• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.369-376
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• 2007

This experiment was carried out to investigate optimum conditions of coir-based substrates for the red pepper plug seedlings. Eleven different coir based substrates prepared by mixing of coir, vermiculite, rice hull, perlite, zeolite, mixed at different ratios were tested. The physical and chemical properties of the substrates were analyzed by the CEN (European committee for standardization) method. Fresh and dry weights of shoot and root, leaf area, root length, and T/R ratio (dry shoot weight/dry root weight) were determined at 55 days after sowing. The results showed that the growing media CRZ 8(coir:rice hull: vermiculite=8:1.9:0.1) and CVSZ 6(coir:silver vermiculite: zeolite=6:3.9:0.1) can successfully be used for pepper plug seedlings judging from dry weight and T/R ratio of the plug seedlings. The optimal range of total pore space, water volume, air volume, easily available water content and water buffering capacity of the coir-based growing substrates for pepper plug seedlings were in the range of 92~94%, 52~60%, 32~43%, 18~21%, and 0.9~8%, respectively.

• Journal of the Korean Society for Railway
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• v.13 no.5
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• pp.481-487
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• 2010

A room scale fire test was done for interior materials from a subway vehicle installed within an ISO 9705 fire test room. The interior materials are the old ones which were made before the new fire safety guideline of subway vehicles. The output of ignition burner was increased in controlled steps to CEN/TS 45545-1. The objectives of this interior fire test are to assess the fire performance in terms of ignition and flame spread on interior lining materials and to provide data on an enclosure fires involving subway vehicle interior materials that grow to flashover. Temperatures, heat flux and heat release rate variations verse time of the test are measured. Heat release rate is compared with that of calculated by modified flaming area based summation method. These test results will be used for verification of CFD fire simulation of full subway vehicle.

• Resources Recycling
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• v.25 no.6
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• pp.29-40
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• 2016

Effects of crushed coal bottom ash (CBA) with maximum size of 1 mm on the properties of mortar with various water-to-binder ratios (w/b) were evaluated. The present work is a fundamental study to establish a method of mix proportion design for mortar and concrete with CBA. The workability, air contents, and compressive strength of mortar were measured. Efficiency of CBA on the compressive strength at 28 days, which was adopted for mix proportion design, was evaluated based on concepts of 'equivalent strength' in CEN/TR 16637. It was found that the CBA could be contributed as a binder in mortar in some cases, while in other cases act as at aggregates. The efficiency of CBA was influenced by types of CBA and their replacement ratio, and w/b of mortar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1017-1021
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• 1995

Geometric and thermal errors are responsible for major components of the errors of a computer numerically controlled turning center. The planar error of a CNC turning center are comprised of 11 geometric and thermal error components. The error synthesis model is formulated by homogeneous coordinate transformation method and expresses the effect of such error components on the planar error of a CNC turning center. In this paper, the sensitivity analysis of the model on the noises through sensing and the change of temperature is addressed. The sensitivity analysis show that the error systhesis model is robust on the noses and z planar error is much affected by the change of temperatures.

• Communications of the Korean Mathematical Society
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• v.14 no.4
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• pp.815-832
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• 1999

High-order weighted difference schemes with uniform meshes are considered for the convection-diffusion problem depending on Reynolds numbers. For small Reynolds numbers, a weighed cen-tral difference scheme is suggested since there is no boundary layer. For large Reynolds numbers, we propose a modified up wind method with an artificial diffusion in order to overcome nonphysical oscilla-tion of central schemes and obtain good accuracy in the boundary later. Existence and corresponding error estimates of the solution for the difference scheme have been shown. Numerical experiments are provided to back up the analysis.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.293-301
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• 2005

We conducted several different leaching experiments for assessing the potential environmental risk when utilizing recycled concrete for stabilizing bridge pier. The methods include continuous batch leaching test (DIN 38414-S4), availability test (NEN 7341), pH-stat test (CEN/TC 292/WG6) and tank diffusion test (NEN 7345). The concentration ranges vary depending on the testing method. Nearly all the trace elements were low, some elements recording under detection limit. The maximum concentrations for trace elements leached throughout the whole tests are (as mg/L); Cd (0.029), Cu (0.437), Pb (0.14), Ni, Zn (0.95), Hg (0.005). Although the testing methods we used in this study are much more rigorous than other commonly adapted method including TCLP and domestic testing method for solid waste, the trace elemental concentrations are under the criteria for hazardous material set by the TCLP and domestic method. The result seems to suggest that applying the recycled concrete on stream water will be accepatable practice as for as trace elements are concerned. However, the influence of inorganics such as Ca, Mg, Ni and $SO_4^{2-}$ on aquatic ecology should be further examined.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.572-575
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• 2004

A fundamental study was executed in order to evaluate quantitatively the effect on strength characteristic of concrete or mortar by fly ash. As a result, it was confirmed that the appropriate usage of fly ash is in existence comply with mix condition and characteristic of fly ash. And, we could evaluate the activity factor of fly ash. But, there are many problem in actual application because that the object of this study is only Method(2) out of the evaluation methods of activity factor proposed by CEN. Therefore, it is necessary to keep up an additional study.

• Carbon letters
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• v.15 no.3
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• pp.198-202
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• 2014

Amorphous agglomerates of carbon nanospheres (CNS) with a diameter range of 10-50 nm were synthesized using the solution combustion method. High-resolution transmission electron microscopy (HRTEM) revealed a densely packed high surface area of $SP^2$-hybridized carbon; however, there were no crystalline structural components, as can be seen from the scanning electron microscopy, HRTEM, X-ray diffraction, Raman spectroscopy, and thermal gravimetric analyses. Electrochemical and thermo catalytic decomposition study results show that the material can be used as a potential electrode candidate for the fabrication of energy storage devices and also for the production of free hydrogen if such devices are used in a fluidized bed reactor loaded with the as-prepared CNS as the catalyst bed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1988.10a
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• pp.24-29
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• 1988

In this paper, it is proposed hew the rigid element method suggested in the first paper can be applied to the elastic and elasto-plastic analysis of spherical shell with the open stiff ring. In the analytical model, the solution domain is divided into rectangular-shaped spherical bending elements. Each contact surface of two adjacent elements is interconnected with four elastic springs, and it is assumed that the internal forces are distritributed into springs. The 6 degrees of freedom of the element are placed in the center of elements, and the 6 cen-teroidal rigid displacements affect other elements through springs around elements. And then the solution domain is estimated by the behavior of elements and springs. In this study, these concepts are applied to the elastic and elasto-plastic analysis for the eight cases of the spherical shell according to the condition of stiff ring, the condion of loading and the size of opening. And then some numerical results such as the distribution of stresses, the force-displacement curves and the mode of fractures will he shown.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.392-399
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• 2007

This study was carried out to assess optimum conditions of peatmoss-based substrates for red pepper plug seedlings. Peatmoss-based substrates prepared by mixing of peatmoss with vermiculite, perlite, rice hull and zeolite at various mixing ratios were used for growing pepper plug seedlings. The physical and chemical properties of the peatmoss substrate were analyzed by the CEN(European committee for standardization) method. Fresh and dry weights (shoot, root), leaf area, root length and T/R ratio (dry shoot weight/dry root weight) were determined at 55 days after sowing. The results showed that the growing media PVSZ 6 (peatmoss:silver vermiculite: zeolite=6:3.9:0.1) and PVGZ 6 (peatmoss:gold vermiculite: zeolite=6:3.9:0.1) can successfully be used for red pepper plug seedlings judging from dry weight and T/R ratio of the plug seedlings. The optimal ranges of total pore space, water volume, air volume, easily available water content and water buffering capacity of the peatmoss based growing media for pepper plug seedlings were 87~93%, 52~71%, 20~41%, 10~37% and 0.6~10%, respectively.