• Title/Summary/Keyword: 위성 군집

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Analysis on the Sedimentary Environment and Microphytobenthos Distribution in the Geunso Bay Tidal Flat Using Remotely Sensed Data (원격탐사 자료를 이용한 근소만 갯벌 퇴적환경 및 저서미세조류 환경 분석)

  • Choi, Jong-Kuk;Ryu, Joo-Hyung;Eom, Jin-Ah;Roh, Seung-Mok;Noh, Jae-Hoon
    • Journal of Wetlands Research
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    • v.12 no.3
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    • pp.67-78
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    • 2010
  • Surface sedimentary facies and the change of microphytobenthos distribution in Geunso Bay tidal flat were monitored using remotely sensed data. Sediment distribution was analyzed along with the spectral reflectance based on the in situ data, and the spectral characteristics of the area where microphytobenthos occupied was examined. A medium to low spatial resolution of satellite image was not suitable for the detection of the surface sediments changes in the study area due to its ambiguity in the sedimentary facies boundary, but the seasonal changes of microphytobenthos distribution could be obviously detected. However, area of predominance of sand grains and seagrass distribution could be distinctly identified from a high spatial resolution remote sensing image. From this, it is expected that KOMPSAT-2 satellite images can be applied effectively to the study on the surface sedimentary facies and detailed ecological mapping in a tidal flat.

Structural Design of SAR Control Units for Small Satellites Based on Critical Strain Theory (임계변형률 이론에 기반한 초소형 위성용 SAR 제어부 전장품 구조설계)

  • Jeongki Kim;Bonggeon Chae;Seunghun Lee;Hyunung Oh
    • Journal of Aerospace System Engineering
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    • v.18 no.2
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    • pp.12-20
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    • 2024
  • The application of reinforcement design to ensure the structural safety of electronics in small satellites is limited by the spatial constraints of the satellite structure during launch vibrations. Additionally, a reliable evaluation approach is needed for mounting highly integrated devices that are susceptible to fatigue failure. Although the Steinberg fatigue failure theory has been used to assess the structural integrity of electronic devices, recent studies have highlighted its theoretical limitations. In this paper, we propose a structural methodology based on the critical strain theory to design the digital control unit (DCU) of the X-band SAR payload component for the small SAR technology experimental project (S-STEP), a small satellite constellation. To validate the design, we conducted modal and random analyses using simplified modeling techniques. Based on our methodology, we ultimately demonstrated the structural safety of the electronics through analysis results, safety margin derivation, and functional tests conducted both before and after the launch test.

A Study on the Search Behavior of Digital Library Users: Focus on the Network Analysis of Search Log Data (디지털 도서관 이용자의 검색행태 연구 - 검색 로그 데이터의 네트워크 분석을 중심으로 -)

  • Lee, Soo-Sang;Wei, Cheng-Guang
    • Journal of Korean Library and Information Science Society
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    • v.40 no.4
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    • pp.139-158
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    • 2009
  • This paper used the network analysis method to analyse a variety of attributes of searcher's search behaviors which was appeared on search access log data. The results of this research are as follows. First, the structure of network represented depending on the similarity of the query that user had inputed. Second, we can find out the particular searchers who occupied in the central position in the network. Third, it showed that some query were shared with ego-searcher and alter searchers. Fourth, the total number of searchers can be divided into some sub-groups through the clustering analysis. The study reveals a new recommendation algorithm of associated searchers and search query through the social network analysis, and it will be capable of utilization.

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Selection and Evaluation of Vertiports of Urban Air Mobility (UAM) in the Seoul Metropolitan Area using the K-means Algorithm (K-means 알고리즘을 활용한 수도권 도심항공 모빌리티(UAM) 수직이착륙장 위치 선정 및 평가)

  • Jeong, Jun-Young;Hwang, Ho-Yon
    • Journal of Advanced Navigation Technology
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    • v.25 no.1
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    • pp.8-16
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    • 2021
  • In this paper, locations of vertiports were selected and evaluated to operate urban air mobility (UAM) in the Seoul metropolitan area. Demand data were analyzed using the data from the survey of commuting population and were marked on a map using MATLAB. To cluster the data, the K-means algorithm function built in MATLAB was used to identify the center of the cluster to as the location of vertiports, and using the silhouette technique, the accuracy and reliability of the clustering were evaluated. The locations of the selected vertiports were also identified using satellite maps to ensure that the locations of the selected vertiports were suitable for the actual vertiport location, and, if the location was not appropriate, final vertiports were selected through the repositioning process.

Analysis of Forest Fire Damage Areas Using Spectral Reflectance of the Vegetation (식생의 분광 반사특성을 이용한 산불 피해지 분석)

  • Choi, Seung-Pil;Kim, Dong-Hee;Ryutaro, Tateishi
    • Journal of Korean Society for Geospatial Information Science
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    • v.14 no.2 s.36
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    • pp.89-94
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    • 2006
  • Forest damage is a worldwide issue and specially, a forest fire involves damage to itself and causes secondary damage such as a flood etc. However, actually, clear analysis on forest fire damage can be hardly conducted due to difficulty in approaching a forest fire and quite a long period of time for analysis. To overcome such difficulty, recently, forest fire damage has been actively investigated with satellite image data, but it is also difficult to obtain satellite image data fitted to the time a forest fire occurred. In addition, it is burdensome to verify accuracy of the obtained image. Therefore, this study was attempted to look into the damaged districts from forest fires by reference to spectroradiometric characteristics of the obtained vegetation with a spectroradiometer as preliminary work to use satellite image data. To begin with, the researcher analyzed the field survey data each measured 3 months and 6 months after occurrence of a forest fire by judging the extent of the damage through visual observation and using a spectroradiometer in order to investigate any potential errors arising out of one-time visual observation. Besides, in this study, groups showing possibilities that trees might be restored to life and wither to death could be classified on the sampling points where forest fire damage is minor.

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한국의 기후학 반세기:회고와 전망

  • 이현영
    • Journal of the Korean Geographical Society
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    • v.31 no.2
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    • pp.128-137
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    • 1996
  • 한국의 기후학 연구성과는 1958년 발표된 이후 약간의 기복은 있었으나 꾸준히 발 전하여 왔다. 연구성과를 하부 분야별로 보면 기후학 일반(43.5%)이 가장 많았고, 종관기후 학(34.7%), 기후변화(13.0%) 그리고 응용기후학(8.8%)으로 구성되어 있으나 근래에는 응용 기후학 분야에 대한 연구가 서서히 증가하고 있다. 1970년대 이전에는 주로 지상 기후요소 간의 기상자료를 사용하여 상관관계 출현빈도.시계열분석 등으로 전국 규모의 기후특성을 규명한 데 반하여 최근에는 시계열분석과 더불어 군집.주성분.인자분석 등 다변량 분석기 법 등의 통계기법이 많이 활용되고 있다. 초기에는 지상기상자료를 주로 연구에 사용하였는 데 점차 고층기상자료와 인공위성자료를 활용하면서 국지기후 연구와 더불어 기후예측 모델 의 구축단계까지 발달하였다. 그러나 한국기후학이 당면한 문제는 인적자원의 절대적인 빈 곤과 더불어 인접분야에 비하여 연구환경이 열악한 것이다. 즉, 대학에서는 비전공자에 의한 기후학 교육이 빈번하고, 국지기후 연구의 경우는 실측을 요하기도 하는데 자료의 생성 및 분석에 필요한 장비가 절대적으로 부족하다. 따라서 한국의 기후학의 발전을 도모하려면 기 후학자의 배출이 급선무이고, 기후학자는 물론, 대학 및 연구소간의 연구 및 자료 교류 등의 상호협조가 요청된다.

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Development and Analysis of COMS AMV Target Tracking Algorithm using Gaussian Cluster Analysis (가우시안 군집분석을 이용한 천리안 위성의 대기운동벡터 표적추적 알고리듬 개발 및 분석)

  • Oh, Yurim;Kim, Jae Hwan;Park, Hyungmin;Baek, Kanghyun
    • Korean Journal of Remote Sensing
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    • v.31 no.6
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    • pp.531-548
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    • 2015
  • Atmospheric Motion Vector (AMV) from satellite images have shown Slow Speed Bias (SSB) in comparison with rawinsonde. The causes of SSB are originated from tracking, selection, and height assignment error, which is known to be the leading error. However, recent works have shown that height assignment error cannot be fully explained the cause of SSB. This paper attempts a new approach to examine the possibility of SSB reduction of COMS AMV by using a new target tracking algorithm. Tracking error can be caused by averaging of various wind patterns within a target and changing of cloud shape in searching process over time. To overcome this problem, Gaussian Mixture Model (GMM) has been adopted to extract the coldest cluster as target since the shape of such target is less subject to transformation. Then, an image filtering scheme is applied to weigh more on the selected coldest pixels than the other, which makes it easy to track the target. When AMV derived from our algorithm with sum of squared distance method and current COMS are compared with rawindsonde, our products show noticeable improvement over COMS products in mean wind speed by an increase of $2.7ms^{-1}$ and SSB reduction by 29%. However, the statistics regarding the bias show negative impact for mid/low level with our algorithm, and the number of vectors are reduced by 40% relative to COMS. Therefore, further study is required to improve accuracy for mid/low level winds and increase the number of AMV vectors.

Survey on Research and Development of Field Emission Electric Propulsion Thrusters (전계방출 전기추진 추력기 연구개발 현황)

  • Park, Jeongjae;Lee, Bok Jik;Jeung, In-Seuck
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.5
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    • pp.36-52
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    • 2021
  • As the application of nano-satellites constellation increases worldwide in the wake of New Space era, there is growing demand for the development of thrusters for precise attitude and orbit control of small satellites. Field Emission Electric Propulsion(FEEP) thruster uses a liquid metal as a propellant and accelerates the ionized liquid metal through a strong electric field at the tip of the metal surface. FEEP thruster technology is suitable for nano-satellites which require various missions for attitude and orbit control, because it provides thrust ranging from 1 µN to 1 mN with high specific impulse up to about 10,000 s and can be miniaturized due to its simple structure. In this paper, the basics of FEEP thrusters are introduced, then the current status of research and development of FEEP thrusters are presented.

A Study to Improve the Accuracy of Segmentation and Classification of Mosaic Images over the Korean Peninsula (한반도 모자이크 영상의 분할 및 분류 정확도 향상을 위한 연구)

  • Moon, Jiyoon;Lee, Kwang Jae
    • Korean Journal of Remote Sensing
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    • v.37 no.6_3
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    • pp.1943-1949
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    • 2021
  • In recent years, as the demand of high-resolution satellite images increases due to the miniaturization and constellation of satellites, various efforts to support users to utilize satellite images more conveniently are performed. Accordingly, the Korea Aerospace Research Institute produces and provides mosaic images on the Korean Peninsula every year to improve the convenience of users in the public sector and activate the use of satellite images. In order to increase the utilization of mosaic images on the Korean Peninsula, a study on satellite image segmentation and classification using mosaic images was attempted. However, since mosaic images provide only R, G, and B bands and processes such as image sharpening and color balancing are applied, there is a limitation that the spectral information of original images is distorted, so various indices were extracted and classified using R, G, and B bands to compensate for this. As a result of the study, the accuracy of image classification results using only mosaic images was about 72%, while the accuracy of image classification results using indices extracted from R, G, and B bands together was about 79%. Through this, it was confirmed that when performing image classification using mosaic images on the Korean Peninsula, the image classification results can be improved if the indices extracted from R, G, and B bands are used together. These research results are expected to be applied not only to mosaic images but also to images in which spectral information is limited or only R, G, and B bands are provided.

Hybrid Path Planning of Multi-Robots for Path Deviation Prevention (군집로봇의 경로이탈 방지를 위한 하이브리드 경로계획 기법)

  • Wee, Sung-Gil;Kim, Yoon-Gu;Choi, Jung-Won;Lee, Suk-Gyu
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.5
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    • pp.416-422
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    • 2013
  • This paper suggests a hybrid path planning method of multi-robots, where a path deviation prevention for maintaining a specific formation is implemented by using repulsive function, $A^*$ algorithm and UKF (Unscented Kalman Filter). The repulsive function in potential field method is used to avoid collision among robots and obstacles. $A^*$ algorithm helps the robots to find optimal path. In addition, error estimation based on UKF guarantees small path deviation of each robot during navigation. The simulation results show that the swarm robots with designated formation successfully avoid obstacles and return to the assigned formation effectively.