• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.362-363
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• 2006

Nano-structured tungsten carbide compacts with cobalt matrices (WC-Co) offer new opportunities for achieving superior hardness and toughness combinations. A unified modeling and simulation tool has been developed to produce maps of sintering pathways from nanocrystalline WC powder to sintered nano-structured WC-Co compacts. This tool includes (1) die compaction, (2) grain growth, (3) densification, (4) sensitivity analysis, and (5) optimization. All material parameters were obtained by curve fitting based on results with two WC-Co powders. Critical processing parameters are determined based on sensitivity analysis and are optimized to minimize grain size with high density.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.57-64
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• 2021

Maneuvering motions of a ship in calm water are studied through the concept of MMG model. Governing forces are defined by the use of available empirical formulae that require only main ship particulars as input variables. In order to validate the calculation tool, a full-scale sea experiment was carried out in Osaka Bay using a 17-m twin-screw passenger ferry. Test execution and data measurement were performed through the utilization of an autopilot control unit and satellite compass. The result of a straight running test confirms the acceptable accuracy in addressing the surge motion problem. Reasonable agreement between simulation and experiment is also confirmed for 5°/5° and 10°/10° zig-zag tests despite the strong environmental disturbance. The current model can generally represent the subject ship maneuvering motions and is promising for the application to other ship hulls.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1334-1337
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• 2011

HLA(High Level Architecture)는 분산 환경의 모델링 및 시뮬레이션(Modeling & Simulation)을 위한 공통 아키텍처를 제공하는 기술 표준이며, RTI(Run-Time Infrastructure)를 통해 HLA 서비스를 제공한다. HLA는 연동 객체 모델인 FOM(Federation Object Model)을 기반으로 시뮬레이션 환경을 구성하며, 시뮬레이션에 참여하는 모든 시뮬레이터는 동일한 FOM을 소유해야 한다. 따라서 시뮬레이션 체계 간 연동을 수행하기 위해서는 FOM을 통합하거나 FOM 간 연동을 위한 게이트웨이를 구현해야 한다. 한편, FOM을 통합하는 방법은 각 시뮬레이션의 연동 인터페이스 수정이 필요하기 때문에 게이트웨이를 구현하는 방법이 기존 시스템의 변경을 최소화할 수 있다. 따라서 본 논문은 HLA기반 시뮬레이션의 체계 간 연동을 제공할 수 있는 게이트웨이 구조를 제시한다. 특히, XML 형태의 객체 모델을 기반으로 교환 메시지를 정의하고, 메시지 처리 모듈을 게이트웨이에 플러그인 함으로써 시뮬레이션 체계 간 연동의 용이함을 보여준다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1375-1378
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• 2011

국방 분야의 모델링 및 시뮬레이션(Modeling & Simulation) 분야에서 재사용성 및 상호운용성 확보는 기 개발된 모델을 연동하여 시뮬레이션을 확장할 수 있다는 측면에서 핵심이 된다. 이러한 핵심기술 확보를 위해 시뮬레이션 소프트웨어의 공통 컴포넌트를 설계하고, 표준 연동 미들웨어인 Run-Time Infrastructure(RTI)를 적용한 프레임워크가 개발되었다. 한편, 시뮬레이션 환경은 목적에 따라 시뮬레이션 모델의 기능이 달라지거나, 동일한 모델이 분산 컴퓨팅뿐만 아니라 단일 컴퓨팅 환경에서도 수행되도록 요구된다. 본 논문은 이러한 요구사항을 만족시킬 수 있도록 모델 연동을 위한 플러그인 방식의 인터페이스 설계 방안을 제시하고, 분산 시뮬레이션의 동일한 모델을 단일 시스템에서 시뮬레이션 할 경우 모델 컴포넌트 간 데이터 교환 및 메시지 순서화를 제공할 수 있는 메커니즘을 기술한다.

• Design & Manufacturing
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• v.17 no.3
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• pp.61-66
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• 2023

In this study, we developed a simulation methodology for a technology that rapidly cools molds by directly spraying them with CO₂ in its liquefied gaseous state. Initially, a simulation verification process was conducted using ANSYS Fluent's heat transfer analysis based on temperature values measured in prior research experiments, ensuring a comparable temperature could be calculated. Subsequently, the validated analysis method was employed to evaluate design factors that exert the most significant influence on cooling. An evaluation was conducted based on three factors: part thickness, mold thickness, and the melting temperature of material. Using a full factorial design approach, a total of 27 analyses were completed and subsequently calculated through analysis of means. The impact assessment was carried out based on the temperature values at the product's core. The results indicated that the thickness of the mold had the highest influence, while the melting temperature of material had the least.

• Journal of Korea Foundry Society
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• v.24 no.4
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• pp.225-230
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• 2004

Computer simulation of mold filling and solidification has been performed in order to analyze the flow and solidification phenomena for the casting process of cylinder liner. The simulation result of mold filling shows that the molten metal flows into the mold in stable without scattering. The simulation results of solidification indicate that the last solidified area is located in the feeder. The temperature variation in casting is measured in actual casting and the result is compared with calculation result.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.176-187
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• 2015

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1559-1564
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• 2004

The process design of hot forging, asymmetric to symmetric rib-web shaped steel, which is used for the turnout of express rails has been studied. Owing to the great difference in shape between the initial billet and the final forged product, it is impossible to hot forge the rail in a single stage operation. The numerical simulation for hot forging of asymmetric shape to symmetric shape was carried out by using commercial FEM code, DEFORMTM-2D. For comparison with the simulation results, a experiment of flow analysis using plasticine was also carried out. The results of the flow experiment showed good agreement with those of the simulation.

• Korean System Dynamics Review
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• v.15 no.2
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• pp.27-50
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• 2014

Korea government established the energy technology development plan (2011-2020) and declared to be a leader of the green energy technologies. The plan aims for 10% market share in the green energy industry, 12% energy efficiency improvement, and 15% greenhouse gas reduction. In order to achieve these goals, the government has tried to calculate the whole scale of national energy R&D investment, annual budget and specific expenditures for new technologies by computer simulation. The simulation modules include the R&D investment model, GDP model, energy consumption and $CO_2$ emission model by System Dynamics. Based on these simulation modules, I tested various scenarios for effectiveness of energy R&D investments until 2020. The results show that Korea should increase national energy R&D investment to 2.3 billion U.S. dollars, and switch the investment from electricity and nuclear power to the renewable energy.

• The KSFM Journal of Fluid Machinery
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• v.9 no.2 s.35
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• pp.13-18
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• 2006

This paper was studied to design Process considered flexibility and reliability of suction and discharge valves. Flexibility and reliability of valves are main important factors in compressor valves design. And they are incompatible with efficiency of compressor. In this study, we have performed the optimal design of CO2 compressor valves to consider these factors. At first, we analyzed performance simulation of compressor to obtain optimal flexibility level of valves. From this simulation, we could get some important data at valve design like the optimal natural frequency and the height of retainer. After that we studied to reliability of valves corresponding to optimal flexibility level by finite element method. For each case bending stress and natural frequency were obtained by it. Also we investigated the fatigue stability to obtain optimal valve shape that ensured to reliability.