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STS 304 강의 크리프 및 고온 저사이클피로균열전파 거동에 미치는 응력크기 및 응력파형의 영향
이치우,허정원,김광영,조용배 경남대학교 신소재연구소 1994 論文集 Vol.4 No.-
본 연구는 고온용 구조물 재료로 널리 사용되고 있는 STS304강을 650℃ 고온에서 공칭응력 σ_(n)=130 MPa와 σ_(n)=150MPa으로 실험하여 균열 전파거동에 미치는 응력 크기의 영향과 고온 저사이클 균열 전파 실험은 하중제어 하에서 대칭 삼각파형 fast-fast, 비대칭 삼각파형 fast-slow와 slow-fast 등으로 실험을 실시하여, 파형효과 중 반복속도 및 속도 비대칭 거동에 미치는 효과를 조사하였고, 모든 시험편에서 파단면의 형상을 조사하여 변형률 파형효과 및 응력파형효과에 따른 손상기구를 해석하고, 피로수명과 균열 전파속도의 결과를 비교 및 고찰하였다. 크리이프 균열전파 실험에서, 최대 응력강도 계수 K_(max)는 응력 크기 (σ_(n)=130MPa, σ_(n)=150MPa)에 관계없이 균열전파속도를 평가할 수 잇는 파라미터임을 보였다. 저사이클 고온피로 균열전파 실험에서, 반복속도가 빠른 fast-fast 파형에 비하여 반복속도가 느린 fast-slow와 slow-fast 파형의 경우에 균열전파속도는 현저하게 가속되며 또한, fast-slow 및 slow-fast 파형에서, 균열전파속도는 slow-fast 파형 경우가 fast-slow 파형보다 훨씬 빠르게 나타났으며, 이는 제하(negative loading)쪽보다 부하쪽(positive loading)의 하중속도가 느린 파형이 크리프 영향을 더 크게 받음을 의미한다. 그리고 파단면의 형상은 fast-fast 파형의 경우는 입내파괴를 보이고 fast-slow 파형의 경우는 입내파괴와 입계파괴가 혼재하며, slow-fast 파형의 경우는 입계파괴를 보였다. 입계파괴의 형상은 fast-slow 파형의 경우는 r형이며, slow-fast 파형의 경우는 w형이었다. The effects of stress amplitudes in creep and wave shape in fatigue on crack growth behavior of STS304 stainless steel have been investigated. Two kinds of stress amplitudes were considered in creep crack growth test : they were nominal stresses of σ_{n}=130MPa and an=150MPa Three types of wave shapes were considered in fatigue crack growth test : they were fast-fast, fast-slow and slow-fast(fast : 0.5sec, slow 500sec). The maximum stress intensity factor K_{max}, was a parameter able to evaluate crack growth behavior regardless of stress amplitude in creep crack growth test. The crack growth rates of wave shapes having long loading time were accelerated better than that of wave shape having short loading time, that is, the case of fast-slow and slow-fast were faster than that of fast-fast. The acceleration of the crack growth rate was affected much better by positive loading than negative loading, that is, the case of slow-fast was faster than that of fast-slow. Fractography of fractured surfaces correlated with the result of the crack growth behavior test.
Electropolymerization of Pyrrole Applied to Biosystem
Lee, Chi-Woo,Yoon, Jung-Hyun,Cho, Hyun-Woo,Bae, Sang-Eun,Lee, Kang-Bong The Korean Electrochemical Society 2002 한국전기화학회지 Vol.5 No.4
We have been investigating electropolymerization of pyrrole in aqueous electrolyte solutions in acidic as well as in neutral conditions by in situ electrochemical quartz crystal oscillator method, where resonant frequency and resonant resistance can be monitored simultaneously with current-voltage measurements during electropolymerization of pyrrole. The properties of thin PPy films prepared on electrode surfaces depended strongly on the experimental variables of electrode potentials applied, solution pH, kinds and quantity of supporting electrolytes, added chemicals, and the mode of electrochemical method employed. We are applying our experience gained on electropolymerization of pyrrole to immobilizing biomolecules onto electrode surfaces to develop a biosensor system. In this work, we wish to present the results on electrochemical monitoring on electropolymerization of pyrrole in the presence of DNA and albumin in different electrochemical conditions. Additionally we will summarize our investigations on the miniaturization of biomolecules/PPy composites by means of scanning tunneling microscopy.
Bae, Sang-Eun,Oh, Mi-Kyung,Min, Nam-Ki,Paek, Se-Hwan,Hong, Suk-In,Lee, Chi-Woo J. Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.12
Electrochemical, in situ electrochemical scanning tunneling microscope (EC-STM), and attenuated total reflectance-FTIR (ATR-FTIR) spectroscopic methods were employed to investigate the preparation of atomically flat Si(111)-H surface in ammonium fluoride solutions. Electrochemical properties of atomically flat Si(111)-H surface were characterized by anodic oxidation and cathodic hydrogen evolution with the open circuit potential (OCP) of ca. -0.4 V in concentrated ammonium fluoride solutions. As soon as the natural oxide-covered Si(111) electrode was immersed in fluoride solutions, OCP quickly shifted to near -1 V, which was more negative than the flat band potential of silicon surface, indicating that the surface silicon oxide had to be dissolved into the solution. OCP changed to become less negative as the oxide layer was being removed from the silicon surface. In situ EC-STM data showed that the surface was changed from the initial oxidecovered silicon to atomically rough hydrogen-terminated surface and then to atomically flat hydrogenterminated surface as the OCP moved toward less negative potentials. The atomically flat Si(111)-H structure was confirmed by in situ EC-STM and ATR-FTIR data. The dependence of atomically flat Si(111)-H terrace on mis-cut angle was investigated by STM, and the results agreed with those anticipated by calculation. Further, the stability of Si(111)-H was checked by STM in ambient laboratory conditions.
Bae, Sang-Eun,Youn, Young-Sang,Lee, Chi-Woo The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.4
Silicon surface nanostructures, which can be easily prepared by electrochemical etching, have attracted considerable attention because of its useful physical properties that facilitate application in diverse fields. In this work, electrochemical and electrochemical-scanning tunneling microscopic (EC-STM) techniques were employed to study the evolution of surface morphology during the electrochemical etching of Si(111)-H in a fluoride solution. The results exhibited that silicon oxide of the Si(111) surface was entirely stripped and then the surface became hydrogen terminated, atomically flat, and anisotropic in the fluoride solution during chemical etching. At the potential more negative than the flat band one, the surface had a tendency to be eroded very slowly, whereas the steps of the terrace were not only etched quickly but the triangular pits also deepened on anodic potentials. These results provided information on the conditions required for the preparation of porous nanostructures on the Si(111) surface, which may be applicable for sensor (or device) preparation (Nanotechnology and Functional Materials for Engineers, Elsevier 2017, pp. 67-91).
Transdermal scopolamine for the treatment of recurrent parotid sialocele: a case report
Chi Hyun Lee,Changryul Claud Yi,Yong Chan Bae,Jae Woo Lee,Byung-Joo Lee,Joo Hyoung Kim 대한두개안면성형외과학회 2024 Archives of Craniofacial Surgery Vol.25 No.1
Recurrent parotid sialocele is rare and challenging to treat. Treatment options are limited for cases of parotid sialocele that recur despite ductal ligation. This case study presents a patient who underwent wide excision of the right buccal mucosa due to squamous cell carcinoma. During the wide excision, a segment of the parotid duct was excised, and ductal ligation was performed to prevent the occurrence of a sialocele, followed by reconstruction using a folded anterolateral thigh free flap. Twenty-two days after surgery, parotid sialocele occurred despite the initial ductal ligation and subsequent ductal ligation was performed; however, the sialocele recurred. As an alternative therapeutic option, a transdermal scopolamine patch was applied for 3 weeks, with one patch used every 3 days. The results were encouraging, with complete resolution of the sialocele. A transdermal scopolamine offers a noninvasive, convenient method of treating parotid sialocele with minimal side effects. The successful outcome of this case suggests that a transdermal scopolamine can be an effective therapeutic option for recurrent parotid sialocele in conjunction with surgical treatment