• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.21-31
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• 2012

In this study, we modified the surface of ground calcium carbonate (GCC) with polyelectrolytes with different molecular weight using Layer-by-Layer (LbL) multilayering technique and investigated its effect on the paper properties. Polydiallydimethylammonium chloride (poly-DADMAC) and poly sodium 4-styrene sulfonate (PSS) which have different molecular weights were used for LbL multilayering. Zeta potential and particle size of the LbL modified GCC were measured. After preparation of handsheets, their structural and mechanical properties were evaluated. The zeta potential and average particle size of the modified GCC were affected by the molecular weight of anionic polyelectrolyte (PSS). The zeta potential was higher and the particle size was smaller when GCC was treated by PSS with high molecular weight compared to the case with low molecular weight of PSS. The tensile and internal bond strength of the handsheets was increased with an increase in the number of layers on GCC particles, but the molecular weight of polyelectrolyte did not significantly affect the paper strength.

• Journal of Powder Materials
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• v.20 no.5
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• pp.359-365
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• 2013

In this study, we fabricated $Nd_2Fe_{14}B$ hard magnetic powders with various sizes via spray drying combined with reduction-diffusion process. Spray drying is widely used to produce nearly spherical particles that are relatively homogeneous. Thus, the precursor particles were prepared by spray drying using the aqueous solution containing Nd salts, Fe salts and boric acid with the target stoichiometric composition of $Nd_2Fe_{14}B$. The mean particle sizes of the spray-dried powders are in the range from one to seven micrometer, which are adjusted by controlling the concentrations of precursor solutions. After debinding the as-prepared precursor particles, ball milling was also conducted to control the particle sizes of Nd-Fe-B oxide powders. The resulting particles with different sizes were subjected to subsequent treatments including hydrogen reduction, Ca reduction and washing for CaO removal. The size effect of Nd-Fe-B oxide particles on the formation of $Nd_2Fe_{14}B$ phase and magnetic properties was investigated.

• Asian Journal of Turfgrass Science
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• v.20 no.1
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• pp.47-55
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• 2006

Golf course community has always been concerned about water quality regarding to pesticide and fertilizer managements. This study conducted to investigate sorption and leaching behavior of common pesticides used for golf course in granular activated carbon I (GAC 1), granular activated carbon II(GAC II), and charcoal. We used batch study to investigate the influence of concentrations of Smithion and Folicur and particle sizes of GAC I, GAC II, and charcoal on sorption. Also, column study was used to investigate the leaching effect of Smithion in GAC I and charcoal. We found that sorption of Smithion and Folicur were higher in less $45{\mu}m$ of particle size for GAC I, GAC II, and charcoal compared to $1.7{\sim}2.0mm$ size, and the sorption of Smithion and Folicur in less $45{\mu}m$ of particle size ranged from 90 to 99%. In the column study, there was no difference in leaching effect between GAC I and charcoal. Overall, we found that charcoal might offer a cost effective adsorbent as a pesticides in leachate.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.21-26
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• 2020

Natural soil is composed of particles of various sizes, and the shear behavior which is a kind of mechanical behavior of the soil is affected by the particle size distribution. In addition, since the natural soil contains a large mixture of coarse and fine grained soil, it is difficult to clearly understand the shear behavior of the soil. Therefore, a ring shear test was conducted on sandy soils that has various particle size distribution in order to identify the effect of the distribution on shear characteristics of soils. At this time, sand and silt were used for coarse and fine grained soils, respectively, to make sandy soils by changing the silt content. Also the water was supplied during the test to confirm shear characteristics of sandy soils with various particle size distributions. The result shows that the shear strength increases as the silt content increases, and the strength decreases as the silt content increases over the sand. Besides, residual shear strength gradually decreases because of the silt content when the water is supplied.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.59-64
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• 2011

Degree of unsaturation in fatty acid molecules plays an important role in the formation of vesicles. Vesicle formation from C18 fatty acids with different amount of double bonds such as oleic acid, linoleic acid and linolenic acid with the incorporation of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DPPE-PEG2000) have been examined by TEM. Critical vesicular concentrations (CVC) of the vesicle suspension are determined by turbidity and surface tension methods. The CVC of fatty acids increases when the amount of unsaturation in the alkyl chain increases. On the other hand, stability of vesicle suspension has been examined by using particle size and zeta potential at $30^{\circ}C$. There was a dramatic decrease in particle size measurement from mono-unsaturation to tri-unsaturation which could be due to the effect of fluidity in the membrane bilayer caused by different degree of unsaturation. The values of zeta potential for vesicles that were formed without the incorporation of DPPE-PEG2000 were in the range of -70 mV to -100 mV. It has been observed that the incorporation of DPPEPEG2000 to the vesicle reduces the magnitude of zeta potential. However, this phenomenon does not obviously seen in fatty acid vesicles formed by linoleate-linoleic acid and linolenate-linolenic acid. We therefore conclude that the addition of DPPE-PEG2000 does not effectively improve the stability of the linoleate-linoleic acid and linolenatelinolenic acid vesicle at pH 9.0 after the evaluation of their particle size and zeta potential over a period of 30 days. Although the vesicles formed were not stable for more than 10 days, they have displayed the potential in encapsulating the active ingredients such as vitamin E and calcein. The results show that the loading efficiencies of vitamin E are of encouraging value.

• Particle and aerosol research
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• v.4 no.1
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• pp.9-20
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• 2008

The effect of light intensity on the ozone formation and the aerosol number concentration during the photochemical reactions of ambient air was investigated in an indoor smog chamber. The smog chamber consists of a housing, 64 blacklights, and a $2.5-m^3$ reaction bag made of Teflon film. The bag was filled with the unfiltered ambient air in Seoul from January 10 to March 18, 2002. In this work, the photolysis rate of $NO_2$, $k_1$ was used as an index of light intensity. Three levels of light intensity were controlled by changing the number of blacklights turned on among 64 blacklights: $0.29min^{-1}$ (50%), $0.44min^{-1}$ (75%), $0.57min^{-1}$ (100%). The ozone concentration increased rapidly within 10 minutes after irradiation irrespective of light intensity, thereafter it increased linearly during the irradiation. The ozone production rate seems to be dependent on both the light intensity and the quality of ambient air introduced into the reaction bag. The change in aerosol number concentration also depended on both the light intensity and the ambient air quality, especially aerosol size distribution. Based on the initial ambient aerosol size distributions, the photochemical potential for aerosol formation and growth is classified into two cases. One is the case showing aerosol formation and growth processes, and the other is the case showing no apparent change in particle size distribution.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.191-203
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• 2018

This study was investigated the effect of the morphology change of copper (Cu) powders under the different rotational speed and milling time by using three kinds of grinding media with different size and materials, and performed DEM simulations of ball behavior. In order to clarify the mechanism of grinding by three - dimensional simulations of the ball behavior in a traditional ball mill, the force, kinetic energy, and medium velocity of the grinding media were calculated. In the simulation, the amount of change of the input energy was also calculated by adjusting the rotational speed, ball material, kinetic velocity, and friction coefficient in the same as the actual experimental conditions. The scanning electron microscope results show that the particle morphology changes from irregular to spherical when the ball size is small.

• Journal of environmental and Sanitary engineering
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• v.14 no.1
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• pp.62-69
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• 1999

In this study, the synthesis of PZT powder by bubble column reactor was investigated at various reaction conditions. As a result, the volume % of $NH_3$ gas used as a precipitator had no effect on the synthesis, but the more research is needed to control particle size.As a carrier gas, Ar, $O_2$ and air only increased the stirring effect but had no effect chemically on the synthesis. The calcination temperature of prepared PZT powder was about $500-600^{\circ}C$ and the meanparticle size of synthesized PZT powder was about $0.17{\mu}m$. The grain size of sintered body is about $0.5~3{\mu}m$ and this is similar with the value of commercial products.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.5
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• pp.597-607
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• 1998

Processing is generally employed to alter the physical and chemical properties of feeds used in pig diets, using hammer/roller mills, pellet mills and extruders/expanders. The reported optimum particle sizes of corn are approximately $500{\mu}m$, $500-700{\mu}m$, $400-600{\mu}m$, for nursery, growing-finishing, and breeder pigs respectively. Optimum particle size of grains are affected by diet complexity. There was a trend towards reducing particle size in order to increase ADG in pigs fed a simple diet, though such was not the case for pigs fed a complex diet. Uniformity of particle size also affects the nutritional values of swine feeds. Uniform particle sizes would consistently give greater nutrient digestibilities. In terms of pellet quality, it is reported that a higher incidence of fmes in pelleted feeds has a direct correlation with poorer feed conversion ratio in pigs. Particle and pellet sizes are also very important for pelleting in terms of grinding, digestibility, stomach ulceration and pellet durability. A particle size of $600{\mu}m$, or slightly less, seemed optimal for com in fmishing pigs, and the 5/32 in. diameter pellets supported the best efficiencies of gain during nursery and finishing phases. Extruder and/or expander processes would allow the feed industry an increased flexibility to utilize a wider spectrum of feed ingredients, and improve pellet quality of finished feeds. It would appear that extruded or expanded diets containing highly digestible ingredients have little effect on the growth performance of pigs, and the feeding values of the feeds over pelleted diets were not improved as pigs grew. The extruder or expander is much more effective than a pelletizer in salmonella control. Gastric ulcerations and/or keratinizations were consistently reported in pigs fed mash and processed diets containing finely ground grains, whereas carcass quality was not affected by diet processing methods such as pelleting, extruding or expanding. In corn- or sorghum-based diets, the electrical energy consumption is 4-5 times higher in the expanding than in the pelleting process. But the expander's processing cost was half of that shown by an extruder. Finally, the decision of which feed processing technology to adopt would depend on the processing cost, and any potential improvement in growth performance and digestibilities of nutrients should offset the increased operating and capital costs related to the extruder/expander technology over mash or pelleting processes in pigs.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.3
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• pp.69-78
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• 2003

The main purpose of this study was to verify the shore margin protection effect of the root system of Salix gracilistyla Miq. developed from direct sticking cuttings on wetland, focusing on the effect of the root system reducing soil particle dissociation rate in water. The soil dissociation rate was examined through slaking tests with cylindric pure soil column at maximum particle density and the same size column of root reinforced soil. The dry weight of remained soil was measured after 5, 10, 15, 30minutes and 1, 6, 12, 24, 48hours inundation. As results, the soil particles began to dissociate severely at 10 minutes and only 10% of soil particles were left after 25minutes inundation. The stable slope angle of pure soil was $36^{\circ}$after 24 hours. On the other hand, the columns of root reinforced soil were stable even after 24hours, being dissociated only 7.2% of soil particles. So, it was revealed that the root system was very effective materials protecting more than 80% of soil particle from dissociation in inundation.