based polyurethane matrix. The CFRR specimen were prepared with 6.16% chopped carbon fiber and 11.6% chopped carbon fiber. We carried out the shear tests for three types of specimen. The shear modulus and strength of the CFRR was inspected with the increasing contents of chopped carbon fiber. In the other hand the shear strain of the CFRR was inspected with the decreasing contents of chopped carbon fiber.

• Journal of Welding and Joining
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• v.6 no.4
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• pp.16-26
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• 1988

The effect of carbon content on hot cracking of welded carbon steel was investigated Eight steel plates whose carbon content range from 0.02 to 0.23 percent were welded by autogeous gas tungsten are process. Constant strain was applied to the hot crack test specimen under the strain rate of 0.15 mm per second during welding. The hot cracking susceptibility ws high in the rnage of 0.02-0.05 and 0.12-0.23 percent carbon contents. The critical carbon content immune to hot cracking is in the range from 0.07 to 0.12 percent carbon. By electron probe microanalyser, amanganese segregation was not seen significantly in the whole carbon range. But segregation of silicon was higher in the region of low carbon contents. However, sulphur was segregated remarkably in the region betwen 0.18 and 0.23 percent carbon by peritectic reaction. Very smal lamount of dnedritic structure was observed in the region from 0.02 to 0.05 percent carbon by peritectic reaction. Very small amount of dendritic structure was observed in the region from 0.02 to 0.05 percent carbon but the predominant solidification structure was smooth by cellular growth. The higher the carbon content is, the more the columnar dendritic structure was observed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.663-667
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• 2005

Surface modified carbon nanotubes were applied into the epoxy composites to investigate its tribological property. Carbon nanotubes reinforced epoxy composites were fabricated by casting. Effects to the tribological property of loading concentrations and types of surface modification of carbon nanotubes were investigated under sliding condition using linear reciprocal sliding wear tester. The results show that the small amount of carbon nanotubes into the epoxy exhibited lower weight loss than the pure epoxy. It is concluded that the effect of an enormous aspect ratio of carbon nanotubes surface area which wider than conventional fillers that react as interface for stress transfer. As increased the contents of carbon nanotubes, the weight loss from the wear test was reduced. And the surface modified carbon nanotubes show better tribological property than as produced carbon nanotubes. It is due that a surface modification of carbon nanotubes increases the interfacial bonding between carbon nanotubes and epoxy matrix through chemical bonding. Changes in worn surface morphology are also observed by optical microscope and SEM for investigating wear behaviors. Carbon nanotubes in the epoxy matrix near the surface are exposed, because it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the carbon nanotubes.

• Asian Journal of Atmospheric Environment
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• v.5 no.2
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• pp.113-120
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• 2011

Adsorbent combination studies have been carried out to remove nitrogen dioxide ($NO_2$) and volatile organic compounds (VOCs: BTEX) out of a subway environment characterized by high flow and low concentration. Optimal conditions for the high removal efficiency of the concerned target compounds were obtained through testing a series of control factors such as adsorbent sorts, thicknesses, and superficial velocity. It was found that the efficiencies increased as the specific surface area of activated carbon and its thickness increased, and external void fraction decreased. Furthermore, mixed activated carbon with granular and constructed contents was extensively tested to reduce pressure drop through the carbon bed. It was found that the performance of higher contents of granular activated carbon was better than that of higher contents of the constructed carbon. When the mixed carbon was applied to the subway ventilation system in order to eliminate $NO_2$ and VOC simultaneously, the removal efficiencies were found to be 75% and 85%, respectively.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.4
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• pp.176-180
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• 2016

In this study, a microstructural investigation was conducted on the cracking phenonmenon occurring during hot rolling of Fe-23Mn high-manganese steels with different aluminium and carbon contents. Particular emphasis was placed on the phase stability of austenite and ferrite dependent on the chemical composition. An increase in the aluminum content promoted the formation of ferrite band structures which were easily deformed or cracked. In the steels containing high carbon contents of 0.4 wt.% or higher, on the other hand, the volume fraction and thickness of ferrite bands decreased and thus the cracking frequency was significantly reduced. Based on these findings, it is said that the microstructural evolution occurring during hot rolling of high-manganese steels with different aluminium and carbon contents plays an important role in the cracking phenomenon. To prevent the cracking, therefore, the formation of second phases such as ferrite should be minimized during the hot rolling by the appropriate control of the chemical composition and process parameters

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.486-490
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• 2014

This study was conducted to investigate the effect of carbonized biomass from crop residues on soil carbon storage during soybean cultivation. The carbonized biomass was made by field scale mobile pyrolyzer. The treatments consisted of control without input and three levels of carbonized biomass inputs as $59.5kg10a^{-1}$, C-1 ; $119kg10a^{-1}$, C-2 ; $238kg10a^{-1}$, C-3. Soil samples were collected during the 113 days of experimental periods, and analyzed soil pH and moisture contents. Soil carbon contents and soybean yield were measured at harvesting period. For the experimental results, soil pH ranged from 6.8 to 7.5, and then increased with increasing carbonized material input. Soil moisture contents were slightly higher by 0.1~1.5% than the control, but consistent pattern was not observed among the treatments. Soil carbon and organic carbon contents in the treatments increased at 24 and 15% relative to the control at 15 days after sowing, respectively. Loss rate of SOC (soil organic carbon) relative to its initial content was 7.2% in control followed by C-1, 6.8%> C-2, 3.5%>C-3, 1.1% during the experimental periods. The SOC change rate decreased with increasing carbonized biomass rate. It was appeared that soybean yields were $476.9kg10a^{-1}$ in the control, and ranged from 453.6 to $527.3kg10a^{-1}$ in the treatments. However, significant difference was not found among the treatments. It might be considered that the experimental results will be applied to soil carbon sequestration for future study.