• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.603-604
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• 2005

A precise ratio transformer which is used to a ratio arm of a precise impedance measurement bridge at low frequencies was developed. The developed ratio transformer has the ratio taps of 1:1, 2:1, $\cdots$, to 10:1 in order to measure the primary impedance standards by substitution and special winding techniques for 10:1 ratio that is used frequently for impedance build up/down. The calibration results of the transformer has inphase and quadrature error of $0.073\times10^{-6}$ and $0.14\times10^{-6}$ respectively at 1.6 kHz.

• Journal of Bio-Environment Control
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• v.9 no.2
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• pp.85-93
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• 2000

This study was carried out to investigate the effects of several substrates and ratio of NO3--N to NH4--N in nutrient solution on growth, yield and mineral uptake of sweet pepper(Capsicum annuum L.) in bag culture. The content of minerals such as P, K, Ca and Mg showed difference in concentration among media: P and Mg were the highest in vermiculite in vermiculti+rice hull, K in perlite+vermiculite and Ca in perlite+peatmoss; with the lowest in the single perlite medium respectively, Ca of mineral made fairly higest level in concentration compared with the others in all of the media. The concentration of mineral content was lower in the ratio of 8:2 than that of 10:0. Admitting that the pH made difference depending on the kind of substrates and ratios of NO3--N to NH4--N. The pH of 10:0 ratio in all the substrates was higher and more stable than that of 8:2. The range of EC in all the substrates showed from 1.78ds·m-1 to 2.10 ds·m-1, which was optimum range for growth of sweet pepper, and range of EC is larger in 8:2 ratio than that in 10:0 ratio. Plant height and stem diameter were nothing to do with the kind of substrates, but leaf area was the largest at vermiculite+rice hull of the 8:2 ratio, fresh and dry weights were heavier at peatmoss+carbonized rice hull, but were the lightest at perlite. All indexes related to the growth which had something to do with the kind of substrates higher in 8:2 ratio than those in 10:0 ratio. The number of fruit and fresh weight related to the ratio of the 8:2 were the highest as 17.5 at vermiculite+rice hull with 1,588g of fresh weight, while the yield from perlite was the lowest. The number of fruit was the highest as 16.4 at virmiculite+rice hull, yield was the higest as 1,394a at perlite+ peatmoss. The yield of 8:2 ratio at all substrates was higher than that of 10:0 ratio. Of the mineral content related to the plant part, K+ and Mg2+ were higher in concentration at leaf; Ca2+ were higher at root; PO4- was higher at stem and fruit; The content of mineral showed no difference between the ratio of the 8:2 and the ratio of the 10:0 with no regrading to the difference of mineral content among substrates; and K+, Ca2+, and Mg2+ uptake of sweet pepper were higher at 10:0 ratio than that of 8:2; 2while PO4- uptake of sweet pepper was lower at 10:0 ratio than that of 8:2 ratio.

• International Journal of Concrete Structures and Materials
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• v.19 no.1E
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• pp.17-23
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• 2007

In rainy weather, permeable concrete pavement has advantages such as good drainage, increased skid resistance, reduced splash and spray behind vehicles for improving the safety of driving vehicles as well as reduction of the traffic noise. It also contributes to improvement of traffic environment. In this study, the fundamental properties of permeable concrete in accordance with maximum size of aggregate, sand percentage and unit cement content were investigated for practical use of permeable concrete pavement. Although the permeability standard for typical permeable asphalt-concrete pavement is $1{\times}10^{-2}cm/sec$, the researchers determined that the coefficient of permeability of the permeable concrete should be set higher at $1{\times}10^{-1}cm/sec$. Then, the researchers measured the coefficient of permeability, strength, void ratio, and continuous void ratio of the permeable concrete while varying maximum size of the aggregate, sand percentage, unit cement content for detailed analysis. It was found that the void ratio, continuous void ratio, and flexural strength were about 15%, 12%, and 5.0MPa, respectively, when the permeability of the concrete was set at $1{\times}10^{-1}cm/sec$. Given that the maximum size of aggregate was $10{\sim}13mm$, we reached the conclusion that the best mix design for permeable concrete was $0{\sim}20%$ of sand percentage and $380kg/m^3$ of unit cement content.

• Journal of Broadcast Engineering
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• v.18 no.1
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• pp.106-114
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• 2013

This paper deals with the effect of the internal sampling frequency and core band down sampling ratio on the overall performance of the MPEG USAC. Here, the internal sampling frequency is the sampling frequency of a signal actually coded. The core band down sampling ratio is the ratio of the width of the core band over that of the coded band. The performance was measured on 6 different test sound sources by the MUSHRA test with 10 subjects. The experiments showed that 1/3 or 1/4 core band down sampling ratio could yield the better performance than the conventional 1/2 ratio, especially at low rates.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2247-2252
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• 2012

In this paper, we produced CIGS thin film by co-evaporation method. During the process, substrate temperature and Ga/(In+Ga) composition ratio was altered to observe the change of resistivity and absorbance spectra measurements. As substrate temperature increased, resistivity decreased and as Ga/(In+Ga) composition ratio increased from 0.30 to 0.72, band gap also increased with the range of 1.26eV, 1.30eV, 1.43eV, 1.47eV. With the constant condition of composition ratio, resistivity decreased with increased thickness of the thin film. On this experiment, we assumed that optical absorbance ratio and optical current will be increased with CIGS thin film fabrication.

• Journal of Environmental Science International
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• v.20 no.1
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• pp.71-79
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• 2011

In this study, a series of soil concrete mixtures were tested for the compressive strength according to ratio of aggregate to binder, compaction energy, maximum aggregate size, ratio of silica fume to cement, and ratio of water to binder. The optimum mixing ratio of soil concrete mixtures composed of volcaniclastic, cement, silica fume, concrete polymer and water were analysed. The test results for optimum proportion were as follows ; (1)ratio of aggregate to binder was 4 : 1, (2)compaction energy level was level 2, (3)maximum aggregate size was 13 mm, (4)ratio of silica fume to cement was 10%, (5)ratio of water to binder was 25%. Also, dry type construction techniques were applied using the optimum soil concrete mixture. From the results of this study, the compressive strength of soil concrete and construction techniques were suitable for making eco-friendly soil pavement.

• Journal of information and communication convergence engineering
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• v.13 no.1
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• pp.56-61
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• 2015

The demand for high-aspect-ratio structures has been increasing in the field of semiconductors and other applications. Here, we present the commercially available negative-tone SU-8 as a potential resist that can be used for direct patterning of high-aspect-ratio structures at the submicron scale and the nanoscale. Such resist patterns can be used as polymeric molds to create high-aspect-ratio metallic submicron and nanoscale structures by using electroplating. Compared with poly (methyl methacrylate) (PMMA), we found that the negative tone resist required an exposure dose that was less than that of PMMA of equal thickness by a factor of 100-150. Patterning of up to 4:1 aspect ratio SU-8 structures with a minimum feature size of 500 nm was demonstrated. In addition, nanoimprint lithography was studied to further extend the aspect ratio to realize a minimum feature size of less than 10 nm with an extremely high aspect ratio in the negative resist.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.9 no.1
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• pp.15-19
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• 2013

In this Study, effect of core position, area ratio and orientation of building on energy load is examined using TRNSYS17. This parameters are major parameters of the conceptual design stage. Reference model is square floor plan($1,444m^2$), centered core and 29% core area ratio. As the results, without considering the building orientation, the annual heating load of central building with 1:1 area ratio is lowest ($10.33kWh/m^2yr$) and the annual cooling load of off-central building with 1:1 area ratio is lowest ($59.27kWh/m^2yr$). As area ratio is bigger, cooling load is lower and heating load is higher. But if we consider building orientation, orders of heating load and cooling load are changed for area ratio and orientation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.1
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• pp.52-72
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• 1984

This study was performed to obtain the basic data which can be applied to the use of epoxy resin mortars. The data was based on the properties of epoxy resin mortars depending upon various mixing ratios to compare those of cement mortar. The resin which was used at this experiment was Epi-Bis type epoxy resin which is extensively being used as concrete structures. In the case of epoxy resin mortar, mixing ratios of resin to fine aggregate were 1: 2, 1: 4, 1: 6, 1: 8, 1:10, 1 :12 and 1:14, but the ratio of cement to fine aggregate in cement mortar was 1 : 2.5. The results obtained are summarized as follows; 1.When the mixing ratio was 1: 6, the highest density was 2.01 g/cm$^3$, being lower than 2.13 g/cm$^3$ of that of cement mortar. 2.According to the water absorption and water permeability test, the watertightness was shown very high at the mixing ratios of 1: 2, 1: 4 and 1: 6. But then the mixing ratio was less than 1 : 6, the watertightness considerably decreased. By this result, it was regarded that optimum mixing ratio of epoxy resin mortar for watertight structures should be richer mixing ratio than 1: 6. 3.The hardening shrinkage was large as the mixing ratio became leaner, but the values were remarkably small as compared with cement mortar. And the influence of dryness and moisture was exerted little at richer mixing ratio than 1: 6, but its effect was obvious at the lean mixing ratio, 1: 8, 1:10,1:12 and 1:14. It was confirmed that the optimum mixing ratio for concrete structures which would be influenced by the repeated dryness and moisture should be rich mixing ratio higher than 1: 6. 4.The compressive, bending and splitting tensile strenghs were observed very high, even the value at the mixing ratio of 1:14 was higher than that of cement mortar. It showed that epoxy resin mortar especially was to have high strength in bending and splitting tensile strength. Also, the initial strength within 24 hours gave rise to high value. Thus it was clear that epoxy resin was rapid hardening material. The multiple regression equations of strength were computed depending on a function of mixing ratios and curing times. 5.The elastic moduli derived from the compressive stress-strain curve were slightly smaller than the value of cement mortar, and the toughness of epoxy resin mortar was larger than that of cement mortar. 6.The impact resistance was strong compared with cement mortar at all mixing ratios. Especially, bending impact strength by the square pillar specimens was higher than the impact resistance of flat specimens or cylinderic specimens. 7.The Brinell hardness was relatively larger than that of cement mortar, but it gradually decreased with the decline of mixing ratio, and Brinell hardness at mixing ratio of 1 :14 was much the same as cement mortar. 8.The abrasion rate of epoxy resin mortar at all mixing ratio, when Losangeles abation testing machine revolved 500 times, was very low. Even mixing ratio of 1 :14 was no more than 31.41%, which was less than critical abrasion rate 40% of coarse aggregate for cement concrete. Consequently, the abrasion rate of epoxy resin mortar was superior to cement mortar, and the relation between abrasion rate and Brinell hardness was highly significant as exponential curve. 9.The highest bond strength of epoxy resin mortar was 12.9 kg/cm$^2$ at the mixing ratio of 1:2. The failure of bonded flat steel specimens occurred on the part of epoxy resin mortar at the mixing ratio of 1: 2 and 1: 4, and that of bonded cement concrete specimens was fond on the part of combained concrete at the mixing ratio of 1 : 2 ,1: 4 and 1: 6. It was confirmed that the optimum mixing ratio for bonding of steel plate, and of cement concrete should be rich mixing ratio above 1 : 4 and 1 : 6 respectively. 10.The variations of color tone by heating began to take place at about 60˚C, and the ultimate change occurred at 120˚C. The compressive, bending and splitting tensile strengths increased with rising temperature up to 80˚ C, but these rapidly decreased when temperature was above 800 C. Accordingly, it was evident that the resistance temperature of epoxy resin mortar was about 80˚C which was generally considered lower than that of the other concrete materials. But it is likely that there is no problem in epoxy resin mortar when used for unnecessary materials of high temperature resistance. The multiple regression equations of strength were computed depending on a function of mixing ratios and heating temperatures. 11.The susceptibility to chemical attack of cement mortar was easily affected by inorganic and organic acid. and that of epoxy resin mortar with mixing ratio of 1: 4 was of great resistance. On the other hand, when mixing ratio was lower than 1 : 8 epoxy resin mortar had very poor resistance, especially being poor resistant to organicacid. Therefore, for the structures requiring chemical resistance optimum mixing of epoxy resin mortar should be rich mixing ratio higher than 1: 4.

• ALGAE
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• v.32 no.4
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• pp.275-284
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• 2017

Microcystis aeruginosa causes harmful algal blooms in the Nakdong River of Korea. We studied the effect of different concentrations and ratios of ammonium ($NH_4{^+}$), nitrate ($NO_3{^-}$), and phosphate ($PO{_4}^{3-}$) on growth of this species in BG-11 medium: each nutrient alone, $NO_3{^-}:NH_4{^+}$ ratio, the N : P ratio with fixed total N (TN), and the N : P ratio with fixed total P (TP). The single nutrient experiments indicated that M. aeruginosa had the highest growth rate at $NH_4{^+}$ and $NO_3{^-}$ concentrations of $500{\mu}M$, and at a $PO{_4}^{3-}$ concentration of $5{\mu}M$. The $NO_3{^-}:NH_4{^+}$ ratio experiments showed that M. aeruginosa had the highest growth rate at a ratio of 1 : 1 when TN was $100{\mu}M$ and $250{\mu}M$, and the lowest growth rate at a ratio of 1 : 1 when the TN was $500{\mu}M$. The N : P ratio with fixed TN experiments indicated that M. aeruginosa had the highest growth rates at 50 : 1, 20 : 1, and 100 : 1 ratios when the TN was 100, 250, and $500{\mu}M$, respectively. In contrast, the N : P ratio with fixed TP experiments showed that M. aeruginosa had the highest growth rates at 200 : 1 ratio at all tested TP concentrations. In conclusion, our results imply that the $NO_3{^-}:NH_4{^+}$ ratio and the $PO{_4}^{3-}$ concentration affect the early stage of growth of M. aeruginosa. In particular, our results suggest that the maximum growth of M. aeruginosa is not simply affected by the $NO_3{^-}:NH_4{^+}$ ratio and the N : P ratio, but is determined by the TN concentration if a certain minimum $PO{_4}^{3-}$ concentration is present.