• Carbon letters
• /
• v.14 no.2
• /
• pp.121-125
• /
• 2013

In this study, PtRu nanoparticles deposited on binary carbon supports were developed for use in direct methanol fuel cells using carbon blacks (CBs) and multi-walled carbon nanotubes (MWCNTs). The particle sizes and morphological structures of the catalysts were analyzed using X-ray diffraction and transmission electron microscopy, and the PtRu loading content was determined using an inductively coupled plasma-mass spectrometer. The electrocatalytic characteristics for methanol oxidation were evaluated by means of cyclic voltammetry with 1 M $CH_3OH$ in a 0.5 M $H_2SO_4$ solution as the electrolyte. The PtRu particle sizes and the loading level were found to be dependent on the mixing ratio of the two carbon materials. The electroactivity of the catalysts increased with an increasing MWCNT content, reaching a maximum at 30% MWCNTs, and subsequently decreased. This was attributed to the introduction of MWCNTs as a secondary support, which provided a highly accessible surface area and caused morphological changes in the carbon supports. Consequently, the PtRu nanoparticles deposited on the binary support exhibited better performance than those deposited on the single support, and the best performance was obtained when the mass ratio of CBs to MWCNTs was 70:30.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.2
• /
• pp.123-129
• /
• 2020

We analyzed the drift current by charged particles according to the loading methods applied into a closed cell by electronic ink at a reflective-type display panel using an electrophoretic mechanism. For this experiment, various panels were fabricated with injection voltages for electronic ink taking values in the range -4~0 V. The size of each cell was 220 ㎛ × 220 ㎛ and height of the barrier rib was 54.28 ㎛. The electronic ink was fabricated by mixing electrically neutral fluid and single-charge white particles. Drift current was measured by moving charged particles. A biasing voltage of 6 V was applied to the display panel. As a result, the drift current was proportional to the injection voltage for electronic ink, but it decreased in case of an injection voltage above -3 V. Our experimentation ascertained that the concentration of charged particles injected into closed cells is controlled by the injection voltage and the selective injection of charged particles above movable q/m is possible.

• YAKHAK HOEJI
• /
• v.39 no.5
• /
• pp.487-494
• /
• 1995

Solid lipid microspheres (SLMs) were prepared using various lipids and solidifying agents, in order to enhance the gastrointestinal absorption of Cyclosporine A (Cs A) which is a practically water-insoluble drug with low systemic bioavailability. Egg lecithin and HCO-60 (polyoxyethylated 60 mol, hydrogenated castor oil) were used as lipids. Stearic acid and stearyl alcohol were used as solidifying agents. Emulsion concentrates containing Cs A were prepared by mixing the melted lipid and solidifying agent with water, employing bile salts as a cosurfactant. SLMs were obtained by dispersing the warm emulsion concentrate in cold distilled water under mechanical stirring, followed by freeze drying. Physical characteristics of each SLM were investigated by particle size analysis, optical microscopy and scanning electron microscopy. Mean particle size of SLMs was in the range of 30 to 40.mu.m. The SLMs were in good appearance with spherical shape before freeze drying, but were deformed partially after freeze drying. Drug loading efficiencies of SLMs were observed as high as 80 to 90% in average. The systemic bioavailability of Cs A from different SLM formula was investigated in rats following oral administration. Cs A in whole blood was extracted and assayed by HPLC. SLMs revealed the higher bioavailabilities than the standard formula based on the marketed product. SLMs might have several advantages over standard formula for enhanced gastrointestinal absorption, controlled release properties, high loading capacity of the water-insoluble drug, and feasibility of solid dosage forms with better stability in storage.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.10
• /
• pp.1777-1787
• /
• 2000

The purpose of this study was to select an effective and economical alkali source for sulfur-utilizing autotrophic denitrification. Tests on acid neutralization and denitrification at various alkali/sulfur mixing ratios were performed for charcoal, briquette ashes, sea shell, and limestone. The results of the experiments showed that sea shell was the most effective alkali source because it could provide more surface area than limestone, and the optimal alkali/sulfur mixing ratio was 1/1(V/V). In a sulfur/sea shell packed bed reactor, the denitrification efficiency was above 90% up to a loading rate of 116 g $NO_3{^-}-N/m^3-day$. but the denitrification efficiency deteriorated to 48% at the loading rate of 145 g $NO_3{^-}-N/m^3-day$. The average $SO_4{^{2-}}$ generation per g of $NO_3{^-}-N$ removed was 7.02 g, which is lower than the theoretical value of 7.54 g. Denitrification and sulfate generation appeared to be a first-order and a zero-order reaction with a reaction rate constant of 0.146 /hr and -53.1 mg/L-hr, respectively. According to nitrogen mass balance, 71~109%, with an average of 90%, of the removed nitrogen was recovered as $N_2$ gas.

• Journal of the Korean Magnetics Society
• /
• v.8 no.2
• /
• pp.86-92
• /
• 1998

Homegeneous feedstock is necessary to make plastic magents with uniform magnetic properties, therefore the optrimized mixing route and the homogeneity evaluation method are demanded. In this paper, method of homogeneity evaluation and effect of homogeneity on the magnetic prperites were investigated using Sr-ferrite /EVA plastic magnets. The feedstocks with different homogeneity were prepared using batch mixer and single screw extruder. The homogeneities of feedstocks were tested by torgue sensor, capilary rheometer, and measurement of magnetic properties. Mixing torque measurement using torque sensor was an effective method to determine the critical powder loading, but it was nor suitable to suitable to determine the feedstock mixing quality. Particle alignment measurement of a plastic magent was very accurate to evaluate the homogeneity, but expensive equipments were required to make and measure the samples. Pressure measurement using capillary rheometer was a very effective and easy method with high accuracy. Homogeneous feedstock increased the particle alignment of plastic magnet. Remanet flux density and maximum energy product increased linearly and quadratically with increasing particle alignment, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.8
• /
• pp.47-55
• /
• 2009

This research has the purpose to examine the potential of shell, a byproduct of maritime products to be utilized as alternative environment-friendly construction material by mixing and applying it with residual soit which is used as burial or filling material to recycle it. To that end, the research looked into the mechanical characteristics of shell through cyclic triaxial test by mixing it with residual soil. With the mixing ratios of shell of 5 groups set at 5.0%, 10.0%, 20.0%, 40.0% and 60.0%, the mixture soils was processed through a series of cyclic triaxial tests. And it was shown that liquefation resistance has limitation in the mixed soils with shell substitute content ratios exceeding 20.0%. To increase the liquefaction resistance of the mixed soil, this research has shown that addition of moderate amount of glass fibers would suffice.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.8
• /
• pp.99-109
• /
• 2008

The standard consolidation tests using the incremental loading technique test (IL) were performed on remolded normal consolidation and undisturbed clay samples to find out the effects of plastic index and loading period on consolidation in this study. The remolded samples used were prepared by mixing Gunsan-Samangum clay with bentonite so that they may have plasticity indexes of 15, 30, 45, and 60%, respectively. The undisturbed clay samples were collected from Inchon, Kwangyang, and Uoolsan. The samples were tested at the condition of 4 different loading periods (1, 2, 4, and 8 days). Settlement, coefficient of consolidation, compression index, secondary compression index, and pore water pressure characteristics were investigated from the plastic index and loading period aspects, and the compression index, coefficient of consolidation, and secondary compression index were formulated in terms of the plastic index and loading. To verify the applicability of proposed equations, the settlements obtained from Terzaghi's theory, modified Cam-Clay model (elasto-plastic model), and the Sekiguchi model (elasto-viscoplastic mode) were compared with the test results. The comparison indicates that the Sekiguchi model incorporating the secondary consolidation characteristic well predicts the results.

• Journal of Periodontal and Implant Science
• /
• v.32 no.2
• /
• pp.403-414
• /
• 2002

I. Purpose of Study Zea Mays L. has been known to be effective for improving periodontal health and Magnoliae cortex to have effective antibacterial and antimicrobial activity against periodontal pathogens. The purpose of this study was to examine the biologic effects of Zea Mays L. and Magnoliae cortex extract mixtures on healing of rat calvarial bone defects. II. Materials & Methods 8mm circular defects were prepared on rat calvaria during surgical procedures of 180 Sprague-Dawley rats. The ethanolic extracts of Magnoliae cortex and Zea Mays L. and these two natural extract 1:1 and 2:1 (Magnoliae: Zea Mays L.) ratio mixtures were oral administrated by oral zondes once a day at two different dose of 94.5mg/kg, 189mg/kg body weight. There are nine groups of rats in this study: control group (no sample loading), Magnoliae cortex extract loading groups (I,II)(94.5mg/kg,189mg/kg respectively), Zea Mays L. extract loading groups (I,II), M:Z(1:1) loading groups (I,II), M:Z(2:1) loading groups(I,II). Rats were sacrificed at 4 weeks and 6 weeks after surgery. New bone formations around calvarial defects were radiographically and histologically measured by computerassisted histomorphometry. Each data was statistically analyzed by One-way ANOVA test. III. Results There were statistical significances between negative control group and the other test groups on radiographical and histological quantitative assessments. Among test groups, mixture groups showed statistical significances, especially, M:Z (2:1) groups (I and II) were highly significant.(p<0.05) These results implicated that the mixture of Magnoliae and Zea Mays L. (2:1 mixing ratio) with 94.5mg/kg concentration might be highly effective on the wound healing of bony defected site and have potential possibilities as a useful drug to promote bone tissue regeneration.

• Economic and Environmental Geology
• /
• v.38 no.3 s.172
• /
• pp.237-245
• /
• 2005

The batch tests were performed to evaluate the applicability of the permeable reactive barrier (PRB) to in-situ treatment of groundwater with high concentration of heavy metals. The lead\chates used in this study were collected from waste rock dump of the Imgy mine, and have a low pH and high metal concentration. The acidity loading was 65kg as $CaCO_3/day$, metal loading of Fe+Al+Mn was 11.6kg/day. This type of water could be treated with biological-mediated sulfate reduction using the organic carbon mixture as a reactive media. The batch tests were carried out with five mixtures that were composed with different mixing ratios of mushroom compost, pine-tree bark, and limestone cheep. Results indicated that the PRB could reduce the acidity loading $CaCO_3/day$ to 12.3kg and reduce the metal loading to 3.3kg/day. Considering about the low pH and high metal loading, the contaminated water may be ameliorated by passing it through the buffering PRB composed with inorganic carbonate materials and then through the PRB composed with the organic carbon mixture which can induce sulfate reduction.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.9 no.6
• /
• pp.454-458
• /
• 2004

A study of the POSE (predispersed solvent extraction) for succinic acid by colloidalliq­uid aphrons was conducted. The organic phase contaning TOA (tri-n-octylamine) and 1-octanol permits a selective extraction of succinic acid from its aqueous solution. There was no difference of the extractability of POSE and that of conventional mixer-settler type extraction. Taking into account the no mechanical mixing in POSE, it was concluded that the POSE process is more adaptive than the conventional mixer-settler type extraction process. From mass transfer analysis at the various concentration of TOA in counter-current continuous operation, the concentration of TOA had no influence on the mass transfer coefficient. The loading values in continuous POSE were almost same as those in batch operation.