탄소 / 탄소 복합 재료의 pyrolysis 과정 모델링에 관한 연구

김정인,이우일 ( Jung In Kim,Woo Il Lee ) 한국복합재료학회 1998 Composites research Vol.11 No.1

Inverse Estimation of Surface Temperature in Nanoscale Using the Artificial Neural Network

Bup Sung Jung(정법성),Sun Kyung Kim(김선경),Woo Il Lee(이우일) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The inverse heat conduction problem (IHCP) is a problem of estimating boundary condition from temperature measurement at one or more interior points. In this work, an inverse heat conduction problem for nanoscale structure is studied. The conduction phenomenon is modeled using the Boltzmann transport equation. Phonon-mediated heat conduction in one-dimension is considered. One boundary is exposed to an unknown temperature and the other boundary, where temperature observation takes place, is subject to a known boundary condition. The artificial neural network with back-propagation algorithm is applied to inverse estimation of the unknown temperature. Sample results are presented and discuss.

InhA-Like Protease Secreted by Bacillus sp. S17110 Inhabited in Turban Shell

Sang Chul Jung,Hyoung-Rok Paik,Mi Sun Kim,백근식,이우일,성치남,최상기 한국미생물학회 2007 The journal of microbiology Vol.45 No.5

A strain producing a potent protease was isolated from turban shell. The strain was identified as Bacillus sp. S17110 based on phylogenetic analysis. The enzyme was purified from culture supernatant of Bacillus sp. S17110 to homogeneity by ammonium sulfate precipitation, SP-Sepharose, and DEAE-Sepharose anion exchange chromatography. Protease activity of the purified protein against casein was found to be stable at pH 7 to pH 10 and around 50°C. Approximately 70% of proteolytic activity of the enzyme was detected either in the presence of 100 mM SDS or Tween 20. The enzyme activity was enhanced in the presence of Ca2+, Zn2+, Mg2+, but was inhibited by EDTA, indicating that it requires metal for its activity. The purified enzyme was found to be a monomeric protein with a molecular mass of 75 kDa, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography. The purified enzyme was analyzed through peptide fingerprint mass spectra generated from matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) and a BLAST search, and identified as immune inhibitor A (inhA) deduced from nucleotide sequence of B. cereus G9241. Since InhA was identified as protease that cleave antibacterial proteins found in insect, inhA-like protease purified from Bacillus sp. S17110 might be pathogenic to sea invertebrates.

컬러센서를 위한 TiO2/Se : Te 이종접합의 스펙트럼 응답

우정욱,박욱동,김기완,이우일 ( Jung Ok Woo,Wug Dong Park,Ki Wan Kim,Wu Il Lee ) 한국센서학회 1993 센서학회지 Vol.2 No.1

TiOz/Se : Te heterojunction for color sensor has been fabricated by RF reactive sputtering and thermal evaporation methods onto glass substrate. The optimum deposition condition of TiO₂ films was such that RF power was 120 W, substrate temperature was 100℃, oxygen concentration was 50%, working pressure was 50 mTorr for the TiO₂ film thickness of 1000Å. In this case, the optical transmittance of TiO₂ film at 550 nm-wavelength was 85 %, resistivity was 2 X 10^9 Ω·cm, refractive index was 2. 3, and optical bandgap was 3. 58 eV. The composition ratio of 0 to Ti by AES analysis was 1.7. When TiO₂ films were annealed at 400℃ for 30 min. in O₂ ambient, the optical transmittance of TiO₂ films at the wavelength range of 300∼580 nm was improved from 0 to 25 %. When Se : Te films were annealed at 190℃ for 1 min, photosensitivity under illumination of 1000 lux was 0.75. The optical bandgap of Se : Te films was 1.7 eV. The structures of Se : Te films were the hexagonal with (100) and (110) orientation. The spectral response of a-Se was improved by the addition of Te, especially in the long wavelength region. The TiO₂/Se : Te heterojunction showed wide spectral response. and more improved one than that of a-Si film in the blue light region.

멀티스케일 모델링 기법을 이용한 섬유강화 복합재료의 미시역학적 파손예측 및 검증

김명준(Myung-jun Kim),박성호(Sung-ho Park),박정선(Jung-sun Park),이우일(Woo-il Lee),김민성(Min-sung Kim) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.1

본 논문에서는 복합재료의 미시적 파손모드를 고려하는 복합재 파손예측 프로그램을 개발하였다. 개발된 프로그램의 검증을 위하여 원공이 있는 복합재 적층판 시편의 인장시험 및 정적 파손해석을 수행하였다. 먼저 적층각도별 복합재 시편에 대한 인장시험을 통하여 논문에 사용된 재료에 대한 SIFT 허용치를 산출하였고, 미시역학적 모델인 RVE에 대한 유한요소 해석을 통하여 변형률 증폭계수를 결정하였다. 또한 원공이 있는 복합재 적층판 시편에 대한 인장시험을 수행하고, 실험을 통해 얻어진 파손하중 결과를 바탕으로 유한요소 모델에 대하여 정적 파손해석을 수행하였다. 마지막으로 실험결과를 바탕으로 예측된 파손지수 결과를 평가함으로써 개발된 프로그램의 효용성을 검증하였다. In this paper, a micro-mechanical failure prediction program is developed based on SIFT (Strain Invariant Failure Theory) by using the multi-scale modeling method for fiber-reinforced composite materials. And the failure analysis are performed for open-hole composite laminate specimen in order to verify the developed program. First of all, the critical strain invariants are obtained through the tensile tests for three types of specimens. Also, the matrices of strain amplification factors are determined through the finite element analysis for micro-mechanical model, RVE (Representative Volume Element). Finally, the microscopic failure analysis is performed for the open-hole composite laminate specimen model by applying a failure load obtained from tensile test, and the predicted failure indices are evaluated for verification of the developed program.

Nano Cavity 유동의 분자동역학 해석을 통한 폴리머 Melting point 예측

김석범(S. P. Kim),이우일(W. I. Lee),정재민(J. M. Jung),이동언(D. E. Lee),문성남(S. N. Moon) 한국정밀공학회 2011 한국정밀공학회 학술발표대회 논문집 Vol.2011 No.6월

자동차 내장재 적용을 위한 PLA 복합재료의 물성개선에 관한 연구

정재원 ( Jae Won Jung ),김성호 ( Seong Ho Kim ),김시환 ( Si Hwan Kim ),박종규 ( Jong Kyoo Park ),이우일 ( Woo Il Lee ) 한국복합재료학회 2011 Composites research Vol.24 No.3

환경 문제가 대두 됨에 따라 세계 각국에서는 환경규제를 통해서 산업계에 친환경 제품의 개발을 독려하고 있어 생분해성 재료에 대한 산업계의 관심이 높아지고 있다. 생분해성 재료인 Polylactic acid(PLA)는 강성과 내화학성이 뛰어나지만 내열성과 내충격성이 낮아서 자동차용 재료로서 요구되는 성능을 만족시킬 수 없다. 이에 본 연구에서는 천연섬유(황마)를 강화재로 사용하여 PLA의 내열성과 내충격성을 향상 시키기 위한 실험을 수행하였다. 특히 PLA와 황마 계면 간의 결합력을 증가시키기 위해 다양한 표면처리를 수행하였고 내충격성이 향상됨을 확인하였다. 또, 어닐링 처리를 통해서 PLA의 내열성이 크게 증가함을 보였다. Since the environmental problems and new stricter regulations are forcing the industries to introduce more ecological materials for their products, biodegradable materials have attracted increasing attention. Among these materials, Polylactic acid(PLA) is a promising candidate for its modulus, strength, chemical resistance. However, PLA could not be used for automobile industries for its low heat resistance and impact strength. In this study natural fibers were (jute fiber was) introduced as reinforcements in order to improve heat resistance and impact strength of PLA. Especially for improving the adhesion between PLA and jute, various surface treatments were tried. With each treatment, we verified that the impact strength of composite was improved. With annealing treatment, we found a remarkable increase of heat resistance of PLA composite.

컬러센서를 위한 $TiO_{2}$/Se : Te 이종접합의 스펙트럼 응답

우정옥,박욱동,김기완,이우일,Woo, Jung-Ok,Park, Wug-Dong,Kim, Ki-Wan,Lee, Wu-Il 한국센서학회 1993 센서학회지 Vol.2 No.1

컬러센서를 위한 $TiO_{2}$/Se : Te 이종접합을 고주파 반응성 스퍼터링법과 진공증착법을 이용하여 제작하였다. 제조된 $TiO_{2}$ 막형성의 최적조건은 $1000{\AA}$의 $TiO_{2}$ 두께에서 고주파전력 120 W, 기판온도 $100^{\circ}C$, 산소농도 50% 및 분위기압 50 mTorr였다. 이 때 광투과율은 파장 550 nm에서 85%, 저항률은 $2{\times}10^9{\Omega}{\cdot}cm$, 굴절률은 2.3이었다. 제조된 $TiO_{2}$막은 직접천이형 에너지 밴드구조를 가지며 광학적 밴드갭은 3.58 eV였다. 제조된$TiO_{2}$막을 $400^{\circ}C$에서 30분간 열처리함으로써 광투과율이 파장 $300{\sim}580$ nm범위에서 $0{\sim}25%$까지 개선되었다. 또한 화학양론적 조성비를 조사하기 위하여 AES 분석을 한 결과 Ti 및 0의 조성비는 1 : 1.7로 나타났다. 한편 Se : Te 막형성의 최적조건은 $190^{\circ}C$에서 1분간 열처리했을 때였다. 이러한 조건으로 제조된 Se : Te막의 광학적 밴드갭은 1.7 eV였으며 육방정계구조의 (100) 방향 및 (110) 방향으로 Se : Te 막이 결정화됨을 알 수 있었다. 1000 lux의 조도에서 Se : Te막의 광전변환률은 0.75였다. 또한 Se에 Te를 첨가함으로써 장파장영역의 분광감도가 향상되었다. $TiO_{2}$/Se : Te 이종접합의 분광감도는 가시광 전영역에서 비교적 넓은 분광감도를 나타내었으며, 특히 청색영역에서 a-Si박막보다 우수한 분광감도를 나타내었다. $TiO_{2}$/Se : Te heterojunction for color sensor has been fabricated by RF reactive sputtering and thermal evaporation methods onto glass substrate. The optimum deposition condition of $TiO_{2}$ films was such that RF power was 120 W, substrate temperature was $100^{\circ}C$, oxygen concentration was 50%, working pressure was 50 mTorr for the $TiO_{2}$ film thickness of $1000{\AA}$. In this case, the optical transmittance of $TiO_{2}$ film at 550 nm-wavelength was 85%, resistivity was $2{\times}10^9{\Omega}{\cdot}cm$, refractive index was 2.3, and optical bandgap was 3.58 eV. The composition ratio of 0 to Ti by AES analysis was 1.7. When $TiO_{2}$ films were annealed at $400^{\circ}C$ for 30 min. in $O_{2}$ ambient, the optical transmittance of $TiO_{2}$ films at the wavelength range of $300{\sim}580$ nm was improved from 0 to 25%. When Se : Te films were annealed at $190^{\circ}C$ for 1 min., photosensitivity under illumination of 1000 lux was 0.75. The optical bandgap of Se : Te films was 1.7 eV. The structures of Se : Te films were the hexagonal with (100) and (110) orientation. The spectral response of a-Se was improved by the addition of Te, especially in the long wavelength region. The $TiO_{2}$/Se : Te heterojunction showed wide spectral response, and more improved one than that of a-Si film in the blue light region.

직병렬형 8비트 고속 A/D 변환기의 설계

정명수(M. S. JUNG),김태형(T. H. KIM),이우일(W. I. LEE),정호선(H. S. CHUNG),한철희(C. H. HAN),권태욱(T. W. KUEN) 대한전자공학회 1986 대한전자공학회 학술대회 Vol.1986 No.12

박막의 두께에 따른 잔류 응력이 나노 패턴의 무너짐에 미치는 영향에 대한 연구

김범래(Beom Rae Kim),문성남(Sung Nam Moon),정재민(Jae Min Jung),최성학(Sung Hak Choi),이우일(Woo Il Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

After Nano Imprint Lithography (NIL) process, the collapse of imprinted nano patterns which are major problem for pattern fidelity is commonly found. We assumed that insufficient relaxation time and the initial stress of polymer resist on which the pattern is imprinted have a relation with that collapse phenomenon. In this study, therefore, we measured the stress of polymer nano films for the different film thickness by varying spin-coating speed. The results show that the stress of PMMA film was found to decrease with increasing film thickness and the patterns was rapidly collapsed when the stress-thickness ratio increased.