금형압축성형공정 해석용 CAE 프로그램 개발 및 적용

정석환,권영삼,Chung Suk-Hwan,Kwon Young-Sam 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.5

Crack generation during die compaction and distortion during sintering have been critical problems for the conventional pressing and sintering process. Until now, trial and error approach with engineers' industrial experiences has been only solution to protect the crack generation and distortion. However, with complexity in shape and process it is very difficult to design process conditions without CAE analysis. We developed the exclusive CAE software (PMsolver/Compaction) for die compaction process. The accuracy of PMsolver is verified by comparing the finite element simulation results with experimental results. The simplified procedures to find material properties are proposed and verified with iron based powder and tungsten carbide powder. Based on the accurate simulation result by PMsolver, the optimal process conditions are designed to get uniform density distribution in a powder compact after die compaction process by using a derivative based optimization scheme. In addition, the effect of non-uniform density distribution in a powder compact on distortion during sintering is shown in case of the fabrication of tungsten carbide insert.

로이유리의 저방사 코팅 적용 위치에 따른 실내 온도변화 및 에너지 성능 비교 분석

정석환,김성우,박상현,이종찬,임정희,김병선 대한건축학회 2007 대한건축학회논문집 Vol.23 No.8

In the high oil prices age, intensification of energy efficiency promotion in the building sector is required. Windows are dominating large percentage whole building loads and are regarding as the primary target of energy efficiency. The purpose of this study is to improve energy efficiency of windows in high-rise residential buildings through the evaluation of their indoor temperature change & heating and cooling energy consumption. Analysis of Indoor temperature change and building energy consumption was performed through the use of simulation programs EnergyPlus and Window. The process of this study is as follows. First, In each case, estimated indoor temperature change, window heat gain and window heat loss. Then, the annual heating and cooling energy consumption according to the different glazing types are compared one another. The results show that the application of Low-E coating applying in the outside glazing can substantially increase the energy performance.

경요골 동맥 관상동맥 조영술 시 생긴 이상성 우측 빗장밑 동맥의 합병증 1예

정석환,금동성 대한내과학회 2011 대한내과학회지 Vol.80 No.-

Right transradial coronary catheterization is very popular and performed by many clinicians with few complications. An aberrant right subclavian artery (arteria lusoria) arising from the descending thoracic aorta is an uncommon congenital variant. Here, we present the case of a patient with an aberrant right subclavian artery dissection after right transradial coronary catheterization, which is a rare complication. We diagnosed the complication by chest CT, which showed the dissection of the aberrant right subclavian artery. Dissection of an aberrant right subclavian artery is a rare complication of right transradial coronary angiograph. (Korean J Med 2011;80:S157-S160) 우측 요골 동맥을 이용한 관상동맥 조영술은 환자의 편이성 등 여러 가지 장점 때문에 많이 시행되는 술식이다. 그러나 여러 장점에도 불구하고 우측 요골 동맥을 이용한 관상동맥 조영술에 따르는 여러 가지 합병증 역시 있을 수 있다. 이상성 우측 빗장밑 동맥을 가진 환자의 경우 이로 인한 시술상의 어려움, 시술의 실패 등은 잘 알려져 있으나, 시술 후에 생긴 우측 빗장밑 동맥 박리는 많이 알려져 있지 않다. 본 증례는 흔하지 않은 합병증을 경험했기에 이에 대한 증례 보고를 하는 바이다.

정수장 고효율 혼화 장치 자동제어 시스템 개발

정석환 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

Inability of Mate and Species Recognition by Male Asian Toads, Bufo gargarizans

정석환,박시룡,성하철 한국통합생물학회 2008 Animal cells and systems Vol.12 No.2

In recent years, we frequently observed miss-matched pairs between male Asian toads, Bufo gargarizans,and bullfrogs, Rana catesbeiana , at the toad breedingponds, where scramble competition for mating occurredamong the male toads. Thus, we performed two-choiceexperiments to investigate recognition ability of mates andspecies in male toads. The test males did not discriminatesexes, but the clasped stimulus males imediatelyproduced release calls and stopped it while the claspednot discriminate reproductive state of females and evenspecies. However, male toads chose larger individuals. Thepresent results indicate that the main reason of miss-matched amplexus by the male toads is due to 1) the lack ofrecognition cues of conspecifics, 2) the lack of comunicationtools like release calls, and 3) the larger size of bullfrogsthan male toads themselves.

포스트모더니즘에 근거 한 한국 다문화교육의 재개념화

정석환 안암교육학회 2012 한국교육학연구 Vol.18 No.2

The purpose of this study was to re-conceptualize the concept of multicultural education in the view of post-moderrnism. Firstly, the concept of multicultural education utilized in Korean culture was discussed. Secondly, philosophical issues related to multicultural education in Korea was closely exmined. Lastly, postmodern re-conceptualization of Korea's multicultural education was conducted. The result of this study showed that the multicultural education in Korea was progressing toward integrating diverse cultures to the Korean culture. During the process, ideological viewpoint that takes Korean cultures as superior culture and other cultures as subordinates seemed to exist. Therefore, it was demonstrated that educating tolerant attitude about diverse differences using postmodern viewpoint(viewpoint of post-modernism) to solve the problem is educationally signigicant. 본 연구는 한국에서 활용되고 있는 다문화교육에 대한 인식과 그 지향점에 내재한 이중적 성격을 밝히고 이를 포스트모더니즘의 시각에서 비판적으로 논의하여 새로운 다문화교육의 가능성을 탐색하기 위한 목적으로 진행되었다. 본 연구의 목적을 달성하기 위해 먼저 한국 의 다문화교육에 대한 다양한 일차자료를 분석하여 한국에서 다문화교육이 어떻게 인식되 고 있으며 그 지향점은 무엇인지를 논의하였다. 다음으로 한국의 다문화교육에 내재한 이 중적 성격을 밝히고 이를 포스트모더니즘의 관점에서 비판적으로 논의하여 새로운 다문화 교육의 가능성을 제시하였다. 본 연구의 결과 한국 다문화교육의 전반적인 전개 양상은 국제화 교육과는 매우 다른 이중 적인 태도를 지향하고 있었다. 또한 한국의 다문화교육에는 다양한 다문화교육 당사자 간 의 ‘차이의 인정’이 아니라, 문화, 경제, 사회 등의 다양한 측면에서 다문화교육의 대상자 들에 대한 이데올로기적 시각이 존재하고 있었다. 필자는 이러한 차별적 관점을 지양하고 다양한 차이를 무관심의 태도로 대할 것을 제안하였다. 즉 차이라는 구분 자체를 무의미한 것으로 보는 것이 오히려 진정한 다문화적 환경을 갖추는 기본 여건이 될 것이다. 그리고 포스트모더니즘의 교육원리는 다문화교육의 바람직한 실천을 위한 논리적 기반을 제공 할 수 있을 것이다.

Skeletochronological Age Determination and Comparative Demographic Analysis of Two Populations of the Gold-spotted Pond Frog (Rana chosenica)

정석환,박대식,성하철,이정현,박시룡 한국생태학회 2007 Journal of Ecology and Environment Vol.30 No.1

To obtain demographic information on threatened gold-spotted pond frog (Rana chosenica Okada,1931) populations, we determined the ages of 45 male and 13 female frogs (20 males and 9 females from Cheongwon and 25 males and 4 females from Tae-an) and compared the age structures and growth patterns of the two populations in 2006. The snout-vent length (SVL) and body weight of female frogs were greater than 3 to 6 years old. In both populations, 4 years old male frogs were the most abundant age-sex class. The age structures of the two populations were significantly different and the growth coefficients of male frogs from the Cheongwon population were greater than those from the Tae-an population. The mean age of males from the Tae-an population was higher than that from the Cheongwon population. However, the SVL and body weights of male frogs were not different between two populations and there was no difference between the two populations in the mean male SVL at any age. The results could increase our understanding of the life-history of this threatened frog and may be useful in conservation planning.

Initial Experience of Retrograde Wire Approach in Coronary Chronic Total Occlusion Intervention

정석환,김무현,Long Hao Yu,김경호,금동성,박태호,차광수,김영대,Jong Sung Park 대한심장학회 2009 Korean Circulation Journal Vol.39 No.6

Background and Objectives: Retrograde wire approach has been emerged as a useful tool to enhance success rate in coronary chronic total occlusion (CTO) intervention. Therefore, we tried to report the initial experience of retrograde approach and its clinical implication on CTO intervention. Subjects and Methods: From February 2007 to July 2008, retrograde approaches were performed in 28 patients with 31 CTO lesions out of 61patients. A hydrophilic coated guidewire was inserted by using microcatheter or over-the-wire (OTW) balloon through the collateral channel (septal or epicardial artery) via several strategies. Results: Mean age of patients was 63.4± 11.6 years. Male and female were 20 and 8 patients, respectively. The target artery with CTO lesions included the right coronary artery (45.2%), the left anterior descending artery (51.6%), and the left circumflex artery (3.2%). The mean length of CTO lesion was 18.4±16.4 mm. Overall technical success rate was 64.5%. The success rate of primary attempt was 78.9%, while the success rate of immediate and secondary attempt was 41.7%. Collateral channel dissections were observed in 3 patients and no patients among these patients developed cardiac tamponade. One patient had a silent non-Q wave myocardial infarction (MI) after the procedure. One failed patient died suddenly 3 days after the procedure. After percutaneous coronary intervention (PCI) procedure, no case was performed target vessel revascularization (TVR), urgent coronary artery bypass graft (CABG), and urgent PCI. Conclusion: Retrograde approach is an evolving technique to improve the success rate of CTO intervention. After the learning curve period, this technique could be the useful tool to enhance success rate in CTO intervention. Background and Objectives: Retrograde wire approach has been emerged as a useful tool to enhance success rate in coronary chronic total occlusion (CTO) intervention. Therefore, we tried to report the initial experience of retrograde approach and its clinical implication on CTO intervention. Subjects and Methods: From February 2007 to July 2008, retrograde approaches were performed in 28 patients with 31 CTO lesions out of 61patients. A hydrophilic coated guidewire was inserted by using microcatheter or over-the-wire (OTW) balloon through the collateral channel (septal or epicardial artery) via several strategies. Results: Mean age of patients was 63.4± 11.6 years. Male and female were 20 and 8 patients, respectively. The target artery with CTO lesions included the right coronary artery (45.2%), the left anterior descending artery (51.6%), and the left circumflex artery (3.2%). The mean length of CTO lesion was 18.4±16.4 mm. Overall technical success rate was 64.5%. The success rate of primary attempt was 78.9%, while the success rate of immediate and secondary attempt was 41.7%. Collateral channel dissections were observed in 3 patients and no patients among these patients developed cardiac tamponade. One patient had a silent non-Q wave myocardial infarction (MI) after the procedure. One failed patient died suddenly 3 days after the procedure. After percutaneous coronary intervention (PCI) procedure, no case was performed target vessel revascularization (TVR), urgent coronary artery bypass graft (CABG), and urgent PCI. Conclusion: Retrograde approach is an evolving technique to improve the success rate of CTO intervention. After the learning curve period, this technique could be the useful tool to enhance success rate in CTO intervention.

A Model for Midlife Pastoral Counseling

정석환 한국기독교학회 2006 한국기독교신학논총 Vol.48 No.-

Desmoplastic small round cell tumor 1예

정석환,이상엽,금동성,김성현,권혁찬,김재석,김효진 대한내과학회 2003 대한내과학회지 Vol.65 No.5

결합조직형성 소원형세포암은 젊은 남자의 복강에 발생하는 드문 종양으로 비교적 최근에 독립된 질환으로 분류되었으며, 아직 표준화된 치료법이 없는 실정이다. 저자들은 다발성 간내종괴로 내원한 59세 여자 환자에서 조직검사 시행 후 결합조직형성 수원형세포암으로 진단하고 다제복합화학요법후 종괴의 현저함 감소를 보인 1예를 경험하였기에 문헌고찰과 함께 보고하는 바이다. Desmoplastic small round cell tumor (DSRCT) is a rare neoplasm that develops in the abdominal cavity in young people. Microscopically, nets of small undifferentiated cells within a desmoplastic stroma are observed and immunohistochemical studies show polyphenotypic differentiation with expression of epithelial, neural and muscle markers. A specific chromosomal translocation, t(11:22)(p13:q12) has been documented in DSRCT and is increasingly used to confirm the diagnosis. We had experienced a 59-year-old female with right upper quardrant pain for 1 month. On abdominal computerized tomography, multiple demarcated intrahepatic mass lesions were found, but other organs metastasis or abnormal lymph node enlargement and fluid collection were not found. Fine needle aspiration biospy of hepatic mass was performed and DSRCT was diagnosed by H&E and immunohistochemical staining. She was treated with cyclophosphamide, etoposide, doxorubicin and cisplatin. After three cycles of chemotherapy, computerized tomography demonstrated distinct shrinkage of tumor. At present, she continues in the state of partial remission for 15months after chemotherapy was started.