• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.59-62
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• 2003

This study investigated the phase transformation of the $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, By) superconductor, and CCT (Continuous-Cooling-Transformation) along with the TTT (Time-Temperature-Transformation) diagrams are suggested according to the isothermal and continuous cooling heat-treatments. According to result of fabricated single crystal of RE-123 superconductor through TSMG method based on phase transformation neted among heat treatment process, when the ionic radius elements was decreased, RE-211 phase was well-distributed. According to result that examine about seed of pretreatment effect of TSMG method, magnetic hysteresis improved when preprocess among oxygen atmosphere in same seed. and used after. Effect of miscut expressed good superconducting special quality in case miscut uses big seed.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.6
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• pp.249-255
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• 2019

This study is intended to clarify the main microstructural factors that contribute to an increase of hardness during isothermal aging in Mg-Al alloy. For this work, Mg-9.3%Al alloy specimens were solution-treated at 688 K for 24 h followed by water quenching, and then aged at 473 K for up to 24 h. The aging at 473 K yielded nodular discontinuous precipitates (DPs) with (${\alpha}+{\beta}$) lamellar morphology at the grain boundaries, and the volume fraction of DPs increased from 0% to ~30% with increasing aging time up to 12 h. For the aging times longer than 12 h, further formation of DPs was substantially inhibited owing to the occurrence of significant continuous precipitation within the ${\alpha}-(Mg)$ matrix, and the density of continuous precipitates (CPs) becomes greater with increasing aging time. Hardness of the specimen was steadily increased with aging time up to 24 h. Microstructural examination on the aged specimens revealed that the increased overall hardness at the early stage of aging is associated with the increased volume fraction of DPs, but at the later stage of aging, where the amount of DPs was hardly changed, the increased hardness of the ${\alpha}-(Mg)$ matrix in response to the higher density of CPs within the matrix, plays a key role in increasing the overall hardness value.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.343-348
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• 2011

Since 2005, food waste has been separately collected and recycled to animal feed or aerobic compost in South Korea. However, the conventional recycling methods discharge process wastewater, which contain pollutant equivalent to more than 50% of food waste. Therefore, anaerobic digestion is considered as an alternative recycling method of food waste to reduce pollutant and recover renewable energy. Recent studies showed that hydrogen can be produced at acidogenic stage in two-stage anaerobic digestion. In this study, the authors investigated the effects of pretreatment time and pH low set value on continuous mesophilic hydrogen fermentation of food waste. Food waste was successfully converted to $H_2$ when heat-treated at $70^{\circ}C$ for 60 min, which was milder than previous studies using pH 12 for 1 day or $90^{\circ}C$. Organic acid production dropped operational pH below 5.0 and caused a metabolic shift from $H_2/butyrate$ fermentation to lactate fermentation. Therefore, alkaline addition for operational pH at or over 5.0 was necessary. At pH 5.3, the result showed that the maximum hydrogen productivity and yield of 1.32 $m^3/m^3$.d and 0.71 mol/mol $carbohydrate_{added}$. Hydrogen production from food waste would be an effective technology for resource recovery as well as waste treatment.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.197-206
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• 2017

The microstructure of a high-carbon and high-chromium cast steel (HK700) for cold-work die inserts was analyzed by advanced scanning electron microscopy. A continuous network of primary $M_7C_3$ carbide was developed among austenitic matrix after casting. A small amount of $M_2C$ was added to the carbide network owing to the enrichment of Mo and W during the solidification. After quenching in which the austenitization was performed at $1030^{\circ}C$ and double tempering at $520^{\circ}C$, the network structure of $M_7C_3$ was preserved while most of the matrix was transformed to martensite because of additional carbide precipitation. The $M_2C$ in the as-cast microstructure was also transformed to $M_6C$ due to its instability. The continuous network of coarse carbides owing to the absence of hot-working had little influence on the hardness after quenching and tempering, whereas it resulted in severe brittleness upon flexural loading.

• The Journal of Korean Medicine
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• v.40 no.1
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• pp.114-123
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• 2019

Objectives: The purpose of this study was to report the result and the satisfaction of Korean medicine treatment for patients with dysmenorrhea who participated in support program of Jeollabuk-do. Methods: The subjects of this study were 33 volunteers, suffering from primary dysmenorrhea. As the 'Dysmenorrhea Treatment Project', we conducted a dysmenorrhea program at 22 Korean medicine clinic and 1 Korean medicine hospital in Jeollabuk-do. From May to December 2018, we conducted the program and assessed the effect and satisfaction twice after first two menstrual cycles after Korean medicine treatment through questionnaire. They were treated by Korean medicine treatment such as herbal medicine, acupuncture, moxibustion, heat therapy, physical therapy and others in 2017. The results were measured by the visual analogue scale (VAS) and multidimensional verbal rating scale (MVRS) of overall pain. The disturbance in school activity for menstrual period and satisfaction of Korean medicine treatment were investigated by continuous rating scales. Results: The VAS score of overall pain was decreased significantly. Also the amount of the analgesic taken for menstrual period and the degree of disturbance in school activity were decreased significantly. Besides, the satisfaction of Korean medicine treatment was increased. Conclusions: This study might suggest that the Korean medicine treatment on dysmenorrhea is effective.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.800-808
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• 2008

Heat treatment is an important step for tool manufacture, but unavoidably generates dimensional distortion. This study investigated the continuous dimensional change and the anisotropic behavior of STD11 tool steel during austenitizing and tempering heat treatment especially using quenching dilatometer. Dilatometric results represented that the dimensional change along longitudinal direction was larger than that along transverse direction. Anisotropic phase transformation strain was produced in forged STD11 tool steel during heat treatment. Anisotropic dimensional change increased with increasing austenitizing temperature. After tempering, anisotropic distortion was partially reduced. FactSage thermodynamic equilibrium phase simulation and microstructural observation (FE-SEM, TEM) showed that large ($7{\sim}80{\mu}m$) elongated $M_7C_3$ carbides could be formed along rolling direction. The resolution of elongated carbides during austenitizing was found to be related with the change of martensite transformation temperature after heat treatment. Anisotropic size change of STD11 tool steel was mainly attributed to large elongated carbides produced during rolling process. Using dilatometric and metallographic examination, the possible mechanism of the anisotropic size change was also discussed.

• Journal of Korea Foundry Society
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• v.38 no.1
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• pp.9-15
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• 2018

Electromagnetic continuous casting (EMCC) was used to fabricate Ti-6Al-4V alloys with properties suitable for medical applications. Ti-6Al-4V alloy ingots fabricated by EMCC were subjected to heat treatment, such as residual stress removing (RRS), furnace cooling after solution treatment (ST-FC) and water-cooling after solution treatment (ST-WC), in order to obtain characteristics suitable for the standard. After component analysis, the microstructure and mechanical properties (tensile strength and elongation) were evaluated by ICP, gas analysis, OM, SEM, a Rockwell hardness tester and universal testing machine. The Ti-6Al-4V alloy ingot fabricated by EMCC was fabricated without segregation, and the lamellar structure was observed in the RRS and ST-FC specimens. The ST-WC specimen showed only martensite structure. As a result of evaluating the mechanical properties based on the microstructure results, we found that the water-cooled heat treatment condition after the solution treatment was most suitable for the Ti-6Al-4V ELI standard.

• Journal of Ocean Engineering and Technology
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• v.16 no.1
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• pp.64-70
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• 2002

This paper shows the results of the development of a small size of digital type continuous and intermittent welding auto-carriage based on microprocessor (Intel 80196KC) for welding process with long welding line. The developed welding auto-carriage loads welding torch and tracks welding line. It is an automaton largely used for welding process with a lot of long welding lines such as shipbuilding and structure. Most traditional auto-carriages have been developed based on analog circuit for open loop control. So this analog circuit welding auto-carriage cannon control welding speed. Specially welding auto-carriage for intermittent welding condition is so complicated and has the low precision of control performance in welding distance and non-welding distance. The auto-carriage developed in this paper has the following characteristics: It has not only functions of traditional carriage but also functions such as pseudo-welding process of big iron structures, intermittent welding in order to limit heat for welding thin plates, crater treatment of the final step of welding, acceleration at the initial step of welding and deceleration in the final step of welding. The main control board of auto-carriage, power supply system and DC motor drive wee developed and manufactured. The welding speed and the welding distance of the developed auto-carriage are controlled accurately by feedback control using photo-sensor. Hardware and software robust against the heat and noise produced on the welding process are developed.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.2
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• pp.90-96
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• 2003

The effect of betatizing temperature on microstructure and transformation characteristics in a Cu-AI-Ni based pseudoelastic alloy fabricated by heated mold continuous casting by using metallography, XRD and calorimetry. The microstructure of cast rod betatized at $600^{\circ}C$ revealed a ${\beta}_1$ parent phase and a ${\gamma}_2$ phase precipitated along the casting direction. When the cast rod was betatized at the elevated temperature above $600^{\circ}C$, the ${\gamma}_2$ phase is completely dissolved into the matrix so that the volume fraction of the ${\gamma}_2$ phase was decreased. The parent phase was stabilized by betatizing at $600^{\circ}C$. However, the ${\beta}_1$ parent phase was transformed to both ${{\beta}_1}^{\prime}$ and ${{\gamma}_1}^{\prime}$ martensites with increasing betatizing temperatures above $600^{\circ}C$, while $M_s$ and $A_s$ temperatures were decreased. The stress-strain curves for compression test were not same with betatizing temperature; the stress-strain curves of the specimen betatized at $600^{\circ}C$ and $700^{\circ}C$ were linear but those of the specimen betatized at $800^{\circ}C$ and $900^{\circ}C$ were not linear.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.1-5
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• 2010

Silver stabilizing layer of coated conductor has been prepared by dip coating method using organic silver complexes containing 10 wt% silver as a starting material. Coated silver complex layer was dried in situ with hot air and converted to crystalline silver by post heat treatment in flowing oxygen atmosphere. A dense continuous silver layer with good surface coverage and proper thickness of 230 nm is obtained by multiple dip coatings and heat treatments. The film heat treated at $500^{\circ}C$ showed good mechanical adhesion and crystallographic property. The interface resistivity between superconducting YBCO layer and silver layer prepared by dip coating was measured as $0.67\;{\times}\;10^{-13}\;{\Omega}m^2$. Additional protecting copper layer with the thickness of $20\;{\mu}m$ was successfully deposited by electroplating. The critical current measured with the specimen prepared by dip coating and sputtering on same quality YBCO layer showed similar value of ~140 A and proved its ability to replace sputtering method for industrial production of coated conductor.