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2 상조직강의 항복 및 변형거동에 미치는 퍼얼라이트의 영향
최병영,오상엽 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.9
The dual phase steels of ferrite-martensite and ferrite-martensite-pearlite were prepared by two step cooling or isothermal holding after intercritical annealing. And this research investigated the effect of pearlite on the yielding and deformation behavior of these dual phase steels. It was observed that second phase particles with pearlite-martesite interfaces were distributed in the ferrite matrix. The structure of pearlite-martensite interface was also observed by using SEM. Continuous or discontinuous yielding apeared in the specimens of ferrite-martensite-pearlite. The lower yielding ratio and continuous yielding were shown in the specimens with more martensite content (≥5.8 vol%). The microstructure observed by TEM showed that the mobile dislocations causing continuous yielding and the pinned dislocations by solute atoms were distributed in the ferrite. The effect of pearlite on the variation of work hardening exponents during tensile deformation was also discussed in terms of the Modified Crussard-Jaoul analysis.
3차원 지하수 유동과 반응성용질이동 모델을 활용한 우라늄 흡착 및 이동에 관한 개념 모델링
최병영,고용권,윤성택,김건영,Choi, Byoung-Young,Koh, Yong-Kwon,Yun, Seong-Taek,Kim, Geon-Young 대한자원환경지질학회 2008 자원환경지질 Vol.41 No.6
본 연구에서는 지구화학 모델을 활용하여 지하수 환경에서의 우라늄의 존재 형태, 흡착 및 이동 특성을 모사해 보았다. 흡착에 의한 우라늄의 지연 이동을 효과적으로 모사하기 위하여 3차원 지하수 유동 모델과 반응성 용질 이동 모델을 활용하였다. 모사 결과, $pCO_2=10^{-3.6}$조건에서 대부분의 우라늄 흡착(최대 99.5%)은 pH 5.5와 띠에서 발생하였다. $pCO_2$가 $10^{-2.5}$인 경우 우라늄이 대부분 흡착되는 pH범위는 6에서 7사이로 매우 좁았으며, 반면 $pCO_2=10^{-4.5}$인 경우에는 흡착되는 pH가 범위가 상대적으로 넓어 pH 5.5에서 8.5사이에서 대부분 흡착되었다. 음이온 화합물을 고려한 경우에는 pH 6 이하에서는 불소착물의 형성에 의해 우라늄 흡착이 감소하였다. 본 연구를 통하여, 우라늄 이동이 pH, $pCO_2$ 및 음이온의 종류와 농도 등 지하수의 지화학적 조건에 의해 상당히 영향을 받음을 알 수 있었다. 향후 여러 부지 조사 및 평가와 관련하여 우라늄 및 기타 유해성 화합물의 환경 영향을 예측하는데 있어 지구화학 모델이 중요한 도구로 활용되어야 할 것이다. In this study, the speciation, adsorption, and transport of uranium in groundwater environments were simulated using geochemical models. The retarded transport of uranium by adsortption was effectively simulated using 3-D groundwater flow and reactive transport models. The results showed that most uranium was adsorbed(up to 99.5%) in a neutral pH(5.5<pH<8) under low $pCO_2(10^{-3.6}atm)$ condition. Under the higher $pCO_2(10^{-2.5}atm)$ condition, however, the pH range where most uranium was absorbed was narrow from 6 to 7. Under very low $pCO_2(10^{-4.5}atm)$ condition, uranium was mostly absorbed in the relatively wide pH range between 5.5 and 8.5. In the model including anion complexes, the uranium adsorption decreased by fluoride complex below the pH of 6. The results of this study showed that uranium transport is strongly affected by hydrochemical conditions such as pH, $pCO_2$, and the kinds and concentrations of anions($Cl^-$, ${SO_4}^{2-}$, $F^-$). Therefore, geochemical models should be used as an important tool to predict the environmental impacts of uranium and other hazardous compounds in many site investigations.
중ㆍ저준위 방사성 폐기물 처분부지의 지구화학 특성 :Ⅰ. 지하수
최병영,김건영,고용권,신선호,유시원,김두행 한국방사성폐기물학회 2008 방사성폐기물학회지 Vol.6 No.4
본 연구는 방사성 폐기물 처분장의 지하수 화학 조건을 조절하는 수리지구화학 특성을 규명할 목적으로 수행되었다. 이를 위해 처분장 주변의 관측공 중 12개의 관측공이 선정되었으며, 이들 시료를 심도별로 총 46 지점에서 채취하였다. 또한 지표수 3점과 해수 1점의 시료도 채취하였다. 채취된 시료는 양/음이온 분석이 수행되었으며, 물과 용질의 기원을 규명할 추적자로서 산소-수소, 삼중수소, 탄소, 황 동위원소도 분석되었다. 산소-수소 동위원소 분석 결과 지표수와 지하수는 모두 강우 기원임을 보여주었으며, 삼중수소 농도는 깊이가 깊어짐에 따라 감소하고는 있으나 높은 삼중수소 농도는 최근에 충진된 물임을 나타내고 있었다. 양/음이온 분석 결과를 통한 수질 유형 분석에서는 연구 지역 지하수는 Ca-Na-HCO3 유형과 Na-Cl-SO4 유형이 대표적이었으며, 상관 분석 결과 이들 이온은 해염, 물-암석 반응의 영향을 받은 것으로 판단된다. 특히 연구 지역에서 Na 비율이 높은 이유는 양이온 교환 반응에 의해 이루어지고 있음을 보여 주었다. 연구 지역의 산화-환원 조건의 경우에는 심도가 깊어짐에 따라 낮은 DO와 Eh 값을 나타내어 환원 환경이 형성되었음을 나타내며, 높은 Fe와 Mn의 농도는 Fe와 Mn 산화물의 환원 반응이 산화-환원 조건을 조절하고 있음을 보여주었다. This study was carried out to identify the characteristics of hydrochemistry controlling groundwaterchemical condition in a repository site of Gyeongju. For this study, 12 bore holes of all monitoringbore holes in the study area were selected and total 46 groundwater samples were collected with depth.In addition, 3 surfacewater samples and 1 seawater sample were collected. For water samples, cationsand anions were analyzed. The environmental isotopes(18O-D, Tritium, 13C, •34S) were alsoanalyzed to trace the origin of water and solutes. The result of 18O and D analysis showed thatsurface water and groundwater were originated from precipitation. Tritium concentrations ofgroundwater decreased with depth but high concentrations of tritium indicated that groundwater wasrecharged recently. The results of ion and correlation analysis showed that groundwater types of thestudy area were represented by Ca-Na-HCO3and Na-Cl-SO4, which was caused by sea spray andwater-rock interaction. Especially, high ratio of Na content in groundwater resulted from ion exchange.For redox condition of groundwater, the values of DO and Eh decreased with depth, which indicatedthat reducing condition was formed in deeper groundwater. In addtion, high concentration of Fe andMn showed that redox condition of groundwater was controlled by the reduction of Fe and Mn oxides.
二段冷却과 Ms溫度以下에서 恒溫維持에 依한 二相組織鋼의 機械的 性質의 改善에 關한 硏究
崔秉濚,李成載 전북대학교 공업기술연구소 1984 工學硏究 Vol.15 No.-
The improvement of mechanical properties in dual phase steels by two step cooling and isothermal holding below Ms temperature was studied. The experimental results obtained are summarized as follows : 1. Optimum mechanical properties in dual phase steels were obtained by two step cooling Mn-Si steels from 790℃(holding time : 2min). 2. During primary cooling of two step cooling the transformation of ferrite resulted in dispersion of martensite. 3. As a result of isothermal holding below Ms temperature, the volume fraction of retained austenite increased. 4. In case of isothermal holding at 350℃ or 400℃, yield point phenomena appeared due to smaller volume fraction of martensite. 5. With isothermal holding at 300℃, continuous yielding appeared because the volume fraction of martensite was above critical value. 6. Two types of retained austenite were observed by transmission electron microscope.
반응성용질이동 모델링을 이용한 장기간의 콘크리트 변질과정과 우라늄의 용해도에 대한 개념 모델링
최병영,고용건,김건영,유시원,안상원,배대석,Choi, Byoung-Young,Koh, Yong-Kwon,Kim, Geon-Young,Yoo, Si-Won,An, Sang-Won,Bae, Dae-Seok 한국방사성폐기물학회 2008 방사성폐기물학회지 Vol.6 No.1
Long-term degradation of coment barrier by diffusion was studied with reactive transport modeling. The result of modeling showed that cement barrier was altered about 30cm thickness after 50,000 years. The pH decreased from 13.0 to 11.9 because of depletion of alkali ions, and dissolution/precipitation of portlandite and CSH (Calcium Silicate Hydrate). In addition, porosity increased about 0.3 because of dissolution of portlandite and $CSH2.0(Ca_2SiO_3(OH)_2:0.17H_2O)$. The solubility of uranium also increased with the increase of pe value The results of this study indicate that long-term degradation of comet can enhance the transport of nuclide by changing pH, pe, porosity in barrier.