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김형순,Kim, Hyeong-Sun,Robers, S.G 한국재료학회 1994 한국재료학회지 Vol.4 No.5
취성재료의 균열첨단에서 전위의 이동에 대한 거동을 이해하기 위하여 단결정의 알루미나에 대한 취성-연성 전이(BDT)에 대한 한 연구가 진행되었다. 여러 온도에서, 예비균열된 시편으로 4점 굽힘시험을 이용하여 임계응력확대계수와 항복강도가 측정되었다. 그 결과로, BDT온도는 변형속도와 시편 방향에 따라 달랐다.:(1120)파단면에 대하여 $4.2 \times 10^{-6}$와 $4.2 \times 10^{-7}s^{-1}$에서 BDT온도는 각각$1034^{\circ}C$, $1150^{\circ}C$이었다. 또한 4점굽힘 시험을 이용하여 연성영역에서 균열첨단으로 부터 방출된 전위의 이동거리과 방향은 에칭 피트법에 의해서 측정되었다. 이중 에칭법을 이용하여 즉정된 사파이어에서 전위의 이동속도는 모델링 연구에 응용되었다. A work on the brittle to ductile transition (BDT) in single crystal alumina has been performed to understand and assess the dynamics of dislocation mobility around crack tip of brittle material. The critical stress intensity factor and yield strengths were obtained from bending test using precracked specimens at elevated temperatures. It was found that the BDT temperature was dependent on strain rate and orientation of specimen : for (1120) fracture surface, $1034^{\circ}C$, $1150^{\circ}C$ for $4.2 \times 10^{-6}$, $4.2 \times 10^{-7}s^{-1}$ respectively. Under a 4 point bending test, the moving distance of dislocation generated near crack front in ductile range is determined by an etch pits method. The velocity of dislocation in sapphire obtained from the double etching method was applied to modelling study.
The United States and Northeast Asia: Present and Future
( Rober A. Scalapino ) 인하대학교 국제관계연구소 2007 Pacific Focus Vol.22 No.2
Two issues have dominated the political-security scene in Northeast Asia in recent times: the North Korean nuclear program and the issue of Taiwan`s sovereignty. In both matters, the U.S. is deeply involved, and while the North Korean problem has shown recent progress, neither issue can be considered close to resolution. Meanwhile, U.S. relations with the major Northeast Asian powers vary. With Japan, the relationship is strongly positive. Relations with China are characterized by complexity, with cooperation and competition coexisting. Relations with Russia have fluctuated, with problems mounting in the recent past. Among other nations, the ROK remains a significant ally despite certain differences both with respect to policies and political atmosphere. Mongolia represents a nation seeking balanced relations with near neighbors and closer relations with Japan and the United States. When the current scene is viewed in its full dimensions, there is reason for cautious optimism.