• 한국압력기기공학회 논문집
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• 제17권1호
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• pp.8-17
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• 2021

The seat leakage test is required after the maintenance work on the valve seat. Either the test has been performed outside of the plant after cutting the valve from the pipe system or the simplified test has been performed so far. It was unable to perform the test at the plant site because it is hard to make a steady pressure on the valve inlet when it is installed in the pipe. This research aims to perform the leakage test in the nuclear power plant while it is installed in the pipe system. The mock-up test is performed by pressurizing the leak-off pipe on the valve body. The result is compared with traditional test result by pressurizing the valve inlet. Furthermore the chamber mock-up tests are performed under various conditions. The leak rate by the developed test using the leak-off pipe is found to be similar but greater than the leak rate by the existing test method. It implies that the test using the leak-off pipe is more conservative than the existing test. The methodology and the equipment which this paper suggests that on-site seat test is possible and the application of the technology could reduce the time and cost for the valve maintenance work significantly.

• Journal of Biosystems Engineering
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• 제22권2호
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• pp.237-246
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• 1997

굴 까는 작업을 자동화하기 위한 방법으로 굴의 껍질 안쪽에 붙어 있는 근육질을 제거하고 굴 껍질의 힌지(Hinge)를 절단하는 작업을 필요로 한다. 본 논문에서는 굴을 까는 자동화 기계를 개발하기 위한 연구의 일환으로써 컴퓨터 시각 시스템을 이용하여 굴의 힌지 위치를 판단하는 영상처리 알고리즘을 개발하였다. 본 실험에 사용한 굴들은 컴퓨터 비젼 시스템이 굴의 바깥쪽 힌지표면을 감지할 수 있도록 굴을 물로 씻은 후굴 껍질의 힌지(Hinge)부분을 약간 절단하였다. 칼라 비디오 카메라(color video camera)를 이용하여 굴의 절단된 힌지표면의 영상을 잡은 후 개발한 영상처리 알고리즘을 이용하여 굴의 힌지(hinge)위치를 감지하였다. 영상내의 굴의 힌지(Hinge)와 그 밖의 다른 물체를 구별하기 위하여 4개의 변수 (원형도, 사각형도, 장단축비, 유크리드(Euclidian)거리 )를 이 용하였다. 또한 영상(image)내 의 굴의 힌지(Hinge) 위치를 쉽고 효과적으로 파악하기 위하여 몇 가지 영상처리 즉, 수축-확장, 문턱갑 처리 등의 방법들을 이용하였다.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2096-2106
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• 2023

Rotating machinery is widely applied in important equipment of nuclear power plants (NPPs), such as pumps and valves. The research on intelligent fault diagnosis of rotating machinery is crucial to ensure the safe operation of related equipment in NPPs. However, in practical applications, data-driven fault diagnosis faces the problem of small and imbalanced samples, resulting in low model training efficiency and poor generalization performance. Therefore, a deep convolutional conditional generative adversarial network (DCCGAN) is constructed to mitigate the impact of imbalanced samples on fault diagnosis. First, a conditional generative adversarial model is designed based on convolutional neural networks to effectively augment imbalanced samples. The original sample features can be effectively extracted by the model based on conditional generative adversarial strategy and appropriate number of filters. In addition, high-quality generated samples are ensured through the visualization of model training process and samples features. Then, a deep convolutional neural network (DCNN) is designed to extract features of mixed samples and implement intelligent fault diagnosis. Finally, based on multi-fault experimental data of motor and bearing, the performance of DCCGAN model for data augmentation and intelligent fault diagnosis is verified. The proposed method effectively alleviates the problem of imbalanced samples, and shows its application value in intelligent fault diagnosis of actual NPPs.

• Journal of Chest Surgery
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• 제56권4호
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• pp.255-261
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• 2023

Background: The surgical threshold for bicuspid aortic valve (BAV)-related aortopathy is a matter of debate due to its uncertain etiology and prognosis. This study investigated the prognosis of unrepaired BAV aortopathy in patients undergoing surgical aortic valve replacement (SAVR). Methods: We retrospectively analyzed data from 720 patients (age, 60.8±11.5 years; 246 women) who underwent SAVR for BAV disease without aortic repair between 2005 and 2020 at Asan Medical Center. The clinical endpoints were defined as occurrences of sudden death, aortic dissection or rupture, and elective aortic repair. To estimate postoperative changes in the dimensions of the unrepaired aorta, the individual annual aortic expansion rate was calculated. Multiple linear regression models were used to evaluate the risk of aortic expansion. Results: The mean ascending aortic diameter was 39.5±4.6 mm, and 299 patients (41.5%) had a baseline ascending aorta diameter >40 mm. During 70.0±68.3 months of follow-up, the mean annual aortic expansion rate was 0.39±1.96 mm/yr, no aortic dissection or rupture was observed, and sudden deaths were reported in 12 patients (0.34% per person-year). Linear regression analysis revealed no significant correlation between the baseline ascending aortic diameter and postoperative aortic expansion (R²=0.004, β=-0.84, p=0.082). Conclusion: In selected patients undergoing SAVR for a BAV (<55 mm), the risk of adverse aortic events was very low. As this observation contradicts current practice guidelines advocating for proactive aortic replacement in dilated ascending aortas measuring >45 mm, the study results need further validation by studies involving larger populations or randomized controlled trials.

• 문화기술의 융합
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• 제9권4호
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• pp.577-585
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• 2023

이 연구는 LPG 충전소의 가스누출로 발생이 예상되는 화재 및 폭발에 따른 피해예측에 ALOHA 프로그램을 적용 영향범위와 거리를 도식화함으로 피해방지 방안을 제시하였다. LPG 충전소에서 프로판 가스가 누출될 경우 LPG 충전소 주변지역 주민들에게 호흡곤란 등의 인명피해 및 건물파괴 등 재산피해를 입히는 것으로 나타났다. 이의 감소방안으로 첫째 LPG 충전소의 위험물안전관리자는 수시로 계측기와 안전밸브가 제대로 작동하는지 점검하여 누출을 사전에 방지할 필요가 있다. 둘째 LPG 충전소에서 저장탱크에 충전하는 작업은 위험물안전관리법 규정에 따라 "위험물안전관리자 교육"을 받고, 소방관서에서 "위험물안전관리자"로 선임된 사람의 책임하에 해야 한다는 것이다. 셋째 LPG차량의 과충전 방지장치 등 각종 안전장치의 기능을 평상시 정기적으로 점검할 필요가 있다. 마지막으로 LPG 충전소에 가스가 누출될 때 정전기에 의해 화재가 발생할 수 있으므로 정전기를 방지할 수 있는 작업복·작업화를 착용하는 등의 조치로 정전기발생을 억제하는 것이 바람직하다.

• Journal of Chest Surgery
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• 제24권7호
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• pp.663-668
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• 1991

To evaluate risks, complications and mortality of reoperations on heart valve prosthesis, we reviewed clinical records of 53 patients who underwent reoperation because of prosthetic valve failure[PVF], from Jan 1959 through Jun. 1991. They had undergone 48 mitral, 10 aortic valve rereplacement Primary tissue failure was the main cause of reoperation : it occurred in 51 valves at a mean postoperative interval of 58 months. Calcification and collagen disruption of prosthesis were main causes of primary tissue failure in macro and micropathology, In 3 failing mechanical prostheses, paravalvular leak was in 2 cases, another one case had the thrombi at the hinge portion. If conditions such as emergency operation with or without endocarditis, thromboembolism and advanced NYHA functional class are prevented, we think that reoperative valve replacement has similar morbidity and mortality to initial valve replacement surgery. But our sturdy represents higher mortality [22.6%] because of late surgical intervention failing the prevention of conditions leading to myocardial damage. In conclusion if the tearing, calcification, and a new murmur were detected the early reoperation should be considered to increase late survival.

• 한국환경보건학회지
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• 제49권5호
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• pp.247-250
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• 2023

This case report aims to introduce the safety campaign activities for preventing chemical accidents that were cooperatively conducted by an environmental office and chemical-handling workplaces located in the Ulsan area. A chemical safety campaign was initiated to examine and manage chemical-handling facilities at high risk for chemical accidents, specifically valves, flanges, and switches (VFS) from October 2020 to December 2022. The VFS safety check campaign was conducted to raise workers' safety consciousness based on a campaign of advertisements in the workplace from October 2020 to December 2021. In addition, a VFS plus [+] campaign was initiated to encourage actual management activities for chemical-handling facilities at high risk of chemical accidents in 2022. A total of 49 corporations participated in the VFS plus [+] campaign. In contrast to the VFS safety check campaign, which simply focused on publicity and resulted in changes in worker awareness, practicable safety management activities focusing on the handling facilities were carried out. Although notable short-term impacts have yet to be discerned from the campaigns, it is expected that they will eventually serve as a starting point for developing a proper safety culture and environment.

• 한국재료학회지
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• 제34권1호
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• pp.44-54
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• 2024

High-Manganese (Mn) austenitic steel, with over 24 wt% Mn content, offers outstanding mechanical properties in cryogenic settings, making it a potential replacement for existing cryogenic materials. This high manganese steel exhibits high strength, ductility, and wear resistance, making it promising for applications like LNG tanks, flanges, and valves. To operate in cryogenic environments, hot forging and heat treatment processes are vital, especially in flange production. The cooling rate during high-temperature cooling after hot forging plays a critical role in influencing the microstructure and mechanical properties of high manganese steel. The rate at which cooling occurs during this process influences the size of the grains and the distribution of manganese and consequently has an impact on mechanical properties. This study assessed the microstructure and mechanical properties based on different cooling rates during the hot forging of High-Mn steel flanges. Comparing air and water cooling after hot forging, followed by heat treatment, revealed notable differences in grain size. These differences directly impacted mechanical properties such as tensile strength, hardness, and Charpy impact property. Understanding these effects is crucial for optimizing the performance and reliability of High-Mn steel in cryogenic applications.

• Korean Circulation Journal
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• 제53권8호
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• pp.550-562
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• 2023

Background and Objectives: To identify the factors associated with adverse outcomes following surgery for functional insufficiency of the mitral valve (MV) or tricuspid valve (TV) associated with atrial fibrillation (AF). Methods: We evaluated 100 patients (age, 66.5±10.0 years; 47 males) who consecutively underwent surgery for functional insufficiency of the MV or TV associated with AF between January 2000 and December 2020 at our center. The primary outcome was a composite endpoint of all-cause death, valve reoperation, congestive heart failure (CHF) requiring rehospitalization, and stroke. Results: During follow-up (532 patients-years [PYs]), adverse events included death in 16 (3.0%/yr), MV reoperation in 1 (0.2%/yr), CHF in 14 (2.6%/yr), and stroke in 5 (0.9%/yr) patients, demonstrating a 5-year rate of freedom from the primary endpoint of 69.5%. The rate of postoperative AF was high even in those who underwent AF ablation (n=92), with cumulative rates of 48.1% at 1 year and 60.2% at 5 years. In multivariable analyses, the primary outcome was significantly associated with age (adjusted hazard ratio [aHR], 1.06; 95% confidence interval [CI], 1.02-1.10; p=0.005), chronic kidney disease (aHR, 7.76; 95% CI, 2.28-26.38; p=0.001), left atrial appendage exclusion (aHR, 0.35; 95% CI, 0.16-1.78; p=0.010), and postoperative AF as a time-varying covariate (aHR, 3.33; 95% CI, 1.50-7.40; p=0.003). Conclusion: Among patients undergoing surgery for functional atrioventricular insufficiency associated with AF, a significant proportion showed recurrence of AF over time after concomitant AF ablation, which was significantly associated with poor clinical outcomes.

• 대한영상의학회지
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• 제85권2호
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• pp.308-326
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• 2024

심장 기능의 포괄적인 결과는 심장박출량과 전신 정맥 환류로 표현된다. 심장의 4개의 방실은 각자 고유한 기계적 기능을 가진다. 심장방실과 판막, 폐순환 시스템은 전부하 또는 후부하의 형태로 상호 연관되어 있다. 심장 기능 장애는 전반적인 심장 기능의 실패로 전형적인 임상 증상을 나타낸다. 심장 기능 장애의 근본 원인을 조사하려면 심장 내 혈류 유동 경로에 대한 단계별 평가가 필요하다. 이러한 맥락에서, 심장의 세부 구조를 볼 수 있는 영상검사의 표지자는 심장 기능 평가에 중요한 역할을 한다. 영상기반 평가를 통해 개별 심장 구성 요소의 기능을 단계별로 조사할 수 있다. 심장 기능 평가를 위한 영상검사 중 최근 심장 CT가 포함되고 검증되었다. 본 종설에서는 포괄적 및 단계별 심장 기능 평가를 위한 심장 CT 기반 영상 표지자에 대해 논의하겠다.