• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.2
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• pp.150-158
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• 1988

On a refrigeration compressor, damage of a discharge valve is one of the annoying troubles for an engineer. Small size compressors, having ring plate type discharge valve are recently used. Therefore, it is very important for engineers to measure and analyze strains of discharge valve. The purpose of this study is to obtain the basic data of the strain of the flexible ring valve. Measurements were performed by the strain gauge bonded on the surface of the flexible ring valve. Stress and strain of the valve were calculated by the method of uniformly loaded circular plates with a central hole. The results obtained are as follows; (1) the strain of flexible ring discharge valve in refrigeration compressor was influenced by tension and compression strain simultaneously. (2) for a given discharge pressure, the tangential and radial strains was increased with increasing discharge pressure. (3) the valve of radial strain was larger than that of tangential strain.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.880-885
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• 2000

Flow patterns and steady flow characteristics of an intake 3valve cylinder head are not obviously declared. Thus, in the study, the characteristics and limitation of intake flow coefficient which applied to multi intake valve engine are introduced. The flow coefficient and tumble characteristics are investigated by means of the steady flow test and flow visualization method. As the results, it is found that the intake flow rate is dominated by effective valve open area. In addition, this paper shows that the mass flow rate of intake 3valve engine is greater than that of intake 2valve engine and tumble flow of intake 3valve engine is superior to that of intake 2valve engine.

• Journal of Power System Engineering
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• v.18 no.2
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• pp.31-36
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• 2014

In this paper, pneumatic valve which consists of valve body, valve controller, nozzle and a multi-bender PZT actuator was suggested and fabricated. The fabricated pneumatic valve was experimented for performance evaluation. From the experimental results, we know that the flow rate of the suggested valve is 23 lpm at the pressure difference of 1bar and the maximum flow rate is 30 lpm at the pressure difference of 4 bar. The flow rates after endurance test of 9.8 million were 22.57 lpm and 28.62 lpm at the pressure difference of 1bar and 4bar, respectably. Finally, it was verified that the B10 life of the suggested pneumatic valve is over 50 million.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.151-158
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• 2007

The mechanism of power transmission from motor torque to stem thrust and the operation characteristic of each stroke position are analyzed using the diagnostic signal, and effects of differential pressure on the performance of motor operated flexible wedge gate valve are investigated. Test facility consists of 76 mm motor operated valve(flexible wedge type), pump and pipe system. Static and dynamic test are performed separately, and two differential pressure conditions are applied in the dynamic test. To evaluate the performance of valve, test signals for the torque, thrust, current, voltage and stroke length are acquired by using UDS which is diagnosis device for motor operated valve, and each diagnostic signal is analyzed and compared. The characteristic of valve performance factors such as stem factor, rate of loading, valve factor, are evaluated, and these factors are found to be severely influenced by the fluid differential pressure.

• Journal of Drive and Control
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• v.16 no.2
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• pp.30-35
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• 2019

EPPR (Electro-hydraulic Proportional Pressure Reducing) valves are pressure control valves. In this study, an independent metering valve (IMV), which is a combination of a spool valve opened and closed with the help of an EPPR valve, was discussed. The overall performance of the valve (IMV) was obtained by the respective modeling and simulation of the system. The valve investigated in this study is to be used for independent metering of hydraulic excavator actuator e.g. boom, arm, bucket etc. To design the model, continuity equations and force balance equations were used. The set of differential equations were then simulated in Simulink using ODE45 option in the configuration toolbox. The valve has to be able to control the flow rate going in and out of the cylinder separately, which is why the particular configuration was needed and selected.

• Journal of Chest Surgery
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• v.11 no.2
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• pp.185-193
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• 1978

Between April 1976 and March 1978, six cases of tricuspid valve replacement were done in the Department of Thoracic Surgery, Seoul National University Hospital. There were 4 men and 2 women and the age of the patients ranged from 17 years of the youngest to 48 years of the oldest. Most of them had characteristic symptoms of tricuspid valve disease, such as a systolic murmur audible over the lower sternum and varying with respiration, pulsatile and distended neck vein, and an enlarged and pulsatile liver. Preoperative functional levels according to NYHA Calcification were class III in 4 cases, and class IV in 2 eases. Most of the cases showed moderate to severe cardiomegaly in chest films and elevated right atrial pressure on preoperative right heart catheterization. Five of them underwent concomittent mitral valve replacement and one pulmonary valvotomy. All of them showed tricuspid insufficiency resulted from massive dilatation of annulus, destructive lesions of valve structure, or both anomalies. One postoperative hospital death was encountered and the cause of death was low out-put syndrome. All survivors showed clinical improvement and cardiomegaly regressed and left hospital in a good condition . *Attendum; Recently 2 more cases of tricuspid valve replacement with mitral valve replacement were done after this review.

• Journal of Chest Surgery
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• v.22 no.6
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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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• v.33 no.2
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• pp.160-166
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• 2000

Background: The purpose of this study is to evaluate and analyze the surgical results in patients undergoing operations for multiple for multiple valvular heart diseases. Material and method: From April 1982 to June 1997 multiple valve replacement was performed in 150 patients mitral and aortic valve replacement were done in 135 patients mitral and tricuspid valve replacements in 10 patients triple replacements in 4 patients and aortic and tricuspid valve replacement in 1 patient. Of the valves implanted 157 were St. Jude 104 Duromedics 20 Carpenter-Edwards 6 Bjork-Shiley 6 Ionescu-Shiley and 2 Medtronics. Result: The hospital mortality rate was 10.7% (16/150) and the late mortality rate was 7.2% (8/134) The mortality rate was high in early operative period but decreased with time. The causes of death were low cardiac output in 9 sudden death in 3 congestive heart failure in 3 bleeding in 2 cerebral thrombosis in 1 leukemia in 1 multiorgan failure in 1 and so on . The actuarial survival rate excluding operative death was 83.1% at 15 years. Conclusion: With a follow-up now extending to 15 years the multiple valve replacement continues to be reliable procedure with relatively low mortality and morbidity.

• Journal of Chest Surgery
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• v.21 no.3
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• pp.479-487
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• 1988

Valve replacements in 82 children, aging up to 15 years[mean 11.67 years] were done at Seoul National University Hospital during 13 years period from 1974 to 1986. The patients were composed of 5] males and 31 females and 50 patients had acquired heart disease and 32 patients congenital heart disease. 75 patients received single valve replacements, 6 patients double valve replacements, 1 patient triple valve replacement, and among all of them, 11 patients redo-replacements. The bioprosthetic valves have been applied to 58 patients and prosthetic valve to 24 patients and the latter was the main artificial valve since 1984. Among the 69 patients who had definite post-operative records, the overall mortality was 27.5%[20.3% was early mortality and 7.2% late mortality] and the overall mortality was lowered to 4.3% since 1984. There were early post-operative complication rate of 26.1% and late complication rate 34.8%, and among the latter, the valve failure rate was 11.4% patient-year, and the thrombo-embolism rate 1.76%/patient-year. 55 patients among the survivals after post-operative 1 month, were received follow-up with various anticoagulating medication for total 2046 patient-months[mini-mum 1 month to maximum 90 month, mean 37.2*25.44 months] and actuarial survival rate was 82*8% at 5 years and valve failure free and thrombo-embolic free survival rate were 61*8% and 90*3% respectively. And among them, valve failure free survival `rate of tissue valve were 91*6% at post-operative 2 years, 78*3% at 3 years, 59*9% at 4 years, 54*10% at 5 years, 53*15% at 6 years, so markedly decreased at 3-5 years post-operatively. These results suggest that cardiac valve replacement in children have been effective therapeutic method though various problems are still remained, and the choice of valve should be prosthetic valve mainly due to its durability at the present.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.1
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• pp.30-38
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• 1987

One of the important characteristics of a disk valve is the thrust force. This thrust force has close relationship to the clearance between valve and valve seat in the disk valve. When the clearance is very small, it is very important to analyze the thrust force. This paper deals with the variation of the thrust force by comparing the experimental ed results and theoretical results in accordance with d the valve clearance. In case of the theoretical problems, the pressure gradient of the radial flow in a narrowly spaced disks was calculated by Sui Lin and Pai-Mow Lee already. Therefore, the thrust force of the disk valve was computed by utilizing this pressure gradient in the radial flow. In the experiment, the hydraulic oil which has high viscosity was used. Making the comparative study of the calculated results and the experimental results, the characteristics of the thrust force in the disk valve were investigated. The results obtained are as follows: 1. When the disk valve clearance was comparatively small, the experimental values had fairly good agreement with the calculated values independently of inlet pressure and valve size. 2. When the disk valve size was constant in the wide range of the disk valve clearance, the lower the inlet pressure was, the better the agreement between the experimental values and the calculated values was. 3. In case of the small clearance, the thrust force was depended on the outer diameter of the disk valve. In opposite case the thrust force was constant as the disk valve size varied.