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고대환,송성재 한국기계기술학회 2016 한국기계기술학회지 Vol.18 No.5
Three-dimensional motion analysis systems and force plates are used for gait phase detection and ground reaction force(GRF) or ground reaction moment(GRM) data collection. But force plates as measurement systems are restricted to laboratory environments and have limitations for abnormal walking with foot dragging. Therefore the methods were proposed to compute the GRM from the kinematic data of three-dimensional motion analysis systems. Gait phase detection with kinematic data using foot velocity algorithm(FVA) was performed. The validity of gait phase detection was obtained comparing with the results of force plates. A gait model with 7 segments was composed to compute GRM. The results of gait model with kinematic data were compared with those of force plates. The result of the vertical direction is similar. But anterior-posterior direction and lateral direction show similar tendency with some gaps.
슈퍼 오스테나이트계 스테인리스강의 소성 변형률에 따른 부식특성 평가
고대환,신용택 대한용접접합학회 2018 대한용접·접합학회지 Vol.36 No.6
In this study, corrosion properties of UNS S32654 (654SMO), which is a kind of super austenitic stainless steel, were evaluated according to the change of strain. Strain of base metal was applied from 0% to 57%, and then microstructure evaluation, CPT, CCT and polarization tests were performed. As a result of microstructure, it was confirmed that the slip was increased as the strain increased. CPT of all strain ranges was 90 ℃ or more, and the CCT was from 80 ℃ to 90 ℃, respectively. In the polarization test, it was difficult to find the change of the corrosion potential according to the change of the strain, and it was confirmed that plastic induced martensitic phase which could be generated by the deformation in the austenite stainless steel was not occurred by XRD. Finally, it was confirmed that there was no difference in the corrosion resistance characteristic of 654SMO steel according to the strain change
슈퍼오스테나이트계 스테인리스강 GTA 용접부의 용접 적층 및 입열에 따른 공식 부식 특성
고대환(Dae-Hwan Ko),박영일(Young-Il. Park),신용택(Yong-Taek Shin) 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.6
This study investigated the corrosion characteristics of weldments on superaustenitic stainless steels for various heat inputs and numbers of welding passes during gas tungsten arc welding(GTAW). The heat input was changed to 0.7 or 1.4 kJ/mm and the weldment microstructure and chemical composition were analyzed. The weldment corrosion resistance was evaluated by potentiodynamic polarization, and the critical pitting temperature (CPT) was determined. The CPT dropped from 85 to 55 ℃ with both increasing heat input and number of welding passes. The microstructural and chemical compositional analyses revealed that the Mo segregated and precipitated in the interdendritic region, and that the Mo content in the dendritic core was lower than that in the surrounding area. The Mo content decreased when the pitting corrosion initiated. The precipitate content and dendrite core size both increased, and the pitting corrosion resistance decreased with both increasing heat input and number of welding passes.
체세포 핵치환 기술을 이용한 hGCSF와 GFP 유전자 동시발현 형질전환 소 배아 생산
양정석,조소영,구본철,허영태,강만종,송 혁,이수민,고대환,엄상준 한국수정란이식학회 2015 한국동물생명공학회지 Vol.30 No.3
The purpose of this study is to develop transgenic cell line expressing targeted human granulocyte colony stimulating factor (hGCSF) and green fluorescence protein (GFP) genes as well as production of Somatic Cell Nuclear Transfer (SCNT) embryos derived from co-expressed transgenic donor cells. Constructed pPiggy-mWAP-hGCSF-EF1-GFP vector was chemically transfected into bovine fetus cells and then, only GFP expressed cells were selected as donor cells for SCNT. Cleavage and blastocyst rates of parthenogenetic, SCNT embryos using non-TG cell and hGCSF-GFP dual expressed SCNT embryos were examined (cleavage rate: 78.0±2.8 vs. 73.1±3.2 vs. 70.4±4.3%, developmental rate: 27.2 ±3.2 vs. 21.9±3.1 vs. 17.0±2.9%). Result indicated that cleavage and blastocyst rates of TG embryos were significantly lower (P<0.05) than those of parthenogenetic and non-TG embryos, respectively. In this study, we successfully produced hGCSF-GFP dual expressed SCNT embryos and cryopreserved to produce transgenic cattle for bioreactor system purpose. Further process of our research will transfer of transgenic embryos to recipients and production of hGCSF secreting cattle.
송성재,고대환 한국기계기술학회 2015 한국기계기술학회 학술대회논문집 Vol.2015 No.11
In order to select the supporting points for large glass panels used for TFT-LCD monitors, an optimization method selecting the supporing points is presented. In this method we reduce the problem of 1 degree of freedom. ANSYS optimization module is used and optimization criterion is to minimize the maximum deflection.