• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.2
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• pp.193-200
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• 2010

Due to the characteristic of culvert structure, the standard section of the culvert has been established and applied in field. However, this becomes a limitation in selecting a section design corresponding to various field conditions although it can improve the design and applicability of culvert structure. In order to overcome this limitation, we have developed the design and application technology of culvert structure corresponding to the field conditions that various shapes of culvert structure can be covered by assembly of precast segments. Because the structural characteristics of assembling-type waterway culvert structure, the thickness of structure and amount of reinforcing rods can vary according to the fixation or internal hinge status in the connection part of precast segments. This has a strong influence on the applicability and economic efficiency of culvert structure. Accordingly, in order to suggest a reasonable modeling technique of segment connection parts, this study has conducted the field experiment and numerical analysis. According to the results of field experiment and numerical analysis, the slab, wall and base slab with mortar splice sleeves have shown that the assembling-type of waterway culvert structure behaves like an integrated structure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.176-182
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• 2012

Recently, a new theoretical and methodological approach for computational science is becoming more and more popular for analyzing and solving scientific problems in various scientific disciplines and applied research. Computational science is a field of study concerned with constructing mathematical models and quantitative analysis techniques and using large computing resources to solve the problems which are difficult to approach in a physical experimentally. In this paper, we present R&D of EDISON open integration platform that allows anyone like professors, researchers, industrial workers, students etc to upload their advanced research result such as simulation SW to use and share based on the cyber infrastructure of supercomputer and network. EDISON platform, which consists of 3 tiers (EDISON application framework, EDISON middleware, and EDISON infra resources) provides Web portal for education and research in 5 areas (CFD, Chemistry, Physics, Structural Dynamics, Computational Design) and user service.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.375-383
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• 2016

High-speed trains have been developed widely in many countries in order to transport a large quantity of people and commodities rapidly. When a high speed train enters a tunnel, aerodynamic resistance is generated suddenly. This resistance causes micro pressure wave and discomfort to passengers. Therefore, it is essential to incorporate a pressure relief system in a tunnel and streamlined shape of a train in order to reduce aerodynamic resistance caused by a high-speed train. Additionally, the cross-sectional area of a tunnel should be carefully determined to reduce discomfort of passengers. A pressure relief duct and a vertical shaft are representative measures in a tunnel. This study represents the effect of pressure relief ducts in order to alleviate pressure changes within a time period in a tunnel. One-dimensional network numerical simulations were carried out in order to estimate the effect of pressure relief systems.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.241-248
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• 2010

This paper deals with the performance analysis and design of the Darrieus-type vertical axis turbine to evaluate the effect of key design parameters such as number of blade, blade chord, pitch and camber. The commercial CFD software FLUENT was employed as an unsteady Reynolds-Averaged Navier-Stokes (RANS) solver with k-e turbulent model. Grid system was modelled by GAMBIT. Basic numerical methodology of the present study is appeared in Jung et al. (2009). Two-dimensional analysis was mostly adopted to avoid the barrier of massive calculation required for parametric study. It was found that the highly efficient turbine model could be designed through the optimization of design parametrrs.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.65-73
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• 2013

Ground-coupled heat pump system has attracted attention as a promising renewable energy technology due to its improving energy efficiency and eco-friendly mechanism for space cooling and heating. Pipes buried in the ground play a role of direct thermal interaction between circulating fluid inside the pipe and surrounding soils in the geothermal exchange system. However, both complexities of turbulent flow coupling thermal-hydraulic phenomena and very long aspect ratio of the pipe make it difficult to model the heat exchange system directly. Energy balance for fluid flow inside the pipe was derived to model thermal-hydraulic phenomena, and one-dimensional pipe element was proposed through Galerkin formation and time integration of the equation. Developed element is combined to pre-developed FEM code for THM phenomena in porous media. Numerical results of Thermal Response Test showed that line-source model overestimates equivalent thermal conductivity of surrounding soils due to thermal interaction between adjacent pipes and finite length of the pipe. Thus, inverse analysis for the TRT simulation was conducted to present optimal transformation matrix with utmost convergence.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.266-266
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• 2019

금강의 주요 지류인 미호천과 갑천은 대전광역시와 청주시가 위치하고 있으며, 두 도시지역에서 유입되는 오염물질로 인하여 금강 본류에 높은 오염부하를 제공하고 있다. 따라서 본 연구에서는 3차원 수리동역학 모델인 EFDC 모델을 사용하여 미호천과 갑천의 수질개선이 금강의 수질에 미치는 효과를 분석하였다. 대상유역은 대청댐부터 백제보 까지 70km 구간이며, 모델의 격자는 Curvilinear-Orthogonal Coordinate를 사용하였으며 횡단방향 8개로 분할하여 총 6,698개의 격자로 구성하였다. 경계조건구성 및 모델의 보정은 국가정보 포털인 수자원관리종합정보시스템(WAMIS), 물환경정보시스템(WEIS), 국가기후데이터센터(data,kma,go,kr) 등에서 제공하는 유량, 수질, 기상 등 데이터를 활용하였으며, 모의 기간은 2017년이다. 수질의 보정은 대상유역 내 6곳의 수질 측정 지점에서 수행되었으며, 적합성 평가를 위해 R-square와 NSE(Nash-Sutcliffe Efficiency) 두 가지의 통계 지표를 활용하였다. 수질의 경우 TN, TP, TOC, Chl-a 순으로 평균 R-square값은 0.75, 0.51, 0.36, 0.57이고 평균 NSE (Nash-Sutcliffe Efficiency)값은 0.59, -0.18, -1.10, 0.27으로 모의 값과 실측값 사이의 상관관계는 TN에서 가장 높았으며 반대로 TOC는 가장 낮았다. 모의결과가 실측값을 정확히 반영하지는 못했지만, 수질의 평균적인 현상은 반영한 것으로 판단된다. 두 주요 지류의 수질이 동시에 15% 또는 30% 개선되었을 경우를 모의하여 금강 본류의 수질변화를 6곳의 수질 측정 지점에서의 실측값과 비교하여 분석하였다. 두 지류가 동시에 15%의 수질 개선 시에는 금강 본류 수질은 TN, TP, TOC, Chl-a 순으로 평균 11.80%, 7.90%, 8.63%, 7.04%의 개선되었으며, 30% 수질 개선 시에는 평균 23.66%, 15.92%, 17.36%, 14.26%의 개선되었다. 각 지점에서 고른 개선이 확인되었으며, 개선 효과는 TN이 가장 컸고, 반대로 Chl-a가 가장 적었다. 갑천과 미호천의 수질이 별개로 개선되었을 경우를 모의한 결과, 미호천의 개선이 갑천에 비해 금강의 수질 개선에 영향이 컸다. 이는 두 지류의 수질 농도는 비슷하나 갑천에 비해 유량이 많은 미호천의 오염 부하량이 높은 것으로 분석된다. 연구 결과 금강의 수질을 개선하기 위해서는 두 지류의 수질 개선이 필수적인 것으로 판단된다. 금강의 TN 농도는 두 지류의 영향이 가장 컸으며, 개선 효과는 Chl-a에서 가장 적었다. 또한 갑천에 비해 미호천이 금강 수질에 영향이 큼을 확인하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.144-152
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• 2011

In order to investigate the operation performance behaviors of the UAV's propulsion system to be operated long time in high altitude, the engine performance tests, which are simulated in the altitude engine test facility should be needed. If the test is performed in a existing altitude engine test facility, additional test apparatuses are required. Among them a proper design of the inlet and exhaust ducts that may directly affect the engine performance is very important. If the design is not adequate, the engine performance loss due to the flow behavior change and the pressure loss may be not similar to the real engine performance. In this work, firstly the engine inlet and exhaust ducts to be mounted to the existing altitude facility are modelled in 3D and its flow behaviors and pressure losses are analyzed using a commercial CFD tool, ANSYS's CFX, and the engine performance with the duct losses is calculated using the performance analysis program developed by C. Kong et al. Finally, the optimized inlet and exhaust ducts' configurations are proposed through the repeated analyses of various duct configurations.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.27 no.2
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• pp.75-81
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• 2018

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of $45^{\circ}$ to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.4
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• pp.284-291
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• 2021

In this paper, we study the consensus problem for multi-agent systems with input saturations. The goal of consensus is to achieve a swarming behavior of multi-agent systems by reaching the agreement through information exchange. This paper considers agents modeled by first-order dynamics with input saturations. In order to guarantee the global convergence of the agents, it is assumed that the agents are stable. Moreover, considering the disturbances, we propose the PI based duplex control method to achieve the consensus. The proposed P controller and I controller are composed of different information network. Then, we investigate the conditions of the information networks and the control gains of P, I controllers to achieve the consensus applying the Lyapunov stability theorem and the Lasalle's Invariance Principle. Finally, we conduct the simulations to validate the theoretical results.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.24-34
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• 2022

This paper investigates the capture of a 12U-sized CubeSat space object using a spider-web structure-based space net. The structural dynamics analysis program ABAQUS is used to simulate the shock-absorbing capability of the space net with a diagonal length of 2.828 m. The space object is modelled as a rigid body, and the space net is modelled using non-linear elastic beam elements. The simulations reveal that the spider-web structure-based space net outperforms the squared space net of the same structural weight in capturing the space object. The numerical simulations are conducted to examine the successful or unsuccessful captures of the space object in various cooperative and non-cooperative motions.