• Journal of the East Asian Society of Dietary Life
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• v.13 no.1
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• pp.56-63
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• 2003

The dough fermentation and the quality of bread prepared with different kinds of water such as distilled water, tap water and diluted hot spring water(SW) from Gyungsan Sipan hot spring were investigated. Content of total soluble solid in the hot spring water was 8,765 ppm and contents of Na, Ca, Mg and K as major elements was 2,296, 287, 65 and 8 ppm, respectively. Content of Fe, Cu, Co, F, Zn, Al, S, Mo, Se and Si as minor elements was in the range of 0.002~5.2 ppm. The pH(6.95~7.68) of the dough prepared with diluted hot spring water(I, 55 times; II, 4 times; III, 2 times) was higher than that of distilled water. The dough volume after the 1st fermentation was expecially lower in the III, but the volume of the dough prepared with III adjusted pH to 5.5 was higher than that of the control. The hardness and the strength were higher than those of the control, but the scores were love. than those of the control in case of pH adjustment(pH 5.5). The cohesiveness was also lower than that of the control in the bread with diluted hot spring water. Softness and stickiness of the bread(III) were hisher than those of the control. But overall acceptability was the highest in the II.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.2015-2022
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• 2008

The effect of content of $Al_2O_3+Y_2O_3$ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites was investigated. The $SiC-ZrB_2$ electroconductive ceramic composites were pressurless-sintered for 2 hours at 1,700[$^{\circ}C$] temperatures with an addition of $Al_2O_3+Y_2O_3$(6 : 4 mixture of $Al_2O_3$ and $Y_2O_3$) as a sintering aid in the range of $8\;{\sim}\;20$[wt%]. Phase analysis of $SiC-ZrB_2$ composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and In Situ YAG($Al_5Y_3O_{12}$). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.02[%], 81.58[MPa], 31.44[GPa] and 1.34[GPa] for $SiC-ZrB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from $\beta$-SiC into $\alpha$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. The electrical resistivity showed the lowest value of $3.l4{\times}10^{-2}{\Omega}{\cdot}cm$ for $SiC-ZrB_2$ composite added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at 700[$^{\circ}C$]. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all negative temperature coefficient resistance (NTCR) in the temperature ranges from room temperature to 700[$^{\circ}C$]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• Journal of Conservation Science
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• v.26 no.1
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• pp.25-32
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• 2010

The yellowing is always occurred phenomena in epoxy restoration material of antic-ceramics. For re-restoration of remains with epoxy restoration material, the epoxy elimination step is the first one in all course of restoration In this paper, the chemically elimination treatments methods of epoxy in various antic-ceramics were discussed. We fabricated the epoxy elimination material for antic-ceramics restoration which were made up Dichloromethane and Dichlormethane based Dimethylformamide solution. Dichloromethane and Dichloromethane + Dimethylformamide mixture were applied to epoxy in various antic-ceramic sample. Particularly, Dichloromethane + Dimethylformamide solution had the best result in variation of color change, gloss, vending strength, weight, exfoliation time test after deposition in this solution. Dichloromrthane had the volume increase characteristics for epoxy material and Dimethylformamide had the mollification ones. So, Dichloromathane increased exfoliation in approximal surface of the epoxy material and antic ceramic, and Dimethylformamide decreased the surface hardness of epoxy. In this result, epoxy material even inside of ceramic that have very weak inside bonding is adaptable and stable eliminated. And in order to show the perfect elimination of this material, we successfully dissolve the epoxy restoration material in one antic pottery that is in one university museum's possession using this mixture. So, there is guarantee in the eternity and stabilization of restoration for antic-ceramics.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.811-823
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• 2019

Slip form method is applied to many cases of a shaft these days because it is safer, more economical and faster than cast-in-place method. Slip-up height of the method is approximately 2.5 to 4.0 m/day. If the temperature of concrete is outside the range of 10 to 30℃, the effects of changes in strength or elastic characteristics are significant. Therefore, it is difficult for slip-up speed to be higher than 3 m/day during winter construction. In addition, concrete has heat caused by hydration, which causes temperature cracking of hardened concrete. Therefore, temperature control of concrete curing is necessary for the continuous slip-up of slip form. In this study, the rebound hardness, time of ultrasonic waves propagation, heat of hydration, and external temperature are measured by developing heating panels and test devices for the continuous slip-up. Based on this, heating slip form is manufactured; this was applied to "Kimpo sites" and "Sinwol sites". The compared slip-up speed samples were 1.9 m/day or 0.200 m/hr on average at Gimpo sites (08:00~17:30) and 2.0 m/day or 0.210 m/hr at Sinwol sites.

• Journal of the Korean Wood Science and Technology
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• v.34 no.4
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• pp.15-21
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• 2006

Composite materials were prepared by impregnating water glass into the wood, followed by soaking in solutions of boric acid or phosphoric acid. The effects of these treatments on the physical and mechanical properties of the specimens and especially on its heat resistance were investigated. 1) Weight Percent Gain (WPG)s increased with increase of concentrations of water glass. However, there was little relationship between treatment temperatures and WPG. Generally, WPGs of double treated specimens were higher than single treated ones. 2) Percent shrinkages in each directions of the specimens treated with water glass had higher value than other specimens. Percent shrinkages of the specimens treated with boric acid or phosphoric acid were decreased as compared with untreated specimen. However, the specimens treated with water glass or phosphoric acid showed very high hygroscopicity. 3) The bending strengths of all specimens treated inorganic substances were slightly decreased. However, the values of compressive strength and hardness of most specimens treated with inorganic substances increased or similar to that of untreated specimen except for a phosphoric acid treated specimens. 4) The specimens had good heat resistance. Weight losses of all specimens treated inorganic substances were about 50~70%. In particular, the specimens treated at $300^{\circ}C$ and $400^{\circ}C$ almost kept their shapes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.5
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• pp.808-815
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• 2008

The composites were fabricated 61[vol.%] ${\beta}$-SiC and 39[vol.%] $TiB_2$ powders with the liquid forming additives of 8, 12, 16[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressureless annealing at 1650[$^{\circ}C$] for 4 hours. The present study investigated the influence of the content of $Al_2O_3+Y_2O_3$ sintering additives on the microstructure, mechanical and electrical properties of the pressureless annealed SiC-$TiB_2$ electroconductive ceramic composites. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), ${\beta}$-SiC(3C), $TiB_2$, and In Situ YAG($Al_2Y_3O_{12}$). The relative density of SiC-$TiB_2$ composites was lowered due to gaseous products of the result of reaction between SiC and $Al_2O_3+Y_2O_3$. There is another reason which pressureless annealed temperature 1650[$^{\circ}C$] is lower $300{\sim}450[^{\circ}C]$ than applied pressure sintering temperature $1950{\sim}2100[^{\circ}C]$. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[Mpa], 54.60[Gpa] and 2.84[Gpa] for SiC-$TiB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature. Abnormal grain growth takes place during phase transformation from ${\beta}$-SiC into ${\alpha}$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. The electrical resistivity showed the lowest value of 0.0117[${\Omega}{\cdot}cm$] for 16[wt%] $Al_2O_3+Y_2O_3$ additives at 25[$^{\circ}C$]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from $25^{\circ}C$ to 700[$^{\circ}C$]. The resistance temperature coefficient of composite showed the lowest value of $-2.3{\times}10^{-3}[^{\circ}C]^{-1}$ for 16[wt%] additives in the temperature ranges from 25[$^{\circ}C$] to 100[$^{\circ}C$].

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.10
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• pp.467-474
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• 2006

The effect of pressureless-sintered temperature on the densification behavior, mechanical and electrical properties of the $SiC-TiB_2$ electroconductive ceramic composites was investigated. The $SiC-TiB_2$ electroconductive ceramic composites were pressureless-sintered for 2 hours at temperatures in the range of $1,750{\sim}1,900[^{\circ}C]$, with an addition of 12[wt%] $Al_2O_3+Y_2O_3(6:4\;mixture\;of\;Al_2O_3\;and\;Y_2O_3)$ as a sintering aid. The relative density, flexural strength, vicker's hardness and fracture toughness showed the highest value of 84.92[%], 140[MPa], 4.07[GPa] and $3.13[MPa{\cdot}m^{1/2}]$ for $SiC-TiB_2$ composites of $1,900[^{\circ}C]$ sintering temperature at room temperature respectively. The electrical resistivity was measured by the Pauw method in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. The electrical resistivity showed the value of $5.51{\times}10^{-4},\;2.11{\times}10^{-3},\;7.91{\times}10^{-4}\;and\;6.91{\times}10^{-4}[\Omega{\cdot}cm]$ for ST1750, ST1800, ST1850 and ST1900 respectively at room temperature. The electrical resistivity of the composites was all PTCR(Positive Temperature Coefficient Resistivity). The resistance temperature coefficient showed the value of $3.116{\times}10^{-3},\;2.717{\times}10^{-3},\;2.939{\times}10^{-3},\;3.342{\times}10^{-3}/[^{\circ}C]$ for ST1750, ST1800, ST1850 and ST1900 respectively in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. It is assumed that because polycrystallines, such as recrystallized $SiC-TiB_2$ electroconductive ceramic composites, contain of porosity and In Situ $YAG(Al_5Y_3O_{12})$ crystal grain boundaries, their electrical conduction mechanism are complicated. In addition, because the condition of such grain boundaries due to $Al_2O_3+Y_2O_3$ additives widely varies with sintering temperature, electrical resistivity of the $SiC-TiB_2$ electroconductive ceramic composites with sintering temperature also varies with sintering condition. It is convinced that ${\beta}-SiC$ based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.312-318
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• 2008

In a pear fruit 'Chuhwangbae' was investigated the effect of the calcium-coated double paper bag on the physical properties of the paper bag, micro meteorological phenomena, and calcium contents in quality of fruit. The calcium-coated paper bag, compared with official paper bags, did not give any effect on light transmission ratio and tensile strength. The change of the inside relative humidity of the paper bag was a little compared with conventional paper bags, but there was no difference in temperature. The contents of the accumulated calcium of the pericarp was remarkably greater than conventional paper bags during the period of 65 days to 160 days after the full bloom, but the flesh remarkably increased at 160 days. The calcium content per concentration of calcium coating greatly increased in 12% of yellow double paper bags and 9, 12% of newspaper double paper bags in case of the pericarp, and in 3% of yellow double paper bags and 6, 9, 12% of newspaper double paper bags in case of the pericarp. As a result of treatment of a radioactive isotope, the amount of accumulated calcium in the pericarp continued until 60 hours after treatment, but there was no difference in the calcium amount between the flesh and no-treatment pericarp. As to the hardness of fruits at the time of harvest, there was no difference in the concentration in case of a yellow double bags. But newspaper double paper bags 6, 12% was significantly difference. Soluble solid remarkably increased in yellow double paper bags 6, 9% and yellow double paper bags 3, 6, 9%. Also, it did not effect on changes of the pericarp, fruit weight and the color of the pericarp.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.25-32
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• 2004

Some amount of cements can be added into the soil with high water content to improve the engineering properties. In such a case, it is difficult to predict and figure out the phase changes of the soil-cement mixture which is closely associated with workability of the soil-cement mixture. Changes in heat of hydration and hardness of the cement pastes are known to provide the useful information about the phase changes of the soil-cement mixtures. In this study, heat of hydration and cone penetration depth were measured from the specimens of cement paste and 3 soil-cement mixtures. From the experimental results, it was found that the phase changes of the soil-cement mixtures are the same as those of cement paste, and that shear strength of the mixtures abruptly increases when the heat of hydration is minimum. Initial setting time of the mixtures coincides with the state when fall cone penetration depth was 1.0 mm and it is defined as plastic limit of the mixtures. Initial setting time of the mixtures is retarded as soil/cement ratio is increased. Measurements of heat of hydration and fall cone apparatus could be the useful tools to predict the phase changes of tile soil-cement mixtures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.688-694
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• 2018

The mixture ratio of two-component liquid silicone is important for the inherent physical characteristics of the finished product. Therefore, it is necessary to uniformly control the ratio of the main material and the sub-material. In this paper, a mixing-ratio control system was designed, which consists of a digital flow meter and a flow control system to measure the flow rate of the raw materials and a pumping system to maintain constant pressure and transfer of the raw materials. In addition, a program was developed to control the organic interlocking and mixing ratio. For the verification of the developed system, we compared the actual weight of raw material with the value measured by the flow meter during pumping, and we measured the physical properties of the mixed material by making test samples with and without the application of the mixing-ratio improvement algorithm. The measured value was close to the reference value with a hardness range of 46-47 and tensile strength of 9.3-9.5 MPa. These results show that the mixing ratio of the liquid silicone is controlled within an error range of ${\pm}0.5%$.