• Fire Science and Engineering
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• v.29 no.3
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• pp.21-30
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• 2015

In this study, we try to suggest measures to reduce leakage at a joint between CPVC piping for a sprinkler system and a pipe expansion through reviews of domestic and foreign standards and related tests. The quality of the waterproof rubber packing material between a valve socket and pipe expansion nut was examined. In the leak test, the valve socket material over the expansion part of the metal pipe nut was found to use a metal part or a schlorinated polyvinyl chloride pipe nut part. In addition, the KS B 0221 standard for parallel pipe threads with threaded and thread inspection criteria and inspection standards in order to ensure an acceptable quality of valve socket, there is a need to amend the regulations to comply with the KS B 5223 (screw thread limit gauges parallel pipe threads). We do not have detailed standards for expansion piping nuts for waterproof rubber ring material, so we need to amend the relevant criteria for EPDM material to be used with excellent waterproofing, for which both NBR and EPDM are currently used.

• Journal of Chest Surgery
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• v.31 no.12
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• pp.1165-1171
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• 1998

Background: All currently available mechanical and bioprosthetic valves are associated with various types of deterioration leading to dysfunction and/or valvular complications. Reoperation on prosthetic heart valves is increasingly under consideration for both clinical and prophylactic indications. This review was conducted to determine the factors affecting the risk of reoperation for prosthetic valve replacement. Material and method: From January 1985 to July 1996, 124 patients underwent reoperation on prosthetic heart valves, and 3 patients had a second valve reoperation. The causes of reoperation were prosthetic valve failure(96 cases, 77.4%), prosthetic valve thrombosis(16 cases, 12.9%), prosthetic valve endocarditis(7 cases, 5.6%) and paravalvular leak(5 cases, 4.1%). This article is based on the analysis of the experience with particular emphasis on the preoperative risks affecting the outcome of the reoperation. Result: Overall hospital mortality rate was 8.9%(11/124). Low cardiac output was the most common cause of death(70.6%). Left ventricular systolic dimension(p=0.001), New York Heart Association functional class IV(p=0.003) and serum creatinine level(p=0.007) were the independent risk factors, but age, sex and cardiothoracic ratio did not have any influence on the operative mortality. Follow-up period was ranged from 3 to 141 months (mean, 50.6 months). A late mortality rate was 1.8%. Conclusion: The surgical risk of reoperation on heart valve prostheses in the advanced NYHA class patients is higher, therefore reoperation is recommended before the hemodynamic impairment become severe.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.1-7
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• 2019

Most oil refineries and chemical plants have flare systems designed to mitigate pressure rises in process facilities in case of emergencies that require the release of large amounts of gas due to sudden process shutdowns such as power outages. However, the rise of the flame of the flare system causes civil complaints from residents around the factory due to visible pollution, and economic loss occurs in the company, which requires constant management. In this study, two items were diagnosed and analyzed in order to derive the optimal operation method of flare system. First, to detect the cause of the rise in flame height, the acoustic leak detector was used to check gas leaks in safety valves and pressure control valves. Second, to identify the cause of flame instability, the pulsation phenomenon was diagnosed through the CFD simulation and modeling experiments of the sealing drum. By confirming the leak at 4.3% of the safety valve and 10% of the pressure control valve, the cause of abnormal sparking was derived. The information presented in this study can be easily applied to any company that has a flare system, and is expected to prevent complaints and product loss.

• Journal of Mechanical Science and Technology
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• v.20 no.3
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• pp.426-434
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• 2006

The impact of leakage was incorporated into the transfer functions of the complex head and discharge. The impedance transfer functions for the various leaking pipeline systems were also derived. Hydraulic transients could be efficiently analyzed by the developed method. The simulation of normalized pressure variation using the method of characteristics and the impulse response method shows good agreement to the condition of turbulent flow. The leak calibration could be performed by incorporation of the impulse response method with Genetic Algorithm (GA) and Harmony Search (HS). The objective functions for the leakage detection can be made using the pressure-head response at the valve, or the pressure-head or the flow response at a certain point of the pipeline located upstream from the valve. The proposed method is not constrained by the Courant number to control the numerical dissipation of the method of characteristics. The limitations associated with the discreteness of the pipeline system in the inverse transient analysis can be neglected in the proposed method.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.59-64
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• 2006

A closed-loop cryogenic cooling system for high field magnets is presented. This design is motivated by our recent development of cooling system for 21 tesla Fourier Transform ion Cyclotron Resonance (FT-ICR) superconducting magnets without any replenishment of cryogen. The low temperature superconducting magnets are immersed in a subcooled 1.8 K bath, which is connected hydraulically to the 4.2 K reservoir through a narrow channel. Saturated liquid helium is cooled by Joule-Thomson heat exchanger and flows through the JT valve, isenthalpically dropping its pressure to approximately 1 6 kPa, corresponding saturation temperature of 1.8 K. Helium gas exhausted from pump is now recondensed by two-stage cryocooler located after vapor purify system. The amount of cryogenic Heat loads and required mass flow rate through closed-loop are estimated by a relevant heat transfer analysis, from which dimensions of JT heat exchanger and He II heat exchanger are determined. The detailed design of cryocooler heat exchanger for helium recondensing is performed. The effect of cryogenic loads, especially superfluid heat leak through the gap of weight load relief valve, on the dimensions of cryogenic system is also investigated.

• Journal of Chest Surgery
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• v.28 no.3
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• pp.263-267
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• 1995

A total and consecutive 87 patients underwent aortic valve replacement[AVR with the St. Jude Medical prosthesis between 1984 and 1993. Age ranged from 14 to 66 years[mean:38.6$\pm$ 14.0 years .Twenty-one patients [24.1% had undergone previous valve replacement. There were 8 early deaths with an operative mortality rate of 9.2% [7.6% for primary AVR and 14.3 % for re-replacement AVR . Seventy-nine early survivors were,followed for a total of 309.1 patient-years[mean:3.9$\pm$ 2.5 years . A late mortality rate was 5.1% [4 patients or a linearized incidence of 1.294 %/patient-year. All were anticoagulated with coumadin to maintain the international normal ized ratio[INR between 1.5 and 2.5. One patient experienced thromboembolism[0.324%/patient-year , and none did bleeding. Endocarditis occurred in one[0.324%/patient-year . Paravalvular leak was the most frequent complication and was experienced by 8 patients[2.588%/patient-year , and 5 of them required re-replacement AVR[1.618 %/patient year of reoperation rate . There was no structural failure of the prosthesis. Actuarial survival including operative death was 83.9%$\pm$ 4.6% at 10 years.The actuarial estimates of freedom from thromboembolism and of freedom from late death and all complications were 95.1% $\pm$ 4.8 % and 81.4% $\pm$ 6.1%, respectively, at 10 years. These clinical results suggest that less intensive anticoagulation may be allowed for patients of AVR with the St. Jude Medical valve with low incidences of both thromboembolic and bleeding complications.

• Journal of Chest Surgery
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• v.21 no.4
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• pp.619-629
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• 1988

The increasing number of replacement of the substitute cardiac valves were seen in these 2 years. Out of a total 1,408 patients with cardiac valve replacement, 54 required replacement of the substitute valves. Fifty-nine substitute valves replaced were 43 in mitral, 14 in aortic and 2 in tricuspid positions; and they were 36 Ionescu-Shiley, 15 Hancock and 3 Angell-Shiley bioprosthetic valves and 3 St. Jude Medical and 2 Bjork-Shiley prosthetic valves. Primary tissue failure was the most frequent reason of replacement[38 patients] followed by paravalvular leak[9 patients], prosthetic valve endocarditis[6 patients] and valve thrombosis[1 patient] in order. The most pronounced pathology of the failed xenograft valves seen in the primary tissue failure group was calcification and fixation of the cusps with or without tear and defect of the cuspal tissue. The operative mortality rate was 7.4%. Fifty early survivors were followed up for a total of 82.6 patient-years and there was no late death. Actuarial survival rate was 92.3*3.8% at 6 years after surgery. Although the definite tendency toward early and accelerated degeneration of the xenograft valves has been seen in patients younger than 20 to 25 years of age, no strict age limit from where the tissue failure slows down could be determined. The requirement of the ideal substitute valves would be the durability of the recently developed mechanical prostheses armed with the low thrombogenicity of the bioprostheses. At the present time, the need of compromise in selection between less thrombogenic bioprosthetic and more durable mechanical valves should be stressed. The difficulty in choice is yet important in patients of middle age and children where the use of homograft valves may be one of the solution despite of certain limitations from sociomedical reasons.

• Journal of Chest Surgery
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• v.30 no.10
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• pp.979-985
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• 1997

Between October 1991 and May 1995, 256 "New Duromedics Valve"(Edward TEKNA Bileaflet Valve) were implanted in 208 adult patients(171 mitral, 82 aortic and 3 tricuspid) with age ranging from 18 years to 70 years(mean 48.2$\pm$ 11.6 years). Postoperative complication rates were 12.2%, but there was none valve related one. Overall early mortality rate were 1.4%(1.6% for MVR, 2.1% for DVR, and none for AVR or TVR) respectively. Follow-up was 99% completed ranging in duration from 2 months to 46 months. There were 6 valve-related late complications(2.9%) with 2 patients with upper gastrointestinal bleeding, 2 with cerebral thxomtioembolism, 1 with valve thrombosis and 1 with valve endocarditis. Freedom from these valve-related major complications were 89.9% at 40 months. There were 5 late deaths(2.4%). one of these late deaths was considered valve-related. Overall actuarial survival rates at 40 months were 95.5%, 96.8% for mitral, 97.1% for aortic, 100% for tricuspid, and 92.0% for double valve replacement respectively. Preoperative New York Heart Association functional class were 2.9, and 1.3 in post-operative state. We have been trying to keep the international normalized ratio(INR) with range of 2.5 to 3.0. The INR of 4 patients of 5 with anticoagulant ralated complications was beyond the range. To reduce the rate of anticoagulant related complications, we felt very strongly that the INR should be kept between 2.5 and 3.0. In our cases, there was no structural failure or significant hemolysis in the absence of periprosthetic leak. This experience encourages us to continue using the "New Duromedics Valve".omedics Valve".uot;.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.645-649
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• 1997

In case of swash plate type axial piston hydraulic motor, hydrostatic bearing used to achieve the lubrication effect on the mechanical sliding contact areas between the following parirs ; sliooer-pad and swash plate,piston and cylinder bore,valve plate and cylinder block, etc. This study discussed the basic charateristic for the hydrostatic slipper-pad bearings with the capillary or orifice restrictor under static load condition. And, we also development of hydrostatic bearing tester for hydrostatic balancing test of pistion & slipper-pad assembly, and some experimental data on supply pressure step responce are reported.

• Journal of Chest Surgery
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• v.30 no.2
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• pp.152-157
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• 1997

From August 1986 until June 1995, single aortic valve replacement was performed in 65 patients at the Chonnam National University Hospital. worthy-eight were male and 17 were female patients, ranging from 19 to 68 years of age(median : 43 years). The causes of the valve lesions were rheumatic in 29 patients (44.6%), bicuspid aortic valve in 6 patients (6.2%), endocarditis in 6 patients(6.2%), unknown in others. Concomitant surgical procedures were performed in 10 patients : repair of congenital defect in 5, pericardiectomy in 1, coronary artery bypass grafting in 1, noncoronary sinus plication in 1, Valsalva sinus aneurysmectomy in 1, subaortic membrane resection in 1 Used valves were 51. Jude-Medical valve in 42, Duromedics valve in 22, Bjork-Shiley valve in 2, Carpentier-Edward valve in 1. There were 3 hospital deaths (4.6%), and 2 late deaths (3.2%). Follow-up was 95.2% complete. The 10-year acturlal survival rate was 85.3%. Postoperative complications were low cardiac utput in 8, arrythmia in 5, valve related hemolysis in 1, cerebral infarction in 1, and gastrointestinal bleeding in 2. Reoperation was performed in 4 for surgical bleeding, in 3 for paravalvular leak. The mean improvement in New York Heart Association functional class is from 2.79 $\pm$ 0.66 preoperatively to 1.25 $\pm$ 0.49 postoperatively(p < 0.001) The change of cardiothoracic ratio from preoperative to postoperative is 0.57 $\pm$ 0.06 to 0.54 $\pm$ 0.05 (p < 0.05). The left ventricular ejection fraction change is not significant perioperatively. There are no mechanical failures. This early and intermediate-term follow-up suggests that in adults in whom valve repair is not possible, the mechanical valve is a reliable and durable prosthesis with good hemodynamic function and a low rate of thromboembolic event.