• Journal of Chest Surgery
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• v.52 no.5
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• pp.368-371
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• 2019

A unicuspid aortic valve is a rare congenital malformation that frequently presents with valvular dysfunction and dilatation or aortic aneurysm, requiring combined aortic valve surgery and aortic repair. Some patients show severe valve calcification extending into the interventricular septum, possibly resulting in damage to the conduction system during debridement for valve replacement. We present a rare case of severe aortic stenosis with a unicommissural unicuspid aortic valve diagnosed by preoperative transesophageal echocardiography in a 36-year-old man. After composite graft replacement of the aortic valve, aortic root, and ascending aorta, a permanent pacemaker was placed because of postoperative complete heart block.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.2
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• pp.8-14
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• 2004

Abstract: In the oil hydraulic piston pumps the clearance between the valve plate and cylinder block plays an important role for volumetric and overall efficiency. Thus, adequate lubricational fluid film is needed for the interface. In this study, fluid film thickness is measured by a gap sensor and a slip ring under operational conditions to observe the behavior of the lubrication mechanism in detail. To investigate the effect according to the valve plate types in view of the fluid film, three different types were designed. Leakage flow rate and shaft torque were also measured to clarify the effect according to the valve plate types. A broad range of experiments were conducted to provide reasonable data on the effect of fluid film. In this experiments two main parameters were found, of which the one is the discharge pressure and the other is valve plate geometry. As a result, we found that the spherical valve plate could get more stable fluid film thickness, maintain good efficiency for high pressure range than the other types.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.197-206
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• 2006

The leakage in the water distribution system means both the loss of money and water resource. To minimize the leakage, we introduced the pressure control method using the pressure reducing valve and pump schedule. For the pressure control, the total leakage is needed to divide into each node. In this study, EPANET 2.0 was used to simulate the water networks in two selected blocks after the total leakage was distributed with each node by four ways. The leakage was allocated into each node as water measured by meter, water pressure, water faucets and Lpcd and simulated by EPANET 2.0. Regardless of the leakage distribution ways, there was no significant difference between the measured water and the estimated water pressure. Thus, the leakage distribution way using water pressures estimated by simulation could be recommended. The scenarios controlling the pressure reducing valve and pump were made in two blocks(A and B). $86,713m^3/year$ leakage in the A block and $11,442m^3/year$ in the B block could be reduced as controlling the pressure reducing valve and pump schedule. It was shown that the fifty million won a year can be saved in the A block and 6.8 million won in the B block.

• Journal of Mechanical Science and Technology
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• v.17 no.2
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• pp.246-253
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• 2003

The tribological mechanism between the valve plate and the cylinder block in oil hydraulic axial piston pumps plays an important role on high power density. In this study, the fluid film thickness between the valve plate and the cylinder block was measured with discharge pressure and rotational speed by use of a gap sensor, and a slip ring system in the operating period. To investigate the effect of the valve plate shapes, we designed two valve plates with different shapes . the first valve plate was without a bearing pad, while the second valve plate had a bearing pad. It was found that both valve plates behaved differently with respect to the fluid film thickness characteristics. The leakage flow rates and the shaft torque were also experimented in order to clarify the performance difference between the valve plate without a bearing pad and the valve plate with a bearing pad. From the results of this study, we found out that in the oil hydraulic axial piston pumps, the valve plate with a bearing pad showed better film thickness contours than the valve plate without a bearing pad.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.221-227
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• 2000

The design of the valve plate is most important to increase efficiency in the oil hydraulic axial piston pump. A theoretical study was carried out to clarify the pressure characteristics at the land of the valve plate in the oil hydraulic axial piston pump. Dynamic pressure acts on the land of the valve plate was computed numerically with discharge pressure, rotational speed and swash plate angle. Pressure distribution between the valve plate and the cylinder block also was obtained with dynamic pressure. The results are applicable to improve the design technique of the valve plate in the oil hydraulic axial piston pump.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.99-105
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• 2016

The present study has been carried out to analyze the flow characteristics with geometric shape and control conditions in subsea by-pass valve. The function of by-pass valve is to prevent reverse flow. In this study, the static analysis has been perform for analyzing fluid flow in open state. In order to consider the turbulent effect, the standard ${\kappa}-{\varepsilon}$ model was used. A variety of parametric studies, such as by-pass valve type or size, volume flow rate, leakage hole size, leakage hole position, block type, block shape, were performed. The pressure difference across the valve in the model broadened the flow channel cross-sectional area was greater than the base model for the same operating conditions. As the pipe diameter in the block decreases the pressure difference is greatly increased. The pressure difference according to block shape such as edge type and round was almost negligible. For the same Reynolds number the pressure difference was little changed according to the size of the valve.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.251-258
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• 2011

The objective of this study is to propose two empirical correlations to predict the mass flow rate through an automotive block type thermostatic expansion valve and then to evaluate the correlations. The first correlation is deduced by modifying the basic equation of the orifice meter for the mass flow rate and the second correlation is deduced by using the Buckingham's ${\pi}$ theorem. The first correlation showed very good agreement on the measured data for R134a, given by Monforte. Average relative deviation and standard deviation of it are 2.5% and 1.6%, respectively. The second correlation agreed on the same measured data with a little greater deviations. The two correlations may apply to common expansion valves which have different geometrical sizes of the same shape.

• Journal of Yeungnam Medical Science
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• v.31 no.2
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• pp.113-116
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• 2014

A 52-year-old man was referred to our hospital due to fever and myalgia that occurred 2 weeks earlier. He showed a complete atrioventricular block on his electrocardiogram, and his vital signs were unstable. On his transthoracic echocardiograph, the 1.5 cm vegetation in the aortic valve with severe aortic regurgitation suggested infective endocarditis. His transesophageal enchocardiograph showed abscess in his mitral-aortic intervalvular fibrosa and vegetation was suspected on his anterior mitral valve leaflet. The patient underwent an emergent operation for valve replacement with temporary epicardial pacing. Intraoperatively, the septal leaflet of his tricuspid valve was injured during the debridement of the abscess pocket that was extended to the membranous septum. The aortic, mitral, and tricuspid mechanical valves were replaced with annular reconstruction without complications. After 14 days of intravenous antibiotics, we successfully changed the epicardial pacemaker into a transvenous DDD-type permanent pacemaker by placing a left ventricular lead via the coronary sinus and an atrial lead in the right atrium appendage. The patient was discharged in a tolerable state and was examined uneventfully in our hospital's outpatient clinic for 8 months.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.655-662
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• 1985

From January 1985 to July 1985, prosthetic heart valves were replaced in 5 patients at Keimyung University Dongsan Medical Center. The patients included three women and two men ranging in age from 22 to 41 years. Three mitral valve replacements, one aortic valve replacement and one double valve replacement [mitral and aortic valve replacement] were done at the first valve operations. Reoperation were performed 2 to 76 months after the first operations, Prosthetic valve endocarditis occurred in 3 patients, early in one and late in two and primary valve failure occurred in 2 patients. In operative findings, vegetation in prosthetic valve endocarditis and calcification in primary valve failure were found. All except one had relatively successful operative results. One died of early fungal prosthetic valve endocarditis due to relapsed prosthetic valve endocarditis with heart failure and block.

• Journal of Korea Foundry Society
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• v.20 no.3
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• pp.181-187
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• 2000

There are two types of vacuum die casting, one is known as the chill block method, and the other is the valve block method. Efficiency of the valve block method is better than the chill block method. However purchasing and maintaining cost of the former one is very high, the latter method is popular in many small and medium die casting shops. Simple evacuation system using chill vent was prepared to investigate the effect of the air pressure, hose length and chill vent type on the pressure change in die cavity in this study. The rate of evacuation was influenced by the evacuation method, chill vent condition and hose length. Evacuation time became longer and vacuum level lower when evacuating cavity via chill vent. It took a longer time to evacuate the cavity when a longer hose was used. Vacuum level in the cavity also decreased with increase in hose length.