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이선엽,최원빈,김창기,이석환,오세철,이정우 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.1
The effects of intake pressures and EGR rates on the natural gas/diesel dual-fuel combustion under a high load condition (brake power of 100 kW) were evaluated using a 6-L CI engine in this study. Natural gas fraction was fixed as 80 % of total input energy for all the dual-fuel combustion operations and engine rotation speed was set to 1,800 rpm. Intake pressure was varied from 0.15 to 0.21 MPa by controlling the waste gate type turbocharger system. EGR rate was changed mainly by controlling EGR valve opening from fully closing to mid-opening to fully opening, but it was also affected when intake pressures were varied. In addition to these intake mixture parameters, diesel injection timing was adjusted in two cases–early and late injections and all the experimental results were compared to those of the neat diesel combustion cases. The results emphasized that the dual-fuel combustion was more sensitive to overall equivalence ratio determined by intake pressures and EGR rates than the neat diesel combustion because it had flame propagation process of premixed natural gas and air mixture. Thus, during the dual-fuel operations, in-cylinder temperature and brake thermal efficiency were decreased as intake pressure was increased.
튜브 직경에 따른 과냉각 유동 내 단일 기포 응축의 영향
이선엽,Cong-Tu Ha,이재화 한국가시화정보학회 2023 한국가시화정보학회지 Vol.21 No.1
Bubble condensation, which involves the interaction of bubbles within the subcooled liquid flow, plays an important role in the effective control of thermal devices. In this study, numerical simulations are performed using a VOF (Volume of Fluid) model to investigate the effect of tube diameter on bubble condensation. As the tube diameter decreases, condensation bubbles persist for a long time and disappear at a higher position. It is observed that for small tube diameters, the heat transfer coefficients of condensation bubbles, which is a quantitative parameter of condensation rate, are smaller than those for large tube diameters. When the tube diameter is small, the subcooled liquid around the condensing bubble is locally participated in the condensation of the bubble to fill the reduced volume of the bubble due to the generation of a backflow in the narrow space between the bubble and the wall, so that the heat transfer coefficient decreases.
소형 분화류의 포장재 및 포장용기에 대한 소비자의 기호도 조사
이선엽,우현정,이윤석,Lee, Sun Yup,Woo, Hyun Jeong,Lee, Youn Suk 한국포장학회 2017 한국포장학회지 Vol.23 No.1
최근 화훼 산업의 활성화를 위하여 정부 주도의 캠페인, 꽃 문화 확산 운동 등 화훼 소비 증대를 위한 활동들이 꾸준히 진행되고 있다. 절화류 상품은 MA 포장, 기능성 포장 개발 등 다양한 방법을 통하여 상품의 품질 유지를 위한 연구가 진행되고 있으나, 국내 분화류 제품의 경우 품질 개선 및 포장 디자인 등에 대한 연구가 여전히 미비한 실정이다. 또한 소형 분화류의 온라인 마켓 유통량이 점차 증가되고 있음에 따라, 산지에서 소매점, 소비자에게 이르기까지 제품의 품질 유지를 위한 다양한 구조 형태의 포장 개발이 요구되고 있다. 본 조사 연구는 소형 분화류 제품에 대한 소비자의 요구에 적합한 포장을 고려하기 위하여 기존 포장을 개선하는 목적으로 포장 소재 및 형태, 투명도, 편리성, 및 기타 포장 선호도 등에 대한 조사를 실시하였다. 결과로 플라스틱 포장 소재, 분리형 포장, 투명 포장 그리고 상품의 안정성 및 품질 유지를 위한 포장을 선호하는 것으로 파악되었다. 따라서 국내 소비자의 소형 분화류 상품 선호도 조사 연구를 바탕으로 향후 다양한 분화류 제품 및 제품 크기에 따른 상품화 가능성, 가격 변화 요인 등을 고려한 연구가 추가적으로 진행되어야 될 것으로 판단된다. In this study we surveyed the preferences of consumer packaging for mini pot flower plants to improve the flower market application in Korea. The surveys were consisted of the consumers residing in Seoul metropolitan (221), Gyeonsang (70), Jeonla (29), Chungceong (19), Gangwon (7), other provinces (3). A total of 349 eligible respondents (male 173, female 176) were surveyed with a self-administered questionnaire asking on the general characteristics for residents, packaging material, packaging design, type of flower pot, degree of transparency, convenience, consumer's demand for packaging development, a significant point when purchasing the flower pot product. The collected date was analyzed using a chi-square (${\chi}^2$) statistical test in SPSS program. Most residents prefer for mini pot flower plants packed with packaging characteristics of plastic material (56.4%), packaging design of separated type (76.2%), angled type (62.5%), and transparency (48.6%). The other question results showed that major consumer's demand for mini pot flower plants is maintaining the freshness quality and stability structure for them. Transparency of packaging can also affect directly the preferences for purchasing the mini pot flower plants. The packaging structure with a proper shape design may protect the fresh mini pot flower plants from shock or any other damage during distribution. The results of this study help to provide consumer's demand for packaging development and to give the greatest advantages in terms of production and marketability of mini pot flower plants.
이선엽,유솔,이동재,송현선,김보경,윤동민,김성렬 한국생활환경학회 2015 한국생활환경학회지 Vol.22 No.3
Recently, a large number of studies have indicated that exposure to outdoor air pollution, including fine particulate matter (PM2.5), caused serious health risks of lung cancer and cardiovascular diseases. We conducted this study to assess the level of awareness among Korean adults on the characteristics and health risks of PM2.5. We randomly recruited 507 adults aged 20 years or older through a commercially available survey institute. Our questionnaire consisted of five categories, including demographic information, definition of PM2.5, characteristics of PM2.5, health risks of PM2.5, and control policies currently applied in South Korea. Data analyses were conducted using SPSS version21.0. Of the participants, only 10% accurately distinguished the definition of PM2.5 from that of PM10 and 28.8% were aware of the fact that exposure to outdoor particulate matter causes carcinogenic effects. Only 10.5% of all the respondents recognized that reinforced airquality standards were conducted in January 2015. Most of the participants lacked information about the definition of PM2.5 and the potential health risk caused by exposure to PM2.5. Therefore, in this regard, policy makers and public health experts need to improve the public’s awareness and disseminate this information effectively.