• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.51-57
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• 2018

The objective of the present study is to examine the feasibility on the development of high-insulation concrete using aerogels with hydrophilic surface treatment. To prevent the segregation and enhance the dispersibility of agerogels in the cement pastes, the substrate of aerogels was modified to be hydrophobic property using surfactant. The modified aerogels were added from 0% to 100% of the cement volume at the interval of 25% under the constant cement content. Some cement pastes showed segregation phenomenon and flocculation of aerogels during mixing phase. The addition of aerogels decreased the compressive strength of cement pastes but enhanced the thermal conductivity. The thermal conductivity of pastes with 100% aerogels was lower by 43% when compared with that measured in the conventional paste. To improve the compressive strength and insulation capacity of concrete containing aerogels, a reliable surface treatment method of aerogels needs to be further investigated.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.1
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• pp.89-94
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• 2006

Traditionally fatty acid composition used to be analysed by a GC and the sample preparation process includes lipid extraction from sample and subsequent methyl esters preparation, which are time-consuming and cumbersome. As an alternative, simultaneous extraction/methylation methods are being developed for rapid and simplified sample preparation. To optimize one-step extraction/methylation method for analysis of fatty acid composition in brown rice, various reaction factors such as sample to reaction solution ratio, reaction time and temperature, shaking intensity were changed and resultant fatty acid composition data were evaluated in comparison with previous reports. The ratio of sample weight to reaction solution volume was the most critical factor in that higher sample to reaction solution ratio caused overestimation of palmitic acid and linoleic acid composition, resulting in underestimation of oleic acid. Lower reaction temperature also induced overestimation of linoleic acid and underestimation of oleic acid. Reaction duration and the intensity of shaking prior to and during the reaction, however, caused no significant changes in analysis results. In conclusion, the optimum condition was mixing 5 grains (about 0.2 g) of brown rice with $680{\mu}L$ of extraction/methylation mixture and $400{\mu}L$ of heptane, followed by reaction at $80^{\circ}C$ for 2 hours.

• Journal of Bio-Environment Control
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• v.2 no.1
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• pp.37-45
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• 1993

The purpose of this research was to develop ideal substrates for the production of good quality tomatoes in bag culture system and also to improve media with low or no environmental pollution by blending and mixing artificial substrate including peatmoss, perlite, vermiculite, granular rockwool, polyphenol resin foam, bark, and smoked rice hull. The highly efficient media proved by experiments were vermiculite, smoked rice hull, polyphenol resin foam, granular rockwool, and perlite, which showed good results in the early growth as well as the marketable yield of tomato in the bag culture. Tomato plants grown in the media mixed with peatmoss, vermiculite and granular rockwool at the ratio of 3 : 1 : 1(by volume) showed the highest marketable yield, and the next at the ratio of 2 : 1 : 1. The perlite-granular rockwool mixtures at the ratio of 2 : 3 and 1 : 4, and the peatmoss vermiculite mixtures at the ratio of 2 : 3 and 3 : 2, seemed to be promising media for bag culture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.325-325
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• 2007

The perovskites in the $LaAlO_3-BaZrO_3$ system (i.e., $(1-x)LaAlO_3-xBaZrO_3$ were fabricated by a solid state reaction and their dielectric properties were investigated. For the compositions of x=0.1~0.9, the mixture of $LaAlO_3$ with a rhombohedral structure and $BaZrO_3$ with a cubic was observed when the sintering was conducted at $1500^{\circ}C$, indicating that the solubility of constituent elements was very low and a narrow solid solution region might exist. The large difference of ionic radii between $La^{3+}$ ion (0.136nm, C.N.=12) and $Ba^{2+}$ ion (0.161nm) or $Al^{3+}$ ion (0.0535nm, C.N.=6) and $Zr^{4+}$ ion (0.072nm) might hinder the mutual substitution. Within the compositions of x=0~0.7, the dielectric constant of the mixture increased with the amount of $BaZrO_3$, i.e., x value, which was in good agreement with the logarithmic mixing rule (In $_{r,i}={\Sigma}v_iln\;_{r,i}$). The increase in $BaZrO_3$ doping decreased $Q{\times}f$ value significantly due to the low $Q{\times}f$ value of $BaZrO_3$ itself, a poor microstructure of the mixture with an increased grain boundary area per volume, and defects in the cation and oxygen sub-lattices which were respectively caused by the evaporation of barium during the sintering process and the substitution of Ba on La-site or Al on Zr-site.

• Journal of Korea Soil Environment Society
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• v.3 no.1
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• pp.75-81
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• 1998

In most of studies on solidification/stabilization with waste, small columns have been used to examinate adsorption or leachate. However, these experiments using small apparatus have been limited to apply with the field. In this study, considering an application to the field, a large Lysimeter(100cm$\times$100cm$\times$100cm) used for the simulation. Then, the open dumping waste was mixed directly with bentonite to simulate the stabilization of waste, environmental aspects and several basic tests. As a result, the concentration of heavy metals and contaminated substances changed with bentonite rate. Most of contaminated substances were decreased in leaching with increased mixing rate of bentonite. Especially, the concentration of CODcr removed 25~30%. Also, the residual soil in dumping waste produced approximately 80% of total volume by 40$\times$40mm screen.

• Journal of Animal Environmental Science
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• v.5 no.3
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• pp.189-196
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• 1999

Anaerobic digestion is a naturally occuring microbial process involving the decomposition of organic materials such as livestock manure. This study explores the effect of the operating conditions, HRT (Hydraulic Retention Time) and feeding frequency on treatment efficiency for digestion of pig slurry, which has been one of most difficult organic waste for proper treatment in livestock production industry in Korea at the present time. The pilot-scale CSTR of 5 m3 in volume was designed. manufactured, and operated at the temperature of 35$\pm$1$^{\circ}C$. The digester was designed to hydraulically stir for complete mixing and to supply heat from the water bath to maintain mesophilic temperature. The HRT of the digester for Test 1 and Test 2, and Test 3 was set for 17 days and 13 days respectively and pig slurry was fed once a day with 300$\ell$ each for Test 1 and Test 3, while twice with 150$\ell$each for Test 2. Test 2 showed better performance by increase of 4% in VS removal efficiency and 5% in biogas production rate. This is mainly attributed to smaller temperature drop by feeding frequently with half amount, which eventually led to lesser impact on anaerobic mocrobes in the digester. Test 2 maintained optimum pH 7.8 which uplifted the activaton of sulfur-reduction bacteria, alkalinity of around 4,000mg/$\ell$, VA of over 3,000mg/$\ell$ for whole period of experiment. Further research may require to provide the practical operation strategy of anaerobic treatment system for treatment of pig slurry.

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.15-21
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• 2005

In this study, the utilization of coal-ash and phosphogypsum was considered as the evapotranspiration final landfill cover(ET cover) material. Cover material considered was the mixture of the weathered granite soil, coal-ash and phosphogypsum and so we sequentially performed the leaching test, column test and field model test to investigate the environmental effects of mixtures of coal-ash and phosphogypsum. In the leaching test, all materials had lower heavy metal concentration than the regulated threshold values. The column test and the review of related regulations were carried out to determine the optimum mixing ratio(OMR) and OMR was soil(4):coal-ash(1): phosphogypsum(1) on the volume base, which was applied to field model test. Field model tests were continued from February to June, 2004 in the soil box that was constructed with cement block. It was verified that coal-ash and phospogypsum mixed with soil was safe environmentally and the mixture of both wastes could improve the water retention capacity of cover materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.202-209
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• 2019

The objective of this study is to examine the reproducibility for compressive strength development and mechanical properties of lightweight concrete made using bottom ash aggregates and foam(LWC-BF). Based on the mix proportions conducted by Ji et al., six identical mixes were prepared with different actual foam volume ratios from 0% to 25% and water-to-binder ratios from 25% to 30%. The presently measured properties, including initial slump, slurry density, compressive strength gains at different ages, splitting tensile strength, and modulus of rupture, were very close to those determined in the previous tests by Ji et al. Thus, the developed LWC-BF has a good potential in obtaining a reproducibility for compressive strength development and mechanical properties even though the troubles of mixing control owing to the addition of preformed foam.

• Journal of the Korean Geotechnical Society
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• v.35 no.10
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• pp.67-78
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• 2019

The efficiency of suppressing fine dust was evaluated by conducting indoor and field experiments for the ground treated with EICP solution, which is an eco-friendly ground improvement method. In laboratory experiments, the EICP solution was prepared with inexpensive materials for the field applicability, and the optimal mixing ratio and optimal spraying volume of EICP solution were calculated. The optimum amount of calcium carbonate was shown when the ratio of urea/calcium chloride and white powder were 1.5 and 15 g/L, respectively. The optimum spraying amount of the EICP solution was $7L/m^2$ determined by fine dust suppression and cone tip resistance experiments. The spraying of water and EICP solution was conducted at the test-bed where dump trucks pass for the effect of suppressing fine dust of each method. The effective fine dust suppression method can be chosen depending on the situation of the site.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.243-257
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• 2016

The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.