• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.46.3-47
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• 2016

We construct a solar eruption model with a background solar wind by performing three-dimensional zero-beta magnetohydrodynamic (MHD) simulation. The initial configuration of a magnetic field is given by nonlinear force-free field (NLFFF) reconstruction applied to a flux emergence simulation. The background solar wind is driven by upflows imposed at the top boundary. We analyzed the temporal development of the Lorentz force at the flux tube axis. Based on the results, we demonstrate that a solar eruption is caused by the imbalance between magnetic pressure gradient force and magnetic tension force. We conclude that this imbalance is produced by a weak but continuously existing solar wind above an active region.

• Steel and Composite Structures
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• v.20 no.6
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• pp.1221-1236
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• 2016

Modular structures consist of standardized modules and their connections. A modular bridge pier is proposed to accelerate bridge construction. Multiple concrete-filled steel tubes (CFTs) using commercial steel tubes were chosen as the main members. Buckling restrained bracings and enhanced connection details were designed to prevent premature low-cycle fatigue failure upon cyclic loading. The pier had a height of 7.95 m, widths of 2.5 m and 2.0 m along the strong and weak axis, respectively. Cyclic tests were performed on the modular pier to investigate structural performance. Test results showed that four CFT columns reached yielding without a premature failure of the bracing connections. The ultimate capacity of the modular pier was reasonably estimated based on the plastic-hinge-analysis concept. The modular CFT pier with enhanced bracing showed improved displacement ductility without premature failure at the welding joints.

• Steel and Composite Structures
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• v.17 no.6
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• pp.951-965
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• 2014

Point bending is commonly used for cambering and curving steel girders to large radii. In this system, a hydraulic ram or press is used to apply concentrated loads at selected points to obtain the required vertical (cambering) or horizontal (curving) curved profile from induced permanent deformations. This paper derives closed form solutions that relate loads to permanent deformations for horizontally curving wide flange steel beams based on their post-yield response. These solutions are presented in a parametric form to identify the relationship between key variables and their impact on the accuracy of the curving operation. It is shown that point bending could yield parabolic curved profiles that are within 1% of a desired circular curve if the span length to radius of curvature ratio (L / R) is less than 1.5 and the point loads are spaced at one third the beam length. Safe limits are then established on loads, strains and curvatures to avoid damaging the steel section. This leads to optimization of the point bending operation for inducing a circular profile in wide flange steel beams of any size.

• Journal of the Korean Geophysical Society
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• v.6 no.2
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• pp.89-97
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• 2003

For safety evaluation of a rockfill dam, it is often necessary to investigate spatial distribution and dynamic characterization of weak zones such as fractures. For this purpose, both seismic and electric methods are adopted together in this research. The former employs the multichannel analysis of surface waves (MASW) method, and aims at the mapping of 2-D shear-wave velocity (Vs) profile along the dam axis that can be associated with dynamic properties of filled materials. The latter is carried out by DC- resistivity survey with a main purpose of mapping of spatial variations of physical properties of dam materials. Results from both methods are compared in their signature of anomalous zones. In addition, downhole seismic survey was carried out at three points within the seismic survey lines and results by downhole seismic survey are compared with the MASW results. We conclude that the MASW is an efficient method for dynamic characterization of dam-filling materials, and also that joint analyses of these two seemingly unrelated methods can lead to an effective safety evaluation of rock-fill dam.

• Journal of Powder Materials
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• v.8 no.1
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• pp.61-69
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• 2001

Spark-Plasma Sintering(SPS) is one of the new sintering methods which takes advantages both inconventional pressure sintering and electric current sintering. It is known that SPS is very effective for the densification of hard-to-sinter materials like refractory metals, intermetallic compounds, glass and ceramics without grain growth. However, a clear explanation for sintering mechanism and an experimental evidence for the formation of weak plasma during SPS are not given yet. In this study, fundamental study on sintering behavior and mechanism of SPS was investiged. For this study, various spherical Fe powders were prepared such as as-received, as-reduced, and as-oxidized and then sintered by SPS facility. In order to confirm the surface cleaning effect during SPS neck region and fracture surface of sintered body was observed and analyzed by SEM/EPMA. Densification behavior was analyzed from the data of deflection along the pressure axis. Some specimens were additionally produced by Hot Pressing and the results were compared with those of SPS.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1561-1565
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• 2018

The dielectric properties of the uniaxial relaxor ferroelectric $Sr_xBa_{1-x}Nb_2O_6$ with x = 0.75 were investigated along the polar [001] direction as a function of temperature. The capacitance maximum showed the frequency dispersion commonly observed in relaxors. Additional weak dielectric anomalies were observed in the paraelectric phase; they were only seen during the heating process and disappeared upon subsequent cooling. These were attributed to the existence of large polar clusters strongly pinned at defects and/or to random fields and their metastable characters. Aligning the ferroelectric domains along the polar axis at room temperature removed the high-temperature dielectric anomalies. The dependences of the capacitance and the dielectric maximum temperature on the magnitude of the poling field were investigated.

• Archives of Pharmacal Research
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• v.8 no.3
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• pp.139-147
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• 1985

Americal A from the seeds of Phytolacca americana, was investigated for the antiinflammatory activity. The compound significantly inhibited edema induction, granuloma formation, arthritis induction and leucocyte emigration in CMC-pouch. But its anticarrageenin activity was not exhibited in adrenalectomized rats. These findings together with decrease in the contents of ascorbic acid and cholesterol in adrenals by administration of the compound suggest that its activity is mediated through stimulation of the pituitary-adrenal axis. The acute toxicity of the compound is very weak and gastric ulceration was not produced by the compound.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.37-45
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• 2009

An objective of this study is to evaluate the structural performance of the weak axis SRC column-RC beam joints by experiments. Although one of common joint types is the connection with standard hooks, it has been required to examine its safety and to settle problems of the joint among practical engineers. Specimen types are classified into two categories, namely the type of standard hook and the type of shape improvement. The first one is consisted of three specimens which are reference type, development length modification type, and development length supplement type. Three specimens for shape improvement were made with variations on the arrangement of longitudinal reinforcements and the development length. Test results based on cyclic loadings were discussed with load-deflection curves, maximum strengths, strength degradations beyond the maximum. It was found that the standard hook types showed premature failures and consequent strength degradations due to splitting of joint concrete. However, satisfactory performance was obtained with the shape improvement type with wing-plate welding. No premature failures and strength degradations were detected with the specimens.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.4
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• pp.509-518
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• 2019

Analyses with various Sea Surface Temperature (SST) products indicate that the interannual variability of the area-averaged SST in the East/Japan Sea (EJS) is well correlated to that of Pacific Decadal Oscillation (PDO) during 1979-2018, especially in the autumn. The regression analysis with the wind vectors at 200 hPa, where the strongest jet stream flows, suggests that the long-term variability of the intensity as well as the meridional movement of the jet stream are related to the coupling of the autumn EJS SST and PDO. When the axis of the jet stream moves poleward (equatorward) with its weakening (strengthening), both the EJS SST and North Pacific SST increase (decrease). This suggests that both the intensity and meridional movement of the jet stream are possibly related to the coupling of the autumn EJS SST and PDO. However, effects of a weak jet stream during the summer and the strong East Asian winter monsoon make weak coupling between the EJS SST and PDO.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.1
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• pp.1-6
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• 1995

A recording current meter was deployed in the shallow western part of Deukryang Bay from 1 July to 7 August 1992 during which the wind was weak. Principal component in NNE-SSW direction parallel to the axis of the bay had $98.7\%$ of the total variance and the orthogonal component of only $1.3\%$. Spectral analysis of the principal component revealed that the semidiurnal component comprised about $91.2\%$ of total energy. Whereas the diurnal and longer components were less than $2.5\%$ the shallow water tide was about $6.3\%$ . Weak mean current of 0,8cm/sec in SSE direction implies that the slow circulation in the bay is counterclockwise having the northward net flow in the deep eastern part.