• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.70-73
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• 2023

To improve superconductor properties, the size of the crystal grains of the superconductor should be adjusted, the amount of electricity flowing through the superconductor should be increased, and the superconductor should be designed to withstand external magnetic fields. It is necessary to control the microstructure so that many flux pinning centers are developed inside the superconductor so that defects are generated physically or chemically, and the micro secondary phase for trapped magnetic flux must be dispersed inside the superconductor. In order to measure the superconducting magnetic force of the superconducting bulk in a simplified manner, the superconducting magnetic force was analyzed using an Nd-Fe-B permanent magnet of 3.80 kG. In particular, by delaying the growth of partially melted Y₂BaCuO₅ particles, we devised a plan to refine Y₂BaCuO₅ particles to effectively improve superconducting magnetic force, and analyzed superconducting magnetic force in a single crystal YBa₂Cu₃O_7-y superconducting bulk using a gauss meter. The melted superconducting bulk traps 80% or more of the applied magnetic field, and can be used as a bulk magnet of high magnetic field magnetization applicable to electric power equipment.

• Membrane and Water Treatment
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• v.4 no.2
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• pp.143-155
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• 2013

Four membranes were used to separate Chlorella sp. from their culture medium in cross-flow microfiltration (MF) experiments: cellulose acetate (CA), cellulose nitrate (CN), polypropylene (PP) and polyvinylidenefluoride (PVDF). It was found that the hydrophilic CA and CN membranes with a pore size of 1.2 ${\mu}m$ exhibited the best performances among all the membranes in terms of permeation flux. The hydrophobicity of each membrane material was determined by measuring the angle between the water (liquid) and membrane (solid). Contact angle measurements showed that deionized (DI) water had almost adsorbed onto the surfaces of the CA and CN membranes, which gave $0.00^{\circ}$ contact angle values. The PP and PVDF membranes were more hydrophobic, giving contact angle values of $95.97^{\circ}$ and $126.63^{\circ}$, respectively. Although the pure water flux increased with increasing pore diameter (0.8 < 1.2 < 3.0 ${\mu}m$) in hydrophilic CA and CN membranes, the best performance in term of filtration rate for filtering a microalgae suspension was attained by membranes with a pore size of 1.2 ${\mu}m$. The fouled membrane pore sizes and pore blocking were inspected using a scanning electron microscope (SEM). MF with large pore diameters was more sensitive to fouling that contributed to intermediate blocking, where the size of the membrane pores is almost equivalent to that of cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.11-20
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• 2002

This paper describes the magnetic flux leakage(MFL) type non-destructive testing(NDT) system to detect the 3D defects on underground gas pipe. Magnetic systems with permanent magnets and yokes are analyzed by 3D non-lineal finite element method(FEM) with optimum design. In case of under-saturation of gas pipe, sensing signals are too weak to detect. In case of over-saturation, the changes of the sensing signals are too low to detect the defects sensitively. So, the operating points of the magnetic system are optimized to increase the changes of the MFL signals. The effects of the depth and size of the defects on the sensing signals are analyzed to define the range and resolution of the MFL sensors. To increase the sensor's sensitivity, the back-yoke sensors are introduced and tested.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.34-41
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• 2021

A commercial HVOF torch (originally designed for coating applications) has been modified as a high temperature flow source for material testing. In this study, a water cooled commercial Gardon gauge was used to measure heat fluxes at four locations away from the nozzle exit. The cooling water temperature data were used to calculate calorimetric heat fluxes at the same locations. The heat fluxes from both methods were compared and the calorimetric heat fluxes were found to be many times higher than the Gardon gauge heat fluxes. A hypothesis is applied to the calorimetric method to understand the discrepancy seen between the methods. The Gardon gauge heat fluxes are seen to be in the range of the hypothesized calorimetric calculations. This can be considered as a considerable validation for the hypothesis, but further refinement needed using appropriate numerical models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.114-114
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• 2009

ZnO has received considerable attention due to its potential applicability to optoelectronic devices such as ultraviolet-light emitting diodes (UVLEDs) and laser diodes (LDs). As well known, however, polar ZnO with the growth direction along the c-axis has spontaneous and piezoelectric polarizations that will result in decreased quantum efficiency. Recently, nonpolar ZnO has been studied to avoid such a polarization effect. In order to realize applications of nonpoar ZnO-based films to LEDs, growth of high quality alloys for quantum well structures is one of the important tasks that should be solved. $Mg_xZn_{1-x}O$ and $Cd_xZn_{1-x}O$ is ones of most promising alloys for this application because the alloys of ZnO with MgO and CdO provide a wide range of band-gap engineering spanning from 2.4 to 7.8 eV. In this study, we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios. The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). With the relatively low Mg/Zn flux ratios, a typical striated anisotropic surface morphology which was generally observed from the nonpolar (11-20) ZnO film on r-plane sapphire substrates. By increasing the Mg/Zn flux ratio, however, additional islands were appeared on the surface and finally the surface morphology was entirely changed, which was generally observed for the (0001) polar ZnO films by losing the striated morphology. Investigations by X-ray $\Theta-2{\Theta}$ diffraction revealed that (0002) and (10-11) ZnO planes are appeared in $Mg_xZn_{1-x}O$ films by increasing the Mg/Zn flux ratio. Further detailed investigation by transmission electron microscopy (TEM) and photoluminescence (PL) will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.20-21
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• 2005

[ $BaZrO_3$ ], nanopowder was added to YBCO powder to make ($BazrO_3)_x(YBCO)_{(100-x)mol.-%}$ ($BZO_x$-YBCO) ($0{\leq}x{\leq}10$) composite targets fur pulsed laser deposition of superconducting layer in order to investigate the effect of the addition of BZO nanopowder in the YBCO target on the flux pinning properties of $BZO_x$-YBCO thin films. All the $BZO_x$-YBCO thin films were grown on single crystal STO substrate under similar conditions in the PLD chamber. The effect of YBCO targets doped with BZO on the flux pinning properties of $BZO_x$-YBCO thin films has been investigated comparatively. The isothermal magnetizations M(H) of the films were measured at temperatures between 5 and 80 K in fields up to 5 T, employing a PPMS. The optimal amount of BZO nanopowders in $BZO_x$-YBCO thin films to obtain the strongest flux pinning effects at high magnetic fields is about 6 mol.-%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.255-256
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• 2006

In this paper, we investigated the. characteristics of fault current limiting according to fault angle in the integrated three-phase flux-lock type SFCL in fault types such as the single-line-to-ground fault, the double-line-to-ground fault and the three-line-to-ground fault. When the SFCL is operating under normal condition, the magnetic flux generated between primary and secondary coils of each single phase is canceled out perfectly, so that the impedance of the SFCL is also not generated and the power system can be operated normally without any loss, However, if a fault occurs even in any phase out of three phases, quench happened in SFCL elements and the current flowing secondary coil is restricted abruptly. Finally, the balance of magnetic flux in whole SFCL system is destroyed, and the fault currents in every phase could be limited at the same time irrespective of the fault types. As a result, the developed SFCL in this study were operated normally as expected and the purpose of the integration of 3 phase current limiting was also achieved successfully. However, the fault current limiting characteristics of the SFCL was dependant on the quench characteristics of HTSC elements in each phase, and it was expected that the improvement of the SFCL could be possible through the introduction of HTSC elements which have better critical characteristics.

• Economic and Environmental Geology
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• v.53 no.5
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• pp.543-552
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• 2020

In this study, we measured groundwater fluxes with a passive flux meter and a borehole dilution test in the Upper Floridan Aquifer. In addition, the feasibility of the passive flux meter is also evaluated within matrix and non-matrix zones. The results of the PFM (5.96 ± 1.75 cm/day) showed good agreement with those of the BHD (4.68 ± 2.99 cm/day) in matrix zones, whereas the results of the PFM (9.94 ± 0.90 cm/day) showed poor agreement with those of the BHD (1817.37 ± 1795.50 cm/day) in non-matrix zones. We assumed that the groundwater passes through the sorbent material inside the PFM. However, it could not pass through the sorbent when the groundwater flux is faster than 11 cm/day. The flow might bypass between monitoring well and the PFM. The PFM used in this study might be suitable for measuring the groundwater fluxes under 11 cm/day. Therefore, more extensive research is needed in the future to measure fast groundwater fluxes (> 11 cm/day).

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.81-88
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• 2009

This study has shown the tendency to enhance Sand Flux, a device of separating screening the foreign matter, for the recycling of construction waste possible to improve the quality of wet type production system meaningfully as part of research. As a result of experiment on the basic material properties, this study had a tendency to improve the quality and performance significantly in case of absolute surface dried density, 0.08mm sieve throughput, volume of clay lumps, and content of organic foreign matter. In addition, as a result of examining the quality characteristics of mortar, this study has shown the tendency that the flow and compressive strength more increased than the mortar using RS-II by utilizing RS-VI recycled sand produced finally through the device Sand Flux. As for the shrinkage properties, this study has shown the character the generation rate of crack of mortar using RS-IV recycled sand produced finally through the device Sand Flux.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.211-221
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• 2012

The ascidian Styela clava has been one of the favorite seafood in Korea. Suspended culture of Styela clava was initiated in 2001 and the annual production reached 15,084 M/T, but declined to 2,655 M/T in 2011. In order to solve this problem, it is necessary to estimate the material balance according to the farm-environment. Vertical particulate fluxes and release fluxes were estimated at 2 stations, an ascidian farm (AF) and a non-cultivated area (control) in Jindong Bay. An in-situ benthic chamber(BelcI) was used in summer and winter season. The sedimentation fluxes of organic carbon were 72 mmol C $m^{-2}\;d^{-1}$, 93 mmol C $m^{-2}\;d^{-1}$, 34 mmol C $m^{-2}\;d^{-1}$ in Jul. AF, Feb. AF, Feb. control. The organic carbon oxidation rates were 13 mmol C $m^{-2}\;d^{-1}$, 81 mmol C $m^{-2}\;d^{-1}$, 31 mmol C $m^{-2}\;d^{-1}$, in each. The release fluxes of nutrients followed the general pattern, well. Consequently, the ratio of the organic carbon burial fluxes were 20:4:1, in each. By the estimation of the carbon circulation, it could be a scientific basis to analyze the reason of production decline for cultivated organism.