• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.136-145
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• 2009

Factors influencing shear behavior of granular material include particle size, shape, distribution, relative density, particle crushing, etc. In this study, these factors are characterized by viewpoint of shear behavior using numerical analysis based on DEM. Geometrical particle shape is represented by a combination of small circular particles and influence of particle shape on crushing is studied through relative comparisons between clump (uncrushable) and cluster (crushable) models which are modeled using DEM. Also, particle shape is quantified by the dimensionless parameters such as circularity and convexity. The results indicate that particle shape indexes have a negative association with internal friction angle. Also, internal friction angle becomes reduced and failure envelop curve becomes nonlinear due to the particle crushing. It is also found that numerical results are quite good agreement with the experimental test conducted in this study.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.272-274
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• 2006

In this paper, we concentrate on the mask design problem for optical micro-lithography. The pre-distorted mask is obtained by minimizing the error between the designed output image and the projected output image. We use the particle swarm optimization(PSO) and fuzzy system to insure that the resulting images are identical to the desired image. Our method has good performance for the iteration number by an experiment.

• The KSFM Journal of Fluid Machinery
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• v.5 no.1 s.14
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• pp.20-26
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• 2002

This study reports the analysis of the pressure drop characteristics for the air-particle flow in powder transport piping system. The pressure drop characteristics of air-particle flow in piping system is not well understood due to the complexity of particles motion mechanism. Particles or powders suspended in air flow cause the increase of the pressure drop and affect directly the transportation efficiency. In this study, the pressure drop in powder transport piping system with straight and curved pipes is analyzed for the interactions of air flow and particle motion. The total pressure drop increases with increasing of the pipe length, the mixture ratio, and the friction factor of particles due to the increasing friction loss by air and particles in a coal piping system. For the coal powders of $74{\mu}m$ size and powder-to-air mass mixture ratio of 0.667, the total pressure drop by the consideration of powders and air flow is $30\%$ higher than that of air flow only.

• Particle and aerosol research
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• v.5 no.2
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• pp.63-70
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• 2009

The size distribution and number concentration of atmospheric aerosol were measured and compared using APS 3321 and Dust Monitor 1.108. The particle size distribution and number concentration measured by two devices were also compared at a particle generation system of standard PSL and fly ash. The number concentration of atmospheric aerosol measured by APS was higher than that by Dust Monitor in particle size range of less than $3.0{\mu}m$, but there was good accordance between them in particle size range of over $3.0{\mu}m$. In the particle generation system of PSL and fly ash, different measurement results were shown because the particle concentration was higher than that of atmospheric aerosol. The number concentration measured by Dust Monitor was higher than that by APS in most particle size ranges. However, the peak concentration of PSL particles measured by Dust Monitor was lower than that by APS. The difference of the collection efficiency in a scrubber by APS and Dust Monitor measurement was less than 10%, but in the particle size of $1.5{\mu}m$, it was over 20%.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.51-58
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• 2020

Many types of optical plastic films are essential in optoelectronics display unit fabrication and it is important to develop high precision laser cutting methods of optical films with extremely low level of film surface contamination by fume particles. This study investigates the effects of suction and blowing air motions with air flow misalignment in removing fume particles from laser cut line by employing random particle trajectory simulation and probabilistic particle generation model. The computational results show fume particle dispersion behaviors on optical film under suction and blowing air flow conditions. It is found that suction air flow motion is more advantageous to blowing air motion in reducing film surface contamination outside designated target margin from laser cut line. While air flow misalignment adversely affects particle dispersion in blowing air flows, its effects become much more complicated in suction air flows by showing different particle dispersion patterns around laser cut line. It is required to have more careful air flow alignment in fume particle removal under suction air flow conditions.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.204-207
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• 2011

A particle counting system that can also provide sensitive, specific chemical information, while consuming very less power, occupying less space, and being inexpensive has been developed. This system uses a microwave plasma torch (MPT) as the excitation source for atomic emission spectrometry (AES). Emission from a single particle can be detected, and the wavelength at which the emission is observed indicates the elements present in the particle. It is believed that correlating the particle size and emission intensity will allow us to estimate the particle size in addition to abovementioned capabilities of the system. In the long term, this system can be made field-portable, so that it can be used in atmospheric aerosol monitoring applications, which require real-time detection and characterization of particles at low concentrations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.539-546
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• 2002

The Holographic Particle Velocimetry system can be a promising optical tool leer the measurements of three dimensional particle velocities. In this research, validation experiments for the development of holographic particle velocimetry system for spray droplets were conducted with measuring the velocities of glass beads on a rotating disk. Uncertainty analysis was performed to identify the sources of all relevant errors and to evaluate their magnitude. The measurement results of distance between glass beads, size, and velocities obtained with holographic method are compared reasonably well with the known values within acceptable range of errors.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.281-290
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• 2001

Particle contamination has been an ongoing problem affecting the reliability of the magnetic hard disk drives. Especially the recent use of MR head requires much tighter control of particle contamination due to thermal asperity (TA) phenomenon. In this study, the effects of slider air bearing surface design of TA reduction capability were investigated by manufacturing two types of sliders. Numerical methods were used to simulate the motion of particles in the head/media interface. Experiments were conducted to verify the results predicted by the numerical simulation. Drives were built and exposed to particle contamination using a particle injection chamber, which turned out to be a very simple and reliable particle generation method over conventional aerosol technique. Then the number of TA generated in the drives was recorded and compared. Also the contacts between slider and particles were investigated by acoustic emission study. It was found that a new ABS design, which has aerodynamic U-shaped rail and central flow passage, was beneficial in reducing the particle contamination on the slider.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.1
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• pp.1-8
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• 2018

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solid-liquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from $1.09g/cm^3$ to $1.75g/cm^3$. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of $1.09g/cm^3$ hit the tongue on the left side, while collision location of particles of $1.75g/cm^3$ is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

• Journal of Powder Materials
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• v.20 no.2
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• pp.129-133
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• 2013

In this paper we have studied the effect of water droplet size on nano-particle size distribution using SMPS(Scanning Mobility Particle Sizer)system. It can be seen that the unknown peak at >100 nm was caused by water droplets which did not dry completely when DI water was used as a solvent in the SMPS system. Therefore, it is important to dry water droplets generated from atomizer in the SMPS system when measuring the particle size distribution using less than 100 nm nano-particles in diameter. From this study, It can be concluded that the napion was a useful material as dryer ones and using EAG(Electro Aerosol Generator) as a particle generator was the most effective in reducing the effect of water droplets.