• Journal of Chest Surgery
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• v.10 no.2
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• pp.315-326
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• 1977

From 1958 to October 1977, 294 cases of acquired heart disease were operated. There were 68 cases of pericardium, 3 trauma, 2 foreign body, one cardiac thrombus, 3 atrial myxoma, 2 left atrial and 1 right atrial, 2 Budd-Chiari syndrome, and 214 valvular heart disease. Out of 214 cases of valve operation 73 valves were replaced in 64 patients. Male to female ratio was 1.46: 1. The youngest age was 14 years in male and 18 in female. The oldest was 54 years in male and 52 in female. Fifty-five cases of single valve were replaced, consisting of 47 mitral and 8 aortic valves. There were 9 double valve replacement cases which consist of 7 mitral and aortic and 2 mitral .and tricuspid valves. Six varieties of prosthetic valves, 3 ball and 3 disc types and 3 kinds of xenograft tissue valves were utilized. Beall, BjSrk-Shiley and Starr-Edwards prosthetic valves and Hancock valves were used mainly. For single valve 34. 5% and for double valve replacement 44% mortality were noted. There were 23 operative deaths out of 64 patients, over all mortality rate of 36.9%. Mortality for mitral valve replacement was 29.5%. But in recent 12 consecutive cases one death occurred, showing 8.3% mortality. In earlier days thrombocyte anti-adhesive drug dipyramidole-persantin-aspirin and/or SP 54 were adminstered. But in recent cases after heparinization, coumadin and Persantin were prescribed routinely.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.771-775
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• 2008

Concerns related to protecting, identifying, and isolating of subsystems of a water distribution network have led to the realization of the increased importance of valves in the system. The most important purpose of valves in water distribution systems is to isolate subsystems due to breakage, maintenance activities, or contamination. A subsystem called segment is isolated by the closure of adjacent valves and an efficient algorithm should identify the adjacent valves to minimize the pipe failure impact. In this paper, an algorithm to identify adjacent valves to be closed to isolate a subsystem from the remainder of a network in case of a pipe failure is presented. An application to the water distribution system in Ottawa, Canada demonstrates the developed algorithm efficiently locates the adjacent valves for the isolation of a broken pipe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.387-392
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• 2020

This paper proposes a flow-rate control system for industrial valves. Industrial valves are used in piping systems to control the flow rate and pressure. In general, valves used in pipelines are classified into globe valves, butterfly valves, and ball valves according to the shape. Motor, hydraulic, and pneumatic systems are used for operating valves. The flow meter should measure the flow rate when configuring the flow-rate control system. On the other hand, because the flow rate of the valve can be expressed by flow coefficient, a control scheme is proposed using the pressure deviation, which measures at the front and rear of the valve. The transfer function for the valve, according to the control input, was estimated using the signal compression method. Based on the induced transfer function, the disturbance observer was designed to improve the command following the performance of the valve stem. The performance of the proposed control method is compared with the flow-rate control result using the flow meter used.

• Journal of Chest Surgery
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• v.19 no.1
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• pp.83-91
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• 1986

The Carpentier-Edwards porcine xenograft valve was used in 21 patients at Seoul National University Hospital during the period between 1977 and 1979. Twenty-four Carpentier-Edwards valves were implanted along with 2 others. Three patients died within 30 days of operation, an operative mortality rate of 14.3%. Eighteen early survivors were followed up for a total 67.5 patient-years [mean, 45.0$\pm$32.0 months]. There were 2 late deaths with a linealized late mortality rate of 2.96%/patient-year; one died from cerebral bleeding [1.48% bleeding/patient-year] and the other from prosthetic valve endocarditis [1, 48% endocarditis/patient-year]. There was no case of thromboembolism. Two patients developed mitral regurgitation [2.96% failure/patient-year]. Symptomatic improvement was excellent. The actuarial survival rate and the probability of freedom from overall valve failure were 75.3$\pm$9.6% and 80.7$\pm$12.9% at 9 years after surgery respectively. During the period from October, 1968, through June, 1985, 1, 190 substitute heart valves were used in a total of 967 patients at Seoul National University Hospital; of which, 90.9% were either porcine aortic or bovine pericardial xenograft valves. For the evaluation of the xenograft tissue valves, the consecutive patients with lonescu-Shiley valve in the mitral, aortic and both positions, Angell-Shiley valve and Carpentier-Edwards valve were recently studied on the clinical ground. They were 531 patients, and 643 xenograft valves were used. The operative mortality rate was 6.97% and a linealized late mortality rate 2.94%/patient-year. A total of 490 early survivors were followed up for 917.6 patient-years [mean, 22.5 months], and 70% of patients completed the follow-up. The linealized incidences of complications were: 2.29% emboli/patient-year, 1.98% bleeding/patient-year, 1.20% endocarditis/patient-year, and 3.49% failure/patient-year. These clinical resutls are fully comparable with those in the major reports. The durability of the glutaraldehydepreserved xenograft heart valves remains as a great concern and a continuing debate, expecially for the group of patients in the pediatric age. The need of more durable material for the improved tissue valves was also discussed.

• Journal of Chest Surgery
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• v.19 no.1
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• pp.108-115
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• 1986

During 12 years period from 1974 to 1985, 76 valve replacement procedures were performed at Seoul National University Hospital in 67 pediatric patients aging up to 15 years [mean 12.3 years] and it was 7.3% of total valve replacement procedures in same period. Sixty seven patients were composed of 44 males and 23 females. Of the 67 patients, 43 patients had acquired valve lesions and 24 patients congenital valve lesions. Sixty cases received single valve replacement, 7 cases double or triple valve replacement and 9 cases redo-valve replacement. Sixty seven patients received 84 valves [65 bioprosthetic valves and 19 prosthetic valves by] 76 operations, Sixty three of 65 bioprosthetic valves had been replaced before 1983 and 15 of 19 prosthetic valves in recent 2 years. Eleven patients [14.6%] died within one month post-operatively and 8 patients [10.5%] during the follow-up period with the overall mortality rate of 25.1%. There were early post-operative complication of 23 cases [30.3%] and late post-operative complication of 27 cases [35.3%] with the total complication rate of 65.8%. In 58 patients received bioprosthetic valves, there were 14 cases of restenosis of replaced valves. Of the 14 cases of bioprosthetic valve restenosis, 8 cases received redo-valve replacement procedures without mortality in 1 5/12-5 years after initial operation but 4 cases died without reoperation and 2 cases lost during follow-up. The overall mortality and complication rate were still high but they markedly decreased during recent 2 years. So, in spite of its containing many problems, valve replacement in children is becoming safe and useful procedure in whom valve reconstructive procedures are impossible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.4937-4943
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• 2012

Butterfly valves have been used to control the flow rate of various fluids in many industries because it have unique manageability compare to other valves. The flow rate passing through the butterfly valves can be controlled according to the coefficient of capacity calculated by disk angle change. In this study, flow analysis by 3D modeling was performed to derive the coefficient of capacity to evaluate and improve newly developed butterfly valves. Also, required measurement system was established to verify the performance of the valves, and to compare with the calculated results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.129-135
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• 2016

Various type of valves are manufactured for different industrial uses. Among them, check valves are used to allow fluid to flow in one direction but not in the opposite direction. There are many different types of check valves, but Y-shaped check valves are widely used these days. Not many studies have been carried out on Y-shaped check valves and the flow coefficients obtained through numerical analysis have the problem of low reliability. In order to solve this problem, this study performed flow analysis, flow-structure coupled analysis, and flow coefficient measurement experimentally, and through these analyses derived and verified the flow coefficients and assessed the structural safety based on numerical analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.568-572
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• 2009

We present a ternary microfluidic multiplexer unit, capable to address three flow channels using a pair of control lines with two different threshold pressure valves. The previous binary multiplexer unit addresses only two flow channels using a pair of control line with identical threshold pressure valves, thus addressing $2^{n/2}$ flow channels using n control lines. The present ternary multiplexer addressing three flow channels using a pair of control lines, however, is capable to address $3^{n/2}$ flow channels using n control lines with two different threshold pressure valves. In the experimental study, we characterized the threshold pressure and the response time of the valves used in the ternary multiplexer. From the experimental observation, we also verified that the present ternary multiplexer unit could be operated by two equivalent valve operating conditions: the different static pressures and dynamic pressures at different duty ratio. And then, $3{\times}3$ well array stacking ternary multiplexers in serial is addressed in cross and plus patterns, thus demonstrating the individual flow channel addressing capability of the ternary multiplexer. Thus, the present ternary multiplexer reduces the number of control lines for addressing flow channels, achieving the high well control efficiency required for simple and compact microfluidic systems.

• Journal of Power System Engineering
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• v.21 no.6
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• pp.56-61
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• 2017

The check valves are mechanical valves that permit fluids to flow in only one direction, preventing flow from reversing. It is classified as one way directional valves. There are various types of check valves that used in a marine application. A lift type check valve uses the disc to open and close the passage of fluid. The disc lift up from seat as pressure below the disc increases, while drop in pressure on the inlet side or a build up of pressure on the outlet side causes the valve to close. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. On the other hand, optimization is a process of finding the best set of parameters to reach a goal while not violating certain constraints. The AMESim software provides NLPQL(Nonlinear Programming by Quadratic Lagrangian) and genetic algorithm(GA) for optimization. NLPQL is the implementation of a SQP(sequential quadratic programming) algorithm. SQP is a standard method, based on the use of a gradient of objective functions and constraints to solve a non-linear optimization problem. A characteristic of the NLPQL is that it stops as soon as it finds a local minimum. Thus, the simulation results may be highly dependent on the starting point which user give to the algorithm. In this paper, we carried out optimization design of the check valve with NLPQL algorithm.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.105-108
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• 1994

A comparative study was made of the valvular sounds produced by normal prosthetic valves with thrombosed prosthetic valves. Comparisons of the closing sound were made for the power frequency spectra associated with individual valves. We used periodogram approach to obtain the spectral characteristics of the valve. Spectral analysis system was tested in mock circulatory system by comparing normal valves with those produced by the same valves but having simulated thrombosis at the hinge of the valve. The heart sounds was recorded from two patients having normal mechanical valve and thrombosed mechanical valve. The estimated spectrum of the thrombosed mechanical valve displayed lower apparent peak frequency than that of the normal valve. The results showed that frequency spectra gave information pertinent to the valve malfunction. Sound spectral analysis is simple and alternative diagnostic tool for early detection of prosthetic valve mal function.