• Journal of Environmental Science International
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• v.15 no.6
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• pp.579-586
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• 2006

The purposes of this paper were to monitor the temperature rising courses and spark discharge of the modified granular activated carbon (GAC) by microwave (MW) irradiation and to evaluate absorption of benzene. The GAC coated on $SiO_2$, boron, talc, ferrite was named as the modified GAC. Thermal and spark discharge measurement of virgin GAC and modifed GAC has been carried out using a MW device operating at 2450 MHz under various energy conditions. The results of this paper as follows. First, the modified GAC is more efficient than the virgin GAC in temperature control. Temperature gradient of the modified GAC is more lower than that of virgin GAC. The temperature gradient of GAC was observed in the following order : virgin GAC, Mn-Zn ferrite/GAC, Ni-Zn ferrite,/GAC, $SiO_2/GAC$, Boron/GAC, Talc/GAC. Second, the spark discharge of the modified GAC was diminished, compared with that of virgin GAC. Because of its excellent electrical insulating properties, the coating material prevents the spark discharge. Finally, the benzene adsorption capacity of the modified GAC decreased due to diminishing of adsorption site by the coating material. Considering the temperature gradient and spark discharge of GAC, the GAC coated $SiO_2$ would be appropriate absorbent under irradiation of MW.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1369-1374
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• 2014

Most accidents of medium-voltage cables installed in nuclear power plants result from the initial defect of internal insulators or the initial failure due to poor construction. However, as the service years of plants increase, the possibility of cable accidents is also rapidly increases. This is primarily caused by electric, mechanical, thermal, and radiation stresses. Recently, much attention is paid to the study of cable diagnoses. To date, partial discharge and Tan${\delta}$ measurements are known as reliable methods to diagnose the aging of medium-voltage cables. High frequency partial discharge measurement techniques have been widely used to diagnose cables in transmission and distribution systems. However, the on-line high frequency partial discharge technique has not been used in the nuclear power plants because of the plant shutdown risk, degraded measurement sensitivity, and application problems. In this paper, the partial discharge measurement with a portable device was tried to evaluate the integrity of the 4.16kV and 13.8kV cable lines. The test results show that the high detection sensitivity can be achieved by the high frequency partial discharge technique. The present technique is highly attractive to diagnose medium voltage cables in nuclear power plants.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.975-976
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• 2007

Thermal and mechanical stresses, caused by repetitive start and stop and load fluctuation during long time operation, on winding stator bars are one of the main causes for electrical degradation of insulating materials. To understand the degradation process, we manufactured bar specimens with the same processes that make generator winding stator bars and the specimens were subjected to various degrees of thermal cycling. Measurements of the insulation properties, such as dissipation factor, tip-up and partial discharge, for un-aged specimens and for specimens aged by thermal cycling at 50, 100, 250, 500 and 1000 thermal cycles were performed. Finally all specimens were tested to obtain electrical breakdown voltages. In this paper we present the data and electrical degradation analysis results obtained during this program.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.761-768
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• 1997

A numerical model is developed to analyze the incompressible unsteady flow induced by the pump trip-out in the cooling water discharge culvert of thermal power plants. The numerical models has various features to deal concureently with the overall behavior of complicated unsteady flow due to the presence of cooling water internal system, seal well, air chamber, culvert, manholes, open channel and sea water. A leap-frog finite difference scheme is employed to solve governing equations, and the model is tested for a simple case of two tanks connected with a pipe. A fixed free surface boundary condition used earlier at the downstream end of culvert for large water body is investigated.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.1-6
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• 2004

In this study, heat and discharge treatments are arbitrary simulated for finding out the initiations and processes of surface degradation on the surface of polymer for using as a PCB substrate. Thermal-treatment changed the surface to the hydrophobic one with the increase of contact angle and surface potential decay, respectively. The XPS spectrum showed that the increased hydrophobicity in thermal treatment was originated from the continuous decrease of side-chains caused by secessions of oxygen groups and the increase of unsaturated double bond in carbon chains. Also, thermal-treatment caused the discoloration on the point of treated surface. These phenomena were attributed to the generation of ether group. In the chemical change by discharge treatment, a lot of side-chains occurred on the treated surface, and so the hydrophilicity increased as time elapsed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.78-84
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• 2010

This paper describes the safety assessment of power cable splices connecting different sized 6/10[kV] class power cables. To assess the safety, AC withstand voltage tests, partial discharge tests and impulse tests were carried out to the cable splice specimens and thermal rise due to overload and cross section of joint were examined as well. As a result, a breakdown due to the $4.5[U_0](27[kV_{ac}])$ application could not found for 5 minutes. Under $1.73[U_0](10.4[kV_{ac}])$ application, partial discharges of 4~8[pC] were detected. In impulse tests, all the specimens withstood to the standard waveforms of $75[kV_{peak}](1.2{\times}50[{\mu}s])$ without any breakdowns. In addition, the temperature on the splice rose by $3[^{\circ}C]$ when the 200[A] flew through the splice for 20minutes, however the thermal rise of $3[^{\circ}C]$ was considered due to the atmospheric temperature. After all the electrical tests, the cross section of the splice was visually examined. The conditions of the conductors of both $185[mm^2]$ and $240[mm^2]$ were good.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1660-1669
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• 2014

Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.6
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• pp.910-916
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• 2022

The purpose of this study is to evaluate the effect of underwater non-thermal dielectric barrier discharge plasma (DBD plasma) on the sterilization of three types of pathogenic bacteria that cause diseases in freshwater fish and the reduction of a tetracycline antibiotics. This experiment was conducted in the DBD plasma generator, and the voltages used to generate plasma were 11.6 kV and 23.1 kV. The measurement intervals were 0, 1, 5, 10 and 15 min. As a result of DBD plasma treatment, Aeromonas hydrophila, Edwardsiella tarda and Pseudomonas fluorescens were removed 93-99% after 5 min at 23.1 kV, and the tetracycline antibiotics were reduced 70-95% after 15 min at 23.1 kV. In this study, as a result of treating the effluent with DBD plasma at a fish farm where the medicinal bath was conducted with oxytetracycline-HCl (OTC-HCl) products, OTC-HCl decreased by 62% after 10 min at 23.1 kV.

• International Journal of Advanced Culture Technology
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• v.11 no.2
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• pp.375-380
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• 2023

The study was conducted in Manu-stream, located in Paju, Gyeonggi-do, from January 2021 to December 2021. The survey points were selected in the upper and lower streams based on where thermal discharged to investigate water temperature and fish species and biological community analysis and growth rate were analyzed. The average annual water temperature difference between the upper and lower stream is about 11.0℃, and in the case of the lower stream area, the water temperature is maintained at 20.0℃ or more per year. Fish that appeared during the survey period decreased lower stream compared to the upper stream, which is believed to be the result of a decrease in temperature-sensitive species as the simple riverbed structure and water temperature increased compared to the upper stream. As a result of biological community analysis, it showed a relatively stable community state at the upper stream. The growth rate of fish has a high regression coefficient b value in lower streams throughout the four seasons. It showed relatively good growth lower stream, with a high water temperature. However, the results of each survey point are similar from season to season. The indicator species is a resistant intermediate species, and the range of resistance to water temperature is wide, so it is judged that water temperature's effect on the indicator species' growth is low.

• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.225-235
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• 1999

For a comparative evaluation of three turbulence models in the analyses of thermal discharge behavior into a crossflow, a 2-dimemsional near-field numerical model is developed. The selected models are k-$\varepsilon$ and k-ι turbulence models as a 2-equation turbulence model and a 4-equation turbulence model in which the transport equations for mean of the temperature fluctuation squared and its dissipation rate for the consideration of buoyancy production and turbulent heat flux terms are added to a k-$\varepsilon$ turbulence model. The developed models are applied to a steady flow in an open channel with simple geometry and the numerical results agree with the existing experimental data. Numerical results of buoyancy induced gravitational lateral spreading by 4-equation turbulence model agree with the experimental data better than those of 2-quation turbulence models. The flow patterns by 4 and 2-equation turbulence models are similar.