• Journal of Korea Foresty Energy
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• v.21 no.2
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• pp.51-61
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• 2002

This study was conducted to investigate and compare species composition, stand structure, and growth pattern for two different sites in which silvopastoral system has been taking place. One site was the pasture area where a number of trees were removed and grasses were planted for cattle grazing, and the other site was the deciduous forest that has been established by ecological succession. The results were as follows: 1. Nine tree species were present equally in the pasture area and the deciduous forest. Of these species, seven tree species were growing in common for two sites. However, the species composition, including density and frequency, was varied by sites. 2. The number of stems per hectare in the pasture area was 71, and that in the deciduous forest was 1,433, having shown the big difference. It is estimated that, considering the growth rate, better grown trees were remained at the time of harvesting in 1996. 3. The growth of diameter, height, and basal area in the pasture area was superior to that in the nearby deciduous forest. In spite of higher values of diameter and height, the timber volume of pasture area per unit area was less than 15% of that in the deciduous forest. 4. Providing sufficient growing space, the pasture area supported higher values of diameter and height. The wider growing space also had influence on the expansion of crown of trees by the result of deliquescent growth pattern. From this point of view, more research would be needed to establish appropriate number of trees for silvopastoral system.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.100-109
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• 2016

Low impact development (LID) facilities are established for the purpose of restoring the natural hydrologic cycle as well as the removal of pollutants from stormwater runoff. Improved efficiency of LID facilities can be obtained through the optimized interaction of their major components (i.e., plant, soil, filter media, microorganisms, etc.). Therefore, this study was performed to evaluate the performances of LID facilities in terms of runoff and pollutant reduction and also to provide an optimal maintenance method. The monitoring was conducted on four LID technologies (e.g., bioretention, small wetlands, rain garden and tree box filter). The optimal SA/CA (facility surface area / catchment area) ratio for runoff reduction greater than 40% is determined to be 1 - 5%. Since runoff reduction affects the pollutant removal efficiency in LID facilities, SA/CA ratio is derived as an important factor in designing LID facilities. The LID facilities that are found to be effective in reducing stormwater runoff are in the following order: rain garden > tree box filter > bioretention> small wetland. Meanwhile, in terms of removal of particulate matter (TSS), the effectiveness of the facilities are in the following order: rain garden > tree box filter > small wetland > bioretention; rain gardens > tree box filter > bioretention > small wetland were determined for the removal of organic matter (COD, TOC), nutrients (TN, TP) and heavy metals (Cu, Pb, Cd, Zn). These results can be used as an important material for the design of LID facilities in runoff volume and pollutant reduction.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.484-492
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• 2019

The aim of the present study was to compare the cold tolerance of seven different types of trees growing in southern Korea to select evergreen broad-leaved trees that can be used as street trees in large land areas experiencing climate change. The trees compared were the thorn tree, Cinnamomum camphora, Camellia japonica, Machilus thunbergii, Dendropanax morbifera, Daphniphyllum macropodum Miq., Quercus glauca Thunb., and Raphiolepis indica. When the trees were subjected to low temperature treatment, their electrolyte elution volume values appeared to increase with the decreases in the treatment temperature. The analysis of the cold tolerance of each type of tree was based on the estimated temperatures in the following order: C. japonica (-11.586℃) > R. indica (-9.348℃) > Q. glauca (-8.719℃) > M. thunbergii (-8.090℃) > D. macropodum (-7.409℃) > D. morbifera (-7.085℃) > C. camphora (-6.995℃). The relative cold tolerance difference found in the seven tree species was more than 5℃, as evaluated previously. In the Lauraceae family, the difference in cold tolerance was more than 2℃, even in the same species. The analysis showed that trees with excellent cold tolerance included Q. glauca Thunb., C. japonica, R. indica, and the thorn tree. This knowledge is required for the evaluation of the possibility of the survival of trees under cold temperature conditions in cities.

• Journal of Cadastre & Land InformatiX
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• v.50 no.1
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• pp.181-200
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• 2020

This study used the OLS model to estimate the determinants affecting the tenure of a home and then compared the predictive power of each model with SVM, Decision Tree, Random Forest, Gradient Boosting, XGBooest and LightGBM. There is a difference from the preceding study in that the Stacking model, one of the ensemble models, can be used as a base model to establish a more predictable model to identify the volume of housing transactions in the housing market. OLS analysis showed that sales profits, housing prices, the number of household members, and the type of residential housing (detached housing, apartments) affected the period of housing ownership, and compared the predictability of the machine learning model with RMSE, the results showed that the machine learning model had higher predictability. Afterwards, the predictive power was compared by applying each machine learning after rebuilding the data with the influencing variables, and the analysis showed the best predictive power of Random Forest. In addition, the most predictable Random Forest, Decision Tree, Gradient Boosting, and XGBooost models were applied as individual models, and the Stacking model was constructed using Linear, Ridge, and Lasso models as meta models. As a result of the analysis, the RMSE value in the Ridge model was the lowest at 0.5181, thus building the highest predictive model.

• Journal of Korean Society of Forest Science
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• v.111 no.4
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• pp.502-510
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• 2022

In the national greenhouse gas inventory, a settlements category has never been included owing to the lack of activity data. Therefore, this study was conducted to obtain basic data for estimating biomass carbon storage in settlements. Nondestructive stem analysis with a laser dendrometer was performed on four major street tree species (Metasequoia glyptostroboides, Prunus armeniaca, Ginkgo biloba, and Acer buergerianum) in Wonju city, South Korea. Allometric equations of the aboveground volume were developed using five models, and allometric equations of crown area were developed with diameter at breast height (DBH) as an independent variable. The best performing allometric equations were aD²+bD+c for M.glyptostroboides and G. biloba, aD+bD² for P. armeniaca, and a+bD² for A. buergerianum. Regarding the allometric equations of crown area with DBH as an independent variable, G. biloba and A. buergerianum exhibited low coefficients of determination (R²), i.e., < 0.364, whereas M. glyptostroboides and P. armeniaca exhibited satisfactory R² values, i.e., > 0.767, probably due to different street tree management practices. The allometricequations in this study will support the carbon inventory of settlements and urban tree monitoring in management practices.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1992-1994
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• 1999

Dicumyl peroxide (DCP) is used for crosslinking agent in general. And the correlation between polyethylene and DCP is significant in particular radiation environment. On this paper, The effects on $Co^{60}{\gamma}$-ray irradiation of polyethylene doped dicumyl peroxide(DCP) were investigated. We experimented on electrical properties as following; electrical tree inception and growing type for applying AC step voltage, AC breakdown strength, volume resistivity, capacitance and dissipation factor at high frequency as increasing dosage. Also, chemical analysis was performed TGA, gel content.

• The Korean Journal of Ecology
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• v.16 no.2
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• pp.199-208
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• 1993

To estimate the level of the air pollution in Taejon city, the contents of S, Pb and Cd of the leaves of the roadside trees were deterimined. And we analyzed the relationship between the contents of S, Pb and Cd in the leaves of the roadside trees and traffic volume. The ranges of S, Pb and Cd contents in all the samples were 1.82~4.34 mg/g, 1.95~$246.80{\mu}g/g$ and 2.00~$20.50{\mu}g/g$ respectively. Areas with the high contents of S, Pb and Cd in the leaves were the road from Taejon railroad station to the provincial government, West Taejon crossroad, Taehwa-dong, Kasuwon-dong and Yongmun crossroad.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.65-68
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• 2000

Polyethylene, has long history and is widely used, was researched due to good electrical properties by many authors. But PE under stress has the critical defects of space charge accumulation and tree growth, so various methods such as catalyst, additives and blend to improve these problems have been execute, of which we selected blending method. As in our previous papers we investigated electrical conduction, dielectric and AC dielectric breakdown characteristics, we did DC dielectric breakdown characteristics in this paper. We selected pure LLDPE, pure EVA and LLDPE films mixed with EVA as specimens, which were mixed with the weight percentages of 50, 60, 70 and 80[wt%] to be thin film. DC applying voltage speed was 500[V/sec]. The relation between dielectric breakdown characteristics and the variations of super structure due to mixing was investigated, and especially trap level at amorphous region, threshold energy increment of conductive electron at free volume were considered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.81-84
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• 1998

New diagnostic techniques have been tried on the applications of chemical, physical and micro-structural methods because there was a limit to diagnose degradation in Korean Underground Residential Distribution (URD) power cables with the conventional electrical methods. In this study, non-electrical properties were carried out as such. Characterization of interface layer was analyzed by X-ray, characterization of insulator by water tree, degree of crosslinking, shrinkage as well as ${\mu}$ -FTIR, characterization of semiconductive layer by volume resistivity. Electrical properties were also performed by leakage current.

• The Journal of Information Systems
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• v.20 no.3
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• pp.1-24
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• 2011

Recently, six sigma has been widely adopted in a variety of industries as a disciplined, data-driven problem solving approach or methodology supported by a handful of powerful statistical tools in order to reduce variation through continuous process improvement. Also, data mining has been widely used to discover unknown knowledge from a large volume of data using various modeling techniques such as neural network, decision tree, regression analysis, etc. This paper proposes a six sigma methodology based on data mining for effectively and efficiently processing massive data in driving six sigma projects. The proposed methodology is applied in the hot stove system which is a major energy-consuming process in a "P" steel company for improvement of heat efficiency through reduction of energy consumption. The results show optimal operation conditions and reduction of the hot stove energy cost by 15%.