• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.185-188
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• 2007

Lately, the modulated EGR system that includes EGR valve and EGR cooler is being installed in diesel engines fur the purpose of the simultaneous reduction of NOx and PM. In this study. we designed and constructed a test bench for the performance evaluation of the modulated EGR system, and tested an electronically controlled EGR valve for 2.0 L diesel engines. The performance of the EGR valve was evaluated in terms of the valve lift behavior. the valve opening/closing response, and the mass flow rate through the valve. The valve lift with respect to the duty ratio of PWM signal was non-linear, and followed a different path fur valve opening and closing, that is, hysteresis. The valve opening response was concluded satisfactory falling within the usual standard response time. For the duty ratio of 40 to 60%, the mass flow rate through the valve was observed to depend on the pressure difference across the valve as well as the duty ratio, while it solely depended on the pressure difference fur the duty ratio above 60%.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.117-125
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• 2022

This study examines whether engine fuel efficiency is improved by optimization of the exhaust valve timing in a state where the intake valve timing has been optimized in a small turbo gasoline engine that has intake cams and exhaust cams with fixed valve opening periods. When the exhaust valve is opened late, the expansion stroke is longer, and the efficiency can be improved. A 2-cylinder turbo gasoline engine with 0.8 liters of displacement and an MPI (Multi Point Injection) fuel system was used. The engine was operated at 1,500 and 3,000 rpm, and the load conditions included a partial load of 50 N·m and a high load of 70 N·m. Data was recorded as the exhaust valve timing was controlled, and this was used to calculate the efficiency of combustion using a heat release, the fuel conversion efficiency, and the pumping loss. Results and the hydrocarbon concentrations in the exhaust gas were compared for each condition. Experiment results confirmed that additional fuel efficiency improvements are possible through exhaust valve timing control at 1,500 rpm and 50 N·m. However, in other operating conditions, fuel efficiency improvements could not be obtained through exhaust valve timing control because cases where the pumping loss and fuel/air mixture slip increased when the exhaust valve timing changed and the fuel efficiency declined.

• Journal of Chest Surgery
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• v.21 no.6
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• pp.984-989
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• 1988

2-D echocardiographic examination of the aortic root diameter was known to be useful in the selection of the size of the prosthetic valve. Valve-patient mismatch was occasionally a serious problem after valve replacement, especially in aortic valve disease. Preoperative knowledge of the patient`s valve annulus size is therefore of great importance in the surgical management of these patients. So the relationship between preoperative 2-D echocardiographic diameter of the annulus size and replaced prosthetic valve were evaluated. 13 patients were analyzed in this study. 2-D echocardiographic measurements of aortic annulus diameter, as determined from the parasternal long axis view and apical four chamber view, demonstrated a high correlation with actual prosthetic valve size implanted at surgery[r=0.86, p< 0.001, SEE=1.08].

• Journal of Chest Surgery
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• v.25 no.2
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• pp.158-166
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• 1992

From 1985 to 1990, a total of 160 new valves were implanted for 125 adult patients to whom prosthetic valve replacement had been performed [One patient had consecutive 2 reoperations]. Following data are the results from the follow-up study from January 1985 to February 1991. Mean age of the patients was 37.9$\pm$12.1 years. Mean follow-up period was 25.8$\pm$18.8 months. In bioprosthesis, mean interval between the previous operation and reoperation was 85.6$\pm$36.4 months in aortic valve, and 87.3$\pm$30.0 months in mitral valve. The causes of reoperation were prosthetic valve failure[103 patients, 81.7%], prosthetic valve endocarditis[17 patients, 13.5%], periprosthetic leakage[5 patients, 4.0%], and aneurysm of ascending aorta[1 patient, 0.8%]. Fourteen patients[11.1%] died in hospital; 5 in 22 replacement of aortic valve[22.7%], 6 in 73 rereplacement of mitral valve[8.2%], and 3 in 31 replacement of multiple valves [9.7%] Except for 3 intraoperative deaths, postoperative, major and minor complications occurred in 39 patients[31.0%]. And the actuarial 5-year survival rate of operative survivors was 95.5$\pm$8.6%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.311-315
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• 2012

Diaphragm type noncontact automatic control valve is a valve for controling acidic PR(Photo Resist) liquid used in the semiconductor process. PR is photosensitive liquid that changes phases depending on light transmittance. PR is very toxic and expensive; the purpose of this paper is to address methods that prevent loss due to leaks. The design of noncontact precise automatic control valve is expected to play an important role in controlling fluid flow, therefore influencing energy conservation and environmental improvement. In this paper, diaphragm type automatic control valve's part design, assembly and simulation are introduced. Also, through the analysis of fluid flow the valve's internal velocity, pressure, and turbulent intensity are interpreted. This paper proposes to contribute to the improvement of the valve's performance.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.667-675
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• 1990

From June, 15th, 1987 to June, 14th, 1989, 105 Duromedics bileaflet cardiac valve prostheses were implanted in 81 patients. Mitral valve replacement was done in 42 patients, 7 underwent aortic valve replacement, 28 underwent double valve replacement, & 4 patients underwent triple valve replacement. Concomitantly used valves were 13 cases; 11 cases were St. Jude Medical valves[M: SJM #29 X4, #27 X5, #25 X 1, T: SJM #33] & two cases were Carpentier Edwards bioprostheses[T: C - E #31X2]. The early mortality rate[within 30 days] was 3.7%[2 patients] & the late mortality rate was 7.4%[3 patients]. Follow-up was done on 72 surviving patients; mean follow-up period was 21.17$\pm$5.36 months. Anticoagulant-related hemorrhage was observed in two patients, possible prosthetic valvular endocarditis was observed in one patient and other specific valve-related complications were none. We concluded, therefore, that good clinical results & a low complication rate could be achieved with Duromedics bileaflet valve in short-term follow-up, & long-term follow-up was also necessary.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.102-108
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• 2010

In this study, the authors investigate the basic characteristics of a two stage directional control valve with pilot spool assembled in main spool coaxially. The step response characteristics and effects of major design parameters' values on valve performances arc clarified through numerical simulations. In addition, the authors examined the possibility of applying the object valve for this study as a proportional control valve. Based on the numerical simulation results, new design values for the reformed design as a proportional control valve were suggested.

• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.13-19
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• 2008

Butterfly valves are widely used as control valves for industrial process. For the definition of optimum configuration of the valve, wide range of related studies has been actively conducted in the case of working fluids of water or air under the normal temperature. Recently, internal flow and performance characteristics of cryogenic butterfly valve for LNG carrier take a growing interest in the field of research and development. Therefore, present study is aimed to investigate the internal flow and performance characteristics of the cryogenic butterfly valve because the study result for the valve can be hardly found at present. Part 1 of this paper describes the study result of a butterfly valve model under the condition of the normal temperature. Succeeding Part 2 of this paper will describe the internal flow characteristics of a cryogenic butterfly valve for LNG carrier. The results of Part 1 show that pressure loss coefficients and flow rate coefficients obtained by the present experiment and CFD analysis agree well each other. Moreover, internal flow visualization for the valve by CFD analysis and PIV measurement have revealed complicated flow patterns of the internal flow field in detail.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.2_2
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• pp.307-313
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• 2023

This study conducts the flow analysis on the basis of the impeller RPM of water metering valve. The software used for the flow analysis is STAR-CCM+. In terms of the structure of the metering valve, it has an impeller installed inside, and a metering chamber has inlet and outlet holes. The flow analysis on the water metering valve drew the following conclusions: Regarding the flow field in the valve, the impeller had the highest velocity distribution, and complex flow field was generated in the metering chamber. In particular, since the path between the inlet and outlet holes in the metering chamber and the valve body was narrow, there was a section that had flow field interference. The flow rate and flow coefficient distribution according to the impeller RPM were on the linear increase. Given that, it showed the feature of the valve used for water metering on the basis of the impeller RPM.

• Journal of Chest Surgery
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• v.24 no.11
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• pp.1090-1097
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• 1991

Between January 1981 and January 1991, 554 patients underwent prosthetic valve replacement. A bioprosthetic valve was replaced in 238 cases and mechanical valve 316 cases. Thirty-eight patients underwent 40 reoperations for repair or replacement, an average of 53.6 months after initial implantation. There were 21 women and 19 men, aged 12 to 60 years[mean 35.3]. A bioprosthetic valve was implanted in 31 cases and a mechanical valve in 9 cases for initial operation. Indications for reoperation were primary tissue failure in 23 cases[57.5%], endocarditis in 9[22.5%], periprosthetic leak in 4[10%]. and valve thrombosis in 4[10%]. Operations performed included 5 aortic valve replacements, 26 mitral valve replacement, 8 double valve replacements, and 1 thrombectomy. A mechanical valve was replaced in 33 cases[84.6%] and a bioprosthesis in 6[15.4Zo] for reoperation. A second reoperation was required in 2 patients. Surgical mortality was 10% . Among the 34 early survivors followed-up for an average of 19.8 months. there was 1 late death and 3 were lost to follow-up. Among the 30 late survivors being followed up, 28[93.3%] remained in New York Heart Association Class I or II and two in Class III [6.7%].