• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.56-65
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• 2024

Cast austenitic stainless steels (CASS) and austenitic stainless steel weldments with a ferrite-austenite duplex structure are widely used in nuclear power plants, incorporating ferrite phase to enhance strength, stress relief, and corrosion resistance. Thermal aging at 290-325℃ can induce embrittlement, primarily due to spinodal decomposition and G-phase precipitation in the ferrite phase. This study evaluates the effects of thermal aging by collecting and analyzing various mechanical properties, such as Charpy impact energy, ferrite microhardness, and tensile strength, from various literature sources. Different model expressions, including hyperbolic tangent and phase transformation equations, are applied to calculate activation energy (Q) of room-temperature impact energies, and the results are compared. Additionally, predictive models for Q based on material composition are evaluated, and the potential of machine learning techniques for improving prediction accuracy is explored. The study also examines the use of ferrite microhardness and tensile strength in calculating Q and assessing thermal embrittlement. The findings provide insights for developing advanced prediction models for the thermal embrittlement behavior of CASS and the weldments of austenitic steels, contributing to the safety and reliability of nuclear power plant components.

• Elastomers and Composites
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• v.17 no.3
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• pp.151-158
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• 1982

The purpose of this study is to get comparitive results on the combined accelerator systems comprised of MBT, MBTS, DPG and CBS with TMTD, TMTM, Zn-MDC and DPG to SBR compound. Vulcanization characterstics and physical properties of the combined accelerators have been studied by mean of the Mooney viscometer, tensile testing machine, aging chamber and so on. According to the test results, TMTD with DPG system has shown faster Mooney scorch time than other system. The vulcanizate comprise of Zn-MDC with DPG and TMTD with DPG accelerator system has taken advantage of heat resistance.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1697-1699
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• 1996

EPDM compound can be cured with either the sulfur and peroxide based systems. In this study, heat resistance and weatherability of EPDM compounds depending on curing systems were investigated. The test results showed that the peroxide-cured EPDM was more resistant to heat ageing and UV photo-degradation than the sulfur-cured EPDM and it is due to C-C bond is more stable than C-S, S-S bond.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1408-1410
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• 1997

Arrhenius plots are useful in predicting long-term use temperatures of organic materials and in choosing parameters for accelerated aging. The effects of antioxidant on the heat resistance and temperature index of EPDM rubber used for electrical insulation were investigated. The short-time points were obtained by 50% retention of elongation at break.

• Fibers and Polymers
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• v.3 no.4
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• pp.174-178
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• 2002

A plasma treatment using saturated $CF_4$ gas was employed to improve the resistance of polypropylene fabrics to water wetting. The fabrics were significantly fluorinated even within a short treatment time of 30 seconds. The result of contact angle measurement indicated that such highly hydrophobic surface was considerably durable even after 150 days of aging.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.41-44
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• 1991

Time dependent analysis of prestressed concrete beams subjected to pure torsion is studied. The present theory covers the behavior from the service load range to the ultimate stage. The tensile resistance of concrete is appropriately considered. The biaxial stress effects due to diagonal cracking are also taken into account. The time dependent aging, creep and shringkage effects are modelled by employing the equivalent nonmechanical torque concept. The present theory allows more accurate prediction of the service load behavior of pretressed concrete members.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.501-504
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• 1997

We investigated the tracking and erosion resistance of the silicone rubber by Inclined-Plane Method. And. with the variation of experiment time, the chance of the leakage current waveform was evaluated. The typical leakage current waveform was the form of mixture of sinusoidal wave and rectifying wave. It is thought that the sinusoidal wave is due to conductivity of contaminant when wet. and the rectifying wave is due to arc of dry band.

• Archives of Pharmacal Research
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• v.27 no.4
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• pp.361-370
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• 2004

The discovery of insulin receptor substrate (IRS) proteins and their role to link cell surface receptors to the intracellular signaling cascades is a key step to understanding insulin and insulin-like growth factor (IGF) action. Moreover, IRS-proteins coordinate signals from the insulin and IGF receptor tyrosine kinases with those generated by proinflammatory cytokines and nutrients. The IRS2-branch of the insulin/IGF signaling cascade has an important role in both peripheral insulin response and pancreatic $\beta$-cell growth and function. Dysregulation of IRS2 signaling in mice causes the failure of compensatory hyperinsulinemia during peripheral insulin resistance. IRS protein signaling is down regulated by serine phosphorylation or protea-some-mediated degradation, which might be an important mechanism of insulin resistance during acute injury and infection, or chronic stress associated with aging or obesity. Under-standing the regulation and signaling by IRS1 and IRS2 in cell growth, metabolism and survival will reveal new strategies to prevent or cure diabetes and other metabolic diseases.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.48-53
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• 2000

The effects of added elements, such as Co or Nb, on wear properties of high speed steel by powder metallurgy(PM-HSS) had been evaluated in previous paper. The wear properties of materials, in fact, have been a]so influenced by heat-treating conditions. In this paper, the effects of heat-treating conditions on wear properties of PM-HSS have been evaluated. The wear tests have been performed as same conditions as previous paper using PM-HSS(5%Co-1%Nb) heat-treated under different quenching and tempering temperature. The result of this paper shows that wear resistance of PM-HSS is improved with relatively high quenching temperature. However tempering temperature is not sensitve to the wear resistance in range of high quenching temperature. It may be deduced by the fact that the shear strength of matrix by strengthening mechanisms of quenching aging in addition to dispersion-hardening is improved.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.84-86
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• 2001

Acrylonitrile Butadiene Rubber (NBR) has been used as a transformer gasket material because the transformer gaskets should have high resistivity to oil and should not swell and deform when it contact to insulating oils. Serious cracks were observed in the gaskets being used and ozone test was performed on new, specimens. Cracks were also observed on specimens. So we have performed the following tests on the anti-oxidants containing new gaskets according in accordance with KEPCO purchase specifications; ozone resistance, oil resistance, mechanical properties before and after aging.