• Proceeding of EDISON Challenge
• /
• 2014.03a
• /
• pp.591-596
• /
• 2014

본 논문에서는 EDISON_전산열유체 시스템을 활용하여 군집주행 형태 변화에 따른 항력계수 및 연료효율 변화를 분석하였다. 해석 대상은 자동차 형상을 단순화한 모델인 아흐메드 형상(Ahmed body)을 이용하였다. 동종차량 간 거리변화에 따른 항력계수 및 연료효율의 변화, 이종차량의 배열순서변화에 따른 항력계수 및 연료효율을 분석하며 연구를 수행하였다. 연구 결과, 4대의 동종차량 군집주행시 항력계수를 최대 69% 감소할 수 있으며 이에 따라 km 당 0.073L의 연료를 절감할 수 있다.

• Proceedings of the Korea Inteligent Information System Society Conference
• /
• 2002.05a
• /
• pp.401-409
• /
• 2002

인터넷과 같은 대량의 정보에 대응할 수 있는 고성능 정보검색시스템을 구축하기 위해서는 지금까지 고가의 중대형 컴퓨터를 주로 활용하여 왔으나, 최근 가격대 성능비가 높은 PC 클러스터 시스템을 활용하는 방안이 경제적인 대안으로 떠오르고 있다. PC 클러스터 상에서의 병렬정보검색시스템을 효율적으로 운영하기 위해서는 사용자가 입력한 질의를 처리하는데 요구되는 개별 PC의 디스크 I/O 및 검색관련 연산을 모든 PC에 가능한 균등하게 분배할 필요가 있다. 본 논문에서는 같은 질의에 동시에 등장할 가능성이 높은 색인어들끼리 군집 화하고 생성된 군집을 활용하여 색인어들을 각 PC에 분산저장함으로써 보다 높은 수준의 병렬화를 달성할 수 있는 방안을 제시한다. 대용량 말뭉치를 활용한 실험결과 본 논문에서 제시하는 분산저장기법이 충분한 효율성을 가지고 있음을 확인하였다.

• Proceedings of the KIEE Conference
• /
• 2008.10b
• /
• pp.353-354
• /
• 2008

본 논문에서는 GPS, Bleutooth 모듈을 사용하여 이동로봇의 군집이동에 관한 연구를 다루었다. 로봇 통신 모델로는 특정한 수신자가 정보를 받을 것을 기대하지 않고 통신가능 범위 안으로 들어왔을 때 상대방에게 정보를 보내는 방법인 사인보드 모델을 선택하였다. 군집간 제어를 위한 총 3대의 실외 이동을 로봇제작과 로봇의 좌표인식, 방향을 찾기 위해 GPS수신 모들과 Bluetooth 송 수신기를 사용하였다. 실험에 쓰인 모든 이동용 로봇에 GPS수신기와 Bluetooth 송 수신기를 장착하였고, GPS수신기로부터 받은 Master-이동로봇의 위치좌표를 Bluetroth 통신 영역 내에 있는 모든 이동로봇에게 송신을 한다. 각 Slave-이동로봇을 Master-이동로봇으로부터 받은 위치 좌표로 로봇간의 거리와 방향을 계산하며 이를 토대로 군집 로봇의 이동 알고리즘을 구현하였다. 본 논문에서는 군집간 제어를 위해 군집 로봇 시스템을 제작하였으며 상대적인 위치, 거리 유지, 진행방향을 계산한다. Master-이동로봇과 Slave-이동로봇 간의 1:N 실시간 통신과 일정거리를 유지함으로써 군집간 제어를 하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2002.04a
• /
• pp.519-522
• /
• 2002

일반적으로 PubMed와 같은 인터넷을 이용한 대규모 의료 문헌정보 검색시스템에서 포괄적인 주제어나 간결한 주제어를 이용한 검색을 시도할 경우, 종종 매우 다양한 세부주제의 문헌리스트들이 다량으로 검색된다. 이러한 경우 이용자는 실제로 본인이 원했던 세부주제에 부합되는 문헌들을 찾기 위해서는 검색결과로 주어진 긴 문헌리스트상의 문헌 하나하나에 대해 다시 문헌제목이나 혹은 요약 등의 내용을 직접 읽어보고 내용을 확인하여야 한다. 이러한 작업은 매우 번거럽고 시간과 노력을 많이 필요로 한다. 따라서 본 논문에서는 이러한 노력을 줄이기 위한 한 가지 방안으로, PubMed 시스템의 주제어 검색결과로 주어진 문헌들에 대해 내용의 유사성과 차별성에 따라 자동으로 몇 개의 그룹으로 나누어주는 군집화시스템 MedCluster의 설계와 구현에 대해 소개한다. MedCluster의 큰 특징은 기존의 문서 군집화 방법과는 다른 신경망 GHSOM을 이용한 군집화 방법을 사용하는 점이다. GHSOM은 미리 문서 그룹의 개수를 정해줄 필요가 없고 다양한 레벨의 문서 그룹들을 얻을 수 있는 계층적 군집화를 이루어낸다는 장점을 가지고 있다. 본 논문에서는 신경망 GHSOM의 구조와 특성에 대해 간략히 살펴보고, GHSOM을 채용한 의료문헌 군집화시스템 MedCluster의 설계와 구현에 대해 설명한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.12
• /
• pp.981-988
• /
• 2021

This paper presents a decentralized guidance algorithm for swarm flight of fixed-wing UAVs (Unmanned Aerial Vehicles). Considering swarm flight missions, we assume four representative swarm tasks: gathering, loitering, waypoint/path following, and individual task. Those tasks require several distinct maneuvers such as path following, flocking, and collision avoidance. In order to deal with the required maneuvers, this paper proposes an integrated guidance algorithm based on vector field, augmented Cucker-Smale model, and potential field methods. Integrated guidance command is synthesized with heuristic weights designed for each guidance method. The proposed algorithm is verified through flight tests using up to 19 small fixed-wing UAVs.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.5
• /
• pp.730-743
• /
• 1997

Community structure and distribution patterns of benthic polychaetes were studied in Aug. 1983 and Feb. 1984 in Kwangyang Bay, Korea. During the study period, the large-scale reclamation and dredging operations were taking place. Polychaetes were composed of 76 species with a mean density of $342\;ind.{\cdot}m^{-2}$ during the summer 1983 and 77 species with a mean density of $437\;ind.{\cdot}m^{-2}$ during the winter 1984. Community structure indices were applied to the seasonal data. The stations influenced by the Seomjin river are characterized by a low species number and low diversity, while the stations located in channel regions represent high species richness and highdiversity. The inner bay stations showed the intermediate level in terms of species richness and diversity. On the basis of taxa composition and abundance in summer, the cluster analysis indicated that the study area was divided into live regions. The main factors that govern the polychaete distributions appeared to be the fresh water run-off and bottom sediment composition. However, a slight difference was observed in winter community, and changes in composition of the dominant species were found from Lagis bocki and Chone teres to Glycinde gurjanovae and Heteromastus filiformis. As a result, the broad scale reclamation and dredging activities may have played a role in changes of the polychaete community structure and the dominant species composition in Kwangyang Bay.

• 한국해양학회지
• /
• v.23 no.1
• /
• pp.1-12
• /
• 1988

To clarify the community structure of phytoplankton in the Kyeonggi Bay, the community analysis were performed to investigate the relationship between the environmental factors and the phytoplankton communities. Low diversity with occurrence of few dominant species throughout the year, except summer, implies that ecological environment of this study area is very unstable due to incessant physical perturbation and large fluctuation of other environmental factors. According to the results of the cluster analysis this study area could be divided into river discharge, polluted and unpolluted area. Principal component analysis of overall phytoplankton community in this area clearly showed four seasonal succession patterns grouped into the spring type, the summer type, the late summer type, the late autumn-winter type. Summer communities composed of common phytoplankton are highly correlated with temperature and transparency. Winter communities composed of most tychopelagic plankton are positively correlated with suspended substances and nutrient, while negatively correlated with transparency.

• Korean Journal of Environment and Ecology
• /
• v.6 no.1
• /
• pp.44-54
• /
• 1992

A survey of subalpine zone (altitude is 1, 440-1, 700m) in Mt. Halla, was conducted using 37 sampling plots of l00$m^2$ size. The classification by TWINSPAN and RA. DCA ordination were applied to the study area in order to classify them based on woody plants and environmental variables. And to investigate vegetation deterioration by livestock's and user's impact on subalpine zone, seventeen plots were set up. By TWINSPAN techniques, the plant community were divided into five groups by the altitude. The dividing groups are Abies koreana-Taxus cuspidata community, Rhododendron yedoense var. poukhanense-Rh. mucronulatum var. ciliatum-Sasa quelpaertensis community, Ilex crenata- Elaeagnus umbellata-S. quelpaertensis community, Rh. yedoense var. poukhallense-Juniperus chinensis var. sargentii-Rh. mucronulatum var. ciliatum community and Empetrum nigrum var. japonicum-J. chinensis var. sargentii community. The species divirsity of plant community were decreased severely by livestock's and user's impact.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.11
• /
• pp.758-764
• /
• 2018

Digital documents such as patents, scholarly papers and research reports have author keywords which summarize the topics of documents. Different documents are likely to describe the same topic if they share the same keywords. Document clustering aims at clustering documents to similar topics with an unsupervised learning method. However, it is difficult to apply to a large amount of documents event though the document clustering is utilized to in various data analysis due to computational complexity. In this case, we can cluster and connect massive documents using keywords efficiently. Existing bottom-up hierarchical clustering requires huge computation and time complexity for clustering a large number of keywords. This paper proposes an inverted index based bottom-up clustering for keywords and analyzes the results of clustering with massive keywords extracted from scholarly papers and research reports.

• Korean Journal of Environment and Ecology
• /
• v.26 no.3
• /
• pp.313-321
• /
• 2012

To analyze the bird communities by the land use type, we surveyed 43 plots in Siheung City, Korea from Mar. 2009 to Feb. 2010 and classified the community by TWINSPAN and DCA. Classification result by TWINSPAN was classified into 4 communities. In the first division, waterbirds, such as spot-billed duck(Anas poecilorhyncha) and great egret(Egretta alba) operated as the differential species. In the second and third division, little grebe(Tachybaptus ruficollis) and eurasian sparrow(Passer montanus) were operated as the differential species. The relationship between land use types and classified bird communities, all plots of community I were located in the forest. Community II plots were contained all urban and several semi-natural land use types. Community III contains stream and rice paddy. Plots in the reservoir were classified community IV. The stream and rice paddy were classified into different communities, which were colsely related with the size of wetland paddy. Community III had the highest species diversity index and community II had lowest. Community III also had the highest maximum species diversity index and evenness index. The result of this study, small stream and small rice paddy located within the city have insignificant characteristics as the habitat for birds. Management size of semi-natural land use for wildbird habitat in the urban area should be considered for showing their habitat characteristics. If the classification of biotope type based on the scale of rice paddy and urban park and the type of landuse type in the riverside then we should be consider the standard of minium area.