• 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.

• 한국농공학회지
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• 제39권2호
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• pp.62-73
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• 1997

The application of nutrients and pesticides to agricultural lands has been reported to contribute to groundwater contamination, which can be explained by preferential flow in lieu of convective-dispersive flow. An one-dimensional numerical model depicting preferential water and solute movement was modified to describe multi-layer flows. The model is based on a piecewise linear conductivity function. By combining conservation of mass and Darcy's law and using the method of characteristics a solution is obtained for water flow in which water moves at distinct velocities in different flow regions instead of an average velocity for the whole profile. The model allows transfer ofqr solutes between pore groups. The transfer is characterized by assuming mixing coefficients. The model was applied to undisturbed soil columns and an experiment site with structured sandy clay loam soil. Chloride, bromide, and 2, 4-D were used as tracers. Simulated solutes concentrations were in good agreement with the soil column data and field data in which preferential flow of solute is significant. The proposed model is capable of describing preferential solute transport under laboratory and field conditions.

• 대한기계학회논문집B
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• 제23권1호
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• pp.92-103
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• 1999

The fuel spray behavior in the intake port of an electronic control port irijection gasoline engine has a strong influence on engine performance, exhaust emission and fuel consumption. Thus, in this study, fuel spray behavior and flow characteristics of the air assist gasoline spray injected into a suction flow in a simulated rectangular intake port have boon investigated. Macro-behavior of spray characteristics was investigated by means of visualization and the measurements of SMD and velocity were made by PDPA. For analysis the flow field with droplets size, droplets are classified five droplets size groups. As a result, the normal distance of suction flow increasing, the relatively large droplets distribution and SMD increase because small droplets easily follow suction flow. Near impinging wail, after impinging against the wall, secondary atomized small droplets of D < $30{\mu}m$ bound from the wall. And the increasement of suction flow progress to the large droplets of D > $100{\mu}m$ distribution. Therefore, SMD are apparently increased near impinging wall, Z/d = 9.0.

• The Journal of Korean Physical Therapy
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• 제11권2호
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• pp.37-42
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• 1999

The purpose of this study was to determine whether percutaneous interferential current stimulation on thoracic sympathetic ganglia with amplitude modulated frequency (AMF) $90\~100$ bps and subthreshold of muscle contraction for 10 minutes on peripheral blood flow velocity in healthy subjects. Thirty-seven healthy volunteers were assigned randomly into an experimental group (n=25) and a control group (n=12). the experimental group received interferential current stimulation with subthreshold of the muscle contraction of current at AMF $90\~100$ bps on $1st\~5th$ thoracic sympathetic ganglial region for 10 minutes. The control group received same handling and electode placement, but no current was applied. Using a Doppler blood flow meter, the radial arterial blood flow velocities and the pulse raters were determined for two-way analysis of variance for repeated measures on time and group. There were no significant difference between the two groups with respect to the changes in arterial blood flow velocity and pulse rate over the four measurement times. Interferential current stimulation did not change in mean blood flow velocity and pulse rate. We conclude that interferential current stimulation on the thoracic sympathetic ganglia, as used in this study, did not dilate peripheral artery. This results suggests that interferential current stimulation dose not alter the activtiy of sympathetic nerve.

• The Korean Journal of Physiology and Pharmacology
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• 제11권3호
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• pp.89-95
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• 2007

Polygala tenuifolia (PT) is one of the most well-known traditional herbal medicines in Korea which is commonly used for the treatment of cardiovascular symptoms. The anti-ischemic effects of PT in isolated rat heart was investigated by analyzing changes in blood pressure, aortic flow, coronary flow, and cardiac output. And, its underlying mechanism was examined by quantitating intracellular calcium content in rat neonatal cardiomyocytes. Rats were divided into two groups: an ischemia-induced group without any treatment, and an ischemia-induced group treated with PT. Ischemia of isolated heart was induced by stopping the supply of oxygen and buffer for 10 min. The isolated heart was exposed to PT for the first 5 min of 10 min ischemia. PT treatment significantly prevented the decreases of perfusion pressure, aortic flow, coronary flow, and cardiac output under ischemic conditions. In addition, hemodynamics (except heart rate) of the PT-treated group was significantly recovered 60 min after reperfusion compared to the control group (systolic aortic pressure: 83.3% vs. 64.9%, aortic flow volume: 69.5% vs. 48.7%, coronary flow volume: 77.7% vs. 58.4%, and cardiac output: 71.6% vs. 51.2%, p < 0.01). As for the underlying mechanism, PT significantly prevented intracellular calcium increase which was induced by isoproterenol (p < 0.01), suggesting that the anti-ischemic effect of PT is mediated by inhibition of intracellular calcium increase.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.624-635
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• 2024

In two-fluid simulations of flow boiling, the modeling of the mean bubble diameter is a key parameter in the closure relations governing the intefacial transfer of mass, momentum, and energy. Monodispersed approach proved to be insufficient to describe the significant variation in bubble size during flow boiling in a heated pipe. A population balance model (PBM) has been employed to address these shortcomings. During nucleate boiling, vapor bubbles of a certain size are formed on the heated wall, detach and migrate into the bulk flow. These bubbles then grow, shrink or disintegrate by evaporation, condensation, breakage and aggregation. In this study, a parametric analysis of the PBM aggregation and breakage models has been performed to investigate their effect on the radial distribution of the mean bubble diameter and vapor volume fraction. The simulation results are compared with the DEBORA experiments (Garnier et al., 2001). In addition, the influence of PBM parameters on the local distribution of individual bubble size groups was also studied. The results have shown that the modeling of aggregation process has the largest influence on the results and is mainly dictated by the collisions due to flow turbulence.

• Journal of Information Technology Applications and Management
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• 제9권4호
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• pp.127-149
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• 2002

Online consumers were classified four groups by online buying frequency and shopping mall loyalty in this study; high frequency-high loyalty, high frequency-low loyalty, low frequency-high loyalty, and low frequency-low loyalty groups. Four groups were compared by Internet usage, flow experience, innovativeness, perceived risks of Internet shopping, Internet shopping behaviors, and demographics. Through an online survey of 396 Internet shoppers, there found significant differences of those variables among four groups. The implications for customer relationship management of Internet shopping mall are discussed and further researches are suggested.

• 한국물환경학회지
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• 제35권6호
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• pp.497-509
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• 2019

After the Total Maximum Daily Loads(TMDLs) was applied, it became beyond the limit of concentration management. However, it does not adequately reflect the characteristics of various watersheds, and causes problems with local governments because of the standard flow set. Thus, in this study, the Han River system is organized into four groups in estimating the Pollution Contribution by applying the Flow Duration Curve(FDC) created by the daily flow of data from the HSPF. And the method of this study is expected to be valuable as basic data for the TMDLs. As a result, Group I contains the main watersheds with no large hydraulic structures and tributary watersheds. There is no specificity in the FDC and the Pollution Contribution is estimated as rainfall runoff. Group II contains watersheds near the city where the FDC is maintained above a certain level during the Low Flow Conditions and the Pollution Contribution is estimated as the discharge flow of large scale point pollution facilities. Group III contains the main watersheds in which the large hydraulic structures are installed and FDC is curved in the Low Flow Conditions. So the Pollution Contribution is estimated as the water quality of the large hydraulic structures. Group IV contains the upstream in mainstream watersheds in which the large hydraulic structures are installed and the FDC is disabled before the Low Flow Conditions. As the flow is concentrated in the High Flow Conditions, the non-point pollution sources are estimated as the Pollution Contribution.

• 한국산학기술학회논문지
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• 제22권1호
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• pp.633-640
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• 2021

본 연구는 동영상 학습에서 텍스트와 이미지 제시방식이 학습자의 학습몰입, 학습만족, 학업성취에 미치는 차이를 분석하였다. 이때 텍스트 제시방식은 2~3단어로 구성된 짧은 문장형태와 키워드형태로 구분하였고, 이미지 제시방식은 상세정보와 관계정보를 모두 표현하는 이미지와 관계정보만을 표현하는 이미지로 구분하였다. 실험연구를 위해 중국 형태대학교 1학년 167명을 텍스트와 이미지 제시방식에 따른 4가지 유형의 동영상 집단에 무선배정한 후 학습하게 하였다. 분석하기 위해 SPSS 25.0을 사용하여 다변량분산분석(MANOVA)을 실시하였다. 연구결과, 짧은 문장형태로 텍스트가 제시된 동영상을 학습한 집단이 키워드 형태의 텍스트가 제시된 동영상을 학습한 집단보다 학습몰입, 학습만족, 학업성취가 통계적으로 유의하게 높았다. 둘째, 상세정보와 관계정보를 모두 표현하는 이미지가 제시된 동영상을 학습한 집단이 관계정보만 표현하는 이미지가 제시된 동영상을 학습한 집단보다 학습몰입, 학습만족, 학업성취가 통계적으로 유의하게 높았다. 짧은 문장형태의 텍스트와 관계정보만 표현한 이미지가 제시된 동영상을 학습한 집단의 종속변인 평균이 가장 높았다. 반면에, 키워드 형태의 텍스트와 관계정보만 표현한 이미지가 제시된 동영상을 학습한 집단의 종속변인 평균이 가장 낮았다. 이러한 결과는 교수자 내레이션이 포함된 동영상을 설계할 때 이미지와 텍스트의 제시할 때 시사점을 준다.

• Journal of Pharmaceutical Investigation
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• 제27권4호
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• pp.331-335
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• 1997

Xerostomia is caused by organic or functional changes affecting the salivary system at different levels. Patients suffering from xerostomia may also complain of an oral burning sensation, ulceration or soreness, difficulty in swallowing, and poor denture retention. And pilocarpine is administered orally to induce salivary secretion. In Seoul National University Hospital(SNUH) pharmacy, the pilocarpine chewing tablets are prepared and supplied to patients of xerostomia in request of the dental hospital in SNUH. And we tested the salivary flow induction and the dissolution patterns of these products in saliva by a double-blind, sequential cross-over trials to eight healthy human volunteers with placebo. The pilocarpine chewing tablet contained 5 mg of pilocarpine, and placebo consisted of same materials as test drug, but didn't contain pilocarpine. In vivo experiment, all subjects were instructed to chew as 60-80 times/min. Mixed saliva was collected in the ranges of intervals such as 0-2, 2-5, 5-10, 10-15, 15-20, 20-30, 30-45 and 45-60 min after pilocarpine chewing tablet or placebo administration. Saliva volume was measured in each collecting time interval, and saliva pilocarpine concentrations were determined by reversed phase HPLC. The 82.5 percent $(4.13{\pm}0.69\;mg)$ of pilocarpine was extracted from chewing tablets during mastication of 60-80 times per minute for 60 minutes. Among these dissolved amounts, 90 percent was extracted within 20 minutes. The salivary flow rates were more increased in a group who administered pilocarpine chewing tablet at the interval of 5-10, 10-15, 20-30 and 45-60 min rather than a placebo-group, but only extracted amount of pilocarpine at 45-60 min interval is significanly different between two groups (p<0.05). But total amounts of saliva secreted for 1 hour in two group-pilocarpine and placebo treated- were $46.36{\pm}9.72\;ml\;and\;39.09{\pm}7.81\;ml$, respectively, and were not significantly different between two groups.