• 한국항공우주학회지
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• 제37권4호
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• pp.392-398
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• 2009

노즐의 팽창 조건에 따라 적용할 수 있는 이론적인 추력을 구하고 구해진 추력식을 이용하여 고체 추진기관의 추력을 조절하는 핀틀 추진기관의 설계변수, 즉 압력지수, 최소 작동압력, 대기압, 소화압력이 추력 조절 성능에 미치는 영향을 분석하였다. 분석결과 압력지수가 클수록, 최소 작동압력이 낮을수록, 대기압이 높을수록, 그리고 소화압력이 높을수록 핀틀로 노즐목 면적 크기를 조금만 조절하여도 낮은 연소관 압력 조절 범위에서 충분히 원하는 추력비를 얻을 수 있음을 확인하였다.

• 플랜트 저널
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• 제10권4호
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• pp.24-28
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• 2014

본 연구에서는 150 MW 화력발전소를 기준하여 발전소 건설지역의 최저 대기온도 $-17.1^{\circ}C$부터 최대 대기온도 $36.7^{\circ}C$까지를 $3^{\circ}C$의 일정한 간격으로 구분하여 복수기 압력이 증기터빈의 배압조건을 만족하는 대기온도별 송풍기 수량을 검토하였다. 공랭식 복수기는 대기온도 및 송풍기 운전수량 변화에 따른 냉각공기 순환량에 영향을 받아 운전조건이 변경이 되므로, 대기온도가 복수기 설계기준온도 이상의 경우에는 공랭식 복수기 송풍기의 운전수량을 최대로 해야 하고, 대기온도가 복수기 설계기준온도 미만의 경우에는 증기터빈 배압 운전조건을 만족하는 범위 내에서 송풍기 운전수량을 변화시켜 공랭식 복수기에 가해지는 공기 순환량을 감소시키는 것이 안정적인 발전소 운영을 하는 것임을 확인하였다.

• 한국분무공학회지
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• 제19권1호
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• pp.1-8
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• 2014

Liquefied petroleum gas (LPG) is regarded as an alternative fuel for spark ignition engine due to similar or even higher octane number. In addition, LPG has better fuel characteristics including high vaporization characteristic and low carbon/hydrogen ratio leading to a reduction in carbon dioxide emission. Recently, development of LPG direct injection system started to improve performance of vehicles fuelled with LPG. However, spray characteristics of LPG were not well understood, which is should be known to develop injector for LPG direct injection engines. In this study, effects of operation condition including ambient pressure, temperature, and injection pressure on spray properties of n-butane were evaluated and compared to gasoline in a multi-hole injector. As general characteristics of both fuels, spray penetration becomes smaller with an increase of ambient pressure as well as a reduction in the injection pressure. However, it is found that evaporation of n-butane was faster compared to gasoline under all experimental condition. As a result, spray penetration of n-butane was shorter than that of gasoline. This result was due to higher vapor pressure and lower boiling point of n-butane. On the other hand, spray angle of both fuels do not vary much except under high ambient temperature conditions. Furthermore, spray shape of n-butane spray becomes completely different from that of gasoline at high ambient temperature conditions due to flash boiling of n-butane.

• 한국표면공학회지
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• 제45권5호
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• pp.206-211
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• 2012

Process analysis was carried out during deposition of MgO by inductively coupled plasma assisted reactive magnetron sputtering in Ar and $O_2$ ambient. At the initiation of Mg sputtering with bipolar pulsed dc power in Ar ambient, total pressure showed sharp increase and then slow fall. To analyse partial pressure change, QMS was used in downstream region, where the total pressure was maintained as low as $10^{-5}$ Torr during plasma processing, good for ion source and quadrupole operation. At base pressure, the major impurity was $H_2O$ and the second major impurity was $CO/N_2$ about 10%. During sputtering of Mg in Ar, $H_2$ soared up to 10.7% of Ar and remained as the major impurity during all the later process time. When $O_2$ was mixed with Ar, the partial pressure of Ar decreased in proportion to $O_2$ flow rate and that of $H_2$ dropped down to 2%. It was understood as Mg target surface was oxidized to stop $H_2$ emission by Ar ion sputtering. With ICP turned on, the major impurity $H_2$ was converted into $H_2O$ consuming $O_2$ and C was also oxidized to evolve CO and $CO_2$.

• 세라미스트
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• 제22권1호
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• pp.56-69
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• 2019

Recent advances in low-power sensors and transmitters are driving the search for standalone power sources that utilize unused ambient energy. These energy harvesters can alleviate the issues related to the installation and maintenance of sensors. Particularly piezoelectric energy harvesters, with the ability to convert ambient mechanical energy into useful electricity, have received significant attention due to their high energy density, low cost and operational stability over wide temperature and pressure conditions. In order to maximize the generated electrical power, the natural frequency of the piezoelectric energy harvester should be matched with the dominant frequency of ambient vibrations. However, piezoelectric energy harvesters typically exhibit a narrow bandwidth, thus, it becomes difficult to operate near resonance under broadband ambient vibration conditions. Therefore, the resonating of energy harvesters is critical to generate maximum output power under ambient vibration conditions. For this, energy harvesters should have broadband natural frequency or actively tunable natural frequency with ambient vibrations. Here, we review the most plausible broadband energy harvesting techniques of the multi-resonance, nonlinearity, and self-resonance tuning. The operation mechanisms and recent representative studies of each technique are introduced and the advantages and disadvantages of each method are discussed. In addition, we look into the future research direction for the broadband energy harvester.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.185-188
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• 1999

KSTAR cryostat is a large vacuum vessel that provides the necessary thermal barrier between the ambient temperature test cell and the liquid helium cooled magnets. In this work, the structural analyses for the cryostat under the normal operation condition were performed. As a result, it turns out that the vessel would be safe when it is exposed to normal operation loads, such as system weight, vacuum pressure, and plasma vertical disruption load. And, the preliminary result on the modal analysis is presented.

• 산업경영시스템학회지
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• 제30권1호
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• pp.96-104
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• 2007

Glass melting process is influenced by both control and observation factors, where control factors include quantity and mixing ratio of raw material, the amount of fuel and air in-take. Further observation factors include temperature and pressure at each step of process inside glass melting furnace. Ambient Control is an effective means to eliminate complications from excessive variation among raw materials, or external disturbance from wide fluctuation of environment around equipments. Ambient Control uses both control and observation factors mentioned above. This study suggests an effective Proactive Control System that can enable genuine 4M standardization in glass melting furnace by applying Ambient Control.

• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.384-391
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• 2017

Effects of operating variables on solid circulation rate were measured and discussed using two-interconnected circulating fluidized bed system at ambient temperature and pressure. OCN 706-1100 particles were used as oxygen carrier. The measured solid circulation rates increased as the lower loop seal gas flow rates and the solid height in the fuel reactor increased. Suitable operating conditions to avoid choking of the air reactor were confirmed. Continuous long-term operations of steady-state solid circulation were also demonstrated at two different conditions based on the operating window.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.139-151
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• 2011

The sulfur-iodine (SI) thermochemical water splitting cycle is one of promising hydrogen production methods from water using high-temperature heat generated from a high temperature gas-cooled nuclear reactor (HTGR). The SI cycle consists of three main units, such as Bunsen reaction, HI decomposition, and $H_2SO_4$ decomposition. The feasibility of continuous operation of a series of subunits for $H_2SO_4$ decomposition was investigated with a bench-scale facility working at ambient pressure. It showed stable and reproducible $H_2SO_4$ decomposition by steadily producing $SO_2$ and $O_2$ corresponding to a capacity of 1 mol/h $H_2$ for 24 hrs.

• 대한기계학회논문집B
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• 제32권11호
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• pp.849-855
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• 2008

The paper addresses modeling and analysis of the part load performance of a hybrid fuel cell system integrating a polymer electrolyte membrane fuel cell(PEMFC) and a gas turbine(GT). The system is a pressurized one where the working pressure of the PEMFC is higher than the ambient pressure. In addition to the two major components, the system also includes auxiliary parts such as a steam reformer, a humidifier, and afterburner and so on. Based on design analysis, component off-design models are incorporated in the analysis program and part load operation is simulated. The mode for the part load operation of the PEMFC/GT hybrid system is a variable rotational speed operation. The operating characteristics and variations in the system efficiency and component performance parameters at part load are analyzed.