• 한국식품영양과학회지
• /
• 제18권3호
• /
• pp.348-355
• /
• 1989

Alkaline protease 생성능이 강한 Aspergillus fumigatus 균주를 토양에서 분리하고, 생성효소를 정제하여 특성을 조사한 결과 최적 pH는 9.0, pH안정성은 $pH\;8.0{\sim}10.0$, 최적온도는 $50^{\circ}C$였으며, $50^{\circ}C$이하의 온도에서 안정하나 그 이상의 온도에서는 급격한 효소 불활성화를 보였고, 금속염 $Mn^{++},\;Cu^{++},\;Ba^{++},\;Mg^{++}$ 등에 의해서 활성이 다소 증대되나 $K^+,\;Fe^{+++},\;Ag^{++},\;Pb^{++},\;Na^+,\;Ca^{++},\;Hg^+,\;Zn^{++}$에 의해 저해를 받았다. 활성저해제인 EDTA, 2,4-DNP, ${\varepsilon}-amino$ caproic acid에는 큰 저해를 받지 않으나, PCMB에 많은 저해를 받는 것으로 미루어 활성 부위가 SH기인 cystein protease로 추정되었다. Km값은 $8.33{\times}10^{-4}mole/{\ell}$, Vmax는 $47.62{\mu}g/min$였으며, casein과 hemoglobin을 trypsin보다 더 잘 분해하고, casein을 hemoglobin보다 잘 분해하였다.

• 한국수소및신에너지학회논문집
• /
• 제23권4호
• /
• pp.412-419
• /
• 2012

Increasing demand for natural gas and higher natural gas prices in the recent decades have led many people to pursue unconventional methods of natural gas production. POSCO-Gwangyang synthetic natural gas (SNG) project was launched in 2010. As the market price of natural gas goes up, the increase of its price gets more sensitive due to the high cost of transportation and liquefaction. This project can make the SNG economically viable. In parallel with this project, KEPCO (Korea Electric Power Corporation) joined in launching the SNG Quality Standard Bureau along with KOGAS (Korea Gas Corporation), POSCO and so on. KEPCO Research Institute is in charge of SNG fueled gas turbine combustion test. In this research, several combustion tests were conducted to find out the effect of hydrogen contents in SNG on gas turbine combustion. The hydrogen in synthetic natural gas did not affect on gas turbine combustion characteristics which are turbine inlet temperature including pattern factor and emission performance. However, flame stable region in ${\Phi}$-Air flow rate map was shifted to the lean condition due to autocatalytic effect of hydrogen.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2181-2185
• /
• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• 설비공학논문집
• /
• 제21권9호
• /
• pp.519-526
• /
• 2009

Environmental control system is adopted to control the thermal load from the avionic equipment in the reconnaissance pod which is mounted under a fighter aircraft, undergoing large and rapid environmental changes with the variations of flight altitude and velocity. In this study, an environmental control system was designed and built by adopting vapor compression cycle using R-124. The cooling performance characteristics of the system were measured varying operating parameters: thermal load in the pod, air mass flow rate through evaporator, condenser inlet air temperature, and air mass flow rate through condenser. The effects of the experimental parameters on the system performance were analyzed based on the experimental results. The problems on the designed system were also analyzed and the solutions were suggested to improve system efficiency and to obtain stable operation.

• 한국건설순환자원학회논문집
• /
• 제6권4호
• /
• pp.236-244
• /
• 2018

본 연구에서는 시멘트 복합재료와 직접 혼합 가능한 액상 무기재료 활용 자기치유 마이크로 캡슐을 제조하고자 하였다. 액상 무기재료의 기초특성을 평가하였으며, 마이크로 캡슐화를 수행하였다. 또한 본 논문의 포커스는 자기치유 마이크로 캡슐의 치유 효과보다는 시멘트 복합재료에 적용하기 위한 품질 및 제조 특성에 대하여 검토하였다. 자기치유 마이크로 캡슐은 상온에서 안정하고 균열 추종성이 큰 액상 무기재료를 캡슐화하였으며, 수득률은 90% 이상으로 나타났다. 자기치유 마이크로 캡슐의 크기는 합성 교반 속도에 따라 크기를 변화할 수 있었으며, 목표 크기에 대하여 70% 이상 확보할 수 있었다. 또한 자기치유 마이크로 캡슐의 막강화를 통하여 10% 이내의 손실량이 발생하는 것으로 나타났으며, 막 강화를 하지 않은 것과 비교하여 50% 저감할 수 있었다.

• 한국농공학회논문집
• /
• 제63권4호
• /
• pp.33-41
• /
• 2021

The emission characteristics and emission factors were determined by measuring the concentration of methane (CH₄) and nitrous oxide (N₂O), the amount of ventilation, etc. in the two fattening rooms which have the same environment in winter. As a result of monitoring, the average concentration of CH₄ and N₂O was 20.7-26.7 ppm and 1.4-1.6 ppm. The average temperature inside the room was measured at 20.0-21.4℃, and the average ventilation was 1345.4-1567.3 m³/h. The daily emission of CH₄ for the first 30 days showed a constant emission of 3.6-8.2 g/d/m²/pig, but thereafter, the emission increased rapidly. The daily emission of N₂O was 0.7-1.3 g/d/m²/pig, showing stable emission during the test period, and relatively insignificant emission compared to the emission of CH₄. After repeated test, it was confirmed that there was no significant difference between the two rooms. As a result, the CH₄ 6. 21 g/d/m²/pig and N₂O 1.02 g/d/m²/pig average emission for each room was derived.

• Journal of Ecology and Environment
• /
• 제46권4호
• /
• pp.282-291
• /
• 2022

Background: The Arctic permafrost stores enormous amount of carbon (C), about one third of global C stocks. However, drastically increasing temperature in the Arctic makes the stable frozen C stock vulnerable to microbial decomposition. The released carbon dioxide from permafrost can cause accelerating C feedback to the atmosphere. Soil organic matter (SOM) composition would be the basic information to project the trajectory of C under rapidly changing climate. However, not many studies on SOM characterization have been done compared to quantification of SOM stocks. Thus, the purpose of our study is to determine soil properties and molecular compositions of SOM in four different Arctic regions. We collected soils in different soil layers from 1) Cambridge Bay, Canada, 2) Council, Alaska, USA, 3) Svalbard, Norway, and 4) Zackenberg, Greenland. The basic soil properties were measured, and the molecular composition of SOM was analyzed through pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Results: The Oi layer of soil in Council, Alaska showed the lowest soil pH and the highest electrical conductivity (EC) and SOM content. All soils in each site showed increasing pH and decreasing SOC and EC values with soil depth. Since the Council site was moist acidic tundra compared to other three dry tundra sites, soil properties were distinct from the others: high SOM and EC, and low pH. Through the py-GC/MS analysis, a total of 117 pyrolysis products were detected from 32 soil samples of four different Arctic soils. The first two-axis of the PCA explained 38% of sample variation. While short- and mid-hydrocarbons were associated with mineral layers, lignins and polysaccharides were linked to organic layers of Alaska and Cambridge Bay soil. Conclusions: We conclude that the py-GC/MS results separated soil samples mainly based on the origin of SOM (plants- or microbially-derived). This molecular characteristics of SOM can play a role of controlling SOM degradation to warming. Thus, it should be further investigated how the SOM molecular characteristics have impacts on SOM dynamics through additional laboratory incubation studies and microbial decomposition measurements in the field.

• 한국수소및신에너지학회논문집
• /
• 제34권5호
• /
• pp.535-548
• /
• 2023

The intermittent nature of renewable energy is a challenge to overcome for safety and stable performance in water electrolysis systems linked to renewable energy. Oxygen removal using the catalyst is suitable for maintaining the oxygen concentration in hydrogen below the explosive level (4%) even in intermittent power supply. Metals such as Pd, Pt, and Ni are expected to be effective materials due to their hydrogen affinity. The oxygen removal performance was compared under high hydrogen concentration conditions by loading on γ-Al₂O₃ with high reactivity and large surface area. The characteristics of the catalyst before and after the reaction were analyzed through X-ray diffraction, transmission electron microscope, H₂-temperature programmed reduction, X-ray photoelectron spectroscope, etc. The Pd catalyst that showed the best performance was able to lower 2% oxygen to less than 5 ppm. Changes in catalyst characteristics after the reaction indicate that oxygen vacancies are related to oxygen removal performance and catalyst deactivation.

• 한국항행학회논문지
• /
• 제28권1호
• /
• pp.116-122
• /
• 2024

본 논문에서는 ILS (instrument landing system) 로컬라이저 전력증폭기의 변조도, 출력, 그리고 위상 변화량 규격의 요구성능을 도출하기 위하여, 시스템의 주요 성능 중에서 course structure와 course width를 연구하였다. Course structure의 편차 규격(± 5 uA)을 만족하기 위한 CSB (carrier with sideband) 증폭기의 변조신호 DDM (difference in depth of modulation) 편차 규격을 ± 1 uA(0.001 DDM)로 규격화하였다. CSB 30 W 전력증폭기를 설계하였고, 변조도 보상회로를 통하여 동작운용 출력범위(45 dBm ~ 35 dBm)에서 SDM (sum in depth of modulation)은 40% ± 0.1%, DDM은 ± 0.0005 DDM의 특성을 얻었다. 그리고 course width와 displacement sensitivity 규격에 대하여 시뮬레이션으로 분석하고, 가장 엄격한 규격인 운용개시 점검시에 적용되는 ± 0.1 ° 변화량을 적용하여, SBO (suppressed with sideband only) 증폭기의 출력변동은 ± 2 mW, 위상은 ± 3 ° 로 규격화하고 특성을 만족하였다. 출력과 온도에 따른 보상회로를 적용하여, 안정적인 변조지수, 출력, 그리고 위상 특성을 얻었다.

• 대한화장품학회지
• /
• 제48권1호
• /
• pp.55-64
• /
• 2022

Cleansing foam이라 불리는 지방산 칼륨 cream soap은 crystal gel 구조로 이루어져 있어 유화계와는 달리 전단응력에 약하며 고온의 보관조건에서 쉽게 분리되는 특성을 보여준다. Crystal gel 구조는 지방산의 종류 및 비율, 중화도, polyol의 종류와 사용량에 따라 크게 영향을 받는다. Crystal gel 구조에 미치는 이들의 영향을 조사하기 위해 water/potassium hydroxide (KOH)/fatty acid ternary system에서 실험을 실시하였다. Differential scanning calorimeter (DSC) 측정 결과 myristic acid (MA) : stearic acid (SA) = 3 : 1 비율에서 공융점(eutectic point)를 갖고 이 혼합비가 가장 안전한 삼성분계(ternary system)를 만든다는 것을 발견했다. 점도 측정과 편광현미경 (POM) 관찰 결과 중화도는 75% 부근이 최적이라고 판단된다. 삼성분계의 melting point (T_m)이 보관온도보다 높을 때, 그리고 crystal phase가 lamellar gel phase로 상 전이가 일어날 때 안정하나 지방산 함량의 증가는 안정성에 거의 영향을 미치지 않는다. 삼성분계에 polyol의 첨가는 T_m을 변화시키고 상전이를 일으키는데 중요한 역할을 한다. 클렌징폼의 구조는 저온 주사전자현미경 (Cryo-SEM), 소각 및 광각 X-선 산란 (SAXS, WAXS) 분석으로 규명하였다. Butylene glycol (BG), propylene glycol (PG), dipropylene glycol (DPG)은 T_m을 낮추어주며 lamellar gel phase 형성을 어렵게 하는 반면 glycerin, PEG-400, sorbitol은 T_m을 상승시키고 lamellar gel phase 형성을 용이하게 하며 안정한 삼성분계를 만든다.