• Journal of Ginseng Research
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• v.19 no.1
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• pp.39-44
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• 1995

Total saponin from Korean red ginseng changed thermodynamic parameters of membranes from dipalmitoylphosphatidylcholine (DPPC) and ghost erythrocytes of human. In liposomes from DPPC, temperature of the main transition (Lb'-La) in liquid-crystalline phase increases by 0.2$^{\circ}C$ in average, but enthalpy does not change. Total saponin at a concentration of smaller than $10^5$% "stabilizes" the timid bilayers. At larger than 0.07 of saponin/DPPC ratio, saponin leads to an exclusion of the bound lipid molecules from the main phase transition into lamella liquid crystalline La-phase. Total saponin influences specifically all erythrocyte membrane transitions in a concentration-dependent manner, i.e. on the structures of all the main membrane skeleton proteins. A high structural specificity of saponin with membrane proteins, could be a base of specificity of physiological response of not only erythrocytes, but also other cells.her cells.

• Korean Journal of Materials Research
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• v.19 no.6
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• pp.300-304
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• 2009

The domain structures of annealed (001)-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$ (PMN-x%PT) crystals for x = 10, 20, 30, 35, and 40 at% were investigated by Polarized Optical Microscopy (POM) and Scanning Force Microscopy (SFM) in the piezoresponse mode. Both Polar Nano-Domains (PND) and long strip-like domains were clearly observed. The results also showed how the domain structure changed between phases with an increasing x in the PMN-x%PT crystals and the domain hierarchy on various length scales ranging from 40 nm to 0.1 mm. Distorted pseudo-cubic phase (x < 20%) consisted of PNDs that did not self-assemble into macro-domain plates. The rhombohedral phase (x = 30%) consisted of PNDs that began to self-assemble into colonies along preferred {110} planes. The monoclinic phase (x = 35%) consisted of miniature polar domains on the nm scale, whereas, the tetragonal phase (x = 40%) consisted of {001} oriented lamella domains on the mm scale that had internal nano-scale heterogeneities, which self-assembled into macro-domain plates oriented along {001} the mm scale.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.573-579
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• 1994

1-O-oleoyl glycerol, 2-O-oleoyl myo-inositol and methyl 2-O-oleoyl-${\alpha}$-D-glucopyranoside were used as surfactants in this study. The solution properties and solubilization process of those nonionic surfactants were examined by the phase equilibria. As a result of this study, we have found that phase behavior of two component systems of surfactants/$H_2O$/cyclohexane depends on temperature respectively. The three phase regions of three component systems appeared in the temperature range of $27^{\circ}C{\sim}32^{\circ}C$, $36^{\circ}C{\sim}45^{\circ}C$ and $38^{\circ}C{\sim}52^{\circ}C$ and solubilization of water and oil was high in those three phase ranged As the temperature was varied in the two component systems, liquid crystals of hexagonal were observed to in the case of 1-O-oleoyl glycerol, and liquid crystal of lamella types were observed in the case of 2-O-oleoyl myo-inositol and methyl 2-O-oleoyl-${\alpha}$-D-glucopyranoside.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.6
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• pp.320-328
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• 2003

A specimen of Cu-35%Sn alloy has been subjected to the unidirectional heat treatment in an attempt to examine the evolution of microstructures under varying thermal conditions. The specimen was cast in the form of a cylinder 10 mm in diameter and 200 mm in length, which was then installed in the temperature gradient field established inside a vertical tube furnace. The furnace temperature was adjusted to make the upper part at $750^{\circ}C$ and bottom end part at $300^{\circ}C$ of the specimen. The experiment was terminated by dropping it into water after the 30 minutes holding at given temperature. By the rapid cooling, the high temperature phases, ${\gamma}$ and ${\zeta}$, were retained at ambient temperature with some of ${\gamma}$ phase transformed to ${\varepsilon}$ phase, especially at the grain boundaries of ${\gamma}$ phase. The presence of ${\varepsilon}$ phase was found to determine the nature of phase transformations of the ${\zeta}$ phase undergoes upon cooling. In the close area of the ${\varepsilon}$ phase, ${\varepsilon}$ phase grew separately out of ${\zeta}$, and adds to the preexisting ${\varepsilon}$ whereas in areas away from ${\varepsilon}$, both ${\delta}$ and ${\varepsilon}$ grew simultaneously out of ${\zeta}$, and formed a lamella eutectoid structure. The transformation to ${\delta}$ was found to occur only in slow cooling. The hardness on each phase showed that the retained phases, ${\gamma}$ and ${\zeta}$, could be plastically deformed without brittle fracture while the phases, ${\varepsilon}$ and ${\delta}$, were too brittle to be deformed.

• Journal of the Korean Applied Science and Technology
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• v.36 no.1
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• pp.348-354
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• 2019

Dipalmitoyl phosphatidyl choline(DPPC), Polyphenol Derivatives, and Hematoxylin-Eosin were directly sonicated in acidic condition for 6 minutes to give clear stock solutions. Absorbtion properties of Polyphenol Derivatives in lecithin vesicle of Diphalmitoyl phosphatidyl choline system at $25^{\circ}C$ have been studied by absorbtion spectroscopy. The equilibrium of Polyphenol Derivatives between monomer and dimer in lecithin vesicles have been existed at low concentration of Polyphenol Derivatives, but oligomer has been formed in vesicle at high concentration of lecithin vesicles. By adding Bacteriorhodopsin(BR) to constant concentration of Polyphenol Derivatives decreased the absorbtion ratio(${\alpha}/{\beta}$) of Polyphenol Derivatives was increased during phase transition of dipalmitoyl phosphatidyl choline. In the presence of column eluted lamella vesicle and mixture of uni- and multilamella aggregates. The differences of rate between column eluted- and mixture were observed, therefore column eluted lamella reaction was represented more catalytic effect. The phase transition temperature of hydrolysis on Dipalmitoyl phosphatidyl choline and Polyphenol Derivatives were measured higher than it of Dipalmitoyl phosphatidyl choline and no Polyphenol Derivatives.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1388-1390
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• 2013

Macroporous $SnO_2$ foam was successfully synthesized via a simple soft-chemical route by hybridization between alkylamine and tin(IV) oxide. According to X-ray diffraction (XRD) analysis, the as-prepared $SnO_2$ foam had a highly ordered lamella structure along the crystallographic c-axis, which transformed to a rutile phase after thermal treatment at $300^{\circ}C$. X-ray absorption spectroscopy (XAS) at the Sn K-edge revealed that $SnO_2$ particles in the hybrid material maintained their nanosized structure after hybridization with alkylamine. Scanning electron microscope (SEM) images clearly showed that the as-prepared $SnO_2$ foam had a macroporous structure. This synthetic route can be extended to the development of open frameworks with good electrochemical properties in battery applications.

• Journal of Technologic Dentistry
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• v.31 no.3
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• pp.9-14
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• 2009

This study evaluated the mechanical properties of Ti-Cu alloys with the hope of developing an alloy for dental casting with better mechanical properties than unalloyed titanium. Ti-Cu alloys with four concentrations of Cu(2,5,10wt%) were made in an argon-arc melting furnace. The microstructure and micro-Vickers hardness were determined. X-ray diffraction pattern test was performed on the polished specimens. The microstructure of 2%Cu and 5%Cu alloys are shown acicular ${\alpha}Ti$ phase formed on the surfaces of previously formed $\beta$grains. The 10%Cu alloys has essentially a eutectoid structure; this structure includes lamella of ${\alpha}Ti$ and $Ti_2Cu$ phase that transformed from ${\alpha}Ti$ at the eutectoid temperature. The micro-Vickers hardness of CP Ti specimens was significantly(p<0.05) lower than that of any of the other alloys. Among the Ti-Cu alloys, the 10%Cu alloys exhibited a significantly(p<0.05) higher hardness value. but lower than that of Ti-6%Al-4%V alloy. From these results, it was concluded that new alloys for dental castings should be designed as Ti-Cu based alloys if other properties necessary for dental castings were obtained.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.1-8
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• 1999

This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.21-35
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• 1997

The Ag-Pd-Cu alloys containing a small amount of Au is commonly used for dental purposes, because this alloy is cheaper than Au-base alloys for clinical use. However, the most important characteristic of this alloy is age-hardenability, which is not exhibited by other Ag-base dental alloys. The specimens used were Ag-20Pd-20Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electic furace and centrifugal casting machine in Ar atmoshpere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at $350{\sim}550^{\circ}C$ Age-hardening characteristics of the small Au-containing Ag-pPd-Cu dental alloys were investigated by means of hardness testing, X-ray diffraction and electron microscope observations, electrical resistance, differential scanning calorimetric, emergy dispersed spectra and electron probe microanalysis. Principal results are as follows : Hardening occured in two stages, I. e., stage I in low temperature and stage II in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the Llo type face centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affedted by the Cu concentration. In stage II, decomposition of the $\alpha$ solid solution to a PdCu ordered phase(L1o type) and an Agrich ${\alpha}2$ phase occurred and a discontiunous precipitation occurred at the grain boundary. Form the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipitation procedure was ${\alpha}\to{\alpha}+{\alpha}2+PdCu\to{\alpha}1+{\alpha}2+PdCu$ at Pd/Cu = 1 Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at $450^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.629-636
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• 2014

For surface modification, bulk metallic glass coatings were fabricated using metallic glass powder and a mixture of a self-fluxing alloy or/and hard metal alloys with a heat-resisting property using a high velocity oxy-fuel coating thermal spraying process. Microstructural analyses and mechanical tests were carried out using X-ray diffraction, a scanning electron microscope, an atomic force microscope, a three-dimensional optical profiler, and nanoindenation. As a result, the monolithic metallic glass coating was found to consist of solid particle and lamellae regions that included many pores. Second phase-reinforced composite coatings with a self-fluxing alloy or/and hard metal alloy additives were employed with in-situ $Cr_2Ni_3$ precipitate or/and ex-situ WC particles in an amorphous matrix. The mechanical behaviors of the solid particles and lamella regions showed large hardness and elastic modulus differences. The mechanical properties of the particle regions in the metallic glass composite coatings were superior to those of the lamellae regions in the monolithic metallic glass coatings, but indicated similar trends in matrix region of all the coating layers.