• International Journal of Highway Engineering
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• v.15 no.5
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• pp.31-45
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• 2013

PURPOSES : Determination of particle packing model variables that can be used for formulation of new DEM based particle packing model by examining existing particle packing models METHODS : Existing particle packing models are thoroughly examined by analytical reformulation and sensitivity analysis in order to set up DEM based new particle packing model and to determine its variables. All model equations considered in this examination are represented with consistent expressions and are compared to each others to find mathematical and conceptual similarity in expressions. RESULTS : From the examination of existing models, it is observed that the models are very similar in their shapes although the derivation of the models may be different. As well, it is observed that variables used in some existing models are comprehensive enough to estimate particle packing but not applicable to DEM simulation. CONCLUSIONS : A set of variables that can be used in DEM based particle packing model is determined.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.556-561
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• 2011

It is generally known that particle filters can produce consistent target tracking performance in comparison to the Kalman filter for non-linear and non-Gaussian systems. In this paper, I propose a Rao-Blackwellized multiple model particle filter(RBMMPF) to enhance computational efficiency of the particle filters as well as to reduce sensitivity of modeling. Despite that the Rao-Blackwellized particle filter needs less particles than general particle filter, it has a similar tracking performance with a less computational load. Comparison results for performance is listed for the using single sensor information RBMMPF and using multisensor data fusion RBMMPF.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.62-69
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• 2007

A kinetic model fur the particle coarsening behavior was developed. The proposed model considered the critical particle size which can be derived from Gibbs-Thomson equation unlike the conventional approach. In this study, the proposed particle coarsening model was applied to study the coarsening behavior of titanium nitride (TiN particle) in microalloyed steel weld HAZ. Particle size distributions and mean particle size by the proposed model were in agreement with the experimental results. Meanwhile, using additivity rule, the isothermal model was extended to predict particle coarsening behavior during continuous thermal cycle.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.416-421
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• 2000

We have developed a simple model for describing the non-spherical particle growth phenomena using modified 1-dimensional sectional method. In this model, we solve simultaneously particle volume and surface area conservation sectional equations which consider particles' irregularities. From the correlation between two conserved properties of sections, we can predict the evolution of the aggregates' morphology. We compared this model with a simple monodisperse-assumed model and more rigorous two dimensional sectional model. For the comparison, we simulated silica and titania particle formation and growth in a constant temperature reactor environment. This new model shows a good agreement with the detailed two dimensional sectional model in total number concentration, primary particle size. The present model can also successfully predict particle size distribution and morphology without costing very heavy computation load and memory needed for the analysis of two dimensional aerosol dynamics.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.05a
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• pp.94-97
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• 2003

본 연구에서는 반도체제조에 필수적으로 사용되는 플라즈마장비의 성능을 예측.분석하여 개발 시간 및 비용의 절감과 장비의 성능을 극대화 할 수 있도록 이론적 전산모사 환경(VIP-SEPCAD)을 개발하고 있다. VIP-SEPCAD는 플라즈마의 물리.화학적 특성을 예측하는 plasma model, 중성화학종들의 반응 및 유돈 특성을 예측하는 neutral reaction-transport model, particle의 유동 특성을 예측하는 particle transport model, particle의 생성 및 성장 특성을 예측하는 particle formation-growth model, 식각 또는 증착되는 웨이퍼 표면변화를 예측하는 surface evolution model로 구성되어 있다. 현재 개발된 VIP-SEPCAD를 이용하여 산소 플라즈마의 특성과 각종 화학성분들의 분포를 예측하고 particle의 거동에 대하여 분석하였다.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.445-452
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• 2018

In this paper the effects of particle size and model scale of concrete have been investigated on point load index, tensile strength, and the failure processes using a PFC2D numerical modeling study. Circular and semi-circular specimens of concrete were numerically modeled using the same particle size, 0.27 mm, but with different model diameters of 75 mm, 54 mm, 25 mm, and 12.5 mm. In addition, circular and semi-circular models with the diameter of 27 mm and particle sizes of 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, and 1.27 mm were simulated to determine whether they can match the experimental observations from point load and Brazilian tests. The numerical modeling results show that the failure patterns are influenced by the model scale and particle size, as expected. Both Is(50) and Brazilian tensile strength values increased as the model diameter and particle sizes increased. The ratio of Brazilian tensile strength to Is(50) showed a reduction as the particle size increased but did not change with the increase in the model scale.

• Environmental Engineering Research
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• v.11 no.4
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• pp.201-207
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• 2006

A simple empirical model with good quantitative prediction of inter-particle and intra-particle distance in a cake layer with respect to ionic strength was developed. The model is an inverse length scale with functions of interaction energy and hydrodynamic factor and it explains that the inter-particle and intra-particle distance in a cake is directly related to the effective size of particles. Particle compressibility with respect to ionic strength was also predicted by the model. The model corroborated very well with experimental results of polystyrene microsphere latex particles microfiltation in a dead end operation. From the results of the model, specific cake resistance could be controlled by the same variables affecting the height of particle energy barrier described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.

• Particle and aerosol research
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• v.10 no.1
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• pp.27-31
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• 2014

A simple bimodal model has been developed to analyze charged particle coagulation by modifying previously suggested bimdal model for evolution of particle generation and growth. In the present model, two monodisperse modes are used and 40 charge nodes are assigned to each mode to account both change of the particle size and charge distribution. In addition, we also implemented the effect of electrostatic dispersion loss in the present model. Based on the developed model, we analyzed coagulation of asymmetric bipolar charged particles by computing evolutions of particle number concentration, geometric mean diameter of particles, charge asymmetric ratio and geometric standard deviation of particle size distribution for various initial charge asymmetric ratios. The number concentration of asymmetric bipolar charged particles decreases faster than that of neutral particles but that does not give faster growth of particles since the electrostatic dispersion loss overwhelms particle growth by coagulation.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.301-304
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• 2015

With the experiment observation of single particle combustion, this model is built for the numerical analysis of the process. It's about the single coal particle combustion process under different conditions with reasonable assumptions. The model can express the mass, radius, density, temperature changing with different particle sizes, oxygen concentration and gas temperature. It also includes the flame sizes change in different condition and the diffusion of each species. The result shows the characters of the combustion.

• Computers and Concrete
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• v.9 no.3
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• pp.179-193
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• 2012

The hydration of cement contributes to the performance characteristics of concrete, such as strength and durability. In order to improve the utilization efficiency of cement and its early properties, the particle size distribution (PSD) of cement varies considerably, and the effects of the particle size distribution of cement on the hydration process should be considered. In order to evaluate effects of PSD separately, experiments testing the isothermal heat generated during the hydration of cements with different particle size distributions but the same chemical composition have been carried out. The measurable hydration depth for cement hydration was proposed and deduced based on the experimental results, and a PSD hydration model was developed in this paper for simulating the effects of particle size distribution on the hydration process of cement. First, a reference hydration rate was derived from the isothermal heat generated by the hydration of ordinary Portland cement. Then, the model was extended to take into account the effect of water-to-cement ratio, hereinafter which was referred to as PSD hydration model. Finally, the PSD hydration model was applied to simulate experiments measuring the isothermal heat generated by the hydration of cement with different particle size distributions at different water-to-cement ratios. This showed that the PSD hydration model had simulated the effects of particle size distribution and water-to-cement ratio on the hydration process of cement with satisfactory accuracy.