• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.619-628
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• 2011

Human soft tissues, including muscles, ligaments, skin, and blood vessels, are an interesting subject because damage to them can be observed in everyday life. Besides the lack of available experimental data and the large deformation upon loading, the anisotropic and compressible nature of annulus fibrosus makes it more difficult to find a simple material model. A fiber-reinforced hyperelastic material model is used to determine the stress-strain curves upon uniaxial loading. The energy potential function for annulus fibrosus is composed of three different parts: matrix, fibers, and matrix-fiber interaction, which accounts for the angles between two families of fibers. In this paper, two different types of energy potential function for the matrix are considered, and are inserted into the fiber-reinforced model. The calculated results are compared with the Neo-Hookean model and experimental data, and reasonable agreement is observed overall.

• Journal of Chest Surgery
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• v.30 no.7
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• pp.677-685
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• 1997

Thromboelastography(TEG) is the unique measure that gives rapid information about the whole clotting process. Simplifying the diagnosis of coagulopathy during operations, TEG can provide an adequate therapy for postoperative bleeding. Remarkable improvement in hemostasis after cardiopulmonary bypass(CPB) has been achieved by the treatment with proteinase inhibitor aprotinin, but the hemostatic mechanism of aprotinin during CPB is still unclear. This study was designed to evaluate the effects of aprotinin on coagulation system during CPB by using TEG. Forty patients who underwent CPB were divided into two groups: aprotinin(2u 106 kallikrein inhibition units, as a single dose into the cardiopulmonary bypass priming solution) treatment group(male 14, female 8, mean age=50.Byears) and no aprotinin treatment(control) group(male 10, female 8, mean age=53.4 years). TEG, activated clotting time, prothrombin time, activated partial thromboplastin time, platelet counts, fibrinogen an (ibrinogen degradation product(FDP) concentrations were checked before and after CPB(30 minutes after neutralization of heparin effect by protamine sulfate). There was no significant difference in other conventional coagulation tests of two groups except postcardiopulmonary bypass FDP concentration in control group, which was significantly increased compared to that in aprotinin group(p<0.05). In TEG variables of both groups, clot formation time(K) and alpha $angle(\alpha^{\circ})$ were significantly increased and decreased, respectively, after CPB(p<0.05), but fibrinolytic index(LYS60) was not changed during CPB. In aprotinin group, reaction time(R) was decreased significantly after CPB(p<0.05) but maximum amplitude(MA) was not changed(p>0.05). On the contrary, R was not changed markedly but MA was decreased significantly in control group after CPB(p<0.05). This result shows that main change in coagulation system during CPB is not hyperfibrinolysis but cecrease in clot strength by platelet dys unction, and the main effect of aprotinin during cardiopulmonary bypass is the maintenance of clot strength to the pre-CPB level by the preservation of platelet function.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.229-235
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• 2013

To investigate the effect of the flexible artery wall on the blood flow, three-dimensional numerical simulations were carried out for analyzing the time-dependent incompressible flows of Newtonian fluids constrained by a flexible wall. The Navier-Stokes equations for fluid flow were solved using the P2P1 Galerkin finite element method, and mesh movement was achieved using an arbitrary Lagrangian-Eulerian formulation. The Newmark method was employed for solving the dynamic equilibrium equations for the deformation of a linear elastic solid. To avoid complexity due to the necessity of additional mechanical constraints, we used a combined formulation that includes both the fluid and structure equations of motion to produce a single coupled variational equation. The results showed that the flexibility of the carotid wall significantly affects flow phenomena during the pulse cycle. The flow field was also found to be strongly influenced by the bifurcation angle.

• Journal of East-West Nursing Research
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• v.22 no.1
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• pp.32-40
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• 2016

Purpose: This study aimed to provide basic data for vascular health of patient who underwent percutaneous coronary intervention (PCI) by verifying the mediating effect of compliance in the relationship between risk level of coronary artery disease (CAD) and blood vessel elasticity. Methods: This is a descriptive study with 115 patients, who underwent the PCI a year ago and visited in the cardiology department from January to March, 2015. The risk level of CAD, blood vessel elasticity and the compliance were measured. For data analysis, SPSS/WIN 21.0 and AMOS (IBM) 21.0 were used. Results: There were a positive correlation with blood vessel elasticity score (i.e. inelasticity of the blood vessel wall) (r=.189) and a negative correlation with compliance (r=-.658) in mediating effect of risk level of CAD. There was a negative correlation between compliance and blood vessel elasticity (r=-.482). The direct effect (${\beta}=-.226$), indirect effect (${\beta}=.415$) and total effect (${\beta}=.186$) of mediating effect of risk level of CAD on blood vessel elasticity were significant. Compliance had a partial mediating effect of risk level of CAD on blood vessel elasticity. Conclusion: The results of this study suggest that managing and preventing moderating effect of risk level of CAD on compliance is helpful in restoring blood vessel elasticity.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.5
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• pp.35-43
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• 2008

In this study we confirmed for the cardiopulmonary ability improvement of the cycling exercise which uses a target heart beat. Consequently, we looked the resting systolic blood pressure down at 2.98% and THBI(Total Heart Beat Index) also decrements at 7.59%. But, increase of $VO_2$ max and PTT(Pulse Transit Time)were each point 24.60% and 4.92%. Increase of $VO_2$ max showed the growth of stroke volume by myocardial development. The increase of a stroke volume induces the decrease of Heart rate. The blood pressure was reduced also though the blood of many quantity was supplied at the artery. The reason is the phenomenon to be due to by an elasticity increase of the artery. We found out it through the decrease of PTT. So the cycling exercise to use consequently the target heart beat will become big aid at the health care.

• Journal of Chest Surgery
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• v.30 no.6
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• pp.580-584
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• 1997

To overcome the problems of classical pulmonary banding procedure, we developed a percutaneously adjustable pulmonary artery ba ding device. The banding device consists of banding portion of zig-zag shaped self-expandable stainless steel wire, shaft portion made by a polyvinyl catheter and a screw adjuster which includes a bolt and a nut. As the screw moves, the diameter of banding portion changes. Four Mongrel dogs ranging from 15 kg to 20 kg in weight underwent the banding of the mid portion of descending aorta with this devices through the left thoracotomy. One month after operation, we evaluated the pressure changes by controling the banding with the devices and then the dogs were sacrificed to study the microscopic changes in the aorta. The diameter and circumference of the band could be easily and finely adjustable by the screw control. The pressure recordings . revealed a linear increase and decrease in pressure gradient according to percutaneous ad;ustment of the banding device. Since the banding device can be easily placed and simply adjusted percutaneously, we hope the banding device may be applicab e clinically to improving the safety of pulmonary artery banding and debanding procedures in the future.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.51-56
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• 2021

The brachial systolic blood pressure and pulse pressure are the predictors of cardiovascular disease in individuals over 50 years of age. As the stiffness increases, the reflex amplitude and pressure in the late systole increase, resulting in an increase in left ventricular load and myocardial oxygen demand. Therefore, it is necessary to study how stiffness affects blood pressure. In this study, the blood pressure pulse waves were measured before and after taking the drug, and the blood pressure pulse wave was measured before and after myocardial heart transplantation in patients with heart failure. The correlation between R, L, and C components of the Windkessel model was estimated by increasing blood pressure. As a result of modeling the parameters of the Windkessel model using the curve fitting method, the increase in blood pressure and decrease in systolic rise time were due to the increase in the L component in the RLC Windkessel model. Among the various mechanical characteristics of blood vessels, the most important parameter affecting high BP waveform is the inertance.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.42-44
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• 2006

Up to the present, finger replantation patients have complained about various symptoms because of blood circulatory failure. Objective evaluation methods for the level of the blood circulatory failures in fingers were needed other than patient's subjective symptoms and complaints. Photoplethysmogram(PPG) measured from fingers is very useful for evaluation of vascular aging and sclerosis level since the PPG signal represents characteristics of peripheral vascular. Several researchers have reported that second derivative of the finger PPG waveform was useful to evaluate vascular compliance and developed various analysis methods for vascular compliance. However, vascular compliance study for finger replantation patient was never evaluated by using second derivative of PPG. Therefore, we aimed to objectively compare and to assess normal and replanted finger vascular compliance using the second derivative of PPG waveform in this study. The evaluated factors of second derivative of PPG are 'a', 'b', 'c', 'd', 'e' and b/a represents vascular compliance. Study found out that when vascular compliance is decreased, b/a is increased, the absolute value of b/a is decreased. For 43 finger replantation patients, the average vascular compliance of replanted finger is lower than the normal finger statistically(p=0.001). we suggested an objective evaluation of finger vascular compliance for finger replantation patients and effect of surgical operation.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.67-69
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• 2007

Recently, the prevalence rate of diabetes in Korea has been increasing rapidly due to high growth of economy and changes in dietary lifestyle. Vascular complication is one of diabetic complications which have frequently occurred by obesity, hyperglycemia and impaired glucose metabolism. Photoplethysmogram(PPG) measured from finger and toe is very useful for evaluation of vascular aging and sclerosis level since the PPG signal represents characteristics of peripheral vascular. Several researchers have reported that second derivative of the finger PPG waveform was useful to evaluate vascular compliance and developed various analysis methods for vascular compliance. However, peripheral vascular compliance study for diabetic patient was never evaluated by using second derivative of PPG. Therefore, we aimed to objectively compare and to assess normal and diabetic group vascular compliance using the second derivative of PPG waveform in this study. The evaluated factors of second derivative of PPG are 'a', 'b', 'c', 'd', 'e' and b/a represents vascular compliance. Study found out that when vascular compliance is decreased, b/a is increased, the absolute value of b/a is decreased. The average vascular compliance of 50 diabetic patients with neuropathy is statistically lower than the normal group(p<0.05). We suggest an objective evaluation of peripheral vascular compliance for diabetic patients and prevention of vascular complication.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.361-369
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• 2017

Hemodynamic information in the carotid artery bifurcation is very important for understanding the development and progression mechanisms of cerebrovascular disease and for its early diagnosis and prediction of the progress. In this paper, we constructed a mock pulsatile blood circulation system using an anthropomorphic elastic vessel of the carotid artery bifurcation and ex vivo pig blood to acquire ultrasound images from blood and vessels synchronized with internal pressure while controlling the blood flow. Echogenicity, blood flow velocity, and blood vessel wall motion from the ultrasound images, and internal blood pressure were extracted over a cycle averaged from five cycles when the pulsatile pump rates are 20 r/min, 40 r/min, and 60 r/min. As a result, respectively, the peak systolic blood flow velocities were 20 cm/s, 25 cm/s, and 40 cm/s, the blood pressure differences were 30 mmHg, 70 mmHg, and 85 mmHg, the arterial walls were expanded to 0.05 mm, 0.15 mm, and 0.25 mm. Time-delayed cyclic variation of echogenicity compared to blood flow and pressure was observed, but the variation was minimal at 20 r/min. Time-synchronized cyclic variations of these parameters are important information for accurate input parameters and validation of the computational hemodynamic experiments which will provide useful information for the development and progress mechanisms of carotid artery stenosis.