• 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.508-511
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• 2008

The most landing gear use oleo-pneumatic shock strut to absorb the impact energy during touchdown. The shock strut is composed of the oil damper and the gas spring, especially the oil damper provides resistance force which is proportional to the square of landing speed. In case of high landing speed, the abnormal peak load can be occurred and transferred to the airframe structure. To prevent this, the pressure-relief valve is used to limit the damping force under the specific level. In this paper, it is presented the design process to find optimal damping and analysis results using pressure-relief valve.

• Journal of Chest Surgery
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• 제22권4호
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• pp.667-671
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• 1989

Cor triatriatum is a rare congenital malformation of the heart in which a diaphragm stretches in a transverse plane through the left pulmonary venous chamber, thus creates two subchambers. The proximal chamber connects with the pulmonary veins, and the distal one has left auricle and the mitral valve. A 3 year old boy who had Cor triatriatum underwent surgical excision of the abnormal diaphragm in March, 1989 in Chungnam University Hospital. An obliquely oriented fibromuscular diaphragm divided the left atrium into a proximal chamber which was connected to the pulmonary veins and a distal chamber which had the atrial appendage and the mitral valve. The opening in the diaphragm was 5 mm in diameter. There were no associated abnormalities. The abnormal diaphragm was completely excised. The postoperative result was excellent.

• 한국기계가공학회지
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• 제9권6호
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• pp.7-15
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• 2010

Recently, with the high performance and efficiency of machine, there have been required the multi-functions in various machine parts, such as the heat resistance, the abrasion resistance and the stress resistance as well as the strength. Fatigue crack growth tests were carried out to investigate the fatigue characteristics of high carbon steel (SM53C) experienced by high-frequency induction treatment. The Cam nose part of the Automobile's Cam shaft is strongly bumped with rocker arm or valve-lift. Therefore abnormal wear such as unfair wear and early wear occur in the surface. This abnormal wear causes a defect that bad timing open and close actions of the engine valve happen in the combustion chamber so the fuel gas will be combustion imperfect. Therefore, the cam shaft demands high hardness and wear resistance. In this study, high frequency heat treatment has been accomplished while wear test for material SM53C.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2509-2522
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• 2021

A valve assembly used in nuclear power plants must be qualified and supervised. New technical standards such as ASME QME-1 2007 particularly require detailed qualification using experiment and analysis. Particularly, diagnostic tests and engineering studies are required for qualification of ASME QME-1 2007. Among these studies, the research on the measurement of friction coefficient and packing stress is important. The irregular change of packing stress along the stroke distance occurs because of the abnormal phenomenon, which must be found and studied with quantitative methods. Packing stress should be analyzed conservatively through experimentation and analysis. In this study, various formulas were applied to measure and calculate coefficient of friction and packing stress. This study can be used in relation to qualification and supervision of packing materials. And the calculation using static diagnosis test can be used to find the packing frictional force in dynamic diagnosis test with flow pressure in a pipe. This study has made it possible to reliably consider packing frictional force generated in a valve body. And so, it is believed that more margin can be secured when evaluating the capacity of valve actuator by applying the accurate frictional force generated in the valve assembly.

• Journal of Chest Surgery
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• 제19권2호
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• pp.300-305
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• 1986

We have experienced two cases of ascending aorta aneurysm with aortic regurgitation in Marfan`s syndrome. There were abnormal findings in cardiovascular system associated with abnormalities of skeletal systems. They had total replacement of the ascending aorta and aortic valve with Bjork-Shiley`s aortic valve composite graft and reimplantation of coronary ostia on the graft. Their postoperative courses were uneventful and discharged with good clinical results for follow up.

• Journal of Chest Surgery
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• 제20권3호
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• pp.458-472
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• 1987

A heart supplies bloods of about 15, 000 liters to each human organ in a day. A normal function of heart valves is necessary to this act of heart. The disease of heart valve develops to a narrowness of a closure, resulting in an abnormal circulation of bloods. In an attempt to eliminate the affliction of heart valves, the operation method to repair with artificial heart valves has been developed and saved numerous patients over past 30 years. This replacement operation has been performed since early 1960`s in Korea, but all the artificial heart valves used are imported from abroad with very high costs until recent years. The artificial heart valve using pyrolytic carbon has been developed at KAIST, which was proved to be stable in the mechanical performance and durability. Therefore, the in viva performance of this valve was examined through animal tests. The artificial heart valves used in this study are tilting disc type valves, in which the disc were made of graphite coated with pyrolytic carbon and the cages were made of titanium. In viva testings of these valves were performed in 12 dogs, in which right ventriculo-pulmonary arterial [Croup I] or inter-aortic [Croup IV] valved conduit was implanted using polytetrafluoroethylene conduits containing KAIST valve and aortic valve [Group II] or pulmonary valve [Croup III] was replaced by a KAIST valve with a 21mm or 19mm tissue annulus diameter. In group I and II, pre-and post-operative transvalvular pressure gradient was measured and compared with other prosthetic valves. During post operative period laboratory examination was performed including hemoglobin, hematocrit, red cell count, white cell, lactic acid dehydrogenase and platelet. The eight surviving dogs were sacrificed and autopsy was performed at 2, 6, and 8 weeks. KAIST valve has low transvalvular gradient and relatively high orifice area. Average ventriculo-aortic peak systolic transvalvular gradient was 14 mmHg in 21 mm valve and 19 mmHg in 19 mm valve. The valve has slight intravascular hemolysis effect. Thrombogenic effect of low polishing quality and eddy currents around small orifice is high. The valve has vulnerability of disc movement. These animal tests suggest that the improvement of the heart valve design, surface polishing state and prescription methods.

• 비파괴검사학회지
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• 제30권2호
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• pp.110-115
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• 2010

발전용 밸브 내부의 누설은 냉각 기능 상실 및 방사선물질 방출 동 안전계통의 성능 저하와 수많은 에너지 손실 등 발전소 운전에 막대한 손상 및 사고를 초래하게 된다. 본 논문은 신뢰성 높은 진단 방법 개발을 위하여 국내 원자력발전소 2차계통의 누설 발생 또는 내부 부품의 손상이 발생할 수 있는 밸브를 대상으로 현장시험 및 모의누설실험시의 적외선열화상 측정 실험을 수행함으로써 단일계측방식의 불확실성을 제거하고 향후 누설진단에 대한 확대 적용을 도모하고자 하였다. 발전소 현장시험 및 밸브 모의누설시험시의 밸브 누설 상태에 따른 적외선열화상 이미지 측정 실험을 통하여, 적외선열화상 측정 방법은 밸브 누설 상태의 과정을 신속하고 정밀하게 측정 가능하며 향후 많은 종류의 밸브 누설진단에 활용함으로써 누설에 따른 막대한 에너지 손실 및 사고 예방의 유용한 기법으로 확대 적용이 가능할 것으로 생각된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.425-430
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• 2008

To verify the system performance of portable AE leak diagnosis system which can measure with moving conditions, AE activities such as RMS voltage level, AE signal trend, leak rate degree according to AE database, FFT spectrum were measured during operation on total 11 valves of the secondary system in nuclear power plant. AE activities were recorded and analyzed from various operating conditions including different temperature, type of valve, pressure difference, valve size and fluid. The results of this field study are utilized to select the type of sensors, the frequency band for filtering and thereby to improve the signal-to-noise ratio for diagnosis for diagnosis or monitoring of valves in operation. As the final result of application study above, portable type leak diagnosis system by AE was developed. The outcome of the study can be definitely applied as a means of the diagnosis or monitoring system for energy saving and prevention of accident for power plant valve. The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the major valves at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized temperature water and steam flowed through glove valve(main steam dump valve) and check valve(main steam outlet pump check valve) on the normal size of 12 and 18 ". The valve internal leak monitoring system for practical field was designed. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. To improve the reliability, a judgment of leak on the system was used various factors which are AE parameters, trend analysis, frequency analysis, voltage analysis and amplitude analysis of acoustic signal emitted from the valve operating condition internal leak.