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        검색결과 3

        1.
        2017.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm (Dstmin  -75 nT) driven by the X1.6 high speed flare-associated CME (1267 km s−1) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm (Dstmin  -223 nT) caused by a CME with moderate speed (719 km s−1) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long- duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.
        4,200원
        2.
        2011.06 구독 인증기관 무료, 개인회원 유료
        This paper describes the concept to design ship detection and identification systemwith combined use of Automatic Identification System (AIS) reports over Synthetic Aperture Radar (SAR) data. TerraSAR-X data (HH-polarization) in spotlight mode acquired on May 2, 2010 is used in this work with AIS-reports taken as ground truth. Till so far, only ship detection algorithms like CFAR (Constant False Alarm Rate), Alpha-stable distribution etc. were presented in most of the literatures for ship detection but also there are some limitation for ship detection performance like metrological conditions, image properties, speckle noise occurrence etc. Here, we present integration concept of both data by means of time matching of AIS-reports with image acquisition in order to estimate ship’s dead-reckoning (DR) location from AIS-report and are projected over an image along with the ship’s hull design for suitability and accurate reliability results. Nearest distance search method are applied to designate the SAR-derived ship targets within certain region of interest around DR. At last, DR based ship’s hull pattern is shifted over SAR-derived ship targets to conclude matched performance result in a well suitable manner.
        3,000원