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관측중단 데이터를 고려한 배전용 전력기기 수명평가에 관한 고찰
한상조,김창희,김재중,채희석 한국신뢰성학회 2018 한국신뢰성학회 학술대회논문집 Vol.2018 No.10
전력 시스템의 운용 중 고장 및 사고를 사전에 예방하기 위한 대표적인 방법론으로 RAMS를 적용한 시스템의 설계 수준 분석과, RCM을 적용한 예방정비의 기준 분석이 연구되고 있다. 이들 연구와 더불어 분석 결과에 큰 영향을 미치는 기기 신뢰도(수명) 데이터 정확성에 대한 요구 또한 높아지고 있는데, 일반적으로 필드 데이터를 이용한 wear out 수명은 기기의 생애 전주기를 통해 추정해야 하지만 기업 보안 등의 현실적 문제로 확보할 수 있는 이력 데이터에 한계가 있어 정확한 수명 추정에 어려움이 있다. 본 연구에서는 필드 데이터 활용 방법에 따라 전력용 배전기기의 수명 모델을 도출하여 비교하였다. 정상작동(생존)데이터를 고려한 수명 이 기존 대비 높게 추정되었으며 합리적 수명추정을 위한 정상작동(생존)데이터의 중요성을 확인하였다.
한상조,백수정,윤영훈,김지현,이혜선,전소영,박효진 대한소화기학회 2023 대한소화기학회지 Vol.81 No.4
Background/Aims: To investigate the risk of metabolic syndrome and fatty liver diseases in gastric cancer survivors compared to non-cancer subjects. Methods: The data from the health screening registry of the Gangnam Severance Hospital from 2014–2019 was used. Ninety-one gastric cancer survivors and a propensity-score-matching 445 non-cancer subjects were analyzed. Gastric cancer survivors were divided into those with surgical treatment (OpGC, n=66) and non-surgical treatment (non-OpGC, n=25). Metabolic syndrome, fatty liver by ultrasonography, and metabolic dysfunction-associated fatty liver disease (MAFLD) were assessed. Results: Metabolic syndrome was in 15.4% of gastric cancer survivors (OpGC; 13.6%, non-OpGC; 20.0%). Fatty liver by ultrasonography was in 35.2% in gastric cancer survivors (OpGC; 30.3%, non-OpGC: 48.0%). MAFLD was in 27.5% of gastric cancer survivor (OpGC; 21.2%, non-OpGC; 44.0%). After adjusting for age, sex, smoking, and alcohol, the risk of metabolic syndrome was lower in OpGC than in non-cancer subjects (OR, 0.372; 95% CI, 0.176-0.786, p=0.010). After adjusting, OpGC showed lower risks of fatty liver by ultrasonography (OR, 0.545; 95% CI, 0.306-0.970, p=0.039) and MAFLD (OR, 0.375; 95% CI, 0.197-0.711, p=0.003) than did non-cancer subjects. There were no significant differences in the risks of metabolic syndrome and fatty liver diseases between non-OpGC and non-cancer subjects. Conclusions: OpGC showed lower risks of metabolic syndrome, fatty liver by ultrasonography, and MAFLD than non-cancer subjects, but there were no significant differences in the risks between non-OpGC and non-cancer subjects. Further studies on metabolic syndrome and fatty liver diseases in gastric cancer survivors are warranted.
Development of a 200 kW ORC radial turbine for waste heat recovery
한상조,서종범,최범석 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12
There has recently been a growing interest in sustainable energy converters. One such technology is the organic Rankine cycle, whichuses conventional turbine technology with a low temperature waste heat source. A 200 kW organic Rankine cycle system was designedfor waste heat recovery application using R245fa as a working fluid. A radial type turbine with 15,000 rpm was employed to generatemore than 200 kW with an expansion ratio of 9. Since R245fa has Ma = 1 at low velocity of the working fluid (about 1/3 of air sound ofspeed) at about 100°C, it reaches supersonic flow conditions easily with small pressure expansion. To avoid supersonic flow conditionsin the turbine, the expansion ratio was evenly divided and applied to two turbine stages. Two radial type rotors were placed in the backto-back layout in a single shaft. The inlet temperature of the turbine was about 124°C, and the inlet pressure was about 2 MPa. The designedturbine was fully tested in the 200 kW ORC system using the design conditions. It succeeded in generating more than 200 kWwith R245fa. The performance of the turbine was validated with the experimental results and CFD analysis. Herein, the design procedureand performance evaluation of the ORC turbine was described using R245fa.
Fabrication of Al2O3 Dispersion Strengthened Copper Alloy by Spray In-Situ Synthesis Casting Process
한상조,서정혁,조경환,김명호 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.2
Al2O3 dispersion strengthened (ODS) copper alloy was made by Spray in-situ synthesis casting process, whichis a new method of the spray casting that can produce ODS preform in a single process. Its microstructureand mechanical properties of sintered compact was investigated. Cu/Al2O3 ODS alloys were produced byspraying with the mixed gas containing various oxygen volume fraction between 0-8 vol%. Al2O3 at depositedalloy was observed from the oxygen content of 3 vol%, and the area fraction of Al2O3 increased with increasingoxygen contents. Al2O3 was observed at the interface between droplets, and its morphology was irregular suchas linear or circular shape. It seemed that oxide layer was broken and deposited on the substrate owing to theselective oxidation at the atomization zone. In sintered compacts, Al2O3 was found at grain boundary. Mechanicalproperties improved with the increase of oxygen volume fraction owing to the dispersion strengthening of Al2O3.
한상조(Sangjo Han),서종범(JongBeom Seo) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.12
최근 전세계적으로 재생에너지의 관심이 증가하고 있다. 그 중 많은 관심을 받고 있는 것이 상대적으로 낮은 온도의 폐열을 사용하는 유기랭킨사이클(ORC)이다. 유기랭킨사이클은 기존의 증기터빈사이클과 유사한 기술을 사용하지만 낮은 온도의 폐열을 사용하기 위해서 증기대신 냉매를 작동유체로 사용한다. 작동유체를 냉매로 사용함으로 인해 이상기체 가정을 사용할 수 없고, 이는 ORC 시스템에 이용되는 터빈의 설계를 좀 더 복잡하게 만든다. 또, 냉매의 큰 분자량과 복잡한 분자구조로 인하여 낮은 음속을 가지게 되고 이로 인해서 쉽게 초킹 조건에 접근하게 된다. 본 연구에서 R245fa 를 작동유체로 하여 입구온도 124℃에 팽창비 9 의 조건에서 터빈의 효율을 증가시키기 위해 다단으로 설계된 아음속 ORC 터빈을 설계하는 과정과 터빈의 성능에 대하여 설명하고자 한다. 설계된 터빈은 200kW 급의 ORC 발전 시스템에 사용될 예정이다. Recently, there has been a growing interest in sustainable energy. One method that has been used is an organic Rankine cycle using conventional turbine technology with a low-temperature waste heat source. A 200-kW organic Rankine cycle (ORC) system was designed for a waste heat recovery application using R245fa as the working fluid. A radial turbine running at 15,000 rpm was employed to generate more than 200 kW with an expansion ratio of nine. Because an ORC turbine uses a refrigerant as the working fluid, the ideal gas law was not employed to design the turbine. In addition, the complexity of the molecular structure of R245fa made it difficult to design the turbine. Because R245fa has an Ma value of one at a low velocity for the working fluid (about 1/3 of the speed of sound in air) at about 100°C, it easily reaches a supersonic flow condition with a small pressure expansion. To increase the efficiency of the turbine, a dual stage radial-type turbine with a subsonic speed was suggested. This paper will describe the design procedure and performance evaluation of the ORC turbine using R245fa.