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김상주(Sang-Joo Kim),신준호(Joonho Shin),김윤재(Yun-Jae Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
A two-dimensional finite element model for polarization switching in ferroelectric materials developed by Kim and Jiang<SUP>(1)</SUP> and Sang-Joo Kim<SUP>(2)</SUP> is used to predict the formation of domains in a ferroelectric thin film. Initially the ferroelectric film is poled upward and the bottom electrode is grounded. A strong downward de field is imposed on a point of the top surface of the film. A region of switched domains with downward polarization is nucleated and is grown with time. It is found that initially the shape of the nucleated domains is that of a bulgy dagger, but later it turns into the shape of a reversed cup with the lower part wider than the upper part. It can also be concluded that the size of nucleated domains increases with the period of applied electric potential. The present results are qualitatively consistent with experimental observations.
원주방향 관통균열이 존재하는 배관의 J-적분 및 COD 계산을 위한 새로운 공학적 계산식
김윤재,허남수,김영진,Kim, Yun-Jae,Heo, Nam-Su,Kim, Yeong-Jin 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.3
A new method to estimate the elastic-plastic J-integral and the crack tip opening displacement (COD) for circumferential through-wall cracked pipes under tension and under bending is proposed for Leak-Before-Break (LBB) analysis. Being based on the reference stress method with further modifications, the proposed method is simple to use and easy to be generalised in practice. Comparison of the CODs, predicted using the proposed method with published pipe test data show overall excellent agreement.
초고온 고세균 Thermococcus pacificus P-4로부터 내열성 β-glucosidase의 새로운 기질 특이성
김윤재,이재은,이현숙,권개경,강성균,이정현,Kim, Yun Jae,Lee, Jae Eun,Lee, Hyun Sook,Kwon, Kae Kyoung,Kang, Sung Gyun,Lee, Jung-Hyun The Microbiological Society of Korea 2015 미생물학회지 Vol.51 No.1
Thermococcus pacificus P-4의 유전체 서열 분석을 통하여 예측되는 GH1 ${\beta}$-glucosidase를 암호화하는 유전자를 동정하였다. 그 유전자는 487 아미노산들을 암호화하는 1,464 bp 나타내었으며, 그 아미노산 서열은 Pyrococcus furiosus ${\beta}$-glucosidase와 77% 상동성을 나타내었다. 그 유전자는 Escherichia coli 시스템 내에서 복제 및 발현하였다. 재조합 된 단백질은 금속 친화크로마토그래피를 통하여 정제하고 특성을 분석하였다. 정제된 단백질(Tpa-Glu)은 pH 7.5와 $75^{\circ}C$에서 최적활성을 나타내었으며, 열안정성은 $90^{\circ}C$에서 약 6시간의 반감기를 보였다. Tpa-Glu는 pNP-${\beta}$-glucopyranoside, pNP-${\beta}$-galactopyranoside, pNP-${\beta}$-mannopyranoside, 그리고 pNP-${\beta}$-xylopyranoside 순으로 우수한 $k_{cat}/K_m$ 값을 나타내었다. 또한, Tpa-Glu는 ${\beta}$-1,3-linked polysaccharide (laminarin) 그리고 ${\beta}$-1,3-와 ${\beta}$-1,4-linked oligosaccharides에 대하여 exo-hydrolyzing 활성을 보였다. 본 연구는 초고온 고세균으로터 ${\beta}$-glucosidase가 exohydrolyzing 활성을 처음 확인한 것으로 이 효소는 laminarin의 당화공정에 ${\beta}$-1,3-endoglucanase와 함께 적용할 수 있을 것으로 기대된다. Based on the genomic analysis of Thermococcus pacificus P-4, we identified a putative GH1 ${\beta}$-glucosidase-encoding gene (Tpa-glu). The gene revealed a 1,464 bp encoding 487 amino acid residues, and the deduced amino acid residues exhibited 77% identity with Pyrococcus furiosus ${\beta}$-glucosidase (accession no. NP_577802). The gene was cloned and expressed in Escherichia coli system. The recombinant protein was purified by metal affinity chromatography and characterized. Tpa-Glu showed optimum activity at pH 7.5 and $75^{\circ}C$, and thermostability with a half life of 6 h at $90^{\circ}C$. Tpa-Glu exhibited hydrolyzing activity against various pNP-glycopyranosides, with kcat/Km values in the order of pNP-${\beta}$-glucopyranoside, pNP-${\beta}$-galactopyranoside, pNP-${\beta}$-mannopyranoside, and pNP-${\beta}$-xylopyranoside. In addition, the enzyme exhibited exo-hydrolyzing activity toward ${\beta}$-1,3-linked polysaccharide (laminarin) and ${\beta}$-1,3- and ${\beta}$-1,4-linked oligosaccharides. This is the first description of an enzyme from hyperthermophilic archaea that displays exo-hydrolyzing activity toward ${\beta}$-1,3-linked polysaccharides and could be applied in combination with ${\beta}$-1,3-endoglucanase for saccharification of laminarin.
직관과 곡관의 경계 용접부에 존재하는 원주방향 관통균열에 대한 탄소성 파괴역학 해석
김윤재(Yun-Jae Kim),오창균(Chang-Kyun Oh),송태광(Tae-Kwang Song),박치용(Chi-Yong Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The present paper presents an elastic-plastic fracture mechanics method for the circumferential throughwall crack in weldment joining pipes and pipe bends. Welds not explicitly considered and all materials are assumed to be homogeneous. Based on finite element (FE) limit analyses using elastic-perfectly plastic materials, limit loads for the circumferential through-wall crack in weldment joining pipes and pipe bends are obtained, and it is found that they are similar to those for circumferential through-wall cracks in pipe bends. The method to estimate elastic-plastic J and crack opening displacement (COD) for the circumferential through-wall crack in weldment joining pipes and pipe bends is proposed based on the reference stress approach
비표준 시편의 J-적분 시험에서의 3차원 구속효과 영향 연구
김윤재(Yun-Jae Kim),김진수(Jin-Su Kim),조수만(Soo-Man Cho),김영진(Young-Jin Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
This paper compiles solutions of plastic ? factors and crack tip stress triaxialites for standard and non-standard fracture toughness testing specimens, via detailed three-dimensional (3-D) finite element (FE) analyses. Fracture toughness testing specimens include a middle cracked tension (M(T)) specimen, SE(B), single-edge cracked bar in tension (SE(T)) and C(T) specimen. The ligament to thickness ratio of the specimen is systematically varied. It is found that the use of the CMOD overall provides more robust experimental J estimation than that of the LLD, for all cases considered in the present work. Moreover, the J estimation based on the load-CMOD record is shown to be insensitive to the specimen thickness, and thus can be used for testing specimen with any thickness. The effects of in-plane and out-of-plane constraint on the crack tip stress triaxiality are also quantified, so that when experimental J value is estimated according to the procedure recommended in this paper, the corresponding crack tip stress triaxiality can be estimated. Moreover, it is found that the out-of-plane constraint effect is related to the in-plane constraint effect.
도시하천 복원계획을 통한 하천변 가로환경개선에 관한 연구 -안산시 화정천을 중심으로-
김윤재 ( Yun Jae Kim ),유응교 ( Eung Kyo Ryu ) 전북대학교 공학연구원 (구 전북대학교 공업기술연구소) 2006 工學硏究 Vol.37 No.-
Today there is a lot of interest in the river because people need to their own spiritual property and they finally know the value of river. Now many people think that a river is a open space for leisure and environment in our city and they needs to be protected and restored by ourselves. Based on this conditions, this research is focused on Hwajungchon which is a major river in Ansan city. 1. We wanted to provide essential source to find how to improve the river and to know the policy about improvements of streets across river. 2. We reviewed the function of the river, city`s river, space for the water`s edge, campaigns for revitalizing the river through citizen`s participation. 3. We found our ways to improve river`s arrangements in the future according to preference about citizens` use of the river and riverside. 4. We suggested a plan to improve our policy about space for river and operation of roads, based on improvements for water environment in Hwajungchon. 5. We suggested a plan to improve our policy about streets of Hwajungchon which had a lot of history about Ansan.
참조응력법의 표면균열의 비선형 파괴역학 해석 적용성 연구
김윤재(Yun-Jae Kim),김진수(Jin-Su Kim),심도준(Do-Jun Shim),김영진(Young-Jin Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
This paper discusses applicability of the enhanced reference stress method to estimate J along the semi-elliptical surface crack front. It is found that angular variations of normalised J are strongly dependent on the geometry, loading mode and loading magnitude. As application of the reference stress approach to semi-elliptical surface cracks implies proportional increases in the normalised J, the present results pose a question in applicability of the reference stress approach. However, it is also found that the reference stress approach can still provide reasonably accurate J results from an engineering point of view, provided that the maximum J along the crack front is accurately estimated. In this respect, investigation of the error in the estimated J in the present work suggests that the enhanced reference stress approach, recently proposed by authors, provides an effective engineering tool for estimating crack driving force along the semi-elliptical surface crack front.