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이은택(Lee Eun-Taik),이용제(Lee Yong-Jae),심현주(Shim Hyun-Ju),장경호(Chang Kyong-Ho) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.11
Many researches have been performed to describe the elastic and inelastic behavior of H-shaped beams with web openings, and were generally concentrated on the monotonic loading conditions. In this experimental study, local buckling behaviour of welded light H-shaped beams with web openings under cyclic loading were investigated, and the adequacy of design method of web openings beams proposed by Darwin was examined. The commencement and the effect of local buckling, the strength and stiffness deterioration after local buckling, and the fracture around the web openings under cyclic loading condition were also investigated through the observation of the test results with various openings with or without stiffeners.
Seok Ryoul Lee,Sang-Yun Sung,Kyong Taik Lee,Seong Gook Cho,Ho Seong Lee 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.9
We investigated the mechanism of mobility enhancement after the dehydrogenation process in polycrystalline silicon (poly-Si) thin films. The dehydrogenation process was performed by using an in-situ CVD chamber in a N2 ambient or an ex-situ furnace in air ambient. We observed that the dehydrogenated poly-Si in a N2 ambient had a lower oxygen concentration than the dehydrogenated poly-Si annealed in an air ambient. The in-situ dehydrogenation increased the (111) preferred orientation of poly-Si and reduced the oxygen concentration in poly-Si thin films, leading to a reduction of the trap density near the valence band. This phenomenon gave rise to an increase of the field-effect mobility of the poly-Si thin film transistor.
상온에서 증착된 IGZO 박막의 열처리 온도에 따른 특성
이석열(Seok-ryeol Lee),이경택(Kyong-taik Lee),김재열(Jae-yeal Kim),양명수(Myoung-su Yang),강인병(In-byeong Kang),이호성(Ho-seong Lee) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.4
We investigated the structural, electrical and optical characteristics of IGZO thin films deposited by a roomtemperature RF reactive magnetron sputtering. The thin films deposited were annealed for 2 hours at various temperatures of 300, 400, 500 and 600℃ and analyzed by using X-ray diffractometer, transmission electron microscopy, atomic force microscope and Hall effects measurement system. The films annealed at 600℃ were found to be crystallized and their surface roughness was decreased from 0.73 nm to 0.67 nm. According to XPS measurements, concentration of oxygen vacancies were decreased at 600℃. Optical band gap were increased to 3.31eV. The carrier concentration and Hall mobility were sharply increased at 600℃. Our results indicate that the IGZO films deposited at a room temperature can show better thin film properties through a heat treatment.
Lee, Young Soo,Kim, Duk Soo,Kim, Ki Hong,Kim, Hee Taik,Yoo, Kyong Ok 한국화학공학회 1996 Korean Journal of Chemical Engineering Vol.13 No.4
In order to investigate the effects of sulfidation/oxidative regeneration cycle on the change of structural properties and removal capacity of sorbent, sulfidation/regeneration cycle was carried out up to 15 times in a fixed-bed reactor. The effluent gases from the fixed-bed reactor were analyzed by gas chromatography, and XRD, SEM, and liquid nitrogen physisorption method were used to characterize the reacted sorbents. The sorbent treated first sulfidation/regeneration cycle exhibited maximum specific surface area and the highest H₂S removal capacity. Hysteresis of adsorption isotherm of the regenerated sorbent reflected the growth of pores of fresh sorbent and pore size distribution confirmed this fact. Furthermore constant H₂S removal capacity was maintained up to 15 times of sulfidation/regeneration cycle.
반복하중을 받는 유공 강구조 부재의 국부좌굴 및 소성거동
이은택(Lee Eun-Taik),심현주(Shim Hyun-Ju),장경호(Chang Kyong-Ho) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.11
Many researches have been performed to described the elastic and inelastic behavior of the general steel with web opening, and were generally concentrated on the uniaxial loading conditions. With those results of researches, the formulae for design of beams with web openings have been proposed by Darwin(1990). Though the formulae are so simple and useful to apply to real situation, it needs more research on cyclic loading condition. <br/> In order to investigate the strength and deformation characteristics of H beams with web openings, 9 steel beams with web openings were tested. The dimensions of beams are based on the formulae proposed by Darwin. The suitability of existing design formulae, the effects of plastic hinges on beams with web openings, and the local bucking around the web openings to the beam strength were also investigated through the observation of the behaviors of these beams with various opening types.<br/> And the effect of local buckling, the strength and stiffness deterioration after local buckling, and fracture around the web openings under cyclic loading condition were investigated and studied through the observation of the test results with various openings with or without stiffeners.
허혈-재관류에 의한 흰쥐 간의 손상에 있어서 반응성 산소종의 역할
지경천,권년수,이희성,김상준,장선택 중앙대학교 의과대학 의과학연구소 1992 中央醫大誌 Vol.17 No.4
Increased generation of reactive oxygen species is thought to be a major cause of tissue in ischemia-reperfusion injury. Left and median lobes of rat livers were subjected to 20 minutes of ischemia followed by reperfusion for up to 120 minutes. Superoxide radical generation was enhanced to 338 μmol/minute/g tissue after 60 minutes of reperfusion,and 367 μmol/minute/g tissue after 120 minutes. Superoxide generation in the liver of the control animal was 260 μmol/minute/g tissue. The activity of xanthine oxidase, a superoxide radical-generating enzyme, was also elevated in the liver treated with ischemia-referfusion. These results indicate that xanthine oxidase-catalyzed reaction is an important source for the superoxide generation in rat liver treated with ischmia-referfusion. The activities of superoxide dismutase and catalase, enzyme responsible in removing superoxide radical and hydrogen peroxide, were measured. Cu, Zn-superoxide dismutase activity was significantly higher in reperfused liver after ischemia than in control. However, the activity of Mn-containing superoxide dismutase was significantly low in reperfusion. The extent of tissue damage by ischemia-reperfusion was evaluated by measuring lipid peroxidation. Thiobarbituric acid reactive substance was significantly elevated in the liver treated with 60 minutes of ischemia followed by 60 minute of reperfusion. These results suggested that increased reactive oxygen species and diminished activities of enzyme removing toxic oxygen species rendered the damages on the liver which was sujected to ischemia followed by reperfusion.
Pyrolysis Characteristics of Acrylonitrile - Butadiene - Styrene Resin
Kim, Hee Taik,Yoo, Kyong Ok,Oh, Sea Cheon,Lee, Hae Pyeong,Jun, Hyun Chul 한국공업화학회 1999 Journal of Industrial and Engineering Chemistry Vol.5 No.2
The pyrolysis characteristics of acrylonitrile-butadiene-styrene resin were investigated at various heating rates. Methane, ethane and ethylene were major gaseous products from pyrolysis of acrylonitrile-butadiene-styrene resin. The recovered oil products were mainly composed of styrene monomer and benzene, and showed the calorific value of 8400∼9000 ㎈/g, which may be suitable as fuel oil. In order to obtain the kinetic parameters of ABS pyrolysis, the dynamic thermogravimetric analysis curve and its derivative have been analyzed using a variety of analytical methods reported in the literature.
Oxydative Regeneration of Sulfided Sorbent by H2S without Emission of SO2
Young Soo Lee,Do Hyeon Park,Hee Taik Kim,Kyong Ok Yoo 한국화학공학회 1995 화학공업과 기술 Vol.13 No.2
N/A Much SO₂, another perilous air pollutant, was emitted during the oxidative regeneration of sulfided sorbent by HZS. In order to prevent emission of SO₂, we carried out oxidative regeneration with the physical mixture of CaO and sulfided sorbent and investigated the effect of regeneration temperature and oxygen concentration on the reactivity of CaO with SO₂. The effluent gases were analyzed by G.C. and the properties of sorbent were characterized by XRD, SEM, TG/DTA and EPMA. Deterioration of reactivity of CaO with SO₂ resulted in increment of emission of SO₂ due to the structural changes of CaO above 750℃ and that at 850℃ was more severe. Furthermore EPMA and XRD analysis revealed that product layer diffusion through the solid product, CaSO₄, was the rate limiting step for CaO sulfidation. The reaction of CaO with SO₂ was first order approximately and that was accelerated by high O₂ concentration.
Kinetics of Nonisothermal Thermal Degradation of Styrene - Butadiene Rubber
Kim, Hee Taik,Yoo, Kyong Ok,Oh, Sea Cheon,Lee, Hae Pyeong 한국화학공학회 1999 Korean Journal of Chemical Engineering Vol.16 No.4
The kinetics of thermal degradation of styrene-butadiene rubber (SBR) was studied by conventional thermogravimetric technique with various heating rates under nitrogen. A kinetic model which accounts for the effects of scission of polymeric chain at any time was proposed to describe the thermal degradation of SBR. Results showed that the contribution of the thermal degradation of zero-order reaction is greater than that of first-order and second-order reactions. The activation energy of the thermal degradation of SBR was calculated to be 172kJ/㏖ using the Arrhenius equation.