• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1278-1281
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• 2004

Several workers reported the relationship between osteoporosis and age-related reductions in the BV/TV (bone volume fraction) of vertebral trabecular bones. However, there were few micro finite element (micro-FE) models to account for the treatments of the osteoporotic trabecular bone. In the present study, micro-FE models of osteoporotic and hormone-treated bone models were constructed to analyze the effect of specimen location and boundary condition on mechanical characteristics of hormone treatment model for osteoporotic trabecular bone. Top and bottom sections of specimens were also investigated individually to study the effect of specimen location. Hormone-treated models were allowed to have the same relative BV/TV (13.4％) as that used in models of previous researchers. The present study reported the elastic and plastic characteristics of the osteoporosis and hormone-treated bone models. In the present study, in-situ boundary condition was applied to the simulated compression tests for in-vivo condition of vertebral trabecular bone. The present study indicated that the hormone therapy was likely to improve the mechanical characteristics of osteoporotic bones and the mechanical characteristics of vertebral trabecular bone specimen were dependent on the captured location and boundary condition.

• Journal of Powder Materials
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• v.24 no.3
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.55-59
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• 1991

The temperature-dependent magnetization curves of amorphous Fe-Co-(Nd, Sm, Gd, Tb)-B alloys were measured using a vibrating sample magnetometer from 77 K up to 900 K. The spin wave stiffness constants and the range of the exchange interaction were calculated from the saturation magnetization values at 0 K. Curie temperatures and the Bloch coefficients estimated from the saturation magnetization curves. The low temperature dependence of magnetization is in good agreement with Bloch relation, $M_{s}(T)=M_{s}(O)(1-BT^{3/2}-CT^{5/2})$. The spin wave stiffness constant and the range of exchange interaction are decreased by substitution of heavy rare earth (Tb, Gd).

• Advances in nano research
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• v.3 no.2
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• pp.111-121
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• 2015

$CoFe_2O_4$ nanotubes and porous nanorods were prepared via a simple one-pot template-free hydrothermal method and were used as an adsorbent for the removal of dye contaminants from water. The properties of the synthesized nanotubes and porous nanorods were characterized by electron diffraction, transmission electron microscopy and x-ray powder diffraction. The Adsorption characteristics of the $CoFe_2O_4$ were examined using polar red dye and the factors affecting adsorption, such as, initial dye concentration, pH and contact time were evaluated. The overall trend followed an increase of the sorption capacity reaching a maximum of 95% dye removal at low pHs of 2-4. An enhancement in the removal efficiency was also noticed upon increasing the contact time between dye molecules and $CoFe_2O_4$ nanoparticles. The final results indicated that the $CoFe_2O_4$ nanotubes and porous nanorods can be considered as an efficient low cost and recyclable adsorbent for dye removal with efficiency 94% for Cobalt ferrite nanotubes and for Cobalt ferrite porous nanorods equals 95%.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.149-154
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• 1995

The alloying of 6.5wt % Silicon in iron decreases the magnetization and the anisotropy and minimizes the iron loss noticeably. But it is very difficult to make thin sheets because of its poor ductility which is due to an ordering reaction (body centered cubic to CsCI type crystal structure). However the ordering reaction can be suppressed by rapid solidification method. The cooling rate of rapidly solidified Fe-6.5wt % Si alloy is about $10^3K/s$ and rapidly solidified structure are fine structure, cellular structure, dendrite and equiaxed grain from surface. The precipitates of $DO_3$ Phase emerges on $B_2$ matrix and the coercive force was 0.51 Oe (50cycle, 15KGauss) in Fe-6.5wt% Si alloy which was processed by heat treatment of $1150^{\circ}C$ for 1hr in high vacuum.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.885-886
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• 2010

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.215-219
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• 2020

MnCo₂S₄/CoS₂ electrode with highly accessible electroactive sites is prepared using the hydrothermal method. The electrode exhibits an areal capacitance of 0.75 Fcm^-2 at 6 mAcm^-2 in 1 M KOH. The capacitance is further increased to 2.06 Fcm^-2 by adding K₃Fe(CN)₆ and K₄Fe(CN)₆ (a redox couple) to KOH. This increment is associated with the redox-active properties of cobalt and manganese transition metals, as well as the ion pair of [Fe(CN)₆]^-3/[Fe(CN)₆]^-4. The capacitance retention of the MnCo₂S₄/CoS₂ electrode is 87.5% for successive 4000 charge-discharge cycles at 10 mAcm^-2 in a composite electrolyte system of KOH and ferri/ferrocyanide. The capacitance enhancement is supported by the lowest equivalent series resistance (0.62 Ωcm^-2) of MnCo₂S₄/CoS₂ in the presence of redox additive couple compared with the bare KOH electrolyte.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.148-152
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• 2005

A novel interferometric isolator has been proposed and designed to fabrticate waveguide magnetooptic isolator operating at a wavelength of $1.55{\cal}um$. The device consists of MMI (multimode interference) couplers and has a magnetooptic guiding layer with different layer structure in arms of the inteferometer. The layer structures in the arms of inteferometer are $HfO_2/CeY_2Fe_5O_{12}/NOG$ and $SiO_2/CeY_2Fe_5O_{12}/NOG$, respectively. This configuration give rise to different nonreciprocal phase shift. In consequence, the isolator operates under a unidirectional magnetic field. The optimized structure of the isolator was determined by a 3D beam propagation method.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.211-218
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• 2000

The effects of alloying elements, Cr, Mo, and N on repassivation characteristics of stainless steels were investigated by using the abrading electrode technique and a.c impedance spectroscopy. The role of alloying elements on the stability of passive film and their repassivation characteristics were examined using alloy steels such as Fe-Cr, Fe-Cr-Mo, 304, 304LN, 316, and 316LN. The electrochemical characteristics of the passive film were investigated by in-situ d.c. and a.c. electrochemical methods. Localized corrosion resistance is believed to have much to do with the stability and repassivation characteristics of the passive film. The effects of alloying elements on the current transients and repassivation kinetics were systematically examined by using the abrading electrode technique and a.c. impedance spectroscopy. The experimental results were analyzed in order to elucidate the relationship between passive film stability, repassivation characteristics, and alloying elements.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.105-111
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• 1999

When the preparation method of iron silicide films possess the annealing process, the interfacial state of the films is not fine. The good quality films were obtained as the plasma was used without annealing processing. Since the injected precursors were various active species in the plasma state, the organic compound was contained in the prepared films. We confirmed the formation of Fe-Si bonds as well as the organic compound by Fe and Si vibration mode in Raman scattering spectrum at $250cm^{-1}$ and Ft-IR. Because of epitaxy growth being progressed by the high energy of plasma at the low temperature of substrate, iron silicide was epitaxially grown to ${\beta}$-phase that had lattice structure such as [220]/[202] and [115]. Band gap of the prepared films had value of 1.182~1.174 eV and optical gap energy was shown value of 3.4~3.7 eV. The Urbach tail and the sub-band-gap absorptions were appeared by organic compound in films. We knew that the prepared films by plasma were obtained a good quality films because of being grown single crystal.