• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.982-988
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• 2002

• Proceedings of the Korea Water Resources Association Conference
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• 2003.05b
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• pp.827-830
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• 2003

• 대한핵의학회:학술대회논문집
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• 1990.04a
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• pp.213.2-213.2
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• 1990

• Proceedings of the Materials Research Society of Korea Conference
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• 2004.05a
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• pp.58-58
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• 2004

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.790-793
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• 2009

In the case of projection type display, it needs to use the screen in order to project the image clearly and wide viewing angle. We have been developing the step in type display system using the smoke screen. However, the image with smoke screen was flickered by gravity and air flow. Then we considered to reduce the flicker of the image and we found that flicker can be reduced and viewing angle becomes more large. This time we report the large viewing angle step in type display system using screen made up with very small particle size smoke and flow controlled nozzle. Hence, at first we considered the most suitable particle for the screen and then the shape of screen and then we constructed the array of flow controlled smoke screen. By the results of experiment we could get considerably high contrast flicker-less image and get the viewing angle more than $60^{\circ}$ by this flow controlled nozzle attached new type smoke screen and make clear the efficiency of this method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.665-670
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• 2010

The effect of a particle's spin is investigated numerically by taking into account the effect of lift forces originating due to difference between the rotations of a particle and of a fluid, such as the Saffman and Magnus lift forces. These lift forces have been ignored in many previous studies on particle-laden turbulence. The trajectory of the particles can be changed by the lift forces, resulting in a significant modification of the stochastic characteristics of heavy particles. Probability density functions and autocorrelations are evaluated from the velocity of solid particle, acceleration of solid particles, and acceleration of fluid at the position of solid particle. Changes in velocity statistics are negligible but statistics related with acceleration are affected by the rotation of particle. When a laden particle encounters coherent structures during its motion, the particle's rotation might significantly affects the motion due to intermittently large fluid acceleration near the coherent structures.

• Journal of Environmental Science International
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• v.31 no.9
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• pp.803-813
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• 2022

In this study, we improved the water-based condensation particle counter in Atmospheric Research Aircraft NARA and investigated the condensation particle number concentration over the Korean peninsula. Pump and set point information were changed to improve the instrument used by aircraft for observation. Ground-based observational result showed that the error between two instruments, which are water-based condensation particle counter and butanol-based condensation particle counter, was 4.7%. Aerial observational result revealed that the number concentration before improvement indicate large variation with unstable condition, whereas the number concentration after improvement indicate a reasonable variation. After improvement, the number concentration was 706±499 particle/cm³ in the West Sea and 257±80 particle/cm³ in Gangwon-do, and these are similar to the concentration range reported in previous studies. Notably, this is the first attempt to use aerial observation with water-based condensation particle counter to investigate condensation particle number concentration.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.25-33
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• 1984

The effect of particle size on adsorption of trihalomethane have been studied. Using mean particle sizes ranging from 0.73 to 2.03 mm, physical properties of carbon and trihalomethane adsorption characteristics have been investigated experimentally. With increasing particle size specific surface area and pore volume decreased, and the mean pore radius increased significantly. Large pores were dominant in large particles, while small particles were composed of small pores. Isotherm studies were conducted using static bottle point technique and the results were well described by the Freundlich isotherm equations. The adsorption capacity increased significantly with decreased particle size. Additionally micro-column tests were carried out, and the results were compared with the model simulation. From the micro-column studies it was found out that the film transfer coefficient were almost constant, and the differences in the trihalomethane removal efficiency was mainly due to the differences in the adsorption capacity of the particles of different size.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.71-74
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• 2007

This study investigates the fundamental properties of high strength concrete made with various blame values of cement, manufactured by the particle screening method in a pulverizing process. Test showed that concrete using lower blame of cement, such as large particle (L) and both ordinary and large particle (OL), increased the fluidity of fresh concrete. As tine progressive, it was noticeable that the specimens using ordinary cement (OPC) gradually decreased the fluidity, but the other specimens showed the sudden decline until 30 minutes, which is followed by a gradual decrease after 60 minutes. For the setting time, higher blaine of cement accelerated the initial and final setting time, especially concrete using minute size of cement (M) was 10 hours faster than OPC. Compressive strength of L exhibited similar value at 1 days as to that of strength in OPC at 3 days. Importantly, the specimens using M also revealed the similar strength value, regardless of curing temperature between $-5^{\circ}C$ and $20^{\circ}C$, which means that using this minute particle of cement in concrete can secure the strength development even in the lower temperature circumstance. Therefore it is clear that using OPC+M simultaneously at cold weather concreting can resist the early frost and develop the early strength of concrete.

• Particle and aerosol research
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• v.12 no.4
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• pp.145-150
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• 2016

During the chemical mechanical planarization (CMP) process, slurry that comprises abrasive particles can directly affect the CMP performance and quality. Mainly, the large particles in the slurry can generate the defects on the wafer. Thus, many kinds of filters have been used in the CMP process to remove unwanted over-sized particles. Among these filters, the point-of-use (POU) filter is used just before the slurry is supplied onto the CMP pad. In the CMP research field, analysis of the POU filter has been relatively exceptional, and previous studies have not focused on the standardized filtration efficiency (FE) or filter performance. Furthermore, conventional evaluation methods of filter performance are not appropriate for POU filters, as the POU filter is not a membrane type, but is instead a depth type roll filter. In order to accurately evaluate the POU filter, slurry FE according to particle size was measured in this study. Additionally, a CMP experiment was conducted with filtered slurry to demonstrate the effects of filtered slurry on CMP performance. Depending on the flow rate and the filter retention size, the FE according to particle size was different. When the small and large particles have different FEs, the total filtration efficiency (TFE) can still have a similar value. For this reason, there is a need to measure the FE with respect to the particle size to verify the effects of the POU filter on the CMP process.