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김범준(Bumjoon Kim),임병수(Byeongsoo Lim),류승진(Seungjin Ryu),김대욱(D. Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3
The use of aluminum alloys is an attractive possible option in order to reduce the weight of automobile body structures and to achieve the subsequent improvement of fuel economy and driving performance. In this study, the post-weld cold working process was used to improve the fatigue strength of aluminum resistant spot welds (Al RSW). The post-weld cold working process includes the special shaped indenters that are pressed or driven into the weld nugget area in order to induce the compressive residual stresses. Comparisons of the fatigue life and the failure modes between the as-welded specimens and the post-weld cold worked Al RSW specimens are discussed. Also, in order to analyze the failure behavior, finite elements method (FEM) was employed to compare the results with the experimental results.
소형 펀치 크리프 실험변수 변환에 의한 크리프 특성 평가
김범준(Bumjoon Kim),배시연(Siyeon Bae),심언태(Untae Shim),임병수(Byeongsoo Lim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Generally, the conventional creep specimen is tested under uniaxial stress whereas the small punch creep specimen is under multiaxial stress. The focus of this work is to investigate the relationship between the small punch creep test data and conventional creep test data by the analysis similar to the Monkman-Grant relationship using the experimentally acquired test data. Creep behavior of 9Cr-2W ferritic steel was studied at elevated temperature. Creep tests were performed using a small punch creep tester at constant loads and a conventional creep tester at constant stress. Time to fracture and the minimum displacement rate measured during the small punch tests are related in a similar manner to the corresponding conventional creep tests. From the relation derived similar to the Monkman-Grant relation, a correlation between the displacement rate in small punch creep test and the strain rate in conventional creep test is established and creep lives were evaluated by it.
P92강 용접부의 피로균열 성장거동에 미치는 미세조직의 영향
김범준(Bumjoon Kim),임병수(Byeongsoo Lim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8
Fatigue strength and life of weldment at high temperature is very important for high temperature materials used in power plants. In this study, fatigue crack growth tests were performed to examine the effect of microstructure on the crack growth resistance in P92 steel weldment. Microhardness of the weldment was also investigated for better analysis. Residual stresses were removed by heat treatment to focus the study on the microstructural effect. CT specimens were made from the welded plate with notch at different distances from the fusion line. The fatigue crack growth rate was found highest along the fusion line and fusion line+2㎜ line into the heat affected zone.
CRISPR 간섭에 필요한 sgRNA 표적 인식 서열 길이의 결정
김범준 ( Bumjoon Kim ),김병찬 ( Byeong Chan Kim ),이호중 ( Ho Joung Lee ),이상준 ( Sang Jun Lee ) 한국미생물 · 생명공학회 2021 한국미생물·생명공학회지 Vol.49 No.4
CRISPR/Cas를 이용한 유전체 편집과 유전자 발현 조절을 위한 기술에서 sgRNA는 표적서열을 인식하는 역할을 한다. gal 프로모터를 표적서열로 하여 유전체 편집에 필요한 sgRNA의 표적인식서열의 길이와 유전자 발현 조절에 필요한 sgRNA의 표적인식서열의 길이를 Cas9-NG에서 체계적으로 비교하였다. 유전체 편집의 경우, sgRNA의 표적인식 서열을 구성하는 20개의 뉴클레오티드에서 3개의 뉴클레오티드의 결손만을 허용하였다. 하지만, 유전자 발현 조절에는 표적인식서열에서 11개의 뉴클레오티드가 결손되어도 표적 서열을 인식하고 결합할 수 있다는 것을 밝혔다. 따라서, sgRNA의 표적인식서열에서 4개 이상의 뉴클레오티드의 결손이 있는 경우에 sgRNA/Cas9-NG는 표적 DNA 서열에 특이적으로 결합을 하지만, 엔도뉴클레아제의 활성을 갖지 못하기 때문에 유전체 편집을 할 수 없는 것으로 판단된다. 이 결과는 인공전사인자 개발과 합성생물학 분야의 다양한 CRISPR 기술 발전에 도움을 줄 것이다. Single-molecular guide RNA (sgRNA) plays a role in recognizing the DNA target sequence in CRISPR technology for genome editing and gene expression control. In this study, we systematically compared the length of the target recognition sequence in sgRNAs required for genome editing using Cas9-NG (an engineered Cas9 recognizing 5’-NG as PAM sequence) and gene expression control using deactivated Cas9-NG (dCas9-NG) by targeting the gal promoter in E. coli. In the case of genome editing, the truncation of three nucleotides in the target recognition sequence (TRS) of sgRNA was allowed. In gene expression regulation, we observed that target recognition and binding were possible even if eleven nucleotides were deleted from twenty nucleotides of the TRS. When 4 or more nucleotides are truncated in the TRS of the sgRNA, it is thought that the sgRNA/Cas9-NG complex can specifically bind to the target DNA sequence, but lacks endonuclease activity to perform genome editing. Our study will be helpful in the development of artificial transcription factors and various CRISPR technologies in the field of synthetic biology.