• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.663-668
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• 2003

In this paper, an environmental factor and a durability resistance factor which adapts the concept of the Load Resistance Factor Design for safety design of RC structures is derived and a basic principle of a durability evaluation for RC structures using the factors is proposed. It is shown that durability of RC structures can be evaluated by comparing predicted value of chloride ion concentration with limit value of concentration for steel corrosion generation in reinforcement steel position and the durability of concrete manufactured for the RC structures can be also evaluated by comparing characteristic diffusion coefficient of concrete with predicted diffusion coefficient during mixture design.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.678-682
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• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.52-53
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• 2016

Mechanical properties and durability of recycled aggregate concrete was known to decrease due to the adhesive mortar of recycled aggregate. But in this study, As the result of chloride diffusion resistance of recycled fine aggregate mortar, the mechanical properties are reduced according to the increase of the substitute ratio of recycled fine aggregate. But the chloride diffusion coefficient was almost same with natural fine aggregate mortar.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.537-540
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• 2001

This paper presents the characteristics of Ta-N thin-film for high precision resistors, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4~16 %)$N_2$). Structural properties studied using X-ray diffraction(XRD) indicate the presence of TaN, $Ta_3N_5$ or a mixture of Ta-N phases in the films depending on the amount of nitrogen in the sputtering gas. The chemical composition are investigated by auger electro spectroscopy(AES). The optimized conditions of Ta-N thin-film resistors were deposited in 4 % $N_2$ gas flow ratio. Under optimum conditions, the Ta-N thin-film resistors are obtained a high resistivity, $\rho=305.7{\mu}{\Omega}cm$, a low temperature coefficient of resistance, TCR=-36 $ppm/^{\circ}C$.

• Journal of Surface Science and Engineering
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• v.44 no.6
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• pp.233-238
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• 2011

The friction and wear characteristics of CrN and TiN coatings on SKD61 which is mold material using for extrusion of AZ80 magnesium alloy were investigated. The coatings were deposited by the arc ion-plating method, and the thickness were about $3.59{\mu}m$ and $3.28{\mu}m$, respectively. Reciprocating friction wear tests were conducted by varying pin load and temperature of counter substrate at un-lubricated condition. The pin loads were 11, 15 and 19 kgf, and the substrate temperatures were room temperature and $120^{\circ}C$. CrN coating which has a lower friction coefficient and a smaller adhesive wear with AZ80 magnesium alloy showed better wear resistance than TiN coating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.66-70
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• 2003

This dissertation is about the development of $BaTiO_{3}$-type PTC(Positive Temperature Coefficient) thermistor by composition method. PTC samples were fabricated after setting the experimental composition equation as $(Ba_{0.95-x}Sr_{0.05}Ca_x)TiO_3\;-\;0.01TiO_2\;-\;0.01SiO_2\;-\;aMnCO_3\;-\;0.2Nb_{2}O_{5}$ and their testing results were analyzed. a PTC thermistor, having the characteristics of relatively low resistance at room temperature and c and a good temperature coefficient, has been developed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1305-1306
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• 2006

A new material was developed to achieve improvement of heat durability, improvement of wear resistance, stability of friction coefficient and reduction in aggression to counterpart, because it is difficult to maintain braking properties by using currently available materials in the train wagons used for high-speed transportation. As a result, the new material showed a stable wear resistance even in the speed range of 350km/h, where improvement was also confirmed in reduction of aggression to counterpart material by more than approximately 10%. This development was adopted for the brake lining in the Taiwan High Speed Rail project.

• Geotechnical Engineering
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• v.10 no.3
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• pp.33-40
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• 1994

The effects of smear and well resistance should be taken into account for the design of sand drains. Practically, simple design, which employs the method using 112 reduced diameter of drains or assuming the coefficient of consolidation in horizontal direction equals to that in vertical direction, based on the theory neglecting these effects, has been used. In this study, the reliability of existing simple design methods as well as the influences of smear and well resistance was investigated with the equations proposed by Hansbo and Onoue. It is shown that the consolidation time is chiefly governed by the effect of smear for drains with highly permeable sands. For general soil condition and placing type of sand drain, consolidation time is underestimated for simple design wi어. 1/2 reduced diameter of drains, and it is overestimated for that with the assumption that the coefficient of consolidation in horizontal direction equals to that in vertical direction. Through the investigations on different reduced diameter, it was shown that simple design with 1/4 reduced diameter of drains yielded the reliable results with errors less than 6%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.537-540
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• 2001

This paper presents the characteristics of Ta-N thin-(ibm for high precision resistors, which were deposited oni substrate by DC reactive magnetorn sputtering in an argon-nitrogen atmosphere(Ar-(4∼16%)N$_2$). Sturcutural properties sutided using X-ray diffraction (XRD) indicate the presence of TaN, Ta$_3$N$\sub$5/ or a mixture of Ta-N phases in the films depending on the amount of nitrogen in the sputtering gas. The chemical composition are investigated by auger electro spectroscopy(AES). The optimized conditions of Ta-N thin-film resistors were deposited in 4 % N$_2$ gas flow ratio. Under optimum conditions, the Ta-N thin-film resistors are obtained a high resistivity, $\rho$=305.7 ${\mu}$Ωcm, a low temperature coefficient of resistance, TCR=-36 ppm/$^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.97-100
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• 2001

This paper presents the characteristics of Ta-N thin-film strain gauges as high-temperature strain gauges, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4∼16 %)N$_2$). These films were annealed for 1 hour in 2x10$\^$-6/ Torr vaccum furnace range 500∼1000$^{\circ}C$. The optimized conditions of Ta-N thin-film strain gauges were annealing condition(900$^{\circ}C$, 1 hr.) in 8% N$_2$ gas flow ratio deposition atmosphere. Under optimum conditions, the Ta-N thin-films for strain gauges is obtained a high resistivity, $\rho$=768.93 ${\mu}$Ω cm, a low temperature coefficient of resistance, TCR=-84 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal gauge factor, GF=4.12.