• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.3
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• pp.161-167
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• 1997

Determination of several cationic surfactants in cosmetics has been investigated. Reverse phase ion pair chromatography was used to identify and quantitate cationic surfactants. Cationic surfactants analyzed in this experiment were cetylpyridium chloride, stearyltrimetylammonium chloride, bezalkonium chloride, benzyldicethylcetylammonium chloride, and bihenyltrimethyl ammonium chloride. The separation was achieved on a reverse phase coumn with 10mM HCl-acetonitrile eluent. In this condition, the most of cationic surfactants with exception of CPC and CTAC respectively with suppressed conductivity detector and UV detector connected in series. The calibration curves obtained by plotting the peak areas of the cationic surfactants were linear at levels ranging from 0.005 to 0.1% correlation coefficient, r=0.9988. The detection limits were 1 to 5ppm in sample solution. The average recoveries of cationic surfactants added to hair treatment cream and hair rinse in three to five experiments were 96.7 105.2% and relative standard deviations were 1.1-3.8%. The case that there were CPC and CTAC in same solution was also tested. CPC and CTAC which couldn't be separated on reverse phase column were quantitated with suppressed conductivity detector and UV detector connected in series. Recovery of CPC and CTAC were 101.6 and 89.2% respectively. The proposed method was applied to the determination of cationic surfactants in commercial hair treatment cream.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.199-206
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• 1997

For the Korean Next Generation Reactor(KNGR) development, LBB is considered for the Main Steam Line(MSL) piping inside its containment to achieve cost and safety Improvement. To apply LBB concept to MSL, leak sensors highly sensitive to humidity is required. In this paper, a ceramic material, MgCr$_2$O$_4$-TiO$_2$ has been developed as a humidity sensor for MSL applications. Experiments peformed to characterize the electrical conductivity shows that the conductivity of MgCr$_2$O$_4$-TiO$_2$ responds sensitively to both temperature and humidity changes. At a constant temperature below 10$0^{\circ}C$, the conductivity increases as the relative humidity increases, which makes the sensor favorable for application to the outside of MSL insulation layer But as temperature increases beyond 10$0^{\circ}C$, the sensor composition should be adjusted for the application to KNGR is to be made at temperature above 10$0^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.6
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• pp.311-314
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• 2003

In Mo-Xwt%Cu compound, Physical and thermal properties were systematically evaluated in terms of Cu contents and sintering temperature. Typically Cu contents were varied from 15 to 25wt% and also the Sintering temperatures were changed from $1115^{\circ}C$ to $1350^{\circ}C$. In physical properties, Mo-15~25wt%Cu has the maximum density of 95% while Mo-20wt%Cu has the maximum thermal conductivity of 165.179[${\mu}/m^{\circ}C$] at sintering temperature of $1300^{\circ}C$. Especially, Mo-25wt%Cu has the maximum hardness of 173.4 at sintering temperature of $1150^{\circ}C$ and the maximum thermal expansion of 9.0[W/mK] as the specimen heated in the range of temperature from $50^{\circ}C$ to $400^{\circ}C$. Based on electrical conductivity measurements, the relative density increased within creasing Cu contents and the values were in the range of 100~150[W/mK].

• Journal of Powder Materials
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• v.14 no.5
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• pp.292-297
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• 2007

The present study was focused on the synthesis of a $TiB_2$ dispersed copper matrix composite material by the combination of the mechanical milling and plasma activated sintering processes. The $Cu/TiB_2$ mixed powder was prepared by the combination of the mechanical milling and reduction processes using the copper oxide and titanium diboride powder as the raw material. The synthesized $Cu/TiB_2$ mixed powder was sintered by the plasma activated sintering process. The hardness and electric conductivity of the sintered bodies were measured using micro vickers hardness and four probe method, respectively. The relative density of $Cu/TiB_2$ composite material sintered at $800^{\circ}C$ showed about 98% of theoretical density. The $Cu-1vol%TiB_2$ composite material has a hardness of about 130Hv and an electric conductivity of about 85% IACS. The hardness and electric conductivity of $Cu-3vol%TiB_2$ composite material were about 140 Hv and about 45% IACS, respectively.

• Journal of Powder Materials
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• v.25 no.5
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• pp.384-389
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• 2018

Nanoparticles of PbTe are prepared via chemical reaction of the equimolar aqueous solutions of $Pb(CH_3COO)_2$ and Te at $120^{\circ}C$. The size of the obtained particles is 100 nm after calcination in a hydrogen atmosphere. Dense specimens for the thermoelectric characterization are produced by spark plasma sintering of prepared powders at $400^{\circ}C$ to $500^{\circ}C$ under 80 MPa for 5 min. The relative densities of the prepared specimens reach approximately 97% and are identified as cubic based on X-ray diffraction analyses. The thermoelectric properties are evaluated between $100^{\circ}C$ and $300^{\circ}C$ via electrical conductivity, Seebeck coefficient, and thermal conductivity. Compared with PbTe ingot, the reduction of the thermal conductivities by more than 30% is verified via phonon scattering at the grain boundaries, which thus contributes to the increase in the figure of merit.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.367-371
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• 2018

Plywood is one of the important materials in LNG cargo containment systems, and, due to the characteristics of the wood, its properties vary greatly depending on the humidity conditions in the storage facility. Due to the distribution environment of plywood, there is a high probability of long-term exposure to the domestic seasonal environment. Considering an environment in which the humidity changes greatly according to the seasons in Korea and the characteristics of the wood, it is necessary to acquire data on changes in the characteristics of the plywood for accurate quality control. In this study, the moisture content of plywood was determined experimentally to reflect the seasonal environmental conditions of shipyards in Korea. A noticeable change in the thermal conductivity was confirmed experimentally.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.119-124
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• 2015

This paper investigates the change of the percolation threshold in the carbon powder-filled polystyrene matrix composites based on the experimental results of changes in the resistivity and relative permittivity of the carbon powder filling, the electric field dependence of the current, and the critical exponent of conductivity. In this research, the percolation behavior, the critical exponent of resistivity, and electrical conduction mechanism of the carbon powder-filled polystyrene matrix composites are discussed based on a study of the overall change in the resistivity. It was found that the formation of infinite clusters is interrupted by a tunneling gap in the volume fraction of the carbon powder filling, where the change in the resistivity is extremely large. In addition, it was found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon powder where non-ohmic current behavior becomes ohmic. It was considered that the mechanism for changing the gaps between the carbon powder aggregates into ohmic contacts is identical to that of the connecting conducting phases above the percolation threshold in a random resister network system. The electric field dependence is discussed with a tunneling mechanism. It is concluded that the percolation threshold should be defined at this volume fraction (the second transition of resistivity for the carbon powder-filled polystyrene matrix composites) of carbon powder.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.402-409
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• 2024

High energy neutron irradiations impact on structural and electrical properties of alumina are studied with particular emphasis on real time in-situ radiation induced conductivity measurement in low flux region. Polycrystalline Al₂O₃ samples are subjected to high energy neutrons produced from D-T neutron generator and Am-Be neutron source. 14 MeV neutrons from D-T generator are chosen to study the role of fast neutron irradiation in the structural modification of samples. Real time in-situ electrical measurement is performed to investigate the change in insulation resistance of Al₂O₃ due to radiation induced conductivity at low flux regime. During neutron irradiation, a significant transient decrease in insulation resistance is observed which recovers relative higher value just after neutron exposure is switched off. XRD results of 14 MeV neutron irradiated samples suggest annealing effect. Impact of relatively low energy neutrons on the structural properties is also studied using Am-Be neutrons. In this case, clustering is observed on the sample surface after prolonged neutron exposure. The structural characterizations of pristine and irradiated Al₂O₃ samples are performed using XRD, SEM, and EDX. The results from these characterizations are analysed and interpreted in the manuscript.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.3-6
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• 2006

There are three types of frequency-domain loop-loop EM induction method, depending on the loop separation and their location relative to the ground surface: horizontal-loop EM (HLEM), fixed small-loop EM, and helicopter-borne EM (HEM) methods. Multidimensional inversion provides tomographic images of the subsurface resistivity structure and thus enhances the interpretational accuracy of loop-loop EM data. HLEM method is shown to be effective for exploring groundwater resources in weathered and fractured crystalline basement terrains in semi-arid regions. Also, HEM method is useful for locating weak zones in landslide areas. The applicability of inversion to small-loop EM data depends solely on the S/N ratio. The quadrature response of small-loop EM data can only give the equivalent conductivity of a homogenous half-space model, and thus the in-phase component is essential in inverting EM data. However, the in-phase response is much lower and decreases more rapidly with decreasing frequency than the quadrature response. Further work is needed to obtain conductivity-depth images from small-loop EM data.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.302-306
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• 2004

Probabilistic approaches are applied to the problem of groundwater remediation design to consider the risk of design and heterogeneity of real condition. Hydraulic conductivity fields are generated by two methods. First, the homogeneous domains which have the hydraulic conductivity with log-normal distribution are constructed by using Latin Hypercube method. Second, random fields with a certain spatial correlation are also generated. The optimal solutions represented by cumulative distribution function (CDF) of relative cost are calculated by three different manners. The one uses the homogeneous domains with the optimal design of base condition. It shows that ver)'wide range of cost and the influences of different penalty values. The other one uses the random field with same design and shows narrow range of cost. These CDF can reflect on the risk of optimal solution in a simple exampie condition and be effective in estimating the cost of groundwater remediation.