• Journal of Korean Society for Atmospheric Environment
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• v.19 no.5
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• pp.503-513
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• 2003

A single particle analytical technique, called low-Z electron probe X-ray microanalysis (low-Z EPMA) was applied to characterize atmospheric particles collected in Busan, Korea, over a daytime period in Dec. 2001. The ability to quantitatively analyze the low-Z elements, such as C, N, and 0, in microscopic volume enables the low-Z EPMA to specify the chemical composition of individual atmospheric particle. Various types of atmospheric particles such as organics, carbon-rich, aluminosilicates, silicon oxide, calcium carbonate, iron oxide, sodium chloride, sodium nitrate, ammonium sulfate, and titanium oxide were identified. In the sample collected in Busan, sodium nitrate particles produced as a result of the reaction between sea salt and nitrogen oxides in the atmosphere were most abundantly encountered both in the coarse and fine fractions. On the contrary, original sea salt particles were rarely observed. The fact that most of the carbonaceous particles were distributed in the fine fraction implies that their origin is anthropogenic.

• Journal of the Korean Society of Combustion
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• v.8 no.4
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• pp.1-8
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• 2003

In this study, the quantification of soot particles in laminar diffusion flame with LII/LIS methods was performed. In these quantification, soot diameter, number density and volume fraction are included. For the quatification of soot particles, calibration tests are needed and the development of algorithm has to be performed. So, in this study, extinction and scattering test at co-flow burner were performed to acquire calibration data. And algorithm for LII/LIS simultaneous measurement for the quantification of soot were developed. The algorithm, which was the quantification of simultaneous photographing using one ICCD camera, to measure LII/LIS signal simultaneously, the best fitted light intensity and acquisition time was needed.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.19-26
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• 2003

Experimental measurements of flame structure and soot characteristics were performed for 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.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.29-35
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• 1996

For semi-solid forging with aluminuim alloys, it is required to develope the globular grain structure. It was studide that cold upsetting ration in SIMA process has effect on the globularization of grain structure. Globular microstructure was generated without cold upsettings for commercial aluminium alloys. In the case of A12024, the range of grain size was 40 .approx. 50 .mu. m. The grain growth in growth in globular microstructure depend on heating time. Spur gear was forged in semi-solid state to investigate the forging condition for A12024 with hydraulic press.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.237-242
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• 2012

In this study, the skin moisturing effect and stability of cream containing L. cuneata G. Don extract (ethyl acetate fraction) were evaluated. The skin hydrating effect of the cream containing extract was 1020% higher than the placebo cream, and the TWEL of the cream containing extracts was decreased to $7.7g/m^2h$ compared to the control ($10.2g/m^2$) and placebo cream ($8.9g/m^2$). The pH, viscosity, and absorbance were measured under the 4, 25, 37, $45^{\circ}C$ and the sun light during the 12 weeks. The pH change between cream containing extract and placebo cream did not show the significant difference under the 4, 25, 37, $45^{\circ}C$ except for the sun light. Both creams showed high decrease (about 59%) of viscosity at $45^{\circ}C$. However, there was no significant change under other conditions. The absorbance of the cream containing the extract and the placebo cream was decreased similarly at all conditions. This decrease in absorbance was relatively small compared to the decrease of absorbance of the extract in ethanol solution under the sun light (Fig. 7). In addition, any change in color or smell of the cream was not observed during the 12 weeks. Also physical changes as creaming and cohesion were not shown. These results indicate that the cream containing L. cuneata extract has the skin moisturizing effect and is relatively stable. Therefore, it is suggested that the ethyl acetate fraction of L. cuneata extract could be applicable to cosmetics as a new cosmetic material with its antioxidative and antibacterial activities reported previously.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.423-423
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• 2007

In this study, the effects of annealing conditions on the structural and optical properties of ZnO films were investigated. ZnO oxide (ZnO) films were deposited onto $SiO_2$/Si substrates by RF magnetron sputtering from a ZnO target. The substrate was not heated during deposition. ZnO films were annealed in temperature ranges of $500{\sim}650^{\circ}C$ in the $O_2$ flow for 5 ~ 20 min. The film average thicknesses were in the range of 291 nm. The surface morphologies and structures of the samples were characterized by SEM and XRD, respectively. The optical properties were evaluated by PL measurement at room temperature using a He-Cd 325 nm laser. According to the results, the optimal annealing conditions for the best photoluminescence (PL) characteristics were found to be oxygen fraction, ($O_2/O_2+Ar$) of 20%, RF power of 240W, substrate temperature of RT (room temperature), annealing condition of $600^{\circ}C$ for 20 min, and sputtering pressure of 20 mTorr. The obtained wavelength of light emission was found at 379 nm (ultraviolet-UV region). However, the optimal parameters for the best PL characteristics of ZnO thin films were not consistent with those obtained from the (002) intensities of XRD analyses. As a result, XRD pattern was not considered as the key issue concerning the intensity of PL of ZnO thin film. The intensity of the emitted UV light will correspond to the grain size of ZnO film.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.527-534
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• 2006

Modern passenger cars with diesel engines are equipped with DOC(diesel oxidation catalyst) for the purpose of reducing HC and CO in the exhaust stream. Cold start exhaust emissions pose troubles here as on gasoline engine vehicles. As a result, some of the diesel passenger cars roll off todays the assembly lines with WCC(warm-up catalytic converter). Oxidation characteristics of the particulates in WCC is analyzed in this study by EEPS(engine exhaust particulate size spectrometer). The maximum number of PM is found to come out of WCC in sizes near 10nm when an HSDI diesel engine is operated under the conditions of high speed and medium to heavy load. When the temperature of the WCC exceeds $300^{\circ}C$, the number of PM smaller than 30 nm in diameter sharply increases upon passing through the WCC. Total mass of emitted PM gets reduced downstream of the WCC under low speed and light load conditions due to adsorption of PM onto the catalyst. Under conditions of high speed and medium to heavy load, the relatively large PM shrink or break into fine particles during oxidation process within the WCC, which results in more mass fraction of fine particles downstream of the WCC.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.4
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• pp.568-574
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• 2000

Phytofluene was subjected to ozonolysis in ice-cold dichloromethane. The ozonolysis products were fractionated with a silica column and the carbonyl fraction was analyzed by ODS-HPLC with a photodiode array detector. Phytofluene was solubilized in 5% tween 40, and then oxidized by incubating under dim yellow light at 37$^{\circ}C$, 24 hr with continuous shaking. Carbonyl compound and acidic compound were produced. In comparison with autoxidation and ozonolysis, each compound showed the same retention time and UV-vis spectra were identical to the reference cleavage products prepared by ozeonolysis of phytofluene. Absorption spectrum of acidic compound was similar to that of standard 4,5-didehydrogeranyl geranyl acid which is known to possess biological activity. Thus, eccentric cleavage of phytofluene was confirmed to occur in vitro under oxidation condition.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.24 no.3
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• pp.129-133
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• 1998

We have studied a relationship between the pattern of complex modulus change versus internal phase volume ratio and the rheological consistency of concentrated W/O emulsions with Magnesium Sulfate in the range 0.0 to 0.5 wt% and with different oil polarities, respectively. The rheological consistency with time of concentrated W/O emulsion was checked using Fudoh Rheometer and the coalescence of deformed water droplets was examined using polarized light microscope(LEICA DMRP). To find the pattern of complex modulus change of the concentrated emulsions versus internal phase volume ratio, the effect of varying water phase volume fraction from 0.78 up to 0.85 on viscoelastic measurements was investigated using rotational rheometer (HAAKE Rheostress RS 50). The rheological consistency was mainly destroyed by the coalescence of the deformed water droplets. The greater the increase of complex modulus was, the less coalescence occurred and the more consistent the concentrated emulsions were. And the pattern of complex modulus increase versus volume ratio has been explained with the resistance to coalescence of the deformed interfacial film of water droplets in concentrated W/O emulsion.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.194-205
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• 1994

In this research, we attempt to fabricate an excellent CFRC(Carbon Fiber Reinforced Carbon), which has good thermal and mechanical properties, with 8H/satin woven fabric prepreg, high modulus and high strength type continuous carbon fiber and raw coal tar pitch(RCTP) matrix or THF soluble fraction(THFSP) matrix which has good graphitizability. Green bodies were fabricated with hot press molding technique and CFRC samples were made after carbonization, impregnation, recarbonization and graphitization steps. For the purpose of characterization of the physical properties, SEM, polarized light microscope, TGA were observed, and tested flexural strength, modulus and ILSS. After heat treating the THFSP matrix up to $2300^{\circ}C$, the value of $C_0$/2 was 3.380$\AA$, which is analogous to the structure of natural graphite and the value of 2$\theta$ is $26.276^{\circ}$ approached to the Bragg's angle of natural graphite. As a result of TGA to test the high temperature air oxidation, the THFSP matrix, graphitized up to $2300^{\circ}C$, exhibited the best air oxidation resistance. And mechanical properties were increased up to 65~70% as fiber volume fraction increased. Because of the good orientation graphitizability, the fracture surface of THFSP matrix CFRC is very good.