• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.665-676
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• 2011

In this study, the nucleate pool boiling heat transfer coefficients (HTCs) and critical heat flux (CHF) for a smooth and square flat heater in a pool of pure water with and without carbon nanotubes (CNTs) dispersed at $60^{\circ}C$ were measured. Tested aqueous nanofluids were prepared using CNTs with volume concentrations of 0.0001%, 0.001%, and 0.01%. The CNTs were dispersed by chemically treating them with an acid in the absence of any polymers. The results showed that the pool boiling HTCs of the nanofluids are higher than those of pure water in the entire nucleate boiling regime. The acid-treated CNTs led to the deposition of a small amount of CNTs on the surface, and the CNTs themselves acted as heat-transfer-enhancing particles, owing to their very high thermal conductivity. There was a significant increase in the CHF- up to 150%-when compared to that of pure water containing CNTs with a volume concentration of 0.001%. This is attributed to the change in surface characteristics due to the deposition of a very thin layer of CNTs on the surface. This layer delays nucleate boiling and causes a reduction in the size of the large vapor canopy around the CHF. This results in a significant increase in the CHF.

• Korean Journal of Environment and Ecology
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• v.7 no.1
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• pp.35-48
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• 1993

To compare ecological succession stage between 1987 and 1992, this study was executed in Mt. Puk'an. 26 sample plots of 500$m^2$ were set up. The results were summarized as follows; 1. To analysis plant community structure, the classification by TWINSPAN and CCA, DCA and RA ordination were applied to the study area. That of Mt. Puk'an was divided 4 groups by altitude. The dividing groups are Robinia pseudo-acacia-Quercus spp. community, mixed forest community, Q. serrata community, and Q. mongolica community. The successional trends of tree species over 500m seem to be from Pinus densiflora to Q. mongolica and below 500m in altitude seem to be from Robinia pseudo-acacia through Quercus acutissima, Q. mongolica, Prunus sargentii, Sorbus alnifolia to Q. serrata in the canopy layer. In the case of understory and shrub layer, the successional trends to be from Corylus sieboldiana, Zanthoxylum schinifolium through Rhus trichocarpa, Rhododendron mucronulatum, Rh. schlippenbachii to Acer pseudo-sieboldianum. 2. In comparing successional trends with 1987', the advanced data was not obtained in 1992. It was postulated that succession is not progressed by human disturbance and air pollution.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.233-233
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• 2017

Algal communities are important to maintain the aquatic ecosystems function. Algae have short life cycles, they respond quickly to environmental change and their diversity and density can indicate and the quality of their habitat. The bloom forms before the rice seedings have emerged, it may present a physical barrier that prevents the seedlings from penetrating the floodwater. Wind may also move the algal bloom, pushing the young plants beneath the surface. Another harmful action develops when the water dries up and the algae form a layer at the bottom of the field. The layer envelops the seedlings, which are not yet deeply rooted, and drag them to the surface when the water is let in again. Soil utilization pattern can be the mail facter affecting soil physico-chemical properties, especially in soil phosphorus (P). Solid content of the algae culture solution increased with the increase in the nitrogen rather the phosphors concentration. Phosphoric acid was treated with conventional treatments (100-0%, before transplanting time-tillering stage), 50-50%, 0-100%, and un-treated. The herbicide was treated on the 7 DAT (day after transplanting). Green algae samples were collected 20 DAT. Total phosphoric acid was the highest at 0.06 in 50-50% treatment in 20 DAT. The amount of green algae was about twice (9.8 mg/20ml) that of un-treated. Total number of green algae was 54 species(Green algae 35 species, Euglena 9 species, Stone wheel 10 species). Among the phosphoric acid treatment methods, the number of occurrences of green algae were the highest with 39 species in 0-100%, followed by 50-50%, 28 species, conventional treatments, 22 species, non-treatment, 18 species, respectively. Rice Yield was not significantly different by phosphoric treatment time, but slightly higher than un-treated. The maximal algal biomass was observed about 2weeks or 1 month after transplanting; the subsequent decrease of the biomass was related to the consumption by grazers and to a deficient light under the rice canopy. Maximal algal growth was observed just before tillering. To estimate the suitable method of phosphorus application in puddled-soil drill seeding of rice, available phosphorus appearance of algal water bloom, and rice yield were investigated in paddy soil of rice-barley double cropping system.

• Korean Journal of Environment and Ecology
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• v.32 no.2
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• pp.215-224
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• 2018

The climate change is expected to weaken the habitat of Pinus densiflora and P. thunbergii, but they are still in high demand for planting. This study aims to suggest the rational community planting design based on natural forests' community structure in the southeastern region of Korea (warm temperate zone). For this study, we surveyed 22 plots of Pinus densiflora community and 60 plots of P. thunbergii community in Busan Metropolitan City which is located in the southeastern part of the Korean peninsula. We investigated the diameter of breath hight (DBH) and population of each tree layer in a $100m^2$ quadrat and used a regression analysis to derive a regression equation for estimating the mean number of planting individuals in each DBH. The coefficient between canopy layer's DBH and growth individuals per unit area ($100m^2$) was 0.700 for P. thunbergii communities and 0.533 for P. densiflora communities, indicating very high explanatory power by single factor. The predicted regression equation of between DBH and growth density was $Y=31.176e^{-0.055x}$ (X=DBH, Υ=growth individuals per $100m^2$) for P. thunbergii communities and $Y=38.351e^{-0.059x}$ for P. densiflora communities. Planting densities of P. densiflora communities and P. thunbergii communities in southeast region were higher than the central region.

• Korean Journal of Environment and Ecology
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• v.9 no.1
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• pp.15-29
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• 1995

To investigate plant community structure of Uiryung valley, Harujae valley, Kugi valley, Songchu valley, Tobongsan valley in Bukhansan National Park, each thirty eight, forty, twenty six. twenty eight, thirty six plots (plot size 100$m^2$) were set up and surveyed. The surveyed data were integrated and classification by TWINSPAN and DCA ordination techniques were applied to the study area. The plant community were divided into nine groups in seventy nine plots by TWINBPAN and the dividing groups were Carpinus laxiflora community(I), Quercus mongolica community(II), Pinus densiflora community(III), Q. mongolica-P. densiflora community(IV) Q. mongolica-Q. serrata- Prunus sargentii community(V), Q. mongolica Q. variabilis community(Ⅵ), Robinia pseudoacacia-Q. serrata community(Ⅶ). P. rigida-Q. serrata community(Ⅷ), Q. mongolica- Q. variabilis- Styrax obassia community(Ⅸ). So the successional trends of tree species at the natural forest seem to be from P. densiflora to Q. mongolica and at the artificial forest seem to be from R. pseudoacacia, P. rigida to Q. acutissima, Fraxinus rhynchophylla in canopy layer And in the subtree and shrub layer, it wag supposed that from Deotzia prunifolia, Rhus trichocarpa. Rhododendron yedoense var. poukhasleilse, Euonymus oxyphyllous to Magnolia sieboldii, Acer psuedo-sieboldianum, Lindera obtusiloba. In comparing successional trends with past study, it was postulated that successtion is not progressed by human disturbance and soil acidification by the air pollution.

• Journal of Korean Society of Forest Science
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• v.79 no.2
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• pp.173-186
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• 1990

To investigate the structure of the plant community of Soribong area in Kwangnung forest, forty-six plots were set up by the clumped sampling method. The classification by TWINSPAN and four kinds of multivariate ordination(PO, PCA, RA, DCA) were applied to the study area in order to classify them into several groups based on woody plants and environmental variables. The classification had been successfully overlayed on an ordination of the same data using DCA. The plots can be classified into four groups by TWINSPAN and DCA. The successional trends of tree species by both techniques seem to be from Pinus densiflora through Quercus mongolica, Q. serrata, Q. aliena, Carpinus laxiflora, Sorbus alnifolia to C. cordata, Fraxinus rhynchophylla, Cornus controversa in the canopy layer, and from Rhododendron mucronulatum, Rhus triohocarpa, Lespeoleza cyrtobotrya, Weigela subsessilis through Corylus sieboldiana, Lindera obtusiloba to Slaphylea bumalda, Callicarpa japonica, Lonicera maackii in the understory layer. As a result of the analysis for the relationship between the stand scores of DCA and environmental variables, they had a tendancy to increase significantly from the P. densiflora community to C. cordata community that was soil pH and the amount of humus, total nitrogen and exchangeable cations.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.36-42
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• 2001

Changes in breeding bird community and forest structure by thinning were investigated from April 1997 to August 1998 in 10ha ($400{\times}250m$) of temperate mixed hardwood forest in Mt. Gariwang which is located in National Forest, Pyoungchang, Kangwon Province, Korea. Bird community was surveyed by the territory mapping method and forest structure was done by analyzing the vertical structure of foliage, distribution of diameter at breast height (DBH) of trees and tree species composition. After the thinning, tree density, number of tree species and basal area were decreased from 195ea/ha, 18 species and 6.69 $m^2/ha$ into 100ea/ha, 13 species and 3.04 $m^2/ha$, respectively. Foliage coverages in upper and mid layer were decreased, but coverage in low layer was increased. Large trees (Over 40cm of DBH) were decreased. Number of breeding bird species and pairs were decreased from 14 species and 23 pairs into 8 species and 12 pairs after the thinning. Number of breeding pairs of Yellow-breasted bunting Emberiza elegans incresed. There were decrease in number of species in hole & bush-nesting and canopy & bush-foraging guild. The results suggested that the thinning affect the species composition of breeding bird community and the forest structure. Changes of habitat structure might influence in breeding bird's density, species diversity and habitat using pattern of breeding bird community.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.565-577
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• 2019

The purpose of this study was to understand the factors influencing the decline and the patterns of changes in Abies nephrolepis populations on Mt. Seorak. We installed permanent quadrats in the areas of the Gwittagicheongbong (peak), Gwanmoneungseon (ridge), and the Seorak Falls and have monitored the community structure, population dynamics, radial growth, and vitality in the quadrats since 2009. Excluding the Seorak Falls, the three research sites showed a three-layer structure in which the low-tree layer forms the canopy. Major tree species were Khingan fir, Korean arborvitae, Mongolian oak, Erman's birch, and Korean maple. The significance of Khingan fir in Seorak Falls decreased from 45.3% in 2009 to 36.8% in 2018. The number of shoots ($DBH{\geq}5cm$) was highest at 1,800 individuals/ha and 1,700 individuals/ha at the Gwittagicheongbong 2 and the Gwanmoneungseon, respectively. The mortality rates over the past 10 years were very high, at 38.3% and 35.3%, respectively, in the Gwittagicheongbong 1 and Seorak Falls. The most stable inverse J-shaped distribution in the Gwittagicheongbong 1 area was shown in the size-frequency distribution of the Khingan fir populations. The average annual ring growth of the Khingan fir was 0.96 ~ 1.73 mm/year, and the ring growth tended to decrease in the areas of Gwittagicheongbong 1, Gwanmoneungseon, and Seorak Falls, where the vitality was low. If the monitoring process continues, it will be possible to obtain basic data for the conservation and management of subalpine vegetation.

• Journal of Korean Society of Forest Science
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• v.100 no.1
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• pp.34-41
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• 2011

Vegetation structure, composition and diversity were quantified for 10 samples ($10m{\times}10m$) representing woody vegetation and for 30 samples ($1m {\times}3m$) representing understory vegetation in Pinus parviflora and Tsuga sieboldii forest of Taeharyeong, Ulleung-gun (Gyeongsangbuk-do). P. parviflora was limitedly advanced to sapling layer from seedling stage, and based on Mantel tests, composition of canopy layer was not established in ground woody vegetation. Non-metric multidimensional scaling revealed influence of biotic and abiotic factors in species composition of woody and understory vegetation. In the result of multiple regression model, abundance of P. parviflora (density and breast height area) and percent cover of woody debris were significant predict variables for understory diversity. These results suggest that relatively large disturbance is required for regeneration of P. parviflora and T. sieboldii forest, and control of expansion of monocultural understory species that monopolize resources such as Carex blepharicarpa and Maianthemum dilatatum, is necessary for maintenance of diversity.

• Korean Journal of Environment and Ecology
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• v.36 no.5
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• pp.507-524
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• 2022

In this study, we revealed the location environment and community structural characteristics after extensively investigating Korea's warm-temperate island areas and categorizing vegetation through TWINSPAN analysis. Based on it, this study aims to suggest the direction of the vegetation restoration plan for warm-temperate forests by deriving a restoration strategy for each vegetation type. The vegetation types were clearly divided into eight types, and communities I through IV were good evergreen broad-leaved forests dominated by Machilus thunbergii and Castanopsis sieboldii. On the other hand, communities V through VIII were Pinus thunbergii forest, deciduous broad-leaved forest, and artificial forest, and retrogressive succession vegetation in the warm-temperate areas. The environmental factors derived from the DCA analysis were altitude (average temperature of the coldest month) and distance from the coastline (salt tolerance). The distribution pattern of warm-temperate forests has been categorized into M. thunbergii, C. sieboldii and Cyclobalanopsis spp. forest types according to the two environmental factors. It is reasonable to apply the three vegetation types as restoration target vegetation considering the location environment of the restoration target site. In communities V through VIII, P. thunbergiiand deciduous broad-leaved formed a canopy layer, and evergreen broad-leaved species with strong seed expansion frequently appeared in the ground layer, raising the possibility of vegetation succession as evergreen broad-leaved forests. The devastated land where forests have disappeared in the island areas is narrow, but vegetation such as P. thunbergii and deciduous broad-leaved forests, which have become a retrogressive succession, forms a large area. The restoration strategy of renewing this area into evergreen, broad-leaved forests should be more effective in realizing carbon neutrality and promoting biodiversity.