• 한국기계기술학회지
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• 제13권2호
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• pp.79-84
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• 2011

In general, a valve body of the automatic transmission(AT) is controlled by the clutch, the brake and lubricating oil flow in a hydraulic system and lubricant flow for each valve can be adjusted independently. To increase the lifetime of AT, the lubrication flow rate in a valve body for a 6 speed AT based parallel hybrid electric vehicle must be provided with proper oil distribution and control. In this study, we carried out several experiments without the inner parts of AT and with a AT assembly. The variation of the flow rate on oil temperature and pressure between an oil supply port and the outlets of the lubrication port was evaluated and analyzed. In the case of AT without the inner parts, it was evident that as the oil required for an operation of the clutch and brake was discharged from the outlet port, the flow rate from each lubrication port is decreased. However, the flow rate of the AT assembly was slightly increased. In addition, the lubrication flow rate was increased with increasing the oil temperature, and also it was reduced with increasing the oil pressure. Details of the resulting data are discussed.

• 한국수자원학회논문집
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• 제52권4호
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• pp.291-300
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• 2019

상수관망시스템 내 관로가 파손될 경우, 수리를 위해 파손 관로와 인접한 밸브를 차폐하게 된다. 이때, 밸브 차폐로 인해 관망의 일부분이 고립되어 용수공급이 차단되는 단수구역이 발생하게 된다. 단수구역은 파손 관을 포함한 직접고립지역과 직접고립지역으로 인해 의도치 않게 수원으로부터 물 공급이 차단되는 간접고립지역으로 구분된다. 따라서, 관 파손에 의한 단수구역 및 단수용량은 시스템 내 설치된 밸브의 개수와 위치에 크게 영향을 받게 된다. 본 연구에서는 상수관망시스템 내 최적의 밸브위치를 결정하기 위해 최적화 모형을 개발하고 적용하였다. 예시 관망을 대상으로 단수용량 최소화를 목적함수로 설정한 단목적 최적화와 단수용량과 밸브 설치비용을 동시에 최소화하는 다목적 최적화를 각각 수행하였으며, 두 가지 모형을 통해 도출된 최적 밸브설치 결과를 비교, 분석하였다.

• 한국가스학회지
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• 제22권6호
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• pp.16-27
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• 2018

대한민국 정부에서 2014년부터 LPG배관망과 LPG소형탱크를 도시가스 공급망 개설이 어려운 산간이나 도서지역에 보급하는 사업을 시작했다. 마을단위와 군단위로 LPG집단공급시설을 설치하면서 기존의 가스공급 압력이 아닌 10배 이상의 높은 준저압(25kPa~100kPa)으로 소비자에게 공급하게 되면서 가스사고의 위험성이 높아졌다. 기존의 가스공급압력보다 10배 이상 높은 압력이기 때문에 가스가 누출 되었을 때 빠른 속도로 많은 양이 누출하게 된다. 이에 준저압 가스배관의 안전성 확보를 위해 과류차단밸브가 필요하게 되었지만, 국내에서는 준저압 매몰배관용 과류차단밸브가 미개발되어 있으며 보급 또한 되어 있지 않는 상황이다. 이에 한국가스안전공사에서는 과류차단밸브의 국산화를 위해 과류차단밸브를 기개발한 해외의 성능기준과 제품을 조사 중에 있으며, 과류차단밸브의 성능평가를 위해 성능시험설비를 구축하여 준저압 연료가스 매몰배관용 과류차단밸브를 연구 개발 중에 있다.

• 한국추진공학회지
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• 제17권6호
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• pp.113-119
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• 2013

발사체 연소기용 산화제 개폐밸브는 비교적 간단한 개폐 작동을 통해, 액체산소를 연소기에 공급 또는 차단한다. 고압, 고유량, 극저온의 액체산소를 운용 유체로 사용할 뿐만 아니라, 설계유량 대비 밸브 차압 또한 낮아야 하는 상당히 까다로운 개발요구조건을 가지고 있다. 본 논문에서는 현재 개발 중인 연소기용 산화제 개폐밸브의 밸브 과도 응답과 같은 기본적인 밸브 특성과 함께, 밸브 성능을 좌우하는 핵심 부분이라고 할 수 있는 밸브 공압 구동부 및 포핏/시트부의 개발 내용을 소개하였다. 밸브의 과도 응답 특성 해석 결과가 시험 측정결과와 매우 잘 일치하는 것을 확인하였으며, 구동 공압부 및 포핏/시트부 구조해석을 통해 밸브 무빙파트의 접촉면 반발력과 마찰력을 정량적으로 평가하였다.

• Journal of Chest Surgery
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• 제19권1호
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• pp.75-82
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• 1986

The use of the Angell-Shiley porcine xenograft cardiac valve was limited in number at Seoul National University Hospital chiefly because of the cessation of supply from the manufacturer, Forty-eight Angell-Shiley valves along with the 5 other mechanical or tissue valves were used in 46 patients during the period from 1977 to 1980, and a total of consecutive cases was studied for their early and long-term clinical results. The operative mortality rate was 4.3%; no death after single and 2 deaths after double valve replacement within 30 days of surgery. The 44 early survivors were followed up for a total of 171.6 patient-years and a mean of 46.8$\pm$31.1 months. Four died during the follow-up period with a linealized late mortality rate of 2.33%/patient-year. Four patients had experienced 5 episodes of thromboembolism and one died; a linealized incidence of 2.91% emboli/patient-year. A single case each had a bleeding complication related to the anticoagulants, 0.58% bleeding/patient-year, and prosthetic valve endocarditis, 0.58% endocarditis/patient-year. The clinical improvement was excellent by 70% of the survivors having no cardiac symptoms at the end of the follow-up. The actuarial survival rates were 89.9$\pm$4.9% at 5 years and 69.2$\pm$15.0% at 9 years after surgery. The probabilities of freedom from thromboembolic complication were 92.3$\pm$5.5% and 80.9$\pm$9.0% at 5 and 9 years after surgery. And, the probability of freedom from overall valve failure was 83.4$\pm$6.3% at 5 years and it declined sharply down to 55.9$\pm$22.2% at 9th year of the follow-up. These results are comparable with those in the major reports, except a more accelerated and time-related increases in valve failure after 5 or 6 years after operation with the Angell-Shiley valve. The durability of the xenograft tissue valve remains as the most important debate and the need of more durable tissue valves was also discussed.

• 유공압시스템학회논문집
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• 제4권1호
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• pp.1-6
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• 2007

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, two pilot operated check valves, two flow control valves. The capacity coefficients of flow control valves should be adjusted for the hoist to operate at moderate speed and minimize the hydraulic energy loss. However, it is difficult to adjust the four capacity coefficients of flow control valves by trial and error for optimal operation. The steady state model of the hoist hydraulic system is derived and the optimal capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• 한국정밀공학회지
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• 제22권3호
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• pp.123-129
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• 2005

The unbalance of the power output, noise, and vibration is happened by the disproportionate pressure variation in the cylinder. For this reason, decrease of the pressure in the cylinder and increase of the residual gas effect on the engine performance. If the abnormal combustion is continued, the crack would be occurred in the engine block. And it could be broken down. For the normal combustion of the SI engine, it is important to supply the balanced mixture by each operating condition. In this study, it was tested the combustion characteristics in the cylinder according to the abnormal adjusting of intake & exhaust valve. This test is willing to set a basic data's analysis fur developing an automotive diagnosis system by analyzing the pressure in the cylinder, the output signal of MAP sensor, the exhaust gas, etc.

• Tribology and Lubricants
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• 제14권3호
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• pp.24-31
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• 1998

A new type squeeze film damper is proposed and its dynamic characteristics are investigated experimentally. The new one has a pulsating flow supply system which properly adds high pressure oil to the oil film of the damper so that the rotor vibration can be controlled actively. As the result, the amplitude of the rotor vibration can be reduced considerably. The algorithm which compensates the phase lag of servo valve as well as the high-performance servo valve are required in order that a new type squeeze film damper can be more effective device to attenuate the rotor vibration than typical one.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.366-372
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• 2000

In a power plant, it is generally accepted that a turbine governor system is necessary to control amount of steam supply toward the turbine system. There are many kinds of trouble at this governor system, which is recognized one of the most sensitive systems in the power plant. Especially we have experienced the internal leakage of motorization oil of servo valve. In the study, we investigated the mechanism of an internal leakage such as erosion by foreign materials and corrosion by chemical reaction between chloric healed oil and motorization oil. A precautionary measures is also performed to help the field service engineers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.103.6-103
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• 2001

Glaucoma is an eye disease which is caused by abnormal high IOP (Intra Ocular Pressure) in the eye. High IOP is caused by the aqueous humor which is produced consistently but not drained due to the malfunction of the trabecular system which has a role of draining the aqueous humor into the venous system. Currently, there are some methods to treat glaucoma, Among these, the use of implants is increasing in these days due to many problems in other methods. However, conventional implants are passive implants and have critical disadvantage. Therefore, it is needed to develop a new implant using MEMS structure which is capable of controlling the IOP actively and copes with personal difference of patients. An active glaucoma implant consists of the valve actuator, pressure sensor, controller, and power supply. In this paper the valve actuator is considered. We make experiments and simulations with the fabricated ...