• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1522-1527
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• 2004

In this paper, slurry fluid motion, abrasive particle motion, and effects of groove sizing on the pads are numerically investigated in the 2D geometry. Groove depth is optimized in order to maximized the abrasive effect. The simulation results are analyzed in terms of shear stress on pad, groove and wafer, streamline and velocity vector. The change of groove depth entails vortex pattern change, and consequently affects material removal rate. Numerical analysis is very helpful for disclosing polishing mechanism and local physics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.898-900
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• 1998

This paper describes the motion characteristics and micro-discharge of the free conducting particles between plain electrodes under alternating voltage. The particles move between both electrodes due to electrostatic force by applied AC voltage. Various types and sizes of free conducting particles were used to study the motion and micro-discharge characteristics. The micro-discharge and breakdown were observed during the particle motion.

• 한국지능시스템학회논문지
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• 제22권3호
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• pp.353-360
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• 2012

본 논문은 파티클 필터 방법을 이용하여 로봇의 외부에 설치된 특징점들과 로봇의 위치를 동시에 추정하는 SLAM 방법을 제안한다. 파티클 필터 방법은 로봇 동작의 비선형성 및 센서 오차의 비가우시안 특성을 고려할 수 있다. 제안된 방법에서 추정할 변수는 로봇의 위치와 특징점들의 위치이다. 본 연구에서 특징점은 초음파 신호를 발생시키는 4개의 비이컨들이 사용된다. 그리고 로봇은 비이컨들로부터 초음파 신호를 수신하여 각각의 비이컨까지의 거리를 계산한다. 그리고 영역센서를 이용하여 이동로봇이 동작하는 환경의 기하학적 지도정보를 생성하는 과정을 보였다. 제안된 방법은 로봇의 위치와 방향을 추정하기 때문에 영역센서에 의해 획득된 데이터를 사용하여 기하학적 지도를 생성할 수 있다. 또한 데드레크닝 방법 및 삼변측량 방법과의 로봇 위치추정 비교 실험을 통하여 제안된 방법을 평가하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.267-267
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• 2019

Driftwood is one of serious problems in a river environment. In several countries, such as Indonesia, Japan, and Italy, the driftwood frequently appears in a river basin, and it can alter the channel bed, flow configuration by wood deposition and jam formation. Therefore, the studies related to driftwood have been actively conducted by many researchers to understand the mechanism of driftwood dynamics. In particular, wood motion by collision is one of the difficult issues in the numerical simulation because the calculation for wood collision requires significantly expensive calculation time due to small time step. Thus, this study conducted the numerical simulation in consideration of the wood motion by water flow and wood collision to understand the wood dynamics in terms of computation. We used the 2D (two-dimensional) depth-averaged velocity model, Nays2DH, which is a Eulerian model to calculate the water flow on the generalized coordinate. A Lagrangian type driftwood model, which expresses the driftwood as connected sphere shape particles, was employed to Nays2DH. In addition, the present study considered root wad effect by using larger diameter for a particle at a head of driftwood. An anisotropic bed friction was considered for the sliding motion dependent on stemwise, streamwise and motion directions. We particularly considered changeable draft at each particle and projection area by an angle between stemwise and flow directions to precisely reproduce the wood motions. The simulation results were compared with experimental results to verify the model. As a result, the simulation results showed good agreement with experimental results. Through this study, it would be expected that this model is a useful tool to predict the driftwood effect in the river flow.

• 자원리싸이클링
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• 제31권6호
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• pp.36-43
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• 2022

순환골재 입도 분리를 위해 사용되는 일반적인 스크린은 막힘 현상으로 인해 함수 시료 처리가 제한적이다. 따라서 본 연구에서는 기존 스크린의 분리 효율을 개선하기 위하여, DEM(Discrete Element Method) 기반의 모사 실험을 통해 스프링 기반의 추가 보조 진동 장치의 우수성을 판단하였다. 스프링 디자인에 따른 변위, 진폭 및 변형 각 분석을 통해 운동 특성을 확인하였으며, 이를 스크린에 적용하여 입자의 거동을 모사하였다. 입자 모사 결과, 스프링이 적용된 스크린의 물질 흐름 및 분리 효율은 각각 9.2 kg/s, 97 %로 나타났으며, 기존 스크린과의 비교를 통해 막힘 방지 스프링의 적용은 기존 스크린을 개선할 수 있음을 확인하였다.

• Nuclear Engineering and Technology
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• 제42권2호
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• pp.211-218
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• 2010

An analysis model on debris transport in the containment floor of pressurized water reactors is developed in which the flow field is calculated by Eulerian conservation equations of mass and momentum and the debris particles are traced by Lagrange equations of motion using the pre-determined flow field data. For the flow field calculation, two-dimensional Shallow Water Equations derived from Navier Stokes equations are solved using the Finite Volume Method, and the Harten-Lax-van Leer scheme is used for accuracy to capture the dry-to-wet interface. For the debris tracing, a simplified two-dimensional Lagrangian particle tracking model including drag force is developed. Advanced schemes to find the positions of particles over the containment floor and to determine the position of particles reflected from the solid wall are implemented. The present model is applied to calculate the transport fraction to the Hold-up Volume Tank in Advanced Power Reactors 1400. By the present model, the debris transport fraction is predicted, and the effect of particle density and particle size on transport is investigated.

• 한국입자에어로졸학회지
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• 제11권2호
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• pp.29-36
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• 2015

The purpose of this research is to find out the collection property of nanoparticle in diffusion filter to know particle size dispersion of nanomaterial using inertial force and principle of Brownian diffusion motion. We used inertial filters which are two different type and diffusion filters made by various kinds of Wiremesh and the different pieces of filter to compare with particle size distribution using NaCl particles. Finally, We made a conclusion as follows : (1) the bigger available charging volume is and the larger specific surface area of inertial filter is, the better collection efficiency is. (2) The higher wire-mesh number of filter is, the more collection efficiency of small particle is increasing because the wire of the higher Wiremesh number filter is thinner and denser. (3) The more pieces of wire-mesh filter, the more collection efficiency is increasing because it makes the residence time longer.

• 정보처리학회논문지B
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• 제18B권1호
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• pp.11-20
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• 2011

Pictorial Structures(PS)는 동적 프로그래밍을 이용하여 인체의 포즈 추적 및 인식 하는 것에 매우 효과적인 방법으로 알려져 있다. 본 논문에서 상반신 포즈는 PS와 Particle filter(PF)에 의한 동적 프로그래밍 기법으로 추적된다. PF와 같은 동적프로그래밍에서 마코프 연쇄 (Markov Chain) 기반 동적 움직임 모델은 높은 자유도를 갖는 상반신 포즈를 예측하기 어려운 단점이 있다. 본 논문에서 제안하는 방법은 키포즈 기반 예측분포이며, 이것은 상반신 실루엣과 키포즈(Key Pose)들 사이의 유사도를 참고하여 파티클(Particle)을 적절히 예측하는 것이다. 실험 결과를 통해 제안된 방법은 기존 방법 성능을 70.51% 향상시킨 것을 확인하였다.

• Structural Engineering and Mechanics
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• 제89권4호
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• pp.383-397
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• 2024

To improve the vibration control performance and applicability of traditional particle tuned mass damper (PTMD) and realize the significant characteristic of lightweight design, this study proposes a novel particle tuned mass inerter system (PTMIS) by introducing inerter system (IS) to the PTMD. In the study, the motion equation of single degree of freedom (SDOF) structure attached with PTMIS is established first, then the variation law of the system's vibration reduction performance (VRP) is discussed through parameter analysis, and it is compared with the PTMD to analyze its VRP advantages. Finally, its vibration reduction (VR) mechanism from the perspective of core control force and energy analysis is explored, and its cavity relative displacement from the application perspective is analyzed. The results show that the PTMIS can remarkably improve the vibration control effectiveness of the PTMD. The reason is that the inerter can store energy and transfer the energy to the cavity and particles, which further stimulates the interaction between the two parts, thereby improving the nonlinear energy consumption effectiveness. Also, the IS can amplify the damping element's energy dissipation efficiency. In addition, the PTMIS can effectively reduce the working stroke of the PTMD, and through the analysis of the lightweight characteristics of the PTMIS, it is found that its lightweight advantage can reach nearly 100%.

• Structural Engineering and Mechanics
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• 제52권2호
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• pp.405-426
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• 2014

In this paper, a new meta-heuristic algorithm named Ranked Particles Optimization (RPO), is presented. This algorithm is not inspired from natural or physical phenomena. However, it is based on numerous researches in the field of meta-heuristic optimization algorithms. In this algorithm, like other meta-heuristic algorithms, optimization process starts with by producing a population of random solutions, Particles, located in the feasible search space. In the next step, cost functions corresponding to all random particles are evaluated and some of those having minimum cost functions are stored. These particles are ranked and their weighted average is calculated and named Ranked Center. New solutions are produced by moving each particle along its previous motion, the ranked center, and the best particle found thus far. The robustness of this algorithm is verified by solving some mathematical and structural optimization problems. Simplicity of implementation and reaching to desired solution are two main characteristics of this algorithm.