DCA-MOD 법에 의한 High $J_c$ YBCO 박막의 제조

김병주,김혜진,이금영,이종범,김호진,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Yi, Keum-Young,Lee, Jong-Beum,Kim, Ho-Jin,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1

High $J_c\;YBa_2Cu_3O_x$ superconducting films were fabricated by MOD method using fluorine-free dichloroacetic acid(DCA) as chelating solvent for preparing precursor solution. Coating solutions were prepared by dissolving Y-, Ba- and Cu-acetates in DCA solvent followed by drying in rota vapor to obtain the blue gel that is diluted in methanol and 2-methoxyethanol for adjusting the cation concentration. DCA-MOD precursor solution was coated on a single crystal(001) $LaAlO_3(LAO)$ substrate by a dip coating method with a speed of 25 mm/min. Coated films were calcined at lower temperature up to $500^{\circ}C$ in flowing oxygen atmosphere with a 7.2% humidity. Conversion heat treatment was performed at various temperatures of $780{\sim}810^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. SEM observations showed that films have very dense microstructures for the films prepared at the temperature higher than $800^{\circ}C$ regardless of diluting solvent; methanol or 2-methoxyethanol. X-ray diffraction analysis showed that YBCO grains grew with a (001) preferred orientation. A High critical current density($J_c$) of 1.28 $MA/cm^2$(@77 K and self-field) was obtained id. the YBCO film prepared using 2-methoxyethanol as a solvent.

DCA-MOD 방법으로 제조된 YBCO 박막의 미세조직에 미치는 열처리 효과

김병주,김혜진,조한우,유석구,유정희,이희균,홍계원,Kim, Byeong-Joo,Kim, Hye-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ryu, Jung-Hee,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1

[ $YBa_2Cu_3O_{7-{\delta}}$ ] films have been prepared on $LaAlO_3$ (100) single-crystal substrates by a metalorganic deposition using dichloroacetate precursors (DCA-MOD). Calcination conditions were varied in order to optimize the microstructure and the superconducting properties of YBCO film. Coated films were calcined at various temperatures ranging from $400{\sim}700^{\circ}C$ in flowing humid oxygen atmosphere. Ramping rate to calcination tempertures was $2.22^{\circ}C/min$. Conversion heat treatment was performed at $800^{\circ}C$ for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. Observations of surface and cross sectional SEM microstructure showed that the particle size in the calcined film increased in the range of 100-200 nm with heating rate and the calcination temperature. SEM EDS analysis showed that 13 a/o of chlorine was contained in the calcined film. It was also observed that the porosity increased with the heating rate and temperature. Porous microstructure was developed when YBCO films were prepared using porous calcined film. Dense microstructure and high $J_c$ over $1\;MA/cm^2$ was obtained when calcination was carried out at the temperature of $500^{\circ}C$ with a heating rate of $2.22^{\circ}C/min$.

하악전돌증환자(下顎前突症患者)의 악교정수술후(顎矯正手術後) 음성변화(音聲變化)에 관(關)한 연구(硏究)

김병주,김여갑,Kim, Byung Ju,Kim, Yeo Gab 대한악안면성형재건외과학회 1993 Maxillofacial Plastic Reconstructive Surgery Vol.15 No.4

This study was done to analyze phonetic dysfunction and the effect of orthognathic surgery to phonation in the patients of mandibular prognathism. 20 persons were chosen as normal group and 20 patients of mandibular prognathism as abnormal for this study. 5 vowel sounds-'ㅏ(a)', 'ㅔ(e)', 'ㅣ(i)', 'ㅗ(o)', 'ㅜ(u)' and 14 consonant sounds-'ㄱ(g)', "ㄴ(n), 'ㄷ(d)', 'ㄹ(l)', 'ㅁ(m)', 'ㅂ(b)', 'ㅅ(s)', 'ㅇ(ng)', 'ㅈ(j)', 'ㅊ(ch)', 'ㅋ(k)', 'ㅌ(t)', 'ㅍ(p)', 'ㅎ(h)', were checked. We recorded these sounds in the period of preopration, postop. 12 months, postop. 24 months. A Formant ratio and a length of consonant time were studied with discriminant analysis. As a result of the study, the following conclusion were gained. 1. As a result of the analysis on vowel dysfunction patiensts of mandibular prognathism, more than 80% of men patients showed the dysfunction in prelingual sound 'ㅔ(e)' and 'ㅣ(i)'. More than 70% of women patients showed the dysfunction in all vowel. 2. One year later from the orthognathic surgery, men patients showed a marked improvement in 'ㅏ(a)'. The next were 'ㅗ(o)', 'ㅜ(u)' and 'ㅣ(i)'. Women patients showed a marked improvement in 'ㅜ(u)'. 3. Two year later from the orthognathic surgery, men patients showed a marked improvement in prelingual sound 'ㅔ(e)' and postlingual sound 'ㅗ(o)'. Women patients showed a marked improvement in 'ㅏ(a)'. More than 20% of patients showed the phonetic improvement compared with the condition of the postop. 12 months. 4. As a result of the analysis on consonant dysfunction patient of mandibular prognathism. more than 80% of men patients showed the dysfunction in lingual sound 'ㅅ(s)'. Most women patients showed the dysfunction in labial sound 'ㅁ(m)' and lingual sound 'ㄴ(n)'. More than 50% of patients showed the dysfunction in labial sound and lingual sound. 5. One year later from the orthognathic surgery. men patients showed a complete improvement in hard palatal sound 'ㅈ(j)'. The next were labial sound 'ㅂ(b)', lingual sound 'ㅅ(s)', soft palatal sound 'ㄱ(g)' and 'ㅋ(k)'. Women patients showed a marked improvement in soft palatal sound 'ㅇ(ng)' and 'ㄱ(g)'. 6. Two year later from the orthognathic surgery, all patients showed remarkable improvement in consonant sounds. except for labial sound 'ㅁ(m)', 'ㅍ(p)' and lingual sound 'ㄴ(n)'. The improvement ratio was increased as the time was going on compared with the condition of postop 12 months.

REBCO 초전도 박막제조를 위한 Fluorine-free MOD 전구체 용액 개발

김병주,임선원,김호진,홍계원,이희균,Kim, Byeong-Joo,Lim, Sun-Weon,Kim, Ho-Jin,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2

New precursor solution with dichloroacetic acid (DCA) was developed for fabricating high $J_c$ REBCO film. DCA based-precursor solution was coated on $LaAlO_3$(001) substrate by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature were controlled in order to obtain a good epitaxial film. The film with thickness of 0.5 micrometer was obtained by single coating and no crack was observed at calcined films. Oxygen partial pressure was controlled in the range of $100{\sim}1,000$ ppm and conversion heat treatment was carried out at the temperature range of $705-765^{\circ}C$. A critical transition temperature ($T_c$) of 90 K and a critical transport current density ($J_c$) of $>0.5\;MA/cm^2$ (77 K and self-field) were obtained for the GdBCO film. It is thought that fluorine-free MOD solution using DCA is promising precursor solution for fabricating high quality REBCO films.

대학재정 확충방안

김병주,Kim, Byeong-Ju 한국대학교육협의회 2007 大學敎育 Vol.150 No.-

부존자원이 부족한 우리나라에서 그간 발전의 원동력이 되어온 것은 바로 "교육"이다. 최근 우리나라의 고등교육재정 부족에 대한 우려의 목소리가 높다. 대학의 경쟁력이 곧 국가의 경쟁력으로 이어지는 현대 사회에서 각 대학의 경쟁력 강화를 위해 재정 투자의 확대와 재정 투자의 효율성에 대한 요구가 각계각층에서 이어지고 있다. 이에 우리나라 고등교육재정 현황 및 재정 부족에 대한 원인과 문제점을 짚어보고, 이를 확충하기 위한 방안에는 어떠한 것들이 있는지 살펴보기로 한다.

토석류 유발 저수지 2차 피해 예측을 위한 3차원 수치해석 연구

김병주,백중철,Kim, Byeong-Ju,Baek, Jung-Cheol 한국수자원학회 2022 물과 미래(한국수자원학회지) Vol.55 No.7

점진적인 주성분분석기법을 이용한 고차원 자료의 특징 추출

김병주,Kim Byung-Joo 한국정보통신학회 2004 한국정보통신학회논문지 Vol.8 No.7

고차원 자료를 효율적으로 처리하기 위해서는 특징 추출 기법이 필요하다. 주성분분석 방법은 대표적인 특징추출 방법이지만 학습 자료의 차원이 큰 경우에는 고유공간을 계산하기 위해 많은 기억공간과 계산량을 필요로 한다. 본 논문에서는 고차원 자료의 특징 추출을 위해 점진적인 주성분분석 방법을 사용한다. 제안한 방법에 대해 신경망에서 점진적인 주성분분석을 하는 대표적인 방법인 APEX모델과 실험을 통해 비교해 본 결과 제안된 방법이 APEX 모델 보다 성능이 우수함을 나타내었다. High dimensional data requires efficient feature extraction techliques. Though PCA(Principal Component Analysis) is a famous feature extraction method it requires huge memory space and computational cost is high. In this paper we use incremental PCA for feature extraction on high dimensional data. Through experiment we show that proposed method is superior to APEX model.

층류-파동 액막 유동에 대한 계면 전단응력의 영향

김병주,정은수,김정헌,Kim, Byeong-Ju,Jeong, Eun-Su,Kim, Jeong-Heon 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.7

In the present study the behavior of laminar-wavy film flowing down a vertical plate was studied analytically. The effects of film Reynolds number and interfacial shear stress on the mean film thickness, wave amplitude, wave length, and wave celerity were analysed. The anayltical results on the periodic-wave falling film showed good agreements with experimental data for Re < 100. As the film Reynolds number increased, mean film thickness, wave amplitude, and wave celerity increased, but wave length decreased. Depending on the direction of interfacial shear stress, the shape of wavy interface was disturbed significantly, especially for the intermediate-wave. As the interfacial shear stress increased, for the periodic-wave film, wave amplitude and wave celerity increased, but mean film thickness and wave length decreased.

실시간 침입탐지 시스템에 관한 연구

김병주,Kim, Byoung-Joo 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.1

인공지능, 기계학습 및 데이터마이닝 기법들을 침입탐지 시스템에 적용하는 연구가 활발히 진행되고 있다. 그러나 많은 연구가 공격패턴의 분류를 위한 분류기(classifier)의 학습 알고리즘 성능 개선에 목적을 두고 있다. 그리고 이러한 학습 알고리즘은 대부분 일괄처리(batch) 방식으로 동작하여 실시간 침입탐지 시스템의 적용에는 적합하지 못하다. 본 논문에서는 실시간 침입탐지 시스템을 위한 점증적 특징 추출 기법과 분류가 가능한 실시간 침입탐지 시스템을 제안한다. 제안된 방법을 KDD CUP 99 자료에 적용한 결과 실시간 기법임에도 불구하고 일괄처리 방식과 비슷한 결과를 나타내었다. Applying artificial intelligence, machine learning and data mining techniques to intrusion detection system are increasing. But most of researches are focused on improving the performance of classifier. These classifiers are performed by batch way and it is not proper method for realtime intrusion detection system. We propose an incremental feature extraction and classification technique for realtime intrusion detection system. Applying proposed system to KDD CUP 99 data, experimental result shows that it has similar capability compared to batch way intrusion detection system.

수직관내 리튬브로마이드 수용액막의 흡수과정에 대한 비흡수가스의 영향

김병주,이찬우,Kim, Byeong-Ju,Lee, Chan-U 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.4

Among the heat/mass exchange units composing an absorption system, the absorber, where the refrigerant vapor is absorbed into the liquid solution is the one least understood. In the present study, the effects of non-absorbable gas on the absorption process of aqueous lithium bromide solution falling film inside a vertical tube were experimentally investigated. In the range of film Reynolds number of 30 ~ 195, heat and mass transfer characteristics were investigated as a function of non-absorbable gas volumetric concentration, 0.2 ~ 20%. An increase of non-absorbable gas volumetric concentration degraded the mass transfer rate dramatically in the absorption process. The reduction of mass transfer rate was significant for the addition of small amount of non-absorbable gas to the pure vapor. At film Reynolds number of 130, an increase of non-absorbable gas concentration from 0.2 to 6.0% resulted in the decrease of mass transfer rate by 36% and 20% of non-absorbable gas by 59%. However the decrease of film Nusselt number with the increase of volumetric concentration of non absorbable gas was relatively smaller than the decrease of Sherwood number. Critical film Reynolds number was identified to exist for the maximum heat and mass transfer regardless of the volumetric concentration of non-absorbable gases.