• 열처리공학회지
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• 제10권1호
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• pp.30-39
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• 1997

After changing the heat treating atmosphere of nitrogen gas, argon gas and vacuum, the nitrogen contents, microstructural changes, hardness and corrosion resistance of 0.25wt.%N alloyed super duplex stainless steel have been investigated in the temperature range from $1050^{\circ}C$ to $1350^{\circ}C$. The nitrogen content showed to be increased up to 0.36wt.% after heat treating the specimen in nitrogen gas at $1200^{\circ}C$, while the decrement of nitrogen content in vacuum atmosphere was shown down to 0.03wt.% at $1350^{\circ}C$. After heat treating in the mixed gas atmosphere of argon and nitrogen at $1250^{\circ}C$, the surface ${\gamma}$ phase existed as ${\alpha}+{\gamma}$ phase increased with increasing nitrogen gas content. The ${\gamma}$ single phase appeared at the surface above $80%N_2$ gas, while the surface ${\alpha}$ single phase was shown below $20%N_2$ gas. When heat treating the specimen in nitrogen gas at $1050^{\circ}C$, the hardness of austenite phases increased above Hv 40 at the surface layer compared to the hardness of the core parts, while decrement of denitriding effect caused to the hardness nearly unchanged between surface and the core parts after heat treating in vacuum atmosphere. The surface ${\gamma}$ single phase specimen showed superior corrosion resistance than the surface ${\alpha}$ single phase specimen. The surface ${\alpha}$ phase existed in the ${\alpha}+{\gamma}$ microstructure showed higher corrosion resistance after heat treating in the nitrogen gas atmosphere than the ${\alpha}$ phase heat treated in the argon gas and vacuum atmosphere.

• 한국건축시공학회지
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• 제2권2호
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• pp.145-150
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• 2002

The hydration of cement paste occurs when the cement is miked with water. During the hydration, hydration heat causes the thermal stress depending on the site of concrete and the cement content. Especially in the high-strength concrete, we must give care to the concrete due to its large cement content. In this study conduction calorimeter and concrete insulation hydration heat meter were used to investigation the hydration heat characteristics of cement and concrete. To reduce hydration heat of high-strength concrete, several types of replacement of fly-ash and blast-furnace slag powder were used in this experiment. As a result of this study, it was found that hydration heat of high-strength concrete was reduced by replacement of fly-ash and blast-furnace slag powder. In case of high-strength concrete using blast-furnace slag powder, the max-heat arrival time was delayed but an effect of heat reduction was lower than a case of high-strength concrete using fly-ash, because it was considered that the heat-dependence property of blast-furnace slag powder was higher than that of fly-ash.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권12호
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• pp.601-605
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• 2004

In this paper, we investigated ionic impurities and physical properties by change of carbon black content, which is asemiconductive material for underground power transmission. Specimens were made into sheet form with three existing resins and nine specimens for measurement. The ionic impurities of the specimens were measured using anICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer), and the density of specimens was measured by a density meter. Specific heat (Cp) was then measured using aDSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from 0[$^{\circ}C$] to 200[$^{\circ}C$], and heating temperature was 4[$^{\circ}C$/min]. Ionic impurities were measured to be high according to increases in the content of carbon black from this experimental result and density was also increased according to these properties. In particular, the impurity content values of A1 and A2, and existing resins, were measured at more than 4000[ppm]. Specific heat from the DSC results was lowered according to augmentation in the content of carbon black. The ionic impurities of carbon black containing Fe, Co, Mn, Al and Zn are forms of rapidly passed kinetic energy that increase the number of times breaking occurs during unit time with the near particles according to an increase in the vibration of particles by the applied heat energy.

• 한국식품과학회지
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• 제23권6호
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• pp.656-660
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• 1991

해바라기 종실제품(종실, 착유박, 농축단백, 분리단백)의 수분흡착열을 $10,\;20,\;30^{\circ}C$에서 측정한 등습곡선(isostere)으로부터 구하였고, 수분함량에 따른 흡착열의 변화를 Hunter 방정식에 의거하여 해석하였다. Hunter 방정식에 의한 예측치는 실측결과와 잘 일치하였으며 단백질함량이 증가할수록 정확도가 높았다. 흡착열은 수분함량이 높을수록 감소하였으며, 단백질함량이 높을수록 증가하였다. 해바라기종실의 흡착열은 건물기준 수분함량 4-12%에서 11.8-10.6 kcal/mole이었으며 분리 단백의 경우 수분함량 6-20%에서 12.4-11.0kcal/mole 이었다.

• 열처리공학회지
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• 제3권4호
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• pp.23-40
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• 1990

This study has been carried out to investigate into some effects of Mn content with varying amounts and austenite grain size on hardenability in boron-added Fe-C-Cr-Mo alloy systems. (1) Austenite grains have been found to hardly grow in the temperature range of $900^{\circ}C$ to $950^{\circ}C$, whereas they grow rapidly in the temperature range of $975^{\circ}C$ to $1100^{\circ}C$. (2) Austenite grain growth is considerably small with increasing holding time at a given austenitizing temperature and is, in particular, hardly found to occur at a temperature of $900^{\circ}C$. (3) The hardenability improves ramarkably as Mn content is increased at three different austenitizing temperatures $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. (4) The maximum hardenability is obtained from steels A, B and C austenitized at the $900^{\circ}C$, although Mn content is varied in each specimen.

• 한국표면공학회지
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• 제38권6호
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• pp.227-233
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• 2005

Electrochemical characteristics of welded stainless steels containing Ti have been studied by using the electrochemical techniques in 0.5 M $H_2SO_4$+0.01 M KSCN solutions at $25^{\circ}C$. Stainless steels with 12 mm thick-ness containing $0.2{\~}0.9 wt\%$ Ti were fabricated with vacuum melting and following rolling process. The stainless steels were solutionized for 1hr at $1050^{\circ}C$ and welded by MIG method. Samples were individually prepared with welded zone, heat affected zone, and matrix for intergranular corrosion and pitting test. Optical microscope, XRD and SEM are used for analysing microstructure, surface and corrosion morphology of the stainless steels. The welded zone of the stainless steel with lower Ti content have shown dendrite structure mixed with $\gamma$ and $\delta$ phase. The Cr-carbides were precipitated at twin and grain boundary in heat affected zone of the steel and also the matrix had the typical solutionized structure. The result of electrochemical measurements showed that the corrosion potential of welded stainless steel were Increased with higher Ti content. On the other hand, reactivation($I_r$), passivation and active current($I_a$) density were decreased with higher Ti content. In the case of lower Ti content, the corrosion attack of welded stainless steel was remarkably occurred along intergranular boundary and ${\gamma}/{\delta}$ phase boundary in heat affected zone.

• 한국토양비료학회지
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• 제45권1호
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• pp.1-8
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• 2012

The thermal properties including volumetric heat capacity, thermal conductivity, thermal diffusivity, and diurnal and annual damping depths of 10 representative soil series of Korea were calculated using some measurable soil parameters based on the Taxonomical Classification of Korean Soils. The heat capacity of soils demonstrated a linear function of water content and ranged from 0.2 to $0.8cal\;cm^{-3}^{\circ}C^{-1}$ for dry and saturated medium-textured soil, respectively. A small increase in water content of the dry soils caused a sharp increase in thermal conductivity. Upon further increases in water content, the conductivity increased ever more gradually and reached to a maximum value at saturation. The transition from low to high thermal conductivity occurred at low water content in the soils with coarse texture, and at high water content in the other textures. Thermal conductivity ranged between $0.37{\times}10^{-3}cal\;cm^{-1}s^{-1}^{\circ}C^{-1}$ for dry (medium-textured) soil and $4.01{\times}10^{-3}cal\;cm^{-1}s^{-1}^{\circ}C^{-1}$ for saturated (medium/coarse-textured) soil. The thermal diffusivity initially increased rapidly with small increases in water content of the soils, and then decreased upon further increases in the soil-water content. Even in an extreme soil with the highest diffusivity value ($1.1{\times}10^{-2}cm^2s^{-1}$), the daily temperature variation did not penetrate below 70 cm soil depth and the yearly variation not below 13.4 m as four times of damping depths.

• Journal of the Korean Wood Science and Technology
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• 제16권4호
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• pp.10-39
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• 1988

This study investigated the temperatures and relative humidities in the semi-greenhouse type solar dryer with a black rock-bed heat storage and without heat storage and outdoor temperature and relative humidity at 9 a.m. and 2 p.m.. A comparison was made of the drying rates, final moisture contents, moisture content distributions, casehardening stresses, drying defects, volumetric shrinkage of dried lumber for solar- and air-drying from the green condition of mixtures of Douglas-fir, lauan, taun, oak and sycamore 25mm- and 50 mm-thick lumber during the same period for four seasons, and heat efficiencies for solar dryer with and without the heat storage for saving of heat energy and the cost of lumber drying using the solar energy. The results from this study were summarized as follows: I. The mean weekly temperatures in the solar dryers were 3 to $6^{\circ}C$ at 9 a.m. and 9 to $13^{\circ}C$ at 2 p.m. higher than mean outdoor temperature during all the drying period. 2. The mean weekly relative humidities in the solar dryers were about 1 to 19% at 9 a.m. higher than the outdoor relative humidity. and the difference between indoor and outdoor relative humidity in the morning was greater than in the afternoon. 3. The temperatures and relative humidities in the solar dryer with and without the heat storage were nearly same. 4. The overall solar insolation during the spring months was highest and then was greater in the order of summer, atumm, and winter month. S. The initial rate of solar drying was more rapid than that of air drying. As moisture content decreased, solar drying rate became more rapid than that of air drying. The rates of solar drying with and without heat storage were nearly same. The drying rate of Douglas-fir was fastest and then faster in the order of sycamore, lauan, taun and oak. and the faster drying rate of species, the smaller differences of drying rates between thicknesses of lumber. The drying rates were fastest in the summer and slowest in the winter. The rates of solar drying during the spring were more slowly in the early stage and faster in the later stage than those during the autumn. 6. The final moisture contents were above 15% for 25mm-thick air dried and about 10% for solar dried lumber, but the mean final MCs for 50mm-thick lumber were much higher than those of thin lumber. The differences of final MC between upper and lower course of pile for solar drying were greater than those of pile for air drying. The differences of moisture content between the shell and the core of air dried lumbers were greater than those of solar dried lumber, smallest in the drying during summer and greatest in the drying during winter among seasons. 7. Casehardening stresses of 25mm- and 50mm-thick dried lumber were slight, casehardening stress of solar dried lumber was severer than that of air dried lumber and was similar between solar dried lumber with and without heat storage, Casehardening stresses of lumber dried during spring were slightest and then slighter in the order of summer, autumn, and winter. Casehardening stresses of Douglas -fir, sycamore and lauan were slight, comparing with those of taun and oak. 8. Maximum initial checks of 25mm-thick lumber occurred above and below fiber saturation point and those of 50mm-thick lumber occurred in the higher moisture content than thin lumber. As the moisture content decreased, most of checks were closed and didn't show distinct difference of the degree of checks among drying methods. The degree of checks were very slight in case of Douglas-fir and lauan, and severe in case of taun and oak. The degree of checks for 50mm-thick lumber were severer than those for 25mm-thick lumber. 9. The degree of warpage showed severe in case of oak and sycamore lumber, but no warping was found in case of Douglas-fir, lauan and taun. 10. The volumetric shrinkages of taun and oak were large and medium in case of Douglas-fir, lauan and sycamore. 11. Heat efficiencies of solar dryer with heat storage were 6.9% during spring, 7.7% during summer, 12.1% during autumn and 4.1% during winter season. Heat efficiency of solar dryer with heat storage was slightly greater than that of without heat storage. As moisture content of lumber decreased, heat efficiency decreased.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.89-96
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• 2005

To improve the mean-life and reliability of power cables, we have investigated the volume resistivity and thermal properties demonstrated by changing the content of carbon black, an additive of the semiconductive shield for underground power transmission. Nine specimens were made of sheet form for measurement. Volume resistivity of the specimens was measured by a volume resistivity meter after 10 minutes in a preheated oven at temperatures of both 25$\pm$1[$^{\circ}C$] and 90$\pm$ 1[$^{\circ}C$]. As well, specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from 0[$^{\circ}C$] to 200[$^{\circ}C$], and heating temperature was 4[$^{\circ}C$/min]. From these experimental results, volume resistivity was high according to an increase of the content of carbon black. Specific heat was decreased, while thermal conductivity was increased according to a rise in the content of carbon black. Furthermore, both specific heat and thermal conductivity were increased by heating temperature because the volume of materials was expanded according to a rise in temperature.

• 한국식품조리과학회지
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• 제32권3호
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• pp.245-252
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• 2016

Purpose: To provide the public with nutritional information on consumption types of garlic, we evaluated the influence of heat treatment method on the nutritional contents of different species of garlic. Methods: We determined the content of general components, minerals, vitamins, and fatty acids in each species of garlic produced in Seosan and Goheung by heating with blanching or microwave roasting. Results: The results of the two-way analysis of variance test indicated that the species in particular, as well as method of heat treatment and interaction, had an influence on nutritional content. The moisture and crude fat content was higher in Southern type garlic than in Northern type garlic, while crude proteins, crude ash, and dietary fibers were more abundant in Northern type garlic than in Southern type garlic. With regard to the total mineral content, K, P, Mg, and Ca were the main components in Northern type garlic and Southern type garlic. Moreover, unsaturated fatty acids showed high levels in both Northern type garlic and Southern type garlic, with more abundant linoleic acid. Overall, Northern type garlic showed a higher content of minerals and fatty acids, while more vitamin B was present in Southern type garlic. In addition, the results indicated that the content of general components (dietary fiber excluded) was increased in both Northern type garlic and Southern type garlic upon heat treatment. Blanching resulted in increased mineral and fatty acid content in Southern type garlic and decreased content in Northern type garlic, indicative of species differences; conversely, microwave roasting contributed to an increase in the content in both Northern type garlic and Southern type garlic. Conclusion: The nutritional content of garlic is more dependent on species than the cooking method, and grilling is associated with less nutrient loss than blanching.