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양유창,송정일,한경섭 대한기계학회 1995 대한기계학회논문집 Vol.19 No.6
Al6061 alloy reinforced with 15 volume% of Saffil fibers was fabricated by squeeze infiltration method. Uniform distribution of reinforcements and good bondings between reinforcements and matrix alloy were found in the microstructure of composites. Comparing with A16061 matrix alloy, tensile strength and elastic modulus of $Al_{2}$O$_{3}$/Al composites were increased up to 26% and 31%, respectively. Cyclic deformation and fatigue behavior of $Al_{2}$O$_{3}$/Al metal matrix composites were studied. The specimens were cycled using tension-tension(R=0.1) loading and under load controlled fatigue test. Cyclic stress-displacement curve through fatigue test was obtained. Fatigue strength of $Al_{2}$O$_{3}$/Al composites was about 200 MPa, i.e.0.55 of applied stress level(q). During fatigue test, $Al_{2}$O$_{3}$/Al composites displayed cyclic hardening at all applied stress levels. The most of resultant displacement due to permanent plastic deformation occurred in less than the first 5% of fatigue life. Displacement-to-failure of the fatigue test was smaller than that of the tensile test because of accumulative damage by cumulative plastic deformation.
양유창(Yoo Chang Yang),한경섭(Kyung Seop Han) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in<br/> damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied<br/> in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix<br/> cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity<br/> impacts. Tensile and indentation test was performed with the measurement of optical signal and acoustic<br/> emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated<br/> by wavelet transform. It was found that damage information of comparable in quality to acoustic emission<br/> data could be obtained from the optical fiber vibration sensor signals.
유창현(Chang Hyun Yoo),윤대영(Dae Young Yoon),조현상(Hyun Sang Cho),민기식(Ki Sik Min),김종완(Jong Wan Kim),유기양(Ki Yang Ryoo) 대한소아신경학회 1999 대한소아신경학회지 Vol.6 No.2
목적: 뇌성마비 환아의 MRI를 후향적으로 분석하여, 뇌손상 평가지 MRI의 역할, 임신 주수에 따른 MRI 소견의 차이를 알아보았다. 방법: 1994년 1월부터 1998년 7월까지 강동성심병원에서 뇌성마비로 진단받은 66명(만삭아 37명 미숙아 29명)의 MRI를 미숙아군과 만삭아군으로 나누어 비교하였다. 결과: 미숙아군 29례에서 13례가 저산소성 허혈성 뇌손상의 소견을 보였는데 PVL이 12례(41.3%)로 가장 많았고 신경 세로 이주 장애가 6례(20.8%), 기타 선천성 뇌기형 5례(17%), multifocal ischemic necrosis 1례(3.4%), 정상 소견이 5례(17%)에서 관찰되었다. 만삭아군 37례에서 22례가 저산소성 허열성 뇌손상의 소견을 보였으며 selective neuronal necrosis 11례(29.7%), PVL 4례(10.8%), focal and multifocal ischemic necrosis 4례(10.8%), 대리석 상태 3례(8.1%), 신경 세포 이주 장애 4례(10.8%), 기타 선천성 뇌기형 5례(13.5%), 정상 소견이 6례(16.2%)에서 관찰되었다. 결론: MRI를 통해서 뇌성 마비 환아에서 다양한 병변을 관찰할 수 있으며 저산소성 허혈성 뇌손상은 미숙아군과 만삭아군에서 유의한 차이를 보였다. 미숙아군에서는 PVL이 흔하고 만삭아군에서는 selective neuronal necrosis가 통계적으로 많았다. Purpose: We used MRI to retrospectively analyze the brain of patients suffering from cerebral palsy. Our aim is to determine MRI's role in the assessment of brain damage, the relationship of gestational age. Methods: A total of 66 patients(29 preterm group and 37 term group), who visited Kang-Dong Sacred Heart Hospital from January, 1994 to July, 1998, where enrolled in study. Results: Among the 29 in the preterm group, 13 patients showed MR images of hypoxic ischemic injury in which periventricular leukomalacia(PVI) and multifocal ischemic necrosis in 12(41.3%) and 1(3.4%) respectively. Neuronal MR images 5(17%) in this preterm group. Among the 37 in the term group, 22 patients showed MR images of hypoxic ischemic injury in which selective neuronal necrosis were 11(29.7%), PVL 4(10.8%), focal and multifocal ischemic necrosis 4(10.8%) and status marmoratus 3(8.1%). Meuronal migration disorders were 4(10.8%), other congenital malformations 5(13.5%) normal MR images 6(16.2%) in the term group. Conclusion: MRI provided useful information in a majority of children with cerebral palsy. Hypoxic ischemic injury was significantly different in preterm and term groups. PVL was frequent in the preterm group and selective neuronal necrosis was statistically common in the term group.