• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• Journal of Chest Surgery
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• v.16 no.4
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• pp.458-469
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• 1983

Between October, 1978, and December, 1982, Glutaraldehyde-stablized pericardial xenografts [Ionescu-Shiley valve] were used for heart valve replacement in 409 patients.[251 mitral, 49 aortic, 11 tricuspid, and 98 multiple valve replacement]. There were 31 early deaths [7.6%], and 371 operative survival were observed for a total of 507.6 years over a period of 1 to 44 months. [mean 17 months]. Actuarial analysis of late results indicates an excepted survival rate at 4 years of 86.25.4% for patients with mitral, 79.37.1% for patients with aortic valve replacement. Actuarial survival rates for total patients at 4 years was 77.88.2%. The rate of systemic embolism has been 1.6% per patient-year for mitral and 1.8% per patient-year for aortic group in the presence of anticoagulation treatment. Among the 6 embolic episodes, 2 patients were died. The incidence of hemorrhagic complication was 1.3% per patient-year for anticoagulated patients. There were 6 confirmed valve failures, five in mitral and one in aortic position. Re-replacement of destructed valve was performed in one patient and others were treated medically. Among the 6 episodes, 3 occurred in children [Below 15 years], it account almost 9 times higher than adult. Our clinical data compare very favorable with those obtained with other available prostheses and tissue valves, but it should be considered to give short-term anticoagulation therapy to hemodynamically stable patients and aortic valve patients, and other prosthetic valve must be considered to use in children.

• The KSFM Journal of Fluid Machinery
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• v.11 no.3
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• pp.43-49
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• 2008

The pump control valve is a butterfly valve that has an eccentric rotating axis. It is not only used as a butterfly valve to control the flow rate or pressure, but also as a check valve to prevent backward flow. A new design method of eccentric rotating axis is proposed to design the valve. The height of the rotating axis is determined through flow field analysis. A general purpose of computational fluid dynamics software system, Fluent is used to simulate the fluid flow. Flow field analysis is performed for various heights of the rotating axis and different opening angles of the valve. A characteristic function is defined for estimating the flow characteristics based on the results of flow field analysis. The characteristic function is defined in order to determine the height of the rotating axis. An optimization problem with a characteristic function is formulated to determine the amount of eccentricity. The height of the Totaling axis of the valve is determined through solving the optimization problem.

• Journal of Drive and Control
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• v.18 no.3
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• pp.8-15
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• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• Journal of Chest Surgery
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• v.31 no.3
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• pp.242-246
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• 1998

From January 1988 to December 1995, 27 patients, 11 men and 16 women, underwent surgical intervention at our institution for prosthetic valve dysfunctions. The mean age was 43.5$\pm$12.2 years. Seventeen(63.0%) patients had the mitral valve replacement, 8(29.6%) the aortic valve, 1(3.7%) the aortic composite graft, and 1(3.7%) the tricuspid valve. Mean follow-up period was 49.5$\pm$30.9 months. In 12 bioprostheses, mean interval between the previous valve replacement and the reoperation was 104.9$\pm$34.9 months. The causes of redo surgery were structural deterioration of the prosthetic valve (12/12, 100%), paravalvular leak (2/12, 16.7%), and prosthetic valve endocarditis(1/12, 8.3%). In 15 mechanical prostheses, the mean interval was 55.2$\pm$43.7 months. The causes of redo surgery were pannus formation (8/15, 53.3%), paravalvular leak(4/15, 26.7%), and valve thrombosis(3/15, 20.0%). Posto- perative complications occurred in 7 patients (25.9%). There was no intraoperative death. But one patient, who received mechanical aortic valve replacement died on the 3rd postoperative day due to low cardiac output and multiorgan failure.

• Journal of Chest Surgery
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• v.40 no.12
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• pp.817-824
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• 2007

Background: There are two choices for heart valve replacement-the use of a tissue valve and the use of a mechanical valve. Using a tissue valve, additional surgery will be problematic due to valve degeneration. If the risk of additional surgery could be reduced, the tissue valve could be more widely used. Therefore, we analyzed the risk factors and mortality of patients undergoing repeated heart valve replacement and primary replacement. Material and Method: We analyzed 25 consecutive patients who underwent repeated heart valve replacement and 158 patients who underwent primary heart valve replacement among 239 patients that underwent heart vale replacement in out hospital from January 1995 to December 2004. Result: There were no differences in age, sex, and preoperative ejection fraction between the repeated valve replacement group of patients and the primary valve replacement group of patients. In the repeated valve replacement group, the previously used artificial valves were 3 mechanical valves and 23 tissue valves. One of these cases had simultaneous replacement of the tricuspid and aortic valve with tissue valves. The mean duration after a previous operation was 92 months for the use of a mechanical valve and 160 months for the use of a tissue valve. The mean cardiopulmonary bypass time and aortic cross clamp time were 152 minutes and 108 minutes, respectively, for the repeated valve replacement group of patients and 130 minutes and 89 minutes, respectively, for the primary valve replacement group of patients. These results were statistically significant. The use of an intra aortic balloon pump (IABP) was required for 2 cases (8%) in the repeated valve replacement group of patients and 6 cases (3.8%) in the primary valve replacement group of patients. An operative death occurred in one case (4%) in the repeated valve replacement group of patients and occurred in nine cases (5.1%) in the primary valve replacement group of patients. Among postoperative complications, the need for mechanical ventilation over 48 hours was different between the two groups. The mean follow up period after surgery was $6.5{\pm}3.2$ years. The 5-year survival of patients in the repeated valve replacement group was 74% and the 5-year survival of patients in the primary valve replacement group was 95%. Conclusion: The risk was slightly increased, but there was little difference in mortality between the repeated and primary heart valve replacement group of patients. Therefore, it is necessary to reconsider the issue of avoiding the use of a tissue valve due to the risk of additional surgery, and it is encouraged to use the tissue valve selectively, which has several advantages over the use of a mechanical valve. In the case of a repeated replacement, however, the mortality rate was high for a patient whose preoperative status was not poor. A proper as sessment of cardiac function and patient status is required after the primary valve replacement. Subsequently, a secondary replacement could then be considered.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.3
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• pp.239-248
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• 2017

According to the structure, solenoid valve can be categorized as spool valve or poppet valve. While various research on spool valve which has simple structure and fine susceptibility to contamination has been conducted, poppet valve which has less susceptibility to contamination and advantage in a long time operation still need much research because of its complicated structure. In order to design the poppet valve, various parameters such as the diameter of the poppet, the angle of the poppet, the diameter of the disk, the spring stiffness, the spring preload and flow path structure should be considered. Conventional studies on poppet valve usually take only one design parameters and did not much focused on the effect of the parameters on flow characteristics. In this paper, the change of the flow characteristics according to the design parameters of the poppet valve for 3/2Way solenoid valve is analyzed. The previous studies and the results of initial model analysis was referred for the selection of the design parameters. The effects of design parameters on maximum pressure, minimum pressure, and pressure drop was examined using analysis of means(ANOM).

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.1-11
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• 2004

Combustion and fuel distribution characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine, Swirl ratio were varied between 1.2, 2.3, and 3.4 following Ricardo swirl number(Rs) definition, Rs=2.3 showed the best results with lower cycle-by-cycle variation and shorter burning duration in the lean region while strong swirl(Rs=3.4) made these worse for combustion enhancement. Excessive swirl resulted in reverse effects due to high heat transfer and initial flame kernel quenching. Fuel injection timings were categorized with open valve injection(OVI) and closed valve injection(CVI). Open valve injection showed shorter combustion duration and extended lean limit. The formation of rich mixture in the spark plug vicinity was achieved by open valve injection. With higher swirl strength(Rs=3.4) and open valve injection, the cloud of fuel followed the flow direction and the radial air/fuel mixing was limited by strong swirl flow. It was expected that axial stratification was maintained with open-valve injection if the radial component of the swirling motion was stronger than the axial components. The axial fuel stratification and concentration were sensitive to fuel injection timing in case of Rs=3.4 while those were relatively independent of the injection timing in case of Rs=2.3.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1261-1262
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• 2011

• Journal of Chest Surgery
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• v.29 no.3
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• pp.326-330
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• 1996

Despite anticoagulation, systemic embolization and anticoagulant-related hemorrhage are the major drawbacks of heart valve replacement with mechanical prostheses. Among many predisposing factors, inadequacy of anticoagulation is the most important one. Surgery can be reserved for patients who do not response to thrombolytic therapy, We have experienced 3 cases of prosthetic valve thrombosis treated by thrombolytic therapy by use of urokinase and heparin. Two patients fully recovered and returned to their employments and active lives but 1 patient,died of intracerebral hemorrhage and infarction. We report prosthetic valve thrombosis thrombolytic therapy with urokinase and heparin which was detected and serially followed by 2-dimensional echocardiography, cinefluoro copy, and monitoring of Swan-Ganz catherterized pressures.