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국제학술회의 참관기 - 제5회 아시아 분석과학 학술대회
이대원,Lee, Dae-Won 한국과학기술단체총연합회 1999 과학과 기술 Vol.32 No.7
제5차 아시아 분석과학 학술대회가 지난 5월 4일부터 나흘동안 중국 하문대학에서 5백여명의 과학자들이 첨석한 가운데 열렸다. 한국대표 38명이 참석한 가운데 열린 이번 학술대회에서 한국은 필자가 한국대표로 축사를 했고, 포항공대 박수문교수의 기조강연에 이어 3건의 초청강연이 있었다. 2년마다 열리는 이 학술대회는 2001년 일본 와세다대학에서 2003년에는 한국에서 개최키로 했다.
지압과 온열의 조합마사지가 인체의 스트레스 완화에 미치는 영향 평가
이대원,박지형,엄시내,김도원,조승현,고창용,김한성,Lee, Dae Won,Park, Ji Hyung,Eom, Si Nae,Kim, Do Won,Cho, Syung Hyun,Ko, Chang-Yong,Kim, Han Sung 대한의용생체공학회 2012 의공학회지 Vol.33 No.4
This study was designed to investigate the effect of a combined stimulus which was composed of chiropractic massage and thermotherapy on the relief of mental and physical stress. Fifteen healthy male subjects were treated with three type of stimuli; control (without any stimulus), a single stimulus (only chiropractic) and a combined stimulus. To evaluate the effects of stimuli, visual analogue scale (VAS), trunk extension, electromyogram (EMG) on erector spinae muscle and electrocardiogram (ECG) were measured and analyzed before and after stimuli. In the control group, there were no significant changes in EMG root mean square (RMS) value and low Frequency/high Frequency (LF/HF) ratio (p > 0.05, p > 0.05). However, both stimulus groups showed significant increases in trunk extension and EMG RMS values (p < 0.05, p < 0.05), but significant decreases in LF/HF ratios (p < 0.05). Particularly the decrement rate in LF/HF ratio was significantly higher in the combined stimulus group than that in the single stimulus group (p < 0.05). Also, a significantly lower VAS was recorded after combined stimulus. Our findings indicate that the combined stimulus might not only improve flexibility and strength of muscle, but also active parasympathetic nerve activity. The combined stimulus may thus contribute to relieve the stress and to enhance the muscle function.
초저온 냉각튜브 내 수소기체의 액체수소로의 상변환 분석
이대원,홍하이응우엔,소명기,나인욱,박동화,김교선,Lee, Dae-Won,Nguyen, Hoang Hai,So, Myeong-Ki,Nah, In-Wook,Park, Dong-Wha,Kim, Kyo-Seon 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.1
에너지 위기 시대를 맞이하여 수소에너지가 가장 가능성 있는 대체에너지 중의 하나로 고려되고 있다. 액체수소는 기체수소와 비교하여 단위 부피당 에너지 밀도가 월등히 높으며 수소에너지의 탁월한 저장 방법으로 간주되고 있다. 본 연구에서는 2 상 모델에 기초를 둔 Navier-Stokes 식을 전산유체역학 프로그램을 이용하여 풀었으며, 초저온 냉각 튜브를 통과하면서 기체수소가 액화되는 과정을 분석하였다. 열전도율이 높은 구리관을 초저온 냉각을 위한 관의 재질로 가정하였다. 기체수소의 유입속도를 5 cm/s, 10 cm/s, 20 cm/s로 변화시키면서 냉각튜브 내 유체 온도분포, 축방향 및 반경방향 유체 속도, 기체 및 액체 수소 부피분율 분포를 각각 분석하였다. 본 연구 결과는 향후 액체수소 제조를 위한 기체수소 초저온 냉각기의 설계 및 제작을 위한 기초자료로 활용이 될 것으로 기대된다. Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.
영업운행 전동차 객실형광등의 플리커(Flicker) 현상에 관한 분석 연구
이대원(LEE DAE WON),하종은(HA JONG EUN),한성호(HAN SEONG HO),박재홍(PARK JAE HONG) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
Generally, there are two types of main factors to affect output power quality of a auxiliary power supply an EMU(electric multiple unit). One is a voltage flicker by amplitude modulation of short time and air compressors. The other is repetitive motion of large capacity motor such as air compressors, HVAC unit etc. in main factors. This paper compared two kinds of fluorescent lamp, 32W (after remodeling interior) and 40W(before remodeling interior) and measured the light output varying input power(AC220V) for a flicker phenomenon related power supply of lamps in EMU. Also, we analyzed a flicker considering EMU operating time and density in order to grasp main factors of a load change to cause a voltage change. As a results of test, a 40W fluorescent lamp was more insensitive with 20.26% degree an eye recognition degree sides about changes of the input power and lower with 19.9% voltage side generating flicker compare with fluorescent lamp 32W. Also, we confirmed the fact which the fluorescent lamp flicker was generated by varying fluorescent lamp output voltage when the commercial EMU was in high driving density and at the busy time. Additionally, we confirmed the frequency band which an EMU passenger could feel sensitively blinking of a fluorescent lamp was visually 8㎐ ~ 15㎐.