• 대한기계학회논문집B
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• 제28권10호
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• pp.1163-1171
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• 2004

The variation of spark plug location have one of the effects on combustion characteristics. Several parameters of the effect on combustion characteristics are shape of combustion chamber, the spark plug position, turbulence flow and so on. This paper presents an experimental study according to variation of spark plug protrusion and PDA valve which have effects on characteristics of combustion and emission in single cylinder gasoline engine. Also, this paper emphasized that combustion stabilization was making by way of the reinforcement of the turbulent flow with the PDA valve. A feasibility and necessity of combustion pressure based cylinder spark timing control according to spark plug protrusion has been examined. So, this was obtained COV$\_$imep/ and the mass fraction burned(MFB) and the specific fuel consumption(sfc). Using the results of the test, the effects of the variable spark plug location and PDA valve can be improved fuel consumption and be available for the combustion stability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3074-3079
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• 2007

The conventional control valves have been used at the locations occurring high differential pressure and high temperature which causes cavitation, flashing, severe vibration due to abrupt flow change, and sudden pressure drop. Previous studies concerning control valves focused to prevent damage of valve trim due to the internal leak and low flow rate. The newly designed helical trim of control valve has been installed at the location of high pressure change and high temperature in a power plant, and operated for evaluation. It is confirmed that the new control valve developed in this study generates flow characteristics in comparison with previous helical trim of control valves.

• 한국산학기술학회논문지
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• 제10권3호
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• pp.500-506
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• 2009

본 논문은 주요 부위에 대한 정적음력 시뮬레이션을 통해 PFA 라이닝 플러그밸브 본체의 설계자를 지원하는 것을 주된 목표로 한다. CAD 작업을 통해 생성된 형상 모델을 스텝(step)파일로 변환하여 해석작업에 사용한다. 전문적인 해석경험이 없는 밸브 생산업체의 설계자가 형상 모델에 대한 인장, 굽힘, 비틀림 모멘트 등을 계산하는 과정을 이해함으로써 구조적 취약점을 사전에 파악하고, 제품에 반영하여 제품 신뢰도 및 설계효율 증대에 기여할 수 있는 기본적인 방안을 제시하고자 하였다.

• Journal of Chest Surgery
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• 제22권6호
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• pp.1001-1012
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• 1989

In 1968, Carpentier and his associates introduced glutaraldehyde as a compound for preparing cardiac tissue valve, and this technique has provided a considerably more suitable and durable tissue valve substitute. To increase further durability of valve tissue, Reis and his colleagues designed a flexible stent to reduce the stress on the heterogeneous tissue valve mounted. However with the advent of more innovative mechanical valve currently, many bioprosthetic valves are being substituted by mechanical valves at our department of cardiothoracic surgery because of bioprosthetic valve failure. Main cause of bioprosthetic valves failure were calcification or/and tear of tissue valves. The purpose of this retrospective study is to clarify the relationship between the patients clinical profile during implantation of tissue valves and pathologic features of the failed bioprosthetic valve. From March, 1982 through June, 1988, 53 bioprosthetic heart valves that had been ex-planted from 45 patients at the department of cardiac surgery of Yonsei University Hospital were subjected to this study. The patients were 10 to 65 year-old [mean age: 30.3 yr] with 17 males and 28 females. Re-replacements of prosthetic valves were carried out twenty nine in mitral position, eight in aortic position and eight in both aortic and mitral position simultaneously. The grading and location for calcification of valves were verified by radiograms. The calcification of the explanted valves leaflets was graded from 0 to 4 plus according to Cipriano and associates method. The types of tear and perforation of leaflet were classified into four types as Ishihara has adopted initially in 1981. In younger age group under thirty three years, explanted tissue valves were significantly more affected in terms of grades of severity of valve calcification as compared with older age group [p < 0.035]. Valve calcification appeared more severe in male as compared to female [p< 0.002]. Ionescu-Shiley bovine pericardial bioprosthetic valves showed more severe calcification than Hancock porcine tissue valves [p< 0.035]. Calcium deposit was found very prevalent at the area of commissural attachment [86 % of all]. Type I of valve rupture was shown to be related with simultaneous calcification. However, the relation of explanted valve position, duration of implanted prosthetic valve, atrial fibrillation and anticoagulant therapy to the severity of bioprosthetic valve calcification were not significantly clear statistically [p > 0.05].

• 한국기계가공학회지
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• 제16권5호
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• pp.78-84
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• 2017

Compared to other types of power, hydraulic energy is the most commonly used for heavy vehicles and ships because it has fewer location and space constraints, and its controllability can be maintained even under adverse conditions. Operators have controlled a main control valve of ship winches by pushing or pulling the lever, which is directly connected to the spool. However, because of the spatial arrangement, the importance of remote control valves has emerged. In this paper, experiments of the hysteresis characteristics were performed by analyzing the remote-control valve using a valve tester and RA2300. The validity was verified by comparing with the analytical model using SimulationX as the hydraulic analysis program. This study examined the effects of the spool's notch (Non, End-mill, and Spherical) and the effects of stiffness and pre-load of the spool spring on Spool stroke, open area, and hysteresis characteristics. It is considered possible to reduce the cost and the, trial and error process in designing remote-control valves in the future.

• 한국수소및신에너지학회논문집
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• 제28권1호
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• pp.106-112
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• 2017

The present study describes flow induced noise generated from a ball valve used for a gas pipeline. Noise generation from a ball valve mainly induces by interference between unstable(or fluctuating) leakage flow and pipe wall when the ball valve is working closed or opened. To measure the positions of the noise source and the amplitude of noise with respect to measuring frequencies, a commercial acoustic camera is introduced. Noise characteristics generated by the ball valve have been performed by four valve opening rates: 30, 50, 70 and 100 percents. It is noted that 100 percent opening rate means that the valve is fully opened. Throughout the experimental measurements using the acoustic camera, the location of the noise source and the noise amplitude with respect to the frequencies for the test ball valve are clearly evaluated. It is found that the dominant frequencies come from the fluctuating flow at the downstream of the ball valve for four opening rates are observed between 3,000Hz and 3,200Hz. Maximum noise amplitude comes from the ball valve reaches 75dB at the valve opening rate of 50 percent.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.78-83
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curls extension of Lighthills. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.657-658
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• 2006

Recently, the micro on-off valves have been focused on core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for bio-medical applications. A key characteristics for micro valve, operated by compressed air, are high speed response and great repeatability. Indeed, it is also important to keep the pressure on the cross-sectional area of the poppet to be constant regardless of the fluctuation of the pressure exerted on the ports. In this study, we have designed and analysed the high-speed and high flow rate micro on-off valve using the analogy of equivalent magnetic circuit and Finite Element Method(FEM) respectively. In case of poppet, flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.463-468
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• 2015

This study describes the effect of upstream curved pipe on internal flow characteristics ball valve. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The upstream curved pipe - ball valve model was assumed that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of pipe and operating condition of pipeline were from report of Alaska pipeline project. The three curvature and three location of upstream curved pipe were analyzed. The results shows that there are typical flow patterns at ball valve and the upstream curved pipe makes some differences to the internal flow of ball valve.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2245-2252
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• 2005

Thermal stratification in the branch piping of power plants can be generated by turbulent penetration or by valve leakage. In this study, a numerical analysis was performed to estimate the thermal stratification phenomenon by in-leakage in the SIS branch piping of nuclear power plant. Leakage rate, leakage area and leakage location were selected as evaluation factors to investigate the thermal stratification effect. As a result of the thermal stratification effect according to leakage rate, the maximum temperature difference between top and bottom of the horizontal piping was evaluated to be about 185K when the valve leakage rate was about 10 times as much as the allowed leakage rate. For leakage rate more than 10 times the allowed leakage rate, the temperature difference was rapidly decreased due to the increased mixing effect. In the result according to leakage area, the magnitude of temperature difference was shown in order of $3\%,\;1\%\;and\;5\%$ leakage area of the total disk area. In the thermal stratification effect, according to the leakage location, temperature difference when leakage occurred in the lower disk was considerably higher than that of when leakage occurred in the upper disk.