• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.46-51
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• 2007

The fault current limiting characteristics of superconducting fault current limiter(SFCL) using magnetic coupling of two coils were investigated. This SFCL consists of a high-TC superconducting(HTSC) element and two coils with series or parallel connection on the same iron. In normal time, the inner magnetic fluxes generated by two coils are canceled in case that the HTSC element keeps superconducting state. However, in case that the resistance of the HTSC element happens by a short-circuit the magnetic fluxes, not cancelled, induce the voltages across two coils and the fault current can be limited by the impedance of this SFCL. This SFCL has the merit that the operational current of SFCL can be increased higher than the critical current of the superconducting element by adjusting the inductance ratio between two coils. To confirm its operation, the circuit for the fault simulation was constructed. From the measured voltage and current of the SFCL, it was confirmed that the operating current of this SFCL increased more than that of HTSC element's independent operation.

• Computers and Concrete
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• v.1 no.3
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• pp.325-354
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• 2004

Slabs in buildings and bridge decks, which are restrained against lateral displacements at the edges, have ultimate strengths far in excess of those predicted by analytical methods based on yield line theory. The increase in strength has been attributed to membrane action, which is due to the in-plane forces developed at the supports. The benefits of compressive membrane action are usually not taken into account in currently available design methods developed based on plastic flow theories assuming concrete to be a rigid-plastic material. By extending the existing knowledge of compressive membrane action, it is possible to design slabs in building and bridge structures economically with less than normal reinforcement. Recent research on building and bridge structures reflects the importance of membrane action in design. This paper describes the finite element modelling of membrane action in reinforced concrete slabs through optimisation of a simple concrete model. Through a series of parametric studies using the simple concrete model in the finite element simulation of eight fully clamped concrete slabs with significant membrane action, a set of fixed numerical model parameter values is identified and computational conditions established, which would guarantee reliable strength prediction of arbitrary slabs. The reliability of the identified values to simulate membrane action (for prediction purposes) is further verified by the direct simulation of 42 other slabs, which gave an average value of 0.9698 for the ratio of experimental to predicted strengths and a standard deviation of 0.117. A 'deflection factor' is also established for the slabs, relating the predicted peak deflection to experimental values, which, (for the same level of fixity at the supports), can be used for accurate displacement determination. The proposed optimised concrete model and finite element procedure can be used as a tool to simulate membrane action in slabs in building and bridge structures having variable support and loading conditions including fire. Other practical applications of the developed finite element procedure and design process are also discussed.

• Economic and Environmental Geology
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• v.29 no.4
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• pp.483-493
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• 1996

The tectonic environment and source characteristics of the Daebo granitic batholith in the central Ogcheon Belt were investigated based upon major and trace element geochemistry. The batholith is comprised of three granite types; a biotite granite (DBBG), K-feldspar megacryst-bearing biotite granite (DBKG), and a more mafic granodiorite (DBGD). The variations of Na and K in the granites can not be explained by simple fractional crystallization from the same primary magma. The irregular behavior of these alkali elements indicates a variety of source materials or incomplete mixing of different source materials. The large ion lithophile (LIL) element enrichment and low Ta/Hf ratios of the granites are typical characteristics of normal, calc-alkaline continental arc granitoids. Based upon REE patterns of the granites, it seems to be unreasonable to regard the felsic DBBG as a late stage differentiate formed by residual melts after the fractionation of major constituent minerals of the more mafic DBGD. Inconsistent variations in ${\varepsilon}_{Nd}(t)$ and LIL element concentrations of the granites preclude a mixing model between primitive melt and LIL element-enriched upper crustal materials. The irregular geochemical variation of the granites is taken to be largely inherited from an already heterogeneous source region.

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.253-263
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• 2024

Slope stability is generally paid more attention to in slope protection works, especially for slope containing weak layers. Two indexes of safety factor and failure model are selected to perform slope stability. Moreover, the finite element limit analysis method comprehensively combines the advantage of the limit analysis method and the finite element method obtaining the upper and lower bounds of the safety factor and the failure mode under the slope stability limit state. In this study, taking a waste dump containing a weak layer as an engineering background, the finite element limit analysis method is adopted to explore the potential failure mode. Meanwhile, the sensitivity analysis of slope stability is performed on geometrical and geotechnical parameters of the waste dump. The results show that the failure mode of the waste dump slope is two wedges if the weak layer is located on the ground surface (Model A), while the slope can be observed as three wedges failure if the weak layer is below the ground surface (Model B). In addition, both failure modes are highly sensitive to the friction angle of the weak layer and the shear strength of waste disposal, and moderately sensitive to the heap height, the dip angle and cohesion of the weak layer, while the toe cutting has limited effect on the slope stability. Moreover, the sensitivity to the excavation of the ground depends on the location of the weak layer and failure mode.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1289-1292
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• 2006

Potassium(I) with 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate (L) assembles to K($H_2O$)L (L = 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate). It was characterized by single-crystal X-ray diffraction, element analysis, IR and $^1H$ NMR spectroscopy. It crystallizes in the monoclinic space group $P2_1$/n and reveals a seven-coordinate complex. Polyhedra potassium chains, C-H${\cdot}{\cdot}{\cdot}\pi$ and C-H${\cdot}{\cdot}{\cdot}$O and O-H${\cdot}{\cdot}{\cdot}$O hydrogen bonds lead K($H_2O$)L to a three-dimensional network structure. The biological activity of resistance to hypoxia was tested, and the results showed that the biological activity of resistance to hypoxia of K($H_2O$)L is as good as that of its precursor, irisolidone.

• Advances in concrete construction
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• v.9 no.1
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• pp.43-54
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• 2020

This paper presents an innovative stress-function variational approach in formulating the interfacial shear and normal stresses in an externally bonded concrete joint using carbon fiber-reinforced plastic (CFRP) plies. The joint is subjected to surface traction loadings applied at both ends of the concrete substrate layer. By introducing two interfacial shear and normal stress functions on the CFRP-concrete interface, based on Euler-Bernoulli beam idea and static stress equations of equilibrium, the entire stress fields of the joint were determined. The complementary strain energy was minimized in order to solve the governing equation of the joint. This yields an ordinary differential equation from which the interfacial normal and shear stresses were proposed explicitly, satisfying all the multiple traction boundary conditions. Lamination theory for composite materials was also employed to obtain the interfacial stresses. The proposed approach was validated by the analytic models in the literature as well as through a comprehensive computational code generated by the authors. Furthermore, a numerical verification was carried out via the finite element software ABAQUS. In the end, a scaling analysis was conducted to analyze the interfacial stress field dependence of the joint upon effective issues using the devised code.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.47-52
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• 2008

Many researches on fire risk for normal electric wiring have been pursued in advanced countries such as the USA and Japan, but comparative studies of the partial disconnection and normal state of electric wires have not been conducted. Detection system for the cause of partial disconnection is not developed and prevention countermeasure for electrical fire by the cause is not effective. Therefore, in this paper, partial disconnection characteristics on electric wires were derived and analyzed by experiment and electrical-thermal finite element method(Flux 3D) on the model wires which consist of VCTF(PVC insulated PVC sheathed Cap Tyre Flexible Cord, KS C 3304) and IV(lndoorwire PVC, KS C 3302). VCTF is used in wiring portable electric appliances and the IV is used indoors. Interrelationships between partial disconnection premonitory symptom and current were derived and analyzed by the characteristics based on experiments and thermal analysis for electric wire according to current under normal state and 200% overload state of rated current.

• Smart Structures and Systems
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• v.26 no.2
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• pp.157-174
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• 2020

The guided wave technique is commonly used in structural health monitoring as the guided waves can propagate far in the structures without much energy loss. The guided waves are conventionally generated by the surface-mounted piezoelectric wafer active sensor (PWAS). However, there is still lack of understanding of the wave propagation in layered structures, especially in structures made of anisotropic materials such as carbon fiber reinforced polymer (CFRP) composites. In this paper, the Rayleigh-Lamb wave strain tuning curves in a PWAS-mounted unidirectional CFRP plate are analytically derived using the normal mode expansion (NME) method. The excitation frequency spectrum is then multiplied by the tuning curves to calculate the frequency response spectrum. The corresponding time domain responses are obtained through the inverse Fourier transform. The theoretical calculations are validated through finite element analysis and an experimental study. The PWAS responses under the free, debonded and bonded CFRP conditions are investigated and compared. The results demonstrate that the amplitude and travelling time of wave packet can be used to evaluate the CFRP bonding conditions. The method can work on a baseline-free manner.

• Journal of the Korean Society of Visualization
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• v.16 no.2
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• pp.31-37
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• 2018

Ischemic mitral regurgitation (IMR) is the primary mitral valve (MV) pathology in the aftermath of myocardial infarction as a consequence of regional left ventricular (LV) remodeling. We investigated the effect of asymmetric papillary muscle (PM) displacement and annular dilation on IMR development. Virtual MV modeling was performed to create a normal human MV. Asymmetric PM displacement, asymmetric annular dilation, and the combination of these two pathologic characteristics were modeled. Dynamic finite element evaluation of MV function was performed across the complete cardiac cycle for the normal and three different IMR MV models. While the normal MV demonstrated complete leaflet coaptation, each pathologic MV model clearly revealed deteriorated leaflet coaptation and abnormal stress distributions. The pathologic MV model having both asymmetric PM displacement and annular dilation showed the worst leaflet malcoaptation. Simulation-based biomechanical evaluation of post-ischemic LV remodeling provides an excellent tool to better understand the pathophysiologic mechanism of IMR development.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.449-455
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• 2015

In this study we propose a new photonic crystal fiber (PCF) design that simultaneously offers broadband single-mode operation, high birefringence, and large normal dispersion in the optical-communication wavelength regime. The waveguide is based on a hybrid square-lattice PCF (HS-PCF) that has circular air holes of two different diameters alternating in the cladding, plus a pure silica defect at the center. The optical properties of the guided modes are analyzed numerically by the finite-element method (FEM) with a perfectly matched layer as the boundary condition. The optimized HS-PCF has a dispersion coefficient of $-601.67\;ps\;nm^{-1}\;km^{-1}$ and a high birefringence of $1.025{\times}10^{-2}$ at $1.55{\mu}m$. In addition, over the S+C+L+U wavelength bands the proposed HS-PCF with ultraflat birefringence with a slope on the order of $10^{-5}$.