• Journal of the Korea Computer Graphics Society
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• v.16 no.2
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• pp.9-17
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• 2010

Minkowski sum of two polyedra is an operation to compute the sum of all pairs of points contained in the polyhedra. It has been a very useful tool to solve many geometric problems arising in the areas of robotics, NC machining, solid modeling, and so on. However, very few algorithms have been proposed to compute Minkowski sum of polyhedra, because computing Minkowski sum boundaries is susceptible to roundoff errors. We propose an algorithm to robustly compute the Minkowski sum boundaries by employing the controlled linear perturbation scheme to prevent numerically ambiguous and degenerate cases from occurring. According to our experiments, our algorithm computes the Minkowski sum boundaries with the precision of $10^{-14}$ by perturbing the vertices of the input polyhedra up to $10^{-10}$.

• Journal of Korea Water Resources Association
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• v.41 no.10
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• pp.1067-1077
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• 2008

An understanding of temporal trends of stream flows can help in the river management and the water resources planning for natural circumstances and human communities. Changes in temperature, precipitation, flow, and land use (agriculture, flood prevention activities, reservoir operation, interbasin diversion, etc.) are all eventually reflected in the flow pattern of the river. An assumption that the stationarity of the hydrologic series implying time-invariant characteristics of the time series accepted in water structure designs can no longer be valid if the flow changes as a result of the climate change or the stream flow use. Therefore, the identification and description of the characteristics of changes in hydrologic time series is a very important task in the river basin management. In this study, the statistical tests on the flow change forced by excess water diversions in the Sumjin River basin were performed by ways of single variable and time series variable comparisons. The tests showed that currently the Sumjin River basin statistically keeps its homogeneity in annual streamflow series, but the changed situation has been appeared in dry season streamflow series.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.629-629
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• 2015

습지는 다양한 생태계가 형성되어있고, 토양과 물의 정화기능, 폭우방지 및 홍수 완화 등 인간이 살아가는데 중요한 역할을 하고 있다. 이처럼 중요한 기능을 제공하는 습지에 대한 관심이 증가하고 있지만 그에 따른 습지관리 방안에 대한 연구가 미흡한 실정이다. 특히, 습지 조성 후 유지관리 방안을 제시하기 위해서는 습지의 생태환경을 모니터링 하여 분석하는 것이 필요하다.이를 위해 본 연구에서는 비내섬(남한강), 옥포지구(낙동강), 세도지구(금강) 3개의 인공습지를 대상으로 생태환경에 대한 모니터링을 실시하였다. 모니터링 결과, 비내섬 습지는 천이초기단계에서 개척자식물이 유입되는 등 향후 천이도중상태의 이차초지로 천이될 것으로 판단되며, 옥포지구 습지는 안정된 천이과정을 보이고 있으나, 안정화 단계에 도달할 때 까지 지속적으로 변화될 것으로 판단된다. 세도지구 습지는 인위적 교란요인이 적기 때문에 미소입지별로 식생천이에 따라 다양한 식생이 형성될 것으로 판단된다. 본 연구의 결과 향후 봄, 여름이 추가된 사계절을 장기적으로 모니터링 하여 식물상 데이터를 구축할 수 있다면 더 정량적인 식성천이 분석을 할 수 있을 것으로 판단된다.

• Journal of the Korean Geographical Society
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• v.36 no.4
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• pp.444-457
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• 2001

Present work aims to analyse the spatio-temporal distribution of Korean bamboos. The northern limit of Korean bamboo species occurs at Baekryung Island(124°10'E, 37°55'N), Hoochang(41°22'N) and Myungchon(129°41\`E, 41°10'N). The presence of bamboo fossils in Korea dates back from Tertiary, but widespread use of bamboos can be noticed since 1454. Reconstructed ranges and temporal changes of bamboo, based upon the eight historical records from 15th to 20th centuries, indicates that both climatic and anthropogenic factors were responsible for the changes of distributional range. The spread of bamboos was balanced by its disappearance due to regional development, and the total bamboo area showing little change. Due to the tendency to spread extensively by means of underground stems, bamboos often invade adjacent forests and disturb natural vegetation. Proper management and conservation strategies, therefore, are required for the maintenance of rural landscape.

• Korean Journal of Environment and Ecology
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• v.23 no.6
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• pp.499-505
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• 2009

This study was carried out to investigate and evaluate the vegetations in the coastal dunes in the vicinity of swimming beaches on the East Sea, South Korea, and the vegetations that were investigated are as follows: Carex pumila community, Cynodon dactylon community, Zoysia macrostachya community, Rosa rugosa community, Vitex rotundifolia community and Carex kobomugi typical community. Some of these vegetations, such as Carex kobomugi, Calystegia soldanella, Ixeris repens, Elymus mollis, Lathyrus japonica, and Glehnia littoralis were found to be differential species which belongs to Caricion kobomugi of Glehnietea littoralis. It was also discovered that Vitex rotundifolia community was the most heterogeneous among vegetation communities of the coastal dunes surrounding swimming beaches, and Zoysia macrostachya community was most closely linked to the typical coastal dune vegetation community. Finally, Rosa rugosa community and Vitex rotundifolia community seemed to have formed near the hinterland of coastal dunes and swimming beaches respectively because of certain unnatural disturbances such as construction of buildings and facilities or natural disasters.

• Korean Journal of Environment and Ecology
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• v.10 no.1
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• pp.87-102
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• 1996

To study vegetational structure of the Korean warm temperate region fifty two plots were surveyed in evergreen broad-leaved forests of southern islands. The vegetational structures among sites were dissimilar in virtue of geographical isolation and artificial disturbance. The surveyed plots were generally classified into three groups; the first, the group in which plant succession has proceeded naturally, the second, the group which was disturbed and managed for a long time, the third, the group which was afforested and has been succeeded into evergreen broad-leaved forest. The species with constancy over 80% in fifty two plots were Machilus thunbergii, Eurya japonica, Trachelospermum asiaticum var. intermidium, Cinnamomum japonicum, and Ligustrum japonicum. The community of Lozoste lancifolia, which is assumed to be a climax community of the Korean warm temperate region, remains in Chudo and Aedo. The secondary succession of seashore forest which were disturbed in the past will be done into Castanopsis cuspidata var. sieboldii

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.242-254
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• 2010

Streams changed by artificial factor those support positive functions but also negative function to humanbeing. Time and pathway exceed the lost of structure and negative function appearing as disturbance. Therefore, it is desirable to prepare right situation to break of a vicious circle. Stream ecology was evaluated with using ichthyofauna during three years at the three disturbed sites and reference sites in Nakdong River. Forty-one species belonging three orders and ten families were identified in six surveying sites of Nakdong River during 2007~2009. Korean endemic species (14 species, 34.1%) and alien (3 species, 7.3%) were identified in Nakdong River ichthyofauna. Species number, species diversity, ecosystem structure and habitat variability of ecosystem were applied to evaluate stream ecosystem. In view of three year comprehended data at six sites; numeric instability appeared Andong Dam and Naeseongcheon sites worse than Gamcheon and reference site, otherwise more numeric diversity appeared Gamcheon and reference site than Andong Dam and Naeseongcheon. As a result of integration, sand stream including downstream of Andong dam, Naeseongcheon and Gamcheon has been having more diversified biodiversity and habitat diversity than those in the pebble stream.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.2
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• pp.66-72
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• 2000

The purpose of this study is establish a recession curve for low flow discharge in the Ssangchi basin. For this study, we selected 34 recession segments and calculated recession constants and initial discharges. The average initial discharge is 0.40 ㎥/sec and the recession constant is 0.86. With using the initial discharge and the recession constant, We got the non-linear recession cure equation. This non-linear equation is more reasonable fit than the linear equation of the recession curve for low flow.

• Ecology and Resilient Infrastructure
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• v.7 no.3
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• pp.145-159
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• 2020

Wetlands are vulnerable to biological invasion by alien species, because they function as sinks that accumulate excess water, sediments, nutrients, and other contaminants from the surrounding watersheds by disturbance. In this study, to understand the status and characteristics of the alien plants based on the type of wetlands, we classified 24 ecologically outstanding wetlands and analyzed the status of alien flora. A total of 130 alien plants were found in the wetlands, accounting for 11% of the total plant species. Among them, the Asteraceae species was the most diverse, with 40 species. Erigeron annuus and Oenothera ordorata had the highest frequency of occurrence. The species richness of alien plants in the riverine and lacustrine wetlands (average: 30 species) was higher than that in the mountainous palustrine wetlands (average: 10 species). The same results were found in the naturalization index, urbanization index, and ratio of annuals and biennials, which indicate the degree of artificial interference. In the cluster analysis, the riverine and lacustrine wetlands were combined, and only the mountainous palustrine wetlands were separated. The number of alien plants is remarkably low in the mountainous palustrine wetlands, and it is considered to be the influence of Erigeron strigosus, Symphytum officinale, and Bilderdykia convolvulus, not found in the other types of wetlands. In particular, invasive alien plants such as Aster pilosus, Ambrosia trifida, Sicyos angulatus, Ambrosia artemisiifolia var. elatior were found intensively in the riverine wetlands. Therefore, it is considered that a methodical management is urgently required considering the dispersal of alien plants in the riverine and lacustrine wetlands with high artificial interference.

• Korean Journal of Plant Taxonomy
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• v.50 no.2
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• pp.199-226
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• 2020

Hwangmaesan Mt. (1,108 m) is rich in forest biodiversity and is a part of the Sobaek mountain range located in Hapcheon-gun, Gyeongsang-do in Korea. Unfortunately, the biodiversity and ecosystem integrity of Hwangmaesan Mt. have recently been threatened by heavy human disturbances. We conducted thirteen field surveys between March and October of 2019 to investigate the vascular flora in Hwangmaesan Mt. Through this extensive survey, we found 628 taxa consisting of 106 families, 349 genera, 554 species, 16 subspecies, 48 varieties, and 10 forma. Based on a comparative analysis between the present findings and former flora reports, our results showed an increase by 28 percent in the number of taxa observed. Of the 628 taxa, dicotyledons made up the largest group (477 taxa, 76.0%) followed by monocotyledons (120 taxa, 19.1%). Endemic plants consisted of 16 taxa, with rare plants designated by the Korea Forest Service numbering 14 taxa. Ten taxa were listed on the Red list by the Ministry of the Environment. The floristic target species designated by the Ministry of the Environment numbered 75 taxa, whereas there were 42 taxa of invasive plants.