• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.64-69
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• 2007

Motion control of the system is a position control of motor. Motion control of an uncertain robot system is considered as one of the most important and fundamental research directions in the robotics. Some distinguished works using linear control, adaptive control, robust control strategies based on computed torque methodology have been reported. However, it is generally recognized within the control community that these strategies suffer from the following problems : the exact robot dynamics are needed and hard to implement, the adaptive control cannot guarantee the performance during the transient period for adaptation under the variation, the robust control algorithms such as the sliding mode control need information on the bounds of the possible uncertainty and disturbance. And it produces a large control input as well. In this dissertation, a motion control for the unmanned intelligent robot system using disturbance observer is studied. This system is affected with an impact vibration disturbance. This paper describes a stable motion control of the system with the consideration of external disturbance. To obtain the stable motion independently against the external disturbance, the disturbance rejection is strongly required. To address the above issue, this paper presents a Disturbance OBserver(DOB) control algorithm. The validity of the suggested DOB robust control scheme is confirmed by several computer simulation results. And the experiments with a motor system is performed to give the validity of applicability in the industrial field. This results make the easier implementation of the controller possible in the field.

• Korean Journal of Environment and Ecology
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• v.17 no.2
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• pp.123-132
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• 2003

This ecological study investigated the vegetation changes of abandoned salt field, 21 plots(1${\times}$lm, 1${\times}$2m) set up by the methods of Braun-Blanquet and Elenberg in a coastal island, Gasado, Jindogun, from July to September,2002. The vascular plants of abandoned salt field in the surveyed site identified 17 families and 48 species. Of these species, halophytes and mesophytes were 20(42%) and 28(58%) species. In addition, the disturbance to this habitat led to the change of halophytes in abandoned sald field, exotic plants was distributed 23 species, which included Dactylis glomerata, Conyza canadensis, Oenothera odorata, Cosmos bipinnatus, etc., in the group of, mesophytes were 20(71%) species, vegetation communities were classified into 3 community types, i.e. the halophyte grassland community(Limonium tetragonum community, Suaeda japonica community, Spergularia marina community), the wetland grassland community(Phragmites communis community, Carex scabrifolia community, Phaceturus latifolius var. angustifolius community), and the mesophyte grassland community(Erigeron bonariensis community, Daucus littoralis var. koreana community). Each communities was described the structual, distribution and changes of the vegetation in the abandoned salt field, the vegetation table and actual vegetation map were prepared.

• The Korean Journal of Ecology
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• v.25 no.5
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• pp.321-328
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• 2002

In order to provide the basic information for restoration of vegetation, conservation of rare species and maintenance of biodiversity, changes of site factors and vegetation by human trampling disturbance were investigated at the subalpine zone near the peak of Mt. Sorak in Korea. The destructed vegetation was found mainly in the southern parts with gentle slope in this study area. Height and coverage of vegetation and the species diversity decreased, and the community structure depended on trampling strength. Soil moisture, organic matter contents and litter thickness in the site with destructed vegetation by human trampling showed lower values than in the undisturbed site. Soil depth decreased, and gravel exposure on the ground surface increased by soil erosion responded to trampling strength.

• Journal of Life Science
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• v.16 no.7 s.80
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• pp.1097-1103
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• 2006

Community structure varies not only in space but also in time. We stand in one position which located at Sinhung-ri, Sacheon-ci and observe the flora of area as time passes. This area begins after disturbance on sites where organisms are already present like secondary succession. In 2001, there are invaded by Trapa japonica, Salvinia natans, and Potamogon cristatus. Four or five years later, this abandoned areas support of clover, pine, and oak, resulting in a shifting pattern of species dominance and diversity through time. Patterns of community structure such as species composition and ecological diversity have shown through seasons and five years, that is the topic of this study. The values of turnover (TO) were changes through time intervals at three regions. The gradual and seemingly directional change in the structure of the community through time from aquatic like to field. Thus, we can observe the process of secondary succession at Sinhung-ri in the very short time.

• Journal of Environmental Science International
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• v.12 no.12
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• pp.1207-1213
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• 2003

Osancheon creek is located in the southwest of the middle area in Korea. Weed community around the Osancheon creek, where various disturbances exert a bad influence directly on its community by human work or nature, was surveyed phytosocialogically. Our surveys have been accomplished from June, 2003 to September, 2003. Weed communities formed around the Osancheon creek were divided into several patterns and analysed. They have been divided into 8 communities. Community A: Humulus japonica community, B: Phragmites communiscommunity, C: Persicaria thunbergii community, D: Zi=ania latifolia community, E: Miscanthus saccharilflorus community, F: Echinochica crusgalli community, G: Typha orientalis community, H: Sataria viridis community. The flora surveyed in these communities was constituted of 19 families, 36 genera, 4 varieties, and 40 species. Wild plants such as Artemisia princeps var. orientalis Erigeron annuus, Bidens frondosa, Aeschynomene indica and Oenothera odorata were mostly light loving plants and higher resistant plants against the disturbance. Our result from the ranking all surveyed areas by the Bray-Curtis ordination method was very similar to the results from phytosocialogical table work.

• Korean Journal of Environment and Ecology
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• v.30 no.4
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• pp.783-792
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• 2016

The purpose of this study is to investigate the characteristics of the vegetation structure and the location environment of Albizzia kalkora (AK) growing in Mt. Yudal located in Mokpo city and in the nearby islands. The AK community in Mt. Yudal in Mokpo city (Community I) is located in a region which is relatively high above the sea level. The average age of the major kinds of trees found in the region is about 30 years. The vegetation structure in the community shows an early stage of vegetation development due to continued disturbance. In Community IV, on the sandy soil in the flatland near the seashores, the average age of the major kinds of trees is about 9 years. In this community, a pure forest is presumed to have been formed in a poor environment which is artificially disturbed in relatively recent times even as AK with its strong adoptability was introduced into the region. In other communities (II, III), the vegetation state shows a competition between AK and deciduous oak trees, and the average age of the major kinds of trees is about 13 to 30 years. AK communities with a better developed vegetation structure are located on the higher steep slopes near the seashore. In the early stage of vegetation development, the forest floor received more effective light for photosynthesis, and thus more seedlings of AK emerged and grew. The probability of AK appearing in the damaged or sterile soil near the seashore was high because of its strong adaptability. However, as the vegetation structure developed further and the soil fertility increased, the domination of AK in the vegetation structure decreased as deciduous oak trees won the competition with AK.

• The Korean Journal of Ecology
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• v.15 no.2
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• pp.103-115
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• 1992

This dissertation, which has been prepared in the region of cheju(33o31'N, 126o32'E) from may,1987 to appril, 1989, is to elucidate the dominant characteristics of early stages in secondary succession, by examining the life history of erigeron annuus for the seeding depth of a seed was dependent upon the degree of shading. That is, on the area of ocm,the more tense the shading was, the more germination percentage was increased, while, in the case of 1.5cm, it was somewhat increased, when shading bwcame ess and less tense. The rosette of e. annuus, through its relative light intensity was decreased by shading, up to 5% of natural light, showed some strong shade tolerance, which had no difficulty in matter production. The species diversity of mixed-species community was the highest in the middle of April, the lowest in the last of may. The dominance index was the highest in the late may, the lowest in the middle of April. Toward the end of may, the occupation rate of dominance species was the highest. There was a neutral relationship between intraspecific and interspecific, owing to the differentiation of its niche, temporally and spatially. Productive structure of the community revealed a narrow leaf type which was concentratively distributed in the mid part of community height. The relative light intensity of community ground surface was 6.1%, the leaf inclination 60o,the extinction coefficient(k) 0.4, biomass of community 1,045.6 g.d.w./m2,T/Rratio 9.3, C/Frate 7.0 and sumgermanition, shade toarance and community characteristics on erigeron annuus l.in chejumed leaf area index 3.88. through the various life cycles o e.annuus, we can say that it decreases mortality of seeding caused by some stress and disturbance, for germination lasts for a long time at any opportunity available, and it promotes population growth. The strong shade tolerance of a rosette and the variableness of a life from differentiate the niche between intraspecific and interspecific within the community, and avoid the direct competition between them, thus poromoting community growth.

• The Korean Journal of Ecology
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• v.26 no.3
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• pp.103-108
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• 2003

This study examined the coastal sand dune vegetation before and after the construction of an embankment on Anmado Island in order to compare vegetation in relation to the development of islands. A total of 24 species distributed on the sand dunes. 18 species were found to be in common before and after the construction of the embankment, which included Vitex rotundifolia, Imperata cylindrica var. koenigii, Zoysia sinica, etc. The species which were not found in this survey included Rumex japonicus, Setaria viridis, Portulaca oleracea, Artemisia japonica, Poiygonum aviculare, etc, and new species included Arena fatua, Carex boottiana, Lycium chinense, Leonurus sibiricus, Torilis japonica, Solanum carolinense, etc. The washing away of sand brought about the changes in habitat and the increase in naturalized plants, which included Oenothera odorata, Lepidium apetalum, Bidens bipinnata, Erigeron canadensis, Datura stramonium, Xanthium strumarium, Arena fatua, Solanum carolinense etc. In addition, the disturbance to this habitat led to the changes in vegetation. The main plant communities in the surveyed site were classified as Vitex rotundifolia-Imperata cylindrica var. koenigil community, Zoysia sinica-Calystegia soldanella community and Messerschmidia sibirica community. The sand dune vegetation on Anmado Island changed with regard to the community and the composition of species after the construction of the embankment, due to the sand being severely eroded. While Vitex rotundifolia community and Commelina communis community were found before the construction of the embankment, they were replaced by Vitex rotundifolia-Imperata cylindrica var. koenigii community, Zoysia sinica-Calystegia soldanella community and Messerschmidia sibirica community, after the construction of the embankment.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.420-443
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• 2012

An Individual-Based Model (IBM) was developed by employing natural and toxic survival rates of individuals to elucidate the community responses of benthic macroin-vertebrates to anthropogenic disturbance in the streams. Experimental models (dose-response and relative sensitivity) and mathematical models (power law and negative exponential distribution) were applied to determinate the individual survival rates due to acute toxicity in stressful conditions. A power law was additionally used to present the natural survival rate. Life events, covering movement, exposure to contaminants, death and reproduction, were simulated in the IBM at the individual level in small (1 m) and short (1 week) scales to produce species abundance distributions (SADs) at the community level in large (5 km) and long (1~2 years) scales. Consequently, the SADs, such as geometric series, log-series, and log-normal distribution, were accordingly observed at severely (Biological Monitoring Working Party (BMWP<10), intermediately (BMWP<40) and weakly (BMWP${\geq}50$) polluted sites. The results from a power law and negative exponential distribution were suitably fitted to the field data across the different levels of pollution, according to the Kolmogorov-Smirnov test. The IBMs incorporating natural and toxic survival rates in individuals were useful for presenting community responses to disturbances and could be utilized as an integrative tool to elucidate community establishment processes in benthic macroin-vertebrates in the streams.

• Korean Journal of Ecology and Environment
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• v.40 no.4
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• pp.546-552
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• 2007

The objectives of this study were to analyze fish compositions, based on trophic guilds and tolerance guilds and determine community characteristics structure at five sampling sites of Yeongsan Lake during July 2006-May 2007. Total number of species sampled was 30 species and the number was 1350. Cyprinidae (77%) and Centrarchidae (15.7%) dominated the community and then followed by Cobitidae(2.7%), Gobiidae(2.4%), Mugilidae (0.5%), and others (0.1%). The relative abundance of tolerant and omnivore species at all sites was 63% and 77% of the total, respectively, suggesting an ecological degradations in the Lake. Exotics species such as large mouth bass (Micropterus salmoides), which is a top-carnivore in the water distributed at all sampling sites, implying that ecological disturbance was severe based on previous reference of US EPA (1991). Also, we found external anomalies such as external deformities, bleeding and tumors and not found migratory fish. Analysis of fish community structure showed that species diversity index and richness index was the highest in Site 1 and the dominance index was the highest in Site 2. In this study, high proportions of tolerant species and omnivore species, widespread exotic species, and frequent observations of abnormal fish. Such problems may be directly or indirectly associated with high nutrient enrichments and the reduced flow velocity by the dam construction. The ecosystem restoration by dam removal or removal of exotic top-carnivore fish may be one of the best strategies for better lak management.