• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.11-14
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• 2003

The magnetization and self-field losses of the four technical high-T$_{c}$ superconducting tapes have been investigated experimentally. The results show that the magnetization losses for parallel or perpendicular fields can be well predicted from the slab model or the strip model for a filamentary region. However the magnetization losses for longitudinal fields can be rather predicted by the slab model for a decoupled filament. The self-field losses are well explained by the Norris ellipse model.l.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.1-6
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• 2009

We report a successful fabrication of $high-J_c\;NdBa_2Cu_3O_{7-{\delta}}$ (NdBCO) films on $SrTiO_3$(STO) (100) substrates by pulsed laser deposition (PLD) in a relatively wide processing window. Under various oxygen pressures controlled by either 1%$O_2$/Ar mixture gas or pure $O_2$ gas, strongly c-axis oriented NdBCO films were grown at the substrate temperature $(T_s)\;of\;800^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas and also in 400 and 800 mTorr with pure $O_2$ gas. These samples exhibited $T_c$ values over 90K and $J_c$ values of $2.8-3.5MA/cm^2$ at 77K in self-field (77K, sf). On the other hand, $J_c$ values over $1A/cm^2$ were obtained at the temperature regions of $700-830^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas at those of $750-830^{\circ}C$ in 800 mTorr with pure $O_2$ gas. Unlike previous reports, resent results support that the PLD processing window for high-Jc NdBCO films is not narrow.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.373-376
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• 2004

전력전자 회로의 고속화에 따라 정류기의 역할은 점차 중요해지고 있다. 전원장치의 compact화 및 초소형화에 따라 스위칭 주파수는 높아지고 있다. 최근 전원장치의 on-line 뿐만 아니라 off-line에서의 효율을 향상시키려면 도통손실 및 스위칭 손실을 최소화를 요구받고 있다. 스위칭 주파수가 증가함에 따라 power rectifier는 도전 및 스위칭 손실의 최소화를 위해서는 스위칭 손실의 주된 원인인 역회복 특성을 잘 파악해야 한다. 이를 위해 본 고에서는 최근 제작된 SiC SBD의 역회복 특성을 분석을 위한 $t_{rr}$, 측정을 위한 $t_{rr}$ Tester를 MIL-STD-750-4031.4에 참고하여 제작하였으며, 제작된 $t_{rr}$ Tester를 이용하여 SiC SBD의 $t_{rr}$의 측정결과에 대해 기술하였다.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.4-4
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• 2004

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.6
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• pp.249-256
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• 2003

Samples with the nominal composition, Ag-$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+{\delta}}$ high $T_{c}$ superconductors containing Ag as an additive were fabricated by a solid-state reaction method. Samples with Ag of 10 wt%, 30 wt%, and 50 wt% each were sintered at $860^{\circ}C$~$870^{\circ}C$ for 24 hours. The structural characteristics, the microstructures and the critical temperature with respect to the each samples were investigated by XRD, four-prove methode, SEM and EDS respectively. The $T_{c}\;^{zero}$ of the sample with the 50 wt% Ag additive at the surface showed 94 K.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.749-755
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• 2002

The effects of noble gas (such as helium, neon, argon, krypton, and xenon) on the sonolytic decomposition of water and 2-methyl-2-propanol(t-butanol) with 200 KHz high power ultrasound were investigated. The physical properties of the noble gas have an effect on the formation rate of products $(H_2O_2,\;H_2,\;O_2)$ and the decomposition rate on the sonolytic decomposition of water. The pyrolysis products, such as methane, ethane, ethylene, and acetylene are formed during the sonolytic decomposition of t-butanol. From the estimation of the ratio $[C_2H_4+C_2H_2] / [C_2H_6]$, the cavitation temperature would be varied by the used noble gas. In all cases for the sonolytic decomposition of water, t-butanol, and diethyl phthalate, the decomposition rates were xenon > krypton > argon > neon > helium with a significant difference and were closely correlated with the formation rate of OH radical and high temperature inside the cavitation bubble under each noble gas.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.1012-1019
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• 2013

Recently, awareness of noise is increased and high performance sound insulation performance wall is designed. But in spite of installing high performance sound insulation performance wall, sound insulation performance in space is reduced by door. In this study, Sound insulation performance of doors which commonly used in buildings was measured to analyze current situation in the field and effect of method which increase sound insulation performance is analyzed quantitatively. As a result, sound insulation performance of doors which commonly used in buildings is FSTC 17~29 and can be increased about 2~3 dB by install rubber seal or mohair.

• International Journal of High-Rise Buildings
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• v.4 no.4
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• pp.271-281
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• 2015

This paper introduces detailed three-dimensional numerical analyses on a bored pile foundation for a high-rise building. A static load test was performed on a test pile and a numerical model of a single pile, which was calibrated by comparing it with the test result. The detailed numerical analysis was then conducted on the entire high-rise building foundation. Further study focused on soil pressures under the base slab of a piled raft foundation. Total seven cases with different pile numbers and raft-soil contact conditions were investigated. The design criteria of a foundation, especially settlement requirement were satisfied even for the cases with fewer piles under considerable soil pressure beneath the base slab. The bending moment for the structural design of the base slab was reduced by incorporating soil pressures beneath the base slab along with bored piles. Through the comparative studies, it was found that a more efficient design can be achieved by considering the soil pressure beneath the slab.

• Horticultural Science & Technology
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• v.32 no.1
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• pp.1-9
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• 2014

This study investigated the effects of temperature on the shoot growth and flowering of potted kumquat [Fortunella margarita ( Lour.) Swingle] trees grown in subtropical conditions of I-Lan County in Taiwan. Temperature treatments included T 25-32, T 17-25, T 22, and T 18. The T 25-32 treatment trees were to the day/night temperatures of $25/18^{\circ}C$ for 2 weeks, followed by 28 weeks at $32/25^{\circ}C$. T 17-25 was exposed for 4 weeks to $17/10^{\circ}C$ followed by 26 weeks at $25/18^{\circ}C$. T 22 and T 18 were exposed at $22/18^{\circ}C$ and $18/13^{\circ}C$, respectively, for the entire duration of the experiment. Control trees were placed in a plastic greenhouse under conditions similar to the natural environment. The kumquat trees exposed to high-temperature environment of $32/25^{\circ}C$ showed more frequent and speedy sprouting of new buds, but induced the earlier termination of shoot elongation growth, resulting in decreased vegetative growth. The temperature treatments lower than $22^{\circ}C$ suppressed the new shoot production but increased the shoot growth period, resulting in increased shoot length and diameter. Temperatures higher than $25/18^{\circ}C$ readily induced flowering, with flowering being advanced under the higher temperature conditions such as $32/25^{\circ}C$. However, flowering was substantially inhibited under temperature conditions lower than $22/18^{\circ}C$, indicating the negative role of relatively lower temperatures on flowering of kumquat trees.

• Progress in Superconductivity
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• v.6 no.1
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• pp.89-94
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• 2004

The policrystalline$SmBa_2$$Cu_2$$O_{y}$ was synthesized by the solid state reaction method. The dependence of AC susceptibility on temperature and applied ac field was studied. The critical temperature $T_{c}$ is about 92 K. As the ac field is increased, the slope and the value of real part of susceptibility become smaller and the peak position of imaginary part $T_{P}$ was shifted to a lower temperature with peak broadening. Using Bean's model, we determined intergrain critical current density $J_{c}$ and obtained $44 A/{cm}^2$ at 75 K. From the relation of the $J_{c}$ (T)=($1-T/T_{c}$ )$^{\beta}$ we obtained $\beta$=0.8 and found that the Josephson junction type of the $SmBa_2$$Cu_2$$O_{y}$ is SIS junction. The peak of the imaginary part shifts to higher temperature with increasing frequency, f. from Arrhenius plot, we obtained the activation energy of about 0.96 eV.