• Journal of Korean Society of Forest Science
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• v.80 no.4
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• pp.360-368
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• 1991

Utilizing chi-square test statistics, inter-species association and covariation were analyzed for the 37 woody plant species in a deciduous forest dominated by Quercus mongolica and Q. variabilis. within 50 temporarily established $20m{\times}20m$ square quadrats, the association for each pair of species was presented based on the presence-absence parameters. Acer palmatum had significant positive association with Acer mono and Kalopanax pictus, but negative association with Pinus densiflora. Other positively associated species pairs were Prunus sargentii-Macckia amurensis, Quercus serrata-Kalopanax pictus, Symplocos chinensis var. pilosa-Euonymus oxyphyllus, and Ulmus davidiana var. japonica-Lindera obtusiloba. The covariation far each pair of species was evaluated based on the quantitative measures, density and basal area. Overall results showed that the association and covariation values among species generally agreed with each other. Because covariation was calculated by density and basal area of the tallied species in the sample plots, the number of species pairs of covariation tended to be greater than those of association. Especially, Pinus densiflora, considered to be pioneer species in the successional stage, had negative covariation with most of climax species. These ecological information could be applied to silvicultural practices, such as ecosystem classification, establishment of mixed hardwood forest, and tending operations for marking crop trees and desirable species.

• Journal of Korean Society of Forest Science
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• v.89 no.1
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• pp.93-104
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• 2000

The ecological characteristics of 10 natural stands of Dendropanax morbifera(Haenam, Wando 1, Wando 2, Bogildo, Kemundo and Hongdo and Sendol, Suoak, Hannam, and Kidowon populations in Cheju island) were studied. In most of the Dendropanax morbifera natural stands, the following tree species appeared predominantly : Camellia japonica, Castanopsis cuspidate var. sieboldii, Castanopsis cuspidate var. thunbergii, Carpinus laxiflora, Quercus acute and Eurya japonica. Especially, Camellia japonica and Eurya japonica appeared in all the stands. Dendropanax morbifera occupied 17.2% of the upper story, 12.9% of the middle story, and 10.3% of the lower story, respectively. The distribution patterns by Morisita's Index showed that Dendropanax morbifera was distributed randomly in all of the three stories, i.e. the upper, the middle and the lower stories. Dendropanax morbifera was positively associated with Camellia japonica, Eurya japonica, Carpinus laxiflora, Cinnamomum japonicum, Ligustrum japonicum, Callicarpa Japonica, Castanopsis cuspidate var. thunbergii, Castanopsis cuspidata var. sieboldii, Daphniphyllum macropodum, Acer palmatum and Euonymus oxyphyllus. This might suggest that the ecological niche is similar to each other. The cluster analysis using percent dissimilarity(PD) based on species composition divided into two groups. One group consisted of the populations located along the south-western coasts. The other group consisted of the populations of Cheju island. This result was agree with that of ordination analysis. From these results, We could find out that the species composition of the populations of Dendrapanax morbifera in Cheju island was quite different from those of other regions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.553-558
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• 2011

This paper describes the development and test result of S-band Transmitter flight model(FM) of STSAT-3 by satellite research center(SaTReC), KAIST. The communication sub-system of STSAT-3 is consist of two different frequency band channels, S-band for Telemetry & Command and X-band for mission data. S-band Transmitter(STX) functionally made of modulator, frequency synthesizer, power amp and DC/DC converter. The transmission data is modulated by FSK(Frequency Shift Keying) and the interface between spacecraft sub-module and STX is RS-422 standard method. The FM STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under $1{\times}10^{-5}$ which meets the specification respectively. The FM STX is delivered Spacecraft Assembly, Integration and Test(AIT) level through the completion of functional Test and environmental(vibration, thermal vacuum) Test successfully.

• Journal of Korean Society of Forest Science
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• v.112 no.1
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• pp.11-22
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• 2023

This study was established to provide basic information necessary for ecological management to restore the naturalness of black locust (Robinia pseudoacacia L.) plantations located in the mountains of Gyeongbuk, Korea. Using vegetation data collected from 200 black locust stands, vegetation types were classified using the TWINSPAN method, the spatial arrangement status according to the environmental gradient was identified through DCA analysis, and a synoptic table of communities was prepared based on the diagnostic species determined by determining community fidelity (Φ) for each vegetation type. The vegetation types were classified into seven types, namely, Quercus mongolica-Polygonatum odoratum var. pluriflorum type, Castanea crenata-Smilax china type, Clematis apiifolia-Lonicera japonica type, Rosa multiflora-Artemisia indica type, Quercus variabilis-Lindera glauca type, Ulmus parvifolia-Celtis sinensis type, and Prunus padus-Celastrus flagellaris type. These types usually reflected differences in complex factors such as altitude, moisture regime, successional stage, and disturbance regime. The mean relative importance value of the constituent species was highest for black locust(39.7), but oaks such as Quercus variabilis, Q. serrata, Q. mongolica, Q. acutissima, and Q. aliena were also identified as important constituent species with high relative importance values, indicating their potential for successional trends. In addition, the total percent cover of constituent species by vegetation type, life form composition, species diversity index, and indicator species were compared.

• Journal of Korea Water Resources Association
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• v.43 no.5
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• pp.455-469
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• 2010

Changes of geomorphology in alluvial river and vegetation recruitment on its floodplain downstream from dams are investigated both qualitatively and quantitatively focusing on the downstream of Andong dam and Imha dam on the Nakdong River. Results of the analyses of river morphology and bed material in the study site show a general trend of riverbed degradation with a max scour of 3 m and bed material coarsening from pre-dam value of 1.5 mm in D50 to post-dam value of 2.5 mm. Decrease in bed shear stress due to the decrease in flood discharge have caused vegetation recruitment on the once-naked sandbars. As result, the ratio of area of vegetated bars over total area of bars has drastically changed from only 7% in 1971 before the Andong dam (constructed in 1976) to 25% after it, and increased to 43% only three year after the Imha dam (constructed in 1992) and eventually to 74% by 2005. Analysis of the vegetation succession at Wicjeol subreach, one of the three subreaches selected in this study for detailed investigation, has clearly shown a succession of vegetation on once-naked sand bars to a pioneering stage, reed and grass stage, willow shrub and eventually to willow tree stages. At the second subreach selected, two large point bars in front of Hahoe Village seem to have maintained their sand surfaces without a signifiant vegetation recruitment until 2005. The sand bars, however, seem to have been invaded by vegetation recently, which warns river managers to have a countermeasure to protect the sand bars from vegetation invasion in order to conserve them for the historical village of Hahoe. On the other hand, recruitment and establishment of vegetation on the sand bars by artificial disturbance of the river, such as damming, can create an unique habitat of backmarsh in the sandy river, as shown in the case of Gudam Wetland, and may increase the biodiversity as compared with relatively monotonous sand bars. Last, the premise in this study that decrease in flood discharge due to upstream dams and decrease in bed shear stress can induce vegetation recruitment on the naked sand bars in the river has been verified with the analyses of the distribution of dimensionless bed shear stress along the selected cross section in each subreach.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.1
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• pp.11-21
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• 2014

The purpose of this study was to furnish basic information for forest community ecology and to accumulate vegetational datum related to hierarchy of forest community for the efficient management of forest vegetation in Mt. Mani. Samples were collected and analyzed by 32 releves from August to October in 2010 using phytosociological analysis methodology of Z-M school and importance value analysis. The results were summarized that the forest vegetation was classified into 5 units in total. Importance value at vegetation unit 1 indicated Pinus densiflora 54.31 (18.10%), Quercus mongolica 39.21 (13.07%), Carpinus coreana 37.29 (12.43%), at vegetation unit 2 Quercus mongolica 89.43 (22.23%), Rhododendron mucronulatum 57.75 (14.43%), Carpinus coreana 47.19(11.80%), at vegetation unit 3 Styrax japonica 53.97 (13.50%), Acer mono 33.60 (8.40%), Carpinus coreana 26.48 (6.62%), Quercus serrata 22.51 (5.64%), at vegetation unit 4 Carpinus coreana 47.70 (11.92%), Quercus acutissima 38.40 (9.60%) and at vegetation unit 5 Evodia daniellii 80.59 (20.14%), Robinia pseudoacacia 35.00 (8.74%), Pueraria thunbergiana 28.63 (7.15%), Quercus dentata 28.20 (7.05%) in the order, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.96.1-96.1
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• 2010

현재 태양광 시장에 진출한 대부분의 Si계열 태양전지는 복잡한 공정과 원재료 고갈, 높은 가격으로 인해 한계에 직면에 있는 상태이다. 최근 많은 연구소나 학교에서는 기존의 Si계열 태양전지를 대체할 대안으로 염료 감응형 태양전지에 대해서 높은 관심을 보이고 있으며, 그동안의 연구개발로 단위 셀 면적에서는 상용화에 근접한 효율을 확보한 상태이다. 염료 감응형 태양전지의 작동과정을 간단히 단계별로 살펴보면 나노 결정 산화물 반도체 표면에 흡착된 염료분자가 가시광선을 흡수하면 전자는 HOMO에서 LUMO로 천이하고 이 들뜬 상태의 전자는 다시 에너지 준위가 낮은 반도체 산화물의 전도띠로 주입된다. 주입된 전자는 나노 입자간 계면을 통하여 투명 전도성막으로 확산, 전달되고 산화된 염료분자는 전해질 I-에 의해 다시 환원되어 중성 분자가 된다. 그러나 표면상태 전자 중 일부는 산화된 염료와 다시 결합하거나, 전해질의 $I^{3-}$ 이온을 환원시키기도 한다. 이와 같은 과정은 암전류를 증가시키면서 반도체 전극 막의 성능을 저해하는 주원인이 된다. 전자의 재결합은 투명 전극을 통해서도 가능하기 때문에 투명 전극에 얇은 blocking layer를 도포한 후 나노 결정 산화물 반도체 전극을 제작하면 전지 특성을 향상시킬 수 있다. 본 실험에서 우리는 졸-젤 법으로 $TiO_2$ blocking layer 졸을 만들었고 간단하며 저가공정이 가능한 스크린 프린팅 방법으로 blocking layer를 형성하는 실험을 진행하였다. 전도띠 에너지가 높은 반도체 물질로 표면을 처리하면 $TiO_2$-전해질 간 계면에 에너지 장벽이 형성되어 재결합을 줄여 모든 광전특성이 향상 되었다.

• Korean Journal of Environment and Ecology
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• v.9 no.2
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• pp.221-231
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• 1996

The planting plan for the establishment of Eco-bridge were suggested to restore the ecosystem where has been ecologically isolated by rood construction in Chimgogae of Odaesan National Park. Eco-bridge contributes as a corridors to the faunal movement. To survey the vegetation, 16 plots within 6 sites were selected and 10 by 10 meters in size set up. In the results of Chingogae's vegetation analysis, succession trends was from Quercus mongolica to Carpinus laxiflora, Carpinus cordata, Fraxinus rhynchophylla, Tilia amurensis and so on. It turned out that the nearer sites had high similariyt and vegetation continuity obviously in the similarity index analysis. In the analysis of the number of species and individuals, final step of planting plan needs about 15 species and 10~12 trees, 17~18 subtrees and 100 shrubs in size 100m$^{2}$. Planting species was selected from adjacent sites. The plant species suited for the eco-bridge establishment in this area can be suggested such as Carpinus cordata, Cornus controversa, Q. mongolica etc. and 12 subtree and shrub such as Syringa reticulata var. mandshurica, Sambucus williacsii var. coreaca, Acer pseudosieboldianum and so on.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.327-332
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• 1997

We fabricated the high speed 1.55${\mu}{\textrm}{m}$ distributed feedback laser diodes (DFB-LD) using both two-step mesa etching process and semi-insulating InP current blocking layers. The devices characteristics were threshold current of ~15mA, slope efficiency of ~0.13mW/mA, and dynamic resistance of ~6.0Ω, with as-cleaved facets. The fabricated DFB-LD showed the single longitudinal mode with more than 40dB up to 6 $I_{th}$(CW condition), emitting at the wavelength of 0.546${\mu}{\textrm}{m}$. The -3dB bandwidth was >10㎓ at the driving current of 27mA, and the maximum -3dB bandwidth was ~18㎓ at 90 mA current, showing the superior frequency response of SI-PBH DFB-LD. In the 10Gb/s transmission experiment for 1.55${\mu}{\textrm}{m}$ DFB-LD module, maximum 10 km of single mode fiber(SMF) or 80 km of dispersion shifted fiber (DSF) could be transmitted with error free.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.47-55
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• 2002

This paper proposes a new improved lumped element equivalent circuit analysis method to analyze withdrawal weighted SAW resonators of irregular electrode configurations, which enables to calculate the frequency response of withdrawal weighted SAW resonators. This method has led to the derivation of Smith equivalent circuit's y-parameters for a single ground electrode and formulated the resonator's admittance by calculating the total current into an IDT assembly. To illustrate the effectiveness of the technique, this method was applied to the design of a simple ladder filter and the change of the filter performance was investigated in relation to the weighting of the series and parallel resonators, respectively. The results shows that the withdrawal weighted resonator ladder filters provide better performance in their bandwidth and transition characteristics than normal ones. This new equivalent circuit analysis method can also serve as a better tool to design and analyze general SAW resonator filters.