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변형구배 결정소성 유한요소해석법을 이용한 니켈기 다결정 합금의 Hall-Petch 관계 모델링
최윤석,조경목,남대근,최일동,Choi, Yoon Suk,Cho, Kyung-Mox,Nam, Dae-Geun,Choi, Il-Dong 한국재료학회 2015 한국재료학회지 Vol.25 No.2
A strain-gradient crystal plasticity constitutive model was developed in order to predict the Hall-Petch behavior of a Ni-base polycrystalline superalloy. The constitutive model involves statistically stored dislocation and geometrically necessary dislocation densities, which were incorporated into the Bailey-Hirsch type flow stress equation with six strength interaction coefficients. A strain-gradient term (called slip-system lattice incompatibility) developed by Acharya was used to calculate the geometrically necessary dislocation density. The description of Kocks-Argon-Ashby type thermally activated strain rate was also used to represent the shear rate of an individual slip system. The constitutive model was implemented in a user material subroutine for crystal plasticity finite element method simulations. The grain size dependence of the flow stress (viz., the Hall-Petch behavior) was predicted for a Ni-base polycrystalline superalloy NIMONIC PE16. Simulation results showed that the present constitutive model fairly reasonably predicts 0.2%-offset yield stresses in a limited range of the grain size.
Glucose Transporter-1 Expression in Squamous Cell Carcinoma of the Tongue
최윤석,Seok Jin Kim,Dae Sik Kim,Seh Jong Park,Yong Park,Hye Jin Shin,Kwang-Yoon Jung,Seung-Kuk Baek,Bong Kyung Shin,Jung Woo Choi,Byung Soo Kim,Sang Won Shin,Yeul Hong Kim,Jun Suk Kim 대한암학회 2007 Cancer Research and Treatment Vol.39 No.3
Purpose: Tumor cells are known to express hypoxia-related proteins such as glucose transporter-1 (Glut-1). These hypoxia-induced changes may allow tumor cells to survive under sustained hypoxic microenvironments, and the surviving tumor cell under hypoxia may develop a more aggressive phenotype and so result in a poor prognosis. Materials and Methods: The Glut-1 expression was analyzed by immunohistochemistry, and its association with the prognosis was assessed in 60 patients with squamous cell carcinoma of the tongue.Results: The Glut-1 expression was diffuse with a membranous pattern, and the median percentage of Glut-1 positive tumor cells was 60% (range: 0.0∼90.0%). A high Glut-1 expression (the percentage of positive tumor cells ≥ the median value, 60%) was associated with the location of primary lesion, lymph node metastasis status and disease stage (p〈0.05).Theexpression of Glut-1 was correlated with the Ki-67 expression (r=0.406, p=0.001). Microvessel density, as represented by CD31 staining, was also correlated with the Glut-1 expression although its significance is weak (r=0.267, p=0.039). On the univariate analysis, the group with a high Glut-1 expression showed poorer overall survival than the group with a low Glut-1 expression (p〈0.05). However, the Glut-1 expression failed to show any independent prognostic significance on the multivariate analysis.Conclusion: The expression of Glut-1 may be useful for predicting the prognosis and determining the treatment strategy for the management of squamous cell carcinoma of the tongue. (Cancer Res Treat. 2007;39:109-115)
브라운관 폐유리 대체율에 따른 모르타르의 감마선 차폐 특성
최윤석 ( Choi Yoon-suk ),장필성 ( Jang Pil-sung ),이선민 ( Lee Seon-min ),장현오 ( Jang Hyun-o ),강동원 ( Kang Dong-won ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1
In this study, the gamma-ray shielding characteristics of mortar specimens substituted CRT waste glass as a fine aggregate were evaluated. According to the results, the linear attenuation coefficient of mortar specimen replaced with CRT waste glass was increased. Especially, the half-value layer of CRT waste glass specimen in radiation source of 122KeV·57Co was 48% higher than that of normal sand specimen.
최윤석 ( Choi Yoon Suk ),장연주 ( Jang Yeon Ju ),박지영 ( Park Ji Young ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1
In this study, the effect of calcium leaching on chloride ion penetration resistance of mortar specimens was evaluated. According to test results, the penetration depth of chloride ion was increased after the calcium leaching attack.