• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.1-6
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• 2017

Stents are widely used as the most common method of treating coronary artery disease with implants in the form of a metal mesh. The blood flow is normalized by inserting a stent into the narrowed or clogged areas of the human body. In this study, the mechanical characteristics of a stent are investigated according to the variations of its design parameters by the Taguchi method and finite element analysis. A stent model of the Palmaz-Schatz type was used for the analysis. In the analysis, an elasto-plastic material model was adopted for the stent and a hyper-elastic model was used for the balloon. The main interest of this study is to investigate the effects of the design parameters which reduce the possibility of restenosis by adjusting the recoil amount. A Taguchi orthogonal array was constructed on the model of the stent. The thickness and length and angle of the slot were selected as the design parameters. The amounts of radial recoil and longitudinal recoil were calculated by finite element analysis. The statistical analysis using the Taguchi method showed that optimizing the shape of the stent could reduce the possibility of restenosis. The optimized shape showed improvements of recoil in the radial and longitudinal directions of ~1% and ~0.1%, respectively, compared to the default model.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.90-97
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• 2010

In order to understand the biomaterial like the blood vessel of artery, there is a need to quantify the biomechanical behavior of the vessel. Using computer-controlled experimental system, the experiment can acquire data such as inner pressure, axial load, diameter and axial gauge length without contacting the specimen. Rubber-liked material which is similar to passive artery was selected as pseudo-biomaterial. Deformations are measured for pressure-diameter curves. The data were collected and stored online to be used in the feedback control of experimental protocols. Finally, the illustrative data obtained from the experimental system were presented and the system shows that strain invariants are controlled to understand the nonlinear elastic behavior of biomaterial which is involved with strain energy function.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.425-434
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• 2005

In order to analyze pulsating flows in elastic blood vessels, a method based on the ALE concept and finite volume method was reformed and modulated to include wall motion of elastic vessels and impedance phase angle(phase difference between wall motion and blood flow). Our study indicated wall shear rates(WSR) were significantly influenced by the wall motion and the impedance phase angle. For larger wall motion more than $5{\%},$ the computed WSR started to deviate from the results of the perturbation theory that assumed smaller wall motion. The study showed that oscillatory shear index increased as the impedance phase angle became more negative like $-70{\circ}\;or\;-80{\circ}$ due to reduced mean WSR and increased amplitude of WSR. This result indicated that hypertensive patients are more vulnerable to atherosclerosis than normal persons because of the role of more negative impedance phase angles usually observed in these patients.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.500-503
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• 2011

Blood flow simulations in an idealized carotid bifurcation model with considering wall compliance were carried out to investigate the effect of wall elasticity on the wall shear stress and wall solid stress. Canonical waveforms of flowrates and pressure in the carotid arteries were imposed for the boundary conditions. Comparing to rigid wall model, generally, we could find an increased recirculation region at the carotid bulb and an overall reduced wall shear stress. Also, there was appreciable change of flowrate and pressure waveform in longitudinal direction. Solid and wall shear stress concentration occurs at the bifurcation apex.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.840-844
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• 2013

In this study, we try to estimate vascular compliance for management vascular disease. Because It is known the vascular compliance represents the state of the blood vessels. In general, the vascular compliance is estimated using an acceleration photoplethymogram from measured by photoplethymogram-based. The acceleration photoplethymogram is come from second derivative of photoplethymogram. By using the acceleration photoplethymogram, we can estimating vascular compliance, vascular age, vascular state. In this study, for measuring acceleration photoplethymogram we have developed a measurement device having analog filters. It has the advantage of miniaturization, low-power because it is simpler than digital filters. Using the developed device, we have estimated vascular compliance and tested the reliability of our device compare with conventional device having digital filters. As a result.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.17 no.3
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• pp.241-252
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• 2013

Objectives The purpose of this study was to investigate the effects of walking exercise on diabetes mellitus indicator and vascular compliance of type 2 diabetes mellitus adults. Methods The subjects were 2 groups; exercise group(n=11, $age=57.36{\pm}8.74$), non-exercise group(n=10, $age=59.20{\pm}5.81$). Walking exercise five or more times a week, and more than 10,000 steps per day with writing the walking diary ordered to the exercise group. For date analysis, mean and standard deviation scores were calculated, and independent t-test was performed. Result After 45 days of walking exercise, weight (p <.01), abdominal obesity rate (p <.05), body fat mass (p <.05) showed significant difference between the groups. but diabetes indicators and vascular compliance tend to decreased in the exercise group, there was no significant difference between the groups. Conclusions Walking exercise is effective in improving body composition.

• Journal of Chest Surgery
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• v.30 no.11
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• pp.1092-1096
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• 1997

Thromboelastography(TEG) enables a global assessment of hemostatic function to be made from a single blood sample, documenting the interaction of platelets with protein coagulation cascade from the time of the initial platelet-fibrin interaction, through platelet aggregation, clot strengthening and fibrin cross linking to eventual clot Iysis. Thirty-five patients(mean age 34$\pm$ 12) undergoing open heart surgery from April 1st, 1996 to August 31th, 1996 were investigated at preoperatively and immediate, one hour, and 24 hours after cessation of cardiopulmonary bypass using TEG. Comparisons were made between classic hematological indices and TEG data. There were statistically significant correlation between maximal amplitude(MA) and platelet count before CPB, activating clotting time(ACT) and TEG date(R time, K time and a angle) at 24-hour after CPB. The data on the predictive accuracy for postoperative bleeding at 24-hour after CPB, the TEG was significantly better than ACT(57%) or the coagulation profiles(43%) as a predictor of postoperative bleeding, with an accuracy rate of 100% (P=0.0043). In conclusion, TEG seems to be easy to use, clinically accurate, cost effective and provides data which can effectively manage a patient's hemostasis.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.484-493
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• 2012

Since the 1980s, there have been many research activities devoted to quantitatively characterizing and imaging human tissues based on sound speed, attenuation coefficient, density, nonlinear B/A parameter, etc., but those efforts have not yet reached the stage of commercialization. However, a new imaging technology termed elastography, which was proposed in the early 1980s, has recently been implemented in commercial clinical ultrasound scanners, and is now being used to diagnose prostates, breasts, thyroids, livers, blood vessels, etc., more quantitatively as a complementary adjunct modality to the conventional B-mode imaging. The purpose of this article is to introduce and review various elastographic algorithms for use in quasistatic or static compression type elasticity imaging modes. Most of the algorithms are based on the crosscorrelation or autocorrelation function methods, and the fundamental difference is that the time shift is estimated by changing the lag variable in the former, while it is directly obtained from the phase shift at a fixed lag in the latter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.813-820
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• 2009

This paper describes the realization of ubiquitous healthcare monitoring system using wearable pulse oximeter based on a wireless sensor network. In order to obtain information of oxygen saturation from a patient, a small size and low power consumption wearable pulse oximeter was designed. Information of oxygen saturation collected by wireless sensor node was transmitted wirelessly to a base-station for storage and display purposes via wireless sensor network. Wireless sensor nodes were programmed by TinyOS application to perform data acquisition and transmission. Lab VIEW server program was designed to monitor information of oxygen saturation and process the measured PPG (photo plethysmogram) signals to APG(Accelerated plethysmogram) signals by appling second order derivatives. PPG signals are simple and cost effective technique to measure blood volume change.

• Journal of the Korea Convergence Society
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• v.8 no.9
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• pp.347-355
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• 2017

The purpose of this study is to develop a formula for predicting weight gain after six months of smoking cessation in men. The subjects are 412 men who succeeded in quitting smoking for 6 months at public health center smoking cessation clinic. They have been undergone nicotine patch therapy and weekly counseling for 8 weeks. The final success of smoking cessation has been confirmed by urinalysis. I have measured body composition and vascular compliance before and after the program. Weight(0.98) and BMI(0.85) have shown high positive correlation. The prediction is as follows. Post Weight(kg) = 1.04636 * Pre-Weight - 0.19535 * Pre-BMI + 4.43528. The explanatory power of this estimation equation is 82.46%(<.0001). Based on these results, it is necessary to develop education and programs for effective counseling of the smoking cessation clinic. In addition, research on women is needed.