• Journal of the Korean Society of Earth Science Education
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• v.16 no.2
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• pp.302-318
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• 2023

The purpose of this study was to study to the effect of presenting SBF questions on the level of conceptual achievement and eye movement of elementary students in seasonal constellation learning that requires systems thinking. In this study, the effectiveness of SBF questions was divided into experimental groups and comparison groups, and scientific texts with different question types were presented to analyze the level of conceptual achievement and differences in eye movement of sixth-grade elementary students. Data analysis quantitatively analyzed the pre- and post-test results of the developed concept test paper and the eye movement data when learning scientific texts related to seasonal constellations. As a result of the study, first, the SBF question was a valid learning strategy for learning seasonal constellations. The SBF question showed a statistically significant difference (p<0.05) in the pre- and post-test between groups, and a statistically significant difference (p<0.001) in the pre- and post-test within the group. Second, SBF questions had a positive effect on students' learning by inducing learners with low preconceptions to area of interest that help them achieve concepts. In other words, when presenting SBF questions with visual data from a space-based perspective, it was confirmed based on the results of eye movement analysis that there was a significant difference in total fixation count (p<0.01) of learners. On the other hand, for learners with high scientific preconceptions, the effect of exploration was not significant because the preconceptions of the learners themselves acted as a hard core rather than the effect of SBF questions. This study is different from existing seasonal constellation learning studies in that it provides quantitative data through pre- and post-test and eye movement analysis in the seasonal constellation learning process, and can help elementary students learn seasonal constellations.

• Advances in Traditional Medicine
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• v.9 no.3
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• pp.252-258
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• 2009

Shade-dried flowers of Sarcostemma brevistigma Wight Syn (SBF) belonging to Asclepiadaceae yielded a rare flavonol glycoside viz., Quercetin 5a prenyl, 3-O-glucosyl, 7-O-(4c-p-coumaroyl) neohesperidoside which were characterized based on chemical and spectral (including 2D NMR) studies. The ethyl acetate fraction of alcoholic concentrate (test sample) of flowers of this plant (SBF) was evaluated for its hepatoprotective and inhibition of lipid peroxidation activities to investigate the scientific basis of the traditional uses. The oral administration in varying doses viz., 125 and 250 mg/kg of aqueous suspension of SBF to rats for 7 days produced significant (P < 0.01) hepatoprotective effect comparable to that of standard drug silymarin. The SBF afforded good hepatoprotection against $CCl_4$ induced elevation levels of serum marker enzymes, serum bilirubin and liver weight. The free radical scavenging effects of SBF and flavonol glycoside (SA) were assigned by $Fe^{2+}$/ascorbate induction method (in vitro), which revealed the inhibition of lipid peroxidation. The SBF and SA showed prominent anti-lipid peroxidation activity ($IC_{50}$ about $\sim$180 mg/ml and 11.0 mg/ml respectively), which was comparable to standard drug curcumin ($IC_{50}$ about $\sim$8.25 mg/ml). Thus the hepatoprotective activity of SB could be correlated to the free radical scavenging property of the flavonol glycoside.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.671-677
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• 2005

Ti and Ti alloys are known to have excellent corrosion properties, which is an important aspect for biocompability of these implants in human body. In our study, four types of samples (Cp-Ti, Ti-6Al-4V, $0.5wt.\%$ Fe-Ti and ECAP Ti) were tested for their apatite forming ability and corrosion properties. The micropolished samples were treated with 5M NaOH solution at $60^{\circ}C$ for 24 hours. Each samples was gently washed with distilled water and heat-treated at 600"C for 1 hour. The heat-treated samples were soaked in Simulated Body Fluid (SBF) solution at $36.5^{\circ}C$ in an incubator for different period of time. The test revealed that $0.5 wt.\%$ Fe-Ti showing faster apatite growth on the surface (7th day) compared to other samples. Polarization curve test (PCT) was also carried out to determine the corrosion resistance of each samples in SBF solution. ECAP-Ti showed highest corrosion resistance compared to any other samples. $0.5wt.\%Fe-Ti$ showed higher corrosion potential and corrosion current compared to other samples.

• Korean Journal of Materials Research
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• v.14 no.6
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• pp.432-435
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• 2004

Ti and Ti alloys are important materials for medical and dental applications. The effect of equal channel angular process(ECAP) and addition of Fe in Ti were studied with optical microstructure and corrosion behavior. Fine grains in Ti was obtained after ECAP. Corrosion behavior of commercial pure(CP)-Ti and Ti alloys was studied by open circuit test and polarization curve test(PCT) at $36.5^{\circ}C$ with SBF in biological environment. The corrosion behavior of ECAP-Ti was similar to that of CP-Ti in PCT, but Ti-Fe alloys were observed to become more corrosive with increasing Fe content.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.585-588
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• 2005

Titanium and Titanium alloys are widely used as an orthopedic and dental implant material because of their excellent biocompatibility and mechanical strength. In this study, ECAP Cp-Ti and Cp-Ti were heat treated for different annealing time of 30 min, 90 min and 3 hours. The grain size for each condition was studied. The micro-Vicker hardness test was carried out f3r each different heat treated samples. The micro-Vicker hardness test for ECAP Cp-Ti, Cp-Ti and Cp-Ti (3hr) revealed hardness values of 239.5, 182 and 144 Hv, respectively. The grain size was increased from approximately $70{\mu}m\;to\;300{\mu}m$ with the increase in heat treatment time from 30 min to 3 hours. The heat treated samples were tested for their biocompatibility in simulated body fluid (SBF) and corrosion rates was determined using Polarization Curve test (PCT). The PCT results showed Cp-Ti with comparatively high corrosion potential of -0.18 V and corresponding corrosion current of $2\times10^{-6}$ A, while the corrosion rate in ECAP Cp-Ti and Cp-Ti (30 min annealed) showed very similar results of corrosion potential about -0.47 V with corresponding corrosion current of $7\times10^{-8}$ A.

• Journal of the Korean institute of surface engineering
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• v.41 no.5
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• pp.226-231
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• 2008

Titanium and its alloy have been widely used in dental implant and orthopedic prostheses. Electrochemical characteristics of dental implant in the various simulated body fluids have been researched by using electrochemical methods. Ti-6Al-4V alloy implant was used for corrosion test in 0.9% NaCl, artificial saliva and simulated body fluids. The surface morphology was observed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The electrochemical stability was investigated using potentiosat (EG&G Co, 263A). The corrosion surface was observed using scanning electron microscopy (SEM). From the results of potentiodynamic test in various solution, the current density of implant tested in SBF and AS solution was lower than that of implant tested in 0.9% NaCl solution. From the results of passive film stability test, the variation of current density at constant 250 mV showed the consistent with time in the case of implant tested in SBF and AS solution, whereas, the current density at constant 250mV in the case of implant tested in 0.9% NaCl solution showed higher compared to SBF and AS solution as time increased. From the results of cyclic potentiodynamic test, the pitting potential and |$E_{pit}\;-\;E_{corr}$| of implant tested in SBF and AS solution were higher than those of implant tested in 0.9% NaCl solution.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.183-190
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• 2022

Diopside (CaMgSi₂O₆) is known to have high bioactivity as well as excellent mechanical properties. In this study, we tried to improve the bioactivity of zirconia ceramics by surface coating of diopside and its bioactivity was investigated through an in vitro test. Surface coating on zirconia substrate was prepared by sol-gel method using a diopside sol which was prepared by dissolving Ca(NO₃)₂·4H₂O, MgCl₂·6H₂O and Si(OC₂H₅)₄ in ethanol with a fixed molar ratio and then hydrolysis. To examine the bioactivity of diopside coating, we examined the surface dissolution and the precipitation of new hydroxyapatite particles through in vitro test in SBF (Simulated Body Fluid) solution. Dense and thick diopside coating layers could be fabricated on zirconia substrate by sol-gel method. Also, we confirmed that they contained high bioactivity from the in vitro test, indicated the precipitation of hydroxyapatite particles after the 14 days immersion in SBF solution. In addition, we checked that the bioactivity of diopside coated layers was dependent on the repeated coating cycle and coating thickness.

• Corrosion Science and Technology
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• v.15 no.2
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• pp.43-53
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• 2016

In this study, electrochemical impedance spectroscopy (EIS) was used to examine the changes in the electrochemical properties of biodegradable pure magnesium implanted into Sprague-Dawley rats for three days. The in vivo test results were compared with those of the in vitro tests carried out in Hank's, dilute saline and simulated body fluid (SBF) solutions. The in vitro corrosion rates were 20~1700 fold higher, as compared to the in vivo corrosion rates. This discrepancy is caused by biomolecule adsorption on the surface, which prevents the transport of water into the magnesium surface on in vivo testing. Among the in vitro experimental conditions, the corrosion rate in SBF solution had the least difference from the in vivo implanted specimen.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.191-198
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• 2022

Zirconia and titanium alloys, which are mainly used for dental implant materials, have poor osseointegration and osteogenesis abilities due to their bioinertness with low bioactivity on surface. In order to improve their surface bioinertness, surface modification with a bioactive material is an easy and simple method. In this study, akermanite (Ca₂MgSi₂O₇), a silicate-based bioceramic material with excellent bone bonding ability, was synthesized by a solid-state reaction and investigated its bioactivity from the analysis of surface dissolution and precipitation of hydroxyapatite particles in SBF solution. Calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃), and silicon dioxide (SiO₂) were used as starting materials. After homogeneous mixing of starting materials by ball milling and the drying of at oven, uniaxial pressing was performed to form a compacted disk, and then heat-treated at high temperature to induce the solid-state reaction to akermanite. Bioactivity of synthesized akermanite disk was evaluated with the reaction temperature from the immersion test in SBF solution. The higher the reaction temperature, the more pronounced the akermanite phase and the less the surface dissolution at particle surface. It resulted that synthesized akermanite particles had high bioactivity on particle surface, but it depended on reacted temperature and phase composition. Moderate dissolution occurred at particle surfaces and observed the new precipitated hydroxyapatite particles in synthetic akermanite with solid-state reaction at 1100℃.

• Korean Journal of Materials Research
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• v.14 no.4
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• pp.287-292
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• 2004

A bio-composites were prepared by mechanical mixing with bioactive sol-gel derived $CaO-SiO_2$ and organic PEEK for bone repairing hybrid materials. The composites were characterized by in-vitro test. A bonelike apatite was formed on the surface of all bio-composites in SBF test. The cell morphology and adhesion on the surface of the composites having below 30% PEEK were clearly observed in L929 cell experiment.