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좌골신경손상 쥐 모델을 이용한 미세전류 자극의 근위축 억제 효과 확인 및 자극 세기 별 비교
황동현,김서현,이한아,장승준,김세빈,김택중,최수임,곽호영,김한성,Hwang, Donghyun,Kim, Seohyun,Lee, Hana,Jang, Seungjun,Kim, Sebin,kim, Tackjoong,Choi, Sooim,Kwak, Hoyoung,Kim, Han Sung 대한의용생체공학회 2017 의공학회지 Vol.38 No.4
Microcurrent electrical stimulation(MES) has been used to accelerate recovery of atrophied skeletal muscle. However, convincing stimulation parameters for suppressing muscle atrophy due to injured sciatic nerve remains unclear. The objective of this study was to investigate the effective intensity of MES on restraining muscle atrophy with rat model underwent sciatic nerve injury(SNI). Twenty-5-week-old Sprague Dawley male rats were equally assigned to five groups : Control group(Control, CON, n = 4), Denervation group(Denervation, D, n = 4), Denervation with MES of $22{\mu}A$ group(Denervation + $22{\mu}A$, D+22, n = 4), Denervation with MES of $100{\mu}A$ group (Denervation + $100{\mu}A$, D+100 n = 4), Denervation with MES of $400{\mu}A$ group(Denervation + $400{\mu}A$, D+400, n = 4). To induce muscle atrophy, all rats in the D, D+22, D+100, and D+400 groups, were subjected to sciatic nerve injury on their right hindlimb and allowed to have 1 week of resting period. Following this period, rats underwent daily MES(60 min/ a day, 5times/1week) for 4 weeks. After that, we investigate morphological changes in muscle volume by using in vivo micro-computed tomography at week 0, 1, 3 and 5. After 5 weeks, the muscle volume had the highest value in D+400 group, and also noticeably increased in D+100 group compared to it in D group. The results of this study imply that MES with current intensities between $100-400{\mu}A$ can suppress muscle atrophy effectively.
황동현,Jung-Hoon Ahn,후이,Kwan-San Hui,손영국 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.2
Al-doped Zinc Oxide (AZO) films were deposited on glass substrates by radio frequency (R.F.) magnetron sputtering technique. The properties of the films were controlled by adjusting the oxygen flow contents as a mixture of Ar and O2 gases. The structural, electrical and optical properties of the films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), a UV-visible spectrometer, as well as Hall effect measurements. Results revealed that a film deposited with an oxygen partial pressure content of 0% had a hexagonal structure, a strongly preferred orientation with the c-axis perpendicular to the substrate and the lowest resistivity of about 6.9 × 10−4 Ω cm. The optical transmittance spectra showed more than 80% transmittance in the visible region, and the band gap was found to be direct. Strong violet emission located at 2.96 eV was observed in the AZO films deposited with an oxygen partial pressure content of 0%.
Correlation between fretting and plain fatigue using fatigue damage gradient
황동현,조성산 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6
Fretting fatigue is correlated with plain fatigue in order to develop a method to estimate fretting fatigue life from plain fatigue data. Fretting fatigue experiments as well as plain ones were conducted to obtain fatigue life data at various conditions. Finite element analyseswere conducted to evaluate the Smith-Watson-Topper (SWT) fatigue damage parameter around crack initiation location. It is revealedthat the SWT in fretting fatigue decays exponentially away from the surface. Moreover, a correlation function exists that relates the gradientof normalized SWT at the surface to the maximum SWT ratio of plain fatigue to fretting fatigue at the same life. It is demonstratedthat equivalent SWT for fretting fatigue, which is determined from the correlation function, can be compared directly with plain fatiguedata for estimation of fretting fatigue life.
Al 도핑된 ZnO 박막에서 방출되는 보라색 발광 스펙트럼
황동현,손영국,조신호,Hwang, Dong-Hyun,Son, Young-Guk,Cho, Shin-Ho 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.4
We report on a strong violet luminescence emitted from the ZnO:Al films grown on glass substrate by radio-frequency magnetron sputtering. The growth of high-quality thin films and their optical properties are controlled by adjusting the mixture ratio of Ar and $O_2$, which is used as the sputtering gas. The crystallinity of the films is improved as the oxygen flow ratio is decreased, as evidenced in both x-ray diffractometer and atomic force microscope measurements. As for the violet luminescence measured by photoluminescence (PL) spectroscopy, the peak energy and intensity of the PL signal are decreased with increasing the oxygen flow ratio. The peak energy of the violet PL spectrum for the thin film with an oxygen flow ratio of 50 % is almost constant, regardless of the increase of laser Power and temperature. These results indicate that the violet PL signal is probably due to defects related to interstitial Zn atoms.