• 한국전기전자재료학회논문지
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• 제17권5호
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• pp.515-520
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• 2004

We report on the development of a Piezoelectric valvc that is designed to have a high reliability for fluid control systems, such as mass flow control, transportation and chemical analysis. The valve was fabricated using a MCA(multilayer ceramic actuator), which has a low consumption power, high resolution and accurate control. The fabricated valve is composed of MCA, a valve actuator die and an seat die. The design of the actuator dic was done by FEM(finite element method) modeling, respectively. And, the valve seat die with 6 trenches was made. and the actuator die, which possible to optimize control to MCA, was fabricated. After Si-wafer direct bonding between the seat die and the actuator die, MCA was also anodic bonded to the scat/actuator die structure. PDMS(poly dimethylsiloxane) sealing pad was fabricated to minimize a leak-rate. It was also bonded to scat die and stainless steel package. The flow rate was 9.13 sccm at a supplied voltage of 100 V with a 50 % duty ratio and non-linearity was 2.24 % FS. From these results, the fabricated MCA valve is suitable for a variety of flow control equipments, a medical bio-system, semiconductor fabrication process, automobile and air transportation industry with low cost, batch recess and mass production.

• 한국압력기기공학회 논문집
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• 제17권1호
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• pp.49-55
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• 2021

In this paper, an application example for fitness-for-service of material is shown. A kind of instrument valve is made of austenitic stainless steel fabricated by the cold working process. The tensile strength of the cold worked austenitic stainless steel has to be limited under 90 ksi to prevent the stress corrosion cracking in power plants. In industrial fields, tensile strengths of some materials were discovered to be over the regulation requirements in a certified material test report (CMTR). Owner's verification tests were performed to compare with that in a CMTR and to check the appropriateness. It is found that, in the case of verification test under the required test speed, valve materials could be used in the field. Although it is only one application sample of material check process in the power generation site, this case study could show an importance of basic experimental technology in academia and research circles.

• Journal of Chest Surgery
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• 제27권10호
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• pp.858-861
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• 1994

Prosthetic valve thrombosis is rare but it is one of fatal complication after heart valve surgery. Improvements of the valve design and the material have decreased the frequency of thrombosis but have not eliminated completely. And some cases of prosthetic valve thrombosis during pregnancy were reported inspite of adequate anticoagulation therapy.Urgent surgical intervention is indicated for prosthetic valve thrombosis but it is associated with high operative risk, therefore medical thrombolytic therapy such as urokinase or streptokinase therapy is regarded as an alternative therapy. This is a case report of the successful thrombolytic therapy for valve thrombosis in a pregnant patient after mechanical mitral valve replacement.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.390-391
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• 2006

This paper describes the design, fabrication and characteristics of a micromachined piezoelectric valve utilizing a multilayer ceramic actuator (MCA). The micromachined MCA valve, which uses a buckling effect, consists of three separate structures: the MCA, the valve actuator die and the seat die. The valve seat die with 6 trenches was made, and the actuator die, which is driven by the MCA under optimized conditions, was also fabricated. After Si wafer direct bonding between the seat die and the actuator die, the MCA was also anodically bonded to the seat/actuator die structure. A polydimethylsiloxane (PDMS) sealing pad was fabricated to minimize the leak rate. Finally, the PDMS sealing pad was also bonded to the seat die and the stainless steel package. The MCA valve shows a flow rate of 9.13 sccm at an applied DC voltage of 100 V with a 50% duty cycle and a maximum non-linearity of 2.24% FS. Therefore, the fabricated MCA valve is suitable for a variety of flow control equipment, as a medical bio-system and in the automobile industry.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.397-398
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• 2006

In late years, from a trend for ecology of auto motive engine, low emission and low fuel consumption of engine become a social assignment. At the same time, the high output (high efficiency) is required, too. In order to meet those requirements, in comparison with conventional engines, lean A/F (Air fuel ratio) setting is becoming popular for the high performance engines of late years. Exhaust valve seat (sintered material) used in these engines has a problem in wear resistance, because it is exposed to the surroundings that is clean and a high temperature in comparison with the conventional engines. Therefore, wear mechanism with lean A/F of engine was analyzed.The exhaust valve seat (sintered material), that was superior in wear resistance, was developed.

• Journal of Chest Surgery
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• 제23권4호
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• pp.622-639
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• 1990

The use of aortic valve homograft has been developed since 1962 when Ross and Barratt - Boyes independently replaced a diseased aortic valve with an orthotopically inserted homograft valve. And also surgical treatment of complex congenital cardiac malformations utilizing homograft extracardiac conduit has been tried with better result than any other prosthetic material. The present study was undertaken to clarify the safety tissue viability, sterility, after following our protocol of procurement of heart, dissection of aortic and pulmonic homograft, sterilization, cryopreservation, thawing and dilution, and transplantation on experimental animal, sheep. Tissue viability of valve and great artery was assessed by tissue culture. Sterility was evaluated by bacterial and fungal culture. The method used was proven no deleterious effect on the integrity of the valve. Tissue culture of valve tissue before, and after cryopreservation process resulted that active fibroblast growth was observed from homograft sterilized with antibiotics. And culture of the transplanted homograft from sacrificed animal showed active fibroblast growth. Pathologic examination of implanted valve tissue from sacrificed sheep showed mild calcification and minor change, but there were moderate and severe calcification of wall of great arteries.

• Journal of Chest Surgery
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• 제21권4호
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• pp.706-710
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• 1988

Intravascular hemolysis occurs in the majority of patient with mechanical valve prosthesis. The primary cause is mechanical trauma to red cells from turbulent blood flow through the prosthesis. Degree of hemolysis is dependent upon the type, size and material of valve and aggravated by paravalvular leakage. Clinically important hemolytic anemia is required medical management or consideration of reoperation. In severe hemolysis, reoperation is recommended without delay when seems to be renal failure. In this case, postoperative severe mechanical hemolysis was developed immediately after aortic valve replacement with St. Jude medical valve in a 13 year-old male patient. Neither significant paravalvular leakage nor valvular dysfunction was found through redo, but the mechanical valve was strongly suspected the cause of severe hemolysis. The St. Jude Medical valve was changed with Ionescu-Shiley bioprosthesis and any significant clinical problems were not noted through the postoperative course.

• Journal of Chest Surgery
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• 제33권2호
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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 Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.801-807
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• 2005

Any failure of intake and exhaust valves of marine diesel engine must be regarded as serious, and any steps which can be taken to prevent such failure are desirable. The purposes of this study is to investigate and to analyse the failure causes of intake and exhaust valves for marine diesel engine during sea trial after completion of overhauling. In this study, to analyse the failure causes, we have carried out on board inspection, fractography test and discussion based on the specimen and repairing report provided by the ship owner. From the results of above inspection, test and discussion, it has been considered reasonable to conclude that the causes of damaged valves of the ship are as follow ; 1) During operation, the stick or seizure of valve spindle occurred and hence the movement of exhaust valve spindle was to be resisted and subsequently the engine was to be operated under an unappropriated valve timing and the exhaust valve sustained the repeated loads exceeding the fatigue strength of valve material. 2) By the loads above described, the fatigue fracture was initiated at the structural noncontinuous part of exhaust valve spindle, and then the valve head was finally fractured and dropped in the cylinder. 3) The fractured exhaust valve head impacted the intake valve at various direction to be bent or damaged.

• 제어로봇시스템학회논문지
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• 제17권9호
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• pp.888-891
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• 2011

This paper presents development of flow control valve using MR fluid. Generally, since the apparent viscosity of MR fluids is adjusted by applying magnetic fields, the MR valves can control high level fluid power without any mechanical moving parts. In this paper, flow control valve using MR fluid on the behavior of the magnetic field influence on the numerical analysis of more accurate electromagnetic parameters were obtained, even if when magnetic field apply inside of surrounding MR fluid from electromagnet, more realistic designing way analysis of characteristic of whole magnetic field distribution is suggested by surrounding magnetic material. Also, comparison of flow rate inlet and outlet, behavior of MR fluid in experiments proposed. A new type of flow control valve using MR fluid is proposed by analysis of behavior of MR fluid in experiments.