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정원택(W. T. Jung),권상우(S. W. Kwon),공유식(Y. S. Kong),김선진(S. J. Kim) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
In this study, dissimilar friction welding were produced using 15mm diameter solid bar in chrome molybedenum steel(SCM440) to carbon steel(S45C) to investigate their mechanical properties and the relationship between the weld parameters and the nondestructive coefficients. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and heat affected zone. The specimens were tested as-welded and post weld heat treated(PWHT). And also, the relationships between the weld parameters and nondestructive coefficients, such as AE counts and ultrasonic attenuation coefficient. The tensile strength of the friction welded steel bars was increased up to 100% of the S45C base metal under the condition of all heating time. The toughness of PWHT specimens is higher than as-welded. It is seem to be that there are not evident relationship between AE counts, ultrasonic attenuation coefficient and heating time.
크리프 파단 데이터의 변동성에 대한 새로운 고찰과 수명예측
정원택(Won-Taek Jung),공유식(Yu-Sik Kong),김선진(Seon-Jin Kim) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.10
This paper deals with the variability analysis of short term creep rupture test data based on the previous creep rupture tests and the possibility of the creep life prediction. From creep tests performed by constant uniaxial stresses at 600, 650 and 700℃ elevated temperature, in order to investigate the variability of short-term creep rupture data, the creep curves were analyzed for normalized creep strain divided by initial strain. There are some variability in the creep rupture data. And, the difference between general creep curves and normalized creep curves were obtained. The effects of the creep rupture time (RT) and steady state creep rate (SSCR) on the Weibull distribution parameters were investigated. There were good relation between normal Weibull parameters and normalized Weibull parameters. Finally, the predicted creep life were compared with the Monkman-Grant model.
스테인리스 강의 단시간 크리프 파단시간의 변동성과 수명예측
정원택(Won-Taek Jung),공유식(Yu-Sik Kong),김선진(Seon-Jin Kim) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.6
This paper deals with the variability of short term creep rupture time based on previous creep rupture tests and the statistical methodology of the creep life prediction. The results of creep tests performed using constant uniaxial stresses at 600, 650, and 700℃ elevated temperatures were used for a statistical analysis of the inter-specimen variability of the short tenn creep rupture time. Even under carefully controlled identical testing conditions, the observed short-term creep rupture time showed obvious inter-specimen variability. The statistical aspect of the short term creep rupture time was analyzed using a Weibull statistical analysis. The effect of creep stress on the variability of the creep rupture time was decreased with an increase in the stress level. The effect of the temperature on the variability also decreased with increasing temperature. A long term creep life prediction method that considers this statistical variability is presented. The presented method is in good agreement with the Lason-Miller Parameter (IMP) life prediction method.
정원택 ( Won Tec Jung ),윤진혁 ( Jin Hyuk Yun ),문희건 ( Hee Kun Moon ),김병희 ( Byung Hee Kim ),유승훈 ( Seung Hoon Ryu ),이창민 ( Chang Min Lee ),김경희 ( Kyeong Hee Kim ),권혁찬 ( Hyuk Chan Kwon ),이성원 ( Sung Won Lee ),정원태 대한류마티스학회 2002 대한류마티스학회지 Vol.9 No.3
Rheumatoid arthritis (RA) is though to be a collagen disease induced by auto-immune mechanism of unknown etiology. Chronic myelogenous leukemia (CML) is a disease characterized by overproduction of cells of the granulocytic, especially the neutrophilic series and occasionally the monocytic series, leading to marked splenomegaly and very high white blood cell counts. There`s no consensus on the risk of leukemia in RA. There are some reports ragarding the relationship between low dose of methotrexate (<20 mg weekly) and the development of leukemia in RA. Although RA is a complex process, it can be considered initially as a stem cell disorder requiring treatment similar to that administered to transplant patient. We experienced a case of CML associated with RA. A 60-year-old woman with RA was treated with low dose methotrexate (7.5 mg weekly), hydroxychloroquine (HCQ), non-steroidal anti-inflammatory drug (NSAID) and low dose steroid. This therapy was continued for 3 years. She was diagnosed CML after 3 years of therapy. CML was confirmed by bone marrow biopsy and the presence of the Philadelphia chromosome.
정원택(Won Taek Jeong),이승재(Seung Jae Yi),김현동(Hyun Dong Kim),김경천(Kyung Chun Kim) 한국가시화정보학회 2011 한국가시화정보학회지 Vol.9 No.4
Oxygen sensitive functional particles(OSParticle) were fabricated by three different methods for using the particles as oxygen sensors and PlV tracers. The used methods were a physical coating method, an ion-exchange method and a dispersion polymerization method. The physical coating method is dipping Si02 hollow particles into dye solution then drying. This method is very simple, but particles are not uniform in diameter and luminescence. The particles fabricated by the ion-exchange method have very uniform diameter and well doped. However, it can not be used in water since the particles are hydrophobic. In case of the dispersion polymerization method, the diameter of OS Particles is quite uniform. The diameter of OS Particles can be changed by controlling the quantity of AIBN (2,2-azobis isobutyronitrile). For the purpose of dissolved oxygen concentration measurement in micro scale water flows, the dispersion polymerized OS Particles turn out to be the most superior functional particles. The luminescent intensity of OS Particles was tested with the variation of dissolved oxygen concentration in water samples. As a result, the luminescent intensity of OSParticles is monotonically decreased with increasing DO (Dissolved oxygen) concentration of water.