• Korean Journal of Materials Research
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• v.10 no.3
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• pp.223-226
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• 2000

The oxygen deficient ferrites $(Ni_x,\; Zn_{1-x})Fe_2O_{4-{\delta}}$ can decompose $CO_2$ as C and $O_2$ at a low temperature of about $300^{\circ}C$. Ultra powders of $(Ni_x,\; Zn_{1-x})Fe_2O_4$ for the $CO_2$ decomposition were prepared by the hydrothermal methods. The XRD result of synthesized ferries showed the spinel structure of ferrites and ICP-AES and EDS quantitative analyses showed the composition similar with the starting molar ratios of the mixed solution prior to reaction. The BET surface area of the synthesized(Ni, Zn)-ferrites was above $110\textrm{m}^2/g$ and its particle size was very as small as about 5~10 nm. The $CO_2$ decomposition efficiency of the oxygen deficient ferrites($(Ni_x,\;Zn_{1-x})Fe_2O_{4-{\delta}}$) was almost independent with composition and the $CO_2$ decomposition efficiency of ternary (Ni, Zn)-ferrites was better than of binary Ni-ferrites.

• Membrane Journal
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• v.17 no.3
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• pp.219-232
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• 2007

The polyethersulfone(PES)-titanium oxide($TiO_2$) hybrid membranes were prepared by immersion precipitation phase inversion method. The casting solution for the preparation of $PES-TiO_2$ hybrid membrane was provided by adding $TiO_2$ nano particles into the basis polymer solution of 14 wt% and 20 wt% PES/N-methyl-2-pyrrolidone(NMP). The $TiO_2$ loading [wt% ($TiO_2/NMP$)] in eating solution was varied from 0 to 60 wt%. Membrane performance and morphological change of the resulting $PES-TiO_2$ hybrid membranes were discussed in aspect of $TiO_2$ loading, by viscosity, coagulation value and light transmittance of the casting solution, measurement of tensile strength, pore size and contact angle, surface and cross sectional SEM images of the hybrid membrane, and ultrafiltration experiments using the hybrid membrane. According as increase of $TiO_2$ loading in the casting solution, viscosity is increased and coagulation value becomes lower, therefore the thermodynamic instability of the casting solution is increased. It is found that when $TiO_2$ loading is increased, 1) precipitation rate becomes faster while instantaneous demixing is maintained, 2) pure water flux, membrane pore size and compaction stability of the resulting membranes are increased, 3) tensile strength and contact angle are decreased. Dead-end ultrafiltration of bovine serum albumin(BSA) solution using the hybrid membrane shows that membrane performance(flux of BSA solution) enhanced up to 7 times compared with the results obtained using the pure PES membrane(not containing $TiO_2$ particle), due to the increase of hydrophilicity.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1621-1625
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• 2015

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.429-438
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• 2017

Monte Carlo N-Particle (MCNP) modeling algorithm based on the Monte Carlo method was used to perform the simulation of neutron logging in order to increase the reliability and utilization of neutron logs applied in geological and resource engineering fields. To perform the simulation using MCNP, we used a realistic three-dimensional configuration of neutron sonde and formation. Validation of the modeling was confirmed by comparing the calibration curves of sonde manufacture with those calculated by MCNP modeling. After the validation, lithology effects, pore fluid effects, borehole diameter change, casing effect, and effects of borehole water level were investigated through modeling experiments. Numerical tests indicate that changes in neutron count ratio according to the lithology were quantitatively understood. In case of a borehole with a diameter of 3 inches, ratio of counting rates was higher than expected to be interpreted as borehole fluid has small effects on neutron logging. Effect of casing was also small in general, particular when porosity increases. Since modeling results above the groundwater level showed a tendency opposite to those below the groundwater level, neutron logs can be used to detect groundwater level. The modeling results simulated in this study for various borehole environments are expected to be used for data processing and interpretation of neutron log.

• Applied Microscopy
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• v.35 no.1
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• pp.23-30
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• 2005

Many studies have been performed on the bovine leukemia virus (BLV) since bovine leukosis had been reported in 1968 in Korea. However, there was no report on the ultrastructural examination of BLV. An attempt to detect C-type viral particles in the cultured peripheral blood lymphocytes of Holstein-Friesian dairy cattle, was made to determine whether in vitro viral expression might be used as a reliable method to identify the cow which is likely to transmit BLV. In transmission electron microscopic (TEM) examination, the virus particles were found predominantly outside of the lymphocytes even though a few particles were also observed within the membrane bound cytoplasmic vacuoles. All of them were C-type particles consisting of a central, electron-dense core separated by a clear area from a limiting envelope with a unit membrane structure. Virus particles were easily detected in the lymphocyte which was cultured with medium supplemented with either T-lymphocyte mitogen (conconavalin A) or B-lymphocyte mitogen (lipopolysaccharide). Identical viral particles, although fewer, were also consistently present in the lymphocytes cultured with medium which was containing foetal bovine serum (FBS) only and which was containing neither FBS or mitogen. By contrast, no virus particle was detected in extensive examination of lymphocytes before culture. In conclusion, the BLV cultivation and detection methods established in this study could be used as a tool to identify and eliminate the cattle which can transmit the BLV.

• Korean Journal of Food Science and Technology
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• v.39 no.1
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• pp.71-76
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• 2007

Foodborne illness caused by Noroviruses (NVs) is increasing rapidly in Korea. This study developed an effective detection protocol for NVs found in contaminated oysters and lettuce through an investigation using the major steps of virus particle separation, concentration and RT-PCR. As a surrogate model for NVs, the cultivable feline calicivirus (FCV) that belongs to the same Caliciviridae family was used. Instead of using a time-consuming ultracentrifugation method, efficient methods based on solvent extraction and PEG precipitation procedure were applied. Direct homogenization of a 25g sample of whole oyster and lettuce in 175mL PBS provided the simplicity that would be needed in the actual field of food product examination. The overnight PEG precipitation step at $4^{\circ}C$ was reduced to 3 h by placing the reaction tube in ice and by adjusting the PEG concentrations. The application of the use of chloroform and 0.2 ${\mu}m$ syringe filtration together showed a better detection efficiency than the use of chloroform alone in removing PCR inhibitors for both oyster and lettuce samples. Also, dilution of the extracted RNA solution before PCR provided increased sensitivity. The improved detection protocol developed in this study could be efficiently applied to detect FCV and most likely NVs from oysters and lettuce.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.385-390
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• 2005

In this study, nano sized colloidal Ag was made by using a seed sol method. Colloidal Ag solution was spouted on the surface of the inorganic pigment using the hybridizer system and spray nozzle. Then, the surface of the inorganic pigment was modified by $TiO_2$ to obtain the antibacterial ability. In the manufacturing process of nano sized colloidal Ag, it was confirmed that the size of particles increased by addition of $AgNO_3$ and increased the reaction time. The antibacterial measurement of the inorganic pigment showed that the growth of fungus decreased as the reaction time was increased. After the antibacterial ability appeared, in 5~7 h of the antibacterial inoculation experiment, it was measured that the antibacterial activity was excellent at a fixed time frame. The photodecomposition of benzene using $TiO_2$ as the photocatalyst showed 60~70% efficiency in about 80 min. reaction time. It was shown that more than 90% of this efficiency was achieved in the reaction time of about 30 min.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.330-338
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• 2018

The proportional-integral-derivative(PID) controller has been widely used in the industry because of its robust performance and simple structure in a wide range of operating conditions. However, the AVR(Automatic Voltage Regulator) as a control system is not robust to variations of the power system parameters. Therefore, it is necessary to use PID controller to increase the stability and performance of the AVR system. In this paper, a novel design method for determining the optimal PID controller parameters of an AVR system using the particle swarm optimization(PSO) algorithm is presented. The proposed approach has superior features, including easy implementation, stable convergence characteristic and good computational efficiency. In order to assist estimating the performance of the proposed PSO-PID controller, a new performance criterion function is also defined. This evaluation function is intended to reflect when the maximum percentage overshoot, the settling time are given as design specifications. The ITAE evaluation function should impose a penalty if the design specifications are violated, so that the PSO algorithm satisfies the specifications when searching for the PID controller parameter. Finally, through the computer simulations, the proposed PSO-PID controller not only satisfies the given design specifications for the terminal voltage step response, but also shows better control performance than other similar recent studies.

• Clinical and Experimental Pediatrics
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• v.48 no.6
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• pp.614-618
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• 2005

Purpose : Cystatin C has been proposed for the assessment of glomerular filtration rate, being more accurate than creatinine determination. We measured serum cystatin C concentrations in the pediatric population, and analysed the correlation between cystatin C and glomerular filtration rate. Methods : Cystatin C and creatinine were measured by the particle enhanced nephelometric immunoassay and Jaffé method, respectively, in 276 children and adolescents without evidence of kidney disease. The glomerular filtration rate was estimated by Schwartz's formula. Results : The mean serum cystatin C concentration was significantly higher in infants under the age of 12 months than in older population. There was a negative correlation between cystatin C and age under 12 months, but not a significant change of cystatin C with age in children older than 12 months. For children older than 12 months, the reference range of cystatin C was 0.46-1.05 mg/L. On the other hand, there was a positive correlation between creatinine and age in the whole population. We also observed a positive correlation between estimated glomerular filtration rate and 1/cystatin C. Conclusion : The measurement of cystatin C is more practical than creatinine for estimating glomerular filtration rate in the pediatric population.

• Journal of Conservation Science
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• v.35 no.6
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• pp.600-611
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• 2019

Yellow to reddish brown soil is generally referred to as hwangto and is used in various industries in Korea. Despite the fact that it is used as an inorganic pigment in dancheong, limited studies have been conducted on the properties of pigments associated with soil and on the mineralogical characteristics of hwangto. This study examines how the pedological and mineralogical features of hwangto affect pigment properties. Results indicate that reddish and yellowish soils have differences in terms of soil texture, mineral composition, oil absorption and stability under light. Reddish soil is mostly found in clay regions, whereas Ulleungdo hwangto is found in loam regions. Yellowish soil is mostly present in the clay loam to loam zones. whereas Haenam hwangto exists in the sandy clay loam zone. As a result of a mineralogical analysis, reddish soil is classified into the feldspar group and clay soil. The major minerals in the yellowish soils are similar however these soils differ in terms of clay mineral compositions. results of the characteristics of pigments prepared by the traditional method revealed that the average particle size is in the range of 10-20 ㎛, reddish soil has an average of 20 ml/100 g higher oil absorption than yellowish soil. In addition, reddish soil is more susceptible to discoloration and deterioration under light than yellowish soil. This study confirms that the soil and mineral characteristics of hwangto affect the physical properties and stability of produced pigments. These result can be used as basic data in future studies natural inorganic pigments using hwangto.