• Nuclear Engineering and Technology
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• 제52권5호
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• pp.956-963
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• 2020

Dose optimization for Radioactive Occupational Personal (ROP) is an important subject in nuclear and radiation safety field. The geometric environment of a nuclear facility is complex and the work area is radioactive, so traditional navigation model and radioactive data field cannot form an effective environment model for dose assessment and dose optimization. The environment model directly affects dose assessment and indirectly affects dose optimization, this is an urgent problem needed to be solved. Therefore, this paper focuses on an environment model used for Dose Assessment and Dose Optimization (DA&DO). We designed a multi-layer radiation field coupling modeling method, and then explored the influence of the environment model to DA&DO by virtual simulation. Then, a simulation test is done, the multi-layer radiation field coupling model for nuclear facilities is demonstrated to be effective for dose assessment and dose optimization through the experiments and analysis.

• Structural Engineering and Mechanics
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• 제89권2호
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• pp.199-211
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• 2024

The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C⁰ continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C¹ continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

• Ocean Systems Engineering
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• 제7권3호
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• pp.195-223
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• 2017

This paper presents 3D numerical simulations of a Free Standing Hybrid Riser under Vortex Induced Vibration, with prescribed motion on the top to replace the motion of the buoyancy can. The model is calculated using a fully implicit discretization scheme. The flow field around the riser is computed by solving the Navier-Stokes equations numerically. The fluid domain is discretized using the overset grid approach. Grid points in near-wall regions of riser are of high resolution, while far field flow is in relatively coarse grid. Fluid-structure interaction is accomplished by communication between fluid solver and riser motion solver. Simulation is based on previous experimental data. Two cases are studied with different current speeds, where the motion of the buoyancy can is approximated to a 'banana' shape. A fully three-dimensional CFD approach for VIV simulation for a top side moving Riser has been presented. This paper also presents a simulation of a riser connected to a platform under harmonic regular waves.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 추계종합학술대회
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• pp.106-109
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• 1999

본 논문에서는 외부에 존재하는 전자파원으로부터 공동 구조의 벽면에 존재하는 개구를 통해 공통 내부로 침투되는 전계의 크기를 모멘트법으로 계산하고 실험결과와 비교 검토하였다. 실험을 통해 측정만 내부 전계의 크기는 수치 해석 결과와 전계의 크기에는 차이가 있으나 전계 분포의 모양은 그 경향이 일치하고 있다는 것을 확인하였다. 또한, 외부 전자파원에 의해 공동의 내부로 침투되는 내부 전계의 감소 기법으로서 개구에 리액턴스를 장하하는 방법을 제안하고 있다.

• 한국시뮬레이션학회논문지
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• 제25권3호
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• pp.41-51
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• 2016

본 연구는 보행자의 물리적 특성(크기, 모양, 자세 등)을 적용한 개선된 플로어 필드 모델(Floor field model; FFM)을 소개하고, 개선된 모델과 널리 알려진 다른 피난시뮬레이션 모델과의 비교를 통해 FFM의 한계점 파악 및 개선된 모델의 특징을 분석하고자 한다. FFM은 셀룰라 오토마타(Cellular automata)를 이용한 대표적 미시적 관점 보행 모델이지만 보행자의 크기, 모양, 자세 등의 물리적 특성을 세밀하게 반영하지 않는다. 이로 인해 보행자들 간의 충돌, 마찰 등의 현상을 모델링하기 어려우며 결과적으로 다른 모델들과 비교하였을 경우에 매우 짧은 대피 시간을 산출하고 있다. 본 연구는 물리적 현상을 반영할 수 있는 개선된 FFM을 제시하며, 개선된 모델과 기존 FFM, 시뮬렉스(Simulex), 패스파인더(Pathfinder) 등 다른 모델들과의 비교 실험을 수행하였다. 실험은 실제 캠퍼스 건물의 일부 공간을 대상으로 진행되었으며, 대피 인원의 변화에 따른 대피 양상의 비교와 각 출구별 대피 양상의 비교가 수행되었다. 이를 통해 FFM에서는 반영되지 않던 물리적 현상들이 개선된 모델에서는 상용 모델 수준으로 적용되는 점과 특히 시뮬렉스와 유사한 형태의 대피 양상을 보임을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1995-2003
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• 2014

Power semiconductor devices have been the major backbone for high-power electronic devices. One of important parameters in view of power semiconductor devices often characterize with a high breakdown voltage. Therefore, many efforts have been made, since the development of the Insulated Gate Bipolar Transistor (IGBT), toward having higher level of breakdown voltage, whereby the typical design thereof is focused on the structure using the field ring. In this study, in an attempt to make up more optimized field-ring structure, the characteristics of the field ring were investigated with the use of theoretical arithmetic model and methodologically the design of experiments (DOE). In addition, the IGBT having the field-ring structure was designed via simulation based on the finding from the above, the result of which was also analyzed. Lastly, the current study described the trench field-ring structure taking advantages of trench-etching process having the improved field-ring structure, not as simple as the conventional one. As a result of the simulation, it was found that the improved trench field-ring structure leads to more desirable voltage divider than relying on the conventional field-ring structure.

• 한국산업보건학회지
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• 제11권1호
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• pp.78-84
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• 2001

A CFD simulation of airflow and temperature field in a heated room has been described in this paper. The thermal wall jet created by a radiator greatly influences the airflow pattern, temperature distribution. The area close La a heat source has a higher risk of air-borne contamination and imposes a harmful effect on occupants in that area. The predicted flow field, temperature results show good agreement with the measured data. As the results were compared with experimental data, the applicability of CFD was satisfactorily verified. Also, the CFD simulation can capture the natural convective flow features. If a CFD simulation is applied ventilation design with a heat source, An effective design will be attained. Further study is required to improve the accuracy of CFD simulation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.118-122
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• 2000

Recently, High accuracy and precision are required in various industrial field especially, semiconductor manufacturing apparatus, Ultra precision positioning apparatus, Information field and so on. Positioning technology is a very important one among them. For composition of this technology, the development of system with high speed and high resolution is needed. At start point and end position vibration must be repressed on this system for composition of position control. This vibration is arisen nose, is increased setting time, is reduced accuracy. Especially, repressed for the lead with high speed. The small actuator with high speed and high resolution is need to repression against this residual vibration. This actuator is, for example, piezo actuator, piezoelectric material that converting from electronic signal to mechanical force is adequate material, beacause of control of control to position and force. In this study, piezo electric material is used to actuator, ultra precision positioning apparatus with stage of hinge structure is designed, simulation is performed, control performance is tested by producing apparatus. For easy usage and stability in industrial field, we perform to simulation and to position control test by digital PID controller.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.274-277
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• 2008

To evaluate high-resolution wind resources for local and coastal area with complex terrain was attemped to combine the prognostic MM5 mesoscale model with CALMET diagnostic modeling this study. Firstly, MM5 was simulated for 1km resolution, nested fine domain, with FDDA using QuikSCAT seawinds data was employed to improve initial meteorological fields. Wind field and other meteorological variables from MM5 with all vertical levels used as initial guess field for CALMET. And 5 surface and 1 radio sonde observation data is performed objective analysis whole domain cells. Initial and boundary condition are given by 3 hourly RDAPS data of KMA in prognostic MM5 simulation. Geophysical data was used high-resolution terrain elevation and land cover(30 seconds) data from USGS with MM5 simulation. On the other hand SRTM 90m resolution and EGIS 30m landuse was adopted for CALMET diagnostic simulation. The simulation was performed on whole year for 2007. Vertical wind field a hour from CALMET and latest results of MM5 simulation was comparison with wind profiler(KEOP-2007 campaign) data at HAENAM site.

• 한국정보통신학회논문지
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• 제18권12호
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• pp.3069-3078
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• 2014

본 연구에서는 다양한 수중무기폭발 체계 중 대표적인 비닉(庇匿) 무기체계인 기뢰를 중심으로 공격형 부설에 의한 억제 시 적함 탐지의 핵심이 될 자력계를 신규 Modeling & Simulation에 의해 성능 개선의 효과를 사전 검증한다. 또한, 신규 3축 자력계를 설계/제작/실험을 진행한 결과를 다룬다. 신규 자력계를 새로운 신형 수중무기체계에 적용하기 위해 상용 전자기장 수치해석 도구를 이용해 잠수함을 모델링하여 실 함정의 자기장특성을 예측한다. 실험의 마지막 단계로 축소 모형을 제작하여 실제 해상시험을 하지 않더라도 육상에서 성능검증 할 수 있는 방법을 제시한다.