• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.132-137
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• 2009

This study has regard to classification by using multi-temporal SAR data. Multi-temporal JERS-1 SAR images are used for extract the land cover information and possibility. So far, land cover information extracted by high resolution aerial photo, satellite images, and field survey. This study developed on multi-temporal land cover status monitoring and coherence information mapping can be processing by L band SAR image. From July, 1997 to October, 1998 JERS SAR images (9 scenes) coherence values are analyzed and then extracted land cover information factors, so on. This technique which forms the basis of what is called SAR Interferometry or InSAR for short has also been employed in spaceborne systems. In such systems the separation of the antennas, called the baseline is obtained by utilizing a single antenna in a repeat pass.

• Korean Journal of Remote Sensing
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• v.29 no.4
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• pp.389-397
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• 2013

Recently high spatial resolution space-borne Synthetic Aperture Radar (SAR) systems have launched and have been operated successfully. Interferometric SAR (InSAR) processing with the space-based high resolution observations acquired by these systems can provide more detail information for various geodetic applications. Coherence is regarded as a critical parameter in the evaluating the quality of an InSAR pair. In this study, we evaluate the coherence characteristics of high-resolution data acquired by TerraSAR-X (X-band) and ALOS PALSAR (L-band) and intermediate-resolution data acquired by Envisat ASAR (C-band) over western Texas, U.S.A. Our coherence analysis reveals that the high-resolution X-band TSX (3.1 cm) data has a high coherence level (0.3-0.6), similar to that of the L-band ALOS PALSAR data (23.5 cm) in short temporal baselines. Further more, the TSX coherence values are significantly higher than those of the C-band (5.6 cm) Envisat ASAR data. The higher coherence of the TSX dataset is a surprising result, because common scattering theories suggest that the longer wavelength SAR data maintain better coherence. In vegetated areas the shorter wavelength radar pulse interacts mostly with upper sections of the vegetation and, hence, does not provide good correlation over time in InSAR pairs. Thus, we suggest that the higher coherence values of the TSX data reflect the data's high-resolution, in which stable and coherent scatters are better maintained. Although, however, the TSX data show a very good coherence with short temporal baseline (11-33 days), the coherences are significantly degraded as the temporal baselines are increased. This result confirms previous studies showing that the coherence has a strong dependency on the temporal baseline.

• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.67-74
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• 2017

The D-InSAR is a technique for precisely measuring the subsidence of subsidence using difference of two SAR images. In order to calculate the subsidence using D-InSAR, a high coherence between master image and the slave image is essential. Since the existing D-InSAR method calculates the displacement based on the total coherence, the accuracy of the subsidence is lowered when the coherence map contains mountains or bare-land. In order to solve this problem, in this study, a point having a temporal coherence and spatial coherence of 0.7 or more was extracted to form TIN, and the subsidence was calculated based on this TIN. In addition, we compared the existing D-InSAR technique with the new D-InSAR technique considering spatial and temporal coherence. As a result, the new D-InSAR technique showed smaller standard deviation, relative variance, variation coefficient and quadrature deviation than the existing D-InSAR technique. It is also easy to grasp the trend of the subsidence.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.271-280
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• 2022

Landfast sea ice forms near coastlines in polar regions. Continuous monitoring of this sea ice is important, as it plays a key role in the marine ecosystem and affects the operation of nearby research stations. This study detected landfast sea ice around Jang Bogo research station in East Antarctica by stacking interferometric coherence images of Sentinel-1 synthetic aperture radar (SAR) data with 6-, 12- and 18-day temporal baselines. A total of 50 landfast sea ice maps were generated covering July 2017 to June 2018. The time series revealed regional differences in the timing of the maximum extent as well as growth rate of landfast sea ice. Overall, detecting landfast sea ice using interferometric SAR coherence seems promisingly feasible; however, limitations remain owing to low backscattering coefficients from new and smooth sea ice surfaces and subtle movements of sea ice in contact with the Campbell Glacier Tongue.

• Korean Journal of Remote Sensing
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• v.31 no.6
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• pp.501-512
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• 2015

Landfast sea ice (LFI) in Terra Nova Bay, East Antarctica where the Jangbogo Antarctic Research Station is located, has significant influences on marine ecosystem and the sailing of an icebreaker. Therefore, it is essential to analyze the spatio-temporal variation of the LFI in Terra Nova Bay. In this study, we chose interferometric pairs with the temporal baseline from 1 to 9 days out of a total of 62 COSMO-SkyMed synthetic aperture radar (SAR) images over Terra Nova Bay obtained from December 2010 to January 2012, and then constructed the coherence image of each pair. The LFI showed coherence values higher than 0.3 even in the interferometric SAR (InSAR) pairs of up to 9-days of temporal baseline. This was because the LFI was fixed at coastline and thus showed low temporal phase decorrelation. Based on the characteristics of the coherence on LFI, We defined the areas of LFI that show spatially homogeneous coherence values higher than 0.5. Pack ice (PI) and open water showed low coherence values due to large temporal phase decorreation caused by current and wind. Distinguishing PI from open water in the coherence images was difficult due to their similarly low coherence values. PI was identified in SAR amplitude images by investigating cracks on the ice. The extents of the LFI and PI were estimated from the coherence and SAR amplitude images and their temporal variations were analyzed. The extent of the LFI increased from March to July (maximum extent of $170.7km^2$) and decreased from October. The extent of the PI increased from February to May and decreased from May to July when the LFI increases dramatically. The extent of the LFI and air temperature showed an inverse correlation with a time lag of about 2 months, i.e., the extent of the LFI decreases after 2 months of the increase in the air temperature. Meanwhile the correlation between wind speed and the extent of the LFI was very low. This represents that the extent of LFI in Terra Nova Bay are influenced more by the air temperature than wind speed.

• Journal of KIISE:Software and Applications
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• v.30 no.7_8
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• pp.681-686
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• 2003

In this paper, we describes a system that extracts important sentences from Korean newspaper articles using automatic paragraphing. First, we detect repeated words between sentences. Through observation of the repeated words, this system compute Closeness Degree between Sentences(CDS ) from the degree of morphological agreement and the change of grammatical role. And then, it automatically divides a document into meaningful paragraphs using the number of paragraph defined by the user´s need. Finally. it selects one representative sentence from each paragraph and it generates summary using representative sentences. Though our system doesn´t utilize some features such as title, sentence position, rhetorical structure, etc., it is able to extract meaningful sentences to be included in the summary.

• Korean Journal of Remote Sensing
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• v.26 no.5
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• pp.497-510
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• 2010

In this study, comparisons of the backscattering coefficients and the coherence values which had been extracted from SAR (Synthetic Aperture Radar) images such as JERS-1, ENVISAT and ALOS satellites with surface roughness, surface geometric and soil moisture content were carried out. As the results of analysis using the backscattering coefficient and coherence values from SAR images, the coherence was shown high in the region containing more of mud fraction due to higher viscosity of fine grain-size. A lot of tidal channels were well developed in the Ganghwa tidal flat, affecting the drainage of seawater and subsequent soil moisture content by exposure time of tidal flat. The backscattering coefficient. consequently, appeared to be lower in sand flat and mix flat with decrease of soil moisture. In contrast, most mud flats were distributed at high elevation so that soil moisture was not much influenced by seawater. The backscattering coefficient in mud flat seemed to have a relationship with the density of tidal channel. In addition, lowering backscattering coefficients in the all Ganghwa tidal flat was observed when surface remnant water increased according to the amount of rainfall. The correlation between backscattering coefficient, coherence and sediment environment factors in the Ganghwa tidal flat was investigated. In the future, more quantitative spatial analysis will be helpful to well understand the sedimentary influence of various sediment environment factors.

• Annual Conference on Human and Language Technology
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• 1994.11a
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• pp.333-352
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• 1994

이 글은 그 동안 '숙어' 또는 '관용어'라는 이름 하에 별 다른 구별 없이 일괄적으로 다루어져 왔던 현대 국어 관용구를 그의 형태적 통사적 의미론적 결합 관계의 특성에 따라 재분류하여 그들의 특성과 하위 분류 등을 밝혀 보았다. 즉, 관용구를 그 내적구조의 특성, 구성요소들 사이의 의미상의 관련성의 긴밀도, 어휘와의 정도에 따라, 어휘화된 정도가 가장 높고 긴밀도에 있어서도 가장 높고 내적구성에 있어서도 여러 가지 특성을 보이는 것을 '숙어'라 하고, 그 이외의 것을 '연어'라 했다. '연어'가 생겨난 요인에 따라 '형태적 연어'와 '통사적 연어', '의미적 연어'로 나누었다. 이러한 분류는 국어 관용구의 특성을 밝혀 줄 수 있을 뿐만 아니라, 이에 더 나아가 각 관용구의 특성에 따른 올바른 기술을 통해 국어의 특수한 어휘 결합에 대한 보다 나은 이해를 꾀할 수 있다고 본다.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2000.06a
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• pp.233-237
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• 2000

본 논문은 단락의 자동 구분을 통한 중요 문장 추출 시스템을 제안한다. 먼저 어휘의 재출현 여부와 어휘의 일치도, 어휘의 역할 변화를 파악하여 재출현 어휘에 대한 양상을 분석하고 이를 통하여 문장 간의 긴밀도를 정량적으로 계산한다. 다음으로 측정된 문장 간 긴밀도를 이용하여 사용자의 추출 범위에 따라 단락을 구분하고, 각 단락의 대표 문장을 선정하여 최종 요약문을 생성한다. 제안한 방법은 문서 제목, 문장의 위치, 수사 구조 등의 정보를 이용하지 않으며, 단순히 어휘의 출현 빈도만을 이용하던 기존의 통계적인 방법보다 질높은 요약문을 생성할 수 있다. 또한 제안한 방법론은 본 논문이 대상으로 삼고 있는 신문기사의 영역뿐만 아니라 다른 영역으로의 적용이 가능하다.

• Korean Journal of Remote Sensing
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• v.23 no.4
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• pp.257-272
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• 2007

This paper analyzed relationships between various features from SAR data with multiple acquisition dates and mode (frequency, polarization and incidence angles), and land-cover classes. Two typical types of features were extracted by considering acquisition conditions of currently available SAR data. First, coherence, temporal variability and principal component transform-based features were extracted from multi-temporal and single mode SAR data. C-band ERS-1/2, ENVISAT ASAR and Radarsat-1, and L-band JERS-1 SAR data were used for those features and different characteristics of different SAR sensor data were discussed in terms of land-cover discrimination capability. Overall, tandem coherence showed the best discrimination capability among various features. Long-term coherence from C-band SAR data provided a useful information on the discrimination of urban areas from other classes. Paddy fields showed the highest temporal variability values in all SAR sensor data. Features from principal component transform contained particular information relevant to specific land-cover class. As features for multiple mode SAR data acquired at similar dates, polarization ratio and multi-channel variability were also considered. VH/VV polarization ratio was a useful feature for the discrimination of forest and dry fields in which the distributions of coherence and temporal variability were significantly overlapped. It would be expected that the case study results could be useful information on improvement of classification accuracy in land-cover classification with SAR data, provided that the main findings of this paper would be confirmed by extensive case studies based on multi-temporal SAR data with various modes and ground-based SAR experiments.