• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.10
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• pp.745-749
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• 2012

Heating pipes burst was occurred in the apartment complex that was applied floor radiant heating system. There were two opinions for the cause of the bursted heating pipes that was the flaw during construction and defects in the product and also there were conflicting among them. Officials analyzed it in order to investigate the cause of the rupture. Tensile test results showed different tensile strength between the lower part of heating pipe and the upper part of heating pipes. The lower tensile strength is maintained while the top was not secured. The reason why rupture heating pipes is that flow velocity isn't secured and then the air get stagnant. Stagnant air makes hardening. It is caused rupturing. The proper flow rate was confirmed 0.166 m/sec after experiment. It isn't make stagnant air inside heating pipes.

• Nuclear Engineering and Technology
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• v.44 no.5
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• pp.523-534
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• 2012

The objective of this study was to experimentally investigate the effect of heat curing methods on the temperature history and strength development of slab concrete exposed to $-10^{\circ}C$. The goal was to determine proper heat curing methods for the protection of nuclear power plant structures against early-age frost damage under adverse (cold) conditions. Two types of methods were studied: heat insulation alone and in combination with a heating cable. For heat curing with heat insulation alone, either sawdust or a double layer bubble sheet (2-BS) was applied. For curing with a combination of heat insulation and a heating cable, an embedded heating cable was used with either a sawdust cover, a 2-BS cover, or a quadruple layer bubble sheet (4-BS) cover. Seven different slab specimens with dimensions of $1200{\times}600{\times}200$ mm and a design strength of 27 MPa were fabricated and cured at $-10^{\circ}C$ for 7 d. The application of sawdust and 2-BS allowed the concrete temperature to fall below $0^{\circ}C$ within 40 h after exposure to $-10^{\circ}C$, and then, the temperature dropped to $-10^{\circ}C$ and remained there for 7 d owing to insufficient thermal resistance. However, the combination of a heating cable plus sawdust or 2-BS maintained the concrete temperature around $5^{\circ}C$ for 7 d. Moreover, the combination of the heating cable and 4-BS maintained the concrete temperature around $10^{\circ}C$ for 7 d. This was due to the continuous heat supply from the heating cable and the prevention of heat loss by the 4-BS. For maturity development, which is an index of early-age frost damage, the application of heat insulation materials alone did not allow the concrete to meet the minimum maturity required to protect against early-age frost damage after 7 d, owing to poor thermal resistance. However, the combination of the heating cable and the heat insulating materials allowed the concrete to attain the minimum maturity level after just 3 d. In the case of strength development, the heat insulation materials alone were insufficient to achieve the minimum 7-d strength required to prevent early-age frost damage. However, the combination of a heating cable and heat insulating materials met both the minimum 7-d strength and the 28-d design strength owing to the heat supply and thermal resistance. Therefore, it is believed that by combining a heating cable and 4-BS, concrete exposed to $-10^{\circ}C$ can be effectively protected from early-age frost damage and can attain the required 28-d compressive strength.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.404-408
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• 1999

Effects of heating time and radiation under high temperature on the properties of thermal, mechanical and shielding ability of modified (KNS-101), hydrogenated bisphenol-A(KNS-201) type epoxy resin and phenol-novolac(KNS-301) type epoxy resin based neutron shielding materials that are used for shipping casks for radioactive material have been investigated. At early stages, the offset temperatures of KNS-101, KNS-201 and KNS-301 increased with the heating time under high temperature, but it was rarely affected by the heating time in the later stages. In addition, the thermal conductivities of KNS-101 and KNS-201 decreased with heating time, but that of KNS-301 increased with the heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials decreased with heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials of KNS-101 and KNS-301 increased with heating time, but those of KNS-201 decreased with heating time. The shielding ability of neutron shielding materials slightly increased with the radiation dose, and shielding abilities of shielding materials of KNS-101 and KNS-201 were affected to a more extent than that of KNS-301 by radiation dose under high temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.6
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• pp.533-539
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• 2008

An high frequency induction hardening technology of vehicle body press-formed of thin sheet steel has been developed to increase the strength of vehicle body parts locally by high frequency induction heating, thereby eliminating the need for reinforcements. And this technique for increasing the tensile strength of sheet steel was practically applied to the front floor cross member and center pillar reinforcement of a passenger car. The side impact behavior has been investigated when induction hardening technology is applied to the conventional low-carbon steel and weight reduction of an automotive body is expected. In this paper, basic experiments were performed for the hat-shaped specimen under high frequency induction heating process. Martensitic transformation was found in the heating zone through microscopic observation which showed higher hardness. In addition, the hardness and strength of the center-pillar specimen made of boron steel increased remarkably by high frequency induction heating.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.155-156
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• 2018

In this study, surface spalling and explosive spalling of ring-type ultra-high strength concrete under rapid heating and slow heating were investigated. In rapid heating, the internal temperature difference of the concrete is large, so that continuous surface spalling occurs. However, in slow heating, the difference in the internal temperature of the concrete is small, resulting in explosive spalling at a time. Since the heating condition has a great influence on the internal temperature of the concrete, it is necessary to consider the spalling of the concrete under various heating conditions.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.86-88
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• 2003

The characteristic of induction heating solder bump(solder ball: Sn-37Pb, Sn-3.5Ag, Sn-3.0Ag-0.5Cu) has analyzed in this paper. The initial condition of induction heating depends on the time and current. The shape of lead-free solder bump is better than lead solder. The shear strength of lead solder bump has decreased with aging time. The average of shear strength of solder bump is about 10N, 11N, and 11N respectively. The lead-free solder bump's shear strength is better than lead solder and varies irregularly with aging time.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.224-225
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• 2017

Ultra-high-strength concrete exposed to high temperature is likely to cause spalling. Spalling is caused by the vapor pressure of the concrete, and the vapor pressure may be different depending on the heating conditions of the concrete. Therefore, in this study, a ring-type restrained specimen was fabricated using ultra-high-strength concrete and the vapor pressure generated in the concrete by heating condition(rapid and slow heating) was evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.139-147
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• 2005

The lubricant impregnated MC nylon has good frictional properties, but its mechanical strength is inferior to steel for the mechanical elements. For the tribological application Nylon as gears, sliding bearings, cam and etc, the steel shafts are fitted in pre-heated nylon cylinder by a process of interference expansion fit and bonded by induction heating method. The joint shear strength of the two materials was measured by a universal test machine. From the study, the adhesive shear strength between these two materials was affected by the factors of the interference between nylon and steel, the size of nylon cylinder, knurl of steel shaft and inducting heating conditions. The most effective jointing conditions were analyzed and decided for the practical application in the industry.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.809-815
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• 1996

When Li2O.2SiO2 glass was crystallized between the temperature of maximum nucleation and the temperature of maximum crystal growth it was found that the control of heating rate had serious effect on the crystallinity and microstructure and the greatly changed physical properties. Density and elastic modulus tends to increase but thermal expansion coefficient decreased with increased crystallinity. When heating rate between the tempe-rature of maximum nucleation and the temperature of maximum crystal growth was 10~5$0^{\circ}C$/hr. crystallinity was increased to result in the increment of strength. When nuclation was done at 44$0^{\circ}C$ for 5 hours and the temperature of crystal growth was held at 575$^{\circ}C$ strength was increased until crystallinity reached 65% and strength was decreased with higher crystallinity. These phenomena could be explained that even for the same crystallinity different heat rates resulted in different number and size of cracks.

• Geophysics and Geophysical Exploration
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• v.23 no.1
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• pp.1-12
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• 2020

In the development of geodynamic structures such as subduction and rift zones, a weakening mechanism is essential for localized weak zone formation in the lithosphere. Shear heating, a weakening mechanism, generates short-wavelength temperature elevation in the lithosphere; the increased temperature can reduce lithospheric strength and promote its breakup. A two-dimensional elastoplastic extensional basin model was used to conduct benchmarking based on previous numerical simulation studies to quantitatively analyze shear heating. The amount of shear heating was investigated by controlling the yield strength, extensional velocity, and strain- and temperature-dependent weakening. In the absence of the weakening mechanism, the higher yield strength and extensional velocity led to more vigorous shear heating. The reference model with a 100-MPa yield strength and 2-cm/year extension showed a temperature increase of ~ 50 K when the bulk extension was 20 km (i.e., 0.025 strain). However, in the yield-strength weakening mechanism, depending on the plastic strain and temperature, more efficient weakening induced stronger shear heating, which indicates positive feedback between the weakening mechanism and the shear heating. The rate of shear heating rapidly increased at the initial stage of deformation, and the rate decreased by 80% as the lithosphere weakened. This suggests that shear heating with the weakening mechanism can significantly influence the strength of relatively undamaged lithosphere.