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차홍원 울산대학교 의과대학 1993 울산의대학술지 Vol.2 No.2
Penetrating keratoplasty in inbred Lewis rat with either Lewis donor corneas(syngeneic transplantation group) or Brown Norway donor corneas(disparate transplantation group) were performed. The kinetic changes of the inflammatory cell subtypes in the corneal transplantation site and the clinical features were studied. All grafts(10 grafts) were remained clear in the syngeneic group. There was a significant inflammatory reaction in the wound especially surrounding the sutures. These cells were mostly macrophages(OX-42). This response in the wound progressively diminished by third week. Rare T helper/inducer cells(W3/25) were noted in the graft early. By the second week this response in the graft had resolved. Nine grafts out of 10 were rejected by the third week in the disparate group. Macrophages were seen in moderate numbers in the graft and wound during the first week. By the second week T helper/inducer cells and T suppressor/cytotoxic cells(OX-8) Increased. In third or fourth week T suppressor/cytotoxic cells were most prominent cells in the rejected graft. The ratio of these three cell types(T suppressor/cytotoxic : T helper/inducer cell:macrophage) in the rejected cornea was 1.5:1:0.8.
차홍원 울산대학교 의과대학 1995 울산의대학술지 Vol.4 No.1
In order to investigate the effects of epidermal growth factor(EGF), fibroblast growth factor(FGF) and transforming growth factor-β(TGF-β), rabbit corneal endothelial cells were cultured. After adding growth factors individually or in combination, DNA synthesis of corneal endothelial cells was measured. EGF and FGF increased DNA synthesis of corneal endothelial cells at all concentration tested(0.03ng/ml-300ng/ml) compared with the control. The maximum increase of DNA synthesis was shown at the concentration of 0.3-10ng/ml of EGF or 10-30ng/ml of FGF. TGF-β reduced DNA synthesis of corneal endothelial cells at all concentration tested (0.03ng/ml-10ng/ml). DNA synthesis of corneal endothelial cells was more increased when EGF and FGF were added in combination. TGF-β inhibited DNA synthesis induced by EGF or FGF when added at the same time. These results indicate that combination of EGF and FGF has maximum effect in DNA synthesis increase of rabbit corneal endothelial cells.
전자부품용 구리 리드선의 도금두께에 따른 납땜특성에 관한 연구
홍원식,장현덕,이관훈,차종범,송병석 대한설비관리학회 2002 대한설비관리학회지 Vol.7 No.1
The purpose of this study is to find out optimum electroplating thickness of Ni and SnPb on electronic component to be warranted the solderability during one year storage. The thickness of electroplating on electronic component has strong relationship with the failure rate of component. This is one of the key factors to make a system to degrade. Because the poor electroplating results in de-wetting or non-wetting status during soldering process. we choose the copper(φ=0.8mm) wire for sample, and then Ni and SnPb electrodeposited on it with different thickness each other. The specimens were tested under the steam ageing tester and dry oven to investigate accelerated ageing factor. In case of steam ageing test, the test times are 4, 20 hours and in the case of dry heat test, 4, 16 hours. Also we measured the intermetallic compounds thickness of Cu/Ni/SnPb using by SEM(Scanning Electron Microscope). From these analyses, we suggest to optimize plating thickness to insure the solderability during one year storage.
B<sup>2</sup>it 플래시 메모리 카드용 기판의 Ag 범프/Cu 랜드 접합 계면반응
홍원식,차상석,Hong, Won-Sik,Cha, Sang-Suk 한국마이크로전자및패키징학회 2012 마이크로전자 및 패키징학회지 Vol.19 No.1
After flash memory card(FMC) was manufactured by $B^2it$ process, interfacial reaction of silver bump with thermal stress was studied. To investigate bonding reliability of Ag bump, thermal shock and thermal stress tests were conducted and then examined on the crack between Cu land and Ag bump interface. Diffusion reaction of Ag bump/Cu land interface was analyzed using SEM, EDS and FIB. The Ag-Cu alloy layer due to the interfacial reaction was formed at the Ag/Cu interface. As the diffusivity of Ag ${\rightarrow}$ Cu is faster than Cu ${\rightarrow}$ Ag, a lot of (Cu, Ag) alloy layers were observed at the Cu layer than Ag. These alloy layers contributed to increase the Cu-Ag bonding strength and its reliability. 본 연구는 고밀도 미세회로 형성 및 원가절감에 유리한 페이스트의 인쇄/건조, 프리프레그 관통 및 적층 공법을 이용한 $B^2it$ 공법을 이용하여 FMC 기판을 제조한 후 열적 스트레스에 대한 범프의 계면반응 연구를 수행하였다. 열적 스트레스에 대한 Ag 범프의 접합 신뢰성을 조사하기 위해 열충격시험, 열응력시험을 수행한 후 전기적 특성 및 단면분석을 통해 균열발생 여부를 조사하였다. 또한 Ag 범프와 Cu 랜드의 접합계면에 대한 계면반응 특성을 분석하기 위해 주사전자현미경(SEM), 에너지분산스펙트럼(EDS) 및 FIB분석을 수행하여 계면에서 발생되는 확산반응을 분석하였다. 이러한 결과를 바탕으로 열적 스트레스에 대한 Ag 페이스트 범프/Cu 랜드 접합계면에서 계면반응에 의해 형성된 Ag-Cu 합금층을 확인할 수 있었다. 이러한 합금층은 Cu ${\rightarrow}$ Ag 보다, Ag ${\rightarrow}$ Cu 로의 확산속도가 빠르기 때문에, Cu층에서의 (Ag, Cu) 합금층이 보다 많이 관찰되었으며, 합금층이 Ag범프의 계면 접합력 향상에 기여하는 것을 알 수 있었다.