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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.
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.
RGP 콘택트렌즈의 진단적 피팅법에 의한 플랫한 피팅과 얼라인먼트 피팅착용 전·후 각막 굴절력의 변화에 관한 연구
이대원(Dae Won Lee),김인숙(In Suk Kim) 한국안광학회 2014 한국안광학회지 Vol.19 No.2
Purpose: This study is for compared the change of corneal refractive power before and after wearing of rigid gas permeable contact lense with diagnostic method which is 1 D flatter than alignment fitting on right eye and alignment fitting on left eye for 2 months and investigate the preference. Methods: Twenty middle school and high school students (40 eyes) who had never worn a contact lense before for no corneal topographical change, no ocular disease, no experience of ophthalmic surgery and have normal tear amount were selected for this study and corneal refractive power were examined before wearing rigid gas permeable contact lense and adaptation status and corneal examination were performed after 10 days of wearing and after cheking up the continuation of wearing, all candidate wear contact lens 8 hours per day for 2 month and corneal refractive power were compared. Results: After 2 months of wearing with 1 D flatter than the alignment fitting on right eyes, there was significant difference in the central corneal refractive power was 43.84±1.33 D, flat K power was 43.05±1.29 D, and steep K power was 44.61±1.42 D decreased than before wearing (p<0.001, 0.001, 0.047). The e-value of the principal meridians also shows statistically significant difference (p=0.037, 0.015). After 2 months of wearing with alignment fitting on left eyes, the central corneal refractive power was 44.40±1.26 D, flat K power was 43.57±1.23 D. and flat K e-value was 0.58±0.05 which showed no statistically significant difference (p = 0.769, 0.614, 0.181). But steep K power was 45.25±1.36, and steep K e-value was 0.45±0.18 which shows statistically significant difference (p=0.018, 0.027). Conclusions: Consider the comfort, clear vision, dryness for preference fitting investment, 6 students (30%) prefer right eye which is 1 D flatter fitting, 14 students (70%) prefer left eye which is alignment fitting. For rigid gas permeable fitting needed for accurate examination and should prescribe the alignment fitting which is suitable for each cornea.
이대원(Lee Dae-Won),이종문(Lee Jong-Moon),이성권(Lee Seong-Gwon),고재현(Ko Jae-Hyun),정수영(Chung Su-Young) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.5
2010년 이전 국책연구과제는 국책연구기관이 민간산업계의 요구사항 위주로 전문기관에 제안하여 수행함에 따라 사용자(운영기관 및 고객)의 불편사항이 지속적으로 제기되었으나 현재 사용자가 제시한 의견을 반영할 수 있도록 연구관련 제도가 개선되는 추세다. 본 논문은 도시철도/경량전철 차량의 핵심부품 및 장치에 관한 기술고도화 및 원천기술 확보를 위한 과제 도출기법에 관하여 연구하였다. 도시철도/경량전철 차량과 연관된 이해당사자 그룹(지방정부, 운영기관, 연구기관, 학계, 산업계, 등)에 관한 정의, 차량전문가에 관한 정의와 설문항목 설계를 위한 기법 적용은 객관성, 공정성, 형평성 확보를 위해 델파이 기법을 적용하여 설계 및 검증하고자 하였다. 또한, 기획연구과제 도출 프로세스를 공유함으로써 도시철도/경량전철 차량분야의 이해관계자 그룹 간 의견을 통합하여 이해관계자 그룹의 요구사항을 충족하는 도시철도/경량전철 차량분야 핵심부품 및 장치에 관한 고도화 연구 과제를 도출하고자 하였다. Before 2010, assignments proposed by government caused inconvenience of users(operation institutions & customers) as performing that National research organization suggested requirements from private organizations to special institutes, but now the institution of assignments is improving to reflect opinions from the present users. This is a study on methods for drawing a task of Rolling stock’s core parts & enhancing of Urban Railway/Light Railway Transit. The definition of multiple stakeholders(local government, operation institution, research organization, academic world, the industrial world, etc.) related to rolling stock of urban railway/Light railway transit, experts in rolling stock and the application for designing of question items verified and designed through Delphi technique for objectivity, justness and fairness. Also, it is to draw a conclusion of assignments through a study on methods for drawing a task of Rolling stock’s core parts & enhancing of Urban Railway/Light Railway Transit as sharing a process of assignments and integrating opinions of each stakeholder of urban railway/light railway transit.