• Macromolecular Research
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• 제13권4호
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• pp.339-343
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• 2005

Microbial hydrogel was prepared by ${\gamma}-irradiation$ of poly(${\gamma}-glutamic acid$) (PGA) which was produced from Bacillus subtilis BS 62 and it's physico-chemical characteristic was examined. The hydrogel, prepared from 10% PGA with the dose of 48 kGy, was swollen up to 1,370 times of specific water content as dry weight basis. The hydrogels obtained above the dose of 48 kGy appeared to have higher compressive strength but lower specific water content. The period to reach a swelling equilibrium for the hydrogel in deionized water at the temperature range of 4 to $45^{\circ}C$ was about 10 h. The swollen hydrogel was shrunk in ionic solutions with the increase of ionic strength, and the rate of shrinkage was greater in calcium chloride solution than in sodium chloride. Specific water content of the hydrogel was quickly decreased at $80^{\circ}C$, showing a thennally hydrodegradable property.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권4호
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• pp.1-9
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• 2011

Bentonite has been generally used as vertical cutoff barrier material and reported to have several problems regarding its low workability, drying shrinkage cracking by particle cohesion, and ineffective waterproof ability under sea water condition. In this study, the particle sealant, the furnace slag coated by the mixture of bentonite, sepiolite and guargum, was developed to compensate these weak points and the hydraulic conductivity of the particle sealant was evaluated. Drying shrinkage cracking and swelling index was estimated to find the optimal mixing ratio of bentonite, sepiolite and guargum. The hydraulic conductivity of the particle sealants having different amount of sealant (bentonite-sepioliteguargum mixture) coating the furnace slag was estimated using the rigid wall permeameter and flexible wall permeameter. The results showed that drying shrinkage cracking was not found in the bentonite-sepiolite mixture with 20% sepiolite contents and the results from free swelling tests for the sealant having 1 : 0.025, 1 : 0.05 and 1 : 0.075 of weight ratios of bentonite-sepiolite mixture and guargum under simulated sea water condition were higher than those for the bentonitesepiolite mixture without guargum under tap water condition. These three sealants were coated on the furnace slag with 50% and 60% of sealant in the particle sealant and the hydraulic conductivity was estimated. In the cases of the particle sealants having 20% sepiolite in the bentonite-sepiolite mixture and 1 : 0.075 weight ratio of the bentonite-sepiolite mixture and guargum, the hydraulic conductivity from the rigid wall permeameter was below $1.0{\times}10^{-7}$ cm/sec under simulated sea water condition. The hydraulic conductivity of the particle sealant having $1.0{\times}10^{-6}$~$1.0{\times}10^{-7}$ cm/sec by the rigid wall permeameter was estimated using the flexible wall permeameter and found to be below $1.0{\times}10^{-7}$ cm/sec.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1184-1189
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• 2004

Coking process is the thermal decomposition of bituminous coal with final temperature of about $900^{\circ}C$ Because coke plays important roles in ironmaking process in a blast furnace it's essential for developing modeling of coke oven. In this study, An unsteady 2-dimesional model is proposed to simulate coking process in a coke oven. In this model, gas and solid phase are assumed homogeneous continnum and solid bed is assumed as porous media . The model contains governing equations for the solid phase and the gas phase. Complicated phenomena such as swelling, softening, resolidification and shrinkage are neglected and mass loss by drying and devolatilization is reflected by generation of internal pores. Drying, devolatilization, heat transfer and generation of internal pores are also reflected in source terms. Calulated results are compared with experimental data

• 한국가구학회지
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• 제18권4호
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• pp.275-281
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• 2007

This study was carried out to know bending process property of bentwood by treatment methods such as microwave and ammonia solution treatment. Bentwood processing was operated on bending-jig form with 60mm and 100mm radius of curvature (ROC). The species was used to Korean red pine (Pinus densiflora). No significant difference was shown in bentwood processing method on ROC. In treatment method, ammonia solution treatment for bentwood was better in dimensional stability and working ability than that of microwave treatment. However, bentwood stress was reduced with ammonia solution treatment. Color of bentwood surface appearance has a dark tendency in ammonia solution treatment. But it seems to beautiful effect of apparent annual ring is rising esthetically by ammonia solution treatment. To utilize wood as a exterior material for living amenity, it has to be closely examined from various angles including surface property, degree of swelling and shrinkage, drying state, retaining strength, durability, safety, and insect damage.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 1999년도 추계 기술심포지움 논문집
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• pp.111-115
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• 1999

The $Li_2O-MgO-MgF_2-SiO_2$glasses with addition of $B_2O_3$ were investigated in order to make glass-ceramics for low temperature firing substrate. Glasses were made by melting at $1450^{\circ}C$ in the electronic furnace and crystallized at $750^{\circ}C$. After the crystallization, crystal phases and microstructure were observed. The crystal phases were polycrystalline of lithium boron fluorphlogopite and lithium fluorhectorite. The crystal shape was changed to grande type from needle type with the increase in $B_2O_3$ contents. Average particle size of the glass-ceramics aftar water swelling was $3.77{\mu}{\textrm}{m}$. The optimum sintering temperature and sintering shrinkage of the substrate were $900^{\circ}C$ and 13.4vol%, respectively.

• Childhood Kidney Diseases
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• 제11권2호
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• pp.145-151
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• 2007

Hypertonicity (hypernatremia) of extracellular fluid causes water movement out of cells, while hypotonicity(hyponatremia) causes water movement into cells, resulting in cellular shrinkage or cellular swelling, respectively. In most part of the body, the osmolality of extracellular fluid is maintained within narrow range($285-295 mOsm/kgH_2O$) and some deviations from this range are not problematic in most tissue of the body except brain. On the other hand, the osmolality in the human renal medulla fluctuates between 50 and $1,200 mOsm/kgH_2O$ in the process of urine dilution and concentration. The adaptation of renal medullary cells to the wide fluctuations in extracellular tonicity is crucial for the cell survival. This review will summarize the mechanisms of urine concentration and the adaptation of renal medullary cells to the hyper tonicity, which is mediated by TonEBP transcription factor and its target gene products(UT-A1 urea transporter etc.).

• 마이크로전자및패키징학회지
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• 제6권4호
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• pp.35-39
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• 1999

The $Li_2O-MgO-MgF_2-SiO_2$glasses with addition of $B_2O_3$ were investigated in order to make glass-ceramics for low temperature firing substrate. Glasses were made by melting at $1450^{\circ}C$ in the electronic furnace and crystallized at $750^{\circ}C$. The crystal phases were polycrystalline of lithium boron fluorphlogopite and lithium fluorhectorite. The crystal shape was chanced to granule type from needle type with increasing $B_2O_3$ content. Average particle size of the glass-ceramics after water swelling was 3.77$\mu\textrm{m}$. The optimum sintering temperature and sintering shrinkage of the substrate were $900^{\circ}C$ and 13.4%, respectively.

• Journal of the Korean Wood Science and Technology
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• 제50권1호
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• pp.46-58
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• 2022

Wood from tropical plantation forests has lower physical and mechanical properties than mature wood. Furfuryl alcohol (FA) impregnation into the wood could help to enhance hydrophobic properties, dimensional stability, and structural strength. Furfurylation was applied to specimens of the following four fast-growing tropical wood species: jabon (Anthocephalus cadamba), sengon (Falcataria moluccana), mangium (Acacia mangium), and pine (Pinus merkusii). The discoloration and physical and mechanical properties were subsequently measured, and the results showed that furfurylated wood had a darker color and better physical and mechanical properties than untreated wood. Specifically, the furfurylated wood had higher density, modulus of elasticity, and hardness and lower moisture content, water absorption, swelling, and shrinkage. The furfurylation significantly enhanced physical and mechanical properties.

• 한국지반공학회논문집
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• 제33권11호
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• pp.97-104
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• 2017

벤토나이트와 현장토를 혼합하여 차수재료로 폐기물 매립장의 차수층에 많이 적용하고 있다. 차수층으로 사용되는 재료는 일반적으로 투수계수가 $1{\times}10^{-7}cm/s$ 이하인 재료를 사용한다. 벤토나이트를 현장에서 차수층 재료로 사용될 때 벤토나이트는 건조-수축 균열 발생 및 염수조건에서 팽창성 떨어지고 차수 기능을 상실하는 등의 문제점이 존재한다. 벤토나이트의 문제점을 극복하기 위해 본 연구에서는 균열 방지 및 해수조건에서 차수성을 확보할 수 있는 내염성 벤토나이트를 개발하였고, 건조수축균역 시험, 팽윤도 시험, 다짐시험 및 투수실험을 통해 내염성 벤토나이트의 혼합비 결정 및 성능을 평가하였다.

• Journal of Forest and Environmental Science
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• 제39권1호
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• pp.55-64
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• 2023

Properties of a lesser-used wood species were investigated to determine its potential for structural utilization. Trees of Delonix regia were felled and sampled at the base, middle and top and then sectioned to inner wood, middle wood, and outer wood for variation across the axial and radial directions. Hence, selected physical and mechanical properties as well as natural durability of D. regia along the radial and axial directions were examined. Obtained data were analyzed using analysis of variance (ANOVA) at α_0.05. There was no significant difference in the Moisture content (MC) of the wood but specific gravity (SG) decreased from base to top ranging from 0.35-0.44. Water absorption, volumetric swelling, and volumetric shrinkage range from 46.18-51.86%, 2.57-4.02%, and 2.26-3.96% respectively along the axial plane. The weight loss for graveyard exposure and accelerated laboratory decay test ranged from 25.14-48.00% and 32.02-44.45% respectively. Modulus of Rupture and Modulus of Elasticity values range from 29.42-72.68 Nmm² and 3,834.54-8,830.37 Nmm² respectively. The SG values has confirmed the species as a medium density wood and values of other properties tested showed that the wood is dimensional stable and moderately resistance to fungi and termite. Hence, it could be used for light construction purposes such as furniture and other interior woodwork.