• 한국항공우주학회지
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• 제35권1호
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• pp.79-86
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• 2007

회전 발사체용 마그너스 효과 풍동실험 측정장치를 개발하였다. 국방과학연구소 풍동실험실에서는 고속풍동실험에 앞서 지상기능시험과 마그너스 저속풍동실험을 수행하였으며 마그너스 모형은 분당 약 6,000~10,000 회전하였으며, 속도 100 m/sec에서 측정한 마그너스 효과는 무차원 회전특성인자에 대해 선형적인 변화특성을 보였다. 동일형상 모형에 대해 미국 AEDC-4T 풍동에서 기 수행하였던 마그너스 측정결과와의 비교검토를 수행하였다.

• 대한조선학회논문집
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• 제60권5호
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• pp.351-357
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• 2023

In this study, we devised methods to enhance the efficiency of rotor sails which have been applied as one of the energy saving devices of ships. The idea of the study originated from the notion that installing protrusions or increasing the surface roughness on the smooth surface of the rotor sail could delay the separation of the incoming wind flow and consequently increase the lift force. Five cylinder models were considered and tested in an open-type wind tunnel at Chungnam National University. A smooth surface cylinder exhibits the highest lift-to-drag ratio at a specific Reynolds number, and as the Reynolds number increases this value decreases sharply. The variation in this typical Magnus force can be significantly improved by altering the surface shape and roughness of the rotor sail. It has been observed that increasing the surface roughness improves the lift characteristics, resulting in increased efficiency. Furthermore, it revealed that the reverse Magnus effect which may occur during actual operation in the low spin ratio region can be significantly enhanced.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2554-2557
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• 2008

Effect of a particle's spin is investigated numerically by considering the effect of lift occurring due to difference of rotations of a particle and of fluid such as the Saffman lift and Magnus force. These lift forces have been neglected in many previous works on particle-laden turbulence. The trajectory of particles can be changed by the lift forces, resulting in significant modification of the stochastic characteristics of heavy particles. Probability density functions and autocorrelations are examined of velocity, acceleration of solid particle and acceleration of fluid at the position of solid particle. Changes in velocity statistics are negligible but statistics related with acceleration are a little bit changed by particle's rotation. When a laden particle encounters with coherent structures during the motion, the particle's rotation might significantly affects the motion due to intermittently large fluid acceleration near coherent structures.

• 대한기계학회논문집
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• 제17권12호
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• pp.3135-3147
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• 1993

A numerical method is presented which can solve the steady flow and heat transfer from a rotating and heated circular cylinder in a uniform flow for a range of Reynolds number form 5 to 100. The steady response of the flow and heat transfer is simulated for various spin parameter. The effects on the flow field and heat transfer characteristics known as lift, drag and heat transfer coefficient are analyzed and the streamlines, velocity vectors, vorticity, temperature distributions around it were scrutinized numerically. As spin parameter increases the region of separation vortex becomes smaller than upper one and the lower region will vanish. The lift force, a large part is due to the pressure force, increases as the Reynolds number and it increases linearly as spin parameter increases. The pressure coefficient changes rapidly with spin parameter on the lower surface of the cylinder and the vorticity is sensitive to the spin parameter near separation region. As spin parameter increases the maximum heat coefficient and the thin thermal layer on front region are moved to direction of rotation. However, with balance between the local increase and decrease, the overal heat transfer coefficient is almost unaffected by rotation.

• 해양환경안전학회지
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• 제28권4호
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• pp.648-656
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• 2022

국제해사기구(IMO)의 온실가스(GHG) 감축 전략과 같은 환경규제를 강화함에 따라 친환경 선박 및 대체 연료 등 기술 개발이 확대되고 있다. 그의 일환으로 해운사와 조선사를 중심으로 에너지 저감과 풍력 추진 기술을 활용한 선박 추진 기술이 대두되고 있다. 풍력 추진 기술의 확보와 실증 연구를 조선 및 해운 분야에 도입함으로써 친환경 기술을 활용한 고부가가치 시장을 창출할 수 있으며, 운항선박의 연료 소비율을 줄임으로써 연비를 약 6~8 % 정도 향상시켜 GHG의 감축을 기대할 수 있다. 로터 세일(Rotor Sail, RS) 기술은 원형 실린더가 일정한 속도로 회전하여 유체를 통과할 때 실린더의 수직 방향으로 유체역학적 힘을 발생시키는 기술이다. 이를 마그누스 효과(Magnus Effect)라고 하며, 본 연구에서는 선박에 설치된 풍력보조추진 시스템인 RS 주위의 난류 유동특성에 관한 수치해석적 연구를 통하여 추진효율을 높일 수 있는 방안을 제시하고자 하였다. 그래서 RS의 공기 역학적 힘에 영향을 미치는 매개변수로써 속도비(Spin Ratio, SR)와 종횡비(Aspect Ratio, AR) 변화에 따른 양력계수(C_L)와 항력계수(C_D)를 도출하였고, RS 끝단 플레이트(End Plate, EP) 적용에 따른 RS 주변 유동특성을 비교하였다.

• 대한조선학회논문집
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• 제47권4호
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• pp.533-542
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• 2010

For a long times it has been believed that the Magnus effect of the rotating cylinder could be utilized for the lifting devices applicable to marine practices. It has been reported that the rotating cylinder installed on upper deck of commercial vessel could play a energy saving role however the idea might be applicable in a very rare case in ship building practices. In this study special high lift rudder system equipped with the trailing edge rotor has been suggested in correspondence with the increasing requirement of greater rudder force. Through the numerical simulation it is cleared that the trailing edge rotor could play a role in enhancement of circulation and refinement of boundary layer of the rudder system. At the same time it is found out that the lift force of the rudder system without rotation of trailing edge rotor could be doubled when the circumferential velocity of the trailing edge rotor is equal to twice of the inflow velocity.

• 대한기계학회논문집B
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• 제34권7호
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• pp.665-670
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• 2010

등방성 난류에서 부유된 무거운 입자의 운동에서, 입자의 회전이 고려되었을 때 입자의 분산 특성에 나타난 변화를 살펴보았다. 입자의 회전을 고려함으로 인해 추가로 고려되는 양력은 그 크기가 작은 것으로 알려져 있고, 따라서 많은 연구에서 회전에 의한 효과는 무시되었다. 본 연구에서는 라그랑지안 기법으로 추적한 입자의 궤적에 미치는 양력의 크기를 속도와 가속도의 자기상관함수 및 확률밀도함수를 통해 정량적으로 살펴보았다. 속도 통계량에서는 양력에 의한 효과가 무시할 만 했으나, 가속도와 관련된 통계는 양력에 의한 영향이 있는 것으로 확인되었다. 난류의 가속도는 간헐성을 띄며, 간헐적인 특성은 난류 구조와 관련이 있다는 것이 알려져 있다. 따라서 입자에 작용하는 양력과 난류구조에 연관성이 있다는 유추가 가능하다.

• The Korean Journal of Physiology
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• 제15권1호
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• pp.61-66
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• 1981

In 1944 Cavallito and Bailey first extracted an essential oil, a powerful antibacterial principle, from the garlic and named it allicin. Later Stoll and Seeback elucidated that allicin was produced from alliin by the enzymatic action of arinase. Damaru observed the depressor responses following intraperitoneal administration of garlic juice in cats. And Thiersch presented evidence that garlic had a protective action against experimental arterosclerosis in cholesterol-fed animals. On the other hand it was also reported that anemias were caused by long-term ingestion of garlic as a result of reduction in hemoglobin and RBC. From the experiment in which the effect of garlic on the blood sugar level was studied, Lee insisted garlic elevated blood sugar level. However, August and Jain claimed that hypoglycemia was induced by garlic administration. Recently Bordia and Bansal suggested that essential oils extracted from onion and garlic have a strong preventive effect on hyperlipemia and prolonged coagulation time resulted from fat-feeding. Furthermore Bordia et al indicated that garlic exerted a strong fibrinolytic activity. In early 1920 s Sugihara reported that essential oil of garlic not only decreased arterial blood pressure but also had a paralytic effect on the isolated heart and intestinal strip of animals. The present study was proposed to investigate the effect of garlic juice and the mechanism of its action on the motility of the isolated rabbit duodenum. The motility of the isolated duodenum was recorded on polygraph by means of force transducer connected with Magnus apparatus. And the isolated duodenum was separtely pretreated with $acetylcholine(5{\times}10^{-7}\;gm/ml)$, $pilocarpine(2.5{\times}10^{-6}\;gm/ml)$, $histamine(5{\times}10^{-6}\;gm/ml)$ and barium $chloride(2.5{\times}10^{-5}\;gm/ml)$ in order to find out interations of these drugs with ASJ. The results obtained were as follows; At concentrations of 0.25%, 0.5% and 1.0% ASJ markedly inhibited contractions of isolated duodenum while tonus as well as contractility of the isolated intestine were decreased also with 0.5% and 1.0% ASJ. Since ASJ markedly abolished augmented motility of isolated intestine by histamine and partly reduced that by $BaCl_2$, it is strongly suggested that inhibitory action of ASJ on the intestinal motility is caused mainly by its antihistamine effect and partly by its direct action on the intestinal smooth muscle.

• The Korean Journal of Physiology
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• 제11권1호
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• pp.27-32
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• 1977

Diospyros Kaki Thunberg is the species of persimmon tree that grows in Korea. Although its fresh or dried fruits are often served as a desert, it has little been known if persimmon tree has any specific pharmacological action. The leaves and branches of persimmon tree has long been used as folk remedies for palsy and frostbite in the southern part of Korea and it is also in use for the treatment of hiccup and nocturnal enuresis in chinese herbal medicine. Recently it was reported that an intravenous administration of Diospyros Kaki Thunberg ethanol extract (KTEE) into the animals lowered arterial blood pressure. Lee concluded from his study on the mechanism of depressor action of KTEE that at least a part of depressor response he observed was caused by acetylcholine-like action of KTEE. On the other hand little study has been made on the effect of KTEE on the motility of isolated animal intestines. Therefore the present study was undertaken to investigate effect of KTEE and the mechanism of its action on the motility of isolated rabbit duodenum. Ethanol extract of Diospyros Kaki Thunberg was prepared by boiling 1 kg of dried branches of persimmon tree in 1 liter of ethanol and the motility of isolated rabbit duodenum was recorded on physiograph by means of force transducer connected with Magnus apparatus. Doses of KTEE used were $5{\times}10^{-4}gm/ml,\;1{\times}10^{-3}gm/ml,\;and\;2{\times}10^{-3}gm/ml$. And the isolated duodenum was separately pretreated with acetylcholine $(5{\times}10^{-7}gm/ml)$, pilocarpine $(2.5{\times}10^{-6}gm/ml)$, histamine $(5{\times}10^{-6}gm/ml)$ and barium chloride $(2.5{\times}10^{-5}gm/ml)$ in order to find out interactions of these drugs with KTEE. The results obtained are as follows: 1. At doses of $5{\times}10^{-4}gm/ml,\;1{\times}10^{-3}gm/ml$ KTEE reduced contractions of isolated duodenum, while tonus as well as contaction of duodenum were depressed with $2{\times}10^{-3}gm/ml$ of KTEE. 2. Since the inhibitory effect of KTEE on the intestinal motility was not blocked by pretreatment with acetylcholine, pilocarpine, and barium chloride, it was strongly suggested that the inhibitory action of KTEE on intestinal motility is mainly Caused by its antihistamine effect. 3. It is also concluded that the principal substance of KTEE responsible for inhibition of intestinal motility may also have a vasodilating activity and would not be an acetylcholine-like substance in case it is same substance as that cause depressor responses.

• Tuberculosis and Respiratory Diseases
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• 제41권3호
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• pp.231-238
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• 1994

연구배경: 저산소증에 의한 폐동맥수축의 기전은 저산소증 자체가 폐혈관 평활근에 직접 작용하여 수축을 유발한다는 것과, 저산소증에 의해 조직으로 부터 여러 매개물질이 유리되어 혈관평활근을 수축시킨다는 설이 제시되고 있지만 정확히 밝혀져있지 않다. 최근에는 저산소증이 EDRF의 생성을 억제하여 혈관수축을 유발시킨다고하여 관심이 되고 있다. 본 연구에서는 흰쥐 폐동맥에서 내피세포 의존형 혈관이완을 조사하고, 저산소증에 의한 폐동맥수축에 EDRF의 작용을 조사하였다. 방법 : 300~350g의 수컷 흰쥐(Sprague Dawley)의 폐동맥을 박리하여 길이가 2mm되는 폐동맥고리를 Krebs용액으로 채워져 있으며, 95% $O_2$/5% $CO_2$(산소상태)와 95% $N_2$/5% $CO_2$(저산소상태)가 각각 공급되는 magnus관에서 가는 stainless 갈고리로 고정한 다음 Gilson사의 polygraph에 부착된 isometric transducer(FT.03 Grass, Quincy, USA)에 의해 등장성 수축곡선을 그리도록 장치하였다. 결과: 1) 내피세포가 있는 폐동맥에서 PE($10^{-6}M$)에 의한 혈관수축은 Ach($10^{-9}-10^{-5}M$) 및 SN($10^{-9}-10^{-5}M$)의 농도에 비례해서 이완되어 거의 기초장력까지 이완되었으나, 내피세포를 제거한 폐동맥에서는 Ach($10^{-9}-10^{-5}M$)에 의한 혈관이완은 거의 상실되었다. 2) L-NMMA($10^{-4}M$)으로 전처치한 경우 Ach($10^{-9}-10^{-5}M$)에 의한 혈관이완은 전처치하지 않은 경우보다 의미있게 감소하였다. 3) L-arginine($10^{-4}M$)과 L-NMMA($10^{-4}M$)을 전처치 하였을 경우 Ach($10^{-9}-10^{-5}M$)에 의한 혈관이완은 L-NMMA에 의해 거의 영향을 받지 않았다. 4) PE($10^{-6}M$)에 의한 폐동맥 수축은 산소상태보다 저산소 상태에서 훨씬 강했으며, Ach($10^{-9}-10^{-5}M$)에 의한 혈관이완은 산소상태보다 저산소상태에서 의미있게 감소하였다. 5) L-arginine($10^{-4}M$)을 전처치 하였을 경우 저산소상태에서의 Ach($10^{-9}-10^{-5}M$)에 의한 혈관이완은 산소상태에서의 Ach 에 의한 혈관이완 정도로 회복되었다. 결론: 흰쥐 폐동맥에서 내피세포의존성 혈관이완은 NO가 관여하며, 저산소증에 의한 폐동맥 수축은 내피세포내의 EDRF 생성의 저하와 관련이 있을 것으로 사료된다.