• Journal of the Korean earth science society
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• v.40 no.1
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• pp.9-23
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• 2019

Super-refraction of radar beams tends to occur primarily under a particular vertical structure of temperature and water vapor pressure profiles. A quality control process for the removal of anomalous propagation (AP) ehcoes are required because APs are easily misidentified as precipitation echoes. For this purpose, we collected X-band polarimetric radar parameters (differential reflectivity, cross-correlation coefficient, and differential phase) only including non-precipitation echoes (super-refraction and clear-sky ground echoes) and precipitation echoes, and compared the echo types regarding the relationships among radar reflectivities, polarimetric parameters, and the membership functions. We developed a removal algorithm for the non-precipitation echoes using the texture approach for the polarimetric parameters. The presented algorithm is qualitatively validated using the S-band Jindo radar in Jeollanam-do. Our algorithm shows the successful identification and removal of AP echoes.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.374-383
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• 2010

Microwave radar can penetrate cloud cover regardless of weather conditions and can be used day and night. Especially a ground-based polarimetric scatterometer has advantages of monitoring crop conditions continuously with full polarization and different frequencies. Kim et al. (2009) have measured backscattering coefficients of paddy rice using L-, C-, X-band scatterometer system with full polarization and various angles during the rice growth period and have revealed the necessity of near-continuous automatic measurement to eliminate the difficulties, inaccuracy and sparseness of data acquisitions arising from manual operation of the system. In this study, we constructed an X-band automatic scatterometer system, analyzed scattering characteristics of paddy rice from X-band scatterometer data and estimated rice growth parameter using backscattering coefficients in X-band. The system was installed inside a shelter in an experimental paddy field at the National Academy of Agricultural Science (NAAS) before rice transplanting. The scatterometer system consists of X-band antennas, HP8720D vector network analyzer, RF cables and personal computer that controls frequency, polarization and data storage. This system using automatically measures fully-polarimetric backscattering coefficients of rice crop every 10 minutes. The backscattering coefficients were calculated from the measured data at a fixed incidence angle of $45^{\circ}$ and with full polarization (HH, VV, HV, VH) by applying the radar equation and compared with rice growth data such as plant height, stem number, fresh dry weight and Leaf Area Index (LAI) that were collected at the same time of each rice growth parameter. We examined the temporal behaviour of the backscattering coefficients of the rice crop at X-band during rice growth period. The HH-, VV-polarization backscattering coefficients steadily increased toward panicle initiation stage, thereafter decreased and again increased in early-September. We analyzed the relationships between backscattering coefficients in X-band and plant parameters and predicted the rice growth parameters using backscattering coefficients. It was confirmed that X-band is sensitive to grain maturity at near harvesting season.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1085-1091
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• 2014

A model based SOC estimation scheme using parameter identification is described and applied to a Lithium-ion battery module that can be installed in electric vehicles. Simulation studies are performed to verify the effect of sensor faults on the SOC estimation results for terminal voltage sensor and load current sensor. The sensor faults should be detected and isolated as soon as possible because the SOC estimation error due to any sensor fault seriously affects the overall performance of the BMS. A new fault detection and isolation(FDI) scheme by which the fault of terminal voltage sensor and load current sensor can be detected and isolated is proposed to improve the reliability of the BMS. The proposed FDI scheme utilizes the parameter estimation of an input-output model and two fuzzy predictors for residual generation; one for terminal voltage and the other for load current. Recently developed dual polarization(DP) model is taken to develope and evaluate the performance of the proposed FDI scheme. Simulation results show the practical feasibility of the proposed FDI scheme.

• Proceedings of the KSRS Conference
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• v.1
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• pp.398-401
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• 2006

Dual channel Radiometer for Earth and Atmospheric Monitoring (DREAM) is the main payload on Science and Technology SATellite-2 (STSAT-2) of Korea. DREAM is two-channel microwave radiometer with linear polarization, and operating at center frequencies of 23.8 GHz and 37 GHz. An equation for DREAM calibration is derived which accounts for losses and re-radiation in the microwave components of the radiometer due to physical temperature. This paper describes the radiometric calibration equation to get antenna temperature ($T_A$) from the measured output data. At lower altitude, the measured deep space temperature is contaminated by middle atmosphere and earth radiation. In this paper, we presented the detail mathematical formulation to find the altitude up to which cold source brightness temperature is not affected by earth and middle atmosphere radiation. The DREAMPFM data is used to calculate the performance parameters (linearity, sensitivity, dynamic range, and etc.) of the system.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.66.1-66.1
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• 2012

We have developed superconducting mixer receivers for 129 GHz VLBI observation in Korean VLBI Network(KVN). The developed mixer has a radial waveguide probe with simple transmission line LC transformer as a tuning circuit to its 5 series-connected junctions, which can have 125-165 GHz as operation RF frequency. For IF signal path a high impedance quarter-wavelength line connects the probe to one end of symmetric RF chokes. DSB receiver noise of the mixer was about 40 K over 4-6 GHz IF band whereas we achieved about uncorrected SSB noise temperature of 70 K and better than 10 dB IRR in 2SB configuration with 8-10 GHz IF band. Insert-type receiver cartridges using the mixers have been assembled for all three KVN stations. On-site performance summary in commissioning phase is presented.

• Proceedings of the KSRS Conference
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• 2009.03a
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• pp.40-45
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• 2009

본 연구에서는 기후 등의 영향을 받지 않고 레이더 산란 측정을 할 수 있는 X-band antenna 기반의 자동관측 시스템을 이용하여 벼 생육시기에 따른 후방산란계수와 벼 생육인자와의 관계를 분석하여 후방산란계수를 이용한 벼 생육인자를 추정한 것을 목적으로 하였다. 2008년도 국립농업과학원 시험포장 ($37^{\circ}$15'28.0"N, $126^{\circ}$59'21.5"E)에서 추청벼를 대상으로 생육시기별 후방산란계수를 관측하였는데 모든 편파별 후방산란계수가 벼 유수형성기 (7월 말경)까지 증가하다가 그 후 감소하다가 수확기가 가까워지는 9월 중순이후 다시 증가하는 dual-peak 현상을 보였고 특히 W-편파의 경우 9월 초순부터 후방산란계수 증가가 다른 polarization에 비해 크게 나타났다. 후방산란계수와 작물생육인자와의 관계를 분석한 결과 고주파수인 X-band는 상대적으로 바이오메스, 엽 면적지수와의 상관이 낮게 나타났지만 이삭 건물중은 VV-편파 후방산란계수와 상관관계를 보였다. 이삭 건물중과 상관관계가 높게 나타난 X-band의 W-편파 후방산란계수를 이용하여 수확기 이삭 건물중을 추정하였는데 VV-편파 후방산란계수와 이삭 건물중과는 결정계수 $(R^2)$가 0.85이었고, 이삭 건물중 실측값과 추정값을 비교해 본 결과 1:1 line에 근접하게 분포하였다 ($R^2$=0.85).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.442-444
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• 2012

Depolarization characteristics of aerosol and cloud measured by dual wavelengths polarization lidar are examined. Ratio of depolarization ratio (RDR) between 1064 and 532nm are analyzed and compared with spherical aerosols and cloud. RDR of dust aerosols is exponentially decreased according to the increase of depolarization ratio at 532nm. The RDR of spherical aerosol is in the range of 1.5~6, dust aerosol is 0.98~4, and cloud is 0.7~1.77. Vertical distribution of dust aerosol and Relative Humidity (RH) are compared. In general, the RH in the dust layer are in the range of 30~60%. However, higher RH is frequently observed in the dust aerosols layer. In the condition of higher RH over 75%, the RDR of the dust aerosol are also increased to the range of 2~4.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.221-227
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• 2013

In this paper, Satellite DMB/WiBro antenna and PCS/WiBro antenna improving indoor coverage for mobile services are designed and fabricated. Satellite DMB/WiBro bands repeater antenna and PCS/WiBro bands repeater antenna are proposed as a simple radiator with loading capacitor to generate LHCP(Left Hand Circular Polarization). The proposed antenna for Satellite DMB/WiBro and PCS/WiBro bands communication are fabricated by copper plate uploader type and substrate uploader type. The designed and fabricated antenna has a bandwidth of 70MHz at 1.816GHz~1.886GHz and bandwidth of 107MHz at 2.247GHz~2.354GHz. Maximum gain of radiation pattern was up to 5dBi.

• Journal of electromagnetic engineering and science
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• v.13 no.4
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• pp.224-232
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• 2013

This paper describes composite cavity-backed crossed scythe-shaped dipoles with wide-beam circularly polarized (CP) radiation for use in Global Navigation Satellite Systems. Each branch of the dipole arm contains a meander line, with the end shaped like a scythe to achieve a significant reduction in the size of the radiator. For dual-band operation, each dipole arm is divided into two branches of different lengths. The dipoles are crossed through a $90^{\circ}$ phase delay line of a vacant-quarter printed ring to achieve CP radiation. The crossed dipoles are incorporated with a cavity-backed reflector to make the CP radiation unidirectional and to improve the CP radiation beamwidth. The proposed antennas have broad impedance matching and 3-dB axial ratio bandwidths, as well as right-hand CP radiation with a wide-beamwidth and high front-to-back ratio.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.183-187
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• 2008

This paper describes a power control scheme to improve the performance of a fuel cell battery hybrid power source for residential application. The proposed power control scheme includes a power control strategy to control the power flow of the fuel cell hybrid power system and a digital control technique for a front-end dc-dc converter of the fuel cell. The power control strategy enables the fuel cell to operate within the high efficiency region defined by the polarization curve and efficiency curve of the fuel cell. A dual boost converter with digital control is applied as a front-end dc-dc converter to control the fuel cell output power. The digital control technique of the converter employs a moving-average digital filter into its voltage feedback loop to cancel the low frequency harmonic current drawn from the fuel cell and then limits the fuel cell output current to a current limit using a predictive current limiter to keep the fuel cell operation within the high efficiency region as well as to minimize the fuel cell oxygen starvation.