• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.121-124
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• 2006

The arteries are very important in cardiovascular system and easily adapt to varying flow and pressure conditions by enlarging or shrinking to meet the given hemodynamic demands. The blood flow in arteries is dominated by unsteady flow phenomena due to heart beating. In certain circumstances, however, unusual hemodynamic conditions cause an abnormal biological response and often induce circulatory diseases such as atherosclerosis, thrombosis and inflammation. Therefore quantitative analysis of the unsteady pulsatile flow characteristics in the arterial blood vessels plays important roles in diagnosing these circulatory diseases. In order to verify the hemodynamic characteristics, in-vivo measurements of blood flow inside the extraembryonic arterial bifurcation cascade of chicken embryo were carried out using a micro-PIV technique. To analyze the unsteady pulsatile flow temporally, the (low images of RBCs were obtained using a high-speed CMOS camera at 250fps with a spatial resolution of $30{\mu}m\times30{\mu}m$ in the whole blood vessels. In this study, the unusual flow conditions such as flow separation or secondary flow were not observed in the arterial bifurcations. However, the vorticity has large values in the inner side of curvature of vessels. In addition, the mean velocity in the arterial blood vessel was decreased and pulsating frequency obtained by FFT analysis of velocity data extracted in front of the each bifurcation was also decreased as the bifurcation cascaded.

• Korean Journal of Veterinary Research
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• v.35 no.2
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• pp.271-278
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• 1995

The objective of the present study was to investigate the inhibitory effect of physiologically pulsatile pattern of testosterone(T) on luteinizing hormone(LH) in wethers. To do this, 3 separate experiments were conducted. Infusion rates and patterns needed to produce normal T secretory profiles found in intact rams were established in Experiment 1, the time-course of the suppressive effect of T on circulating LH concentrations was determined in Experiment 2, and the effectiveness of a pulsatile versus a constant pattern of T to suppress LH secretion in wethers was compared in Experiment 3. In Experiment 1, three different doses(25, 50 or $100{\mu}g$) of T were injected intravenously to animals to do pharmacokinetic analysis of T. Elimination rate constant, volume of distribution, and total body clearance of T averaged $0.18min^{-1}$, 0.531/kg BW, and 0.091/min/ kg BW, respectively. In Experiment 2, three different doses(192,384, or $768{\mu}g/kg/24h$) of T were infused at 4h intervals for 3 days into animals to evaluate the time course of the inhibitory effect of T on mean LH concentration. As duration of T infusion increased, mean LH concentrations gradually reduced. Mean LH concentrations were significantly lower at day 2 or day 3 than at day 0. However, mean LH concentrations did not differ between day 0 and day 1 or between day 2 and day 3. In Experiment 3, animals were subjected to two different intravenous infusion regimens for 3 days: constant T($768{\mu}g/kg/24h$) and pulsatile(one pulse every 4h) T($768{\mu}g/kg24h$). Blood samples were collected at 10-min intervals for 4h both prior to infusion and during the last 4h of the infusion. Mean LH was more suppressed(p=0.045) by constant T than by pulsatile T. LH pulse amplitude was not affected by constant T or pulsatile T. LH interpulse interval was increased more(p=0.034) by constant T than pulsatile T.

• Journal of Veterinary Clinics
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• v.28 no.2
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• pp.225-231
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• 2011

The objective of the present study was to determine the progesterone levels that effects on the pulsatile and surge modes of FSH secretion. In previous studies we have shown that LH surge occurred in the follicular levels of progesterone, whereas there was no surge mode secretion of LH in either the sub luteal or luteal levels of progesterone. LH pulsatile frequencies were high in two groups such as follicular level and sub luteal level. But in the luteal level of progesterone the pulsatile pattern of LH were strongly suppressed. Namely, sub luteal levels of progesterone, around 1 ng/ml, completely suppressed the LH surge but did not affect the pulsatile frequency of LH secretion. Because of this we hypothesized that the two secretory patterns of FSH are similar to that of LH. Long-term ovariectomized Shiba goats that had received implants of estradiol capsules and three different progesterone silastic packet inducing follicular, subluteal and luteal levels of progesterone were divided into three groups such as non-P, low-P and high-P group. Blood samples were collected daily throughout the experiment for the analysis of gonadal steroid hormone levels and at 10-min intervals for 8 h on Days 0, 3, and 7 (Day 0: just before progesterone treatment) for analysis of the pulsatile frequency of FSH secretion. Then estradiol was infused into the jugular vein of all animals at a rate of 3 ${\mu}/h$ for 16 h on Day 8 to determine whether an FSH surge was induced. Blood samples were collected every 2 h from 4 h before the start of the estradiol infusion until 48 h after the start of the infusion. In each group, the mean ${\pm}$ SEM concentration after progesterone implant treatment was 3.3 ${\pm}$ 0.1 ng/ml for the high P group, 1.1 ${\pm}$ 0.1 ng/ml for the low P group, and < 0.1 ng/ml for the non-P group, concentrations similar to the luteal levels, subluteal levels, and follicular phase levels of the normal estrous cycle, respectively. The FSH pulse frequency was maintained highly in all groups on Day 0, Day 3 and Day 7. An FSH surge was induced in all 4 cases of the Non-P group. In the High P and Low P groups, the plasma concentrations of FSH remained low until 48 h after the start of estradiol infusion, and no occurrence of FSH surge was found in any of the animals. The results of this study not only confirm that the pulsatile patterns of FSH were not inhibited strongly relative to LH, they also suggest that some other mechanism and factor may be controlling the FSH secretion.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.77.1-77.1
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• 2008

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.119-126
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• 2009

A numerical analysis is performed to investigate the effect of rotation on the blood flow characteristics with four different angular velocities. The artery has a cylindrical shape with 50% stenosis rate symmetrically distributed at the middle. Blood flow is considered a non-Newtonian fluid. Using the Carreau model, we apply the pulsatile velocity profile at the inlet boundary. The period of the heart beat is one second. In comparison with no-rotation case, the flow recirculation zone (FRZ) contracts and its duration is reduced in axially rotating artery. Also wall shear stress is larger after the FRZ disappears. Although the geometry of artery is axisymmetry, the spiral wave and asymmetric flow occur clearly at the small rotation rate. It is caused that the flow is influenced by the effects of the rotation and the stenosis at same time.

• The Korean Journal of Rheology
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• v.8 no.1
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• pp.1-10
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• 1996

본 논문에서는 협착이 발생된 원관내 뉴턴유체와 비뉴턴유체의 정상 및 맥동유동특 서을 유한요소법으로 해석하였다. 본연구는 맥동유동특성에서 협착관 형상의 변화, 협착이 주기적으로 발생된 협착관에서 협착부사이의 거리와 협착부의 수가유동특성에 미치는 영향 을 검토하였다. 레이놀즈수가 일정할 때 협착이 발생된 원형관내 뉴턴유체와 비뉴턴유체의 맥동유동특성은 정상유동의 경우와 크게 다르게 나타난다. 맥동유동에서는 정상유동보다 관 중앙부에서 속도분포가 훨씬 평탄하고 맥동유동의 속도분포는 감속시에 비하여 가속시에 관 중앙부의 속도분포가 더 평탄하게 나타난다. 정상유동과 맥동유동으 감속시에서는 협착부 하류의 벽면에서 재순환영역이 발생된다. 협착부의 수가 증가하면 각 협착부 주위의 속도장 은 유사하게 나타나지만 전체 압력손실은 크게 증가한다. 협착부사이의 거리가 변화될 경우 맥동유동속도의 국소최대치와 국소최소치의 차이가 가속시에는 거의 없지만 감속시에는 협 착부사이의 거리에 따라 다르게 나타난다.

• Journal of Chest Surgery
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• v.11 no.2
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• pp.185-193
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• 1978

Between April 1976 and March 1978, six cases of tricuspid valve replacement were done in the Department of Thoracic Surgery, Seoul National University Hospital. There were 4 men and 2 women and the age of the patients ranged from 17 years of the youngest to 48 years of the oldest. Most of them had characteristic symptoms of tricuspid valve disease, such as a systolic murmur audible over the lower sternum and varying with respiration, pulsatile and distended neck vein, and an enlarged and pulsatile liver. Preoperative functional levels according to NYHA Calcification were class III in 4 cases, and class IV in 2 eases. Most of the cases showed moderate to severe cardiomegaly in chest films and elevated right atrial pressure on preoperative right heart catheterization. Five of them underwent concomittent mitral valve replacement and one pulmonary valvotomy. All of them showed tricuspid insufficiency resulted from massive dilatation of annulus, destructive lesions of valve structure, or both anomalies. One postoperative hospital death was encountered and the cause of death was low out-put syndrome. All survivors showed clinical improvement and cardiomegaly regressed and left hospital in a good condition . *Attendum; Recently 2 more cases of tricuspid valve replacement with mitral valve replacement were done after this review.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.115-118
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• 1994

Three-dimensional steady and pulsatile flows in an end-to-side anastomosis were investigated using a finite difference method in order to understand the flow dynamics in the preferential development of distal anastomotic intimal hyperplasia or thrombosis. Steady flow results revealed that a double helical vortex was formed in the host artery and flow recirculations near tow and heel regions were limited due to the secondary flow. Oscillating wall shear stress with significant secondary flow might be the flow dynamic reason of developing intimal hyperplasia or thrombosis.

• Journal of Korean Neurosurgical Society
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• v.57 no.1
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• pp.58-60
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• 2015

A 15-year-old female patient with progressive pulsatile exophthalmos caused by intraorbital encephalocele was evaluated with computed tomography (CT) and magnetic resonance imaging (MRI) in our clinic. She had no history of trauma or reconstructive surgery. When she was a little girl, she had undergone surgery for congenital glaucoma on the right eye. On the three-dimensional image of CT, a hypoplasic bone defect was observed in the greater wing of the right sphenoid bone. MRI and CT scan showed herniation through this defect of the arachnoid membrane and protruded cerebral tissue into the right orbita. Intraorbital encephalocele is an important entity that can cause pulsatile exophthalmos and blindness.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.147-149
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• 2003

Using computational fluid dynamics with the fluid-structure interaction, structural effects of intra-luminal thrombus were determined in thrombosed axisymmetric abdominal aorta aneurysm (AAA) models under pulsatile flow. Four different models, varying dilatations of the aneurysm and Young's moduli of intra-luminal thrombus, were defmed. Compared with unthrombosed AAA models, both von Mises stress and radial displacements in the aneurysm wall significantly decreased. Stiffer intra-luminal thrombus reduced von Mises stress in the aneUtysm wall. The present study supported that intra-luminal thrombus might reduce wall stress in the aneurysm.