• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.11-24
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• 2003

This paper presents the results of laboratory investigation performed to study the role of different air sparging system parameters on the removal of benzene from saturated soils and groundwater. A series of one-dimensional experiments was conducted with predetermined contaminant concentrations and predetermined injected airflow rates and pressures to investigate the effect of soil type and the use of pulsed air injection on air sparging removal efficiency. On the basis of these studies, two-dimensional air sparging remediation systems were investigated to determine the effect of soil heterogeneity on the removal of benzene from three different homogeneous and heterogeneous soil profiles. This study demonstrated that the grain size of the soils affects the air sparging removal efficiency. Additionally, it was observed that pulsed air injection did not offer any appreciable enhancement to contaminant removal for the coarse sand; however, substantial reduction in system operating time was observed for fine sand. The 2-D experiments showed that air injected in coarse sand profiles traveled in channels within a parabolic zone. In well-graded sand the zone of influence was found to be wider due to high permeability and increased tortuosity of this soil type. The influence zone of heterogeneous soil (well-graded sand between coarse sand) showed the hybrid airflow patterns of the individual soil test. Overall, the mechanism of contaminant removal using air sparging from different soil conditions have been determined and discussed.

• Journal of the Korean Society of Safety
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• v.35 no.1
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• pp.70-78
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• 2020

Nitrox diving was introduced by the NOAA (National Oceanic and Atmospheric Administration) to increase the oxygen content and lower the nitrogen content in respiratory gases. The commercial diving sector specializing in underwater operations has recently introduced regulations on the use of Nitrox. Because the respiratory gas for Nitrox diving has a lower nitrogen content than the normal air, the amount of nitrogen dissolved in the body is small, which not only significantly reduces the decompression time compared to air diving, but also reduces the chance of exposure to decompression sickness. In this study, we applied the VPM (Varying Permeability Model) algorithm to virtual diving with air and Nitrox as a respiratory gas, respectively, to study the optimal Nitrox diving for the safety at the underwater works. The results showed that Nitrox diving had a longer NDL (No-Decompression Limit), a much shorter depression time. In other words, Nitrox diving in underwater works is safer from decompression sickness than commonly used air diving.

• Textile Coloration and Finishing
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• v.21 no.6
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• pp.22-28
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• 2009

Oil-absorbable nonwovens were produced by melt-blown processing of polypropylene chips. The melt-blown processing conditions, such as air pressure, and gear pump speed, DCD. In this study, these three factors were chosen to produce samples. Experimental array and variance analysis of the design of experiment were used to increase the field repeatability and universality. The effect of the factors on oil absorption properties of melt-blown nonwoven fabric such as oil absorbency were evaluated. As a result, the fiber diameter decreased as gearpump speed decreased or air pressure increased. The oil absorbency increased as air pressure increased or gearpump speed decreased and with the DCD increasing the oil absorbency significantly increased.

• Journal of the Korean Society of Visualization
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• v.20 no.2
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• pp.63-69
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• 2022

In this study, we numerically simulate the condensational growth of micron-sized particles traveling through a pipe filled with humidified air. Using the finite volume method and Lagrangian particle tracking technique, the mixture of particle-laden flow with moist air in a T-juction pipe is simulated. The condensational growth of particles is calculated by considering the mass transfer of vapor in the air onto the particle surface. The results indicate that the growth rate of the particles increases as the relative humidity of air is higher. Furthermore, the placement of a porous media with low permeability in the pipe could enhance the degree of condensational growth.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.1
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• pp.61-69
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• 2001

Polycarbonate(PC) membranes for oxygen enrichment from air were prepared by the wet phase inversion method. In order to improve oxygen separation performances of the PC membrane, the effect of the added ethanol(nonsolvent) and $CuCl_2$(metal salt) concentration in the casting solution on morphology, oxygen permeability ami $O_2/N_2$ separation factor of the membrane was studied. In addition, tensile strength and elongation at break of the membrane were investigated. An asymmetric membrane with a dense top layer and a porous sublayer was obtained. The thickness of the dense top layer decreased with increasing amount of nonsolvent additive. Compared with pure PC membrane without additive(metal salt), the oxygen permeability and $O_2/N_2$ separation factor of the $PC/CuCl_2$ membrane are significantly improved. The oxygen permeability and $O_2/N_2$ separation factor is $5.25{\times}10^{-9}cm^3(STP){\cdot}cm/cm^2{\cdot}sec{\cdot}cmHg$ and 4.5, respectively. This improvement might be due to good interaction between metal salt and oxygen.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.261-273
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• 1993

In order to study hydraulic properties and mechanical properties on unsaturated region, soil-water retention curve was obtained for suction plate method and pressure plate method, respectively. To investigate permeability of unsaturated soil and soil-water retention curve at the same time, unsaturated permeability tests using an improved Richard's method were performed on Joomoonjin Sand. These experimental results were compared with those by empirical equations. The relationship between air entry value and saturated permeability of filter was obtained for selecting a proper filter in unsaturated soil tests.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.3
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• pp.9-17
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• 2001

The floc characteristics of base paper stock for coating by the retention aid system consisting of polyacrylamide (high molecular weight low charge density, HMLC) and PEI without and with anionic inorganic oxide (IO) were investigated under various shear conditions of MDDA (modified dynamic drainage analyzer). The floc size was increased with cationic electrolytes dosage whatever inorganic oxide is applied or not. The effect of inorganic oxide on the floc size showed the different result between PAM and PEI. The smaller floc was obtained by PAM without inorganic oxide, but larger floc was obtained by PAM with inorganic oxide. However, the effect of shear force was not observed. Floc formation index was decreased by the addition of cationic electrolytes with or without inorganic oxide. Floc formation index had better correlation format formation index than floc size. The relationships between wet web permeability and mat air permeability showed the significant linear correlation ($R^2$=0.97~0.98) for HML PAM and PEI. Floc formation index gave more useful information than the retention measurement when the performance of retention aids is evaluated at the laboratory before applying at the paper mill.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.176-179
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• 2004

The latest concrete structure has showed that the deterioration of durability has been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the concrete which has deteriorated durability have been taken. Among them, it has been often used that surface treatment which cuts off the deterioration factors of durability by protecting the surface of concrete. This study was evaluated the surface improving agent for permeability, watertightness, air-permeability, chemical resistance and elution resistance.

• Journal of the Korean Wood Science and Technology
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• v.46 no.6
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• pp.703-712
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• 2018

The sound absorption property, hand feel, air permeability and pore size of 25 kinds of traditional Korean natural wallpapers (Hanji) were measured and analyzed in this study. The sound absorption rate of Hanji became larger with increasing of frequency beginning from 3.2 kHz, reached 2 times in frequency range of nearby 4 kHz. The sound absorption rate of Hanji was increased as the permeability was lowered and the pore size was decreased. The sound absorption property of Hanji wallpaper could be improved by manufacturing process such as super calendering process.