원전사고 평가를 위한 원전 사건유형분석 시스템(ETAS) 개발

최영환,김영미,Choi, Young Hwan,Kim, Young Mi 한국압력기기공학회 2009 한국압력기기공학회 논문집 Vol.5 No.2

In this study, Event Type Analysis System (ETAS) is developed for the accident evaluation in nuclear power plant. The ETAS system can be used in supporting regulator and/or operator under event situation in nuclear power plants. The ETAS system can categorize the all transient events to 3 categories such as Down-2000, Down-2173, and Slow Fluctuation. We develop the program structure for ETAS system and web-based ETAS system. The ETAS system will be used as sub module of Knowledge-Based Event Evaluation Network (K-EvENT) which is developing for the against the accident in nuclear power plants.

국내 가압경수형 원자로에 대한 가압열충격 기준온도 평가

최영환,박정순,정명조,Choi, Young Hwan,Park, Jeong Soon,Jhung, Myung Jo 한국압력기기공학회 2010 한국압력기기공학회 논문집 Vol.6 No.2

The evaluation method for the failure frequency of reactor vessel under pressurized thermal shock(PTS) is developed using probabilistic fracture mechanics. The probabilistic reactor integrity evaluation code, named R-PIE code, is developed. The validity and uncertainty of the R-PIE code is investigated. The reactor failure frequencies under PTS for Kori-1 nuclear power plant and other type of domestic nuclear power plants are evaluated. The reference PTS temperature for domestic nuclear power plants is obtained for the rule making against PTS failure.

호중구 감소된 급성 림프구성 백혈병환아에서 발생한 Pneumocystis carinii 폐렴 1례

최영환,민기식,김종완,김광남,유기양,Choi, Young Hwan,Min, Ki Sik,Kim, Jong Wan,Kim, Kwang Nam,Ryoo, Ki Yang 대한소아감염학회 1997 Pediatric Infection and Vaccine Vol.4 No.1

Pneumocystis carinii pneumonia mainly occurs in immunocompromised patients and it is also known of major cause of death in children with acute lymphoblastic leukemia. After consolidation chemotherapy, acute lymphoblastic leukemia children is developed Pneumocystis carinii pneumonia frequently no an opportunistic infection but there were no controlled studies which have been performed to evaluate the usefulness of corticosteroid in Pneumocystis carinii pneumonia with acute lymphoblastic leukemia. We experienced a case of Pneumocystis carinii pneumonia in acute lymphoblastic leukemia with febrile neutropenic 6 years old girl. She was treated with trimethoprim-sulfamethoxazole and prednisone. We report this case with brief review of related literature.

콘크리트 충전 각형강관 기둥의 폭두께비 제한에 관한 연구

최영환,Choi, Young-Hwan 한국강구조학회 2012 韓國鋼構造學會 論文集 Vol.24 No.4

구조적 우수성이 입증된 콘크리트 충전 강관 (CFT) 시스템은 폭두께비가 큰 강관을 사용할 때 더욱 경제적인 설계가 될 수 있다. 하지만, 현재 국내외의 규준에서는 CFT에 사용할 수 있는 강관의 폭두께비를 제한하고 있어 건설 재료를 보다 더 효율적으로 활용할 수 있는 가능성을 미리 차단하고 있다. 본 연구에서는 폭두께비 60, 70, 80, 90, 100를 갖는 각형 단주 CFT에 대해 압축실험을 실시하여 CFT에서의 좌굴 후 내력을 확인하였고 기존의 규준에서 제시한 폭두께비 제한치를 완화한 식을 제시하였다. The concrete-filled steel tube (CFT) that has an excellent performance can be more economically used when the steel tube has a large width-to-thickness ratio. However, the international provisions such as American Institute of Steel Construction (AISC) limit the use of a slender plate in CFT members, resulting in a less optimal use of CFT. This study verifies the post buckling strength of CFT columns through the experimental program for Hollow Steel Sections (HSS) and CFTs with a with-to-thickness ratio ranged 60 to 100. The study also proposes a relaxed limitations of with-to-thickness ratio compared to the one specified in the current standards.

원주방향균열이 존재하는 원전 배관계통의 파괴거동에 관한 실험적 연구(I) - 직관부에서의 균열거동 평가 -

최영환,박윤원,Choi, Young-Hwan,Park, Youn-Won,Wilkowski, Gery 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7

The purpose of this study is to investigate experimentally the effects of both seismic loading and crack length on the fracture behavior of piping system with a circumferential crack in nuclear power plants. The experiments were performed using both large scale piping system facility and 4 points bending test machine under PWR operating conditions. The difference in the load carrying capacities between cracked piping and non-cracked piping was also investigated using the results from experiments and numerical calculations. The results obtained from the experiments and estimation are as follows : (1) The safety margin under seismic loading is larger than those under quasi static loading or simple cyclic loading. (2) There was no significant effect of crack length on tincture behavior of piping system with both a surface crack and a through-wall crack. (3) The load carrying capacity in cracked piping was reduced by factors of 7 to 46 compared to non-cracked piping.

고강도 콘크리트를 사용한 각형 CFT 기둥의 축력-모멘트 상관곡선

최영환,김강수,최성모,이상섭,Choi, Young Hwan,Kim, Kang Su,Choi, Sung Mo,Lee, Sangsup 한국강구조학회 2007 韓國鋼構造學會 論文集 Vol.19 No.6

본 논문은 55 MPa 이하 강도의 콘크리트를 사용한 CFT 기둥에 대한 P-M 상관곡선을 제안한 선행연구의 후속연구로서, 2005 AISC에서 새롭게 포함된 55 MPa 이상의 고강도 콘크리트를 사용한 정방형 CFT 기둥의 P-M 설계식을 제안하였다. 선행연구에서 제안한 개념을 적용하여 고강도 콘크리트를 사용한 CFT에서의 최대모멘트와 최대모멘트시의 압축력을 구하기 위해 강관의 폭두께비(b/t)와 강관의 항복강도에 대한 콘크리트의 상대강도(fck/Fy)를 중요 변수로 총 36개의 대상단면을 선정하여 Fiber Analysis를 통한 변수해석을 수행하였다. 강관의 응력-변형율 관계는 완전탄소성으로 가정하였고 콘크리트는 고강도 콘크리트에 적용가능한 Sakino의 모델을 이용하였다. 변수해석으로부터 얻어진 결과로부터 상기의 두 변수를 이용하여 고강도 콘크리트를 사용한 각형 CFT 기둥의 설계에 쉽게 사용할 수 있는 설계식을 제안하였다. 기존의 실험결과와 비교한 결과 본 논문에서 제시하는 방법은, 2005 AISC에서 제시하는 방법에 비해 보다 더 쉽고 간단하게 사용될 수 있는 것으로 나타났다. In this study, a new design equation was presented for square CFTs with high-strength concrete subjected to axial compression and bending. In a previous study, a design equation for square CFTs with normal strength concrete was proposed. A parametric study by fiber analysis was performed taking the width-to-thickness ratio (b/t) and the relative concrete strength to the yield strength of the steel tube (fck/Fy) as the main parameters of this study to determine the maximum moment and the axial load at the maximum moment. A new constitutive model for concrete was adopted for fiber analysis in order to take into account the effect of high-strength concrete. The results of the parametric study were embedded into the method which was presented in the previous study to formulate a new design equation that can be easily used for estimating the strength of square CFTs with high-strength concrete.

원전 사고처리 지원시스템(ECAS) 개발

최영환,김영미,고한옥,Choi, Young Hwan,Kim, Yopng Mi,Ko, Han Ok 한국압력기기공학회 2009 한국압력기기공학회 논문집 Vol.5 No.2

In this study, Event Corrective Action Supporting System (ECAS) is developed for the accident evaluation in nuclear power plant. The ECAS system can be used in supporting regulator and/or operator under event situation in nuclear power plants. The ECAS system consists of 5 modules including failure location module, failure analysis module, failure integrity evaluation module, system vulnerability evaluation module, and reporting and operating experience feedback module. The ECAS system will be used as sub module of Knowledge-Based Event Evaluation Network (K-EvENT) which is developing for the against the accident in nuclear power plants.

소셜 빅데이터를 활용한 올림픽 · 월드컵 화제성에 관한 연구

최영환(Choi, Young-Hwan) 한국사회체육학회 2015 한국사회체육학회지 Vol.0 No.62

The purpose of this research is to understand the degree of concern about the Olympic Games and FIFA World Cup and to suggest basic data for establishment of marketing strategies through collecting search volume in the venue of those two events and finding its decision factors and the difference in search volume by country, region, season, and venue. For the purpose of the study, we collected data from 4 countries, Canada, the UK, Brazil, and South Korea - for comparison with domestic data - where Olympics and World Cup were held from 2010 to 2014, and 5 events were selected as the subjects of the study (the Vancouver 2010 Olympic Winter Games, 2010 FIFA World Cup South Africa, the London 2012 Olympics Games, the Sochi 2014 Olympic Winter Games, and 2014 FIFA World Cup Brazil). Oneway ANOVA and DecisionTree were used for statistical processing. The conclusion of this study are as follows. 1. Is there difference between the search volume between the Olympic Games and FIFA World Cup? The search volume was different between the Olympic Games and FIFA World Cup: it was greater in FIFA World Cup in all events and duration between 2010 and 2014. In the UK and Brazil which top soccer countries, the search volume for FIFA World Cup was greater than that of the Olympics. 2. Is there difference by countries regarding the degree of concern about the (summer/winter) Olympics and FIFA World Cup? 1) The search volume for the Olympics was different by countries. In particular, throughout the target period (2010-2014), the greatest was found in Brazil, while low in South Korea and the UK. No difference was found during the events. 2) There was no difference by countries in search volume for FIFA World Cup. 3. Is there difference in the degree of concern by season (off-season, Winter Olympics, Summer Olympics, FIFA World Cup, before and after Winter Olympics, before and after Summer Olympics, and before and after FIFA World Cup)? 1) The search volume for the Olympics was different by season. It reached its peak during the events, with the highest for the Summer Olympics. 2) The search volume for the FIFA World Cup was different by season. It reached its peak during the events, with the highest just before the events. 4. Is there difference according to hosting experience (current venue, previous venue, next venue, no hosting experience)? 1) The search volume for the Olympics was different by hosting experience. It was the highest in the current venue while the lowest in the countries with no hosting experience. 2) The search volume for FIFA World Cup was not different by hosting experience. 5. Is there difference by event (the Vancouver 2010 Olympic Winter Games, the London 2012 Olympics Games, the Sochi 2014 Olympic Winter Games, 2010 FIFA World Cup South Africa, and 2014 FIFA World Cup Brazil)? The search volume was different by event. It was high for the London 2012 Olympics Games, 2010 FIFA World Cup South Africa, and 2014 FIFA World Cup Brazil while low for the Winter Olympics (the Vancouver 2010 Olympic Winter Games and the Sochi 2014 Olympic Winter Games). 6. What are the decision factors in the search volume for the Olympics and FIFA World Cup? The most important decision factor of the search volume was ‘Season’ for the Olympics, ‘Country’ for the Summer Olympics , and ‘Hosting Experience’ and ‘Event’ for other seasons (Winter Olympics, before and after Summer Olympics, before and after Winter Olympics, and off-season) The greatest search volume was found in Brazil during the London Olympics, which is followed by Canada, the venue of the event, during the Winter Olympics. The third was taken by London and South Korea, which showed high search volume during the London Summer Olympics. The fourth was given to Canada during the Sochi Winter Olympics. In regards of FIFA World Cup, Canada’s search volume was the greatest during the

모바일 Broadcasting 환경에서 User Preference 기반 캐시 관리 기법

최영환 ( Young-hwan Choi ),황인준 ( Een-jun Hwang ) 한국정보처리학회 2008 한국정보처리학회 학술대회논문집 Vol.15 No.1

최근 모바일 Broadcasting 환경에서의 캐시 관리 기법에 관한 다양한 연구가 활발히 진행되고 있으며 가장 많이 쓰이는 기법으로는 무효화 보고(Invalidation Report) 기법을 들 수 있다. 하지만 무선 기기들의 대용량 지원 및 많은 사용자의 무선 이용으로, 사용자 요청에 대한 지연이나 Multi-Cell환경과 대용량 갱신 등에 대한 대처 능력의 부족 등이 문제점으로 부각되고 있다. 본 연구는 이런 무효화 보고의 대처 능력을 보완할 뿐 아니라, User Preference 를 추가하여 사용자의 QoS 를 만족시키는 새로운 시스템을 제안한다. 본 연구는 서버 측에서의 일방적인 브로드캐스팅에 의한 데이터 전송이 아닌, 사용자로부터의 요청에 따른 캐시 데이터 관리 기법을 제안한다. 연구의 주된 효과는 사용자로 하여금 선택적 청취(Selective Listening)을 하게 함으로써 서버와의 교류를 적게 하고, 자주 사용하는 많은 양의 데이터를 한번에 가져와 빠른 시간 내에 데이터를 사용할 수 있게 한다. 또한, 자신이 필요한 데이터에 한에서만 자료 갱신(Update) 여부를 확인하여, 짧은 시간 안에 동적으로 자신의 정보를 확인 할 수 있다.

2008 베이징 올림픽 지상파 콘텐츠 특성에 따른 시청률 비교 분석

최영환(Young Hwan Choi) 한국사회체육학회 2008 한국사회체육학회지 Vol.0 No.34

The present study, in order to find out the characteristics of the 2008 Beijing Olympics TV audience, collected the audience rating data of programs related to the Beijing Olympics researched by "AGB Nielsen Media Research", which are composed of 541 items using classification variables of gender (male, female), age (10s, 20s, 30s, 40s, 50 and over), education (high school graduate, university graduate, graduate school graduate), and occupation (speciality occupation/business administration, office job, service job, independent enterprise, housewife, student, unemployed). The results showed that MBC had far higher audience ratings than both KBS2 and SBS, and when it came to the genre, the live broadcast programs had higher audience ratings than other programs. Looking at genre-specific audience ratings, live broadcast had the highest audience ratings, which can be seen as a result that reflected the timely characteristic of sports programs. Sports competitions only have significance when it`s watched live, so it can be said that the value of repeat broadcasts, highlights, and documentaries is cut in half, which was completely reflected in the ratings. Despite the fact that big sport events such as the Olympics are not something that happens often, the audience ratings during different time periods of the day (SA, A, B, C) had the same results as usual. Baseball and handball had relatively high audience ratings, and in contrast to the fact that many males watched baseball, when it came to handball, many females watched it.