• Journal of Chest Surgery
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• 제7권2호
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• pp.189-200
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• 1974

The mitral valve replacement with Beall prosthetic valve was performed on three patients, and double valve replacement. aortic and mitral valve, was performed in this department.1) The preoperative studies about the first case were compatible with mitral steno-insufficency.The diseased mitral valve was replaced with the medium sized Beall prosthetic valve under the cardiopulmonary hypass using hypothermic hemodilution technique. The total perfusion time was eighty minutes. Immediate postoperative course was smooth, but this patient was died of asphyxia due to tracheomalacia complicated after tracheostomy 3 months after operation. Autopsy on this patient revealed that no thrombus and no ball variance could be found, and endothelization on the valve cuff was satisfactory. 2) The preoperative studies on the second case were compatible with mitral insufficiency. The diseased mitral valve was replaced with the medium sized Beall prosthetic valve under the cardiopulmonary bypass using hypothermic hemodilution technigue. The total perfusion time was 123 minutes. This patient was discharged in good condition and follow-up study after 16 months revealed the patient had enjoyed healthy life. 3) The preoperative studies about the third case were compatible with aortic insufficiency and mitral stenoinsufficiency. The diseased valves were replaced with type 2 sutureless Magovern aortic valve and the medium sized Beall mitral prosthesis under cardiopulmonary bypass using hypothermic hemodilution technIque and coronary artery perfusion. The total perfusion time was 155 minutes. This patient was discharged in good condition, but thromboembolism was developed 2 months after discharge. 4) The preoperative studies about the fourth case were compatible with mitral insufficiency. The diseased mitral valve was replaced with the medium sized Beall prosthetic valve. The total perfusion time was 132 minutes. The atrioventricular block developed just after operation but converted to normal sinus rhythmn on the third postperative day. The preoperative NYHA functional classification IV was converted to Class 1 or 11 at the time of discharge and this patient enjoyed healthy life. Attendum; The fifth case, nineteen years old male with mital insufficiency underwent Beall valve replacement and his course was uneventful 2 weeks after operation.

• 전기전자학회논문지
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• 제23권2호
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• pp.675-680
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• 2019

석탄화력발전소는 저부하에서 효율 향상을 위해 변압운전으로, 고부하에서는 정압으로 운전하는 복합변압운전 방식으로 운전하고 있으며, 복합변압운전에는 2밸브 및 3밸브 전개모드로 구분되어 운영되고 있다. 각 발전소는 제작사 권고에 따라 터빈제어밸브 모드를 선택하여 운전하고 있으나 최적의 변압운전 부하범위로 운전되고 있지 않고, 각 발전소별 부하범위 또한 상이하게 구성 되어있다. 최적의 변압운전 부하범위로 설정되지 않으면 터빈밸브 교축 손실 발생에 따른 고압터빈 내부효율 저하가 발생되어 플랜트 효율이 저하된다. 이러한 문제점을 개선하기 위해 본 논문에서는 터빈제어밸브 모드별 최적의 변압운전 부하 범위를 개선하기 위해 각 부하별 열 성능 분석 방법을 통해 최적의 부하범위를 선정하고자 한다.

• International Journal of Automotive Technology
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• 제1권1호
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• pp.17-25
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• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• Journal of Chest Surgery
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• 제22권6호
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• pp.951-959
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• 1989

Between September, 1972 and September, 1989, total 359 patients were operated for acquired heart disease at Department of Thoracic and Cardiovascular Surgery, Hanyang University Hospital. A consecutive series of 293 prosthetic valve replacement was also performed during this period. The results were summarized as follows; 1. There were 141 men and 218 women, whose ages ranged from 6 to 64 years, [mean 35.5 years] 2. Out of 293 cases, mitral valve replacement was 182 cases, aortic valve replacement was 39 cases and double valve replacement was70 cases. 3. Early post-operative death was 30 cases [Mortality; 8.4 %] and late death was 9 cases in the survivors. 4. Re-operation was 30 cases and operative mortality was 10%. 5. Mean post-operative interval was 76 months. [Ranged from 216 months to 2 months] 6. Among re-operation cases, primary prosthetic valve failure was 16 cases and paravalvular leakage was 2 cases. 7. Since January 1988, 79 cases of prosthetic valve replacement were performed and then 1 case was expired. [Mortality; 1.2 %]

• Journal of Chest Surgery
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• 제25권2호
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• pp.158-166
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• 1992

From 1985 to 1990, a total of 160 new valves were implanted for 125 adult patients to whom prosthetic valve replacement had been performed [One patient had consecutive 2 reoperations]. Following data are the results from the follow-up study from January 1985 to February 1991. Mean age of the patients was 37.9$\pm$12.1 years. Mean follow-up period was 25.8$\pm$18.8 months. In bioprosthesis, mean interval between the previous operation and reoperation was 85.6$\pm$36.4 months in aortic valve, and 87.3$\pm$30.0 months in mitral valve. The causes of reoperation were prosthetic valve failure[103 patients, 81.7%], prosthetic valve endocarditis[17 patients, 13.5%], periprosthetic leakage[5 patients, 4.0%], and aneurysm of ascending aorta[1 patient, 0.8%]. Fourteen patients[11.1%] died in hospital; 5 in 22 replacement of aortic valve[22.7%], 6 in 73 rereplacement of mitral valve[8.2%], and 3 in 31 replacement of multiple valves [9.7%] Except for 3 intraoperative deaths, postoperative, major and minor complications occurred in 39 patients[31.0%]. And the actuarial 5-year survival rate of operative survivors was 95.5$\pm$8.6%.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.763-768
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• 2006

Emission reduction in the cold start period of SI engines is crucial to meet stringent emission regulations such as SULEV Emissoin reduction is the starting point of the study in the which the variable valve timing (VVT) technology may be one promising method to minimize cold start emissions while maintaining engine performance. This is because it is possible to change valve overlap and residual gas fraction during cold start and idle operations. Our previous study showed that spark timing is another important factor for reducing cold-start emissions since it affects warm-up time of close-coupled catalysts (CCC) by changing exhaust gas temperature. However, even though these factors may be favorable for reduction of emissions, they may deteriorate combustion stability in these operating conditions. This means that the two variables should be optimized for best exhaust emissions and engine stability. This study investigated the effects of valve and spark timings in idle performance such as combustion stability and exhaust emissions. Experiments showed that valve timings significantly affected engine stability and exhaust emissions, especially CO and $NO_x$, due to change in residual gas fraction within the combustion chamber. Spark timing also affects HC emissions and exhaust gas temperature. Yet it has no significant effects on combustion stability. A control strategy of proper valve timing and spark timing is suggested in order to achieve a reduction in exhaust emissions and a stable operation of the engine in a cold start and idle operation.

• 동력기계공학회지
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• 제19권5호
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• pp.93-98
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• 2015

Nuclear power plants has a number of valves, which are operating at a high temperature-high pressure and radiation environment conditions. Nevertheless, it is important to maintain the reliability of the valves to ensure safe operation of the nuclear power plant. However, the aging of the valves by increasing of years of plant operation and the system transients due to the sudden load change are working the failures of the reliability of the valve. In this paper, we evaluate experimentally the performance change according to the thermal aging of the valve. Results show that the valve stem and the actuator leakages were enlarged by the thermal aging.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.389-394
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• 2017

The limitation of flow control for a bistable fluidic valve has been investigated. The physical model of the fluidic valve includes two main flow outlets and two control flow inlets. The experiments were conducted with pressure regulators, mass flow meters, and piezo sensors to analyze flow switching characteristics of the fluidic valve. The experimental data such as pressure and mass flow rate of control flows and the switching time of the main flow was obtained with various operating conditions. The operation limit of the fluidic valve is identified, and a model equation for pre-estimating the minimum control pressure to switch the direction of the main flow has been proposed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.79-80
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• 2014

Voltage source multilevel module converter attracts more and more attention recently. The core component of the voltage source multilevel module converter is the valve based on IGBT. So the test circuit for the valve is very important, reliable test method can guarantee the converter valve design meet the operation requirement. This paper analyzes the valve voltage and current stress during the operation, and according to IEC standard test requirement, object, condition, introduces a kind of test circuit. Finally, through the simulation model, to verify the test circuit can provide the proper test condition for the voltage source multilevel module converter valve.

• 산업진흥연구
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• 제2권1호
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• pp.9-13
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• 2017

본 연구는 주택용 가스배관 체크앵글 안전밸브에 관한 것으로 긴급 발생시 1초 이내에 수동으로 차단이 가능하고, 또 손의 힘으로 가압 3kg에 터치가 가능 하도록 하고, 또 긴급시 차단 작동 후 차단 볼 지름이 7mm로 번복 사용이 가능하도록 기술 개발 하였다. 연구결과 첫째 밸브 작동 후. 평균 0.61 초로 나타났다. 따라서 안전밸브로서 사용하여도 작동에는 문제가 없는 것으로 나타났다. 둘째, 손의 힘으로 가압 3kg이내 터치에 모두 작동 되었다. 셋째, 차단 볼 지름이 7mm로 번복 사용한 결과 모두 이상 없는 것으로 나타났다. 본 연구에서 가스배관 체크앵글 안전밸브를 개발하고 기존 밸브와의 시험을 통하여 성능을 검증한 것에 의미가 있다.