• The Korean Journal of Applied Statistics
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• v.33 no.5
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• pp.591-601
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• 2020

The self-organizing map (SOM) is a unsupervised learning method projecting high-dimensional data into low-dimensional nodes. It can visualize data in 2 or 3 dimensional space using the nodes and it is available to explore characteristics of data through the nodes. To understand the structure of data, cluster analysis is often used for nodes obtained from SOM. In cluster analysis, the optimal number of clusters is one of important issues. To help to determine it, various cluster validity indexes have been developed and they can be applied to clustering outcomes for nodes from SOM. However, while SOM has an advantage in that it reflects the topological properties of original data in the low-dimensional space, these indexes do not consider it. Thus, we propose a new cluster validity index for SOM based on connectivity between nodes which considers topological properties of data. The performance of the proposed index is evaluated through simulations and it is compared with various existing cluster validity indexes.

• Korean Journal of Environment and Ecology
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• v.15 no.2
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• pp.159-172
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• 2001

본 연구는 수도권 지역의 아까시나무림을 중심으로 식물군집의 식생구조적 특성을 분석함으로써 향후, 도시녹지의 자연성 복원을 위한 기초 자료로 제시하고자 하였다. 조사지역은 서울도심지역으로 중구 남산과 서대문구 안산, 서울외곽지역으로 은평구 봉산과 부천시, 성주산, 비도시지역으로 경기도 천마산을 선정하였다. 주요 연구분야는 생태적 특성과 복원모델로 구분하였가. 생태적 특성평가는 천이단계, 자연성 및 다층적 식생구조와 종다양성을 실시하였으며, 복원모델은 적정수종, 개체수, 흉고단면적, 수목간 최단거리를 선정하였다. 조사결과, 복원모델은 비도시지역 중 자연성이 높으며 다층구조를 이루고 있는 자생식물군집을 선정하였으며 적정식물은 교목성장 3종, 아교목성정 7종, 관목성장 16종, 주연부 수종 4종 초본식물 27종이 적절한 것으로 판단되었다. 향후, 아끼시나무림읜 자연성 복원을 위해서 자연림인 참나무류로의 천이를 유도할 수 있도록 자생종 중심의 생태적 복원방안의 모색이 이루어져할 것이다.

• Korean Journal of Environment and Ecology
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• v.24 no.5
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• pp.582-590
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• 2010

Baekdudaegan field survey has been proposed and presented as a various plan such as field survey analysis, management and restoration plan, etc. Whereas, the concerns of the Jeongmaek has increased continuously, nevertheless there is no research of present condition for Jeongmaek. This paper is to contribute to suggest for management and restoration as a basic study of vegetation structure in Yongso valley. We set up 30 plots($100m^2$) to verify the vegetation structure. As a result of classification analysis used by DCA, the type of 5 communities i.e. Pinus densiflora community, Betula schmidtii community, Populus maximowiczii community, Quercus mongolica community, Q. variabilis community were the most representative of Yongso valley vegetation communities. P. densiflora community was mainly distributed in the ridge of mountain, ridge of steep slope and stony area. In that reason, they avoid to compete with B. schmidtii community and Q. spp. community. In addition, the appearance of Rhododendron micranthum was mainly characteristics in the P. densiflora community. Species diversity indices(H') of groups were ranged from 0.7914~0.9942, the tree ages were 30~115 years. According to these results, the forests of Yongso valley not only form muti-layer vegetation structures but also have a great ecological value for protection and preservation.

• Journal of Korean Society of Forest Science
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• v.105 no.4
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• pp.391-400
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• 2016

This study was conducted to set up ecological database for effective forest management and conservation of KNU Research Forest in Mt. Myeonbong with the characteristic analysis of stand structures. Following the results of clustering analysis, they were classified under 6 communities (Quercus mongolica-Pinus densiflora, Pinus densiflora, Carpinus cordata, Fraxinus rhynchophylla-Acer pseudosieboldianum-Acer pictum subsp. Mono, Quercus mongolica-Quercus variabilis, Quercus mongolica). Importance value tests were estimated that on ridge; Pinus densiflora, valley; Carpinus cordata, Fraxinus rhynchophylla-Acer pseudosieboldianum-Acer pictum subsp. Mono were recorded dominant species. Carpinus cordata and Fraxinus rhynchophylla-Acer pseudosieboldianum-Acer pictum subsp. Mono community, north aspect and valley were investigated high species richness value. It was showed decreasing tendency as altitude and degree of slope were high. Results of NMS, upper & middle layers and shrub & herbal layers were influenced by species richness and the case of species association.

• Proceedings of the Korean Society of Computer Information Conference
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• 2009.01a
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• pp.41-44
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• 2009

데이터 마이닝의 대표적인 기법인 군집화는 군집내의 유사성을 최대화하고, 군집들간의 유사성을 최소화 시키도록 데이터의 집합을 분할하는 것이다. 대용량의 데이터베이스에서 최적의 효율화를 내기 위해서는 원시데이터에 대한 접근 횟수를 줄이고, 이것을 알고리즘 적용 대상이 데이터 구조의 크기를 줄이는 군집화 기법에 많은 관심이 보이고 있다. 본 논문에서는 유전자 알고리즘을 이용하여 자동으로 군집의 개수를 결정하는 군집화 알고리즘을 제안하는 적합도 함수는 보다 양질의 군집을 찾아내는 것으로 평가 되었다. 또한 유전자 알고리즘 중 8가지를 세부 분석하여 평가하였다.

• Korean Journal of Environment and Ecology
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• v.14 no.4
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• pp.296-302
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• 2001

계룡산국립공원 연천봉고개(해발 700m)를 중심으로 남향사면인 시원사~원천봉고개와 북향사면인 갑사~연천봉고개를 대상으로 사면방향과 해발고에 따른 교목층과 아교목층의 산림구조를 조사분석하였다. 남향사면은 북향사면에 비하여 교목측의 밀도는 높은 반면 평균흉고직경은 작았다. 특수한 지형인 주능선부에 위치하는 정부를 제외하며, 해발고가 높아짐에 따라 교목층과 아교목층 전체의 평균흉고직경과 흉고단면적인 남향사면에서는 감소하는 경향을 보였다. 북향사면은 남향사면에 비하여 교목층과 아교목층 전체의 동다양도와 균재고가 높았다. 남향사면에서 해발고가 높아짐에 따라 중요치가 증가하는 수종은 느티나무, 졸참나무, 까지박달, 신갈나무등이었으며, 중요치가 감소하는 수종은 굴참나무, 서어나무, 때죽나무 등이었다. 북향사면의 경우 해발고가 높아짐에 따라 중요치가 증가하는 수종은 까치박달, 쪽동백나무 등이며, 중요치가 감소하는 수종은 때죽나무, 졸참나무 등이었다. Cluster 분석결과 남향사면중, 하부의 굴참나무-낙엽활엽수군집지, 남향사면 상부와 북향사면상, 중의 신갈나무-낙엽활엽수군집, 북향사면 하부와 정부의 신갈나무-소나무군집 등 3개 군집으로 구분되었다. 굴참나무, 산벚나무, 밤나무 등 3개 수종간에는 유의적인 정의 상관이 있었으며, 유의적인 정의 상관을 보인 굴참나무, 산벚나무, 밤나무 등 3개 수종은 당당풍과 유의적인 부의 상관이 있었다.

• Ecology and Resilient Infrastructure
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• v.1 no.2
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• pp.49-60
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• 2014

Fish assemblages play an integral role in stream ecosystem and are influenced by stream environmental conditions and habitat disturbances. Fish community structures and habitat parameters of U.S. EPA rapid bio-assessment protocol were surveyed to investigate the effect of stream environment and habitat disturbance on fish communities at 13 study sites in the Gapyeong Stream, a typical gravel-bed stream. Principal component analysis (PCA) based on data from habitat assessment at each study site indicated that the study sites were differentiated by habitat parameters such as embeddedness, velocity/depth regime and sediment deposition, which were related with bed slope. A total of 46 species belonging to 12 families were collected in the Gapyeong Stream. A dominant species was Zacco koreanus, subdominant species was Z. platypus. Hierarchical cluster analysis based on species abundance classified fish communities into the three main groups along the stream longitudinal change. Non-metric multidimensional scaling (NMDS) portrayed that fish community structures were related to major habitat parameters, i.e., epifaunal substrate/available cover, embeddedness, velocity/depth regime, sediment deposition, channel alternation and frequency of riffles. These results suggested that fish community structures were primary affected by the longitudinal environmental changes, and those were modified by habitat disturbance in the Gapyeong Stream, a gravel-bed stream.

• Korean Journal of Environment and Ecology
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• v.15 no.4
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• pp.330-343
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• 2002

To investigate the vegetation structure of mountain ridge from Pijae to Doraegijae in Baekdudaegan, forty-three sites(size 500$m^2$) were set up and surveyed By using TWINSPAN classification. the plant community was divided into five groups, those are mixed forest on sub-alpine zone. Quercus mongolica - Acer pseudo-sieboldianum community, Q. mongolica-Pinus densiflora community, and Larix leptolepis forest. Quercus mongolica was found as a major woody plant species in the ridge area. And partly the subalpine zone in low elevation was occupied by deciduous tree species and mixed a few conifer such as Abies nephrolepis and Taxus cuspidata etc.. Species diversity index(Area 1,000$m^2$) in the showed calculated 2.0149~3.0139 and it was similar to those of the ridge area of the national parks in Beakdudaegan.

• The Korean Journal of Ecology
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• v.26 no.1
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• pp.29-33
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• 2003

This study was conducted to clarify the influence of national road construction on breeding bird community from April to June 2002 in 8 fragmented forest areas of Baekdudaegan mountain ranges, Korea. There were more observed birds in 50∼100m areas than in 50m areas from road. Guild structures were different between both areas. Number of species and individuals belong to hole nesting and canopy foraging guilds were lower in 50m areas than in 50∼100m areas from roads. Habitat structure of breeding bird community would be changed by road construction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2603-2608
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• 2009

Document clustering is an important method for document analysis and is used in many different information retrieval applications. This paper proposes a new document clustering model using the clustering method based NMF(non-negative matrix factorization) and refinement of documents in cluster by using coherence of cluster. The proposed method can improve the quality of document clustering because the re-assigned documents in cluster by using coherence of cluster based similarity between documents, the semantic feature matrix and the semantic variable matrix, which is used in document clustering, can represent an inherent structure of document set more well. The experimental results demonstrate appling the proposed method to document clustering methods achieves better performance than documents clustering methods.