• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.21-30
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• 2018

In this study, we developed the Soil Moisture Data Assimilation (SMDA) scheme to extract Effective Soil Characteristics-ESC (Sand, Silt, Clay %) from MODerate resolution Imaging Spectroradiometer (MODIS) products. The SMDA scheme was applied to the MODIS-based Soil Moisture (SM) data during the summer (July to September) period. Then the ESC and soil erosion factors (K) were predicted, respectively. Several numerical experiments were conducted to test the performance of SMDA at the study sites under the synthetic and field validation conditions. In the synthetic experiment, the estimated soil moistures values(R: >0.990 and RMSE: <0.005) were identified well with the synthetic observations. The field validation results at the Bangdongri and Chungmicheon sites were also comparable to the TDR-based measurements with the statistics (R: 0.772/0.000 and RMSE: 0.065/0.000). The estimated ESC values were also matched well with the measurements for the synthetic and field validation conditions. Then we tested the SMDA scheme to extract the ESC from the MODIS-based soil moisture products. Although uncertainties exist in the results, the estimated soil moisture and ESC based on the SMDA were comparable to the measurements. Overall, the K factors were similarly distributed based on the derived ESC. Also, the K factors in the mountainous regions were higher than those of the relatively flat areas. Thus, the newly developed SMDA scheme can be useful to estimate spatially and temporally-distributed soil erosion and establish soil erosion management plans.

• 전기의세계
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• v.43 no.12
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• pp.67-72
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• 1994

ITU-T(구 CCITT)의 X.25에 기초한 패킷교환 방식은 회선교환에 비하여 대역폭을 효과적으로 사용할 수 있는 장점을 갖고 있으나 흐름제어와 오류제어 처리에 따른 지연으로 속도가 64Kbps로 제한된다는 것이 단점이다. 특히 90년대에 들어서부터는 문자 정보만 전송하던 80년대와는 달리 데이타량이 큰 그래픽 및 화상데이타의 전송수요가 늘어나고 있으며 LAN 및 클라이언트 서버 환경의 도입으로 대표되는 기업의 컴퓨팅 환경의 변화가 급속히 이루어지고 있어서 기업의 통신환경이 기존의 패킷교환 방식만을 갖고는 도저히 감당할 수 없게 되었다. 이에 따라 고속 패킷교환기술들이 80년대 후반부터 등장하기 시작하였으며, 공중 데이타망 기술로 대표적인 것은 프레임릴레이(FR), SMDA(Switched Multimegabit Data Service), ATM(Asynchronous Transfer Mode) 등이다.