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장영준(Youngjun Chang),차민석(Minseok Cha),정진성(Jinsung Jung),조시행(SiHaeng Cho) 한국정보보호학회 2008 情報保護學會誌 Vol.18 No.3
2008년으로 컴퓨터 바이러스가 제작된 지 이미 20년이라는 세월을 넘기게 되었다. 이 긴 시간 속에서 컴퓨터 바이러스는 파일 감염을 목적으로 하는 바이러스(Virus)로부터 네트워크를 통한 급속한 확산을 시도하는 웜(Worm) 그리고 데이터 유출과 파괴를 목적으로 하는 트로이목마(Trojan Horse)로 발달해왔다. 최근에는 컴퓨터 사용자의 정보를 무단으로 유출하기 위한 스파이웨어(Spyware)에 이르기까지 다양한 형태로 변화를 이룩해 왔다. 이러한 다양한 형태로의 변화가 진행되는 동안에도 컴퓨터 과학의 발달에 따른 새로운 기술들을 흡수하여 더욱더 정교하고 파괴적인 기능들로 발전을 이루게 되었다. 다양한 형태와 기술적인 발전을 거듭한 악성 코드(Malicious Code)는 컴퓨터 운영체제, 네트워크의 발달로 이룩된 컴퓨터 과학사와 함께 하였다고 볼 수 있다. 악성 코드의 발전은 해가 갈수록 수치적인 면에서는 증가 추세를 이루고 있으며 기술적인 면에서도 더욱더 위험성을 더해 가고 있으며 그 제작 목적 또한 전통적인 기술력 과시에서 금전적인 이익을 취하기 위한 도구로 전락하고 있다. 이렇게 제작 목적의 변질로 인해 악성 코드는 인터넷 공간에서 사이버 범죄를 발생시키는 원인 중 하나로 변모하게 되었다. 본 논문에서는 이러한 발전적인 형태를 띠고 있는 악성 코드에 대해서 최근 동향을 바탕으로 어떠한 악성코드와 스파이 웨어의 형태가 발견되고 있는지 그리고 최근 발견되고 있는 악성코드에서 사용되는 소프트웨어 취약점들을 살펴보고자 한다. 그리고 이러한 악성코드의 형태에 따라 향후 발생할 수 있는 새로운 악성 코드의 위협 형태도 다루어 보고자 한다.
설동일(Dongil Seol),이병화(Byounghwa Lee),장영준(Youngjune Chang),전충환(Chunghwan Jeon) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
It is very important to understand the spray characteristics and fuel injection conditions in direct injection diesel engine because the emission gas compositions from diesel engines are related to spray formation processes. In this study, the characteristics of diesel spray has been studied using a computational fluid dynamics code, STAR-CD. The computational grid generation was carried out using the commercial preprocessor ICEM-CFD. The breakup models used were Reitz & Diwarkar model and standard k-ε turbulence model was applied. In this paper, the spray characteristics such as spray tip penetration and SMD studied at various injection conditions.
입자추적법을 이용한 가솔린 기관의 실린더 내 정상유동 해석
정구섭(Kuseob Chung),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2001 한국 자동차공학회논문집 Vol.9 No.4
Analysis and control of intake charge motion such as swirl and tumble are very important to improve the performance of gasoline engines. In this paper, single frame double exposure PTV(particle tracking velocimetry) is used to investigate intake flow characteristic in a steady flow test rig of gasoline engine with 2-valve and pent-roof combustion chamber. To validate this PTV method, we confirmed reliability of this PTV method using chopper, and coaxial burner experiments. The velocity field of intake flow is measured with the intake valve lift variation. It is shown that maximum flow velocity is increased and tumble flow become stronger than inverse tumble flow as valve lift increase.
김현규(Hyunkyu Kim),전충환(Chunghwan Jeon),장영준(Youngjun Chang) 한국자동차공학회 2001 한국 자동차공학회논문집 Vol.9 No.5
Environmental protection on the ocean has been interested and nowadays the International maritime organization(IMO) has advanced on the prevention of air pollution from ships. This study presents the emission characteristics of 4 stroke propulsion diesel engine in E2 cycle (constant speed) and E3 cycle(propeller curved speed). Also the effects of important operating parameters in terms of intake air pressure and temperature, and maximum combustion pressure arc described on the specific emissions. Emissions measurement and calculation are processed according to IMO technical code.<br/> The results show that NOx emission level in E3 cycle is higher than E2 cycle due to lower engine speed and lower maximum combustion pressure by retarding fuel injection timing. Intake air temperature has strong influence on NOx emission production. And CO, HC emissions are not affected by maximum combustion pressure and intake air pressure and temperature.
정적연소기에서의 메탄-공기 혼합기의 연소특성(3) : 배기배출물
최승환(Seunghwan Choi),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.2
A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the CO₂ concentration is proportional to excess air ratio and overall charge pressure, the O₂ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure, In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially CO₂, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, CO₂ and UHC concentration is reduced but O₂ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and CO₂ concentration show lowest values.
CNG 직접분사식 연소기에서의 열량해석(2) : 비균질급기
최승환(Seunghwan Choi),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.2
A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1. 1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased. Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.
정적연소기에서의 메탄-공기 혼합기의 연소특성(1):균질급기
최승환(Seunghwan Choi),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.3
A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, combustion duration, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Combustion duration. flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of300ms.
이병화(Byounghwa Lee),설동일(Dongil Seol),장영준(Youngjun Chang),전충환(Chunghwan Jeon) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
Diesel engines have been widely used in heavy duty vehicles due to their superior fuel economy and high power density. However, they have a relatively high level of NOx and soot emissions. With the increasingly stringent emission standards the main focus of engine research is to simultaneously reduce the fuel consumption and emission. This paper is applied to three-dimensional simulation of in-cylinder phenomena of a direct injection diesel engine for solving the above problem. Ignition used auto ignition model and diffusion burning is modeled by the eddy dissipation model of Magnussen-Hjertager. The results show temperature, pressure, NOx, Soot, fuel concentration distribution which is diesel engine major parameter
정적연소기에서의 메탄-공기 혼합기의 연소특성(2) : 비균질급기
최승환(Seunghwan Choi),전충환(Chunghwan Jeon),장영준(Youngjune Chang) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.4
A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of inhomogeneous charge methane-air mixture under several parameters. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to beneath 0.05m/s gradually at 3 seconds. Second mixture is accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the burn rate.