• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.179-184
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• 2016

For an industrial spin-transfer torque (STT) MRAM, low switching current and high thermal stability are required, simultaneously. For this point of view, it is essential to find magnetic materials which satisfy high spin polarization and strong perpendicular magnetocrystalline anisotropy (MCA). In this paper, we investigate electronic structures and MCA energies of perovskite $CoFeX_3$ (X = O, F, S, Cl). For X = F and Cl, spin polarization at the Fermi level are 97 % and 96 %, respectively, which are close to a half metal. Furthermore, Co-terminated 5-monolayer (ML) $CoFeX_3$ (X = O, F, S, Cl) films show perpendicular MCA. In particular, the MCA energy of the Co-terminated $CoFeCl_3$ is about 1.0 meV/cell which is three times larger than that of a 5-ML CoFe film. Therefore, we expect to realize a magnetic material with high spin polarization and strong perpendicular MCA energy by utilizing group 6 and 7 elements in the periodic table, and to contribute to commercializing of the STT-MRAM.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.514-520
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• 2021

A drug delivery system (DDS) based on nanoparticles has been used as a mediator to improve the efficacy of a drug by controlling the amount of drug released and delivering it to a target place. Chitosan, which is non-toxic and biodegradable, has good biocompatibility and excellent adsorption, so it can be used as a drug delivery vehicle. Valine, the essential amino acids, helps muscle growth and tissue recovery, and along with other amino acids. It lowers blood sugar levels and increases growth hormone production. In this study, Valine was adsorbed on magnetic chitosan which is capable of drug absorption, and Fe₃O₄-Valine CNPs was prepared through cross-linking with TPP (Tripolyphosphate). And then absorption and release trends of valine were investigated with the Fe₃O₄-Valine CNPs. Fe₃O₄, which has relatively high stability, is used to make the drug carrier magnetic so that the drug can be delivered to a target place. At optimal conditions, the absorption and release tendency of Fe₃O₄-Valine CNP was confirmed by analyzing by UV-Vis through the Ninhydrin test which is the color reaction of amino acids and by measuring the size of the particles, it was confirmed that it is suitable as a drug carrier.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.226-232
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• 1994

Rapidly solidified $SmFe_{7+x}M_{x}(M=Mo,\;V,\;Ti)$ compound were found to crystallize in the ${Sm(Fe,\;M)}_{7}$ based stable magnetic phase by introducing a second transition element into the Sm-Fe binary system. The ${Sm(Fe,\;M)}_{7}$ phase exhibits the highest Curie temperatuer ($T_{c}=355^{\circ}C$) ever Known in the Sm-Fe magnetic systems with a quite high intrinsic coercivity($_{i}H_{c}=3~6\;kOe $). The ${Sm(Fe,\;M)}_{7}$ phase remains stable even after annealing if once form during the rapid solidification. The primary reason for the high coercive force is due to the fine grain size($2000~8000\;{\AA}$)of the magnetic ${Sm(Fe,\;M)}_{7}$ matrix phase, and the enhanced Curie temperature is attributed to the extended solid-solubility of the additive transition elements in Fe matrix, which leads to volume expansion of the ${Sm(Fe,\;M)}_{7}$ cell causing an enhanced coupling constant of Fe atoms.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.323-327
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• 1999

To protect ${\beta}-carotene$ at the stomach and to release rapidly at the intestine we prepared alginate beads containing ${\beta}-carotene$. ${\beta}-carotene$ and alginate solution was homogenized and prepared o/w emulsion was prepared. It was poured into $Ca^{2+}$ solution through syringe needle. The gel was formed spontaneously and alginate beads containing ${\beta}-carotene$ were prepared. ${\beta}-Carotene$ was incorporated into the beads more than 95%. The release rate of ${\beta}-carotene$ was dependent on the concentration of $Ca^{2+}$, ${\beta}-carotene$ and surfactants. However, the concentration of alginate did not affect the release rate of ${\beta}-carotene$. The high concentration of $Ca^{2+}$ slowed down the release rate of ${\beta}-carotene$. The addition of surfactants in the ${\beta}-carotene$beads increased the release rate of ${\beta}-carotene$ in the order of Tween 80 > Cremophor > Span 20. The contents of ${\beta}-carotene$ and diameter of ${\beta}-carotene$ beads did not change significantly at $50^{\circ}C$ for 20 days.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.403-406
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• 2013

This paper describes a simple route to synthesis of water-dispersible monodisperse maghemite (${\gamma}-Fe_2O_3$) nanocrystals using 6-aminohexanoic acid (AHA) as a stabilizer. The water-dispersible ${\gamma}-Fe_2O_3$ nanocrystals with an average size of 5 nm were obtained simply by addition of $Fe(CO)_5$ into an octyl ether solution containing AHA at $195^{\circ}C$ under argon condition. As-prepared AHA coated ${\gamma}-Fe_2O_3$ nanocrystals exhibited highly crystallinity and magnetic property while keeping a good dispersity in an aqueous phase. We also obtained water-dispersible AHA coated ${\gamma}-Fe_2O_3$ nanocrystals using ligand-exchange method, demonstrating that AHA can be a good candidate for preparing water-dispersible uniform metal oxide nanocrystals.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.649-652
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• 2001

본 논문은 전용의 2D CAD 그래픽시스템으로 작성한 이미지를 양말에 나타내기 위한 편지컨트롤 시스템의 설계에 관한 연구이다. CAD 그래픽으로 자성된 2D 이미지 데이터를 입력데이터로 사용하고 편직과정에 나타내기 위해 캠을 제어하고 편직기의 동작 과정을 센서의 입력으로 감지하여 제어하는 시스템이다 8비트 MPU를 사용하여 전체의 컨트롤을 주관하는 메인CPU부와 공정의 진행사항 및 사용자와의 인터페이스를 위한 패널CPU부, 외부의 입출력을 위한 IO CPU부와 모터의 속도를 제어하기 위한 모터제어부로 구성되었다. 구현된 시스템은 고속의 편직에서도 필요한 패턴을 자유롭게 나타낼 수 있고 실시간으로 작업과정을 감시 제어할 수 있다. 또한 안정적이고 신뢰성을 갖는 자동화시스템의 실현으로 생산 및 운용상의 효율을 높일 수 있다.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.64-67
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• 2002

IrMn pinned spin valve (SV) films with stacks of Ta/NiFe/IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared by dc sputtering onto thermally oxidized Si (111) substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of exchange coupling field (H$_{ex}$), magnetoresistance (MR) ratio, and coercivity (H$_{c}$) were investigated. By optimizing the process of deposition and post thermal annealing condition, we obtained the IrMn based SV films with MR ratio of 3.6%, H$_{ex}$ of 1180 Oe for the pinned layer. The H$_{ex}$ is stabilized after the second annealing cycle and it is thought that this SV reveals high thermal stability. The H$_{ex}$ maintained its strength of 600 Oe in operation up to 24$0^{\circ}C$ and decreased monotonically to zero at 27$0^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.162-166
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• 2012

V-I characteristics of Fe(100)/MgO(100)/Cu-phthalocyanine (CuPc)/Co hybrid magnetic tunnel junctions were investigated at different temperatures. Fe(100) and Co ferromagnetic layers were separated by an organic-inorganic hybrid barrier consisting of different thickness of CuPc thin film grown on a 2 nm thick epitaxial MgO(100) layer. As the CuPc thickness increases from 0 to 10 nm, a bistable switching behavior due to strong charging effects was observed, while a very large magenetoresistance was shown at 77 K for the junctions without the CuPc barrier. This switching behavior decreases with the increase in temperature, and finally disappears beyond 240 K. In this work, high-potential future applications of the MgO(100)/CuPc bilayer were discussed for hybrid spintronic devices as well as polymer random access memories (PoRAMs).

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.217-223
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• 2015

The patterning of microbead in microfluidics channel is a practical technique for application in bio and medical areas. An approach is described for a direct patterning of magnetically active microbeads in microfluidic devices without inner structure. Local magnet arrangements - flat arrangement and stack arrangement - contacting same poles or opposite poles of magnet were utilized for generating trapping magnetic fields. The arrangement of magnets contacting same poles generated isolated patterns by repelling of magnetic field. The flat arrangement of vertically reverse magnet arrays shaped trapping patterns repelling magnetic field line between same poles. Spatially, the stack compositions of magnet arrangements allow diverse isolated trapped patterns of magnetic particles. Trapped magnetic particles in fluidic channels were stable on the $18m{\ell}/hr$ flow conditions and magnetic force of 1.08 mT in the all experiments. This experimental study suggests the simple and versatile methods to pattern magnetic particles, and has potential of wide application to bio and medical area.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.51-60
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• 2001

One-pot Mannich reaction of substituted hydroxy aromatic compounds with secondary amines in an aprotic solvent has been studied. The results demonstrate that the relative reactivity and regioselectivity of the Mannich reaction depend on the steric hindrance of amines as well as the nucleophilicity of hydroxy aromatic rings.