• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.160-166
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• 2018

The worldwide semi-conductor market has been growing for a long time. Manufacturing lines of semi-conductors need to handle several types of toxic gases. In particular, they need to be controlled accurately in real time. This type of toxic gas control system consists of many different kinds of parts, e.g., fittings, valves, tubes, filters, and regulators. These parts obviously need to be manufactured precisely and be corrosion resistant because they have to control high pressure gases for long periods without any leakage. For this, surface machining and hardening technologies of the metal block and metal gasket need to be studied. This type of study depends on various factors, such as geometric shapes, part materials, surface hardening method, and gas pressures. This paper presents strong concerns on a series of simulation processes regarding the differences between the inlet and outlet pressures considering several different fluid velocity, tube diameters, and V-angles. Indeed, this study will very helpful to determine the important design factors as well as precisely manufacture these parts. The EP (Electrolytic Polishing) process was used to obtain cleaner surfaces, and hardness tests were carried out after the EP process.

• Nuclear Engineering and Technology
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• v.27 no.4
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• pp.470-482
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• 1995

The Ulchin 3&4, which are 2825 MWt PWRs, adopted Safety Depressurization System (SDS) to mitigate the beyond design basis event of Total Less of Feedwater(TLOFW). In this study the results and methodology of the analyses for the determination of SDS bleed capacity are discussed. The SDS design bleed capacity has been determined from the CEFLASH-4AS/REM simulation according to the following design criteria : 1) Each SDS flow path, in conjunction with one of two High Pressure Safety Injection (HPSI) pumps, is designed to have a sufficient capacity to prevent core uncovery if one SDS path is opened simultaneously with the opening of the Pressurizer Safety Valves (PSVs). 2) Both SDS bleed paths are designed to have sufficient total capacity with both HPSI pumps operating to prevent core uncovery if the Feed and Bleed (F&B) initiation is delayed up to thirty minutes from the time of the PSVs lift. To verify the results of CEFLASH-4AS/REM simulation a comparative analysis kas also been per-formed by more sophisticated computer code, RELAP5/MOD3. The TLOFW event without operator recovery and TLOFW event with F&B are analyzed. The predictions by the CEFLASH-4AS/REM of the transient too phase system behavior are in good qualitative and quantitative agreement with those by the RELAP5/MOD3 simulation. Both of the results of analyses by CEFLASH-4AS/REM and RELAP5/MOD3 have demonstrated that decay heat removal and core inventory make-up can be successfully accomplished by F&B operation during now event for the Ulchin 3&4.

• Safety and Health at Work
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• v.9 no.3
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• pp.356-359
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• 2018

This case report attempts to present a case of acute toxic hepatitis in fire extinguisher manufacturing workers exposed to 2,2-dichloro-1,1,1-trifluoro-ethane (HCFC-123) in August 2017 in Korea. Twenty-two-year-old male workers were exposed to HCFC-123 for 1.5 hours one day and for 2.5 hours the other day, after which one worker died, and the other recovered after treatment. The workers were diagnosed with acute toxicity of hepatitis. However, exposure levels of HCFC-123 were not known with no work environment measurement done. Therefore, this study was conducted to estimate the exposure concentration of HCFC-123 via a job simulation experiment. In the simulation, the HCFC-123 exposure concentration was measured with the same working practice and working time as with the workers aforementioned. As a result, the workers who infused HCFC-123 into storage tanks were estimated to be exposed to HCFC-123 at a concentration of $20.65{\pm}10.81ppm$, and a mean concentration of area samples within a working radius were estimated as $70.30{\pm}18.10ppm$. Valve assembly workers working on valves of a fire extinguisher filled with HCFC-123 were exposed to HCFC-123 at concentrations of $91.65{\pm}4.03ppm$ and $115.55{\pm}7.28ppm$, respectively, in the simulation, and area samples simulated within the working radius were also found to be high with concentrations of $122.75{\pm}91.15ppm$ and $126.80{\pm}60.25ppm$, respectively. Nitrogen gas packing workers, who did not handle HCFC-123 directly, were exposed to the agent at a concentration of $71.80{\pm}8.49ppm$. These results suggest that exposure to HCFC-123 at high concentrations for 1.5-2.5 hours caused acute toxic hepatitis in two workers.

• Journal of Chest Surgery
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• v.32 no.3
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• pp.262-269
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• 1999

Background: To review the middle and long term results of aortic valve replacement(AVR) for 11 years, we surveyed and followed up the patients who underwent AVR. Material and Method: Between Feb. 1986 and May 1997, 134 patients underwent AVR. The patients consisted of 71 men and 63 women whose mean age was 38.9 years, ranging from 17 to 70. Result: The concomitant operations were 62 mitral valve replacement(MVR), 14 MVR + tricuspid valve annuloplasty, 10 Cabrol operation, 16 aortic annulus widening, and so forth. We used 119 mechanical(75 St. Jude Medical, 38 CarboMedics, 6 Sorin) and 15 tissue (Carpentier-Edwards) valves. Early postoperative complications occurred in 35 cases; 9 congestive heart failure, 6 low cardiac output, 5 postoperative bleeding, 5 pleural effusion, and so forth. There were 13 early postoperative deaths(9.7%) due to low cardiac output(5), CHF (2), disseminated intravascular coagulopathy(2), and so forth. The cumulative total follow-up period was 452.7 patient-years with a mean of 3.4${\pm}$3.1 years/patient. There were 9 cases of valve-related complications; anticoagulant-related bleeding(4), prosthetic valve endocarditis(2), thromboembolism(2) and prosthetic valve failure(1) occured at rate of 0.9, 0.4, 0.4, 0.2%/ pt-yr, respectively. Late valve-related death occurred in 3 cases(2.0%/pt-yr) associated with anticoagulant-related bleeding(2) and prosthetic valve endocarditis(1). Conclusion: Actuarial survival rate by Kaplan-Meier method was 91.0${\pm}$4.3 % at 11 years.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1009-1015
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• 2012

Valves are one of the most important components of a pipeline system in a nuclear power plant, and it is important to ensure their structural safety under seismic loads. A crucial aspect of structural safety verification is the seismic qualification, and therefore, an optimal shape design and experimental seismic qualification is necessary in case the configuration of the valve parts needs to be modified and their performance needs to be improved. Recently, intensive numerical analyses have been performed before the experimental verification in order to determine the appropriate design variables that satisfy the performance requirements under seismic loads. In this study, static and dynamic numerical structural analyses of a 200A butterfly valve for a nuclear power plant were performed according to the KEPIC MFA. The result of static analysis considering an equivalent static load under SSE condition gave an applied stress of 135 MPa. In addition, the result of dynamic analysis gave an applied stress of 183 MPa, where the CQC method using response spectrums was taken into account. These values are under the allowable strength of the materials used for manufacturing the butterfly valve, and therefore, its structural safety satisfies the requirements of KEPIC MFA.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.48-53
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• 2017

Liquid rocket engines (LREs) are very complex systems that include combustion chambers, turbopumps, gas generators, ducts and tubes, valves and etc. Most components of the LREs require higher than or equal to level 6 IT (ISO Tolerance). The components along with pipe line and/or tubing must dispose not to interfere each other. In addition, effectiveness of maintenance and service after assembling should be considered when the allocation of the components are determined. Especially at the stage of the development, tolerance accumulations or unpredictable errors may result in misalignment and/or mismatches at interfaces of the parts. Namely, it is the engine assembling process that many inherent risks are realized and crises or incidents occur. Therefore, a rapid reaction system should be prepared. In this research, 7 tonf class liquid rocket assembling process was studied and actual building steps were introduced.

• Journal of the Korean Institute of Gas
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• v.25 no.3
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• pp.1-8
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• 2021

Among the flare systems that handle discharged substances from safety valves, the knockout drum was a key facility for safety, but the installation standards were not clear, so it was necessary to review the standards acceptable to the workplace and regulatory agencies. After investigating the domestic and foreign technical standards of knockout drums and the deficiencies of previous studies, research was first conducted on the degree of mass discharge, the installation location of the intermediate knockout drum, and the effect of changes in the composition of the discharged material. As a result of the study under the process simulation conditions, the gas-liquid separation of the knockout drum was completed in a small amount of less than 7,500kg/hr. However, when more than that was released, the gas-liquid separation effect was small even with the addition of an intermediate knockout drum. In addition, when the composition ratio of the material easily condensed was increased (molar fraction 10%), the gas-liquid separation effect of the knockout drum increased in the case of mass release. The gas-liquid separation effect was analyzed to be greater when the knockout drum was installed adjacent to the stack than the knockout drum was installed adjacent to the process equipment.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.76-89
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• 2018

The distribution of the combined heat and power system is active as a solution to the instability of energy supply and environmental pollution caused by continuous industrial development. In Korea, the safety standards for combined heat and power system using a gas engine are insufficient therefore the study on this is needed. In this study, the safety performance and structural/material assessment items of domestic and international standards applied to the combined heat and power system were analyzed to carry out a standardization study on safety performance applicable to 20 kW gas engine combined heat and power system. In addition, the safety performance assessment (plan) of the gas engine combined heat and power system was derived by performing risk analysis and risk assessment using HAZOP. Assessment items include engine ignition systems related to safety performance, piping tight performance, watering and temperature rise performance, combustion performance, electrical efficiency, thermal efficiency, overall efficiency and humidity performance. Gas and water pipes, gas control and shut-off valves, durability, heat resistance, and cold resistance of metal or non-metallic materials related to the structure and materials of the gas engine combined heat and power systems.

• Journal of Chest Surgery
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• v.55 no.5
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• pp.388-396
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• 2022

Background: In this study, we present recent trends in heart valve surgery in Korea through analyses of data from the Korea Heart Valve Surgery Registry (KHVSR). Methods: We enrolled 8,981 patients who were registered in the KHVSR from 2017 to 2020. Yearly trends in patients' baseline characteristics, surgical profiles, and early mortality rates were explored. The observed/expected mortality ratio (O/E ratio), calculated from the actual mortality in the KHVSR and the predicted mortality estimated using the EuroSCORE II, was also analyzed. Results: The proportion of aortic valve surgery significantly increased from 56.8% in 2017 to 60.3% in 2020. The proportion of all combined procedures and minimally invasive surgery significantly increased over the 4-year study period. The operative mortality rate was 2.9% in the entire cohort, while mitral valve repair showed the lowest mortality risk (0.9%). The mortality rates of isolated aortic valve replacement (AVR) significantly decreased from 2.1% in 2017 to 0.8% in 2020 (p=0.016). Overall, the O/E ratio was 0.784 (95% confidence interval [CI], 0.677-0.902) demonstrating significantly lower actual mortality risks than expected based on the EuroSCORE II. In particular, the O/E ratios were as low as 0.364 (95% CI, 0.208-0.591) for isolated AVR. Conclusion: The recent data from the KHVSR showed increasing trends for complex procedures and minimally invasive surgery in heart valve surgery in Korea, and demonstrated remarkably low risks of operative mortality.

• Korean Journal of Plant Taxonomy
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• v.52 no.3
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• pp.184-195
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• 2022

The invasive alien species Brassica tournefortii Gouan (Brassicaceae) is herein reported for the first time in Korea, from Gunsan-si, Gochang-gun, and Jeju-si. Brassica tournefortii can easily be distinguished from B. juncea and B. napus by its dense stiff hairs at the base of the stem and leaves, basally and distally branched stems, partially dehiscent fruits, and seeds that become mucilaginous in the presence of moisture. Although some taxonomists have classified this species as belonging to Coincya Rouy based on its fruit and seed characteristics, the existence of one vein on the fruit valves and our maximum likelihood analysis using internal transcribed spacer sequences placed it in Brassica. Distribution data, photographs, and a description of B. tournefortii are presented herein. Moreover, potential changes in the distribution of B. tournefortii were predicted under different climate scenarios, but our analysis showed that the probability of the spreading of this species is low. Nevertheless, continuous monitoring is necessary for an accurate assessment. The results of the present study can be used to conduct an invasion risk assessment and can assist with the effective management of this invasive alien species.