• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.15-22
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• 2018

A compressible multiphase flow was investigated using a DIM consisting of seven equations, including the fifth-order MLP and a modified HLLC Riemann solver to achieve a precise interface structure of liquid and gas. The numerical methods were verified by comparing the flow structures of the high-pressure water and low-pressure air in the shock tube. A 2D air-helium shock-bubble interaction at the incident shock wave condition (Mach number 1.22) was numerically solved and verified using the experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4671-4676
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• 2010

This study is intended to understand flame behavior of the pool fire by height of fire source. Liquid fuels were methanol and n-Heptane which are used in many studies of pool fire. Size of vessel was $100mm{\times}100mm{\times}50mm$ and the vessel was made by stainless steel. Combustion time, mass loss rate, flame temperature, flame height and air entrainment rate from the outside to flame were measured, and flame behavior was visualized with video camera. Based on the experiment, it was found that combustion characteristics of pool fire was decreased according to increase of height of fire source because entrainment volume of relative cold air was increased from the outside to flame.

• Prospectives of Industrial Chemistry
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• v.23 no.4
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• pp.1-12
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• 2020

최근 실내 공기질(IAQ; indoor air quality)을 악화시키는 물질 중 하나인 이산화탄소 저감 연구가 다수 진행되고 있다. 현재 이산화탄소를 저감하는 방법에는 흡착법, 흡수법, 막분리법 등이 있다. 그 중 흡수법은 액체 상태의 흡수제를 분사하는 공정 특성상 실내에 적용하기 어렵고 2차 오염물 또는 폐수가 발생할 수 있다. 또한, 막분리법은 이산화탄소 분리를 위한 응집 및 침전과 같은 전처리 과정이 필요하므로 실내 이산화탄소 저감에 적합하지 않다. 반면, 흡착법은 비교적 저렴하고 운영이 간단하여 적용 사례가 증가하였으며, 유동 인구가 많고 환기가 어려운 지하철, 버스 등의 대중교통 차량 내부 및 교실, 사무실, 공공시설에서 배출되는 실내 이산화탄소를 제어할 수 있다는 장점이 있어 가장 적합한 해결책으로 알려져 있다. 흡착 공정에 사용되는 대표적인 흡착제 종류에는 활성탄, 제올라이트, 알루미나 등이 있으며, 이 흡착제들을 개질 및 성형하여 흡착제의 성능 및 기계적 강도를 증진시키는 고도화 연구가 활발히 수행되고 있다. 이처럼 적용 대상 내 설치 및 교체가 용이하도록 하는 흡착제 제조 기술 개발이 필요한 실정이며, 흡착제를 상용화 수준까지 발전시킴으로써 강화된 실내 공기질 규제 기준에 대한 대응 및 삶의 질 향상이 기대된다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.345-357
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• 2011

Recently, as part of diversifying energy sources and earth environmental issues, technology development of new renewable energy using wave energy is actively promoted and commercialized around Europe and Japan etc. In particular, OWC(Oscillating Water Column) wave power generation system using air flow induced by vertical movement of the water surface by waves in an air-chamber within caisson is known as the most efficient wave energy absorption device and therefore, is one of the wave power generation apparatus the closest to commercialization. This study examines air flow velocity, which operates turbine(Wells turbine) directly in oscillating water column type wave power generation structure from two-and three-dimensional numerical experiments and discusses optimal shape of oscillating water column type wave power generation structure by estimating the maximum flow rate of air according to change in shape. The three-dimensional numerical wave flume was applied in interpretation for this study which is the model for the immiscible two-phase flow based on the Navier-Stokes Equation. From this, it turned out that size of optimal shape appears differently according to the incident wave period and air flow is maximized at the period where minimum reflection ratio occurs.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.232-232
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• 2011

DAF는 기존 침전 공정에 비해 뛰어난 정수 품질과 빠른 처리 시간으로 차세대 정수 공정으로 각광 받고 있다. DAF는 기포 생성 방법에 따라 용존 공기 부상법, 분산 공기 부상법, 진공 부상법, 전해 부상법, 미생물학적 부상법 등이 있다. 이 중 가장 많이 쓰이는 방식은 용존 공기 부상법으로, 과포화 상태의 기체와 액체의 혼합액을 압력을 급격히 감소시켜 기포를 발생 시키는 방법이다. 이 방법은 기포의 발생은 많지만 장비의 크기가 거대하고 시설제조 비용이 많이 드는 단점이 있다. 수중에서 발생되는 플라즈마는 그 구조와 메카니즘에 따라 생성되는 버블의 양을 제어할 수 있음을 확인하였다. 모세관 형태의 전극을 이용한 수중 방전은 전원 공급 장치만 있다면 적은 공간으로도 효과적으로 기포를 생성 할 수 있기 때문에, 수중 방전을 이용하여 기포 발생 후 DAF에 적용 가능한지 알아보고자 한다. DAF공정에서 필요한 요인으로는 기포의 크기, 개수, 성분 물질 등이 있는데, 그 중 가장 핵심은 기포의 크기 이다. 그래서 간단한 전원 장치와 리액터 제작 후 방전에 최적화 된 전극으로 기포를 발생시켜 기포의 크기를 측정하였다. 기포의 크기는 전극의 직경과 방전공간의 비율에 따라 제어가 가능함을 확인하였고 평균 기포의 크기는 약 50 ${\mu}m$로서, DAF에 적용 할 수 있는 크기이다. 일반적으로 기포의 사이즈가 작을수록 입자 제거율이 높은데, 실제 DAF공정에서 사용되는 기포의 사이즈는 80 ${\mu}m$정도 이다. 따라서 개발된 기포 발생장치를 DAF 공정에 응용한다면 높은 효율을 가질 것으로 판단된다.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.359-366
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• 2012

Zn-Air energy storage cell is an attractive type of batteries due to its theoretical gravimetric energy density, cost-effective structure and environmental-friendly characteristics. The chargeability is the most critical in various industrial applications such as smart portable device, electric vehicle, and power storage system. Thus, it is necessary to reduce large overpotential of oxygen reduction/evolution reaction, the irreversibility of Zn anode, and carbonation in alkaline electrolyte. In this review, we try to introduce recent studies and developments of bi-functional air cathode, enhanced charge efficiency via modification of Zn anode structure, and blocking side reactions applying hybrid organic-aqueous electrolyte for high power density rechargeable Zn-Air energy storage cells.

• Journal of the Korean Chemical Society
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• v.51 no.6
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• pp.577-584
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• 2007

The purpose of this study is to suggest how to use the phase diagram for water to explain the evaporation and sublimation in the atmospheric condition. In principle, the phase diagram for water represents a one component system so it cannot be applied to the water contact with the air. When the liquid or solid phase of water exists in the air, always water vapor also exists in the air. In this case, we cannot present this state as a single point on the phase diagram because the pressure of the liquid or solid is different from that of the vapor in the air. However, since the saturation vapor pressure of liquid or solid is altered by negligible amount due to the presence of air, the evaporation and sublimation in the atmospheric condition can be explained using the vapor pressure line and sublimation line on the phase diagram.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.79-86
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• 2014

A turbopump real-propellant test facility(TPTF) is to verify the performance of a turbopump unit(TPU) based on liquid oxygen and kerosene. One of the most important sub-facilities is a hot-gas generation system which makes the driving force of the TPU with an alcohol burner. The alcohol burner generates the required flow rates and temperature at the facility using high pressure air and ethanol. In the study, the verification tests of the alcohol burner which was manufactured entirely with domestic technology were performed and fabrication technique and operation skill for the burner could be obtained ahead of the construction of the facility. Two burners will be operated simultaneously for the real-propellant test of 75tf class turbopump and satisfy the power requirement from the turbine of the TPU.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.345-358
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• 2021

This study focuses on the development of the liquid air production process that uses LNG (liquefied natural gas) cold energy which usually wasted during the regasification stage. The liquid air can be transported to the LNG exporter, and it can be utilized as the cold source to replace certain amount of refrigerant for the natural gas liquefaction. Therefore, the condition of the liquid air has to satisfy the available pressure of LNG storage tank. To satisfy pressure constraint of the membrane type LNG tank, proposed process is designed to produce liquid air at 1.3bar. In proposed process, the air is precooled by heat exchange with LNG and subcooled by nitrogen refrigeration cycle. When the amount of transported liquid air is as large as the capacity of the LNG carrier, it could be economical in terms of the transportation cost. In addition, larger liquid air can give more cold energy that can be used in natural gas liquefaction plant. To analyze the effect of the liquid air production amount, under the same LNG supply condition, the proposed process is simulated under 3 different air flow rate: 0.50 kg/s, 0.75 kg/s, 1.00 kg/s, correspond to Case1, Case2, and Case3, respectively. Each case was analyzed thermodynamically and economically. It shows a tendency that the more liquid air production, the more energy demanded per same mass of product as Case3 is 0.18kWh higher than Base case. In consequence the production cost per 1 kg liquid air in Case3 was $0.0172 higher. However, as liquid air production increases, the transportation cost per 1 kg liquid air has reduced by $0.0395. In terms of overall cost, Case 3 confirmed that liquid air can be produced and transported with $0.0223 less per kilogram than Base case.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1978.04a
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• pp.96.3-96
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• 1978

Biotin 요구성 glutamic acid 생산능을 가진 Br-evibacterium sp.의 isoleucine 영양요구성 변이주가 다량의 L-leucine을 생성함을 발견하였다. 본균주에 관한 탄소원, 질소원, 무기염, vitamin, amino acid 등의 영양물질과 온도, 공기주입량, pH등에 관한 실험으로 다음과 같은 결과를 얻었다. 본균주는 탄소원, 질소원으로서 10% glucose와 4% $(NH_4)_2SO_4를$ 공합하여 $30^{\circ}C,$ 88시간 배양시킨 결과, 액중에 21 mg/ml의 L-leucine이 축적되었다. Fe$^{2+}$와 $Mn^{2+}$의 동시첨가는 L-leucine생성에 효과적이었으며 thiamine 역시 L-leucine 생성에 효과적이었다. 30ι jar fermentor 에서 폐당밀을 주원료로 한 실험결과, 폐당밀, $(NH_4)/SO_4,$ $KH_2PO_4,$ $MgSO_4ㆍ7H_2O로$ 구성된 액체배지에서 $30^{\circ}C,$ 36시간 배양시킨 것이, 27mg/ml의 L-leucine이 축적되었으며 이때의 대당수율은 16%이었다.