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Si<sub>3</sub>N<sub>4</sub> 세라믹스의 균열 치유와 굽힘 강도 특성
남기우,박승원,도재윤,안석환,Nam, Ki-Woo,Park, Seung-Won,Do, Jae-Youn,Ahn, Seok-Hwan 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
Crack-healing behavior of $Si_3N_4$ composite ceramics has been studied as functions of heat-treatment temperature and amount of additive $SiO_2$ colloidal. Results showed that optimum amount of additive $SiO_2$ colloidal and coating of $SiO_2$ colloidal on crack could significantly increase the bending strength. The heat-treatment temperature has a profound influence on the extent of crack healing and the degree of strength recovery. The optimum heat-treatment temperature depends on the amount of additive $SiO_2$ colloidal. Crack healing strength was far the better cracked specimen with $SiO_2$ colloidal coating on crack surface. After heat treatment at the temperature 1,273 K in air, the crack morphology almost entirely disappeared by scanning prob microscope. At optimum healing temperature 1,273 K, the bending strength with additive $SiO_2$ colloidal 0.0 wt.% without $SiO_2$ colloidal coating recovered to the value of the smooth specimens at room temperature for the investigated crack sizes $100\;{\mu}m$. But that with $SiO_2$ colloidal coating increase up to 140 %. The amount of optimum additive $SiO_2$ colloidal was 1.3 wt.% and crack healed bending strength with $SiO_2$ colloidal coating increase up to 160 % to smooth specimen of additive $SiO_2$ colloidal 0.0 wt.%. Crack closure and rebonding of the crack due to oxidation of cracked surfaces were suggested as a dominant healing mechanism operating in $Si_3N_4$ composite ceramics.
플랜트 승압펌프 재순환 배관 용접부의 용접비드에 의해 발생한 감육결함 분석 및 건전성 평가
남기우(Ki-Woo Nam),안석환(Seok-Hwan Ahn),도재윤(Jae-Yoon Do) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.4
The wall thinning phenomenon of pipes was simulated as metal loss due to erosion and corrosion. Such wall thinning defects in the pipes of power plants are a very important safety consideration, In this study, we analyzed wall thinning dejects thar occurred by weld bead of weld zone of boost pump recirculation. pipe. From the results of the analysis of pipe failures, numerical analysis was performed by Fluent v6.3.26 using the standard k-ε model of the weld bead shape, such as an elliptical or a spherical shape, on the inner wall of the pipe. Using the results obtained, we showed the overlap effect by cavitations corrosion and erosion-corrosion at the bottom of the wall-thinning defect.
남아름(Aram Nam),박정안(Jeong-Ann Park),도태구(Taegu Do),최재우(Jae-Woo Choi),최웅수(Ungsu Choi),김경남(Kyung Nam Kim),윤성택(Seong-Taek Yun),이상협(Sanghyup Lee) 大韓環境工學會 2017 대한환경공학회지 Vol.39 No.3
PAN 기반 아크릴계 섬유와 DETA 및 AlCl3・6H2O를 반응시켜 아민기(-NH2)를 가진 이온교환섬유 PADD를 합성하였다. 개발된 섬유상 소재는 FT-IR과 SEM을 이용하여 그 특성을 확인해 보았다. 회분식 실험으로 수행된 PADD를 이용한 크롬제거 실험 결과는 Langmuir 등온흡착모델에 잘 적용되었으며, 이때 계산된 이론적 최대흡착능 (Qmax)은 6.93 mmol/g으로 나타났다. 한편 동적흡착실험은 Lagergren 유사이차속도모델에 잘 부합되었다. PADD의 크롬 흡착능은 pH 2에서 가장 높은 값인 4.11 mmol/g을 나타내었고 pH 변화에 많은 영향을 받는 것으로 확인되었다. 또한, 인산과 비소(V)에 대한 공존이온 실험을 통해 PADD가 크롬에 대한 높은 선택성을 갖고 있음을 확인할 수 있었다. 산-염기 역적정으로 구한 PADD의 총이온교환능 (4.70 mmol/g)을 통해 소재의 선택적 제거 가능성을 검증하였다. Ion exchange fiber, PADD was synthesized by the reaction between PAN based acrylic fiber and DETA with AlCl3・6H2O, and was analyzed by FT-IR and SEM to investigate its characteristics. The experimental results of Cr(VI) removal by PADD were better fitted with Langmuir adsorption isotherm, and the maximum uptake value (Qmax) was calculated to be 6.93 mmol/g. The kinetic data can be well described by Lagergen pseudo-second order rate model. The Cr(VI) adsorption capacity of PADD was 4.11 mmol/g at pH 2, which shows the effect of pH changes on the removal of Cr(VI). The adsorption selectivity of Cr(VI) was higher than phosphate and As(V). Total ion exchange capacity of PADD was 4.70 mmol/g, which was measured by acid-base back titration.
남기우(Ki Woo Nam),박승원(Seung Won Park),도재윤(Jae Youn Do),안석환(Seok Hwan Ahn) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
Crack-healing behavior of Si₃N₄ composite ceramics has been studied as functions of heat-treatment temperature and amount of additive SiO₂ colloidal. Results showed that optimum amount of additive SiO₂ colloidal and coating of SiO₂ colloidal on crack could significantly increase the bending strength. The heat-treatment temperature has a profound influence on the extent of crack healing and the degree of strength recovery. The optimum heat-treatment temperature depends on the amount of additive SiO₂ colloidal. Crack healing strength was far the better cracked specimen with SiO₂ colloidal coating on crack surface. After heat treatment at the temperature 1,273 K in air, the crack morphology almost entirely disappeared by scanning prob microscope. At optimum healing temperature 1,273 K, the bending strength with additive SiO₂ colloidal 0.0 wt.% without SiO₂ colloidal coating recovered to the value of the smooth specimens at room temperature for the investigated crack sizes 100 ㎛. But that with SiO₂ colloidal coating increase up to 140 %. The amount of optimum additive SiO₂ colloidal was 1.3 wt.% and crack healed bending strength with SiO₂ colloidal coating increase up to 160 % to smooth specimen of additive SiO₂ colloidal 0.0 wt.%. Crack closure and rebonding of the crack due to oxidation of cracked surfaces were suggested as a dominant healing mechanism operating in Si₃N₄ composite ceramics.
남상훈(Sang-Hun Nam),정도운(Do-Un Jung),김성진(Sung-Jin Kim),문정준(Jung-Joon Moon),전동욱(Dong-Wook Jeon),김연수(Yeon-Sue Kim),신동진(Dong Jin Shin),최현석(Hyeon-Seok Choi),정재훈(Jae-Hoon Jeong) 대한생물치료정신의학회 2020 생물치료정신의학 Vol.26 No.3
Objectives:We aimed to evaluate the relationship between disability self-awareness and insight in patients with schizophrenia. Methods:We enrolled 58 clinically stable patients with schizophrenia. The World Health Organization Disability Assessment Schedule (WHODAS) self-report was used to identify self-awareness of functional ability. The Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Schizophrenia Scale (CGI-SCH), and Personal and Social Performance Scale (PSP) were utilized to evaluate clinical symptoms and global function. Whereas Insight Scale for Psychosis (ISP) was applied for insight. Statistical analyses were performed using correlation and linear regression. Results:The WHODAS had a significant correlation with the general psychopathology subscale and total score of PANSS, CGI-SCH, and PSP. Moreover, ISP had a strong correlation with the overall WHODAS score and all domains. In the linear regression analysis, ISP had significant effects on the overall WHODAS score after adjusting for additional variables. Conclusion:Disability self-awareness was significantly correlated with the level of insight in patients with schizophrenia. Clinicians need to consider patients’ insight during the discussion of functional ability.
인간 상피성장인자 유전자 발현 유전자변형 콩의 생태계 침입성 평가
김도영(Do Young Kim),엄민식(Min Sik Eom),김혜진(Hye Jin Kim),백인순(In-Soon Pack),박정호(Jung-Ho Park),박기웅(Kee Woong Park),남경희(Kyong-Hee Nam),오성덕(Sung-Dug Oh),김재광(Jae Kwang Kim),서주석(Ju Seok Seo),김창기(Chang-Gi Kim) 한국잡초학회·한국잔디학회 2020 Weed & Turfgrass Science Vol.9 No.2
유전자변형(genetically modified, GM) 작물의 생태계 침입성 또는 잡초화 가능성은 환경 측면에서 주요 우려 사항의 하나이다. 인간 상피성장인자 유전자(egf, igf-1, trx)를 발현하는 GM 콩 3개 이벤트가 재배관리되지 않는 환경에서 지속할 수 있는지 여부를 평가하고, 토양에 매몰된 종자의 활력을 조사하기 위해 본 연구를 수행하였다. GM 콩과 비변형 콩종자를 2017년 6월에 파종하고 연구기간 동안 물과 병해충 및 잡초 관리를 하지 않은 채 시험구에 출현한 콩 식물체 수를 조사하였을 때 GM 콩과 비변형 콩 식물체는 생장하고 종자 생산도 하였지만 17개월까지만 개체군을 유지할 수 있었다. 콩 종자를 2017년 11월에 매몰한 뒤 4, 6, 8, 10개월 후에 활력을 조사하였다. GM 콩과 비변형 콩 종자 모두 월동은 가능했지만, 모든 종자는 6개월 이내에 활력을 잃었다. 이와 같이 GM 콩과 비변형 콩 모두 정착에 성공하지 못했으며, 수명이 짧은 콩 종자는 일시적으로만 토양종자은행을 형성하였다. 따라서 3개 GM 콩 이벤트가 생태계에서 침입식물 또는 잡초가 될 가능성은 거의 없을 것으로 판단된다. The invasiveness or weediness of genetically modified (GM) crops is considered as one of the major environmental concerns regarding the cultivation of these crops. This study was conducted to evaluate whether three events of GM soybeans expressing human epidermal growth factor gene (egf , igf-1 , or trx ) can persist in the environment without cultivation management and to determine the viability of their seeds buried in soil. Seeds of GM and non-GM soybean were sown in June 2017, and the number of soybean plants grown in the plots was counted. During the study period, water and pest management were not applied in the plots. Both GM and non-GM soybean plants were able to grow and produce seeds; however, they maintained their populations only for up to 17 months. The GM and non-GM soybean seeds were buried in November 2017, and their viability was measured 4, 6, 8, and 10 months after seed burial. Both GM and non-GM soybean seeds were able to overwinter. However, they lost viability within 6 months. GM and non-GM soybeans could not be successfully established in the environment, and short-lived soybean seeds could form only a transient soil seed bank. Therefore, GM soybean events are highly unlikely to become invasive plants or weeds in the ecosystem.