• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.66-72
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• 2002

A premixed charge compression ignition engine is experimentally investigated for the reduction of NOx and smoke emissions from diesel engines. In this study, the premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber and then this pre-mixture is ignited by small amount of diesel fuel directly injected into the cylinder. In the premixed charge compression ignition engine, NOx and smoke concentrations of the exhaust emissions were reduced simultaneously as compared with the conventional diesel engine. But HC emission was increased with the increase of premixed ratio. Also, when EGR system was applied to the PCCI diesel engine, the effect of EGR rate on the combustion characteristics and the exhaust gas emissions was discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.9-14
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• 2002

A homogeneous premixed charge compression ignition engine has been experimentally studied far the reduction exhaust emissions of diesel engines. In this study, the gasoline fuel is injected into the intake manifold to from homogeneous pre-mixture in the combustion chamber and then this pre-mixture is ignited by small amount of diesel fuel directly injected into the cylinder. In the premixed charge compression ignition engine, NOx and smoke concentration of the exhaust emissions were reduced simultaneously as compared with the conventional diesel engine. The combustion characteristics of premixed charged diesel engine such as the power output, the rate of heat release, and the other characteristics are discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.895-904
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• 2011

Stratified charge has been thought as one of the ways to avoid a sharp pressure rise on HCCI combustion. The purpose of this study is to evaluate the potential of stratified charge for reducing PRR on HCCI combustion. The pre-mixture with thermal, mixing and EGR stratifications is charged in Rapid Compression Machine. After that, the pre-mixture is compressed and in that process, in-cylinder gas pressure and temperature are analyzed. Additionally numerical calculation with multi-zones modeling is run to know the potential of stratified charge for reducing PRR.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.49-54
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• 1998

In the catalytic combustor, combustion characteristic and deterioration of catalysts were affected by non-uniformity of pre-mixed gas, Therefore, formation of uniform pre-mixed gas is one of important subjects. In this study, the effect of uniformity and non-uniformity of pre-mixed gas supplied to the catalyst was examined to clarify reaction acceleration and combustion characteristic of the catalytic combustion. It was clarified that static mixer or vaporizer tube length of about 150mm and weak swirl to a combustion air were effictive expedient to make uniform pre-mixed gas. And catalystic inlet temperature needs more than $600^{\circ}C$ with rich pre-mixed gas to active reaction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1220-1226
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• 2001

This study investigates the effects of the pre-strain level on mechanical properties of the solid-phase formed thermoplastic composite. A uniaxial solid-phase forming was performed at the temperature of 125$\^{C}$ and at the constant cross-head speed of 3mm/sec. The composite sheet was formed to various pre-strain levels of 10%, 20%, and 30%. Tension, flexural, and impact tests were carried out to characterize the material properties of a solid-phase formed part. Tensile and flexural strengths decreased with increasing the pre-strain level, while impact strength increased. Various microstructures of the formed part explained the above material behavior.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.1-8
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• 2010

The introduction of mixture heterogeneity has been considered to be one of the ways to avoid knocking, as it reduces the pressure rise rate in HCCI Combustion. The purpose of this research was to investigate the effects of heterogeneity, in particular thermal stratification and fuel strength stratification, on HCCI Combustion fueled with DME and n-Butane. Thermal stratification is formed in the Combustion Chamber of a Rapid Compression Machine with three kinds of pre-mixture, each with different properties. The stratified charge mixture was adiabatically compressed, throughout which cylinder gas pressure and two-dimensional chemiluminescence images were measured and analyzed.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.3 no.1
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• pp.37-47
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• 1995

It is very important to determine the performance and operating envelope of engine for aircraft's flight. The basic performance is provided by manufacturer, but installed engine's operating envelop is only determined by flight test. First, this study was measured cylinder head temperature(CHT), exhaust gas temperature(EGT) and oil temperature. At pre-determined altitude and power rate, these temperatures were measured by change of mixture ratio and mixture ratio condition for economic operation and max. power were found. And secondly, with the measured temperatures, possible positions of mixture lever were determined by flight test for stable flight Chang-91 and Lycoming IO-360-A series four cylinders engine with 200 hp was used for this study.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.1
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• pp.5-10
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• 2008

A flame speed of methane mixture of water vapor and air have been measured to study the process of flame propagation using schlieren photographs. The quantity of water vapor contained were changed 5% and 10% of total mixture, and equivalence ratio of mixture between 0.8 and 1.2 were tested under the ambient temperature 323K and 373K. The results showed that the burning velocity was decreased by increasing the water vapor contents due to the interruption of flame development. And, the reduction rate of burning velocity was smaller by increasing the water contents under the same ambient temperature. The effects of ambient temperature on burning velocity was decreased by increasing the water vapor contents.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.9
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• pp.4115-4121
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• 2015

Background: Colorectal cancer is the second most common cause of cancer death with half a million deaths per year. Incidence and mortality rates have demonstrated notable changes in Asian and African countries during the last few decades. In this study, we first aimed to determine the trend of colorectal cancer mortality rate in each Institute for Health Metrics and Evaluation (IHME) region, and then re-classify them to find more homogenous classes. Materials and Methods: Our study population consisted of 52 countries of Asia and North Africa in six IHME pre-defined regions for both genders and age-standardized groups from 1990 to 2010.We first applied simple growth models for pre-defined IHME regions to estimate the intercepts and slopes of mortality rate trends. Then, we clustered the 52 described countries using the latent growth mixture modeling approach for classifying them based on their colorectal mortality rates over time. Results: Statistical analysis revealed that males and people in high income Asia pacific and East Asia countries were at greater risk of death from colon and rectum cancer. In addition, South Asia region had the lowest rates of mortality due to this cancer. Simple growth modeling showed that majority of IHME regions had decreasing trend in mortality rate of colorectal cancer. However, re-classification these countries based on their mortality trend using the latent growth mixture model resulted in more homogeneous classes according to colorectal mortality trend. Conclusions: In general, our statistical analyses showed that most Asian and North African countries had upward trend in their colorectal cancer mortality. We therefore urge the health policy makers in these countries to evaluate the causes of growing mortality and study the interventional programs of successful countries in managing the consequences of this cancer.

• Korean Journal of Adult Nursing
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• v.20 no.2
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• pp.209-218
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• 2008

Purpose: Regarding the respiratory function of patients with an artificial airway, this study compared the effects between normal saline with chest vibration and normal saline with expectorant mixture, administered before endotracheal suction. Methods: The study was conducted in the ICUs of one university hospital located in Incheon. The experimental group I received normal saline with chest vibration administered before endotracheal suction while the experimental group II received normal saline with expectorant mixture administered before endotracheal suction. For respiratory function, $PaO_2$, $PaCO_2$, and $O_2$ saturation were measured by ABGA at 3 minutes after endotracheal suction for both pre-test and post-test. Results: The two groups were not different significantly regarding $PaO_2$ level and $O_2$ saturation after the treatments, while, the experimental group II had lower $PaCO_2$ level than the experimental group I after the treatments (t = 2.075, p = .042). For experimental group II, post-test score of $PaCO_2$ level was significantly lower than that of the pre-test score (t = 1.842, p = .075). Conclusion: The administration of normal saline with expectorant mixture before endotracheal suction reduced $PaCO_2$ level and improved the respiratory function.