• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.301-311
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• 2017

Aerosol optical properties as well as vertical location of layer can alter the radiative balance of the Earth by reflecting and absorbing solar radiation. In this study, radiative transfer model (RTM) and satellite-based analysis have been used to quantify the top-of-atmosphere (TOA) radiative effect of aerosol layers in the cloudy atmosphere of the northeast Asia. RTM simulation results show that the atmospheric warming effect of aerosols increases with their height in the presence of underlying cloud layer. This relationship is higher for stronger absorbing aerosols and higher surface albedo condition. Over study region ($20-50^{\circ}N$, $110-140^{\circ}E$) and aerosol event cases, it is possible to qualitatively identify absorbing aerosol effects in the presence of clouds by combining the UV Absorbing Aerosol Index (AAI) derived from Total Ozone Mapping Spectrometer (TOMS), cloud parameters derived from the Moderate Resolution Imaging Spectro-radiometer (MODIS), with TOA Upward Shortwave Flux (USF) from the Clouds and the Earth's Radiant Energy System (CERES). As the regional-mean radiative effect of aerosols, 6 - 26 % lower the USF between aerosols and cloud cover is taken into account. These results demonstrate the importance of estimation for the accurate quantification of aerosol's direct and indirect effect.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.1-8
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• 2011

In this paper, data transmission corrugated horn antenna for RF sensor satellite system and its radiation characteristic are presented. The proposed antenna is designed, fabricated and measured to obtain the maximum gain at ${\pm}60^{\circ}$ of its radiation patterns. The result of the proposed antenna is that the return loss is less than -15 dB and the gain is over 5 dBi at ${\pm}60^{\circ}$ of its radiation patterns. From these results, it is confirmed that the proposed can be used as data transmission corrugated horn antenna for RF sensor satellite system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.511-519
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• 2003

In this paper, to achieve a broad-band and high-gain antenna, we thus designed and analyzed the CRLPDA(Corner Reflector Antenna feeding by Log-Periodic Dipole Antenna) made up of 90$^{\circ}$corner reflector, which is trough-reflector type installed a planar reflector at the folded line. CRLPDA for operating frequency band of 1,400 MHB ~ 2,400 MHz was designed and radiation characteristics of the designed antenna were analyzed by moment method. To verify the analysis results, CRLPDA was fabricated and the calculated results were compared with the measured results. The measured results showed good agreement with the calculated results. As the result of measurements, bandwidth(VSWR＞2) for 1,000 MHz was achieved and gain was 13 dBi.

• Journal of the KSME
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• v.25 no.3
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• pp.236-241
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• 1985

본 고에서는 일반적으로 노즐 부위 열해석에서 무시되는 복사열전달율과 점성소산효과를 수치적 모델을 통하여 그 필요성 여부를 조사한 것이며 다음과 같은 결론을 얻었다. (1)연소실 및 수 렴부위에서는 복사열전달율이 대류열전달율과 같은 차수의 크기로 나타나고 있어서 고 복사율을 갖는 연소가스에서는 특히 중요하다. 특히 최근에 많이 사용되는 연료에는 연소가스에 산화알 루미늄 성분이 증가하는 추세이므로 노즐부위 열해석에는 복사열전달이 차지하는 비중이 커질 것이다. (2)노즐의 확산부위에서는 고속으로 인하여 가스자체의 점성소산이 일어나 특성치 보 정계수 값이 감소한다. 따라서 Bartz의 예측치 보다는 열전달계수의 값이 적어지고 있다. (3) 따라서 노즐수렴부위에서는 일반적으로 Bartz의 예상치보다 높고 확산부에서는 낮은 결과를 얻 었던 실험결과와를 비교할 때 고온고속 노즐에서의 열전달해석은 복사 열전달과 점성열 소산을 고려함으로써 정확하게 될 수 있다. (4)이상 고려된 실험 데이터와 수치모델의 고찰은 노즐내의 침식이 없는 경우이나 실제의 경우 노즐벽 표면에서 화학적 반응이 일어난다. 그러나 이때 발 생될 수 있는 순수한 발한효과는 미미하며 단지 전체적인 단면의 열 해석시 상기에서 예측된 열전달율을 근간으로 화학반응열 및 온도분포를 계산하여야 할 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.7
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• pp.598-609
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• 1991

A generalized expression of radiation intensity from multiple non linear transmission lines is derived from the circuit model of radiation phenomena and the phased array antenna theory, for PC traces having independent signal sources. An adequacy of this proposed analitical method was verified comparing with computer simulation and experimental result for two and three non linear transmission lines feeded by 600 MHz signal.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.3
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• pp.150-157
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• 2002

A nonlinear shaping method for a wire antenna is presented to improve the limited pulse radiation ability due to the frequency characteristics with nulls which are found in the conventional straight or V antennas. The developed scheme is based on the minimization of frequency-dependence of the radiated electric field intensity over wide band, hence giving the ripple-type frequency characteristics. It is shown that the synthesized shape has more advantage in the case of shorter pulse. That is, we found that for shorter pulse exciting, the radiated peak value of the synthesized antenna is larger than that of the conventional linear antenna. The inverse discrete Fourier transform based on the moment method is used for the transient analysis of current distribution and far field electric field.

• Fire Science and Engineering
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• v.21 no.3
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• pp.41-46
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• 2007

The combustion characteristics of surface forest fire fuels was analysed using variable external irradiation level. The characteristics such as ignition time, ignition temperature, critical heat flux and mass loss rate were measured. Fuel samples were exposed to incident heat fluxes from 8 to $50\;kW/m^2$. For the measurement of various combustion characteristics, the size of specimen holder was $100\;mm{\times}100\;mm{\times}12\;mm$ and the fuel samples grinded by electric mill were the fallen leaves of Quercus variabilis and Pinus densiflora. As results, the occurrence of ignition is possible to the heat flux more than $9\;kW/m^2$. The fuel of Pinus densiflora keeps its high temperature longer than that of Quercus variabilis during the combustion process. The results of measurement shows that the maximun and average mass loss rate of Quercus variabilis larger than that of Pinus densiflora.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.193-197
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• 2006

Radiation properties of flush mounted circular patch antennas are investigated. The patch is fed axis-symmetrically by a coaxial cable. Rigorous analysis iscarried out using integral transform and mode matching techniques. The presented method can accommodate a radiating patch, integrated matching section and band pass filter.

• Proceedings of the KSRS Conference
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• 2007.03a
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• pp.305-307
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• 2007

KOMPSAT-2(K-2) 의 MSC 는 CCD pixel 별 band 별 특성, 감도 및 시간에 따른 변화, CCD Geometry 등에 의해 왜곡 현상이 일어나며 위성 발사 전에 실험실에서의 충분한 실험과 Calibration 작업 을 통해 얻어진 값들을 사용하여 Image Restoration, 상대 복사 보정, 절대 복사 보정 등의 작업들을 거쳐서 왜곡 현상을 보정하게 된다. 그 중 복사 보정에 해당하는 NUC(NonUniformity Correction)은 MSC 각각의 픽셀들이 상이한 특성을 나타내는 것을 균일한 이미지로 보정하는 작업으로 무엇보다 우선시 되는 검보정 작업이다. K-2 NUC table 생성에는 시스템 특성상 몇 가지 사항을 고려 하여 위성에 upload 하는 high frequency NUC(HF NUC)과 지상국에서 처리할 수 있는 low frequency NUC(LF NUC)으로 구분하여 알고리즘을 생성하였다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.360-361
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• 2002

대기 중의 에어로졸은 지구의 복사평형에 직·간접적으로 영향을 끼친다. 직접적인 영향으로는 에어로졸이 가시광선과 자외선 영역의 에너지를 산란 또는 흡수함으로써 기후에 영향을 미치며, 간접적으로는 microphysical process에 의한 구름의 특성을 변화시키거나 불균일적인 화학반응을 통해서 복사특성을 지니는 가스들을 변화시킴으로써 기후에 영향을 미친다. 또한 동북아 지역 및 인접한 태평양 지역은 중국과 인접해 있는 관계로 매년 봄철이민 고비사막이나 중국의 황토고원에서 발생한 황사(Asian Dust) 현상에 의해 많은 고통을 겪고 있다. (중략)