• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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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.

• 동의신경정신과학회지
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• 제20권1호
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• pp.199-214
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• 2009

Objectives : This study was performed to change of blood flow in In-Young(ST9) after treatment on chronic daily headache patients. Methods : Monitoring of TCD was examined in 10' s chronic daily headache patients before and after treatment. Mean velocity flow, systolic velocity and pulsatility index were analyzed from TCD at In-Young(ST9). The patients was laid for 20 minutes before treatment and also for treatment. Results : The results showed a significant(p<0.05: Paired T-test) decrease in mean velocity flow and systolic velocity. but there were no significant differences in pulsatility index. Conclusions : These results suggest that there were significant change on blood flow in In-young of chronic daily headache patients.

• 한국유체기계학회 논문집
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• 제7권3호
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• pp.14-22
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• 2004

Bileaflet mechanical valves have the complications such as hemolysis and thromboembolism, leaflet damage, and leaflet break. These complications are related with the fluid velocity and shear stress characteristics of mechanical heart valves. The first aim of the current study is to introduce fluid-structure interaction method for calculation of unsteady and three-dimensional blood flow through bileaflet valve and leaflet behavior interacted with its flow, and to overcome the shortness of the previous studies, where the leaflet motion has been ignored or simplified, by using FSI method. A finite volume computational fluid dynamics code and a finite element structure dynamics code have been used concurrently to solve the flow and structure equations, respectively, to investigate the interaction between the blood flow and leaflet. As a result, it is observed that the leaflet is closing very slowly at the first stage of processing but it goes too fast at the last stage. And the results noted that the low pressure is formed behind leaflet to make the cavitation because of closing velocity three times faster than opening velocity. Also it is observed some fluttering phenomenon when the leaflet is completely opened. And the rebounce phenomenon due to the sudden pressure change of before and after the leaflet just before closing completely. The some of time-delay is presented between the inversion point of ventricle and aorta pressure and closing point of leaflet. The shear stress is bigger and the time of exposure is longer when the flow rate is maximum. So it is concluded that the distribution of shear stress at complete opening stage has big effect on the blood damage, and that the low-pressure region appeared behind leaflet at complete closing stage has also effect on the blood damage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1484-1486
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• 2008

Characteristics of pulsatile flow in 3-dimensional elastic vessel wall should be investigated in order to understand the physiological blood flow in human body. In this study, the modelling of the physiological blood flow in the elastic blood vessel is proposed. Variation of the pressure and the velocity wavefroms are obtained using the FSI method

• 대한의생명과학회지
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• 제10권4호
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• pp.467-472
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• 2004

Transcranial Doppler sonography (TCD) is a useful diagnostic method to measure cerebral blood flow velocity in various cerebral disorders. However, we haven't data enough to be available for young persons, especially in the twenties in Korea. This study was performed to collect the basic data of the cerebral blood flow velocity and to understand the cerebral physiology in the twenties. We determined the mean velocities of middle, anterior, and posterior cerebral artery, and vertebral and basilar artery (MCA-V, ACA-V, PCA-V, VA-V, and BA-V, respectively) in eighty-two healthy volunteers. For evaluating cerebral autoregulation, only the MCA- V was measured under various conditions such as stable, apnea, and hyperventilation state. Right and left MCA-V were 80.66±14.03 and 83.22±14.40 cm/sec at stable state, 90.13±17.47 and 90.26±16.38 cm/sec at apnea, and 54.83±11.09 and 55.33±10.74 cm/sec at hyperventilation. Right and left ACA-V were 49.11±15.71 and 48.19±13.75 cm/sec. Right and left PCA-V were 39.44±9.12 and 37.91±6.74 cm/sec. Right and left VA-V were 33.65±9.26 and 36.l8±10.39 cm/sec. BA-V was 48.49±11.16 cm/sec. Right and left MCA- V, V A-V, and right ACA- V and PCA- V in women were higher than those of men (P<0.05). No significant differences were found between men and women in the others. These findings indicate that cerebral hemodynamics and autoregulation were normal in young people in their twenties. The velocities of MCA, ACA, PCA, and BA were high values in women as compared with men.

• 대한임상검사과학회지
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• 제36권1호
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• pp.43-48
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• 2004

Cerebral vasoreactivity is an index of autoregulation of cerebral perfusion, and can be measured using functional images such as Xe CT, SPECT and PET in reponse to hypercapneic stimulus. In order to measure cerebral $CO_2$ vasoreactivity in routine TCD study conveniently and reliably, we devised a method of rebreathing into closed volume of reservoir bag as a hypercapneic stimulus, and applied it to 44 healthy volunteers. As a hypercapneic stimulus, we applied fitting mask connected with closed reservoir bag for about 90 seconds, and mean blood flow velocity(MBFV) and pulsatility index(PI) were evaluated at proximal middle cerebral arteries(MCA) of 50-55 mm depth, before and after the hypercapneic stimulus. Age affected the MFV and PI value showed significant and the MFV was 56.45(SD=9.75)cm/sec, while PI was 0.406(SD=0.089). As age increases the flow velocity decreased significantly whereas PI value increased(P<0.05). The vasoreactvity significantly decreased with age(P<0.05). The decrease of cerebral blood flow quantity and cerebral blood flow velocity is not only because of increase of diameter of cerebrovascular resulting from aging, but the resistance increase of small blood vessel resulting from the increase of PI & RI value is regarded. We suppose that the rebreathing method is a reliable and convenient technique as a hypercapneic stimulus in determining cerebral $CO_2$ vasoreactivity. The rebreathing method could be non-invasive and useful methods in estimation of the cerebrovascular reactivity and could be applied to the basal and follow-up evaluation of the cerebrovascular reserve of the ischemic stroke patients.

• 한국자기학회지
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• 제22권4호
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• pp.130-135
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• 2012

요골동맥의 중심인 "관" 위치에 영구자석을 붙인 후 바로 위쪽에 자성측정용 반도체 홀소자를 장착하여 전압 신호를 검출하는 하드웨어 시스템이 적용된 집게형 맥진기 시제품을 개발하였다. 집게형 맥진기와 용적맥파계를 동시 분석하는 시스템으로 20대 나이 임상참가자 40명 각각에 대한 맥진파형과 용적맥파형 두 피크값을 비교 측정한 결과 혈류속도가 평균 0.8 m/s로 기존 값과 거의 비슷하였다. 이로써 요골동맥파형-용적맥파형을 환자감시장치에서 제시하는 주요 임상의 주요값으로 적용할 수 있음을 제시하였다.

• 대한한방내과학회지
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• 제21권5호
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• pp.805-811
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• 2000

Objectives : To determine the effects on blood flow of vertebrobasal vascular system in cerebral infarction, Methods : We altered 33 normal patients and 12 patients who were diagnosed cerebral infarction on Rt. middle cerebral artery(MCA) region and 8 patients who were diagnosed cerebral infarction on Lt, MCA region, and measured the mean velocity, systolic to diastolic rate(SD rate), asymmetrical index(A/I) by TCD. Results : The mean velocity of posterior cerebral artery(PCA), vertebral artery was increased in same direction as infarcted site and the mean velocity of basal artery was more increased than control, and the SD rate of PCA, vertebral artery, basal artery was larger than control. The A/l of PCA, vertebral artery was revealed that mean velocity of vertebrobasal vascular system is increase the same direction as infarcted area. Conclusion : TCD examination within 7 days(acute stage) after stroke can help to predict the infarcted direction.

• The Journal of Korean Physical Therapy
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• 제22권6호
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• pp.71-76
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• 2010

Purpose: The purpose of this study was to examine changes in autonomic nerve responses after low-frequency transcutaneous electrical nerve stimulation (TENS). Methods: Research subjects were 24 students who attend University. Subjects were divided into two groups: 1 = a low intensity group; 2 = a high intensity group. Electrodes were attached to the forearm of the dominant arm and electrical stimuli were administered for 15 minutes. Outcome measures were skin conduction velocity, skin temperature, blood flow, and pulse frequency, each of which was measured a total of 4 times. The data were analyzed using a repeated measures ANOVA. Results: In changes in conduction velocity, the main effect of time variation (in black) was statistically significant. The interaction between time and group main effects was not statistically significant; nor was the difference between the groups. Results showed that skin conduction velocity changed without any relation to group. Conclusions: Low frequency TENS selectively increases skin conduction velocity, which may be helpful for activating sudomotor function regardless of intensity.

• 한국가시화정보학회지
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• 제14권1호
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• pp.33-39
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• 2016

Radio-cephalic arteriovenous fistula(RC-AVF) is the most recommended operation of achieving access for hemodialysis. However, it has high rates of early failure depending on the many haemodynamic conditions. To increase RC-AVF patency rate, many researches were performed by in-vitro experiment via artificial vessel and blood analogue fluid, and there were conflicting opinions about whether the non-Newtonian properties of blood have an influence on the flow in large arteries. To investigate the influence of viscoelasticity of blood within the RC-AVF, we fabricated three dimensional artificial RC-AVF and two kinds of blood analogue fluid. The velocity field of two fluids within the vessel were measured by micro-particle velocimetry(m-PIV) and compared with each other. The velocity profiles of both fluids for systolic phase were matched well while those for diastolic phase did not correspond. Therefore, it is desired to use non-newtonian fluid for in-vitro experiment of RC-AVF.