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Yoo H.-S.,Korea Institute of Industrial Technology | Yoo H.-S.,Mokpo National University | Kim Y.-H.,Korea Institute of Industrial Technology | Kim J.-H.,Korea Institute of Industrial Technology | And 4 more authors.
Korean Journal of Materials Research | Year: 2014

In this research, magnesium powder was prepared by gas atomizing. Refinement behaviors of magnesium powder produced under different conditions were investigated using a mechanical milling (attrition milling) process. Analyses were performed to assess the characterization and comparison of milled powder with different steel ball sizes and milling times. The powders were analyzed by field emission scanning electron microscope, apparent density and powder fluidity. The particle morphology of the Mg powders changed from spherical particles of feed metals to irregular oval particles, then plate type particles, with an increasing milling time. Because of the HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, which results in producing plate-type powders. An increase in ball size and the impact energy of the magnesium powder maximizes the effect of refinement. Furthermore, it is possible to improve the apparent density and fluidity according to the smoothness of the surface of the initial powder. © Materials Research Society of Korea.

Oh Y.I.,University of Ulsan | Pyo Y.D.,Korea Institute of Energy Research | Kwon O.B.,Korea Gas Corporation | Beak Y.S.,Korea Gas Corporation | And 2 more authors.
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2012

The experimental test was conducted for a heavy-duty DME bus in JE-05 exhaust gas test mode using a chassis dynamometer, exhaust gas analyzers, and a PM measurement system. The heavy-duty DME bus was not equipped with after-treatment systems such as DOC or DPF. The dynamic behavior, emission characteristics, and fuel economy of the bus were investigated with an 8.0-liter, 6-cylinder conventional diesel engine. The results showed that the dynamic behavior in DME mode was almost the same as in diesel mode. However, there was little difference among the two operation modes for NO x and CO emissions. THC emissions were lower for DME mode than for diesel mode. Also, the amount of PM emissions was remarkably lower than for the diesel mode because DME contains a greater amount of oxygen than diesel. The data showed that CO 2 emissions were almost similar in the two modes but fuel economy (calculated using heating value) was lower for DME mode than for diesel mode. © 2012 The Korean Society of Mechanical Engineers.

Lee S.,Chonbuk National University | Moon N.,Jeonbuk Institute of Automotive Technology | Lee J.,Chonbuk National University
Journal of Mechanical Science and Technology | Year: 2012

A multi-perforated tube indicates the existence of multiple holes in various shapes on the surface of long cylinder-type or rectangular tubes, and the hole installed on the surface is called an orifice as it is relatively small in size, compared with the surface area of the tubes. In this study, flowrate distribution features and changes in discharge angle according to the blockage ratio resulting from the changes in the number of orifices and the thickness of multi-perforated tubes were investigated by means of analysis and experiment, targeting the multi-perforated tubes where rectangular orifices are installed on the both sides of square tubes. In addition, contraction coefficient and flow coefficient between orifices were analytically investigated. The more increase in blockage ratio of multi-perforated tubes, the more uniform flowrate distribution between orifices. The discharge angle becomes more and more perpendicular in the longitudinal direction of multi-perforated tubes as it gets closer to the end of orifices, exhibiting big differences at the entrance if blockage ratio is small. The more increase in the thickness of multi-perforated tubes, the more uniform flowrate distribution between orifices become as contraction coefficient increases. The flow coefficient distribution of orifices using the pressure at the entrance of the orifices of multi-perforated tubes increases in the longitudinal direction of the multi-perforated tubes, exhibiting values ranging from 0. 66 to 0. 68 as to BR = 0. 893 ~ 0. 979. © 2012 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Ko S.C.,Jeonbuk Institute of Automotive Technology | Oh K.C.,Korea Automotive Technology Institute | Seo C.K.,Howon University | Lee C.B.,Korea Automotive Technology Institute
International Journal of Automotive Technology | Year: 2014

Several NOx reduction technologies under development in recent years have now been commercialized, including selective catalytic reduction (SCR) with NH3 or hydrocarbons, and Lean NOx Trap. The aim of the present study is to investigate characteristics on NOx adsorption according to the oxygen concentration, de-NOx performance according to lean/rich injection cycle and toxic intermediates at LNT downstram for lean-burn gasoline engine. Under oxygen of 6%, NOx storage capacity was the highest, showed the highest NOx conversion of 98%. The reason for this phenomena is because the excited oxygen atoms at high oxygen concentration increased oxidizing power of NO. Under low temperature of 205°C, LNT catalyst showed the least NOx conversion of 14% because its activity became lower, while the generation rate of toxic HNCO was highest as CO which is generated during the rich condition, reacts with NOx stored on Ba site. © 2014 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

Kang S.-S.,Jeonju University | Cho S.-K.,Jeonbuk Institute of Automotive Technology
Journal of Mechanical Science and Technology | Year: 2012

The present study was conducted to analyze which the geometry of vents in motorcycle disk brakes affects the surface of the disk. In order to analyze the thermal characteristics of disk brakes, thermal deformation analysis and thermal stress analysis due to heat transfer was carried out through the finite element analysis for ventilated disk and solid disk. By comparing the maximum temperature in the braking process, the ventilated disk showed a lower temperature than the solid disk and effect of temperature increase and decrease, depending on the vent area generated in the flange part of the disk. The thermal deformation in ventilated disk type occurs in all directions by 0. 1162 mm, thermal distribution in the circumferential direction showed large deviation, about 0. 017 mm due to the vents. © 2012 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

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