• Journal of the Optical Society of Korea
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• 제17권3호
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• pp.269-274
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• 2013

The effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light-emitting diodes (OLEDs) was studied by optical simulation based on the point-dipole model. The diffusing substrate included Mie scatterers by which the condition of total internal reflection could be broken. The finite-difference time-domain method was used to obtain the intensity distribution on the transparent electrode of an OLED, which was used as a light source to carry out a ray-tracing simulation of the OLED and the diffusing substrate. It was found that the outcoupling efficiency of the OLED was sensitive to the thickness of organic layers and could be increased by 21.0% by adopting a diffusing substrate in which Mie scatterers whose radius was $2.0{\mu}m$ were included at the density of $10^7mm^{-3}$ and by 65.5% by forming one pillow lens with the radius of 2 mm on the front surface of the glass substrate. This study revealed that the outcoupling efficiency could be improved by adopting diffusing substrate and pillow lenses along with the optimization of the thickness of each layer in the OLED.

• 한국진공학회지
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• 제17권6호
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• pp.511-517
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• 2008

기체 방전의 수치적 시뮬레이션을 위하여 FE-FCT(Finite-Element Flux-Corrected Transport) 방법을 이용한 준 2차원 수치적 모델을 제시한다. 이 모델에서는 전자와 이온에 대한 1차원 연속방정식을 풀어 시 공간적으로 변하는 전하 분포를 계산하고, 공간 전하 분포에 의한 전기장의 변화는 2차원적 전하 분포를 고려하는 디스크 방법을 적용하여 푸아송(Poisson)방정식을 풀어 계산한다. 다양한 벤치마크 문제에 대해 계산한 결과는 이 모델의 정확성과 적용성을 잘 보여준다. 또 스트리머 방전에 대해 계산한 결과는 앞선 연구 결과와 잘 일치하는 것을 보여 준다.

• International Journal of Contents
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• 제7권4호
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• pp.1-5
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• 2011

Physics based fluid animation schemes need large computation cost due to tremendous degree of freedom. Many researchers tried to reduce the cost for solving the large linear system that is involved in grid-based schemes. GPU based algorithms and advanced numerical analysis methods are used to efficiently solve the system. Other groups studied local operation methods such as SPH (Smoothed Particle Hydrodynamics) and LBM (Lattice Boltzmann Method) for enhancing the efficiency. Our method investigates this efficiency problem thoroughly, and suggests novel paradigm in fluid animation field. Rather than physics based simulation, we propose a robust boundary handling technique for procedural fluid animation. Our method can be applied to arbitrary shaped objects and potential fields. Since only local operations are involved in our method, parallel computing can be easily implemented.

• 한국정보통신학회논문지
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• 제10권10호
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• pp.1752-1758
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• 2006

자동차 경주 게임은 실시간에 시뮬레이션 될 수 있는 사실적인 물리 모델을 요구한다. 자동차 경주 게임에서는 움직임의 사소한 오류도 쉽게 눈에 띄며, 다른 게임과 같이 상호작용적으로 동작해야 한다. 타이어와 지면의 정확한 물리를 모델링하여 이를 실시간 환경에 구현하는 것은 어려운 일이다. 이 논문에서는 효율적이며 효과적인 '가상 벽(imaginary wall)' 모델을 제안한다. 이 기법은 사용된 물리 모델의 단순성 때문에 쉽게 구현이 가능하며, 시뮬레이션의 결과가 자동차 경주 게임에 사용하기에 충분한 사실성을 가진다.

• 천문학회보
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• 제41권1호
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• pp.69.2-69.2
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• 2016

We study the environmental dependence of the mass-size relation for the most massive early type galaxies (M>$10^{10.7}M_{\odot}$) in the redshift range 0.10~0.15. The sizes of galaxies are measured by non-parametric method. We find that galaxies more massive than $10^{11.1}M_{\odot}$ show the environmental dependence in the mass-size relation. The galaxies with M>$10^{11.1}M_{\odot}$ located in the densest, cluster like environment have larger sizes and extended surface brightness profiles than their counterparts located in a low dense environment. We also find that the environmental dependence of the mass-size relation is more significant for the brightest cluster galaxies (BCGs) than non-BCGs. We use the semi analytic galaxy formation simulation based on the Millennium 1 Simulation for interpretation. Our result can be explained with a hierarchical growth of the most massive galaxies through dissipation-less merger in dense environment.

• Wind and Structures
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• 제5권5호
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• pp.441-462
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• 2002

This paper presents a practical numerical method to determine both the spatial and temporal distribution of driving rain on buildings. It is based on an existing numerical simulation technique and uses the building geometry and climatic data at the building site as input. The method is applied to determine the 3D spatial and temporal distribution of wind-driven rain on the facade a low-rise building of complex geometry. Distinct wetting patterns are found. The important causes giving rise to these particular patterns are identified : (1) sweeping of raindrops towards vertical building edges, (2) sweeping of raindrops towards top edges, (3) shelter effect by various roof overhang configurations. The comparison of the numerical results with full-scale measurements in both space and time for a number of on site recorded rain events shows the numerical method to yield accurate results.

• 한국자기학회지
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• 제18권4호
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• pp.127-130
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• 2008

본 논문에서는 수 백 나노미터 크기의 자성 소자에서 존재하는 강자기 소용돌이 구조의 운동에 대한 이론을 제시한다. LLG 방정식으로부터 유도된 운동방정식, 즉 Thiele 방정식에 그 이후 밝혀진 이론적 결과들을 도입하여 강자기 소용돌이의 감쇠 단조화 운동방정식을 도출하였다. 이러한 운동방정식으로부터 감쇠 단조화 운동의 고유 진동수와 감쇠 상수를 나타내는 수식을 유도하였으며, 유도된 수식을 micromagnetic 시늉 실험을 통하여 검증하였다.

• 한국광학회지
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• 제32권1호
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• pp.29-33
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• 2021

본 논문에서는 주기적 분극된 비선형 결정(periodically poled potassium titanyl phosphate; PPKTP)에서 자발매개하향변환(spontaneous parametric down conversion; SPDC)과정으로 생성된 예고된 단일 광자 광원을 이용하여 레겟-가르그 부등식(Leggett-Garg inequality; LGI)의 위배를 실험적으로 모사하였다. 생성된 광자의 편광 방향에 따라서 편광된 광자 수를 측정하여 n-측정수에 따른 레겟-가르그 부등식을 모사하였다. 단일 광자의 편광 기반 LGI에 대한 실험 결과는 이론적인 계산 결과와 일치하는 것을 확인하였다.

• 천문학회보
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• 제45권1호
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• pp.48.2-48.2
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• 2020

We present a new void definition that connects voids with clusters, the high-density counterpart. We use a pair of ΛCDM simulations whose initial density fields are sign inverted versions to each other, and study the relation between the effective void volume and the corresponding cluster mass. Massive cluster halos (M ≥ 1013M⊙/h) are identified in one simulation at z=0 by linking dark matter particles. The corresponding void to each cluster is defined in the other simulation as the region occupied by the member particles of the cluster. We find a universal functional form of density profiles at z=0 and 1. We also find a power-law relation between the void effective radius and the corresponding cluster mass. Based on these findings, we identify cluster-counterpart voids directly from a density field without using the pair information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We identified voids corresponding to clusters more massive than M ≥ 3 × 1014M⊙/h at approximately 70-74 \% level of completeness and reliability. Our results suggest that we can detect voids comparable to clusters of a particular mass-scale.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.451-462
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• 2024

In order to optimize the operational safety and reliability of the upper launcher for the CFETR ECRH system, a design of the launcher based on the remote steering concept is currently being carried out for comparison with the front steering equivalent. This paper presents the remote steering system's conceptual design and simulation analysis. A Square Corrugated Waveguide (SCW) of 65 × 65 mm has been designed with an optimized length of 9.35 m. By changing the relative length of the waveguide, the transmission efficiency of the SCW is optimized within the range of steering angles ±12°. Different error factors are investigated in detail, and corresponding acceptable error ranges are provided. Considering these error factors and ignoring ohmic losses and thermal effects, the relative transmission efficiency of the SCW is estimated to be >98 % within the steering angle range. A matching steering unit for the SCW is designed, which consists of an ellipsoidal focusing mirror and a steerable flat mirror. The detailed design of the steerable mirror motion trajectory is presented. Also, the influence of the possible beam incident errors caused by the steering unit on the transmission efficiency is analyzed in detail.