• Journal of the Korean School Mathematics Society
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• v.18 no.4
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• pp.353-370
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• 2015

This study was conducted as a qualitative case study that explored how gifted 3rd-grade elementary school children who had learned the primary concepts of division and fraction, when they studied contents about decimal, formed the transformed primary concept and transformed schema of decimal by the learning of accurate primary concepts and connecting the concepts. That is, this study investigated how the subjects attained relational understanding of decimal based on the primary concepts of division and fraction, and how they formed a transformed primary concept based on the primary concept of decimal and carried out vertical mathematizing. According to the findings of this study, transformed primary concepts formed through the learning of accurate primary concepts, and schemas and transformed schemas built through the connection of the concepts played as crucial factors for the children's relational understanding of decimal and their vertical mathematizing.

• Korean Journal of Pharmacognosy
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• v.45 no.2
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• pp.141-146
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• 2014

In this study, we investigated on antioxidative activities and tyrosinase inhibitory activities of methanol extract and its fractions from roots of Arctium lappa. The total phenolic compound and flavonoid content of the ethylacetate fraction was found to be 818.29 mg/g and 360.59 mg/g as the highest content. In the measurement of DPPH radical scavenging ability and tyrosinase inhibitory activity, the ethylacetate fraction was higher than the other fractions and the extract. In addition, comparative analysis of phenolic compounds by liquid chromatography-mass spectrometry (MS)/MS system under the multiple-reaction monitoring (MRM) with negative-ion electrospray ionization mode. The main phenolic compounds in the extract and fractions of roots from Arctium lappa were cynarin and chlorogenic acid. The main phenolic compound of the ethylacetate fraction was cynarin. n-Butanol fraction had a significantly higher chlorogenic acid content than other samples. In conclusion, DPPH radical scavenging ability and tyrosinase inhibitory activity of the cynarin-riched ethylacetate fraction showed the highest activity.

• Korean Journal of Materials Research
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• v.18 no.11
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• pp.617-622
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• 2008

In this study, the additivity factors of compositions to density and glass transition point ($T_g$) in a $xLi_2O-(1-x)[(1-y)TeO_2-yZnO]$ (0$T_g$ was discussed. As a method for predicting the relation between glass structure and ionic conductivity, density was measured by the Archimedes method. The glass transition point was analyzed to predict the relation between ionic conductivity and the bonding energy between alkali ions and non-bridge oxygen (NBO). The relation equations showing the additivity factor of each composition to the two properties are as follows: Density(g/$cm^3$) = $2.441x_1\;＋\;5.559x_2\;＋\;4.863x_3\;T_g(^{\circ}C)$ = $319x_1\;＋\;247x_2\;＋\;609x_3\;－\;1950x_1x_3$ ($x_1$ : fraction of $Li_2O$, $x_2$ : fraction of $TeO_2$, $x_3$ : fraction of ZnO) The density decreased as $Li_2O$ content increased. This was attributed to change of the $TeO_2$ structure. From this structural result, the electric conductivity of the glass samples was predicted following the ionic conduction mechanism. Finally, it is expected that electric conductivity will increase as the activation energy for ion movement decreases.

• Composites Research
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• v.28 no.6
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• pp.366-371
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• 2015

In order to improve the mechanical properties of tungsten at room and elevated temperature, hafnium carbide (HfC) reinforced tungsten matrix composites were prepared using the spark plasma sintering technique. The effect of HfC content on the compressive strength and flexural strength of the tungsten composites was investigated. Mechanical properties of the composites were also measured at elevated temperatures and their trends, with varying reinforcement volume fraction, were studied. The effect of reinforcement fraction on the thermal properties of the composites was investigated. The thermal conductivity and diffusivity of the composites decreased with increasing temperature and reinforcement volume fraction. An inherently low thermal conductivity of the reinforcement as well as interfacial losses was responsible for lower values of thermal conductivity of the composites. Values of coefficient of thermal expansion of the composites were observed to increase with HfC volume fraction.

• The Mathematical Education
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• v.60 no.4
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• pp.409-429
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• 2021

This study investigated instructional methods for fractional division emphasizing algebraic thinking with sixth graders. Specifically, instructional elements for fractional division emphasizing algebraic thinking were derived from literature reviews, and the fractional division instruction was reorganized on the basis of key elements. The instructional elements were as follows: (a) exploring the relationship between a dividend and a divisor; (b) generalizing and representing solution methods; and (c) justifying solution methods. The instruction was analyzed in terms of how the key elements were implemented in the classroom. This paper focused on the fractional division instruction with problem contexts to calculate the quantity of a dividend corresponding to the divisor 1. The students in the study could explore the relationship between the two quantities that make the divisor 1 with different problem contexts: partitive division, determination of a unit rate, and inverse of multiplication. They also could generalize, represent, and justify the solution methods of dividing the dividend by the numerator of the divisor and multiplying it by the denominator. However, some students who did not explore the relationship between the two quantities and used only the algorithm of fraction division had difficulties in generalizing, representing, and justifying the solution methods. This study would provide detailed and substantive understandings in implementing the fractional division instruction emphasizing algebraic thinking and help promote the follow-up studies related to the instruction of fractional operations emphasizing algebraic thinking.

• Journal of the East Asian Society of Dietary Life
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• v.26 no.3
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• pp.278-284
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• 2016

Anthocyanins, a class of flavonoids, are natural water-soluble pigments, mainly found in vegetables and fruits. Anthocyanins have attractive pharmacological activities, such as anti-oxidant, anti-inflammatory, anti-cancer, and anti-diabetic effects. The purpose of this study was to investigate the inhibitory effects of the anthocyanin-rich fraction (ANF) from purple sweet potato on high fat diet-induced insulin resistance and hepatic steatosis. C57BL/6J mice were assigned to the following groups (n=8 per group): normal fat diet (NF); high fat diet (HF); high fat diet with ANF 50mg/kg (ANF50). Normal fat or high fat diets were fed for a total of 17 weeks, and ANF was orally administrated for 8 weeks (from 10 to 17 weeks, five times/week). In our results, there were no significant differences in body weight, food intake, and tissue weight upon ANF supplementation. The levels of serum triacylglycerol, total-cholesterol, and glucose were also not affected by ANF supplementation. However, ANF supplementation significantly decreased serum insulin and HOMA-IR levels as well as prevented hepatic fat accumulation in high fat-fed mice. These results show that ANF may be beneficial for improving high fat-induced insulin resistance and protecting against development of hepatic steatosis.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.12
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• pp.1732-1739
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• 2016

The general components and cyclitol compounds of ice plant (Mesembryanthemum crystallinum) were analyzed to examine the possibility of using extracts as functional food materials, the antioxidant effects and antidiabetic activities of the extracts by solvent fraction were tested. Among the mineral contents, contents of K and Na were the largest ($1,213.33{\pm}2.52$ and $545.53{\pm}12.01mg/100g$, respectively), followed by S, Ca, P, and Mg in order of precedence. Among cyclitol compounds, content of D-pinitol was the largest ($4.04{\pm}0.08mg/g$) while contents of chiro-inositol and myo-inositol were relatively small ($2.82{\pm}0.01$ and $0.25{\pm}0.01mg/g$, respectively). Among total phenol contents by solvent fraction, contents of chloroform and ethyl acetate fractions were large ($35.80{\pm}1.33$ and $23.70{\pm}0.62mg\;GAE/g$, respectively). Among antioxidant activity levels examined by DPPH, ABTS, FRAP, and lipid/MA assays, the chloroform fraction commonly showed the highest level of activity while the ethyl acetate fraction showed relatively high levels of activity. The antioxidant activity levels were proportional to total phenol contents by solvent fraction. As for antidiabetic effects, all solvent fractions showed at least 50% ${\alpha}-glucosidase$ inhibitory activity levels while the ethyl acetate, butanol, and chloroform fractions showed high levels activity of $90.33{\pm}0.40$, $87.98{\pm}0.16$, and $86.38{\pm}0.51%$, respectively. The ${\alpha}-amylase$ inhibitory actively levels were in the range of $25.63{\pm}1.45{\sim}60.34{\pm}2.67%$, which was lower than the ${\alpha}-glucosidase$ inhibitory activity levels, but the inhibitory activity levels by solvent fraction were similar. Given the above study results, ice plant can be utilized as a natural material with antioxidative and antidiabetic functionality.

• Computational Structural Engineering : An International Journal
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• v.1 no.1
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• pp.21-29
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• 2001

The general topology optimization can be considered as optimal material distribution. Such an approach can be unstable, unless composite materials are introduced. In this research, a nodal volume fraction method is used to obtain the optimum topology of continuum structures. This method is conducted from a composite material model composed of isotropic matter and spherical void. Because the appearance of the chessboard patterns makes the interpretation of the optimal material layout very difficult, this method contains a chessboard prevention strategy. In this research, several topology optimization problems are presented to demonstrate the validity of the present method and the recursive quadratic programming algorithm is used to solve the topology optimization problems.

• Food Science and Preservation
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• v.17 no.2
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• pp.267-274
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• 2010

To obtain basic information on the potential use of Camellia japonica leaf as a raw material in functional food, leaf antioxidant and anticancer activities were investigated. The radical-scavenging activity of various solvent fractions from the leaf, as shown by the DPPH radical test, increased in a dose-dependent manner, with the water fraction showing the highest activity. The reducing power of various solvent fractions from the leaf was also dose-dependent, and, again, the water fraction showed the highest reducing power. The water fraction showed strong antioxidant activity in the linoleic acid test and was also capable of scavenging nitrite in a dose-dependent manner. Proportions of 92.15% and 95.61% of available nitrite were scavenged by the water and butanol fractions, respectively, at levels of $1,000{\mu}g/mL$. Both butanol and water fractions exhibited strong inhibitory effects on the growth of human lung and colon cancer cells. The total phenolic contents of the butanol and water fractions were 216.26 mg/g and 220.68 mg/g, respectively. High-performance liquid chromatography (HPLC) showed that quercetin and epicatechin were the predominant phenolic compounds in the water fraction. The activities of this fraction are attributable to the presence of these phenolic compounds, particularly quercetin and epicatechin.

• Applied Biological Chemistry
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• v.15 no.3
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• pp.199-206
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• 1972

As a study on the konjak mannan-hydrolyzing enzymes from Aspergillus awamori, the culture conditions for enzyme formation, purification and properties of the enzymes and the effect of gamma-irradiation on the enzymatic hydrolysis were investigated. The results are summarized as follows: 1) A strain of A. awamori was selected as having the highest productivity of mannanase among 81 species of molds. 2) The optimum conditions for solid culture on wheat bran were 3 days of culture period, pH 4 of spraying water and 100% addition of tap water. 3) The optimum conditions for shaking culture were 6 days of culture period, addition of 0.1% xylose plus 0.5% konjak mannan and of 0.04% peptone. 4) Konjak mannan-hydrolyzing enzymes were separated into fraction I and fraction II by ammonium sulfate fractionation and DEAE-Sephadex column chromatography. 5) Fractions I and II showed pH optima of 4, pH stability of $3.5{\sim}5$ and $3{\sim}6$ and the extent of hydrolyzing konjak mannan 9% and 50%, respectively. 6) Hydrolysis of konjak mannan by a crude enzyme preparation was partially accerelated by gamma-irradiation of substrate above 0.5 Mrad and the effect was more remarkable by irradiating in wet state than in dry state. 7) Gamma-irradiation of konjak mannan brought about the increase in reducing power and decrease in viscosity and the effect was more remarkable in wet state than in dry state.