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정적연소실내에서의 플라즈마 제트 점화에 대한 연소기간중의 열손실산정
김문헌(Munheon Kim),문경태(Kyungtae Mun),박정서(Jungseo Park),김홍성(Hongsung Kim) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.2
wall was investigated using instantaneous heat flux sensor, schlieren visualization, pressure rise curve. And the heat loss characteristics of plasma jet ignition were compared with conventional spark ignition. In case of plasma jet ignition, the flame kernel moves toward the center of combustion vessel in the initial period of combustion, and the flame surface spread out to the vessel wall. However, in case of conventional spark ignition, the flame surface contact with combustion vessel wall in the initial period of combustion. As a result, heat loss in the combustion duration for conventional spark ignition increase faster than that of plasma jet ignition. And the combustion enhancement rate of plasma jet ignition is higher than that of conventional spark ignition, and it was found that the heat loss rate is inversely proportional to the combustion enhancement rate.<br/>
도시고속도로의 진입연결로 접속부내 선형의 밀도예측모형 구축에 관한 연구
김태곤(Kim Tae Gon),신광식(Shin Kwang Sik),김승길(Kim Seung Gil),김정서(Kim Jeong Seo) 대한토목학회 2006 대한토목학회논문집 D Vol.26 No.1D
이 연구는 도시고속도로의 진입연결로 접속부내 선형의 밀도예측모형 구축에 관한 연구로서 실시간 교통특성분석과 선형의 밀도예측모형 구축 및 검증을 통해 밀도예측모형 구축에 있어서 결정계수(R²)값이 대체적으로 0.7이상으로 나타나 선형회귀모형구축에 상당히 높은 설명력을 보이는 것으로 나타났고, 선형모형검증에 있어서 상관계수(r)값도 대체적으로 0.8 이상으로 상당히 높은 상관성을 보이는 것으로 나타났다. 따라서 향후 선형의 밀도예측모형을 이용하여 도시고속도로의 진입연결로 접속부내 차량의 밀도추정 및 지체분석에 상당히 유효할 것으로 판단된다. This study was to construct the linear density predictive models on the on-ramp junctions in urban freeway. From the analyses of the real-time traffic characteristic data, and the construction and verification of the linear density predictive models, the models showed a considerable explanatory power with the determination coefficients (R²) of over 0.7 between the density and speed data. Also, they showed a considerably high correlativeness with the correlation coefficients (r) of over 0.8 between the calculated density data and the expected ones estimated by the models.
직접분사식 디젤 연소실 벽면에서의 열유속에 미치는 메탄올 혼입의 영향
김영호(Y.H. Kim),오병진(B.J.Oh),방정서(J.S. Park),기학영(H.Y.Kim),김문헌(M.H.Kim),이종태(J.T.Lee) 한국자동차공학회 1993 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The effect of methanol fumigation on heat flux in combustion chamber wall of direct injection diesel engine have been investigated. The instantaneous surface temperature and heat flux of combustion chamber wall are decreased according to<br/> increase methanol fumigation. Maximum heat flux at methanol<br/> volume ratio 30% decrease 2.3 MW /㎡ and maximum heat flux reduction rate decrease 39% than that of diesel engine.<br/>
정서현(Seo-hyun Jeong),이성주(Sung-ju Lee),정용화(Youngwha Chung),김상춘(Sang-chun Kim),민병기(Byoung-ki Min) 한국정보보호학회 2011 정보보호학회논문지 Vol.21 No.3
모바일 응용에서 MPEG 비디오 스트림 등 대용량 데이터의 이용이 증가함에 따라, 전송되는 대용량 데이터의 정보보호가 중요한 문제로 부각되고 있다. 대용량 데이터의 효과적인 보호를 위한 부분 암호화 방법으로 SECMPEG이 존재한다. 그러나 SECMPEG의 보안 레벨 3은 B- 나 P-프레임에 비해 상대적으로 용량이 큰 I-프레임을 모두 암호화하기 때문에, 모바일 응용에 적용하기에는 암호화 오버헤드가 크다는 문제가 있다. 그러므로 MPEG2 표준의 압축 특성을 분석하여 I-프레임에서의 부분 암호화를 효과적으로 적용할 필요가 있다. 본 논문에서는 수신단에서 I-프레임 내의 에러 전파 특성을 이용하는, 슬라이스 레벨에서의 부분 암호화 방법을 제안한다. 실험 결과를 통하여 SECMPEG 보안 레벨 3과 비교하여 제안 방법은 보안 성능의 저하없이 수행 시간을 약 30배 이상 단축함을 확인하였다. According to increased multimedia data(i.e., MPEG video stream) in mobile application, protecting data becomes an important problem in the multimedia data delivery. SECMPEG is a selective encryption approach for protecting multimedia data. However, the computational overhead of SECMPEG's security level 3 is quite large because it encrypts the whole I-frames whose size is relatively larger than P/B-frames. Therefore, we need to analyze the characteristics of MPEG2 standard and derive an effective encryption of the I-frames. In this paper, we propose a slice-level, selective encryption approach by using the error-propagation characteristics of I-frames by a receiver. Our experimental results show that the proposed approach can reduce the execution time of SECMPEG's security level 3 by a factor of 30 without degradation of the security.
플라즈마 제트 플러그의 형상이 정적연소기내 연소특성에 미치는 영향
김문헌,유호선,오병진,박정서,Kim, Munheon,Yoo, Hoseon,Oh, Byungjin,Park, Jungseo 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5
This paper presents combustion characteristics of LPG-air mixture ignited by the plasma jet in a cylindrical vessel with constant volume, in which our focus is placed on the multi-hole plug configuration. Four types of the plug configuration depending on the number of orifice and the arranged angle are considered, along with two cases of conventional spark ignition for comparison. Not only the flame propagation is photographed at intervals, but the pressure in the combustion chamber is also recorded through the entire combustion process. The results show that the plasma jet ignition enhances the overall combustion rate remarkably in comparison to the spark ignition by generating irregular flame front and penetrating through the unburned mixture. The combustion enhancement rate agrees favorably with the available data, which supports the validity of our experiment. Synthetically estimating, the two-hole sixty-degree plug appears to be the most desirable, in that the maximum pressure as well as the combustion duration is less affected by the sub-energy level than the others. It is also deduced that there may exist an optimal plug configuration capable of rapid combustion for a specific combustion chamber.
박정서(J.S.Park),오병진(B.J.OH),김문헌(M.H.Kim) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_2
The investigation regarding the ignition mechanism of a plasma jet ignition was explored by using a constant volume vessel. The purpose of this study is to elucidate relation between the characteristics of plasma jet proftles (length and width) and the configuration of plasma jet plug, when sub energy were supplied.<br/> From the result of the visualization, the plasma jet profiles are dependent of the configuration of plasma jet plug shape, sub-energy, surrounding pressure. As increasing of sub-energy and electrode diameter at constant surrounding pressure, plasma jet length is increased. And also increasing of surrounding pressure and cavity depth at constant sub-energy, plasma jet length is increased.<br/> It is important design factors of which cavity depth, orifice and electrode diameter and sub-energy in order to optimum design of plasma jet profiles.<br/>
층류유동장에서의 LPG-공기 혼합기에 대한 플라즈마 제트 점화의 연소특성
박정서(J. S. Park),오병진(B. J. Oh),김문헌(M. H. Kim) 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.1
Experimental investigation of the effects of a plasma jet ignition on LPG-air mixture was executed in laminar flow field. Plasma jet ejection forms highly turbulent ignition surface in the initial stage of combustion. And by the plasma jet ejection into the center of combustion chamber, flame fronts have spherical shape as central ignition type. From the result of the visualization, it shows that the plasma jet ignition causes faster bum than conventional spark ignition. And also the lean limits are extended, the combustion enhancement effects of plasma jet ignition are shown compared to conventional spark ignition. But in case of the lean fuel-air equivalence ratio ø=0.6, the initial flame is separated from the plasma jet plug, therefore extensibility of lean limit will be restricted by this phenomenon in real engine combustion chamber with turbulent motion.<br/>