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- 저자 : 김재경(Jae Gyeung Kim) (검색결과 3 건)
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초미세결정립 Fe73.5Cu₁Nb₃Si16.5B6 합금의 뫼스바우어 효과 연구
김재경(Jae Gyeung Kim),신영남(Young Nam Shin),양재석(Jae Suk Yang) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Amorphous Fe_(73.5)Cu₁Nb₃Si_(16.5)B_6 ribbons were annealed for different time at 500℃ and 552℃, just before and after the exothermic reaction in DSC curve. The development of nanocrystalline phase was investigated by means of Mossbauer spectroscopy. The crystalline phase consists mainly of DO₃ Fe-Si. Though slight in amount (5 %), another ferromagnetic phase which could be presumed t-Fe₃B was detected Si content of DO₃ Fe-Si, Si/(Fe+SO, was 0.218 under the heat treatment at 500℃ for 60 min and 0.222 at 552℃ for 10 min. Since then both of those values decreased with time until 120 min and finally these two values remained constant at 0.210. The variation in Si content with annealing time results in the variation in the hyperfine field and the isomer shift. The increase in the mean hyperfine fields and the decrease in the mean isomer shifts of Fe-Si are caused by the increase in Si content. The volume fractions of residual amorphous phase rapidly decrease during the early stage of annealing and come nearer to saturation after 120 min both at 500℃ and 552℃. The decrease in the mean hyperfine field of residual amorphous, in spite of slight changes in the volume fractions of Fe-Si and of residual amorphous after 120 min, is caused by the increase in the content of Nb and B in residual amorphous phase. The saturated volume fraction of the crystalline phase was 81 % for 500℃ (180 min) and 77 % for 552℃ (960 min), different from expectation.
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초미세결정립 Fe73.5Cu₁Nb₃Si16.5B6 합금의 Mossbauer 효과 연구
신영남(Young Nam Shin),김재경(Jae Gyeung Kim),양재석(Jae Suk Yang),조익한(Ick Han Cho),강신규(Sin Giu Kang) 한국자기학회 1994 韓國磁氣學會誌 Vol.4 No.1
The crystallization behavior of the amorphous Fe_(73.5)Cu₁Nb₃Si_(16.5)B_6 alloy with isothermal annealing at 552 ℃ was studied by Mossbauer spectroscopy. The amorphous phase was revealed to coexist together with DO₃-FeSi nanocrystalline and Cu-duster in annealed alloys by Mossbauer spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual amorphous, in spite of a slight change in the volume fraction of the FeSi and the residual amorphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and 0.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.
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김병업,김재경 大邱敎育大學校 科學敎育硏究所 1977 과학·수학교육연구 Vol.2 No.-
Among the objectives of the Korean elementary science curriculum there is such one as "Children should be able to formulate models and explain the natural phenomena by it". But the concrete meaning of this model seem to be uncertain because under this objective there are not the sub-objectives which delineate this model. This uncertainity make the teacher have some difficulties of how to lead the children's activities and evaluate their achievement on this objective. And the children's abilities to formulate a model and explain the phenomena by it is not yet apparent. In this study we had attempted to define the characteristics of a model within the elementary science curriculum through the various references. At the same time we had investigated the children's abilities to formulate a scientific model and explain the phenomena. To investigate the children's abilities we sellected 339 children from three elementary schools, Daegu Teacher's College attached school, Waeqwan Chungang School, Haepyung School. The questions presented to the children were as to molecular model, the magnetic field model by the electric current, the atmospheric pressure model, the rotational motion model of the earth, respectively. The conclusions and suggestions are as following; 1.The scientific model which the current elementary science curriculum indicates can be interpreted as the theoretical model. 2.The children were already given a molecular model through their science learning. By the use of molecular model children could explain fairly the phenomena not learned through their science learning. 3.The children almost couldn't correlate the various phenomena of the movement of the compass needle positioned near the straight electric current and formulate a magnetic field. 4.Among the fifth grade children there are only 30~40% children who could formulate the atmospheric model and explain the phenomena appropriately. 5.Among the sixth grade children there are less than 30% children who could formulate the rotational movement model of the earth and explain the phenomena appropriately. 6.When the children were given a theoretical model they seem to have ability to explain the phenomena observed, but they couldn't formulate the theoretical model based on the observation and other information by themselves. 7.In order to increase the children's ability to formulate a theoretical model, the more experiences to infer, explain the phenomena and formulate hypothesis must be offered to children.
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