• Nuclear Engineering and Technology
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• v.36 no.5
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• pp.388-402
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• 2004

A phenomena identification and ranking table(PIRT) was developed for a main steam line break (MSLB) event for the Advanced Power Reactor-1400 (APR-1400). The selectee event was a double-ended steam line break at full power, with the reactor coolant pump running. The developmental panel selected the fuel performance as the primary safety criterion during the ranking process. The plant design data, the results of the APR-1400 safety analysis, and the results of an additional best-estimate analysis by the MARS computer code were used in the development of the PIRT. The period of the transient was composed of three phases: pre-trip, rapid cool-down, and safety injection. Based on the relative importance to the primary evaluation criterion, the ranking of each system, component, and phenomenon/process was performed for each time phase. Finally, the knowledge-level for each important process for certain components was ranked in terms of existing knowledge. The PIRT can be used as a guide for planning cost-effective experimental programs and for code development efforts, especially for the quantification of those processes and/or phenomena that are highly important, but not well understood.

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.775-784
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• 2009

This paper summarizes the tests performed in the ATLAS facility during its first two years of operation (2007${\sim}$2008). Two categories of tests have been performed successfully: (a) the reflood phase of the large-break loss-of-coolant accidents in a cold leg, and (b) the breaks in one of four direct vessel injection lines. Those tests contributed to understanding the unique thermal-hydraulic behavior, resolving the safety-related concerns and providing an evaluation of the safety analysis codes and methodology for the advanced pressurized water reactor, APR1400. Several important and interesting phenomena have been observed during the tests. In most cases, the ATLAS shows reasonable accident characteristics and conservative results compared with those predicted by one-dimensional safety analysis codes. A wide variety of small-break LOCA tests will be performed in 2009.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.41-50
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• 1985

The mathematical analysis of the outflow hydrograph resulting from earth dam-break was studied. DBFW(Dam Break Flood Wave) model based on the breach mechanism and reservoir storage equation was developed and was applied to the Teton and Buffalo-Creek dam. The modeling results showed that the shape of outflow hydrograph, peak discharge and failure duration time had a good agreement with the data analyzed by NWS. The breach mechanisms which exert influence on the outflow hydrograph were consisted of geomorphological characteristics of the reservoir, breach mode, breach width and failure duration time. The earth dams in Korea were classified into four types by the reservoir geomorphology, and water surface elevation-failure duration time-peak discharge relationships were also presented. The methodological procedure made in this paper will provide a basic contribution to dam-break study in river system.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.2 s.21
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• pp.45-50
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• 2006

When we build the tunnel, occasionally, the blasted section exceed the designed section because of geological properties and the lack of blasting technologies, and the exceed section is remained as over break after the construction of tunnel lining. When the underground water leaks with silt and clay through the cracks of rocks, the large over break cause a structural stability problem in tunnel, and the back charging of over break is very important subject, because the undoing of back charging cause the drop of crashed rocks and serious problem in the stability of tunnel lining. Therefore, the theory of blast is studied and purpose the structural analysis of back charging and propose the safe method about the drop of crashed rocks.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1059-1069
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• 2023

Dam-break flow occurs when an elevated dam suddenly collapses, resulting in the catastrophic release of rapid and uncontrolled impounded water. This study compares laminar and turbulent closure models for simulating three-dimensional dam-break flows using OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) model, specifically the k-ε model, is employed to capture turbulent dissipation. Two scenarios are evaluated based on a laboratory experiment and a modified multi-layered block obstacle scenario. Both models effectively represent dam-break flows, with the turbulent closure model reducing oscillations. However, excessive dissipation in turbulent models can underestimate water surface profiles. Improving numerical schemes and grid resolution enhances flow recreation, particularly near structures and during turbulence. Model stability is more significantly influenced by numerical schemes and grid refinement than the use of turbulence closure. The k-ε model's reliance on time-averaging processes poses challenges in representing dam-break profiles with pronounced discontinuities and unsteadiness. While simulating turbulence models requires extensive computational efforts, the performance improvement compared to laminar models is marginal. To achieve better representation, more advanced turbulence models like Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) are recommended, necessitating small spatial and time scales. This research provides insights into the applicability of different modeling approaches for simulating dam-break flows, emphasizing the importance of accurate representation near structures and during turbulence.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.1
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• pp.35-44
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• 2015

This paper deals with the economic analysis of domestic fuel cell vehicles considering subsidy and hydrogen price in 2015 and 2025. We selected TFCV (Tucson fuel cell vehicle) and TDV (Tucson diesel vehicle) to identify the economic feasibility of fuel cell vehicles compared with conventional internal combustion engine vehicles. We made some sensitivity analysis by changing input factors such as the size of the subsidy, the hydrogen price and the discount rate. Also, we made a break-even point analysis on hydrogen prices that equalize the economic feasibility of TFCV and TDV in 2025. As a result, TFCV is not economical in 2015 due to the relatively high prices of hydrogen and vehicles. If the sale prices of TFCV are 30,000,000 won and 35,000,000 won in 2025, then the break-even points of hydrogen prices are equal to 7,483 won/kg and 5,043 won/kg.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.127-131
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• 2002

This paper presents the a measured path-loss characteristics in urban line-of-sight(LOS) and non line-of-sight(NLOS) environments for 3.4, 5.3, and 6.4 ㎓ band signals. A two-ray model is applied to analyse the path-loss characteristics in LOS areas. In LOS areas, an empirical break point, whose distance is shorter than a theorical break point, is founded. Further, a sudden power level drop occurs at a transition point from LOS region to NLOS area and different path-loss exponents are occured various cases. The power level drop due to comer loss and path-loss exponents both increase as the distance between the transmitter and the corner increases.

• Korean Journal of Medicinal Crop Science
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• v.14 no.5
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• pp.311-316
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• 2006

The content of four phonolic acids 1-4, and two flavonol aglycones 14 and 15 from Orostachysjaponicus A. Berger grown under night-break and day-length controlled experiments was estimated and compared with those in wild plants. The amount of the phenolic acids 1-4 and the flavonol aglycones 14 and 15 increased with increasing light irradiation under both the night-break and day-length control conditions. It was disclosed that the cultivation conditions such as the night-break and the day-length control were not adversely affect the production of phenolic acids and flavonols in Orostachys japonicus A. Berger extracts.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.89-91
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• 2011

In this paper, phrase boundaries in sentence are predicted and a phrase break information is applied to an HMM-based Korean Text-to-Speech synthesis system. Synthesis with phrase break information increases a naturalness of the synthetic speech and an understanding of sentences. To predict these phrase boundaries, context-dependent information like forward/backward POS(Part-of-Speech) of eojeol, a position of eojeol in a sentence, length of eojeol, and presence or absence of punctuation marks are used. The experimental results show that the naturalness of synthetic speech with phrase break information increases.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.532-534
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• 2015

This is a dissertation is in urgent announce of the domestic legislation about bungee jumping. A bungee jumping operator puts the blame on us for causing the bungee jumping accident but before calling it, equipment of bungee jumping was old and deficient. Fee of bungee jumping is fifty thousand won. A rope seller has raised the price, as operator break the rope used limit. So that is reasonable price. Even now, operator break the rope used limit and legislation about bungee jumping is nonexistent so bungee jumping accidents occur with frequency in domestic.