• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.414-420
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• 2017

The thermal characteristics of concrete fabricated with blast furnace slag were investigated in this paper. Test parameters included water-binder ratio and the content of furnace slag. Experimental program were performed to measure mechanical properties including compressive strength and split tensile strength under high-temperature thermal cycling, and to measure thermal properties including thermal conductivity and specific heat. Test results showed that the residual compressive strength of mixtures with blast furnace slag was greater than that of mixture without blast furnace slag. In addition, thermal conductivity of mixtures with blast furnace slag was greater than that of mixtures without blast furnace slag. It indicates that blast furnace slag was favorable for charging and discharging in thermal energy storage system. Test results of this study would be used to design concrete module system of thermal energy storage.

• The Korean Journal of Food And Nutrition
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• v.17 no.1
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• pp.32-40
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• 2004

This Study was conducted to predict temperature profile of Jangjorim (boiled beef in soy sauce) food during retorting using the commercial NISA (Numerical Integrated Elements for System Analysis) program. NISA program is a good tool to simulate the temperature profile of a specific material based upon the finite element method. The cold point of Jangjorim food located not at the geometrical center but at 26.9 mm backward in y plane because specific heat of soy sauce was 20% higher than that of boiled beef. The effects of heat transfer coefficients on heat transfer during retorting process of Jangjorim were analyzed by response surface methodology (RSM). Independent variables were thermal conductivity of soy sauce, thermal conductivity of boiled beef, and convection heat transfer coefficient and dependent variables were temperature error and lethality error. Thermal conductivity of soy sauce was the most significant contributor among those (P<0.01).

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.204-211
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• 2021

We report, synthesis of high surface area composite carbon aerogel using additive based polymerization technique by incorporating graphitic porous carbon as additive. This additive was separately prepared using sol-gel polymerization of resorcinol-furfuraldehyde in iso-propyl alcohol medium at much above the routine gelation temperature to yield porous carbon (CA-IPA) having graphitic layered morphology. CA-IPA exhibited a unique combination of meso-pore dominated surface area (~ 700 m²/g) and good conductivity of ~ 300 S/m. The composite carbon aerogel (CCA) was synthesized by traditional aqueous medium based resorcinol-formaldehyde gelation with CA-IPA as additive. The presence of CA-IPA favored enhanced meso-porosity as well as contributed to improvement in bulk conductivity. Based on the surface area characteristics, CCA-8 composition having 8% additive was found to be optimum. It showed specific surface area of ~ 2056 m²/g, mesopore area of 827 m²/g and electrical conductivity of 180 S/m. The electrode formed with CCA-8 showed improved electrochemical behavior, with specific capacitance of 148 F/g & ESR < 1 Ω, making it a better choice as super capacitor for energy storage applications.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.387-397
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• 2011

In this study, we conducted the study of the merits and demerits of the laser flash and the divided-bar methods for measuring the thermal conductivity of rocks and investigated applicability of the divided-bar apparatus which was developed by KIGAM. The laser flash method can measure thermal diffusivity, specific heat capacity, and thermal conductivity of rocks with even small thickness (< ~3 mm) in the high temperature range($25-200^{\circ}C$) in non-contact mode. For the laser flash method, samples must be uniform and homogeneous. In the case of the divided-bar method, the apparatus measures only thermal conductivity of rock samples at the room temperature. We measured thermal conductivities of 12 rock samples with low density and high porosity using two methods. In the laser flash method, there exist potential errors caused by the effect of pulse dispersion and reflection by various minerals and porosity in rock samples; the difference in thermal conductivity values measured on the front surface and the opposite surface ranges from 0.001 to 0.140 W/mK with the standard deviation of 0.003~0.089 W/mK, which seems to be caused by heterogeneity of rock samples. On the contrary, the divided-bar apparatus shows stable thermal conductivity measurements and relatively small measurement errors; the difference in thermal conductivity values, just as we applied to the laser frash method, is 0.001~0.016 W/mK with the standard deviation 0.001~0.034 W/mK. In turn, the divided-bar method can be applied to more thick samples that are more representative of bulk thermal conductivity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.2
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• pp.105-109
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• 1983

Electrical conductivity of raw milk obtained from milk cans transported from various dairy farms was discussed in relation to the contents of lactose, chloride and Koestler number to check the possibility of its application as a method for evaluation and detection of abnormality of raw milk. Correlation between the electrical conductivity and Koestler number was recognized with a coefficient of 0.76. The percentages of abnormal milk based on the Koestler number 3.5, chloride content 0.14% and the electrical conductivity $6.260({\mu}mho/cm){\times}10^3$ were 14.0%, 15.3% and 14.0%, respectively. In case of, the watered and salted milk, measurement of the specific gravity was necessary as an auxiliary process because of the decreasing electrical conductivity with increasing water content.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.187-193
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• 2018

In this study, the electrical conductivity, transmittance and gas barrier properties of diamond-like carbon (DLC) thin films were studied. DLC is an insulator, and has transmittance and oxygen gas barrier properties varying depending on the thickness of the thin film. Recently, many researchers have been trying to apply DLC properties to specific industrial conditions. The DLC thin films were deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) process. The doping gas was used for the DLC film to have electrical conductivity, and the optimum conditions of transmittance and gas barrier properties were established by adjusting the gas ratio and DLC thickness. In order to improve the electrical conductivity of the DLC thin film, $N_2$ doping gas was used for $CH_4$ or $C_2H_2$ gas. Then, a heat treatment process was performed for 30 minutes in a box furnace set at $200^{\circ}C$. The lowest sheet resistance value of the DLC film was found to be $18.11k{\Omega}/cm^2$. On the other hand, the maximum transmittance of the DLC film deposited on the PET substrate was 98.8%, and the minimum oxygen transmission rate (OTR) of the DLC film of $C_2H_2$ gas was 0.83.

• Composites Research
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• v.34 no.5
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• pp.277-282
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• 2021

Graphene oxide can be reduced to graphene under supercritical fluid condition even without using a specific reducing agent or applying a high thermal process. In this study, a process for converting graphene oxide into graphene was studied under supercritical fluid conditions in methanol and ethanol solvents. When the structure of asprepared graphene was analyzed by using FE-SEM and XRD, the reduction of graphene oxide in supercritical fluid condition was more affected by the change of solvent than other variables such as concentration of graphene oxide and reaction time. The use of ethanol showed better results for the reduction than the use of methanol. The graphene prepared in this study was mixed with epoxy resin up to 20 wt.% to make composites, and the thermal conductivity of the composites were analyzed. Thermal conductivity of the composite increased proportionally with graphene loadings. The graphene prepared in supercritical ethanol condition was more effective on the thermal conductivity of the composite.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.550-557
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• 2023

In zinc-air batteries, the gel polymer electrolyte (GPE) is an important factor for improving performance. The rigid physical properties of polyvinyl alcohol reduce ionic conductivity, which degrades the performance of the batteries. Zinc acetate is an effective additive that can increase ionic conductivity by weakening the bonding structure of polyvinyl alcohol. In this study, polymer electrolytes were prepared by mixing polyvinyl alcohol and zinc acetate dihydride. The material properties of the prepared polymer electrolytes were analyzed by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Also, Electrochemical impedance spectroscopy was used to calculate ionic conductivity. The electrolyte resistances of GPE, 0.2 GPE, 0.4 GPE, and 0.6 GPE were 0.394, 0.338, 0.290, and 0.213 Ω, respectively. In addition, 0.6 GPE delivered 0.023 S/cm high ionic conductivity. Among all of the polymer electrolytes tested, 0.6 GPE showed enhanced cycle life performance and the highest specific discharge capacity of 11.73 mAh/cm² at 10 mA. These results verified that 0.6 GPE improves the performance of zinc-air batteries.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.182-189
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• 2021

Porous ceramics were manufactured using the foaming method for the development of inorganic insulating materials. Silica fume and SiO₂ were used as main raw materials, and bentonite was used as a rapid setting agent for uniform structure formation of porous ceramics. The porous ceramics were sintered at 1200℃, and porosity, density, compressive strength, microstructure and thermal conductivity were analyzed. As the content of silica fume to SiO₂ of the porous ceramics increased 70 to 90 %, the specific gravity increased from 0.63 to 0.69, and the compressive strength increased from 9.41 Mpa to 12.86 Mpa. But, the porosity showed a tendency to decrease from 72.07 % to 70.82 %, contrary to the specific gravity. As a result of measuring the thermal conductivity, the porous ceramic with a silica fume content of 70 % showed a thermal conductivity of 0.75 to 0.72 W/m·K at 25 to 800℃, respectively, and, another that a silica fume content of 90 % showed a 0.66~0.86 W/m·K. So the lower the silica f ume content, the lower the thermal conductivity, which was conf irmed to be consistent with porosity result. As a result of microstructure analysis using SEM (Scanning Electron Microscope), pores in the range of tens to hundreds ㎛ were observed inside and outside the porous ceramic, and it was confirmed that the pore distribution was relatively uniform.

• Journal of Korean Society of Forest Science
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• v.88 no.3
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• pp.292-298
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• 1999

Huber value and leaf specific conductivity were investigated for determining the hydraulic conductance of six deciduous hardwood species subjected to five levels of artificial shade treatments. Huber values measured in full sun were in the ranges of $1.5{\sim}9.1mm^2/dm^2$, $1.3{\sim}2.6mm^2/dm^2$, $1.5{\sim}5.3mm^2/dm^2$ in June, July, and September, respectively in the first year. The values generally decreased with increasing the shading in most of the species studied. Because of early defoliation in September, most of the values measured were also higher in September than in July. Huber values were quite different between those of the first year and those of the second year in most of the species studied, but the seasonal variation of Huber values and shading effects to the values seemed to be similar between the first and the second years. The values of leaf specific conductivity(LSC) measured in Betula platyphylla var. japonica. B. schmidtii, Zelkova serrata, Acer mono for 2 years were in the range of $4.0{\sim}80.0{\mu}{\ell}/dm^2$ by season and by shading treatment. But in Ligustrum obtusifolium and Prunus sargentii, the values were in the ranges of $4.0{\sim}280.0{\mu}{\ell}/dm^2$ and $8.0{\sim}120{\mu}{\ell}/dm^2$, respectively with having quite different values compared with those of the above species. Seasonal variation of LSC values was more or less irregular by species and by treatment year, but the LSC values of B. platyphylla vac. japonica, B. schmidtii, and P. sargentii in the first year and also those of Z. serrata and P. sargentii in the second year were mostly higher in September than in July. The LSC values seemed to be generally decreased with increasing the artificial shading in all of the species studied.