• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.3
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• pp.190-198
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• 2006

Radiation use efficiency (RUE), the amount of biomass produced per unit intercepted photosynthetically active radiation (PAR), constitutes a main part of crop growth simulation models. The objective of the present study was to evaluate the variation of RUE of rice plants under various nitrogen nutritive conditions. from 1998 to 2000, shoot dry weight (DW), intercepted PAR of rice canopies, and nitrogen nutritive status were measured in various nitrogen fertilization regimes using japonica and Tongil-type varieties. These data were used for estimating the average RUEs before heading and the relationship between RUE and the nitrogen nutritive status. The canopy extinction coefficient (K) increased with the growth of rice until maximum tillering stage and maintained constant at about 0.4 from maximum tillering to heading stage, rapidly increasing again after heading stage. The DW growth revealed significant linear correlation with the cumulative PAR interception of the canopy, enabling the estimation of the average RUE before heading with the slopes of the regression lines. Average RUE tended to increase with the increased level of nitrogen fertilization. RUE increased approaching maximum as the nitrogen nutrition index (NNI) calculated by the ratio of actual shoot N concentration to the critical N concentration for the maximum growth at any growth stage and the specific leaf nitrogen $(SLN;\;g/m^2\;leaf\;area)$ increased. This relationship between RUE (g/MJ of PAR) and N nutritive status was expressed well by the following exponential functions: $$RUE=3.13\{1-exp(-4.33NNNI+1.26)\}$$ $$RUE=3.17\{1-exp(-1.33SLN+0.04)\}$$ The above equations explained, respectively, about 80% and 75% of the average RUE variation due to varying nitrogen nutritive status of rice plants. However, these equations would have some limitations if incorporated as a component model to simulate the rice growth as they are based on relationships averaged over the entire growth period before heading.

• Journal of Animal Science and Technology
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• v.47 no.3
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• pp.481-490
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• 2005

Nitrate contamination in water system is a critical environmental problem caused by excessive application of chemical fertilizer and concentration of livestock. In order to prevent further contamination, therefore, it is necessary to understand the origin of nitrate in nitrogen loading sources and manage the very source of contamination. The objective of this study was to examine the nitrate contamination sources in different agricultural system by using nitrogen isotope ratios. Groundwater and runoff water samples were collected on a monthly basis from February 2003 to November 2003 and analyzed for nitrogen isotopes. The nitrate concentrations of groundwater in livestock fanning area were higher than those in conventional and organic fanning area and exceeded the national drinking water standard of 10mg N/ l. The ${\delta}^{15}N$ranges of chemical fertilizer and animal manure were - 3.7${\sim}$+2.3$\textperthousand$ and +12.5${\sim}$26.7$\textperthousand$, respectively. The higher ${\delta}^{15}N$ of animal manure than those of chemical fertilizer reflected isotope fractionation and volatilization of '''N. The different agricultural systems and corresponding average nitrate concentrations and ${\delta}^{15}N$ values were: conventional farming, 5.47mg/e, 8.3$\textperthousand$; organic fanning, 5.88mg/e, 10.1$\textperthousand$; crop-livestock farming, 12.5mg/e, 17.7%0. These data indicated that whether conventional or organic agriculture effected groundwater and runoff water quality. In conclusions, relationship between nitrate concentrations and ${\delta}^{15}N$ value could be used to make a distinction between nitrate derived from chemical fertilizer and from animal manure. Additional investigation is required to monitor long-term impact on water quality in accordance with agricultural systems.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.7
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• pp.941-947
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• 2000

Three fistulated Malaysian local bulls were used in a $3{\times}3$ Latin square design to determine the effects of different levels of concentrate with oil palm (Elaeis guineensis Jacq.) frond (OPF) on rumen pH and $NH_3$-N concentration, and DM degradability of different fractions of OPF. Three diets namely, 60% OPF pellet and 40% concentrate (Diet 1), 50% OPF pellet and 50% concentrate (Diet 2) and 40% OPF pellets and 60% concentrate (Diet 3) were used. The levels of concentrate in the diets affected rumen pH and $NH_3$-N concentration. The pH and $NH_3$-N concentration almost in all hourly samples did not show any difference (p>0.05) among the diets except the 6 h and 9 h samples. The highest (p<0.01) $NH_3$-N concentration was obtained on Diet 3 followed by Diet 2 and Diet 1, but there was a slightly higher (p>0.05) pH on Diet 1. The $NH_3$-N concentrations of rumen liquor at 9 h sampling on Diet 1 and Diet 2 were below the critical level (50 mg/liter) required for efficient fermentation of fibrous feeds. The in sacco DM degradation of different fractions of OPF was affected by diets. The DM degradation of fractions of OPF was higher on Diet 3, which showed differences (p<0.01) with the other diets. It was found that a higher level of concentrate (60%) with OPF gave a higher rumen $NH_3$-N concentration that increased the DM degradation of OPF fractions. The results showed that OPF could support an efficient rumen function in terms of $NH_3$-N concentration and pH when ${\leq}50%$ in the diet. A higher level of OPF (>50%) does not support an efficient rumen fermentation in terms of $NH_3$-N concentration, and resulted in lower DM degradation values of the fractions. The results suggested that there is a need to supplement additional nitrogen to OPF based diets.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.2
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• pp.74-82
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• 2004

This study was conducted to estimate the optimum application rate of fertilizer N based on $NO_3-N$ concentration in soils for tomato (Lycopersicon esculentum Mill.) cultivation in plastic film house. Tomato plants were cultivated with and without fertilizer in twelve soils which have different concentrations of $NO_3-N$ ranging from 46 to $344mg\;kg^{-1}$. Dry weight (DW) of above-ground part of tomato with no fertilizer ranged from 28.9 to $112.5g\;plant^{-1}$, depending on N-supplying capability of soils. The soil $NO_3-N$ was positively correlated with DW ($r=0.83^{**}$) and N uptake ($r=0.78^{**}$) by tomatoes in no fertilizer treatment, and negatively correlated with fertilizer effciencies resulted from the differences of DW and N uptake between fertilized and non-fertilized plot. The relationships between soil $NO_3-N$ concentration and DW, N uptake, and fertilizer efficiency were analyzed to determine the critical levels of soil $NO_3-N$ for tomato cultivation. The limit critical levels of soil $NO_3-N$ were estimated to be more than $280mg\;kg^{-1}$ for no application of fertilizer N and to be less than $50mg\;kg^{-1}$ for recommended application of fertilizer N. These critical levels of soil $NO_3-N$ were nearly the same as those calculated from regression equation between electrical conductivity(EC) and soil nitrate for critical levels of EC in recommendation equation of fertilizer N for tomato under the plastic film house by NationaI Institute of Agricultural Science and Technology. Consequently, the optimal application rate of ferdilizer N for tomato cultivation in the soils containing $NO_3-N$ concentration between $280mg\;kg^{-1}$ and $50mg\;kg^{-1}$ was estimated by the equation Y = -0.4348X＋121.74, where Y is the percent(%) to the recommended application rate of N fertilizer and X is the soil $NO_3-N$ concentration ($mg\;kg^{-1}$).

• Fire Science and Engineering
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• v.17 no.3
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• pp.20-25
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• 2003

Measurements with filaments and thermocouples and computations with Oppdif and FDS were carried out to investigate the impact of flame strain, agent addition, and buoyancy on the structure and extinction of nonpremixed counterflow flames. Measurements through 2.2 s drop tests in microgravity conditions and experiments in normal gravity conditions were compared with the results of computations. For the global strain rates 7 s$^{-1}$ through 100 s$^{-1}$ , the turning point behavior in the critical nitrogen concentration at O-g was confirmed. The effects of buoyancy, that is, changes in the flame curvature and thickness were also confirmed by the computations with FDS. There was agreement in the peak flame temperature and its position between the computations and the measurements in the near extinction methane/air diffusion flames in microgravity.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.25-34
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• 2013

The efficiency of three complex surfactants based on sunflower oil and nitrogen containing compounds as corrosion inhibitors for mild steel in $CO_2$-saturated 1% NaCl solution, has been determined by weight loss and LPR corrosion rate measurements. These compounds inhibit corrosion even at very low concentrations. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive media. The inhibition efficiency increases with increasing the concentration of the studied inhibitors. Maximum inhibition efficiency of the surfactants is observed at concentrations around its critical micellar concentration (CMC). Adsorption of complex surfactants on the mild steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. Energy dispersive X-ray fluorescence microscopy (EDRF) observations of the electrode surface confirmed the existence of such an adsorbed film.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.561-567
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• 2004

The influence of ultrasound frequency, dissolved gases, and initial concentration on the decomposition of sodium dodecylbenzene sulfonate(DBS) aqueous solution was investigated using ultrasound generator with 200 W ultrasound power. The decomposition rates at three frequencies(50, 200, and 600 kHz) examined under argon atmosphere were highest at 200 kHz. The highest observed decomposition rate at 200 kHz occurred in the presence of oxygen followed by air and argon, helium, and nitrogen. The effect of initial concentration of DBS on the ultrasonic decomposition was decreased with increasing initial concentration and would depend upon the formation of micelle in aqueous solution. It appears that the ultrasound frequency, dissolved gases, and initial concentration play an important role on the sonolysis of DBS. Sonolysis of DBS mainly take place at the interfacial region of cavitation bubbles by both OH radical attack and pyrolysis to alkyl chain, aromatic ring, and headgroup.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.1
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• pp.1-13
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• 2006

Response of grain yield and milled-rice protein content to nitrogen topdress (N) timing at panicle initiation stage (PIS) is critical for quantifying real-time N requirement for target grain yield and milled-rice protein content. Two split-split-plot experiments with three replications, one in 2004 and the other in 2005, were conducted in Experimental Farm, Seoul National University, Suwon, Korea. The experiments included three N rates at tillering stage (TS), three N timing treatments at panicle initiation stage (PIS) and two rice cultivars. The N rates at TS, N timing at PIS, and rice cultivars were randomly assigned to main plot, sub plot, and sub-sub plot, respectively. Results showed that the delayed N application at PIS reduced grain yield in 2004 and increased milled-rice protein content in both years significantly at 0.05 probability level. The calculated optimum N timing at PIS from pooled data by N rates and rice cultivars in two years was at 28 days before heading (DBH). However, real-time of N timing at PIS was dependent on plant growth and N status around PIS that in turn was dependent on applied N rates at TS. The optimum N timing at PIS was at 30 DBH for no N treatments at TS while at 27 DBH for 3.6 and 7.2 kg N/10a treatments and at 27 and 29 DBH for Hwaseongbyeo and Daeanbyeo, respectively. In general, earlier applied N at PIS resulted in lower milled-rice protein content but the highest grain yield was expected to be obtained when N topdress at PIS was applied at the time when shoot N concentration started to drop below about 23 mg/g due to dilution effect after transplanting. In conclusion, the results of our experiments imply that the currently recommended N topdress time (24DBH) at PIS in Korea should be reconsidered for the higher grain yield and the better quality of rice.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.518-524
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• 2013

In this study, we conducted a study on characteristics of exhaust gas emissions from boiler when water-bunker oil mixed by homogenizer was burned in boiler. The results showed that NOx concentration and CO concentration of the homogenized bunker oil was decreased by 19% and 54% compared to pure bunker oil pretreatment was not being performed. And, in the case of water-bunker A oil, the NOx concentration was decreased with increasing water mixing ratio in bunker A oil. In particular, the NOx concentration in exhaust gas of 20 %water-80 %bunker A oil decrease by 45 % compared with pure bunker-A. However, the CO concentration in exhaust gas of 20 %water-80 %bunker A oil shows irregular changes. This means that the mixing of water more than a certain amount can cause a decrease in combustion performance. From this result, it can be found that critical mixing ratio of water in bunker A oil for normal combustion is 15% in this study. Deposition amount of soot that is collected in the vicinity of the chimney was decreased with increasing water mixing ratio.

• Applied Biological Chemistry
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• v.48 no.2
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• pp.109-114
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• 2005

A bacterium capable of emulsifying hydrocarbon, n-hexadecane, and decreasing surface tension of the culture media using oil collapsing method was isolated. The bacterium was partially identified as Bacillus sp. and named BJS-51. n-Hexadecane was the most effective carbon source for production of biosurfactant. Surface tension was decreased from 76 dyne/cm to 31 dyne/cm and CMD (critical micelle dilution) had the highest value of 5.7 at 3% n-hexadecane. Ammonium phosphate was the most effective nitrogen source, when C/N ratio was 60, surface tension and CMD were 29 dyne/cm and 9.2, respectively. Optimum pH and temperature were 7.2 and $30^{\circ}C$, respectively. Produced biosurfactant was extracted and purified using organic solvent extraction method and preparative HPLC systems. After analysis by various color reaction, this biosurfactant was identified as lipopolysaccharide. Surface tension and CMC (critical micelle concentration) of purified biosurfactant were 27 dyne/cm and 0.08 g/l, repectively. CMD was 9.2, so the yield of biosurfactant was about 0.74 g/l at the optimal conditions. The biosurfactant was very stable at wide range of $pH\;2{\sim}12$ with surface tension $29{\sim}31\;dyne/cm$ and showed $29{\sim}30\;dyne/cm$ of surface tension after heat treatment at $100^{\circ}C$ for 60 min.