• 한국응용과학기술학회지
• /
• 제28권4호
• /
• pp.386-392
• /
• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• 한국자동차공학회논문집
• /
• 제9권6호
• /
• pp.1-7
• /
• 2001

Recently, several LPG engines for heavy-duty vehicles have been developed, which can replace some diesel engines that are one of a main source for air pollution in urban area. As a preliminary study on the liquid phase LPG injection (hereafter LPLI) system applicable to a heavy duty LPG engine, the engine output and combustion performance were investigated with various combustion chambers and fuel compositions using a single cylinder engine equipped. Experimental results revealed that ellipse, double ellipse and nebula type combustion chamber made a more advantage in breaking swirl flow into small turbulence scale than bathtub type. Especially, performance of nebula type showed most highest efficiency and engine output under lean mixture conditions. An investigation fur various LPG fuel compositions was also carried out, and revealed that the case with 40% propane and 60% butane shows the lowest efficiency at stoichiometry, however, as the mixture became leaner its efficiency increased and became even higher for 100% propane case.

• 한국자동차공학회논문집
• /
• 제10권2호
• /
• pp.73-79
• /
• 2002

The NO emissions at the exhaust manifo1d were investigated with a fast NO analyzer to investigate the cycle-by-cycle variations on NO emissions level and the dependence of NO emissions on combustion. The measurement was performed with a part load condition with respect to the mixture ratios and the changes in loads at 1800rpm. The averaged values were obtained during 200 cycles. We found that there is characteristic pattern in 70 emissions from exhaust port and it was possible to set a representative value with the data sampled during specific period. As the load increased, the characteristics of NO emissions were more dependent on combustion pressures. It was also analyzed that the correlation between combustion pressures and NO emissions for different equivalence ratios tends to increase as the mixture goes leaner, Furthermore, this correlation for the lean mixture near the lean limit seemed to be kept.

• 한국자동차공학회논문집
• /
• 제10권5호
• /
• pp.107-113
• /
• 2002

LPG has been well known as a clean alternative fuel for vehicles. Recently, several LPG engines for heavy duty vehicles have been developed, which can replace some diesel engines that are one of the main sources for air pollution in the urban area. Because cylinder bore of heavy duty LPG engine is larger than that of gasoline, the study of knock characteristics of LPG engine are needed. In this study, the knock characteristics were investigated with various engine speed, air excess ratios and LPG fuel compositions. Experimental results indicated that the Knock occurrence probability decreases with increasing engine speed and propane fraction of fuel. The Knock occurrence probability is highest at excess air ratio of 1 and decreases as the mixture strength became leaner.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.393-394
• /
• 2006

Highly compressible Ni-Mo steels are attractive materials for PM due to high sinter density and ease of processing. Extra-fine Ni admixed PM steels have demonstrated improved mechanical properties and rolling contact fatigue resistance due to a more uniform microstructure and increased Ni diffusion during sintering. Sinter densities of single press single sinter XF Ni-Mo steels can approach $7.5\;g/cm^3$ at moderate compaction pressures. Leaner alloys based on extra-fine Ni powder are possible depending on the performance requirements of the PM steel part. Extra-fine Ni steels are particularly attractive for the growing market of high performance PM gears and sprockets.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
• /
• pp.183-188
• /
• 1999

For two engine design parameters; compression ratio and intake swirl ratio, measurement of concentrations of hydrocarbon species has been made as a function of various air-fuel ratio in order to investigate the ozone formation of HC emissions from LPG fuel. Higher compression ratio gave lower SR values due to larger aIkan species and higher BSR values because of larger NMHC generation. Swirl ratio did not affect HC emissions and ozone formation. For ${\lambda}=1.1{\sim}1.2$, higher SR values resulted from the species of aIken which has higher MIRs were highly produced. Leaner mixture showed lower SR values due to the increase of the aIkan which has a lower MIR.

• Journal of Mechanical Science and Technology
• /
• 제17권9호
• /
• pp.1371-1379
• /
• 2003

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• International Journal of Automotive Technology
• /
• 제2권1호
• /
• pp.25-31
• /
• 2001

It is necessary to understand the combustion process and cycle-by-cycle variation in combustion to improve the engine stability and consequently to improve the fuel economy and exhaust emissions. The pressure related parameters instead of mass fraction burned were compared for the effect of initial combustion pressures on the following combustion and the analysis of cycle-by-cycle variation in combustion for two pen injected SI engines. The correlation between IMEP and pressures at referenced crank angles showed almost the same trends for equivalence ratios, but the different mixture preparations indicated different tendency. The dependency of IMEP on pressure at the referenced crank angles increases as the mixture becomes leaner for both engines. The mixture distribution in the combustion chamber was varied with the coolant temperature and intake valve deactivation due to the evaporation of fuel and air motion. The correlation between pressure related parameters were also compared for the coolant temperatures and air motion.

• 태양에너지
• /
• 제12권3호
• /
• pp.21-27
• /
• 1992

본 연구는 아트리움 빌딩에 대한 자연채광의 영향을 모델에 의해서 실험하였다. 이러한 방법에 의하여 아트리움 빌딩에서의 자연채광의 단계를 예측하는 방법은 여러 가지가 있으나, 그러나 지금까지는 선형아트리움 건물에서 실내자연채광의 다양한 영향을 예측하기에는 충분치 못하였다. 본 연구에서는 효율적인 방법의 제시를 위하여 선형아트리움의 자연채광에 대한 환경 평가를 위해 모형을 제작하고, 평가모델에서의 천공상태, 방위, 종횡비, 층의 변화를 주어 전부 80가지의 변화에 대한 모형측정을 하여, 층높이의 변화와 공간비를 사용하여 분석하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.147-149
• /
• 2004

Although most of the people have studied English for a long time, their English conversation capability is low. When we provide them portable conversational-type English learners by the application of computer and information process technology, such portable learners can be used to enhance their English conversation capability by their conventional conversation exercises. The core technology to develop such learner is the development of a voice recognition and synthesis module under an embedded environment. This paper deals with voice recognition and synthesis, prototype of the learner module using a DSP(Digital Signal Processing) chip for voice processing, voice playback function, flash memory file system, PC download function using USB ports, English conversation text function by the use of SMC(Smart Media Card) flash memory, LCD display function, MP3 music listening function, etc. Application areas of the prototype equipped with such various functions are vast, i.e. portable language learners, amusement devices, kids toy, control by voice, security by the use of voice, etc.