• 한국산림과학회지
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• 제99권3호
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• pp.312-322
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• 2010

한국에서 비자나무는 남해안 및 제주도의 온난 기후대에 주로 분포하고 있으며, 사찰과 향교 주변 등에서 주로 보호림으로 조성되어 오고 있다. 본 연구의 주된 목적은 한반도의 대표적 비자나무 임분에서 식생구조분석을 실시함으로서 현재 비자나무 식생군락의 동태를 파악하고 이로부터 적절한 임분 보전대책을 수립하는데 있다. 비자나무 임분 내에서 조사된 종수는 총 148종이었으며, 교목층 임분에서 출현수종 28종, 아교목층 출현수종 38종, 그리고 관목층 출현수종 82종의 목본 관속식물이 생육하고 있는 것으로 나타났다. 조사된 비자나무 임분에서 공통적으로 나타난 종은 쥐똥나무, 송악 및 마삭줄이었다. 조사지역 모든 층위에서 비자나무가 우점종 이었으나, 아교목층 및 관목층에서는 그 우점치가 다소 떨어져 임분 쇠퇴현상이 나타났는데, 이러한 사실은 교목층 임분의 수관발달 및 아교목층에서의 생장편의에 의한 결과이다. 비자나무림의 교목층과 아교목층은 천연발아에 의해 조성된 임분이 대부분이다. 따라서 조사된 우리나라 비자나무림에 대한 건강한 임분을 유도하기 위해서는 도태 간벌시업을 응용함으로서 과도한 수관경쟁의 조정이 필요할 것으로 판단되는 바이다.

• Journal of Ecology and Environment
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• 제29권1호
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• pp.17-22
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• 2006

Since the demands not only for value-added timber but the environmental functions of forests had been increased, native tree species has been, and is rapidly being replaced by foreign tree species in many parts of the world. However, the studies on population structure and regeneration characteristics of native tree species were not conducted enough. Regeneration of Kalopanax septemlobus growing among other hardwoods in natural forests is very difficult because of its low seed viability and germination rate. The study examined the distribution of mature trees of K. septemlobus and their regeneration pattern at the 1.12 ha study plot in natural deciduous broad-leaved forest of Mt. Jeombong. The density and mean DBH of K. septemlobus was 97 trees per ha and 32 cm, respectively. The spatial distribution of K. septemlobus showed a random pattern (aggregation index is 0.935) in the 1.12 ha study plot. The age of 90 trees among 99 sample trees of K. septemlobus ranged from 90 to 110 years and represented a single cohort, thus suggesting that K. septemlobus in advance regeneration has regenerated as a result of disturbances such as canopy opening.

• ETRI Journal
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• 제27권1호
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• pp.95-101
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• 2005

Waveguide structures of the stand-alone electroabsorption (EA) modulator and the electroabsorption modulated laser (EML) are investigated using the 3D beam propagation method. The EA waveguide structures with InP-based passivation layers show saturation in the extinction ratio (ER) due to the stray light traveling through the passivation layers. This paper demonstrates that narrower passivation layers suppress stray-light excitation in the EA waveguide, increasing the ER. A taper structure in the isolation section of the EML waveguide can reduce the mode mismatch and suppress the excitation of the stray light, increasing the ER further. Low-index-polymer passivation layers can confine the mode more tightly in the active waveguide, yielding an even higher ER.

• The Korean Journal of Ecology
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• 제19권6호
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• pp.499-506
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• 1996

Forest stand development in Kwangnung Experimental Forest, Korea, was simulated with a forest succession gap model of the JABOWA/FORET type, in order to predict climax species and characterime the trend of community structure along the succession. The model runs for a period or 1, 000 yr and is based on the averaged successional characteristics of 50 forest plote with an individual size or 1/12 ha gap consisted of the 15 major tree species. The total bimass and leafarea index have arrived at a steady state since about 200 yr and these values are smaller than that or field survey. Carpinus cordata, C. laxiflora, Quercus mongolica and Q. serrata were epected to be climax species that represent about 86% or total biomass in later stage and these results coincided with the previous succession studies from field survey in the area.

• International Journal of Railway
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• 제7권4호
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• pp.94-99
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• 2014

Urban railway systems are located under populated areas and are mostly constructed for underground structures which demand high standards of structural safety. However, the damage progression of underground structures is hard to evaluate and damaged underground structures may not effectively stand against successive earthquakes. This study attempts to examine initial damage-stage and to access structural damage condition of the ground structures using Earthquake Damage Monitoring (EDM) system. For actual underground structure, vulnerable damaged member of Ulchiro-3ga station is chosen by finite element analysis using applied artificial earthquake load, and then damage pattern and history of damaged members is obtained from measured acceleration data introduced unsupervised learning recognition. The result showed damage index obtained by damage scenario establishment using acceleration response of selected vulnerable members is useful. Initial damage state is detected for selected vulnerable member according to established damage scenario. Stiffness degrading ratio is increasing whereas the value of reliability interval is decreasing.

• Smart Structures and Systems
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• 제16권6호
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• pp.1049-1068
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• 2015

In the paper, the authors propose the application of operational deflection shapes (ODS) for the detection of structural changes in technical objects. The ODS matrix is used to formulate the spatial filter that is further used for damage detection as a classical modal filter (Meirovitch and Baruh 1982, Zhang et al. 1990). The advantage of the approach lies in the fact that no modal analysis is required, even on the reference spatial filter formulation and other components apart from structural ones can be filtered (e.g. harmonics of rotational velocity). The proposed methodology was tested experimentally on a laboratory stand, a frame-like structure, excited from two sources: an impact hammer, which provided a wide-band excitation of all modes, and an electro-dynamic shaker, which simulated a harmonic component in the output spectra. The damage detection capabilities of the proposed method were tested by changing the structural properties of the model and comparing the results with the original ones. The quantitative assessment of damage was performed by employing a damage index (DI) calculation. Comparison of the output of the ODS filter and the classical modal filter is also presented and analyzed in the paper. The closing section of the paper describes the verification of the method on a real structure - a road viaduct.

• 한국환경복원기술학회지
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• 제14권1호
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• pp.23-33
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• 2011

Habitats loss and fragmentation are major threats to biodiversity. There are various kinds of environmental assessment have been developed for various problems to solve. Yet, there are no well-developed methods for quantifying and predicting about biodiversity. To achieve a sustainable conservation for biodiversity, the structural diversity of forest must be assessed by proper indexes. This study aim to quantitatively assess the diversity of forest structure as habitats and results of the verification by bird survey for objective presentation of evidence. As a result of literature review, some indexes were selected as potential prediction tools for biodiversity; area of patch, area of core regions, shape of patch and average age of stand. The assessment results were estimated by monitoring of birds for accuracy verification and the results were almost in agreement with each others. But, 1 and 2 level of forests were showed ambiguous results. Certainly, this study was limited in some valuation indexes on landscape scale. Further studies should be considered that different environmental factors such as land use, disturbances by human and vegetation index. Also, we expect that the additional monitoring of birds should give rise to the result which is improved assessment results.

• Journal of the Korean Wood Science and Technology
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• 제34권4호
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• pp.66-75
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• 2006

충북 월악산 북동 사면 지역(해발 380 m)에서 24년생 잣나무 인공림의 바이오매스와 에너지량을 조사한 결과, 잣나무림의 바이오매스는 줄기부 26.6 ton/ha, 수피부 4.3 ton/ha, 1년생 가지 0.2 ton/ha, 가지부 8.6 ton/ha, 고사지 1.5 ton/ha, 당년생 잎 1.3 ton/ha, 전년생 잎 6.1 ton/ha로서 고사지를 제외한 지상부 전체는 47.0 ton/ha으로 나타났다. 또한 연간 순생산량은 줄기부 3.0 ton/ha/yr, 수피부 0.4 ton/ha/yr, 1년생 가지 0.2 ton/ha/yr, 가지부 1.1 ton/ha/yr, 당년생 잎 1.3 ton/ha/yr이며, 지상부 합계는 6.0 ton/ha/yr로 추정되었다. 이것을 열 에너지량으로 환산하면 지상부 전체의 에너지량은 1,028 GJ/ha, 연간 에너지 고정량(지상부)은 133 GJ/ha/yr로 나타났다. 한편, 잣나무림의 엽면적 지수는 20.2로 나타났다.

• 한국산림과학회지
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• 제106권2호
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• pp.150-168
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• 2017

이 연구는 2000년도 동해안 산불이 발생한 강원도 삼척 비화진 유역을 대상으로 2003년도와 2014년도의 식물사회학적 식생유형분류, 층위별 중요치, 종다양도, 군락유사도 분석을 통해 임분 구조 변화를 구명하기 위하여 32개소의 식생조사를 각각 실시하였다. 식생유형분류 결과, 7개의 식생단위에서 4개의 식생단위로 감소하였으며, 11개의 종군에서 7개의 종군으로 감소하였다. 중요치 분석 결과, 교목층에서 신갈나무(Quercus mongolica), 졸참나무(Q. serrata), 굴참나무(Q. variabilis)가 각각 6.8%, 5.2%, 2.9% 증가하였으며, 소나무(Pinus densiflora)가 각각 2.8%로 가장 많이 감소하였으며 밤나무(Castanea crenata), 이팝나무(Chionanthus retusa), 살구나무(Prunus armeniaca var. ansu), 복자기(Acer triflorum), 모감주나무(Koelreuteria paniculata) 등 대부분의 조림 수종들의 중요치가 감소되었다. 종다양도의 경우, 교목층에서 0.252에서 0.287로 증가하였고, 아교목층에서 0.252에서 0.434로 증가하였고, 관목층에서 1.293에서 1.333으로 증가하였지만 초본층에서는 1.745에서 1.646으로 감소하였다. 군락유사도의 경우, 각 층위별로 0.78, 0.65, 0.72, 0.55로 나타나 초본층의 변화가 가장 심하였다. 결론적으로 본 연구는 이 조사지와 유사한 산불피해지의 생태계 진단 및 관리를 위한 기초자료로 활용될 것으로 판단된다.

• Journal of Forest and Environmental Science
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• 제33권3호
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• pp.202-225
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• 2017

Non Timber Forest Products (NTFPs) has gained a lot of significance over the years as a means of income generation. Forests are playing a vital role in the supply of these products, however, due to their continuous extraction, the population of many species might have depleted. Very little information is known about community structure and population status of NTFPs. No specific studies have been made to find out the occurrence, availability of species and population status in the forests, supplying the resources. The present study has been carried out in community forests of the naturally occurring NTFPs in the temperate forest of the Ziro valley of Arunachal Pradesh. The main aim is to determine community structure, species composition and population status of NTFPs. Three forest stands viz., Nyilii, Dura and Gyachi were selected which are used by the Apatani tribe for extraction of the NTFPs. For evaluation of species composition and community characteristics, the sampling of the vegetation was done using the quadrat method. A total 137 species representing 68 families and 116 genera were recorded. Herbs represent the maximum diversity with 71 species followed by 35 shrub species and 31 tree species. The families Asteraceae and Rosaceaeae exhibited maximum representation followed by Urticaceae. The species under Fagaceae, Lauraceae, Rosaceae and Rutaceae were found to be important NTFP yielding species. Highest species richness was recorded in Nyilii having 124 species, while lowest in Dura with 102 species. Density of tree, shrub and herb ranged between 376 to $456\;individuals\;ha^{-1}$, 2848 to $3696\;individuals\;ha^{-1}$ and 31.44 to $36.64\;individuals\;m^{-2}$, respectively. The total basal area was found to be highest ($51.64m^2\;ha^{-1}$) in Dura followed by Nyilii ($25.32m^2\;ha^{-1}$) and lowest in Gyachi ($22.82m^2\;ha^{-1}$). In all the three study stands the species diversity indices showed the trend, herbs > shrubs > trees while the evenness index showed the trend as shrubs > herbs > trees. The overall species similarity index was highest (82.35%) between Dura and Gyachi. About 80% of the total recorded species showed clumped distribution while, no regular distribution was shown by any species. The three selected stands harbor about 50 important NTFP yielding species which are being used commonly by the Apatani people in their day to day life. Among the three study sites, overall diversity of NTFP was found highest in the Nyilii stand while the density of population was found better in Dura and Gyachi stands. The population of many species was found to be low due to continue harvesting without any sustainable management by the communities. All the selected forest stands have the potentiality to grow the high value NTFP yielding species and if managed properly, they can support the livelihood and economy of the local communities.