• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.4
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• pp.201-209
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• 2016

Damages of large embankment dams by recent strong earthquakes in the world highlight the importance of seismic security of dams. Some of recent dam construction projects for water storage and hydropower are located in highly seismic zone, hence the seismic performance evaluation is an important issue. While state-of-the-art numerical analysis technology is generally utilized in practice for seismic performance evaluation of large dams, physical modeling is also carried out where new construction technology is involved or numerical analysis technology cannot simulate the behavior appropriately. Geotechnical centrifuge modeling is widely adopted in earthquake engineering to simulate the seismic behavior of large earth structures, but sometimes it can't be applied for large embankment dams due to various limitations. This study proposes a dynamic centrifuge testing method for large embankment dams and evaluated its applicability. Scaling relations for a case which model scale and g-level are different could be derived considering the stress conditions and predominant period of the structure, which is equivalent to previously suggested scaling relations. The scaling principles and testing method could be verified by modified modeling of models using a model at different acceleration levels. Finally, its applicability was examined by centrifuge tests for an embankment dam in Korea.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.136-140
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• 2001

The 3rd generation mobile telecommunication fields are being standardized and developed in two parts, 3GPP and 3GPP2. These two parts have established each Network Architecture Models to achieve the goals basically required in the 3rd generation and to make it progress to IP network in the future. To achieve these goals many system architectures are proposed. Not only functional aspects but also performance aspects are considered as major factors. This paper proposes a new method of performance evaluation modeling and simulation that improved the existing way. The method proposed in this paper is Aspect oriented logical performance analysis Modeling and Simulation method. This proposed method is expected to improve efficiency of performance analysis modeling and simulation on the 3rd generation mobile telecommunication system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.333-340
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• 2006

In these days the floor vibration is beginning to make its appearance of the environmental dispute in apartment building. Standard floor system are suggested for the settlement of this issue by government. The sound of floor impact sound is needed to secure comfortable quality in housing. Also, it is required an accurate analysis and a proper evaluation for floor vibration. Refine model is necessary for the floor system of housing to analyze accurately the floor vibration. But this refine model is not efficient because it is required so much running time for vibration analysis and it is difficult of modeling of standard floor slab. In this paper, new modeling methods of standard floor slab are proposed for the accurate rigidity evaluation. By using the new modeling method, the accurate vibration response can be obtained and can accurately evaluate the rigidity of standard floor system with resilient materials. Therefore the proposed modeling method is of practical use for vibration analysis of floor system of apartment building.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.33-42
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• 2012

In the present study, CFD is employed to investigate phenomena occurring during a process of thermal stratification in U-bent pipes at transitional Reynolds number. URANS evaluation had been chosen for its low computational costs during transient analysis and for the evaluation of modeling performance in these conditions. Application of CFD at transitional Reynolds number and buoyancy driven flows indeed contains deeper uncertainties in relation to the range of applicability for hydrodynamic and thermal models. The methodology applied in the work points out, through validations with the basic problems constituting the complex stratified phenomenon, the applicability of the current turbulence modeling. Accurate predictions have been found in relation to transitional Reynolds number in bent pipes and region of stability induced by the gravitational field. On the other hand the defects introduced in the unstable region of the U bent pipe, are discussed in relation to the adopted modeling.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.74-80
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• 2016

In this paper, the modeling and implementation results of the operational test and evaluation tool of the KASS up-link station composed of the GEO(Geostationary Earth Orbit) satellite signal analysis tool model that analyzes the GEO satellite signal and the GEO message analysis tool model that analyzes the GEO satellite navigation message. In addition, we describe the results of software modeling and implementation of some software models of GEO satellite and KASS up-link stations that can generate and provide simulated signals to operational test and evaluation tools of these KASS up-link stations.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.1
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• pp.15-24
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• 2006

In simulation input modeling, it is important to identify a probability distribution to represent the input process of interest. In this paper, an appropriate sample size is determined for parameter estimation associated with some typical probability distributions frequently encountered in simulation input modeling. For this purpose, a statistical measure is proposed to evaluate the effect of sample size on the precision as well as the accuracy related to the parameter estimation, square rooted mean square error to parameter ratio. Based on this evaluation measure, this sample size effect can be not only analyzed dimensionlessly against parameter's unit but also scaled regardless of parameter's magnitude. In the Monte Carlo simulation experiments, three continuous and one discrete probability distributions are investigated such as ; 1) exponential ; 2) gamma ; 3) normal ; and 4) poisson. The parameter's magnitudes tested are designed in order to represent distinct skewness respectively. Results show that ; 1) the evaluation measure drastically improves until the sample size approaches around 200 ; 2) up to the sample size about 400, the improvement continues but becomes ineffective ; and 3) plots of the evaluation measure have a similar plateau pattern beyond the sample size of 400. A case study with real datasets presents for verifying the experimental results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.4
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• pp.229-236
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• 2005

This paper presents a system level architecture evaluation technique that leverages transaction level modeling but also significantly extends it to the realm of system level performance evaluation. A major issue lies with the modeling effort. To reduce the modeling effort the proposed technique develops the concept of worst case scenarios. Since the memory controller is often found to be an important component that critically affects the system performance and thus needs optimization, the paper further addresses how to evaluate and optimize the memory controllers, focusing on the test environment and the methodology. The paper also presents an industrial case study using a real state-of-the-art design. In the case study, it is reported that the proposed technique has helped successfully find the performance bottleneck and provide appropriate feedback on time.

• Journal of Platform Technology
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• v.8 no.1
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• pp.33-40
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• 2020

The purpose of this study is to identify factors in selecting the elective ICT utilization lecture and to find positive and negative elements of the lecture through conducting topic modeling analysis of text mining of the narrative lecture evaluation. In order to do so, from pre-processing of data, keyword frequency analysis to wordcloud visualization and topic modeling analysis have been conducted from 'reasons of selecting the lecture,' 'improvements to be made on the lecture,' and 'what I liked about the lecture' categories regarding the ICT utilization lecture which was opened in the second semester of 2019 at M University. The analysis results show that students mostly registered for the ICT utilization lecture at M University to obtain a certificate and the fact being certified and taking the lecture can be done simultaneously is a positive element of taking the lecture. On the other hand, negative element included inconvenience of the classroom setting environment.

• Korean Journal of Radiology
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• v.22 no.10
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• pp.1697-1707
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• 2021

The recent introduction of various high-dimensional modeling methods, such as radiomics and deep learning, has created a much greater diversity in modeling approaches for survival prediction (or, more generally, time-to-event prediction). The newness of the recent modeling approaches and unfamiliarity with the model outputs may confuse some researchers and practitioners about the evaluation of the performance of such models. Methodological literacy to critically appraise the performance evaluation of the models and, ideally, the ability to conduct such an evaluation would be needed for those who want to develop models or apply them in practice. This article intends to provide intuitive, conceptual, and practical explanations of the statistical methods for evaluating the performance of survival prediction models with minimal usage of mathematical descriptions. It covers from conventional to deep learning methods, and emphasis has been placed on recent modeling approaches. This review article includes straightforward explanations of C indices (Harrell's C index, etc.), time-dependent receiver operating characteristic curve analysis, calibration plot, other methods for evaluating the calibration performance, and Brier score.

• Journal of the Ergonomics Society of Korea
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• v.25 no.2
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• pp.161-172
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• 2006

This study aims to compare and contrast the Kansei modeling methods for building a luxuriousness model that people feel about appearance of mobile phones. For the evaluation based on Kansei engineering approaches, 15 participants were employed to evaluate 18 mobile phones using a questionnaire. The results of evaluation were analyzed to build luxuriousness models through quantification I method, neural network, and decision tree method, respectively. The performance of Kansei modeling methods was compared and contrasted in terms of accuracy and predictability. The result of comparison of modeling methods indicated that model accuracy and predictability was closely related to the number of variables and data size. It was also revealed that quantification I method was the best in terms of model accuracy while decision tree method was the best modeling method with small variance in terms of predictability. However, it was empirically found that quantification I method showed extremely unstable predictability with small number of data. Consequently, it is expected that the research findings of this study might be utilized as a guideline for selecting proper Kansei modeling method.