• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2438-2446
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• 2023

To cool down a nuclear reactor core and prevent the fuel damage without a pump-driven active component during any anticipated accident, the passive emergency core cooling system (PECCS) was designed and adopted in an advanced light water reactor, i-POWER. In this study, for a validation of the cooling capability of PECCS, thermal-hydraulic integral effect tests were performed with the ATLAS facility by simulating intermediate and small break loss-of-coolant accidents (IBLOCA and SBLOCA). The test result showed that PECCS could effectively depressurize the reactor coolant system by supplying the safety injection water from the safety injection tanks (SITs). The result pointed out that the safety injection from IRWST should have been activated earlier to inhibit the excessive core heat-up. The sequence of the PECCS injection and the major thermal hydraulic transient during the SBLOCA transient was similar to the result of the IBLOCA test with the equivalent PECCS condition. The test data can be used to evaluate the capability of thermal hydraulic safety analysis codes in predicting IBLOCA and SBLOCA transients under an operation of passive safety system.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.229-234
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• 2012

Operator's action time is evaluated from MAAP4 analysis used in conventional probabilistic safety assessment(PSA) of a nuclear power plant. MAAP4 code which was developed for severe accident analysis is too conservative to perform a realistic PSA. A best-estimate code such as RELAP5/MOD3, MARS has been used to reduce the conservatism of thermal hydraulic analysis. In this study, operator's action time of core cooling recovery operation is evaluated by using the MARS code, which its Fussell-Vessely(F-V) value was evaluated as highly important in a small break loss of coolant(SBLOCA) event and loss of component cooling water(LOCCW) event in previous PSA. The main conclusions were elicited : (1) MARS analysis provides larger time window for operator's action time than MAAP4 analysis and gives the more realistic time window in PSA (2) Sufficient operator's action time can reduce human error probability and core damage frequency in PSA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.386-390
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• 2006

Global consumption of aspheric lens will expand rapidly due to golbal transformation of the electronics based industry to optics based mechatronics. Especially, F-Theta lens is one of important parts in Laser Scanning Unit(LSU) because it affects the optical performance of LSU dominantly. Non axisymmetric machine based processing techologies are required to obtain high accuracy in utlra-precision aspheric core, the most important component in plastic injection molded F-Theta lens assembly. In this study, the core with non-axisymmetric aspheric shape which is used to emit the F-Theta lens was processed using the ultra precision processing technology and the shape accuracy of the core was measured. And the results there of were evaluated and compared with the emitted shape accuracy of F-Theta lens.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.368-370
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• 2005

Superconducting fault current limiter (SFCL) provides the effect such as enhancement in power system reliability due to limiting fault current in a few miliseconds. The flux-lock type SFCL among various type SFCLs consists of two coils wound on the same iron core and a component using the YBCO thin film. In the SFCL, operation characteristics can be controlled by adjusting the inductances and the winding directions of the coils. In this paper, we investigated the various fault current limiting characteristics according to the voltage level. To analyze the current limiting performance, we compared operational characteristics on the subtractive polarity winding direction on in case of open-loop iron core.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.295-295
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• 2006

In present study, poly(acrylic acid) (PAA) and hydrophobically modified poly(ethylene oxide) (HM-PEO) multilayers based on the hydrogen bonding between the component polymer pair have been prepared by the LbL deposition method. Dip assembled HM-PEO/PAA multilayers yield unique film morphologies in comparison with PEO/PAA multilayers due to the micellar formation of HM-PEO owing to the hydrophobic attraction between alkyl chains end-capped with the PEO chains. Individual HM-PEO micelles were connected through the bridging PEO chains to form temporary networks on multilayer surface and induced peculiar surface morphology on HM-PEO/PAA multilayers above the critical number of bilayers.

• Nuclear Engineering and Technology
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• v.29 no.5
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• pp.375-384
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• 1997

Relative power density distributions of the Kori Unit 1 pressurized water reactor are calculated by Monte Carlo modeling with the MCNP code. The Kori Unit 1 core is modeled on a three-dimensional representation of the one-eighth of the reactor in-vessel component with reflective boundaries at 0 and 45 degrees. The axial core model is based on half core symmetry and is divided into four axial segments. Fission reaction density in each rod is calculated by following 100 cycles with 5,000 test neutrons in each cycle after starling with a localized neutron source and ten noncontributing settle cycles. Relative assembly power distributions are calculated from fission reaction densities of rods in assembly. After 100 cycle calculations, the system converges to a k value of 1.00039 $\geq$ 0.00084. Relative assembly power distribution is nearly the same with that of the Kori Unit 1 FSAR. Applicability of the full-scope Monte Carlo simulation in the power distribution calculation is examined by the relative root moan square error of 2.159%.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.695-696
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• 2008

This paper deals with the reduction of DC component of cogging toruqe by using the heat treatment of the stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress at the edge of stator tooth induces significant plastic and elastic deformation and influences magnetic properties. Then, these phenomenon in the sheared region has influence on the magnetic unbalance in the air-gap of motor. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation and proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.42.3-43
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• 2016

We present multiband photometric analyses of 10 core-collapse supernovae in the near-infrared and visible wavebands. Our infrared data is from observations of the supernovae using the Wide Field Infrared Camera at the Palomar 5-m telescope as part of the Caltech Core-Collapse Supernova Program, while we obtain the visible data from publicly available data base. By fitting the broadband spectral energy distribution with a black body and, when necessary, modified black body component, we estimate physical parameters of the supernovae more accurately and also conduct a systematic investigation of when the supernovae show any indication of dust formation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.4
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• pp.29-35
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• 2014

The purpose of high frequency transformer in the inverter is to reduce the voltage and current stresses of switch components when it operates at the large conversion ratio. But the loss of transformer is the major contributor in the efficiency of inverter. This paper presents the method of core design to minimize the loss of transformer. The total loss of transformer is minimized by adjusting the effective cross-sectional areas of core. The component ratio of losses are compared by using the finite-element analysis.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2007.11a
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• pp.82-82
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• 2007