• Title/Summary/Keyword: High Pressure Environment

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Characteristics of high-temperature single-crystalline 3C-SiC piezoresistive pressure sensors (고온 단결정 3C-SiC 압저항 압력센서 특성)

  • Thach, Phan Duy;Chung, Gwiy-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.274-274
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    • 2008
  • This paper describes on the fabrication and characteristics of a 3C-SiC (Silicon Carbide) micro pressure sensor for harsh environment applications. The implemented micro pressure sensor used 3C-SiC thin-films heteroepitaxially grown on SOI (Si-on-insulator) structures. This sensor takes advantages of the good mechanical properties of Si as diaphragms fabricated by D-RIE technology and temperature properties of 3C-SiC piezoresistors. The fabricated pressure sensors were tasted at temperature up to $250^{\circ}C$ and indicated a sensitivity of 0.46 mV/V*bar at room temperature and 0.28 mV/V*bar at $250^{\circ}C$. The fabricated 3C-SiC/SOI pressure sensor presents a high-sensitivity and excellent temperature stability.

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An experimental study on the evaporation of paraffin family fuel droplet under high temperature and high pressure (고온 고압기류중을 비행하는 파라핀계 연료액적의 증발에 관한 연구)

  • ;川口修
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.2125-2131
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    • 1991
  • Evaporation rate constant, obtained by in this experimental study, of freely falling liquid fuel droplet on the condition of hot and pressurized environment are converted to critical evaporation constant according to Eq. of Ranz and Marshall. Critical evaporation constant, on constant environment pressuire, actively increase almost linearly with environment temperature increasing, but, on constant temperature, increases more or less with pressure increasing. Multycomponent droplet mixed with the fine fuel having a different of boiling point evaporate in order to boiling point, and each evaporation rate constant of mixed fuel equal to each fuel.

Effects of Key Operating Parameters on the Efficiency of Two Types of PEM Fuel Cell Systems (High-Pressure and Low-Pressure Operating) for Automotive Applications

  • Kim Han-Sang;Lee Dong-Hun;Min Kyoungdoug;Kim Minsoo
    • Journal of Mechanical Science and Technology
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    • v.19 no.4
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    • pp.1018-1026
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    • 2005
  • The proton exchange membrane (PEM) fuel cell system consisting of stack and balance of plant (BOP) was modeled in a MATLAB/Simulink environment. High-pressure operating (compressor type) and low-pressure operating (air blower type) fuel cell systems were con­sidered. The effects of two main operating parameters (humidity and the pressure of the supplied gas) on the power distribution characteristics of BOP and the net system efficiency of the two systems mentioned above were compared and discussed. The simulation determines an optimum condition regarding parameters such as the cathode air pressure and the relative humidity for maximum net system efficiency for the operating fuel cell systems. This study contributes to get a basic insight into the fuel cell stack and BOP component sizing. Further research using muli­object variable optimization packages and the approach developed by this study can effectively contribute to an operating strategy for the practical use of fuel cell systems for vehicles.

The Relationship Between High School Teachers Health Perception and Health Promotion Behavior (고등학교 교사의 건강지각과 건강증진행위의 관계)

  • Kim, Dong-Hwan;Park, Young-Soo
    • The Journal of Korean Society for School & Community Health Education
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    • v.4
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    • pp.21-41
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    • 2003
  • The purposes of this study were to ; first, investigate High School Teachers health promotion behavior types; second, explore the effects High School Teachers perceived benefits and perceived barriers have on their health promotion behavior ; third, suggest a desirable course that will increase teachers health. To this end, this researcher conducted a survey on health promotion behavior, perceived benefits, and perceived barriers to 329 High School teachers working in Goyang-si, Gyonggi-do. The results of the survey are as follows: Health Promotion Behavior A closer look at high school teachers health promotion behavior shows that male teachers, compared with female teachers, more actively promote their health. However, female teachers are more aware of their personal hygiene and disease risks. Older teachers, rather than younger teachers, are more willing to promote their health through better eating habits and more frequent exercise. A comparison between married and single teachers revealed that married teachers promote their health through better eating habits, and single teachers receive less stress and are better at managing their stress. Teachers working in technical high schools are better at managing their stress and personal hygiene than academic high schools teachers. Teachers working after 8 o'clock show better health promotion behavior through proper eating habits, stress management, regular exercise, disease prevention: however, teachers working before 7:30 are poor at managing their stress. Teachers not teaching supplementary lessons and not supervising night self-study are better at managing their stress, exercise schedule, and disease prevention than teachers who are. Perceived Benefits, Perceived Barriers, and Health Promotion Behavior A Comparison between male and female teachers shows that female teachers firmly believe improved eating habits and regular exercises would greatly enhance their health. However, female teachers felt more discomfort in their working environment and in utilizing medical institutes. Teachers in the 20s and 40s perceived health benefits through regular lifestyle and exercise. Teachers with less experience feel more pressure from their work environment. Teachers below their 30s feel more dissatisfaction towards using medical facilities. Teachers working in Technical High Schools are more aware of promoting their health through regular health checkups, exercise, and lifestyle ; however, teachers from Academic High Schools feel more pressure from their work environment. Teachers not performing supplementary lessons and supervising night self-study sessions are more willing to go through regular health checkups than those performing them. Also, teachers with supplementary lessons and night self-study supervisions claimed lack of leisure time, pressure from work environment, and inconvenience in using medical facilities a deterrent to promoting their health behavior. The Relationship between Health Promotion Behavior, Perceived Benefits, and Perceived Barriers The correlation ratio between Health Promotion Behavior and Perceived Benefits shows a positive relationship. The results show that High School teachers believed regular health checkups are necessary in maintaining their health. This research shows that teachers consider the following factors important in the order shown ; regular lifestyle and exercise, prevention of geriatric diseases, improving ones eating habits. In short, teachers who are more aware of the importance of regular health checkups are also more aware of the importance of promoting their health. The correlation ratio between Health Promotion Behavior and Perceived Barriers shows negative relationship. High School Teachers believe that lack of leisure activity, pressure from work environment, familys financial burden, fear of diseases, inconvenience in using medical facilities are a deterrent in promoting their health behavior. In other words, teachers with less leisure time and negative pressures from their work environment were less active in promoting their health behavior. This study shows that High School teachers will be able to promote their health behavior by maintaining regular health checkups, lifestyle, exercise, and preventing geriatric diseases. However, teachers believed that insufficient leisure time and negative pressure from their work environment acted as a deterrent to maintaining their health behavior. Most High School teachers believe they are at present healthy, and they were actively engaged in Preventative Health Promotion. The result of this study demonstrates that External factors have a large impact on teachers, which in turn acts negatively on their Health Promotion Behavior. In order to guarantee teachers health promotion behavior, systematic health checkups and increased leisure time, improvement in their work environment are necessary. Teachers also need to take a more active interest in their health.

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Development of a Low Pressure Auxiliary Fan for Local Large-opening Limestone Mines (대단면국내석회석광산용저풍압국부선풍기개발연구)

  • Lee, Chang Woo;Nguyen, Van Duc
    • Tunnel and Underground Space
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    • v.25 no.6
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    • pp.543-555
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    • 2015
  • At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.

Analysis on Meteorological Factors related to the Distribution of PM10 Concentration in Busan (부산지역 미세먼지 농도 분포에 따른 기상요소 분석)

  • Kim, Min-Kyoung;Jung, Woo-Sik;Lee, Hwa Woon;Do, Woo-Gon;Cho, Jung-Gu;Lee, Kwi-Ok
    • Journal of Environmental Science International
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    • v.22 no.9
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    • pp.1213-1226
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    • 2013
  • $PM_{10}$ concentration is related to the meteorological variables including to local and synoptic meteorology. In this study the $PM_{10}$ concentrations of Busan in 2007~2011 were analyzed and the days of yellow sand or rainfall which is more than 5 mm were excluded. The sections of $PM_{10}$ concentration were divided according to 10-quantiles, quartiles and 90-quantiles. The 90-quantiles of daily $PM_{10}$ concentration were selected as high concentration dates. In the high concentration dates the daily mean averaged cloudness, mean daily surface wind speed, daily mean surface pressure and PBL height were low and diurnal variation of surface pressure and daily maximum surface temperature were high. When the high $PM_{10}$ dates occurred, the west and south wind blew on the ground and the west wind blew strongly on the 850 hPa. So it seemed that long range transboundary air pollutants made effects on the high concentration dates. The cluster analysis using Hysplit model which is the backward trajectory was made on the high concentration dates. As a result, 3 clusters were extracted and on the short range transboundary cluster the daily mean relative humidity and cloudness were high and PBL height was low.

Analysis of Fuel Droplet Vaporization at High-Pressure Environment (고압상태에서의 연료액적의 증발특성 해석)

  • Lee, J.C.;Kim, Y.M.
    • Journal of ILASS-Korea
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    • v.1 no.1
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    • pp.35-43
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    • 1996
  • A vaporization model for single component fuel droplet has been developed for applying to sub- and supercritical conditions. This model can account for transient liquid heat ins and circulation effect inside the droplet, forced and natural convection, Stefan flow effect, real gas effect and ambient gas solubility into the liquid droplet in high-pressure conditions. Thermodynamic and transport properties are calculated as functions of temperature and pressure in both phases. Numerical calculations are carried out for several validation cases with the detailed experimental data. Numerical results confirm that this supercritical vaporization model is applicable to the high-pressure conditions encountered in the combustion processes of diesel engine.

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A Study on the Safety Management of High Pressure Underground Pipeline in Industrial Estate (산업단지 고압매설배관 안전관리 향상방안 연구)

  • Choi, Hyun-Woog;Lee, Dong-Min;Kim, jin-jun
    • Journal of the Korean Institute of Gas
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    • v.22 no.5
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    • pp.100-106
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    • 2018
  • pressure buried pipes in domestic industrial estate have many long-term use pipes, Toxic, flammable, Inflammable, etc. as well as a variety of toxic chemicals are embedded in a complex be buried, A high level of safety management is required as it can damage other pipes installed nearby in the event of accidents such as various external interference. Therefore, in this study, the safety management practices of high-pressure gas distribution and urban gas distribution are utilized to derive efficient safety management methods for high-pressure gas installation piping through in-depth comparative analysis.