• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.343-346
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• 2000

This study was carried out to investigate the effects of influent $NH_4^{\;+}-N$ load, C/N ratio and superficial air velocity on the nitrogen removal efficiencies. Laboratory scale upflow biological aerated filter(BAF) was consisted of an anoxic-aerobic filter packed with porous ceramic media and operated with synthetic wastewater. BAFs requires less energy and space for the system when compared to conventional activated sludge process. The influent C/N ratios were varied from 0 to 1 by adjusting acetate. Various superficial air velocity had been applied to investigate aeration effect on nitrogen removal. The BAF reactor showed more than 90% average $NH_4^{\;+}-N$ removal efficiencies at $NH_4^{\;+}-N$ loading in the range of $0.26{\sim}1.33$ kg $NH_4^{\;+}-N/m^3{\cdot}d$ and 62% average T-N removal efficiencies at the C/N ratio of 1. Moreover, average T-N removal efficiencies increased as the superficial air velocity increased, because of the increase $NH_4^{\;+}-N$ removal efficiencies.

• Macromolecular Research
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• v.14 no.4
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• pp.438-442
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• 2006

Novel sulfonated poly(aryl ether ketones) containing benzoxazole were directly synthesized by aromatic nucleophilic polycondensation using various ratios of 2,2'-bi[2-( 4-flurophenyl)benzoxazol-6-yl]hexafluoropropane to sodium 5,5'-carbonylbis(2-fluorobenzenesulfonate). The copolymers were soluble in polar aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide at a relatively high solid composition (>15 wt%) and formed tough, flexible and transparent membranes. The membranes exhibited a degradation temperature of above $290^{\circ}C$. The exact dissolution times of these membranes at $80^{\circ}C$ in Fenton's reagent (3 wt% $H_2O_2$ containing 2 ppm $FeSO_4$) were undetectable, confirming their excellent chemical stability in fuel cell application. The membranes showed a moderate increase in water uptake with respect to increasing temperature. The proton conductivities of the membranes were dependent on the composition and ranged from $1.10{\times}10^{-2}$ to $5.50{\times}10^{-2}Scm^{-1}$ at $80^{\circ}C$ and 95% relative humidity (RH). At $120^{\circ}C$ without externally humidified conditions, the conductivities increased above $10^{-2}Scm^{-1}$ with respect to increasing benzoxazole content, which suggested that the benzoxazole moieties contributed to the proton conduction.

• Proceedings of the Korean Society of Crop Science Conference
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• 2023.04a
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• pp.179-179
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• 2023

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1374-1382
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• 2001

Fifteen Inner Mongolian wethers with permanent ruminal and duodenal cannulas were used to study the effects of dietary rumen-undegradable protein (RUP) to rumen-degradable protein (RDP) ratios or protein sources on fiber digestion in the gastrointestinal tract and ruminal fluid characteristics. Fiber digestion and ruminal fermentation were not affected (p>0.05) by dietary RUP to RDP ratios (from 1.54 to 0.72). Soybean meal supplementation improved ruminal digestion. Fish meal supplementation increased (p<0.05) the ruminal degradability of fiber. The different RUP to RDP ratios (from 1.54 to 0.72) did not influence (p>0.05) ruminal fluid pH, but there were differences (p<0.05) in ruminal fluid $NH_3-N$ concentration because of urea replacement. Soybean meal as a dietary protein source decreased (p<0.05) ruminal fluid pH and increased (p<0.05 or p<0.01) $NH_3-N$, acetate, propionate and butyrate concentrations in the rumen. Fish meal as a dietary protein source decreased (p<0.05 or p<0.01) ruminal $NH_3-N$ and acetate concentrations and increased (p<0.05) ruminal propionate concentration. It can be concluded that dietary protein sources have more significant effect on fiber digestion and ruminal fermentation than different dietary RUP to RDP ratios, when the dietary crude protein requirements of growing sheep are satisfied.

• Microbiology and Biotechnology Letters
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• v.12 no.4
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• pp.271-276
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• 1984

Effect of C/N ratios on the cell growth, cell lipid, cell protein and fatty acids of Rhodotorula sp. was examined. At low concentration of nitrogen in cultural medium the growth of the yeast was retarded, whereas its growth was favorable at high concentration but lipid yield was decreased due to a high content of cell protein. In order to increase lipid yield, the optimum C/N ratio obtained was 45-50 (5% glucose, 0.0414% nitrogen). During the cultivation cell protein synthesis occurred mainly in initia stage and the lipid was accumulated rapidly at the late phase. The highest content of total fatty acid was observed at the optimum C/N ratio. The higher C/N ratio was the more unsaturation degree of fatty acid decreased. It was attributed principally to a decreased oleic acid with palmitic acid increased. No significant changes occurred in content of other fatty acids.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.130-132
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• 2005

Tungsten carbon nitride (W-C-N) thin films were produced by reactive radio frequency (RF) magnetron sputter-ing of tungsten in $Ar-N_2$ gas mixture. The effects of the variation of nitrogen partial pressure on the composition, and structural properties of these films as well as the influence of post-deposition annealing have been studied. When $La_{0.67}Sr_{0.33}MnO_3$ was coated on the W-C-N/Si substrate, coercivity ($H_c$) and magnetization at room temperature shows 58.73 Oe, and 29.4 emu/cc, respectively. In order to improve the diffusion barrier characteristics, we have studied the impurity behaviors to control the ratios of nitrogen and carbon concentrations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.451-460
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• 1989

This paper dealt with the effect of the ratios N2 to H2 gas on the corrosion fatigue failure behavior of ion-nitrided SM45C steel specimens. The specimens were water cooled after ion-nitriding at 500.deg. C for 3hrs in 5 Torr, 0.8N$_{2}$ and 0.5N$_{2}$ atmospheres. As the nitrogen concentration increases, the higher compressive residual stresses developed in the surface layer and the depth of nitrided layer increased, which in turn gave rise to increases in fatigue strength and corrosion fatigue life. In the region less than 1.5 * 10$^{5}$ cycles, fatigue failure initiated at the brittle nitrided case, whereas in the region higher than 1.5 * 10$^{5}$ cycles crack initiated from the non-metallic inclusions in the subsurface. The initiation of corrosion fatigue failure was mainly attributed to pitting of case hardened surface layer.

• Biomedical Science Letters
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• v.13 no.1
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• pp.39-45
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• 2007

Numerous psychological stressors playa role in development of the cardiovascular disease. The aim of this study was to determine whether a combined mental activity with experimental subway noise affects hematological physiology. Fifty-four healthy volunteers were divided group I which underwent subway noise (n=24) and group II which underwent a combined mental activity with subway noise (n=30). Venous blood samples were collected for measuring CBC, prothrombine time (PT), activated partial thromboplastine time (APTT), erythrocyte sedimentation rate (ESR), D-dimer and high sensitive C-reactive protein (H-CRP) levels before, 50 min of stress task (S-50m) and 60 min of recovery (R-60m). Changed ratios of granulocyte, lymphocyte, monocyte and platelet counts at S-50m and R-60m were higher in group II compared to group I. RBC count and hematocrit level in group I increased whereas those in group II decreased at S-50m. PT, APTT and ESR in the both groups were shortened at R-60m and the decreased ratios were high in group II compared to group I. H-CRP and D-dimer in the both groups were elevated at S-50m and R-60m while the increased ratios in group II were greater than those in group I. These observations imply that a combined mental activity with experimental subway noise may be a stressor which affects hematological physiology.

• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.62-66
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• 2003

The biological denitrification batch tests were conducted to optimize the operating conditions with various temperature and initial SCO $D_{Cr}$ /N $O_3$-N ratio. and the denitrification rates were analyzed various SCO $D_{Cr}$ /N $o_3$-N ratio of influent with swine wastes fermented and temperature. The finishing time of denitrification was within 15 hours, 12 hours, and 6 hours as the temperature of denitrification applied were 15$\pm$1$^{\circ}C$, 25$\pm$1$^{\circ}C$, and 31$\pm$1$^{\circ}C$, respectively. From the batch tests, denitrification rate was operated with over 3 of SCO $D_{Cr}$ /N $O_3$-N ratio. Denitrification rate was increased as the temperature of denitrification, increased such as 2.40-3.90 mg N $O_3$-N/gMLVSSㆍhr, 6.10-7.60 mgN $O_3$-N/gMLVSSㆍhr, and 14.40-15.88 mgN $O_3$-N/gMLVSSㆍhr, respectively. The denitrification rate was increased as the ratio of initial SCO $D_{Cr}$ N $O_3$-N increased. However, it was found that the suitable ratio of SCO $D_{Cr}$ /N $O_3$-N for denitrification should be considered because the ratio of mg SCO $D_{Cr}$ , consumed per mg N $O_3$-N removed varied depend on the influent SCO $D_{Cr}$ /TKN ratios.

• Journal of the Korean Geographical Society
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• v.45 no.5
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• pp.541-552
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• 2010

Geochemical and physical investigations such as ${\delta}^{13}C$ isotope ratio, carbon/nitrogen (C/N) ratio, magnetic susceptibility (MS), and particle size analyses were carried out on the estuarine tidal flat sediments from the west coast of Korea in order to reconstruct the East Asian summer monsoon variability during the late Pleistocene and Holocene Our results indicated that the summer monsoon probably peaked around 7,700-7,800 yr BP and then started to decline about 7,400 yr BP in the Korean peninsular, and that the monsoon was relatively weak between 24,000-24,500 yr BP but relatively strong between 18,500-19,500 yr BP during the Last Glacial Maximum. Our estuarine geochemical data have proven to be valuable as a new proxy for detecting the shifts in monsoon strength. This new evidence will be helpful, especially for Korean paleoenvironmental studies with few proxy data archives.