• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.4 s.44
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• pp.29-42
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• 2005

Total 350 borehole profiles were selected from the database of borehole logs in Seoul, for the site-specific seismic evaluation at two 4km${\times}$4km plain areas. Equivalent-linear site response analyses for the selected 350 sites were conducted based on shear wave velocity (Vs) Profiles, which were determined from the N-Vs correlation established using borehole seismic testing results in the inland areas of Korea. Most sites were categorized as site classes C and D based on the mean Vs to 30 m in depth (Vs30) ranging from 250 to 550 m/s. The she periods of the plains in Seoul ranging between 0.1 and 0.4 sec were significantly lower than those of the western US, from which the site coefficients in Korea were derived. For plains in Seoul, the site coefficients, Fa's and Fv's specified in the Korean seismic design guide, underestimate the ground motion in short-period (0.1-0.5 sec) band and overestimate the ground motion in mid-period (0.4-2.0 sec) band, respectively, because ol the differences in the geotechnical conditions between Seoul and the western US, although the Fa's in several sites overestimate the motion due to the base Isolation effect resulted from the soft layer in soil deposit.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.101-115
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• 2005

For the site characterization at two inland areas, Gyeongju and Hongsung, which represent geomorphic and geologic characteristics of inland region in Korea, in-situ seismic tests containing borehole drilling investigations and resonant column tests were peformed and site-specific seismic response analyses were conducted using equivalent linear as well as nonlinear scheme. The soil deposits in Korea were shallower and stiffer than those in western US, from which the site coefficients and site classification system in Korea were derived. Most sites were categorized as site classes C and D based on the mean shear wave velocity $(V_s)$ of the upper 30 m $(V_s30)$, ranging between 250 and 650 m/s. According to the acceleration response spectra determined from the site response analyses, the site coefficients specified in the current Korean seismic design guide underestimate the ground motion in the short-period band and overestimate the ground motion in mid-period band. These differences can be explained by the differences in the bedrock depth and the soil stiffness profile between Korea and western US. The site coefficients, $F_a$ for short-period and $F_v$ for mid-period, were re-evaluated and the site classification system, in which sites C and D were subdivided according to $V_s20,\;V_s15,\;and\;V_s10$ together with the existing $V_s30$ was introduced accounting for the local geologic conditions at inland region of the Korean peninsula. The proposed site classification system in this paper is still rudimentary and requires modification.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.501-509
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• 2019

The construction of foundation piles for buildings and bridges is changing from pile driving to an injected precast pile method. The goal is to minimize environmental damage, noise pollution, and complaints from neighboring residents. However, it is necessary to develop economic piles that are optimized for precasting by a centrifugal method in terms of both the material and structural system. A reinforced joint method is proposed for reinforced concrete piles (RC piles) manufactured by centrifugal casting. A previous study concluded that the structural performance of the current joint system for RC piles could be improved by using a reinforced joint composed of extended circular band plates and studs. In this study, the structural performance of such a joint was validated experimentally by bending and shear strength measurements. The proposed joint reinforcement method showed adequate structural performance in terms of bending and shear strength. The overall load-deflection behavior is close to that of a structure without joints, so it is expected that the behavior and performance of the design can be reliably reflected in site structures.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.57-63
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• 2005

In case of general structures, it has been known that the strain amplitude band experienced by the base in a state of service load is less than 1% and most of the base show low, strain amplitude behavior less than 0.01%. In this study examining the influence affected to dynamic behavior in a condition of the low strain amplitude of unsaturated decomposed granite soils, the resonant column test, using some samples in Su-won area, has been performed for each degree of saturation resulted from different void ratios and confined stress. It is found out that the minimum value of the damping ratio occurred in roughly $17{\sim}18%$ according to void ratios regardless of confined pressure in the same manner with the case of the maximum shear elastic modulus; and it is estimated that for the influence of surface tension in the optimum degree of saturation, the damping ratio appears to be least.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.3
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• pp.501-505
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• 2020

Objective: The purpose of this study was to investigate the effects of aging methods (AM) i.e. dry-aging (DA) and wet-aging (WA) on the physicochemical properties and in vitro digestibility of proteins in beef short loin. Methods: Short loins (M. longissmus lumborum), were trimmed and boned-out on the fifth day postmortem, from a total of 18 Hanwoo, which were purchased from a commercial slaughterhouse. Short loins were separated randomly grouped into one of the three treatments: control, WA (1℃, 7 days), and DA (1℃, 0.5 m/s, 85% relative humidity [RH], 30 days). Results: Dry-aged beef (DAB) exhibited higher pH, water holding capacity (WHC), myofibrillar fragmentation index (MFI), and digestibility, however lower lightness, redness, and yellowness values, cooking loss, and shear force (SF), than those of wet-aged beef (WAB) (p<0.05). The myosin light chain band intensity of DAB was higher than that of control and WAB in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The in vitro digestibility of aged beef was highly (p<0.001) correlated to physicochemical properties except WHC. The correlation coefficient between AMs and WHC was higher than that between AM and SF (p<0.05) or MFI (p<0.001). A high correlation was observed between SF and MFI (p<0.001). Conclusion: Thus, we believe that DAB is more advantageous than WAB owing to its high digestibility and WHC and low SF.

• Journal of Conservation Science
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• v.31 no.2
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• pp.115-123
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• 2015

This study aims to increase the transparency of the natural adhesives made with lacquer and glue. For the purpose, samples were prepared by mixing urushiol with glue in varied proportion and the characteristics and adhesive properties were investigated. By adding glue on urushiol, IR spectra of the natural adhesives became similar to that of glue as the N-H band related with protein of glue increased, while that of methylene C-H bond related to urushiol decreased. Samples were dried within a day and maintained a bright color without blackening by oxidation during the curing process. The natural adhesives with urushiol and glue showed various range of viscosity and tensile shear strength as Cemedine C or Epoxy resin according to mixing ratio. In addition, the sample of mixing ratio of 6:4 showed bright and transparency in appearance and tensile shear strength similar to that of Araldite AY103-1/HY956 for earthenware layer.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.91-103
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• 2006

The objective of this study is to analyze the characteristics of flow and bed change at the wide, shallow confluence of the Geum river and Mihocheon, which has different bed slope, height, and sediment concentration condition between the main channel and tributary. RMA-2 and SED2D were used to simulate flow and bed changes at the site. Flow simulations showed that the overall flow velocity, shear layer and vortex generated at the left bank of the confluence increase as the discharge was increased. Sediment transport simulations indicated that because of the high inflow sediment concentration from Mihocheon, sediment concentration in the main river increases after the confluence, the high sediment concentration band was kept along the shear layer boundary and the left bed was aggraded after confluence.

• Journal of Ocean Engineering and Technology
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• v.35 no.5
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• pp.347-359
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• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.35-41
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• 2009

It is necessary to consider the site amplification for estimating SSI (soil structure interaction) and seismic source with more confidence. The horizontal to vertical (H/V) ratio technique in spectral domain is one of several techniques to estimate empirical site transfer function. The technique, originally proposed by Nakamura (1989), is applied to analyze the surface waves in the microtremor records. However, the application of this technique has been widened to the shear wave energy of strong motions for estimating site amplification. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that each station has the its own characteristics of the specific resonance, high-band, and low-band frequency. The characteristics of the resonance frequency is more important because the quality of the seismic records are dependent on the resonance frequency. The result can be used for the study of site classification and removal of the site amplification effects from observed records can give us more reliable seismic source parameters.

• Atmosphere
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• v.31 no.5
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• pp.563-576
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• 2021

The performance of East Asian summer monsoon is assessed for GC2 and GC3.1, which are climate change models of the current and next climate prediction system in the Korea Meteorological Administration (KMA), GloSea5 and GloSea6. The most pronounced characteristics of GC models are strong monsoon trough and the weakening of the Western North Pacific Subtropical High (WNPSH). These are related to the weakening of the southwesterly wind and resulting weak monsoon band toward the Korean Peninsula. The GC3.1 is known to have improved the model configuration version compared to GC2, such as cloud physics and ocean parameters. We can confirm that the overall improvements of GC3.1 against GC2, especially in pressure, 850 hPa wind fields, and vertical wind shear. Also, the precipitation band stagnant in the south of 30°N in late spring is improved, therefore the biases of rainy onset and withdrawal on the Korean Peninsula are reduced by 2~4 pentad. We also investigate the impact of initialization in comparison with GloSea5 hindcast. Compared with GCs, hindcast results show better simulation within 1 month lead time, especially in pressure and 850 hPa wind fields, which can be expected to the improvement of WNPSH. Therefore, it is expected that the simulation performance of WNPSH will be improved in the result of applying the initialization of GloSea6.