• Journal of the Korean GEO-environmental Society
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• v.19 no.12
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• pp.33-39
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• 2018

In this study, important characteristics were identified for the Geosynthetic-soil interface using overburden pressure and saltwater and fresh water to evaluate silt shear behavior of the Geosynthetic-soil interface. In addition, waste landfill can secure spaces for waste disposal in the sea and this spaces can be used for additional facilities which will be necessary in the future. Analysis of behavior characteristics on interface of Geosynthetic-soil shows that, if analyzed using standard consolidometers, the consolidation stress of fresh water increased significantly more than saltwater. When analyzed using cyclic shear apparatus, saltwater and freshwater in both conditions, the displacement value increases as the wire gauges become closer to the lower module, and the shear fracture tends to occur radically under saltwater conditions than fresh water. Therefore, seawater, fresh water that act on the interface of geosynthetic-soil, and installation of facility using geosynthetic should be considered as important parameters that are essential for the dynamic design factor of the water controlling facility.

• Geomechanics and Engineering
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• v.18 no.2
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• pp.179-188
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• 2019

This paper presents an experimental study to evaluate the effect of palm oil on the selected basic physical-chemical and geotechnical properties of kaolin. The experimental findings are further compared with literature outcomes investigating similar properties of fine grained soils subjected to contamination by different types of oils. To this end, palm oil was mixed with oven dried kaolin samples-aiding oil's interaction (coating) with dry particles first, in anticipation to emphasize the effect of oil on the properties of kaolin, which would be difficult to achieve otherwise. Oil content was limited to 40% by dry weight of kaolin, supplemented at intervals of 10% from clean kaolin samples. Observations highlight physical particle-to-particle bonding resulting in the formation of pseudo-silt sized clusters due to palm oil's interaction as evinced in the particle size distribution and SEM micrographs. These clusters, aided by water repellency property of the oil coating the kaolin particles, was analyzed to show notable variations in kaolin's consistency-measured as liquid and plastic limits. Furthermore, results from compaction tests indicates contribution of oil's viscosity on the compaction behavior of kaolin - showing decrease in the maximum dry unit weight (${\gamma}_{d,max}$) and optimum moisture content ($w_{opt}$) values with increasing oil contents, while their decrease rates were directly and inversely proportional in ${\gamma}_{d,max}$ and $w_{opt}$ values with oil contents respectively. Comparative study in similar terms, also validates this lower and higher decrease rates in ${\gamma}_{d,max}$ and $w_{opt}$ values of the fine grained soils respectively, when subjected to contamination by oil with higher viscosity.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.1
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• pp.1-8
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• 2019

Developing reliable soil moisture prediction techniques at agricultural regions is a pivotal issue for sustaining stable crop productions. In this study, a physically-based SWAP(Soil-Water-Atmosphere-Plant) model was suggested to estimate soil moisture dynamics at the study sites. ROSETTA was also integrated to derive the soil hydraulic properties(${\alpha}$, n, ${\Theta}_r$, ${\Theta}_s$, $K_s$) as the input variables to SWAP based on the soil information(Sand, Silt and Clay-SSC, %). In order to predict the soil moisture dynamics in future, the mid-term TIGGIE(THORPEX Interactive Grand Global Ensemble) and long-term S2S(Subseasonal to Seasonal) weather forecasts were used, respectively. Our proposed approach was tested at the six study sites of RDA(Rural Development Administration). The estimated soil moisture values based on the SWAP model matched the measured data with the statistics of Root Mean Square Error(RMSE: 0.034~0.069) and Temporal Correlation Coefficient(TCC: 0.735~0.869) for validation. When we predicted the mid-/long-term soil moisture values using the TIGGE(0~15 days)/S2S(16~46 days) weather forecasts, the soil moisture estimates showed less variations during the TIGGE period while uncertainties were increased for the S2S period. Although uncertainties were relatively increased based on the increased leading time of S2S compared to those of TIGGE, these results supported the potential use of TIGGE/S2S forecasts in evaluating agricultural drought. Our proposed approach can be useful for efficient water resources management plans in hydrology, agriculture, etc.

• Fashion & Textile Research Journal
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• v.21 no.1
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• pp.67-74
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• 2019

This study aims to investigate the relation between pressure, 3D length change, and subjective pressure sensation in sports brassieres. Seven Korean women in their 20s and 30s were chosen as subjects. In the experiment, the subjects evaluated four types of sports brassieres wherein the lower band was changed. The results of the study were as follows. The pressure according to the measurement position was lower at the front part than at the side and back parts (p<.05), and there was no difference in the pressure according to the brassiere type. It was observed that brassiere C, which had the higher extension band, was elongated more than the other brassieres when worn. In the case of brassiere B, which had a slit in the front center, it was observed that the 3D length of the front part changed very little as the slit spreads, and the back part stretched in a manner similar to those of the other brassieres. Subjective pressure sensation was statistically different only at the front and the side of the lower band. Brassiere B(with a silt) demonstrated the least subjective pressure sensation; the pressure sensation was high when wearing brassieres A and D (p<.05). Brassieres B and C were also preferred for overall comfort. In conclusion, it was observed that the substitution of material and morphological transformation affect subjective sensation.

• Smart Structures and Systems
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• v.23 no.1
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• pp.81-90
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• 2019

The shear behavior of soil-concrete interface is mainly affected by the surface roughness of the two contact surfaces. The present research emphasizes on investigating the effect of roughness of soil-concrete interface on the interface shear behavior in two-layered laboratory testing samples. In these specially prepared samples, clay silt layer with density of $2027kg/m^3$ was selected to be in contact a concrete layer for simplifying the laboratory testing. The particle size testing and direct shear tests are performed to determine the appropriate particles sizes and their shear strength properties such as cohesion and friction angle. Then, the surface undulations in form of teeth are provided on the surfaces of both concrete and soil layers in different testing carried out on these mixed specimens. The soil-concrete samples are prepared in form of cubes of 10*10*30 cm. in dimension. The undulations (inter-surface roughness) are provided in form of one tooth or two teeth having angles $15^{\circ}$ and $30^{\circ}$, respectively. Several direct shear tests were carried out under four different normal loads of 80, 150, 300 and 500 KPa with a constant displacement rate of 0.02 mm/min. These testing results show that the shear failure mechanism is affected by the tooth number, the roughness angle and the applied normal stress on the sample. The teeth are sheared from the base under low normal load while the oblique cracks may lead to a failure under a higher normal load. As the number of teeth increase the shear strength of the sample also increases. When the tooth roughness angle increases a wider portion of the tooth base will be failed which means the shear strength of the sample is increased.

• Journal of Environmental Science International
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• v.30 no.6
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• pp.487-500
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• 2021

To evaluate the geochemical characteristics and assess the pollution in surface sediments of the Nakdong River estuary, two sites adjacent to the estuary bank (Hh1 and Hh2) and one site at the upper part of the estuary bank (Hh3) were investigated. The surface sediments were analyzed for their contents of metals (Cu, Pb, Ni, Cr, Zn, and Al), organic matter (IL, COD, TOC, and TN), and grain size from 2018 to 2020. As a result of the pollution assessment, there was little anthropogenic contamination by most of the metals. The surface sediments in Hh2 had comparatively abundant silt and clay, whereas the other sites were mainly composed of sand. The organic index and contents of organic matter were highest at Hh2. Multivariate statistical analyses (cluster analysis and Pearson correlation analysis) showed that the contents of organic matter and pollution were associated with fine sediment. These results suggest that the geochemical characteristics were changed by the estuary bank built in the research area and that the increase in fine sediment attributable to the low-energy environment resulted in an increase in organic matter pollution.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.43-51
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• 2011

Marine clays are widely distributed in Korean eastern, western and southern coastal areas. Understanding engineering characteristics of the soft ground is very important, whenever civil structures are constructed in those coastal areas. It is because the ground is composed of highly compressible marine clay. In this paper, the physical and compression characteristics of Incheon, Mokpo, Gwangyang and Busan marine clay were analyzed and the characteristics between western and southern coastal marine clays were compared. For this, test results of 1,471 samples from 114 sites were used. As a result, Incheon clay showed the lowest plasticity and the highest unit weight due to influx of silt from the Yellow River and the turn of the tide of Incheon area. However, Gwangyang clay showed highly compressible characteristic due to extensive reclamation. On the other hand, Mokpo and Busan clay showed partially similar levels of characteristics. The compression index of Mokpo and Busan clay was high more than twice in comparison with Incheon clay and that of Gwangyang clay was higher than seventy percents in comparison with Mokpo and Busan clay.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.31-45
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• 2018

This study investigated the characteristics of sedimentary environment changes across a tidal flat in Gagyeongju of Anmyeondo Island. We performed a spatio-temporal analysis on the grain sizes composition of sediments and micro-landform changes during the winter from 2013 to 2016. The results showed that erosion was a dominant processthroughout the study flat, reducing the surface elevation even by 1 m around the upper sand flat. As a consequence, headlands have formed in the entire region of Gagyeongju village. In addition, erosion quickly progressed along the low-lying subtidal zone and tide way and, in contrast, sedimentation progressed in the mid-elevation tidal flat. We posit that a jetty, which had been constructed as a pier facility on the eastern part of the study area, interfered with the flow of tidal current, thereby enhancing these erosional processes. This is because such interference can block the supply of fine-textured sediments from the nearby Cheonsu Bay and therefore reduce surface elevation. According to the surface sediment analysis, the sediments were categorized into 7 sedimentary facies, and generally displayed a high ratio of silt and clay. The result of time-series analysis (2012-2013) showed that the sediments on the tidal flat became fine-grained, and that sorting became worse. However, the sediments on the subtidal zone, embayment and along inside of the jetty tended to be coarse-grained. In conclusion, the tidal flat microlandform change in the study area was caused by a disruption in the seawater circulation due to the jittery construction within the tidal flat, which had a direct effect on erosional and sedimentary environment processes.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.9-18
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• 2021

In this study, the overconsolidation ratio (OCR) of soft clay soil was calculated by conducting an indoor physical experiment and a dynamics test using undisturbed soil samples from a soft clay soil field in South Korea. The OCR by depth was predicted by comparing the experimental results with the existing empirical equations. Methods using the liquidity index and the existing empirical equation by the Naval Facilities Engineering Systems Command (NAVFAC) were examined, and the results were compared with the actual measured values. The method using the liquidity index was found to be suitable for estimating the rough OCR of the ground. However, the effect of drying was not considered for the ground above the groundwater level. Therefore, an equation for the correlation equation between the depth and OCR of each region, including the ground above the groundwater level, was proposed. The proposed equation was applied to the OCR prediction of the adjacent area. The predicted values in the area composed of clay (CL, CH) were found to be in good agreement with the actual values. In the region composed of silt (ML), however, the predicted values were not consistent with the actual values. This suggests that the sedimentation and compositional characteristics, rather than the engineering characteristics of the soil, are important factors that affect the OCR prediction.