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박현태,권의표,임익태,Park, Hyeon Tae,Kwon, Eui Pyo,Im, Ik-Tae 한국재료학회 2019 한국재료학회지 Vol.29 No.12
In this study, the direct water quenching technique is applied to validate the applicability of direct water quenching as a cooling method in the hot stamping process of 3.2 mm thick boron steel sheet. Cooling performance of conventional die quenching and direct water quenching is compared. Higher cooling rate is obtained by hot stamping with direct water quenching compared to die quenching. As the flow rate of cooling water increases, the cooling rate increases, and a high cooling rate of 71 ℃/s is achieved under flow rate conditions of 0.8 L/min. Through direct water quenching, the cooling time required for sufficient cooling of the sheet is reduced. Full martensitic microstructure is obtained under flow rate condition of 0.8 L/min. Hardness increases with increasing flow rate. From these results, it is verified that the direct water quenching is applicable to the hot stamping of thick boron steel sheet.
3.2t 보론강 판재 직수냉각 핫스탬핑시 냉각수 유량에 따른 미세조직 및 기계적 특성
박현태,권의표,임익태,Park, Hyeon Tae,Kwon, Eui Pyo,Im, Ik Tae 한국재료학회 2020 한국재료학회지 Vol.30 No.12
Direct water quenching technique can be used in hot stamping process to obtain higher cooling rate compared to that of the normal die cooling method. In the direct water quenching process, setting proper water flow rate in consideration of material thickness and the size of the area directly cooled in the component is important to ensure uniform microstructure and mechanical properties. In this study, to derive proper water flow rate conditions that can achieve uniform microstructure and mechanical properties, microstructure and hardness distribution in various water flow rate conditions are measured for 3.2 mm thick boron steel sheet. Hardness distribution is uniform under the flow condition of 1.5 L/min or higher. However, due to the lower cooling rate in that area, the lower flow conditions result in a drastic decrease in hardness in some areas in the hot-stamped part, resulting in low martensite fraction. From these results, it is found that the selection of proper water flow rate is an important factor in hot stamping with direct water quenching process to ensure uniform mechanical properties.
마운팅부 영향인자에 따른 래치의 예상수명 시뮬레이션과 개발기간 개선에 대한 연구
박현태(Hyeon-Tae Park),전남규(Nam-Kyu Jeon),여덕종(Deok-Jong Yeo),윤성민(Sung-Min Yoon),허상범(Sang-Bum Hur) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11
Mostly automotive latch fatigue has been proved by predict stiffness analysis and breaking strength test or direct durability test. Durability test needs dozens of days by design lifecycle and same by changing various factors. We use MSM(Modal Superposition Method) which predicts fatigue by adapting modal stress & modal displacement in Fe-Safe, after stiffness and modal analysis using Abaqus. In addition, We proved analysis accuracy by compare direct endurance test data, expecting to be able to reduce development time by predicting design lifecycle of brand new latch system through the result.
Cisplatin 내성 난소암 세포주에서 Cisplatin 처리 후 p53, p16, PTEN, c-myc 유전자의 발현
박현태 ( Park Hyeon Tae ),김상배 ( Kim Sang Bae ),이용호 ( Lee Yong Ho ),이낙우 ( Lee Nag U ),이규완 ( Lee Gyu Wan ),김미혜 ( Kim Mi Hye ),김영태 ( Kim Yeong Tae ) 대한산부인과학회 2003 Obstetrics & Gynecology Science Vol.46 No.7
본 연구는 cisplatin의 내성을 갖는 난소암 세포주를 대상으로 세포의 전달체계에서 종양억제 역할을 하는 유전자 p53, p16, PTEN, c-myc의 발현이 어떻게 변화되는지를 통해 항암제 내성의 원인을 밝히고자 수행하였다. 연구 방법 : Cisplatin 내성 난소암 세포주 (cisplatin resistance ovarian carcinoma cell line; A2780/CP70)과 민감성 난소암 세포주 (cisplatin sensitive ovarian carcinoma cell line; A2780)를 대상으로 cisplatin을 처리한 후 MTT assay로 cytotoxicity를 확인하였고, p53, p16, PTEN, c-myc에 대한 western blot analysis를 실시하였다. 결과 : Cisplatin 처리 전 p16은 발현되지 않았고, p53, PTEN, c-myc 유전자는 모두 발현됨을 확인하였다. p53, PTEN 유전자의 경우 A2780/CP70에서 각각 40, 30% 적게 발현하였다. Cisplatin 처리 후 cisplatin을 처리하기 전과 비교해서 유전자의 발현이 양적으로 약 2-3배 증가함을 보였다. PTEN 발현이 A2780과 비교하여 A2780/CP70의 경우 A2780 보다 36% 낮게 발현되었음을 확인하였다. 결론 : 난소암 세포주 A2780/CP70에서 PTEN 유전자의 발현이 상대적으로 낮게 확인된 점으로 볼 때, p53 유전자의 변이와 함께 cisplatin 약제 내성을 결정하는 한 요소일 수 있으며, PTEN 기능에 대한 추가적 연구가 요구된다. Objective : The chemotherapeutic agent Cisplatin (cis-diammminedichloroplatinum (Ⅱ)) is particularly effective against ovarian carcinoma, however, its clinical success is limited by recurrent drug resistant tumors. It is mandatory to reveal the mechanism of cisplatin resistance for the ovarian cancer treatment or prognosis. This study assessed the expression of p53, p16, PTEN, and c-myc genes with cisplatin treatment in human ovarian cancer cell lines; cisplatin-sensitive (A2780) and cisplatin-resistan (A2780/CP70) ovarian cancer cell line to elucidate the mechanism of cisplatin resistance. Methods : Cytotoxic assay for cisplatin was performed in cisplatin-sensitive ovarian cancer cell line, A2780 and cisplatin-resistant ovarian cancer cell line, A2780/CP70. After cisplatin treatment, expression of p53, p16, PTEN, c-myc was analyzed by Western blot analysis. Results : PTEN expression was significantly about 30% higher in A2780 than in A2780/CP70. p16 expression was defective in both cell lines. p53 and c-myc expression was no difference in cancer cell lines. After cisplatin treatment, the expression of p53, PTEN, c-myc genes increased 2-3 times in both cell lines. Conclusion : Relatively lower expression of PTEN was detected in A2780/CP70 suggesting that PTEN expression might play a role in the development of cisplatin resistance in ovarian cancer cell line, A2780/CP70.