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보일러용 T23/T91 이종용접부의 탄소이동에 관한 연구
박기덕 ( Ki Duck Park ),정병호 ( Byong Ho Jung ),강창룡 ( Chang Yong Kang ) 한국열처리공학회 2014 熱處理工學會誌 Vol.27 No.6
The study on the migration of carbon in T23/T91 dissimilar metal welds for the boiler was conducted at 600℃ with an increase of aging time from 1 to 100 hrs. Following results were obtained. The heavily etched dark band tended to increase from a molten boundary owing to an increase of aging time, which leads to form hard (T91) and soft (T23) zones with different hardness. It was found that carbon was migrated from T23 area toT91 area due to different carbon activities. In addition, soft and hard zones were formed in regional area mainly resulted from carbide dissolutions and precipitates.
파킨슨병 환자의 정량적 뇌파분석 -비선형분석을 이용한 정상인 및 본태성 진전 환자와의 비교
조은경,최병옥,김용재,박기덕,김응수,최경규,Cho, Eun-Kyoung,Choi, Byung-Ok,Kim, Yong-Jae,Park, Ki-Duck,Kim, Eung-Su,Choi, Kyoung-Gyu 대한임상신경생리학회 2006 Annals of Clinical Neurophysiology Vol.8 No.2
Background: Parkinson's disease is movement disorder due to dopaminergic deficiency. It has been noted that cognitive dysfunction also presented on Parkinson's disease patients. But, it is not clear whether such a cognitive dysfunction was a dopaminergic dysfunction or cholinergic dysfunction. Using linear and non-linear analyses, we analysed the effect of cognitive and motor symptom on EEG change. Methods: EEGs were recorded from patients with Parkinson's disease and essential tremor, and normal controls during rest. We calculated the power spectrum, correlation dimension and Lyapunov exponent by using 'Complexity'program. The power spectrum, correlation dimension, and Lyapunov exponent were compared between Parkinson's disease patients and essential tremor patients. Results: Theta power was increased in Parkinson's disease patient group. Correlation dimension was increased in Parkinson's disease patients. Positive correlation was noted between MMSE and correlation dimension, and negative correlation was noted between MMSE and Lyapunov exponent. Lyapunov exponent was decreased in Parkinson's disease patient. Conclusions: We conclude that the state of Parkinson's disease patient is characterized by increased correlation dimension and decreased Lyapunov exponent.
발전소용 이중보온용 강관의 홈부식(Grooving Corrosion)에 의한 파손 분석
함종오(Jong-Oh Ham),박기덕(Ki-Duck Park),박성진(Sung-Jin Park),선일식(Il-Sik Sun) 한국신뢰성학회 2015 신뢰성응용연구 Vol.15 No.3
Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water (95~110℃) for a plant was carried out. The damaged area (Ф 5㎜) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.