Al 6061-T6 단조 성형품의 기계적 특성

박철,김상식,권용남,이영선,이정환,Park, C.,Kim, S.S.,Kwon, Y.N.,Lee, Y.S.,Lee, J.H. 한국재료학회 2003 한국재료학회지 Vol.13 No.6

The effect of forging parameters, including different forging stock, strain rate and strain, on the mechanical properties of hot-forged Al 6061-T6 was investigated. The forging was conducted using either hydraulic press, crank press or hammer press, respectively, at a forging temperature of $400^{\circ}C$. When using an extruded bar as a forging stock, the tensile strength was lower for the specimens prepared by hammer forging than those by crank press forging. It was found that the coarsening of recrystallized grain was responsible for the decrease in tensile strength with hammer forging. Systematic studies on the effects of strain and strain rate on the tensile properties of hot-forged Al 6061-T6 products using extruded bar as a forging stock further suggested that the coarsening of recrystallized grains and$ Mg_2$Si precipitates complexed the observed trends in the tensile behavior. In case of hot forging with continuous cast bar as a forging stock, on the other hand, the mechanical properties of the specimen were largely improved with hammer press compared to those with crank press, which appeared to be due to the homogenization of microstructure.

이동통신 소프트웨어 라디오 플랫폼 개발동향

박철,이승규,김진업,김일규,Park, C.,Lee, S.Q.,Kim, J.U.,Kim, I.G. 한국전자통신연구원 2016 전자통신동향분석 Vol.31 No.6

소프트웨어 기반의 이동통신 시스템 개발 기술 즉, 소프트웨어를 이용하여 재구성이 가능한 이동통신 시스템 개발 기술이 연구되어 왔다. 최근에는 소프트웨어 기반 이동 통신 시스템 개발에 가상화 기술이 적용된 가상화 기반의 이동통신 플랫폼 개발 기술에 대한 연구가 활발히 진행되고 있다. 가상화 기반 이동통신 플랫폼 개발 기술은 소프트웨어를 이용하여 범용 하드웨어 컴퓨팅 플랫폼상에서 무선 접속 기능, 프로토콜 처리 기능 및 RF/IF 신호처리 기능의 구현이 가능할 뿐만 아니라, 가상화 플랫폼을 통하여 다양한 무선 접속 규격 수용 및 유연한 시스템 자원 활용이 가능한 기술이다. 본고에서는 가상화 기반의 이동통신 플랫폼 개발 기술에 대해 간략히 소개하고, 소프트웨어 기반 이동통신 플랫폼 개발 현황 및 가상화 기반의 이동통신 시스템 플랫폼에서 소프트웨어를 통해 RF 신호처리 기능을 용이하게 하는 상용 소프트웨어 RF 플랫폼 즉, Software Radio Frontend의 개발 동향에 대해 살펴보고자 한다.

난소임신 : 20 례에 대한 분석

박철(C Park),정승관(SK Jung),주명식(MS Ju),이재민(JM Lee),문용호(YH Moon),양화윤(HY Yang) 대한산부인과학회 1994 Obstetrics & Gynecology Science Vol.37 No.10

Primary ovarian pregnancy is a rare form of ectopic pregnayc and occurs usually with the rupture of the ovary and a massive hemoperitoneum. It is frequently misdiagnosed as a ruptured corpus luteum and the differentiation an be made only by microscopic examination of tissue specimens. This study was undertaken to investigate 20 cases of ovarian pregnancy indentified by retrospective analysis of 14,797 deliveries at Hae Sung General Hospital between 1986 and 1993. The prevalence rate is 1:740 deliveries and comprises of 6.5% of all extrauterine pregnancies. Risk factors include a history of pelvic inflammatory disease, prior pelvic surgery, and use of an intrauterine contraceptive devices. Clinical characteristics are similar to those of tubal pregnancies. The early diagnosis of ovarian pregnancy is important and concervative treatment is of importance too because these patients are usually young, healthy, and fertile.

Esculetin의 caspase-3 활성을 통한 U937 인체 혈구암세포의 세포사멸 유도

박철(Cheol Park),현숙경(Sook Kyung Hyun),신우진(Woo-Jin Shin),정경태(Kyung Tae Chung),최병태(Byung Tae Choi),권현주(Hyun Ju Kwon),항혜진(Hye Jin Hwang),김병우(Byung-Woo Kim),박동일(Dong Il Park),이원호(Won Ho Lee),최영현(Yung Hyun C 한국생명과학회 2009 생명과학회지 Vol.19 No.2

Esculetin, a coumarin compound, has been known to inhibit proliferation and induce apoptosis in several types of human cancer cells. However, the molecular mechanisms involved in esculetin-induced apoptosis are still uncharacterized in human leukemia cells. In this study, we have investigated whether esculetin exerts anti-proliferative and apoptotic effects on human leukemia U937 cells. It was found that esculetin could inhibit cell viability in a time-dependent manner, which was associated with the induction of apoptotic cell death such as increased populations of apoptotic-sub G1 phase. Apoptosis of U937 cells by esculetin was associated with an inhibition of Bcl-2/Bax binding activity, formation of tBid, down-regulation of X-linked inhibitor of apoptotic protein (XIAP) expression, and up-regulation of death receptor 4 (DR4) and FasL expression. Esculetin treatment also induced the degradation of β-catenin and DNA fragmentation factor 45/inhibitor of caspase-activated DNase (DFF45/ICAD). Furthermore, a caspase-3 specific inhibitor, z-DEVD-fmk, significantly inhibited sub-G1 phase DNA content, morphological changes and degradation of β-catenin and DEE45/ICAD. These results indicated that a key regulator in esculetin-induced apoptosis was caspase-3 in human leukemia U937 cells.

미세조직이 반응 357-T5 합금의 인장거동에 미치는 영향

박철(C. Park),김상식(S. S. Kim),이영선(Y. S. Lee),이정환(J. H. Lee) 한국소성가공학회 2002 한국소성가공학회 학술대회 논문집 Vol.2002 No.10

반응고 357-T5 합금의 파괴 특성

박철(C. Park),김상식(S. S. Kim),배명환(M. H. Bae),강신우(S. W. Kang),권용남(Y. N. Kwon),이영선(Y. S. Lee),이정환(J. H. Lee) 한국소성가공학회 2003 한국소성가공학회 학술대회 논문집 Vol.2003 No.5

노트북 LED 영상장치 내부의 전도열전달 해석과 성능 지수 평가

박일석(IS. Park),손창현(C.H Sohn),손동현(D.H. Son),백성민(S.M. Baik),박철(C. Park) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.3

Dark Mura phenomena which can happen at the region with high temperature gradient in a Notebook LCD Monitor using LED light source has numerically been studied. The calculation was conducted under the nearly realistic conditions by considering the anisotropic thermal properties of materials and the real dimensions of each component. The two performance indices of LED monitor, i.e., the maximum temperature and the spacial gradient of temperature were examined for the various shapes, lengths and thickness of heat sink plate. Calculated results give more reasonable temperature distribution comparing with experimental results.

리포좀을 이용한 형질전환 닭 생산에 대한 연구

변승준,박철,양보석,김태윤,손시환,김상훈,전익수,Byun S. J.,Park C.,Yang B. S.,Kim T. Y.,Sohn S. H.,Kim S. H.,Jeon I. S. 한국가금학회 2004 한국가금학회지 Vol.31 No.4

Microinjection of DNA is a general method for generating transgenic animals, but the rate of transgenesis in chickens is very low. So it was carried out to investigate the efficiency of liposome-mediated gene transfer in stage one cell of chicken embryo with GFP expression vector. In order to determine efficiency and duration of the introduced foreign gene, it was microinjected DNA with liposome or naked DNA into the germinal disc of stage one cell or stage-X chicken embryo. Analysis of reporter gene expression in day-4 embryos showed that GFP expression was observed only in the liposome-mediate embryo groups and detectable up to day-8 embryos. The results suggest that stable integration of the introduced gene using liposome is a rare event. Nevertheless the liposome-mediated gene transfer may be a useful method to transfer a foreign gene into the stage one cell of chicken embryos.

아산만 해역 중형동물플랑크톤의 시공간적 변동

이창래,박철,양성렬,신용식,LEE C. R.,PARK C.,YANG S. R.,SIN Y. S. 한국해양학회 2006 바다 Vol.11 No.1

서해 중부 연안에 위치한 아산만의 과거 동물플랑크톤 연구는 주로 3개월 간격의 계절별 자료에 근거하고 있다. 본 연구에서는 상대적으로 짧은 주기의 월별 채집을 바탕으로 동물플랑크톤의 월 변동을 파악하고, 수온과 염분, 식물플랑크톤의 출현량을 환경 요인으로 취급하여 이들의 변화 특성 및 이와 동물플랑크톤 분포와의 관계를 파악하였다. 수온은 시간적으로 전형적인 온대수역의 변화양상을 보여주며, 공간적으로는 만의 안쪽에서 연간 변화의 폭이 다소 크게 나타났다. 염분의 계절변화는 장마에 의한 계절변화가 크며 이 시기 인공담수호의 간헐적인 담수유출이 플랑크톤 생태계에 적지 않은 영향을 미칠 것으로 판단되었다. 식물플랑크톤의 클로로필 양은 과거에 비해 상당한 증가를 보였는데 만의 안과 밖에서 봄철 대증식의 시작과 기간에서 차이가 있었다. 만 안쪽에서 바깥쪽으로 가면서 춘계 대증식이 2월에서 4월로 늦춰졌고, 만 안쪽과 중앙에서는 대증식 기간이 3개월 정도 유지된 반면, 만 바깥쪽에서는 약 1개월 정도로 그 기간이 짧아졌다. 식물플랑크톤의 클로로필 양과 동물플랑크톤의 양, 특히 최 우점종 Acartia hongi의 양 간에는 약하지만 의미있는 양의 상관관계를 보였다(p<0.05).과거 계절별 자료에 근거한 시간변동과 비교하여 월별 채집의 필요성이 확인되었다. Previous studies on zooplankton in Asan Bay were mostly based on samples collected seasonally with three months intervals. Present study was aimed to know the temporal variation of meso-zooplankton distribution using the data collected monthly. Relationships between zooplankton abundances and environmental factors such as seawater temperatures, salinities and chlorophyll-a contents were also studied. Seawater temperature showed typical pattern of seasonal variation found in temperate waters. The fluctuations of environmental factors ranged relatively wider In the inner part of the bay than those in outer part of the bay. Salinity was very low right after the summer rainy period due to the sporadic outflow of freshwater from the adjacent artificial lakes. Sudden changes in salinity seemed to have significant impact on zooplankton assemblages. Chlorophyll-a contents were increased in general when compared with previous reports probably due to the recent human exploitations in the coastal zone, which might enhance the nutrients level . The timing and duration of spring bloom showed geographical differences. In the inner part of the bay it began earlier (February) and last longer (three months) while in the outer part of the bay it began late (April) and last just one month. Zooplankton abundance, especially most abundant taxon Acartia hongi, showed weak but significant positive correlation with chlorophyll-a contents. The difference in temporal variation found with two different sampling intervals indicated the necessity of shorter time interval samplings.

닭 수정란에서 Retrovirus를 이용한 형질전환 닭 생산 연구

변승준,박철,김성우,박진기,장원경,양보석,김태윤,손시환,김상훈,전익수,Byun S. J.,Park C.,Kim S. W.,Park J. K.,Chang W. K.,Yang B. S.,Kim T. Y.,Sohn S. H.,Kim S. H.,Jeon I. S. 한국가금학회 2005 한국가금학회지 Vol.32 No.4

Microinjection of recombinant retrovirus beneath the blastoderm of non-incubated chicken embryo is now the most widespread method for generating transgenic chickens, but transgenesis rates are very low. So to improve this problem, we first introduced retrovirus vector carrying RSV-GFP gene to an one-cell embryo culture system. To investigate whether retrovirus could work on an one-cell chicken embryo, we microinjected the concentrated retrovirus stocks into the germinal disc of one cell or stage-X chicken embryos. Analysis of reporter gene expression on day 4 embryos showed that GFP expression was observed in the only stage-X chicken embryo but was not in the one-cell embryo group. These results suggest that retrovirus system is the most efficient method to generate transgenic chickens in the stage-X embryo.