• Journal of Chest Surgery
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• v.25 no.1
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• pp.57-65
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• 1992

St.Jude Medical cardiac valve replacement was performed in 322 patients: 191 had mitral, 58 had aortic, 72 had double valve and 3 had tricuspid valve replacement. Motality rate in early period was 2.8%[9 patients]. The most common cause of early death was low cardic output syndrome. Follow up extended from 1 to 90 months[mean: 34 months] in 292 patients among 313 in all surviving patients [93.6%]. There were thrombolic complications in eighteen patients. The probability of free from thromboembolism at 5 yerars in MVR, AVR and DVR were 84.7%, 91.8% and 90.2% respectively. And also, actuarial event free rate at 5 years in MVR, AVR and DVR were 80.1%, 82.2%, and 81.4% respectively. There were fourteen late death during follow up period: six from thromboembolism, one from hemorrhage and the others from non valve related -or unknown complications. The acturial survival rate at 5 years were 93.1% in mitral, 92.1% in aortic and 97.1% in double valve replacement. In conclusion, the performance of the St. Jude Mecanical valve compares most favorably with other artificial valves. But it remains still hazards of mechanical prosthesis such as thromboembolism and anticoagulant related hemorrhage.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.121-126
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• 1993

Artificial muscle actuators are used in various fields. Especially, they are applied to the power assist circuit to make use of their characteristics. The purpose of this paper is to and analyze the power assist circuit using an artificial muscle actuator. As a result, it is found that the operating feeling of the power assist circuit depends mainly on the flow gain of the pneumatic servo valve. The required flow gain is calculated from the proposed model, and the experimental results agreed with the calculated results.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.438-451
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• 1990

Pneumatic total artificial heart[TAH] has been clinically applied for the purpose of permanent or temporary use followed by cardiac transplantation in the patients with end stage heart diseases. In spite of the good durability of the pneumatic TAH, thrombus formation, bleeding and infection resulted in death. The Tomasu heart, which is a type of pneumatic TAH, was used in this study. This model is a modified Jarvik heart and consists of atrial cuffs, outflow vascular grafts and thin-layer seamless diaphragm type of ventricles. Cardiac outputs of the left artificial heart were measured by Donovan`s mock circulation under variable conditions of driving parameters, and an experimental artificial heart implantation was performed in 4 calves to observe the changes of hemodynamic parameters in early postoperative period and hematologic and bio-chemical changes in a long-term survival case. In the mock circulation test, cardiac output of the heart was increased with the increase of the left atrial pressure and left driving pressure. Maximum cardiac output was obtained at the heart rate of 120 to 130/min and percent systole of 40 to 45Zo under the condition of a constant left driving pressure of 180mmHg and left atrial pressure of 10mmHg. During the first 24 hours of TAH pumping, driving pressure ranged from 178$\pm$5mmHg to 187$\pm$8mmHg for the left heart and from 58$\pm$6mmHg to 78$\pm$28mmHg for the right heart. The Mean arterial pressure significantly increased between 2 and 8 hours after the start of pumping. The survival time ranged from 27 hours to 46 days. The causes of death were respiratory failure in 2 cases, mechanical valve failure in one, and left ventricular outflow obstruction due to thrombus in a 46-day survival case. This study demonstrated that Tomasu artificial heart operated effectively during the first 24 hours of artificial heart pumping, but thrombus formation around the valve holding area was the main problem in long-term survival case.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.530-535
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• 2002

Pneumatic control system has been applied to build many industrial automation systems. But most of them are sequence control type because of their low costs, safety, reliability, etc. Pneumatic servo system is rarely applied to real industrial fields because accurate position control is very difficult due to its nonlinearity and compressibility of air. In pneumatic servo control system, a pneumatic servo valve can be applied, But it is very expensive and has no advantage of low cost compared with a common pneumatic system. This paper is concerned with the accurate position control of a rodless pneumatic cylinder using on/off solenoid valve. A novel Intelligent Modified Pulse Width Modulation(MPWM) is newly proposed. The control performance of this pneumatic cylinder depends on the external loads. To overcome this problem, switching of control parameter using artificial neural network is newly proposed, which estimates external loads on rodless pneumatic cylinder using this training neural network. As an underlying controller, a state feedback controller using position, velocity and acceleration is applied in the switching control the system. The effectiveness of the proposed control algorithms are demonstrated through experiments nth various loads.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.624-632
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• 2015

A self-diagnostic monitoring system is a system that has the ability to measure various physical quantities such as temperature, pressure, or acceleration from sensors scattered over a mechanical system such as a power plant, in order to monitor its various states, and to make a decision about its health status. We have developed a self-diagnostic monitoring system for an air-operated valve system to be used in a nuclear power plant. In this study, we have tried to improve the self-diagnostic monitoring system to increase its reliability. We have implemented three different machine learning algorithms, i.e., logistic regression, an artificial neural network, and a support vector machine. After each algorithm performs the decision process independently, the decision-making module collects these individual decisions and makes a final decision using a majority vote scheme. With this, we performed some simulations and presented some of its results. The contribution of this study is that, by employing more robust and stable algorithms, each of the algorithms performs the recognition task more accurately. Moreover, by integrating these results and employing the majority vote scheme, we can make a definite decision, which makes the self-diagnostic monitoring system more reliable.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.65.2-65
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• 2002

This paper is concerned with the accurate position control of a rodless pneumatic cylinder using On/Off solenoid valve. A novel Intelligent Modified Pulse Width Modulation(MPWM) is newly proposed. The control performance of this pneumatic cylinder depends on the external loads. To overcome this problem , switching of control parameter using artificial neural network is newly proposed, which estimates external loads on rodless pneumatic cylinder using this training neural network. As an underlying controller, a state feedback controller using position, velocity and acceleration is applied in the switching control the system. The effectiveness of the proposed control algorithms are demonstrated...on/off solenoid valve, load estimation, MPWM, Artificial neural network.

• Journal of Chest Surgery
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• v.13 no.4
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• pp.405-413
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• 1980

A total of 63 patients [42 males and 21 females] underwent multiple valve replacement with artificial valves between January 1975 and August 1980 at Seoul National University Hospital. There were 38 patients with aortic and mitral valve replacement, 22 with mitral and tricuspid, and 3 with aortic, mitral and tricuspid valve replacement. The valve lesions varied from trivial to severe and most aortic and mitral valves had mixed stenosis and insufficiency, while tricuspid valves had only insufficiency. The patients were severely symptomatic in majority of the cases, and belonged to the Classes III and IV [III:45, IV:16] of the NYHA functional criteria. Hemodynamic studies were performed on all the patients. The mean pulmonary wedge pressure was remarkably increased to 19.8 mmHg in aortic and mitral valve lesions and 18.0 mmHg in mitral and tricuspid valve lesions. The mean pulmonary arterial pressure was also increased, while the cardiac index was reduced. In 1977, the average perfusion time was 245.5 minutes for aortic and mitral valve replacement and 181.6 minutes for mitral and tricuspid valve replacement. It has progressively declined to 169.2 minutes for aortic and mitral valve replacement and 123 minutes for mitral and tricuspid valve replacement in 1980. The average period of aortic occlusion also declined after the use of cardioplegic solution. Twenty deaths occurred among the 63 patients operated upon, an overall mortality rate of 30.8%. The operative mortality has declined with successive year from a level of 66.7% before 1977 to 21.1% in 1980. Fourteen patients suffered from a list of postoperative complications, which eventually resolved with adequate treatment. All the survivors were enjoying the levels of daily life activities greater than those existing before the operation.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.10a
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• pp.105-106
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• 1997

• Journal of Power System Engineering
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• v.10 no.3
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• pp.97-103
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• 2006

In this study, a position trajectory tracking control algorithm is proposed for a pneumatic artificial muscle driving apparatus composed of a actuator which imitates the muscle of human, a position sensor and a control valve. The controller applied to the driving apparatus is composed of a state feedback controller and disturbance observer. The feedback controller which feeds back position, velocity and acceleration is derived from the linear model of pneumatic artificial muscle driving apparatus. The disturbance observer is designed to improve trajectory tracking performance and to reduce the effect of model discrepancy. The effectiveness of the designed controller is proved by experiments and the experimental results show that the pneumatic artificial muscle driving apparatus with the proposed control algorithm tracks given position reference inputs accurately.

• Journal of Chest Surgery
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• v.24 no.2
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• pp.171-181
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• 1991

Result of St. Jude Medical valve replacement are presented in 106 patients who underwent operation from January 1985 through July 1989. The patient were 52 males and 56 females. Total 136 of St. Jude Medical valves were implanted; 91 in mitral position, 45 in aortic position. The hospital mortality rate was 5.7%o[6 patients] and the late mortality rate was 2.0%[2 patients]. The causes of death were low cardiac output in 5, iatrogenic right ventricular rupture in 1, heart failure in 1, ventricular arrhythmia in l. And, the causes of valve related complication were anticoagulant related hemorrhage in 5 patients[0.03% /patient-year] and thromboembolism[0.01% /patient-year] in 2 patients. In conclusion, the performance of the St. Jude Medical valve compare most favorably with other artificial valves. But it remains still hazards of mechanical prosthesis such as thromboembolism and anticoagulant related hemorrhage.