• Economic and Environmental Geology
• /
• v.44 no.5
• /
• pp.387-397
• /
• 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 Soil and Groundwater Environment
• /
• v.13 no.2
• /
• pp.36-43
• /
• 2008

A method estimating unsaturated hydraulic conductivity using Guelph permeameter was developed and applied to the Ddanseom area of Kimhae in Nakdong River basin where the facilities producing bank-filtrated groundwaters are currently under construction. It is believed that the hydraulic conductivity values obtained from this study are useful in determination of recharges through unsaturated zone or from the river. The distribution of the surface hydraulic conductivity shows that sediments are finer downstream, implying the downstream part of Ddanseom has the higher potential of groundwater production.

• Journal of the Korean Ceramic Society
• /
• v.23 no.6
• /
• pp.37-44
• /
• 1986

Yttria-antimonia-stabilized zirconia was investigated with respect to the amount of $Sb_2O_3$ addition in the range of 0.5~5mole% to the base composition of $(ZrO)_{0.92}(Y_2O_3)_{0.08}$ The sinterbility modulus of rupture Vickers hardness evaporation of components phase form-tion and mcicrostructure were evaluated with antimonia content. Also two probe A. C conductivity measurement was subjected to all specimens and the best results are achieved with 1mol% $Sb_2O_3$ as a sinter agent and relative density of~98% obtained at 140$0^{\circ}C$ and this composition has a maximum electrical conductivity due to the possible substition of $Sb^{3+}$ for $Zr^{4+}$ site. The effect of $Sb_2O_3$ on the electrical conductivity of th bulk and the grain boundaries has on investigated using frequency dispersion analysis (5~106 Hz) Antimonia addition has a negative in-fluence on both the bulk and the grain boundary conductivity except for a 1 mon% addition. The additive antimonia has improve a modulus of rupture to 60~MPa due to metastable-tetragonal phase apparence and decrease the hardness with increasing the $Sb_2O_3$ content.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.10
• /
• pp.245-251
• /
• 2013

An impedance of ground electrode for information and communication facilities has a significant relationship with the electrical characteristics of soil where the ground electrode is buried. Especially, the impedance of ground electrode is directly affected by the characteristics of permittivity and conductivity in soil as a function of a frequency of an applied electric field. The program based on the electromagnetic field model was developed in MATLAB. Because both permittivity and conductivity can not be modified in commercial programs. The permittivity of soil was applied with the Debye equation which is a model of dielectric relaxation. And the empirical equation of the conductivity in soil was quoted in other paper. In order to confirm the reliability of proposed program, the impedance measurement of ground electrode was carried out, which were compared with the results of simulation in commercial program. In result, it was confirmed that the impedance and phase different simulated by appling the characteristics of permittivity and conductivity in soil are in good agreement with the measured values than results of NEC.

• Korean Journal of Veterinary Research
• /
• v.24 no.1
• /
• pp.91-98
• /
• 1984

A total of 466 foremilk from dairy farms in Chonnam district was examined for the subclinical mastitis over a period of one year, using a method of the electrical conductivities(EC); absolute conductivity(AC) and differential conductivity(DC) and quarter difference value(QD), in relation to the California mastitis test(CMT) and the direct somatic cell count(DSCC). The compatibility and efficiency rating between the EC values and the other screening tests was conducted. Obtained results are summarized as follows. 1. A linear relationship was found between the EC values and the CMT scores and direct somatic cell counts and it was found that electrical conductivity measurements were comparable with other screening tests for diagnosing animals with mastitis. 2. Compatibilities between the EC and CMT were 70.4% in AC, 74.6% in DC and 70.7% in QD, and that of the EC and DSCC were 53.0% in AC, 63.1% in DC and 53.2% in QD. On the other hand, relative efficiency ratings of Postle's equation between EC and CMT were 37.3% in AC, 26.5% in DC and 13.6% in QD, and that of the EC and DSCC were 33.1% in AC, 20.2% in DC and 11.9% in QD. 3. In the foremilk samples collected from damaged quarters determined by EC, the false positive rate wart higher than the false negative rate, and consequently tests of EC produced lower compatibility or efficiency rating scores. These tendencies suggested that any factors other than the mastitic condition influencing the EC values might be existed.

• Journal of IKEEE
• /
• v.19 no.2
• /
• pp.219-224
• /
• 2015

Electrical impedance tomography is an imaging technique to reconstruct the internal conductivity distribution based on applied currents and measured voltages in a domain of interest. In this paper, a modified Gauss-Newton method is proposed for conductivity image reconstruction. In the proposed method, the dimension of the inverse term is reduced by replacing the number of elements with the number of measurement data in the conductivity updating equation of the conventional Gauss-Newton method. Therefore, the computation time is greatly reduced as compared to the conventional Gauss-Newton method. Moreover, the regularization parameter is selected by computing the minimum-maximum from the diagonal components of the Jacobian matrix at every iteration. The numerical experiments with several scenarios were carried out to evaluate the reconstruction performance of the proposed method.

• Korean Chemical Engineering Research
• /
• v.59 no.1
• /
• pp.35-41
• /
• 2021

Silicon is a promising next-generation anode material for lithium-ion battery, and it has been studied for commercialization due to the high theoretical capacity. However, it has problems of the volume change during charge-discharge and the poor electrical conductivity. To solve these problems, formation of SiO2 and carbon coating on the surface of silicon crystal were performed to protect the side reaction and enhance the electrical conductivity of silicon. CNT and CNF were also added to mitigate the volume change and increase the conductivity. Physical properties of asprepared samples were analyzed by XRD, SEM, and EDS. Electrochemical characteristics were investigated by electrical conductivity measurement, EIS, CV and cycle performance test. (Si/SiO2/C)+CNT&CNF showed high electrical conductivity and low charge-transfer resistance, and the capacity was 1528 mAh/g at 1st cycle and 1055 mAh/g at 50th cycle with 83% capacity retention.

• Korean Journal of Soil Science and Fertilizer
• /
• v.16 no.1
• /
• pp.14-19
• /
• 1983

Comparison and evaluation of various wellknown methods to determine the saturated hydraulic conductivity of soil were attempted in order to choose a convenient and reliable method applicable, at least, to Bonryang sandy loam (coarse loamy over sandy, mixed, mesic family of Typic Udifluvents). Three experimental methods, inversed auger hole, infiltrometer, and core sample method, were used for this purpose. The results were summarized as follows: 1. The inversed auger hole method was highly correlated with the infiltrometer method while the core sample method was poorly correlated with other two methods. 2. The inversed auger hole method was proved to be convenient and reliable method to measure the hydraulic conductivity of upland coarse textured soils in situ. 3. The hydraulic conductivity determined by the infiltrometer method converged to a constant value after 80 to 100 minutes from starting of measurement. 4. The conductivity determined by the inversed auger hole method approached to a constant value at 5 or 6th run of measurement. 5. The hydraulic conductivity determined by the core sample method was greatly under estimated in comparison with the values obtained by other two methods.

• Composites Research
• /
• v.36 no.3
• /
• pp.162-166
• /
• 2023

Although composite materials are increasingly utilized in general high-strength structures, the demand of performance characteristics as the multifunctional materials has been increased especially in the area of complex electronic devices. While the heat dissipation properties of devices are typically required properties, control of thermal property of composite material especially in the vertical direction is one of the problems to be solved due to its lamination process. In this study, CFRP was manufactured using the Vacuum filtration method for three types of solvent and CFs. In the composite material manufacturing process, the effect of solvent was examined using three solvents where solvents are most frequently used for the dispersion of fibers. Morphology of fiber was observed through a microscope to confirm the arrangement of CFs in the vertical direction. The alignment of fiber was examined through the measurement of the thermal conductivity of the manufactured specimen. For the thermal conductivity measurement, the higher thermal conductivity was obtained with the lower aspect ratio of CF. For the thermal conductivity in the through-plane direction, 8.687 W/m·K, 10.322 W/m·K, and 13.005 W/m·K of thermal conductivity was measured in the DMF, NMP and Acetone, respectively.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.1
• /
• pp.39-43
• /
• 2003

Thermal management is very important for the success of high density circuit design in LTCC. In this paper, LTCC substrates containing thermal via and pad were fabricated in order to study the influence of the thermal dissipation. To realize the accurate thermal analysis for structure design, a series of simple thermal conductivity measurement by laser flash method and parametric numerical analysis have been carried out. The LTCC substrate including via and Ag pad has good thermal conductivity over 103 W/mK which is 44% value of pure Ag material. Thermal behaviors with via arrays, size and density in the LTCC substrate were studied by numerical method.