• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.3
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• pp.587-592
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• 2018

An adaptive beam forming system using a phased array antenna improves communication quality by beam forming adaptively to a communication environment having an interference signal. For adaptive beam forming, a good combination of the phases of the excited signals to each radiating element of the phased array antenna should be calculated. In this paper, improved particle swarm optimization algorithm that adds a re-spreading procedure according to particle density was proposed to increase the probability of good phase shift combination output.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.748-751
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• 2003

The electron temperature and plasma density in coplanar alternating-current plasma display panels (AC-PDPs) have been experimentally investigated by a micro Langmuir probe and the high speed discharge images in this experiment.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.547-555
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• 1996

Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.

• Journal of environmental and Sanitary engineering
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• v.17 no.1
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• pp.12-19
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• 2002

This study was carried out to investigate the optimal condition for granite particle coagulation process by using various chemical coagulation agents. The coagulation of a suspended granite particle was monitored by using various different coagulants, such as $Al_2(SO_4)_3{\cdot}14H_2O,{\;}FeCl_3{\cdot}6H_2O,{\;}SA-solution(KOH{\;}+{\;}Al(OH)_3{\;}+{\;}K_2CO_3{\;}mixture)$ and jade particle. To accomplish this study, analysis of water quality, removing Turbidity and Packing Density were measured with jar-tester. In the results of this experiment, it was found that the removal rate of the granite particle was increased with the decrease of the pH of the sludge. The turbidity(NTU) at the above coagulants was reduced from 95% to 98%. Removed of Turbidity and Packing Density was more efficiency to the SA-solution than others.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.97-105
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• 2009

Analysis was done on the particle size distribution of sediments flown into Saemangeum from the Mankyung and Dongjin River. The organic pollutants and heavy metal existing in the sediments were analyzed, which was further used to study the properties of pollution in the sediments according to the particle size distribution. Conclusions shown below were made from these analyses. The particle size distribution showed a big difference between the upriver areas of Mankyung and Dongjin River. Particles under $75{\mu}m$ showed to be around 85% at Dongjin River, while it showed to be around 70% at Mankyung River. This kind of distribution in particle size concluded in greatly affecting the contamination density of the sediments. From the analysis done on the soil type of sediments, deposition in Mankyung River categorized into Silty loam and Sandy loam, where Silty loam covered most of area and deposition in Dongjin River categorized into Sand, Loamy sand, Silty loam, Sandy loam. Considering the weight ratio, the density of contamination of the sediments by particle size at Dongjin and Mankyung River has been analyzed to show that organic pollutants and heavy metals occupy more than 70% of the whole contamination in the range under the particle size of $75{\mu}m$.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.96-106
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• 2017

In pressable polymer bonded explosives (PBXs), densification occurs due to rearrangement and deformation of explosive particles during pressing. If brittle explosives are compressed till particle fraction become higher than theoretical random close packing fraction (RCPF), bigger particles should be fractured to fill the void. In this study, multi-modal particle system was introduced for the decrease in possibility of particle fracture during compression expecting decrease in shock sensitivity of highly filled pressable PBX. The experimental results showed the trimodal particle system had low sensitivity with high density, compared to bimodal particle system.

• Journal of Powder Materials
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• v.5 no.2
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• pp.111-121
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• 1998

Thick and dense deposit of higher than 97% of theoretical density was formed by induction plasma spraying. To investigate the effects of powder morphology on the density of deposit, two different kinds of Yttria-Stabilized-Zirconia powder, METCO202NS (atomized & agglomerated) and AMDRY146 (fused & crushed), were used and compared. After plasma treatment, porous METCO202NS powder was all the more densely deposited and its density was increased. In addition to the effect of powder morphology, the process parameters such as, sheath gas composition, probe position, particle size and spraying distance, and so on, were evaluated. The result of experiment with AMDRY146 powder, particle size and spraying distance affected highly on the density of the deposit. The optimum process condition for the deposition of -75 ${\mu}m$ of 20%-Yttria-Stabilized-Zirconia powder was 120/201/min of Ar/$H_2$ gas rate, 80 kW of plasma plate power, 8 cm of probe position and 150 Torr of spraying chamber pressure, at which its density showed 97.91% of theoretical density and its deposition rate was 20 mm/min. All the results were assessed by statistical approach what is called ANOVA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.271-271
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• 2010

$BaTiO_3$(BT) has high permittivity so that has been applied to dielectric and insulator materials in 3D system-level package integration. In order to achieve excellent performance of device, the BT layer should be highly dense. In this study, BT thick films were prepared by the inkjet printing method. And these films were cured at $280^{\circ}C$ after infiltration of polymer resin. As a result, we have successfully fabricated not only the inkjet-printed hybrid BT film but also metal-insulator-metal(MIM) capacitor without sintering process. Changes in the dielectric constant of BT hybrid film with particle size and packing density were investigated. The dielectric constant was increased with increasing packing density and particle size. Further, the BT hybrid film using two different size particles had even higher packing density and dielectric constant.

• Clean Technology
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• v.29 no.4
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• pp.249-254
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• 2023

In this study, porosity estimation was conducted by the physical properties of zeolite. Because of the difficulty of directly measuring the porosity of particulate matter, the porosity was calculated by applying the measured physical properties of zeolite to the calculation formula presented in various literature. For this purpose, the average particle size, particle size distribution, specific surface area, and pore characteristics of three types of zeolite - zeolite beta, zeolite Y, and ZSM-5 - were measured. In addition, the true density using gas and liquid phases, and two types apparent density (tap and untapped density) were measured. We calculated the porosity using these results, compare and analyzed the results, and evaluated main factors that determine the porosity.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3197-3202
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• 2007

An analysis program for pedestrian flow has been developed to investigate the flow patterns of passenger in railway stations. Analysis algorithms for pedestrian flow based on DEM(Discrete Element Method) are newly developed. There are lots of similarity between particle-laden two phase flow and passenger flow. The velocity component of 1st phase corresponds to the unit vector of calculation cell, each particle to passenger, volume fraction to population density and the particle velocity to the walking velocity, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger. By using the developed program, we compared the simulation results of the effects of the location and size of exit and elapsed time.