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李龍鎬,南勝義,宋昌燁 弘益大學校 1981 弘大論叢 Vol.13 No.-
The previous report stated that the direct graphitizing process without decomposition of pearlite could be practised experimentally in malleable cast iron annealing, that is, by holding the iron for about sixtyhours. After cooling transformation begins, a fully ferritized malleable cast iron is obtained. It has also been clarified that it is rather difficult to keep the castings in such narrow temperature range as 730 to 740℃ under foundry conditions. With the view of investigating the resolution vehavior of pearlite remaining after direct graphitiaztion into austenitic matrix, specimens haveing bull's eye structure or pearlite were quenched after holding for various periods at predetermined temperatures and their microstructures were examined. The results obtained are summarized as follows: 1) The existence of a trace of cementite after resolution of pearlite into austenitic matrix when the specimen is reheated above critical temperatues accelerates the precipitation and growth of pearlite depending upon the volume and number of remaining pearlitic cementite during slow cooling through the critical range. In other words, a trace of cementite retards the direct graphitization in the critical range. 2) As lamellar pearlite precipitated during cooling deccomposes extremely slowly at subcritical temperatures, it is important to prevent the formation of pearlite during cooling in order to have the direct graphitization completed during slwo cooling in the appropriate temperature range. 3) It is necessary to hold the iron for at least 1hr. at 900℃ to dissolve the pearlitic cementite into austenite. 4) It was found by the author's experiment that a blackherat malleable iron having fully ferritized matrix can be obtained by extremely slow cooling through critical direct-graphitzing temperature range. Ⅰ. 緖 言 Ⅱ. 基礎理論 Ⅲ. 實驗方法 Ⅲ-1 試料의 製作 Ⅲ-2 實驗器機 Ⅲ-3 實驗方法 Ⅳ. 實驗結果 및 考察 Ⅳ-1 加熱溫度에 따른 黑鉛化 Ⅳ-2 黑鉛化에 미치는 維持時間의 影響 Ⅳ-3 反復 加熱 冷却時 黑鉛化 및 機械的 性質 Ⅳ-4 變態 範圍는 徐冷하여 長時間 等溫維持할 때의 黑鉛化 Ⅴ. 結 論
신태희,백승엽,이은상 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
For the graceful design and durability, cellular phone frame is been changing from the external to internal. Most of external frames are made by aluminium alloy, because that is required to be light and cheap while that should be hard. Due to the mass product using injection molding method or die casting method, these external frames have a lot of burrs. Moreover, microscopic burrs affect for parts badly, how that makes electric jamming. In addition, microscopic burrs could injure workers or users. In this paper, for the removal of microscopic burrs on the cellular phone external frame, electrochemical deburring is conducted and electrochemical conditions are researched.
마이크로 핀을 이용한 니티놀 형상기억 합금의 마이크로 전해가공 특성 분석
신민정,백승엽,김백겸,이은상 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-
Electrochemical micro machining, the anodic dissolution process without contact with tools, can achieve a wanted shape of the surface using electrochemical reaction between anode and cathode. Nitinol is a metal alloy composed of Ni and Ti around 50% respectively which has shape memory effect. Nitinol can be put various applications which require micro scale structure. The aim of this study is to investigate the characteristic of electrochemical micro machining for nitinol workpieces. In order to analyze the characteristics of electrochemical micro machining for nitinol, tungsten carbide micro pin was used for electrode and the machined area was observed by optical microscope.
김백겸,신태희,백승엽,이은상 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
Electro-chemical Machining, the anodic dissolution process is able to achieve wanted a sharp shape and high quality surface without contact with workpiece and low heat effect using electrochemical reaction between anode and cathode. In hence this process useful to apply micro structure. A shape memory alloy for micro-structure and micro industrial technique, Nitinol is composed of approximately 55% Nikel and 45% Titanium by weight. This material is able to function as to transform specific shape from a certain deformation when the alloy is heated. Therefore Nitinol is used for several industries such as a medical industry, a aerospace, electrical application on a part of micro structure. In this paper, effect of electrolyte is studied on electrochemical machining for Nitinol shape memory alloy, copper is used for electrode, diameter and depth are measured as a extent of processing using optical microscope.
Lee, Seung-Youl,Son, Eunjung,Kang, Jin-Young,Lee, Hee-Seok,Shin, Min-Ki,Nam, Hye-Seon,Kim, Sang-Yub,Jang, Young-Mi,Rhee, Gyu-Seek Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.4
Parabens, the esters of p-hydroxybenzoic acid, have been widely used as antimicrobial preservatives in cosmetic products, drugs, and processed foods and beverages. However, some parabens have been shown to have weak estrogenic effects through in vivo and in vitro studies. Because such widespread use has raised concerns about the potential human health risks associated with exposure to parabens, we developed a simultaneous analytical method to quantify 4 parabens (methyl, ethyl, propyl, and butyl) in human urine, by using solid-phase extraction and high-performance liquid chromatography coupled with triple quadrupole mass spectrometry. This method showed good specificity, linearity ($R^2$ > 0.999), accuracy (92.2-112.4%), precision (0.9-9.6%, CV), and recovery (95.7-102.0%). The LOQs for the 4 parabens were 1.0, 0.5, 0.2, and 0.5 ng/mL, respectively. This method could be used for quick and accurate analysis of a large number of human samples in epidemiological studies to assess the prevalence of human exposure to parabens.
Seung-Youl Lee,Eunjung Son,Jin-Young Kang,Hee-Seok Lee,Min-Ki Shin,Hye-Seon Nam,Sang-Yub Kim,Young-Mi Jang,Gyu-Seek Rhee 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.4
Parabens, the esters of p-hydroxybenzoic acid, have been widely used as antimicrobial preservatives in cosmetic products, drugs, and processed foods and beverages. However, some parabens have been shown to have weak estrogenic effects through in vivo and in vitro studies. Because such widespread use has raised concerns about the potential human health risks associated with exposure to parabens, we developed a simultaneous analytical method to quantify 4 parabens (methyl, ethyl, propyl, and butyl) in human urine, by using solid-phase extraction and high-performance liquid chromatography coupled with triple quadrupole mass spectrometry. This method showed good specificity, linearity (R2 > 0.999), accuracy (92.2-112.4%), precision (0.9-9.6%, CV), and recovery (95.7-102.0%). The LOQs for the 4 parabens were 1.0, 0.5, 0.2, and 0.5 ng/mL, respectively. This method could be used for quick and accurate analysis of a large number of human samples in epidemiological studies to assess the prevalence of human exposure to parabens.
Lee, Jeong Yub,Kim, Yongsung,Han, Seunghoon,Kim, Jaekwan,Yoon, Jae Woong,Lee, Ki Young,Song, Seok Ho,Yang, Kiyeon,Lee, Chang Seung IOP 2019 Nanotechnology Vol.30 No.4
<P>A low-temperature laser crystallization is newly devised for producing polycrystalline silicon (poly-Si) thin films of low-loss, low surface roughness enough for nanoscale patterning, applicable to practical Si metasurface elements on complementary metal-oxide semiconductor (CMOS) electronic architectures in visible lights. The method is based on dielectric encapsulation of an amorphous Si film and subsequent laser-induced local crystallization. Such poly-Si thin film yields order-of-magnitude smaller surface roughness and grain size than those obtained with the conventional laser annealing processes. The mechanism of the formation of small and uniform crystalline grains during solidification is studied to ensure the smooth surfaces enough for nanoscale patterning. By obtaining root mean square of surface roughness <2.49 nm and extinction coefficient <4.8?×?10<SUP>–2</SUP> at 550 nm, visible metasurface color-filter elements are experimentally demonstrated with the resonant transmission-peak efficiency approaching ∼85%. This low-loss poly-Si metasurface is favorably compatible with embedded CMOS electronic architectures in contrast to the conventional thermal annealing processes that often cause failure of electrical device functionalities due to delamination and material-property degradation problems. The proposed fabrication in this study provides a practical method for further development of various Si metasurfaces in the visible domain and their integration with CMOS electronic devices as well.</P>
백승엽(Seung-Yub Baek),이광호(Kwang-ho Lee),최승건(Seung-Geon Choi),김성현(Seong-Hyun Kim),최웅걸(Woong-Kirl Choi),김중호(Jung-Ho Kim),박종범(Jong-Beom Park) 한국산학기술학회 2015 한국산학기술학회 학술대회 Vol.2015 No.1
다양한 농작업을 수행하기 위한 농업용 트랙터의 후방에 작업시기에 맞는 다양한 작업기를 장착하게 된다. 트랙터를 전방으로 진행하면서 후방에 장착된 작업기를 동시에 조정하는 것은 많은 문제점을 가지고 있다. 본 논문에서는 후방에 장착된 작업기를 원활히 조정할 수 있도록 회전형 캐빈의 개발을 앞서 압쇄 시험에 따른 구조해석을 진행하였다. ISO기준에 따라 첫 번째 압쇄 시험과 두 번째 압쇄 시험에 관하여 구조해석을 진행하였으며, 해석 결과를 바탕으로 트랙터용 캐빈의 개발을 진행할 것이다.