• 한국미생물·생명공학회지
• /
• 제25권1호
• /
• pp.68-74
• /
• 1997

The conversion of D-sorbitol to L-sorbose by Gluconobater suboxydans was analyzed, and continuous production of L-sorbose was carried out in immobilized cell reactors. L-Sorbose production by high densities of resting cells was more effective than by conventional batch fermentations. Sorbitol dehydrogenase, an enzyme converting D-sorbitol to L-sorbose, did not suffer from substrate inhibition, but from product inhibition. When L-sorbose production was carried out with Ca-alginate-immobilized cells, about 60 g/l of L-sorbose was obtained. On the other hand, when the corn steep liquor (CSL) concentration of medium was reduced to 0.08%, 80 g/l of L-sorbose was obtained. Outgrowth inside the immobilized carriers was thought to block the pores of the carriers so that substrate could not easily diffuse through the carriers. Continuous production of L-sorbose was well accomplished in a bubble column reactor, and 6. 5 g/l.h of productivity and 81.2% of yield were obtained at a substrate feeding rate of 0.08h$^{-1}$ under the optimum conditions with carrier volume of 55% and aeration rate of 3 vvm.

• 한국식품영양과학회지
• /
• 제19권5호
• /
• pp.395-402
• /
• 1990

The semicontinuous production of blue pigment from gardenia fruit by immobilized cells of Bacillus subtilis KS-380 which excreted $\beta$-glucosidase was investigated in comparison with free cells, . The blue pigment produced higher productivity under the conditions of aeration of 0.2m$\ell$/min and 2mm diameter of gel beads by using 3.5% sodium alginate. Semicontinuous production by immobilized cell showed the highest productivity with replacement of fresh production medium in every 24hr for fourth fermentation cycle following the conditions of blue pigment productivity.

• Nuclear Engineering and Technology
• /
• 제38권8호
• /
• pp.733-752
• /
• 2006

Severe accidents in PWRs are characterized by a continuously changing geometry of the core due to chemical reactions, melting and mechanical failure of the rods and other structures. These local variations of the porosity and other parameters lead to multi-dimensionnal flows and heat transfers. In this paper, a comprehensive set of multi-dimensionnal models describing heat transfers, thermal-hydraulics and melt relocation in a reactor vessel is presented. Those models are suitable for the core description during a severe accident transient. A series of applications at the reactor scale shows the benefits of using such models.

• Tribology and Lubricants
• /
• 제20권3호
• /
• pp.140-144
• /
• 2004

Water-lubrication ball bearings are required to install in aqueous medium where water is used as coolant or working fluid. However water-lubricated frictional characteristics of stainless steel ball bearing is not will known compared to oil-lubricated frictional characteristics. Furthermore study on friction at high temperature is rare because bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is mostly based on change of failed bearings and parts. Ball bearings and ball screws are used to transmit power in the control rod drive mechanism for an integral reactor and are lubricated with high temperature and high pressure chemically-controlled water. Bearings and power transmitting mechanical elements for a nuclear reactor require high reliability and high performance during estimated lifetime, and their performance should be verified. In this paper, experimental research results of frictional characteristics of water-lubricated ball bearing are reported.

• 한국자원식물학회지
• /
• 제30권6호
• /
• pp.699-706
• /
• 2017

For rapid production of freesia 'Shiny Gold' shoots by using a bioreactor, several culture conditions were investigated. Young shoots (< 1 cm) obtained from freesia corm section in vitro were used as plant materials for this experiment. As a basic experimental environment, 20 young shoots were inoculated into a 5 L balloon type bubble reactor which contained 1 L 1/2 strength MS medium supplemented with 30 g sucrose (3%), and the aeration was 0.1 vvm (vessel volumes per minute). The bioreactors were placed in a growth room with $23^{\circ}C$ temperature, 60% relative humidity and $60{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ light condition (16 h/8 h, day/night). The concentrations of MS media were set with 1/4, 1/2, 1 strength, medium volume 10, 20, 40%, sucrose concentration 3, 6, 9%, and aeration 0.1, 0.2, 0.4 vvm. After 4 weeks of cultivation, the growth indexes including the fresh and dry weight, and plant height were evaluated. At the same time, the consumption, pH, and EC of medium were estimated 4 weeks after incubating. The best results were achieved when 40 young shoots were incubated in a bioreactor in which 1 L of 1/2 strength MS medium supplemented with 6% sucrose was used for the rapid production of freesia shoots. The shoots were 17 cm in plant height and 1.0 g in fresh weight only 4 weeks after incubation which could be a good plant material suitable for corm enlargement in vitro. No correlation was observed between the growth of freesia shoots and the consumption, pH or EC of medium.

• KSBB Journal
• /
• 제20권6호
• /
• pp.431-437
• /
• 2005

1. 고온 CSTR은 비교적 짧은 start-up 기간과 높은 $H_2$ 수율을 나타내었다. $H_2$ 생산속도와 $H_2$ 수율의 안정화를 근거로 판단컨대 start-up 기간은 30일 이내이었으며, 최고 $H_2$ 수율은 2.4 mol $H_2/mol$ glucose이었다. 2. 비교적 긴 HRT와 침전조를 이용한 biomass의 재순환에도 불구하고, 유입 포도당의 농도가 낮아 biomass 농도는 다른 중온 반응기에서 보고된 것에 비해 낮은 편이었다. 3. 운전 초기에 $CH_4$이 발생하였으나 8일 이후부터는 pH를 1.0 이하로 유지하였더니 14일 이후로는 거의 검출되지 않는 것으로 봐서 메탄생성균이 식종균에 남아 있더라도 반응기 운전조건을 통해 $CH_4$ 발생을 억제할 수 있었다. 4. 식종 미생물과 반응기로부터 취한 시료의 DGGE band 패튼이 다른 것으로 보아 고온 CSTR 조건에서 식종된 미생물 군집의 조성이 변화하였음을 알 수 있었다. 5. DGGE 분석결과 초기 43일간의 운전기간 동안에 관찰된 미생물 군집조성은 동적인 변화를 나타내었다. 약 14일부터는 biogas 조성이 거의 일정하였으나 미생물 군집은 동적 변화를 나타내었다. F. gondwanens와 T. Thermoanaerobacterium과 계통발생학적으로 가장 연관이 있는 개체군들이 운전 21일과 41일째에 각각 우점으로 나타났다. 6. 본 연구에서 식종 슬러지를 열처리하는데 사용한 조건은 메탄생성균을 완전히 제거하는데 불충분하다는 것은 운전 초기에 $CH_4$이 biogas에서 검출되었고, 식종 슬러지와 반응기로부터 취한 시료에서 메탄생성균이 가지는 mcrA 유전자가 PCR로 증폭되었으므로 알 수 있었다. 7. 메탄생성균의 주요 목에 특이적인 primers를 사용하여 PCR을 실시한 결과 식종슬러지에 있는 메탄생성균들은 주로 Methanosarcinales와 Methanomicrobiales 목에 속하였으며, $CH_4$이 발생했던 때의 반응기에 있는 메탄생성균들은 주로 Methanobacteriales 목에 해당되는 것으로 나타났다.

• 한국수소및신에너지학회논문집
• /
• 제14권1호
• /
• pp.24-34
• /
• 2003

For gaseous fuel combustion with inherent $CO_2$ capture and low NOx emission, chemical-looping combustion may yield great advantages for the savings of energy to $CO_2$ separation and suppressing the effect on environment, In chemical-looping combustor, fuel is oxidized by metal oxide medium in a reduction reactor. Reduced particles are transported to oxidation reactor and oxidized by air and recycled to reduction reactor. The fuel and the air are never mixed, and the gases from reduction reactor, $CO_2$ and $H_2O$, leave the system as separate stream. The $H_2O$ can be easily separated by condensation and pure $CO_2$ is obtained without any loss of energy for separation. In this study, five oxygen carrier particles such as NiO/bentonite, NiO/YSZ, $(NiO+Fe_2O_3)VYSZ$, $NiO/NiAl_2O_4$, and $Co_{\chi}O_y/CoAl_2O_4$ were examined &om the viewpoints of reaction kinetics, oxygen transfer capacity, and carbon deposition characteristics. Among five oxygen particles, NiO/YSZ particle is superior in reaction rate, oxygen carrier capacity, and carbon deposition to other particles. However, at high temperature ($>900^{\circ}C$), NiO/bentonite particle also shows enough reactivity and oxygen carrier capacity to be applied in a practical system.

• Nuclear Engineering and Technology
• /
• 제52권5호
• /
• pp.897-907
• /
• 2020

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

• 대한토목학회논문집
• /
• 제26권6B호
• /
• pp.683-687
• /
• 2006

본 연구에서는 혐기성 소화에서 aeration이 수소생성에 미치는 영향에 대해 살펴보았다. 혐기성 소화슬러지를 0, 1, 3, 6, 12, 24 시간 동안 aeration 실시 후 glucose(20 g/L)를 기질로 이용하여 batch test를 실시하였다. Aeration 시간이 길어질수록 메탄가스가 감소하고, 수소가스가 증가하였으며, 6시간 동안 aeration을 실시한 반응조에서 가장 높은 수소 생성율(570 ml/L)을 나타내었다. 연속운전의 경우 aerated reactor는 메탄가스의 생성 없이 수소가 지속적으로 발생하였으며, non-aerated reactor의 경우 낮은 pH와 짧은 HRT만으로는 메탄 생성균의 활성을 완전히 저해할 수 없었다. 그러나 미생물관점에서의 보다 명확한 규명을 위해 향후 연구가 추가적으로 진행되어야 하며, 현장 적용성을 고려한 aeration 처리의 최적조건 도출도 이루어져야 할 것이다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2228-2231
• /
• 2007

Water gas shift reactor in fuel processing is an important part that converts carbon monoxide into hydrogen. Fuel processing system for PEMFC usually has two stages of WGS reactors, which are high temperature and low temperature shifter. In this study we prepared noble metal catalysts and compared their performances with that of a commercial iron chromium oxide catalyst. Noble metal catalysts and the commercial catalyst showed quite different temperature dependence of carbon monoxide conversion. The conversion of carbon monoxide at the commercial catalyst was very low at medium temperature(${\sim}300^{\circ}C$) and increased rapidly as temperature increased while the conversion at noble metal catalysts was high in the medium temperature range and decreased as temperature increased, which is thermodynamically expected. Their characteristics agreed well with the literature published, and we are accomplishing further study for improvement of the noble metal catalysts.