• Title/Summary/Keyword: Fine structure

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Magnetic Domain Structures with Substrate Temperatures in Co-22%Cr Alloy Thin Films (자가정렬형 나노구조 Co-22%Cr합금 박막의 기판온도에 따른 미세 도메인 구호)

  • 송오성
    • Journal of the Korean Magnetics Society
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    • v.11 no.5
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    • pp.184-188
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    • 2001

  • Using a DC-sputter and changing the substrate temperature to room temperature and 200$\^{C}$, we manufactured each Co-22%Cr alloy thin-films, which has a uniform micro-structure at room temperature, and a fine self-organized nato structure (SONS) at the inside of the grain at the elevated temperature. We also investigated the microstructure and domain structure using a transmission electron microscope (TEM) and a magnetic force microscope (MFM). We managed to corrode selectively Co-enriched phase, then investigate the microstructure using a TEM. We found that it has a uniform composition when it is manufactured at room temperature, but, we found that it has a unique microstructure, which has a plate-like fine Co-enriched phase, with the formation of SONS at the inside of the grain at the elevated temperature. In MFM characterization, we found maze-type domains at the period of 5000 when the substrate temperature maintains at room temperature. We define that the maze-type domain has a disadvantage at the high density recording because it generates noises easily as the exchange coupling energy between the grains is big. On the other hand, there is only a fine domain structure at the period of 500 when the substrate temperature maintains at 200 $\^{C}$. We define that the fine domain structure has an advantage at the high density magnetic recording because it has thermal stability due to small exchange coupling energy.

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Numerical Study on Fine Migration in Geo-materials (지반내 세립토 유동에 대한 수치해석적 연구)

  • Shin, Hosung
    • Journal of the Korean Geotechnical Society
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    • v.34 no.11
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    • pp.33-41
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    • 2018

  • Soil internal erosion is a phenomenon in which fines attached to the solid skeleton are detached by fluid flow, and this continuous fine migration weakens the hydro-mechanical characteristics of the ground structure. This paper proposed governing equations for fine migration in pore spaces and its related scheme for the numerical analysis. Phase diagram for fine particles includes three different states: detached fines in the liquid phase ($c_e$), attached fines in the solid phase (${\sigma}_a$), and pore-clogged fines in the solid phase (${\sigma}_s$). Numerical formulations for finite element method are developed based on the hydraulic governing equations of pore fluid and fine migration. This study proposed a method of estimating model parameters for fine detachment, attachment, and clogging from 1D erosion experiments. And it proposed an analytical formula for hydraulic permeability function considering fine clogging. Numerical analysis of the previous erosion test developed the numerical scheme and verified the adequacy of fine migration models.

  • https://doi.org/10.7843/kgs.2018.34.11.33 인용 PDF KSCI HTML