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Enhanced Multiferroic Properties in Epitaxial Yb-Doped BiFeO3 Thin Films
장준경,안윤호,서정대,손종역 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4
We report the enhanced multiferroic properties of a ytterbium (Yb)- doped BiFeO3 thin film (Bi0.85Yb0.15FeO3) deposited on a (001) SrRuO3/ (100) SrTiO3 substrate by pulsed laser deposition. The crystal structure, surface morphology, ferroelectric domain structure, and the electrical and magnetic behavior of the epitaxial Bi0.85Yb0.15FeO3 film, 100 nm in thickness, were investigated. The results were compared with those of an undoped BiFeO3 thin film. The x-ray diffraction patterns showed that both films have tetragonal-like crystal structures. Atomic force microscopy showed that the Bi0.85Yb0.15FeO3 and BiFeO3 films have flat and clear surface steps, characteristic of a layer-by-layer growth mechanism. Furthermore, the strip-like ferroelectric domain structures were clearly observed in piezoelectric force microscopy. The Bi0.85Yb0.15FeO3 films had significantly higher remanent polarizations of approximately 73 μC/cm2 and lower leakage currents compared to the BiFeO3 thin film. Ferromagnetic enhancement was also observed in the Bi0.85Yb0.15FeO3 film at room temperature.
장준경,이호철,이현철 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7
In this paper, McCARD code was verified using various models listed in the NUREG/CR-6361 benchmarkguide, which provides specifications for single pin-cells, single assemblies, and the whole core classifieddepending on the nuclear properties and structural characteristics. McCARD code was verified bycomparing its results with those of SCALE code for single pin-cell and single assembly benchmarkproblems. The difference in the multiplication factor obtained through the two codes did not exceed 90pcm. The benchmark guide treats a total of 173 whole core experiments. The experiments are categorizedas simple lattices, separator plates, reflecting walls, reflecting walls and separator plates, burnableabsorber fuel rods, water holes, poison rods, and borated moderator. As a result of numerical simulationusing McCARD, the mean value of the multiplication factors is 1.00223 and the standard deviation of themultiplication factors is 285 pcm. The difference between the multiplication factors and the experimentalvalue is in the range of -665 pcm to þ 1609 pcm. In addition, statistics of results for experimentscategorized by reactor shape, additional structure, burnable poison, etc., are detailed in the main text.
장준경 ( Joon Kyung Jang ),석승훈 ( S. Hun Seog ),김준석 ( Joon Seok Kim ) 한국금융학회 2007 金融學會誌 Vol.12 No.1
본 연구는 2002년 11월부터 시행되고 있는 공정공시제도가 당초 도입 취지대로 잘 기능하고 있는지를 검증하기 위하여 영업이익 공시시점에서의 주가 및 거래량 반응을 살펴보았다. 본 연구로부터 도출된 결과를 정리해 보면 다음과 같다. 첫째, 공정공시 도입 이후에는 호재정보와 악재정보 모두에서 사건일을 전후한 기간 동안 통계적으로 유의한 주가반응이 나타난 반면 공정공시 도입 이전에는 호재정보에서만 유의한 주가반응이 도출되어 공정공시 도입으로 정보효과가 개선되었음을 보이고 있다. 둘째, 공정공시 도입 이후 호재정보에 대한 주가변동성과 악재정보에 대한 거래량변동성이 낮아졌다. 이는 공정공시제도가 도입 당시에 우려했던 정보공개 지연 등의 부작용 없이 정보의 비대칭성을 해소하는 긍정적인 역할을 수행하고 있음을 말해준다. 셋째, 악재정보가 호재정보에 비하여 공시일 전후의 주가변동성이 큰 것으로 나타나 악재정보가 정보지연의 부작용을 초래할 수 있는 정보의 속성을 지니고 있는 것으로 판단된다. 마지막으로 확실성이 높은 잠정정보와 불확실성이 높은 예측정보의 주가반응을 비교해 보았는데 호재정보에 대해서는 잠정정보에 대한 반응이 크게 나타났으나 유의성을 찾지 못하였고 악재정보에 대해서는 예측정보에 대해 더 큰 주가반응이 나타났다. 이는 악재정보를 자발적으로 공시한 데에 따른 투자자의 과민반응으로 해석된다. This study focuses on analyzing the information effects to review the role of Regulation Fair Disclosure (Reg. FD) since the enforcement of Reg. FD in November 2002. The results of this research are as follows. First, in the post Reg. FD period, the results show that there are stronger abnormal return and trading volume responses over a 3-day period (-1, +1) compared to the new regulation before. However, abnormal return and trading volume responses are also observed in a statistically significant manner in the post-event day. Second, in the post Reg. FD period, stock price and trading volume fluctuations caused by disclosure of companies around the time of shareholders` meeting have decreased compared to the new regulation before. Third, bad news has demonstrated significantly bigger range of stock fluctuations than good news around around the time of shareholder`s meeting.