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- 저자 : Joonho Choi (검색결과 158 건)
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Effects of Porcine Seminal Plasma in In Vitro Culture of Embryos
JoonHo Moon,SuJin Kim,JungTaek Kang,SolJi Park,JiYei Choi,JiHyun Lee,Islam M. Saadeldin,HyunJu Oh,JungEun Park,MinJung Kim,GeonA Kim,Eun Jung Park,Jin Choi,Goo Jang,Byeong Chun Lee 한국동물번식학회 2012 Reproductive & developmental biology Vol.36 No.2
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Effects of Porcine Seminal Plasma in In Vitro Culture of Embryos
JoonHo Moon,SuJin Kim,JungTaek Kang,SolJi Park,JiYei Choi,JiHyun Lee,Islam M. Saadeldin,HyunJu Oh,JungEun Park,MinJung Kim,GeonA Kim,Eun Jung Park,Jin Choi,Goo Jang,Byeong Chun Lee 한국동물번식학회 2012 Reproductive & Developmental Biology(Supplement) Vol.36 No.2s
Semen can be divided into two parts. One is cellular part which contains sperms the other is liquid part which is called by seminal plasma. The seminal plasma is a nutritive and protective medium for the sperms. Fructose, which is major energy source, is supplied to sperms swim to female oocyte. Alkalic property protects sperms from hostile environment of female reproductive organ. Also, seminal plasma induces tolerance to preexisted immune cells, and changes intra-uterine environment to better conditions for fertilized embryos to implant. However, the effects of seminal plasma in in vitro culture of fertilized embryos are unclear. Second fraction of fresh semen was obtained from a normal farm pig. The semen was centrifuged to remove sperms, and then supernatant was filtrated. The filtered seminal plasma was stored in - 30℃. In this study, electrically activated and chemically activated porcine embryos were employed to investigate the developmental rate after 2 hours treatment of none, 0.1%, 0.5%, and 1% seminal plasma in culture media by two days of activation. Both electrically and chemically activated embryos, cleavage rate and cell numbers of blastocysts were not significant difference within four groups. Blastocyst formation rate of electrically activated embryos also did not show significant difference within any groups. However 0.1% seminal plasma treatment group showed significantly increase of blastocyst formation rate in chemically activated group (None; 24.8%, 0.1%; 31.7%, 0.5%; 19.4, and 1%; 16.5%, respectively. p<0.05).
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Integrated fire dynamic and thermomechanical modeling of a bridge under fire
Joonho Choi,Rami Haj-Ali,김희선 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.6
This paper proposes a nonlinear computational modeling approach for the behaviors of structural systems subjected to fire. The proposed modeling approach consists of fire dynamics analysis, nonlinear transient-heat transfer analysis for predicting thermal distributions, and thermomechanical analysis for structural behaviors. For concretes, transient heat formulations are written considering temperature dependent heat conduction and specific heat capacity and included within the thermomechanical analyses. Also, temperature dependent stress-strain behaviors including compression hardening and tension softening effects are implemented within the analyses. The proposed modeling technique for transient heat and thermomechanical analyses is first validated with experimental data of reinforced concrete (RC) beams subjected to high temperatures, and then applied to a bridge model. The bridge model is generated to simulate the fire incident occurred by a gas truck on April 29, 2007 in Oakland California, USA. From the simulation, not only temperature distributions and deformations of the bridge can be found, but critical locations and time frame where collapse occurs can be predicted. The analytical results from the simulation are qualitatively compared with the real incident and show good agreements.
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Integrated fire dynamic and thermomechanical modeling of a bridge under fire
Choi, Joonho,Haj-Ali, Rami,Kim, Hee Sun Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.6
This paper proposes a nonlinear computational modeling approach for the behaviors of structural systems subjected to fire. The proposed modeling approach consists of fire dynamics analysis, nonlinear transient-heat transfer analysis for predicting thermal distributions, and thermomechanical analysis for structural behaviors. For concretes, transient heat formulations are written considering temperature dependent heat conduction and specific heat capacity and included within the thermomechanical analyses. Also, temperature dependent stress-strain behaviors including compression hardening and tension softening effects are implemented within the analyses. The proposed modeling technique for transient heat and thermomechanical analyses is first validated with experimental data of reinforced concrete (RC) beams subjected to high temperatures, and then applied to a bridge model. The bridge model is generated to simulate the fire incident occurred by a gas truck on April 29, 2007 in Oakland California, USA. From the simulation, not only temperature distributions and deformations of the bridge can be found, but critical locations and time frame where collapse occurs can be predicted. The analytical results from the simulation are qualitatively compared with the real incident and show good agreements.
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Joonho Choi,Rami Haj-ali,김희선 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.2
The objective of this study is to formulate a general 3D material-structural analysis framework for the thermomechanical behavior of steel-concrete structures in a fire environment. The proposed analysis framework consists of three sequential modeling parts: fire dynamics simulation, heat transfer analysis, and a thermomechanical stress analysis of the structure. The first modeling part consists of applying the NIST (National Institute of Standards and Technology) Fire Dynamics Simulator (FDS) where coupled CFD (Computational Fluid Dynamics) with thermodynamics are combined to realistically model the fire progression within the steel-concrete structure. The goal is to generate the spatial-temporal (ST) solution variables (temperature, heat flux) on the surfaces of the structure. The FDS-ST solutions are generated in a discrete form. Continuous FDS-ST approximations are then developed to represent the temperature or heat-flux at any given time or point within the structure. An extensive numerical study is carried out to examine the best ST approximation functions that strike a balance between accuracy and simplicity. The second modeling part consists of a finite-element (FE) transient heat analysis of the structure using the continuous FDS-ST surface variables as prescribed thermal boundary conditions. The third modeling part is a thermomechanical FE structural analysis using both nonlinear material and geometry. The temperature history from the second modeling part is used at all nodal points. The ABAQUS (2003) FE code is used with external user subroutines for the second and third simulation parts in order to describe the specific heat temperature nonlinear dependency that drastically affects the transient thermal solution especially for concrete materials. User subroutines are also developed to apply the continuous FDS-ST surface nodal boundary conditions in the transient heat FE analysis. The proposed modeling framework is applied to predict the temperature and deflection of the well-documented third Cardington fire test.
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한국언론을 통해 본 미래학에 대한 사회적 인식의 변화 연구
최준호(Joonho Choi) 미래학회 2017 미래연구 Vol.2 No.2
본 연구는 국내 최초로 2013년 KAIST에서 미래전략대학원이 출범하는등 한국에서 미래학 연구의 기틀이 갖춰지는 시점에서 과거를 돌아본 것이 다. 1968년 한국미래학회가 출범하고, 한국에서 미래연구가 시작된 지 50년 가까이 세월이 지났음에도 한국 일간신문의 시각으로 볼 때 국내에서는 그간 미래연구에 대한 눈에 띄는 발전이 보이지 않았던 이유를 알고자 했다. 이를 통해 지난 세월 동안 한국에서 미래학에 관심이 있는 사람들이 무엇을 했으며, 어떤 생각을 했는지를 분석했다. 분석의 기본 틀로는 일간신문 분석을 사용했다. 더불어 빅데이터 텍스트마이닝(text-mining) 기법, 심층 인터 뷰를 통해 신문 기사 분석의 한계를 보완하고자 했다. 연구분석 결과에 나타난 언론에 나타난 한국의 미래학의 출범은 1967년 도였다. 이듬해 한국미래학회가 출범하고, 이 학회가 일본, 미국 등 외국의 미래학회와 교류하면서 한국 미래학의 지평을 넓혀갔다. 1970년대 초 중반 이들의 활동은 21세기 오늘날에 내놔도 손색이 없을 만큼 진지하고 학술적 이며, 미래학의 정신에 충실했다. 하지만 이후로 오랫동안 한국의 미래학 연구는 침체기에 빠진다. 박정희 정권이 1972년 10월 유신체제를 출범시키 면서 국가의 미래구상은 수출을 통한 경제발전의 한 방향으로만 치달았기 때문인 것으로 분석된다. 그 시절에는 서구 선진국이 고민하던 제대로 된 미래학을 추구할 여유가 없었을지 모른다. 1960년대 초 1인당 국민소득이 100달러도 안되던 시절에 미국과 같은 선진국을 따라잡기 위해서는 허먼 칸의 말대로 강력한 리더십을 통한 압축성장이 필요했을 수 있다는 생각도 든다. 유신 이후부터 전두환 정권에 이르기까지 신문기사 분석을 통해 들여 다본 한국의 미래연구는 적어도 이 같은 모습을 보이고 있다. 당시에 비춰진 미래학은 우리가 주도하는 미래학이 아니었다. 미국과 유럽, 일본 등이 제시 하고 있는 미래 모습이 뭔지를 파악하고, 이를 한국의 2000년대에 투영시켜 비전을 만들고 분주히 따라가는 모습이었다. 이 같은 서구 종속적인 한국 미래학의 모습은 21세기가 들어서면서 조금씩 변화의 조짐을 보이기 시작했다. 꾸준히 이어지지는 못했지만, 곳곳에서 미래학연구소가 생겨나고, 대학에서도 미래관련 학위 과정을 설립하고자 하는 시도가 있었다. 하지만 여전히 많은 오피니언 리더(opinion leader)들은 미래학에 대한 이해가 부족했다. 이들은 자기 논리나 글을 위한 장식품 정도로 미래학을 이용하기도 했다. 이 속에서도 발전은 진전되고 있었다. 수량적 으로도 신문에서 미래학과 관련한 기사들이 해가 갈수록 늘어나고 있으며, 단순히 미래학에 대한 호기심과 미래학 소비자의 수준을 넘어 미래전략을 통해 미래를 만들어가는 미래연구의 주체자로 등장하는 사람들이 늘어나고 있다. This research looks back to the time in history when the foundation on the futures studies was established in South Korea. The Korean Society of Future Studies was first established in 1968 and the research on the field has been going on for nearly half a century. However, I wanted to know why future studies haven’t seen a visible development here in Korea despite of its long history. This research focuses on analyzing what people interested in futures studies have done throughout the years. The elementary tool used on the analysis was newspaper articles. To cover the limit of analyzing newspapers articles, I have also utilized the big data text-mining method as well as focus interviews. According to the research analysis, the start of Korea’s futures studies was in 1967. In the following year, the Korean Society of Future Studies was launched. This society expanded the realm of futures studies here in Korea through exchanges with other futures studies societies overseas such as the U.S. and Japan. By the early 1970s, those participating in the societies were dedicated to their studies and they were academic and thorough, which even stands out until today. But since then, the research on the field enters recession for a long period of time. At that time, it seemed that South Korea didn’t have the leisure to study on futures unlike the advanced western countries. The Korean national in-come per capita in early 1960s was less than $100. As preeminent futurist Herman Kahn has once said that Korea should keep up with the advanced economies like that of the U.S., it was believed that it needed a compressed growth under strong leadership. When analyzing the newspaper articles during the Yushin regime and the Chun Doo-hwan administration, at least Korea’s futures studies shows such trends. The futures studies at that time was not led by Korea itself but it just followed the visions set by advanced economies like the U.S., Japan and Europe and then reflected it in its vision for the 2000s and was busy trying to follow it. However, Korea’s futures studies, which were heavily dependent to the western economies, started to show signs of changes as the country has entered the 21st century. Although it didn’t continue those changes with persistence, futures studies research centers started to pop up and related classes with degrees started to be established in colleges. However, there is a lack of understanding on the idea of futures studies among opinion leaders. There have been those who only used future studies as a garnish to their writings or rationality. Yet, there are progresses underway. Each year, articles on futures studies are growing in number. Additionally, those who are studying futures studies in hopes of building the future through strategy rather than out of pure simple curiosity are growing as well.
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