• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.220-224
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• 1983

The hydration of water, at $20^{\circ}\;30^{\circ}$ and $40^{\circ}C$ for 10-360 minutes, by the two varieties of husked barley and of naked barley which were polished to 40 and 30%, respectively, was investigated. The absorption was directly proportional to the square root of the hydration time and accounted for by the diffusion equation: 1-M = $(2/{\sqrt\pi})\;(S/V){\sqrt{Dt}}$, where 1-M is the relative moisture gain and S/V is the surface-to-volume ratio. The average diffusion coefficient (D) was given by the Arrhenius relation: D = $D_{0}\;exp\;(-Ea/RT)$, where the activation energy for both husked and naked barley was about 7.2 Kcal/mole. The average value of D for naked barley was slightly higher than that for husked barley.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.88-94
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• 2001

Physical and chemical properties, the salt accumulation and leaching of salt by water of coal fly ash ball (ash ball) were evaluated in comparison with perlite and granule rockwool (rockwool). Bulk density, particle density, solid phase, and porosity of ash ball were 0.93 g.cm$^{-3}$ , 2.29 g.cm$^{-3}$ , 40.6%, 59.4%, respectively. The bulk density of ash ball was greater, while porosity was smaller, than that of perlite and rockwool. Saturation moisture capacity was 52% in ash ball, 71% in perlite, and 90% in rockwool. Water contents after drainage for 1 hr of ash ball, perlite, and rockwool were 21%, 27%, and 80%, respectively. Water content of small granules (3-5 mm) of ash ball was 5% greater than that of large (7-15 mm) grannules. The ash ball was a weak alkali substrate with pH 7.6, but not electric conductivity (EC), of the nutrient solution supplied to ash ball slightly increased. When the absorption of mineral ions to substrates were analyzed, ash ball and RW absorbed mainly PO￣$_4$. On tomato culture, salt accumulation in ash ball substrate was similar to that in perlite. Most of the salts in the ash balls were removed by submerging the substrate eight times in distilled water. It is concluded that water holding capacity of ash ball substrate was lo as compared to other substrates, but air permeability, and water diffusion was excellent, making control of medium water content easy.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.3
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• pp.313-325
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• 2011

From October 2009 to June 2010, major greenhouse gases (GHG: $N_2O$, $CH_4$, $CO_2$) soil emission were measured from upland cabbage field at Kunsan ($35^{\circ}$56'23"N, $126^{\circ}$43'14"E), Korea by using closed static chamber method. The measurements were conducted mostly from 10:00 to 18:00LST during field experiment days (total 28 days). After analyzing GHG concentrations inside of flux chamber by using a GC equipped with a methanizer (Varian CP3800), the GHG fluxes were calculated from a linear regression of the changes in the concentrations with time. Soil parameters (e.g. soil moisture, temperature, pH, organic C, soil N) were also measured at the sampling site. The average soil pH and soil moisture were ~pH $5.42{\pm}0.03$ and $70.0{\pm}1.8$ %WFPS (water filled pore space), respectively. The ranges of GHG flux during the experimental period were $0.08\sim8.40\;mg/m^2{\cdot}hr$ for $N_2O$, $-92.96\sim139.38mg/m^2{\cdot}hr$ for $CO_2$, and $-0.09\sim0.05mg/m^2{\cdot}hr$ for $CH_4$, respectively. It revealed that monthly means of $CO_2$ and $CH_4$ flux during October (fall) were positive and significantly higher than those (negative value) during January (winter) when subsoil have low temperature and relatively high moisture due to snow during the winter measurement period. Soil mean temperature and moisture during these months were $17.5{\pm}1.2^{\circ}C$, $45.7{\pm}8.2$%WFPS for October; and $1.4{\pm}1.3^{\circ}C$, $89.9{\pm}8.8$ %WFPS for January. It may indicate that soil temperature and moisture have significant role in determining whether the $CO_2$ and $CH_4$ emission or uptake take place. Low temperature and high moisture above a certain optimum level during winter could weaken microbial activity and the gas diffusion in soil matrix, and then make soil GHG emission to the atmosphere decrease. Other soil parameters were also discussed with respect to GHG emissions. Both positive and negative gas fluxes in $CH_4$ and $CO_2$ were observed during these measurements, but not for $N_2O$. It is likely that $CH_4$ and $CO_2$ gases emanated from soil surface or up taken by the soil depending on other factors such as background concentrations and physicochemical soil conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.112-120
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• 2012

A numerical model considering the internal vaporization and the creep effect, in the form of a analytical program, for tracing the behavior of high strength concrete(HSC) members exposed to fire is presented. The two stages, i.e., spalling procedure and fire resistance time, associated with the thermal, moisture flow, creep and structural analysis, for the prediction of fire resistance behavior are explained. The use of the analytical program for tracing the response of HSC member from the initial pre-loading stage to collapse, due to fire, is demonstrated. Moisture evaporates, when concrete is exposed to fire, not only at concrete surface but also at inside the concrete to adjust the equilibrium and transfer properties of moisture. Finite element method is employed to facilitate the moisture diffusion analysis for any position of member, so that the prediction method of the moisture distribution inside the concrete members at fire is developed. The validity of the numerical model used in this program is established by comparing the predictions from this program with results from others fire resistance tests. The analytical program can be used to predict the fire resistance of HSC members for any value of the significant parameters, such as load, sectional dimensions, member length, and concrete strength.

• KSBB Journal
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• v.28 no.5
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• pp.319-326
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• 2013

This study was carried out to investigate the in vitro and in vivo moisturizing properties and percutaneous absorption of PEG-impregnated Aloe vera gel. The PEG-i-Aloe gel was obtained from dewatering and impregnation by soaking (DIS) of Aloe vera leaf slice. The moisturizing property of the obtained sample was evaluated by moisture determination using gravimetric method in desiccator under different RH% and by water sorption-desorption test on human skin. The transdermal penetration characteristics of PEG-i-Aloe gel was investigated by Franz diffusion cell in vitro transdermal absorption method. PEG-i-Aloe gel had high moisture retention ability and could significantly lead the enhancing skin hydration status as well as reducing the skin water loss due to the film formation as a skin barrier. The skin penetration rate of PEGi- Aloe gel at steady state was 9.76 ${\mu}g/(h{\cdot}cm^2)$ and the quantity of the transdermal absorption was 144 ${\mu}g/cm^2$ in 9 hr. The penetration mechanism was well fitted with Higuchi model ($R^2$ = 0.974-0.994). The results show that PEG-i-Aloe gel has the significant moisturizing effect and strong penetration of the animal skin. It could be used as the moisturizing additive in cosmetic skin products.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.59-63
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• 2008

The surface runoff is one of the important components for the surface water balance. However, most Land Surface Models(LSMs), coupled to climate models at a large scale for the prediction and prevention of disasters caused by climate changes, simplistically estimate surface runoff from the soil water budget. Ignoring the role of surface flow depth on the infiltration rate causes errors in both surface and subsurface flow calculations. Therefore, for the comprehensive terrestrial water and energy cycle predictions in LSMs, a conjunctive surface-subsurface flow model at a large scale is developed by coupling a 1-D diffusion wave model for surface flow with the 3-D Volume Averaged Soil-moisture Transport(VAST) model for subsurface flow. This paper describes the new conjunctive surface-subsurface flow formulation developed for improvement of the prediction of surface runoff and spatial distribution of soil water by topography, along with basic schemes related to the terrestrial hydrologic system in Common Land Model(CLM), one of the state-of-the-art LSMs.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.75.2-75.2
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• 2010

Polymer electrolyte fuel cells (PEFCs) have received a lot of attention as a power source for both stationary and mobile applications due to their attractive feature. In general, the performance of PEFCs is highly affected by the property of the electrodes. A PEFC electrode essentially consists of a gas diffusion layer and a catalyst layer. The gas difusion layer is highly porous and hydrophobicized with PTFE polymer. The catalyst layer usually contains electrocatalyst, proton conducting polymer, even PTFE as additive. Particularly, the proton conducting ionomer helps to increase the catalytic activity at three-phase boundary and catalyst utilization. Futhermore, it helps to retain moisture, resulting in preventing the electrodes from membrane dehydration. The most widely used proton conducting ionomer is perfluorinated sulfonic acid polymer, namely, Nafion from DuPont due to its high proton conductivity and good mechanical property. However, there are great demands for alternative ionomers based on non-fluorinated materials in terms of high temperature availability, environmental adaptability and production cost. In this study, the electrodes with the various content of the sulfonated poly(ether sulfone) ionomer in the catalyst layer were prepared. In addition, we evaluated electrochemical properties of the prepared electrodes containing the various amount of the ionomers by using the cyclic voltammetry and impedance spectroscopy to find an optimal ionomer composition in the catalyst layer.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.413-416
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• 2008

Reinforcement corrosion is generally prohibited under normal condition by the alkalinity of the pore water in the concrete. However, concrete structures in marine environment are subjected to chloride attack due to the high salinity of the sea water. Thus the probability of steel corrosion becomes higher when the chloride ions are introduced into the concrete. Steel corrosion is a decisive factor for the determination of service life of the marine concrete structure because chloride ions are abundant in the sea, and piers are the typical construction elements in concrete structures in marine environment. Hence, it is of great importance to evaluate the service life of the piers. In this paper, chloride penetration analysis for the rectangular pier in the marine environment is performed considering the diffusion and convection movement of chlorides. Result reveals that the service life of the reinforcement with drying-wetting cycles is much shorter than that of the reinforcement with saturated condition. This may be due to the fact that moisture movement is much faster that chloride diffusion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.75-83
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• 2012

Porosity in concrete has close relationship with durability characteristics. Additionally mixed water can help easy mixing and workability but causes increased porosity, which yields degradation of durability performance. In this paper, cement mortar samples with 0.45 of w/c (water to cement ratio) are prepared and durability performances are evaluated with additional water from 0.45 to 0.60 of w/c. Various durability tests including strength, chloride diffusion, air permeability, saturation, and moisture diffusion are performed. Then they are analyzed with changing porosity. Changing ratios and the patterns of durability performance are quantitatively evaluated considering pore size distribution, total porosity, and additional water content.

• Korean Journal of Food Science and Technology
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• v.16 no.3
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• pp.297-302
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• 1984

Kinetics of water diffusion during soaking of two brown rice varieties, Akibare (traditional rice) and Milyang 23 (high-yielding rice), were studied. Brown rice reached at the equilibrium moisture content after 18 hours. The absorption of liquid water by brown rice grain was directly proportional to the square root of hydration time and could be described by the simplified solution of Fick's diffusion equation. The diffusion coefficient was given by the Arrhenius relation: $D\;=\;2.738{\time}10^{-1}\;exp\;(-9,300/RT)$ for Akibare and $D\;=\;4.302{\time}10^{-1}\;exp\;(-9,500/RT)$ for Milyang 23. Hydration rate calculated from hardness change followed the equation of a first order reaction. Hydration mechanism of brown rice was changed at the gelatinization temperature of rice starch.