• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1309-1315
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• 2014

The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder, the articulation angle, the length between two centers of a fixed girder at its ends, and the number of girders. On the basis of the effects of the considered design variables, we establish an optimized design of a switch with improved safety.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.25-33
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• 1997

To investigate the effects of cow manure compost(CMC) on soil and water environment as non-point source, the elution patterns of anions were determined in muti-layered soil columns which were consisted of one top and one bottom in combination. The top soil columns were uniformly packed with Ap horizon soils amended with air-dried CMC at different ratios(0, 2, 4, 6%, wt/wt), the bottom ones were packed with of B horizon soils of 15, 30, and 45cm in length. After saturating the each soil column, the leachate were collected from the bottom of the column while the double-ionized water was applied from the surface of the column by constant head method. From the hydraulic conductivity and anion eluted were measured in the leachate. Each saturated hydraulic conductivities for top and the bottom soils were 3$\times$$10^{-4}$sec and 1.6$\times$$10^{-3}$cm/sec. Most of water soluble chloride and sulfate, having non-specific adsorption characteristics onto the soil particles, were eluted within 1 PV, showing that there was no apparent retardation of anion movement with increasing CMC contents in the top soils. The effect of soil depths on anion movement were similar to the results of CMC contents. Sulfate of having both of non-specific and specific adsorption characteristics was also recovered in the effluent within 1 PV, while the elution curves were slightly skewed to the right showing that the CMC affected the movement of sulfate. Phosphate of specific adsorption characteristics was hardly eluted within 5 PV.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.190-197
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• 2000

Anions such as C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, P $O_4$$^{3-}$, and organic anions, that do not become a part of the clay mineral crystal lattice, are of considerable interest in soils which are a potential sink caused by acid rain. In this paper, elution of native sulfate and breakthrough curves (BTC) were obtained from miscible displacement of non-specifically or specifically adsorbed anions through non-saturated or saturated Bt soil of Chungwon series. The shape and position of the BTC's could be affected by adsoprtion and ion exchange onto the soil particle surfaces. Measured BTC's for oxalic acid under unsaturated and saturated conditions showed that less pore volumes were required to displace the native S $O_4$$^{2-}$S from the soil column, and that maximum detection limit of oxalic acid reached earlier than under unsaturated. The retarded BTC's to the righthand side could be attributed by different adsorption behavior of each anion, although BTC's may be influenced by the smaller order of velocity change. The alternate breakthrough and elution curves show the rapid approach to the maximum detection limit of C/Co = 1, compared to progressive tailing of elution curve to reach to C/Co = 0. The probable explanation for asymmetric elution patterns for both anion is that the anion was selectively adsorbed on the positively charged soil surface from the solution passing in the soil column. On the other hand, the variations of pH in effluent showed that pH was increased to 7 in the first 6 pore volume and then gradually decreased to pH 4.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.682-689
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• 2010

The purpose of this study was to determine any detrimental effects on surrounding environments by using bottom ash, waste tire, and mixture as a fill material to raise the ground level. Three different initial pHs (4, 6, 8) were applied to bottom ash and initial pH of 4 was used to waste tire and mixture. Among 7 heavy metals, Pb and Zn were exceeded drinking water standards but their concentrations decreased below drinking water standards within 1 PVE. Among 5 anions, sulfate exceeded 10 times of drinking water standards and further higher partition coefficients resulted in increased PVE of 8.21. For the mixture of bottom ash and waste tire, its concentrations of heavy metals and anions were decreased due to the dilution effect and lowered PVE from 8.21 (BA) to 5.89.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.465-468
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• 2008

This study investigated the best condition when mixed sand with a river and crushed sand was used though the experiment for the properties of the concrete corresponding to the control of fine aggregate ratio to apply the mixed sand and properties of the fine aggregate at the ready-mixed concrete factory on Yeongnam and Honam. The physical properties of Yeongnam and Honam is satisfied with KS F 2526 and KS F 2527 except fineness modulus and passing amount of 8mm sieve. And, the mixed sand above two types which were incongruent to use individually was being used at each factory, and it was managed in accordance with KS. The flowabillity of the mixture proportion of concrete which was estimated by method of unit volume weight according to the fine aggregate ratio at each factory on Yeongnam and Honam was higher than existing mixture proportion. It was analyzed that the residual water due to decline of the surface area caused by reducing fine aggregate ratio was increased relatively. Accordingly, it was considered that the effect on the economic mixture proportion and improvement of durability might be possible.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.435-444
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• 2009

In situ stabilization of heavy metals through adsorption onto indigenous bacterial biofilm developed on soil particles was investigated. Biofilms were developed in soil columns by supply of various carbon sources such as acetate, lactate and glucose. During development of biofilms, acetate, lactate, and glucose solutions were flew out from the soil columns with volume ratios of 98.5%, 97.3%, and 94.7%, respectively, when compared with soil column supplied with deionized water. Decrease in effluent amounts through the soil columns amended with carbon sources over time indicated the formation of biofilms resulting in decrease of soil porosity. Solutions of Cd, Cr(VI), Cu, Pb, and Zn were injected into the biofilms supported on soil particles in the columns, and the dissolved heavy metals in effluents were determined. Concentrations of dissolved Cd, Cr(VI), Cu, and Zn in the effluents through biofilm columns were lower than those of control column supplied with deionized water. The result was likely due to enhanced adsorption of the metals onto biofilms. Efficiency of metal removal by biofilms depended on the type of carbon sources supplied. The enhanced removal of dissolved heavy metals by bacterial biofilms in this study may be effectively applied to technical development of in situ stabilization of heavy metals in natural soil formation contaminated with heavy metals.