• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.345-352
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• 2004

The radiation impedance of a magnetostatic surface wave excited in a microstrip line haying ferrite film and its dependence on the width of the microstrip line and the height of the ferrite film are calculated by the full-wave moment analysis. The radiation resistance calculated by the full-wave analysis closely agrees with the measured radiation resistance, while that by the magnetostatic approximation greatly differs from the measured result in the higher-frequency region.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.52.2-52.2
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• 2021

우리는 quiescent state magnetar의 물리적 특성을 연구하기 위해 복사특성이 잘 알려진 24개의 대상을 선정하였고 가장 어두운 시기(quiescent state)의 Chandra와 XMM-Newton의 X-ray 관측 데이터를 분석하여 복사특성과 시간 특성을 측정하였다. 이 측정을 이용하여 복사특성과 시간 특성 사이의 여러 경우에 대해 상관관계를 분석하였다. 그 결과 기존에 높은 상관관계를 갖는 것으로 알려진 표면 자기장(B_s)과 흑체복사 광도(L_BB), B_s와 X-ray photon index (Γ_X) 관계를 더 많은 magnetar에 대하여 재확인하였으며, spin-down rate (Ṗ)와 L_BB, characteristic age (𝜏_c)와 L_BB의 새로운 유의미한 관계를 찾았다. 또한 magnetar의 pulsed fraction (PF)과 흑체복사 반경(R_BB), PF와 Γ_X, 그리고 Ṗ과 Γ_X가 서로 상관되어 있다는 단서를 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.288-296
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• 2019

Radiation cooling has used ceilings or floors as cooling surfaces. In such cases, to avoid moisture condensation on the surface, the surface temperature needs be higher than the dew point temperature or an additional dehumidifier is added. In this study, with a goal for residential application, intentional moisture condensation on the cooling surface was attempted, which increased the cooling capacity and improved the indoor comfortness. This method included two separate refrigeration cycles - convection-type dehumidifying cycle and the panel cooling cycle. Test results on the panel cooling cycle showed that, at the standard outdoor ($35^{\circ}C/24^{\circ}C$) and indoor ($27^{\circ}C/19.5^{\circ}C$) condition, the refrigerant flow rate was 8.8 kg/h, condensation temperature was $51^{\circ}C$, evaporation temperature was $8.8^{\circ}C$, cooling capacity was 376 W and COP was 1.75. Furthermore, the panel temperature was uniform within $1^{\circ}C$ (between $13^{\circ}C$ and $14^{\circ}C$). As the relative humidity decreased, the cooling capacity decreased. However, the power consumption remained approximately constant. In the convection-type dehumidification cycle, the refrigerant flow rate was 21.1 kg/h, condensation temperature was $61^{\circ}C$, evaporation temperature was $5.0^{\circ}C$, cooling capacity was 949 W and COP was 2.11 at the standard air condition. When both the radiation panel cooling and the dehumidification cycle operated simultaneously, the cooling capacity of the radiation panel cycle was 333 W and that of the dehumidification cycle was 894 W, and the COP was 1.89. As the fan flow rate decreased, both the cooling capacity of the radiation panel and the dehumidification cycle decreased, with that of the dehumidification cycle decreasing at a higher rate. Finally, a possible control logic depending on the change of the cooling load was proposed based on the results of the present study.

• The Korean Journal of Nuclear Medicine Technology
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• v.23 no.1
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• pp.50-53
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• 2019

Purpose Yttrium-90 (Y-90) is high-energy beta emitters ($E{\beta}$, max = 2.28 MeV) with the mean penetration depth of 2.5 mm in tissue. Radioactive microspheres containing Y-90 is widely used for the transarterial radioembolization of hepatocellular carcinoma. However, bremsstrahlung radiation from Y-90 can cause the external radiation exposure to medical staff who handle the Y-90 microspheres. In this study, shielding device for Y-90 microspheres was developed to minimize the external radiation exposure. Materials and Methods Y-90 microsphere shielding device was made from 6 mm thicknesses of tungsten including the lead glass window. Radiation shielding ability of Y-90 microsphere shielding device was evaluated using 4 GBq of $SIR-Spheres^{(R)}$ Y-90 microspheres. The bremsstrahlung radiation was measured using radiation survey meter. Results The mean radiation dose of Y-90 microspheres in acrylic shield was $261.7{\pm}2.3{\mu}Sv/h$ (n=5) at 10 cm away from the shield. With the additional tungsten shielding device, it was $23.7{\pm}1.3{\mu}Sv/h$ (n=5). Thus, the bremsstrahlung radiation dose was decreased by 90.9%. At 50 cm away from the shield, bremsstrahlung radiation was reduced by 89.2% after using tungsten shielding device. Conclusion During the preparation and radioembolization of Y-90 microsphere, medical staff are exposed to external radiation. In this study, we demonstrated that the use of tungsten shielding device devices significantly reduced the amount of bremsstrahlung radiation. Y-90 microsphere tungsten shielding device can be highly effective in reducing the bremsstrahlung radiation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.957-967
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• 2008

In this paper, we propose the prediction algorithm of radiation emission from the PCB in an enclosure with a rectangular aperture. PCB scanner is used to measure the near field, which is substituted with an equivalent electric dipole source. Green function and Fourier transform are utilized to represent the electromagnetic fields within and outside the enclosure, respectively. The radiation emission is estimated by using the mode matching technique and surface equivalent theorem. The theoretical results are compared with the measurement to check the accuracy of our analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.89-96
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• 2005

This study has been performed on the mechanism of heat transfer between stratospheric airship and its surroundings while the airship is staying in the air at the altitude of 20km. The computational grid of airship has been generated and the results influenced by the number and the shape of grids have been compared. The temperature distributions have been obtained through this thermal analysis considering three modes of heat transfer - conduction, convection and radiation - in stratospheric conditions. Based on the airship's surface and inner temperature variations, the influence of temperature distributions on the helium envelope and the payload has been predicted.

• 한국해양학회지
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• v.20 no.2
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• pp.1-9
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• 1985

A simple analytic model of the sea surface temperature(SST) is developed in order to understand the effects of the Asian monsoon and the Kuroshio on the annual variations of SST by the Asian monsoon is almost in phase with the incoming radiation whereas that by the Kuroshio is out of phase with the incoming radiation. In the Yellow Sea, due to the heat advection by the Asian monsoon, the yearly mean SST is low and the annual range of SST exceeds 20$^{\circ}C$. The annual range of SST in the northwestern Japan Sea is large because of the combined effects of the Asian monsoon and the cold water advection. In the Kuroshio and in the Tsushima Current regions, the annual range of SST is small and the mean SST is high due to the heat advection by warm currents.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.157-164
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• 2002

본 연구에서는 실생활에 응용되는 Chloroprene계 고무에 대하여 30개월 동안 옥외 폭로를 행하였으며 동시에 Xenon-arc Type의 촉진 내후성시험기를 이용하여 그에 따른 내후성의 변화를 평가하였다. 폭로기간에 따른 인장강도와 신장률의 변화를 측정하였고 폭로면의 표면층에 대하여 FT-IR과 SEM을 사용하여 화학적 특성 및 미세구조를 분석하였다. 태양복사와 습도에 노출된 고무의 표면은 매우 짧은 기간에 파괴되었고, 고무 내부에 존재하는 가교제들의 용출을 확인할 수 있었으며, 산소와의 결합으로 내부층보다 고무의 표면에서 더 많은 가수분해와 광분해가 이루어진다는 것을 확인할 수 있었다. 이와 같은 표면층의 변화와 파괴는 고무의 기계적 성질에도 의미 있는 영향을 주었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.455-461
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• 2016

Survivability of an aircraft has been greatly threatened by the development of a weapon system using infrared. Therefore, the infrared stealth technology is a very important technique to improve the survivability of an aircraft. In this study, the infrared signal of an aircraft was analyzed which corresponding to the aircraft surface temperature and environmental conditions with various surface conditions(especially emissivity changed). Based on the analyzed infrared signal, the optimized surface emissivity was suggested to reduce the average contrast radiance and contrast radiant intensity(CRI). In addition, we confirmed that the infrared contrast radiant intensity between the aircraft and the background can be minimized through an appropriately controlled surface emissivity of the aircraft at specific background.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.388-402
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• 2000

The radiation characteristics of leaky antenna from the dielectric-coated conducting cylinder with periodic corrugation are investigated theoretically for the infinite and finite periodic structures. For the infinite periodic structure, mode-matching method is applied. The integral equation is derived for the finite periodic structure by use of the Fourier transform and mode expansion and a simultaneous linear equation is obtained. The influences of the corrugation slot width, corrugation depth, dielectric thickness, cylinder radius, and finite corrugation number on the radiation characteristics (leakage constant, phase constant, and radiation pattern) are investigated. The results of the finite periodic corrugations are compared with those of the infinite extent structure and good agreement is found. To reduce high side lobe levels of the uniform finite periodic structure, tapering process on the beginning and end section of antenna and nonuniform quasi-period slot arrays are considered. Especially, for the corrugation period, width and depth used for a corrugated surface wave antenna, through the proper tapering process, end-fire radiation pattern with reduced side lobe levels is given.