• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.630-635
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• 2001

The stem thrust required to unwedging a gate valve is influenced by the pressure and temperature when the valve is closed and by the changes in these conditions between closure and opening. "Pressure Locking" and "Thennal Binding" refer to situations where pressure and temperature effects cause the unwedging load to be much higher than normal. A model of these phenomena has been developed. The effects of pressure and temperature are analyzed to determine the change in this disk-to-seat "interference". Flexibilities or Stiffness of the disk and body strongly influence the unwedging thrust. Calculation and limited comparison to data have been performed for the RHR motor operated valve designs and scenario. Pressure changes can increase the unwedging thrust when bonnet pressure exceeds the pressure in the adjacent piping and temperature changes can increase the unwedging thrust when a temperature change after closure produces an increase in the disk-to-seat interference.

• 한국세라믹학회지
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• 제35권2호
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• pp.163-171
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• 1998

Continuously contacting with camshaft the face of Valve Lifter made of cast iron brings about abnormal wear such as unfairwear or earlywear because it is heavily loaded in the valve train systems as the engine gets more powered. This abnormal wear becomes a defet namely over-clearance when the valve is lifting so that the fuel gas imperfectly combusted by unsuitable open or close aaction of the engine valve in the combustion chamber. The imperfect combustion in the end results in the major cause of air pollution and combustion chamber. The imperfectly combusted by unsuitable open or close action of the engine valve in the combustion chamber. The imperfect combustion in the end results in the major causes of air pollution and decrease of the engine output. Consequently to prevent this wear this study was to develop the valve lifter which is joined by brazing process with SCM435H and a tip by manufacturing the face as a superhardened which is joined by brazing process with SCM435H and a tip by manufacturing the face as a superhardened ceramics alloy which has high wear resistance. Having the excellent surface hardness with Hv1100-1200 the sintered body developed with superhardened alloy(WC) can endure the severe face loading in the valve train system. We experienced with various brazing alloys and obtained the excellent joining strength to the joint had 150MPa shear strength. Interface analysis and microstructure in a joint were examined through SEM & EDS Optical microscope. Also 2,500 hours high speed(3,000-4,000 rpm) and continuous (1step 12hr) engine dynamo testing was carried out to casting valve liter and ceramics-metal joint valve lifter so that the abnormal wears were compared and evaluated.

• 비파괴검사학회지
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• 제30권2호
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• pp.110-115
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• 2010

발전용 밸브 내부의 누설은 냉각 기능 상실 및 방사선물질 방출 동 안전계통의 성능 저하와 수많은 에너지 손실 등 발전소 운전에 막대한 손상 및 사고를 초래하게 된다. 본 논문은 신뢰성 높은 진단 방법 개발을 위하여 국내 원자력발전소 2차계통의 누설 발생 또는 내부 부품의 손상이 발생할 수 있는 밸브를 대상으로 현장시험 및 모의누설실험시의 적외선열화상 측정 실험을 수행함으로써 단일계측방식의 불확실성을 제거하고 향후 누설진단에 대한 확대 적용을 도모하고자 하였다. 발전소 현장시험 및 밸브 모의누설시험시의 밸브 누설 상태에 따른 적외선열화상 이미지 측정 실험을 통하여, 적외선열화상 측정 방법은 밸브 누설 상태의 과정을 신속하고 정밀하게 측정 가능하며 향후 많은 종류의 밸브 누설진단에 활용함으로써 누설에 따른 막대한 에너지 손실 및 사고 예방의 유용한 기법으로 확대 적용이 가능할 것으로 생각된다.

• Journal of Chest Surgery
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• 제28권12호
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• pp.1122-1131
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• 1995

One hundred eighty-eight patients[August.23,1988,through July.30,1994 underwent aortic[AVR , mitral[MVR , or double [DVR valve replacement with the St.Jude Medical prosthesis. The author analyzed 100 patients with valvular heart disease,who underwent valve replacement with the St.Jude Medical prothesis from 1990 to 1994, at Hanyang University hospital Cardiovascular department. Information on volume and functional change of the heart chamber can be obtained by cardiac echocardiography and cartheterization. Out of 100 patients, 40 patients were male[40% and 60 patients were female [60% . Age ranged from 13 years to 68 years, with mean age of 42.6 years. Mean height was 160.3cm and mean body weight was 54.9Kg. According to NYHA functional classification, class III is most frequent and 60 patients could be classfied under it. MVR [involved Redo MVR was performed in 40 patients, AVR [involved Redo AVR was performed in 18 patients, and DVR [involved Redo DVR was performed in 42 patients. Warfarin [Coumadin anticoagulation was recommended for all patients. Life long warfarin anticoagulation was necessary to all patients who underwent valve replacement with St.Jude Medical prosthesis. Ideal prothrombin time was maintained about 30% during warfarinization. There were no case of mechanical failure. It followed a comparison of echocardiography before and after valve replacement at Hanyang University hospital [30 patients and a preoperative evaluation of cardiac catheterization and angiography [64 patients . The St.Jude Medical cardiac valve is a viable alternative in the surgical therapy of valvular heart disease.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2509-2522
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• 2021

A valve assembly used in nuclear power plants must be qualified and supervised. New technical standards such as ASME QME-1 2007 particularly require detailed qualification using experiment and analysis. Particularly, diagnostic tests and engineering studies are required for qualification of ASME QME-1 2007. Among these studies, the research on the measurement of friction coefficient and packing stress is important. The irregular change of packing stress along the stroke distance occurs because of the abnormal phenomenon, which must be found and studied with quantitative methods. Packing stress should be analyzed conservatively through experimentation and analysis. In this study, various formulas were applied to measure and calculate coefficient of friction and packing stress. This study can be used in relation to qualification and supervision of packing materials. And the calculation using static diagnosis test can be used to find the packing frictional force in dynamic diagnosis test with flow pressure in a pipe. This study has made it possible to reliably consider packing frictional force generated in a valve body. And so, it is believed that more margin can be secured when evaluating the capacity of valve actuator by applying the accurate frictional force generated in the valve assembly.

• Journal of Chest Surgery
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• 제33권2호
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• pp.146-150
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• 2000

background: The prognosis after an aortic valve replacment can be affected significantly by the transprosthetic pressure gradient which is determined mainly by the size of the patients body and the prosthesis used. We analyzed the hemodynamic feature of two relatively new prosthese the ATS and the evensized Medtronic-Hall(M-H) valves by measuring the transprosthetic pressure gradient in the cases where small sizes (23mm or smaller) were used. Material and method: There were 94 patients who received whom aortic valve replacement with prosthesis smaller than 23 mm from October 1994 to June 1998. In these patients the transprosthetic pressure gradient clalculated from the pressure half time during postoperative Dopper echocardiographic examination was compared between the prostheses of different sizes. The body surface area of each patient was also taken into consideration. result: The mean pressure gradient and body surface area in each group were 21.7$\pm$10.2 mmHg and 1.52$\pm$0.14m2 in ATS 19mm 11.4$\pm$6.5 mmHg and 1,57$\pm$0.20m2 in M-H 20mm 15.2$\pm$6.3 mmHg and 1.54$\pm$0.13m2 in ATS 21mm 9.3$\pm$2.5 mmHg and 1.63 $\pm$0.14m2 in M-H 22 mm and 12.9$\pm$5.3 mmHg and 1.69$\pm$0.13m2 in ATS 23mm. Conclusion: The 19mm ATS prosthesis showed significant trasprosthetic pressure gradient which is similar to the values previously reported with other bileaflet prosthesesm Close follow-up was needed in terms of exercise capacity and change in left ventiricular geometry. In patients with small aortic valve annulus the 20mm M-H valve is recomendable as an alternative to 19mm bileaflet valves because it has less pressure gradient with similar outer diameter.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.549-554
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• 2003

EPRI PPM (Performance Prediction Methodology), a method used for the prediction of required thrust of valves, can not be applied to unbalanced-disk globe valves operated in the fluid when the fluid temperature is above $150^{\circ}F$ because the thrust increase caused by the friction between the valve disk and body is not considered in the PPM. In order to apply PPM to the valves, EPRI suggested new friction prediction method to be added in the code. This paper analyzes the applicability of the prediction method comparing the disk-to-body friction load predicted from the method with the measured friction load from the field tests. The maximum values from the prediction method and those obtained from the test were 268lbs and about 1500lbs, respectively. It is included that the prediction method should be improved for the realistic prediction of disk-to-body friction load.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1766-1769
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• 2005

Air-operated valve(AOV) is one of principal valves that are using to control fluid flow in nuclear power plants. AOV is suffered from damage and malfunction by the abrasion, corrosion and vibration of valve parts under the long time operation. This mechanical trouble and malfunction of valve is critical for the safety of power plant. So a periodic diagnosis for safety of power plants is inevitable to guarantee the safety of the power plant. But depending on the type of the actuator and valve body, various types of AOV exist. In this study, It is developed the diagnostic system that users of power plants are easy to handle in this paper.

• Journal of Chest Surgery
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• 제19권2호
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• pp.250-258
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• 1986

From Aug. 1984 to May 1986, 116 cases of cardiovascular surgery including 85 cases of open heart surgery were performed at Korea Veterans Hospital. There were 108 congenital anomalies and 8 acquired valvular heart diseases. Among 108 congenital malformations 92 operations were done for acyanotic group, and 16 operations for cyanotic group. Thirteen cases of open heart surgery for infants or small children under 10kg of body weight were performed, which occupied 15.3 percent of total open heart surgery done in the same period. Common congenital cardiovascular anomalies were ventricular septal defect [40.7%], patent ductus arteriosus [29.6%], tetralogy of Fallot [12.[%], atrial septal defect [11.1%], and pulmonary stenosis [1.9%] in order of frequency. Valve replacement using lonescu-Shiley or Carpentier-Edwards valve was performed for 8 cases of acquired mitral valve disease, and valve replacement using St. Jude valve was done for a case of patent ductus arteriosus with severe mitral insufficiency. There was no mortality in acyanotic congenital malformations and acquired valve lesions, and 5 cases of mortality in cyanotic congenital malformations. Overall mortality was 4.3 percent for total cases and 5.9 percent for 85 cases of open heart surgery.

• 한국기계가공학회지
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• 제4권4호
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• pp.39-47
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• 2005

In this paper, a novel high power micropump using active check valves in place of conventional passive check valves employed at the inlet and outlet ports is presented. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. A prototype micropump having an effective size of $17mm{\times}8mm{\times}11mm$ is fabricated. Frequency-dependent flow rate characteristics, bi-directional flow characteristics and load characteristics are experimentally investigated using a timing control method for valve closing motion. From the obtained experimental results, it is ascertained that optimal values of the phase shift compared to the voltage to drive pump chamber are $15^{\circ}$ for inlet check valve and $195^{\circ}$ for outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with an effective size of $10mm{\times}10mm{\times}10mm$ is fabricated and the basic characteristics are experimentally investigated.