• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.159-160
• /
• 2008

차세대 위성항법 시스템은 높은 변조율을 갖는 이진 천이 반송파 변조된 확산신호를 사용한다. 그런데 부호 획득을 위해 기존 선형탐색 기법을 사용할 경우 변조율 증가에 따라 탐색회수가 크게 증가하여 초기고정시간도 증가하는 단점이 나타난다. 이에 본 논문은 차세대 위성항법 시스템이 사용하는 높은 변조율을 갖는 이진천이 반송파 변조된 확산신호를 위한 빠른 부호획득 기법을 제안하고, 복잡도를 분석한다.

• Microbiology and Biotechnology Letters
• /
• v.32 no.2
• /
• pp.158-165
• /
• 2004

This study concerns the succession process of protozoa populations in two activated sludge pilot plants. Protozoa populations with similar structures developed and succeeded each other in two plants. It was observed that initial sludge inoculum did not influence the protozoan composition but shorten the period of the plant stabilization. It seemed the protozoan in aeration tank was come from the influent. The composition of the influent sewage influenced the structure of protozoa in the pilot plants. The flagellates was very abundant during the initial starting phase. These rapidly decreased after growth peak. Then sarcodina, ciliates were increased in succession. In ciliates, free-swimming forms appeared at first and crawling forms and stalked forms were followed. After 36 days from the start, the sludge stabilization phase was characterized by a populations of ciliates dominated by stalked and crawling type and low value of effluent BOD was achieved.

• Journal of Ecology and Environment
• /
• v.29 no.3
• /
• pp.227-235
• /
• 2006

Changes of the species diversity and development of vegetation structure during abandoned field succession after shifting cultivation were investigated in Pyoungchang, Gangwon-Do, Korea. The height of top layer tended to increase rapidly during the earlier successional stages and stabilize in the later successional stage. The heights of top layer in the 10, 20, 50 and 80 year old-field were 4, 9, 18 and 18 m, respectively. In this region, thirty five year after abandonment need for the development to the normal forest formed by 4 stratum structure, tree, sub-tree, shrub and herb layer. Among the vegetation values, Ivc showed a tendency to increase logarithmically, and Hcl a tendency to increase linearly during abandoned field succession. Species diversity showed the peak in mid-successional stages ($10{\sim}20$ year old-field) and declined slightly thereafter. Species diversity was correlated closely with the species richness than the evenness. The most woody species established in the earlier stage ($2{\sim}6$ year old-field) and turned over their dominance step by step during succession. These results support the IFC model proposed by Egler (1954).

• Korean Journal of Environment and Ecology
• /
• v.19 no.2
• /
• pp.90-98
• /
• 2005

To investigate the vegetation structure of the Woraksan National Park, twenty-two plots were set up and surveyed. According to the analysis of classification by TWINSP AN, the communities were divided by six groups; Pinus densiflora-Quercus serrata, Q. mongolica-Q. serrata, Q. mongolica-Betula davueica, P. densiflora-Q. mongolica, Q. mongolica, Q. mongolica-Acer pseudosieboldianum. Successional sere of the forest vegetation in the surveyed area were proeeding from Pinus densiflora to Quercus serrata, Quercus monogolica in the canopy layer group and from Rhododendron Rhododendron schlippenbachii to Fraxinus sieboldiana and Acer pseudosieboldianum in the understory layer group. But Q. mongolica might be edaphic climax species in some area.

• Korean Journal of Environment and Ecology
• /
• v.37 no.2
• /
• pp.163-178
• /
• 2023

This study was conducted to understand the vegetation characteristics of Cheongwansan Provincial Park through the analysis of the plant community structure and to build data necessary for the continuous management and protection of Cheongwansan Provincial Park. The TWINSPAN and DCS analyses of the plant community structure of 63 survey districts in Cheongwansan Provincial Park identified eight colonies, including Cryptomeria japonica Community (I), Chamaecyparis obtusa-Pinus densiflora Commuity (II), P. rigida-P. densiflora Community (III), mixed coniferous and broad-leaved Community (IV), P. densiflora Community (V), deciduous broad-leaved such as Quercus spp. Community (VI), Q. mongolica-P. densiflora Community (VII) and P. thunbergii Community (VIII). The colonies can be grouped into afforestation communities (I, II, and III) dominated by C. obtusa, C. japonica, and P. rigida and natural forest communities (IV, V, VI, VII, and VIII) dominated by native species. Although Cheongwansan Provincial Park is a provincial park area that can represent natural ecosystems and landscapes, the rate of artificial forests is higher than that of other provincial parks. Most of the artificial forest communities are expected to maintain their current state, but since native species such as Machilus thunbergii, Neolitsea sericea, and deciduous broad-leaved, which are warm-temperate trees introduced through surrounding natural forests, appear in the lower layer, it is determined that it is possible to induce succession to natural forests suitable for climatic characteristics through management, and monitoring for continuous management is also necessary. Deciduous broad-leaved such as Quercus spp. Copete with P. densiflora in most natural forest communities. The vegetation series in the warm-temperate region of Korea appears to be in the early stages, and it is believed that the succession to Q. serrata or Q. mongolica, which appears next to coniferous in the series, is in progress. However, M. thunbergii and N. sericea, which appear in the middle stage of the succession in the warm-temperate region, have started to appear, and since Jangheung-gun belongs to the warm-temperate region considering the climate characteristics, the eventual succession to the warm-temperate forests dominated by evergreen broad-leaved is also expected. In this study, we built vegetation data from Cheongwansan Provincial Park, which lacks research on vegetation. However, since vegetation research in Cheongwansan Provincial Park is still insufficient, it is believed that further research should be continuously conducted to establish forest vegetation data and observe vegetation changes.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.2
• /
• pp.171-186
• /
• 2009

Various Earth-Moon transfer trajectories are designed and analyzed to prepare the future Korea's Lunar missions. Minimum fuel trajectory solutions are obtained for the departure year of 2017, 2020, 2022, and every required mission phases are analyzed from Earth departure to the final lunar mission orbit. N-body equations of motion are formulated which include the gravitational effect of the Sun, Earth and Moon. In addition, accelerations due to geopotential harmonics, Lunar J2 and solar radiation pressures are considered. Impulsive high thrust is assumed as the main thrusting method of spacecraft with launcher capability of KSLV-2 which is planned to be developed. For the method of injecting a spacecraft into a trans Lunar trajectory, both direct shooting from circular parking orbit and shooting from the multiple elliptical intermediate orbits are adapted, and their design results are compared and analyzed. In addition, spacecraft's visibility from Deajeon ground station are constrained to see how they affect the magnitude of TLI(Trans Lunar Injection) maneuver. The results presented in this paper includes launch opportunities, required optimal maneuver characteristics for each mission phase as well as the trajectory characteristics and numerous related parameters. It is confirmed that the final mass of Korean lunar explorer strongly depends onto the initial parking orbit's altitude and launcher's capability, rather than mission start time.

• Journal of Wetlands Research
• /
• v.20 no.3
• /
• pp.243-248
• /
• 2018

This study was carried out to clarify changes in community structure of Quercus acutissima dominant stand on the south slope of Mt. Danseok-san with fixed twenty quadrates. Five field surveys were conducted from Aug. 1999 to May 2018. During the period, the density lessened to 0.20 in 2012 comparing with 0.33 in 1999. However recent field study in 2018 showed moderate rising to 0.24. In 1999, the DBH class distribution of all trees formed reverse J curve. However, the reverse J curve was torn down, forming bell curve. In 2018, the curve showed similar shape of reverse J shape on the group of young trees, forming bell shape on the group of mature trees. It reveals that DBH 13cm is on the threshold of trees competition trend where the downtrend in the trees are on uptrend. The most dominant Q. acutissima formed bell curve. The peak of the curve shows the shift to the right of the graph as it gets lower by year.In case of Q. mongolica, shows a change in the shape of a low bell as the distribution curve increases. The oak stand in this study is in the process of changing from the initial stage of the secondary forest succession to the intermediate stage. The most dominant tree is Q. acutissima, and the sub-dominant tree is Q. mongolica in present. Considering the age distribution of the two competing tree species, the succession of this stand is expected to transfer to the Q. mongolica-dominant community.

• Korean Journal of Environment and Ecology
• /
• v.34 no.1
• /
• pp.27-41
• /
• 2020

The purpose of this study was to survey vegetation characteristics of Jeopdo (island) for the construction of a database. We installed and analyzed 52 plots with 100㎡ quadrat to investigate the vegetation characteristics. The community classification based on TWINSPAN found seven categories of vegetation communities in the surveyed region: Pinus thunbergii-Pinus densiflora community, Pinus densiflora-Quercus serrata community, Carpinus turczaninowii-Quercus variabilis community, Carpinus turczaninowii-Quercus acutissima community, Quercus variabilis-Carpinus turczaninowii community, Castanopsis sieboldii community, and Actinodaphne lancifolia-Camellia japonica community. The vegetation in Jeopdo is largely composed of evergreen conifer trees community (communities I and II), Carpinus turczaninowii-deciduous broad-leaved trees such as Quercus spp. community (communities III, IV, and V), and evergreen broad-leaved trees community (communities VI and VII). The evergreen conifer tree (Quercus serrata) community is currently competing with Pinus densiflora and Pinus thunbergii. The current state is expected to continue due to the lack of forces, such as Castanopsis sieboldii and Actinodaphne lancifolia, in the succession middle stage and climax stage. The current state of Carpinus turczaninowii-deciduous broad-leaved trees such as Quercus spp. community is expected to last for a long time due to slow vegetation development because of soil conditions. The evergreen broad-leaved trees community is transforming from the initial stage of Pinus densiflora and Pinus thunbergii through the stage in Quercus serrata to Castanopsis sieboldii and Actinodaphne lancifolia. The overall ages of the specimens were similar, and the oldest tree was the 59-year old Castanopsis sieboldii. The correlation analysis of major species showed a high positive correlation between Pinus thunbergii and Eurya japonica, Pinus densiflora and Fraxinus sieboldiana, and Actinodaphne lancifolia and Camellia japonica and a high negative correlation between Pinus densiflora and Carpinus turczaninowii and Carpinus turczaninowii and Eurya japonica.

• Journal of Korean Society of Forest Science
• /
• v.82 no.2
• /
• pp.176-187
• /
• 1993

Based on the analysis of ecomorphological characters for 84 tree and shrub species, climax indices were estimated so as to interpret the position of the successional sere for the species in the natural deciduous forest. Nineteen ecomorphological characters, considered to be associated with successional gradient in the forest, were selected for the study. One of 2 to 4 steps per character for each species was given on a standardized scale of increasing climaxness, and the index was computed by percent of the sum of the scoring values for total score. Calculated mean value of 54.2 for all indices. Carpinus laxiflora had the highest index value of 83.3, and Populus davidiana recorded the lowest of 18.8. The most climax group, greater than 70 of the index, contained only 9 species, intermediate group, between 40 to 70 of the index, had 58 species, and the most pioneer group, less than 40 of the index comprised 17 species. The result has noticed that the large number of species would take advantage of most diverse resource and niche in the intermediate stage of the sere in the forest. The three components, i.e., light absorption, reproduction, and wood quality were used as axes for a 3-dimensional projection of the relative position for 44 species by principal component analysis. Along the similar ecomorphological characters, four recognized species group were classified by cluster analysis. The distribution pattern of plant families on the index gradient showed that the Betulaceae and Aceraceae had the widest seral amplitude, and the Salicaceae was a family typified as pioneer. There were no families specializing entirely with climax niche.

• Korean Journal of Environmental Agriculture
• /
• v.3 no.2
• /
• pp.55-61
• /
• 1984

농업(農業)은 동식물(動植物)을 대상으로 하는 응용생태학(應用生態學)의 한 분야(分野)로 그의 발전과정(發展過程)은 환경(環境)과 밀접(密接)한 관계가 있다. 환경조건(環境條件)의 다양성(多樣性)은 대상생물(對象生物)의 종류(種類)를 풍부하게 하고 순화(馴化)된 생물(生物)의 사양(飼養) 과정에서 다양(多樣)한 농업형태(農業形態)를 발전시켰다. 생웅계(生熊系)는 자연(自然)의 한 단위로 구성요소(構成要素)들은 기능적(機能的)으로 통일성(統一性)을 유지하고 있다. 농생태계(農生態系)는 생산(生産)을 목표(目標)로 하는 동식물(動植物)을 중심(中心)으로 하는 생태계(生態系)로 자연생태계(自然生態系)와 기본적(基本的) 성질(性質)은 동일하나 인위적(人爲的) 요소(要素)가 크게 작용하고 있는 특리(特異)한 생태계(生態系)이다. 작물(作物)이나 가축(家畜)은 수천년에 걸친 생산력(生産力)의 증대(增大)를 목표(目標)로 인위적(人爲的)인 선발을 거친 것으로 자연조작하(自然條作下)에서 심한 경쟁(競爭)을 거치면서 진화(進化)한 야생생물(野生生物)들에 비하면 선천적(先天的) 포약성(胞弱性)을 갖고 있어 인간(人間)의 보호(保護)(에너지보조(補助))를 필요로 하고 있다. 농생태계(農生態系)는 공간적(空間的) 격리(隔離)와 구성종(構成種)의 단순화(單純化)로 공간적(空間的) 연쇄성(連鎖性)과 종다양도(種多樣度)가 큰 자연생태계(自然生態系)에 비하면 외적(外的) 충격에 대한 내부적(內部的) 완충능력(緩衝能力)이 약하다. 더우기 농생태계(農生態系)는 시간적(時間的) 연속성(連續性)이 없어 극상천이(極相遷移)단계에 달할 수 있는 시간적(時間的) 여유가 없어 생물상호간(生物相互間)의 관계는 초기(初期) 천이(遷移)단계의 특성(特性)인 종다양도(種多樣度)가 낮고 직선적(直線的)이고 단순(單純)한 먹이연쇄성(連鎖性)을 갖고 있다. 생물군집(生物群集)의 천이진행(遷移進行)에 따르는 종다양도(種多樣度)의 증가(增加)는 생물군집내(生物群集內) 현재량(現在量) 증가와 더부러 먹이 연쇄상(連鎖相)을 직선상(直線狀)에서 망상(網狀)으로 변화시키고 주된 물질(物質)${\cdot}$유전회로(流轉回路)를 포식(捕食)먹이 연소회로(連銷回路)에서 부식(腐食)먹이연쇄회로(連鎖回路)로 전환시켜 생태계(生態系)의 물질(物質)은 생태군집내(生態群集內)에 보존(保存)하는 능력(能力)을 증대(增大)시키고 토양(土壤)의 물리(物理) 화학적성질(化學的性質)을 개선하여 계내(系內) 물질(物質)의 유실(流失)을 억제하기도 한다. 농생태계(農生態系)는 생산성(生産性)의 증대(增大), 관리(管理)의 편의(便宜) 기타의 이유(理由)로 구성종수(構成種數)를 인위적으로 제한(制限)하고 관리(管理)를 통하여 발아(發芽), 생장(生長), 개화(開花)등 여러가지 생물학적(生物學的) 현상을 극도로 균질화(均質化)시키고 있어 어떤 생육단계(生育段階)의 생물(生物)이 넓은 면적(面積)에 동시에 존재하게 되는데 이것은 외적조건(外的條件)의 변동(變動)에 대한 감수성(感受性)을 증대시킨다. 이와 같은 자연생태계(自然生態系)와 농생태계(農生態系)의 생태학적(生態學的) 특성(特性)에 관한 이해(理解)와 인식(認識)은 농생태계(農生態系)의 생산성(生産性) 증대(增大)와 영구적(永久的) 유지(維持)를 위한 합리적(合理的) 관리(管理)를 위한 기본(基本)이 될 것이다.