• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.75-86
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• 1994

Garbage composting was studied in a controlled batch reactor with the addition of cooked rice as a biodegradable carbon source to find the effect of C/N ratio control on composting. And composting of bulking agents such as sawdust and wheat straw were tested with the addition of ammonium sulfate as a nitrogen source. As expected, biodegradation of the garbage having low C/N ratio was improved to some extent when foreign carbon was added. But bulking agents used in this study exerted slightly biodegradable carbon potential, indicating that the estimation of the dose of additional carbon considering desirable C/N ratio was not reasonable when lignocellulosic bulking material was added to garbage. It was found that the optimum moisture content increased with sawdust addition meaning the C/N ratio increment. Considering the above results, it was suggested that 78g sawdust per 100g garbage should be mixed to make C/N ratio to 25 and moisture content to 56% for effective composting of the garbage studied in this paper.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.641-646
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• 2008

In this research, recovery of high quality organics from excess activated sludge and its potential as a external carbon sources for BNR process was studied. By simultaneous treatment of alkali and ozone, TSS concentration was reduced by 32%, and RBDCOD fraction was increased by 76.2%, and major constitute of produced organic were acetic acid and propionic acid. Also, nitrogen and phosphorus were greatly solubilized. However, because acid-hydrolyzable phosphorus(AHP) was major part of solubilized phosphorus, $NH_4{^+}-N$ and $PO_4{^3}-P$ concentration were insufficient for effective formation of crystal like as MAP(Magnesium Ammonium Phosphate) and hydroxyapatite. By placing BPR reactor before alkali-ozone treatment reactor, $PO_4{^3}-P$ concentration in pretreated sludge was increased by 1.8 times, and improved potential of phosphorus recovery by crystallization. In experiment of crystallization, hydroxyapatite formation was more easily applied than MAP. By hydroxyapatite formation, $SCOD/PO_4-P$ ratio was greatly increased from 32.7 at control to 141.9 at $Ca^{2+}/PO{_4}^{3-}-P$ mole ratio of 2.4. The results based on this study indicated that the proposed system configuration has potential to reduce the excess sludge production, to recover phosphorus in usable forms as well as utilize organics as a external carbon source in BNR process.

• Journal of Microbiology and Biotechnology
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• v.16 no.2
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• pp.226-231
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• 2006

Several white-rot fungi are able to produce extracellular lignin-degrading enzymes such as manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase. In order to enhance the production of laccase and MnP using Trametes versicolor KCTC 16781 in suspension culture, the effects of major medium ingredients, such as carbon and nitrogen sources, on the production of the enzymes were investigated. The decolorization mechanism in terms of biodegradation and biosorption was also investigated. Among the carbon sources used, glucose showed the highest potential for the production of laccase and MnP. Ammonium tartrate was a good nitrogen source for the enzyme production. No significant difference in the laccase production was observed, when glucose concentration was varied between 5 g/l and 30 g/l. As the concentration of nitrogen source increased, a lower MnP activity was observed. The optimal C/N ratio was 25 for the production of laccase and MnP. When the concentrations of glucose and ammonium tartrate were simultaneously increased, the laccase and MnP activities increased dramatically. The maximum laccase and MnP activities were 33.7 U/ml at 72 h and 475 U/ml at 96 h, respectively, in the optimal condition. In this condition, over 90% decolorization efficiency was observed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.165-166
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• 2002

Hydrogen free diamond like carbon (DLC) films were prepared on steel substrates by using a single ion beam in a configuration that allowed sputtering of a graphite target and at the same time allowed to impact the substrate at a grazing angle. The DLC films so prepared have improved properties with increased disorder and with modest hardness that is slightly higher than previously reported values. We have studied the effects of $N_2^+$ ions implantation on such films. It is found that the implantations of nitrogen ions into DLC films lead to chemical modifications that allowed N atoms to be incorporated into the carbon network to produce a nitrogenated DLC. Nano-indentation experiments indicated that the nitrogenated films have consistently higher hardnesses ranging from 30 to 45GPa, which represents a considerable increase in surface hardness, compared with non-nitrogenated precursor films. The investigations by XPS and Raman spectroscopy suggests that the $N_2^+$ implanted DLCs had undergone both chemical and structural modifications through the incorporation of N atoms and the increased ratio of $sp^3/sp^2$ type bonding. The observed high hardness was therefore attributable to these structural and chemical modifications. This result has implication for the preparation of super hard wear resistant films required for tribological functions in devices.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.382-389
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• 2009

An in-situ probe-based spectrophotometer has been developed. This system used two spectrometers to measure soil reflectance spectra from 450 nm to 2200 nm. It collects soil electrical conductivity (EC) and insertion force measurements in addition to the optical data. Six fields in Kansas were mapped with the VIS-NIR (visible-near infrared) probe module and sampled for calibration and validation. Results showed that VIS-NIR correlated well with carbon in all six fields, with RPD (the ratio of standard deviation to root mean square error of prediction) of 1.8 or better, RMSE of 0.14 to 0.22%, and $R^2$ of 0.69 to 0.89. From the investigation of carbon variability within the soil profile and by tillage practice, the 0-5 cm depth in a no-till field contained significantly higher levels of carbon than any other locations. Using the selected calibration model with the soil NIR probe data, a soil profile map of estimated carbon was produced, and it was found that estimated carbon values are highly correlated to the lab values. The array of sensors (VIS-NIR, electrical conductivity, insertion force) used in the probe allowed estimating bulk density, and three of the six fields were satisfactory. The VIS-NIR probe also showed the obtained spectra data were well correlated with nitrogen for all fields with RPD scores of 1.84 or better and coefficient of determination ($R^2$) of 0.7 or higher.

• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.353-358
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• 2010

In this study, we investigated the relationship of tree-ring growth with total nitrogen content, and stable carbon and nitrogen isotopes from the core samples of Pinus koraiensis (35-year-old). Annual ring width showed significant positive correlations with the ${\delta}^{13}C$ (P=0.003). The total nitrogen content (P=0.024), and the ${\delta}^{13}C$ content was also correlated with total nitrogen content (P=0.038), indicating that the growth of P. koraiensis was stimulated as the contents of both ${\delta}^{13}C$ and total nitrogen were increased. On the other hand, the less the ${\delta}^{15}N$ content and the C/N ratio were, the larger the annual ring width was. Moreover the families with relatively better growth performance contained the higher levels of ${\delta}^{13}C$ in the xylem compared to other families. These results suggest that the ${\delta}^{13}C$ and total nitrogen contents are the important determinants in the growth performance of P. koraiensis.

• Journal of Mushroom
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• v.2 no.1
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• pp.21-27
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• 2004

Distribution and in vitro growth characteristics of entomopathogenic Paecilomyces species were studied based on the specimens and isolates deposited in Entomopathogenic Fungal Culture Collection (EFCC), Kangwon National University, Chuncheon, Korea. Paecilomyces species were frequently collected from different mountains and valleys and were almost distributed uniformly. Collection period of Paecilomyces species ranged from July to September, with most of the collections at the end of September. P. tenuipes was mostly collected one among different Paecilomyces species. The optimum medium for mycelial growth of P. tenuipes was PDA, whereas in other media such as SDAY and HMA also produced similar growth. The optimum temperature and pH levels were $25^{\circ}C$ and 6.0~7.0, respectively. Best carbon and nitrogen sources were dextrose and tryptone, respectively, while $KH_2PO_4$ was the best mineral source for mycelial growth. Highest mycelial growth was observed when the C/N ratio was 20:1.

• Korean Journal of Environmental Biology
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• v.31 no.2
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• pp.61-68
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• 2013

Microalgae can grow autotrophically with the supply of light, carbon dioxide and inorganic nutrients in water through photosynthesis. Generally, microalgal growth is limited by the concentrations and relative ratio of nitrogen (N) and phosphorus (P) among the nutrients in the aquatic environment. Each microalga has its specific optimum N : P ratio resulting in dominance in a particular water having similar nutrient composition. Algal bloom is an immense growth of certain microalga commonly cyanobacterium and can be sequestrated by reducing the limiting nutrient, generally P in the freshwater. Moreover, dominance of a less toxic blooming strain can be established by manipulating N : P ratio in the water. On the other hand, microalgal biomass of a certain species can be enhanced by increasing limiting nutrient and adjusting the N : P ratio to the target species. The above-mentioned eco-physiological features of microalgae can be more completely interpreted in connection with their genomic informations. Consequently, microalgal growth regulation which can be achieved on the basis of its eco-physiological and further genomic insights would be helpful not only in the control of algal bloom, but also for an increased yield of algal biomass.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.8
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• pp.701-706
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• 2006

In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. In this study, DLC films were prepared by the RF PECVD (Plasma Enhanced Chemical Vapor Deposition) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas. We examined the effects of the post annealing temperature on the structural variation of the DLC films. The films were annealed at temperatures ranging from 300 to $900^{\circ}C$ in steps of $200^{\circ}C$ using RTA equipment in nitrogen ambient. The thickness of the film and interface between film and substrate were observed by surface profiler, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), respectively. Raman and X-ray photoelectron spectroscopy (XPS) analysis showed that DLC films were graphitized ($I_D/I_G$, G-peak position and $sp^2/sp^3$ increased) ratio at higher annealing temperature. The variation of surface as a function of annealing treatment was verified by a AFM and contact angle method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.3
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• pp.256-263
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• 2021

In this study, blending oils of diesel oil and butanol were used as fuel oil for diesel engine to measure combustion pressure, fuel consumption, air ratio and exhaust gas emission due to various operating conditions such as engine revolution and torque. Using these data, the results of analyzing the engine performance, combustion characteristics and exhaust emission characteristics such as NOx (nitrogen oxides), CO₂ (carbon dioxide), CO (carbon monoxide) and soot were as follows. The fuel conversion efficiency at each load was highest when driven in the engine revolution determined by a fixed pitch propeller law. Except 30% butanol blending oil, fuel conversion efficiency of the other fuel oils increased as the load increased. Compared to diesel oil, using 10% and 20% butanol blending oil as fuel oil was advantageous in terms of thermal efficiency, but it did not have a significant impact on the reduction of exhaust gas emissions. On the other hand, future research is needed on the results of the 20% butanol blending oil showing lower or similar levels of smoke concentration and carbon monoxide emission rate other than those types of diesel oil.