계단형 텅스텐 결정면의 질소 흡착에 관한 연구 : Ⅱ. W(210) 및 W(310)면

최대선(D. S. Choi),한종훈(J. H. Han),백선목(S. M. Paik),박노길(N. G. Park),김욕욱(Y. W. Kim),황정남(C. N. Whang) 한국진공학회(ASCT) 1996 Applied Science and Convergence Technology Vol.5 No.4

장전자 방출법으로 텡스텐 (210)면 및 (310)면(100)면의 질소 흡착에 의한 일함수의 변화에 heat of desorption을 측정하였으며 Thermal Desortion Spectra(TDS) 결과로부터 adsorption site를 예측하였다. 텅스텐 (210)면 및 (310)면에 에 질소가 흡착될 때 흡착율에 따라 일함수는 증가하다가 각 면에 대하여 흡착율 5 Langmuir일때 최대 변화량 0.29 eV및 0.20 eV에서 포화되었다. TDS 결과는 이 면들은 낮은 dose의 영역에서 각각 3개의 흡착 site가 있음을 보였으며 이 흡착 site들 중 α₁state의 spectrum의 강도는 (210)면에서 보다 (310)면에서 상대적으로 강해짐을 보였다. 또한 (210)와 (310)면의 α₁ 과 β₂ state의 흡착 site에 흡착된 질소의 dipole moment의 방향은 이 흡착 site들에 대응되는 (100)면의 α₁ 과 β₂state의 흡착 site에 흡착된 질소의 dipole moment의 방향과 반대 방향으로 측정되었으며 이 현상으로부터 질소의 상대적인 흡착 위치를 예측하였다. The heat of desorption and the work function change induced by nitrogen adsorption on the stepped tungstein surface planes, W(210) and W(310), are measured using the Field Electron Emission Microscope(FEM). The adsoption sites are predicted from the Thermal Desortion Spectra(TDS). The work function change of both W(210) and W(310) planes increase as increasing the nitrogen dose and saturates at the nitrogen dose about 5 Langmuir to 0.29 eV and 0.20 ev respectively. We find three adsorption site on each plane for the low dose range. The TDS result shows that the intensity of α₁, state on W(310) is much stronger than that of α₁ state on W(210), and the direction of nitrogen dipole moment adsorbed on the sites correspond to α₁, and β₂ states on W(210) and W(310) planes are in the opposite direction to that of the equivalent states on W(100) plane. From this observation we can predict the relative atomic position in the zdirection (perpendicular direction to the surface) of nitrogen molecules/atoms adsorbed on these sites.

Estimation of Genetic Parameters for Direct, Maternal and Grandmatemal Genetic Effects for Birth, Weaning and Six Month Weights of Hanwoo (Korean Cattle)

Choi, S.B.,Lee, J.W.,Kim, N.S.,Na, S.H.,Keown, J.F.,Van Vleck, L.D. Asian Australasian Association of Animal Productio 2000 Animal Bioscience Vol.13 No.2

The objectives of this study of Hanwoo (Korean Cattle) were 1) to estimate genetic parameters for direct and maternal genetic effects for birth weight, weaning weight, and six months weight which can be used for genetic evaluations and 2) to compare models with and without grandmatemal effects. Data were obtained from the National Livestock Research Institute in Rural Development Administration (RDA) of Korea and were used to estimate genetic parameters for birth weight (BW, n=10,889), weaning weight at 120-d (WW, n=8,637), and six month weight (W6, n=8,478) in Hanwoo. Total number of animals in pedigrees was 14,949. A single-trait animal model was initially used to obtain starting values for multiple-trait animal models. Estimates of genetic parameters were obtained with MTDFREML using animal models and derivative-free REML (Boldman et al., 1995). Estimates of direct heritability for BW, WW, and W6 analyzed as single-traits were 0.09, 0.03, and 0.02 from Model 3 which included direct and maternal genetic, maternal permanental environmental effects, and effects due to sire ${\times}$ region ${\times}$ year-season interaction, respectively. Ignoring sire ${\times}$ region ${\times}$ year-season interaction effect in the model (Model 2) resulted in larger estimates for direct heritability than for Model 3. Estimates of maternal heritability for BW, WW and W6 were 0.04, 0.05, and 0.07 from Model 3, respectively. The estimates of direct-maternal genetic correlation were positive for BW, WW, and W6 with Model 3 but were negative with Model 2 for WW and W6. Estimates of direct genetic correlations between BW and WW, BW and W6, and WW and W6 were large: 0.52, 0.45, and 0.90, respectively. Genetic correlations were also large and positive for maternal effects for BW with maternal effects for WW and W6 (0.69 and 0.74), and even larger for WW with W6 (0.97). The log likelihood values were the same for models including grandmatemal effects as for models including maternal effects for all traits. These results indicate that grandmatemal effects are not important for these traits for Hanwoo or that the data structure was not adequate for estimating parameters for a grandmatemal model.

확산펌프 기반의 BCl<SUB>3</SUB> 축전결합 플라즈마를 이용한 GaAs와 AlGaAs의 건식 식각

이성현,박주홍,노호섭,최경훈,송한정,조관식,이제원,Lee, S.H.,Park, J.H.,Noh, H.S.,Choi, K.H.,Song, H.J.,Cho, G.S.,Lee, J.W. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4

본 논문은 확산펌프 기반의 축전 결합형 $BCl_3$ 플라즈마를 사용하여 GaAs와 AlGaAs를 건식 식각한 연구에 관한 것이다. 실험에서 사용한 압력 범위는 $50{\sim}180$ mTorr, CCP 파워는 $50{\sim}200\;W$, $BCl_3$ 가스 유량은 $2.5{\sim}10$ sccm 이었다. 식각 후에 GaAs와 AlGaAs의 식각 속도와 표면 거칠기분석은 표면 단차 측정기를 이용하여 하였다. GaAs의 식각 벽면과 표면 상태는 전자현미경으로 분석하였다. 식각 중 플라즈마의 광 특성 분석은 광학 발광 분석기를 이용하였다. 본 실험을 통하여 5 sccm의 소량의 $BCl_3$ 가스 유량으로 공정 압력이 130 mTorr이내인 경우에는, 100 W CCP 파워의 조건에서 GaAs는 약 $0.25{\mu}m$/min 이상의 우수한 식각 속도를 얻을 수 있었다. AlGaAs의 경우는 GaAs의 식각 속도보다 조금 낮았다. 그러나 같은 유량에서 공정압력이 180 mTorr로 높아지면 GaAs와 AlGaAs의 식각 속도가 급격히 감소하여 거의 식각되지 않는 것을 알 수 있었다. 또한 CCP 파워의 경우에는 50 W의 파워에서는 GaAs와 AlGaAs 모두 거의 식각되지 않았다. 그러나 $100{\sim}200\;W$의 조건에서는 $0.3{\mu}m$/min 이상의 높은 식각 속도를 주었다. 두 결과를 보았을 때 축전결합형 $BCl_3$ 플라즈마 식각에서 GaAs와 AlGaAs의 식각 속도는 CCP 파워가 $100{\sim}200\;W$ 범위에 있으면 그 값에 비례하지 않고 거의 일정한 값이 된다는 사실을 알았다. 75mTorr, 100 W의 CCP 파워 조건에서 $BCl_3$의 유량 변화에 따른 GaAs와 AlGaAs의 식각 속도의 경우, $BCl_3$의 유량이 2.5 sccm의 소량일 때는 GaAs는 식각 속도가 높았지만 AlGaAs는 거의 식각되지 않는 흥미로운 결과를 얻었다. 플라즈마 발광 특성을 보면 $BCl_3$ 축전 결합 플라즈마는 주로 $500{\sim}700\;mm$ 범위를 가지는 넓은 분자 피크만 만든다는 것을 알 수 있었다. 전자 현미경 사진 결과에서는 5 sccm과 10 sccm의 $BCl_3$ 플라즈마 모두 식각 중에 GaAs의 벽면을 언더컷팅 하였으며, 10 sccm의 $BCl_3$유량을 사용하였을 때 언더컷팅이 더 심했다. We report the etch characteristics of GaAs and AlGaAs in the diffusion pump-based capacitively coupled $BCl_3$ plasma. Process variables were chamber pressure ($50{\sim}180$ mTorr), CCP power ($50{\sim}200\;W$) and $BCl_3$ gas flow rate ($2.5{\sim}10$ sccm). Surface profilometry was used for etch rate and surface roughness measurement after etching. Scanning electron microscopy was used to analyze the etched sidewall and surface morphology. Optical emission spectroscopy was used in order to characterize the emission peaks of the $BCl_3$ plasma during etching. We have achieved $0.25{\mu}m$/min of GaAs etch rate with only 5 sccm $BCl_3$ flow rate when the chamber pressure was in the range of 50{\sim}130 mTorr. The etch rates of AlGaAs were a little lower than those of GaAs at the conditions. However, the etch rates of GaAs and AlGaAs decreased significantly when the chamber pressure increased to 180 mTorr. GaAs and AlGaAs were not etched with 50 W CCP power. With $100{\sim}200\;W$ CCP power, etch rates of the materials increased over $0.3{\mu}m$/min. It was found that the etch rates of GaAs and AlGaAs were not always proportional to the increase of CCP power. We also found the interesting result that AlGaAs did not etched at 2.5 sccm $BCl_3$ flow rate at 75 mTorr and 100 W CCP power even though it was etched fast like GaAs with more $BCl_3$ gas flow rates. By contrast, GaAs was etched at ${{\sim}}0.3{\mu}m$/min at the 2.5 sccm $BCl_3$ flow rate condition. A broad molecular peak was noticed in the range of $500{\sim}700\;mm$ wavelength during the $BCl_3$ plasma etching. SEM photos showed that 10 sccm $BCl_3$ plama produced more undercutting on GaAs sidewall than 5 sccm $BCl_3$ plasma.

포스터 전시 : 간 ; 빙초산 음독후 발생한 DIC와 간경색증 1예

최원욱 ( W. W. Choi ),조정수 ( J. S. Cho ),정인수 ( I. S. Jung ),이진혁 ( J. H. Lee ),김태헌 ( T. H. Kim ),최일주 ( I. J. Choi ),박영숙 ( Y. S. Park ) 대한소화기학회 2002 대한소화기학회 춘계학술대회 Vol.2002 No.-

<서론> 간은 간동맥과 간문맥으로부터 이중으로 혈액을 공급받는 장기로서 경색증이 발생하는 경우는 드문 것으로 알려져 있으며 대부분 수술이나 방사선학적시술의 합병증으로 나타난 예들이 보고되고 있다. 파종성 혈관내 응고장애(DIC)와 동반된 간경색은 세계적으로도 매우 드물게 보고 되고 있는데 이는 위장관 점막손상에서 생성된 독성물질이 간문맥의 순환장애를 일으킨 결과로 추측되고 있다. 연자 등은 빙초산 음독 후 DIC와 함께 간경색증이 발생한 예를 경험하였기

FEM 을 이용한 경추용 Cage 의 구조해석

정우철(W. C. Jung),최진화(J. W. Choi),최길운(G. W. Choi),김성민(S. M. Kim),조명우(M. W. Cho) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

Intervertebral cages in the cervical spine have been advantage in spinal fusion to relieve low back pain. In this study the effects of an intervertebral cage insertion on a cervical spine functional spinal unit investigate and cage structural analysis using finite element method. Three-Dimensional finite element models to create computed tomography (CT) scan C3-C4, obtain healthy young male which 1-mm slice section.

Key Factors Affecting Pollutant loads from Paddy Fields

Jung, J.W.,Yoon, K.S.,Choi, W.J.,Choi, W.Y.,Lim, S.S.,Kwak, J.H.,Lee, J.B.,Choi, H.G. 한국토양비료학회 2009 한국토양비료학회 학술발표회 초록집 Vol.2009 No.10

Herbicidal efficacy of Streptomyces formicae strain W-200 for the biocontrol of invasive weeds

B. B. Aung,K. M. Cho,J. S. Choi,K. W. Park 한국잡초학회 2021 한국잡초학회 별책(학술대회 초록집) Vol.41 No.1

Chemical herbicides are primarily used to control of invasive weeds. However, chemical herbicides pose to environmental problems, can persist in soil, and are related to weed resistance. Furthermore, invasive weeds are generally managed physical control such as cutting in Korea. There is a limit to physical control because the invasive weeds are highly regenerative. Secondary metabolites produced by microorganisms cause phytotoxic symptoms such as necrosis, chlorosis, deformation, and stunting on the plant. Therefore, this study aimed to investigate the herbicidal activity of Streptomyces formicae strain W-200 culture filtrate against the growth stages of three invasive weeds: Sicyos angulatus, Ambrosia trifida, and Ambrosia artemisiifolia. In case of soil application for the seed growth, culture filtrate of S. formicae stain W-200 were observed against S. angulatus, A. trifida, and A. artemisiifolia. Form the results, it can be seen that the higher concentrations the greater inhibition. The highest seed growth inhibition was found on A. artemisiifolia at 75% and 100% culture filtrate concentrations. S. angulatus did not showed highly differences compared to untreated control by percentage of seed germination. However, though some seeds still germinated at low concentrations, the roots and shoots were substantially shorter than untreated control plant. In the foliage application on the different growth stages, the highest herbicidal activity (85-100%) was observed at 2-3 leaf stages of treated weeds. The control efficacy of S. formicae strain W-200 declined as growth stages of plants increased. In the middle and late leaf stages, the control efficacy of Streptomyces was lower than 85% and 50% in all concentrations. In addition, the greenhouse trials showed that A. artemisiifolia has higher susceptibility to culture filtrate of S. formicae strain W-200 than S. angulatus and A. trifida in all concentrations at different leaf stages. As the results of herbicidal activity in foliage application, the results were showing the culture filtrate of S. formiace strain W-200 has potential as a bio-herbicidal agent against the A. artemisiifolia especially in early leaf stage of plant growth.

1987년 및 1988년에 한국에서 발생한 쭈쭈가무시병의 혈청역학적 조사

장우현(W.H. Chang),최명식(M.S. Choi),박경희(K.H. Park),이우곤(W.K. Lee),김석용(S.Y. Kim),최인학(I.H. Choi),기선호(S.H. Kee),김익상(I.S. Kim),최강원(K.W. Choe),우준희(J.H. Woo),송영욱(Y.W. Song),최두혁(D.H. Choi),이증훈(J.H. Lee),김우열(W.Y. K 大韓微生物學會 1989 大韓微生物學會誌 Vol.24 No.2

1986년부터 1988년사이에 우리나라에서 발생한 신증후 출혈열의 혈청역학 조사

장우현(W.H. Chang),이범구(B.G. Lee),최성배(S.B. Choi),김익상(I.S. Kim),최명식(M.S. Choi),최인학(I.H. Choi),기선호(S.H. Kee),김석용(S.Y. Kim),이우곤(W.K. Lee),최강원(K.W. Choe),최두혁(D.H. Choi),이증훈(J.H. Lee),윤태영(T.Y. Yoon),김우열(W.Y. K 大韓微生物學會 1989 大韓微生物學會誌 Vol.24 No.5

Fabrication of 3D biocompatible/biodegradable micro-scaffolds using dynamic mask projection microstereolithography

Choi, J.W.,Wicker, R.,Lee, S.H.,Choi, K.H.,Ha, C.S.,Chung, I. Elsevier 2009 Journal of materials processing technology Vol. No.

Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue engineered scaffolds with controlled biochemical and mechanical micro-architectures. A μSL system for tissue engineering was developed using a Digital Micromirror Device (DMD(TM)) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365nm for crosslinking the photoreactive polymer solution. The μSL system was designed with x-y resolution of ∼2μm and a vertical (z) resolution of ∼1μm. To demonstrate the use of μSL in tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight of ∼1200Da. The viscosity of the PPF was reduced to ∼150cP (at 50<SUP>o</SUP>C) by mixing with diethyl fumarate (DEF) in the ratio of 7:3 (w/w). Finally, ∼2% (w/w) of bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO) was added to the solution to serve as a photoinitiator. Cure depth experiments were performed to determine the curing characteristics of the synthesized PPF, and the resulting system and prepolymer were used to construct a 3D porous scaffold with interconnected pores of ∼100μm. Scanning electron microscopy (SEM), and micro-computed tomography (μCT) images of the micro-architecture illustrate that the developed μSL system is a promising technology for producing biodegradable and biocompatible 3D micro-scaffolds with fully interconnected pores.