• Annals of Clinical Neurophysiology
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• 제1권1호
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• pp.70-75
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• 1999

Trancranial Doppler(TCD) monitoring is a new application of ultrasonography which allows the nonivasive detection of blood flow velocity in the horizontal (M1) segment of the middle cerebral artery (MCA) and detects microembolic phenomena in the cerebral circulation. Recent studies emphasized the potential of using this technique in vascular surgery (carotid endarterectomy, cardiopulmonary bypass), interventional and intensive care setting. Although the disparity between CBF and blood flow velocity and number of microemboli could be used to prevent cerebral ischemic and embolism based on clinical studies. A reduction of more than 60% of MCA can reflex hemodynamic ischemic state and acoustic feedback of high intensity transient signals(HITS) from the TCD monitoring unit has a direct influence on surgical technique. TCD monitoring can immediately provide information about thromboembolism and hemodynamic changes, which may be a useful tool in the study and prevention of stroke.

• 한국연소학회지
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• 제7권4호
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• pp.10-20
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• 2002

This paper discusses effect of solid mass inventory on the hydrodynamic characteristics of circulating fluidized bed(CFB). Operating parameters of solid mass inventory and air flow rates were varied to understand their effects on fludization pattern. Experimental measurements were made in a CFB of which height and diameter are 3m and 0.05m respectively. Black SiC particles ranging from $100{\mu}m\;to\;500{\mu}m$ were employed as the bed material. Superficial gas velocity of riser and J-valve fluidizing velocity were in the ranges of $1.39{\sim}3.24m/s\;and\;0.139{\sim}0.232m/s$, respectively. The axial solid fraction and solid circulation rate of CFB were calculated based on the experimental data and compared with modellings through IEA-CFBC Model and commercial CFD code.

• 연구논문집
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• 통권34호
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• pp.11-19
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• 2004

An Experimental study on the characteristics of high pressure gas quenching system was carried out in the present study. The characteristics of gas quenching system have been studied with high pressure gas chamber and specimen for various gas pressure and velocity which are the design parameter of quenching system. The quenching gas was used compressed air which properties are very similar with Nitrogen gas usually used in industrial gas quenching system. The result shows that the quenching rate of mid surface of specimen is lower than each ends of them which are close to low temperature quenching surface. And to increases the quenching intensity, the increment of quenching gas pressure is more efficient than the increment of quenching gas velocity at the point of reducing the circulation fan power.

• 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.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.663-668
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• 1996

A two-dimensional continuum model for the prediction of the hydrogen mixing phenomena in the containment compartment under the severe accident conditions is developed. The model could predict well the distribution of time-dependent hydrogen concentration for selected HEDL Experiment. For a simulation of these experiments, the hydrogen is mixed uniform over the test compartment. To predict the extent of non-uniform distribution, the dominant factors such as the geometrical shape of obstacle and velocity of source injection in mixing phenomena are investigated. If the obstacle disturbing the flow of gas mixture exists in the compartment, the uniform distribution of hydrogen may be not guaranteed. The convective circulation of gas flow is separately formed up and down of the obstacle position, which makes a difference of hydrogen concentration between the upper and lower region of the compartment. The recirculation flow must have a considerable mass flow rate relative to velocity of the source injection to sustain the well-mixed conditions of hydrogen.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.266-268
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• 2011

We present a mathematical model of left heart governed by the partial differential equations. This heart is coupled with a lumped model of the whole circulatory system governed by the ordinary differential equations. The immersed boundary method is used to investigate the intracardiac blood flow and the cardiac valve motions of the normal circulation in humans. We investigate the intraventricular velocity field and the velocity curves over the mitral ring and across outflow tract. The pressure and flow are also measured in the left and right heart and the systemic and pulmonary arteries. The simulation results are comparable to the existing measurements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.686-691
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• 2000

Animation technique from the PIV database is particularly emphasized to give macroscopic and Quantitative description of complex flow fields. As an example, an experimental study was carried out investigate the fundamental (low characteristics of the freezer with the domestic refrigerator. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. Image intensifier CCD camera to cope with illumination problem is arranged for the accurate PIV measurement of large flow field. As a results, continuous pictures of the spatial distribution of the instantaneous and time-mean velocity distribution are displayed in real-time sense.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.165-172
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• 2002

This paper discusses hydrodynamic characteristics of cold circulating fluidized bed(CFB) in different solid mass inventories. Operating parameters of solid mass inventory, primary air and J-valve fluidizing air were varied to find out the effect on the flow fludization pattern. Experimental measurements were made in a 3m tall CFB that has 0.05m riser diameter and black silica-carbonate of particle sizes from $100{\mu}m$ to $500{\mu}m$ were employed as the bed material. The operating conditions of superficial gas velocity and J-valve fluidizing velocity were in the ranges of 1.39~3.24 m/s and 0.139~0.232 m/s respectively. The axial solid fraction and solid circulation rate of CFB were observed and compared with modelling through IEA-CFBC Model and commercial CFD code.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.104-112
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• 2010

The thermal influential factor of energy pile system is investigated by considering the seasonal effect, saturation of ground, and fluid velocity based on the finite volume method. Analysis includes the evaluation of thermal resistance and corresponding heat exchange rate for each case. It is shown that the efficiency of heat exchange rate is more pronounced with higher fluid velocity due to the larger number of circulation for a given period. Through the parametric studies, it is also found that the degrees of saturation a little influenced thermal effect during 8 hours of operational scenario.

• 대한의용생체공학회:의공학회지
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• 제18권1호
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• pp.51-64
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• 1997

A dynamic model of the Korean total artificial heart(TAH) which contains a brushless DC motor, all of mechanical components, the pump system with integrated variable volume space(WS) and the circulatory system model including the bronchial circulation were established Two different sets of seven differential equations were separately derived for the left and right systolic period of the Korean TAH operation. Throughout the computer simulation, a full-state fEedback optimal controller that minimizes the power consumption of the Korean TAH and drives the end stage velocity of the energy converter to zero was developed based upon the optimal control theory. Robustness of the controller were also analyzed with the dynamic model of the Korean TAH.