• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.478-484
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• 1993

The influence of reaction conditions on the MnZn ferrite coprecipitation process were investigated using mixed metla sulfate solution and ammonium oxalate. In order to minimize the metallic ion losses and to control the particle size, the optimum reaction conditions were as follows; reaction temperature $25^{\circ}C$, metal sulfate concentration 0.3M, molar ratio of ammonium oxalate/mixed metal sulfate 1.1:1. The production yield was as high as 97.6% of theoretical yield at optimum reaction condition.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.190-195
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• 2007

The transesterifications of beef tallow and the mixture of beef tallow and rapeseed oil were conducted at $65^{\circ}C$ respectively using TMAH, NaOH and their mixed catalysts. The reactants were emulsified with 1vol% emulsifier and propylene glycol. The overall conversion of beef tallow was 95% at such optimum conditions as the 1:8 of molar ratio and 0.8 wt% TMAH. The overall conversion of mixed fat at the 1:8 of molar ratio and mixed catalyst of 70 wt% TMAH 30 wt% NaOH was close to 97% which appeared at 0.8 wt% TMAH in 80min. And the kinematic viscosity of biodiesel mixture using the mixed catalyst was $6.5mm^2/s$ at $40^{\circ}C$.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.118-123
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• 2004

In this study, genetic algorithm mixed binary and real encoding is proposed to deal with design variables of various types. And that is applied to optimum design of Multi-stage gear drive. Design of pressure vessel which is mixed discrete and continuous variables is applied to verify reasonableness of proposed genetic algorithm. The proposed genetic algorithm is applied for the gear ratio optimization and the volume minimization of geared motor which is used in field. In result, it shows that the volume has decreased about 8% compared with the existing geared motor.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.53-66
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• 2015

Plastic wastes, particularly polyethylene terephthalate (PET) generated from used bottled water constitute a worldwide environmental issue. Reusing the PET waste for geotechnical applications not only reduces environmental burdens of handling the waste, but also improves inherent engineering properties of soil. This paper investigated factors affecting shear strength improvement of PET-mixed residual soil. Four variables were considered: (i) plastic content; (ii) plastic slenderness ratio; (iii) plastic size; and (iv) soil particle size. A series of unconfined compression tests were performed to determine the optimum configurations for promoting the shear strength improvement. The results showed that the optimum slenderness ratio and PET content for shear strength improvement were 1:3 and 1.5%, respectively. Large PET pieces (i.e., $1.0cm^2$) were favorable for fine-grained residual soil, while small PET pieces (i.e., $0.5cm^2$) were favorable for coarse-grained residual soil. Higher shear strength improvement was obtained for PET-mixed coarse-grained residual soil (148%) than fine-grained residual soils (117%). The orientation of plastic pieces in soil and frictional resistance developed between soil particles and PET surface are two important factors affecting the shear strength performance of PET-mixed soil.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.9
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• pp.1461-1466
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• 2008

This study provides effects of mixed activators on enzymatic activation and determines optimum mixture ratio for enzymatic treatment. Wool 80% and polyester 20% blend fabric and papain from carica papaya are used in this experiment. L-cysteine and sodium sulfite are used as activators for papain treatment process. The treatment condition is pH 7.5, $70^{\circ}$, papain concentration 10%(o.w.f), 60 minutes. L-cysteine and sodium sulfite are added in enzyme solution with various concentrations($0{\sim}50mM$). The optimum treatment condition is determined by measuring weight loss, tensile strength, whiteness, water contact angle(WCA), dyeability and surface micrographs. The results are as follow; The optimum mixture ratio of activators is L-cysteine 2mM and sodium sulfite 10mM. Mixed activators assists in improving the activation of papain. WCA of papain treated fabrics is decreased since papain treatment with activator mixture makes wool polyester blend fabrics more hydrophilic. Dyeing property of papain-treated fabrics more improves by the treatment with mixed activators than with single activator. It means that this method can save time and lower cost. After papain treatment in the presence of mixed activator, the surface of fabrics is modified. The surface of wool fiber shows to be descaled and hydrolyzed, and that of polyester fiber shows to be cracked.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.59-70
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• 2005

A series of resonant column test was performed to investigate the dynamic deformation characteristics of silty sand soils mixed with polypropylene fibrillated type fiber. Results show that optimum mixing ratios were $0.2\%$ for 19mm of cut fiber for shear modulus and $0.1\%$ for 60mm cut fiber fur damping ratio. As shear strain was increased, normalized values of shear modulus (G(Reinforced)/ G(Unreinforced)) of fiber reinforced soil were increased up to $10^{-3}\%\~10^{-1}\%$ ranges. However, normalized damping ratio (D(Reinforced/D(Unreinforced)) was diminished with an increase in strain beyond $10^{-3}\%\~10^{-1}\%$ for the damping capacity of soils mixed with fiber. Normalized shear modulus $(G/G_{max})$ obtained from the test was plotted in the chart suggested by Seed and Idriss. The shear modulus of silty sand was located between sand and gravel curves.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1175-1180
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• 2008

This study explored the compacition characteristics of organic weathered soils. Weathered soils were collected around the Gwangju University in Jinwol-dong, Gwangju city, and coal was used as organic material. Weathered soils were mixed with coal so that the ratio of organic elements against mixed soil can be 0%, 25%, 50%, and 75% respectively. Compaction tests were carried out on these organic mixture soils in different ratios of organic materials. And soap water instead of water in compaction tests was used. Through this study, We knew that the bigger the organic material ratio was, the more the optimum moisture content increased and the less the maximum dry unit weight reduced. In case of using small compaction energy, using soap water instead of water improved the compaction efficiency a little.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.597-604
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• 2001

In this study, the engineering characteristics of soil-bentonite mixed liner are investigated using the laboratory hydraulic conductivity and strength tests. The soil used for the liner is clayey silt in the site and the weathered granitic soil located near the waste landfill studied. Mixing ratio of the bentonite which satisfies the requirement of hydraulic conductivity is determined and the optimum mixing ratio of betonite is recommended for the landfill. After the mixed liner is constructed, the block samples of the constructed liner are obtained and the properties of interest satisfy the requirements of the liner of the landfill.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.93-99
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• 2000

The physical properties of freshly mixed steel fiber reinforced recycled concrete(SFRRC) were_investigated. Physical state and quality of fresh concrete were monitored batch by batch. the properties of freshly mixed SFRRC were determined in terms of slump, air content, superplasticizer, and bleeding ratio. Concrete mixtures were produced for three kinds of aggregate proportions. So, the experimental variables are various aggregate proportions, steel fiber contents(0, 0.5, 1.0, 1.5%) and steel length(30, 50, 60mm). From experimental results, optimum s/a by various experimental variables, variations of the slump by the air contents, and optimum superplasticizer to decrease unit water were presented.

• Journal of the Korean Society of Tobacco Science
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• v.11 no.2
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• pp.211-224
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• 1989

10. Three major factors, freeness, filler and blend ratio that exercised considerable influence on physical properties of cigarette papers were chosen for the sake of their optimization at this experiment. An optimization of those above factors in paper manufacturing was investigated using response surface analysis. Optimum beating degree for Kenaf, Flax and NBKP showed around 72。SR, 68。SR and 85 SR, respectively, in considering of five quality index such as porosity, tensile strength, stretch, whiteness and opacity. The best blending ration of reciprocal pulps treated under optimum beating degree were diversified and combination scope of the bast fiber (Kenaf, Flax) to the NBKP was range from 30% to 65% in case of the Kenaf, from 25 to 40% in Flax at the same receipe. The optimum range of calcium carbonate content revealed 25%~30% in Kenaf mixed NBKP and 24%~31% in Flax mixed NBKP.