• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.96-103
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• 2019

In this study, a comparison was conducted to verify the propellant isolation assembly of the Korea Pathfinder Lunar Orbiter (KPLO). An engineering validation model (EVM) is being developed to simulate the flow of the flight model. Three factors were selected for comparison: the total pressure drop during propellant isolation assembly, the waterhammer by driving thruster valve, and the orifice set up for flow control and damping the waterhammer. The analysis results are compared with EVM test results. In the future, backup data to confirm the design will be established.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.963-971
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• 2022

Water pipeline network in local and metropolitan area is buried underground, by which it is hard to know the degree of pipe aging and leakage. In this study, assuming various sensor combinations installed in the water pipeline network, the optimal algorithm was derived by predicting the water flow rate and pressure through artificial intelligence algorithms such as linear regression and neuro fuzzy analysis to examine the possibility of detecting pipe leakage according to the data combination. In the case of leakage detection through water supply pressure prediction, Neuro fuzzy algorithm was superior to linear regression analysis. In case of leakage detection through water supply flow prediction, flow rate prediction using neuro fuzzy algorithm should be considered first. If flow meter for prediction don't exists, linear regression algorithm should be considered instead for pressure estimation.

• Bangmulgwan gwa yeongu (The National Museum of Korea Journal)
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• v.1
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• pp.234-257
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• 2024

Great Dharani Sutra of Undefiled Pure Light (Gwi) (LKH 10703) donated by the family of the late Lee Kun-Hee to the National Museum of Korea in 2021 is a calligraphy album consisting of sixty-two leaves compiled using butterfly binding. It contains Great Dharani Sutra of Undefiled Pure Light, "Record of the Production of Mugujeong Pagoda by the Order of King Munseong," a postscript by Kim Jeonghui, and an appreciation record by Oh Sechang. This paper has revealed that this album is identical to the material that Suematsu Yasukazu introduced in Volume 15 of the journal Cheonggu hakchong in 1934 and that it includes elaborate copies of Great Dharani Sutra of Undefiled Pure Light and "Record of the Production of Mugujeong Pagoda by the Order of King Munseong" on yellow Chinese paper, both of which were excavated from inside the Mugujeong Pagoda at Changnimsa Temple in Gyeongju in 1824. It has also reconfirmed that it is highly probable that the Great Dharani Sutra of Undefiled Pure Light that Jo Byeongsun, the former director of the Seongam Old Books Museum, unveiled in 1998, is a transcription of the original sutra excavated from Mugujeong Pagoda at Changnimsa Temple in Gyeongju. Moreover, it has concluded that the Great Dharani Sutra of Undefiled Pure Light owned by Park Cheolsang is likely to be another example of copying the transcription of the original sutra excavated from the Mugujeong Pagoda at Changnimsa Temple in Gyeongju. In the album of copies donated by the estate of Lee KunHee, six of the Chinese characters promulgated by Empress Wu were used fifteen times in total. Four of the characters of Empress Wu were utilized ten times in the Great Dharani Sutra of Undefiled Pure Light (national treasure, Bulguksa Temple collection) found among the reliquaries from the Three-story Stone Pagoda at Bulguksa Temple in Gyeongju and were also seen in the album of copies donated by the estate of Lee Kun-Hee. The use of the same characters of Empress Wu and other variant characters suggests that both the album of copies donated by the estate of Lee Kun-Hee and the Bulguksa sutra were based on an edition distributed in the Unified Silla Period during the eighth century. Kim Jeonghui confirmed the exchange of calligraphy between Korea and China through studies on bronze and stone epigraphs. He believed that the Great Dharani Sutra of Undefiled Pure Light and "Record of the Production of Mugujeong Pagoda by the Order of King Munseong" excavated from Mugujeong Pagoda at Changnimsa Temple were authentic materials showing the elegant calligraphic styles that prevailed before the Ouyang Xun style. Thus, the album of copies donated by the estate of Lee Kun-Hee holds great historical and artistic significance in that it is a rare example of Kim Jeonghui's evidential study of a transcribed sutra and an original record of the production of a pagoda from the Unified Silla period.

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.53-68
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• 2015

Longitudinal strain is an important component of seismic design for buried pipelines. A design procedure which determines the wavelength from site natural period and shear wave velocity of the soil layer and closed-form solutions of pipelines under a harmonic motion is typically used in design. However, the applicability of the procedure has not yet been thoroughly investigated. In this paper, displacement-time histories extracted from 1D site response analyses are used in 3D shell-spring model to accurately predict the response of pipelines. The results are closely compared to those from the design procedure. The area of interest is East Siberia. Performing a site response analysis to determine site specific displacement time history is highlighted. The site natural period may be used to predict the predominant period of the acceleration time history, but cannot be used to estimate the predominant period of the displacement time history. If an accurate estimate of the predominant period of the displacement time history is provided, it is demonstrated that the design equation can be successfully used to predict the response of pipelines.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.67-76
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• 2008

A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), has been constructed at KAERI (Korea Atomic Energy Research Institute). Recently several integral effect tests for the reflood period of a LBLOCA (Large Break LOss of Coolant Accident) of the APR1400 have been performed with the ATLAS. In the APR1400 a high flow condition is changed to a low flow condition due to an fluidic device during an operation of the SIT. As the self-controlled fluidic device was not installed in the ATLAS, a set of characterization tests was performed to simulate its injection capability from the SIT for the APR1400 simulation. In the ATLAS the required SIT flow rate in the high flow condition was acquired by installing orifices with an optimized flow area to throttle the SIT discharge line and the low flow condition was achieved by changing the opening of the flow control valve in the SIT injection line. The test results showed that the safety injection systems of the ATLAS could simulate the required high and low flow rates of the SIT for the APR1400 simulation efficiently.

• Journal of IKEEE
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• v.19 no.3
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• pp.282-287
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• 2015

In this study, an optical fiber detector was constructed by using a Ce:GAGG scintillator, optical fiber, and photomultiplier. The single crystal size of the scintillator was set to $3{\times}3{\times}20mm^3$ after simulating the counting efficiency of gamma rays in the scintillator by using the MCNPX code. The constructed detector used the standard gamma ray sources $^{137}Cs$ and $^{133}Ba$ to measure radiation and analyze the spectral characteristics of gamma rays. The resulting trend curve showed excellent linearity with an R-squared value of 0.99741, and the detector characteristics were found to vary 2% or less with distance based on comparison with the MCNPX value. Furthermore, the spectroscopic analysis of the gamma ray energy from the single-ray and mixed-ray sources showed that $^{137}Cs$ had its peak energy at 662 keV, and $^{133}Ba$ had at 356 keV. It seems that if the fiber-optics detector is used, working hours and exposure of worker can be reduced.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.1-8
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• 2001

This study was carried out for the purpose of determination of maintenance period and investigation of weak point due to freeze when the gas heater of KOGAS valve station Is not operated in winter season. 3-dimensional non-linear numerical simulation was conducted in order to predict the time and location which bath water in heater reaches to ice point. FLUENT V 5.0, commercial code, is used for thermal fluid flow analysis. We thought this was problem of heat conduction solving the energy equation and modeled gas heater by using the real geometry and scale for performing the 3-dimensional simulation. It was analyzed complex heat transfer phenomena considering convection due to air on surface, conduction in insulation material, natural convection of liquid in heater and heat loss through the pipe.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.103-112
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• 2007

Flood issue for nuclear power plants designed and built in 1970 is extremely severe for main steam header compartment and main feedwater line region of intermediate building and lower floor. A calculation for flood level at the main feedwater line isolation compartment is now performing by hand calculation. But, this methodology is quite conservative assumption. The goal of this study was to develop method to analyze flowrate using the RETRAN-3D computer code, and the developed method was applied to flood level analysis following main feedwater line break. As a result of analysis, flood level was low remarkably.

• Fire Science and Engineering
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• v.17 no.3
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• pp.61-73
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• 2003

Most of the accidents occurred from the chemical plants are related to the catastrophic gas release events when the large amount of toxic materials is leaked from its storage tank or transmitting pipe lines. In this case, the greatest concerns are how the spreading behaviors of leakages are depended on the ambient conditions such as air stability and other environmental factors. Hence, we have focused on the risk assessments and consequential analysis for chlorine as an illustrative example. As appeared in the result, Fire & Explosion Index depicted it a bit dangerous with presenting the comprehensive degrees of hazard 90.7. And as a result of Phast6.0/ALOHA, the trends of each scenario appeared considerably identical although there are some differences in the resulting effects according to the input data for the Gas Model. The consequence analysis is performed numerically based on the dense gas mode. In the future, using more correct input data, material properties, and topographical configuration, the method of this research will be useful for the guideline of the risk assessment when the release of toxicants breaks out.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.77-87
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• 2018

In the case of high-energy line breaks in nuclear power plants, supersonic steam jet is formed due to the rapid depressurization. The steam jet can cause impingement load on the adjacent structures, piping systems and components. In order to secure the design integrity of the nuclear power plant, it is necessary to evaluate the load characteristics of the steam jet generated by high-energy pipe rupture. In the design process of nuclear power plant, jet impingement load evaluation was usually performed based on ANSI/ANS 58.2. However, U.S. NRC recently pointed out that ANSI/ANS 58.2 oversimplifies the jet behavior and that some assumptions are non-conservative. In addition, it is recommended that dynamic analysis techniques should be applied to consider transient load characteristics. Therefore, it is necessary to establish an evaluation methodology that can analyze the dynamic load characteristics of steam jet ejected when high energy pipe breaks. This research group has developed and validated the CFD analysis methodology to evaluate the transient behavior of supersonic impinging jet in the previous study. In this study, numerical study on the transient load characteristics of supersonic steam jet impingement was carried out and amplitude and frequency analysis of transient jet load was performed.