• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.244-250
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• 2020

β-Tricalcium phosphate (β-TCP, Ca3(PO4)2) is a kind of biodegradable calcium phosphate ceramics with chemical and mineral compositions similar to those of bone. It is a potential candidate for bone repair surgery. To improve the bioactivity and osteoinductivity of β-TCP, various ions doped calcium phosphate have been studied. Among them, Iron is a trace element and its deficiency in the human body causes various problems. In this study, we investigated the effect of Fe ions on the structural variation, degradation behavior of β-TCP. Fe-doped β-TCP powders were synthesized by the coprecipitation method, and the heat treatment temperature was set at 925 and 1100℃. The structural analysis was carried out by Rietveld refinement using the X-ray diffraction results. Fe ions existed in a different state (Fe2+ or Fe3+) with different heat treatment temperatures, and the substitution sites (Ca-(4) and Ca-(5)) also changed with temperature. The degradation rate was fastest at Fe-doped β-TCP with heated at 1100℃. The cell viability behavior was also enhanced with the substitution of Fe ions. Therefore, the substitution of Fe ion has accelerated the degradation of β-TCP and improved the biocompatibility. It could be more utilized in biomedical devices.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.305-312
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• 2023

Purpose: Although the damage caused by abnormal temperatures is extensive, blow-up or black ice is typical in concrete structures. In this study, PCM with high phase change energy was mixed with concrete to reduce temperature damage to concrete pavement. Method: In order to reduce temperature damage to low temperatures and high temperatures, capsule-type PCM with phase change temperatures of 4.5℃ and 44℃ was replaced by 10%, 30%, and 50%, and thermal performance experiments and compressive strength experiments were conducted using thermocouples and variable chambers. Result: As a result of the thermal performance experiment, it was found that the incorporation of PCM improves temperature resistance by up to 25% or more, and increases thermal resistance at all temperatures with high specific heat when substituted in large amounts. As a result of the compression strength experiment, a substitution of 30% or more resulted in a decrease in the compression strength, and a large strength difference was shown based on the phase change temperature of the PCM. Conclusion: The incorporation of PCMs has been shown to increase the thermal performance of concrete, with the greatest increase in thermal performance near the phase change temperature of PCM. In addition, a small strength reduction of 10% to 20% occurs at the highest substitution rate of 50% substitution, so there is no significant problem with usability, and additional PCM substitution is expected to improve thermal performance.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.194-214
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• 1993

This paper purports to study on interactive fuzzy goal programming model which leads to the compromise solution which the decision maker satisfies through the interactive approach. We also attempted to calculate local proxy preference function from utility function of sum-of-logarithms in connection with marginal rate of substitution and interactive approach for the purpose of applying weight of multiobjective function. In an attempt to grasp compromise solution from fuzzy efficient solution, we decided to take the interactive method and presented stopping rule for this.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.152-155
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• 2003

The automotive industry is currently trying to develop light- weight vehicle for both improvement of fuel efficiency and reduction of environmental pollution. For the reduction of vehicle weight, the substitution of aluminum for steel has been increased. However, the change of material causes a significant problem with respect to the method of joining. In this paper, strength of several aluminum joining methods such as spot welding, metal insert gas(MIG) welding, adhesive bonding was evaluated by performing lap test.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.675-680
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• 2002

This study was to operate a fitting production specific of concrete product for proper mixing discovery. Testing method was to operate slump, air content, compressive strength test. The standard was water-cement ratio 50% and weight substitution 0%, 10%, 20% by Fly-ash and using Silica-fume and HPMC(Hydroxy propyl methyl cellulos) by additive. The result of this study showed when add Fly-ash to Silica-Fume is better than HPMC.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1990.04a
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• pp.355-364
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• 1990

In the classical research, technological forecasting was used in the field of substitution of a new technology product for a old in the developed countries. But in the developing or underdeveloped countries, more interested in the forecasting of technological level in certain industry than technological forecasting in certain product. This article shows the forecasting method of technological level by using a procedure of AHP(Analytical Hierarchy Process). With the historical data of the technological levels in the Korean Civil Aerospace(KCA) industry using AHP questionaire, the Gompertz curve was used to forecast the technological levels of KCA industry.

• The Journal of Korea Robotics Society
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• v.2 no.2
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• pp.178-182
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• 2007

Precision stages are essential device for micro machines, fiber optic assembly systems, and biology instruments. In this paper, a precision inchworm type actuator for a linear stage is proposed and evaluated. An analytic method to design an inchworm type motor is proposed. Developed actuator provides fast motion compared with a commercial inchworm actuator, and can be used as an actuator for a stage in substitution for a conventional rotary actuator.

• Journal of the Korean Chemical Society
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• v.63 no.1
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• pp.51-55
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• 2019

The synthesis of N-substituted POSS-imidazole in one pot typically prepared using the condensation method from diketone and aminopropylisobutyl-POSS. A wide variety of functional groups and substitution patterns were tolerated under the present procedure. The resulting compounds can be used as valuable products allowing for the elaboration to OLED, DSSC building block.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.289-292
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• 1989

Electronic structures and ethylene addition reaction for halocyclopentynes are investigated using MNDO method. Electronic effects due to the halogen substitution are very small for halocyclopentynes. Fluorocyclopentyne is slightly more stable than cyclopentyne and other halocyclopentynes, but reactivities for cycloaddition reactions are about the same for all halocyclopentynes and cyclopentyne. Stabilization effect is substantial for hexafluorocyclopentyne.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.248.3-249
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• 2003

Objectives: Galatosylated PEI was synthesized and characterized for gene delivery to hepatocytes. It was modified by conjugating with hydrophilic PEG to improve in vivo circulation. And we studied the possibility as an imaging modality for monitoring of gene delivery using gal-PEI derivatives. Methods: The substitution values of galactose in PEI were calculated by resorcinol/sulfuric acid method and quantity of PEG was calculated by comparing NMR peak. Cytotoxicity was determined by MTT. (omitted)