• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.45-49
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• 2006

The thermal degradation of carbon fiber reinforced phenolic composites have been studied at high temperature by using thermogravimetry analysis (TGA). The aim is that ultimately it can be used to predict the service temperature during solid rocket firing for any level and type of mechanical loading and to recommend protection systems required. To simulate the high heating rate in firing condition, the modified thermal decomposition constant (1000 K/min) was used for FEM analysis. The temperature distribution and the thickness of thermal decomposition were estimated well and we could predict the thickness of thermal decomposition within ${\pm}1mm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.538-541
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• 2002

탄소나노튜브 (CNT)가 도포된 평면형 에미터와 원형 개구의 게이트 전극을 가지는 삼전극 전계방출 소자의 전계방출 특성을 시뮬레이션하였다. 체계적인 시뮬레이션을 위해 소자 내 전위의 공간적 분포 특정을 결정하는 전계형상인자 $\gamma$를 정의하고 이 값에 따른 전위분포의 특성과 방출 전자의 궤적을 계산하였다. 계산 결과$\gamma$ > 1 인 전압조건에서는 에미터의 가운데를 중심으로 강한 전자방출이 발생하고 전자빔이 구조의 축 방향으로 자체 집속됨을 알 수 있었다. 이렇게 되면 에미터와 게이트의 정렬이 전혀 필요하지 않게 되며 또한 별도의 전자집속회로 없이도 에미터와 양극에 있는 형광체가 1:1 로 대응하는 획기적인 디스플레이 구조를 가능하게 해 준다 적정 전압조건에서 CNT의 전계강화인자 $\beta$의 변화에 따른 총 전류를 계산한 결과，$\beta$ >3000인 CNT를 사용할 경우 실제 소자로서 구현이 가능함을 확인하였다.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.781-785
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• 1998

Material and electrochemical characteristics of petroleum coke of the nongraphitic carbon prepated with attrition milling for 6~48 hours and heat-treatment at $700^{\circ}C$ for 1 hour was investigated. The milling condition affects the particle size distribution, BET specific surface area and interlayer distance of petroleum cokes. Carbon electrode with petroleum cokes prepared at the milling time of 12~24 hours and having average particle size of $6{\sim}8{\mu}m$ showed best electrochemical characteristics form the investigation of cyclic voltammogram and charge-discharge characteristics.

• The Korean Journal of Ecology
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• v.28 no.5
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• pp.265-270
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• 2005

In order to investigate the organic carbon distribution, net primary production, annual litter production, organic carbon in litter layer, soil organic carbon and soil respiration were studied in an oak forest, Kongju, Chungnam Province in Korea. Net primary production was estimated to 15.84 ton $C{\cdot}ha^{-1}{\cdot}yr^{-1}$. The amount of carbon allocated to leaf and reproductive organ, branch, stem and root was 1.71, 4.03, 7.34, 2.76 ton $C{\cdot}ha^{-1}{\cdot}yr^{-1}$ respectively. Annual litter production was 5.21 $ton{\cdot}ha^{-1}{\cdot}yr^{-1}$, which amounted to 2.35 ton $C{\cdot}ha^{-1}{\cdot}yr^{-1}$. Average amount of organic carbon in litter layer (L+F) was 6.06 ton C/ha, and that of L layer decreased from winter through summer. Soil organic carbon decreased along the soil depth. Average amount of soil organic carbon in this oak forest was 165.19 ton C/ha. The amount of carbon evolved through soil respiration was 11.24 ton $C{\cdot}ha^{-1}{\cdot}yr^{-1}$. Net amount of 4.60 ton $C{\cdot}ha^{-1}{\cdot}yr^{-1}$ was absorbed from the atmosphere by this oak forest.

• Journal of computational fluids engineering
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• v.7 no.2
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• pp.33-42
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• 2002

Numerical estimation for concentration of mono-carbon oxygen (CO) gas inside an underground parking lot with auxiliary jet fans for enhancement of ventilation is carried out by using a commercial program. Main interest lies on the diagnosis of the present ventilation system including position and selection of auxiliarly fans in addition to main suppliers and exhausts. Details of both flows and concentration of CO gas that is most important component among car exhaust gases are illustrated in this investigation and those are presented for engineering construction of an underground parking pool. Prediction data of computational work is also validated by real measurements of concentration of CO gas.

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.1-8
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• 2001

선택적 가스분리를 위한 분자체탄소(Molecular Sieve Carbon: MSC)로서의 활용을 위해 제조된 활성탄소섬유의 흡착능과 분자체 특성이 다양한 분자크기를 갖는 가스 흡착실험을 통해 조사되었다. 각 활성화 조건별 세공크기분포와 세공발달 전개과정을 유추함으로서, 세공크기분포의 조절이 가능하게 되었으며 활성탄소섬유의 분자체 탄소로서 활용을 용이하게 할 수 있었다. 800, 85$0^{\circ}C$의 온도로 수증기에 의해 활성화한 활성탄소섬유의 경우 burn-off가 각각 50, 40% 정도를 가진 활성탄소섬유가 비교적 작은 분자크기(0.3~0.4nm)의 흡착질에 대한 분자체 특성을 나타냈다. 또한, 다양한 분자크기의 흡착질을 포함하는 혼합가스의 유속과 흡착온도의 조절로서 원하는 흡착질의 선택적 분리를 위해 활성탄소섬유가 갖는 분자체 특성 향상을 보였다.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.153-162
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• 2002

This paper predicted the engineering constants of spatially reinforced carbon/ carbon composites and analyzed the mechanical behaviour of the kick motor nozzle. Those equivalent engineering constants are used to analyze the mechanical behaviour of the kick motor nozzle. Because the distribution of equivalent engineering constants is varying as change its structure, we made a program to predict engineering constants of spatially reinforced composites. The kick motor nozzle consists of graphite or spatially reinforced carbon/ carbon composites for the nozzle throat, carbon/ phenol for the nozzle entrance and the expansion part, and steel for the outer surface of the expansion part. The 4-D carbon/ carbon composite shows the smallest deformed shape of the nozzle throat, which has a favorable effect on the rocket thrust, and the most uniform deformation of all nozzle throat materials. In addition to analysis, ground firing tests of 4D C/ C nozzle throat and graphite nozzle throat were performed.

• 한국전기화학회:학술대회논문집
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• 2000.10a
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• pp.43-43
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• 2000

• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.627-633
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• 2014

Annual biomass production and amount of organic carbon in Abies koreana forest at Mt. Halla were conducted as a part of Korea National Long-Term Ecological Research (KNLTER). We measured standing biomass change of litter, soil production and organic carbon amounts of the forest floor and soil layer of A. koreana forest in Mt. Halla from 2009 to 2013 in permanent plots. Standing biomass, which was determined by allometric method, was converted into $CO_2$. The standing biomass in A. koreana forest was 98.88, 106.42, 107.67, 108.31, $91.48ton\;ha^{-1}$ in 2009, 2010, 2011, 2012 and 2013 year, respectively. The amount of annual carbon allocated to above ground was 35.95, 38.69, 38.96, 39.46, $33.2ton\;C\;ha^{-1}$ and below ground biomass was 8.54, 9.2, 9.49, 9.28, $7.97ton\;C\;ha^{-1}$ in 2009, 2010, 2011, 2012 and 2013 year, respectively. Amount of organic carbon returned to the forest via litterfall was 1.09, 1.80, 1.32, 2.46 and $1.20ton\;C\;ha^{-1}$ in 2009, 2010, 2011, 2012 and 2013. Amount of organic carbon in annual litter layer on forest floor was 2.74, 2.43, 2.00 and $1.16ton\;C\;ha^{-1}$ in 2010, 2011, 2012 and 2013 year, respectively. Amount of organic carbon within 20cm soil depth was 55.77, 54.9, 50.69, 44.42 and $41.87ton\;C\;ha^{-1}20cm^{-1}$ in 2009, 2010, 2011, 2012 and 2013 year, respectively. Then standing biomass and organic carbon distribution increased steadily until 2012. But there declined in 2013 because of the typhoon Bolaven. Thus, standing biomass and organic carbon distribution of this subalpine forest were largely affected by natural disturbance factor.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.29-35
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• 2010

Soil organic carbon (SOC), being a help to forest formation and control of carbon dioxide in the air, is found to be an important factor by which global warming is influenced. Excavating the samples by whole area is very inefficient method to discovering the distribution of SOC. So, the development of suitable model for expecting the relative amount of the SOC makes better use of expecting the SOC. In the present study, a model based on a decision tree algorithm is introduced to estimate the amount of SOC along with accessing influencing factors such as altitude, aspect, slope and type of trees. The model was applied to a real site and validated by 10-fold cross validation using two softwares, See 5 and Weka. From the results given by See 5, it can be concluded that the amount of SOC in surface layers is highly related to the type of trees, while it is, in middle depth layers, dominated by both type of trees and altitude. The estimation accuracy was rated as 70.8% in surface layers and 64.7% in middle depth layers. A similar result was, in surface layers, given by Weka, but aspect was, in middle depth layers, found to be a meaningful factor along with types of trees and altitude. The estimation accuracy was rated as 68.87% and 60.65% in surface and middle depth layers. The introduced model is, from the tests, conceived to be useful to estimation of SOC amount and its application to SOC map production for wide areas.