• Journal of the Korean Wood Science and Technology
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• v.41 no.6
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• pp.594-605
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• 2013

This study was performed to analyze GHG (Greenhouse gas) reduction effectiveness and economic feasibility in the wood pellet fuel switching project using JCDM (Japan Clean Development Mechanism) and KVER (Korea Voluntary Emission Reduction)data. The major data for the analyses consist of investment costs, annual GHG reductions, fuel prices and GHG credit prices. The wood pellet fuel switching projects are the $CO_2$-zero projects. Therefore, these projects are essential to accomplish the GHG mitigation target, especially in Korea. In order to raise the economic feasibility of the wood pellet fuel switching project, the results of this study suggest that the Korean government should reduce the price of wood pellet through the supply on a large scale and raise the KCER price of wood pellet fuel switching project.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.563-569
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• 1999

The numerical simulation method was utilized to investigate the optimal condition for synthesizing ultrafine SiC powders by using $TMS[Si(CH_3)_4]-H_2$ gaseous mixtures in the horizontal reactor. As a result of the theoretical analysis, the conversion percentage of TMS source was increased with increasing reaction temperature, however, which was decreased with increasing H$_2$flow rate. Though the SiC particles concentration synthesized was decreased with increasing the reaction temperature due to the higher collision rate in the gas phase, they were increased with increasing the H$_2$flow rate and TMS concentration. The SiC particle size showed a tendency to become larger as the reaction temperature and the initial TMS concentration were increased and smaller as the H$_2$ flow rate was increased. The variation of experimental particle size with the reaction temperature, H$_2$flow rate and TMS concentration was agreed with the theoretical results.

• Polymer(Korea)
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• v.24 no.5
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• pp.610-620
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• 2000

Vinyl acetate (VAc) was polymerized at 30, 40, and 5$0^{\circ}C$ using 2,2'-azobis (2,4-dimethylvaleronitrile) (ADMVN) and tertiary butyl alcohol (TBA) as the initiator and the solvent, respectively. High molecular weight (HMW) atactic poly(vinyl alcohol) (PVA) was prepared by saponifying the poly(vinyl acetate) (PVAc) synthesized. The effect of polymerization conditions were investigated in terms of conversion, degree of branching for acetyl group of PVAc, and molecular weight of both PVAc and PVA. The polymerization rate of VAc in TBA was proportional to the 0.49th power of ADMVN concentration in good accordance with the theoretical value of 0.5. HMW-PVA with high yield could be obtained successfully, probably due to lower polymerization temperature and decreased chain transfer reaction rate which was achieved by adopting ADMVN and TBA. PYAc having average degree of polymerization (P$_{n}$) of 10000~13000 was obtained at the conversion of 35~70%. Saponification of so prepared PVAc yielded PVA having P$_{n}$ of 2400~6100. The syndiotactic diad content increased with decreasing polymerization temperature and increasing VAc concentration due to a steric hindrance effect of TBA during polymerization.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.969-973
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• 1997

In order to produce transglucosylated steviosides continuously, some types of bioreactors were investigated with cyclodextrin glucanotransferase immobilized on a high porous anion exchange resin, Diaion HPA75. Among the bioreactors, the packed-bed reactor (PBR) showed the highest specific productivity. The effect of linear velocity in a PBR on the stevioside conversion was not significant in the range of $10{\sim}60\;cm/hr$ at the same space velocity of $1.2\;hr^(-1)$. When the space velocity of bioreactor was varied from 0.2 to $1.1\;hr^{-1}$, the optimal velocity of substrate solution was determined as $0.7\;hr^(-1)$. The stevioside conversion of more than 70% was maintained during 20 days in the continuous operation, if about 20% of immobilized enzyme was replaced in the top of reactor after two weeks operation as the one of the control methods in bioreactor. The specific production, which refers to as the amount of commercially valuable transglucosylated steviosides produced by a unit amount of immobilized cyclodextrin glucanotransferase, was found to be ca. 150g product/g immobilized enzyme.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.3
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• pp.298-307
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• 2010

The purpose of this study was to assess the effect on oxygen inhibition layer(OIL) for the interfacial bonding between resin composite layers, including shear bond strength, fracture modes and degree of conversion. The first layer of specimen was filled with Z-250(shade A3) and was cured for 40s. The second layer of specimen was filled with same composite(shade A1) and was cured for 40s. The first layer of specimens for each group were prepared by methods as followings. Control(curing in atmospheric air), Group1(curing against Mylar strip), Group2(scrubbed with a acetone-soaked cotton), Group3(using Tescera light cup), Group4(using Tescera heat cup), Group5(stored in disti1led water for 30days at $37^{\circ}C$), Group6 (using bonding agent). The results were as follows: 1. There was no statistically significant different shear bond strength between control and group 1(p>0.05). 2. Group 2 showed significantly lower shear bond strength than control and group 1(p<0.05). 3. The observation of the fracture surface leads to the evidence that a major difference occurs in the case of control, group1 and group 3 samples which break mainly cohesively while the other groups break in majority adhesively. 4. The results of FTIR showed that the degree of conversion was the highest in group 2 and the lowest in control group(p<0.05). It can be concluded that an OIL is not necessary for bonding with composite resin. But if a reduced critical amount of the unreacted monomer is present, it was detrimental to bonding additional layers of composite. Further study, such as the quantitative analysis of the unreacted monomer are required.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.3
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• pp.101-109
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• 2006

Earthworms(Eisenia fetida) were fed with paper mill sludge produced from P&G or Yuhan Kimberly paper manufacturing factory, or cow dung manure. Turnover rate of feed into earthworm biomass and excreting rate on each feed were investigated on dry weight base. Biomass of earthworm population was increased on paper mill sludge, but it was fallen to death on cow dung manure, which had high electrical conductivity and low redox potential. When P&G paper mill sludge was supplied to adult, elder juvenile or younger juvenile for 84 days, turnover rate of feed into earthworm biomass was 0.48, 0.40 and 0.76%, respectively, and on Yuhan Kimberly paper mill sludge 0.26, 0.45, 0.42%. When P&G paper mill sludge was supplied to adult, elder juvenile or younger juvenile, excreting rate was 49.02, 54.32 and 55.39%, respectively and on Yuhan Kimberly paper mill sludge 32.22, 41.86, 40.69%, and on cow dung manure, 73.73, 57.89. 76.38%.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.183.1-183.1
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• 2010

본 논문에서는 풍력발전기의 회전속도센서의 고장 발생 시 고장을 검출하고 회전속도센서의 사용 없이 Sensorless 제어로의 전환에 관한 연구를 기술하였다. 최근 풍력발전은 급속한 성장함에 따라 풍력발전기의 대형화 및 해상풍력화 추세에 있다. 특히 해상풍력발전은 바람 및 설치장소의 제약에서 벗어나는 이점에 반해 염해, 습도 및 파도에 의한 진동 발생으로 센서의 고장 발생률이 높을 것으로 예상된다. 이에 따라 풍력발전기의 회전속도센서 고장 발생 시 이를 검출하는 방법을 제시하였다. 또한 회전속도센서의 고장이 검출되면 회전속도센서를 이용한 풍력발전기 제어방식에서 Sensorless 제어로의 전환을 통해 안전하게 풍력발전기를 운전할 수 있도록 하였다. 연구된 제어기법은 PSIM을 이용한 시물레이션을 통해 결과를 검증하였다.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.19-20
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• 2012

본 논문은 독립 다상 대용량 전동기의 상수 전환 기법에 관한 것이다. 독립 다상 전동기는 DC단 전압 이용률이 높고 고장에 강한 특성을 가지는 장점이 있지만, 많은 스위치 개수로 인하여 높은 스위칭 손실이 발생한다는 단점 역시 존재한다. 그러므로 저속 영역에서 독립된 다상 중 일부를 직렬 연결하여 상의 수를 감소시켜 저출력 영역에서의 효율을 개선할수 있다. 제안된 방법은 전류가 비도통 되는 구간에서 독립다상 BLDC 전동기의 일부 상을 순차적으로 직렬 연결함으로써 상수전환으로 인한 토크 맥동을 야기시키지 않으며 스위치의 스트레스를 줄일수 있고, 수명을 연장할수 있다. 제안된 방법의 효용성은 시뮬레이션을 통해서 증명하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1182-1185
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• 2013

도로명주소가 법적 주소체계로 지정되고 2014년도부터 전면 시행을 앞두고 있는 상황에서 기존의 지번주소를 도로명주소로 변경하려는 수요가 늘고 있으며 그에 따라 주소 전환 서비스를 제공하는 솔루션들이 증가하고 있다. 행정구역 체계에 따라 단계별로 입력된 지번주소의 도로명주소로의 변환은 크게 어렵지 않고 변환 성공율도 상당히 높지만 자유롭게 입력하여 정제되지 않은 형태의 주소는 전환에 실패하는 경우가 많다. 본 논문에서는 전산입력된 지번주소를 도로명주소로 변환시 주소형태가 정제되지 않은 상황에서도 변환 성공률을 높이기 위해 행정구역 줄임, 일부 주소정보 누락, 오타 등 여러 가지 변형 케이스에 대해서도 유연하게 변환을 수행하는 방안을 연구하였다. 이를 통해 기존 지번 주소의 표준 형태로의 정제는 최대 두 배까지 변환효율을 높일 수 있었다. 그러나 변환시 사용하는 도로명주소 매칭 테이블에 자료의 누락, 건물명의 불일치, 지번과 건물의 1:1 매칭이 되지 않는 경우가 존재하여 원활한 주소 전환을 위해서는 데이터의 정비가 필요하다.

• The Korean Journal of Financial Management
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• v.14 no.3
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• pp.183-201
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• 1997

본 논문은 우리나라의 주가지수수익률의 변동특성이 카오스를 내재하고 있는지 아니면 랜덤과정을 따르는지를 분석하기 위하여 Hurst의 R/S분석을 중심으로 분석하였다. 우리나라 증권시장의 1980년 1월 5일부터 1996년 말까지 총 4,982일 동안의 일별종합주가지수를 대수수익률로 전환한 시계열자료로 R/S분석한 결과 안정성과 주기유무를 판별하는 V-통계량 그래프에 의하면 83일과 33일의 비주기적 순환을 나타내고 있음을 알 수 있었다. 이러한 분석결과는 가우시안 랜덤과정과 그다지 큰 차이가 나지 않음을 알 수 있었다. 또한 선형성을 제거한 ARMA잔차와 비선형성을 제거한 GARCHM잔차자료에 대한 R/S분석한 결과도 원래 시계열보다 더 가우시안 랜덤과정에 더 근접함을 알 수 있었다. 한편 총 10개의 대리자료를 만들어서 평균을 취한 값으로 분석한 결과도 마찬가지로 나타나고 있다. 일별주가지수수익률에 내재하는 선형성분을 ARMA과정에 의정에 제거하고 남은 잔차중에는 비선형성분이 여전히 잔존하는데 그것이 일부 GARCHM과정에 의해서 미미하고 가우시안 랜덤과정이 보다 크게 나타남을 알 수 있었다.