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자외선 및 Li^+이온에 의하여 여기된 단결정 KCㅣ의 열자극 발광
柳命浩,李丁柱,鄭基守,崔洪守 慶尙大學校 기초과학연구소 1985 基礎科學硏究所報 Vol.1 No.-
Thermoluminescence(TL) of KCI single crystal and Li^+ ion implanted KCI have been investigated below room temperature. The TL curves for KCI single crystal irradiated with UV at 77K to 300K. The thermal activation energy obtained from the initial rise method are 0.11eV and 0.19eV at 125K and 167K respectively, and the values of escape frequency S are 1.6×10^9 sec^-1 for 125K peak and 3.14×10^9 sec^-1 for 167K peak. The TL glow curves for KCI single crystal increased UV dosage showed that the 125K peak overlapped partially with the lower part of 167K peak and the 167K peak increased. As the low energy Li^+ ion were implanted in KCI single crystal at 77K, the 167K peak disappeared and 125K peak increased. The value of δ/ω was 0.54 for 125K peak which means that the TL curve is due to the second order kinetics mechanism. The thermal activation energy obtained from the peak shape method was 0.10eV for Li^+ ion implanted KCI at 125K peak.
불활성가스로 희석된 Jet A1-순산소 동축류 확산화염의 점화특성에 관한 실험적 연구
류명호(Myung-Ho Ryu),박설현(Seul-Hyun Park) 한국화재소방학회 2022 한국화재소방학회논문지 Vol.36 No.6
본 연구에서는 JET A1 확산화염의 동축류에 공급되는 순산소 가스를 불활성가스(질소와 헬륨가스)로 희석시킬 때 달라지는 점화특성을 고찰하였다. 확산화염 동축류에 공급되는 산소 가스의 몰농도가 높아지면 불활성가스의 희석효과가 감소하여 측정된 최소점화에너지도 급격하게 감소하였다. 불활성가스의 희석없이 동축류에 순산소 가스만 공급되었을 때 가장 쉽게 점화가 관찰되었으며 점화 가능 영역도 가장 넓은 것을 확인하였다. 동축류에 동일한 유량으로 산소-불활성가스가 공급될 때 점화 억제력은 헬륨가스로 산소가스를 희석하는 경우가 질소 가스로 희석하는 경우에 비해 산소 몰농도가 낮아질수록 보다 우수한 것을 확인할 수 있었다. In this study, the ignitability characteristics affected by an oxygen coaxial flow diluted with inert gases (nitrogen and helium) were experimentally investigated using Jet A1 oxygen diffusion flame configurations. As the molar concentration of oxygen supplied to the coaxial flow increased, the dilution of the inert gas decreased, which drastically lowered the measured minimum ignition energy. When only oxygen gas was supplied to the coaxial flow without dilution with the inert gas, ignition was most easily observed, thereby widening the ignition range. With a constant oxygen-inert co-flow rate, the ignition suppressibility under helium dilution was superior to that under nitrogen dilution as the molar concentration of oxygen decreased.
전역 광소멸법을 이용한 확산화염 내 그을음 입자의 농도 측정에 관한 연구
류명호 ( Myung-ho Ryu ),이종원 ( Youn-won Lee ),김연규 ( Youn-kyu Kim ),이원주 ( Won-ju Lee ),박설현 ( Seul-hyun Park ) 조선대학교 공학기술연구원 2016 공학기술논문지 Vol.9 No.4
In the present study, non-intrusive technique for the concentration measurements of soot particles formed within the flames was experimentally investigated. As part of this study, the full-field light extinction apparatus that enables us to obtain the spatial distribution of soot particle concentration within the flames was developed and implemented. In addition, the 3 point abel deconvolution algorithm was coded using a Fortran software to determine the spatial distribution and concentration of soot particles. The abel inversion analysis clearly indicates that the spatial distribution of soot particles within the flame can be faithfully reconstructed from the projected light extinction image captured by a CCD camera.
대기조성 치환 및 압력이 Jet A1 액적화염의 매연입자 생성에 미치는 영향에 관한 연구
남원식,류명호,이종원,박설현 한국화재소방학회 2019 한국화재소방학회논문지 Vol.33 No.5
In this study, the soot formation characteristics of Jet-A1 liquid fuel droplet flames were investigated by measuring thesoot concentration under atmospheric conditions similar to the working environment of the Korea Space Launch Vehicle(KSLV) To obtain the desired atmospheric conditions, the oxygen concentration in the combustion chamber was maintainedat 30% and the pressure was varied between 0.1 and 0.06 MPa. The full-field light extinction technique was used tomeasure the concentration of soot particles generated by applying the identical to 2-mm-diameter Jet-A1 fuel droplets. Thesoot concentration of the Jet-A1 droplet flames was the highest in the nitrogen-substituted atmosphere and the lowest inthe carbon dioxide-substituted atmosphere, despite the pressure. the pressure was decreased the measured soot concentrationsreduced as a function of Pn. 본 연구에서는 한국형발사체와 유사한 작동환경에서 Jet A1 액체연료의 매연 입자특성에 대해 농도를 측정함으로써 그 결과를 고찰하였다. 발사체환경과 유사한 대기 조건을 모사하기 위해 연소챔버의 산소 농도를 30%로 유지하고 내부 압력을 0.06 MPa에서 0.1 MPa 까지 변화시켜가며 실험을 통해 수행하였고, 대기의 조성을 질소, 헬륨, 이산화탄소 가스로 치환하여 실험을 수행하였다. 직경이 2 mm인 Jet-A1 액적에 동일한 점화에너지를 인가하여 발생 되는매연 입자의 농도를 전역 광소멸 기법을 이용하여 측정하였다. Jet-A1 액적 화염의 매연 입자입자의 농도는 모든 압력조건에서 대기의 조성이 질소로 치환된 경우 높았으며, 이산화탄소로 치환된 경우 가장 낮았다. 압력이 낮아질수록 매연의 입자농도가 감소하였고, 대기압력의 Pn 형태로 감소하는 경향을 확인하였다.
Optimized Design of Bi-Directional Dual Active Bridge Converter for Low-Voltage Battery Charger
정동근,류명호,김흥근,김희제 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.3
This study proposes an optimized design of a dual active bridge converter for a low-voltage charger in a military uninterruptedpower supply (UPS) system. The dual active bridge converter is among various bi-directional DC/DC converters that possess ahigh-efficiency isolated bi-directional converter. In the general design, the zero-voltage switching(ZVS) region is reduced when thebattery voltage is high. By contrast, efficiency is low because of high conduction losses when the battery voltage is low. Variableswitching frequency is applied to increase the ZVS region and the power conversion efficiency, depending on battery voltagechanges. At the same duty, the same power is obtained regardless of the battery voltage using the variable switching frequency. Theproposed method is applied to a 5 kW prototype dual active bridge converter, and the experimental results are analyzed and verified.
Jet A1-공기 확산 화염에서 배출된 입자상 물질의 광학 및 형상학적 분석에 관한 연구
강별,류명호,박설현 한국연소학회 2023 한국연소학회지 Vol.28 No.4
Many aircraft and launch vehicles that use Jet A1 as a fuel operate at high altitudes and emit large amounts of particulate matter into the atmosphere. The impact of particulate matter is steadily increasing and requires continuous monitoring and source reduction efforts. Morphological and optical characterization data of PM can be used in concentration measurement and reduction techniques to help quantitatively analyze the damage caused by PM. In this study, dimensionless light extinction coefficient measurements and morphological analysis of PM produced from burning Jet A1 in a coaxial flow burner were performed. The values of fractal dimension and prefactor which can help to quantify the morphological properties of the aggregates of Jet A1 PM, were found to be 1.68 and 2.85, respectively. The scattering albedo value estimated from the morphological properties was 0.094, indicating that the contribution of scattering to the total extinction was about 10%. The results were strongly supported by the fact that the fraction of elemental carbon (EC) composed of PM is dominant compared to organic carbon (OC). These empirical results highlighted that the light extinction by Jet A1 PM was dominated by the effects of light absorption rather than those of light scattering.