• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1254-1255
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• 2006

For precise property control of sintered products, it is important to understand accurately the packing density of the powder. We developed a packing simulation program that could make a packed bed of spherical particles having particle size distribution. In addition, the influence of the particle shape of the actual powder on the packing density was quantitatively analyzed. The predicted packing densities corresponded well to the actual data.

• Fibers and Polymers
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• 제7권4호
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• pp.436-441
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• 2006

An integrated platform for garment drape simulation system has been developed. In this system, garment patterns from conventional two-dimensional CAD systems can be assembled into a three-dimensional garment on a parametrically resizable realistic human body model. A fast and robust particle-based physical calculation engine has been developed for garment shape generation. Then a series of geometric and graphical techniques were applied to create realistic impressions on simulated garments. This system can be used as the rapid prototyping tool for garments in the future quick-response system.

• 한국입자에어로졸학회지
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• 제13권4호
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• pp.173-182
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• 2017

An Eulerian-Lagrangin approach is used to compute particle dispersion from a power plant chimney. For air flow, three-dimensional incompressible filtered Navier-Stokes equations are solved with a subgrid-scale model by integrating the Newton's equation, while the dispersed phase is solved in a Lagrangian framework. The velocity ratios between crossflow and a jet of 0.455 and 0.727 are considered. Flow fields and particle distribution of both cases are evaluated and compared. When the velocity ratio is 0.455, it demonstrates a Kelvin-Helmholtz vortex structure above the chimney caused by the interaction between crossflow and a jet, whereas the other case shows flow structures at the top of the chimney collapsed by fast crossflow. Also, complex wake structures cause different particle distributions behind the chimney. The case with the velocity ratio of 0.727 demonstrates strong particle concentration at the vortical region, whereas the case with the velocity ratio of 0.455 shows more dispersive particle distribution. The simulation result shows similar tendency to the experimental result.

• Fibers and Polymers
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• 제4권4호
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• pp.169-175
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• 2003

A simulation system for versatile garment drape has been developed. Using this system, the shape of a garment can be simulated in consideration of fabric physical properties as well as the interaction between fabrics and other objects. Each fabric piece in a garment is modeled using a geometrically constrained particle system and its behavior is calculated from an implicit numerical integration algorithm in a relatively short time. The system consists of three modules including a preprocessor for the preparation of fabric patterns and external objects, a postprocessor for the results of three-dimensional visualization, and a drape simulation engine. It can be used for the design process of textile goods, garments, furniture, or upholsteries.

• 한국대기환경학회지
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• 제12권1호
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• pp.43-53
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• 1996

Numerical simulation was performed for the 3-dimensional flow filed of gas and particle phase for cyclone dust collector. FVM(Finite Volume Method) was employed for gas phase. The flow was solved suing the k-.varepsilon. epsilon turbulence model. The particle exit at the bottom of the cone was treated as a solid wall in this model because the gas flow through the effective dust exit is usually insignificant. The major parameters considered in this study was vortex finder diameter, effective dust exit diameterm vortex finder length, inlet type for dimension performance. Particle trajectory calculations were made for three different, particle sizes of 1, 25 and 50 .mu.m. The results obtained from this study give some physical insight of dust particle collection mechanism together with the indication of the collection efficiency. The simulation results were in generally good agreement with empirical knowledge. The application of this kind of computer program looks promising as a potential tool for the design of cyclone and determination of optimum operating condition.

• 한국전산유체공학회지
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• 제14권4호
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• pp.101-108
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• 2009

We present a new finite-element scheme for direct numerical simulation of particle suspensions in simple shear flow of a viscoelastic fluid in 3D. The sliding tri-periodic representative cell concept has been combined with DEVSS/DG finite element scheme by introducing constraint equations along the domain boundary. Rigid body motion of the freely suspended particle is described by the rigid-shell description and implemented by Lagrangian multipliers on particle boundaries. We present the bulk rheology of suspensions through the numerical examples of single-, two- and many-particle problems, which represent a large number of such systems in simple shear flow. We report the steady bulk viscosity and the first normal stress coefficient, which show shear-thickening behavior for both properties.

• 천문학회보
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• 제41권1호
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• pp.47.2-47.2
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• 2016

The protons and helium ions in the solar wind are observed to possess anisotropic temperature profiles. The anisotropy appears to be limited by various marginal instability conditions. One of the efficient methods to investigate the global dynamics and distribution of various temperature anisotropies in the large-scale solar wind models may be that based upon the macroscopic quasi-linear approach. The present paper investigates the proton and helium ion anisotropy instabilities on the basis of comparison between the quasi-linear theory versus particle-in-cell simulation. It is found that the overall dynamical development of the particle temperatures is quite accurately reproduced by the macroscopic quasi-linear scheme. The wave energy development in time, however, shows somewhat less restrictive comparisons, indicating that while the quasi-linear method is acceptable for the particle dynamics, the wave analysis probably requires higher-order physics, such as wave-wave coupling or nonlinear wave-particle interaction. We carried out comparative studies of proton firehose instability, aperiodic ordinary mode instability, and helium ion anisotropy instability. It was found that the agreement between QL theory and PIC simulation is rather good. It means that the quasilinear approximation enjoys only a limited range of validity, especially for the wave dynamics and for the relatively high-beta regime.

• Computers and Concrete
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• 제9권2호
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• pp.119-131
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• 2012

Optimum packing of aggregate is an important aspect of mixture design, since porosity may be reduced and strength improved. It may also cause a reduction in paste content and is thus of economic relevance too. Several mathematic packing models have been developed in the literature for optimization of mixture design. However in this study, numerical simulation will be used as the main tool for this purpose. A basic, simple theoretical model is used for approximate assessment of mixture optimization. Calculation and simulation will start from a bimodal mixture that is based on the mono-sized packing experiences. Tri-modal and multi-sized particle packing will then be discussed to find the optimum mixture. This study will demonstrate that computer simulation is a good alternative for mixture design and optimization when appropriate particle shapes are selected. Although primarily focusing on aggregate, optimization of blends of Portland cement and mineral admixtures could basically be approached in a similar way.

• Korean Chemical Engineering Research
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• 제58권3호
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• pp.480-485
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• 2020

Onsager 이론으로 확장된 Maxwell-Wagner 분극 모델을 이용하여 전도성 입자로 제조된 전기유변(Electrorheological, ER) 액체의 전기유변 현상에 대한 전산 모사를 수행하였다. 확장된 Maxwell-Wagner 분극 모델을 이용한 전산 모사는 전도성 입자로 제조된 전기유변 액체의 특성인 비제곱 전기유변 현상(Δτ∝Eⁿ, n≈1.5)을 확인하였다. 전단 흐름에서 전단응력이 정상상태에 도달하는 시점은 전기장 하에서 생성된 사슬 모양 구조가 전단 흐름에 의해 깨짐과 재생성이 정상상태에 도달하는 지점으로 나타났다. 또한, 전단 속도의 증가에 따라 전단응력이 최솟값을 보이는 전도성 입자를 기반으로 한 전기유변 액체의 현상도 관찰하였으며, 이것은 입자의 사슬 모양 구조가 무작위 배열로 바뀌는 순간에 발생하는 것임을 관찰하였다. 입자의 부피 분율 ϕ가 증가에 따라 전단응력은 증가하다가 일정해지는 경향도 관찰하였다.

• 한국해양공학회지
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• 제23권1호
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• pp.38-42
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• 2009

Recently, various particle based simulation techniques, which solve the Navier Stokes and continuity equations, have been developed and applied to complicated engineering problems. However, although progress is being made on their visualization or rendering techniques, these are still insufficient. In this study, to render a smooth configuration for a free surface, a rendering technique was developed that included the generation of density fields from the location information for simulated particles and the creation model for a polygonal surface. The developed rendering technique was applied to the visualization of a dynamic free surface flow interacting with a structure using a particle based simulation technique.