• Korea-Australia Rheology Journal
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• v.13 no.3
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• pp.125-130
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• 2001

Block copolymers of PC-b-PMMA (polycarbonate-b-polymethylmethacrylate) and PC -b-SAN (polycarbonate-b-(styrene-c-acrylonitrile)), were examined as compatibilizers for blonds of PC with SAN copolymer. The average diameter of the dispersed particles was measured with an image analyser, and the interfacial properties of the blonds were analysed with an imbedded fiber retraction (IFR) technique. The average diameter of dispersed particles and interfacial tension of the PC/SAN blends reached a minimum value when the SAN copolymer contained about 24 wt% AN. Interfacial tension and particle size were further reduced by adding compatibilizer to the PC/SAN blends. PC-b-PMMA was more effective than PC-b-SAN as a compatibilizer in reducing the average diameter of the dispersed particles and interfacial tension of PC/SAN blend. A direct proportionality between the particle diameter and interfacial tension was also observed. The interfacial properties of the PC/SAN blends were optimized by adding a block copolymer and using an SAN copolymer that had minimum interaction energy with PC.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1295-1296
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• 2012

• 한국초전도학회:학술대회논문집
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• 2007.07a
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• pp.77-77
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• 2007

• Bulletin of the Korean Mathematical Society
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• v.56 no.1
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• pp.57-71
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• 2019

Let R be an associative ring with identity, M a t.u.p. monoid with only one unit and ${\omega}:M{\rightarrow}End(R)$ a monoid homomorphism. Let R be a reversible, M-compatible ring and ${\alpha}=a_1g_1+{\cdots}+a_ng_n$ a non-zero element in skew monoid ring $R{\ast}M$. It is proved that if there exists a non-zero element ${\beta}=b_1h_1+{\cdots}+b_mh_m$ in $R{\ast}M$ with ${\alpha}{\beta}=c$ is a constant, then there exist $1{\leq}i_0{\leq}n$, $1{\leq}j_0{\leq}m$ such that $g_{i_0}=e=h_{j_0}$ and $a_{i_0}b_{j_0}=c$ and there exist elements a, $0{\neq}r$ in R with ${\alpha}r=ca$. As a consequence, it is proved that ${\alpha}{\in}R*M$ is unit if and only if there exists $1{\leq}i_0{\leq}n$ such that $g_{i_0}=e$, $a_{i_0}$ is unit and aj is nilpotent for each $j{\neq}i_0$, where R is a reversible or right duo ring. Furthermore, we determine the relation between clean and nil clean elements of R and those elements in skew monoid ring $R{\ast}M$, where R is a reversible or right duo ring.

• Progress in Superconductivity
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• v.9 no.1
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• pp.5-10
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• 2007

We prepared four different $MgB_2$ films on $Al_2O_3$ by hybrid physical chemical vapor deposition method with thicknesses ranging from $0.65\;{\mu}m$ to $1.2\;{\mu}m$. X-ray diffraction patterns confirm that all the $MgB_2$ films are c-axis oriented perpendicular to $Al_2O_3$ substrates. The superconducting onset temperature of $MgB_2$ films were between 39.39K and 40.72K. The residual resistivity ratio of the $MgB_2$ films was in the range between 3.13 and 37.3. We measured the angle dependence of critical current density ($J_c$) and resistivity, and determined the upper critical field ($H_{c2}$) from the temperature dependence of the resistivity curves. The anisotropy ratios defined as the ratio of the $H_{c2}$ parallel to the ab-plane to that perpendicular to the ab-plane were in the range of 2.13 to 4.5 and were increased as the temperature was decreased. Some samples showed increase of $J_c$ and decrease of resistivity when a magnetic field in applied parallel to the c-axis. We interpret this angle dependence in terms of enhanced flux pinning due to columnar growth of $MgB_2$ along the c-axis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1297-1298
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• 2012

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.126.1-126.1
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• 2000

• Progress in Superconductivity and Cryogenics
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• v.18 no.1
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• pp.37-40
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• 2016

We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of $MgB_2$. NiO-added $MgB_2$ samples were prepared by the solid-state reaction method. The superconducting transition temperature ($T_c$) of 37.91 K was obtained for pure $MgB_2$, and $T_c$ was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of $MgB_2$ was occurred. The microstructural analysis shows that the pure $MgB_2$ sample consists of plate shape $MgB_2$ grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density ($J_c$) were obtained for small amount NiO-added $MgB_2$ samples as compared to pure sample. The enhancement in $J_c$ could be attributed to the refinement of $MgB_2$ grains which leads to high density of grain boundaries in NiO-added $MgB_2$ samples.

• Journal of Magnetics
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• v.11 no.1
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• pp.25-29
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• 2006

Recent experiments have demonstrated high TMR ratios in MTJs with the MgO barrier [1,2]. The CoFeB/MgO/CoFeB junctions showed better properties than the CoFe/MgO/CoFe junctions because the MgO layer had a good crystalline structure with (001) texture and smooth and sharp interface between CoFeB/MgO [3]. The amorphous CoFeB with 20 at%B starts the crystallization at $340^{\circ}C$ [4] and this crystallization of the CoFeB helps obtaining the high TMR ratio. In this work, the compositional changes in the MgO barrier and at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization were studied in annealed MTJs. XPS depth profiles were utilized. TEM analyses showed that the MgO barrier had (100) texture on CoFeB in the junctions. B in the bottom CoFeB layer diffused into the MgO barrier and B-oxide was formed at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.781-782
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• 2010