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축소형 액체로켓엔진에서 기체산소/케로신 정상상태 연소 분무의 가시화
최송이(Songyi Choi),신봉철(Bongchul Shin),이건웅(Keonwoong Lee),김도헌(Dohun Kim),구자예(Jaye Koo) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
축소형 액체 로켓 엔진에서 기체산소/케로신, 기체아산화질소/에탄올 추진제 조합의 정상상태 연소의 분무를 관찰하고 비교하였다. 분무의 가시화에는 shadowgraph 기법을 사용하였으며 실험결과를 분석하기 위해 shadowgraph를 후처리하여 밀도구배강도 이미지를 사용하였다. 정상상태 연소압력이 동일한 조건에서 기체산소/케로신 추진제의 액체 제트 표면의 굴곡이 심하고 분사기 팁 근처에서 급격한 밀도구배를 보이는 것이 관찰되었다. 밀도구배강도의 평균 이미지에서 분무 중심 길이를 도출하였으며 더 낮은 운동량 플럭스비 조건에서도 기체산소/케로신의 분무 중심 길이가 더 짧은 것으로 나타났다. The reactive sprays of two propellant combinations ―GOX/Kerosene and GN₂O/Ethanol― were observed and compared with each other. Shadowgraph method was used to visualize the reactive sprays and converted to density gradient magnitude images to analyse the structure of reactive sprays. The gas-liquid interface of GOX/Kerosene spray showed rougher boundary and steeper density gradient near the injector face than the N₂O/Ethanol at the similar combustion chamber pressure. Spray core length was calculated from averaged density gradient magnitude images and it was reveald that spray core length of GOX/Kerosene was shorter than that of GN₂O/Ethanol, although momentum flux ratio of GOX/Kerosene propellant combination was lower.
경기, 강원 지역 농업용수의 미생물학적 특성 및 농업용수 분리 대장균의 항생제 내성
황인준 ( Injun Hwang ),박대수 ( Daesoo Park ),채효빈 ( Hyobeen Chae ),김은선 ( Eunsun Kim ),윤재현 ( Jae-hyun Yoon ),나겐드란라자린감 ( Nagendran Rajalingam ),최송이 ( Songyi Choi ),김세리 ( Se-ri Kim ) 한국환경농학회 2020 한국환경농학회지 Vol.39 No.4
BACKGROUND: Irrigation water is known to be one of the major sources of bacterial contamination in agricultural products. In addition, anti-microbial resistance (AMR) bacteria in food products possess serious threat to humans. This study was aimed at investigating the prevalence of foodborne bacteria in irrigation water and evaluating their anti-microbial susceptibility. METHODS AND RESULTS: Surface water (n = 66 sites) and groundwater (n = 40 sites) samples were collected from the Gyeongi and Gangwon provinces of South Korea during April, July, and October 2019. To evaluate the safety of water, fecal indicators (Escherichia coli) and foodborne pathogens (E. coli O157:H7, Salmonella spp., and Listeria monocytogenes) were examined. E. coli isolates from water were further tested for antimicrobial susceptibility using VITEK2 system. Overall, detection rate of foodborne pathogens in July was highest among three months. The prevalence of pathogenic E. coli (24%), Salmonella (3%), and L. monocytogenes (3%) was higher in surface water, while only one ground water site was contained with pathogenic E. coli (2.5%). Of the 343 E. coli isolates, 22.7% isolates were resistant to one or more antimicrobials (ampicillin (18.7%), trimethoprim-sulfamethoxazole (7.0%), and ciprofloxacin (6.7%)). CONCLUSION: To enhance the safety of agricultural products, it is necessary to frequently monitor the microbial quality of water.