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박재원(J. W. Park),이철구(C. K. Lee) 한국도시철도학회 2014 한국도시철도학회논문집 Vol.2 No.3
To understand the basic principles of corrosion of the metal, it is essential to understand the corrosion resistance properties of stainless steel. The corrosion is a phenomenon that the metal structures react with the environment resulting in dissolving in the aqueous solution of the metal ion or the deterioration in the oxide or hydroxide. This corrosion is a spontaneous electrochemical reaction occurring at the interface in contact with the metal and the corrosive environment; the metal structures are eventually destroyed because they lose the inherent mechanical properties of themselves. Therefore, the life of the metal structures that is used in a corrosive environment is determined by the rate of corrosion reaction. It is important that understanding the corrosion properties of stainless steel and selecting the best alloy for the given environment to determine the life of the structure. In the reliability evaluation of the stainless steel welds, the regulations on the radiation exposure are getting stricter. Computer radiographic testing can reduce the amount of exposure that is about 1/2 to 1/80 compared to the conventional testing method. The aim of this study was to examine the reliability evaluation compared to stainless steel welds by radiographic testing and film welding process computer systems and conventional manual ultrasonic testing. As a result, there was no discontinuity on the reliability on the weld zone of built-in stainless steel material.
철도 차량 운송용 압력용기 클래드강의 용접 공정에 따른 신뢰성 평가
박재원(J. W. Park),이철구(C. K. Lee) 한국도시철도학회 2014 한국도시철도학회논문집 Vol.2 No.4
Due to the recent tightening of regulations on environmental issues and improvement in the performance and efficiency of marine structures, pressure container made of stainless clad steel is being constructed in the upper structure. Austenitic stainless steel is excellent in its mechanical nature and corrosion resistance, and is thus used in various conditions in a wide range of temperatures from extremely low to high. In this research, butt welding of clad steel is carried out with FCAW, SAW, and SMAW with the welding process as a variable, in order to find the optimum welding process for clad steel comparing the strength, reliability, and structure of the welded part. This research concludes that Flux-Cored Arc Welding (FCAW) demonstrates the highest reliability in the production of pressure vessel for railway vehicles as a result of the reliability test of the welded part in different welding processes.
김창근(C . K . Kim),정영채(Y . C . Chung),박재원(J . W . Park),송해범(H . B . Song) 한국축산학회 1988 한국축산학회지 Vol.30 No.4
These studies were conducted to investigate the effects of GTH, steroids and serums on the in vitro matutation of bovine follicular oocytes and to assess the fertilizing ability of the in vitro matured oocytes. The bovine oocytes recovered from follicles 1-3㎜ and 4-6mm in size were cultured for 16hr or 30hr at 38℃ with 5% CO₂ in moist air. In order to assess fertilizing ability of oocytes the in vitro matured oocyteswere transferred to the uterus or oviduct of rabbits inseminated into the uteruswith bull semen 4-6hr before oocyte transfer. 1. After 30hr of culture in m-KRB solution contains FSH and HCG, 411.3% and 25.0% of oocytes matured to metaphase II, respectively. Oocyte maturation was not increased by FSH but was significantly inhibited by HCG as compared with the control (44.2%). 2. The maturation rate (46.3%) of oocytes from 4-6 ㎜ follicles was higher, not significant, than that (31.4%) of 1-3mm follicular oocytes. The maturation of small follicular oocytes was more greatly inhibited by the addition of SIU HCG/㎖ However, this inhibitory effect was significantly improved when the time of HCG exposure shortened to 16hr and FCS instead of BSA was added to m-KRB solution. 3. More than 70% of oocytes reached metaphase II when oocytes were cultured in m-KRB solution containing only 15% (v/v) FCS or 10% (v/v) estrous cow serum, while 53.3% oocytes in m-KRB solution containing BSA. Maturation rate (70∼80%) was increased by the addition of FCS, FSH and steroids as compared with m-KRB containing only BSA (41.3%). 4. A higher fertilization rate (25%) was obtained when oocytes were cultured in m-KRB solution containing FCS, FSH and progesterone, while 8% in m-KRB solution plus BSA. Fertilization rate of oocytes matured in m-KRB plus FCS or estrous cow serum was not higher than that in m-KRB plus BSA but 28.6%o of (4/14) of the fertilized oocytes were cleaved to 2-3 cell stage.