• Journal of Advanced Marine Engineering and Technology
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• v.31 no.2
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• pp.173-181
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• 2007

Recently, galvanizing method is predominantly being used not only a economical point of view but also due to it s stability and long life. For example, guard rail of high way, all kinds of structures for ship etc. were protected with galvanizing and demand of galvanized structural materials was being increased with more and more. However, galvanized structures were inevitably being deteriorated with time eventually because they were corroded with solution of galvanizing film and exfoliation of it s film in the present severe corrosive environment. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment. In this study, three test specimens such as pure galvanizing, galvarium, and chromate treatment were submerged at tap water with inhibitor addition. And the effect of their corrosion resistance improvement was comparatively investigated with electrochemical method. Corrosion current density of the galvanized steel was the largest among three specimens, however, the galvarium steel showed the lowest corrosion current density. Futhermore, these three kinds of test specimens indicated considerably excellent corrosion resistance by dipped at tap water with inhibitor addition. Especially, the galvanized steel showed the best effect of corrosion resistance improvement than other test specimens.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.429-429
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• 2008

Li$[Ni_{1/2}Co_{1/2}]O_2$ powder were synthesized from co-precipitation spherical metal oxide, $[Ni_{1/2}Co_{1/2}](OH)_2$. The preparation of metal hydroxide was significantly dependent on synthetic conditions, such as pH, amount of chelating agent, stirring speed, etc. The optimized condition resulted in $[Ni_{1/2}Co_{1/2}](OH)_2$, of which the particle size distribution was uniform and the particle shape was spherical, as observed by scanning electron microscopy. Calcination of the uniform metal hydroxide with LiOH at higher temperature led to a well-ordered layer-structured Li$[Ni_{1/2}Co_{1/2}]O_2$, as confirmed by X-ray diffraction pattern. Also these materials have ${\alpha}-NaFeO_2$ ($R\bar{3}m$) structure. Due to the homogeneity of the metal hydroxide, $[Ni_{1/2}Co_{1/2}](OH)_2$, the final product, Li$[Ni_{1/2}Co_{1/2}]O_2$, was also significantly uniform, i.e., the average particle size was of about 10 to 15 ${\mu}m$ in diameter and the distribution was relatively narrow. As a result, the corresponding tap-density was also high approximately 2.41 $gcm^{-3}$, of which the value is comparable to that of commercialized $LiCoO_2$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.265-270
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• 2002

Most of all the mechanical devices are becoming more high-speed and high-power as well as their used condition being more pollution with rapid development in industrial part. So, it is necessary for these devices to equip cooling system to overcome that kind of severe using condition. Industrial development and income increase causes rapid increase in using fossilenergy and it results in accelerating environmental pollution owing to the increasement in emission of air pollution substance. Specially, fresh water like stream and river water is acidified. Therefore, corrosion damage is accelerated in radiator for automobile that is using acidified water. So, in this study, corrosion test was carried out in distilled and tap water for the investigation on the corrosion behavior of Al-alloy that is using as material for radiator of automobile The main results obtained are as follows According to increase of temperature, open circuit potential is decreased in fresh water. And open circuit potential after deaeration is lower than that before deaeration. Corrosion current density in distilled water is less drained than that of tap water. And Corrosion current density after deaeration is less drained than that before deaeration.

• Journal of Aquaculture
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• v.21 no.1
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• pp.47-53
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• 2008

The purpose of this study was to suggest that selecting method of rotifer with high activity of digestive enzymes for the enrichment effect of rotifer and the increasing of digestive enzymes of fish larvae. the populations assayed the activities of the digestive enzymes were randomly selected out of several population communities cultured with freshwater condensed Chlorella. The relationship with the population density and the growth rate of selected populations was shown to RD=5865 SGR-350.08(P<0.001). The relationships with fecundity of the growth rate and the population density were shown to F=-36.147 SGR+61.652(P<0.05) and F=-0.0085 RD+66.38(P<0.001), respectively. The relationships of the growth rate and the individual activities of digestive enzymes in rotifer were assayed to Amyl=-1.6482 SGR+3.2498(P<0.05), TAP=-0.8115 SGR+1.1361(P<0.001) and TGL+0.0055 SGR+0.0079(P=0.239), respectively. But in TG-lipase was not related significantly with the growth rate. Also the relationships of the fecundity and the individual activities of digestive enzymes in rotifer were shown to Amyl=0.0296 F+1.0981(P<0.001), TAP=0.0252 F+0.0975(P<0.001) and TGL=-6E-06 F+0.0113(P=0.915), respectively. But in TG-lipase was not related significantly with the fecundity. And the relationships with the specific activity of TG-lipase of the fecundity, the growth rate and the population density were TGL=-0.024 F+0.2332(P=0.132), TGL=0.1267 SGR+0.005(P<0.01) and TGL=0.0002 F-0.0594(P<0.001), respectively. In this case, specific activity of TG-lipase was shown the significant relationship with the population density and the growth rate, but it was not related significantly with fecundity. Therefore, Because a population shown the high activity of digestive enzymes for increasing a lipid enrichment effect of a rotifers and receiving the many exogenous digestive enzymes to fish larvae was the population of high fecundity than the population of high rotifer density, to select the population of a high fecundity was suggested to benefit than a high growth rate for fish larvae.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.462-470
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• 1995

The characteristics of spray-dried granules are important for dry pressing operation since they have great influences on die-filling, compaction ratio, and resulting green microstructure. An attempt was made to control granule morphology and the packing structure of fine Si3N4 particles in granules by adjusting suspension property. Mercury porosimetry was used to characterize the pore structures of both granules and green compacts. Finally, the effects of particle packing structure in granules and green microstructure on sintering behavior were investigated.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.135-139
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• 2002

Most of all the mechanical devices are becoming more high-speed and high-power as well as their used condition being more polluted. So, it is necessary for these devices to equip cooling system to overcome that kind of severe using condition. In this study, corrosion test was carried out in distilled and tap water for the investigation on the corrosion characteristics of Al-alloy that is using as material for radiator.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.3
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• pp.221-227
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• 1989

This study was conducted to understand the influence of soil compaction on root growth and nutrient uptake characteristics of the soybean roots grown in two soils with different texture. Tap root elongation was measured on young seedling grown in cores compacted to different bulk densities of 1.2, 1.4 and $1.6/cm^3$ with different soil water retention in laboratory. The soil used were Samgag sandy loam and Baegsan loam soils. The wet and dry weight, total length, average radius and total surface area of roots were measured on soybean plants grown in 1/5000 a Wagner pots compacted to different bulk density of 1.2 and $1.4g/cm^3$. The nutrient uptake of soybean shoot was measured and evaluated with the unit surface area of roots at the 7th, 17th and 27th days after germination. The results were as follows: 1. The tap root elongation rate was faster in the loam soil with low bulk density than in the sandy loam soil with high bulk density. The elongation rates were remarkedly decreased when soil water was lower than the retention of 4 bars in loam soil and that of 1 bars in sandy loam soil. 2. Tap root elongation rate sharply decreased as increased soil strength higher than $2kgf/cm^2$ measured by ELE penetrometer showing curvillinear regression. However, it was low regardless of soil strength when soil water retention was 10 bars in sandy loam soil. 3. From the pot experiment, the total length of roots were longer in loam soil than in sandy loam soil and was longer in the soils with lower bulk density. The average radius of fine roots grown in sandy loam soil was larger than that grown in loam soil. The total surface area of roots was greater in the loam soil with low bulk density than in the sandy loam soil with high bulk density as the total length of roots. 4. The amounts of nutrient uptake by soybean shoots were greater in loam soil primarily due to more production of dry matter than in sandy loam soil. The nitrogen influx rates through the unit surface area were 597 to $753nmoles/day-cm^2$ in loam soil and 222 to $365nmoles/day\;cm^2$ in sandy loam soilshowing higher value in higher bulk density. The potasium influx rates were 99 to $175nmoles/day-cm^2$, and those of phosphate were 26 to $46nmoles/day\;cm^2$. Those of Ca and Mg were 175 to 246 and 163 to $205nmoles/day\;cm^2$. The difference in nutrient influx rates between bulk densities of these elements were lower than that of nitrogen.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.11-20
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• 2001

This laboratory study examined the impact of free chlorine residual and pipe material on the formation of biofilm in drinking water distribution pipe surfaces. Result of heterotrophic plate counts(HPC) of the biofilm in the tap water-supplied reactor averaged $2.17{\times}10^5CFU/cm^2$ on PVC and $2.43{\times}10^5CFU/cm^2$ on STS 316, respectively. HPCs on the surface exposed to the tap water containing 0.2mg/L of free chlorinne residual averaged $4.24{\times}10^4CFU/cm^2$ on PVC and $6.54{\times}10^4CFU/cm^2$ on STS 316, respectively. Average of HPC/Total direct counts in the tap water-supplied reactor ranged from 1.08%(PVC) to 1.26%(STS 316) and from 0.38%(PVC) to 0.65%(STS 316) in the reactor supplemented with disinfectant, respectively. No correlation was observed between disinfectant addition and biofilm density. With regard to the biofilm formation, little difference existed between PVC and STS 316. Yellow and red pigmented bacteria were the dominant expressions in bulk fluid, whereas non-pigmented bacteria were found dominant in the biofilm. Pink/red pigmented bacteria were found to be facultative anaerobic, while yellow pigmented bacteria and non-pigmented bacteria were found to be obligate aerobic.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.31.1-31.1
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• 2011

$Li_4Ti_5O_{12}$ is emerging as a promising material with its good structure stability and little volume change during the electrochemical reaction. However, its electrochemical performance is significantly limited by low electronic or ionic conductivity. In addition, high tap density is needed forim proving its volumetric energy density and commercialization. To enhance these properties, the spherical-like $Li_4Ti_5O_{12}$ particles were synthesized and carried out doping with yttrium. Prepared Y-doped $Li_4Ti_5O_{12}$ as a anode material showed great capacity retention rate of 92% (5C/0.2C), compared with no dope done. Consequently, it was found that Y doping into $Li_4Ti_5O_{12}$ matrix reduces the polarization and resistance on SEI layer during the electrochemical reaction.

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.1
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• pp.115-122
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• 2003

Generally, material for radiator of automobile is composed of Al-alloy, but part of radiator material is still composed of Cu. Specially, Al-alloy replaces Cu and Cu-alloy as cooling and heating system material for light weight. Therefore, galvanic electronic cell is formed between Al-alloy and Cu for automobile radiator material, and Al-alloy corrosion is accelerated. So, in this study, galvanic corrosion test of Al-alloy coupling with Cu was carried out in distilled water, tap water, polluted environment and non-freezing solution. And thus corrosion potential and galvanic currrent density of Al-alloy coupling with Cu is investigated.