• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.66-73
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• 2019

Approximately 80% of the mines are vacated or abandoned mines and are mostly left without suitable environmental treatment facilities. In the area around the abandoned mine site, problems such as drainage of acidic city drainage and leakage of leachate occur, and ground subsidence caused by this can cause a safety accident due to sink hole occurrence. In this study, flow, compressive strength, water uptake, pore and hydration characteristics were investigated to investigate the basic properties of liner and cover material based on the replacement ratio of nano silica and silica fume in the existing blast - furnace slag fine powder. As a result, as the substitution ratio of nano silica and silica fume increased, the flow and compressive strength of nano silica specimens increased and the absorption rate decreased. In the case of pore characteristics, the amount of pores decreased as the substitution ratio of nano silica and silica fume increased. Especially, the capillary porosity of 10-1,000 nm diameter decreased. Ray diffraction analysis and SEM measurement showed that the peak positions of the hydration products were almost the same when compared with the 5% alternative test samples of Plain and silica fume.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.134.1-134.1
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• 2017

In this study, we propose a new scaffold fabrication method, "direct electro-hydrodynamic jet process," using the initial jet of an electrospinning process and ethanol media as a target. The fabricated threedimensional (3D) fibrous structure was configured with multilayered microsized struts consisting of randomly entangled micro/nanofibrous architecture, similar to that of native extracellular matrixes. The fabrication of the structure was highly dependent on various processing parameters, such as the surface tension of the target media, and the flow rate and weight fraction of the polymer solution. As a tissue regenerative material, the 3D fibrous scaffold was cultured with preosteoblasts to observe the initial cellular activities in comparison with a solid-freeform fabricated 3D scaffold sharing a similar structural geometry. The cell-culture results showed that the newly developed scaffold provided outstanding microcellular environmental conditions to the seeded cells (about 3.5-fold better initial cell attachment and 2.1-fold better cell proliferation).

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.181-187
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• 2014

In order to use the spherical atomizing reduction steel slag (ladle furnace slag, LFS) instead of the fine aggregate of polymer concrete composites, various specimens were prepared with various replacement ratios of atomizing reduction steel slag and the addition ratios of polymer binder. Physical properties of these specimens were investigated through the absorption test, the compressive strength test, the flexural strength test, the hot water resistance test, the pore analysis and the micro-structure using scanning electron microscope. Results showed that the compressive strength and flexural strength of specimens with 7.5% of polymer binders increased with the increase of replacement ratios of atomizing reduction steel slag, but those of the specimens with 8.0% or more of polymer binders showed a maximum strength at a certain replacement ratio due to the material segregation causing the increase of fluidity. By hot water resistance tests, the compressive strength, flexural strength, average pore diameter, and bulk density decreased but the total pore volume and pore diameter increased. It was concluded that the amount of polymer binders could be reduced by maximum 23.8%, because the workability of the polymer concrete was remarkably improved by using the atomizing reduction steel slag instead of fine aggregate. However, since the use of atomizing reduction steel slag decreased the resistance of the polymer concrete to hot water, further studies are required.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.501-507
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• 2011

To develop environmental-friendly insulating composite materials, natural cellulose and porous ceramic balls were used as core materials and activated Hwangtoh was used as a binder. Various specimens were prepared with different water/binder ratios and core material/binder ratios. The physical properties of these specimens were then investigated through compressive strengths, flexural strengths, absorption test, hot water resistance test, pore analysis, thermal conductivity, and observation of micro-structures using scanning electron microscope. Results showed that the maximum compressive strength varied appreciably with the water/binder ratios and core material/binder ratios, but the flexural strength increased with the core material/binder ratios regardless of water/binder ratios. The compressive strength and the flexural strength measured after the hot water resistance test decreased remarkably compared to those measured before test. The pore analysis measured after the hot water resistance test showed that total pore volume, porosity and average pore diameter decreased, while bulk density increased by the acceleration of hydration reaction of binder in the hot water. The thermal conductivity decreased gradually with an increase of core material/binder ratios. It can be evaluated that the composite insulation materials having good insulating properties and mechanical strengths can be used in the field.

• Architectural research
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• v.12 no.2
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• pp.93-98
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• 2010

This paper describes a numerical method for estimating the elastic moduli of cement paste. The cement paste is modeled as a unit cell which consists of three components: the unhydrated cement grain, the gel, and the capillary pore. In the unit cell, the volume fractions of the constituents are quantified using a single kinetic function calculating the degree of hydration. The elastic moduli of cement paste are calculated from the total displacements of constituents when a uniform pressure is applied to the gel contact area. The cement paste is assumed to be a homogenous isotropic matrix. Numerical simulations were conducted through the finite element analysis of the three-dimensional periodic unit cell. The model predictions are compared with experimental results. The predicted trends are in good agreement with experimental observations. This approach and some of the results might also be relevant for other technical applications.

• International Journal of Concrete Structures and Materials
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• v.6 no.3
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• pp.155-163
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• 2012

In order to predict the neutralization of concrete which is the reaction of carbonation dioxide from the outside and cement hydration product, such as calcium hydroxide and C-S-H, it was studied the numerical analysis method considering change of the pore structure and relative humidity during the neutralization reaction. Diffusion-reaction neutralization model was developed to predict the neutralization depth of concrete with coating finishing material. In order to build numerical analysis models considering outdoor environment and finishing materials, the adaption of proposed model was shown the results of existing outdoor exposure test results and accelerated carbonation test.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.251-256
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• 2012

This paper presents an experimental study on the pore and penetration of chloride in seashore concrete depending on types of curing forms. Three types of concretes (Plain concrete, MSF concrete and FA concrete) with four different form types (wood, coating wood, steel and polypropylene film) were examined. The test results show that the air volume in concrete was relatively higher with steel and polypropylene forms than others, and wood form shows the least air volume. The penetration of chloride depending on type of form is showed a wide variability, that is, the values on plain concrete, MSF concrete and FA concrete are 115.2, 125.5 and 121.6 %, respectively. Based on the present study, concrete should be considered the conditions of curing form-type for durable concrete.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.749-752
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• 2001

Very fine cobalt oxide xerogel and ambigel powder were prepared using a unique solution chemistry associated with the sol-gel process. The mesoporous structure of the initial gel is maintained by removing fluid under conditions where the capillary forces that result extraction are either low or no existent, are either low or nonexistent. Controlling both the pore and solid architecture on the nanoscale offers a strategy for the design of supercapacitor. The results materials determine by using electrode that mixed ketjen black and PVdF. But CoO$\_$x/ have the low voltage, so we experimente to change electrolyte and various concentration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.577-580
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• 2001

Very fine cobalt oxide ambigel powder were prepared using a unique solution chemistry associated with the sol-gel process. The mesoporous structure of the initial gel is maintained by removing fluid under conditions where the capillary forces that result extraction are either low or no existent, are either low or nonexistent. Controlling both the pore and solid architecture on the nanoscale offers a strategy for the design of supercapacitor. But $CoO_x$ have the low voltage, so we experiment using Co/PVA composite electrode.

• Polymer(Korea)
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• v.38 no.6
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• pp.820-826
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• 2014

The objective of this study is to find the relationship between the tensile strength of the polymer film and the bond strength and tensile strength of the polymer-modified mortar using styrene (St) and butyl acrylate (BA), and porosity. In the test results, the bond strength and tensile strength of the polymer-modified mortar increased with increases in the tensile strength of polymer film and the fine pore volume.