• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.10-16
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• 2007

In this study, we examined the preparation and hydrolysis property of immobilized urease membrane to decompose harmful urea in the body and remove ammonia which was produced by its decomposition. Urease immobilized membrane was prepared by introducing anion-exchange group DEA into porous hollow-fiber membrane by radiation graft polymerization method, and immobilization of urease. When urease was immobilized at membrane introduced with anion-exchange group, the more increasing grafting rate, the more increasing immobilization amount. The result originates from the fact that a greater amount of protein was immobilized by forming a multilayer on the longer grafted chain. Meanwhile, the addition of the cross-linker was possible not only to suppress separation phenomenon produced during a washing process of immobilized urease membrane but also to enable the recycling of membrane. Urease Immobilized membrane with no separation phenomenon was prepared by cross-linking reaction for 5 h, and the hydrolysis rate of prepared urease immobilized membrane was over 98% and 50%, respectively, in 1 mol and 4 mol urea solutions.

• Polymer(Korea)
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• v.24 no.3
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• pp.314-325
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• 2000

Thermal degradation of thermoplasitc polyurethane modified polycarbonate has been investigated by means of DSC, GPC and FT-IR techniques. The polyurethanes used in this study are TPU-35 and TPU-53 containing 35.5 and 53.4 wt% of hard segments, respectively. The more content of hard segment, the higher the glass transition temperature (T$_{g}$) of TPU was observed. On the other hand, the T$_{g}$ of the TPU modified PC decreased with the content of TPU and the annealing temperature regardless of the hard segment contents. The latter behavior nay arise from the thermal degradation of TPU upon annealing process: the observed thermal degradation temperatures were at 240 and 25$0^{\circ}C$ for the PC/TPU-35 and PC/TPU-53, respectively. The molecular weight, molecular weight distribution and viscosity agree well with the DSC measurement, which implicates a thermal degradation of TPU. In addition, thermal stability of the TPU modified PC linearly decreased with an incorporation of TPU. Transesterification or any interaction was not observed using FT-IR: the evidence was no frequency shift or any variance betwere the carbonyl stretching and NH group. For the specimens prepared below the degradation temperature, the enhancement of the thickness dependent impact strength of the PC/TPU blend was observed, and the morphology of the two blends was compared.d.

• Korean Journal of Microbiology
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• v.33 no.4
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• pp.267-273
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• 1997

Various physico-chemical and microbiological parameters of a composting system were compared with respect to their potential use for the monitoring and evaluation of composting processes for cattle manure. The temperature changed within a range of $30-65^{\circ}C$ during the whole composting process, and the period of active composting (>$40^{\circ}C$) persisted for 16 days. The concentrations of total carbon, total nitrogen, and organic matter decreased by 15% during active composting, but significant changes in C/N ratio were not observed. The decrease of temperature in the latter period of active composting caused a decrease of $NH_4^+-N$ and an increase of $NO_3^--N$ in the composting pile. When temperature exceeded $50^{\circ}C$, the population of thermophiles was higher than that of mesophiles by more than 1 or 2 orders of magnitude. Correlation analyses showed that amylase activity correlated positively with the population of mesophiles and reducing sugar content, but negatively with the population of thermophiles. Amylase activity was higher at the beginning of active composting, whereas cellulase, xylanase and ligninase activities which showed close relationship with each other, increased continually during active cornposting, suggesting the distinction of temporal niches between amylose-degrading and lignocellulose-degrading bacteria in the same habitat.

• Clean Technology
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• v.27 no.1
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• pp.61-68
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• 2021

Selective catalytic reduction (SCR) is widely used as a method of removing nitrogen oxide in large-capacity thermal power generation systems. Uniform mixing of the injected ammonia and the inlet flue gas is very important to the performance of the denitrification reduction process in the catalyst bed. In the present study, a computational analysis technique was applied to the ammonia injection system design process of a denitrification facility. The applied model is the denitrification facility of an 800 MW class coal-fired power plant currently in operation. The flow field to be solved ranges from the inlet of the ammonia injection system to the end of the catalyst bed. The flow was analyzed in the two-dimensional domain assuming incompressible. The steady-state turbulent flow was solved with the commercial software named ANSYS-Fluent. The nozzle arrangement gap and injection flow rate in the ammonia injection system were chosen as the design parameters. A total of four (4) cases were simulated and compared. The root mean square of the NH3/NO molar ratio at the inlet of the catalyst layer was chosen as the optimization parameter and the design of the experiment was used as the base of the optimization algorithm. The case where the nozzle pitch and flow rate were adjusted at the same time was the best in terms of flow uniformity.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.2
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• pp.116-123
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• 2004

This study was conducted to investigate the changes in physicochemical and microbiological properties during fermenting process of organic fertilizer which was made from the mixture of organic materials such as sesame oil cake, fish meal, blood meal, rice bran, ground bone meal, and natural minerals such as illite, crusted oyster shell and loess. They were mixed and fermented for 70 days. The sesame oil cake and rice bran, major ingredients for organic fertilizers, consisted of 7.6 and 2.6% total nitrogen, 3.6 and 4.6% $P_2O_5$, 1.4 and 2.2% $K_2O$, respectively. The ground bone meal included 29.2% $P_2O_5$ and illite included 3.8% $K_2O$. Temperature of organic fertilizer during the fermentation rapidly increased over $50^{\circ}C$ within 2 days after mixing and stabilized similar to outdoor temperature after 40 days. Moisture content decreased from 36.3 to 16.0% after 1 month. C/N ratio of organic fertilizer slightly increased until 30 days and thereafter, it slowly decreased, It resulted from the faster decrease of total nitrogen concentration compared with organic matter. Concentration of $NH_4-N$ in organic fertilizer rapidly increased from 1,504 to $5,530mg\;kg^{-1}$, the highest concentration after 10 days. Meantime, $NO_3-N$ concentration was low and constant about $150mg\;kg^{-1}$ over the whole fermenting period. This result seemed to be due to the high pH. The organic ferfilizer fermented for 70 days was composed of 2.7% N, 2.8% $P_2O_5$, 1.8% $K_2O$, and 35.9% organic matter. Total populations of aerobic bacteria, Bacillus sp. and actinomycetes, after fermenting process, were $12.5{\times}10^{10}$, $45.5{\times}10^{5}$ and $13.6{\times}10^{5}cfu\;g^{-1}$ respectively. Pseudomonas sp. was $71.9{\times}10^{7}cfu\;g^{-1}$ at first, but it rapidly decreased according to the rise of temperature. Yeasts played an important role in the early stage of fermentation and molds did in the late stage.

• Korean Journal of Environmental Agriculture
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• v.24 no.1
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• pp.24-28
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• 2005

Waste of the hydroponic solution from the plastic film house cultivation was recycled to grow the red pepper(Capsicum annum L.) in upland fields as supplement for plant nutrients and irrigation sources. Application of hydroponic waste solution increased the pH and EC of the soils, coupled with the increases in the concentrations of exchangeable cations(Ca, Mg, and K), total nitrogen, $NH_4-N,\;and\;NO_3-N$. Growth and yield of red pepper were highest when the treatment of chemical fertilizer(70%) was combined with hydroponic waste solution(30%). Amounts of the daily producing hydroponic waste solution were 2,880 L $ha^{-1}\;day^{-1}$ from the experimental facilities and this could irrigate $409.86m^2$ of area to compensate for the amount of water loss by evapotranspiration(3%). The overall results demonstrated that hydroponic waste solution could be recycled as plant nutrients and irrigation water resources for enhancing soil fertility and environmental quality.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.491-504
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• 2000

In clinical therapy, the current goal of dental implants is to enhance quantity and quality of osseointegration. Surface roughness and oxide structure are considered to influence the behavior of adherent cells. The purpose of this study is to evaluate the effect of different surface treatment on cellular response. The attachment and proliferation of osteoblast-like cell on sandblasted, sandblasted and etched, thermal oxidated surfaces have been compared. Sandblasting was done with $Al_2O_3$ particles(grain size of $50{\mu}m$), etching was processed with $NH_4OH$ : $H_2O_2$ : $H_2O(1:1:5)$ at $90^{\circ}C$ for 1 minute. Thermal oxidation was followed sandblasting and etching at $400^{\circ}C$, $600^{\circ}C$, $800^{\circ}C$ for 2 hours. Measurement of surface roughness after the different treatment did not show any differences of Ra value between terated surfaces. Cell attachment and proliferation were increased during experiment period, but no difference was observed. SEM evaluation revealed a similar pattern of osteoblast-like cells, well attached with dendritic extension and producing numerous matrix vesicles on cell surface. The results of this study showed that oxide layer alteration by thermal oxidation did not affect the attachment and proliferation of osteoblast-like cells. This suggests the possibility that the cellular responses are further influenced by surface roughness than titaniun oxide structure.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.3
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• pp.117-125
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• 2006

A microorganism capable of degrading toluene was isolated from crude oil contaminated soil and identified as Pseudomonas fluorescence. The effects of environmental factors on the degradation of toluene were investigated. The optimum temperature for toluene degradation was $30^{\circ}C$ and the maximum specific cell growth and toluene degradation rates were $0.76hr^{-1}$ and $0.36hr^{-1}$, respectively. Although the wild cells were not able to degrade toluene at $10^{\circ}C$ and $40^{\circ}C$, the cells adapted to toluene at $30^{\circ}C$ degraded 100mg/L of toluene completely at $10^{\circ}C$ and 80% of the toluene at $40^{\circ}C$. The wild cells were not able to degrade more than 200mg/L of toluene but the toluene-adapted cells degraded up to 300mg/L of toluene. Although the optimum pH was 7.0, the degradation rates were not much different in the range of 5.5 to 9.0. When nitrate was used as a nitrogen source instead of ammonium, the adaptation period became longer by 2~10 hours and the cell growth yield became lower by 45%. The toluene degradation rates after adaptation period, however, were almost same in both cases. The observations in this study will be used in the future biofilter design and operation.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.3
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• pp.164-169
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• 2008

This experiment was carried out to find the growth response and changes of nitrate and soluble sugar content in tomato leaves with salt stress. Tomato (Solanum lycopericum) seedlings were grown under different electrical conductivity (EC) levels adjusted with $CaCl_2$ as 1, 2, and $6dS\;m^{-1}$. The growth response and contents of nitrate and soluble sugar in tomato plants were examined at 7 and 14 days after salt treatment. Leaf area and dry weight ratio of shoot to root of tomato plants were decreased as EC level increased. Photosynthetic rate of leaves was reduced under high EC level due to the stomatal closure and the reduction of transpiration rate. The soluble sugar and starch content were lower in the tomato leaves grown under high EC level. Total nitrogen and nitrate contents were decreased in high EC level, whereas the ammonium content was increased. High-salt stress induced the accumulation of salt crystal in mesophyll cells of tomato leaf.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.1
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• pp.44-49
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• 2008

Sufficient inorganic nitrogen supply for crop growth is crucial for economically sustainable organic farming. The effects of an application of cover crop biomass on crop growth, nitrogen utilization and carbohydrate composition were investigated during early stage. Short-term changes in soil nitrogen after incorporating fresh hairy vetch and rye shoots were measured. The inorganic nitrogen from cover crops reached the peak at 15 ($NH_4-N$) and 24 ($NO_3-N$) days after incorporation, and then decreased rapidly. The highest concentration of soil nitrate showed at 27 days of incorporation in hairy vetch and at 18 days in rye, and three fold differences exhibited between two treatments. Crop growth under hairy vetch or rye incorporation significantly differed. At 20 DAT, dry matter production in NPK and hairy vetch was about two fold greater than that in rye. Difference in decomposing rates of hairy vetch and rye had also influence on nitrogen status in leaves and roots of pepper plants. Total nitrogen was greater in NPK and hairy vetch than in rye until 20 DAT, whereas inorganic nitrogen (nitrate and nitrite) concentration was higher in rye. Temporal changes in soluble sugars and starch in pepper plants among treatments were similar, although difference in the amount existed. It was suggested that hairy vetch as an alternative nitrogen source promoted crop growth and mineral utilization during early growth stage, whereas an obvious effect in rye was not found.