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Ionic Diffusion Oxidation Model of Uranium - A Revisit Study
Myungjin Kang,Kunok Chang,Kwangheon Park 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1
After the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) was signed, Korea is undergoing nuclear inspection by the International Atomic Energy Agency (IAEA) as a non-nuclear-armed state. By the inspection, nuclear material measurement and management have been carried out according to safety measures. Uranium dioxide, a major component of nuclear fuel, is a material that naturally oxidizes at room temperature, yielding a volume change. In this case, it will have an impact on the management of nuclear material measurement, and a model for predicting this will be required. At room temperature, an oxide film is grown by oxygen diffusion on the surface of uranium dioxide, and if the thickness of the oxide film is predicted based on this, the volume change of uranium dioxide can also be predicted. In relation to this, Ghargozloo’s ionic diffusion oxidation model exists. Therefore, in this paper, an modified oxidation model based on Ghargozloo’s oxygen diffusion in uranium dioxide is presented and the volume change of uranium dioxide due to oxidation is predicted.
유한요소법을 이용한 크랭크 축의 진동 해석에 관한 연구
강승주,오택열,최명진 慶熙大學校 材料科學技術硏究所 1994 材料科學技術硏究論集 Vol.7 No.-
High speed engines with high powers are increasingly in demand and engines employ crankshafts. Accordingly, such problems as bending and torsional vibrations become the point at issue in crankshaft design. In this study, modelling techniques for dynamic analysis of a crankshaft system are presented to investigate crankshaft system vibrations. The crankshaft was idealized by structure containing beams and shells, front pulley and flywheel modelled by a set of lumped masses and moments of inertia, and journal bearing modelled by a set of springs and dampers. These modelling and solution were applied for the analysis of four cylinder in-line engine, with free-free boundary condition, and with oil film supported boundary condition. The calculated natural frequencies and mode shapes were compared with the experimental results, and coincided well.
Lee, Myungjin,Kang, Narae,Kim, Jongsung,Kim, Hung Soo 한국수자원학회 2018 한국수자원학회논문집 Vol.51 No.3
최근 기후변화로 인한 국지성 호우 및 태풍 피해가 자주 발생하고 있다. 이와 같은 피해를 저감하기 위해서는 정확한 강우의 예측과 홍수량 산정이 필요하다. 그러나 지점 및 레이더 강우 시 ․ 공간적 오차를 포함하고 있고, 유출 모형에 의한 유출수문곡선 역시 보정을 실시하더라도 관측유량과 오차를 가지고 있어 불확실성이 존재한다. 따라서 본 연구에서는 확률론적 강우 앙상블을 생성하여 강우의 불확실성을 확인하였다. 또한 유출 결과를 통해 수문 모형의 불확실성을 확인하였고, 블랜딩 기법을 이용하여 하나의 통합된 유출 수문곡선을 제시하였다. 생성된 강우앙상블은 강우강도 및 지형적인 영향으로 레이더가 과소 관측이 될 때, 강우 앙상블의 불확실성이 큰 것을 확인하였고, 블랜딩 기법을 적용하여 산정된 최적 유출 수문곡선은 유출모형의 불확실성을 크게 줄이는 것으로 나타났다. 본 연구 결과를 활용한다면, 정확한 홍수량 산정 및 예측을 통해 집중호우로 인한 피해를 줄일 수 있을 것으로 판단된다. Recently, the flood damage by the localized heavy rainfall and typhoon have been frequently occurred due to the climate change. Accurate rainfall forecasting and flood runoff estimates are needed to reduce such damages. However, the uncertainties are involved in guage rainfall, radar rainfall, and the estimated runoff hydrograph from rainfall-runoff models. Therefore, the purpose of this study is to identify the uncertainty of rainfall by generating a probabilistic radar rainfall ensemble and confirm the uncertainties of hydrological models through the analysis of the simulated runoffs from the models. The blending technique is used to estimate a single integrated or an optimal runoff hydrograph by the simulated runoffs from multi rainfall-runoff models. The radar ensemble is underestimated due to the influence of rainfall intensity and topography and the uncertainty of the rainfall ensemble is large. From the study, it will be helpful to estimate and predict the accurate runoff to prepare for the disaster caused by heavy rainfall.
600 MPa급 플럭스 코어드 아크 용접금속의 저온균열에 미치는 예열 온도 및 미세조직의 영향
이명진 ( Myungjin Lee ),조경목 ( Kyungmox Cho ),강남현 ( Namhyun Kang ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.4
The influence of preheat and microstructure on cold cracking for high strength and low hydrogen flux cored arc (FCA) weld metal was analyzed using Y-groove test. The weld microstructure consisted of acicular ferrite and martensite. As the preheat temperature increased, the volume fraction of acicular ferrite increased and that of martensite decreased, thereby decreasing the volume expansion during the transformation from austenite to martensite. This result was consequently associated with a reduced cold cracking ratio. Cold cracking progressed mainly along the prior austenite grain boundary of martensite, and the fractograph of cold cracking consisted of intergranular fractures and quasi-cleavage fractures. With increasing the preheat temperature and decreasing the carbon equivalent, the fraction of intergranular fractures decreased and quasi-cleavage fractures increased. The microstructure related with intergranular fractures was martensite; quasi-cleavage fractures were associated with acicular ferrite.
( Guo Xian ),( Myungjin Lee ),( Junghoon Lee ),( Namhyun Kang ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.7
Cold cracking is one of the most common catastrophic defects in welds. In this study, we investigated the effect of the shield gas composition (specifically Ar+5 ~ 20% CO2) on the cold-crack ratio on the preheating temperature of 20℃~100℃ in flux-cored arc welds. Critical assessment of the cold-crack ratio was achieved by observing the weld cross-section, appearance of surface cracks, and fractography. The cold-crack ratio decreased as the preheating temperature increased from 20 to 100℃. For the preheating temperature of 50℃, the shield gas (containing 20% CO2) provided higher oxygen content in the weld metal and increased the number of nucleant inclusions for acicular ferrite; thereby eliminating cold cracks. The shield gas with 15% CO2 produced welds that had nearly the same amount of acicular ferrite as compared with the 5% and 10% CO2 cases. However, the 15% CO2 shield gas produced the greatest hardness and largest amount of non-nucleant inclusions in the weld metal, therefore exhibiting the largest cold-crack ratio. If the volume fraction of acicular ferrite remains unchanged, hardness and non-nucleant inclusions should be considered roughly for assessment of the cold-crack ratio.