• Journal of Korean Society of Forest Science
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• v.76 no.4
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• pp.418-424
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• 1987

Considering the seral stage of succession, phytosocialogical analysis was carried out to investigate the structure and property of community of Pinus densiflora, Pinus densiflora-Quercus spp.-Carpinus laxiflora, and Quercus spp.-Carpinus laxiflora. The study area included a section of 200m high at the sea level in Mt. Jokye, Seungju-gun, Chunlanam-do. The results show that density of forest trees tended to be decreased, Shannon species diversity index increased, and dominance decreased as seral stage progressed. Patterns of DBH class distribution showed nearly S types. In the study area succession of forest community might progressed toward climax, leading from Pinus densiflora community to Quercus spp.-Carpinus laxiflora community with intermediary Pinus densiflora-Quercus spp.-Carpinus laxiflora community. The fact that there was no pure community of Quercus spp. might be due to the rapid development of forest community investigated.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.4
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• pp.29-41
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• 2015

Abandoned paddy field provides an excellent opportunity to improve the species diversity and habitat quality. Ecological characteristic on the changing of plant communities at different seral stages is a major basis data for ecological restoration. In this study, we investigated changes of the species composition and community indices on the plant community associated with abandonment of cultivated rice paddies. The ecological stability of the habitat was evaluated by using eco-floristic characters(Di; Disturbance index, AUI; Actual urbanization index). Survey sites were grouped into six stages(stageI (${\leq}3years$), stageII(3-5years), stageIII(5-7years), stageIV(7-10years), stageV(10-15years), stageVI(${\geq}20years$). Vegetation investigation was done from May 2009 to October 2012 and carried out phytosociological approach. The total flora were summarized as 176 taxa including 58 families, 127 genera, 157 species, 3 subspecies, 15 varieties and 1 forms. At each of successional stages, 64 taxa in stage I, 34 taxa in stage II, 84 taxa in stage III, 83 taxa in stage IV, 92 taxa in stage V, 23 taxa in stage VI were identified. Of the occurrence plants, the species with the highest r-NCD value were Alopecurus aequalis, Juncus effuusus var. decipiens, Persicaria thunbergii, Artemisia princeps, Salix koreensis and Alnus japonica at each stages. Herbaceous annual plants were dominated in the early stage, but its r-NCD value declined in the middle stage and the late stage. On the other hand, herbaceous perennial plants and Persicaria thunbergii, annual hydrophytes, increases in the middle stage. Woody plant and herbaceous plant which appeared in the forest edge increases in the late stage. Community indices correlate with successional stages. Richness and diversity index increase along the successional gradient. But dominance index decrease along the successional gradient. Evenness index was correlated with lower. In the ecological stability analysis of the habitat that evaluated by eco-floristic characters, stage I was the most unstable habitat. And the stability of the habitat has improved according to the successional stage.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.129-144
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• 2010

We have studied the changes of the environmental and vegetational factors according to the hydro-seral stages in the shoreline of the lagoons, Korea. We have divided seral stages into 7 stages from open water stage to the stratified forest stage considering as the characteristics of water body, dominance of submerged and emergent plant, and development of the shrub, subtree and tree layer. According to the successional stage, water depth gradually decreased and water quality changed from seawater to brackish water and from brackish water to fresh water, organic matter in a soil layer gradually increased, and the litter layer grew up. As the development of the vegetation structure, the life-form of the vascular plants changed as follows; open water ${\rightarrow}$ submerged plant and floating-leaved plant ${\rightarrow}$ emergent plant and submerged plant ${\rightarrow}$ emergent plant ${\rightarrow}$ emergent plant, mesophyte and scrub ${\rightarrow}$ mesophyte. In the late seral stage, the 3 different forest types were established by the water retention or drainage and nutrient accumulation of the soil layer. Salix dominant forest developed in the wetted sites, the forest type dominated by Pinus thunbergii, Carex pumila and mesophytes developed in the well drained sites causing by sand substrate, and the forest type dominated by the planted or ruderals such as Pinus densiflora, Robinia psedo-acacia, Festuca ovina, Setaria viridis ect. developed in the sites composed of forest soil introduced by artificial reclamation.

• Korean Journal of Environment and Ecology
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• v.23 no.6
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• pp.535-544
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• 2009

This study was conducted to establish the selection criteria for the trees to be transplanted in the forest reserves which are expected to be developed in the future. The main task in this endeavor was to access the transplantability of the trees focused on their feature, diameter at breast height (D.B.H.), soil feature, etc. The selection of the trees for transplantation consisted of two stages. The first stage was to select trees on the basis of their indigenousness and forest successional stage. The second was to select trees on the basis of their type, D.B.H., the layers of soil, etc. At the first stage, the trees which are not indigenous or expected not to survive were eliminated from the selection list, and the result showed that approximately 5.9% (about 3,841 trees) of the trees proved to be inadequate for transplanting. At the second stage, the investigation of the trees based on the criteria of tree type, D.B.H., the layers of soil was carried out, and the result showed that approximately 33.7% (1,218) out of 3,613 trees turned out to adequate for transplanting however, 23.0% of the trees, which are 829 trees, were found to be impossible to transplant. In addition, it was discovered that in the case of approximately 43.3%(1,566 trees) of the trees there was little difference between transplanting cost and planting cost of new trees. Therefore the investigation indicated that it is more advisable to transplant trees to preserve the ecological environment. However, the study showed that there are other elements to be considered, such as tree feature and soil condition, for the successful tree transplantation, and the necessary information can be provided by the managing personnel who are in charge of the forest.

• 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.

• Korean Journal of Environmental Agriculture
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• v.32 no.3
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• pp.185-192
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• 2013

BACKGROUND: As a result of rural exodus, aging of rural population, development of high-yield rice varieties and so on, abandoned paddy fields of South Korea have generally increased. The phytosociological studies are needed to recommend the effective vegetation management methods of abandoned paddy fields. The current study performed an analysis of vegetation characteristics by classifying plant communities for abandoned paddy fields in South Korea. METHODS AND RESULTS: A comparative analysis of syntaxonomy, synecology, and syndynamics was performed by using the Z.-M. method of phytosociology and vegetation survey which was obtained from an enumeration district of total 203 phytosociological releves of 5 regions in Gangwon-do, 5 regions in Gyeonggi-do, 2 regions in Chungcheong-do, 18 regions in Gyeongsang-do, and 10 regions in Jeolla-do. Alopecurus aequalis community, Juncus effusus var. decipiens community and Salix koreensis community were, respectively, identified as successional plant communities of the early stage, the middle stage, and the late stage in the vegetation of abandoned paddy field. Sere of abandoned paddy field can be classified, developmentally, into annual plant stage, perennial plant stage, shrub plant stage, and forest tree stage. Several kinds of dominant species rather than a distinct species were found in the middle stage of abandoned paddy field. CONCLUSION(S): In this study, changing pattern in vegetational communities of abandoned paddy field were understood. These results will provide important information for restoring and conserving the ecology of fallow ground.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.40.2-40.2
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• 2009

이 연구에서는 달천이(TLI: Trans Lunar Injection) 및 달포획(LOI: Lunar Orbit Injection) 기동 시 대전 지상국의 가시성을 고려한 최적의 임무를 설계하였다. TLI 기동은 탐사선이 지구 주차궤도에서 지구-달 천이궤적으로 진입하기 위하여 주어지는 기동이며, LOI 기동은 탐사선이 지구-달 천이궤적에서 달의 중력권으로 진입하기 위하여 주어지는 기동이다. TLI 및 LOI 기동 시 대전 지상국에서의 가시성의 확보는 실제적인 미래 한국의 달 탐사를 대비하였을 때 중요한 요소이다. 따라서 이 연구에서는 TLI 및 LOI 기동 시 대전 지상국에서의 가시성을 모두 고려하여, 최소연료로 지구 주차궤도에서 달 임무궤도 진입까지의 모든 단계에 대해 임무설계를 실시하였다. TLI 및 LOI 기동 시 추력은 순간 추력(Impulsive thrust)로 가정하였으며, KSLV-II 발사체의 성능을 적용하여 설계하였다. 임무 설계 시 태양, 지구, 달의 섭동력을 고려한 N체 운동 방정식을 탐사선에 적용하였으며, 지구의 비대칭 중력장, 태양 복사압, 달의 J2 섭동에 의한 영향도 고려하였다. JPL의 정밀 천체력인 DE405를 사용하였고, 상용 소프트웨어인 SNOPT(Spares Nonlinear OPTimizer)를 이용하여 비행 궤적의 최적해를 도출하였다. 임무 설계 결과를 통해, 대전 지상국의 가시성을 고려한 TLI 및 LOI 기동의 크기에 의한 임무설계의 분석을 수행하였다. 또한 최적화된 달 탐사 임무의 단계별 기동의 크기와 지구-달 천이 궤적의 형상 및 다양한 임무 요소들의 해석을 도출하였다.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.401-411
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• 2006

We propose an optical encryption/decryption technique for a security system based on 2-step phase-shifting digital holography. Phase-shilling digital holography is used for recording phase and amplitude information on a CCD device. 2-step phase-shifting is implemented by moving the PZT mirror with phase step of 0 or ${\pi}/2$. The binary data and the key are expressed with random code and random phase patterns. The digital hologram is a Fourier transform hologram and is recorded on CCD with 256 gray level quantization. We remove the DC term of the digital hologram fur data reconstruction, which is essential to reconstruct the original binary input data/image. The error evaluation fer the decrypted binary data is analyzed. One of errors is a quantization error in detecting the hologram intensity on CCD, and the other is generated from decrypting the data with the incorrect key. The technique using 2-step phase-shifting holography is more efficient than a 4-step method because 2-step phase-shifting holography system uses less data than the 4-step method for data storage or transmission. The simulation shows that the proposed technique gives good results fur the optical encryption of binary information.

• Korean Journal of Environment and Ecology
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• v.26 no.4
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• pp.604-619
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• 2012

According to the concept of woodland aesthetic in Germany and forest design in United Kingdom, artificial forest should be restore ecologically step by step in National Park, Korea. This study was carried out to provide the density criterion of thinning for the inducement of the ecological succession by analysing of vegetational structure in Artificial Forest, National Parks. Eleven plots(size is $20m{\times}20m$) were set up in the artificial forest such as Pinus koraiensis forest, Abies holophylla forest, Chamaecyparis obtusa forest, Populus tomentiglandulosa forest, and Larix kaempferi forest and in the natural forest such as Pinus densiflora community, Pinus densiflora-Quercus serrata community, and Quercus serrata community in Chiaksan, Songnisan, Deogyusan, and Naejangsan National Parks, Korea. We classified the artificial forest into undeveloped type of succession, type of alien young trees developing, and early phase type of succession based on the vegetational structure. According to the index of Shnnon's diversity(unit: $400m^2$), undeveloped type of succession was ranged from 0.9681 to 1.1323, type of alien young trees developing was ranged from 1.0192 to 1.1870, early phase type of succession was ranged from 1.3071 to 1.3892, and natural vegetation was ranged from 1.2202 to 1.3428, therefore early phase type of succession forest and natural vegetation are more higher than simple-layered artificial forest with one needle leaf tree species. The limit for the step-by-step thinning was in the range of 30~60%. In case of undeveloped type of succession, we should thin out from large trees throughout three phases, because alien species dominated high value 88~90% in canopy layer. In case of type of alien young trees developing, we should thin out from alien young trees such as Populus tomentiglandulosa throughout one or two phases, because alien species dominated high value 60~97% and young trees with saplings growing up in understory and shrub layer. In case of early phase type of succession, we should thin out from alien trees that compete with native species throughout one or two phases, because alien species dominated less than value 30%.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1995.06a
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• pp.11-17
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• 1995

본 연구에서는 SiC 및 SiC-TiB$_{2}$복합재료의 마모 및 마모천이기구를 비교 실험한 결과 다음과 같은 결론을 얻었다. 두 재료의 마모천이현상은 각각의 하중이 200N(SiC)과 80N(SiC-TiB$_{2}$)이상에서 나타나게 되었다. 마모기구는 임계미끄럼시간에서 두 단계로 나뉘어진다. 소성변형에 의한 grooving과정과 잔류응력에 의한 grain pull-out과정들로써 미세 구조를 통해 관찰할 수 있었다. grain pull-out과정은 초기단계에서 부터 생성된 전위가 축적되어 잔류응력을 발생시키므로 일어난 과정이다. SiC에 TiB$_{2}$를 첨가하므로 마모는 더욱 심하게 일어나게 되었다. 입계의 강도를 더 약하게 하였기 때문이다. 그러나, 파괴인성은 입계강도가 약할수록 증가하였다. 결국 파괴인성이 큰 재료가 마모는 더 심하게 일어남으로 서로 상반된 관계를 갖고 있슴을 결론지을 수 있었다.