• ETRI Journal
• /
• v.35 no.6
• /
• pp.1156-1159
• /
• 2013

We investigate the characteristics of $Cu_2O$ thin films deposited through the addition of $N_2$ gas. The addition of $N_2$ gas has remarkable effects on the phase changes, resulting in improved electrical and optical properties. An intermediate phase ($6CuO{\cdot}Cu_2O$) appears at a $N_2$ flow rate of 1 sccm, and a $Cu_2O$ (200) phase is then preferentially grown at a higher feeding amount of $N_2$. The optical and electrical properties of $Cu_2O$ thin films are improved with a sufficient $N_2$ flow rate of more than 15 sccm, as confirmed through various analyses. Under this condition, a high bandgap energy of 2.58 eV and a conductivity of $1.5{\times}10^{-2}$ S/cm are obtained. These high-quality $Cu_2O$ thin films are expected to be applied to $Cu_2O$-based heterojunction solar cells and optical functional films.

• KSBB Journal
• /
• v.26 no.6
• /
• pp.529-532
• /
• 2011

Whey based medium was optimized for the production of viable Lactobacillus crispatus KLB 46 isolated from the vagina of Korean women. Among the various nitrogen sources such as yeast extract, beef extract, and proteose peptone no. 3 supplemented to whey, beef extract showed the highest viable cell production. The addition of Tween 80 to the whey based medium increased viable cell concentration. As beef extract supplementation is not economically attractive, corn steep liquor was added as a supplementary nitrogen sources. When corn steep liquor was supplied with beef extract with the ratio 5 : 1, the viable cell count was $3.11{\times}10^9$ CFU/mL. Also, the addition of mineral salts containing sodium acetate (5 g/L), potassium phosphate dibasic (2 g/L), magnesium sulfate (0.1 g/L) and manganese sulfate (0.05 g/L) to the whey medium increased viable cell count further ($5.00{\times}10^9$ CFU/mL).

• Journal of environmental and Sanitary engineering
• /
• v.16 no.1
• /
• pp.108-116
• /
• 2001

It is difficult to task to achieve high biological nutrient removal from municipal wastewater because of low organic content. Volatile fatty acids(VFAs) produced from acid fermentation of food wastes can be utilized as external carbon sources for the biological nutrient process. Significant reduction and stabilization of the food wastes can also be obtained from the acid fermentation. The objective of this study is to evaluate characteristics of acid fermentation of the food wastes. Results obtained from the batch experiment of various organic wastes showed that the food wastes had high potential to be used as an external carbon source because of the largest production of the VFAs with low nitrogen and phosphorus content. The fish waste was found to be the next possible organic waste, while the others such as radish cabbage and molasses waste showed high VFAs consumption potential as a results of high nitrogen and phosphorus content. alkaline hydrolysis of the food waste was carried out using NaOH prior to the acid fermentation. As the alkali addition increased, solubilization of the organics as well as TSS reduction increased. However, fraction of soluble COD to total COD became stable after a sharp increase. Alkali addition greater than 0.5g NaOH per g TS resulted in significant increase in pH.

• Journal of Korean Society on Water Environment
• /
• v.23 no.1
• /
• pp.155-160
• /
• 2007

Constructed wetland has been widely used for the treatment of sewage, stormwater runoff, industrial wastewater, agricultural runoff, acid mine drainage and landfill leachate. For the removal of nitrogen and phosphorus, uptake by plants and adsorption to media material are the major processes, and, therefore, the selection of media with specific adsorption capacity is the critical factor for the optimal design of wetland along with the selection of appropriate plant species. In this study, two media materials (loess bead and mixed media) possessing different adsorption characteristics for ammonium and phosphate were selected, and their adsorption characteristics were evaluated. In addition, the performance of subsurface-flow wetland systems employing these media was evaluated in both batch and continuous flow systems. With LB medium, beter phosphorus removal was observed, while better ammonia removal was obtained with MM medium. In addition, enhanced removal efficiencies were observed in the wetland systems employing both media and aquatic plants, mainly due to the better environment for microbial growth. As a result, appropriate selection or combination of media with respect to the inflow water quality maybe important factors for the successful design and operation of wetland systems.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.37 no.1 s.109
• /
• pp.1-9
• /
• 2005

Many factors which affect the adsorption of cationic polymers on fibers and fines have been investigated by many researchers that include contact time, pH, collision frequency, properties of cationic polymers and adsorbent, etc. But the effect of white water quality on the adsorption of cationic polymer have not been examined throughly. In this study, the adsorption of cationic PAM was analyzed as a function of white water quality. The adsorption of the cationic PAM was analyzed by two analysis methods, Kjeldahl nitrogen content measurement and electrokinetic measurements. When the distilled water was used, adsorbed amount of C-PAM and zeta-potential of fibers increased as a function of the addition of C-PAM. When closure level increased, nitrogen content of fibers increased indicating that the cationic PAM was adsorbed. Zeta-potential of fibers, however, showed no significant change with the increased addition of C-PAM. This showed that adsorption of C-PAM was not reflected by zeta-potential of fibers due to the deteriorated efficiency of C-PAM by the anionic contaminants in white water.

• Journal of Forest and Environmental Science
• /
• v.36 no.4
• /
• pp.274-280
• /
• 2020

As the importance of biological resources increases, the conservation technology is becoming important for rarities. This study was conducted to establish an efficient cryopreservation conditions for the Deutzia paniculata, endangered plant species, by using both cryopreservation methods of vitrification and encapsulation. As a result, the sucrose pretreatment seed viability showed up to 30.7% in the treatments. The cryoprotectant treatment improved the viability of the seeds, and was found to be excellent in the vitrification method using PVS3. The vitrification method had over 10% higher germination rate than the seeds preserved by encapsulation. In addition, the germination rate showed a significant difference according to the cryopreservation treatment time, and the germination rate of seeds decreased very much as the long time became longer. Plants germinated from preserved seed in liquid nitrogen showed poor growth compared to untreated, and good growth in PVS3 120 minutes. In addition, the growth of germinated plants by liquid nitrogen treatment time was better in the vitrification method. These results are expected to be useful for long-term preservation of D. paniculata, endangered plants.

• Proceedings of the National Institute of Ecology of the Republic of Korea
• /
• v.4 no.1
• /
• pp.49-62
• /
• 2023

Phthalates are animal carcinogens. Potassium hydrogen phthalate (KHP), which has the least complicated structure among phthalates, is used for the analysis of total organic carbon and formaldehyde. However, its toxicity has not been confirmed. A 24-hour acute toxicity test was performed using Daphnia magna, a water flea used to evaluate aquatic toxicity owing to its high sensitivity. The lowest observed effect concentration of KHP was found to be 240 mg/L. The effects of phosphorus, nitrogen, and Cr(6+), which are able to be discharged along with KHP, were also confirmed using tests. At 240 mg/L KHP, toxicity increased as phosphorus, nitrogen, and Cr(6+) increased. In addition, tests were performed to confirm the half maximal effective concentration of KHP. Through 10 test repetitions, the average ecotoxicity value was found to be 0.3, the average half maximal effective concentration was 327.75 mg/L, and the coefficient of variation (%) was 3.16%; because the latter value is lower than 25%, which is what is generally suggested for the water pollution standard method, the reproducibility of the tests is sufficient to replace the existing standard reference toxicity test that uses potassium dichromate. In addition, the half maximum effective concentration of potassium hydrogen phthalate is approximately 218 times more than that of potassium dichromate; therefore, toxicity is relatively low. In conclusion, KHP is a feasible alternative to the highly toxic potassium dichromate for performing the standard reference toxicity test.

• Korean Journal of Soil Science and Fertilizer
• /
• v.17 no.3
• /
• pp.265-273
• /
• 1984

To investigate nitrogen supplying effect of some slowrelease N-fertilizers on barley in upland soil sulfurcoated urea(SCU), ureaform and melamine (1,3,5-Triazine-2,4,6-triamine) were treated and compared to urea. In addition, thiourea as a nitrification inhibitor was also tested. Effects of variable soil condition such as moisture content, pH and temperature on nitrogen supplying ability of the fertilizers and on growth of barley were studied through incubation test and pot culture and the obtained results were summarized as follows: The releasing rate of ammonia from urea, SCU, ureaform and melamine were resulted as 27-59%, 25-39%, 9-34% and 0.7-4.3% at maximum conversion rate, respectively. Nitrification rate of the tested fertilizers was higher at pH 6.54 markedly than at pH 4.73. Addition of thourea depressed the formation of $NO_3$ during four weeks of incubation period. Mixed application of ureaform with small amount of urea contributed to nitrogen supply till latter growth stage of barely Basal application of melamine showed lowest nitrogen supplying ability and injurious response on barley growth.

• KSBB Journal
• /
• v.24 no.1
• /
• pp.75-79
• /
• 2009

The effect of inorganic, organic nitrogen sources and amino acids on the coenzyme $Q_{10}$ production and coenzyme $Q_{10}$ component ratio was investigated. Among the nine organic nitrogen sources, CSP showed a remarkable enhancing effect on the production of coenzyme $Q_{10}$. But this enhancement was not observed in medium containing Bacto peptone, tryptone, casamino acid and soybean meal. These differences on the production of coenzyme $Q_{10}$ may be due to differences in kinds and amounts of component amino acids and peptides in the various organic nitrogen sources tested. In the addition of inorganic nitrogens, only $(NH_4)_2SO_4$ increase the coenzyme $Q_{10}$ production by 2.0 times compare to the control group. The addition of L-tyrosine to the medium containing Bacto tryptone, was also determined to be crucial for the coenzyme $Q_{10}$ production. But phenylalanin and tryptophan, other aromatic amino acids, had no stimulatory effect on the coenzyme $Q_{10}$ production. These results show that the production and components ratio of coenzyme $Q_{10}$ was greatly affected by the kinds and the concentration of inorganic, organic nitrogen sources as well as amino acids.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.2
• /
• pp.181-188
• /
• 2012

The present study on nitrogen-diluted non-premixed counterflow flames with finite burner diameters experimentally investigates the important role of the outer edge flame in flame extinction. Flame stability diagrams mapping the flame extinction response of nitrogen-diluted non-premixed counterflow flames to varying global strain rates in terms of the burner diameter, burner gap, and velocity ratio are explored. There exists a critical nitrogen mole fraction beyond which the flame cannot be sustained, and also the curves of the critical nitrogen mole fraction versus the global strain rate have C-shapes in terms of burner diameter, burner gap, and velocity ratio. In flames with sufficiently high strain rates, the curves of the critical nitrogen mole fractions versus global strain rate collapse into one curve, and the flames can have the 1-D flame response of typical diffusion flames. Three flame extinction modes are identified: flame extinctions through the shrinkage of the outer edge flame with and without an oscillation of the outer edge flame prior to the extinction and flame extinction through a flame hole at the flame center. The measured flame surface temperature and a numerical evaluation of the fractional contribution of each term in the energy equation show that the radial conductive heat loss at the flame edge destabilizes the outer edge flame, and the conductive and convection heat addition to the outer edge from the trailing diffusion flame stabilizes the outer edge flame. The radial conductive heat loss at the flame edge is the dominant extinction mechanism acting through the shrinkage of the outer edge flame.