• Journal of ILASS-Korea
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• v.2 no.1
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• pp.18-28
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• 1997

The present study is mainly aiming at numerically analyzing the combustion and emission characteristics of the diesel spray in a high-pressure environment. Computations are peformed for the peak chamber pressure with range from 4.08 MPa to 162 MPa. Numerical results indicate that the pressure increase in combustion chamber significantly influences the mechanism for droplet dynamics and mixing characteristics, spray penetration autoignition, flame lift-on height and the propagation or fuel vapor and flame. By increasing the ratio or the ambient density to injected liquid density, the fuel-air mixing rates and the burning rates increase and the $NO_x/soot$ emission level decreases.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.15-26
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• 1997

The present study is mainly motivated to numerically simulate the autoignition and combustion process of a diesel spray in RCM and effects of design parameters on combustion and engine performance in the DI diesel engine using EGR. In case of the burning spray in RCM, special emphasis is given to the autoignition process coupled with the fluid mechanics and chemical reaction. Computations are carried out for a wide range of operating condition in terms of temperature, concentration of oxygen and carbon dioxide of the intake gas in the DI diesel engine. Numerical results indicate that the mixing process along the edges of spray jet has a crucial role for autoignition and combustion process. Temperature and concentration of O2 and CO2 of intake gas significantly influence the combustion characteristics and engine performance in the diesel/EGR environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.659-669
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• 1997

The effects of exhaust gas recirculation on diesel engine combustion and soot/NOx emissions are numerically studied. The primary and secondary atomization is modelled using the wave instability breakup model. Autoignition of a diesel spray is modelled using the Shell ignition model. Soot formation is kinetically controlled and soot oxidation is represented by a model which account for surface chemistry. The NOx formation is based on the extended Zeldovich NOx model. Effects of injection timing and concentration of $O_{2}$ and CO$_{2}$ on the pollutant formation and the combustion process are discussed in detail.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.223-230
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• 2006

We have investigated the characteristics of hydrogen (H) plasma treated quantum dot infrared photodetectors (QDIPs). The structure used in this study consists of 3 stacked, self assembled $In_{0.5}Ga_{0.5}As/GaAs$ QD layer separated by GaAs barrier layers that were grown by molecular beam epitaxy. Optical characteristics of QDIPs, such as photoluminescence (PL) spectra and photocurrent spectra, have been studied and compared with each other for the as grown and H plasma treated QDIPs. H plasma treatment, resulted in the splitting of PL peak, which can be attributed to the redistribution of the size of QDs. The activation energies estimated from the temperature dependence of integrated PL intensity for as grown and H plasma treated QDIPs are found to be in good agreement with those determined from corresponding peaks of photocurrent spectra. It is also noted that photocurrent is detected up to 130 K for the H plasma treated QDIP, suggesting the future possibility for the development of infrared photodetectors with high temperature operation.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.39-46
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• 2011

This study investigates the effects of the DME and n-Butane mixture and of the stratification on combustion characteristics of HCCI engine by chemical reaction calculation. First, the existing DME reaction scheme and n-Butane is combined to make new chemical reaction model, then validating the effectiveness of new scheme. Furthermore, this study verify the HCCI combustion characteristics according to the changes of DME and n-Butane mixture ratio, which shows different auto ignition characteristics. Finally, it confirms the effects of stratification of mixture fuel on the reduction of pressure rise rate.

• 대학교육
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• s.145
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• pp.48-55
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• 2007

현재 우리 대학은 입학자원의 급격한 감소와 같은 변화된 환경에 적합한 대학별 특유의 새로운 성장 동력을 찾지 못하고 전략적 혼란을 거듭하고 있다. 최근 많은 대학들이 특성화에 대한 인식을 전에 없이 달리하고 있는 것은 입학자원의 감소로 더이상의 확대전략이 한계에 부딪치고 한정된 입학자원을 두고 치열한 유치경쟁을 벌이는 가운데 교육품질을 제고하지 않고는 경쟁우위를 가질 수 없다는 사실을 현장에서 스스로 인식한 결과이다. 대학의 특성화는 구성원의 자발성과 경쟁, 이를 바탕으로 한 구성원 컨센서스를 추진동력으로, 일관되고 지속적으로 추진하지 않으면 실현 불가능한 시대적 난제임에 틀림없다.

• 프린팅코리아
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• v.11 no.8
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• pp.140-143
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• 2012

일본의 전 산업계는 지난해 발생한 동북대지진의 여파로 2년째 전력 사용감축에 나서고 있다. 자의반 타의반이라는 시선도 있지만, 일본 인쇄업도 정부의 지침에 따른 강제적인 조업시간 단축 및 조정에 나서고 있다. 자발적으로 나선 에너지 사용량 감축은 아니었지만, 조업시간 단축 및 조정의 결과로 비용 절감에 도움이 되고, 나아가 기업의 체질 개선에도 효과가 있는 것으로 나타났다.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.9-16
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• 2001

End-gas temperatures were measured using CARS technique in a conventional DOHC spark- ignition engine fueled with PRF80. The measured pressure data were analyzed using band pass filter method. The measured CARS temperatures were compared with adiabatic core temperatures calculated from measured pressures. Significant heating by pre-flame reaction in the end gas zone was observed in the late part of compression stroke under both knocking and non-knocking conditions. CARS temperatures measured at 10 crank angle degree before knock occurrence was higher than adiabatic core temperatures. These results indicate that there exist some exothermic reactions in low pressure and temperature region. CARS temperatures began to be higher than the adiabatic core temperature when the end-gas temperatures reached look. The temperature elevation due to the pre-flame reaction correlated better with CARS temperature than with cylinder pressure.

• MALSORI
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• v.68
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• pp.17-32
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• 2008

The purpose of the present study is to investigate syntactic development of Korean by analysing the spontaneous speech data. Thirty children(3, 5, and 7-year-old and 10 per each age group) and 10 adults are employed as subjects for this study. Speech data were recorded and transcribed in orthography. Transcribed data are analysed syntactically: sentence(simple vs complex) patterns and clause patterns(4 basic types according to the predicate) etc. The results are as follows: 1) simple sentences show higher frequency for the upper age groups, 2) complex sentences with conjunctive and embedded clauses show higher frequency for the upper age groups.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.143-149
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• 2008

The present study is mainly motivated to investigate the vaporization, auto-ignition and spray combustion processes in DI diesel engine using DME and n-heptane. In order to realistically simulate the dimethyl ether (DME) spray dynamics and vaporization characteristics in high-pressure and high-temperature environment, the high-pressure vaporization model has been utilized. The interaction between chemistry and turbulence is treated by employing the Representative Interaction Flamelet (RIF) model. The detailed chemistry of 336 elementary steps and 78 chemical species is used for the DME/air reaction. Based on numerical results, the detailed discussion has been made for the distinctly different combustion characteristics of DME diesel engine in term of vaporization, ignition delay, pollutant formation, and heat release rate.