• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.75-78
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• 2001

Authors evaluated the feasibility of a permeable reactive biobarrier (PRB) treated with biofilm formed by Beijerinckia indica (B.indica). This study focused on evaluating two potentials of B.indica for the requirements of PRB: reducing the hydraulic conductivity and degrading the polycyclic aromatic hydrocarbons (PAHs). The hydraulic conductivity was estimated by rigid wall column test and finally the values were converted to the values of intrinsic permeability. The nutrient solution was passed through the biobarrier column to activate the bacterium and then leachate was in turn carried into the column to evaluate the durability of the biobarrier. Phenanthrene was selected as a representative substance of PAHs. The ability of degrading phenanthrene by B.indica was evaluated by two-phase partitioning bioreactor after estimating the possibility with two pretests: observing the colony formation and the optical density on glucose-free medium containing phenanthrene. With the results, B.indica produced large amount of strongly adhesive exopolysaccharides (EPS) and reduced several orders of magnitude of the hydraulic conductivity after 2 weeks of cultivation. Furthermore, about 1000mg/1 of phenanthrene could be degraded by B.indica in the two-phase partitioning bioreactor. In conclusion, the application of the bacterium, B.indica, was found to have a potential role of a PRB to retain and remove contaminants in porous media.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.465-469
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• 2006

Two mesophilic trickling bed bioreactors filled with two different types of media, hydrophilic- and hydrophobic-cubes, were designed and tested for hydrogen production via anaerobic fermentation of sucrose. Each reactor consisted of a column packed with polymeric cubes and inoculated with heat-treated sludge obtained from anaerobic digestion tank. A defined medium containing sucrose was fed with changing flow rate into the capped reactor, hydraulic retention time and recycle rate. Hydrogen concentrations in gas-phase were constant, averaging 40% for all conditions tested. Hydrogen production rates increased up to $10.5 L{\cdot};h^{-1}{\cdot}L^{-1}$ of reactor when influent sucrose concentrations and recycle rates were varied. Hydrophobic media provided higher value of hydrogen production rate than hydrophilic media at the same operation conditions. No methane was detected when the reactor was under a normal operation. The major fermentation by-products in the liquid effluent of the both trickling biofilters were acetate and butyrate. The reactor filled with hydrophilic media became clogged with biomass and bio gas, requiring manual cleaning of the system, while no clogging occurred in the reactor with hydrophobic media. In order to make long-term operation of the reactor filled with hydrophilic media feasible, biofilm accumulation inside the media in the reactor with hydrophilic media and biogas produced from the reactor will need to be controlled through some process such as periodical backwashing or gas-purging. These tests using trickling bed biofilter with hydrophobic media demonstrate the feasibility of the process to produce hydrogen gas in a trickle-bed type of reactor. A likely application of this reactor technology could be hydrogen gas recovery from pre-treatment of high carbohydrate-containing wastewaters.

• 에너지공학
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• 제23권4호
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• pp.95-105
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• 2014

CUPID 코드는 기기 스케일(Component scale)의 2상 유동(Two-phase flow) 해석 코드로서 다양한 2상 유동 조건의 실험 자료를 이용하여 검증되어 왔다. 특히, CUPID 코드의 CANDU형 원자로 감속재 탱크 내부 유동 해석능력을 평가하기 위해 1/4 규모 축소 실험장치의 실험결과를 이용하여 검증한 바가 있다. 본 연구에서는 이전 연구를 바탕으로 CUPID 코드를 사용하여 실제 원자로 감속재탱크 내부의 열수력 거동을 해석하였다. 감속재 탱크의 내부 구조는 아주 복잡하기 때문에 다공질 매질 방법을 적용하였으며 탱크 입구노즐 또한 기기 스케일 코드의 취지에 부합하게 아주 단순화하여 모델하였다. 해석결과의 정확성을 결정하는 가장 중요한 요소는 입구노즐의 모델 방법에 있는 것으로 나타났다. 입구노즐을 단순하게 모델하여 입구유량을 경계조건으로 부여하고 발전소 정상운전조건으로 계산한 결과, 부력에 의한 열성층화 현상이 발생하였다. 이는 전혀 타당하지 않은 것으로 입구 유동의 모멘텀을 정확하게 모의하지 않아 발생한 것이 나타났다. 이를 개선하고자 입구 유량과 운동량을 동시에 보존시킬 수 있도록 입구 노즐 면적을 축소하고 속도는 증가시켜서 계산한 결과, 사실적인 내부 유동장을 얻을 수 있었다. 결론적으로 계산 비용효과가 뛰어난 다공질 매질 방법에 입각하여 CUPID 코드를 실규모 감속재 탱크 열유동 해석에 적용할 수 있음을 보였고, 입구노즐의 적절한 모델이 가장 중요한 요소임을 확인하였다.

• 환경위생공학
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• 제13권2호
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• pp.34-39
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• 1998

For more convenient and rapidly isolation of Bacillus thuringiensis subsp. israelensis(Bti), 1) heat treatment spore forming bacteria, 2) growth in enrichment culture media for Bacillus sp. and 3) selection of bacteria producing a lecithinase for Bacillus thuringiensis subsp. israelensis, were performed. Spore forming bacteria were counted 4.8 $\times $ 10$^{8}$cells/g soil on NAPGCY media, 9.2 $\times $ 10$^{7}$cells/g soil on NA media, and 3.6 $\times $ 10$^{8}$cells/g soil on NAAC media, respectively. Bacteria producing only a lecithinase were reached at 25.2% on medium contained egg york, bacteria only producing a delta-endotoxin were reached at 23.2% by phase contrast microscope, and bacteria producing a lecithinase & a delta-endotoxin simultaneously were reached at 13.7%. Bacillus thuringiensis which producing a lecithinase and a delta-endotoxin simultaneously among bacteria producing a lecithinase, were reached at 56.5%; A half of Bacillus thuringiensis was produced a delta-endotoxin, but not produced a lecithinase. Among 8 isolates of Bacillus thuringiensis, two strain of Bti which has a mosquito-cidal toxin, were detected by PCR using a specific primer of $\delta $-endotoxin gene from Bti.

• Steel and Composite Structures
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• 제38권2호
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• pp.141-150
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• 2021

In the present paper we have investigated the Stoneley wave propagation at the interface of two dissimilar homogeneous nonlocal magneto-thermoelastic media under the effect of hall current applied to multi-dual-phase lag heat transfer. The secular equations of Stoneley waves have been derived by using appropriate boundary conditions. The wave characteristics such as attenuation coefficients, temperature distribution and phase velocity are computed and have been depicted graphically. Effect of nonlocal parameter and hall effect are studied on the attenuation coefficient, phase velocity, temperature distribution change, stress component and displacement component. Also, some particular cases have been discussed from the present study.

• Wind and Structures
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• 제35권6호
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• pp.395-403
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• 2022

The present research is concerned with the study of Stoneley wave propagation at the interface of two dissimilar homogeneous orthotropic magneto-thermoelastic solids with fractional order theory of type GN-III with three phase-lags and combined effect of hall current and rotation. With the help of appropriate boundary conditions the secular equations of Stoneley waves are obtained in the form of determinant. The characteristics of wave such as phase velocity, attenuation coefficient and specific loss are computed numerically. The effect of rotation on the Stoneley wave's phase velocity, attenuation coefficient, specific loss, displacement components, stress components and temperature change has been depicted graphically. Some particular cases are also derived in this problem.

• 상하수도학회지
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• 제23권2호
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• pp.175-180
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• 2009

This study was conducted to improve biological degradation efficiency of toluene as a model volatile organic compound (VOC) using yeast Candida tropicalis and to suggest an effective method for bioreactor operation. The yeast strain was immobilized with polyethylene glycol (PEG), alginate, and powdered activated carbon (PAC). The yeast-immobilized polymer media were used as fluidized materials in an airlift bioreactor. Polymer media without PAC were also made and operated in another airlift bioreactor. The two bioreactors showed toluene removal efficiencies ranging 80-96% at loading rates of $10-35 g/m^3-hr$, and the bioreactor containing the polymer media with PAC achieved higher removal efficiency. Protein contents in the liquid phase showed that the bioreactor using the yeast-immobilized polymer media with PAC had a higher rate of microbial growth initially than that without PAC. In addition, the microbial growth rate inside of the polymer media with PAC was five times higher than that without PAC. Consequently, the polymer media containing the yeast strain and PAC could enhance removal efficiencies for VOCs, and the immobilization method improve microbial activity and stability for a long-term operation of biological systems.

• 상하수도학회지
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• 제20권4호
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• pp.519-526
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• 2006

In this study, the major operating factors in SND(simultaneous nitrification and denitrification) using bioreactor packed with submerged cilia media and granular sulfur such as variation of nitrification rate, organic matter removal efficiency and denitrification efficiency in different DO concentration were mainly evaluated. Synthetic wastewater and actual sewage were used as influent wastewater. Experiment with synthetic wastewater as influent wastewater was divided into three phases with the adjustment of DO concentration. As the results, nitrification efficiency and T-N removal efficiency in the Phase 3(DO 1.0~2.0 mg/L) were 99% and 52.3%, which is significantly greater than those in other two phases. Also, loading rate and denitrification efficiency of SCPGS(Submerged Cilia media Packed with Granular Sulfur) were calculated as $0.44kg\;NO_3^--N/m^3-day$ and 50%, respectively. On the other hand, nitrification rate was decreased from 99% to 64% according to the DO concentration with the variation from 3.0~3.5 mg/L(phase1) to 0.4~0.6mg/L(phase2). Although the nitrification rate was decreased in 64% according to the variation of the DO concentration, T-N removal rate was rapidly increased to 49% by increasing of the denitrification efficiency. Experiment with actual sewage as influent wastewater was carried out to evaluate efficiency of SCPGS in real operation condition of full-scale sewage water treatment plant. At the time, T-N removal rate in this experiment and full-scale wastewater treatment plants were given by 43% and 20%, respectively. The above results indicate that SCPGS can be used as an advanced treatment process for economical efficiency considered.

• Ocean Systems Engineering
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• 제12권1호
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• pp.63-86
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• 2022

A refined projection-based purely Lagrangian meshfree method is presented towards reliable numerical analysis of fluid flow interactions with saturated/unsaturated porous media of uniform/spatially-varying porosities. The governing equations are reformulated on the basis of two-phase mixture theory with incorporation of volume fraction. These principal equations of mixture are discretized in the context of Incompressible SPH (Smoothed Particle Hydrodynamics) method. Associated with the consideration of governing equations of mixture, a new term arises in the source term of PPE (Poisson Pressure Equation), resulting in modified source term. The linear and nonlinear force terms are included in momentum equation to represent the resistance from porous media. Volume increase of fluid particles are taken into consideration on account of the presence of porous media, and hence multi-resolution ISPH framework is also incorporated. The stability and accuracy of the proposed method are thoroughly examined by reproducing several numerical examples including the interactions between fluid flow and saturated/unsaturated porous media of uniform/spatially-varying porosities. The method shows continuous pressure field, smooth variations of particle volumes and regular distributions of particles at the interface between fluid and porous media.

• 한국자기공명학회논문지
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• 제15권2호
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• pp.115-127
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• 2011

A newly developed cost-effective approach to prepare $^{15}N/^{13}C$-labeled protein for NMR studies is presented. This method has been successfully applied to isotopically labeling of PTK6 SH2 domain and MTH 1880 protein. The production method generates cell density using a growing media containing $^{15}NH_4Cl$, $^{12}C_6$-D-glucose. Following a doubling time period for unlabeled metabolite exhaustion and then addition $^{13}C_6$-D-glucose into a M9 growing media, the cells are induced. Our results demonstrate that in order to get full incorporation of $^{13}C$, the isotopes are not totally required during the initial growth phase before induction. The addition of small amounts of $^{13}C_6$-D-glucose to the induction phase is sufficient to obtain more than 95% incorporation of isotopes into the protein. Our optimized protocol is two-thirds less costly than the classical method using $^{13}C$ isotope during the entire growth phase.