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고고도 환경 모사용 Center Body Diffuser의 형상 변화에 따른 성능특성에 관한 연구
김준철(Junechul Kim),이현섭(Hyunseob Lee),박진(Jin Park),김홍집(Hongjip Kim) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
고고도에서 작동하는 로켓의 작동 환경을 지상에서 모사하기 위한 방법 중에 하나로 사용할 수 있는 Center Body Diffuser (CBD)의 유동 특성을 파악하기 위하여 상온 실험과 수치해석을 병행하였다. 본 연구의 목적은 CBD의 설계 변수 중에 Diffuser 2차목 길이와 2차 목의 직경비 (L/D)st의 변화에 따른 고공환경 모사성능과 Diffuser의 시동특성을 확인하기 위함이다. 연구 결과 2차목의 직경비가 커질수록 시동압력이 낮아지는 것을 확인하였다. To elucidate the flow characteristics of center-body diffuser which has been used to simulate a high altitude for rocket at sea level, cold flow experiments were conducted with sub-scaled equipment with numerical analyses through ANSYS FLUENT. Objective of this study is to evaluate the performance characteristic of high altitude pressure by varying the ratio of second throat length and second throat diameter (L/D)st. The study results show that present diffuser with the bigger ratio of second throat length and second throat diameter has had the lower startup pressure.
청소년의 FTO유전자 다형에 따른 3년간 신체구성과 체력의 변화
박기준 ( Park Kijun ),김준철 ( Kim Junechul ) 대한통합의학회 2020 대한통합의학회지 Vol.8 No.3
Purpose : To identify changes and relationships in the fat mass and obesity associated (FTO) gene polymorphism, body composition, and physical fitness from childhood to adolescence over a three-year period spanning elementary school to middle school (2015-2018) Methods : A total of 84 male student participants were divided into two groups based on FTO genotype: aa+at (group A) and tt (group T) and tracked down. Body composition, cardiovascular endurance, flexibility, muscle strength, power, and other characteristics were measured in the two groups in both 2015 and 2018, respectively, and the changes over the three-year period were analyzed and compared. Results : Increases in height and weight did not differ significantly between the two groups, but body mass index (BMI) was significantly higher in group A (p=.035). With regard to physical fitness, there was no significant difference in flexibility, but cardiovascular endurance, strength, and power were significantly higher in group T (p<.001, p=.063, and p=.040, respectively). Conclusion : Group A is more likely to become obese than group T because of their lower level of physical fitness and increased BMI relative to group T. This result supports previous studies showing that group A has a relatively low level of physical activity and a greater tendency to eat fatty foods as compared with group T. Therefore, we suggest that the FTO gene polymorphism should be identified early and that students educated on diet and physical activity to help prevent adult obesity.