• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.433-440
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• 2014

In this study, a method for the low-carbon active distribution system (ADS) planning is proposed. It takes into account the impacts of both network capacity and demand correlation to the renewable energy accommodation, and incorporates demand response (DR) as an available resource in the ADS planning. The problem is formulated as a mixed integer nonlinear programming model, whereby the optimal allocation of renewable energy sources and the design of DR contract (i.e. payment incentives and default penalties) are determined simultaneously, in order to achieve the minimization of total cost and $CO_2$ emissions subjected to the system constraints. The uncertainties that involved are also considered by using the scenario synthesis method with the improved Taguchi's orthogonal array testing for reducing information redundancy. A novel cuckoo search (CS) is applied for the planning optimization. The case study results confirm the effectiveness and superiority of the proposed method.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.136-139
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• 2001

In this study, we have examined potential degradation of MTBE (methy1 tert-butyl ether) by pure culture ENV425 and mixed culture isolated from gasoline contaminated soil using n-butane as the sources of carbon and energy. The results described in this study suggest that MTBE is degraded cometabolically by ENV425 and mixed culture grown n-butane, and the disappearance of TBA after complete degradation of MTBE suggest the further degradation of TBA. Butane and MTBE degradation was completely inhibited by acetylene, which indicated that both substrates were degraded by butane-utilizing bacteria. MTBE was degraded ENV425 and mixed culture grown n-butane, and TBA (tert-butyl alcohol) was produced as product of MTBE oxidation. TBA production was accounted 54.7% and 58.6% for MTBE oxidation by ENV425 and mixed culture, respectively. The observed maximal transformation yield (T$_{y}$) were 44.7 and 34.0 (nmol MTRE degraded/$\mu$mol n-butane Utilized) by ENV425 and mixed culture, respectively.y.

• Journal of Microbiology and Biotechnology
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• 제12권5호
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• pp.722-728
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• 2002

Eight strains producing bacterial cellulose (BC) were isolated from rotten fruits and traditionally fermented vinegars. One of the isolated strains from the rotten grape in Gwangju, Korea, maintained a relatively stable BC production in shaking cultures. This isolated strain proved to be Acetobacter xylinum, based on several biochemical and morphological tests. It was shown that the slant-baffled flask was more efficient than the conventional flask for the BC production in shaking cultures. To determine the most suitable carbon and nitrogen sources for the production of BC, various compounds were examined. Fructose was found to be the most effective carbon source with an optimal concentration of 2%. Mixed carbon source (glucose:fructose=1:3) was also better than glucose or fructose alone. Optimal nitrogen source, when basal medium was used, was 10% (v/v) com steep liquor (CSL). When com steep liquor was used with a mixed carbon source (glucose:fructose=1 :3),4% CSL exhibited the best BC production. Based on these results, a defined medium was developed for the BC production by Acetobacter xylinum KJ-1. When this medium was used under optimal culture conditions, the BC production was 7.2 g/1, which was approximately 3 times higher than that with the traditional HS medium.

• KSBB Journal
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• 제19권6호
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• pp.446-450
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• 2004

수소생산을 증진하기 위하여 탄소원의 농도가 수소생산에 미치는 영향을 조사하였다. 단일당으로 glucose를 이용하였을 때 최적 농도는 $2\%$로서 975.1 mL을 생산하였다. 혼합당을 이용하여 수소생산을 향상시킬 목적으로 그 혼합비를 조사한 결과 glucose와 sucrose의 비가 25 : 75이었을 때 가장 높은 수준을 보였다. 수소를 생산할 때 기질의 발효가 진행됨에 따라 배양액의 pH 저하가 생겨 세포성장에 영향을 주게 된다. 인산염의 첨가로 pH 저하에 따른 완충작용을 하여 생산능이 향상되었음을 확인할 수 있었다. 특히 회분식 배양시에는 배양액의 유출이 없기 때문에 수율을 향상하기 위하여 적절한 농도의 인산염의 첨가가 필수적이다. 미네랄의 영향을 시험하기 위하여 배지에 각종 미네랄원을 첨가하여 그 영향을 조사한 결과 $CuCl_2$와 $NiCl_2$을 제외하고 모두 높은 수소생산성을 나타내었다. 그 중에서도 Ferric citrate와 $Na_{2}MoO_4$에서 더 많은 수소가 생산됨이 확인되었다. 이는 수소생산에 있어 Ferric citrate와 $Na_{2}MoO_4$가 중요한 요소라고 생각된다. 반대로 $CuCl_2$와 $NiCl_2$는 필수적인 물질이 아님을 보여준다. 따라서 이들 Ferric Citrate와 $Na_{2}MoO_4$을 첨가하여 수소생산을 증가시키는 원인으로 앞으로 세밀히 관여한 효소의 생리적 역할에 많은 연구가 필요하다.

• 한국수소및신에너지학회논문집
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• 제19권1호
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• pp.41-48
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• 2008

Fermentative $H_2$ production was studied using microbial consortia isolated from heat-treated ($90{\circ}C$, 20 min) sewage sludge. Important parameters investigated were carbon(C) and nitrogen(N)-sources, C/N ratio, phosphate concentration, pH and temperature during anaerobic cultivation in serum bottles. Starch, ribose, sucrose and glucose were good C-sources for the culture growth and $H_2$ production. Yeast extract was better N-source than $(NH_4)_2SO_4$ or peptone when individually added to the synthetic media, however the combination of above three N-sources exhibited the additional effect for cell growth and $H_2$ evolution. Addition of 100 mM phosphate as a buffering agent prevented the rapid pH drop during the cultivation. The optimum initial pH for the cell growth was at 7.0, whereas $H_2$ production was observed at pH 5.5. Optimum temperature for the cell growth and $H_2$ production was $37{\circ}C$. Initial C/N ratio of 1.22 in the media using glucose and yeast extract as the C- and N-sources, respectively, showed the $H_2$ yield 1.0 mol $H_2$/mol glucose.

• 천문학회지
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• 제37권4호
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• pp.289-294
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• 2004

The main sources of interstellar dust are believed to be dust envelopes around AGB stars. The outflowing envelopes around the long period pulsating variables are very suitable place for massive dust formation. Oxygen-rich silicate dust grains or carbon-rich dust grains form in the envelopes around AGB stars depending on the chemical composition of the stellar surface. The dust grains expelled from AGB stars get mixed up and go through some physical and chemical changes in interstellar medium. There are similarities and differences between interstellar dust and dust grains in AGB stars. The mass cycle in the Galaxy may be best manifested by the fact that the dust grains at various regions have many similarities and understandable differences.

• Journal of Microbiology and Biotechnology
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• 제15권2호
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• pp.337-345
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• 2005

The degradation of phenanthrene, a model PAH compound, by microorganisms either in the mixed culture or individual strain, isolated from oil-contaminated soil in oil refmery vicinity sites, was examined. The effects of pH, temperature, initial concentration of phenanthrene, and the addition of carbon sources on biodegradation potential were also investigated. Results showed that soil samples collected from four oil refinery sites in Korea had different degrees of PAH contamination and different indigenous phenanthrene-degrading microorganisms. The optimal conditions for phenanthrene biodegradation were determined to be 30$^{circ}C$ and pH 7.0. A significantly positive relationship was observed between the microbial growth and the rate of phenanthrene degradation. However, the phenanthrene biodegradation capability of the mixed culture was not related to the degree of PAH contamination in soil. In low phenanthrene concentration, the growth and biodegradation rates of the mixed cultures did not increase over those of the individual strain, especially IC10. High concentration of phenanthrene inhibited the growth of microbial strains and biodegradation of phenanthrene, but was less inhibitory on the mixed culture. Finally, when non-ionic surfactants such as Brij 30 and Brij 35 were present at the level above critical micelle concentrations (CMCs), phenanthrene degradation was completely inhibited and delayed by the addition of Triton X100 and Triton N101.

• 한국대기환경학회지
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• 제23권2호
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• pp.250-260
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• 2007

It was investigated that the emission characteristics of volatile organic compounds (VOCs) from small and medium companies located on industrial complexes in Metropolitan area. The emission characteristics are intermittent sources in which VOCs emissions are highly depends on the working condition. Optimized ventilation system to improve air quality in working area for the three typical companies were installed. Adsorption characteristics of major VOCs such as MEK, IPA, and toluene emitted front the companies were investigated for design of the activated carbon vessel as a VOCs control facility in each company. Concentration of total hydrocarbon and gas amounts needed to ventilation were also used as a design parameter. Mixed adsorbent to improve adsorption characteristics of problematic solvents like IPA and the design guideline of the activated carbon vessel have been suggested.

• 한국대기환경학회지
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• 제29권2호
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• pp.152-162
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• 2013

The physico-chemical characteristics and nanostructure of the aerosol samples from a coal-fired power plant, a charcoal kiln and diesel vehicles were investigated with focusing on black carbon (BC). Aerosols from the coal-fired power plant were mostly comprised of mineral ash spheres which are heterogeneously mixed. The main components of the aerosols from coal-fired power plant were calcium compounds, iron oxide, alumino-silicate without BC. The typical combustion-generated BC which shows the shape of bunch of grapes with 20~50 nm particles which were detected in aerosol particles from diesel vehicles. The nanostructure of each BC particle shows the shape of concentric circles which is comprised of closely-packed graphene layers. Aerosols from charcoal kiln were likely condensed organic carbon generated from the low-temperature combustion process.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.344-350
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• 2010

The improved photocatalytic performance of a carbon/$TiO_2$ composite was studied for the Bisphenol A (BPA) decomposition. Titanium tetraisopropoxide (TTIP) and a rice husk from Korea were heterogeneously mixed as the titanium and carbon sources, respectively, for 3 h at room temperature, and then thermally treated at $600^{\circ}C$ for 1 h in $H_2$ gas. The transmission electron microscopy (TEM) images revealed that the bulk carbon partially covered the $TiO_2$ particles, and the amount that was covered increased with the addition of the rice husk. The acquired carbon/$TiO_2$ composite exhibited an anatase structure and a novel peak at $2{\theta}=32^{\circ}$, which was assigned to bulk carbon. The specific surface area was significantly enhanced to 123~164 $m^2/g$ in the carbon/$TiO_2$ composite, compared to $32.43m^2/g$ for the pure $TiO_2$. The X-ray photoelectron spectroscopy (XPS) results showed that the Ti-O bond was weaker in the carbon/$TiO_2$ composite than in the pure $TiO_2$, resulting in an easier electron transition from the Ti valence band to the conduction band. The carbon/$TiO_2$ composite absorbed over the whole UV-visible range, whereas the absorption band in the pure$TiO_2$ was only observed in the UV range. These results agreed well with an electrostatic force microscopy (EFM) study that showed that the electrons were rapidly transferred to the surface of the carbon/$TiO_2$ composite compared to the pure $TiO_2$. The photocatalytic performance of the BPA removal was optimized at a Ti:C ratio of 9.5:0.5, and this photocatalytic composite completely decomposed 10.0 ppm BPA after 210 min, whereas the pure $TiO_2$ achieved no more than 50% decomposition under any conditions.