• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.44.2-44.2
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• 2004

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.132-136
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• 2003

• 한국도로학회:학술대회논문집
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• 2008.10a
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• pp.119-124
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• 2008

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.127-136
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• 2006

Prediction of diesel particulate filtration is typically made by virtue of modeling of particulate matter(PM) collection. The model is closed with filtration parameters reflecting all small scale phenomena associated with PM trapping, and these parameters are to be traced back by inversely analyzing large-scale empirical data-the pressure drop histories. Included are soot cake permeability, soot cake density, soot density in the porous filter wall, and percolation constant. In the present study, a series of single channel DPF experiment is conducted, pressure histories are inversely analyzed, and the essential filtration parameters are deducted by DPF filtration model formulated with non-linear description of soot cake regression. Sensitivity analyses of model parameters are also made. Results showed that filtration transients are significantly altered by the extent of percolation constant, and the soot density in the porous filter wall is controlling the filtration qualities in deep-bed filtration regime. In addition, effect of soot particle size on filtration quality is distinct in a period of soot cake regime.

• Journal of Environmental Science International
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• v.18 no.7
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• pp.797-802
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• 2009

To control degradation rate of biodegradable poly(lactide)s (PLA), the stereochemical PLAs with different ratios of d-lactide and l-lactide units were synthesized by the ring open polymerization and the their degradation kinetics were measured by a Langmuir film balance. The alkaline (pH=11) degradation of poly(l-lactide) (l-PLA) monolayer showed the faster rate at a surface pressure of 4 mN/m in the ranges from to 0 to 7 mN/m. However, the enzymatic degradation of l-PLA with Proteinase K did not occur until 4 mN/m. Above a constant surface pressure of 4 mN/m, the degradation rate was increased with a constant surface pressure. These behaviors might be attributed to the difference in the contacted area with degradation medium: alkaline ions need small contact area with l-PLA while enzymes require much bigger one to be activated due to different medium sizes. The stereochmical PLA monolayers showed that the alkaline degradation was increased with their optical impurities while the enzymatic one was inversed. These results could be explained by the decrease of crystallinity with the optical impurity and the inactivity of enzyme to d-LA unit.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.974-980
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• 1998

This study is concerned with the production of carbon fiber reinforced carbon(C/C) with polyaromatic mesophase pitch as matrix precursor and with the investigation of friction-wear characteristics in ambient air using a constant speed type of friction tester. The main problem in using the polyaromatic mesophase as the matrix precursor is the high viscosity which may limit the complete impregnation of the fiber preform in the vacuum. To solve these problems two dimensional carbon fiber fabrics were infiltrated with meso-phase pitch in the pitch impregnator. After the impregnation and the heat treatment process. C/C com-posites were characterized by density porosity to monitor the influence of high pressure and temperature. It showed that the bulk density was increased and the apparent porosity and the density increasing rate was reduced as repeating the impregnation the carbonization and the heat treatment. The friction-wear charac-teristics of C/C composites were investigated by measuring the average friction coefficient and the specific wear rate as functions friction speed and friction pressure using a constant speed type of friction tester. C/C composite4s showed the average friction coefficient to be reduced as increasing the friction speed and the friction pressure.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.243-249
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• 2010

The improvement of fuel economy and the reduction of diesel exhaust PM(Particulate Matter) and $NO_X$ have been successfully achieved by supplying diesel engines with emulsified diesel oil. However, combustion analysis of emulsified C-heavy oil is difficult because the combustion characteristics of emulsified C-heavy oil compared to other fuels have a special form. Therefore, these experimental researches have analyzed the combustion characteristics of emulsified C-heavy oil in a chamber with high pressure and temperature. The pressure and the rate of heat releases in a combustion chamber was decreased with increasing the water content and the ignition delay time was increased with increasing the water percent.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.105-108
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• 2005

The radiated noise from the automotive intake system should be predicted at the design stage. To this end, the precise measurement of in-duct acoustic source parameters of the intake system, i.e., the source strength and source impedance, is essential. Most of previous works on the measurement of acoustic source parameters were performed under a fixed engine speed condition. However, the requirement of vehicle manufacturer is the noise radiation pattern as a function of engine speed. In this study, the direct method was employed to measure the source parameters of engine intake system under a fixed engine speed and engine run-up condition. It was noted that the frequency spectra of source impedance hardly changes with varying the engine speed. Thus, it is reasonable to calculate the source strength under the engine run-up condition by assuming that source impedance is invariant with engine speed. Measured and conventional source models, i.e., constant pressure source, constant velocity source, and non-reflective source, were utilized to predict insertion loss and radiated sound pressure level. A reasonable prediction accuracy of radiated sound pressure level spectra from the intake system was given in the test vehicle when using the measured source characteristics which were acquired under the operating condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1608-1614
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• 2000

For the purpose of obtaining fundamental data which is needed to develope combustion system of LPG engine, we made constant volume chamber and analyzed flame propagation characteristics under different intial temperature, initial pressure and equivalence ratio which affect combustion of LPG. We investigated flame propagation speed of each fuel using laser deflection method and compared with the investigated flame propagation speed of each fuel using laser deflection method and compared with the results of image processing of flame. As a result, the maximum flame propagation speed was found at equivalence ratio 1.0 and 1.1 for LPG and gasoline, respectively. In the lean region, we can see that flame propagation speed of LPG surpasses that of gasoline. On the contrary, flame propagation speed of gasoline surpasses LPG in the rich region. As initial temperature and initial pressure were higher, flame propagation speed was faster. And, as equivalence ratio was larger and initial temperature was higher, combustion duration was shorter and maximum combustion pressure was higher.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.