• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1832-1834
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• 2005

In the electrical equipments, there are lots of phenomena such as loosening of connectin parts, So, heat generation and oxidation growth is considered to have a possibility to cause fire. In this Paper, we were carried out to study the oxidation growth and voltage waveform of connecting parts. In case of copper and copper connection, the growing of Cu2O elongated more than the other copper alloys. According to oxidation growth, the voltage waveform is distorted. And the contact voltage and the power dissipation increased rapidly.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.975-980
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• 2017

Overhead catenary system of electric railway has overlap sections which devide and tighten trolley wire supplying electric power to train, where current collection performances may become worse according to railway speed-up. Current collection tests conducted at 400 km/h test-bed section of Honam high-speed railway show that balanced line arrangement at overlap section is needed to secure current collection without arc generation between trolley wire and train current collection device. This paper proposes a design procedure of the overlap section to allow for tension increase and uplift of the trolley wires according to railway speed-up. By applying the proposed procedure to the overhead catenary system of Honam high-speed railway, it is suggested that the minimum span length should be 33.2 m for railway speed-up to 350 km/h and 43.7 m for speed-up to 400 km/h.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.234-235
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• 2006

In this study, we experimented deterioration characteristics of PVC insulation wires for electrical apparatus by series arcing and analyzed the heat generation at the contacts of wires, glowing/growing process of copper oxide, waveforms of contact voltage, current, power dissipation, and so on. We found out that how glowing contacts and surface arcing can decompose PVC insulation and that subsequent series arc can lead to ignition. We expect that these results are useful for improving fire protection technology by providing a better understanding of how electrical fires can initiate.

• Corrosion Science and Technology
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• v.20 no.1
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• pp.7-14
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• 2021

PosMAC^® is a brand of Zn-Mg-Al hot-dip coated steel sheet developed by POSCO. PosMAC^® can form dense surface oxides in corrosive environments, providing advanced corrosion resistance compared to traditional Zn coatings such as GI and GA. PosMAC^® 3.0 is available for construction and solar energy systems in severe outdoor environments. PosMAC^®1.5 has better surface quality. It is suitable for automotive and home appliances. Compared to GI and GA, PosMAC^® shows significantly less weight reduction due to corrosion, even with a lower coating thickness. Thin coating of PosMAC^® provides advanced quality and productivity in arc welding applications due to its less generation of Zn fume and spatters. In repeated friction tests, PosMAC^® showed lower surface friction coefficient than conventional coatings such as GA, GI, and lubricant film coated GA. Industrial demand for PosMAC^® steel is expected to increase in the near future due to benefits of anti-corrosion and robust application performance of PosMAC^® steel.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.690-696
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• 2021

The purpose of this study is to develop a zirconium-based alloy with low modulus and magnetic susceptibility to prevent the stress-shielding effect and the generation of artifacts. Zr-7Cu-xSn (x = 1, 5, 10, 15 mass%) alloys are prepared by an arc melting process. Microstructure characterization is performed by microscopy and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness and compression test. The magnetic susceptibility is evaluated using a SQUID-VSM. The average magnetic susceptibility value of the Zr-7Cu-xSn alloy is 1.176 × 10^-8 cm³g^-1. Corrosion tests of zirconium-based alloys are conducted through polarization test. The average Icorr value of the Zr-7Cu-xSn alloy is 0.1912 ㎂/cm². The elastic modulus value of 14 ~ 18 GPa of the zirconium-based alloy is very similar to the elastic modulus value of 15 ~ 30 GPa of the human bone. Consequently, the Sn added zirconium alloy, Zr-7Cu-xSn, is very interesting and attractive as a biomaterial that reduces the stress-shielding effect caused by differences of elastic modulus between human bone and metallic implants. In addition, this material has the potential to be used in metallic dental implants to effectively eliminate artifacts in MRI images due to low magnetic susceptibility.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.1
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• pp.8-19
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• 2022

The metallic implant materials are widely used in biomedical industries due to their specific mechanical strenth, corrosion registance, and superior biocompatability. These metallic materials, however, suffer from the stress-shielding effect and the generation of artifacts in the magnetic resonance imaging exam. In the present study, we develope a Zr-based alloys for the biomedical implant materials with low elastic modulus and low magnetic susceptibility. The Zr-7Si-xSn alloys were fabricated by an arc melting process. The elastic modulus was 24~31 GPa of the zirconium-based alloy. The average magnetic susceptibility value of the Zr-7Si-xSn alloy was 1.25 × 10^-8cm³g^-1. The average I_corr value of the Zr-7Si-xSn alloy was 0.2 ㎂/cm². The Sn added zirconium alloy, Zr-7Si-xSn, is very interested and attractive as a biomaterial that reduces the stress-shielding effect caused by the difference of elastic modulus between human bone and metallic implant.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.119-126
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• 2022

A growing number of gas-insulated transformers in underground power substations in urban areas are approaching 20 years of operation, the time when failures begin to occur. It is thus essential to prevent failure through accurate condition diagnosis of the given facility. Various solid insulation materials exist inside of the transformers, and the generated decomposition gas may differ for each gas-insulated equipment. In this study, a simulation system was designed to analyze the deterioration characteristics of SF₆ decomposition gas and insulation materials under the conditions of partial discharge and thermal fault for diagnosis of gas-insulated transformers. Degradation characteristics of the insulation materials was determined using an automatic viscometer and FT-IR. The analysis results showed that the pattern of decomposition gas generation under partial discharge and thermal fault was different. In particular, acetaldehyde was detected under a thermal fault in all types of insulation, but not under partial discharge or an arc condition. In addition, in the case of insulation materials, deterioration of the insulation itself rapidly progressed as the experimental temperature increased. It was confirmed that it was possible to diagnose the internal discharge or thermal fault occurrence of the transformer through the ratio and type of decomposition gas generated in the gas-insulated transformer.

• Journal of Environmental Health Sciences
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• v.41 no.6
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• pp.449-457
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• 2015

Objectives: In Korea, the system of management of medical waste largely relies on the incineration method. Our study aimed to identify any regional imbalances between the generation and treatment of medical waste, and provide reference data for future policy in Korea. Methods: We analyzed data on the amount of medical waste from 2,000 hospitals in 2012, 2013, and 2014 obtained from the Korea Environment Corporation. In the Arc GIS program (version 10.2.3), the addresses of hospitals and incinerators were transformed into map coordinates. The amount of waste generated by each hospital and the amount incinerated were represented by density and size of a triangle symbol, respectively. Results: As of 2014, the total amount of medical waste from the top 2,000 hospitals was 136,073 tons, out of which about half (49%) was generated in the capital area. Eleven incineration companies (three in the capital area, two in the Chungcheong Provinces area, one in the Jeolla Provinces area, and five in the Gyeongsang Provinces area) treated this waste. For the years 2012, 2013, and 2014, about 60% of the medical waste generated from the hospitals in the capital area was treated within the capital area and about 40% was transported to other areas, especially the Gyeongsang Provinces area, for treatment. On the other hand, about 90% of the medical waste incinerated in the capital area originated from the capital area. Conclusion: Our results suggest a spatial imbalance between the generation and treatment of medical waste in Korea and warrants multilateral policies, including the expansion of on-site treatment, strengthening regulation of the containment of medical wastes, promoting reductions in medical waste and more.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.89-97
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• 2021

Purpose: The purpose of this study is to compare and evaluate the dose change according to the gas volume variations in the rectum, which was not included in the treatment plan during radiation therapy for cervical cancer. Materials and methods: Static Intensity Modulated Radiation Therapy (S-IMRT) using a 9-field and Volumetric Modulated Arc Therapy (VMAT) using 2 full-arcs were established with treatment planning system on Computed Tomography images of a human phantom. Random gas parameters were included in the Planning Target Volume(PTV) with a maximum change of 2.0 cm in increments of 0.5 cm. Then, the Conformity Index (CI), Homogeneity Index (HI) and PTV D_max for the target volume were calculated, and the minimum dose (D_min), mean dose (D_mean) and Maximum Dose (D_max) were calculated and compared for OAR(organs at risk). For statistical analysis, T-test was performed to obtain a p-value, where the significance level was set to 0.05. Result: The HI coefficients of determination(R²) of S-IMRT and VMAT were 0.9423 and 0.8223, respectively, indicating a relatively clear correlation, and PTV D_max was found to increase up to 2.8% as the volume of a given gas parameter increased. In case of OAR evaluation, the dose in the bladder did not change with gas volume while a significant dose difference of more than D_mean 700 cGy was confirmed in rectum using both treatment plans at gas volumes of 1.0 cm or more. In all values except for D_mean of bladder, p-value was less than 0.05, confirming a statistically significant difference. Conclusion: In the case of gas generation not considered in the reference treatment plan, as the amount of gas increased, the dose difference at PTV and the dose delivered to the rectum increased. Therefore, during radiation therapy, it is necessary to make efforts to minimize the dose transmission error caused by a large amount of gas volumes in the rectum. Further studies will be necessary to evaluate dose transmission by not only varying the gas volume but also where the gas was located in the treatment field.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.227-232
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• 2012

Inconel 617 and Hastelloy X are the most promising candidate materials for the heat exchanger of next generation nuclear reactor. Surface coating and its effects on high temperature properties for the Inconel 617 and Hastelloy X under molten FLiNaK (LiF-NaF-KF) salt environment have been investigated. For TiAlN and $Al_2O_3$ overlay coatings, the two different PVD (physical vapor deposition) methods of an arc discharge and a sputtering were applied, respectively. A study for the thermal stability of the surface modified Ni-Cr alloy substrates has been conducted. To evaluate the corrosion mechanism of Ni-Cr alloys in the molten salt, a ruptured Inconel pipe used for the molten salt transportation has been analyzed. The thermal properties of morphological and structural properties each sample were characterized before and after heat-treatment at $600^{\circ}C$ in molten FLiNaK salt. The results showed that the TiAlN and $Al_2O_3$ overlay coated specimens had the enhanced high temperature stability.