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Adaptive Finite Element Mesh Generation for Dynamic Planar Problems
윤종열 한국방재학회 2012 한국방재학회논문집 Vol.12 No.6
In structural design and analysis used for hazard mitigation systems, automation is becoming an essential feature. For analysis,the finite element method has proven to be an effective approximate method if proper element types and meshes are chosen. Recently, the method has been successfully applied to solve complex dynamic and nonlinear problems; and with a properly chosen element type and mesh, reliable results have been obtained. However, in automation and in complex analyses of a structures,using the initial mesh throughout the analysis may involve some elements to go through strains beyond the elements' reliable limits. Thus, the finite element mesh for these types of analyses must be dynamically adaptive, and considering the rapid process of analysis in real time, the dynamically adaptive finite element mesh generating schemes must be computationally efficient. In this paper, a computationally efficient dynamically adaptive finite element mesh generation scheme for dynamic analyses of planar problems is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method (node movement) and the r-method (element division). A coefficient that depends on shape of elements is used to correct overly distorted elements. The validity of the scheme is shown by a deep cantilever beam example under a dynamic concentrated load. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural problems such as those under severe environmental hazards such as seismic or erratic wind loads.
기계적 압금화에 의한 $MoSi_2$-TiC 복합분말의 제조
윤종열 한국분말야금학회 1999 한국분말재료학회지 (KPMI) Vol.6 No.2
MoSi$_2$-TiC composite powders were fabricated by in-situ reaction through mechanical alloying. Also the monolithic MoSi$_2$ as well as TiC were synthesiced by mechanical alloying for comparison. An abrupt increase of vial surface temperature was detected due to a sudden reaction between elemental powders during milling. The reaction time for synthesis of composite powders decreased with increasing the content of (Ti+C) powder. It was found that a significant decrease of Ti grain size was observed with increasing the milling time. And the synthesis reaction of MoSi$_2$-TiC composite powders were largely dependent on the reaction between Ti and C powders.
윤종열,국승용,이상희,이병훈 한국농촌경제연구원 2018 농촌경제 Vol.41 No.1
This study aims to analyze the effect of rice public stockholding on rice price in harvest season and the decreasing rate of rice market supply (MSDR) and to identify how the rice public stockholding program affects the price of rice harvests over time by calculating time varying estimates of the MSDR. For this purpose, both an autoregressive distributed lag (ARDL) model and a rolling regression model are applied. The empirical findings show that 1%p of change in the MSDR leads to 1.9% of change in the rice price in harvest season. Additionally, the impact of the rice public stockholding program on rice price support continued in the sample periods, but the degree of its influence was enhanced by 2010, and has weakened since then. These findings suggest that it is necessary to reset the appropriate volume of rice public stockholding by considering the recently decreasing trend of rice consumption in order to improve policy effect. 본 연구의 목적은 수확기 쌀 시장가격에 대한 정부의 공공비축 매입 효과를 분석하는데 있다. 이를 위해 수확기 쌀 가격 반응모형을 개발하여 수확기 공공 매입규모가 수확기 쌀 가격에 얼마나 영향 미치는지 수확기 쌀 가격 결정의 동태적 특성을 고려한 자기회기시차분포모형을 이용하였다. 2004년∼2016년 기간을 대상으로 분석한 결과 공공 매입규모를 확대하여 시장공급을 감소시키면 수확기 쌀 시장가격 지지 효과가 있는 것으로 분석되었다. 또한, 공공비축제도의 정책효과가 시간의 흐름에 따라 수확기 쌀 가격에 얼마나 영향을 미치는지 이동회귀분석을 실시한 결과 해당기간 동안 공공비축 매입 정책이 수확기 쌀 시장가격지지 역할을 하고 그 영향력도 지속되고 있는 것으로 나타났으나, 2010년 이후로는 시장가격지지에 대한 영향력이 약화되고 있는 것으로 나타나고 있다. 공공비축 매입효과의 극대화를 위해서는 쌀 소비량과 생산량이 동시에 연계되도록 소비량 및 생산량 간의 적정 비율로 당해년 매입규모를 재설정할 필요가 있다. 본 연구 결과는 수확기 가격 예측에 활용되어 수급관리를 위한 매입규모 최적 설정 시 도움이 될 것으로 판단된다.