• 한국수자원학회논문집
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• 제43권12호
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• pp.1083-1091
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• 2010

분포형 수문 모형의 일강우 입력 자료는 불가피하게 불규칙하고 밀도가 낮은 관측망에서 기록된 값을 내삽해 사용하게 되나, 흔히 사용되는 대부분의 내삽법들은 실제 일강우의 다양한 공간적 분포를 잘 재현하지 못하는 문제가 있다. 본 연구에서는 널리 사용되는 다섯 가지의 강우 내삽 방법을 두개의 유역에 사용하여 비교하고 실제 공간적 분포를 보다 잘 나타낼 수 있는 2단계 내삽법을 제안하였다. 비교에 사용된 내삽법은 (1) 역가중치 방법(IDW), (2) 다중회귀분석 (MLR), (3) 월강우를 이용한 다중회귀분석법(CMLR), (4) 국지가중치 다중회귀분석(LWP) 등이다. 보다 향상된 내삽을 위한 2단계 내삽법은 먼저 로지스틱 회귀분석으로 강우-비강우 지역을 구분하고 강우 지역에서만 기존의 내삽법을 적용하여 강우량을 구하는 방법이다. 기존 방법과의 비교결과 공간적인 편차가 심한 일강우의 특성을 2단계 내삽법에서 잘 표현하고 있는 것으로 나타났다. 제안된 방법은 수문모형에의 적용뿐만 아니라 유출량의 예보 및 대기 순환 모형의 다운 스케일링에도 효과적으로 사용될 수 있을 것으로 기대된다.

• Computers and Concrete
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• 제15권6호
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• pp.989-999
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• 2015

An advanced continuum-based multi-physical single particle model was recently introduce for the hydration of tricalcium silicate ($C_3S$). In this model, the dissolution and the precipitation events are modeled as two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted core and product growth is characterized via a two-step densification mechanism having rapid growth of a low density initial product followed by slow densification. Although this modeling strategy has been shown to nicely mimic all stages of $C_3S$ hydration - dissolution, dormancy (induction), the onset of rapid hydration, the transition to slow hydration and prolonged reaction - the major criticism is that many adjustable parameters are required. If formulated correctly, however, the model parameters are shown here to be statistically independent and significant.

• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.104-108
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• 2015

Al thin films were deposited on TiN/Si(100) via metal-organic chemical vapor deposition using N-methylpyrrolidine alane as a precursor. Characterization of the deposited films were investigated with SEM, XRD, ${\alpha}$-step, AFM, 4-point probe. The early stage of Al thin film deposition was analyzed by in-situ surface reflectance measurement with laser and photometer apparatus. The surface reflectance were changed greatly during the initial 30~40 seconds. There were two increases and two decreases in the surface reflectance, thus the sequence of Al films were deposited at 8 significant points of the surface reflectance change. Surface topograph and cross-sectional view of each film were analyzed with SEM. Al films were grown in the complex mechanism of Volmer-Weber and Stranski-Krastanov process.

• Journal of the Korean Data and Information Science Society
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• 제23권2호
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• pp.393-401
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• 2012

This paper deals with the estimations of the least squares support vector regression when the responses are subject to randomly right censoring. The estimation is performed via two steps - the ordinary least squares support vector regression and the least squares support vector regression with censored data. We use the empirical fact that the estimated regression functions subject to randomly right censoring are close to the true regression functions than the observed failure times subject to randomly right censoring. The hyper-parameters of model which affect the performance of the proposed procedure are selected by a generalized cross validation function. Experimental results are then presented which indicate the performance of the proposed procedure.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1457-1463
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• 1999

Structure and their redox property of the vanadium oxides prepared by decomposing NH₄VO₃ at various temperatures were studied by XRD, SEM, XPS, and temperature programmed reduction/temperature programmed oxidation (TPR/TPO) experiment. All TPR profiles have two sharp peaks in the temperature range 650-750℃, and the area ratio of the two sharp peaks changed from sample to sample. There were three redox steps in TPR/TPO profiles. The oxidation proceeded in the reverse order of the reduction process, and both the reactions proceeded via quite a stable intermediates. The changes of the morphological factor $(I_{(101)}/I_{(010)})$, the ratio of $O_{1S}$ peak area (O$_{1S}$( α)/O$_{1S}$( β)) in the XPS results, and the ratio of hydrogen consumption in TPR profiles with various vanadium oxides showed the distinct relationship between the structural property and their redox property of vanadium oxides. The change of the specific yield of phthalic anhydride with various vanadium oxides showed a very similar trend to those of the peak area ratio in TPR profiles, which meant that the first reduction step related to the partial oxidation of o-xylene on the vanadium oxide catalyst.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.339.1-339.1
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• 2002

Since two selective COX-2 inhibitors. celecoxib and rofecoxib, showed good biological activity as antiinflammatory agents. many medicinal chemists are interested in specific COX-2 inhibitors. The distinguished feature of these drugs is that the 5-membered heterocycle ring is substituted with two aryl groups. Therefore, in this study, we designed a new hydantoin derivatives via the reaction of unnatural amino acids as selective COX-2 inhibitors, In systematically steps. 5-phenyl-1 (or substituted) hydantoin derivatives were prepared through esterification. bromination, C-N bond formation, cyclization from phenyl acetic acid. Particularly. a novel hydantoin ring was converted from unnatural amino acids with potassium isoyanate. In last step. the final analogs were synthesized the substitution at 3-position with alkyl reagents.

• Korean Journal of Geomatics
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• 제2권1호
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• pp.37-46
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• 2002

Accurate classification of water area is an preliminary step to accurately analyze the flooded area and damages caused by flood. This step is especially useful for monitoring the region where annually repeating flood is a problem. The accurate estimation of flooded area can ultimately be utilized as a primary source of information for the policy decision. Although SAR (Synthetic Aperture Radar) imagery with its own energy source is sensitive to the water area, its shadow effect similar to the reflectance signature of the water area should be carefully checked before accurate classification. Especially when we want to identify small flood area with mountainous environment, the step for removing shadow effect turns out to be essential in order to accurately classify the water area from the SAR imagery. In this paper, the flood area was classified and monitored using multi-temporal RADARSAT SAR images of Ok-Chun and Bo-Eun located in Chung-Book Province taken in 12th (during the flood) and 19th (after the flood) of August, 1998. We applied several steps of geometric and radiometric calculations to the SAR imagery. First we reduced the speckle noise of two SAR images and then calculated the radar backscattering coefficient $(\sigma^0)$. After that we performed the ortho-rectification via satellite orbit modeling developed in this study using the ephemeris information of the satellite images and ground control points. We also corrected radiometric distortion caused by the terrain relief. Finally, the water area was identified from two images and the flood area is calculated accordingly. The identified flood area is analyzed by overlapping with the existing land use map.

• 대한화학회지
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• 제19권2호
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• pp.104-115
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• 1975

요오드의 전기화학적 환원과정을 여러가지 특성을 가진 물아닌 용매 속에서 polarography, chronopotentiometry, cyclic voltammetry, controlled potential coulometry 등의 전기분석적 방법을 이용하여 적하수은전극, 백금, 금 및 백금아말감전극등을 사용하여 상세히 조사하였다. 메탄올, 에탄올, 이소프로판올 및 피리딘과 같은 양쪽성 용매 속에서는 $I_2{\longrightarrow}I^-$의 I단계 환원과정을 거치며 아세톤, 디메틸포름아미드, 메틸에틸케톤, 디메틸술폭시드, 아세토니릴과 같은 반양성자 용매속에서는 $I_2{\longrightarrow}I_3^-{\longrightarrow}I^-$의 2단계 환원과정을 거쳤다. 적하수은전극, 고인 수은전극, 백금, 금 그리고 백금아말감전극등 전극조건을 다르게 하였을 때에도 $^'I_2$의 환원과정은 같았으며 사용한 모든 전극에서 확산지배적이었다. 반양성자용매에 물을 첨가하여 그 영향을 걸토한 결과 물의 첨가량이 약 $50v/v{\%}$ 이상일때 2단계의 환원과정이 1단계의 환원과정으로 줄어들었다. 또 chronopotentiometric data와 Send의 식으로부터 계산한 각 용매 속에서의 요오드의 확산계수는 $D_{I2}^{AN}=5.96{\times}10^{-6}cm^2/sec,\;D_{13-}^{AN}=9.63{\times}10^{-6}cm^2/sec,\;D_{I2}^{MeOH}=5.30{\times}10^{-6}cm^2/sec$이였다. 전기화학적 환원과정의 stoichiometry를 알아 보고저 controlled potential coulometry로 使用하였으며, 얻은 생성물은 은법적정으로 확인 및 정량하였다.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.109-115
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• 2007

Solar energy conversion to hydrogen was carried out via a two-step thermochemical water splitting using metal oxide redox pair. To simulate the solar radiation, a 7 kW short arc Xe-lamp was used. Partially reduced iron oxide and cerium oxide have the water splitting ability, respectively. So, $Fe_3O_4$ supported on $CeO_2$ was selected as the active material. $Fe_3O_4/CeO_2$(20 wt/80 wt%) was prepared by impregnation method, then the active material was washcoated on the ceramic honeycomb monolith made of mullite and cordierite. Oxygen was released at the reduction step($1673{\sim}1823\;K$) and hydrogen was produced from water at lower temperature($873{\sim}1273\;K$). The result demonstrate the possibility of the 2-step thermochemical water splitting hydrogen production by the active material washcoated monolith. And hydrogen and oxygen was produced separately without any separation process in a monolith installed reactor. But the SEM and EDX analysis results revealed that the support used in this experiment is not suitable due to the thermal instability and coating material migration.

• Journal of the Korean Wood Science and Technology
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• 제45권3호
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• pp.278-287
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• 2017

본 연구에서는 2단계 촉매 분해공정 시스템을 이용하여 효과적으로 리그닌을 분해하였으며 리그닌 분해산물로 액상의 리그닌 오일, 촤, 가스가 생성되었다. 1차 촉매 분해공정에서는 MgO, CaO, Pt/C 촉매를 사용하였으며 Pt/C 촉매를 사용했을 때 가장 높은 리그닌 오일 수율(76.2 wt%) 및 가장 낮은 촤 수율(4.1 wt%)을 얻을 수 있었다. 리그닌 오일의 GC-MS/FID 분석을 통해 guaiacol, 4-ethylphenol, 4-methylguaiacol, 4-ethylguaiacol, syringol 등 18종류의 페놀화합물을 검출하였으며 Pt/C 조건에서 생산된 페놀화합물 수율이 97.8 mg/g lignin로 가장 높았다. 한편 MgO와 CaO에서 생산된 페놀화합물은 촉매에 흡착되어 상대적으로 낮은 수율을 보였다. Pt/C 조건에서 생산된 리그닌 오일을 다공성 구조를 가지는 Pd/activated carbon aerogel 촉매 하에서 추가 분해하였다. 2차 촉매 분해공정을 통해 상대적으로 선택성이 높은 4가지 페놀화합물(4-ethylguaiacol, 4-propylguaiacol, 4-ethylsyringol, 4-propylsyringol)을 0.89 - 1.82 wt% 수준으로 생산하였다.