• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.312-322
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• 2010

In Korea, Torreya nucifera (L.) Siebold & Zuccarini is widely distributed in the warm temperate zone of South coastal area and Jeju island, mainly as preserved forest in the vicinity of the Buddhist temple and Confucian temple. The objective of this study is in order to develop the conservation method and comprehension of vegetation community by current vegetation structure analysis of Torreya nucifera stand. As the results, the number of surveyed species in Torreya nucifera stand were total 148 species with 28 species of tree layer, 38 species of subtree layer, and 82 species of shrub layer. The appearance of the common species were Ligustrum obtusifolium Siebold & Zucc., Hedera rhombea Bean, and Trachelospermum asiaticum Nakai var. asiaticum. All the story of the surveyed region, Torreya nucifera maintained the current dominant species, but the subtree layer and shrub layer was decreased dominant rate because of the development of the crown of tree layer and biased growth of the subtree layer. Most of the tree layer and subtree layer in Torreya nucifera stands are composed of the sprout forest. Therefore, these results suggest that in order to maintain the healthy stand it is demanded for the application of selection thinning method for reducing crown competition in Torreya nucifera forests.

• Journal of Ecology and Environment
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• v.29 no.1
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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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• v.27 no.1
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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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• v.19 no.6
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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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• v.7 no.4
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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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• v.16 no.6
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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.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.1
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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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• v.34 no.4
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• pp.66-75
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• 2006

This study was conducted to understand the biomass and the energy content of 24-year-old Pinus koraiensis stand planted in Mt. Wolak, Chungcheongbuk-do, Korea. Nine sample trees were selected and harvested for the study. Stem, bark, branches and leaves were weighed respectively with the stratified clipping method, and analyzed for productive structure. The allometric regression equations between dry weight of each component and $D^2H$ were obtained to estimate the total biomass of aboveground (47.0 ton/ha) and other parts (56.5% from stemwood, 9.1% from stembark, 0.5% from current twigs, 18.4% from live branches, 2.6% from current leaves, and 12.9% from previous leaves). Annual net production of aboveground was 6.0 ton/ha/yr, and the ratios of stemwood, stembark, current twigs, live branches, and current leaves to that of aboveground were 49.8%, 7.3%, 3.5%, 18.6%, and 20.8%, respectively. Energy content of aboveground was 1,028 GJ/ha, and annual energy content was 133 GJ/ha/yr. Leaf area index (LAI) of P. koraiensis plantation was 20.2 in Mt. Wolak.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.150-168
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• 2017

This study was carried out to compare stand structure in Bihwajin basin Samcheok-si, Gangwon-do, Korea for ten years between 2003 and 2014, in which occurred the east coastal forest fire in 2000. Data were collected from 32 quadrates that followed by the analysis of vegetation classification according to plant sociology, importance value by Mclntosh and Curtise, species diversity and similarity index. In the result of vegetation classification, the vegetation unit decreased from 7 units to 4 units, and the number of species groups changed from 11 to 7. As a result of importance value (IV) changes, IV of Quercus mongolica, Q. serrata and Q. variabilis was increased by 6.8%, 5.2% and 2.9% in the order, respectively. However, that of Pinus densiflora was decreased by 2.8%. That of major planted species such as Castanea crenata, Chionanthus retusa, Prunus armeniaca var. ansu, Acer triflorum and Koelreuteria paniculata was reduced. As a result of species diversity, it was increased from 0.252 to 0.287 in tree layer, from 0.252 to 0.434 in subtree layer, and from 1.293 to 1.333 in shrub layer. But that in herb layer was decreased from 1.745 to 1.646. As a result of similarity index, it was 0.78, 0.65, 0.72 and 0.55 by layers that showed most difference in herb stratum. Considering the results, this study would be applied to the ecosystem diagnose and management of forest fire damaged area similar to the investigated area.

• Journal of Forest and Environmental Science
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• v.33 no.3
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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.