• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.293-297
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• 1992

A proper combination of complex permeability and permittivity is necessary to produce the zero-reflection microwave absorber with an impedance matching. Increasing of dielectric permittivity and development of an impedance matching was investigated in ferrite-rubber composite specimens by addition of conducting materials. Graphite powder of high dielectric constant was added to the composite specimens to increase the permittivity. The precise estimation of graphite content to produce the matched-wave-impedance absorber at a given frequency can be made by using the numerically derived solution map of impedance matching. It was suggested that permittivity adjustment is an effective technique to obtained the microwave absorber with both good absorbing properties and small thickness as well.

• Journal of Pharmaceutical Investigation
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• v.31 no.2
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• pp.107-112
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• 2001

In order to reduce the systemic side effects and gastrointestinal irritation after its oral adminitration, ketoprofen was formulated as water-soluble packs. The effects of fatty acids and fatty alcohols on the penetration of ketoprofen through excised rat skins were evaluated. The role of stratum corneum as a protective barrier was also investigated. Fatty acids and fatty alcohols were generally effective in promoting ketoprofen penetration. The flux of ketoprofen through rat skin was maximized when oleic acid or lauryl alcohol was used as an enhancer. As the concentration of fatty acids and fatty alcohols varied from 0% to 10%, the amounts of ketoprofen penetrated were in direct proportion to that of fatty acids but those had no relationship with that of fatty alcohols. The penetration of ketoprofen through stripped skin was enhanced compared to normal skin irrespective of enhancer type, which indicated that the action site of enhancers would be stratum corneum.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.655-660
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• 2002

The purpose of this study is to analyze void ratio, coefficient of water permeability, and strength characteristics when silica fume and carbon fibers were added in order to improve the strength of porous concrete, and when recycled aggregates were used. Comparing with the case that recycled aggregate was not used, as the replacement ratio of recycled aggregate increased, the differences in void ratios and strength characteristics were decreased. In the case that silica fume was used, the content of 10% silica fume was most effective in improving strength. In the case that carbon fibers were used, the content of 3% carbon fiber were good to achieve the highest flexural strength, and Pan-derived CF was much better than pitch-derived CF in improving these effects.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.818-821
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• 2004

Generally, the high performance concrete of drying cracking and autogenous shrinkage are tend to be increased. In the previous study, it was found that the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separtely using method of that. This study is to investigated the durability of high performance concrete using expansive additive and shrinkage reducing agent. Test results showed that the high performance concrete using expansive additive and shrinkage reducing agent had very good not only the durability performance such as salt injury, carbonation, resistance to freezing-thawing and permeability but also the resistance to shrinkage.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.810-813
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• 2004

Air void systems in hardened concrete has an important influence on concrete durability such as freeze-thaw resistance, water permeability, surface scaling resistance, and etc. Linear traverse method and point count method described at ASTM have been widely used to estimate the air void system in hardened concrete. These methods, however, are rarely used at present, because they require many efforts, are time consuming works, depend on each person's decision, and are not repeatable. Thus, new image analysis method using microscope and computer processes has been approached for analyzing air void system in hardened concrete. However, it is just in initial step. The purposes of this study were to develope an effective and reliable image analysis technique for estimating air void system in hardened concrete. The developed technique was proved to be accurate, reasonable and repeatable.

• Economic and Environmental Geology
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• v.33 no.2
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• pp.139-146
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• 2000

Development of an effective liner by utilization of the tailings frm the Imcheon mine and polymer has been tried. The tailings piled in the Imcheon mine, whose true specific gravity is about 2.86, are composed mainly of quartz, alkali-feldspar, muscovite and pyrite, and mostly (93.7% in volume) coarser than sand grain size (50${\mu}{\textrm}{m}$). Strength, leaching and permeability tests have been performed on the test specimens of polymer concrete manufactured with various mixing proportions of tailings, unsaturated polyester resins(UPR), calcium carbonates, stone powder sludges and granite soils. Polymer concrete specimens with stone powder sludges or granite soils as fillers and aggregates indicate 2.5 to 3 fold higher flexural and compressive strengths and lower permeabilities than those with calcium carbonates, which shows their usability as a waterproof liner. Also, the polymer concrete liner with stone powder sludge fillers is more advisable in aspects of utilization of waste sludges than that with other fillers.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.181-181
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• 2006

We developed a novel method to fabricate a nerve guide conduit (NGC) with the porosity of submicron pore sizes (to prevent fibrous tissue infiltration) and hydrophilicity (for effective oxygen and nutrient permeation) using poly(lactic-co-glycolic acid) (PLGA) and Pluronic F127 by a modified immersion precipitation method designed by our laboratory. It was recognized that the hydrophilized PLGA/F127 (3 wt%) tube can be a good candidate as a NGC from the analyses of its morphology, mechanical strength, hydrophilicity, model nutrient permeability and in vivo nerve regeneration behavior using a rat model.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.3
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• pp.44-51
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• 2004

The effect of refining conditions and grammage on the stiffness of linerboard was investigated. The correlations between Taber stiffness and resonance stiffness were very low due to the different measuring principle. The refining conditions did not affect sig nificantly on both Taber and resonance stiffness estimated here. This means that it is strongly recommended to find and apply the refining conditions which can reduce specific energy consumption. Taber stiffness showed very high correlation for the thickness and elastic modulus of linerboard, while the resonance stiffness showed much lower correlation. Effective thicknesses for Taber stiffness were very well fitted with measured thickness, while those for resonance stiffness depended on the grammage of linerboard.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.4
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• pp.23-29
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• 1999

The effect of dilute sulfuric acid treatment was examined to improve recyclability of coated brokes. Turbidity , electric conductivity , and cationic demand of the white water from coated broke prepared from an alkaline base paper was determined. Sulfuric acid treatment was found to be effective in dissolving undisintegrated substances such as binders, pigments, and fibers. The properties of papers prepared by adding the broke to pulp stock up to 30% dry weight were examined . With the increase of broke addition, retention, sizing degree and smoothness were improved ; on the other hand, formation uniformness, air permeability and internal bonding strength were decreased. The extent of improvement by broke addition was greater for the surfuric acid-treated broke than the control broke. It was concluded that the use of coated broke should be limited within 10-15% weight of the product for either type of broke.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.2
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• pp.316-319
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• 2011

Biopiles which offer the potential for cost-effective treatment of contaminated soils are above-ground, engineered systems that use oxygen to stimulate the growth and reproduction of aerobic bacteria for degradation of the petroleum constituents adsorbed to soil in excavated soils. This technology involves heaping contaminated soils into piles and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Inside the biopile, microbially mediated reactions by blowing or extracting air through the pipes can enhance degradation of the organic contaminants. The influence of a aeration system on the biopile performance was investigated. Air pressure made to compare the efficiency of suction in the pipes showed that there were slightly significant difference between the two piles in the total amount of TPH biodegradation. The normalised degradation rate was, however, considerably higher in the aeration system than in the normal system without aeration, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile.