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김연욱 대한내과학회 2022 대한내과학회지 Vol.97 No.1
Early detection and treatment is important to reduce mortality from lung cancer. Based on the positive results of lung cancer-related mortality reduction from large randomized trials of low-dose chest computed tomography (LDCT)-based screening in high-risk populations, LDCT-based screening programs have been implemented in several countries including Republic of Korea. This review focus on the current evidence and state of the art of LDCT-based lung cancer screening, and further discuss the ongoing efforts to develop more efficient screening programs worldwide. This article includes recent updates on the identification of high-risk population eligible for screening and management for screen-detected nodules. Additionally, aspects on future research direction would be addressed.
김연욱 啓明大學校 産業技術硏究所 1992 産業技術硏究所 論文報告集 Vol.15 No.1
Submicron droplets of pure silicon and germanium have been sprayed by electrohydrodynamic atomization. The submicron droplets of pure materials were produced and cooled in free flight through a vacuum chamber. Because they are very small, the surface area - to - volume ration is very high and the droplets cooled at 10bK/S. Furthermore, the volume of liquid in each droplet is extremely small. This combination of high cooling rate and very small liquid volume makes it difficult for a nucleation event to occur even in very fluid metals and an amorphous phase solidify in small droplets. A systemic study has been conducted for silicon and germanium of the distribution of the amorphous phase with droplet size. When the effect of droplet size was considered in pure semiconductor materials that amorphous phase was observed, the amorphous phase is formed predominantly in the smaller droplets and a transition between amorphous spheres and crystalline spheres clearly exists with increasing droplet size for each element. these transitions occur about 45 and 50 nm for Si and Ge.
다층원소박판에서 $TiAl_3$의 고온자전합성에 미치는 승온속도의 영향
김연욱,김병관,남태운,허보영,김영직,Kim, Yeon-Uk,Kim, Byeong-Gwan,Nam, Tae-Un,Heo, Bo-Yeong,Kim, Yeong-Jik 한국재료학회 1998 한국재료학회지 Vol.8 No.11
Ti 과 AI의 고순도 원소 박판을 이용하여 열간프레스장치에서 고온자전합성법으로 TiAI계 금속간화합물을 제조하였다. 원소 박판에서 $TiAl_3$ 금속간화합물을 제조하는 데 승온속도, 압력, 온도 등의 변수가 고온자전합성에 영향을 미치는 중요한 인자다. 특히 승온속도는 반응합성온도를 결정하는 인자로서 본 실험에서 DTA 분석을 이용하여 공정변수를 결정하였다. DTA 분석결과에 따르면, Ti와 AI의 계면에서 반응합성은 AI의 용융점 이하와 이상의 온도에서 두 번 발생함을 알 수 있다. 또한 승온속도가 증가할수록 두 반응합성온도는 증가하였다. 10층의 Ti 박판과 9층의 AI 박판을 $20^{\circ}C$/min의 승온속도로 고온자전합성시킨 후, $810^{\circ}C$와 240MPa의 압력에서 4시간 동안 열처리한 결과 $700\mu\textrm{m}$ 두께의 TiAI계 금속간화합물 판재를 제조하였으며, XRD 회절과 SEM으로 확인하였다. Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.
급냉응고에 의한 Mg-5wt%Zn 합금의 결정립 미세화
김연욱,이은종,허보영 ( Yeon Wook Kim,Eun Jong Lee,Bo Young Hur ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3
N/A In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.