• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.298-302
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• 1997

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.34-52
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• 2002

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.163-177
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• 2004

• Transactions of Materials Processing
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• v.1 no.2
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• pp.14-19
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• 1992

분말단조 공정의 해석을 위한 기초연구로서 고용 업셋에 의한 다공질 합금강 프리폼의 치밀화와 소성 변형거동에 관하여 조사하였다. 다공질 프리폼의 소성 유동응력은 용도의 상승에 떠라 감소하였고, 변형속도의 증가에 따라 증가함을 보였다. 또한, 다공질 프리폼의 초기밀도가 더 높을수록 동일한 온도와 하중조건에서 더 높은 치밀화를 보였다. 또한, 밀도변화에 따른 프와송 비를 실험치로 부터 구하였고, 배불림 현상과 체적변화를 고려하여 온도에 따른 진응력-진변형률 관계를 구하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.196-202
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• 2018

In this study, we investigated phosphate removal efficiency according to pretreatment (pyrolysis temperature, pyrolysis time, particle size) of oyster shells as a basic study for their recycling. And XAFS analysis and isothermal adsorption experiments were performed to investigate the phosphate removal characteristics of oyster shells. As a result, the removal efficiency was good at $600^{\circ}C$ pyrolysis temperature with 6 hour pyrolysis time and 0.355 ~ 0.075 mm particle size. Isothermal adsorption experiments showed that the Langmuir model is suitable for adsorption of oyster shells. XAFS analysis showed that calcium phosphate formed on the oyster shell pyrolyzed at $600^{\circ}C$. In other words, it was confirmed that the formation of calcium phosphate by the calcium ion elution of the oyster shell contributes to the decrease of phosphate concentration.

• Journal of the Korea Institute of Building Construction
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• v.19 no.5
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• pp.401-409
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• 2019

This paper aims to recycle red mud from a byproduct in the alumina industry as an alternative raw material for depleted natural resources. In order to apply red mud as a ceramic material, red mud ceramics were prepared according to mixing and temperature in a laboratory environment. Compared with KS L 4201 in terms of compression ratios and absorptions, it is found that two kinds of conditions for one type and three conditions for two types meet the standard. When red mud is used as a clay brick raw material, the substitution ratio of red mud is 10% or less, and the firing temperature is considered to be appropriate at $1200^{\circ}C$. In order to apply red mud to clay brick raw material in actual field, various samples and firing temperature should be considered in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.795-808
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• 2006

In this paper, an analytical method which can predict the occurrence of plastic shrinkage cracking on concrete slabs with sequential placement is proposed on the basis of the numerical model introduced in the previous study. The influence of many design variables on plastic shrinkage cracking such as the number of layers and the time interval between layers is quantitatively analyzed through parametric studies using the analytical method. In advance, two equations are introduced to take into account the effect of sequential placement on the plastic shrinkage cracking of concrete slab; The first one is to calculate the time at which the surface of concrete slab begins to dry, and the second one is to determine the critical time interval to prevent the surface drying of previously placed concrete layers. The timing of curing and the sequence of concrete placement, which are important for the prevention of plastic shrinkage cracking, can be effectively planned using the introduced both equations without any rigorous analysis.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.247-256
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• 2003

FEM analyses which are based on modified Cam-clay theory have been generally used in such cases as analyses of stability and displacement fur embankment construction on soft clays. However, the Modified Cam Clay Model can generate some problems in anisotropic stress conditions of field because the critical state theory has been developed through many laboratory tests in isotropic conditions. Thus, the applicability on the prediction of undrained shear strength and pore water pressure which was based on the critical state theory was evaluated by triaxial tests and numerical analyses in isotropic and anisotropic conditions. Used samples often come out in domestic area, together with general low plastic clays which are showing dilatant behavior in shearing process. They were evaluated by laboratory tests and FEM based on MCCM. From the results of test and numerical analysis, the predictions of undrained strength in low plastic clays well coincided with each other in both isotropic and anisotropic conditions. However, the generation of porewater pressure was often overestimated during undrained shearing in anisotropic conditions. The results can generate the errors in the prediction of stress path of field sites during loading such as construction of embankment on soft clays because the field is subjected to anisotropic conditions during loading.

• Resources Recycling
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• v.11 no.6
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• pp.24-30
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• 2002

Reduced and modified converter slag was ball milled and sieved to -200/+325 mesh. CaO,$SiO_2$, $Fe_2$$O_3$ was added to slag powder and mixed to make it similar to the composition of normal portlant cement. The pellet made of this powder was heated from $1250^{\circ}C$ to $1450^{\circ}C$ for 15 min～45 min. Most feasible condition for making slag cement clinker is the heating more than 20 min at $1450^{\circ}C$. The compressive strength of the mortar made of this slag cement clinker was better than that of normal port-lant cement in long time curing.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.107-114
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• 2009

In present study, an alternative process for manufacturing ultra marine blue by using kaolin, sulfur, sodium carbonate, silica, and rosin was investigated. From the experiments, it was found in the reductive calcination process that the temperature variation with the bed height of input materials is relatively high due to the inadequate thermal conductivity of them. It was also found that the color of the ultramarine blue manufactured is sensitive for the shape of the input materials and the calcinations conditions, and specially the heating rate is very important to form ultramarine. For manufacturing green ultramarine by using sulfur, sodium carbonate, silicon, and pine resin, an optimum condition was investigated to be the heating rate region below $0.6^{\circ}C/min$, the reaction temperature of $850^{\circ}C$ and the reaction time of 4 hr. At the oxidative calcination process to manufacture ultra marine blue from green ultramarine, the optimum flow rate of air is $500{\sim}550\;{\ell}/kg$ (green ultramarine) and the reaction temperature is $500{\sim}550^{\circ}C$.