• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.419-425
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• 2022

This paper aims to evaluate the acoustic detection performance for the deployment of the source and receiver positions of a bi-static sonar. In contrast with a mono-static sonar, a bi-static sonar has a large amount of computation and complexity for deployment. Therefore, in this study, we propose an assessment method that reduces the amount of computation while considering the variability of the ocean environment as a method to apply to the placement of the source and receiver of a bi-static sonar. First, we assume the representative ocean environment in the shallow and deep water. The signal excess is calculated with the source to receiver ranges and sensor depths. And the result is compared with the proposed assessment method of acoustic detection performance.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.151-167
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• 2023

This study compares the revised method in loose saturated sandy ground where the LNG storage tank will be installed with an evaluation method by one-dimensional effective stress analysis using the UBC3D-PLM model. Various laboratory and field tests were conducted to establish the parameters necessary for evaluation. The revised liquefaction evaluation method using the seismic response analysis result and N value from standard penetration testing evaluated the possibility of liquefaction as high, but assessment using effective stress analysis, which can consider various liquefaction resistance factors, found the site to be somewhat stable against liquefaction. One-dimensional finite element analysis using UBC3D-PLM modeling facilitated easier assessment of stability against liquefaction than the other methods and minimized the area required for reinforcement against liquefaction. In addition, it is expected that two-and three-dimensional numerical analysis considering the foundation of the LNG storage tank can identify the seismic design and behavior when liquefaction occurs.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.69-77
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• 2007

In this study, the consolidation behavior of clayey ground improved by vertical drain method was analyzed by the finite difference method based on the three-dimensional elasto-viscous consolidation theory, which can express the behavior of the secondary consolidation without considering the distinction of the normally consolidated and overconsolidated states. And the applicability of the elasto-viscous consolidation theory was discussed by comparing with the test results obtained from the model test of ground improved by vertical drain system. From these results, it is found that the amount of the settlement when the excess pore water pressure almost dissipated in the clay ground with vertical drains became smaller than that of the one-dimensional condition, and then the amount and rate of the residual settlement at secondary consolidation process became larger than those of the one-dimensional condition. finally, the effect of soil parameter on behavior of consolidation process was investigated by the results of a series of numerical analysis for the normalized and overconsoldiated states.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.93-101
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• 2008

This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground improvement. A number of cases were analyzed using a 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement provides additional confinement effect that reduces vertical stress in the soft ground, thus resulting in less excess pore water pressures and associated settlement. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.67-78
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• 2008

In this study, artificial cemented sand made of a few portland cement and Nak-Dong river sand was researched closely to investigate cementing effect quantitatively through unconfined tests and triaxial tests. The peak strength and elastic modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation and negative excess pore water pressure increased. In stress-strain curve, strain-softening behavior appeared in drained condition but strain-hardening behavior was appeared in undrained condition as a result of the increase of effective stress. The test was quantitatively analyzed by multiple regression models, correlating each response variable with input variable. The equations are valid only over the range investigated. Its adjusted coefficient of determination was $0.81{\sim}0.91$, and dry density is important factor for estimating strength of cemented sand.

• The Korea Journal of Herbology
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• v.38 no.1
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• pp.31-43
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• 2023

Objective : Alcoholic liver disease (ALD) is caused by excess alcohol intake. In the liver, alcohol breakdown results formation of toxic byproducts that lead to damage to tissue. This study is to investigate the therapeutic effects of Paeoniae Radix Alba and Puerariae Radix combination (PP) on ALD. Methods : PP was analyzed for polyphenolic compounds and free radical scavenging activity. ALD mouse model was induced by feeding ethanol and water (Control), silymarin (50 mg/kg), low-dose (PP: 100 mg/kg) or high-dose (PP: 200 mg/kg) was orally administrated to ALD mice for 14 days. The serum was assessed with levels of AST, ALT, total bilirubin, total cholesterol, and triglyceride. Liver tissues were evaluated for ROS levels, degree of liver damage and protein expression. Results : The 3:1 (Paeoniae Radix Alba:Puerariae Radix) ratio showed the best antioxidant values for the experiment. In ALD model, levels of AST, ALT, total bilirubin, total cholesterol, and triglyceride were significantly increased in the Control and the levels were decreased by treatment of PP. In addition, increased ROS, ONOO^- and MDA levels in the Control were reduced in the PP groups. Western blot analysis figured out that proteins related to ROS and cholesterol metabolism were higher in ALD than in PP-treated ALD. Antioxidant enzyme expression was low in the control group and increased by PP treatment. Conclusion : Our results suggest that PP has the potential to be a medicine in ALD in terms of regulating oxidative stress and adjusting lipid metabolism.

• Geomechanics and Engineering
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• v.35 no.4
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• pp.449-464
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• 2023

Advanced nonlinear effective stress constitutive models are started to be frequently used in one-dimensional (1D) and two-dimensional (2D) site response analysis for assessment of porewater generation and liquefaction potential in soft soil deposits. The emphasis of this research is on the assessment of the implementation of this category of models at the element stage. Initially, the performance of a coupled porewater pressure (PWP) and constitutive models were evaluated employing a catalogue of 40 unidirectional cyclic simple shear tests with a variety of relative densities between 35% and 80% and effective vertical stresses between 40 and 80 kPa. The authors evaluated three coupled constitutive models (PDMY02, PM4SAND and PDMY03) using cyclic direct simple shear tests and for decide input parameters used in the model, procedures are recommended. The ability of the coupled model to capture dilation as strength is valuable because the studied models reasonably capture the cyclic performance noted in the experiments and should be utilized to conduct effective stress-based 1D and 2D site response analysis. Sandy soils may become softer and liquefy during earthquakes as a result of pore-water pressure (PWP) development, which may have an impact on seismic design and site response. The tested constitutive models are mathematically coupled with a cyclic strain-based PWP generation model and can capture small-strain stiffness and large-strain shear strength. Results show that there are minor discrepancies between measured and computed excess PWP ratios, indicating that the tested constitutive models provide reasonable estimations of PWP increase during cyclic shear (r_u) and the banana shape is reproduced in a proper way indicating that dilation and shear- strain behavior is well captured by the models.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.65-75
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• 2024

This study investigates liquefaction-induced settlement through strain-controlled tests using a cyclic direct simple shear device on clean sand specimens. By focusing on the accumulated shear strain, soil density, sample preparation method, and cyclic waveshape, this study attempts to enhance the understanding of soil behavior under seismic loading and its further deformation. Results from tests conducted on remolded samples reveal insights into excess pore water pressure development and post-liquefaction volumetric strain behavior, with denser samples exhibiting lower volumetric strains than looser samples. Similarly, the correlation between the frequency and amplitude variations of the wave and volumetric strain highlights the importance of wave characteristics in soil response, with shear strain amplitude changes, varying the volumetric strain response after reconsolidation. In addition, samples prepared under moist conditions exhibit less volumetric strain than dry-reconstituted samples. Overall, the findings of this study are expected to contribute to predictive models to evaluate liquefaction-induced settlement.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.2
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• pp.217-223
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• 2015

This study was conducted to serve as a basis for establishing a stable production of proso millet on the rotational paddy-upland field by looking out the physicochemical and moisture characteristics of soil and the growth characteristics of proso millet by ridge width. Plant height showed Manhongchal was the smallest 71.3 cm in 240 cm wide of ridge in the first year, Ibeakchal was the highest 69.7 cm in 60 cm wide in the second year, Hwanggeumchal was the highest 72.8 cm in 60 cm wide in the first year. The retention time of the excess water in the soil during cultivation was extended wider the width of ridge. The variation width of the water content was higher by the wider the width of ridge. Yield components showed the longest ear length were 35.1 cm of Manhongchal, 34.8 cm of Ibeakchal in 60 cm wide of ridge in the first year. As the width of ridge extended, ear weight of all variety increased. 1,000 seed weight of the 60 cm wide of ridge was Manhongchal 6.8%, Ibeakchal 46.2% heavier than the 240 cm wide of ridge. Yield showed Manhongchal 221, Ibeakchal 223, Hwanggeumchal $225kg{\cdot}10a^{-1}$ in 60 cm wide of ridge in the first year. The similar pattern of amount showed Manhongchal 278, Ibeakchal 221, Hwanggeumchal $200kg{\cdot}10a^{-1}$ in 60 cm wide of ridge in the second year. This showed Manhongchal 103%, Ibeakchal 119%, Hwanggeumchal 85.2% was more than the 240 cm wide of ridge.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.332-344
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• 1996

The vertical profiles of the natural $^{210}Po,\;^{210}Pb\;and\;^{234}Th$, activities were measured at the upper 150 m or 200 m of water column from west-east intersection in the east-southern coastal area of the Korea Peninsula during the period from 26 to 29 April 1994 to compare the removal rates (residence time) and removal processes for $^{210}Po\;and\;^{234}Th$. At the inshore stations, the $^{210}Po$ activity was generally higher in the thermocline and its under layer than in the surface mixed layer, while represented the reversed pattern at the offshore stations. However, the $^{210}Pb$ activity decreased generally with depth. Also, the activity of $^{210}Po$ relative to its parent $^{210}Pb$ was deficient in the water column above the main thermocline, but was slightly excess or close to equilibrium in the thermocline and its under layer. The vertical profiles for the activity of $^{210}Pb$ relative to its parent $^{226}Ra$ showed the reversed pattern with the vertical variation of $^{210}Po$ excess (or deficiency). The $^{234}Th$ activity was significantly lower in the surface mixed layer and thermocline than in the deeper layer. The residence time of $^{210}Po$ ranged from 1 to 4 years at the five stations except station E8 that showed yet long residence time (approximately 10 years). The long residence time at the station E8 may resulted from the thicker surface mixed layer and subsequent the vertical mixing of $^{210}Po$ which was recycled in the lower surface mixed layer compared to at the other stations. Also, the residence time of $^{210}Po$ was shorter at the inshore stations than at the offshore stations. However, the residence time of $^{234}Th$ ranged from 52 to 74 days at all station without the significant variation, was very much shorter relative to the residence time of $^{210}Po$. The correlation between the removal rate of dissolved $^{234}Th$ and the concentration of total suspended matter (TSM) was generally positive. Therefore, it seems that the major route of the removal mechanism of $^{234}Th$ from seawater in the surface mixed layer is via adsorption onto suspended particle surfaces (most likely inorganic particles) and subsequent settling to the bottom layer. Between the removal rate of dissolved $^{210}Po$ and the concentration of chlorophyll-a was positively good correlation. Consequently, most likely the removal of $^{210}Po$ may be occurred by uptake to organisms (mainly such as planktonic debris or fecal pellets) and subsequent settling.