• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.162-169
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• 2000

This study was carried out to develop a continuously variable-speed transmission(CVT) for agricultural tractor. A full-toroidal CVT mechanism with four discs and six rollers was selected as a device for changing speed ratio continuously. In the step of system layout design, the sizes of roller cylinders and end-load cylinder, which were critical factors for controlling the variator, were designed. Also the control pressure range was designed to limit the contact pressure of variator. In order to make the maximum speed of vehicle as 30km/h, the planetary gear and the six pairs of gears were designed. Also the hydraulic clutch, silent chain, hydraulic manifold and electronic controller were designed. After the design, a prototype with CVT controller was developed and tested. The speed of vehicle was changed continuously to the speed set by driver and the settling time was about 0.52 second at the step-response test (reduction ratio of variator 2.0 to 1.0), which was acceptable as a response time for working with tractor.

• Journal of Powder Materials
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• v.9 no.6
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• pp.422-432
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• 2002

Mechanically driven decomposition of intermetallics during mechanical milling(MM 1 was investigated. This process for Fe-Ce and Fe-Sn system was studied using conventional XRD, DSC, magnetization and alternative current susceptibility measurements. Mechanical alloying and milling form products of the following composition (in sequence of increasing Gecontent): $\alpha$(${\alpha}_1$) bcc solid solution, $\alpha$+$\beta$-phase ($Fe_{2-x}Ge$), $\beta$-phase, $\beta$+FeGe(B20), FeGE(B20), FeGe(B20)+$FeGe_2$,$FeGe_2$,$FeGe_2$+Ge, Ge. Incongruently melting intermetallics $Fe_6Ge_5$ and $Fe_2Ge_3$ decompose under milling. $Fe_6Ge_5$ produces mixture of $\hat{a}$-phase and FeGe(B20), $Fe_2Ge_3$ produces mixture of FeGe(B20) and $FeGe_2$ phases. These facts are in good agreement with the model that implies local melting as a mechanism of new phase for-mation during medchanical alloying. Stability of FeGe(B20) phase, which is also incongruently melting compound, is explained as a result of highest density of this phase in Fe-Ge system. Under mechanical milling (MM) in planetary ball mill, FeSn intermetallic decomposes with formation $Fe_5Sn_3$ and $FeSn_2$ phases, which have the biggest density among the phases of Fe-Sn system. If decomposition degree of FeSn is relatively small(<60%), milled powder shows superparamagnetic behavior at room temperature. For this case, magnetization curves can be fitted by superposition of two Langevin functions. particle sizes for ferromagnetic $Fe_5Sn_3$ phase determined from fitting parameters are in good agreement with crystalline sizes determined from XRD data and remiain approximately chageless during MM. The decomposition of FeSn is attributed to the effects of local temperature and local pressure produced by ball collisions.

• Journal of the Korean earth science society
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• v.35 no.1
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• pp.1-18
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• 2014

The purpose of this study was to analyze the sensitivity of meteorological fields and the variation of concentration of particulate matters (PMs) due to aerosol schemes and dust options within the WRF-Chem model to estimate Asian dusts affected on 29 May 2008 in the Korean peninsula. The anthropogenic emissions within the model were adopted by the $0.5^{\circ}{\pm}0.5^{\circ}$ RETRO of the global emissions, and the photolysis option was by Fast-J photolysis. Also, three scenarios such as the RADM2 chemical mechanism and MADE/SORGAM aerosol, the MOSAIC 8 section aerosol, and the GOCART dust erosion were simulated for calculating Asian dust emissions. As a result, the scenario of the RADM2 chemical mechanism & MADE/SORGAM aerosol depicted higher concentration than the others' in both Asian dusts and the background concentration of PMs. By comparing of the daily mean of PM10 measured at each air quality monitoring site in Seoul with the scenario results, the correlation coefficient was 0.67, and the root mean square error was $44{\mu}gm^{-3}$. In addition, the air temperature, the wind speed, the planetary boundary layer height, and the outgoing long-wave radiation were simulated under conditions of no chemical option with these three scenarios within the WRF or WRF-Chem model. Both the spatial distributions of the PBL height and the wind speed of u component among the meteorological factors were similar to those of the Asia dusts in range of 1,800-3,000 m and $2-16ms^{-1}$, respectively. And, it was shown that both scenarios of the RADM2 chemical mechanism and MADE/SORGAM aerosol and the GOCART dust erosion were interacted on-line between meteorological factors and Asian dusts or aerosols within the model because the outgoing long-wave radiation was changed to lower than the others.