• 한국자동차공학회논문집
• /
• 제15권5호
• /
• pp.24-29
• /
• 2007

This study aims to provide a fundamental data for directly injected hydrogen fuel engines. Spray, ignition and combustion characteristics of hydrogen were studied using constant volume chamber. For spray visualization, hydrogen was vertically injected into a combustion chamber at various condition, for example, injection pressure, ambient pressure. And an argon laser was used for the shadowgraph photography by applying optical method. Also, to investigate heat-release rate and flame propagations, spark was ignited on hydrogen injected at the different time after injection and the duration of injection was also changed. Processes of ignition and combustion were analyzed by heat-release rate calculated by pressure history and were observed by shadowgraph photography The results gave much knowledge of spray, ignition and combustion characteristics of hydrogen.

• 한국분무공학회지
• /
• 제15권2호
• /
• pp.67-73
• /
• 2010

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail direct injection system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors with different electric driving characteristics, including solenoid-driven and piezo-driven type. Namely three common-rail injectors with different electric current wave were investigated in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. As this research results, it was found that pilot injection of common-rail system was effected by rate of injection with different electrical characteristic for injector driving.

• 대한기계학회논문집A
• /
• 제30권6호
• /
• pp.615-621
• /
• 2006

Increased application of optical disks requires more improved dynamic stability of rotating disks. In this study, a new concept of controlling the processing conditions of injection molded disks was developed to improve vibration characteristics. The critical speed, which shows stiffness and dynamic stability of disk, is affected by the residual stress distribution; this varies as functions of distance from the gate and processing condition. The critical speed of disk was calculated with the initial stress taken into consideration, which was determined from injection molding simulation. Choosing melt temperature, mold temperature, filling speed and packing pressure as design parameters, critical speed is maximized with the method of response surface. It is shown that the stability of injection molded disk has been improved for the new condition obtained as a result of the study proposed.

• 한국가시화정보학회지
• /
• 제2권2호
• /
• pp.45-51
• /
• 2004

Initial flame development and propagation were visualized under different fuel injection timings to relate the initial flame development to the engine stability in a port injection SI engine. Experiments were performed in an optical single cylinder engine modified from a production engine and images were captured through the quartz window mounted in the piston by an intensified CCD camera. Stratification state was controlled by varying injection timing. Under each injection condition, the flame images were captured at the pre-set crank angles. These were averaged and processed to characterize the flame. The flame stability was estimated by the weighted average of flame area, luminosity, and standard deviation of flame area. Results show that stratification state according to injection timing did not affect on the direction of flame propagation. The flame development and the initial flame stability are strongly dependent on the stratified conditions and the initial flame stability governs the engine stability and lean misfire limit.

• 한국정보통신학회논문지
• /
• 제9권4호
• /
• pp.811-815
• /
• 2005

We theoretically studied synchronization of chaotic oscillation in semiconductor lasers with chaotic light injection feed-back induced chaotic light generated from a master semiconductor laser was injected into a solitary slave semiconductor laser. The slave laser subsequently exhibited synchronized chaotic output for a wide parameter range with strong injection and frequency detuning within the injection locking scheme. We also analytically examined chaos synchronization based on a linear stability analysis from the view point of synchronization based on a linear stability analysis from the view point of modulation response of injection locked semiconductor lasers to chaotic light signal.

• 한국분무공학회지
• /
• 제15권1호
• /
• pp.25-30
• /
• 2010

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail direct injection system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors with different electric driving characteristics, including solenoid-driven and piezo-driven type. Namely three common-rail injectors with different electric current wave were investigated in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. As this research results, it was found that pilot injection of common-rail system was effected by rate of injection with different electrical characteristic for driving the injector.

• Journal of the Optical Society of Korea
• /
• 제11권4호
• /
• pp.158-161
• /
• 2007

We proposed a novel linearization technique for a DFB LD in the RoF link. The proposed scheme is based on the cross gain modulation(XGM) effect of a reflective semiconductor optical amplifier(RSOA) with light injection. We experimentally demonstrated and evaluated the enhanced CIR performance using the proposed linearization scheme.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2007년도 동계학술발표회 논문집
• /
• pp.209-210
• /
• 2007

• 한국광학회:학술대회논문집
• /
• 한국광학회 2007년도 동계학술발표회 논문집
• /
• pp.28-29
• /
• 2007

• 광학세계
• /
• 통권101호
• /
• pp.43-45
• /
• 2006

근래에 일본을 비롯하여 한국과 대만 등 아시아 여러나라에서 광학소자의 플라스틱화로 흐름이 급속히 진행되고 있는 가운데 광학소자에 생기는 성형불량을 예측하는 기술에 관심이 모아지고 있다. 도레이 주식회사에서는 3차원 유한요소 모델용 시스템을 세계에서 처음 실용화에 성공한 바 있으며, 본 고에서는 이 기술에 대해 소개하고자 한다. 광학소자에 관한 CAE 해석의 역사는 아직 시작단계지만 요구 정밀도는 상당히 높기 때문에 끊임없이 해석기술의 정밀도화에 노력하고 있다. 또 미세 V(브이)홈에 있어서 전사성 평가에 대해서도 요구가 높기 때문에 예측 기술의 확립을 도모하고 있다.