• Journal of Chest Surgery
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• v.16 no.4
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• pp.444-451
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• 1983

Valve replacement in children and adolescents, aging below 20 years [Mean 15 years 4 months], has been done at Seoul National University Hospital from March 1977 to September 1982 . Seventy-Seven patients have received 91 artificial valves 4 prosthetic valves and 87 bioprosthetic valves. 63 patients had acquired valve lesions and 14 patients had congenital valve lesions. Among the patients with acquired valve lesion, 32 patients had the history of rheumatic fever. Seventy-five patients survived operation: 12 patients [ 15.6%] died within one month postoperatively and 3 patients [3.9%] during the follow-up period with the overall mortality rate of 19.5% Thromboembolic complication occurred in 3 patients with 2 deaths: 3.9% embolic rate or 3.74% emboli per patient-year. One patient who had been on coumadin anticoagulation died from cerebral hemorrhage. Actuarial survival rate was 77.6% at 1 years after surgery, after then there were no death.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.283-290
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• 2000

To maintain the specific volumetric efficiency of a heavy-duty diesel engine, an understanding of the behavior of each part of the valve train system is very important. The stiffness of the valve train system has a strong influence on the behavior of the valve train than valve clearance, heatresistance, or the durability of parts. In this study, a geometrical cam design profile using a finite element model of the valve train system is suggested. The results of the valve behavior according to the change in stiffness is analyzed for further tuning of the valve train system.

• Journal of Chest Surgery
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• v.20 no.4
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• pp.655-658
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• 1987

Aortic annulus size was measured by two-dimensional echocardiography [2DE] in 29 patients undergoing aortic valve replacement or double valve replacement in order to predict prosthetic aortic valve size. Fifteen patients had aortic stenoinsufficiency, eleven had aortic insufficiency, and three had aortic stenosis. 2DE measurements of aortic annulus diameter, as determined from the parasternal long-axis view, demonstrated a high correlation with actual prosthetic valve size implanted at surgery [r=0.85, p<0.05]. 2DE exactly predicted actual prosthetic valve size in 8 of 29 patients [27.6%], was within 1mm of prosthetic valve size in 11 of 29 patients [37.9%], was within 2mm of prosthetic valve size in 8 of 29 patients, and was within 3mm of prosthetic valve size in 2 patients.

• 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.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.10 no.1
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• pp.58-62
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• 1999

Previously, laryngectomized patients can achieve speech with tracheoesophageal device. Tracheoesophageal speech is currently one of the best methods of postlaryngectomy voice rehabilitation. But, tracheoesophageal speakers have some troublesome with digital occlusion of tracheostoma in every speaking time. Therefore, the tracheostoma valve has been introduced since 1982, and this valve could eliminate the need of tracheostoma digital occlusion. Currently, couple of tracheostoma valves has been introduced and developed. In this article, we introduced the 3 representative tracheostoma valves. Also, we discussed their use and characteristics. Traditionally the tracheostoma valve is used in total laryngectomized patients. We introduced one case using a tracheostoma valve after near total laryngectomy. Advantage and disadvantage of Blom-Singer valve and BIVONA II valve during using in this patients are discussed.

• Journal of Chest Surgery
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• v.27 no.12
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• pp.995-1001
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• 1994

The CarboMedics valve prosthesis is a relatively new. low profile bileaflet prosthesis. During a 6 year period from Aug. 1988 to July 1994. 158 patients had CarboMedics prostheses implanted in the mitral [n=94], aortic [n=25], or aortic and mitral [n=39] in National Medical Center. Hospital mortality was 9.4% and the main cause of death was low output syndrome. Follow up was 96% complete, with 365.4 patient-years and a mean follow up of 30 months [ range 1 to 72 months ] . The overall actuarial 6 year survival rate was 91.61 3.47% and actuarial 6year freedom from all valve related complications was 73.9 7.67%. The linearized incidence of vavle related complications was as follows: thromboembolism 1.37%/patient-year ; valve thrombosis 0.82%/ patient-year ; anticoagulant related hemorrhage 0.85%/patient-year ; perivalvular leakage 0.55%/paitent-year: prosthetic valve endocarditis 0.82%/patient-year ; reoperation 1.37%/patient-year. There were no instances of structural failure. We conclude that the Carbomedics valve has a low rate of complications that further improves the quality of life in patients with heart valve prostheses.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.64-67
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• 2008

The valve applied air pressure type of high pressure packing is developed to prolong the lifetime and to enhance the airtight. The effective valve developed enables to get remove the remaining pressure through the part of valve in handle so that a separate valve to drain is no need. The character of valve developed in this experiment is high packing of valve through special form and having drain hole in stem that enables a drainage regardless the status of vale is closed or opened.

• Journal of Chest Surgery
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• v.38 no.3 s.248
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• pp.204-213
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• 2005

In spite of the improvement in the quality of artificial heart valves and surgical techniques, the incidence of the complications following valve replacement is still high. We reviewed the clinical results of the valve replacements peformed in Korean University Anam Hospital during the last 26 years. Material and Method: The data of 571 patients who received valve replacement between December 1976 and December 2003 were reviewed. Result: There were 304 cases of MVR which was the most common procedure performed. There were 122 cases of AVR, and 111 cases of AVR with MVR. Among the 47 patients who received redo operation 38 cases were redo cases including 31 cases of MVR. $32.5\%$ of the patients who had tissue valve replacement had second valve replacement with 10.2 $\pm$ 3.9 years interval. $24.3\%$ (139/571) of the patients developed valve related complications and cerebral infarction was the highest in frequency. Atrial fibrillation was related with increased complication rates and the mechanical valve replaced group had higher hemorrhagic complication rate than tissue valve replaced group. The operative mortality was $3.68\%$ and the most common cause of the failure was low output syndrome. The operative mortality was higher in the patient group who had valve replacement before the year 1990. The patient group who had mechanical valve replacement had higher operative mortality rate th;3n the tissue valve group. The 5-year survival rate was $92.2\%$ and 10 year survival rate was $85.7\%$. Conclusion: The operative mortality of valve replacement has been improved. The mechnical valve replaced patients had higher hemorrhagic complication rate than the tissue valve replaced patients and more tissue valve replaced patients received redo valve replacement.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.3
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• pp.179-187
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• 2009

This paper presents a static and dynamic characteristics of the relief valve which is a kind of direct operated pressure control valve for hydrogen compressor. The valve is consisted of a main poppet, a spring, an adjuster and a valve body. The purpose of this study is development of the simulation model for relief valve by using commercial AMESlM$^{(R)}$ tool. Poppet with sharp edge seat type and ball poppet with sharp edge seat type compare for P-Q characteristic. The dynamic simulation results are presented the operating pressure characteristics of relief valve. High pressure power unit of which maximum pressure control range is 100MPa was manufactured, and the pressure control valve was experimented using the above-mentioned power unit. The new model of pressure control valve from this results was suggested. It was confirmed that the suggested valve has a good control performance from experimental setup.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.4
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• pp.87-99
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• 1993

Nowadays, the cartridge valve can be controlled proportionally in remote place by adopting proportional solenoid and it becomes widely used as control component in hydraulic systems. Especially, multi stage proportional valve is attractive because it consumes less input power though its characteristics might slightly be defected. But, the system parameter should be carefully chosen to obtain optimistic characteristics. This study concerning three stage proportional throttle control valve is purposed to examine the influences of paameters to the dynamic characteristics. The typical transient and frequency responses of proportional throttle control valve were inspected through the experiments and compared to those derived from the theoritical analyses. And it was confirmed that the analyses are appropriate. Then the influences of various system parameters to the dynamic characteristics were examined by means of simulations. For the analyses, the basic equations derived from lumped model were linearized and the linearized equations were transformed to the transfer functions between inputs and outputs. Then the transient responses and frequency responses were obtained from transfer functions. 1. It is appropriate to estimate the dynamic characteristics of valve which has relatively sophisticated structure by means of system analyses using linearized equations. 2. Though the valve has two pilot stages, fairly good characteristics can be obtained by carefully choosing system parameters. 3. Main valve very quickly follows the movement of second pilot valve when the parameters of main valve(the oil supply passage and discharge passage fpr second pilot valve) are appropriately chosen.