날개의 모서리 형상이 플래핑 운동의 공기역학적 특성에 미치는 영향

오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

Birds and insects have wings of rounded edge profiles. In the experiment, the wing of the square edge profiles had been employed. In this study, two wings which have different shapes of edge are used to investigate the aerodynamic characteristics. One wing has rounded edge profiles and the other has square edge profiles. Two half elliptic shaped wings were designed and scaled up according to the planform of a black-chinned hummingbird, Archilochus alexandri. While the wings were operated in the water, the aerodynamic forces were measured and the flow structures around the wings were visualized using the DPIV. The lift for the wing of rounded edge profiles was higher than that for the wing of square edge profiles. But drag for the wing of rounded edge profiles was lower than that for the wing of square edge profiles. Also the lift to drag ratio for the wing of rounded edge profiles at angle of attack from 0° to 40° was higher than that for the wing of square edge profiles.

날개 길이방향 유동과 날개 회전이 날개짓 운동의 공기역학적 특성에 미치는 효과

오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.9

3-D 날개짓 운동은 왕복운동과 회전운동으로 구성된다. 3-D 날개짓 운동은 왕복운동하는 동안 날개 길이방향의 유동이 발생된다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 회전에 의한 순환이 발생한다. 본 연구에서는 날개 길이방향 유동과 날개 회전이 3-D 날개짓 운동의 공기역학적 특성에 미치는 영향을 알아보기 위하여 3-D 날개짓 운동과 2-D 병진운동을 비교하였다. 각각의 날개짓 운동에서 받음각과 레이놀즈수에 따라 공력을 측정하였다. 2-D 병진운동의 공력이 3-D 날개짓 운동의 공력 보다 크다. 하지만 3-D 날개짓 운동시 발생되는 양력은 왕복운동의 중반부에서 받음각 50˚까지 증가하였고 2-D 병진운동시 발생되는 양력은 받음각 30˚이상에서 감소하였다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 공력이 급격하게 증가하였다. In a 3-D flapping motion, the spanwise flow is generated while the wing is moved on the stroke plane. And at the end of each stroke, the rotational circulation is generated due to a wing rotation. In this study, to evaluate the effect of spanwise flow and wing rotation on the aerodynamic characteristics in 3-D flapping motion, a 3-D flapping motion was compared with a 2-D translating motion. In each flapping motion, the aerodynamic forces were measured with respect to the angles of attack and Reynolds number. The aerodynamic forces generated by 2-D translating motion were higher than those generated by 3-D flapping motion. While the lift of 3-D flapping motion was increased until the angle of attack 60˚ at mid-stroke, the lift generated by 2-D translating motion was decreased above the angle of attack 40˚ at mid stroke. Also, at the end of each stroke, the aerodynamic forces were increased rapidly due to wing rotation.

날개 길이방향 유동이 날개짓 운동의 공기역학적 특성에 미치는 효과

오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

Flight performance of birds and insects is superior to conventional fixed wing aircrafts at low Reynolds number regime. While they flap their wings, aerodynamic characteristics such as span-wise flow and rotational circulation are appeared on the wing. To study on the effect of span-wise flow, 3-D flapping motion was compared with 2-D flapping motion. In 3-D flapping motion, the measured lift forces were increased until the angle of attack 50° at mid-stroke. But in 2-D flapping motion, the lift forces were decreased above the angle of attack 30° at mid-stroke. Also, the mean lift to drag ratio of 3-D flapping motion is higher than that of 2-D flapping motion.

날개의 종횡비가 날개 짓 운동의 공기역학적 특성에 미치는 영향

오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

The lift and drag forces produced by a wing of a given cross-sectional profile are dependent on the wing planform and the angle of attack. Aspect ratio is the ratio of the wing span to the average chord. For conventional fixed wing aircrafts, high aspect ratio wings produce a higher lift to drag ratio than low ones for flight at subsonic speeds. Therefore, high aspect ratio wings are used on aircraft intended for long endurance. However, birds and insects flap their wings to fly in the air and they can change their wing motions. Their wing motions are made up of translation and rotation. Therefore, we tested flapping motions with parameters which affect rotational motion such as the angle of attack and the wing beat frequency. The half elliptic shaped wings were designed with the variation of aspect ratio from 4 to 11. The flapping device was operated in the water to reduce the wing beat frequency according to Reynolds similarity. In this study, the aerodynamic forces, the time-averaged force coefficients and the lift to drag ratio were measured at Reynolds number 15,000 to explore the aerodynamic characteristics with the variation of aspect ratio. The maximum lift coefficient was turned up at AR=8. The mean drag coefficients were almost same values at angle of attack from 10° to 40° regardless of aspect ratio, and the mean drag coefficients above angle of attack 50° were decreased according to the increase of aspect ratio. For flapping motion the maximum mean lift to drag ratio appeared at AR=8.

산천어(Oncorhynchus masou)의 함유성분 분석

오현택(Hyun-Taek Oh),김수현(Soo-Hyun Kim),유수정(Su-Jung Yoo),최현진(Hyun-Jin Choi),정미자(Mi-Ja Chung),함승시(Seung-Shi Ham) 한국식품영양과학회 2008 한국식품영양과학회지 Vol.37 No.7

산천어를 식이로 사용하는 부분만을 취하여 일반성분, 무기질, 비타민, 아미노산 및 지방산 함량을 분석하였다. 수분, 조단백질, 조지방, 조회분 그리고 탄수화물 함량이 각각 73.6±0.4, 17.7±0.3, 3.3±0.2, 1.3±0.1 그리고 4.1±0.2%이었다. 분석한 무기질 중에는 칼슘 함량이 가장 높았고 다음은 인, 칼슘, 나트륨, 철 순으로 높은 함량을 나타내었다. 산천어에 함유된 비타민 C와 E는 각각 600와 200 ㎍/100 g이었다. 16종류의 아미노산이 검출되었으며 그들 중에 필수아미노산은 threonine, valine, methionine, isoleucine, leucine, phenylalanine, lysine, arginine, 그리고 histidine이었다. Oleic acid가 산천어의 가장 풍부한 지방산이고 불포화지방산으로는 EPA, DHA, linoleic acid, α-linolenic acid, γ -linolenic acid, and arachidonic acid를 함유하고 있었다. 이연구 결과들은 산천어를 상업적으로 이용하기 위한 유용한 과학적 기초 자료를 제공하여 주는 것이라고 생각된다. Levels of minerals, vitamin, amino acids, fatty acids and chemical compositions were determined in the fleshy parts that are used for food. The moisture, crude protein, crude lipid, crude ash and carbohydrate contents of masou salmon were 73.6±0.4, 17.7±0.3, 3.3±0.2, 1.3±0.1 and 4.1±0.2%, respectively. Potassium was the highest followed by phosphorus, calcium and sodium. The vitamin C and E levels in masou salmon were 600 and 200 μg/100 g, respectively. Sixteen amino acids were detected and essential amino acids among them are threonine, valine, methionine, isoleucine, leucine, phenylalanine, lysine, arginine, and histidine. Oleic acid was the most abundant fatty acid in masou salmon and polyunsaturated fatty acids were EPA, DHA, linoleic acid, α-linolenic acid, γ-linolenic acid and arachidonic acid. These results may offer a scientific basis for the commercial use of masou salmon.

인간 HepG2 Cell에서 항산화 효소의 mRNA 발현에 대한 잔대 에틸아세테이트 추출물 효과

최현진(Hyun-Jin Choi),김수현(Soo-Hyun Kim),오현택(Hyun-Taek Oh),정미자(Mi-Ja Chung),최승필(Cheng-Bi Cui),함승시(Seung-Shi Ham) 한국식품영양과학회 2008 한국식품영양과학회지 Vol.37 No.10

잔대 뿌리는 우리나라에서 예로부터 민간약으로 이용되어 오고 있다. 본 연구에서는 인간 간세포인 HepG2에 잔대 뿌리의 에틸아세테이트 추출물을 처리했을 때 sodium nitroprusside(SNP)에 의해 유도된 세포 독성 및 항산화 유전자 발현에 미치는 영향력을 알아보았다. 먼저, 잔대 에틸아세테이트 추출물이 NO에 의해 유도된 세포 사멸을 저해할 수 있는지를 알아보기 위하여 HepG2 세포에 잔대 에틸아세 테이트 추출물(각각 50과 100 ㎍/mL)을 24시간 먼저 처리한 후 세포내에서 NO을 생성시킬 수 있는 0.5 mM SNP를 처리하였다. NO에 의한 세포독성이 에틸아세테이트 추출물에 의해 저해되었다는 것을 mitochondrial dehydrogenase 활성을 알아보는 MTT assay를 실시하여 알아보았다. 더하여 우리는 잔대 에틸아세테이트 추출물이 세포내 항산화 방어 시스템인 Cu,Zn superoxide dismutase(SOD 1), Mn SOD(SOD 2), glutathione peroxidase(GPx), catalase와 glutathione metabolism과 관련되어져 있는 glutathione reductase(GR), γ-glutamyl-cystein synthetase(GCS), glutathione-S-transferase(GST), γ-glutamyltranspeptidase (γ-GT), glucose-6-phosphate dehydrogenase(G6PD)의 mRNA 발현에 미치는 영향을 RT-PCR로 알아보았다. CAT, GCS 그리고 G6PD mRNA 수준이 잔대 에틸아세테이트 추출물 처리 후 증가하였으나, SOD 1, SOD 2, GPx, GST 그리고 γ-GT mRNA 수준은 변화지 않았다. 따라서 잔대 에틸아세테이트 추출물이 간접적 항산화 효과가 있고, 이들 효과는 아마 CAT, GCS, GR 그리고 G6PD 유전자 발현 증가에 의한 것이라고 추정되었다. The root of Adenophora triphylla is widely used as traditional herbal medicine in Korea. We studied its effects on sodium nitroprusside (SNP) cytotoxicity and antioxidant genes expression in HepG2 cells. To study whether Adenophora triphylla ethylacetate extract (ATea) inhibited NO-induced cell death, HepG2 cells were preincubated for 24 hr with 50 and 100 ㎍/mL ATea followed by 24-hr exposure to 0.5 mM SNP (exogenous NO donor). No-induced cytotoxicity was inhibited by pretreatment of ATea, as assessed by mitochondrial dehydrogenase activity (MTT assay). We further investigated the effects of ATea on mRNA levels of various enzymes of the antioxidant system such as Cu, Zn superoxide dismutase (SOD 1), Mn SOD (SOD 2), glutathione peroxidase (GPx), catalase and several enzymes of the glutathione metabolism [glutathione reductase (GR), γ-glutamyl-cystein synthetase (GCS), glutathione-S-transferase (GST), γ-glutamyltranspeptidase (γ-GT), glucose-6-phosphate dehydrogenase (G6PD)] by RT-PCR. CAT, GCS, GR and G6PD mRNA levels were increased after treatment with ATea. The SOD 1, SOD 2, GPx, GST and γ-GT mRNA levels were not affected in ATea-treated HepG2 cells. We concluded that ATea have an indirect antioxidant effects, perhaps via induction of CAT, GCS, GR and G6PD.

표고버섯 분말을 첨가한 천연 조미료 추출물의 항산화성, 항돌연변이성 및 세포독성 효과

유수정,김수현,최형택,오현택,최현진,함승시,Yoo, Su-Jung,Kim, Soo-Hyun,Choi, Houng-Taek,Oh, Hyun-Taek,Choi, Hyun-Jin,Ham, Seung-Shi 한국식품영양과학회 2007 한국식품영양과학회지 Vol.36 No.5

표고버섯 분말을 첨가한 천연조미료의 추출물 및 분획물에 대한 항산화 활성은 에틸아세테이트 분획물에서 $RC_{50}$값 $155{\mu}g$으로서 다른 시료보다 강한 항산화 활성을 나타내었다. 표고버섯 분말을 첨가한 천연조미료 추출물 및 그 분획물들의 항돌연변이 효과의 검토는 Salmonella Typhimurium의 변이주인 TA98과 TA100을 이용한 Ames test로 확인하였다. 그 결과 직접변이원인 MNNG에 대해 시료농도 $200{\mu}g/plate$에서 핵산과 에틸아세테이트 분획물은 TA100에서 $79{\sim}84%$의 강한 항돌연변이원성을 보였고 다른 시료에서도 65% 이상의 저해효과를 보였다. 4NQO에 대해서는 TA98과 TA100에서 에틸아세테이트 분획물이 가장 높은 저해효과를 나타내었다. 암세포 성장 억제효과를 검토한 결과 표고버섯 분말을 첨가한 천연조미료 에탄을 추출물 1 mg/mL 첨가 시 HeLa, Hep3B, MCF-7, AGS 및 A549에서 각각 83.3%, 61%, 81.3%, 58.9% 및 36.7%의 억제효과를 보였다. 표고버섯 분말을 첨가한 천연조미료 분획물에 대한 억제효과는 시료 농도 1 mg/mL 첨가 시 에틸 아세테이트 분획물의 경우 폐암세포인 A549 세포에 대하여 55.7%의 억제효과를 보인 것을 제외하고는 $71{\sim}85%$ 정도의 높은 억제효과를 보였으나 물 분획물의 경우 다른 추출물과 비교 시 암세포에 대해 상대적으로 낮은 억제효과를 나타내었다. 이러한 암세포에 대한 높은 억제효과에 비해 인간 신장 정상세포 293에 대한 시료를 첨가 시 40% 이하의 생육 억제율을 나타냄으로써 정상세포에 대해서는 낮은 독성효과를 가짐을 알 수 있었다. This study was peformed to determine the antioxidative, antimutagenic and cytotoxic effects of the natural seasoning using Lentinus edodes powder (NSLP) by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical donating method, Ames test, and cytotoxicity, respectively. The scavenging effect on DPPH radical in ethyl acetate fraction of NSLP showed $155{\mu}g\;of\;RC_{50}$. The direct antimutagenic effects of ethanol extract and its solvent fractions of NSLP were examined by Ames test using Salmonella Typhimurium TA98 and TA100. In the Ames test, ethanol extract of NSLP alone did not exhibit any mutagenicity and most of the samples showed high antimutagenic effects against mutation induced by N-methyl-N'-nitro-N-nitroso guanidine (MNNG) and 4-nitroquinoline-1-oxide (4NQO). Ethyl acetate fraction of NSLP ($200{\mu}g/plate$) showed approximately 82% inhibitory effect on the mutagenesis induced by 4NQO against TA98 strain, whereas 84% and 80% inhibitions were observed on the mutagenesis induced by 4NQO and MNNG against TA100 strain. In anticancer effects of ethanol extract and its solvent fractions of NSLP against cancer cell lines including human lung carcinoma (A549), human breast adenocarcinoma (MCF-7), human hepatocellular carcinoma (Hep3B), human cervical adenocarcinoma (HeLa) and human gastric carcinoma (AGS) were investigated. The treatment of 1 mg/mL ethyl acetate fraction of NSLP showed strong cytotoxicity of 56.7%, 84.9%, 64.6%, 85.1% and 71.5% against A549, MCF-7, Hep3B, HeLa and AGS, respectively. In contrast 1 mg/mL treatment of NSLP extract and its solvent fractions had only $4{\sim}40%$ cytotoxicity on human transfomed primary embryonal kidney cell (293). From this result, it is suggested that NSLP is believed to have possible antioxidative, antimutagenic and anticancer capacities.

압전 PMN-PZT 단결정의 유전 및 압전 특성에 미치는 전극 종류의 영향

이종엽,오현택,최균,이호용,Lee, Jong-Yeb,Oh, Hyun-Taek,Choi, Kyoon,Lee, Ho-Yong 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.1

The effect of the electrode type on the dielectric and piezoelectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbZrO_3-PbTiO_3$ (PMN-PZT) single crystals was investigated in an effort to improve their properties for various piezoelectric applications. First, three different types of PMN-PZT single crystals [PMN-PZT-A (piezoelectrically soft type; dielectric constant ~ 10,000), PMN-PZT-B (piezoelectrically soft type; phase-transition temperature between the rhombohedral and tetragonal phases ($T_{RT}$) ~ $145^{\circ}C$), PMN-PZT-C (piezoelectrically hard type; high mechanical quality factor ($Q_m$) ~ 1,000)] were fabricated using the solid-state single crystal growth (SSCG) method. Then, four different types of electrodes [sputtered Au, sputtered Cr/Au, sputtered Ti/Au, and fired Ag] were formed on the single crystals, and their dielectric and piezoelectric properties were measured. The single crystals with a sputtered Ti/Au electrode showed the highest dielectric and piezoelectric constants but the lowest coercive electric field ($E_C$). The single crystals with a fired Ag electrode showed the lowest dielectric and piezoelectric constants but the highest coercive electric field ($E_C$). This dependence on the type of electrode was most significant in the piezoelectrically hard PMN-PZT-C single crystals. However, the effects of the electrode type on the phase transition temperatures ($T_C$, $T_{RT}$) and dielectric loss were negligible. These results clearly demonstrate that it is important to select an appropriate electrode so as to maximize the dielectric and piezoelectric properties of single crystals in each type of piezoelectric application.

인간 HepG2 세포에서 더덕 및 도라지 에틸아세테이트 분획물의 항산화 효과에 의한 세포보호 효과

김수현(Soo-Hyun Kim),최현진(Hyun-Jin Choi),오현택(Hyun-Taek Oh),정미자(Mi-Ja Chung),최승필(Cheng-Bi Cui),함승시(Seung-Shi Ham) 한국식품과학회 2008 한국식품과학회지 Vol.40 No.6

이 연구의 목적은 더덕 및 도라지 에틸아세테이트 분획물(CLEA나 PGEA)이 다양한 항산화 시스템을 가동시켜 sodium nitroprusside(SNP)에 의해 유도된 산화적 스트레스에 대항하여 세포를 보호해 줄 수 있을지 연구하는 것이다. 0.5 mM의 SNP를 HepG2 세포주에 24시간 동안 노출시켰을 때 세포 생존율이 감소하였으나, CLEA와 PGEA 천처리에 의해 SNP 노출에 의한 세포 생존율 감소가 저해되었다. 또한 항산화 시스템들 발현에 미치는 CLEA와 PGEA의 영향을 RT-PCR로 알아보았다. Catalase, glucose-6-phosphate dehydrogenase(G6PD) 그리고 metallothionein (MT)-1A mRNA 수준이 CLEA를 세포에 24시간 동안 처리한 후 증가하였고, Mn superoxide dismutase, catalase, G6PD, MT-1A 와 MT-2A mRNA 수준이 PGEA 처리에 의해 증가하였다. 우리는 CLEA와 PGEA가 아마 다양한 항산화 시스템들을 증가시키는 간접적인 항산화 효과를 나타내며, 이들 효과들이 산화적 스트레스로부터 세포를 보호해 줄 것이라 추정하였다. The objective of this study was to determine whether Codonopsis lanceolata or Platycodon grandiflorum ethyl acetate fraction (CLEA or PGEA) protect cells against sodium nitroprusside (SNP)-induced oxidative stress via the expression of various antioxidant systems. The HepG2 cells exposed for 24 hr to 0.5 mM SNP showed a reduction in the cell viability by an MTT assay. Pretreatment with CLEA and PGEA resulted in an inhibition of SNP-induced cell death. In addition, the effects of CLEA and PGEA on the expression of antioxidant systems via RT-PCR analyses was assessed. The levels of catalase (CAT), glucose-6-phosphate dehydrogenase (G6PD) and metallothionein (MT)-1A mRNA were increased after 24 hr of CLEA exposure. The levels of Mn superoxide dismutase CAT, G6PD, MT-1A, and MT-2A mRNA were increased after PGEA treatment. In conclusion, CLEA and PGEA exert indirect antioxidant effects, perhaps via the induction of a variety of antioxidant systems which, may protect cells against oxidative stress.

플래핑 운동의 공기역학적 특성에 관한 연구

김윤주(Yoon-Joo Kim),오현택(Hyun-Taek Oh),정진택(Jin Taek Chung),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim) 한국가시화정보학회 2005 한국가시화정보학회지 Vol.3 No.2

Birds and insects flap their wings to fly in the air and they can change their wing motions to do steering and maneuvering. Therefore, we created various wing motions with the parameters which affected flapping motion and evaluated the aerodynamic characteristics about those cases in this study. As the wing rotational velocity was fast and the rotational timing was advanced, the measured aerodynamic forces showed drastic increase near the end of stroke. The mean lift coefficient was increased until angle of attack of 50° and showed the maximum value of 1.0. The maximum mean lift to drag ratio took place at angle of attack of 20°. Flow fields were also visualized around the wing using particle image velocimetry (PIV). From the flow visualization, leading-edge vortex was not shed at mid-stroke until angle of attack of 50°. But it was begun to shed at angle of attack of 60°.