• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.157-161
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• 2006

Generally, a silicone rubber and a chlorinated polyethylene(CPE) have been used as a binder for the development of high-performance composite EM(Electro Magnetic) wave absorbers. In this paper, the EM wave absorption performance of natural lacquer, which is newly proposed as a binder was investigated. The prepared MnZn ferrite EM wave absorbers are mixed with natural lacquer showed excellent EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers which are mixed with the conventional binders. MnZn ferrite EM wave absorbers mixed with natural lacquer were prepared and their absorption ability was also investigated. The EM wave absorbers are fabricated in different proportions of MnZn, or NiZn ferrite and natural lacquer, and their reflection coefficients are measured. The permittivity and permeability are calculated by using the measured reflection coefficients. The EM wave absorption abilities are calculated according to different thicknesses of the EM wave absorbers.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.5
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• pp.482-488
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• 2017

The measurement based on reliable standard operating procedures (SOPs) is important for consistent information. The objective of this study is to investigate reliable SOPs of soil physical methods, including core method for bulk density, Yamanaka hardness, and air permeameter method for air permeability. The coefficients of variation in bulk density (core method), Yamanaka hardness, and air permeability were ranged of 1~6%, 8~13%, and 10~84%, respectively. The variation in situ measurement such as bulk density, hardness, and air permeability due to spatial variability at measuring site was larger due to the number of replicates, organic matter content, and soil texture. Nevertheless, air permeability had different values as different number of replicates, and thus, it is thought that more replicates can result in higher reliability. It suggested that investigation of soil physical properties for the target sites should required to consider about soil texture, organic matter content, and number of replications before measurement. In conclusion, core sampling for bulk density measurement in upland soil recommended to perform in 3 repetitions with 2 inch core, and 3 inch core sampling for higher organic matter content.

• Geotechnical Engineering
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• v.2 no.3
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• pp.27-36
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• 1986

To investigate the seepage effect on the compacted backfill of retaining walls, an expriment and an analytical study were carried out First, the expriment was performed with a two-way permeameter newly designed for the do- termination on the degree of permeability anisotropy of compacted soils. As a result, e-log(kz/ky) plot showed a linear relationship, where kz and ky were permeability coefficients for the normal and the parallel directions to the compaction. The degree of permeability anisotropy, kz/ky was 2 to 4 at Dr>90% for sands, regardless of the methods of compaction. The kz/ky of the fine sand was greater than that of the coarse sand. Second, the exprimental results were applied to the extention of Gray's theory for the investigation of the active thrust affected by the seepage of permeability anisotropy. The active thrust was decreased with the increase in the degree of permeability anisotropy, and it It.as a little effect on wall friction.

• Journal of the Korean Wood Science and Technology
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• v.39 no.4
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• pp.326-332
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• 2011

Radial variation of sound absorption capability and air permeability of yellow poplar (Liriodendron tulipifera) wood in cross sectional surface and effect of steam explosion treatment were estimated by the two microphone transfer function method and the capillary flow porometry, respectively. The sound absorption coefficients of steam explosion treated wood was higher than those of control wood and these values increased with frequency. Abundant and big vessel may behave as sound absorbing pore observed on the cross sectional surface of yellow poplar wood. The sound absorption coefficients and air permeability of sapwood were higher than those of heartwood for Liriodendron tulipifera.

• Polymer(Korea)
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• v.30 no.6
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• pp.568-571
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• 2006

Poly(vinyl alcohol) (PVA)/gelatin(GEL) blend membranes were prepared under a high electric field, and their swelling and ion permeation behaviors were investigated. For alkali metal salts such as LiCl, NaCl and KCl, the permeability coefficients were increased until the electric field of 10 kV due to the decreased tortuosity, whereas they were decreased over 10 kV owing to the increase of the degree of crystallinity. The swelling ratios of the blend membranes showed the minimum values at pH 6, while the permeability coefficients exhibited the maximum values at the same condition. The minimum swelling ratios result from the repulsion effect between charged groups in acidic or basic regions, and the maximum permeabilities result from Donnan exclusion effect in the same regions. Especially, the per-meability coefficient for KCl of the membrane increased steeply to five times at $40^{\circ}C$ than below $35^{\circ}C$.

• Journal of the Korean GEO-environmental Society
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• v.8 no.3
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• pp.27-33
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• 2007

The vertical drain method recently being used in Korea is one of the popular soft ground improvement methods, and it is divided into the sand drain method, the pack drain method, the paper drain method, and the PBD method according to the drainage. However, these methods generate the disturbed zone called the smear zone when the drainage is penetrated into the in-situ ground. The characteristics of the smear zone generated cause the problems that the coefficient of permeability decreases, and then the consolidation time in the design becomes longer than expected. Even though the coefficient of horizontal consolidation and the coefficient of permeability in the smear zone are very important design factors directly influencing the degree of consolidation, in the existing studies, these coefficients have been empirically derived by the coefficient of vertical consolidation and used for the design. However, in case that these coefficients derived by the coefficient of vertical consolidation are applied to the actual design, a loss of the duration of construction and a loss of economical efficiency can be happened because of the inaccuracy of the coefficient of horizontal consolidation and the coefficient of permeability. Hence, in this study, in order to understand such influence, the laboratory test was carried out so as to reasonably determine the coefficient of permeability and the coefficient of consolidation in diverse ground conditions. Then, the range of smear effect on clay and silt was estimated with monitoring data through the laboratory test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.9-17
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• 2019

Cement hydrates and the related characteristics change with ages, and the behaviors are much related with chloride diffusion. In this work, 30% replacement ratio with FA(Fly Ash) and GGBFS(Ground Granulated Blast Furnace Slag) are considered for concrete with three levels of W/B (Water to Binder ratio) and 2 years of curing period. Chloride diffusion coefficients from accelerated condition are obtained at 5 measurement period (28days, 56days, 180days, 365days, and 730days), and the results are compared with porosity, binding capacity, and permeability from program-DUCOM. The similar changing pattern between chloride diffusion and permeability is observed since permeability is proportional to the square of porosity. Curing period is grouped into 4 periods and the changing ratios are investigated. Cement hydrate characteristics such as porosity, permeability, and diffusion coefficient are dominantly changed at the early ages (28~56 days), and diffusion coefficient in OPC concrete with low W/B continuously changes to 180days.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.20-30
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• 2014

To develop a unconventional gas reservoir, an analysis of tight rock property are required. Especially, conventional measurements are difficult to be applied to unconventional resources such as tight gas reservoir because the permeability are extremely low compared to a conventional gas reservoir. In this study, an apparatus was developed for measuring low permeability and porosity based on a pressure pulse decay method under unsteady state conditions. The apparatus was applied for measuring the porosity and permeability of tight sand core samples from Gyeongsang basin in Korea. As a validation of the measurement, regression analysis was carried out using the dimensionless pseudo-pressure between the measured data and analytical solution. The results show the correlation coefficients above 0.96. Therefore, it is believed that the apparatus has a high accuracy.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.4
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• pp.51-59
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• 2007

Recently, concrete has been made porous and used for sound absorption, water permeation, vegetation and water purification according to void characteristics. Many studies are carried out on the utilization of sewage sludge, fly ash and waste concrete to reduce the environmental load. This study was performed to evaluate the void, strength, relationship between void and strength, permeability and chemical resistance properties of porous polymer concrete for pavement with different fillers. An unsaturated polyester resin was used as a binder, crushed stone and natural sand were used as an aggregate and bottom ash, fly ash and blast furnace slag were used as fillers. The mix proportions were determined to satisfy the requirement for the permeability coefficient, $1{\times}10^{-2}$ cm/s for general permeable cement concrete pavement in Korea. The void ratios of porous polymer concrete with fillers were in the range of $18{\sim}23%$. The compressive strength and flexural load of porous polymer concrete with fillers were in the range of $19{\sim}22$ MPa and $18{\sim}24$ KN, respectively. The permeability coefficients of porous polymer concrete with fillers were in the range of $5.5{\times}10^{-1}{\sim}9.7{\times}10^{-2}$ cm/s. At the sulfuric acid resistance, the weight reduction ratios of porous polymer concrete immersed during 8-week in 5% $H_{2}SO_{4}$ were in the range of $1.08{\sim}3.56%$.

• Advances in concrete construction
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• v.6 no.2
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• pp.159-175
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• 2018

The main aim of this study is to investigate the possible effects of metakaolin on strength and durability properties of concrete. For this purpose, concrete mixtures are produced by substituting cement with metakaolin 0, 5, 10 and 20% by weight. The amount of binder for the concrete mixtures are 300 and $400kg/m^3$ with a constant water to cement ratio of 0.6. Compressive and bending strengths, freeze-thaw and high-temperature resistances, capillary coefficients and rapid chloride permeability properties were determined and compared each other. Because of all the experiments conducted, it has been found that the use of metakaolin as a pozzolanic additive in concrete have positive effects especially on compressive and bending strengths, capillary, rapid chloride permeability, freeze-thaw resistance, and high temperatures, up to $800^{\circ}C$. The results indicated that the performance of concrete can be enhanced by metakaolin. Particularly, compressive strength and durability properties have found to be improved with increasing metakaolin content which is attributed to pozzolanic activity and filler effect. Furthermore, metakaolin has relatively positive impacts under elevated temperatures and freeze-thaw effects. However, almost all the strengths of entire concrete specimens are lost at $800^{\circ}C$. Consequently, the optimum metakaolin substitution ratio can be suggested to be 20% as per this study.