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배치형과 연속흐름형에 의한 토양 중 RDX의 아임계 분해특성 비교연구
최재헌,이환,이철효,김주엽,박정훈,조영태,Choi, Jae-Heon,Lee, Hwan,Lee, Cheol-Hyo,Kim, Ju-Yup,Park, Jeong-Hun,Jo, Young-Tae 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.6
The purpose of this study is to compare the degradation characteristics by subcritical water of RDX contaminated soil using batch mode and dynamic mode devices. First, upon application of RDX contaminated soil, RDX treatment efficiency was increased with increasing the temperature in both modes. At 150℃, the treatment efficiency was 99.9%. RDX degradation efficiency got higher with lower ratio of solid to liquid. However, the treatment efficiency in the dynamic mode tended to be decreased at a certain ratio of solid to liquid or lower. The treatment efficiency was increased when it took longer time for the reactions in both modes. As the results of analysis on concentration of treated water after subcritical water degradation, the RDX recovery rate of dynamic and batch modes at 150℃ was 10.5% and 1.5%, respectively. However, both modes showed very similar recovery rates at 175℃ or higher. RDX degradation products were analyzed in treated water after it was treated with subcritical water. According to the results, RDX degradation mechanism was mostly oxidation reaction and reduction reaction was partially involved. Therefore, it suggested that most of RDX in soil was degraded by oxidation of subcritical water upon extraction. According to this result, it was found that both batch and dynamic modes were very effectively applied in the treatment of explosive contaminated soil.
단롤법으로 제조한 AISI 310 스테인레스강의 급냉 조직에 관한 연구
최재헌,오명석,조성석,이용호 ( J . H . Choi,M . S . Oh,S . S . J,Y . H . Lee ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.1
Melt-quenching of steels leads to various metallographic effects such as refinement of grain size, extension of the solid solubility of carbon and alloying elements, and is expected to improve the mechanical properties of conventional steels. Furthermore, this technique is a useful method for producing sheet directly from liquid state. And it will lend itself to development as a continuous cast process which offers significant savings in energy and product costs. The purpose of this study is to present the microstructures of melt-quenched austenitic stainless steels. As the results of this study. the morphology of melt-quenched microstructure show that the roll contact area is columnar structure. and the free surface area is dendrite structure. As the line speed increases, the ratio of d_(colunnar)/d_(total) increases from 0.12 to 0.60, but the ribbon thickness decreases from 150㎛ to 30㎛.
논문 : 용산 미군기지의 문화유산 가치와 도시발전 방향
최재헌 ( Jae Heon Choi ),남영우 ( Young Woo Nam ) 한국도시지리학회 2014 한국도시지리학회지 Vol.17 No.2
본 연구는 용산 미군기지가 갖는 문화유산 가치를 장소성을 가지는 유산으로 파악하여 지리적 환경과 도시발달사를 고려한 지역 변천에 초점을 맞추어 용산 미군기지의 상징성과 문화유산 가치를 고찰해보고 바람직한 개발 방향을 논의하였다. 용산 미군기지 일대는 13세기 몽골군의 병참기지로부터, 조선시대의 강촌, 도성관문, 물류유통기지로서의 성격을 거쳐, 일제강점기에 군사경관이 형성되고 외세에 의한 식민기지로서 특징이 나타나며, 해방 이후에는 군사경관이 유지된 성역화된 군사기지, 금단의 경관으로서의 특징을 보인다. 현재에는 과거의 경관요소가 그대로 남아있는 화석화된 경관(fossil landscape)으로서 외세에 의한 천이의 공간이기도 하다. 용산 미군기지의 발전 방향은 개발위주, 보존위주, 절충적 입장에서 접근이 가능하다. 그러나 향후 용산의 다양한 층위를 고려하여 유산 가치를 보존하는 방안을 강구하고 세계유산으로 등재 조건을 충족할 수 있는 완전성과 진정성을 확보하며, 지역 상징성을 유지하면서 교육적 가치와 정체성 확보를 위한 활용 가치를 극대화할 수 있어야 한다. This paper intends to discuss the various directions of urban development of Yongsan military base, highlighting the heritage value in the context of urban development and regional changes in each time period including Joseon Dynasty, open port period, Japanese Colonial Times and after the liberalization. Yongsan military base has shifted from military storage yard in the 13th century, to river port as a gateway city in Joseon Dynasty, to a military base during the Japanese Colonial Times, and has been continuously keeping a forbidden military space for the US forces after the liberalization. It can be defined as a fossil landscape, functioning as a space of succession for foreign military forces in different time periods. Either development oriented, preservation oriented or eclectic approach can be adopted for future development. However, it needs to figure out the most appropriate way of both preserving cultural heritage for multi-layered structure of Yongsan military base and confirming integrity and authenticity for possible inscription on the World Heritage List in the context to keep symbolic meaning as well as to enhance place identity and educational value for future generation.
NPC 인버터의 DC-link 커패시터 전류 리플 감소를 위한 전압 변조 방법 비교 평가
최재헌(Jae-Heon Choi),최의민(Ui-Min Choi) 전력전자학회 2021 전력전자학술대회 논문집 Vol.2021 No.11
DC-link 커패시터는 전력 변환 시스템에서 신뢰성이 취약한 소자 중 하나이다. 커패시터의 수명은 동작 온도가 상승할수록 감소하며 전류 리플에 의한 손실은 커패시터 온도를 상승시키는 주요 원인이다. 따라서 NPC 인버터의 DC-link 커패시터의 전류 리플을 감소시켜 커패시터의 수명을 향상시키기 위한 다양한 연구들이 수행되고 있다. 그러나 전류 리플을 감소시키기 위한 전압 변조 방법들은 인버터 출력 품질을 저하시키는 단점이 존재한다. 본 논문에서는 3-레벨 NPC 인버터의 DC-link 커패시터의 전류 리플을 감소시키기 위해 제안된 공간 벡터 전압 변조 방법들을 비교 분석한다. 제안된 방법들이 적용되었을 때, 커패시터 전류 리플에 의한 전력 손실을 분석하고 이에 의한 예측 수명과 NPC 인버터 출력 전류의 THD에 미치는 영향을 비교 분석한다.
세계화 시대의 도시지리 연구를 위한 글로벌 패러다임 ( global paradigm ) 의 쟁점과 연구동향
최재헌(Jae Heon Choi) 한국도시지리학회 1998 한국도시지리학회지 Vol.1 No.1
This paper examines the research agenda for the urban geography concerning the basic trends and characteristics of globalization process in the changing nature of urban places. The cities themselves change their role towards active agents of global economic competition, image-makers and high technology innovator, which lead urban geographers to develop new perspectives towards urban place and urban process, so caved, the global paradigm. New urban research themes come from urban systems perspective including world cities/global cities, global urban system and global network etc., as well as from urban structure perspective including many conceptions out of postmodern urbanism and post-Fordism reflecting globalization, fragmentation, cultural hybrid, cybercities and so on. However, the global-local connection remains the critical issues of the new urban geography in the global era.