• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.19-23
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• 2008

We have fabricated pressure sensitive paint films consisting of PtTFPP activators dispersed in fluorinated polymer matrix. This matrix material is unique in its composition and structure. We evaluated the oxygen quenching effects, and thus the pressure sensitivity, of the fabricated films in terms of various processing parameters. Based on the experimental results, we anticipate that a good but new pressure sensitive paint would be presented through further elaboration of the polymer compositions and optimization of the processing conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.240-243
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• 1997

The Quenching and Self Tempering (QST) rolling is treated in terms of an advance process on Controlled Rolling and Cooling Technology (CRCT). In the analysis, the effect of this process is governed by both quenching and finishing conditions in the related with temperature. The objective of the QST model is to simulate the temperature gradient of the stock being rolled in the rolling mill. A comparison of computer simulated and manufactured micro structure as well as mechanical properties shows a good consistency. The micro structure of this high-strength round bar consists of tempered martensite and ferrite + pearlite phases.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.2
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• pp.11-16
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• 1989

Understanding and control of thermal history of heat-treated components are very important in heat treating process. A computer program was developed for prediction of thermal history in quenching process with various cooling media and agitation conditions. Computer simulation of heat flow in quenching treatment of spur gear of SCM 22 H was carried out by two and three dimensional finite difference method. Distributions of microstructure and hardness in heat-treated spur gear were predicted by computer simulation, and the results showed a good agreement with the experiments. It was concluded that the

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.252-261
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• 2017

This study examined the effect of heat treatment on the microstructure and mechanical properties of J55 line pipe steel. The experiments were carried out at under the following various conditions: austenization temperature($880^{\circ}C$, $910^{\circ}C$, $940^{\circ}C$), cooling methods(water quenching, oil quenching) and tempering temperature(none, $550^{\circ}C$, $650^{\circ}C$). The phase diagram and CCT curve were simulated based on the chemical composition of J55 steel to predict the microstructures. In the results, A1, A3 temperature decreased. As the austenization temperature increased, existing austenite grains grew exponentially which seriously degraded their mechanical properties. Various microstructures, including martensite, bainite, ferrite, and pearlite, developed in accordance with the heat treatments and were closely correlated with hardness, tensile strength and toughness. Martensite was formed after water quenching, but bainite and ferrite appeared after oil quenching. FeC precipitation formed and coarsened during tempering, which improved their toughness.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.3 no.1
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• pp.11-21
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• 1999

The effect of sulfite on barley seedlings was investigated through Chl content, the electron transport activity of the photosystem, and Chl fluorescence. Barley leaves were harvested every 12 hrs during greening periods, and were then treated with a sulfite solution in either light or dark conditions. In both cases, the Chl content decreased in comparison with the control at any greening period. After sulfite treatment in the light, the activity of PS I decreased slightly, yet that of PSII showed a decrease of about 15%. The values of Fv, qP and qE decreased, however, the value of ql increased compared with the control. In addition, the value of qE decreased in leaves greened more than 12 hrs compared with that of the control. This indicates that the photosynthetic complex involved in energy dependent fluorescence quenching is undeveloped in a 12 hrs greened leaf, accordingly, it was a hardly affected by sulfite. After sulfite treatment in the dark, the activities of PSII and PSI decreased slightly, there was a small change in the value of Fv, qP decreased, and qE and the ratio of qNP/q increased in comparison with the control. As a result, PSII and PSI were not inhibited, however, the redox of QA was inhibited, and the excited energy was lost through the nonphotochemical pathway. The effects of sulfite in light or dark conditions were not considerably different with the Chl fluorescence quenching analysis method. In both light and dark conditions, the value of qP significantly decreased with sulfite compared to that of the control. This implies that the redox of QA was inhibited by sulfite in both light and dark contions.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.6
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• pp.300-309
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• 2015

The aim of the present study was to predict the variations in microstructure and deformation occurring during gas carburizing and quenching processes of a SCM420H planetary gear in a real production environment using the finite element method (FEM). The motivation for the present study came from the fact that previous FEM simulations have a limitation of the application to the real heat treatment process because they were performed with material properties provided by commercial programs and heat transfer coefficients (HTC) measured from laboratory conditions. Therefore, for the present simulation, many experimentally measured material properties were employed; phase transformation kinetics, thermal expansion coefficients, heat capacity, heat conductivity and HTC. Particularly, the HTCs were obtained by converting the cooling curves measured with a STS304 gear without phase transformations using an oil bath with an agitator in a real heat treatment factory. The FEM simulation was successfully conducted using the aforementioned material properties and HTC, and then the predicted results were well verified with experimental data, such as the cooling rate, microstructure, hardness profile and distortion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1221-1226
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• 2012

The hot-stamping technique is a forming method used for manufacturing high-strength parts, in which a part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the mechanical properties of boron steel according to the heat-treatment conditions and the formability by using an Erichsen cupping test. Die quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching at 1173 K-0 s has a tensile strength of 1203 MPa. This is 79% of the tensile strength of the base metal (1522 MPa). The formability of boron steel was not significantly different from that at the mold temperature. However, it decreased with increasing forming speed. These properties provide practical information for the use of boron steels for hot stamping.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1479-1484
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• 2010

Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). Chlorophyll binding by the photosystem II subunit S protein, PsbS, was found to be necessary for energy-dependent quenching (qE), the major energy-dependent component of non-photochemical quenching (NPQ) in Arabidopsis thaliana. It is proposed that PsbS acts as a trigger of the conformational change that leads to the establishment of nonphotochemical quenching. However, the exact structure and function of PsbS in PSII are still unknown. Here, we clone and express the recombinant PsbS gene from Arabidopsis thaliana in E. coli and purify the resulting homogeneous protein. We used various biochemical and biophysical techniques to elucidate PsbS structure and function, including circular dichroism (CD), fluorescence, and DSC. The protein shows optimal stability at $4^{\circ}C$ and pH 7.5. The CD spectra of PsbS show that the conformational changes of the protein were strongly dependent on pH conditions. The CD curve for PsbS at pH 10.5 curve had the deepest negative peak and the peak of PsbS at pH 4.5 was the least negative. The fluorescence emission spectrum of the purified PsbS protein was also measured, and the ${\lambda}_{max}$ was found to be at 328 nm. PsbS revealed some structural changes under varying temperature and oxygen gas condition.

• Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.71-90
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• 2016

Steel nitriding is a thermo-chemical process leading to surface hardening and improvement in fatigue properties. The process is strongly influenced by many different variables such as steel composition, nitrogen potential, temperature, time, and quenching media. In the present study, the influence of such parameters affecting physic-chemical and mechanical properties of nitride steels was evaluated. The aim was to streamline the process by numerical-experimental analysis allowing defining the optimal conditions for the success of the process. Input parameters-output results correlations were calculated through the employment of a multi-objective optimization software, modeFRONTIER (Esteco). The mechanical and microstructural results belonging to the nitriding process, performed with different processing conditions for various steels, are presented. The data were employed to obtain the analytical equations describing nitriding behavior as a function of nitriding parameters and steel composition. The obtained model was validated, through control designs, and optimized by taking into account physical and processing conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.491-498
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• 2007

Flame characteristics of a methane-air premixed flame stabilized in a heat-regenerative small combustor were investigated experimentally. A small combustor having two counter-current shallow channels and a combustion space at one side was developed. In which the channel-gap was less the ordinary quenching distance of a stoichiometric methane-air premixed flame. Two design parameters of channel gap and thickness of the middle wall, which is located between two channels for unburned and burned gases, were varied. Flame stabilization conditions and characteristic flame behaviors were experimentally examined. Conclusively, Blowout conditions were governed mostly by the scale of the combustion space, and flashback conditions into the channel are dominated by the channel gap. Surface temperatures of the combustor were between 100 to 500$^{\circ}C$. Additionally, two distinctive flame stabilization modes of radiation and well-stirred?reaction were observed and their applicability was discussed.