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균질 혼상 모델을 이용한 항공기 엔진과 AMAD 베이의 화재소화 성능 평가를 위한 수치해석 절차 정립
조정훈,구가람,안철희,박원규,정철웅 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.2
To meet the certification requirement in terms of fire extinguishing performance of aircraft, the Air Force Research Laboratory requires that the measured extinguishant concentrations at all of the selected probe locations inside aircraft engine and AMAD (Airframe Mounted Assessory Drive) bays are higher than the specified level for a minimum of 0.5 seconds simultaneously. In this study, the transport of extinguishant in internal flow field of aircraft engine and AMAD bays are numerically investigated to assess fire extinguishing performance of aircraft under development. First, three-dimensional and unsteady CFD methods based on RANS solver with homogeneous mixture model are applied to predict the extinguishant concentrations at the selected monitoring points for six operation conditions of aircraft. For further detailed analysis, the transport of the agent through the engine and AMAD bays was visualized and compared between operating conditions. Theses comparisons help to characterize the effects of cruise speed, altitude and atmospheric temperature on the fire extinguishing performance of aircraft.
Effects of pressurized PFO-based pitch coking conditions on coke yield and graphite conductivity
조정훈,배병철 한국탄소학회 2021 Carbon Letters Vol.31 No.5
In the present study, pyrolyzed fuel oil (PFO)-based pitch without impurities was used to prepare coke under pressure, and the preparation yield and the powder resistance depending on the graphitization were investigated. The preparation yield of green coke by pressurized coking at 500 °C was about 26–27% higher than that at normal pressure. However, the coke yield after the thermal treatment of green coke at 900 °C was lower by 10.6–14.8% at the pressurization conditions than under normal pressure. This may be because the substances that are not vaporized under the pressurized conditions remain in the reactants and then are discharged later. The coke yield after the thermal treatment at 900 °C was higher by 14.9–28.3% under the pressurized conditions than under the normal pressure, indicating that the low-boiling point materials of the pitch participated more in coke polymerization under the pressurized conditions. The density of the coke prepared under the pressurized conditions was lower than that of the coke prepared under normal pressure, because the low-boiling point materials of the pitch participated in the reaction. However, after graphitization, the density values became similar (2.27–2.26 g/cm3 ). The volume resistivity of the graphitized samples was in a range of 0.499×10–2–0.384×10–2 Ω cm, indicating that the coke samples have similar electrical properties. The results of the present study show that, in comparison with the conventional normal-pressure process, the pressurized coking process can improve the yield through the participation of low-boiling point materials in the polymerization reaction, while maintaining the properties of the prepared coke and graphite, such as the conductivity and density.
태음조위탕(太陰調胃湯)과 전기침(電氣鍼) 병행치료의 비만에 대한 효과
조정훈,송병재,장영주,Cho, Jung-Hoon,Song, Byung-Jae,Jang, Young-Ju 한방비만학회 2001 한방비만학회지 Vol.1 No.1
We wanted to study the effect of Taeyeumjowee-tang and electroacupunctre combined-therapy on obese patients. From 1 March, 2000 to 30, September, 2000 we studied 33 out-ward patients who clinically diagnosed obesity and classified Tae-Em-In by QSCC(Questionnaire of Sasang Constitution Classification). We treated the patients by electroacupuncture therapy and taeyeumjowee-tang for 6 weeks, We investigated the change of mean body weight, mean body mass index, mean obesity degree, percent body fat and waist-hip circumference ratio. To analyze the results we used repeat measure method by SPSS ver 7.5. The results were as follows: 1. From $70.4{\pm}11.4\;to\;64.9{\pm}8.7$, mean body weight was significantly decreased according to combined-therapy. 2. From $27.2{\pm}3.2\;to\;24.6{\pm}2.7$, mean BMI was significantly decreased according to combined-therapy. 3. From $116.7{\pm}13.9\;to\;104.4{\pm}12.1$, mean obesity degree was significantly decreased according to combined-therapy. 4. From $32.1{\pm}6.8\;to\;27.4{\pm}7.5$, percent body fat was significantly decreased according to combined-therapy. 5. From $0.90{\pm}0.06\;to\;$0.86{\pm}0.06$, waist-hip circumference ratio was significantly decreased according to combined-therapy. In this study we knew the combined-therapy of electroacupuncture and taeyeumjowee-tang is very efficient in obese patient.