• Journal of Microbiology and Biotechnology
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• 제31권6호
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• pp.890-901
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• 2021

The 11α-hydroxylation of canrenone can be catalyzed by Aspergillus ochraceus in bioreactors, where the geometry of the impeller greatly influences the biotransformation. In this study, the effects of the blade number and impeller diameter of a Rushton turbine on the 11α-hydroxylation of canrenone were considered. The results of fermentation experiments using a 50 mm four-blade impeller showed that 3.40% and 11.43% increases in the conversion ratio were achieved by increasing the blade number and impeller diameter, respectively. However, with an impeller diameter of 60 mm, the conversion ratio with a six-blade impeller was 14.42% lower than that with a four-blade impeller. Data from cold model experiments with a large-diameter six-blade impeller indicated that the serious leakage of inclusions and a 22.08% enzyme activity retention led to a low conversion ratio. Numerical simulations suggested that there was good gas distribution and high fluid flow velocity when the fluid was stirred by large-diameter impellers, resulting in a high dissolved oxygen content and good bulk circulation, which positively affected hyphal growth and metabolism. However, a large-diameter six-blade impeller created overly high shear compared to a large-diameter four-blade impeller, thereby decreasing the conversion ratio. The average shear rates of the former and latter cases were 43.25 s^-1 and 35.31 s^-1, respectively. We therefore concluded that appropriate shear should be applied in the 11α-hydroxylation of canrenone. Overall, this study provides basic data for the scaled-up production of 11α-hydroxycanrenone.

• Geomechanics and Engineering
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• 제17권5호
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• pp.485-496
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• 2019

Sealing of leakage in waterfront or water-retaining structures is one of the major issues in geotechnical engineering practices. With demands for biological methods as sustainable ground improvement techniques, bioclogging, defined as the reduction in hydraulic conductivity of soils caused by microbial activities, has been considered as an alternative to the chemical grout techniques for its economic advantages and eco-friendliness of microbial by-products. This study investigated the feasibility of bioaugmentation and biostimulation methods to induce fermentation-based bioclogging effect in coarse sands. In the bioaugmentation experiments, effects of various parameters and conditions, including grain size, pH, and biogenic gas generation, on hydraulic conductivity reduction were examined through a series of column experiments while Leuconostoc mesenteroides, which produce an insoluble biopolymer called dextran, was used as the model bacteria. The column test results demonstrate that the accumulation of bacterial biopolymer can readily reduce the hydraulic conductivity by three-to-four orders of magnitudes or by 99.9-99.99% in well-controlled environments. In the biostimulation experiments, two inoculums of indigenous soil bacteria sampled from waterfront embankments were prepared and their bioclogging efficiency was examined. With one inoculum containing species capable of fermentation and biopolymer production, the hydraulic conductivity reduction by two orders of magnitude was achieved, however, no clogging was found with the other inoculum. This implies that presence of indigenous species capable of biopolymer production and their population, if any, play a key role in causing bioclogging, because of competition with other indigenous bacteria. The presented results provide fundamental insights into the bacterial biopolymer formation mechanism, its effect on soil permeability, and potential of engineering bacterial clogging in subsurface.

• 플랜트 저널
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• 제17권2호
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• pp.32-41
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• 2021

최근 미세먼지 등 대기환경 문제가 국가적 이슈로 급부상 하고있는 추세이며 특히 석탄화력발전소에 대한 강도높은 환경규제치가 적용되고 있는 실정이다. 본 연구는 석탄화력발전소 주요 대기오염 배출물질인 황산화물과 먼지 제거를 위한 탈황설비 성능개선 사례에 대해 소개하고 있으며 현재 운영중인 1,000 MW 발전소의 성능개선을 위한 네가지 Case Study를 수행하고 공사를 하였다. 탈황설비 흡수탑 개조를 통해 액기비를 증대시켰으며 산화공기 유량을 증대시켜 기액 반응을 촉진하였다. 또한 가스가스히터 누설률을 개선하여 최종 탈황설비 효율을 향상시켰다. 기존 설비와 조화를 고려한 성능개선 공사를 통해 2023년부터 적용될 규제치(황산화물 25ppm, 먼지 5mg/Sm³)를 만족할 것으로 예상되며 타 화력발전소에 검토 및 적용하는데 참고될 수 있다고 기대된다.

• 한국정보통신학회논문지
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• 제26권11호
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• pp.1644-1652
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• 2022

체험자의 안전 문제로 실질적인 훈련이 불가능한 안전 훈련의 경우 가상현실이나 증강현실 같은 실감미디어를 이용한 훈련 콘텐츠가 새로운 대안이 되고 있다. 본 논문에서는 실감미디어 기술로 구현되는 안전 훈련 콘텐츠에 적용될 수 있는 연기 모델링 방법을 제안한다. 석유화학 플랜트와 같은 위험 지역에 사고가 발생하면 가스 유출 및 화재 발생으로 인해 시야가 확보되지 않는 상황이 발생한다. 이런 상황을 연출하기 위해서는 연기를 사실적으로 표현하는 것이 중요하다. 제안하는 방법은 석유화학 플랜트와 같이 통로와 장치가 복잡한 배경에 효과적으로 적용할 수 있는 연기 모델 기법이다. 제안하는 방법에서는 장면 렌더링이 완료된 이미지에 대한 포스트 프로세싱 단계에서 볼륨 렌더링을 이용하여 연기를 표현한다. 공장을 배경으로 구현한 결과를 보면 제안하는 방법이 사용자의 움직임에 따른 연기의 변화를 사실적으로 표현하는 것을 볼 수 있다.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• 한국산업융합학회 논문집
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• 제26권3호
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• pp.499-507
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• 2023

The core of the liquefied natural gas (LNG) carrier cargo containment system (CCS) is to store and transport LNG safely under temperatures below -163 degrees Celsius. The secondary barrier of the LNG CCS is adopted to prevent LNG leakage from CCS to the ship's hull structure. Recently, as the size of the LNG CCS increases, various studies have been conducted on the applied temperature and load ranges. The present study investigates the working condition-dependent bonding strength of the PU15 adhesives of the secondary barrier. In addition, the mechanical performance is analyzed at a cryogenic temperature of -170 degrees Celsius, and the failure surface and failure mode are investigated depending on the working condition of the bonded process. Even though the RSB and FSB-based fracture mode was confirmed, the results showed that all the tested scenarios satisfied the minimum requirement of the regulation.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.397-399
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• 2021

사회적으로 1인 가구의 증가와 Home IoT 기술의 발전에 따라 주거 환경의 편의성 개선이 중요시된다. 또한 'COVID-19'에 의한 실내 활동 증가에 따라 1인 가구의 주거 편리성을 위한 제품 개발이 요구되고 있다. 이러한 추세로 그 전보다 현재 주거 환경과 상호작용이 수월해졌으며, 이에 따라 Home IoT 기술 발전의 필요성이 대두되고 있다. 따라서 본 논문은 온도, 습도, 미세먼지와 같이 실내 환경 유지에 필요한 정보를 모니터링하여 사용자와 상호작용 할 수 있도록 하였으며, 가스 누출 및 화재와 같은 안전사고 예방에 필요한 IoT 센서를 탑재하여 증가하는 실내 활동에 안전성을 향상하는 시스템을 제안하였다.

• 한국정보통신학회논문지
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• 제26권11호
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• pp.1706-1712
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• 2022

최근 석유화학 산업단지에서 발생하는 가스누출, 화재 등의 사고로 화학물질에 관한 안전이 더욱 중요시되고 있다. 특히 우리나라의 울산, 여수지역의 산단들은 석유화학 산업에 크게 이바지하고 있어 유익함이 있는 반면에, 화학 누출 사고 등으로 인하여 재해가 발생할 수 있다. 따라서 본 논문에서는 화학 사고 대응을 위해 실외 설비 기준 20[m] 간격으로 센서 노드를 구성하고, TLVs의 8시간 기준(TWA)과 15분 기준(STEL)의 노출 허용농도를 제시하였다. 제안된 시스템은 멀티 홉 통신에서 0.6~0.75[s] 주기로 수집된 데이터를 Python으로 전처리하여 SQL 문을 통해 MySQL 데이터베이스에 저장하였으며, MySQL과 Grafana를 연동하여 저장된 데이터를 5초에 1회씩 갱신하는 실시간 원격 모니터링 시스템을 구현하였다.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2628-2641
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• 2023

Nuclear safety is the lifeline for the development and application of nuclear energy. In severe accidents of pressurized water reactor (PWR), aerosols, as the main carrier of fission products, are suspended in the containment vessel, posing a potential threat of radioactive contamination caused by leakage into the environment. The gas-phase aerosols suspended in the containment will settle onto the wall or sump water through the natural deposition mechanism, thereby reducing atmospheric radioactivity. Aiming at the low accuracy of the aerosol model in the ISAA code, this paper improves the natural deposition model of aerosol in the containment. The aerosol dynamic shape factor was introduced to correct the natural deposition rate of non-spherical aerosols. Moreover, the gravity, Brownian diffusion, thermophoresis and diffusiophoresis deposition models were improved. In addition, ABCOVE, AHMED and LACE experiments were selected to validate and evaluate the improved ISAA code. According to the calculation results, the improved model can more accurately simulate the peak aerosol mass and respond to the influence of the containment pressure and temperature on the natural deposition rate of aerosols. At the same time, it can significantly improve the calculation accuracy of the residual mass of aerosols in the containment. The performance of improved ISAA can meet the requirements for analyzing the natural deposition behavior of aerosol in containment of advanced PWRs in severe accident. In the future, further optimization will be made to address the problems found in the current aerosol model.

• 한국응급구조학회지
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• 제3권1호
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• pp.7-19
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• 1999

Background : We are in the edge of some human made disasters such as hazardous materials and air pollution, for example, the world news reported that the city of Bhopal, India had serious victims related with a leaking out of the chemical materials, Methyl Isocyanate and many people in India were killed by. These situations many people who live in this world are world are worrying about are not others, but just ours and people consider about that kind of the disasters are the possible situation to happen to all the people. Therefore, we performed this basic study to recognize the risk of Methyl Isocyanate leak accident and to prepare local disaster plan with EMS system. Method : Trace 8.0, a simulation software made by the U.S. company Safer System was used as a tool to estimate the diffusion distance, area and its victims at the concentrations of 0.02ppm, 0.2ppm 5ppm respectively for an assumed B-city of 2 hundred thousands population count in which was presumed 500kg Methyl Isocyanate gas to leak out. Results : 1. During 1 hour, maximum diffusion distances of 0.02ppm 0.2ppm and 5ppm were 5.41km, 1.61km and 0.29km respectively on the plume impact. 2. Maximum population counts influenced by Methyl Isocyanate gas at the concentrations of 0.02ppm 0.2ppm and 5ppm were 40838, 4346 and 222 on the plume impact, while those were 138238, 17261 and 1588 on the vulnerability impact, respectively. 3. Therefore, 17261 persons must put on respiratory device and 138283 persons must be evacuated to safety place within 1 hour. Conclusions : Only small amount leak of Methyl Isocyanate may cause tremendous chemical disaster in urban area, so its disaster plan must be prepared with an accident simulation program and Material Safety Data Sheets(MSDS). Especially, nearby emergency center of an industrial complex must have a strong position about preparation of chemical disaster plan and perform a disaster dill of hazardous material accident annually.