• Journal of Korean Society of Transportation
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• v.25 no.3
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• pp.137-144
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• 2007

This study involves an analytical approach to determine transit dispatching schedules (headways) Determining a time schedule is an important process in transit system planning. In general, the transit headway should be shorter during the peak hour than at non-peak hours for demand-responsive service. It allows passengers to minimize their waiting time under inelastic, fixed demand conditions. The transit headway should be longer as operating costs increase, and shorter as demand and waiting time increase. Optimal headway depends on the amount of ridership. and each individual vehicle dispatching time depends on the distribution of the ridership. This study provides a theoretical foundation for the dispatching scheme consistent with common sense. Previous research suggested a dispatching scheme with even headway. However, according to this research, that is valid for a specific case when the demand pattern is uniform. This study is a general analysis expanding that previous research. This study suggests an easy method to set a time table without a complex and difficult calculation. Further. if the time axis is changed to the space axis instead, this study could be expanded to address the spacing problems of some facilities such as roads. stations, routes and others.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.335-358
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• 2020

We present a numerical model to simulate coupled hydro-mechanical behavior of fault using TOUGH-FLAC simulator. This study aims to develop a numerical method to estimate fluid injection-induced fault reactivation in low permeability rock and to access the relevant hydro-mechanical stability in rock as part of DECOVALEX-2019 Task B. A coupled fluid flow and mechanical interface model to explicitly represent a fault was suggested and validated from the applications to benchmark simulations and the field experiment at Mont Terri underground laboratory in Switzerland. The pressure build-up, hydraulic aperture evolution, displacement, and stress responses matched those obtained at the site, which indicates the capability of the model to appropriately capture the hydro-mechanical processes in rock fault.

• Composites Research
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• v.19 no.3
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• pp.7-14
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• 2006

In this paper, an integrated probabilistic strength analysis was conducted to predict the reliability of a composite pressure vessel under inner pressure loading condition. As a probabilistic strength analysis, the probabilistic progressive failure model consisting of progressive failure model and Monte Carlo simulation was incorporated with a commercial FEA code, ABAQUS Standard, to perform the probabilistic failure analysis of composite structure which has a complex shape and boundary conditions. As design random variables, the laminar strengths of each direction were considered. Finally, from probabilistic strength analysis, the scattering of burst pressure could be explained and the reliability of composite pressure vessel could be obtained for each component. In case of composite structures in mass production, the effects of uncertainties in material and manufacturing on the performance of composite structures would apparently become larger. So, the probabilistic strength analysis is essential for the structural design of composite structures in mass production.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.25-33
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• 2020

In this study, flow and structural computational analysis were performed to investigate the structural safety of the lightweight butterfly valve disc designed by topology optimization. After flow analysis, as the opening angle increased, the flow coefficient increased non-linearly and showed a gentle slop. When the opening angle was 12 degree, the cavitation could be predicted. After FE analysis, all FE von-Misses stresses of the lightweight disc were smaller than the yield strength of the material, and all FE maximum deformations were also smaller than the conservative deformation of the previous study. Ultimately, it was confirmed that the structural safety of the lightweight valve disc based on computational analysis is effective.

• Tunnel and Underground Space
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• v.30 no.6
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• pp.573-590
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• 2020

This study presents the current status of DECOVALEX-2023 project Task G and our research results so far. Task G, named 'Safety ImplicAtions of Fluid Flow, Shear, Thermal and Reaction Processes within Crystalline Rock Fracture NETworks (SAFENET)' aims at developing a numerical method to simulate the fracture creation and propagation, and the coupled thermohydro-mechanical processes in fracture in crystalline rocks. The first research step of Task G is a benchmark simulation, which is designed for research teams to make their modelling codes more robust and verify whether the models can represent an analytical solution for displacements of a single rock fracture. We reproduced the mechanical behavior of rock and embedded single fracture using a three-dimensional grain-based distinct element model for the simulations. In this method, the structure of the rock was represented by an assembly of rigid tetrahedral grains moving independently of each other, and the mechanical interactions at the grains and their contacts were calculated using 3DEC. The simulation results revealed that the stresses induced along the embedded fracture in the model were relatively low compared to those calculated by stress analysis due to stress redistribution and constrained fracture displacements. The fracture normal and shear displacements of the numerical model showed good agreement with the analytical solutions. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated using various experiments in a further study.

• Journal of Christian Education in Korea
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• v.61
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• pp.61-80
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• 2020

This study mark a high complexity of the field, which is further enhanced by the fact, that these discussions are transposed into religious education and professionalism research relating to religious education teachers. It seriously considers very unique semantics and practice of leadership emerge then, crosswise and as a background to the educational hermeneutics. Obviously, besides didactic implications, professional ethical implications in an elementary sense are also at play here. The researcher will proceed in four steps: Firstly, I examine aspects of professionalism theory, into which, secondly, professional ethical considerations are entered in their significance for the topic of leadership, then deepen this through discourse-theoretical considerations before finally, fourthly, perspectives are opened up.

• Journal of the KSME
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• v.33 no.7
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• pp.636-647
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• 1993

평판과 셸은 그 하중 지지의 효율성 때문에 각종 구조물에 널리 사용되고 있다. 그러나 여러 종류의 불연속은 어쩔 수 없이 존재하게 된다. 대형 구조물의 출입을 위한 개구부의 존재나, 관과 노즐의 결합 부위 등 복잡한 형상을 가지면서 생기는 기하학적 문제, 재료에 원래 존재하는 균 열이나 개재물(inclusion) 등의 문제가 그 예가 될 것이다. 집중하중이나 선하중 등은 넓은 의미의 불연속으로서 힘에 의한 것으로 볼 수 있으나, 보다 문제가 되는 것은 변위의 불연속으로 이해될 수 있는 균열의 문제일 것이다. 이균열의 존재는 구조물의 안전성에 미치는 효과가 커서 중요한 연구 대상이 되어 있다. 또 해석적 방법으로 풀기도 까다로운데, 여기서는 이 문제를 다루는 해 석적 방법들을 살펴보고, 또 효율적으로 계산할 수 있는 반해석적(semi-analytical) 방법을 도입한 수 대표적인 평판과 셸 문제를 예로 들어본다.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.670-691
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• 2018

This study presents the research results of the BMT(Benchmark Model Test) simulations of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to predict fault reactivation and the coupled hydro-mechanical behavior of fault. BMT scenario simulations of Task B were conducted to improve each numerical model of participating group by demonstrating the feasibility of reproducing the fault behavior induced by water injection. The BMT simulations consist of seven different conditions depending on injection pressure, fault properties and the hydro-mechanical coupling relations. TOUGH-FLAC simulator was used to reproduce the coupled hydro-mechanical process of fault slip. A coupling module to update the changes in hydrological properties and geometric features of the numerical mesh in the present study. We made modifications to the numerical model developed in Task B Step 1 to consider the changes in compressibility, Permeability and geometric features with hydraulic aperture of fault due to mechanical deformation. The effects of the storativity and transmissivity of the fault on the hydro-mechanical behavior such as the pressure distribution, injection rate, displacement and stress of the fault were examined, and the results of the previous step 1 simulation were updated using the modified numerical model. The simulation results indicate that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing interaction and collaboration with other research teams of DECOVALEX-2019 Task B and validated using the field experiment data in a further study.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.485-486
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• 2010

In this research, a new analysis method which is able to examine the safety and to assess the serviceability of high-rise buildings from construction period to service life has been developed. The effect of both construction sequence and inelastic behavior of concrete has been considered in the developed analysis method in three dimensions. The more efficient analysis technique and modeling method for practical use were also suggested. For verification of the developed analysis method, the data measured in a high-rise building under construction was compared with the analysis results. Through comparison of the analysis results with the measured data, it was found that the analysis results generally simulated the trend of the measured data well in all cases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.957-962
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• 2012

Fluid/structure interaction (FSI) analysis is necessary to predict the response of a system in which aerodynamic pressure causes deformation of the structure, and vice versa. In dealing with a nonlinear behavior of the structure, however, a simple iterative algorithm of aerodynamic analysis with structural analysis yields no accurate results since aerodynamic pressure need to be changed in accordance with the deformation of structures. In this study, we explore an efficient and accurate method for integrating FSI analysis into structural nonlinear systems. During the course of nonlinear structural analysis, loading conditions are periodically updated by aerodynamic analysis. The accuracy and efficiency of the method is demonstrated with a high-aspect-ratio flexible wing of Global Hawk.