• Journal of the Society of Cosmetic Scientists of Korea
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• v.37 no.2
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• pp.129-136
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• 2011

The moisturizing effect and stability of a cream containing 0.25 % Inula britannica flower ethyl acetate fraction were investigated. The pH, viscosity, and absorbance were measured under 4 different temperature conditions(4, 20, 37, and $45^{\circ}C$) and under the sun light at 2 week intervals for 12 weeks. The variations in pH and viscosity of all experimental creams were similar to those of control cream. The absorbance variations of the extract from experimental cream at 330 nm were in the order: under the sun > 45 > 37 > 25 > $4^{\circ}C$. It shows that ethyl acetate fraction in the cream can be oxidized under the sun. In addition, any change in color or smell was not observed through 12 weeks of the experimental period. These results showed that the cream were stable. Accordingly, it is suggested that further study is needed to provide more information to the manufacturers, who are seeking for the application of the extract to improve the anti-oxidant and antibacterial activities and stability of cosmetic products.

• Journal of the Korean Applied Science and Technology
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• v.29 no.2
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• pp.205-213
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• 2012

In this study, the stability of cream containing the ethyl acetate fraction of C. obtusa leaf extract was evaluated. The pH, viscosity, and absorbance were measured under the 4 different temperatures (4, 25, 37 and $45^{\circ}C$) and under the sun light during the 12 weeks. The control cream without containing the extract did not show pH change under the different temperatures mentioned above. However, the pH of the cream with the extract was decreased 0.11 at $4^{\circ}C$ and $25^{\circ}C$. Under the $37^{\circ}C$, $45^{\circ}C$ and sun light condition, the pH was decreased 0.55, 0.84 and 0.59, respectively. After treating the cream for 12 weeks under the different temperatures, the viscosity was measured for the cream containing the extract and control cream. The values were decreased by 2,404 cPs in average compared to the initial value for the former and control cream were decreased by 1,296 cPs in average for the latter. On the other hand, the viscosity of control cream treated under the $45^{\circ}C$ for 12 weeks was decreased (1,915 cPs) relative to the cream containing the extract, which showed 3,810 cPs decrease in viscosity. The cream containing the extract did not show absorbance change at $4^{\circ}C{\sim}37^{\circ}C$ for 12 weeks. Instead, the absorbance of the cream treated under $45^{\circ}C$ and sun light condition was decreased 32.5 % and 35.2 %, respectively. This decrease in absorbance is relatively small compared to the 54.8 % decrease of the extract sampled from the cream using ethanol solution. This indicates that the extract is stabilized in the cream. In addition, any change in color or smell was not observed through 12 weeks of the experimental time period. Also physical changes as creaming and cohesion were not shown. The results show that the cream containing C. obtusa leaf extract was relatively stable. However, it is concluded that it is still not clear in the stability of the cream containing the extract when it is stored for a long time. Accordingly, it is suggested that further study is needed for the application of the extract to cosmetics.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.4
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• pp.470-482
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• 2008

Seasonal variations of chemical composition and optical properties of aerosols at Seoul and Gosan were investigated using the ground-based aerosol measurements and an optical model calculation. The mass fraction of elemental carbon was $8{\sim}17%$, but its contribution on light absorption was high up to $29{\sim}48%$ in Seoul. In Gosan, the contribution of water soluble aerosols on aerosol extinction was $83{\sim}94%$ due to the high mass fraction of these particles in the range of $56{\sim}88%$. Model calculation showed that the water holding capacity of aerosols was larger in Gosan than in Seoul because of higher relative humidity and temperature along with abundant water soluble aerosols. Difference between measured and calculated aerosol optical depths was the highest in summer. This was because aerosol optical depth calculated from ground-based measurements could not consider aerosol loadings at high altitude in spite of high column-integrated aerosol loadings observed by Sun photometer. Although hygroscopic growth was expected to be dominant in summer, the mass concentration of water soluble aerosols was too low to permit this growth.

• Education of Primary School Mathematics
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• v.25 no.3
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• pp.213-232
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• 2022

With the importance of number line in learning fractions, this study investigated how 4th grade students understand fractions and its operations in number line. The questionnaire consisted 22 items which were related to representing fractions, comparing the size of fractions, and operating addition and subtraction of fractions. Both structured number line and sub-structured number line were presented in the items. As results of the study, the overall success rates were not high and even some items showed higher incorrect answer rates than the success rates. Also, the students showed a difficulty in solving non-structured number line tasks. It was also noticeable that students showed several types of incorrect answers, which means that students had incomplete understanding of both fractions and number line. This paper is expected to shed light on elementary students' understanding of fractions and number line and to provide implications of how to deal with number line in teaching and learning fractions in the elementary school.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.237-241
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• 2004

Amorphous silicon (a-Si) films are used in a broad range of solar cell, flat panel display, and sensor. Because of the greater ease of deposition and lower processing temperature, thin films are widely used for thin film transistors (TFTs). However, they have lower stability under the exposure of visible light and because of their low field effect mobility ($\mu$$_{FE}$ ) , less than 1 c $m^2$/Vs, they require a driving IC in the external circuits. On the other hand, polycrystalline silicon (poly-Si) thin films have superiority in $\mu$$_{FE}$ and optical stability in comparison to a-Si film. Many researches have been done to obtain high performance poly-Si because conventional methods such as excimer laser annealing, solid phase crystallization and metal induced crystallization have several difficulties to crystallize. In this paper, a new crystallization process using a molybdenum substrate has been proposed. As we use a flexible substrate, high temperature treatment and roll-to-roll process are possible. We have used a high temperature process above 75$0^{\circ}C$ to obtain poly-Si films on molybdenum substrates by a rapid thermal annealing (RTA) of the amorphous silicon (a-Si) layers. The properties of high temperature crystallized poly-Si studied, and poly-Si has been used for the fabrication of TFT. By this method, we are able to achieve high crystal volume fraction as well as high field effect mobility.

• Journal of Microbiology and Biotechnology
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• v.11 no.3
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• pp.369-375
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• 2001

Urushiol, a natural monomeric oil, was used to prepare a detergentless micro-emulsion with water and 2-propanol The formation of micro-emulsion was verified by conductivity measurements and dynamic light scattering. The conductivity data showed phase change dynamics, a characteristics of micro-emulsions, and subsequent dynamic light scattering study further confirmed the phenomenon. Average water droplet diameter was 10 nm to 500 nm when the molar ratio of 2-propanol ranged from 0.40 to 0.44 . Earlier studies were performed on toluene and hexane, in which the insoluble substrate in water phase was added to the solvents to be reacted on by enzymes. However, in the present urushiol system, urushiol was used as both solvent and substrate in the laccase polymerization of urushiol. The laccase activity in the system was examined using polymerization of urushiol. The laccase activity in the system was examined using syringaldezine as a substrate, and the activity increased rapidly near the molar ratio of 2-propanol at 0.4, where micro-emulsion started. The activity rose until 0.46 and fell dramatically thereafter. The study of laccase activity in differing mole fractions of 2-propanol showed the existence of an ‘optimal zone’, where the activity of laccase was significantly higher. In order to analyze urushiol polymerization by laccase, a bubble column reactor using a detergentless micro-emulsion system was constructed. Comparative study using other organic solvents systems were conducted and the 2-propanol system was shown to yield the highest polymerization level. The study of laccase activity at a differing mole fraction of 2-propanol showed the existence of an ‘optimal zone’ where the activity was significantly higher. Also, 3,000 cP viscosity was achieved in actual urushi processing, using only 1/100 level of laccase present in urushi.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.111-115
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• 2005

Recently, natural fibers draw much interests in composite industry due to low cost, light weight, and environment-friendly characteristics compared with glass fibers. In this study, mechanical properties were evaluated for two extreme cases of jute fiber orientations, i.e. the unidirectional yarn composites and the felt fabric composites. Samples of jute fiber composites were fabricated by RTM process using epoxy resin, and tensile, compression, and shear tests were conducted. As can be expected, unidirectional fiber specimens in longitudinal direction showed the highest strength and modulus. Compared with glass/epoxy composites of the similar fabric architecture and fiber volume fraction, the tensile strength and modulus of jute felt/epoxy composites reached only 40% and 50% levels. However, the specific tensile strength and modulus increased to 80% and 90% of the glass/epoxy composites. The main reason for the poor mechanical properties of jute composites is associated with the weak interfacial bonding between fiber and matrix. The effect of surface treatment of jute fibers on the interfacial bonding will be examined in the future work.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1101-1109
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• 2004

Experimental measurements of flame structure and soot characteristics were performed fur ethene inverse diffusion flames (IDF). IDF has been considered as the excellent flow field to study the incipient soot because soot particle do not experience the oxidation process. In this study, LIF image clarified the reaction zone of IDF with OH signal and PAH distribution. laser light scattering technique also identified the being of soot particle. To address the degree of soot maturing, C/H ratio and morphology of soot sample were investigated. From these measurements, the effect of flow residence time and temperature on soot inception could be suggested, and more details on soot characteristic in the IDF was determined according to fuel dilution and flame condition. The fuel dilution results in a decrease of temperature and enhancement of residence time, but the critical dilution mole fraction is existed for temperature not to effect on soot growth. Also, the soot inception evolved on the specific temperature and its morphology are independent of the fuel dilution ratio of fuel.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1263-1263
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• 2001

The amounts of organic matter present in soil and the rate of soil organic matter (SOM) turnover are influenced by agricultural management practice, such as rotation, tillage, forage plow down direct seeding and manure application. The amount of nutrients released from SOM is highly dependent upon the state of the organic matter. If it contains a large proportion of light fractions (low-density) more nutrients will be available to the glowing crops. However, if it contains mostly heavy fractions (high-density) that are difficult to breakdown, then lesser amounts of nutrients will be available. The state of the SOM and subsequent release of nutrients into the soil can be predicted by NIRS as long as a robust regression equation is developed. The NIRS method is known for its rapidity, convenience, simplicity, accuracy and ability to analyze many constituents at the same time. Our hypothesis is that the NIRS technique allows researchers to investigate fully and in more detail each field for the status of SOM, available moisture and other soil properties in Alberta soils for precision farming in the near future. One hundred thirty one (131) Alberta soils with various levels (low 2-6%, medium 6-10%, and high >10%) of organic matter content and most of dry land soils, including some irrigated soils from Southern Alberta, under various management practices were collected throughout Northern, Central and Southern Alberta. Two depths (0- 15 cm and 15-30 cm) of soils from Northern Alberta were also collected. These air-dried soil samples were ground through 2 mm sieve and scanned using Foss NIR System 6500 with transport module and natural product cell. With particle size above 150 microns only, the “Ludox” method (Meijboom, Hassink and van Noorwijk, Soil Biol. Biochem.27: 1109-1111, 1995) which uses stable silica, was used to fractionate SOM into light, medium and heavy fractions with densities of <1.13, 1.13-1.37 and >1.37 respectively, The SOM fraction with the particle size below 150 microns was discarded because practically, this fraction with very fine particles can't be further separated by wet sieving based on density. Total organic matter content, mechanical texture, ash after 375$^{\circ}C$, and dry matter (DM) were also determined by “standard” soil analysis methods. The NIRS regression equations were developed using Infra-Soft-International (ISI) software, version 3.11.