• 한국수소및신에너지학회논문집
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• 제8권2호
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• pp.79-90
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• 1997

Extensive work has been done on investigating the inner cell pressure characteristics of sealed type Ni-MH battery in which Zr-Ti-Mn-V-Ni alloy is used as anode. The inner cell pressure of this type Ni-MH battery much more increases with the charge/discharge cycling than that of the other type Ni-MH battery where commercialized $AB_5$ type alloy is used as anode. The increase of inner cell pressure in the sealed type Ni/MH battery using Zr-Ti-Mn-V-Ni alloy system is mainly due to the accumulation of oxygen gas during charge/discharge cycling. The accumulation of oxygen gas arises mainly due to the low rate of oxygen recombination on the MH electrode surface during charge/discharge cycling. The difference of oxygen recombination rate between $AB_5$ type electrode and Zr-Ti-Mn-V-Ni electrode is caused by the difference of electrode reaction surface area resulting from different particle size after their activation and the difference of surface catalytic activity for oxygen recombination reaction, respectively. After EIS analysis, it is identified that the surface catalytic activity affects much more dominantly on the oxygen recombination reaction than the reaction surface area does. In order to suppress the inner cell pressure of Ni-MH battery where Zr-Ti-Mn-V-Ni is used as anode, it is suggested that the surface catalytic activity for oxygen recombination should be improved.

• 한국분말재료학회지
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• 제21권1호
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• pp.34-38
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• 2014

Cu-Ni alloys with unidirectionally aligned pores were prepared by freeze-drying process of CuO-NiO/camphene slurry. Camphene slurries with dispersion stability by the addition of oligomeric polyester were frozen at $-25^{\circ}C$, and pores in the frozen specimens were generated by sublimation of the camphene during drying in air. The green bodies were hydrogen-reduced at $300^{\circ}C$ and sintered at $850^{\circ}C$ for 1 h. X-ray diffraction analysis revealed that CuO-NiO composite powders were completely converted to Cu-Ni alloy without any reaction phases by hydrogen reduction. The sintered samples showed large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The pore size and porosity decreased with increase in CuO-NiO content from 5 to 10 vol%. The change of pore characteristics was explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.

• 한국초지조사료학회지
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• 제13권1호
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• pp.58-65
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• 1993

가을에 파종한 사초용유채(Brassica napus Subsp. oleifera cv. Swiss)의 생육기간 동안의 질소대사와 관련하여 건물수량 및 조단백질의 축적정도를 규명하기 위해. 생육기간중 수량 및 조단백질 함량을 측정하고, 엽내 carbon, nitrogen 및 hydrogen 함량을 비교. 분석하였다. 월동기인 '91년 11월 7일부터 '92년 2월 4일 동안의 생초량 및 건물량의 축적은 매우 적었으며, 엽내 C함량은 건물 1g당 382mg에서 435mg으로 증가하였으나. 질소 및 조단백질 함량은 55mg에서 46mg 및 345mg에서 289mg으로 각각 감소하였다. 월동후 춘계 재생초기(2월 3일부터 3월 30일까지) 동안 생초수량의 점차적인 증가에 따라 엽내 C함량은 일당 37mg의 감소를 보였으나, 월동기 동안 감소 되었던 N함량은 다소 증가를 보였다. 영양생장기(3월 31일)부터 추태기인 4월 16일까지 일당 개체당 생초 및 건물축적량은 각각 5.2g 및 0.5g으로 전 생육기간중 가장 높았는데, 엽내의 C/N 의 정상적인 균형을 유지하며 직선적인 증가를 보였고, 조단백질 함량 역시 지속적인 축적이 있었다. 이 시기 이후 개화최성기('92년 5월 19일)까지 엽내 C, N, H 및 조단백질 함량은 공히 유의적인 감소를 보였는데, 특히 N과 조단백질 함량이 추태기에 비해 각각 45.7% 및 46%의 감소로 뚜렷하였다 이들 결과들은 월동기나 월동 후 초기재생 기간중 식물체내 C/N 균형의 현저한 변화를 가져오며, 춘계 영양생장기에서 추태기 동안(3월 31일부터 4월 16일까지)가장 원활한 물질대사에 따라 엽내의 건물 및 조단백질 축적이 왕성하다는 것을 보여준다. 따라서 예취이용의 적기는 추태기이며 생육기간 중 추비적기는 춘계 영양생장기 이전으로 사료된다.

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.131-135
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• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• 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.

• The Korean Journal of Ecology
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• 제27권2호
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• pp.107-114
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• 2004

Tomato (Lycopersicon esculentum) seedlings exposed to various concentrations of $CdC1_2$ (0∼100 $\mu$M) in the nutrient solution for up to 9 days were analyzed with the seedling growth, $H_2O_2$ production, glutathione levels and activity changes of enzymes related to $H_2O_2$ removal. The growth of seedlings was inhibited with over 50 $\mu$M Cd, whereas the levels of $H_2O_2$ and glutathione were enhanced with Cd exposure level and time. Meanwhile, Cd exposure increased the activities of catalase (CAT) and glutathione reductase (GR) but decreased the activities of dehydroascorbate acid reductase (DHAR) and ascorbate peroxidase (APX) in both leaves and roots. These results suggest that the altered activities of antioxidant enzymes particularly involved in the $H_2O_2$ removal and the subsequent $H_2O$$_2$ accumulation could induce the Cd-induced phytotoxicity.

• Journal of Plant Biotechnology
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• 제6권4호
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• pp.259-264
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• 2004

The present study describes the ameliorating effect of $Ca^{++}\;on\;Cd^{++}$ toxicity on the germination, early growth of mungbean seedlings, nitrogen assimilation enzyme. s-nitrate reductase (NR), nitrite reductase (NIR), anti-oxidant enzymes (POD, CAT and SOD) and on the accumulation of hydrogen peroxide and sulphydryls. $Cd^{++}$ inhibited seed germination and root and shoot length of seedlings. While NR activity was down- regulated, the activities of NIR, POD and SOD were up- regulated with $Cd^{++}$ treatment. $Cd^{++}$ treatment also increased the accumulation of sulphydryls and peroxides, which is reflective of increased thiol rich proteins and oxidative stress. $Ca^{++}$ reversed the toxic effects of $Cd^{++}$ on germination and on early growth of seedlings as well as on the enzyme activities, which were in turn differentially inhibited with a combined treatment with calcium specific chelator EGTA. The results indicate that the external application of $Ca^{++}$ may increase the tolerance capacity of plants to environmental pollutants by both up and down regulating metabolic activities. Abbreviations: $Cd^{++}= cadmium,\;Ca^{++} = calcium$, NR= nitrate reductase, NIR=nitrite reductase, POD = peroxidse, SOD= superoxide dismutase, CAT= catalase, EGTA= ethylene glycol-bis( $\beta-aminoethyl ether$)-N,N,N,N-tetraacetic acid.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.17-24
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• 2005

We experimented on growth in light and production of hydrogen and organic matters in dark fermentation by using C. reinhardtii. In the light, growth rate of C. reinhardtii following $CO_2$ fixation was proportional to consumption rate of nitrogen source. And the starch in cell was accumulated more when the period of culture was lengthened more. But the accumulation rate of starch in cell was decreased when the growth rate of cell become dull. In the dark fermentation, the production volume and production rate of hydrogen were the highest value in the mid exponential state among other states. The utilization efficiency of substrate was better in the early exponential state than other states. In production of organic matters, acetic acid didn't change remarkably and ethanol showed the highest value in early exponential state.

• KSBB Journal
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• 제20권6호
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• pp.464-469
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• 2005

가정쓰레기 매립지 토양에서 분리된 Enterobacter sp. SNU-1453은 Enteric bacteria에 속하는 종(species)으로서 혐기 발효 시 효과적으로 수소를 생산하였다. 이러한 fermentative bacteria는 여러 가지 외부 요인에 의해 다른 metabolism을 나타내어 수소생산량에 영향을 준다. 혐기 발효가 진행됨에 따라 배지의 pH가 급격히 감소하여 미생물 성장과 수소생산에 영향을 미치므로, pH에 따른 metabolism변화를 관찰함으로써 수소생산을 극대화하기 위한 최적 pH 조건을 선정하여 제어할 필요가 있다. 본 연구에서는 수소생산에 대한 pH의 효과 및 pH 제어에 따른 metabolic flux를 분석하였다. 실험 결과 이 분리 균주는 매우 넓은 영역의 pH(4-7.5)에서도 수소를 생산하였으며, pH 7에서 가장 높은 수소생산량을 나타내었다. pH 7로의 제어는 butanediol pathway로부터 수소 생산에 더 유리한 mixed acid fermentation pathway로 metabolic flux를 변화시킴을 알 수 있었다.

• 생태와환경
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• 제34권1호통권93호
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• pp.54-61
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• 2001

저온에서 메탄발생 경로의 변화에 대하여 팔당호 연안대에서 채취한 저질토 슬러리를 배양하여 실험하였다. 저질토 슬러리의 메탄발생속도는 5${\sim}$45$^{\circ}C$ 범위에서 온도가 상승함에 따라서 지수함수적으로 증가하여 45$^{\circ}C$에서 7.4 nmol${\cdot}$g$^{-1}{\cdot}$h$^{-1}$로서 최대에 달한 후 급격히 감소하였다. 배양온도를 고온인 30$^{\circ}C$에서 저온인 15$^{\circ}C$로 감소시키면 메탄발생속도와 수소축적속도가 감소하였고 아세트산은 일시적으로 축적되었다. 배양온도 15$^{\circ}C$와 30$^{\circ}C$에서 클로로포름은 메탄발생을 완전히 억제하였고 메탄발생의 직접적 기질인 수소와 아세트산이 축적되었다. 이 수소와 아세트산의 축적량을 메탄발생량으로 환산하면, 아세트산으로부터의 메탄발생량은 30$^{\circ}C$와 15$^{\circ}C$에서 각각 총메탄발생량의 14%와 75%로 추정되었다. 또한 저온에서 저질토 슬러리에 아세트산을 19 mM 이상으로 첨가하면 메탄발생이 저해되었다. 결국 저온 조건에서는 메탄발생에 대한 아세트산의 상대적 기여도가 증가하고, 고농도의 아세트산에 의하여 메탄과정이 저해되었다. 그러므로 팔당호 연안대 저질토의 유기물 혐기분해에서 아세트산-이용 메탄발생과정은 저온에서 핵심과정이 되고, 고농도의 아세트산에 의한 병목현상이 일어난다고 판단된다.