• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.464-467
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• 2001

A good arithmetic random number generator should possess full period, uniformity and independence, etc. To obtain the excellent random number generator, many researchers have found good parameters. Also an initial seed is the important factor in random number generator. But, there is no theoretical guideline for using the initial seeds. Therefore, random number generator is usually used with the arbitrary initial seed. Through the empirical tests, we show that the choice of the initial values for the seed is important to generate good random numbers.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.56.2-56.2
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• 2017

We in the Korea Institute for Advanced Study are preparing the fifth Horizon Run in a series of large-scale cosmological simulations. For the first time we will include full hydrodynamics and astrophysical processes using a RAMSES code. I will discuss the impact of large-scale structures on smaller scale properties in cosmological hydrodynamic simulation to justify our choice of simulation boxsize, whose one side length is up to 1 Gpc.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.919-922
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• 2008

The objective of this study is to design the full-scale fire test facility of the railroad vehicle with CFD simulation. In the results, the step expansion system should be good enough for the measuring system. Uniform flow is achieved at eight-to-ten diameters of the expanded duct behind the step for moderate expansion ratios($D_{orifice}/D_{duct}$ = 2 being a good choice). To optimization of the fire products collector system with 5 dampers, the additional CFD simulation was also carried out. These results will be help for the railroad fire safety research.

• Journal of Korean Society of Transportation
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• v.20 no.3
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• pp.83-92
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• 2002

Freight mode choice models are essential to the analysis of many areas of transport research. However, observations of actual market choices have only been made in a limited number of situations. Therefore, stated preference(SP) techniques have emerged as an alternative source of actual market choices to be used for estimating freight mode choice models. Considerable confidence exists about SP data, but little consideration has been given to the potential for estimation bias. This paper has been motivated by the theoretical side of estimating SP discrete choice models, focusing on a case study of freight mode choice. Recently developed simulation methods are used to construct inherent random heterogeneity legit models, which consider individual heterogeneity, its inheritance to the next choices and overcome the independence from irrelevant alternatives (IIA) property. This Paper contributes to the development of models dealing with heterogeneity and its inheritance, and sheds light on the heterogeneity of freight transport.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.354-356
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• 2003

The study of pedestrian behavior covers wide topics, including way finding, choice and decision make, as well as spatial cognition and environmental perception. To address the problem, simulation is now put forward as suitable technique and method for analyzing human spatial behavior. In the paper we present a development architecture for simulating tracking pedestrian in a distributed environment. We introduce and explore the potential of using mobile agent-enabled distributed implementation model as a tool for development and implementation of the simulation. Three kinds of mobile agents are designed for implementation of managing and querying data of pedestrian. Finally, simulation result of JR 10,000 passengers’ movement is developed and implemented as a case study.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.485-499
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• 2012

With the maturity of department stores and discount stores, many Korean retail companies have an interest in developing outlet shopping centers such as Yeoju Premium Outlet so on. To develop a successful outlet shopping center, developers should understand consumer's preferences on many attributes of development alternatives. This study analyzes consumer's preferences on outlet shopping center and evaluates various development alternatives by using conjoint analysis. With empirical research for outlet shopping center development, this study can elicit potential shopper's preference for outlet shopping center. The empirical result shows discount rate is most important attribute to develop outlet shopping center. The potential shoppers have higher preference for higher discount rate. Location is the second important attribute. Brand is the least important attribute. By using utilities derived from analysis, this study performs various choice simulations. Through choice simulation analysis, this study tries to find the best development alternative for new outlet shopping center.

• Journal of the Korean Data and Information Science Society
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• v.20 no.4
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• pp.695-703
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• 2009

Currently, various cellular phone products with multiple functions and diverse designs are coming out in the cellular phone market. Companies have been developing their products for profit maximization, considering preferences of customers. In this article, we have created 18 profiles using the SPSS program and executed a survey to analyze preferences of college students. Also, we have grasped the relative importance of each attribute using conjoint analysis and executed clustering analysis to make market segmentation by binding the respondents who have similar partial value utilities. Lastly, by choice simulation, we have predicted market shares of 18 virtual products.

• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.1
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• pp.161-176
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• 2005

In a situation that ordinal preferences on multiattribute weights are captured, we present two solution approaches: an exact approach and an approximate method. The former, an exact solution approach via interaction with a decision-maker, pursues the progressive reduction of a set of non-dominated alternatives by narrowing down the feasible attribute weights region. Subsequent interactive questions and responses, however, sometimes may not guarantee the best alternative or a complete rank order of a set of alternatives that the decision-maker desires to have. Approximate solution approaches, on the other hand, can be divided into three categories including surrogate weights methods, dominance value-based decision rules, and three classical decision rules. Their efficacies are evaluated in terms of choice accuracy via a simulation analysis. The simulation results indicate that a proposed hybrid approach, intended to combine an exact solution approach through interaction and a dominance value-based approach, is recommendable for aiding a decision making in a case that a final choice is seldom made at single step under attribute weights that are imprecisely specified beyond ordinal descriptions.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.3
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• pp.264-268
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• 2011

This paper presents a Takagi-Sugeno (T-S) type Fuzzy Logic Controller (FLC) with only 3 rules. The choice of parameters of FLC is very difficult job on design FLC. Therefore, the choice of appropriate linguistic variable is an important part of the design of fuzzy controller. However, since fuzzy controller is nonlinear, it is difficult to analyze mathematically the affection of the linguistic variable. So this choice is depend on the expert's experience and trial and error method. In this paper, we propose the method to choose the consequence linear equation's parameter of T-S type FLC. The parameters of consequence linear equations of FLC are tuned according to the system error that is the input of FLC. The full equation of T-S type FLC is presented and using this equation, the relation between output and parameters can represented. The parameters are tuned with gradient algorithm. The parameters are changed depending on output. The simulation results demonstrate the usefulness of this T-S type 3 rule fuzzy controller.

• Wind and Structures
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• v.20 no.2
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• pp.169-189
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• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.