• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.278-278
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• 2010

We have characterized the previously undescribed parameters for engineering the electrical properties of single-walled carbon nanotube (SWCNT) films for technological applications. The surface tension of the top coating passivation material and matching coefficients of thermal expansion for the substrate and carbon nanotube network are two crucial parameters for the fabrication of reliable and highly conductive single-walled carbon nanotube network thin films.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.470-475
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• 2013

In this study, we report that effects of a filler with a high coefficient of thermal expansion on a sealant for high-temperature ($750{\sim}850^{\circ}C$) SOFC. We designed a $SiO_2-BaO-ZnO-B_2O_3-Al_2O_3$ glass system with a softening temperature higher than $750^{\circ}C$. The properties of the glass system show not only low volumetric shrinking but also low swelling. The glass system did not create a crystal phase during along-term heat treatment. We fabricated a seal gasket with 0, 10, 15, and 20 wt% cristobalite added as filler materials with glass powder. The coefficient of thermal expansion of the seal gasket increased according to cristobalite content. During along-term heat treatment, the leak rate decreased by about 5% after a heat treatment in an oxidizing atmosphere at $750^{\circ}C$ for 2000 h, also decreasing by about 6% after a heat treatment in a reducing atmosphere at $750^{\circ}C$ for 1000 h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1092-1100
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• 2005

We investigated a carbon nanotube (CNT) oscillator controlled by the thermal gas expansion using classical molecular dynamics simulations. When the temperature rapidly increased, the force on the CNT oscillator induced by the thermal gas expansion rapidly increased and pushed out the CNT oscillator. As the CNT oscillator extruded from the outer nanotube, the suction force on the CNT oscillator increased by the excess van der Waals(vdW) energy. When the CNT oscillator reached at the maximum extrusion point, the CNT oscillator was encapsulated into the outer nanotube by the suction force. Therefore, the CNT oscillator could be oscillated by both the gas expansion and the excess vdW interaction. As the temperature increased, the amplitude of the CNT oscillator increased. At the high temperatures, the CNT oscillator escaped from the outer nanotube, because the force on the CNT oscillator due to the thermal gas expansion was higher than the suction force due to the excess vdW energy. By the appropriate temperature controls, such as the maximum temperature, the heating rate, and the cooling rate, the CNT oscillator could be operated.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1064-1069
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• 2010

Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.321-327
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• 2009

This paper studied the influences of the main design parameter-the expansion angle and the material properties of the self-expansion anterior cruciate ligament fixation device on the contact condition with the bone and the initial stability of the device. Using finite element analysis, the stress distributions of the ring part of the device and the wall of the bone tunnel were calculated. And the micro-migration of the device by the pull-out force was calculated. From the analysis results, it was found that when designing the self-expansion type anterior cruciate ligament fixation device, it is desirable to use the material having higher Young's modulus and to design the fixation device that all wedges uniformly maintain contact with bone to obtain initial stability after operation.

• Structural Engineering and Mechanics
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• v.60 no.2
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• pp.313-335
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• 2016

In this article, a four-variable refined plate theory is presented for buckling analysis of functionally graded plates subjected to uniform, linear and non-linear temperature rises across the thickness direction. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. Young's modulus and Poisson ratio of the FGM plates are assumed to remain constant throughout the entire plate. However, the coefficient of thermal expansion of the FGM plate varies according to a power law form through the thickness coordinate. Equilibrium and stability equations are derived based on the present theory. The influences of many plate parameters on buckling temperature difference such ratio of thermal expansion, aspect ratio, side-to-thickness ratio and gradient index will be investigated.

• Fire Science and Engineering
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• v.29 no.3
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• pp.21-30
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• 2015

In this study, we try to suggest measures to reduce leakage at a joint between CPVC piping for a sprinkler system and a pipe expansion through reviews of domestic and foreign standards and related tests. The quality of the waterproof rubber packing material between a valve socket and pipe expansion nut was examined. In the leak test, the valve socket material over the expansion part of the metal pipe nut was found to use a metal part or a schlorinated polyvinyl chloride pipe nut part. In addition, the KS B 0221 standard for parallel pipe threads with threaded and thread inspection criteria and inspection standards in order to ensure an acceptable quality of valve socket, there is a need to amend the regulations to comply with the KS B 5223 (screw thread limit gauges parallel pipe threads). We do not have detailed standards for expansion piping nuts for waterproof rubber ring material, so we need to amend the relevant criteria for EPDM material to be used with excellent waterproofing, for which both NBR and EPDM are currently used.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.1
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• pp.109-115
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• 2011

Implants were placed after performing ridge expansion by inserting screws of gradually increasing thickness. Favorable clinical outcome was obtained. During surgery, buccal cortical plate fracture did not occur. Autogenous tooth bone graft material was grafted around the implant dehiscence defects and over the buccal cortical plate. The method involving the insertion of screws for ridge expansion is a successful and predictable technique for implant placement in narrow alveolar bone. Autogenous tooth bone graft material can be used for ridge augmentation and GBR.

• Journal of the Society of Disaster Information
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• v.14 no.1
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• pp.79-88
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• 2018

In this study, the changes of the expansion and strength according to the temperature of the emergency repairing expansion material were examined by cup foaming test and uniaxial compressive strength test, and the accelerated compression creep test was carried out to confirm the long term stability. Ramp & Hold test and accelerated compressive creep test were performed to evaluate the creep performance. The short - term creep test was used to determine the initial creep strain of the expanding material. The isothermal method using time - To evaluate the long - term compressive creep performance.

• Transactions of Materials Processing
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• v.18 no.7
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• pp.565-571
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• 2009

This paper is concerned with the analysis on the surface stress profiles of perfectly plastic material in backward extrusion process. Due to heavy surface expansion appeared usually in the backward extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the analyses have focused to reveal the surface conditions at the contact boundary for various punch shapes in terms of surface expansion, contact pressure, and relative movement between punch and workpiece which consists of sliding velocity and distance, respectively. Punch geometries adopted in the analysis include concave, hemispherical, pointed and ICFG recommended shapes. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward extrusion process under different punch geometries. The simulation results are summarized in terms of surface expansion, contact pressure, sliding velocity and sliding distance at different reduction in height, deformation patterns, and load-stroke relationship, respectively.