• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.804-807
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• 2007

The acid gas removal (AGR) system was designed and installed to remove $H_2S$ in coal syngas in the pilot-scale coal gasification system for producing chemicals like Dimethyl Ether(DME). The syngas from the coal gasification at the rate of $100{\sim120$ $Nm^3$/hr included pollutants such as fly ash. $H_2S$, COS, $NH_3$, etc. The designed temperature and pressure of the AGR system are below 50oC and 8 kg/$cm^2$. Fe-chelate was used as an absorbent. $H_2S$ was stably removed below 0.5 ppm in the AGR system when the concentration of $H_2S$ was $150{\sim}450$ ppm. The pH of Fe-chelate solution was also stably maintained between $8{\sim}9$. FeMgO absorbent was also tested to remove $H_2S$ in the lab-scale AGR system and $H_2S$ was also removed below 0.5 ppm in the initial operation.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.32-39
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• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, HCCI's operating range is limited by an excessive rate of pressure rise during combustion and the resulting engine knock in high-load. The purpose of this study was to gain a understanding of the effect of only initial temperature and thermal stratification for reducing the pressure-rise rate in HCCI combustion. And we confirmed characteristics of combustion, knocking and emissions. The engine was fueled with Di-Methyl Ether. The computations were conducted using both a single-zone model and a multi-zone model by CHEMKIN and modified SENKIN.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.1-5
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• 2016

In this paper, High Power Pulsed Amplifier with wide-band characteristic is implemented for L-band Navigational Aid(NAVAID). Due to the characteristics of L-Band NAVAID, implemented SSPA is demanded characteristics of high RF power, high linearity and high efficiency. Therefore, in this paper, efficiency characteristic is improved by modified class F technique. And linearity characteristic is improved by balance structure using hybrid coupler, $2^{nd}$ & $3^{rd}$ harmonic trap and anti-phase technique using non-linear characteristics of drive amplifier. Implemented SSPA shows that bandwidth of 300MHz, RF Output power of 1.5KW and efficiency of 55%.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.2
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• pp.99-115
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• 2020

Since GNSS is easily affected by jamming and/or spoofing, alternative navigation systems can be operated as backup system to prepare for outage of GNSS. Alternative navigation systems are being researched over the world, and a multi-radio integrated navigation system using alternative navigation systems such as KNSS, eLoran, Loran-C, DME, VOR has been researched in Korea. Least Square or Kalman filter can be used to estimate navigation parameters in the navigation system. A large number of measurements of the Kalman filter may lead to heavy computational load. The decentralized Kalman filter and the federated Kalman filter were proposed to handle this problem. In this paper, the decentralized Kalman filter and the federated Kalman filter are designed for the multi-radio integrated navigation system and the performance evaluation result are presented. The decentralized Kalman filter and the federated Kalman filter consists of local filters and a master filter. The navigation parameter is estimated by local filters and master filter compensates navigation parameter from the local filters. Characteristics of three Kalman filters for a linear system and nonlinear system are investigated, and the performance evaluation results of the three Kalman filters for multi-radio integrated navigation system are compared.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.433-436
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• 2007

가스화기술은 화석연료에 의한 기존의 화력발전기술을 대체할 수 있는 차세대 발전기술로 여겨지고 있어 전 세계적으로 기술개발은 물론 상용 플랜트를 앞 다투어 도입 건설 중에 있다. 현재 국내에서도 2014년까지 실증플랜트 완공에 매진을 가하고 있는 실정이다. 가스화기술은 온실가스인 이산화탄소를 동시에 감축하면서 전력뿐만 아니라 수소, DME, 화학원료와 같은 2차 고급 에너지원을 생산할 수 있다는 장점을 가지고 있다. 이 연구에서는 ASPEN plus를 이용하여 다양한 원료 공급에 따른 300 MW급 IGCC 플랜트에 대한 운전 특성을 알아보고자 하였다. 가스화기에 공급되는 원료는 석탄(역청탄), 중질유(납사, 벙커C유) 등으로 구분해 고려하였으며, 가스화 플랜트 해석모델에 대한 성능을 평가하기 위하여 해외에서 운전 중인 상용 IGCC 플랜트에 대한 운전자료와 상대오차로 비교 산출해 검증하였다. 그 다음으로 가스화(gasification)공정, 산가스 제거(acid gas removal)공정, 복합발전 공정(combined cycle)등과 같은 IGCC 플랜트를 구성하고 있는 각각의 단위공정에 대한 운전 특성에 대한 해석결과를 확인하였다. 해석 결과를 바탕으로 가스화기의 냉가스 효율(cold gas efficiency)과 탄소 전환율(carbon conversion), 산가스 제거공정에 대한 이산화탄소 포획 성능과 복합발전에 따른 플랜트 발전량 및 발전 효율(plant net efficiency)을 예측하였다.

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1957-1963
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• 2005

In this study, external condensation heat transfer coefficients (HTCs) of six flammable refrigerants of propylene (RI270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of $39^{\circ}C$ on a 1023 fpm low fin and Turbo-C tubes. All data were taken under the heat flux of $32\~116\;and\;42\~142kW/m^2$ for the low fin and Turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to $30\%$ higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of $7.3\%$. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate.

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.228-233
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• 2016

It is hard to employ the carbon materials or the lithium metal foil for the anode of lithium sulfur batteries because of the poor passivation in ether-based electrolytes and the formation of lithium dendrites, respectively. Herein, we investigated the electrochemical characteristics of lithium sulfur batteries with lithiated silicon anode in the liquid electrolytes based on ether solvents. The silicon anodes were lithiated by direct contact with lithium foil in a 1M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) solution in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) at a volume ratio of 1:1. They were readily lithiated up to ~40% of their theoretical capacity with a 30 min contact time. In particular, the carbon mesh reported in our previous work was employed in order to maximize the performance by capturing the dissolved polysulfide in sulfur cathode. The reversible specific capacity of the lithiated silicon-sulfur batteries with carbon mesh was 1,129 mAh/g during the first cycle, and was maintained at 297 mAh/g even after 50 cycles at 0.2 C, without any problems of poor passivation or lithium dendrite formation.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.1
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• pp.37-45
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• 2015

These days many systems use the gps signal to get their own position. Because it's cheap and accurate and convenient. But, the strength of gps signal is very weak and can be easily interrupted by GPS jamming and GPS spoofing. Normally, fighter can use DME, TACAN, etc to correct their position error when GPS is not working. But, many aircraft which does not have those kinds of hardware need to pay additional cost to get it. In this paper, we propose how to overcome GPS jamming and GPS spoofing by only using data link system. The main purpose of this paper is to make the data link protocol to get an exact position information of own unit at gps error environment.

• Journal of ILASS-Korea
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• v.16 no.3
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• pp.126-133
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• 2011

In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.247-253
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• 2006

In this work, pool boiling heat transfer coefficients (HTCs) of hydrocarbon refrigerants are measured from a horizontal smooth tube of 19.0 mm outside diameter. Tested pure refrigerants are Propylene, Propane, Isobutane, Butane and Dimethylether (DME). The pool temperature was maintained at saturation temperature of $7^{\circ}C$ and heat flux was varied from $10kW/m^2$ to $80kW/m^2$ with an interval of $10kW/m^2$. Wall temperatures were measured directly by thermocouple hole of 0.5 mm out-diameter, 152 mm long and inserting ungrounded sheathed thermocouples from the side of the tube. Tested results show that HTCs of Propane, Propylene are 2.5%, 10.4% higher than those of R22 while those of Butane and Isobutane are 55.2%, 44.3% lower than those of R22 respectively. For pure refrigerants, new correlation can be applied to all of CFCs, HCFCS, HFCs, as well as hydrocarbons was developed. The mean deviation was 4.6%.