• 대한핵의학회지
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• 제21권2호
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• pp.183-190
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• 1987

In Raynaud's phenomenon, the authors measured finger blood flow after ice water exposure by analyzing the time activity curve of radionuclide angiography on both hands. The results were as follows: 1) The digital blood flow did not decrease after ice water exposure in normal subjects. 2) In the patients with Raynaud's phenomenon, there were two groups: the one had decreased digital blood flow after cold exposure, and the other had paradoxically increased digital blood flow after cold exposure. 3) There was no difference in the digital blood flow of hand in room temperature between the normal and the patients with reduced digital blood flow after cold exposure, but the digital blood flow of the hand in room temperature was markedly reduced in the patients with paradoxically increased flow after cold exposure. 4) In the static image the difference was not significant in comparision with the dynamic study, because it represents pooling of the blood in the vein rather than flow. 5) After the treatment with nifedipine, the digital blood flow increased. In conclusion, the radionuclide angiography was useful in measuring the digital blood flow in Raynaud's phenomenon, and further studies with various drugs is expected.

• Journal of Chest Surgery
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• 제26권2호
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• pp.148-153
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• 1993

To compare two methods of mammary pedicle graft preparations with free internal mammary artery flow, we studied 31 patients who had the left internal mammary artery harvested for coronary artery bypass grafting. The free flow was measured at the transected opening of 2 to 3 cm distal to the point of bifurcation on mean arterial pressure of 50 to 55 mmHg during cardiopulmonary bypass. Group I comprised 14 patients, whose grafts were sprayed and wrapped in sponges soaked in diluted papaverine solution (60 mg in 40 ml Hartmann's solution). An average 80 minutes after the preparations, free flow of the internal mammary artery ranged from 20 to 80 ml/min (mean 37.7 ml/min). Group II comprised 17 patients, who had internal mammary artery takedown under the exact conditions used in group I. The grafts were sprayed and wrapped in sponges soaked in the diluted papaverine solution as in group I. After an average of 28 minutes, free flow ranged from 8 to 28 ml/min (mean 17.6 ml/min). Intraluminal papaverine of the same dilution was then injected without any hydrostatic dilatation and flows increased upto 37 to 150 ml/min (mean 74.7 ml/min). This study shows that intraluminal papaverine preparation method markedly increases free mammary artery flow which is inadequate with external papaverine preparation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.29-33
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• 2010

본 연구는 Kerosene-LOx를 추진제로 하는 가스발생기용 스월 동축형 인젝터의 리세스 길이에 따른 내부 유동의 특성 파악을 목표로 하였다. 리세스 길이는 분무 안정성, 내부 LOx post 손상 등에 영향을 미치는 중요한 요소로 액막두께, 매니폴드 압력 측정 및 내부 유동 가시화를 통해 리세스의 영향을 분석하였다. 또한, 리세스 길이에 따른 내부 또는 외부 인젝터 각각의 분무특성도 살펴보았다.

• 한국해안해양공학회지
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• 제8권4호
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• pp.287-296
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• 1996

해저 riser관내에 내부유체 금이 발생한 때 그 흐름으로 인해 riser system의 자유진동에 미치는 영향을 조사하기 위해 수학적 모델이 유도된다. System의 고유진동수를 계산하기 위해 조화함수 확장을 적용하여 고유치 방정식을 유도하는 부분해석적 방법을 사용하였다. 그리고 이 방법론은 기존 해석론에 의해 비교 검증된다. 컴퓨터 프로그램을 위한 알고리즘이 개발되어 내부유체 흐름이 system 고유진동수에 미치는 영향을 상부인장력, 내부 유체흐름 속도 등과 같은 인자의 변화에 따라 조사하였다 분석결과 내부유체흐름의 영향은 상부인장력에 의해 지배되나 심해저 riser와 같은 장대 riser의 경우에 설계시 세심한 주의가 요구된다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.110-115
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• 2000

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and an internal recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.

• 한국가시화정보학회지
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• 제15권1호
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• pp.25-31
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• 2017

This study aims to visualize the Marangoni flow inside a droplet placed on heated hydrophobic surface and to measure its internal velocity field. The experimental result shows that the internal velocity increases with the increase of the plate temperature. In addition, the temperature difference induces the initial flow and drives the Marangoni circulation inside the droplet as soon as the evaporation starts (i.e. the thermal Marangoni flow). The fluorescence particles in the droplet trace two large-scale counter-rotating vortex pairs yielding the downwards flow along the vertical central axis. These vortex pairs gradually become small and move towards the contact line as time goes by, and this Marangoni flow sustains only for a half of the total evaporation time.

• Journal of Advanced Marine Engineering and Technology
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• 제37권3호
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• pp.274-281
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• 2013

The variable demand on the energy market requires a great flexibility in operating hydro turbines. However, Francis turbine operated at off-design conditions poses technical challenges related to large unsteady forces given by residual swirl and angular momentum. In order to improve the performance of a Francis turbine, the paper presents a numerical investigation of the 3D flow in the turbine at off-design conditions and discusses the influence of variable guide vane openings on the internal flow of a Francis turbine with the help of computational fluid dynamics. First, the internal flow characteristics of Francis turbine operated by varied guide vane angle at off design condition are computed and the optimal guide vane angle is obtained. Secondly, the Francis turbine is operated with guide vane number varies at the optimal guide vane angle. Finally, pressure contours and velocity distributions in the distributor are discussed and compared.

• 한국가시화정보학회지
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• 제8권2호
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• pp.31-39
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• 2010

Hysteresis is an effect by which the order of previous events influences the order of subsequent events. Hysteresis phenomenon of supersonic internal flows with shock waves has not yet been clarified satisfactorily. In the present study, experiments are carried out on internal flow in a supersonic nozzle to clarify the hysteresis phenomena for the shock waves. Flow visualization is carried out separately on the straight and divergent channels downstream of the nozzle throat section. Results obtained were compared with numerically simulated data. The results confirmed hysteresis phenomenon for shock wave in the Laval nozzle at a certain specific condition. The relationship between hysteresis phenomenon and the range of the rate of change of pressure ratio with time was shown experimentally. The existence of hysteretic behavior in the formation, both the location and strength, of shock wave in the straight part of the supersonic nozzle with a range of pressure ratio has also been confirmed numerically.

• Journal of Advanced Marine Engineering and Technology
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• 제32권3호
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• pp.404-412
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• 2008

As a suitable volute configuration in the range of low specific speed, circular casing is suggested in this study. The internal flows in a centrifugal pump with the circular and spiral casings are measured by PIV and analyzed by CFD. The results show that the head and efficiency of the pump by a circular casing of very small radius are almost same as those by the spiral casing. Even at the best efficiency point, the internal flow of the pump by circular casing is asymmetric, and vortex and strong secondary flow occurs in the impeller passage. The radial velocity becomes higher remarkably only near the region of the discharge throat. The flow in the impeller outlet is strongly controlled by the circular casing because the velocity distribution almost does not affected by the position of the impeller blades.

• 대한가정학회지
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• 제42권4호
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• pp.127-142
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• 2004

The Purpose of this study was to compare the school life of Korean high school students between Public and proprietary schools, especially focused on their internal experiences and flow. Internal experiences were composed of three dimensions: emotion, cognitive efficiency, and satisfaction. How was classified into four conditions: apathy, boredom, anxiety, and flow. The study results are: 1. Korean high school students felt more flow when they were in public school than in proprietary school,. In public school, they felt relatively more bored, and on the other hand, they were relatively more anxious in proprietary school. 2. Korean high school students felt more positive emotions when they were in public school than in proprietary school. 3. Korean high school students were more involved into study when they were in public school than in proprietary school. 4. Korean high school students were more satisfied when they were in public school than in proprietary school.