• 한국컴퓨터그래픽스학회논문지
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• 제25권1호
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• pp.13-22
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• 2019

본 논문에서는 입자 기반 유체 시뮬레이션에서 과하게 보존되는 액체 시트를 제거함으로써 유체 표면의 디테일을 개선시키는 새로운 방법을 제안한다. 지금까지 울퉁불퉁하고 구멍이 생기는 유체 표면의 고질적인 문제를 해결하기 위한 다양한 비등방성 접근법들은 제안되었지만, 액체 시트의 보존과 분해를 안정적으로 표현할 수 있는 방법은 제시되지 않았다. 본 연구에서는 비등방성 커널과 밀도를 기반으로 하여 물 입자를 동적으로 추가/삭제함으로 입자 기반 유체시뮬레이션에서 액체 시트의 보존과 분해라는 두 가지 특징을 동시에 표현할 수 있는 새로운 프레임워크를 제안한다. 이 방법은 입자 기반 유체 시뮬레이션 접근법에서 과하게 보존되는 액체 시트를 제거함으로써 분열되는 유체 시트의 특징을 잘 표현했으며, 결과적으로 노이즈를 없애 액체 시트의 품질을 개선시켰다.

• 해양환경안전학회지
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• 제24권1호
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• pp.119-125
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• 2018

입자기반 전산유체역학 기법은 유체역학에서의 라그란지안 접근법에 기반을 두고 있다. 입자기반 방식은 입자 각각이 물리량을 가지고 움직이며 이러한 입자의 움직임을 추적하는 방식으로 유체의 거동을 구현할 수 있다. 이러한 방식은 격렬한 움직임에 의한 자유표면 혹은 경계면의 운동 재현에 우수성이 있으나 연속체역학을 위반할 수 있다는 문제점 역시 포함하고 있다. 이를 반대로 말하자면 특별한 조치를 취하지 않는 경우에는 연속체가 아닌 물질에 대한 구현이 매우 쉽게 가능하다는 것이기도 하다. 이에 따라, 기존의 유체에서 사용되는 입자기반 전산해석방식을 지배방정식 단계에서부터 고체입자형으로 변형이 가능하다는 것을 알 수있다. 본 연구에서는 입자기반 전산해석방식을 고체입자에 알맞은 형태로 변환하였다. 변환을 위해 유체에서 사용되는 점성항을 제거하고 대신 마찰항을 추가하였다. 본 연구에서 개발된 고체입자형 전산해석 프로그램을 이용하여 고체입자의 붕괴를 구현하였으며 이를 유체입자 붕괴와의 비교를 통해 입증하였다. 또한 유체입자가 가질 수 없는 고체입자만의 특성인 안식각을 구현하여 고체입자를 위한 입자기반 전산해석 프로그램을 완성하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.433-436
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• 2006

In this study we perform Lagrangian stochastic model simulation for heavy particle. Reynolds(2002) construct simple LSM for heavy particle, which lack in detailed parameter study and statistics of turbulent flow within his paper. we investigate more simple but important turbulent statistics such as autocorrelation for velocity and acceleration, Lagrangian structure function and dispersion statistics parameterized by using DNS.

• 전자공학회논문지A
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• 제31A권5호
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• pp.134-148
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• 1994

A full two-dimensional MOSFET simulator utilizing the Mixed Particle Monte Carlo method is introduced. Particle simulation for both electrons and holes are self-consistently coupled with Poisson 's equation. To demonstrate the performance of the simulator, steady state and transient state solutions of the terminal characteristics and the internal physical quantities are obtained for 0.25$\mu$m MOSFETs with three different structures` conventional single drain, LDD and GOLD MOSFET structures.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.803-806
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• 2002

The dispersion of Lagrangian fluid particles in a turbulent channel flow is studied by a direct numerical simulation. Four points Hermite interpolation in the homogeneous direction and Chebyshev polynomials in the inhomogeneous direction is adopted by assesing the acceleration of fluid particles. In order to characterize the inhomogeneous Lagrangian statistics, accurate single particle Lagrangian statistics are obtained along the wall normal direction. Integral time scales of Lagrangian velocity can be normalized by Eulerian mean shear stresses.

• 대한기계학회논문집B
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• 제26권2호
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• pp.227-237
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• 2002

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.242.1-242.1
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• 2014

The electron cyclotron resonance plasma source with a belt-type magnet assembly (BMA) is designed for effective plasma confinements. For characterizing the plasma source, the plasma parameters are measured by Langmuir probe. However, the plasma parameters and the motion of charged particles near the ECR zone are not easy to diagnostics, because of the high plasma density and temperature. Thus, as an alternative method, the electromagnetic simulation of the plasma source has been performed by using three-dimensional particle-in-cell and Monte Carlo collisional (PIC-MCC) simulation codes. For considering the limitation of simulation resources and time, the periodic boundary condition is applied and the coulomb collision is neglected. In this paper, we present the results of 3D PIC simulations of ECR plasmas with BMA and we compare them with the experimental results.

• 로봇학회논문지
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• 제4권2호
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• pp.97-104
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• 2009

Recently, simultaneous localization and mapping (SLAM) approaches employing Rao-Blackwellized particle filter (RBPF) have shown good results. However, due to the usage of the accurate sensors, distinct particles which compensate one another are attenuated as the RBPF-SLAM continues. To avoid this particle depletion, we propose the strategic games to assign the particle's payoff which replaces the importance weight in the current RBPF-SLAM framework. From simulation works, we show that RBPF-SLAM with the strategic games is inconsistent in the pessimistic way, which is different from the existing optimistic RBPF-SLAM. In addition, first, the estimation errors with applying the strategic games are much less than those of the standard RBPF-SLAM, and second, the particle depletion is alleviated.

• 한국가시화정보학회지
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• 제21권1호
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• pp.119-126
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• 2023

Acquiring experimental data for PIV verification or machine learning training data is resource-demanding, leading to an increasing interest in synthetic particle images as simulation data. Conventional synthetic particle image generation algorithms do not follow physical laws, and the use of CFD is time-consuming and requires computing resources. In this study, we propose a new method for synthetic particle image generation, based on a Physics-Informed Neural Networks(PINN). The PINN is utilized to infer the flow fields, enabling the generation of synthetic particle images that follow physical laws with reduced computation time and have no constraints on spatial resolution compared to CFD. The proposed method is expected to contribute to the verification of PIV algorithms.

• ETRI Journal
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• 제45권3호
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• pp.394-403
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• 2023

Direct tracking problem of moving noncircular sources for multiple arrays is investigated in this study. Here, we propose an improved unscented particle filter (I-UPF) direct tracking method, which combines system proportional symmetry unscented particle filter and Markov Chain Monte Carlo (MCMC) algorithm. Noncircular sources can extend the dimension of sources matrix, and the direct tracking accuracy is improved. This method uses multiple arrays to receive sources. Firstly, set up a direct tracking model through consecutive time and Doppler information. Subsequently, based on the improved unscented particle filter algorithm, the proposed tracking model is to improve the direct tracking accuracy and reduce computational complexity. Simulation results show that the proposed improved unscented particle filter algorithm for noncircular sources has enhanced tracking accuracy than Markov Chain Monte Carlo unscented particle filter algorithm, Markov Chain Monte Carlo extended Kalman particle filter, and two-step tracking method.