• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1184-1193
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• 2010

The upper frequency of international EMC regulations is being expanded above 1 GHz. Radiated emissions above 1 GHz are different from those below 1 GHz that is existing upper regulation frequency, and which have lower field strength and sharper and tilted beam-width, relatively. In this paper, an effective evaluation method to be used above 1 GHz is studied using an offset parabola antenna system having a double-ridged horn antenna as a feed. First, simple model is proposed for calculating antenna factor and field uniformity of the parabola antenna system, and then real radiated emission and radiated susceptibility measurements are performed using a constant noise emitter and the suggested antenna system. The results show that the proposed antenna system has higher gain and power efficiency, and wider field uniformity relative to a conventional double-ridged horn antenna. Therefore, it is confirmed that the proposed system can be effectively used for EMC measurements above 1 GHz.

• Publications of The Korean Astronomical Society
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• v.5 no.1
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• pp.40-64
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• 1990

복사전달식, 통계평형식 및 전하 입자 보존식을 동시에 만족시키는 비열평형상태의 대기에 대하여 그 방출원자스펙트럼을 수치계산하였다. 등온, 중압의 비열평형 태양홍염을 대상모델로 선정하였는데 여기에 적응한 제한조건중 복사전달에 관련된 편미분방정식은 3점 근사 차분법에 의해 정리하였고 홍염중심에 대칭성을 가정하여 경제조건을 부여하였으며 대기의 물리상태에 관련된 비선형 연립방정식의 해는 완전선형화 기법을 통한 퓨트리에 소거법을 이용해 구하였다.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.52.1-52.1
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• 2021

Low mass X-ray binary(LMXB) 중 accretion disk가 존재하지 않으며 매우 작은 질량 (1 ≪ M_⊙)의 동반성을 가지는 pulsar binary system에서 중성자별과 동반성의 항성풍은 상호작용하여 intrabinary shock(IBS)을 형성한다. 이곳에서 입자들은 상대론적으로 가속되어 싱크로트론 복사를 방출한다고 생각된다. 이 복사는 X-선 영역으로 관측되며 이때 관측된 X-선 궤도 광도곡선은 IBS의 모양에 따라 달라진다. 우리는 IBS의 X-선 복사 과정을 모델화하여 shock의 모양과 내부의 전자 특성을 파악하고, 광학 관측을 통해 얻은 orbital parameter와 비교하며 binary의 geometry를 보다 정확히 이해하고자 한다. 이 발표에서는 다양한 pulsar binary system의 Chandra, XMM 그리고 NuSTAR의 X-선 관측 데이터에 IBS 모델을 적용해보고 IBS와 binary의 geomerty를 분석한 결과를 제시한다.

• Fire Science and Engineering
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• v.34 no.1
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• pp.72-78
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• 2020

In this paper, the risk of damages to humans and properties due to fire explosions in gasoline storage tanks is identified, and the effects of radiant heat on adjacent tanks are evaluated to present the necessary area to secure safety. A simulation was conducted to evaluate the effect of radiant heat (Maximum emission) on adjacent tanks in an oil storage tank fire due to environmental conditions (Wind speed and temperature) in the Northern Gyeonggi Province. The result indicated that the radiant heat released in the fire of an oil storage tank was increased by approximately 1.9 times by the maximum wind speed and the difference occurred in the range of 700~800 kW by the maximum temperature. If a storage tank fire occurs, securing approximately 34.4 m of holding area is necessary. In the future, evaluating the radiant heat emitted by the fire of gasoline storage tanks will be required by applying various environmental conditions, and through this, research on specific and quantitative holding area is required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.336-344
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• 2011

The purpose of this study is to analyze the radiation-pattern characteristics above 1 GHz for the electromagnetic wave radiated from multi-slot such as ventilations, etc. on the enclosure of an EUT and so to make recommendations for suitable test methods. An experimental EUT was formed by putting a comb-generator at the center of a rectangular enclosure with 4 slots, and its radiation pattern was analyzed in the frequency range of 1~6 GHz. As analysis results, multi-lobe appears above 2 GHz and the number of multi-lobes is growing as the frequency increases. And real radiated-emission measurements were performed for the experimental EUT by scanning a receiving antenna in the height of 1~4 m and tilting toward maximum radiation, as well as setting the height of a receiving antenna to the central position of the EUT which is prescribed at the present standards. The measured results are +12.8 dB in the scanning and +16.4 in the scanning and tilting compared with the present standard test method. Therefore, the latter must be revised in order to consider the radiation pattern above 1 GHz.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.187-196
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• 2009

Synthetic Aperture Radar(SAR) satellite system for broad-area imaging has RF systems including SAR radiating a high power, data link system transmitting the acquired image data from the SAR, TC&R(Telemetry, Command, and Ranging) to communicate with a ground segment to control a satellite. Each system transmits RF signal having various frequencies and radiates a high power, RS(Radiated Susceptibility) specification should be verified at an electronic unit mounted in satellite. RF interference can be happened because of non-linearity of a RF system. Therefore, we manufactured a structure model installed antennas which have a similar pattern with a real antenna, the effect by RF interference is analyzed and verified.

• Fire Science and Engineering
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• v.17 no.2
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• pp.35-42
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• 2003

In this study, we tried to evaluate the ignitibility, flammability, heat release rate, and toxicity of five different types of burning artificial leather sofa covers that are widely used in entertainment service industry buildings. As the results of this study, putting the artificial leathers under fire conditions we found out following results auto-ignition temperature was$ 427~437^{\circ}C$, limiting oxygen index was 19~20%; at heat flux of $25 kW\m^2$, ignition time was 10~16s and peak heat release rate was $147~277 kW\m^2$; and at heat flux of$ 35 kW\m^2$, ignition time was 6~9s and peak heat release rate was $176~296 kW\m^2$. The toxic materials discharged from the burning leathers were 5,550~6,290 ppm of CO, 18,500~23,400 ppm of $CO_2$, 110~140 ppm, of HCl, 13~65 ppm of HCN and 145~220 ppm of NOx.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.66.2-66.2
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• 2010

별 탄생 초기 진화 단계에 있는 원시항성들은 별 주변 물질들에 의해 둘러싸여 있고, 낮은 온도로 인해 대부분의 에너지를 원적외선 영역에서 방출한다. 그러므로, 원시항성 진화 연구에서 진화단계와 물리적 특성을 바르게 유도하기 위해서는 원적외선 관측이 필수적이다. 본 연구는 원적외선 자료의 중요성을 정량적으로 보이기 위하여 이미 c2d 스피처 레거시 팀에서 동정한 원시성 중, IRAS Point Source Catalog에는 존재하지 않지만, AKARI FIS Catalog에는 존재하는 원시성들을 뽑아내어 AKARI 원적외선 플럭스의 유무에 따른 Bolometric Luminosity와 Bolometric Temperature의 차이를 비교하였다. 뿐만 아니라 AKARI 원적외선 플럭스의 유무에 따라 연속복사전달 모델로부터 얻어지는 물리량, 특히 성간복사장의 세기가 어떻게 달라지는지 연구하였다.

• Journal of the Korea Convergence Society
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• v.9 no.2
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• pp.1-6
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• 2018

In this study, the investigation results of conducted and radiated emission for DC/DC converter circuit applied in electric vehicles are presented. A frequency spreading circuit was used to improve the EMI characteristics of a power converter designed by using MPQ4433 chip. The frequency spreading circuit using a TLV3201 chip was designed and applied to the power converter. A PCB was fabricated based on the EMI minimization procedures and simulated and measured results were presented for the far-field and near-field conducted and radiated emissions using the fabricated circuit. The measurement were done as CISPR 25 standardized test procedures. It is clearly showed that the EMI characteristics were improved 20% in case frequency spreading was applied. The EMI reduction technique using the frequency spreading proposed in this study was first applied to the design of power converter module for automobile. It is expected that the method presented here can be effectively used for EMI improvement in the future.

• Analytical Science and Technology
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• v.6 no.3
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• pp.297-305
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• 1993

Generally, it is difficult to analyze cast iron samples with spark discharge emission spectrometry since the content of carbon in these samples is high as a few percent. The cast iron samples were analyzed with the developed glow discharge emission spectrometer composed of glow discharge emission source and polychromator. The discharge condition of glow discharge lamp(GDL) has been optimized by variation of Ar gas pressure, discharge voltage and discharge time. Under the optimum conditions obtained in this work, relationships between the measured emission intensities and concentration of two types of cast iron standard samples(BAS, LECO) were investigated. Most of elements(Mn, Si, P, S etc.) showed the good linearity in one calibration curve. And the carbon showed slightly the systematic difference according to the type of standard samples.