• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.877-880
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• 2009

A curing process in post-printing section of R2R process is required for an electrical property of the printed pattern when devices such as RFID, Solar cell are printed. PEN as well as heat-stabilized PET which is used as a plastic substrate would be deformed at high temperature due to change of its elastic modulus. And crack in the printed pattern, which is on the plastic substrate is occurred due to the deformation of the substrate. The occurrence of crack causes electrical resistance to increase and the quality of the device to deteriorate. In case of RFID antenna, the range of reading distance is shortened as the electrical resistance of the antenna is increased. Therefore, the deformation of the plastic substrate, which causes the occurrence of crack, should be minimized by setting up low operating tension in R2R process. In low tension, slippage between a moving substrate and a roller would be generated when the operating speed is increased. And scratch would be occurred when slippage is generated due to an air entrainment, which is related to the thickness of the air film. The thickness of the air film is increased when operating speed is increased as shown by simulation based on mathematical model. The occurrence of scratch in conductive pattern printed by roll to roll process is a critical damage because it causes degradation or failure of electrical property of it.

• International Journal of Concrete Structures and Materials
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• v.6 no.2
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• pp.87-100
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• 2012

The process of selecting a repair material is a typical one of multi-criteria decision-making (MCDM) problems. In this study Analytical Hierarch Process was applied to solve this MCDM problem. Many factors affecting a process to select an optimal repair material can be classified into quantitative and qualitative requirements and this study handled only quantitative items. Quantitative requirements in the optimal selection model for repair material were divided into two parts, namely, the required chemical performance and the required physical performance. The former is composed of alkali-resistance, chloride permeability and electrical resistivity. The latter is composed of compressive strength, tensile strength, adhesive strength, drying shrinkage, elasticity and thermal expansion. The result of the study shows that this method is the useful and rational engineering approach in the problem concerning the selection of one out of many candidate repair materials even if this study was limited to repair material only for chloride-deteriorated concrete.

• Journal of the Korea Institute of Building Construction
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• v.12 no.1
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• pp.64-72
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• 2012

Recently, prepackaged-type surface preparation materials using redispersible polymer powders are widely used for interior and exterior finishing in the construction work. The purpose of this study is to evaluate the performance and the quality of prepackaged-type surface preparation materials using a VA/E/MMA terpolymer powder. Surface preparation materials using a VA/E/MMA terpolymer powder were prepared with shrinkage reducing agent contents of 0, 4 % and cellulose fiber contents of 0, 0.5, 1.0 %, and tested for drying shrinkage, strengths, adhesion in tension, crack and impact resistance, water absorption, permeability. As a result, prepackaged-type surface preparation materials show outstanding performance depending on the shrinkage reducing agent and cellulose fiber contents.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.543-548
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• 2001

The corrosion monitoring methods of reinforcing steel in concrete are the various methods such as half cell potential method, galvanic current method, resistivity method, polarization resistance method, AC impedance method and etc. In this study, the corrosion monitoring methods of reinforcing steel in concrete were investigated for the test specimens using corrosion inhibitors, zinc-mortar, zinc-plate, respectively. For this purpose, the accelerated corrosion tests for reinforcing steel were conducted according to the periodic cycles(140 days) of wetting($65^{\circ}C$, 90% R.H.) and drying period(15$^{\circ}C$ , 65% R.H.) for the test specimens. As a result, it can be concluded from the test that half cell potential and galvanic current method as monitoring techniques for corrosion were found to be relatively reliable and easily usable method in the field.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.72-77
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• 1995

Blast-furnace slag cement has been used widely as a structural material due to the latent hydraulicity of granulated ground blast furnace slag(GGBS)for a long time as The wall as ordinary portland cement. In this study, based on the fundamental investigation on the high strength and high durable concrete using the high fineness GGBS the following remarks can be made. 1) The average desired strenth of concrete is Or=600~800kg/$\textrm{cm}^2$. 2) The above high strength concrete using the high fineness GGBS is more workable than those using only OPC. 3) The adiabatic temperature and drying shringkage decrease, so the density and resistance to sea water attack increase as results. 4)The unit cement content and unit air entrained admixture at the same desired strength of concrete decrease, so the economical high strength concrete can be manufactured from using the high fineness GGBS.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.790-793
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• 2004

The factors influencing concrete deterioration in marine environment can be generally divided into the physical and chemical action. The physical attack due to drying and wetting would increase the internal stress of concrete. The chemical attack resulting from the diffusion of ions$(i,e,\;Cl^-,SO_4^{2-},Mg^+)$ from seawater through the pores in concrete. The objective of this study is to evaluate corrosion characteristics of steel when using the various concrete materials under marine exposure environment. After 3 years of exposure, concrete specimen incorporating $40\%$ blast-furnace slag as replacement for type I cement with low w/c ratio of 0.42 and using the inhibitor shows excellent performance.

• Journal of the Korean Graphic Arts Communication Society
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• v.12 no.1
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• pp.13-27
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• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printablility of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular weight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• Journal of the Korean Graphic Arts Communication Society
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• v.12 no.1
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• pp.145-157
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• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printability of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular \veight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• Membrane and Water Treatment
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• v.4 no.3
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• pp.215-222
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• 2013

The maximum current density that can be achieved in bipolar membrane electrodialysis is limited by the sharp increase in resistance that is experienced when the water content at the membrane interface is not adequately replenished and the membranes dry out. In this paper we show how the water content near the interface depends on the properties of the membranes. A water retaining parameter is introduced, which characterizes the thermodynamic properties of the membrane material and may be used to guide the choice of polymers for mitigation of the dry-out problem.

• Tribology and Lubricants
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• v.12 no.3
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• pp.33-38
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• 1996

High temperature wear behaviors of plasma-sprayed ZrO$_{2}$-$Y_{2}O_{3}$ composite coatings were investigated for high temperature wear resistance applications. The composite powders containing 20, 50, 80 vol% of alumina for plasma spray were made by spray drying method. Wear tests with composite coated specimens were performed at temperature ranges from room temperature to 800$^{\circ}$C. Wear tests were also carried out with heat treated specimens at room temperature. The microstructural change of coatings and the worn surface were examined by SEM and XRD. Sharp increase of wear loss at high temperature wear test was observed in specimens containing 50 and 80 vol% alumina. Similar trend was observed in the heat treated coatings. The measured residual stress was increased with increased alumina contents and heat treating temperatures. Residual stress induced during heat treatment appeared to be responsible to the observed harmful effect of alumina additions on the high temperature wear.