• Corrosion Science and Technology
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• v.2 no.3
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• pp.117-126
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• 2003

Due to excellent corrosion resistance and mechanical properties, austenitic stainless steel is widely used as the material for chemical plants. nuclear power plants, and food processing facilities. But, the zone affected by heat in the range of 400 to $800^{\circ}C$ during welding loses corrosion resistance and tensile strength since Cr-carbide precipitation like $Cr_{23}C_6$ forms at the grain boundary and thereby takes place the intergranular corrosion. In this study, AISI 304 stainless steel with the added Nb of 0.3 to 0.7 wt% was solutionized at $1050^{\circ}C$ and sensitized at $650^{\circ}C$. Specimen was welded by MIG. The phase and the microstructure of the specimens were examined by an optical microscope, a scanning electron microscope, and a x-ray diffractometer. The corrosion characteristics of specimens were tested by electrolytic etching and by double loop electrochemical potentiokinetic reactivation method(EPR) in the mixed solution of 0.5M $H_2SO_4$ + 0.01M KSCN. The melting zone had dendritic structure constituted of austenitic phase and $\delta$-ferrite phase. Cr carbide at the matrix did not appear, as Nb content increased. At the grain boundaries of the heat affected zone, the precipitates decreased and the twins appeared. The hardness increased, as Nb content increased. The hardness was highest in the order of the heat affected zone>melted zone>matrix. According to EPR curve, as the Nb content decreased, the reactivation current density(Ir) and the activation current density(la) were highest in the order of the melted zone

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.477-482
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• 2005

We have investigated volume resistivity and thermal properties showed by changing the content of carbon black which is the component parts of semiconducting shield in underground power transmission cable. Specimens were made of sheet form with the nine of specimens for measurement. Volume resistivity of specimens was measured by volume resistivity meter after 10 minutes in the preheated oven of both 25$\pm$1[$^{\circ}C$] and 90$\pm$1[$^{\circ}C$]. And specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The measurement temperature ranges of specific heat using the BSC was from 20[$^{\circ}C$] to 60[$^{\circ}C$], and the heating rate was 1[$^{\circ}C$/min]. And the measurement temperatures of thermal conductivity using Nano Flash Diffusivity were both 25[$^{\circ}C$] and 55[$^{\circ}C$]. Volume resistivity was high according to an increment of the content of carbon black from these experimental results. And specific heat was decreased, while thermal conductivity was increased by an increment of the content of carbon black. And both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.6
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• pp.338-343
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• 2010

Mechanical properties and microstructures of medium carbon high manganese steels were investigated in terms of alloying elements such as Mn, C contents, and heat treatment condition. Austenite volume fraction was increased with increasing Mn content, leading to hardness decrease in the range of Mn content of above 10% after quenching and tempering. Such results are also supported by microstructural analysis and X-ray diffraction in that the increase in mangaese content results in the increase in austenite fraction. Studies on tempering condition indicated that not only hardness and tensile strength but also charpy impact values were reduced as tempering temperature were raised in the range of $250^{\circ}C$ to $600^{\circ}C$. It was also observed that fracture mode was changed from dimple to intergranular fracture. Such results are thought to be due to very fine carbide precipitation or impurity segreagation at grain boundaries as tempering temperature goes up. Heat treatment of Fe-5Mn-2Si-1Al-0.4C can be optimized by austenitizing at $850^{\circ}C$, air cooling and tempering at $250^{\circ}C$, resulting in 1950 MPa in Tensile strength, 17% in elongation and 23.3 $J/cm^2$ in charpy impact energy with high work hardening characteristics.

• Journal of Korea Foundry Society
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• v.24 no.4
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• pp.217-224
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• 2004

The effect of casting variable on the fluidity of high silicon, especially hypereutectic, heat-resistant ductile cast iron melt was investigated. When pouring temperature and silicon content were constant, that was increased with carbon content. When the pouring temperature and carbon content were constant, that also increased with the silicon content. Even though these results were thought to be caused by the high heat of fusion evolved during the crystallization of proeutectic graphite nodules, further research seemed to be needed. The fluidity for taller sprue was higher than that for smaller one.

• Korean Journal of Human Ecology
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• v.8 no.1
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• pp.125-134
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• 1999

The purpose of this study was to investigate the effects of heat transfer characteristics of fibers on the Qmax of insulating nonwovens. The effects of fiber type, moisture content, washing cycles on the Qmax were observed. The correlations between Qmax measured by KES-F7 system and subjective warm/cool touch perception test was analyzed. The results obtained were as followed: 1. Heat transfer characteristics of fibers effected on the Qmax of insulating nonwovens. 2. Moisture transport properties of fibers effected considerably on the Qmax of nonwovens and the increasing rate of Qmax by increasing moisture content was much higher at wool than polyester. 3. As a result of subjective perception test, subjective warm/cool touch and wettness of wool nonwoven was increased obviously by increasing moisture content. 4. At the same moisture content, wool nonwoven showed higher subjective cool touch and wetness than polyester. 5. In the physical properties of nonwovens, thickness was the most effective factor on the Qmax of insulating nonwovens.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.2
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• pp.144-151
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• 2004

The effect of the cobalt content on the thermodynamic and, heat and mass transfer properties of the $MmNi_{5-y}B_{y-z}C_z(y=0.5{\sim}1.5,\;z=0.5)$hydrogen storage alloys has been studied systematically. The P-C isotherms curves show that with increasing cobalt content in the alloys, the plateau pressure of the hydrogen absorption and desorption and enthalpy(${\Delta}H$) increases steeply and the plateau region becomes flat, while entropy(${\Delta}S$) decreases. Also at the constant cobalt content the hydrogen transfer rate decreases with the reaction temperature, while the initial reaction kinetics increases. But the initial reaction with hydrogen completes within 1min, although the reaction proceeds about 30minutes thereafter.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.10
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• pp.1549-1554
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• 2014

This study analyzed the production and heat stability of an emulsion made from buckwheat sprout extracts with high rutin content. To obtain high rutin contents, buckwheat was sprouted and the polyphenols and rutin were extracted from buckwheat sprouts. Concentrated extracts were made into an emulsion using a homo mixer and hydraulic homogenizer, after which heat stability was analyzed. The polyphenol contents were highest in ground sprouts grown for 8 days (10.66 mg/g), which was 10 times higher than those of buckwheat seeds. Extraction with 50% ethanol after blanching was the most effective method for obtaining extracts with higher polyphenol content and rutin content. Extracts were concentrated up to 60% soluble solid content and then emulsified using a homo mixer and hydraulic homogenizer. Heat stability of the emulsion passed through the hydraulic homogenizer was slightly higher than that made using the homo mixer. The heat stability of the emulsion was more strongly affected by heating time than temperature. In conclusion, the buckwheat concentrate emulsion passed through the hydraulic homogenizer was more heat stable than buckwheat extract alone.

• Journal of the Korean Home Economics Association
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• v.27 no.2
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• pp.75-83
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• 1989

In this study, effect of heat treatment on phytic acid, phosphorus compounds, and minerals in Korean soybean varieties was investigated. Results were summarized as follwo: 1. In the soybeans tested, protein content ranged from 34.6 to 44.6%, lipid content from 15.4 to 20.2%, fiber content from 4.8 to 6.1% and ash content from 4.5 to 5.9%. 2. Content range for phytic acid in soybean varieties was 1,300 to 1,542mg/100g and its mean was measured 1,392mg/100g. With increasing of the temperature, the phytic acid tends to be destroyed, especially at 6$0^{\circ}C$ the loss was averaged about 20%. 3. Total phosphorus content in soybean ranged from 607 to 681mg/100g and the decending order of phosphors content in soybean varieties was Millyang > Hwangkeum > Kwangkyo > Danyoup > Hill > Jangyoup. It was also destroyed with increasing temperature. 4. Phytate phosphorus content range in soybean was from 315.6 to 318.0mg/100g and decreased with increasing temperature. 5. Inorganic phosphorus content ranged from 95.5 to 110.0mg/100g and it was increased by temperature rising among soybean varieties. 6. Phytate phosphorus to total phosphorus ratio ranged from 5.2 to 5.7 and decreased by temperature rising. 7. The content of nonphytate phosphorus varied widely between soybean varieties and decreased with temperature increase. 8. The content of calcium, iron and magnesium ranged from 15.7 to 25.7mg/100g from 8.8 to 16.8mg/100g and from 121.9 to 143.6mg/100g respectively. The content of Mg showed small difference among soybean varieties. The change of mineral content with heat treatment in soybean did not give any meaningful change mineral content.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.427-432
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• 1995

Surface heat treatment using a laser beam or an electron beam is studied through numerical analyses and experiments. For the surface heat treatment process, a theoretical model is developed to predict the effects of laser beam power, travel speed and properties of a workpiece on the depth and width of the heat affected zone(HAZ). The shape of HAZ and the hardness of heat-treated surface are experimentally obtained using an electron beam. Three materials(SS41, S45C and S55C) are selected as workpiece materials. The hardness of HAZ is increased up to 3 times for materials of a low carbon content. The results of the numerical analysis are compared with those of experiments. The comparison shows that the numerical model predicts larger depths and widths.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.431-434
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• 2012

In this paper, heat-releasing sheets made of AlN powder and acryl binder as thermoset were prepared using tape casting method. The crystal structure and morphology, the thermal properties as nonvolatile solid content and thermal conductivity, and the surface resistance of heat-releasing sheet were measured by using X-ray diffractometer, field emission-scanning electron microscopy, thermo gravimetric analyzer and laser flash instrument, and surface resistance meter. It was proved that thermal conductivity is greatly affected by the content of binder in heat-releasing sheet. Superior thermal conductivity above 3.5 W/mK and suface resistance were obtained at heat-releasing sheet with above 90% of AlN powder.