• 순환기질환의공학회:학술대회논문집
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• 2001.11a
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• pp.66-67
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• 2001

• Science of Emotion and Sensibility
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• v.4 no.2
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• pp.79-88
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• 2001

The objectives of this study were to investigate the relationship of sound parameters with subjective sensation and physiological responses, and to figure out the interrelationship between the subjective sensation and physiological responses. Sound parameters calculated were LPT, ΔL, Δf, loudness[Z], and sharpness[Z]. Subjective sensation was evaluated in 7 aspects(soft-hard, loud-quiet, pleasant-unpleasant, sharp-dull, clear-obscure, rough-smooth, high-low) by thirty participants. We acquired physiological responses when each fabric sound was presented to 10 participants. Physiological signals obtained in this study were electroencephalogram(EEG), pulse volume(PV), skin conductance level(SCL), and LF/HF of heart rate variability. The larger the values of loudness[Z] and LPT, the louder and the rougher the subjective sensation of the perceived fabric sound. Also, the larger the values of loudness[Z] and LPT, the harder, the duller, and the less pleasant. As LPT increased, PV decreased. Loudness[Z] increased in proportion to SCL and so did sharpness[Z] to LF/HF. As the sound perceived to be quieter and clearer, the relative power of slow alpha rose. As the sound perceived to be more pleasant and smoother, PV rose.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.57-60
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• 1995

The objective of this investigation is to understand the role of hemodynamics in the formation and development of atherosclerosis lesions in the human left coronary artery This study also aims to compare the blood flow characteristics of steady and physiological flows. Three dimensional, steady and physiological flows of blood in the left coronary artery are simulated using the Finite Volume Method. Apparent viscosity of blood is represented as a function of shear rate by the Carreau model. Distributions of velocity, pressure and shear stress in tile left coronary artery bifurcation are presented to compare tile steady and physiological flow characteristics.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.113-116
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• 1995

Steady and physiological flows of a Newtonian fluid and blood in the bifurcated arterial vessel are numerically simulated. Distributions of velocity, pressure and wall shear stress in the bifurcated arterial vessel are calculated to investigate the differences between steady and physiological flows. For the given Reynolds number physiological flow characteristics of a Newtonian fluid and blood in the bifurcated arterial vessel are quite different from those of steady flows. No flow separation or flow reversal in the bifurcated region in the downstream after stenosis appears during the acceleration phase. Also, no recirculation region is seen for steady flows. However, during the deceleration phase the flow began to exhibit flow reversal, which is eventually extended to the entire wall region.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.149-155
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• 2013

For in-depth research of blood flow, it is important to create pulsating flow like the blood flow from heart beat. In this study, we developed a heart mimicking pulsatile pump and evaluated its performances. Main body of pump was produced using a piston pump, and its rpm and duty ratio was modulated by DC motor and encoder. To determine the part dimensions, principle stress theory and simple fluidic pressure analysis were used. The performance of pulsating pump was evaluated by comparing the pressure values and their deviations according to experimental variables. For the results, the output value of pressure followed the distribution of pulsating flow and its deviation was negligible. Through this study, we expect the established pulsating pump can be widely used in study of blood flow produce easy ways to related researchers.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.357-360
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• 2002

혈관에 흐르는 혈류 속도의 측정은 혈압 및 심박수와 관련된 혈류의 역학적 변화를 관찰하는 데 있어서 주로 사용되는 방법 중의 하나이다. 이 혈류 속도는 일반적으로 도플러 효과에 의하여 주파수가 변화하는 현상을 이용하여 추정하게 된다. 그런데 기존의 주파수 추정 방법들은 시불변 시스템을 가정하고 있지만 실제 혈관 속은 혈구가 일정하지 않은 속도를 갖는 시변 시스템이라 할 수 있기 때문에 이러한 시변 특성이 강한 경우 기존의 방법을 이용하게 되면 그 성능이 저하되는 경향을 보인다. 또 피시험자의 몸 상태에 따라서 서로 다른 주파수 변화 추이를 보이므로 하나의 고정 변수로써 최적화된 성능을 기대하기도 어렵다. 그러므로 본 논문에서는 시변 시스템에서 좋은 성능을 갖는 가변 망각 인자(variable forgetting factor, VFF)를 사용한 순환적인 완전 최소 자승법(recursive total least squares, RTLS) 기법을 이용한 주파수 추정 방법을 제안한다. RTLS란 TLS 기법을 순차적으로 계산하는 방법으로 시변 적응력을 향상시키는 방법이다. 또한 이 기법에 가변 망각 인자(VFF)를 적용시키는 것은 시변 시스템에서 외부적인 변화에 대하여 좀더 효율적으로 대응할 수 있기 위함이다. 기존의 방법과 성능 비교를 위하여 컴퓨터 시뮬레이션을 하였으며 그 결과 시변 시스템에서 본 논문에서 제안한 VFF를 이 용한 RTLS 기법이 보다 향상된 성능을 가지고 있음을 확인 할 수 있었다.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.393-402
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• 2001

A computational model representative of cardiovascular circulation was built using 12 standard lumped compartments. Especially, both the baroreceptor reflex and the cardiopulmonary reflex control model were implemented to explain the auto-regulation of cardiovascular system. Another important aspect of this model is to utilize the impulse-response curve of the nerve system in transferring the impulse error signals to autonomous nerve system. For the verification of this model, we have computed the normal hemodynamic conditions and compared those with the clinical data. Then. hemodynamic shock of 20% hemorrhage to cardiovascular system was simulated to test the effects of the control system model. The results of these two simulations were well matched with the experimental ones. The steady state LBNP simulation was also performed. The transient changes of hemodynamic variables due to ramp increase of bias pressure of LBNP showed good agreement with the physiological experiments. Numerical solution using only the baroreflex model showed relatively a larger deviation from the experimental data. compared with the one using the control model haying both the baroreflex and the cardiopulmonary reflex systems, which shows an important role of the cardiopulmonary reflex system for the simulation of the hemodynamic behavior of the cardiovascular system .

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.449-457
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• 2013

In this study, we performed a numerical analysis to investigate the effect of rotation on the blood flow and arterial wall behavior by using the FSI (fluid-structure interaction) technique. The geometry of the artery included 50% stenosis at the center. To simulate the rotational effect, 2-6 rps of axial velocity was applied to the arterial model. A spiral wave and asymmetric flow occurred due to the stenosis and axial rotation both in the rigid body model and in the FSI model. However, the arterial wall motion caused periodic and transient blood flow changes in the FSI model. The FRZ (fluid recirculation zone) decreased in the FSI model, which is a known predictor for the formation and vulnerability of plaque. Therefore, it is observed that arterial wall motion also influences the generation of the FRZ.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.927-932
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• 2013

The intracranial aneurysm model is extracted based on the Computed Tomography (CT) scan images. Computational fluid dynamics simulations were conducted under both steady and realistic flow conditions in ANSYS-FLUENT. The minimum wall shear stress in the intracranial aneurysm tended to occur in the aneurysmal region. The magnitude of wall shear stress along inner wall of the curvature in the right M1 segment of middle cerebral artery is approximately 20 times higher than that along both the proximal and distal walls. However, the magnitudes of the wall shear stress at the aneurysm region were considerably low. The blood flow has the complex distribution in the aneurysmal region during the systolic period. Complex helical flow patterns are observed inside the aneurysm. Through an analysis of the hemodynamic characteristics, one may predict the rupture of the cerebral aneurysms.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.238-243
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• 2011

In this study, we attempted a structural analysis in order to design a balloon type extracorporeal membrane oxygenator that can induce blood flow without using blood pumps for the purpose of complementing the weakness in the existing extracorporeal membrane oxygenator. To analyze the flow characteristic of the blood flow within the virtual model of extracorporeal membrane oxygenator, computational fluid dynamics(CFD) modeling method was used. The operating principle of this system is to make the surface of the extracorporeal membrane oxygenator keep contracting and dilating regularly by applying pressure load using a balloon, and the 'ime Function Value'that changes according to the time was applied by calculating a half cycle of sine waveform and a cycle of sine.waveform Under the assumption that the uni-directional blood flow could be induced if the balloon type extracorporeal membrane oxygenator was designed as per the method described above, we conducted a structural analysis accordingly. We measured and analyzed the velocity and pressure of blood flow at both inlet and outlet of the extracorporeal membrane oxygenator through CFD simulation. As a result of the modeling, it was confirmed that there was a flow in accord with the direction of the blood by the contraction/dilation. With CFD simulation, the characteristics of blood flow can be predicted in advance, so it is judged that this will be able to provide the most optimized design in producing an extracorporeal membrane oxygenator.