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        Discharge header design inside a reactor pool for flow stability in a research reactor

        윤현기,최용석,서경우,김성훈 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

        An open-pool type research reactor is designed and operated considering the accessibility around the pool top area to enhance the reactor utilization. The reactor structure assembly is placed at the bottom of the pool and filled with water as a primary coolant for the core cooling and radiation shielding. Most radioactive materials are generated from the fuel assemblies in the reactor core and circulated with the primary coolant. If the primary coolant goes up to the pool surface, the radiation level increases around the working area near the top of the pool. Hence, the hot water layer is designed and formed at the upper part of the pool to suppress the rising of the primary coolant to the pool surface. The temperature gradient is established from the hot water layer to the primary coolant. As this temperature gradient suppresses the circulation of the primary coolant at the upper region of the pool, the radioactive primary coolant rising up directly to the pool surface is minimized.Water mixing between these layers is reduced because the hot water layer is formed above the primary coolant with a higher temperature. The radiation level above the pool surface area is maintained as low as reasonably achievable since the radioactive materials in the primary coolant are trapped under the hot water layer. The key to maintaining the stable hot water layer and keeping the radiation level low on the pool surface is to have a stable flow of the primary coolant. In the research reactor with a downward core flow, the primary coolant is dumped into the reactor pool and goes to the reactor core through the flow guide structure. Flow fields of the primary coolant at the lower region of the reactor pool are largely affected by the dumped primary coolant. Simple, circular, and duct type discharge headers are designed to control the flow fields and make the primary coolant flow stable in the reactor pool. In this research, flow fields of the primary coolant and hot water layer are numerically simulated in the reactor pool. The heat transfer rate, temperature, and velocity fields are taken into consideration to determine the formation of the stable hot water layer and primary coolant flow. The bulk Richardson number is used to evaluate the stability of the flow field. A duct type discharge header is finally chosen to dump the primary coolant into the reactor pool. The bulk Richardson number should be higher than 2.7 and the temperature of the hot water layer should be 1 C higher than the temperature of the primary coolant to maintain the stability of the stratified thermal layer.

      • KCI등재
      • KCI등재후보

        코로나시대 탈북민의 정신건강과 한국교회

        윤현기 기독교통일학회 2021 기독교와 통일 Vol.12 No.1

        North Korean defectors live with trauma for the psychological shock they experienced during defection and the pain they went through at the crossroads of life and death. Various studies on their trauma have followed one after another. The latest ones include “Effects of Domestic Violence on Mental Health of Victimized Female North Korean Defectors” (Cho Sung-hee et al., 2019). This study is to look into North Korean defectors’ mental health-related difficulties increasing in the contactless way of life caused by the sudden COVID-19 outbreak. This study utilizes existing studies and literature studies on factors affecting North Korean defectors’ mental health during their empirical settlement in the two Korean societies. This study examines the background of mental health they experienced in the closed North Korean society and their settlement process in South Korea and seeks measures for their mental health stability. The analysis was conducted by referring to the “Emergency Survey: North Korean Defectors’ Society in COVID-19” seminar of Radio Free Asia and Saejowi Initiative for National Integration in November 2020 and an online seminar Hanawon and National Mental Health Center hosted in December. According to the result of the analysis, the threat of unemployment attributable to economic difficulties, loneliness, and social relations are three of the factors that threaten North Korean defectors’ mental health amid COVID-19. In view of their negative mental health status and its seriousness in the pandemic era, the conclusion of this study presents cases and roles of relevant institutions and organizations, South Korean churches in particular. 탈북민들은 탈북과정에서 얻은 심리적 충격과 생과사의 갈림길에서 경험한 고통으로 트라우마를 가지고 살아간다. 탈북민들의 트라우마에 관한 연구는 꾸준히 이어져 왔다. 최근의 연구로 “북한이탈여성의 가정폭력피해가 정신건강에 미치는 영향”등 다양하다. 본 연구는 급작스럽게 닥친 코로나로 비대면 문화속에 심화되어지는 탈북민 정신건강의 어려움에 대해 살펴본다. 본 연구는 탈북민들의 경험적 북한사회와 한국사회 정착에서 정신건강에 영향을 미치는 요인에 대해 기존의 연구와 문헌연구를 활용하였다. 탈북민들이 폐쇄된 북한사회에서, 한국사회 정착과정에서 겪은 정신건강의 배경에 대해 알아보고 탈북민들의 안정적인 정신건강의 방안을 모색하였다. 2020년 11월 자유아시아방송, 새조위가 실시한 “긴급설문: 코로나19속 탈북민 사회”세미나와 12월 하나원, 국립정신건강센터가 주최한 온라인 세미나를 참조하여 분석하였다. 분석결과 코로나이후 탈북민들의 정신건강에 위협을 미치는 요소는 첫째, 경제적 어려움으로 인한 실직에 대한 위협, 둘째, 외로움, 셋째 사회관계성이다. 결론에서는 코로나시대 탈북민들의 부정적인 정신건강의 실태와 심각성에 비추어 관련기관, 단체, 특히 한국교회의 사례와 역할을 제시하였다.

      • Preparation, physical properties, and biodegradability of crosslinked jerusalem artichoke/mungbean starch/PVA blended films added various plasticizers

        윤현기,탁혜영,이창문,변헌수,윤순도 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

        In this work, biodegradable films were prepared by using jerusalem artichoke-JA, mungbean starch-MBS, polyvinyl alcohol-PVA, and plasticizers( glycerol-GL, citric Acid-CA, and ascorbic Acid-AsA). The prepared films were synthesized by using UV curing process. The films were characterized by scanning electron microscope-SEM and fourier transform infrared(FT-IR). The physical/optical properties of the films was investigated including their tensile strength-TS, elongation at break-%E, swelling behavior-SB, solubility-S, and water vapor absorption. The results, it could be verified that TS and water resistance were improved by the addition of JA. In addition, the biodegradability in soil and applicability of the coating on a fruit were evaluated. The degree of biodegradability revealed that the films are degraded by about 40-80% after 170days. When compared with the decomposition of an uncoated apple and a coated apple revealed that even after 70 days, the coated apple did not decompose.

      • KCI등재

        미술품 시장의 현황과 문제점

        윤현기,최화열 서비스마케팅학회 2010 서비스마케팅저널 Vol.3 No.1

        2010년 현재 미술품 시장은 새로운 전환기를 맞고 있다. 2008년에 벌어진 미국발 금융위기 이후에 미술시장은 극심한 침체를 벗어나지 못하고 2009년을 보냈다. 2010년 경기가 조금씩 풀리기 시작하면서 미술경매시장도 다시 활성화 되고 있다. 하지만 2008년에 보여주었던 시장의 비 견고성은 다시금 시장이 살아나는데 있어서 불안감을 주고 있다. 이러한 불안감은 투자자들의 투자기피 현상과 경매 참가자들의 구매 기피 현상으로 나타날 수 있는 현상이라고 볼 수 있다. 미술시장에서 많은 영향을 미치고 있는 경매 시장이기 때문에 이러한 현상은 미술시장 전체에 독이 될 수도 있다고볼수있다. 따라서 이 연구에서는 현재 미술시장의 현황과 더불어서 지속가능한 성장 및 현재의 문제점을 가격설정에 초점을 맞춰서 논의하고자 한다.

      • KCI등재

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