• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.646-656
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• 2012

This study area was Saemangeum Reservoir in Korea and the applied model was Environmental Fluid Dynamics Code(EFDC). It was the same as the scenarios to the boundary and initial conditions except the resolutions of the model grids. The resolutions were about 800 and 2,000 cells. It was considered scenario 1 and 2. The model was performed to simulate the water temperature, salinity, water quality parameters such as dissolved oxygen(DO), chemical oxygen demand(COD), total nitrogen(T-N), and total phosphorus(T-P) at 2008. The simulation results of the two scenarios were reflected in the trend of observed data tolerably. However, water flow, water temperature, and salinity showed high confidence level at the scenario 1. The water quality items did not present high confidence level at the scenario 1 because which concept was considered to biochemical and physical processes. This result shows that grid resolution has an influence on the water transport and the effect is reflected directly shallow and narrow water area. But, the selection of grid resolution should be considered the purpose of model simulation and the process of target items.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.139-143
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• 2019

In this study, we tried to derive the most severe scenario and its critical speed by 1-D collision simulation with a variable formation vehicle in order to prepare for the change of demand in Seoul Metropolitan Subway Line 3, which is operated by fixed arrangement. After establishing various collision scenario conditions, the friction coefficient between the wheel and the rail was evaluated as 0.3, which is considered to be severe. As a result of analysis according to all scenarios, the most severe scenario conditions were confirmed by comparing rubber shock absorber performance and vehicle collision deceleration. In addition, a typical wheel-rail friction coefficient was derived through accident cases, and the analysis was performed again and compared. Finally, the criterion of the critical speed in the condition of the friction coefficient of the normal wheel - rail condition was confirmed.

• East Asian Economic Review
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• v.25 no.2
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• pp.205-230
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• 2021

This study examines the impact of the number of coronavirus cases on regime-switching in stock return volatility. This study documents the empirical evidence that the COVID-19 cases had an asymmetric effect on the regime of stock return volatility. When the stock return is in the low volatility regime, the probability of switching to the high volatility regime in the next trading day increases as the number of cumulative cases increases. In contrast, in the high volatility regime, the effect of cumulative cases on the transition probability is not statistically significant. This study also documents the evidence that the government measures against the pandemic contribute to promoting the high volatility regime of the KOSPI during the pandemic. Besides, this study projects future stock prices through the Monte Carlo simulation based on the estimated parameters and the predicted number of the COVID-19 new cases. Under a scenario where the number of new cases rapidly increases, stock price indices in Korea are expected to be in a downward trend over the next three months. On the other hand, under the moderate scenario and the best scenario, the stock indices are likely to continue to rise.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.6
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• pp.233-240
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• 2021

The stochastic method is applied to simulate strong ground motions at seismic stations of seven metropolises in South Korea, creating an earthquake scenario based on the causative fault of the 2016 Gyeongju earthquake. Input parameters are established according to what has been revealed so far for the causative fault of the Gyeongju earthquake, while the ratio of differences in response spectra between observed and simulated strong ground motions is assumed to be an adjustment factor. The calculations confirm the applicability and reproducibility of strong ground motion simulations based on the relatively small bias in response spectra between observed and simulated strong ground motions. Based on this result, strong ground motions by a scenario earthquake on the causative fault of the Gyeongju earthquake with moment magnitude 6.5 are simulated, assuming that the ratios of its fault length to width are 2:1, 3:1, and 4:1. The results are similar to those of the empirical Green's function method. Although actual site response factors of seismic stations should be supplemented later, the simulated strong ground motions can be used as input data for developing ground motion prediction equations and input data for calculating the design response spectra of major facilities in South Korea.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2529-2539
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• 2022

Stochastic and an empirical Green's function (EGF) methods are preliminarily applied to simulate strong ground motions (SGMs) at seismic stations within nuclear power plant (NPP) sites in South Korea by an assumed large earthquake with M_W6.5 (scenario earthquake) on the causative fault of the 2016 Gyeongju earthquake with M_W5.5 (mainshock). In the stochastic method, a ratio of spectral amplitudes of observed and simulated waveforms for the mainshock is assumed to be an adjustment factor. In the EGF method, SGMs by the mainshock are simulated assuming SGMs by the 2016 Gyeongju earthquake with M_W5.0 (foreshock) as the EGF. To simulate SGMs by the scenario earthquake, a ratio of fault length to width is assumed to be 2:1 in the stochastic method, and SGMs by the mainshock are assumed to be EGF in the EGF method. The results are similar based on a bias of the simulated response spectra by the two methods, and the simulated response spectra by the two methods exceeded commonly standard design response spectra anchored at 0.3 g of NPP sites slightly at a frequency band above 4 Hz, but considerable attention to interpretation is required since it is an indirect comparison.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.446-459
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• 2017

Naval ships are assigned many and varied missions. Their performance is critical for mission success, and depends on the specifications of the components. This is why performance analyses of naval ships are required at the initial design stage. Since the design and construction of naval ships take a very long time and incurs a huge cost, Modeling and Simulation (M & S) is an effective method for performance analyses. Thus in this study, a simulation core is proposed to analyze the performance of naval ships considering their specifications. This simulation core can perform the engineering level of simulations, considering the mathematical models for naval ships, such as maneuvering equations and passive sonar equations. Also, the simulation models of the simulation core follow Discrete EVent system Specification (DEVS) and Discrete Time System Specification (DTSS) formalisms, so that simulations can progress over discrete events and discrete times. In addition, applying DEVS and DTSS formalisms makes the structure of simulation models flexible and reusable. To verify the applicability of this simulation core, such a simulation core was applied to simulations for the performance analyses of a submarine in an Anti-SUrface Warfare (ASUW) mission. These simulations were composed of two scenarios. The first scenario of submarine diving carried out maneuvering performance analysis by analyzing the pitch angle variation and depth variation of the submarine over time. The second scenario of submarine detection carried out detection performance analysis by analyzing how well the sonar of the submarine resolves adjacent targets. The results of these simulations ensure that the simulation core of this study could be applied to the performance analyses of naval ships considering their specifications.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.223-228
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• 2001

In this paper, crashworthiness of the KHST carbodies is evaluated by numerical simulation under the SNCF accident scenario (collision against a movable rigid mass of 15 ton at 110 kph) and the scenario of train-to-train collision at 30 kph. The numerical results of the several simulations, such as the accident collided against a deformable dump truck of 15 tons at 110 kph, the driver's dummy analysis using the integrated analysis method, and the accident of train-to-train collision for the first three units at 30 kph, show good performances in the viewpoint of energy absorption and survival space.

• Journal of the Korea Society for Simulation
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• v.24 no.1
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• pp.25-34
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• 2015

It is necessary for us to undergo trial and error for eliciting the rational requirement of the acquisition of weapon systems, but the M&S is general approach due to costs and risk of the development. In addition to the acquisition of weapon systems, M&S is extensively employed in the analysis and the training of developed weapon systems. The ADD (Agency for Defense Development) has developed DEVS integrated development environment (QUEST) that provides M&S general ground technique composed of simulation model implementation services, simulation result analysis services, and simulation interface services. This paper describes the interface architecture and the implementation of torpedo target detection section interface simulation system using QUEST. The torpedo target detection section interface simulation system is composed of torpedo target detection section which calculates a result of target detection and the QUEST scenario generator which provides simulation scenario for performance test of the torpedo target detection section. The interface architecture of torpedo target detection section interface simulation system is designed to verify the interface and performance of the torpedo target detection section by linking with the QUEST scenario generator.

• Journal of Nutrition and Health
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• v.46 no.1
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• pp.50-60
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• 2013

The aims of this study were to estimate daily intake of macrominerals from beverages, liquid teas, and liquid coffees and to evaluate their potential health risks for Korean children and adolescents (1-to 19 years old). Assessment of dietary intake was conducted using the actual level of sodium, calcium, phosphorus, potassium, and magnesium in non-alcoholic beverages and (207 beverages, 19 liquid teas, and 24 liquid coffees) the food consumption amount drawn from "The Fourth Korea National Health and Nutrition Examination Survey (2007-2009)". To estimate the dietary intake of non-alcoholic beverages, 6,082 children and adolescents (Scenario I) were compared with 1,704 non-alcoholic beverage consumption subjects among them (Scenario II). Calculation of the estimated daily intake of macrominerals was based on point estimates and probabilistic estimates. The values of probabilistic macromineral intake, which is a Monte-Carlo approach considering probabilistic density functions of variables, were presented using the probabilistic model. The level of safety for macrominerals was evaluated by comparison with population nutrient intake goal (Goal, 2.0 g/day) for sodium, tolerable upper intake level (UL) for calcium (2,500 mg/day) and phosphorus (3,000-3,500 mg/day) set by the Korean Nutrition Society (Dietary Reference Intakes for Koreans, KDRI). For total children and adolescents (Scenario I), mean daily intake of sodium, calcium, phosphorus, potassium, and magnesium estimated by probabilistic estimates using Monte Carlo simulation was, respectively, 7.93, 10.92, 6.73, 23.41, and 1.11, and 95th percentile daily intake of those was, respectively, 28.02, 44.86, 27.43, 98.14, and 3.87 mg/day. For consumers-only (Scenario II), mean daily intake of sodium, calcium, phosphorus, potassium, and magnesium estimated by probabilistic estimates using Monte Carlo simulation was, respectively, 19.10, 25.77, 15.83, 56.56, and 2.86 mg/day, and 95th percentile daily intake of those was, respectively, 62.67, 101.95, 62.09, 227.92, and 8.67 mg/day. For Scenarios I II, sodium, calcium, and phosphorus did not have a mean an 95th percentile intake that met or exceeded the 5% of Goal and UL.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.441-447
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• 2004

Information security simulator is required for the study on the cyber intrusion and defense as information security has been increasingly popular Until now, the main purposes of information security simulation are security estimation of small network as well as performance analysis of information protection systems. However, network simulators that can simulate attacks in a huge network are in needs since large scale internet attacks are very common in these days. In this paper we proposed a simulator design and its implementation details. Our simulator is implemented by expanding the SSFNet program to the client-sewer architecture. A cyber attack scenario used in our simulator is composed by the advanced attack tree model. We analyzed the simulation results to show the correctness of our network defense simulator.