• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.166-172
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• 1999

The magnetic properties between Mn-Ir antiferromagnetic layer and Ni-Fe ferromagnetic layer have been investigated in Mn-Ir/Ni-Fe/Zr on Si wafer formed by magnetron sputtering. Mn-Ir was sputtered from Ir chips and Mn target using D.C. power, Ni-Fe and Zr were deposited from Ni-Fe and Zr targets using D.C. power under Ar atmosphere. We studied the dependence of the magnetic properties on Ir content of Mn-Ir layer for Mn-Ir/Ni-Fe bilayer, and obtained the highest $H_ex$ of 219 Oe and the low $H_c$ of 30 Oe. And then focused on the effect of base pressure for Mn-Ir containing multilayers. Our experimental data showed that if the base pressure is higher than $3.0{\times}10^{-6}\;Torr$, the exchange anisotropy of Mn-Ir/Ni-Fe/Zr disappeared probably due to the grain refining of Mn-Ir film. In addition we have studied the dependence of Zr buffer on magnetic properties of Mn-Ir/Ni-Fe/Zr multilayers, and observed that Zr buffer about (111) texture and lower $H_c$ of Mn-Ir/Ni-Fe/Zr multilayer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.125-135
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• 2012

The FE model for shot peening often assume that shots impact vertically on the engineering parts to generate compressive residual stresses. However, the shots obliquely impact on the surface in actual peening. In this work, we propose a 3D finite element (FE) model for evaluation of residual stress under angled shot peening. Using the FE model for angled multi-impact, we examine the effects of factors such as impact angle, impact pattern and the number of shots. Plastic deformation of shot is also considered. To validate the model, we then compare the FE solution with experimental result by X-ray diffraction (XRD). The proposed model will be a base of 3D multi-impact FE model with diverse impact angles.

• Corrosion Science and Technology
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• v.11 no.1
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• pp.9-14
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• 2012

The formation of the Fe-Al inhibition layer in hot-dip galvanizing is a confusing issue for a long time. This study presents a characterization result on the inhibition layer formed on C-Mn-Cr and C-Mn-Si dual-phase steels after a short time galvanizing. The samples were annealed at $800^{\circ}C$ for 60 s in $N_{2}$-10% $H_{2}$ atmosphere with a dew point of $-30^{\circ}C$, and were then galvanized in a bath containing 0.2 %Al. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) was employed for characterization. The TEM electron diffraction shows that only $Fe_{2}Al_{5}$ intermetallic phase was formed. No orientation relationship between the $Fe_{2}Al_{5}$ phase and the steel substrate could be identified. Two peaks of Al 2p photoelectrons, one from metallic aluminum and the other from $Al^{3+}$ ions, were detected in the inhibition layer, indicating that the layer is in fact a mixture of $Fe_{2}Al_{5}$ and $Al_{2}O_{3}$. TEM/EDS analysis verifies the existence of $Al_{2}O_{3}$ in the boundaries of $Fe_{2}Al_{5}$ grains. The nucleation of $Fe_{2}Al_{5}$ and the reduction of the surface oxide probably proceeded concurrently on galvanizing, and the residual oxides prohibited the heteroepitaxial growth of $Fe_{2}Al_{5}$.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.339-360
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• 2023

In this paper, to assess the performance of a multi-span simply supported RC bridge, the dynamic characteristics of the bridge were measured and determined by structural health monitoring and resilient assessment via operational modal analysis as well as FE modeling. Supporting finite element (FE) models were created and analyzed according to the design drawings. This study used 2D plane monitoring of locations of hole in the infill wall and used 3D health monitoring and resilient assessment. From the results of 3Dsymmetric frame, if the frame is unsymmetrical, the used model can lead to the reduction in the internal forces. The recommendations from this study is from some discrepancies observed between 2D and 3D models, if possible 3D model should be used in analyzing the real frames.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.321-325
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• 2004

국내 충적층의 철, 망간 문제는 지속적으로 지적되어오던 수질항목이다. 충적층 지하수 내 철과 망간의 용존 특성을 확인하고자 강변여과수 부지에서 지하수의 수리지화학적 특성을 조사하였다. Fe와 Mn에 의해 오염된 관정은 D-2와 DS-3로 모두 3월에 채취한 시료이며 NO$_3$-N는 모두 0 m/L 이다. NO$_3$-N에 대해 다른 관정은 2 mg/L NO$_3$-N를 넘고 있으며, DS-8와 DS-3에서 11.30과 20.2 mg/L NO$_3$-N의 값으로 먹는물 수질기준을 초과하고 있다. Mn에 대해 오염된 관정은 SJ-3이다. 10월에 채취한 시료에서 DS-2+l8 m에서 채취한 시료가 1.16 mg/L인 것을 제외하고 대부분의 시료가 2 mg/L를 초과하고 있고, DS-6+l3 m과 SJ-3＋10 m에서 채취한 시료가 각각 10.71과 10.31 mg/L NO$_3$-N로 먹는물 수질기준을 초과하고 있다. DO 검층 자료와 NO$_3$-N 농도를 이용하여 Fe와 Mn이 먹는물 수질 기준을 초과하는 D-2와 DS-2 관정의 지하수 체의 혐기성 상태임을 확인하였다. 강변여과수 지역은 전반적으로 NO$_3$-N에 대해 인위적인 오염이 발생하고 있으며, 혐기성 상태 구간이 존재함에 따라서 Fe와 Mn이 먹는물 수질 기준을 초과하여 용존 상태로 존재한다.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.995-1002
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• 2010

This study investigated the effect of process temperature on the alloying process during synthesis of $Sm_2Fe_{17}$ powder from ball-milled samarium oxide ($Sm_2O_3$) powders and a solid reducing agent of calcium hydrides ($CaH_2$) using iron nanopowder (n-Fe powder) by a reduction-diffusion (R-D) process. The $n-Fe-Sm_2O_3-CaH_2$ mixed powders were subjected to heat treatment at $850{\sim}1100^{\circ}C$ in $Ar-H_2$ for 5 h. It was found that the iron nanopowders in the mixed powders are sintered below $850^{\circ}C$ during the R-D process and the $SmH_2$ is synthesized by a reduced Sm that combines with $H_2$ around $850^{\circ}C$. The results showed that $SmH_2$ is able to separate Sm and $H_2$ respectively depending on an increase in process temperature, and the formed $Sm_2Fe_{17}$ phase on the surface of the sintered Fe nanopowder agglomerated at temperatures of $950{\sim}1100^{\circ}C$ in this study. The formation of the $Sm_2Fe_{17}$ layer is mainly due to the diffusion reaction of Sm atoms into the sintered Fe nanopowder, which agglomerates above $950^{\circ}C$. We concluded that nanoscale $Sm_2Fe_{17}$ powder can be synthesized by controlling the diffusion depth using well-dispersed Fe nanopowders.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.149-153
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• 2001

This paper describes on the fabrication of Fe-Co hydrophilic magnetic fluids from the waste pickling liquor of steel. By adding with HNO$_3$in the waste liquor oxidation is proceeded from Fe$^{3+}$ion at 6$0^{\circ}C$ with air blowing. Ultra-fine Co-ferrite particles with the mean particle size of 50 $\AA$ were produced at pH 12 after adjusting the ratio of Fe$^{3+}$Co$^{2+}$=7/3(wt%) and Fe-Co particles with the mean particle size of 94 $\AA$ were produced by reducing the Co-ferrite particle with H$_2$at the temperature of 50$0^{\circ}C$. After triple adsorption of oleic acid dodecyl benzene sulfonate(D.B.S.) and tetra methyl ammonium(T.M.A.) ions on the surface of Fe-Co particles Fe-Co hydrophilic magnetic fluid was produced by dispersing the Fe-Co particles in ethylene glycol solution. The magnetization of the Fe-Co hydrophilic magnetic fluid increased with increasing the Fe-Co concentration. The magnetic fluid containing 70% (g/cc) Fe-Co showed 73 emu/g in magnetization at the magnetic intensity of 10 kOe.kOe.e.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.733-739
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• 2001

In Al-25Nb binary system, it was observed only formation of $D0_{22}$ $Al_3Nb$ intermetallic compound after 5hr milling but it was not observed formation of meta stable phase like L1$_2$ phase. In this state, $D0_{22}$ $Al_3Nb$ fabricated had nano sized grain of approximately 20nm. Ternary systems, transition metals such as Cr, Cu, Fe, Mn were added 6~12at.% as substitution of Al, showed formation of $D0_{22}$ $Al_3Nb$ like Al-25Nb binary system. In Al- l2Cu-25Nb system, it was observed that broad XRD pattern like amorphization of Al and not observed formation of $D0_{22}$ $Al_3Nb$ after 5hr milling. But there was mixed phase of a lot of amorphous Al and little $D0_{22}$ $Al_3Nb$ through TEM. In the states of unalloyed, 5~7hr milling time, those showed exothermic reaction at 35$0^{\circ}C$, which was formation of $D0_{22}$ $Al_3Nb$ like Al-25Nb binary system. With increasing milling time to 10hr, $D0_{22}$ $Al_3Nb$ was transformed to mixed phase of amorphous and nanocryatlline, having approximately 10nm grain but the meta stable $Al_3Nb$ was not fabricated by adding transition metals.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.38.2-38.2
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• 2013

Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at $5895{\AA}$ (NaD) and $8190{\AA}$ that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy proposed that low-mass stars (0.3M) are more prevalent in massive early-type galaxies, which may lead to a strong NaI 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as NaD, Mgb, and Fe5270, which can be measured with a significantly higher signal-to-noise ratio than NaI 8190. We identified a new sample of roughly one thousand NaD excess objects (NEOs; ~8% of galaxies in the sample) based on NaD line strength in the redshift range 0.00${\alpha}$-enhanced" ([${\alpha}/Fe$] ~ 0.3), "metal-rich" ([Z/H] ~ 0.3), and, especially, "Na-enhanced" ([Na/Fe] ~ 0.3).