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천주홍,이동률,이정운,신새론,박경희 대한가정의학회 2010 Korean Journal of Family Medicine Vol.31 No.11
Background: Attention deficit hyperactivity disorder (ADHD) is caused by multiple risk factors and accompany many problems. This study aimed to analyze the association of childhood obesity with ADHD and to know the related factors of ADHD. Methods: In 2006, 427 students in fourth grade were recruited from two elementary schools in Gwangmyeong city. Height and weight were measured and children’s weight status was classified as normal weight, overweight and obese using the age and gender-specific BMI established by Korean Academy of Pediatrics. The Korean abbreviated Conners’ parent rating scale (ACRS) was used to measure the ADHD state. Results: The obesity rate was higher in ADHD group than in non-ADHD group (P = 0.005). The Kovacs’ children’s depression inventory score (CDI score) of ADHD group was higher than that of non-ADHD group (P = 0.003). In ADHD group, there were many cases where students were looked after by members of the family other than the parents after school (P = 0.01). ADHD group had a tendency to have breakfast heavily (P = 0.01). The average monthly income of the parents of ADHD group was relatively higher than that of the non-ADHD group (P = 0.03), and the fathers of ADHD group tend to have night eating syndrome (P = 0.003). Conclusion: The ADHD was significantly associated with childhood obesity, and was likely to be more depressive and had different life styles than non-ADHD group. 연구배경: ADHD는 여러 위험요인 등에 의해 발생하며, 많은문제점을 동반한다. 본 연구는 소아비만과 ADHD의 관계 및관련된 ADHD의 요인에 대해 알아보고자 하였다. 방법: 2006년 광명시 소재 2개 초등학교 4학년 학생 427명을연구대상자로 하여 신장과 체중을 측정 후 2007년 대한소아과학회에서 발표한 한국소아의 신체발육표준치 중 성별, 연령별 체질량지수 그래프를 이용하여 정상군, 과체중군, 비만군으로 분류하였다. ADHD 평가는 한국어판 단축형 Conners 부모 평가 척도를 사용하였다. 결과: 정상군보다 ADHD군에서 비만학생의 비율이 높았으며(P=0.01), ADHD의 소아우울지수는 정상군보다 높은 점수를 나타냈다(P=0.003). ADHD군은 방과 후 부모 이외 다른 가족이 돌보는 경우가 많았다(P=0.01). ADHD군은 아침식사를배불리 먹는 경우가 많았고(P=0.01), 부모의 월평균수입이 정상군보다 상대적으로 많았으며(P=0.03), 아버지가 야식증후군을 나타내는 경우가 많았다(P=0.003). 결론: ADHD와 소아비만은 서로 연관성이 있으며, ADHD군은 정상군에 비해 더 높은 우울성향과 다른 생활습관을 갖고있다.
Winglet geometry effects on tip leakage loss over the plane tip in a turbine cascade
천주홍,이상우 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4
The effects of winglet offset distance, winglet coverage, and winglet cross section on the over-tip leakage loss for the plane tip have been investigated experimentally in a turbine blade cascade for a tip gap height-to-span ratio of h/s = 1.36 %. The results show that the over-tip leakage loss for the full coverage winglet increases steeply with increasing the winglet offset distance. This loss generation is attributed to flow disturbances over the forward-facing and backward-facing steps within the tip gap. The winglet flush mounted to the tip surface provides the best result. With the leading edge winglet portion or without it, the both-side winglet always provides better aerodynamic performance than the corresponding pressure-side winglet or suction-side winglet. Longer coverage of the both-side winglet leads to lower loss. Therefore, the full coverage winglet performs best in the loss reduction for the plane tip. In general, thinner winglet leads to better aerodynamic result, and the winglet cross section having a slant bottom surface with the smallest thickness at its outer end is recommended.
압력면윙렛/흡입면스퀼러형 터빈 동익 팁누설영역에서의 3차원유동 및 압력손실
천주홍(Joo Hong Cheon),강동범(Dong Bum Kang),이상우(Sang Woo Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.5
본 연구에서는 압력면윙렛/흡입면스퀼러형 터빈 동익 팁에 대하여 익렬 하류에서 3차원 유동 및 압력손실을 측정하였다. 팁간극비 h/s = 1.36%에 대하여, 흡입면스퀼러의 높이는 hs/s = 3.75%로 일정하게 유지하고, 압력면윙렛의 폭은 w/p = 2.64%, 5.28%, 7.92%, 10.55% 등으로 변화시키면서 실험을 수행하였다. 그 결과, 본 연구의 팁은 평면팁 대비 통로와류 영역에서 압력손실의 저감 효과가 매우 뛰어났지만, 팁누설와류 영역에서는 오히려 압력손실을 크게 증가시켰다. 본 연구의 질량평균 압력손실은 평면팁에 비해 크게 낮았지만, 전면스퀼러팁보다는 더 크게 나타났다. 압력면윙렛의 폭이 증가할수록 질량평균 압력손실은 감소하는 경향을 보였다. Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a turbine blade equipped with both a pressure-side winglet and a suction-side squealer have been measured for the tip gap-to-span ratio of h/s = 1.36%. The suction-side squealer has a fixed height-to-span ratio of hs/s = 3.75% and the pressure-side winglet has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results are compared with those for a plane tip and for a cavity squealer tip of hps/s = 3.75%. The present tip delivers lower loss in the passage vortex region but higher loss in the tip-leakage vortex region, compared to the plane tip. With increasing w/p, its mass-averaged loss tends to be reduced. Regardless of w/p, the present tip provides lower loss than the plane tip but higher loss than the cavity squealer tip.
압력면익단소익이 터빈 동익 압력면스퀼러팁 하류의 팁누설유동 및 압력손실에 미치는 영향
천주홍(Joo Hong Cheon),이상우(Sang Woo Lee) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.10
본 연구에서는 압력면익단소익의 폭이 터빈 동익 압력면스퀼러팁 하류의 팁누설유동 및 압력손실에 미치는 영향에 대하여 연구하였다. 팁간극비 h/s = 1.36%에 대하여, 흡입면스퀼러의 높이는 hp/s = 3.75%로 일정하게 유지하고, 압력면익단소익의 폭은 w/p = 2.64%, 5.28%, 7.92%, 10.55% 등으로 변화시키면서 실험을 수행하였다. 일반적으로 압력면익단소익의 폭이 증가할수록, 통로와류 영역에서의 압력손실은 감소하였지만 팁누설유동 영역에서는 압력손실이 오히려 증가하였다. 그 결과 익단소익의 폭이 증가할수록, 질량평균 압력손실은 매우 소폭 감소하는 경향을 보였다. 본 연구 결과, 압력면스퀼러팁에 설치된 압력면익단소익은 압력손실 저감에 거의 기여를 하지 못함을 확인할 수 있었다. Effects of pressure-side winglet width on the tip leakage flow and aerodynamic loss downstream of a turbine blade with a pressure-side squealer rim have been investigated for the tip gap-to-span ratio of h/s = 1.36%. The pressure-side squealer has a fixed height-to-span ratio of hp/s = 3.75% and the pressure-side winglet, which is installed at an elevation of tip surface, has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results show that with increasing w/p, aerodynamic loss in the passage vortex region decreases, whereas that in the leakage flow region increases. As a result, the mass-averaged loss coefficient all over the measurement plane tends to decrease minutely with the increment of w/p. It is concluded that the pressure-side winglet for the pressure-side squealer tip can hardly contribute to the tip-leakge loss reduction.