• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.122-129
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• 2001

A characterization procedure for analyzing symmetric coupled MIS(Metal-Insulator-Semiconductor) transmission line is used the same procedure as a general single layer symmetric coupled line with perfect dielectric substrate from the extraction of the characteristic impedance and propagation constant for even- and odd-mode. In this paper, an analysis for a new substrate shielding symmetric coupled MIS structure consisting of grounded crossbar at the interface between Si and SiO2 layer using the Finite- Difference Time-Domain(FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded crossbar lines over time-domain signal has been examined. Symmetric coupled MIS transmission line parameters for even- and odd-mode are investigated as the functions of frequency, and the extracted distributed frequency- dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor for the new MIS crossbar embedded structure are also presented. It is shown that the quality factor of the symmetric coupled transmission line can be improved without significant change in the characteristic impedance and effective dielectric constant.

• Corrosion Science and Technology
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• v.16 no.6
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• pp.278-284
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• 2017

The effects of TIG welding and post-treatment procedures on the microstructure and the pitting corrosion resistance of welded lean duplex stainless steel S82441 were investigated. Autogenous TIG welding was used with different amounts of heat input and shielding gases such as Ar, and mixtures of $Ar-N_2$ and Ar-He. The addition of 5% to 15% of nitrogen to argon practically did not affect the level of the pitting corrosion resistance. However, the application of gas mixtures (50% Ar + 50% He) resulted in a significant decrease in pitting corrosion resistance. We found that increased current (200 A and 250 A) led to lower values of CPT of welds compared with welds obtained with 50 A, 100 A and 150 A. In addition, the removal of the weld surface layer (0.2 ~ 0.3 mm thickness) in most cases not only resulted in a significant increase in resistance to the pitting corrosion but also post-treatment of weld, implying that corrosion resistance depended on factors such as surface roughness or the presence of undesirable oxides.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.173-178
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• 2018

Lead is a very useful material in shielding radiation in hospitals. But lead is toxic. Therefore, there are many studies on substitutable materials, Typically, there are many studies using tungsten. In this study, we investigated the physical properties of lead and tungsten and the Half value layer. As a result, lead having higher atomic number showed higher cross - sectional area than tungsten. But, at the same size, the electron density of tungsten with a high density is about 1.7 times higher than that of lead. In MCNPX simulation, the shielding effect of tungsten is about 1.4 times higher than that of lead, It was confirmed that tungsten had better shielding efficiency than lead. However, considering the economic aspect, tungsten is a rare metal, which is about 25 times more expensive than lead, which is considered to be inappropriate as an alternative to lead.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.149-155
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• 2020

Most of radiation protection clothing is made of lead with excellent radiation shielding because it has excellent process ability and economic efficiency and has a high atomic number. However, lead is classified as a hazardous heavy metal, and there is a risk of lead poisoning. Recently, research to replace lead has been actively conducted. In this study, a research on a shielding sheet with improved physical properties while maintaining the radiation shielding ability equivalent to that of conventional materials by mixing two materials that are harmless to the human body, such as BaSO₄ and Bi₂O₃, and a silicone material binder Was performed. For comparison evaluation with the existing lead shielding sheet, the shielding rate was evaluated using a 40 degree shielding sheet having the highest porosity. As a result, it was analyzed that the shielding rate was superior to 9 % or more at the same thickness. In addition, as a result of studies to improve the physical properties of the shielding sheet, it was analyzed that the shielding sheet mixed with BaSO₄/nylon/Bi₂O₃ was the best.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1328-1329
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• 2008

2000년 대 이후 송전선의 상태 및 송전선 주변 환경을 감시하기 위한 각종 센서들을 하나의 시스템으로 통합하여 실 선로에 적용하는 연구가 활발히 진행되고 있으며, 국내에서도 최근 765kV급 송전선을 감시하기 위한 통합 센서 시스템 개발을 진행 중에 있다. 이를 위해서는 송전선로에서 발생되는 자계로부터 센서 통합 시스템을 보호하기 위한 자계 차폐에 대한 연구가 선행되어야 한다. 따라서 본 논문에서는 상용 주파수에서 약 80,000[H/m]이상의 투자율(${\mu}_r$ : relative permeability)를 갖는 강자성체인 ${\mu}$-metal을 사용하여 765kV급 송전선 (2,000A/single phase)에 대한 차폐율을 연구하였고, 이를 위해 ${\mu}$-metal의 차폐율을 검증할 수 있는 magnetic probe를 자체 설계 제작하였다. 그 결과 magnetic probe에 의해 측정된 자계의 크기 및 분포를 통해 ${\mu}$-metal의 layer의 개수에 따라 변화하는 자계 차폐율을 분석할 수 있었다.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.481-485
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• 2001

Laser cladding processing allows rapid transfer of heat to the material being processed with minimum conduction into base metal. The effect of $CO_2$ laser cladding with high viscosity mixed powders was investigated. High viscosity mixed powder consists of bronze powder and flux that is used at a high temperature condition. The mixed powder has a high viscosity that it can be easily pasted over a curved or slope substrate. The device for mixed powder was designed and manufactured. It consists of the high viscosity mixed powder feeding system, the preheating system and the shielding gas system which prevents the clad layer from being oxidized. The results of experiment indicated that the feed rate of high viscosity mixed powder was important for later cladding with mixed powder feeding. The high viscosity mixed powder and substrate must be preheated to prevent porosity from breaking at the clad layer. The experimental result shows that the high viscosity mixed can be applied for laser cladding process.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.3
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• pp.44-53
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• 2003

Cu/C films were prepared at room temperature under $Cu(hfac)_2-Ar-H_2$ atmosphere in order to obtain metallized polymer by using ECR-MOCVD(Electron Cyclotron Resonance Metal Organic Chemical Vapor Deposition) coupled with a DC bias system. The room temperature MOCVD on polymer substrate could be possible by collaboration of ECR and a DC bias. Structural analysis of the films by ECR was found that fine copper grains embedded in an amorphous polymer matrix with indistinctive interfacial layer. The increase in $H_2$ contents brought on copper-rich film formation with low electric resistance. On the other hand carbon-rich films with low sheet electric resistance were prepared in argon atmosphere. The electric sheet resistance of Cu/C films with good interfacial property were controlled at $10^8$~$10^0$ Ohm/sq. ranges by the $H_2$/Ar mole ratio and the shielding effectiveness of the film showed maximum up to 45dB in the our experimental range.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.83-88
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• 2006

In this paper, we propose a new cross bar embedded structure for improvement of attenuation characteristics along the different lossy media. A general characterization procedure based on the extraction of the characteristic impedance and propagation constant for analyzing a single MIS(Metal-Insulator-Semiconductor) transmission line used and an analysis for a new substrate shielding MIS structure consisting of grounded crossbars at the interface between Si and Sio2 layer using the Finite-Difference Time-Domain(FDTD) technique is used. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded cross bar lines over time-domain signal has been examined. The extracted, distributed frequency-dependent transmission line parameters as well as the line voltages and currents, and also corresponding equivalent circuit parameters have been examined as function of frequency. It is shown that the quality factor of the transmission line can be improved without significant changes in the characteristic impedance and effective dielectric constant.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.61-67
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• 2010

A characterization procedure for analyzing symmetric coupled MIS(Metal-Insulator-Semiconductor) transmission line is used the same procedure as a general single layer symmetric coupled line with perfect dielectric substrate from the extraction of the characteristic impedance and propagation constant for even- and odd-mode. In this paper, an analysis for a new substrate shielding symmetric coupled MIS structure consisting of grounded crossbar at the interface between Si and SiO2 layer using the Finite-Difference Time-Domain (FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded crossbar lines over time-domain signal has been examined. Symmetric coupled MIS transmission line parameters for even- and odd-mode are investigated as the functions of frequency, and the extracted distributed frequency-dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor for the new MIS crossbar embedded structure are also presented. It is shown that the quality factor of the symmetric coupled transmission line can be improved without significant change in the characteristic impedance and effective dielectric constant.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.31-34
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• 2001

Laser cladding Processing allows rapid transfer of heat to the material being minimum conduction into base metal. The effects of CO$_2$ laser cladding with high powder were investigated. High viscosity bronze powder consists of bronze powder used at a high temperature. The material has a high viscosity So that it can be substrate. Therefore. Laser cladding can be processed on a curved or slope surface. CO$_2$ laser cladding was designed It consists of the high viscosity bronze powder the shielding gas system and the preheating system The high viscosity powder properly at 0.3g/s and 0.50g/s. Because of the metallic bond between bronze per the hardness of dilution layer was suddenly increased. Experimental as results viscosity mixed powder can be a useful cladding material.