• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.100-108
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• 1998

Compost stability represents the state of microbiological activity and measurements of respiration either through $CO_2$ evolution or $O_2$ uptake should provide the best indication of this state. Hog manure amended with sawdust was composted in a pilot-scale reactor vessels using continuous and intermittent aeration for 3 weeks. In this study we evaluated the $CO_2$ respiration rate effect of aeration method on the reduction of $CO_2$ evolution, and investigated the stability of fresh and finished compost for plant growth. The intermittently aerated composting is a practical proposition for a very stable compost making. The $CO_2$ respiration rate in the fresh and finished compost during intermittently aerated composting was maintained from 0.3 to 1.4 and was good for use in horticulture, while the continuously aerated composting was 7 to 23 and needed more time for compost curing.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1272-1278
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• 2019

A lumped kinetic modeling platform is developed to investigate the coupled nuclear/thermo-fluid features of the closed natural circulation loop in a low power lead cooled fast reactor. This coolant material serves a reliable choice with noticeable thermo-physical safety characteristics in terms of natural convection. Boussienesq approximation is resorted to appropriately reduce the governing partial differential equations (PDEs) for the fluid flow into a set of ordinary differential equations (ODEs). As a main contributing step, the coolant circulation speed is accordingly correlated to the loop operational power and temperature levels. Further temporal analysis and control synthesis activities may thus be carried out within a more consistent state space framework. Nyquist stability criterion is thereafter employed to carry out a sensitivity analysis for the system stability at various power and heat sink temperature levels and results confirm a widely stable natural circulation loop.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2162-2172
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• 2020

Due to its computational efficiency and geometrical flexibility, the Method of Characteristics (MOC) has been widely used for light water reactor lattice physics analysis. Usually acceleration methods are necessary for MOC to achieve acceptable convergence on practical reactor physics problems. Among them, Coarse Mesh Finite Difference (CMFD) is very popular and can drastically reduce the number of transport iterations. In OpenMOC, CMFD acceleration was implemented but had the limitation of supporting only a uniform CMFD mesh, which would often lead to splitting MOC source regions, thus creating an unnecessary increase in computation and memory use. In this study, CMFD acceleration with a non-uniform Cartesian mesh is implemented into OpenMOC. We also propose a quadratic fit based CMFD prolongation method in the axial direction to further improve the acceleration when multiple MOC source regions are contained in one CMFD coarse mesh. Numerical results are presented to demonstrate the improvement of the CMFD acceleration capability in OpenMOC in terms of both efficiency and stability.

• Journal of Animal Environmental Science
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• v.15 no.1
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• pp.59-68
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• 2009

This study investigated the evaluation of maturity, stability, nutrient and heavy metal from rotating drum composter of food waste amended with poultry manure composting inoculated with effective microorganisms(EM). Composting were performed for the first, drying reactor($15m^3$) 3 hours and the second, composting reactor($30m^3$) 24 hours, and parameters monitored this period included moisture content, NaCl, pH, electrical conductivity(EC), C/N ratio, organic matter(OM), nutrient content and heavy metal. Changes in compost temperature during composting were maintained constantly in the range of $60{\sim}80^{\circ}C$ using firewood boiler(450 MJ/h). We examined physicochemical parameters and heavy metals in order to assess their effectiveness as stability and maturity, nutrient and harmful indicators such as seed germination rate<60%, potassium 1>%, dm and NaCl>1%, dm at the end of the final compost. The finished compost obtained after decomposition phase at the end of the 2nd composter could not be utilized for land improvement or reclamation.

• KSBB Journal
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• v.5 no.2
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• pp.141-149
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• 1990

$\beta$-glucosidase derived from Aspergillus niger was immobilized by (1) covalent linkage on chitin and chitosan with glutaraldehyde, (2) adsorption on DEAE-cellulose and Amberite IRA93 after succinylation, and (3) entrapment on alginate and polyacrylamide gels with various cross linking agents. The retention yield of $\beta$-glucosidase immobilized on chitosan was 31.5% and operational stability was 69% after continuous operation at column reactor(5$0^{\circ}C$ at pH 4.8) for 15 days. The retention yield and operational stability were 24.7% and 60% respectively, in adsorption on Amberite IRA 93. On the other hand, the entrapment method by alginate and polyacrylamide gel was identified to be not appropriate due to the continuous elution of inlmobilized $\beta$-glucosidase. Optimum conditions for the immobilization on chitosan were also studied with optimum pH of 4.8 and glutaraldehyde concentration of 0.4%(w/v). The properties and stability of immobilized $\beta$-glucosidase are also investigted. The conversion yield of cellobiose to glucose was also analyzed using the column type enzyme reactor to evaluate the effectiveness of immobilized enzyme.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.306-310
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• 2009

Packed-bed reactor for removing ammonia was tested at different loading rates. Nitrifiers for ammonia removing was encapsulated in gel media which consisted of polyethlene glycol, alginate and activated carbon. The removal efficiency was nearly 100% when ammonia loading was $12g/m^3/hr$, and the maximum elimination capacity (EC) achieved on this study was $18g/m^3/hr$. The initial microbial portion of nitrifiers in the media was about 82% and it was increased to more than 90% at the end of the operation. Short-term shock loading test was carried out to survey the stability of the media. The inlet loading rates were varied from 2 to $20g/m^3/hr$. The packed-bed reactor overcame the shock loading i.e. removal efficiency recovered rapidly from about 80% to almost 100% within 6 hrs. The results of Live/Dead cell test showed that nitrifiers maintained there activity in the encapsulated media during the test and also against ammonia shock load.

• Journal of Environmental Science International
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• v.9 no.4
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• pp.351-367
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• 2000

Air-lift biofilm reactor should be an admirable process substituting conventional activated sludge process, because of its small area requirement as well as high volumetric loading capacity and stability against loading and chemical shocks. However most of the past research on the performance of ABR was focused on the sewage treatment. This research studied the applicability of ABR to treat high strength wastewater. A bench-scale ABR was operated to treat high strength synthetic wastewater, tannery wastewater and petrochemical wastewater, and its applicability was conclusive In case of synthetic wastewater, ABR showed good performance in which the substarate removal efficiency was higher that 80% even under short HRT(1.4 hr) and high volumetric loading rate(9.3 kgCODcr/$m^3$.day). When ABR was applied to treat tannery wastewater, it was suggested that the maximum volumetric loading rate and F/M ratio should be 7.7kgCODcr/$m^3$.day, 0.76 $day^{-1}$, respectively. And high substrate removal efficiency over than 90 % was observed with 4,000 mgCODcr/L of petrochemical wastewater. Even though effluent concentration was quite high, ABR should be applicable to treat the high strength wastewater, because of its high loading capacity.

• Microbiology and Biotechnology Letters
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• v.43 no.3
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• pp.300-305
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• 2015

The glutamate decarboxylase gene (gadB) from Lactobacillus plantarum WCFS1 was cloned and expressed as an N-terminal hexa-histidine-tagged fusion protein in Escherichia coli BL21 (DE3) as the host strain. Purified glutamate decarboxylase (GAD) was immobilized onto porous silica beads by covalent coupling. The pH dependence of activity and stability of the immobilized GAD was significantly altered, when compared to those of the free enzyme. Immobilized GAD was stable in the range of pH 3.5 to 6.0. The resulting packed-bed reactor produced 41.7 g of γ-aminobutyric acid/l·h at 45℃.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.146-151
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• 2003

Reduced Activation Ferritic/Martenstic (RAFs) are leading candidates for structural materials of D-T fusion reactor. One of The RAFs, JLF-1 (9Cr-2W-V, Ta) has been developed and proved to have good resistance against high-fluency neutrino irradiation and good phase stability. Recently, in order to clarify the strengthening mechanical at high temperature, a new scheme to improve high temperature mechanical properties is desired. Therefore, the creep properties and creep life prediction by Larson-Miller Parameter method for JLF-1 to be used for fusion reactor materials or other high temperature components were presented at the elevated temperatures of $500^{\circ}C$, $550^{\circ}C$, $600^{\circ}C$, $650^{\circ}C$ and $704^{\circ}C$. It was confirmed experimentally and quantitatively that a creep life predictive e벼ation at such various high temperatures was well derived by LMP.

• Journal of environmental and Sanitary engineering
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• v.10 no.3
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• pp.67-77
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• 1995

This study was performed for minimization of excessive biofilm effects at the high strength organic wastewater treatment. As a results of biofilm attachment experiment using piggery wastewater, aggravation of water quality due to excessive biofilm showed after 15 days of operating times.4 excessive biofilm phase, the equivalent biofilm thickness and VSS contents per unit aura were observed in the range of 1,100 to $1,200{\mu}m$ and 2.5 to 3.0mg $VSS/cm^{2}$, respectively. In the aerobic fixed biofilm reactor/anoxic fixed biofilm reactor(AFBR/ANFBR) process with endogenous respiration phase, the BOD removal efficiency was obtained more than 90 percentage at the surface loading rate and volumetric loading rate of the AFBR maintained less than 17 g $BOD/m^{2}{\cdot}$day and 1.7kg $BOD/m^{3}{\cdot}$day, respectively. The removal efficiency of TKN and $NH_{3}$-N at the loading rates below 5.60g $NH_{3}-N/m^{2}{\cdot}day$ and 0.56kg $NH_{3}-N/m^{3}{\cdot}$day were above 76 percentage and 82 percentage, respectively. In order to reduced sludge production rate and aggravation of water quality, endogenous respiration phase was accepted at first AFBR reactor. As a results of this operating condition, sludge production was minimized and removal efficiency was maintained stability.