• Proceedings of the KSME Conference
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• 2007.05a
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• pp.780-785
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• 2007

Accurate and fast haptic simulations of deformable objects are desired in many applications such as medical virtual reality. In haptic interactions with a coarse model, the number of nodes near the haptic interaction region is too few to generate detailed deformation. Thus, local refinement techniques need to be developed. Many approaches have employed purely geometric subdivision schemes, but they are not proper in describing the deformation behavior of deformable objects. This paper presents a continuum mechanics-based finite element adaptive method to perform haptic interaction with a deformable object. This method superimposes a local fine mesh upon a global coarse model, which consists of the entire deformable object. The local mesh and the global mesh are coupled by the s-version finite element method (s-FEM), which is generally used to enhance accurate solutions near the target points even more. The s-FEM can demonstrate a reliable deformation to users in real-time.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.373-380
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• 2006

Accurate and fast haptic simulations of deformable objects are desired in many applications such as medical virtual reality. In haptic interactions with a coarse model, the number of nodes near the haptic interaction region is too few to generate detailed deformation. Thus, local refinement techniques need to be developed. Many approaches have employed purely geometric subdivision schemes, but they are not proper in describing the deformation behavior of deformable objects. This paper presents a continuum mechanics-based finite element adaptive method to perform haptic interaction 'with a deformable object. This method superimposes a local fine mesh upon a global coarse model, which consists of the entire deformable object. The local mesh and the global mesh are coupled by the s-version finite element method (s-FEM), which is generally used to enhance accurate solutions near the target points even more. The s-FEM can demonstrate a reliable deformation to users in real-time.

• Electrical & Electronic Materials
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• v.7 no.3
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• pp.200-205
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• 1994

The FEM technique was applied to simulate the change of stress characteristics for various structural parameters and loading positions of the load cell. The output voltage of the load cell was then computed to compare with the manufactured load cell. The tendency of the stress variations of the load cell was well agreed with the basic formula of the single fixed. beam. Also, the stress characteristics according to the change of loading positions showed respective featured results as different structure. The calculated output voltages of the load cell were very close to those of the real manufactured ones.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.426.2-426.2
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• 2014

Wavefront control은 렌즈, 거울 등을 포함한 많은 광학소자를 대체할 수 있는 기술이며, 이는 광 직접 소자 개발에 매우 유용하다. 기존의 Distributed bragg reflector (DBR) 구조의 경우 lattice mismatch, 낮은 효율, 작은 굴절률 차이의 물질만을 사용해야 하는 문제 등으로 광 직접 소자에의 적용에는 한계가 있다. 본 연구에서는 이러한 한계점을 극복하고, 더 나아가 광학소자 구조 내에서의 빛의 거동을 조절하기 위해서 High-index contrast grating (HCG), 즉, 큰 굴절률 차이가 나는 물질로 이루어진 격자 구조 내의 빛이 가지는 waveguide 특성에 대한 연구가 수행되었다. 굴절률 차이가 큰 물질을 sub-wavelength의 주기적인 혹은 비주기적인 격자 구조로 만듦으로써 투과된 빛의 투과도와 위상 등을 조절할 수 있고 이를 통해 빛의 초점 거리, 휘어짐을 조절 할 수 있다. HCG 구조 내의 빛의 거동을 Rigorous coupled wave analysis (RCWA) 및 Finite element method (FEM) 계산을 이용하여 시뮬레이션 하였다. RCWA 계산을 통해 주기 격자구조의 투과도 및 반사도, 빛의 위상을 계산하여 비주기를 갖는 전체적인 HCG 구조를 결정하였고, FEM 계산을 통하여 그 구조 내에서 빛의 거동을 시뮬레이션 하였다. 1,300 nm 파장의 빛이 광원으로 사용되었고 시뮬레이션을 위해 낮은 굴절률의 물질로 ITO, 높은 굴절률의 물질로는 Si이 사용되었다. $15{\mu}m$ 포커싱, $7.91^{\circ}$의 휘어짐을 시뮬레이션 하였고, 실제 소자 공정을 하여 제작한 후, 광 측정 결과 포커싱은 $15{\mu}m$, 휘어짐은 $4.5{\sim}6.5^{\circ}$를 확인하였다. 이러한 결과를 바탕으로 HCG구조체를 통하여 빛의 엔지니어링이 가능함을 알 수 있었다. HCG구조체는 빛이 투과하는 광학 소자의 전반에 적용이 가능하며 더 나아가 인위적인 빛의 엔지니어링이 가능함을 시사한다.

• Journal of Internet Computing and Services
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• v.24 no.2
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• pp.27-36
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• 2023

Waveguides are transmission lines that guide electromagnetic waves in the desired direction and are utilized in various fields such as medical devices, radar systems, and satellite communications. Computational electromagnetics (CEM) is essential for designing and optimizing waveguides. The finite element method (FEM), which is one of the numerical analysis techniques, is efficient in solving closed problems such as waveguides. In order to apply FEM for waveguide analysis, boundary conditions that truncate the computational domain are required. This paper performs electromagnetic simulations using absorbing boundary conditions (ABC) and waveguide port boundary conditions (WPBC) in 2/D and 3/D waveguides using the finite element method and compared their performances. The accuracy of the analysis was verified by comparing the results with HFSS, a representative commercial electromagnetic simulation software. Simulation results confirm that applying WPBC allows for smaller analysis domains than ABC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.15-21
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• 2011

This paper presents an analyzing method of the capacitance of the power transformer for initial voltage distribution and insulation design. When a high incoming surge voltage is accidently occurred in windings of transformer, it does not distribute equally in the windings. This phenomenon makes electric field concentration and the insulating material could be break. Initial voltage distribute mostly depends on capacitances between winding to winding or winding to core in the transformer. If the C network can be structuralized into the equivalent circuit model and be calculated each capacitance element value by circuit analysis and FEM(Finite Element Method) simulation program, the transformer designer could know the place where the structure is to be modified or the insulation to be reinforced. This method quickly provides the data of the voltage distribution in each winding to the designer.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.565-567
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• 2000

In this paper, the discharge characteristics of AC PDP, one of the leading technologies currently under development for large-area flat displays, is computed by using Finite Element Method(FEM) combined with Flux-corrected Transport(FCT) algorithm. Up to now, many simulations of AC PDP have been mainly done by Finite Difference Method(FDM). But we simulated the AC PDP by using FEM-FCT method which discretizes the region of interest with unstructured grids. FEM-FCT method can reduce the computational cost because of refining locally where the physical quantities have steep gradients and is more efficient in solving discharge problems, such as a AC PDP. Results are presented in Ne-Xe(4%) gas mixture for a gas pressure of 400 Torr and as the discharge proceeds, the space and time variations of the electron and ion densities, potential and wall charges on the dielectric are described. Results from our simulation by FEM-FCT are similar to those from simulation by FDM and are more efficient in computational cost reduction.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.471-480
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• 2022

Inductive power transfer (IPT) is an attractive power transmission solution that is already used in many applications. In the IPT system, optimal coil design is essential to achieve high power efficiency, but the effective design method is yet to be investigated. The inductance formula and finite element method (FEM) are popular means to link the coil geometric parameters and circuit parameters; however, the former lacks generality and accuracy, and the latter consumes much computation time. This study proposes a novel coil design method to achieve speed and generality without much loss of accuracy. By introducing one-turn permeance simulation in each FEM phase combined with curve fitting and optimization by MATLAB in the efficiency calculation phase, the iteration number of FEM can be considerably reduced, and the generality can be retained. The proposed method is verified through a 100 W IPT system experiment.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.419-421
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• 2008

본 논문에서는 Ansoft의 PExprt를 소개하고 PExprt를 사용하여 변압기 및 인덕터를 설계하는 방법을 다루었다. PEprt에서 지원하는 FEM 해석을 이용하여 설계된 변압기와 인덕터를 Simplorer용 모델로 변환하고 시뮬레이션에 사용함으로써 보다 정확한 시뮬레이션 결과를 얻을 수 있었다. 변압기와 인덕터의 실제 제작을 통하여 PExprt의 설계 결과를 확인하고 실험 결과를 통하여 FEM 해석을 통한 Simplorer 모델의 동작을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.118-119
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• 2006

현재의 소자간 연결을 위해 사용되는 금속배선의 한계로 인해 보다 고속/대용량의 광연결(Optical Interconnection)이 크게 각광받고 있다. 본 논문에서는 FEM 시뮬레이션(Finite Element Method Simulation)을 통해 온도변화에 따른 기판에서의 온도분포를 살펴보고, 열응력 분포와 열응력 집중에 의한 기판의 변형으로 인한 문제를 연구하였다. 이를 통해 향후 Optical Passive Component 설계시 Optical Passive Component 변형의 원인이 될 수 있는 열원들의 배치를 최적화 시키고 기판의 취약부운을 보강하여 우수한 성능의 Optical Passive Component 제작을 목표로 하고 있다.